2 Advertisements. TELEGRAPHIC ADDRESS : ENGINEERING, LONDON,” TELEPHONE: No. 3663 GERRARD. << ENGINEERING : An Illustrated Weekly Journal, Edited by WILLIAM H. MAW and B. ALFRED RAWORTH. PRICE SIXPENCE. "ENGINEERING," besides a great variety of Illustrated Articles relating to Civil, Mechanical, Electrical, and Military Engineering and Notes of General Professional Interest, devotes a considerable space in each issue to the illustration and description of all matters connected with the PRACTICAL APPLICATION OF PHYSICAL SCIENCE. EACH NUMBER ALSO CONTAINS AN ILLUSTRATED PATENT RECORD. SUBSCRIPTIONS (Home, Foreign and Colonial). "ENGINEERING" can be supplied, direct from the Publisher, post free for Twelve Months at the following rates, payable in advance :-- For the United Kingdom all places abroad :- "" CODES: A. B. C. and WESTERN UNION. Thin Paper Copies Thick 4 11 Subscribers residing abroad are strongly recommended to order copies ou thick paper, as the illustrations are necessarily very much less effective in the thin paper edition; and to remit when possible, by Post Office Order made payable at Bedford Street, Strand, London, W.C. When Foreign Subscriptions are SO forwarded, advice should be sent to the Publisher. Foreign and Colonial Subscribers receiving Incomplete Copies through Newsagents are requested to communicate the fact to the Publisher, together with the Agent's Name and Address. Cheques should be crossed Union of London and Smith's Bank, Limited, Charing Cross Branch." All accounts are payable to "ENGINEERING, LIMITED.” ADVERTISEMENTS. Prepaid Advertisements on Wrapper, Classified under headings: Tenders- Appointments Open-Situations Wanted--Partnerships-Wanted, &c. - For Sale- Auction Sales- Publications-Miscellaneous-Patent Agents- &c. £1 9 2 .. £1 16 0 £2 0 6 OFFICES OF "ENGINEERING," 35 & 36, By the Line-Four Lines or under, 3s., each additional Line, 8d. The line averages Seven Words By the Inch-8s. per Inch Single Column, One Insertion. 5% allowed on 6, 10% on 13, 15% on 26, and 20% on 52 Insertions. Advertisements intended for insertion in the current week's issue must be delivered not later than 5 p.m. on Thursday. For Displayed Advertisements, Specia! STRAND, LONDON, W.C. ᏞᎬᎢ, Advertisements. 3 THE BRUSH ELECTRICAL Transportation Library IF 855 D27 ENGINEERING CO. The only British firm who have delivered any considerable number of ALL-STEEL Passenger Cars for Electric Railways, and the only firm at whose works Electric Rolling Stock-Cars, Trucks, and Equipment-can be manufactured complete. RECENT CONTRACTS for Rolling Stock : GREAT CENTRAL RAILWAY. CHESHIRE lines coMMITTEE. GREAT NORTHERN AND CITY RAILWAY. METROPOLITAN DISTRICT RAILWAY. CITY AND SOUTH LONDON RAILWAY. SUDAN RAILWAYS. BUENOS AYRES AND PACIFIC RAILWAY. LONDON COUNTY COUNCIL (STEEL TRAMWAY CARS.) BRUSH CARS ARE RUNNING ON MOST OF THE TRAMWAY UNDERTAKINGS OF GREAT BRITAIN. Works: LOUGHBOROUGH. Chief Office : Belvedere Road, LONDON, S.E. 4 Advertisements. Robert W. BLACKWELL & Co., Ltd. ENGINEERS & CONTRACTORS ELECTRIC RAILWAYS TRAMWAYS POWER TRANSMISSION "KURKEE, LONDON" PARLIAMENT CHAMBERS 14, Great Smith Street WESTMINSTER 766, WESTMINSTER Advertisements. 5 LO "ELECTRIC Price £2 2s. net. Demy 4to. 604 pp. Half Calf. Illustrated by 20 Plates and numerous Figures in the Text. ELECTRIC & MACHINE DESIGN. Being a Revised and Enlarged Edition of HENRY HORACE FIELD PARSHALL GENERATORS." • BY • AND METCALFE HOBART. EXTRACTS FROM PRESS NOTICES : "It is rarely that a reviewer of technical books has such good cause to congratulate the publishers as in this instance. The treatment, by the authors, of electric machine design calls for notice from the original manner in which they merge theory into practice, teaching always by numerical examples. "The Times. "" 'The volume before us needs no higher recommendation than the statement that it is a revision and an enlargement of the same authors' well-known standard work entitled 'Electric Generators.' is a fund of reliable information relating to the materials with which the whole vast structure of present-day electric machine design is built up."-The Electrician. • (C To those who have found the previous volume of continual use as a work of reference it is unnecessary to recommend its successor; they will get it as a matter of course. -Electrical Times. " LONDON: Offices of "ENGINEERING," 35 and 36, BEDFORD STREET, W.c. 2 6 CO Advertisements. BRITISH INSULATED AND HELSBY CABLES, LIMITED. Electrical Cable Makers. 3-Core Cable for 20,000 Volts Working Pressure. Test Pressure 90,000 Volts. WORKS: PRESCOT, HELSBY AND LIVERPOOL. Advertisements. 7 The Phosphor Bronze Co. LIMITED, Sole Makers of the following ALLOYS: PHOSPHOR BRONZE. "Cog Wheel Brand" and "Vulcan Brand." Ingots, Castings, Plates, Strip, Bars, etc. PHOSPHOR TIN AND PHOSPHOR COPPER. "Cog Wheel Brand." The best qualities made. WHITE ANTI-FRICTION METALS: PLASTIC WHITE METAL. ፡፡ The best filling and lining Metal in the market. BABBITT'S METAL. "Vulcan" Brand. Nine Grades. PHOSPHOR" WHITE LINING METAL. Fully equal to Best White Brass No. 2, for lining Marine Engine Bearings, &c. ፡፡ WHITE ANT" METAL, No. 1. Cheaper than any Babbitt's, and equal to best Magnolia Metal. 87, SUMNER STREET, SOUTHWARK, LONDON, S.E. Telegraphic Address: "Phosbronze, London." Telephone No. : 557, Hop. 8 Advertisements. Western Electric Co., Bridge Chambers, 171, Queen Victoria St., E.C., NORTH WOOLWICH, LONDON, E. CHICAGO, NEW YORK, ANTWERP, PARIS, BERLIN. THREE-PHASE COPPER SHEATHED AND AND W. E. CABLES ELECTRIC TRACTION. LEAD COVERED CABLE. FOR WORKING PRESSURE, 6600 VOLTS. AS MANUFACTURED AND LAID FOR THE LONDON COUNTY COUNCIL TRAMWAYS (South Side). ELECTRIC LIGHT CABLES, TELEPHONE CABLES, AND ALL TELEPHONIC APPARATUS. MOTORS, FANS, ARC LAMPS, &c. Telegrams: "RELAY, LONDON." Codes: A1, A.B.C., LIEBER. Telephone Nos.: 418 BANK, 2389 CENTRAL; and 549 EAST. Advertisements. 9 Felten & Guilleaume-Lahmeyerwerke Actien-Gesellschaft, Dept. Carlswerk, MULHEIM-ON-RHINE. MANUFACTURERS OF ALL KINDS OF ELECTRIC LEADS AND CABLES For Telegraphy, Telephony, Electric Light and Power Transmission, of any Section and Pressure, Testing up to 120,000 Volts. 9900 NO SOLID AND FLEXIBLE NEPTUNE COPPER RAIL BONDS. TROLLEY WIRE. GUARD-SPAN WIRE. BARE COPPER OF ALL DESCRIPTIONS. WIRE ROPES. .. UD AGENTS FOR THE UNITED KINGDOM:- For Insulated Wires and Cables for Electric Light and Transmission of Power, and for Rail Bonds: THE LAHMEYER ELECTRICAL CO., LTD., 109-111, NEW OXFORD STREET, LONDON, W.C. For all other Manufactures: W. F. DENNIS & CO., 49, QUEEN VICTORIA STREET, LONDON, E.C. 10 Advertisements. THE BROUGHTON COPPER CO., LTD. Telegrams: "COPPER CO." Trunk Calls, 638T. MANCHESTER. COPPER SMELTERS. MANUFACTURERS OF FOR COPPER, BRASS, AND BRONZE TUBES, LOCOMOTIVE AND MARINE BOILERS, Feed and Exhaust Pipes, Condenser, Steam, Gas, Water, and other purposes. Telephone: Nos. 638 and 5198. Copper Stay Bolts, Hollow Rods, Ingots, Plates, Sheets, Boiler Rivets, &c. | Electro-Coppered Hydraulic Press Rams, Shafts, Cylinders, Tubes, &c. Manganese & Phosphor Bronze, Cupro-Nickel, Aluminium-Copper, Babbitt Metal & other Alloys. ALSO AT DITTON COPPER WORKS, WIDNES. 6 BROAD STREET PLACE, LONDON, E.C. 49 & 51, OSWALD STREET, GLASGOW. Advertisements. 11 DAVEY, PAXMAN Ic 643 & CO., COL LTD., COLCHESTER, 200 ENGLAND. PAXMAN'S PATENT GAS ENGINES -AND- SUCTION GAS PRODUCERS. CATALOGUES ON APPLICATION 12 Advertisements. TRAMWAY SPECIALITIES. "LANCASHIRE * 99 GENERATORS. AUTOMATIC 95 "LANCASHIRE' REVERSIBLE BOOSTERS, The Lancashire Dynamo & Motor Co., Ltd., TRAFFORD PARK, MANCHESTER. TELEGRAMS: IRONCLAD, MANCHESTER. THE "G. B." SURFACE CONTACT COMPANY, 107, Hamilton House, Bishopsgate St. Without, London, E.C. Double Junction under construction for the Lincoln Corporation, whose tramways are now equipped on this system. The lines have been open to public service, and giving every satisfaction, since November, 1905. For description, see page 736 of this work. Advertisements. 13: HADFIELD'S STEEL FOUNDRY CO., LTD., SHEFFIELD. TRAMWAY POINTS AND CROSSINGS MADE THROUGHOUT OF HADFIELD'S... PATENT "ERA" MANGANESE STEEL BEST TOUGHENED CAST STEEL, OR WITH “Era” Manganese Steel Insert Pieces, Supplied Complete With Fishplates, Bolts, and Joints. (6 Demy 4to, xvi-380 pp., Buckram, gilt top. With 51 Plates and numerous Illustrations in the Text. ~ Price 16s. net. SIR HENRY BESSEMER, · F.R.S. AN AUTOBIOGRAPHY. EXTRACTS FROM PRESS NOTICES: • The name of Sir Henry Bessemer will always remain associated with a great invention. Sir Henry Bessemer had a remarkably shrewd eye for detecting the weak points of a process, and showed striking abilities in rectifying them by various means, some of which were of brilliant inductive ingenuity. He was not trained to any particular trade or profession, but gradually acquired the vocation of professional inventor, a career for which he appears to have been eminently qualified by his natural characteristics. His lack of training in any particular field was probably a distinct advantage to him. "The Times. • • • "The autobiography is simple, concise, full, and always to the point, like the man himself."-Daily Telegraph. "We shall not attempt to deal with it in detail, but shall content ourselves. with a general recommendation to our readers. It is, indeed, a narrative of ingenuity and fertility of resource applied to the affairs of life such as it would scarcely be possible to parallel elsewhere."-The Spectator. LONDON: Offices of "ENGINEERING,”" 35 & 36, Bedford Street, W.c. NEW YORK: JOHN WYLEY & SONS, 43, East Nineteenth Street. 14 Advertisements. JOSEPH BOOTH & BROS., LTD., RODLEY, LEEDS. 8928 Яи ra Overhead, Locomotive, Goliath, Derrick, Breakdown Cranes, also Winding Engines. ร่องคอน THREE-MOTOR ELECTRIC CRANE. SPECIALITY: Telegrams:- "CRANES, RODLEY." ELECTRIC CRANES. Advertisements. 15 THE UNITED ASBESTOS CO., LTD. DOCK HOUSE, BILLITER STREET, LONDON, E.C. Manufacturers of every class of Asbestos Goods. 46 OF THE GLADIATOR. ECLIPSE GLADIATOR" and Patent "ECLIPSE" Packings. WHICH, BEING Special Combinations of ASBESTOS and METAL, give excellent results, and outlast ordinary packings by many months. Made from Victor Asbesto-Metallic The United Asbestos Patent "SALAMANDER" Joints ASBESTOSOITOART combined Copper Cloth, with Jointless Ring. SOLE a MANUFACTURERS eиоIMPOR COPPER ASBESTUS REUNITED ASBESTOS SALAMANDER JOINT (No 16398) REC Washers, Rings, or Ovals for man- hole doors, &c., made to order in any size required. IMPORTANT TESTIMONIALS RECEIVED. These Joints have VICTOR been satisfactorily tested up to 2,500 lb. pressure. We can therefore confidently recommend them. The United Asbestos "VICTOR" Metallic Sheeting, Tape, and Joints. The Lords of the Ad- miralty have awarded us the Contract for the supply of these Joints again and again. Boiler Covering Composition, Lubricating Oils, and Engineers' Stores of all Kinds Supplied. THE UNITED ASBESTOS CO., LTD. Manchester, Newcastle, Liverpool, Hull, Glasgow, Bristol, Sheffield, Colchester, &c. 16 Advertisements. TUDOR ACCUMULATORS. SPECIAL TYPES.. TRACTION FOR GENERATING, AND SUB STATIONS. THE TUDOR ACCUMULATOR CO., LTD., 119, VICTORIA STREET, LONDON, S.W. Telegraphic Address: "SUBCONICAL,” LONDON. WORKS: Dukinfield, near Manchester. Advertisements. 17 Babcock & Wilcox Ltd. PATENT WATER-TUBE BOILERS. OVER 5,500,000 H.-P. (LAND TYPE) AND 1,100,000 H.-P. (MARINE TYPE) IN USE IN ALL INDUSTRIES THROUGHOUT THE WORLD. Side View of Babcock and Wilcox Boiler, fitted with Patent Steam Superheater (integral with boiler). BABCOCK & WILCOX ALSO MANUFACTURE: STEAM SUPERHEATERS. MECHANICAL STOKERS. FEED-WATER HEATERS. FEED-WATER PURIFIERS AND WATER SOFTENERS. STEEL CHIMNEYS. COAL-CONVEYING MACHINERY. STRUCTURAL STEEL WORK. AND ELECTRIC CRANES. COMPLETE INSTALLATIONS OF STEAM PIPING. HEAD OFFICE: Oriel House, Farringdon St., LONDON, E.C. Works: RENFREW, SCOTLAND. WRITE FOR CATALOGUE. 18 Advertisements. SCHAFFER &ded BUDENBERG, LTD. 2 LONDON. MANCHESTER. GLASGOW. Sole Agents for Jena "Robax" Gauge Glasses PATENT NICKEL- SEATED STEEL or IRON VALVE 800 Ga 750 700 650 900 High-class Engine and Boiler Fittings. 600 REVOLUTIONS per Kin TACHOMESER 1000 550 Schae WT125795 Matter of diving pullaye 90 60 30 500 r&Budenberg Geile HOT, 73 450 120 for all Purposes. 2833-0337 150 200 400 PRESSURE, VACUUM, AND HYDRAULIC GAUGES Mchester Lendan & Glasgow. pras N3177484 250 180 300 DOHODOCHT 210 Pressure Ga Schäffer & Buberg Lid. 240 270. 350 300 Advertisements. 19 What is the PROFIT and LOSS ACCOUNT of your BOILER HOUSE? BENNIS Stokers and Compressed Air Furnaces Will secure you SMOKELESS STEAM RAISING and MAXIMUM DUTY from LOW-GRADE and LOW-PRICED FUELS. BENNIS Patent IMPROVED CHAIN-GRATE STOKER has UNIQUE FEATURES: NO DUMPING-BAR NECESSARY. NO BURNT-OUT BARS. PATENT CLOSE-LINKS SAVE COAL, MINIMISE WEAR AND TEAR, AND ADJUST AIR SUPPLY. BENNIS Stokers and Compressed Air Furnaces, BENNIS Patent Improved Chain-Grate Stokers, BENNIS Elevators and Conveyors Are SAVING FORTUNES IN ELECTRIC LIGHT and POWER STATIONS, FACTORIES, MILLS, DYE-HOUSES, SUGAR REFINERIES, BREWERIES, Etc. BENNIS PLANT is APPLICABLE to ONE BOILER or MANY. SIMPLE in construction. EFFICIENT in operation. ECONOMIC in results. 1000 ED. BENNIS & CO., LTD BOLTON. LONDON OFFICE: 28, Victoria Street, S.W. 20 Advertisements. MAGNOLIA ETAL. MARK Flower Brand. META BERLIN PARIS LIEGÉ TIFRICTION BEWARE OF IMITATIONS. AGNOLIA ZAGNOL ROTTERDAM GENOA VIENNA WADE MARK 20 Flower Brand. The NAME and TRADE MARK appear on each Box and Ingot. TO PREVENT IMPOSTURE, GENUINE ORIGINAL METAL ALWAYS IN THIS FORM OF INGOT. SPECIFY MAGNOLIA METAL FLOWER BRAND' HEAD OFFICE- LONDON: 49, Queen Victoria St. ALSO AT Friedrichstrasse, 71. Rue Taitbout, 50. Rue de l'Université, 36. Wijnstraat, 46. Via Sottoripa, 1. Gumpendorferstr. 15. MAGNOLIA ANTI-FRICTION METAL CO. OF GREAT BRITAIN, LTD. FOURTH EDITION, 1906. (REVISED AND REWRITTEN.) THE → "ENGINEERING” AND " ELECTRIC TRACTION POCKET-BOOK. BY PHILIP DAWSON, M. INST. C.E.; M.I. MECH. E.; M.I.E.E. TRANSPORTATION LIBRARY AUTHOR OF ELECTRIC RAILWAYS AND TRAMWAYS.” UNIVERSITY OF MICHIGAN LONDON OFFICES OF “ENGINEERING,” 35 AND 36, BEDFORD STREET, STRAND, W.C. NEW YORK: JOHN WILEY AND SONS, 43 AND 45, EAST 19TH STREET. 1906. مت Frampe s —___ #2 -Y( DH for CONTENTS. SECTION 1.-THE LINE. PART I.-MATERIALS AND CONSTRUCTION. GENERAL, 3 SIMPLE FORMULE FOR RAILS, 20 DURABILITY of Rails, 23 POINTS, CROSSINGS, &C., 24 CURVES, 32 DRAIN RAILS, 44 COST OF RAILWAYS AND TRAMWAYS, 45 PAVEMENTS, 49 PART II.-RETURN CIRCUIT AND BONDING. GENERAL, 51 THE "CHICAGO" RAIL BOND, 52 CHICAGO "CROWN" BOND, 54 THE COLUMBIA RAIL BOND, 57 THE NEPTUNE BOND, 57 THE EDISON-BROWN PLASTIC COPPER BOND, 59 THE EDISON-BROWN PLASTIC RAIL BOND, 61 RAIL WELDING, 63 PART III-OVERHEAD DISTRIBUTION. OVERHEAD LINE, 68 INSULATORS AND LINE MATERIAL, 72 TESTS FOR TENSILE STRENGTH, 80 POLE PLANTING AND RAKING, 82 LINE ERECTION, 93 PART IV.-FEEDERS. VARIOUS TYPES OF CABLES, 99 CABLE LAYING, 99 MANHOLES, 106 JUNCTION BOXES, 108 DETERMINATION OF SIZE OF FEEDERS, 114 ALUMINIUM For Electrical ConductoRS, 121 FEEDER AND COPPER WIRE FORMULÆ, 122 BRITISH STAndard SizeS OF STRANDED ConductORS FOR ELECTRIC SUPPLY, 123 BRITISH STANDARD RADIAL THICKNESSES FOR JUTE DIELECTRIC, Etc., 125 BRITISH STANDARD RADIAL THICKNESSES for RUBBER DIELECTRIC, ETC., 127 MISCELLANEOUS DATA AND TABLES RELATING TO CONDUCTORS, 131 X CONTENTS. F SECTION II.-THE POWER STATION. PART I.-STEAM ENGINES. HEAT, 145 THE INDICATOR Diagram, 153 COMPOUND ENGINES, 159 ENGINES FOR ELECTRIC POWER STATIONS, 165 CRANK-SHAFTS, 171 CONDENSERS, 174 WATER-COOLING ARRANGEMENTS, 175 STEAM PIPING, 179 STEAM PIPE RANGES, 187 STEAM PIPE COVERING, 191 PIPE HANGERS AND BRACKETS, 193 VALVES, 194 STEAM SEPARATORS, 195 LUBRICANTS, 196 PART II.-STEAM TURBINES. GENERAL, 201 IMPULSE STEAM TURBINES, 204 THEORY OF THE COMPOUND TURBINE, 214 COMPARTMENT-COMPOUNDED TURBINES, 218 THEORY OF THE COMPOUND REACTION TURBINE, 230 THE PARSONS TURBINE, 235 THE WESTINGHOUSE-PARSONS TURBINE, 240 DESIGN OF A COMPOUND REACTION TURBINE, 242 THE CURTIS TURBINE, 244 SECTION III.-THE POWER STATION. (Continued.) STEAM BOILERS. BOILERS, 251 MEMORANDA USEFUL IN BOILER CONSTRUCTION, 258 BOILER SETTING, 288 FIREGRATES AND FURNACES, 289 MANHOLES AND SAFETY VALVES, 292 ACCESSORIES, 299 REFUSE DESTRUCTORS, 301 MECHANICAL STOKERS, 307 COAL CONVEYORS, 315 INCRUSTATION AND CORROSION, 327 FEED HEATERS, 337 CALORIMETRIC TESTS (DRYNESS OF STEAM), 342 SUPERHEATERS, 347 FEED PUMPS AND INJECTORS, 350 WATER, 355 CHIMNEYS, 361 MECHANICAL DRAUGHT, 372 FUEL, 384 LIQUID FUELS, 400 MISCELLANEOUS SOLID FUELS, 404 SECTION IV. THE POWER STATION. (Continued.) ELECTRIC GENERATORS. ELECTRIC AND MAGNETIC UNITS, 409 DYNAMO DETAILS, 421 MODEL SPECIFICATION FOR DIRECT-CONNECTED RAILWAY GENERATOR, 427 RUNNING OF GENERATORS AND THEIR Care, 427 ALTERNATING CURRENTS, 449 ROTARY CONVERTERS AND MOTOR GENERATORS, 486 ALTERNATING CURRENT STATIC TRANSFORMERS, 500) TRANSFORMER CONNECTIONS, 515 + CONTENTS. SECTION V.-THE POWER STATION. (Continued.) SWITCHBOARDS. GENERAL, 527 MATERIALS OF CONSTRUCTION, 527 EXTRA-HIGH TENSION BOARDS, 529 HIGH-TENSION BOARDS, 544 REVERSIBLE BOOSTERS, 552 BOARD OF TRADE REGULATIONS FOR TRAMWAY CIRCUITS AND TESTS, 559 ACCUMULATOR SWITCHBOARD, 562 SYNCHRONISING ALTERNATors, 563 PARALLELING CONTINUOUS-CURRENT GENERATORS, 564 STARTING POLYPHASE INDUCTION MOTORS, 565 AUTOMATIC PROTECTIVE DEVICES, 566 CIRCUIT BREAKERS, ETC., 567 SWITCHBOARD INSTRUMENTS, 586 THE MEASUREMENT OF POWER IN CIRCUITS, 519 RHEOSTATS, 613 WIRE TABLES, 614 SECTION VI.-THE POWER STATION. (Continued.) GAS ENGINES. GENERAL, 623 GAS ENGINE DETAILS, 623 GAS PRODUCERS, 654 SCRUBBERS AND WASHERS, 666 GAS AND COAL, 666 SERVICE PIPES, 669 GAS HOLDERS, 670 SECTION SECTION CONSUMPTIOn and Cost, 671 COMPARISON BETWEEN STEAM- AND GAS-DRIVEN PLANTS, 678 THE DIESEL OIL ENGINE, 681 VII.-THE POWER STATION. (Concluded.) BUILDINGS AND MISCELLANEOUS. BUILDINGS: GENERAL, 685 LIMES, MORTAR AND CEMENTS, 689 CONCRETE, 692 BRICKWORK, 693 STONE-MASONRY, 695 PLASTER, 696 ROOFS, 697 COLUMNS, POSTS AND FLOORS, 703 PAINTS, 704 SECTION VIII.-STORAGE BATTERIES. LEAD CELLS, 707 BATTERIES, 714 PORTABLE CELLS, 719 NON-LEAD CELLS, 720 SULPHURIC ACID TABLES, 722 Caustic Potash and Caustic Soda TablES, 723 XI SECTION IX.-SURFACE AND CONDUIT SYSTEMS. SURFACE CONTACT SYSTEMS, 727 OPEN CONDUITs, 738 ******* 2 XII CONTENTS. ï I SECTION X.—GENERAL TRACTION DATA; ROLLING STOCK AND MOTORS. GENERAL TRACTION DATA, 759 ELECTRIC LOCOMOTIVES, 776 CONDUCTOR Rails, 783 HEAVY ELECTRIC TRACTION, 786 THREE-PHASe Railways, 794 CARS AND CAR-BODIES, 803 TRUCKS, 814 AXLES AND WHEELS, 832 TROLLEYS, 838 CAR WIRING, 848 CAR LIGHTING, 850 HEATING, 850 CONTROLLING, 853 MOTORS, 868 BRAKES, 896 MISCELLANEOUS DETAILS, 909 SECTION XI.—EFFICIENCY, MAINTENANCE, DEPRE- CIATION, AND COST OF POWER. EFFICIENCY, MAINTENANCE, ETC., 913 SECTION XII.-TRANSMISSION OF POWER. TRANSMISSION OF POWER, 937 SECTION XIII.-ALTERNATING CURRENT TRACTION. GENERAL, 959 SINGLE-PHASE MOTORS, 960 APPENDIX. CONVERSION TABLES FOR WEIGHTS AND MEASURES, 995 TRIGONOMETRICAL FORMULÆ, 1003 SOLUTION OF PLANE TRIANGLES, 1003 DIFFERENTIALS AND INTEGRALS, 1004 MENSURATION, 1005 ELECTRIC TRAMWAY AND MOTOR OMNIBUS COMPARED, 1008 RESISTANCE AND LOSSES IN RETURN-CIRCUIT WITH ALTERNATING CURRENTS, 1013 1 BIBLIOGRAPHY. SECTION 1.-THE LINE. MATERIALS AND CONSTRUCTION; RETURN CIRCUIT AND BONDING; OVERHEAD DISTRIBUTION; FEEDERS. Bau und Betrieb Elektrischer Bahnen. Max Schiemann. (Oskar Leiner, Leipzig, 1900). Die Kleinbahnen. A. Haarmann. (Siemenroth and Troschel, Berlin, 1896.) Economic Theory of the Location of Railways. Arthur M. Wellington. (John Wiley and Sons, New York, 1896.) Eisenbahn Technic der Gegenwart. (Kreidel, Wiesbaden, 1899.) Blum, Barkhausen, and Von Borries. (Whittaker and Company, London, 1892.) (Longmans and Company.) Electric Light Cables. Stuart Russell. Light Railway Construction. Parkinson. Light Railways. McKay. (Crosby Lockwood and Company, London.) Light Railways at Home and Abroad. W. H. Cole. (Charles Griffin and Company, London, 1899.) Louis Bell. (The Street Railway (Crosby Lockwood and Company, (Engineering News Street Railway Road Bed. Pratt and Alden. (Street Railway Publishing Com- pany, New York, 1897.) Power Distribution for Electric Railroads. Publishing Company, New York.) Principle and Practice of Levelling. Simms. London.) Railway Track and Track Work. E. E. Russel Tratman. Publishing Company, New York, 1897.) Austin. Steward. (Summerson and Sons, Darlington, 1895.) Tramways. D. K. Clark. (Crosby Lockwood and Company, London.) Tramways, Their Construction and Working. D. K. Clark. (Crosby Lockwood and Company.) The Light Railways Act. The Light Railways Act. The Platelayer's Guide. (Reeves and Turner, London.) (Eyre and Spottiswoode, London.) SECTION II.-THE POWER STATION. STEAM ENGINES; STEAM TURBINES. Alloys, Brasses, and Bronzes. Thurston. (John Wiley and Sons, New York.) American Foundry Practice. T. D. West. (John Wiley and Sons, New York.) Constructive Steam Engineering. Whitham. (John Wiley and Sons, New York.) Engine Tests. Barrus. (D. Van Nostrand and Company, New York.) Engineering Laboratory Practice. Smart. (John Wiley and Sons, New York.) Evaporating, Condensing, and Cooling Apparatus. Hausbrand. (Scott, Greenwood and Company.) High-Speed Steam Engines. Norris and Morgan. (P. S. King and Son.) Handbook of the Steam Engine. Haeder and Powles. (Crosby Lockwood and Company, 1896.) Indicator Diagrams and Engine and Boiler Tests. Charles Day. (The Technical Publishing Company, Manchester, 1897.) Indicator Practice and Steam Engine Economy. Hemenway. (Chapman and Hall, London, 1898.) Machine Design. Forrest R. Jones. (John Wiley and Sons, New York.) XIV BIBLIOGRAPHY. • ! Manual of Marine Engineering. A. E. Seaton. (Charles Griffin and Company, London, 1896.) Manual of the Steam Engine. R. H. Thurston. (John Wiley and Sons, New York, 1898.) Steam Engine Design. Whitham. (John Wiley and Sons, New York, 1898.) Steam Engine Theory and Practice. Ripper. (Longmans and Company.) Steam-Power Plants. H. C. Meyer. (McGraw Publishing Company, New York.) Text-Book on Steam and Steam Engines. Andrew Jamieson. (Charles Griffin and Company, London.) Text-Book on the Steam Engine. T. M. Goodeve. (Crosby Lockwood and Com- pany, London.) The Development and Transmission of Power. W. C. Unwin. (Longmans, Green and Company, London, 1894.) The Elements of Machine Design. W. C. Unwin. (Longmans, Green and Com- pany, London, 1897.) The Practical Engineer's Handbook. W. S. Hutton. (Crosby Lockwood and Com- pany, London.) Thermo-Dynamics of the Steam Engine. Peabody. (John Wiley and Sons, New York, 1898.) The Steam Engine. D. K. Clark. (Blackie and Sons, London.) The Steam Engine. George Holmes. (Longmans, Green and Company, 1897.) Valve Gears. Spangler. (John Wiley and Sons, New York.) SECTION III.-THE POWER STATION. STEAM BOILERS. Boilers, Marine and Land. Traill. (Charles Griffin and Company, London.) Chemical Analysis of Iron. Blair. (Lippincott and Company, Indianapolis.) Chimney Design. Christie. (D. Van Nostrand.) Engineering Contracts and Specifications. J. B. Johrson. (Engineering News Publishing Company, New York, 1898.) (Charles Griffin and Company, Heat Efficiency of Steam Boilers. Bryan Donkin. London.) Iron and Steel. Thurston. (John Wiley and Sons, New York.) Manual of the Steam Boiler. R. H. Thurston. (John Wiley and Sons, New York.) Mechanical Draft. Sturtevant. (The Sturtevant Engineering Company, Boston, 1898.) Non-Metallic Materials. R. H. Thurston. (John Wiley and Sons, New York.) Steam Boiler Construction. W. Hutton. (Crosby Lockwood and Company, London.) Steam Boilers. Munroe. (Charles Griffin and Company, London.) SECTION IV.-THE POWER STATION. ELECTRIC GENERATORS. Alternating Current Phenomena. Steinmetz. (The W. J. Johnston Company, New York, 1898.) Alternating Current Wiring and Distribution. W. Le Roy Emmet. ("Electrical Engineer," New York.) Alternating Currents. Bedell and Gehre. (The W. J. Johnston Company, New York, 1895.) Alternating Currents of Electricity. Blakesley. (Whittaker and Company, London.) Alternating Currents. Rhodes. Alternating Electric Currents. Company, New York, 1899.) (Longmans and Company.) Houston and Kennelly. (The W. J. Johnston BIBLIOGRAPHY. XV Continuous Current Dynamos. J. Fisher-Hinnen. (Biggs and Company, London, 1899.) Die Versorgung Von Städten. Uppenborn. (Julius Springer, Berlin.) Dynamo Electric Machinery; Alternating-Current Machinery, Vol. II. Silvanus P. Thompson. Dynamo Electric Machinery. Silvanus Thompson. (E. and F. N. Spon, London, 1898.) Dynamo Electric Machines. Wiener. (The W. J. Johnson Company, New York, 1898.) Dynamo Machinery. J. Hopkinson. (Whittaker and Company, London, 1893.) Dynamos, Alternators, and Transformers. Gisbert Kapp. (Biggs and Company, London, 1893.) Electric Light Cables. Stuart Russell. (Whittaker and Company, London, 1892.) Electric Light Installations. Sir D. Salomons. (Whittaker and Company, London.) Electric Street Railways. Houston and Kennelly. (The W. J. Johnston Company, New York, 1896.) Magnetism. 1896.) Electric Wiring. Perren Maycock. (Whittaker and Company, London.) Electrical Engineering. Slingo and Brooker. (Longmans and Company, London.) Electrical Engineering Leaflets. Houston and Kennelly. (Electrical Engineer, New York, 1897.) Electricity. Sprague. (E. and F. N. Spon, London.) Electricity and Magnetism. Gerard. (W. J. Johnston Company, New York.) Electricity and Magnetism. Houston and Kennelly. (The W. J. Johnston Com- pany, New York.) Electrolyse. Fontaine. (Baudry et Compagnie, Paris.) Houston and Kennelly. (The W. J. Johnston Company, New York, Polyphase Electric Currents. Silvanus P. Thompson. (E. and F. N. Spon, London, 1895.) Practical Electricity. Ayrton. (Cassell and Company, Limited, London.) Standard Polyphase Apparatus and Systems. Oudin. (Sampson, Low, Marston and Company.) The Dynamo. C. C. Hawkins. (Whittaker and Company, London.) The Practical Management of Dynamos and Motors. Crocker and Wheeler. (E. and F. N. Spon, London, 1896.) SECTION V. THE POWER STATION. SWITCHBOARDS. Direct-Reading Measuring Instruments for Switchboard Use. Kenelm Edgcumbe and Franklin Punga. (Minutes Inst. E.E., 1904.) Electricity Control. Leonard Andrews. (Charles Griffin and Company, Limited, London.) Measurement of Power in Alternating-Current Circuits. Patrick Hamilton. (Proc. Inst. C. E., Vol. LIV., 1903.) Modern Switchboards. A. Herrick. (The Cutter Electrical Manufacturing Com- pany, Philadelphia, 1898.) SECTION VI.-THE POWER STATION. GAS ENGINES. Gas and Oil Engines. D. Clerk. (John Wiley and Sons, New York.) Gas and Petroleum Engines. Elliot. (Whittaker and Company, London.) Gas and Petroleum Engines. Robinson. (E. and F. N. Spon.) Gas, Oil, and Air Engines. Bryan Donkin. (Griffin and Company.) Modern Gas and Oil Engines. Grover. chester.) (Technical Publishing Company, Man- XVI BIBLIOGRAPHY. SECTION VII.-THE POWER STATION. BUILDINGS AND MISCELLANEOUS. Architectural Iron and Steel. Birkmire. (John Wiley and Sons, New York.) Architectural Surveyor's Handbook. J. Hurst. (E. and F. N. Spon, London, 1898.) Building Construction. (Longmans and Company.) Practical Treatise on Foundations. Patton. (John Wiley and Sons, New York.) SECTION VIII.-STORAGE BATTERIES. Automobile Tests at Paris. Bainville. ("Electricien,” 1899.) Batteries with Reversible Boosters. C. Turnbull. (Journ. Inst. E.E., 1904.) Bildung von Bleisuperoxyd. Fr. Peters, Rokotnitz. (Centralbl. Accum. from 1901.) Bleischwammplatten. M. V. Schoop. (Centralbl. Accum. from 1902.) Calculation of Line Batteries. W. E. Winship. (Amer. Inst. E.E. Trans., 1904.) 'Chemistry of Secondary Batteries. J. H. Gladstone and A. Tribe. (London, 1884.) Congrés d'Automobiles, Paris, 1903. Lavezzari and Rosset. (Indust. Electr., 1903.) Détermination de la Capacité Massique Maxima d'un Accumulateur au Plomb. Loppé. (Ind. Electr., 1904.) Die Accumulatoren. C. Heim. (Berlin, 1889.) Die Accumulatoren für Elektricität. Hoppe. (Berlin, 1892.) Die Akkumulatoren für Elektricität. Edmund Hoppe. (Julius Springer, Berlin.) Die Sekundär-Elemente. Paul Schoop. (Wilhelm Knapp, Halle a S.) Floating and Booster-Controlled Batteries. L. Lyndon. (Amer. Inst. E. E. Trans., 1903.) Handbuch der Accumulatoren. P. Schoop. (Stuttgart, 1898.) Masseplatten und Bindemittel für Accumulatoren. from 1903.) Point of Cut-off in Battery Discharge. C. Hering. (Amer. Inst. E.E. Trans., 1902.) Recherches sur l'Electricité. G. Planté. (Paris, 1879.) 'Secondary Batteries. E. J. Wade. (London, 1902.) Storage Battery Engineering. Lamar Lyndon. (New York, 1903.) Storage Batteries and Electric Tramways. G. A. Grindle. (Journ. Inst. E.E., 1901.) Storage Batteries and Reversible Boosters. J. S. Highfield. (Journ. Inst. E.E., 1901). Leimer. (Centralbl. Accum. Storage of Electrical Energy. (London, 1887.) Storage Batteries in Sub-stations. Goldsborough and Fansler. (Amer. Inst. E.E. Trans., 1903.) The Edison Accumulator. Hibbert (also Fleming, Joly). Journ. Inst. E.E., 1903. Hospitalier, Ind. Electr., 1903. Janet, Eclair. Electr., 1903. H. E. Kennelly and S. E. Whiting (American Electrochem. Soc. Trans., Vol. VI.) M. de Kay Thompson and H. K. Richardson (American Electrochem. Soc. Trans., Vol. VII.) The Jungner-Edison Electrodes. J. Zedner. Zeitschr. für Elektrochem. 1905. Elbs and Gräfenberg. The Storage Battery. A. Treadwell. (New York, 1900.) Theorie Chimique des Accumulateurs. nationale des Electriciens. 1892.) Theorie der Stromerzeugung. Elbs, Le Blanc, Liebenow. (Zeitschrift für Electro- chemie, 1896, 1897.) Theorie des Bleiaccumulators. Fr. Dolezalek. (Halle, 1901.) Darrieus. (Bulletin de la Société Inter- BIBLIOGRAPHY. XVII SECTION X.-GENERAL X.-GENERAL TRACTION DATA. MOTORS. ROLLING STOCK AND Bau und Betrieb Elektrischer Bahnen Max Schiemann. (Oskar Leiner, Leipzig, 1900.) Car Builders' Dictionary. Wait. (Railway Gazette.) Car Lubrication. Hall. (John Wiley and Sons, New York, 1895.) Electric Heating. Houston and Kennelly. (The W. J. Johnston Company, New York, 1895.) Electric Incandescent Lighting. Houston and Kennelly. (The W. J. Johnston Company, New York, 1896.) Electric Motors. Urquhart. (Emmott and Company, London.) Electric Railway Motors. Perry. Motive Power and Gearing. Company, London, 1896.) Motors. Crocker and Wheeler. (E. and F. N. Spon, London, 1896.) Regelung der Motoren Elektrischer Bahnen. Rasch. (R. Oldenburg, Munich, 1900.) The Electric Motor and its Applications. M. J. Wetzler. (The W. J. Johnston Company, New York, 1895.) The Motor Engineer's Handbook. (William Lintern, West Park, Ohio.) Electric Railway Economics. York, 1903.) (The W. J. Johnston Company, New York.) E. Tremlett Carter. (The Electrician Publishing SECTION XI.—EFFICIENCY, MAINTENANCE, ETC. EFFICIENCY, MAINTENANCE, AND COST OF POWER. Central Station Book-keeping. Foster. (The W. J. Johnston Corapany, New York.) Directory of Electric Lighting and Traction. C. Vesey-Brown. (Hazell, Watson and Viney, London.) Engineering Estimates and Costs Accounts. Burton. (The Technical Publishing Company, Manchester.) Street Railway Investments. Higgins. (Street Railway Publishing Company, New York.) The Manual of Electrical Undertakings. Garcke. (King and Son, London.) The Works Manager's Handbook. pany, London.) W. S. Hutton. (Crosby Lockwood and Com- Gotshall. Electric Railway Engineering. Trevert. Massachusetts.) GENERAL ELECTRIC TRACTION. Central Electrical Stations. Wordingham. (Griffin and Company.) Central Station Electricity Supply. Gay and Yeamen. (Whittaker and Company.) Electrical Installations. Rankin-Kennedy. (Caxton Publishing Company.) Electric Power Transmission. Crosby and Bell. (The W. J. Johnston Company, New York, 1893.) (McGraw Publishing Company, Ne (Bubier Publishing Company, Lynn 1 Electric Traction. Reckenzaun. (Biggs and Company, London.) Electric Traction. (W. J. Johnston Company, New York. Electric Railways. C. Hering. Electric Railways. J. D. Keiley. (A. Constable and Company, Limited, 1905.) Electric Railways and Tramways. P. Dawson. (Engineering, 35 and 36, Bedford Street, Strand, London, W.Ü.) Robert H. Smith. (Harper Brothers, London and New York, 1905.) High-Tension Power Transmission. (McGraw Publishing Company, New York 1905.) b A XVIII BIBLIOGRAPHY. La Traction Electrique. Paul Dupuy. (H. Bécus, Paris.) La Traction Electrique sur Voies Ferrées. André Blondel and Paul Dubois. (Baudry and Company, Paris, 1898.) Power Distribution for Electric Railroads. Louis Bell. (The Street Railway Publishing Company, New York, 1897.) Production et Distribution de l'Energie pour la Traction Electrique. Martin. (Béranger, Paris.) Recent Progress in Electric Railways. Hering. (The W. J. Johnston Company, New York.) Refuse Disposal and Power Production. W. F. Goodich. (A. Constable and Company, Limited, 1904.) Report of the Royal Commission on London Traffic. (Wyman and Son, 109, Fetter Lane, E. C., 8 vols., 1906.) (The W. J. Tables and Formula for Electric Street Railway Engineers. Merrill. Johnston Company, New York, 1898). The Electric Railway. Crosby and Bell. (W. J. Johnston Company, New York.) The Electric Railway. Luce. (Harris and Company, New York.) - The Electric Transmission of Energy. Abbott. (Van Nostrand, New York, 1898.) The New York Electrical Handbook; and The Boston Electrical Handbook. (McGraw Publishing Company, 1904.) Traité Pratique de Traction Electrique. Barbillon et Griffisch. (Bernard et Cie., Paris.) Traité d'Electro-Traction. Ernest Gerrard. (P. Weissenbruch, Brussels, 1897.) POCKET BOOKS, &c. Clark. The Mechanical Engineer's Pocket-Book. (Crosby Lockwood and Com- pany, London.) Formulaire Pratique de l'Electricien. E. Hospitalier. (G. Masson, 120, Boulevard St. Germain, Paris.) Foster's Electrical Engineer's Pocket-Book. (E. and F. N. Spon, London.) Fowler's Mechanical Engineer's Pocket-Book. (Scientific Publishing Company, Manchester.) Gas Engine Handbook. Roberts. (Gas Engine Publishing Company.) Herrick. Practical Electric Railway Handbook. (Street Railway Publishing Company.) Hurst. Architectural and Surveyors Handbook. (E. and F. N. Spon, London.) Hutte. Ingenieurs Taschenbuch. (Ernst and Rorn, Berlin.) Kallender für Elektrotechniker. (Uppenborn, 24, Monbijouplatz, Berlin, N.) Low's Pocket-Book for Mechanical Engineers. (Longmans, Green and Company) London.) Matheson Aid-Book. (E. and F. N. Spon, London.) Mechanical Engineer's Pocket Book. W. Kent, 1898. (John Wiley and Sons, New York; Chapman and Hall, London.) Mechanical World. Pocket Diary and Year-Book. (Emmott and Company, Man- chester.) Molesworth. Pocket-Book of Engineering Formulæ. (E. and F. N. Spon, London.) Munro and Jamieson. Electric Rules and Tables. (Charles Griffin and Company, London.) Notes et Formules de l'Ingénieur du Constructeur Mécanicien. (Bernard et Compagnie, Paris.) Pocket Companion. Carnegie Steel Company. Practical Engineer's Pocket-Book. (Manchester.) Rules and Tables. Rankine. (Charles Griffin and Company, London.) Wrought Iron and Steel Construction. Pencoyd Ironworks. (Philadelphia.) BIBLIOGRAPHY. XIX LIST OF JOURNALS AND REPORTS. Monthly. American Electrician, 120, Liberty Street, New York. Annales de l'Association des Ingénieurs de Gand, Boulevard Frère-Orban, 6, à Gand. Monthly. Bibliographie des Sciences et de l'Industrie, Paris; Quai des Grands-Augustins, 49, Bulletin de l'Association des Ingénieurs Electriciens Montefiore, Quai des Grands- Augustins, 55, Paris. Monthly. (P. S. King and Son, Bulletin of the International Railways Congress, London. Parliamentary and General Booksellers, 2 and 4, Great, Smith Street, S. W.) Electrician, 1 to 3, Salisbury Court, London, E.C. Weekly. Electrical Engineer, 139, 140, Salisbury Court, London, E.C. Weekly. Electrical Review, 4, Ludgate Hill, London, E.C. Weekly. Electrical Times, 8, Bream's Buildings, Chancery Lane, London, E.C. Weekly. Electrical World and Engineer, 120, Liberty Street, New York. Weekly. Electrotechnische Zeitschrift, Berlin, N., 24, Monbijouplatz, 3. Weekly. Elektrische Bahnen u. Betriebe. R. Oldenbourg, Munich. Engineering, 35 and 36, Bedford Street, Strand, London, W.C. Weekly. Journal of the American Society of Civil Engineers, 127, East Twenty-Third Street, New York. Journal of the American Society of Electrical Engineers, 26, Cortlandt Street, New York City. Journal of the American Society of Mechanical Engineers, 12, W. Thirty-First Street, New York City. Journal of the Institution of Civil Engineers, Great George Street, Westmin- ster, London, S.W, Journal of the Institution of Electrical Engineers, 28, Victoria Street, Westminster, London, S.W. Journal of the Institution of Mechanical Engineers, Storey's Gate, Westminster, London, S.W. Journal of the Iron and Steel Institute. E. and F. N. Spon, London. Manual of the Railroads of the United States. H. V. Poor, New York. Memoires de la Societé des Ingénieurs Civils de France, Rue Blanche 19, Paris. Mittheilungen des Vereines für die Forderung des Local und Strassenbahnwesens, Wien, Elisabethstrasse 2. Monthly. New York Railroad Commissioners' Report, Albany, New York. Yearly. Railroad and Tramway Commissioners' of Massachusetts Report, Boston. Yearly. Railway and Tramway World, Amberley House, Norfolk Street, Strand, W.C. Monthly. Report of the American Railway Mechanical and Electrical Association, Philadel- phia, 1905. Street Railway Journal, 120, Liberty Street, New York, U.S.A. Monthly. Street Railway Review, 324, Dearborn Street, Chicago. Monthly. The Engineer, 33, Norfolk Street, Strand, London, W.C. Weekly. The Manual of Electrical Undertakings. Garcke. Street, London. Zeitschrift des Vereines Deutscher Ingenieure, Berlin, N. W.; Charlottenstrasse, 43, Weekly. Donington House, Norfolk 4 SECTION I. THE LINE PART I MATERIALS AND CONSTRUCTION PART II RETURN CIRCUIT AND BONDING PART III OVERHEAD DISTRIBUTION PART IV FEEDERS B SECTION I. THE LINE. PART I.-MATERIALS AND CONSTRUCTION. GENERAL. The track, and methods adopted in laying, is the groundwork on which the ultimate success or failure of a railway or tramway depends. The essential difference between a railway and a tramway, as generally understood, is that the railway runs on its own ground, and the track can be built to suit the conditions of running exclusively; while a tramway usually follows a public road, and the track must be constructed so as not to obstruct the vehicular traffic. There are an infinite number of sections and types of rails employed, some exclusively for either railways or tramways, others for both. Railway Track in England. (FIGS. 1 to 12, pages 4 and 5.) Railway track in England is always composed of bull-headed rails supported on cast-iron chairs spiked on cross wooden sleepers. Fig. 1 is a cross-section of the rail used on the Great Northern Railway; Fig. 2 is a cross-section of the rail used by the Midland Railway Company; and Fig. 3 that adopted by the London and South-Western Railway. Figs. 4 to 6 show a fishplate and joint such as is generally used on English Railways. The following is an abstract from the specification of rails for the Great Northern Railway Company: Each rail shall be made from a single ingot, which shall be perfectly solid and regular in quality, and free from defects of every kind. The rails must be sawn off perfectly square to the requisite length, and the ingots in all cases must be of ample length to ensure a long crop being cut off, clear of the least appearance of scallops at both ends of the rails; and should any imperfection in the quality, or unsoundness arising from gas cells, cold shuts or otherwise, be apparent either in the ingots or during their subsequent treatment, such ingots or rails will be rejected and set aside as not being admissible under this contract. The rails when finished are to be in every respect perfectly sound and homogeneous, free from flaws, blisters, and other defects, and perfectly straight. The rails are to weigh 85 lb. per yard, and none which either exceed or fall short of that weight by more than 1 lb. per yard will be accepted. The rails are to be cut to the exact length of 30 ft. The engineer will, however, receive for the contractor's convenience a few lengths in even yards from 12 ft. upwards, but together not exceeding 5 per cent. of the whole quantity. Each rail is to have at each end of it two holes, measuring 14 in. by 1 in., drilled truly to a template and gauge. No punching to be allowed. Each rail is to be marked "G. N. R.," with the initials of the makers, name of the works where manufactured, and the month and year when supplied. Rails will be taken indiscriminately from each parcel made, as frequently as the engineer may require, and be subjected to the following test, viz. :- A piece of rail 5 ft. long shall be cut off and placed directly on solid iron bearings 3 ft. 6 in. apart in the clear, fixed on a solid cast-iron block well bedded, and shall then receive successive blows from a weight of 1120 lb., falling from a height of 10 ft. Should the rail break before or under the third blow, or should it take a permanent set after the first blow exceeding 13 in., the whole of the parcel from which it has been selected will be rejected. On the Midland Railway the rail weighs 85 lb. per yard, and tests required are: (a) Weight of 1 ton dropped from a height of 12 ft., on rail placed on bearings 3 ft. 6 in. apart. Rail must bear two such blows without breaking, and without deflecting more than 3 in. (b) Rails placed on bearings 3 ft. 6 in. apart must not deflect more than 1 in. under the weight of 20 tons in the centre, and the permanent set must not exceed in SECTION I.-THE LINE. 5 6 J. (57) <1/16 * GREAT NORTHERN -8/4----- (58) Fig. 2. Fig. 3. - - - - Nor LTYIS- 1 10 4 cpm to ·2% ·· 1. TA ĐỀN ĐÔ Đ L NOLANO RADIUBS ŽINCHES RY 2. 3/1. -2% x+.. 42 20 4/2 [10/16 dia™ ·4% · O CONTINUIN O ………… STAT V MAOTUS 54 INGHE 2 - □ ****** 2% + Fig. 4. Fig. 5. Standard Fishplate. Fig. 6. Standard Fishplate. 18". 4/1/2... CHES. …………………a à à van……… 25 O ·18.mmm.... 4/2 Of t NE 4 cm • à la tra dia…………….. *****NOSA 41/2 LONDON & SOUTH WESTERN 42 Standard Rail Sections. 3 • Fig. 1. Standard Rail Section, Great Northern Railway. Standard Rail Section, Midland Railway. Ce putem on a à de 2% 3 24. 2 Para a Standard Rail Section, London and South-Western Railway. Standard Rail Joint. MATERIALS AND CONSTRUCTION. 5 9 10 (60) 8 (59.) 4%". 7 ·6.” / storm ano de la va a ½ 14" 14" 18 " ·1%/%" ----- gadg K-31 U Inchination haz Fig. 11. Oak Key, Midland Railway. Fig. 12. Oak Key, London and North-Western Railway. 11 12 Rail Fastenings. Figs. 7 and 8. Standard Chair, London and South-Western Railway. Figs. 9 and 10. Oak Trenail and Iron Fishbolt, London and South-Western Railway. 6 SECTION I.-THE LINE. On the London and South-Western Railway the rails weigh 87 lb. per yard. Test as follows:-Each length of rail being set on bearings 3 ft. apart, and a 1-ton weight allowed to fall upon the centre between the bearings from a height of 20 ft. The rails must not show a permanent set of less than 1 in., or more than 17 in. The 82-lb. rails must not show a set less than 1 in., or more than 2 in. Figs. 7 and 8 show the chairs used by the London and South-Western Railway Company: they weigh 46 lb. each. 三 ​Their shape must be such that the tilt and inclination of the rail when it is keyed up is 1 in 20 from the perpendicular, the chairs standing level. 13 ·4 '8'-* Cant fin.20 15 ! 14 ---- 8′3 SECTION OF SLEEPER % FULL SIZE 4:8. do con de ce que v ------ --8:9~~~. 8× tro 8/3/2 SECTION AT CENTRE Figs. 13 to 15. Steel Sleepers. Co 眼 ​The chairs used for the most recent arrangement of the main-line permanent way on the Great Western Railway weigh 46 lb. each. The chairs in use on the Midland Railway weigh 50 lb. Length, 15 in.; width, 7 in. in centre. They are required to bear without fracture a weight of 17 tons, when placed at the centre of bearings 12 in. apart. Chairs are held in place by iron and oak spikes and trenails. Fig. 9 shows a trenail in use on the London and South-Western Railway. The wood, which is cleft and not sawn, is first turned down to a size in. larger than required; then the taper hole is bored to the diameter shown in the figure; finally, the whole is compressed to the required outside dimensions. 1 MATERIALS AND CONSTRUCTION. 7 The rails are connected by fishplates, held in place by bolts. Fig. 10 shows the fish-bolt in use on the London and South-Western Railway; and Fig. 4, the ends of the rails and the drilling of them. The rails are kept in position by oak keys, driven on the inside or the outside of the rails. The forms of oak keys used on the Midland, and London and North-Western Railways, are shown by Figs. 11 and 12, and in both cases the keys are 7 in. long, of best English oak. The keys are cut in. larger than required, and then com- pressed by machinery to the required size. 16. (728.) MACĀDĀM; K 1 4×5" GRANITE SETS 17. 1:0 (730) Y (729) 18 --1, 6--- OFS RAIL 100 LBS. PER YARD. FISHPLATES 56 LBS PER PAIR. 4-87 GRANITE SETT PÁVING 6 DEEP3WIDE. | CEMENT PARGING FINE" CONCRETE BEDDING. PORTLAND CEMENT: CONCRETE 6 TO I STANDARD CONSTRUCTION FOR MAIN ROADS.(GRANITE SETTS.) CONCRET PO TE BAR! 4.8% GAUGE __973×4″WOOD BLOCKS TO CEMENT CO 9X3X4" WOOD BLOCKS app and Maple della 6:9% --3' 6----- GRANITE SETTS. DA 8:0° C.L. TO CL. OF TRACKS K-6*~ لا →2H--- 1:5¾"→→→ CEMENT PARGING OR FILLETING, Op ↳ INTERSPACE 3:312- CONCRE BETW, GAUGE LIKES ------1: 6 K-.6· Figs. 16 to 18. British Tramway Track. As regards the space between sleepers, this in the case of the Midland Railway is 1 ft. 1 in. from end of rail to centre of first sleeper; other spacing is graduated so that 11 sleepers are put down with each 30-ft. rail. The depth of the ballast should be 2 ft. below the top of the rails - that is, 1 ft. 6 in. in thickness above the formation level. The ballast is usually laid in a double thickness, the upper layer consisting of stones not exceeding 3 cubic inches in bulk, and averaging about 2 cubic inches. The lower layer may be of stones varying in size from 3 to 30 cubic inches in bulk. The width of the top ballast beyond the cross-sleepers should be about 18 in.. the total width in the case of a single line of rails being 12 ft. ; in the case of a double line, 23 ft. ; in the case of a triple line, 34 ft. ; and for a quadruple line, 45 ft. Slope of ballast at sides 1 to 1. Figs. 13 to 15 (page 6) show a metallic construction used for railway work by the Ebbw Vale Co. 8 SECTION 1.-THE LINE. 19 F 1 42. 22 -2° " 32.. (2120) 10-76 lbs per yard A 22 2" ----- 21121. 77 lbs. per yḍ 121 tons per Mile 20 -8/2 C 2 " ་ 11 " 11 I " 11 5* tt 52" 127122. 98 lbs. per yard, 154 tons per mile. Standard American Tramway Rails. Figs. 19 and 20. Step Rails. Figs. 21 to 23. Grooved Girder Rails. 23 mc. 21 77/2. M-1/2- 316 21 716 H&R H 62 lbs. per yard #1 276--1 af 3% -~-~~-~196"--- el 1 SNI 11 6" van alle van die oggi T 80 to 90 lbs. per yard. MATERIALS AND CONSTRUCTION. 9 އ Ala 27/2.V. 4%* 4 ~ --1/- + - - - J% 27/2.6. 16 下​!!! 24 P K ·3½"-- 11. 26 5' 7--13% ------ 2" # myile Mili Ri › A G //// 1/1 $2712 M 63 to 10 lbs per yd. 99 to 110 tons per 25 mile IPI ۱۱ American Tramway Rail Sections. Fig 24. Solid Guard Rail. Fig. 25. Centre Bearing Rail Fig 26. (Philadelphia) Step Rail Track Section. B2 10 SECTION 1.-THE LINE. OF $////PAS -2¾ J Fig. 27. Fig. 28. Fig. 29. 27/20 (114) 27 29 28 Cement о O O O O о Sand m m #51441,11 Tramway Track Sections. Track with Brick Paving, Denver Railway. American T Rail Steel Track Construction. Scarfed Joint, as used on Continent. MATERIALS AND CONSTRUCTION. 11 Tramway Track in England. (FIGS. 16 to 18, page 7.) The standard track constructed in England is girder rail directly laid on a concrete foundation. Wood paving, asphalte, or granite setts are used for paving inside and outside the tracks. Figs. 16 and 17 show cross-section of standard construction in main thoroug fares and city roads; and Fig. 18 that for country roads. The rails are laid directly on the concrete, and held to gauge by tie-bars. American Tramway Track. (Figs. 19 to 28, pages 8 to 10.) The rails used in America differ materially from those used in this country. Where grooved rails are used, the grooves are not only much larger than in England, but the outside wall of the groove is inclined about 45 degrees to the perpendicular (see Figs. 21 and 22), thus allowing the dirt which accumulates in the groove to be pushed out by the flange of the wheel, instead of the latter mounting up and riding on it, as is the case with dirty grooves having vertical sides. Fig. 26 shows one of the best typical American constructions (Philadelphia). The rails weigh 90 lb. per yard, are 9 in. high, spiked on steel sole-plates 6 in. by 10 in. by in., on wooden sleepers or ties 3 ft. centres, and held in position by tie-rods 13 in. by § in. at 6 ft. centres. The fishplates are 27 in. long and have 7 inch bolts. In many western cities T or Vignoles rails are used with great success. Fig. 27 is an example of such construction combined with brick paving, as used at Denver. Fig. 28 shows a steel construction for T rails, as used in America. Tramway Track on the Continent. (FIG. 29, page 10, and FIGS. 30 to 31, below.) On the Continent concrete foundations are not usually employed. When they are used (as at Hamburg), the rails are not laid directly on the concrete, but on a (115) 128 5 to 6 m/in -- OAK BLOCKS A. 1300 T SETTS $1!• · ASPHALT 2 CM Fig. 30. Hamburg Tramways. SAND CONCRETE WOL Fig. 31. St. Gallen Tramways. JO layer of asphalte, which makes a more elastic track, Fig. 30, and gives softer and better running. Girder rails are usually laid directly on sand or macadaın. (Fig. 31, track construction at St. Gallen, Switzerland.) Figs. 32 to 34, on page 12, show type of Demerbe rail as used to some extent on the Continent. 12 SECTION I.-THE LINE. ・A 32 SECTION AT JOINT DEMERRE RAIL’GENEVA (187) TH. IA - SECTION AT AND BETWEEN TIE RODS GENEYA Figs. 32 to 34. Type of Demerbe Rail. CYRUSIA PERKO:] British Standard Specification. (FIGS. 35, 36, 38 and 39, pages 13, 14, and 15.) RAIL SECTIONS. 33 34 The narrow-groove type Girder Rail has been adopted in England, the cheek of the rail forming a safe edge to the paving. Up to 1903, many different sections and specifications were devised, each design necessitating costly rolls; the price of rails per ton was exceedingly high. With all these different sizes, the rail-makers found it impossible to stock rails, and in case of a small lot being required for repairs or extensions, the price was liable to be much increased, and the delay great, on account of the rolls having to be picked out, re-turned and refixed in the mills. A committee of experts was formed in 1902, which issued a standard specifi- ⚫ation and sections. Engineers have fallen in with the views of the committee, and these sections have generally been adopted. A choice of five sections is given in order to suit various conditions of traffic. Figs. 35 and 36 show two of these sections, weighing respectively 90 lb. and 116 lb. per yard. Fig. 38 shows sizes of standard wheel, flange and tread, with relation to standard groove. The principal points of the specification are given below:- RAILS AND FISHPLATES. Chemical Composition. Steel to be made by the acid Bessemer or basic Bessemer process. Carbon from 0.40 to 0.55 per cent. Manganese from 0.70 to 1.00 per cent. Silicon not to exceed 0.10 per cent. Phosphorus not to exceed 0.08 per cent. Sulphur not to exceed 0.08 per cent. MATERIALS AND CONSTRUCTION. 13 35 NI -234 K 이거 ​10x1 k------2 लाल 32 K--- 13/------ 2 MINIS 18" R LIN 21 Fig. 35. Fig. 36. alm 91 32 Kids&r--x 459 29 RAIL 90 LBS PER YARD D INNER FISH PLATE OUTER FISH PLATE 2FT LONG 22ŹLBS WEIGHT 2FT LONG 27½LBS WEIGHT (731) 37. K...1 FISH PLATE, 36 ·1%%' 15108 iR K-14: IA + q = my 432 ---- គ IR 3420 12" -Tic-* British Standard Sections. ·---- -- 2 ½ ----- 18 R ** 24" *----13 INNER FISH PLATE 2 FEET LONG.26 LBS.WEIGHT. ·FISH PLATE -0³//--> " “B.S." Section No. 1. 90 lb. Standard Rail. "B.S." Section No. 5c. 116 lb. Standard Rail for Curves. 6 CROSS SECTION OF RAIL FOR CURVES WEIGHT OF CURVE RAIL 92 LBS.PER 1. WEIGHT OF FISH PLS 38 LBS FER YARD 88,7 3 -7---7 -RED- 7 RAIL 116 LBS PER YARD OUTER FISH PLATE 2FT LONG. 30ŹLBS. WEIGHT Fig. 37. Check Rail (Curves). Fig 37 illustrates a type of renewable check rail for sharp curves with heavy traffic. 14 SECTION 1.-THE LINE. General Dimensions of Rail. No. 1 B.S. Section 1c 2 "" ,, 2c >> "" " "" Go Go 4 3 3 c 19 40 5 » 15c 22 "" "" 99 "" "" " "" 99 (792.) 38. LIP. OF RAIL FOR USE ON 14- CURVE IS SHOWN · DOTTED. 99 28 " ·· NOTE. THE PROFILE TO BE USED WITH BS 3 &3C IS HERE SHOWN; WITH REGARD TO THE OTHER SECTIONS. ÅIS THE ONLY DIMENSION WHICH VARIES WITH THE WEIGHT OF RAIL. ·· ·· 33 ·· Fig. 38. Size and Weight of Fishplates. "" •• "" "" Height. in. 6) 7 7 "C" rails for sharp radii curves. For sections, see drawings 1 to 10. 7 7 41 A 3 FOR BS SEC "$ Nº$3 &3! GAUGE LINE OF TYRE. GAUGE LINE OF RAIL- Width of Flange. in. 7 7 "" 99 "" 7 7 7 " 7 7 7 Weight of Inner Fishplate. lb. For rails of No. 1 and No. 1 c Section 224 2 2 c 221 3 3 c 22 4 4 C 26 5 5 с 26 Length of Fishplates 24 in. .. A A- WIDTH OF STANDARD TYRE. FOR BS SECTIONSN??I&Ic A-2}. "" 19 90 lb. per lineal yard. 96 95 101 100 106 105 111 110 116 * GAUGES. WITH TRACK GAUGE 48½ WHEEL GAUGE TO BE 48 H ** • • 4:0 3-6 3-11雀​. 3-5%* Standard Wheel Flange. "" "" 99 "" "" 19 "" "" "" Normal Weight. * · 2»2cm-24 " ་་ »3»3¢ »•3 " · 4n4c » •3£ « 19 ❤ "" "" "" 261 30 30 "" "" "" 59 "" "" Weight of Outer Fishplate. lb. 27 27 Weight Per Pair. Ib. 50 49) 49 561 MATERIALS AND CONSTRUCTION. 15 39. (798.) MIX T 735. kzi* B k2** 2-*- --5 734. 14 k. 41 4.0 J 4 <7 DIA ----5.0 /-- 4 30 :*- 4 RE ADIA Usual Form of Fishplates, Bolts, and Tie-bars. Fig. 39. Holing for Fishes and Bolts. Fig. 40. Fishbolt and Nut. 4-2-2-2--2α 不 ​---X Fig. 41. Tie-bar. 16 SECTION I.-THE LINE. RAIL TESTS. Impact Test for Rails up to 100 lb. per Yard. Sample selected out of 80 rails and a length of 5 ft. cut therefrom. Supported horizontally head uppermost on iron bearings, 3 ft. 6in. centres shall receive a blow from a tup weighing 1 ton, having a fall of 15 ft. The rails to show no signs of fracture. Rails 100 lb. per Yard and Over. Ditto ditto ditto, but with a fall of 18 ft. Tensile Test. From each 100 tons of rails, test piece to be cut and prepared to a sectional area equal approximately to half a square inch and to a length of 2 in. between test gauge points. Ultimate tensile strength to be not less than 40 tons per square inch, with an elongation of not less than 12 per cent. on a length of 2 in. Bending Test. From each 100 tons of rails a rail to be selected and curved to a radius of 30 ft. without showing signs of cracking. Fishbolt Holes. Three round holes in web at each end, 1 in. diameter, the centre of the hole nearest the end to be 2 in. therefrom, the remaining holes to be 4 in. pitch, centre to centre. Vertically the centres to be:- 24 in. from underside of flange for rails 6 in. deep. 3 in. from underside of flange for rails 7 in. deep. Fig. 39 illustrates the holing for fishbolts and bonds. Holes for Electric Bonds, Staggered. For joint bonds, two round holes in the web of the rail at each end, & in. in diameter; the upper hole to be 134 in. distance from end of one rail, and the lower 15 in., and vice versa for the corresponding rail vertically, the centres to be respectively in. above or below the horizontal line of the fishbolt holes. Tie-bar Slots. One oval slot in the web of the rail at each end, 3 in. long by 1 in. high, with half round ends, 2 ft. 6 in. from the end of rail, and at a vertical distance of 24 in. from the underside of flange for 6 in. deep rail. Joint Plate Holes. Six round holes at each end in the flange, in. diameter of the same longi- tudinal pitch as for fishplates, and transversely at 4§ in. centres in flange 64 in. wide, and at 5 in. centres in flange 7 in. wide. Intermediate Plate Holes. Six round holes in flange midway between the ends, in. diameter, 6 in. longitudinal pitch, and transversely at the same centres as for similar holes at the rail ends. All holes to be drilled except tie-bar holes, which may be punched. GENERAL RAIL Data. Fishbolts. One inch steel fishbolts, cup-sq.-sq. with lock-nuts are used for the rail-joints. The lengths required are for Nos. 1 and 2 sections, 4 in.; for Nos. 3 and 4, 44 in., and for No. 5, 4§ in. The tensile test is generally 36 to 40 tons, with an elongation in 10 in. of 18 per cent. Fig. 40 shows the usual type of fishbolt with lock nut. Tie-bars. These are made of the best mild steel, the tensile test being 25 to 30 tons, with an elongation in 8 in. of 20 per cent. They are generally screwed one end for a length of 5 in., and fitted with two nuts and two washers. The other end is notched, the notch being and greater in width than the web of the rail, and being 1 in. from the end. The total length of a tie-bar for 3 ft. 6 in. track is 3 ft. 10 in., and for a 4 ft. 8 in. track, 5 ft. 0 in. The thread is a in. Whitworth. In order to obtain this thread with a welded tie-bar, the section of the metal has to be 24 in. deep and in. in thickness; but in the Bayliss patent it has been made possible to have a lighter tie-bar of 2 in. in depth and in. in thickness, by thickening up the end where the greatest strain is by a rolling process, thus making the tie-bar withouc a weld. This decreased thickness is of course much better for the paving, doing away with an unsightly joint in same. Fig. 41 illustrates the usual type of tie-bar. MATERIALS AND CONSTRUCTION. 17 rails English some years ago English rails pre- sent day American rails German rails (Haarmann) Table 1.-Chemical Composition of Rails. The following Table gives the limits which are generally adopted in various countries for the percentage of foreign elements contained in the steel used for rail manufacture:- Element. Carbon Manganese Silicon Phosphorus Sulphur .. .. ·· • Carbon. per cent. 0.25 to 0.35 0.4 0.55 0.4 0.25 0.35 0.70 "" 0.76 ,, 0.6 "" Table 2.—Effects of Various Elements in Steel. The effects of the various ingredients are tabulated. Some of the elements vary. with the weight of the rail. These elements notably affect the electrical conduc tivity; these effects are considered in the section dealing with the return circuit. Necessary for. Boston Elevated Buffalo Railroad Ductility in rolling and for chemical process in manu- facture Company.. Denver City Tram- way Twin City Rapid Transit United Railroad, San Francisco Manganese. per cent. 0.8 to 1.00 ... 0.7 1.00 ·· Fluidity, and for ma- king metal dense, compact, and of small crystallisa- tion .. ·· ·· ·· "" "" Carbon. per cent. 0.5 to 0.6 0.43 to 0.53 0.46 to 0.56 0.45 to 0.55 0.45 to 0.55 0.1 0.08 0.08 1.00 0.066 to 0.20 0.06 to 0.11 0.047 to 0.07 0.90 0.3 to 0.35 0.08 0.10 0.06 Weight of Rail in Lbs. per Yd. 60 70 89 95 100 Silicon. per cent. 0.05 65 100 ·· :: Phosphorus. per cent. 0.08 0.10 0.1 0.1 0.1 Per Centage. 0.40 to 0.45 0.45 0.50 0.45 0.55 0.50 0.60 0.65 0.70 "" Phosphorus. Sulphur. per cent. 0.06 per cent. 0.06 19 "" 39 0.75 to 1.00 0.066 to 0.15 0.1 0.25 15 0.05 to 0.11 0.05 to 0.07 "" Seamy metal. The chemical composition of the rail, of course, varies according to the different ore used, according to the weight of the rail itself, and principally according to the design and personal judgment of the manufacturer. Table 3.-American Steel Rail Chemical Specification. Name of Road. Silicon. per cent. 0.1 to 0.15 0.20 0.1 0.2 0.2 In Excess Causes. Brittle metal and lia- bility to fracture under severe tem- perature or shock. Great reduction in con ductivity, coarse crystallisation, too. much abrasion, and flow of metal under traffic. Brittleness. Manganese. Sulphur. per cent per cent. 0.8 to 1.0 0.08 0.8 to 1.0 0.8 to 1.0 0.8 to 1.0 1 18 SECTION 1.-THE LINE. UC - 45- Table 4.-Haarmann Standard Rail. Weight per yard of principal rail guard rail Two fishplates, 600 millimetres long Six fishbolts, 19 millimetres X 85 millimetres.. One-end cast iron distance piece (717) "" -51.. Ten cast-iron distance pieces Four tie-bars, 70 millimetres x 10 millimetres.. ·-122· -158- 30 42 "" 45 37- F Fig. 42. Fig. 43. Fig. 44. ·· ·· A (FIGS. 42 to 44.) lb. 64 32 50 5 81 (718) 43 44 :: Haarmann Rail. Haarmann Track at Joint. Haarmann Track between Joints. 46 ·· 30 63 ימן $ Figs. 42 to 44 show types of Haarmann's rail construction, consisting of two rails held together by cast-iron distance pieces and bolts every few feet. Figs. 45 and 46 show the type of joint used by the Weber Railway Joint Co., of New York. It is claimed for this joint that its mechanical strength, combined with the elasticity of the wood, does away with all hammering or extra wear on the ends of the rails. MATERIALS AND CONSTRUCTION. 19 American T Railway Rails. (FIGS. 47 to 50.) The following four sections of rails and fishplates (Figs. 47 to 50) have been recommended for railways as standard by the committee on standard rail sections of the American Society of Civil Engineers. ---12°F~~- 12 Br J BAL 327285 #$240 121. Weight Per Yard in Pounds. 100 95 90 SABIFFUSB 85 80 1710 Figs. 47 to 50. Sections of Railway Rails, recommended by the American Society of Civil Engineers. 75 70 65 47 Table 5.-Weights and Dimensions of American Standard Tee Rail Sections. 60 55 50 45 49 Area in Square Inch. 12 R-. 9.8 9.3 8.8 8.3 7.8 7.4 6.9 6.4 5.9 5.4 4.9 4.4 Width of Base and Height in Inches. *ako make LO LO LO LOLO HERE CD co 52 5,1% 53 51 5 413 48/ 47% 41 311 48 Web in Inches. „KOLORESCEN "Heckomkacako™ coko mko HAKO mkucki, kozmet $9/16-- K----2 50 ~~~~~~~~~~~~ esteticko H==‰¤ H=40000/00=#=800) Width of Head in Inches. 211 2§ 2% 2 --12 2 -122 : Loka, kochies * 20 SECTION 1.-THE LINE. SIMPLE FORMULAE FOR RAILS. Tons of rail per mile of single track=approximately y the weight of rail ir pounds per yard. Sectional area in square inches of rail=approximately the weight of rail in pounds per yard. Average size of wooden sleepers or ties for 4 ft. 8 in. (standard gauge) 90 in. by 9 in. by 7 in. Ordinary quantity of spikes per mile of single track 54 in. by fin. =5,500 lbs. Maximum safe weight per wheel for rails properly supported on sleepers or ties one ton per each ten pounds of weight per yard. Table 6.-Weight per Mile, Steel Rails. Weight per Yard. "" "" lb. 40 45 50 AAZOJUJURSE "" ** 56 60 62 65 B. S. No. 1 "" 59 "" 99 Section of Rail. Weight per Yard. "" Table 7.-Cross Ties or Sleepers, Per Mile. Centre to Centre. Centre to Centre. 18 in. 27 in. 30 21 24 36 "" "" "" Sleepers. 3520 3017 Sleepers. 2348 2113 2640 "" "" 1760 Table 8.-Weight of Metal Work per Mile of Single Track. B. S. RAILS. B. S. No. 1 33 Section of Rail. 59 "" "" 1234H LO "" "", 5 1234 LO 5 ·· • • • ·· ·· Weight per Mile. • tons. lb. 62 1920 70 1600 78 1280 81 1600 88 000 89 1280 94 640 97 960 100 1280 102 320 ·· • lbs. 50 491 49 Weight per pair. 564 561 lb. 90 95 100 105 110 Weight per Yard. CORONINORF 80 186 186 186 186 186 90 100 No. of Pairs per Mile. Weight per Mile. tons. 141.43 149.29 157.14 165.00 172.86 B. S. FISHPLATES. 60-Ft. Rails. Weight. Weight per Mile. tons. 4.15 4.11 4.07 4.67 4.67 tons. 105 106 ·· 110 114 117 125 133 141 157 •• lb. 640 1920 000 1600 1920 1600 1280 No. of Pairs per Mile. 244 244 244 244 960 320 Yards of Track per Ton. 45-Ft. Rails. 12.44 11.79 11.20 10.67 10.18 Weight. tons. 5.45 5.39 5.34 6.15 6.15 NOTE.-10 joints extra allowed for per mile, to allow for short lengths, points and crossings, and special work. MATERIALS AND CONSTRUCTION. 21 I "" B. S. No. 1 *** "" "" " "" "" Gauge of Track. STEEL BOLTS, LOCKNUTS AND WASHER, 1 in. in Diameter. Cup.-sq.-sq. Weight per Set of Six. 60-Ft. Rails Weight Per Mile. 45-Ft. Rails. Weight Per Mile. Section of Rail 1 metre 3 ft. 6 in. 4 ft. 0 in. 4 ft. 8 in. : B. S. No. 1 "" Section of Rail. "" "" "" 39 "" در 123SCH LO STEEL TIE-BARS; screwed one end 3 in.; notched the other 7 ft. 6 in. apart. "" 4 5 B. S. No. 1 : Section of Rail. "" "" "" 1234H LO · 1234H LO 5 9 9 10 12 2 In. by In. Lb. each. • ·· ·· ·· ·· Tons per Mile. 2.83 2.98 3.03 3.77 60 63.3 66.6 70 73.3 Weight of Each in Pounds. 45 47 50 521 55 Length. Weight of Each in Pounds. in. 400000 2 In. by In. Lb. each, Tons per Mile. 10 11 12 14 No. lb. 14.4 14.4 15.0 15.0 15.3 NOTE.-If screwed both ends, add ½ lb. to each bar. ANCHOR JOINTS, 24 in. long. (Cooper and Howard Smith's.) 186 186 186 186 186 No. 3.3 3.46 3.77 4.4 186 186 186 186 186 60-Ft. Rail. Tons per Mile. 4.98 5.25 5.53 5.81 6.09 Lb. each. 2 In. by & In. 60-Ft. Rail. Tons per Mile. 3.73 3.94 4.25 4.39 4.57 10 11 12 14 .37 060 60 60 60 Rivets No. .37 .37 INTERMEDIATE ANCHORS, 18 in. long. tons. 1.15 1.15 1.24 1.24 1.27 .37 .37 Tons per Mile. 3.3 3.46 3.77 4.4 .19 .19 .19 .19 .19 244 244 244 244 244 Rivets No. 244 244 244 244 244 N.B.—Weight of 12 rivets, 4 lb. 8 oz. 2 In. by In. Lb. each. Tons per Mile. 12 13 14 161 tons. 1.57 1.57 1.63 1.63 1.66 45-Ft. Rail. Tons per Mile. 6.53 6.89 7.26 7.62 8.00 45-Ft. Rail. Tons per Mile. 4.90 5.17 5.44 5.71 6.00 3.85 4.08 4.56 5.18 Rivets .49 .49 .49 .49 .49 Rivets .25 .25 .25 .25 .25 22 SECTION I.-THE LINE. Table 9.-Weights of other Material appertaining to Tramway Works. Excavation in Macadam Portland Cement concrete Portland cement Pit sand "" Norway ** "" Leicester granite setts, "" .. "" 129 • River or Thames ballast Broken granite, 2 in. Broken limestone, 2 in. 1 ton Macadam, 2 in. thick, covers 15 superficial yards. Guernsey granite setts, 4 in. by 5 in., 1 ton covers 3.6 superficial yards. 4 19 19 "" Aberdeen granite setts, 1 "" "" ** ** ?? 3 in. by 5 in., 1 4 in. by 5 in., 3 in. by 5 in., 1 4 in. by 5 in., 1 3 in. by 5 in., 1 4 in. by 5 in., 1 3 in. by 5 in., 1 99 "" "" >> .. ·· 1 gallon of Creosote oil weighs 1 barrel of Creosote Oil = ·· 52 • .. "" ·· .. "" HALIFAX ·· ·· •* • ·· •• 1 cube yard=1.35 tons. =1.56 1 "" "" 1 cube foot = 86 lb. 1 cube yard=1.1 ton. 1 "" "" "" SWANSEA 1 1 51 12 4% of thread Weight complete 10% Vbs 11 "" >> "" "" "1 >> 39 1000 Jarrah wood blocks, 1000 1000 Creosoted deal blocks, 1000 50 9-in. by 3-in. blocks will cover 1 superficial yard and allow for cutting. 1 standard of timber (London measure) = 165 cubic feet. 9 in. by 5 in. by 3 in. weigh 2.5 tons. 9 in. by 4 in. by 3 in.. 2,0 $3 9 in. by 5 in. by 3 in. 1.56 "J 9 in. by 4 in. by 3 in. 1.25 11 99 "1 "} "" 880 feet run of 9 in. by 3 in. deals. = with 5 per cent. loss in cutting 2000 9-in. by 3-in. by 5-in. blocks. 1 load of timber (Country measure) =50 cubic feet. = 270 feet run of 9 in. by 3 in. deal. "" "" 2/2 3.8 4.2 4 with 5 per cent. loss in cutting 616 9-in. by 3-in. by 5-in. blocks. 1 cubic foot of coal-tar pitch weighs 62 lb. 10.5. 42 gallons. 4.25 3.9 4.1 Fig. 51. Tie Rod, Swansea. Fig. 52. Tie Rod, Halifax. Ma =1.21 =1.13 = .93 Tie Rods. (Figs. 51 to 53, pages 22 and 23.) Tie Rods are used where track is laid direct on concrete or ground without eepers. Figs. 51 and 52 show two standard types, as used at Halifax and Swansea. TE Tie Bar 2׳/s Flat Iron 96 34%'s "" "" "> ** *-2* - 7´- -* "" "" " 4 The first tie bar in each rail is placed from 2 ft. to 3 ft. from the end of the rail, and the spacing between them varies from 6 ft. to 12 ft. Fig. 53 shows the Cork tie-rod. Weight varies from 10 lb. to 16 lb. each. MATERIALS AND CONSTRUCTION. 23 Anchor Joints. (FIGS. 54 and 55.) In order to prevent the rails rising above the concrete, so called "anchor joints" are often used. There are many forms on the market, the one most frequently met with being the Cooper and Howard Smith anchor. This consists of inverted pieces of rail, either bolted or rivetted to the underside of joint. These are 24 in. long and are six-holed. Intermediates 18 in. long are used about every 20 ft. length of rail. Figs. 54 and 55 show types of anchor joints and holding-down clips. 54. EUREKA LOCK NUT BOLT 4x1 WES CURVE RAILS TO HAVE SPECIAL LIP SHEWN BY DOTTED LINES. (WEIGHT 106 LBS. PER YARD. *** K (736) Fig. 54. I HESAPEN 9½" Anchor Joint. Fig. 53. Tie Rod, Cork. *-*-* --3′ 0″ : -6---· If 55. 11 Mga Alam, Ma Fig. 55. Anchor Chair. DURABILITY OF RAILS. Experiments over three years, on rails of three grades of chemical composition (shown in Table 10), and laid on one line with very heavy traffic, have shown that what is wanted is a hard ductile rail, which can only be produced by low phos- phorus and high manganese. Anything below 0.10 of phosphorus can only be got by greatly increased cost of inanufacture, equal approximately to eight per 24 SECTION 1.—THE LINE. cent. of the total cost of the rails. The wear at the joints was entirely neglected, the service was at the rate of 11,600 cars per day passing over the rails, and the results are shown in Table 10. Had the joints given way, the rate of wear of rails would have rapidly increased. Rails are not taken out of service in tramway work because too much worn down all their length, but because of hammering at joints; in fact, wear of rail due to traffic can be neglected as far as life of rail is concerned. Life of rail is now determined by life of joints. Table 10.-Results of Three Years' Tests on Rails. (A. J. Moxham.) Soft Rail Hard Rail Hard and duc- tile .. •• ·· .. .280.026.106 .066 790 98.732 7.355 7.956 .590.056.097 .059.830 98.368 7.8417.971 :-570 .570 .234 .050 .078.980 98.088 7.135 7.977 120,380 53,160 47,100.00205 GAUGE OF TRACK. The gauge of a railway is measured inside the rails; if the sides are sloping the measurement is taken from half the depth of the head. In tramways where grooved rails are used, the gauge is the distance between the points of intersection of the tangents of the outside groove and the top of the rail. The standard gauge in England, the United States, and the Continent for railways is 4 ft. 8 in. The Irish gauge is 5 ft. 3 in. The Indian gauges are the metre (3 ft. 3 in.), and 5 ft. 6 in. Russian gauge is 5 ft. and Spanish 5 ft. 5 in. Usual Gauges of Tramwayɛ. ·· ·· ·· ·.· E Irish gauge Standard gauge Narrow gauge Metre gauge Extra narrow gauge Gauges of mining lines.. "" "" "" "" >> "" "" "" ·· -- ·· • lb. per lb.per lb.per sq. in. sq. in. sq. in. 75,860 45,730 35,000.00488 118,100 62,500 50,000.00345, ·· ·· ·· ·· .. ·· 25 35 60 .. ft. in. 5 2,3% 4 8 3 6 3 3 3 0 2 6 2 0 1 6 POINTS, CROSSINGS, ETC. These should change the direction of the car's another with the least amount of resistance possible. said to be either left or right hand, according to the from the track, as seen from the switch when looking towards the cross. In a tongue switch the long rail has to be properly curved and slotted, or bent for the tongue to fall into place. The tongue is made of hammered steel, and the turnpin is shrunk in; this is dropped into place, and all measurements checked before being considered ready for the track. motion from one line into Crossovers and turnouts are direction in which they curve MATERIALS AND CONSTRUCTION. 25 In the blind switch and mate, one rail is planed so as to leave a long notch on one side, while the other rail is planed to a point which fits into the notch. The two are strongly bolted or rivetted together, and sometimes finished on a planer. The curve crosses have usually two pieces of rail, one of which has the upper part so shaved at the crossing point as to allow a second one to drop down on the first, and fit accurately into the place allowed for it; the second has the lower part shaped so as to allow the first rail to pass through, the two rails jointing into one another. Care is necessary, in fitting, to have the angles of the intersection exactly as required. In railway work, points and crossings on main lines of standard gauge are 12 ft., 15 ft., and 18 ft. long. In sidings the lengths are respectively 6 ft. and 9 ft. The lengths should be adapted to the radius of the curve; there is little or nothing gained by making a switch longer than twice the angle of the crossing in feet. The angle of a crossing is the one formed by the tangent at the point of crossing with the main line. The usual way in England of expressing the angle is shown in Fig. 56. ·A·· 35 Fig. 56. Determination of Angle of Points. B The point or crossing would be designated a crossing of A, or supposing that the chord B-1 ft., and the length A is 8 ft., the point or crossing would be called one in eight. In India the points or crossings are defined by the tangent of their A angle, which in this case would be expressed by C Figs. 57 and 58, pages 26 and 27, illustrate a crossing and movable joint as constructed by Messrs. Hadfield's Steel Foundry Company, Limited. Where tram- ways cross rails, great care has to be used in construction so that there be no interference whatever with the rail tracks; a method adopted by the writer at Burton is illustrated in Fig. 59, page 28. Fig. 60 shows a curve cross, made by the Lorain Steel Company; the crossing point is made of specially hardened cast steel, and is renewable. Figs. 61 and 62 show a tongue switch and mate, made by the same firm. As in the curve cross, the crossing point is specially hardened and renewable, and guaranteed to wear as long as the abutting curve rails. Figs. 63 and 64 show sections through the points of a girder mate, and a girder run off respectively. In the latter case it will be seen that the guard extends beyond the tangent. Fig. 65 is a longitudinal section through a steel tongue switch (Lorain Steel Company). The tongue is made of solid forged steel, and the tongue pin is solid with the tongue itself. A T bolt in advance of the pin holds the point of the tongue firmly down to the bed of the switch, the nut of the bolt being prevented from turning by means of a zinc key. By turning the nut the tongue can be either tightened or removed. When renewing the tongue it is not necessary to disturb the surrounding pavement. Points and Crossings. (Figs. 66 to 72, page 31.) (According to Askham Bros.) For single lines with loops the standard crossings are 1 in 6, 1 in 7 and 1 in 8, the latter can only be used where the streets permit of a longer lead, say 40 ft. to 45 ft. Usually, however, the lead is 30 ft. to 36 ft. from the heel of the point to the centre of crossing. This is a good working lead for a 1 in 6 crossing, and ensures easy running. 26 SECTION I.—THE LINE. (737) 24 1640** ·1'4". ***4*4* İYU DIA. CORED HOLES SECTION A. B. 1182: 00000000 SPELTER 4: 7 GROOVE_RAISED TO ✯ 8' 6 CROSSING I IN 6 Fig. 57. INSERTION PIECE RIB % THICK SECTION THRO' G.D. 3'. 10% BOND HOLE po po to – Points, Crossings, Etc. Hadfield's Crossing and Movable Joint. 000 - tang van Marjan ka kan d 7" CROSSING MADE TO THIS SECTION WITH SA PLESS ENDS AS SHEWN IN YED LINES. *4*4* HOLE TAKE YOUMATY O 1'. 4*------> } to g V& DIA. ← CORED HOLES MATERIALS AND CONSTRUCTION. 27 58. TOE OF POINTS – – – M DIA.CORED HOLES 1.2* 'YÈDIA, HOLES 1.5%-+ (738.) ∙HOLES! 1:2 2:34 CIRKUNGAN 5* - 7----+ SECTION AB 2 Ὁ 36°DIA.HOLES.FOR ¾4"DIA. BOLTS 1% SECTION CD 6 +5/6 BOX FITTED UP AS AUTOMATIC SPELTER Fig. 58. SALZBURTSTAG NI MAKALATES ་ BAR HOLE JJË DIE -12, 6 OVERALL COSMORTAL MILD STEEL FERRULE 7.6 LENGTH OF TONGUE MILD STEEL FERRULE, J; K YA'DIA, HOLE!H S TONGUE SECTION EF SPELTER ' E FI Points, Crossings, Etc. Hadfield's Crossing and Movable Joint. SECTION GH 3X1" TIE BAR HOLE ht II 0000000000000 St.-- 1'4" G q**9* 1.5% H DEEP SPELTER 1 。 ő 0000000000000000 WEBS98 THICK HTT SECTION JK 1'4' - O 1.4 Af 土 ​28 SECTION I.—THE LINE. O O 59 (799.) O O O O O O O O • O a NOUNEIZ O O O O 10 O Opal SECTION A.B. TRAMWAY TRACK → O E ELEVATION AT K C. — 10 O! O O DIENC Ome 15.40 SECTION C.D. I O O 10 CAST STEEL SOLEPLATE O O O O O O -D B A SECTION E.F. Points, Crossings, Etc. Fig. 59, Burton Level Crossing. MATERIALS AND CONSTRUCTION. 29 Savaite W ny bin Fig. 60. Curve Cross. 61 62 Points, Crossings, &c. Figs. 61 and 62. Tongue Switch and Mate. Inova His cl Lada lue 30 SECTION I. THE LINE. The leads are at all times subject to the space in the streets. Some junctions can be laid with crossings as flat as 1 in 6 to commence with, whereas others require special sharp curved crossings to suit, but rarely sharper than an angle of 1 in 1 at the apex of the rails. If, however, the junction is a double curved one, running away from the centre, special patterns should be made to suit the two radii, and this ensures easier running. Ordinary crossings for loops are usually 4 ft. long for angles 1 in 44 to 1 in 6 Fig. 63. Section through Point of Girder Mate. .00 Fig. 64. Section through Point of Girder Run-off Fig. 65. Steel Tongue Switch. after that, varying from 4 ft. 6 in. to 6 ft. for angles up to 1 in 9, to suit the width of rails and discretion of engineer. It is sufficient, however, if the crossings are made sufficiently long to take in two rails at either end, within. space between. Standard points are 7 ft. 6 in. and 8 ft. 6 in. long, principally 7 ft. 6 in., the angle being determined by the width of the rails. Dover, Bristol, Birmingham, Leeds, Blackpool, Middlesboro', London United Blackburn, all use crossings 1 in 6, with 7 ft. 6 in. points. MATERIALS AND CONSTRUCTION. 31. 67 COMMERCIAL 8* --- 89 99 NORTH_BRIDAS- (68) በለ I.M MOVEABLE POINT KH OPEN 70´R 62'R INTENDED TRANY, R.HSPRING WARDA END EXISTING TA HALL END 60'R BRIDGENT END 1103 LHOPEN TINZE JIRL "FIR Fort & 200: A L.H OPEN 62!R NSON'T 70: A CRH SPRING TINE'S KHMOYSABLE 60_R R.H OPEN L.H OPER R.HL.NOVLABLE. COMMERCIAL ST "TUM ATIUN NEW BANK : 69 70 71 72 HEATH RA BROAD ORANGE ST. ERBAD Special Tramway Crossings and Points. Figs, 66 to 72. Tramway Curves, Crossings, and Points, BG'R AESAT TING LH OPEN RH OPEN 90 UNITE] NEMONT KTING LM MOVE ABLEPT OMI **** ING. ONINWS H'N 981 NINO NT MIVÉABLE PT LM NOVEABL. IN R.M OPEN 346 WATERHOUSE 87 NORTHGATE EN AVODUİNG. NEATH RO LING... FREE SCHOOL LINE 32 SECTION 1.-THE LINE. Bradford uses points Dublin St. Helens "" "" "" Bradford Wigan Halifax Dundee Wyke GO .. ·· .. .. ·· .. • ·· 99 1 "" Swansea Liverpool Wigan Huddersfield Bury and Rochdale use points Sheffield uses points 7 6 1 6 99 7 6 1 6 "" 7 6 1 "" 7 6 1 "" 1 5 "" 99 The Potteries use points Oldham and Ashton use points 7 6 For crossover roads in double lines the same points are used as above, with crossings 1 in 4, 1 in 5, and 1 in 6, as the engineer decides. The latter is chiefly used. The crossings weigh from 2 cwt. to 4 cwt., according to length and depth; average usually 3 cwt. The patent points, consisting of automatic fixed points 7 ft. 6 in., with side spring (or moveable stud point), average 10 cwt. per pair for 6-in. rail, and 11 cwt. for 7 in. rail. If 8 ft. 6 in. long 10 cwt. for 6-in. rail. .. ·· ft. in 8 5 8 6 ·· 7 6 8 6 7 6 7 6 ·· Birmingham Leeds, Bristol and Blackburn ·· ·· ·· Crossings 1 in 42 "" .. · "" "" "" ·· "" ·· "" "" "" vary "" 12 cwt. for 7-in. rail. Patent rolled steel heel plates are now adopted on new lines. They can be made to suit any lead and angle up to 3½ in. wide at heel; being rolled from the same material as the rails, they wear equally. They are machined to correct taper. 1 in 5 1 They are made in two forms; one for all new work, when the rails can be punched when being rolled. These have been adopted at Halifax, Bristol, Wigan, Blackburn, Bradford, &c. The other form of plate is for old roads when converted to electric traction, being easily fixed, and when fitted with locknuts will last the life of the rail. The standard size is 20 in. x 10 in. x 30 in. x 12 in. x 3 in. in., but some run up to 1 "" "" 10 00 LO "" "" 8 5 5 lead 36 ft. in. in. 30 X 12 X 30 X 12 X 24 X 8 X 20 × 91 X 16 x 12 x "" 99 16 x 10 X 20 x 10 x 35 ft. 33-38 ft. in. LOJAN CO}<°CE—«ka05/0066/30-47 Figs. 66 to 72 (page 31) are diagrams of special work done by Askham Bros., on the Halifax Electric Tramways. Approximate Rule for Leads of Crossings. The lead of any crossing is equal to twice the gauge multiplied by the angle of the crossing. If curves are carefully plotted to an enlarged scale of, say, 10 or 20, or often even 33 ft. to an inch, the leads and angles of the crossings can be scaled off with sufficient accuracy for all practical purposes. The gauge should be generally about 1 in. tighter at the nose of the crossing and points than anywhere else on the lead, in order to prevent the wheels having any lateral play. CURVES. The radius of a curve is generally given in feet, and is taken to the centre line of the track. In this country, as a rule, a curve is nearly always given by its radius in feet. In America the curvature is given in degrees; this being the number of degrees of central angle subtended by a cord of 100 ft. The radius of a curve of one degree subtended by a chord of 100 ft. is 5730 ft. in round numbers-and relation of the radius R expressed in feet and the angle D expressed in degrees which is subtended by a chord of 100 ft. is the following- 5730 D= R I MATERIALS AND CONSTRUCTION. 33 M. O. • ook CONHE HAHA t 1 to WO icko 1% 1룹 ​150 1,8% 141 1급 ​133 11 126 11 120 114 1 HA 102) -KOMP Hoi to Han Na cho -----HAARAANNNNNNNN IONMIOL2, barue-N 2 133 109 17% 104 1골 ​100 11% 96 15 111 133 132 23-5 213 232 24 23 Table 11.-Middle Ordinates on 10 ft. Chords. Radius. to ft. in. 300 266 240 218 200 184 171 160 92 90 ARABOJINZIIIII..∞∞∞888 87 85 82 81 77 76 75 73 72 66 65 5730 2865 1910 1433 1146 955 717 574 383 288 230 200 180 ko-a H-5:00/00-160 NNNNNNNNNNNNNNNNNNNN∞∞∞∞ð að october 1-kocok

«<<]) ====<^\]-A-KI 321 параноидне ко 118 17% •• 2 -- 15% •• 3 Ft. 6 In. Gauge. .. Speed of Train in Miles per Hour. •• 10. 20. 30. 40. FO. 33 estel-ko 216 oko-ka NH- LOKO ******* <===<>|<$65/20—THE ◄ 22 - • onko mko ļ oste 2f 11% ·· • ·· Widening of Gauge on Railway Curves. To ease the running and save the road from the wedging action, the gauge is eased. Thomas Summerson and Sons, of Darlington, state that a good rule for a 44 rigid wheel base equal to twice the gauge is to widen the gauge by R' in which R is the radius of the curve in feet. Ꭱ ·· 4 Ft. 8 In. Gauge. Table 20.-Widening of Gauge on Saxon Narrow Gauge Light Railways. Gauge, 750 Millimetres. ·· ·· Speed of Train in Miles per Hour.· 10. 20. 30. | 40. | 50. 61 5 KOHN WHA who mo 4, 21 (n400 m ==co Mo LÔ GA CH 56420 m2) maletanoff -* 1o. to 13221 kalco antal mámem ko B542 - ocko 111 11. 5 →→ Hamp Widening of Gauge. 5 millimetres 10 15 20 611 "" 4 "" "" 3 (Russell Tratman, condensed.) On standard gauge railway track it is a general practice to widen the gauge on curves, but the details of this practice vary considerably. One factor in deciding as to the amount of widening required is the length of rigid wheelbase ordinarily running over the line. Some roads in America widen the gauge on curves of 1 deg., while others only widen it on curves of over 10 deg. or 20 deg. Where the widening is extreme, as on a sharp curve, an inside guard rail may be laid against the track rail to prevent driving wheels with blind tyres from dropping off the track rail. The gauge at points and crossings should be normal, and not tight or slack in relation to the open track. If on a tangent, the gauge at such places would be 4 ft. 8 in.; and if on a curve the gauge at the point should be the same as on the rest of the curve. Some roads, however, widen the gauge at these places; the Atchison, Topeka, and Santa Fe railway makes the gauge 4 ft. 9 in. at all turnouts, whether on curves or tangents. This widening extends through the crossings and points, and narrows to 4 ft. 8 in. in a distance of 31 ft. beyond the point. The gauge of 4 ft. 9 in. is also used for yard tracks from which many leads turn out. The widening should be effected by shifting the inner rail outward, keeping the MATERIALS AND CONSTRUCTION. 43 5.6- (WHEEL BASE) A 79. B 17450 p 1 S can make d— — 2 1 CROSS SEC. A.B. GROOVE PLAN SHOWING APPLICATION OF SQUARE M 35-0 Rad. A me qen d ELINE CORRESPONDIN GAUGE FOR GROOVE. 3.4% 8. Ge 65 GAUGE FOR I GROOVE. <16> CROSS SEG. AB. GROOVE. RADIAL LINE 3.47 3. 65 Special Curve Gauge on Curves. Fig 79. Wheel Base Square for Gauging Curved Tracks. · S 44 SECTION 1.-THE LINE. outer rail at a uniform distance from the track centres throughout, and using this as the line rail. Special Curve Gauge on Curves.-Tramway tracks are not laid as railway tracks are, in respect to gauge, as owing to the presence of the check forming the groove on tramway rails, it becomes necessary to have a tight gauge, as will be better explained by the diagram, Fig. 79. The distance between the two templates is equal to the wheelbase of the truck proposed to be used. Table 21.-Widening Gauge (American Practice.) Radius in Feet. 5730 2860 1910 1433 1146 955 717 574 383 288 Curve in Degrees. 123+00∞02 4 5 6 8 15 Atchison, To- peka, and Santa Fè. in. -{00~*~##-##000000]=$ca «t<* 1 Lines. Philadelphia and Reading. in. ::-40000-kacja 1 New York Central. Wal C Fig 80. Dawson's Drain Rail. in. 10000mm+0}={0\}{2} DRAIN RAILS. Dawson's Patent Drain Rail, manufactured by Askham Brothers, deals with and removes water standing upon the tramroads. No more serious difficulty is encountered than the trouble caused by the large amount of water continually flowing in wet weather along the grooves of the rails. The water ultimately finds its way between the joints of the rails and under the bottom flanges, softening the concrete, and causing the setts to become loose and rise above the level of the rail whenever the cars pass over the joints. In winter, when the water finds its way under the setts, it freezes and damages the joints, loosening the setts immediately round, frequently causing the upheaval of the pavement for the whole width of the tramway. The rail is made of best crucible cast steel, and is usually 6 ft. to 8 ft. 6 in. long; curved drain rails also can be made. A slot 12 in. long is cast in the groove of the rail casting, which allows the water to flow freely from the rail to the sewer. The rail, which is equal in strength to the ordinary rolled girder tramrail, takes the place of this for the length of the casting, and is fished up to the rails in the MATERIALS AND CONSTRUCTION. 45 ordinary manner. It is practically self-cleaning, but every part is easily accessible, and can be regularly cleaned out when required, by removing the lid of the dirt box and passing a rod down the pipe to the sewer, Fig. 80. The expense of connecting to the sewer is small, a few 4 in. earthenware pipes only being required. Tramway Drainage. On hills, at the bottom of hills, and in low-lying ground where there is any likelihood of the tracks being flooded, it becomes necessary to make some provision for carrying off the water which would otherwise accumulate in the rails. Figs. 81 to 83 (pages 46 and 47) show the methods adopted by the writer in Burton and Scarborough; in these drain boxes it will be observed that care has been taken to prevent any possibility of the exit provided for the water being filled up with mud. COST OF RAILWAYS AND TRAMWAYS. Table 22.-Cost of Light Railways. Approximate cost of narrow-gauge railways, including works and rolling stock but not land: Ballast. Gauge. For gauges up to 2 ft. 6 in. 8 in. above 10 Cuttings and embankments taken at 2 ft. deep. 99 "" "" "" ft. in. 2 0 2 6 3 0 3 0 3 6 Weight of Engines Exclu- sive of Tender. tons 6 9 12 17 20 Formation. Width. Wide. Maximum Load per Wheel. tons 1 11 2 3 3초 ​4 in. 6 "" Weight per Yard of each Rail. lb. 20 Thick. 6 in. to 7 in. 14 9 25 30 40 50 "" "" "" Cost per Mile. £ 1500 to 2000 2500 3000 3000 3500 3500 4500 4000 5000 "" "" "" "" These prices include stations and permanent work, but not land and rolling stock. In a hilly country the cost would be much greater. Cost of Rolling Stock depends on kind of traffic; £790 to £1000 per mile has been found necessary on single lines. Double Line.-The cost of making will be from 50 to 75 per cent. in excess of above figures, the cost of rolling stock only 10 to 30 per cent. more for the same traffic. Cost in Different Countries.-In England, £40,000 per mile; Scotland, £28,000; Ireland, £15,000. Single-line railways in poor districts of Ireland and Scotland, £6000. Europe, £12,000 to £25,000; India, £12,000; Great Indian Peninsula, £22,000; Ceylon, £19,000; United States, £8200; in Norway, light railways, 3 ft. 6 in. gauge, in a very difficult country, have been constructed at from £3000 to £6000; Queensland, £6000 to £12,000. The working expenses average 40 per cent. of the gross receipts in Ireland, 45 per cent. in Scotland, and 50 per cent. in England. In England 50 per cent of capital was expended in works of construction, 20 in purchase of land, 10 in carrying stock, 20 in law expenses, discounts, &c. 46 SECTION 1.-THE LINE. Approximate Cost of Construction of Tramway Track. The following figures give the cost per mile for a double track laid in a paved street where no extraordinary difficulties have to be encountered, the foundation being of gravel or broken stone. Fig. 81. Rail Drain Box. Table 23.-Cost in U.S.A. of One Mile of Straight Double Track laid with 78-lb. Step Rails, 30 ft. Long. ** 704 rails, including channel points, chains, and spikes 4224 sleepers, 24 ft. centres Labour, excavating and laying, including teams and super- intendence 1024 cubic yards of gravel.. 352,000 granite blocks Labour of paving 30 T609 Total cost per mile of double track ** £ s. d. 2640 00 380 3 2 633 12 0 226 16 0 1971 4 0 3598 4 0 £9449 19 2 MATERIALS AND CONSTRUCTION. 47 : 707 CATCH BOX CATCH BOX 82 83 T PODA J DOUBLE SINGLE TRACK TRAPPED SUMP BOX SENNINNI TRACK Fig. 82. Single Track Drain. CATCH BOX CATCH BOX Tramway Drainage. Maio TRAPPED SUMP BOX SEREREM Fig. 83. Double Track Drain. 48 SECTION 1.-THE LINE Table 24.-Quantities and Cost of T-Rail Construction at Denver, Col, U.S.A. Track Construction with 60-lb. T-Rail. 84, tons of steel rails (including freight, inspector, and hauling) 10,800 lb. angle bars (30 lb. each), including hauling 1150 lb. track bolts (in. by 34 in.), including freight and hauling.. Nut locks 3017 hewn red spruce ties (including hauling and inspection) 6050 lb. railway spikes (5 in. by 1 in.), including freight and hauling *360 bonds placed complete 9 hauled away Track laying, including blocking Total 360 cast-iron joint boxes 2080 cubic yards excavation (trench 8 ft. wide, 16 in. deep), all "" ·· ·· • 25,700 ft. lumber (2 in. by 14 in. pine) Carpenter work, nails, hauling "" "" ·· "" • .. " .. Paving. 4400 square yards Blake asphalte (7.5 ft. wide, 3 in. thick) 36,178 cubic feet cement concrete "" · · .. : .. ·· • ·· .. • .. .. ·· ·· "" 4.08 tie bars, 15 lb. each, with nuts and washers, at £14 "" 1760 1760 linear yards laying permanent way, including packing at 1s. parquing sides of rails with concrete, at 6d. 4350 super. yards granite sett paving, 6 in. by 3 in., including laying, grouting with pitch, and bedding, at 11s. 6d. 1760 linear yards making good margins, at 6d. 1760 lighting and watching, &c., at 9d. · .. ·· 4393 Total cost per mile of single track Table 25.-Cost of Girder Rail Construction (English Standard) in Main Roads. (FIG. 16, page 7.) Rails 7 in. deep, 100 lb. per yard. Concrete foundation, 6 in. deep. Paving, 6 in. by 3 in. Granite Setts. PER MILE OF SINGLE TRACK, 4 FT. 8 IN. GAUGE. 1614 cubic yards excavation, at 3s. 807 Portland cement concrete, at 16s. 157 tons steel rails, 100 lb. per yard, at £7 .. 8.8 fishplates, 56 lb. per pair, at £8 10s. • "" "" 1.88 fishbolts, 1 in. diameter, with locknuts, at £18 .. Cost per Mile of Single Track. £ • .. • .. • .. ·· :: • .. .. • ·· Total for way and paving per mile of single track 4891 14 3 Table 26.-Cost of Girder Rail Construction in Country Roads. (FIG. 18, page 7.) Rails 6 in deep, 90 lb. per yard. Paving 5 in. by 3 in. granite sett margins to rails. Macadam between rails and 18 in. margins. PER MILE OF SINGLE TRACK, 3 FT. 6 IN GAUGE. 1051 cubic yards excavation, at 3s. 391 Portland cement concrete sleepers, at 16s. 141.2 tons steels rails, 90 lb. per yard, at £7.. fishplates, 37 lb. per pair, at £8 10s. ·· 6.6 1.88 fishbolts. 1 in. diameter, with locknuts, at £18 ·· + · 4.08 tie bars, 13 lb. each, at £14 "" 1760 linear yards laying permanent way, including packing and parqu- ing sides of rails, at 1s. 6d. 1468 super. yards granite setts 5 in. by 3 in. margins including laying, and grouting, and bedding, at 118. 2200 super. yards macadam 6 in. deep including rolling, at 4s. 6d. lighting and watching, at 6d. 1760 Total for way and paving per mile of single track ·· ·· 730 44 7 2 343 31 18 · 37 .. 129 207 1548 1632 1124 74 15 £ s. d. 242 2 0 645 12 0 1099 0 0 74 16 0 33 16 10 57 2 5 88 0 0 44 0 0 2501 5 0 40 0 0 66 0 0 £ s. d. 157 13 0 312 16 0 988 8 0 56 2 0 33 16 10 57 2 5 132 0 0 807 8 0 495 0 0 44 0 0 3084 6 3 MATERIALS AND CONSTRUCTION. 49 Table 27.-Quantities and Cost of Construction for Permanent Way on Metallic Sleepers. Way, 151 tons, 1760 yards at 15s. 4d. Bessemer steel rails, 58 lb. per yard, 91 tons Wrought-iron sleepers and clips, 36 lb. per yard, 57 tons fishplates, 2 tons "" "" bolts and nuts, ton Excavation, 1207 cubic yards, at 3s... Portland cement concrete, 600 cubic yards, at 15s. Cost of way Paving, 3670 square yards granite sets, at 10s. Bituminous grouting, 3670 square yards, at 2s. 3d. Cost of paving .. ·· Cost of way and paving PAVEMENTS. : •• : .. ·· ·· ·· .. ·· £ s. d. 1349 6 8 190 10 0 495 0 0 2034 16 8 1835 0 0 412 17 6 2247 17 6 4282 14 2 Specification for Wood Pavement. Description of Pavement and Mode of Laying.-The pavement is to be com posed of creosoted blocks, cut from the best yellow deal of first quality, 9 in., 8 in., and 7 in. long by 6 in. deep and 3 in. wide; no block to be more than 9 in. nor less: than 7 in. in length. Each block to be cut perfectly to size and shape. The joints. to be filled in with mastic asphalte of approved quality to a height of at least in., measured from the bottom of the block, the rest to be filled in with Portland cement grouting, and no joint to be more than 2 in. in width. The blocks, laid transversely, are to be only laid to within 3 in. of the curb on each side of the street (to allow for expansion), the space so left to be filled in with Portland cement and sand, as shall be directed, but subsequently made good with blocks if neces sary. No paving to be commenced on any portion of the foundation until ten clear days after the concrete has been laid. Creosoted Blocks.-The whole of the blocks used in the work to be creosoted with 12 lb. per cubic foot, by a mixture of pure creosote, G. oil, and pure distilled tar, in proper proportions, as shall be approved; but no blocks shall undergo this process until they have been first inspected and approved of by the surveyor or other authorised officer; and the surveyor shall have full power, not- withstanding such inspection, to split in two any reasonable number of blocks selected indiscriminately from those brought on to the works, and to reject any that he may consider unfit for use; the same to be at once removed by the contractor. Excavation.-The contractor to excavate the whole of the present macadamised roadways to the required depth to form foundation and pavement, such of the old macadam as the surveyor shall approve, if sifted and mixed with Thames ballast, to be used for concrete; the surplus to be the property of the contractor, who shall at once remove the same at his own cost. Cement. The whole of the cement supplied for the works must be of the best quality, and from an approved manufacturer, and must conform to the usual tests to the satisfaction of the surveyor. Concrete.-The concrete to be composed of Thames ballast (mixed with such of the old macadam and in such proportions as the surveyor shall approve) in the pro- portion of 7 parts by measure of hard core to 1 part by measure of cement; the surface to be finished off to a smooth face with concrete 1 in. in depth, composed of Thames sand and Portland cement, in the proportions of 3 in. of sand to 1 in. of cement, and to be laid a depth of not less than 6 in. over the whole area of the street (from curb to curb), and to be composed of the best Portland cement, subject in every respect to the approval of the surveyor. Cement Foundations.-Cement foundations for wood-block paving ought to have 10 to 12 days to set. 50 SECTION I-THE LINE. Asphalte Roadways. On a solid bed of concrete, used to give a foundation, the asphalte surface is laid, about 24 in. thick. The preparation of this surface requires great care. The asphalte rock, quarried from the mines, is crushed in pieces of about 3 in. cube. These are passed through toothed rollers, and through smooth rollers, until reduced to powder. This is then heated in revolving cylinders to about 280 deg. Fahr., and the heated powder carried to where it is to be used; there it is spread on the concrete and raked with hot iron rakes until it forms a uniform layer of loose powder, about twice its ultimate thickness. This is then compressed by pounding with hot iron rammers, after which a small amount of hydraulic cement is swept over the surface, and the pounding is continued until the pavement will no longer yield under the rammer. It is left until the next morning to cool Tar Pavement. The surface of walk should be removed to the depth of 3 in. or 4 in., and the ground well beaten. Some coal-tar should be poured over shingle or coarse gravel, and the whole worked together until the gravel is thoroughly impregnated with the tar. This composition must be spread over the surface of the walk, and rolled down with a heavy roller. Another mixture must now be made of tar and fine gravel, or sifted ashes, a thin layer spread over the layer of rougher stuff first put on, fine sand or gravel sand or gravel then sprinkled over the top of this, and the whole beaten flat Concrete Footpaths and Floors. These are made from 3 in. to 6 in. thick of Portland cement concrete, varying from one part of cement to three parts of clean sand, to one part of cement to six parts of sand; sometimes crushed stone is used instead of sand. A layer of about 3 in. of broken stone is laid down first, and the concrete then spread over it. Stone Block Pavement. All the stones should be sound, uniform in quality, hardness, colour and grain; no brittle, soft, or laminated blocks should be used. If from different quarries, it is better that stones from each quarry should be piled and laid in separate sections of the work to ensure even wear. The foundation for stone blocks may be formed of gravel, concrete, or rubble stone grouted with concrete. The depth of the foundation should be proportional to the amount of traffic, not less than 6 in. in city streets. Upon this foundation a layer of not less than 1 in. of sand or cement mortar forms a good bed for paving blocks. Good results have been obtained by using, between track, sets 3 in. to 4½ in. wide by 5 in. to 6 in. deep, and not exceeding 9 in. in length. In 18 in. borders outside track, blocks 4 in. wide, 6 in. deep, and 9 in. long should be used, allowing about in. to in. interstices for joints grouted for half their depth with bitumen, and remainder filled up with cement (3 to 1). The following results are some interesting compression tests on four 2-in. granite samples, averaging nearly 41 square inches sectional area, made by Professor Alex. B. W. Kennedy. Table 28.-Crushing Force in Tons. Quenast 50 Leicester 45.35 Guernsey. 44 Aberdeen .. 31.2 .. •• .. Sample. Per Square Inch. Per Square Foot. 11.75 1,692 1,541 10.7 10.48 1,509 7.31 1,952 Remarks. Remained uninjured. Started to crack at 38 tons. Completely crushed. All granites do not possess good paving qualities; a formation too soft and too brittle is very slippery when wet, and has no durability. Great toughness and hardness are the essentials of granite to make a better and more lasting pavement than sandstone, and others of its class. Paving blocks made of tough and sound granite may be expected to retain for a long time the sharp edges given to them, when dressed and trimmed. The crystals scattered through some granite rock will wear more readily than the harder matrix in which they are set, resulting in a rough surface with a good foothold. PART II.-RETURN GENERAL. A slight fall in voltage will cause electrolytic action. It is important to reduce resistance of return circuit to a minimum. The conclusions drawn by Professor Dugald C. Jackson, of the University of Wisconsin, are as follow: "1. In no case is the action due to the electrolysis of water; where oxygen is liberated at the anode it does not attack iron. BONDING. 2. A mere directive force in the nature of the pressure will cause electrolysis. 3. The corrosion is dependent only upon the current which flows, and is therefore as dependent upon the resistance of the soil as the pressure tending to cause the current. 4. A small quantity of soluble salt will start the action, which will continue as long as the current flows. 5. The corrosion of a pipe depends on the amount of current flowing from a given area and the nature of the salts in the soil, the order of their activity being : 2. Nitrates. 3. Sulphates. 1. Chlorides. CIRCUIT AND The surface exposed for leakage of current from track is very great; in ordinary double-track it is some 50,000 square feet per route mile. With so great a surface, and with a fairly good conductivity of the concrete and earth, a large fraction of the current may be diverted from the rails, even in short lines, and with the maximum drop as small as that specified for by the Board of Trade. In a given system of distribution the variable features in the earth return are limited to the method of bonding the rails, the cross section or weight, and the chemical composition of the rails. The chemical composition of the rails cannot be greatly varied, since rails of high electrical conductivity wear away too rapidly to allow of their use. weight now general in the best practice is approximately 100 lb. per yard. The The factor which practically determines the resistance of the return circuit, and the drop in voltage, is the additional resistance due to bonding. The best results, as far as copper bonds are concerned, have been obtained with a current not exceeding 25 amperes per square inch of contact area of copper within the web of the rail. 0.378 0.446 0.536 0.568 0.588 0.610 Table 29.-Influence of Chemical Composition on Conductivity of Steel. (H. F. Parshall) Carbon. Manganese. Silicon. Phosphorus. Sulphur. 0.550 0.568 0.592 0.603 0.632 0.650 0.111 0.188 0.201 0.204 0.214 0.220 0,040 0.046 0.051 0.053 0.056 0.062 0.041 0.044 0.059 0.061 0.065 0.071 Resistance Compared with Copper at 20 deg. Cent. 10.8 11.1 11.3 11.4 11.5 12.1 Resistance in Ohms of 1 Mile 1 Sq. In. Sectional Area at 20 deg. Cent. 0.468 0.482 0.490 0.495 0.499 0.560 52 SECTION I.—THE LINE. THE "CHICAGO" RAIL BOND. (FIGS. 84 and 85, page 53.) The "Chicago" Rail Bond, Fig. 84, consists of a copper rod or flexible cable, having tubular or thimble-shaped terminals which are bent at right angles to the bond, the whole being composed of one solid piece of rolled copper. The tubular or thimble-shaped terminals are inserted into holes through the web of the rail, and the slitted ends of the terminals are spread or clinched over on the rail with a hammer and punch; this holds them from drawing back out of the hole. Rust should be cleaned out of holes with a straight rose reamer not exceeding the size of the terminals more than in., or they should be cleaned with a round file a size smaller than the holes. If from any cause they should be made too large for the terminals, making a loose connection, pins in. larger than the original pins sent out with the bonds should be used, and in applying these larger pins a punch should be used to open out the terminals to start the pins straight. The drift pin is larger in diameter than the opening in the tubular or thimble-shaped terminal by in. This pin is driven into the hole in the terminal, permanently expanding and wedging the terminal into solid contact with the surface of the hole through the web of the rail, by stretching or swaging the metal of the bond against the sides of the hole in the rail. This makes an absolutely perfect and solid contact between the two metallic surfaces in connection, excludes all air and moisture, and renders corrosion or electrolytic action in the connection very nearly impossible. Table 30.-Standard Dimensions of “Chicago” Rail Bond. Size of Wire, B and S. Gauge. 0000 000 00 0 Lengths. in. 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 50 Diameter of Hole in Rail into which Terminal of Bond Fits. in. DOKAWOS 27888 lb. 77 83 Diameter of Hole in Terminal. 93 99 in. 104 109 115 120 125 131 136 141 147 152 157 1-201 H Table 31.-Weights of Chicago Rail Bonds. lb. 99 Weight of 100 1/0 Weight of 100 2/0 Weight of 100 3/0 Weight of 100 4/0 Chicago Bonds. Chicago Bonds. Chicago Bonds. Chicago Bonds. 165 112 119 125 132 139 145 152 159 Sectional Area of Rail Bond. 166 172 179 sq. in. 0.166 0.132 0.104 0.083 180 192 199 Diameter of Pin. in. Ib. 134 142 -- 151 159 168 176 185 193 201 210 218 227 235 244 252 261 D Contact Surface in Rail. sq. in. 1.57 1.18 0.98 0.785 lb. 171 181 192 202 213 224 235 245 250 267 277 288 290 300 320 331 RETURN CIRCUIT AND BONDING. 53 Table 32.—Weights of Bonds, Crown or Chicago. 4/0 B. and S. STANDARD "JOINT" BONDS PER MILE OF SINGLE TRACK. Centres Bent. £ in. 28 30 Gauge of Track. 1 metre 3 ft. 6 in. "" "" 4. 0 4 ,, 81,, Size. in. 80 90 Weight Each. 100 110 lb. 2.0 2.13 120 130 140 Size of Bond. in. 48 straight 54 60 66 1 X 4/52 (1) STANDARD "BETWEEN TRACK" BONDS PER MILE OF SINGLE TRACK. "" "" Number per Mile. 4-.-- 11/15 60-ft. Rails. Fig. 84. 372 372 --- 1°----! 1". lb. 2.95 Weight per Mile. 3.27 3.59 3.91 lb. 744 792.3 22. Weight per 100. lbs. 466.1 519 4 572.7 626.0 679.3 732.6 785.9 Weight Each. Number perMile. Weight per Mile. lb. 129.8 145.9 158.0 172.0 Dram 460 Area 766 Number per Mile. "Chicago" Solid 4/0 Bond. 45-ft. Rails. 44 44 44 44 t Fig. 85. "Chicago" Bond Fixed in Rail. WEIGHTS OF OTHER SIZES OF BONDS PER 100 (Straight) FOR WAYS BETWEEN TRACKS, SPECIAL WORK, &c. Size. in. 150 160 170 180 488 488 The Number per Mile depending upon width of Ways, Length of Points and Crossings, &c. 190 200 Weight per Mile. Ib. 976 1039.4 O For intermediate sizes add 5.33 lb. per in. per 100. Weight per 100. lb. 839.2 892.5 945.8 999.1 1052.4 1105.7 54 SECTION I.—THE LINE. 鈉 ​The "Chicago" and rivetted Bonds should be 10 in. longer than the fishplate. If distance between centres of hole be given into which bond has to be fixed, 3 in. must be allowed at each end of the bond for the bend. When inserting a "Chicago" Bond, the terminal is held in place by a bar shaped to fit. A conical punch is then used to expand the opening of the terminal against the rail, and the pin is then driven home with a 4-lb. machinist's hammer. The protruding circle of copper is then flattened down against the rail. Approximate Formulæ for Ascertaining Weight of Solid Chicago Bonds. W=weight of bond in pounds. 7=length of bond in inches. L-distance between centres of holes in rails in inches. 4/0 BOND 3/0 BOND in. Chicago (4/0) terminals: Web of rail, in. thick; hole in rail, in. in dia. contact area, 1.37 square inch 2/0 BOND W=1×0.0335+0.12. W=(L+6)+0.0335+0.12. The depth of the hole in the terminal (not including point) is 1 in. in all sizes of the bond. Table 33.-Results of Tests made by Mr. Parshall. in. Chicago (4/0) terminals Same as above Columbia bond: in. hole; web of rail, in. thick; contact area, 1.37 square inch {W { W=1×0.0533+0.21. W=(L+6)0.0533+0.21. W=1×0.0423+0.17. W=(L+6)×0.0423+0.17. Resistance in Microhms of Two Terminals Single Bonding per Mile Single Track. in Series. 1.97 average 2.15 2.06 2.50 7.2 9.5 7.7 } Resistance of Terminals only. average 8.1 173.5 (aver- 189.5 181.5 age 220 635 aver- 835 680 age 716 Conditions of Bonding. Clean bond, clean hole, drilled with- out oil, bonded. well Bond well bonded, hole drilled with oil. Hole clean, well bonded. CHICAGO "CROWN" BOND. (FIGS. 86 to 92, pages 55 and 56.) The "Chicago " bond, as originally made, fulfils all that can be required of a bond so far as electrical conductivity and mechanical efficiency are concerned. Its disadvantage lies in the fact that in fixing it to the rail it is necessary that both sides of the rail be exposed. Where a line had already been laid, this necessitated the removal of the paving on both sides of each joint, and it was also difficult to attach the bond to the castings at frogs and crossings. Furthermore, a demand arose for bonds of greater flexibility than could be obtained from a solid wire, and considerations of economy made it desirable to have short, flat, and flexible bonds which could be inserted close to the ends of the rails at joints, and between the rails and the fishplates. These requirements led to the development of the "Crown" type of the "Chicago" bond, which, made in many shapes, and of solid and stranded copper wire of different degrees of flexibility, meets every practical need. In the stranded "Crown" bond, the strand is laid with all of its wires crossing each other at such an angle that they provide sufficient flexibility for all expansion RETURN CIRCUIT AND BONDING. 55. and contraction. The connection between strand and terminal is accomplished. by welding-no solder being used. The strand, when first inserted in the terminal, extends beyond and around the point where the hole is drilled. When a terminal is sawn apart and across the strand, examination shows that the wires in the strand have lost their identity, having been thoroughly welded to the terminal, and forming a perfectly homogeneous mass of copper. Testing the 0000 bonds by placing the terminals in the jaws of a testing machine, showed that under a strain of 3740 lb. the copper strand was torn apart near the centre; but the connection between strand and terminals remained unimpaired. A 4-in. straight-T Bond, 4 in. between centres elongated 2 in., or 50 per cent before breaking. Fig. 86. Special T Fixed in Foot of Rail. Fig. 87. Fig. 88. Standard T in Foot of Rail. Standard F round Fishplate. O Fig. 89. Special Straight T under Fishplate. There are four shapes of these standard bonds; and the bonds are made either solid, stranded, or in leaf. The types are as follows, all having the prefix Chicago Crown:-"Special T"-"Special straight T"-"Standard T"-"Standard U"_ "Standard F"-"Special F"-"Special S"-"Standard S." Figs. 86 to 92 show some of the various types. The "T" Bond will go into an exceedingly limited space. It is less rigid than a solid bond of equal capacity. Expansion and contraction of rails are provided for by the style of the strand, and the slight curve of the bond. The variation.S in. caused by expansion and contraction will not exceed in. for a 30-ft. rail, or for a 60-ft. rail, and actual tests show that when the terminals are firmly inserted in two pieces of steel, and these are drawn apart in., the only effect is to elongate the connecting strand slightly by drawing the individual wires closer together, without reducing the cross-section area of copper. When the process is reversed to correspond with the expansion of the rail, the strand assumes a slight curve the terminals meanwhile remaining solidly fixed within the rails. The process of con- traction and expansion takes place very slowly, and is so gradual as not to interfere with the efficiency of the bond. The distance between the centres on all of "Crown" T Bonds sizes is the same (4 in.), and all sizes are milled to the same diameters as "Chicago" Bonds of corresponding gauge · 56 SECTION I.—THE LINE. Nog 90 91 1.21 92 (12) ___ Fig. 90. Fig. 91. Fig. 92. 3" * - U de de d @ Chicago "Crown" Bonds. W **· %* Terminals of 4/0 Standard 8. Standard 3/0 T. Standard 4/0 U. CAR AU CAD de Soə น RETURN CIRCUIT AND BONDING. 57 The "T" Bond is adapted for use underneath the foot or base of either girder or Trails. When thus applied, holes in rails should be countersunk upon the upper side. The Standard "U" style by its shape provides for all expansion and contrac-. tion. By bending, the bond is readily adapted to holes varying from 2 in. to 5 in. between centres. All sizes of the "U" Bond have the same length strand. The "U," like the "T" Bond, is well adapted for use underneath the foot or base of either a girder or "T" rail. Style "F" goes over or around the fishplate on a girder or "T" rail. The flexibility renders it easy of application, and provides for a little variation, and for errors in drilling holes. The "F" Bond terminals of each size are milled to the same diameters as "Chicago" Bonds of corresponding sizes. Terminals of all Chicago "Crown" Bonds, whatever their type, have exactly the same dimensions as the corresponding "Chicago" bonds. Approximate Formula for Ascertaining Weight of Chicago "Crown" Bonds. 7 = length in inches from centre to centre of terminal measured along centre line of bond. W = 3/0 BONDS weight of one bond in ounces. UP TO 6 IN. W = 5.2 +0.7 (7–13). OVER 6 IN. W = 5.2 +0.67 (7 −13); 4/0 BONDS UP TO 6 IN. W = 7.34 +0.9 (7-13). OVER 6 IN. W = 7.34+0.86 (l – 13). The superiority of a "one-piece" bond, having forged terminals expanded against the web of the rails by internal pressure, has been so conclusively demon- strated by experience, that it is unnecessary to describe cast-copper bonds or those in which the heads are riveted into holes in the rails, or held against the web. of the rails by pressure. Cast copper is greatly inferior in electrical conductivity to forged copper: and the action of copper differs so widely from that of iron or steel under climatic changes causing expansion or contraction, that it is practically impossible to secure a permanent and effective contact between the two metals, unless the softer be held in place by constant pressure applied, and constantly maintained, by such steel wedges as are used with the "Chicago" and "Crown" bonds 。 Terminal of Columbia Bond. THE COLUMBIA RAIL BOND. (FIG. 93.) This consists of three rod. On each end of this parts, two copper thimbles and the connecting copper copper rod is a truncated cone-head with a fillet at the base. The inside of the thimble is tapered to fit the head on the bond, while the outside is slightly tapered in the opposite way. In applying the bond, the cone-shaped heads are placed in the holes in the rail from one side, and the thimbles are slipped over them from the other. A portable hand-press is then applied, and the wedge-shaped head of the bond is forced into the thimble. The total length of a bond is 3 in. more than the distance from centre to centre of holes in rails. The total length of a bond should be 8 in. more than that of the fishplate. For a 0000 B. & S. G. or 000 B. & S. G. bond, the holes in the rails should be 3 in., and for a 00 B. & S. G. or a 0 B. & S. G. bond, § in. THE NEPTUNE BOND. (FIGS. 94 to 99, page 58.) This bond resembles the "Crown" bond; some of the various types of this bond are shown in Figs. 94 to 99, and data regarding sizes are given, Table 34. The bonds are produced from the highest conductivity solid-drawn copper. The ordinary Neptune solid bonds are made from a single piece of wire, the terminals being drop-forged into shape, and finished to an even surface. The Neptune flexible bonds are of various designs to meet special requirements, the form the most 58 SECTION 1.-THE LINE. 96 94 95 100 (726) 101 Miscellaneous Bonds. Fig. 94. Bond for Use under Fishplate. Figs. 95 and 96. Bonds for Heavy Currents. Figs. 97 to 99. Bond Terminals. FIG. 100. Protected Rail Bond. Fig. 101. The Atkinson Cast Bond. 99 97 98 RETURN CIRCUIT AND BONDING. 59 used being obtained from stranded wires or strips; the heads are drop-forged. The Neptune extra flexible bonds are made in the same manner as the flexible bonds, with the exception that the connecting wires are of copper-wire rope instead of ordinary stranded wires; by this means a maximum degree of flexibility is attained. A special tool is used for this bond, consisting of two parts: the outer holds the head of the bond in position, and acts as a guide to the drift pin; the inner closes behind the pin, and a few strokes with a heavy hammer on it drives the pin home. .. Gauge of bond, S. W. G. 1/0 = .324 in. = Sectional area .. .0824 sq. in. = Diameter of hole in rail Diameter of hole in in. head of bond Thickness of pin Contact surface when web of rails=10 mm. thick Contact surface when web of rails=11 mm. thick ·· Table 34.-Neptune Copper Bonds. ·· ·· .. .683 Gauge of bond, S. W. G. 4/0 Sectional area .. Diameter of hole in rail Diameter of hole in head of bond Thickness of pin Contact surface when web of rails=10 mm. thick Contact surface when web of rails=11 mm. thick.. .. .. T6 11 ·· bomko "" ** IT"," 1.02 .619 sq. in. = 399 sq. mm. .928 sq. in. || 11 = 439 4/0 = .4 in. = 10.16 mm. .1256 sq. in. = 81.07 sq. mm. in. 19 mm. "" 8.23 mm. 53.2 sq. mm. 13 mm. M 8 9 = 11 = 12 95 "" = 659 135 in. = 598 sq. mm. "" "" 2/0.348 in. = 1.0951 sq. in. § in. 18 " " .773 sq. in. = " 18 19 $ || || "" 1.19 549 .851 |6/0 = .464 in. = 11.78 mm. .169 sq. in. = 109 sq. mm. in. — 22 mm. "" = 8.84 mm. 61.375 sq. mm. 16 mm. 8 Y "" 99 449 mm. "" = 12 = 13 >> 1.08 sq. in. = 698 sq. mm. = 677 " "" Fig. 100 shows one terminal of a protected rail bond, made by the Forest City Electric Co. The terminals are of pure copper, cast on to flexible middle portion, the casting temperature being sufficiently high to weld the two parts together. The weld is further completed by reheating and drop-forging. The terminals are not rivetted into the rails, but are expanded by pressure. THE EDISON-BROWN PLASTIC COPPER BOND. (FIG. 102, page 60.) The bond is made of a rectangular piece of rolled copper, 3 in. long, in. thick (or thicker), and 1½ in. (or more) high. A cup-shaped projection is pressed near each end, so as to give a contact against rail web close to the end of each rail. Inside the cups is a piece of sheet steel supporting a pair of steel springs; the steel is used to keep springs from wearing into copper. These pieces are held together by a small iron strap until bond is applied, when the sharp web on outside of spring cuts it away and enters the fishplate, thus adding to the conductivity of the joint. The bond is amalgamated to prevent rusting, and the contact surfaces are covered with Edison-Brown plastic alloy. The springs are proportioned to give a pressure of 4000 lb. per square inch when the fishplate is bolted up. The bond must be specially designed to fit each particular rail and joint. When in service, the springs serve merely as distance pieces as long as the joint is tight; if the nuts become loose or the fishplate wears, the springs will hold the bond in contact. To apply this bond it is necessary to brighten the web of rail beyond the end bolt hole with a flat-nosed drill or emery wheel. The surfaces are then amalgamated 60 SECTION I.—THE LINE. ! by the Edison process, and covered with a thin layer of plastic alloy. This unites with the amalgamation of the bond, and maintains an electrical contact of low resistance which does not rust. The lubrication afforded by the plastic alloy permits the rails to move slightly in any direction. Test No. 1234 LO 5 6 O (603) 7 The size of the copper can be varied, up to the full area of the space between rail web and angle plate, and between end of bolt holes in rail. The smallest size made is equivalent to No. 0000 B. and S. gauge; less than that amount of material will not give sufficient mechanical strength. Table 35.-Comparison of Resistances of Various Rail Bonds not including in any case Resistance of Rail. . Fig. 102. The Edison-Brown Plastic Copper Bond Kind of Bond. One 4/0 Plastic Copper Bond Two 4.0 Plastic Copper Bonds One 6/0 Plastic Copper Bond Two 6/0 Plastic Copper Bonds One 2/0 Copper Bond with steel driving pin Two 2/0 Copper Bonds with steei driving pin One 4/0 Flexible Copper Bond J ·· .. .. Current in Ampéres. 1,915 1,915 1,910 1,880 1,610 1,805 1,830 Difference of Potential in Volts. 0.0234 0.0127 0.0114 0.00678 0.75 0.278 0.119 Resistance in Ohms. 0.0000122 0.00000668 0.00000593 0.0000036 0.00046 0.000154 0.000065 The tests from which the above results were obtained were carried out by the École d'Electricité, under the auspices of the French Government, at Paris, in July, 1900. RETURN CIRCUIT AND BONDING. 61 THE EDISON-BROWN PLASTIC RAIL BOND. (FIG. 103.) This bond, Fig. 103, is made up of a plastic metallic composition which makes contact between the rail and the fishplate, and an elastic cork case to hold the plastic compound in position as near the end of the rail as possible. The current passes from one rail through the bond to the fishplate, and then from the fishplate through a second bond to the next rail. Contact spots about 2 in. in diameter are cleared of scale and rust, and treated with a solid alloy which instantly silvers the surfaces and prevents rusting. The conductivity of the completed joint is practically equal to that of the rail. Plastic Bonds have been in service several years without any change. The plastic compound is packed for shipment in small wooden boxes, each of which holds the exact amount necessary to make the contact between rail and Plastic Rail Bonds Affixed to Web of RAIL AND FISHPLATE READY TO BE BOLTED UP. SVE BRAK END SECTION THROUGH BOND, Rail and Fishplate. Side View OF RAILS WITH BOND CASES IN POSITION BEFORE FISHPLATE IS PUT ON. SUSIGELI (19) HORIZONTAL SECTION THROUch Bond, Rail and Fishplate, showing Path os Return Circuit, Fig. 103. The Edison-Brown Plastic Bond} fishplate. Each rail joint requires two boxes. For heavy rails each box holds one amalgamated spring washer which can be compressed to less than the minimum distance between web of rail and inner surface of fishplate. The cases which hold the plastic compound are made of flexible cork, treated on the surface with a sticky compound; they will not deteriorate in service. To prevent their sticking together, they are packed in waxed paper and powdered chalk, and should be kept in a cool place until used. The solid alloy for amalgamating the contact spots on rails and fishplates is shipped in hermetically-sealed tubes. With each shipment an extra box is sent, in which are the wooden holders for handling the solid alloy. This extra box should be used to seal up the holder containing the rod of alloy when not in use, as the metal softens on exposure to air. When track is being laid, the Plastic Bonds should be applied by the plate- layers. One extra labourer to clean the contract spots, and one mechanic to amalgamate the contact spots and put the bonds in place, should be added to the gang. Besides the regular tools each gang should have: One heavy track drill and clamp, with 12-in. handle. One template of -in steel, attached to clamps so as to fit against web of rails, with hole for guiding drill so as to bore midway between first and second bolt holes from end of rail. 62 SECTION I. I.—THE LINE. Four flat drills 1 in. in diameter for 50 to 59 lb. rail. 60 to 70 Or, 14 Or, 1 ** "" 71 to 90 "" "" These drills should have very broad points, as they are used only to cut away the surface scale; their sides should fit the template so as to be easily guided. One can of soda and water for lubricating drill points; oil must not be used on drills. 99 Four coarse new 18-in. files, bent into arc of circle and re-tempered. One gasoline torch and can of gasoline (or one charcoal pot and bag of charcoal). One small can white paint and brush for marking completed joints. 1 lb. solid alloy for every 30 joints; this must be kept in air-tight screw-top box when not in actual use, to prevent its softening. Two split wooden holders with rubber bands, for holding solid alloy; these and an extra screw-top box are sent with each shipment. One small pail of clean water. 2 lb. clean cotton waste. One coil thin iron wire for fastening cork receptacles to the rails in wet or cold weather. The drills, clamp and template can be made by any toolmaker to use with ordinary ratchet drill. Directions for Applying the Plastic Bond.-Remove surface scale or rust from spots about 2 in. in diameter on the web of the rails and on the fishplates where the cases are to be fixed, between first and second bolt holes from ends of rail. Use for this purpose a drill as above described, or a bent file or grind- stone. Wet the cleaned spots with water, and remove chips and filings. While still very wet, rub these spots with a piece of the solid alloy until the surface is silvered; then apply more water by squeezing wet waste over it. Do not rub off the compound or the mercury from the rail. As soon as the bubbling stops, wet the places again with clean water. (Use the split wooden holders in handling this solid alloy, as it is corrosive to the flesh. When not in use, keep it covered in one of the screw-top boxes to prevent it from softening.) Then hold the cork case over the gasoline torch or charcoal fire until the black coating has softened slightly. Do not burn it. Press the cork against its proper place on the rail until it sticks. On some shapes of rail it is more convenient to wire the case in place on web of rail or on the angle plate, using thin iron wire. This is often necessary in cold or wet weather. Be careful not to get any of the black coating of the cork on the silvered surface, and be sure to have the hole in the case opposite the cleaned contact spots on rail and fishplate. As soon as the case sticks firmly in place against the rail, carefully put into the centre of the hole the plastic metal contained in the little wooden box; use a rounded strip of sheet iron as funnel to guide it into the hole, and be careful not to lose any of the liquid in the box, as its presence is necessary. If the plastic metal is not soft throughout, work it in the palm of the hand until it softens; then place it in the hole in the cork case. After placing a bond and case on the end of each rail, put on the fishplate and tighten the nuts evenly. Get the nuts halfway down before hammering rail for alignment. After completing each joint, mark the onter fishplate with white paint to indicate the presence of the bonds. 98 Contact Area of Alloy with Rail is square inch for every 10 lb. of weight of rail per yard; thus, a 60-lb. rail would require a contact surface of 1 square inch. Cork is made twice as thick as distance available between fishplate and rail. Plastic alloy is equal to surface of contact by available distance between web of rail and fishplate; it should not be compressed, otherwise it will harden. Washer inserted in case of large plugs, and so designed that it will expand at least in.; thus, if fishplates get loosened from any cause, it will insure contact with surface of rail and fishplate. Thickness of cork between the edge of hole and outside of cork should be 2 in. 104 RETURN CIRCUIT AND BONDING. 63 Method of Bonding Points and Crossings. (FIG. 104, page 62.) is shown in Fig. 104. Short bonds connect the rails to the castings, but long ones insure continuity should these have to be replaced at any time. RAIL WELDING. FIGS. 105 to 107, pages 63 and 65.) The continuous rail without fishplates, bolts and bonds is the ideal, as all troubles, mechanical and electrical, are due to poor joints. Two methods of attaining this end have so far actually been tried. The first consists in electrically welding the ends of the rails together; the second in casting a sleeve of cast. 105 2 -3/16" (748) R Fig. 105. Sketch of Bar used in Welding. DIAGRAM OF CONNECTIONS OF RAIL WELDER m J+ M B T Q R.T - ROTARY TRANSFORMER W.T WELDING TRANSFORMER S.W=SWITCH R Fig. 106. O T- TROLLEY C.B-CIRCUIT BREAKER R.R-RHEOSTATS M - MOTOR B - BOOSTER DOO R.C S.W W. R.C - REACTIVE COIL W.C WELDING CLAMP W.C iron round the adjacent ends of the rails. This latter is known under the name of "The Falk Cast Weld. There is still a prejudice against the continuous rail, the chief reason being that standard railway practice makes special allowances for contraction and expansion at joints. It was thought that if a continuous track were laid and the paving on a length of road removed, the track would buckle, or that the paving might be damaged, owing to contraction and expansion of rails; but experience has demonstrated that in tramway track, joints are all held so firmly that rails are practically immovable, and differences of temperature simply change the molecular condition and the stresses in the rail. In tramway work variations of temperature do not effect the rails much, owing to their being entirely covered in by pavement of some kind which is a non-conductor of heat. It is easy to ascertain the strain on rails due to variations of temperature. Assuming a co-efficient of expansion for steel of 0.0000065, and multiplying this by seventy-five, which is a liberal figure for the number of degrees of maximum deviation from the temperature at which the welding is done, we get 0.000487, which is that part of its length which a rail would expand when exposed to a rise 64 SECTION 1.-THE LINE. 4 of 75 deg., or contract when exposed to a fall of 75 deg. in temperature. A steel bar will expand 0.00003 of its length, due to a load of 1000 lb. per square inch. Dividing the estimated expansion by this figure, we get for the strain 16,200 lb. per square inch. As 40,000 lb. per square inch is a safe value for the elastic limit of steel, it can readily be seen that the elastic limit will never be reached. This means that these expansions and contractions may go on indefinitely, and as long as the joints remain unbroken, no harm will be done to the rail, for stresses within the elastic limit work no harm. Assuming 80,000 lb. per square inch as the ultimate strength of steel, there is still, as far as the strength of the rails themselves is concerned, a factor of safety of five. Wherever joints have broken, in no case have they pulled apart more than two inches. This would seem to show that the pull which broke the joint was not a cumulative effort extending all along the line, but merely the result of a local strain extending but a short distance on either side of the joint. Electrically-Welded Joints. In making a joint, flat rolled steel bars (see Fig. 105) are used, having at each end a boss or projection on one side, which forms the contact surface between the bars and the web of the rail, and confines the welded area to these sections. A flat strip of steel, in. thick and 1 in. wide, is placed across the middle of the bars on the same side as the bosses. The middle weld is a vertical one, and made the full width of the bar, the end welds being horizontal. After rails and bars are cleaned by means of the sand-blast, the welder is swung into place, and the jaws made to engage the rail at the centre weld. The current is turned on, and flows from contact to contact, through the bars and the rail web. As soon as the metal is brought to a welding heat, the current is cut off, and, simultaneously, the pressure, by means of the hydraulic jack, is applied to the maximum amount. The same process is followed as regards each of the end welds, except that here when the final pressure has been applied, it is held in each case until the weld has been permitted to cool and set under the pressure. A remarkably tough weld is secured by holding the pressure after the weld is made, this operation having the same effect on the steel as though wrought under a hammer. By making the centre weld first and proceeding at once to the end welds without waiting to cool the centre weld under pressure, the greatest elonga- tion of the bars is secured, so that after the ends are welded, as the bars cool, they contract and exert a powerful pull to bring the abutting rail ends together, and closing the slightest opening, thus leaving practically no joint at all. The finishing operation in the process consists of grinding the head of the rail to true surface. In old track, where the rail ends have been battered, the receiving rail is welded slightly higher than the other, and the grinder run over it to grind out the inequalities and bring it to a true surface. With a continuous service, working day and night, it takes about thirteen minutes to complete each joint; eighty joints in twenty-four hours is considered a fair average. The electric welding bars are made of low carbon steel and therefore of low resistance, and the cross-section being large, the conductivity of the electric welded joint averages over 50 per cent. higher than that of the rail itself. The welding plant consists of five cars:-1. The sand-blast car; 2. Welding car; 3. Rotary converter car; 4. Booster and motor car; 5. Motor and emery wheel car for finishing. The cars run on the tramway lines by their own equipment of motor and trolley. The secondary of the welding transformer consists of one turn of copper, the terminals of which form the clamps that grip the weld. The current used is taken rom the trolley line, the connections being arranged as in the diagram. Great pressure up to 35 tons is maintained on the joint until it cools, by an hydraulic jack. The pressure, which prevents crystallisation of the steel, and the absence of burning secured by the larger contact area, are the improvements which have determined the success of the method. The welding transformer is run at 300 volts, from 5 to 7 volts being maintained at the welding clamp terminals. The welding current runs as high as 25,000 amperes. Falk Cast Weld. (FIG. 107.) The system consists in casting an iron sleeve round the sides and bottom of the rail joints, the rail ends being first placed firmly together. In cases where they do not absolutely touch, thin plates of steel are driven in between the heads RETURN CIRCUIT AND BONDING. 65 of the rails before casting. Before fixing the moulds, which are of cast iron, the sides and bottom of the rail are cleaned, and this is generally done with an emery wheel or a sand blast. The cast iron used is of special chemical composition to give good results, and is run at a much greater heat than is used in making ordinary castings. The cast iron running into the iron moulds cools rapidly on the outer surface, thus causing a tremendous pressure to be exerted on the metal which is still in its molten state in contact with the web and foot of the rail. As the metal is poured in from one side and comes in contact with the web or thinnest part of the rail at its greatest heat, this part of the rail is brought to a white heat; and owing to the tremendous pressure exerted on the molten cast iron, this is practically forced into the interstices of the steel, thus not only making a thoroughly good mechanical joint, but also ensuring a good electrical joint. Although not actually welded, as it would be impossible to weld cast iron to steel rails, the result obtained is practically equivalent to a weld, as, if the cast iron is torn away from the web of the rail it always brings away part of the rail with it. Also, on examining a welded joint which has been sawn through, the section of the web of the rail can no longer be clearly distinguished, and it is impossible to say where the cast iron ceases and the web of the rails commences. The surface where such a contact exists is higher on the pouring side than on the other, as shown in Fig. 107. The section of the cast-iron joint is so designed as to have at least the same tensile strength as that possessed by the rail. The cast welded joints used are generally about 14 in. long, and the weight of cast iron varies in accordance with the weight of the rail, from 70 lb. to 140 lb. per joint. POURING {SIDE #30 CONTACT SURFACE A.8 AND C.D. ENLARGED. Fig. 107. The "Falk Cast Weld" Rail Joint. The cast iron must necessarily be melted close to where the work is being done, and for this purpose a cupola on wheels is necessary. The fear has been expressed that water would get in and cause rust, which would destroy the conductivity of the joint, and diminish its mechanical strength to such an extent as to cause rupture, or that the great heat of the molten cast iron would anneal the steel rails, rendering these softer at the joints and liable to In ten miles of track which were cast-welded at St. Louis in the early part of 1894, and over which there has been a very heavy traffic, the joints are stated to be to-day in as good condition as when they were first made, and so perfect that it is practically impossible to detect them. wear. At the present moment there are some 20,000 cast joints in the United States, and a large amount of the work has been done in France and Germany. The makers guarantee that within the first two years the number of breakages will be less than 2 per cent. of the total number of joints made, and that the conductivity will be equal to that of the solid rail, provided that the joints are .properly made to start with. The Goldschmidt Process of Rail Welding. In this process the welding heat is obtained by means of chemical combination between aluminium and oxygen. By combustion with aluminium metals can be separated from their combinations. Dr. Goldschmidt discovered that it was not necessary to heat the whole mass to the requisite heat of ignition, but that if ignition can be started at one point the reaction will proceed throughout the whole mass. He further found out that if an oxide, which combines with aluminium at a temperature which can be created by an ordinary lighted match, is placed upon a mixture of refractory oxide requiring a much higher temperature and ignited, the reaction is started and proceeds automatically as before. The D 66 SECTION I.—THE LINE. Rail including Joint. Table 36,-Result of Conductivity Tests on Falk Joints by the Author. Current in Amperes. Drop in Millivolts. 292 270 300 284 320 380 277 309 370 273 276 303 304 360 362 240 291 302 349 360 272 278 310 319 877 387 18 17.5 20 12.4 19.5 18 13 15.6 18.5 14.4 14.5 16.4 16.3 17.6 19.8 13 14.5 16 17.6 18 7.4 7.9 8.4 7.9 293 270 300 282 320 380 274 305 Current in Amperes. 364 250 270 282 308 335 355 251 254 280 330 332 Solid Rail. 270 276 Drop in Millivolts. Length of Rail Tested = 5 feet. 18 17.5 19.5 12.5 14 17.5 13.6 15.4 18.5 12.7 13 14 15.4 17 18 12.6 12.5 14 14.2 16.6 Falk Weld Drop_re-Solid duced to Current of 1000 Amperes. Millivolts. Length of Rail Tested = 2 feet. 6.5 6.6 6.7 Rail Drop re- Conductivity of Joint duced to Current of in Per Cent of Solid 1000 Amperes. Rail. Millivolts. 61.8 64.9 66.7 43.7 61 47.4 47 50.6 50 52.7 52.6 54.1 53.8 49 54.5 54.1 50.4 53 50.5 50.1 61.3 64.9 65 44.4 43.8 45 48.7 50.5 50.8 50.8 48.2 49.6 50.1 50.7 50.7 50.5 49.2 50 43 50 24.1 23.9 27.2 28.5 310 27.2 21.6 319 6.6 24.8 20.7 13 375 7.6 34.5 20.2 18 387 8.0 46.5 20.7 Rails should not be worked at more than 50 Amperes per Square Inch Sectional Area. 99 100 97 101 74 95 103 99 101 96 92 92 93 103 93 93 98 94 85 99 89 84 75 83 58 45 ↓ RETURN CIRCUIT AND BONDING. 67 method of making a weld with this mixture is as follows:-A crucible is filled with a mixture of aluminium and iron oxide in a state of fine powder. To enable this mixture to be ignited by a match, a little mixture is put on the top of the crucible, composed of an oxide, which reacts at a low temperature; the heat developed when this mixture is united by the aid of a match is sufficient to start the reaction between the iron oxide and the aluminium mixture. The chemical action may be expressed as follows:- Fe2O3 + Al2 = Al2O3 + Fe2 In a minute or two the crucible will contain reduced molten iron, covered by a thick layer of alumina slag. The temperature reached in this reaction is about 3000 deg. Cent. When this process is applied to welding rails, the crucible, which is held in position by means of a tripod or crucible holder, is tapped in such a way that the streain of molten iron runs directly in the runner of the mould, which is fixed and luted by means of sand. The metal flows round the web and foot of the rail, and melting them forms one mass with them. The liquid slag, which follows the metal, is diverted to the top of the rail, and brings the latter to welding heat; the whole section is thus heated equally, and the rail ends will not buckle. Umma (6051) O 10000! Fig. 108. The weld can be made with or without clamps; in the first case a complete butt-weld, without even the smallest slip, is obtained. For each weld from 15 lb. to 20 lb. of the compound are required, varying with the section of the rail; the metal welded around the joint, therefore, only weighs from 8 lb. to 10 lb. The system has the advantage of not requiring a bulky outfit, and of being applicable to practically any number of joints, however small: a strong point specially with repair work. The moulds are generally made on the spot according to a model designed specially for each section: its two parts, one on each side, firmly enclose and exactly fit the rail; they are made by tamping an ordinary mixture of clay and sand into a sheet-iron case placed over the model, which has afterwards to be dried. The cost is only a few pence. The crucibles consist of an iron shell lined with magnesia, provided at the bottom with an exchangeable outlet, which will stand 9 to 10 runs, the crucible itself lasting for about 25 to 35 runs, the wear and tear, therefore, amounting to very little indeed. The welding compound is supplied in bags, so-called welding portions con- taining the exact weight necessary to effect the weld. It is claimed that the strength of the weld is about 80 per cent. of the strength of the rail, the shoe welded on to the foot of the rail materially strengthening the joint. The head, it is stated, does not get soft although brought to welding heat, the reason being that the operation takes place without the air having access to it. PART III.—OVERHEAD DISTRIBUTION, The trolley wire can be suspended by span, centre, or side pole construction, the best results being obtained by using the first mentioned, and running the wire over the centre of the track. Rosettes attached to buildings can in places be used instead of poles. Where side pole construction is used, the wire should preferably not be suspended more than 8 ft. from the centre of the track; and where this entails the use of a bracket more than 15 ft. long, span or centre-pole construction should, if possible, be adopted. B. & S. G. The trolley wire should be doubly insulated at every attachment by means of special insulators, as shown in the cuts. Care should be taken at all anchors and terminal attachments to place one insulator close to the trolley wire, and the second at the pole. 0000 000 M LELO C78 .460 .409 00 .364 0 .325 1 2 3 4 5 6 Table 37.-Tensile Strength of Copper Wire. Diameter in Inches. OVERHEAD LINE. .289 .257 .229 .204 .182 .162 .144 .128 Hard- drawn. Breaking Strain in Pounds. 8310 6580 5226 4558 3746 3127 2480 1937 1559 1237 980 778 (Roebling.) An- nealed. 5650 4480 3553 2818 2234 1772 1405 1114 883 700 555 440 B. & S. G. 9 10 11 12 13 14 15 16 17 18 19 20 Diameter in Inches. .114 .102 .090 .080 .072 .064 .057 .050 .045 .040 .035 .031 Breaking Strain in Pounds. Hard- drawn. 617 489 388 307 244 193 153 133 97 77 61 48 An- nealed. 349 277 219 174 138 109 87 69 55 43 34 27 The strength of soft copper wire varies from 32,000 lb. to 36,000 lb. per square inch, and of hard copper wire from 45,000 lb. to 68,000 lb. per square inch, accord- ing to the degree of hardness. The above Table is calculated for 34,000 lb. for soft wire and 60,000 lb. for hard wire, except for some of the larger sizes, where the breaking strain per square inch is taken for B. & S. G. at 50,000 lb. for 410 to 2/0, 55,000 for 1/0, and 57,000 lb. for 1. OVERHEAD DISTRIBUTION. 69 Table 38.-Trolley Wire Tensile Test. (Copper 98 per cent. conductivity, as given by E. Talbot, Assoc. M. Inst. C.E.) ¦ Diameter. Area. - in. sq. in. per cent per cent 0.409 0.1314 3.2 54.1 0.408 0.1307 6.0 54.6 51.2 0.408 0.1307 5.3 0.408 0.1307 6.2 46.7 Extension on Whole Length of Reduction 10 In. of Area at Frac- ture. Diameter in Inches of Strand Outside. Approximate Outside Gauge, Iron and Steel Wire Manufacturers' Association. ·· { Wire in Inches. Diameter of Ib. 6194 6226 6082 6194 Thickness of wire ·· Number of strands Gauge of strand, British Iron and Steel Wire Manufac- turers' Association Total approximate diameter in inches Weight per 100-ft. run in pounds Yards per cwt. Breaking strain in pounds Breaking Load. Washburn and Moen wire gauge Diameter in inches.. ·· .. 7/0 0.162 5/0 0.146 3/0 0.125 10/ 1/0 0.104 12 3 0.083 13 0.054 16 Table 39.-Galvanised Steel Span Wires Generally Used. .. Single Break- Yards Approximate Gauge of each Wire used, Iron and Steel Manufac- turers' Association. ing Strain of Strand Approximate Approximate in Pounds. per Cwt. ·· ·· cwt. 55.3 55.6 54.3 55.3 Approximate Weight per 100 Ft. in Pounds. 7/1/ 8320 71 52 8 6050 88 42 4550 3950 2400 1600 130 28 200 189 307 12 •• .. : lb. per tons per sq. in. sq. in. No. B.W.G. 8 9 Limit of Elasticity. 5857 6012 • 11 12 14 465 83 17 • 15 0.07 7 Nearest Wire, B.W.G. of each wire. Table 40.-Galvanised Mild Steel Wires for Span and Guard Wires. English Practice (Seven-ply). 3 1 10 307 200 2400 3900 to to 2600 4000 Dia- meter in Inches. 52.3 53.7 0.165 0.148 0.120 0.109 11 0.11 77 0.083 0.058 1/0 Tő 21 Remarks. granular fracture silky 11 0.12 7 8 9 10 12 14 17 "" "" No. L.S.W.G. 10 0.135 7 3/0 5/0 29 36 130 88 4600 6100 Nearest Wire, L.S.W.G. of each wire. Dia- meter in Inches. 0.160 0.144 0.128 0.104 0.080 0.056 70 I. SECTION 1.-THE LINE. ! Table 41.-Imperial Standard Wire Gauge. (Issued by the Iron and Steel Wire Manufacturers' Association, March 1, 1884.) Size on Wire Gauge. 76854NI cooo 5/0 12.7 7/0 .500 6/0 .464 11.8 .432 11.0 .400 10.2 .372 2/0 .348 .324 .300 .276 .252 232 4/0 3/0 1/0 161 00 TH LOD 2 3 4 5 6 7 3 9 10 11 12 13 14 15 16 17 18 Diameter. 19 20 Inch. Milli- metres. .212 .192 .176 .160 .144 .128 .116 -104 .092 .080 .072 .064 .056 .048 .040 .036 9.4 8.8 8.2 7.6 7.0 6.4 5.9 5.4 4.9 4.5 4.1 3.7 3.3 3.0 2.6 2.3 2.0 1,8 1.6 1.4 1.2 1.0 .9 Sectional Area in Square Inches. .1963 .1691 .1466 .1257 .1087 .0951 .0824 .0707 .0598 .0499 .0423 .0365 .0290 .0243 .0201 .0163 .0129 .0106 .0085 .0066 .0050 .0041 .0032 .0025 .0018 .0013 .0010 Weight of 100 Yards. lb. 193.4 166.5 144.4 123.8 107.1 93.7 81.2 69.6 58.9 49.1 41.6 34.8 28.5 24.0 19.8 16.0 12.7 10.6 8.4 6.5 5.0 4.0 3.2 2.4 1.8 1.2 1.0 Mile. lb. 3404 2930 2541 2179 1885 1649 1429 1225 1037 864 732 612 502 422 348 282 223 183 148 114 88 70 56 42 32 21 18 Length of Cwt. yards 58 67 78 91 105 120 138 161 190 228 269 322 393 467 566 700 882 1,077 1,333 1,723 2,240 2,800 3,500 4,667 6,222 9,333 11, 200 Breaking Strain. Annealed Bright lb. 10,470 9,017 7,814 6,702 5,796 5,072 4,397 3,770 3,190 2,660 2,254 1,883 1,544 1,298 1,072 869 687 564 454 355 268 218 172 131 97 67 55 lb. 15,700 13,525 11,725 10,052 8,694 7,608 6,595 5,655 4,785 3,990 3,381 2,824 2,316 1,946 1,608 1,303 1,030 845 680 532 402 326 257 197 145 100 82 Sag in Trolley Wire. Table 42 shows the theoretical effect of temperature change on a 1/0 (B. & S. gauge) trolley wire, 125 ft. span. In this case the supports are supposed to be absolutely rigid and the wire inelastic. In practice, of course, the wire is elastic and stretches under the tensile stress, and thus greatly diminishes the difference which would otherwise exist between the sag in cold weather and the sag in warm weather. According to Professor Ewing, hard-drawn trolley-wire of 0.4 in. diameter stretches approximately th of its length for every 1000 lb. of tension up to 3500 lb., at which point the elasticity becomes imperfect. It is necessary to ascertain what strain can be safely put on the trolley wire, in order that at the lowest temperature to which the line will be subjected, the strain on the wire will not surpass the point of safety. In the case of hard-drawn 1/0 B. & S. trolley-wire, it is quite safe to allow 2000 lb. strain at lowest temperature, but no more. Rule for Fixing Sag of Trolley Wire. A rough but safe rule for England, where 20 deg. of frost is the maximum to be expected, is to allow per cent. of the span at average temperature of 60 deg. to 65 deg. Fahr. The sag of trolley wire in the warmest weather should not exceed 15 in. OVERHEAD DISTRIBUTION. 71 Table 42.-Sag on Trolley Wire, and Corresponding Strain for an Initial Maximum Strain of 2000 Pounds. Temperature Fahr. M deg. -10 0 988 Span in Feet. 40 50 60 70 80 90 100 110 120 ONORO 70 30 40 50 60 70 80 90 Span in Feet. .100 110 120 500 in. 15.4 20.8 26.3 31.9 37.6 43.5 49.5 55.6 61.9 Dip. 500 in. ft. in. 0 3.7 0 9.7 1 6 7.8 10.6 13.6 16.7 19.9 23.2 26.7 30.3 34.0 37.9 1 10 2 1 2 4 Table 43.—Sag on Span Wire and Strain on Side Poles for Two Trolley Wires 10 Ft. Apart.* 800 in. 9.6 13.0 16.4 19.9 23.5 27.2 30.9 34.7 38.7 Strain. lb. 2000 774 415 340 300 267 800 in. 4.9 6.5 8.5 10.4 12.4 14.5 16.7 18.9 21.3 23.7 1000 in. Dip. 7.7 10.4 13.1 15.9 18.8 21.8 24.8 27.8 30.9 ft. in. 0 3.7 1 2 1 6 1 10 2 1 Strain on Poles in Pounds. 1000 in. 3.9 5.3 6.8 8.3 9.9 11.6 13.4 15.2 17.0 18.9 1500 in. 5.1 6.9 8.8 10.6 12.5 14.5 16.5 18.5 20.6 Strain. lb. 2000 1500 in. 2.6 3.5 4.5 5.6 6.6 7.7 8.9 2000 in. 10.1 11.3 12.6 534 415 340 300 3.9 5.2 6.6 8.0 9.4 10.9 12.4 13.9 15.5 Strain on Poles in Pounds. * Trolley wire is 0.3249 diameter (1/0 B. and S. G.) 125 ft. span. 2500 in. Table 44.—Sag on Span Wire and Strain on Side Poles for Single Trolley Wire.* 2000 in. 3.1 4.2 5.3 6.4 7.3 8.7 9.9 11.1 12.4 1.9 2.7 Dip. 3.4 4.2 4.9 5.6 6.6 7.6 8.5 9.5 ft. in. || 0 3.7 1 0 1 5 1 10 3000 in. 2500 in. 4.4 5.3 2.7 3.3 4.0 4.6 5.3 6.1 6.8 7.6 6.3 7.3 8.3 9.3 10.3 Strain, lb. 2000 623 440 340 3500 in. 5.4 6.2 7.1 7.9 8.7 3000 in. * in. in diameter of span wire with seven galvanised steel strands. 1/ 2.8 3.3 3.9 4.5 5.1 5.7 6.3 72 SECTION 1. THE LINE. Trolley Wire Lengths, Joints, Spacing of Supports. The trolley wire must be of an absolutely even quality and supplied in at least -mile lengths, and should be evenly and tightly rolled on a reel and without kinks. The joints should be silver brazed in the copper rod before final pulling. The diameter of 1/0 B. & S. G. (0.325 in. diameter) copper trolley wire should not vary more than 0.0004 ins. The breaking strain of trolley wire should not be less than that given in the following figures: 0 B. & S. G. (.325 in. diam.) 24 tons per sq. in. 00 24 "" (.3648 (.4096 23 (.4600 ) 23 0 S. W. G. (324 24 00 000 0000 Inches 50 Sag of Span - Wire in inches 45 40 35 30 25 20 15 10 5 0 Lbs. 200 000 0000 500 (727) 30 "" "" 40 "" "" "" Feet 1000 -80- 60 +50- (.348 (.372 (.400 120 feet 110 90• 700 span. 1,000 "" "" "" "" "" "" "" 24 ) 23 23 "" span "" "" "" Sag of transverse or Span Wire carrying longitudinal or Trolley Wire; Longi 99 "" >> and corresponding Pull on Poles Poles. "" "" "" "" 1,500 2,000 Pull on Poles in lbs. "" "" 2,500 3,000. 3,500 Fig. 109. Poles or rosettes are spaced from 110 ft. to 150 ft. apart; the limit recominended by the Board of Trade is 120 ft. For fixing the maximum sag to be allowed for span wires in spans ranging from 30 ft. to 120 ft., the curves given in the diagram, Fig. 109, are useful, showing the corresponding pull produced upon the poles by a seven-stranded steel span wire, fin. diameter, carrying in the centre of its sag a single trolley wire, 0.325 in. diameter, having a span of 125 ft. between successive span wires. INSULATORS AND LINE MATERIAL. The efficient and convenient operation of a line must greatly depend upon the use of insulators of high electrical resistance and mechanical strength. The best modern apparatus supplies every possible want. Considering the great importance of reliable and durable insulation and suspension material, its cost is a mere trifle in the total cost of equipment, and undue economy, or the selection of new and untried appliances, is most unwise. No test is worth consideration but that of long use under the same conditions of strain and climate. OVERHEAD DISTRIBUTION. 73 Table 45.-Names of Parts and Approximate Quantities of Material Used in One Mile of Line Construction. Names of Pieces Used. Straight line insulator Single pull-off Double "" Bracket arm insulator Frog ·· Plain ears or clips Strain "" Splicing Globe insulators Insulated turnbuckle pull-off 27 Crossing "" Number of poles Suspension wire in feet Trolley wire in feet ،، .. · • • • • · • • · • • · • Bracket Cross Suspen- Arm Sus- sion. pension. ·· Single Track. 46 -- •• .. Uninsulated turnbuckle.. 46 :::-2: 45 1 92 ·· Double Track. 2 : : : :8 :~: 92 92 . Single Track. 45 44 :-: ·· Double Track. · :~: 88: 8: : | 90 .. 46 90 90 3000 3000 5280 10,560 5280 10,560 • 45 45 Simple Curve. Single Track. NOT: IA∞l 3 | 44 .. .. 2 Double .. *80847 10 4 * < 4 4 3 3 11 3 12 ❤ Branch Anchor- Curve. age. ·· Single Track. | | 151 2 2 2 Double Track. ·· ION NON |~~~ INNO- 5 .. 2 15 2 2 6 1 .. 2 2 2 •• 2 1 Single Track. ~8: ||: 1 -- :| 2 Double Track. .. | | 11 22 One 200 ft. Turnout. ·· 4 1 24 11 00 | 800 800 800 800 500 500 100 200 200 4 4 2 2 Electric railway and tramway insulating material is composed of ingredients which, while still in a plastic state, form a homogeneous mass which is readily moulded under pressure. The finished product is exceedingly tough, strong, durable, and non-absorbent, impervious to water and weather, and possesses superior qualities as an insulator. It is hard, though not brittle, and is resonant when struck. It will stand an extraordinary amount of ill-treatment. British lines have employed, almost exclusively, the "West End" appliances, which received their trade name from the great West End Street Railway Company of Boston, U.S.A., where they were first made standard. The West End" type of insulators possess the following advantages:— The insulation is completely protected from rain or blows from the trolley by nieans of a metallic skirt. The insulating part is removable and interchangeable in the different forms. Ears can be soldered to wire and attached to insulators afterwards. There is a minimum leakage through moisture. The improved cap now furnished with "West End" hangers and pull-offs prevents unscrewing through vibration of the line. On each side of the cap there is a downward projecting finger, one of which is bent to engage with one of three lugs on the upper part of the body. These last lugs being equidistant, provide for locking the cap at six points in the circle. The metal is sufficiently pliable to allow of bending the finger back and forth several times to renew insulation if desired. Specification for Overhead Material. Specifications for the various forms of insulators used in trolley construction must vary with local conditions, and with the policy of the user. Specifications for Globe and Brooklyn Strain Insulators should cover the following points :- 1. All samples tested shall break in the eye. 2. The average ultimate tensile strength of all samples subjected to mechanical test shall not be less than .. pounds, and no individual sample shall show a tensile strength of less than 85 per cent. of the average tensile strength of all the samples that are tested. 3. The average breakdown voltage for samples which have been broken in the eye in the mechanical test shall not be less than .. volts, and no individual sample shall break down at less than 90 per cent. of .. volts. D2 74 SECTION 1.—THE LINE. As to the values to be specified for ultimate tensile strength and breakdown voltage, the following are suggested, where high-class insulators for use on 500-volt lines are to be specified :- 24-in. globes 3-in. globes Small Brooklyn Large Brooklyn Owing to the comparatively low softening temperature of the insulating materials generally used, and to the close proximity of the working conductor when in service, it is important that specifications for round top hangers should impose a test for softening temperature. The following "hot-rod test" is suggested :— - Round top hangers, when suspended free from draught in an inverted position by means of a bronze ear weighing 8 oz., and being 5 in. long, the ear clamping the middle of a round rod of soft iron in. in diameter and of at least 20 in. in length between connectors, must be able, without breaking down or becoming per- manently deformed by more than 1 in., to sustain a weight of 200 lb. from the cap for one hour, a current of 200 amperes being passed continuously through the iron rod, the rod being cold at the start. ·· .. .. •• ·· "" Ultimate Tensile Strength in Pounds. 6,000 9,000 9,000 18,000 .. Breakdown Voltage. ·· Fig. 110.-Fittings and Accessories. 1. "West End" Straight Line Insulator. Weight: bronze, 2 lb. 12 oz. ; malleable iron, 2 lb. 8 oz. 2. "West End" Single Pull-Off. Weight: bronze, 2 lb. 13 oz. ; malleable iron, 2 lb. 9 oz. 3. "West End" Double Pull-Off. 5. Weight: bronze, 3 lb. 3 oz. ; malleable iron, 2 lb. 13 oz. 4. "West End" Bridge Insulator. Weight, 2 lb. 12 oz. "West End" Car House Insulator. Weight, 2 lb. 12. oz. 6. "West End" Bracket Arm Hanger (Double Insulation). Weight; bronze, 8 lb. 12 oz. ; malleable iron, 7 lb. 14 oz. "West End" Insulating Bolt, 12 oz. 7. 8. Bronze Metal Feeder Plug, 1 lb. 1 oz. used when desirable to feed the current to the trolley wire through the hanger or pull-off. This plug is inserted in place of the insulating bolt. Weight, small, diameter, 2 in. "" 9, 10, and 11, “J.A." Insulators, and 12 to 15, "Boston" Insulators, are neither so reliable nor so expensive as the "West End" type, the metal em- ployed being less, and the insulation of a cheaper class. 7,000 10,000 10,000 10,000 16 represents a straight-line insulator of the "A" type, in which the ear is supported from a stud screwed into a tube imbedded in the insulating material itself. 17 shows such an insulator in section. 18, 19, and 20 show the different "A" forms. Insulators of this class should be used only on lines where first cost is the greatest consideration, for they totally lack a great advantage of the "West End” type, viz., the insulated bolt which will not allow the wire to fall even if its insulated coating be wholly destroyed. 21. Brooklyn Strain Insulator. For span wire insulation combined with turnbuckle. 6 in. slack can be taken up by two of these insulators. Made of bronze metal, eyebolt drop-forged steel. medium, diameter 233 in. large, diameter 3 in. Weight: regular size, 2 lb. 10 oz.: extra heavy, 5 lb. 12 oz. 22. Double Brooklyn Strain Insulator, Heavy. 23. Globe Strain Insulator. Bronze Metal Castings. lb. oz. 0 10 1 1 2 3 9 畢 ​4 5 6 2 3 8 31 82 33 7 84 25 26 10 11 22 28 On 35 21 24 17 27 29 30 16 Fig. 110. Fittings and Accessories. 13 雙魚 ​14 19 15 23 18 感 ​20 76 SECTION 1.-THE LINE. 睡 ​24. Globe Insulator, dotted lines show the interlocking internal metallic parts which prevent the line falling even should the insulating material be wholly destroyed. 25. Globe Frog Pull-off. Weight, 1 lb. 4 oz. 26. Combination Brooklyn Strain and Globe Insulators. 27. King Insulated Turnbuckle. A combination of span wire insulator and turnbuckle. Each turnbuckle will take up 6 in. slack. Weight, 1 lb. 14 oz, 28. Heavy Terminal Insulator. 29. Straight Under-Running Section Insulator. To divide up trolley-wire into sections. The wooden piece between terminals is renewable. Weight, 12 lb. 4 oz. 30. Brass Cap Feed-wire Insulator. This insulator is used for heavy feed-wire. The cap being removed from the top, the feed-wire is dropped in the yoke and cap then screwed on over it, holding it securely in position. Weight, 2 lb. 4 oz. 31 to 34. Guard Wire Hangers, Porcelain Insulation. Weight, 10 oz. to 1 lb. 4 oz, 35. Globe Guard Wire Insulator. Weight, 1 lb. 4 oz. Fig. 111.-Fittings and Accessories. Anchor. 38. Splicer. 39. Feeder. Bronze, 12 oz. to 18 oz. 36. Straight Line. 37. 15 in. long. 40. Combination Anchor and Splicing Ear. 41, 42, and 43. Mechanical Ears. (14 oz. and 11 oz.) Straight Under-running Trolley-wire Frogs and Crossings. These require no solder, By their use, the trolley wheel runs smoothly through branching points without "dip." 44. Two-Way Frog. Weight, 6 lb. 45. Three-way Frog. Weight, 7 lb, 3 oz. 46. Right Angle Crossing-Rigid. Weight, 5 lb. 10 oz. 47. Right Angle Crossing-Adjustable. Weight, 8 lb. 48. Diagonal Crossing-Adjustable. Weight 8 lb. 49. Insulated Crossing-Adjustable. This crossing will take an angle of 90 deg. to 75 deg. The insulated runners are renewable and provided with auxiliary metal terminals, so that the sparking is all taken by the renewable parts. A fibre hood covers the centre. 50. Head of Tubular Steel Pole, with Pole Strap and “King” Insulated Turnbuckle in place. 51, 52, and 53. Pole Straps to which to attach Span Wire. These should be painted and not galvanised. 54. Terminal (1 lb. 12 oz.) 55. “Come Along” Clamps (5 lb. 8 oz.) 56. Trolley Wire Soldering Iron. Weight, 8 lb. 10 oz. 57. Special Tool for putting up "West End" Straight Line Insulators. 58. Tool for putting up Frogs. Weight, 5 lb. 86 40 37 38 38 44 51 48 O 49 50 52 41 48 47 53 45 46 58 X 42 56 C Fig. 111. Fittings and Accessories. 54 55 f 57 78 SECTION 1.-THE LINE. · 16½º° 112 113 114 (719) 115 150 116 Frogs and Crossings. Fig. 112. Fig. 113. Fig. 114. Fig. 115. Fig. 116. Wood's Fixed Frog. Wood's Fixed Crossing. Wood's Movable Frog. Blackwell Fixed Crossing. Blackwell Trailing Frog. OVERHEAD DISTRIBUTION. 79 117 118 (82) 119 花 ​136 128 Web META BONGAOLO Web Fig. 117. Fig, 118. Fig.119. Leather Washer WINDERS Whanga Insulator, Pull-Off and Splicing Sleeve. 午 ​Cap and Cone Insulator. Anderson's Double Pull-Off. Wire Splicing Sleeve. to 80 SECTION I.-THE LINE. Fig. 112. Wood's Fixed Frog. Fig. 113. Wood's Fixed Crossing. Fig. 114. Wood's Moveable Frog. Fig. 115. Fig. 116. Blackwell Fixed Crossing. Blackwell Trailing Frog. These fixtures are specially adapted to the side trolley system. Fig. 117. Cap and Cone Insulators. Fig. 118. Section through Anderson West End Double Pull-off. Used for light work. Straight line hanger; single and double pull-off bracket-arm hanger. Fig. 119. Wire Splicing Sleeve. Fig. 120. Wire Stretching Device. Kessleretta il Fig. 120. Wire Stretching Device. Used when necessary to take tension of trolley wire, as in splicing or inserting switches, frogs, &c., &c. Weight 79 lb. The line material, &c., above described and illustrated, are all standard shapes and sizes, and made by all manufacturers of these goods. As illustrating the qualities of good insulating material, the following tests are quoted :- TESTS FOR TENSILE STRENGTH. (Nos. 23 and 24, page 75.) (Made at Boston, U.S.A.) Globe Strain Insulators, “Aetna” Insulation Bronze Castings. Small globe broke under a load of 3700 lb. Eye stretched out and one eye broke open. The insulation did not break. Medium globe broke under a load of 5000 lb. insulation broke. Eyes stretched out and Large globe globe broke under a load of 7300 lb. insulation broke. Eyes stretched out and Globe Strain Insulators, "Hecla " Insulation Bronze. Eyes stretched and one broke. Eyes stretched and insulation Eyes stretched and insulation Small globe broke under a load of 4503 lb. Insulation just started to crack. Medium globe broke under a load of 5400 lb. broke. Large globe broke under a load of 7000 lb. broke. Globe Strain Insulators, “Hecla” and Malleable Iron. First, small globe broke under a load of 4900 lb. Insulation broke. Second, small globe broke at 5500 lb. First, medium globe broke at 7200 lb. Second, medium globe broke at 8300 lb. Third, medium globe broke at 7800 lb. OVERHEAD DISTRIBUTION. 81 Tests on “Aetna” Globe and Turnbuckle Strain Insulators. Made for the late Dr. John Hopkinson, F.R.S., on material used on Liverpool Corporation Electric Tramways. The first globe started drawing at a load of 45.0 cwts., equal to 5040 lb., and broke through the eye at a load of 48.2 cwts., equal to 5398 lb. ; the metal at fracture being sound. The other started drawing at a load of 40.8 cwts., equal to 4562 lb., and broke through the eye at a load of 41.9 cwts., equal to 4693 lb. ; the metal at fracture was ´sound. Remarks. Broke across screw, metal at fracture sound. Three "King" turnbuckles were also tested with the following results: Maximum Load. 83.5 cwts. 9350 lb. 86.6 9697 "" 87.0 9742 "" In every case the insulating material started flaking off at a load of from 65 to 70 cwts., but the insulation in no case was forced entirely out. "" "" No. of Insulator. I2MSH LO CO "" "" 1 · 3 Tests of Small “Ætna” Globe Insulators. (Testing Department, Brush Electrical Engineering Company, Limited.) This is a sphere of insulating material, on the opposite sides of which are two brass eyes. 4 The insulation resistance of this could not be measured by the deflection method, and may therefore be taken as co. 5 ·· 6 .. 6000 volts were also placed across it, without the slightest sign of breaking down the insulation. "" By means of a lever and weights, it was submitted to a tensile strain of 3000 lb., which did not affect the insulating material, 09 Tests on Brooklyn Strain Insulators, Smaller Size. (By Massachusetts Electrical Engineering Society.) These insulators were submerged in salt water for twelve days by the wreck of the steamer "H. M. Whitney," which was sunk in Boston Harbour. Insulation Resistance.-Column 1 gives insulation resistance in megohms on the day of removal from the wet hay in which they were taken from the wreck, Table 46,-Insulation Resistance of some "Etna" Insulators. 1 Insulation Resistance First Day. 160 m.o. 580 m.o. 550 m.o. 34,000 m.o. 250 m.o. 600 m.o. 1 "" "" 2 Insulation Resistance after Washing. 8,000 m.o. 33,000 m.o. 36,000 m.o. 220,000 m.o. 110,000 m.o. 3 Insulation Resistance after drying Ten Days. 25,000 m.o. 60,000 m. o. 100,000 m.o. 300,000 m.o. 100,000 m. o. 300,000 m.o. the outer surface having been merely wiped over to remove the dirt; column 2 gives the insulation resistance after washing the surfaces with water, and allowing the insulator to dry four days; column 3 gives the same after drying ten days. Tensile Strength.-Insulator No. 5 was tested for tensile strength, and broke under a load of 7280 lb., giving way round the circumference of the metallic head. Medium size Globe Strain Insulator tested for insulation resistance found to be 156,000 megs. at a temperature of 70 deg. Fahr. While the standard size of "West End" insulators fill every need of the average tramway, heavier and stronger types have been developed. In tramway practice these are desirable when extra heavy trolley wire is to be used, and where sharp curves and taut construction occasion extraordinary strains. The late Mr. John Hopkinson, F.R.S., specified for lines constructed under his 82 SECTION I.-THE LINE. care at Liverpool and elsewhere, insulators of at least 50 per cent. greater mechanical strength than is usual, 3/0 B. & S. trolley wire being employed. For high-speed electric railways a still heavier and stronger line of "West End" material is used; and as it is essential to high-speed work that nothing should give the trolley-wheel a tendency to leave the wire, very heavy "Fig. 8" wire has been employed (6/0 B & S.), with mechanical clips which grip the upper side of the "8," thus leaving the under surface of the trolley wire wholly free from all unevenness. This has not proved very satisfactory in practice, and better results have been obtained with a heavy circular wire with grooves cut in the upper surface by which the ear can grip it. Mechanical clips of many kinds have been tried, but so far none have proved nearly as efficient as the soldered ear. It is, of course, very much quicker and easier to put up a trolley wire with mechanical clips. Ears are made of every length from 4 in. to as many feet for special work and strains. Very long and stiff ears are used to ease sharp curves in the trolley wire. Where the side-trolley system of suspension is employed, a series of special frogs and crossings have been developed to run with the swivelling trolley. These are of great value in securing effective operation. Figs. 112 to 114 show some frogs and crossings designed by Mr. William Wood, the engineer in charge of the Bristol Electric Tramways. Figs. 115 and 116 show a 16 deg. trailing frog and crossing designed by Messrs. Blackwell & Co. Splicing tubes are chiefly used to connect the ends of broken wires quickly, to minimise the interruption of traffic during breakdown. On no account should they be used on running lines. POLE PLANTING AND RAKING. In ordinary soil, poles should be set 5 ft. to 6 ft. deep, the holes being 6 in. deeper, and the lowest 6 in. filled by a concrete block made previously, on which the pole is rested to prevent sinking. The hole should, under average conditions, allow 6 in. of concrete all round the pole, and the walls of the hole should be vertical, not sloping. Where the ground is soft, 12 in. to 18 in. of concrete all round the pole may be necessary. When sunk in rock, holes 4 ft. 6 in. to 5 ft. deep are sufficient. On straight lines bracket poles should have a backward rake of not less than 3 in. for arms up to 10 ft. This rake must be increased for longer arms or soft ground. Span poles in good ground require a rake of 6 in. to 8 in., and pull-off and anchor poles from 12 in. to 24 in. The raking of poles should always be carried out by experienced men, as it is impossible to lay down a fixed rule varying conditions of ground. to meet the Table 47.-Weight of Different Woods. Name of Wood. Dry Ash Red cedar Dry chestnut Live oak Dry white oak White dry pine Yellow dry pine Spruce Black walnut Beech.. Elm ·· .. • per Weight Cubic Foot in Pounds. 47 65 41 59 44 25 45 25 38 48 37 Tensile Strength in Pounds per Square Inch. 16,500 Endwise Crush- ing Strength in Pounds per Square Inch. 12,000 6,000 6800 12,000 7000 8,000 5400 10,000 8500 10,000 4500 7000 7300 Sidewise Crush- ing Strength in Pounds per Square Inch. 3000 4000 1200 2600 1200 1900 2600 Transverse Strength in Pound per Sq. Inch. 650 600 800 450 850 Splitting Strength in Pounds per Square Inch. 1 550 550 500 OVERHEAD DISTRIBUTION. 83 The best quality wooden poles are chestnut, cedar, or Georgia pine. The poles used must be free from shakes, checks, or large knots. The following is a suggested specification for cedar poles :- All poles to be cut of white live cedar, peeled, sound at top and not more than 15 per cent rot at butt; base area to taper gradually and be free from large knots; a crook of in. to 5 ft. in length will be allowed. Poles must be free from wind twists and large cracks, and measure :- Length. 12 ft. 6 ft. from Butt. 7 in. 20 ft. 8 in. 25 ft. 10 in. 30 ft. 14 in. 35 ft. 14 in. 15 in. 16 in. 17 in. 18 in. 40 ft. 45 ft. 50 ft. 55 ft. 60 ft. 65 ft. 70 ft. ft. 27 27 27 28 28 28 28 30 30 30 30 30 Length. Diameter. in. in. 6 x 8 Wooden Railway Poles (not creosoted). 7X 9 7 X 9 .. 7 X 9 7 × 9 8 x 10 8 × 10 7 X 9 7 X 9 8 x 10 8 x 10 9 x 12 .. Table 48.-Sizes, Weights, and Strains of Wooden Poles. Section. Circular "" Octagonal Circular Octagonal Circular At Top. 4 in. 5 in. 6 in. 8 in. 7 in. 7 in. Octagonal Circular 7 in. 7 in. 7 in. 7 in. 7 in. 7 in. Octagonal Circular Octagonal "" Cubic Feet. 7.36 9.56 10.10 9.92 10.46 12.52 13.20 10.63 11.21 13.41 14.15 19.06 •• Best American Yellow Pine or Cedar. Approximate Weight in Pounds. 360 to 450 450 560 620 500 490 600 520 650 620 750 650 800 530 670 560 700 660 820 700 850 900 1150 " "" "" "" "" "" "" "" 20 in. 20 in. 21 in. "" "" "" Approximate Strain Pole will Stand in Pounds with 7-in. De- flection.* 350 500 500 500 500 750 750 450 450 700 700 850 * For Baltic wood poles allow about 80 per cent. of figures given. In Great Britain none but mild steel or iron tubular or conical poles are used. For the sake of appearances it is as well to have wooden poles as straight as possible; not more than 5 in. per 10 ft. in length deviation from the straight should be permitted. The pole should be allowed to season with the bark on if exposed to the weather, otherwise it will develop cracks running parallel to the trunk, which tend towards rotting. Chestnut poles are considerably weakened by being trimmed into special shapes. as this cuts up the surface sap wood. Where poles cannot be left naturally, hard pine is the best wood to use. Cedar poles are neither so tough or so strong as either hard pine or chestnut. Some authorities consider it inadvisable to use cedar for poles exceeding 50 ft. in length. + 84 SECTION 1.-THE LINE. I + The following figures show the strains which ordinary average round wooden poles may be expected to stand without deflecting more than 7 in. Diameter at Bottom. Diameter at Top. in. Approximate Strain in Pounds. Chestnut. Cedar. 420 380 550 490 720 590 B 4250.8 in. 10 11/ 12/ 121 2-2 Length in Feet. 30 35 41 123 Figs. 121 to 124. Construction of Poles. 122 124 Poles.-General. Upon the amount of sag allowed for the span-wires depends the strain which the side-poles must stand. Round curves these strains are often great, and tubular In the poles composed of ordinary pipes wedged together by liners are useless. following pages are given data of standard poles specially designed for this work. All poles must be of such strength that when in position they will stand, without permanent set, the greatest side strains to which they may be subjected. Terminal poles and pull-off poles on curves should be the strongest. Ordinary side poles must stand a direct strain of at least 750 lb. without deflecting more than 6 in. Their strength must be sufficient to carry, besides the trolley wire itself, the additional weight when the wires are covered with ice and snow. The poles are always subject to vibration communicated by the trolley wire. It is of the utmost importance that joints should be well constructed; which renders it necessary that the several lengths of the pole should be joined together as shown in Fig. 121, The joint is made by heating the outside pipe to a welding heat, slipping it over the inner pipe, and then passing the two together through special rollers. After completion, if a piece is cut from the joint, between A and B, the two pipes will be found practically welded together, the joining line, A B, having entirely disappeared. The tubes used in making these poles are lap-welded. The lengths of pipe are so put together that the seams of each consecutive length are 120 deg. apart when the poles are made in three lengths, as is generally the case, Figs. 121 to 124. If OVERHEAD DISTRIBUTION. 85 joints are not so made, the pole, instead of bending uniformly, after a short time gives at the joints. Poles constructed with proper joints can be accurately calcu lated to stand any determined strain without exceeding a fixed temporary or permanent deflection, This is not possible with other joints, which always give trouble sooner or later, The following is a specification of standard poles :- British Standard Specification for Tubular Tramway Poles. 1. The poles shall be of mild steel free of all defects, and shall be of three classes: light, medium, and heavy poles. 2. The sectional poles shall be either solid-drawn, or lap-welded wrought steel, free of all defects, made up in three sections, swaged together when hot so as to make a perfect joint. The lap-welded seams in the sections shall be set at an angle of one hundred and twenty degrees (120 deg.) to each other. The taper poles shall be of wrought steel, free of all defects, rolled in one length and butt-welded the entire length. The butt-welding shall be carried out at an even temperature without overheating, and no pole shall show any signs of burning at the weld. 3. The overall length of poles of all classes shall be thirty-one feet (31 ft.). 4. The length of the telescope joint in the sectional poles shall be eighteen inches (18 in.). 5. The length of the sections shall be :~ Top section Middle section Bottom section Class. Light Medium Heavy Class. Light Medium Heavy ·· 6. The outside diameters, in inches, of the three classes of both sectional and taper poles, shall be :- SECTIONAL POLES. Light Medium Heavy .. ·· ·· Top. in. · ·· .. TAPER POLES. Top. in. 433 Middle. in. 61 8131415 T Load in Pounds for Temporary Deflection not exceeding 6 in. lb. 750 1,250 2,000 ·· 7. The thickness of metal in any pole shall not be less than one-quarter of an inch (in.). 8. The completed poles shall be straight and true over their entire length to within one quarter of an inch (in.). 9. The section of any pole shall be as nearly circular as possible, not varying in diameter more than one-sixteenth of an inch (1 in.) from the adopted standard. 10. Five per cent. (5 per cent.) of each class of sectional pole shall be subjected to the following drop test: The pole shall be dropped vertically, butt downwards, three times in succession, from a height of 6 ft., on to a hard wood block, 6 in. thick, laid on a concrete foundation, without showing any signs of telescoping or loosening of joints. ft. in. 11. Five per cent. (5 per cent.) of each class of both sectional and taper pole shall be subjected to the following bending tests: The pole shall, in each case, be rigidly supported for 6 ft. from the butt, and loaded, as a cantilever, eighteen inches (18 in.) from the top, the load being applied at right angles to the axis of the Pole, which shall be fixed horizontally. Upon the application of the following loads in pounds, the temporary deflection and permanent set, measured at the point of application of the load, shall not exceed the figures stated in the Tables. Class of Pole. 5000 in. 74 81 9 •• 8 6 8 6 17 0 Outside Diameter 9 ft. 6 in. from Base. Bottom. in. 7 8 Load in Pounds for Permanent Set not exceeding ½ in. lb. 1,000 1,750 2,500 86 SECTION I. THE LINE. 12. In the event of any pole of the above-mentioned five per cent, (5 per cent.) not fulfilling the test requirements, a further five per cent. (5 per cent.) shall be subjected to the tests enumerated above. Should any further failure occur, the whole parcel from which the poles have been selected shall be liable to rejection. 13. The maker, at his own expense, and to the satisfaction of the engineer, shall provide all the necessary testing apparatus at his own works, for carrying out the above-mentioned tests. Table 49.-English Conical Steel Tramway Poles. Diameter Outside. Bottom. in. 6 6 7 7 50000000 10 Top. in. 31/1 ' << 03 4 3/1/ 4 HEBELL HK-A 4 4 5 5 Thickness. ft. in. ft. Length 18 6 to 20 lb. lb. Weight 340 to 420 in. Length Weight Length. ft. 31 31 29 31 31 31 31 31 31 31 31 Outside diameter in inches of bottom section of pole Weight of each base in pounds Weight of finial.. Weight of pole joint rings 2 .. 31 · Approximate Weight of Pole. lb. 530 510 These poles are made from one plate, half the length being parallel and remain- ing half tapered. 600 620 720 Bracket Arms. (Figs. 125 to 147, pages 88 to 92.) Great care should be taken that all castings used to fix the scroll work are malleable, or strengthened with wrought-iron U bolts, and accurately fit the pole and bracket-pipe, and that stay rods, where required, are adjustable. All brackets up to 6 ft. length have no stay rods as a rule. From 6 ft. 6 in. and up to 12 ft. 6 in. or 14 ft., one stay. Over this length, two stays. These stays are made of 4-in. to 4-in. rod, according to the length of the arm. Where centre poles are used, refuges with pillars on each side are often required. Where refuge pillars are not used, a small cast-iron guard can be put round the centre pole. 900 940 800 960 1100 1100 1350 Weight of Side Brackets. ft. in. ft. in. 12 6 to 16 6 lb. lb. 300 to 380 Weight of Double Brackets. 8 ft. to 10 ft. 6 in. 300 lb. to 350 lb. ft. ft. in. 8 to 10 6 Ib. lb. 210 to 290 Approximate Strain Pole will Stand. ft. in. 7 0 lb. lb. 180 to 260 Table 50.-Weights of Standard Bases. (Robert W. Blackwell and Co.) 5 ft to 7 ft 6 in. 190 lb. to 280 lb. iske o lb. 550 500 700 700 1000 1200 1250 1400 1500 1700 2000 2300 78 10 8/9/ 380 to 450 295 to 350 240 to 290 ft. in. 6 0 lb. lb. 170 to 250 65 220 to 260 Table 51.-Sizes, Weights, and Deflections of Steel Poles. These poles consist of three parallel sections of lap-welded steel tube, shrunk together, and are made from Siemens-Martin steel, having a tensile strength of 24 to 28 tons per square inch, and an elongation of 20 per cent. in 8 in. Length of pole, 31 ft., when shrunk 18 in. at each joint. Butt planted 6 ft., and weight applied; also deflection measured 18 in. from end. The Elastic Limit is reached under the various weights where the Table of Deflections stops. BottomSection, 17 ft. 0 in. Thickness. O.D. O.D. kocok k | Thickness. − − − − 98 Sizes of Poles. in. in in. in in. in 102 9 109 109 103 9 102 9 10 98 9 9 9 8 10 10 8 10 8 108271023 101 88 9§ 18 98 8 Middle Section, 9 ft. 6 in. MojOO Kojos Vol3D VOĴOGO LO’GD KOŠOD MOŠTO KOŠKO KOPO KOJOO ∞ ∞ ∞ ∞ AB XO AQ 00 00 00 NTNE 7 7 0000000000000000 7/22 78 11 7 6 Lojas kalan Kajao katon vajao kojao kojao kojao volan kakao voĴOO ~~~~~~~~∞ ∞ ∞ ∞ ∞ ∞ ∞ ∞ ∞ ∞o no ∞ ∞ ∞ 76 68 11 5 65% 5,1% 51% оптово Андо Top Section, 7 ft. 6 in. Long. -430-450**** O.D. -** 1798 7 8 1604 71424 71242 73 1067 78 1694 71510 Weight of Poles in Pounds. * | Thickness. 18 7927 7 1472 71299 71141 998 853 2.275 1.869 1252 1099 2.107 MOĴOD LOĴOD KOŠKO 4 4 4 *H 5804 5729 58 5% 658 5% 584 5 663 18 32 NHA 967 792 700 600 532 | 8 .931 1.022 1.141 1.302 1.484 1.141 1.260 1.620 2.160 2.880 3.600 5,040 1.791 2.388 3.184 3.980 5.572 7 1171 1.582 2.034 2.712 3.616 | 4.520 | 6.328 7 1342 1.393 1.792 2.304 3.072 4.096 5.120 2.511 3.348 4.464 5.580 1.953 1.372 10/1 900 Load in Pounds. 。 | 3 681193 61069 6g966 885 6756 962 846 770 3.773 4.851 6.468 694 4.165 5.355 7.140 5.247 6.996 5.706 7.608 6.246 | 8.328 616 558 498 435 9.611 524 10.374 50 | 10 1200 1600 4.081 4.438 4.858 5.383 6.921 5.845 7.515 6.391 8.217 7.063 9.081 7.182 9.234 7.749 8.575 00 | 3 2000 1.526 1,722 1.967 2.529 3.372 4.496 | 5.620 2.925 3.900 | 5.200 2.403 3.204 4.272 5.340 2.709 3.612 | 4.816 | 6.020 2.345 3.015 4.020 5.360 6.700 2.821 3.627 4.836 6.448 2.135 2.745 3.660 4.880 6.100 2.373 3.051 4.068 5.424 6.780 2.597 3.339 4.452 | 5.936 2.800 3.600 4.800 | 6.400 3.234 4.158 5.544 7.392 3.094 3.978 5.304 7.072 3.479 4.473 5.964 7.952 00 | 36 1.764 2.3523.136 | 3.920 | 5.488 1.962 2.616 3.488 4.360 6.104 2.214 2.952 3.936 4.920 2800 Deflection in Inches. | 1.197 1.596 | 2.128 | 2.660 | 3.724 | 4.788 | 5.985 1.314 1.752 2.336 2.920 4.088 5.256 1.467 1.956 2.608 3.260 4.564 5.868 1.674 2.232 2.976 3.720 5.208 1.908 2.544 | 3.393 | 4.240 5.936 1.467 1.956 2.608 3.260 4.564 5.868 3600 10 | 42 Permissible variation in deflection equals 5 per cent. more or less. 4500 88 SECTION 1.-THE LINE. प्र ل. ② (145) .N D 125 M E ★... ¿ N 126 *..M K--- E N P Figs. 125 and 126. Designs of Single and Double Bracket Arms. (See page 86.) #0 OVERHEAD DISTRIBUTION. 89 8 ! 3' D · 0,08 128 V43 130 131 6 TOD Wire 129 127 1 Guard wire attachment 132 FISCINE ZHIT. Poles and Brackets. Fig. 128. Fig. 129. Fig. 180. Fig. 131. Fig. 132. Fig. 127. Bracket for Coventry Electric Tramways. Pole for Douglas (Isle of Man) Southern Electric Tramways Bracket, with Flexible Suspension, Liverpool Tramway. Standard Type of Flexible Suspension. Top of Pole for Arc Light, Liverpool. Ornamental Bases for Poles. 90 SECTION 1.-THE LINE. waj 133 134 * · 0. RBXD 137 135 136 138 Ol &ER 30 139 Poles and Brackets. Fig. 133. Bracket for Douglas (Isle of Man) Southern Electric Tramway. Fig. 134. Standard Pole and Setting. Fig. 135. Standard Double Bracket. Fig. 136. Bracket and Arc Light Top; Bristol Electric Tramway. Figs. 137 to 139. Ornamental Bases for Poles. OVERHEAD DISTRIBUTION. 91 140. Standard Flexible Suspensions. Double Trolley Single Bracket Type. (FIGS. 140 to 147, see page 92.) (Robert W. Blackwell and Co.) 5 OM 345 141 142. 5 Пост TYPE ES." FOR STRAIGHT LINES tho Om 246 143 +0000 TYPE "EC" FOR CURVES IAA S 5 tomm (155) Figs. 140 to 143. Types of Trolley Wire, Suspensions on Bracket Arms. The flexibility is obtained by arranging a small span on the end of the bracket arm, and using straight line hangers or pull-offs in the same way as on the span- wire system. They are arranged as shown, with or without guard wire attachment. Flexible suspensions are now nearly universally used in Great Britain. 92 SECTION 1.-THE LINE. T с 144. CN 349 145 5 ban 146. OM 350 147 TYPE FS." FOR STRAIGHT LINES TYPE "FC "FOR CURYES Jha (756) BU A Bo Figs. 140 to 147. Types of Trolley Wire, Suspenders om Bracket Arms. OVERHEAD DISTRIBUTION. 93 ! 169 LINE ERECTION. (Fig. 148.) A trolley wire erection gang usually consists of one foreman and twelve to thirty men, who dig holes in which poles are to be set. Before commencing, the poles have been left along the road approximately in their proper places. Another .. ت M # → CLEANSE Fig. 148. Tower Wagon for Line Erection. gang, consisting or one foreman and five or six men, follow to plant poles. They should put up from twenty to fifty poles a day, according to location and nature of ground. When the poles have set five to eight days, the wire gang follows. To hang the wire a tower wagon is employed, generally a special waggon, on which is a strong scaffolding with a platform and railing at the top, reached from the 94 SECTION I.—THE LINE. ground by means of a ladder forming one or more sides of the scaffolding. Fig. 148 shows such a waggon as used in England. Tower wagons are also used which have an adjustable ladder and platforms, and sufficiently wide gauge to stand astride the tracks. When necessary to change position, ladder and platform are let down. Beneath the driver's seat and on the body of the wagon, tool-boxes are provided. In front of the tower wagon, a wagon drawn by one or two horses carries the reel on which the trolley wire is wound in mile or half-mile lengths. The wire-gang generally consists of one foreman, two drivers, three or four labourers, and two or three wiremen. Such a gang should string from 3 to 1 mile of double-track cross-suspension a day, and about mile double bracket-arm suspension a day, when mechanical clips or ears are used, If soldered ears are used-and this is the best practice-the same gang will, in the case of cross- suspension, only do from to mile per day of ten hours. The above, of course, only applies to straight line work which can be done by day, or with special "Wells" lights at night, and without adopting special precautions so as not to hinder street traffic. A double curve on a double track takes one driver, three to four labourers, and two or three wiremen, from two to six days to put up. Soldered ears or clips have always to be used on curve work, if it is to be well done. The modus operandi is generally as follows:-- In case of cross-suspension, the cross wire is first put up and made taut, being attached to the pole heads by means of strain insulators fixed to the poles by iron straps. An insulated turnbuckle is generally used for these points. The span wire is strained into position by fixing a single block and fall to the wire, by means of a "come-along clamp." The tension should be about 500 lb., and two men can generally exert that strength. While still under strain it is attached to the turn- buckle, and any slight slack remaining taken up. When span wires are in place, the trolley wire is in turn hung. It is first anchored securely at the end of the line; half a mile is run out, or as much as can be done without hindering traffic. Hooks of stiff iron wire, bent in S form, are hung over the span wires near the middle, and the trolley wire is raised over the tower wagon and hung in these hooks. At the end of the unreeled part of the trolley wire a "come-along clamp" is fixed, and by means of a double block and fall, the part hung is pulled up tight and temporarily anchored. Whenever a curve is reached, a temporary anchorage is made at each end of the curve, and as much slack allowed as may be needed to get around. On curves the trolley wire should be placed slightly over the inside of the curve and not over the centre. After this is done, the ears or clips are fixed to the wire. Soldering. Great care should be taken in soldering, and each ear should be carefully inspected to see that it is milled out perfectly smoothly and is well tinned. Before B A D 2738 R Fig. 149. Diagram for Position of Line Switch. the ear is put on, the wire should be thoroughly cleaned with emery paper for a distance slightly more than the length of the ear. The U-shaped soldering clamp should next be attached firmly to the wire, the body of the clamp being held OVERHEAD DISTRIBUTION. 95 vertically over the wire. The wire is then twisted by allowing the clamp to turn over until the back rests on the floor of the wagon. The ear should then be placed on the wire, boss downwards, and its edges should then be hammered over carefully and evenly along the whole length. The flux should then be applied, and the solder poured well in by means of a ladle and melting-pot. A frog or line switch on centrally-strung wire should not be put up in line with the track points, but as shown in Fig. 149, that is to say, over the centre of gravity of the triangle A B C; in many cases, however, the frog may have to be moved forward several feet. If on trial its position should not prove quite satisfactory, the trolley wheel should be chalked and run over it, so as to see where it runs off, and the frog set right. For this purpose turnbuckles are put on the end of the wire, from which the frog is suspended. All the preceding applies to putting up a line with bracket-arm suspension, the only difference being that the ears through which the trolley wire is first passed are hung on to the bracket-arms (e.g. Nos. 6 and 15, page 75), instead of the span wires (e.g. Nos. 1 and 9, page 75). Guard Wires. (FIGS. 150 to 160, page 96). Where telephone or other wires cross the trolley wire, guard wires are some- times hung over the trolley wire to prevent a short circuit, in case of one of these cross-wires breaking and falling. If there is a single line of track, two guard wires are employed, which are hung about 18 in. to 2 ft. above the trolley wire, one on each side. These must be insulated from the poles. These guard wires are much more unsightly than the trolley wire, and as often as not cause as much trouble as falling telephone wires. If they are not very strong, the weight of a falling wire frequently causes them to break. To a great extent guard wires have been abandoned in America. Where a large quantity of wires cross the track, a guard wire netting is sometimes used, A substitute for guard wires consists of pentagonal wooden strips about 20 ft. to 30 ft. long, fixed to the trolley wire by means of clips, which are spaced 3 ft. 6 in. apart, and let in grooves. A hook also is used to prevent a fallen wire sliding off the ends of the wood strip on to the trolley wire. At insulators the strips are cut short, and a protecting bridge is formed by bending two iron wires upwards, apart and fixed to the wood. This method is still largely adopted on the Continent, but has been discarded in England. In Germany the telegraph and telephone wires, where crossing trolley wires, are made up of small collapsible sections not long enough to reach from trolley wire to ground, and joined together; or where a perfect contact is essential, a lead bond is used-which will give way when left to support any strain. Mr. Ulbricht's (Zwickau) device is said to be working satisfactorily. The instant a telephone wire falls and comes in contact with a trolley wire, an electro-magnetic relay is brought into action, causing a permanent short circuit to earth of the trolley wire, and prevents the automatic circuit-breaker at the power station being replaced until the fallen telephone wire is removed. An earth loop protects the telephone and telegraph instruments, by shunting the large currents to earth, and by making their protective fuses go. To prevent arcing, metallic caps should be avoided in these fuses, cork or sealing-wax being used. For suspending the guard wires, a very neat device has recently been brought out by Messrs. Blackwell and Co. The bolt is slotted so that the wire can be at once placed in position, and all that is required to secure the clamp is to put on the washer and tighten the nut. They are made in three types, for straight lines, single pull-off, or double pull-off. Board of Trade Regulations for Guard Wires on Electric Tramways. Efficient guard wires shall be erected and maintained at all places where tele- graph or telephone wires unprotected with a permanent insulating covering cross above, or are liable to fall upon, or to be blown on to, the electric conductors of the tramways. EXPLANATORY MEMORANDUM. (Note. The expression "telegraph wire" includes all telegraph and telephone wires.) Each guard wire must be well earthed at one point at least, and at intervals of gga 96 SECTION I.—THE LINE. : J 4 150 151 152 -8- 153 154 **-8*-* 1 O 8= (724) * 8" LA M 155 * 8° *· 8ˆ* MIN. 24 - ANY DISTANCE - de la qua DE NIW ·8: 8 UP TO 15- MIN.24 OVER 48° MIN 24 OVER IS "AND UP 7848 *-> Mi ca va MIN 24" MIN 24* 156 HOOK *2* 1 1 30" MAX t HOOK HOOK 2 30 MAX ANY DISTANCE GUARD WIRES GUARD ·8 GUARD WIRES TROLLEY WIRES TROLLEY WIRES マン ​157 30" MAX 158 TROLLEY WIRES XC WIRES 159 160 OVERHEAD DISTRIBUTION. 97 not more than five spans. The resistance of earth must be such that a short circuit between a guard wire and a trolley wire will open the circuit-breaker, and this resistance should in no case exceed one ohm. The earth connection should be made by connecting the support to the rails by means of a copper bond. When first erected, the resistance to earth of the guard wires should be tested, and periodical tests should be made to prove that the before-mentioned resistance of 1 ohm is at no time exceeded. Guard wires should be, in general, of galvanised steel, but in manufacturing districts in which such wires are liable to corrosion, bronze or hard-drawn copper wires should be used. The gauge of the guard wire must be such that it will carry, without fusing, a current 50 per cent. greater than that required to open the circuit-breaker, and the guard wire must be maintained in such a manner that it will at all times meet these requirements. The supports for the guard wires should be rigid, and of sufficient strength for their purpose, and at each support each guard wire must be securely bound in or terminated. The rise of the trolley boom should be so limited, that if the trolley leaves the wire it will not foul the guard wires. For the purpose of this regulation, telegraph lines are divided into two classes, namely:- (a) Wires weighing less than 100-lb. per mile. (b) Wires weighing 100-lb. or more per mile. Minimum guarding requirements for Classes (a) and (b) are shown hereunder, but in exceptional cases, such as in very exposed positions, or for unusually heavy telegraph lines, special precautions should be taken. CLASS (α).—WIRES WEIGHING LESS THAN 100-LB. PER MILE. The guard wires may be of the cradle or hammock type, attached to the arms of telegraph poles. It is necessary that the spans should be short; and if required, additional pole or poles should be set. ORDINARY PARALLEL GUARD WIRES. 1. Where there is one trolley wire, two guard wires should be erected (Fig. 150), 2. Where there are two trolley wires any distance apart, two guard wires should be erected (Fig. 151). SPECIAL GUARD WIRES. 3. In special cases, at junctions and curves, where parallel guard wiring would be complicated, two guard wires may be so erected that a falling wire must fall on them before it can fall on the trolley wire. CLASS (b).—WIRES WEIGHING 100-LB. OR MORE PER MILE. 4. Where there is only one trolley wire, two guard wires should be erected (Fig. 152). 5. Where there are two trolley wires not more than 15 in. apart, two guard wires should be erected (Fig. 153). 6. Where there are two trolley wires and the distance between them exceeds 15 in., but does not exceed 48 in., three guard wires should be erected (Fig. 154). 7. Where the distance between the two trolley wires exceeds 48 in., each trolley wire should be separately guarded (Fig. 155). Classes (α) and (b).—TELEGRAPH WIRES PARALLEL TO TROLLEY WIRES. 8. Where the distance between a telegraph wire and a trolley wire is 10 ft. or less, and the highest telegraph wire is at the same height as, or higher than, the trolley wire, guard wires should be fixed as shown in Figs. 156 and 157, the guard wires being erected on the side nearest the telegraphs. Multiple insulated cables erected parallel to trolley wires will not require guard wires. 9. Where the distance between a telegraph wire and a trolley wire is more than 10 ft. and less than 30 ft., and the highest telegraph wire is at a height greater than the height of the trolley wire by one half, or more than one half the lateral distance between the telegraph and trolley wires (the lateral distance being the distance measured horizontally between the vertical planes in which the trolley and the nearest telegraph wires are respectively erected), guard wires should be fixed as shown in Figs. 156 or 157. 10. Where there is a line of telegraphs on each side of the tramway trolley E 98 SECTION I.-THE LINE. line, guard wires should be provided as shown in Figs. 152 to 155, except that the maximum height of the guard wires should be 30 in. 11. When the telegraph wires are of such a height relatively to the trolley wires as to make it possible for a broken wire to fall on an arm stay or span wire, and so slide down into proximity to a power wire, guard hooks should be fitted as shown in Figs. 158 to 160. In the case of span wire construction, if there is a telegraph line on each side of the tramway trolley line, a second hook should be fixed at x in Fig. 160. It is desirable, where possible, to divert telegraph lines from above trolley junctions and trolley wire crossings, and undertakers should endeavour to make arrangements to that effect with the owners of telegraph wires. No tramway pole, span wire, or trolley wire may be erected laterally within 3 ft., or vertically within 6 ft., of a Post Office telegraph wire. Induction Troubles. Induction troubles due to variable impulses of currents are proportional to the strength of current, and inversely to the distance. When telephone wires are over 200 yards away, little or no trouble is experienced. When the trolley and telephone wires are parallel the troubles are objectionable. Table 52-List of Tools for Line Erection. Trolley wire cutters. 2 Hammers, 2 lb., and stone hammers: 2 Sledges, 12 lb. Chisels. Files. 3 Draw vices. Tool for putting up frogs. 1 Tool for putting up straight line hangers. 1 Reel wagon. 1 Fixed tower wagon. 1 Collapsible tower wagon. Digging tools, twelve to twenty-four sets, consisting of :- 1 Digging bar, 8 ft. 6 in. long, octagonal steel tool. 1 Digging bar, 5 ft. long. 1 Augur, 5 ft. long, 15 in. over blade. 1 Augur, 7 ft. 6 in. long, 15 in. over blade. Spanner, Clyburn. 12 Rope and blocks, 4 in. rope. 2 Hack saws and blades. 1 Spoon. 1 Plumb line. 1 (Grafting tool) Spade with extra long 12 "Come along" clamps. handle. 1 Special lever for pole setting. 1 Right- and left-hand strainer and coupling screws. 6 lb. of solder per mile of single wire. Steel tape measure. 12 Picks. 12 Shovels, No. 4. 4 Rammers. 4 Soldering irons. 2 Soldering pots. 1 Brazier, or fire-devil. 2 Clamps soldering, 3 ft. 6 in. between jaws. Plyers, 7 in. and 8 in.; gas, 8 in. 2 Ladders, rungs 9 in. apart, 24' ft. · long. Acid jug and charcoal. Vice. Screwdriver. PART IV.-FEEDERS. VARIOUS TYPES OF CABLES. (FIGS. 161 and 162, page 100.) Feeders may be suspended in the air, in which case they are supported on insulators, and are only covered with a waterproof covering, which is sufficiently insulating to prevent shocks being sustained by workmen handling them. Such feeders are usually made of hard-drawn copper wire, so as not to require steel suspension wires. Feeders which are laid underground must have a good insulating covering, as well as one to preserve them mechanically, the strength and quality of the latter depending upon how the cables are laid. Cables can roughly be subdivided as follows, according to the insulation used: Rubber, composition, paper and oil. Each of the first two classes can be either taped and braided, or lead covered. Paper cables are always lead covered. Each of the three classes if laid direct in the ground must be armoured. There are three different methods of armouring :-Lock armouring with specially-shaped steel wires, as practised by Callender in this country, and Felten and Guilleaume in Germany, Fig. 161. Armouring with two layers of steel tape, wound round in opposite directions, Fig. 162, or two layers of steel wires wound round in opposite directions. Armouring in its turn is generally protected by a weatherproof covering of jute and bitumen. CABLE LAYING. (FIGS. 163 to 186, pages 101 to 106.) Cables are usually laid in one of three ways. 1. Direct in the ground, the top sometimes protected by bricks laid on; in this case armoured cable is used. 2. Drawn through conduits made of cast iron, bitumen, terra-cotta, or wrought iron lined with cement or wood. 3. Laid in troughs of cast or wrought iron, terra- cotta, concrete, bitumen or wood, and run in solid with bitumen; this is known as the "solid system." When cables are laid direct in the ground, joints and branches are made in cast-iron boxes, which are then filled with bitumen or a similar insulating material, Figs, 163 and 164. Where lead covered cables having fibrous insulation. which is very hygroscopic, are jointed, the ends must be specially protected to prevent moisture getting in. Fig, 165 shows a system adopted by Messrs. Felten and Guilleaume in Germany. In some Where cast iron pipes are used to draw the cable through, the joints should be leaded so as to prevent any possibility of water or gas getting in. cases, to make doubly sure, the pipes are filled with a heavy oil after the cables have been drawn in. Doulton Conduits. The Doulton Conduit is manufactured of glazed stoneware in the following standard sizes:-4 in. x 4 in., 3 in. x 3 in., 2 in. × 2 in., 24 in. × 2 in., 2 in. x 2 in. Number of Ducts, 2, 3, 4 and 6. The joint is made by bedding the ends in Portland cement on stoneware cradles, and the upper part of the joint is then covered in with cement, Fig. 166. When laying the conduits it is usual to employ plugs of wood, which are inserted into the ducts to ensure their alignment, and to exclude cement from the interior. The conduits are sometimes laid in concrete, and joint cradles are then dispensed with. Fig. 167 shows 24 ducts built up of 3-way conduits in concrete. In this method of construction the blocks of stoneware are bedded in Portland cement mortar upon a foundation of concrete, and the trench at the sides of the conduit and above them is filled in with concrete. Fig. 168 shows a Doulton single duct, of glazed stoneware, circular inside and octagon outside. This type is specially suit- able for conduits with a large number of ducts. The blocks are built up in cement- mortar, and the whole encased in concrete. Fig. 169 shows a 16-way condui constructed in this manner. 100 SECTION 1.-THE LINE, SEPPANE FFERTS KO. FFFFER LEAD SHEATHED & LOCK COIL ARMOURED SINGLE CONDUCTOR CABLE 161 This space filled with Bitumen 163 3547.K. 164 155 162 Insulation Sulbe £É Armouring H Cables and Cable Joint Boxes. Fig. 161. Lock Armoured Single Cable. Fig. 162. Double Armoured Cable, Fig. 163 and 164. Cast-iron Joint Boxes. STEEL LEAD COPPER COPPER COPPER : FEEDERS. 101. : (762) 165 168 Ebonite Cover Metalor Earthenwear bax Heavy Oil or other Insulating Material --- Rubber Ring Screw Cap 167 158 Terminal Insulation Lead Cover Weather proof cover 166 Portland Cement – Stoneware Chair Amon 169 ECODE Joint Box and Cable Conduits. Fig. 165. Felten and Guilleaume's Joint Box. Figs. 166 to 169. Doulton's Conduits and Ducts. Detalj 102 SECTION I.—THE LINE. Doulton troughs for the "solid system" of laying cables are manufactured of glazed stoneware in 2-ft. lengths with socket joints. Fig. 170, a and b, shows 170 sizes. (763) U-shape and rectangular troughs respectively intended to take a single cable. These troughs are supplied in the following standard sizes:- 4 in. × 4 in., 3 in. × 3 in., 3 in. × 3 in., 24 in. × 24 in., 24 in, × 23 in., 2 in. × 2 in., 2 in. × 2 in., 13 in. × 132 in., and 1½ in. x 1 in. Troughs similar to c, Fig. 170, to take several cables are supplied in numerous Size. Callender-Webber Conduit. The Callender-Webber conduit (Figs. 171 and 172) is made of bitumen mixed with sand and wood fibre. Joints are made by leaving a space of 2 to 3 inches between the sections, putting mandrils through the holes which accurately fit them, and running in bitumen concrete. Where this is not desired, jointing saddles (Fig. 172) made of bitumen are used; the ends of the ducts are laid touching in these, and jointed by the use of a hot iron and a little bitumen. Two way Three way Four way Six way a Table 53.-Sizes of Standard Callender-Webber Conduits. MADE IN 6-ft. LengthS. ·· • .. .. 14 Inch Ways 17 Inch Ways 23 Inch Ways for 14 or 11 Cable. for Cable. for Cable. in. 4 63 4 432 с in. X 22 in. in. 34 × 6 3 × 85 6 x 6 6 × 9 in. 4 4 6 7 in. × 63 X x 9 × 61 X 3 Inch Ways for }} Cable. in. in. 5 X 9 5 X 13 9 x 9 9 x 13 National Conduit Company's System. A system which, owing to its comparative cheapness and ease of laying, is greatly used in America, and has been employed for the tramway feeders in Dublin and Sheffield, is that of the National Conduit Company. It consists of very thin wrought iron rivetted pipe, filled in with a cement lining about 1 in. thick. One end of the tubes is conical, fitting into a corresponding recess in the other end (Fig. 173). They are laid on a foundation of 3 in. of concrete, with 3 in. all round them and 1 in. between the different pipes, and this construction can be threaded through anywhere. The pipes are always made with 3 in. internal diameter, and this is so accurate and smooth that the manufacturers guarantee to draw a 213 in. diameter cable through. The pipes are made in 8 ft. lengths, and weight about 8 lb. per foot. Fig. 174 is a section through a junction box, and Fig. 175 is a section of a group of tubes as laid. British Insulated Wire Company's and Callender's Systems. Fig. 176 shows the solid system adopted by the British Insulated Wire Company, who make paper insulated and lead covered cables. A treble concentric lead- FEEDERS. 103 0611 172 000 174 173 Sheet Iron Cement mm (162) 66 Min” depth + 180 một th mmm nay was a mound water or JOINT 175 171 184 Winged Grat? Sec Ventilats Bax 176 Conduits and Manholes. Figs. 171 and 172. The Callender-Webber Conduit. Figs. 173 to 175. The National Conduit Company's System. Fig. 176. British Insulated Wire Company's Solid System. Fig. 184. Ventilated Manhole in Concrete and Cockrill-Doulton Tiles. (111) TILE 177 BITUMEN WOOD BRIOC EARTHENWARETROUGH (764) 179 [ 181 180 (0000 (a) BITUMEN DOO OODEN BRIDGE VOOR TROUGH 1.2:0 -72 "|-}|| |¦ **** Conduits and Manholes. Figs. 177 and 178. Callender's Solid System. Figs. 179 to 181. Sykes Conduits. 178 FEEDERS. 105 covered cable is shown laid in a concrete culvert filled in with bitumen. Callender's solid system is shown, Figs. 177 and 178. The cables in this system are laid on wooden distance pieces, placed every few feet in a cast iron or earthenware trough; bitumen is then poured in, and, if necessary, a second set of cables also kept in their place by distance pieces laid over the first. Bitumen is then run in up to the top, and the trough covered in with cast iron or tile covers. The method of jointing the troughing is shown in Figs. 177 and 178. (766) a 182 (765) 183 ww Figs. 182 and 183. Sykes' Troughs. Sykes' Stoneware Conduits. Stoneware conduits of the above type are manufactured by the Albion Clay Company, Limited, of Woodville, Burton-on-Trent. These conduits are fitted with spigot and socket ends; on the spigot and in the socket are cast bituminous linings (Fig. 179). These linings are cast on by means of steel dies, at the works, and the conduits are despatched with the joints fixed ready for laying. The linings are made tight-fitting, so that when the conduits are pushed home a perfect joint is made without the aid of mandrils or Portland cement. Owing to the simplicity of the joint, these conduits can be rapidly laid by unskilled labour. They are manufactured in 2 in., 2½ in., 3 in., or 4 in. ducts, in either 2-way, 3-way or 4-way types. Fig. 180 shows a perspective sketch of the conduits. Bell-mouth ends are supplied to these conduits, and when more than one tier of conduits are laid, they are staggered as shown in Fig. 181. Sykes Troughs.-The Albion Clay Company are also manufacturers of Sykes' stoneware troughs for the reception of cables laid on the solid system. This trough, Fig. 182, is fitted with a longitudinal receptacle or socket so as to prevent the tile from being displaced, as is often the case with the ordinary U-shaped troughing. E2 106 SECTION 1.-THE LINE. Sykes' Multiple Troughing.-The same company also makes Sykes' multiple troughs in stoneware, either 2-way, 3-way, or 4-way, as shown. These troughs possess many advantages over single troughs where more than one cable is required. They not only make a stronger job, but effect a great saving in labour and digging. Fig. 183 illustrates the multiple troughing. ĮMANHOLES. (FIGS. 174, 181, 184 to 186, pages 103 to 106.) Manholes for drawing in cables are located at different distances, according to the curvature of the ducts. These manholes must be covered with water- tight covers, and yet be properly ventilated so as to prevent any possibility of gas collecting in them, and a possible consequent explosion. Manholes, where 亞 ​Dry Rubble Section at A.B. A Brickwork 186 3way Stone- wore casing 185 Tin. 1 przed przed przeł Plan at C.D Brick Draw Box Figs. 185 and 186. Standard Type of Brick Manhole. practicable, should be made large enough for the workmen to stand up in. The type of manhole as built in Dublin is shown in Fig. 174. Manholes often reach 10 ft. in depth. A ventilated concrete manhole lined with Cockrill-Doulton patent tiles is shown in Fig. 184, and another form in brickwork in Figs. 185 and 186. 1 1 1 1 1 4 Table 54.-Fusing Point of; Tin.-Lead Alloys. Lead. Fusing Point. deg. Fahr. 25 10 5 3 2 321 2 • ·· • NHHHHH 1 Pavement 1 1 Stoneware Casing 1 1 558 541 511 482 441 370 365 356. 340 334 FEEDERS. 107 .:: SECTION INSULATOR 187 189 191 چمک 192 Figs. 187 to 192. SECTION INSULATOR TRO %% TROLLEY WIRE FEEDER FEEDER 188 190 ههههه SECTION INSULATOR. FEEDER FEEDER TROLLEY WIRE FEEDER TROLLEY WIRE TROLLEY WIRE FEEDER TROLLEY. WIRE Diagrams of Junction-Box Connections. 108 SECTION 1.-THE LINE. : Used for Soldering. Gold .. Gold.. Silver Silver German Silver Aluminium Bronze ·· Lead.. Tin Pewter Brazing hardest Brazing hard Brazing soft. Brazing soft Common Solder Table 55.-Composition of Solders. E Hard Silver Solder Soft Silver Solder.. F A G ·· •• ·· •• 4 ·· ·· ·· ·· 193 ·· ·· A Switch B Lighting Arrester. C Telephone D Telephone Cells E Main Feeders F Trolley Feeders 3664 A • .. -- .. .. •• •• •• .. Bismuth. .. · • 61 • ·· A DIAGRAM OF CONNECTIONS Silver. Brass. ::: Gold. 14 25 · ·· • · · • •• .. .. · 6 145 .. ·· .. ·· 42 4 Fer:: 12 H 73 .. 2 1 Copper. Zinc. 4 ::: JOUR :888888 100 : • 60 — TH 38 54 8 1 4 IAL+ 3 1 1 7 TO EARTH TEST WIRE 4 LEPHONI = | || WIT 1 3 Nickel. :| E 00 ·· Tin. ||| Lead. 11 18/ 1900 JUNCTION BOXES. (FIGS. 187 to 200, pages 107 to 112.) The overhead line has to be divided into-at least-half-mile sections, and these must be connected to the feeders. This connection is generally made by switches fixed in cast-iron boxes, which are usually erected on the side-walk. B HHG || 1 1 2 121 1 121 G G Three-core Cable for Telephone & Test H Terminal Board -ka 2 || || Antimony. 111 € D Fig. 193. Diagram of Feeder Pillar Connection. Diagrams (Figs. 187 to 192) show various methods of connecting up. In some cases a metallic telephone service connects the junction boxes with one another, and the power-house. A twin cable is then laid, along with the Board of Trade test wire, which has to be connected to all the extremities of the line. A portable telephone can be inserted in the circuit at each junction box, as seen in Fig. 193, which shows the connections of the junction boxes installed by the author on the FEEDERS. 109 first Bristol line. Lightning arresters are fixed in the section boxes, with or with- out choking coils. Figs. 201 and 202 show such an arrangement, with overhead and underground feeders. "Blackwell Improved" Junction Box. (FIGS. 194 to 196, page 110.) Box. The box is made of cast-iron about ½ in. thick. It has a removable top, and good ventilation is insured without having to make any holes through the box itself. The base, which is let into the ground, is also a separate casting, and this offers a special advantage, viz., that the box and panel are easily removable as a whole for giving access to the feeder cables. There are doors both at the front and the back; these are fitted with bronze locks and hinges. PANEL. The panel may be either of slate or marble, and is usually made about 1 in. thick. It is supported on insulated cradles at the bottom, and by a teak batten on the top, which themselves are bolted on to suitable lugs as part of the box casting. INSTRUMENTS: (a) Line Switches.-Four fuse switches of porcelain are shown, which have the fuses enclosed and spring contacts; one terminal of each switch connects to a bus- bar, the others have ordinary thimbles for connecting up to the trolley wires. (b) Feeder Switches.-Two quick-break switches are shown. These have the hinge of the switch entirely independent of both contacts; the contacts themselves are of the improved laminated spring type. (c) Lightning Arrester.-An "Ajax" lightning arrester is shown, which is capable of taking repeated discharges; this is fully described on page 114. (d) Test Terminals.-Three are shown, mounted on an independent vulcanite panel. (e) Telephones.-If telephonic communication is required between the station and the box, it is usual to fit a small plug-jack box on the floor of the junction box, and to carry a combined receiver and transmitter on each car; if preferred, this instrument may be permanently fixed inside the box. ALTERNATIVE ARRANGEMENT OF PANEL-If desired, four quick-break switches, similar to the feeder switch described above, may be used instead of the fuse switches on the line side. A Würts arrester can be substituted for an Ajax" if desired. Although it is not the usual practice, some engineers specify choking coils in these boxes; if so specified, these can be placed at the back of the panel behind the arrester. It should be specially noted that all bolts used in the construction of this box are accessible from the inside of the box only (for example, top and bottom joints, and door-hinges). This renders the box practically "fool proof." The construction of this box in three portions also greatly facilitates the manufacture. Two methods are in general use for connecting the line cables from the junction box to the trolley wire :- 1. The cables from the four line switches are carried down the back of the panel and into the base, where they are led by iron or porcelain pipes to the nearest pole. Entering the interior of the pole below street level, the cables are carried up to the bracket arm, along which they are led to the section insulator. 2, When the junction box is attached to the pole, the cables are taken out by an iron pipe leading straight from the box into the interior of the pole, above the pole-base. The pipe must be sufficiently large to take all four cables from the Îine switches, and can be held in position by lock-nuts, placed inside and outside the box. (C When desired, these boxes can be fitted with a very simple "throw-over" arrangement, Fig. 196. By means of this, the negative feeder (from the rails back to the power-house) may temporarily be thrown over to take the place of the positive feeder, should the latter be damaged from any cause, whilst the positive feeder acts as a return. This is an economical arrangement, as it practically duplicates all the positive feeders, and at the same time enables the duplicates to perform useful work as returns when not being used as positive feeders. British Thomson-Houston Junction Boxes. The British Thomson-Houston have a set of junction boxes the connections of which are shown in Figs. 197 to 200. One of these boxes is a special Board of Trade box, which is insulated in those cases where the tramways proper do not pass the power station; such boxes are then placed where the rail return feeders leave the track for the power station. 110 SECTION 1.-THE LINE. M5 WESTE 194 • • 1.5 a MAZDA, SAKITOKAKK O (611) 195 +36 ! CARACOLI AU” TO FEEDER j 196 ·TO RAIL mule. 70 Lane | HEIN (606) Figs. 194 and 195. The "Blackwell Improved" Junction Box. Fig. 196. "Throw-Over" Arrangement for Feeders. FEEDERS. 111 Fig. 197. Fig. 198. Connections of Street Pillar, with One Positive) Feeder Panel only. Feeder Panel. Connections of Street Pillar, with One Positive and Negative British Thomson-Houston Junction Boxes. 197. SECTION INSULATORS TROLLEY WIRES CSP POSITIVE FEEDER 3 CORE TEST&TELEPHONE CABLE NEGATIVE FEEDER (157) TROLLEY WIRES NEGATIVE RAIL CONNECTION 3 CORE TEST& TELEPHONE CABLE 198. SECTION INSULATORS TROLLEY WIRES Love 5t POSITIVE FEEDER 3 CORE TEST &TELEPHONE CABLE TROLLEY WIRES NEGATIVE RAIL CONNECTION 3 CORETEST ETELEPHONE CAAE 112 SECTION 1.—THE LINE. · Fig. 200. Connections of Steel Pillar Complete for B.O.T. Tests. Fig. 199. Connections of Steel Pillar Complete for Sectional Control. British Thomson-Houston Junction Boxes. 199. TROLLEY WIRES SECTION INSULATORS Sa 3 CORE TEST&TELEPHONE CABLE (758) 35 TROLLEY WIRES TOA NEGATIVE RAIL CONNECTION 3CORE TEST & TELEPHONE CABLE 200. TROLLEY WIRES, SECTION INSULATORS NOTE. TO AVOID CONFUSION TEST & TELEPHONE CONNECTIONS ARE OMITTED. POSITIVE FEEDER' NEGATIVE FEEDER PILOT WIRES, SHUNT FOR RECORDING AMMETER TROLLEY WIRES EARTH PLATES TO TESTEFFICIENCY OF EARTH PLATES, LOOSEN FOUR BINDING POSTS,DROP LINKS & CONNECT BATTERY TO OUTER TERMINALS AS SHOWN BELOW. THEN CALL UP GENERATING STATION TO HEAR IF RESULT HAS BEEN RECORDED. THEN REPLACE CONNECTIONS FOR NORMAL WORKING. RAILS PILOT Q WIRES ---> HICH PORTABLE BATTERY CONNECTIONS FOR NORMAL WORKING FIONEG CONNECTIONS FOR B.O.7. TEST OF EARTH PLATES FEEDERS. 113 201 202 • WIRE TROLLEY WIRE TROLLEY COIL { ARRESTER FEEDER CABL IBLEY GROUND WIRE FEEDER #000000003 |LIGHTNING RRESTER GROUND Lightning Arresters. Figs. 201 and 202. Arrangement of Lightning Arresters. : 114 SECTION I.-THE LINE. Lightning Arresters. (Figs. 201 to 203.) The " Ajax” Arrester is much in use in England and America. It consists of a series of fuses, as shown in Fig. 203. The fuse consists of two pieces of Number 26 brass wire, each 3 in. long, having a single silk insulation, and laid side by side for about 1 in., like consecutive coils in an armature. This 1 in. lap of the wires offers abundant surface for the discharge gap, which is formed by the two thicknesses of silk, and amounts to little more than 0.002 in. Small pellets of highly insulating wax secure these wires in the above position, and a small glass tube is hermetically sealed over this part of the fuse, to keep the discharge clean and dry until used. The extreme sensitiveness of this part of the apparatus is made possible by its being called upon to act but once. The soft rubber plugs serve to hold the Fig. 203. The Ajax Lightning Arrester. fuse in the corrugated cover of the arrester, and the bare ends of the wires project through_the_cover, ready to be brought into contact with the line and ground terminals. Into the back of the case containing the fuses, two strips of metal are fixed, one a plain flat strip to which one end of each fuse is connected, the other a U-shaped strip into which the remaining end of the fuse projects, contacts being made between it and the U-shaped strip by means of a carbon ball resting on the projecting end of the fuse. When the arrester is assembled and in position, only the top fuse is in parallel on the circuit ready for action. The static discharge will short-circuit the line through the fuse, which is at once utterly destroyed, allowing the carbon ball to drop, and putting the second fuse in circuit. type of arrester has proved successful on lines up to 1000 volts. This DETERMINATION OF SIZE OF FEEDERS. (FIGS. 204 to 207, page 115.) In working out the sizes of feeders, there are three principal factors to be considered:-1. The most economical conductor. 2. The permissible drop of pressure. 3. Maximum current density admissible without undue heating. The mean economical area is given by Lord Kelvin's law, which says that "the most economical area is that for which the annual cost of energy lost just equals the annual interest of the capital invested." In the case of a railway circuit, it must, however, be borne in mind that in many cases where the line extends some distance beyond the power station, the drop in voltage, which, according to Lord Kelvin's law, would give the most economical feeders, is too large, and would cause the speed of the motors and the lights in the car to run too low. The late Dr. John Hopkinson stated that a maximum of economy is obtained when a ratio of the gross annual revenue derived from the conductor to the total gross annual expenditure on it, and on the energy supplied through it, reaches a maximum. A fairly satisfactory current density to assume is 1000 amperes per square inch of sectional area, or 0.87 amperes per circular mil. The maximum drop of voltage allowed in ordinary line feeders does not exceed 10 per cent. In the case of a single line with one power-house (Fig 204), the determination of the sectional area to be given to the feeder depends practically only on the current, the length of the line, and the voltage drop. To determine the current a plan is laid out showing the position of the various lines, the power-house, and the section insulators. The service, number of cars, their headway, speed and weight, the gradients, and the position of power-house being known, the cars are distributed over the various lines and in places which would require most power. The efficiency of motors and gearing is known, so the calculated horse-power at the axle of each car can be transformed into amperes. If there are no stiff grades, an allowance of 15 to 20 amperes per motor car, according to the number, the size, average speed, and whether trailers are used or not, is a safe figure in calculating feeders at a pressure of 500 volts. FEEDERS. 115 LINE 204 FEEDER 205 (165) E • SANO - tv vi Line Feeder. Main Feeder. Overhead Line. A (167) 20 a a' (168) Power House., 206 at the ti ------ --- Thành thành trà me to deter welke getah dan menu --------- we madh qe duan mau v BAD EN HEL Power House. D 207 SEND CHINE CA meme me nën engem e eu me that Ⓡ Centres of Gravity. ---Line Feeders. BED AND CD vir die de tour mom n de añ -- - D Power House 8+ C MONTS 1 jed RESULTANT 200 AMPERES ino B 1200 AMPERLS C SPAMPERE e RES {40AMPERE SOAMPERES Figs. 204 to 207. Diagrams Illustrating the Determination of Size of Feeders. 116 SECTION I. THE LINE. According to Mr. Conant, the following formulæ give good results in cases of large towns and heavy traffic. G ―― economical constant. 1.5=a constant representing the ratio between total drop and feeder drop. The properties of G are somewhat peculiar and interesting. It may have any value between 1 and 2: not a very great range, but sufficient to make the expression. G-2 cm = V² (G—1) cm=cross-section of feeder in circular mils. P =power delivered to cars in watts, nominal. specific resistance of copper per mile-mil. M =distance to centre of load, miles. A V pressure at power station in volts. G For overhead lines Formula No. 1. 1.5 PAM G2 of a very considerable range. 1 Formula No. 2 to find G. G=1+A For underground lines G=1+ ✔ 2.25 M² A (C D+Eo Fo) 2.25 M² A (CD+Eo Fo) + V² (H I 8760+J K) 2.25 M² A (CD+Eu Fu) 2.25 M² A (C D+Eu Fu)+V²(HI8760+J K) where G =economical constant required. M = distance to centre of load. A = specific resistance of copper per mile-mil. C=cost of copper in dollars per mile-mil (copper only, and does not include cost of insulation and installing). D =interest and depreciation on above amount. Eo =cost of insulating and installing copper overhead per mile-mil. Eu =cost of insulating and installing copper underground per mile-mil. Fo=interest and depreciation on above amount for overhead lines. Fu interest and depreciation on above amount for underground lines. V voltage at bus bars. = H = time factor of energy lost in feeder. I =cost of producing this energy per watt-hour. J =cost of generating plant per Watt installed. K =interest and depreciation on plant. NOTE.-The constant 2.25 is the square of the ratio of the total drop to the feeder drop, and is arrived at as follows: As the rails are used as a return, we assume that the return drop is equal to one half the feeder drop. While this may vary in different localities, and under different conditions, it is in a general way pretty accurate. Following this assump- tion, the total drop is 3 of the feeder drop, hence the constant above is (3)2=2.25. Calculation of Most Economical Current Density. (Lord Kelvin's Law.) Rate of ohmic loss=C2 r watts, where C = current in amperes, and r=resistance in ohms. 100 Ꭱ Rate of interest and depreciation loss in £ sterling per annum = pma + constant. Where R = rate per cent. per annum of interest and depreciation; p price in £ per ton of copper in the form of cable. m = tons of copper per mile of conductor of one square inch cross-section. a = cross-section of cable in square inches. The constant represents such costs of laying and other expenses as are dependent only upon the length of cable laid, and independent of its size. To add these losses they must be equated for definite conditions of load and period of use. For this purpose assume the period to be one year; the load to be · h steady and lasting for a certain fraction of every day A certain cost per Board of Trade unit delivered to the conductor = n pence. 24 = FEEDERS. 117 or 240 n Then £1 per annum is the cost of Board of Trade units wasted per annum, and the rate of waste in watts which gives such a loss is 240,000 h n x 365 657.5 h n Call this w. It is the number of watts which, wasted during all the working hours in a year, will cost £1. Then wp m a is the interest cost of the cable expressed as a loss in watts R 100 during working hours, and the total rate of cost of distributing the current c R through the cable is y=C2r+ w p m a. 100 • K The resistance of the conductor affects the value of the two quantities making up the total loss in opposite ways, and the problem is to find the value of r, which makes y least. Consider a cable 1 mile in length. If the resistance of 1 mile of copper conductor of 1 square inch in cross-section is .045 w, then a = .045 and * the second item of the total cost= R wp m .045 100 r Since this has been equated to a rate of loss in watts it may be written C2 2 72 where t = C₂r, r C₂ being such a current as would produce the required loss in watts on traversing the resistance r. We then get y = C2r+ Where t = +2 T ✔ C ܒ -- t2 12 +2 Ga 7 > whence which is a minimum when C2 The most economical current density, therefore, is C t a .045 √ dy = C2 dr or r = where t = † (Kelvin's law). and the most economical rate of voltage drop is t volts per mile. If load is not steady, but varies in a known way, then C2 = mean square of the current in respect to time, and C = square root of that. Rpm 100 is the annual cost of 1 mile of cable of 1 square In the expression for t2, inch copper section, i.e., of 9.1 tons copper weight. Rp m w.045 100 .41 Rpw Then may be written C economical current density written t2 22' 100 t .045 R wp m .045 100 a According to Professor W. E. Ayrton, the most economical current is t √ √² + n² t2 n t V (amperes). yo i as 67.84 b r = resistance per mile of conductor. n = total length of conductor in miles. V = • potential difference at dynamo end of line. or .0041 Rp w, and the most ✓ .0041 Rp w .045 i = rate per cent. of interest on money value of conductor. a = cost in £ sterling of a ton of copper. s = resistance of a mile of copper conductor 1 square inch in section. b = annual cost in £ sterling of an electric horse-power for the number of hours the power is used. 118 I. SECTION 1.-THE LINE. 1 Table 56-Amount of Copper for Feed Wire, Pounds. LENGTH OF TRACK, MILES. Headway 1.5 2 Minutes. 4577 CO 3 6 8 10 12 15 20 1 2.5 3 4 5 6 7 a b 8 65,620 405 857 321 857 810 1716 3412 6506 13,756 27,343 45,820 72,595 109,365 510 1361 2703 5159 10,938 19,439 37,041 53,456 79,378 510 1079 2145 4095 8,673 15,404 26,724 43,213 1701 3245 6,878 13,672 23,327 38,278 1701 2574 6,878 13,672 21,197 31,177 2574 6,878 13,672 21,197 34,318 5,458 10,842 16,406 27,215 4,327 8,598 16,406 21,588 3,431 6,823 13,009| 19,140| 2,721 5,407 8,817 15,179 405 857 1701 405 679 1349 2041 405 679 1071 405 679 1071 2041 1618 1618 405 679 1071 52,039 44,858 49,387 39,221 32,788 28,261 21,874 10 202,927 152,731 123,009 103,710 89,074 93,562 76,366 61,733 49,026 38 878 Assumed-nine miles per hour average speed. For a rapid estimate, Table 56 may be useful for ascertaining approximately the amount of copper in the feeders. Fifteen per cent. drop in voltage is assumed, and for headways under seven minutes 25 amperes per car is allowed, 30 amperes being taken for headways exceeding seven minutes. These assumptions are, if anything, too liberal. In a large complex system as shown, Fig. 205, there are two sets of feeders to be worked out. First, the line feeders which parallel and feed into the trolley wire, and in which the drop in voltage should not certainly exceed 10 per cent. Second, the main feeders which feed the line feeders, and in which the drop has to be fixed by the law of greatest economy. The order of procedure in tackling such a problem is: 1. Divide system into groups, each group is to be fed by one line feeder, Fig. 206, starting from the centre points A, B, C, D and E. At these points the feeders are to be interconnected in junction boxes by means of switches or circuit breakers. 2. Determine the electrical centre of gravity of each system, which is done as shown, Fig. 207,in which a to e are points of line where current is taken, al is the resultant of a and b, and cl of cand d, c2 the resultant of al and c¹, and el the final resultant of c2 and e applied at the centre of gravity of the system el. The points al and bl being respectively distant from a and b in the inverse and · C These are the theoretical points into proportion of currents which the main feeder should feed, though other considerations generally prevent this. 3. Determine the section of the main feeders. Fig. 205.-The voltage at which the current must be delivered at their extremity is known, and the current they have to carry can be worked out approximately by supposing that the current flows along each line feeder from both ends, and that the current flowing from each extremity of the feeder is inversely proportional to the combined resistance of the trolley wire and line feeder, the sum of the currents flowing from each end being equal to the total current required on that section. From this the current, which has to be brought by the main feeders to the main feeding points, A, B, C, D, &c., will be known, and their section can be calculated. These feeding points have been chosen to allow the system to be more flexible in case of breakdown. One feeder can feed into all sections at one point. In cases where the main feeders should feed into the centre of gravity, the current to be carried by the main feeder would be the current at that particular centre of gravity. This method is approxi- mate, but the great and constant variation of load and its point of application prevent the use of more exact methods. To ensure the best results being obtained, all main and line feeders, as well as the overhead line, should work in parallel, section insulators and switches, however, being everywhere provided to enable any FEEDERS. 119 Feeders should always be section of line or feeder to be cut out when required. divided into at least half-mile sections-as required by the Board of Trade-so as to allow any faulty half-mile to be cut out practically instantaneously. When lines are very long the drop on the return circuit, if the rails alone are utilised, exceeds the 7-volt limit imposed by the Board of Trade. In that case "Negative Boosters," described later (see index), are used, and the current, before entering into the main line feeders, goes round the fields of these boosters, one- pole of the armature being connected at the power-house to the negative bus bar, and the other through a return feeder of the same section as the main feeder to the rails at the point where the main feeder is connected to the line feeders. Where the drop in the return circuit only slightly exceeds the limit, auxiliary return cables by themselves may suffice. "" "" Soft copper Hard-drawn copper Galvanized iron Cast steel.. Aluminium Silicon bronze i Material. "" 9 13.4 18 22.4 "" Diameter. 7.75 11.61 15.5 19.36 Table 57.-Conductivity of Various Metals. Breaking Weight in Pounds per Square Inch. .. in. .3937 .5905 .7874 .9842 ·· .. •• .. mm. 10 15 20 25 40 1.575 1256. 100 3.937 7854. 1000 39.37 785.4 Conduc- tivity, Pure Copper =100. sq. mm. 78.54 176.7 314.16 490.8 .3543 63.62 .5280 141.3 .7086 254.4 .8826 394.0 98 97 14 10.5 55 97 80 45 .3013 47.2 .4570 106.0 .6102 189.0 .7622 294.0 Table 58. Virtual Resistance of Conductors with Alernating Currents. (W. M. Mordey.) Area. Specific Gravity. sq. in. .122 .274 .487 .760 1.95 12.17 1217 .098 .218 .394 .611 8.9 8.9 7.7 8.0 2.6 .071 .164 .292 .456 8.9 8.9 8.9 30,000 64,000 55,000 130,000 26,000 64,000 76,000 110,000 Increase over Ordinary Resistance. per cent. less than 2} 8 17 68 3.8 times 35 "" less than o 2 8 17 Wire with a Resistance of 1 Ohm per 1,000 Yards at 32 deg. Fahr. Weight. Diameter. 270 273 1632 2260 140 273 330 587 less than roo 2 8 17 Current at 450 Amperes. sq. in. 55 133 220 45 98.5 178 32 74 131.4 .173 .174 .456 .527 .230 .174 .191 .265 Watts Watts at 2000 at 100 Volts. Volts. 110,000 5,500 266,000 13,300 440,000 22,000 90,000 4,500 197,000 9,850 356,000 17,800 ·· 64,000 3,200 7,400 148,000 263,000 (13,140 .. Second. -80- 100 133. 120 SECTION 1.-THE LINE. Table 59.-Insulation Resistance of Various Substances. Benzine Distilled water Ebonite Glass, flint ordinary Gutta-percha…. "" Ice Mica Micanite "" "" Oil asbestos Olive oil Paper, parchment ordinary 35 Material. "" "" "" Wood, ordinary paraffined "" cloth paper "" *9 ·· 99 Paraffin Sea water Shellac Vulcanised fibre, black red white tar walnut ·· "" "" "I Black "" Red press board Vulcabeston Micanite plate cloth • ,, Empire cloth No. 1 Micanite paper Oiled asbestos muslin ·· ·· ·· •-• ·· ·· • · * ·· ·· ·· •• -- Material. .. •• ·· ·· • • ·· "" ·· "" ·· •• .. ·· ·· Single cotton covered magnet wire Double Single silk Double ·· · • ** • •• • ·· •• 99 "" 29 "" "" "" Single cotton covered, heated with shellac Double Single silk Double Single cotton, covered with paraffin White Bristol board Red fibre.. ·· ·· Insulation in Megohms per Cubic Centimetre. • Table 60.-Breaking down Voltage per Thousandth of an Inch Thickness; Cold. • 28,000 × 106 20,000 × 106 91 × 106 450 X 106 2,240 : 84 × 106 2,490 × 106 310 × 106 1,240 × 106 850 × 103 1x 106 0.03 x 106 0.0485 X 106 24,000 × 106 30 ohms 9,000 × 106 68 × 106 14 × 106 7 572 × 106 3,690 x 106 1,670 × 106 53 × 106 ·· 19 17 95 10 x 106 14 × 106 • ·· ·· •• .. •• • .. ·· .. ·· .. ·· .. ·· • • .. Insulation in Megohms per Cubic Inch. ·· Volts. 289.5 205 565 412 369 297 534 511 337 240 307 101 405 76 1012 439 506 5.22 × 106 2.66 467 320 355 1,103 × 106 788 x 106 3.59 x 106 177 × 106 882 33 x 106 981 x 108 122 x 106 488 x 106 315 × 103 0.394 × 106 0.112 × 106 191 x 106 13,396 × 106 11.8 ohms 3,546×106 26.8×106 3.9 × 106 5.5X106 225 × 106 1,453 × 106 658 × 106 20.8×106 "" "" 19 >> 59 *3 25 23 ** .. "" 29 8 8 8 ະ ະ Temperature ด deg. C. 99 119224121888│ Observer. Canfield and Robinson. 20 46 20 20 20 30 20 20 46 ?? 29 >> *? "" >> "" "" Herrick and Burke. 29 03 ** . 22 າງ 88822 29 99 95 23 FEEDERS. 121 -ALUMINIUM FOR ELECTRICAL CONDUCTORS. Aluminium has, for the last two or three years, been used for electrical conductors. The following facts regarding this metal and copper are of interest: Aluminium. Copper. 8.93 3.33 96 to 99 Specific gravity Relative specific gravity. Conductivity 2.68 1.00 54 to 63 (Matthiessen Standard Scale.) Tensile strength per square inch, aluminium, 24,000 to 55,000 lb. copper 30,000 to 65,000 lb. ·· "" "" "" Method of Calculation of Comparative Cross-Section, Price, &c. The cross-sections of aluminium and copper wire or bars of same resistance are in the inverse ratio of their conductivity. This ratio is approximately the same as that between wires separated by one number in the Brown and Sharp gauge. Thus No. 1 aluminium wire is equivalent to No. 3 copper; No. 2 is equivalent to No. 4 copper, &c. The comparative weights of equal volumes of aluminium and copper are as 1 for the aluminium and 3.33 for copper. Therefore the relative weights of given lengths of same conductivity will be as 47.77 for aluminium to 100 for copper, or, the weight per mile or per thousand feet of aluminium wire is 47.77 per cent. of the weight of the same length of copper of same conductivity. Breaking Load. "" M It is necessary to use a larger cross-section of aluminium in order to obtain equal conductivity with copper. A load which would break a copper wire of 100,000 circular mils area would not break an aluminium wire of 159,000 circular mils area. In order to obtain relative breaking loads, the tensile strength per square inch of aluminium should be multiplied by 1.59, and compared with the tensile strength per square inch of copper. Price. The question of price of aluminium or copper is a question of price per mile or of any given length. Aluminium conductors will cost the same per mile as copper of equal conductivity, if the price per pound of the copper is 47.77 per cent. of the price per pound for the aluminium. To obtain aluminium price corresponding to a known copper price, divide the cost of copper per pound by .4777, or multiply by 2.1. To obtain copper price corresponding to a known aluminium price, multiply the cost of aluminium per pound by .4777 or divide by 2.1. The following is an average Specification for No. 2 B. & S. wire for long-distance transmission work; wire to have a conductivity of 59 per cent.: Weight. The weight is not to exceed 320 lb. per mile. Conductivity and Resistance.-Conductivity of wire is not to be less than 59 in Matthiessen Standard Scale, and is thus to have a resistance at 15.5 degrees Centigrade, not greater than .2443 ohms per 1000 ft. Tensile Strength and Elastic Limit.-The tensile strength of wire is not to be less than 29,000 lb. per square inch, and the elastic limit not less than 14,000 lb. per square inch. Elongation. The elongation of the tension test pieces by breaking is to be not less than 10 per cent. in 2 in. Ductility.-(Wrapping Test). Wire shall be capable of being wrapped in six turns around its own diameter, unwrapped, and again wrapped in six turns around its own diameter in the same direction as the first wrapping, without showing any cracks. Packing for Shipment.-The wire is to be packed in coils 18 in. to 24 in. internal diameter. No joints will be permitted in any coil. Coils must not weigh less than 80 lb. each. Each coil must be securely tied with aluminium wire protected by burlap wrapping. Telephone and Telegraph Wires. On account of the small sizes of wire used for these purposes, the breaking of the wire is to be specially guarded against in some instances. In such cases. a wire of a slightly reduced conductivity but high tensile strength is used, the low conductivity being in most cases not objectionable, inasmuch as the conductivity is not so materially reduced as to interfere with the successful working of the wire. 122 SECTION I.—THE LINE. Table 61.-Circular Mils Required to Transmit 100 H. P. 1000 Ft. (From Generator) at Different Pressures and Per Cent. Losses. EFFICIENCY OF MOTOR 90%. E.M.F. at Motor. 500 volts. 1000 1500 2000 3000 6000 "" 39 "" "" "" 10% Loss. 64455.04 16113.76 7161.67 4028.44 1790.42 447.60 15% Loss. CM = 40582.52 10145.63 4509.17 2536.41 1127.29 281.82 1790400 V A very convenient formula by which the Circular Mils can be calculated, assuming the above conditions of horse-power and distance transmitted, for 1000 volts is where v is volts lost. Sectional area of feeder in circular mils Resistance of copper wire in Ohms. Resistance of copper wire at 60 deg. Fahr. in Ohms. per mile 20% Loss. Resistance of copper wire at 60 deg. Fahr. in Ohms. per yard 28646.40 7161.60 3182.93 1790.40 795.73 198.93 The Circular Mils vary directly as the horse-power and distance transmitted, and inversely as the square of the electro-motive force. The cost of copper for long-distance transmission varies directly with the horse-power transmitted and as the square of the distance. (See Index, Power Transmission.) 25% Loss. 21484.88 5371.22 FEEDER AND COPPER WIRE FORMULA. = || * 2387.21 1342.80 596.80 149.20 331% Loss. 14318.88 3579.72 1590.58 894.93 397.74 99.43 746 × 10.8 × distance in feet × E.H.-P. of motor volts at motor × loss of volts on line x efficiency of motor. length in feet x 10.8 area in circular mills. 0.043598 sectional area in square inches. 0.00024466 sectional area in square inches. Expansion coefficient of copper per deg. Fahr. C.000009545. Expansion coefficient of copper per deg. cent. = 0.000017182. Resistance of hard-drawn copper wire = 1.0226 × resistance of soft-drawn copper wire. Weight of copper wire per Weight of copper wire per mile in lb. = sectional area in square inches x 20350. mile in lb. = sectional area in circular mils÷62.567. Weight of copper wire per yard in lb. = sectional area in square inches x 11.5625. One cubic foot of copper in lb. = 555 lb. One mil = 0.001 in. Area in circular mils = (diameter in mils)ª. Sectional area in square inches = (diameter in in.)2 x 0.7854. BRITISH STANDARD SIZES OF STRANDED CONDUCTORS FOR ELECTRIC SUPPLY. Table 62.-Small Sizes. Approximate Weight per Statute Mile in Pounds 2* *** *** 46 55 66 89 117 148 182 Approximate Weight per Statute Mile in 100 Pounds. 113 .005323 3/18 ©£451 6 Nominal Area of Con- ductors in Square Inches. 7 Number and Gauge of Strands. .000924 | 3/25 .001118 3/24 .001330 3/23 .001812 3/22 .002366 3/21 262 .012460 7/18 357 .016950 7/17 .022140 7/16 466 39 51 65 .002994 3/20 .003697 3/19 .002162 7/25 .002616 | 7/24 .003114 7/23 .004238 7/22 .005535 7/21 .0070057/20 .008649 7/19 Nominal Area of Con- ductors in Square Inches. Number and Gauge of Strands. 7 .03375 19/18 Resistance in Standard Ohms per 1000 Yards, at 60 Deg. Fahr. (15.6 Deg. Cent.). Calcu- lated. 26.01 21.50 18.07 13.27 10.16 8.029 6.504 4.516 11.120 9.190 7.721 5.672 4.343 3.431 2.779 1.930 1.418 1.086 Calcu- lated. .02803 7/15 0.8578 .03459 7/14 0.6949 .01899 19/20 1.2666 .02343 19/19 1.0260 0.7125 10 0.5234 .0459319/17 .06000❘ 19/16 13 0.4007 20 .09372 19/14 0.2565 25 .11680 37/16 0.2059 31 .14780 37/15 0.1627 Maximum Maximum Allowable Allowable for Tinned Wires. 26.53 21.93 .18240 37/14 0.1318 .24129 37/13 0.0996 .30832 37/12 0.0780 18.43 13.54 10.36 8.19 6.63 4.61 11.34 9.37 7.88 5.79 4.43 3.50 2.84 1.97 1.45 1.11 Resistance in Standard Ohms per 1000 Yards at 60 Deg. Fahr. (15.6 Deg. Cent.). 0.8750 0.7088 1.2920 26.79 22.14 1.0460 0.7267 18.61 13.67 10.46 0.5339 0.4087 0.2616 0.2100 0.1660 8.27 6.70 4.65 11.45 9.47 0.1344 0.1016 0.0795 7.95 5.84 4.47 3.54 2.86 Maximum Maximum Allowable Allowable for Tinned Wires. 1.99 1.46 1.12 Table 63.-Intermediate Sizes. 0.8838 0.7158 1.3050 1.0570 0.7340 0.5391 0.4129 0.2642 0.2121 0.1676 Weight in Pounds per 1000 Yards. 0.1358 0.1026 0.0803 Calcu- lated. 11.12 13.45 16.01 21.79 28.45 36.02 44.47 64.02 25.87 31.29 37.24 50.70 66.21 83.81 103.50 149.00 202.80 264.80 Calcu- lated. 335 414 228 281 405 551 720 1125 1403 1776 Minimum Allowable 2192 2899 3705 10.90 19.57 13.18 23.67 15.69 21.35 27.88 Weight in Pounds per 1000 Yards. 35.30 43.58 62.74 25.35 30.66 36.50 49.69 64.89 82.13 101.40 Minimum Allowable 328 406 223 276 397 540 706 Weight per Statute Mile in Pounds. Calculated 1103 1375 1740 146.00 262.20 198.70 356.90 259.50 466.10 2148 2841 3631 28.17 38.35 50.08 63.38 78.25 112.70 45.52 55.07 65.54 89.22 116.50 147.50 182.10 Weight per Statute Mile in Calculated Pounds 590 728 401 495 713 970 1267 1981 2469 3126 3859 5103 6521 H 124 SECTION 1.-THE LINE. aca Approximate Weight per Statute Mile in 100 Pounds. PARON 2DED ON*** Nominal Area of Con- ductors in Square Inches. 7/.068 7/.095 10 .050 19/.058 16 .075 19/.072 21 .100 19/.082 5 .025 10 .050 Number and Diameter of Strands. 61 73 41 .200 37/.082 51 Table 64.-Large Sizes. Resistance in Standard Ohms per 1000 Yards, at 60 Deg. Fahr. (15.6 Deg. Cent.). Calcu- lated. 26 .125 19/.092 .1940 32 .150 19/.101 .1610 31 .150 37/.072 .1627 .9618 .4928 .4880 .3167 .2440 .1254 .250 37/.092 .0997 .300 37/.101 .0827 .350 37/.110 .0697 84 .400 37/.118 .0606 84 .400 61/.092 .0605 95 .450 61/.098 .0533 101 .500 61/.101 .0502 116 .550 61/.108 .0439 121 .600 61/.110 .0423 .650 61/.118 .0368 .700 | 91/.098 .0357 138 142 151 .750 91/.101 .0336 160 .800 91/.104 .0317 179 207 .900 91/.110 .0283 1.000 91/.118 .0246 1.000 127/.101 .0241 211 Maximum Maximum Allowable Allowable for Tinned Wires. .9810 .5027 .4977 .3230 .2490 .1978 .1640 .1660 .1280 .1016 .0843 .0711 .0618 .0617 .0543 .0512 .0447 .0431 .0375 .0364 .0343 .0323 .0289 .0251 .0246 .9910 .5077 .5027 .3262 .2515 .1998 .1658 .1676 .1292 .1027 .0852 .0718 .0624 .0623 .0549 .0517 .0452 .0436 .0379 .0368 .0346 .0327 .0292 .0254 .0248 Weight in Pounds per 1000 Yards. Calcu- lated. 299 584 591 911 1,182 1,488 1,793 1,776 2,303 2,900 3,494 4,145 4,770 4,781 5,425 5,762 6,588 6,836 7,865 8,094 8,597 9,115 10,200 11,730 12,000 Minimum Allowable 293 572 580 893 1,158 1,458 1,757 1,740 2,257 2,842 3,424 4,062 4,674 4,685 5,317 5,647 6,456 6,699 7,708 7,932 8,425 8,933 9,993 11,500 11,760 Weight per Statute Mile in Pounds. Calculated 526 1,027 1,041 1,604 2,080 2,619 3,156 3,125 4,054 5,103 6,150 7,295 8,395 8,414 9,548 10,140 11,600. 12,030 13,840 14,240 15,130 16,040 17,950 20,650 21,120 FEEDERS. 125 BRITISH STANDARD RADIAL THICKNESSES FOR JUTE OR PAPER DIELECTRIC, LEAD AND ARMOUR, FOR UNDERGROUND CABLES. Table 65.—For Working Pressures up to 660 Volts. Test at works for paper, 2500 volts for half an hour; when laid and jointed, 1000 volts for half an hour. Test at works for jute, 1500 volts for half an hour; when laid and jointed, 1000 volts for half an hour Single. Triple Eccentric. Nominal Area of Conductors. sq. in. .025 .050 .075 .07 .100 .09 .125 .09 .150 .07 .08 .200 .09 .08 .250 .10 .09 .300 .10 .09 .350 .10 .09 .10 .400 .10 .10 .500 .10 .600 .11 .700 .11 .11 .11 .750 .11 .11 .800 .12 .12 .900 .12 .12 1.000 .13 .12 Nominal Area of Conductors. 8q. in. .025 .050 .075 .100 .125 .150 888888 Dielectric. .200 .250 in. .08 in. in .06 .08 .08 .06 .08 .08 .07 .08 Concentric. Dielectric. Inner Dielectric Inner. Dielectric Outer. 8 Earthed in. in. .12 .08 2200 Volts.* BEE888F Lead. .09 .09 .09 .09 .10 .10 .10 .10 .10 .11 .11 .11 .11 .11 .12 .12 .15 .12 .12 ..15 .13 .13 .15 Outer .12 .08 .12 .08 .13 .09 .10 .13 .09 .13 .09 .09 .13 .14 .10 Dielectric. .10 .11 .12 in. in. .08 .07 .08 .08 .08 .08 .09 .09 .09 .09 .09 .10 .09 .10 .09 .11 .10 .11 .10 .12 .10 .10 .10 .09 .09 .10 .10 .10 .10 .12 .10 .13 .13 .11 in. .08 .15 .09 .15 .09 .15 .16 .16 .16 .16 .17 Dielectric. Inner .14 .14 in. Intermediate Dielectric. 3300 Volts.t in. .08 .08 .08 .08 .08 .08 .09 .09 .09 .09 .09 .10 .10 .10 .10 .10 Outer 3888 Dielectric. .08 .08 Table 66.-Concentric Cables-Working Pressures. (Paper only.) in. .08 .09 .10 .10 .09 .11 .09 .11 .09 .10 .10 .10 .10 .10 .12 For Reference Notes see next page. .13 .13 .14 .14 .15 6600 Volts.‡ Three-Core. between Con- Dielectric Eductors, and from Conduc. tors to Lead. .09 .09 .09 in. in. in. in. in. in. .09 .09 .23 .10 .10 .35 .09 .10 .23 .10 .11 .35 .09 .10 .23 .10 .12 .35 .24 .11 .12 .36 .24 .11 .13 .36 .12 .13 .10 .10 .10 .11 .11 .11 .24 .11 .12 .36 .24 .12 .11 .13 .25 .12 .14 .37 .13 .36 .10 .10 .10 .10 .11 .11 .11 .11 .11 88 Lead. .08 .09 .10 .10 .11 .11 .12 .13 .13 .14 .14 .15 11,000 Volts. § in. in. .12 :12 .12 .13 .12 .14 .14 .12 .12 .14 .12 .15 .12 .15 .12 .16 126 SECTION 1.-THE LINE. Nominal Area of Conductors. .100 .125 .150 .200 .250 Table 67.-Three-Core Cables-Working Pressures. (Paper only.) 2200 Volts.* Dielectric Between and Outside. Dielectric Outer on Star Winding with Centre Earthed. 8q. in. in. in. in. .13 .10 .08 .025 .050 .13 .10 .09 .075 .13 .10 .10 .14 .11 .11 .14 .11 .11 .14 .12 .13 .13 .11 .14 .11 .15 .12 3300 Volts.t Dielectric Between and Outside. in. .15 .15 .15 .16 .16 .16 .16 .17 Dielectric Outer on Star Winding with Centre Earthed. in. in. .12 .09 .12 .10 .12 .10 .13 .11 .13 .12 .13 .12 .13 .13 .14 .14 6600 Volts.‡ Dielectric Between and Outside. Dielectric Outer on Star Winding with Centre Earthed. Lead. 11,000 Volts.§ Dielectric Between and Outside. .36 .36 .36 .18 .14 .36 .19 .15 .37 in. in. .23 in. in. in. in. .35 .17 .10 .23 :12 .23 .13 .23 .17 .11 .35 .23 .17 .12 .35 .24 .18 .12 .24 .18 .13 .24 .18 .13 .24 .25 Dielectric Outer on Star Winding with Centre Earthed. Lead. .23 .13 .24 .14 .24 .14 .24 .15 .24 .16 .25 .17 * Test_at_works: 10,000 volts for half an hour. Test when laid and jointed; 4000 volts for half an hour. + Test at works: 12,000 volts for half an hour. Test when laid and jointed : 6000 volts for half an hour. Standard Armouring. ‡ Test at works: 20,000 volts for half an hour. Test when laid and jointed; 12,000 volts for half an hour. § Test at works: 30,000 volts for half an hour. Test when laid and jointed: 20,000 volts for half an hour. In concentric cables the mean resistance of the conductors shall be that shown in the Table, with a maximum allowable variation between the conductors of 4 per cent. The standard armouring to be as follows: For cables below .50 in. diameter over lead, galvanized steel wires .072 in. diameter. For cables from .50 in. to 1 in. over lead, two layers of compounded steel tape, each .030 in. thick. For cables from 1.01 in. to 2 in. diameter, two layers of compounded steel tape, each .040 inch thick. Above 2 in. diameter, 2 layers of compounded steel tape, each .060 in. thick. The standard thicknesses of jute serving when applied to diameters less than .50 in. to be .06 in., and for larger diameters.10 in. All test pressures may be applied either with alternating or direct current, the former to be at the standard frequency, Tables 68 and 69. For pressures from 330 to 660 volts applied to wires in Table No. 69, the thick- nesses of dielectric and lead are to be used as given in Table No. 68 for the next largest sectional area. FEEDERS. 127 BRITISH STANDARD RADIAL THICKNESSES FOR RUBBER. DIELECTRIC, FOR LEAD SHEATHING AND ARMOURING. Nominal Area of Conductors. Table 68.-Underground Cables for Working Pressures up to 660 Volts. Test at works 2500 volts for half an hour. Test when laid and jointed, 1000- volts for half an hour. sq. in. .025 .050 .075 .100 .125 .150 .200 .250 .300 .350 .400 .500 .600 .700 .750 .800 .900 1.000 Single. Dielectric. Lead. Volts. 2,200 3,300 6,600 11,000 in. .062 .062 .066 .071 .076 .080 .087 .094 .101 .107 .113 .121 .125 .129 .131 .133 .137 .141 in. .07 .07 .07 • • .08 .08 .08 .09 .09 .09 .10 .10 .11 .11 .12 .12 .12 .12 .13 Concentric. Dielectric Inner and Outer. in. .062 .062 .066 .071 .076 .080 .C87 .094 .101 .107 .113 .121 .125 .129 .131 .133 .137 .141 1 Lead. Test at Works. Pressure Applied for Half an hour. Volts. 10,000 12,000 20,000 30,000 in. .08 .08 .09 .09 .10 .10 .11 .11 Tables 70, 71 and 72. The pressure tests for the cables in these Tables shall Working Pressure. .12 .12 .13 .14 .14 .15 .15 .16 .16 .17 • • Three-Core. Dielectric between Con- ductors and from Conduc- tors to Lead. in. .062 .062 .066 .071 .076 .080 .087 .094 .101 .107 .113 .121 4,000 6,000 12,000 20,000 Lead. in. .08 .09 .10. .11 .11 .12 .13. .13. .14 .15 .16 .17 be as follows: Test when Laid and Jointed. Pressure Applied for Half an hour.. Volts. 128 SECTION I.—THE LINE. ! Table 69.—Internal Wiring Cables for Working Pressures up to 330 Volts. Test at Works, 2,500 volts for half an hour. Test when laid and jointed, 1,000 volts for half an hour. Nominal Area of Conductors. Sq. in. .001810 .001812 .002463 .002994 .003217 .004072 .004238 .005027 .005323 .007005 .001246 .01899 .02214 .03375 .03459 .05000 .05000 .06000 .09372 .10000 .11680 .12340 .14940 .15000 .15840 .18240 sq. in. 0.25 0.50 .075 .100 .125 .150 .200 .250 From 660 to 2,200 Volts. in. .11 .11 Number and Gauge (or Diameter) of strands S.W.G. .12 .12 .12 .13 .13 .13 in. .07 .07 1/18 3/22 1/17 3/20 455800888 1/16 1/15 7/22 .09 .09 .09 1/14 3/18 7/20 7/18 19/20 7/16 19/18 7/14 7/.095 19/.058 19/16 19/14 19/.082 37/.16 19/.092 19/.101 37/.072 19/12 37/14 From 2,200 to 3,300 Volts. Minimum Safe Thickness of Vulcanized Rubber. in. .13 .13 Table 70. Single Core Underground Cables for Pressures Exceeding 660 Volts. .14 .14 .14 .15 .15 .15 in. .07 .08 in. .035 .08 .08 .09 .036 .036 .038 Nominal Area of Con- ductors. Dielectric. Lead. Dielectric. Lead. Dielectric. Lead. Dielectric. Lead. .09 .09 .10 .036 .037 .039 .038 .040 .041 .044 .048 .049 .054 .054 .059 .059 .062 .070 .071 .075 .076 .081 .080 .082 .086 From 3,300 to 6,600 Volts. in. .20 22 222222 .20 .21 .21 .21 Lead. in. '08 .08 in. .031 .031 .631 -033 .09 .09 .09 .10 .10 .10 .032 .032 -033 .033 .034 .035 .037 .039 .040 .043 .043 .045 .046 .047 .052 .053 .055 .056 .059 .058 .059 062 From 6,600 to 11,000 Volts. in. .29 .29 .30 .30 .30 .31 .31 .31 in. .09 .09 .10 .10 .10 .10 .11 .11 FEEDERS. 129 Conductors. Nominal Area of Table 71.-Concentric Underground Cables for Pressures Exceeding 660 Volts. sq. in. .025 .050 .075 .100 .125 .150 .200 .250 .025 .050 .075 .100 .125 .150 .200 .250 Nominal Area of Con- ductors. sq. in. .025 .050 .075 .100 Inner Di. electric. Earthed. .125 .150 .200 .250 in. .11 .11 .12 .12 .12 .13 .13 .13 .20 .20 .21 .21 .21 .22 .22 From 660 to 2200 Volts. Outer Dielectric. .22 in. .07 .07 .08 .08 .08 .09 .09 .09 From 3300 to 6600 Volts. in. .11 .11 .12 .12 .09 .09 .12 .13 .13 .13 .10 .10 .10 .11 .11 .11 From 660 to 2220 Volts. Dielectric on each Core. Lead. in. .09 .10 .11 .12 Not Earthed. .12 .13 .13 .14 in .11 .11 .12 .12 .12 .13 .13 .13 .20 .20 .21 .21 .21 .22 .22 .22 Lead. in. .08 .09 .09 .10 .10 11 in. .13 .13 .14 .14 · .14 .15 .15 .15 .11 .12 .09 .10 .10 .11 .11 .12 .12 .13 From 2200 to 3300 Volts. Dielectric on each Lead. Core. in. Table 72.-Three-Core Underground Cables for Pressures Exceeding 660 Volts. .10 .11 .11 .12 From 2200 to 3300 Volts. Outer Dielectric. Inner Di- electric. Earthed. .12 .13 .14 .14 in. .13 .13 .14 .14 .14 .15 .15 .15 .29 .29 .30 .30 .30 .31 .31 .31 in. .08 .08 .09 .09 .09 .10 .10 .10 in. .10 .10 .20 .20 .21 .21 From 6600 to 11,000 Volts. .11 .11 From 3300 to 6600 Volts. .21 .22 .22 .22 .11 .12 .12 .12 Dielectric on each Lead. Core. in. .11 .12 Not Earthed. .13 .13 in. .13 .14 .14 .15 .16 .13 .14 .14 .14 .15 .15 .15 .29 .29 .30 .30 .30 .31 .31 .31 Lead. in. .08 .09 .10 .10 .10 .11 .11 .12 in. .29 .29 .30 .30 .30 .31 .31 .31 .10 .10 .11 .11 .12 .12 .13 .13 From 6600 to 11,000 Volts. Dielectric on each Lead. Core. in. .12 .13 .14 .15 .15 .16 .17 .17 The dielectric and lead on all conductors, whether mains or pilot wires, smaller than .025 sq. inch, shall have the thicknesses given for .025 sq. inch. All inter- mediate sizes shall have the thicknesses given for the next larger size on the list. Twin cables shall have the same thicknesses as three-core cables. The allowable variation in radial thicknesses of dielectric and lead at any point shall be 10 per cent. below the standard minimum thicknesses given in the table but the mean of the thicknesses shall be at least that specified. F 130 SECTION I.-THE LINE. ! : British Standards for Copper Conductors. A wire 1 metre long, weighing 1 gramme, and having a resistance of 0.1539 standard ohms at 60 deg. Fahr. (15.6 deg. Cent.) is adopted as standard for hard- drawn high-conductivity commercial copper. The hard-drawn copper is defined as that which will not elongate more than 1 per cent. without fracture. A wire 1 metre long, weighing 1 gramme, and having a resistance of 0.1508 standard ohms at 60 deg. Fahr. (15.6 deg. Cent.), is adopted as standard for annealed high-conductivity commercial copper. The copper taken as weighing 555 lb. per cubic foot (8.89 grammes per cubic centimetre) at 60 deg. Fahr., which gives a specific gravity of 8.9. The average temperature coefficient of 0.00238 per deg. Fahr. (0.00428 per deg. Cent.) is adopted for commercial purposes. A variation of 2 per cent. from the adopted standard of resistance is allowed in all conductors. A variation of 2 per cent. from the adopted standard of weight is allowed in all conductors. An allowance of 1 per cent. increased resistance, as calculated from the diameter, is given on all tinned copper conductors between diameters 0.104 and 0.028 (Nos. 12 and 22 S W G) inclusive. In the calculation of Tables 62 to 72, a lay involving an increase of 2 per cent. in each wire, except the centre wire, for the total length of the cable, has been taken as standard. The legal standard wire guage, as fixed by Order in Council, August 23rd, 1883, is adopted as standard for all wires. Table 73. Temperature Corrections for Copper Wire. (Based on Matthiessen standard of 9,612 legal ohms per mil-foot at 0 deg Cent.) To correct the resistance of copper wire for temperature, find the mil-foot resistance K, in the first column of the accompanying table, corresponding to the L given temperature, and use formula R = K. d2 R = required resistance in legal ohms at the given temperature. L= length in feet. d = diameter of wire in mils. K = mil-foot resistance from the table. Resistance per Mil-Foot in Legal Ohms. K. 10.00 10.10 10.20 10.30 10.40 10.50 10.60 10.70 Tempera- ture in Fahrenheit Degrees. 50.47 55.15 59.79 64.40 68.97 73.51 78.01 82.47 Tempera- ture in Centigrade Degrees. 10.26 12.86 15.44 18.00 20.44 23.06 25.56 28.04 Resistance per Mil-Foot in Legal Ohms. 10.80 10.90 11.00 11.10 11.20 11.30 11.40 11.50 Tempera- ture in Fahrenheit Degrees. 86.90 91.31 95.69 100.04 104.36 108.64 112.90 117.14 Tempera- ture in Centigrade Degrees. 30.50 32.95 35.38 37.80 40.20 42.58 44.95 47.30 FEEDERS. 131 Numbers. MISCELLANEOUS DATA AND TABLES RELATING TO CONDUCTORS. Table 74.-Comparison of Wire Gauges in Mils. (THOUSANDTHS OF AN INCH.) 000,000 00,000 0,000 000 00 0 1 2 3 4 5 6 77 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 28 24 25 26 27 28 29 30 81 32 33 34 35 36 Washburn and Moen Roebling. Gauge. 460. 430. 393. 362. 331. 307. 283. 263. 244. 225. 207. 192. 177. 162. 148. 135. 120. 105. 092. 080. 072. 063. 054. 047. 041. 035. 032. 028. 025. 023. 020. 018. 017. 016. 015. 014. 013.5 013.0 011.0 010.0 009.5 009. 460. 430. 393. 362. 331. 307. 283. 263. 244. 225. 207. 192. 177. 162. 148. 135. 120. 105. 92. គន៩៩៨៩៩៩ រ 23. 20. 18. 17. 16. 15. 14. 13.5 13. 11. 10. 9.5 9. Brown and Birmingham Sharpe. or Stubs. (B. & S. W. G.) (B.W. G.). 460. 409.6 364.8 324.9 289.3 257.6 229.4 204.3 181.9 162. 144.3 128.5 114.4 101.9 90.74 80.81 71.96 64.08 57.07 50.82 45.26 40.3 35.89 31.96 28.46 25.35 22.57 20.1 17.9 15.94 14.2 12.64 11.26 10.03 8.93 7.95 7.08 6.3 5.62 5. : 454. 425. 380. 340. 300. 284. 259. 238. 220. 203. 180. 165. 148. 134. 120. 109. 95. 83. 72. 65. 58. 49. 42. 35. 32. 28. 25. 22. 20. 18. 200±3200 NL H 16. 14. 13. 12. 10. New British Standard (S.W. G.). 464. 432. 400. 372. 348. 324. 300. 276. 252. 232. 212. 192. 176. 160. 144. 128. 116. 104. 92. *80. 72. 64. 56. 48. 40. 36. 32. 28. 24. 22. 20. 18. 16.4 14.8 13.6 12.4 11.6 10.8 10. 9.2 8.4 7.6 C 132 SECTION 1.—THE LINE. B. W. G. No. 0000 000 00 012 3 VOGA 8 PAFARERAHRA&I 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 228980 30 Area. Circular Inch. Mils=d₂ Diameter. .454 .425 .380 .34 .300 .284 .25€ .238 .22 .203 .18 .165 .148 .134 .12 .109 .095 .083 .072 .065 .058 .049 .042 .035 .032 .028 .025 .022 .020 .018 .016 .014 .013 .012 206,116 180,625 144,400 115,600 90,000 80,656 67,081 56,644 48,400 41,209 32,400 27,225 21,904 17,956 14,400 11,881 9,025 6,889 5,184 4,225 3,364 2,401 1,764 1,225 1,024 784 625 484 400 324 256 196 169 144 Pounds per Foot. .623924 .54676 .437105 .349928 .272435 .244151 .203058 .171465 .14651 .124742 .098076 .082411 .066305 .054354 .04359 .035964 .027319 .020854 .015692 .012789 .0101828 .00726796 .00533972 .00370815 .00309972 .00237312 .0018919 .0014650 .00121082 .00098077 .00077492 .0005933 .000511571 .0004859 Table 75.-Dimensions for Copper Wire. Copper Wire-Weight and Length. Pounds per Mile 1,760 Yards. Feet per Pound. 3294.32 2886.89 2307.92 1847.62 1438.43 1289.11 1072.15 905.333 773.56 658.638 517.844 435.135 350.089 286.99 230.152 189.893 144.245 110.1061 82.855 67.5276 53.7665 38.3748 28.1937 19.579 16.3665 12.5301 9.9892 7.7357 6.39315 5.17844 4.0916 3.13264 2.7011 2.30152 ( 1.60276 1.82895 2.28777 2.85773 3.6706 4.0958 4.9247 5.8321 6.8255 8.0165 10.1962 12.1345 15.0818 18.398 22.9413 27.805 36.6046 47.954 63.7267 78.1902 98.203 137.590 187.276 269.676 322.610 421.384 528.570 682.55 825.883 1019.61 1290.44 1685.48 1954.76 2294.13 Miles per Pound. .000303553 .000334639 .0004333 .00054124 .00069519 .00077573 .0010327 .00110457 .0012927 .0015183 .0019311 .0022981 .0028564 .0034845 .004345 .005266 .0069326 .009082 .012069 .014809 .018589 .0260587 .035469 .051075 .061100 .0798078 .100108 .129271 .156417 .193108 .24440 .31922 .370220 .434496 Area Sq. Inch. .0908 .070 .063 .052 .044 .038 .032 .025 .021 .0172 .014 .011 .0093 .0070 .0054 .0040 .0033 .0026 .0018 Ohms. / /Ft. .000089 .00011 .00012 .00015 .00018 .00021 .00025 .0003 .00037 .0004 .0005 .0007 .0008 .0011 .0014 .00199 .0024 .003 .0042 .00138 .0058 .00096 .0084 .00080 .010 .00061 .013 .00049 .016 .00038 .021 .00025 .031 .00015 .052 .00011 .071 Ft. Ohms. 8718 7813 6498 5487 4688 3991 3138 2637 2121 1739 1394 1150 874 667 502 409 325 232 170 118 99 75 60 46 31 18.9 13.9 Ohms. | Lib. .0004 .0005 .0007 .001 .0014 .002 .016 .024 .041 .071 .126 .191 .301 .591 1.09 2.27 3.25 5.54 8.73 14.5 32.4 88.7 164.4 Lb/Ohms .0032 307 .0046 217 .0071 140 .010 94 2375 1907 1319 940 686 497 60 41 23.8 13.9 7.88 5.23 3.31 1.69 .912 .44 .307 .18 .114 .068 .030 .011 .0060 FEEDERS. 133 Strands of Copper Wire. (Roeblings.) Copper wires are twisted into concentric strands or into ropes of seven strands. A rope of seven strands each composed of seven wires, is called a seven-by-seven rope, and is usually written 7x7. The number of wires that can be made into a strand is limited by the capacity of the stranding machinery: 200 wires is the usual limit of a concentric strand, and 133 wires of a rope. In a strand of circular milage, C M, composed of n wires of diameter d, with a weight per 1,000 feet w, we have Number of Wires. CM=d² × N. C M d2 N Number of Wires. d= P No The weights of strands are calculated about 1 per cent. heavier than a solid wire of the same circular milage, while the resistance is calculated for the solid wire. The diameter of a strand may be calculated by multiplying the diameter of one wire by the factors given in the table, according to the number of wires composing the strand. CM n w=.00305 x C M Table 76.-Number of Wires and Diameter in Strand Required to Equal a Given Circular Milage. Area in Circular Mils. 7.0845 19 | .0513 37 61 .1463 .1203 .1690 .189 .207 .2236 .239 .0725 .0889 .1025 .1147 .1256 .1357 .145 .0367 .0519 .0636 .0735 .0821 .090 .0972 .1039 .0496 .0286.0405 .0572 .064 .0757.0809 .0701 .0343 .0396 .0443 .0199 .028 .0486 .0561 .0526 .0297.0344 .0421 .0384 .0455 .0486 .0172.0243 .0214 .0262 .0304 .0339 .0371 .0401 ,0151 127 169 217 50,000 100,000 150,000 200,000 250,000 300,000 350,000 400,000 450,000 500,000 Diameter of Wires in Inches. 19 7.2803 .1701 .1776 .1849 .1919 37 .1219.1273 .1325 .1375 61 .0949 .0991 .1032 .1071 127 .0658 .0687 .0715.0742 169 .0571.0595 .062 .0643 217 .0503 .0525 .0547.0567 Area in Circular Mils. .2535 .2672 .1538 .1622 .1103 .1162 .0858 .0905 .0595 .0627 .0543 .0480 .0516 .0429 .0455 550,000 600,000 650,000 700,000 750,000 800,000 850,000 900,000 950,000 1,000,000 550,000 600,000 650,000 700,000 850,000 900,000 950,000 1,000,000 I Diameter of Wires in Inches. .2927 .3047 .3163 .3273 .338 .3484 .3585 .3684 .1986 .205 .2115 .2176 .2236 .1423 .147 .1515 .1559 .1602 .1108 .1145 .1180 .1214 .1247 .0768 .0793 .0818 .0841 .0864 .0666 .0687 .0709 .0729 .0749 .0588 .0607 .0625 .0644 .0661 .377 .2294 .1644 .1280 .0887 .0769 .0678 134 SECTION I.—THE LINE. S.W.G. 7/0 6/0 5/0 4/0 3/0 ☺☺☺☺☺OÍ~M 2/0 1/0 1 2 3 6789 *GOODBROEDREBOLA 10 11 12 13 14 15 16 17 18 Table 77.—Details of Conductors.—Showing Dimensions, Capacity, Resistance and Weight. (Glover and Co.). At 1000 per Square Inch, Loss 24 Volts per 100 Yards. = Ampères. 196.34 169.09 146.57 125.66 108.68 95.11 82.44 70.685 59.828 49.875 42.273 35.298 28.95 24.32 20.106 16.28 12.86 10.56 8.49 6.64 5.02 4.07 3.21 2.46 1.80 Diameter of each Wire. Inch. .500 .464 .432 .400 .372 .348 .324 .300 .276 .252 .232 .212 .192 .176 .160 .144 .128 .116 .104 .092 .080 .072 .064 .056 048 M/M. 12.700 11.786 10.972 10.160 9.449 8.839 8.229 7.620 7.010 6.400 5.893 5.385 4.877 4.470 4.064 3.658 3.251 2.946 2.642 2.337 2.032 1.829 1.626 1.422 1.219 Diameter of the Strand. Inch. •• •• • .. ·· .. • · · ·· • .. • ·· ·· • • • ·· M/M. • ·· ·· • ·· ·· ·· ❤ ·· ·· .. .. → Square Inches. M/M. Square .196349 .169093 .146574 .125663 .108686 .095114 .082447 .070685 .05982 .01987 .04227 .03529 .0289 .0243 .0201 Area. .0163 .0128 .0105 .0085 .0066 .0050 .0040 .0032 .0024 .0018 126.672 109.090 94.560 81.070 70.117 61.362 53.190 45.603 38.597 32.176 27.272 22.772 18.678 15.659 12.97 10.507 8.301 6.818 5.480 4.288. 3.243 2.627 2.075 1.589 1.167 Resistance in Ohms at 60 deg. Fahr. Per 1000 Yds. Ohms. .1246 .1446 .1669 .1946 .2251 .2572 .2967 .3461 .4089 .4905 .5787 .6931 .8450 1.0056 1.2168 1.5022 1.9012 2.3150 2.8800 3.6803 4.8673 6.0089 7.6049 9.9332 13.5198 Per Mile. Ohms. .219301 .254651 .293774 .342658 .396183 .452713 .522266 .609171 .719719 .863337 1.01860 1.21986 Per Per 1000 Kilo- metre. Yards. 2.14161 2.64397 3.34626 4.07442 5.0688 6.4744 8.5665 10.5758 13.3847 17.4826 23.7951 Ohms. .1363 .1581 .1825 .2813 .3245 .3786 .4473 .5366 .6330 .7582 1.48723 .9244 1.76993 1.1001 1.3311 1.6434 2.0799 2.5326 3.1507 4.0262 5.3248 .2128 .2462 6.5737 8.3197 10.867 14.790 Lb. 2270 1955 1694 1454 1256 1099 953 817 691 576 488 405 334 281 232 188 148 122 98 76 58 47 37 28 21 Weight. Per Mile. Lb. 3995 3441 2982 2557 2211 1935 1677 1439 1218 1015 860 718 589 495 409 331 261 215 173 135 102 83 65 50 36.8 Per Kilo- metre. Kilogs. 1126 969 840 721 623 545 472 405 343 286 242 201 165 139 115 93 73 60 48 37 28 23 18.3 13.5 10.4 FEEDERS 135 19 20 21 22 3/25 3/24 3/23 3/22 3/21 3/20 3/19 3/18 7/25 7/24 7/23 7/22 7/211 7/21 7/20 7/20 7/19 7/18 7/17 7/16 7/15 7/14 7/13 7/12 7/10 7/9 7/8 7/7 7/6 19/24 19/23 19/22 19/21 1.25 1.01 0.804 0.615 0.9614 1.1631 1.3843 1.8843 2.4608 3.1147 3.845 5.5373 2.200 2.7139 3.2301 4.3968 5.0469 5.7419 6.504 7.2078 8.972 12.9207 17.5858 22.989 29.0705 35.889 47.4638 60.6535 75.4576 91.897 116.282 143.55 206.72 7.3807 8.7847 11.9576 15.6159 .040 .036 .032 .028 .020 022 .024 .028 .032 .036 .040 .048 .020 .022 .024 .028 .030 .032 .033 .036 .040 .048 .056 .064 .072 .080 .092 .104 .116 .128 .144 .160 .192 .022 .024 .028 .032 1.016 0.914 0.813 0.711 .. • 0.508 .042 0.559 .047 0.610 .051 0.711 .059 0.813 .068 0.914 .077 1.016 .082 1.219 .102 0.508 .060 0.559 .066 0.610 .072 0.711 .084 0.762 0.813 0.838 .090 .096 .099 .108 .120 0.914 1.016 1.219 .144 1.422 .168 1.626 .192 1.829 .216 2.032 .240 2.337 .276 2.642 .312 2.946 .348 3.251 .384 3.658 .432 4.064 .480 4.877 .576 .559 .110 .610 .120 .711 .140 .813 .160 .. .0012 .0010 .0008 .0006 1.018 .00096 1.120.00116 1.222 .00138 1.425 .00188 1.780.00246 1.830.00311 2.035 .00384 2.440.0055 · 1.54 .0022 1.677 .0027 1.83 .0032 2.13 .0043 2.28 .0050 2.439 .0057 2.51 .0064 2.74 .0072 3.04 .0089 3.66 .0129 4.27 .0175 4.88 .0229 5.49 .0290 6.10 .0358 7.111 .0474 7.926.0606 8.838 .0754 9.753.0918 10.974.1162 12.192.1435 14.631.2067 2.795.0073 3.050.0087 8.555.0119 4.065.0156 0.8107 | 19.4097 0.6567 24.0354 0.5189 30.422 0.3972 39.729 0.619 25.955 45.671 0.748 21.454 37.761 0.890 18.026 31.726 1.212 13.243 23.3080 10.144 17.853 14.100 11.420 7.931 1.586 2.000 2.476 3.547 14.77 18.705 23.091 30.573 39.087 48.633 59.211 74.94 92.55 133.32 8.0118 6.4899 4.5066 1.419 1.741 2.064 2.773 3.225 8.702 3.676 7.648 4.100 4.0864 7.164 4.644 3.4336 6.043 5.740 2.7813 4.895 8.320 1.9314 3.399 11.287 2.497 1.4190 1.0864 1.912 .8584 1.510 .6953 1.224 .5257 .925 .4114 .724 .3307 .2716 7.67 10.06 134.2668 21.299 42.3025 26.294 53.5426 33.281 69.9249 43.463 11.124 19.578 9.1952 16.183 7.7256 13.597 5.6757 9.989 4.9445 4.3460 .2146 .1752 .1207 4.708 3.3877 5.611 2.8463 2.0910 1.6011 .5820 .4780 .3776 .3083 .2124 5.9623 5.0094 3.6801 2.8179 [28.395 23.472 19.720 14.484 11.097 8.764 7.099 4.930 12.44 10.059 8.451 6.209 5.409 4.754 4.450 3.756 3.042 2.112 1.552 1.188 .938 .760 .575 .450 .361 .297 .234 .191 .132 3.706 3.113 2.287 1.752 14.5 11.7 9.3 7.1 11 13.5 16 22 28 36 44 64 25.5 31.5 37 51 58 66 75 84 104 149 203 266 336 415 549 701 872 1062 1343 1660 2390 85 101.5 138 180 25.5 20.7 16.3 12.5 ***898 99 112 89 102 147 183 263 357 468 591 730 967 1233 1533 1869 26 149 178 242 316 7.1 5.8 4.6 3.5 5 6 8 11 13.9 17.8 21.8 31.7 13.0 15.6 18.3 25.2 28.7 32.7 37.0 41.6 51.5 74.0 100.6 131.8 166.6 205.8 272.3 347.6 432 527 2363 666 2921 823 4206 1185 2008 42 50 68 89 136 SECTION I.—THE LINE. S.W.G. 19/20 19/19 19/18 19/17 19/16 19/15 19/14 19/13 19/12 19/11 19/10 19/9 19/8 19/7 37/24 37/23 37/22 37/21 37/20 37/19 37/18 87/17 37/16 87/15 Table 78.-Details of Conductors.-Showing Dimensions, Capacity, Resistance, and Weight. (Glover and Company.) At 1000 per Square Inch, Loss=2} Volts per 100 Yards. Amperes. 19.765 24.400 35.138 47.826 62.467 79.060 97.604 129.083 164.953 205.215 249.870 316.241 390.422 472.410 14.344 17.157 23.354 30.499 38.603 47.656 68.629 93.409 122.004 154.411 Diameter of each Wire. Inch. .036 .040 .048 .056 .064 .072 .080 .092 .104 .116 .128 .144 .160 .176 .022 .024 .028 .032 .036 .040 .048 .056 .064 .072 M/M. .914 1.016 1.219 1.422 Diameter of the Strand. Inch. 1.626 1.829 2.032 2.337 2.642 2.946 .580 3.251 .640 3.658 .720 1.422 1.626 .180 .200 .240 .280 .320 .360 .400 .460 .520 4.064 .800 4.470 .880 1.829 .559 .610 .711 .813 .224 .914 .252 1.016 .280 1.219 .336 .392 .448 .504 .154 .168 .196 M/M. 4.57 .0197 5.08 .0244 6.10 .0351 7.10 .0478 8.12 .0624 9.14 .0790 .0976 .1290 .1649 .2052 .2498 .3162 .3904 .4724 10.1 11.6 13.2 14.73 16.25 18.2 20.3 22.3 Square Inches. 3.9 4.2 4.97 .0233 5.69 .0304 6.4 .0386 7.1 .0476 8.5 .0686 9.9 .0934 11.3 12.8 .0143 .0171 Area. .1220 .1544 Square M/M. 12.70 15.73 22.63 30.83 40.24 50.95 62.95 83.20 106.36 132.35 161.12 203.94 251.80 304.79 9.22 11.02 15.02 19.60 24.89 30.70 44.24 60.24 78.69 99.58 } Per 1000 Yds. Ohms. 1.2650 1.0247 .7115 .5228 .4002 .3162 .2561 .1937 .1515 .1218 .1000 .07906 .06406 .05292 Resistance at 60 deg. Fahr. .6496 .5262 .3654 .2684 .2055 .1624 Per Mile. Ohms. 2.2264 1.8034 1.2522 9201 .7043 .5565 .4507 .3409 .2666 .2142 .1760 .1391 .1127 .09313 1.7396 1.4647 1.0737 1.8897 .8222 1.4470 1.1432 .9261 .6431 .4723 3616 .2858 3.0616 2.5724 Per 1000 metre. Yards. Per Kilo- Ohms. 1.384 1.121 .778 .572 .438 .346 .280 .212 .166 .133 .109 .0865 .0700 .0579 1.903 1.599 I.175 .8994 .7106 .5756 .3997 .2936 .2248 .17 G Lb. 228 282 406 553 722 914 1128 1491 1906 2372 2888 3655 4513 5461 165 198 270 352 446 550 793 1080 1410 1785 Weight. Per Mile. Lb. 401 496 714 973 1270 1608 1985 2624 3354 4174 5082 6432 7942 9611 290 348 475 619 784 968 1395 1900 2481 3141 ї Per Kilo- metre. Kilogs. 113 139.8 201 274 358 453 559 739.5 945 1176 1432 1812 2238 2708 81.8 98 134 174.5 221 272.8 393 535 699 885 ་ FEEDERS. 137 37/14 37/13 37/12 37/11 37/10 37/9 37/8 61/24 61/23 61/22 61/21 61/20 61/19 61/18 61/17 61/16 61/15 61/14 61/13 61/12 61/11 61/10 91/18 91/17 91/16 91/15 91/14 91/13 91/12 91/11 190.630 252.110 322.169 400.809 488.108 617.646 762.520 23.788 28.3139 38.540 50.3316 63.706 78.645 113.255 154.149 201.339 254.811 314.588 416.046 531.661 661.427 805.356 169.202 230.296 300.797 380.695 469.900 621.567 794.294 988.162 .080 .092 .104 .116 .128 .144 .160 .022 .024 .028 .032 .036 .040 .048 .056 .064 .072 .080 .092 .104 .116 .128 .048 .056 .064 .072 .080 .092 .104 .116 2.032 2.337 .560 .644 .728 .812 3.251 .896 3.658 1.008 4.064 1.120 2.642 2.946 .559 .198 .216 .252 .610 .711 .813 .914 .288 .324 1.016 .360 1.219 .432 .504 1.422 1.626 1.829 2.032 2.337 2.642 2.946 3.251 1.219 1.422 .576 .648 .720 .828 .936 1.044 1,152 .528 .616 1.626 1.829 2.032 2.337 2.642 1.144 2.946 1.276 .704 .792 .880 1.012 .1906 .2521 .3221 .4008 22.77 .4880 25.6 28.4 14.2 16.3 18.4 20.6 .6176 .7625 5.031 .02378 5.490.02831 6.399.03854 7.317 .0503 8.226.0637 9.144.0786 10.971.1132 12.798 | .1541 14.634.2013 15.461.2548 18.288 .3145 21.033.4160 23.778.5316 26.514.6614 29.259.8053 13.409.1692 15.642 .2302 17.886.3007 20.119.3806 22.352 .4699 25.707 .6215 29.062 | .7942 32.406.9881 122 93 162.60 207.75 258.51 314.76 398.3 491.8 15.3 18.2 24.8 32.4 41.0 50.6 73.0 99.3 129.8 164.3 202.8 268.3 342.8 426.6 519.4 109.1 148.4 193.9 245.4 303.0 400.8 512.2 637.3 .1315 .09947 .07783 .06265 .05138 .04060 .03288 1.0551 .8865 .6513 .4987 .3940 .3191 .2216 .1628 .1246 .09850 .07979 .06033 .04721 .03795 .03116 .14857 .10915 .08357 .06603 .05348 .04044 .03164 .02543 .2314 .17506 .13698 .11026 .09042 .07145 .05786 1.8569 1.5602 1.1462 .8777 .6934 .5616 .3900 .2865 .2192 .17336 .14043 .10618 .08308 .06679 .05484 .02615 .1921 .1471 .1162 .0941 .0711 .0556 .8447 .1438 .1088 .0851 .0685 .0562 .0444 .0360 .0415 .0340 1.154 .970 .7125 .5455 .4310 .3490 .2434 1309 .1781 1781 .1363 2327 .1077 2945 .0872 3636 .0660 4809 .0516 6145 7646 9309 .1625 .1194 .0914 .0722 .0585 .0442 2203 2914 3723 4633 .0346 .0279 5641 7140 8815 275 327 446 572 736 909 1956 2661 3476 4400 5432 7185 0181 11422 3877 5128 6552 8154 9928 12566 15514 484 575 784 1006 1295 1599 2303 3134 4095 5183 6399 8463 10815 13456 16383 3442 4683 6117 7744 9560 12645 16158 20102 1098 1445 1847 2298 2798 3541 4372 136 162 221 284 365 451 649 883 1154 1460 1803 2385 3047 3792 4617 970 1319 1724 2182 2694 3563 4553 5665 F2 138 SECTION 1.-THE LINE. Am- Size in peres. S.W.G. 1000 800 700 600 500 400 300 250 200 175 150 125 100 90 80 70 60 50 40 35 30 22420-07ODEBATINA 10 1.75 1.50 1.25 1 19 Strand. S.W.G. Area in 8quare Inches. 19/7 .472410 19/8 .390422 19/9 .316241 19/10 .249870 19/11 .205215 19/12 .164953 19/13 .129083 19/14 .0976045 19/15 .0790603 ·· 19/23 .0087847 19/24 ·· .. 19/16 .0624677 19/17 .0478265 19/18 .0351388 1.0247 282 19/19 .0244006 19/20 .0197655 1.2650 228 19/21 .0156159 1.6011 180 19/22 .0119576 2.0910 138 •• •• •• Resist- ance per 1000 Yards at 60° Fahr. ohms. ·· .0073807 3.3877 .05292 5461 .06404 4513 .07906 3655 .10000 2888 .1218 2372 .1515 1906 .1937 1491 .2561 1128 .3162 914 .4002 722 .5228 553 .7115 406 Lbs. per 1000 Yards. ·· .. • • Table 79.-Comparative Table SHOWING THE RELATION OF To obtain the diameter of the strand, multiply the diameter of one wire by 5. Size in S.W.G. 2.8463 101.5 7/19 85 7/6 7/7 7/8 7/9 7/10 7/11 7/12 7/13 7/14 7/15 7/16 7/17 7/18 7/20 7/21 ·· ·· 7 Strand. S.W.G. .. Area in Square Inches. .206723 .173705 .143558 .116282 .0918775 .0754576 .0606535 .0474638 | Resist- ance per 1000 Yards at 60° Fahr. ohms. .. .0072678 3.4336 .0057419 4.3460 7/211 .0050469 4.9445 7/22 .0043968 5.6757 7/23 .0032301 7.7256 7/24 .3307 .4114 .5257 • .1207 2390 .1436 2008 .1752 1660 .2146 1343 .2716 1062 872 ·· ·· .0358892 .6953 415 .0290705 .8584 336 í .0229800 .0175858 .0129207 1.9314 149 .0027139 9.1952 Pounds per 1000 Yards. 1.0864 266 .0089721 2.7813 104 1998 889 28O7A) : : • 701 1.4190 203 ·· 549 ·· 84 66 58 51 37 31.5 .. ·· To obtain the diameter of the strand, multiply the diameter of one wire by 3. FEEDERS. 139 of Equivalent Conductors. VARIOUS SIZES TO EACH OTHER. Area in Size in Square S.W.G. Inches. ·· ·· •• ·· .. ·· .. 3 Strand. S.W.G. 3/18 3/19 3/20 3/21 .. ·· •• Resist- ance per 1000 Yards at 60° Fahr. ohms. 3/22 .0018843 3/23 3/24 3/25 •• • • •• ·· • • • ·· •• I Pounds per 1000 Yards. ·· .. .. .0055373 4.5066 64 .0038451 6.4899 44 36 8.0118 .0031147 .0024608 10.1441 28 13.2433 22 16 .0013843 18.0265 .0011631 21.4554 13.5 .00096145 25.9555 11.0 To obtain the diameter of the strand, multiply the diameter of one wire by 2. Size in S.W.G. 7/0 6/0 5/0 4/0 +32 3/0 2/0 0 1 P .196349 .500 .169093 .464 .146574 .432 .125663 .400 .108686 .372 .0951149 .348 .0824479 .324 .0706858 .300 .0598285 .276 .0498759 .252 .0422733 .232 .0352989 .212 6 .0289529 .192 7 .0243285 .176 8 .0201062 .160 9 .0162860 .144 .0128680 .128 2 3 BHDOTO ARROPA 192 4 10 12 13 1 14 691 576 .5787 488 .6931 408 .8450 334 1.0056 281 1.2168 232 1.5022 188 1.9012 148 122 11 .0105683 .116 2.3150 .0081949 .104 2.8800 98 76 58 47 .0066476 .092 3.6803 .0050265 .080 4.8673 .0040715 .072 6.0089 .0032170 .064 7.6049 .0024630 .056 9.9332 .0018096 .048 13.5198 15 16 17 Solid. S.W.G. 18 Area in Square Inches. Dia- meter in In- ches. .0012566 Resist- ance per 1000 Yards at 60° Fahr. ohms. Pounds per 1000 Yards. .1246 2270 .1446 1955 .1669 1694 1454 .1946 .2251 1256 .2572 1099 .2967 .3461 .4089 .4905 .040 19.4697 20 .0010179 .036 24.0354 953 817 2002102 14.5 11.7 E 140 SECTION I.—THE LINE. : : Equivalent Resistance and Weight of Pure Copper Wire carrying 1000 Amperes per Square Inch. Am- peres. 1000 800 700 600 500 400 300 250 200 175 150 125 100 90 80 70 60 50 40 35 30 25 20 15 12 10 9 8 7 #cros 3 2 1.75 1.50 1.25 1 Equiva- lent Dia- meter in Inches. • 1.128 1.009 .9440 .8740 .7978 .7136 .6180 .5641 .5046 .4720 .4370 .3989 .3568 .3385 .3191 .2985 .2763 .2523 .2256 .2111 .1954 .1784 .1595 .1381 1236 .1128 .1070 .1009 Resist. ance per 1000 Yards at 60° Fahr. ohms. .0244 .0305 .0349 .0407 .0489 .0611 .0815 .0978 .1223 .1398 .1631 .1957 .2446 .2718 .3058 .3495 .4077 .4893 .6116 .6990 .8155 .9786 1.2232 1.6310 2.0388 2.4465 2.7184 3.0582 .09440 3.4951 .08740 4.0776 .07978 4.8931 6.1164 .07136 .06180 8.1552 .05046 12.2328 .04720 13.9804 .04370 16.3105 19.5726 .03989 .03568 24.4657 Pounds per 1000 Yards. 11560 9248 8092 6936 5780 4624 3468 2890 2312 2013 1734 1445 1156 1040 925 809 694 578 462 405 347 289 231 173 139 116 104 92.5 81.0 69.5 58.0 56.5 34.5 23.0 20.0 17.5 14.5 11.5 Table 80.-Comparative Table SHOWING THE RELATION OF Size in S.W.G. 19/11 91/12 91/13 91/14 91/15 91/16 91/17 91/18 • •• .. •• ** 91 Strand. S.W.G. Area in Square Inches. • .988162 .794294 .621567 .469990 .380695 .06603 .300797 .08357 230296 .10915 ·· ·· .169202 .14857 .. .. ·· Resist- ance per 1000 Yards at 60° Fahr. ·· ohms. .02543 ·· .03164 .04044 .05348 •• • ·· • • •• .. • Pounds per 1000 Yards. 11422 9181 7185 5432 4400 3476 2661 1956 ·· ·· ·· • .. ·· To obtain the diameter of the strand, multiply the diameter of one wire by 11. FEEDERS. 141 of Equivalent Conductors. VARIOUS SIZES TO EACH OTHER. Size in S.W.G. 61/10 61/11 61/12 61/13 61/17 61/18 1 61/14 61/15 .254818 61/16 .201339 61 Strand. S.W.G. 61/22 Resist- ance per 1000 Yards at 60° Fahr. ohms. .805356 .03116 .661427 .08795 .531661 .04721 .416046 .06033 .07979 .314588 .09850 .1246 1 Area in Square Inches. .154149 .113255 61/19 .0786455 .3191 61/20 .0637062 3940 61/21 .0503316 .4987 .0385404 .6513 .1628 .2216 .8865 61/23 0283139 61/24 .0237889 1.0551 Pounds per 1000 Yards. 9939 7646 6145 4809 3636 2945 2327 1781 1309 909 736 572 446 327 275 ·· To obtain the diameter of the strand, multiply the diameter of one wire by 9. Size in S.W.G. 37/8 37/9 37/10 37/11 37/12 37/13 37/14 37/15 37/16 37/17 37/18 37/19 37/20 37/21 37/22 37/23 37/24 37 Strand. S.W.G. Area in Square Inches. .762527 .617646 .488018 .400802 .322169 .252110 .190630 .154411 .122004 .0934092 .0686290 .0476565 .0386038 Resist- ance per 1000 Yards at 60° Fahr. ohms. .03288 .04060 .05138 .06265 .07783 .09947 .1315 .1624 .2055 .2684 .3654 .5262 .6496 .0304992 .8222 .0233542 1.0737 .0171572 1.4616 0143449 1.7396 Pounds per 1000 Yards. 8815 7140 5641 4633 3723 2914 2203 1785 1410 1080 793 550 446 352 270 198 165 To obtain the diameter of the strand, multiply the diameter of one wire by 7. 142 SECTION I.—THE LINE. A : Numbers. 000,000 00,000 0,000 000 00 0 1 2 3 ~ +28+∞ 9 10 11 12 13 14 15 16 17 18 19 20 21 E-A222******2.♫***** 23 24 25 26 27 28 29 30 31 32 33 34 35 36 Table 81.-Wire Gauges in Millimetres. Brown and Sharpe. Birmingham or Stubs. 11.683 10.404 9.266 8.251 7.348 6.544 5.827 5.19 4.621 4.115 3.665 3.263 2.906 2.588 2.305 2.052 1.828 1.628 1.449 1.291 1.15 1.024 .9116 .8118 .7229 .6438 .5732 .5105 .4546 .4049 .3605 .3211 2859 .2545 .2267 .2019 .1799 .1601 .1426 .127 ·· .. 11.531 10.794 9.652 8.636 7.62 7.213 6.579 6.045 5.588 5.156 4.572 4.191 3.759 3.404 3.048 2.768 2.413 2.108 1.829 1.651 1.473 1.245 1.067 .889 .8128 .7112 .635 .5588 .508 .4572 .4064 .3556 .3302 .3048 .254 .2286 .2032 .1778 .127 .1016 New British Standard. 11.785 10.972 10.16 9.448 8.839 8.229 7.62 7.01 6.401 5.893 5.385 4.877 4.47 4.064 3.657 3.251 2.947 2.641 2.337 2.032 1.829 1.026 1.422 1.219 1.016 .9144 .8128 .7112 .6096 .5588 .508 .4572 .4166 .3759 .3454 .315 .2946 .2743 .254 .2337 .2134 .193 Test of High-Tension Cables. High-tension cables are frequently tested with an alternating current equal to three times the pressure for a period of thirty minutes with long cables; care should be taken that the transformer used for testing purposes should have a capacity of at least 50 kilowatts. The requirement is also frequently made that the cables should be able to be bent, without any damage, in a circle having a diameter equal to five times the diameter of the cable. SECTION II. THE POWER STATION. PART I. STEAM ENGINES. PART II. STEAM TURBINES. SECTION II. THE POWER STATION. PART 1.-THE STEAM ENGINE. HEAT. Unit of Heat. Here and in America quantities of heat are measured in British Thermal Units, each of which represents the heat required to raise the temperature of 1 lb. of water 1 deg. Fahr., at a certain standard temperature. There is much discord as to what this standard temperature should be. Professor Callendar, in his article "Calorimetry," Encyclopædia Britannica, adopts 20 deg. Cent. = 68 deg. Fahr. as the standard, this being the most convenient temperature, all things considered. Frequently the temperature of the maximum density of water, viz. 39.1 deg. Fahr., is adopted as the standard temperature, but the matter is of small importance from an engineering point of view, the difference in the unit based on these two different temperatures being under deg. per cent. On the Continent the unit of heat is the calorie, one calorie being 3.968 B.T.U. 1 B.T.U. calorie. " = 0.252: Mechanical Equivalent of Heat. Heat being a form of energy can also be measured in other units, thus:- 1 B.T.U. = 778 foot-pounds = 1055 volt-ampere-seconds. = 2545 B.T.Ü. 1 H.-P. hour 1 kilowatt hour = 3412 B.T.U. Specific Heat. The specific heat of a body is the heat required (measured in B.T.U.) to raise the temperature of 1 lb. of it by 1 deg. Fahr. This quantity varies generally with the temperature at which the body may be. In the case of water, the specific heat is a minimum at about 104 deg. Fahr., at which it is 0.9982. There is still some uncertainty as to the specific heat of water at temperatures above 212 deg. Fahr. Regnault's values are generally adopted, but are stated to be too great by Professor Callendar. Taking the figures quoted by the latter, and calling & the specific heat of water, we may write : s = 0.5277 Tro where T denotes the absolute temperature (q.v.). This expression is reliable between the limits of 80 deg. Fahr. and 420 deg. Fahr., which practically covers the range needed in steam engine work. • Absolute Temperatures. Temperatures measured on the Fahrenheit scale are reduced to absolute temperatures by adding to the readings the constant 459.4. Thus the freezing point of water 32 deg. Fahr. on the Fahrenheit scale is 491.4 deg. on the absolute scale. Fluids. All fluids tend to expand if heated. Should the expansion be prevented the pressure rises. If the fluid is a gas, the following relation holds between its pressure, its volume, and its absolute temperature: PV = RT (1) where P = pressure in pounds per square foot, V = volume of 1 lb. weight of the • · 146 SECTION II.-POWER STATION. gas in cubic feet T = the absolute temperature, and R is a constant, varying with the gas in question. For air R = 52.7. For superheated steam R And for other gases R molecular weight For vapours such as saturated steam, equation (1) is unreliable. Saturated Steam. The addition of heat to a vessel, containing both steam and water, and fitted with a safety-valve so as to prevent a rise of pressure, simply causes the generation of more steam which passes off through the valve or into the engine, its tempera- ture and pressure remaining unaltered. Steam produced in this way is known as saturated steam. If it also contains no particles of water in suspension, it is described as "6 dry saturated steam." Generally, steam as furnished by an ordinary boiler is not "dry saturated," but contains at least 2 per cent. of moisture in sus- pension. Superheated Steam. If after being withdrawn from the boiler, steam is passed through a heated chamber, any particles of moisture suspended in it are converted into steam, rendering it "dry." After having attained this condition, any further heat absorbed by the steam raises its temperature (its pressure remaining unaltered), and steam with its temperature thus raised is known as superheated steam. Specific Heat of Superheated Steam. For moderate degrees of superheat (70 deg. to 100 deg.) Professor Carpenter states that for steam at pressures between 15 lb. and 120 lb. absolute, the specific heat of superheated steam may be taken as C = 0.462 + 0.001,525 p (2) where p = the absolute pressure in pounds per square inch. Lorenz's experiments are in agreement with this, but for high degrees of superheat the latter finds that the specific heat diminishes and approaches.5. Then T= Properties of Saturated Steam. Saturated steam at any temperature has always a definite pressure and a definite specific volume, i.e., the volume in cubic feet occupied by 1 lb. weight of the dry saturated steam. Unwin's formulas connecting the pressure volume, temperature, &c., of dry saturated steam are the simplest, and are as follows:- Let T = absolute temperature of saturated steam P = absolute pressure in pounds per square inch V = volume of 1 lb. in cubic feet L= latent heat M = 5.8031 2297 0.8 m Ma log. P : log. P = 5.8031 V = 1.8626 L p m L= 1443.8 - • Temperature, Fahr. Latent heat, B.T.U. = +0.016 1632 84.7. m ·· 1525 .. 0.8 15900 T1.25 = 1443.8 - No formula for latent heat is reliable above about 400 deg. Fahr. Above that point the following figures may be used:- - .71 T. deg. deg. deg. deg. deg. deg. 450 500 550 600 650 698 786.5 728.2 650.8 546.3 393.7 0 The temperature 698 deg. Fahr. is the "critical temperature" of water. At this temperature the specific volume of water is equal to the specific volume of dry saturated steam, and above this temperature water cannot exist in the liquid state, no matter what the pressure. The pressure of dry saturated steam at this tempera- ture (the critical pressure) is 2882 Ib. per square inch. THE STEAM ENGINE. 147 Latent Heat. Latent heat is the quantity of heat absorbed or given out in changing a unit weight of substance from one state to another without altering its temperature. Entropy. If a quantity of heat, L units say, is added to 1-lb. weight of a body, the temperature of which remains constant at T degrees absolute during the addition L of the heat, the entropy of the body is said to be increased by the amount T ΦΩ Or if ₁ be the entropy of the body before the addition of the heat, and ø2 its final entropy, then- L - Φι 882.9 787.0 Thus, in the evaporation of 1 lb. of water at a pressure of 100 lb. per square inch, the corresponding absolute temperature is 787.0 deg., the heat added, in the evaporation (the latent heat) is 882.9 B.T.U., and the increase of entropy o say, is = 1.1219. • where T is the absolute temperature. That is to say, the entropy of 1 lb. of saturated steam at 787 deg. absolute is 1.1219 more than the entropy of 1 lb. of water at the same temperature. The total entropy of the steam may be denoted as ø, and if o be the entropy of the water and the increase of entropy on evaporation, we have $ = $1 + $s. Adopting Callendar's values for the specific heat of water, we may for all temperatures between 80 deg. Fahr. and 420 deg. Fahr. write 9.8064, Φι = 5.277 Tro T, as before, being the absolute temperature. Values of 1 and ø are given for different pressures and temperatures in the steam tables, pages 148 to 150. S h = 0.4797 T1.1 437.34 Sensible Heat. By the sensible heat of steam at any temperature is denoted the quantity of heat required to raise the temperature of 1 lb. of water at freezing point to the temperature in question. For the range of temperature required in steam practice the sensible heat is - Efficiency of Perfect Heat Engine. R1-R2_T1-T2 R1 T1 Efficiency of Perfect Heat Engine is expressed by formula which R1 is the quantity of heat supplied from the heat source at the absolute temperature T₁, and R₂ the quantity of heat rejected at the absolute temperature T2. This equation expresses the Second Law of Thermodynamics, which may be expressed in various ways. (C 'It is impossible, by means of inanimate material agency, to derive mechanical effect from any portion of matter by cooling it below the temperature of the coldest surrounding objects." (Thomson.) in "It is impossible for a self-acting machine, unaided by any external agency, to convert heat from one body to another at a higher temperature." (Clausius.) "If all heat absorbed be at one temperature, and that rejected at a lower temperature, then the heat transformed into work will be in the same ratio to the entire heat absorbed as the difference between the absolute temperature of the source and refrigerator is to the absolute temperature of the source. In other words, the second law is an expression for the efficiency of the perfect elementary engine." (Wood.) 148 SECTION II.-POWER STATION. Vacuum Inches of Mercury. 29.5 29.4 29.3 29.2 29.1 29.0 28.9 28.8 28.7 28.6 28.5 28.4 28.3 28.2 28.1 28.0 27.9 27.8 27.7 27.6 27.5 27.4 27.3 27.2 27.1 27.0 26.9 26.8 26.7 26.6 26.5 26.4 26.3 26.2 26.1 26.0 25.9 25.8 25.7 25.6 25.5 25.4 25.3 25.2 25.1 25.0 Table 1.—The Properties of Saturated Steam. (VACUUM IN INCHES OF MERCURY.) t, Temperature Fahrenheit. 59.05 63.43 67.56 71.45 75.13 78.55 81.77 84.79 87.58 90.08 92.36 94.51 96.41 97.75 99.10 101.07 103.05 104.59 106.13 107.57 109.00 110.32 111.63 112.86 114.10 115.28 116.46 117.57 118.68 119.72 120.76 121.77 122.77 123.78 124.79 125.76 126.73 127.53 128.33 129.14 129.96 130.76 131.56 132.35 133.15 134.21 T, Absolute Temperature. 518.4 522.8 527.0 530.8 534.5 537.9 541.2 544.2 547.0 549.5 551.8 553.9 555.8 557.1 558.5 560.5 562.4 564.0 565.5 567.0 568.4 569.7 571.0 572.3 573.5 574.7 575.9 577.0 578.1 579.1 580.2 581.2 582.2 583.2 584.2 585.2 586.1 586.9 587.7 588.5 589.4 590.1 591.0 592.7 592.5 593.6 h, Sensible Heat. 27.31 31.65 35.72 39.61 43.21 46.63 49.84 52.82 55.59 58.07 60.34 62.45 64.31 65.66 66.99 68.95 70.87 72.46 73.95 75.41 76.84 78.14 79.42 80.67 81.92 83.09 84.25 85.38 86.50 87.52 88.53 89.56 90.58 91.58 92.58 93.53 94.48 95.28 96.08 96.92 97.77 98.57 99.37 100.12 100.87 101.97 L, Latent Heat. 1074.8 1071.1 1067.9 1065.1 1062.6 1060.3 .0532 2.0733 .0614 2.0492 2.0264 .0694 .0764 2.0066 .0832 1.9880 .0895 1.9712 1058.2 .C955 1.9553 1056.3 .1010 1.9410 1054.5 .1063 1.9278 1052.8 1051.2 1049.8 1048.4 1047.1 P1, Liquid Entropy. .1108 .1149 .1187 .1220 .1243 1045.8 .1268 1044.6 .1302 1043.4 .1337 1042.3 .1366 1041.2 .1392 1040.1 1039.1 1038.1 1037.2 1036.3 1035.4 .1417 .1442 .1465 .1488 .1511 .1532 1034.6 .1552 1033.7 .1573 1032.9 .1593 1032.3 .1612 1031.4 .1631 1030.6 .1649 1029.9 .1666 1029.2 .1683 1028.6 .1700 1028.0 .1717 1027.4 .1734 1026.8 .1750 1026.1 .1763 1025.4 .1775 1024.7 .1790 1024.1 .1805 1023.5 .1818 1022.9 .1832 1022.3 .1845 1021.8 .1858 1021.3 .1871 Steam Entropy. $s, 1.9159 1.9050 1.8953 1.8863 1.8795 1.8727 1.8619 1.8553 1.8480 1.8412 1.8344 1.8281 1.8222 1.8165 1.8108 1.8054 1.8002 1.7949 1.7973 1.7855 1.7810 1.7763 1.7720 1.7678 1.7637 1.7597 1.7556 1.7519 1.7483 1.7448 1.7412 1.7375 1.7344 1.7308 1.7248 1.7246 1.7205 V, Volume of 1 Lb. Cubic Feet. 1274.00 1073.50 925.25 815.06 728.74 658.72 602.32 554.34 514.01 478.10 447.31 421.22 398.53 377.23 358.19 341.31 326.17 311.95 299.02 287.22 276.47 266.34 256.95 248.27 240.21 232.58 225.45 218.78 212.55 206.60 200.99 195.70 190.71 185.91 181.40 177.11 173.06 169.13 165.40 161.83 158.45 155.15 152.05 149.07 146.20 143.44 Table 2.-The Properties of Saturated Steam. P, Absolute* Pres- sure in Pounds per Square Inch. 14.7 15 16 17 18 19 20 25 30 35 40 45 HKÖNJROGgAbg 55 60 65 70 75 80 85 90 * 95 100 105 110 115 120 125 130 135 140 145 150 155 100 165 170 175 180 185 190 195 200 205 210 215 220 225 230 235 240 245 250 (PRESSURE IN POUNDS PER SQUARE INCH.) t, Temperature Fahrenheit. 212.0 213.1 216.3 219.4 222.4 225.3 228.0 240.0 250.3 259.2 267.2 274.3 280.9 286.9 292.6 297.8 302.8 307.4 311.9 316.1 320.1 323.9 327.6 331.2 334.6 337.9 341.1 344.1 347.1 350.0 352.8 355.6 358.2 360.7 363.3 365.7 368.2 370.4 372.9 375.0 377.3 379.4 381.6 383.7 385.7 387.7 389.7 391.6 393.6 395.5 397.4 399.2 401.1 T, Absolute Temperature. 671.4 672.5 675.7 678.8 681.8 684.7 687.4 699.4 709.7 718.6 726.6 733.7 740.3 746.3 752.0 757.2 762.2 766.8 771.3 775.5 779.5 783.3 787.0 790.6 794.0 797.3 800.5 893.5 806.5 809.4 812.2 815.0 817.6 820.1 822,7 825.1 827.6 829.8 832.3 834.4 836.7 838.8 841.0 843.1 845.1 847.1 849.1 851.0 853.0 854.9 856.8 858.6 860.5 1, Sensible Heat. 180.21 181.32 184.56 187.70 190.74 193.68 196.42 208.60 219.07 228.13 236.28 243.53 250.28 256.40 262.23 267.56 272.68 277.39 282.01 286.32 290.43 294.33 298.13 301.83 305.33 308.73 312.02 315.11 318.20 321.19 324.08 326.97 329.65 332.23 334.91 337.39 339.97 342.25 344.83 347.00 349.38 351.55 353.83 356.00 358.07 360.14 362.22 364.18 366.26 368.22 370.20 372.07 374.03 L, Latent Heat. 966.1 965.3 963.0 960.8 958.7 956.7 954.8 946.3 939.0 932.7 927.0 921.9 917.3 912.9 908.9 905.2 901.6 898.3 895.1 892.1 889.2 886.4 883.8 881.2 878.7 876.4 874.1 P1, Liquid Entropy. .3114 .3130 .3178 .3225 .3270 .3313 .3352 .3528 .3677 .3804 .3916 .4016 .4107 .4189 .4265 .4336 .4403 .4467 .4527 .4583 .4636 .4686 .4734 .4780 .4825 .4867 .4907 871.8 .4947 869.7 .4986 867.6 .5023 865.5 .5059 863.6 .5094 861.6 .5127 859.7 .5158 857.9 .5190 856.1 .5221 854.4 .5251 852.6 .5280 851.0 .5309 849.3 .5337 847.7 .5365 846.1 .5392 844.6 .5418 843.0 .5444 841.5 .5469 840.0 .5494 838.6 .5518 837.2 .5542 835.8 .5565 834.5 .5588 833.1 .5611 831.8 .5634 830.5 .5656 Steam Entropy. $8. 1.4396 1.4354 1.4252 1.4154 1.4061 1.3973 1.3890 1.3530 1.3231 1.2979 1.2758 1.2565 1.2391 1.2232 1.2086 1.1955 1.1829 1.1715 1.1605 1.1504 1.1407 1.1317 1.1230 1.1146 1.1067 1.0992 1.0919 1.0850 1.0784 1.0719 1.0656 1.0596 1.0539 1.0483 1.0429 1.0376 1.0324 1.0274 1.0225 1.0178 1.0132 1.0087 1.0043 .9999 .9957 .9916 .9876 .9837 .9798 .9760 .9723 .9687 .9651 V, Specific Volume in Cubic Feet. 26.36 25.85 24.33 22.98 21.78 20.70 19.73 16.00 13.48 11.66 10.28 9.21 8.34 7.62 7.02 6.52 6.08 5,69 5.36 5.06 4.80 4.56 4.34 4.15 3.97 3.81 3.66 3.52 3.39 3.27 3.16 3.06 2.96 2.88 2.79 2.72 2.63 2.56 2.49 2.43 2.37 2.31 2.26 2.21 2.15 2.11 2.06 2.02 1.98 1.94 1.90 1.86 1.83 * Absolute pressure equals gauge pressure, plus 14.7 lb. per square inch. 150 SECTION II.-POWER STATION. Table 3.-The Properties of Saturated Steam at Different Absolute Temperatures. deg. 520 530 540 550 560 570 580 590 600 610 620 630 640 650 660 670 680 690 700 710 720 730 740 750 760 770 780 790 800 810 820 .260 .382 .523 .716 .967 1.285 1.706 2.242 2.918 3.694 4.810 6.075 7.609 9.455 11.66 14.29 17.39 21.10 25.25 30.16 35.83 42,33 49,76 58.21 67.77 78.55 90.65 104.2 119.2 136.0 154.8 830 175.3 840 197.9 850 222.2 860 248.7 28.89 1073.66 38.76 1066.51 48.65 1059.37 58.56 1052.23 68.49 1045.09 78.43 1037.95 1030.80 1023.66 1016.52 1009.38 1002.24 995.10 987.95 980.81 973.67 966.53 959.39 952.25 945.10 937.96 88.39 98.37 108.37 118.38 128.41 138.46 148.52 158.59 168.69 178.80 188.92 199.06 209.21 219.38 229.56 239.75 249.97 .0561 .00188 2.0646 .0749 .00185 2.0122 .0934 .00182 1.9617 .1116 .00179 1.9131 .1295 .00176 1.8662 .1471 .00173 1.8209 .1644 .00171 .1815 .00168 .1983 .2148 .2311 .2472 .2630 .00156 .2786 .00155 .2941 .3093 260.19 270.42 280.67 290.94 301.22 311.51 321.81 866.54 332.13 859.40 342.48 852.26 352.83 845.12 363.18 837.97 373.52 830.83 .5650 $12 1.7772 1.7353 .00165 1.6942 .00163 1.6547 .00161 1.6165 .00158 1.5795 1.5437 1.5090 .00152 1,4753 .09150 1.4426 .3243 .00148 .3391 .00146 .00299 .3537 .00144 1.3502 .00291 .3681 .00142 1.3211 .00283 930.82 .3833 .00141 1.2928 .00275 923,67 .3864 .00139 1.2653 .00267 916.53 .4103 .00137 1.2386 .00260 909.39 .4240 .00136 1.2126 902.25 .4376 .00134 1.1873 895.11 .4510 .00132 1.1626 887.97 .4642 .00131 1.1385 .00235 880.83 .4773 .00130 1.1150 .00229 873.68 .4903 .00128 1.0921 .00223 .00126 1.0698 .00217 .5031 .5157 .00125 1.0481 .00212 .5282 .00124 1.0269 .00207 .5406 .00123 1.0062 .00203 .5529 .00121 .9859 .00198 .9661 .00524 1203.6 .00505 837.8 .00486 619.9 .00469 460.2 .00453 .00437 .00422 .00408 .00395 .00382 .00370 .00358 .00347 .00337 .00327 .00317 1.4109 .00308 1.3801 U = h1 — h2—T2 ($11 − $12 ) + $81 (T1 — T2) - $11 Pl₁ = water entropy at temperature T₁ = water entropy at temperature T2 ቀ81 = steam entropy at temperature T₁ (ie., .00253 .00247 .00241 L1) T1 346.0 264.2 202.0 155.0 121.6 Steam Engine Efficiency. With an ideal steam engine working between the temperature limits T1 and T2 absolute (T₁ being higher than T2), the number of heat units which can be converted into mechanical work per pound of steam is (3) h₁ and h₂ represent the heat required to raise 1 lb. of water from freezing point to the temperatures T1 and T2 respectively. 97.21 75.85 60.79 49.14 40.04 32.85 27.12 22.53 18.85 15.86 13.41 11.40 9.747 8.371 7.222 6.259 5.447 4.760 4.175 3.679 3.250 2.878. 2.560 2.284 2.048 1.842 THE STEAM ENGINE. 151 The number of foot-pounds of work done by such an engine per pound of steam passing through it is 778 U. Equation (3) is specially useful in steam turbine work, as by it can be found the velocity with which saturated steam flows from an orifice, the temperature on one side of which is T₁, and on the other T2. This velocity in feet per second (subject to certain limitations, see STEAM TURBINES), is V 223 √ U. (4) The weight of steam needed in an ideal engine per indicated horse-power hour in pounds is 2545 U (5) K = An empirical expression for K, due to Professor Rateau, which gives good results so far as tested, is 16.202.05 log P K = 2.13+ log. Plog p (6) where P = the absolute boiler pressure in pounds per square inch, and p = the con- denser pressure (absolute) in lb. per square inch. Thus, with a condenser temperature of 100 deg. Fahr., the weight of steam per horse-power hour needed in an ideal engine, working with different boiler pressures, would be as follows:- Boiler pressure absolute in pounds per square inch. 50 75 100 150 175 200 Weight of steam needed per horse-power hour in pounds. 9.31 8.72 8.32 8.00 7.77 125 10.26 7.59 Willans' Efficiency. In actual engines the weight of water required per horse-power hour is much greater than K, and if W be the weight actually needed, then Willans' efficiency is : η K W (7) In practice, ʼn ranges from .25 up to.80. The Temperature Entropy (✪ ø) Diagram. The quantity of available heat U (equation (3) supra) can be readily calculated for all conditions of working by the Tables 1 to 3, pages 148 to 150, but many prefer to scale it off a temperature entropy diagram, such as that shown in Fig. 1. This is drawn by plotting down against each other the absolute temperatures and entropies given in the above Tables. Consider any point such as A in the diagram, then the distance AO represents the liquid entropy of 1 lb. of water at, in this case, the absolute temperature 800 deg. The distance A B represents the steam entropy of 1 lb. at the same temperature, and the total distance O B the total entropy of dry saturated steam at this temperature. The area FG ABCDF is equal to the heat units required to produce 1 lb. of steam at the absolute temperature 800 deg. absolute from feed water at freezing point. This area is measured by multiplying its mean breadth measured on the entropy scale by its total height measured on the temperature scale. If the steam is used in an ideal engine with a condenser temperature of, say 550 deg. absolute, the amount of heat which will be turned into work is found by drawing on the diagram the horizontal line G H at this temperature. Then the area A BHG is equal to U, the maximum number of units of heat which it is possible, under the conditions stated, to turn into useful work. If G H is produced GH to cut the temperature entropy curve at L, the fraction is the "dryness frac- GL tion" of the steam at exhaust. In actual practice the quantity of heat turned into work is always less than U, some of the energy which should have been converted into work being wasted in heating and drying the steam instead. By this addition of heat the entropy of the steam at exhaust is increased, and on exhaust the total entropy is therefore I K, G K instead of G L say instead of I H, and the dryness fraction on exhaust is similarly GH GL + 152 SECTION II.-POWER STATION. In other words, the steam does not in practice expand along the vertical line B H, but along some other line such as BJK, which lies more closely to BH, the more perfect the engine. ABSOLUTE TEMPERATURE 1200° 1100 1000 900 800 700° 600 I 500 0 F 400 300 200 100 O G / ·2·3 4 5 6 .7 (761) W = GABK-CBJKP = U Fig. 1. Temperature Entropy Diagram. The energy wasted in partially drying the steam during its expansion is equal to the area CBJKP, and the amount turned into work is then. HK 2 (T1 T2) nearly. U+ U 8 ct 1 (2 Engines Working with Superheated Steam. Let t be the amount of superheat, c, the specific heat from equation 2, page 146. Then the total number of heat units added to 1 lb. of steam since it left the boiler is ct. Of this amount the quantity which can be turned into work in an ideal engine is (very nearly) U₂ = ct (1 T2 CP ·9 10 11 12 13 14 15 16 17 18 19 20 2·1 2·2ENTROPY UNITS = 0) t (8) where T₁ is the absolute temperature of the steam before superheat, and T₂ the absolute temperature of the condenser. It is here assumed that the steam is saturated or over-saturated at the lower temperature. The total heat per pound of steamturned into work by such an engine will be: H Ti + 2 K dodan 恨 ​t شانه h1 – hq - T2 (P1, – Ol½2 ) + Ø8, (T1 − T2) + – фlz 81 T2 T₁ + (See equation (3), page 150.) THE STEAM ENGINE. 153 .➖➖➖➖➖➖➖➖ | THE INDICATOR DIAGRAM. The line showing the atmospheric pressure is drawn; this indicates whether the pressure at any part is greater or less than that of the atmosphere. The shape of the diagram depends upon the manner in which the steam is. admitted to and released from the cylinder of the engine. A diagram shows the pressure acting on one side of the piston only, during both the forward and return stroke, whereon all the changes of pressure may be properly located, studied and measured. To show the corresponding pressures on the other side of the piston, another diagram must be taken from the other end of the cylinder. 2 The names by which the various points and lines of an indicator diagram are known and designated are given below, and their significance fully explained. See Fig. 2. * c* -2- * с Clearance. ** 3 Pi J A A 0 L-Length of stroke to cut-off. L-Length of stroke. Pi-Absolute initial pressure. Pt-Absolute terminal pressure. Pb-Back pressure. Y с H (734) B K D Absolute Vacuum -L F Pb G B X Pt The closed figure or diagram, Fig. 3, C, D, E, F, G, H is drawn by the indicator, and is the result of one indication from one side of the piston of an engine. The straight line A B is also drawn by the indicator, but at a time when steam connection with the engine is closed and both sides of the indicator piston are subjected to atmospheric pressure only, and is called the atmospheric line. The straight lines O X, O Y, and J K, when required, are drawn by hand as explained below, and may be called reference lines. The admission line CD (see Fig. 3) shows the rise of pressure due to the admission of steam to the cylinder by the opening of the steam valve. If the steam is admitted quickly when the engine is about on the dead centre, this line will be nearly vertical. The steam line D E is drawn when the steam valve is open and steam is being admitted to the cylinder. The point of cut-off E is the point where the admission of steam is stopped - 154 SECTION II.—POWER STATION. ! by the closing of the valve. It is sometimes difficult to determine the exact point at which the cut-off takes place. It is usually located where the outline of the diagram changes its curvature from convex to concave. The expansion curve E F shows the fall in pressure as the steam in the cylinder expands behind the moving piston of the engine. The point of release F shows when the exhaust valve opens. The exhaust line F G represents the loss of pressure which takes place when the exhaust valve opens at or near the end of the stroke. The back pressure line G H shows the pressure against which the piston acts during its return stroke. On diagrams taken from non-condensing engines it is either coincident with or above the atmospheric line, as in Fig. 3. On cards taken from a condensing engine, however, it is found below the atmospheric line, and at a distance greater or less according to the vacuum obtained in the cylinder. 160 150 140 130) བླ་ཁྭ་ 120 110 100 80 4% Clearance ॥ (601) Table 4.-Steam Expansion Curves and Mean Effective Pressures. 0 lb. Terminal. Steam in Pounds. Per Cent. of Cut-Off. Atmos. Line M. E. P. 80 12.33 37.1 90 10.58 38.4 100 110 7.91 40.1 120 6.75 40.7 130 6.05 41.3 140 5.50 41.8 150 5.00 42.3 160 4.60 42.9 12 Vacuum 2 lb. Terminal. Per Cent. of Cut-Off. 9.75 33.2 8.33 34.0 9.16 38.95 | 7.06 34.8 6.80 35.3 5.16 36.0 4.58 36.5 4.16 37.1 3.83 37.5 3.50 37.8 M. E. P. 4 lb. Terminal. Per Cent. of Cut-Off. M. E. P. I 6 lb. Terminal. Scale 160 tr Per Cent. of Cut-Off. M. E. P. 8 lb. Terminal. Per Cent. of Cut-Off. 7.33 28.7 5.16 | 23.95 | 2.83 | 18.85 5.91 29.65 | 4.15 24.5 2.33 19.1 5.0 29.93 | 3.5 24.9 1.80 19.2 4.0 30.35 | 2.41 | 25.1 0.50 19.4 3.25 30.6 1.83 25.35 | 0.33 | 19.4 2.83❘ 31.0 1.5 25.70 2.66 31.45 1.16 25.75 2.43 31.65 1.08 25.9 2.31 31.8 1.00 26.0 19.4 19.4 19.4 19.4 .. •• M. E. P. 0 LB TERMINAL Fig. 4. Steam Expansion Curves. The point of exhaust closure H is the point where the exhaust valve closes. It cannot be located very definitely, as the change in pressure is at first due to the gradual closing of the valve. The compression curve H C shows the rise in pressure due to the compression of the steam remaining in the cylinder after the exhaust valve has closed. The atmospheric line A B is a line drawn by the pencil of the indicator when its connections with the engines are closed and both sides of the piston are open to the atmosphere. This line represents on the diagram the pressure of the atmos- phere, or zero of the steam gauge. The zero line of pressure, or line of absolute vacuum O X, is a reference line, and is drawn by hand, 14 lb. by the scale, below and parallel with the atmos- pheric line. It represents a perfect vacuum or absence of all pressure. The line of boiler pressure J K is drawn by hand parallel to the atmospheric line, and at a distance from it by the scale equal to the boiler pressure shown by 1 THE STEAM ENGINE. 155 1 the steam gauge. The difference in pounds between it and the line of the diagram D E, shows the pressure which is lost after the steam has flowed through the contracted passages of the steam pipes and the ports of the engine. The clearance line O Y is another reference line drawn at right angles to the atmospheric line, and at a distance from the end of the diagram equal to the same per cent. of its length as the clearance bears to the piston travel or displacement. The distance between the clearance line and the end of the diagram represents the volume of the clearance and waste room of the ports and passages at that end of the cylinder. To find the Mean Effective Pressure from the Diagram. Divide the length into any number of equal parts, say ten, setting off half a part at each end, and nine other parts between; erect ordinates perpendicular to the atmospheric line at the points of division of A B, cutting the diagram; add together the lengths of these ordinates intercepted between the upper and lower lines of the diagram, and divide by their number. This gives the mean height, which, multiplied by the scale of the indicator-spring, gives the M.E.P. Or find the area by a planimeter, or other means. Setting out a Theoretical Indicator Diagram. (FIGS. 5 and 6.) Draw vacuum line, Fig. 5, first, then a perpendicular to it, and at a distance equal to the clearance in per cent. of stroke c, another perpendicular line; on this set-off to a given scale Pi, the absolute initial steam pressure. At the end of the H 1 2 Pi Pi kc H -L 3 4 Vacuum Vacuum Line 5 6 Cod pro Pb 10 Pt U I I ces B * Pt Pb F (135) clearance set-off on the vacuum line the stroke L; at its end erect a perpendicular, and set off on it the absolute terminal pressure Pt, and the absolute back pressure Pb. On this perpendicular at a height equal to or greater than that equal to Pi, the initial pressure, draw a parallel to the vacuum line. Connect A to the 156 SECTION II.-POWER STATION. intersection F of the vacuum line with the line of no clearance, and from B draw a parallel to the vacuum line; at the intersection D erect a perpendicular DH. To find other points of the expansion curve, connect any points between H and A to F, and from the points of intersecting of these diagonals with the perpendicular D H, the points will be found as shown in the diagram. This curve once drawn to get diagram, round off corners as shown (Fig. 6) by the dotted lines. Horse Power's. Diagrams for Ascertaining Diameters of Low-Pressure Cylinders. (FIGS. 7 and 8, pages 156 and 157.) Given mean effective pressure from Fig. 7, follow on Fig. 8 vertical line corresponding to this mean effective pressure, till it intersects the diagonal line corresponding to the piston speed at which the engine is working. From this point follow diagonal running parallel to line on which piston speeds indicated to intersection with diagonal corresponding to piston speed of 600 ft. per minute, Cylinder Diameter in Inches 2200 18° 2Ë ZËNË 26 28 36 32°37′ 36 38 40 Œ2 44 46 48 60° SE 54 56 58 60 až 66 00° 68 70 72 74 2100 2000 1900 1800 1700 1600 1500 1400 1300 1200 1100 1000 900 800 700 600 300 400 300 800 100 BIO XUNTOX LINDRUTNIK MURT BOW Fig. 7. 42 70 M.E.P BOILER THESE NONCONDE. CONO. 100 20 106 21 110 31 2.2 118 $2 120 38 126 $4 180. 35 185 36 140 37 145 SA Liso 39 |15 5 40 160 41 165 42 72 170 49 173 44 180 45 ******** 25. 28 29 36 for which Fig. 7 is originally correct. From this point drop a perpendicular on to the line of mean effective pressure. This will give the new mean effective pressure, which, applied to Fig. 7, will give diameter of low-pressure cylinder for required rated indicated horse-power. To get by Fig. 7 diameter of low- pressure cylinder required for any rated indicated horse-power, follow on Fig. 7 diagonal corresponding to mean effective pressure previously found till it inter- sects with horizontal corresponding to required indicated horse-power. Following the perpendicular line from this will be obtained the diameter of low-pressure cylinder in inches required. THE STEAM ENGINE. 157 (178) a201 440 60 400. ARO 55 500 Piston Speeds. $289 520 50 45 1029 600 40 -1089 740 720 700 X\\\\\ XNXXIXAA! * % ! ! ! ! ! ! ! ! 760 36 780 820 380 960 940 80. 1000 X x 26 Fig. 8. Diagram for Ascertaining Diameters of Low-Pressure Cylinders. (Used in connection with Fig. 7, page 156.) 20 NOTE.-The diagonal lines on the diagram, Fig. 7, correspond to the mean effective pressures (15 lb., 25 lb., 50 lb. per square inch) marked on them. 15 158 SECTION II.-POWER STATION. +1 : Mean Pressure of Steam in Engines of Different Types. The expansion curve of an indicator diagram is generally assumed to be an hyperbola, though the more perfect the engine the less closely does the actual ex- pansion line approach the hyperbola. Adopting this curve, however, the mean effective pressure of the steam may be taken as where P m Cut-off in Fractions of the Stroke. coj Number of Times the Steam is Expanded. = mean effective pressure, μ = diagram factor (see Table below). p Pb According to Seaton, μ may be taken as follows:- 14 the boiler pressure (absolute) in pounds per square inch. the back pressure (absolute) in pounds per square inch. Expansive engine, special valve-gear, or with a separate cut-off valve, cylinder jacketed Expansive engine having large ports, etc., and good ordinary valves, cylinder jacketed Expansive engines with the ordinary valves and gear as in general practice, and unjacketed Compound engines with expansion valve to high-pressure cylinder; cylinders jacketed, and with large ports, etc. Compound engines, with ordinary slide valves, cylinders jacketed, and good ports, etc. Compound engines as in general practice in the merchant service, with early cut-off in both cylinders, without jackets and expansion valves .. Fast-running engines of the type and design usually fitted in war-ships -KO GOR¬-İA CARkuba HT THIN∞ ∞ 1 ∞ 4G7 Intel mfc 140=X- Some values of 13 11 1 1 2 P GOES BO 3 m 5 : μῃ (1 + 6 = coped hyp. log. R R ·· ·· Mean. 0.968 0.952 0.934 0.919 0.913 0.846 0.766 0.750 0.699 0.664 0.596 0.522 0.465 0.421 .. ·· ·· ·· -- PV) ·· 1+ hyp. log. R R Cut-Off in 1+hyp. log. R|| Fractions R. of the Stroke. -20-4 ·· .. .. ·· ·· are given below. 8 9 10 11 12 13 14 15 16 17 18 19 .. 223 ·· 20 .. ·· .. Number of Times the Steam is Ezpanded. ·· .. 0.90 μ 0.86 to 0.88 0.77 to 0.82 0.86 to 0.88 0.77 to 0.82 0.58 to 0.77 0.58 to 0.77 1+hyp. log. R R. Mean. 0.385 0.355 0.330 0.309 0.290 0.274 0.260 0.247 0.236 0.226 0.216. 0.208 0.200 In practical work the mean effective pressure in a compound engine is roughly P m = √6p. (Macfarlane Gray.) 24 159 THE STEAM ENGINE. Indicated Horse-Power of an Engine. 2PLAN Indicated horse-power = I.H.P. = 33000 where P = the mean effective pressure in pounds per square inch L = length of stroke in feet A = area of piston in square inches, less half the area of the piston rod N = number of revolutions per minute or I.H.-P. = 0.000,047,6 PLND2 = 0.000,023,8 P D2 S where D = diameter of the piston in inches piston speed in feet per minute. S = Cylinder Condensation. At the time the exhaust port closes, the temperature of the cylinder head and piston face is that of the exhaust steam. As compression increases the tempera- ture rises, but never in practice attains that of the live steam immediately after- wards admitted. As a consequence, some of this live steam is immediately condensed on entering the cylinder, evaporating off afterwards during expansion, and more especially during exhaust. The amount of steam thus initially condensed may readily be half the total taken by the engine. Compression. High compression tends to diminish losses from initial condensation but has other drawbacks, and losses arise from the fact that much more power is needed to compress the steam into the clearance space than is given back by this steam during the working stroke of the engine. In the working stroke this steam expands down to say 12 lb. per square inch only, whilst in the return stroke it has to be compressed from the condenser pressure of, say, 2 lb. per square inch. COMPOUND ENGINES. A compound engine has two or more cylinders, in which the steam after doing work in the first or high-pressure cylinder completes its expansion in the other cylinder or cylinders, in two stages; the terms triple-expansion and quadruple- expansion engines being used when the expansion takes place respectively in three and four stages. The number of cylinders may be greater than the number of stages of expansion; in the compound or two-stage expansion engine the low-pres- sure stage may be effected in two cylinders, so as to obtain the advantages of nearly equal sizes of cylinders and of three cranks at angles of 120 deg. In two crank triple-expansion engines there are frequently two low-pressure cylinders, one of them placed tandem with the high-pressure, and the other with the inter- mediate cylinder. In triple-expansion engines with three cranks at 120 deg., there are sometimes five cylinders, two high, one intermediate, and two low, the high- pressure cylinders being tandem with the low. Advantages of Compounding. The advantages secured by dividing the expansion into two or more stages are: (1) Reduction of waste of steam by cylinder condensation, clearance, and leakage; (2) dividing the pressure on the cranks and shaft, so as to avoid excessive pressures and friction. The diminished loss by cylinder-condensation is due to decreasing the range of temperature or the difference of temperature of the steam at admission and exhaust. When high-pressure steam is admitted into a single- cylinder engine, a large portion is condensed by the cold metal surfaces; at the end of the stroke and during the exhaust the water is re-evaporated, but the steam so formed escapes into the atmosphere or into the condenser; if it is taken into a second cylinder, as in a compound engine, it does work. The steam lost, in the first cylinder, by leakage and clearance, does work in the second cylinder. A compound engine, or a triple-expansion engine, requires a low-pressure cylinder quite as large as if all the work were done in a single-cylinder. The following Table due to Professor W. H. Weightman, illustrates some of the advantages gained by compounding, in the way of reducing the maximum crank-pressure and the range of temperature in the cylinders. 160 SECTION II.-POWER STATION. Table 5.—Comparisons between Single, Compound, and Triple- Expansion Engines. Diameter of cylinders, inches Area ratios Expansions • Initial steam - pressures absolute-pounds.. Mean pressures, pounds Mean effective pressures, pounds 366° .. Steam temperatures into cylinders Steam temperatures out of cylinders Difference in temperatures 181°.8 Horse-power developed Speed of piston 184°.2 800 322 Total initial pressures on pistons, pounds .. • .. "" ·· ·· .. Single Cy- linder. ·· 88120 60 165 32.96 28.96 Compound Cylinders. 165 86.11 53.11 366° 259°.9 106°.1 33 1 5 ·· 399 290 61 .. 3.416 4 •• 33 19.68 15.68 259°.9 184°.2 75°.7 28 1 403 290 269 238 455,218 112,900 84,752 64,162 Triple-Expansion Cylinders. 2.744 366° 293°.5 72°.5 165 60.8 121.44 44.75 60.64 22.35 293°.5 234°.1 59°.4 ·· 46 .. 2.70 2.714 "Woolf" and "Receiver" Types. In the "Woolf" type the steam from the high-pressure cylinder is exhausted direct into the low-pressure cylinder. In the "Receiver" type the steam from the high-pressure cylinder is exhausted into an intermediate reservoir, whence it is supplied to, and expanded in, the low-pressure cylinder. 268 238 If the steam be cut off in the first cylinder before the end of the stroke, the total ratio of expansion is the product of the ratio of expansion in the first cylinder, into the ratio of the volume of the second to that of the first cylinder; that is, the product of the two ratios of expansion .. 63,817 Thus, let the areas of the first and second cylinders be as 1 to 31, the strokes being equal, and let the steam be cut off at first at Expansion in the 1st cylinder stroke; then 2nd "" "" 61 4.740 2.714 ·· 22.4 16.49 12.49 234°.1 184°.2 49°.9 •• 264 238 53,773 1 to 2 1 to 31 Total or combined expansion, the product of the two ratios 1 to 7 In a compound engine, the low-pressure cylinder, communicating with the condenser, requires to be at least as large as if the entire work of the engine had to be performed by it. Woolf Engine, without Clearance-Ideal Diagrams. The diagrams of an ideal Woolf engine are shown in Fig. 9, as they would be described by the indicator, according to the arrows. In these diagrams p q is the atmospheric line, m n the vacuum line, cd the admission line, dg the curve of expansion in the first cylinder, and g h the consecutive expansion-line of back pressure for the return-stroke of the first piston, and for positive pressure for the steam stroke of the second piston. At the point h at the end of the stroke of the second piston, the steam is exhausted into the condenser, and the pressure falls to the level of perfect vacuum, m n. The diagram of the second cylinder below g h is characterised by the absence of any specific period of admission; the whole of the steam line g h being expan- sional, generated by the expansion of the initial body of steam contained in the first cylinder into the second. When the return stroke is completed, the whole of the steam transferred from the first is shut into the second cylinder, so that the effective pressure in the low-pressure cylinder is the back pressure in the high- pressure cylinder. The final pressure and volume of the steam in the second cylinder is the same as if the whole of the initial steam had been admitted at once into the second cylinder, and then expanded to the end of the stroke in the manner of a single-cylinder engine. The net work of the steam is also the same, according to both distributions. THE STEAM ENGINE. 161 g P k $1 Receiver-Engine, without Clearance-Ideal Diagrams. In the ideal receiver-engine the pistons of the two cylinders are connected to cranks at right angles to each other on the same shaft. The receiver takes the steam exhausted from the first cylinder and supplies it to the second, in which the steam is cut off and then expanded to the end of the stroke. On the assumption that the initial pressure in the second cylinder is equal to the final pressure in the first, and, of course, equal to the pressure in the receiver, the volume cut off in the second cylinder must be equal to the volume of the first cylinder, for the second cylinder must admit as much steam at a stroke as is discharged from the first cylinder. p n d 9 Fig. 10. C ď WOOLF.ENGINE.-IDEAL h RECEIVER ENGINE-IDEAL INDICATOR (736) DIAGRAMS. INDICATOR DIAGRAMS. 60 Ube 40 q h -20 m P k -60lbs -40 -20 2/3- mga ky for al 1/3. d c h q 1, RECEIVER ENGINE-IDEAL DIAGRAMS REDUCED AND COMBINED. Fig. 11. In Fig. 10, c d is the line of admission, and h g the exhaust line for the first cylinder; and d g is the expansion curve, and p q the atmospheric line. In the region below the exhaust line of the first cylinder, between it and the line of perfect vacuum, o l, the diagram of the second cylinder, is formed; h i, the second line of admission coincides with the exhaust line, h g, of the first cylinder, showing in the ideal diagram no intermediate fall of pressure, and ik is the expansion curve. The arrows indicate the order in which the diagrams are formed. In the action of the receiver-engine, the expansive working of the steam, though clearly divided into two consecutive stages, is, as in the Woolf engine, essentially continuous from the point of cut-off in the first cylinder to the end of the stroke of the second cylinder, where it is delivered to the condenser; and the first and second diagrams may be placed together and combined to form a continuous diagram. For this purpose, take the second diagram as the basis of the combined diagram, namely, h i k lo, Fig. 11. The period of admission, hi, is G 162 SECTION II.-POWER STATION. one-third of the stroke, and as the ratios of the cylinders are as one to three, hi, is also the proportional length of the first diagram as applied to the second. Produce o h upwards, and set off o c equal to the total height of the first diagram above the vacuum line; and upon the shortened base hi, and the height hc, complete the first diagram with the steam line c d, and the expansion line di. Combined Diagrams for Two-Cylinder Compound Engines. Lay off (Fig. 12) on a scale a distance O V proportional to the total cubic con- tents of cylinder, including the clearance of the high-pressure cylinder. Lay off P Pressure at throttle... "L 0 I- a se va pe a p V V₁ 12 Atmospheric line Line of perfect V₁ Vacuum (223) another distance O V₁ to same scale, equal to total cubic contents of low-pressure cylinder, including clearance. I represents clearance in high-pressure, and O C clearance in low-pressure cylinder. Draw O P equal to absolute pressure at throttle. Divide Ô V and O V1, each into ten equal parts. Then take the two cor- responding indicator diagrams of high and low-pressure cylinders, and divide each into ten equal parts, and measure either from vacuum or atmospheric line the corresponding pressures, and plot them to the proper scale on the corresponding combination diagram. Receiver Capacity (Two-Cylinder Engines). The receiver capacity between high and low-pressure cylinders, inclusive of pipes and passages, &c., need not exceed the capacity of the high-pressure cylinder under ordinary circumstances. Where engines are compounded on the tandem" principle, the pipes and connections may at a pinch be found to have sufficient volume. When the cranks are at right angles, a receiver should be provided with a capacity equal to not less than the volume of high-pressure cylinder, to permit of sufficient early cut-off. This is an absolute minimum, and with variable loads more should be provided. Seaton states that the receiver capacity should be from 1 to 1.5 times the capacity of the high-pressure cylinder, when the cranks are at an angle of from 90 deg. to 120 deg. When the cranks are at 180 deg., or nearly this, the space may be very much reduced. In the case of triple-compound engines, with cranks at 120 deg., and the intermediate cylinder leading the high pressure, a very small receiver will do. The pressure in the receiver should never exceed half the boiler pressure. Cylinder Ratios (Two-Cylinder Engines.) A considerable variation in the ratio of the cylinders of compound engines is permissible without affecting the economy. The ratio should be determined by the boiler pressure available, the load to be driven, and the desired ratio of expan- sion. A simple rule, in ordinary two-cylinder compound engine practice where the load is fairly constant, is to multiply the absolute initial pressure by 4 and divide by 105. The quotient will be cylinder ratio. Cr, if P = the initial pressure in cylinder; n, the number of tenths of the THE STEAM ENGINE. 163 stroke during which it is required to admit the steam in high-pressure cylinder; and r the cylinder ratio, Pounds per Square Inch V ÷ v If we designate volume of high-pressure cylinder by v, and of the low-pressure by V, Grashof gives V ÷ v = 0.85 √r; Hrabak, 0.90 √r; Werner, √ĩ; r being the ratio of expansion. Busley makes the ratio dependent on the boiler pressure thus; •• Boiler Pressure per Gauge. Pounds per Square Inch. 130 140 150 160 lb. 100 to 120 120 150 150 160 "" "" r = Piston Speed. The mean piston speed of an engine is found by multiplying twice the stroke in feet by the revolutions per minute. The common piston speed for small horizontal engines of about 12-in. stroke is from 300 ft. to 400 ft. per minute, but large engines and high-class small engines run at about 700 ft. per minute, while locomotive pistons frequently exceed 900 ft., and even 1000 ft. per minute. Marine engines run at from 700 ft. to 900 ft., torpedo boats 1000 ft. to 1200 ft. per minute. The engines in the Royal Navy have higher piston speed than those in the mercantile marine. Most Economical Absolute Terminal Pressures for Compound Corliss Condensing Engine. Boiler Pressure. Pn 105 Small Cylinder. 1 1 1 60 3 1 Cylinder Ratios, Three-Cylinder Engine. This type of engine is now adopted for marine purposes almost entirely. A useful rule for determining the size of intermediate cylinder is to make the ratio between first and second cylinders equal to the square root of ratio between small cylinder and large cylinder, or √r. When the piston speed varies from 750 ft. to 1000 ft. per minute, the following cylinder ratios are recommended: - 90 4 105 4.5 120 5 Absolute Terminal Pressure. lb. 10 9 8 Cylinder Ratios. Intermediate. 2.25 2.40 2.55 2.70 Normal absolute mean effective pressure = Normal absolute mean effective pressure for greatest economy boiler pressure in pounds 170 and upwards quadruple-expansion engine to be used. Approximate Rules for Compound Condensing Corliss Engine. absolute pressure at throttle 5 Large. 5.00 5.85 6.90 7.25 5 Maximum absolute mean effective pressure = norma absolute mean effective pressure x 1.4. Largest diameter of low-pressure cylinder is not to exceed length of stroke; diameter a good ratio of 1 stroke 1 Maximum allowable piston speed 900 ft. per minute; it should not, however, exceed 760 ft. Engines have been built and run satisfactorily with a piston speed of 1100 ft. Diameter of high-pressure cylinder = half diameter of low-pressure cylinder. I 164 SECTION II.-POWER STATION. Table 6.-Some Standard Direct-Connected Slow-Speed American Tramway Engines. •• Type of engine Cylinder diameter 10 by 19 Stroke, inches 30 Crosshead piu. in. Crank pin, inches.. Journals, inches Flywheel diameter, feet.. 3 by 3 4 hy 4 83 by 15 Weight of wheel Shaft diameter, in. K.W. of dynamo Weight of dynamo, pounds Weight of armature Engine shipping weight Revs. per minute ·· ·· .. ·· ·· • ·· ·· • • Type of engine Ссс Cylinder diameter 18 by 34 18 Stroke, inches 42 Crosshead pin, in. 4 by 415 Crank pin, inches..53 by 51 63 Journals, inches 14 by 24 16 Flywheel diameter, 18 feet 16 Weight of wheel 40,000 Shaft diameter, inches Kilowatts of dynamo Weight of dynamo, pounds • .. •• •• Weight of wheel Shaft diameter, in. K.W. of dyanmo Weight of dynamo, pounds •• 400 400 30,000 72,000 31,000 Weight of armature Engine shipping weight 155,000 | 183,000 Revs. per minute.. 100 90 .. cc TCC 14 by 26 14 by 26 36 36 CC CCC TCC CC ccc ccc ссс 16 by 30 16 by 30 16 by 30 16 by 32 16 by 32 17 by 34 30 42 42 42 42 31 by 31 41 by 4 5 by 5 by 41 53 by 514 by 41 5 by 5 4 by 443 by 415 by 51 by 51|51 by 51|41 by 41 5 by 5 10 by 17 10 by 18 13 by 22 by 26 14 by 28 11 by 19 12 by 20 36 4 by 44 4 by 45 11 by 19 15 inches K. W. of dynamo Weight of dynamo, pounds Weight of armature Engine shipping weight Revs. per minute .. 10 13,500 10 125 .. 21,000 7000 .. 150 Type of engine ссс CCC Cylinder diameter 22 by 42 22 by 42 Stroke, inches 48 48 Crosshead pin, in. 5 by 5 5 by 5 Crank pin, inches 5 by 551 by 5 Journals, inches 15 by 28 12 by 22 Flywheel diameter, feet.. •• .. 14 20,000 111 200 17 50,000 18 500 72,000 90,000 Weight of armature 31,000 30,000 Engine shipping weight Revs. per minute.. 37,000 37,000 14,500 14,500 173,000 100 89,500 85,000 120 120 21 800 by 514 by 6 by 28 18 45,000 19 co c c CC CC C by 34 18 by 36 19 by 36 42 30 48 by 415 by 5 8 by 6 5 by 5 9 by 17 12 by 22 12 24,000 111 200 20 800 10 24,000 107,000 107,000 44,000 44,000 101 2001 200 [21,000 121,000 7000} 120 18 18 38,000 100,000 18 500 22 850 .. + } 94 20 12 35,000 15 300 .. 45.000 40,000 17,000 15,000 150 347,000 308.000 308.000 90 90 80 16 31,000 15 .. 141,000 100 18 50,000 21 400 }21,000 60,000 CC VCCC TCC cc ccc 23 by 46 23 by 46 24 by 40 24 by 44 48 48 42 48 7 by 76 by 61 61 by 61 8 by 76 by 61 61 by 61| 20 by 36 18 by 36 15 by 30 6 by 6 6 by 6 15 by 24 18 70,000 21 800 16 25,000 16 225 116,000 90 5 6 16 267,000 100 25 1,200 158,000 68,000 80 cc c CC C 20 by 38 20 by 38 42 48 by 5151 by 51 by 66 by 61 by 28 16 by 28 16 40.000 17 300 18 35,000 16 500 90 107,000 69,000 45,000 44,000 27,000 25,000 61,000 61,000 21,000 21,000 21,000 7,000 24 1,200 415,000 80 201 60,000 17 500 128,000 180,000 100 75 16 18 60,000 65,000 19 70,000 19 19 19 500 425 500 72,000 74,000 76,000 31,000 32,000 32,000 25,000 181,000 197,000 80 110 c c c | ccc CCCVCC C 48 48 60 60 48 -- Type of engine ссс CCC TCC CCC T.CC c c c Cylinder diameter 26 by 50 26 by 50 28 by 52 28 by55) 30 by 60 30 by 60 32 by 62 32 by 62 36 by 72 Stroke, inches 48 48 60 60 Crosshead pin, in. 7 by 7 7 by 7 10 by 10 9 by 9 10 by 10 10 by 10 10 by 10 10 by 10 10 by 10 Crank pin, inches.. 8 by 8 7 by 7 10 by 10/10 by 10 11 by 11 10 by 10 10 by 10/10 by 10 10 by 10 Journals, inches 20 by 36 20 by 36 20 by 36 22 by 38 22 bv 42 22 by 4822 hy 48 22 by 48 22 by 42 Flywheel dia., feet 21 20 20 24 20 25 24 24 Weight of wheel | | | 100,000 120,000 140,000 120,000 160,000 160,000 160,000 140,000 | Shaft diameter, ·· 25 85,000 28 1,500 16 40,000 16 300 :: :12 75 144,000 141,000 100 90 5 by 5 6 by 6 17 by 30 42 CCCVC C C 20 by 40 20 by 40 42 by 5 6 by 6 17 by 33 5 90 ccc CCC 24 by 48 48 8 by 8 8 by 8 20 by 36 18 16 28,000 31,000 15 15 500 ·· 24 1,500 158.000 68,000 :12 90 75 20 241/3 20 100,000 | 139,625 | 96,000 22 24 14 750 1500 = 87,600 158,000 36,000 68,000 285,000 | 509,000 | 306,000 85 75 80 90,000 30,000 90 TC VCCC 24 by 48 26 by 48 60 48 10 by 106 by 61 10 by 107 by 7 22 by 42 14 by 28 26 1,500 C C C 20 by 40 48 6 by 6 6 by 6 15 by 30 :12 20 65,000 17 400 72,000 31,000 187,000 85 75 24 1,500 158,000 68,000 460,000 75 THE STEAM ENGINE. 165 Steam Pressure at Throttle above Atmosphere. Table 7.-Ratio of Cylinders used in American Corliss Engines. lb. 80 90 100 110 120 125 130 140 150 160 Rated Capacity of Plant in Kilo- watts Requred. Compound Non-Condensing. 200 400 600 1,000 1,500 2,000 3,000 4,000 5,000 6,000 8,000 10,000 15,000 20,000 30,000 75,000 1 to 2 1 1 "" "" ·· 1 to 24 • .. 222 1403100 • 21 Compound Condensing. Three 100 .. Three 200 Three 300, or four 200 Three 500 Five Four Four 5000 Five 5000 Seven 5000 Eleven 7500 Three 750, or four 500 Five 500, or four 750 Four 1000 ·· Five 1000, or four 1500 Four 1500 Five 1500, or four 2000 2000, or four 2500 3500, or five 2500 1 to 3 1 1 1 1 •• "" Number and Size of Units to be Installed, in Kilowatts, including Reserves. •• "" .. "" •• >> ENGINES FOR ELECTRIC POWER STATIONS. In early days the engines employed in electric power stations were far too small and weak. At the present time dynamos for tramway work are so constructed that accidents to them are quite as rare as to the driving engines themselves. Countershafts have been abandoned, as wasteful in power and useless. Large reserves of power were also provided on the earlier electric lines; this practice has been modified, and Table 8 shows the reserve power which should be allowed. With this the machinery can be kept in perfect repair, one engine being held in reserve. Table 8.-Number and Size of Economical Units in Power Stations. .. að að að ∞ < 3 1 to 4 1,, 4 a oslep onlar 33 .. • • Triple-Expansion, Condensing Jacketed Cylinders. • • 1 to 2% to 5% 1 2.975 6.075 "" "" 1 1 "" "" 3.0448,, 6.625 3.1087,, 6.625 •• 1 to 3.2198 to 7.175 1 3.267 7.45 "" "" 1 3.308 7.725 1 3.344 8 "" "" "" "" Remarks. One reserve unit "" "" "" 1) "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" >> "" "" "" "" "}" "" "" "" "" ** The conditions under which a tramway engine works are, if anything, more onerous than those of a rolling-mill engine. A slight variation, either in number of revolutions per minute, or in angular velocity per revolution, is of the greatest importance in a traction station, whereas it is of small importance in a rolling-mill. A uniform speed is especially important where compound-wound dynamos are run in parallel direct on to the line. If the momentary difference in speed between two engines exceeds very narrow limits, the voltage of the machines differ, causing very heavy currents in the equalising bars, and largely increased core losses, hence great waste. If the difference becomes too great, one of the generators may 166 SECTION II.-POWER STATION. even be reversed. Where multiphase machines run in parallel, constant speed is of even greater importance to keep the machines in step. In cases where shunt- wound generators with heavy batteries of accumulators run in parallel on the line, the question of engine regulation is not so important. A traction station where compound-wound dynamos are used should be so arranged that, if the normal load be suddenly thrown on or off an engine, the speed shall not vary more than 2 per cent. In some cases a maximum variation of 14 and 11 per cent. is all that is allowed. Where polyphase currents are used, constant speed is of even greater importance; and a guarantee should be required that under no circumstances shall the angular velocity during one revolution vary more than one-half per cent. With heavy fly-wheels, and governors properly designed for tramway work, it is quite practicable to fulfil the above con- ditions. In polyphase work the engine should not produce by variation of angular velocity a phase displacement of more than 5 deg. per half cycle. Driving. The great objection advanced against direct coupling was the want of elasticity in connection with the engine. It was said that belts and ropes acted as springs, preventing sudden shocks from damaging the engine. Direct coupling is now practically universal, and should always be used for units of 100 kilowatts and upwards. Power. Tramway work is such that in the large stations the average load rarely exceeds two-thirds of the maximum; it therefore becomes necessary, in order to have an economical engine, for it to be so constructed, that, at its most economical cut-off it will give out two-thirds of its maximum power. Thus, supposing an engine at its most economical cut-off of 28 per cent. will give 350 horse-power; at its maximum cut-off of 80 per cent. it will give 520 horse-power. When, therefore, an engine of 350 horse-power is ordered, it is expected to be able to run at 50 per cent. overload, the generators being constructed to stand the same strain. All bearings must be of such ample dimensions as to run perfectly cool when the engine is working at 50 per cent. above its rated power. Table 9.-Mean Effective Pressure and Steam Consumption of Slow-Speed Condensing Engines. Steam Pressure on Gauge at Throttle in Pounds per Square Inch. sure Steam consumption normal load per indicated horse-power Steam consumption 40 per cent. over load per indicated horse- power ·· .. Ratio of volume of low-pressure to high-pressure cylinder Normal cut-off on high-pressure 23 22 cylinder, per cent. Maximum cut-off on high-pres- sure cylinder, cent. 40 40 40 Absolute normal terminal pressure 7.45 7.7 Absolute maximum terminal pres- 40 40 40 40 8.7 10.75 11.45 11.7 12.7 8.7 10 13.7 15.2 16.2 14.5 14 13.5 17.2 16.16 18 16 15 13 .. Mean effective pressure normal load Mean effective pressure maximum load 80 ·· 3:1 13:1 25 20 19 100 27 32:14:1 23 150 130 140 150 1 19 23 32 17 27 38 4:1 22 29 4:1 4:1 41 22 16.75 16.25 15.4 31 33 43 22 160 46 4:1 14.85 | 35 49 ! THE STEAM ENGINE. 167 High-Speed Engines. Properly-designed high-speed engines have proved perfectly capable of handling traction loads. The oldest satisfactory type of these engines is the Willans central valve engine, illustrated in Fig. 13. The piston-rod is hollow, and has formed in it FRAIN COCK AIR BUFFER RELIEF COCK (759) HO EDI STEAM CHEST EXHAUST ΤΟ LUBRICANT H.P. |CHAMBER CRANK CHAMBER CO LOW PRESSURE D 1000 መበስበስ PISTON 0 0 0 #↓ ↓ ↓ 10 0.00 OW PASARE PISTON cr \GUIDE DRAIR CUSHION CYL. rafa CYL. AG |CYLINDER GUIDE PISTON LUBRICAN #13 OIL FUNNEL GOVERNOR GUARD AND OIL CATCHER Fig. 13. Willans' Central-Valve High-Speed Engine. the ports through which steam is admitted and exhausted from the cylinders, which are arranged tandem fashion, as shown. The valves, which are of the piston type, work inside the hollow piston-rod, the whole string for a series of cylinders being driven by a single eccentric keyed to the crank-pin. A simple engine may be 168 SECTION II.—POWER STATION. · Size Symbol. 2 F 3 F 2 G 3 G 2 H 3 H 21 3 I 20 30 2 P 3 P 2 Q CORR 3 R 2 S 3 S 2 T 3 T 2 V.S. 2 V.L. 3 V.S. 3 V.L. 3 W.s. 3 W.L. 3 X.s. 3 X. L. Approximate Floor Space Required. Engine on Short Base, with Pulley and Outer Bearing. Engine on Short Base. ft. in. ft. in. 5 11x 3 0 7 2x 3 6 6 6x 2 10 7 9× 4 0 7 5X 4 6 9 3x 5 0 9 8x 4 9 11 10× 6 0 7 4x 4 0 9 2× 4 0 10 1× 5 3 12 7× 5 3 10 9× 5 7 13 6× 5 7 11 10× 5 11 15 0x 5 11 11 5× 6 0 15 3× 6 0 12 6× 6 0 16 2x 6 0 | | × Table 10.-Willans' Central Valve Engine. (APPROXIMATE DIMENSIONS.) Approximate Height to Top of Grease Cups. 19 8x 8 10 19 8x 8 10 24 6×10 6 24 6×10 6 27 5×12 2 27 5×12 2 ft. in. ft. in. 8 0x 3 0 9 8x 3 6 8 10x 2 10 10 6× 4 0 0× 4 6 10 12 3× 5 0 12 9x 4 9 15 9× 6 0 10 12 0X 4 0 3× 4 0 13 6× 5 3 9× 5 3 16 14 7× 5 7 18 2x 5 7 15 11x 5 11 19 11 × 5 11 15 11 × 6 0 20 11× 6 0 17 1x 6 0 21 11x 6 0 11 3x 28 3× 8 10 28 3× 8 10 35 11×10 6 35 11×10 6 40 8x12 2 40 8×12 2 Engine on Combination Base. ft. in. ft. in. 10 0× 4 0 12 0× 5 0 11 12 13 14 14 18 11 14 15 18 16 0X 5 0 6× 5 2 0× 6 3 0 6× 5 6 6x 6 3 0× 6 0 0× 7 0X 6 Simple. ft. in. | LO LO LO LO 1 1 ∞ ∞∞∞∞==~2 CHOTTTOO~~—BON 5 5 5 6 0x 6 6 6× 7 0× 8 0 8 4 3× 7 8 10 9 25 5 10 19 6X 7 9 10 7 1 7 12 6 7 6 7 8 10 8 10 4 0 2 3 11 1 11 3 12 0 2 Com- pound. ft. in. 6 6 6 9 6 7 6 10 8 3 10 Danawo 6 9 6 7 7 9 9 10 1 11 9 11 11 12 11 2 25 13 1 14 0 14 15 15 20000 8 8 18 6 20 22 641 4 Triple- Expansion ft. in. 7 3 7 6 7 6 7 9 9 5 9 8 0000000∞∞ 1 1 1 0 0 1 TO 00 ∞ ∞ 10 6 10 10 8 8 8 8 11 11 13 13 14 14 15 6 5 20 23 24 5 28 31 1 3 3 15 8 5 17 17 3 3 0500 8 10 6 1 ∞ fund 3 Dia- Dia- meter of meter of Steam Exhaust Pipe. Internal Internal Approximate Width and Depth of usual Concrete Founda- I.H.P. tions. The Length being Dependent on Type of Bed-plate. Pipe. in. oo co 3 3 3 3 4 4 5/ 5/1/ 5급 ​5/ 71% 1400140 7799aa in. 31 5744 ( 8 718 918 10 OONELLORE 10 12 12 dointer 14 14 16 15 173 171 177 218 218 2518 251% ft. in. ft. in. 5 0x 5 5 6× 5 4 10X 5 6 6 6 7 6 8 6 6 11-∞∞ 7 0X 6 3× 6 7X 7 8 7X 7 8 0X 5 0 6× 7 0 0x 5 6 9X 7 0 0x 6 0 0x 6 0 0x 6 0 8 10× 8 8 10× 8 9 9 9 9 0x 8 0x 8 DOGE 0x 9 0X 9 6 ☺c=cocooo 6 0 0 0 0 11 10×10 0 11 10×10 0 13 6x11 0 13 6x11 0 15 0x11 6 15 0x11 6 75 112 100 150 165 250 240 360 120 180 240 360 300 450 385 575 470 705 550 825 $35 835 1250 1250 1875 1875 2500 2500 THE STEAM ENGINE. 169 compounded, or a compound engine tripled, by adding another cylinder at the top of the engine. Special care is taken as to drainage, there being no pockets in which water can lodge. The engine is single-acting, and the piston-rod is always in compression. To ensure this, the upper part of the guide chamber is closed in forming an air cushion, or air pocket, the pressure in which prevents the inertia of the pistons and rods on the up-stroke carrying the top brass away from the crank-pin. A simple centrifugal governor is mounted direct on the crank-shaft, as shown and opens and closes a throttle-valve above. Splash lubrication is relied on, and 21 20 LBS. WATER PER B.H.P. HOUR 19 18 17 Q:16 15 G さ ​32 512 // 10 9 TRIPLE EXPANSION CONDENSING 400 R.P.M.,185 LBS B P.,28″VACUUM 4 LOAD LOAD 3/4 LOAD FULL LOAD 20 40 60 80 100 120 140 160 180 200 220 240 260 °F SUPERHEAT STEAM CONSUMPTION OF 210 B.H.P.WILLANS ENGINE WITH VARYING LOADS & DEGREES OF SUPERHEAT (760) Fig 14. is remarkably efficient; the wear of the crank-pins and crank-shaft journals being almost imperceptible after several years' run. The cylinders are simple ring castings without valve chests at the side or any flat surfaces. The engine is thus particularly well adapted for the use of superheated steam, and with this the makers have attained a remarkable degree of economy We reproduce above (Fig. 14) a curve showing the results obtained with an engine of 210 H.-P. only. Willans' engines are made in a large range of standard sizes, of which we give a list on page 168. The Belliss Engine. Another excellent high-speed engine is the Belliss engine. This differs from the Willans engine in being double acting and in having its cylinders arranged side by side instead of tandem fashion. All the bearings are lubricated with oil under pressure, and, as in the Willans engine, the wear is almost imperceptible. On the following page we give a list of the standard sizes of this engine, and the floor space occupied. + G2 170 SECTION II.-POWER STATION. Table 11.—“Belliss" Patent Self-Lubricating Three-Crank Triple-Expansion Type “T” Engines. TABLE OF STANDARD POWERS AND REVOLUTIONS. Approximate Approximate Maximum Maximum Brake H.-P. Killowatts. 180 180 225 225 300 300 400 400 500 500 600 600 260 260 325 325 430 430 570 570 720 720 860 860 Type of Engine. Simple non-condensing slide valve .. Compound non-condensing slide or piston valve . Compound condensing slide or piston valve Revolu- tions. Simple non-condensing Corliss Compound condensing Corliss and gridiron slide valve High-speed compound marine type double-acting engines.. Triple - expansion slow speed Corliss and Sulzer type - 550 500 475 450 400 375 400 350 350 330 ·· 330 280 Approximate Approximate Maximum Maximum Brake H.-P. Kilowatt. ngine. I.H.-P. 200 to 2000 200 to 2000 250 to 1500 150 to 400 300 to 6000 200 to 1200 1500to 10,000 NOTE.-A steam pressure of 170-200 lb. per square inch is recommended with triple-expansion engines wherever possible; but they will be found to give a superior economical performance to compound engines at lower pressures down to 125 lb. per square inch under condensing conditions, though the full-rated output cannot in every case be reckoned upon. Steam in Pounds per Rated Board of Power Trade Unit. of Table 12.—Approximate Coal and Steam Consumption of Steam Engines in Tramway Power Stations. Steam pressure 100 lb. to 150 lb. Fair average steam-coal used. 750 750 750 900 900 1180 1180 1180 1180 1500 1500 1500 Limits of Variation. Average. 27 36 19 40 46 to 85 65 8 to 13 9 35,, 70 60 6 10 8 6 7 "" "" "" "" 93 1100 1100 1100 60 40 3 1300 1300 1700 1700 1700 1700 2140 2140 2140 Coal in Pounds per Board of Trade Unit. 17 21 Limits of Variation. "" "" 9 60 50 4,, 9 40 24 2 7 "}} 85 60 6 9 "" 19 21,, 4 Average. Revolu- tions. Limits of Variation. 30 45 Ratio of Average Load to Rated Power of Engine Per Cent. 40 300 280 44 to 17❘ 54 50 75 60 "" 270 300 270 250 240 230 215 250 "" 200 170 33 "" Average. 75 65 4 7 3 75 to 100 $5 60 65 75 70 “་་ 1 THE STEAM ENGINE. 171 Type of Engine. Table 13. Economical Steam Engine Results. The following are some of the most economical results that have been obtained up to the present with steam engines of various makes and types. Simple- Sulzer ·· Corliss .. Simple Superheating- Schmidt Field Compound- Dujardin Sulzer ·· Wheelock Leavitt.. Bollinckx Triple- Willans .. ·· ·· • • Compound Superheating- Schmidt ·· ·· Willans (Superheated Steam) Sulzer Allis Quadruple- = ·· .. .. •• • ·· Indicated Horse- Power. Me Me 284 137 18 136 548 247 = 590 643 305 76 30 210* 615 574 Boiler Pressure. 268 135 113 85 160 135 91 180 170 185 141 120 ·· 500 Piston Speed in Feet Experimental engine at Cor- nell University * Brake horse-power. † Consumption per brake horse-power hour. } M + }√/M² + T². per Minute. 372 = M + √ M² + T2. T². 350 490 570 493 612 471 479 380 384 516 203 CRANK-SHAFTS. Crank-shafts are subject to both twisting and bending. These combined actions are generally reduced to a single equivalent bending moment by the formula:- e. Where T = the actual twisting moment and M the actual bending moment. In this case the maximum stress on the shaft under the combined moments is the same as it would be were the shaft subject to the simple equivalent moment M It should be noted, however, that the stress is not of the same kind in the two cases, being in one case a shear, and in the case of the combined moments a tension or compression. Experience with crank-shafts run at a high speed shows that the above formula is unreliable. This may be partly due to the rapidity with which the stress alternates; but it is also to be noted that experiment and theory both lead to the conclusion that the real criterion of the strength of a shaft is not the maximum tension or compressive stress in it, but the maximum shear. In that case, to reduce a combined twisting moment and bending moment to a single equivalent bending moment we should write (9) Me √M² + T2 which is always greater than Steam per Indicated Horse- Power Hour. lb. 18.4 17.5 ·· 17.18 18.6 13.46 13.35 12.84 12.16 12.19 10.17 12.74 10+ 11.85 11.68 10 With slow-speed engines, the latter formula gives fair results, though even with these many cases of breakage under stresses of only some 8000 lb. to 10,000 lb. per 172 SECTION II.-POWER STATION. " square inch are on record, the shafts failing from fatigue after some millions of revolutions. It is safer, therefore, even here, to use formula No. 9. There is little doubt, however, that the working stress may be higher in a slow-speed shaft than in a high-speed one, but sufficient data are not yet available to provide for this in a rational manner. When the crank-shaft carries on it an armature, allowance must be made for the unbalanced magnetic pull, which may arise if the armature is slightly out of centre. How important this may be will be understood on reference to the following Table :- Table 14.-Pull on Shaft from Actual Practice due to -In. Displacement of Constant - Current Railway Generator Armature. Kilowatts. 100 150 200 250 300 1500 Rated Capacity of Generator in Kilowatts. Revolutions per Minute. 225 325 425 525 800 1000 1200 1500 2500 3500 A practical rule for determining approximate diameter of shaft for direct-con- nected slow-speed Corliss engine with two bearings is :-Diameter of shaft in bear- ings not less than half diameter of low-pressure cylinder. Pressure on journals not to exceed 200 lb. pressure per square inch of projected area, which is diameter of journals x length of journals. 250 225 180 100 160 75 Shaft in bearings is 2 in. less diameter than thickest part up to 18 in. shaft, and above that 3 in. smaller in bearings. The following is a specification for the hollow-forged shafts for 7500 horse- power engines for Metropolitan Street Railway Company, New York: Speed in Revolutions per Minute. 130 110 100 95 Tensile strength, 74,860 lb. per square inch. Elastic limit, 41,760 lb. per square inch. Elongation, 25 per cent. Contraction, 45.24 per cent. (on United States Standard Test Bar). 90 85 Table 15.-Approximate Weight of Flywheels used for Con- tinuous-Current Railway Generators. (Armature between Two Journals, next to Flywheel). 80 75 75 75 Weight of Armature in Pounds. 3,000 4,000 8,000 15,000 12,000 70,000 20,000 30,000 40,000 50,000 Diameter Weight of Flywheel in of Flywheel Pounds. in Feet. 100,000 110,000 125,000 150,000 180,000 225,000 14 16 17 18 19 20 22 24 Magnetic Pull in Pounds due to -In. Displacement. 2*** 26 28 3,500 5,000 7,000 10,000 8,000 40,000 Diameter of Shaft at Centre in Inches. 12 15 16 18 20 22 24 26 32 37 Size of Journals in Inches. 10 x 18 12 x 20 14 X 24 16 x 28 20 x 36 X 20 × 36 22 x 48 22 X 48 28 x 48 34 x 60 THE STEAM ENGINE. 173 W*H= 24 amperes 009. 1000! {bord A 0001 1509 400) Minutes 32 Fig. 15. Load Diagram of Light Street Power Plant. Two Dynamos in Parallel. Baltimore, Md. savedwo 62 09 es 99 34 28 50 ** #+ 44 es 36 JO 20 26 24 22 20 78 14 12 ao from which we get the moment of inertia of the required flywheel. Rankin' gives as the usual mean radius of the flywheel on steam engines from three to five times the length of the crank. Or we may take another approximate formula, which will give us the weight W of the flywheel in tons, if the niean radius R in feet, the revolutions n per minute, the co-efficient M giving the value of the relative variation in speed permitted, and the variation of energy ▲ E during one revolution in foot-tons are given. Then we have approximately : number of W = 331 Flywheels. A most important detail is the fly. wheel. As the average output of an engine in traction work is generally from one to two-thirds of the maximum load, it follows that if the engine were built with a view to taking full load, it would ordinarily be working with a very low efficiency. The usual practice, therefore, is to employ engines, the greatest efficiency of which is reached when running at about two-thirds of the maximum power required. As seen from a load diagram of an electric railway (Fig. 15), the very heavy loads come on for a period of a few seconds only. The . engines are therefore furnished with fly- wheels having such a weight that their live energy is able, during a few seconds, to give out the extra amount of work called for. The weight of the wheel must be such that within the permissible variation of speed the power called for can be given off. Thus, supposing an engine is running at 200 revolutions, and must govern within 2 per cent. the number of foot-pounds stored in the flywheel, must be such that the required storage can be given off without slowing down more than at the rate of about four revo- lutions per minute. It will be seen therefore, that the heavy rim of a flywheel in an electric tramway power-house does not merely serve, as in most other instances, as Rankin puts it, to "reduce the co-efficient of fluctuation of speed to a certain fixed amount," varying in most cases between to, but that its chief object is to take care of momentary overloads. If I is the moment of inertia of the I S flywheel, the coefficient of fluctua- tion permitted, g the acceleration (32.2 ft. per second, A E the energy the flywheel has to furnish during one period, ao the mean angular velocity, then we may admit : m I mg 545 + A E n² × R2 × M (m + 2) ΔΕ : • 174 SECTION II.-POWER STATION. An empirical formula which gives fair results is 1000 PLA W = KR W = weight of flywheel. K = rate of gyration in feet. P = mean effective pressure referred to low-pressure cylinder. A = area of low-pressure cylinder in inches. L = length of stroke in feet. R = speed in revolutions per minute. CONDENSERS. To obtain the best vacuum surface condensers are necessary, about 1 square feet of cooling surface being allowed per horse-power indicated by the engine. As the efficiency of engines varies greatly it is, however, better to proportion the cooling surface for the weight of steam to be condensed per hour, allowing 1 square foot of surface for every 10 lb. of steam to be condensed. In the case of reciprocat- ing engines a specially high vacuum is of no advantage, as the cost of the engine increases much faster than does the power gained by the additional vacuum. Hence one of 27 in. is actually better than one of 29 in., and for such engines the circulating water may be about thirty times the weight of steam condensed per hour. With steam turbines the output increases largely with a better vacuum, and at turbine stations the circulating water should be fully fifty times the weight of steam condensed per hour. With jet condensers a vacuum of 25 in. is about the highest advisable, since the injection water carries with it a considerable quantity of air. The amount of injection water may be twenty-eight times the weight of steam condensed per hour. The air pump and jet condenser of horizontal engines are often combined in one casting, the pump being mounted on a prolongation of the low-pressure piston-rod. This casting is commonly made with flat sides, and accidents due to the adoption of so weak a form are frequent. In other cases air pump and condenser are placed below the floor level, the pump being driven by a bell-crank lever. This arrange- ment provides a neat-looking engine-room, but the pumps are very liable to be neglected, with a consequent breakdown. The general practice in electrical work in this country is to drive the air and circulating pumps of condensers by electric motors. Air pumps should have plain buckets without packing rings, which are a constant source of failure, and "trunk" motions should never be used. Two or three water grooves are quite sufficient to keep the bucket steam and air-tight. The air pump displacement for a surface condenser may be 1 cubic foot per minute for every 90 lb. of steam condensed per hour. The valves of the air pump are either of metal, india-rubber, or vulcanised fibre. The bucket, plunger, or piston, piston rings (best omitted), grids and bolts are of gun-metal. Metallic packing is the best packing for the air-pump rod, as it considerably reduces friction, requires little attention, and is least liable to admit air. The area of delivery and suction valves should each be equal to area of air pump multiplied by .7. For a high speed of plunger, the valves should not have an area less than that of the pump. In jet condensers the displacement of the air pump allowed for is from four to five times the injection water. If independently driven, the air pumps require about 14 per cent. of the total output of the station. Ejector Condensers. In the ejector condenser the momentum of flowing water is taken advantage of to get rid of the ejection water without the aid of any mechanical pump. There are two classes, (1) ejector condensers which are supplied with water under pres- sure, usually from some overhead tank or from supply mains; and (2) ejector condensers in which the water receives its momentum, not from the pressure due to any head, but wholly from the inrushing exhaust steam. The second class will work wholly immersed in water, the cooling steam being drawn into it at one end through a strainer, and ejected at the other end with the condensed steam. The vacuum obtainable by means of a submerged condenser is not so high as the maximum obtainable with water forced into the apparatus under pressure, but a vacuum of from 22 in. to 24 in. of mercury can be obtained with a copious supply of cold water. THE STEAM ENGINE. 175 The overhead ejector condenser does not, as a rule, require a greater head than about 15 ft. for the cold stream. Its efficiency is higher than that of the submerged type, and owing to its complete independence of the exhaust steam it can be relied on to supply the proper vacuum. Under favourable conditions a vacuum of nearly 27 in. of mercury can be obtained when using about 100 lb. weight of water, at 50 deg. Fahr., under a head of 15 ft. per pound weight of exhaust steam. With an overhead condenser the vacuum can be obtained before the engine starts, while with an immersed condenser it can only be developed after exhaust has com- menced. Where the supply of injection water can be delivered to the engine under a head of about 15 ft., ejector condensers may be used with advantage; the arrangement is simple and easily applied; the cost is much less than the ordinary arrangement of air pumps. Condensers of this type will work without head, or may even be arranged to lift their supply some distance, but, under such conditions, they are easily rendered inoperative, and are liable to give trouble, Under a head of 15 ft. the velocity of the jet is maintained independently of the steam supply, and is capable of creating a vacuum either without steam or with any varying quantity up to the maximum for which the jet is made. These con- densers require about 100 gallons of water per indicated horse-power per hour, allowing 40 lb. of steam per indicated horse-power per hour, the amount, of course, varying with the steam consumption. WATER-COOLING ARRANGEMENTS. When the condensing water is kept in circulation, and not rejected into the overflow, the provision of means for cooling the water becomes a very important matter. A considerable amount of heat has to be got rid of as fast as it is taken up by the cooling water, otherwise the water in the reservoir will rise in temperature and the vacuum will fall. There are three methods or combinations of these, which are used in practice; (1) the simple cooling pond or tank, (2) the spray or fountain, and (3) the cooling tower. In all three the action depends on the absorption of heat into the atmosphere, partly by direct heating of the air itself; but chiefly by evaporation of the warm water. The cooling pond or tank, without the aid of either fountain or tower, is the most expensive method; but it may be adopted where it is necessary to have a large quantity of water in reserve. The cooling action is independent of the depth of the water, and varies directly as the surface. The amount of heat dissipated from each square foot of pond surface depends on the temperature of the water, and the vapour pressure of the moisture already in the air and the wind. Cooling Towers. These may be divided into two classes; (1) towers with artificial draught, (2) those with natural draught. Examples of the former types are those constructed by Worthington and Barnard. Fig. 16 shows a Worthington tower. The heated water is discharged by the circulating pumps at the top of the tower through a distributor, a motor-driven fan producing the requisite draught. In the Barnard tower, the warm water from the condenser is pumped into narrow tanks or distributors of special construction, placed above the upper ends of sets of mats, and the water is so distributed that every part of each mat is equally and uniformly supplied with a continuous but limited quantity of water. The water spreads over the mats in thin films, presenting a large water surface to the air currents, which evaporate a small quantity of the water, sufficient to cool it to the desired temperature. This process is assisted in cold weather by the refrigerative effect of the cool air. The intervening spaces between the mats allow a free direct upward passage of the air currents, enabling the fan-blower (which is located below the mats) to circulate the air. The fan requires a comparatively small amount of power, usually less than 2 per cent. of the indicated horse-power of the main engines. This power can be taken either from the shafting or from an electric motor or small steam engine, if the tower is located any considerable distance from the main source of power. The water is sufficiently cooled after passing over the mats to enable it to be immediately used in the condenser, and it is kept in continuous circulation so that no great amount of water storage capacity is necessary. The supply of water required to meet losses by evaporation is less than that used for supplying the boilers with feed-water. The power required to drive both the fan and elevate the water to the top of 176 SECTION II.-POWER STATION. the tower varies with conditions; it usually ranges about 3 per cent. of the power developed by the main engines. OVERFLOW The alternate heating and cooling of the water, together with the ærating effect, helps to deposits any soluble scale-forming ingredients the water may 230 (0-3 DISTRIBUTOR MAN-HOLE TOWER ! DELIVERY INJECTION EXHAUST CONDENSOR Fig. 16. Worthington Cooling Tower. contain, such as lime, magnesia, &c., thus purifying it and making it suitable fo boiler-feeding purposes. In Klein's natural draught water-cooling tower the principle consists in cooling the hot water by allowing some of it to evaporate, the process being accelerated by a current of air. The apparatus consists of two parts, see Fig. 17, the lower part being the cooler, j { THE STEAM ENGINE. 177 thirigh WHA . TULOUĮ FURTO GEN ש, את צו נל! J Ka HA HA IT 608 eko Exhaust Steam T ka Jess IVN ZALJKLAUSURIZY, …………………………………………………Ï 344 41 97 200 & JEANS. HÊ…}+⠀⠀⠀⠀Ÿ?…]||⠀⠀¦Ð¦Ð?ŸÐ¿Ã¿214}ƒŸ|| INUTLAR Fig. 17. General Arrangement of Klein's Central Jet-Condensing Plant. ………/…………… ' 178 SECTION II.-POWER STATION. t and the upper merely a chimney to increase the draught. The lower portion is occupied by a number of wooden strips, set close together, but not touching one another. By means of perforated pipes, the hot water is distributed, and allowed to trickle down over these strips, finally reaching a tank at the bottom. Air is drawn in at the bottom of the tower, and meeting the descending water, greatly accelerates the process of evaporation, thereby lowering its temperature consider- ably before it reaches the tank. The current of air is obtained quite naturally. The hot water heats the air in the tower, which ascends, and so draws in more air through the openings at the bottom. The whole apparatus is made of wood. Evaporative Condensers. The evaporative condenser is a form of surface condenser consisting of a large number of pipes, usually cast iron. Through the inside the exhaust steam is passed; over the exterior cold water is continually trickled. The outer surfaces of the pipes are kept wet. The heat of the steam is carried off by the evaporation of water. Sometimes there is a draught of cold air forced past the pipes to assist the evaporation. A vacuum of from 20 in. to 25 in. of mercury can be obtained with a supply of cold water, copious enough to limit the evaporation to from 0.75 to 1.00 times the weight of steam condensed. The actual consumption of water may be much less than where non-condensing engines of equal power are used. In one case there was only a rise of in. of mercury between the condenser and the engines, the length of connecting exhaust main being 140 ft., and the total length of piping, including the condenser, being 350 ft. Ledward's Evaporative Condenser. The condensing pipes are fitted with corrugations, whereby the radiating or cooling surface is very largely increased. The pipes are bolted together with flanged faced joints, so as to form a series of continuous coils for the passage of the steam. The height, width, and length of the coils depend on the amount of space available. A vacuum ranging from 22 in. to 26 in. of mercury can be constantly maintained by this condenser. Reservoir Capacity. A rough rule generally adopted in practice is to allow a storage capacity equal to the total amount of injection water passed through the engine in a day. This, however, is manifestly capable of considerable modification, and the reservoir capacity may be varied within wide limits. With a good supply of fresh water, the temperature can be kept low even with a small capacity, while, in its absence, and with poor facilities for cooling, a capacity equal to a day's supply may be inade- quate. In order to secure a good vacuum, the temperature of the injection water should not be allowed to rise much over 100 deg. Fahr. Surface Evaporation. Results of tests of evaporation of water in the open air, such as from the sur- face of a reservoir, are very discordant. In perfectly calm air, when the necessary motion issues only from the change of density and rate of diffusion, the rate of evaporation from liquids is fairly constant. If R = the rate of evaporation in grains per square foot per hour with the air perfectly calm; F = the pressure, called vapour tension, of the liquid at the tem- perature of the ambient air, as distinguished from that of the liquid itself; and ƒ the pressure of the vapour of water actually present in the air as indicated by the hygrometer, then the following rule will be found to agree very closely with experimental results: R = (F − ƒ) × 378. Box's Experiments. In tests made by M. Box, he found that 56.7 grains were evaporated per square foot of surface per hour when the mean temperature of the air was 60 deg., and the wet bulb hygrometer 55 deg., i.e, a difference of 5 deg., showing humidity 71 per cent. of saturation. By the above rule, F, we find from a Table of the elastic force of vapour of water calculated from Regnault's experiments, to be equal at 60 deg. to .518 in. THE STEAM ENGINE. 179 '' i mercury. If the air were fully saturated, ƒ would be the same pressure, but the humidity being 71 per cent. of saturation: 71 f=.518 x = .368 and R = (.518 368) × 378 = .15 x 378 = 56.7 grains per 100 hour, or the same as by experiments. Évaporation is greatly affected by the force of the wind, and the same vessel exposed on three successive days to westerly winds, varying from a fresh breeze to a gale, gave ratios of evaporation of 4.4, 8.8, and 12.4, taking calm air as unity. a 10 Steam Pipe Systems of Distribution, and Steam Receivers. (FIGS. 18 to 24.) a 10 по a 10 201 Added STEAM PIPING. VALVE VALVE VALVE VALVE WATER CATCHER TO TRAP VALVE SZPARATOR dy JE Fig. 18. Simple Steam Pipe Arrangement. The systems of distribution mostly used are shown in Figs. 18 to 24. Im principle, some authorities consider that there should be a complete duplicate system leading to each engine. But owing to the extra possible losses due to 180 SECTION II.-POWER STATION. condensation, he increased cost, the better material and methods used, duplicate systems are no longer considered essential. Furthermore, it is not rational, as steam piping does not, as a rule, give out sooner than the engines, to require a duplicate system of piping, as duplicate engines are never now thought necessary. Pipe systems, therefore, which combine simplicity with the least likelihood of one pipe causing the stoppage of any engine are those to be preferred. In getting out a system of steam piping, it must be so designed as to cause the least loss by condensation, and the least drop in pressure. On the piping of the power plant depends the safety, economy, and reliability of the stations. Where possible, high-pressure steam piping should be supported from underneath and not suspended. This method eliminates that vibration which results in leaky joints caused by racking and straining. The whole system of piping should be blown out thoroughly with steam before the engine connections are made, so as to prevent chips or dirt being carried through into the cylinders. The pipe lines should be as short as possible, otherwise, the loss by radiation and condensation may become very great. Where duplicate pipes are used, valves should be arranged to cut out pipe ranges not actually in service. The accom- panying diagrams show the very simplest system of steam piping with the fewest possible valves. By judicious use of bends, expansion joints can be avoided. The size of the pipes is so proportioned that the steam velocity does not exceed -8000 ft. per minute as a maximum, and is often only 6000 ft. per minute. The following table, compiled from a series of compound engines especially built for railway work, gives the diameter of the steam inlet and exhaust. It must be borne in mind that these dimensions necessarily depend upon the steam con- sumption of the engine and the steam pressure, hence the difference in the sizes of the pipes in this table :- Table 16.—Compound Engines; Dimensions of Steam and Exhaust Pipes. Rated Indi- cated Horse- Power of Engine. 123 195 160 223 235 300 300 350 340 447 460 525 538 550 623 757 918 1070 1200 1220 1240 1290 2275 2745 Maximum Indicated Horse-Power of Engine. 175 •• 376 430 480 546 480 605 800 760 860 880 981 1250 1425 1650 1850 1950 2000 2050 3260 3900 Condensing. Steam Inlet Pipe. Inches in Diameter. ·· 45 6 .. ~ 667 ∞∞∞∞∞∞∞∞ 8 8 9 12 12 Exhaust Pipe. Inches in Diameter. 8 10 12 10 | | +1 :* : : : :2 229 :09222222 1011100 14 12 12 12 16 18 Non-Condensing. 16 Steam Inlet Pipe. Inches in Diameter. 31/12 Lors 5 4 to 6 6 8 Exhaust Pipe. Inches in Diameter. MANFAAT 800 7 8 10 12 12 12 12 18 THE STEAM ENGINE. 181 Flow of Steam in Pipes. The quantity of steam flowing through a pipe under a given head, increases directly as the square root of the density, of the loss of pressure, and inversely as the square root of the length. A formula used for flow of steam in pipes is V = 50 D D, in which V = velocity in feet per second, L = length, and D = diameter of pipe in feet, H = height in feet of a column of steam, of the pressure of the steam at the entrance, which would produce a pressure equal to the difference of pressures at the two ends of the pipe. If Q = quantity in cubic feet per minute, d = diameter in inches, L and H being in feet, formula reduces to 5/ 221 A pipe 1 in. in diameter, 100 ft. long, carrying steam of 100 lb. gauge-pressure at 6,000 ft. velocity per minute, would have a loss of pressure of 8.8 lb. per square inch, while steam travelling at the same velocity in a pipe 8.8 in. in diameter would lose only 1 lb. pressure. Initial Pressure by gauge. lb. per sq. in.} Q 79289A823888 = 4.7233 10 20 30 40 50 √ d5, H = 60 The following generally accepted formula gives the weight of steam (which, with a given loss of pressure, will flow through a given pipe :— = .0448 = W = Weight in pounds avoirdupois. D Density or weight per cubic fost d = Diameter in inches. P1 Initial pressure. P2 = Pressure at end of pipe. L - Length in feet. W = 87 VD L The following table is worked out by this formula: Table 17.-Table of Flow of Steam Through Pipes. (Babcock.) Q2 L d5 | | 1 | 13 | 2 | 23 | 3 | • D (pr -- P2) do (1+3.6) d Diameter of Pipe in Inches. 1.16;2.071 5.7 10.27 | 15-45 | 25.38 1.44 2.57 7.1| 12.72 | 19.15 | 31.45 1.70 3.02 8.3 14.94 22.49 36.94 1.91 3.40 9.4 16.84 | 25.35 | 41.63 2.10 3.74 10.3 18.51 27.87 45.77 76.84 2.27 4.04 11.2 20.01 30.13 49.48 84.49 91.34 97.60 32.19 | 52.87 70 2.43 4.32 11.9 21.38 2.57 4.58 12.6 22.65 34.10 | 56.00 | 103.37 2.714.82 13.3 23.82 | 35.87 58.91 108.74 2.83 5.04 13.9 24.92 37.52 | 61.62 | 113.74 2.95 5.25 14.5 25.96 39.07 64.18 118.47 120 3.16 5.63 15.5 27.85 41.93 68.87 127.12 3.45 6.14 17.0 30.37 45.72 | 75.09❘ 138.61 80 90 100 150 d Length of each=240 Diameters. 8❘ 10 | 12 5 5 | Weight of Steamer Minute in Pounds, with one Pound Loss of Pressure. = .5374 46.85 58.05 68.20 828.1 862.6 925.6 12 15 18 622.5 341.1 502.4 804 1177 422.7 496.5 559.5 996 1458 1170 1713 731.3 824.1 1318 1930 615.3 1450 2122 665.0 1567 2294 77.3 115.9 | 211.4 95.8 143.6 262.0 112.6 168.7 307.8 126.9 190.1 | 346.8 139.5 209.0 | 381.3 150.8 226.0 412.2 161.1241.5 4140.5 170.7 255.8 | 466.5 179.5 269.0 | 490.7 791.7 187.8 281.4 | 513.3 195.6 293.1 534.6 209.9 314.5 | 573.7 228.8 343.0 625.5 1009.2 710.6 1675 2451 752.7 1774 2596 1866 2731 1951 2856 906.0 979.5 1046.7 1108.5 1166.1 1219.8 1270.1 1363.3 1486.5 2032 2975 2181 3193 2378 3481 For any loss of pressure, multiply by the square root of the proposed loss. For any other length of pipe, divide 240 by the given length expressed in diameters, and multiply the table figures by the square root of this quotient to get the flow for one pound loss of pressure. The resistance due to-steam entering pipe = 60 diameters additional length : to a globe valve = 60: to an elbow = 40, or of a globe valve. All these equi- valents must be added in getting out total length of pipe, with corresponding losses 182 SECTION II.-POWER STATION. ► - Table 18.-Flow of Steam in Straight or Curved Pipe with Loss of Pressure Due to Friction of 1 lb. per 100 ft. of Pipe. (E. T. Carter.) Diameter of Pipe in Inches. 1236 9 12 15 18 24 a a 예 ​201 2 Absolute Pressure of Steam in Pounds per Square Inch. 10 20 50 150 Quantity of Steam delivered per Hour in Pounds. 35. 104 144 199 590 815 549 1620 2245 9170 25,300 51,800 90,500 48.7 275 760 2015 4290 11,820 5550 11,380 24,300 42,400 58,900 19,900 31,400 48,400 67,000 93,000 143,000 64,400 99,200 137,000 | 190,500 5 22.8 129 356 3100 8550 17,500 30,610 VALVE VALVE 67.6 382 WATER CATCHER. 1054 5960 16,400 33,700 NIVYO TRAP LVI ## VÁLYZ = 100 VALVES 174 984 2715 12,700 15,350 17,640 35,000 42,300 48,600 71,700 86,600 99,600 12,550 睁 ​SEPA Fig. 19. Duplicate Steam Pipe Arrangement. RATOR HRE. — LPG 3 ye 17 200 200 1130 3120 " 1 + ! 1 THE STEAM ENGINE. 183 !! 200 Diameter at Elbow in Inches. .. Equivalent Length in Feet. 1 .. Equivalent Length in Feet Fig. 20. Method of Arranging Steam Piping. Table 19.-Length of Straight Pipe Equivalent to a Bend. 2 1 2.0 TOH 3 2 SECTION ON A.B. 6.3 ICHIST 3 6 7.8 B EXHAUST TO CONDENSER 9 Resistance of globe valves corresponding to above diameters is approximately 50 per cent. greater, or as below. 6 1.3 4.2 5.2 21.6 37.0 53.2 69.6 $5.9 123.8 Table 20.-Length of Straight Pipe Equivalent to Globe Valve. Diameter of Globe Valve in Inches BIJ IE 9 12 32.4 55.5 15 18 12 15 24 18 24 79.8 104.4 128.9 185.7 184 SECTION II.-POWER STATION. 3 : 1 :v ra 4. 10 [예 ​예 ​예 ​a a 203 21 22 205 VALVE VALVEK VALVE DRAIN VALVE VALVE TO TRAP DRAINS SEPARATOR By pu CATCHER 23 Methods of Arranging Steam Piping. Figs. 21 and 22. Ring System of Steam. Fig. 23. Bye-Pass System. A ENGINE ENGINE ENGINE O ! THE STEAM ENGINE. 185 į Area through Stop and Throttle Valves. The friction through a number of small openings is considerably more than through one of an area equal to the collective areas of those openings, especially if perimeters of the latter exceed that of the single opening, and the "loss of head MAIN EXHAUST| C RECEIVER Ja m RECEİVER Bye-Pass System. Fig. 24. Method of Arranging Steam Piping. COMBINED AIR PUMP AND CONDENSER bell drivan. +10 100 will be large if due allowance is not made. For this reason there should always be an excess of area around valves and other obstructions to the free passage of steam, and the passages leading to and from them should be as easy as possible, so as to avoid violent changes, both of direction and velocity of flow. 186 SECTION II.-POWER STATION. A Sizes of Steam Pipes for Stationary Engines. Steam pipes supplying engines should be such that mean velocity of steam in them does not exceed 6000 ft. per minute. Velocity is calculated on the assump- tion that the cylinder is filled at each stroke. In very long pipes, 100 ft. and upward, it is well to make them larger, and to place a large steam receiver on the pipe near the engine. The following Table shows the practice of leading builders for comparison, all the engines have been rated in horse-power at 40 lb. mean effective pressure. Diam. of pipe, in. 2 2 3 Av. horse-power of engine 25 39 56 According to Kent, a formula which gives results closely agreeing with practice. Horse-power "" Diameter of pipe, inches Velocity 4000. 6000.. 8000 .. Horse - power, approximate "" • =408√ H.P. Table 21.-Diameters of Cylinders corresponding to Various Sizes of Steam pipes based on piston speeds of 600 ft. per per Minute, and allowable Mean Velocity of Steam in pipe of 4000 ft., 6000 ft., and 8000 ft. per Minute. (Steam assumed to be admitted during full stroke.) ***** 6 d², or pipe diameter = Diameter of pipe, inches Velocity 4000 .. 6000 .. "" 8000.. Horse - power, approximate Formula Piston speed in feet per minute. 700 600 500 400 300 • •• Area of pipe 31 4 5 6 7 8 9 10 77 100 126 225 306 400 506 625 21/ 3 7.7 7.9 9.5 - 2 5.2 6.3 7.3 9.1 20 31 6.5 TE t 26 N 31/1 9.0 11.1 10.9 12.8 45 62 = For piston speed of 600 ft. per minute and velocity in pipe of 4000 ft., 6000 ft., and 8000 ft. per minute area of pipe respectively .15, .10, and .075 x area of cylinder. Diameter of pipe respectively .3873, .3162, and .2739 × diameter of cylinder. Reciprocals of these figures are 2.582, 3.162, and 3.651. = The first line in the above table may be used for proportioning exhaust pipes, in which a velocity not exceeding 4000 ft. per minute is advisable. The last line, approximate horse-power of engine, is based on the velocity of 600 ft. per minute in the pipe, using the corresponding diameter of piston, and taking 1 H.P. = (diameter of piston in inches)2. Approximate Ratio of Area of Steam Pipe to Area of Low-Pressure Cylinder. H.P. 6 8 9 10 7 18.1 20.7 23.2 25.8 22.1 25.3 28.5 31.6 25.6 29.2 32.9 36.5 245 320 406 500 606 "" >> "" 4 10.3 11.6 14.6 80 "" Ratio of area of steam pipe. to area of low-pressure cylinder 99 "" 14 11 12 13 28.4 31.0 33.6 36.1 34.8 37.9 41.1 44.3 43.8 47.5 51.1 718 845 981 40.2 43 11.6 14.2 16.4 100 "" 5 12.9 "" "} 15.8 19. 18.3 21.9 125 180 "" " Area of cylinder x piston speed" mean velocity of steam in pipe 6 15.5 # : THE STEAM ENGINE. 187 STEAM PIPE RANGES. Materials. Up to a pressure of 120 lb. to the square inch, cast iron may be used for all steam piping. For pressures higher than this, riveted or lap-welded steel pipes are adopted. A specially good grade of cast iron or cast steel may be used for the bends or elbows; but the best British practice invariably uses cast steel for elbows or tees and valve bodies. Pipes, however, should be uniform in thickness. If the pipes are cast horizontally it often happens that the core floats if the core bar is not sufficiently rigid, thus making the upper part of the pipe thin. Copper is some- times used for bends, and sometimes even for straight line piping. The greatest care must be taken in the laying of the joints (where solid-drawn tubes are not used), as the copper easily gets overheated and burns, losing thus much of its strength, becoming brittle and unreliable. Solid-drawn copper piping is often of unequal thickness, and may develop longitudinal splits without giving any warning. Lap-welded wrought-iron and steel piping is generally used in high tension work, and for sizes up to 12 in. in diameter solid-drawn steel tubing may also be used; it is, however, more expensive than welded tube. The bends, tees, elbows, &c., are made either of copper, cast steel, or special. grade of cast iron. TAL Bends can be made of lap-welded pipe bent to any desired template up to any sizes which are in general use in steam work. The pipe should be of ample bore, to allow for any roughness in its internal surface. Draining. This should be very carefully attended to, particularly with steel piping, and every precaution should be taken to insure that all steam piping is free from water at starting. A pocket in which water may lodge must never be permitted; steam or exhaust pipes should be kept as much as possible in the same hori- zontal plane. All sharp bends are sources of danger, and a pipe which has been led for some distance horizontally should never be suddenly turned up into the vertical. Expansion should be allowed for, one end of the pipe being left free to move, or bends or expansion joints should be fitted. Pipes have to be so heavy, for pressures now used, that it is not always well to arrange for expansion by a special loop. In a free system of this kind, nearly all the movements come on the weakest bend. If the length of piping is considerable, it ought to be anchored at several points so as to insure the several bends taking their fair share of movement. The ordinary ranges of steam pressure are sufficient to produce an expansion of 2 in. in 100 ft. Thickness of Cast-Iron Steam Pipes. For pressures ranging up to 100 lb. per square inch, and for diameters between 2 in. and 12 in. : D = diameter of pipe in inches. D+ 4 = thickness of pipe in sixteenths of an inch. For 100 lb. and upwards the rule should be:- T D. P. 4000 + 1/1/2 Where T = thickness of pipe in inches. P = pressure in pounds per square inch. Board of Trade Rule for Welded Wrought-Iron Steam Pipes. The Board of Trade give the following rule for good lap-welded wrought-iron pipes, the thickness of which is not less than in. 6000 × T D where P = working pressure in pounds per square inch T thickness in inches D = inside diameter in inches. P = Riveted Steel Steam Pipes, Secure necessary stiffness for caulking purposes; it is not customary to make these of plates less than in. thick, it is better to use plates. To avoid risk of the rivet heads being sprung off during caulking, rivets should not be less than in. n diameter. 188 SECTION II.-POWER STATION. Copper Steam Pipes, Factor of Safety. Pipes of small diameter are generally solid drawn ; many steam pipes are made with brazed joints. Factor of safety varying from 10 to 15 is generally allowed, taking the copper to possess an ultimate tenacity of about 15 tons per square inch. Board of Trade Rules for Strength of Steam Pipes. The Board of Trade give the following rule for copper pipes with brazed joints: Copper Pipes: Cast-iron Pipes: Lap-welded Iron Pipes: .. •·· ·· ·· D= inside diameter in inches P = pressure in pounds per square inch t = thickness of metal in inches PD Brazed t = +18 6000 PD 6000 PD 6000 PD 4000 Bursting Tests of Copper Steam Pipes. (Chief Engineer Melville, U.S.N.) Some tests were made at the New York Navy Yard, which show the unrelia- bility of brazed seams in copper pipes. Each pipe was 8 in. in diameter inside, and 3 ft. 1ğ in. long. Both ends were closed by ribbed heads, and the pipe was sub- jected to a hot-water pressure, the temperature being maintained constant at 371 deg. Fahr. Three of the pipes were made of No. 4 sheet copper ("Stubbs " gauge), and the fourth was made of No. 3 sheet. The following were the results in pounds per square inch of bursting pressure: Pipe number Actual bursting strength.. "" Material of which the Pipe, or Tube, or Cylinder is Composed. Mild Bessemer steel Phosphor-bronze Homogenous metal Lowmoor or best Yorkshire iron. Solid-drawn wrought-iron tubes. Good ordinary wrought iron Copper, wrought Best bronze Gun metal Good brass Common brass Cast iron Zinc Lead Solid drawn t = .. .. .. ·· .. • .. ·· .. ·· ·· t • t Calculated Difference The tests of specimens cut from the ruptured pipes shows the injurious action of heat upon copper sheets. While a white heat does not change the character of the metal, a heat of only slightly greater degree causes it to lose the fibrous nature that it has acquired in rolling, and a serious reduction in its tensile strength and ductility results. 1 835 1336 501 • = w ·· ·· Table 22.—Strength of Materials used for Pipes. + 32 .. + 3/ .. 2 785 1336 551 ·· 71,680 56,000 56,000 ·· 53,760 49,200 47,040 33,600 33,600 31,360 18,000 16,000 15,000 6,720 2,240 3 950 1569 619 .. Bursting Tension in Pounds. ·· ·· 4 1225 1568 343 ·· •✔ ·· .. 11,940 9,330 9,330 8,960 8,200 7,840 5,600 41 Safe Working Tension in Pounds. 5,600 5,200 1275 1568 293 3,000 2,670 2,500 1,120 370 THE STEAM ENGINE. 189 Reinforcing Copper Steam Pipes. In the Italian Navy copper pipes above 8 in. in diameter are reinforced by wrapping them with a close spiral of copper or Delta metal wire. Two or three independent spirals are used for safety, in case one wire breaks. They are wound at a tension of about 1 tons per square inch. Wire-Wound Steam Pipes. The system instituted by the British Admiralty of winding all steam pipes over 8 in. in diameter with in. copper wire, thereby about doubling the bursting pressure, has been adopted on many merchant steamers using high-pressure steam. The results of some of the Admiralty tests showed that a wire pipe stood just about the pressure it ought to have stood when unwired, had the copper not been injured in the brazing. Bursting Strength of Tubes. Let p = bursting pressure in pounds per square inch inside tube. D= outside diameter of tube in inches. Then d = = inside Tempera- ture Fahr. deg. 122 212 302 .. Steel (60 deg. Fahr.) 95,000 28,800 (800 deg. Fahr.) Wrought iron (60 deg. Fahr.).. 50,000 "" Pounds. 33,079 32,187 30,872 "" ·· p = Values of ƒ: Brass (rolled) (60 deg. Fahr.) .. Table 23.-Tensile Strength of Copper at Different Temperatures. "" D2-d2 f. D² + d²* Tempera- ture Fahr. deg. 482 545 602 Cast iron (60 deg. Fahr.) 20,000 Copper (rolled) (60 deg. Fahr.) 35,000 (640 deg. Fahr.) 14,700 30,000, "" Pounds. 26,981 25,420 22,302 Tempera- ture Fahr. deg. 801 912 1010 Pounds. 18,854 14,789 11,054 Deterioration of Strength of Copper Pipe. The radius of curvature measured to the centre of the pipe should not be less in solid-drawn pipes than three times the diameter of the pipes; even this radius of curvature causes a reduction in thickness of 20 to 25 per cent. on the outside of the bend, and a corresponding increase of thickness on the inside. Sharper bends can, if necessary, be made by working the pipe out of two plates with a brazed joint along each side. This construction is more expensive than solid-drawn copper pipes. Copper may suffer considerable loss in strength when exposed for a prolonged period to variable temperatures, even if as low as 400 deg. Fahr. Le Chatelier found that at this temperature the ultimate tenacity of good copper thoroughly annealed is not more than 10 tons per square inch; while this figure cannot be depended on in the case of brazed pipes, as the metal is often seriously injured in the neighbourhood of the joint. Hard copper suffers more than soft annealed copper from the effects of heat. Le Chatelier's test showed that with a hard copper, having a tenacity of 31.5 tons per square inch at 60 deg. Fahr., the strength was reduced to 11.4 tons, after being exposed to a temperature of 482 deg. Fahr. for 30 minutes. Under the same conditions the tenacity of soft copper was reduced from 15.9 tons to 10.4. Professor Roberts-Austen showed that minute quantities of impurities in copper seriously affect its tenacity. The presence of P of 1 per cent. of bismuth reduced the breaking load of a sample from 8 tons per square inch at 64 deg. Fahr. to 1.7 tons at 390 deg. Fahr. 190 SECTION II.-POWER STATION. Internal Diameter in Inches. Table 24.-Thickness of Copper Main Steam Pipes. Working Pressure of Steam in the Boiler in Pounds per Square Inch. A Famfufuo S-2-2 10 101 Pipe "" Steel, cast "" "" Brass, cast Bronze (Baily's) Copper Iron, wrought .. "" Swedish cast 5 in. pipe X = 6 in. 6 "" 7 X = 7 X = 8 X 9 "" 8 →→ .. .. ·· • • lb. 100 "" in. .140 .145 .150 .155 .160 .165 .170 .175 .180 .185 .190 .195 .200 .205 .210 .215 .220 .225 .230 .335 .240 .245 • "" "" lb. 125 "" Pipe Bends. The radius of any bend should not be less than 5 times diameter of pipe, and a larger radius is much preferable. The length "X" of straight pipe at each end of bend should be not less than as follows:- in. .143 .150 .156 Thickness of the Pipe in Inches. in. in. .147 .152 .161 .170 .179 .188 .197 .206 .215 .224 .233 .242 .162 .168 .175 .181 .187 .193 .200 .206 .212 .218 .225 .231 .237 .243 .250 .256 .262 .268 .275 lb. 150 .155 .162 .170 .177 .185 .192 .200 .207 215 22z .230 237 .245 .252 .260 .267 .275 .282 .290 .297 €305 0.00000636 0.00000556 0.00000636 C "" "" >> Table 25.-Linear Expansion of Material Used in Steam-Pipe Ranges. lb. 180 10 in. pipe X = 12 in. X = 14 X = 16 12 14 "" "" ! .251 .260 .269 .278 .287 .296 .305 .314 .323 .332 .341 Length = 1. Per 1 Deg. Fahr. Per 1 Deg. Cent. 0.00000957 0.00001722 0.00001774 0.00000986 0.00000887 0.00000648 0.00001596 0.00001166 0.00001145 0.00001001 0.00001144 "" lb. 200 "" in. .155 .165 .175 .185 .195 .205 .215 .225 .235 .245 .255 .265 .275 .285 .295 .305 .315 .325 .335 .345 .355 .365 Expansion from 32 Deg. to 212 Deg. in Length of 10 Feet. 0.2066 in. 0.2129 0.1915 0.1399 0.1374 0.1201 0.1373 "" "" "" "" "} "" With steel or with wrought-iron piping the expansion will average about 1 in. in 50 ft. of piping. 1 Pipe Screw Threads. Pipes having an internal diameter of in. or in. have 19 threads to the inch. Those ofin., §in., & in., and in. have 14 threads to the inch, and all other sizes of pipes have 11 threads to the inch. THE STEAM ENGINE. 191 Size of Pipe. in. Phot 22233456 H Inside Diameter of Pipe. A in. in. 2345C7 192 23 с 27 27 31 77 J B in. 26 291 31 34 35 392 45 51 58 64 Table 26.-Expansion Joints. с in. 172 197 211 23 Loss in Heat Units Per Foot Run Per Hour. 494 692 869 1067 1221 1420 27 323 42 471 Diameter Number Centre of Flange. of Holes. of Holes. in. in. 63 8 9 10 11 13 14 4 4 4 4 4 4 4 4 6 6 Steam at 115 lb. Absolute Condensed Per Foot in Length Per Hour. lb. .563 .790 .992 8 9 101 12 STEAM PIPE COVERING. A considerable loss may be caused by radiation and consequent loss of heat from uncovered pipes, and this loss is increased by the delivery of wet steam to the engines. Table 27.-Loss in Uncovered Steam Pipes. (SURROUNDING AIR 62 DEG. FAHR.) 1.218 1.393 1.621 Loss from an Uncovered Steam Pipe. (Bjorling.) The amount of loss by condensation in a steam pipe carried down a deep mine-shaft has been ascertained by actual practice at the Clay Cross Colliery, where there is a pipe 7 in. internal diameter, 1,100 ft. long. The loss of steam by condensation was ascertained by direct measurement of the water deposited in a receiver, and was equivalent to about 1 lb. of coal per indicated horse-power per hour for every 100 ft. of steam pipe; there is no doubt that if the pipes had been well covered with a good non-conducting material, the loss would have been less. The following is a summary of results of Rudiger's investigations : The flow of steam in a pipe is determined in the same manner as the flow of water, the formula for the flow of steam being modified by substituting the equivalent loss of pressure, divided by the density of the steam, for the loss of head. The losses in the flow of steam are two-the loss due to friction of flow and that due to radiation from sides of pipe. The sum of these is a minimum when the equivalent of the loss due to friction of flow is equal to one fifth of the loss of heat by radiation. For a greater or less loss of pressure the total loss increases very rapidly. The most economical loss of pressure for a pipe of given diameter is equal to the most economical loss of pressure in a pipe of 1 in. diameter for same conditions, divided by the diameter of the given pipe in inches. Any suitable substance which is used to prevent the escape of steam heat should not be less than 1 in. thick. Any covering should be kept perfectly dry, for not only is water a good carrier of heat, but it has been found that still water conducts heat about eight times as rapidly as still air. Inside Diameter of Pipe. Size Thickness of Holes. of Flange. in. in. 8 9 10 11 12 LOJOO LARGO LAJKO ESIET ETTERP 1580 1738 1935 Loss in Heat Units Pea Foot Run Per Hour. 2093 2290 in. 1 sako sako - LAKO 1-400 11% 11/ lb. 1.803 1.984 2.209 2.389 2.614 Steam at 115 lb. Absolute Condensed Per Foot in Length Per Hour. 192 SECTION II.-POWER STATION. in. 1 1 1 (The Practical Engineer.) Covered composition equal in efficiency to woollen felt, or 7th the conductivity of cast iron. Steam 115 lb. pressure absolute = 338 deg. Fahr. Surrounding air, 62 deg. Fahr. 14-07 Units Bore of Pipes. Lost per Foot in Length per Hour. Thermal 12 3 4 41 56700 8 9 10 11 12 13 14 15 16 17 18 20 22 24 26 Table 28.-Loss of Heat and Condensation in Covered Cast-Iron Steam Pipes. t 28 30 -In. Covering. T.U. 93 105 122 146 175 204 227 256 280 315 361 419 466 513 571 618 676 722 781 827 874 920 979 in Steam Condensed Foot Length per Hour. per lb. .1062 .1199 .1363 .1667 .1993 .2329 .2592 .2923 .3197 .3596 .4121 .4783 .5320 .5857 .6519 .7055 .7718 .8243 .8916 .9442 .9978 1.0504 1.1177 1.2239 1072 1165 1258 1363 1456 1.6622 1561 1.7882 1.3300 1.4362 1.5560 Cotton wool Sheep's wool Infusorial earth 1-In. Covering. Units Lost per Foot in Length per Hour. Thermal T.U. 58 64 73 84 99 114 125 140 151 169 192 221 245 268 297 320 350 373 402 425 449 472 501 548 594 641 693 .. 740 792 Silicate cotton (mineral wool) Hair felt The relative results were as follows: • in Foot Steam Condensed Length per Hour. per • lb. .0662 .0731 .0833 .0959 .1130 .. .1301 .1427 .1598 .1724 .1929 .2192 .2523 .2797 .3060 .3391 .3653 .3996 .4258 .4589 .4852 .5126 .5388 .5720 .6256 .6781 .7318 .7912 .8448 .9042 .. •• .. 14-In. Covering. 100 117 122 136 136 Units Lost per Foot in Length per Hour. Thermal 2858 T.U. 57 63 72 83 94 103 114 122 135 153 175 192 210 232 249 271 288 310 328 345 363 385 420 454 489 529 564 603 in Foot Steam Condensed Length per Hour. per lb. .0594 .0651 .0719 .0822 .0948 .1073 .1176 .1301 .1393 .1541 .1747 .1998 .2192 •2397 .2649 .2843 .3094 .3288 .3539 .3859 .3939 .4144 .4396 .4795 .5183 .5583 .6039 .6439 .6884 Heat Conducting Power of Covering Materials. (J. J. Coleman.) Experiments were made by filling a 10 in. cube with ice, surrounding it with the different materials to be tested, and noting the quantity of ice melted per hour with each insulator. 2-In. Covering. .. Units Lost per Foot in Length per Hour. Thermal Charcoal Sawdust Gas works breeze Wood and air space ·· T.U. 41 44 48 54 61 68 74 82 87 96 108 122 134 146 160 172 186 198 213 224 236 248 262 285 309 332 358 382 407 .. ·· Steam Condensed Per lb. .0468 .0502 .0543 .0616 .0696 .0776 .0845 .0936 .0993 .1095 .1233 in Foot Length per Hour. .1393 .1530 .1667 .1827 .1964 .2123 .2260 .2432 .2557 .2694 .2831 .2991 .3254 .3528 .3790 .4087 .4361 .4647 ·· ·· .. 140 163 230 280 THE STEAM ENGINE. 193 The Rate of External Conduction. (Rankine.) The rate of external conduction through the bounding surface between a solid body and a fluid is approximately proportional to the difference of temperature, when that is small; but when that difference is considerable, the rate of conduction increases faster than the simple ratio of that difference. Thickness of Covering in Loss Due to Condensation in Long Steam Pipes. Some tests were carried out by Mr. Henry Davey on a 7½ in. diameter steam pipe, 1 in. thick, and 1100 ft. long, conveying steam at a pressure of 45 lb. per square inch to an underground pumping engine in the Morton Pit at Clay Cross, the pipes being covered with a non-conducting material. As the result of careful observations it was found that the condensation of steam in the pipe amounted to 500 lb. per hour when the engine was standing, and 750 lb. per hour when the engine was working, equivalent to 0.185 and 0.274 lb. per square foot of surface of pipe per hour respectively. 22 In another experiment carried out by Mr. W. Worby Beaumont, at the Staveley Hill Colliery, it was found that in a total length of 2300 ft., 1900 ft. of which was underground, and covered in some instances to a depth of 2 ft. with rough stuff left after cutting away the coal, the condensation in a 64 in. pipe, 1 in. thick, conveying steam at an average pressure of 34 lb. per square inch, was 600 lb. per hour with the engine standing, 1400 lb. per hour with the engine at work, equivalent respectively to a condensation of 0.113 and 0.265 lb. per square foot of surface of pipe ner hour. Table 29.-Loss of Heat from Steam Pipes. · 1246 Dim to b 2-in. Diameter. 219.0 100.7 1.00 152 .46 331 507 65.7 .30 43.8 .20 761 28.4 .13 1173 19.8 .09 1683 ·· Suitable for pipes of inter- nal diameter Dimension (a) Weight ·· (approx.) 4-in. Diameter. 16. kilos. Outside Diameter of Pipe, without Felt. 6-in. Diameter. in. 3 in. 10 12 390.8 1.00 86 624.11.000 180.9 .46 182 117.2 73.9 44.7 28.1 23.4 Details of Pipe Hangers. Table 30.-Pipe Hangers for One Pipe. (FIG. 25, page 194.) PIPE HANGERS AND BRACKETS. (FIGS. 25 and 26, page 194.) These are designed to suspend the pipes, whilst offering no hindrance to free expansion. They, of course, vary in design to suit the arrangement of building; Figs. 25 and 26 show the arrangement employed wherever possible by Babcock and Wilcox. 40 18 53 729.8 1.000 46 1077.4 1.000 31 .30 284 187.2 .300 177 219.6 .301 151 301.7 .230 114 .18 451 111.0 .173 300 128.3 .176 259 185.3 .172 179 .11 745 66.2 .106 504 75.2 .103 41 443 98.0 .091 340 .071186 41.2 .066 808 46.0 .063 724 G0.3 .001424 33.7 .054 939 34.3 .047 972 45.2 .056 553 .042❘ 735 4 11 12 42 19 LO 5 2442 12 14 20 8-in. Diameter. 6 12 16 45 201 7 13 20 49 22 8 13 20 50 22/ 12-in. Diameter. 9 14 22 53 24 10 144 23 55 25 H 12 15 26 Horse-Power Lost. 9985 60 27 194 SECTION II.-POWER STATION. Table 31.-Pipe Hangers for Two Pipes. (FIG. 26.) Dimension (α) (b) (c) 99 Weight (approx.) 249. ·· 10 12 12 "" lb. 50 kilos. •• ·· 12 13 13 16 20 20 ILLILIT 15 17 17 57 64 26 29 in. "" 11 12 12 14 13 14 52 56 22 23 25 a 25 Bla VALVES. Location of Valves. BIB ·· Figs 25 and 26. Pipe Hangers and Supports. • 65 29 ·· a 26 14 22 Place valves with the stems horizontal to avoid the formation of a water pocket. Never put the junction valve close to the boiler if the main pipe is above the boiler, but put it on the highest point of the junction pipe. If the other plan is followed, the pipe fills with water whenever this boiler is stopped and the others are running, and breakage of the pipe may cause serious results. Never let a junction pipe run into the bottom of the main pipe, but into the side or top. Always use an angle valve where convenient, as there is more room in them. Never use a gate valve under high pressure unless a by-pass is used. Never open a blow-off valve on a boiler a little and then shut it; it is sure to catch the sediment and ruin valve; throw it well open before closing. Never use a globe valve on an indicator pipe. For water always use gate or angle valves or stop-cocks to obtain a clear passage. Valves with renewable discs should be used. Where only one boiler is used, the valve is generally so placed as to get boiler pressure underneath it. Where several boilers are connected to one steam pipe, pressure is on top of valve. Table 32-Greatest Allowable Pressure on Valve Seat Surface. 2000 pounds per square inch. ·· Gun metal Phosphor Bronze Cast iron 3000 1000 Leather and India-rubber These valves determine the minimum width of valve seat. 700 "" "" "" "" "" 14 23 19 21 68i 75 31 34 15 26 24 81 37 372 THE STEAM ENGINE. 195 A. sa Reducing Valves. Frequently it is desirable in case of cross compound engines to be able to use both sides, each as a single cylinder engine, in that case a reducing valve is put between the steam range and the low-pressure cylinder. It is a very common fault on the part of engineers to make reducing valves much too large for the amount of steam they have to pass. This is a serious defect, and often gives rise to trouble and annoyance in consequence of the range of movement being so restricted. Before the size of the reducing valve can be deter- mined for any particular case, the maximum consumption of steam should be determined either empirically or by calculation. The required maximum opening of the valve may then be calculated with sufficient accuracy for practical purposes, by assuming that steam will pass through the valve at a velocity in feet per second of V = 10 Ř, where R is the reduction of pressure in pounds per square inch. The valve should then be chosen such that when fully open the thoroughfare should not in any case exceed four times the area calculated as above, while it might, without any sacrifice of efficiency, be considerably less even than this. 27 28 29 Figs. 27 to 29. Steam Stop-Valves for High Pressure. STEAM SEPARATORS. If moist steam flowing at a high velocity in a pipe be suddenly diverted in its course, the particles of water, by their inertia, are projected along in their original direction against the bend of pipe in which this diversion takes place. By drawing off the water thus separated the steam may be dried. Professor R. C. Carpenter made a series of tests of six steam separators, furnishing them with steam containing different percentages of moisture, and testing the quality of steam before entering and after passing the separator. A condensed Table of the principle results is given on page 196. Conclusions from the tests were :- (1) That no relation existed between the volume of the several separators and their efficiency. (2) No marked decrease in pressure was shown by any of the separators, the most being 1.7 lb. in E. (3) Although changed direction, reduced velocity, and, perhaps, centrifugal force are necessary for good separation, still some means must be provided to lead the water out of the current of the steam. 196 SECTION II.-POWER STATION. I The high efficiency obtained from B and A was largely due to this feature. In B the interior surfaces are corrugated, and thus catch the water thrown out of the steam and readily lead it to the bottom. In A, as soon as the water falls or is precipitated by the steam, it comes in contact with a perforated diaphragm through which it runs into a space below, where it is not subjected to the action of the steam. In D, the next in efficiency, this is accomplished by means of a shaped diaphragm which throws the water back into the corners out of the current of steam. Separators are usually put just above the engine throttle valve] BADCEF с Table 33.-Efficiency of Steam Separators. · Make of Separator. Quality of Quality of Steam Before. Steam After. Test with Steam of about 10 per cent of Moisture. per cent. 87.0 90.1 89.6 90.6 88.4 88.9 per cent. 98.8 98.0 95.8 93.7 90.2 92.1 Efficiency per cent. 90.8 80.0 59.6 33.0 15.5 28.8 Tests with Varying Moisture. Quality of Quality of Steam Before. Steam After. per cent. 66.1 to 97.5 51.9 98.0 72.2 96.1 67.1 96.8 68.6 98.1 70.4 97.7 "" "" "" "" "" per cent. 97.8 to 99.0 97.9 99.1 95.5 98.2 93.7 98.4 79.3 98.5 84.1 97.9 "" "" "" "" "" 1 Average Effi- ciency. 87.6 76.4 71.7 63.4 36.9 28.4 LUBRICANTS. (Thurston.) Friction is a resistance which is met when two bodies are compelled to move, one upon another. There are three kinds of friction; rolling, and sliding with solids, and fluid friction with liquids and gases. Lubrication has for its objects the reduction of friction, and the prevention of excessive development of heat. In order that any substance may be efficient as a lubricating material, it must possess the following characteristics. 1. Enough "body" or combined capillarity and viscosity to keep the surfaces between which it is interposed from coming in contact under maximum pressure. 2. The greatest fluidity consistent with the preceding requirements, i.e., the least fluid friction allowable. 3. The lowest possible co-efficient of friction under the conditions of actual use, i.e., the sum of the two components, solid and fluid friction, should be a minimum. 4. A maximum capacity for receiving, transmitting, storing, and carrying away heat. 5. Freedom from tendency to decompose, or to change in composition by gum- ming or otherwise, on exposure to the air or while in use. 6. Entire absence of acid or other properties liable to produce injury of materials or metals with which they may be brought in contact. 7. A high temperature of vaporization and of decomposition, and a low tem- perature of solidification. 8. Special adaptation to the conditions as to speed and pressure of rubbing surfaces under which the unguent is to be used. 9. It must be free from grit and from all foreign matter. THE STEAM ENGINE. 197 The petroleums are found in Russia, China, India, Italy, Roumania, and other parts of the world. The island of Trinidad contains a lake of petroleum. A great part of the petroleum of the world is produced in Pennsylvania, West Virginia, and Ohio. According to Spon: 1. A mineral oil flashing below 300 deg. Fahr. (150 deg. Cent.) is unsafe. 2. A mineral oil losing more than 5 per cent. in 10 hours at 60 deg. to 70 deg. Fahr. (15 deg. to 20 deg. Cent.), is inadmissible, as the evaporation creates a gum, or leaves the bearing dry. 3. The most fluid oil that will remain in its place, fulfilling ocher condicions, is the best for all light bearings at high speeds. 4. The best oil is that which has the greatest adhesion to metallic surfaces, and the least cohesion in its own particles. In this respect fine mineral oil stands first, sperm oil second, neat's-foot oil third, and lard oil fourth; consequently the finest mineral oils are best for light bearings and high velocities. The best animal oil to give body to fine mineral oils is sperm oil; lard and neat's-foot oils may replace sperm oil when greater tenacity is required. 5. The best mineral oil for steam cylinders is one having a density of 0.890 and a flashing point of 680 deg. Fahr. (360 deg. Cent.). 6. The best mineral oil for heavy machinery has a density of 0.880 and a flash- ing point of 520 deg. Fahr. (269 deg. Cent.). 7. The best mineral oil for light bearings and high velocities has a density of 0.871 and a flashing point of 500 deg. Fahr. (262 deg. Cent.). 8. Mineral oils alone are not suited for very heavy machinery on account of their want of body, but well purified animal oils are applicable to the heaviest machinery. 9. Olive oil stands first among vegetable oils, as it can be purified without the aid of mineral acids. The other vegetable oils, which, though far inferior to olive oils, and admissible as lubricants, are, in their order of merit, sesamé, earthnut, rape and colza, and cotton-seed oils. 10. No oil is admissible which has been purified by means of mineral acids. Pure natural West Virginia oil, 29 deg. gravity Baumé is suitable for all kinds of heavy machinery, and will remain limpid in the coldest climates. It is pre- ferred by many consumers to sperm or lard oils. Oil of heavy body, and a fire test of from 330 deg. to 350 deg. Fahr. (165.5 deg. to 177 deg. Cent.). is often used for railroad car axles, heavy machinery, locomotives, or for any purpose where great heat is to be provided against, and for bearings where heavy weight is sustained. It has excellent wearing properties, and will lubricate and keep car journals and heavy bearings cool when oils of a lower fire test would volatilise. It can be used during all seasons of the year. Properly refined, it is entirely free from sand, tar, and still-bottom impurities. For factory use, high speed, with both heavy and light bearings, and wherever the lubricato: is fed to bearings by capillary attraction, it is a good lubricant. All vegetable and animal oils are compounds of glycerine with fatty acids. When they become old, decomposition takes place and acid is set free, by which action, as is commonly said, the oils become rancid. This rancid oil or acid will attack and injure the machinery. Again, all animal oils contain more or less gummy matter, which accumulates when exposed to the action of the atmosphere and will consequently retard the motion of the machinery. Mineral oil does not absorb oxygen, whether alone, or in contact with cotton wool, and cannot therefore take fire spontaneously as animal and vegetable oils do. The greases, or semi-fluid lubricants, are sometimes used in their natural state, as tallow, lard, and other similar substances, and sometimes are made up artificially, e.g. the various kinds of soaps. Mixtures of tallow and black lead white lead and oil, and other mixtures containing sulphur, are often used. For some special purposes, certain mixtures are used, as for cooling hot journals, mixtures of oil, and of white or black lead, oil and sulphur, or greases composed of oil to which some alkaline water has been added. For a railway grease a mixture of equal parts of tallow and palm oil, with water to which one-eighth of its weight of caustic soda has been added, is a good one, mixing them quite warm. Two parts paraffin, one of lard, and three of lime water is said to be a good grease, especially for heavy, slow-moving journals. 198 SECTION II.-POWER STATION. Steam Cylinder Lubricants. Steam cylinder lubricants are tested upon bearings heated to a temperature corresponding to any desired steam pressure. When the maximum temperature has been attained, the flame is removed, and the behaviour of the oil noted as the temperature falls to the boiling point, which corresponds to atmospheric pressure, or to zero on the steam gauge. Any effervescence or excessive friction at higher temperatures condemns the lubricant. For comparison, it is customary to take the average of the coefficients of friction for temperatures ranging from 340 deg. Fahr. (171 deg. Cent.), corresponding to a gauge pressure of seven atmospheres-to 212 deg. Fahr. (100 deg. Cent.) Results are recorded in tables furnished on blanks, thus: 1. The pressure and speed of rubbing at each trial. 2. The observed temperatures. 3. The readings on the arc of the machine. 4. The calculated coefficients of friction. The best lubricants are in general the following, for usual conditions met with in practice. Under low temperatures-as in rock drills driven by compressed air-light petroleums. Under very great pressure with slow speed-graphite, soapstone, and other solid lubricants. Under heavy pressure with slow speed, the above, and lard, tallow, and other greases. sperm oil, castor oil. Heavy pressures and high speed Light pressures and high-speed: sperm, refined petroleum, olive, rape, cotton Ordinary machinery: lard oil, tallow oil, heavy mineral oils, and the heavy vegetable oils. seed. Steam cylinders: heavy mineral oils, lard, tallow. Watches and other delicate mechanism: clarified sperm, neats' foot, porpoise, and olive oils. For mixture with mineral oils sperm is best; lard is much used. Measurement of the Durability of Lubricants. (J. E. Denton.) CC Practical differences of durability of lubricants depend not on any differences of inherent ability to resist being worn out" by rubbing, but upon the rate at which they flow through and away from the bearing surfaces. The conditions which control this flow are so delicate in their influence, that all attempts thus far made to measure durability of lubricants may be said to have failed to make dis- tinctions of lubricating value having any practical significance. In some kinds of service the limit to the consumption of oil depends upon the extent to which dust or other refuse becomes mixed with it, as in railroad-car lubrication, and in the case of agricultural machinery. The economy of one oil over another, so far as the quality used is concerned that is, so far as durability is concerned-is simply proportional to the rate at which it can insinuate itself into and flow out of minute orifices or cracks. Oils will differ in their ability to do this, first, in proportion to their viscosity; and second, in proportion to the capillary properties which they may possess by virtue of the particular ingredients used in their composition. Where the thickness of film between rubbing surfaces must be so great that large amounts of oil pass through bearings in a given time, and the surroundings are such as to permit oil to be fed at high temperatures or applied by a method not requiring a perfect fluidity, it is probable that the least amount of oil will be used when the viscosity is as great as in the petroleum cylinder stocks. When, however, the oil must flow freely at ordinary temperatures, and the feed of oil is restricted, as in the case of crankpin bearings, it is not practicable to feed such heavy oils in a satisfactory manner. "Oils of less viscosity or of a fluidity approximating to lard oil must then be used. Relative Value of Lubricants. (J. E. Denton.) The three elements which determine the value of a lubricant are the cost due to consumption of lubricants, the cost spent for coal to overcome the frictional resistance caused by use of the lubricant, and the cost due to the metallic wear on the journal and the brasses. THE STEAM ENGINE. 199 Weights of Oil per Gallon. The following are approximately the weights per gallon of different kinds of oil (Pennsylvania Railroad Specifications): Lard oil, tallow oil, neats'-foot oil, bone oil, colza oil, mustard-seed oil, rape- seed oil, paraffin oil, 500 deg. fire-test oil, engine oil, and cylinder lubricant, 7½ Îb. per gallon. Well oil and passenger-car oil 7.4 lb. per gallon; navy sperm oil 7.2 lb. per gallon; signal oil 7.1 lb. per gallon; 300 deg. burning oil 6.9 lb. per gallon, and 150 deg. burning oil 6.6 lb. per gallon. Pennsylvania Railroad Specifications for Petroleum Products. Five different grades of petroleum products will be used. The materials desired under this specification are the products of the distilla- tion and refining of petroleum unmixed with any other substances. 150 deg. Fire-test Oil.-This grade of oil will not be accepted if sample (1) is not "water-white" in colour; (2) flashes below 130 deg. Fahr.; (3) burns below 151 deg. Fahr.; (4) is cloudy or shipment has cloudy barrels when received, from the presence of glue or suspended matter; (5) becomes opaque or shows cloud when the sample has been 10 minutes at a temperature of 0 deg. Fahr. The flashing and burning points are determined by heating the oil in an open vessel, not less than 12 deg. per minute, and applying the test flame every 7 deg., beginning at 123 deg. Fahr. The cold test may be conveniently made by having an ounce of the oil, in a four-ounce sample bottle, with a thermometer suspended in the oil, and exposing this to a freezing mixture of ice and salt. It is advisable to stir with the thermometer while the oil is cooling. The oil must remain trans- parent in the freezing mixture 10 minutes after it has cooled to zero. 300 deg. Fire-test Oil. -This grade of oil will not be accepted if sample (1) i not "water-white" in colour; (2) flashes below 249 deg. Fahr.; (3) burns below 298 deg. Fahr.; (4) is cloudy or shipment has cloudy barrels when received, from the presence of glue or suspended matter; (5) becomes opaque or shows cloud when the sample has been 10 minutes at a temperature of 32 deg. Fahr. The flashing and burning points are determined the same as for 150 deg. fire- test oil, except that the oil is heated 15 deg. per minute, test flame being applied first at 242 deg. Fahr. The cold test is made the same as above, except that ice and water are used. Paraffin Oil.-This grade of oil will not be accepted if the sample (1) is other than pale lemon colour; (2) flashes below 249 deg. Fähr.; shows viscosity less than 40 seconds or more than 65 seconds when tested as described under "Well Oil” at 100 deg. Fahr. throughout the year; (4) has gravity at 60 deg. Fahr., below 24 deg. Baumé, or above 29 deg. Baumé; (5) from October 1 to May 1 has a cold test above 10 deg. Fahr. The flashing point is determined same as for 300 deg. fire-test oil. The cold test is determined as follows: A couple of ounces of oil is put in a four-ounce sample bottle, and a thermometer placed in it. The oil is then frozen, a freezing mixture of ice and salt being used if necessary. When the oil has become hard, the bottle is removed from the freezing mixture and the frozen oil allowed to soften, being stirred and thoroughly mixed at the same time by means of the thermometer, until the mass will run from one end of the bottle to the other. The reading of the thermometer when this is the case is regarded as the cold test of the oil. Well Oil.-This grade of oil will not be accepted if the sample (1) flashes, from May 1 to October 1, below 249 deg. Falır., or from October 1 to May 1 below 200 deg. Fahr.; (2) has a gravity at 60 deg. Fahr. below 28 deg. Baumé or above 30 deg. ; (3) from October 1 to May 1 has a cold test above 10 deg. Fahr.; (4) shows any pre- cipitation in ten minutes when 5 cubic centimetres are mixed with 95 cubic centi- metres of 88 deg. gasoline; (5) shows a viscosity less than 55 seconds or more than 100 seconds, when tested as described below. From October 1 to May 1 the test must be made at 100 deg. Fahr., and from May 1 to October 1 at 110 deg. Fahr. For summer oil the flashing point is determined the same as for paraffin oil; and for winter oil the same, except that the test flame is applied first at 193 deg. Fahr. The cold test is made the same as for paraffin oil. The precipitation test is to exclude tarry and suspended matter. It is easiest made by putting 5 cubic centimetres of the oil in a 100 cubic centimetre graduate, then filling to the mark with gasoline and thoroughly shaking. The viscosity test is made as follows: A 100 cubic centimetre pipette of the long bulb form is regraduated to hold just 100 cubic centimetres to the bottom of SECTION II.-POWER STATION. } 200 the bulb. The size of the aperture at the bottom is then made such that 100 cubic centimetres of water at 100 deg. Fahr. will run out the pipette down to the bottom of the bulb in 34 seconds. Pipettes with bulbs varying from 18 in. to 1 in. in diameter outside, and about 44 in. long, give almost exactly the same results, pro- vided the aperture at the bottom is the proper size. The pipette being obtained, the oil sample is heated to the required temperature, care being taken to have it uniformly heated, and then is drawn up into the pipette to the proper mark The time occupied by the oil in running out down to the bottom of the bulb, gives the test figures. 7 C 500 deg. Fire-Test Oil. This grade oil will not be accepted if sample (1) flashes below 415 deg. Fahr.; (2) shows precipitation with gasoline when tested as described for well oil. The flashing point is determined the same as for well oil, except that the test flame is applied first at 438 deg. Fahr. PART II.—STEAM TURBINES. GENERAL. In many respects the steam turbine is closely allied to the water turbine, and it will be convenient, as a preliminary, to give here a slight discussion of the latter. In a water turbine, one or more jets of water issuing from a nozzle or from guide- blades impinge on the vanes of a wheel capable of rotation. Impulse and Pressure Wheels. Turbines are classified either as impulse or pressure wheels. The latter are also sometimes called reaction wheels. The Girard and Pelton wheels are both of the impulse type. In these the water issues from the guide-blades or nozzles at a velocity corresponding to the full available head. Thus, all the "pressure-head" is turned into "velocity-head" before the fluid leaves the guide-blades. There is thus no hydrostatic pressure whatever within the buckets of the turbine wheel. Indeed, the water seldom fills them, touching one side of the bucket only, the back of the. bucket being quite clear of the water flowing along the face of the next one. This face is curved, and, owing to this curvature, there is a centrifugal pressure developed between it and the water moving over it, which is forced to move in a curved path. It is this centrifugal pressure on the bucket which drives the wheel. Guide-blade and Bucket Angles. In order to allow of this pressure being fully developed, every precaution is taken against the formation of eddies or the breaking-up of the jet, which should move solid till it leaves the wheel. Any jet striking a solid surface is broken up A. BL g Ꮄ F ނ A μ L с D μ S μ E Fig. 1. more or less completely, save in the special case in which the surface at the point of impingement is tangential to the direction of the jet. Hence the leading edge of the buckets of a turbine should be tangential to the jets which meet them. If the bucket were stationary, this condition would be easily provided for by making the axis of the jet a tangent to the leading edge of the bucket. Since, however, H² { 202 SECTION II.-POWER STATION. the bucket is itself in motion, the direction of the jet in space is not the same as the direction in which it meets the bucket. Given the speed of the bucket and the velocity of the jet, this "virtual velocity" of the jet relatively to the bucket can be readily found by the usual diagram of velocities as in Fig. 1. Here A B is drawn to scale, to represent, in magnitude and direction, the velocity of the jet. The angle a is the angle this velocity makes with direction of motion of the bucket. This angle is generally 15 deg. to 20 deg. The distance C B represents, in magni- tude and direction, the speed of the bucket. Then the closing line A C of the triangle represents the velocity of the jet relatively to the bucket, and the angle represents the angle the inlet edge of the bucket makes with its own direction of motion. In impulse wheels, the angle μ at the discharge edge of the bucket is commonly the same as 0. Neglecting frictional losses in the bucket, the closing line A C also represents the speed with which the water moves over the curved face of the bucket, and issues at its discharging edge at D. Then, if D E is set off, as indicated, it will represent the velocity of the water relatively to the bucket on leaving. To find the true velocity in space of the issuing water, the velocity of the bucket must be set off from E in the proper direction. Then the closing line D F represents the final velocity in space of the fluid after it has passed through the turbine. The kinetic energy carried away is, of course, proportional to the square of D F; whilst the kinetic energy of the water entering the wheel is proportional to the square of A B. The smaller D F the more efficient the wheel; but D F must not be made too small, or the water to be discharged from one bucket will fail to clear the edge of the next. If v = the velocity of the jet and s the speed of the bucket, it will be obvious from the figure that and sin a sin In water-wheel practice, s is commonly about v cosa; but in steam turbines it is not usually practicable to run the wheel as fast as this, which, moreover, is only correct if the relative velocity with which the jet leaves the wheel is sensibly the same as the relative velocity with which it entered it. Steam impulse wheels must work "drowned," and hence the friction loss is relatively larger than with water im- pulse wheels. The latter are generally more efficient than pressure turbines; but in the case of steam impulse wheels, this advantage is not maintained, the frictional loss in the bucket and disc friction being, at least, equally as great as in a reaction wheel. S sin (0 - a) V sin (939) AC V Pressure or Reaction Turbines. The simplest type of reaction wheel is Barker's mill. In this, a horizontal tube is arranged to rotate at its centre round a vertical shaft. This shaft is hollow, and down it water is conveyed under pressure to the horizontal tube. The latter Pressure-p₁ GUIDE BUCKETS BLADES Pressure-p₂ Pressure-p3 Fig. 2. is closed at its ends, but is fitted with nozzles there directed tangentially to the path of rotation. The water escaping through these nozzles by its reaction causes the tube to rotate. A very high efficiency is possible, the best speed of rotation being such that the nozzles move backwards with the velocity v √2gh, where h is the available head. This form of turbine is but little used, the speed STEAM TURBINES. 203 being difficult to govern, so that in the most common type of pressure turbine the fluid acts partly by impulse and partly by reaction. A section through the buckets and guide-blades of such a turbine is represented in Fig. 2. Here the pressure above the guide-blades is pi. In passing through the guide-blades, a portion of this pressure-head is converted into velocity-head, with the result that the energy of the fluid in the clearance space is partly pressure energy and partly kinetic energy. The velocity of flow from the guide-blades is thus that corresponding to the difference between pressures p₁ and p2. The water moving with this velocity and under the pressure p2 enters the buckets of the moving wheel, the leading edges of which are by the same process as in Fig. 1 designed to be tangential to the relative direction in which the discharge from the guide-blade meets the bucket. Thus, in Fig. 3, AB represent v₁, the velocity due to the pressure difference p₁ -P2, and CB the speed of the bucket. Then, as before, A C is the velocity of the jet relatively to the pi B Jo q Vi < S в C/e μ A √2 D (940) ทุ Fig. h bucket, and the bucket angle at entrance. In its passage through the bucket, the pressure-head p2 pg is also converted into velocity-head, p3 being the pressure below the bucket. Hence, whilst at its upper end the water moves through the bucket with the velocity A C, at its lower it is moving much faster. Let v₂ be the velocity due to the pressure difference p2 - P3; then if CH P3; then if C H = v2 is the set-off, at right angles to AC, the closing line A H represents the magnitude of the velocity of the water relatively to the bucket on leaving. Then if DE is set off equal to AH, but at the angle μ, which is the bucket angle at discharge, this line DE will represent, both in magnitude and direction, the velocity of the water relatively to the same bucket at discharge. Then making EF=CBs we have, as before, D F the absolute velocity with which the water leaves the wheel. If this is r, the energy +2 carried away by the water per pound is, of course, If the total head in feet cor- 29 responding to the pressure difference P1-P3 is h, the total energy in the water originally available per pound was h, and the efficiency, neglecting frictional losses (which generally amount to 20 or 25 per cent. of the total available energy) is +2 F h S 2g H μ < 204 SECTION II.-POWER STATION. The Velocity of Flow of Steam from Guide-blades. In the case of water turbines, the energy producing flow is h foot-pound for every pound of water discharged, where h is the total available head in feet. The kinetic energy of the moving jet per pound must be the same, or whence, v = √2gh. In the case of saturated steam, the energy per pound available for producing flow is given in British thermal units by the equation Where T1 is the absolute temperature on the inlet side, and T₂ the absolute 2 temperature on the discharge side of the guide-blades, $11 and $1, the correspond- ing liquid entropies (see Tables 1, 2, and 3, page 148), Ø81 the steam entropy at the temperature T₁, and h₁ and h₂ the sensible heats of 1 lb. of steam at the tem- peratures T1 and T2 respectively. The velocity of discharge corresponding to U is v = 223 √U. feet. per second. In practice, owing to friction, the velocity is almost always considerably less, so that the velocity thus calculated requires correction, as explained below, for different types of turbine. 5 H.-P. IMPULSE STEAM TURBINES. Impulse steam turbines are of two types, viz., simple turbines and compound turbines. The theory of the former is in every respect similar to that of the water turbine, but for application to compound turbines some modifications are required. The two principal, if not the only, makes of simple impulse turbines are the Riedler-Stumpf (Allgemeine) and the de Laval; the former is built on the lines of the Pelton wheel, while the latter is merely a Girard turbine built to take steam instead of water. Size of Turbine. 15 30 50 The de Laval Turbine. (Figs. 4 and 5, pages 205 and 206.) The general arrangement of de Laval Turbine is represented in Fig. 4. The wheel is shown in position. The nozzles through which the steam supply is delivered are not represented in this view, but one is shown separately in Fig. 5 with the buckets below it. The steam is supplied to one side of the wheel and escapes to exhaust at the other, as indicated by the arrow in Fig. 5. 100 300 The Wheel. (FIGS. 4 and 6, pages 205 and 206.) Two patterns of wheel are in use, that represented in Fig. 4 being the type used for smaller patterns where the centrifugal forces are relatively small, whilst in Fig. 6 is represented the type of wheel used for the larger 200 and 300 horse- power units. The standard sizes of wheel for different powers are as follows:- Table 1.-Speeds of the Turbine Wheels. "" ― U = h1 – h₂ – T2 ($ 11 — $ 12) + $ 81 (T1 — T2). "" "" "" "" v2 =h, - 29 100 mm. 150 225 300 500 760 33 Middle Diameter of Wheel. "" "" "" "" ******** 4 in. 6 "" 87,, = 11} " 192,, = 30 "" Revolutions per Minute. 30,000 24,000 20,000 16,400 13,000 10,600 Peripheral Speed in Feet per Second. 515 617 774 846 1115 1378 STEAM TURBINES. 205 As shown in Fig. 4, the smaller wheels are pierced at the centre to take the shaft, whilst the large wheels, Fig. 6, are solid at the centre. The forces producing stress are much greater at the centre of the wheel than elsewhere, hence in both cases the metal is greatly thickened here. 0 4 O 15 O O O 98 RIGHT HAND SPIRAL LEFT HAND SPIRAL ·· O O .. 5000* Radial stress in pounds per square inch = q = A Tangential stress $COO* TOTAL END PLAY = {GOVERNOR{ 毖 ​< In the case of a rotating steel disc of constant thickness, the stresses at any point are given by the following equations :- B 7.2 B = t = A + p² FULCRUMS TOTAL END PLAY BETWEEN SHOULDER OF GOV. SHAFT AND END OF THE BÉARING 1.0073 AUX AMMOOOM (935) 1.69 r² n². Fig. 4. De Laval Steam Turbine .91 r² n³. 206 SECTION II.-POWER STATION. Herer n = revolutions per second. A and B are constants to be determined by the boundary conditions. If the wheel has no hole at centre, B = 0. If, on the other hand, there is a hole at the centre, the radial stress at the circumference of this hole must be zero, or if r2 is the radius of this hole B r22 1.69 r₂² n² (1) If there are no buckets the radial stress at the other circumference is again zero, or if r₁ be the outer radius 92 = 0 (996) = radius of the disc in feet. = 0 91 0 = A B r12 1.69 r₁² n² (2) If, on the other hand, there are buckets, the centrifugal force of one of these wv2 where "v" is the velocity of the bucket 32r LO 5 << A must be calculated by the formula ƒ = < CCCCCE - Fig. 5. Nozzle for De Laval Turbine. Fig. 6. Wheel for De Laval Turbine. Then we have 91 = • in feet per second, "w" its weight in pounds, and "r" the mean radius of the bucket path in feet. • Nf 2π r2l (3) Where "N" is the number of buckets and "7" the width of the rim. Knowing 91, the constants A and B can then be found from equations (1 and 2). For small wheels, such as shown in Fig. 4, the width "z" of the wheel where с its profile is curved is given by the equation z = r2 Here C is a constant chosen so as to make z a convenient width, generally in. toin., at the periphery of the wheel. The stresses are then given by the relation 1.58 1.58 Br • - 6 8.95 n2r2. . 1.58 tto Radial stress = q = Ar 1.58 Tangential = t = .58 Ar 4.82 n² r². + 2.58 Br Here, as before, A and B are constants determined by the conditions that q = 0 when r = r2, the inner radius, and Gaming STEAM TURBINES. 207 21 22 64 π r²l 91 = (4) ι when r₁, the outer radius in feet, r₁, l and "v" denote the same quantities as before, whilst w₁ is the total weight of the buckets and of that portion of the rim included between the outer circumference and the depth of the notches in which the buckets are fixed. It will be readily understood that by combining the four equations 1, 2, 3, 4, just given, the stresses can be found in a wheel which is in part a simple cylinder, whilst in the remainder of the wheel the thickness follows the law Z = Cr According to Mr. Konrad Andersson, the maximum stress in the body of a 50 horse-power wheel is 18 kilos per square millimetre, or about 11.2 tons per square inch. În the thinned "breaking section," just under the rim, the stress is about 50 per cent. more. 2 The stresses for the general case, in which Z = Cr q = Ar 2 2 + n + √ 4 + " + n' 2 - -Br d q t = 4.11 r² + rär + (1 − n) q. 7 n 2 + n - V 4 + n 4 + n + n² 2 are as follows: Su + The width at any point of the solid type of wheel Fig. 6 is given by the relation : Z=Ce - hr². (5) C is chosen, as before, so as to make the width whatever is desired at the r2 outer circumference, say in. h = 2.065 where 91 is determined by equation (4) 91 supra, "e" is the base of the Naperian logarithms, and "" the radius in feet, as before. In this case the radial and tangential stresses are equal and constant throughout, or q₁ = t = q. 91 It will be noticed that in all cases the wheel is thinned by deep grooves immediately under the rim. This is done with the object of causing it to break here, if by any chance the speed gets dangerously high. The fragments that fly are then light and small, and are stopped by the casing; whereas, in the absence of this provision, the wheel would part in heavy fragments capable of doing serious damage. If the rim goes, the buckets go too, and the steam can no longer impel the wheel. At the same time that the rim goes the wheel is practically certain to be thrown out of balance, so that the extensions on the hub foul the holes in the casing in which they normally rotate quite clear, and the friction then soon brings what is left of the wheel to rest. 53.42 r2 13 n-32 The Buckets. The buckets used in the Laval turbine are drop-forgings of the shape shown in Fig. 7. The rim is drilled and slotted to receive them, as shown. pitch is about in. This method of securing the buckets has the advantage that The 1837) they can be readily replaced: a necessary precaution, in view of the fact that they wear out in from one to five years, the wear being greatest at the leading edge. The buckets for all wheels are of the same width, viz., 10 millimetres, and the notch in which they fit is also always 8 millimetres deep. For a 5 horse-power wheel they are in. long; for a 30 horse-power wheel, in. long; and for a 208 SECTION II.—POWER STATION. 300 horse-power turbine, 1 in. long. The largest size weigh each 250 grains. The angles at entrance and exit are identical, being 36 deg. in the case of large wheels, and 32 deg. in that of the smaller sizes. The Shaft. (FIGS. 4 and 6, pages 205 and 206. A special feature of the de Laval turbine is the shaft, which is of very small diameter compared to its length and the power transmitted through it. Thus a 5 horse-power turbine has a shaft in. in diameter, and one of 30 horse-power, in. in diameter, whilst a turbine of 150 horse-power has a fin. shaft, and one of 300 horse-power a shaft 1 in. in diameter. The shaft being flexible, it is not necessary to expend special care in balancing the wheel, which, in fact, can be run successfully even when one bucket is missing. The yielding of the shaft allows the whole rotating system to turn about its centre of gravity, and also permits of the shafts being supported on four bearings. The use of this flexible shaft is not essential to the running of wheels at high speeds, since the degree of elasticity necessary for steady running can be provided for by bearings of the Parsons type. If stiff shafts are used, however, at these high speeds, it is essential that they shall run in two bearings only. With the flexible shaft the wheel runs unsteadily till a certain critical speed is past. It then "settles down" and runs at the higher speeds with perfect steadiness. In the case of the smaller wheels, the attachment of the shaft to the wheel is effected as indicated in Fig. 4. The shaft is provided with a boss, as shown, turned with a taper of 1 in 24. Õn this taper is forced a thin steel bush, which is then secured to the shaft by a pin. This bush is drawn into the hub of the wheel by a nut at one end, the frictional grip of which is sufficient to take the torque of the wheel. With the larger wheels the arrangement shown in Fig. 6 is adopted. The flanged ends of the shafting are turned to a taper of 1 in 24, and forced into holes in the wheel bored to a corresponding taper, and secured by studs and nuts as shown. The other end of the shaft is provided with a right-hand and with left-hand spiral pinion, the teeth being cut out of the solid. These gear with mild steel spiral pinions, as shown. The speed ratio is about 10 to 1, and the linear speed of the pitch line is 100 ft. per second. The teeth are of fine pitch, so as to reduce the noise. They are also somewhat short, as the following Table shows, the height being about half the pitch. Table 2.—Pinions. (FIG. 4, page 205.) Horse- Power. 10 75 110 300 Outside Diameter. 1.077 1.53 1.82 2.65 Number of Teeth. 21 19 23 31 Depth of Teeth. .075 .1169 .1169 .1275 Diametral Pitch. 21 14 14 12 The tooth pressure per inch of wheel face is very small, being only about 10lb. in the case of a 5 horse-power wheel, the pitch of which is about No. 27 diametral pitch, 30 lb. per inch width in the case of a 30 horse-power wheel, and 45 lb. in that of a 300 horse-power turbine. With so high a gear ratio as 10 to 1, it is advisable to make the teeth of the driving pinion practically all point, and those of the wheel practically all root. That is to say, the teeth of the driving pinion should extend but little below the pitch circle, and those of the gear wheel but little above the pitch circle. Thus made, almost the whole interaction of the teeth occurs during recess, all tendency to interference is eliminated, the teeth wear well, and the friction is reduced. In small turbines the helical spur-wheels are cut out of solid forgings of mild steel; but in the larger sizes they are cut in rings of mild steel, bored to a taper of 1 in 24, and forced on to a cast-iron centre, as shown in Fig. 4. These centres are also fitted to their shafts with the same taper. The Nozzle. (FIG. 5, page 206.) This is represented in Fig. 5. It is turned parallel externally, and is a good fit for its hole in the casing. The upper end is screwed to take a jam nut to start it, should it require renewal or replacement. Its length is such that there is a clearance of about in. between its lower end and the buckets. Its axis makes an angle of 20 deg. with the plane of the buckets. It is tapered internally, the angle of the taper being altered to suit the initial steam pressure; about 10 deg. is an average value. STEAM TURBINES. 209 Flow through the Nozzle. On page 151 it was stated that with certain limitations the velocity of flow through an orifice was given by the relation v = 223 √Ū, where where U is the "available heat" per pound of steam calculated by equation (3), page 150. Actually, v is always less than thus obtained, since it is reduced by frictional losses To allow for these, we may write v = 223 √ūi, Hence, U₁ = U With a suitably-designed nozzle, this equation gives a close approach to the actual velocity of the steam flowing into free air. If, however, the pressure p2 on the discharge side of the nozzle is less: than .58, the pressure pi on the inflow side, the nozzle must be divergent. With a straight or convergent nozzle, the velocity through the orifice becomes constant, once the lower pressure falls below .58 p1. Any further reduction of the pressure on the discharge side leads to no increase in the weight of steam discharged. The discharge through a divergent nozzle can be calculated by assuming the pressure at the throat is .58 p1. Thus, if p₁ is 100 lb. per square inch absolute, the pressure at the throat may be taken as 58 lb. absolute. From Table 2, page 149, we find :- Ф81 T₁ = 787.0 deg. Të = 749.7 deg. absolute h1 = 298.13 h2 = 259.90 $12 = .4734 $12 = .4235 = 1.1230 U = m-họ-T2 (Phì - b) + 81 (T1 – T2) = 42,71 units v = 223 √σ = 1456 ft. per second. The specific volume of steam at 58 lb. absolute is 7.26 cubic feet. The dryness- fraction is: W = + $13 - $12 1.1729 1.2143 $82 Hence, at the throat the volume occupied by 1 lb. of the mixture of steam and water will be 7.01 cubic feet. If the nozzle has a cross-section of square inch, then the weight passed per second will be: $ 51 U2 1660 v 1456 10 x 144 × 7.01 1440 × 7.01 2 = Napier has given an empirical formula for the weight discharged in such a. case as that just considered. "It is: ↓ = P1 W 70 144 =.966. where w = area of the orifice in square inches. Taking p1 as 100 lb. absolute, we find W = .143 lb., which agrees closely with that just calculated by the theoretical formula. • Having obtained the size of the throat necessary to pass a given weight of steam in the above manner, the area necessary at the discharge end is given in square inches by the formula = .144 lb. w x3 V3 • V3 here w is the total weight of steam passed per second, xg is the dryness fraction at the outlet end, V3 the specific volume, and vs the speed of flow. Taking the same initial pressure as before, and assuming the nozzle discharges. 210 SECTION II. POWER STATION. direct into atmosphere, we have p3 the discharge pressure = 14.7 lb. per square inch, and from Table 2, page 119, we get .3114, T3 = 671.4 h3 = 180.21, $13 = 1.4396, V3=26.36 cubic feet. $53 Also Now U3 = hi x $81 ძვ. hi - h3 T2 (Pi (φ Pl = + $11 - $1.2 ቀ $8.3 + 1.2850 1.4396 223√Uğ¹ and U3¹ 12) + d U32 U3 1600 8, T1 - T3) $81 Hence, Ugl - 125.5 Whence v3 = 2495 ft. per second. If "w" is taken as .144 lb. per second, we get 144 x .144 × .892 × 26.36 2495 ΩΞ = .892. — = 137.19 B.T.U. = .195 square inch. Strictly speaking, x3, as taken, is subject to a slight correction, since the work lost in friction goes to increase the entropy of the steam as it is discharged, but the error involved is not here of any importance. tis important to note that is the area through the discharge end of the nozzle, measured at right angles to the axis, and not the inclined area through it, due to its being cut off at an angle. The Bearings. (FIG. 4, page 205.) The bearings are lined with white metal. Those on the wheel casing are solid rings, but those in the gear casing are split. Referring to Fig. 4, it will be seen that the outermost bearing at the turbine end of the shaft is carried in a cage having a spherical seating against which it is maintained by a spring. The other bush is more of a gland than a bearing, as it can vibrate with the shaft. All the bearings for the first-motion shaft are supplied with oil from wick lubricators, ring lubrication having proved unsatisfactory here. To ensure a satisfactory distribution of the oil, a shallow spiral groove, about deep and pitch, is turned in the bush. Drip lubrication is also used for the teeth of the gear wheels. Ring lubrication is fitted to the second-motion shaft, which rotates much more slowly. The Governor. (Figs 8 and 9, page 211.) The governor is of the ordinary centrifugal type, but very compactly designed. The balls are replaced by two semi-circular shells, B in Fig. 8, which pivot about the points A, resting on the supporting piece shown. The springs shown abutting on the washer D tend to keep the half-shells together. If the speed rises the shells move apart, raising D, and with it the rod G, which in turn pushes over the vertical arm of the bell-crank L, to which it is spring- connected. This bell-crank in its turn closes the double-beat governor valve, shown separately in Fig. 9. Should this valve stick for any reason, an emergency device is provided, represented at T, Fig. 8. This consists of a spring-closed valve communicating with the interior of the wheel casing. If this is opened, air rushes in, destroying the vacuum, and consequently greatly reducing the possible speed of the wheel. The spring connection between the rod G and the bell-crank arm permits this rod to move, even if the main governor valve is stuck, so that in this case it simply moves forward and strikes the head of the valve T. The whole governor is fixed to one of the second-motion shafts of the turbine simply by reaming a taper hole in the end of this shaft, which the stem of the governor frame fits. The taper is, as before, 1 in 24. The maximum speed variation is under 1 per cent. Efficiency. The overall efficiency of a 10 horse-power turbine, taking steam at 155 lb. absolute, and worked non-condensing, is about .25 per cent. That is to say, out of every 100 foot-pounds of work theoretically due from the steam 25 foot-pounds are actually realised. With a 30 horse-power turbine, the overall efficiency was .5 when worked non-condensing with steam at 45 lb. absolute, .44 with steam at 100 lb. absolute and non-condensing, and .42 with steam at 140 lb. absolute and a vacuum of 254-in. mercury. With a 300 horse-power wheel an overall efficiency of 57 per cent. was attained with steam at 210 lb. absolute and a vacuum of 27 in. STEAM TURBINES. 211 8 1938) A A 9 B BLO do u.b T Fig] 8. Governor for De Laval Turbine. Fig. 9. Governor Valve. { 212 SECTION II.-POWER STATION. Mechanical Efficiency. There is little or no trustworthy information available as to the mechanical efficiency of the de Laval turbine. In some experiments by Lewicki, a 30 horse- power turbine was run idle, by means of an electromotor, and the power taken noted. This amounted to 3 horse-power, when the wheel was run at 20,000 4-536 in Air of 1 Atm. THE RESISTANCE OF A 30 H.P. TURBINE-WHEEL. CA Resistance of the Wheel in P 2 21 Bod *+ AN AN 100' (544) 125' Hence In Steam of 364tm in absolute press-191 Vacuum.. --- In Steam of 1 Atm pressure. a being 20 deg. and 150* 175* 200° 225" 250" Temperature of the Steam. Fig. 10. U1 = U 8- revolutions per minute in steam at atmospheric pressure. A curve showing his results with superheated steam is represented in Fig. 10. It would seem, how- ever, unsafe to assume that the resistance is the same when the wheel is running under steam. In the latter case (assuming ideal conditions), the steam will meet the buckets tangentially, and the resistance should be substantially reduced. Mr. Konradsen states that at full load the mechanical efficiency of the larger turbines is about 924 per cent. This includes both gear and wheel friction. U2 1000 Speed of the Wheel. (FIG. 1, page 201.) Let v denote the velocity of flow from the nozzle, and 8 the velocity of the wheel. Then, from Fig. 1, it is apparent that to avoid shock we should have v sin (0-a) sin where a = the guide-blade angle and @ the bucket angle at entrance. In the case of Laval wheels, the actual wheel speed is always much less than this, as shown by the data given above. Thus, with steam at 215 lb. absolute and a vacuum of 27 in., we readily find from the equation that U = 321 B.T.U. nearly. Hence v = 223 √ti - a 16 deg., we have sin 16 deg. = 257 B.T.U. 8 = 3640 sin 36 deg. 500- = 3640 ft. per second. 275* 550 Fahr 300 Cent 1706. ft. per second. The actual speed, it will be seen from page 204, is 1378 ft. per second. It has, however, to be remarked that in the velocity of flow through the nozzle the latter has been taken as discharging into free space. There is every reason for believing that the velocity, will be less when the mouth of the nozzle is close to a rapidly- revolving wheel. This is known to be the case with water wheels of the pressure type, to which the Laval wheel, from this point of view, must be likened, since the wheel of necessity works "drowned." Some experiments by the Allgemeine Company showed that with Pelton type wheels the best bucket speed was 42 per cent of the theoretical speed of the jet. This would correspond to a nozzle loss of STEAM TURBINES. 213. about 23 per cent., which is much more than is found to be the case with nozzles discharging into free air. The actual weight of steam passed is not, however, diminished, since this depends only on the pressure at the throat of the nozzle. The buckets, as they come round to the nozzles, are full of inert fluid, and not empty, as are those of an impulse water wheel. In this particular regard the impulse steam wheel is worse off than the steam-pressure turbines, the buckets of which never contain fluid at rest. That the point is of some importance is clearly shown by the fact that in the turbines made by the Allgemeine Electricitäts Gesellschaft of Berlin, it has been found that the economy is increased by grouping all the nozzles close together in one batch, instead of spacing them symmetrically round the wheel. In view of the known fact that the discharge from the guide-blades of a water-pressure turbine is increased by the removal of the wheel, and of the other fact that the steam impulse wheel works under worse conditions, it is reasonable to suppose that here also the presence of the wheel lessens the speed of flow from the nozzle. This, it should be noted, does not necessarily imply any sensible decrease in the weight discharged, as it would with an inelastic fluid, such as water. A moderate back pressure from Stodola's experiments appears to have no influence on the pressure at the throat of a divergent nozzle. It only means that the velocity with which the steam leaves it is reduced, but its pressure being higher, its volume is also less. It would be of great interest to fix a thermopile to the exit end of a de Laval nozzle, and note the temperature with the wheel rotating in place and. with the wheel absent. The Simple Impulse Turbines of the Allgemeine Electricitats Gesellschaft. Combining the ideas of de Laval in adopting a single impulse wheel, and of Rateau in adopting a Pelton form of bucket, the above well-known company have recently put in the market a series of turbines, which, if embodying no novel principles, have been very carefully designed, and are very highly finished, so that a very good degree of economy is attained by them. The most striking feature of these wheels is their size, no less than 2000 horse-power having been developed by a single wheel, at the Moabit Electric Lighting Station, Berlin. The Wheel. This is of 15 per cent. nickel steel, with buckets cut out of the solid. In the particular wheel illustrated in Fig. 11, double buckets are used, but it is now 1075-- 460 JE 1855 * 4-857 · 555 -- 30 510 Fig. 11. Wheel for Riedler-Stumpf Turbine. 2000- I 720 83 214 SECTION II.-POWER STATION. the practice of the firm to use single buckets. The jet is then directed against one side of the wheel instead of centrally. The Moabit wheel is 6 ft. in diameter, and runs at 3000 revolutions per minute. It is made solid at the centre, and the profile of the web is the same as with the larger de Laval turbines. Its profile can therefore be calculated in the same way by equation 5, page 207. The Shaft. The shaft is a stiff one, having two bearings only. It is made in two parts, bolted to the wheel by flanges. The Nozzle. The nozzle is peculiar in being drawn to a square section after finishing, as indicated in Fig. 12. This has the advantage of enabling a group of them to be packed more closely, and also gives a jet better fitted to the shape of the buckets. On the other hand, the rubbing surface and consequent friction (8095.C.) Q 0 0 0 0 0 SECTIONS A-A. B-8. ヨ ​ C-C. D-D. Fig. 12. Nozzle for Riedler-Stumpf Turbine. is increased as compared with the cross-section of the nozzle; but it is claimed that there is a net gain. As already stated, it is found advantageous to arrange the nozzles in a single group instead of symmetrically round the wheel. Before drawing to the square section the interior of the nozzle is very highly finished, so as to reduce the fluid friction. The Buckets. These, as stated, are cut out of the solid rim of the wheel. No data have been published as to whether they are subject or not to the same severe wear of the de Laval buckets. The steel being very tough, and highly rust-resisting, the wear may be small, but the machines have scarcely been long enough in use to thoroughly test this. THEORY OF THE COMPOUND TURBINE. Two systems of compounding are in use, viz., pressure compounding and velocity compounding The simplest form of pressure compounding is that adopted by the Allgemeine Company, in which a number of compartments are arranged in series, the exhaust steam from one being the admission steam to the next. The whole fall of pressure between the inlet to the turbine and the exhaust is thus divided up between these compartments, in each of which is a single set of guide-blades and a single turbine wheel. Since each wheel has to deal with only a fraction of the total fall of pressure, its speed can be reduced, as compared with that of a single wheel, utilising the whole fall of pressure, in the ratio of 1 to √n, where n is the number of separate compartments. The Rateau and Parsons' turbines are also examples of pressure compounding. In velocity compounded turbines the steam issues from a set of nozzles or guide-blades with the full velocity due to the whole drop of pressure between the inlet to the turbine and the exhaust. It enters then the buckets of a wheel revolving at a relatively low speed, and leaves this wheel at a velocity which is still high. It is then caught by a second set of guide-blades, and turned into STEAM TURBINES. 215 another wheel, which abstracts from it some more of its velocity, delivering on to another set of guide-blades, and thence on to a third wheel. In the absence of friction, the series might be repeated indefinitely; and as the bucket speed is. reduced in direct proportion to the number of buckets, a very compact and simple turbine, running at as moderate a speed as might be desired, would be obtained. The frictional losses are such, however, that the system of velocity compound- ing is intrinsically less efficient than that of pressure compounding, and is therefore most suitable for turbines of small power and low cost of manufacture. Pressure-Compounded Turbines. In pressure-compounded turbines the whole fall of the temperature takes. place in a series of steps. The section of a turbine included between the beginning of one temperature step and the beginning of the next drop in temperature we shall call a "stage." In compound-impulse turbines of, say, the Rateau type, each stage comprises one set of guide-blades and one set of buckets, whereas in a "reaction" turbine, such as the- Parsons type, each stage includes either a set of guide-blades or a set of buckets, but not both. In a Curtis turbine, on the other hand, there are usually three or four stages, each of which includes, say, three sets of guide-blades and three sets of buckets. A simple A simple turbine, such as the de Laval, is, it will be seen on this defini- tion, a single-stage turbine, a set of nozzles and a set of buckets being included in the stage. nternal Efficiency of a Compound Turbine. (FIGS. 13 to 15, pages 215 to 217.) The over-all internal efficiency of a multi-stage turbine is always higher than that of each stage considered alone, since some of the heat wasted in friction in the higher stages is "available" for producing mechanical work in the lower ones. This over-all internal efficiency is most satisfactorily determined by measuring the heat carried away by the exhaust; or, what amounts to the same thing, the "dry- ness fraction at exhaust. The latter could, in theory at least, be found by taking small samples of the total steam exhausted; but in practice it is very difficult to obtain a really fair average sample of flowing steam. "" 900 800 Absolute Temp. (Fah. Degrees) 700 600 500 A 400 300 200 100 £ tata safna Mana Man 1 I N 0 (8563A) B Date meta · Gabr .6 .8 Entropy D M 10 1-2 1.4 1.6 1-8 2.0 2-2 Units Fig. 13. F Ir a perfect compound-turbine taking in dry saturated steam at an absolute temperature of T₁ and exhausting at a temperature of T2 absolute, the number of heat units per pound of steam passing which would be turned into mechanical work is given by the equation u = h1 − h₂ + T2 ($1, −(12) + $81 ) + $81 (T1 − T2) (6) 216 SECTION II.-POWER STATION. where the quantities h1, h2, Pl1 › Pl2' are taken from Tables 1, 2, or 3, page 148. * If T₁ = 820 deg. absolute, and T2 = 560 deg. absolute, we get on substituting the values from Table 3, u = 319.6 heat units. The corresponding temperature entropy-diagram is represented in Fig. 13. The dryness fraction of the steam LM at exhaust would be LP This is usually denoted by x, and the turbine taking in dry steam at 820 deg. absolute, delivers to the condenser at 560 deg. absolute, x lb. of steam and 1 ≈ lb. of water, for every pound of steam passed. B NI (85698) - Fig. 14. In actual practice, owing to friction in guide-blades and buckets, some portion of the water thus produced is re-evaporated in passing through the turbine, so that the dryness fraction at exhaust is represented by the fraction IH η ης P and U $81' of the fraction I L Calling this dryness fraction x, the heat units carried away at exhaust by each pound of the steam supplied, are x L₂+ h2, where L2 is the latent heat at exhaust. The heat supplied per pound is, of course, Li + h1, and the difference of these is equal to the "indicated" work of the turbine per pound of steam passing. Calling this w, and taking it in heat units, we have w = L₁ +hi x L2-h₂, and the thermodynamic efficiency of the turbine is W • C ← M L 1 - k. At each stage of the turbine a certain number of heat units are "available, owing to the temperature drop, for producing work in that stage. The number per pound of steam is given by the above equation, where T1 and T2 are now the temperatures at the beginning and end of the stage, instead of, as before, the initial and final temperatures of the turbine as a whole. Out of the u units thus available in any particular stage, a fraction ku is always, owing to friction, degraded back into heat. Assuming for the moment that no kinetic energy is carried over to the guide-blades of the next department, the mechanical work done in the stage will be (1-k) u (measured in heat units). As the number of units available was u, the stage efficiency is evidently (1 - k) u IM IL (Fig. 14), instead 33 น Of the ku units degraded back into heat, a certain proportion are available for doing work in the next compartment, so that they 'are not wholly wasted, the STEAM TURBINES. 217 consequence being that, as already stated, the efficiency of the turbine as a whole is greater than that of its separate constituents. If the number of compartments were infinite, the efficiency with different. values of k would be as follows (see Engineering, January 13, 1905):- k .4 700 .6432 = 0 1 10 Values of Noo •9 ස .6 5 0 4563 C .1. .916 •1 .2 .8286 -2 .3 Values of k Fig. 15. .3 .7378 Z= .4 With k = .3, the stage efficiency would be, of course, .7, so that in this case the efficiency of the turbine as a whole is 5.4 per cent. greater than that of each compartment. With a fair number of compartments, the total efficiency may be taken as identical with n∞o. The curve, Fig. 15, has been plotted from the above valves of k and noo• noo• A 9.8064 10 k T* 10k+1 10k+1 Pi "Available” Heat in a Compound Turbine. (FIGS. 14 and 16, pages 216 and 218.). 2 k u T₁+ T In an ideal compound turbine the heat "available" for producing mechanical work is represented by the area IBCH of Fig. 14. In practice, however, the frictional losses increase the available heat, so that the amount is represented by the whole hatched area IBCM of Fig. 14. In fact, the whole hatched area of Fig. 14 represents the available heat in a turbine subject to losses from fluid friction; whereas, in a perfect turbine the available heat would be represented by the area IBC H only. The distance H M = Z, represents the increase of entropy due to the fraction of the available heat wasted in friction at each stage. With an infinite number of stages we may write (see Engineering, January 13, 1905) Z + (7) Here A is a constant determined by the condition that when T = T1; Z T₁; Z=0;k is the fraction of available heat wasted in friction per stage; 1 is the liquid entropy of water at any absolute temperature T₁; and 1 is the total entropy of the steam at the temperature T₁. A simpler formula, sufficiently exact for prac- trical purposes, is (8) .5 .5 .5445 Φι • 218 SECTION II.-POWER STATION. The triangular area C H M, of Fig. 14, represents the additional heat available owing to the fluid friction. Its value is given by the equation (Tl—k — Tl−k) ~1 (T1-T)+ 100 k (T1 911 −TO1) 10k + 11 110k+11 9.8064 (T1-T) . (9) 110k + 11 where A, 41, and k have the same values as in equation (7) supra. In Engi- neering, January 13, 1905, it was shown that, taking the inlet temperature to the turbine as 820 deg. and the exhaust as 560 deg., the number of additional heat units available per pound of steam were as follows for different values of k :- √2z T 201 10 k = 0 .1 5.48 Additional units = 0 "These values have been plotted down as a curve in Fig. 16. An approximate expression, near enough for practical purposes, for the area of the triangular portion C H M is 30 Heat Units Zdt = .0 85630 A 1-k -2 .2 11.05 $820° zdr 550 -3 Values of k Fig. 16 .3 16.98 ku (T₁ -- T) .4 22.85 n = [1-(1-2)²] S 15 (10) Szdt = T1+T Z It will be seen that with given initial and final temperatures the heat available for producing mechanical work is less in a perfect compound turbine than in the turbines actually built; yet the former gives, of course, a greater actual output of mechanical energy. Professor Rateau states that the internal efficiency of his turbines may be 69 to 70 per cent., and accepting these figures k for a Rateau turbine as obtained from the curve, Fig. 3, is about .345. For a Parsons type turbine the corresponding value of k may be as little as .24, whilst for a two-wheel per stage velocity com- pounded turbine k may be about.4. .5 28.84 Efficiency of Underspeeded Turbines. Experiment shows that the "hydraulic" efficiency of a turbine at various speeds is well represented by a parabola. Hence, if 71 be the efficiency at the best bucket speed S, say, the efficiency at any other speed, s may be written 71 (11) COMPARTMENT - COMPOUNDED TURBINES. In compartment- compounded turbines, the whole drop of steam pressure between the stop valve and the condenser is divided up between a number of compartments, in each of which one or more wheels revolve. The impulse type of compartment-compounded turbine was patented by Moorhouse in 1878, but its STEAM TURBINES. 219 DE L *====* LONGITUDINAL SECTION. H F OM==== * THE G Ins. 12 Fig. 17. 500 Electric Horse-Power Rateau Turbo-Dynamo. 2400 Revolutions (Penarroya). ZFeet. 220 SECTION II.-POWER STATION. commercial development has been mainly due to Professor Rateau, though turbines on the same principle are also made by the Allgemeine Electricitats Gesellschaft, and by Von Zoelly, of Messrs. Escher, Wyss and Co. Considering the predominating share which has been taken by Professor Rateau in the intro- duction of this kind of turbine, it may perhaps be permissible to class all these as turbines on the Rateau principle. The differences between them are in points of construction only, and thus have involved little or no real originality on the part of their designers. Reaction turbines, compounded on the compartment principle, were patented by Parsons in 1892, but have not been taken up industrially. The Rateau Turbine. (FIGS. 17 and 18, pages 219 and 220.) A section through a Rateau turbine, rated at 500 horse-power, is illustrated in Fig. 17. In this there are in all twenty-four compartments in each of which ST OLD JATT 16 7-pro Fig. 18. Wheel for Rateau Turbine. rotates a single wheel. One of these is shown separately in Fig. 18. It is made out of a steel plate dished as indicated, and about in. thick. The wheels stand about 3 to 4 millimetres clear of the casing all round. STEAM TURBINES. 221 19. GUIDE-VANES AND MOVING VANES OF AN IMPULSE TURBINE. 20 D 8363 [J 0 F )) Fig. 19. Buckets for Rateau Turbine. • Ն cl E • Ø C A S B D Fig. 20. Velocity Diagram for Rateau Turbine. 222 SECTION 11.-POWER STATION. The Buckets. (Figs. 19 and 20, page 221.) The buckets are drop-forged in pairs, and then cut in two, and have their admission and outlet edges ground sharp on an ordinary grindstone. They are otherwise of uniform thickness throughout. These buckets are secured to the rim by a single rivet for each. To stiffen them, a band of steel, made in halves, is rivetted over their outer ends. The bucket and guide-blade angles are 30 deg. and 20 deg. respectively, as shown in Fig. 19. The diagram of velocities for this turbine is represented in Fig. 20. Here v represents the velocity and direction of the steam. as it issues from the guide-blades, & the speed of the wheel, and 7 the speed of the steam relatively to the bucket at entrance. If there were no bucket friction, its velocity relatively to the bucket at outlet would be represented by DC AC = l, and the residual absolute velocity with which the steam finally escapes would be represented by CE, the diagonal of the parallelogram DCBE. Actually, however, the steam, owing to friction, leaves the bucket with a lessened velocity. CF = cl, say, where c is a fraction. In that case, the residual absolute velocity of the steam in space will be r = CG, the diagonal of the parallelogram CFGB. The leading edge of the next set of guide-blades must, of course, be made tangential to CG. In practice, c may be taken as 0.85. As already stated, in the Rateau turbine the angle = 30 deg. and the angle a = 20 deg. The speed v, with which the steam issues from the guide-blades may be taken as that corresponding to 0.787, the total thermodynamic head. This consists, in the first place, of ▲ U, representing by this the number of units available per pound at any particular set of guide-blades; and, secondly, of the kinetic energy carried over by the steam from the previous stage. Or, if E represents the total head producing flow, we may write r2 =778×2g+AU heat units, E = and the speed of issue from the guide-blades will then be v = 223 №0.787 E. The whole heat available for the turbine can be found, as explained above, in the section on "Theory of the Compound Turbine," and then for any particular wheel we have U x d₁2 Σ đ2 AU where d represents the mean diameter of the particular wheel in question, and Σ d2 the sum of the squares of the mean diameters of all the wheels. The Diaphragms. (FIG. 21, page 223.) The diaphragms between each compartment are castings, made in halves, and having cast in them the guide-blade orifices. They are represented in place in Fig. 21. As there indicated they stand quite clear of the shaft, the hole through which the shaft passes being, according to M. Rey, about 1 millimetre larger than the shaft. The clearance between the guide-blades and the wheel is about 3 to 4 millimetres. Leakage Losses. The loss by leakage and shaft friction combined is stated by Professor Rateau at 1 per cent. at full load. The shaft friction may be taken as about per cent. at full load, leaving about 14 per cent. as the leakage loss. This loss is not constant, In but is nearly proportional to the amount of steam passing through the turbine. short, the leaks form a "shunt" to the main flow of steam, and as the latter increases, so also must the leakage loss. Disc Friction and Losses by Fan Action. From trials made with turbines run idle, Professor Rateau estimates that the losses in disc friction and fan action amount to about 24 per cent. at full load. The method of testing is, however, open to criticism, as the wheel is not working under the same conditions when run idle as when at work. If running under load at its proper speed, the steam meets the blades tangentially, and, save in the case of wheels working with partial admission, the loss by "fan action" should dis- appear, and the resistance be due solely to disc friction. A large proportion of the Rateau wheels work, however, with partial admission. From the experiments of STEAM TURBINES. 223 Mr. Odell (Engineering, Vol. lxxvii., page 33), the horse-power wasted in disc friction may be approximately estimated by the formula: H.-P. 10 G = Po d 100 Here d = the diameter of the disc in inches. X ៩. C1 1080] 20 })}) = velocity of the periphery in feet per second. G = the weight of 1 cubic foot of the steam in which the disc revolves. 2.5 P2 CRCRCRCR P3 C (1 Thrust balanced ONOLON Fig. 21. Wheels and Diaphragms for Rateau Turbine. If the friction varied directly as the square of the velocity the index of v should be 3 instead of 23; but experiment seems to show that rate of increase is less than as the square of the velocity. Experiments on air, by Dr. Zahn, make the friction vary as v1.85. Hence, in equation (12) the index of v has been taken as 2.5. Where a large proportion of the total resistance of a disc is due to fan action the exponent should, of course, be three instead of 2.5. It is important to note that the horse-power thus wasted varies with the density of the steam, and thus, at low loads in which the steam is much wire-drawn before admission to the turbine, the loss is much diminished. Some writers assume that the loss by leakage and by disc friction may be taken as constant at all loads, but this leads to a most serious over-estimate of the power of the turbine at low loads, and hence to very €224 SECTION II.-POWER STATION. incorrect estimates of the internal efficiency. As a first approximation it may be assumed that the loss by leakage and disc friction is proportional to the indicated horse-power of the turbine. If we assume this to be the case, and take a Rateau turbine of 500 horse-power, then, adopting Professor Rateau's estimates of the losses by shaft friction and leakage and by fluid friction we have, for a turbine giving 500 brake-horse-power at full load, a total loss of 20 horse-power. Of this, I horse-power may be taken as shaft friction, leaving 18.75 horse-power, or 3.75 per cent. for the other losses. If I = indicated horse-power and B = brake horse-power, we may write for this turbine · I = 1} + B + .0375 I. Hence when the turbine is running light, and B = 0, we get I = 1.3 horse-power, instead of 20 horse-power, as it would be did the leakage and other losses remain constant. This former is perhaps too low, but the latter is certainly much too high. Steam Consumption of the Rateau Turbine. In Table 3, we give the data from trials of a Rateau turbine, carried out by Messrs. Sautter, Harlé and Co. The "horse-power" are not British horse-power, but the Continental, which are nearly 14 per cent. smaller. Internal Efficiency of the Rateau Turbine. The internal efficiency of the Rateau turbine is stated by its designer to be 69 to 70 per cent. Judging from the published experiments, we should be inclined to take it as a little lower, say 65 per cent., but possibly the higher figure given is based upon unpublished data, and hence it will be adopted here. Design of a Turbine on the Rateau System. (Fig. 22, page 226.) To proportion a turbine working on the Rateau principle, it is most convenient to prepare a series of curves such as those reproduced in Fig. 22. Here the lower curve represents the heat units available in 1 lb. of saturated steam, supplied at 820 deg. absolute to a perfect turbine, and exhausting at any lower temperature. The upper curve marked k = .345 represents the heat units available in a turbine taking steam at the same initial temperature, but having an efficiency of 69-70 per cent. in place of unity. The curve marked dryness fraction shows how the dryness of the steam varies as it passes through a turbine of 70 per cent. efficiency. The specific volume of dry saturated steam at any absolute temperature can be found from Table 3, page 150, and multiplying this by the dryness fraction it is possible to plot down on the diagram a curve showing the actual volume of 1 lb. of steam at different points in its passage through a turbine having an efficiency in this case of 70 per cent. To avoid confusion this latter curve has not been added in Fig. 22, but in reproducing the curves on a large scale for practical application this should be done, using a bigger scale for the steam volume at the high-pressure end of the diagram than at the other. Details as to the preparation of these curves will be found in Engineering, January 13 and February 3, 1905. With the aid of these curves the proportioning of a turbine for any "indicated" horse-power is a simple matter. With a guide-blade angle of 20 deg. and bucket angles of 30 deg., the efficiency may be taken as 70 per cent.; hence if q be the weight of steam needed per second, and I the indicated horse-power required, U is the available heat per pound of steam calculated from equation (6), page 215. If the turbine consists of N wheels all of equal diameter, v the velocity of flow of the steam through the guide-blades is Here x n q = I .7 U Ωる ​ing to the expenditure of The area needed at the nth guide set of guide-blades is v = 207 之 ​q x n v V square feet. v = the dryness fraction at the nth guide-blade, taken from Fig. 22, and V the specific volume of dry saturated steam at the temperature correspond- n U N available heat units. N n STEAM TURBINES. 225 Test Number Load at terminals, in kilowatts Revolutions per minute Duration of test, in minutes Absolute pressure above stop valve, Table 3.-Trial Data of 500 Horse-power Rateau Turbine. .. ·· • ·· .. pounds per square inch Amount of superheat, degrees Fahr. Absolute pressure in front of first set of guide-blades Amount of superheat before first set of guide-blades .. .. O ·· ·· .. Absolute pressure in junction pipe Absolute pressure in exhaust pipe, pounds per square inch Total steam used per hour Steam per kilowatt hour, exclusive of work of driving air pump, in pounds Efficiency of dynamo Effective load on turbine, horse-power Steam per effective horsepower hour (work in air pump not allowed for) Over-all efficiency of the unit taking the steam in its condition below the stop valve ·· 1 Run light (excited) 2196 30 175.3 0.0 9.38 62.3 1.71 1.51 745.0 : : 2 Run light (un- excited) 2181 18 180.0 0.5 12.44 52.6 1.99 1.46 980.9 • .. ·· : 3 4 32.0 3.78 5 6 32.6 32.2 20.9 5.45 7.76 11.4 8 1.25 1.29 1.33 1.51 2211 3270 4507 6559 9 10 11 58.45 107.5 172.35 279.9 127.9 366.0 440.1 436.5 344,7 462.9 470.27 2310 2186 2184 2181 50 25 40 30 2190❘ 1054 2101 2200 2200 1998 2360 35 20 180 30 26 10 22 174.3 176.0 175.0 170.5 155.1 168.3 181.0 161.5 162.8 223.7 216.1 1.3 5.2 9.0 14.8 10.8 20.0 14.6 20.5 20.5 23.6 21.2 32.42 44.65 63.85 95.41 64.56 119.9 143.6 123.4 123.0 152.3 146.7 12 13 32.2 18.9 11.9 23.0 17.6 21.8 21.2 7.76 14.20 17.06 17.91 4.08 17.63 | 18.06 1.29 1.63 1.86 2.00 1.82 2.15 1.85 4596 8275 96.65 10,123 8306 10,230 10,244 37.82 30.42| 26.14 | 23.43 74.0 84.0 90.2 92.0 35.93| 22.59| 21.96| 23.19|24.09 22.09 21.78 86.0 92.4 93 92.9 92.3 93.3 93.4 107.3 174.0 260.2 422.5 202.0 538.2 643 637.7 507.4 674.1 684.0 20.61 18.78 17.33 15.52 22.75 15.37 15.03 15.87 16.36 15.16 14.97 43.3 49.5 52.4 54.4 37.7 54.3 54.9 54.6 51.6 55.2 54.9 ļ 226 SECTION II. POWER STATION. The best speed of the wheel is .346v. If the number of revolutions is given, this fixes the mean diameter. If the turbine is divided up into two or three sections, the wheels in each section being all of the same mean diameter, but this diameter being different for different sections, the total heat available should be divided up between the sections in the proportion of squares of the diameter of each section multiplied by the number of wheels in it. Each section should then be designed as an independent turbine, the exhaust steam from one section being the admission steam to the next. 1310⋅ 290- 270- 250 Total Units of Heat available if t/345 230- 210 190- 170 150 Heat Units Available. |110 130- 90 70 50- 130- Trits of Heat availabl no Friction loss. on. -99 98 Scale for Dryness Fra 97 +96 95 Dryness Fraction for k-345. Hoga ⚫93 *92 +91 4.90 189 -88 i 182 ·86 10 560 580 600′ 620° 640* 660° 680° 700* 720° 740′ 760° 780′ 800* 820° (8563F) Absolute Temperatures. Fig. 22. As a rough guide, the maximum possible area which can be provided with a wheel d inches in mean diameter and a guide-blade opening h`inches wide is dh 150 square feet. This fixes the proportions of the last wheel of a section At the other sections partial admission may be used, taking care to make the guide-blade orifices form a single group, instead of spacing them symmetrically round the circumference of the guide-blade disc. Turbines Working with Superheated Steam. (Figs. 23 and 24, pages 227 and 228.) Where superheated steam is to be used, exactly the same principle may be followed, a curve of available heat being plotted on a large scale just as before. This available heat may be taken as made up of two portions-viz., the heat units STEAM TURBINES. 227 available in the saturated steam, and, secondly, the extra units available due to the superheat. Refering to Fig. 23, which represents a temperature entropy diagram for superheated steam, the point D corresponds to dry saturated steam at the absolute temperature represented by X H = T1, say. Superheating this steam raises its temperature and increases its entropy, so that its final temperature and entropy may be represented by the point G, say. If this steam is expanded in a perfect engine down to the absolute temperature represented by LS T2, say, the heat units available are represented by the sum of the two areas, TCDS = 匠 ​X656. B T U 8 = Y t 1 0 T₂ T₁ + t 2 S Ꮮ 6 R W Fig. 23. and DG US. The former is, of course, simply the u of equation (6), page 215, whilst the area DGSU may be taken as QYM M (13) where t is the total amount of superheat and y is the specific heat of the steam. At the point N, where the vertical & N cuts the curve D N˚F, the steam is saturated; whereas at all higher temperatures it is superheated, and at all lower temperatures is partially condensed. The heat available in expanding from the conditions represented at G to some lower pressure at which the steam is still superheated, as, for example, that corre- sponding to the point P, is evidently the area O DO B+ the area D G RO - the triangle P Q R, Q corresponding to the temperature and state of saturated steam at the same pressure as the superheated steam represented on the diagram by the point P. • The simplest way of determining this area is to calculate the total heat in the superheated steam in its initial and final states. The difference of the two repre- sents the available heat. It should be noted that for moderate amounts of super- heat the specific heat y varies with the pressure. According to Professor Carpenter, with which the results of H. Lorenz are in good agreement, Y = 0.462 + 0.001,525 p Ύ (14) where p is the absolute pressure. The formula applies, in the case of moderate superheat, up to an absolute pressure of 120 lb. per square inch, and perhaps to higher pressures; but experimental information as to this is lacking. For high superheats y appears to be nearly constant, and has a value not very far from the 0.48 originally given by Regnault. • 228 SECTION II.-POWER STATION. Consider, for example, steam at a pressure of 110 lb. per square inch, super- heated 80 deg. Then, from equation (14) y = 0.630, and the heat units required to superheat the steam to the extent named are 50.4. In dealing with superheated steam it is convenient to use Table 2, page 149, giving the properties of steam at different pressures. From this Table we get h= 305.33, and L=878.7; whence the 200 200 220 200 Heat Units available. 180 120 Units available in Superheated Steam (k dan ma con un de wana wa k Untle available in Superheated cam (24) 560* (947) Units Argilable in Saturated Steam Values of xy Sanu 600° ed Steam 3-4 # * Pressure of SQ €40° Values Dryness Fraction (ke- Steam TV Superheated 680° 720- Abs Temp. Deg.Fahr Fig. 24. = Steam 2 X 50.4 874 + 794 T¹2 T₂ { = 760* - 2γ + Δ φ + 27 800° ressure of Superheated, Steam ( ressure of Superprated Steam (k=24) 27 840° Δ.Φ. Absolute Pressure Ubs. per Sq.In. Dryness Fradion 171077 • 71007-00 23 · 8 total thermal units in the superheated steam amount to 1234.43. The increase in entropy due to the superheat is -90 2 x 50.4 = 0.0604, T₁¹ + T₁ where T11 is the absolute temperature of the superheated steam. The total entropy of the superheated steam is therefore, taking the values for saturated steam from Table 2, page 149. -80 880° 20 60 $ = 0.4825 +1.1067 + 0.0604 = 1.6496. Consider now the steam when expanded adiabatically down to 60 lb. pressure. The total entropy of saturated steam at this pressure is 1·6351; and from the diagram, Fig. 23, it is obvious that the steam must be superheated sufficiently to bring the total entropy up to 1.6496. If To be the temperature of the saturated steam, and T¹ its temperature when superheated to the required deg., we have (15) 50 8 8 8 STEAM TURBINES. 229 erę ▲ is the requisite increase of entropy. In this case Δ Δφ = 1.6496 · 1.6351 = 0.0145. From equation (13) y = 0.553, whence from (15) we get T₂¹ = 771.3, and as T₂ = 752, the amount of superheat is 19.3 deg., so that 0.553 × 19.3 = 107 units are T2 required to superheat saturated steam at 60 lb. absolute to the degree required. The total heat of the steam in this condition is, of course, 262.2+908.9 +10.7 = 1181.8 heat units. As already stated, the difference between this and the total heat of the steam in its original condition is the available heat. Absolute Pressure of Steam p. On making the same calculation for other points we get the following figures, from which the curve, Fig. 24, page 228, has been plotted:- Table 4.-Heat Units Available in Superheated Steam. 110 100 90 80 70 60 50 40 . 7.64 0.97 Absolute Temperature of Superheated Steam T¹. 874.0 857.0 840.3 820.6 798.2 771.3 740.3 726.6* 640.0* 560.0* Additional Units = ul k [T¹ı - T¹₁] T₁¹+ T¹2 Heat Units Available in Perfect Engine u¹. 0 8.80 18.16 27.67 39.52 52.63 66.91 84.09 198.46 314.79 * Temperature of saturated steam. The dryness fraction curve can be drawn exactly as in Fig. 22. In the case of an actual turbine the heat units available are increased by the heat degraded by the friction of the steam on its passage through the turbine. The amount of this increase can readily be determined with sufficient accuracy for practical purposes by the formula (16) The curve in Fig. 24 has been thus plotted. The effect of this friction heat is to lower the pressure at which the steam becomes saturated. This point is best determined by laying down on the tempera- ture entropy diagram the total entropy of the steam at different points. This is repre- sented by the dotted line G T in Fig. 23, and the point where this cuts the curve DN F is that in which the steam is saturated. If we assume k If we assume k = 0.24, we find this to be 719 deg. absolute, corresponding to a pressure of about 35 lb. per square inch instead of one of 50 lb. per square inch, as would be the case if k = 0. By prolonging Q P to cut the dotted curve in W, the temperature of the superheated steam corresponding to steam at the same pressure as saturated steam at the temperature represented on the diagram by the point Q can be obtained. In this way the dotted curve of pressures given on the diagram can be obtained. It will be seen that the preparation of these diagrams for superheated steam is somewhat tedious; but once such a curve is obtained, it can be used for pro- portioning any number of turbines. In practice, however, we imagine, turbines are proportioned for saturated steam whether or no it is intended to run them with superheated steam. Though it is, in point of fact, less troublesome to proportion accurately a turbine using superheated steam, since the range of expansion is less. These curves can be used in precisely the same way as those in Fig. 22. It will be seen in the diagram that a "dryness fraction" has been given for superheated steam. In strictness, perhaps, the use of the term here is hardly justifiable, but it is convenient to retain the term as denoting the number by which the volume of dry saturated steam has to be multiplied in 230 SECTION II.-POWER STATION. order to get the actual volume occupied by steam of the same pressure, but either over-saturated or superheated." In the latter case it has been taken as TI x = where T1 = the absolute temperature of the superheated steam, and T that of saturated steam at the same pressure. T, It is convenient also to plot on the diagram a curve showing the actual volume of 1 lb. of steam at any point, that is, the values of x V when V is the specific volume of saturated steam at any specified pressure. This has been done in the dotted lines shown. That on the right refers to the superheated steam, and that on the left to saturated steam. The scale for the former is the scale of pres- sures, whilst the scale for the latter is the same as that for the heat units available. It is sometimes asserted that the increase of output noted with superheated steam, particularly with small amounts of superheat, is greater than can be theoretically accounted for. The evidence on this point is, however, by no means conclusive, and it appears probable that the bulk of the discrepancy arises from two causes. In the first place, the comparison is made, not between superheated steam and dry saturated steam, but between superheated steam and ordinary boiler steam, which always contains at least 2 per cent. of moisture. Secondly, the specific heat of steam at low degrees of superheat is underestimated. If both these factors are taken into account, the gain in work per pound of steam due to super- heat seems to agree well with what would be expected from theoretical considera- tions. For example, the following trial data were obtained in a test of a 300-horse- power de Laval turbine by Messrs. Dean and Main, of Boston:- Table 5.--Steam Consumption of Laval Turbine. Pressure Above Governor Valve --lb. per sq. in. 207.0 206.4 Superheat. deg. Fahr. 84 0 Vacuum, Inches of Mercury. 27.2 26.6 Steam Used per Brake Horse-Power Hour. lb. 13.94 15.17 The saving with the superheated steam is, it will be seen, 8.8 per cent. The available units in the first case, if we take y as 0.762, amount to 344.36, and those in the second case to 312.06, so that the theoretical increase in the output should be over 10 per cent. There is, however, some uncertainty as to what is the true value of the specific heat of steam at 200 lb. pressure, since the experiments on which equation (13) is based do not extend beyond 120 absolute, and extrapolation is never very safe. However, the figures given are sufficient to show that the saving due to the use of superheated steam does not differ materially from what might be theoretically expected. It has been assumed that the steam pressures given are absolute pressures, though this is not stated in the report. But even if this is not so, the relative theoretical saving will be very little affected. THEORY OF THE COMPOUND REACTION TURBINE. In reaction turbines of the Parsons type there is a pressure in the clearance space between the guide-blades and the buckets. Both guide-blades and buckets are identical in form, and from a purely kinematical point of view, the turbine would work under the same conditions if the shaft were held fast, and the casing allowed to revolve. The relative velocity to the bucket, which it enters, of the steam leaving a guide-blade, is exactly the same as the relative velocity to a guide-blade of the steam leaving a bucket. The conditions in the two being kinematically identical, the losses in each must be the same. Velocity Diagram for Reaction Turbine. (Fig. 25, page 231. In Fig. 25 we give the diagram of velocities for such a turbine. Here A B = v, represents the velocity of the steam leaving a guide-blade, and a the angle which this velocity makes with the path of the bucket. The speed of the latter is represented by CB = 8. Then AC represents the velocity of the steam relatively to the bucket, and ℗ is the bucket angle at entrance. Taking any point D on AC produced, and setting off D E = v at angle a with the bucket path, STEAM TURBINES, 231 then D E represents the tangent to the curve of the bucket at discharge, and the bucket may accordingly be sketched in as indicated. If E F is set off equal to 8, the bucket speed, the closing line D F represents the absolute velocity in space of A B J (8641. A) ά Ꮴ S D G C Q от Ꮎ F H I 5 α1 LI S E Fig. 25. the steam discharged from the bucket, and it is obvious that the angle DFG = the angle A UH = 0. Producing D F to I, and setting off at the angle a the length I J = v, the tangent to the guide-blade at discharge is obtained and the guide-blade can accordingly be also sketched in as indicated. The series can, of course, be prolonged indefinitely. Comparative Efficiency of Impulse and Reaction Turbines. There is a drop of temperature as the steam passes through a set of the guide- blades, and a similar drop as it passes through a set of buckets. Each set of guide- blades, therefore, constitutes a "stage" of the turbine, as already defined; and, similarly, each set of buckets constitutes another stage. In an impulse turbine a stage consists of at least one set of guide-blades and one set of buckets. Thus the losses in a stage of a reaction turbine consist of guide-blade friction alone or bucket friction alone, but not both; whilst in an impulse turbine the friction losses per stage consist of the bucket friction added to the guide-blade friction. There is absolutely no reason why the guide-blade loss should be larger in a com- pound reaction turbine than in a compound impulse turbine; hence it is evident, from the foregoing, that the latter is intrinsically inferior to the former. In water- wheel practice this is not necessarily the case, as generally a pressure turbine has to work "drowned," and, consequently, has losses from obstructed guide-blade discharge and disc friction, from which the impulse wheel is free. Nevertheless, the Barker's mill type of pressure turbine is intrinsically superior to any impulse wheel, since the losses in it are due to nozzle friction only, whilst in the case of an impulse wheel the losses in bucket friction must be added to the nozzle losses. The objections to the Barker's mill type of wheel arise from its relatively high speed and 232 SECTION II.-POWER STATION. its liability to "hunt," as it is very difficult to maintain its speed constant. These objections much more than offset its theoretically higher efficiency. Returning to the compound steam turbine, it will be seen that, as the impulse type must also work "drowned," it gains nothing in the matter of lesser disc friction or clearance losses to offset its intrinsic lower theoretical efficiency. On the other hand, leakage losses are generally greater in the reaction wheel, and in small sizes this may substantially reduce the difference between the two types. In large units, however, the leakage is relatively small any way. According to the Hon. Geoffrey Parsons, it is under 2 per cent, in the case of large Parsons turbines, whilst from Professor Rateau's figures it appears to be about 14 per cent. in his turbine. In the matter of fan action and disc friction the superiority should lie with the reaction wheel. The latter must have an all-round admission, and has then no idle buckets. The fan action must be mainly due to idle buckets, as the steam meets, or should meet, the working buckets tangentially, in which case fan action should disappear. As regards disc or drum friction, the drum opposes much less surface than the discs, and consequently the loss at equal average surface speeds must be less. Values of k ·50 •40 ·30 •20 ∙10 0 (8641. C) m 10° Values of a m 20° $75 m • 80 m ·85 30° 40° Fig. 26. Stage Efficiency of a Reaction Turbine. The heat wasted in any stage may be written as a fraction of the available heat at that stage, or if this be denoted by ▲ U, the heat wasted may be written as kAU, where k is a fraction. The total energy available for producing flow STEAM TURBINES. 233 consists, in addition to A U, also of the kinetic energy carried over from the previous stage of the series. Thus, if r be the residual velocity of the steam leaving the previous stage, the total energy available for producing flow at the next stage is *2 +778 AU foot-pounds. 2g It is important to note that r is the velocity of the steam relatively to the next stage. Thus, in Fig. 25 the velocity of the steam leaving one stage is A B v, and the velocity of the same steam measured relatively to the next stage is A C = r. The kinetic energy of the steam leaving one stage is always less than the v2 energy producing flow. Or, if this kinetic energy per pound of steam is we 2g' may write v2 2g E = 2 甾 ​+ 778 AU) fo The following relation subsists between m and k. m sin² a sin2 0 mE = m 1 k 1 1 M 1 [1 - Thus, k can be found if m is known, and vice versa. Knowing k, the over-all efficiency of the turbine as a whole can be read off the curve, Fig. 15. In the fore- going it has, of course, to be assumed that the wheel is being run at its most economical speed. Values of k for different values of m and different guide-blade angles are plotted in Fig. 26. Here the abscissæ are the angles at discharge of the guide- blades and buckets. The full lines are plotted for an entrance angle of 60 deg., and the dotted curves for one of 90 deg. With a small guide-blade angle at discharge it will be seen that a large change in the angle at entrance makes little change in the value of k, and hence in the over-all efficiency of the turbine. For the Parsons turbine m = .787 and k = .24. Speed of Flow from the Guide-Blades. (FIGS. 27 and 28, page 234.) If v¹ = 223 √A U, that is to say, if U¹ be the theoretical velocity of issue due to ▲ U units of available heat, then if v is the actual velocity of issue, we have (19) S sin (0 — a). vl sin m m sin² a sin2 0 foot-pounds 14 1 Speed of the Bucket. The proper speed of the bucket is given by the relation G = σ Values of o for different values of m, and different angles at the entrance to guide-blades and buckets, are given in Fig. 27. For all the curves in this figure the guide-blade angle at discharge is constant at 20 deg., whilst varies from 60 deg. up to 90 deg. (17) m m sin2 a sin2 0 (18) 1448 = d. (20) Values of s for different values of m and different values of 0 are plotted in Fig. 28. The angle a is taken as 20 deg. throughout. It will be seen that with a discharge angle of 20 deg. the change of 0 from 90 deg. to 60 deg. allows of a large reduction of the bucket speed; whilst from Fig. 26 it will be seen that this change "but little affects the efficiency of the turbine as a whole. With 0 = 67 deg. and a = 20 deg., we get 8 = .8 nearly. If the bucket speed is too low the efficiency falls off, according to a parabolic law, as already given in equation 11, page 218. 12 234 SECTION II.-POWER STATION. · 1.00 Values of o 0.90 0.80 60° 0.90 0.80 1·00 Values of 5 0.70 0-60 60° ∞=20° (8641.2) 70 27 80° Values of e α=20° 70° Values of 8 e 28 m = ·85 m = ·80 m = .75 m = 90° Ө •70 m = 0·85 m = 0-80 in = 0.75 m = 0·70 90° Ө Fig. 27. Ratio of Actual Steam Velocity to Theoretical Velocity. Fig. 28. Ratio of Actual Bucket Speed to Theoretical Bucket Speed. STEAM TURBINES. 235 fal THE PARSONS TURBINE. He Ul B n |(108) Fig. 29. Parsons' Steam Turbine. The Parsons turbine is made in two general patterns, represented respectively in Figs. 29, 30 and 31. Fig. 29 represents the pattern easiest to machine, but Fig. 30 is some- what more easy to proportion accu- rately. The only difference between the two lies in the fact that the interior of the casing has to be bored to eight different diameters in Fig. 30, and to three only in Fig. 29. The Drum. or This is made of the general shape shown in Fig. 29. In small sizes of turbine it is made out of a solid forging, but in large sizes it is a heavy steel casting about 2 in. thick, mounted on a stiff shaft, which is sometimes made of nickel steel, though this is not now thought neces- sary. This drum carries from 50 to 60, or more, rings of blades buckets, there being, say, 28 in the small or high-pressure portion of the turbine, 22 in the intermediate por- tion, and 12 in the low-pressure por- tion. Steam enters the turbine at A, and flows through the buckets to the exhaust pipe B. The turbine being of the pressure type, there is a thrust in the direction of the flow of the steam, which is balanced by the three pistons k, l, m, shown to the left, which are respectively the same sizes as the high, intermediate, and low-pressure wheels, and by means of the passage i, j, and l, are main- tained subject to the same pres- sures, so that a perfect end balance is assured. These pistons have grooves cut in them, into which fit corresponding projecting brass rings secured to the casing, so that any leakage of steam has to escape by a very tortuous path. Balancing. The drum is balanced by being run in the shop up to a speed of 20 per cent. in excess of its designed speed. In accordance with the well- known laws of rotating bodies, it tends to rotate about its centre of gravity so that when run as described it endeavours to bring its centre of gravity into the axis of rotation. By this bending the light side is caused to project, and if a coloured chalk is held against the rotating mass, it will mark it where weight requires to be added. With large sizes, owing, per- haps, to the rigidity of the casting not being the same in all directions, 236 SECTION 11.—POWER STATION. 31. H 30. 32. T₂ I, B 21 (767) Figs. 30 and 31. Parsons Steam Turbine. W 11 10 !!! 33. 12 F! 34.T, B Figs. 32 to 34. Bearing for Parsons Steam Turbine. STEAM TURBINES. 237 the chalk mark is not an entirely reliable guide, and with these the time needed to obtain a satisfactory balance is to some extent a matter of luck. The "high part" marked by the pencil is there frequently displaced 60 deg. to 90 deg. from the point at which weight should be added. By reversing the motion a new "high point" different from the former is obtained, and a mean of these is about right. The adjustment for balance is made by plugs screwed into the shoulders at the points, where the drum diameter is increased to take the intermediate and low-pressure wheels. The operation of balancing is performed three times, viz. after rough-turning, after finish-turning, and after the buckets are in place. • The Casing. The casing is necessarily made in halves. As the buckets work with extremely small clearance, it is very essential that the accuracy of the bore shall be main- tained. After rough boring, it is therefore steamed for some hours before being finish bored, in this way relieving possible strains in the metal. If a cylinder is made in halves, connected together by flanges and bolts, distortional strains arise when it is put under pressure, since the line of action of the bolts is eccentric to the cylinder wall. This tendency to distort can be reduced by using somewhat heavy flanges for the connection of the two halves of the casing. Under steam the casing of a 1500 kilowatt turbine lengthens in. to in., so that provision must be made for expansion. It is deemed best to fix the low-pressure end, and to let the high-pressure end slide in machined ways on the bed-plate. In making the casing it is most important to avoid any dissymmetry between opposites sides of the casting. When under steam a lack of symmetry is liable to cause the fouling by the revolving blades of the wall of the casing, owing to unequal expansion strains. The Glands. There are glands at each end of the turbine casing, best seen at J, Fig. 30. These are exposed to the condenser pressure on the one side, and to the atmosphere on the other. They consist of circular bushes, made in halves, with grooves in their inner surfaces, in which fit collars turned on the spindle. To the middle of the bush is led steam exhausted from the governor relay, so that the pressure inside the bush is greater than that of atmosphere, and any leakage that does take place is of steam outwards from the turbine, instead of from outside inwards. In some cases, water is used instead of steam to secure the tightness of the packing. The Bearings. (Fies. 32 to 34, page 236.) The drum is supported on two bearings only, a flexible coupling, W, being used to connect it to the generator, which is also carried on two bearings. The area provided is sufficient to reduce the pressure on the projected area of the journal to about 40 lb. or 50 lb. per square inch. The surface speed is commonly 3000 ft. per minute, and the co-efficient of friction measured at the surface of the journal is then about 0.02. According to Mr. London, a rule frequently worked to is that the pressure per square inch on the projected area of the journal multiplied by the surface speed shall not exceed 2500 to 3000. Experimental bearings, he states, have, however, been run under a load of 70 lb. per square inch, and a surface speed of 70 ft. per second. It is important to arrange for a copious and cool supply of oil. The bearings are sometimes water-cooled. For machines of small size up to 500 kilowatts the bearings consist of a solid gun- metal bush, B, Figs. 32, 33, and 34, which takes the drum spindle, and is itself surrounded and supported by three concentric tubes, T, T1, and T2. The outer- most of these fits the turbine casing, and the others fit loosely into each other and to the bush, the clearance being about in. The space between the bushes is kept filled with oil, supplied both to these and to the journal, under a pressure of 14 lb. to 3 lb. per square inch. For larger sizes, ordinary split bearings lined with white metal are used. The Buckets. (FIG. 35, page 238.) These are drawn or rolled to the required section. The material used is a brass for the low-pressure and intermediate buckets; but for the high-pressure ones, which, with superheated steam, may be exposed to a high temperature, the alloy used is nearly pure copper. The section is of the shape indicated in Fig. 35. The guide-blades are, of course, fixed to the casing, and the moving blades to the rotor. The method of fixing is special to the Parsons turbine. Dovetailed grooves about in. deep, are turned in the drum and in the casing, of such a width at the top that the blade when placed therein, with its edges resting against the upper edges of the 238 SECTION II.-POWER STATION. groove, stands at its proper angle. Spacing pieces of a soft-drawn brass are placed between the blades and caulked into the groove. When this is thoroughly done, the blade will pull in two rather than draw out. A blade and a packing-piece are shown in Fig. 35. The area through the guide-blades and buckets is adjusted to the requirements of the case by using larger or smaller caulking pieces, thus separating the blades more or less. The maximum pitch of the blades appears to be about three-quarters of the width. This width varies with the length from in. upwards. In small turbines, the shortest blades N Fig. 35. Blade for Parsons' Steam Turbine. used fare about in. long. In the 3000 horse-power Hartford turbine, the shortest blades were 13 in. long, and the longest 8 in. The short high-pressure blades stand up so stiffly that they can be turned without difficulty in the lathe. The longer ones are stiffened by soldering to them a wire ring, one such stiffening ring being sufficient for blades up to 5 in. long; whilst a 7-in. blade, & in. wide, has two such stiffening rings-one near the top, and the other midway between the top and the foot of the blade. The notch for this wire can be seen in Fig. 35. In the casing, which has necessarily to be made in halves, stout making-up pieces are substituted for the blades on either side of the joint. The mean bucket angle at entrance is 674 deg., and at discharge 20 deg. The Governor. (FIGS. 36 and 37, page 239.) The governor is represented in Fig. 36, where E is the stop valve, T the governor valve, and A a port leading to the cylinder. On opening the stop valve, steam enters the steam chest, and leaks through the small hole O, raising the spring- loaded piston B, which carries with it the double-beat governor valve T; this steam is exhausted periodically from below B by the opening of the valve G to ex- haust. The piston then falls, cutting off the supply of steam to the turbine. The valve G is kept in constant vibration by link-work connecting it to an eccentric on a vertical shaft L, driven by worm gearing from the turbine spindle. The mid position about which G vibrates is, however, alterable by link-work connecting it with a centrifugal governor R, mounted on the same vertical shaft. If the governor is at its lowest position, the mid position about which G vibrates is, however, so low that a very small momentary opening is afforded to the steam exhausting from below B. Hence this piston remains raised, and a full supply of steam is admitted to the turbine. If, on the other hand, the governor balls rise, so does the mid position about which G vibrates, and a fuller opening to exhaust is afforded to the steam below B. This piston accordingly falls, shutting off steam to the turbine. It will be seen that the valve T is thus kept in constant vibration, and the pressure of steam above the first set of guide-blades undergoes similar oscillations, which are represented in Fig. 37, in which the ordinates represent the pressure. The steam, it will be seen, has its average pressure lowered, and, STEAM TURBINES. 239 in effect, the operation is equivalent to throttling. Hence there must be some loss of available energy. In the Elberfeld turbine the steam pressure was thus wire drawn from 148.9 lb. down to 95.3 lb. when the turbine was running at full Kg. per Sq. cm. 10 5 L (768) (942) R L 82.5% M A Ε Fig. 36. Governor for Parsons Turbine. 10 55% AWAN 5 G 000 0 (943) Atm line. Condenser Press. -0.9Kg.per Sq.Gm. Condenser Press-0·9Kg.per Sq.Gm. Fig. 37. 肉肉​肉 ​WAR P Fig. 38. Thrust Blocks for Parsons Turbine. load. The corresponding loss of energy otherwise available was about 27 British thermal units, or more than 8 per cent of the total. Where very steady governing is not required over a wide range of power, this loss is avoidable 240 SECTION II.-POWER STATION. + Thrust Block. (FIG. 38, page 239.) A thrust or, rather, aligning block is fitted at K, Fig. 30, to keep the rotor in alignment; very little thrust comes on it. The arrangement used is represented in Fig. 38. The bush is divided horizontally. The upper one is fixed in the casing, but the lower can be adjusted longitudinally, so that on the upper half the left- hand faces of the thrust-collars bear on the right-hand faces of the lower block, whilst the upper block, being set to the left, its rings bear against the right-hand faces of the spindle-collars. The whole is lubricated under a slight pressure. Weight and Space. Turbine-driven electric-generating units weigh little and occupy little space. The 3000-kilowatt turbo-generator at Frankfort measures 54.1 ft. long by 8.2 ft. high. The complete weight of the unit is 66 tons, of which the turbine-rotor weighs 9 tons and the generator-rotor 11 tons. A Sulzer engine-driven unit of similar capacity weighs 400 tons, of which 142 tons is the weight of the rotating parts. Marine turbines, having to run at a much lower speed, are much heavier and save little in weight as compared with reciprocating engines, though much in space. The 3000-horse-power turbine for Hartford is 19 ft. 8 in. long over all, 12 ft. 3 in. between bearings, is 6 ft. in its largest diameter, and weighs 28 tons. A 1000-kilowatt turbine unit is 12 ft. 6 in. long over all, and 4 ft. in extreme height. A turbine unit can be built complete in the time required to merely erect a Corliss unit of equal power. Foundations. The foundations needed are insignificant, a 2000-kilowatt unit taking, say, 100- cubic yards of concrete wall. Starting-up and Running. The 5000 horse-power turbine at Frankfort can be started up from the cold in fifteen minutes. The steam speed being never more than 600 ft. per minute, there is no wear of the blades, as has been shown by careful examination after several thousand hours' run. The efficiency therefore remains unaltered. The bearings also do not wear, the pressure on them being so small that the metal of the shaft never touches the bush in which it runs, being supported on the film of oil. The oil required is extraordinarily small, and in the case of large units its cost does not exceed th of the coal bill. The condensed steam being oil-free, can be returned to the boilers without treatment. Efficiency. The loss due to fan action in turbines has often been grossly exaggerated, many engineers having neglected to observe that the whole aim of the designer has been to cause the steam to meet his guide blades and buckets "tangentially.” Hence it is improbable that the fan action is appreciable when the turbine is running at its designed load. Mr. Geoffrey Parsons gives the leakage loss as under 2 per cent. The internal efficiency of the Elberfeld turbine appears to be about 70.5 per cent.; but it is probable that 80 per cent. could be reached with careful design. THE WESTINGHOUSE-PARSONS' TURBINE. (FIG. 39, page 241.) A section through the Westinghouse-Parsons' turbine, taken from a paper read before the Manchester section of the Institution of Electrical Engineers, by Mr. W. J. A. London, A.I.E. E., is given in Fig. 39. The steam is admitted to the turbine centrally, and flows both ways towards the ends. If this arrangement were adopted with an ordinary Parsons' turbine, the length would be nearly doubled ; and the blades being halved in height, the proportion borne by the leakage space to the steam way through the buckets would be doubled. Hence, the ordinary Parsons' turbine is constructed with the steam flowing in one direction only, so that the introduction of balance pistons is necessary. Further, in order to keep the blades in the high-pressure end of a reasonable length, it is necessary to use a stepped drum, since partial admission being impossible, the diameter of the drum at the high-pressure end must be relatively small, if very short blades are to be avoided. With a view to getting a short turbine self-balanced, without the aid of balancing-pistons, the Westinghouse Company have adopted the arrange- STEAM TURBINES. 241 (948.) 39. 00 2 1 ID ODDI Fig. 39. Westinghouse-Parsons Turbine, оо DDDDDDD 242 SECTION II.-POWER STATION. ment shown. For the high-pressure portion of the turbine, that is, the central portion, velocity compounding is relied on, the remainder being pressure com- pounded on the Parsons' principle. The latter is much the most efficient method of compounding; but in the high-pressure system, in which the relatively inefficient system of velocity compounding is adopted, the steam is expanded down to a pressure of 60 lb. only, so that in this section only about one quarter of the total heat available in the steam is accounted for; hence the lessened efficiency applies only to a fraction of the whole temperature range, with the result that the efficiency of the turbine as a whole is not much affected, whilst there is a considerable gain in the compactness and simplicity of the unit. DESIGN OF A COMPOUND REACTION TURBINE. To obtain the best results it is essential that the velocity of the steam shall be the same through all stages having the same mean diameter. Except for a very low range of total expansion this is not possible with the pattern shown in Fig. 29, but it is possible with the pattern shown in Fig. 30, by having a sufficient number of changes in the mean diameter. Each portion of a turbine in which the stages have the same mean diameter may be called a section. At each change of section the kinetic energy carried over from the previous stage is wasted almost entirely, the loss thus arising being about the heat available at the last stage of each :section. The latter is generally about 5 or 6 units as a maximum or as a rough average 3 units for the turbine as a whole; hence, even with 20 sections, the total loss of available energy at the change of section would be only about 5 units on a total of probably over 300. Were the blades infinitely thin it would be impossible, by altering the number of them in a stage, to increase the area available for the flow of steam. On the other hand, the increase in this area, which can in practice be effected by reducing the number of blades, is limited by the fact that they cannot be spaced less than a certain distance apart, since there must be room enough between them to admit of their being caulked into place, and this fixes a lower limit. For blades to fit into grooves of from in. up to in. wide, the following empirical formula, based on measurements of actual buckets, may be used as a guide as to what is possible in practice. The shape of the buckets adopted will, of course, alter the constants, which will also be affected by extreme variations in the length of the blade, since very long blades cannot be caulked as closely together as shorter ones, nor can their maximum pitch be relatively as great. The necessary corrections can be made when the type of blade is decided on. Minimum pitch of buckets in inches p= .345 w. Maximum pitch of buckets in inches Minimum area through a stage Possible ratio of expansion Here Hence = 2.64 • = .75 w. h (d + h) 173 sq. ft. .756 W // 0 • W = width of the groove in which the buckets lie in inches. h = height of blade in inches. d = diameter of drum in inches. (21) (22) (23) (24) p = the pitch of the blades in inches, measured at the circumference of the drum. d + h = the mean diameter of a stage. The formulas are purely empirical, and apply only to the actual blades measured. With short and wide blades the expansion possible would be rather greater than that given by the formula above, since the minimum pitch adopted makes provision for the fact that wide blades are generally longer than short ones, and hence more space is needed between them to permit of caulking. On the other, with long blades, the maximum pitch advisable will be less than w. If the velocity of the steam remains constant in a section, the possible ratio of expansion in that section is fixed by equation 24. If this is r, the volume of the steam at the end of the section will be r times its volume at the beginning. If, for example, the steam is supplied at a pressure of 110 lb. absolute, and a superheat of 80 deg. Fahr., Fig. 24 shows that its initial volume per pound is 20 Vo= 4.4 cubic feet. Then if r is the ratio of expansion in the first section, its volume at the end of this section will be ≈₁ V1 rxo Vo. Hence, if r is known from equation (24), the number of heat units, Uo say, expended in the section is found from Fig. 24. - STEAM TURBINES. 243 With bucket angles of 67 deg. and 20 deg. respectively, the diameter and length of blade needed is given by the relation where q is the weight of steam passed per second, and R the number of revolutions per second. A convenient value being selected for họ, the diameter is then given, ând vice versa. The speed of flow of the steam through the guide-blades in feet per second is v = .327 (d + h) R. If the total number of stages in the section is N + 1, then 769 Uo ho I xo Vo R N+1= 0 Where Up is the heat available in the section, the nearest even number should be taken, as the last stage must be a set of buckets, and not a set of guide-blades. Number Dia- of meter of of Section. Drum. 1234567 The succeeding sections may be designed in the same way; the exhaust steam from one section being the admission steam to the next. The condition_of the steam at the entrance and end to each section can be read off the diagram, Fig. 24. Proportions for a turbine of 2000 horse-power are given in the annexed Table. 9 10 Table 6.-Proportions for Turbine giving 2000 Indicated Horse-Power at 35 Revolutions per Second. in. 14 15 17 172 172 24 24 24 37 37 in. (do + ho)2 Number Length Width of of Bucket, Bucket. in 1 -2-2-2 HAHN 00 00 Pekorater erster 18 -to-ka-ka —dea coleti poft cotton onl 1 2 3 to yo = in. Number of Buckets in Stages First Stage Last Stage of Section. of Section. 529 q xo Vo ho R Section. 22 34 32 40 24 18 12 12 6 255 224 231 231 231 253 253 253 296 296 Number of Buckets in 234 170 150 151 156 134 147 145 176 170 Actual Volume of Steam at End of Section in Cubic Feet. Three-Section Compound Reaction Tnrbines. 4.96 6.90 10.75 16.87 26.4 41.6 67.5 108 175 300 In a three-section compound reaction turbine it is impossible, under ordinary conditions, to maintain constant the velocity of the steam through all the stages of a section, and there is thus some loss of efficiency by shock, the steam entering each stage at an angle to the guide-blades or buckets instead of tangentially. If, for example, a turbine of this pattern is to be built to work with steam at an absolute pressure of 110 lb. per square inch below the governor valve, and a superheat of 80 deg. Fahr., the initial volume of the steam, xo Vo, will be 1.11 x 3.97 = 4.40 cubic feet; and if the exhaust temperature is 560 deg. absolute, its final volume, x1 V¹, will, from the diagram, Fig. 24, be 301 cubic feet. The total ratio of expansion is thus 301 4.4 68.4. At first sight it would seem reasonable to make the ratio of expansion in each section the same, but if this is done it will be found that the "available heat” in each section will also be much the same; and hence the best bucket speed for the low-pressure section will be nearly identical with that for the high-pressure section, which leads to somewhat impracticable proportions for the turbine. We shall, therefore, take it that the heat units utilised in the first section is half that utilised in the last, and that the heat utilised in the intermediate section 244 SECTION II.-POWER STATION. is three-quarters that in the last. Hence, if U₁ be the units accounted for in the first section, we have for the total heat utilised, U₁ (1+1.5+ 2) = 333, whence U₁ = 74. The volume occupied by 1 lb. of steam corresponding to an expenditure of 74 available units, is found from Fig. 24 to be 10.4 cubic feet. 10.4 Hence the ratio of expansion in the first section will be = 2.37. 4.4 If we assume that -in. blades are used here, a possible ratio of the area of the last stage to the first will be, from equation (24), 1.41. Hence the where v is the velocity of flow at the last stage will be v UN ρυο velocity at the first stage and p is a constant. In this case p = 2.37 V 1.41 "%' = Heat Available at each Stage. The velocity of the steam at any stage of the section will be - ρ on = v。 (1+ ² = ²n) ยู N 0 2.37 1.41 The total number of stages in the section being N + 1, and n the number of any stage after the first. The value of vo (the velocity of the steam at the first stage of the section) is given by the relation 2 8 = .800 (1+ P-1), 2 L = N - )) 3 - 3 ρ U1 U₁ = 3(P = 1) (2005) { (1 + ( − 1) (N + 1)³ - (1-2) ³ } . N N (p − Here U₁ is the heat available in the section. Any convenient odd number may be chosen for N. = 1.68. The best speed for the buckets of a section in feet per second, is given by the relation where p as before is the ratio of the velocity through the last stage to that through the first stage of the section. The loss from shock in the section, measured in heat units, is \3 (1190) 2 N 6-12² (1 + 1)³. N THE CURTIS TURBINE. (FIGS. 40 and 41, pages 245 and 246.) "" The Curtis turbines are of the vertical type, arranged for direct coupling to generators placed immediately above them. A typical cross-section is represented in Fig. 40. They are designed for a normal steam pressure of 150 lb. to 175 lb. per square inch, and a vacuum of 28 in. The turbine is "velocity-compounded." Velocity is imparted to the steam through an expanded nozzle, so designed as to effectively convert into kinetic energy the potential energy of the steam between the pressure limits used. After leaving the nozzle the steam passes successively through two or more rows of buckets on the moving element, which are placed alternately with reversed buckets on the stationary part of the turbine, as in- dicated in Fig. 41. Thus the steam is thrown first against the first set of buckets on the moving element, and then re-directed against the second moving set of buckets by passing through the first set of the fixed buckets, rebounding alter- nately from stationary to movable buckets, until the steam is brought to relative rest. By this means a high steam velocity is made to efficiently impart motion to a comparatively slowly-moving element. The nozzle is generally made up of a number of sections or units adjacent to each other, so that the steam passes to the buckets in a broad belt when all the sections are open. This process of expansion in the nozzle, and subsequent abstraction of velocity by successive impacts with the buckets, is generally repeated two or more times, each repetition constituting a stage," as defined in the theory of the compound turbine, supra. " STEAM TURBINES, 245 946. O j 100 00 000 0 AWLMAILA ASINS, www. ALTA b d TEAE d Fig. 40. Curtis Steam Turbine. a 246 SECTION II.-POWER STATION. A steam-tight diaphragm is placed between each stage, the only outlet for the steam passing to the next stage being through the nozzles in the diaphragm. The operation of this type of turbine at light loads is virtually the same as at full load, the only difference being that the belt of advancing steam is narrower, which STEAM CHEST DDD DDDD «« NOZZLE MOVING BLADES STATIONARY BLADES MOVING BLADES STATIONARY BLADES ATI MOVING BLADES Fig. 41. results in there being very little diminution of economy at light loads. The carry- ing of overloads with this type of turbine is effected by the simple opening of additional sections of admission nozzles; i.e., by widening the belt of advancing steam, which impinges upon the first row of buckets. This increase of flow is well taken care of by the later stages, and involves very little reduction in steam economy. Bearings. One of the most noticeable features in the Curtis turbine is the vertical shaft. A foot-step bearing is fixed to the bottom of the base and is removable from below, a pit or opening being provided in the foundation for this purpose. The bearing proper, which supports the rotating element of the turbine and generator, consists of two circular cast-iron plates, one being fixed to and rotating with the shaft. The other is fixed to the base. Through a hole in the stationary plate oil is forced between the plates from centre outwards in a thin film, separating the two plates by about .005 in. From the foot-step bearing the oil passes upwards and lubricates the guide-bearing, which is placed immediately above it. The oil is forced between the plates by a pressure pump designed to give approximately a constant pressure and a constant flow. In some more recent examples water is substituted for oil, and lignum vitæ is then used for the bearing surfaces. The oil pressure in the step-bearing varies from 175 lb. per square inch in the 500-kilowatt to about 900 lb. in the 5000 kilowatt turbine. Experiments have demonstrated that the minimum safe amount of oil required for the bearings per minute is from half-a-gallon for the 500-kilowatt to four gallons for the 5000-kilowatt turbine. A small amount of this oil is shunted through a resistance and delivered to the upper and middle bearings, a sight-feed arrangement being introduced in each branch. The oil from all three bearings is returned to a common tank, where it is strained and cooled before being put in circulation again. The top and middle bearings of the vertical shaft have no load to carry, save that due to want of balance and to unbalanced magnetic pull in the generator. All the bearings can be taken out without disturbing the turbine or generator. The foot-step blocks and the guide-bearing are lowered into the pit below, the middle bearing is split and can be removed sideways, and the upper bearing is lifted out, it being necessary to first remove the governor. As the step- bearing works under atmospheric pressure, a packing is provided round the shaft at this point to prevent air entering the exhaust base when the turbine is working under vacuum, or steam escaping when the pressure in the turbine is higher than the atmospheric pressure. For the same reason packing is provided where the upper end of the shaft passes through the turbine cover. STEAM TURBINES. 247 Buckets and Nozzles. The turbines have either two, three, or four stages, each consisting of two or more rows of movable buckets. The number of stationary buckets is dependent on the number of nozzles in the stage, as they need only cover the same periphery. of the wheels as the nozzles do. On account of the large increase in volume of the steam, and to keep the depth of the buckets as small as possible, the last stage wheels are completely surrounded by nozzles and stationary buckets. The buckets are milled out of the solid. Clearances. The clearances between stationary and rotating parts vary from .02 in. in the small to .08 in. in the 5000-kilowatt turbines. These are the clearances between the outer shrouding of the buckets and the rings of metal from which the fixed buckets are cut, these presenting broad smooth surfaces to one another. The buckets are made a little narrower than the rings, so that they cannot possibly come into contact with each other. Adjustment of the clearance is made by means of a heavy screw-bolt at the bottom of the step-bearing, which supports the foot-step blocks. Inspection holes are provided in the casing, so that the clearance between the buckets can be readily seen. Governor. The governor is of the centrifugal spring-loaded type, and is generally set for a speed regulation of 2 per cent. between full load and no load, with a maximum momentary variation of 4 per cent. For the purpose of synchronising, and to make the turbine take its proportional share of the load, a supplementary spring is introduced which acts in conjunction with the main governor spring, and allows the speed of the turbine to be varied 2 per cent. on each side of the normal speed. Admission Valves. The governor operates a controller, opening or closing the electrical circuits of magnets which operate pilot-valves, these in turn admitting steam or exhausting it from the spaces behind the pistons of the main valves, one of which is provided for each nozzle or group of nozzles, the governor thus opening and closing these valves and varying the number of nozzles in service in proportion to the load. Emergency Governor. In addition to the speed-regulating governor, which will always hold the no-load speed of the turbine within about 2 per cent. of the full-load speed, an emergency governor is provided, whose function is to trip a trigger should the speed of the turbine increase 15 per cent. above normal, and thus permit a weight to fall and give a hammer-blow to a butterfly or damper valve in the main steam pipe, closing the valve instantaneously. The governor is located on the shaft between the turbine and the generator, and consists of an ordinary centrifugal device balanced against a spring. The governor restores itself to normal position when the speed is reduced to normal, so that it is not necessary to stop the turbine, but the butterfly valve and weight must be brought to their normal position by hand. Such a precautionary device is rarely called upon to act, but experience with large engines has shown it to be desirable. Condenser Gear. All the vertical turbines are so designed that the exhaust base on which the turbine stands can be replaced by a condenser base. Placing the condenser directly under the turbine makes a very compact and efficient arrangement. Its simplicity, saving in floor space, and foundations are at once evident. By this means a better vacuum is obtained, due to reduction in air leakages, and to the shorter and more direct path of the exhaust steam. The condensers are usually arranged so as to be capable of maintaining a vacuum within 2 in. of the barometric pressure, and consist of one cast-iron casting, fitted with suitable branches for air-pump suction and circulating-water inlet and outlet. The air-pump customarily employed is a motor-driven three- throw vertical single-acting Edwards' type. The circulating pump is of the centrifugal type, and is motor-driven. Oil Supply. As a stand-by to the pumps an oil accumulator is supplied, capable of main- taining the requisite pressure, and having a capacity equivalent to five minutes' supply of oil at the bearings, so that in the event of the oil pump failing, the accumulator will automatically continue the supply. 248 SECTION II.-POWER STATION. To prevent the turbine being run either by steam or through the generator acting as a motor before oil begins to flow into the step-bearing, or in case the flow should cease while the turbine is working, an automatic oil-flow switch is placed in the high-pressure oil-supply pipe. The switch is actuated by the oil pressure, and opens and closes the electric current for the valve magnets in response to the change in pressure in the pipe. If the flow of oil in the bearings falls below the predetermined quantity of pressure, the switch opens the valve circuit, and all the valves close, immediately shutting off the steam from the turbine. When the switch opens, a special relay is closed, which trips the generator circuit breaker, and prevents the generator from running as a motor and driving the turbine. The following advantages are claimed for Curtis turbo-generator sets :- No oil is required except that used for the lubrication of the bearings, and as this oil is free from water it may be used repeatedly without waste. The amount of oil used by the Curtis turbine is, on the average, about one-sixth of that demanded by a slow-speed reciprocating engine of the same output. Another feature is the absence of oil in the condensed steam, which may be returned direct into the boilers without filtering. The floor space required by a 5000-kilowatt Curtis combined turbo-alternator set is about 300 square feet, as compared with approximately 1500 square feet for a slow-speed engine-driven set of similar capacity, and about 630 square feet required for a turbine set of the Parsons type. The turbine, having no reciprocating parts, runs with a minimum of vibration, and permits the use of a light foundation, whereas the foundations of a steam engine must often be very heavy and expensive in order to resist the inertia of its reciprocating parts. The turbine has comparatively few bearings, and a minimum of movable parts subject to adjustment or to exceptionally heavy strains, thus requiring much less attention than demanded by reciprocating engine sets. The continuous passage of steam through the turbine eliminates the tendency to pulsation, and thus prevents variation in angular velocity. This property is of the highest importance in the parallel operation of alternators and rotary con- verters, or other synchronous apparatus. The construction of the Curtis turbine is extremely simple, and the number of buckets or vanes approximately one-thirtieth as great as in a Parsons turbine of equal capacity. 500 750 1000 Standard sizes of this turbine are as follow: Direct Current.-The direct current turbo-generators are arranged as com- pound-wound machines, giving 500 volts at no load and 550 volts at full load. If necessary they can be arranged also to give 460 volts as shunt-wound machines. Kilowatt Output. Speed, Revolutions per Minute. 44 Kilowatt Output. 2500 5000 Size of Turbines. Kilowatt Output. 250 500 750 1000 1500 2500 5000 。. ·· • Alternating Current.-The following alternators are designed for 2300 volts, 6600 volts, or 11,000 volts, three-phase. They can, however, be wound to give two-phase and single-phase currents at slightly reduced outputs.. 25 CYCLES. ·· • .. ·· .. · • 50 CYCLES. •• ·· .. Speed, Revolutions per Minute. 750 500 ·· .. • •• •• Speed, Revolutions per Minute. 3000 1500 ·· ·· ·· 1500 1500 1200 ·· ·· ·· 1500 1000 1000 750 500 ! ין SECTION III. THE POWER STATION. STEAM BOILERS. 7 SECTION III. THE POWER STATION. STEAM BOILERS. BOILERS. The Choice of Type of Boiler, and its Location. The type best adapted is determined by the conditions of location and purpose by the pressure and quantity of steam required, the fuel and feed water and cost of it, and by the facilities for repairs. When repairs are difficult the plain cylindrical is chosen when the cost of fuel is low and the feed water is bad. As the necessity for economy in fuel increases, and the feed water is good, the complicated flue or tubular boiler is preferable. The boiler should be located in a dry place, and so erected that it may be easy of access for inspection and repair. The nearer the point at which its steam is delivered the better. When the space is restricted in floor area, but of good height, the upright tubular boiler may be advisable; if the floor area is unrestricted, but head-room is small, the horizontal forms of boiler are available. Boiler power is often calculated by allowing a certain number of square feet of heating surface per horse-power. The following is a fair average: Table 1.—Average Heating Surface per Horse-Power for Various Boilers in Square Feet. Plain cylinder boiler Flue boiler.. Water-tube or sectional boiler Locomotive boiler Return tubular boiler Upright .. "" · .. .. .. ·· 1 ·· 8 22330 10 12 13 15 18 Main Features in Boiler Designing. To secure complete combustion of fuel without diluting products of combustion by excess of air. To secure a high temperature of furnace. To arrange heating furnaces that available heat is completely taken up and utilised to the best advantage. To make the form of boiler as simple as possible, and to arrange for ample water surface and large steam and water capacity, so as to avoid fluctuation of steam supply. To make it durable under the action of hot gases, and of corroding elements of atmosphere and water. To make every part accessible for cleaning and repairs. To make all parts as uniform as possible in strength, so that the boiler shall not be rendered useless or dangerous by local defects. To adopt reasonably high "factor of safety "in parts, and to provide against irregular strains. To provide efficient safety valves, steam gauges, mud drums, and other appurtenances. To secure intelligent and careful management. 252 SECTION III.-POWER STATION. In designing a boiler plant the following elements have first to be determined: Height of chimney and rate of combustion desirable. Type of boiler, taking into consideration quality of water to be used, and costs of construction, operation, and maintenance. Quantity of steam required. Efficiency of boiler that will be economical to secure, and thus ratio of heating surface to grate area. Kind and quantity of fuel required, with the proposed efficiency, to produce demanded quantity of steam. The forms, sizes, and proportions of details. Then the amount of power necessary to be obtained from a single boiler is decided, the number of boilers to be constructed, the area of heating surface and grate area to be given each, and, finally, the form of setting, method of making steam and water connections. Types of Boilers for Traction Work. The question as to what type of boiler is the most suitable in connection with electric traction is a very disputed one, and different engineers hold very different opinions on this subject. No decision can be come to, however, on this point without a clear knowledge of the conditions which have to be fulfilled in each case. Some points specially called for are simplicity of construction, supply of dry steain, rapidity of getting up steam and possibility of overworking for a short period. There are many stations in America where colossal vertical boilers are used. The types of boilers most frequently met with may be roughly divided as follows:- Horizontal boilers of the Lancashire type. Marine type of boilers. So-called safety water-tube boilers, and Vertical boilers. "From the economical point of view for steady loads, no boiler surpasses the horizontal Lancashire type. The objections which can be made to it when applied to a tramway power plant are that it takes a long time to get up steam, and that it is very difficult, if not impossible, to force these boilers at short notice, when sudden calls for power are made. It is probable, however, that in very large stations where the load, although varying, remains fairly constant, this type of boiler could be used very successfully. Some American engineers, where loads are subject to very violent fluctuations, are inclined to use the internally-fired marine type of boiler, with a few modifica- tions. The special advantage claimed for this boiler is that it has an enormous capacity, and can furnish almost any amount of steam when forced, and that the steam is of good quality as regards percentage of moisture. A very favourite form of boiler in the United States, owing probably to the small space it occupies, is the vertical type, often reaching 30 ft. to 40 ft. in height. There are any number of boilers of this type, slightly varying in con- struction. The care of boilers is always an important point, and should only be entrusted to competent men. Great care must be exercised to see that the proper water level is maintained, and that there is no sudden drop of the steam pressure, which, owing to the very large and often unexpected variation in load, is always likely to occur. The Classification of Steam Boilers. The classification of steam boilers may be based upon a comparison either of their type or of their purpose. Under the former we have the plain cylindrical, the flue, the tubular, or the sectional boiler; under the latter, stationary, locomo- tive, or marine boilers. Stationary: Plain cylindrical boilers. Cornish or single-flue. Lancashire or two-flue. Multiflue and return-flue boilers. Cylindrical fire-tube boilers. Firebox boilers. Sectional boilers. Special, as for heating simply. STEAM BOILERS. 253 Locomotive: Common type. Wooton boilers. Special devices. Marine : Flue, older types. Flue and tube, older types. Tubular, older types. Scotch or drum boilers. Water-tube and sectional. Miscellaneous forms. Horse-Power of Boilers. In the case of boilers, the work done cannot be expressed in foot-pounds of available energy; the usual value given to the term horse-power is the evapora tion of 30 lb. of water of a temperature of 100 deg. Fahr. into steam at 70lb. pressure above the atmosphere, 30 lb. of water evaporated per hour being con- sidered to be the steam requirement per indicated horse-power of an average engine. The Committee of Judges of the Centennial Exhibition of Philadelphia in 1876, agreed to adopt as the unit, 30 lb. of water evaporated into dry steam per hour from feed water at 100 deg. Fahr., and under a pressure of 70 lb. per square inch above the atmosphere, these conditions being considered by them to represent fairly average practice. The quantity of heat demanded to evaporate a pound of water under these conditions is 1110.2 British thermal units, or 1.1496 English units of evaporation. The unit of power proposed is thus equivalent to the development of 33,305 heat units per hour, or 34.488 English units of evaporation. Horse-Power of Lancashire or Cornish Boiler. Multiply the area of firegrate by 4. The product is the horse-power which will be developed by the boiler when supplying an engine consuming 30 lb. of steam per hour, or requiring 4 lb. of coal per indicated horse-power per hour. A lower steam consumption, or higher evaporative duty of the coal, would give a correspondingly higher power for the boiler. A modern high-pressure condensing or compound engine using only 2 lb. of coal, or 15 lb. of water per indicated horse-power per hour, will, of course, develop double the power with the same quantity of steam evaporated by the boiler. Theoretical Quantity of Water and Coal required for the Development of One Theoretical Indicated Horse-Power. One indicated horse-power is equivalent to 33,000 foot-pounds = 42.746 B.T.U. = 42.746 x 60 minutes = 772 foot-pounds 2564.76 British thermal units per hour. The heat required to evaporate 1 lb. of water from 212 deg. Fahr. to steam of the same temperature, is 966 units, and 2564.76 thermal units per hour 966, the unit of evaporation the quantity of water theoretically required for the development of one indicated horse-power per hour. If steam coal having a calorific power of, say, 14,973 units per pound be used in the boiler, the quantity of water evaporated from 212 deg. Fahr." per pound of coal is = 2.655 lb. of water, 14,973 thermal units = 15.5 lb., 966, the unit of evaporation and the consumption of coal per indicated horse-power per hour is = 2.655 lb. of water per indicated horse-power per hour 15.5 lb. of water evaporated per pound of coal Two and three-quarter ounces of coal will theoretically develop ore indicated = .1712 lb. of coal. 254 SECTION III.-POWER STATION. horse-power per hour; and 1.1712 lb. = 5.841 indicated horse-power per hour may theoretically be developed by 1 lb. of coal. These results are very much better than are obtained in practice, owing to loss of heat in its conversion into work. English Unit of Evaporation. The results of boiler-tests are reduced to the common standard of weight of water evaporated by the unit weight of the combustible portion of the fuel, the evaporation being considered to have taken place at mean atmospheric pressure, and at the temperature due to that pressure, the feed water being also assumed to have been supplied at that temperature. This is said to be the equivalent evaporation from and at the boiling point at atmospheric pressure. This unit of evaporation, or 1 lb., of water evaporated from, and at, 212 deg. is equivalent to 965.7 British thermal units. Measures of Efficiency of Boilers. The measure of the efficiency of a boiler is the number of pounds of water evaporated per pound of fuel, the evaporation being reduced to the standard equivalent evaporation from feed water at a temperature of 212 deg. Fahr. into steam at the same temperature. The measure of the capacity of a boiler is the amount of "boiler horse-power" developed, a horse-power being defined as the evaporation of 30 lb. of water per hour from 100 deg. Fahr. into steam at 70 lb. pressure, or 34 lb. per hour, from and at 212 deg. + The measure of relative rapidity of steaming of boilers is the number of pounds of water evaporated per hour per square foot of water-heating surface. The measure of relative rapidity of combustion of fuel in boiler furnaces is the number of pounds of coal burned per hour per square foot of grate surface. Equivalent Evaporation from and at 212 deg. Fahr. For comparing boiler tests, the results obtained are often reduced to a common standard, reckoned from and at 212 deg. Fahr. For example : If Then W = pounds of water evaporated per pound of fuel, with the feed at a temperature of t deg. Fahr. H = total heat of steam at the temperature corresponding to the pressure, calculated from O deg. Fahr. W, the equivalent evaporation from and at 212 deg. Fahr. H-t deg. 966 H can be got from the Table of Properties of Saturated Steam (see page 172). W = W Evaporative Power of Steam Boilers. According to Hutton the following formula gives this very approximately H W × C+ H H = total heating surface of boiler in square feet. W = weight of coal burnt on firegrate per hour. P = theoretical calorific value of coal burnt or the total heat of combustion of 1 lb. of dry coal in pounds of water evaporated at and from 212 deg. Fahr. E = estimated evaporative power of boiler in pounds of water evaporated per pound of fuel at and from 212 deg. Fähr. C = a constant. = E = X P .40 for Galloway boilers. .42 for locomotive boilers, burning coal. .45 for Lancashire boilers. .50 for marine return-tube boilers. .65 for Cornish boilers. = .90 for externally fired plain cylindrical boilers. = 1.60 for boilers of portable engines of the ordinary locomotive type. STEAM BOILERS. 255 Temperature of Feed Water. Deg. Fahr. 30 40 32 40 50 Table 2.—Factors of Evaporation. Boiler Pressure in Pounds per Square Inch. 50 60 70 80 90 100 110 120 130 140 150 60 70 80 90 100 110 120 130 140 1.207 1.211 1.214 1.2171.220 1.223 1.225 1.227 1.228 1.231 1.233 1.234 1.236 1.199 1.203 1.206 1.209 1.2121.214 1.217 1.219 1.221 1.223 1.224 1.226 1.228 1.188 1.192 1.196 1.199 1.201 1.204 1.206 1.208 1.210 1.212 1.214 1.216 1.217 1.178 1.182 1.186|1.188|1.191|1.194|1.196 1.198 1.200 1.202] 1.204 1.205| 1.207 1.167 1.171 1.175 1.178 1.181 1.183.1.185 1.188 1.190] 1.191 1.193 1.195 1.196 1.157 1.161 1.165 1.168 1.170 1.173 1.175 1.177 1.179 1.181 1.183 1.185 1.186 1.147 1.151 1.154 1.157 1.160 1.162 1.165 1.167 1.169 1.171 1.172 1.174 1.176 1.136 1.140 1.144 1.147 1.150 1.152 1.151 1.156 1.158 1.160 1.162 1.164 1.165 1.126 1.1301.133 1.136 1.139 1.142 1.144 1.146 1.148 1.150 1.152 1.153 1.155 1.116 1.120 1.123 1.126 1.129 1.131 1.134 1.136 1.138) 1.140 1.141 1.143 1.145 1.105 1.109 1.113 1.116 1.118 1.121 1.123 1.125 1.127 1.129] 1.131| 1.133 1.134 1.095 1.099 1.102 1.105 1.108 1.110 1.113 1.115 1.117 1.119 1.120 1.122 1.124 150 1.085 1.088 1.092 1.095 1.098 1.100 1.102 1.104 1.106 1.108 1.110 1.112| 1.113 160 1.074 1.078 1.081 1.084 1.087 1.090 1.092 1.094 1.096 1.098 1.100 1.101 1.103 170 1.064 1.067 1.071 1.074 1.077 1.079 1.081 1.084 1.086 1.087 1.089 1.091 1.092 180 1.053 1.057 1.064 1.069 1.066 1.069 1.071 1.073 1.075 1.077 1.079 1.080 1.082 190 1.043 1.047 1.050 1.053 1.056 1.058 1.061 1.063 1.065 1.067 1.068 1.070 1.072 200 1.032 1.036 1.040 1.043 1.045 1.048 1.050 1.052 1.054 1.056 1.058 1.059 1.061 1.022/1.026 1.029 1.032 1.035 1.037 1.040 1.042 1.044 1.046 1.047 1.049 1.051 210 In estimating the evaporative power of steam boilers it is usual to give the number of pounds of water evaporated from and at a temperature of 212 deg. Fahr. For a given boiler pressure and temperature an evaporation factor will be obtained from the above table, which, multiplied by the pounds of water evapor- ated per pound of coal, will give the equivalent evaporation from and at 212 deg. Measurement of Heating Surface. Authorities are not agreed as to the methods of measuring the heating surface of boilers. The usual rule is to consider as heating surface all the surfaces that are surrounded by water on one side and by flame or heated gases on the other; there is a difference of opinion as to whether tubular heating surface should be figured from the inside or from the outside diameter. Kent gives the following rules for finding the heating surface of various boilers: For finding heating surface of vertical tubular boilers: Multiply the circum- ference of the firebox (in inches) by its height above the grate; multiply the com- bined circumference of all the tubes by their length, and to these two products add the area of the lower tube sheet; from this sum subtract the area of all the tubes and divide by 144; the quotient is the number of square feet of heating surface. Rule for finding the heating surface of horizontal tubular boilers: Take the dimensions in inches; multiply two-thirds of the circumference of the shell by its length; multiply the sun of the circumferences of all tubes by their common length; to the sum of these products add two-thirds of the area of both tube sheets; from this sum subtract twice the combined area of all the tubes; divide the remainder by 144 to obtain the result in square feet. Rule for finding the square feet of heating surface in tubes: Multiply the number of tubes by the diameter of a tube in inches, by its length in feet, and by .2618. Proportion of Heating Surface to Grate Area. The ratio of heating surface to grate area in boilers varies. In the Lanca- shire and Cornish types it ranges from 15 to 25; in multitubular marine boilers from 25 to upwards of 50; in locomotives from 50 to 75; in tubular boilers from 25 to 50. 256 SECTION III.-POWER STATION. Boilers with high proportion of heating surface give higher evaporative efficiencies. The improvement is not proportionate to the increase in heating surface, and after the lower value of the above ratios is reached, the gain is relatively very slow. The proportion of heating surface it is desirable to allow will depend on the rate of combustion, the price of the fuel used, and also the cost of the heating surface. With forced draught a greater extent of heating surface Is necessary than with ordinary draught. If fuel is expensive, a slight increase in boiler efficiency may effect considerable saving in coal, and additional heating surface be desirable on that account. Against this saving must be set the cost of the heating surface. Heating Surface per Horse-power. It is a general practice among builders to furnish 12 square feet of heating surface per horse-power, but this practice is not uniform. Not less than one- third square foot of grate area should be furnished per horse-power. The amount of grate area required per horse-power under various conditions may be estimated from the following Table: Table 3.-Grate Area per Horse-power for Various Qualities of Coal. (Kent.) Good coal and boiler Fair coal or boiler Poor coal or boiler Lignite and poor boiler Pounds Water Pounds Coal from and at 212 deg. per Pound Coal. per Horse- Power per Hour. 10 9 8.61 8 7 6.9 6 5 3.45 45 3.83 4. 4.31 4.93 5. 5.75 6.9 10. Pounds of Coal Burned per Square Foot of Grate per Hour. 8 31 201 Square foot grate per horse-power. ·· 12 -- 15 20 25 30 35 40 In designing a boiler for a given set of conditions, the grate area should be made as liberal as possible, say sufficient for rate of combustion of 10 lb. per square foot of grate for anthracite, and 15 lb. per square foot for bituminous coal, and in practice a portion of the grate area may be bricked over if it is found that the draught, fuel, or other conditions render it advisable. .43 .35 .28 .23 .17 .14 .11 .10 .09 .48 .38 .32 .25 .19 .15 .13.11.10 .50 .40 .33 .26 .20 .16 .13.12.10 .54.43.36.29.22 .17 .14 .13 .11 .62 .49.41 | .33 .24 .20 .17 .14 .12 .63 .50 .42.34 .25 .20 .17.15.18 .72 .58.48.38.29.23 .19.17.14 .86 .69 .58.46 .35 .28 .23 .22.17 1.25 1.00 .83.67.50 .40 .33 .29 .25 Proportion of Areas of Flues and other Gas Passages. A common rule for horizontal tubular boilers is to make the area over the bridge wall one-seventh of the grate area, the flue area one-eighth, and the chimney area one-ninth. Total Heating Surface. Total heating surface for boilers worked with natural draught, except loco- motive and portable boilers having exhaust steam blast, may be found according Hutton by the following formula: Heating surface in square feet required for a given evaporation = Pounds of water evaporated per hour × C Total heat of the working pressure of the steam. In which C is a constant varying for each type of boiler, as follows:- Locomotive boilers C 90 Externally-fired plain cy- Marine return-tube boilers C = 180 lindrical boilers Portable engine boilers of the locomotive type. C = 280 C = 205 Lancashire boilers Cornish boilers C = 220 с C = 530 STEAM BOILERS. 257 Values of Different Forms of Heating Surface. (Hutton.) The relative value of different forms of heating surface, compared with flat horizontal surface above the fire, is as follows : One square foot of flat horizontal surface above the fire, such as the crown-plate of the firebox of the boiler of a locomotive engine One square foot of circular surface above, and concave to, the fire, such as the crown-plates of the circular furnace of an internally fired boiler One square foot of circular surface above, and convex to, the fire, such as the furnace plates of an externally fired plain cylindrical or egg-ended boiler One square foot of flat surface at right angles to the current of gases, exposed to direct impingement of flame, such as the firebox tubeplate of a locomotive boiler One square foot of water-tube surface at right angles to the current of hot gases, such as that portion of the surface of a Galloway tube which faces the fire One square foot of sloping surface at the side of, and inclined towards, the fire, such as the sides of a firebox when inclined sufficiently to facilitate evaporation One square foot of vertical surface at the side of the fire, such as the sides of a firebox when vertical .. One square foot of the surface of the tubes of a locomotive boiler, contained in a length not exceeding 3 ft. from the firebox tube- plate ·· .. .. ·· .. ·· ·· ** • ·· • .. 1.00 .95 .30 Horizontal surfaces below the fire and the under portions of internally heated tubes, have practically no evaporative value, and cannot be considered as effective heating surface, therefore the lower half of a furnace tube below the grate bars should not be included in calculating the heating surface of a steam boiler. .90 .80 .70 .65 .50 Draught Area of Smoke Tubes. The area of aperture of boiler tubes, or smoke tubes of multitubular boilers, that is, the area through which the products of combustion pass, is generally pro- portioned to the area of the firegrate. The smaller the diameter of the tubes, the greater the heating surface obtainable in a given space. Small tubes are liable to become choked with ashes and soot, and are not suitable for coal which yields tarry deposit. The larger the tube, the greater the distance travelled by the flame before extinction. Excessive area through the smoke tubes produces a low velocity of gaseous products of combustion and bad draught. Deficient area through the tubes produces a high velocity of the fuel gases, which may not allow sufficient time for absorption of heat. The cross-sectional area of the smoke tubes of steam boilers with natural draught should not be greater than two-ninths, or less than one-eighth of the area of the firegrate; one-fifth is a common proportion. When forced draught is employed, the area through the tubes may be from one-tenth to one-twelfth the area of the firegrate, according to the strength of the draught. K Area through the Smoke Tubes of Boilers of Various Types. The area through the tubes of a steam boiler, or the area of aperture of the tubes, is = (internal diameter of tube)2 x .7854 × number of tubes. The following are good proportions for the aperture area of smoke tubes : Area through the tubes of locomotive boilers in square inches = area of fire- grate in square feet x 19. Area through the tubes of portable engine boilers of the locomotive type in square inches area of firegrate in square feet x 26. Area through the tubes of marinė return-tube boilers with natural draught, including the area of aperture of the stay tubes, in square inches = area of fire- grate in square feet x 28. `Area through the tubes of horizontal internally fired cylindrical multitubular boilers with natural draught, including the area of aperture of the stay tubes, in square inches = area of firegrate in square feet × 40. - 258 SECTION III.-POWER STATION. Length of Boiler Smoke Tubes. The length of the smoke tubes of multitubular steam boilers depends prin- cipally upon the strength of the available draught. The ratio of the length to the diameter of the smoke tubes of boilers with natural draught is limited by the necessity of not presenting excessive resistance to the passage of the fuel gases. The length of the smoke tubes may be as great as that equal to 40 times the internal diameter of the tubes for boilers with a strong natural draught, but it should not exceed 30 times the internal diameter for a moderately strong natural draught. The length of the tubes of locomotive and other boilers with a steam blast in the chimney may be as great as that equal to 120 times the internal dia- meter of the tubes. Heating Surface of Smoke Tubes. The external surface of smoke tubes of steam boilers is generally included in calculating their heating surface. The heating surface of smoke tubes may be found as follows: Heating surface of one tube in square feet = External diameter of tube in inches x 3.1416 x length of tube in inches 144 MEMORANDA USEFUL IN BOILER CONSTRUCTION. Material for Riveting. Board of Trade.-Tensile strength of rivet bars between 26 and 30 tons, el. in 10 in. not less than 25 per cent., and contr. of area not less than 50 per cent. Lloyd's.-T. S., 26 to 30 tons; el. not less than 20 per cent. in 8 in. The material must stand bending to a curve, the inner radius of which is not greater than 14 times the thickness of the plate, after having been uniformly heated to a low cherry red, and quenched in water at 82 deg. Fahr. United States Statutes.-No special provision. Bureau Veritas.-T. S., 53,000 lb. German Lloyd's.-T. S. 45,000 to 51,000 lb., el. 23.5 per cent. to 26 per cent. depending on thickness of plate. Rules Connected with Riveting. Board of Trade. The shearing resistance of the rivet steel to be taken at 23 tons per square inch, 5 to be used for the factor of safety independently of any addition to this factor for the plating. Rivets in double shear to have only 1.75 times the single section taken in the calculation instead of 2. The diameter must not be less than the thickness of the plate, and the pitch never greater than 8 in. The thickness of double butt straps (each) not to be less than & the thickness of the plate; single butt straps not less than . Distance from centre of rivet to edge of hole = diameter of rivet × 1. Distance between rows of rivets = 2 x diameter of rivet or = [(diameter x 4)+ 1]÷2, if chain, and √[(pitch × 11)+ (diameter × 4)] × (pitch ÷ diameter × 4) if zigzag. 10 Diagonal pitch (pitch × 6+ diameter × 4) ÷ 10. Lloyd's.-Rivets in double shear to have only 1.75 times the single section taken in the calculation instead of 2. The shearing strength of rivet steel to be taken at 85 per cent. of the T. S. of the material of shell plates. In any case where the strength of the longitudinal joint is satisfactorily shown by experiment to be greater than given by the formula, the actual strength may be taken in the calculation. * United States Statutes.-No rules. 1 Bureau Veritas.-Shearing strength assumed = 0.8 T. S., at working pressure shearing strength to be part of full shearing strength. Double shear twice single section. Circular seams to be double rivetted if plates exceed in. 4.4 German Lloyd's.- Shearing assumed = 0.8 T. S. of plates-factor of safety = 5 for lap joints and 1.15 x 5 for double butt joints-total rivet area to be taken. Butt straps at least 0.75 of plate diameter of rivets not over twice, or less than, thickness of plate for thin and thick plates respectively. Pitch of rivets not over eight times thickness of plate strap. STEAM BOILERS. 259 Riveted Joints. Riveted joints are made in several ways, either overlap or butt joint with single or double cover straps. The riveting may be single, double, or treble, and zig-zag or chain riveted. The diameter of the rivet should not be less than thickness of plate, and in most cases greater, especially for thin plates. It is not usual to use rivets less than in. diameter even for in. plates. If rivets are small in diameter and long, they are liable to pull the heads off in contracting. The width of the outer overlap of a riveted joint should never be less than the diameter of the rivet, measuring from the edge of the plate to the edge of the hole. For single riveting, width of lap equal three times diameter of rivet, but 3 or even 31 times is not too much. With punched plates the diameter from edge of plate to edge of hole should be 13 times the rivet's diameter, or equal to the diameter with drilled holes. For double riveting, width of lap equals five times diameter of rivet, if zig-zag riveting and drilled holes; 5 if punched. For chain riveting, 5 and 6 respectively for drilled or punched holes. For treble riveting, 62 and 73 respectively for drilled or punched holes, with zig-zag riveting; with chain riveting, 8 and 89 times respectively. Butt Straps. Butt straps should be cut from plates, and have the fibre in the same direction as the plates they unite. Single butt straps greater in thickness than plate con- nected. Double butt straps one-eignth thicker than half thickness of plate. Lloyd's rules require the inner butt strap to be three-fourths of plate thickness. Butt straps should be drilled in position and afterwards taken apart to remove the burrs from the holes before riveting. Diameter of Rivets. Practical reasons often prevent the seams being proportioned to give greatest theoretical strength. In lap joints rivets and pitch as large as practicable may be adopted, as the limit of bearing pressure is not likely to be used. In butt joints as small a rivet and as large a pitch as practicable should be used, as the shearing area is in excess. For these the diameter may be made equal to one-third its length. The following sizes of rivets are used by Lancashire boilermakers :— For in. and in. plates in. rivets. in. gin. tlin. ğin. 19 ** 55 2 in. 1 in. Iron boiler plates Steel "" .. "" .. "" •• 99 Table 4.-Proportional Breaking Stresses in Tons per Square Inch. -- ·· 19 • "" "" 13in. Jin. }ğin. "" "" 20 28 "" Tensile. Shearing. Bearing. 20 40 42 2223 Safe stresses not to exceed one-quarter the above. Rivets in Double Shear. Strength may be taken as twice that of single shear. Diameter of hole taken in all cases as the size of rivet. The Board of Trade take the strength of rivets in double shear as 1.75 times that of single shear. Professor Alexander Kennedy's experiments for the Inst. M.E. showed that the strength per square inch of rivets in double shear is fully as great as that of rivets in single shear. Percentage of Strength of Joints. To be taken from tensile strength of plates at seam, or from shearing strength of rivets, whichever is weakest. Strength of joint, single riveting, usually .56 of solid plate, and double riveting, .7. 260 SECTION III.-POWER STATION. Diagonal Pitch of Double Riveting. Allow not less than 30 per cent. more sectional area between rivets taken in zigzag direction than in straight line : P₁ = .65 p + .35 d. .65 p +.35 d. The Board of Trade rule gives slightly less than this: p₁ = .6p + .4d. P₁ = diagonal pitch, p = P₁ = straight pitch. Material for Cylindrical Shells Subject to Internal Pressure. Board of Trade.-T. S. between 27 and 32 tons. In the normal condition, elongation not less than 18 per cent. in 10 in., but should be about 25 per cent.; if annealed, not less than 20 per cent. Strips 2 in. wide should stand bending until the sides are parallel at a distance from each other of not more than three times the plate's thickness. Lloyd's.-T. S. between the limits of 26 and 30 tons per square inch. Elonga- tion not less than 20 per cent. in 8 in. Test strips heated to a low cherry-red and plunged into water at 82 deg. Fahr. must stand bending to a curve, the inner radius of which is not greater than one and a-half times the plate's thickness. U. S. Statutes.-Plates of in. thick and under shall show a contr. of not less than 50 per cent.; when overin. and up to in., not less than 45 per cent.; when over 2 in., not less than 40 per cent. Bureau Veritas.-Tensile strength not over 61,000 lb. Elongation 20-31 per cent. for various tensile strengths. Quench strips must bend 180 deg. around diameter = 3 t. German Lloyd's.-Tensile strength not over 61,000 lb. Elongation 20-26 per cent. for various tensile strengths. Quench strips must bend 180 deg. around dia- meter = 4 t. Shell-Plate Formulæ. TxBxt x 2 DX F D = diameter of boiler in inches P = working pressure in pounds per square inch t = thickness in inches Board of Trade.—P = B = percentage of strength of joint compared to solid plate T = tensile strength allowed for the material in pounds per square inch Fa factor of safety, being 4.5, with certain additions depending on method of construction. Lloyd's.—P = Cx (t - 2) x B • D t = thickness of plate in sixteenths; B and D as before; C = a constant depending on the kind of joint. When longitudinal seams have double butt-straps, O= 20. When longitudinal seams have double butt-straps of unequal width, only covering on one side, the reduced section of plate at the outer line of rivets, C 19.5. When the longitudinal seams are lap-jointed, C = 18.5. United States Statutes.-Using same notation as for Board of Trade. tx 2x T P = for single rivetting; add 20 per cent. for double rivetting DX 6 where T is the lowest T S stamped on any plate. Bureau Veritas.—P = T×B× (t − 0.04)² D x 4.4 x 100 B = per cent. of plate section at joint. P also depends on rivet section. tx 2 x B x T DX FX 100 Fraries from 4.65 to 5, depending on thickness of plate Rules for Flat Plates. Board of Trade.—P =C (t + 1)2 S-6 German Lloyd's.—P = P = working pressure in pounds per square inch S = surface supported in square inches t = thickness in sixteenths of an inch = a constant as per following table. STEAM BOILERS. 261 C = 125 for plates not exposed to heat or flame, the stays fitted with nuts and washers, the latter at least three times the diameter of the stay, and the thickness of the plate C = 187.5 for the same condition, but the washers the pitch of stays in diameter, and thickness not less than plate с 200 for the same condition, but doubling plates in place of washers, the width of which is the pitch and thickness the same as the plate C = 112.5 for the same condition, but the stays with nuts only C = 75 when exposed to impact of heat or flame and steam in contact with the plates, and the stays fitted with nuts and washers three times the diameter of the stay and the plate's thickness C = 67.5 for the same condition, but stays fitted with nuts only C = 100 when exposed to heat or flame, and water in contact with the plates, and stays screwed into the plates and fitted with nuts C = 66 for the same condition, but stays with riveted heads. U. S. Statutes.-Using same notations as for Board of Trade. P = greatest pitch in inches, P and t as above; = 112 for plates 7 in. thick and under, fitted with screw stay-bolts and nuts, or plain bolt fitted with single nut and socket, or riveted head and socket; where p = с = 120 for plates above in. under the same conditions ; C = 140 for flat surfaces where the stays are fitted with nuts inside and out- side; C = 200 for flat surfaces under the same condition, but with the addition of a washer riveted to the plate at least half plate's thickness, and of a diameter equal to & pitch. N.B.-Plates fitted with double angle-irons and riveted to plate, with leaf at least the thickness of plate and depth at least of pitch, would be allowed the same pressure as determined by formula for plate with washer riveted on. N.B.-No brace or stay-bolt used in marine boilers to have a greater pitch than 104 in. on fire-boxes and back connections. Certain experiments were carried out by the Board of Trade which showed that the resistance to bulging does not vary as the square of the plate's thickness. There seems also good reason to believe that it is not inversely as the square of the greatest pitch. Bureau Veritas.—P = (t − 1)2 T a² + b² <73 German Lloyd's. -P = X T tensile strength in tons per square inch. a = pitch in one row in inches. b = distance between rows. C = factor depending on method of supporting, and varies from 0.055 to 0.084. t2 C2 × p2 cxt, p2 O varies from 0.00425 to 0.00639 depending on exposure and method of sup- porting. Plates for Flanging. The Board of Trade gives the following rule for the strength of furnaces stiffened with flanged seams, provided the pitch of the flanges does not exceed 120 T-12, and the flanging is of suitable design and effected at one heat. P = 9900 × T 3 X D (5- C L12) 1:23) 60 x T P = working pressure per square inch. T= thickness of plate, in inches. L = pitch of flanges in inches. D = outside diameter of tubes in inches. Bureau Veritas.-Tensile strength not over 61,000 lb. cent. for various tensile strengths. Quench strips must diameter = 3 t. Elongation 20-31 per bend 180 deg. around German Lloyd's.—Tensile strength not over 53,000 lb. Elongation not under 224 per cent. Quench strips must bend 180 deg. around diameter = 4 t. 262 SECTION III.-POWER STATION. Furnace Flue Formulæ. C x 12 Board of Trade: Long Furnaces.-P = (L+ 1) × D' but not where L is shorter than (11.5t—1), at which length the rule for short furnaces comes into play. P = working pressure in pounds per square inch; t = thickness in inches D = outside diameter in inches; L = length of furnace in feet up to 10 ft. C = a constant, as per following table, for drilled holes : C = 99,000 for welded or butt-jointed with single straps, double riveted; с C = 88,000 for butts with single straps, single riveted; C = 99,000 for butts with double straps, single riveted. Provided always that the pressure so found does not exceed that given by the following formulæ, which apply also to short furnaces : P = Cx t D Cxt for all the patent furnaces named ; L X 12 67.5 x t 8,800 for plain furnaces; 14,00 for Fox; minimum thickness to exceed 6 in. in length; 13,500 for Morison; minimum thickness not to exceed 6 in. in length; C = 14,000 for Purves-Brown; limits of thickness 9 in. in length; P = C = C с S < 1 ( 3 x D = 5 C 8800 for Adamson rings; radius of flange next fire 1 in. = United States Statutes: Long Furnaces.-Same notation. P = 89,600 × 12 but L not to exceed 8 ft. LX D when with Adamson rings. N.B.-If rings of wrought iron are fitted and riveted on properly around and to the flue in such a manner that the tensile stress on the rivets shall not exceed 6000 lb. per square inch, the distance between the rings shall be taken as the length of the flue in the formulæ. Patent. P as before, when not 8 ft. Short Furnaces, Plain and 89,600 × 12 long 1:5 LX D tx C P = in., greatest § in.; plain part not in., greatest § in.; plain part in. and § in.; plain part when Ꭰ C = 14,000 for Fox corrugations where D = mean diameter C 14,000 for Purves-Brown where D = diameter of flue; = C = 5677 for plain flues over 16 in. diameter and less than 40 in. when not с over 3 ft. lengths. • 2) 1259 × (T D Lloyd's Bureau Veritas for Jones' Furnace.—W P : T being in this case the thickness in sixteenths of an inch; D the greatest diameter in inches; and W P the working pressure in pounds per square inch. Lloyd's and Bureau Veritas for Morison's Suspension Furnace :— WP = thickness in sixteenths of an inch; D = greatest diameter in inches ; and W P = working pressure. 1259 X (T-2) D << Material for Stays. The qualities of material prescribed are as follows:- Board of Trade.-The tensile strength to lie between the limits of 27 and 32 tons per square inch, and to have an elongation of not less than 20 per cent. in 10 in. Steel stays which have been welded or worked in the fire should not be used. Lloyd's.-26 to 30 ton steel, with elongation not less than 20 per cent. in 8 in. U. S. Statutes.-The only condition is that the reduction of area must not be less than 40 per cent. if the test bar is over in diameter. Bureau Veritas.-Same as for shell plates. German Lloyd's.-Large stays tensile strength 45,800 to 61,200 lb. Elongation same as shell plates. Screwed stays tensile strength 44,600 to 53,400 lb., and cor- responding elongation. STEAM BOILERS. 263 nace Inside Corrugations. B. of T. Lloyd's B. of T. ID CO CD CD CD CD CD co co co co 09 33 1~~~~~~ Diameter of Fur- ft. in. 4 4 Table 5.-Fox's and Purves' Furnace Tubes. Working Pressures allowed by Board of Trade and Lloyd's. 4 4 4 Working Pressures in Pounds per Square Inch. & in. 13 in. 7 in. 1 in. in. in. 1 in. in. 32 in. 16 Thick. Thick. Thick. Thick. Thick. Thick. Thick. Thick 4 5 6 Lloyd's B. of T. 6 164 145 177 163 191 181 7 159 141 172 158 185 176 171 166 162 8 154 137 167 154 180 9 150 133 162 150 175 10 145 129 157 146 170 11 141 126 153 142 165 158 0 138 123 149 138 161 154 1 134 120 145 135 157 150 135 157 150 2 131 117 142 132 153 146 138 129 149 143 |129 149 143 140 126 145 140 3 128 114 137 4 125 112 135 126 145 5 122 109 |132 |123 142 6 119 107 129 120 139 7 116 105 126 118 136 8 114 102 134 Lloyd's B. of T. Lloyd's B. of T. | Lloyd's B. of T. Lloyd's B. of T. 205 199 218 217 232 235 246 254 259 272 273 290 198 193 212 211 225 229 238 246 251 264 265 282 193 188 205 205 218 222 231 239 244 257 257 274 187 183 200 200 212|216 225 233 237 250 250 266 182 178 194 194 206 211 218 227 230 243 243 259 177174189 189 201 205 212|221 224 237 236 253 172 169 184 185 195 200 207 215 218 231 230 246 168 165 179 180 190 195 201|210|213 225 224 240 164 161 175 176 185 190 196 205 207 220 218 235 160 157 170 172 181 186|192|200 202 215 213 229 156 154 166 168 177 182 187|196 197 210 208 224 152 150 162 164 172 178183 191 193 205 203 219 149 147 159 160 169 174 178187 188 201198214 145 144 155 157 165 170|175|183|184|196|194|210 142 141 152 154 161 167 171 179 180 192 190 2C5 9 111 100 121 139 138 148 151 158 163 167 176 176 188 186 201 10 109 98 118 136 135 145|148|154|160 164 172 173 185 182 197 11 107 96 116 108 125 120 133133142|145|151|157|160|169|169 181 178 193 0 105 94 113 106 122 118 106 122 118 131 130 140 142 148 154 157 166 166 177 175 189 1 102 93 111 104 120 116 128 128 137 139 145 151 154 162 162 174 171 186 2 100 91 109 91 109 102 117 114 126 125 134 137 143 148 151 159 159 171 168 182 89 107 100 115 112 123 123 132|134|140|145|148|157 156 168|165 179 88 105 99 113 110 121 121 129 132 137 143 145 154 153 165 162 176 86 103 97 111 108 119 119 127|129|135|140|143|151|151 162 159 173 93 85 101 95 109 106 117 117 125 127 132 138 140 148 148 159 156 170 131 123 115 133 128 115 133 128 113 130 125 113 130 125 111 127 123 111 127 123 4 3 99 97 95 Lloyd's B. of T. Internal flues should be so constructed as to allow for expansion. K 1 5.75 ğ in. Thick. Lloyd's B. of T. Lloyd's Loads Allowed on Stays. Board of Trade.-9000 lb. per square inch is allowed on the net section, pro- vided the tensile strength ranges from 27 to 32 tons. Steel stays are not to be welded or worked in the fire. Lloyd's. For screwed and other stays, not exceeding 13 in. in diameter effec- tive, 8000 lb. per square inch is allowed; for stays above 12 in., 9000 lb. No stays are to be welded. U. S. Statutes.-Braces and stays shall not be subjected to a greater stress than 6000 lb. per square inch. Bureau Veritas.- of lower test limit on net section. Then add § in. to diameter of stay. German Lloyd's.-Not to exceed of tensile strength, or about 8,500 lb. per square inch. Stay Girders. Board of Trade.—P = P = working pressure in pounds per C x d² xt (Wp) Dx L square inch; W = width of flame-box in inches; L = length of girder in inches; P pitch of bolts in inches; D distance between girders from centre to centre in inches; d = depth of girder in inches; t = thickness of sum of same in = 264 SECTION III.—POWER STATION. inches; C = a constant = = a constant = 6600 for one bolt, 9900 for two or three bolts, and 11,220 for four bolts. 11,000 for four or Lloyd's. The same formula and constants, except that C five bolts, 11,550 for six or seven, and 11,880 for eight or more. U. S. Statutes.—The matter appears to be left to the designers. Board of Trade.-P = Tube-Plates. (t (D — d) × 20,000 W X D D= least horizontal distance between centres of tubes in inches; d = inside diameter of ordinary tubes; t = thickness of tube-plate in inches; W = extreme_width of combustion-box in inches from front tube-plate to back of fire-box, or distance between combustion- box tube-plates when the boiler is double-ended and the box common to both ends. The crushing stress on tube-plates caused by the pressure on the flame-box top is to be limited to 10,000 lb. per square inch. Strength of Plates. (The Mechanical World.) The Board of Trade requires that the steel for shell plates shall have a tensile strength not exceeding 32 tons per square inch, nor less than 27 tons; plates exposed to heat or flame, and those to be flanged or worked, should have a tensile strength of not more than 30 tons, nor less than 26 tons. Elongation in 10 in. should not be less than 20 per cent.; 25 per cent. is considered a good mean in both cases. For iron plates the Board of Trade requires a tensile strength for shell plates of from 20 to 22 tons with the grain, and 19 to 21 tons across the grain, the elongation in a length of 10 in., with the grain being from 8 to 10 per cent., and across 5 to 7 per cent. For plates subjected to the impact of heat or flame the tensile strength with the grain should be 22 tons, across 20 tons; and the elongation with the grain 16 to 18 per cent., and across 8 to 12 per cent. Lloyd's rules require the plates to have a tensile strength of not less than 26, nor more than 30 tons per square inch, with an elongation of not less than 20 per cent. in 8 in. Hydraulic Tests. The following rules are those of the principal Boiler Inspecting Companies and Supervising Authorities for new boilers. ·· Authority. Board o. Trade Lloyd's and Bureau Veritas Manchester Steam Users' Association Vulcan Boiler Insurance Co., for boilers under 100 lb.. over 100 lb. "" National Boiler Insurance Co. Engine and Boiler Insurance Co. Scottish Boiler Insurance Co. : For boilers up to80 lb. Above 80 lb. andunder 150 lb. 150 lb. and upwards United States Statutes "" •• -- ·· • • ·· • • Lancashire Boiler. (FIGS. ·· •• .. Hydraulic Test Pressure. working pressure × 2 "" X 2 × 12 X 2 "" "" "" 39 "" "" "" "" "> "" (FIGS. 1 to 4, page 265.) "" "" "" "" "" **** "" + 80 lb. × 13 x 1/ X 2 + 80 lb. × 1 x 11 It has a horizontal cylindrical shell, and two furnace tubes extending the whole length, sometimes corrugated or provided with cross Galloway conical water- tubes. The whole is set in brickwork with external brick flues. The direction of gases is generally as follows: Through each furnace tube, then under bottom brick flue to the front of the boiler, where they divide and pass through the two side flues to the chimney (Fig. 2). Sometimes after leaving the furnace tubes they pass through the two side flues, and uniting, pass along the bottom flue to the chimney, the gases of lowest temperature coming in contact with the coolest part of the boiler, where location of sediment is most likely to be. Tests with mechanical stokers give an efficiency without economisers of 52 to 74 per cent. With the latter, 62 to 87 per cent. The best results were obtained when using economisers, and evaporating from 4 to 5 lb. of water per square foot of heating surface per hour. STEAM BOILERS. 265 K² 266. 2x 1 = Set Kam sa set for the 1 FOR HIS DE 1: men sal 199 Q б Q b o b 이요 ​•E=cAFOBA== TO GAI 0 0 2 Plan Plaza pe Ma ==== FRONT 19/7/ MAZ 1//// 122021] BACK Figs. 1 to 4, Lancashire Boiler with Galloway Tubes, 1. 2 4 3 ( SINA 712 $2286. MEZ DECLA WOMEN TINTEDEG/1 EFFENTIAN) ENNNNGGG 15:05:22 12. 7/1 PAZ YEL 266 SECTION III.-POWER STATION. Table 6.-Some Standard Lancashire Boilers (Two Flues). Diameter of Length. Boiler. ft. in. 6 6 6 6 6 6 6 6 7 0 7 0 7 0 7 0 7 6 7 6 7 6 7 6 8 0 8 0 8 0 8 0 Size. ft. ft. in. 14 × 5 6 16 x 5 6 18 × 5 6 16 x 6 0 18 X 6 0 20 × 6 0 22 × 6 0 20 × 6 6 22 × 6 6 24 × 6 6 26 × 6 6 24 x 7 0 26 X 7 0 28 x 7 0 30 x 7 0 28 x 7 6 ft. 18 21 24 27 21 30 × 7 6 30 x 8 0 32 x 8 0 X 30 x 8 6 24 27 30 21 24 27 30 21 24 27 30 Diameter Length of of Flues. Grates. ft. in. 2 6 2 6 2 6 2 6 2300 2700 3000 3000 3400 3800 4200 4200 4600 5000 5400 5400 5800 6300 6700 6800 7300 2 9 2 9 2 9 2 9 3 0 3 0 3 0 3 0 3 3 3 3 3 3 3 3 Pounds of Water Evapo- rated per Hour. 7800 8200 8400 20 Lb. of Water. 77 77 100 100 113 127 140 140 153 167 180 180 193 210 223 227 245 ft. in. 4 6 5 0 5 6 6 0 5 0 5 6 6 0 6 0 5 0 5 6 6 0 6 0 5 0 5 6 6 0 6 0 261 Horse- Power Diameter at of Flues. 273 280 tt. 2 NNNNNNNNNNNNNNN) CO OD OD os ca 2 2 2 2 2 2 Table 7.-Dimensions, Approximate Horse-Power, &c., of Lan- cashire or Two-Flued Boilers Fitted with Galloway Tubes. 2 2 2 2 2 2 Grate Surface. 2 sq. ft. 22.5 25. 27.5 30. 27.5 30.25 3 3 2 91 in. 1 1 1 4 33. 33. 30. 33. 36. 36. 32.5 35.75 O336 3 3 3 3 6 39. 39. Effective Heating Surface. 22424 Number of Cone Tubes. 4 4 4 6 8 6 5555∞∞∞o 8 sq. ft. 420 493 564 633 541 620 695 775 585 10 673 752 839 626 719 805 898 10 10 12 10 Approximate Weight of Boiler and Mountings for 105 Lb. Working Pressure. tons. cwt. 11 9 12 13 16 15 13 12 15 16 18 15 17 318 362 415 398 457 508 557 559 615 680 745 726 794 852 922 924 20 17 1001 1071 1151 1151 2222 19 20022222-IX 21 12 18 18 12 12 5 11 7 4 1 Heating Surface. 18 In Square In Square Feet. Metres. 29.55 33.04 38.56 36.08 42.47 47.21 51.76 51.95 57.15 63.19 68.58 67.47 73.79 79.18 85.68 85.87 93. 99.53 106.97 106.97 STEAM BOILERS. 267 Diameter of Shell. Cornish Boiler, with Short Smoke Tube, (FIG. 5, page 268.) The boiler has external brick flues, cylindrical shell, and central furnace tube, which in illustration is corrugated. The latter is carried about half way through the shell, and the passage of the gases continued in the short smoke tubes to the end of the boiler. "The direction of gases is through the smoke tubes, two or three times along the external brick flues, and then to the chimney. The average efficiency of this type of boiler is from 55 to 76 per cent. The best results seem to have been obtained with 2 lb. of water evaporated per square foot of heating surface per hour. This type of Cornish boiler, with internal grate, with or without smoke tubės, is used for stationary purposes in England and on the Continent. Table 8.-Dimensions of Cornish Boilers. (Galloways, Manchester.) ft. in. 4 0 4 0 4 0 4 6 4 6 4 6 5 0 5 0 5 0 5 0 5 0 5 6 5 6 5 6 5 6 6 0 6 0 6 0 6 0 6 6 6 6 6 6 7 0 7 0 7 0 7 0 5 6 5 6 5 6 6 0 6 0 6 0 6 0 6 3 6 6 6 6 6 6 7 0 7 0 7 0 7 0 7 6 7 6 8 0 8 0 8 6 Length of Shell. ft. 10 12 14 10 12 14 12 14 16 18 20 16 18 20 **22*22*******.-----22AN***** 18 20 24 26 24 26 28 30 14 16 18 16 18 20 20 24 26 28 30 28 30 30 32 30 Diameter of Furnace. ft. in. 2 14 2 1 2 1 2 41 2 44 2 44 2 7 2 7 2 2 7 2 9 2 9 2 9 2 9 3 3 3 3 04 3 3 3 3 3 3 3 6 3 6 3 6 3 6 2 1 2 1 2 14 2 44 2 4 2 4 2 44 2 7 2 7 2 74 2 74 2 9 2 91 2 94 2. 94 3 3 3 3 3 3 3 6 Number of Cone Tubes. NNNN N N N Y að 2 2 2 2 2 2 3 3 4 4 3 4 4 5 4 4 5 5 5 5 6 5 6 6 7 •22421 4 4 4 4 4 6 6 8 62550500 10 10 10 12 19 Heating Surface. sq. ft. 142 169 196 158 189 219 208 247 281 320 354 300 342 378 420 370 409 455 492 497 539 588 580 632 677 730 318 362 415 398 457 508 557 559 615 680 745 726 794 852 922 924 1001 1071 1151 1151 Water Evaporated per Hour. lb. 800 1000 1200 900 1100 1300 1300 1400 1550 1700 1850 1700 1850 2000 2150 2000 2200 2400 2600 2600 2800 3000 2900 3150 3300 3450 1600 1800 2000 2100 2400 2700 3000 3000 3400 3800 4200 4200 4600 5000 5500 5500 6000 6700 7200 7800 268 SECTION III.-POWER STATION. 6 Fig. 5. Fig. 6. •j% 7/16 211. 5 Shell 1 -4.70€. * 12-16 Manhole O O 020 O О O O • O (~~~~~~4 '10.½-- Types of Steam Boilers. 00 O O O - - - In vi Cornish Boiler with Corrugated Furnace Tube. Marine Type of Boiler. THEFFALENCHILD STEAM BOILERS. 269 ! meter. Dia-Length. Heating Grate ft. in. ft. in. 33 0 8 6 30 0 28 0 8 0 7 6 7 0 66 6 0 5 6 Dimensions of Boiler. 5 0 33 0 30 0 28 0 30 0 28 0 26 0 30 0 28 0 26 0 28 0 26 0 24 0 28 0 26 0 24 0 22 0 20 0 18 0 24 0 22 0 20 0 18 0 16 0 20 0 18 9 16 0 14 0 sq. ft. 1150 1040 966 1066 966 898 910 845 785 Surface. Area. Pipes. 840 780 725 700 650 600 Table 9.-Cornish Boilers. (Yates and Thom, Blackburn.) 520 480 445 405 365 330 400 365 330 300 265 300 270 240 210 sq. ft. 44 41 41 # 80 83 388 272 20000 41 38 38 36 36 33 33 33 30 30 25 18 16.5 15 15 13.5 16.5 15 13.5 12 11 Econo- miser 12.5 12.5 11 10 for one Boiler. Number of 128 128 128 128 128 128 112 112 112 888 NNN JIIIII 00000000 0000 0000 ♡♡♡♡♡ 96 96 96 72 72 72 64 64 64 64 64 64 48 48 48 48 48 36 36 36 36 Evapor- ation. Pounds of Water per Hour. 8000 7250 6759 7450 6750 6250 6350 5900 5450 5850 5450 5050 4900 4550 4200 3600 3350 3100 2800 2550 2200 2800 2550 2300 2100 1850 2100 1850 1650 1450 Indicated Horse- Power at 200 lb. Pressure 12 lb. of Water 640 580 540 per Indi- per Indi- cated Horse-cated Horse- Power Hour. Power Hour. 595 540 500 520 470 430 465 430 405 390 365 335 290 270 250 225 205 185 225 205 185 170 150 170 150 130 115 Indicated Horse- Power at 150 lb. Pressure 14 lb. of Water 570 510 480 530 480 450 455 420 390 415 390 360 350 325 300 255 240 220 200 180 165 200 180 165 150 130 150 130 120 105 If the boiler is worked without an economiser the powers in this table must be reduced one-seventh. With forced draught and higher rates of combustion the power of the boiler is proportionately increased. 270 SECTION III-POWER STATION. Table 10.-Dimensions, Horse-Power, &c., of Standard Galloway Boilers. Size. ft. in. ft. 14 x 5 6 16 × 5 6 18 x 5 6 16 × 6 0 18 X 6 0 20 X 6 0 22 × 6 0 20 × 6 6 22 x 6 6 24 × 6 6 26 X 6 6 24 X 7 0 26 × 7 0 28 × 7 0 30 X 7 0 28 x 7 6 30 × 7 6 30 x 8 0 32 x 8 0 30 x 8 6 Pounds of Water Evapo- rated per Hour. 2300 2700 3000 3000 3400 3800 4200 4200 4600 5000 5400 5600 5800 6300 6700 6800 7300 7800 8200 8400 Horse- Power at Size of Galloway Boiler. 20 Lb. of Water. 77 77 100 100 113 127 140 140 153 167 180 187 193 210 223 227 243 263 273 280 Diameter of Flues. 6 ft. 6 in. in diameter, 22 ft. long 7 ft. in diameter, 28 ft. long 8 ft. in diameter, 30 ft. long ft. in. 2 1 2 1 2 1 2 4 2 4 2 4 2 4 2 73 2 74 2 2 2 9 2 91 2 9 2 9 3 3 04 3 3 3 3 3 6 Evapora- tion in Pounds of Water Evapo- rated per Hour. 4200 6000 8000 Furnaces about one-fifth length of boiler. Indicated Horse- Power of a good Modern Compound Engine the Boiler will Supply Steam for. 250 350 470 Number of Cone Tubes. 9 12 14 14 15 17 20 20 21 24 Table 11.-Average Evaporative Capacity, Thickness and Weight of Galloway Boilers. 27 28 30 33 35 33 35 38 40 40 Thick- ness of Shell Plates. in. Number of Pockets. మనిషా 22424 4 4 4 4 4 4 4 4 4 4 4 4 4 6 4 Heating Surface. 310 364 412 412 461 514 574 584 636 700 766 775 838 905 968 983 1052 1120 1189 1211 Approximate Weight. Weight Weight of of Boiler. Fittings. 10 15 20 tons. tons. 21 2 3 Marine Boiler. (Fig. 6, page 268. The ordinary type of Marine Boiler is shown in the engraving, and the general arrangement of furnace combustion chamber and smoke tubes will readily be followed. As its name implies, its use has been mostly on shipboard, where economy of space is a desideratum, but it has been adopted in several large power stations on shore with satisfactory results. STEAM BOILERS. 271 સ Diameter of the Boiler. Table 12.-Evaporative Capacity and Power of Marine Return-Tube Boilers with Natural Draught. ft. in. 8 6 9 0 9 6 10 0 10 0 11 0 11 0 11 0 11 2 11 6 11 6 11 9 11 9 12 0 12 0 12 0 12 2 12 5 12 6 12 6 12 6 12 9 13 0 13 0 13 0 13 3 13 3 13 4 13 6 13 6 13 6 13 6 13 6 13 14 14 14 14 3 8 0 0 3 14 3 14 3 14 3 Length of the Boiler. ft. in. 8 0 9 0 9 0 9 6 10 0 9 3 0 10 16 0 18 0 12 0 14 9 10 6 17 0 10 0 10 0 10 3 14 0 16 9 11 0 18 6 10 6 10 8 10 6 11 4 16 6 10 0 16 6 9 9 10 0 10 6 16 0 18 0 18 0 9 4 10 7 18 0 10 0 10 2 11 6 17 0 18 0 Number Diameter of Furnace Tubes. of the Furnace Tubes. 1222NANHNEN H 2 63 63 4 4 4 6 6 3 3 3 3 3 3 3 6 6 6 Om ∞ ∞ 3 6 ft. in. 2 5 2 6 2 9 3 0 3 3 3 3 3 3 3 0 3 0 3 10 3 0 3 5 3 0 3 4 0 3 3 0 3 0 3 1 3 1 3 2 3 2 3 2 3 2 3 4 3 3 3 3 3 3 3 4 3 4 3 4 3 4 3 4 3 0 3 5 3 5 3 5 3 5 3 3 5 3 5 Total Heating Surface. 520 650 850 1000 1200 1000 1142 2063 1685 1330 2097 1317 2357 1279 1500 1284 2000 2291 1500 2666 1487 1662 1655 1743 2730 2000 2605 1662 1675 1763 2880 2940 3021 1713 1878 3250 2206 1900 2173 3480 4000 Area of the Fire- Grate. 171 21 281 331 40 331 38 ******ONEL 68 56 44 70 43 78 42 50 42 66 76 50 88 49 55 330788888888togforg 55 58 91 66 86 55 55 58 96 98 100 57 62 63 72 116 133 Evaporative Power of the Boiler in Pounds of Water per Hour. 3,640 4,550 5,950 7,000 8,400 7,000 8,000 14,440 11,800 9,310 14,680 9,220 16,500 8,950 10,500 8,990 14,000 16,040 10,500 18,660 10,410 11,630 11,580 12,200 19,110 14,000 18,230 11,630 11,720 12,340 20,160 20,580 21,150 12,000 13,140 22,750 15,440 13,300 15,210 24,360 28,000 Elephant Boilers. (FIGS. 7 to 10, page 272.) These types are extensively used in France and on the Continent. They are called "Chaudières à bouilleurs.” The external grates are under the “bouilleurs” (heaters), and the whole is enclosed in brick flues. The direction of gases is generally first under the "bouilleurs," then backwards and forwards, below and around the boiler shell. The general construction is to pass them two or three times along it before they are allowed to flow into the chimney. Boiler efficiency varies from 55 to 65 per cent. Evaporation, 4 lb. of water per square foot of heating surface per hour, without feed-water heaters. With the latter, the efficiency rises from 55 to 78 per cent. with 5 lb.water evaporation per square foot of heating surface per hour. 272 SECTION III.-POWER STATION. 276. (217) 7 9 T Fire Grata 11 kate winslette allan att 定 ​8 10 12 01 Figs. 7 to 12. Types of Elephant Boilers. Flus tu Chimnuy STEAM BOILERS. 273 756 II III I III MELL'ETATIO (0751|1312*245019LIST III Fig. 13. Composite Lancashire and Tubular Boiler. Continental Туре. 1 274 SECTION III.-POWER STATION. Elephant Boiler with Smoke Tubes. (Figs. 11 and 12, page 272.) The addition of smoke tubes makes it less necessary to use feed-water heaters, as the temperature of gas is already considerably reduced by the time it leaves the smoke tube. The efficiency varies from 59 per cent. to 70 per cent. without feed-water heaters. With the latter it rises from 61 per cent. to 71 per cent. Water evaporated per square foot of heating surface per hour, 24 lb. to 34 lb. Coal burnt per square foot of grate per hour, 12 lb. to 30 lb. The drawback to this boiler is that it is rather difficult to clean internally. Two-Storey Cylindrical Boiler. (FIG. 13, page 273.) Fig. 13 shows a type of boiler which is very largely used on the Continent, where two-storied boilers are fairly common. It consists, as shown, of a Lancashire boiler below, and a cylindrical boiler with smoke tubes above. Babcock and Wilcox Water-Tube Boiler. (FIGS. 14 to 16, pages 275 and 276.) Standard Land Type.-The construction of this boiler may be practically considered as having three distinct parts, namely: A Series of Inclined Water Tubes placed over the furnace in which the water, being divided into small volumes, is quickly raised to a high temperature, and rises at the front end through vertical connecting boxes or headers, into which the tubes are expanded, up to A Horizontal Steam and Water Drum where the steam separates from the water, the remaining body of water returning through the vertical tubes and headers at the back end into the inclined water tubes, where it is again subjected to the action of the fire, and again passes into the steam and water drum; thus a continuous and rapid circulation is kept up and a uniform temperature maintained throughout the boiler. A Mud Collector is attached to the lowest point of the inclined water tubes, and into this the matter held in suspension in the water is, to a large extent, precipitated by its specific gravity. The inclined water tubes are all steel, and the headers at each end into which they are expanded are sinuous (or staggered) and of mild steel, each header containing one zigzag row of tubes, thus forming a complete section. The headers are provided with hand-holes placed opposite the end of each tube to permit of cleaning, or in case of need, the removal of a tube, each hand-hole being provided with a cap fastened with a wrought steel bolt and clamp, and a cap nut, the hand-hole covers being placed metal to metal. The top ends of each section are connected by tubes to the steam and water drum, not directly, but are first expanded into specially designed crossboxes, which in turn are rivetted to, and extend from, the underside of the drum at each end. The steam and water drum is made of the best selected mild steel, double rivetted for ordinary pressures; the mud drum is made of mild steel, and is provided with ample facilities for cleaning. The entire boiler, except the furnace, is suspended by wrought iron slings from iron girders resting on wrought iron columns, to allow the boiler to expand or contract without straining the brickwork. The boiler and furnace are enclosed in masonry lined with firebrick, the furnace being arranged below the tubes; firebrick baffles compel the hot gases to pass upwards, then downwards, then upwards again before escaping to the chimney. These hot gases strike the tubes at right angles, thus intercepting the radiant heat from the fuel as effectively as possible; the tubes being zigzagged the gases are thoroughly broken up as they rise, and passing into the combustion chamber under the drum they expand and combine before again passing the second and third time through the tubes and on to the flue; thus complete combustion, rapid steaming, and consequent economy are secured. The damper for regulating the draught and flow of the gases is placed in the back chamber, whilst doors for cleaning the tubes and removing soot are placed on one side of the brickwork. A comparison of space occupied is afforded by a new electricity works, where six Lancashire boilers evaporating 48,000 lb. of water per hour are placed beside four Babcock and Wilcox boilers of the above type, evaporating 40,000 lb. of water per hour under the same conditions. The ground space occupied by each range of boilers is as 10 to 4 for the Lancashire, and Babcock and Wilcox boilers respectively. STEAM BOILERS. 275. AHHAROST fosqic 15 .......000. 102 14 TIRE TJER T 时 ​50000 Babcock and Wilcox Boiler. Fig. 14. Standard Land Type of Water-Tube Boiler, showing Integral Superheater. Fig. 15. Water-Tube Boiler, showing Header. 276 SECTION III.-POWER STATION. 17 HEH 16 AUX 22 13385922139513 SETTE JEPEATESPARKLETENES Water-Tube Boilers. Fig. 16. Integral Superheater of Water-Tube Boiler. Fig. 17. The Sterling Water-Tube Boiler. KARUTHUSAYN \WWW A STEAM BOILERS. 277 Crosstype Boiler. The general construction of this form of the boiler is the same, but the drum is placed transversely instead of longitudinally with the tubes, and the whole boiler is constructed in pieces of comparatively light weight suitable for transport in countries where ordinary means of carriage are not available. Portable Boiler. This form is similar to the last described, but can be still further sectionalised in the drum portion, which can be arranged to be rivetted up on site. The boiler is also provided with an iron casing lined with firebrick, and is thus self-contained and independent of the brickwork. This type is also used for countries where transport and facilities in the matter of construction are not available. In addition to the above types, the boilers are arranged with special furnaces for burning sawdust, lignite, rice husks, bagasse, coke breeze, refuse-coal, gas, and oil fuels. Marine Type Boiler. In general construction this is similar to the foregoing, but with the steam and water drum placed transversely and brought to the front of the boiler. The principal difference between this boiler and those already described, is the much larger grate area which enables the boiler to give a greatly increased evaporation per square foot of heating surface compared with the other types. Table 13.-Test Made at the Shoreditch Vestry Electric Light Station, Haggerston. BY MESSRS. KINCAID, WALLER, MANVILLE, AND DAWSON, CONSULTING ENGINEERS. Description of Boiler :-Babcock Marine Type, Fitted with Feed-water Heater and Chain Grate. .. Heating surface Grate surface (8 ft. 6 in. long by 8 ft. wide) Ratio of heating to grate surface Kind of fuel used: West Hallam, screened nuts 2720 sq. ft. 68 1 to 40 6 hours 163 lb. Average temperature of water fed to boiler by heater (average temperature of water supplied to the heater, 78 deg. Fahr.) 120 deg. Fahr. Pounds of coal fired, 13,524 lb., less 7.7 per cent. moisture Pounds of refuse, actual Pounds of combustible, actual Per cent. of ashes, obtained from analysis of coal Coal consumed per square foot of grate per hour Total water evaporated (neglecting water in coal) Water evaporated per hour, actual conditions Water evaporated per hour, from and at 212 deg. Fahr. Water evaporated per square foot of heating surface per hour, Duration of test .. Average observed gauge pressure (atmospheric pressure, 14.7 lb.) ·· .. •• •• .. ·· ·· .. ·· ·· ·· ·· · ·· • ·· ·· actual conditions Water evaporated per pound of coal, actual conditions of feed- water, 78 deg. Fahr. Water evaporated per pound of coal, from and at 212 deg. Fahr. Water evaporated per pound of combustible, from and at 212 deg. Fahr. Temperature of boiler room Temperature of flue gases Forced draught. Calorific value of coal.. Efficiency ·· ·· ·· ·· • * ·· • .. .. • • • ·· ·· .. ·· •• 10.16 lb. 75 deg. 590 deg. ...38 in. in water. 11,219 B.T.U. 80.3 per cent. .. 12,483 lb. 1,008 Ib. 11,475 lb. 11.44 per cent. 30.6 lb. 98,000 lb. 16,333 lb. 19,436 lb. 6 lb. 7.85 lb. 9.34 lb. 278 SECTION III. POWER STATION. Table 14.—Ĺist of Standard Sizes of Babcock and Wilcox Patent Water Tube Steam Boilers. W.I.F. Type. Heating Grate Surface. Area. Square Square Number Feet. Feet. of 119 150 181 219 293 5.20 6.25 7.28 8.33 10.64 10.64 11.97 13.30 13.30 13.30 343 401 460 526 593 735 16.33 870 19.15 19.15 983 1098 1218 1265 1411 1426 1619 1741 23.00 23.00 26.50 26.50 26.50 30.00 36.65 so so so 3 4 4 4 5 6 6 Sections. 12 Height. Length. ft. 4 CTA HA 67∞∞1 ∞ — — 0aaa7 7732 4 9 9 9 ft. 6 8 8 10 10 12 12 14 14 14 14 16 16 16 18 18 18 00000 18 18 16 Number of 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 INV1 2 Drum. Dia- meter. in. 24 24 24 24 30 30 30 30 30 30 36 36 36 36 36 36 36 42 42 36 Length. ft. 12 10 12 4 16 17 19 19 19 14 5 19 in. 14 7 CO HILO £ £~ O on so on so ****** 23 23 3 23 23 21 4 7 2 3 3 21 4 21 4 21 4 23 7 3 3 -77774 Weight of Boiler. Tons Gross. PRONG-PROD- 6666T CTIA IN IC 4 6 -des 71 8 101 101 111 12} 131 14 -CON 141 142 19 Tons Net. 3 湯​4+ 5 51 1-ig coment 00! 92 10 10 11 121 13 134 131 17/ Brickwork. Number Number of of Fire- Ordinary bricks. Bricks. 930 1120 1210 1420 1450 1650 2490 2890 3010 3190 3260 3490 3630 3760 4270 4200 4350 4430 4500 4080 2,830 3,260 3,720 4,400 4,500 5,100 7,620 8,900 9,292 9,700 10,090 10,860 11,270 11,710 13,160 12,970 13,460 13,740 13,940 12,210 Space, Including Brickwork. Length. ft. in. 9 6 6 6 6 6 6 0 0 0 0 0 21 0 21 0 21 0 23 0 23 0 23 23 0 11 11 13 13 15 16 19 19 19 19 Oooo 23 0 21 0 Width. ft. in. 4 4 4 5 5 5 4 5 5 5 5 1O 1O 1O 1O — — 00 00 00 00 00 5 -778 5 10 0 8 8 8 6 6 10 6 10 8 3 6 10 6 10 Poaaad555 w 8 0 STEAM BOILERS. 279 Table 14.-List of Standard Sizes of Babcock and Wilcox Patent Water Tube Steam Boilers. W.I.F. Type.—Continued. Heating Grate Surface. Area. Square Square Number Height. Length. Feet. Feet. of 1790 1827 1966 2010 2197 2255 2437 2531 2690 2823 2852 3140 3240 3580 3654 4020 4510 4780 5540 6182 35.00 33.50 36.65 39.00 44.00 43.00 44.00 51.00 51.00 51.00 51.00 59.5 58.00 67.5 65.00 76.00 78.00 76.00 76.00 84.00 8 9 12 9 12 10 12 14 12 14 14 14 16 16 18 18 2302 18 Sections. 18 ft. 10 9 8 10 9 10 9 8 10 9 y 10 9 10 9 10 10 12 14 14 ft. 18 18 16 18 16 18 18 18 18 18 18 18 18 18 18 18 18 18 18 18 Number Dia- meter. of 1 HANHNHNNNNNNNNNN NOIN N 1 2 1 1 2 2 2 2 2 Drum. 2 in. 42 48 36 48 36 54 36 36 36 36 ************ 42 42 42 42 48 48 54 48 48 54 Length. ft. 23 23 21 23 **X*XXXX 21 23 23 23 23 7 23 7 23 7 23 7 23 7 7 7 23 23 in. 23 77474777 7 23 7 •••II• 7 23 23 23 7 Weight of Boiler. Tons Gross. 161 17 19 191 201 201 22 251 251 263 271 32 34 39 38 42 461 Tons Gross. 151 16 17 18 19 19 201 23 231 23/1 241 251 25 27 301 32 37 36 40 441 Brickwork. Number Number of of Fire- Ordinary bricks. Bricks. 4640 4680 4120 4680 4270 4440 4710 4690 4880 4890 5020 5060 5060 5200 5280 5280 5640 5680 6020 7070 14,480 14,420 12,600 14,420 12,310 15,520 14,500 14,670 15,120 15,210 15,480 16,030 15,980 16,520 16,700 16,700 18,140 18,310 19,680 21,210 Space, Including Brickwork. Length. ft. in. 23 0 23 0 21 0 23 0 21 0 0 0 0 ( 0 23 23 23 23 23 23 0 23 0 23 0 23 0 23 0 23 0 23 0 23 0 23 6 23 6 : Width. ft. in. 10000000000 8 0 ON 7 4 7 4 2 $ 11 6 10 4 11 6 11 6 11 6 12 8 12 8 13 10 13 10 15 0 13 10 13 10 15 0 4 280 SECTION III.-POWER STATION. The Sterling Boiler. (FIG. 17, page 276.) This boiler consists of three upper or steam drums, and one lower or mud drum, connected together by means of tubes slightly bent so as to allow them to enter the drums normal to their periphery. All of the upper or steam drums are connected by steam circulating tubes, but the front and middle drums only are connected by water circulating tubes. The tubes used are 34 in. in diameter, and are made of lap-welded mild steel, subjected to a cold water pressure test of 1500 lb. per square inch. The drums are made of flange steel. A 200 horse-power boiler can be built to occupy from 12 ft. to 20 ft. in height, 10 ft. to 15 ft. in width, and 14 ft. to 17 ft. in depth. It is, therefore, equally well adapted to boiler rooms having low ceilings and ample width, as well as to those having little width and ample height. In tests for economy, the boiler has evaporated as high as 12.49 lb. of water, from, and at, 212 deg. per pound of fuel, whilst in capacity tests it has been forced as high as 133 per cent. above its rating. The boiler is sustained entirely independent of the brickwork. The three upper or steam drums are supported by wrought-iron beams, resting on wrought- iron columns, with cast-iron bases; the mud drum is suspended and left free to allow for contraction and expansion. Owing to this arrangement, the varying temperatures, extending from about 500 deg. Fahr. at the out-take of the stack to 2000 deg. Fahr. or more at the furnace, produce little strain. The Fraser Dry Back Multitubular Boiler, with Air Heating Arrangement. (Figs. 18 and 19, page 282.) Method of Working.-The boilers are stoked in the ordinary way, the flames passing over the bridges to the back combustion chamber S, which becomes incan- descent and thereby ensures perfect combustion before the gases enter the tubes T; after passing through these fire tubes to the front smokeboxes R, they return through the side flues, past the outside of the air heating tubes N, and out to chimney shaft or economiser flue at O. The air for combustion passes in at the back of boilers at M, through the air heating tubes N, and out at L to the front hot air chamber P, thence the hot air passes under the fire bars, and also through the smoke consuming regulating valves Q as usual. Table 15.-Average Evaporative Capacity and Power of Stationary Boilers of Locomotive Type. WITH NATURAL Draught anD ALSO WITH FORCED DRAUGHT, EQUAL 1 IN. of WATER, PRODUCED BY A STEAM BLAST IN THE CHIMNEY. Dia- Length meter of the Barrel of the Boiler. ft. in. ft. in. 3 5 7 3 3 7 7 9 4 2 8 3 4 3 8 9 4 6 4 8 4 11 5 0 5 2 of the Total Area of Boiler Heating the Fire- between Surface Grate of the the Tube- Boiler. Plates. of the Boiler. 10 7 9 9 10 0 10 6 10 9 sq. ft. 270 318 390 450 714 675 735 818. 885 sq. ft. 10 11 13 15 20 21 22 23 26 With Draught Forced With Natural Draught. by a Steam Jet in the Chimney. Evapora- tive Power of the Boiler Pounds of Water per Hour. in lb. 1080 1270 1560 1800 2850 2700 2940 3270 3540 easily Power of Compound Indicated Horse- Engine which the Non - Condensing supply Steam for. Boiler will I. H. P. 40 47 58 67 105 100 109 120 130 Evapora- tive Power of the Boiler in Pounds of Water per Hour. lb. 1890 2230 2730 3150 5000 4725 5145 5726 6200 easily Power of Compound will Indicated Horse- Engine for which the Non - Condensing supply Steam. Boiler I. H. P. 70 82 100 113 185 175 190 212 230 STEAM BOILERS. 281 400 999 Portable Engine Boilers. (FIG. 20, page 282.) The portable boilers are usually of the locomotive type. A boiler for 8 nominal horse-power is shown in Fig. 20. The barrel is 2 ft. 6 in. in diameter, and 6 ft. 4 in. long, of mild-steel plates in. thick. The fire-box shell is 3 ft. 14 in. wide exter- nally. The fire box is 2 ft. in. long, 2 ft. 7 in. wide, and 2 ft. 10 in. high. The water space at the sides of the fire-box is 2§ in. wide. The fire-box plates are 16 in. thick, and the roof is supported by three girder stays. There are 28 tubes of wrought iron 6 ft. 10 in. long, 24 in. external diameter, and in. thick. The tube plates are in. thick. The total heating surface of the boiler is 167 square feet. The area of the firegrate is 5.27 square feet. The chimney is 10 in. in diameter. Boilers of portable engines have from 17 to 20 square feet of total heating surface per nominal horse-power, and a ratio of heating surface to grate area ranging from 23 to 30 square feet. They are covered with felt, or other non- conducting material, and lagged with wood cased with sheet iron. Table 16.-Lancashire Boilers (no Smoke Tubes). 16.5 35 17.8 25 15 26 32.9 23.4 355 860 582 612 477 965 640 21 886 32 1050 34.8 1068 36.5 907 33.2 1075 Square Feet of Heating Surface. 33 30 900 1270* 38 8888888 19.7 30 Square Feet Grate Area. 26 21 25 19.1 26 24.5 33.8 32.6 Length in Feet. 26 20.5 20 .. 5.2 7.4 014 ·· .. 6.5 7 6 .. 32.8 30 NOTE.-No economiser. 6.6 6.5 6.25 7.2 6.6 6.8 8.5 140 92 46 52 Diameter in Feet. 236 9.7 945 19.4 10 · 1345 21.5 1991 37.5 12.8 19.7 7.2 7.2 1345 23.5 2044 40.2 ·· 1600 33.5 12.5 16.5 6.2 7.0 2100 53.7 18 16.4 6.5 68 69 2.7 2.0 5.5 6 ·· 52.5 93 85 85 80 61 8827728 Table17.-Two Storey-Lancashire Below and Smoke Tubes Above. 96 102 100 168 82 758 953 3200 4186 5033 6100 6300 7200 7810 * This boiler has smoke tubes. 110 53 1100 1230 1438 1673 1804 2050 2500 126 130 690 1800 2150 1.96 0.95 3.1 1.43 2.5 26 3.8 2.14 3.8 3.7 4 3293 3500 4300 5100 5900 4.73 6.7 5.9 8 6.1 2.9 1.9 1.6 1.6 2.6 2.1 3.2 2.8 12,135 12,500 12,700 9.220 12,366 13,700 11,560 9,658 12,300 8,015 13,980 14,646 11,360 11,800 14,100 13,050 12,320 9,334 11,900 10,310 11,570 12,130 12,400 4,370 282 SECTION III. -POWER STATION. j 18 19 267 MODE R 0,00 200%- P L ·2·7% $ple. 1-832-* N 20 6.4 *AIR HEATING||TUBES Explo Types of Steam Boilers. Figs. 18 and 19. Fraser Multitubular Boiler. Fig. 20. Portable Engine Boiler. 0 (~--~1.8-2 Apla STEAM BOILERS. 283 Square Feet of Heating Surface. Table 18.-Return Large Smoke Tubes (Cylindrical American. Type). 877 329 728 728 939 939 1692 Square Feet of Heating Surface. Square Feet Grate Area. 1374 1893 2050 38.6 25 25 58 53 64.5 Square Feet Grate Area. 34 33 28 Type of Boiler. ·· 16. 20 18 18 24 24 20 ·· ·· 16 16.5 17.0 Length in Feet. 27 30 Lancashire Do. Egg-ended 30 6 Marine Thornycroft Water-tube 15 13 12 103 Table 19.-Elephant Boilers (with Rather Large Smoke Tubes). ཋ Dimen- sions of Boiler. Pounds per Working Pres- sure by Gauge. Diameterin Feet. 6 3.8 4.5 4.5 Inch. 5 5 6 6 7 6.6 Approx. Weight. 69 74 Boiler. Water. Steam. 73 71 Tons. Tons. Pounds. 98 99 95.5 Table 20.-Energy in Steam Boilers Available in the Event of Explosion. 96 85 67 1,840 2,929 Water. 4,412 5,420 6,840 7,610 10,697 Foot- Tons. 4090 5495 5290 Available Energy. Steam. Foot- Tons. Total. 100 |12|11| 46 93,000 2351 150 24 17 110 200,991 6606 6606 80 5, 10 88 64,740 4083 150 39 24 100 289,663 6005 205 14 130 2.1 8.86 6.1 7.5 7.3 8.1 6.2 3.0 2.9 3.1 Foot- Tons. 13,361 11,100 14,700 15,125 9,722 Feet. 95,351 7,628 207,597 8,473 68,823 12,513 295,668 7,581 28,420 2060 30,480 1,855 9,976 10,980 14,260 12,700 14,530 Height to which Energy would Gunpowder Equivalent to Total Avail- able Energy. Lift Boiler. Pounds. 795 1730 574 2464 253 284 SECTION III.—POWER STATION. I Table 21.-Efficiency and Coal Consumption, &c., of Various Types of Boilers. (Bryan Donkin.) Class of Boiler. Cornish, no smoke tubes .. Lancashire, no smoke tubes, two internal furnaces Lancashire, with smoke tubes * Two internal furnaces + Three "" Heating Total Surface. sq. ft. 890 1.5 to.35 890 .3 .5 to.4 890 645 0.3 0.3 0.3 0.8 1008 1040 1040 907 907 1130 or Vacuum Draught in Chimney in Inches of Water. 355 355 355 1614* 1186† 1186+ ∞∞ 176 0.8 0.7 0.7 0.6 .. Efficiency of Boiler. • per cent lb. per | deg. F. sq. in. 64.0 105 341 64.5 106 342 66.0 103 340 73.5 120 350 62.4 157 369 63.1 157 369 67.2 155 368 68.3 155.5 368 48.3 125 352 52.0 122 351 115 347 52.8 53.7 60.2 74.3 Steam Pressure by Gauge. 66.1 66.7 Steam Tempera- ture. 137 142 140 156 100 100 359 362 361 368 338 338 Pounds of Water per Pound of Coal from and at 212 deg. Fahr. 6.3 7.4 9.0 10.3 8.3 10.6 cold feed 11.38 11.68 6.9 7.1 7.3 6.95 7.06 7.93 9.3 9.3 9.3 Name of Coal or Fuel Bohemian lignite Moravian lignite Heating Value of Fuel in B.T.U. per Pound. Ashes or Clinkers in Fuel. " Burnley 19 per cent 9,550 3.4 11,100 3.7 2.7 Silesian hard | 13,150 Clean Ruhr 13,712 8.0 12,963 nuts Shaw slack, Wigan Shaw slack 12,963 Townley slack 13,843 13,843 Slack'Bolton 14,659 14,342 Maude rough 12,000 small 43.7 23.2 29.5 24.5 24.0 5.5 24.0 7.5 14.0 8.25 13.5 11.0 20.3 11.25 19.0 10.7 25.0 5.5 Prussian coal 12,700 12,700 12,700 12,070 13,492 8.5 13,492 9.8 .. per Pounds of Fuel Square Foot of Grate per Hour. Burnt B.T.U. per Pound of Water Eva- porated. ·· 17.6 18.5 15.0 17.5 19.3 18.8 1515 1500 1462 1330 1564 1224 1218 1185 1465 2021 1645 1827 1798 1600 1300 1450 1450 T | STEAM BOILERS. 285 Table 21.—Efficiency and Coal Consumption, &c., of Various Types of Boilers.—(Continued.) (Bryan Donkin.) Class of Boiler. Dry back, two internal furnaces, and smoke tubes Wet back marine, two or more internal furnaces Locomotive and agricultural Locomotive running on rails Two-storey, one internal furnace…. Heating Total Surface. sq. ft. 930 3324 1580 2240 265 859 249 202 202 125 218 192 211 or Vacuum Draught in Chimney in Inches of Water. ·· 0.31 0.25 0.5 .. 1.0 0.2 0.26 227 1358.5 7 to 15 1358.5 6.5,, 11 1358.5 6.5 ,, 14 1358.5 800 4 to 7 0.6 Efficiency of Boiler. per cent lb. per sq. in. 160 145 165 140 188 130 188 195 197 125 73.4 62.0 69.2 70.0 .. 80.7 ·· : 69.6 78.6 79.4 83.9 84.0 66.6 70.0 71.1 Steam Pressure by Gauge. 75.5 69.5 125 250 120 150 169 167 171 170 143 Steam Tempera- ture. deg. F. 370 363 373 361 383 356 383 385 386 352 352 405 350 366 374 373 376 374 362 Pounds of Water per Pound of Coal from and at 212 deg. Fahr. 9.55 8.23 10.63 9.6 11.71 12.2 11.7 11.3 11.0 12.27 12.26 12.96 12.99 9.3 10.3 10.4 10.9 8.2 Name of Coal or Fuel. Scotch Scotch Tyne Pittsburg Powell Duffryn Nixon's Navigation Powell Duffryn Welsh "" Powell Duffryn Welsh "" 99 " ·· Heating Value of Fuel in B.T.U. per Pound. ·· ·· 12,770 14,830 13,226 14,200 15,560 14,200 13,600 13,600 14,940 14,940 14,940 Ashes or Clinkers in Fuel. per cent 6.5 3.0 3.0 4.5 5.7 : ·· 14,940 14,940 12,840 13,903 13,583 13,477 ·· Small ordinary 13,300 6.0 .. ·· ·· •• per Square Foot of Pounds of Fuel Grate per Hour. Burnt 40 to 45 19.0 22.5 12.7 14.8 35.5 15.0 16.8 17.8 17.5 13.5 13.0 12.0 8.7 81.0 70.0 72.0 72.5 20.0 B.T.U. per Pound of Water Eva- porated. 1553 1396 1380 1210 1275 1212 1204 1236 1218 1218 1153 1150 1381 1350 1305 1237 1675 286 SECTION III. POWER STATION. Table 22.—Efficiency and Coal Consumption, &c., of Various Types of Boilers.—(Continued). (Bryan Donkin.) Class of Boiler. Two-storey, one internal furnace.. Two-storey; two internal furnaces; Lancashire below smoke tubes above Two-storey; external furnace and smoke tubes Babcock and Wilcox * Two grates .. ·· Heating Total Surface. sq. ft. 800 2100 1347 1345 1856 882 882 1667 1667 1667 1619 983 1614 1614 2727 3737* or Vacuum Draught in Chimney in Inches of Water. 0.6 0.25 ·· ·· :: 0.5 0.5 0.5 .. 0.4 ·· 0.5 Efficiency of Boiler. 73.0 79.0 per cent Ib. per deg. F. sq. in. 75.4 141 76.7 130 70.6 147 73.8 168 75.0 144 61.6 62.9 *65.8 70.5 72.6 54.5 58.6 72.2 Steam Pressure by Gauge. 74.0 136 138 148 142 140 144 155 155 166 154 Steam Tempera- ture. 157 361 11.7 355 3.0 364 7.7 370 9.1 363 5.5 356 357 365 362 360 362 368 368 373 368 Pounds of Water per Pound of Coal from and at212 deg. Fahr. 369 5.0 5.25 9.4 9.4 9.1 10.8 7.2 NN∞ 242 7.7 8.2 11.2 Name of Coal or Fuel. Nixon's 15,000 Navigation Saxon brown 4,370 coal Washed small | 10,640 Austrian Brown coal and slack 11,900 7,192 Turf "" Gas coke Heating Value of Fuel in B.T.U. per Pound. Prussian coal Vienna gas coke New River coal 6,450 6,450 "" "} 13,404 Good gas coke 12,800 Nixon's Navi- | 14,400 gation, Welsh 14,656 14,376 12,700 12,700 11,065 14,559 Ashes or Clinkers in Fuel. per cent 4.0 .. ~~ 7 · 7 9.3 5.7 11.8 8.5 7.0 .. ·· 5.0 Pounds of Fuel per Grate per Hour. Square Foot of Burnt 20.8 36 18.7 13.4 30.9 23.0 28.0 24.5 27.0 15.3 19.0 21.0 20.0 17.0 13.0 25.5 upper, 12.0 both B.T.U. per Pound of Water Eva- porated. 1282 1457 1384 1308 1305 1290 1230 1560 1530 1475 1332 1762 1650 1350 -1300 STEAM BOILERS. 287 Table 23%-Comparison as regards Efficiency and Value of Heating Surface in Various Types of Boilers. Type of Boiler. Cornish boiler Cornish boiler with one set of smoke tubes at end of furnace Lancashire mechanical stoking with econ omiser .. ► } .. • Ditto, hand stoking with economiser Ditto, hand stoking without economiser . Ditto, with short smoke tubes Ditto, with three furnace tubes Dry back Wet back, marine type ·· • •• ·· •. ·· ·· Locomotive boilers • Two Storeyed. Cornish, with short sinoke tubes and plain cylindrical above Cornish below, smoke tubes above.. Lancashire below, smoke tube above Ditto, ditto, with two water lines, one in each boiler Elephant boilers Ditto, with smoke tubes Babcock and Wilcox Stirling .. .. ·· •• D L ·· .. .. ·· ·· •• S • • ·· .. NHP = NHP = When D1 = diameter of flue in feet. .. = ► • ·· ·· • Efficiency in Per Cent. 50 to 82 55 to 67 62 to 87 Average83 70 to 77 65 to 75 61 to 74 55 to 65 62 to 70 59 to 84 56 to 75 Average 68 61 to 81 Average 70 55 to 78 59 to 79 74 to 81 74 to 77 Cornish Boilers. English Nominal Horse-Power of Boilers Plain Cylindrical or Egg-Ended Boilers. DX L 6 _(D + D¹) × L 8 When NHP = nominal horse-power Pounds of Water Evaporated per Square Foot of Heating Surface, Giving Best Re- sults. 2 to 3 2 Lancashire Boilers. NHP (D+ 2 D¹) × L 8 4 to 5 to 5 4 3 to 4 Average 2 5 to 6 = diameter of boiler in feet length of boiler in feet. 3 to 4 22 to 10 (best results with 3) 1 to 5% (best with 2) 3 to 6 3 1000g 2 4 to 5 24 to 4 2 to 4 3 Vertical Cross-Tube Boilers. NHP = .(D + F + D¹ + U) × L 10 When F = diameter of fire-box in feet U = diameter of uptake in feet D1 = diameter of cross-tubes in feet. of Coal Burnt per Square Foot Grate Sur- Pounds face per Hour, Giving Best Re- sults. 10 to 20 9 to 56 15 to 30 15 to 22 19 to 31 9 to 30 35 13 to 31 10 to 18 12 to 30 13 to 47 288 SECTION III.-POWER STATION. Vertical Tubular Boilers. NHP =(D + F + T) × L 12 When T = diameter of all the tubes in feet. Table 24.-Approximate Weight of Boilers in Cwts. Vertical cross-tube boilers Egg-ended boilers Cornish boilers Diameter in feet Length in feet. Vertical tubular boilers Lancashire boilers .. Return-tube boilers Portable engine boilers under 10 horse-power Portable engine boilers 10 horse- power and upwards ·· -S+ ·· 299 ·· ·· 11 11 11 11 }} !! "" "" "" "" W "" "" "" D. "" "" "" "" "" "" "" X X .50 X X .95 X X 1.10 X •S• X 1.34 X X 2.00 X X 2.20 X X 2.70 X " 21 "" "" "" 99 "1 BOILER SETTING. The principal objects to be arrived at in setting boilers are: Accessibility of the flues for examination and cleaning; allowing the minimum of brickwork in contact with the plates so as to avoid concealment of the plates and harbouring of moisture; deflecting and distributing the gases in such a manner as to obtain the greatest useful effect, and obviate as far as practicable unequal expansion and contraction of the shell without checking the draught. It is usual to seat the boiler on special fire-clay blocks, so that it is supported on a narrow surface on each side, the surface in contact with the plates being from a mere circular ridge in the case of Poulton's patent seating blocks up to 3 in. and 4 in. wide in the ordinary blocks. The blocks are shaped so as to support the weight of the boiler without "" "" "" "" "" f Length in feet of the barrel. 18 crushing, and to give the greatest amount of room in the side flues and conduct away from the plates any moisture which may run down the sides of the boilers. Special arched fire-clay tiles are also used for the flue covers. The products of combustion on leaving the flues should first pass under the bottom of the boiler, splitting at the front end and flowing along the side flues to the back end and thence to the chimney. By this means the bottom and sides of the boiler are maintained at a more equable temperature than would be the case if the gases passed through the side flues first. The top of the side flues should not be above the level of the furnace crowns. Care should be taken that the seating blocks and flue covers do not come in contact with the longitudinal seams of the shell. The front cross wall should be clear of the shell angle iron, and recessed so as to leave the elbow pipe to the blow-off cock free for expanding and contracting, and the connection to the shell accessible for examination. The following table gives the standard dimensions: STEAM BOILERS. 289. Table 25.-Flues for Lancashire and Cornish Boilers of Various Diameters. (FIG. 21, page 288.) D ft. in. 3 6 4 0 4 6 5 0 5 6 6 0 6 6 7 0 7 6 8 0 8 6 "" "" 4 in. from outside of wall 16 28 ** I د. "" Place of Observation. (282) S "" 12322 "} 12 12 12 12 12 12 12 Sharp angles and sudden enlargements in the flues should be avoided. The flues should be faced with firebrick, and no lime mortar should be used, but only fire- clay. The boiler should be about 1½ in. lower at the front end to allow of its being drained through the blow-off cock. Table 26.-Temperatures of Brick Setting of Horizontal Return Tubular Boiler. W V • ft. in. 1 9 2 0 2 3 2 6 2 9 3 0 3 3 4 0 4 3 4 6 4 9 22 B Inclination "ic Inches per foot. ft. in. 1 9 1 9 deg. 140 285 297 1 9 2 0 2 0 2 3 2 3 2 6 lakwatery 2 6 2 6 2 9 Minimum Maximum Temperature. Temperature. FIRE GRATES AND FURNACES. Fire Grate of Steam Boilers. (Fig. 22.) The length of the fire grate is, in some cases, 7 ft. ; it is preferably limited to 6 ft., that being the greatest length of fire that can be readily worked by a stoker. Grates of these lengths cannot, however, be efficiently fired, and in order to enable the fire to be properly stoked, the length of fire grate should not exceed 4 ft. 6 in., or 5 ft. as a maximum. deg. 182 353 460 A short fire grate is more economical than a long one; the grate should not be longer than necessary to burn the required quantity of fuel per hour. The width of the fire grate is limited by the diameter of the furnace tube in internally-fired boilers, and by the diameter of the shell in externally-fired boilers. The fire grate of internally-fired boilers is inclined downwards from the front to the back (Fig. 22), at the rate of from in. to 1 in. per foot in length of the grate. L 290 SECTION III.-POWER STATION. 1 Fire Bars. (FIG. 23.) These are generally made of cast iron, and of the form shown in Fig. 23. The following are approximate rules for proportioning common cast-iron fire bars :-- 17849 1/2 L L L = length of fire bar (usually from 2 ft. to 3 ft.) L + 1} in. D d -16 32 + & in. t₁ = t. t = in. to 3 in. t1 b = in. to in., depending on the kind of fuel and the force of the draught. The area of the air spaces between the fire bars varies from .15 to .4 of the grate area. The average of a large number of examples gave area of air spaces equal to .28 of grate area. 23 Fire Bridges of Steam Boilers. (FIG. 24.) The fire bridge at the back of the grate is employed to prevent the fire from being pushed over the grate bars. It is composed of fire-brick laid on a wall in 24 externally-fired boilers, and laid on a casting fixed in the furnace tube of internally- fired boilers. Space above the Fire Bridge. The space provided above the bridge for the escape of the fuel gases from the furnace depends upon the rate of combustion. It may generally be from ⇓ to the area of the fire grate. Split Bridges. (Fig. 25.) The fire bridge of a steam boiler is sometimes split or formed hollow, for the purpose of admitting air at the back of the fire to promote combustion and prevent 25 STEAM BOILERS. 291 the emission of smoke. A split bridge is shown in Fig. 25. It consists of a box casting, forming an air chamber, with a perforated air-plate at the back, and having a door at the front. Furnace for Burning Saw-Mill Refuse. (Fig. 26.) A furnace for burning saw-mill refuse is shown applied to externally-fired multitubular boiler (Fig. 26). The furnace is 7 ft. 6 in. long, 5 ft. 6 in. wide, and 3 ft. 6 in. high, measured from the top of the back end of the fire grate to the roof of the furnace, which is arch-shaped in section. The dead plate at the front of the furnace is 12 in. wide. The fire bars are 5 in. lower at the back end than at the front. They are 7 in. deep and 6 in. wide on the top, and have air spaces in. wide and 4 in. long, arranged diagonally across the bar and in a different direction in alternate bars, so that the air spaces of two contiguous bars form a V shape. 26 Boiler •-.4.6° Combustion Chamber ----7·6---. Fire Grate Water Trough (281) There are narrow air spaces at sides of bars. There are two compustion chambers the flue opening between them is 3 ft. wide and 1 ft. 9 in. deep. The furnace and combustion chambers are lined with fire brick on the inside, and they are cased with strong iron plates on the outside. A water trough is placed under the fire grate. The fuel is fed into a hopper at the top of the furnace. Air is supplied through an opening in the fire bridge, and is regulated by a door. The products of combustion pass from the furnace through the combustion chambers, where ashes and dust carried in suspension are deposited, then under the boiler to the end plate, then into and return through the tubes to the end of the boiler from which they started, and finally enter the flue leading to the chimney. Dust Fuel Furnace. Dust fuel is generally either coke breeze and coke dust, or coal dust. It requires a fire-brick furnace to facilitate combustion, and that the grate bars should be thin and close together, so that as much opening as possible is allowed for air to enter the furnace, and the fuel cannot fall through the grate. More air is required for the combustion of dust fuel than for large coke or coal, because it lies closer on the bars; and because a larger quantity has to be consumed on a certain unit of grate area in a given time. The way of securing the additional air required is by means of forced draught. This forced draught can be produced by a fan, by blowers fixed underneath the grate bars, or by creating a suction at the rear end of the boiler, increasing the velocity of the gases. The latter is called induced draught. In an installation of one or two boilers, steam-jet blowers are the most con- venient. No motive power is required, and the forced draught can be stopped at a moment's notice by shutting the valve which supplies steam to the jets. A boiler fitted with blowers can not only burn dust fuel, but also large fuel, particularly anthracite coal. Furnace for Lignite (Brown Coal). The best arrangement of furnace for burning lignite (brown coal), a fuel largely used in Germany, Austria, France, and Italy, is a step-grate furnace. This fuel has a very low calorific value, and hence the furnace must be constructed so that the maximum quantity can be consumed in a given time. 2 The construction of furnace is similar to that for saw-mill refuse. The angle of the grate and the arrangement of fire doors differ from that of the furnace as made for saw-mill refuse. 292 SECTION III.-POWER STATION. MAN-HOLES AND SAFETY VALVES. (Figs. 27 to 38.) Man-Holes. (Figs. 27 to 31.) The principal man-hole in a boiler should be 16 in. in diameter if round, and 16 in. x 12 in. if oval. The joint for the cover should be a faced joint. The 27 Gast Icon Cast Steef Wrot Iron 16 dia 29 Wrot Iron ❤ Area of bolts = CAST IRON WROT IRON T 128 Number of bolts = BAN 189 28 30 31 14½ MANHOLE STRENGTHEMING 22D -1!/*--*| RING 16-1 Bolts cover for a circular man-hole 16 in. in diameter is of wrought iron, mild steel, or cast iron in. to 1 in. thick, and generally held by 16 bolts 7 in. to 1 in. in diameter. Man-holes in the ends of boilers are from 14 in. x 12 in. to 15 in. x 11 in. Mud-holes and hand or sight holes are from 6 in. x 4 in. to 9 in. x 6 in. Various types of cast and wrought-iron and steel man-holes and covers are shown in Figs. 27 to 31. Proportions of Bolts. (Hutton.) The total cross-sectional area in square inches at the bottom of the thread of the bolts for a steam pipe, and the number and pitch of the bolts, may be found by the following Rules:- The total load on the bolts in pounds per square inch Working load on the bolts in pounds per square inch स Total cross-sectional area of the bolts in square inches Cross-sectional area of one of the bolts in square inches STEAM BOILERS, 293 Pitch of bolts = Circumference of the circle of the centres of the bolts Number of the bolts The sectional area and number of the bolts required for the blank flange of the branch of a steam pipe of 10 in. internal diameter, for a working-pressure of steam of 150 lb. per square inch, are as follows:- The surface of the blank flange presents to the steam pressure an area of 10 in. x 10 x.7854 = 78.54 square inches. The flange resists a total pressure of 78.54 square inches x 150 lb. per square inch = 11,781 lb. If iron bolts be used, the total cross-sectional area of the bolts required=11,781 lb. ÷ 2,500 lb. per square inch, the area of working load on the bolts = 4.712 square inches. = 4.712 square inches. If Whitworth bolts of 1 in. diameter be used, the number of bolts required is=4.712 square inches÷ .554 square inch, cross-sectional area at bottom of thread 8.5, or 9 bolts are required for this flange; but 10 would be used in practice, for securing a tight joint. If the diameter of the circle of the centres of the bolts in the flange be 154 in., its circumference is = 15.25 × 3.1416 = 47.91 in., and the pitch of the bolts is = 47.91 ÷ 10 – 4.791 in. Safety Valves. (FIGS. 32 to 38.) The office of a safety-valve on a steam boiler, is to discharge steam rapidly, when pressure within boiler reaches a fixed limit, that no important increase of pressure can then occur, however rapidly steam may be made. It should be constructed and arranged so that, in case of accident, it may be opened by hand and the steam pressure lowered very rapidly, even when the fires in the boilers are burning brightly and generating steam with maximum rapidity. The size of a safety valve is determined by the character of the valve itself, by the pressure at which the steam is to be discharged, by the difference permissible between the pressure at which the valve is to be opened automatically, and that at which it is intended to be capable of discharging steam as fast as the boiler can make it. It has been common in the United States to allow one square inch of area of valve opening for 25 square feet of heating surface, or a ratio of 0.0003, nearly; while another rule gives one square inch to three feet of grate-surface: an English rule allows an area equal to a half square inch per each half square foot of grate, or 0.003 the grate-surface, nearly; while still another authority nearly doubles the area of valve; Professor Thurston has been led by experience to adopt the rule: Multiply the maximum weight of steam which the boiler is expected to generate per hour by 5, and divide by 10 times the gauge pressure increased by 10 in pounds per square inch; or, divide that weight by twice the latter quantity, or: 290 *--F· WL P = AF a = where w is the maximum weight of steam made per hour in pounds, p the pressure in pounds per square inch, and a the area of the valve opening in square inches. с 0.5 w p+10 Rule for Calculating Load on Lever Safety Valve. (Fig. 32.) Let A = Area of valve in square inches. F Fulcrum distance in inches. L = Length of lever in inches. W = Weight of ball in pounds. Blowing-off pressure in pounds per square inch. (See Fig 32.) Ι ** • AFP L = W 32 W W = AFP L 294 SECTION III.-POWER STATION. If lever is not balanced, its effect, and the effect of valve and spindle, must be added to pressure, and be taken into account in calculating Land W. It w = weight of lever and v = weight of valve and spindle in pounds; c = distance of centre of gravity of lever from fulcrum; then, if p = pressure per square inch on valve due to weight of lever and valve alone, p = 33 291 W x c AF In most cases effect of valve and spindle may be neglected; with long heavy levers p will require adding to P to ascertain the blowing-off pressure. Sometimes lever is extended backwards beyond fulcrum, and fitted with a small weight at end, to cause lever to balance exactly about the fulcrum pin. When such is the case the weight of the lever may be entirely neglected in estimating the pressure on the valve. 4. + --- v A "TO POINT OF WEIGHT 31 With 35 00 Safety valve levers should be made of wrought iron. Malleable cast iron is sometimes adopted for the purpose, but its use is not advisable. It is easily fractured, and more than one serious case of scalding has resulted in consequence. When lever valves are adopted they should be designed so that working pressure requires the weight to be placed at end of lever, and thus prevent accidental overloading. Figs. 33 and 34 are types of lever safety valves from ordinary practice. Dead-Weight Safety Valves. (FIG. 35.) Dead-weight safety valves, shown in Fig. 35, are employed for stationary boilers. The centre of gravity of casing and weights with which the valve is loaded being below valve, it keeps its position on seat without aid of guides. S /E 3/3 XD с = d. Size of Steel for Safety Valve Springs. (Board of Trade Rule). The size of steel for safety valve springs is to be that found by the following formula:- Where S = the load on the spring in pounds. D = the diameter of the spring in inches, from centre to centre of wire. d = the diameter, or side of square, of the wire in inches. C = 8000 for round steel. C = 11000 for square steel. The springs are to be protected from steam issuing from the valves when valves are loaded by direct springs; the compressing screws should abut against metal- stops or washers, when the loads sanctioned by the surveyors are on the valves. STEAM BOILERS. 295 Spring-Loaded Safety Valves. (FIG. 36.) Spring-loaded safety valves, shown in Fig. 36, are suitable for all types of steam boilers. 26 - Then d Table 27.-Size of Steel in Sixteenths of an Inch Required for the Spring of a Safety Valve. According to Hutton, this may be found by the formulæ :— Let W = the load on the spring in pounds. D= the diameter of the spring from centre to centre of the wire coil. the diameter of round steel, or side of square of square steel. Size of steel for the spiral spring :- d d 2.93 = 3 V W X D 2 3/W E W x D 3 Deflection of safety-valve springs :- = for round steel. D3 x S for square steel. d4 x C Where S = load on spring in pounds. E = compression of spring from centre to centre of metal in inches; D = diameter of spring from centre to centre of metal in inches; d = diameter for round or length of side for square wire in sixteenths; C = a constant; = 22 for round steel; = 30 for square steel. .. Pressure of a spring on a safety valve:— Pressure in pounds per square inch due to springs of round steel Pressure in pounds per square inch due to springs of square steel .. 8000 × (diameter of steel)³ centres of spring in inches 11,000 × (side of square of steel)3 centres of spring in inches Spring Safety Valves. (Board of Trade Rule.) When spring-loaded valves are used in place of dead-weighted valves, two separate valves are to be fitted to each boiler, except in the case of small boilers, in which the grate area does not exceed 14 square feet, in which case a single safety valve may be passed, provided it is not less than 3 in. diameter. The springs and valves are to be cased in, so that they cannot be tampered with; provision must be made to prevent the valves flying off, in case of the springs breaking; and screw lifting gear must be provided to ease all the valves. 296 SECTION III.-POWER STATION. 295. Pop Safety Valves. (Fig. 37.) AMAD These valves have an auxiliary valve which is held in position by a spiral spring similar to the spring holding main valve on its seat, but which is entirely independent of main valve spring. For example: Main valve being, say, at 100 lb. pres- sure with auxiliary, set at 3 lb. waste; if main valve pressure is too heavy and you desire to reduce to 70 lb. pressure, this auxiliary valve will still have 3 lb. waste. If the main valve is set to blow off at 100 lb., and the auxiliary set to waste at 3 lb., this valve will reseat at 97 lb. These valves can be taken apart and cleaned without disconnecting from boiler. The valves can be furnished with lock-up if desired. These valves are accepted in America by all local inspectors on a basis of 1 square inch of valve area to 3 square feet of grate area. Safety Valve for High Steam and Low Water. (Fig. 38.) A safety valve for high steam and low water, used for Lancashire and other stationary boilers. The central spindle projecting into the boiler is loaded by a weight. A float is attached to a lever; when water falls below desired level, float also falls and raises valve, allowing steam to blow off. The cage of the valve is 38 60 48 70 $2 80 2112ANIA loaded by an external lever and weight, and lifts along with the valve in case of steam rising in pressure above the desired limit. The valve-lever requires to be accurately balanced to secure efficient action of the valve. The valve and connections should be examined at each cleaning of the boiler, and maintained in good order. STEAM BOILERS. 297 Table 28.—Minimum Size of Safety Valve Areas Allowed by Board of Trade. Boiler Pressure in Pounds. 15 16 17 18 19 20 21 22 per Valve Square Feet of Fire- grate : Square Inches. of Area 1.250 1.209 1.171 1.136 1.102 1.071 1.041 1.013 0.986 0.961 0.937 0.914 0.892 0.872 23 24 25 26 27 28 20 0.852 30 0.833 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 0.614 0.604 0.595 Boiler Pressure in Pounds. 0.585 0.576 0.568 52 53 54 55 56 57 58 59 60 61 62 63 31585882F 64 65 66 67 0.815 0.797 0.781 0.765 71 0.750 72 0.735 73 0.721 74 0.707 75 0.694 76 0.681 77 0.669 78 0.657 0.646 0.935 0.625 68 69 70 79 80 81 82 83 84 8*8858 86 87 of Valve_per Square Feet of Fire- grate : Square Inches. Area 0.559 0.551 0.543 Boiler Pressure in Pounds. 89 90 91 0.535 92 0.528 93 0.520 94 0.513 95 0.506 96 0.500 97 0.493 98 0.487 99 0.480 100 0.474 101 0.468 102 0.462 103 0.457 104 0.451 105 0.446 106 0.441 107 0.436 108 0.431 109 0.426 110 0.421 111 0.416 112 0.412 113 0.407 114 0.403 115 0.398 116 0.394 117 0.390 118 0.386 119 0.382 120 0.378 121 0.375 122 0.371 123 0.367 124 0.364 125 Valve per Square Feet of Fire- grate: Square Inches. of Area Boiler Pressure in Pounds. 0.360 0.357 0.353 0.350 0.347 0.344 0.340 0.337 0.334 0.331 0.328 0.326 0.323 0.320 0.317 0.315 0.312 0.309 143 0.307 144 0.304 145 0.302 146 0.300 147 0.297 148 0.295 149 0.292 150 0.290 151 0.288 152 0.286 153 0.284 154 0.281 155 0.279 156 0.277 157 0.275 158 0.273 159 3.271 160 0.269 161 0.267 162 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 Valve Square Feet of Fire. grate : Square Inches. Area of Boiler Pressure in Pounds. 0.256 0.255 0.265 163 0.264 16-1 0.262 165 0.260 166 0.258 167 168 169 0.253 170 0.251 171 0.250 172 0.248 173 0.246 174 0.245 175 0.243 176 0.241 177 0.240 178 0.238 179 0.237 180 0.235 181 0.234 182 0.232 183 0.231 184 0.230 185 0 228 186 0.227 187 0.225 188 0.224 189 0.223 190 0.221 191 0.220 192 0.219 193 0.218 194 0.216 195 0.215 196 0.214 197 0.213 198 0.211 200 per Valve Square Feet of Fire- grate: Square Inches. of Area Area of fire-grate in square feet × 4 2/working-pressure of steam in pounds per square inch 0.210 0.209 0.208 0.207 0.206 0.204 0.203 0.202 0 201 0.200 0.199 0.198 0.197 0.196 0.195 0.194 0.193 0.192 0.191 0.190 0.189 0.188 0.187 0.186 0.185 0.184 0.183 0.182 0.181 0.181 0.180 0.179 0.178 0.177 0.176 0.176 0.174 Area of Safety Valve for a given area of Fire-grate. (Hutton). The area of safety valve in square inches for given working-pressure of steam is equal to : L2 298 SECTION III.-POWER STATION. Area of Safety Valve in Square Inches for a given Rate of Evaporation. Area of safety valve for a given quantity of water evaporated per hour, equal to Evaporative capacity of boiler in pounds per hour 40 × 2√/ working-pressure of steam in pounds per square inch Two small safety valves give better results than one large one. Table 29.-Dimensions of Safety Valves in America. Area of Valves Expressed in Square Inches. Diameter of opening valves "" Length of lever Distance of fulcrum Angle of valve's face Width of face Length of fulcrum link ·· .. ·· · ·· 5 in. | 2.525 1 2.76 ¡ 25. 2.5 45° .15 4.5 10 in. 15 in. 3.37 3.77 30. 3. 45° .15 4.5 4.371 4.58 35. 3.5 Uniformity of action at different pressures. Reliability of action under continued use. Simplicity. 45° .12 4.5 20 in. 5.047 5.28 40. 4. 45° .17 4.5 25 in. 5.642 5.86 45. 4.5 45° .17 4.5 30 in. 6.781 6.375 47.5 4.75 45° .15 4.5 When well proportioned and well made, these valves may be expected to keep the steam under usual conditions within 1 or 2 per cent. of its working pressure; but the smaller valves are less exact than the larger sizes. The essential requirements are considered to be :- Capability of discharging any excess of steam above a fixed working pressure. A minimum limit of variation of pressure within which the valve will open and close. The weight of steam in pounds discharged through 1 square inch of orifice per hour is given by the formula, Pounds of stean per hour discharged: Absolute pressure of steam in pounds 0.023 Lloyd's Rules for Safety Valves. Two safety valves to be fitted to each boiler, and loaded to the working pressure in the presence of the surveyor. In the case of boilers of greater working pressure than 60 lb. per square inch, the safety valves may be loaded to 5 lb. above the working pressure. If common valves are used, their combined areas to be, at least, half a square inch to each square foot of grate surface. If improved valves are used, they are to be tested under steam in the presence of the surveyor; the accumulation in no case to exceed 10 per cent. of the working pressure. An approved safety valve also to be fitted to the superheater. In winch boilers one safety valve will be allowed, provided its area be not less than half a square inch per square foot of grate surface. Each valve to be arranged so that no extra load can be added when steam is All safety up, and to be fitted with easing gear which must lift the valve itself. valve spindles to extend through the covers, and be fitted with sockets and cross handles, allowing them to be lifted and turned round in their seats, and their efficiency tested at any time. Board of Trade Rules for Safety Valves. The locked-up valves, i.e., those out of the control of the engineer when steam is up, should have an area not less, and a pressure not greater, than those which are not locked up, if any such valves are fitted. The valve-chest should be placed directly on the boiler; and the neck, or part between the chest and the flange, which is bolted on to the boiler, should be as short as possible, and be cast in one with the chest. Care should be taken that the safety-valves have a lift equal to one-fourth their diameter; that the openings for the passage of steam to and from the valves, including the waste-steam pipe, should each have an area not less than the area of the valves; and that each valve-box has a drain pipe fitted at its lowest part. In the case of lever valves, if the holes in the lever are not bushed with brass, the pins must be of brass; iron and iron working together must not be passed. The valve seats should be secured by studs and nuts. STEAM BOILERS. 299 -ACCESSORIES. Minor accessories and details, as kind and location of steam and water gauges, dampers, automatic controlling devices, &c., should be as carefully considered as any other parts of the work. Pressure Gauges. The most common form is the Bourdon spring pressure-gauge, of which a number of modifications are in use. The case encloses a coil of flattened tube, closed at the free end, and open to boiler steam at the supported extremity. As the pressure rises and falls, a tendency to expand the tube into circular section produces greater or less effect, and the tube, as a whole, assumes a greater or a smaller radius of curvature, throwing its free end one way or the other in such a manner as to measure, by the traverse of the attached pointer, the pressure at each moment of the confined fluid. Sometimes the tube is held at its middle point, both ends being free, and their relative motion affecting the pointer. The more stable the tube, and the more reliable the mechanism connecting it with the hand at the dial, the better the gauge. Gauge Cocks and Water Gauges. Gauge cocks and water gauges should be set where they will not be affected by foaining that may occur within boiler; they should be as far from the furnace as is convenient, or their connection should be led to a quiet part of the boiler as a foaming boiler, in deceiving the eye by the gauges, may discharge a dangerously large amount of water undetected. 39 Hopkinson's Patent "Absolute” Water Gauge. (FIG. 39.) When the glass breaks, the water pressure in the lower arm forces the safety column ball valve A to its seat (as shown in dotted lines), and shuts off the water. Simultaneously the water pressure in the supplemental tube C assisted by the escaping steam in the top arm, forces the ball valve B to its seat (as shown in dotted lines), and shuts off the steam. EK A 298 B с 40 41 bil JO It is impossible for the gauge glass to indicate other than the true water lever in the boiler, as safety column ball valve A is sufficiently heavy to fall from its seat if the glass is intact, and overbalance the preponderance of upward pressure acting on the underside of the valve, due to the column of water. Therefore, the passages between the glass and the boiler will always remain open. The ball valves can only be forced to their seats when the glass is actually broken. 300 SECTION III.-POWER STATION. Scum Cock. (FIG. 40, page 299.) A scum cock is to blow off scum from surface of water in boiler. A trough- shaped pipe is carried from the scum cock inside the boiler, the top of which is placed a little below the working water level of the boiler, for the purpose of col- lecting scum and refuse floating on the surface of the water. According to Hutton, the cross-sectional area of a scum cock in square inches may = the evaporative capacity of the boiler in pounds of water per hour x .00053. The taper of the plugs of scum cocks may be 1 in 8. Blow-off Cock. (FIG. 41, page 299.) Blow-off cocks are preferably of gun-metal, they are sometimes of cast iron with or without gun-metal linings for the plugs to work in, and with gun-metal plugs. The gun-metal may be composed of 88 parts of copper, 10 of tin, and 2 of zinc. The taper of the plug may be 1 in 6 for steam pressures up to 90 lb. per square inch; 1 in 3 up to 180 lb. per square inch; for higher pressures the taper should be 1 in 10. The cock should have a solid bottom and a stuffing-box top. Metallic packing is the best for blow-off cocks for boilers producing steam of very high pressure. A screw should be fitted to the bottom of the cock to ease the plug when it sticks fast. The cross-sectional area of a blow-off cock in square inches may = the evaporative capacity of the boiler in pounds of water per hour x .00082. (Hutton.) A guard should be fixed over the plug, with a featherway to receive a feather on the box key for turning the plug, so that key cannot be withdrawn unless cock be shut. Blow-off cocks are liable to stick fast. They should be opened at least once a day, and the plugs should be removed, cleaned, and replaced, and the packing of the stuffing-boxes adjusted at each cleaning of the boilers. The elbow-pipe for attaching the blow-off cock to the boiler should be of steel. The diameter of the end attached to the seating block on the boiler should be double that of the end to which the blow-off cock is fixed. Steam Collecting Pipe. (FIG. 12.) Steam should be drawn from boiler by perforated collecting, or anti-priming pipe, fixed below the stop valve close to the shell, into which steam flows without creating rapid current, which is liable to carry water with it. Total area of the perforations should not be more than one-third greater than the sectional area of the stop valve in order to prevent priming, which excessive area tends to produce. 00000000000 296 42 HET The total area of the perforations divided by the area of one perforation will give the number of perforations in the collecting pipe. Steam collecting pipes are frequently made too short to be efficient. It is desirable that they should extend the entire length of the steam space, or as great a portion of the length as convenient, in order to distribute the withdrawal of the steam over as great a length as possible. STEAM BOILERS, 301 Hopkinson's Accessible Feed Check Valve. (FIGS. 43 and 44.) 44 3 Hot 801144 FE311AFRYKIE 279. ~ food EMBOTITIAL. B sland ( T Ordinary feed valves are liable to become leaky, and this proves a great annoyance. It is desirable that the valve should be able to be examined and, if necessary, repaired whilst the boiler is under steam. Should the valve become leaky or inoperative from dirt or any other cause, access is afforded to the same whilst the boiler is working, by closing the valve and removing the elbow C, which contains both the valve and valve seat. The screwed portion of the spindle is outside the valve, and not subject to fluid pressure or the action of water. The Low-Water Detector and Alarm. The low-water detector and alarm consists of a vertical tube closed at the top by a fusible plug, or by a valve actuated by a rod having a different coefficient of expansion from the tube itself. The tube communicates at the lower end with the water space of the boiler. It ordinarily stands full of water, but should the water level fall below its lower end, steam displaces the water in the tube, the fusible plug melts, or the valve is opened by the difference in expansion of the tube and rod, and steam at once issues, giving warning of danger. The upper end of the tube is fitted with a steam-whistle, the blowing of which, when the steam makes its exit, attracts attention. REFUSE DESTRUCTORS. Ashbin Refuse. The production of ashbin refuse varies considerably in different districts, but it generally ranges from 4 cwt. to 7 cwt. per head of the population per annum, or from 200 to 350 tons per annum per 1000 of the inhabitants of a town. Destructor Furnaces. A high temperature in the furnace, a strong draught, and a well-distributed supply of air to the burning fuel, are essential to efficient and rapid combustion of ashbin refuse. The lowest temperature necessary to deodorise the offensive fumes from burning refuse of this description is 1350 deg. Fahr. The temperature of a furnace for burning ashbin and other refuse from towns, should not, however, be less than 2000 deg. Fahr. in order to obtain rapid and efficient combustion of fuel gases, or noxious vapours, and to prevent any portion escaping unconsumed. Performance of Refuse Destructors. In well-arranged destructors, two-thirds of the weight of unscreened ashbin refuse is destroyed by fire, residue of one-third being clinker and ash. Quantity of unscreened ashbin refuse that may be readily burnt in efficient furnace, having 25 square feet of firegrate area, is about 6 cwt. per hour with good natural draught, and 1 ton per hour with forced draught of from 24 in. to 34 in. of water. Composition of Ashbin Refuse. (Hutton.) The contents of ashbins vary considerably; the following is a representative xample of composition of contents of the ashbins in towns: ! 302 SECTION III.-POWER STATION. Table 30.-Composition of Ashbin Refuse in Towns. : Breeze and cinder Paper, straw, fibrous material, and vegetable refuse Coal .. Bones and offal Rags Coke .. •• Ash Dust and dirt ·· .. Carbon Hydrogen Nitrogen Sulphur Oxygen Ash Moisture •• ·· Screened ashbin refuse, the best Ditto ditto averages Unscreened ashbin refuse, the best Ditto ditto averages Ditto ditto Ditto ditto Ditto ditto ·· .. ·· • ·· Description of Town Refuse. .. • •• .. .. .. ·· ·· .. .. • Bottles, 1 per cent. ; tins, .7 per cent. ; metals, .2 per cent. ; crockery, .6 per cent. ; broken glass, .5 per cent. = a total of.. of inferior quality seldom exceeds 2 parts, mixed with street sweep- ings, 1 part, by weight 2 parts, mixed with street sludge, 1 part, by weight .. .. .. ·· · Table 31.-Average Evaporative Power of Town Refuse Obtained in Practice. (Hutton.) · • Table 32.-Calorific Value of Refuse. (King's Norton, near Birmingham.) Percentage of the Weight of Ashbin Refuse. ·· .. • • •• • The ashbin refuse fuels described in the above Table generally yield from 25 to 35 per cent. of clinker and ash. •• 50.0 13.0 Weight of Water Evaporated from and at 212 deg. Fahr. per Pound of Refuse Fuel in Pounds. .7 .6 .4 .3 12.0 20.0 3.0 100.0 2.00 1.50 1.25 1.00 .75 .75 .50 0.29 0.29 0.19 7.3 41.7 12.12 ATL per cent. 36.8 It is not contended that the average refuse has a calorific value of 4500 B.T.U.; this particular sample was obviously a very good one. The average calorific value of refuse as a fuel may be safely put at 3000 B.T.U. The average number of Board of Trade units generated per ton of refuse depends principally upon the quality or composition of the refuse, other things being equal. The units per ton of refuse destroyed vary between 15 and 80 Board of Trade units, the average ton gives results nearer 30 units per ton. The pounds of water evaporated per pound of refuse from, and at, 212 deg. Fahr., varies between about 0.65 lb. and a possible maximum of 2.35 lb.; and the weight of refuse burnt per square foot of grate per hour, between 25 lb. and 82 lb. STEAM BOILERS. 303 Table 33.-Heating Power of Ashbin Refuse. The heating power of the combustibles of ashbins averages as follows: Coal Coke ·· Bones and offal Breeze and cinder ·· .. Coal Bones and offal® Coke Rags ·· .. .. Rags Paper, straw, fibrous material, and vegetable refuse * • Breeze and cinder Paper, straw, fibrous material, and vegetable refuse.. ·· • • ·· ·· ❤ .. Table 34.—Heating Power and Evaporative Power of Dry Ashbin Refuse. The heating power of the combustible matter forming part of the contents of ashbins, when in dry state, is about: .. • • .. · • ·· •• Calorific Power, or Units of Heat Developed per Pound of the Combustible. When in a Dry State. 14,000 12,000 8,000 6,000 5,000 3,800 Units of Heat Developed per Pound of the Combustible. Quantity of the Combustible. Pounds. 6,000 X .500 3,800 X .130 14,000 X .007 .006 8,000 X 12,000 5,000 .003 .004 When Containing an Average Quantity of Moisture. XX 9334 8000 5334 4000 3334 2534 || | || | || Units of Heat Developed by this Quantity of the Combustible. 3000 494 98 48 36 20 3696 The total quantity of heat developed by complete combustion of this mixture of combustibles is 3696 units, and its evaporative power is = 3696 lb. ÷ 966 lb. = 3.826 lb. of water, from and at 212 deg. Fahr., per pound of the combustibles, when in a dry state. Refuse Destructors at Shoreditch, London. (Fig. 45, page 304.) The vestry and parish of Shoreditch has built an electricity generating and refuse-destruction station. Twenty thousand tons of refuse per annum have to be destroyed, and by Mr. Manville's advice the Druitt Halpin system was adopted. The destructors are all of the downward discharge type, delivering the air to underground ducts extending beneath them, and hence distributing it to the destructor cells. The inlets of the fans are arranged to draw their air supply from the main sewer, thereby ventilating the same for a considerable distance in the neighbourhood of the destructor works. Connection is also made to the inlet trunks from the space immediately above the cells, which in hot weather becomes almost unbearable for the men employed in dumping the rubbish, unless the fans are used to draw the hot air. The fans are located in the room to which the door at the farther end of the boiler-room admits. They are proportioned on the estimated requirement of only 190 cubic feet of air per pound of refuse, and a rate of combustion of 26 lb. of refuse per square foot of grate per hour. Formerly it cost 3s. 2d. per ton of refuse for barging it away; now it would cost 1s. 2d. per ton for burning it in the dust destructor-a saving of 2s. per ton. The destructor house (Fig. 45) is 80 ft. square, and contains 12 cells, each having 25 square feet grate area, and six water-tube boilers, each with 1300 square feet of heating surface. The boilers are designed to work at a pressure of 200 lb. 304 SECTION III-POWER STATION. (310) 46 STURTEVANT FANS 12 312 AAAAAAA Fig. 45. Fig. 46. H | | 45 ND. | | II 마 ​Plac BIH H H H H H H H НІН НІНІТ Refuse Destructors. Plan of Destructor at Shoreditch. Meldrum's Refuse Destructor. Do 47 य REGENERATOR 178181538:8:ETH/BIN. FO 49 48 NOT AIR DOWN TAKE ណ BOILER HOT AIR CONDUIT ↓ 3:5 ណ FURNACE TROLLEYO ** 回事 ​!!! hundia CONTAINING HOPPER 1.7 COMBUS AND ETTLING BRIDGE Figs. 47 to 49. Meldrum's Refuse Destructor. 306 SECTION III.-POWER STATION. 50 FLUE TO |CHIMNEY 51 1 52 Micas Q TIPPING BRIDGE GRATE bl NOT AIR C BOILER PLATFORN VÜLYA B F GRATE HOPPER ?t?#}} 100 Figs. 50 to 52. Meldrum's Refuse Destructor. COMB CHAMBER wwwwwwiinukaitisks STEAM BOILERS. 307 per square inch, and are supplied with duplicate fittings throughout to guard against breakdown. There are three (Sturtevant) motor-driven fans calculated to deliver each 8000 cubic feet of air per minute, with a maximum ashpit pressure of 3 in. of water. Meldrum's Destructor. (FIGS. 46 to 52, pages 304 to 306.) This destructor is practically the adaptation of Meldrum's forced-draught boiler furnaces, designed for dealing with difficulties encountered in treating refuse, and to utilise economically the heat therefrom for power purposes. The grates are placed side by side, forming practically one large cell, charged in sections; and as the products of combustion of each section pass either over or under the gases from the other sections, they co-mingle completely. Any section can be cut out without interfering with the working or lowering of temperature at any time. This is uniform, and in the combustion chamber is found to range from 1800 to 2200 deg. Fahr., so that all noxious fumes are completely destroyed, The gases pass through and around the steam boiler, and afterwards the heat. from the waste gases is passed through a regenerator (as shown in Figs. 51 and 52), thus warming the air which supplies the blowers to about 300 deg. Fahr., which heat materially assists combustion, and is of advantage in the case of very wet material,. frequently to be dealt with. Refuse is tipped into a hopper (Fig. 52) placed in front of the furnace and at a convenient height for the fireman. It is then thrown directly on to the fire, requir- ing no more attention until it is removed as clinker. There is one handling of the refuse instead of the three necessary in overhead systems of charging, viz. : shovel- ling on to the drying hearth, raking on to the firebars, and levelling. To facilitate the operation of clinkering, tipping bars are provided so arranged that the clinkers can be dropped through into a trolley in the ashpit. This is. left for a short time, so that most of its heat is utilised for combustion. The firing doors are made in two parts lined with firebrick, and worked with counterbalance weights. One-half can be gradually lifted, the fireman thus being screened to a great extent from the glare of the fire. A special door is arranged at one end for charging mattresses, diseased meat, &c. The forced draught is on the closed-ashpit principle, and the necessary volume of heated air is supplied by steam-jet blowers. It is found that each ton of average refuse, if burnt in a well-designed plant, is capable of giving 160 indicated horse-power, taking 20 lb. of steam per indicated horse-power. MECHANICAL STOKERS. These can roughly be divided into three classes: the "Over Feed" type, the "Chain Grate" type, and the "Under Feed" type. Examples of the first are Vicars' and Bennis' stoker; of the last is the American stoker. The American Stoker. (FIG. 53, page 309.) (Underfeed Stoker Company.) The American stoker consists of a hopper in front of the furnace at the side of the fire door. Immediately behind the hopper, and connected to it, is the conveyor, which communicates with the coal magazine, which is in direct line with it. A worm or screw conveyor extends nearly the entire length of the magazine. Underneath the conveyor chamber is the wind box, which has an opening under- neath the hopper, and at this point the piping from the blast is connected. The other end of the wind box opens into the air space between the magazine and outer casing or envelope. The upper edge of this magazine is surrounded by tuyeres or air blocks, these being provided with openings for the discharge of the air blast. The space on each side of the stoker, between the tuyere blocks and the side walls of the furnace, is occupied by dead plates or air-tight grates. The coal is fed into the hopper, carried by the conveyor into the magazine, and is there forced upward, "overflowing" on both sides, and spreading upon the dead grates the entire width of the furnace, as shown in Fig. 53. The entire mass of coal above the tuyeres and all of that upon the dead grates is ignited, carrying a bed of burn- ing coke from 14 in. to 18 in. in depth. The volume blower is used for air, and is actuated either by a small engine of a convenient line-shaft. The air is delivered in the approximate proportions of 150 cubic feet of air to each pound of coal fed, and at a pressure ranging from 1 oz. to 1 oz. at the tuyeres. This pressure is only such as to admit of the thorough. 308 SECTION III.-POWER STATION, mixing of the air with the coal, and is in no sense of the word a blast. A wind gate, controlled by a lever, enables the operator to regulate the supply of air to suit the amount of coal fed. Being thus independent of natural draught, and the supply of coal under complete control, the fire can be forced at a moment's notice, and can be as quickly reduced. As a result of a long series of chemical analyses of the chimney gases, collected under precisely similar conditions, both when fired by hand and by stoker, it is shown that the amount of air required per pound of coal when burned with this stoker, is from 20 to 55 per cent. less than that which would have been used in the common hand-fired practice. This efferts a twofold economy in decreasing the volume of heated gases passing up the chimney, and likewise decreasing the velocity of the gases as they pass over the heating surfaces, thus allowing more time for the absorption of heat by the boiler surfaces. This economic use of air is due to the method of operation peculiar to this stoker, in that it carries a bed of coal of unusual depth, the air being supplied from underneath, the volume of which being under control, and the continuous feeding action overcoming the tendency of holes burning through the fire. Table 35.-Tests of an American Stoker on a 150 Horse-Power Babcock and Wilcox Boiler. Steam pressure by gauge Temperature of feed water.. flue gases 11 Kind of coals used ·· ·· .. Total coal consumed lb. Refuse.. per cent. Total water evaporation Ib. Total evaporation from and at 212 deg. Fahr. lb. Water evaporation per pound of coal from and at 212 deg. Fahr... Increased evaporation per pound of coal per cent. .. •·· ·· ·· "" .. .. System of stoking Duration of trial Designation of coal Area of fire-grate total Coal consumed.. Hand Fired Stoker Fired. "" Coal consumed per hour Water evaporated, total per hour " 92.5 86.78 86.26 55.6 548 388 Pittsburg Pittsburgh Youghiogheny Nut and Slack Nut and Slack] Nut and Slack 4757 3225 12.5 31,466 36,686 11.37 40 5/10 4880 18.1 32,917 39,479 8.09 The first and second tests were made to determine the economy of stoker firing over hand firing, using the same grade of coal; the third and fourth tests, for determining the economy with the higher grades of coal. .. Vicars' Mechanical Stoker. (FIG. 54, page 309.) Vicars' Mechanical Stoker is shown in Fig. 54. The hopper A is filled with small coal, which falls into the boxes B. The boxes are fitted with self-acting plungers, which push the coal alternately into the furnace and on to the dead- plate, whence it is delivered to the fire-grate. The fire-bars travel, and carry the fire very slowly for a short distance along the furnace-tube. Any unconsumed fuel which reaches the end of the grate-bars, and the clinkers and ashes, are dis- charged over the ends of the grate-bars into the bottom of the furnace-tube. The following results are given by Hutton of a test of Lancashire boiler of 7 ft. 5 in. diameter and 30 ft. long, with furnace-tubes 2 ft. 9 in. diameter, fitted with this mechanical stoker, compared with the results of a test of the same boiler with ordinary hand-firing :- per pound of fuel ·· • • ·· 101.0 89.1 .. •• 12.3 38,654 45,155 9.49 172/10 ·· Stoker Fired. Vicars' stoker 10 hours Bituminous slack 22 ft. 5936 lb. 560 lb. 5330 gallons 533 gallons 8.98 lb. .. ·· ·· ·· .. · •• ·· ·· Stoker Fired. ·· 87.67 87.24 329 New River, W.Va Nut and Slack. .. 2900 8.9 29,729 34,699 11.96 47 8/10 Hand-firing. 10 hours Welsh small. 33 ft. 7168 lb. 672.45 lb. 5020 gallons. 502 gallons. 7 lb. Bennis Mechanical Stoker. In this stoker the fuel falls from the hopper, in front of a simple pusher-plate contained in a cast-iron feed-box, and is pushed over a ledge on to a flat plate called the shovel-box. The amount of fuel dealt with is regulated by a cam on the STEAM BOILERS. 309 A 8 PARENTS FOFOFOFOF GOODDOO (820) DE T L Mechanical Stokers. 54 American Mechanical Stoker. Fig. 53. Fig. 54. Vicars' Mechanical Stoker. 53 310 SECTION III.—POWER STATION. driving shaft. From the shovel-box the fuel is kicked into the fire by means of a shovel propelled by a steel spring. This spring is contained in a cylinder, and is attached to a piston, forming an air cushion which absorbs all shocks. The cam which draws back the shovel has four varying lifts, and scatters the fuel on the fire in four divisions, thus allowing each portion of the furnace to become incan- descent between the charges. The compressed-air self-cleaning furnace used with this stoker consists of tubular fire-bars, into which air is forced, the draught being evenly distributed over the whole firegrate. The bars all move into the fire together, and are then withdrawn one at a time by cams, carrying the clinker to the back ends of the bars, which are higher than the front, thus making it impossible for any clinker to leave the bars unless actually pushed off the end. The clinker falls into a closed chamber, where it gives up its heat to the boiler. This cleaning arrangement is most important where low-class or waste fuels, containing a large proportion of clinker and ash, are used; as with these the air spaces in the fire-bars of ordinary furnaces become more or less covered and stopped up, and the fire suffers in •consequence. Table 96.-Comparative Tests of Bennis and Empire Stokers. (Supplied by Ed. Bennis and Co., Ltd.) Date of trial Duration of trial…. Firegrate surface ·· Average temperature of feed to boiler gases leaving boiler flue ditto "Total fuel consumed Average fuel consumed per square foot of firegrate surface per hour URATION TRADAZHAMA • •• .. • Total water evaporated Water evaporated per pound of fuel from temperature of feed •• ditto as from and at 212 deg. Fahr. Average steam pressure maintained Extra power developed by the "Bennis" stoker and furnace Economy by "Bennis" stoker and furnace Empire Economic Furnace. August 29th 6 hours 18 sq. ft. 178.5 deg. Fahr. 757 deg. Fahr. 27 c. 1 qr. 0 lb. 28.2 lb. 1,925 gallons :: Bennis Stoker and Self-cleaning Furnace. August 29th 6 hours 20 sq. ft. 173.5 deg. Fahr. 985 deg. Fahr. 33 c. 0 qr. 9 lb. 6.37 lb. 6.797 lb. 8.0 lb. 8.536 lb. 50.25 lb. persq. in. | 50.25 lb. per sq. in. 55 30.8 lb. 2,965 gallons The Jones Underfeed Stoker. (Erith's Engineering Company.) Fig. 55 shows a longitudinal section through the stoker. It consists of a steam ram with a fuel hopper outside of the furnace proper, and a retort or fuel 54 per cent. 25 per cent. magazine and auxiliary ram within, tuyere blocks for the admission of air being placed on either side thereof. The ram is worked by steam, either automatically or by opening the throttle valve, as desired. By means of the ram and its STEAM BOILERS. 311 F auxiliary, fuel is forced underneath the fire, its movement being upwards and backward. The fuel is thoroughly coked before reaching the zone of combustion. Air at low temperature is admitted through the openings in the tuyere blocks, the air being supplied by a blower operated by a small independent engine, or by connection with a line-shaft. The tuyere openings are above the level of the green fuel in the retort, but below the fire; the air is thus thoroughly mixed with the gases liberated from the coking coal below, and the combustible mixture passes upwards through the mass of fuel. The Hawley Down-Draught Furnace. A foot or more above the ordinary grate there is carried a second grate, com- posed of a series of water-tubes, opening at both ends into steel drums or headers through which water is circulated. The coal is fed on this second grate, and as it is partially consumed falls through it upon the lower grate, where the combustion is completed in the ordinary manner. The draught through the coal on the upper grate is downward through the coal and the grate. The volatile gases are there- fore carried down through the bed of coal, where they are thoroughly heated and are burned in the space beneath, where they meet the excess of hot air drawn through the fire on the lower grate. In tests in Chicago from 30 lb. to 45 lb. of coal were burned per square foot of grate upon this system, with good economical results. The "Koker" Stoker. (Fig. 56, page 313.) (Meldrum and Clayton's Patent.) This stoker works upon the coking principle. The fuel is burned by under- grate blowers worked by superheated steam, and the air supply to the coking plates is adjustable, so that the rate of coking can be varied to suit the rate of combustion. The air supply keeps the inside of the stoker front cool, thereby minimising wear and tear, and allowing of efficient lubrication of the cams, &c. The fire-bars are simple, with a corrugated surface; and an alternating reciprocating motion, the speed of which is easily adjusted, automatically breaks up the fire. The ram works on a pivot, and requires much less power than is necessary with a sliding ram or pusher. The boiler can easily be hand-fired when necessary, as the fire-doors are full size, and the ash-pit doors are practically the full size of the ash-pits. Very little drilling of the boiler front is required for fixing the stoker in position, as the main weight is carried on brackets slung over the top of the boiler front. The "Koker” Stoker combined with the "Meldrum” Furnace. Result of test at the Bristol Corporation Electricity Works, of Babcock and Wilcox boiler, with 2852 square feet of heating surface, and 55 square feet of grate. Date of test Duration of test .. Fuel used Weight of fuel burned (actually fired) per square foot of grate per hour Weight of water evaporated per pound of fuc! fired ·· .. ·· ·· ·· ·· Weight of water evaporated from, and at, 212 deg. Fahr... Total fuel used Fuel used per hour Total water used Water used per hour •• • Jan. 30th, 1900. 6 hours 5 minutes. Rhymney washed peas. 28.23 lb. 9.64, 11.2 9490 1560 "" 9150 gallons 1501 " "" 99 Fig. 57 shows one of Meldrum and Clayton's patent sprinkling stokers fitted to a Lancashire boiler. 312 SECTION III.—POWER STATION. Table 37.---Test of Jones Underfeed Stoker with Babcock and Wilcox Boilers. (Erith's Engineering Company.) Date of test Kind of coal-Pittsburg Mine Run.. ·· Duration of test in hours Heating Surface in square feet Grate surface in square feet. Average gauge pressure Average absolute pressure Average feed temperature Fahr. Average temperature of escaping gases Fahr. Total amount of coal burned in pounds Total refuse • .. ·· .. • • ·· • ·· .. • ·· ·· ·· ·· ·· · ·· .. ·· ·· ·· ·· ·· ·· • ·· ·· ·· ·· ·· ·· • • Heat transmitted to feed water per pound of combustible Horse-power developed (344 lb. from and at 212 deg.).. Rating of boilers (builder's) Water evaporated from and at 212 deg. per square foot of grate surface Heating surface per horse-power of 34 lb. Increase over builder's rating ·· ·· ·· ·· ·· ·· • •• • .. · ·· Percentage refuse • ❤ .. Coal burned per boiler per hour in pounds Coal burned per square foot of original grate surface per hour Total weight of water fed into boiler at actual temperature of feed Total equivalent from and at 212 deg. Fahr., fed into boiler and apparently evaporated Equivalent hourly evaporation from and at 212 deg. per pound coal Water actually evaporated per pound coal in pounds Equivalent evaporation from and at 212 deg. per pound coal Actual evaporation per pound combustible Equivalent evaporation from and at 212 deg. per pound combustible Heat given to every pound of water to evaporate same into steam at boiler pressure British thermal units ·· ·· ·· ·· ·· .. ·· .. ·· • ·· ·· • •• .. ·· · ·· ·· ·· • A ·· …… • · • • ·· ·· .. ·· ·· ·· • ·· • L • · ·· • .. ·· .. March 16th and 17th, 1900. 9.4 5.9 1750 39 127 141.7 143.1 485 7425 709 9.55 1258 32.2 59263 66179 11154 7.98 8.913 8.824 9.854 1078.8 9519 323.3 160 6.197 5.56 102 per cent. 1750 39 128.3 143 145.7 597.5 12000 779.5 6.5 1276 32.7 96287 107263 11413 8.24 8.940 8.581 9.561 · 1076.3 9236 330.8 160 6.34 5.29 106.1 per cent. i 56 57 Ka 1 to 24′ -LII 00 [0000.000 500 I Mechanical Stokers. ΤΟΥ ΤΟΧΟΙ ΟΙ Fig. 56. The "Koker" Stoker. Fig. 57. Meldrum and Clayton's Patent Sprinkling Stok 314 SECTION III.-POWER STATION. Woodward's Patent Furnace. This is a furnace designed for forced draught, and consists of an arrangement of hollow firebars combined with a special system of air distribution. Connected to the central passage, through the centre of each bar, are a series of tapering rectangular slits, which pierce the bars at intervals along each side. These slits are inclined in an upward direction and spaced so that they alternate with those of the next bar. At the front end a small steam-pipe, fed with live steam from the boiler, runs transversely across the furnace mouth, just below the dead-plate. This pipe is fitted with a number of small nozzles, which blow down the passages in the firebars, and cause an induced current of air to enter, where, by means of the slits, it is distributed over the entire grate area. A steam-tap on the pipe enables the air-pressure to be controlled at will. When the length of grate requires two or more lengths of firebars, the passages are made continuous by means of spigot joints. At the back the bars are connected to the transverse bearer, which forms a dust box, fitted with a lid, operated from the front, so that dust or impurities can be blown through at a moment's notice. 191 8880 O 60 58 LANGH (LEINTLIKE ONE = 20 ) 61 Figs. 58 to 61. Babcock and Wilcox Patent Chain-Grate Stoker. - AHA (Page 315.) STEAM BOILERS. 315 Babcock and Wilcox Patent Chain-Grate Stoker. (FIGS. 58 to 61, page 314.) The grate consists of an endless chain of short cast-iron grate-bars, linked together and actuated by passing over drums at the front and rear, the front drum being revolved by a worm and worm-wheel. The whole stoker can be brought out clear of the boiler, the frames being provided with wheels running on rails placed at the sides of the ash-pit; although this is not necessary for merely replacing a defective bar, which can be done in a few minutes with the stoker in place. The coal is fed over the whole width of the grate, and the depth of the fire- regulated by the adjustment of the vertically lifting fire-doors. The feed of the coal is slow, and the gas evolved from the fresh fuel as it drops on to the grate readily perfects its combustion by passing over the incandescent fuel further on. The speed of the travel of the grate is regulated by a ratchet and pawl adjust- ment on the driving worm, which latter gears into a worm-wheel, on the shaft of which are drums which revolve the grate. The stoker can be adjusted in a moment to suit the class of fuel to be consumed, and varying demands for steam, both by the depth of the fire and speed of the grate. The fire does not require to be touched with firing tools, the stoker being self- clinkering. Undue admission of air at the back end is prevented. Hand-firing may be resorted to without removing the coal from the hopper, and at a moment's notice. The fire-doors are large, extending the whole width of the grate. Only small power is required to drive it either overhead or underground. Width of Band (inches). COAL CONVEYORS. (FIGS. 62 to 70, pages 316 to 321). With the ever-increasing size of electric generating plants, and the improved. load factor obtained by supplying electricity for industrial and traction purposes,. as well as for lighting, the economic handling of fuel assumes a very important aspect. American firms, as C. W. Hunt Co., John A. Meade and Co., Hosher Platt Co., Brown Hoisting and Conveying Co., Link Belt Co., Robins Conveying Belt Co., originated special types of coal and ash-handling machinery. The demand for similar apparatus in the United Kingdom has been efficiently met by British manufacturers such as the Temperley Transporter Co., Ed. Bennis. and Co., Limited, The Conveyor and Elevator Co., Pott, Cassels and Williamson, Watson, Laidlaw and Co., Graham Morton Co., Mirrlees Watson Co., Babcock and Wilcox, Ltd., Vicars and Co., the New Conveyor Co., Avery's, and others. The following gives a brief description of the types of conveyors most in use. Table 38.-Data regarding Speed, Capacity, and Horse-power of Belt Conveyors. 20000 12 18 24 30 36 Speed (feet per minute). 150 to 600 150 to 600 150 to 600 150 to 600 150 to 600 Capacity (tons per hour). 10 to 35 50 to 175 125 to 475 250 to 900 350 to 500 Size of Material. From 2-in. cubes to dust From 4-in. cubes to -in. cubes From 6-in. cubes to 1-in. cubes From 7-in. cubes to 2-in. cubes From 9-in. cubes to 2-in. cubes B.H.P. for Conveyor 100 ft. long. 3.2 4.8 6.0 7.6 9.2 Belt Conveyors. This type consists essentially of an endless band passing round two pulleys, supported at such points as may be found necessary. There are two distinct varieties: the first is a flexible cotton or canvas belt, the wearing surface of which is usually protected by india-rubber. The second is also an endless band, but is. made up of a series of flat metal links or plates, known as a steel plate conveyor. These can be used as elevators to a limited extent. A belt conveyor can dump its. 316 SECTION III.-POWER STATION. load at any convenient point along its length. For handling coal, the idler pulleys upon which a flexible belt runs, are usually placed so as to cause it to assume a trough-like shape. Table 38 (on page 315) gives general data of the size, speed, capacity, and horse-power required to operate belt conveyors. Steel Plate Conveyors. These are frequently constructed too flimsily, the plates in many cases not being more than in. thick. Even for light work-in. plates are desirable, while for carrying large coal they should not be less than in. or in. thick. Good wrought-iron plates do not wear out or scale so quickly as mild steel plates. Bucket Conveyors. (Figs. 62 to 68, pages 316 to 320.) These consist essentially of a series of buckets suspended or fastened to a chain, from which they hang loosely, keeping their vertical position by gravity; the buckets may be entirely independent, with spaces between (when moving horizontally), or they may overlap. The chain of buckets can be driven either by sprocket wheels gearing into the chain, or by pawls pushing the chain along. (323) O wwww www ˇˇˇ www.s www wwww O pum. Fig. 62. Pushing Device for Coal Conveyors. The bucket chain is run at a very low speed. The ordinary capacity of the buckets is 2 cubic feet each; the average speed is about 15 buckets per minute, or above 40 tons of coal per hour. The speed can be increased to 25 buckets per minute, or about 90 tons of coal per hour. This conveyor has also been used very successfully for conveying ashes and clinkers from the stoke-hold. Fig. 64 shows the cross-section of the Brooklyn Heights Railroad Company's boiler house and coal storage. As the buckets swing freely on pivots, some special method of loading them is required. Two methods of doing this are adopted by the Hunt Co. and Babcock and Wilcox,one known as the "measuring," and the other as the "spout' filler. The first delivers to each bucket a given quantity; the latter is a con- tinuous feed, each bucket being filled as it passes underneath it. This conveyor is driven by a set of pawls which push the endless chain along. (Fig. 62.) "" The Link Belt Company make a special feature of the device they employ for driving their conveyors, which is an arrangement for eliminating the jerky motion usual when a sprocket wheel drives a pitch-chain. If the sprocket moves with -constant angular velocity, the linear velocity of the chain is not uniform. This is easily demonstrated if we take an extreme case, and imagine a three-tooth sprocket driving a pitch-chain (shown diagrammatically in Fig. 65). It is clear that if the sprocket A B C revolves uniformly, the linear speed of the chain when the wheel is STEAM BOILERS. 317 ! 64 00000 (332) 63 322. 009988888800 }) 20 0002000 X X X X X X X X 1000 Figs. 63 and 64. Coal Conveyors, Brooklyn Heights Railway Company. (C. W. Hunt Company.) 318 SECTION III.-POWER STATION. in the position shown by the full lines, is exactly twice what it is when it has made one-sixth of a revolution, and taken up the position A1 B1 C1. This variation will occur six times per revolution, and results in a very jerky and irregular motion. For wheels with a larger number of teeth the speed variations are not so great, but they occur at more frequent intervals in the same number of revolutions. To counterbalance this undesirable feature, the Link Belt Engineering Company give the driving sprocket a pulsating motion by means of an eccentric pinion mounted upon an axis rotating uniformly. The number of teeth on this A B wwww ¿' A C ~~ˇˇˇˇˇˇˇˇˇˇˇˇˇˇˇˇˇˇˇˇˇˇˇˇˇˇˇ AAAABAAAAAA 6299 Q 66 Figs. 65 and 66. Compensating Device. pinion is th of the number of teeth on the gear-wheel with which it engages where N is the number of teeth on the chain sprocket, the latter and the gear- wheel being mounted on the same shaft. The pinion is so arranged that it drives through its shortest radius when the chain is at its greatest, so that the two counterbalance each other. Fig. 66 shows the arrangement applied to a push- plate conveyor. The pitch line of the gear-wheel must be made specially wave-shaped so as to gear properly with the eccentric pinion, the number of elevations and depressions thus formed being equal to the number of teeth in the chain sprocket. Fig. 67 shows the equalising gear applied to a Link belt conveyor. STEAM BOILERS. 319 A gravity bucket conveyor is manufactured by the New Conveyor Co., of Smethwick. This firm has installed plants at the Central Electric Light Supply Co., London; the Mersey Railway Central Station; the Manchester Electric Light Station; the Sheffield Tramway Station; the Newport (Mon.) Tramway Station; the Leeds Electric Light Station, &c. In the New Conveyor Co.'s chain, the supporting wheels or rollers are not placed directly upon the pivots which connect the side plates of the chain, but the wheels revolve on separate and independent axles, situated about one-third way down the length of the link. L O O O O gag ervi www REL 0000.0 ୦ wwwwww 10% yuram O 6299 R Fig. 67. Compensating Device. The buckets are filled by a chute and guiding device, or "filler," to prevent material falling anywhere but into the buckets. This filler (Fig 68) consists of a hollow box casting in the form of a polygon, with openings at regular intervals around the periphery. This structure is mounted upon an axle above the line of buckets to be filled, and is rotated by a spur-wheel attached to the same axle, and gearing into the conveyor chain. The whole apparatus is so designed that, as it revolves, each opening in turn comes immediately over one of the buckets under- neath. When coal is fed into the central hollow portion of the filler, it is guided without waste into the buckets, and, by properly regulating the rate of flow, each bucket can be completely filled as it passes on its way. Where it is not possible to employ these, the New Conveyor Company recommends malleable cast buckets, but the first cost is much greater than pressed steel. In the conveyor installed at the Mersey Railway, the buckets have malleable cast sides and steel-plate bottoms, the latter being belted on so as to be renewed. 320 SECTION III.—POWER STATION. (6319 Wank Fig. 68. Travelling Automatic Filler by the New Conveyor Co., Smethwick. Heyl and Paterson Coal Conveyor. (FIGS. 69 and 70, page 321.) This is a bucket conveyor, worked by electricity, the buckets being arranged on an endless belt or chain. At the lower end there is a boot, into which the coal feeds by gravity from the main storage bin. The supply of coal to the boot is controlled by a valve. The buckets carry the coal to the top of the conveyor, and discharge it into a small storage bin which is fixed there. This bin and the conveyor move together on gantries, so arranged that the former can be brought in turn over each of the hoppers of the mechanical stokers. The traversing power is obtained from the same motor that works the elevator. The hoppers are filled by bringing up the conveyor to each and opening a valve in the small bin, which has sufficient capacity to fill all the hoppers at one journey. If mechanical stokers are not used, the coal can be fed into suitable bins placed conveniently near the furnaces. This conveyor (Fig. 69) will work in an extremely confined space, with perfect satisfaction. A second system, equally applicable to any power station, but requiring somewhat more room than the first to instal, is shown in Fig. 70. The construction and operation is as follows:-The coal is discharged into a storage bin, or, in cases where it is taken from barges, the barges themselves may be used as a storage place. An elevator is built into the bin and carried to a considerable height above the boilers, and then on in a horizontal direction over the top of a number of bins which are supported at some height above the boilers, and usually a short distance in front. The bottom of each bin is made conical and fitted with a valve and chute, or chutes, which communicate with the hopper of the mechanical stoker. Where the boilers are divided into batteries containing two each, it is convenient to make one bin with a double chute serve for both. At intervals STEAM BOILERS. 321 Fig. 69. (801) HD Arrangement of Heyl and Paterson Coal Traversing Elevator for Steam Plants. Fig. 70. Arrangement of Heyl and Paterson Coal Elevator and Conveyor for Steam Plants. M 322 SECTION III.—POWER STATION. ▸ corresponding to the positions of these storage bins, openings are provided in the horizontal conveyor, through which the coal may be fed into the bins; these openings are provided with doors, so that the supply can be cut off when desired. By this means, any or all the bins may be filled as required. The third system is similar to the first, with the exception that the vertical elevator does not move along the fronts of the boilers. A separate conveyor is provided between each pair of furnaces, and the supply of coal is taken either from a bin running the whole length of the boilers, and provided with suitable openings, or else from separate bins. Combined Belt and Bucket Conveyors. The Link Belt Engineering Company make a conveyor in which also the buckets are rigidly attached to the chain links, and move with them, being specially constructed to retain their contents in every position but one. buckets form a continuous chain or belt in any position of the apparatus. The Push-plate Conveyors. " In a push-plate conveyor the material is moved along in a trough by a series of plates known as "flights." These are connected to each other by means of a chain, or a series of jointed rods forming a chain, as in the "Monobar con- struction. A modification of the push-plate conveyor is the worm conveyor, in which the coal or other material is also pushed forward in a trough by means of plates. Swinging Conveyor. The swinging conveyor is a trough supported upon flexible or springy legs, slightly inclined to the vertical. The trough is given a reciprocating motion by means of a crank working on a connecting rod fixed to the bottom of the conveyor. Owing to the obliquity of the supporting legs, the trough does not receive a plain horizontal motion from the connecting rod and crank, but moves slightly upwards and downwards as well. Table 39.-Customary Speeds and Power Required for Various Types of Conveyors. Type. Band conveyor Worm conveyor Push-plate conveyor Swinging conveyor Bucket conveyor •• ·· ·· • ·· Speed in Feet per Minute. 200 to 500 40 to 60 60 to 180 40 to 70 20 to 40 ·· The following figures may be taken as a rough guide to the cost of gravity bucket conveyors, of a capacity of approximately 70 tons per hour, at 50 ft. per minute. •• £ S. d. Total cost. 37. 4s. per linear foot of bucket chain. The total cost of conveyors, according to American figures, may be divided as follows:- Cost in Sterling. Bucket chain, links, buckets, stands, rails, bolts, &c., in- cluding everything except fillers, driving mechanism, driver and dumpers For each standard curve of 90 deg. radius add For each stationary filler add For each moveable filler add For each foot of track for movable filler add Driving mechanism complete up to motor pinion, exclusive of motor ·· Electric motor, according to size and type Drivers for use with steam, including engines.. Dumpers Coal crushers-each .. •• ·· ·· Approximate Power re- quired for Driving per 100 ft. Length for Capacity of 50 tons, (not including any Lift). 5 horse-power 20 to 25 horse-power ** 13 horse-power 8 to 9 horse-power ·· •• .. •• M .. .. 2 1 8 5 61 19 72 6 12 82 12 to 154 19 258 2 1 154 19 0 3 1 206 4400 31 5 8 3 = 11 N342 STEAM BOILERS. 323 Apparatus. Elevator Elevator Elevator Push-plate conveyor Push-plate conveyor ·· ·· Plate-belt conveyor . • Canvas band Band conveyor Band conveyor Swinging conveyor First Cost. Total. £ 1554 819 428 295 1486 2026 Table 40.-Data of Cost and Maintenance of Conveyors. (W. Chester.) 443 296 172 1767 Per Linear Foot. £ 8. d. 4 4 0 6 6 0 5 7 0 2 9 4 5 3 11 3 12 6 4 10 2 9 0 4 1 11 3 1 0 6 Tons of Material Trans- ported. 335,237 178,541 37,685 149,350 29,769 149,350 (say) 10,000 149,350 2,180 250,000 . Distance of Traverse. Ft. · 74 58 and 72 40 30 90 90 106 125 125 125 60 98 30 110 21 conveyors total length 1722 Cost for Repairs and Renewals. Total. £ s. d. 86 1 6 679 6 8 7 4 0 70 6 0 110 11 3 2311 0 0 40 0 0 70 6 0 42 1 1 15 0 0 Per Ton. d. 0.061 0.913 0.046 0.113 0.891 3.714 (say) 1.00 0.113 4.63 0.114 Per Ton for 100 Ft. of Traverse. d. 0.082 1.4 0.115 0.377 0.938 2.070 (say) 1.00 0.377 4.21 0.0003 Description of Material Conveyed. Coal Partially hot coke Oxide of iron and lime Coal Hot coke Hot coke Small coke and breeze Coal Sulphate of ammonia Coal 324 SECTION III.—POWER STATION. 71 73 Mark M®® Tran 234 706 Mot to scalat 15 i to deale Total 1.augth -H. L' Rosalina Anan • ny 708 5. ELEVATION Burgm Joù PLAN ON TOP (Shawing Tua Gardar Beam, & Host Brazing) Inclineam of Bram OWL 30 0 • n 2001ATESSE The Figs. 71 to 74. The Temperley Temperley Transporter. 14 Baishing Rape 170 Cantrva Bailway Ber $50 an SIDE ELEVATION PLAN OF PLATFORM FROHRIE 72 74 17 STEAM BOILERS, 325 767 The Temperley Transporter. (Fies. 71 to 76.) The appliance consists essentially of a beam or spar, which can be hoisted and supported by a suitable hook. A traveller runs on this rail, and carries a skip. The traveller can be stopped at any one of a large number of fixed points in this rail, and the skip raised or lowered. When the load is being lowered, the traveller is rigidly locked to its ways, and when travelling the load is locked, so that it cannot be lowered. The whole of the various motions of lowering and travelling are controlled by a single wire rope, passing over a pulley at one end of the spar. The spar is stayed at frequent intervals by wire ropes, which at their upper ends are connected to a single ring. The whole appliance can thus be slung, if desired, from an ordinary derrick or crane. The ends of the spar are stayed to fixed points, and when all is hauled taut, the transporter is quite rigid. 76 75 CC G A complete cycle may be described as follows:-The skip being filled and hooked on, the attendant hauls on the single rope which governs the whole series of movements. This lifts the skip until the fall-block is finally raised into contact with the traveller, when it releases a lock securing the latter to the beam, and by the same operation locks itself to the traveller, so that the two move as one. Continuing to haul on the rope would cause the traveller to slide up the beam, but if the rope is now paid out, the traveller with the skip suspended therefrom will slide down the beam, and on reaching the end, the fall-block is automatically unlocked from the traveller, and descends into the hold of the vessel being loaded. If the attendant now hauls on the rope, whilst the skip is freely suspended in mid- air, the latter will be automatically tipped; this done, further hauling on the rope will raise the bucket till the hook reaches the traveller and locks itself there, after which continued hauling on the rope will cause the two to move up the beam. This motion is checked after the traveller has passed the desired stopping-place on the beam; and the rope being now paid out, the traveller runs back to the stop and locks itself, at the same time unlocking the bucket, which then descends to the loading point for a fresh supply. 326 SECTION III.-POWER STATION. Table 41.-Data of Coal-Handling Plants at Electric Lighting and Traction Works. Name of Station. 96th Street Station, New York Glasgow Corporation Tramways …… .. Bristol Tramways Midland Electric Power Corpora- tion } London United Tramways Third Avenue Station, New York. Dublin United Tramways Central London Railway City and South London Railway Union Traction Company, Indiana Mersey Railway • Underground Electric Railway, London Shoreditch Electricity Works Rapid Transit, New York • .. ·· .. .. Station Capacity in Kilowatts. 36,900 10,000 2,000 3,000 48,500 3,600 5,100 3,000 4,000 3,700 55,000 1,600 98,000 Capacity of Coal Bunker in Tons. 10,000 2,400 920 500 12,000 1,500 850 1,000 1,200 600 15,000 750 25,000 Type of Conveyor. Bucket Bucket Bucket Bucket Bucket Bucket Bucket Bucket Push-Plate Bucket Bucket Bucket Automatic Rly. Bucket Maker of Conveyor. John A. Mead Mirrlees Watson C. W. Hunt C. W. Hunt C. W. Hunt C. W. Hunt C. W. Hunt New Conveyor Co. McCaslin New Conveyor Co. Babcock & Wilcox Babcock & Wilcox Capacity of Conveyor in Tons per Hour. Rated 8 100 60 42 ≈ 9 || | || 40 181 30 Remarks. Linear speed of chain, 45 ft. per minute {P Power taken by conveyor, 5 horse-power Power taken by conveyor, 10 horse-power Each bucket has a capacity of 2 cubic feet Linear speed of chain, 35 ft. to 40 ft. per minute Power taken by conveyor, 15 horse-power Coal crusher driven by one 7 horse-power motor Whole plant operated by two 35 horse-power motors STEAM BOILERS. 327 INCRUSTATION AND CORROSION. Incrustation and Scale. Incrustation (as distinguished from sediments due to dirty water) is due to presence of salts in feed water (carbonates and sulphates of lime and magnesia chiefly); these are precipitated when water is heated, and form hard deposits or scale upon the boiler plates. Where the quantity of salts is not large, say 10 to 12 grains per gallon, scale preventatives may be found effective. The chemical preventatives form with salts new salts soluble in hot water; or precipitate them in form of mud, which can be washed out. The selection of the chemical depends upon the.composition of the water, and should be introduced regularly with the feed. Hardness of Water. The hardness of water is indicated by the ease with which it will form a lather with soap. Almost all soaps con ist, chemically, of oleate, stearate, and palmitate of an alkaline base, usually soqa and potash. The more lime and magnesia in a sample of water, the more soap a given volume of the water will decompose, so as to give insoluble oleate, palmitate, and stearate of lime and magnesia; and consequently the more soap must be added to a gallon of water in order that the necessary quantity of soap may remain in solution to form the lather. relative hardness of samples of water is generally expressed in terms of the number of standard soap measures consumed by a gallon of water in yielding a permanent lather. The The standard soap measure is the quantity required to precipitate one grain of carbonate of lime. It is commonly reckoned that one gallon of pure distilled water takes one soap measure to produce a lather. Therefore, one is deducted from the total number of soap measures found to be necessary to use to produce a lather in a gallon of water, in reporting the number of soap measures, or "degrees" of hardness of the water sample. In actually making tests for hardness, the "miniature gallon," Dr 70 cubic centimetres, is used. The standard measure is made by completely dissolving 10 grammes of pure castile soap (containing 60 per cent. olive oil) in a litre of weak alcohol (of about 35 per cent. alcohol). This yields a solution con- taining exactly sufficient soap in one cubic centimetre of the solution to precipi- tate one milligramme of carbonate of lime, or, in other words, the standard soap solution is reduced to terms of the "miniature gallon " of water taken. If a water charged with a bicarbonate of lime, magnesia, or iron, is boiled, it will, on the excess of the carbonic acid being expelled, deposit a considerable quantity of the lime, magnesia, or iron, and, consequently, the water will be softer. The hardness of the water after this deposit of lime, after long boiling, is called the permanent hardness, and the difference between it and the total hard- ness is called temporary hardness. Lime salts in water react immediately oleate, palmitate, or stearate of lime at once. require some considerable time for reaction. hardeners; one equivalent of magnesia salts one-half equivalents of lime. on soap solutions, precipitating the Magnesia salts, on the contrary, They are, however, more powerful consuming as much soap as one-and- The presence of soda and potash salts softens rather than hardens water. Each grain of carbonate of lime per gallon of water causes an increased expendi- ture for soap of about 2 oz. per 100 gallons of water. Temporary Hardness is due to the presence of carbonates, and can be removed by boiling, which drives off the carbonic acid, and causes the carbonate of lime or magnesia to be precipitated. Permanent Hardness is due to the presence of sulphates. Ordinary boiling at atmospheric pressure does not precipitate these, but they are precipitated at a temperature of 300 deg. Fahr. This is often exceeded in steam boilers, and then the sulphates are precipitated as well as the carbonates. Carbonate Waters. Before treating a water, a sample should be analysed in a scientific manner to ascertain what impurities are present. When the impurity consists almost entirely of carbonate of lime (which is soluble only in the presence of carbonic acid), it may be treated by the addition of caustic lime or milk of lime, or by what is known as Clark's process, before being sent to the boiler 328 SECTION III.-POWER STATION. Dr. Clark's process softens water rendered hard by calcium bicarbonate. It consists in mixing with it about one-tenth (for spring water from chalk) of water saturated with lime in solution, the lime in which, combining with the free car- bonic acid of the bicarbonate, forms a solid precipitate of chalk. If the water on analysis is found to contain, say 50 grains of carbonate of lime per gallon, an addition of 28 grains of lime per gallon of water to be purified, or 4 lb. of powdered caustic lime for every 1000 gallons of water, will require to be added; this will combine with the carbonic acid in the water, and cause a precipi- tation of nearly 8 lb. of carbonate of lime per 1000 gallons. Tanks containing not less than from six to eight hours' water supply are required for the caustic lime process, to allow time for the precipitates to settle. Where the carbonate and sulphate of lime are shown by analysis to be both present in the feed water, caustic soda and soda ash may be used for the elimination of the lime salts. Where carbonate of lime alone is present: for each grain per gallon of carbonate of lime found in the water, 14 oz. of pure caustic soda per 1000 gallons of water used will be required to effect the precipitation of the lime. Sulphate Waters. Where there is only the sulphate of lime present: for every grain of sulphate per gallon found in the water, 12 oz. of pure carbonate of soda (soda ash) are required per 1000 gallons of water used. Carbonate and Sulphate Waters. Where carbonate of lime and sulphate of lime are both present, as is often found to be the case, the use of caustic soda will be sufficient to precipitate both salts in the following proportions. A water containing six grains of carbonate of lime per gallon would require 6 × 1½ oz. = 9 oz. of pure caustic soda per 1000 gallons of water, and this quantity of caustic soda would suffice for eliminating also 8.16 grains of sulphate of lime, so that a water containing 14.16 grains of solid matter per gallon, of which 6 grains were carbonate and 8.16 grains sulphate of lime, could be treated by simply adding a sufficient quantity of caustic soda to remove the carbonate of lime. The mineral matters causing the most troublesome boiler scales are bi-car- bonates and sulphates of lime and magnesia, oxides of iron and alumina, and silica. Water with Large Amounts of Solid Residue. In cases where water containing large amounts of solid residue is used, a heavy petroleum oil, free from tar or wax, and which has a vaporising point at nearly 600 deg. Fahr., will give the best results in preventing boiler scale. Its action is to form a thin greasy film over the boiler surfaces, protecting them largely from the action of acids in the water and greasing the sediment which is formed, thus preventing the formation of scale, and keeping the solid residue from the evaporation of the water in such a plastic suspended condition that it can be easily ejected from the boiler by the process of blowing off." If the water is not blown off sufficiently often, this sediment forms into a "putty" that will necessitate cleaning the boilers. Any boiler using bad water should be blown off every twelve hours. 66 Tannate of Soda Compound. (T. T. Parker.) Fifty pounds sal-soda, 35 lb. japonica; put the ingredients in a 50-gallon barrel, fill half full of water, and run a steam hose into it until it dissolves and boils. Remove the hose, fill up with water, and allow to settle. Use one quart per day of ten hours for a 40 horse-power boiler, and, if possible, introduce it as you do cylinder oil to your engine. Barr recommends tannate of soda as a remedy for scale composed of sulphate and carbonate of lime. As the japonica yields the tannic acid, the resultant is equivalent to the tannate of soda. Petroleum Oils. Petroleum oils heavier than kerosene have been used with good results. Crude oil should never be used. The more volatile oils it contains make explosive gases, and its tarry constituents are apt to form a spongy incrustation STEAM BOILERS. 329 Sulphate of Lime. Electrolytic Corrosion Preventive. Zinc is often used in boilers to prevent the corrosive action of water on the metal. The action appears to be an electrical one, the iron being one pole of the battery and the zinc being the other. The hydrogen goes to the iron shell and escapes as a gas into the steam, The oxygen goes to the zinc. Table 42.-Analyses of Boiler Scale. (Chandler.) 74.07 71.37 62.86 53.05 46.83 30.80 4.95 0.88 4.81 30.07 } Coal-mine water Salt well Spring Monongahela "" "" "" Allegheny river near oil works " .. .. Magnesia. ·· • river Substance. •• 9.19 18.95 31.17 2.61 2.84 Carbonate of lime Sulphate of lime Carbonate of magnesia Phosphate of lime Oxide of iron. Silica • 44 Table 43.-Analysis in Parts per 100,000 of Water giving Bad Results in Steam Boilers. (A. E. Hunt.) .. Bicarbonate of Lime Deposited on Boil- ing. 110 151 25 38 75 89 130 21 70 82 50 80 32 390 ·· ·· ·· Silica. ·· 0.65 1.76 2.60 4.79 5.32 7.75 2.07 0.65 2.92 8.21 Bicarbonate of Mag- nesia Deposited on Boiling. Total Lime. Peroxide of Iron. 0.08 0.92 ·· 62,500 500 5,500 Table 44.-Solubilities of Scale-Making Minerals. Soluble in parts of Pure Water at 30 Deg. Fahr. Soluble in parts of Pure Water at 212 Deg. Fahr. I 1.08 1.03 0.36 Total Magnesia. Sulphuric Acid. Chlorine. 8 29 68 Water. 1.14 1.28 Soluble in parts of Carbonic Acid, Water Cold. 2.44 0.63 0.15 30 640 119 1.90 39 890 590 780 48 360 990 38 21 30 95 120 310 21 75 10 80 210 38 70 219 210 90 28 1.90 38 161 33 94 81 61 1.04 41 890 42 23 150 150 1,333 Undetermined Organic Matter. Iron. Carbonate of Lime. 14.78 12.62 62,500 460 9,600 oco Alumina. ·· 26.93 86.25 93.19 212 212 212. Chloride of Sodium. Insolnble in Water at 13.10 36 302° Fahr. 302 [ "" "" " 19 M2 330 SECTION III.-POWER STATION. Table 45.-Prevention and Cure of Boiler Troubles Due to Water. Incrustation Corrosion Priming Sediment, mud, clay, etc. Readily soluble Salts Bicarbonate of Magnesia, Lime, Caustic Soda. and Iron Lime. Magnesia. { Carbonate of Soda. Barium Chloride. Sulphate of Lime Filtration. Blowing off. Blowing off. Heating feed and precipitating. Dissolved Carbonic Acid and Oxygen Precipitate with Alum Ferric Chloride. Organic matter Grease Slaked Lime Carbonate of Soda Chloride or Sulphate of Magnesia Carbonate of Soda. Acid Alkali. Slaked Lime. Caustic Soda. "" } Jand and filter. and filter. Heating. Precipitate with Alum or Ferric Chloride and filter. {Barium Chloride. Sewage Carbonate of Soda in large quantities Foaming (L. F. Lyne and C. P. Carpenter.)-Kerosene has recently been highly recommended as a scale preventive. Kerosene used in moderate quan- tities will not make the boiler foam. It is recommended and used for loosening the scale and for preventing the formation of scale. Neither will a small quantity of common oil always cause foaming; it is sometimes in- jected into small vertical boilers to prevent priming, and is supposed to have the same effect on the disturbed surface of the water that oil has when poured on the rough sea. Yet oil in boilers will not have the same effect and give the desired results in all cases. The presence of oil in combination with other impurities increases the tendency of many boilers to foam, as the oil with the im- purities impedes the free escape of steam from the water surface. The use of common oil not only tends to cause foaming, but is dangerous otherwise. The grease appears to combine with the impurities of the water, and when the boiler is at rest this compound sinks to the plates and clings to them in a loose, spongy mass, preventing the water from coming in contact with the plates, and thereby producing overheating, which may lead to an explosion. Foaming may also be caused by forcing the fire, or by taking the steam from a point over the furnace, or where the ebullition is violent; the greasy and dirty state of new boilers is another good cause for foaming. Kerosene should be used at first in small quantities, the effect carefully noted, and the quantity increased if necessary for obtaining the desired results. Pure water may be obtained by collecting rain, or condensing steam by means of surface condensers. The water thus obtained should be mixed with a little bad water, or treated with a little alkali, as undiluted pure water corrodes iron; or, after each periodic cleaning, the bad may be used for a day or two to put a skin upon the plates. Corrosion may be produced by the use of pure water, or by the presence of acids in the water, caused perhaps in the engine-cylinder by the action of high- pressure steam upon the grease, resulting in the production of fatty acids. Acid water may be neutralised by the addition of lime. Babcock and Wilcox Patent Water Softener. (FIGS. 77 to 79, page 331.) (Guttmann Patent.) The apparatus consists of a chemical tank into which the quantity required for the day is put, and the tank is then filled with water. The tank is provided with a perforated steam coil, for the purpose of heating the water and dissolving the soda ash. Underneath the chemical tank is a reaction tank. Connected to the chemical tank is an auxiliary chemical tank, the design of which is to provide a uniform STEAM BOILERS. 331 St 여기 ​O 77 www EVREYSTIETYST ………………………… U visada KUHU HOLLAGEENA 78 79 Le Figs. 77 to 79. Babcock and Wilcox Patent Water Softener. 332 SECTION III.-POWER STATION feed of the dissolved chemical into the reaction tank; the flow of this dissolved chemical is regulated by a rod attached to the lever of the feed inlet valve, making the supply of both hard feed water and chemical automatic in working. By the above arrangement the chemical in solution is mixed with the feed water before it enters the reaction tank, instead of being simply poured into the body of hard water therein, and the result is a better mixture of the hard water with the chemical. The admission of hard water, as implied above in the description of the auxiliary chemical tank, is controlled by a valve actuated by a rod, which is in turn connected to a float in the soft-water storage tank; thus the quantity of hard water admitted is regulated by the amount of soft water used. For dissolving the chemical, live steam is admitted to the perforated steam coil in the chemical tank. In the auxiliary chemical tank a small ball-cock is fixed, which automatically regulates the supply from the main tank according to the depth of chemical in the auxiliary tank. In order to regulate the quantity of dissolved chemical passing through the auxiliary tank to the reaction tank, a regulating valve with index is provided, the design of which is to restrict the flow of chemical as may be desired. This is, of course, in addition to the chemical valve already mentioned, which is operated by the rod from the feed-inlet valve. The hard water and chemical solution in the reaction tank are raised to boiling point, and at the same time thoroughly agitated by means of one or more specially designed steam injectors. The exhaust steam injector raises the temperature of the water to 180 deg., thus requiring only small assistance from the live steam injector to raise the temperature to boiling point. The softened water flows over a weir into the filter tank, which has divisions arranged, reaching alternately to within a few inches of the bottom and top, forming compartments which compel the water to take a zigzag course. A perforated plate forms the bottom of each compartment, which is filled, as a filtering medium, with wood wool compressed to the required density, a similar perforated plate being placed on the top of the wood wool in each compartment. Below the bottom perforated plates is a settling chamber for the interception of sludge, which is removed by opening the drawing- off valves attached. These are bolted to the bottom of the filter tank, and are of a special pattern, designed to rapidly draw off the sludge; thus a free passage-way is provided for the water, which leaves the filter in a perfectly clear state, and flows into a storage tank placed below the filter. By this arrangement the plant is made most compact, and the capacity of the reaction tank is correspondingly large. The apparatus requires no attention or labour, other than the filling of the chemical tank every morning and periodical cleaning. It can be used with any softening process employing either lime, caustic soda, or other chemical; but the use of carbonate of soda (alkali) or mono-silicate of soda is preferable. All carbonate and sulphates, whether lime or magnesia, are removed in a thoroughly efficient manner, and the softened water will not attack the boiler plates or fitting. The Guttmann apparatus is built in the following standard sizes :— Quantity Treated per Hour. Quantity Treated per Hour. 300 Gallons. 600 1,000 2,000 3,000 4,000 "" "" "" "" 5,000 Gallons. 6,000 7,000 8,000 9,000 10,000 "" "" "" "" "" 3. For larger plants, up to and above 20,000 gallons per hour, special plans are made to suit the existing space. The Archbutt-Deeley Water Softening and Purifying Apparatus. (FIG. 80.) (Mather and Platt.) The Purifier consists of a cast-iron tank divided into two equal parts. The two tanks thus formed are identical, and are used to make the process a continuous one, the purifled water being drawn off from one whilst the other is under treatment. STEAM BOILERS. 333 = せ ​110 2 11 11 NOWN t entent + MON 11 2 A 15 2 1. Hard Water Supply. 2. Tank for Dissolving Chemicals. 3. Blower for Air and Mixing Chemicals. 4. Perforated Rose. 5. Three-way Tap. 6. Perforated Pipe for Cheini- cals. 7. Tap on Suction Pipe for Chemicals. 8. Air Tap on Blower. 9. Perforated Pipes for Air. 10. Floating Discharge Pipe. 11. Coke Stove. 12. Blower for Fuel Gas. 13. Discharge Nozzle. 14. Ball Tap for Regulating Outlet. 15. Gas Escape. 13 HOTE Fig 80. Archbutt-Deeley Water- Softening and Purifying Apparatus. 334 SECTION III.-POWER STATION. The chemicals used are quicklime and sodium carbonate (58 per cent. alkali), which are boiled up with water, in a small tank, by means of live steam. The main tank is filled with hard water, whieh is caused to circulate by admitting steam to a blower. It is drawn through a rose vertically upwards, and then down a pipe to near the bottom of the tank, connection being made by a small pipe to the chemical tank. The chemicals are drawn into the current and diffused throughout the water. Air is then forced into a perforated pipe at the bottom of the tank, which stirs up the precipitate from previous operations. This materially assists the rapid settling of the new precipitate, which otherwise would not coagulate. After the blower has been in operation about 10 minutes, the steam is turned off and the precipitate allowed to settle, which takes about an hour. The water is then tested with silver nitrate, to see if the right amount of lime has been added. The next process consists in carbonating the water to prevent it forming any deposit in the pipes, etc., which otherwise is very liable to happen. This is done whilst drawing off the water, which is done from the top by means of a hinged pipe whose mouth is kept just below the water by means of floats. Gas from a coke stove (CO2) is forced into this pipe, and the water is caused to splash about, by means of baffles, and consequently dissolve a considerable quantity of the gas. No water is drawn off below a certain level, and a stop is provided to prevent the hinged pipe from descending too far. The precipitate and mud in the tanks is removed periodically. Table 46.-Showing Number and Size of Tanks Required for Various Quantities, under Ordinary Conditions. TANK CALCULATED TO FILL IN 20 MINUTES, AND TO EMPTY IN 20 MINUTES INTO RESERVE TANK, ALLOWING 90 MINUTES FOR TREATING AND SETTLING. 2. Gallons Gallons per per Hour. Minute. 1. 600 1,000 1,500 2,000 2,500 3,000 3. Number of Tanks and Approximate Dimensions of same. 10 17 25 33 41 ft. in. One One ft. in. ft. in. 7 0 X 7 0 X 70 8 0 x 80 x 80 ..12 0 0 X 80 x 8 0 One ..12 0 x 8 0 x10 0 One ..12 0 x10 0 × 10 50 One ..12 0 x12 0 x10 0 One 0 ·· .. 0 0 0 5,000 83 6,000 100 7,000 117 8,000 134 9,000 150 10,000 167 0 4,000 67 Two ..12 0 x12 0 x10 0 Two ..13 6 x13 6 × 10 Two .15 0 x15 0 x10 Two ..16 6 x16 6 ×10 Two ..17 6 x17 6 × 10 Two ..18 6 x18 6 ×10 0 Two ..19 6 ×19 6 ×10 Three..15 6 x15 6 × 10 Three..17 0 x17 0 x10 Three..18 0 x18 12,500 208 15,000 250 0 ×10 17,500 291 334 20,000 25,000 417 6 6 Three..19 6 x 19 Three..21 6 ×21 6 ×21 Three..23 6 x23 Four ..21 0 ×21 30,000 500 6 35,000 583 40,000 666 750 45,000 50,000 833 0 × 21 Four ..22 6 × 22 Four ..24 ..24 0 ×24 Four ..25 0 ×25 0 × 25 Four..27 6 x 27 60,000 1000 × 10 × 10 x 10 0 6 0 0 0 0 0 0 × 10 0 0 × 10 0 6 ×10 0 × 10 × 10 0 0 0 0 5. 6. 4. Supply Required Diameter Diameter of Inlet of Outlet Pipes. Pipes per Minute in Gallons. 70 120 180 240 300 360 EACH TANK CALCULATED TO FILL IN 20 MINUTES, AND TO GIVE CONTINUOUS DELIVERY, ALLOWING 90 MINUTES FOR TREATING AND SETTLING. 360 450 560 680 765 855 950 600 720 810 950 in. 3 4 4 5 6 6 1,160 1,380 1,100 1,270 1,440 1,560 1,850 6 7 8 8 9 10 10 8 9 9 10 10 12 02221 in 14 30 + LO CO7 4 5 6 6 4 4 4 5 O LO LO 5 5 5 6 6 7 7 ∞∞☺oogg 10 10 12 In cases where the supply available is only equal to the demand, larger tanks, or more of them than given above, are required. STEAM BOILERS. 335 The "Desrumaux” Water Softener and Purifier. (FIG. 81.) The apparatus consists of three parts 1. The saturator, wherein a portion of the water is saturated with lime. This consists of a cylindrical chamber, containing a revolving mixer actuated by the water to be purified. 2. The reagent tank, fitted with a special device for ensuring a constant and uniform supply of the liquid it contains. 3. The settling chamber or decanter, in which the impurities are deposited. It is arranged o that the matter deposited on the settling surfaces gravitates to the bottom of the chamber, and are thus easily removable by a small rush of water. H The water to be softened and purified is delivered into a receiving tank, from which a due proportion is diverted to form the lime water, the remainder passing into the centre cylinder over the water-wheel, and thus providing the necessary motive power to drive the automatic mixer. (3.) CINE HAHINTHESEST Fig. 81. The lime water flows over a sluice in the central cylinder, where it joins the water to be treated and the solution of soda from the reagent tank. Chemical reactions take place in the central cylinder, and in the upward journey of the chemically-treated water; the suspended matters and resolved impurities are attracted by and deposited upon the spiral settling plates, from which they gravitate to the mud-box, and are removed by the action of the purging lever. After completing its journey round the settling-plates, the water passes through a filter of wood fibre, which arrests any light particles having escaped settlement, and ensures a perfect clarification of the already softened water. 336 SECTION III.-POWER STATION. The quantities of the chemical solutions are proportional to the quantity of water being treated; as the supply varies, the quantity of the diverted water (forming the lime solution as above stated) varies in exact ratio, and the supply of solution from the reagent tank also varies by the automatic motion of the soda scoop actuated by the water-wheel. When the water supply stops, the flow of lime water ceases, and the valve of the reagent tank is closed. This arrange- ment precludes the possibility of wasting the chemical solutions. Should the character of the water vary, the chemical solutions can be adjusted to deal with such variation. Holden and Brooke's Grease and Oil Separator. Figs. 82 and 83 shows these separators; the makers claim the following advantages;- 1. It has ample internal area without being of unreasonable or unwieldy size. 2. No back pressure is set up; it contains no baffles, small holes or passages, or any device that can hinder the free flow of steam to the condenser (thereby reducing vacuum). 83 1 B C E ܚܢ. A D B с 82 191 Figs. 82 and 83. Holden and Brooke's Grease Separator. 3. No part of the separator is likely to become clogged or ineffective by the grease. 4. The grease-depositing surface offers no resistance to the flow of steam. 5. The depositing surface always remains equally active and effective. 6. The grease can always get freely away from the coils. Torrent Filter. (Pulsometer Engineering Company, Limited.) The outside casing or body of the filter is of wrought or cast iron, inside which is the filtering material, arranged in a layer on a grating. Underneath the grating STEAM BOILERS. 337 is a distributing apparatus for air. The dirty water enters at the top, and after passing through the filtering material, emerges clean at the bottom. The filter should be cleaned about once every ten hours. This is done by sending a small quantity of water and a large quantity of steam through the filter in a reversed direction, which quickly removes all the collected dirt. Bruun's Automatic Water Softener. (FIG. 84, page 338.) This apparatus is adapted for using caustic soda or carbonate of soda. The water to be treated is led through the pipe k into one of the chambers of the oscillating receiver c. When this chamber is filled the receiver tips over, pouring its contents into the mixing tank below, at the same time bringing the other chamber of the receiver below the orifice of the pipe k. To the receiver is fixed a system of levers, which at every oscillation actuates a valve, fixed on the bottom of the circular tank d, and which can be regulated by two small nuts. A given quantity of chemicals can, by this arrangement, be mixed with the water. The impurities are precipitated to the bottom of the tank a, the pure water ascending through the intermediate filter i, and leaving the apparatus through the pipe l The precipitated impurities are removed through the cock f every four to six weeks, and the filtering material is taken out at the same intervals to be cleansed, and can be used repeatedly. In larger apparatus the chemicals are, by means of the pump g, pumped to the top of the apparatus, thus saving time and labour. This apparatus is supplied for purifying large quantities of water, from 670- gallons and upwards per hour. Employment of Soda. When it is found necessary to employ soda (carbonate) for the removal of sulphates in the water, a small tank should be provided, into which is fitted a sheet-iron basket, for taking the daily charge of carbonate of soda. The water supply should be arranged so that water is allowed to flow on to and through the soda so as to melt the latter, and thus the tank will contain the requisite solution of soda. Ordinary washing soda is the simplest kind to employ. The soda contained in the carbonate combines with the sulphur of the sulphate of lime, forming a salt, and no active soda passes into the boilers. For supplying the exact quantity of soda solution in proportion to the water drawn from the apparatus, it is recommended to employ a small pump attached to the feed pump, so that each stroke or revolution of the latter will ensure a definite amount of solution being delivered to the heater detartariser. By this means the quantity injected is exactly proportioned to the quantity thrown by the feed pump. into the boilers FEED HEATERS. It is essential that the feed water shall enter boiler as warm as possible, both for economy of fuel and to avoid wear of boiler. Economy can only be effected: by using heat that would be otherwise wasted. A fuel saving of 10 per cent. has been secured by the adoption of the "Auxiliary" feed-water heater systems. The following are the methods of warming feed water before injecting it into the boilers : By means of exhaust steam, by passing the heat of the steam exhausted from the engines on the feed pumps through metal partitions into the feed water. By taking the feed water from the condenser hot well. 'By taking the warm water from a jet condenser. The temperature in this. case is only slightly raised. By taking some of the heat from the gases after they leave the boiler flues, and passing this heat through metal partition into the feed water. Compactum Feed-Water Heater. An exhaust steam feeder is a sort of surface condenser with insufficient surface to condense more than a small proportion of steam. The condensed 338 SECTION III.-POWER STATION. 2 www In order harth, af fed ad pinigine www.degl Lalo Apo Make Wor I www CA Ja na 12 seine 201 aalll Jake Tent sachaill did) Minode 7501-SET unclip How estoy a yuo 2000 bre boot So So he ולה 77 70 Fig. 84. Bruun's Water Purifier. k 32150 bro3 fon gruell $700 2200 110 Lecca ON we Days 12 tel MP 2010s ohtripl gooboo at o 300 og st Yo Vuonins Simmery 元​包 ​in A STEAM BOILERS. 339 steam is trapped out and the feed water kept in circulation by the feed pumps. In the "Compactum," manufactured by Messrs. Kirkaldy, Limited, the steam passes through a large number of parallel pipes of thin sheet brass, which termi- nate at each end in a small chamber; and from the chamber at the lower end the cooled steam passes away to the exhaust uptake, and the condensed water is drained off. The system of pipes is contained within a vertical cylinder, into the bottom of which the feed water enters, and from the top of which it passes on to the boilers. The feed water has free circulation between the parallel steam pipes, enabling it to become considerably raised in temperature between the inlet and outlet points. Weir's feed heater is designed to raise the temperature of the feed water to nearly 212 deg. Fahr. by means of a portion of the steam from the receiver of the compound engine. The feed water is forced by one of the feed pumps into a chamber in such a way that it is broken up into spray, and exposed to steam from the receiver when in this state; it is still further mixed with the steam by having to fall over a number of dashplates in this chamber., as it falls down and drains into the second feed pump, to be pumped by it to the boiler. With this instru- ment economy of fuel is not so fully realised as increased durability of the boiler. Wheeler's Patent Feed-Water Heater. (FIG. 85, page 340.) The heater is provided with both mud-blow and surface blow-off connections. The tubes are drawn thick at one end, and are screwed into the upper tube head and secured in the lower tube head with brass ferrules and special asbestos packing, both tube heads being made of high-grade charcoal iron. This arrange- ment provides for expansion and contraction without danger of strain to any part. The tubes can be unscrewed and replaced by any ordinary mechanic. The tubes are made of best quality seamless drawn brass-well tinned inside and outside, and tested to 700 lb. pressure per square inch. By removing the upper cover of the heater, and the bottom hand-hole plates, the tubes can be readily cleaned, and the settling chambers emptied with little trouble and loss of time. The shell of the heater is made of cast-iron, or steel plate, as preferred. Vertical as well as horizontal types are furnished in sizes ranging from 50 horse-power to 6000 horse-power. Green's Economiser. (FIGS. 86 and 87, page 340.) Green's economiser is selected for notice as a type of this class of heat-saving devices. It consists of a series of cast-iron tubes, 9 ft. in length by 4 in. in diameter, which are arranged vertically in sections of various widths across the main flue, between boilers and chimney. The size of an economiser required for a given boiler plant is determined by the amount of water evaporated in the boilers per hour. Where this is not readily attainable, the number of tubes required may be judged approximately thus; calculate four tubes per ton of coal consumed in the boilers per week. When in position the sections are connected by branch pipes running length- wise, one at the top and the other at the bottom, on opposite sides, the latter being outside the brickwork which encloses the apparatus, and the former secured to the flanges of top boxes. The waste gases are led to the economiser by the ordinary flue from the boilers to chimney, and the feed water is forced into economiser by boiler pump or injector, at the lower branch pipe nearest the point of exit of the gases, and emerges from the apparatus through the upper branch pipe, at the opposite end, where the gases enter. Each tube is encircled by a set of triple overlapping scrapers, the top of which rests on a lifting bar with guard placed above to keep in position. These travel continuously by suitable mechanism up and down the tubes at a slow rate of speed, the object being to keep the external surface free from soot. The economiser absorbs a large proportion of the waste heat stored up in the furnace gases. The temperature of the gases is reduced from 650 deg. Fahr. on the boiler side of the economiser to 350 deg. when leaving the economiser to pass into the stack, and the temperature of the feed water is increased about 150 deg. Economiser Details. (Mechanical Engineer's Pocket Book.) Sweating of Economiser Pipes.-It is not desirable to introduce the feed to the economiser at too low a temperature, as it causes the vapour in the furnace • 340 SECTION III.-POWER STATION. UME 85 86 C MUD BLOW FEED WATERT OUTLET Cha HAND HOLE FEED WATER INLET 11800 (235) EXHAUST THAT ME 7 224 £ ww EXHAUST OUTLET WWTH SURFACE BLOW MUD BLOW Feed-Water Heaters. Fig. 85. Wheeler Horizontal Feed-Water Heater, Figs, 86 and 87. Green's Economiser. 87 STEAM BOILERS. 341 gases to condense on the tubes, and sets up external corrosion. When the feed water is below 90 deg. Fahr., the suction side of the pump should be connected with a in. pipe to the hot water outlet on the top of the economiser, to take the chill off the feed, and prevent condensation or "sweating" of the pipes. Width of Economiser Chambers.-Messrs. Green's economisers are usually constructed in sections containing 4, 6, 8, or 10 tubes, according to convenience, the widths of chamber required for these sizes being as follows:- 4 tubes in width 3 ft. 4 in. inside chamber. 4 8 0 4 6 8 10 "" "" "" "" "" 6 7 ** "" "" When a passage is required down the side of the economiser for purposes of inspection, and it is wise to provide one, an additional 2 in. should be added to above dimensions. "" .. .. Size of Economisers.-In ordinary practice it is usual to allow not less than 4 tubes per ton of coal consumed in the boilers per week. Thus, if 20 tons are burnt, the economiser should contain not less than 20 x 480 tubes. If coal con- sumption is not ascertainable, another fairly equivalent rule is to allow one tube for each 3 indicated horse-power. Thus 300 indicated horse-power would require about 300 ÷ 3 = 100 tubes. If the feed water is very sedimentary, the tubes soon become encrusted; if the boilers are worked at a high pressure, it is well to allow a few extra tubes. It is a good fault to have the economiser of ample size; the resulting economy is well worth the outlay. This is especially the case where the boilers are worked with forced draught. See further remarks on this point under "Heating Surface." On account of the scraper arrangements, the economiser can only be increased or diminished four sections at a time. Thus, if the economiser is 6 tubes in width, the number of tubes can only be increased or diminished 6 x 4 = 24 tubes at a time. Duration of test in hours Weight of coal burnt in pounds Steam pressure in pounds per square inch Temperature of water entering economiser Temperature of water entering boiler Degrees feed water heated by economiser Temperature of gases entering economiser. Temperature of gases entering chimney Degrees gases cooled by economiser Evaporation per pound of coal from and at 212 deg. F., lbs. Saving effected by economiser, per cent. ·· ▼ Provision for Expansion and Inspection. - When an economiser contains more than about 96 tubes it is well to divide it into two or more groups, with a passage between the groups to permit of inspection, the groups being also connected by suitable bends to allow for expansion. Heating Surface and Water Capacity of Economisers.-Each tube averages about 10 square feet in area, and holds about 6 gallons of water, including the top and bottom boxes. Thus the total heating surface of an economiser of 96 tubes is 96 × 10 = 960 square feet, and the capacity 96 × 6 = 576 gallons. Table 47.-Tests of Steam Boiler with and without Economiser. (Hutton.) • "" ·· "" •• • "" .. With Without Economiser. Economiser. 11.5 7856 58 88 deg. F. 225 deg. F. 137 deg. F. 618 deg. F. 365 deg. F. 253 deg. F. 10.613 28.9 11.5 10,282 57 85 deg. F. 645 deg. F. 8.235 The Berryman Feed-Water Heater. The steam passes through the tubes, which are bent in the shape of an inverted U, and both ends secured to one tube plate. 342 SECTION III.-POWER STATION. CALORIMETRIC TESTS. (DRYNESS OF STEAM.) Priming, or Wet Steam. A fault frequently met with in steam boilers is the carrying over of water mechanically mixed with the steam, which water not only takes away heat with- out any useful effect, but when present in any inarked quantity, itself becomes a source of danger and of serious loss in the engine. If steam rises from a surface of water faster than about 2 ft. 6 in. to 3 ft. per second, it carries water with it in the form of spray; and when a fine spray is once formed in steam it does not readily settle against a rising current of very low velocity, as a current of 1 ft. per second will carry with it a globule of water of an inch in diameter. The cause of priming may be either impure water, too much water, or im- proper proportions in the boiler. When a boiler is found to form wet steam with good water, carried at a proper height, it is a proof of wrong design. The amount of priming in different boilers varies greatly, and as yet there is not sufficient data to establish any definite ratio for boilers in ordinary use. The experiments of M. Hirn, at Mulhouse, showed an average of at least 5 per cent. ; Zeuner sets it down as approximately from 7 to 15 per cent. Dryness of Steam. The colour of a jet of steam near the orifice whence it is escaping, is blue when it contains less than 2 per cent. of moisture, and white when it contains more. To determine quantity of water in steam, Calorimeters are used. The Barrel Calorimeter. (FIG. 88.) (Hutton.) As its name implies, this consists of a barrel placed on a pair of scales. (Fig. 88.) The mixture of steam and water must be constantly stirred. Steam from the main steam pipe is admitted through a rose at the bottom. The steam pipe is provided with a waste pipe for discharging steam to waste for a few minutes, in order to heat the pipe, and obtain steam free from water of L ZETTE ELE KOMENTONIO C Steam pipe from boiler WIJEHJA Waste pipe Fig. 88. Barrel Calorimeter. condensation, before steam is admitted to the calorimeter. When the barrel and pipes are fixed in position, they are thickly clothed with felt or some other non- conductive material, to prevent loss of heat by radiation. The steam pipe of the calorimeter should project horizontally into the main steam pipe, to avoid drawing off water of condensation and water carried with the steam along the surface of the pipe. STEAM BOILERS. 343 In using the calorimeter, not less than 80 lb. of cold water is put in the barrel, and the temperature noted. Steam is then discharged through the waste pipe until the pipe is properly heated, and the steam appears to be free from water of condensation. The cock on the waste pipe is then closed, steam is admitted to the calorimeter, and when 4 lb. of steam are added to the water, the steam is turned off. The water is mixed with the stirring-rod and its final temperature noted. Let T = the final temperature of the mixture of steam and water in degrees Fahr. t = the initial temperature of the cooling water. W = the weight of cooling water in pounds. w = the weight of steam in pounds mixed with the water. L = the latent heat of steam of the given pressure. H = the sensible heat of the steam, or the boiling point of water and the condensing point of steam under a given pressure. D = the weight of dry steam contained in the number of pounds of steam as supplied from the boiler and discharged into the calorimeter. [ (T − t) × W] — [ (H − T) × w0]. L Then D = The percentage p, of dry steam contained in 1 lb. of steam from the boiler is- www.ee D x 100 N p in which N = the number of lbs. of steam mixed with the water in the calorimeter. Example: In a calorimeter containing 80 lb. of water at a temperature of 56 deg. Fahr., 4 lb. of steam of a pressure of 76 lb. per square inch by the steam gauge were discharged, which resulted in raising the temperature of the water to 110 deg. Fahr. Required, the percentage of dry steam contained in the steam as supplied by the boiler, and also the percentage of moisture or water carried from the boiler with the steam. Then, the boiling point of water under steam of 76 lb. per square inch pressure is, from Table, Properties of Saturated Steam = 320.6 deg. Fahr., the latent heat of the steam is = 888 units. • The weight of dry steam contained in the steam as supplied by the boiler is = [ (110° — 56°) × 80 lb.) — [ (320.6° — 110°) × 4 lb.] 4320—842.4 888.9 888 = 3.91 lb. of dry 3.91 lb. = .09 lb. of water. steam; the steam therefore contains 4 lb. The weight of dry steam contained in 1 lb. of the steam as supplied by the boiler is= 3.91 lb. x 100 4 lb. + = 97.75 per cent. The percentage of moisture carried with the steam from the boiler in the form of spray is = 100 - 97.75 2.25 per cent. In practice the quantity of moisture in steam generally averages from 1 to 5 per cent. It is, however, frequently more, and is generally considerable in boilers in which steam is generated in confined spaces and free circulation is not obtained. The quantity of water carried with the steam from the boiler, as determined by a calorimeter, should be deducted from the quantity of water apparently evaporated in the test of a boiler. For instance, if the percentage of moisture in steam be 4 per cent., and 20,000 lb. of water were apparently evaporated by the boiler, then 20,000 × .04 - 800 lb. of water were carried from the boiler unevaporated, and the quantity of water actually evaporated is only 20,000-800 19,200 lb. Recent experiments by Professor D. S. Jacobus show that it is practically impossible to obtain a true average sample of the steam flowing in a pipe. For accurate determinations, all the steam made by the boiler should be passed through a separator, the water separated should be weighed, and a calorimeter test made of the steam just after it has passed the separator. Coil Calorimeters. Instead of the open barrel in which the steam is condensed, a coil acting as a surface condenser may be used, which is placed in the barrel, the water in coil and barrel being weighed separately. This calorimeter may be used continuously, if desired, instead of intermittently. In this case a continuous flow of condensing water into and out of the barrel must be established, and the temperature of inflow and outflow and of the condensed steam read at short intervals of time. 344 SECTION III.-POWER STATION. Peabody's Throttling Calorimeter. (FIGS. 89 and 90.) The calorimeter, shown in Fig. 89, is a closed cylindrical metallic chamber K, having an inlet passage at A, controlled by the valve E, an outlet passage at the bottom, controlled by the valve N, and a thermometer cup at T. The chamber is thickly wrapped with asbestos and hair felt, protected by wood lagging to reduce radiation. The U-shaped tubes or syphons for attaching the pressure gauges B and Care furnished with the calorimeter. The nipple A, connecting the inlet valve E with the chamber K, is made of composition, cut with pipe thread and provided with a well-rounded orifice for gauging the flow of steam to an enlarged scale in Fig. 90. 89 90 B U 339 MAIN STEAM THERMOMETER. T PIPE E HALA FELT. of C U Figs. 89 and 90. Peabody's Throttling Calorimeter. The connection with the main steam pipe from which a sample of steam to be used is taken, should be as short and direct as possible, and should be well wrapped to reduce radiation. The supply pfpe should enter the main steam pipe at least half an inch, or it may be long enough to reach across the bore of the steam pipe, and be pierced with numerous small holes and closed at the end. The waste pipe from N should be at least in. in diameter for its entire length, and may be larger if longer than 20 ft. The gauge C for measuring the presure in the main steam pipe may be attached directly to that pipe, if more convenient than as shown in the cut. To use the calorimeter, fill the thermometer cup with oil, and insert the ther- mometer; see that the syphons are filled with cold water, and that they do not leak; open both the valves E and N wide, and wait 10 or 15 minutes till the whole STEAM BOILERS. 345 apparatus is heated. Read the gauge B, and add the pressure of the atmosphere to get the absolute pressure in the calorimeter. The pressure of the atmosphere is commonly assumed to be 14.7 pounds per square inch. Inches of mercury can be reduced to pounds per square inch by multiplying by 0.49. Find the corresponding temperature from a table of the properties of saturated steam, and compare with the temperature in the calorimeter given by the thermometer; the excess of the latter over the former is the superheating of the steam in the calorimeter. Should the superheating exceed 20 deg., the exit valve at N may be partially closed to raise the pressure in the calorimeter 5 lb. or 10lb. above that of the temperature; this last operation is only for convenience in the use of the tables of the properties of saturated steam. The flow of steam through the calorimeter will suffice to make the loss by radiation of no conse- quence, and no correction need be applied. When a test is to be made, the valve on the pipe N is opened wide (this valve is frequently omitted), and the valve at E is opened wide enough to give a pressure of 5 lb. to 15 lb. in the reservoir K. Readings are then taken of the boiler gauge, of the gauge at C and the gauge at B, and of the thermometer at T. It is well to wait about 10 minutes after the instrument is started before taking readings, so that it may be well-heated. Let the boiler pressure be p, and let and q be the latent heat and heat of the liquid corresponding. Let p be the pressure in the calorimeter, and A1 and t₁ the total heat and the temperature of saturated steam at that pressure, whilst ts, is the temperature of the superheated steam in the calorimeter. Op the specific heat at constant pressure shown by Regnault's experiments to be 0.48, then : xr+ q = λ1+Op (ts—t₁) ; x = = Example: The following are the data of a test made with this calorimeter :- 14.8 pounds. 69.8 12.0 "" "" 268.2 deg. Fahr. Pressure of the atmosphere Steam pressure by gauge Pressure in the calorimeter guage Temperature in the calorimeter 1156.4 +0.48 (268.2 Pressure. X Absolute. 300 250 200 175 150 Gauge. 285.3 235.3 185.3 160.3 135.3 ·· Priming. .. 892.9 Per cent. of priming, 100 0.077 0.070 0.061 0.058 0.052 — (^ 1 + Op (t; — t₁) — 2). — * 243.9) 286.2 This type of calorimeter can be used only when the priming is not excessive; otherwise the throttling will fail to superheat the steam, and in such case nothing can be told about the condition of the steam either before or after throttling. To find this limit for any pressure ts may be made equal to t7 in above equation: that is, we may assume that the steam is just dry and saturated at that limit in the calorimeter. Ordinarily, the lowest convenient pressure in the calorimeter is the pressure of the atmosphere, or 14.7 pounds to the square inch. The following Table has been calculated by Peabody for several pressures in the manner indicated. It shows that the limit is higher for higher pressures, but that the calorimeter can be applied only where the priming is moderate. When this calorimeter is used to test steam supplied to a condensing engine, the limit may be extended by connecting the exhaust to the condenser. For example, the limit at 100 lb. absolute, with 3 lb. absolute in the calorimeter, is 0.064, instead of 0.046 with atmospheric pressure in the calorimeter. Table 48.-Limits of the Throttling Calorimeter. - Pressure. .. 98.8 = 1.2. Absolute. .. 125 100 75 50 = 0.988; Gauge. 110.3 85.3 60.3 35.3 Priming. 0.046 0.040 0.032 0.023 346 SECTION III.-POWER STATION. In case the calorimeter is used near its limit-that is, when the superheating is a few degrees only-it is essential that the thermometer should be entirely reliable; otherwise it might happen that the thermometer should show super- heating when the steam in the calorimeter was saturated or moist. In any other case, a considerable error in the temperature will produce an inconsiderable effect on the result. Thus at 100 lb. absolute with atmospheric pressure in the calori- meter, 10 deg. Fahr. of superheating indicates 0.035 priming, and 15 deg. Fahr. indicates 0.032 priming, so also a slight error in the gauge reading has little effect. Suppose the reading to be apparently 100.5 lb. absolute instead of 100, then with 10 deg. of superheating the priming appears to be 0.033 instead of 0.032. The following Tables, worked out by Kent for the throttling calorimeter, are very handy. Table 49.-Moisture in Steam-Determinations by Throttling Degree of Superheat- ing T-212 deg. 10 20 30 40 50 60 70 Degree of Superheat- ing T-212 deg. deg. 0 0.51 0.90 1.54 2.06 2.50 2.90 3.24 3.56 3.71 3.86 3.99 4.13 0.01 0.39 1.02 1.54 1.95 2.36 2.71 3.02 3.45 3.58 3.03 2.49 .51 1.02 1.45 1.83 2.17 2.48 .00 .50 .92 1.30 1.64 1.94 .30 .77 1.10 1.40 .24 .57 .87 1.94 1.40 deg. 0 10 20 30 40 50 8288 70 5 | 10 | 20 | 30 | 40 | 50 | 60 | 70 | 75 | 80 · 80 90 100 110 ·· • ·· ·· • • • ·· ·· ·· ·· .. ·· ·· ·· Calorimeter. (Kent.) ·· ·· Gauge Pressures. Per Cent. of Moisture in Steam. ·· Dif.p.deg..0503.0507.0515.0521.0526.0531.0535.0539 .0541 .0542 .0544 .0546 ļ :: 5.48 4.91 4.39 4.63 4:85 5.08 5.29 5.49 5.68 5.87 6.05 3.84 4.08 4.29 4.52 4.73 4.93 5.12 5.30 3.29 3.52 3.74 3.96 4.17 4.37 4.56 4.74 2.74 2.97 3.18 3.41 3.61 3.80 3.99 4.17 2.19 2.42 2.63 2.85 3.05 3.24 3.43 3.61 1.64 1.87 2.08 2.29 2.49 2.68 2.87 3.04 60 1.09 1.32 1.52 1.74 1.93 2.12 2.30 2.48 4.34 3.78 3.21 2.64 2.07 .55 .77 .97 1.18 1.38 1.56 1.74 1.91 .00 22 .42 .63 .82 .00 1.18 1.34 .07 .26 1.50 .94 .44 .61 .78 .05 .21 .37 .03 .33 .47 Gauge Pressures. 3.17 2.63 2.09 1.55 1.01 Per Cent. of Moisture in Steam. ·· 100 | 110 | 120 | 130 | 140 | 150 | 160 | 170 | 180 | 190 | 200 | 250 .. 85 | 90 3.32 2.77 2.23 1.69 1.15 .60 .06 Dif.p.deg..0549.0551.0554.0556.0559.0561.0564.0566 .0568 0554. 1 2.90 2.35 1.80 1.26 .72 .17 .85 .31 6.22 6.39 7.16 5.65 5.82 6.58 5.08 5.25 6.00 4.51 4.67 5.41 4.10 4.83 3.53 4.25 3.91 3.37 2.80 2.96 2.23 2.38 1.66 1.81 1.09 1.24 *52 3.67 3.09 2.51 1.93 .67 1.34 .10 .76 .0570 .0572 .0581 STEAM BOILERS. 347 SUPERHEATERS. Superheating of Steam. (W. H. Fowler.) The superheating of steam conduces to economy by preventing initial con- densation in the cylinder. Superheating may be used either to evaporate water in the boiler, or to dry the steam supplied to the engines. Mr. Michael Longridge states that if steam is superheated for the latter purpose, the superheater shoula, to secure full advantage, be heated with gases from 1000 deg. to 1200 deg. Fahr. in temperature, and that if the difference between the temperature of the gases out- side and the steam inside the superheater is 450 deg. to 500 deg. Fahr., the quantity of heat transmitted per hour is about six British thermal units per square foot of surface for each degree difference of temperature. But if the difference or head of temperature falls to about 150 deg. to 200 deg. Fahr., the rate of transmission falls to about one British thermal unit per square foot per hour. Unless, therefore, the waste gases from a boiler possess a temperature of considerably more than 200 deg. Fahr. above that of the steam in the boiler, they are of little use for superheating purposes. The same authority, in a paper before the Institution of Mechanical Engineers, gave it as his opinion, that 400 deg. of superheat is inadequate to pre vent initial condensation. Messrs. Fairbairn and Tate, Hirn, and Siemens, all found that saturated steam was not a true gas, and that its expansion on the application of further heat was at first much greater than that of a perfect gas. When a temperature of about 20 deg. Fahr. above that of the saturated steam was reached, the volume increased at about the same rate as that of a perfect gas. No data appear to be yet available as to the expansion of steam with high degrees of superheat; but there is little doubt that it would be that of a perfect gas. ·· Aim of Superheating. The greatest advantage to be gained by the use of superheated steam is in engine cylinders, and is due to the immediate absorption of the film of water on the metal surfaces by the surplus heat, thereby counteracting cylinder conden- sation, which is the heaviest loss in the expansive working of steam. In this connection superheated steam would appear to have an advantage over steam- jackets, inasmuch as the heat is applied exactly where it is wanted, and during the period that it is wanted, that is, up to the point of cut-off; whereas a steam-jacket wastes a considerable part of its heat and time in warming up the exhaust. Table 50.-Loss of Steam Produced by Initial Condensation in Cylinders. (W. S. Hutton.) Type of Engine. ·· Single expansion, or simple, stationary engines.. Portable engines Locomotive engines Double expansion, or compound, engines.. Triple expansion engines Quadruple expansion engines ·· ·· ·· ·· ·· .. ·· · Pressure in Pounds of Steam Used. 40 to 100 50 120 140 200 80 120 150 200 170 220 "" "" "} "" 99 Loss caused by Initial Condensa- tion in Cylinder in per Cent. 25 to 60 25 50 "" "1 20 40 20 35 15 25 12 20 "" "" "" Economy of Superheated Steam. (W. S. Hutton.) The economy obtained from the use of super-heated steam varies considerably, as it depends upon the type, size, speed and condition of the engine, and the grade of expansion. The economy increases with the degree of superheat, all things being equal. The economy in fuel and steam that may, under favourable conditions, be obtained by the use of superheated steam in many steam engines, may be ascertained approximately from the following Table, deduced from the results of careful experiments. 348 SECTION III-POWER STATION. Table 51.-Economy in the Consumption of Coal and Steam that may, under Favourable Conditions, be Effected by the Use of Superheated Steam, as Compared with Satur- ated Steam. Superheat of the Steam in degrees. Fahr. 15 20 25 30 35 40 50 60 70 Saving in Coal Con- sumption. per cent. 10 14 16 17 18 20 21 22 23 Saving in Superheat of Steam Con- the Steam in sumption. degrees. per cent. 12 16 18 20 21 23 24 25 26 Fahr. 80 90 100 115 130 160 200 250 300 €191-7:1 ELERI Saving in Coal Con- sumption. 1111-1 ISINIATS per cent. 24 25 26 28 30 32 35 40 45 W Saving in Steam Con- sumption. per cent. 27 28 30 32 34 36 99999 40 Schmidt's Superheater. (FIG. 91.) This apparatus, as applied to a Cornish steam boiler, is shown in Fig. 91. It consists of a series of coils of pipe surrounding a vertical flue. The steam 45 50 Fig. 91. Schmidt's Superheater. passes through the two lower coils into the separator on the right-hand sides then down through the remainder of the coils, except the two upper layers which constitute a feed-water heater. Babcock and Wilcox Superheater. Babcock and Wilcox superheater is placed in a position where there is practically no deteriorating condensation of the gases, and where the temperature is sufficiently high to ensure the steam receiving from 100 deg. to 150 deg. Fahr. of superheat. This superheater is not subject to the immediate action of the fire, as the furnace gases must first pass through the front part of the boiler, which comprises STEAM BOILERS. 349 a considerable heating surface. Assuming the boiler to be in regular work, and the firing even, no great fluctuations in temperature can take place where the superheater is fixed. It is readily accessible for examination, and for the renewal of tubes. There are no flanged joints: all the tube joints are expanded. Freedom for expansion is provided for by the tubes being free at one end, and by the manifolds not being rigidly connected with each other. Prevention against overheating during steam raising is ensured by the arrange- ment for flooding with boiler water, and using the superheater as part of the boiler heating surface, whilst steam is being raised, or when it is desired to use saturated steam. The tubes are bent into a "U" shape, and connected at both ends with mani- folds, one of which receives the natural steam from the boiler, the other collecting the superheated steam after it has traversed the superheater tubes, and delivering it to the valve, placed above the boiler. The flooding arrangement consists merely in a connection with the water space of the boiler drum, and a three-way cock, by which at will the water enters the lower manifold and fills the superheater to the boiler water level. Any steam formed in the superheater tubes is returned into the boiler drum, through the collecting pipe. The Babcock and Wilcox independently-fired superheater, shown in Fig. 92, is designed for positions where the setting of the boilers and steam pipes do not admit of constructing superheaters to form part of the boiler proper without stopping the works, or costly alterations in the steam pipes, or where it is desired to superheat steam passed through an engine that has been exhausted at a pressure of 50 lb. to 60 lb., such as, for instance, in sugar refineries, also for testing engines. 88 88 88 88 88 188 88 88 88 88 2 HRT IHEI ▬▬▬ O Fig. 92. Babcock and Wilcox Superheater. This superheater consists of a series of boxes or manifolds, connected together by U-shaped tubes. The steam from the steam main enters the first box, and is conveyed through the tubes into the second, third, and fourth box, and so on, passing through the last box back into the steam main. The gases generated on the grate rise upward, passing through a perforated wall (which muffles the flames and ensures a comparative evenness of temperature) into the superheater chamber, and thence through a similar perforated wall into the chimney. The amount of heat passing through the superheater chamber can be regulated at will. The temperature is kept comparatively low, the grate surface required being small. Any fuel can be burned. The superheater is provided with a by-pass in case of any necessity for repairs, and also with the necessary valves to enable the super- heater to be shut off from the steam main, if desired, without interfering with the general running of the plant. The quantity of fuel required is exceeding small. 350 SECTION III.—POWER STATION. FEED PUMPS AND INJECTORS. Work of feed pumps consists of two parts; first, work required to draw water into cylinder or barrel of pump, and, secondly, work required to force water into boiler against pressure. When hot water is pumped care must be taken to let water flow by gravity into pump, otherwise pumps will not act properly. Speed of Pumps. The greatest speed at which water flows in a suction pipe is 500 ft. per minute; water should not, however, flow through a suction pipe at a greater speed than 200 ft. per minute, and a pump should work at such a speed that it will deliver per minute the quantity of water contained in 200 ft. of its suction pipe. Diameter of Suction and Delivery Pipes. The suction and delivery pipes should have a diameter equal to from half to three-fourths of the diameter of the pump barrel. This makes the velocity of the water in the pipes 1.78 times the speed of the plunger or piston. The suction pipe should be made larger than the delivery pipe. According to Seaton, if d is the diameter of the feed-pump plunger, and 8 its mean velocity in feet per minute, then Diameter of feed pipe and 24 = Diameter of feed pipe V8 for large pumps. Example.-To find the diameter of the feed pipes for a pump whose diameter 1s6 in., and the length of stroke 2 ft., worked from the levers of an engine, making 60 revolutions per minute. Here s = 2 × 60 × 2, or 240 ft. 6 √240, or 4 in. 23 If there are two pumps which deliver alternately the pipes will be the same size throughout; but if the two pumps may deliver at the same time, the pipe beyond the junction of the two from the pumps must be nearly double the sectional area of one, as the resistance of pipes is due greatly to friction at the surface, and will consequently vary as the diameter, while the area of section varies as the square of the dianieter, the resistance in the single pipe will be considerably less than the confined resistance in the two, and for this reason its sectional area may be less. In practice this area may be 0.8 of the combined area of the two. Hence, when there are two pumps delivering together Diameter of main pipe = 1.265 x diameter of branches. If there were two pumps, as in the last example, delivering together, the diameter of the main pipe would be 4 x 1.265, or 5.06 in. Diameter of pipe = " = A rose should be placed at the bottom of the suction pipe of a pump, for preventing admission of small stones and dirt, and is generally either cylindrical, circular, or egg-shaped. Aggregate area of the perforations should be equal to from 1 to 2 times area of section pipe. "" d 20 Air Vessels. To secure a more uniform delivery of water, and to avoid shocks at the beginning of a stroke, an air vessel is placed near to the delivery valve. The volume of the air vessel varies greatly in practice, and may be from two to six times capacity of pump barrel. Size of Steam Cylinder for Direct-Acting Steam Pump. D = diameter of steam cylinder. d = pump barrel. .75 D2 P = d2 p. d 23 8 for small pumps, P = mean effective pressure of steam on steam piston. water on water piston. "" D = 1.15 d √ 1. STEAM BOILERS. 351 This allows 25 per cent. of the work done in the steam cylinder for the friction of the machine. In small pumps 25 per cent. is too little, as much as 50 per cent. having to be allowed, in which case above formula becomes D = 1.414 ď √ T A Quantity of Steam Consumed in Working a Feed Pump. The quantity of steam consumed in a feed pump which is driven by an eccen- tric fixed on the crankshaft of a steam engine varies from 1 to 11 per cent. of the quantity of steam used by engine. Power Required to Work a Feed Pump. In computing power required to work feed pump, an allowance of 50 per cent. is generally made for total loss due to friction. The maximum quantity of water required is assumed to be equal to twice quantity of steam consumed by engine. The head is equal to the sum of the suction and delivery-lift in feet, or the distance from the surface of the water to the point of delivery. The pressure, in pounds per square inch of water in pipes, is equal to the product of the head of water in feet multiplied by .433. The head of water in feet is equal to the product of the pressure of water in pounds per square inch multiplied by 2.31. Indicated horse-power required to work feed pump: Weight of feed water in pounds per hour × 2 × head of water in feet 33,000 × 60 minutes × 0.5 Capacity of the Feed Pump. The capacity of the feed pump of a steam boiler should be equal to supplying at least double the quantity of water evaporated by the boiler per hour, in order to have a margin, and to enable the pump to keep down the supply of steam in case the engine is stopped for any reason unexpectedly when the fires are brisk. Power Required to Raise Water. Multiply the quantity of water raised in gallons per minute by 10, and by the height lifted in feet, and divide by 33,000. For losses due to friction and slip of valves add one-third to two-thirds. General Directions for Fixing and Working Feed Pumps. The suction pipe should never be smaller than the size corresponding to the suction opening of the pump. When long suction pipes are used, it is necessary to increase the diameter to allow for the increased friction. The suction pipe should be made as short as possible, and with as few bends as practicable; use full round bends rather than elbows. The same applies to discharge pipe, although not so strongly, as the discharge pipe has full power of pump always available to force water through. In laying the suction pipe to maintain a uniform grade, so as to avoid air pockets, where the water supply is taken from a pond, it is well to lay suction below level of water if possible, all the way to the pump, and then to carry the pipe up vertically directly to the pump. In this way, most of the suction pipe will always remain full of water, and liability to air leakage is prevented. Where pipe has to be laid underground, use cast-iron flanged pipe for all sizes where it can be obtained. Use every precaution in laying pipe to prevent foreign matter, as sand or iron chips, from entering the pipe. The suction pipe and its connections must be air-tight. Before covering suction it is advisable to test pipe with pressure of 25 lb. per square inch, to make sure that no leaks exist. All valves in the suction and discharge pipe should be grate valves. Where pump is to lift water by suction, provide a priming pipe leading to the cylinders of the pump, or if suction pipe is provided with a foot-valve, this priming pipe may be led to the suction box of the pump. This priming pipe may take its supply from a tank, or from the discharge pipe of the pump; being connected to the discharge pipe at a point beyond the main discharge valve. An air cock is provided for the water cylinder cap, and by opening this air cock the water is allowed to fill the cylinders, displacing the air which they contain. • 352 SECTION III.-POWER STATION. In admitting water to the suction box of the pump, sufficient pressure must not be developed at the point to burst any portion of the suction piping. A relief valve placed in the suction pipe will prevent possibility of this. When water cylinders of pump have been filled with water, the valve in priming pipe and the air cock, may be closed, and pump is then ready for starting. In the case of light suction lifts the pump will readily pick up water in the suction pipe. Pumps of piston pattern, owing to the facility with which packing can be renewed, and smaller clearance spaces in pump cylinders are particularly efficient for lifting water by suction, where it is impossible to prime suction piping before starting pump. Locate suction chamber in continuation of line of flow in suction pipe, to relieve pulsations in suction pipe. Water at a high temperature cannot be raised any considerable distance by suction. For pumping very hot water, place supply high enough (or pump low enough) so that water will gravitate to pump. Throttle valve should be placed in steam pipe as close to pump as possible. Means should be provided for draining this pipe before starting pump. For boiler feeding, the pump should be run at not more than from 30 to 40 strokes per minute when the boiler is evaporating its normal rating (30 lb. of water per horse-power per hour). The Worthington Standard Feed Pump. The Worthington standard feed pump is constructed to working pressures not exceeding 160 lb. per square inch. 10 Fig. 93. The Worthington Feed Pump. The steam valve motion is the standard Worthington motion. The water ends of these pumps are fitted with gun-metal valves working on gun-metal seats. The capacities given below are those recommended for heavy pressures, and may fully be relied upon for continuous working, and in cases of emergency may be considerably increased. Whenever it can be arranged to utilise the exhaust steam from these feed pumps for heating the feed water this should be done, as the economy thus effected is greater than that obtained by exhausting direct to a condenser. Brass-fitted pumps are recommended when the water to be dealt with is hot or salt, or if the machine has to stand idle for long periods. STEAM BOILERS. 353 21 The Weir Direct-Acting Feed Pump. (J. and G. Weir, Limited.) Fig. 94 shows a sectional view of the Weir Standard Feed Pump. The makers claim the following advantages for it :- The valve-gear is positive, i.e., the steam valve can never be in such a positio that the pump will not start immediately steam is turned on. The valve arrange- ment also insures constant length of stroke and certainty of action. 752 20 8 +10 13 194 D 18 -15 - 17 6 1. Steam side valve chest, complete with double joint. 2. Double joint. 3. Front stay. 4. Bottom spindle. 5. Ball rods. 6. Front stay bush. 7. Ball crosshead. 8. Main crosshead. 9. Crosshead pin. 10. Piston rod. 11. Piston body. 12. Piston ring. 13. Cylinder cover. 14. Discharge valve seat. 15. Discharge valve seat ring, 16. Suction valve seat. 17. Suction valve guard. 18. Discharge valve gland. 19. Water valves. 20. Bucket body. 21. Brass bucket rings. 22. Ebonite bucket rings. Fig. 94. Weir Standard Feed Pump. The steam valve is practically a D slide valve, with a small auxiliary valve working on the back. These are the only two moving parts proper in the steam chest, so that there is little opportunity for wear, and no delicate adjustments to go out of order. The steam is used expansively, and the cut-off can be regulated from the out- side, while the pump is working. N 354 SECTION III.-POWER STATION. It works noiselessly without shock or jar, as the piston is slowed down towards the end of the stroke, thus enabling the water valves to settle quietly in their seats. The water valves are of the Weir group type, which provide a large area with only a small lift, thus ensuring easy working, and little wear and tear. The Weir Differential Feed Pump. This pump was designed to meet the demand for a well-made, efficient, and reliable pump for moderate powers. The principal feature is the Weir two-speed attachment. The capacity of a pump is limited by the size of its suction valves in a single suction pump which runs on the discharge stroke at the same speed as on the suction stroke, only a limited number of strokes is possible. In the Weir differential pump this disadvantage is overcome, as follows:— A regulating connection is made to the upper side of the bucket, whereby the speed of the suction stroke is limited, but the discharge stroke is made at a speed considerably greater. A larger number of suction strokes per minute is therefore obtained than in the ordinary single-acting plunger pump, although the velocity through the valves is at no time greater than in the old type. This pump, there- fore, becomes nearly equal to the double-acting pump. The pump can very easily be overhauled. By taking off the nuts on the bottom flange of the pump barrel, the barrel may be drawn up along the plunger, thus exposing the bucket rings, and also the suction valves for examination if desired. Then by taking off the packing gland nuts the plunger and bucket may be drawn up, and the barrel be taken clear away and another substituted. The Sinclair Variable-Stroke Feed Pump. (Hayward-Tyler and Co.) The pump body, valves and plungers, do not differ from ordinary three-throw pumps of first-class workmanship. The special features of the pump are in the shaft, and in the method of altering the stroke of the plungers. The mode of operation may be described as follows:- On the main shaft three eccentrics are mounted, and so arranged that when they are revolved round the axis of the shaft the distance of the centres of the eccentrics from the axis of the shaft is changed. By this means the centre of the eccentric may be brought co-axial with the shaft, or removed from it a distance equal to half the maximum stroke of the pump or any intermediate distance. The change of position of the eccentrics is effected by means of an arrangement of gearing contained in the gear-box, the operation being controlled by the move- ment of a hand-wheel. This gear is only in operation during the time the stroke of the pump is being altered. While the pump is running at a fixed stroke, no extra friction over and above that of the ordinary three-throw pump is introduced. The change from no-stroke to full stroke or any intermediate distance is effected gradually without any shocks, and while the pump and motor are running. The pump is driven by a shunt-wound motor, and as the plungers can always be brought to the no-stroke position for starting, the starting torque on the motor and the constant wear and tear is reduced to a minimum. An indicator can be attached to the pumps showing exactly what stroke the machine is doing at any particular moment; also the discharge in gallons per minute or per hour. Rules for Finding Size of Injector Required. Find the quantity of exhaust steam given off by the engine in cubic feet per minute. This is obtained by multiplying the area of the piston in square feet (see Table 52) by the piston speed in feet per minute (i.e. stroke in feet x 2 x number of revolutions per minute). Next refer to the Table of quantities of steam required by exhaust injectors, find the size of injector that requires not more than three-quarters of the steam given off by the engine. This will be the largest size of injector that should under ordinary circumstances be worked from the engine in question. Example: Engine with (one) cylinder 14 in. in diameter x 2-ft. 6-in. stroke, and running 80 revolutions per minute. Find size of injector it will work. Area of cylinder in square feet x piston speed per minute = cubic feet of steam exhausted per minute. 1. Area of a 14-in. cylinder in square feet (see Table 52) = 1.069. 2. Piston speed per minute = 2 ft. 6 in. × 2 × 80 = 400. ... 400 x 1.069 = 427.6 cubic feet of steam exhausted = per minute. STEAM BOILERS. 355 Table 52.-Diameter of Cylinders in Inches, and their Areas in Square Feet. .196 5 .136 9 .441 .164 9.492 10.545 .230 10 .601 .267 11 .659 .306 11.721 12 .783 .349 8.394 ざのお ​14 1.069 22 2.639 30 4.908 15 1.227 232.885 31 5.24 16 1.396 24 3.141 32 5.58 17 1.576 25 25 3.408 33 5.93 18 1.767 26 3.687 34 6.30 191.08 27 27 3.976 35 20 2.181 13 .921 21 2.405 6:68 36 7.06 28 | 4.276 29 4.586 37 7.46 45 " "" The Steam Loop. (Kent.) The steam loop is a system of piping by which water of condensation in steam pipes is automatically returned to the boiler. In its simplest form it consists of three pipes, which are called the riser, the horizontal, and the drop-leg. When the steam loop is used for returning to the boiler the water of condensation and entrainment from the steam pipe through which the steam flows to the cylinder of an engine, the riser is generally attached to a separator; this riser empties at a suitable height into the horizontal, and from thence the water of condensation is led into the drop-leg, which is connected to the boiler, into which the water of condensation is fed as soon as the hydrostatic presssure in drop-leg in connection with the steam pressure in the pipes is sufficient to overcome the boiler pressure. The action of the device depends on the following principles :-Difference of pres- sure may be balanced by a water column; vapours or liquids tend to flow to the point of lowest pressure; rate of flow depends on difference of pressure and mass; decrease of static pressure in a steam pipe or chamber is proportional to rate of condensation; in a steam current water will be carried or swept along rapidly by friction. "" gallon ton WATER. Useful Data for Water. One cubic foot of pure water at 32 deg. Fahr. weighs 62.418 lb. 62 212 "" "" "" 62.355 lb. 59.640 lb. "3 "" One British Imperial gallon = 277.274 cubic inches = 10 lb. at 62 deg. Fahr. 81 lb. U.S.A. 29 = 0.433 lb. per square inch. = 231.0 Pressure of column 1 ft. high = Pressure of 1 lb. per square inch = column of water 2.309 ft. high. Point of maximum density of water is 39.1 deg. Fahr., or 4 deg. Čent. 1 lb. of water at 32 deg. Fahr. = 27.684 cubic inches. Volume of bulk of 1 lb. of water at 62 deg Fahr. = 27.712 cubic inches. One cwt. of water at 62 deg. Fahr. 11.2 gallons. "" 29 "" ton = 224 One cubic foot of water at 62 deg. Fahr. sea "" "" "3 "" "" "" "" "" 38 7.87 46 11.54 39 8.29 47 8.72 48 12.04 12.55 40 41 9.16 49 13.09 42 9.62 50 13.63 43 10.08 51 14.18 14.74 44 10,55 52 11.04 53 15.32 " Diameter in Inches. "" = 61 gallons. = 65.05 lb. >> "" "One British gallon' One U.S.A. gallon × 1.2003. U.S.A. British X 0.8343. "" "" Area in Square Feet. = 10.276 lb. = 35 cubic feet. "" Flow of Water through Pipes. In arranging the water supply of a power station, the following data will be found of value. 356 SECTION III.-POWER STATION. O Tempera- ture. Fahr. 32 35 39.1 40 45 46 50 52.3 Table 53.-Expansion and Weight of Water at Various Temperatures. (Hutton.) 88895 65 60 62 Mean Tem- pera- ture. KERUNYR 80 85 90 95 Head, in Feet. 1234 LO CO £= ∞ ❤ 5 6 7 Relative Volume by Expan- sion. 10 1.00000 .99993 .99989 .99989 .99993 1,00000 1.00015 1.00029 1.00038 1.00074 1.00101 1.00119 1.00160 1.00239 1.00299 1.00379 1.00459 1.00554 per Cubic Feet Discharged per Minute, Area of Stream in 1 Inch Square. Feet { Velocity Weight of Weight of One Cubic One Gallon. Foot. Second. lb. lb. 62.418 10.0101 62.422 10.0102 62.425 Maximum density. 62.425 62.422 62.418 62.409 62.400 for ordi- nary cal- culations. 62.355 62.344 62.313 62.275 62.232 62.182 62.133 62.074 10.0112 62.394 10.0063 62.372 10.0053 10.0112 10.0103 10.0101 10.0087 10.0072 3.34 4.73 5.79 13.89 16 13.37 6.68 16.04 18 14.18 7.47 17.93 20 14.95 10.0000 9.9982 9.9933 9.9871 9.980 9.972 9.964 9:955 Minute, Area of Stream Cubic Feet Discharged per in Head, in Feet. 1 Inch Square. per Table 54.—Discharge and Speeds Due to Heads of 1 to 100 Feet. Feet Second. Tempera- ture. Velocity • Fahr. 100 105 110 115 120 125 130 135 140 145 150 155 160 165 170 175 180 185 190 195 200 205 210 212 20098888 230 250 300 400 500 Relative Weight of Weight of Volume by Expan- One Cubic One Gallon. Foot. sion. 50 1.00639 1.00739 1.00889 1.00989 1.01139 1.01239 1.01390 1.01539 1.01690 1.01839 1.01989 1.02164 1.02340 1.02589 1.02690 1.02906 1.03100 1.03300 1.03500 1.03700 1.03889 1.0414 1.0434 1.0466 1.0529 1.06243 1.09563 1.15056 1.22005 Minute, Area of Stream Cubic Feet Discharged per in Head, in Feet. 1 Inch Square. per Feet Velocity lb. 62.022 61.960 61.868 61.807 61.715 61.654 61.563 Second. 61.472 61.381 61.291 61.201 61.096 60.991 60.843 60.783 60.665 60.548 60.430 60.314 60.198 60.081 59.93 59.82 8.18 19.64 22 15.67 37.61 42 8.84 21.21 24 16.37 39.29 44 8 9.45 22.68 26 17.04 40.89 46 22.65 54.39 90 9 10.02 24.06 28 17.68 42.43 10.57 25.36 30 18.30 43.92 59.64 59.36 58.75 59.97 54.25 51.16 8 Head, in Feet. 48 23.14 55.56 95 23.61 56.71 100 lb. 9.947 9.937 9.922 Minute, Area of Stream Cubic Feet Discharged per 1 Inch Square. 9.913 9.897 9.887 9.873 9.859 9.844 9.829 9.815 9.799 9.781 9.757 9.748 9.728 9.711 9.691 9.672 9.654 9.635 9.611 9.594 9.565 9.520 9.422 9.136 8.700 8.204 8.02 12 11.57 27.78 32 18.90 45.36 55 24.76 11.34 14 12.50 59.48 46.76 60 25.87 48.12 65 26.92 62.12 64.66 30.00 34 19.49 32.08 36 20.05 34.02 38 20.60 35.86 40 49.44 70 27.94 67.1 50.72 75 28.93 69.45 21.13 21.64 51.97 80 22.15 53.2 85 29.87 71.73 30.79 73.94 31.68 76.08 32.55 78.17 33.40 80.0 per Feet Velocity in Second, STEAM BOILERS. 357 A Imperial Gallons. Table 55.-Friction in Pipes. (G. A. Ellis.) FRICTION LOSS IN POUNDS PRESSURE FOR EACH 100 FT. IN LENGTH OF CAST IRON PIPE DISCHARGING THE STATED QUANTITIES PER MINUTE. 33 37 41 3″ 1″ | 11″ .12 4 3.3 0.84 .31 813. 3.16 1.05 .47 .12 1228.7 6.98 2.38 .97 .27 16 50.4 12.30 4.07 1.66 20 78. 19.00 6.40 2.62 25 29 62 83 103 124 145 166 207 249 290 332 373 415 621 830 1037 1245 1450 1660 1867 2075 2490 2905 3320 3735 4150 4,980 ·· · ·· .. .. .. ·· ·· ·· .. ·· ·· .. ·· ·· ·· .. 137. 48. ·· ·· 12 .. .21 .10 .30 .12 .42 .14 .42 .67 27.5 9.15 3.75 .91 12.4 5.05 1.26 16.1 20.2 24.9 10.00 2.44 .81 56.1 22.40 5.32 1.80 39. 6.52 1.60 .51 .17 8.15 2.01 .62 .27 • • .. • ·· · 11″ Sizes of Pipes, Inside Diameter. 2" 21" 3" •• .. .. 4″ 6" 8" 10" 12" 14" 16" 18" ·· ·· .. * • · .. .. ·· .35 .09 .21 .. .74 9.46 3.20 1.31 .33 .05 |48.1 |14.9 | 4.89 1.99 .51 .07 21.2 7.00 2.85 .69.10.02 28.1 9.46 3.85 .95 .14 .03 37.5 12.47 5.02 1.22 .17 .05 .01 47.7 19.66 7.76 1.89 .26 .07 .03 28.06 11.20 2.66 .37 .09 33.41 15.20 3.65 .50 .11 42.96 19.50 4.73 .65 .15 25.00 6.01 .81 .20 30.80 7.43.96 .25 .09 .04 .05 .06 .08 ·· • • •• ·· ·· ·· ·· .. •• ·· .. ·· .. •• • •• 150 175 200 250 300 350 400 450 .02 .95 1.23 .04 .017.009.005 500 14.32 2.21 .53 .18 .08 .036.019.011 750 3.88 .94 .32 .13 .062.036.020 1000 1.46 .49 .20 .091.049 .02 1250 2.09 .70 .29.135 .071.040 1500 .38 .181.095.054 1750 .49.234.123 .071 2000 .63.297.153.086 2250 .77.362.188.107 2500 1.11 .515.267.150 3000 .697.365.204 3500 .910 .472 263 4000 .593.333 4500 .730.4085000 .585 6000 ·· ·· ·· ·· ·· ·· .005 .007 .01 : ·· ·· ·· ·· ·· ·· ·· ·· ·· ·· ·· .. ·· .. ·· .. U.S. Gallons. The frictional loss is greatly increased by bends or irregularities in the pipes. 5 10 15 20 25 30 35 40 45 50 75 100 125 358 SECTION III.-POWER STATION. Velocity in Feet per Second. 123 Table 56.-Loss of Head, in Feet, by Friction of Water in Pipes 100 ft. Long. 9 500TOCACON Loss of Head, in Feet. 4 5 6 7 .049 .042.037 .033 .029 .027 .025 .023 .021 .019 .164.141.123 .110 .099 .090 .082 .076 .071 .066 .339 .291 .255 .225 .204 .185 .169.157.145.136 .570 .489 .428 .380 .343 .312 .285 .263 .242 .228 .855 .735 .640 .570 .51 .466 .428 .364 .368 .342 1.30 1.20 1.03 .895 .795 .715 .650 .600 .550 .515 .478 2.12 1.90 1.73 1.59 1.36 1.19 1.06 .950 .865 .705 .730 .680 .635 8 2.71 2.45 2.23 2.04 1.75 1.53 1.36 1.23 1.12 1.02 .940 .875 .815 9 3.37 3.03 2.76 2.53 2.47 1.89 1.68 1.51 1.38 1.27 1.17 1.08 1.01 10 4.11 3.73 3.36 3.08 2.64 2.31 2.06 1.85 1.68 1.54 1.42 1.32 1.23 12 5.77 5.19 4.72 4.32 3.71 3.24 2.89 2.59 2.36 2.16 2.00 1.86 1.73 14 7.71 6.93 6.30 5.78 4.95 4.33 3.86 3.47 3.15 2.89 2.67 2.48 2.31 16 9.91 8.92 8.11 7.43 6.37 5.58 4.96 4.46 4.06 3.72 3.43 3.19 2.97 18 12.38 11.14 10.13 9.29 7.96 6.97 6.19 5.57 5.07 4.65 4.29 3.98 3.72 20 15.11 13.60 12.36 11.33 9.71 8.50 7.19 6.80 6.18 5.67 5.23 4.86 4.58 7 10 | 11 | 12 .065 .220 .059 .054 .198 .180 .407 .370 .760 .685 .623 1.14 1.03 .932 .450 1.59 1.43 Inside Diameter of Pipes, in Inches. .062 .14 .25 .571 .39 .857 .562 1.19 .765 1.59 1 1.99 9 1.26 2.5 3 10 1.56 14 | 16 | 18 | 20 | 22 | 24 | 26 | 28 | 30 .165 .339 Table 57 -Velocity and Discharge of Water through Straight Smooth Cylindrical Iron Tubes, with the "Friction Head' Required for Each 100 Ft. in Length; also the Velocity Head. Velocity in Feet per Second. The velocity head remains the same for any length of pipe, being dependent only on the velocity of the water in the pipe. 123 94 .141 128 .123 167 .110 212 141 .291 192 .255 251 .226 318 181 .489 256 .428 335 .380 424 234 .734 321 .645 419 .571 530 283 1.02 385 .897 502 .798 636 742 848 1.20 330 1.36 362 1.72 414 2.11 468 2.57 449 1.09 512 1.49 576 1.70 642 2.25 586 1.06 670 1.36 754 1.32 838 2 1.35 954 1060 1.8 4 .099 .204 .342 .514 .718 .953 7 8 9 12 in. Diam. 14 in. Diam. 16 in. Diam. 18 in. Diam. 20 in. Diam. Area 113.1 Area 153.94 | Area 201.06 Area 254.47 Area 314.16 10 12 14 16 18 20 262 393 523 654 785 916 1046 1177 1308 STEAM BOILERS, 359 24 in. Diam. 28 in. Diam. 30 in. Diam.40 in. Diam. | 60 in. Diam. Area 452.38. | Area 615.75. | Area 706.86. | Area 1256.6. Area 2287. Moololololo OT 60 E LA 2 3 4 5 .14 .062 .082 377 .070 512 .066 589 .049 1048 .033 2,356 .170 565 .102 1572 .068 3,532 .285 754 .172 2092 .114 4,712 .257 2616 3140 .145 768 .244 1024 .136 883 .228 .25 1178 .39 .428 942 .367 1284 .343 1472 5,888 .172 .230 .562 .598 1131 .513 1540 .478 1767 .359 7,068 .765 .635 2061 .476 3664 .318 8,244 8 1 4184 .794 1319 .681 | 1796 .900 1508 .86 2048 9 1.26 1.22 1696 1.04 2304 10 1.56 1.5 1884 1.24 2568 1.2 .400 | 9,424 .8 2356 .987 2650 2944 4708 .497 10,596 5232 .602 11,776 6 7 Gallons about 228 Feed Water Tanks. To find quantity of water contained in a circular tank in English Imperial gallons: A G H x 6.25 [Outside Dimensions. Lengths. G H'= D2 x 0.7854 × 6.25 When A = area of tank in square feet ; H = depth of tank in feet; G = contents of tank in gallons; D = diameter of tank in feet. If the tank is taper the diameter should be measured 0.4 from the large end Table 58.-Approximate Contents of Rectangular Tanks, in English Gallons. 20 1 8 Widths. ft. in. ft. in. ft. in. 1 3 20 2 0 1 0 1 8 1 0 1 9 1 1 1 4 2 1 20 2 0 20 3 2 25 2 1 25 2 1 25 3 3 30 2 1 30 2 1 30 30 2 1 3 3 40 2 1 40 2 1 1 8 40 3 4 2 1 40 2 4 1 9 50 2 8 2 1 50 2 1 2 1 5C 3 4 2 7 Depths. 1 4 1 7 1 7 2 1 Table 57.-(Continued.) 1 6 1 8 1 0 1 0 1 3 2 0 1 0 1 3 2 0 1 0 1 7 1 7 2 0 1 0 1 8 1 7 2 0 1 0 Gallons about Outside Dimensions. 50 60 Lengths. Widths. Depths. ft. in. ft. in. ft. in. 2 6 3 1 70 3 1 1 11 2 1 2 1 80 3 1 2 3 100 3 1 2 7 125 3 3 2 7 3 8 150 175 3 11 3 1 200 4 1 3 1 250 5 1 3 1 300 6 1 3 1 350 6 6 3 3 400 7 1 500 8 1 600 8 1 8 1 9 1 800 1000 .6 .74 .9 2 11 2 6 Gallons about D= 4.909 √ A Lengths. 2,200 3,750 10 4,500 10 1 10 1 9 2 0 2 1 5,250 10 2 3 6,000 10 2 6 7,000 10 8,000 10 2 710,000 10 2 9 11,200 10 2 9 12,500 2 913,500 2 915,000, 12 10 12 3 7 2 9 15,700 14 3 10 2 917,500 Cubic Feet per Minute. Widths. 14 4 1 3 118,700 15 4 7 3 820,000 3 8 25,000 20 16 5 1 Outside Dimensions. 16 18 20 18 20 18 20 20 2222 ft. ft. ft. 10 6 6 10 6 12 6 12 7 12 8 14 16 20 20 G II Depths. ∞∞∞99999A9ARA 8 8 10 10 10 10 10 10 10 10 10 : 10 360 SECTION III.POWER STATION. Capacity of Tanks. To find the quantity of water contained in a rectangular tank, in gallons: G = LX B x D x 6.24; When G I B Capacity. Gallons. 100 150 200 250 300 250 400 = imperial gallons; = length of tank in feet; = breadth To find size of tank when quantity is given in imperial gallons: D = depth 6.24 = number of imperial English gallons in one cubic foot. cwt. 3 5 7 8 9 B D = L x B x 6.25 Ꮐ LX D X 6.25 G B x D x 6.25 Table 59.-Approximate Weight of Wrought-Iron Tanks, Plates Quarter Inch Thick. L= Weight qr. 3 = 0 0 O 10 11 0 ib. 4 = 0 "" 0 "" 0 0 @ 0 (Whittaker.) T Capacity. Gallons. 450 500 1000 1500 2000 3000 4000 Weight. cwt. qr. lb. 12 0 0 อ 0 0 0 0 0 47 0 72 0 80 0 13 26 30 0 0 0 To find estimated weight of cast-iron tanks, P = A × 30; When P = weight in pounds; A = superficial area of tank in square feet. This is for in. plates with 3-in. thickness of flanges, including brackets, &c. Fo other thicknesses add 5 lb. per square foot for every additional of an inch in thickness. Bolts, nuts, and washers cwt. per ton of plates. Dr. Angus Smith's Pipe Composition. Pipes to be thoroughly cleaned from mould, sand, and rust, heated to about 700 deg. Fahr., then dipped vertically into a mixture of coal tar, pitch, linseed oil (5 or 6 per cent.), and rosin heated to about 300 deg. Fahr., and allowed to remain until the iron acquires the temperature of 300 deg. Fahr., then gradually with- drawn and allowed to cool in a vertical position. Perfect cohesion must take place in the casting, and the pipe must be free from blisters of any kind. The original recipe was 30 gallons of coal tar, 30 lb. of fresh slaked lime, 6 lb. of tallow, 3 lb. lamp black, 14 lb. rosin, well mixed, boiled 20 minutes and put on hot. The usual practice now is 3 barrels coal tar, barrel coal oil, barrel pitch, with 6 tons gas coke for heating pipes. In a wrought-iron tank long enough for a 9-ft. pipe, put sufficient coal tar to half cover the pipe, then powder the pitch and sprinkle it on the tar, and the coal oil poured on the pitch. The pipes must be heated to 180 or 200 deg. Fahr., and put into the liquid separately and turned over and over for two or three minutes, then placed at an angle to drain, with the lower end clear of the liquid. This quantity is enough for 1000 pieces, bends, branches and straight pipes, or about & barrel of coal tar for 100 lengths of 9 ft. long and 4 in. diameter of bore. P. and B. Pipe Compound. Pipes should be cleaned with paraffin well first to free them from rust, and then simply dipped in this well-known compound. The results obtained have been most satisfactory. This compound is very adhesive, and is acid and alkali proof, besides being absolutely tasteless when once applied. STEAM BOILERS. 361 CHIMNEYS. In proportioning chimneys the height is first assumed, with consideration to the heights of surrounding buildings or hills near to the proposed chimney, the length of horizontal flues, the character of coal to be used, &c.; and then the diameter required for the assumed height and horse-power is calculated by the formula. The following formula has been found to give satisfactory results for the horse- power of a chimney: A This is founded on rated horse-power of boilers on the 11 square-foot basis of Babcock and Wilcox, or a coal consumption of 5 lb. per horse-power. Where the rate of coal consumption is likely to be much less than 21 lb. per square foot of firegrate per hour, the area of chimney opening may be found from the actual fuel consumed, by the following formula, G being the pounds of coal consumed per hour :- H.P. = 2.5 d² √πT, where d = diameter of chimney in feet, and h = height above grate bars in feet. where A area of chimney shaft in square feet at top of the smallest part. G = area of firegrate in square feet. H = height of chimney in feet above fire-bar level. Length of Flues in Feet. To do this, having found the area, A = 50 100 · 200 400 600 Where there is a great length of horizontal flue, a greater chimney area is advisable. The proportionate effect of great length of external flues may be allowed for from the following Table, where a flue circuit of 100 ft. is taken as unity, and a proportionate additional area of chimney must be allowed accordingly. 1.5 G divide it by the constant in second VH column opposite the length of flue for which it is required to make allowance. A = Constant. Table 60.-Relation of Area of Chimney and Length of Flues. 1.076 J .07 G NT .853 .708 .625 > Length of Flues in Feet. 800 1000 1500 2000 3000 Constant. .561 .514 .413 .312 .317 The flues may be made about one-eighth the area of fire grate, but should not be less in area than throatway of chimney at top. All corners should be well rounded. Amount of Gas in Flues. Each pound of coal consumed yields from 10 lb. to 40 lb. of gas. The average weight, at 32 deg. Fahr., of the gases produced from the coal usually burnt in the furnaces of steam boilers, exclusive of air, is 11 lb. per pound of dry coal burnt, the volume of which varies with the temperature. N2 362 SECTION III.-POWER STATION. Diameter. Inches. 18 21 24 27 30 33 36 39 42 48 54 **FOUN Area A. Square Feet. 72 78 1.77 2.41 3.14 3.98 4.91 5.94 7.07 8.30 9.62 0.6 √A. Area. Effective - E = A Square Feet. .97 1.47 2.08 2.78 3.58 4.48 5.47 Table 61.-Size of Chimneys for Steam Boilers. Formulæ, H.P. 6.57 7.76 12.57 10.44 13.51 15.90 60 19.64 16.98 66 20.83 23.76 28.27 25.08 33.18 29.73 84 38.48 34.76 90 44.18 40.19 96 50.27 46.01 102 56.75 52.23 108 63.62 58.83 114 70.88 65.83 120 78.54 73.22 132 95.03 89.18 144 113.10 106.72 ft. ft. 60 50 ·· ·· 28 25 27 35 38 41 49 54 65 72 84 92 •• •• (Kent.) = 3.33 (A — 0.6 √A) √H. (Assuming 1 H.P. (Assuming 1 H.P. = 5 lb. of coal burned per hour.) ·· ft. ·· 70 58 78 100 107 115 125 133 141 152 163 183 216 1 • ft. 80 29 44 62 66 83 88 ·· ft. .. 90 .. | ft. 100 .. ::: 119 113 141 149 156 173 182 191 196 208 219 229 231 245 258 271 311 330 348 365 427 449 472 536 565 593 694 728 835 876 1038 1214 | ft. 110 Height of Chimney. ft. 150 ft. 125 Commercial Horse-Power of Boiler. · • 204 245 289 389 503 632 776 934 1107 1294 1496 1712 1944 2090 • •• ·· ·· ·· 316 426 551 692 849 1023 1212 1418 1639 ft. 175 1876 2130 2399 2685 2986 3637 4352 ·· ·· ·· ·· ·· · 595 748 918 1105 1310 1531 1770 2027 2300 2592 2900 3226 ft. 200 3929 4701 .. ·· .. O 981 1181 1400 1637 1893 ft. 225 1253 1485 1736 2008 2298 2609 2939 3288 3657 4455 5331 For pounds of coal burned per hour for any given size of chimney, multiply the figures in the Table by 5. 2167 2459 2771 3100 3448 4200 5026 ·· ·· .. ft. 250 .. .. .. · • 1565 1830 2116 2423 2750 3098 3466 3855 4696 5618 ft. 300 ·· ·· ·· ·· ·· ·· · ■ • 2005 2318 2654 3012 3393 3797 4223 5144 6155 Chimney. Side of Equivalent Square Square √E + 4 inches 16 19 22 24 27 30 32 35 38 43 48 54 59 64 70 75 80 86 91 96 101 107 117 128 STEAM BOILERS. 363 Height of the Chimney above Fire- grate in Feet. Table 62.-Draught Power of Chimneys, having a Temperature of 552 deg Fahr. Internally and 62 deg Fahr. Externally. (Kent.) 10 20 25 30 35 40 50 60 70 80 90 100 110 120 Draught Power in Inches of Water. .073 .146 .182 .219 .256 .291 .364 .437 .512 .583 .657 .729 .802 .875 .. Table 63.-Rate of Combustion. (Thurston.) WITH NATURAL CHIMNEY DRAUGHT. ·· Height of the Chimney above Fire- grate in Feet. 1. The slowest rate of combustion in Cornish boilers 2. Ordinary rate of these boilers 3. Ordinary rates in factory boilers 4. Ordinary rates for marine boilers 5. Quickest rates of complete combustion of anthracite coal, the supply of air coming through the grate only 6. Quickest rates of complete combustion of bituminous coal, with air-holes above the fuel the area of grate FORCED DRAUGHT. ·· 130 140 1.50 160 170 180 190 200 225 250 275 300 350 400 Best Anthracite Best semi-anthracite and bituminous Ordinary coals-soft Ordinary coals-anthracite • Relatively. 100 110 80 75 .. ·· Draught Power in Inches of Water. Pounds of Coal per Square Foot per Hour. 4 to 6 10 15 12 18 15 25 "" "" "" "" 15 20 .948 1.029 1.095 1.167 1.240 1.313 1.386 1.459 "" 7. Locomotives ·· 8. Torpedo boats .. "" Fuels of the several classes should evaporate respectively, from feed water at the boiling point and at atmospheric pressure, under the most favourable possible conditions, about as follows: 20 25 1.641. 1.825 2.006 2.189 2.553 2,918 "" 40 100 60 125 13.5 15 11 10 Weight of Water per Unit Weight of Fuel. Main Flue Proportions, The main flue should be of larger area than the chimney, to provide for the reduction of area due to accumulation of soot. The area of the cross-section of the main flue between the boiler and the chimney may be from one-third to one-fifth the area of the fire-grate surface. The main flue is best made circular, as this form offers the least resistance to the flow of the gases. It should be as short and direct as possible, and have no sudden changes of cross-section, sharp bends, or currents, entering at right angles. The internal surfaces of the flue should be as smooth as possible. 364 SECTION III.—POWER STATION. + Stability of Factory Chimneys. (FIGS. 95 to 98.) Figs. 95 to 98 illustrate the construction of two factory chimneys, one 350 ft., and the other 162 ft, in height. The stability of a well-built chimney to resist being overturned by the force of wind depends only upon its weight, and is independent of the tenacity of the 95 Putside Qia .--- .0;08 ------ -21-6° -270. ·50:0* ·-· - · (303) 16.0 #13 Wall 36:0 0.92 0:06 „0:06 Wall 10:0 350' 0* 96 www O Rucion *10-8 ... 10.11 Diam - 11:3 ·11·7° -12 0 .12 5 --12-11 .-13.6 --14 2`--- 14'11"- 15 9 -16 8 ·-17·8.--. ·18· ·19·17- 97 +80+ 8:0 9.7 ; " 0,291 98 LOLAN ☺ ·-28′0″- Figs. 95 to 98. Construction of Factory Chimneys. mortar. The inclination of the sides of the chimney, or the batter, is so small that its influence may be neglected in calculating the force of the wind on factory chimneys. The pressure of the wind is greater on a square than on a round chimney of equal width and height. The maximum pressure of the wind may be assumed to be 56 lb. per square foot on a square chimney, and the pressure and other forms of section is as follows:- STEAM BOILERS. 365 Pressure of wind on a chimney of square section = 1.00 = 56 × of hexagonal - "" of octagonal "" "" .75 = 56 X = .65 = 56 x .55 56 x 56 × "" of circular - "" "" The limit of stability to be observed for chimneys is that the wind must never bring tension on any joint. Where this limit is reached, the weight of the shaft on that joint will vary from nil at the windward edge to a maximum at the leeward edge, and the maximum intensity of pressure will = mean pressure × 2. Height of Chimney above the ground in Feet. "" 19 "" 40 60 70 80 90 100 110 120 135 150 155 160 170 180 200 225 250 300 450 Table 64.-Proportions of Chimneys for Factory-Steam Boilers, Collated from Practice. (Hutton.) Internal Dimensions. Size of base at the Ground Line. ft. 2 6 4 in. 2 11 3 3 =*=*∞∞∞0 4 8 6 4 4 10 5 16 19 8 5 6 6 ~~~~~~~ ECO LOLO E Conag 43 0006 14 4 6 6 0 9 7 6 21 6 Size of Top. ft. in. 1 2 2 2 2 3 3 3 4 4 5 3 O diam. 6 diam. 0 sq. O diam. 6 diam. 6 diam. 5 4 3 6 13 9 sq. 0 sq. 3 sq. 6 sq. 10 9 8q. O diam. 3 diam. 6 diam. O diam. 6 sq. O diam. 9 O diam. 2 diam. Internal Area Ratio of Bottom to Top. 2.04 2.12 2.13 2.18 2.27 2.40 2.33 2.40 2.30 2.25 1.78 3.24 2.25 2.00 2.28 4.00 2.13 1b Ib. per sq. ft. 1.00* = 56 .75 = 42 .65 36.4 .55 .55 = 30.3 ܒ 2.42 4.35 Thickness of Walls. Thickness at base in Inches, at Ground Line. 00008 18 18 23 28 28 28 28 28 28 28 56 36 36 54 36 36 40 48 59 Thickness at the Top in Inches. 9 9 9 9 9 9 9 9 9 14 14 14 14 14 14 14 14 14 14 Factory chimneys have been constructed of concrete, but it is liable to be cracked by heat, and it is not a suitable material for this purpose. To Calculate the Stability of Stack at Any Height. W = weight of material, in pounds per cubic feet-say 100 lb. for brickwork. W= total weight of shaft, in pounds, above given joint. p = wind pressure in pounds per square foot, generally taken at 50 to 60 lb. against side of square shaft, and at 25 to 30 lb. on sectional area through axis of round shaft, owing to its reduced action on a cylindrical surface. h = height of shaft, in feet, above given joint. h1= height in feet of centre of area supposed to be acted on by the wind, above given joint. * d = outer side of square, or diameter of round shaft, in feet, above given joint. A = area of masonry, in feet, at a given joint. m = leverage of W, in feet, d & minimum distance of centre of pressure from leeward edged for round and d for square shafts. } Then, at the limit of stability laid down, phi, hh, or moment of wind pressure at given joint = Wm, or moment of stability. 366 SECTION III.-POWER STATION. 2W or maximum intensity of pressure at leeward edge, must = or A " ·· ·· • per Carbon, per Cent. Hydrogen, Cent. .. "" 95 It burns freely, and develops on an average 9660 units of heat per pound, This is equal to an evaporation of 9660 ÷ 966 = 10 lb. of water per pound of fuel. from and at 212 deg. Fahr. Coke-Dust Briquettes, or block-coke, are generally composed of washed coke- dust 100 lb., pitch 7 lb., tar 21 lb. It is made from gas-coke refuse, and has on an average a heating power of 8970 units of heat per pound. This is equal to an evaporation of 8970 ÷ 966 = 9.28 lb. of water per pound of fuel, from and at 212 deg. Fahr. 19.5 to to .. .. *L**UNNIH 15 3 .. Oxygen, per Cent. Ratio of Oxygen to Hydrogen. Ammonia Syrup. Crude Tar. * Gas. Coke. to ·· 2 ·· Table 75.-Classification of Coals. 75 5.5 to 80 4.5 80 5.8 14.2 3 to to to 85 5 10 85 5.5 11 2 to to to to 89 5 5.3 1 1 10 15 88 5.5 6. to to to 91 4.5 5.3 90 4.5 5.5 to to to 93 4 3 1 4 12 18 to to to Products of Distillation. LOLO UMUH 20 50 to to 5 13 30 60 5 15 20 60 to to to to 3 12 17 68 68 3 BORHUNACAAgioi goi 13 from 70 to 87 per cent. 4.25 5.6 "" 1 2 "" 1 1.8 "" 1 1.6 3 5.0 to to 10 1 1 to "" "" 1 5 to to •OOPPIANO. .. 16 5 12 · to 15 to 0 2 8 12 to 74 74 to $2 82 to to 90 "" "" "" • 19 A bushel of bituminous coal weighs 76 lb., and contains 2688 cubic inches = 1.554 cubic feet; 29.47 bushels = 1 gross ton. A bushel of coke weighs 40 lb. (35 lb. to 42 lb.). ·· One acre of bituminous coal contains 1600 tons per foot of thickness of coal worked; 15 to 25 per cent. must be deducted for waste in mining. 41 to 45 cubic feet bituminous coal, when broken down 34 41 anthracite, prepared for market 123 70.9 "" of charcoal of coke >> 1 cubic foot of anthracite coal 1 bituminous coal Cumberland coal Cannel coal charcoal (hardwood) .. (pine).. "" ·· "" Pulverulent or only slightly coherent. "" Caked, but with many crevices, soft. ·· "" {Caked, compact, mode- rately {Caked, compact, hard • "" Pulverulent or slightly coherent. · Nature of Coke. • .. || || = 1 ton =1 1 = 1 "" = 55 lb. to 66 lb. = 50 55 ****** "" "" = 53 lb. "" "" = 18.5 18 50.3 lb. 99 ": " STEAM BOILERS. 387 Constituents, &c. Table 76.-Chemical Composition, Weight, &c., of Coal. Carbon, per cent. Hydrogen Oxygen Nitrogen Sulphur Ash ·· ·· ·· .. Specific gravity Weight of a cubic foot in pounds in solid state Weight of a cubic yard in tous, in solid state Average bulk of 1 ton, heaped, in cubic feet.. How it burns • .. Draught required Quantity of smoke Pounds of water per pound of fuel .. .. Description of Coal. "" "" ·· Anthracite Welsh coal Newcastle coal Lancashire Derbyshire Staffordshire coal Yorkshire coal Scotch coal Lignite .. • ·· .. ·· Anthra- cite Coal. 92.00 3.80 1.00 1.00 .70 1.50 1.37 85.60 1.031 41 With difficulty Quick None 44.7 52.2 60.4 48.7 42.5 Aber- dare Coal. 56.4 62.0 54.5 20.1 88.28 4.24 1.65 1.66 .91 3.26 1.32 82.50 .994 42 Slowly Welsh Coal. 86.26 4.66 2.60 1.45 1.77 3.26 1.31 81.90 New- Lanca castle shire Coal. Coal. 83.60 5.28 4.65 1.22 1.25 4.00 1.25 78.10 .941 Quick Quick Ordi- Scarcely Very Large little nary any 12.50 12.25 48.87 36.30 26.64 35.56 40.00 26.61 20.40 29.38 8.94 18.42 22.10 80.70 5.50 8.48 1.12 1.50 2.70 1.27 79.40 Table 77.-Composition of Coal Ash. 12.00 Derby-York- shire shire Coal. Coal. 2.96 3.86 3.25 6.34 7.87 6.37 5.73 2.18 80.00 71.90 4.85 4.83 9.90 1.35 1.10 2.30 1.30 81.20 .987 .957 .978 43 46 45 44 44.5 45.5 Slowly Quickly Quickly Quickly Quickly Quickly and cakes Ordi- Ordi- Brisk nary nary Large Large Large Alumina Sul- Phos- Silica. and Oxide Lime. Mag- phuric phoric nesia. of Iron. .58 2.00 2.27 4.55 1.67 7.00 1.54 6.83 1.37 7.46 1.76 7.91 8.40 1.87 4.26 2.48 33.00 10.10 1.40 1.00 10.85 1.45 2.77 4.00 1.29 1.26 80.60 78.70 .972 .918 Scotch Coal. 79.50 5.58 8.33 1.14 .62 .78 .84 .69 .76 .87 .89 .85 3.84 Total Per- Acid. Acid. centage. Ordi- nary Very large 99.73 99.94 99.80 99.66 99.96 99.92 99.60 99.80 99.94 Calorimeter for Determining the Calorific Power of Coal. (FIG. 117, page 388.) A simple apparatus for determining the power of coal is the small brass calorimeter in Fig. 117. The tube A is filled with a mixture of coal, potassium chlorate, and potassium nitrate, which is lighted by means of a fuse. The cylinder B is placed over the tube A, and is held in position by spring clips; near the bottom of this cylinder are two rows of holes of in. in diameter, and at the top is a small tube and air-cock. The outer cylinder contains a known weight of water, and is fitted with sockets to hold a thermometer. In testing a sample of coal, 2 grammes of pulverised coal are thoroughly mixed with 7.5 grammes of potassium chlorate, and 2.5 grammes of potassium nitrate. This mixture is rammed in the tube A, and a fuse, consisting of a small piece of filter-paper coated with a mixture of the chlorate and nitrate of potassium is 1 388 SECTION JII.—POWER STATION. inserted. The tube A is then placed in its socket, the fuse lighted, the cylinder B is slipped into its place, the air-cock being closed, and the whole is placed under water in the outer cylinder. As combustion takes place in the tube A, the gases find their way through the small holes in the cylinder B, and thence up through the water, giving up most of their heat to it. When the combustion is completed, DONATOM A B G CHINHAN Fig. 117. Testing Fuel. which is indicated by the cessation of bubbles of gas, the air-cock is opened, and water flows into the cylinder B through the small holes therein, and cools the firing tube A. Then, by moving the cylinder B up and down, the water is thoroughly agitated and its temperature rendered uniform. The heating power of the coal is determined from the weight of coal and water and the initial and final temperature of the water; allowance being made for the heat taken up and radiated by the metal of the calorimeter, and for the heat of combustion of the fuse. Combustion. When heat evolved by chemical combination is sufficiently intense to evolve light, combustion is said to take place. Combustion is complete when the whole of the combustible is oxidised to its highest state of oxidisation. It is incomplete when either some incombustible is left unconsumed, or escapes in a lower form of oxidation. The combustion of a hydrocarbon, such as coal gas, is complete when the pro ducts of combustion are only water and carbon dioxide. It is incomplete when the products of combustion contain carbon (soot), hydrocarbons, or carbon mon- oxide. At moderate temperatures carbon burns readily to carbon-dioxide, but at high temperatures only carbon monoxide is produced, even in presence of excess of air, so that under those circumstances the combustion will be incomplete. Gaseous fuels always burn with a flame which in some cases is luminous, in others not. The luminosity of flame is due to the presence of incandescent solid particles of carbon, and should these escape from the flame, unconsumed smoke is produced. Solid carbon is a more powerful radiating body than gas; a luminous flame is much better for heating by radiation than a much hotter one which is not luminous. STEAM BOILERS. 389 Air Required for Combustion. Theoretically, any combustible requires air equal to at least five times the weight of oxygen with which it combines. In practice, however, one and a-half to twice this quantity of air is required in furnaces to avoid incomplete combustion. For instance, 11 lb. of air is required per pound of coal to supply necessary oxygen but with natural draught, it is found that 22 lb. are required in practice. Description of Fuel. Table 78.-Quantity of Atmospheric Air Required in Practice for the Combustion of 1 Lb. of Different Fuels. (Hutton.) Petroleum Creosote, or tar refuse. Coal gas Coal, average Coal, best, very carefully stoked Charcoal Patent fuels, average Coke .. Coal gas Peat, well dried Peat, moderately dry Sawdust, dry Wood, well-dried Straw, dry Wood, moderately dry .. .. • ·· .. •• .. ·· ·· ·· ·· .. ·· ·· ·· Air Required for Combustion with Natural Draught. Weight in Cub. Ft. at Pounds. 62deg. Fahr. 36 32 29 24 17 23 22 CEZZZZUNNN! 21 16 16 13 13 12 11 10 474 434 382 316 224 303 290 275 211 211 170 170 158 145 132 Air Required for Combustion with Forced Draught. Weight in | Cub. Ft. at Pounds. 62 deg. Fahr. 30 24 22 18 16 17.25 16.5 15.75 12 9.75 9.75 9 8.25 7.5 394 316 290 237 210 227 217 207 158 128 128 119 109 99 Smoke Prevention. The one essential for the prevention of smoke is the mixing of excess of air with the burning gas before the temperature has fallen below that necessary for combustion. The tendency of coal to produce smoke increases with volatile combustible matter in its composition. Pure carbon and coke are smokeless, the best anthracite practically so. Bituminous coals are distinguished for their smoke-producing qualities. The amount of unconsumed carbon passing away from a well-constructed boiler in smoke seldom exceeds 1 per cent. of total amount of carbon in the coal. Smoke is a result of incomplete combustion. To prevent it, provide an ample supply of air, with sufficient intensity of draught and the maintenance of high temperature of fuel bed. Methods of smoke prevention may be classed as follows:— 1. Mechanical stokers. 2. Mechanical or forced draught. 3. Arrangements for admission of air above the fire, under which may be in- cluded steam jets for inducing a flow of air. 4. Firebrick arches or checker work, placed over the bridge wall or near the end of the fireplace, for the purpose of mixing and heating the gases. 5. Hollow walls for preheating air. 6. Coking arches or chambers constructed in front of the fireplace, whence the coke is pushed to the rear as the volatile matter is distilled off. 7. Double combustion, whereby part or all of the gases are passed a second time through the fuel. 8. Down-draught furnaces, in which air is admitted above the grate, and the gases pass down through it, and thence to the heating surface. 390 SECTION III.—POWER STATION. 29 Nixon's Navigation " "" " "" "" "" Powell Duffryn "" Pure Anthracite Table 79.-Draught Required for Various Coals under Babcock and Wilcox Boilers. 1G1 2 34C789 " 6 "" Test. CO2 со 13.8 2.5 11.5 8.5 2.3 5.7 8.4 Class of Coal. 12 3.4 6 "" "" Semi-bituminous hard coal: Belgian and French >> "" Transvaal "" "" | 1.2 1 ·· ·· ·· ·· ·· Clear cherry-red Deep orange Clear orange White Bright white Dazzling white .. .. 0 ·· 2.5 6 •• ·· Incipient cherry-red Cherry-red • ► ·· ·· • ·· N 81.6 82.5 83 80.5 79.6 .99 "" "" "} •• "" ·· "" ·· "" ** .. Incipient red-heat corresponds to Dull red " .. .. .. ·· .. •• "" "" + ·· ·· .. • • ·· Table 80.-Analyses of Gases of Combustion. (P. H. Dudley.) The following are selected from a large number of analyses of gases from loco- motive boilers, to show the range of composition under different circumstances. ·· .. "" .. •• 4 ·· • ·· .. ·· ·· .. .. .. .. 8 17.2 14.7 8.4 82 New fire, engine not working hard. 4.4 82.6 Smoke black, engine not working hard. 16.8 76.8 13.5 81.5 .. ·· ·· In analyses on the Cleveland and Pittsburgh road, in every instance when the smoke was the blackest, there was found the greatest percentage of unconsumed oxygen in the product, showing that something besides the mere presence of oxygen is required to effect the combustion of the volatile carbon of fuels. Table 81.—Temperatures Corresponding to Appearance. (Pouillet.) No smoke visible. Old fire, escaping gas white, engine working hard. Fresh fire, much black gas. Old fire, damper closed, engine standing still. smoke white, engine working hard. Draught Measured by Water Column. ·· ** .. ·· •• in. ·· bo¬kami --K¢**— ·· MIME-KH .. ·· dark, blower on, engine standing still. white, engine working hard. : ·· Coal Burnt per Square Feet of Grate per Hour. .. ·· •• lb. 16 18-20 25-30 30-40 18 20-25 8-10 15-20 20-25 .. 24222 • 12 15 20 700 800 900 1000 1100 1200 1300 12 1400 1500 to 1600 20 Deg. Cent. Deg. Fahr 525 977 1292 1472 1652 1832 2012 2192 2372 2552 2732 to 2912 STEAM BOILERS. 391 The “Ados" Automatic CO2 Recorder. (Figs. 118 and 119, pages 392 and 393.) (Sanders, Rehders and Co.) This apparatus automatically records the amount of carbon dioxide present in the furnace gases, at intervals of five or ten minutes. Its working is based on the well-known fact that a solution of caustic potash absorbs CO2 gas. A quantity of the flue gases is pumped through the recorder; part of it is bottled up, measured, and passed through a solution of caustic potash which absorbs all the CO2 gas; the quantity of gas absorbed, which represents the percentage of CO2 gas, is determined and recorded on a diagram by means of vertical lines. This process is repeated about every five minutes. The tops of the various lines form a curve which shows the fluctuation of the percentage of CO2 in the flue gases during the time the recorder has been working. It is advisable to have one recorder for each furnace. Where it is, however, desired to test several furnaces by one recorder only, the recorder may be connected with each furnace by means of a system of tubes, and the furnace to be tested switched on. The recorder consists of motor, gas pumps, and analysing and recording apparatus. Motor.-The motor consists of tank, bell, and fittings. The interior of the bell is connected with the chimney by means of a tube. The draught in the chimney creates a vacuum under the bell, which is pressed into the tank by atmospheric pressure. Air is then admitted into the bell by the automatic action of a valve, and the bell rises again. This motion re-occurs about every five minutes, and it is utilised to raise and to lower a bottle filled with glycerine, and to drive a pair of specially-designed pumps, which pump flue gases through a tube from the chimney through the analysing and recording apparatus. As long as there is any draught in the chimney, the motor will work without any further aid or supervision. Gas Pumps.-The gas pumps consist of two cylinders which dip into oil tanks and rise and fall alternately, drawing flue gases from the chimney, and forcing them through the recorder. Analysing and Recording Apparatus.—The analysing and recording apparatus consists in the main of a glass tube which serves as a measure to bottle up 100 cubic centimetres of gases, of a bottle containing a solution of caustic potash which absorbs the CO2 gas, and of a pen which records the percentage of CO2 gas ascertained. The following is a more detailed description of this part of the apparatus. (See Figs. 118 and 119.) Bottle F, filled with a mixture of glycerine and water, is periodically raised and lowered through the action of the motor. When the bottle is in its lowest position, the glycerine mixture will touch mark my; when the bottle is in its highest position, the glycerine will touch mark m2; the cubic contents of the tube between O and m2 is 100 cubic centimetres. When the glycerine touches m1, the flue gases which enter through tube Stg will pass through passage G₁, and eventually through the tube St4 into the open air. When the bottle is raised, the glycerine rises and shuts off passage G1; the moment the glycerine reaches mark O, 100 cubic centimetres are bottled up. The flue gases will be unable to pass through tube G1, but they will pass through tube St₂ into the open, after overcoming the resistance offered by the glycerine in bottle S. When the bottle rises still further, the glycerine is forced into tube G₁, and presses the 100 cbcm. through tube S4 into the bottle A filled with solution of caustic potash, which absorbs the CO2 gas contained in the above volume of flue gases. The non-absorbent volume of gas replaces an equal volume of caustic solution. The solution is forced up tube R₂ into globe a₁, and shuts off tube R3. By rising in globe a2, it presses the air in this vessel through tube S5 into the bell T, which rises and raises the lever R. The less CO2 gas has been absorbed in bottle A, the higher bell T will rise. The lever R sets pen F in motion, and causes it to make a vertical stroke on the 392 SECTION III.-POWER STATION. : : K A S 764 Fig. 118. IRAAMATUHRING JUMETTIMUKTIN [IHMW7/HMISHIHA LILATINĮ B E T b αν D ULINUKAI H WILDJENSEN LPUP IN PËR K The "Ados" Automatic CO2 Recorder. STEAM BOILERS. 393 diagram. The higher the bell rises, i.e., the less CO2 gas has been absorbed, the longer will be the stroke made by the pen. The moment the bottle F has reached its highest position, its downward motion commences, the glycerine goes back to mark mi, the gas shut off in bottle A recedes into the tube G1, and is forced into the open air through tube St by the action of the pumps. BOTTLE B}{ILMUKHAR|| Stroke 16}}}}, U S, 165 R GLOBE GLOBEG MOSASSI mi GLYCERINE GAS INLET GAS JOUTLET GLYCERINE V/3 DOUBLE ACTING GASPUMP GLYCERINE GLYCERIN องกษ GLYCERINE Fig. 119. The "Ados" Automatic CO2 Recorder. UNSTHAN GAS MUTAN SI As the pumps deliver about twenty times the volume of gas required for an analysis, the same gas is never analysed over again. The above process is repeated every five to ten minutes, according to the rapidity with which the motor works; each analysis is recorded by a stroke of the pen on the diagram, and the work of the furnace is thereby automatically recorded. 0⁹ 394 SECTION III.-POWER STATION. Table 82.-Theoretical Heating Value of Coals. (Babcock and Wilcox.) HEATING POWER OF COALS OF ENGLAND, UNITED STATES, GERMANY, FRANCE, BELGIUM, AUSTRIA-HUNGARY, AUSTRALIA, JAPAN, AND TRANSVAAL. Coals. Locality of Beds. GREAT BRITAIN. Welsh Coal : Ebbw Vale, 1848.. Powell Duffryn, 1848 Graigola, 1848 Llangennech, 1848 Llangennech, 1871 Nixon's Navigation Gwaun Cae Gurwen Newcastle Derbyshire and Yorkshire. 13,860 14,820 .. Lancashire Scotch UNITED STATES. Pennsylvania "" "9 Kentucky 19 Illinois Indiana Virginia Arkansas ·· Zwickau Hohndorf Oelsnitz ·· ·· Unseberg Atzendorf Neudorf Görzig Halle a S. .. Bitterfield Naumburg • Ruhr Coal: Dortmund.. Witten Bochum Bommern Essen Saar coal • GERMANY. Rhenish Prussia. ·· Saxony. ·· ·· .. • .. •• Hanover. • Osnabrück Obernkirchen · .. ·· ·· ·· Lower Saxony, Anhalt, and Brunswig. • · ·· .. .. • ·· • ·· ol B.T.U 16,214 8998 15,715 8710 14,689 8152 14,998 8318 14,964 8305 15,000 8325 15,123 8402 8225 7692 13,918 7724 12,870 7150 14,221 7892 13,143 7293 13,155 7301 14,391 7987 15,198 9,326 13,123 14,146 13,097 13,100 9,215 14,518 15,125 13,514 13,212 14,985 11,511 Calories. 11,964 11,343 10,674 8434 5175 7283 7851 7268 7270 5114 10,789 12,718 8066 8403 7508 7340 8325 6395 6647 6302 5930 5,769 3205 6,444 3580 6,093 3385 2140 3,852 4,165 2314 3,830 2128 4,563 2235 5994 7066 Almost pure anthracites, having 84 to 89 per cent. of carbon. Smokeless steam coal. Called smokeless. Pure hard anthracite. Bituminous coal, having 77 to 82 per cent. of carbon. Bituminous coal, having 78 per cent. of carbon. Anthracite, having 88 per cent. of carbon. Cannel coal. Bituminous coking. Cannel coke. Lignite (good). Bituminous coking. "" Nature. "" Cannel coal. Bituminous cooking. Lignite (good). "" Cannel coal. "" "" "" "" Short flame coal, semi-anthracite. Cannel coal. Cannel coal. "" "" "" "", "" "} Brown coal or lignite, low grade Semi-anthracite, low grade. Bituminous. STEAM BOILERS. 395 Coals. Locality of Beds GERMANY. • Silesia (Prussia). Carlssegen Myslowitz Waterloa Königshülle . Paulusgrube.. Waldenburg.. Brandenburg Neurode Freienstein Maxgrube •• Bavaria. Hanshamer coal Peipenberg Penzberg ·· Table 82.-Theoretical Heating Value of Coals. Blanzy Epinac ·· "" .. "" .. ·· .. .. "" ·· ·· Bassin du Pas-de-Calais. Marles Bully Hessin Lens Naux l'Escarpelle Les Courrières ·· ·· ·· .. Bassin de la Saône. ·· .. FRANCE. 15,566 Anthracite de la Mayenne Anthracite de Lamure 13,782 (Isère) .. • Couson "" Bassin de l'Aveyron. Lavaysse Céral Bassin d'Alais Rochbelle • ·· ·· ·· ·· • Bassin de la Loire. Rive-de-Gier, puits Henry 99 "" No. 1 Cimetière 1 2 • ·· • Bassin de Valenciennes. Denain, Fosse Renard Fosse Lelvet 1 2 ·· •• .. .. .. .. (Continued.) ·· B.T.U. Calories. 10,422 5790 10,758 5977 11,412 12,247 12,425 6903 12,637 7021 6774 7441 5362 5604 12,193 13,393 9,651 10,087 9,821 8,186 8,921 14,175 15,120 6340 6804 5456 4548 4956 15,481 15,472 8616 7657 7875 8400 8529 8477 15,352 15,258 15,256 8476 15,400 8556 14,265 7925 13,127 7293 14,086 7826 "" St. Wast, Fosse de la Réus- site 14,353 7974 St. Wast, Grande Fosse Fosse Tinchon Anzin, Fosse Chauffour la Cave 14,549 8083 St. Louis 15,397 8554 Fresne, Fosse Bonnepart.. 15,228 Vieux-Condé, Fosse Sârteau "" "" 8460 8561 15,409 8601 8596 14,493 8052 15,309 8505 14,770 8206 14,630 8128 13,203 7335 15,643 8691 15,244 8469 15,100 8389 15,316 8509 15,105 8392 15,188 8438 15,082 8379 Long flaming, semi-bituminous. Anthracite. Lignite or brown low grade. ** Bituminous hard coal. "" 39 "" "" Semi-bituminous coal. "" Nature. "" ;; Semi-bituminous coal, long flame. Bituminous coal, long flame. Bituminous hard coal. 12 "" coking. hard coal. coking. "" "" "" "" Semi-bituminous coal. Bituminous coking. "" "" "" "" "" "" >" ?? Bituminous coal, long fla:ne. long flame. Bituminous coking. "" "" 99 "" "" "" short flame. Semi-bituminous coal. + 396 SECTION III.-POWER STATION. K Table 82.—Theoretical Heating Value of Coals.-(Continued.) Coals. Locality of Beds. BELGIUM. Bassin de Mons. Haut-flenu 14,576 Belle et Bonne, Fosse No. 21 14,326 Levant de flenu 14,508 Couchant 14,446 8037 Midi 14,553 8085 14,943 8302 14,407 8004 14,877 8265 15,217 8454 15,107 8393 Grand-Hornu Nord du bois de Bossu Grand-Buisson Escouffiaux St. Hortense, bonne veine Bassin du Centre. Grünbach Thallern Haine St. Pierre Bois du Luc.. La Louvière Bracquegnies Mariemont Bascoup Sars-Longchamps Houssu Bassin de Charleroi. St. Martin, Fosse No. 3 Trieukaisin .. Leoben Fohnsdorf Göriagh Wies Trifail.. ·· •• .. Aussig Dux Bilin Brüx ·· ·· ·· ·· Kladno Buschtehrad Libuschin Schlan .. ·· Poirier, Fosse St. Louie Bayemont, Fosse St. Charles Sacré-Madame AUSTRIA-HUNGARY. Lower Austria. ·· ·· ·· Rakonitz-Lubna Pilsen.. Schatzlar 15,204 Sars-les-Moulins, Fosse 15,125 No. 7 Carabinier-française No 7 14,911 Roton, veine Greffier Pont-du-Loup Upper Austria. Wolfsegg Trannthal Styria. Bohemia. .. .. ·· ·· ·· .. • ·· ·· ·· ·· ·· ·· .. ·· ·· ·· ·· ·· ·· • ·· • B.T.U. Calories. • • 14,702 14,358 15,127 15,363 15,168 14,911 14,895 14,945 14,954 15,069 14,421 13,806 8098 7.959 8060 8168 7977 8404 8535 8427 8284 8275 8303 8308 8372 8012 7670 8447 8403 8284 14,311 7951 14,947 8304 6,408 7,808 8,182 8,274 11,458 7,057 6,006 3337 9,666 5370 9,187 5104 6,222 3457 7,997 4443 7,556 4198 6366 3921 10,675 5931 8,865 4925 9,900 5500 7,979 4433 7,257 4032 9,318 5177 6,552 5307 3560 4338 4546 4597 • Semi-bituminous hard coal. Semi-bituminous coking. Bituminous hard coal Semi-bituminous coking. Semi-bituminous hard coal. Nature. Semi-bituminous >Lignite or brown coal. Semi-bituminous coal. "" "" "" "" "" "" "" Lignite or brown coal. "" ** "" >> "" "" "" "" "" "" STEAM BOILERS. 397 Coals. Locality of Beds. AUSTRIA-HUNGARY. Moravia. Rossitz M. Ostran Gaya Göding .. Arsa Table 82.-Theoretical Heating Value of Coals. (Continued.) P. Ostran Orlan-Lazy Poremba Karwin Taklowetz Siveric .. .. Silesia. • Fünfkirchen.. Anina.. Neufeld ·· Brennberg Aika Salgo-Tarjan Dorog-Annathal Tokod.. ·· ·· Hungary. Petrozsény Egeres Zenica Dalmatia. ·· Istria. ·· ·· Bosnia. ·· ·· ·· ·· ·· Transylvania. ·· •• .. ·· .. • ·· ·· .. ·· 1 .. B.T.U. Calories. 12,553 6974 12,623 7013 2699 2809 4,858 5,056 12,564 12,389 11,057 13,021 11,932 10,276 11,356 5,200 8,325 6,913 7,966 7,709 8,069 8,087 10,182 11,286 8,692 7,911 6980 6883 6143 7234 6632 5709 6309 2889 4625 3841 4426 4283 4483 4493 5657 6270 4829 4359 Lignite or brown coal. "" "" "" Bituminous coal. "" "" "" Cannel coal. "" "" "" "" ?? Nature. "" "1 39 99 "" "" "" " 59 Lignite or brown coal. "" " The Commercial Value of Fuel. "" ** "" "" >> Lignite or brown coal. Lignite or brown coal. Lignite or brown coal. Lignite or brown coal. (Thurston.) The commercial value of fuel is modified by the depreciation produced by presence of non-combustible matter. 1. A certain amount of carbon is required to heat the whole mass to the temperature of the furnace. Of this a large part is lost. Therefore, a coal con- taining a certain small quantity of combustible would have no calorific value, and consequently would be worthless. 2. The presence of a high percentage of ash in the fuel checks combustion by its mechanical mixture with the combustion portion of the coal. A coal will have no commercial value when the proportion of refuse reaches a limit at which com- bustion becomes impossible in consequence of the action. 3. The cost of transportation of ash being as great as that of transporting the combustible, the consumer paying for ash at the same rate as for the carbon, and being compelled to go to additional expense for the removal of ash; these facts also determine a limit beyond which an increased proportion of ash renders the fuel valueless. 4. The determination of the financial losses due to increased wear and tear to furnaces and boilers, of incidental losses due to inequality or insufficiency of heat- supply, and to the many other direct and indirect charges to be made against a poor fuel, also indicate a limit which has a different value for each case, but which in most cases is difficult of even approximate determination. 398 SECTION III.-POWER STATION. Table 83.-Average Composition of Some American Coal. Mine. D L. V. Buckwheat Wilkesbarre, Pa. Jermyn Woodward Cayuga Mount Pleasant L. V. Pea Forty Foot Manville Shaft .. Scranton, Pa. Schuylkill Co., Pa. Scranton, Pa. Scranton, Pa. Scranton, Pa. L. V. Region Scranton, Pa. ·· Continental Avondale Oxford Mammoth Buck Mountain Scranton, Pa. Avondale, Pa. Scranton, Pa. Drifton, Pa. Cross Creek, Pa. .. ·· ·· • • ·· ·· .. · ·· Locality. Kind of Wood. Hickory or hard maple White oak Beech, red and black oak Poplar, chestnut and elm Average pine.. .. ·· ·· ·· ·· •• .. ·· ·· .. ·· .. 1 ·· ·· · • .. • • 1.34 6.42 15.3 76.94 1.3 1.7 5.78 10.84 ..3.33 3.73 13.71 .97 5.37 9.2 • • • • • • • .. • • • • .. The weight of solid coal varies from 80 lb. to 100 lb. per cubic foot. The weight of heaped coal varies from 45 lb. to 56 lb. per cubic foot. The bulk of one ton of heaped coal varies from 50 to 40 cubic feet. Moisture. Volatile Matter. .. Wood as Fuel. Wood newly felled contains proportion of moisture which varies much in different kinds, ranging from 30 per cent. to 50 per cent. After 8 or 12 months drying in the air, proportion of moisture 20 to 25 per cent. This degree of dryness can be produced by a few days' drying in an oven supplied with air at about 240 deg. Fahr. When coal or coke is used as the fuel for that oven, 1 lb. of fuel suffices to expel about 3 lb. of moisture from the wood. This is the result of ex- periments by Mr. J. R. Napier. If air-dried wood used as fuel for oven, 2 to 2 lb. of wood required to produce same effect. Specific gravity of different kinds of wood varies from 0.3 to 1.2. Perfectly dry wood contains about 50 per cent of carbon, remainder consisting almost entirely of oxygen and hydrogen. The coniferous family contain a small quantity of turpentine, which is a hydrocarbon. The proportion of ash in wood is from 1 per cent. to 5 per cent. The total heat of combustion of all kinds of wood, when dry, is almost exactly the same, and is that due to the 50 per cent. of carbon. According to S. P. Sharpless, the ash varies from 0.03 per cent. to 1.20 per cent. in American woods, and the fuel value, instead of being the same for all woods, ranges from 3667 (for white oak) to 5546 calories (for long-leaf pine) = 6600 to 9883 British thermal units for dry wood, the fuel value of 0.50 lb. carbon being 7272 B. T. U. Table 84.-Weight and Calorific Value of Wood per Cord, well Dried. 1.35 5.03 2.97 2.3 3.62 1.96 Ash. Fixed Carbon. Specific Gravity. 1.277.54 10.65 | 80.54 | 1.42 1.44 7.36 1.124.99 16.00 | 75.2 1.52 9.91 83.98 1.415 7.31 85.7 1.42 1.04 5.95 1.27 5.98 1.23 5.89 Weight. 9.75 11,801 81.68 1.425 9.80 79.23 1.42 2.51 84.46 1.49 6.2 12,294 0.162 12,307 12,036 12,149 8.21 12,423 3.5412,903 0.589 | 12,934 5.48 12,943 0.228 13,051 0.11 13,254 0.00 13,324 13,723 lb. 4500 3850 3250 2350 2000 9.62 83.13 1.615 6.15 86.68 1.44 91.45 1.415 2.17 6.77 87.96 | 1.55 5.23 89.19 1.56 0.63 Per Cent. Slate. B. T. U. in 1 ĽH. Combustible Matter. Weight of Coal of Equivalent Calorific Value. lb. 1800 1540 1300 940 800 About 24 lb. of dry wood are equal to a pound of average soft coal; the calorific value of the same weight of various woods is substantially the same. The average chemical composition of the ordinary kinds of wood, when prefectly dry, is shown by Table 86, page 399, to be substantially the same. STEAM BOILERS. 399 Table 85-Approximate Weight of One Cord of Different Kinds of Kiln-Dried Woods, and their Evaporative Power Com- pared with Coal of Average Quality. (Hutton.) English oak .. Ash, beech, and thorn Red oak, hard maple, and walnut Apple tree, pear tree, cherry tree, and plum tree.. Birch, elm, plane tree, and hazel Chestnut, brushwood, and yellow pine Pitch pine, alder, aspen, and poplar Willow, white pine, or deal Hemlock .. • .. Kind of Wood. .. ·· .. ·· .. ·· Carbon. 49.36 49.64 50.20 49.37 49.96 49.70 ·· ·· .. .. each "" "" "} "" "} " ·· Approxi- mate Weight Wood is approxi- Weight of Coal that one Cord of of one Cord of the, mately equiva- Cord of the lent to in Eva- Wood. porative Power. lb. 3850 3520 3310 3140 2880 2520 2130 1920 1220 Table 86.-Composition of Wood. (Rankine.) Kind of Wood. Composition. Hydrogen. Oxygen. Nitrogen. 6.01 42.69 0.91 5.92 Z TTTT! Beech Oak Birch Poplar Willow.. 6.20 41.16 41.62 41.60 39.56 1.29 1.15 0.96 0.96 6.21 5.96 Averages 6.06 41.30 1.05 lb. 1560 1420 1340 1260 1190 1130 1050 970 580 Ash. 1.06 1.97 0.81 1.86 3.37 1.80 Boiler Furnace for Burning Wood. A cord of wood can be burnt per hour on 60 square feet of fire-grate surface. Wood fuel requires one-third more fire-grate surface and two-thirds more space in the furnace than is required for coal, for equal generation of steam. A Cord of Wood. A cord of wood contains 4 x 4 x 8 = 128 cubic feet, of which 73 cubic feet are solid wood, and the remainder, 55 cubic feet, is space. The weight of coal that one cord of different kinds of dry wood is equivalent to, in evaporative power in a steam boiler, is given in Table 85. The quantity of ash yielded by wood averages from 1 to 4 per cent. The quantity of ash yielded by English oak is 1.7 per cent. The Heating Power of Soft Wood. The heating power of soft wood, such as pine, or of mixed soft woods, not kiln- dried, but in a moderately dry state, varies considerably. It may be assumed that 1 lb. of wood of this description is equivalent in heating power to lb. of coal, or that 4 lb. of wood are equivalent in evaporative power to 1 lb. of good coal. Wood Burning. With a draught of from in. to 1 in. of water, from 25 lb. to 80 lb. of wood may be burnt per square foot of fire-grate surface per hour. 400 SECTION III.—POWER STATION. Peat. Intermediate between wood and coal is peat. In swampy regions in temperate latitudes occur quantities of semi-aquatic plants, which, under special conditions of heat and moisture, are undergoing chemical transformation, the oxygen of the plant is eliminated, leaving behind as peat a spongy carbonaceous residue. This is found in beds varying from 1 ft. or 2 ft. to 40 ft. in depth. That near the surface is light, spongy, and fibrous, of yellow or light reddish-brown colour; lower down it is more compact, and darker in colour; in the lowest strata the colour is almost black, the peat is pitchy and unctuous, with scarcely any evidence of the fibrous texture. In its natural condition, peat generally contains from 75 to 80 per cent. of its entire weight of water, occasionally amounting to 85 or even 90 per cent. It is thus unfitted for use as a fuel until dry. By the process of drying it shrinks, its specific gravity, when dry, varying from 0.22 or 0.34 for the surface peat to 1.06 for the lowest peat. Lignite. Lignite occupies a position between peat and bituminous coal. It is believed to be of later origin than bituminous coal, and is in a less advanced stage of decom- position. The woody fibre and vegetable texture of lignite are almost wanting in coal, although there is little question as to their common origin. Although much like brown coal in appearance, lignite differs in the fact that upon distillation it yields acetic acid, while brown coal produces only ammoniacal liquor. Like peat, lignite presents much variety in appearance, some specimens being almost as hard as true coal, while others possess a distinctly woody structure and are of light- brown colour. It has an uneven fracture, and a dull and somewhat fatty lustre. Being easily broken, it will not readily bear transportation, while exposure to the weather causes it to rapidly absorb moisture and to crumble easily. Its value as a fuel is limited, for it must be used near its place of occurrence, and very soon after it is mined. It is non-caking, aud yields but moderate heat, being inferior to even the poorer varieties of bituminous coal. Table 87.-Average Composition of Irish Peat. Constituents. Carbon Hydrogen Oxygen Nitrogen Ash Moisture • .. .. •• ·· ·· • Perfectly Dry. 59.0 6.0 30.0 1.25 4.0 .. Including 25 Per Cent of Moisture. Carbon.. Hydrogen Oxygen and impurities 44.0 4.5 22.5 1.0 3.0 25.0 • LIQUID FUELS. The natural oils are usually distilled and the heavier portions used as fuels. Petroleum, petroleum refuse, tar, and creosote oil or tar refuse, have a much higher calorific power than coal; they contain a much larger quantity of hydrogen. Petroleum is a natural hydrocarbon oil, in its crude state it has calorific power one-and-a-half times that of coal. Petroleum oil is obtained by distillation from petroleum. Its calorific power is from two-and-a-half to three times as great as that of coal. The best petroleum fuel oil has a specific gravity of .818, and weighs 10 lb. X .818 lb.-8.18 Îb. per gallon. Its composition averages as follows: ·· Including 30 Per Cent of Moisture. ·· .. 41.2 4.2 21.0 0.8 2.8 30.0 85.34 13.51 1.15 100.00 It contains three times the hydrogen contained in good coal. Theoretical heating power of fuel oil is 20,822 thermal units, it has theoretical evaporative power = 20,822 lb. ÷ 966 lb. 21.56 lb. of water, from and at 212 deg. Fahr., per pound of oil. Its actual evaporative power is 15 lb. to 17 lb. of water, from and at 212 deg. Fahr., per pound of oil. Its flashing point is about 217 deg. Fahr. In a general way, 104 gallons, or 104 × 8.18 lb. 851 lb., of this oil are equal in evaporative power to one ton of good coal. STEAM BOILERS. 401 Distilled Oils. These may be made by distilling natural oils, shale, or blast-furnace tar. Advantages of Oil Fuel. Reduction of weight by about 40 per cent., and bulk by about 35 per cent. Reduction of number of stokers in about the ratio of 4:1. Fuel. Prompt kindling of fires, which can also be extinguished at any moment. The advantage or disadvantage of oil will, of course, depend very much on the relative prices of coal and oil. Roughly speaking, the cost per 1000 units of heat. would be about the same with coal at 12s. a ton, and oil 14d. to lid. a gallon. Table 88.-Relative Heating Values of Petroleum and Coal. Pennsylvanian heavy crude oil Caucasian light oil Caucasian heavy crude oil Petroleum refined ·· •• .. Good English coal, mean of 8 samples • • Specific Gra- vity 32 deg. Fahr. C. Composition. H. 1 lb. anthracite coal evaporated 1 lb. bituminous coal .. 1 lb. fuel oil, 36 deg. gravity 1 cubic foot gas, 20 C. P. .886 84.9 .884 86.3 .938 86.6 .928 87.1 1.380 80.0 5.0 8.0 1.25 13.7 13.6 12.3 11.7 .. 0. .. 1.4 .1 1.1 1.2 S. • ·· .. Oil versus Coal as Fuel. In 1892 there were reported to the Engineers' Club of Philadelphia some comparative figures from tests undertaken to ascertain the relative value of coal, petroleum, and gas. ·· Evapora- tion in Calorific Pounds of Power. Water at B.T.U. 212 deg. 20,736 22,027 20,850 17,832 14,112 Pounds Water from and at 212 deg. Fahr. 9.70 10.14 16.48 1.28 •• 21.48 22.79 17.30 17.10 12.16 .. The gas used was that obtained in the distillation of petroleum, having about the same fuel value as natural or coal gas of equal candle power. Taking the efficiency of bituminous coal as a basis, the calorific energy of petroleum is more than 60 per cent. greater than that of coal; whereas, theoreti- cally, petroleum exceeds coal only about 45 per cent.-the one containing 14,500 heat units, and the other 21,000. The liquid fuels are almost invariably the crude petroleums. They are sometimes burned in a furnace in which they are allowed to drip from shelf to shelf in a series arranged vertically at the front of the furnace, the flame passing to the rear, with the entering current of air supporting their combustion. In many cases they are sprayed into the furnace by a jet of steam, which should be superheated at high pressure. The use of the steam is considered to have a peculiar and beneficial effect, possibly through chemical reactions facilitating the formation of hydrocarbons. The petroleums are all liable to cause accident if carelessly handled, and special precaution must be observed in their application to the production of steam. : The gaseous fuels are seldom used under steam boilers, except where "natural” gas from gas wells is obtainable, or where a very large demand, or the use of metal- lurgical processes, justifies the construction of gas-generators. Even greater pre- cautions against accidents by explosion are needed than with the liquid fuels.~ In burning gas, maximum economy is secured by careful apportionment of the air- supply to the gas consumption, and especially in avoiding excess. The regenerator system is not generally economically applicable to boilers. 402 SECTION III.-POWER STATION. Value of Petroleum as Fuel. (FIGS. 120 to 122.) Thos. Urquhart gives the preceding Table of the theoretical evaporative power of petroleum in comparison with that of coal, as determined by Messrs. Favre and Silbermann: In experiments on Russian railways with petroleum as fuel, Mr. Urquhart obtained an actual efficiency equal to 82 per cent. of the theoretical heating value. 120 LAMMASHOIDALNHIHNA 326. 326 HOKER. 121 PETROLEUM. 122 zum STEAM " WATER SPACE OF FIRE BOX *W EQUINTANILO Figs. 119 to 122. Urquhart's System of Burning Petroleum. Figs. 120 to 122 show the system of burning adopted by him. the intense heat, part of the firebox has to be lined with firebrick. 'The petroleum is fed to the furnace by means of a spray injector driven by steam. An induced current of air is carried in around the injector nozzle, and additional air is supplied at the bottom of the furnace. Because of Steam Boilers Fired with Liquid Fuel A steam boiler arranged for combustion of fuel oil should produce no soot, the tubes may be smaller diameter than for coal, and heating surface increased to the extent of from 33 per cent. to 50 per cent. A boiler fired with this oil may be from one-third to one-fourth smaller than when fired with coal, for same evaporative power, and same draught. STEAM BOILERS. 403 Petroleum Refuse or Astaki. The flashing point of petroleum refuse is about 212 deg. Fahr. The highest evaporative duty of the petroleum refuse used in Mr. Urquhart's locomotive is 14 lb. of water per pound of fuel. The theoretical evaporative value of this fuel is 17.1 lb. of water per pound of fuel; the actual efficiency of petroleum refuse is therefore = 14 lb. ÷17.1 lb. = 82 per cent. of the theoretical efficiency. Holden's System of Burning Liquid Fuel. (FIGS. 123 and 124.) In this system the liquid fuel is carried in tanks in the top of the tender, and is taken by a pipe to the engine footplate, there being a suitable flexible connec- tion. Through the water space between the firebox and shell, two openings are 821. Gremie 328. 123 1001 ADNU 124 FID-AI) tet Figs. 123 and 124. Holden's System of Burning Liquid Fuel. made in the front of the boiler at a level with the footplate, and through these the two oil injectors used protrude. There is also provided a ring blower. This con- sists of an annular chamber surrounding the nozzle of the injector, and pierced vith holes. From these steam issues, and in this way the oil injected is more com- pletely atomised, so that very rapid combustion is obtained. No extra firebrick is 1 A 404 SECTION III.-POWER STATION. required in the firebox when burning liquid fuel on Mr. Holden's system, beyond the wall beneath the arch. F The usual practice in working on Mr. Holden's system of liquid fuel burning, is to keep the bars of the grate covered with about 3 in. of solid fuel. This may be coal, coke breeze, or a mixture of coal and chalk, or coal and broken firebrick may be used. The combustion of this solid fuel is checked by partially closing the dampers, the necessary air for the combustion of the fuel being introduced by the action of the ring blower above the solid fuel base. The fuel used is usually astaki, but coal and oil gas tars and creosotes can be burnt with equal facility. One ton of these liquid fuels will replace 2 tons of coal; and this large difference in the economic value of the two fuels is attributed to the higher calorific effect of the liquid fuel, and also to the fact that complete combustion is insured by the action of the ring blower without it being necessary to heat up to any large volume of superfluous air. It is evidently not necessary to open the firedoor to admit liquid fuel; moreover, the fire can be regulated exactly to the requirements of the work simply by a turn of the controlling valves. On the express engines in operation on the Great Eastern Railway the coal consumption is 35.4 lb. per mile, taking the average of over 3000 miles, or a month's running. With liquid fuel the average for the same work is 11.8 lb. per mile for coal for lighting up, standing, &c., and 10.5 lb. of oil per mile; making a total of 22.3 lb. of combined liquid fuel and coal per mile. Method of Burning Fuel Oil. Fuel oil is burnt in a boiler furnace in spray, after being pulverised by steam or compressed air. It cannot be burned in an ordinary furnace as arranged for coal-burning, because it makes an enormous quantity of smoke. To prevent the production of smoke it is necessary to burn oil with large supply of air in a furnace arranged to accumulate heat, or in a brick-lined chamber. Air Required for the Combustion of Fuel Oil. The quantity of air required for the complete combustion of fuel oil is one- third greater than required for good coal. The minimum quantity of air that should be provided is 22 lb. of air per pound of oil. It is necessary to provide a larger quantity to prevent smoke. Steam Used in Pulverising Fuel Oil. The system of effecting combustion by pulverising the oil with steam involves the expenditure of from 8 per cent. to 13 per cent. of the total quantity of steam produced by the boiler in atomising the oil, or converting it into spray. MISCELLANEOUS SOLID FUELS. Dust Fuel-Dust Explosions. Dust when mixed in air burns with such extreme rapidity as in some cases to cause explosions. Explosions of flour mills have been attributed to ignition of the dust in confined passages. Experiments in England in 1876 on the effect of coal dust in carrying flame in mines, showed that in a dusty passage the flame from a blown-out shot may travel 50 yards. Experiments made in Germany in 1893, show that pulverised fuel may be burned without smoke, and with high economy. The fuel, instead of being introduced into the firebox in the ordinary manner, is first reduced to a powder by pulverisers of any construction. In the place of the ordi- nary boiler firebox there is a combustion chamber in the form of a closed furnace lined with firebrick, and provided with an air injector similar in construction to those used in oil-burning furnaces. The nozzle throws a constant stream of the fuel into the chamber. This nozzle is so located that it scatters the powder throughout the whole space of the firebox. When this powder is once ignited and it is very readily done by first raising the lining to a high temperature by an open fire, the combustion continues in an intense and regular manner under the action of the current of air which carries it in. STEAM BOILERS. 405 Sawdust as Fuel The heating power of sawdust is naturally the same per pound as that of the wood from which it is derived, but if allowed to get wet it is more like spent tan. The conditions necessary for burning sawdust are that plenty of room should be given it in the furnace, and sufficient air supplied on the surface of the mass. The same applies to shavings, refuse, lumber, &c. Sawdust is frequently burned in saw mills, &c., by being blown into the furnace by a fan blast. Straw as Fuel. 4.1. Experiments in Russia showed that winter-wheat straw, dried at 230 deg. Fahr., had the following composition: C, 46.1; H, 5.6; N, 0.42; 0, 43.7; Ash, Heating value in British thermal units: Dry straw, 6290; with 6 per cent. water, 5770; with 10 per cent. water, 5448. With straws of other grains the heat- ing value of dry straw ranged from 5590 for buckwheat to 6750 for flax. Clark gives the mean composition of wheat and barley straw as C, 36; H, 5; O, 38; 0, 0.50; Ash, 4.75; water, 15.75, the two straws varying less than 1 per cent. The heating value of straw of this composition, according to Dulong's formula, and deducting the heat lost in evaporating the water, is 5155 heat units. Clark erroneously gives it as 8144 heat units. 7 • SECTION IV. THE POWER STATION (Continued). ELECTRIC GENERATORS. ܀ + 1 SECTION IV. THE POWER STATION (Continued). ELECTRIC AND MAGNETIC UNITS. The centimeter (length) = 0.3937 in. the second (time). The fundamental units on which all the various standards are based are :- The gramme (mass) The gramme (mass) = 15.432 grains and ELECTRIC GENERATORS. A dyne is the unit of force in absolute C G S, and is that force which, acting upon a mass of one gramme, produces an acceleration of one centimetre per second. 63.568 dynes = 1 grain, 981 dynes = 1 gramme. Erg is the C. G. S. unit of work, and is the work expended to move a body through a distance of one centimetre with a force of one dyne. 1 erg = 1 dyne centimetre, 1 megohm 1 microhm 13,562,600 ergs = 1 foot-pound. Table 1 gives the relations existing between the practical units which have been adopted and the C.G.S. units on which they are founded. 1 milliampere 1 micro-farad 1 millivolt 1 kilowatt 1 electrical horse- power 1 Joule 1 ft. lb. 1 B.T.U. 1 erg = .000,000,1 joule, or joule 10−7 981 ergs = 1 granime centimetre, 1 kilogramme metre 1 kilowatt hour 1 French or metric horse-power 1 English horse- power Derived Units. = 1 million ohms; = 1 millionth of an ohm ; = 1 thousandth of an ampere ; = 1 millionth of a farad; = thousandth of a volt. = 1000 watts = 44,240 ft. lb. per minute = 1.34 horse-power; = 746 Watt hours = 33,000 ft. lb. = 1 Watt second = 0.7373 ft. lb. ; = 1.356 Joules; - 3,600,000 Watt seconds; 7.233 ft. lb. = 1.34 horse-power hours; 33,000 ft. lb. per minute; = 75 kilogramme metres per second = 736 Watts = 0.9863 English horse-power; = 1.01385 French horse-power (“ force de cheval.") 32,549 ft. lb. per min. = The Board of Trade Unit. For commercial purposes electrical energy is charged for in units of 1000 Watt hours each, generally known as Board of Trade units. 1000 1 Board of Trade unit = 746 13 horse-power hours breaka Name of Unit. Ampere Volt Ohm Watt Coulomb Henry Symbol. Joule C E R જ Farad K P L W Table 1.-Equivalents and Expressions of Electrical and Mechanical Übits. What it Measures. Electric re- sistance Electric power Electric quantity Electric capacity Definition. rent The Ampere is the constant electric current which, when Electric cur- passed through a particular solution of nitrate of silver in water, LM T-1 deposits 0.001118 gramme per second. Or the flow of one coulomb per second. Electrical in-l ductance, or self-in- duction Difference of potential or The Volt is the electrical pressure, which, if applied to a con- electric pres- ductor where resistance is 1 Ohm, will produce a current of LM T2 sure or elec-1 ampere, and which is represented by 0.6974 of the pressure tromotive between the poles of a Clark's voltaic cell at 15 deg. Centigrade. force Electric energy or work Formulæ of Stand- ard Units The Ohm is the resistance offered by a column of mercury at the temperature of melting ice 14.4521 grammes in mass of constant cross-section, and 106.3 centimetres long. Is the rate of doing work when a current of 1 ampere flows between two points, having a difference of potential of 1 volt. The quantity of electricity that flows per second past a given point in a conductor which is carrying a current of 1 ampere. Is capacity of condenser which would require a charge of one coulomb to produce difference of potential of 1 volt between the two conductors forming the condenser. inAbsolute Equation. System (C.G.S.) Is the inductance in a circuit when current is changing at the rate of 1 ampere per second, and producing in that circuit a difference of potential of 1 volt. It corresponds to a rate of change of magnetic field strength through the circuit. LT-1 L2MT-3 L*M* L-1 T2 L C (Ohm's Law) E E=0XR K G R== E L= R - P-EXC, horse-power 1.118 m. of silver Q=CxT deposited pr.sec. E+T с Equivalent. Is the work done in one second when 1 ampere flows in conductor between two points having difference of potential L2 MT-2W-}E>Q of 1 volt. Flow of one coulomb per second. 0.926 Standard Daniel cell. 0.7373 ft. pounds per second NOTE.—In above C.G.S. (centimetre, gramme, second), L is the unit of length, M of masse, and T of time Multiplier to get Number of C.G.S Correspond- ing Units. 10-1 10-8 10~9 10-7 10-1 10-9 10-9 10 ELECTRIC GENERATORS, 411 Magnetic Units. The British Association proposed the adoption of a unit of magnetic flux under the name of the Weber, equal to 108 magnetic lines of the C.G.S. system. The multiples kiloline for 1000 lines, and megaline for 1,000,000 lines have been found convenient for dynamo designers. One Weber is equal to 100 megalines per square centimetre. A wire cutting one Weber per second will have induced in it an electro-motive force of one volt. The Gauss is the C.G.S. unit of magnetic 10 To convert ampere turns into potential, being equal to of an ampere turn. 4π Gausses one must multiply by 4π or by 1.257. 10 Analogies Between the Flow of Water and Electricity. ELECTRICITY. WATER. Head, difference of level, in feet. Difference of pressure per square inch in- pounds. Resistance of pipes, apertures, &c., in- creases with length of pipe, with con- tractions, roughness, &c. ; decreases with increase of sectional area. The law of increase and decrease is ex- pressed by complex formulæ. " Rate of flow, as cubic feet per second, gallons per minute, &c., or volume divided by the time. In the mining regions sometimes expressed in miner's inches.” Quantity, usually measured in cubic feet or gallons, but is also equivalent to rate of flow x time, as cubic feet per second for so many hours Work, or energy, measured in foot- pounds: product of weight of falling water into height of fall; in pumping, product of quantity in cubic feet into the pressure in pounds per square foot against which the water is pumped. Power, rate of work. Horse power, foot-- pounds of work done in 1 minute ÷ 30,000. In falling water, pounds falling in one second ÷ 150. In water flowing in pipes, rate of flow in cubic feet per second × pressure resisting the flow in pounds per square foot ÷ 550. Volts; electromotive force; difference of potential or of pressure; E. or E.M.F. (Ohms, resistance, R. The resistance in- creases directly as the length or the conductor or wire, and inversely as its sectional area. It varies with the nature or quality of the conductor. Conductivity is the reciprocal of specific resistance. (Amperes; current; current strength; intensity of current; rate of flow; one ampere one coulomb per second. volts ohms = Amperes= E ; C = ; E=CR. R Coulomb, unit of quantity, Q = rate of flow x time, as ampere seconds, one ampere hour 3600 coulombs = (Joule, volt-coulomb, W, the unit of work product of quantity by the electro-motive force = volt-ampere. If C (amperes) = rate of flow, and E (volts) of = difference pressure between two points in a circuit, energy expended = CEt, = C2Rt, since E CR. Watt, unit of power, P = volts x am- peres, current or rate of flow X difference of potential. 1 Watt = .7373 foot-pound per second = 4 of a horse-power. Analogies Between Elastic Fluid and Alternating Currents. (FIGS. 1 and 2.) 1. Self Induction. -The following analogy may be of use to explain the facts of self induction in an alternating current circuit. Let us suppose an elastic fluid in a pipe under pressure in the circuit of which is a water wheel, fitted with a heavy fly wheel, (Fig. 1). If we suppose pressure applied to the fluid, owing to the inertia of the water wheel it will take some time to start a flow or current in the pipe, but once started, the water wheel, supposing it to have an efficiency equal to 100 per cent., will not in any way interfere with the flow of the current. If the wheel and the pipe line are subjected to a current flowing alternately first in one and then in the opposite direction, it is evident that, owing to the inertia of the fly wheel, the 412 SECTION IV.-POWER STATION. flow of current would only commence some time after the pressure tending to make it flow in either direction has been exerted on the fluid, or, in other words, the maximum flow of current in any direction will not coincide with maximum pressure on the liquid, tending to make it flow in that direction. 2. Capacity or Condenser Effect.-Supposing again an elastic fluid, let us consider that in series with it is placed a cylinder containing an elastic diaphram, (Fig. 2). If the pressure is brought to bear, making the current flow in one direction, this will continue to flow until such time as the diaphragm is expanding to such an extent as to make the pressure caused by the extension of the diaphragm equal to the pressure exerted on the liquid, in order to produce a current. The moment the pressure is exerted in the opposite direction, tending to produce a current flowing in the reverse direction, the diaphram will come back to its natural position, and the flow of current will start before the pressure exerted on the liquid has reached its maximum. Elastic Fluid, D Water-wheel with fly-wheel (949) on end of shart. 1 Elastic Fluid 丸 ​Elastic diaphragm 2 3. Capacity and Self-Induction in Series.-From this it will be seen that by putting a water wheel and the diaphragm in series, they can be so dimensioned as practically to counteract each other. 4. Capacity and Self-Induction in Parallel.—If a water wheel and the diaphragm are in parallel on a circuit, the alternating pressure on the fluid stores up energy on the diaphragm; and when the pressure on the fluid is reversed the diaphragm will continue for a certain amount of time to supply a pressure required to make the water wheel continue to revolve in the same direction. The water wheel, therefore, obtains current from the diaphragm instead of from the cylinder, and by properly proportioning the water wheel and the diaphragm currents can be made to flow through two pipes, the one containing the water wheel and the other the diaphragm, proportional to the section of the pipes. Determination of Direction of Movement, Electric Current Magnetic Flux. (FIG. 3, page 413 When two quantities are known-direction of current always is taken as flowing from positive to negative brush, and the flux from north to south pole-Fig. 1 illustrates Dr. Fleming's useful rule for remembering connection between motion, magnetism, and induced current. Hold the thumb and the first and middle fingers of the right hand as nearly as possible at right angles to each other, so as to represent three rectangular axes in space. If the thumb point to the direction of the motion, and the forefinger point along the direction of the magnetic lines, then the middle finger will point in the direction of the induced electromotive force. This induced electromotive force, as shown by Faraday, is proportional to the intensity of the magnetic "field," and to the length and velocity of the moving conductor. ELECTRIC GENERATORS. 413 Magnetic Flux. The space surrounding a magnet is called a magnetic field, and is traversed by what is known as a magnetic flux. The magnetic flux goes from the north or positive pole of the magnet to the south or negative pole. The direction of the flux at any point of its path may be ascertained by hanging a magnetic needle in it, and the direction which the north pole takes is the direction of the flux. The unit of magnetic flux is called the "Weber." Flux density is the quantity of flux which passes through a sectional area one square centimeter, which intersects the flux normally to it. The unit of flux density is called "A Gauss.” The flux is supposed to be made up by a number of magnetic lines, and the number of these lines which pass through one square centimeter of cross section of the magnetic material is usually denoted by B. Magnetomotive Force. Magnetomotive force is the total magnetising power of an electric current circulating in a coil when a current flows along a wire coiled in turns round a core. the magnetising power is proportional to the strength of the current and to the DIRECTION OF CURRENT INDUCED ལ་་་་ Dime Top + HEM SPEEDHAM DIRECTION OF RIGHT HAND MÅGNETISM INDUCED CUARENT MAGNETIC LINES Y MOTION ⇒x DIRECTION OF → MOTION 2 (32) Fig. 3. Fleming's Hand Rule. number of turns in the coil. The magnetising power is independent of the size of material of the wire and of its shape, and is the same whether the spirals are together or wide apart. If N stands for the number of turns in the coil, and C be the number of amperes that are flowing through it, C x N are ampere turns. Armature Reaction. 1 When an armature turns in a magnetic field, and when current passes through its windings, it tends to distort the magnetic field, and this effect is called "Armature reaction," and varies with the load. Efficiency and Losses in Dynamos. There are two ways of expressing the efficiency of a dynamo. The first is called the electrical efficiency, and the second the commercial efficiency. The first expression is of very little practical use, and need not be considered. The com- 414 SECTION IV.-POWER STATION. 4 mercial efficiency is equal to the output of the machine divided by the intake. The intake is equal to the output + the losses which occur in the dynamo. These losses are of four kinds :- Firstly, heat losses in the armature and field magnet winding, which are due to the heating of these caused by the current passing through them. These losses are proportional to the square of the current and of the resistance, and may be represented by the expression C2R. Secondly, losses due to parasitical or Foucault currents. These are set up in the metal owing to the variation of the magnetic field, and they are avoided by dividing the magnetic circuit, whenever the magnetic field is variable, as much as possible; and by building up the conductors forming the windings in such a way that any parasitical currents which may have a tendency to form will counteract each other. Thirdly, the purely magnetic losses due to the inertia of the iron in changing its magnetisation. This is termed loss by "hysteresis." This property entails an expenditure of energy which takes the form of heat. The hysteresis varies with the quality of the iron employed, and great care has to be exercised in its choice. Fourthly, the mechanical losses due to friction of the bearing, friction of the brushes on the commutator, friction of the armature spider against the air when revolving. The latter is rather an advantage, and the armatures are often purposely designed so as to act as ventilators, sucking in the air through the centre of the armature, and expelling it through ducts specially provided at the surface. Loss due to Hysteresis in Various Metals. Mr. C. P. Steinmetz gives the law connecting the hysteresis loss h in ergs per cubic centimeter of iron per cycle and the flux density B, as follows:- h = n B 1.6 where n is a constant called the hysteretic constant depending upon the kind of iron. This law is true for cycles performed either slowly or as rapidly as 200 per second. Table gives the hysteretic constant n for different materials for ordinary frequencies. Table 2.-Hysteretic Constants for Different Materials. | Hysteretic Constant n. Material. Very soft iron wire Very thin soft sheet-iron. Thin good sheet-iron Thick sheet-iron.. Most ordinary sheet-iron Transformer cores ·· ·· Hysteretic Constant n. .002 .0024 .003 .0033 .004 .0045 Material. Soft annealed cast steel .. Soft machine steel ¡Cast steel Cast iron ·· .. Hardened cast steel • .. .008 .0094 .012 .016 .025 Besides the hysteretic loss in the iron plates, there is also a loss due to eddy currents in the iron. This varies as the square of the thickness of the iron, the square of the frequency, and the square of the flux density. Characteristic Curves. (S. P. Thompson.) The characteristic curve stands to the dynamo in a relation very similar to that in which the indicator diagram stands to the steam engine. The characteristic curve is a curve constructed by plotting as ordinates the voits produced at the terminals, and as abscissæ the amperes generated in the armature. When a current is allowed to flow through the armature, the electro-motive force which we measure at the brushes is not exactly the same as that generated in the armature, but either smaller or larger, according to whether the machine is used as a dynamo or motor. Three conditions of working have therefore to be dis- tinguished, namely: (1) No current, running on open circuit; (2) dynamo current ; and (3) motor current passing through the armature. ELECTRIC GENERATORS. 415 : I Watts lost in armature Watts lost in magnet coils Lost volts Total electri- cal energy (per sec). Useful elec- trical out- put. Economic co-efficient Commercial efficiency (per cent.) Table 3.-Dynamos-Efficiency Formulæ. (Munro and Jamieson.) Series Machine. Ee E Ea C² R C² R a m Ca Ra C C² Re a Re Ra+Rm +R Shunt Machine. Ea Ca R. c² 8 02 (R₂+R+R) 02 ( R₂+4) 02 (R+- a a a 100 × Ee Ce÷ (H.-P. × 746) C² Ra C₂R, = E²+R, 2 E÷R Ca Ra Ea Ca= Re E.C.-C. R = &² Re 2 C₂ Re+ Ca Rat C2 R* 100 × Ee Ce÷ с (H.-P. X 746) Compound Machine (Short Shunt). C² Ra C²R+C¸R¸ Ca Ra+ Ce Rm Ea Ca R¸ (Rm+R₂) Rs + Rm + Re E. C. = C. R. C² R e 2 C²R₂+C²R₂+ C²R + a CR a m 100 × E C÷(H.-P. × 746) N.B.-Horse-power * This will be a In well-constructed com- is converted into maximum when pound machines the dif- watts (so as to com-R is a mean pro-ference between "short- pare with electric portional between shunt" and "long shunt" output of the ma-R and R is very slight, as, Rm, is so chine) by multiplying|**s, small. by 746. a. The appendix a, refers to armature; e, to external circuit; m, to field magnet;. s, to shunt winding. "External" Characteristics. The name "external characteristic" may be given for the sake of distinction to those curves which exhibit the relation between the potentials and the currents of the external circuit. In the series dynamo the magnetization of the magnets increases with the current, and therefore, at first, the electro-motive force increases also, giving the first straight portion of the curve. As the magnets approach saturation the curve turns, and, as the reactions due to the current in the armature now become of relatively great importance, flattens itself, and ultimately turns down again. Critical Current of Series Dynamo. (FIG. 7.) The first part of every characteristic for any speed is nearly straight up to a point where for that speed the electro-motive force is nearly two-thirds of its maximum value. When the current is such that the electro-motive force has attained to this value, any very small change either in the speed of the engine or in the resistance of the circuit produces a great change in the electro-motive force, and therefore in the current; this critical current corresponding to the point on all the curves where the straght line begins to turn-may be called the "critical 416 SECTION IV.-POWER STATION. "current" of the dynamo. The series dynamo only "builds" its magnetism when the resistance is low enough, and when excited and running will "unbind" or Each lose its magnetism, if the resistance of the circuit is increased too much. series dynamo has its own critical current, and it will not work with a less one. Characteristics of Shunt Dynamo. (FIGS. 4, 5, and 8.) For the shunt dynamo there are two separate characteristics: the external characteristic, in which the quantities plotted are the amperes of current in the external circuit, and the volts of potential between terminals; and the internal characteristic in which the volts and amperes of the shunt circuit are plotted. The internal characteristic of the shunt dynamo is quite similar to the external characteristic of a series dynamo (Fig. 6), and shows the saturation of the field 5 IVOLTS 1301 eut Voi 857 60 50 40 30| 20 10 2001 160 120 Silemens 800 S219A 40 "AMPERES 720 Rev. EXTERNAL CHARACTERISTIC OF SHUNT WOUND DYNAMO. Ampères 10 30 30 40 60 60 CHARACTERIStic Curve of A Series DYNAMO. 6 Figs. 4 to 8. TOO 400 300 CHARACTERIStic ofa Shunt Dynam 0. હ 4. 70 200 VOLTS ន 50- 201 10- 9/70A 70F 60 88 300 20 oh ·Ampères 500 7 Ε SERIES MACHINE 8 OHMS 600 SHUNT MACHINE 5 6 OHMS 8 Series and Shunt Dynamo Curves. 8 9 8081 magnets. It is better to plot with ampere turns instead of amperes, because the magnetisation depends on the number of turns in the coil as well as the amperes. The curve of the shunt dynamo is different from that of the series dynamo. It begins with a straight, or nearly straight portion, which turns up in a curve, and eventually returns nearly horizontally to the axis of electromotive force. The straight portion represents the unstable state when the shunt current is less than ELECTRIC GENERATORS. 417 its true critical value. The critical external current is that current for which the shunt begins to act fully. From this point the shunt current acts with great power, and the electromotive force here rises very rapidly. The comparison of the characteristic of the shunt dynamo with that of the series dynamo is interesting. In the series dynamo, the first part of the characteristic is a sloping line. The series dynamo will only work if the resistance of the external circuit is less than the critical value, and the shunt dynamo will only work if the external resistance is greater than the critical value. The contrast is shown by a couple of curves in the two cases-not charac- teristics-showing the relation between the potential at terminals and the resistances of the external circuit. Fig. 7 shows this for a series machine, and Fig. 8 for a shunt machine. The electromotive force of the one drops suddenly when the resistance exceeds 2 ohms; that of the other rises suddenly when the resistance attains the value of 1 ohm. External Characteristic of a Self-regulating Dynamo. Simultaneous observations of the external current and the external potential enable us to plot the external characteristic; which in a perfectly self-regulating dynamo would be a horizontal line. If the number of regulating coils in series is too small, the characteristic will fall as the current rises; if too large, it will droop slightly at the end near the origin. Series Wound Dynamo. (FIG. 9.) Fig. 9 shows a diagram of connections. This machine may also be called a constant current machine. It does not magnetise unless the resistance to current is sufficiently low, and speed attained high enough; it is liable to have its polarity reversed. It has been used mainly for series are lighting and power transmission; the resistance of series winding must be very low. It can be run well in series with another machine. 10 Shunt field 9 ш ст Armature SERIES WOUND |_ DYNAMO. Series field. · Lumm I+ :Pl 12 SEPARATELY EXCITED DYNAMO. Let +Armature SHUNT WOUND DYNAMO. 11 Shunt field + W Armature. Series field. COMPOUND WOUND Equalizer DYNAMO. ست CONNECTIONS OF COMPOUND WOUND DYNAMOS RUNNING IN PARALLEL, 13 Figs. 9 to 13. Diagrams of Dynamo Windings and Connections. Shunt Wound Dynamo, or Constant Potential Machine. (FIG. 10.) Field winding has very high resistance; it is composed of many turns, and does not have more than 14 per cent. to 2 per cent. of total current output pass through it. Can be run in parallel with one another with ease. Used for lighting and for charging accumulators. Not liable to have its polarity reversed. If much over- loaded, demagnetises. Shunt circuit must not be opened while machine is running, otherwise there is likelihood of burning up generator. P 418 SECTION IV.-POWER STATION. Compound Wound Dynamo. (FIGS. 11. and 13, page 417.) A compound wound dynamo can be wound so as to raise the voltage as current increases; this is known as overcompounding. To run in parallel, it must have brushes, from which series-winding starts, interconnected; this connection is known equaliser"; otherwise there is likelihood of polarity reversing. No as the "C 354. Generators CONNECTIONS OF SHUNT WOUND DYNAMOS RUNNING IN SERIES 15 Figs. 14 and 15. Diagrams of Dynamo Windings and Connections. tendency to demagnetise with overloads. Practically exclusively used for traction work. By putting variable resistance in shunt-winding, the voltage at the terminals can be varied. Figs. 14 and 15 show diagramatically the connections required when running series-wound generators in parallel and shunt-wound generators in series. Table 4.-Classification of Three Principal Types of Con- tinuous-current Generators and their Principal Uses. Series-wound 14 Shunt-wound ·· CONNECTIONS OF TWO SERIES DYNAMOS RUNNING IN PARALLEL. .. Compound-wound •• ·· Series-arc lighting. Series-incandescent lighting. Central station incandescent- parallel system. Some motor circuits. Traction work with storage batteries in parallel. Isolated incandescent paral- lel systems. Street railroad systems. Motor systems. The Electromotive Force Produced by a Dynamo. (Houston and Kennelly.) The electromotive force produced by a dynamo expressed in C.G.S. units, is the product of the flux, the revolutions per second and the number of conductors counted once around the armature, divided by the number of poles. The electrical capability of a dynamo, in watts, is equal to the square of its E.M.F. in volts, divided by its resistance in ohms. FALI The ratio of the total to useful flux varies in different machines between 1.2 and 2.1. The flux density that can be employed without unduly increasing the reluc- tivity of the circuit is about 7.5 kilolines in cast iron, and up to 17 kilolines in wrought iron or soft cast steel per square centimetre. ELECTRIC GENERATORS. 419 Armature Windings. Armature windings may be subdivided into two classes-one, in which the conductors are arranged on the external surface of a cylinder, so that each turn includes, as a maximum, the total magnetic flux from each pole, termed drum windings; the other, in which the conductors are arranged on and threaded through the interior of a cylinder, so that each turn includes as a maximum only one-half of the flux from each magnet pole; this is known as the gramme or ring winding. The Limitations to the Output of a Dynamo. The limitations to the output of a dynamo are of three kinds: limitations by excessive drop of pressure in the armature; by excessive heat; and by excessive sparking. Sparking at brushes is the result of inductance. That is to say, to the effect of an electromotive force produced in that coil or section of winding which is leaving contact, through its commutator segment, with the brush. Dynamo Running Temperature. The operating temperature of dynamos should not exceed 80 deg. Fahr. above the temperature of the engine room; the armature should be provided with ventilating slots, which are of value when the machine is overloaded. Sparkless Running. In many railway generators with toothed armatures, large air gaps are required to avoid sparking. Laminated pole pieces of proper design, good materials, and construction, obviate this. The principal cause of satisfactory operation is a powerful field which counter- acts the armature reaction and prevents the shifting of the line of commutation. A brush contact, allowing about 30 amperes to the square inch, and a large number of commutator bars, contributes to sparkless running, and the pole pieces should be carefully shaped for this purpose. A deep slot in the centre of the pole piece prevents the magnetic field from being deflected by the action of the armature, and good brush holders contribute largely to sparkless operation. Dynamos for Traction Work. The question as to the type of generator to be used for electric traction is very important. As in the case of engines, railway generators must usually stand very heavy overloading without damage. As one pole is earthed, the greatest care must be taken that the very best insulation is used throughout in their construction. The loads to which they are subject are extremely variable; dynamos as usually constructed for lighting work would require the position of their brushes to be constantly altered. To obviate this, very heavy magnetic inductions are allowed for in designing these generators, thus rendering it unnecessary to shift the brushes, and avoiding sparking. It is the universal practice to use toothed armatures in railway work. As to the type of field winding to be adopted, tests made on a large scale, with separately excited, shunt, and compound-wound machines by American dynamo manufacturers and engineers, show that the best suited for railway work from every point of view is the over-compounded type of generator. The usual pressure of current used on trolley lines in America is 500 volts, this pressure being increased to 550 and 600 volts when the full load comes on. The over-compounding can be regulated up to 10 per cent. by varying a German-silver shunt placed on the series coil. Where accumulators are used as a reserve, shunt-wound generators are em- ployed usually. Where the same generators are used for traction and lighting, and with 500 volt three-wire system, the series winding of the generators and the equalising bus bar may be thrown out of circuit when dynamos are used for lighting. Where alternating current generators are used either single, three, or quadri- phase may be adopted, the current being either generated directly at the high- pressure at which it is transmitted, 2000 to 12,000 volts, or transformed by static step-up transformers up to 40,000 volts, and possibly more. Where such machinery is used and units run in parallel, it is of the utmost importance to keep the peri- pheral speed as uniform as possible: this means a heavy fly-wheel on the engine. To work entirely satisfactorily, a displacement of more than five degrees per half cycle 420 SECTION IV.-POWER STATION. from that at constant speed should not take place. With the polyphase generators, as now generally designed, this corresponds to a maximum variation of angular velocity during one revolution not exceeding one-quarter to one-half of 1 per cent. Principal Features of Railway Generators. A railway generator should have the following characteristics :- 1. Slow speed. 2. Sparkless running. 3. Exact regulation. 4. Iligh insulation. 5. Ease of inspection and repair. 6. 7. 8. 9. 10. Strong and durable construction. Low running temperature. Low rating. High efficiency at all leatis. Graceful shape and good finish. Points to be Considered in Choice of Dynamos for Railway Work. Frames to be of cast iron or steel: the large section insures rigidity and, on over-compounded generators gives a voltage variation corresponding exactly to the load. Poles to be of laminated iron, thus minimising losses due to eddy currents in the pole faces. These may be either bolted to the frame or preferably cast in, thus insuring a good magnetic joint. Frames adjustable in every direction, so that armature can be properly centred. Compounding proportional to current, so that machines will operate perfectly in parallel with each other; and machines should have characteristic curves as similar as possible. Cool fields and permanency of insulation, due to the careful and correct proportioning of generator and ample use of copper. Brush-holders easy of access and supported radially from the frame, securing freedom from vibration and maximum arcing distance between brushes. Commutator separated from armature, giving advantage of deeper segments, and securing successful operation of carbon brushes: a fact not assured when the commutator is on the periphery of the armature. Use of mica throughout the commutator. Commutator ring to be in one piece over entire circumference; segmental con- struction not to be permitted. Commutator of hard-rolled drop-forged copper, insuring long life and uniformity of wear. Great number of segments in commutator, reducing volts per bar to a safe minimum, and insuring freedom from sparking. Commutator mounted on armature hub, giving firm support, maintaining true centre, and preventing vibration between armature and commutator. Armature hub bolted direct to flywheel on larger sizes, removing strain from shaft and key's. Armature laminations individually dovetailed into armature hub, resulting in a strong and durable construction. Armature ventilation through spacings in lamination, reducing temperature. Absence of all bolts through laminations as far as possible to reduce Foucault currents. Armature laminations separated from each other by fireproof insulation, preventing loss from eddy currents, and maintaining permanent solidity of construction. Ironclad armature, i.e., with armature laminations punched with teeth on the periphery between which are located the conductors, giving the double advantage of good mechanical construction and low magnetic resistance. Flexible leads from armature conductors to commutator, avoiding crystalliza- tion and constant breaking of leads. Ample cross-section of conductors and liberal insulation of same, increasing efficiency of the machine, minimising heating, and guarding against grounds, short- circuits, or burn-outs. Drum winding, avoiding troublesome "interior" winding and its high self- induction. Barrel winding, a modification of drum winding, having all the conductors held symmetrically on the cylindrical periphery of the armature. The end flanges, extended laterally like a pulley, form a support for the end connections, the con- ductors being firmly secured in the armature slots and on the end flanges by metal bands, so that vibration is rendered impossible. ELECTRIC GENERATORS. 421 . DYNAMO DETAILS. Insulation, Brushes, Fields, &c. Fields, &c. (FIGS. 16 to 20, pages 422 to 425.) Figs. 16 to 19 illustrate a brush-holder, the sectional elevation of a generator, an armature hub, and a commutator. A railway generator needs higher insulation than a lighting dynamo. The armature coil may be formed of flat copper ribbon bent double edgewise. A number of these ribbons are stacked together and bent to shape. These coils can be lifted out and inserted with facility, if the teeth of the armature are perfectly straight. A The type of brush and brush-gear used by Messrs. Dick, Kerr and Co., is illustrated in Figs. 16, 17, and 20. The brush-holder support is a cast-iron ring of channel section, provided with clamps to secure the brush-holder yokes. It is made in halves and bolted together, so that it may be removed without disturbing any other part of the machine. The entire ring is carried in brackets, rigidly attached to the magnet frame, and is fitted with a screw and hand-wheel for rocking the ring, with its brushes, to the proper commutating position. In no part of the brush-holding gear is the current permitted to pass through moving joints, but a continuous metallic path is provided from the carbon to the cross-connecting rings, which are located inside the hollow rocker-ring. These cross-connecting rings deliver the entire current of the machine to a terminal board at the bottom of the magnet frame, and from this point the main cables pass underground to the switchboard. Field Magnets. The field magnet is usually cast in halves. The frame is generally of cast iron or of mild cast steel. The poles of the field magnet are laminated iron; often, instead of being planed and bolted to a joint to the field frame, they are cast welded into it. The field bobbins are easily removable, and are confined in position by a rectangular frame which forms the pole shoe. The armature plates are now nearly universally slotted, and this is certainly the best practice for railway work. After the slots in the armature have received the coils, they are usually closed with strips of wood which protect the conductors mechanically. Many dynamos are wound on the barrel plan, with the connectors sticking out in a defenceless position; others are wound on the Eickmeyer plan, with the con- nectors passing in spiral curves over the ends. The laminations are staggered as the armature is built up, and form a compact mass. Commutator. The heating of the commutator arises from three causes-the mechanical friction of the brushes, that due to the useful currents flowing across the contact resistances, and the heating due to the waste currents caused by short-circuiting of adjacent segments, and by sparking. Carbon brushes should not be run above 30 to 40 amperes per square inch of contact surface. The pressure need seldom exceed 2 lb. per square inch of brush-bearing surface, and a pressure of 20 oz. per square inch corresponds to good practice. At a peripheral speed of commutator of 2500 ft. per minute, which is good practice, the rise of temperature of the commutator will seldom exceed 20 deg. Cent. per watt per square inch of peripheral radiating surface for unventilated commutators; the peripheral speed varies from 2000 ft. to 2800 ft. per minute; and with special ventilating arrangements depending upon centrifugal flow of air, this figure may be considerably improved upon. The total rise of temperature should not exceed 50 deg. Cent. for continuous running at full load. The radiating surface of the commutator should be from 3 to 5 square inches per kilowatt output. Carbon Brushes. For generators the safe general pressure runs at 1 to 3 lbs. for a brush 21 in. wide and in. thick. The contact resistance offered by carbon brushes at a pressure of 20 oz. per square inch of bearing surface, and at ordinary current densities and peripheral speeds, may be taken at .03 ohms per square inch of contact surface. The specific resistance of a good grade of carbon brush is about 4000 times that of copper-a fair average is 0.03 ohm per square inch of contact. The contact resistance of copper brushes need not exceed .003 ohm per square inch of contact area. The current density varies from 25 to 40 amperes per square inch, according to the load. 422 SECTION IV.-POWER STATION. 1 (950) 16 17 UDRU EEEE JEU MBAHE ATAMISINY I Details of Dynamo Construction. Fig. 16. Standard Brush-Holder; Dick, Kerr and Co. Fig. 17. Sectional Elevation; Dick, Kerr Generator. ELECTRIC GENERATORS. 423 (952). !! C DAAL ACUT (953) 18 19 wrote in math the fly thing is utt. Here for V ARMSTRONG AS ANYONE as we wtore Ph trans d = ON HAIR W fun and bear D for ↑ «> «» Q din toa Details of Dynamo Construction. Fig. 18. Armature Hub; Dick, Kerr Generator. Fig. 19. Commutator Construction; Dick, Kerr Generator. 424 SECTION IV.—POWER STATION. Table 5.-Number and Size of Carbon Brushes used on Four- Pole Railway Generators. No of Brushes. 8 10 16 20 Capacity in Kwts. 100 200 300 500 Number of Poles. 6 ❤❤❤❤❤∞∞∞∞∞2- 6 6 8 6 6 8 8 8 8 10 10 10 12 12 12 12 16 Table 6.-Carbon Brushes in Direct-Driven Railway Generators. Rated Capacity in Kilowatts. 225 225 225 325 325 425 425 425 425 525 525 525 525 850 850 850 1200 1600 Copper brush Brass gauze brush Carbon brush .. Revolutions Number per of Minute. Brushes. Type of Brush. ·· 120 150 200 100 150 150 80 100 120 125 •. 75 90 100 80 100 120 80 75 ·· 000088 ·· 18 18 30 36 30 42 32 32 32 56 40 40 56 72 .72 72 120 128 in. in. in. 2 × 1 × 2 1 1 1 1 x 1 × 1 Size of Brushes. HTT dk-kat Amperes per Square Inch. Size of Carbon Brush. in. in. 21 × 21 × 2 × 2 × 21 × 2 × 21 × 2 × 1 × 1 x 1 x 1 x 11 1 1 × 1 150 to 175 100 to 125 25 to 40 -- 11 × 1 × 1 1 X X X x 1 x 2 × 1 × 2 × 1 × 2 ENANN -2-2-2 7 x × 2 X 2 X 2 2 x 2 × 2 X 2 × 2 × 11 × 21 Contact Surface in Square Inches per Brush. 1.125 1.125 0,937 1,25 23 to 28 15 to 20 4 to 6 1.458 1.458 1.50 1.50 1.50 1.458 1.50 1.50 1.458 1 25 Table 7.-Comparison between Copper and Carbon Brushes. in. 1.25 1.25 1.25 1.25 LOjOD LOJAT LOjKO Lajo Amperes per Square Inch of Contact. Total Maxi- mum Contact Surface Avail- able for Current in Square Inches. 10.125 10.125 14.055 22.50 21.87 30.618 24.0 24.0 24 0 40.824 30.0 30.0 40.824 45.0 45.0 45.0 75.0 80.0 Square Milli- metre per Ampere. 31 to 41 5 to 7 14 to 22 Armature Cores Made of thin sheet iron or annealed soft steel, .015 in. .025 thick. These discs are insulated by very thin tissue paper, varnish, oil, or paint. Japan is chiefly used now, with a sheet of good insulating paper every in. Open spaces are left in the core about every 2 in. for ventilation. The end plates are generally made of gun- metal or bronze. ELECTRIC GENERATORS. 425 Friction between Commutator and Brushes. The friction co-efficients given below-referring to a circumferential commu- tator speed of 5 metres per second-were obtained from experiments by Messrs. E. V. Cox and H. W. Buck. 0.3 lubricated. Carbon brushes, radially set, tangentially 1.0 dry 0.64 1.31 0.2 "" "" "" 0.32 "" "" "" "" "" "" Copper For velocities greater than 5 metres per second, the co-efficients must be multiplied by (1 40 The following example shows that the friction due to the brushes cannot always be neglected. Consider a dynamo giving 180 amperes at 100 volts, provided with radially set carbon brushes, the circumferential speed of the commutator being 9 metres per second. The area of contact surface should not be less than 0.15 square centimetre per ampere, with a pressure equivalent to about 0.15 kilogrammes per square centimetre. The total pressure of the two lines of brushes will therefore be : 2 x 180 x 0.15 × 0.15 8.1 kilogrammes. x Friction co-efficient (with lubrication) = 0.3 (1 – O 954 • Hence friction loss is : W = 9 x 8.1 × 0.27 kg.-metres per second. = 193 watts = 1.07 per cent. Should the lubricant be insufficient this loss might easily be doubled. 20 D 9165) 40 drst PLATED = 0.27. EOPPER T Fig. 20. Brush-Holder; Dick, Kerr Generator. Insulation to be Employed. (H. F. Parshall.) Composite sheets of mica, alternating with sheets of paper specially prepared so as to be moisture-proof, have been found highly suitable for the insulation of armature and field magnet coils. The following Table shows roughly the electrical properties of composite sheets of white mica :- p2 426 SECTION IV.-POWER STATION. Good vulcanised fibre, varying in thickness from 3 in. to 1 in., should withstand 10,000 volts, this puncturing voltage not increasing with the thickness, owing to the increased difficulty of thoroughly drying the inner part of the thick sheets. Sheet leatheroid possesses substantially the same qualities, and is made according to the same processes as vulcanised fibre. A thickness in this material of in. should safely withstand 5000 volts, and should have a tensile strength of 500 lb. per square inch. • •634, With such materials as vulcanised fibre and sheet leatheroid, increase in thick- ness is not necessarily accompanied by increased insulation resistance, owing to the difficulty of obtaining uniformity throughout the thickness of the sheet. This is well shown in the tests of leatheroid sheets of various thicknesses given in the following Table :- Table 8.-Sheets of Leatheroid-Insulation Strength. Volts per Unit. 320 256 256 240 120 32 24 Thickness. Mica Hard rubber Slate Marble Thickness. 0.005 0.007 0.009 0.011 ·· 13 16 ·· Vulcabeston Asbestos Vulcanised fibre Oiled linen Shellaced linen.. ·· •• Puncturing Voltage. 3,600 to 5,860 7,800,, 10,800 8,800,, 11,400 11,600 ,, 14,600 Hard rubber in various forms is sometimes useful, owing to its high insulating qualities. Its use is restricted, however, from the fact that at 70 deg. Cent. it becomes quite flexible, and at 80 deg. Cent. it softens. Slate is used for insulation of the terminals of dynamos, &c. Ordinarily good slate will, when baked, withstand about 5000 volts per inch in thickness. Electrical. Excellent "" Where practicable, it is desirable to boil it in paraffin until it is thoroughly impregnated Total Volts. 5,000 8,000 12,000 15,000 15,000 6,000 6,000 Table 9.-Summary of Quality of Insulating Materials. Very poor Good Fair Good Fair Good Thermal. Excellent Poor Good ·· "" Excellent · 99 Good Fair "" .. • ·· SISTA MD Mechanical. Hygroscopic. Excellent Fair Poor Poor Good "" "" 99 Poor 99 Fair Poor Good "" Poor Fair Poor Power of Engine for Direct-Coupled Dynamo. RULE-To find approximate power of engine to drive dynamo of given kilowatt capacity, add one-third and then 10 per cent. Example dynamo 150 kilowatts. 150 150 I.H.P. of direct-connected steam engine = 150 + + 150 + 3 100 = 200 + 20 = 220 I.H.P. 10 (150 10) 3 ELECTRIC GENERATORS. 427 MODEL SPECIFICATION FOR DIRECT-CONNECTED RAILWAY GENERATOR. General Design. • • Machine to be of multipolar type, having poles and rated capacity of. kilowatts, adapted for direct connection to engine shaft, and designed for maximum potential of 500 volts at no load and 550 volts at full load, when running at a speed of . . . revolutions per minute. • Armature. To be of slotted drum type, with special ventilating ducts. Core to be built up of laminated sheet steel or charcoal iron of highest magnetic quality. Laminæ to be individually dovetailed into cast-iron spider, keyed to shaft and insulated from each other. Laminations to be thoroughly japanned, to prevent formation of eddy currents. Winding to consist of well-insulated copper bars, set in slots in periphery of core. Insulation of armature, when connected up, to be capable of withstanding an alternating current electromotive force of 2500 volts for five minutes. Commutator. To be of hard-drawn copper, insulated with mica throughout. The degree of hardness of the mica to be arranged so that the mica and copper wear equally. Segments to be so arranged that one or more bars may be removed without disconnecting other bars, and their number to be such that there will be entire freedom from sparking. Fields. Shunt and series coils to be wound on separate forms so that they can be readily slipped on and off, and insulation of complete coils to be capable of successfully withstanding an alternating current of 2500 volts for five minutes. Brushes. Brush - holder arms to be supported from ring accurately fitted to yoke. Handwheel and worm gear to be provided for shifting ring and adjusting brushes. Brush-holders to be so constructed that the current will not pass through moving joints or tension springs. The brushes to be of carbon, and of such size and number as to carry full load current continuously without undue heating, and 40 per cent. overload for two hours without injurious heating. Normal current density in carbon brushes when operating at full load not to exceed 32 amperes per square inch. Temperature. Not to exceed 40 deg. Cent. above the temperature of surrounding air after continuous run of twenty-four hours at full load. Sparking. Design to be such that the machine can sustain sudden fluctuations in load, up to 50 per cent. above its rating and down to zero, without injurious sparking at commutator and without shifting brushes. Insulation. To be capable of withstanding a pressure of 2500 volts alternating for five minutes. RUNNING OF ĠENERATORS AND THEIR CARE. General. (FIGS. 21 and 22, pages 428 and 429.) In running a dynamo, great care must be taken to keep the commutator perfectly smooth. Fine sandpaper should occasionally be applied to the com- mutator while it is revolving slowly, at a point midway between the pole-pieces. Emery cloth should never be used, as particles get between the bars, and cause short circuits, or else become fixed in the carbon brushes and cut the commutator. 428 SECTION IV.—POWER STATION. Great care should be used in starting a new generator. When first started, it is advisable to run the generator slowly with lightly excited field on to some external resistance—say a series of lamps-for several hours. By this means the armature, which may have absorbed a certain amount of damp, will dry. When 21 -LINE (955) -LINE CLOCKWISE TO BUS BARS 00 COMMUTATOR SIDE +LINE CLOCKWISE ++ LINE EQUALIZER TO BUS BARS Oo COMMUTATOR SIDE COUNTER CLOCKWISE -UNE TO BUS BARS 00 COMMUTATOR SIDE COUNTER CLOCKWISE -LINE + LINE EQUALIZER TO BUS BARS 00 COMMUTATOR SIDE +LINE. EQUALIZER Fig. 21. Connections of Railway Generators, 557 volts; British Thomson-Houston. new carbon brushes are put on, a piece of sandpaper should be fitted round the commutator, rough side out, and the commutator slowly revolved. This will cause the brushes to take proper shape, and will prevent sparking. Great care should at all times be taken to keep all parts of a generator perfectly free from dust and oil, and to see that no dirt accumulates about the brush- holders. The carbon dust coming off the brushes should frequently be rubbed off. ELECTRIC GENERATORS. 429 The commutator should be kept lubricated, by occasionally applying to it a cloth slightly saturated with oil. Waste should on no account be used for this purpose, as it is apt to catch on the brushes, thus causing sparking. POSITIVE BUS BAR 10 22 CIRCUIT BREAKER TERMINALS O DJINKLER SHUNT NEÇAYIZ PUS BAR · JOISHI Z INSIDE INSIDE ว WTONY ! PVYCLE BREAKS COMMUTATÉR ENDİ 101313 ANEOSIMY TO VOLNĚTEN MAIN SWITCHES POSITIVA MEGAWOR SERIES WUNDING SHUNT WIND INSIDE SYNFRE (0 FROM SENJES TO SERIES 2 INSIDE WIK (966) EQUALIZER CABLE HA RESIST EQUALIZER HOLIMS SERIES SHUNT STRĪBS NESTADALAF RUNNING IN OPPOSITE DIRECTION REVERSE BRUSH NOTE. WHEN ARMATURE IS A &E & BRUSHES C LEADS. NOTE:ALL FIELDS ARE NUMBERED CLOCKWISE REGARDLESS OF THE NUM- BER OF POLES Fig. 22. Diagram of Generator Connections; Dick, Kerr Generator. It may sometimes happen that a generator fails to excite itself. If this is not due to bad contacts, or to a breakage, or wrong connections in the shunt winding, it may become necessary to charge the fields from another machine. When com- pound generators are in parallel, it is necessary to connect them in three places, so as to prevent the possibility of one generator running the other as a motor. When machines of different sizes are connected in parallel, care should be taken that the wwwx 430 SECTION IV.-POWER STATION. resistance of the series winding and connections of all the generators be equal. Otherwise the machines will not divide the load in proportion to their capacity. In large machines it generally takes several hours for the shunt coil to get to its normal temperature. This means that the rheostat in this circuit will very frequently have to be altered so as to maintain the current in the shunt-winding constant. The following instructions must be observed when putting compound gene- rators on an already live circuit: 1. The generator must be got up to it normal speed. 2. The rheostat in the shunt winding must be adjusted so as to give the same voltage between the terminals of the generator as that of the line. 3. Throw in the positive and negative generator main switches, and equalising switch. 4. The ammeter of the generator must be watched, and the field rheostat adjusted so as to make it take its proper share of the load. If a generator should be thrown in parallel with another before its voltage is up to the same point, it will not do its proper work, and it may even be run as a motor with a current from another machine. If this should happen, resistance should be thrown out of this machine. If the generators are run by means of belts, 23 (383) 24 3024.F. Figs. 23 and 24. Details of Bearings. and one of the belts should break, the generator will continue running as a motor by a current off the line. To shut down a generator running in parallel it is necessary :- 1. To throw resistance in with the rheostat so far as to cut down its load. 2. To open the circuit-breaker and the three main switches. 3. To slow down and stop the engine. In any case, the greatest care should be taken that the shunt circuit of the generator be not broken while it is running. If this should happen, it is more than probable that the armature and series winding of one or more machines will be burnt out, unless these are instantly cut off by their fuses melting. When it becomes necessary to raise or lower the voltage of the line, the voltage of each generator has to be regulated. If the bearings should heat, the following alterna- tives should be tried before the generator is shut down. The load should be lightened, the belt slackened, the caps on the boxes slightly loosened, and more oil put into the bearings. If these remedies fail, a heavy lubricant such as vaseline or cylinder oil should be used. If all the above remedies are useless, it becomes necessary to shut down. The belt should be got off as quickly as possible, the machine meanwhile being kept revolving, so as to prevent sticking. The caps should be screwed off the bearings, and the flow of oil kept up. When the caps have been taken off, the machine should be stopped, and the linings of the bearings taken out and allowed to cool in the open air. Figs. 23 and 24 are sections through standard bearings, as used by the General Electric Company on their railway generators. When a machine is shut down, care should be taken that the brushes are all off the commutator, and that all switches and circuit- breakers are open. ELECTRIC GENERATORS. 431 Table 10.-Slow-Speed Continuous-Current Generators for Direct Coupling.-Type L.E.G. (Allgemeine Elektricitäts-Gesellschaft, Berlin.) Output. 18 24 32 40 50 65 80 100 125 160 200 250 275 350 450 550 650 850 800 1000 1200 Number Speed. of Poles. 250 230 215 200 190 180 170 165 160 155 150 140 135 130 125 120 110 100 94 90 83 8 8 8 8 10 10 10 10 10 10 12 12 12 12 12 13 14 14 14 16 18 70 40 80 Arm.Temp, în degrees Centigrade. 2015 10! a 464 ft. in. 4 1 4 1 4 1 4 1 6 0 6 0 7 4 7 6 7 6 9 4 9 4 9 4 10 10 11 4 11 4 12 6 13 0 13 2 17 0 17 4 し ​ft. in. 1 4 1 4 1 4 1 6 1 1 1 1 6 1 7 1 1 1 1 1 8 1 9 1 10 1 11 2 0 2 2 2 4 2 4 -2-2 6 - i Dimensions. C ft. in. 1 6 1 8 1 10 2 0 1 10 1 10 time in hours 4 1 10 1 10 2 0 2 2 2 2 3 0 3 4 3 10 3 10 4 2 4 6 5 0 5 0 f ft. in. 0 10 0 10 0 10 0 10 0 10 TEMPERATURE CURVE 300K.W. SIZE 280. DIRECT DYNAMO Under Constant Full Load. 1 0 1 2 1 2 1 2 1 2 1 4 4 1 4 1 1 6 1 8 1 8 1 8 1 10 2 0 2 0 hours & 7 8 8 2 TEMPERATURE CURVE WITH CONSTANT LOAD. Fig. 25. Performance and Rating of Continuous-Current Generators for Railway Work. To meet varying conditions, machines can be so constructed as to give either 500 volts at no load and 550 volts at full load, or 525 volts at no load and 600 volts at full load. The kilowatt capacity and commercial efficiency of the machines remains the same in either case; the amperes vary inversely as the voltage. TO 3 ..$2 k ft. in. 20 2 2 2 2 2 2 0 2 0 2 0 2 6 2 6 2 6 2 6 2 6 6 6 6 6 3 0 3 0 3 0 3.0 3 0 p ft. in. 4 1 4 1 4 1 4 2 5 5 5 51 5 5 6 1 6 4 6 4 8 1 8 3 8 3 8 11 9 10 9 11 11 3 11 6 11 8 14 0 15 3 It is important that the machine should run at its rated speed, and also that the speed be uniform from no load to full load, as any variation from the normal speed directly affects the degree of compounding. The efficiency of a dynamo expresses the ratio of output to input. The difference between these values represents the total losses in the machines, which may be classified under three heads:- 432 SECTION IV.—POWER STATION. § KILOWATTS 800 700 600 500 400 300 200 100 26 VOLTS 500 450 © FIELD AMPERES જ 4 (957) 8.POLE #172 ENG.TYPE 500K.W.550/600 VOLT SHUNT & COMPOUND GENERATOR. 320 R.P.M. AS SHUNT MACHINE -100 90- 80 ·70 -60 50 40 30아 ​•20 -10 0 E.M.F. REGULATION EFFICIENCY FIELD AMPERES 200 KILOWATTS OUTPUT KILOWATTS INPUT 400 600 800 1,000 1,200 1,400 1,600 AMPERES Kilowatts. § § § Volts. 2% Efficiency & 1000-600 900-500-90 800 700 600 500 400 300 200 700 100 (953) Field Amperes 7 6 80 10 60- 50 40 30 20 10 0 27. .8 ·º8 POLE 500 K.W 5‰00 VOLT SHUNT & COMPOUND GENERATOR 320 R.P. M. AS COMPOUND MACHINE. EMF Regulation. Efficiency Kilowatts Input. Kilowatts, Output Field Amperes 200 400 600 800 1000 1200 1400Amp 1 ELECTRIC GENERATORS. 433 Watts Lost. 14,000 12,000 10.000 8,000 28. -100 1 90 80 70 60- -50 40 30 6.000 4,000 -20 2000 10· (959) 10 Watts Lost % Efficiency Luffy ·100 90 FY 20 30 40 50 60 70 80 90 100 110 120 130 Per Cent Load 80 70000 60000 -60 50000H -50 40000 ·40· 30000 30: 20000 20. -70- 4 POLE, 350REVS.,220K.W,550 VOLTS CURVES SHOWING EFFICIENCY AND DETAILED LOSSES. Efficiency Curve. 10000 10 (960) C²R Series 29. R CR Armature and Brush Contact Surface Shunt Losses Tron Losses. CURVES SHOWING EFFICIENCY AND DETAILED LOSSES FOR LOOK.W.GENERATOR, 12 POLES, 100R.P.M,550VOLTS. -Efficiency Gurve: C&R Series CR Armature and Brush Contact/Surface Shunt Losses. Lasses. Iron Losses. Per Cent Loade 10 20 30 40 50 60 70 80 90 100 110 120 130 434 SECTION IV.-POWER STATION. 30 Vad kan du (196) C ? J Jb Thu 2: • H.. Fig. 30. LEG Type of Generator; Allgemeine Elektricitats Gesellschaft. ELECTRIC GENERATORS. 435 Volts 1st. Electrical, that is, copper or C2R losses due to resistance and consequent heating of conductors. 2nd. Magnetic or iron losses due to hysteresis and eddy currents in the mag- netic circuit. 3rd. Mechanical losses due to friction, windage, &c. In calculations of so-called "electrical efficiency," the mechanical losses are not considered, and the magnetic losses are also disregarded. The term is a survival from the early days of dynamo construction, when the mechanical losses 600 500 400 300 200 100 100 90 % Efficiency 2 8 8 8 8 8 8 8 80 70 60 50 40 30 20 31. (962) Amperes in Field & Core Losses in KW. 4 16 20 32. Core Losses Load Saturation Cury Load CORE LOSSES AND NO LOAD SATURATION CURVE FOR LOOK.W. GENERATOR, 12 POLES 100R.P.M. 55QVOLTS. /½ Ld. 34 Ld. FullLdLd Load EFFICIENCY CURVE OF TYPE MP. FORMH. GENERATOR 16 POLES, 1000K,W, 80R.P.M., 550VOLTS, COMPOUND WOUND. 10 0 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 (963) Per Cent Load. were very small in comparison with the large electrical losses, and the importance of the iron losses was not recognised. The term "electrical efficiency" should be regarded as obsolete, and is meaningless. In direct-connected machines, the friction losses are chargeable to the engine or other source of power, since the weight of the flywheel may be less (by an amount corresponding to that of the armature) than would otherwise be necessary for similar service; and any additional friction which may possibly be due to the use of an outboard bearing is more than counterbalanced by the absence of the strain which would be caused by the belt or rope if the machine were not direct- connected. 436 SECTION IV.-POWER STATION. The factors above referred to may be expressed in symbols as follows: 0=Output, A=Electrical losses, B-Iron losses, and C=Mechanical losses. Electrical efficiency= Commercial efficiency, direct-connected Py orni. 100 Efficien oy Kilo - walls 90 80 60 8 20 8 LO K.W. 45 40 $5 Commercial efficiency, belt-driven = * 1.5 10 ✔ 550 volts, 320 revolutions -volle Electromotive Force 8kgulation for constant speed, (365) Compound Generatore. 6 polas 500 kilowatts, 100 200 CSPLE.| Efficiency Effiz [C³R = (Current)' x Resistanca butput Mechanical kilo-walts applied Electrical minute. = 400 600 800 1000 1900 1400 Load în ampèu Fig. 33. 0 (0+A) 0 (0+A+B) 0 (0+A+B+C) Valle 1800 2000 650 550 500 460 400 |350 500 250 200 150 100 Load in ampères 300 400: 500 600 700 600 900 1000 1100gárne 12 poles. 1,500 kilo-watts, 75 revs. per min. 50 KW Kilo · walle and 2200 2400 Volta C⭑R. Arma- bure C'R Surina C'R Shunt ---- from. Cora Loss Fidion Figs. 25 to 29, and 31 to 33, are curves relating to various railway generators, and are self-explanatory. Fig. 30 illustrates the LEG type of generator built by the Allgemeine Elektricitäts Gesellschaft. Fig. 31 shows the core losses, and the no-load saturation curve for one of Messrs. Dick, Kerr's 1100-kilowatt gene- rator, 12 poles, 100 revolutions, 550 volts; whilst Fig. 29 gives the detailed losses, and also the efficiency of the same machine. Fig. 28 gives similar information of a 4 pole, 350 revolutions per minute, 220 kilowatt, 550 volt generator made by the same firm. ELECTRIC GENERATORS. 437 Fig. 32 gives the efficiency curve of a 16 pole, 1000 kilowatt generator of the British Thomson-Houston Company. The useful output can be computed as a certain fraction of the electrical capability, depending on the output of the machine. The fraction of the electrical capability which represents the output of a machine may be called the coefficient of reduction from capability to output, and varies with the size of the generator, and the details of its structure. The electrical capability of a generator is independent of the character of the winding, provided the amount of winding space remains constant. This is true, however, only so long as the proportion of winding space, devoted to insulation, remains constant through all sizes of wire; thus, if the number of turns in the armature be doubled, the E.M.F. will be doubled, but the resistance will be quadrupled, since there will be twice as great a length of wire of half the cross section; hence the ratio of the square of the voltage to the resistance remains the same Table 11.-Output and Efficiencies of British Thomson-Houston Form H Continuous-Current Railway Generators. For British Thomson-Houston Standard 550 V. Ratings. Direct-Connected Machines. Poles. Kilowatts. 69999 ∞ ∞ ∞ ∞ ∞ ∞ 8 8 8 8 8 8 10 10 10 10 12 12 14 14 16 18 H00222* Rating. 28 28 100 150 200 200 200 300 300 300 400 400 400 500 500 500 500 650 800 800 800 1000 1200 1600 1600 2000 2400 Revolu- tions per Minute 275 200 200 150 120 150 120 100 150 120 100 120 100 90 80 90 120 100 80 80 80 100 75 75 75 Amperes. Full Load. 550 V. 182 273 364 364 364 545 545 545 726 726 726 910 910 910 910 1180 1460 1460 1460 1820 2180 2900 2900 3640 4370 150 per Cent. Load. 92.5 92.5 92.5 92.5 92.5 93 93 93 93.5 93.5 93.5 93.5 93.5 93.5 93.5 94 94.25 94.25 94.25 94.25 94.5 95 95 95 95 Commercial Efficiency. 100 75 per Cent. per Cent. Load. Load. 92.5 92.5 92.75 92.75 92.75 93 93 93 93.75 93.75 93.75 93.75 93.75 93.75 93.75 94 94.25 94.25 94.25 94.5 94.5 95 555 95 95 95 92 92 92 92 92 92.5 92.5 92.5 93 93 93 93 93 93 93 93.5 93.5 93.5 93.5 93.75 93.75 94.25 94.25 94.25 94.25 50 per Cent. Load. 90.25 90.25 90.25 90.25 90.25 90.5 90.5 90.5 91.25 91.25 91.25 91.25 91.25 91.25 91.25 91.5 91.75 91.75 91.75 92 92 92.5 92.5 92.5 92.5 In calculating the above efficiencies, Tables 11 and 12, all electrical and mag- netic losses, including those in the commutator and brushes, have been taken into account. When generators are furnished with base and bearings, as in the case of belt-driven machines, the friction of the latter is included in computing the efficiency; but when machines are furnished without bearings, as in the case of direct-connected generators, the friction is not included. In direct-connected machines these friction losses are regarded as chargeable to the engine or other source of power, since the weight of the flywheel may be less (by an amount corresponding to that of the armature) than would otherwise 438 1 SECTION IV.-POWER STATION. be necessary for similar service; and any additional friction which may possibly be due to the use of an outboard bearing is more than counterbalanced by the absence of the strain which would be caused by the belt or rope if the machine were not directly driven. Table 12.-Output and Efficiencies of British Thomson-Houston Form H Continuous-Current Railway Generators. For British Thomson-Houston Standard 500 V. Ratings. Machines. ♡♡♡♡∞ ∞ ∞ ∞ ∞ ∞ ∞ Poles. Kilowatts. 6 6 6 6 6 8 8 8 ∞∞∞000002LIL-22** 10 10 10 10 12 12 14 14 16 18 28 28 Ratings. 85 130 175 175 175 260 260 260 350 350 350 425 425 425 425 550 700 700 700 850 1000 1400 1400 1750 2100 Revolu- tions per Minute 240 175 175 130 105 130 105 87 2856582825RRR688 130 105 87 105 87 80 70 80 105 87 70 70 70 87 65 Amperes Full Load 500 V. 170 260 350 350 350 520 520 520 700 700 700 850 850 850 850 1100 1400 1400 1400 1700 2000 2800 2800 3500 4200 150 per Cent. Load. 91.75 91.75 92 92 92 92.5 92.5 92.5 92.75 93 93 93 93 93 93 93.5 93.5 93.5 93.5 93.5 93.75 94.5 94.5 94.5 94.5 91.75 92.5 92 92 92 Commercial Efficiency. 50 100 75 per Cent. per Cent. per Cent. Load. Load. Load. 92.5 92.5 92.5 92.75 93 93 93 93 93 93 93.5 93.5 93.5 93.5 93.5 93.75 94.5 94.5 94.5 94.5 Direct-Connected 91.25 92 92 92 92 92 92 92 92 92.5 92.5 92.5 92.5 92.5 92.5 93 93 93 93 93 93.25 94 94 ཚ་ཚ་ 94 94 88.5 89 89.5 89.5 89 90 90 90 90 91 91 91.5 91.5 91.5 91 90.5 91 91 91 91 91.3 92.5 92.5 92.5 92.5 "Boosters" or Motor-Dynamos. (FIG. 34, page 439.) "Boosters," or motor-dynamos, as they are commonly called, are in reality step-up transformers for direct currents; they give an added pressure to compensate for extra long circuits or portions of circuits, or raise the voltage where that may be necessary. The usual form has a double field and two armatures mounted on one shaft, or connected by a coupling, the motor armature driving that of the generator. This apparatus is self-regulating, as the main current passes through the generator field and armature with the line, so that, as the load on the main circuit increases, the strength of the field on the booster is increased, and the necessary additional pressure is furnished to the booster circuit. These machines may be wound for any desired increase in voltage. The arrangement of circuits that is used on the Baltimore and Ohio Railroad is as follows:-The main circuit from the generators passes through the motor end of the booster with a shunt field, and in series through the field and armature of the generator end, where the necessary 200 volts extra are added, delivering the current to the locomotive feeders at 700 volts. Where the drop in the return circuit becomes too great, negative boosters are employed with success. A negative booster is a generator generally directly connected to a shunt-wound motor. The armature is connected to the negative ELECTRIC GENERATORS. 439 i | + 6:09A. (1769) 1: Bus Bars Fig. 34. Fig. 35. www S "" 9 to 10 9 ,, 1144 11,, 14 49 12 15 " "} 14 16 14 16 15 18 15 18 49 16 18 16 18 16 "" "" 41 49 45 49 48 49 45 49 48 50 45 48 18 84 50 84 51 16 18 18 20 84 48 19 22 84 48 19 22 84 46 48 19 22 84 22 25 100 50 48 24 27 100 24 27 120 27 30 150 48 52 27 "" 5 9 "" >> "" "" "" "" N "" 24 32 44 "" 11 "} 8 60 84 28 35 36 41 30 180 | 52 442 SECTION IV.—POWER STATION. Poles Revolutions per minute Kilowatts Table 14.—Standard Slow-Speed Continuous-Current Generators. (Dick, Kerr and Company.) (FIG. 36, page 440.) (Dimensions are for Reference only.) ABODELGF-UKLEZOPDD Volts Weight of arma- ture in pounds.. Total weight in pounds Diameter of shaft I H J .. (Minimum) .. ·· ·· •• .. .. ·· .. ·· ·· ·· ·· ·· 6 6 6 6 8 10 150 100 200 100 100 100 100 100 250 100 150 500 500 500 500 200 250 300 500 500 100 550 560 550 550 550 550 560 7 371 23 4 72 20 3,700 5,300 6,600 5,500 12,500 15,700 31,000 32,000 16,300 27,500 30,000 28,000 44,000 54,000 98,000 100,300 in. in. in. in. in. in. in. in. 93 30 123 13 26 12 22 15 12 36 24 * * 020007 8 45 28 4 78 20 12 36 135 15 26 14 22 18 13 42 *** 30 8 46 28 4 78 20 12 36 135 16 28 152 244 22 151 42 18838** 30 * 100000 8 45 28 45 15 29 CC 14}} 25 18 13 42 30 S 78 84 20 12 36 135 ** 12 28288352 18 13 48 165 16 52 15 26 17 13 66 54 -k-a 51/ 13 58 32 S 84 18 13 48 165 18 59 16 28/ 23 15 772 36 13-15 10 96 15 20 67 216 18 61 17 291/1 21 161 17 66 90 54 78 581 60/ 1 10 100 400 500 550 16 771 36 10 96 15 20 67 216 20 64 18 32 23 18 90 78 63 10 90 500 500 550 17 773 96 15 20 67 216 20 64 191 32 23 181 90 78 63 12 90 750 500 550 35,800 40,000❘ 48,000 105,300 116,000 142,000 168,000 in. in. in. in. 21 86 41 12 102 15 20 78 236 18 62 17 * These Machines have No Sliding Base. 311 22 17 108 90 61 1 12 IN 90 1000 500 550 22 869 41 12 102 15 20 78 236 21 72 19 16 80 1200 500 550 362 27 19 108 90 71 1 16 20 24 75 70 70 1500 2000 2500 500 500 +00 550 550 550 67,000 81,000 114,000 140,000 168,000 202,000 285,000 350,000 in. in. in. 24 96 48 12 108 15 22 85 261 211 59 20 38 26 201 126 96 58 1 26 96 48 12 108 15 22 85 261 26 73 25 481 36 25 126 96 72 1 30 102 50 12 108 15 22 90 270 24 82 22 42 32 23 144 120 81 1 36 126 70 15 120 15 24 106 306 26 63 21 44 30 25 186 138 62 1 ELECTRIC GENERATORS. 443 Poles Revolutions per Kilowatts Volts Weight of armature in pounds Total weight in pounds ARODELGHL-KLWZOLORSH B I J N ·· D (Minimum) T Diameter of shaft (Minimum ·· ·· ·· • • .. .. • ·· Table 15.-Standard High-Speed Continuous-Current Generators. (Dick, Kerr and Company. (FIG. 37, page 440.) (Dimensions are for Reference only.) ·· ·· •• ·· ·· ·· •• .. ·· minute •• • ·· • ·· ·· ·· ·· ·· ·· •• • •• • • • .. ·· ·· .. .. ·· • ·· .. ·· ·· 4 400 500 100 500 550 3,000 12,500 in. 6 35 *** *****fon~O~e 43 108 18 121 6 360 400 150 500 550 3,730 16,500 in. 61 371 23 4: 72 91 301 -key-dea 118 18 391 14 T∞∞DERE! 141 34 17 4 340 380 200 500 550 4,900 20,000 in. 73 40 25 4 75 20 10 32 123 15 401 11 24 18 13} 41 25 33 13 101 19 6 320 350 250 500 550 7,300 28,000 in. 8 45 28 41 78 20 12 361 135 19 40 14 24 18 13 42 24 3 13 101 19 6 300 325 300 500 550 8,100 30,000 in. 8 46 28 4 78 20 12 36 135 20 47 15 30 22 151 42 30 4 13 10 19 6 300 400 500 550 9,100 35,000 in. 8 46 28 4호 ​78 20 12 361 135 211 50 16 33}} 24 161 42 30 4 13 10 19 8 230 400 500 550 12,500 39,0 0 in. 10 501 30 84 18 13 41 144 21 47 16 NEWLOPEED 151 * Weights do not include Shaft and Bearings. 8 230 500 500 550 15,400 48,000 in. 10 58 32 8 84 16 18 48 162 22 51 18$ 32 21 151 66 44 5 13 11 24 8 200 600 500 550 18,800 58,500 in. 16 58 32 8 84 16 13 48 162 22 56 18 -kirk 37 25+ == 171 66 48 5 14 111 24 10 180 700 500 550 24,000 75,000 in. 16 60 34 8 90 15 14 51 170 22 55 18 34 26 18 ∞∞HOL20 78 54 6 15 12 26 10 165 1,000 500 550 29,400 98,0 in. 18 772 36 10 96 15 20 67 216 23 62 191 39 23 18 90 60 6 17 14 28 16 135 1,500 500 550 46,000 143,000 in. 22 85 40 12 102 Ag¤APHR8ABI***** 15 20 76 114 : 444 SECTION IV.—POWER STATION. Table 16.-Westinghouse Direct-Current Engine-Type Generators, with Vertical Field Division. (FIG. 38, page 445.) Kilowatts. For Lower Speeds. 75 100 150 200 250 300 400 500 325 375 400 500 500 630 650 800 800 800 1050 1200 1200 Amperes at 550 Volts. 134 182 270 364 455 546 725 910 590 682 725 910 910 1140 1180 1455 1455 1455 1910 2180 2180 1500 2730 2250 4100 Poles. 6 6 6 6 6 8 8 10 8 10 10 10 10 10 10 12 12 12 14 20 Revolutions per Minute. 400 to 450 380 420 354 390 340 380 330 370 320 360 300 340 290 330 >> "" "" "" >> "} "" "" 90 100 125 90 to 100 150 160 90 100 95 105 "" "" ,, 140 190 to 200 110 80 to 90 80 100 to 110 75 80 228888 "," 75 80 Approximate Approximate Total Weight. Weight of Armature. lb. 7.900 8,875 13,400 18,250 22,000 26,100 33,000 34,800 61,500 61,500 78,000 62,000 102,000 103,000 83,200 80,000 103,600 135,000 147,000 147,000 186,800 203,600 309,000 lb. 1,600 2,200 3,100 4,000 5,000 6,400 8,000 9,400 14,900 14,900 21,700 15,200 28,900 29,300 26,000 26,000 30,500 39,200 43,200 43,500 58,000 68,200 112,000 A 18 19 22 B 10 13/ 23 12 26 13 27 15 30 17 34 18 18 23 22 222 23 22 23 24 20 2000 !!** 36 37 12-6 18 21 41 211 44/ 21 435 20 46 22 39 38 463 49 50 51 52 57 55 Approximate Dimensions in Inches. ii i b 18 20 22 24 28 29 30 31 b 94 10 12 14 15 15 18 18 ·· • C 37 381 434 464 50$ 534 59 611 71 71 731 71 804 80 Ꭰ 671 69 79 851 934 99 108 114 E 64 64 732 79 88 233 100 108 130g 144 130g 144 1383 176 1309 144 171 152% 152 171 733 1383 176 73 138 176 SO 152 171 881664 204 951 180 252 951 180 252 100% 191 252 1093 2099 276 | 1374 2631 324 F 25 25 301 31 10015 001 37 39 G 30 31 33 341 449 38 494 71; 511 36 381 42 53 55 62 60% 39 60 471 39 42 42 475 47. 42 523 76 53% F3 83 63 603 70 70 634 63 70 88 97 119 H 45 46 521 58 63 66Я oche ocke 79 120 120 126 120 144 144 NOTE. In the above Table the machines which are indicated as having either of two speeds may be operated at 550 volts at either speed, or at 575 volts at the higher speed, 126 126 144 144 168 168 192 204 233 ELECTRIC GENERATORS. 445 : • (964) 38 ఎ 75 134 6 400-450 100182 6 380-420 150 270 6 350-390 | 200 364 6 340-380 250 455 6 330-370 300 546 6 320-360 500 725 6|300-340 500 910 8 290-330 E O E H Fa A B LIMITING LINE OF ENGINE PARTS lb. lb. 6,500 1,600 11 20 7,550 2,200 12 23 12,000 | 3,100 | 14|| 25 16,000 4,000 15 27 18,650 | 5,000 | 16 30 22,600 | 6,400 | 17 34 31,000 8,000 18 36 31,300 9,400 181 36 Fig. 38. Diagram of Westinghouse Generator. Table 17.-Westinghouse Direct-Current Engine-Type Gene- rators, with Horizontal Field Division. (Fig. 39.) -B Approximate Dimensions in Inches. 18 20 10 22 12 24 14 28 15 29 15 30 18 31 18 HƠN - ----- 91 i * ii b b с D E F G LIMITING LINE OF ENGINE PARTS 20 291 70 29 70 22 3581 25 39 88 26 42 96 28 44 102 29 48 110 32 51 118 31 H 9 37 9 37 9 43 9 46 9 52 12 534 12 572 12 61 NOTE.-In the above Table the machines which are indicated as having either of two speeds may be operated at 550 volts at either speed, or at 575 volts at the higher speed. * In the case of each of the above generators the dimensions B may be reduced to b i. if required, providing that the pedestal of the outer bearing be not less than bii. high. 446 SECTION IV.-POWER STATION. Oo, 00 (965). .) 20 26 34 39 H Kilo- Maximum Out- put in watts. 54 90 114 180 265 350 440 530 620 750 840 CHP 101 Indicated Horse- Power of En- gine. 37 48 61 80 87.5 139 172 272 400 522 350 783 915 1095 1215 bo v vlogi od Table 18.-Dimensions of Siemens and Halske Railway Generators. (FIG. 40.) Maximum No. of Revolutions per Minute. E Fig. 39. Diagram of Westinghouse Generator. 600 600 560 450 415 375 330 250 235 205 195 180 175 140 110 Weight in Kilo- grammes of Dy- namos. 1,100 1,200 1,500 2,200 A 3,000 3,900 00 1050 1050 1220 1335 1380 1600 B CQ LIMITING_LINE Dimensions in Millimetres. 1 ¦ -B-- C с 900 900 1000 1000 780 1440 1050 780 780 1440 1050 780 880 1540 1100 840 980 1590 1100 900 1110 1655 1100 1000 1200 1815 1200 1100 1500 2160 1470 1200 1550 1750 2525 1650 1300 1600 1870 2935 2000 1450 1800 2000 1500 1230 4,900 1685 1380 6,100 1970 8,200 2050 2255 12,000 2160 | 3080 2200 2200 1600 2400 14,700 2400 2270 3335 17,000 2450 2420 3710 2500 1600 2600 3770 2500 1600 3000 20,000 2540 2540 2600 3040 28,000 4520 3000 1650 3200 35,500 3500 3400 2200 4400 + 3800 5300 10 D LIMITING E F i. ELECTRIC GENERATORS. 447 (366) 41 fo Ja ··· с a d + e * App Fig. 40. Siemens and Halske's Railway Generator. (Table 18.). 9 K P (966) Fig. 41. EG Type of Generator; Allgemeine Elektricitats Gesellschaft. (Table 19.) 4 448 SECTION IV.-POWER STATION. Table 19.-High-Speed Continuous-Current Generators for Direct Coupling.-Type E G. (FIG. 41.) (Allgemeine Elektrieitäts-Gesellschaft, Berlin.) Output in Kilowatts. 100 125 150 175 220 300 450 3800 Horse- Power. Type. 1- C Ve 15 20 30 40 " 11 70 66 82 97 130 160 200 300 99 "" 99 ****UNU "" ,, 150 200 Revolutions. 560 500 430 390 360 340 330 325 Speed. Kilowatts. Capacity in Kilo- watts. 50 55.0 60 66.0 80 » 100 33 44 55 66 88 110 135 200 16.5 30 800 22.0 40 700 33.0 60 600 44.0 80 500 Ampères. Revolutions per Number of Poles. 4 Number of Pole- Pieces. Horse-Power. CÓ GÌ GÌ CP nhân nhìn nhận ∞ ∞ ∞ ∞ 00 00 00 6 100 400 120 350 88.0 160 300 110.0 200 275 165.0 300 210 8 270 400 175 12 320 220.0 8 R2R3558 8 Table 20.-Data of Oerlikon Railway Generators. 10 550 550 550 550 559 550 550 550 Volts. Amperes. Table 21.-Dimensions of Compound-Wound Belt, Rope, or Directly-Driven Railway Generators. (Ganz and Co., Budapest.) Method of Driving. Pulley a ft. in. 3 93 4 03 4 5 4 92 4 5 6 2 6 8 19 19 9 8 NAIN 97 130 Rope Pulley direct-connected 8 160 Rope Pulley direct-connected Rope Pulley direct-connected Rope Pulley direct-connected 60 80 98 123 160 200 250 364 Dimensions. b ft. in. 3 91 3 91 3 111 3 11 4 9 4 9 6 4 9 4 Total Dia- meter. Revolutions per Minute. 700 600 500 450 400 350 300 300 Breadth. Number of Ropes. 400 180 470 270 550 320 675 360 770 400 940 430 1274 562 1436 1842 2248 .. : Dimensions of the Pulley in Millimetres. ::0 ft. in. 2 10 9 740 15 • 830 15 h 2 10 3 3/3/ 3 33 3 33 3 5 ·· 3 11 4 14 -- *: *: *:::: Diameter of Diameter of Pitch Cir- Ropes. cle. Pitch. 45 •• 30 560 13 p ft. in. 4 022 4 12 4 8 Weight in Pounds. 1220 60 1400 42 35 1800 48 40 2200 54 4 81 5 2 5 3 4,409 7,275 9,038 11,684 15,432 23,148 25,353 37,478 5 8 7 8 Total Weight in Kilogrammes 2,000 2,600 3,400 4 300 5,100 5,800 7,000 6,500 8 600 8,100 12 200 10.100 14,700 12,000 These machines are built chiefly for railway service. service. They have a strong cast-iron yoke, with a compound winding to keep the potential constant. ELECTRIC GENERATORS. 449 ALTERNATING CURRENTS. A conductor through which an alternating current is flowing has apparently more resistance than one through which a direct-current circulates; this is due to two quantities which combine with resistance to make up the apparent resistance or impedance of alternating-current circuits, namely, self-induction and capacity. Inductance, or Self-Induction. (FIGS. 42 and 43, page 450.) Electromotive force of self-induction (or inductance) acts as an extra resistance to choke the flow of current. It is due to the magnetic lines threaded through the circuit itself by the current flowing in it. In a simple circuit the number of lines is proportional to the area enclosed, but for a loop of many turns the coefficient of self-induction is proportional to the square of the number of lines. Self-induction depends on: 1. The shape of circuit. 2. The magnetic permeability of the space surrounding the circuit. 3. The magnetic permeability of the circuit itself. Self-induction can be defined: 1. As the ratio of the C.E.M.F. in any circuit to the time rate of variation of current producing it. 2. As the ratio of total induction through the circuit to the current producing it. 3. As the coefficient by which half the square of the current must be multiplied to obtain the electric energy of the circuit at that instant. For practical unit of induction, see Table 1, page 410. Capacity. Capacity in a circuit means that some part of the circuit is so shaped that it stores up energy in the form of electrostatic stress when there is a certain impressed electromotive force, and as soon as this electromotive force dies away the energy returns to the circuit as so much current. Electrostatic capacity, as typically developed in condensers, in some circuits is almost entirely absent, but at other times exists in a marked degree. (a) C = Impedance. (FIGS. 42 and 43, page 450.) The current strength in an alternating current circuit is not that which would be obtained from Ohm's law. We may consider that the resistance of an alternat- ing current circuit is different from that of the same circuit operated by continuous currents; or, in other words, that the resistance becomes converted into a hypo- thetical quantity called the impedance (Fig. 42), and expressible in ohms. Ohm's law, applied to alternating current circuits, is therefore, E ―――――― J amperes, instead of (b) C: E R² + L2 W2 ―― R amperes. where J is the impedance. Another form of formula (a) giving J its proper value becomes E C = N π where C is the current, R is the ohmic resistance of the circuit, L2 is the inductive resistance, L is the coefficient of self-induction, and W = 2 times the frequency. The denominator of the above fraction represents the impedance of the circuit (J). In a coil of insulated copper wire, having no appreciable electrostatic capacity, the impedance is composed of two parts; the resistance and the reactance due to the inductance of the coil. This reactance is determined by multiplying the inductance by the angular velocity of the electromotive force. The angular velocity is the number of revolutions per second, which is equal to the frequency, and since there are 2 π radians per second in a revolution per second, multiplying this angular velocity by the inductance in henrys, we obtain the reactance in ohms. It may be stated here that one radian per second is the C.G.S. unit of angular velocity. A radian is the angle subtended at the centre of a circle by an arc equal in length to the radius. The reactance is always graphically set off at right-angles to the resistance of a circuit. If this impedance is divided into the pressure, Q 450 SECTION IV.-POWER STATION. Lag and Lead. Figs. 42 and 43. Diagrams of Impedance, Inductance, Reactance, Frequency, Alternating Currents. Impedance $37. Resistance of Circuit A Q Angle of Lag VOLTS ERES .098 पं ❤- Angle of Lay 42 5 Reactance 0 Impedance Resistance R Capacity ↳ Inductance Reactance Reactance 06 Q Capacity Reactance 1081 0 06 Impedance Curve of Siries 43 180 Resistance R Inductance Reactance C ELECTRIC GENERATORS. 451 ! according to the modified form of Ohmn's law, we have the effective current strength. The reactance of a condenser is equal to the reciprocal of the product of the angular velocity of the electromotive force by its capacity in farads. The effect of impedance, including the size of conductors and the spacing of the same, may be noted by Table 22, which is for a frequency of 40. The figures are the coefficients by which the ohmic resistance is multiplied to give the correct impedance or resistance of the circuit. CC Impedance of Circuit with Resistance, Inductance, and Capacity. (FIGS. 42 and 43, page 450.) If a condenser were in series with a resistance coil having an inductance, then it is necessary to determine the impedance of a circuit composed of resistance, inductance, and capacity combined. The resistance in this case will be partly due to inductance and partly due to capacity. The reactance in the impedance diagram is always set off at right-angles to the resistance that due to capacity below and that due to inductance above. In the former, capacity is larger; in the latter, smaller than inductance. Inductance reactance = a b; capacity re- actance = a c; difference between a b and a c = ae: line e o gives impedance of circuit, which is always equal to the geometrical sum of the reactance of resistance. The inductance-reactance will be the self-induction or inductance of the circuit in henrys multiplied by the angular velocity in radians per second, and the capacity reactance will be the reciprocal of the product of the angular velocity in radians by the capacity in microfarads; but inductance-reactance is always laid off above the resistance line, or in the opposite direction, because capacity and inductance tend to neutralise each other's influence. The resultant reactance is the difference (a e) of the two. Table 22.-Impedance Co-efficients for a given Size, and Spacing of Conductor. B and S. 0000 000 00 0 1 in. 3 1.38 1.27 1.17 1.12 1.09 in. 12 1.73 1.53 1.34 1.25 1.18 ft. 100 3.13 2.59 2.13 1.83 1.58 ft. 1000 3.87 3.10 2.50 2.17 1.83 The Table shows that wires of small diameter should be used, and several of them, rather than one large conductor; also that the wires should be placed as close together as is consistent with safety. As these factors increase with the frequency, this should be as low as the design of the machine permits. Drop in an Alternating Current Circuit. In a continuous-current circuit, the drop at the terminals of any resistance R ohms, traversed by a current C amperes, is C R volts; likewise in an alternating- current circuit, the drop at the terminals of any impedance J ohms, traversed by a current of C amperes effective, is C J volts. "Resonant” Circuit. By the combination of an inductance with a condenser, the pressure at the terminals of a condenser may exceed that of the impressed electromotive force. If the reactance of a condenser is equal to the reactance of the inductance in a circuit, the impedance of the circuit is reduced to its simple resistance, so that an alternating-current circuit in a coil having a small resistance but large inductance, in circuit with a properly selected condenser, may develop an exceedingly high pressure at the condenser and at the coil terminals. Such a circuit is said to be resonant." Frequency or Periodicity. (FIG. 43, page 450.) A simple revolving coil, cutting the lines of the magnetic field, sets up periodic electromotive forces, which change at every half-turn, giving rise to alternate currents. In each whole revolution there will be an electromotive force which 452 SECTION IV.-POWER STATION. rises to a maximum and then dies away, followed immediately by a reversed elec- tromotive force, which also grows to a maximum and then dies away. The heights of the curve above the horizontal line represent the momentary values of the electromotive forces; the depths below in the second half of the curve represent the inverse electromotive forces that succeed them. Each such complete set of operations is called a period, and the number of periods accomplished in a second is called the frequency or periodicity of the alternators. In two-pole machines, the frequency is the same as the number of revolutions per second; in multipolar machines it is greater in proportion to the number of pairs of poles. Thus in a ten-pole field, with five north poles and five south poles, there will be produced five complete periods in one revolution. By revolving in a uniform field, the elec- tromotive forces set up are proportional to the sine of the angle through which the coil has turned from the position in which it lay across the field. (Fig. 43.) In actual machines the magnetic fields are not so uniform, nor the coils simple loops, so the periodic rise and fall of the electromotive forces will not strictly follow a sine law. The form of the waves will depend on the shape of the polar faces and on the form and the breadth of the coils. But in most cases it is sufficiently accurate to assume that the impressed electromotive force follows a sine law. A low frequency is very desirable, not only for diminishing the effect of self- induction, but also on account of the better mechanical design of the generators- fewer poles being used, the generators and motors can run at lower speed, which is nearly directly proportional to the frequency and inversely proportionate to the number of poles. General Relations or Relative Values. (Fig. 44.) induction E.M.F. consumed on line current Reactance of line impressed E. M.F. current Impedance Impressed E.M.F. ❤- Angle of lag. IR Energy EMF. 44 Induction E.M.F. The energy loss in a conductor with alternating currents due to heating depends on the current and ohmic resistance only, and is C2 R. Drop of Potential due to Power Factor.-The electromotive force consumed by the impedance does not represent the drop of voltage in the conductor, as it is generally not in phase with the impressed electromotive force as well as with the current. The drop in the line can vary between CR and IR, and will depend upon the difference in phase between the current and impressed electromotive force or the angle of lag. It can easily be determined when the power factor is known. Virtual Resistance. The internal portions of a conductor carrying an alternating current are subject to greater induction effects than those next the surface. In consequence of the reduction of a conductor carrying alternating current, the resistance is increased, and less current will flow than if the specific resistance and the induct- ance of the conductor were alone considered. The increment of resistance of a conductor is called virtual resistance. ELECTRIC GENERATORS. 453 Energy in Alternating Circuits is the product of the measured current and the component of the impressed electromotive force in phase with the current. The component electromotive force in quadrature with the current, i.e., the induction component, drives a wattless current. The product of the impressed electromotive force and the current is the apparent watts of the circuit. The difference between the real and apparent energy will depend on the angle of displacement in phase between the impressed electromotive force and the amount known as angle of lag, and generally denoted by p. Impressed Electromotive Force. To drive a current through, a system of alternating conductors with inductance requires a greater electromotive force than is needed in a direct-current system to produce the same current. The inductance of the circuit determines the counter electromotive force, and this must be overcome by an amount added to the electromotive force required to produce the same current in a direct-current system. This resultant is called impressed electromotive force. The counter electromotive force works at right angles to the current, and is greatest when the current is reversing its sign, or when the rate of change of magnetic lines of force is greatest. Energy Electromotive Force is that component electromotive force in phase with the current, which is effectively doing the work in the circuit. "Virtual" or Effective Electromotive Force. Alternate current voltmeters and amperemeters do not measure the true average values of the volts and of the amperes. They measure what are called "virtual volts" and "virtual amperes. "In a hot-wire voltmeter the heating of the wire depends on the square of the current. In an electro-dynamometer the torque depends on the products of the currents in the fixed and moveable parts; therefore, as in an amperemeter, it depends on the square of the current. The readings which these instruments give us, if calibrated by using continuous currents, are not true means, but are the square roots of the means of the squares. The mean of the squares of the sine is ; the square-root-of-mean-square value of the sine functions is got by multiplying their maximum value by 1 ÷ √2, or by 0.707. The arithme- tical mean of the values of the sine is 0.637. An alternating current that obeys the sine law will produce a heating effect greater than that of a steady current of the same average strength, by the ratio of 0.707 to 0.637; or about 1.1 times greater. The term virtual or effective has been used to denote these square-root-of-mean- square values. The virtual electromotive force of a dynamo wound for alternate currents will be 2.2 times higher than that of the same dynamo wound as an ordinary direct-current dynamo. The following equations hold good, whether maximum or virtual values are used. Maximum c = Maximum c = Virtual c Virtual c maximum E resistance maximum E impedance virtual E resistance virtual E impedance 66 x cos o x cos p Skin Effect.' Another peculiarity of the alternating currents is the "skin effect," which tends to concentrate the density of the current more at the surface of conductor, making only a part of the cross-section of same available for conducting the currents. "J Simple Graphic Methods of Solving Alternating-Current Problems. (FIGS. 45 to 49, pages 454 to 456.) As already shown, reactance (due to capacity) and inductance (due to self- induction) are at right angles to ohmic resistance, but in opposite directions (see 454 SECTION IV.-POWER STATION. 1 Figs. 45 and 46). The apparent resistance expressed in ohms, due to self-induction (inductance) is expressed by 2 πf L. The reactance expressed in ohms is 2 π ƒ s Taking an to represent a non-inductive resistance, and m a capacity, the following diagram drawn to inductive resistance, and the same scale clearly shows the relations which in a series circuit exist between the various quantities:- 46. (953) ~R. (974) 4,5 wo w K SERIES CIRCUITS R P,L W L R¹ RIL¹ S¹ www R" R11 L" S17 R Ri J = 2πfL 111 R¹¹¹ R¼"L" S111 2πfS 2πfL 2 rfs Adde M S DIAGRAM IF 2TfL< 1 2 nfs DIAGRAM IF 2TIF.L > 1 2 πfs IMPEDANCE = J¹ ANGLE OF LEAD OR LAG=ع IMPEDANCE J 17 ANGLE OF LEAD OR LAG-Ø” IMPEDANCE - J 117 ANGLE OF LEAD OR LAG-Ò¹¹¹ L = self-induction expressed in henrys. ƒ = frequency or periods per second. c = current in amperes. R = resistance in ohms. S = capacity in farads. angle of lag in degrees. impedance of circuit expressed in ohms. ELECTRIC GENERATORS. 455 Parallel Circuits.-From the diagram for series circuits we know that .1 2 (R' + R₁')² + { 2 π L' f - − 778)² 2 π ƒ S' elem J' = and J" and J'" can be determined in the same way. Also cos p' = similarly for cos o" and cos //. The impedance J and the angle of lead or lag found by constructing the following diagram (see Fig. 49). (975) 47 Jo ✓ WME MME MME The diagram is drawn as follows :-0 A, 0 B, O C, represent in magnitude the reciprocals of the various impedances, the angle which each line makes with the horizontal being the angle of lead or lag, as the case may be. Leading angles are (976) = J-IMPEDANCE -ANGLE OF LAG OR LEAD 48 J-IMPEDANCE OF R'+RI' J' for the combined circuit is PARALLEL CIRCUIT -ANGLE OF LAG OR LEAD HORIZONTAL DIAGRAM FOR COMBINED SERIES and AND PARALLEL CIRCUITS drawn above the horizontal, and lagging angles below. BB1 is drawn parallel and equal to O A, and B C¹ is drawn parallel and equal to OC. Then the line O C¹ is the reciprocal of the impedance J of the combined circuit, whilst the angle which it makes with the horizontal is the angle of lead or lag (in this case lag). In this diagram it has been assumed that the characteristic of the alternator is a true sinusoid, and that the different parts of the circuit have no appreciable magnetic effect upon each other. Parallel and Series Circuits.-When such circuits are encountered they are treated as combinations of the two cases already enumerated. Consider a circuit as shown. J, Jo, 4, and to can all be determined by the methods previously described. 456 SECTION IV.-POWER STATION. J1 and 61, the impedance and angle of lag or lead for the combined circuit, are obtained by laying out Jo and J, each making its proper angle of lag or lead with the horizontal, leading angles being laid out above and lagging angles below, as in 49 !!!! 뉴 ​с (967) A गे • • Single phase Single phase Two phase Two phase Three phase (Y connection) Three phase (A connection) + C' the diagram 48. Then J1 is represented in magnitude by the diagonal of the parallelogram, of which J and Jo are adjacent sides, and the angle which it makes with the horizontal is the resultant angle of lag or lead. Distribution of Alternating Currents. In Table 23 the weights of copper required for the various methods of trans- mission are given. As long as only overhead transmissions are being considered, where bare copper wire is used, the use of the star connected (Y) system with earthed centre will be by far the most economical. Where it is a question of using underground cables, matters are quite different, as the cost of the insulation of å high tension cable is from five to ten times the cost of the copper used in it, and the cost of the ducts and drawing in is practically independent of the type of cable used; thus in practice of up to 12,000 volts there is little if any difference as regards the cost of the cables used in poly-phase or single-phase transmissions. In practice in this country cables are not made for working pressures above 12,000 volts. In America, on the other hand, cables are at the present moment laid and in operation at pressures of 25,000 volts; they have not, however, been down long enough for any definite results to be given as regards the use of such high pressures. •• Table 23.-Comparison of Copper for Single-, Two- and Three- Phase Current Transmission Lines. .. DIAGRAM OF IMPEDANCE FOR CIRCUITS IN PARALLEL ·· ㅎ ​·· B ·· ·· Number of Wires Used. B 29 30 30 < OD OD 4 3 3 Copper per Cent. 100 32 72 100 25 75 The amount of copper required in the two wires of a single-phase system is taken in Table as 100 per cent Allowance should also be made for the loss due to self-induction. ELECTRIC GENERATORS. 457 For polyphase currents the area of cable required is proportional to the inverse square of the power factor, other things being equal. As compared to continuous current, the area must2 times as great for the same loss per pound of copper. General Wiring Formulæ. (General Electric Company.) The following general formulæ may be used to determine the size of copper conductors, volts loss in lines, current per conductor, and the weight of copper per circuit for any system of electrical distribution. Area of conductor, circular mils. Where System. Single phase.. Two-phase (4 wire) Three-phase (3 wire) Current in main conductors = Volts loss in line Pounds copper = W = Total watts delivered. D = Distance of transmission (one way) in feet. P = Loss in line in per cent. of power delivered; that is, of W. E = Voltage between main conductors at receiving or consumer's end of circuit. For continuous-current C = 2160, T = 1, B = 1, and A = 6.04. Table 24. ·· ·· ·· DX WX C P x E2 WX T E Values of A. PX EX B 100 D2 × W × CX A PX E2 × 1,000,000* Values of C. Percentage of Power Factor. 100 95 90 86 80 100 95 90 | 85 | 80 6.04 2160 2400 2660 3000 3380 1.00 1.05 1.11 1.17 1.25 12.08 1080 1200 1330 1500 1690|| .50 .53 .55 .59 .62 9.06 1080 1200 1330 15001690|| .58 .61 .64 .68 .72 Pounds copper The following formula will be found a convenient one for calculating the copper required for long-distance three-phase transmission circuits. Values of T. Percentage of Power Factor. M2 x Kw. X 300,000,000 P X E2 M = distance of transmission in miles. Kw. = the power delivered in kilowatts. Power factor is assumed to be approximately 95 per cent. Application of Formulæ. The value of C for any particular power factor is obtained by dividing 2160, the value for continuous current, by the square of that power factor for single-phase, and by twice the square of that power factor for three-wire three-phase, or four- wire two-phase. The value of B depends upon the size of wire, frequency, and power factor. It is equal to 1 for continuous current, and for alternating current with 100 per cent. power factor, and sizes of wire given in the preceding Table of wiring constants. The figures given are for wires 18 in. apart, and are sufficiently accurate for all practical purposes, provided the displacement in phase between current and Q2 458 SECTION IV.—POWER STATION. • electromotive force at the receiving end is not very much greater than that at the generator; in other words, provided the reactance of the line is not excessive or the line loss unusually high. For example, the constants should not be applied at 125 cycles if the largest conductors are used, and the loss 20 per cent. or more of the power delivered. At lower frequencies, however, the constants are reasonably correct, even under such extreme conditions. They represent about the true values at 10 per cent. line loss, are close enough at all losses less than 10 per cent., and often, at least for frequencies up to 40 cycles, close enough for even much larger losses. Where the conductors of a circuit are much nearer each other than 18 in., the volts loss will be less than that given by formulæ, and if close together, as with a multiple conductor cable, the loss will be only that due to resistance. The value of T depends on the system and power factor. It is equal to 1 for continuous current and for single-phase current of 100 per cent. power factor. The value of A and the weights of the wires in the Table are based on .00000302 lb. as the weight of a foot of copper wire of one circular mil area. In using the above formulæ and constants it should particularly be observed that P stands for the per cent. loss, in the line, of the delivered power, not for the per cent. loss in the line of the power at the generator; and that E is the power at the end of the line and not at the generator. When the power factor cannot be more accurately determined, it may be assumed to be as follows for any alternating system operating under average conditions: incandescent lighting and synchronous motors, 95 per cent.; lighting and induction motors together, 85 per cent. ; induction motors alone, 80 per cent. In continuous-current three-wire-systems, the neutral wire for feeders should be made of one-third the section obtained by formula for either of the outside wires. In both continuous and alternating current systems, the neutral conductor for secondary mains and house wiring should be taken as large as the other conductors. The three wires of a three-phase circuit and the four wires of a two-phase circuit should all be the same size, and each conductor should be of the cross- section given by the first formula. Long Distance, High-Tension Power Transmission. Till recently 30,000 volts was considered the limit of pressure available for prac- tical purposes. Now there are several plants in existence using 40,000 volts and the Bay Counties Power Company intend to raise the pressure to 60,000 volts eventually. In long distance lines the effect of self and mutual induction, and of capacity, have to be considered besides resistance. Mutual induction can be eliminated by transposing or "spiraling" the wires. Self-induction in long lines is rather beneficial, as it helps to counteract the effect of capacity. The most important effect of capacity is its effect upon the regulation of the transformers and generators connected to the line. A leading current taken from such apparatus increases the voltage, while a lagging current decreases it. Where a line operates sometimes at full load and sometimes at no load, the change of power factor will cause the voltage to vary an amount which is generally considerably beyond what has been allowed for in the regulating apparatus. The ideal transmission line is one in which the capacity and self-induction are neutralised by a leading load which varies with the variations of the load on the line. With lines of high capacity there is a rise of potential along the circuit, but this is not so important as the rise of potential which it causes in the apparatus itself. With pressure up to 30,000 volts, glass or porcelain insulators of 6 in. to 8 in. diameter are sufficient; these can easily be manufactured, and are mechanically strong. With voltages rising as high as 60,000 volts, the insulators must be 12 in. to 14 in. in diameter, and must be mounted 7 in. to 9 in. above the cross-arm; such insulators are difficult to manufacture, and are somewhat fragile. With the high voltage mentioned, the sparking distance may be 5 in. to 6 in. The surface tension, which exists at high pressures, renders the use of wires of less diameter than in. dangerous, and causes a high energy loss, independent of any leakage over the surface of the insulators. The charging current due to capacity may, in long lines, easily amount to some thousand kilo-volt amperes, which means that a unit of that size is necessary to charge the line. This, and the large conductors required on account of surface tension, point to the fact that except for very large amounts of power, long- distance transmission should not be considered. Some tests on breaking a 40,000-volt circuit at Kalamazoo, Michigan, with a long break, open-air switch, showed that the arc held and flared to a distance of over 30 ft., producing at the same time high voltage oscillations nearly three times as great as the normal potential of the system. ELECTRIC GENERATORS. 459 Gauge. Number of Wire B. & S. 3 4 5 6 7 8 9 Area of Wire in Circular Mils. 10 Wire per 1000 ft. Weight of Bare Resistance of Wire per 1000 ft. at 20 deg. Cent 25 Cycles. 95 Table Percentage of Power Factor. 90 85 80 25 -Values of B. 40 Cycles Percentage of Power Factor. 95 90 85 80 lb. ohms. 4/0 211,600 €40.73 .04879 1.23 1.29 1.33 1.34 1.52 1.53 1.61 1.67 1.62 1.84 1.24 1.49 1.66 3/0 167,805 508.12 .06154 1.18 1.22 1.24 2/0 133,079 402.97 | 1/0 105,560 | 319.00 1.34 1.52 1.31 1.40 1.40 1.41 1.48 1.51 .07758 1.14 1.16 1.16 1.16 1.25 1.32 1.35 1.37 .09775 1.10 1.11 1.10 1.09 1.19 1.24 1.26 1.26 .1234 1.07 1.07 1.05 1.03 1.14 1.17 1.18 1.17 .1556 1.05 1.04 1.02 1.00 1.11 1.12 1.12 52,633 159.38 .1962 1.03 1.02 1.00 1.00 1.07 1.08 1.07 1 83,694 253.43 1.24 1.30 2 66,373 200.98 1.10 1.18 1.23 1.05 1.14 1.17 41,742 126.40 1.03 1.00 1.11 1.12 33,102 | 100.23 1.00 1.03 .2473 1.02 1.00 1.00 1.00 1.05 1.06 .3120 1.00 1.00 1.00 79.49 .3934 100 1.00 1.00 1.00 1.08 1.08 1.01 1.00 1.00 26,250 1.00 1.00 1.05 1.04 20,816 1.00 1.02 63.03 .4958 1.00 1.00 1.00 1.00 1.01 49.99 .6250 1.00 1.00 1.00 1.00 1.00 1.00 1.03 1.02 16,509 1.02 1.00 13,090 39.60 .7886 1.00 1.00 1.00 1.00 10,382 31.40 .9940 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 :: 60 Cycles. Percentage of Power Factor. 95 90 85 125 Cycles. Percentage of Power Factor. 80 95 90 85 80 1.99 2.09 2.35 2.86 3.24 3.49 1.77 1.95 2.08 2.48 2.77 2.94 1.60 1.66 1.86 2.18 2.40 2.57 1.46 1.49 1.71 1.96 2.13 2.25 1.34 1.36 1.56 1.75 1.88 1.97 1.25 1.26 1.45 1.60 1.70 1.77 1.18 1.17 1.35 1.46 1.53 1.57 1.11 1.10 1.27 1.35 1.40 1.43 1.06 1.04 1.21 1.27 1.30 1.31 1.02 1.00 1.16 1.20 1.21 1.21 1.00 1.12 1.14 1.14 1.13 1.00 1.00 1.00 1.09 1.10 1.09 1.07 1.00 1.00 1.06 1.06 1.04 1.02 1.00 1.00 1.04 1.03 1.00 1.00 American Gauge. B. & S. No. Table 26. Dimensions and Resistances of Copper Wire and Line Constants for Polyphase Power Transmission. Diameter in Mils. 0000 460.000 000 4 204.310 5 181.940 Weight and Length, Specific Gravity = 8.9. 00 | 364.800 0 324.950 1 289.300 2 257.630 3 229.420 159.03 126.12 100.01 79.32 62.90 49.88 6 162.020 7❘ 144.280 8 128.490 Pounds Per 1000 Ft. 9 | 114.430 10 101.890 639.33 3375.7 1.56 409.640 507.01 2677.0 1.97 402.09 2123.0 319.04 1684.5 252.88 1335.2 200.54 1059.8 2.49 3.13 3.95 4.99 839.68 6.29 665 91 7.93 10.00 12 61 15.90 332 11 263.37 20.05 208.88 25.28 31.38 Pounds Per Mile. 528.05 418.81 per 39.56 31.37 165.63 Feet Pound. Resistance at 75 deg. Fahr. Ohms, per 1000 Ft.(R). Ohms per Mile. per Ohm. Feet Ohms per Pound. I 8062.3.00048994 6393.7.00078045 5070.2.0012406 4021.0.0019721 3188.7 .0031361 2528.7.0049868 2005 2.0079294 1590.3.012608 1261.3 | .020042 1000.0.031380 Area in Circular Mils. L = Inductance in Milli-Henrys. K = Capacity in Micro-Farads. Charging Per 1000 Ft. Current. Ic = S = Reactance in Ohms. 25 Cycles. 40 Cycles. .04906 .25903 20383. 0.282 0.00388 .00007673 211.600 .00012039 .12404 .65490 105.592 83 694 66.373 .15640 .82582 .19723 1.0414 0.024 0.0443 0.0708 .06186 .32664 16165. 167.805 0.290 0.00378 0.0238 0.0455 .07801 .41187 12820. .00019423 133.079 0.296 0.00368 0.0232 0.0465 .0983 .51909 10409. .00030772 0.303 0.00358 0.0226 0.0476 0.310 0.00351 0.0220 0.0486 0.317 0.00342 0.0215 0.0498 52.633 0.324 0.00334 0.0210 0.0509 41.742 0.332 0.00326 0.0205 0.0521 33.102 0.339 0.00320 0.0201 0.0532 26.250 0.346 0.00313 0.0197 0.0543 20.816 0.352 0.00306 0.0193 0.0553 16.509 0.360 0.00300 0.0189 0.0565 ❘ 13.094 0.366 0.00294 0.0185 0.0575 10.387 0.373 0.0081 0.0585 24869 1.3131 31361 1.6558 39546 2.0881 .49871 2.6331 .62881 3.3201 .79281 4.1860 1.0000 5.2800 0.00288 60 Cycles. 0.0727 0.0743 0.0761 0.0775 0.0796 0.0814 125 Cycles. 0.221 0.1062 0.1090 0.227 0.1113 0.232 0.1141 0.238 0.11660.243 0.1194 0.249 0.1220 0.254 0.1243 0.261 0.0832 0.0850 0.1277 0.266 0.0867 0.0885 0.0904 0.0920 0.1301 0.271 0.1327 0.276 0.1355 0.283 0.1380 0.288 0.1405 0.293 0.0936 . ¦ ELECTRIC GENERATORS. 461 Gauge Number, B. and S. Wire. 0000 000 00 Q 1 2 3 1-8 TDI-STO 4 9 10 Resist- ance in Ohms. per Mile of Wire. .259 .324 .412 .519 .655 .826 1.041 1.313 1.656 2.088 2.633 3.320 4.186 5.280 Reactance and Inpedance in Ohms. per Mile of Wire at a Frequency of 60. 12 In. between Centres. Reactance. .508 .523 .534 .550 .565 .580 .591 .606 .620 .633 .647 Table 27.-Reactance and Impedance for Various Circuits. (D. C. and J. P. Jackson.) .662 .677 .688 Impedance. .570 .616 .682 .756 .865 1.008 1.196 1.448 1.76 2.18 2.71 3.38 4.21 5.32 18 In. between Centres. Reactance. .557 .573 .588 .603 .614 .629 .644 .656 .670 .685 .700 .712 .727 .742 Impedance. .615 .658 725 .796 .896 1.038 1.223 1.467 1.78 2.20 2.72 3.39 4.22 5.33 24 In. between Centres. Reactance. B .591 .607 .618 .633 .648 .663 .674 .690 .704 .720 .730 .742 .761 .776 Impedance. .646 .686 .749 .818 .920 1.06 1.24 1.48 1.80 2.21 2.73 3.40 4.23 5.34 Reactance and Impedance in Ohms. per Mile of Wire at a Frequency of 125. 12 In. between Centres. Reactance. 1.06 1.09 1.12 1.15 1.18 1.21 1.24 1.26 1.30 1.32 1.35 1.38 1.41 1.44 Impedance. 1.092 1.138 1.194 1.258 1.349 1.466 1.61 1.82 2.10 2.46 2.93 3.59 4.39 5.47 18 in. between Centres. Reactance. 1.17 1.20 1.23 1.26 1.28 1.31 1.34 1.37 1.40 1.43 1.46 1.48 1.51 1.54 Impedance. 1.190 1.237 1.297 1.360 1.436 1.55 1.70 1.89 2.17 2.51 3.00 3.63 4.33 5.50 24 In. between Centres. Reactance. 1.23 1.26 1.29 1.32 1.35 1.38 1.41 1.44 •1.47 1.49 1.52 1.55 1.58 1.62 Impedance. 1.260 1.305 1.357 1.415 1.50 1.61 1.75 1.94 2.22 2.56 3.04 3.66 4.45 5.53 2 462 SECTION IV.-POWER STATION. · Diagrams showing Division of Current and Pressure in Various Transmission, on Basis of 100-Kilowatts Total Energy Trans- mitted. (FIGS. 50 to 56.) 50 52 m 53 SINGLE PHASE IDO AMPS TWO PHASE FOUR WIRE INDEPENDENT 51 50 AMPS (968) 100 AMPS 50 AMPS ΛΟΙ 50 AMPS 50 AMPS TWO PHASE MESH 1000.V ~1000 VOLTS ·A OIDI· VOLTS two PHASE FIVE WIRE 500 VOLTS → X 0001: 50 AMPS 1000 VOLTS 25√2 AMPS 25√2 AMPS OqVOLTSt 25√2AMPS 25√2 AMPS ↓ 500 VOLTS * 1000 VOLTS→ 50 AMPS 50 AMPS Y 50 AMPS 1000 50 AMPS COPPER COPPER ! COPPER 100% 100% 70% COPPER = 100% +AREA OF CENTRE WIRE 'i : ELECTRIC GENERATORS. 463 $1000 : 54 VOLTS 55 56 THREE PHASE STAR CONNECTED 100 √3 AMPS THREE PHASE (989) 100 √3 AMPS 100 √3 100 V3 100 VR AMPS 100 V3 Δ CONNECTED AMPS AMPS AMPS TWO PHASE THREE-WIRE 50 AMPS SO√Z AMPS 50 AMPS 1000> *1000*1000€ 0014A0001 1410 V· 1000 V. 1000.V →→ COPPER - 75% COPPER 75% COPPER 75% Lag and Lead. (FIGS. 57 and 58, page 464.) Alternating currents do not always keep in step with the alternating volts impressed upon the circuit. If there is inductance in the circuit, the currents will lag; if there is capacity in the circuit, they will lead in phase. When the curves of current and voltage are not in phase, one will sometimes be positive and the other negative; the product of these, or the energy, will be a negative one, as shown below base line: this watt curve represents negative -energy, which is energy returned back to the line or to the source of supply. Alternators in Parallel. (FIG. 59, page 464.) When two alternators are connected in parallel they must keep step, and their phase difference must be constant within certain limits. Suppose two alternators, running independently, be suddenly connected together at a time when their phase difference is, for example, as represented in Fig. 59. The electromotive force existing in the circuit connecting the two armatures, whose electromotive forces are represented by OA and O B, will be represented by the line A B, and this electromotive force tends to send a current through the armatures, whose effect will be to accelerate the lagging armature and retard the leading armature, thus bringing the machines into phase. On the other hand, by armature reaction the current will tend to produce a counter-magnetomotive force in the various magnetic circuits, tending to weaken the electromotive force of the machine. The machines will, therefore, rapidly fall into step or out of step, according to which of these influences preponderates. The smaller the phase difference (p) existing at the time of inter-connection, the lesser the liability of derangement in 464 SECTION IV.-POWER STATION. - operation. The lower the frequency and the smaller the armature reaction, the more readily the inter-connection can be brought about. If connection is made at an unfavourable moment, the current in the armatures may reach unduly great strengths, sufficient to blow the fuses, and the mechanical strains brought to bear upon the machines are liable to be excessive. With alternators at frequencies from 120 0 to 135 parallel working has not come into use, although where the + 888.) VOLTS AMPS VOLTS AMPS 58 WATTS WATTS CIRCUIT WITHOUT INDUCTANCE CIRCUIT WITH INDUCTANCE Parallel running of Alternators 59 Figs. 57 and 58. Diagrams of Lag and Lead. Alternators in Parallel. Fig. 59. 57 frequencies are from 40 to 100, parallel working is the general practice. Instruments called phase detectors are frequently employed to ascertain the right moment at which to throw the switch connecting two machines in parallel. (See Synchronisers.) Figs. 57 and 58 are lag and lead diagrams. Alternating Current Generators. Alternating current generators may be divided into single-phase, monocyclic, two-phase and three-phase, or ordinary alternating; and according as these machines are constructed they may be divided into three types: Revolving field machines, revolving armature machines, and revolving inductor machines. Machines of the revolving field type are best suited for very low or very high voltages, and they can without difficulty be wound to generate current at a pressure as high as 12,000 volts. Machines of the rotating armature type should not be required to generate current at a pressure exceeding 3500 volts. T ELECTRIC GENERATORS. 465 Some Points in the Specification of Direct-Connected Revolving Field Alternators. ARMATURE, The armature to be built up of laminations of sheet iron of high permeability and low hysteresis loss, securely held in a circular frame of cast-iron. The winding to consist of copper bars, thoroughly insulated before assembling, and held in place either by wedges (British Thomson-Houston method), or the overhanging tips of the teeth (Dick, Kerr and Westinghouse method). The coils to be easily removable for purposes of repair. REVOLVING FIELD. The field to consist of a cast-iron spider carrying the steel magnet ring, to which are attached the removable poles. The poles to consist of sheet iron or steel punchings, bolted together. The field-windings to be machine wound upon forms, and the coils to be securely held in place by retaining wedges of non-magnetic metal (Westinghouse method), or by the poles themselves (British Thomson-Houston method). The exciting current to be conveyed to the field by carbon brushes, pressing on two insulated collector-rings, mounted on the shaft. RISE OF TEMPERATURE. The generator to run for 24 hours, at full load, without rise in temperature in any part exceeding 40 deg. Cent. (Dick, Kerr and Westinghouse practice), 35 deg. Cent. (British Thomson-Houston practice), above the surrounding atmosphere. With 50 per cent. overload, 90 to 100 per cent. power-factor, for one hour, the rise not to exceed 60 deg. Cent. above that of the atmosphere. (The British Thomson- Houston Company guarantee that, with 50 per cent. overload, non-inductive, their generators will run for two hours without the rise of temperature exceeding 55 deg. Cent. above that of the atmosphere.) Types of Multiphase Currents. (FIGS. 60 and 61.) At present there are three varieties of multiphase currents in use: diphase triphase, and monocyclic. Armature Windings Two alternating electromotive forces are called diphase, when they have. the same frequency, magnitude and wave character, but differ in phase by a cycle, or 90 deg., being what is called in quadrature. ! ары 60 A Collector Rings Coo 00 8 396 DIPHASE DISTRIBUTION D 61 00 Armature Windings Col actor Ringe O 10 Separate Circuits Interconnected Circuits The current which these two electromotive forces will send through indepen-. dent circuits will also be in quadrature; if the impedances of the circuits are equal, the lag of each current behind its electromotive force will be the same in each circuit. Four wires and two separate circuits may be used to. distribute diphase currents, or three wires can be employed, one wire forming a common return, Figs. 60 and 61. Each circuit considered separately is an ordinary uniphase circuit; the combination of the two currents enables non-synchronous or inductive motors to be operated. Diphase currents are generated by two sets of coils wound on the armature in such a manner with respect to the field poles, that the electromotive force generated in one is 90 deg., or cycle, ahead of the electromotive force generated in the other. 466 SECTION IV.-POWER STATION. Three alternating electromotive forces are called triphase electromotive forces, when they have the same frequency, magnitude, and wave character, but differ in phase cycle or 120 deg. Triphase electromotive forces are generated by three sets of coils, so wound on the armature with respect to the field poles that the electromotive forces in them are 120 deg. apart. Power Factor. The power factor in alternating circuits is the ratio of the real watts to the volt-amperes. Real watts = cos volt-amperes, where is the angle of lag. Hence cos o represents the power factor. Activity or Rate of Expending Energy in Alternate Current Circuit. In a continuous-current circuit, the activity is the product of the pressure in volts and the current strength in amperes. In an alternating current circuit, the activity is still the product of the pressure and current, provided that they are in step, that is co-directed. When, however, the current is not in step with the electromotive force, the activity is not the simple product of the two, but their co-directed product. Therefore, the further the current lags behind, or advances before, the electromotive force, or the greater the difference of phase between the current and the electromotive force, the less will be the activity, or rate of expending energy in the circuit for a given current strength. The lag or lead of the current in a circuit cannot exceed 90 deg. from the electromotive force producing it. It can never in practice actually equal 90 deg., for in such a case, the projection of the current on the line of electromotive force would vanish, and the activity in the circuit would be sustained without any energy being supplied, which is impossible. Advantages of Polyphase Generators. They, as a class, give a rather better output for their weight than single-phase machines, owing to a better utilization of the armature space by the distributed windings. One of the best examples of the two-phase type is to be found in the 5000 horse-power Niagara generator. The stationary armature has its coils set in deep slots in the laminations, and is provided with ample ventilating ducts. The armature winding does not consist simply of one coil per phase per pole, but each phase winding consists of a number of coils in adjacent slots, thus occupying the armature surface to better advantage. Such a construction is often employed in large polyphase machines. The revolving field is here external to the armature, so that its weight gives the effect of a flywheel. The commercial efficiency of this generator at full load is 97 per cent. Machines with vertical armature shafts are rather rare in America, the ordinary horizontal arrangement being more generally convenient. Star and Delta Grouping. (FIGS. 62 to 64.) Star and Delta group of armature conductors may be made. Fig. 62 shows diagrammatically the Star connection, and Fig. 63 the Delta connection in the case STAR. CONNECTION 62 63 YA -000 DELTA · CONNECTION roos eeee COMBINED STAR & DELTA CONNECTION 000. olell Well oood 64 morr cell Figs. 62 to 64. Diagram of Star and Delta Grouping. of a three-phase generator. shown (Fig. 64.) It is also possible to combine the two systems as Whichever method is adopted the electromotive force is always measured ! 467 ELECTRIC GENERATORS. between any two of the three terminals. In the star winding, the electromotive force between any two terminals is 1,732 times the electromotive force in either winding, as the resultant of two electromotive forces is the geometrical sum or equal to the length connecting the two terminals, as is evident from the geometry of the figure. When connected in the triangular or delta system, the electromotive force between terminals is the electromotive force of the winding. The output of a machine will be the same under both conditions. Multiphase Alternators. A multiphase alternator or multiphaser, as distinguished from a uniphase alternator, or uniphaser, is a machine which generates two or more alternating currents in definite phase relationship with each other. Multiphase alternators are diphase when they produce two separate alternating electromotive forces in quadrature or separated by a cycle, and triphase when they produce three separate alternating electromotive forces separated by one- third of a cycle. Diphase generators employ on the armature two sets of coils or windings so arranged that the electromotive forces generated in them shall have the same magnitude, frequency, and wave type, but shall differ in phase by 90 deg. or a cycle. The current produced by these two electromotive forces may be carried in two independent circuits, necessitating four wires and four collector rings, or in two interconnected circuits, with one common return requiring three wires and three collector rings. When the third wire is employed as a common return circuit (Fig. 61) the current it carries will be the sum of the two currents in the other two circuits, which being in quadrature will be C2, where C is the current strength in each circuit. The cross section of wire will, therefore, have to be 41 per cent. greater than that of either of the two other wires, in order to have the same drop of pressure when the two other circuits are similar in all respects. The winding of a triphase alternator may be effected by employing three separate sets of coils, each generating an electromotive force of equal magnitude, frequency and type, but differing in phase by cycle or 120 deg. ? Measurement of Power in Three-Phase System. In a Y-connected generator the electromotive force induced in each phase is E E √3 and the energy in that phase is C XE being electromotive force at 3 generator terminals. C In a ▲-connected generator the current in each phase is √3 current. The energy in both Y and ▲-connected generators is CE - C being the line If the phase CE √3 displacement is equal to the angle of lag, then the expression becomes Co8 ф The power factor depends upon the displacement . The energy in each CE phase x power factor. As the circuits are usually regulated to give equal 3CE √3 power, the total output for a three-phase generator becomes √3CE × power factor. √3 The power supplied by a three-phase circuit can be measured by means of one, two, or three wattmeters. Three give the power of the circuits irrespectively of conditions of balancing or lag. The sum of the readings of the three instruments is the total power. Each meter must be connected to the common centre or neutral of the system. If the system is A, an artificial neutral must be created by means of resistances. Two wattmeters can be used as long as power factor is greater than 50 per cent. Sum of readings equal total power. This method is not used, however. Usual method of measuring power by one wattmeter, the three circuits being balanced in respect to load and power factor. reading will give total power in circuits if they are balanced. Then three times or 468 SECTION IV.—POWER STATION. : Measurement of Power in Two- and Three-Phase Circuits. (D. C. and J. P. Jackson.) Two-Phase Circuits. (Figs. 65 to 68).—If the circuits are separate, a watt- meter can be placed in each circuit, the sum of the readings giving the total power (Fig. 65). Or one wattmeter may be inserted successively in the two circuits, provided the load does not vary between the two readings. For circuits with a common return, the instruments should be arranged as shown in Fig. 66. Two instruments placed as in Fig. 67 are equivalent to the arrangement shown in Fig. 68, with only one wattmeter, and is not correct except the balance is exact. The dotted line shown in the last figure indicates that successive readings are taken with the pressure coil terminal, first on one and then on the other of the outside wires. 65 66 67 68 (977) L Three-Phase Circuits (Figs. 69 to 74).—If the generator or motor is star- connected, three wattmeters connected as in Fig. 69, will give the correct result, provided that the neutral point is accessible. The sum of the readings gives the total power. With a mesh connection the wattmeters may be arranged as in Fig. 70, which shows the current coils of the instruments inserted directly in the coil circuits. When this is not possible, the instruments may be arranged as in Fig. 71, in which ELECTRIC GENERATORS. 469 69 70 (978) 71 72 73 74 (979) ww mn m 470 SECTION IV.—POWER STATION. a neutral point has been artificially created, by means of three [non-reactive resistances, connected together at one end, and the other lends connected to the respective corners of the mesh circuit. The resistances of the wattmeter pressure- coils must be sufficiently large, compared to the three auxiliary resistances, not to disturb the pressure of the neutral point. If all three pressure-coils are identical PRIMARY SYNCHRONISING SECONDARY m GENERATOR سوم LAMPS SECONDARY www PRISART GENERATOR (654) Fig. 75. Diagram of Synchronising Arrangments. BUS BARS in resistance, the auxiliary coils may be dispensed with, and the free ends of the three pressure-coils simply joined together. The power may also be measured by two wattmeters connected as in Fig. 71, the algebraic sum of the two readings giving the power independent of balance or current lag. If the current lag is less than 60 deg., or the power factor is greater than 0.5, the power is the arithmetical sum of the two readings. If the lag is greater than 60 deg., and the power factor is less than 0.5, the reading of one of ELECTRIC GENERATORS. 471 the wattmeters will be negative, and the arithmetical difference of the two readings gives the power. To find out what state of affairs exists (if it is not evident), the two instruments may be interchanged without altering the relative positions of the main and pressure coils. If the deflections of both needles are reversed one reading is negative, but if the deflections are the same as before, both are positive. In a balanced circuit one wattmeter may be used, as in Fig. 74, the end of the pressure-coil being connected successively to each of the two other leads. Another way is to connect the free end of the pressure-coil to the middle of a high non-inductive resistance, the ends of which are connected to the other circuits. The single reading thus obtained is equal to the sum of the readings with the former arrangement, but the wattmeter constant must be determined with one-half of the high resistance in series with it. Table 28.-Efficiency of some Three-Phase Generators. 750 kilowatts, direct-connected 800 >> "" "" ·· -Load. per cent. 84 87 -Load. per cent. 91 92 -Load. Full Load. per cent. 94 951 per cent. 93 941 Polyphase Machines to Run in Parallel should have moderate armature- impedance. Too small impedance causes too large exchange of current with small inequality in field excitation. Too large impedance will cause hunting, owing to small synchronising current that can be exchanged. Excitation, when many machines are running in parallel, should be separately adjusted for each machine, so that each generator supplies the same current. Synchronism must be obtained before putting two machines in parallel. Commonest form of synchroniser consists of two transformers, primaries of which are connected to each generator, connections being in each case made to similar phases. The secondaries are connected in series with one or two lamps in circuit. When lamps cease to glow, machines are in synchronism. (See Fig. 75, page 470.) Synchronisers for Three-Phase Generators. (Fig. 76, page 472.) Paralleling alternators require special precautions to avoid strains upon the machines. Two conditions must be fulfilled for parallel running. They are: (1) The two machines must have the same voltage and frequency; and (2) At the moment of switching them into parallel the instantaneous voltages of the two machines should be equal and of the same sign. The voltages of the machines can easily be made approximately equal, by varying the excitation and reading the voltmeters between the machine terminals. Incandescent lamps are generally used to determine the exact moment of synchronism. In the United states it is usual to arrange so that the lamp remain- ing dark indicates synchronism, but in England it is more usual for the time to be denoted by the lamp glowing its brightest. The chief difficulty in running steam-driven alternators in parallel is due to the variation in speed during each revolution, caused by periodic variation in the cut-off. A low armature reaction means a large amount of synchronising power, but heavy cross-currents flow between such machines if they are accidentally thrown out of step. Machines with high armature reaction, though more difficult to synchronise, are less likely to give trouble when out of step. It is easy to see that if a d2 and b₁ b₂ are corresponding terminals of the machines, there will only be zero potential difference between a and b₁ or a2 and by when the electromotive forces of the two machines are identical in frequency and phase, even though the voltmeters between the terminals of the machines read alike. The consequence is that if the machines are switched in parallel without being accurately synchronised, there will be a sudden rush of abnormal current through these armatures. A simple method of detecting when the machines are or are not in synchronism, is to connect α1 and α and by and b₂ by 472 SECTION IV.-POWER STATION. means of incandescent lamps. This device forms a good indicator as to whether there is or is not a difference of phase between the electromotive forces of the machines, but it gives no indication as to which of the two machines is running the quicker. The Siemens and Halske synchroniser gets over this difficulty. /07 N/ C3 B L2 a. 2 L In 2 b ALTERNATOR II. B 65 e3 a 3 723 (400) ALTERNATob 1. Fig. 76. Siemens' Synchroniser for Three-phase Generator. ; ALTERNATOR III. The phases a b1, b1 c1, c1 a1, of the first alternator are connected to the ter- minals a1 b1 c1, of two triple-pole switches, A B, which are themselves coupled in parallel. The phases of the other two alternators are respectively connected to the terminals, a2 by cz, az b3 cg, of two other switches. The lamp device is still used, but now there are three terminals to each machine, and three lamps are used as indicators between corresponding terminals of the machines already connected to the bus-bars and the incoming machine. The extinctions of the three lamps do not occur simultaneously, but succes- sively, and if the lamps are mounted in a triangle, as shown in the diagram at L1 L2 L3, the order of extinction will travel round the triangle in a clockwise or counter-clockwise direction, according as the incoming machine is slower or quicker than those already on the bus-bars. The direction of the order of extinc- tion of the lamps tells at once whether the incoming machine is running too quickly or too slowly. Suppose it is desired to parallel machine II. with machine I., which is already connected to the bus-bars. The first thing to do is to see that the voltages of the two machines are alike by means of the voltmeters. Having done this, the switch, B, is left on the terminals a2 b2 c2, and the switch, A, is placed on the terminals a1 by c₁ of the alternator I. The direction, f or fi, of the order of the extinctions of the lamps is then noted; if the order is ƒ the incoming alternator has to be accele- rated, and if the order is fi it has to be retarded. The main switches are closed at the instant that the lamp L, is dark, when the rate of the extinctions shows that the speed of the machines are almost exactly the same. To increase the sensibilty, a voltmeter, V₁, is between the terminals of the lamp, L₁, and should register zero voltage at the instant of switching on. Speed Regulations for Running in Parallel should be such that maximum deviation from position of absolute uniform speed should not exceed 11 deg. in phase, two complete poles being counted as 360 deg. Thus, for machines with ELECTRIC GENERATORS. 473 n poles, position of revolving part per revolution should not differ more than 11 n in circumference from the position it would occupy at absolutely uniform speed. 2 Authorities differ somewhat as to how much angular variation of speed throughout one revolution is allowable. The British Thomson-Houston Company has fixed upon 2 deg. of phase departure from a mean as the limit in ordinary cases. This means that the maximum departure from the mean position during 21 any revolution shall not exceed of an angle corresponding to two poles of a machine. The angle of circumference, which corresponds to 24 deg. of phase variation, can be ascertained by dividing 2 by half the number of poles. Thus if the machine has 2 n poles, the allowable angular variation from the mean is 23/ 360 n deg. Some foreign engine-makers say that the difference between the maxi- mum and minimum speed during a revolution should not exceed th to th of the average speed during the revolution. The Westinghouse Company specifies as follows: Variation of the rotating part of the generator through one revolution at any constant load, not exceeding 25 per cent. overload, should not exceed th of the pitch angle between two consecutive poles from the position it would have if the motion were absolutely uniform at the same mean velocity. The maximum allowable variation, which is the amount the rotating part forges ahead, plus the amount which it lags behind the position of uniform rotation, is, therefore, th the pitch angle between two poles. Generally, this regulation is secured by means of a heavy flywheel. In a two-pole machine this variation is equivalent to 3 deg., as measured on the circumference of the rotating part; in a four-pole machine it would be 14 deg., and in a six-pole machine 1 deg., or, as the number of poles increases, the permissible angular variation decreases. Table 29.-Maximum Permissible Variation on either side of Uniform Rotation. Number of Poles. 4 6 8 12 16 20 24 28 32 36 40 44 48 52 NHOJONKS 56 60 64 68 72 76 80 Angular Degrees. 1.500 1.000 0.750 0.500 0.375 0.300 0.250 0.214 0.187 0.167 0.150 0.136 0.125 0.115 0.107 0.100 0.094 0.088 0.083 0.079 0.075 Per cent. of Circumference. 0.41666 0.27777 0.20833 0.13888 0.1041 0.0833 0.0693 0.0594 0.0520 0.0462 0.0416 0.0378 0.0347 0.0320 0.0297 0.0278 0.0260 0.0245 0.0231 0.0219 0.0208 Alternators in Parallel. (Foster.) To connect an idle alternator in parallel with one or more already in (use, excite the fields of the idle machine until at full speed the indicator shows bus-bar pressure, or the pressure which may have been determined on as the best for connecting the particular design of alternator in circuit. 3 474 SECTION IV.—POWER STATION. 44 Connect up the synchroniser to show when the machines are in step, at which point the idle machine may be connected with the bus-bars. The load will now be unequally divided, and must be equalised by increasing the driving power of the idle dynamo until it takes on its proper part of the load. Very little control over the load can be had from the field rheostats. To disconnect an alternator from the bus-bars, decrease its driving power slowly until the other machines have taken all the load from it, when its main switch may be opened and the dynamo stopped and laid off. Connections of Westinghouse Two- and Three-Phase Generators. (FIGS. 77 and 78, page 475.) The armature winding is of the closed circuit type. In the case of the two- phase machines, connection is made to the winding at four points, an insulated conductor conveying the current from each of these points to one of the four -collector rings. The connections of the armature winding, auxiliary winding, collector rings, and circuit are illustrated in Figs. 77 and 78, page 475. Referring to Fig. 78, in the case of a 2000-volt generator, the electromotive force between 1 and 3 is 2000 volts, and between 2 and 4 2000 volts. The eloctro- motive force between any other pair of terminals is 1400 volts. If the electromotive force is raised or lowered the same proportions hold. In practice, potentials from 5 to 10 per cent. higher than these figures are generally used. The current in -circuit 1-3 is at 90 deg., or quarter-phase from current in circuit 2-4. In diagram Fig. 77 the electromotive force between 1 and 2, 2 and 3, 3 and 1, is in each case 2000 volts (for a 2000-volt machine). In practice about 2100 to 2200 volts would ordinarily be carried at the generator. "The current in each of the three circuits is 120 deg. from the current in the other two circuits. The three leads from the generator are connected to the switchboard. Metropolitan New York Generators. The 96th Street Station contains 11 direct-connected sets, each of 3500 kilowatts, room for extension being allowed, and a capacity having been foreseen of nearly double that amount. The following gives the particulars of the General Electric Company's dynamos which are used. The machine has a frequency of 25 cycles per second, at 6600 volts. It has 40 poles, and runs at 75 revolutions per minute. It is of the stationary armature type, the core being built up of laminations 0.14 in. thick, which lamination has two dovetail projections which fit in corresponding slots in a heavy cast-iron spider. Spaces are left between the laminations at intervals, through which currents of air are driven by the rotating field, and circulate by intimate contact with core and windings. The armature winding consists of form-wound coils placed in slots in the core, and retained by wooden wedges, the edges of which fit into recesses in the teeth. The field-frame consists of a cast-steel ring supported upon a cast-iron spider. To this are bolted laminated sheet-iron pole-pieces, the tips of which project over and support the copper field windings. The field winding_consists of copper strip wound on edge, with paper insulation between turns. The insulation is such as to stand a test of 4000 volts aiternating between the winding and the core. The exciting electromotive force is 125 volts. The collecting rings are of copper, and carbon brushes are used. The armature winding is tested to 12,000 volts alternating. The temperature rise of the machine after ten hours' run at full load is well under 40 deg. Cent. The efficiencies are as follows: One and a-quarter load Full load Three-quarter load .. Half-load ·· ·· Quarter-load.. Inherent regulation • •• .. : ·· ·· The rim of the flywheel weighs 225,000 lb. ·· : : : Per cent. 90 95.5 95 92.5 88 9 ELECTRIC GENERATORS. 475 77 78 1 2007$2000 2 (CDP) ado. AUXILIARY FIELD Fig. 77. Fig. 78. l l l l l l l l l l COLLECTOR RINGS Leeeee 0000000 0000000 COMMUTATOR SERIES TRANSFORMER AUXILIARY FIELD e l l l l l l l l l COMMUTATOR COLLECTOR RINGS CTOR 00000 SERIES TRANSFORMER ele 0000000 0000000 еее t ёше ARMATURE eee! تووه ARM/ Diagrams of Westinghouse Two- and Three-phase, Composite- Wound, Revolving Armature Generator Connections. Connections for Three-Phase Generator. Connections for Two-Phase Generator. PRE 476 SECTION IV.-POWER STATION. Dick, Kerr Alternators. (Figs. 79 to 84, pages 476 to 479.) Figs. 79, 80, 81, show three different types of construction employed in the alternators built by Messrs. Dick, Kerr and Co. The rotor spider in each case is made of cast iron, which is pressed on to the shaft by hydraulic pressure, and then keyseated. Fig. 79 shows a field constructed with dovetailed laminations fixed on the spider-rim by means of cast-iron flanges and machined bolts, the pole-pieces being then firmly secured in the dovetails. The field spools can readily be removed by sliding the pole-pieces along the dovetailed groove, without disturbing any other part of the machine. 79 ත H O (980.) Fig. 79. Type of Dick, Kerr Alternator, with Laminated Poles and Laminated Rim. Fig. 80 shows a construction which employs a cast-steel rotor-rim, on which the pole-pieces are securely bolted by means of special bolts. This method is used for large machines of low frequency, when the number of poles is not too large. The pole-pieces are constructed of steel laminations, which are held together between two cast-steel end plates of strong construction. Another form of construction is shown in Fig. 81, in which the poles are of cast-steel, usually oval-shaped, with polar tips built up of laminated steel. Fig. 82, page 478, illustrates a three-phase, 20-pole, 150 revolutions, 1500- kilowatt, 6500-volt, 25-period, Dick, Kerr alternator. Fig. 83, page 478, a three-phase, 40-pole, 75 revolutions, 1500-kilowatt, 7500- volt, 25-period alternator, by the same firm. Fig. 84, page 479, a three-phase, 24-pole, 300 revolutions, 450-kilowatt, 11,000- volt, 60-period, Dick, Kerr alternator. ELECTRIC, GENERATORS. 477 80 O [⠀⠀:29T110E 981 fifue ****** O 19 I Fig. 80. Type of Dick, Kerr Alternator with Laminated Poles and Solid Rim. 81 TO # (982) Fig. 81. Type of Dick, Kerr Alternator with Solid Steel Poles and Laminated Tips. ! 478 SECTION IV.—POWER STATION. 82 -4987) · ֿ -11'6 "bore---E O 17 B 83 PIET 01 ==== # Figs. 82 and 83, Dick, Kerr Three-Phase Alternators. 甩 ​: ELECTRIC GENERATORS. 479 (984) ! BJELLULITEET - ERIJAL 8.2" dia. о 00 Fig. 84. Dick, Kerr Three-Phase Alternator. OD 00 00 T O 10 1 480 SECTION IV.—POWER STATION. Fig. 85. (986) wwwx < < W WE ve WASTE AND I 85 Allgemeine Elektricitats-Gesellschaft Alternators. (See Table 30, page 481.) ELECTRIC GENERATORS. 481 Output. in Kilowatts. Table 30.-Slow-Speed Polyphase Alternating-Current Gene- rators for Direct-Driven Types, K.S.D., N.S.D., and G.S.D. (Allgemeine Electricitäts-Gesellschaft.) (FIG. 85, page 480.) Dimensions. 160-290 :350-780 960-2100 180-400 410-910 1100-3000 210-460 470-1250 1300-3400 240-430 520-1400 1450-3800 Kilowatts. 121 75 75 100 100 150 -150 ↓. T 200 :200 -250 :250 :300 300 400 400 500 500 Speed. 375 500 375 25-Period Machines. 500 375 Three-phase. Revolutions per Minute. 500 11 375 500 300 375 300 375 125 125 125 300 375 107 107 107 .300 .375 94 94 94 83 83 83 f ft. in. ft. in. ft. in. 14 0 5 3 18 0 6 6 23 0 8 10 с Table 31.-Westinghouse Standard High-Speed Engine-Type Alternators. Polyphase, 220, 440, and 2200 Volts. 16 0 20 6 26 0 17 6 22 6 29 3 19 6 24 6 32 6 Poles. ∞ ∞ | ∞ ∞ | ∞ ∞ | | ∞ ∞ | | 9° | 19° 19° 19° 8 6 8 6 8 (FIG. 86, page 482.) ROTATING FIELD. 6 8 6 10 8 10 8 10 8 e 10 11 0 14 6 18 9 8 12 6 16 6 21 6 14 0 18 6 24 0 15 6 20 6 26 9 6 3 8 10 11 6 7 3 9 6 12 10 75 75 75 Kilowatts. 100 100 100 150 150 150 150 200 5 3 7 8 9 10 200 200 200 250 250 250 250 300 300 300 400 400 400 500 500 g ft. in. 1 8 2 5 2 5 223 LD LOO -- 3 0 2 5 2 5 3 0 2 5 3 0 3 3 375 428 500 375 428 500 333 375 h ft. in. 11 1 14 6 18 9 428 500 333 12 6 16 6 21 4 50-Period Machines. Two and Three-Phase. 375 428 500 300 333 375 428 300 333 375 300 333 375 300 333 14 O 18 6 24 0 Revolutions per Minute. 15 6 20 6 26 8 p ft. in. 4 11 5 3 5 9 5 1 5 3 6 0 5 1 5 5 6 0 4 11 5 5 6 0 Poles. 16 14 12 16 14 12 18 16 14 12 18 16 14 12 20 18 16 14 20 0920920 18 16 R 18 16 18 482 SECTION IV.-POWER STATION. 30 100 200 200 200 200 200 400 75 75 86 150 150 150 175 175 300 Kilowatts 4,000 3,500 8,000 150 2,500 125 1,500 Field Amperes 2,000 100 1,000 500 Kilowatts. Phase. 3 ~~~~~~~~ 2 3 3 2 2 2 ∞ M M NI MO 00 00 - 3 3 Volts 11,000 2 3 3 3 1 Efficiency -100 -90- 80 70 60 Table 32.-Westinghouse Engine-Type Alternators. ROTATING FIELD. 40 30 50 Field Amperes -20 -10 0 (987) 50 60 25 25 50 50 60 60 Periods. 50 30 50 60 33888 60 TURBO-REVOLVING FIELD 2000 K.W.3 PHASE GENERATOR, 11000 VOLT, 3000 ALT, 2 POLE, 1,500 R.P.M. E.M.F Regulation 50 Efficienc 50 est 80 (C ROTATING ARMATURE. 440 220 440 2200 440 440 290 2300 Output Kilowatts Input 50 100 150 200 250 300Amps Volts. 440 220 440 3300 220 440 3000 2200 Poles. 14 14 12 12 20 20 220 22 30 30 36 30 16 16 28 Revolutions per Minute. 428 514 250 250 300 300 360 360 274 120 200 200 240 375 375 343 1 ELECTRIC GENERATORS. 483 Points in the Specification of Alternators for Railway Work. The alternators should be capable of running continuously at full load for 12 hours without a rise in temperature of more than 45 deg. Cent. in either spools or armature, as measured by increase of resistance, or 30 deg. Cent. as measured by a thermometer placed in any accessible part of the armature or field. The armature should be subjected to a test of twice the normal voltage, and the field coils to five times the normal voltage for five minutes. The inherent regulation of the generator should not be less than 92.5 per cent., as between no load and non-inductive full load at constant speed. The following practice is the standard of the Westinghouse Company for alternators of the rotating armature type: The armature consists of a cast-iron spider, upon the outside of which a laminated steel rim is built. The surface of the armature is grooved in a direction parallel to the shaft by a large number of openings, or slots, and these are intersected at right angles by other openings, which extend around the armature. The former are for the reception of the insulated conductors, forming the winding; the latter for the purpose of securing thorough ventilation of both core and windings. The armature winding consists of wire, strap or bars, depending on the current to be carried. Wire winding, which is usually employed in high voltage machines of low current capacity, consist of machine-wound coils which are entirely formed and insulated before being placed in the armature slots. Strap winding is used for machines of lower voltage and of greater current capacity, and it consists of copper strap forged into the required shape and carefully insulated. The windings are secured in the open slots by hard fibre. Bar windings are held in place by the overhanging tips of the teeth; the bars after being carefully insulated are slipped into the slots from one end of the armature. The end connections of the bar winding are bolted and secured to the bars after the conductors are in place. There are no band wires on the armature. British Thomson-Houston Standard Three-Phase Alternators. MODERATE SPEED, 50 CYCLES. The standard British Thomson-Houston alternators are of the revolving field type. The armature coils being stationary and not subject to vibration, can be wound for higher pressure than would be practicable with moving armatures, and all exposed conducting parts are avoided. The stationary armature is built up of laminations of specially selected sheet iron of high permeability and low hysteresis loss, which are securely held in a circular frame of cast iron. Eddy currents are prevented by coating the lamina- tions with japan, and by the insertion of sheets of paper at regular intervals. Thorough cooling of the core and winding is provided by means of air ducts, allowing a free circulation of air through the armature. The laminations are provided with slots in their inner periphery to receive the windings. For normal voltages partially closed slots are used; but for high voltages open slots are used, the specially insulated former wound coils being held in place by hard wood wedges. The field poles are of high permeability cast steel, except when open slots are used. In the smaller sizes these are cast in one with the spider, but in the larger sizes the spider is of cast iron and the steel poles are securely bolted to it. When the exciting current is large enough to require it, the field coils are wound with copper strip on edge. The coils are held in place by the poles themselves, and are readily removable. The exciting current is conveyed to the field by carbon brushes pressing on two insulated collector rings mounted on the shaft. All insulation employed is such as safely to withstand the application of twice the normal working voltage, for one minute, between conductors and frame, and also between individual coils. The field circuits are tested with an alternating voltage of 1500 for one minute. Standard alternators are arranged for a normal exciting voltage of 100 volts. Table 33, page 484, gives a list of standard moderate speed three-phase alternators. The kilowatt rating is on the basis of 80 per cent. power factor, with a temperature rise not exceeding 40 deg. Cent., after a continuous run at the rated output. If the power factor is not required to be below 95 per cent., the ratings can be increased 20 per cent. 7 484 SECTION IV.-POWER STATION. Overloads of 25 per cent. at 80 per cent. power factor, or 50 per cent. at 100 per cent. power factor, can be carried for two hours with a temperature rise not exceeding 55 deg. Cent. The inherent regulation, i.e., the rise in voltage when full load is thrown off, will not exceed 6 per cent. at unity power factor, or 18 per cent. at 80 per cent. power factor. These particulars hold equally well for two-phase alternators. The flywheel effect given is approximately the amount of kinetic energy stored in the rotor when running at normal speed. Table 33.-British Thomson-Houston Standard Three-Phase Type. ABT 27/40 ABT 35/31 ABT 27/29 10 12 ABT 35/40 ABT 35/48 Poles. ABT 35/60 ******∞ON ODONTOLINING99 8 8 10 12 8 10 12 8 10 12 10 12 14 10 12 14 12 ABT 52/28 ABT 52/36 ABT 52/44 20 ABT 52/52 20 16 ABT 70/30 20 16 ABT 70/40 20 20 ABT 70/50 24 16 12 16 16 16 20 ABT 70/60 24 20 ABT 88/30 24 20 ABT 88/40{ 24 24 ABT 88/50 28 24 ABT 88160 28 per cent. Power Kilowatts at 80 Factor. 60 50 35 90 70 50 120 100 75 170 140 100 180 130 110 230 170 140 225 160 320 225 275 225 350 260 400 300 575 450 450 300 580 400 550 Alternators. MODERATE SPEED, 50 CYCLES. 500 800 700 900 750 1100 950 Revolu- per Minute. Speed. tions 750 600 500 750 600 500 750 600 500 750 600 500 600 500 428 600 500 428 500 375 500 375 375 300 375 300 375 300 375 300 300 250 300 250 300 250 300 250 250 214 250 214 80 Per Cent. Power Factor. Full Load. 90 89.5 89 91 90.5 90.5 91 90.5 90 92 91.5 91 92.5 92 91.5 92.5 92.5 92 92.5 92 93 93 Efficiencies. 93.5 93 93.5 93 93 92.5 94 93.5 94 93.5 94 93.5 93.5 93 94.5 94 94.5 94 94.5 94.5 344 Load. 89 89 88.5 90 90 89 90 89.5 89.5 91 90.5 90.5 91.5 91 90.5 92 91.5 91.5 92 91.5 92.5 92 92.5 92 92.5 92.5 92.5 92 93 92.5 93 92.5 93.5 93 93 93 93.5 93.5 94 93.5 94 93.5 11/1 Load. 86.5 86.5 86 87.5 87 86.5 88 87.5 87 89 88.5 88 89.5 89 89 88.5 90 89 89.5 90.5 90 91 90.5 90.5 91 90.5 91 90.5 91.5 91 91.5 91 92 91.5 92.6 92 92.5 92 92.5 92 92.5 92 100 Per Cent. P.F. Full Load. 91.5 91.5 91 92.5 92.5 92 92.5 92 92 93 93 93 93.5 93 93 94 93.5 93.5 94 93.5 94.5 94 94.5 94 94.5 94.5 94.5 94 95 94.5 95 94.5 95 94.5 95 94.5 95.5 95 95.5 95 95.5 95 Flywheel Effect in Foot-Tons. 24 15 10.5 33 21 14.5 70 45 30 90 55 40 70 50 35 85 60 40 145 80 180 100 125 80 145 95 325 210 410 260 315 215 365 250 540 375 680 470 570 420 660 485 i ELECTRIC GENERATORS. 485 Table 34.-Single and Multiphase Generators, Fixed Armatures, Rotating Poles, Direct-Driven, up to 8000 Volts, 40 Cycles per Second. (Brown, Boveri and Co.) Single-phase. Horse- Kilo- Horse- Kilo- Power. watts. Power. watts. 70 90 135 170 160 185 220 140 165 190 220 290 350 460 135 100 150 200 47 60 90 115 340 300 380 380 230 110 125 150 95 115 130 150 195 235 310 600 300 950 Single-phase. Horse- Kilo- Horse- Power. watts. power. 90 67 100 135 230 200 Multiphase. 260 260 160 400 200 650 85 110 160 200 190 220 260 165 200 330 360 350 420 550 175 140 200 270 450 380 500 500 300 "" 800 400 1250 57 75 110 135 130 150 175 110 135 155 Multiphase. 175 235 280 370 Kilo- watts. 120 95 135 180 300 260 340 340 200 550 270 850 ·· Capacity in kilowatts Current in amperes per phase.. Length Revo- Weight in Milli- lutions. in Tons. metres. Table 35.-Single or Multiphase Horizontal Multipolar Genera- tor, Fixed Armature, Rotating Magnets, up to 10,000 Volts, to be Direct-Driven by Turbine. (Brown, Boveri and Co.) 300 400 300 Brake horse-power required to drive Efficiency Revolutions per minute 400 240 300 400 150 172 200 240 300 300 400 Revolu- Weight tions. in Tons. 298 200 215 180 360 125 360 325 60 130 48 120 5.0 5.0 6.4 6.9 8.45 8.45 9.05 11.8 12.2 12.6 13.5 14.0 18.0 18.5 .. Weight in kilogrammes, including exciter without "9 "" 5.4 5.5 6.5 11.5 13.0 14.0 15.0 18.5 22 • 23 26 42 2165 2165 2390 2390 2630 2630 2630 Length in Milli- metres. 100 333 3000 3000 3000 3000 3000 2900 2900 150 91 350 6600 6100 2050 2170 2240 2750 2800 3950 2850 3000 4360 4660 5100 5950 Table 36.-Three-Phase Generators, Maschinenfabrik Oerlikon Low Tension, up to 190 Volts. 135 410 Breadtn Height in Milli- in Milli- metres. metres. 1520 1520 1710 200 92 260 1710 1980 1980 1980 2400 2400 2400 2400 2400 2830 2830 Breadth in Milli- metres. 2050 2170 2240 2750 2800 3950 2850 3000 4360 4660 5100 5950 205 620 300 93 190 1630 1630 1855 1855 2090 2090 2090 2550 8000 12,000 7600 11,300 2550 2550 2550 2550 2700 2700 Height in Milli- metres. 1140 1300 1175 1415 1450 1632 1450 1500 1725 1690 1670 1795 350 1,080 500 95 150 18,000 17,200 486 SECTION IV.-POWER STATION. Table 37.-High Tension Three-Phase Generators, Maschinen- fabrik Oerlikon. Capacity in kilowatts Current in amperes at 1000 volts 2000 3000 "" .. " Brake horse-power required to drive ·· Efficiency Revolutions per minute Weight, including exciter kilogrammes ·· ·· .. •• } ·· .. ·· 100 33.3 16.6 11.1 150 91 500 5000 135 45 22.5 15 200 92 375 7000 200 66 33 22 a. Asynchronous or induction motor generators. b. Synchronous motor generators. 300 92 250 9000 342 114 57 38 500 93 190 13,000 Rotary Converters and Motor Generators. For converting alternating current into continuous current, there are three kinds of machines which can be used: c. Rotary converters. In the first two cases the high-tension current from the generators is usually led directly into the alternating side of the machine; but with rotaries step-down transformers are required to lower the voltage, because of the fixed relation which exists between the continuous and alternating currents in the armature circuits. For asynchronous or induction motor generators the arrangement is very simple. There is no synchronising to be done, and a simple resistance in the rotor is all that is required in the way of starting gear. If the rotors of the motors are permanently short-circuited instead of the rotor resistance, some automatic transformer regulation in the stator may be used. Where three-wire systems are employed there is generally one generator mounted on each end of the motor shaft, the two machines being in series. Instead of asynchronous motors, synchronous motors, working at the line pressure, can be employed. The standard practice is to make these with revolving fields. They are not self-exciting, and require to be synchronised before being switched in, and so are not so simple as induction motors. There are several points of difference between rotary converters and motor generators. For one thing, the former cannot be operated at high pressure, and this necessitates the use of step-down transformers between the slip rings of the converter and the high-pressure feeders. This is owing to the fact that a fixed relation exists between the alternating currents circulating in the armature of a rotary converter and the continuous current delivered by it at the commutator. The following tabulated form is taken from Professor S. P. Thompson's "Polyphase Electric Currents," it being supposed that the continuous current is supplied at 100 volts, and that the currents given are for an output of 10 kilowatts, the circuits being supposed non-inductive. If the circuits are inductive there will be a lag, and for an equal output of power the currents given will have to be divided by the power factor or the cosine of the angle of lag. It is the usual American practice to employ a separate transformer for each phase, and in the case of three-phase transformers they are usually connected up in A on both high- and low-pressure sides, because then the supply need not be interrupted if one transformer should from any cause be put out of service, and all three phases of the rotary will continue to receive three-phase current from the two remaining transformers. With three-phase star-connected transformers, single- phase current would be supplied if one of them should fail, and the rotary has to be cut out immediately. In a rotary converter the motor and generator currents in the armature conductors overlap. It is evident that the currents which the armature of a rotary converter receives into the motor end will generally be flowing against the electromotive forces induced internally by its rotation in the magnetic field, while the currents which it gives out at the commutator end will be flowing with these electromotive forces. As one armature and set of windings serve both for the alternating currents which drive the motor and the continuous currents given out at the commutator, hysteresis and eddy current losses are reduced, as compared to either ELECTRIC GENERATORS. 487 a continuous-current generator or a synchronous-current motor, taken separately. The thermal losses due to heating of conductors will also be greatly reduced, because one single winding has only to carry the difference of the two currents. But there is another great gain due to the practical non-existence of armature reactions, these being neutralised. In a motor generator the brushes on the commutator of the generator have to be given some lead exactly as in the ordinary continuous-current generator, so as to avoid sparking. In a rotary converter this is generally unnecessary, and current collection at practically all loads, without shifting of brushes, is sparkless. This is because the armature reactions due to the motor portion are generally opposed, and equal, to those due to the generator part. This property is common to all motor generators or converters which use a common armature core and common magnetic circuit. On this account, the cross-section of the conductors may be made very small for a given output, from the thermal standpoint; and also, since the armature Table 38. Number of Rings. 2 3 4 4 6 6 Angle Between Connections to Rings. deg. 180 120 90 90 60 60 Number of Phases. Single Three Two Four HA Six Three 1x 계열 ​열어 ​X Virtual Volts. X 160|12 √3 √2 2.2 × 100=70.71 Line Armature Currents. Current. X 100=61.23 Virtual. × 100=35.35 Max. × 100-70.71 50.0 70.7 × 100=50.00 X 100=61.23 54.5 77.0 94.3 133.3 Virtual. 70.7 100.0 141.4 200.0 47.2 66.2 Max. 70.7 100.0 ¡ 47.2 66.7 reactions are neutralised, a very large number of conductors may be used. This permits of a very small flux per pole-piece and a small cross-section of magnetic oircuit. The commutator must, however, be as large as for a direct-current generator of the same output. Three-phase transformers can be connected up to supply six-phase rotaries, which are not more expensive to build, but slightly more complicated than three- phase machines, and which have some distinct advantages. For the same mean rise in temperature of the armature coils, the output of a six-phase converter is nearly half as great again as that of a three-phase machine, and the heating of the armature is also much more uniform. The heating is always greatest near the connections to the slip rings. The regulation of the direct-current pressure on motor generators is done entirely on the generators, either automatically by compound winding, or by hand through field regulation. With rotaries, however, the pressure on either side is almost wholly independent of the strength of the field, and other methods have to be employed. There are two means generally used, the principle being the same in both cases, and consisting of regulating the pressure on the slip rings on the alternating side, the ratio of the pressure on the alternating side to that on the direct-current side being practically a constant. 488 SECTION IV.-POWER STATION. The impressed pressure can be altered by changing the ratio of transformation of the transformers by means of a multiple contact switch, which allows the number of either the primary or secondary turns to be altered by hand. The regulating switches for each set of transformers are interlocked so as to simulta- neously produce equal changes in each unit. An induction regulator is, however, much better if hand regulation is required. The regulator consists of an iron coré in connection with a shunt and series-winding in each phase, arranged so that the mutual induction between the two windings is altered by the movement of the core. The core being moved inwards, the pressure on the converter slip rings is reduced because of the inductive action of the shunt winding. When the core is moved outwards, the series coils are less influenced by the shunt winding, and the pressure rises. In the second method the rotaries are compound, and choking coils are inserted in the leads between the slip rings and the secondary windings of the transformer. In working with motor generators of the asynchronous type, it is important to keep them as fully loaded as possible: below three-quarter load the power factor of the motor is less than 90 per cent. It is also important to watch the air gap, which is made as small as possible so as to obtain a large power factor. With motor generators the overload capacity is entirely dependent on the direct-current machines, and will approximate to 20 per cent. for two hours. The overload capacity of rotaries is determined by the heating of the commutator, and may be reckoned as 40 to 50 per cent. for two hours. This is the permanent over- load capacity; the momentary overload capacity is the most important thing. Compared with synchronous motor generators and rotary converters, asyn- chronous motor generators are simpler and easier to operate, but their use involves a lower efficiency. Some Important Points in the Specification of Rotary Converters for Railway Work. (FIGS. 87 to 89, pages 488 and 489.) Rise in Temperature.—The rotary converter shall run at rated load for twelve hours without a rise in temperature of more than 45 deg. Cent., as measured by increase of resistance in armature or spools, or more than 30 deg. Cent., as measured by thermometer placed on any accessible part of the field or armature except the commutator. The rise in temperature of the commutator shall not exceed 45 deg. Cent. Motor Generator of 300KW. Oerlikon. Synchronous Three phase Motor Type 6080, 3500 Volts. 375 Rev: 50Cycles coupled to a direct current dynamo Type N.N.XV. 260Volte. 135QAmp. cosen {case? Cosp N COS 1002 90%-08- 80% 0/8 N 3 coss 100 200 300 400 19 500 KWV, Wombat 87 The rotary shall be capable of over-compounding from 500 volts at no load to 550 volts at full load. The efficiencies, including all field losses and the losses in any auxiliary apparatus which may be deemed necessary for the proper regulation of the field shall not be less than 94.5 per cent. at full load, 94.0 93.0 at three-quarter load, at half load, "" or an average efficiency of 93.8 per cent. between half load and full load. ▸ : Oerlikon Motor Generator: 230KW. 370 Revs. Asynchronous Motor Type 3071. 6000 Volts. 500ycles. Coupled with a direct turrent generator. Type N.N.XIV. 450Volt. 510 Amp. 100% Cas 80%0A (6085.8) 100, 90 Kilowatts Lost. 801 70 60 50 40 % Efficiency. 20 10 Q 40 35 30 25 20 15 JO Cose 100 Load 200 88 1/21 tska L. Core Loks 800 EFFICIENCY & LOSSES. on 900 Kw. 25 Cycles 500 Volts Three Phase Rotary Converter. Total of Losses Beaking&att Brush F + Wintage. 5 C²R. Shina Field & Theostat H Full Load 41 N cos ♡ 400KW. C2R Armature 60 55 50 45 162 A Bruishi's CR Series Field & 0 Diverter. 200 490 600 800 1000 1200 1400 1600 1800 2800 2200 2400 (5142 D) Ampere Output. 89 • R2 490 SECTION IV.-POWER STATION. " } The machines shall stand 50 per cent. overload without sparking, the brushes being kept fixed, and 100 per cent. overload without surging or falling-out of synchronism. The following Table from Traction and Transmission gives the results obtained by the Oerlikon Company with two of their motor-generators. (See also Figs. 87 to 89.) Table 39.-Efficiencies of Synchronous motor, 3500 volts, 50 cycles direct-coupled to continuous- current generator 350 kilowatt, at 375 revolutions. Full load Half load Quarter load Full load Half load Quarter load ·· • · Iron core Windings Commutator ** • .. Motor. 96 93 88 ·· Motor. Generator. 12 11 • Gene- Com- rator. bined. 95 91 •• Efficiencies Per Cent. Full load 87 Half load 80 Quarter load Power-Factor at Constant Excitation. Per cent. 1.00 0.9 0.7 92.5 90 ·· Full load .. Half load Quarter load ·· * Rise of Temperature in Degrees Centigrade. Per cent. 30 30 35 •• Oerlikon Motor Generators. Asynchronous motor, 6000 volts, 50 cycles, direct-coupled to continuous- current generator 230 kilowatt, at 370 revolutions. ? ·· .. Combined Set. 23 Iron core Windings Commutator .. .. ·· .. Motor. 94 99 89 Weight in Tons. Motor. 8 * After ten hours run at full load. •• • ·· Generator. 8.5 Gene- Com- rator. bined. 95 90 92.6 88 • •• · 86 78 Per cent. 0.91 0.84 0.68 ·· Per cent. 30 30 30 Combined Set. 16.5 Impressed, Counter, and Impedance Electromotive Force in Rotary Converters. In a synchronous converter system one must distinguish between three electromotive forces: the impressed electromotive force, that is, the electromotive force at the collector rings of the rotary converter; the counter electromotive force, which is the electromotive force induced in the rotary converter by the armature revolving in the magnetic field, and which is proportional to the field excitation: the electromotive force of impedance, or the electromotive force consumed by impedance, which is that caused by the current flowing through the reactance and resistance of the converter. The impressed electromotive force is entirely dependent upon the generator voltage; the counter electromotive force is entirely dependent upon the field excitation of the converter, and is constant regardless of the load on a machine; and the electromotive force consumed by the impedance changes with the load, and is proportional to the current. Since the work done by a synchronous rotary converter is the product of the current taken by the rotary, and the projection of the counter electromotive force on this current at no load, the current must be in quadrature, that is, at right-angles to the counter electromotive force. The input of a rotary converter is expressed by the product of the impressed electromotive force and the projec tion of the current on the impressed electromotive force, under the assumption that no energy is consumed, the current is also in quadrature, or at right-angles to the impressed electromotive force. Consequently, the impressed electromotive force and the counter electromotive force must be in phase and in opposition to each other, if the field excitation of the converter is reduced, so that the counter electromotive force is less than the impressed. Since only three electromotive forces are acting in the system, and their sum must always be zero, the impressed electromotive force must at any time be equal to the counter electromotive force, plus the electromotive force consumed by ELECTRIC GENERATORS. 491 the reactance. The counter electromotive force is assumed to be less than the impressed, therefore the electromotive force consumed by reactance must be in phase with the counter electromotive force, and add itself thereto. But since the current is always 90 deg. ahead of the electromotive force of self-induction, it must be 90 deg. behind the impressed electromotive force, and, consequently, be lagging. If, on the contrary, the field excitation of the converter is increased so that its counter electromotive force is higher than the impressed, it is evident that the electromotive force consumed by reactance must be in phase with the impressed electromotive force, and add itself thereto. Consequently, since the current is 90 deg. ahead of the electromotive force of self-induction, it must be also ahead of the impressed electromotive force. In other words, the current is leading. By a similar discussion it is readily seen that the same argument is true if the converter is loaded. That is, in this case, the wattless lagging or leading current due to the difference between counter electromotive force and impressed electromotive force, merely adds itself in its proper phase relation to the energy current representing the load. It is thus seen how, by means of converter, leading or lagging currents are caused to flow in the lines. It is readily shown how the voltage at the receiving end of the system can be changed, by causing a leading or lagging current to flow over a line with some self-induction. Usually it is required that the converter voltage shall remain constant or increase with the load, when the generator voltage or excitation is kept constant. If each converter is operated from its own generator, it is preferable to leave the generator field excitation constant, and thereby use the generator reactance for phase control, and avoid any necessity of regulation in the generating station. If, however, many converters are operated from one generator, or if all generators in the power station are operated in multiple, it is preferable to keep the generator terminal voltage constant, and control the converter voltage by outside reactances in a low reactance transmission, or by the line reactance in a highly inductive transmission. Since a converter can be made to take leading or lagging current by changing its field excitation, and thus its counter electromotive force, such an installation gives the most favourable opportunity to study the fundamental principles of alternating current. The problem is simple, and resolves itself into adjusting the shunt excitation for a given current running light, which is predetermined by calculation, and afterwards to adjust the series field so that the converter takes minimum current, that is, runs non-inductively at the desired load. It will then follow that the potential control for all intermediate loads is perfect, at least within very close limits. Maximum Output with a Given Line Impedance. The converter should run non-inductively at higher outputs as the generator voltage increases, so that, for instance, if the system has 10 per cent. energy loss, and 40 per cent. reactance, and the generator voltage is kept 12 per cent. above the converter voltage, the maximum output is 2.12 times rated output, and the converter should run non-inductively at of rated load. If the generator voltage were 18 per cent. higher than the converter voltage, the output would have been 24 times the rated, and the converter would run non-inductive at full load; and, finally, if the generator voltage were 30 per cent. higher than the converter volt- age, the maximum output would be 2.55 times the normal output, but the non- inductive load would have been 1 times full load. In other words, the converter should run with lagging current up to 50 per cent. overload. In commercial installations, however, where there is always a limit to the generator voltage, which limit is caused by saturation of the machine or outside conditions which do not permit of excessive voltage in the power station, the output of a converter is by no means unlimited; and thus some care has to be taken to get the proper reactance, since with a given difference in generator and converter potential, the output changes as we change the reactauce and resistance. Regulation of Converter Electromotive Force. In practice, the shunt field is so adjusted that the converter takes the required lagging current running light, and the series field is made to increase the excitation so as to give the required field strength at non-inductive load. Since, however, the series excitation is proportional to the load, it is evident that without hand adjust- 492 SECTION IV. POWER STATION. ment it would be theoretically impossible to accomplish perfect phase control; or rather, it would be impossible to have constant voltage at the rotary converter with constant voltage at the generator. The difference, however, is exceedingly small, the series field being slightly too strong at light loads and too weak at overload; in other words, the voltage will be slightly increased at the converter up to non-inductive load, and will drop slightly at overload. Converters have, as a rule, compound excitation. Shunt-wound converters do not permit of automatic phase control, but at constant adjustment of the field will always run at the same wattless current at all loads; so that, for instance, if the field is adjusted for non-inductive load at one load, the converter will run non-inductively at all loads; and therefore the drop in voltage at full load will correspond to the energy loss in the system, and the con- verter voltage will be higher at lighter loads than at heavier loads, therefore will vary as the load varies; and phase control is thus feasible only by hand regulation, that is in systems where the load varies only slowly as in lighting circuits. Proportion of Compounding in Rotary Converters. The compound field of the rotary is proportioned so that at no load it is under- excited. Thus the electromotive force of the rotary is less than the impressed electromotive force, and the current on the line is made lagging. This increases the electromotive force of self-induction cutting down the voltage in the system, giving, say, 500 volts direct current. As the load increases the excitation increases, increasing the rotary electromotive force, and at some point bringing current and electromotive force into phase. The drop of voltage is then due to resistance only. At full load the converter is over-excited, and the rotary electromotive force is greater than the impressed. The best results are obtained when the rotary is operated from its own independent circuit. The adjustment not infrequently includes an artificial resistance, such as a choking coil. Equalisers must always be used with compound rotary converters. The equalisers should be closed before machines are thrown in parallel. To compound rotaries to any considerable extent circuit must contain reactance. The more reactance over a certain limit the more liability of unstable operation, the more the wattless current, and the poorer the power factor. Fifteen per cent. reactance in line gives good results. With such a reactance in a circuit with 6 per cent. resistance, it is possible to obtain constant potential at all loads with- Quarter load Three-quarter load .. If the series-winding of the converter is so inductively at three-quarter load, then- Per Cent. Power Factor. 73.5 97.5 100.0 ·· Quarter load Half load Three-quarter load .. Per Cent. Power Factor. 60.0 91.5 ·· ·· ·· Full load.. 50 per cent. overload .. ** adjusted that the converter runs non- Full load One and a-half loads Two loads .. Per Cent. Power Factor. 100.0 95.5 -- Per Cent. Power Factor. 99.5 98.0 96.0 .. ·· Power Factor.-The power factor of the compound-wound rotary converter excited for unit power factor at full loads is not so good at light loads. The power factor of the shunt-wound converter is the same at all loads. A variation of the reactance in the supplying circuit will change the curve of power factor for various loads. To obtain 10 per cent. over-compounding, the fields of the compound rotary converter are excited to give a power factor of unity at usually three-quarter load; and when it is desired to maintain a constant voltage at the commutator, the fields are ordinarily adjusted to give this power factor at full load. Starting up Motor Generators and Rotary Converters. Asychronous motor generators can be started up from the direct or continuous- current side, if direct current is available, but this is not generally convenient. The best way to start up synchronous motor generators is from the generator side, using it as a continuous-current motor. This requires a source of continuous current. The set having been brought to approximately synchronous speed, the exact speed is obtained by regulating the field of the generator, which runs as a ELECTRIC GENERATORS. 493 shunt motor with all the resistance out; the main high-pressure switch is then closed, and the fields of both motor and generator adjusted. When no continuous current is available, the machine can be started up by using a starting motor of the induction type, mounted direct on the shaft of the motor generator. The starting motor is switched in, and the combination brought to maximum speed by cutting out the rotor resistance. The field circuit of the synchronous motor is then closed, the correct pressure being obtained by regulating the exciting current. By adjusting the rotor resistance, the speed is reduced to exact synchronism, and the motor switched on the line. Nothing then remains to be done but cut out the starting motor and adjust both the fields. There is another method of starting, by opening the field circuit of the synchronous motor, and connecting the armature to the line; the hysteresis drag supplies the torque, being assisted by eddy currents in the pole-pieces. Starting of Rotary Converters.-Self-starting rotary converters are set in operation by introducing either alternating current to the collector rings, or direct current to the commutator. When starting from the alternating-current end, the 90 THREE COMPENSATORS. (OR ONE THREE PHASE COMPENSATOR.) (5/784) LINE pp COLLECTORU RINGS ARMATURE CONTINUOUS CURRENT. COMMUTATOR fields should not be excited. The starting current in a well-designed rotary is rarely more than 50 per cent. greater than normal full-load current. In this method, the action is analogous to what takes place in starting an induction motor. The rotating magnetic field set up by the alternating currents entering the armature induces secondary currents in the pole-pieces; the mutual action between the rotating field and induced currents imparts a torque to the armature, which causes the armature to revolve with increasing speed until it attains synchronism. In a normally proportioned field-winding, a dangerously high secondary voltage is generated. The insulation between the field spools must therefore be of the very best, as well as the insulation between spools and frame. To avoid this danger, terminals of field spools should be connected to a switch, which enables spools to be conveniently broken up into several sections. By means of a compensator, heavy current in line at starting may be done away with. A compensator consists of a series of reactance coils, each coil being arranged so as to give a number of different starting voltages. After synchronism is reached, compensator is cut out or short-circuited. Connections for such an arrangement are shown in Fig. 90. The rotary converter is started from the direct-current end in the same way as a shunt-wound direct-current motor. The fields should be fully excited, and there should be a resistance in series with the armature when the motor switch is closed. Failure to excite the field may cause the rotary to race like any shunt motor. Converters are also frequently started by auxiliary induction motors. Rotary converters can be run in parallel, either on the direct-current or the alternating-current ends. When two or more rotaries are to be run together, they can be brought into synchronism by the same method as is the practice with alternating-current generators. After the main switch is closed, the field switch is then closed, if the rotary has been started from the alternating - current end. 494 SECTION IV.-POWER STATION. When started from the direct-current end, the machine is synchronised; then the field switch, which supplied excitation for starting, is opened, and finally the switch supplying its own field is closed. In starting a self-exciting or shunt-wound rotary from the alternating side, there is no way of telling whether the polarity will be positive or negative. This is due to the fact that the rotary is dependent for its excitation upon the polarity that its commutator happens to have at the moment it attains synchronism. If there are two rotary converters at the sub-station, and the first comes up with the wrong polarity, then it may be allowed to run so, temporarily, till the second one is synchronised. The second one can be given either polarity desired, by using the first as an independent source of continuous current. Then from the second one, the polarity of the first may be reversed into the correct direction, and the second rotary converter shut down. In the case of large capacity, slow-speed rotary converters, consequently machines with heavy armatures, it has been found practical to control the polarity of the first machine when it is started up from the alternating current side. One must stand ready by the field switch as the machine approaches synchronism, when the pointer of the continuous-current voltmeter will commence to vibrate rapidly about the zero mark with short swings. These will finally be followed by a couple of fairly slow, indecisive, long swings, in opposite directions from the zero mark. Near the maximum point of whichever of these swings is in the direction of the desired polarity, the field switch should be closed, and the machine will excite itself, provided the field terminals are correctly positive and negative. Otherwise-which might happen on the first run, or after alterations- the field terminals will require to be reversed. The required line current is greatly reduced by starting generator and rotary converter up simultaneously. The latter is then, from the instant of starting, always in synchronism with its generator, and the conditions of running are arrived at with a minimum strain to the system. But the conditions of routine operation rarely render this plan practicable. Method of Starting Westinghouse Rotary Converters. The standard practice of the Westinghouse Company is to start the rotary by means of a small induction motor mounted on the rotary shaft. As soon as the rotary is thus brought up to speed, it may be connected to the alternating-current mains. In this method of starting, the only demand on the capacity of the circuit is the little current required for the small induction motor. Where possible, the converter is started up from the direct-current side. A convenient source of direct current for this purpose is a small motor generator, consisting of an alternating- current motor driving a direct-current generator capable of giving sufficient current to start any one of the rotary converters, as a shunt-motor under no load. Method of Starting British Thomson-Houston Rotary Converters. All converters are made to be readily self-starting by means of alternating current applied directly to the armature winding; this current being impressed upon the winding at a lower voltage than that normally used after the converter is up to speed, and is in synchronism with the source of supply. The low-voltage alternating current is obtained from the step-down transformer by means of switches which cut in only part of the transformer windings. This method of starting has the advantage of requiring no synchronising. Difficulty with Parallel-Connected Rotary Converters. Unless rotary converters are carefully designed they will not run in parallel without hunting. Hunting is generally caused by uneven running on the part of the main generating engines, but it can be started in various ways quite indepen- dently of the engines. Machines are said to "hunt" when, whilst running at synchronous speed as measured by revolutions per minute, their angular velocities during one revolution oscillate about the value corresponding to exact synchronism. When the rotor oscillates in this way, the field flux of the converter is weakened and distorted; the machine is either acting as a generator or motor, and con- sequently shifts the diminished field flux to one or other of the pole horns. The armature tries to follow the change in the field, in doing which it takes a large current in the reverse direction. The field flux is, however, immediately distorted in the opposite direction by the change of current, and the armature again tries to correspond. The swinging may thus become greater and greater, until at last the machine is put out of step. Thus, to prevent hunting, the distortion of the field must be prevented as far as possible. ELECTRIC GENERATORS. 495 The causes of hunting are various; if the form of the electromotive force wave of the generators differs from that of the rotaries, hunting will in some cases follow. A strong armature reaction (or if the machine is much under-excited) will favour hunting more than if the field is strong, as distortion of the magnetic flux is more easily produced. The distortion of the field can be prevented or damped by means of "damping coils." These consist of copper strips, which bridge the poles from horn to horn. The eddy currents in these strips, due to the large leading and lagging armature currents, produce a flux which opposes the distortion of the field, and drives it away from between the pole horns. When two rotary converters are operated in parallel between bus-bars, on both direct and alternating-current ends, and the wave form of the counter-electro- motive force differs somewhat in the two machines, parasytic direct currents will be exchanged between the armature windings, over the alternating conductors. This will give the result of one machine having a greater current coming out of its positive brush than goes in at its negative, while the other has a greater current going in at the negative than comes out of the positive; which, of course, upsets commutation and renders ammeter readings useless. Consequently, it is becoming customary to provide a separate group of step-down transformers for each rotary, with no cross-connectors between the low-tension leads. One single group of transformers can, however, be used to supply two rotaries without this trouble, by winding two or more low-tension coils, one for each rotary, in each transformer, and connecting these in electrically-separate deltas. Table 40.-British Thomson-Houston Rotary Converters. 25 CYCLES AT 250 TO 300 VOLTS. Type. TC TC HC HC HC HC TC TC TC TC HC HC HC HC TC HC HC HC TC TC HC HC* Number of Number of Phases. Poles. 3 3 6 6 6 6 03 03 03 03 0∞ ∞ 6 6 6 6 3 mn co co c 6 6 6 m ma co O 3 3 6 6 4 6 8 12 14 16 4 4 6 6 6 10 12 14 Capacity in Kilowatts. 150 300 25 CYCLES AT 600 VOLTS. 150 200 300 400 500 750 1000 1500 500 750 6 6 8 12 1000 1000 60 CYCLES AT 250 TO 300 VOLTS. 6 8 12 16 75 150 300 500 60 CYCLES at 600 Volts. 100 200 300 500 Speed, Revolutions per Minute. 750 500 375 250 214 188 750 750 500 500 500 300 250 214 1200 900 600 450 1200 1200 900 600 Amperes. 545 1090 1815 2725 3630 3630 250 334 500 667 834 1250 1667 2500 273 545 1090 1815 167 333 500 834 * Furnished with an induction motor, direct-connected to machine, for starting up. 496 SECTION IV.-POWER STATION. 33 (988). 91 JINRKUAI K SWITCH ON SWITCH PILLAR ISELETTER BULU 80· amo 乘​。 WUBE Fig. 91. Dick, Kerr Rotary Converter. Six Phase, 8 Pole, 375 Revolutions, 600 Kilowatts, 600 Volts, 25 Cycles. ELECTRIC GENERATORS. 497 3000 3000 3000 3000 Alternations. D.C. Voltage. 3000 3000 3000 3000 3000 3000 3000 3000 3000 3000 3000 3000 3000 3000 3000 3000 3000 3000 3000 · 3000 3000 3000 3000 3000 3600 3600 3600 3600 3600 3600 3600 3600 3600 3600 3600 3600 3600 3600 3600 3600 3600 3600 3600 3600 3600 7200 7200 7200 7200 7200 7200 7200 7200 7200 7200 Table 41.-Westinghouse Rotary Converters. 250 250 250 250 250 250 250 550 550 550 550 550 550 550 550 550 550 650 650 650 650 650 650 650 650 650 650 650 250 250 250 250 250 250 220 550 550 550 550 550 550 550 650 650 650 650 650 650 650 125 125 125 125 125 250 250 250 250 250 Kilowatts. 100 150 200 250 300 400 500 100 150 200 250 300 400 500 600 800 1000 100 150 200 250 300 400 500 600 800 1000 1500 100 150 200 250 300 400 500 100 150 200 250 300 400 500 100 150 200 250 300 400 500 1.87 5 7.5 37.5 75 37.5 75 100 150 200 Revolutions per Minute. 500 500 500 500 375 375 375 500 500 500 500 500 500 500 375 375 300 500 500 500 500 500 500 500 375 375 300 250 600 600 600 600 450 450 450 600 600 600 600 600 600 450 600 600 600 600 600 600 450 1800 1800 1800 1200 720 1200 720 900 720 720 Weights. lb. 9,600 13,600 18,700 18,700 23,600 31,200 36,800 9,600 13,600 18,700 18,700 23,600 31,200 36,800 48,000 62,000 84,220 9,600 13,600 18,700 18,700 23,600 31,200 36,800, 48,000 62,000 84,220- 120,460 9,600+ 13,600 18,700 18,700 23,600 31,200 36,800+ 9,600 13,600. 18,700 18,700 23,600 31,200 36,800 9,600 13,600 18,700 18,700 23,600 31,200 36,800 500 1,050 1,225 4,600 9,200 4,600 9,200 10,000 14,000 22,000 · 498 SECTION IV.-POWER STATION. Table 41.-Westinghouse Rotary Converters.-(Continued.) Alternations. D.C. Voltage. Kilowatts. 7200 7200 7200 7200 7200 7200 7200 7200 7200 7200 250 250 250 550 550 550 550 550 550 550 300 400 500 37.5 100 150 200 300 400 500 Revolutions per Minute. 514 400 360 1200 900 720 720 600 450 400 Weights. lb. 31,000 37,000 43,000 4,600 9,600 13,100 21,700 29,900 35,900 41,800 Fig. 91, page 496, illustrates a six-phase, 8-pole, 375-revolution, 600-kilowatt, 600-volt, 25-period rotary converter by Messrs. Dick, Kerr and Co., Limited. British Thomson-Houston Type CR Feeder Regulators. (FIG. 92.) In modern central stations various feeders are often supplied from the same group of machines. Since the amount of compounding required on any one of these feeders depends on the amount of load carried by that feeder at the time, and since the peak of the load occurs at different times in different feeders, some device for independently regulating the voltages of these feeders becomes necessary. The British Thomson-Houston Company's Type C R feeder regulator is designed specially for this purpose. The CR regulator is of the transformer type, having its primary connected across the bus-bars, and its secondary wound in several sections controlled by a dial switch. The amount by which the generator voltage is raised or lowered on the feeder is determined by the amount of secondary winding included in the feeder circuit. The control of the feeder by means of this regulator is as follows: Starting with the regulator in position of maximum voltage, that is, with the dial switch turned to the extreme left as far as it will go, a continuous right-handed movement of the dial switch for two complete revolutions is obtained. During the first revolution the switch cuts out, step by step, the ten sections of secondary winding. When the first revolution has been completed, the voltage on the feeder is the same as that of the generator, no secondary winding being included. A further movement of the switch in the same direction automatically throws a reversing switch on the back of the panel, and continuing the movement of the dial switch, still in the same direction, the secondary windings are again switched in, step by step, this time with reversed polarity; so that when the second revolution is complete the whole secondary winding is again included in the feeder, but now opposing the voltage of the generator. Thus, by one continuous movement of the switch, covering two revolutions in one direction, the complete range between maximum and minimum feeder voltage is covered. Át either end of this range the switch is automatically arrested, so that it is impossible to turn it too far. The travelling contact is operated by the controlling lever through compres- sion springs, and is held in position opposite any one of the dial contacts by a steel bolt stepping into a hardened steel bolt plate on the switch panel. A movement of the controlling handle in either direction first compresses the spring, tending to move the travelling contact, and when this spring has been compressed a predetermined amount the locking bolt is released by a cam, and the travelling contact flies over to the next_position, where it is again locked by the bolt until the controlling handle is moved another step. The contact blades are of heavy copper with turned edges arranged to chill, by their mass, the momentary arc which occurs when passing from point to point; ELECTRIC GENERATORS. 499 thus avoiding damage from arcing. If it should become desirable to renew these contact blades, they can be readily removed and replaced BUS BARS OR ALTERNATOR (686) FROM GENERATOR OF REGULATOR VIEWED FROM BACK 92 TAP PRIMARY ww www DIAL SWITCH REVERSER SEEN FROM FRONT FEEDER FEEDER TO CENTRE STUD ON SWITCH PRI. PRI. www TO FEEDER TO REVERSER ON SWITCH SEC. Fig. 92 shows the general arrangements for connecting the various sections of the secondary winding to the dial switch; also the electrical connections of the reversing switch. This latter is operated by an arm attached to the main shaft. 500 SECTION IV.-POWER STATION. זי Westinghouse Stillwell Regulators for Polyphase Circuits. This regulator consists of two face-plates with brush arms and switches, mounted in adjacent planes, both being operated by the same lever, a forward movement of the lever operating the brush arm in one phase, and the backward movement operating the brush arm in the other phase. It is encased in a cast-iron MAN (774) Line Contacts Face Plate Rings Preventive Resistance Secondary Coils Primary Coils Reversing Switch i. Dynamo Fig. 93. Internal Connections of a Stillwell Regulator. frame, with swinging doors on each side. Switches are provided on the face-plates to automatically change the transformer coils, which are used with the regulator, so that twice as many points of regulation are obtained as there are contacts on the face-plate. There are 30 points of regulation in each phase. The maximum capacity is 100 amperes and 25 volts per step. Fig. 93 shows the connections of one of these regulators. ALTERNATING CURRENT STATIC TRANSFORMERS. An alternating-current transformer consists essentially of an induction coil in which an alternating current is induced in a secondary circuit by the variations of an alternating current in the primary circuit. If the number of turns in the secondary coil is the same as the number of turns in the primary coil, the electromotive force induced by the alternating magnetic flux will be the same in both circuits, provided no magnetic leakage exists. An alternating-current transformer is reversible. A transformer which lowers the pressure is called a step-down transformer; when it raises the pressure it is called a step-up transformer. The principal loss of energy in transformers is due to hysteresis ; every reversal of magnetization means expenditure of energy in the iron core. The softest and best iron is, and must be, selected for the cores, which should be built of thin laminated sheets, in order to reduce the hysteretic loss as much as possible. ELECTRIC GENERATORS. 501 The output of a transformer is limited by the amount of heating, and the drop of voltage in the secondary coil. The efficiency of transformers increases with their size, and varies with their load. Large transformers have an efficiency of 0.983 at full load, and about 0.95 at quarter load; a small transformer may have a full-load efficiency of 0.9, and 0.7 at quarter load. The size and weight of a transformer can be reduced within limits by increasing the frequency. Separate Coils. The coils should be wound separately, and individually insulated and taped, obviating the danger of contact between coils which are wound on the same mould. When the secondary coil has its circuit closed it has a given impedance, and a given current will pass through the secondary circuit, and a M. M. F. due to the secondary ampere turns will be imposed on the magnetic circuit. If the secondary load be non-inductive, and there is no leakage in the magnetic circuit of the transformer, the M. M. F. will be in step with the induced secondary E. M. F. and with the primary C. E. M. F., and practically in opposition to the impressed E. M. F. It will, therefore, be opposed to the M. M. F. in the primary circuit. The resultant will be an intermediate M. M. F. at a phase. In order to maintain the resultant M. M. F. at the magnitude and phase of the M. M. F. of excitation, a greater current strength will enter the primary coil. As load is added to the secondary circuit, the primary current must vary both in magnitude and phase to maintain the fixed M. M. F. of excitation as a resultant. The effect of magnetic leakage is to increase the drop at secondary terminals under load. If there were no leakage, the secondary coil would act as though devoid of inductance and possessing only ohmic resistance, its inductive reaction being entirely expended against the primary circuit; if some of its flux escapes the primary coil, that portion develops a C. E. M. F. of self-induction in the secondary coil, and an apparent inductance is added to the secondary circuit within the transformer, increasing the drop at load. When the load in the secondary circuit is non-inductive, the wave force of secondary current will be very nearly the same as the wave type of secondary E. M. F., and of the impressed E. M. F. When the secondary load is inductive, the secondary current and M. M. F. lag behind the secondary E. M. F. This necessitates a greater primary M. M. F. and current to maintain the resultant M. M. F. of excitation. A condenser connected to secondary terminals tends to diminish the secondary drop and increase the power factor. Losses in Transformers. The losses can be divided into two classes-i.e., core losses and copper losses. The core loss can be further sub-divided into the hysteresis and eddy-current losses in the core, and a small copper loss in the primary coil, which can usually be neglected. The former are caused by the reversals of magnetism, and vary according to the quality of the iron, the magnetic density, the weight of the core, the frequency, the thickness of the iron, and the insulation used between the laminations. The eddy-current losses depend on the last two conditions. The copper losses are the sum of the C2 R losses in both the primary and secondary coils. There is also a certain amount of loss in the coils by eddy currents, but in well-designed apparatus this should be practically negligible. Transformer Insulation. Materials most generally used are: Oiled linen or silk, mica, micanite and fibre. Efficiency. Output. Output The efficiency Input Output losses In a constant potential transformer, the core loss remains constant at all loads, but the copper loss depends on the square of the current in the primary and secondary. = Where transformers are only used for a few hours out of the twenty-four, but are excited during the whole of that period, the following formula gives the average efficiency (n = number of hours full load). Full load = n Average efficiency = Core loss x 24 C2 R + Full load = n Hence for intermittent work a large core loss means a low efficiency. 502 SECTION IV.-POWER STATION. Magnetic Fatigue or Ageing. Unless this is prevented, the core losses may be increased from 25 per cent. to 100 per cent. after the transformer has been in use some time. Power Factor. The power factor of an alternating-current transformer with ferric circuit varies from 0.7 at no load, to, perhaps, 0.99 in large transformers at full load; but in aero-ferric transformers, whose magnetic circuits are formed only partly of iron, the power factor at no load may be as low as 0.4. Heating and Current Density in Transformers. (Parshall and Hobart.) The current densities used in various cases are approximately as follows :— Amperes per Square Inch. 800 to 1500 500 900 500 1100 "" In the case of small transformers, the current density could be very much higher without causing excessive temperature rise, but such transformers would have poor regulation. On the other hand, large transformers, when properly designed, have better regulation than is necessary, the current density being limited from thermal considerations. Although many large transformers are so poorly designed that a few hours' run at full load heats them up to above 100 deg. Cent., this is bad practice, as it causes deterioration both of insulation and of iron. A rise of not more than 60 deg. Cent. should be aimed at, even with large transformers. Transformers with forced circulation of oil or air.. Large transformers immersed in oil or air Small A rise of 60 deg. Cent. reduces the insulation resistance of a transformer to a small percentage of its resistance when cold. In other words, insulating sub- stances have a very large negative temperature coefficient. In one case, where the insulating material was a composition of mica and cloth, the transformer being immersed in oil with which the insulation was thoroughly impregnated, the average temperature coefficient between 20 deg. Cent. and 80 deg. Cent. was-.8, that is, the insulation resistance increased 80 per cent. per deg. Cent. decrease of tempera ture. But the ability of this insulating material to withstand the disruptive effects of very high potentials is practically unimpaired. Consequently, it is important to distinguish carefully between the ability to withstand the application of high voltages and the insulation resistance, as measured in megohms. Important Points in Specifications for Static Transformers. The iron or steel used in the laminations shall be guaranted free from ageing or increase in hysteresis loss. At the end of twelve hours' run at the rated load, the rise of temperature in either winding shall not exceed 35 deg. Cent., as measured by increase of resistance. (The British Thomson-Houston air-blast transformers are designed to insure a rise not exceeding 40 deg. Cent. above temperature of surrounding atmosphere when working under normal conditions.) The drop in voltage on the secondary between no load and full-rated non- inductive load shall not exceed 1 per cent. The efficiency shall be as follows: •• 97.5 per cent. at 20 deg. Cent. 97.5 "" 97.0 99 "" Full load Three-quarter load Half load Quarter load or an average efficiency from quarter to full load of 97.0 per cent. All high-tension terminals and fittings to be shielded. 20 20 20 "" "" 76.0 .. "" "" Each transformer shall be subjected to a test pressure of .... volts for five minutes between winding and case, and between primary and secondary windings. The current density in the primary and secondary windings at rated full load shall not exceed 1000 amperes per square inch. ·· ·· ·· ·· "" "" "" "" "" Constructive Details of Transformers. Static transformers may be divided in four classes: 1. Air-cooled transformers. 2. Air-blast transformers. 3. Oil-cooled transformers, with air circulation. 4. Oil-cooled transformers, with water circulation. 99 ELECTRIC GENERATORS. 503 Air-Cooled Transformers. Plain air-cooled transformers are those in which the coils are cooled by the natural circulation of air through and around them. The coils are specially disposed with a view to obtaining through ventilation, and a current of cold air is drawn through from the bottom to the top by the heating of the coils in causing the air in their vicinity to rise. The following gives some details of the Westinghouse method of constructing this type of transformer. Westinghouse Air-Cooled Transformers. Parallel Coils.-The coils in Westinghouse transformers are similar in form,. and are placed together side by side, avoiding the straining of the coils or the insulation to make them fit into one another. The insulation between coils is in the form of flat plates. Primary Winding. The primary coil is generally wound in many layers, with few turns per layer to reduce leakage. Secondary Winding.-The secondary coils of the larger sizes are usually wound with a continuous strip of thin copper of uniform thickness, wound on edge in the form of a spiral. The insulation between the turns lies between perfectly flat surfaces, and is not liable to injury. The secondary coils for intermediate sizes are wound with square wire, so as to avoid the crossing of the wires at the ends of the layers, with the liability to cut through the insulation. The section of copper available for carrying current in a coil of given size, wound with strip or with square wire, is increased about 25 per cent. as compared with the construction in which round wire is used. The resistance of the circuit is correspondingly reduced, and the efficiency of the transformer improved. Ventilation.-A large portion of the coils is outside of the iron. The ends of the coils in the larger sizes are spread apart by bending the outer coils, thus leaving free circulation of air between them. The spread coil transformer presents four or five times as much exposed coil surface as would be secured if the coils were built together compactly. Terminals.—The terminal wires in transformers of the Westinghouse outdoor type are brought out of the case without mechanical joints of any kind. Cases.-The cases on the Westinghouse outdoor type are made without joints, except at the bottom. The wires are all brought out from the bottom, which prevents the danger of water entering through defective joints. Tests.-During the process of manufacture, the coils are carefully tested for short circuits and for insulation, and before shipment the insulation on Westing- house standard transformers is tested at several times the working voltage; it is run on overload, and careful measurements are made of the ratio of the windings. and of the iron losses. Dick, Kerr Natural Draught Transformer. (FIG. 94, page 504.) Fig. 94 illustrates a single-phase 60-kilowatt 50-cycle static transformer, manu- factured by the above firm. The transformer is designed to step down from 5000 volts to 240 volts. The construction, in the main, conforms to the specification of oil-cooled transformers. Witting and Eborall Natural Draught Transformers. (FIGS. 95 and 96, page 505.) Fig. 95 and Table 42 give dimensions of the above firm's single-phase trans- formers, while Fig. 96 and Table 43 give particulars of their three-phase trans- formers. Type. WTB 10 WTB 16 WTB 23 WTB 33 WTB 46 WTB 66 WTB 100 Table 42.-Witting and Eborall Natural Draught Single-Phase Transformers. Type WTB. (Fig. 95.) Kilowatts. 27 38 55 76 108 155 250 I. 760 795 860 950 1050 1160 1330 B. 450 460 470 510 580 610 690 H. 1045 1145 1235 1360 1475 1585 1805 + 504 SECTION 1V.-POWER STATION. (990) O Type. DTB 16 DTB 23 -2.9 ··------ O DTB 33 DTB 46 DTB 66 DTB 100 -2'44 HIT FFFFFFF 94 Kilowatts. 36 54 75 5.2″ Fig. 94. Dick, Kerr Single-Phase Natural Draught Air-Cooled Transformer. 108 155 240 I Table 43.—Witting and Eborall Natural Draught Three-Phase Transformers. Type DTB. (FIG. 96.) រ ·142 L. 1120 1160 1260 1400 1550 1720 B. 420 445 455 500 550 600 H. 1045 1145 1235 1360 1475 1585 ELECTRIC GENERATORS. 505 1 K19911 Kis (992) 95 L 96 L I 1 1 } H 1 } * A M B Figs. 95 and 96. Witting and Eborall Natural Draught Transformers. A 506 SECTION IV.-POWER STATION. ... Air-Blast Transformers. Air-blast transformers are essentially the same as plain air-cooled transformers, with the exception that a current of air is forced through the windings by means of a blower in place of the natural draught of the latter type. By means of this artificial cooling a very large amount of heat can be dissipated. Westinghouse Air-Blast Transformers. (FIG. 97.) The standard voltages employed for these transformers are six in number, with three lower voltages in each group, secured by bringing out a tap from a point near each end of the high-tension winding. The six groups of pressures are as follows:- (1.) (2.) (3.) (6.) (4.) 16,500 2200 6600 11,000 33,000 2100 6300 10,500 15,750 6000 15,000 5700 14,250 2000 1900 (993) 10,000 9,500 97 B COOOOOOO (5.) 22,000 21,000 20,000 19,000 C 31,500 30,000 28,500 Air-blast transformers are built for voltages ranging from 2200 to 33,000 volts. Transformers for pressures higher than the latter figure require so much room for the insulation that this forms a practical limit. Transformers are rated on their kilovolt-ampere output. If they supply a current having a power factor of 100 per cent., the kilovolt ampere output is equivalent to the kilowatt output, but with loads of lower power factors the kilo- watt output is proportionately less than kilovolt-ampere output. Where two or three transformers are connected together in one group, the rating of the group is equal to the sum of the ratings of the separate transformers, except with two transformers on three-phase circuits, and three transformers with secondaries arranged in interconnected star. Two transformers connected in delta to change from three-phase to three-phase, have a rating approximately 15 per cent. less than the sum of their individual ratings. Three transformers with secondaries in interconnected star have a rating approximately 8 per cent. less than the sum of the individual ratings. 2. ELECTRIC GENERATORS. 507 The efficiency of the transformer depends upon the frequency; the greater the frequency the higher the efficiency. The amount of air required by an air-blast transformer depends upon its losses. 150 cubic feet of air is allowed per minute per kilowatt loss. The supply of air to the coils should be so regulated that the rise of temperature of the cooling air does not exceed 20 deg. Cent. 12 deg. Cent. or 15 deg. Cent. is usual for the air coming from the coils. Air-blast transformers are not intended to be operated with forced draught, but in emergencies a reduced load may be thus carried for a short time, or even full load for an hour, provided the transformer is cold to start with. · Table 44.-Westinghouse 25-Cycle Air-Blast Transformers. Capacity in Kilowatts. 500 750 1000 1500 2000 2500 3000 Volts. Per Cent. Efficiency. goo } 1 Full Load. Load. Load. Load. HA 94.9 94.6 2,200 97.7 97.7 97.2 95.1 6,600 97.7 97.6 97.0 11,000 97.6 97.4 96.8 16,500 97.4 97.3 22,000 97.3 97.1 33,000 96.8 96.5 96.6 94.2 96.4 93.9 95.7 92.7 97.9 97.7 97.3 97.2 2,200 6,600 97.9 11,000 97.7 16,500 97.6 97.4 97.7 97.6 97.0 96.7 22,000 97.5 97.2 96.5 33,000 97.1 96.8 96.0 97.5 97.4 97.2 2,200 98.0 97.9 6,600 98.0 97.8 11,000 97.8 97.7 16,500 97.7 97.6 96.9 22,000 97.6 97.4 96.6 33,000 97.4 97.0 96.1 95.3 95.2 94.7 94.3 94.0 93.0 95.7 95.6 95.0 94.7 94.2 93.3 96.1 2,200 98.3 98.1 97.7 6,600 98.2 98.1 97.7 96.0 11,000 98.0 97.9 97.4 95.5 16,500 97.9 97.7 97.2 95.1 22,000 97.8 97.7 97.0 94.7 33,000 97.6 97.3 96.4 93.8 2,200 98.4 98.3 97.9 96.5 6,600 98.3 98.2 97.8 96.3 11,000 98.2 98.0 16,500 98.1 97.9 22,000 98.0 97.8 33,000 97.7 97.6 97.6 95.9 97.5 95.5 97.3 95.2 96.8 94.4 96.6 2,200 98.5 98.4 98.0 6,600 98.5 98.3 97.9 11,000 98.3 98.2 97.7 96.5 96.1 16,500 98.3 98.1 97.6 95.9 22,000 98.2 98.0 97.5 95.5 33,000 97.9 97.7 97.0 94.7 96.8 2,200 98.6 98.5 98.1 6,600 98.6 98.4 98.0 96.7 11,000 98.5 98.3 97.9 96.3 16,500 98.4 98.2 22,000 98.3 98.1 33,000 98.1 97.9 97.7 96.1 97.6 95.9 95.1 97.3 Regula- Weight tion. in P.F.-1.0 Pounds. 1.15 1.20 1.25 1.30 1.35 1.50 1.05 1.05 1.10 1.15 1.15 1.25 .95 1.00 1.00 1.05 1.05 1.10 .90 .90 .95 .95 .95 1.00 .80 .85 .85 .85 .90 .90 .75 .75 .80 .80 .80 .85 9,000 9,700 10,700 Dimensions in Inches. A B BC 73 77 79 11,400 83 12,200 86 14,900 14,500 91 15,800 95 17,500 98 18,700 100 20,000❘ 105 22,200 110 © #**** **AAA* 22222 ANHOO* *888*N AARNNE ANNEES 8850 HHNNOX NAO❤❤: ::*::: *::::N 88ONNK ONNXL8 54 12,000 85 13,200 89 54 54 27,000 108 94 60 52 29,000 109 54 57 49 33,500 111 44 14,700 90 57 49 15,700 95 16,800 96 18,700 101 44 47 47 57 49 47 60 52 93 18,600 20,300 98 22,500 100 63 24,100 102 25,700 107 28,500 111 47 63 54 66 57 49 60 57 49 60 52 63 54 63 54 66 56 52 60 52 54 66 56 22,300 194 63 54 66 56 24,600 104 66 56 69 59 56 69 59 30,900 113 69 59 34,200 114 72 62 26,000 106 66 56 28,300 106 69 59 31, 200 110 69 59 72 62 35,700 115 72 62 39,800 122 76 67 .70 29,400 109 69 59 .70 31,100 114 72 62 35,000 .70 119 72 62 67 .75 37,800 120 76 .75 40,300 125 76 67 .75 44,800 130 80 69 508 SECTION IV.-POWER STATION. British Thomson-Houston Air-Blast Transformers. (FIG. 98.) The British Thomson-Houston Company guarantee that the heating of air-blast transformers will not exceed 40 deg. Cent. rise above the surrounding air, as determined by the rise in resistance. In constructing the air-blast transformer of the British Thomson-Houston Company, both the primary and secondary windings are subdivided into numerous independent coils, each separately and heavily insulated. With subdivided coils the voltage generated in a single section is low, even in transformers wound for a voltage of 15,000 to 20,000 volts, and the arrangement also allows the use of a sufficient number of air-ducts between all coils to limit the rise in temperature of any part of the winding to but a few degrees above that of the temperature of the air used in cooling. The coils are in all cases wound with flat copper conductors, thoroughly cemented together by an insulating compound before the exterior insulation is applied. The method of winding and in- sulating produces a strong coil, which will resist any tendency. of the conductors to vibrate. The use of rigidly constructed coils is very important in large transformers, where the mag- netic force tending to move the conductors is great, and where vibration might consequently be set up which would abrade the insulation. The primary and secondary coils of the transformer are assembled in small intermixed groups with air spaces between the coils. Diaphragms of solid insulating material are placed be- tween every adjacent primary and secondary section, and com- pletely in case the primary wind- ing, except at either end of the coil, which must be open to let the air circulate. At the end the diaphragms project far beyond the coils, so that there is surface insulation of great length between the primary and secondary. An Air-Blast Transformer. additional insulation casing is Fig. 98. British Thomson-Houston Company's placed around the entire struc- ture of assembled primary and secondary coils, and separates the whole winding from the iron punchings, assembled within and around the coils. The diaphragm between the primary and secondary will withstand the primary potential. The air is forced from below through two separate paths at right angles to each other, passing in a vertical direction through the windings and horizontally through the core. The admission of air is controlled by shutters at the top and at the side of the transformer. The air-blast is obtained from a blower operated either by an induction motor, or a direct-current motor, or any other convenient source of power. The power required for the blower seldom exceeds 1 of 1 per cent. of the total capacity of the transformer, and in most cases it is much less, frequently not more than 1 per cent. of The high tension terminals are brought out as flexible cables through heavy porcelain bushings located in the cap. Low potential terminals are located within the base of the transformer. Fig. 98 shows a diagram of an air-blast transformer as constructed by the British Thomson-Houston Company. ELECTRIC GENERATORS. 509 Approximate Dimensions and Weight of British Thomson- Houston Air-Blast Transformers, for Voltages up to 10,000 Volts Primary and 1000 Volts Secondary. (TABLE 45 and FIGS. 99 and 100.) Table 45. Capacity in Kilowatts. 100 150 200 250 300 375 500 750 1000 60 Cycles. 40 Cycles. 25 Cycles. Total Kilowatts of Trans- former. 300 900 1800 2700 4500 6750 7500 lb. 3,720 4,800 6,000 6,900 8,170 9,450 11,000 14,400 19,200 Weight. Kilowatt Size of Trans- former Units. 50 100 200 300 500 750 1250 lb. 4,200 5,520 6,960 7,820 9,320 10,700 12,650 17,000 22,000 24,600 15669 --B Size of Blower in Inches. 4382888 100 • 60 Cycles. • A B с lb. 4,560 in. in. in. in. in. 62 35 28 63 66 35 6,240 28 67 7,900 70 38 33 71 73 38 33 74 8,850 10,460 12,000 80 28625 375 350 325 310 310 295 280 ****** 76 47 1 38 77 14,400 47 38 81 47 38 86 19,200 92 56 45 93 97 56 45 98 99 TAL BA A --- C· Figs. 99 and 100. British Thomson Houston Company's Air-Blast Transformer. Table 46.-Capacity, Pressure, and Driving Power required for Ventilators for Air-Blast Transformers. Speed of Output of Blower, Blower in Revolu- tions per Minute. Cubic Feet per Minute. Dimensions. 100 40 Cycles. 1,800 3,200 5,900 8,800 13,000 17,600 23,600 A BC Pressure in Ounces per Square Inch. 0.3 0.4 0.5 0.6 0.8 0.9 1.0 800ESORT 250 350 25 Cycles | B Al in. | in. in. | in. in. 35 35 28 28 38 33 38 33 38 33 38 33 47 38 47 38 75 38 47 47 38 38 45 47 38 82 47 56 45 87 56 56 45 95 56 56 100 64 64 600 850 1300 ZABIJNORF > Cubic Feet of Air required per Trans- former. 1800 3000 | 45 56 Horse- Power to drive Blower. 0.25 0.60 1.10 2.25 4.25 6.75 12.00 510 SECTION IV.-POWER STATION. Static Transformers, Central London Railway. (British Thomson-Houston.) The transformers are of the air-blast type, and step down from 5000 to 330 volts. As the sub-stations are underground it was necessary to make special arrangements for getting rid of the hot air, and for this purpose the air is sucked through the transformers instead of being forced through in the usual way: the hot air is then expelled through sheet steel pipes running up the centre of the spiral staircase. The transformers are contained in perforated sheet-iron cases, and there are spaces left in the core for the circulation of air. The secondary windings are carried down to a kind of bus-bar at the bottom, and are connected up there. The transformers were specified to have 98 per cent. efficiency at full load, and 97 per cent. at half load: the regulation to be 1.7 per cent., the core loss 1.2 per cent., and the maximum temperature rise 70 deg. Fahr. The weight of each complete is approximately 8000 lb. Dick, Kerr Air-Blast Transformers. (FIG. 101, page 511.) Fig. 101 shows the type of an air-blast transformer manufactured by Dick, Kerr and Co. The figure illustrates a 200-kilowatt single-phase machine, designed for transforming from 7000 volts to 395 volts at 25 cycles. Oil-Cooled Transformers. In oil-cooled transformers the coils and core are immersed in oil, which acts as a medium to conduct the heat from the coils to the surrounding tank. If the containing case is made with deep vertical corrugations, the increased radiating surface thus obtained greatly increases the amount of heat which can be dissipated. The function of the oil is fourfold. It acts as a heat conductor from the coils to the tank; it increases the breakdown resistance of the insulation; it preserves the insulation from oxidation; it repairs the insulation in case of a puncture. The oil-cooled transformer thus has many advantages, but there is always a certain danger of the oil catching fire, and where such transformers are employed provision should always be made for dealing with cases of fire. Westinghouse Oil-Cooled Transformers. Transformers of the above type are built in sizes from 10 to 500 kilowatts, when the oil is self-cooling. For sizes above 500 kilowatts the oil is cooled by water circulation, as self-cooling transformers for these capacities are too bulky in design. When transformers are connected in groups, the efficiency of the group is usually the same as that of the individual transformers which make up the group. There are, however, three exceptions:—(1) Two transformers connected in A or Y for three-phase. (2) Two transformers on the two-phase and three-phase system. (3) Three transformers, with their secondaries arranged in interconnected star. The rise in temperature when operating at full kilovolt-ampere output is guaranteed not to exceed 40 deg. Cent. above that of the surrounding air. After operating at 25 per cent. overload for 24 hours, the temperature rise above the surrounding atmosphere is guaranteed not to exceed 55 deg. Cent. After operating at full load for 24 hours, the transformer is guaranteed to stand 50 per cent. overload for one hour, without the temperature exceeding by 60 deg. Cent. that of the surrounding air. The following Table gives the test voltage employed by the Westinghouse Company. The insulation test from high-tension winding to low-tension winding, and from the former to the core, is determined by the voltage of the high-tension winding. The test from the low-tension winding to the core is determined by the voltage of the low-tension winding. Rated Voltage of Winding. Exceeding 1,000 volts 3,500 5,000 12,000 17,000 23,000 33,000 "" "" "" 9" "" "" •• Not Exceeding 1,000 volts . 3,500 5,000 12,000 17,000 23,000 33,000 44,000 "" Tim ": "" "" ?? •• Insulation Test. 7,500 volts 10,000 ** 3 times rated voltage 2 21 2 2 2 "" "" 19 "" ?? ?? >> 71 >" "" ELECTRIC GENERATORS. 511 Fig. 101. Dick, Kerr Single-Phase Air-Blast Transformer. 7994 3'8/2 3'5'4" magkapat Bolts 2'3 FR EN ER EN CAS [FULLTEL* 4|1||||||||||49454BRAYDEE ALMEIRELE 14$……………………………4:18…………………AKI — — TEAU MAIN: CARA | 2………………………………………THE SILENTETTEÉTITIATIOshie cintiquiti KONTOPFIT: FELELIJEM VARJOITEEL KARJAL kanarchii^arit*gen. LiftSK TESUSJEDI PERSEIM. 4 8 5: 114 m AIR 101 ܬ ܕ ܪܢ ܪܕܝ į 312 SECTION IV.—POWER STATION. Kilo- watts. 250 800 375 500 Volts. 22,000 33,000 44,000 2,200 6,600 11,000 16,500 22,000 33,000 44,000 2,200 6,600 11,000 16,500 22,000 33,000 44,000 2,200 6,600 11,000 16,500 22,000 33,000 44,000 Full Load. 97.3 97.1 96.9 97.7 97.7 97.65 97.6 97.5 97.3 97.1 97.9 97.9 97.85 97.8 97.7 97.5 97.2 98.1 98.0 98.0 98.0 Table 47.-Westinghouse Oil-Cooled Transformers. 25 Cycles. Efficiency. Load. Load. Load. 97.3 97.1 96.8 97.7 97.6 97.65 97.6 97.55 97.0 97.2 96.8 91.1 96.7 97.7 97.5 97.2 96.9 96.7 96.4 97.9 97.6 97.9 97.9 97.85 97.5 97.8 97.4 98.1 98.0 98.0 98.0 97.4 97.3 97.3 97.2 97.9 97.8 97.75 97.7 97.4 97.4 97.2 97.1 96.8 97.9 97.7 97.7 97.6 97.5 97.3 97.0 95.0 94.0 94.2 95.8 95.7 95.6 95.4 95.1 94.7 94.2 96.2 96.1 96.0 95.8 95.4 95.2 94.8 96.6 96.4 96.2 96.0 95.7 95.6 95.2 Regu lation. Per cent. 1.80 1.90 2.10 1.60 1.60 1.60 1.60 1.70 1.80 2.00 1.50 1.50 1.50 1.50 1.60 1.70 1.80 1.40 1.40 1.40 1.40 1.40 1.60 1.90 1 Trans- former. lb. 4200 4500 4800 3800 3950 4100 4600 4900 5200 5500 5000 5150 5300 5500 5800 6100 6500 6200 6300 0450 6600 6900 7200 7600 Case. Ib. 3200 3200 3200 3200 3200 3200 3200 3200 3200 3200 3200 3200 3200 3900 3900 4400 4400 3900 3900 3900 4400 4400 4400 4400 Net Weights. lb. 4080 3970 3860 3720 3640 3560 3860 3820 3750 3700 3970 3930 3900 3970 3860 4950 4850 3970 3960 3930 4850 4800 4750 4650 Oil. gal. 545 530 515 495 485 475 515 510 500 500 530 525 520 530 515 660 645 530 530 525 650 645 635 620 Total. lb. 11,480 11,670 11,860 10,720 10,790 10,860 11,660 11,920 12,150 12,400 12,170 12,280 12,400 13,370 13,560 15,450 15,750 14,070 14,160 14,280 15,850 16,100 16,350 16,650 Dimensions. Floor Space. in. 67 × 54 67 × 54 67 × 54 67 × 53 67 × 53 67 X 53 67 × 54 67 × 54 67 X 54 67 X 54 67 X 54 67 X 54 67 × 54 74 × 57 74 X 57 77 x 61 77 X 61 74 × 57 74 X 57 74 x 57 77 x 61 Height. in. 92 INN 100% *** *... *** RRR ~~~ 68 68 80 80 70 82 92 77 × 61 77 × 61 77 × 61 92 92 1 ELECTRIC GENERATORS. 513 90 80 70 7. EFFICIENCY GO 50 30 20 10 100 KONDIDIASI & 90 80 70 G2 20 30 20 10 "/ Efficiencies at Different Loads. Full Load Efficiency......97.5 per cent. • 34. 12½ 1/4 (778) 14 44 O .2 .3 PROPORTION OF NORMAL OUTPUT. Fig. 102. Efficiency Curve of Westinghouse 150-Kilowatt Self- Cooling Transformer. (E.M.F. 500 to 15,000 Volts. 60 Cycles.) · ' Régulation Non-Induct- ive Load..... Load having .9. Power Factor 14 .ގ .97.4 ....97. .94:9 3/4 3/2 1/4 Regulation Non-Induct- ive Load…..... Load having 9 Power Factor.. C .. 1.5 …………… 3.5 Efficiencies at Different Loads. Full Load Efficiency..... 98. per cent. Ga * .98. .....97.6 ......96.1 S 44 .6. .7 .8 1.4 01 3.3 Co ·· • • 44 • 9 1. .2 .3 .ym .6 .7 PROPORTION OF NORMAL OUTPUT. Fig. 103. Efficiency Curve of Westinghouse 375-Kilowatt Self- Cooling Transformer. (E.M.F. 500 to 15,000 Volts. 60 Cycles.) .8 S : ་ 1 514 SECTION IV.-POWER STATION. Specification for Dick, Kerr Three-Phase Oil-Cooled Transformer. (FIG. 104.) The transformer to be of the three-phase oil-cooled type, and to be suitable for working continuously at its rated load, and capable of withstanding an overload of 50 per cent. for periods not exceeding one hour. Special attention to be paid to make the insulation between the individual windings, as also between these and the frame, as thorough and efficient as possible. Fibrous material to be used for insulating the high-tension and low-tension conductors, and, when possible, mica. 104 (О 32 CO *(995) 51 3'-11· : EN 3'9%- 1'84". Fig. 104. Dick, Kerr Three-Phase Oil-Cooled Transformer. The high-tension coils will be wound on separate bobbins. They will be individually insulated between turns, and on the outside by means of an insulation not affected by the oil. The secondary winding is insulated from the core by means of paper and mica. The copper wire used in the windings to be of the best quality, the conductivity being not less than 100 per cent. (Matthiessen's standard). The cores and yokes of the transformers to be built up of annealed iron plates, of special quality and high permeability, and of minimum hysteresis loss. The plates to be insulated from one another by special varnish, and held together by means of bolts, which will be insulated from the laminated sheets. The lamina- tions used to be free from ageing or increase in hysteresis loss. The cores and yokes to be securely clamped together in order to reduce the magnetic resistance. A number of ventilating ducts to be left between the plates of the core and between the coils, in order to ensure ample circulation of oil, right through the core and windings. The terminal wires are brought to terminals of ample size for the full-load current of the transformer, well insulated by means of porcelain blocks, and securely attached to the casing. The transformer, when wound for less than 12,000 volts high tension, to be subjected to a breakdown test, which consists in applying double the working tension between the high-tension windings and the low-tension windings or frame. The tension to be kept on for one minute. Fig. 104 illustrates a three-phase transformer of the above type, manufactured by Dick, Kerr and Co. ELECTRIC GENERATORS. 515 Oil-Cooled Transformers with Water Circulation. When oil transformers are constructed in large sizes, the oil alone is not sufficient to produce enough cooling effect, and the oil itself is cooled by means of water-circulating pipes placed in the oil. TRANSFORMER CONNECTIONS. Connections for Starting Motors. (FIGS. 105 to 109, pages 515 to 517.) In cases where transformers are used in connection with rotary converters, the latter are frequently started up by means of small induction motors. If the electromotive force of the bus-bars is not the voltage which enables the starting To Line A mmi Transformer No.1 105 (996) Fig. 105. B C Armature Winding mummi mr Transformer No. 2 In www m Transformer No. 3 A B C Starting Motor Winding Connection Diagram for Obtaining a Lower Voltage for Starting Motor than for Rotary Converter, on the Three-Phase Delta System. motor to give the proper speed to the rotaries for synchronising, the proper voltage can be obtained by connecting to loops from the transformers, in the manner indicated in Figs. 105 to 109. Connections for Polyphase Transformation. (FIGS. 110 and 111, page 518.) Figs. 110 and 111 show various methods of grouping single-phase transformers for polyphase transformations in the case of a two-phase generator and a three- phase generator respectively. 516 SECTION IV.-POWER STATION. -39-V-- 106 107 To Rotary Converter Phase C (998) To Rotary Converter 1997) Phase C Hy d To Motor Phase O ----------390-V- To Motor Phase A wh Transformer No. 1 To Motor Transformer No. 1 -333-V Phase C Transformer No. 2 -390-V…--- ------ To Rotary Converter Phase A Transformer No. 3 1 Transformer No. 2 Transformer No. 3 ► ale dhe qarın dipan at To Motor Phase A · 408-V-~--· 1 To Rotary Converter Phase A ** ** ** * that met tar all-dir qui ne drit un-en-Y D A G WHE To Motor To Rotary Converter Phase B -39-V Phase B To Rotary Converter Phase B To Motor Phase B Transformer Connections. Fig. 106. Diagram of Connections for Obtaining a Lower Voltage for Starting Motor than for Rotary. Fig 107. Diagram with Voltage of Starting Motor Higher than that of Rotary. ELECTRIC GENERATORS. 517 ► 108. Transformers for use with Rotary Converters. (FIGS. 112 to 127, pages 518 to 522.) . Where rotary converters are employed, it is often a necessary requirement that the electromotive force of the direct current be varied over a wide range. This variation is usually obtained by a corresponding variation in the electromotive A mmm m Transformer No. 1 A 109 Armature Winding Transformer No.1 B B C C Armature Winding (999) пити Transformer No. 2 Transformer No. 2 A Starting Motor Winding A B m Transformer No. 3 B с Starting Motor Winding Fig. 108. Fig. 109. Method of Obtaining a Lower Voltage for Starting Motor than for Rotary Converter on the Three-Phase Star System. Method of Obtaining a Lower Voltage for Starting Motor than for Rotary Converter on the Three-Phase V System. force of the alternating current supplied. Where this range in electromotive force is required, transformers are furnished in which the ratio of primary to secondary turns may be changed. This is accomplished by bringing out loops from the windings and connecting them to a regulating dial, so arranged that the electromotive force may be gradually varied by moving from one loop to another. . - + 518 SECTION IV.-POWER STATION. PATA+Ad 110.... |1400|1100 || (00) +2000 Va L2000 V 858 (1001) 111. 2000 2000 NALA. (1002) JÀ 0001 → <2000–V «2000~ V. +100 V Single phase 2000, 2000. 2000 V V. 100 100 V. 1007. 3 Phase Delts(connection 112 A www Transformer No. 1 (1003) B C 2000 V. Food BE |-100-0, 2 Phase 4 wire 37.7V2 -2000➤ Y. 2000 2000, V. V. -2000] V. || 155 V2 || 165 V).–.1155V 7.7% 100 100 V. -100 V: ** 3 Phase Star() connection Armature Winding Transformer No. 2 wwwwwww. -2000✈–1400 V. 12000 V. 2 Phase 3 wire T. connection to 2 phase 4 wire 100V 100 Food 2000, 2000 2000-y ~~~100-v 100 100 V. Commutator 1735V. 2000EV. [80,7Vk MMM Da VIF TV. ←100·7.100 2000 V. V. 100100 100-V→→→ 3 Phase 8 Phase V connection T. connection hmmmmmm Transformer No. 3 -2000 V. D.C. 3 Wire System Middle or Neutral Wire -2000- V. facov -100 V 2 to 3 phase 2000 2000 -2000 v 1735V Foo F 100 3 to 2 phase Transformers. Figs. 110 and 111. Methods of Grouping Single-Phase Transformers for Polyphase Transformations. Ay Fig. 112. Three Transformers in Inter-connected Star, Operating a Three- Phase Rotary Converter on a D.C. Three-Wire System. ELECTRIC GENERATORS. 519 1: Figs. 112 to 114 show various methods of connecting up rotary converters and static transformers in different cases. Fig. 112 shows a special method employed by the Westinghouse Company for interconnected star transformers operating a three-phase rotary converter on a D.C. three-wire system. NEUTRAL WIRE D.C. 3-WIRE SYSTEM (1004) 113 3 En Lumen ummmm Ammun hmm www пишии ни TRANSFORMER NO. 1 www. TRANSFORMER NO. 2 TRANSFORMER NO. A2 B DIAGRAM OF PHASE RELATIONS OF H.T. AND L.T. BEFORE CONNECTING L.T. TO ROTARY. لين مست (1004) www A1 No.1 C2 D. C. COMMUTATOR No.3 B2 A1 O -A2 No.2 ww S B1 Bi B2 Cí (A, A B2 C2 AL DIAGRAM OF PHASE RELATIONS OF L.T. AFTER CONNECTION TO ROTARY. 1 1 I t # A: B Fig. 113. Transformer Connections. A2 C2 -B1 15 Fig. 113 shows a method of connecting three transformers with their high- tension windings in star and their low-tension windings in double star, for operating a six-phase rotary converter from a three-phase line. Fig. 114 shows a method of connecting three transformers with their high- tension windings in delta and their low-tension windings in double delta, for operating a six-phase rotary from a three-phase line. 520 SECTION IV.-POWER STATION. Figs. 115 to 118 show the armature connections of rotary converters. The letters represent phases, and the numbers the first or second wire of each phase. In the three-phase and six-phase combinations, two phases are combined in each wire and in the latter the large and small lettered phases are from the same 114 TRANSFORMER NO. 1 A1 www him ww‍ huu‍ huma TRANSFORMER NO. 2 TRANSFORMER NO. 3 или my A 2 DIAGRAM OF PHASE RELATIONS OF H.T. AND L.T. BEFORE CONNECTING L.T. TO ROTARY, (1005) B1 min hånd wwwwwwww No.2 No.1 B1 No.3 Bìì ни B2 ク ​им B2 minihiw DIAGRAM OF PHASE RELATIONS OF L.T. AFTER CONNECTION TO ROTARY. C2, A B2. C2 Fig. 114. Transformer Connections. A₁₂ i C₁ transformers (see Figs. 119 to 127). The fields of rotary converters are connected to the direct-current side, except in cases where the rotary is started from the alternating-current side, in which case separate excitation is preferable. Figs. 119 to 127 show the most common transformer connections for rotary converters. N 116 115 N S 117 S (779.) B₂ A my -866 V---→ (178) N TWO WIRES N CA B-2 C-1 AC₂ A2 N AB THREE WIRES * B₂ B 2 Phase Secondary to Rotary A-1 A2 B-1 B-2 S CONNECTIONS OF TV S A-1 3 Phase primary transmis™ line. 3 Phase Secondary to Rotary B-1 C-2 A-2 Imm A-B (Herrick.) 119 120 C-A ширину 3Phase primary transmisline. Cy Im S A-B A-2 B-1 Jaberete X + Hooondbup efales A, B www 202 Mo FOUR WIRES N alebeteptetet CA ROTARY CONVERTERS. N BYAZ CA obry BC N 7 BUOY lete peretetelefer Anin defiletely Bi 3Phase Secondary to Rotary B-2 C-1 Kaz a AC2 Cypre SIX WIRES * m C-A سم is 118 S C-2 A-1 3 Phase primary transmisline. 121 3Phase Secondary to Rotary. A-2 C-2 B-2 B-1 A-1 A1 C-1 122 m 3 Phase primary transmis line S' 522 SECTION IV.-POWER STATION. ; 6 Phase Secondary to Rotary. 123 A-2 B-1 124 لس 125 127 ww A-B a-b ping many my In A-B ри ar B-2 C2c1 b1 A-1 b-2 C-1 A1 a2 c2 C-2 A-1 3Phase primary transmis line. Phaseprimary transmission line 6 Phase Secondary to Rotary 42 6-2 B-1 c1 B-2 C-2 C-1 b-1 hm time arb hmm hm C-A .866T ww ww +--- AC www hw be üümüzümününnung www ---V- C-1 ww B-C 2. Phase Secondary to Rotary. A-2 B-1 B-2 3 Phase primary transmission line. 6Phase Secondary to Rotary. A-2 B-2 B-1 C-1 a^2 -8661 ww -Y-- ——-—--- a-c لسا A-C лим T- ·866V--- www. A B-1 3 Phase Secondary to Rotary A-2 C-2 B·A·C fun *V →→½½V- C-A B-A-C www C-1 b-1 C-2 C2 a-2 A-1 0-1 ·~~~T~~~ 2 Phase primary transmission line. ← { √ ~ ~ ~ ~ { V ~ ~ + mhm لسا B риту . B-2. A-1. ww c-a. (7) 2 Phase primary transmission line. (ne • Figs. 123 to 127. #K₂V ++YEV www b-a-c mmmy 0-1 C-2 126 Connections for Rotary Converters. ELECTRIC GENERATORS. 523 Polyphase Transformers. Transformers for polyphase circuits may be either compound-wound poly- phase, or plain single-phase. European firms manufacture two and three-phase transformers; this practice is seldom followed in America. Polyphase trans- formers usually have as many magnetic circuits as there are phases, the flux in which follows the same course as the flow of current in the corresponding conductor. American engineers use an appropriate combination of single-phase trans- formers for all the commercial polyphase systems. This arrangement has the advantage of not being rendered entirely inoperative by damage to one trans- former. The remaining uninjured transformer or transformers can frequently maintain continuous, though possibly crippled, service. PRIMARY Three-phase Transformer Connections. (FIGS. 128 to 133.) The following figures show diagramatically the ratio of pressures between various parts, the ratio of transformation being supposed to be 10: 1. 128 129 130 PRIMARY 132 PRIMARY Horse-power Capacity of Motors. 1235 7 10 15 20 30 50 - 75 100 1000 1000 1000 1000 1000 1000 1000 ·1000 1000 10.0 15.0 25.0 √3 (Oudin.) 173 √3 Kilowatts each. 0.6 1.0 2.0 3.0 4.0 5.0 7.5 Three-Phase. 100√3-173 100 700 3.5 5.0 7.5 10.0 15.0 25.0 30.0 100 SECONDARY (656) Figs. 128 to 133. Three-phase Transformer Connections. Table 48.-Capacity of Transformers to be used with Two-Tand Three-phase Induction Motors. -100√3-173 100 √3-773 SECONDARY 100-58 131 100 700 3-58 #58 √3 √3 ´SECOND 133 Two Transformers. Three Transformers. Two Transformers. Kilowatts each. Kilowatts each. 0.5 0.6 1.0 1.0 1.5 1.5 2.0 3.0 2.5 4.0 5.0 7.5 10.0 15.0 25.0 35.0 45.0 ARY Two-Phase. 6,5 ! --- 1 SECTION V. *** THE POWER STATION (Continued). SWITCHBOARDS. 19 SECTION V. THE POWER STATION (Continued). SWITCHBOARDS. GENERAL. The entire energy of an electric supply station is controlled at the switchboard. Current from the various generating plants is all led to the board, and thence dis- tributed to the outgoing feeders, which in their turn supply the districts served by the system. Usually the board contains two or more common conductors, or "bus-bars," which receive the current from the generators, and from which the feeders, also in parallel, derive their supplies. The switchboard must contain provision for connecting any generator or feeder to the bus-bars, and disconnecting it at will. The bus-bars are often made in sections or duplicated, so that, if desired, certain generators and feeders may be connected together independently of the rest of the plant. Automatic devices to isolate any part of the system in the event of dangerous conditions are necessary, and instruments must be provided for indicating the voltage of supply, the current given by any generator and taken by any feeder. Regulating apparatus for controlling the generator voltage, and instruments for paralleling or synchronising the generators before putting them on to the bus-bars are necessary. Recording instruments for voltage, current, and power are often fitted. The failure of a switchboard paralyses the entire system of electrical supply, and, moreover, may be highly dangerous to life and property. Hence the utmost care is needed in the design. It is better to aim at extreme simplicity, and thus to minimise chances of failure, than to devise complicated ways of dealing with possible occurences. A simple board gives the operator the least number of oppor- tunities of making mistakes, and in cases of emergency this is no small considera- tion. The general appearance of the board should clearly indicate the general arrangement of circuits; all instruments should be in full view of the operator when he is carrying out any manipulation, and whatever occurs he should feel confidence in his apparatus that no harm can possibly happen to him personally. The possibility of fuses blowing under his nose, or of his getting a shock, will dis- tract his attention from the work in hand, often at a juncture when coolness is most imperative. After the safety of the operator the most important feature is the prevention of damage by fire. To provide against fire the board should be entirely of incombustible material. Inflammable cables and insulation should be completely absent, and nothing liable to burn be allowed in the neighbourhood of the board. Fireproof cables are now a commercial article, and all connections on switchboards should be made either with them or with bare copper bars. Where oil devices are used, as on high-tension alternating boards, the possibility of the oil becoming alight must not be overlooked. Materials of Construction. 19 The materials in universal use for the construction of switchboards are slate or marble. The face of the marble is polished, and that of the slate enamelled black, either giving a handsome appearance to the board. Before using, the materials should be tested for the presence of metallic veins by "flashing,' i.e., the momentary application of a voltage, perhaps three times the working voltage. Slate is particularly liable to contain such veins, and has on the whole lower insulating properties than marble; hence it is good practice to bush 528 SECTION V.-POWER STATION. bolt-holes, &c., with ebonite. Before enamelling, slate should be well baked to drive out all moisture. In boards used for high-tension work no live parts must be in contact with the slate; the fittings being fixed in porcelain insulators, and the latter into holes in the slate by sulphur compound or other suitable insulating cement. Single-, double- and triple-flanged insulators glazed, except where in contact with the cement, are made for the purpose, and ample leakage surface should be allowed, bearing in mind the possible presence of dirt and moisture. Porcelain insulators should not depend on the glaze for insulating properties; but the body of the material, with glaze removed, should be entirely non-absorptive, the glaze being merely for cleanliness. The quality of porcelain insulators and other fittings of the same material varies greatly. They should be submitted to a flash test of four times the working pressure, and a "condenser" test of at least twenty minutes with double the working pressure before using. The system of testing insulators, adopted by one of the leading switchboard makers, is as follows. The insulators are "flashed" at voltages of 15,000 volts, 20,000 volts, and 30,000 volts, according to whether they are of the single-, double- or multi-flanged type. Provided they bear this satisfactorily, they are filled with salt water and stood in a tank of the liquid, and the test voltage above applied for half an hour. When this is impossible on account of the insulators being tubular, the inside is filled with lead shot and the outside wrapped with tinfoil, and the test pressure applied as before. If the insulators are bad, they heat up and even crack, any which show appreciable heating being discarded. The tester immediately on applying the "flash" test will often be able to judge whether the insulator is likely to fail, and if so, it may then be withdrawn before destruction and used for a lower voltage. A good insulating porcelain, as a rule, shows a vitreous fracture when broken, which feels cold to the tongue. Inferior qualities have a dull absorbent surface. All porcelain is liable to great shrinkage and warping when baked in the course of manufacture, more especially the better qualities. For this reason articles should be of the simplest possible shape: circular preferably, as box-like articles with flat surfaces, particularly in large sizes, are costly and often unsatis- factory. Metal fittings carrying current should be of pure forged copper. Castings of pure copper are rarely sound, while alloys, such as gun-metal and brass, have to be of two or three times the sectional area to obtain the same conductivity. Stamped and forged fittings for electrical purposes can now be readily obtained from copper works in this country. The bus-bars should be built up of flat copper bars, bolted together to get the necessary area, each not more than in. in thickness. It is good practice to space the separate bars by distance-pieces, as good ventilation is thereby ensured and eddy currents minimised. A further advantage of spacing consists in the greater ease of making connection between the bars and shunts or other fittings, and a built-up bar may obviously be increased or reduced in section at any part with little trouble. Bolts are preferably of mild steel, though often made of brass, both for appearance and conductivity; copper bolts being weak mechani- cally. All bolts in connection with alternating-current bus-bars should be fitted with lock nuts, or other device, on account of the vibration. The current density in bus-bars and copper fittings is of the order of 800 amperes per square inch. Where plenty of cooling surface is exposed to the air in comparison with the cross- section of the metal, this figure may be exceeded, particularly if the ventilation is good. Cast copper and gun-metal should not be worked at more than half the above density. At contact joints 300 amperes per square inch should not be exceeded, and these must be fitted with great care if they are to remain cool in working. The conductivity of any joint or fitting may most easily be tested by putting through it a heavy continuous current, and measuring the voltage drop across it, when the working temperature has been reached, by means of a milli- voltmeter. The product of volts x amperes is the energy degraded into heat at the joint. The heat losses at joints on a switchboard are infinitely more serious than the losses in the conductors themselves, and it is useless to specify low- current density in the latter unless the density or the watts lost at the joints be also specified. Complete switchboards should be tested at three times the working pressure, the voltage being applied between all parts of opposite polarity, and between live parts and earth. The test voltage should be kept on from fifteen to thirty minutes. Low-tension switchboards, i.e., up to 600 volts, should be also tested with an Evershed or similar ohmmeter, having a generator giving 1000 volts. For a whole board the resistance should not be less than 2 or 3 megohms, though it may be as high as 10 to 20 megohms on a well-constructed board. SWITCHBOARDS. 529 Location of Switchboard. The position of the switchboard in the engine-room is of considerable import- ance as regards convenience in working. It is best placed on a raised platform or gallery, so that the operator has a full view of the machinery. Perfect dryness and cleanliness are essential, and no steampipes should be carried near it, on account of the heat and possibility of leakage of steam. The board should not be placed so as to obstruct light from windows, nor yet where light can be reflected from the faces. of the instruments, rendering them difficult to read, although a well-lighted position is of the greatest importance. The position should be chosen, bearing in mind the possible extension both of the board and of the engine-room. Classification of Boards. The appearance, arrangement, and equipment of switchboards vary very widely, according to the purpose for which the switch-gear is designed. Even for the same duty the practice of different makers diverges so largely that it is evident that finality is far from being attained. Whereas other plant in the power-station is. developing along more or less clearly-defined lines, switch-gear, particularly for high tension, is in such a state of evolution that it is not altogether easy to foretell which types will survive. After securing the highest degree of safety to the operator and the system, the object of the designer is to render the board as self- explanatory and easy to work as possible. For this reason, the apparatus belonging. to every generator and every feeder circuit, respectively, should be on a panel by itself. The generator panels should be distinct from the feeder panels, and every panel labelled with the name of the circuit it controls. The simplest arrangement of board is that in which all generators and feeders are put in parallel on one comnion: set of bus-bars. Every panel should be capable of isolation from the bus-bars at will, by means of plugs or disconnecting switches. Simplicity should be aimed at in everything, as complicated cross-connections and interlocking devices cause. more trouble than they prevent. If the operator has only one way of making his connections the chances of mistakes will be as few as possible. For descriptive purposes switchboards can, perhaps, best be dealt with accord-- ing to the classes of circuits they control. In this country 25,000 volts is probably the limit of practical voltage, while 12,000 volts cannot be economically exceeded for underground transmission. Switchboards for controlling voltages above 3000 may be classed as extra high tension (E. H. T.), from 3000 to 600 as high tension (H. T.), and below 600 as low tension (L. T.). E. H. T. and H. T. circuits are practically, without exception, alternating current, of either single, two, or three phase; while L. T. circuits are either alternating or continuous: the large number of tramway systems being, of course, entirely worked by L. T. continuous current. Extra High-Tension Boards. For extra high voltages the greatest possible precautions must be taken in design. The general tendency is to control the switch-gear from a distance, so that all E. H. T. live parts are well out of reach of the operator. Instruments. are worked from the low-tension side of small current and potential transformers. built for the purpose, so that no high-tension parts are present on the operating board, all metal work and fittings there being, in fact, connected to earth. The E. H. T. switches themselves are often totally enclosed in separate brickwork or soapstone compartments, behind, above, or below the board, and worked from the front of the board by a system of levers, or pneumatic or electrical means. Whatever method of operating the switches is adopted, the latter should break the circuit under oil which extinguishes the arc at the zero value of the current, and sets up much less strain on the insulation of the cable than a break in air. A slow air-break causes electric oscillations to be set up in the cable which, when the arc reaches a critical length, synchronise with the impressed frequency, and cause the potential to rise to a value many times the normal. The advantage of remote control consists mainly in the sense of security it affords to the operator. On the other hand, "out of sight" is too often "out of mind," and the greater difficulty of supervision, together with the increased complexity, introduces increased chances of failure. The spacing of the panels, too, is often necessarily very wide, resulting in a board of great length. The remote control system of operating E. H. T. boards appears destined to stay, though possibly electric and pneumatic methods of operation will eventually give way to purely mechanical ones. Switch-gear may be so designed that the actual work of opening or closing any switch of even the largest size is well within the power of a man; and although electric or pneumatic power lends itself to a relay system of 530 SECTION V.-POWER STATION. automatic working as well as pernitting of a comparatively small operating board, it remains to be seen whether these features compensate for the introduction of the unavoidable complications. The switches themselves, however operated, should not be relegated to a cellar or otherwise more or less out-of-the-way place, but should be as near their handles as consistent with safety, and the whole of the gear perfectly accessible to and capable of supervision by an authorised person. The British Thomson-Houston Switch-Gear. (FIG. 1.) Fig. 1 represents the general arrangement of switch-gear for an E. H. T. three- phase system, as installed by the British Thomson-Houston Company. The operating board is on a raised gallery in the engine-house, aud carries nothing but low-tension apparatus, the E. H. T. circuits and switches being separated from the STATIC DISCHARGER CURRENT TRANSFORMER F11006): ISOLATING SWITCH \\FEEDER END BELL 3CORE CABLE AUTOMATIC OIL SWITCH Ann POTENTIAL TRANSFORMER CURRENT TRANSFORMER BUS BAR INSULATORS & CLAMPS GENERATOR END BELL 3CDRE CABLE POTENTIAL TRANSFORMER RHEDSTAT INDICATING INSTRUMENTS FIELD RECULATOR OPERATING SWITCH SWITCH GALLERY ENGINE ROOM Fig. 1. Switch-Gear of the British Thomson-Houston Company. operator by a brick wall. The drawing shows a section of the switch-room, in which the switches are arranged in a continuous line, the poles in the different phases being 16 in. to 18 in. centres throughout the line. All apparatus in the same phase is mounted in the same plane at right angles to the face of the board, which arrangement admits of the use of short straight connections, and of the insertion of barriers between circuits and between phases. As regards connections, each generator cable passes up the inner side of the wall through current transformers to the main switch, and thence through isolating switches to the bus-bars. The current for each feeder circuit then passes through a feeder switch, a current transformer, and isolating switch to the feeder-end bell. The last-mentioned isolating switch is a double-bladed switch serving to disconnect the static discharger. The current and potential transformers are for the purpose of supplying low tension current for the ammeters voltmeters wattmeters, and other instruments. SWITCHBOARDS. 531 The British Thomson-Houston Distance-Controlled Switch. (FIG. 2, below, and FIG. 3, page 532.) The electrically-operated, remote-control oil-switch illustrated in Fig. 2 is designed for exceptionally heavy work. There are two breaks per phase, and each phase is contained in a separate fireproof brick compartment, the top and bottom of which are formed of soap-stone slabs. Each single-pole element consists of two cylindrical vessels containing the oil and contacts. The cylinders are mounted in pairs on sliding-plates, so that they can readily be withdrawn. Connection is made between each pair of vessels, which form a single-pole element, by a U-shaped copper rod, the legs of which make and break connection with the contacts under 1049 Fig. 2. The British Thomson-Houston Distance-Controlled Switch. oil. Mounted on the top slab is the operating mechanism, which consists of a motor driving a worm gear, which transmits the motion to a crank and crosshead through a friction clutch. At both ends of the stroke the crosshead compresses a spring, which, as soon as the crank passes the centre line, instantly throws the crosshead to an opened or closed position, depending upon whether the switch was at the time closed or open. The friction clutch permits of this rapid movement as the pawls hold the disc from moving against the normal direction of rotation, while permitting it to move freely in the direction of rotation. The crossheads and contact rods are connected together by wooden rods, which provide for the mechanical movement, and also thoroughly insulate the different poles. The motor is controlled by means of a single-pole, double-throw, hand-operated switch, one throw being used to open, and the other to close the oil-switch; and in addition, an automatic switch is mounted on the base. When the hand-operated switch is thrown, the motor starts and runs until the crank has arrived at a 532 SECTION V.-POWER STATION. 1015 O 122 PIVOTED TO FRAME RED IND LAMP Holl Switch closed) CLOSING CONTACT FREE-WHEEL CLUTCH Fig. 3. Motor-Gear for E. H. T. Switch. OPENING CONTACT GREEN INDE LAMP Oil Switch open) 125 VOLT CIRCUIT Fig. 4. Form OK Oil-Break Switch. (Open and Closed by Hand.) SWITCHBOARDS. 533 certain position, when the automatic switch opens the motor circuit and lights a lamp, which informs the switchboard attendant that the switch has operated. The arrangement of mechanism is seen in perspective in Fig. 3, which shows the switch open, and also gives the diagram of electrical connections to the operating motor, indicating lamps, &c. These switches can be made automatic by means of relays, which close the motor circuit on a predetermined condition of load. The relays can be made to operate instantaneously on an overload or short circuit, or on reversal of current. A time-limit attachment can also be added. British Thomson-Houston Oil-Break Switches. (FIG. 4, page 532.) Fig. 4 shows a triple-pole oil-break switch for E.H.T. and H.T. circuits, as manufactured by the British Thomson-Houston Company. It is designed for opening and closing by hand, although the addition of a tripping device converts it into a circuit-breaker to open the circuit automatically, under such condition of overload, underload, no-voltage, or reverse current, as may be required to be guarded against. These switches are mounted at the back of the panel, as shown, or at a distance, in which case they are controlled by a system of rods and levers. The handle alone projects through the front of the panel. Each pole is double- break, and when the containing tank (not shown in the illustration) is in place, the clips, contact-pieces, and all exposed live parts are completely submerged in oil. No leads enter the oil tank, which might cause leakage and hinder the easy removal of the tank. The tank contains insulating division plates, which separate the poles. Switches of this type, in various sizes, are designed to rupture, under emergency conditions, loads up to 20,000 kilovolt-amperes. Above 4000 kilovolt- amperes and 3000 volts, they are not, as a rule, mounted directly on the panel. The Electrical Company's Switch-Gear. (FIGS. 5 to 9, pages 534 to 536.) The latest design of E. H. T. switch-gear, by the Electrical Company, is shown in Figs. 5 and 6, the diagram of connections being as given in Fig. 7. The illustrations represent a generator panel and a feeder panel of a central station board for three-phase work up to 10,000 volts. The generator panel is marked A, and comprises :- 1 Three-pole double-break oil switch with tripping device ; 1 Deadbeat edgwise induction voltmeter With voltage and current trans- 1 wattmeter 22 "" "" formers; 1 ammeter 3 Maximum-current time' relays, with current transformers to open the main switch at a predetermined overload; 1 Maximum and reverse-current time relay, worked through voltage and current transformers, closing a local accumulator circuit through the tripping coil; 1 Phase indicator; Synchronising plugs, etc. The whole of above is mounted on a carriage a carriage running on wheels, and connected to the bus-bars through plug contacts so arranged that the carriage cannot be withdrawn unless the circuit has been first broken by the oil switch. În front of the panel is a column from which the resistances for regulating the generator and exciter fields are controlled. An ammeter in the exciter circuit is also mounted on this column. The feeder panel, marked B, is of the same general type, the moveable carriage containing the following apparatus :— 1 Three-pole double-break oil switch; 1 Deadbeat edgewise induction ammeter; 1 Integrating wattmeter; 3 Maximum-current time relays worked through transformers. On the upper gallery are shown three lightning arresters of the cross-horn type, with cut-out link, mounted between slate partitions; a three-pole water resistance, and a choking coil for each phase. Transmission lines are carried out through a special pipe in the station wall. 534 SECTION V.-POWER STATION. 14. 15- 9- (1033) 12 13 16 =000" X 21 20 17 22 A (10) Hot 14 15 (1034) 000 000 14 20 15 887 7 21 B Figs. 5 and 6. E. H. T. Switch-Gear of the Electrical Company. SWITCHBOARDS. 535 6 |3| 4|5| (1036) 7-16 H 12 {12 44416 14. 2 9 7 17 Holladay 23 puque 13 5 127 1-16 19 2 19 12 4441-16 12 210 21 21 21ª 21 @ 20 mmmmun Fig. 7. Diagram of Three-Phase Generator and Feeder-Panels of the Electrical Company. 536 SECTION V.-POWER STATION. 1 Figs. 8 and 9 show a three-phase double break E.H.T. oil switch, with a capacity of 200 amperes at 15,000 volts, designed by the Electrical Company for use on draw-out boards. It is mounted behind the face of the board, and operated by a hand-wheel projecting through the board. It may easily be adapted for distance control by the provision of a chain and sprocket gear. The switch is quick-break the action being as follows: The link A holds the switch in a closed position against the pressure of two spiral springs B. When switching out, as soon as the link A passes the dead KOON! FA q ada dalam me 7 7734" AAA 1 3' 6 I Figs. 8 and 9. E. H. T. Oil-break Switch. (The Electrical Company.) centre, the springs force the contacts C suddenly apart. The lower contacts are carried by insulators mounted on a longitudinal rod, and bolted at the same time to a wooden case D, in the bottom of which are holes E. When the switch opens the wooden case is forced downwards through the oil, causing the latter to rush up through the holes E and extinguish the arc. The oil container may be easily removed for renewing the oil or inspecting the contacts. If the switch is required to open automatically, a small solenoid is mounted over the spindle where it leaves the case, the armature of which when raised releases the switch. A button on the end of the spindle also allows the tripping mechanism to be actuated by hand. The hand-wheel works loose on the spindle when the tripping device is in action, so that it is impossible to close the switch on a short circuit. SWITCHBOARDS. 537 TELL TALE LYO TELLTALE IND GIL SW. PLACE IND OIL STY The Westinghouse Remote Controlled Board. (FIGS. 10 and 11, pages 537 and 538.) The Westinghouse remote control boards are either of the flat-back type, or may consist of individual control stands and keyboards. Boards of the former type are similar to the Westinghouse hand-operated boards, and consist of slabs of marble with bevelled edges, containing the necessary apparatus and instruments. 17009) Of TELL TALE UND DIE SK SKR SYN. PLUS AND RECP → WLİSNĚCH GRİTRİN ENGINE SYM PLUG, ↑ AND RECPT! THES. CONTRIR-CONTROLL. |300 AMP TYPE C FIELD DIS \CHARGE S 4:9 # 1764 Fig. 10. Westinghouse Pillar-Board for Distance Control. Each panel consist of three slabs arranged vertically, and supported by a rigid iron One panel is always. framework, braced to the station wall and bolted to the floor. installed for each machine circuit, and one panel for each one or more feeder circuits. The switches and instruments are mounted directly on to the marble. The connections are all on the back of the panel, the bus-bars being carried on porcelain insulators supported by iron brackets. The instruments are usually mounted on the top slab, the oil switches and circuit-breakers, field rheostats and switches, being operated by means of an auxiliary device controlled from the front of the panels by switches or push-buttons. 538 SECTION V.-POWER STATION. In the case of the second type of board, the instruments for each generator are mounted on an ornamental iron stand, these stands forming supports for the platform handrails. At the back of the platform is a marble board containing the instruments for the feeders and auxiliary circuits generally. The controlling switches and other operating appliances are located on the central space of the platform. This apparatus may be mounted on a single bench board, or arranged on separate stands, as shown in Fig. 10, each stand containing the apparatus for a single circuit. The main-circuit switches, field switches, rheostats, etc., themselves are suitably located in some convenient position. The apparatus for the exciter and station auxiliaries is usually hand-operated, and arranged on flat-back boards in close proximity to the control desks. Fig. 11 illustrates a three-pole, double-break, electrically-operated automatic OMONTAN 1010 O Fig. 11. Westinghouse E. H. T. Three-Phase Switch. oil circuit breaker. This piece of apparatus is also supplied without the magnets, and operates as a non-automatic oil switch, in which case a hand-lever is furnished. The switch is erected in a masonry structure with each pole of the switch, and the oil tank in which it is immersed in a separate fireproof compartment. There are two stationary main contacts per pole, one connected to the incoming lead and the other to the outgoing lead of the same phase, each contact being mounted within a large porcelain insulator. These insulators are mounted SWITCHBOARDS. 539 on a cast-iron frame, which forms the top and supports the enclosing oil tank. In the switch illustrated there are three frames, each fastened in a separate compartment, by means of strain insulators, to the under-side of a stone slab, which is placed on top of the cell structure and under the cast-iron base of the operating mechanism. There are two breaks in series for each pole of the switch, each pole being in a separate compartment. The stationary main contacts are each fitted with a removable arcing plug, which enters a hole in the movable main contact. Contact between this plug and the movable main contact is broken after the main fixed and movable contacts are broken; hence all arcing, whenever any occurs, takes place on the plug, which can be removed and replaced when worn out. Current for the closing and tripping magnets is derived from the exciters, a storage battery, or other convenient source of low voltage direct-current supply. In case of failure of the operating circuit, the switch can be easily operated by hand, without in any way disturbing the mechanism. The oil tank is constructed of a top and bottom casting, and heavy sheet-metal sides. This tank is held in place to the under-side of the frame casting which carries the stationary main contacts. The interior of the oil tank is lined with insulating cement, which is moulded in such a form as to fit closely about the terminals and moving contact piece, leaving just room enough for free movement of the parts in the oil. By this means the amount of oil is reduced to a minimum, thereby reducing the fire risk. Mounted on each switch is a small double-pole, double-throw knife switch. This switch is operated by the motion of the levers of the oil switch, and is used for operating the indicating devices on the controlling-bench board. The control switch and the indicating devices, comprising a tell-tale indicator and lamp, form part of the outfit. A polyphase overload relay, connected to series transformers in the main circuit, is provided for automatic tripping. Westinghouse Electrically-Operated Field Rheostats and Switches. (FIGS. 12 and 13, pages 539 and 540.) Figs. 12 and 13 illustrate respectively the standard Westinghouse motor-operated generator-field rheostat, and the electrically-operated generator field switch, such as are used in the case of large installations employing remote control. 1011 Fig. 12. Westinghouse Generator Field Rheostat. (Electrically operated.) 540 SECTION V.-POWER STATION. The generator field-rheostat face-plate shown above is designed to be operated by an electric motor, which can be controlled at a point distant from the rheostat. The face-plate is mounted vertically, and the motor is connected to the contact arm by suitable gearing. The motor is controlled by a small controller located on the controlling-bench board. A cut-out switch, which is included in the face-plate, is provided to open the motor circuit when the rheostat contact arm assumes either of the limiting positions. The resistances can be located in any convenient position relative to the face-plates. t 90 1012 Fig. 13. Westinghouse Electrically-Operated Field Switch. The switch illustrated above is arranged to be opened and closed by magnets operated by a controlling switch, located at some point distant from the generator. This switch is double-pole, and when operating effects a clean and quick break of the field circuit. The are due to breaking the circuit is taken on carbon tips, which are clearly shown in the illustration; thus no damage, due to arcing, is done to the main contacts. The act of opening the main circuit closes a small auxiliary switch, which in turn shunts a resistance across the field winding. This allows the induc- tion discharge to die out gradually, and prevents any undue strain on the field insulation. The Cowan Extra High-Tension Switch-Gear. (FIGS. 14 and 15, pages 541 and 542.) The general arrangement of extra high and high-tension switch-gear, adopted by Messrs. Cowans is shown in Fig. 14. The cables from the generators or feeders are contained in separate fire-proof pipes in a subway, and are brought up through the floor, each opposite its main switch. Each then passes through a current trans- former, from the low-tension side of which all ammeters, wattmeters, etc., on that circuit are supplied, and then carried through the 9-in. wall at the back and SWITCHBOARDS. 541 connected directly to one terminal of the oil switch. Each switch is placed in a separate compartment, divided from adjoining compartments by 44-in. walls, and closed by an iron door. Each switch is mounted on a carriage, running on rails, not shown in the figure, so that it can easily be drawn from its contacts for in- (1013) MAA *SERIES AND DISCRIMINATING TRANSFORMERS ZAWAIIIIIIIIII BUS BARS AND PLUGS CURRENT DIRECTION INDICATOR LAMPS SWITCH OPERATING HANDLE AMME TER JOANSORY DISCRIMINATING RELAY Fig. 14. Cowan's E. H. T. Switch-Gear. spection. From the switch each lead is taken back through the wall and connected to its respective bus-bar, the bus-bars being in completely-isolated horizontal compartments. The operating face of the board can be placed above, or in any convenient position relative to the cells containing the switches, which are often arranged underneath the switchboard gallery. The main oil switches are of the type shown in Fig. 15, which represents a three-phase switch. There are two breaks per phase, and all live parts are com- pletely enclosed in the oil tanks, there being a separate tank for each phase. The contact pieces are operated by a toothed quadrant above, connected by levers and 542 SECTION V.-POWER STATION. Fig. 15. Cowan's E. H. T. Oil Switch. rods with the operating handle. The flanged wheels on which the switch runs are seen in the illustration. The automatic protective gear used in connection with these boards is dealt with on page 571. Dick, Kerr and Co.'s High-Tension Switches. (FIGS. 16 and 17, pages 543 and 544.) The E. H. T. oil switches, designed by Messrs. Dick, Kerr and Co., for hand operation and electrical distance control, are illustrated in Figs. 16 and 17. The switches are supplied either singly or in multiples to suit any number of phases, the illustrations representing them as arranged for three-phase circuits. Fig. 16 shows a pair of hand-operated oil switches, one switch being open and the other closed; in both cases the oil tanks are lowered so that the contacts may be seen.. The main terminals for connecting the cables are secured to vertical rods, which are highly insulated with mica sleeves and porcelain insulators with large creeping surface, as shown on the right-hand switch, Fig. 16. They are held in position by substantial insulators securely fixed to a cast-iron webbed plate (this SWITCHBOARDS. 543 can be better seen on the left-hand switch, Fig. 16, which shows the main terminals: removed). The webbed plate acts as a cover to the oil box which surrounds the switches, and is bolted to the cast-iron frame. When the oil-box is lowered, the copper jaws which depend from the vertical rods are clearly seen. The switch blade is carried horizontally in a heavy porcelain insulator and attached to the turned steel rod, which is secured to the upper end of the crosshead, guide rods and weight. When in use, the switches are entirely enclosed in the large oil-box, which can, when required, be easily lowered by means of the winch attached SKOCWIEK 303 Fig. 16. Dick, Kerr and Co.'s Hand-Operated Oil-Switch. to the frame. The oil-box is lined with impregnated material, and fitted with fireproof partitions consisting of marble or other suitable material for separating the various switches; it is also dust-proof and oil-tight, and is fitted with an oil-gauge by means of which the height of oil in the box may readily be observed. The top of the cast-iron frame is provided with columns for supporting the trip gear, weight, and horizontal crosshead, from which depend the vertical rods which are attached to the switch-blades. The trip gear is attached to a series of links which connect up through cranks to the operating handle mounted on the switchboard. To close the switch, the handle must be forced down until the spring bolt locks. This motion raises the weight and crosshead, and closes the trip gear and switch. The switch may be opened by withdrawing the spring bolt and raising the switch handle. On releasing the handle the trip gear, which has been already mentioned is immediately brought into action; the weight falls smartly on the crosshead, and throws the switch-blades out with a quick-break action. In addition to the ordinary operating handle each switch is provided with an emergency throw-out. This takes the form of a solenoid attached to the frame of the switch, the armature of which actuates the trip gear. The local circuit for operating the solenoid is closed by a small press-button switch placed immediately above the main switch-handle on the board. These switches may be fitted with automatic overload and no voltage release. Fig. 17 is an illustration of a special type of oil-break switch used for larger work; it is similar in design to the foregoing, but is operated by a motor. This does away with the link and crank gear which connect the switch with the switch- board. 544 SECTION V.-POWER STATION. In place of the switch handle on the board are placed two small press-button switches marked "On and Off." These are joined up by clockwork, and relay through a local circuit which starts and stops the motor. The motor is provided 11 Fig. 17. Dick, Kerr and Company's Motor-Operated Oil Switch. with a fly-wheel and gearing, the gearing actuates a vertical rod which engages the trip gear for releasing the weight placed above the switch frame. The motor and gearing are made in the most compact form, and fitted neatly under the switch frame, while the clockwork and relay are fitted at the back of the switchboard behind the press-button switches. High-Tension Boards. (FIG. 18. page 545.) The second class of boards, controlling circuits from 600 to 3000 volts alternating pressure are intermediate in construction between E.H.T. and L.T. alternating-current boards. The instruments are sometimes connected directly to the mains, and sometimes worked through transformers, the latter method being generally considered advisable as in E. H.T. practice. Oil-break switches should be adopted, especially for currents over 100 amperes, although distance control is not So necessary as in the case of higher pressures. The Ferranti cellular board, shown in Fig. 18, has met with very great favour in this country. In this type of board the dangerous space found at the back of ordinary boards SWITCHBOARDS. 545 is absolutely non-existent, cable connections are entirely absent, and as each piece of apparatus is mounted in a separate cell, the maximum safety both to operator and apparatus is secured. It is also extremely compact; and further it is claimed that its operation has never been attended with a fatal accident. On the other hand it is a comparatively costly board to build, and must he erected with the greatest exactness. Its cellular construction is ill adapted for ventilation, and when heavy currents are dealt with, the large number of plug EN SYNCHRONIZEA VOLTMETER INSTRUMENT 75n3 METER III FUSE STARMETER FIELO SWITCH 4 FEEDERS 4 MACHINES 4 FEEDERS SPINDLETO REGULATING RESISTANCE Q 8 6 9 1217 (148) Fig. 18. Ferranti High-Tension Switchboard, Cellular Type contacts on it cause a considerable temperature rise if the fitting is not extremely good. On the Ferranti board it is the general practice to use electrostatic volt- meters connected directly across the bus-bars. Edgewise ammeters on the "soft iron" principle, in which a piece of laminated iron is attracted into the field of a coil energised by the main current, are fitted, having ambroin cases. Knife- switches, or oil-break switches are supplied, according to the current to be dealt with. Fuses, when fitted, are of the Ferranti oil-break type, and are usually arranged with two pairs of contacts in parallel, so that a fuse may be temporarily T 546 SECTION V.-POWER STATION. inserted in one pair previous to withdrawing the other fuse for examination or other purpose. A small hanging contact is fitted in the upper slate of each of the switch compartments of the generator panels. Before the switch is closed it touches this contact, which connects the incoming machine to the synchronising apparatus, and not until the correct phase relation has been attained is the switch closed. The auxiliary synchronising contacts are connected to a common synchronising bar (or pair of bars for a two- or three-phase system), so that the same synchroniser and machine voltmeter are used for every incoming machine. This is obviously an improvement on the method of using as many synchronising transformers and machine voltmeters as there are generators. For H.T. continuous-current boards, oil-break switches and fuses cannot be used on account of the danger caused by such a sudden rupture of the circuit. The method of blowing out the arc, by causing the contacts of the switch to separate in a strong magnetic field, is often adopted both for H.T. and L.T. continuous currents; while for continuous currents at over 600 volts, the arc may be formed between the adjacent parts of a pair of diverging horns, up which it will run until it becomes of such a length that it can no longer support itself, when it goes out. Switches fitted with horns at the top of the board for this purpose, are in use at Hull on a 2000-volt continuous circuit. Experiments have been made which show that the efficiency of horn-break switches depends greatly upon the class of load to be broken. There seems a particular length, shape, and angle of divergence best suited to each particular load, though in general it appears that horn-break switches are unreliable at voltages below 600, and act better the heavier the current to be broken. Low-Tension Switch Gear. The ordinary flat-backed board is practically universal for pressures up to 600 volts, and is likely to remain so, as it fills all requirements. Such a board consists of an assemblage of slate or marble panels, 1 in. to 2 in. thick, mounted on a skeleton framing of angles or tee iron. The framing is held vertically, about 3 ft. or 4 ft. in front of a wall, to which it is stayed by tie-bolts, and is also fastened to the floor. Doors are sometimes fitted to prevent unauthorised access to the back, but are in most cases unnecessary. All ornamental wooden cornicing and similar inflammable decorative work, often met with in boards of this type, should be avoided, as being a needless source of danger from fire. Between slate and marble panels there is little to choose. Slate is better mechanically, and cheaper, and is not liable to be stained by oil; but marble has advantages from the electrical point of view. For L.T. work the controlling apparatus and instruments are mounted directly on to the slate or marble. Great attention should be paid to the simplicity and straightforwardness of the arrangements behind the board. No cables should cross the back of the board horizontally, and the incoming or outgoing cables should be as straight and open to inspection as possible. The latter consideration depends very largely upon the relative positions of the board and the apparatus controlled, and should not be overlooked in deciding upon them. Iron framing, as well as any handrailing, &c., near the board, should be well earthed. The framing, where immediately accessible, is sometimes covered with insulating material to prevent accidental short circuits between the apparatus and the frame, by the careless use of tools by a person working behind the board. This precaution is, however, of little use, unless means are also provided to prevent similar short-circuiting of the poles. For this purpose the poles may be divided by barriers; or all positive panels may be placed at one end of the board, and all negative panels at the other. The latter arrangement, though not uncommon, is liable to cause mistakes on the part of the operator. Bus-bars are generally carried by porcelain insulators held in cast-iron fittings. The bars may be either side by side, or one at the top, and the other at the bottom of the panel, the latter arrangement being preferable. They should be built up of in. copper strips, with air spaces between the strips, and the current density should not exceed 800 amperes per square inch. Very great attention should be paid to the question of low resistance at all connections. Switchgear Diagrams. Every switchboard controls a number of separate circuits, each complete in itself, and will usually contain in addition certain instruments and apparatus common to all the circuits of each class. To avoid the reproduction of the SWITCHBOARDS. 547 diagrams of connections of a number of entire boards, the principal circuits will be considered separately, and their diagrams given, so that by combining those relating to any system a complete diagram may be built up. The instruments, &c., usually fitted will be shown on the diagrams, and reference made in the text to certain possible variations. It is understood, whether indicated or not in the diagrams given, that alternating instruments and relays may be worked through instrument trans- formers; that circuit-breakers may often be replaced by fuses; that continuous- current ammeters, &c., may be worked from shunts; that auxiliary circuits for relays may be excited from any convenient source. Moreover, the shunt circuits of wattmeters and circuit-breakers are not shown in the diagrams. Three-Phase Generator Panel. (FIG. 19.) This contains: R.R 1 TB.R.C.B 2 (1018) A) PELA IN MAIN ୨୪୪ 88 NIR E IW BUS BARS SYNCHRONIS* BARS D.PF.S -SPEFS woor -WW- NIR Fig. 19. Three-Phase Generator Panel. S S. 1 section of three-phase bus-bars (1, 2, 3.). 1 section of synchronising-bars. 2 alternating-current ammeters (A.). 1 power-factor indicator (P.F.I.). 1 triple-pole reverse-current oil-break automatic switch (T.P.R.C.B.). 2 integrating wattmeters (I.W.). 2 pairs of synchronising plug-contacts (S.S.). 1 double-pole generator field-switch with non-inductive resistance (D.P.F.S.). 1 field-regulating rheostat (R.R.). 1 field-ammeter (A.F.). 1 single-pole field switch with non-inductive resistance (S.P.F.S.). The diagram of connections is as shown in Fig. 19. The power-factor ndicator is not necessary, and if the load is balanced one wattmeter and one ammeter only are required. In general, all alternating-current instruments will be worked from the low-tension side of instrument transformers; and sometimes 548 SECTION V.-POWER STATION. 1 the synchronising bars are also connected through transformers. Connection may also be made between the incoming machine and the synchronising bars as indicated in Fig. 20; a method generally employed in the Ferranti board. An indicating wattmeter is often included in the panel, and sometimes the integrating wattmeters are omitted from generator panels. The diagram shows a generator as excited by its own independent exciter. It is often convenient to be able to use any generator in the case of its exciter having broken down, and to enable this to be done the field windings are connected to a change-over switch, which will put them either across the terminals of their exciter or across a set of exciter bus-bars, on to which any of the exciters can be thrown in parallel. With independent exciters, the power dissipated in the regulating resistance can be much lessened by connecting the resistance in series with the exciter field in the case of shunt-wound machines (see Fig. 21), or in parallel with the field of series-wound machines, instead of in the armature circuit, as shown on the diagram, although the range of control of the generator is not so great. Large generators have usually a resistance in series with both generator fields and exciter fields. The connections of a three-phase generator panel as arranged by the Electrical Company, will be seen in Fig. 7, and the instruments are enumerated on page 533. If the load is not known to be balanced, three main ammeters are fitted; or, for the sake of cheapness, one may be fitted so as to be connected at will by a switch, to the secondary of any of the three current transformers in the respective phases. The maximum current relays for opening the main switch are not usually considered necessary on generator circuits, the reverse-current relay alone being used; or the latter may be replaced by indicating-lamps, leaving the attendant to open the main switch should it be advisable. The synchronising gear may be as in Fig. 20. The indicating wattmeter may be dispensed with. Sometimes an integrating wattmeter is supplied, and a power-factor indicator, but are unnecessary. Three-Phase Feeder Panel. The connections of this panel, on a board by the Electrical Company, are given in Fig. 7, and a list of the various instruments on page 533. With an un- balanced load, the remarks as to ammeters on the three-phase generator panel above apply. With a balanced load one maximum current-time relay only is required, and the integrating wattmeter, if supplied, need only be worked from one phase. The same current-transformer may be used to work all instruments in that phase. Cable-charging gear for long underground high-tension cables is sometimes used to charge the cable before switching on to the bus-bars. A description and connections of this are given on pages 584 and 585. Sometimes the lightning-arrester is omitted. Elliott Three-Phase Feeder Panel The following is a brief description of Messrs. Elliott Brothers' standard three-phase feeder panel, as equipped for a balanced load:— In addition to the usual switch circuit-breaker, with time-limit relay, or switch fuses, three instruments are installed-namely, ammeter, wattmeter, and wattless wattmeter. The ammeter and current circuits of the wattmeter and wattless wattmeter are worked off the secondary of a current transformer; while the volt circuits of the wattmeter and wattless wattmeter are operated from the secondaries of a three-phase step-down transformer. The neutral point resistance of the wattmeter is placed in the base of the step-down transformer, and only two wires are necessary for each wattmeter volt circuit. The instrument cases are made of metal, with black and nickel finish, and when erected they are connected to earth. The windings of the instruments are entirely insulated from the main circuit, and as the cases are earthed there is no possibility of accident to the switchboard attendant through the instruments becoming charged at high potential. The wattmeter is scaled to read the total output of the three-phase feeder; the wattless wattmeter reads total out of phase watts, and the ammeter gives line current. The ratio of the wattless wattmeter reading to that of the wattmeter gives "tan o," and hence, by reference to a curve, the power factor of the circuit 66 cos 4" can be readily obtained. The wattless wattmeter has a centre zero, and deflects to one side for a "lead," and the other side for a "lag." This instrument, SWITCHBOARDS. 549 therefore, enables the switchboard attendant to run rotary converters, synchronous motors, &c., in the most efficient manner, by altering the excitation until the watt- less wattmeter reads zero. These instruments are all spring-controlled and efficiently damped, and are provided with zero adjustment external to the case. If desired, a voltmeter may also be connected to the low-tension side of the three- phase transformer; if this be done, the panel is also suitable for use with a three-phase generator, or for measuring total output. These instruments are interchangeable, both electrically and mechanically. That is to say, if there are two or more sets for circuits of the same capacity, any three instruments may be coupled up together and will read quite correctly. Wattless wattmeters possess this great advantage over power-factor indicators, that they have the same controlling force as the ordinary wattmeter; whereas it is well known that power-factor indicators have no controlling force other than that due to the fields produced by the windings. Consequently, any rough handling or damage to the pivots not only impairs the sensitiveness of the instrument, but destroys its accuracy. Synchronous Motor-Generator Panel. (FIG. 20.) This panel contains: 2 3 3 A A (1025) RED SING NIR VI.A hmpmunt DPS SYNCHRONISER BARS THREE PHASE BUS BARS T.P.M.C.A wwwwx Section of three-phase bus-bars (1, 2, 3). Section of synchronising bars (S.B.). Section of exciter bars (+, −). R R EXCITER BARS Fig. 20. Synchronous Motor-Generator Panel. 1 alternating-current ammeter (A.). 1 power-factor indicator (P.F.I.) 1 triple-pole automatic overload and reverse-current, cut-out switch (T.P.M.C.B.). 1 continuous-current ammeter in motor field (A.F.). 1 regulating resistance in motor field (R.R.). 1 double-pole field switch with non-inductive resistance (D.P.S. & N.I.R.). 550 SECTION V.-POWER STATION. 1 The diagram of connections is given in Fig. 20. The triple-pole switch as shown will make contact with the synchronising contacts before closing the main circuit, which is not done until the synchronous motor has been run up to synchronism by the direct-current machine coupled to it. These auxiliary-syn- chronising contacts are generally adopted in boards of the Ferranti type, but an alternative arrangement is to connect a pair of leads from the incoming machine to the synchronising bars by removable plugs, as shown in Fig. 19. The exciting current may be taken from the lighting bus-bars of the station, but if taken from a three-wire system, it is advisable to have a throw-over field switch, so that the field may be excited from either side of the system at will. Single-Phase Generator Panel. (Fig. 21.) A single-phase generator panel, with insulated outer, contains:- 1 section of main bus-bars (1, 2). 1 section of synchronising bars (S.B.). 1 alternating-current ammeter (A.). 1 double-pole automatic reverse-current circuit-breaking switch (D.P.R.C.B.). 2 D.P.R.G.E D.P.F.S. SP.EFS 1026 A (00000000 ww N.I.R. E oooooo www N.I.R. www.www S.B S.B. 5.5. R.R. Fig. 21. 2 pairs of synchronising plug-contacts (S.S.). 1 double-pole generator field switch, with non-inductive resistance (D.P.F.S.). 1 direct-current field ammeter (A.F.). 1 single-pole exciter field switch, with non-inductive resistance (S.P.E.F.S.). 1 field-regulating resistance (R. R.). Single-Phase Generator Panel. The diagram of connections is as shown in Fig. 21. An indicating wattmeter, an integrating wattmeter, and a power-factor indicator might be added, but are not necessary. The control of the excitation might be done by a regulating resistance in the field circuit of the generator, as shown in Fig. 20, instead of in the exciter field, as in the diagram. For large machines it is usual to have two regulating resistances, one in the generator field, and one in the exciter field circuit. Extra-high and high-tension single-phase systems are usually worked with the SWITCHBOARDS. 551 outer conductor earthed at the generating station. This is considered the best practice in England, though the insulated system, as shown in the diagram, is largely used abroad for overhead distribution. When the outer is earthed, the only switch is on the innér, the outer being bolted to the bus-bar by a link, which is only removed for testing purposes. One synchronising bar only is necessary, the synchronising winding of the synchronising transformer being con- nected between that bar and the outer main bus-bar. Instead of plugging the incoming machine on to the synchronising bar or bars, the main switch may be placed on auxiliary contacts, as shown in Fig. 20. Traction Generator Panel. (FIG. 22.) The apparatus on this panel includes:- Sections of bus-bars (+, −). Section of equaliser bar (E.B.). 1 main ammeter (A.). 1 reverse-current circuit-breaker (R. C. B). 3 single-pole switches: positive, negative, and equaliser (S.S.E.S.). 1 shunt rheostat (R.R.). 1 field switch, with non-inductive resistance (F.S.) 1 pair sockets for centre zero paralleling voltmeter (P. V.S.). Leeeeeeee A E.S ПR.C.B 15 15 3P.V.S G ތކތ TRA PR EB. :1031; игрит тоооты www F.S NIR Fig. 22. Traction Generator Panel. The connections are as in Fig. 22. The equalising switch is shown on the positive pole. This is the usual and better arrangement, though it is occasionally on the negative pole. In the latter case the circuit-breaker is on the positive. The single-pole switch, in series with the circuit-breaker, is advisable, but not absolutely necessary, especially where the circuit-breaker is fitted with a loose handle to prevent it being held in on a short circuit. The two main switches and the equaliser switch might be combined to form a triple-pole switch, but in that case the method of paralleling the generator shown could not be adopted. The 552 SECTION V.-POWER STATION. equaliser switch is very frequently fitted on a separate pillar close to the generator. An integrating wattmeter may be fitted in each generator circuit, or a wattmeter can be connected in the bus-bars to measure the total station output. The latter method is not recommended, owing to the inaccuracy of large-capacity meters at low loads. If the generator is driven by a synchronous motor, which has to be run up from the continuous-current system, a starting resistance will be required in series with the armature. An alternative and quite common method of paralleling consists in using a fixed bus-bar voltmeter and a paralleling voltmeter, plugged across the machine terminals, the two being sometimes combined as a double-scale voltmeter. Traction Feeder Panel. (Fig. 23.) This panel contains the following apparatus, the connections of which are shown in Fig. 23. 1030 *KM.C.B. A 1 single-pole switch (S.). 1 kicking coil (K.C.). 1 lightning arrester (L.A.). 000000 K.C. L.A. -TO EARTH 'TO LINE Fig. 23. Traction Feeder Panel. 1 overload automatic circuit-breaker (M.C.B.). 1 ammeter (A.). The single-pole switch can be discarded if a loose-handled circuit-breaker is employed, but this is not advisable. Reversible Boosters. (FIG. 24, page 553.) It is becoming increasingly common in continuous-current traction systems to employ batteries, either at the generating-station or at sub-stations, connected in parallel with the generators, to steady the load on the latter. Owing to the fact, however, that the voltage of the battery varies considerably with its state of charge, and also falls when a heavy current is demanded, a booster set is provided in series with the battery to compensate for this. The function of the booster is to supply the deficiency of the battery pressure on discharge, so that the battery may feed the system at full voltage; and also to charge the batteries when the demand for current is small, thus maintaining a constant load on the generator. The reversible booster enables the batteries to be worked at their one-hour rate of discharge, or even higher for momentary peaks, so that a smaller battery can be used, or the output of a given battery largely increased. The action of the Highfield booster is as follows:-The combination consists of three machines-booster, motor, and exciter. The battery is in series with the SWITCHBOARDS. 553 booster armature, so that all current passes through the latter, whether on charge or discharge; and it is arranged to correct for any and every variation in pressure given by the battery. The booster is excited by a shunt coil (A), Fig. 24, capable of giving a maximum boost on charge of 120 volts for a 500 to 550 volt machine. The exciter is a small generator arranged to give any pressure between 500 to 550 volts, one pole of which is connected through the booster shunt coil to the battery terminal of similar polarity. The other pole of the exciter is taken direct to the other pole of the battery. Thus, the exciter is connected through the booster shunt-winding across, and in opposition to, the battery. So long, then, as the battery voltage is the same as that of the exciter, the two pressures will balance each other, and no current will flow through the booster shunt-field; but should the cells be called upon to discharge, the pressure across the terminals of tololololbobble- RAIL RETURN A BOOSTER POSITIVE BUS BAR BELLEKELEeeli Leeeeeeeee B MOTOR мотоя STARTER DIVERTER reeeeeee keelifeee TO RHEOSTAT EXCITER el DIFFERENTIAL COIL FOR CONSTANT SPEED heese eller TO RHEOSTAT NEGATIVE BUS BAR Fig. 24. Diagram of Highfield Boosting System. the battery will drop. It will then be less than the pressure given by the exciter, which will send a current through the booster field; and the resulting boost across the booster-armature will be exactly equal to the difference between the battery and exciter pressures. Thus, supposing the exciter is set at 500 volts, should the battery fall to 460 volts, the boost in the discharge direction will be 40 volts. On charge, the battery volts will rise until they overcome the exciter, which will be motored, and the boost will then change its direction and be added to the charging pressure. It will thus be seen that the booster is absolutely automatic, and that the boost is always the right amount to correct for the rise and fall of the battery. In this respect it differs from other types of boosters, in which the value of the boost depends upon the position in which the various controlling rheostats are placed, and these require hand-regulation according to the condition of charge of the battery. T2 554 + SECTION V.-POWER STATION. In addition to the shunt-winding the booster is provided with two series coils; one (B) carries a portion of the whole output of the station, and is termed the diverter coil; the other consists of two or three turns only, and is in series with the armature, for the reaction of which it accounts. The diverter coil gives but a small boost (the maximum being 5 per cent. of the line pressure) in the discharge direction, and serves to keep up the pressure during periods of maximum fluctuations, and to account for the drop in the leads and feeders. The Highfield booster may be used in parallel with either compound or shunt machines. The machine also works well at the end of a long feeder in a battery sub-station. The essential feature of the booster is, that it works with balanced voltages in place of balanced currents; and its efficiency is remarkable as compared with the ordinary differential machine. This is due chiefly to the saving in current taken by the motor, as when the battery pressure is high, the booster "motors and the motor returns current to the system. For obvious reasons the differential machine cannot reverse in this manner, and a further saving is effected in the booster field coils, which in the ordinary machine are arranged in opposition: with the consequence that, on discharging many times, the energy required for excitation is absorbed in the opposing windings. Reversible Traction Booster Panel. (FIGS. 25 and 26, pages 554 and 555.) 100·0·150 VOLTS 3000-50 AMPS 500 AMP FUSE 00 O - B 8 8 (1028) L ||20 WAY SHUNT REG. 600 AMP CO SWITCH - 2:6ˆ 4 WAY SWITCH JOHNSON&PHILLIPS CIRCUIT BREAKER 500 AMPS 2100ANI D.A SWITCH FUSE SERIES REG. 0.700 VOLTS 300.050 AMPS 500 AMP SWITCH 25 HP. MOTOR STARTER [3] 600 AMP CO SWITC 30 WAY SHONT REG ¡ Fig. 25. Reversible Traction Booster Panel 12 www SWITCHBOARDS. 555 This panel may contain all the apparatus for controlling both the booster and motor circuits, as shown in Fig. 25, which represents a panel by Messrs. Johnson and Phillips, or two separate panels may be employed. In either case, the diagram of connections is as in Fig. 26. The apparatus for the motor circuit includes:- 2 fuses (F.F.). 1 double-pole switch (D.P.S.). 1 motor-starting switch (M.S.). 1009 + V F.S. F İM.C.B. AO A P.R. R.R. B.C.S. 40A кои F D.P.S. 1 single-pole switch (S.). 2 centre-zero ammeters (A.O.A.). V.S. 100000 pooro M. 0000000 Booooos dooor 8 SM 1 series-regulating resistance (S. R.). 1 centre-zero voltmeter (V.O.V.). 1 two-way voltmeter switch (V.S.). C.S. A1 TO RAILS www Fig. 26. Reversible Traction Booster Connections. SAL The booster circuit contains:- 1 section of bus-bars (+. −). 1 circuit-breaker (M. C. B.), which, if connected as shown, protects both the motor and booster circuits. 1 battery voltmeter (V.). 1 battery fuse (F.). 1 single-pole booster field switch (F.S.). 1 battery change-over switch (B.C.S.). 1 booster shunt-field regulating resistance (R.R.). 1 potentiometer-type regulating resistance for auxiliary booster field (P.R.). 1 booster change-over switch (C.S.). This switch only to be on contact A when batteries alone are feeding the bus-bars and no generators are in use. 556 SECTION V.-POWER STATION. S.R. Three-Wire Reversible Lighting Booster Panel. (FIGS. 27 and 28, pages 556 and 557.) This panel contains:- Sections of positive, neutral, and negative bus-bars (+, 0, −). Motor apparatus, comprising :— 1 automatic overload circuit-breaker (M.C.B.). 2 .fuses (F.). 1 double-pole switch (D.P.S.), 1 motor-starting switch (S.R.). D.P.S. M KM9 -^^- /M.C.B. M.C.B. C.O.S. .0.A. B Yon B.S. MS V.S. 4B.S. R.R. __~-~- B V 2 single-pole switches in booster circuits (B.S.). 4 single-pole switches for booster fields (F.S.). M.C.B. A.O.A -0/0/0/0/0/0/0/0/0/0/0/0/+ -oooooooooooo Fig. 27. Diagram of Three-Wire Lighting Booster Panel. (Johnson and Phillips.) The diagram of connections is shown on the left-hand side of Fig. 27. The double-pole switch and fuses may be omitted if desired, and another overload circuit-breaker inserted on the negative side. An ammeter is sometimes included in the circuit. C.O.S. Booster apparatus, which is identical on each side of the system. The total apparatus consists of:- 2 overload automatic circuit-breakers (M.C.B.). 2 change-over switches (C.O.S.). 1 mid-wire switch (M.S.). 2 regulating and reversing switches for booster fields (R. R.). 2 centre-zero ammeters (A.O.A. ). 2 centre-zero voltmeters (V.O.V.). 2 voltmeters (V.). 2 two-way voltmeter switches (V.S.). SWITCHBOARDS. 557 The connections for both motor and booster circuits are given in Fig. 27, and an illustration of one panel, containing the whole of the apparatus, in Fig. 28. The regulating resistances for the boosters, shown in the figures, are Johnson and 3.6" O (200-400 100·0-100 VOLTS VOLTS 300-0·200 AMPS |CIRCUIT BREAKER 300 AMPS B O 11020) E S P.40 AMP FIELD SWITCH: 300 AMP SHITCH 30 WAY SHUNT REGS. SPECIAL POTENTIOM" TYPE 100·0·100 VOLTS བཀྲ 2WAYORVM. S CIRCUIT BREAKER FOR MOTOR 30 JAMP C 300AMPCO SWITCH 75AMP D. P SWI ANDİFUSES 300 A SWITCH. 20. H P. NOT. STARTR 200-400 VOLTS B ((00-0-200", AMPS CIRCUIT BREAKER 300 AMPS S. P. 40 AMP FIELD о 30 WAY SHUNT REGS SPECIAL POTENTION"TYPE|| 8 300AMP SWITCH 3000 AMP C.O SWITCH Fig. 28. Fittings of Three-Wire Lighting Booster Panel. Phillips' potentiometer type, in which a resistance connected directly across the bus-bars is tapped at variable points by sliding contacts connected to the terminals of the field winding. Three-Wire Balancer Panel. (FIGS. 29 and 30, page 558.) Two methods of connecting up the balancers to a three-wire system are shown in Figs. 29 and 30, though others are sometimes employed. Fig. 29 represents a panel by Messrs. Johnson and Phillips, which contains:- 1 section of three-wire bus-bars (+, 0, −). 1 three-pole balancer switch; also closing shunts of balancers (T.P.S.). 2 centre-zero ammeters (A.O.A.). 2 fuses (F.). 2 shunt rheostats (S.R.). 1 starting switch (S.S.). In other designs a starting switch is arranged in each balancer circuit, the switches being mechanically connected. 558 SECTION V.-POWER STATION. 29 Another method of connection is shown in Fig. 30. Here the shunt winding of each machine is " cross-connected," which makes the plant, to some extent, self-regulating. The regulation is still further controlled by the rheostat R.R., MOA (1021) WVS.R POSITIVE NEUTRAL NEGATIVE WWS.R T.P.S. www. MOA We MOTOR STARTER 30 ADA (1022) RR mmm B SR : ADA DPS ண 0000000 B Figs. 29 and 30. Three-Wire Balancer Connections. which weakens one field simultaneously with strengthening the other. This method only requires one regulating rheostat, the total resistance of which, however, is always in circuit. A double starter, as in the former case, may be employed. Three-Wire Lighting Feeder Panel. (FIG. 31, page 559.) A three-wire lighting feeder panel for 400 amperes 500 volts contains :- Sections of positive, neutral, and negative bus-bars (+, 0, −). 2 ammeters, say, 0.500 amperes (A.). 1 three-wire integrating wattmeter, 500 amperes 500 volts (I. W. ). 2 automatic overload circuit-breakers (M.C.O.). 1 centre-zero ammeter in middle wire, say, 150-0-150 amperes (A.O.A.). The connections are as shown in Fig. 31. The circuit-breakers may be replaced by switches and fuses, and the wattmeter may be omitted if desired. The midwire ammeter may also be omitted. SWITCHBOARDS. 559 This panel contains: Two-Wire Lighting Feeder Panel. (FIG. 32.) 1 section bus-bars (+. −). 1 ammeter (A.). 31 1 integrating wattmeter (I.W.). 1 overload circuit-breaker (M.C.B.). 2 single-pole switches (S.P.S.). ACO A 】ADA A HORD! .W. A M.C.B TO FEEDER A. Section 6 (1)- Onco Fig. 31. Three-Wire Lighting Feeder Panel. Fig. 32. Two-Wire Lighting Feeder Panel. + /S.P.S. 32 The connections are as shown in Fig. 32. The integrating wattmeter may be omitted, and a circuit-breaker added to the negative pole if desired. If the circuit-breaker is of the loose-handled type, the switch in series with it may be omitted; but this is not to be recommended. Tests Required by the Board of Trade. Board of Trade Regulations for Tramway Circuits. Under the provisions of Special Tramways Acts or Light Railway Orders authorising the construction of lines along public roads, the Board of Trade has made certain regulations calculated primarily to safeguard the interests of owners of gas, water and other pipes along the route. Electrolytic action or fusing of such pipes by stray currents is the most serious danger; and with the object of maintaining the insulation of the line and preventing excessive leakage currents, certain tests of the system are insisted upon. The principal conditions to be observed are enumerated below. That the current passing from the earth connections through the ndicator to the generator shall not at any time exceed either 2 amperes per mile of single tramway line, or 5 per cent. of the total current output of the station. B. Section 5 (b)—— The earth connections referred to in this regulation shall be constructed, led, and maintained, so as to secure electrical contact with the general mass of earth, so that an electromotive force, not exceeding 4 volts, shall suffice to produce a current of, at least, 2 amperes from one earth connection to the other through the earth, and a test shall be made at least once in every month to ascertain whether this requirement is complied with. 560 SECTION V.—POWER STATION. C. Section 7— When the return is partly or entirely insulated, a continuous record shall be kept by the Company of the difference of potential during the working of the tramway between the points of the uninsulated return furthest from and nearest to the generating station. If at any time such difference of potential exceeds the limit of 7 volts, the Company shall take immediate steps to reduce it below that limit. D. Section 11- The insulation of the line and of the return when insulated, and of all feeders and other conductors, shall be so maintained that the leakage current shall not exceed ro of an ampere per mile of tramway. The leakage current shall be ascertained daily before or after the hours of running, when the line is fully charged. If at any time it should be found that the leakage current exceeds one-half of an ampere per mile of tramway, the leak shall be localised and removed as soon as practi- cable, and the running of the cars shall be stopped unless the leak is localised and removed within twenty-four hours; provided that where both line and return are placed within a conduit, this regulation shall not apply. E. Section 12- The insulation resistance of all continuously-insulated cables used for lines. or insulated returns for feeders, or for other purposes, and laid below the surface of the ground, shall not be permitted to fall below the equivalent of 10 megohms for a length of one mile. A test of the insulation resistance of all such cables shall be made at least once in each month. Section 6 (2)- That if at any time and at any place a test be made by connecting a gal- vanometer or other current indicator to the uninsulated return, and to any pipe in the vicinity, it shall always be possible to reverse the direction of any current indicated, by interposing a battery of three Leclanché cells connected in series if the direction of the current is from the return to the pipe; or by interposing one Leclanché cell if the direction of the current is from the pipe to the return. F Daily Records Required. Maximum current from the earth connections, see Regulation 6 (1). Leakage current, see Regulation 11. Fall of potential in return, see Regulation 7. Maximum working current, see Working Pressure. Occasional Records. Localisation and removal of leakage, stating time occupied. Particulars of abnormal occurences affecting the electric working of the line. Suggested Arrangement of Instruments to carry out these Tests. A. Section 6- Recording ammeter to read 5 per cent. of total output, or two amperes per tram mile. Range 0 to 10 amperes connected between earth plates and the negative bus-bar. This instrument to have zero in the centre of the scale, so that direction as well as intensity of current may be determined. B. Section 5(b)- An indicating ammeter to read from 0 to 10 amperes. This instrument would be placed in series with two accumulator cells, or three large Leclanché cells, and the two earth plates, so as to indicate the current passing between the earth plates with an electromotive force of 4 volts, and, therefore, the resistance between them. C. Section 7- Recording voltmeter connected between the negative bus-bar in the station and the point of maximum drop on the rail, to show the fall of potential on the rail; range suggested 0 to 10 volts. It is suggested that a multiple single pole switch shall be used in connec- tion with this instrument to record from any one point at will. SWITCHBOARDS. 561 * f. + D. Section 11- Ammeter for indicating the leakage from the line when no cars are running, preferably made with two ranges, one reading up to .05 ampere, so that .0005 ampere can be read, and the other range reading up to 5 amperes, so that .05 ampere can be read. A multiple switch can be used to join up any desired feeder, so that its insulation may be observed if its distant end is disconnected. TUMBLER SWITCH FUSE RAIL O POINTS EARTH EARTH RECORDING VOLTMETÅR ANMETER 2 WAY D.P. SWITCH (1090) AMMETER Hole RECORDING AMMETER CELLS • FEEDER • POINTS 33 ZAL: -- о TUMBLER SWITCH BUS BAR H.D AMMETER 0 VOLT METER 8 WAY S.P SWITCH 8WAYS PSWITCH EARTH K.TYPE AMMETER 2:0 FUSE -BUS BAR " 2018 2 WAY D.P. SWITCH OF MAETER 34 EARTH O O O Figs. 33 and 34. Board of Trade Panel. (Elliott Brothers.) E. Section 12— Set of instruments for general insulation testing. These are quite apart from the circuit, and therefore can be in the form of a. test table, some portable testing set, or the insulation and bridge test. panel made for such station work, on which a complete set of test. instruments is mounted in convenient form. .562 SECTION V.-POWER STATION. F. Section 6 (2) Galvanometer and Leclanché cells for testing current, and electromotive force at which it flows from the return to any pipe, or vice versa. A detector galvanometer can be used in a small case with three Leclanché cells, with connections arranged so that either one or all three can be placed in series with the galvanometer. Board of Trade Panel. (FIGS. 33 and 34, page 561.) To carry out the Board of Trade regulations a special panel is included on the switchboard of traction stations, and is known as the Board of Trade panel. The equipment and diagram of connections of Messrs. Elliott Brothers' Board of Trade panel are shown in Figs. 33 and 34, on page 561, the insulation testing set required by Section 12 being independent of the panel. Station Panel. This is often called the "load panel," and is a panel primarily for the accom- modation of instruments to measure the total output of the station. With a view to convenience of connections, it is usually situated between the generator panels and the feeder panels. It sometimes contains a switch capable of breaking the maximum output of the station, and is generally equipped with two or more recording voltmeters, recording ammeters, and integrating wattmeters. It may also contain the synchroniser in an alternating current system, and the paralleling voltmeters, &c. On a three-phase system, with the neutral point insulated, it may contain the three voltmeters between each phase and earth; and, in general, it serves to carry all instruments not directly bearing on the operation of the board, or for which no suitable place can be found elsewhere. 5:42 Accumulator Switchboard. (FIGS. 35 and 36.) Fig. 35 shows a good arrangement of all apparatus necessary on an accumu- lator switchboard, and the diagram of connections is given in Fig. 36. The connections are so arranged that either the dynamo, or all or part of the batteries 36 35 $20. DYNAMO „AMMETERÁ DYNAMO CHANGE OVER SWITCH boooo Occo F JAIN DYNAMO SWITCH VOLTMETER/ VOLTMETER SWITCH SWITCHES FOR BATTERY CHARGING & DISCHARGINGO CUT IN & CUT OUT BATTERY AMMETER, SHUNT REGULATOR O200 BATTERY SWITCH I CIRCUIT SWITCH NAKT MATER VOLTMETËR SHUNT RESISTANCE |SHUNT WINDING DYNAMO 1074 BATTERY ANMETZ If CIRCUIT BATTERY Figs. 35 and 36. Johnson and Phillips's Accumulator Switchboard. may be run on the main circuit, or the dynamo may be used to charge the batteries. At the top of the board is the main voltmeter, which may be connected by means of the switch directly beneath it, either across the terminals of the dynamo or of the battery. On each side is an ammeter to measure the dynamo and battery currents respectively. Multiple switches for charging and discharging SWITCHBOARDS. · 563 the battery are provided, and beneath them in the centre of the board is mounted an automatic accumulator switch, which switches in the cells as soon as the dynamo voltage is sufficiently high, and cuts them out when the charging current falls to zero. A change-over switch on one pole of the dynamo serves to put the latter direct on the exterior circuit, or on the batteries as desired, and a single-pole battery switch closes the battery circuit for charging or discharging. Two double- pole main switches with fuses connect the board to the dynamo and the mains respectively, and a shunt regulator for adjusting the dynamo voltage completes the apparatus. All switches belonging to the dynamo circuit are on the same side of the board as the dynamo ammeter, and similarly with the battery switches. A short description of the automatic accumulator switch is given under the section on automatic protective devices. Synchronising Alternators. (FIG. 37.) Before an alternator can be switched on to the bus-bars in parallel with one or more other machines, or a synchronous motor switched on, or two sections of bus-bars served by different generators coupled together, it is essential that the voltage and frequency of the incoming apparatus should be the same as those of the bus-bars, and also that the voltage of both should be exactly in phase. To insure these conditions, the incoming machine is first plugged, or otherwise connected to a pair of synchronising bars, across which is a voltmeter, and also one of the primary windings of a synchronising transformer. The other primary of this transformer is connected across the main bus-bars, and carries a voltmeter giving the bus-bar voltage. The secondary winding of the synchronising trans- former is connected to an alternating-current deadbeat voltmeter, usually of the hot-wire type, and in parallel with the voltmeter the synchronising lamp is connected. When the incoming machine is put on the synchronising bars its SUL 2 (M.V) S.B S. B. S.S. &F F8 [00000 (S. V 0000 S.T. S.S. B.V. 11 Fig. 37. Synchronising Gear. voltage is shown by the synchronising voltmeter; and if out of phase with the bus-bar voltage, the combined effect of the two primary windings of the syn- chronising transformer is to produce a flickering of the synchronising lamp, and an oscillation of the synchronising voltmeter needle. The voltage of the incoming machine is brought to that of the bus-bars, and the speed of the engine regulated until the synchronising lamp and voltmeter remain steady at full voltage, when the main switch is thrown in. The lamp is to serve as a guide to the engine- man, who is unable to see the synchronising voltmeter. Two lamps are often connected in parallel, in case of the failure of one of them. The synchronising voltmeter and lamp are now very frequently replaced by a synchronoscope, a type of which is described on page 608; the other connections remaining the same, except that a switch should be provided to allow the synchroniser to be cut out of circuit when not needed. Polyphase apparatus is synchronised on one phase only, so that the diagram of 564 SECTION V.—POWER STATION. In connections given in Fig. 37, will apply to either single, two, or three-phase. the diagram, 1, 2 are the main bus-bars, S.B. the synchronising bars, S.T., S.,V., and S.L. the synchronising transformer, voltmeter and lamp, respectively, M.V. is the incoming-machine voltmeter, B.V. the bus-bar voltmeter, while F.F. are fuses to protect the apparatus. S.S. are sockets to plug the incoming machines to the synchronising bars. In single-phase work, with the outer earthed, only one synchronising bar is required, the outer bus-bar serving also as an outer synchronising bar. Paralleling Continuous-Current Generators. (FIG. 38.) Before a continuous-current generator can be switched in to supply current to bus-bars which are already being fed by other machines, it is essential that the voltage at the terminals of the incoming machine should be brought up to that of the bus-bars. The usual method of paralleling continuous-current machines is to 100 20 60 40 20 20 40 60 80 100 dawnbea KELVIN'S LORD PARALLELING VOLTMETER 1050 Fig. 38. Kelvin Paralleling Voltmeter. connect the incoming machine to the terminals of a voltmeter, and whenever this instrument reads the same as the main bus-bar voltmeter, to close the machine switch. Another method is to use a differentially-wound voltmeter, one side of which is connected to the bus-bars and the other to the incoming machine, the windings of the voltmeter being in opposition. The instrument has a centre-zero, and when the pointer stands at zero the machine switch is closed. The objections to both these methods are: (1) The time occupied in paralleling; (2) the possible inaccuracy of the instrument or instruments. A simple method, due to Messrs. Kelvin and White, is to use a portable instrument, arranged to plug into sockets mounted on each dynamo panel. These sockets are connected across the terminals of the main switch on one pole, so that when the brushes of the machine are down and the switch on the other pole closed, there is full pressure across the sockets. The Kelvin paralleling voltmeter is shown in Fig. 38. The terminals are in the form of springy prongs, adapted for entering the sockets mentioned above. The instrument itself is of the moving-coil type, with centre-zero. As the incoming SWITCHBOARDS. 565 ! machine is speeded up, the voltage across the sockets is gradually reduced until when the paralleling instrument reads zero, the main switch can be closed. One fifth of the bus-bar voltage will deflect the pointer to the end of the scale in either direction, although the full bus-bar voltage will not injure the instrument. As the reading approaches zero, the sensibility can be further increased five times by pressing a small button in the handle, so that paralleling can be done with absolute certainty. A 500-volt instrument has a scale of 100 volts, which becomes 20 volts on pressing the button, so that one division on the scale (in.) represents one volt. There is another pattern of instrument, working on the same principle, made by Messrs. Nalder Brothers and Thompson, which is particularly suited for bench boards. The advantages of paralleling by the above method are:- 1. Great speed and accuracy. 2. Paralleling is entirely independent of the value of the voltage, as the instrument will only read zero when the voltage across the main switch is nil. 3. The operation is independent of the calibration of the voltmeter, being a pure zero method, as distinct from a differential zero. Starting Polyphase Induction Motors. (FIG. 39.) The method adopted to start polyphase induction motors varies according to the size of the motors. The smallest-size motors are usually started with a resistance in series with the stator circuit, which is gradually cut out as the motor attains speed, the rotor of such motors being permanently short-circuited. Motors of from about 6 horse-power to 55 horse-power may also have the rotors short- circuited, the necessary reduction of pressure in the stator windings at starting being obtained by the use of an auto-transformer, which is cut out of circuit, and FUSES AUTO TRANSFORMER J (1016) RUNNING CONTACTS THREE POLE C.O SWITCH STARTING CONTACTS STATOR WINDINGS Fig. 39. Starting Arrangement for Polyphase Induction Motor. An the stator directly connected to the supply mains when the motor reaches its running speed. This arrangement is shown diagramatically in Fig. 39. alternative to the auto-transformer method, adopted for the largest polyphase motors, is the use of a resistance in the rotor circuit. The ends of the rotor windings are led to slip-rings on the shaft, and a brush on each ring is connected to one of the terminals of the three-phase starting rheostat. At starting there is thus a resistance in series with each of the rotor circuits, and this resistance is gradually cut out as the speed increases, until finally the rotor windings are short-circuited and the brushes lifted from the slip-rings. 566 SECTION V.-POWER STATION. Automatic Protective Devices-General Considerations. Several conditions may arise in which it is advisable that an electric circuit should be automatically disconnected from the source of supply. Devices to effect this may be broadly divided into two classes-fuses and automatic circuit-breakers or cut-outs. Which of these should be used in any particular case depends, of course, on many circumstances; but in general it may be said that fuses, unless of special design, are unsatisfactory for high voltages and heavy currents, although their comparative cheapness, and their ability to stand a momentary overload, render them largely useful for the lighter classes of work. They also deteriorate with time, and become liable to blow when not required, or to fail to protect the circuit. The more elaborate mechanical devices for opening the circuit have the disadvantages of complexity and liability of getting out of order, or of being purposely wedged up, or otherwise tampered with. Like all automatic devices, they must be frequently used to ensure efficiency. Before dealing with the various apparatus in detail, we will shortly consider the principal conditions which such devices may be installed to meet. The main problems which present themselves in this connection are the protection of generators, of feeders, of motors, and of batteries. When generators are operated singly, that is each on an independent circuit, the only protection needed is against excess current, and this may be obtained by a simple overload circuit- breaker on each circuit. When, as is usually the case, generators are supplying current to the bus-bars in parallel, a short circuit on any machine, or the failure of the exciting current, or the breakdown of the driving engine, will lower the voltage at the machine terminals, and consequently cause a motoring or reverse current from the bus-bars to flow through the armature. If this current is excessive the armatures may be burnt out; and in any case the fact that the machine is taking current instead of supplying it to the system, will cause a drop in the bus-bar voltage and overload the other machines. Modern generators will withstand a considerable overload without injury; and as an excess current in the right direction would in most cases be due to a fault on the feeder system, a feeder cut-out would deal with the case. Such a contingency as a short circuit across the bus-bars would, of course, not be guarded against by a cut-out in the feeder circuits; but the possibility of this occuring in a well-designed board is too remote to warrant the installation of special devices to deal with it. The objection to putting an excess current cut-out in the generator circuits is, that a machine is likely to be cut-out just when its help is most needed, consequently overloading the other machines, and bringing out their cut-outs one after another until the whole station is shut down. It follows then that the only automatic protective device advisable for generators working in parallel is a reverse current cut-out. No harm, however, can be done by a slight amount of reverse current, and its presence is not sufficiently serious to warrant the machine being automatically disconnected. Not until the reverse current rises to 25 per cent. of the full load current is there any cause for apprehension, and the cut-out should therefore be adjusted not to come into action until this amount is exceeded. Fuses are thus not suitable for the protection of generators working in parallel, as they are essentially excess current cut-outs; though where generators work each on an independent circuit, as in small installations, no reverse current is possible, and an excess current cut-out is all that is needed. A reverse current cut-out must be entirely independent of the bus-bar voltage within wide limits, as a heavy reverse current is usually accompanied by a drop in the bus-bar voltage. Its operation should be unaffected by anything except the conditions with which it is required to deal. Devices for continuous-current circuits depending upon the action of a polarised relay of the permanent magnet type may be demagnetised and rendered inoperative by a sudden rush of reverse current, though small reverses might be satisfactorily dealt with. In many cases boards are being worked without any protective devices in the generator circuits, the ammeter showing an overload, and a lamp or other indicator showing if reverse current is flowing, when the attendant takes steps to deal with the situation. With ordinary systems of distributing mains it is impossible that a reverse current should occur on a feeder circuit, hence the only protection such circuits need is some form of maximum cut-out. This cut-out, as noted above, indirectly protects the generators also from an excessive current in the right direction. Specially designed oil-break or blow-out fuses are often fitted on the feeder panels, or on a separate fuse-board on the feeder circuits for alternating current work, but an automatic magnetic blow-out or carbon brush switch is preferable for continuous currents. SWITCHBOARDS. 567 Motor circuits require protection from excess current, and, in addition, must be automatically opened in case the voltage drops to zero, otherwise with the resumption of the supply the application of the full voltage to the stationary armature of a shunt-wound machine might result in burning out the machine. Small motors may be protected from overload by fuses, while a no-voltage release on the starting switch opens circuit when the current fails, but the two functions may be combined in one instrument, which operates with either excess or zero current. The apparatus required for the protection of batteries varies according to the conditions under which they are charged and discharged. If the object is merely to charge them safely, such as in the case of automobile or other indepen- dent batteries, provision must be made to open circuit, both on the occasion of an excessive direct current or a reverse current. If the storage batteries are installed in parallel with motor-driven generating sets, relieving the generator of the peak of the load and supplying the whole of the current in case of failure of the gene- rating set, it will be obvious that the current in the battery circuit will be flowing sometimes in the charging direction and sometimes in the discharging direction during normal working. Hence such a system should be protected by inserting a reverse current circuit-breaker on one side of the circuit between the battery and the generator, which will operate if by any mischance the battery should supply a motoring current to the generator, cutting the latter out of circuit and leaving the batteries to carry the load. In lighting and power work, when a battery is used in parallel with the main generating machine to carry it over the peak of the load, the conditions are somewhat different. As before, the battery must be free to take current from the generator, or to discharge into the external circuit, but should the generator volts fall, the battery must be prevented from discharging through the generator by being automatically cut out of circuit, leaving the generator to carry the load. For this purpose a reverse current circuit- breaker is required, the actuating coil of which is in series with the main generator between the latter and the batteries, while the switch is connected in the battery circuit. When boosters are used to regulate both the charge and discharge of storage batteries, it is evident that an ordinary reverse-current cut-out cannot be used to. protect the booster, as the current direction through it varies according as to whether the cells are being charged or discharged. A combined overload and reverse-current breaker may, however, be used for the purpose, provided that it is so set that the reverse-current adjustment corresponds with the maximum safe-- charging current of the batteries, and the overload adjustment with the maximum safe-discharging current. Boosters of the compound or series type will run as motors in the opposite direction, if they remain connected to the system after the driving motor has become disconnected, or has lost its field. The same result would follow if the booster circuit was closed before the motor was started. To protect the system an overload and no voltage circuit-breaker in the motor circuit should be inter-con- nected with the breaker in the battery circuit, in such a manner that the motor circuit-breaker must be closed before the booster circuit-breaker can be made to latch, while the opening of the first-named instrument instantly causes the opening of the second. The interconnection of the circuit-breakers may be either electrical or mechanical. In the former case the opening of the motor circuit- breaker closes the circuit of a tripping coil, which actuates the booster circuit- breaker; while a mechanical interconnection, as the name implies, consists of a mechanism which will hold open the catch of the booster breaker so long as the motor breaker is open. Feeder boosters, being either compound or series-wound, will run as motors at excessive speed in the reverse direction if left in circuit after their motor has lost its field, or has become disconnected from the mains. The booster circuit may be automatically opened under these conditions by a mechanical connection between its switch and an ordinary overload, and no-voltage circuit-breaker in the motor circuit. Messrs. Blackwell and Co. supply a small panel carrying three switches, the outer two of which connect the two boosters to the positive and negative side of the system, while the centre one connected in the motor circuit operates under either overload or no-voltage conditions, and in opening trips the other two. British Thomson-Houston Magnetic Blow-out Circuit-Breaker. (FIGS. 40 and 41, page 568). The current passing through the circuit-breaker is carried normally by copper contact-brushes, which rest upon square studs. The brushes are held in place by 568 SECTION V.-POWER STATION. a latch, which is tripped by the armature of a magnet, through whose coils the total current passes. The tripping current of the magnet is regulated by an adjustable spring, the tension of which can be varied through a considerable range. The breaking of a 500 or 600-volt circuit is likely to cause considerable arcing under any conditions; but when, as happens daily in tramway power stations, this breaking is done instantly, to relieve generators from the effects of excessive overloads or short circuits on the lines, the arc formed at the break is tremendous, and will destroy by burning almost any form of circuit-opening device. Damage is avoided by the use of supplementary contacts, arranged so as to break circuit a moment after the main contact, and placed in a strong magnetic field, which blows out the arc before burning can occur. This transfer of the arcing points .40 S ▸ Trippingslagnet Coul 8 (01) T Blow out Contact M P Y C₁ |M, Main Contact lact 41 Magnet Coil O 8, Figs. 40 and 41. The British Thomson-Houston Company's Magnetic Blow-out Circuit-Breaker. from the main contacts to supplementary ones, and the immediate extinguishing of the arc by the use of a magnet, has rendered possible the construction of practical circuit-breakers up to 8000 amperes capacity. When the circuit-breaker is closed the current flows up through the tripping coil T to the stud M (Fig. 41), crossing over the yoke Y to the stud M¹, and thence to the ground or return circuit. When the current has reached a predetermined volume, which is limited by the tension spring S (Fig. 40), the armature A is depressed, lifting the latch L, yoke Y is drawn away from the studs M and M1 by a spring, and the whole of the current is thrown through the coils B and Bl (Fig. 41), and upper contacts C and C¹. As the yoke Y is drawn down, the plug P which is attached to it follows, and is withdrawn from between the contacts C and C¹, when the whole current is broken between these contacts which are directly under the influence of the magnetic field created by the coils B and B¹. The I.T.E. Circuit-Breakers. (FIG. 42, page 569.) The following advantages are claimed by the makers for this type of circuit breaker :- The electro-magnet is designed to develop more energy than is needed simply to trip the retaining catch, this additional energy being employed to aid in opening main switch. The advantage of this "secondary" action consists in the quicker and more positive opening of the protected circuit, when it approaches a "short- cireuited" condition. "Inverse-time element." That is, the time of opening the circuit becomes less and less as the conditions of the circuit protected approach nearer and nearer a short-circuit. This device will open the circuit in part of a second under the latter condition. SWITCHBOARDS. 569. Positiveness in opening. That is, if the plunger moves at all, the blow struck is, under all conditions, such that the switch will open. The phenomenon called "floating" is impossible, because of this positiveness of action. Constancy of adjustment, which is due to the use of weight at fixed distances. Springs as a means of adjustment have been avoided, because of their utter unreliability. The carrying capacity is actual rating, not nominal. The various types of instruments are specially designed for the particular work for which they are intended. All circuit-breakers are strong and well-proportioned; the current-carrying parts are made of high-grade copper, so proportioned that the heating of any part of the circuit-breaker will not exceed 20 deg. Cent. above They have a wide, surrounding temperature, in constant use at "actual rating." clean break, are quick and reliable in action, and will operate within 5 per cent. of their adjustment, which is readily effected and constant. 14 Fig. 42. The 1.T.E. Circuit-Breaker. The main contacts are protected by a final carbon break, which prevents all injury to the copper knife-blade contacts. Fig. 42 shows the construction of this circuit-breaker in side view and in part section. The main current circulates around the solenoidal coil B, and tends to draw into the solenoid the moveable plunger C. The initial position of this plunger in the solenoid is determined by the adjusting screw M. When the current is sufficient to overcome the weight of the plunger, it is drawn into the coil with constantly increasing velocity, due to the intensified magnetic action, as the polar distance or air space is decreased. When nearing the upward limit of its travel, having acquired a high momentum, it impinges upon the trigger E through the. medium of the push-pin D. The immediate result of this is the release of the switch arm by the displacement of the retaining catch F. The upper projection H of the trigger E is thrust against the striker plate K, thereby utilising the energy of the current to start the inovement of the switch arm. This movement is intensified and sustained beyond the point of final rupture between the switch contacts by the thrust of the spring I, which is released from compression by the initial action of the trigger. Thus the contact arm is thrown away from the contact terminal, and the circuit is opened. 570 SECTION V.—POWER STATION. O I.T.E. Laminated Circuit-Breaker. (Fig. 43.) This circuit-breaker is designed for direct-current work up to 7500 amperes, at 750 volts or less. The shunt circuit is entirely non-inductive, which renders it easy to divert the current from the main bridge to the shunt circuit, and makes any arcing upon the main contacts impossible. The main bridge, as mounted upon the switch arm, is insulated from the shunt circuit. In the act of opening, the bridge is first brought entirely out of circuit prior to the opening of the shunt circuit, thus rendering unlikely the bringing of the bridge into circuit again by the expansion of the arc due to final breaking. (502) Ө Fig. 43. I.T.E. Laminated Railway Type Circuit-Breaker. The armature which operates upon the trigger has a free preliminary move- ment; the trigger is thus worked by a hammer-blow, which render the adjustment of the instrument free from the influence of friction. No parts of the frame are in circuit, whether the breaker is closed or not. I.T.E. Circuit-Breaker for Alternating Currents. This type of circuit-breaker is designed in two styles. 1st. To be placed on the feeder circuit; coil and bridge being in series similar to that of the direct-current type, being operated by, and opening the entire current. 2nd. Arranged for generators in which the coil is connected in the generator circuit; operating to open the exciting current, thus demagnetising the fields. By this means only a small current is broken, thereby eliminating the destructive self-inductive effect of suddenly opening alternating-current circuits of high voltage. The Cowan-Andrews' Reverse-Current Circuit-Breaker for Continuous Currents. (FIGS. 44 and 45, page【571.) This circuit-breaker (Fig. 44), which has been designed for the protection of trac- tion and similar generators working in parallel, is of the loose-handled type, and the final break takes place between carbon contacts. Its special feature consists in the SWITCHBOARDS. 571 arrangement of the magnetic circuit, which opens the switch on the occurence of a predetermined amount of reverse current. This magnetic circuit is similar to that of a "Manchester" dynamo, as shown in Fig. 45, the shunt coil connected across the bus-bars being wound on one limb and the series coil on the other. Normally the magnetic flux will flow through the magnet limbs in series, avoiding SHUNT WINDING 44 BRASS TUBE- 45 CATCH IRON PLUNGER 1073 SERIES WINDING CLOSED IRON CIRCUIT Figs. 44 and 45. The Cowan-Andrews' Reverse-Current Circuit-Breaker for Continuous Currents. the central path; but should the current in the series coil become reversed, the flux is diverted through the plunger, lifting it with considerable force. No amount of current in the right direction will lift the plunger, but a very slight predetermined reverse current will do so, even should the voltage across the bus-bars be 50 per cent below normal. By using a cast-steel core for the shunt winding, the residual magnetism will be sufficient to operate the cut-out, even should the potential fall to zero. The Cowan-Andrews' Discriminating Devices for Alternating- Current Circuits. (FIGS. 46 and 47, page 572.) Automatic devices containing shunt and series coils, for the purpose of protecting alternating-current circuits against a reversal of current, cannot be constructed on the lines of continuous-current apparatus, as the transformer action of a heavy primary current entirely destroys the effect of the impressed E. M. F. on the shunt circuit, and consequently the device loses all sense of direction. Messrs. Cowan and Andrews have therefore designed a reverse-current 1 I 572 SECTION V.-POWER STATION. device, the principle of which is illustrated in Fig. 46. A small transformer of the shape shown is wound with two primary and two secondary windings. One of the primaries, usually consisting of one turn, is connected in series with the 46 47 "UW0 14761* ་་་་་་་ TAAR N 7 Fig. 46. The Cowan-Andrews' Discriminating Transformer for Alternating- Current Circuits. | ôngi ka kán 1000 1041 Fig. 47. The Cowan-Andrews' Reverse-Current Indicating Device. circuit to be controlled. The flux in the central core due to this winding divides equally between the two return paths, and cuts the two secondary windings equally, consequently energising equally the coils of the relay, so that the plunger SWITCHBOARDS. 573 is neither pulled up nor down. The flux due to the shunt primary windings will tend to flow round the outer magnetic circuit of the transformer, and also cut the two secondaries equally. It will be seen, however, that the fluxes due to the two primaries acting simultaneously will oppose each other in the upper half of the transformer, and assist each other in the lower half, so that the core of the relay is forcibly held down. Should the direction of the current in the series primary winding become reversed, the opposite effect is produced, and the core is pulled up, closing the local circuit and operating the circuit-breaker. Usually a red lamp is connected in parallel with the upper coil of the relay, and a green lamp in parallel with the lower. These lamps indicate at a glance the direction of the current, and approximately the amount flowing in the generator circuit. The apparatus would be rendered inoperative by an open circuit occurring in the shunt winding, but in this case both lamps would glow simultaneously, thus indicating that something was wrong. A small discriminating transformer, fitted with indicating lamps, is shown in Fig. 47. This has been designed to replace the fuses in cellular type boards, and is plugged into the existing fuse contacts on the generator panels. It shows at once if a generator is failing, leaving the switchboard attendant to take the necessary steps. Even when automatic cut-outs are fitted the use of the lamps is a valuable safeguard, as in the event of the automatic device failing to act for any reason, the attendant is warned in time to open the circuit by hand. The dis- criminating transformer is perfectly reliable, even should the bus-bar voltage drop to 25 per cent. of the normal: an event which could hardly occur on the severest short-circuit possible on an alternating-current system. Ferranti Maximum Current Time-Limit Relay for Alternating- Current Circuits. (FIG. 48.) O O 1072 Fig. 48. This relay, illustrated in Fig. 48, is used to close the circuit of the tripping coil of a circuit-breaker, when the alternating-current in the main circuit exceeds a 574 SECTION V.-POWER STATION. certain value. A copper disc is pivoted between the poles of a laminated magnet, energised by the secondary of a series transformer, the primary of which is on the circuit to be controlled. Thus the relay is quite unconnected with high-tension current. The poles of the magnet are fitted with copper shading rings, so that a torque is exerted on the copper disc, which, when the primary current exceeds a certain value, causes the disc to rotate. The motion of the disc is controlled by a hanging weight, and its rotation is retarded by a permanent damping magnet. The rotation of the disc commences when the primary circuit is overloaded by about 25 per cent., though by alteration of the hanging weight any adjustment can be made. The raising of the weight lifts a pivoted lever, and closes a pair of carbon contacts on the low-tension direct-current circuit of the tripping coil. Before these contacts are closed the disc has to make a certain number of revolu- tions, and as its speed of rotation is proportional to the overload, it will be seen that the time of operating is inversely proportional to the overload. The time taken to close the tripping coil circuit after the overload occurs can be varied as required; thus, with a 25 per cent. overload, the main circuit-breaker may be opened in anything from 0 to 50 seconds, according to the adjustment of the instrument. The Protection of Duplicate Feeders. (FIGS. 49 and 50.) A -blolol B Fig. 49. The Protection of Duplicate Feeders. OUTERN 1071 Fig. 50. Cowan-Andrews' Relay for the Protection of Duplicate Feeders. SWITCHBOARDS. 575 To ensure continuity of supply, it is usual to duplicate H. T. feeders, working the two members in parallel. In the event of a fault occurring on one feeder,. a heavy current might flow from the sub-station end back to the fault, dangerously overloading the healthy_feeder, or operating its circuit-breaker, and so entirely cutting off the supply. To prevent this occurring, in the Cowan-Andrews' system, the feeders, instead of being connected directly to the sub-station bus-bars, are interconnected at the ends through a choking coil wound entirely in one direction, the connection to the bus-bars being made from the centre of the coil under normaĺ conditions, the current will divide equally between the two feeders, and the coil will be non-inductive, the two halves neutralising each other. Should one of the feeders break down, the current will have to flow from the healthy feeder to the fault, entirely in one direction through the choking coil, which will in consequence become highly inductive, and limit the flow to anything that may have been decided on, down to less than 1 per cent. of the full-load current if desired. In practice the coil is designed to limit the flow to the fault to 25 per cent. of full-load current, so that the healthy feeder will never have to carry more than a 25 per cent. overload, which it can do indefinitely without inconvenience. A still further improvement consists in fitting automatic circuit-breakers at the sub-station end, one of which will cut out the faulty feeder. An alternating- current relay of the pendulum type is used to operate the circuit-breakers; the connections of a pair of feeders, fully protected by choking coil and relay, being given in Fig. 49. The general appearance of the relay with case removed is shown in Fig. 50. A T-shaped pendulum is magnetised by a shunt coil connected across the system, and its free ends acted on by a pair of coils connected in series between the mains at the sub-station end. Normally, no current flows through this pair of coils, but should either feeder break down the coils are energised by the current to the fault, and the magnetised pendulum will close the battery circuit through the tripping coil of the circuit-breaker on the faulty feeder. When this occurs, the two halves of the choking coil are automatically again put in parallel by the cross-con- nections shown in the diagram, and the coil thus rendered non-inductive. The N. C. S. Automatic Accumulator Switch. (FIGS. 51 and 52, page 576.) This device is for the purpose of automatically switching accumulators on to the charging dynamo, as soon as the voltage of the latter is sufficiently above the battery voltage to enable the proper charging current to flow. Its action is entirely differential, and the cells are switched into the charging circuit as soon as the dynamo voltage exceeds the cell voltage by a definite amount, and quite independently of the actual voltage. It also automatically disconnects the cells from the dynamo directly the charging current falls to zero. The arrangement of parts is shown in Fig. 51, and the diagram of connections in Fig. 52. The switch contacts are formed by two cups containing mercury, which can be bridged across by a connector-piece at the end of a pivoted lever. A balance weight at the other end of the lever tends to keep the connector raised out of the mercury cups, and from near the centre of the lêver a soft-iron tongue projects into the interior of the lower coil C. The diagram shows clearly the way in which the switch should be connected up; the connections shown by heavy lines being made of cable of sufficient size to carry the full charging current. The connections being as in the diagram, it will be seen that on closing the main switch the coil C is energised by the full number of cells, and its core becomes magnetised; the difference coil D is also excited by a current depending for its direction and magnitude on the difference between the dynamo and the cell voltage; as soon as the former exceeds the latter by about 6 volts the core C is repelled from D, and the dipper connects the cells to the dynamo through the thick coil E, which is so connected that the charging current confirms the action of the difference coil before-mentioned, and holds the connector firmly in the mercury cups. As soon as the dynamo voltage falls, as on shutting down the engine, or in case of accident, the current in E falls, and the dippers are pulled out of the cups by the action of gravity. There is no spark, as the current at the time of breaking is practically zero. In cases where it is not convenient to connect the switch as in the diagram, in respect of positive and negative, the connections may be reversed, the positive and negative points changing places throughout the diagram. 576 SECTION V.-POWER STATION. It is important that the main switch be closed before starting up the dynamo ; and if it is found that this precaution has been omitted, the speed of the machine must be reduced, and a fresh start made with the switch closed. 51 52 -DYNAMO N.C.S 100 AMPERES HO VELTS &WAVED D +CELLS & DYNAMO MAIN SWITCH E لیا www C -CELL S DYNAMO 2 Figs. 51 and 52. The N. C. S. Automatic Accumulator Switch. It is a good plan to connect the dynamo voltmeter to the distant side of the main switch, so that it does not deflect unless the latter is closed. The automatic switch is made to work with all currents up to 500 amperes at 500 volts. Fuses. The use of simple fuses for high-tension work has been generally abandoned in this country. In continental practice the form employed consists of an open-ended tube of insulating material, with external flanges at each end. The fuse wire is threaded through the tube, and is clamped or soldered to the terminals which project through the walls of the tube. For pressures of 2000 to 10,000 volts, the length of the tube varies from 8 in. to 15 in. They are unsafe to handle except with the aid of long wooden tongs kept for the purpose, and must be located in a safe place, as the tube is liable to be shattered by the explosive effect of the rupture of a high-tension current. Fuses of special design, however, are still used to a large extent upon English boards. The object is, generally, to ensure the arc being immediately suppressed, and though this can be satisfactorily accomplished, the other faults inherent in fuses remain as before. The Ferranti Oil Fuse. (FIG. 53, page 577) Fig. 53 shows the construction of this type as designed for cellular boards. The containing vessel is of porcelain, divided longitudinally into two compartments filled with resin oil. It is provided with a handle for withdrawal, and fitted with a porcelain cover. Plug contacts are cemented into the end of each compartment, and connected by flexible leads to brass blocks, to which the fuse wires are soldered or screwed. A spring in each compartment keeps the fuse wires in tension across the central division, and when the fuse blows the blocks are imme- diately drawn under the oil, and the arc extinguished at zero value of current. Fuses on this principle are made in various forms to suit the requirements of different boards. They are designed to deal with circuits up to 250 kilowatts at 2500 volts, or 200 kilowatts up to 6000 volts. A modified form is constructed, in which a porcelain saddle on the central -division divides the pot into eight compartments. Contacts projecting through SWITCHBOARDS. 577 the back carry the current in and out of the fuse. To each contact is fastened a horizontal rod carrying four drums containing springs. The copper flexible tapes attached to the drums on one side are stretched to the top of the central saddle, against the tension of the drum springs, and connected to the opposite tapes 53 1068 by fuse wires. When the wires melt the flexibles are released, and immediately drawn under the oil by the springs. A fuse of this type, wired to carry 250 amperes, has repeatedly broken the full short-circuit current of a 5000-kilowatt generator at 11,000 volts, in a perfectly satisfactory manner. Partridge's Patent Sparklet Fuse. (Figs. 54 and 55, pages 577 and 578.) Fig. 54. Sparklet Switch Fuse; 100 amperes, 2000 volts. : U 578 SECTION V.-POWER STATION. In this type of high-tension fuse, made by Messrs. Elliott Brothers, a novel method of extinguishing the arc is employed. The fuse wire is threaded through a porcelain tube fitted with plug contacts in the usual way. At each end of the tube, close to the fuse wire or wires, is fixed one or more "sparklets" pointing inwards. о о 1.9 2. ot B о lood __1272 ALTERNATIVE DESIGN Fig. 55. Sparklet Switch Fuse; 200 amperes, 10,000 volts. SHUNTED GAPS SERIES GAPS EARTH SHUNT RESISTANCE SERIES RESISTANCE 1066 រ០០០០០. 62 OBELED 000000 1061 Wurts' Arrester for Direct-Current Circuits. (FIG. 63, page 583.) Fig. 61. Westinghouse Lightning Arrester for 6000-Volt Alternating- Current Circuits. Fig. 62. Spark Gap Unit for above. All low-equivalent arresters are designed for indoor service. The arrester gaps and the shunt resistance are mounted on one or more marble panels. The series resistance is also mounted on the panel in arresters for circuits not exceeding 8500 volts. On arresters for circuits exceeding 8500 volts, the series resistance is mounted on insulated columns separate from the panel. The non-arcing metal arresters are not suitable for use on direct-current circuits; a non-arcing arrester has been devised by Mr. Wurts for this class of work. The principles upon which this arrester is designed are: First.-A discharge will pass over a non-conducting surface, such as glass or wood, more readily than through an equal air gap. Second.-The discharge will take place still more readily if a pencil or carbon mark be drawn over the non-conducting surface. Third.—In order to maintain a dynamo arc, fumes or vapours of the electrodes must be present; consequently, if means are provided to prevent the formation of these vapours, there will be no arc. The instrument, Fig. 63, is single-pole, and consists of two metal electrodes mounted upon a lignum vitæ block, flush with its surface. Charred or carbonised grooves provide a ready path for the discharge. A second lignum vitæ block fits closely upon the first block, completely covering the grooves and electrodes. Dis- ruptive discharges will pass readily between the electrodes over the charred grooves, which act simply as an electrical crack through the air, providing an easy path. SWITCHBOARDS. 583 427. о 00 Ø BUS BARS OUTLET. O о O (422) 63 O о God ge 64 8 IT C ab Ø Ø INLET LINE, Lightning Arresters. Fig. 63. Wurts' Arrester for Direct-Current Circuit. Fig. 64. Westinghouse Tank Arrester. U 584 SECTION V.-POWER STATION. ! The resistance between the electrodes is over 15,000 ohms, there is no leakage current, the lightning discharge does not pass through this high resistance-it leaps over the surface of the charred grooves from one electrode to the other, exactly as it would if there were but a simple air gap. The presence of the charred grooves simply makes the path easier. There being no room for vapour between the two tightly-fitting blocks, no arc can be formed, hence the arrester is non-arcing. Westinghouse Tank Arrester. (FIG. 64, page 583.) This arrester acts by maintaining an artificial earth of comparatively high resistance on the lines to be protected. In any type of spark-gap arrester an abnormal potential is necessary before the device operates, but the provision of an unbroken connection to earth, as in the case of the tank arrester, keeps the line at earth potential, and allows discharges to take place harmlessly. The tank arrester is particularly useful for the protection of generators in districts exposed to frequent and violent thunderstorms. The arrangement of the apparatus is shown in Fig. 64. The groups of kicking coils are connected between the line and the bus-bar, and on the line side of each group is a plug connection with a carbon electrode in the tank below. The inlet to the tank should be metallically con- nected to the water main, and provided with a regulating valve. Under normal conditions the leakage to earth is about 3 amperes per carbon. For small plants the total output, up to 1200 amperes, may be passed through a single arrester, but for larger outputs it is customary to provide one tank arrester complete for each feeder. Tank arresters are only suitable where one side only of the circuit is to be protected; and it is obvious that current and water may be saved by disconnecting the tanks and turning the water off during fine weather, as the arrester needs only to be brought into service when a thunderstorm is anticipated. The Shaw Non-arcing Arrester. (FIG. 65.) (R. W. Blackwell and Company.) This arrester consists of a number of carbon plates separated by mica washers of larger diameter, and clamped together by serrated brass caps, connected one to each terminal. The lightning discharge will jump the mica barriers from carbon 1062 Fig. 65. The Shaw Lightning Arrester. to carbon, but no are can be maintained over the surface of the device. The form illustrated in Fig. 65 is for switchboard use, but weatherproof types are made for outdoor work. This arrester is made for the protection of circuits up to 800 volts direct current, or up to 5000 volts alternating current. The Ferranti Cable-Charging Gear. (FIG. 66, page 585.) In Fig. 66 is shown the arrangement for charging E. H. T. cables, as supplied by Messrs. Ferranti, Limited, to the Manchester system. For each phase is a rectangular cast-iron tank, inside which is a smaller tank supported by porcelain insulators at the sides and the bottom. Two long porcelain tubes are fixed vertically in the inner tank, resting on a block of non-conducting material. The inner tank contains water, the level of which is shown by a gauge-glass. From the ends and centre of a cast-iron beam above are carried pairs of iron rods sheathed SWITCHBOARDS. 585 piston. rod, and having its lower end attached to a plate on the bottom of the ebonite of each terminal is connected a long helix of copper tape, surrounding the ebonited When these pistons are in their lowest position the plates dipjinto 22-0 Approx PORCELAIN TUBE WITH BRASS TERMINAL SULPHURED IN. PORCELAIN INSULATOR (1037) CONNECTING CROSSHEAD EBONITED IRON RODS 7.6*. mga dag PORCELAIN PLATFORM PORCELAIN TUBE SPIRAL TAPE CONDUCTOR "CAST IRON TANKS WATER LEVEL PORCELAIN INSULATOR SHOWI SPIRAL TAPE CONDUCTOR IN THIS TUBE SAME AS SHOWN ON OTHER SIDE. WOOD DISTANCE PIECES. EBONITE PISTON. METALİCONTACT ON PISTON END DIPS IN MERCURY. HAND RELEASE ATTACHMENT AUTOMATIC MAGNETIC RELEASE GEAR GLASS SIGHT DOCR 4.6 Į TERMINALS CHAIN BALANCE WEIGHT TOTAL UPWARD TRAVEL- 2.10 DRAIN COCK DOORS- Calic SWITCHBOARD PLATFORM Gamagazi COM AUTOMATIC MAGNETIC RELEASE GEAR Fig. 66. The Ferranti Cable-Charging Gear. TERMINAL 2 Feet GLASS FILLER SPIRAL TAPE CONDUCTOR] AS SHOWN ON OTHER WEW. BALANCE WEIGHT PORCELAIN PLATFORM PORCELAIN TUBE GLASS WATER GAUGE GLASS SIGHT DOOR DRAIN COCK Current is led in by terminals sulphured in porcelain sleeves. To the interior end with ebonite, insulated from the beam, and terminating in ebonite pistons. U2 586 SECTION V.-POWER STATION. I : recesses containing mercury, and no résistance is in circuit. As the cast-iron beam is raised, resistance is inserted on the three phases simultaneously, and resistance is cut out when it is lowered. The beam is suspended by chains passing over pulleys attached to the underside of the switchboard gallery, and is counter- balanced by heavy weights. To charge the cable, the beam is lowered by means of the handle on the switchboard platform, the water resistance being gradually cut out and finally short-circuited. A ratchet device retains the shaft in this position. To open the circuit and discharge the cable, this catch is released either by hand or by the action of an automatic magnetic device, when the pistons are raised out of the water by the action of the balance weights. Switchboard Measuring Instruments. Under this heading are included indicating instruments, such as ammeters, voltmeters, power-factor indicators and indicating wattmeters; as well as integrat- ing wattmeters, recording ammeters and recording voltmeters. Switchboard instruments differ from laboratory instruments in many ways. While the extreme accuracy of the latter is unnecessary, switchboard instruments must have many qualities quite as difficult of attainment. It is essential that they shall be direct-reading, i.e., the quantity measured shall be indicated directly in the units required without the necessity for any calculation. Their scales must be clear and open, and legible at a considerable distance; they must require no attention, have a reasonable degree of accuracy which shall not be affected by alterations in temperature, stray magnetic fields or other contingencies, and be dead-beat in action. The pointer should be as close as possible to the scale to avoid errors in reading due to parallax, a fault to which edgewise instruments are particularly liable. All instruments, except perhaps those of the electrostatic type, necessarily consume a certain amount of power, but this in comparison with the station output is inconsiderable. The power consumed by an instrument, however, appears in the form of heat, which is liable to cause errors of reading in the instrument itself, or affect neighbouring apparatus; hence it should be kept as low as possible. In a paper read before the Institution of Electrical Engineers, Messrs. Kenelm Edgcumbe and Franklin Punga give the following tables as representing the electrical errors and the power consumption of various switchboard instruments. Table 2.—Electrical Errors of Various Types of Instrument. Type. Direct Current. Moving-coil voltmeter ammeter Moving-iron voltmeter animeter "" "" Hot-wire voltmeter ammeter "" •• Alternating Current. Moving-iron voltmeter ammeter Hot-wire voltmeter ammeter Induction voltmeter.. >> ammeter .. .. .. Hysteresis. Temperature. Frequency. Difference between Up and Down Curves. per cent. of maximum reading. Nil. "" 1 Nii. "" ·· Error Due to 10 deg. Cent. Change.* per cent. of maximum reading. .01 .75 .5 Nil. .75) For short 1.5 periods. .75 .75} .5 Nil. For short periods. .5 1.5 1.0 Stray Fields. † Difference of Error Due to Bar Reading with 1000 Am- from 40 to 60 peres at 1 mile Periods. fromInstrument. per cent. of maximum reading. .. ·· ·· 1.0 .5 Nil. "" 4 15 per cent. of maximum reading. .2 .2 1.0 .25 In cast-iron case. unshielded shielded Nil. } "" 1.0 unshielded }}} .25 shielded Nil. "" Pa 5 .5 * In many cases the passage of the current itself will cause a much greater rise of temperature than 10 deg. Cent., and hence a correspondingly increased tempera- ture error. This is particularly the case with moving-iron voltmeters. In the case of alternating currents the stray field is assumed to have the same periodicity as the current or voltage which is being measured. SWITCHBOARDS. 587 >> "" Moving-iron voltmeter, 10 volts 100 19 200 "} "" 500 "" "" ammeter, 10 amperes 100 "" "" Type of Instrument. "" Table 3.-Power Consumption. Current Taken by Voltmeters. "1 "" "" Dynamometer-type- voltmeter, 200 volts ammeter, 100 amperes "" >> "" "" "" "" 500 Moving-coil voltmeter, 0 to 200 volts 100 to 200 ammeter, 500 amperes Hot-wire voltmeter, 200 volts.. ammeter, 500 amperes Induction-type voltmeter ammeter ·· • .. ·· "" ·· .. .2 ampere .06 "" .05 .04 ·· .. "" "" .01* ampere .02* "" .17* ampere Transformers .05 ampere Voltage-Drop on Ammeters. •• .3 volt .03 .007 to .01 volt "" .08 volt .2* volt usually employed .5 volt } Watts. 2 6 10 20 3 3 3.5 to 5 2 4 40 34 100 5 to 8 5 to 8 10 50 * The same coil winding is as a rule employed for all ranges, so that these values are independent of the actual range. Types of Instruments. For switchboard work, the following are the chief types of instruments in use:- Soft-Iron Type, otherwise called "moving iron," "electro-magnetic," or "gravity-controlled."-Instruments of this class may be used either as ammeters or voltmeters on both alternating- and direct-current circuits, although every instrument must be calibrated with the current for which it is to be used. The principle underlying their action is the attraction of a piece of soft iron suspended in the field of a coil energised by the current, to be measured. The soft iron may be merely drawn into a stronger part of the field of the coil, or attracted to another piece of iron permanently fixed and magnetised by the same current. The chief errors in soft-iron instruments arise from hysteresis, which causes the readings taken with a gradually increasing current to be too low and vice versa. This also prevents an alternating-current instrument being calibrated by direct current, as the consequence would be that it would read low when connected in an alternating circuit. To diminish the effect of hysteresis, the iron is often in the form of a lamination, small enough to be saturated by the working flux. Under these conditions, however, the attractive force depends largely upon the instantaneous value of the current, so that the reading is a measure of the average value of the sine curve instead of the R.M.S. value, and consequently varies with the wave form. If, on the other hand, the moving iron is comparatively large so that it works at a low-flux density, the hysteresis errors will be also small and the instrument fairly independent of frequency and wave form. The latter construc- tion, however, involves greater weight, and consequently more friction and inertia of the moving parts. It is often assumed that an instrument whose indications are practically independent of frequency will also be independent of wave form, and vice versa. While this is true for all errors which depend purely on self- induction, it is far from being true when the error arises from the iron itself. Every instrument whose indications are not dependent on the square of the current, must of necessity give inaccurate readings with any other wave form than that with which they are calibrated, although with a given wave form its indica- tions may be entirely independent of frequency. Stray magnetic-fields, due to the proximity of the generators or the currents in bus-bars or cable-connections, affect the accuracy of all moving-iron instruments, and it should be, therefore, situated as far as possible from such causes of disturbance, even when shielded by an iron case. The dials of soft iron instruments are usually either 6 in. or 8 in. in diameter, and the scale is placed either in the upper or lower portion of the face. The 588 SECTION V.-POWER STATION. terminals may be at the back or front of the case. The controlling force is sup- plied by gravity in most instances, though many instruments are brought back to zero by means of a hair-spring. The scales of instruments of this type can be graduated as desired by suitably proportioning the moving iron and the strength of the magnetic field. The divisions are frequently made more open at the part of the scale corresponding to the normal working load for the sake of cleanliness, while the earlier part of the scale is very cramped, and is usually left ungraduated. The damping of moving-iron instruments presents some difficulty. Eddy- current damping, by means of a permanent magnet, as used in the case of hot-wire and electrostatic instruments, is inapplicable, as the presence of a permanent magnet in the instrument would vitiate the readings. Oil-damping in various forms has been used by several makers, but the presence of oil in the interior of an instrument is entirely objectionable, and is now being abandoned. Air-damping, though used for many years in connection with laboratory instruments, has only recently come into general use for commercial instruments. Messrs. Evershed and Vignoles were probably the first to apply it to such a purpose. Their arrange- ment consists of a sector-shaped box fitted above the coil of the instrument, and in which moves a light vane attached to the spindle. The clearance is reduced to a minimum, and, hence, considerable damping is obtained. This device has since been adopted in a more or less modified form by several Continental manu- facturers. A simple form of damping arrangement was introduced by Messrs. Siemens and Halske some three years ago. It consists of a curved cylinder in which works an aluminium piston, without, however, touching the walls of the cylinder. This device has recently been adopted by Messrs. Everett, Edgcumbe and Co. for use in their commercial ammeters and voltmeters. When it is said that the clearance all round does not exceed 0.015 in., it will be seen that the mechanical difficulties of manufacture are great; but as regards durability and reliability, it is found from experience, as a matter of fact, that blows severe enough to bend the pointer have no effect whatever on the damping arrangement. The cylinder, in fact, by checking the motion of the piston performs much the same function as does the pointer catch, which is often fitted to portable instruments. The piston, moreover, in travelling to and fro, keeps the cylinder clear of dust; while the reverse is the case with magnetic damping, as small particles of iron have a great tendency to accumulate in the air-gap. It will be noticed that this method is equally adapted to portable instruments, as it requires no levelling. A modified form of the above arrangement is made by Messrs. Nalder Brothers and Thompson. In this case the piston works in a rectangular groove, which is closed by a removable lid. On removing the latter, the piston may be examined or withdrawn with very slight difficulty. Hot-Wire Type.-Instruments of the hot-wire type, as the name implies, use the expansion of a fine wire under the heating effect of the current to actuate the pointer. They may be used on either direct- or alternating-current circuits with the same calibration, and their readings are unaffected by frequency or wave-form. Stray magnetic fields also do not influence the readings. A current of .1 ampere to .2 ampere passing through the hot wire will give the maximum deflection of the pointer, a resistance being used in series in the case of voltmeters, while in ammeters the main current is shunted, the fall of pressure across the instrument being about 1.5 volts at full load. Temperature errors are perhaps the most important to be guarded against, and are compensated with more or less success by the use of thin wires, whose expansion under the influence of extraneous heat counteracts the effect of the same on the measuring wire. The principle of the instrument insures a considerable dead-beatness, although this may be increased by the damping effect of a permanent magnet embracing an aluminium dise on the spindle. Such an arrangement being easily applied and very effective, is much used in instruments to obtain deadbeatness. The hot wire is fixed vertically and to its centre is attached a fine wire connected to a spring, tending to pull the hot wire out of the vertical position. Any expansion of the hot wire will be magnified very greatly by the "sag," and this magnification is communicated to the pointer. In the Cardew type the hot wire is of considerable length, and is contained in a tube projecting from the cylindrical case; the scale extending almost the full cir- cumference of the dial. The scale in all hot-wire instruments is most open at the outer end. The inner end is very cramped, and frequently left uncalibrated. The zero position of the pointer is also very indefinite, owing to the stretching of the wire, and means are provided for resetting the pointer to zero should it become necessary. This operation, however, does not affect the accuracy of the instru SWITCHBOARDS. 589 • ment. Fuses are usually inserted for the protection of hot-wire instruments from an overload, but their reliability is doubtful. It is often noticed that when one of these instruments has been in circuit for a short time on a steady load, the pointer gradually creeps backwards a certain extent. This is due to the expansion of the interior parts, by the heat conducted or radiated from the hot wire, and is a common defect. Electrostatic Type.-The only switchboard instruments which depend for their action on the electrostatic attraction between oppositely-charged metallic plates are voltmeters, and then only for high-tension circuits, as a rule. The usual arrangement of the interior of the instrument consists of one or more pairs of fixed segmentally-shaped vanes, between which similar vanes, mounted on a pivoted spindle, may be drawn. When the fixed and moving vanes are connected respectively to points of different potential, the electrostatic attraction draws the moving vanes more or less between the fixed ones, causing a pointer on the spindle to take up a corresponding position on the scale. They may be used on either alternating- or direct-current circuits with the same calibration, and have a slight advantage over other types in that no current passes through them; although the growing tendency to have no high-tension apparatus on the front of the board is causing their displacement in favour of instruments worked from the low-tension X-1*-*- 不 ​10- 44 * -5″ TERMINAL FOR H.T. LEADS 4/--- WATER RESISTANCE CUT OUT, IN METAL CLIPS. A — PLUG CONTACTS PORCELAIN HOLDER 'INSULATION TUBE (1040) Fig. 67. Ferranti Protective Resistance for Electrostatic Voltmeters. side of a transformer. They are independent of wave-form, frequency and tempera- ture, and may be rendered perfectly dead-beat by magnetic damping. The control of the pointer is either by gravity or a spring. The case is usually of ebonite, and the connection to the bus-bars may be made by cables in the ordinary way, or the instrument may stand on the bars, two of the legs being in metallic connection with the fixed and moving vanes respectively. The set of fixed vanes usually are connected to the “inner” bar in an earthed system, the moving vanes, pointer, &c., being then at zero potential. To avoid sparking over" between the vanes, due to their too great proximity or to transient rises of potential on the system, the fixed vanes are often covered with insulating material such as mica, and a spark-gap in addition, connected in parallel with the instrument. Some makers protect the internal portions from the consequences of an accidental short circuit by a fuse consisting of a line drawn in lead pencil. A high resistance is also placed in circuit to keep the current so low that the instrument could not be damaged in the event of a short circuit; and choking coils in series are advantageous for the same purpose, particularly when the circuit contains overhead transmission lines exposed to the influence of lightning. Spark-gaps placed in parallel with the instrument have been also employed, but it is found by experience that they are by no means a certain safeguard against sparking across between the vanes. A voltmeter cut-out now in considerable use for the protection of H. T. and E. H. T. instruments is shown in Fig. 67. It consists of a glass tube filled with water, connected in series with the instrument 590 SECTION V.—POWER STATION. and offering extremely high resistance to the passage of the current. A small valve is made in the glass tube near the bottom, consisting of a hole covered with a piece of rubber tubing, somewhat similar to the valve in a bicycle tyre. The current is led into the top and bottom of the glass tube by means of brass sleeves, from which a platinum wire is fused through the walls of the tube. The tube is held in spring clips terminating outside in plug-contacts, and the whole is enclosed in a porcelain holder something like a Bates fuse in shape. The Kelvin Multicellular Electrostatic Voltmeter.-The dial type of instru- ment is made for circuits up to 8500 volts, the scale being especially open at the working voltage. The case is of ambroin, and the movement controlled by gravity. The horizontal edgewise type is often mounted, so that the scale projects immediately over the top of the switchboard. The ranges of instru- ments of this type are from 80 to 1400 volts; and on account of their accuracy and independence of all disturbing causes, one or more are frequently mounted on L. T. continuous-current boards, as a check upon the moving coil or other types. For measurements of voltages above 8000 or 9000 volts, the electrostatic principle is used in a rather different manner. The pointer is actuated by the movement of a suspended disc under the attraction of a fixed plate, much as in the Kelvin electrostatic balance. The scale is made open at the working voltage, and the ranges vary from 5000 to 30,000 volts. Moving Coil Type.-This class of instrument, also known as the D'Arsonval syphon recorder or Weston type, is only suitable for continuous-current measure- ments, but for this purpose it is much more widely used on central-station switch- boards than any other type. Both ammeters and voltmeters are made on this principle, the former having a definite proportion of the current to be measured shunted through the instrument, and the latter having a high resistance in series. The essential feature of the instrument, as usually constructed, is a small coil so pivoted in a strong magnetic field as to be capable of rotation about its axis under the influence of the current flowing through it. The current is led to it by means of springs of non-magnetic material, which also serve to oppose the motion. A cylindrical iron core is fixed inside the coil, and the poles of the magnet are bored out concentrically with it. By this means a uniform field is produced; and as the torque due to the springs is practically proportional to the angle turned through, it follows that this angle is itself proportional to the current. As a result, an evenly divided scale is obtained throughout the whole range. If the spring is "set up," so that when the pointer is at the beginning of the scale a torque is already exerted by the spring, the pointer will not begin to move until a certain predetermined current is flowing through the coil. The effect is the same as though the instrument were provided with a scale, say, two or three times as long as that which it actually has, of which scale, however, only the upper half or third, as the case may be, is visible. This arrangement, of course, is chiefly of use for voltmeters. The instrument is excellent from an electrical point of view. The permanent magnet field is strong: from 700 to 2000 lines per square centimetre, according to size of instrument. The resistance of the moving coil being only from 10 to 20 ohms, it can be swamped by a series resistance having a negligible temperature coefficient, so that the actual temperature coefficient of a 100-volt moving-coil voltmeter is less than .01 per cent. per deg. Cent. The variation of the permanent magnet and the controlling springs with age is now also negligible. The instruments are very dead-beat, the damping being effected by eddy currents in the copper or aluminium frame on which the moving coil is wound. Moving-coil instruments are usually fitted in cast-iron cases to avoid errors due to stray magnetic fields, and the series resistance for voltmeters is contained in the same case. Shunts for ammeters should be connected to their respective instruments by the same leads as sent by the makers. The external appearance of moving-coil instruments varies greatly, though they have the common feature of an evenly-divided scale. The edgewise types of instruments have the advantage of giving a long scale and yet requiring very little room on the panel. The sector type are mounted either upright or inclined forward at the top of the board, or sometimes a swivelling bracket at the end. Both the edgewise and sector types are well adapted for illumination of the scale by one or more incandescent lamps placed behind it. The instruments in round cases are frequently made with a flange round the front of the case, so that the body of the instrument may be recessed into a hole in the switchboard, the face standing flush with the surface. Messrs. Crompton and Co. have paid much attention to the design of moving SWITCHBOARDS. 591 coil instruments, with the object of standardising their manufacture, and per- mitting of their easy verification and adjustment. Current is led to and from the moving coil through a pair of strips of silver foil, which offer no appreciable resist- ance to the motion of the coil. Only one controlling spring is used instead of two as usual, and as it carries no current, considerations of conductivity and tempera- ture coefficients are neglected, and the mechanical construction is also easier. All parts of the instruments are made to gauge, so as to be perfectly mechanically interchangeable. Similarly-wound movements are also electrically interchangeable, subject to adjustment of controlling spring. The moving coil of the Crompton amperemeter has 15 turns of copper wire, and a resistance, including its flexible silver connections, of about .16 ohm. In series with this is placed a resistance of constantin wire to reduce the effect of change of temperature. The moving coils of voltmeters, which indicate from a zero at one end of the scale, are wound with 133 turns of wire, having a resistance of about 15 ohms, and those which indicate pressures near a centre or mean value are wound with about 250 turns of wire, having a resistance of about 60 ohms. All shunts for amperemeters are adjusted to give an electromotive force between the potential terminals of .075 volts exactly when the full-rated current is passing. The external resistances of all voltmeters which have scales reading from zero at one end to some maximum reading at the other are adjusted, so that .015 ampere passes at the maximum pressure; those of voltmeters which give readings about same central or normal pressure are adjusted to pass .015 amperes at that mean pressure. The design of these instruments has been worked out with the direct object of their easy verification and adjustment by the user as well as in manufacture. Every indicating instrument is either a milliamperemeter reading to 15 milliam- peres, or a millivoltmeter reading to 75 millivolts. Induction Type Instruments.-The induction principle is used in ammeters, voltmeters and wattmeters, for the measurement of alternating currents. The general method of construction embodies a disc of aluminium placed in a strong magnetic field, and tending to rotate by means of the eddy currents induced in it. The motion is opposed by means of a spring in the case of indicating instru- ments, or communicated to a train of wheels in the case of integrating instruments. In the induction ammeters and voltmeters devised by Mr. James Swinburne there are two windings, respectively, inductive and non-inductive, to give the requisite difference of phase in the current measured. In another and very common type of induction instrument a rotating field is produced by means of a single winding. In this case a copper ring is used, the eddy currents in which retard part of the magnetic flux and cause the same result as a rotary field. All induction instru- ments are necessarily very subject to errors from changes of frequency, but their good mechanical features make them widely used on switchboard work where the frequency is practically constant. They can be rendered easily as dead-beat as required by causing the disc to work between the poles of a strong permanent magnet. Description of the Movement of Elliott Alternate-Current Instruments. (FIG. 68, page 592.) These instruments are all of the magnetically damped, moving coil, dynamo- meter type. The movements of all the Elliott alternate-current instruments are the same in dimensions and general appearance, the only difference being that the ammeters are wound in a larger size of wire than the voltmeters, and that the wattmeters have a fine winding for the volt circuit and a larger wire for the current circuit. Fig. 68 gives a general view of this movement. The base is a sole-plate into which are screwed two pillars that support the bridge piece. In the centre of this bridge piece is an ebonite bush that carries the top jewel screw, the bottom jewel screw being also held in a bush. The springs that control the motion of the moving coil are soldered to one end of each of the tail-pieces respec- tively. The whole sole-plate is insulated from the iron case of the instrument, and fixed in position by bushed brass screws. The fixed coil of the instru- ment is held in a strip, supported on an extension of the sole-plate. The motion of the moving coil is damped by the eddy currents generated in the aluminium disc, swinging in the air gap of the four permanent magnets. The deflections of the instrument are indicated on the scale by the pointer, and 592 SECTION V.-POWER STATION. the moving coil is accurately balanced by means of weights on the arms. motion of the coil is limited at either end of the scale by flexible stops. The pivots on which the moving coil swings are of hardened and polished steel, accurately ground to correct shape and size, and the jewels are sapphires specially selected for shape, polish, and hardness. TI До 000000 1075 The Fig. 68. Movement of the Elliott Alternating-Current Instrument. The instrument cases are all fitted with a zeroing device, consisting of a slotted screw and lever that engages with the bottom tail-piece, and thus turns the bush, and with it the spring, and therefore alters the position of the moving coil, until the pointer is on the zero mark. The Measurement of Power in Circuits. The power in a continuous-current circuit can readily be obtained by multi- plying together the amperes flowing in the circuit and the voltage across the terminals, as indicated by the ammeter and voltmeter; but this method cannot be employed in an alternating-current circuit unless the load is perfectly non-induc- tive. In this case, the power-factor of the circuit, or the ratio of the true to the apparent watts is unity; but as inductance is added to the circuit, this ratio is gradually reduced, and it is no longer possible to obtain from the indications of the ammeter and voltmeter the true power absorbed in the circuit. In practice, the measurement of the power in an alternating circuit is made by means of a wattmeter, of which several forms have been devised. Direct-reading wattmeters may be divided into three classes-dynamometer type, rotary-field type, and hot-wire type. Of these the dynamometer type has been by far the most employed, and for accurate work is undoubtedly to be preferred. Rotary-field .. SWITCHBOARDS. 593 wattmeters, however, possess many advantages for switchboard work, while hot-wire wattmeters have been suggested, notably by M. B. Field, and are chiefly of interest owing to the fact that the range of the instrument can be easily varied by means of a shunt. A dynamometer wattmeter consists essentially of a fixed coil or coils, exerting a torque on a moving coil or coils. The fixed coil carries the main current in the circuit, and the movable coil carries a current proportional to the difference of potential between the mains. The deflecting force is at all times proportional to the product of the instantaneous values of the currents in the two coils; and in order, therefore, to obtain a direct measurement of the power in the circuit, it is necessary that the current in the moving coil should agree exactly in phase with the potential difference between the mains. Dynamometer-type Wattmeters.-The chief errors to be guarded against in these instruments are:- 1. Self-induction and capacity of the moving coil and its series-resistance. 2. Eddy currents. 3. Effects of external magnetic fields. It was at one time thought that practically the only error of any importance was that due to the self-induction of the moving coil. It is now recognised, however, that not only can this be rendered quite negligible, but that care has even to be taken that the series-resistance introduces no capacity. Thus the ordinary non-inductive method of winding, in which two wires are laid on a bobbin or frame in parallel, possesses not only the disadvantage that neighbouring wires have often a large difference of potential between them, but also that it has a very considerable electrostatic capacity. The series-resistance of wattmeters, and, in fact, of all alternating-current instruments, should always for this reason be wound in sections. The capacity is, as a matter of fact, inversely proportional to the square of the number of such sections into which the resistance is divided. The self-induction of the moving-coil circuit of a well-designed wattmeter should not exceed 10 milli-henries. The current taken at full load would be about one-thirtieth of an ampere, and in that case the error in a 100-volt instrument would be less than per cent., with a power factor of 0.2, and becomes quite negligible for all power-factors greater than, say, 0.6. The errors due to eddy-currents, which have often been neglected, are usually the more serious of the two. The effect of these eddies is to cause the magnetic flux, which should be proportional to and in phase with the current in the fixed coils, to lag behind it by an amount depending upon the frequency. In a badly. designed wattweter the error from this cause may easily amount to as much as 10 per cent. with a power factor of 0.5, and becomes more and more marked the smaller the power-factor; owing to the fact that the eddy-currents lag practi- cally 90 deg. behind the current in the fixed coil, and are therefore more nearly in phase with the current in the moving coil the greater the lag between current and voltage. The errors caused by external magnetic fields are often considerable, unless the instrument is constructed astatically, and are only to be obviated by taking a second reading after reversing the current in both fixed and moving coils. This precaution should always be taken, whether the instrument be used for direct or alternating current. In the former case, the earth's field has often a quite appreci- able effect. The stray field error may be roughly determined by short-circuiting the current coil of the instrument, while leaving the voltage on the shunt coil. If a deflection is produced, a corresponding amount (in watts) is to be added or subtracted, according to its direction, from the observed power. For low-current measurements the last method will usually be found sufficient, but for heavy currents the effect of the conductors leading the current to and from the instrument have usually some effect on the readings, and this can only be eliminated by reversing, as explained above. Dynamometer-type wattmeters are difficult to construct for currents greater than, say 200 amperes, as, unless very carefully laminated, eddy-currents are produced in the fixed coils, and the effect of the leads just alluded to becomes excessive. In order to increase the range above, say, 400 amperes, or in order to obtain an instrument with more than one current range, recourse must be had either to a series transformer or to a shunt. In both these cases there will be an appreciable phase difference between the current to be measured and that flowing through the fixed coil of the wattmeter. So long as this phase difference is constant, its effect is easily eliminated by so adjusting the self-induction of the 594 SECTION V.-POWER STATION. moving coil that the current in it lags behind the voltage by just the same angle as the current in the fixed coil lags behind that to be measured. For high-tension working the transformer method is much to be preferred, owing to the fact that the instrument can be entirely insulated from the high-tension system. The power consumption also is considerably less. Induction Type Wattmeters. These instruments are similar to the induction ammeters and voltmeters already described, the non-inductive coil being replaced by a coil carrying the current, while the supply voltage is applied to the terminals of the inductive coil. The latter induces a current in the rotating disc, or drum, which is practically 180 deg. out of phase with the voltage; and as the current coil produces a flux which is practically in phase with the current, it follows that the torque will be propor- tional to the product of the instantaneous values of the amperes and volts, that is to say the true watts. In a similar way the current induced by the current coil reacts on the flux due to the volt coil, and again produces a torque proportional to the true watts. As was mentioned when dealing with induction ammeters and voltmeters, the indications are much affected by frequency changes, though almost independent of wave form. They are, therefore, chiefly of use for switchboard work, where the frequency is practically constant. For high-tension systems also, they lend themselves readily to the use of series and voltage transformers. The method of eliminating the frequency error by using a non-inductive shunt, is applicable to these as to other induction instruments. Methods of Connecting Wattmeters. (FIGS. 69 to 77, pages 595 and 596.) In two-phase circuits one or two wattmeters can be used, depending on whether the load is balanced or unbalanced. It is advisable, however, to use two separate instruments (Fig. 70), each measuring the power in one phase, the total power being the sum of the two readings. If the load is balanced, that is, if it is a pure motor load, one wattmeter can be used. This instrument will indicate the power in one phase only, but the scale can be arranged to indicate the total power, or the scale reading can be multiplied by 2. The connections are shown diagram- matically in Fig. 71, but as the conditions of absolute balance are very rarely fulfilled this method is not to be recommended. In three-phase circuits the power can be obtained by using one, two, or three wattmeters. If three instruments are used, they are connected as shown in Fig. 72, and the sum of the readings represents the total power in the circuit whether the load is balanced or unbalanced. The use of three wattmeters is, however, unnecessary, as the total power in a three-phase circuit, supplied either from a star-connected or a mesh-connected generator, can be obtained from two wattmeters, whether the circuit is balanced. or not. The two wattmeters are connected as shown in Fig. 73, and the sum of the two readings gives the total power in the circuit. By the use of two wattmeters, connected as shown in Fig. 73, it is possible to find the power-factor of the circuit from the readings of the two instruments. The readings of the wattmeters are— therefore W1 = √3 E C₁ cos (01 + ☀) √3 E C₂ cos (03 — ); C3 and 01 = = and In balanced circuits C W3 = W1 W3 = ძვ = 30 deg. ; √3 cos − p) $)√3 cos < cos (30 deg. + ☀) cos (30 deg. – sin & + sin W1 W₁ = 3400 watts and W3 = 9000 watts, then 1 W3 the corresponding and by substituting in this equation different values of values of cos are obtained. These values are then plotted as ordinates from a datum-line divided to represent ratios of W₁ to W3 between + 1 and -1, and the curve shown in Fig. 77 is obtained. To find the power factor of a circuit it is therefore only necessary to find the ratio of the wattmeter-readings (taking sign into account) and to refer to the curve. For example, let ; W3 and referring to Fig. 77 it will be found that the power factor corresponding to the W1 = 0.37, SWITCHBOARDS. 595 69 71 75 73 km SINGLE PHASE W-EC cos •W, TWO PHASE (BALANCED) INDEPENDENT OR COMMON RETURN W V3E ee V3E W-EC cos W-2W, Woo 00 THREE PHASE (UNBALANCED) USING TWO INSTRUMENTS ee с THREE PHASE (BALANCED) NEUTRAL POINT NOT AVAILABLE W, พ, 00 100 19 C с W√3EC,cos(0,•p) W√3ECycos(0,-p}) W-W·W DI E V3E VзE TWO PHASE (UNBALANCED) INDEPENDENT OR COMMON RETURN C₁ W 3. /00 00 W₂ lee * W-E,C,cos WE,C₂cos 3 11.1 W-W+W₂ THREE PHASE (UNBALANCED) USING THREE INSTRUMENTS A E, Ci W₁/00 100 00 W wal/00 100 iee C₂ ee E W.EC,cos W-3W, WEC,cos WEСcosø WEС.cos W•w•w•W₂ THREE PHASE (BALANCED) THREE PHASE (BALANCED) NEUTRAL POINT AVAILABLE c, 00 VIE V3E C& V3E Y3E √3E + √3E WV3ECos(90°) •V3ECAIN $ •VS 1 WATTLESS POWER, PER PHASE 70, 72: 74 76 WECcos W-3W2 W-EGcos W-3 W, Fig. 69 to 76. Wattmeter Connections for Different Circuits. 596 SECTION V.-POWER STATION. value + 0.37 of this ratio is 0.775. Sometimes it may be necessary to reverse the shunt-leads of one of the wattmeters in order to get a reading. If this has to be W1 done, the ratio will be negative. W3 The following information concerning the use of wattmeters and the methods of connecting them in circuit for various purposes may be found useful by engineers. In Figs. 69 to 77 the symbols used have the following meanings :-W denotes the total watts in the system; W1, W2, W3, denote the readings on different watt- meters. C, C1, C2, C3, denote the currents; and E, E1, E2, the voltages of the different leads; and r, r₁. r2, denote the external non-inductive resistance in series with the movable coils. Single-Phase.-The connections are shown in Fig. 69. The instrument indicates the total power absorbed in the circuit. Two-Phase.-One or two wattmeters are necessary, depending on whether the circuit is balanced or unbalanced. If the former, the connections are shown in Fig. 71, and the wattmeter reading has to be multiplied by two to obtain the total 1.0 0.8} Sor • POWER FACTOR ❤ Co M 0-2 0.1 W- v$EC cos(30+6) W VSEC cos(30) W, cos (30° of 18cos - Sig W₂ cos(3U-p (3cps &• sin ❤ 1.0 5 •2 0+ ·} RATIO OF READINGS · - •2 FR3 Wi W 1 6 ∞ 10 Fig. 77. Curve for obtaining Power Factor of Three-Phase Circuit from Wattmeter Readings. power. If the latter, the connections are shown in Fig. 70; the sum of the two wattmeter readings giving the total power. Three-Phase.-One, two, or three wattmeters can be used, depending on the .conditions. For unbalanced loads the connections, as shown in Fig. 72 or 73, and the total power is the sum of the wattmeter readings. If the power factor of the system is lower than 0.5, one of the wattmeters shown in Fig. 73 will read on the negative side of zero, and in order to obtain the correct reading the shunt current will require to be reversed. In this case one reading is subtracted from the other. The method illustrated in Fig. 73 is to be recommended in the majority of cases. For balanced circuits the connections will be either Fig. 74, or as in Fig. 75, depending on whether the neutral point is available or not, the resistances r₁ and r2, in Fig. 75, being of the same value and equal to r plus the resistance of the movable coil. The instrument will read the power in each phase, and the reading will require to be multiplied by three to obtain the total power in the system. An artificial neutral point can be produced by means of lamps, thus avoiding the expense of the extra resistances r₁, and r2. In three-phase systems a wattmeter connected like W, in Fig. 76, indicates the p, phase angle; but this method can only be recommended for low voltages, otherwise a considerable difference of potential will exist between the fixed and movable coils, SWITCHBOARDS. 597 which might cause damage. The instrument in this case being arranged with a central zero, a deflection will be obtained to the right or left, depending on whether there is a lag or a lead. Another and a safer method is to connect the fixed coils in series with one arm of the circuit, and to take two readings with the free end of the shunt circuit connected, first to one of the opposite arms (reading obtained d), and then to the other arm (reading obtained d₂). The power-factor can be obtained from the following formula :— Power factor of circuit = In another method two wattmeters, connected as shown in Fig. 73, are used to obtain the power-factor. At the top left-hand corner of Fig 77, the value of the wattmeter readings will be found; and as it is well known that the value of the ratio. of W₁ to W2 varies from + 1 to 1, the curve shown in Fig. 77 is obtained by sub- stituting in the formula different values of (angle of lag) (cos & = power-factor). The method of using the curve shown, which has been obtained in this manner, is as follows:-Find the value of the ratio W1, taking note of the algebraic sign, and W2 then find where the ordinate through this point cuts the curve, this point will represent the value of the power-factor. W1 - 3400 watts W2 = "" - EXAMPLES. WI 1 W2 9000 watts Ni N1+3 "" W1 1 W2 di dz d₁ + d2/ W₁ = (-) 2500 W₂ = 5000 (-) 0.5 = 0.18. Numerous other methods of connecting wattmeters have been suggested at different times, but the few given above are some of the principal ones employed. Figs. 69 to 77 are reproduced with the permission of the Institution of Civil Engineers, from a Paper on "Measurement of Power in Alternating Current Circuits," by Patrick Hamilton, B.Sc., A.M. Inst. C.E. (See Proceedings, vol. 54, 1903.) 2)2. 0.37 Power-factor = 0.77. "" Westinghouse Polyphase Switchboard Integrating Wattmeter. (FIG. 78, page 598.) This wattmeter records on a single dial the total energy delivered in all the phases of a two- or three-phase circuit. It will make a correct registration of the true energy delivered by the circuit into which it is connected under any condition of power-factor, or whether the phases are balanced or not. The counter reads directly in kilowatt hours, no constant or multiplier being required. The action of this meter depends upon the induction principle, and consists of a shunt or electromotive force winding and a series or current winding, the combined effect of which, acting inductively upon an aluminium disc, produces rotation of the latter. The above-mentioned windings are wound on an iron core of such form as to produce an electro-magnet consisting of two magnetic circuits, having an air gap in which the disc is free to move. The shunt winding on the electro-magnet is in two parts, one on each magnetic circuit, the result being that there are two equal and adjacent alternating poles of opposite polarity produced; and when the winding is connected to a source of alternating current, the one half exactly neutralises the other half, as far as any action on the disc is concerned. The series or current winding consists of a single coil interlinking both magnetic circuits, the tendency being, with current in the coil, to produce adjacent poles of the same polarity. The result is that with current in both electromotive force and current windings, the flux in one magnetic circuit is the geometric sum of the fluxes due to the electromotive force and current windings, while in the other magnetic circuit, the resultant flux is the geometric difference of the fluxes. By this means a shifting magnetic field is obtained in the air gap, which because of induced eddy-currents, causes the disc to rotate. In order that the torque of the disc shall be proportional to the true power irrespective of power-factor, it is necessary that there shall be a phase difference of 90 deg. between the flux due to the electromotive force winding and that due to the current winding, when the load is non-inductive, that is, when the current and electromotive force are in phase. This result is obtained by making the shunt 598 SECTION V.-POWER STATION. 1 circuit of comparatively low resistance and very high inductance, the shunt winding of the electro-magnet being in series with an inductive resistance or impedance coil, while the series coil consists of but few turns, having a negligible inductance. A retarding force which is proportional to the speed, and therefore the torque of the disc, is obtained by means of a permanent magnet, between the poles on which the disc moves. The above description applies equally to the single and polyphase meters. The polyphase meter consists simply of two single-phase meters, that is, two electromagnets and two discs, the latter, however, being mounted on a common shaft. It is connected in two- or three-phase circuits, on exactly the same principle as two ordinary wattmeters would be connected in order to measure the power, the total torque of the shaft being the algebraic sum of the torques of the two discs, just as the total power would be the sum of the readings of the two wattmeters. POLYPHASE INTEGRATING WATTMETER IMPEDANCE COILS Twww SHUNT TRANSFORMERS Dimensions: "" 29 Extreme height width depth 0000000 Leeee ·· .. llll 10000 00001 (00006 • www. SERIES TRANS Fig. 78. Diagram of Westinghouse Polyphase Integrating Wattmeter www wwwww SERIES TRANS. In practice, these instruments are often used in connection with series and shunt transformers, as shown in the diagram, Fig. 78. In this case the effect is the same as that already described, the currents in the series and shunt coils being respectively proportional to the currents in the primaries of the series and shunt transformers. The instruments are arranged, however, to read directly the energy of the circuits into which they are connected. Sizes.—5, 10, 20, 40, and 80 amperes. Voltages.-100 and 200 volts at 25 periods; 100, 200, and 400 volts at 60 Connections. periods. Instruments are adapted for higher capacities and pressures by using shunt and series transformers. Weights.-Single-phase, 17 lb. ; polyphase, 36 lb. SHUNT OR E.M.F.COILS SERIES OR CURRENT COILS 1058 Single-phase. 11 in. 6 in. and § in. 6 in. Polyphase. 11 in. 6 in. and § in. 8 in. SWITCHBOARDS. 599 Drop at Full Load: Capacity (amperes) 100 200 400 ·· 5 10 20 40 80 .. Shunt watts taken at 60 periods by single-phase meters. Voltage Capacity. • Single or Polyphase. •• • · · Drop in Volts. 0.111 0.067 0.003 0.028 0.014 Shunt Watts. 1.7 2.0 2.2 In the case of polyphase meters, the shunt watts are double those stated above for any given voltage. Westinghouse integrating wattmeters are adjusted by altering the position of the permanent retarding magnets, until the disc makes 50 revolutions per minute at full load, or proportional at other loads. The spindle pinion has eight teeth, and the wheel gearing therewith 80 teeth. The Westinghouse alternating-current wattmeter for single-phase circuits has the same general appearance as for polyphase circuits, except that the terminals are at the back. It is perfectly dead-beat, and independent of the power-factor of the circuit. The scale subtends an arc of 300 deg., and the divisions are open and uniform throughout. W1 W2 tan = W₁+W2 №3. 1 The instrument depends upon the inductive action of an electro-magnet upon a small metal drum. Except for the opposing force of a controlling spring, the drum is free to revolve within pole-pieces with which the electromagnet is provided, these pole-pieces being energised by two sets of windings, a shunt or electromotive force winding, and a current or series winding. A current in the shunt winding tends to make the two pole-pieces of opposite polarity. The current winding is so arranged as to produce two local magnetic circuits in the pole-pieces, and therefore four poles, two of these helping and two opposing those produced by the shunt winding. The result is that a rotating field is obtained, which tends to produce rotation of the drum due to eddy-currents being induced therein. Wattmeter for Three-Phase Unbalanced Loads. (FIG. 79, page 600.) - For the measurement of power in three-phase circuits, where the load is not necessarily balanced, Messrs. Elliott Brothers make an instrument which consists of two of their standard dynamometer type movements, described on page 591, suit- ably connected together and actuating a single pointer. The movement is spring- controlled, with zero adjustment and magnetically damped. Two current and two potential transformers are required when the instrument is used on commercial currents and voltages, and the diagram of connections is as in Fig. 79. The scale divisions are even, and the readings are unaffected by wave form or frequency. If the load is known to be balanced, the power-factor of the circuit may be ascertained by taking readings with one of each of the current transformers disconnected in turn. Let W₁ be the reading when one side of the instrument is disconnected, and W2 the reading with the other disconnected; then 1 Cos 4-the power-factor-may be then obtained by calculation, or direct from trigonometrical tables. It should always be remembered that, if a current transformer be left in circuit, and the instrument disconnected, the secondary terminals must be short- circuited. The Ferranti Integrating Wattmeter. (Fias. 80 to 83, pages 600 and 601.) In this meter an aluminium disc is mounted on a spindle geared to the train of wheels actuating the index hands. The appearance of the switchboard instrument is shown in Fig. 80, and the details of construction in Figs. 81 to 83. This disc serves the double purpose of an armature, receiving the driving torque of the meter coils, 600 STATION. SECTION V.—-POWER POWER TRANSFORMER) LOAD ~ GENERATOR 3 AMPS +↓ AMPS 3 WATTMETER 2 O Fig. 79. Connections of Elliott Brothers Three-Phase Wattmeter. BOARD OF TRADE UNITS 100000 10000 1000 100 AMPS YOLTS TRANSFORMER) 10 UNIT O 1056 Fig. 0. The Ferranti Integrating Wattmeter. SWITCHBOARDS. 601 and also the retarding torque of the permanent magnets (P.M.). The shunt system consists of one shunt coil (SH. C.) placed round the core (C) of a special tubular electromagnet (T.M.). The core of this magnet has three outward radial poles, P2, alternating with onward radial poles P₁ from the shell or tube of the shunt magnet, the plane of these poles being horizontal and parallel to the disc; the tubular magnet is below the disc. The series system consists of a slotted armature CT 1000 SeC D BOARD OF TRADE UNITS 100 10 TM AMPS P2 pi VOLTS CL 10 pz L PIP2 、 Wattmeter. UNIT PER TS Figs. 81 to 83. The Ferranti Integrating DIVISION SA 81 82 PH 83 above the disc, the series coils being wound in these slots. A wave form of winding is used, and the slots are almost directly over the poles of the shunt magnet. Owing to the inductance of the shunt, the eddy-currents it produces in the disc are practically in phase with the impressed electromotive force. These eddy. currents are acted on by the series field-which is in phase with the load current- giving a torque on the disc proportional to the true watts. The retarding effect of the permanent magnets is proportional to the speed; hence the disc revolves with a 602 SECTION V.-POWER STATION. speed proportional to the true watts. The adjustment of the meter can be most accurately made, by rotating the series system very slightly by means of screws provided for the purpose, and the series armature can also be raised by an indepen- dent device to alter the constant of the meter. The meter is practically independent of the power factor of the circuit, periodicity, wave form, or temperature. It will work at 50 per cent. overload, or variations of voltage of 50 per cent. It will not run on the shunt alone, and the starting current is very low, a 10 ampere meter starting with .05 amperes. The shunt current is only .015 amperes, and the shunt and series losses not more than 1.7 and 0.8 watts respectively in a 10 ampere meter. The Ferranti Indicating Wattmeter. This instrument is constructed on the induction principle, and is similar in its internal arrangements to the standard Ferranti alternating current integrating wattmeter, except that the train of wheels is dispensed with, and the motion of the disc opposed by a spiral spring. It is contained in an iron case, to prevent errors due to stray fields and errors due to change of frequency and temperature are reduced to negligible amounts. On high potential circuits it is worked off transformers, so that the instrument is always at, or near to, earth potential, and therefore safe to handle. The scale is 11 in. long, with very open equal graduations. The Kelvin Engine-Room Wattmeter This instrument is of the electro-dynamometer type, graduated to read directly in watts. It is suited for use on either continuous or alternating-current circuits. It is made in either the dial pattern, as shown in the figure, with a 6-in. scale, or with a vertical scale of 10 in. For H. T. and E. H. T. circuits the dial pattern only is used. The main, or fixed, coils are wound with copper ribbon, and carry the whole current. The moveable coils are mounted astatically on a light aluminium frame, to which the pointer is also attached. In the dial-pattern instruments the moveable system is carried on knife-edges, while in the vertical scale type it is suspended by a flat strip of phosphor-bronze. The self-induction of the moveable coil is kept extremely low, and its effect swamped by the series resistance in circuit with it. The current through the moving coil circuit does not exceed .03 ampere, and the error due to self-induction is less than .5 per cent. at all frequencies on a circuit with a power-factor so low as .3. Wattmeters up to 600 volts have their series resistances fitted inside the case; for higher voltages the resistances are contained in one or more boxes outside the instrument. When it is desired on H. T. circuits to keep H. T. leads away from the instrument, it may be worked through series and current transformers; but where the greatest accuracy is required, non-inductive resistances are recommended for the shunt circuit. The Thomson Wattmeter. (FIG. 84, page 603.) The fields consist of two coils of thick wire, one on either side of the armature, and are connected in series with each other, and with the circuits whose absorption of energy they are to measure. The armature consists of a hollow frame wound with a set of coils of fine wire on the "Siemens' druni" principle, attached to a small silver commutator carried on the shaft near its upper bearing. Two light springs with silver contact-pieces bear upon the commutator and constitute the brushes. The fine wire armature coils are in series with a proportionally high non- inductive resistance carried in the frame at the back of the meter, and form a 'pressure coil," the current in which varies with the voltage. × In such an instrument the torque at any given time will be proportional to the current pressure = watts, and the speed (assuming that there is absolutely no friction, solid, or fluid) will continue to increase indefinitely even with a constant torque. To make the speed vary directly as the watts, it will be necessary to introduce some resistance to the rotation which shall increase in direct proportion to the speed. This is accomplished by placing on the shaft a thin disc of copper. This disc rotates in a constant magnetic field between the poles of three permanent magnets, only one of which is shown in Fig. 84. The fields of these magnets generate Foucault or eddy-currents in the disc, thus forming a drag or load on the motor. The ohmic resistance of this disc remaining constant, in a constant field as supplied by the permanent magnets, the E.M.F. and the current generated in the r SWITCHBOARDS. · 603 disc will also vary as the speed, and the retardation, which is proportional to the current x field, will also vary directly as the speed. A resistance is thus provided which bears the same proportion to the speed as the torque of the motor bears to the watts; the resultant speed is therefore directly proportional to the watts. ( (429) AD 1000 100 ELIHO TEAMSON D. B Fig. 84. Thomson Wattmeter. The indications of the meter are shown in B.T.U. on the dial, the first wheel of the registering train engaging with a worm on the shaft, thus connecting it with the revolutions of the armature. The calibration of the Thomson wattmeter is effectively accomplished by moving the poles of the permanent magnets towards or away from the periphery of the disc, thus increasing or decreasing the load on the motor. Instructions for Installing the Thomson Recording Wattmeter. In unpacking and setting up the meter, it is necessary to handle the several parts with care, and to carry out the following directions in the order in which they are arranged. Set the meter frame on a bench, and after removing the cover, loosen the screw that clamps the sleeve to the upper end of the armature shaft, then remove the wedges from between the disc and the magnets, and support the armature in such a way as to prevent the commutator coming away from the brushes. The top guide of the armature, which will be found in the box containing the dials, should now be inserted in the upper part of of the frame in place of the sleeve used for packing the armature. The The jewel screw may now be inserted and screwed up hand-tight. armature will now be found to revolve freely, if its bottom pivot is resting on 604 SECTION V.-POWER STATION. the jewel screw. If this is the case, nothing remains to be done but to lift the top guide so as to allow about of an inch clearance between the worm and the underside of the guide, which should now be clamped by the set screw provided for that purpose. T to 201 The dials should now be fixed, and the meter connected to the circuit ready to start. A slight sparking will sometimes be noticed on the commutator when it is first started. This will soon disappear, as it is simply due to small particles of dust collected on the commutator and brushes, and may easily be removed by rotating the meter two or three times by hand. Should the commutator ever need cleaning, carefully insert a narrow piece of ordinary tape between it and the brushes, and draw it gently backwards and forwards, at the same time rotating the shaft slowly. Be careful in doing this not to spring the brushes out of their original position, and to cause the armature to revolve counter clockwise, i.e., in the same direction as when registering. The meter should never be moved without loosening the jewel screw sufficiently to take the weight of the armature off it. Care must be taken that the number on the back of the dials corresponds in every case with the number of the meter. In fixing the meter to the wall, insert a screw in the upper right hand-hole and screw it up, and then insert another one in the diagonally opposite hole, which will be found slotted to facilitate levelling. When the meter has been levelled by means of the plumb-bob, the remaining screws may be inserted and screwed up tight. Instructions for Reading Thomson Wattmeters. The armatures of all these meters make one revolution per watt per hour, subject to the multiplication by the constant. They are geared so that 1000 revolutions of the armature produce one complete revolution of the pointer on the right-hand dial, that is to say, every digit on the right-hand dial represents (subject to multiplication by the constant) 100 watt hours, so that one complete revolution of this dial, which is equivalent to one division on the second dial, equals one B.T.U. It must be remembered in reading the dial that the number over or under each circle represents in B.T. U. the value of a complete revolution of its pointer. Polyphase Induction Meter for Unbalanced Three-Phase or Three-Wire Two-Phase Secondary Circuits. (FIG. 85.) 10 Foor but bilind adh FROM LINE - to Vert 823 TO LOAD T Fig. 85. British Thomson-Houston Polyphase Induction Meter. On three-phase circuits pass the current of two of the lines through the meter, entering at the two binding posts on the left, and connecting the load to the two posts at the right. SWITCHBOARDS. 605 Connect the potential post on the right-hand terminal board to the third wire, which does not pass through the meter. On three-wire two-phase circuits the connections are the same as above, but the wire that does not pass through the meter must be the common return. British Thomson-Houston Round-Type Polyphase Meters. (FIG. 86.) The right-hand and left-hand pairs of potential studs correspond to the right- hand and left-hand pairs of current studs. The diagram shows the meter connected on a three-phase or a three-wire two- phase circuit, the wire which does not pass through the meter being the common. return in the latter case. Q Fig. 86. Line (824) Connections of British Thomson-Houston Round-Type Polyphase. Meter, with Two Series and Two Potential Transformers. When so connected, the meter should run forward when one of the potential circuits is opened at a time, and when the lag in the system is less than 60 deg. for the three-phase, or 90 deg. for the two-phase. If the disc rotates in the wrong direction, reverse either or both potential con- nections as may be necessary. The Thomson watt hour-meter can be used on either direct or alternating- current circuits; but there is also another class used exclusively for alternating- current work. The Schallenberger meter, made by the Westinghouse Electric and Manufacturing Company, is an example. The principle involved depends on the rotating of a disc or cylinder by means of induction coils properly situated. Power-Factor Indicator. A power-factor indicator is an instrument for indicating directly the angle of lag, or lead, of the current in an alternating-current circuit. They are principally of use on the switchboards of sub-stations driven by synchronous motor-generators, where the attendant can reduce the wattless current in the lines by suitably regu- lating the excitement of the motor fields. In other cases their provision is of no practical use, as there is no control over the power-factor, which, moreover, may always be found by comparing the wattmeter readings with the combined ammeter and voltmeter readings. As ordinarily constructed, power-factor indicators are of two main types. (1) Instruments which show merely the wattless component of the current, and (2) those in which the actual lag or lead of the current is indicated. Instruments of the first type are really a particular case of the ordinary dynamometer wattmeter 606 SECTION V.-POWER STATION. ST in which the volt coil is made as inductive as possible instead of being non- inductive; and it is obvious that, instead of the deflection of the moving coil being proportional to the power, it will be proportional to the wattless component. Such an instrument is sufficient for the purpose of regulating the power-factor by means of the field excitation; but its actual indications are almost meaningless, so that a true phase meter is generally to be preferred. The Everett Edgcumbe Power-Factor Indicator for Three- Phase Circuits. (FIG. 87.) These instruments belong to the second class, above, and have the advantage of being independent, not only of the voltage supply, but also of the frequency and wave-form. This is a valuable feature, as the construction, in which a phase differ- ence is produced by means of an inductive or a non-inductive resistance is, of course, only accurate at one particular frequency and wave-form. 'VOLT TRANSFORMER wwwww www. www wwwww LOAD C.T.(1) wwwww SERIES RESISTANCE BOX C.T. (2) mo CURRENT TRANSFORMER (3) wwwwwwww A ་་ 4 A3 0000000 Unbalanced Load. 1051 Fig. 87. Everett-Edgcumbe Power-Factor Indicator for three-phase In the case of a balanced three-phase load, the instrument consists of a fixed current coil, inserted in one of the lines, and three volt coils fixed at an angle of 120 deg. to each other and carried by a pivot, which also bears an indicating pointer. Each of the three moving coils has one end connected through a series resistance to one of the three conductors. The three remaining ends are joined together, and form the neutral point. A rotating field is thus produced, and the system will set itself in such a position that, at the moment the current in the fixed coil reaches its maximum value, the field due to the moving system lies along its diameter. The method of connection to the mains of an unbalanced three-phase system is shown in Fig. 87. In the case of an unbalanced system, three fixed coils are employed, set at an angle of 120 deg. to each other, and one being inserted in each line. The moving SWITCHBOARDS. 607 system then takes up a position corresponding to the average power-factor of the whole system; and, if a short-circuiting plug is inserted in each of the circuits, it is possible to obtain either the average power-factor of the system, or the power- factor of each phase separately. For high-tension systems transformers are employed, both in connection with the volt circuit and also the current circuit. The instruments, as usually supplied, are fitted in 8 in. round cases of insulating material, similar to those used by the firm in connection with switch- board wattmeters. The instrument can also, of course, be fitted in portable cases when required. Westinghouse Power-Factor Meter. (FIGS. 88 and 89, pages 607 and 608.) This instrument indicates directly the power factor of the circuit to which it is connected, either for a leading or lagging current, as the illustration shows. It is also possible to see when power is being delivered in the reverse direction, and the instrument thus performs the function of a reverse current indicator. 30 50 70 90 th10 50 70 THE BRITISH WEƐ 70 90 WESTING LAG AMPERES POWER O 100 UUSE 90 mudum ELECTRIC 100 LEAD FACTOR PHASE VOLTB & MFC. 70 50 METER PERIC 90 70 50 1053 88 Fig. 88. Westinghouse Power-Factor Meter. It contains two separate windings, a fine wire winding and a heavy wire winding. The fine wire winding consists of a single fixed coil, the terminals of which are connected to the upper binding posts of the meter, which are in turn connected in shunt across two mains of the system, and the current in this coil is practically in phase with the electromotive force between these mains. The heavy wire winding consists of three fixed coils, connected in star fashion, and so disposed that their axes are displaced 120 deg. from each other; in other words, it is an ordinary three-phase star-connected drum winding. The three terminals from this winding are connected to the lower binding posts of the meter, these being connected to the series transformers on the mains. The currents in the three coils are thus displaced from each other in phase by 120 electrical degrees, and they (the currents) will vary in phase with respect to the current in the electromotive- force coil, as the current on the line does to the electromotive force on the line. The moving element, to which the pointer is attached, consists of two iron vanes, so disposed with respect to the coils that the flux due to the electromotive- force coil induces poles in the vanes, these poles being reversed in unionism with the reversals of current in the coil. Also the flux due to the current coils produces poles, and the vanes tend to move into the direction of the resultant flux due to 608 SECTION V.-POWER STATION. the current windings; and, therefore, if the phase of the current changes with respect to the electromotive force, this resultant changes in direction, and conse- quently the vanes and with them the pointer, which are perfectly balanced and have no mechanical restraining force, follow this change. As the angular degrees between the axes of the current coils are the same as the electrical degrees between the currents in the coils, the movement of the pointer measured in angular degrees is a faithful reflection of the change of phase between the electromotive force and current, measured in electrical degrees. In other words, if the current lags behind the electromotive force a certain number of electrical degrees, the pointer indicates 3 PHASE CIRCUIT SERIES TRANS. www SERIES TRANS, ww m 100 V.K VOLTAGE TRANS. 1052 SERIES RESISTANCE IRON VANES EXTERNAL OR CURRENT COILS INTERNAL OR E.M.F.COIL 3 PHASE POWER FACTOR METER Fig. 89. Westinghouse Power-Factor Meter. in the lag direction an equal number of angular degrees, and in the same manner indicates in the lead direction for a leading current. The pointer is so adjusted that for a generating machine it indicates on the upper part of the scale. If then the machine begins to run as a motor, it means that the direction of the current flow has been reversed, that is, it has changed in phase 180 electrical degrees : therefore, on the above principle, the direction of the pointer must change 180 angular degrees. The scale is marked so as to indicate the power-factor directly, and it will be seen here that the above-mentioned property of showing the actual phase difference between current and electromotive force is a decided advantage, as a small change in the cosine of the angle of lag-i.e., power-factor-when near unity requires a large angular change, thus making the useful part of the scale very open. Westinghouse Two-Phase Power-Factor Meter. This is similar in principle and design to the three-phase power-factor meter, except that the external winding consists of two coils having their axes displaced 90 deg. from each other, one coil being connected in one phase, the other coil in the remaining phase, through the medium of series transformers. The Everett Edgcumbe Synchroniser. (FIGS. 90 and 91, page 609.) This instrument, which is largely used in lighting and power stations for the rapid paralleling of alternators, consists, as will be seen from the accompanying illustration, of a round instrument measuring some 12 in. across the dial, and Li SWITCHBOARDS. 609 having a centrally-pivoted pointer (Fig. 90). One pair of terminals are connected to the bus-bars, through a transformer if necessary, the other pair similarly to the incoming machine. If the latter should be running too fast-that is to say, giving too high a frequency-the pointer will rotate in a clockwise direction, and vice versa. 91 SLOW FAST EVERETT EDGCUMBE SYNCHRONISER BUS BARS ROTOR 40000000 B.B 1054 STATOR 0000000 M → 90 1 GENERATOR IMM 1055 Figs. 90 and 91. Diagram of Connections of Everett-Edgcumbe Synchroniser, The instrument consists essentially of a fixed stator, carrying a two-phase winding and a two-phase rotor, the current being led into the latter by three slip- rings. Two rotary fields are thus produced which revolve in the same direction, and if the frequencies are the same the rotor consequently experiences no torque, X 610 SECTION V.-POWER STATION. A and therefore remains at rest. Should the frequencies, however, differ, the rotor will have to revolve in one direction or the other in order that the fields themselves may rotate "in step." The rotor, of course, carries the pointer, as mentioned above. In order that the instrument may be used on a single-phase circuit, the splitting of phase is produced in the instrument itself by means of an inductive and a non-inductive resistance in each of the two circuits. The former consists of a choking coil, and the latter of an incandescent lamp. For use with polyphase circuits it is only necessary to synchronise on one phase, whereby a considerable simplification is possible, besides which, fewer transformers are required in the case of H. T. plant. When the frequencies are the same, and, as pointed out above, the rotor has no tendency to revolve, the instrument acts a phase meter pure and simple: the position of the pointer showing, in fact, the phase difference between the machine and the bus-bars. The pointer is attached to the spindle in such a position that when it stands vertical (as shown in the illustration) the machines are exactly "in step." The synchroniser thus shows at a glance :- 1. Whether the machine is running too fast or too slow; 2. By how much it is out of step (one revolution of the pointer represents a loss or gain of two complete cycles): 3. The exact moment for switching in. In the case of a large engine-room it may be difficult for the engine-driver, to whom this instrument is extremely useful, to see clearly in which direction the pointer is rotating. In order to get over this difficulty, the round opening seen' in the dial is alternately illuminated by a red or green lamp, according as the generator is being driven at too high or too low a speed. By means of this instrument it is possible for even an inexperienced person to get an alternator into parallel in an extraordinarily short time, and with absolute certainty. И- The current taken by each circuit of the synchroniser is from .7 to I ampere, while the power taken by the primaries of the synchronising transformers varies from 75 to 200 volt-amperes, according to the primary and secondary voltage. If it is wished to employ a synchronising lamp in connection with the instru- ment, a lamp of double the voltage marked on the dial of the synchroniser may be connected between the two upper terminals, the two lower ones being connected together. Westinghouse Synchroscope. Description. The three-phase synchroscope consists of two separate fine-wire windings. One of these is a single-fixed coil called the internal coil, the terminals of which are connected to the upper binding posts of the instrument, which are to be connected in shunt across two of the bus-bars of the machine to be synchronised. The other winding consists of three fixed coils connected in star fashion, and so disposed that their axes are displaced 120 deg. from each other; in other words, it is an ordinary three-phase star-connected drum winding. The three terminals from this winding are connected to the lower binding posts of the instrument, which are to be connected in turn to the main bus-bars to which it is required to run the machine into synchronism. The internal coil is within this second winding, which is called the external winding. The moving element, to which the pointer is attached, consists of two iron vanes, also within the external winding, and so disposed with respect to the coils that the flux due to the internal coil induces poles in the vanes, these poles being reversed in unionism with the reversals of the current in the coil, and, therefore, of the current of the machine to be synchronised. The field, due to the external winding, is a rotating one, and revolving at a uniform speed, which will be propor- tional to the frequency. In order to understand the action of the instrument, first assume that the frequency of the current in the internal coil is the same as that in the external coils, then the vanes will be stationary and in line with the resultant fiux with which their induced poles are in phase. From this it follows that a change in the phase relationship between the currents in the internal and external windings will produce a change in the direction of the vanes, but they will remain stationary as long as the frequency of the currents in the two coils remains the This makes it necessary to always connect the internal coil to the machine to be synchronised, according to the way in which the external coils are connected to the main bus-bars. In practice this result is obtained by always connecting the same. SWITCHBOARDS. 611 書 ​upper binding posts to the phase corresponding to that one to which the two lower right-hand binding posts are connected. If the currents in the two windings are not of the same frequency the vanes will rotate, the rotation being in one direction if the frequency of the current in the internal coil is higher than that of the current in the external winding, and in the opposite direction if it is lower. The action is analogous to the result produced by throwing an intermittent light on a revolving disc with radial lines marked upon it. If the number of the flashes of light per second equals the number of revolutions of the disc per second, the disc appears to stand still. If the frequency of the light is decreased, the disc appears to run forward; if it is increased the disc appears to run backwards. Westinghouse Two-Phase and Single-phase Synchroscopes. Two-Phase Synchroscope.—This is similar in principle and design to the three- phase synchroscope, except that the external winding consists of two coils having their axes displaced 90 deg. from each other, one coil being connected across one phase, the other coil across the remaining phase. The external coils are connected to the main bus-bars, and the internal coil to the machine to be synchronised. Single-Phase Synchroscope. This is similar in principle and design to the two- phase synchroscope, the external winding consisting of two coils having their axes displaced nearly 90 deg. Both coils, however, are connected to the same terminals, and in series with one coil is inserted a non-inductive resistance, while a highly inductive resistance is inserted in series with the other coil, a phase displacement of nearly 90 deg. between the currents in the two coils being thus obtained. Insulation Testing Instruments or Ohmmeters. It is well known by practical engineers that to determine the insulation resistance of an article or a circuit, a voltage must be applied of the same order as the insulation will have to stand in everyday work. The ordinary Wheatstone bridge is unsuitable for the measurement of this class of resistance for many reasons: its readings are usually not high enough, they require a certain amount of skill and time to obtain; and further, a resistance which would appear infinite when measured with very low voltage of the bridge, might break down immediately under working conditions. For these reasons several instruments have been put upon the market for the direct reading of high resistances. They indicate directly in megohms, or fractions of a megohm, and may be safely put into the hands of comparatively unskilled men. The Evershed Patent Ohmmeter. Messrs. Evershed and Vignoles have recently designed an instrument for insulation measurements, known as the Megger, which is shown diagrammatically EARTH PRESSURE COIL LINE ww CURRENT COIL INFIN ZERO Fig. 92. Diagram of Evershed's "Megger." 1060 612 SECTION V.-POWER STATION. in Fig. 92. The ohmmeter and generator are combined in one case, and the same permanent magnetic circuit forms the fields for both parts of the apparatus. The instrument is exceedingly portable and strongly built. Its indications are absolutely deadbeat. For testing dynamo windings, house circuits, &c., a series of instruments are made to read up to 200 megohms, while for cable testing and similar work where there is much capacity in circuit and a high range is required, a special series of instruments are supplied, reading to 4000 megohms. The latter instruments are fitted with constant speed generators, so that an absolutely uniform voltage is used for the test. This instrument has come very largely into use owing to the simplicity of handling it; all resistances are indicated by a deflection, instead of requiring calculation, and the set is portable and able to be used by unskilled men. Nalder Brothers and Thompson's Ohmmeter and Generator. Fig. 93 shows the general appearance of this instrument, and the principle upon which it works is illustrated diagrammatically in Fig. 94. From the latter figure it will be seen that as long as the insulation resistance from line to earth is infinite, no current will flow through the non-inductive resistance R, which is contained in the case of the instrument. If the insulation of the line is defective, the current will flow through the resistance R to earth, and the magnitude of this current will determine the difference in potential between the electrostatic segments A and B; the position of the needle being dependent on the difference of potential between these two can obviously be calculated so as to indicate the resistance of the line. The great advantage of this type of instrument is obviously that, being electrostatic, it is not affected by the field set up by the generator, consequently the two can be mounted in close proximity in one case, which shows a great gain in compactness when compared with types of ohmmeters and generators in two cases. E L INF LL A FIGS. 93 and 94. Nalder's Electrostatic Ohmmeter. www R B 1046 Everett-Edgcumbe Direct-Reading Resistance and Insulation Indicators. These instruments work on the Wheatstone bridge principle, but are so arranged as to be absolutely direct-reading. This is obtained by means of a special high-resistance slide-wire arrangement of circular form, round which a contact travels. The contact is fixed to a central spindle carrying a milled head at the top, and is also provided with a pointer moving over a scale so graduated as to read direct in ohms or megohms, as the case may be. The slide-wire itself is of special construction, and is somewhat similar to what are known as "Wirt Rheostats;" that is to say, it takes the form of a circular drum, wires being wound round it in a direction parallel to the axis. By this means it is possible to secure slide-wires having extremely-high resistances, say 10,000 ohms, and at the same time to make contact with the wire at any point along the circumferential length, which amounts to something like 12 in. In order to reduce the standard resistance to a convenient value, a considerable idle resistance, wound on a bobbin, is inserted in series with the slide-wire, so that the latter only represents a small portion of the two variable arms of the bridge. For an instrument reading up to 50 megohms, a standard is used having a value of SWITCHBOARDS. 613 10,000 ohms, while 100,000 ohms are inserted in series with the slide-wire. For use as a bridge for measuring conductivities, where considerable accuracy is necessary, the scale is opened out by inserting an idle resistance at each end. The actual readings range from 10 to 110; or, in other words, the maximum value is eleven times the minimum. The standard resistances are connected to a change-over switch, three being provided in the case of the insulation sets, and five in the case of the resistance sets. The former sets have a range of reading from 10,000 ohms to 50 megohms, and the latter from of an ohm to 11,000 ohms. The galvanometer, which is also fixed in the same case, is an important feature of these sets, in that, in the first place, there are no pivots, and in the second, no careful levelling is necessary (it will be noticed, in fact, that the sets are not provided with levelling screws). The galvanometer is of the D'Arsonval type, and the coil is supported from above by a spiral suspension, which acts as a spring and so prevents the coil being damaged, even by very rough handling. The coil carries a pointer, which is seen through a small opening at the top of the case. The zero of the galvanometer can be adjusted, if necessary, by turning a brass milled-head. In the centre of the ebonite milled-head is a small galvanometer key, which can be depressed with the same hand as that which moves the milled-head. For insulation measurements, a magneto-generator is supplied, giving 100, 200, or 500 volts, as preferred. It is fitted with carbon brushes, which preclude sparking and wear of the commutator. The whole set is so arranged that one operator can easily work both the ohm- meter and the generator, with the further advantage that the two instruments can be placed as near together as may be convenient, owing to the fact that the former is quite unaffected by stray magnetic fields. RHEOSTATS. A rheostat should be a simple compact machine, and, as is subject to heating, it should have great radiating or dissipating power. A limiting temperature of 90 deg. Cent. for enamel or grid construction, and 50 deg. Cent. for open spiral construction, should not be exceeded. It must be fireproof, and as it will be subject to vibration to a certain extent, the coils or other resistance should be sufficiently supported that there will be no risk of short-circuiting among them- selves. Durability will depend on the likelihood of oxidation and electrolysis. The instrument must be perfectly insulated, that there may be no possibility of short circuiting; for such an accident would be very serious, and with a shunt field the result might be disastrous. The proper size of rheostat will be found to vary for machines of same capa- city but of different makes. On a 400-kilowatt generator one may need 6 ohms, and another 9 ohms. Generally speaking, the proper-sized rheostat for shunt machines will be one in which the resistance exceeds that of the shunt by about one-fifth; a shunt field with a resistance of 75 ohms will need a rheostat of about 90 ohms, which, on a 600-volt circuit, would be 3.63 amperes for the first step, and 8 amperes for the last step with all resistance out. The rheostat resistance should be such that the dynamo's potential can be reduced below the normal at no load, when separately excited at normal potential. When self-excited, it takes far less resistance to properly control the generator than when separately excited. Carrying Capacity of Platinoid. By careful experiment it has been found that Platinoid wires, when exposed to the atmosphere, and held horizontally, attain the temperature of blood-heat, as follows: No. 20 with 1.8 amperes. 18 "" 3.3 6.0 10.0 "" "" "" 16 14 " "" "" "" "" "" "" "" "" "" "" د. "" "" No. 12 with 15 amperes. 10 25 37 "" 8 "" Carrying Capacity of "Eureka." "Eureka" wires, under the same conditions, attain the temperature of blood- heat, as follows: No. 20 with 1.46 amperes. 18 16 2.72 4.89 8.15 14 "" "" "" "" No. 12 with 12.23 amperes. 10 20.37 30.6 ** 8 "" "" "" "" "" 614 SECTION V.—POWER STATION. Size. S.W.G. 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 Diameter. Inch. MM. .0020 .0508 .0024 .0610 .0028 .0711 .0032 .0813 .0036 .0914 .0040 .1016 .0044 .1118 .0048 .1219 .0052 .1321 .0060 .1524 .0068 .1727 .0076 .1930 .0084 .2134 .0092 .2337 .0100 .2540 .0108 .2743 .0116 .2946 .0124 .3149 .0136 .3454 .0148 .3759 .0164 .4166 .018 .020 .022 .024 .028 .5080 .5588 .6096 .7112 Sectional Area. Square Inch. .0000031 .0000045 .0000062 .0000080 .0000102 .0000126 .0000152 .0000181 .0000212 .0000283 .0000363 .0000454 .0000554 .0000665 .0000785 .0000916 .000106 .000121 .000145 .000172 .000211 .4572 .000254 Table 4.-Wire Tables, &c. (The London Electric Wire Company, Limited.) .000314 .000380 .000452 .000616 Square Millimetre. .002027 .002919 .003973 .005188 006567 .008109 .009810 .011674 .013701 .018241 .023430 .029267 .035752 .042887 .050670 .059102 .068181 .077910 .093722 .11099 .13628 .1642 .2027 .2453 .2919 .3973 Copper Annealed 100 per Cent. Conductivity. Weight in Pounds per 1000 Yards. .0363 .0523 .0712 .0930 .1177 .1453 .1758 .2093 .2451 .3272 .4197 .5249 .6406 .7688 .9085 1.059 1.222 1.399 1.676 1.989 2.440 2.942 3.633 4.392 5.233 7.120 Resistance at 60 deg. Fahr. in Ohms per 1000 Yards. Copper. 7653.0 5313.0 3905.0 2988.0 2362.0 1913.0 1581.0 1328.0 1132.0 850.3 662.0 530.0 433.9 461.7 306.1 262.5 227.5 199.1 165.5 139.8 113.8 94.48 76.53 63.24 53.13 39.05 Eureka. 226950.0 157600.0 .. 88654.0 56740.0 39403.0 25217.0 15717.0 10725.0 7783.0 5904.0 4144.0 3375.0 2802.0 2269.0 1875.0 1576.0 1157.0 Manganin. Platinoid. 184665.0 128239.0 .. 47150.0 32875.0 20955.0 13060.0 C 8912.5 6467.5 4907.5 3442.5 2330.0 1560.2 .. 962.0 72136.0 C K 46166.0 32060.160 17699.0 20518.560 11327.0 12789.640 7060.3 8727.120 4818.1 6332.904 3496.2 4803.984 2652.1 1851.7 1516.20 1258.60 1019.50 3372.264 2746.440 2279.808 German Silver. 1846.656 1526.184 1282.392 942.192 101950.0 70798.0 39825,0 25487.0 Kdy 843.58 707.98 520.16 SWITCHBOARDS, 615 Size. S.W.G. 21 20 19 18 17 16 15 DERPOOOON 2010+ 14 13 12 11 10 9 6 5 OH NI 4 Diameter. 1 Inch. MM. .032 .036 .040 1.016 1.219 .048 .056 1.422 .064 1.626 .072 1.829 .104 .8128 .000804 .9144 .001018 .001257 .001810 .002463 .003217 .080 2.032 .092 2.337 2.642 2.946 3.251 .212 5.385 .232 5.893 .252 6.401 .276 7.010 .300 7.620 1/0 .324 8.230 2/0 .348 8.839 3/0 .372 9.449 .400 10.16 4/0 .116 .128 .144 3.658 .160 4.064 .176 4.470 Sectional Area. Square Inch. .004072 .005027 .006648 .008495 .01057 .01287 .01629 .02011. .02433 .192 4.877 .02895 .03530 .04227 .04988 .05983 .07069 .08245 .09511 Table 4.-Wire Tables, &c.-(Continued) (The London Electric Wire Company, Limited.) .1087 .1257 Square Millimetre. .5188 .6567 .8109 1.168 1.589 2.075 2.627 3.243 4.289 5.480 6.819 8.303 10.51 12.97 15.70 18.68 22.77 27.27 32.18 38.60 45.60 53.19 61.36 70.13 81.09 Copper Annealed 100 per Cent. Conductivity. Weight in Pounds per 1000 Yards. 9.301 11.77 14.53 20.93 28.48 37.20 47.09 58.13 76.88 98.24 122.2 148.8 188.4 232.5 281.3 334.7 408.20 488.80 576.70 692.00 817.60 953.40 1099.0 1257.0 1453.0 Resistance at 60 deg. Fahr. in Ohms per 1000 Yards. Copper. 29.90 23.62 19.13 13.28 9.762 7.478 5.904 4.784 3.617 2.831 2.275 1.868 1.476 1.195 .9881 .8307 .6813 .5688 .4821 .4019 .3402 .2917 .2528 .2212 .1913 Eureka. 886.5 700.4 567.3 394.1 ·· 221.6 141.8 .. 83.9 55.4 35.4 Manganin. Platinoid. 582.0 327.4 184.2 ••• 117.8 ·· •• 721.368 569.952 461.664 320.601 180.338 115.416 ·· 68.292 45.084 28.852 German Silver. 398.25 314.66 254.87 176.99 130 033 99.561 78.662 63.719 48.179 37.702 30.305 24.890 19.665 15.929 3 616 SECTION V.-POWER STATION. יו y ! 7000 8 9 10 Table 5.-Allowances to be made for Cotton-Covering on Wires. 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 S.W.G. Inch. 35 36 All sizes to No. 20's Nos. 19 and 18 "" "" Gauge. All sizes to No. 18 .. Nos. 17 to 13 12 and larger.. .176 .160 .144 .128 .116 .104 .092 .080 .072 .064 .056 .048 .040 (The London Electric Wire Company.) DOUBLE LAPPing (Fine). .036 .032 .028 .024 .022 .020 .018 ·· 17 to 13 12 and larger.. .0164 .0148 .0136 .0124 .0116 .0108 .0100 .0092 .0084 .0076 ·· • ·· "" "" "" "" "" "" "" A fine close braiding is generally 5 to 8 mils thicker than the ordinary double lapping. NOTE.-Thickness of covering may be varied to a large extent to suit the user's requirements. Pure Tin. ·· 89.72 75.19 64.87 55.07 45.82 37.15 31.72 26.58 21.76 17.26 13.13 11.21 9.40 7.69 6.10 5.35 4.64 3.96 3.45 2.95 2.60 2.26 2.05 1.84 1.64 1.44 1.26 1.08 DOUBLE LAPPING (ORDINARY.) .. ·· •• Fusing Current. Approximate. amp. 121.23 117.91 ·· · -- .. Platinoid. ·· Table 6.—Fusible Wires for Cut-Outs. (The London Electric Wire Company.) • 341.00 259.55 217.52 187.66 159.31 132.55 107.48 91.76 76.90 62.94 49.95 38.00 32.44 27.19 22.25 17.66 15.50 13.43 Fusing Current. Approximate. amp. 350.72 11.47 9.97 8.56 7.53 6.55 5.93 5.33 4.75 4.19 3.65 3.15 add 6 mils. 8 10 12 "" "" "" 10 12 14 99 "" 99 H. C. Copper. Tinned. Fusing Current. Approximate. amp. 756.38 735.61 559.77 469.12 404.72 343.57 285.86 231.79 197.9 165.86 135.75 107.73 81.95 70.00 58.64 47.87 38.08 33.42 28.97 24.73 21.51 18.44 16.24 14.14 12.80 11.49 10.24 9.04 7.88 6.78 The calculations have been made on the assumption that the several wires would be held horizontally. SWITCHBOARDS. 617 Table 7. SUGGESTIONS FROM RULES OF THE INSTITUTION OF ELECTRICAL ENGINEERS FOR MAXIMUM CURRENTS, THICKNESS OF DIELECTRIC, AND INSULATION RESISTANCE FOR COPPER CONDUCTORS INSULATED AND LAID IN CASING OR TUBING. Size, S.W.G. 18 or 62/38 or 97/40 3/32 17 or 130/40 3/20 16 or 110/38 or 172/40 15 7/22 14 or 172/38 or 7/21 3/18 7/20 7/18 19/20 7/16 19/18 7/14 19/16 19/14 37/16 19/12 37/14 61/15 61/14 37/12 1 61/12 91/12 91/11 10 25 50 80 ·· 100 150 200 300 400 500 • • C Current in Amperes. · • · • • .. .. •• .. .. ·· ·· • ·· .. O •• ·· 7/16 19/17 Maximum Current for High External Temperatures. 2 7/18 3.1 3.3 4.0 4.8 49 5.9 6.2 7.0 7.5 9.3 14.0 20.0 23.0 31.0 32.0 49.0 70.0 83.0 100.0 120.0 150.0 170.0 180.0 200.0 350.0 420.0 " • Total'frictional loss in horse-power .. • .. "" "" CHA N "" 25 Calorific value of gas (Mond) in pound degree units per cubic foot ·· .. • • · • •• ·· Calorific value of gas in kilo-calories per cubic metre, at 0 deg. Cent... Cubic feet of gas (at O deg. Cent.) per I.H.-P. hour kilowatt hour ·· Mean revolutions per minute explosions "" "" Average mean pressure of diagrams indicated horse-power.. Net weight lifted by brake rope Effective circumference of brake rope . .. "" "" "" "" Efficiency of dynamo (makers' figure) Mechanical efficiency of engine Combined efficiency Thermal efficiency calculated on indicated horse-power brake "" "" electrical "" ·· "" • · • ▸ ·· ·· .. .. ·· • · .. .. ·· .. ·· ·.· .. .. ·· .. ·· • •• .. Table 5.-Particulars of Brake Test of Crossley “U” Size Gas Engine by Mr. James Atkinson. MARCH 6TH, 1905. ·· ·· 2/7/00 2 hours • 291.8 217.7 152.4 51.37 377.9 14.5 12.0 29.0 2.0 42.5 90.13 1444.5 60.09 104.3 93 83.04 77.23 26.23 21.78 20.26 64.10 11 in. 21 10/4/00 6 hours 333.4 249.5 148.5 185.45 91.8 94.92 lb. 47.96 518.4 lb. 14.408 ft. 60.43 432.9 15.0 11.5 28.5 2.1 42.9 88.86 1423.5 62.74 108.8 93 83.06 77.25 25.49 21.17 19.69 73.33 "9 1 hour 45 mins. Y : 642 Table 5—Continued. SECTION VI.-POWER STATION. Average brake horse-power Mechanical efficiency Coal gas used per hour, corrected to a temperature of 60 deg. Fahr., and barometer pressure of 30 in. Gas per indicated horse-power در ·· brake "" Average calorific value of gas as corrected to 60 deg. Fahr., and 30 in. Thermal efficiency per indicated horse-power brake "" " • .. "" "" • .. •• • 41.974 87.452 per cent. 572.57 cub. ft. 11.929 13.64 "" "" "" "" 582.6 B.T.U. 36.9 per cent. 32.27 per cent. The engine was tested under ordinary working conditions, the amount of lubrication to the cylinder and bearings being the same as usual. Water was, however, added to the working charge, and the compression was 200 lb. per square inch. Premier Gas Engine. (FIGS. 27 to 28 a, pages 643 to 645.) (Wells Brothers.) "Single-Cylinder" Type.-The engine works on a scavenging system, with ignition by electric spark, which is in duplicate, and so arranged that a pair of sparking points can be withdrawn while the engine is at work. As regards details of construction, the large end of the piston works in the cylindrical part of the bedplate, thus acting as a guide, and relieving the motor cylinder from the lateral pressure due to the obliquity of the connecting-rod. Air enters through suitable pipes, passing through a port and light leather valves, F F, Fig. 27, a portion going through a passage to the motor cylinder, and the remainder going through a port to the pump space. On the return stroke, which is the compression stroke of the motor piston, the air is compressed into the clearance spaces, which are of such capacity that the pressure rises to about 5 lb. per square inch. On the next stroke, which is the explosion stroke, the air expands again to atmospheric pressure. On the next stroke, which is the exhaust stroke of the motor cylinder, the air is again compressed, but at about half stroke, when the air pressure is in the neighbourhood of 2 lb. per square inch above the atmosphere, an admission valve E is opened, and the air rushes through the ports P into the combustion chamber, the continued motion of the piston keeping up the discharge of air till the end of the stroke. The exhaust valve is closed early on the next out or suction stroke, and the gas valve G opened. This is an annular valve having rings attached to it, which partially block the air admission ports P P; thus, during the scavenging operation the air has a free passage through these ports, but during the taking in of a charge the air passage is sufficiently throttled to cause enough suction to draw in the proper amount of gas, which in the case of producer gas is a large proportion. The crankshaft is supported at the outer end by a massive plummer block, having vertical and horizontal adjustments for the position of the brasses, so as to render alignment with the other bearings easy. Indicator cards have shown a mean pressure of 113 lb. The maximum pressure is only 310 lb., so that, although the mean pressure is high, the shock due to the explosion is not excessive. "C Tandem" Type.-This engine, Fig. 28, works on the usual four-stroke cycle, that is to say, in each cylinder the cycle is completed in four strokes. There is thus one impulse per revolution, the cylinder being single-acting. On each out stroke there is an explosion, and for each back stroke a compression. This tends to produce smooth and silent running, because there is no reversal of pressure on the connecting-rod bearings, and consequently no knocking at these joints. In addition to the above there is, as in the single-cylinder engine, a positive scavenging operation, effected as follows:- Towards the end of the exhaust stroke the admission valve A₁ or A2 is opened, and air compressed in the passages behind this valve by the pump P flows into the combustion chamber, or clearance space, driving out before it through the exhaust valve the products of combustion resulting from the previous explosion. The air for this purpose is compressed to a pressure of about 3 lb. per square inch before the opening of the valve by the inclined pump P, placed above the engine and operated from the main crank by means of a rod jointed to the big end of the main connecting-rod. After the admission valve opens the pump piston E 27 Fig. 27. "Premier" Gas Engine. 1089 GAS ENGINES. 643 1 .เ ་ 1 644 SECTION VI.-POWER STATION. f 28 JA1 " P 1 Fig. 28. “Premier Gas Engine, Tandem Type. FURT GAS ENGINES. 645 continues its motion, and keeps up a steady flow of air, and this action is continued till the crank has passed the dead centre and the suction stroke has been com- menced. The exhaust valve is now closed, and the pressure in the air pipe having fallen below atmospheric pressure, air is drawn in through an automatic inlet valve, part of this air passing to the motor cylinder, and on its way mixing with the gas admitted by a separate valve, and part going to the scavenging air pump, the piston of which is also moving forward. The same action is repeated during the next revolution, but the front cylinder takes the place of the back and vice versa. Thus each cylinder is scavenged after every explosion, that is, the foul gases are swept out by a change of air forced positively through the combustion chamber. The one air pump thus serves to scavenge both motor cylinders, and as there is only one additional valve, viz., an automatic air inlet valve, the engine is very little more complicated than an ordinary four-stroke engine without the scavenging arrangement. Positive scavenging in this manner is claimed to have many advantages, some of which are as follows:- 1. The products of combustion ordinarily left in the combustion chamber are very hot, and by expelling these by cool air the combustion chamber is filled previous 1030 Fig. 28 a. Cylinder End, "Premier" Gas Engine. to the admission of the explosive charge with cool air, instead of hot products of combustion, and thus the risk of ignition of the entering charge is avoided. The ignition of the entering charge often occurs in the ordinary type of engine, and is termed back-firing. 2. The explosive charge is not only cooler, but consists of gas and air only, not gas and air contaminated with products of combustion, and is therefore a purer combustible mixture, and the power developed by the explosion is considerably greater than in non-scavenging engines. 3. As a considerable volume of cool air is forced through the valves and com- bustion chamber, and as this air impinges against all the internal heated surfaces it cools down these surfaces and increases the life of the valves. 4. Owing to the coolness of the charge before compression, also to the coolness of the containing walls, a greater degree of compression is permissible than in non- scavenging engines, in which, owing to the heat of the charge and walls, there is danger of premature ignition if worked with high compression. The admission and exhaust valves are placed in the cylinder ends and open directly into the cylinder, and thus there is no broken-up surface, port, nor passage to break the simple outline of the walls containing the explosive mixture, and add to the cooling surface and consequent loss of heat. The valves, being horizontal and parallel to the cam shaft, are operated by grooved cams on the latter. These 646 SECTION VI.-POWER STATION. cams not only open the valves, but also close them in a positive manner without the aid of springs. The gas valve is of the grid type, and is operated by a cam in the usual way and closed by springs; but as its motion is small, and as four springs are used (two being sufficient to close the valve), and as these springs can be easily replaced while the engine is at work, there is no danger of a stoppage due to the breakage of a spring. The governing is effected by varying the stroke of the gas valve in the following manner. On a short arm operated by the cam is fixed a notched and hardened steel plate, and to the gas valve is pivoted a hardened steel blade connected to the governor in such a manner that when the latter is in its highest position the blade engages with the notch nearest the pivot of the rocking arm, and thus engages with the notch farthest from the pivot, receiving then a maximum movement. Inter- mediate positions give intermediate movements to the gas valve; in this way the power is varied. This gear also allows of the strength of the change being reduced to a certain point, and beyond that of the gas being omitted altogether, and thus combined throttling and hit-and-miss governings obtained. The pistons and exhaust valves are water-cooled, the former by means of water admitted through a water service consisting of hollow swinging arms and trunnions to the hollow piston rod, and thence to the water spaces in the piston. The alternate acceleration of the pistons forward and backward is used to assist the circulation, and ensure equal distribution of water to both pistons. Test of 500 Horse-Power Premier Gas Engine with Mond Gas at Winnington Power-House, December, 1900. TRIAL WITH ENGINE GIVING TWO-THIRDS of Maximum Output. (Herbert A. Humphrey.) Engine Direct-Coupled to Mather and Platt Dynamo. Duration of test, 12.30 p.m. to 5.30 p.m. Dimensions of Engine. Two cylinders arranged tandem, each Pump cylinder for scavenging air Length of stroke.. CO2 со H OH4 N •• >> "" "" >> ܝ܂ ·· "" "" "" "" 95 Average speed in revolutions per minute Indicated horse-power, back cylinder front gross total Output of dynamo (electrical horse-power) (kilowatts) Electrical efficiency of dynamo Mechanical efficiency of engine excluding fluid losses Brake horse-power at dynamo coupling Total indicated horse-power lost, including all frictional fluid and electrical losses Combined efficiency between electrical horse-power and in- dicated horse-power ·· .. .. "" "" ·· ·· •• •• ·· .. ·· •• • .. ·· ·· ·· ·· ·· ·· • • • · ·· Gas Consumption. Dry gas, 0 deg. Cent. and 700 millimetres, used per hour Analysis of Gas. ·· ·· ·· · · ·· ·· .. .. •• ·· ·· · • .. .. .. • • Total combustible gases, 42.2 vol. per cent. "" "Higher" calorific value, including latent heat of steam in British thermal units per cubic feet "Lower" calorific value, excluding latent heat of steam in D ·· "" ·· "" "" .. .. ·· .. 160.9 143.8 British thermal units per cubic feet "Mond" gas at 0 deg. Cent. per indicated horse-power hour.. 52.09 cub. ft. "" brake electrical "" 69.20 74.42 99.76 Board of Trade Ünit .. •• 281 in. dia. 43 in. dia. 30 in. •• 5 hours. 16.0 vol. per cent. 12.2 59 27.8 2.2 "" 41.1 128.05 328.72 160.49 489.21 93 per cent. 81.22 per cent. 368.2 121.0 70.0 "" 342.4 255.43 25,482 cub. ft. "" 19 "" "" "" "9 "" "" GAS ENGINES. 647 J The Oechelhaeuser Gas Engine. (FIG. 29.) (Zeit. des Ver. deut. Ing.) 48389 E27259 Kaum danITU This engine in its simplest form has one long water-cooled cylinder in which two pistons work. The front piston is attached by its connecting-rod to a central crank placed at an angle of 180 deg. to two other cranks on either side, which are, 600 H.P. TwO-CYCLE Gas-Engine (ÕechelhauesER). Air Pipe. Teed FRIEND Air Pump Piston. Cyl! with 2 Pistons. Piston. A M >> Fig. 29. The Oechelhaueser Gas Engine in their turn, connected by long side-rods to the crosshead of the back piston. This crosshead is also connected to the piston rod of a double-acting pump, which com- presses the gas and air mixture upon one side of its piston and air only on the other. The explosive mixture is compressed by the two pistons approaching one another, and is fired electrically, driving them apart. Before the completion of the full stroke, the front piston uncovers the annular exhaust port, and allows 648 SECTION. VI.—POWER STATION. ! the hot exhaust gases to be discharged. The rear piston, at the end of its stroke, first opens a port which admits cool air under slight pressure of about 5 lb. per square inch, to scavenge out the remaining products of combustion, and then a second port through which is introduced the previously compressed mixture from the pump. The exhaust port remains open while the explosive mixture displaces the scavenging air, and then the return stroke of the pistons closes all ports, compression takes place, and the cycle is repeated. The advantages claimed for this engine are:- 1. The small size of the cylinder for a given output. 2. The rapid expansion following explosion. 3. An impulse is obtained every revolution. 4. The turning moment on the main shaft is produced by a couple, thus diminishing the unbalanced forces transmitted to the bed-plate. 5. The usual valves are dispensed with, the pistons themselves acting as slide valves. The disadvantages are :- 1. The extra complication of motor and pump. 2. The necessity of having three connecting-rods, two crossheads and rods, and the pump gear; giving, together with the pistons, a large reciprocating mass per unit area of piston. 3. The great length of the complete engine. 4. The wide space between the main bearings and the extra cost of the three cranks. 5. The possible loss of gas, owing to some of the explosive mixture blowing straight through before the exhaust port closes. The Nuremberg Gas Engine. (Figs. 30 to 33, pages 649 to 651.) In Figs. 30 and 31 are shown the principal features of the Nuremberg gas engine, which has of recent years been built in very large sizes, and extensively adopted for running with blast-furnace gas and other cheap gases. In essentials the engine is simply an ordinary Otto double-acting gas engine, but designed so as to have all parts readily accessible, and with a very perfect system of water- cooling for the cylinder walls, covers, and valves. The engine is built both as a single-cylinder engine and as a two-cylinder tandem engine, in which pattern it is made to yield up a maximum of 2000 indicated horse-power; and by coupling a pair of these tandem engines to the same crank-shaft a unit of 4000 horse-power is obtained. Our illustration represents a single-cylinder engine. It will be noted that there are two crossheads, one of which takes the small end of the connecting-rod in the usual way; another supports the end of the tail-rod. The piston-rod is slightly sprung when finished, so as to be straight under the weight of its piston. Hence the whole weight of this piston is transferred direct to the crossheads, and does not rest on the cylinder. The crosshead near the crank is arranged so that the piston-rod can pass through it. Hence, in getting at the piston for examination, the engine is put at its forward dead centre. The tail-rod is disconnected, and also the connecting-rod from the front crosshead. This connecting-rod can then be turned out of the way. The piston-rod can slide then through the front crosshead, so that as soon as the front cover is unbolted, it and the piston can be moved right up to this crosshead, and the piston examined without having to remove the crosshead from its guides. Equivalent arrangements are made as to the other end, so that a thorough examination of the engine can be made with a minimum of trouble. The cylinder is of cast iron and of symmetrical shape. It is therefore unlikely to suffer from unequal expansion when hot. Both sets of valves are mounted in valve-boxes cast independent of the cylinder, and bolted thereto at machined facings. The air and gas-valves (see Figs. 32 and 33) are mounted at the top of the cylinder, and the exhaust-valves (Fig. 30) below. The whole are operated by cams from a side shaft, a trip-gear being used to proportion the quantity of gas admitted to the load on the engine. The water circulation to these latter valves is well shown by the arrows in Fig. 33. The pistons are thoroughly water-jacketed, being supplied by a special pump, whilst the supply to the cylinder covers and exhaust- valve boxes is furnished under a head of about 20 ft. The total quantity needed is about 5 pints per brake-horse-power hour, which can be greatly reduced by the GAS ENGINES. 649 A Y2 104419528 Fig. 30. The Nuremberg] Gas Engine. SURITIUM. 650 SECTION VI.—POWER STATION. 31 Figs. 31 and 32. Details of the Nuremberg Gas Engine. 32 ! 1 " : : GAS ENGINES. 651 installation of a cooling plant. Ring lubrication is adopted for all the shaft bearings, whilst forced lubrication is used to supply the stuffing-boxes and the cylinder, and the oil supply to the exhaust-valve spindles and governor footstep is also effected under pressure. The makers of these engines are the Vereinigte Maschinen-fabrik Augsburg und Maschinenbau-Gesellschaft Nürnberg A.G., of Nürnberg, Germany. Type. Rated brake horse- ·· ·· power Révolutions per minute Flywheel diameter Height of centre above floor Extreme width Extreme length .. Table 6.—Sizes of Nuremberg Tandem Gas Engine. DIMENSIONS IN MILLIMETRES. ·· ·· (3066.8. SLAGAAAA AAAAAA que con Fig. 33. Details of Valves. DT6a DT 7 DT7a DT8 DT9 DT10 DT 11 DT 12 DT 13 350 480 530 685 870 1050 1200 1500 1850 150 4100 150 4900 125 125 120 110 100 4900 4900 5100 5500 6100 94 6500 90 6750 750 765 775 800 850 900 950 975 1000 5500 5750 6000 6250 6500 6750 7000 7250 7500 10550 11700 12450 13200 14170 15250 16550 17500 18375 652 SECTION VI.-POWER STATION. 小 ​Table 6.—Sizes of Nuremberg Tandem Gas Engine (Continued). Ꭰ Ꮾa D7 160 220 150 150 Revolutions per minute Flywheel diameter 4100 4900 Height of centre above floor Extreme width Extreme length Type.. Rated brake horse- • • .. ·· ·· 750 765 4500 5000 7550 8300 D 7a 245 125 125 4900 4900 775 5500 8650 D 8 315 800 6000 9150 D9 400 120 5100 I D 10 D 11 D 12 D 13 480 550 690 845 110 100 94 6500 90 6750 5500 6100 The Deutz Double-Acting Gas Engine. (Figs. 34 to 36, pages 652 and 653.) R 850 900 950 975 1000 6250 6500 6750 7000 6250 9800 10555 11750 12450 13375 For large power the Gas-Motoren Fabrik Deutz build the double-acting, four- cycle engine shown in Fig. 34. The cylinder, it will be seen, is of relatively simple form, the exhaust and inlet valves being mounted on separate castings. They are 36 35 கு Figs 35 and 36. Details of Deutz Gas Engine. operated by cams on a side shaft driven by spiral gearing from the crank shaft. The piston rod is prolonged through the piston to form a tail rod, and is hollow so as to serve as conduct for the water jacketing of the piston. The glands through which the rod passes are also water-cooled as shown. The engine is governed by throttling simultaneously the gas and air supplies, so that the mixture remains the same at all loads. The arrangement is represented diagrammatically in Figs. 35 and 36, where Fig. 35 shows the opening of the throttling valves at full load, and Fig. 36 that at light loads. A sudden unloading of the engine by 25 per cent. causes only a momentary rise of 1 per cent. in the speed, whilst the difference in the engine speed, between full load and running light, is never more than 3 or 4 per cent. Forced lubrication is adopted for the glands, and ring lubrication for the principal bearings. The quantity of oil used amounts to about 15 to 18 drops per brake horse-power hour. GAS ENGINES. 653 MILAR LIQU AIR GAS AIR Fig. 34. The Deutz Double-Acting Gas Engine, molina Ab QUADRA 654 SECTION VI.-POWER STATION. GAS PRODUCERS. Producer Gas and its Application to Gas Engines. Any combustible substance produces more or less gas when heated to a high temperature. In the simple form of gas producer, oxygen passes through a vessel containing red-hot carbon in some form, there being enough oxygen to produce a combustible gas, but not enough to complete combustion. The resulting gas is carbon monoxide; its calorific value would be about 340 British thermal units per cubic foot. Commercially, air is used instead of oxygen; the resulting gas is largely diluted with nitrogen, and has a calorific value of only about 112 British thermal units per cubic foot. Water gas is made by passing steam over red-hot carbon, which results in the production of hydrogen, carbon monoxide, and carbon dioxide, the proportion of which can be varied at will by passing more or less steam for the same amount of carbon. This may be expressed as follows:- 3 H₂0+2C = CO+CO₂+3 H₂ 60 per cent. H., 20 per cent. CO or H,O + C = CO+H, 50 per cent. H., 50 per cent. CO 5H,0+3C =2C0,+C0+5H, 62 per cent. H., 12.5 per cent. CO Strong and Lowe's process for producing water gas consists in passing super- heated steam over coal or coke which has been raised to a bright incandescence by playing upon it with a stream of air in a brick-lined furnace. The steam is decomposed as described in the above formulæ, and the products are collected in a reservoir. The steam is passed through until chemical action ceases, due to cooling of the coke, when it is shut off, and air is passed through to raise the temperature. or Dowson first made a continuous process of it, by blowing in steam and air together. The air maintained the carbon at high temperature, and the steam being decomposed, enriched the gas produced. What is generally known as Dowson gas is made by generating steam in a boiler, and passing it, mixed with air, through a generator containing anthracite coal or coke. The product from the generator passes through an hydraulic seal, a coke scrubber, à sawdust scrubber, and then enters the gas-holder, which automatically shuts off steam when it is full. Dowson was the first who designed a practical commercial producer to work in connection with gas engines, and the greatest credit is due to him. Nearly all the gas producers which are described here are based on the Dowson principle, differing in most cases only in details. Approximately 24 lb. of coke produce 20 cubic feet of water gas. Gas produced by these processes has approximately the following composition:- Hydrogen.. Carbon-monoxide Hydro-carbons Other gases The gas produced, to be available for driving gas engines, should be both mechanically and chemically pure, and should not contain any traces of ashes, dirt, or sulphurous fumes. The latter in particular may cause the entire ruin of the cylinders. It has been estimated that the extra cost of removing the sulphur amounts to about one penny per 1000 cubic feet. The method usually employed is to pass the gas over and through successive layers of oxide of iron mixed with sawdust, which absorbs the free H2 S. The oxide, after having done its work, can be recuperated by contact with oxygen in the air. For this purpose it should be spread in layers 8 in. to 10 in. thick. One ton of oxide of iron should suffice to purify from 1,000,000 to 1,500,000 cubic feet of gas before becoming spent. The gas after passing over the oxide should not contain much over 0.001 per cent. volume of H2 S. This can be ascertained by placing a piece of acetate of lead paper in the gas for twenty-four hours, and excluding light. If more than 0.001 per cent. of H2S is present, the paper becomes tinged. Too great care in cleansing the gas cannot be exercised. ·· ·· • •• ·· Per cent. 30 to 53 by volume 28 35 34 4 8 "" "" •• " "" "" GAS ENGINES. 655 ! 1 Siemens Gas. In the manufacture of Siemens gas the cooling is prevented by using a jet of air instead of steam. CO2 is formed near the bottom of the furnace, and is reduced to CO at the top by the excess of carbon. By this means, a mixture con- taining, approximately, 34 per cent. of carbon monoxide and 65 per cent. nitrogen is produced. Siemens gas is not very uniform in quality, but by drawing the supply from a large number of producers the average may be uniform enough for engine work. The tar must, however, be extracted before it is passed to the engines. Gas to Furnaces or Engines Mond Gas Producer. (FIGS. 37 and 38, pages 655 and 656.) [(H. A. Humphreys, Proc. Inst. Mech. Eng., and Proc. Inst. Civil Eng.) La Sup Regenerators SIMOT SUTIONS STON Washer demoj kianorry muuny To Sulphate Plant PIT it- Produ Liquor POOM Blower HARGA KASZMÁ Hot Water Cold Water Water Pumps Fig. 37. Diagram Illustrating Method of Working Mond Plant. (5688 M) A The chief advantages of this producer are:- 1. Common bituminous slack can be used in place of anthracite coal or coke. 2. The gas obtained is of good and uniform quality. 3. The ammonia existing in the fuel can be recovered as a by-product. The process of manufacture is as follows:- The bituminous slack is deposited in hoppers above the producers, from which it is fed in charges of 8 cwt. to 10 cwt. into the producer "bell." Here the first + 656 SECTION VI.-POWER STATION. heating of the slack takes place, the products of distillation passing downwards into the hot zone of fuel, before joining the bulk of the gas leaving the producer. By this means the tar is, to a great extent, destroyed and converted into a fixed gas, and the slack is prepared for its descent into the body of the producer, where it is acted upon by an air-blast saturated with steam at 85 deg. Cent. (185 deg. Fahr.), and superheated to 250 deg. Cent. before coming in contact with the fuel. The proportion of steam to air is large, amounting to 2 tons of steam per ton of fuel gasified. This proportion keeps the working temperature of the producer sufficiently low to prevent the formation of clinker or the destruction of the 838 Fig. 38. Mond Producer CELOR Small Coal Gas Coal Creeper Hot Air Water 900 18 H Hot Gus Section of "Mond" Gas Producer. ammonia, and yet permits the fuel to be so thoroughly burned that good ashes are obtained. Half a ton of steam is decomposed per ton of fuel burnt, giving about 29 per cent. by volume of free hydrogen in the final gas. An The hot gas and undecomposed steam leaving the producer first pass through a tubular regenerator in the opposite direction to the incoming blast. exchange of heat takes place, and the blast is still further heated by passing down the annular space between the two shells of the producer on its way to the fire- grate. After the regenerator, the hot products from the producer pass into a "washer," where they meet a water spray, thrown up by revolving dashers; the intimate contact thus secured cools the steam and gas down to about 90 deg. Cent. and by the formation of more steam, tending to saturate the gas with water GAS ENGINES. 657 1 vapour at this temperature, the bulk of the sensible heat is converted into the latent form. After washing, the gases pass upwards through a lead-lined tower (filled with tiles to present a large surface), and meet a downward flow: of acid liquor, composed of sulphate of ammonia, with about 4 per cent. free acid, which is circulated by pumps. The free acid converts the ammonia into solid sulphate, which is continuously withdrawn, fresh acid being added to keep the proportions constant. The gas having been freed from ammonia, is further cooled and cleaned in another tower, where it meets a downward flow of cold water, after which it can be used in the gas engines. The cooling water from the last tower is heated up by the condensation of the steam present in the gas, and its heat is utilised in a third tower to heat up the air blast. The contact of hot water and cold air gives hot air saturated with water vapour at 73 deg. Cent., and cold water. Nearly one ton of steam per ton of fuel burnt is added to the air blast in this way, the cyclical exchange of heat forming one of the most distinctive features in the economy of the plant. Fresh charges of fuel can be introduced into the producer at the top, and the ashes withdrawn from the bottom, without in any way interfering with continuity of the process, and the large volume of steam employed acts as a most perfect regulator in keeping the quality of the gas uniform. Extremely bituminous coal, such as the best Durham coking coal, cannot be used in these producers. Fig. 37 is a diagram of a Mond plant. A section through one of the producers belonging to a plant at Messrs. Brunner and Mond's works at Northwich, is given in Fig. 38. It consists of a double wrought-iron shell, cylindrical above and cone-shaped below, partly lined with firebrick. The whole structure is supported over a water seal, into which the outer shell projects. The grate is formed of inclined firebars, which rest upon a. circular casting running round the bottom of the shelf. Typical Figures for the Mond Producer and Recovery Plant. (Herbert A. Humphrey.) •• Moisture at 100 deg. Cent. (212 deg. Fahr.).. Volatile matter (excluding carbon) Total carbon Ash ·· ·· Average Analysis of Fuel by Weight. Slack as Received. Per cent. 8.60 18.29 62.69 10.42 • ·· Carbon Monoxide (CO) Hydrogen Marsh gas (CH4) Carbon Dioxide.. (CO2) Nitrogen (N) .. ·· (H) "" ·· 100.00 Analysis of Ashes Leaving Producer. .. Ash on dried sample by weight Carbon ·· Total carbon lost in ashes, &c., calculated on the fuel used Carbon available for conversion into gas ·· ** .. Calorific Value of Fuel (Tested on Dry Sample). Determined by combustion in compressed oxygen, in a bomb calorimeter, kilogram calories Calories per ton of dry fuel Typical Analysis of Mond Gas (Dry). ·· ·· • •• · -- • • • .. • • • ·· ·· .. • • 132,414 cubic feet of dry gas at 0 deg. Cent. 142,069 gas saturated at 15 deg. Cent. ·· ·· · Calculated on. Dry Slack. Per cent. • • • 0.00 20.01 68.59 11.40 100.00 Per cent.. 87.0 13.0 5.31 57.38. lb. Weight of 1000 cubic feet of dry gas at 0 deg. Cent. = 63.66 Specific gravity of Mond gas (air = 1.0) 0.7882 1 ton of moist fuel gasified yields :- 6,786 6,894,576 Per cent. of volume. 11.0 29.0 2.0 16.0 42.0 100.0 658 SECTION VI.-POWER STATION. # Calorific Value of Mond Gas (Products Cooled to 18 deg. Cent.). Dry Gas at 0 deg. Cent. Per cubic foot. 88.26 In pound deg. Cent. units In British Thermal units 158.8 148.0 Calorific value of total gas made as a percentage on the calorific value of the total fuel gasified = 84.1 per cent. Combustion of Mond Gas and Air. One volume of gas requires for perfect combustion.. Volume of mixture before combustion products (cooled to 0 deg. Cent.).. Contraction due to combustion.. "" Saturated at 15 deg. Cent. Per cubic foot. 82.25 • 1.15 volumes of air. 0 deg. Cent. 2.15 1.95 "" "" 9.3 per cent. The net cost of Mond gas on a large scale is dependent to some extent on the market price of ammonium sulphate, and on the amount of nitrogen in the fuel. In some cases the yield of this has been sufficient to reduce the fuel cost 7s. per ton; and in America, with a plant using 150 tons of coal per day, the reduction in fuel cost due to the sale of ammonium sulphate has in actual practice amounted to 28. per ton. Stand-by Losses. A 1000 horse-power Mond plant standing for a night of fourteen hours will con- sume 225 lb. of fuel in this time. If standing by for eight days, the consumption is 7 lb. per hour. After a week-end stoppage, the plant can be started up again at full load in three minutes. The Crossley Producers. (Figs. 39 to 41, page 659.) (Mr. T. Rigby, Manchester Association of Engineers, 1905.) Messrs. Crossley make both pressure and suction producers. Their pressure producer is represented in section in Figs. 39 to 41, whilst Fig. 41 represents the complete plant. It can be used with either coke or anthracite as the fuel, and has been built up to 330 brake horse-power. Larger sizes than this can, however, be furnished. The makers claim an efficiency of 88 per cent.-i.e, the calorific value of the gas produced is 88 per cent. of that of the fuel from which they were obtained. The producer is worked on the regenerative principle, the heat carried away by the gases produced being utilised in an interchanger (commonly called a superheater) to evaporate the steam required in the producer. In Fig. 41, A represents the producer, B the interchanger; whilst D is a coke scrubber, and E a sawdust scrubber. The air is forced into the producer by means of a fan. It enters B near the bottom, passing over wet surfaces. The gas from the producer passes at the same time down a central tube, giving up its heat on the way to the moist air flowing in the opposite direction. This enters the air jacket of the pro- ducer (see Fig. 39), intercepting any loss by radiation. It leaves this jacket by the pipe on the right, which leads it underneath the fire-grate. The bottom of the producer is closed by a water lute, openings being provided above the water surface through which ashes and clinker can be removed as required. The fire-grate is mounted on a rotary table, a device which keeps it free from clinker; so that these producers can be worked continuously, patterns without this, or some equivalent arrangement, having to be stopped periodically for cleaning purposes. This being unnecessary with the producer in question, no stand-by" is required. "C The fuel is fed into the annular space at the top, whilst the gas escapes through the bell shown. The Crossley Suction Producer. (FIG. 42, page 660.) The Crossley suction producer is represented in Fig. 42, and is designed to work with either anthracite or coke. As in all suction producers, the flow of air through the apparatus is due to the suction of the gas engine, which is coupled direct to the producer, or rather to the scrubbers, without the intervention of any gas holder. In starting up, a hand-fan is used to get the necessary draught. The fuel enters at the top of the producer, passing first into a storage hopper, from GAS ENGINES. 659 39 GAS OUTLET MOIST AIR 4NLET 41 E 1082 Figs. 39 and 40. Section through Crossley Producer. D C B 40 T HOT A Fig. 41. Crossley Producer Plant. 1083 660 SECTION VI.-POWER STATION. whence it descends by its own weight as required. The gas, leaving the producer, passes through a series of concentric baffles, as indicated by the arrows. A layer of water is maintained above these baffle plates, and evaporates in quantity sufficient- to supply the requisite steam. There are two sources of air supply: one through the fan opening and pipe passes direct below the fire-grate; the other enters through a valve into the space above the water at the top of the producer, and passes down below the grate through the "steam" pipe shown dotted in Fig. 42. It is found advantageous to use a smaller proportion of steam to air at low loads than at full loads. This is provided for by closing or opening, as required, the air valve on the "secondary" air supply. These producers have been built up HAND STARTING FAN WATER INLET- FEEDER HOPPER TORRENTER RENTER RENTER STEAM PIPE PLUG 42 BLOW OFF COCK AIR REGULATOR [OVERFLOW PIPE COKE SCRUBBER} WATER INLET HYDRAULIC BOX WNI SEAL BOX Fig. 42. Crossley Suction Producer. GAS TO ENGINE LCOKE SCRUBBER · 1084- to 600 brake horse-power in single units; they use anthracite or coke. In a set of trials made by Messrs. Crompton and Co., using coke from the Manchester Corporation gas-works, the fuel per kilowatt hour was 1.325, equivalent to 1.92 lb. per brake horse-power hour. The coke had the following composition :--- Ash 15.60, moisture 1.30, volatile matter, 1.80, fixed carbon 81.30, calorific value 12.411 British thermal units per pound. The fire can be cleaned even when the engine is running under full load, and there is no difficulty in taking up extreme variations of load. The grate area of suction-gas producers is about 0.8 to 1 square foot per 10 horse-power, or the rate of combustion is 10 lb. to 12 lb. of fuel per square foot per hour. A producer of 30 brake horse-power can stand by overnight at an expenditure of 5 lb. of fuel, and be started up again in five minutes. GAS ENGINES. 661 Producer Plant for Bituminous Fuel. (FIG. 43 to 45, pages 661 and 662.) 43 Messrs. Crossleys' producer, to work with bituminous fuel, is shown in Fig. 43. No attempt is made to destroy the tar in the producer itself; but this is removed afterwards by passing the gas first through an interchanger, and then into a washer-cooling tower, where the gas is met by a stream of water at 100 deg., which removes most of the tar. The remainder is taken out by the centrifugal tar extractor represented in Figs. 44 and 45. This consists of an arrangement whereby the tar is thrown out of the gas by centrifugal force, the idea on which it is based being that work done on the gas in forcing it to the high peripheral speed is mostly given back again before leaving the tar-extractor, the work lost being that due to friction only. The light tars are all removed here, and the gas finally passes through a sawdust filter before proceeding to the engine. A gas holder is not required. 1085 Fig. 43. Crossley Producer for Bituminous Fael. The plant shown in Fig. 43 is for small powers, consuming, say, 100 lb. of coa per hour. The whole of the fuel bed is carried on a rotary fire-table, mounted on a ball race, which in turn rests on a cylindrical ring, the bottom of which is sealed by water. All the air and steam entering the producer does so through this cylinder. The fire-grate is conical, and it will be seen that the air entering only through the fire-bars cannot creep up the sides of the generator. A storage bell is used to keep constant the depth of the fuel. The gas leaves at the outlet shown at the side, the one below being that for admitting the air to the jacket and fire-grate. The ashes fall over the edge of the table into the waterlute, from which they are easily removed as required. Fuel containing as much as 35 per cent. of ash has been successfully gasified in these small producers. Plants up to 2500 brake horse- power are in operation, these larger producers differing slightly in detail from that illustrated. 662 SECTION VI-POWER STATION. 44 45 • *** ** ** *** ******* @ 1086 Figs. 44 and 45. Crossley Centrifugal Tar Extractor. GAS ENGINES. 663 The Deutz Suction Gas Plant. (FIG. 46, page 664.) The Deutz suction gas plant is represented in Fig. 46, where A is the generator, B the scrubber, C the equaliser churn, and D the engine. The anthracite or coke is admitted to the generator through a large plug top as shown. The water pan is mounted directly over the fire as shown, and on each suction stroke of the engine air is drawn in at ƒ, and passing over the water in this pan absorbs vapour which it carries with it to the ash-pan at h. The gas generated passes through the pipe K to the scrubber, where, on rising through the broken coke, it meets a descending stream of water which removes from it any dust or tar. From the top of the scrubber the gas passes through the pipe n to the anti-fluctuator C, and thence to the engine. The valve arrangement shown at m is used in starting up. This is effected by the hand-driven fan shown at p, and the valves at m are then moved, so that the gas discharges up the waste pipe instead of into the scrubber. Blast-Furnace Gas. Making all allowances for the gas needed for heating the blast, for driving blowing engines, &c., gas equivalent to 25 brake horse-power per hour is available for every ton of iron made per day in a blast furnace. A thousand cubic feet of the gas measured at 62 deg. Fahr. weighs 78.14 lb., and contains 13.57 lb. of CO2, 20.27 lb. of CO .042 lb. of H, and 44.25 lb. of N. The hydrogen content, it will be seen, is small. About 28.3 per cent. of the gas is combustible, and the heating value is 90 British thermal units per foot. About 141,000 cubic feet of gas are available for each ton of iron made. Coke-Oven Gas. Coke-oven gas is largely similar in constitution to lighting gas. It varies, however, in composition, being richer during the earlier portion of the coking process than later on. At the outset the calorific value may exceed 700 British thermal units per cubic foot, whilst at the end of 20 hours it is under 450 British thermal units per cubic foot. Table 7, due to Dr. J. D. Pennock, shows the composition of the gas at different times :- Carbon dioxide.. Benzene Ethylene Carbon monoxide Methane Hydrogen Nitrogen. B.T.U. per cubic foot : .. Gross Net .. ·· Gross Net Calories per M³ : ·· •• ·· Table 7.-Composition of Gas. .. ·· ·· :: •• • ·· •• .. :: :: Gas First 8 Hours. per cent. 1.7 0.5 4.7 0.4 4.8 42.0 35.0 10.9 683 614 6078 5466 Gas for 16 Hours After. per cent. 1.9 0.2 1.5 0.5 4.5 32.0 51.0 8.4 565 502 5027 4471 Average Gas for 24 Hours. per cent. 1.8 0.3 2.9 0.5 4.6 36.5 43.8 9.5 618 551 5500 4901 Enriched Gas as Delivered. per cent. 1.6 0.9 4.8 0.5 4.8 42.0 35.0 10.4 701 631 6235 5618 It appears that it is not always necessary to purify the gas from sulphur before use in a gas engine. In Germany one plant is successfully operated with gas con- taining as much as 0.2 per cent. of sulphur. The following Table, due to Dr. Schniewind, shows the usual yield of 100 lb. of coal in a bye-product coke oven :— 664 SECTION VI.-POWER STATION. NIG WE W 2017 2000 Kom B N 11 Omotion zu on? brown. 20 Whatou น 0815 903 PL Fig. 46. Deutz Suction-Producer Plant. Qi shiT untan aiguul GAS ENGINES. 665 Table 8.-Yield of 100 lb. of Coal in a Bye-Product Coke-Oven. 100 lb. of Dry Coal Yield. 71.13 lb. of coke 3.38 lb. of tar 229 cubic feet of surplus gas.. 234 cubic feet of heating gas.. Ammonia liquor, sulphur in purifier and loss ·· Total = 100 lb. dry coal Natural gas Coal gas Water gas Oil gas Carburetted water ·· · ·· .. ·· ·· ·· gas Producer gas from: Anthracite Bituminous .. .. ·· Coke Mond gas Coke-oven gas Blast-furnace gas Hydrogen .. Carbon monoxide Methane Ethylene Table 9.-Composition of Different Fuel Gases. By "surplus" gas is to be understood the gas available over and above that required for heating the oven. • ·· ·· ·· .. Hydrogen. •• ·· •• Methane. 3.0 92.0 46.0 40.0 48.0 2.0 32.0 48.0 16.5 40.0 25.0 8.5 20.0 10.0 3.0 10.0 24.3 2.0 50.0 36.6 1.0 100 100 Ethylene. 3.0 5.0 • Percentage Composition. ·· .. ·· 4.0 ** ·· 100 B.T.U. per Pound. 12,645 12,210 Carbon Monoxide. 686 567 I 6.0 38.0 0.5 23.0 5.0 Carbon Dioxide. .. c . ! | Nitrogen. 2.0 0.5 2.0 0.5 6.0 5.5 0.5 3.0 0.5 19.0 3.0 4.0 0.5 25.0 5.0 49.5 0.5 58.0 0.5 29.0 4.5 56.0 0.5 13.8 13.9 46.0 6.0 1.5 2.0 0.5 27.5 11.5 60.0 .. 100 .. Total Calorific Power. B.T.U. 899,456 51,410 157,504 132,835 2,496 1,243,700 ·· ·· Calorific Value. B.T.U. per Cubic Foot. Oxygen. ·· Per Cent. of Calorific Power of Dry Coal. .. 72.3 4.1 12.7 10.7 0.2 100.0 Air Needed for Combustion per Cubic Foot. || Calorific Value of Mixture. B.T.U. per Cubic Foot. 1000 9.73 91.0 668 6.05 91.7 295 846 2.35 88.0 8.07 93.0 575 5.25 92.0 144 1.12 68.0 144 1.2 65.5 125 .98 63.0 145.6 603 | 5.6 91 0.72 320 | 2.5 320 2.5 1000 1600 K 91.0 53 91 91 Removing Sulphur from Gas. Removing Sulphur from gas costs about one penny per 1000 cubic feet. It is. done by means of oxide of iron, which can afterwards be revivified by exposing it. to the action of the air, the oxide being spread in layers about 8 in. to 12 in. thick. Testing for H2S is done by means of acetate of lead paper. Such paper will become tinged if subjected for 24 hours to a gas containing 0.001 per cent. by volume of H2S, light being excluded during the test. One ton of oxide of iron should purify 11 to 13 millions of cubic feet of gas. before getting spent. 666 SECTION VI.-POWER STATION. - SCRUBBERS AND WASHERS. Herr Reissner's Rule. 5 cubic feet to 6 cubic feet per 1000 cubic feet per 24 hours of scrubbers. Wyatt's Rule. 100 cubic feet internal capacity of vessels (scrubbers and washers) with a gas contact of from 15 to 27 minutes per ton per diem. Gas in scrubbers should equal per cent. of the maximum daily make to give requisite contact time. 1 Horizontal net sectional area of all the scrubbers is 2 square feet per ton per day maximum make. Capacity of scrubbers should be 15 cubic feet per 1000 feet of gas per diem, the vessel being one-third the diameter of its height. (Richards.) Another Rule. Scrubbers should be equal to allowing a contact for 10 to 15 minutes of greatest make. Height is an advantage, so that the gas may be easier broken up and -wetted surfaces presented. Tower scrubbers usually six or seven times the diameter high. Scrubbers should be cylindrical. Height equal to six or seven times the diameter. Capacity equal to 9 cubic feet per 1000 cubic feet per diem maximum make. (Herring.) Newbigging's Rule. Newbigging's rule for tower scrubbers, 9 cubic feet per 1000 cubic feet gas made per day. The washer or scrubber wherein the gas is broken up into small streams passing in contact with wetted surfaces is preferable to that in which the water is divided into small drops and which fall through the gas, as the bulk of the gas is at least 100 times, and more often 1000 times, that of the liquid. A good scrubber should so distribute the water or liquor that the whole of the surfaces exposed to the gas in its passage should be evenly wetted, with length of contact and such contact ensured. The use of a washer requiring a separate engine must be compared with the extra cost of the fuel required, for one throwing some 3 in. or 4 in. pressure upon the exhauster. Scrubbers filled with coke will collect tar, and cause a lowering of illuminating power by absorption of light-giving hydrocarbons. When coke is used in a tower scrubber, a space of 6 in. is usually left above each layer before the next tier of sieves. GAS AND COAL. One ton of coal produces from 8,000 to 12,800 cubic feet of gas, if distilled for from 60 to 110 minutes. One ton of Cannel coal produces from 9,000 to 13,000 cubic feet of gas, if distilled for 50 to 60 minutes. The temperature of distillation is about 2,200 deg. Fahr. Weight of Gas. To find the weight of coal gas, multiply the number of thousands of cubic feet by 37; this will give the weight in pounds. To find the weight of a gas in pounds per cubic foot at 0 deg. Cent. and 760 millimetres of mercury pressure, multiply half the molecular weight of the gas by -0.00559. The molecular weight of a compound is the sum of the atomic weights of its constituents. The smallest indivisible particle of an "element" is called an "atom." The smallest indivisible part of a "compound " is called a "molecule." Each element has its own definite combining weight. Gay-Lussac's Law. The specific gravity of a compound gas, hydrogen being taken as unity, is equal to half its molecular weight; or, expressed otherwise, the combining volume of a compound gas is always equal to double that of the elementary gas. A combustible gas combines with oxygen: (1) when the mixture contains the two gases in proper proportions; (2) when the temperature and pressure of the mixture are within fixed limits. GAS ENGINES. 667 Determination of the Caking of Coal. (Louis Campredon). The coal is powdered to pass through a sieve of 2580 meshes per square inch, and a fixed quantity—say, one gramme of it is mixed with various amounts of uniformly fine sand. Each sample of coal and sand is heated to redness in a small porcelain crucible, and the character of the residue is observed when cool. From the various samples, the maximum quantity of sand which may be added to the given weight of coal with the production of a firm cake on heating is found. The weight of coal is taken as unity in the scale of comparison; and the caking power of coal which leaves a powdery residue is, of course, nil. The highest result found with any coal was 17 deg. on this scale; pitch gave 20 deg. Anthracite Bituminous Cannel.. Coal as stored Gas Coke Tar Space Occupied per Ton of Different Coals. Weight per Cubic Foot. lb. 58.25 .. ·· ·· · Welsh anthracite bituminous "" Lancashire Newcastle Coke in bays measures per chaldron 52 to 52 Coke diminishes in weight by exposure to the weather. .. Scotch Navy allowance for storage Table 10.-Average Weight of Various Coals. (H. O'Connor.) Per Cubic Foot. Heaped. Cubic Foot per Ton. Heaped. gas Percentage of coke ·· • • ·· • ·· •• Ammoniacal liquor Illuminating power of Per Cubic Foot. Solid. ·· .. lb. 85.4 78.3 76.8 • Coal Stores. Coal stores in the open should be payed with a slope to carry off rain water. Ventilation of coal stacks may be effected by constructing open piers of brickwork or wood, or inserting perforated pipes or wicker tubes round which the coal is laid. ¡ Table 11.-Products of Distillation of Coal, per Ton. (K. Clark). Cubic feet. 39 43 Wigan Cannel. 10,900 cubic feet 1436 lb. 44 45 lb. 58.3 49.8 48-3 17 gallons 18 "" 43 48 24 sperm candles 64 per cent. cubic feet per chaldron. 53 53 50 53 cubic feet. 38.4 45.3 46.4 Wigan Coal. 9980 cubic feet 1517 lb. 11 gallons 20 "" 15 candles 68 per cent. Per Cubic Yard. Solid. lb. 2,160 2,100 2,190 1,150 Newcastle Coal. 9700 cubic feet 1540 lb. 9 gallons 10 " 15 candles 70 per cent. 668 SECTION VI.-POWER STATION. : I ܢܚܬܳܐ Table 12.—Average Yield of Bituminous Coal by Weight. (Newbigging.) Gas Tar Coke ·· Cas Coke and breeze Tar ·· Distilled for Gas, at from 1000 deg. to 1200 deg. Fahr. •• Ammoniacal liquor Benzole Coal-tar Naphtha Heavy oil and naphthaline Table 13.-Results of Distillation of One Ton of Newmarket Cannel Coal, for Gas and for Oil. (Gesner.) Products of the Tar. Name of Town. .. Paris (Witz) Birmingham Berlin New York 7450 cubit feet 181 gallons 1200 pounds .. ·· London (Society of Arts) Gas Light and Čoke Company, Ltd., London South Metropolitan Gas Company, London (14-candle) Bristol Norwich Heidelberg (T. Chandler) Leeds (Grover) Kilmarnock (Kennedy) 3 pints 3 gallons 9 123 • • ·· ·· ·· ·· • "" Bonn Brighton Newcastle-on-Tyne Chemnitz (T. Chandler) Manchester (P. Frankland) Glasgow (Dr. Townsend) Nottingham (D. Frankland) "" ·· .. Table 14.-Approximate Composition of Coal Gas in Various Cases. ·· ·· ·· •• .. .. •• ·· .. .. ·· ·· ·· ·· Hydrogen. Gas Crude oil Coke Distilled for Oil, at from 750 deg. to 800 deg. Fahr. ·· • Eupion Lamp oil Heavy oil and Paraffin Marsh Gas. •• .. Carbonic Oxide. Hydro- Carbons. .. Products of the Crude Oil. Per cent. 18 68 5 •• 100 .. 7.14 10.00 5.63 5.63 1400 cubic feet 68 gallons 1280 pounds 2 gallons 22 24 481 Nitrogen. Carbonic Acid. 50.44 37.34 3.96 3.77 3.98 0-51 47.99 37.64 3.75 4.41 5.95 56.06 34.00 5.00 3.00 2.00 52.80 32.30 5.60 5.5 3.80 40.23 39.00 4.05 4.76 10.10 49.75 32.70 2.50 4.61 30.30 | 24.30 | 26.50 | 15.00 44.57 40.70 4.77 4.58 53.79 36.11 3.40 3.26 44.00 38.40 5.73 7.27 ·· || 14.99 6.80 2.24 2.14 "" "1 "" Oxygen. 1 0.26 1.50 0.36 0.68 0.54 2.40 1.00 0.22 0.50 5.11 0.27 0.14 3.03 0.27 4.23 0.37 39.11 41.78 8.22 2.77 8.00 0.12 43.60 42.80 4.30 5.55 2.70 5.35 39.80 43.12 4.66 4.75 4.65 3.02 51.62 38.15 4.14 3.76 50.50 36.71 3.37 3.62 2.07 0.03 0.23 5.29 0.28 0.23 1.08 57.29 36.45 4.45 4.91 1.41 42.90 30.93 32.18 | 40.26 45.52 39.66 11 3.07 0.29 0.06 2.51 0.81 0.24 GAS ENGINES. 669 Table 15.—Amount of Air Required to Burn 1000 Cubic Feet. " Authority. Dr. Gideon Moore 99 "" "" "" d = Fixed carbon Ash ·· .. $/02 Sulphur Moisture Volatile matter Coal gas, 18 candle power Carburetted water gas, 26 candle-power 6190 Carburetted water gas, 22 candle-power 5523 p W Table 16.-Average Analysis of Welsh Anthracite. (J. Hornby.) ·· ·· ·· .. L = • • 5/Q27.062, for lead pipes. ·· 5720 d 2 XC Gas. • = cubic feet of gas to be delivered per hour. diameter, in inches. p = pressure, in inches of water. √E * = 106 for coal gas. ·· • R (1 ·· ❤ · 52 for blast-furnace gas. 58 for producer gas. length of main in feet. - ·· .. d = : ·· · SERVICE PIPES. Diameter of Service Pipes. (Kempe.) • • ·· .. ·· 5 VOC p •• Q2 7 Quantity of Gas Discharged by Pipes. pdx 1,040, for lead pipes. d5 √ pd s Q = √√√√x do ι ι ·· .. •• Q These rules apply only when the fall of pressure is small. With a view to reducing the capital expenditure in mains, it is now becoming common to allow a large drop of pressure in these mains. In the Staffordshire power-gas system the drop of pressure between the supply station and the far end of the mains is 5 lb. per square inch. In America very much larger drops of pressure have been adopted. For such cases Professor Unwin has established a formula which may be written thus:- 5629 cubic feet. Air. 7 = length in yards. α = d x2) 1 [0.00324 +1296 L+ 4.6 log d X "" ?? Per Cent. 89.84 1.20 0.80 2.25 6.01 × .070, for iron pipes. Where Q = the number of cubic feet delivered per hour at the far end of the main, and measured at the pressure at that point. d = diameter of main in inches. p × 775, for iron pipes. x = ratio of the absolute pressure at the end of the pipe to the absolute pressure at the entry (x is always a fraction). R = 64 for Mond gas. The logarithm in the last term of the denominator is a common logarithm. With long pipes this term can be neglected. The formula gives the discharge when the temperature of the gas is 60 deg. Fahr. At higher temperatures the discharge is increased proportionately to the square root of the absolute temperature. The "hydraulic gradient" in a pipe delivering gas is not a straight line as it is in the case of liquids, but a parabola with its vertex at the point of maximum pressure. 670 SECTION VI.-POWER STATION. The following figures for gas distributed under high pressures are due to Mr. H. A. Humphrey. They give delivery in cubic feet (measured at atmospheric pressure) per day of ten hours of Mond gas, from pipes of the diameters and lengths noted. The pressure at inlet was 21.7 lb. per square inch absolute, and at outlet 16.7 lb. absolute. Table 17.-Discharge of Gas Pipes at High Pressures. Diameter of Main. in. 30 27 24 18 12 One Mile. cu. ft. 58,110,000 44,450,000 32,840,000 15,640,000 5,456,000 Length of Main. Five Miles. cu. ft. 25,990,000 19,890,000 14,090,000 6,996,000 2,433,000 Ten Miles. cu. ft. 18,370,000 14,050,000 10,380,000 4,939,000 1,725,000 ·GASHOLDERS. The thickness of plates commonly used in the construction of gasholders varies from No. 18 to No. 11 B. W.G., the first being less than -in. in thickness, weighing 1.86 lb. per square foot; the other is -in., and weighs 5 lb. per square foot. The footing or foundations for the wall of tank should be one-eighth of height of tank-that is, if 40 ft. high, the base of footing should be 5 ft. wide, and the thickness one-third of the width. The wall of the tank should be built as nearly as possible at the centre of the footing; the dome or cone of centre should abut against the side of the footing to its full thickness. To ascertain the weight of a holder, not counterbalanced, giving a certain pressure, and the sides nearly out of the water, multiply the area of the top în feet by 5.208, and by the height of the pressure in inches of water. For example, a holder is 11 ft. 4 in. in diameter, its area being 100 ft., giving 3 in. pressure. Then 100 × 5.208 × 3 = 1562 lb., or the total weight of the holder. Mr. G. Livesey stated (1882) that £20 per 1000 cubic foot capacity was a usual cost of gasholders of moderate size. Single lift holders should not be used except for less than 10,000 cubic feet capacity. Height of lift should = diameter 4 Holders above 500,000 cubic feet capacity should be three lifts. It should be borne in mind that the larger the sheets the less rivets are required, and the liability to leakage is reduced. The strain on top sheets diminishes in exact proportion to the rise, and is uniform throughout the top sheets. Usual rise = Shape of dome equals segment of a sphere. diameter. 20 diameter No. 11 Birmingham wire gauge sheets are sufficient • 20 up to, say 175 ft. diameter, but when larger, No. 10 sheets and an increased rise would be better. Rivets in. diameter. With rise = The crown curb in trussed holders has not much work to do. The best form of curb is an angle iron or steel, but in larger holders where the compressing strain may equal 200 tons, other pattern curbs must be adopted. Mr. Livesey considers 40 lb. per foot as the maximum wind force likely to be exerted on a gasholder, and 57 per cent. of this force is exerted on the cylinder as compared with a flat surface. Mr. Foulis considers 50 lb. per square foot should be allowed for as wind pressure on gasholders. Mr. Cripps suggests gussets to connect the first row of top sheets with the top row of side sheets in small holders. GAS ENGINES. 671 CONSUMPTION AND COST. The average consumption of coal gas on the Continent is 24 to 30 cubic feet per indicated horse-power hour, and 32 to 35 cubic feet per brake horse-power hour. In England it ranges from under 12 up to 24 cubic feet per indicated horse-power hour, and from 13.5 up to 33 cubic feet per brake horse-power hour. The gas used in Great Britain is usually of somewhat higher calorific value than that used on the Continent. Table 18.—Fuel Consumption of Gas Engines with Producer Gas. Crossley Gas Motorenfabrik enfabr Deutz Gas Motorenfabrik Deutz Stockport Crossley Atkinsons Crossley "" 19 "" Name of Engine. 99 ·· ·· ·· ·· •• •* Gas Motorenfabrik Deutz Otto Crossley Simplex Crossley American Otto Crossley Averages. ·· ·· ·· .. .. .. ·· ·· • • •• ·· ·· ·· ·· .. •• .. ·· .. .. I.H.-P. 119.0 76.0 27.5 21.9 150.0 .. 130.0 33.5 124.5 Walthamstow 814,187 15.45 127.6 63.7 d. .46 265,717 14.11 .88 Redditch Northwich 157,198 9.20 .51 B.H.-P. 14.38 ·· 54.5 110.0 164.0 56.8 60.0 60.0 160.0 Total Anthracite Consumed per I.H.-P. Hour in Pounds. 1.315 27.5 1.87 95.8 1.08 77.46 60.18 1.24 57.6 1.12 .555 0.762 d. .19 .19 .15 •• .184 0.86 1.40 1.06 0.92 ·· ·· Total Anthracite Consumed per B.H.-P. Hour in Pounds. d. .36 .53 .50 1.38 1.10 ·· ·· 1.37 1.39 1.11 0.79 1.01 1.54 (Coke) The following Table shows results obtained at certain gas-driven stations :- Table 19.-Results Obtained at Gas-Driven Stations. 1.45 1.60 0.95 1.36 d. .06 .24 .35 .413 .135 Name of Gas Producer Used. Dowson Gas Motorenfabrik Deutz Gas Motorenfabrik Deutz Dowson "" "" Fichet-Heurtey Dowson Mond Dowson "" Gas Motorenfabrik Deutz Lencauchez type Dowson Lencauchez Dowson "" d. 1.07 1.84 1.51 Total Works Cost. 1.29 { Fuel Used. Mond gas Cost of Fuel. Anthra- 268. per cite ton in bunks. coal 2d. per 1000 ft. 672 SECTION VI.-POWER STATION. Fuel Consumption and Costs of some Gas-Driven Electric Plant. Some very interesting results have been obtained at Leyton. The Dowson gas producer is used exclusively for the central lighting station of the Leyton Urban District Council. The first installation for 264 indicated horse-power was started early in 1896; it was increased to 396 indicated horse-power at the end of 1896; it was further increased to 636 in October, 1898. On October 26, 1897, Professor Robinson, of Westminster, made a careful test with two engines and one gas generator under full load. On the following day, four engines and two gas generators were worked at about two-thirds of the full load. The results were officially reported as under : Duration of test, hours Electrical output in Board of Trade units: Engine No. 1 2 3 4 Month. 1897. January February March April May June July August ·· .. January February March ·· ·· September October November December Totals Anthracite consumed in gas generator: Per indicated horse-power per hour Per brake "" ·· 1898. "" "" .. ·· ·· "" Per electric 39 Per Board of Trade unit generated Coke Consumed in boiler per unit generated Total fuel per unit generated • .. ·· " "" ·· ·· ·· ·· units 8,892 9,417 13,464 11,588 10,630 8,552 ·· ·· 10,744 12,573 ·· 23,336 20,800 22,451 .. .. ·· ·· 54,059 47,788 52,436 26,600 1377 1100 21,737 9,319 22,650 1024 27,030 1182 28,256 1384 17,893 42,970 1301 20,577 45,341 2160 25,062 57,561 2306 .. ·· The above figures represent the actual fuel consumed during the trials, and do not include any waste or stand-by losses. Table 23 gives the total fuel consumed each month for 15 consecutive months, and this includes all sources of loss. : Table 20.-Fuel Consumption during 1897-8 in the Gas-Driven Electricity Works of the Leyton Urban District Council. 2 ·· 1242 1908 1116 ·· ·· ·· : • .. ·· .. •• .. Oct. 26. Oct. 27. 5 5 16:1 0.846 0.975 163 314 11:020 lb. 22,311 22,237 lb. 1202 lb. 2.550 1220 2.360 31,543 1164 2.340 29,359 1239 2.535 1.152 1.543 0.225 1.768 2.320 2.310 2.340 2.500 2.540 2.430 2.510 2.240 2.400 2.200 2.300 87 101 105 109 lb. 0.135 0.129 0.086 0.107 0.129 0.129 0.110 0.110 402 0.110 0.073 0.105 0.092 0.942 1.128 1.405 1.880 0.214 2.094 0.053 0.047 0.049 lb. 2.685 2.489 2.426 2.642 2.629 2.669 2.540 2.620 2.350 2.473 2.305 2.392 2.373 2.357 2.389 GAS ENGINES. 673 "" Table 21.-Average Coal, Water, and Gas Consumption. Coal consumed in pounds per Board of Trade unit Management Labour.. Fuel Oil, grease, and waste Water Acid for storage batteries Sundry supplies Maintenance of gas producers "" 1.8 to 3.5 lb. Anthracite in pounds per brake horse-power hour 1.1 1.6 "" Coke in pounds per brake horse-power hour 1.5 2.2 .. "" Water in cubic feet per Board of Trade unit at switchboard.. .. .. •• Items. "" Table 22.-Cost of Production in Pence per Unit at Switchboard. (Lausanne Gas-Driven Plant.) .. .. ·· ·· •• •• • accumulators ·· ·· .. engines and dynamos •• ·· ·· Pension fund.. Insurances Taxes Interest at the rate of 4 per cent. on capital expenditure ·· ·· .. • ·· .. .. .. ·· ·· Total per unit at switchboard Loss due to amount lost in batteries causes rise in price of current delivered on to the line to be ·· ·· · Total cost per unit, delivered on to line, all included .. ▸ .. ་ ·· : ·· "" "" 1 to 3 cubic feet. 1.082 1.154 1.263 Average cost of unit, delivered to line, for three years, 1897 to 1898, 1.166d. Sinking fund (Plant to be paid for in 25 years) 0.208 0.190 0.166 1896. 1897. 1898. d. d. d. 0.036 0.035 0.219 0.166 0.188 0.430 0.259 0.339 0.045 0.021 0.030 0.043 0.015 0.025 0.035 0.001 0.013 0.006 0.004 0.010 0.010 0.050 0.049 0.003 0.014 0.011 1.290 1.344 1.429 Average cost per unit of current delivered on to line, all included, for three years, 1.354d. Cost of fuel, 24s. to 28s. a ton delivered. 0.006 0.014 0.013 0.075 0.067 0.065 0.007 0.008 0.014 0.004 0.004 0.013 0.064 0.027 0.024 0.287 0.263 0.230 0.961 1.024 1,186 i. 1899 d. 0.037 0.185 0.469 0.037. 0.033 0.006 Z Sp Comparison of Steam and Gas-Driven Stations. Mr. Hugh Campbell has published, in a paper read before the Leeds section of the Institution of Electrical Engineers, November, 1904, a comparison between the gas- and steam-driven plants at Guernsey. The station at St. Peter's Port is steam- driven. Its equipment consists of one 270 brake horse-power surface-condensing triple-expansion engine, using steam at 160 lb. per square inch, direct-connected to a 180-kilowatt dynamo driven at 420 revolutions per minute. The first cost of the steam plant, inclusive of boiler, pipes, chimney and accessories, but with no allowance for foundations, buildings, rough labour and cartage, was £3642. At St. Sampson the plant is gas-driven by a 300 brake horse-power Campbell gas engine, driving a 180-kilowatt dynamo at 250 revolutions per minute, which, with its accessories, cost £3200. This engine is supplied with gas from a pressure-gas producer, the steam boiler for which used 15 per cent. of the total fuel consumed. Tables 23 and 24, on the following page, show the working costs of each plant:- 674 SECTION VI.—POWER STATION. Table 23.-Generating Costs, Guernsey Steam and Gas-Driven Stations, in Pence, per Unit, Sold and Generated Respectively. GAS DRIVEN. Coal, per unit Stores and water ·· Wages Repairs, all plant, mains, and buildings Efficiency of distribution Units sold. Units generated Possible units, full load Plant load factor Coil units generated Price of coal in bunkers .. .. Total works cost .. .. : ·· : : .. ť .. : Difference in favour of gas plant per unit generated : •• May. July. August. Sold. Gen. Sold. Gen. Sold. Gen. Sold. Gen. d. l. d. d. d. d. d. d. .255 .30 .32 .240 .30 .240 .28 .224 .09 .072 .13 .104 .07 .26 .206 .19 .152 .24 .22 .175 .15 .17 .136 .89 June. .708 .77 .616 62 per cent. 2.6 lb. 18s. 6d. .120 .142d 76 per cent. 2.44 lb. 18s. 6d. .13.104 .259d. .23 .184 .17 .136 .83 .664 .056 80 per cent. 80 per cent. 80 per cent. 80 per cent. 18,565 26,132 29,153 31,130 23,206 32,665 36,441 38,913 37,620 42,840 47,700 52,200 76.5 per cent. 74.5 per cent. 81 per cent. 2.33 lb. 2.19 lb. 2.32 lb. 18s. 6d. 18s. 6d. 19s. 6d. .099d. .192 .76 .608 September. Sold. Gen. Sold. Gen. d. d. d. d. .31 .248 .31 .248 .06 .048 .06 .048 .20 .160 .19 .152 .15 .120 .13 .128d. October. .72 .576 .69 .552 .104 .346d. 80 per cent. | 80 per cent. 4 35,597 40,289 44,496 50,361 55,080 61,380 65.8 per cent. 2.44 lb. 18s. 6d. .513d. GAS ENGINES. 675 Table 24.-Generating Costs, Guernsey Steam and Gas-Driven Stations, in Pence, per Unit, Sold and Generated ĮRespectively. STEAM DRIVEN. Coal, per unit Stores and water .. Wages Repairs, all plant, mains, and buildings Efficiency of distribution Units sold Units generated Possible units, full load Plant load factor Coal, units generated Price of coal in bunkers ·· .. : Total works cost : : : : : : : : • : : : : : : : : : ·· : : May. July. Sold. Gen. Sold. Gen. Sold. Gen. d. d. d. d. d. d. .71 .502 .69 .503 .74 .452 .06 .042 .06 .044 .07 .184 .25 .182 .29 .122 .20 .146 .15 .26 .17 June. 1.20 .850 1.20 .875 1.25 .042 .177 .092 No Condenser. No Power Load, August. September. October. Sold. Gen. | Sold. | Gen. | Sold. | Gen. d. d. .66 .458 .06 .042 -23 .160 .076 .11 d. .74 .11 .22 .23 d. .525 .078 } .156 .163 1.30 .922 .763 1.06 .736 70.6 per cent. 73 per cent. 61 per cent. 69.5 per cent. 71 per cent. 71 per cent. 37,776 32,354 32.130 41,906 38,911 53,506 44,241 52,574 60,306 55,108 80,700 67,570 68,640 77,460 85,335 66.3 per cent. 65.6 per cent. 76.6 per cent. 78 per cent. 70 per cent. 45.6 per cent. 5.9 lb. 5.8 lb. 5.23 lb. 4.83 lb. 5.56 lb. 6.13 lb. 15s. 10d. 16s. 168. 17s. 10d. 17s. 6d. 17s. 6d. d. .83 39,078 55,133 78.585 .11 .20 .36 d. .589 .078 .142 .256 1.50 1.065 : Date. Dec. 4 "" "" "} "" "" "" Total for Week. "" "" 4567 Dec. 11 >> 8 9 10 "" "" "" Total for Week. Average Start. 10.30 **1.0 10.30 9.30 11.0 { 9.15 {.. Time. 12.0 12 11.45 4.45 13 9.30 5.0 8.30 12.30 14 15 16 17 Finish. 12.30 2.0 64 86 6.0 5.0 75 200 4.30 6.0 4.30 7.0 95 70 9.45 1.45 4.0 75 4.15 6.45 2.30 4.0 12.45 3.45 7.0 11.0 ·· ·· Table 25.-Log Sheet: Milford-on-Sea Electricity Supply Co., 1904. Coal. Units Generated. Run. ·· Stand-by and Blowing up. 5.0 3.30 4.15 8.15 10.45 .. 2.0 2.0 73 5.0 7.30 72 4.0 75 3.15 50 5.30 4.30 75 12.30 70 1.45 72 12.30 188853 98 75 Used During Run. Total for Day. 35.0 587 1274 1861 CONPOKON 39 39.2 38 38.5 40.9 100 135 175 273 597 38.3 135 210 596 39.4 Average Volts. Average Am- peres. 150 275 204 299 237 307 137 212 574 81 170 65 260 581 585 609 608 154 235 593 39 Kilowatt Hours. - Meter Read- ing. 45 114.6 138.7 11,268 50 163.9 11,322 54 811.4 33.15❘ 552 1153 1705 594 |1213.5 | 34.7 569.5 1213.5 1783 593.5 38.95 783.75 * Pounds of Coal per Unit Generated, including stand-by. 152.5 152.5 11,374 52 Units. 114.4 11,440 66 82.3 11,476 36 38.9 756.1 590.7 40.7 48.1 11,500 24 607 37.1 112.6 11,521 174.411,573 21 52 332 586 39.7 135 210 562 39.1 100 187 150 J 262 604 37.9 125.9 215 584 37.3 92.7 75 147 623 39.5 43.1 145 11,197 22 11,218 21 11,389 ·· 301 2223 159.3 11,632 59 11,687 55 11,739 52 11,778 39 Units Sold. 302 - Meter Read- ing. 301.5 11,365 22 ∞& & JONN Units. 11,440 11,497 11,553 11,620 11,656 24 51 57 56 67 36 313 302 Total. Meter 101 111 108 133 72 614 46 11,678 22 11,702 24 45 11,753 51 103 11,816 63 122 55 110 11,871 11,923 11,958 52 104 35 74 604 Units Used in Works. 307.5 609 Reading. Units. 10088 188 48 49 50 53 56 1 57 59 65 67 69 1 71 K 126 585 5 872 211 | 00 3 3 38 30 10 2 221 16 Maximum Observed. Current 13 1 30 30 30 22 182 2 2 2 | 30 24 + 22 18** **I 22 34 32 28 25 2.3* 2*22*| 30 32 26 34 32 24 2.25* 2.275* Remarks. Supply is on the "outers.” 3-wire system at a pressure of 460 volts Dynamo is driven by ropes from the fly- wheel of the engine. between 3.03+ 2.82+ 2.925+ † Pounds of Coal per Unit Sold, including all Losses. expected with small installations. dynamo, worked with a gas engine supplied from a motor plant, show what may be The following figures taken from a Crossley plant, consisting of a 25-kilowatt * 1 ་ GAS ENGINES. 677 Name and Date. Table 26.-Cost per Unit Generated in Various Gas-Driven Stations. Linden, 1898-1899 Orleans Tramways, 1899 Leyton, 1898 (c) .. .. ·· .. d. d. d. d. d. d. d. d. Zurich-Oerliken See- bach Tramways, 1898.484.054 (a) .075 .225.014.005.001 (b) .095 .015.062 Zurich - Bergbahn, 1898-1899 1.294 .026 .022 .134 .022.015.008 .070 .540 .156 1.332 047 .300 .. Fuel. Items. • .5114 .. Water. .250.023 .0933 Total capacity of generators installed in kilowatts Capacity of storage battery in kilo- watts · (a) Water, Acid, and various. (b) Includes switchboard. (c) Cost per unit sold. Cost per unit generated about 35 per cent. less. .. Cost of buildings per kilowatt of generators installed Cost of gas producers and gas engines per kilowatt installed Oil and Waste. Salaries and Wages. Producers. Engines. Cost of electric plant per kilowatt installed Cost of storage battery per kilo- watt of generator plant installed Cost of furniture, tools, and sundries per kilowatt of generator installed 1.2321 Table 27.-Approximate Cost of some Gas-Driven Electric- Power Plants. Zurich* Oerlikon Seebach Electric Tramway. 235 190 Maintenance. 20 0 3 0 £ 8. £ S. 35 10 23 0 22 7 25 7 * Use producer gas made on premises. Lausanne* Electric Tramways. 300 220 0.0359 24 10 Dynamos. Battery. Insurance. Rates and Taxes. Sundries, St. Gallent Light and Traction. .180 £ s. 22 10 21 6 .200 14 10 18 0 250 150 283 100 90 125 £ 8. 26 0 £ s. 18 0 Zurich* Berghabn. Belfast.† 9} 24 0 19 0 9 16 1 12 21 Ot 30 20 ૐ + Use town gas. } d. King's Lynn. 200 40 £ 8. 13 0 24 0 13 6 40 678 SECTION VI.-POWER STATION. ! Table 28.-Approximate Cost of some Gas-Producing Plants. Quantity of Gas Producer has to. Supply per Hour. cubic feet 13,320 24,198 Corresponding Rated Capacity of Generator Station. kilowatts 220 600 Steam-driven plant 11 "" Cost of Gas Producers Erected. Comparison between Steam and Gas-Driven Plants. The amount of coal used in a gas-driven plant is 'nearly always less than the best results obtainable with steam plants, but the amount of water used is greater, as shown by the following Table :— Pounds of Coal per Board of Trade Unit at Switchboard. 2.85 to 12 1.1 to 3.5 ·· £ 2880 4800 Cost of Gas Producer per Kilowatt. £ 13 ·8 Gallons of Water per Board of Trade Unit at Switchboard. 2 to 6 6 to 18 Gas The water can most of it be used over and over again, the greater part being used to keep the jackets cool. The two quantities on which saving is effected in a gas-driven plant running with producer gas are, first, the economy in fuel consumption; and, secondly, the saving in labour necessary to run the plant. When comparing the cost of production in a gas and steam-driven plant, the cost of installation must be considered. The interest on the capital invested, and maintenance and sinking fund must be taken into account, as well as the cost of production of energy pure and simple. The cost of installation of various parts of a gas-driven plant is given in Tables 27 and 28. The amount of labour required to run a gas plant would be from 75 to 50 per cent. of that necessary in the case of a similar-sized steam-driven installation. The amount of space required by a gas-driven plant would be smaller than that necessary for a steam plant. Consequently, the cost of buildings would be less, and no smoke-stack is needed. Yet usually a gas-driven plant would probably involve at least 25 per cent. more in capital expenditure than the corresponding steam- driven plant. Depreciation, maintenance, and sinking fund would consequently be heavier in the case of a gas than of a steam plant. 6 In making the choice between a steam and a gas plant, all the above con- siderations must be most carefully weighed and compared before coming to any definite conclusion. It may, however, be stated definitely that for localities where fuel is expensive, the power to be installed not very large, and where the hours of running are comparatively short, a gas-driven plant is nearly certain to prove far more advantageous than any steam-driven one. This will easily be verified by the wonderfully low costs of power production shown in previous Tables, and which would have been quite out of the question if gas-driving had not been introduced. Every case will differ, and it is therefore impossible to draw any hard-and-fast rule, but the above considerations, and the Tables which have been given, should enable a satisfactory conclusion to be reached in most cases. By the use of sufficiently large storage batteries, in cases where the running hours are not too long, it will become possible to run the station with only one shift of Thus, in a plant which has to operate cars or supply power and lighting, say between seven in the morning and ten at night, the accumulators conld furnish the necessary current for four or five hours, and no supervision would be required. One shift of men working ten hours would in such a case suffice to operate the station, with the addition of one or two necessary night hands. On page 681 are summarised the advantages and disadvantages of gas and steam engines respectively. 1. GAS ENGINES. 679 *-----470· 560 754 Fig. 47. Section through Diesel Oil Engine. dan saya dan at mga de man mag o CAT • 680 SECTION VI.-POWER STATION. Air to sprayer Oil to sprayer – Da a contro (1098) + O 48 49 Suction Fuel Echaus **** ==== 本​宮 ​= Figs. 48 and 49. Details of Valve Gear, Diesel Oil Engine. GAS ENGINES. 681 F !: POSSIBLE ADVANTAGES AND DISADVANTAGES OF GAS-DRIVEN ELECTRIC PLAN Advantages. No smoke and no chimney. Less space required for plant. Less labour. No danger of boiler explosions. Disadvantages. Complicated mechanism. Expensive maintenance. Difficult speed regulations. Costly. (1059) Vibration. Heating effects on atmosphere of engine room. The proportion of space required for a steam plant, a gas engine with its own gas-making plant, and a gas engine using gas from town or company's mains, is in the ratio of 10 to 8 to 3, and the cost of buildings varies in the ratio of 7 to 6 to 5. The Diesel Oil Engine. (Figs. 47 to 50, pages 679 to 681.) In Figs. 47 to 50 we give illustrations of the Diesel oil engine, as made by Messrs. Carels Freres, of Ghent. Fig. 47 represents a section through one cylinder of a three-cylinder engine made by them, rated at 500 brake horse-power. The engine works on the four-cycle principle, in the following manner: On the suction stroke the engine draws in a charge of pure air, which on the return stroke is com- pressed in the cylinder to a pressure of about 500 lb. per square inch. The rise of temperature due to this compression is about 1500 deg. Fahr. Just as the piston reaches the end of its compression stroke, a dose of paraffin or other mineral oil is sprayed into the cylinder by a jet of air supplied at a pressure of about 730 lb. per square inch. This oil spontaneously ignites and burns quietly whilst the piston makes its outward stroke, the amount of heat developed being sufficient to maintain the pressure nearly constant for the first part of this working stroke. A typical diagram is represented in Fig. 50. On the exhaust stroke the products of combustion are expelled. Cylinder No. 56. Scale 1-450ths. M.E.P. 115-6. Fig. 50. Typical Diagram, Diesel Oil Engine. There are four valves to each cylinder, all mounted on the cover as shown in the plan, Fig. 49. These are the exhaust valve, suction valve, oil-admission valve, and the starting valve. All four valves are operated by bell-crank levers (Fig. 48) mounted on one and the same spindle, and driven by cams on a side shaft. The spindle carrying the four valve levers is mounted on eccentrics, and by turning it half round the starting valve can be thrown into operation, whilst the oil and suction valves are thrown out of operation. A single movement, therefore, suffices to throw all three valves of all three cylinders into position for starting the engine. This is done by compressed air stored in gas cylinders at 735 lb. per square inch, which are pumped up by the engine itself when running. A section through the oil-sprayer is shown at Fig. 48. The 500 horse-power engine has cylinders 22 in. in diameter by 29 in. stroke, and is designed to run at 150 revolutions per minute. The governor acts on the supply of oil, reducing this as the load falls off. The maximum speed variation is 2 per cent. on passing from full to no load. In some tests by Mr. Michael Longridge it was found that the consumption of oil per brake horse-power hour ranged from .444 lb. at nearly full load, to .481 lb. at half load, and 1.41 lb. at one-ninth load. The mechanical efficiency was .72 at full load, .59 at half load, and .2 at one-ninth load. Z2 SECTION VII. THE POWER STATION (Concluded). BUILDINGS AND MISCELLANEOUS. • F** SECTION VII. THE POWER STATION (Concluded). BUILDINGS AND MISCELLANEOUS. BUILDINGS: GENERAL. The following tables and data as regards buildings have been extracted from some of the leading authorities on this subject, and have been acknowledged as far as possible. Building Regulations in London and Provinces. In London, by London Building Act of 1894, the unrepealed sections of previous Acts mentioned therein, and by the bye-laws of the London County Council, the district surveyor must be notified of all building work. Publications from P. S. King and Son, Westminster, S. W. In principal provincial towns the local authorities enforce a code of building bye-laws compiled under statutory powers. Information from the borough surveyor. Approximate Cost of Buildings. This may be arrived at by the method of "cubing." Length and width of building taken over all, height from bottom of footings to half-way up roof. Mansions Small suburban houses Public libraries, technical 'schools, &c. Labourers' cottages Electric lighting station buildings Engineering workshops Corrugated iron temporary buildings.. .. ·· * • Per Cubic Foot. pence 10 to 15 6 8 8 10 "} "" · ·· 4/ 4 6 "" 3 2 Of total cost allow masonry and brickwork 50 per cent., carpentry 25 per cent., other trades 25 per cent. Usual trade profit taken at 15 per cent. total cost. Walls of Warehouses, Stores, Factories, and Stables. (Extract from the Building Laws of the City of New York, 1893.) 25 ft. or less in width between walls, not less than 12 in. to height of 40 ft. ; If 40 to 60 ft. in height, not less than 16 in. to 40 ft., and 12 in. thence to top; If 60 to 80 ft. in height, not less than 20 in. to 25 ft., and 16 in. thence to top; If 75 to 85 ft. in height, not less than 24 in. to 20 ft. ; 20 in. to 60 ft.; and 16 in. to top; If 85 to 100 ft. in height, not less than 28 in. to 25 ft. ; 24 in. to 50 ft.; 20 in. to 75 ft.; and 16 in. to top. Over 100 ft. in height, each additional 25 ft. in height, or part thereof, next above the curb, shall be increased 4 in. in thickness, the upper 100 ft. re- maining the same as specified for a wall of that height. If walls are over 25 ft. apart, the bearing-walls shall be 4 in. thicker than above specified for every 12 ft. or fraction thereof that said walls are more than 25 ft. apart. 686 SECTION VII.-POWER STATION. Foundations on Yielding Ground. (Figs. 1 to 7.) (Carnegie.) In designing the foundations of walls and piers of buildings when they rest upon a yielding stratum, proper provision must be made for the uniform distribu- tion of the weight. In case the walls are of different thicknesses and heights, the widths of the foundations must be proportioned according to the different loads, so that the bearing per unit of ground-area will be equal and a uniform settlement of the completed structure be ensured. Figs. 1 to 7 show footings generally used in England where bricks are employed. Rails embedded in concrete offer little resistance to deflection; and for this reason, if allowed to project beyond the masonry to any considerable length, the concrete filling is liable to crack, and the strength of the foundation becomes impaired. I-beams used for this purpose are found to be preferable. A greater depth can be adopted, the deflection thus reduced to a minimuin, and a sufficient saving effected to compensate for their additional cost. 2 460 i 5 3 в 4 Figs. 1 to 7. Diagrams of Footings. The foundation should be prepared by first laying a bed of concrete to a depth of from 4 in. to 12 in., and then placing upon this a row of I-beams at right-angles to the face of the wall. In the case of heavy piers, the beams may be crossed in two directions. Their distances apart, from centre to centre, may vary from 9 in. to 24 in. according to circumstances, i.e., length of their projection beyond the masonry, thickness of concrete, estimated pressure per square foot, &c. They should be placed at least far enough apart to permit the introduction of the concrete filling and its proper tamping between the beams. Unless the concrete is of unusual thickness, it will not be advisable to exceed 20-in. spacing, since other- wise the concrete may not be of sufficient strength to properly transmit the upward pressure to the beams. The most useful application of this method of founding is in localities where a thin and comparatively compact stratum overlies another of a more yielding nature. By using I-beams in such cases, the requisite spread at the base may be obtained, without either penetrating the firm upper stratum or carrying the footing courses to such a height as to encroach unduly upon the basement room. Bearing Power of Soils. Usual limits in practice are from 1 ton per square foot on soft soil or unstable sand, to 4 or 5 tons on hard chalk or rock. Ordinary bottoms of good gravel or stiff clay are safe with a load of 2 tons per square foot. BUILDINGS AND MISCELLANEOUS. 687 Hard, compact gravel is considered excellent bottom, either with or without concrete foundations, provided only that the gravel bed is not thin. In porous soils, foundations should be well drained. Table 1.-Pressure on Foundations of Some Existing Structures. (Mechanical Engineer.) Structure. Cleveland Viaduct Chimney, Newcastle Busigny Bridge Brooklyn Bridge Washington Memorial Busigny Bridge Kurtenburg Bridge Chimney, New York Brooklyn Bridge Nantes Bridge "" Viaduct, Point-de-Jour Coarse gravel Bordeaux Bridge Soil. Gravel Dry sand ** Sand · Vegetable earth Compact earth •• Blue clay Compact clay Yellow sandy clay Compact stony clay Clay and sand ·· Unstable sand Compact sand Wet sand Sand ·· Soil. •• ** Excavator's Memoranda. (Mechanical Engineer.) soils. A man will throw up per day 5 cubic yards in hard, to 10 cubic yards in soft, Three men will remove 30 cubic yards of earth to a distance of 20 yards in one day. One ton = 19 cubic feet of sand, 18 of clay, 20 of gravel, 24 of earth. One load = 27 cubic feet of earth = 11 cubic feet before digging. Sand and gravel increase to 13 volume when dug. Clay excavated may be burnt for road ballast; if well burnt, used for concrete Gravel excavated, if dirty, should be washed before using for concrete. Excavating is measured by the cubic yard, and the cost increases at every 6 ft. in depth. Drains, if small, are often estimated at per foot run, the average depth and size of drain-pipe being stated, the price including excavating, strutting, laying, and filling in. Table 2.-Greatest Depth of Vertical Face of Excavation which will Stand for a Short Time. (Mechanical Engineer.) deg. 40 38 22 Nature of Soil. Clean dry sand and gravel Moist sand and ordinary surface mould Loamy soil, well drained Clay, well drained Compact gravelly soil Table 3.-Natural Angle of Slope of Various Soils with Horizontal Line. ·· 28 50 Angle Ratio. gle Tons per Sq. Ft. Compact sand and gravel [7.36 to 8.17 .. 1.0 to 1.7 1.5 2.1 2.8 5.5 At 9 tons settlement 3.0 9.0 took place 2.3 ·· 11 to 1 |Shingle 1.28,, 1 Rubble "" ** •• • 33 • • 1.8 2.0 Settlement took place. 4.0 4.0 6.78 Settlement took place. 4.4 Soil. •• •• 2.47,, 1 Clay, well drained 1.88,, 1 Clay, wet .. 0.84,, 1 Remarks. .. Depth in Feet. 0 to 1 1 3 5 10 9 12 10 15 .. • • •• ·· .. "" "" "" "" Angle Ratio. deg. 39 45 4999995 16 1.23 to 1 1 1 3.5 "" ະ pool pool pool pl "" 1 7 1 688 SECTION VII.-POWER STATION. • A House drains Branch Sewer.. "" "" "" guet e NN 25 40 ·· 40 ·· 40 "" 25 40 ** * 8888 40 50 50 50 Height in feet. Length in feet. from from to 0 25 0 0 25 50 60 50 60 Purpose. ·· from to 0 25 25 30 25 30 30 40 ·· 30 40 30 40 40 50 40 50 .. Table 4.-Slope of Drains. .. ·· ·· ·· ·· ·· 30 onwards (or if wall is more than two storeys high.) 35 35 upwards 0 30 30 45 45 upwards 0 45 45 upwards to 30 Table 5.—Minimum Thickness of Walls for Houses. (From Schedule of London Building Act.) Length in Feet. from to 0 U 0 45 45 U 0 35 35 45 Diameter. in. 6 45 U 0 30 30 45 +-200 in. 13 13 17} 13 4 17 21 9 12 17 21 18 30 19 "" "" "" "" in. 1 Top storey, 8; bottom storey, 8 (if wall is not more than two storeys). Top storey, 8; all others, 13. Table 6.-Minimum Thickness of Walls for Warehouses, &c. Height in Feet. Minimum Thickness. Height in Feet. Length in Feet. from to 40 50 50 60 1 1 1 Top storey, 8; all others, 13. Top storey, 8; inter. storeys, 13; bottom storey, 17. Top storey, 8; inter. storeys, 13; bottom storeys, 171. All upper storeys, 13; two bottom storeys, 17. inter., 17; bottom, 21. bottom storeys, 17. "" "" inter., 17; bottom, 21. 50 60 60 70 1 1 "" 60 70 70 80 70 80 80.90 Slope. "" Minimum Thickness in Inches. in ** "" " "" 19 ft. .45 10 6 from to 45 U 0 45 45 U 36 50 75 120 0 45 U 0 45 45 U 0 45 Minimum Thickness. in. 26 211 26 214 26 f 211 26 ƒ 26 U-unlimited. The above thicknesses are for the base of walls only. For the rest, the wall shall be 134 in. at top of wall, and for 16 ft. below, the portion below this point to be solid between lines drawn on each side of the wall to the base. If walls, how- ever, are not more than 30 ft. high, the topmost storey may be 9 in. thick if not more than 10 ft. high. Footings to have a width at the base equal to double the thickness of the wall, diminishing in regular offsets, and to be in height equal to one-half the width at the base. Cross walls to be two-thirds of the thickness of the external or party walls, but never less than 8 inches. BUILDINGS AND MISCELLANEOUS. 689 Piles. (Hurst.) Piles should be driven until a sufficient resistance is obtained. This is esti- mated to be the case by French engineers when the further penetration does not exceed one-fifth of an inch with 30 blows from a ram of 800 lb. weight falling from a height of 5 ft. The best materials for bearing piles are beech and elm; fir and pine are, how- ever, more frequently used. The size varies from 9 to 18 in. square, according to the length; baulks of timber 12 to 13 in. square are most commonly used for large works. The heads of piles should be bound with wrought-iron hoops to prevent them from splitting under the force of the ram. The points should be shod with iron to preserve them from being broken by contact with stones or other hard substances. The monkey, or ram, used varies in weight from 5 to 20 cwt., according to the size of the pile and resistance of the ground. A light ram with a high fall is best for clay soils, and a heavy ram with a low fall for sandy soils. A steam hammer which gives rapid blows with a low fall is best for quicksands. The nearest distance apart at which piles can be driven with ease in clay soil is. 2 ft. from centre to centre. 1000 lb. per square inch, in any case, is the maximum load that should be im- posed on a soft wood pile, such as fir or pine. When piles are surrounded by soft ground, precaution should be taken against lateral yielding. This is best done by scooping out the ground between the heads of the piles for some feet in depth, and filling the space up with concrete. Sheeting Piles are usually made of deals or battens 9 to 12 in. wide and 3 to 6 in. thick. They are driven between guide piles and wallings, and are used to enclose the space around a foundation on a yielding soil, or to form a cofferdam. The lower end of the piles are bevelled and shod with iron. The bevelling is to cause the pile in driving to move towards the adjoining one, and so assist in making a water-tight joint. Mayor-Sanders Formulæ W¹ H W = ********* 8 HI W = Weight in tons pile will bear. W1 = Weight in tons of ram. H = Fall of ram in inches at last stroke. H1 = Distance in inches pile moves at last stroke. LIMES, MORTAR, AND CEMENTS. (Mechanical Engineer.) Lias Lime, a lime of a pale grey colour, procured chiefly from the blue lias beds in various parts of England, and manufactured at Rugby, Barrow-on-Soar, Halkin Mountain, Aberthaw and Penarth, Keynsham and Lime Regis. This lime has hydraulic properties, i.e., it will set under water. It is, therefore, in great use in damp situations, and for foundations. It sets in from four to ten days, according to the degree of its hydraulicity. In slaking it increases in bulk 50 per cent. The lime should be slaked only while actually being made into mortar. The mortar should be used immediately, and no more made than will be required in the ensuing few hours. Lias lime usually comes into the market in a finely-ground condition, contained in bags, eleven of which equal a ton in weight, each bag- holding about two bushels. Grey Lime, sometimes called stone lime, or "ground Dorking," is the next most important lime used. It is obtained chiefly in the South of England, from the lower or grey chalk beds at Dorking, Merstham, Lewes, Halling, Petersfield, and other places. The lime is of a light buff colour. It has hydraulic properties of only a feeble character, but is well adapted for ordinary building work above ground. It increases in bulk 75 per cent. in slaking, and sets hard in about a month. Chalk Lime is very extensively used, but is only well adapted for plastering, and for internal work. It is a pure or "fat" lime, and being non-hydraulic, will not set under water, and should never be used for foundations, or in thick masses 690 SECTION VII.-POWER STATION. がぶよ ​of masonry. It is burned from chalk, the oolites, mountain limestone, and from sea shells. It slakes violently, expanding to twice its original bulk, and falling into a perfectly white powder. The thoroughness with which it slakes makes it especially valuable for plastering, on account of the consequent absence of "blower" lumps. Lime, according to Hurst, may also be classed as follows: 1. Rich or Fat Lime.-Obtained chiefly from the mountain limestone, or the pure white (upper) chalk. This lime will not set in damp situations, and is adapted only for plasterers' and other work in the interior of buildings. Mountain limestone when burned into quicklime loses weight (about ) and bulk; it swells again when slaked, so that 1 cubic foot of the original stone (measured solid) becomes 3 cubic feet of slaked lime in powder, and requires for slaking a quantity of water equal to about the weight of the quicklime, and to reduce it to "putty" a further quantity, equal to # of the weight of the quicklime. Chalk lime does not incréase more than about two or two-and-a-half times the bulk of the original stone, the ratio of increase varying with the weight of the stone before burning. 2. Lime slightly hydraulic.-Obtained in England chiefly from the lower or grey chalk, as at Merstham, Dorking, Lewes, and Halling. This was formerly called "stone lime." It will not set, nor even harden, under water until after a great length of time, but for ordinary building in the open air it is well adapted. It increases in bulk after burning and slaking from 1 cubic foot of the solid chalk to 14 of a cubic foot of lime in powder; it requires water to slake it to the extent of about 3 of the weight of the quicklime. } 3. Hydraulic lime.-In England this is obtained from the beds of the blue lias limestone, chiefly situated at Lyme Regis in Dorsetshire, Keynsham in Somerset- shire, Shipston and Rugby in Warwickshire, Barrow-on-Soar in Leicestershire, Aberthaw in Glamorganshire, the Halkin Mountain in Flintshire; besides other places in Lincolnshire and Yorkshire. It was found by experiment that 14 ton of the "Halkin" limestone made 1 ton of lime as burned and drawn fresh from the kiln, which equalled by measure 16 bushels, and when slaked into powder it yielded 24 bushels. Sand to be used for mortar should be perfectly clean. If dirty, it may be washed by stirring in a stream of water, allowed to pass through the vessel con- taining it. It is usual to specify pit sand for building work, but river sand is almost as good, and for plastering, better. Sea sand should not be used unless first thoroughly washed, or the salt will cause weak setting, and also subsequent dampness. Crushed sandstone, brick, clinker, or hard coal cinders, make good substitutes for sand if sifted clear of dust. In some districts clayey subsoil is used as a sub- stitute for sand in fat lime, the clay imparting hydraulic properties to the mixture. The following proportions are used in mixing ordinary mortar :- Lias lime and sand Grey lime 1 to 3 1 2 Chalk lime 1 2 .. "" "" "" "" A load of mortar requires 1 yard of sand and 9 bushels of grey lump lime, or 6 bushels of ground lias lime. ·· Portland Cement. Portland cement is made from artificial mixtures of clay and chalk burnt and ground to powder. Natural lime-stone containing the requisite proportions of these ingredients is, however, found and used in some localities. The cement derives its name from its similarity, when set, in both hardness and colour, to Portland stone. There are large manufactories along the Thames and Medway, and "London" cement has a world-wide reputation. A good sample of fresh cement has a colour that is grey, but with a greenish tinge. If brown, it is old, or contains too much clay, and will be found weak. Strength depends upon and increases with (1) weight, (2) fineness of grinding. Neither must be sacrificed at the expense of the other. Usual limits for these are: Weight, 110 lb. to 120 lb. per bushel; fineness, to pass through a sieve of 900 to 1500 meshes per square inch. The cement is sold in bags by the "cental” of 100 lb. Use this cement wherever great strength is required, as in pillars, in founda- tions subjected to great pressure, and especially in damp situations, or in work under water. For these purposes use three of sharp sand to one of cement. For plastering, the cement will carry nine parts of sand. Trowelled surfaces to plaster are apt to BUILDINGS AND MISCELLANEOUS. 691 blister; finish with a "gritted" surface from the hand float. Always mix in small quantities. Roman Cement. Roman cement, made from natural stone nodules found in the London clay, is valuable on account of its quick-setting properties, usually becoming hard in 15 minutes. It is much used for tidal work. The "labour" on it is found practically to be much less than on Portland cement, probably on account of the rapid manipulation necessary in working it up. Roman cement should not be stored for long periods. It is sold by the bushel at about three-fourths the price of Portland cement; 1 of sand to 1 of cement is usual practice. Strength of Lime and Cement Mortar. (Engineering.) Tests made at the University of Illinois on the effects of adding cement to lime mortar. In all the tests a good quality of ordinary fat lime was used, slaked for two days in an earthenware jar, adding two parts by weight of water to one of lime, the loss by evaporation being made up by fresh additions of water. The cements used were a German Portland, Black Diamond (Louisville), and Rosendale. As regards fineness of grinding, 85 per cent. of the Portland passed through a No. 100 sieve, as did 72 per cent. of the Rosendale. A fairly sharp sand, tho- roughly washed and dried, passing through a No. 18 sieve and caught on a No. 30, was used. The mortar in all cases consisted of two volumes of sand to one of lime paste. Plaster-of-Paris. The basis of most plasters and plaster-cements is produced by calcining 'Gypsum," a hydrated sulphite of lime which is found and quarried in Derbyshire, Nottinghamshire, Cheshire, and Westmoreland, and in great abundance in the neighbourhood of Paris. It sets in a few minutes, but does not attain hardness sufficient to fit it for external use. It is employed for making ceiling ornaments, and for "making good" defects in old work, cracks, &c. "" The lime used in plastering is chiefly that described as "fat lime." This lime, when mixed with once or twice its bulk of pit or fresh-water sand, forms the "coarse stuff" used for the undercoats of plastering, with the addition, when used for good work, of 1 lb. of well-beaten hair to every 2 cubic feet of coarse stuff, and for ordinary work 1 lb. of hair to 3 cubic feet of coarse stuff. The "fine stuff" used for the setting coat of plastering is merely the pure lime slaked, and afterwards saturated with water, which is allowed to evaporate until the lime attains the required consistency. BUILDINGS AND MISCELLANEOUS. 697 Gauged stuff," called "putty and plaster," contains from 3 to 4 parts of plasterer's putty and 1 part of plaster-of-Paris, which makes it set quickly. For cornices, equal parts of putty and plaster are used. Other materials are also occasionally used, such as plaster-of-Paris, Keene's: cement, Parian cement, Martin's cement, &c. They are, however, more frequently used for mouldings, owing to the rapidity with which they set, and the hardness. they attain. Iron roofs having a slope of 2 to 1, and trusses about 15 ft. apart, will approxi- mate in weight as follows, per square foot of building area: 8 lb. Weight of material in frame, including truss and purlins, but not covering: Truss of 75 ft. to 100 ft. span, 8 lb. to 10 lb. per square foot. 50 ft. 75 ft. under 50 ft. To this must be added the following weights of covering material per square: foot of building area: "" "" "" 7 lb. 5 lb. 7 lb. "" "" "" Tin on 1 in. boards 4.5 lb. • 5.7 Corrugated sheets, on 1 in. boards.. Slate in. thick, on 14 in. 15 & in. 1 in. "" Felt and gravel If plastered below rafters, add 11.0 7.5 9-11 10 .. In roofs with inclinations of 45 deg. or over, the snow load can be neglected if no obstructions are attached. On slate roofs with a slope of 2 horizontal to 1 vertical, the snow will not accumulate to any material thickness. Total Span. ft. 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 Total Weight of a Truss. lb. 129 202 290 396 516 654 807 976 1160 1363 1584 1815 2064 2331 2616 2912 ·· ROOFS. (Pencoyd.) lb. 6.46 8.08 9.67 11.3 12.9 14.5 16.1 17.8 19.4 21.0 22.6 24.2 25.8 27.5 29.1 30.7 Weight Weight per Square per Foot Foot of Ground of Span. Covered. "" "" lb. .92 1.15 1.38 1.61 1.84 2.07 2.30 2.33 2.76 2.99 3.22 2.45 3.68 3.91 4.14 4.37 • • .. دو Table 11.-Approximate Weights of Roof-trusses of the Fink System. Total Span. .. (Trautwine.) Rise span. Trusses 7 ft. apart. Load 40 lb. per square foot of roof, including truss. ft. 100 105 110 115 120 125 130 135 140 145 150 155 160 165 170 175 •• • •• "" "" Total Weight of a Truss. lb. 3228 3557 3904 4267 4640 5041 5452 5880 6336 6782 7260 7750 8256 8782 9324 9879 • • • ·· 99. "7 "" lb. 32.3 33.9 35.5 37.1 38.7 40.4 42.0 43.6 45.2 46.8 48.4 50.0 51.6 53.3 54.9 56.5 "" "" Weight Weight per Square Foot of per foot of Span. Ground Covered. lb. 4.60 4.83 5.06 5.29. 5.52. 5.75. 5.98 6.21 6.44 6.67 6.90 7.13. 7.36. 7.59 7.82 8.05 P & B Ruberoid Roofing. (FIGS. 8 to 10, page 698.) P & B Ruberoid Roofing has in actual use demonstrated its value as a covering for buildings. It is not made from paper, but has a foundation of the best wool felt. This felt is saturated with a soft solution of P & B water and acid-proof 698 SECTION VII.-POWER STATION. compound. Before finishing, a harder coating of similar composition is applied, protecting the interior and making it impossible for it to dry out. Ruberoid is pliable, light in weight, and does not run with heat. It is airtight and vermin proof, and acid and alkali proof. The sheathing boards should be of uniform thickness, to secure a level surface. Sweep the boards clean before laying the roofing. Unroll the material and cut it the required length. Lap the courses 2 in., and apply the cement between laps. Drive nails 2 in. from centres at seams only, using the tin caps furnished. When this is done, cover nail-heads and caps with 8 464 9 10 Figs. 8 to 10. Ruberoid Roofing. ☺☺☺☺☺☺... 2000...cen the cement, which will effectually prevent corrosion. The cement is ready for use, and does not require heating. Where there are no coping walls, the roofing should be turned over at the -edges, nailing a wooden strip or moulding over the edge. Give the strips a coat of cement. Care should be taken that nails are uniformly driven, and not too near the edges. Use the barbed nails which are furnished with the material, and be careful not to leave any of them on the roof to be stepped on. If there are copings, walls or chimneys, run the roofing to the angle (Fig. 9), nail edges carefully, and finish with a separate strip, lapping on the roof and on the wall; or if preferred, the roofing which runs up on wall or coping may be firmly nailed with a wooden strip, first coating this strip with cement to make BUILDINGS AND MISCELLANEOUS. 699 **** Jamm a waterproof joint. Roofing around chimneys and upright surfaces must be closely fitted, and the angles cemented before finishing with the strips, as above mentioned. If the roof is steep, a ladder fastened to the top will give a firm footing. When necessary to lay the roofing in very cold weather, let it be kept in a warm room for a few hours before application. To secure the best results, it is not advisable to lay any roof on an extremely cold day. If desired, mouldings or battens may be used at the seams in place of the tin caps, which will give the roofing a handsomer appearance, and will make it less liable to leak through defective laying. If tin or metal-flashing connections are used, see that they are all cemented and nailed. This applies also to leaders, ventilators, pipes, chimneys, &c. Where gutters are lined, use a separate strip of roofing, Fig. 10, with a coat of cement under and above the seams on both sides. The roofing should be laid with the pitch of the roof. Paint of any colour may be applied to the roofing. As manufactured, it is slate colour. Ruberoid roofing does not require to be coated when laid, but an examination of the roof should be made after it has been down eighteen months or two years, when any defects in the seam or elsewhere should be put in order, and the entire surface coated with P and B ruberine paint. If this done every four or five years, the roof will be kept in good condition, and will last for a very long time. There are four types of Ruberoid roofing, half, one, two, and three-ply. The roofing is 36 in. wide, and is put up in rolls containing two squares each. Roof Coverings. Roofs covered with slates or shingles should have a pitch of not less than one- fourth the width of (span; but the roof may be truncated if a lower pitch is required. Table to Facilitate the Calculation of the Area of any Roof. Proportion. Rise or Pitch. One-sixth of span.. One-quarter of span One-third of span…. One-half of span Two-thirds of span Three-quarters of span Equilateral.. Whole pitch ·· ·· ·· : .. : : : : : Angle. deg. min. 18 25 26 35 30 00 33 • 42 45 00 53 00 56 20 60 00 63 30 1 to 1.05 or 1 to 1 1 1.12 1 1급 ​"" 1 1 1 1 1 1 1 "" "" "" "" ,, "" "" "" "" 1.20 1 "" 1.20 1 "" 1.41 1 "" "" "" "" "" "" "" 1.67 1 1.80 1 2.00 1 2.83 1 2층 ​"" "" "" "" 11 "" 11 13 17% 1층 ​2 Multiply span by the number found in the proportion column; this gives the superficial area of the roof on the slope. Load on roof may be taken as 50 lb. per foot superficial; this includes weight of roof, and provides for extra strains thrown on it by snow, wind, &c., from 5 to 6 tons safe load per inch of section of ties. Slates should not be laid at less than 264 deg. with horizontal. 700 SECTION VII.-POWER STATION. Table 12.-Average Sizes of Slates and the Proportions used in Roofing. Name of Slate. Size. Gauge. in. 12 x 8 13 x 6 14 x 12 16 x 8 20 × 10 Vicountesses 18 x 10 Countesse.. Marchionesses Duchesses 22 × 12 24 x 12 Doubles Ladies Imperial Rags.. Queens Princesses Duchesses .. "" "" "" "" .. Description. ·· 99 Marchionesses Countesses.. Viscountesses " ·· Ladies, wide large 99 "" small Plantations Doubles .. 14 GT 60 < LA C 30 X 24 36 x 24 36 x 24 2 3 4 5 6 ·· ·· • .. ·· ·· ·· .. Weight in Pounds per Foot Superficial. in. SH LO 4/ 5 6 7 9! 101 13A 16 16 NOTE.-The sizes of slates of the same name vary in different localities. The dimensions should always be quoted where the size is important. The Table includes for waste. Table 13.-Weight per Thousand (1200.) Size. in. 24 X 14 24 X 12 22 x 12 20 x 10 18 x 10 18 x 9 16 x 10 16 x 8 15 x 8 14 x 12 14 X 8 13 × 10 13 × 6 12 x 8 Number of Squares Covered by 1200. 2.85 2.38 5.26 4.14 5 C4 6.74 9.09 10.00 covered by 1 ton. 2.5 2.2 2.5 0.017 0.034 0.051 0.068 0.085 0.101 Penrhyn or Bangor. Second. First Quality. Quality. cwt. 75 59 54 39 35 33 30 24 25 31.5 21 23.5 15 17 Number required to cover 1 square. cwt. 84 80 39 b2 46 43 41 32 33 42 25 29.5 19 21 420 504 228 290 202 178 132 120 7 8 9 10 48 40 40 11 12 Nails required per Squares. Iron Number. 840 1008 456 580 404 356 264 240 | 31 21 25 cwt. 65.5 57 52.5 38 33 28.5 28.5 22.5 8888 96 80 First Quality. 80 Copper lb. 5 2 Port Madoc. 1929 morskemmel 11 *~46 1 1 1 1888888111 Lead. Lead is usually described according to the weight of a superficial foot in pounds. The thicknesses corresponding to given weight will be found in the following Table. Table 14.—Thickness of Lead. Second Quality. cwt. 76 66.5 62 47.5 43 38 36 27.5 Thickness in Weight in Pounds per Thickness in Inches. Foot Superficial. Inches. 38 23.5 0.118 0.135 0.152 0.169 0.186 J.203 BUILDINGS AND MISCELLANEOUS. 701 The weights quoted are as follows: "" Roofs, flats and main gutters Hips, ridges, and small gutters Flashings Cisterns and sinks, bottom sides "" 2-in. deal boarding 1-in. Common rafters and purlins for wood truss iron "" "" "" "" Asphalted felt "" 7 6 "" Soil pipes 8 "" Gutters and flats should have a fall of at least 1 in. in 10 ft. The lead in gutters at the backs of parapets and chimneys should turn un against the wall from 5 in. to 8 in., and be covered with a flashing or about the same width. 66 apron" of Table 15.-Weight of Various Roofings. (Hurst.) ·· 11-in. "" Battens 3 × 3-laid {3}gauge "" 10 ·· ** Zinc, laid with rolls, 12 gauge 14 .. "" >> .. 7-in. gauge 6-in. ·· "" ·· 99 ·· ·· •• • • : .. • ·· "" · .. ·· ·· • • : • 4 : .. .. : : .. ·· ·· 7 lb. lead. 6 5 • 33 "" ·· "" "" : .. ·· ·· .. ·· 16 "" "" Lead and copper according to weight per foot, adding one-tenth for seams and laps. Rolls to be taken in addition when used. Corrugated iron, galvanised, 20 S. W. Gauge, with 5 in. corruga- tions (measured over all) Ditto, 18 ditto, ditto Slates, 3-in. lap, all sizes, except Duchesses, Rags, or Queens, including nails (but not battens) Duchesses ·· .. .. ·· "" Ceiling, including joists, 10 ft. bearing, and lath and plaster Wind, allow for vertical effect on roof, Ditto, ditto pitch pitch.. 1/3/2018 "" "" ·· Snow, according to climate "" ·· · "" Rags and Queens Tiles, plain, 104-in. × 6-in. × 4-in., including mortar for pointing, 8-in. gauge "" "9 •• : ·· : ·· .. ·· · "" Tiles, pan, pointed with mortar, average, including absorbed rain Thatch of straw ·· .. ·· .. .. •• ·· Pounds per Foot Superficial. 7 6 2 3.4 4.25 1.43 1.32 1.11 0.5 1.5 1.7 1.9 2.00 2.60 8.5 9.0 12.0 16.0 18.5 21.0 11.0 7.0 12.0 20.0 23.0 25.0 3 to 10.0 Roof Drainage. Rain-water or down pipes should have a bore or internal area of at least one square inch for every 60 superficial feet of roof surface in temperate climates, and about 35 ft. superficial in tropical climates. They should be placed not more than 20 ft. apart, and have gutters not to be less in width than twice the diameter of ȧown pipe. ; 702 SECTION VII.—POWER STATION. Seasoned Wood. Soft Woods. Dantzic Red Riga Memel Spruce Pitch Pine 99 ** American Red Beech Jarrah 49 Hard Woods. Oak (English) Ash " Elm " Teak.. Do. Yellow Pine] ** Greenheart.. .. : Lignu.a Vitæ : Mahogany (8pan.) Tenacity, Weight per Lengthwise of Cubic Grain, per Foot (Dry). Square Inch. 34 to 37 34 49 29 32 41 58 43 lb. 58 = ** ::: " 36 + • 34 82 53 37 53 63 2 72 52 Table 16.-Weight, Strength, &c., of Various Woods. (W. H. Fowler) 83 tons. 1.4 to 4.5 1.8 5.5 90 4.2 4.9 " 1.3 4.5 2.1 4.4 ** ". 1.2 6.0 0.9 " 3.4 8.8 1.8 7.6 2.4 6.3 ::: " • 1.8 7.6 3.9 4.1 1.47 6.7 ** 1.3 > 4.3 5.3 .2 Modulus of Rupture. lb. 7,100 9,900 to 12,300 14,088 " 19 10,000 13,600 12,000, 14,009 6,000 9,700 13,806 9,450 "1 12,000,, 14,000 12 10,290 8,45-1 10,800 16,500 27,500 12,000 19,000 .... 9,600 Modulus of Elasticity. lb. 870,000 to 3,000,000 1,252,000 2,000,000 39 ❞ 2,350,000 " 1,460,000 1,252,000 * 8,000,000 1,460,000,, 1,800,000 1,600,000,, 2,480,000 2,300,000 .. " " Resistance to Crushing in Direction of Fibres. | 1,200,000,, 1,750,000 2.9 to 4.5 1,525,000 2,290,000 3.8 4.2 700,000 1,340,000 2.6 4.6 .... tons per square inch. 3.1 3.C 3.0 1,040,000 2.9 3.0 2.1 1.8 1,525,500, 2,290,000 3.4, 4.2 .. 1,187,000 3.2 1,700,000 5.8 6.8 2,167,000 2,414,000 2.3 5.4 " 13 ** 3.1 4.5 Comparative Stiffness and Strength. Oak=100* stiff- ness. 130 73 3 72 2 132 139 100 89 78 77 67 93 126 32. : ·· stren. 108 82 82 86 82 81 66 100 119 32 103 85 165 109 111 Current Price per C. Ft. : ·· : : Remarks Liable to large dead knots, cup shakes and sapwoood, but very durable. Straight growth, free from sapwood and knots. Smaller logs, but most suitable for ordinary carpentry, works easily, strong. Used for cheap joinery, panels, &c., ends shaky. Strong, but brittle; useful for heavy works and ornament. Should always be exposed to air. Very like Memel, does not warp, for internal work. Soft uniform grain, great lengths and widths (up to 3 ft.); principal wood for patterns. Use in wet situations, for piles, pumps, pulley-blocks, cogs, turn. ery, &c. Warps. Close texture, fine surface, used for tools, thin boards, &c.; subject to rot, corrodes iron. For floors full of defects, very weak in tension, brittle. Strongest in crushing, used for piles, &c., hard, liable to splinter. Teak resists worms, does not cor- rode rou, used for floors, furni ture, &c., ornamental Free from defects, ornamental, use- ful for delicate work, and for best patterns. For bearings and turnery. i 1 1 3 3 BUILDINGS AND MISCELLANEOUS. 703 S. W. Gauge. 222222 16 18 20 24 26 Table 16.-Corrugated Iron Roofing. Size of Sheets. ft. 6 x 2 to 8 x 3 6 × 2 6 x 2 6 x 2 6 x 2 6 × 2 "" **** "" "" ft. 7 8 x 3 8 x 3 0 ∞ ∞ QINN -k--a 7 X Weight per Number of Superficial Square as Laid. Feet per Ton Before Laying. lb. 363 274 203 162 140 112 3 lb. of rivets are required for each square (100 superficial feet) of roofing. If the sheets are galvanised, add part to the weight in the Table. .. Floors of office building, not less than COLUMNS, POSTS, AND FLOORS. The strength of all columns and posts should be computed according to Gordon's formulæ, and the crushing weights in pounds, to the square inch of section, for the following named materials, should be taken as the co-efficients in said formulæ, namely Cast iron, 80,000; wrought or rolled iron, 40,000; rolled steel, 48,000; white pine and spruce, 5000; pitch or Georgia pine, 5000; American oak, 6000. The breaking strength of wooden beams and girders should be computed according to the formulæ in which the constants for transverse strains for central load shall be as follows, namely: Hemlock, 400; white pine, 450; spruce, 450; pitch or Georgia pine, 550; American oak, 550; and for wooden beams and girders carrying a uniformly distributed load the constants will be doubled. The factors of safety should be as one to four for all beams, girders, and other pieces subject to a trans- verse strain; as one to four for all posts, columns, and other vertical supports when of wrought iron or rolled steel; as one to five for other materials, subject to a compressive strain; as one to six for tie rods, tie beams, and other pieces subject to a tensile strain. Good, solid, natural earth should be deemed to safely sustain a load of 4 tons to the superficial foot, or as otherwise determined by the superintendent of buildings, and the width of footing courses should be at least sufficient to meet this requirement. In computing the width of walls, a cubic foot of brickwork should be deemed to weigh 115 lb. Sandstone, white marble, granite, and other kinds of building stone should be deemed to weigh 160 lb. per cubic foot. The safe bearing load to apply to good brickwork to be taken at 8 tons per superficial foot when good lime mortar is used, 11 tons per superficial foot when good lime and cement mortar mixed is used, and 15 tons per superficial foot when good cement mortar is used. 746 957 1355 1538 1866 2354 Strength of Floors, Roofs, and Supports. (Kent.) Floors of dwelling, tenement, apartment house or hotel, not less than Floors Calculated to bear Safely per Square Foot in Addition to their own Weight. ·· 70 lb. 100 public assembly building, not less than "" "" store, factory, warehouse, &c., not less than Roofs of all buildings, not less than.. 50 "" Every floor should be of sufficient strength to bear safely the weight to be im- posed thereon, in addition to the weight of the materials of which the floor is composed. 99 120 150 "" Maximum Load on Floors. (Engineering News.) Maximum load per square foot of floor surface due to the weight of a dense crowd. Considerable variation is apparent in the figures given by many authorities, as the following shows : 704 SECTION VII.-POWER STATION, French practice, quoted by Trautwine and Stoney Mr. Page, London, quoted by Trautwine Maximum load on American highway bridges according to Waddell's general specifications Mr. Nash, architect of Buckihgham Palace Experiments by Prof. W. N. Kernot, at Melbourne Experiments by Mr. B. B. Stoney • The highest results were obtained by crowding a number of persons previously weighed into a small room, the men being tightly packed so as to resemble such a crowd as frequently occurs on the stairways and platforms of a theatre or other public building. .. Weight of Crowd, Pounds per Square Foot. 41 70 81 PAINTS. (W. H. Fowler.) Paint consists of a base, a vehicle, a solvent, and a drier. Base.-Whitelead is the base almost invariable used. -46 100 120 126 143.1 147.4 Vehicle.-Linseed oil, being cheap and effective for its purpose-namely, to form a thin protecting skin, impregnated with a durable metallic base-is the vehicle commonly employed. To prevent blistering of this skin in external work, "boiled linseed" oil is used. Solvent.-Turps, the usual solvent, causes the paint to work freer, and thus to form a thinner skin, and to cover more ground. Driers, by absorption of oxygen, causes the skin to solidify quickly, and also to thicken somewhat. Painting, if well done, will last seven years; if inferior materials are used, or the work improperly executed, it will need renewing in three years. Internal woodwork lasts longest when unpainted. For Metals, an ideal paint would be one whose base would to a partial extent combine chemically with the particles of the surface treated. This property is claimed for certain "oxide of iron" paints when applied to slightly rusty surfaces of iron. Grease, and, as far as possible, all old paint, should be carefully removed from iron before repainting. Woodwork should be "" stopped" with putty, knotted with varnish or knotting," and sandpapered before painting. 1 SECTION VIII. STORAGE BATTERIES. ᎪᎪ • SECTION VIII. STORAGE BATTERIES. Lead Cells. General Theory. Electromotive Force.-The chief reactions which take place in the lead cell are expressed by the fundamental equation (Dolezalek) :— PbO2 + Pb + 2 H2SO4 2 PbSO4 + H2O. For the charge, the equation is to be read from right to left; for the discharge, from left to right. The potential difference of a secondary cell can be calculated from thermo- dynamical data (Helmholtz-Kelvin). It increases with the density of the sulphuric acid, first rapidly, then for densities between 1.05 and 1.30, slowly almost as a linear function, and this increase can be deduced (Dolezalek) both from the heat generated by diluting the acid and from the vapour tension of the acid (Dieterici, Wiedem. Annal., vol. 50, 1893). In very diluted acid the electromotive force diminishes rapidly. Any addition to the sulphuric acid which lowers its vapour tension without increasing the conductivity of the acid should raise the poten- tial difference. But an otherwise indifferent substance which would not be destroyed in a storage cell is not easily found. Too concentrated acid attacks the lead plate; amalgamated lead resists longer, but amalgamation-often proposed- has only temporary effects. Increased acid concentration raises the potential difference at both electrodes. The potential difference grows further with rising temperature; or, in other words, the temperature co-efficient of the electromotive force is, on the whole, positive; for very dilute acid it is negative (Dolezalek). While from this point of view, at the ordinary acid density of 1.2-densities are often expressed in thousandths, 1200-a storage cell should become heated during the charge, and cooled during discharge; the opposite would hold when the acid density sinks below 1.044, and at this density the accumulator should neither heat nor cool while working. Two accumutators filled with very dilute acid should hence give an efficient thermo-couple. The internal resistance of accumulators should not exceed a few hundredths of an ohm. Its exact determination is difficult. In determining the electromotive force of a cell, instruments of high resistance have to be applied, as currents of appreciable intensity would at once affect the data. A perfect method for determining the constants of a secondary cell while current is flowing is hardly known. The two electrodes should separately be examined (M. U. Schoop) with the aid of exploring electrodes. The potential difference at the terminals of the cell depends upon the electro- motive force E, and the current J, flowing through the cell of internal resistance R. During the charge we have P=E+J R, and during discharge P-E-J R. Keeping the current constant, we get (Figs. 1 and 2) during the charge a pressure curve which rises from about 2 volts-which corresponds to the acid density of 1.15-very rapidly to about 2.1 volts, and then slowly up to 2.6 or 2.7 volts, when abundant gassing will have set in, and the charging is stopped. If the cell is now left to itself, the pressure will fall again, rapidly at first, to the 2 volts. When the cell is discharged, the potential difference sinks, very slowly at first, down to about 1.8 volts, and then rapidly down to zero. With cells with pasted plates the curves are, as a rule, regular, and do not show any abrupt inflexions and drops, except at the ends. With Planté plates, curves may be less smooth. The higher the current densities, the steeper the curves, and the greater the area enclosed between the charge and discharge curves. This area is a measure of the loss of energy, amounting on average perhaps to 25 per cent., which we have to put up with in storage cells. The loss is directly connected with the fall of potential, but not primarily due to the J R. If the diffusion of the acid out of and into the pores of the electrodes could keep pace with the electrolytic effects, the curves would be smoother. 708 SECTION VIII. Recovery, Self-Discharge, Impurities.-A cell recovers when the discharge is interrupted, and reattains the potential difference corresponding to the acid density within a few minutes. Left to itself for longer periods the cell runs down, however, especially in the presence of impurities more electronegative than the lead plate, which is particularly liable to self-discharge. In the accumulator acid, 2-6 2-5- 2-4 23 2.2 2-1 2-04 Volts 1290 O (1100) 1250- 1210- 1170 1150 1170 Specific Gravity of Electrolyte 24- 23- 22- 21- 2 1.9 1-8- 1.7 mos (1101) 1 ernal Res Specific Gravity 12 11 Fig. 1. Charge. Small "Progress" Cell. 2 Current 80 Amps 11 EMF W.014 1280 Current 20 Amps. 3 Hours 2Hours Fig. 2. Discharge. Fulmen Cell; Type B 25. W⋅01 W.001 4 Int.Res EMF 015 -01 005 lead is, in accordance with Nernst's theory, positive also to nickel, cobalt, and iron, and precipitates their salts. Traces of platinum (from the acid concentration or from experiments) are most dangerous; copper wire should not be filed above a cell lest the filings cause local action. Drops of lead would produce short circuits, and form a local couple with the peroxide plate. The local action between the peroxide and its lead grid is generally unimportant, but may become very destruc- tive if new plates have not been very thoroughly washed of acid or chemicals after STORAGE BATTERIES. 709 formation, so that the grids of the dry plates become incrusted with lead sulphate. According to Jumau, the antimony of the grid is itself injurious. Up to 5 per cent. of antimony is added to lead to make it harder and better to cast. Iron and manganese (traces of which are found in litharge) act as oxygen-carriers, and are, therefore, injurious (Jumau and v. Knorre; Žschr. f. Electrochem., 1897). Yet manganese salts are still proposed as additions to active materials; a pinkish colour of the acid indicates manganese. Arsenic is also bad. According to Haber (Zschr. f. Electrochem., 1903), 20 milligrammes of chlorine per litre of acid may be tolerated. R. W. Vicarey (Faraday Soc., 1905) warns against ammonia and nitrogen compounds. Sulphating-A discharged plate left to itself for some time becomes speckled with crystals of lead sulphate, and assumes a white colour; the resistance increases very much. This sulphate does not represent a special modification of the sulphate which normally forms during discharge. But once crystalised from solutions, especially from warm, strong acid which is a fair solvent for PbSO4, it is not easily re-dissolved or changed. Sulphuric acid of 13 or 14 per cent. of H2SO4, and of density 1.1 or 1.11 dissolves least sulphate. Capacity and Output.-Theoretically a storage cell should give one ampere for one hour-at a very low current-rate-for every 3.86 grammes of lead and 4.45 grammes of peroxide. In practice, nothing like that is ever attained, because it is impossible to discharge a battery completely, and in most cases useless and inad- visable to push the discharge beyond the point when the electromotive force has gone down to 1.8 or 1.17 volt. Hence the capacity or output is stated for special conditions of discharge; and it is generally understood that the potential difference is not to drop below 1.8 volt, or by more than 10 per cent. of its mean value.__ The output decreases when the battery is discharged at higher current rates. Every type of cell has, in this respect, its own properties. In Peukert's formula Jn t = constant, where J is the current density and t the time, the value of n ranges for various batteries between 1.36 and 1.72. If the capacities of the two electrodes are unequal, the capacity of the cell is that of the inferior plate. The output rises with higher temperature by 2 or 3 per cent. per deg. Cent. (Heim); to heat the batteries would, however, be both inconvenient and risky. External pressure also increases the capacity, because it keeps gassing down, but not to any practical extent. Efficiency. The ampere-hour efficiency is the ratio: ampere hours put in during charge to ampere hours re-obtained during discharge; it may exceed 96 per cent., the few per cent. lost being due to heat and gas-generation, &c. Of greater practical interest is the watt-hours efficiency, represented graphically by the ratio of the two areas bordered respectively by the charge and the discharge-curves and the co-ordinates. With normal discharges, the watt-hour efficiency may exceed 87 per cent.; more generally it lies between 70 and 80 per cent. The great difference between the two efficiencies is mainly due to the fall of potential. The ordinary efficiency deduced from normal discharges and recharges, need not tell us what the efficiency may be in traction work when the cells are equalising the load on the generators. In that case we have charges and discharges-sometimes for a few seconds only-in rapid alternation, and the efficiency does not come out badly under these circumstances. Highfield (Inst. E. E., vol. 30) estimated the effi- ciency of a central station lighting battery from one year's records at 74 per cent., and that of a traction battery at 84 per cent. Experimenting on Tudor and Chloride cells, B. Hopkinson (Electrician, vol. 48) found that the efficiency of the cell increased as the length of the cycle-charge and discharge periods decreased from ten minutes down to a few seconds, and he realised a maximum efficiency of 92 per cent. Hence the advantages of automatic boosting. Formation.-1. In Planté formation, smooth lead plates are electrolytically converted, in weak sulphuric acid of density 1.05 to 1.15, into peroxide and spongy lead respectively. Various sulphates, chlorides, &c., are added to the acid; nitrates are apt to corrode the plates, and all inorganic substances must carefully be removed afterwards; hence organic acids and reducing agents which are destroyed during formation deserve preference. 2. In Faure formation, a paste is made of lead oxide (monoxide PbO, known as litharge or massicot, according to mode of preparation, and minium Pb30+ (?) ), sulphuric acid, or sulphates, various salts, &c., some carbon or indifferent salt (afterwards to be dissolved out again) being added to increase the porosity of the material. The paste is smeared on the supports or grids, or worked into them; the addition of cements, gums, rosins, glycerine, cellulose, pitch, pumice stone, &c., ་ 710 SECTION VIII. is not to be recommended. The electrolytic formation is effected in sulphates (alkalies, magnesium) which form soluble double salts with the lead sulphate, rather than in sulphuric acid. Pure Planté formation, without any additions, is hardly practised now, and only positives are now made after Planté. The Manufacture of Accumulators in the United Kingdom is subject to the Regulations for Accumulator Works, a draft of which was issued by the Home Office in August, 1903, and which came into force on January 1, 1904. High porosity, conductivity, and coherence, large actual contact between the material and its support, and mechanical strength are essential for a good electrode. Although only plates of simple strong construction have survived, the most compli- cated types are still patented. Very high surface-developments are obtained by finely laminating the plates. This is done by various means: simply by casting the lead in chills or metal moulds; with the aid of cutting tools applied to the rolled and compressed lead plates; by uniting lead strips, foils, wires or ribbons; by forming textures exclusively of lead or of lead and fibrous materials (Gülcher glass wool). Thin lead ribbons and wires do not last. The plates of the same polarity are "burned" together with the connector bars and leads with the aid of hydrogen flames. In the boxes or containers of glass or of wood, lined with lead, the electrodes stand on lugs for the negatives; while the posi- tives are suspended from glass rods, or rest on ridges in the cell floor (smaller types); more commonly both sets of plates rest with lugs on the cell walls or on special sup- porting glass slabs. There should be ample space-6 in. in large cells at the bottom for any mud to collect without causing short circuits. Plug-holes in the cell bottom are undesirable complications. The electrodes are kept apart by several rows of glass rods, or tubes, going right to the bottom, and held in position by projections on the plates, or by ebonite rods (these are apt to get in the way), or better by per- forated ebonite plates, corrugated and provided with moulded ribs on one or on both sides. It is not necessary to bring the plates very close to one another in order to reduce the resistance. To wrap pasted positives with sheaths of asbestos, celluloid, &c. (protected electrodes), is hardly advisable; the durability of all kinds of celluloid is doubtful. Even asbestos is slowly destroyed in batteries. Separators of impregnated wood, plain or corrugated sheets, have come over from America, but some seem to corrode when in contact with the peroxide. Grids of celluloid and distance-pieces of earthenware are not liked. Both the electrodes proper and the separators must be completely covered by the acid. Treatment of Stationary Batteries.-In traction power stations, reliability, durability under heavy charges and discharges, and long life, are more essential than high capacity. There is, hence, a preference for Planté positives (Planté negatives being too expensive). The cells must be carefully insulated, and the batteries be installed in airy, well-ventilated rooms. An explosion occurred in a new plant in Baku, when charge-tests were made before the fans had been fixed in the windows, the door being closed. Tiers of cells should not be arranged above one another, and to facilitate inspection only cells of one type be put on one floor. In large batteries small immersible glow lamps do good service. The density of the acid (about 1.2) should be taken frequently, with the aid of ordinary hydrometers or gravity beads, at any rate after refilling, as the plates are not all equal. For refilling-"topping up"-only distilled water should be used, and should be poured in through the separator tubes or a funnel tube. Rain and supply water might suit, but it must be remembered that the impurities of the water accumulate in the storage cells. Vicarey condemns rain-water on account of the ammonia and organic matter always contained in it. Impure acid and water are responsible for many battery failures. Water from condensers is bad, on account of iron and oil. The acid must always be previously diluted in special vessels; never pour concentrated acid into a cell. An abnormal density is a symptom of there being something wrong; bringing the acid up to strength is by no means necessarily the right cure. Always keep the battery well charged. The battery is a machine which will remain most healthy when well kept to work. Overcharging is a cure for some evils, and often recommended once a fortnight or every month as a preventative to sulphating. To charge at strictly constant potential-up to 2.5 or 2.6 volts per cell-may not be possible; charging at graduated current intensity, beginning with strong currents, is advisable. A certain amount of gassing is unavoidable, but the cells should begin to gas at fairly the same time. Gassing on open circuit betrays local action. If the negatives run down without gassing, leakage is to be suspected. Sulphating may be cured by overcharging; that soda affords a cure (Barber Starkey) is very doubtful. The regular addition of soda to the electrolyte is certainly to be deprecated. Short-circuiting may be caused by STORAGE BATTERIES. 711 buckling, dropping of material, accumulation of mud, etc. Do not remove dropped material or small growth-lead trees form particularly in diluted acid-with wires; use ebonite or wood. Buckled plates can be straightened between boards. Unless most carefully cleaned of acid, negatives will become hot when taken out of a cell, and will sulphate badly afterwards. Faulty cells should be tested with the galvanometer. When the cell can be cut out, it should be charged up with the others, but cut out during discharge. When not, it may be cured by “milking-up," coupling a booster conveniently run on a truck with a trolley wire, or a cell parallel with it, until the acid turns milky. A day log should be kept of batteries, and charges and discharges, their times and the potential difference taken before charging and just before stopping the charge, and again after beginning and after stopping discharge (Wade). Connecting-up and Regulating--When charging the battery from a shunt dynamo, the engine speed or the series resistance must be so adjusted that the battery cannot be damaged by excessive dynamo currents, nor charge back into the generator. For this purpose, differential switches are used. In coupling-up batteries, four methods are employed :- 1. The battery is placed directly across the bus-bars. As long as the voltage of the mains, of the battery, and of the shunt dynamo keep at the same constant value, the battery will "float" on the mains, neither discharging nor charging. When the potential in the main drops, the battery begins to discharge. But as the battery's own potential goes down as soon as it discharges, the battery cannot take up the whole of the load excess, and the degree to which the battery will respond depends upon the proportion of the charge left in the battery. A regulating device is therefore wanted. Batteries used without special regulation do little good. They have, however, largely been used in this way, and hence a good deal of the distrust with which they are still regarded. 2. Elaborate automatic regulators have been mounted on switchboards to throw in and out cells. Though much perfected later, such devices interfere with the uniformity of the battery, which should be one whole. 3. This objection applies to the use of regulating cells coupled up in opposition to the battery. The electrodes of these regulating cells are simply lead plates, not formed in any way, as they are not to possess capacity. Methods 2 and 3 are now little employed, except in small installations. 4. Regulation by Means of Boosters-In ordinary boosting-up, the charging is effected at intervals when the load is light, for definite periods, the current being regulated with the aid of the shunt coil of a special dynamo booster. The method requires attention, and may strain the batteries, but may be advantageous under circumstances. At Plymouth, two combined sets of engine alternator (for light) and generator (tramways) are coupled on the shaft. The engine can drive only one of the dynamos at full load, or both at reduced load; 260 cells, without regulation cells, are parallel to the generator. When the evening comes the generator is uncoupled, so that the full engine-power is available for lighting, while the battery takes the trams. When, after 11 p.m., the cars stop, the battery will have run down from 520 to 470 volts. A generator is then coupled-up to charge the battery till 2 or 3 a.n., and a booster adds the final volts. The wattmeters used for measuring the charging and discharging currents are connected up automatically According to the way in which the current flows, the north or the south pole of the permanent magnet will be attracted, and the mercury switch, which puts the shunt coil of the charging or of the discharging wattmeter in circuit, will be actuated. With differential reversible boosters (used at Remscheid ir 1892), the number of cells in circuit remains fixed, and the booster is placed in series with the battery, so that the sum or difference of the two electromotive forces equals the pressure across the mains. When the two electromotive forces are of the same direction, the battery will discharge; when the booster opposes the battery, the latter will be charged. The current intensity and the direction of the booster field-current can be changed by hand on the switchboard. If the battery-pressure were constant, a perfect regulation could be obtained in this way. But, as pointed out above, the potential difference of the battery sinks on discharge. In the automatic reversible booster this change in the condition of the battery is automatically controlled without any hand-adjustment in the ratio between the series and shunt coils. The drop in the battery potential is least when the battery is kept nearly charged; and it is, hence, for regulation as well as for other reasons, best to maintain the average voltage high. According to J. S. Highfield, a battery balances best at 2.08 volts. With the aid of reversible boosters the pressure can be maintained within 2.2 and 2.0 volts, instead of the formerly customary 2.0 and 1.8 volts, which means an increased watt hour efficiency. 712 SECTION VIII. AS MA Number of Plates. 9 19 21 41 9 19 21 57 Type and Number of Plates. A S 17 AT 11 A B 15 Table 1.—E. P. 8. Cells, O K Type, for Large Power Stations in Alloy Crates. (Box Height, 2 ft. 5 in.; Overall, 2 ft. 10 in.) Maximum Charge. amperes 200 450 500 1000 • 100 225 250 700 Discharge Amperes for 1 Hour. 3 Hours. Height Overall. in. 111 13 15 400 900 1000 2000 220 495 550 1100 200 450 500 1400 7 Hours. 100 225 250 700 Height. in. 10元 ​12§ 14급 ​140 315 350 700 P. CELLS IN WOOD LEAD-LINED BOXES FOR SMALLER POWER STATIONS AND RAPID DISCHARGES. 60 135 150 420 Box. coke shooto Dimensions, External. Width. Width. in. Length. ft. in. 1 11 1 11 1 11 1 111 1 61 HHHH 1 Friedm 61 1 61 1 62 ft. in. 0 112 1 9 1 11 3 8 Length. in. 68 4 48 0 10 1 72 1 91 4 5 Table 2.-Cells for Motor Cars and Launches. Ebonite Boxes and Covers. Dilute Acid for Each Cell. Carboys. Weight of Cell, complete with Acid and Connectors. Weight. lb. 160 335 lb. 30 22 30 375 740 96 176 194 500 Maximum Charge. in Amperes. 8288 1.35 2.9 3.2 6.4 20 0.8 1.5 1.55 4.2 3 Hours. 1 40 30 42 Weight of Cell,complete with Acid. lb. 730 1450 1580 3000 Discharge in Amperes. 330 670 740 1930 5 Hours. 32 24 30 ! ! STORAGE BATTERIES. 713 Type and Number of Plates. HF 9 HF 19 HF 31 HG 17 HG 29 HG 31 HG 45 LF 9 LF 19 LF 31 LG 17 1. G 29 LG 31 LG 45 hours Discharge. 321 3 2 1 321 321 321 321 BO OL♡ O O O O O O 3 2 1 10 5 3 10 5 3 10 5 3 10 5 3 10 5 3 10 5 3 10 5 3 Table 3.-Tudor Cells. amperes amperes. 120 120 160 280 270 360 630 450 600 1050 480 640 1120 840 1120 1960 900 1200 2100 1320 1760 3080 50 88 132 112 198 297 187 330 495 200 352 518 350 616 924 375 660 990 Charge. 550 968 1452 270 450 480 840 900 1320 80 180 300 320 560 600 880 Approximate Weight. Cell com- plete with Acid. lb. 330 Plates. 166 361 595 694 1200 1284 1875 166 361 595 694 1200 1284 1875 670 1070 1390 2220 2370 3320 330 670 1070 1390 2220 2370 3320 Quantity of Dilute Acid. gallons 8.4 16.4 26.0 44 64 68 92 8.4 16.4 20.0 44 64 68 92 A A2 714 - SECTION VIII. Ben With the aid of suitable batteries and boosters (see Section IV. and V.), the exceedingly irregular load curves of electric tramways, and also of hoisting machinery, can be kept smooth. Of the 260 electricity supply undertakings (not serving tramways) which were in operation in the United Kingdom at the beginning of 1905, only 38 were not provided with batteries; of 112 central stations, supplying both light and power for traction, 15 were working without batteries. In Germany, the battery power of the public tramways and electric railways had risen from 1898, when it represented one-sixth of the dynamo power, to nearly 30 per cent of the dynamo power in 1903. In gas-engine driven traction plants powerful batteries are the rule. On the whole, moderate-sized power-stations are equipped with comparatively larger batteries than big power-stations. Where the plant consists of several units, the battery will be able to replace one unit, and number about 260 cells to give the customary 550 volts for the trolley line. Batteries. The following notes on types of batteries concern, in the first instance, batteries for light and traction. The Electrical Power Storage Company (established 1882; Tables 1 and 2) supplies pasted pure lead plates; antimonious lead is used only for some automobile electrodes and for the crates. Positives for stationary cells: cast web-plates, inclined horizontal ribs on both sides, forming shelf-troughs for the material; no vertical ribs. Negatives: open basket grids of diamond-shaped horizontal bars; vertical ribs, except special strengthening ribs, not quite so high, so that several openings form one con- tinuous pellet of material, and only the horizontal ridges are visible in the pasted plate. In cells for automobiles both plates are of this open-grid construction; none of the vertical ribs apart from the frame are high, and the pellet goes right across the plate. Some other types are also made. In station cells the electrodes are suspended from upright glass slabs, and separated by rows of glass tubes in boxes of glass, of wood lined with lead, or (largest sizes 344 in. in height) in soft lead cases, forming with their framing of alloy a strong crate, which rests, with its stout base of alloy on a lead-covered tray, directly on the insulators, The four sides of the soft lead box are dovetailed and burned together. Clearance under electrodes in the largest cells, 6 in.; plug-holes below at the side, if desired. The first charge lasts thirty or forty hours, and should certainly not be interrupted for the first twelve hours, until the acid density is 1.205, and the electrolyte milky. The acid density may vary between 1.210 and 1.180; in motor cells it may go up to 1.250. Dilute acid in the tables means density 1200. A battery standing idle should be recharged once a fortnight Voltmeter tests should be taken of each cell during normal discharge once a week. Best charging rate, half the maximum rate. The positives of the Tudor Accumulator Company (Table 3) are all cast with fine vertical ribs, strengthened by horizontal ribs giving ten times the apparent surface. The thickness is in all plates -in., and the plates are formed after Planté, without aid of any corrosive acid. The negatives are pasted grids. The plates are suspended from the edges or rest on glass slabs separated by glass tubes; clearance below, 4 in. to 8 in., As in the E. P. S., and some other types, the negatives of one large cell are solidly burned to the same bar as the positives of the next cell. The boxes, glass or lead lined with wood, rest on glass or glass oil insulators which may be supported by pitch-pine bearers, painted acid-proof, lying on porcelain oil insu- lators. The acid density varies between 1.190 and 1.210; the cells are charged up to 2.62 (L type) or 2.67 volts (H type). In calculating the number of cells required, 1.84 volts are reckoned per cell at the 10-hours rate, 1.82 at five hours, 1.80 at three or two hours, 1.70 volts at one hour rate. The L types are for low-working rates, the H types for high rates. The standard plate dimensions are:- Types L E and H E: 7 in. wide by 12 in. deep, LF and H F: 14 in. "" LG and HG: 16 in. 12 in. 20 in. "" "" "" The discharges of H cells are stated in the foregoing Table for the 3, 2, 1 hour- rates; the charge takes 3 or 24 hours. The charge of L cells takes from 5 to 6 hours, and the discharges are stated for 10, 5, and 3 hours. "" "} The Chloride Electric Storage Company (Tables 4, 5, 6) has discontinued the manufacture of the Chloride negative plates, which consisted of pastilles of fused zinc chloride, fixed by casting under hydraulic pressure in a lead plate. The chloride was reduced to spongy lead in a bath of zinc chloride, the lead plates being for this purpose coupled with zinc plates. The Exide STORAGE BATTERIES. 715 Type and Number of Cells. Normal. Rate of Charge in Amperes. RjW 7 56 9 72 "" "" " >> "" 11 88 13 104 15 120 16 130 Table 4.-Chloride Cells, R Type Plates, in Wood Boxes. (Height Overall, 24 in.) Rate of Discharge in Amperes for Capacity in Ampere Hours when Discharging in Width Length Height ·· Maxi- mum. Cell number Discharge in amperes for— 9 hours 6 hours 3 hours 1 hour Normal charge rate.. Maximum charge rate •• 150 130 160 190 220 230 1 3 6 9 1 3 6 9 Hour Hours Hours Hours Hour Hours Hours Hours ·· ·· •• 210 103 63 47 210 308 378 420 270 132 81 60 270 396 486 330 161 99 73 330 87 390 390 191 117 450 220 135 480 540 484 594 660 572 702 780 · 660 810 900 704 869 961 100 235 107 107 • Weight of each section in pounds.. Outside tank measurement in inches :- ·· .. .. AD lined tank, in pounds Height of cell, overall, in inches.. ► .. Table 5.-CR Type, Chloride Cells in Wood Boxes. ·· ·· •• ·· Weight of acid in pounds Weight of cell, complete with acid in lead- ·· ·· : .. 450 480 00 8 117 159 259 528 144 264 364 181 23 213 200 680 29ğ 11 161 218 356 726 198 363 489 223 23 213 236 800 Approximate Weight. Cell complete Acid with Acid. Only. 299 lb. 247 805 366 423 481 510 15 220 298 485 990 270 495 661 28 23 213 326 1100 lb: 52 64 77 89 102 114 29§ 19 279 377 614 1254 342 627 833 341 24, 22 398 1340 303 Acid Parts in Carboy. Height. Length. Width. 0.48 0.58 0.69 0.8 External Dimensions of Box. 0.89 0.95 in. 17 17 17 17 17 17 223 337 456 747 1518 414 759 1005 401 24 mball mle305/20 22$ 470 1580 301 in. 111 141 171 194 231 23 60 880 1190 1940 3960 1050 1980 2596 in. 14 15 15 15 1136 15 15 96 25 231 3800 30g 716 SECTION VIII. • negatives are pasted; they have a grid of thin vertical ribs connected by horizontal bars of triangular cross-section: the bars on the two faces are staggered. The positives are made of grids of antimonious lead cast under pressure, and punched with 124 round holes countersunk on both faces to receive rosettes (buttons) of active materials, to manufacture which lead tape is pressed cold, gimped and cut off to length, and wound to rosettes; the rosettes are placed into filling templets and expanded into the punched holes with a small head on both faces. Such plates are manufactured in sizes from 3 in. by 4 in. to 35 in. by 15 in., with a capacity of 270 ampere hours per plate; the average thickness is in.; the suspending lugs are clear of the acid and rest on the edges of glass boxes, or are suspended on glass hangers. Pure lead boxes, strengthened by wooden bars to prevent bulging, are also used. The board separators introduced five years ago are exceedingly simple (Fig. 3): thin whole sheets of wood, in. thick, supported by two slotted wooden dowels which are pushed over the boards. Fig. 3. Separators of Wood with Dowels. The capacities given in the Tables are understood for a fall of voltage down to 1.85 at the nine-hour rate, 1.8 (6 hours), 1.75 (3 hours), 1.65 (1 hour rate). The M.V. cells have rubber separators for the positives, in addition to the wooden diaphragms. The normal acid density of the fully-charged cell is 1.3. The temperature should not vary outside 70 to 90 deg. Fahr., the discharge should not be pushed below 1.7 volts. In hurrying a charge, high charging density should be used only during the first part of the charge. Overcharging is not recommended. An idle battery should be freshened up once every week; if the battery is to be put out of commission, the electrodes, positives and negatives separately, are raised, washed of acid, dried and stored. Table 6.-Automobile, MV Exide Type Chloride Cell. Ampere Number Hours at of Cell. MV 3 "" "" CO E LO C "" (1102) 4 5 9 Four Hours' Rate. 78 104 130 234 Approximate Weight in Pounds. 22 274 331 56 Acid Parts of Complete Cell. | Electrolyte. Carboy. Height. Length. Width. B44 3} ARAKO 0.03 0.034 0.04 0.066 Approximate External Dimensions in Inches. 114 114 111 Box. === 11 20 3f 4 6133 6,131 6,1% 6,3% 61% The D. P. (Dujardin-Planté) Battery Company (Table 7) makes strip type plates for low rates of charge and discharge. The positives are specially constructed to admit of expansion, and are combined with negatives made up of a strong frame, horizontal bars front and back, and vertical keybars to hold the material on both sides. The Lumford positives are cast, double-comb plates, with deep horizontal grooves of very large surface; they are given a skin of Planté formation. The heavy L. H. central station batteries are provided with a tube-guide resting in the bottom. نہ STORAGE BATTERIES. 717 The strip-plates stand on bottom blocks with 4-in. clearance: the Lumford plates are suspended upon the sides of the glass boxes. The Lumford Light (L. L.) type, and the Yacht strip are type for portable work. Cells are not to be run below 1.8 volts; the acid density should be 1.2 or 1.21 when gassing fully; acid should only be added when the cell is fully charged; the temperature of the battery-room should range between 45 deg. and 75 deg. Fahr. Table 7.-D. P. Batteries. Number. LL3 L L 13 LL 19 L L 27 LH3 LH 13 LH 17 L H 21 Capacity in Ampere- Hours. Capa- city. 60 360 540 780 60 600 660 LH 23 LH 29 840 LH 35 1020 80 120 169 Normal Charge in Amperes. 0000241 8 72 104 10 360 60 480 80 12 18 24 48 Charge-Rate in Amperes. Discharge-Rates Outside Dimensions in Amperes for in Inches. 10 Hrs. 36 48 100 60 110 66 140 84 170 102 36 54 78 6 16 24 32 Normal. Maxim. 885 Hrs. 10 Hrs. 10 8 12 16 60 130 11 66 88 110 121 154 187 3 Hrs. 5 Hrs. 13 78 117 169 13 20 26 15 90 120 150 165 210 255 Discharge-Rates in Amperes for Height. 3 Hrs. 151 15 18 27 36 12 12 151 12 151 12 154 43 111 151 131 111 151 19 111 151 214 111 17 24 13 13 13 The Hart Accumulator Company, Limited (Table 8), manufactures combination Planté-Faure plates. In the C. L. type of station-cells the plates are hung in tension on glass slabs, in. apart, separated by glass tubes, and 5 in. clear space is left underneath in the bottom of the boxes; glass is used for the containers of batteries of 1000 ampere-hours, lead-lined wood or lead tanks for larger batteries. In the C. T. type for motor cars, the negative grid is cast with high horizontal ribs at right angles to the plate; these laminations are then rolled down to the plate level, so as to form shallow troughs for the active material on both sides. They are further covered with a porous cloth, wrapped lengthwise and crosswise, and tightly bound to the surface; ribbed and perforated ebonite separators are interposed, the flat side resting against the positive. These C. T. cells are fitted with ebonite boxes and containing crates for sets of 10 cells. In the Hart battery connection, the vertical faces of adjacent lugs are brought together and fixed by a tapering bolt and nut, both of lead alloy, so that the current passes both through the lugs and the bolt. Table 8.-Hart C. T. Cells. Length. 17 293 17 2 Hrs. 44 131 18 24 22 33 44 CIKAKO 35 Gallons of Acid of 1.19 Re- Width. Length. 225 CERA İNCƏ External Dimen- sions in Inches. quired per Cell. 2.5 6.0 8.5 11.75 2.5 75 6.0 250 7.75 330 9.5 400 10.25 490 12.5 610 14.75 730 Width. ∞ ∞ ∞ Complete Weight_of Cell with Acid. 8 70 200 285 405 8 8 Wood Glass Boxes. Acid per Cell, Part of Car- boy. Weight in lbs. 15 0.03 0.05 21 0.06 27 The chief features of the modern Planté positive electrode, the pure lead web plate with horizontal grooves, are found in many other types, for instance, in the Ashmore, Benson, and Pease (A. B. P.) batteries. The Accumulator Industries, Limited, form the positives of their Leitner cells without nitric acid or nitrates, penetration of the electrolyte through the pure lead plate being secured by mechanical means. The negatives are pasted undercut grids. 718 SECTION VIII. The Accumulatoren Fabrik A.G., of Berlin and Hagen, formerly known as the German Tudor Company, now generally styled the A. F. A., makes Planté positives of soft lead, with close, fine, vertical ribs, and pasted negatives with a strong vertical middle rib for central stations, locomotives, automobiles, etc. Batteries are in the first instance charged for fifteen hours, then rest for an hour or two, and are recharged again, and so on, until the charging at once causes lively gassing. The pressure limits are 2.7 and 2.8 volts. Overcharging is recom- mended once every three months. The Behrend Accumulatoren Werke, of Frankfurt, provide their plates with high zigzag lamellae, those in front crossing those at the back, and further with transverse ribs of triangular section. The spacing glass tubes pass through lugs on the negatives. The active material of the portable cells-also for emergency lighting is forced into the grid by machinery. The station accumulators of Heinz, of Levallois, France, have soft lead grids. Traction cells are given grids with 8 per cent. of antimony. The grid of a positive has a central web, 3 millimetres in thickness, and the vertical ribs are I-shaped in cross-section, giving ten times the apparent surface. The negatives have basket grids consisting of vertical bars, and two systems of staggered horizontal tri- angular bars. The protective coverings of asbestos, etc., have been discarded. The formation in sulphuric acid and magnesium sulphates lasts 500 hours. The cells are charged up to 2.6 volts, and discharged to 1.83 volts. The acid density is 1.06 for treating sulphated cells; 1.2 for station cells; 1.241 for automobile cells. The electrodes of the Kölner Accumulatoren-Werke Gottfried Hagen consist of two halves, united by cross-bars, each built up of rods, triangular in section, the bases being turned outside. The plates rest either in grooves, provided in special supporting plates, leaning against the walls, or the negatives stand on lugs, and the positives are suspended from ebonite rods. The cab batteries of Cologne con- tain 16 positives and 17 negatives per cell, and weigh 550 kilogrammes; the plate dimensions are 130 by 200 by 3 millimetres; the connections are established by means of screws of hard lead and wires of soft lead; the cell covers are hard rubber, with a fringe of soft rubber. Majert (the French Union and the Italian Cruto Companies) cuts exceedingly fine lamellae into the pure lead plate. The Pescetto cells of the latter company have an antimonious lead-grid, cast and machined so that tongues project into the alveoles. The "ulmate" electrolyte of Pescetto is a solution of sugar in sulphuric acid. The Compagnie de Neuilly (Pollak cells) uses only rolled lead; lead ribbon is worked into a plate provided with little hooks or studs. The surface of the automobile electrodes is chemically converted into carbonate and then formed, leaving a lead-core, 1 millimetre in thickness. The Bleiwerk Neumühl, Morian, and Co. subdivide the high, strong lamellae of their electrodes into short bars, which are severally staggered; the connections contain a copper core. The negatives of the Pflüger Company have very close horizontal shelves, the edges of the lamellae being afterwards bent over in several directions to hold the material well. Pritchett and Gold, of Feltham, make accumulators of the Lehmann-Mann type; the vertical ribs of the Planté positives are subdivided by many horizontal grooves right down to the core, which is not plane, but of zigzag shape. The Accumulatoren-Werke E. Schulz, of Witten-on-the-Ruhr, cast Planté positives with deep grooves, which widen out towards the surface; sulphurous acid is used in the formation. In the stationary cells elastic strips of lead are interposed, not only between the end-plates, but also at intermediate points. The connections are copper spirals covered with lead under hydraulic pressure. The Willard Battery Company, of Cleveland, Ohio, used to manufacture cells with concentric electrodes. The actual positives are made of pure lead, rolled with very fine vertical grooves, and provided with a sheath of hard rubber, which is perforated, except at the edges. Wood separators are also used. Trough batteries, consisting of trays, horizontally piled upon one another, have often been proposed. The Schweizer Accumulatoren-Werke Tribelhorn, of Ölten, Switzerland, have succeeded in casting such trays, together with their somewhat elaborate lamellae, by using moulds made up of several sections. The trays, or elements, are separated by glass balls, and charged with sulphuric acid of density 1.18. Little floor-space is needed, and the batteries can be dismounted with com- parative ease. Frame-plates (Masseplatten), consisting entirely or chiefly of active material, have so far not answered on vehicles for which their light weight would | STORAGE BATTERIES. 719 recommend them. Gelatinisation of the electrolyte (P. Schoop) cannot be effected by perishable organic compounds. Soluble silicates have had a moderate amount of success; but the capacity of such cells is low, and the gelatine does not long remain homogeneous. Special Types of Portable Cells for Automobiles, Locomotives, Boats, &c.- In portable cells, which are constantly exposed to concussions, high output per weight is of more importance than long life, and the chief aim is to produce easily interchangeable cheap plates, of moderate durability, with very light grids, supports, and accessory parts. Pasted plates are alone used-apart from the electrodes entirely formed of active material-but experiments with Planté plates continue. Numerous small-size plates are preferable to few large-size plates. Approved dimensions are: 110 by 220 millimetres; thickness, 3 or 3.5 millimetres; the distance between the plates should equal the plate thickness. Examination of individual plates with the aid of lamps, and insertion of hydrometers between the electrodes, are hence out of question. When the density is to be determined at the end of the charge, the acid is withdrawn by means of a rubber balloon. Sheet separators of perforated ebonite, provided with thin spring ribs on one side, are used; further porous or perforated plate casings, made of asbestos, celluloid, rubber, &c., sometimes in combination with separators or distance-pieces of ebonite, earthenware, &c. Wood diaphragms are sometimes combined with ebonite separators or distance-pieces. The lead alloy grids of the plates are best made in two halves (front and back), and provided with straight connecting pins for attaching the connections from cell to cell, preferably by soldering, else by bolts and nuts. The cylindrical projections of the one half fit into holes in the other half, and the halves are riveted together, after the paste has been filled in, while the paste and plates are being compressed. The head of the press bears needles, or studs, which make holes or recesses, or both, in the pasted alveoles. The pressure must carefully be regulated, so that the plates have the same hardness and porosity. The acid is so calculated that the density at the end of the charge is 1.250 or 1.260. Higher densities up to 1.300 are still recommended, but they may cause sulphating of the negatives, unless the material is highly porous. The porosity is hence increased by adding to the paste inert salts and a great variety of other substances which are removed during the formation process. The plates stand in the ebonite containers, on two ribs, rising from the bottom of the container. Any mud settling there is occasionally cleaned out, after taking the whole of the burned-up plates out; the plates themselves may be washed under the tap. The Chicago Storage Battery Company provides the Duntley cells, with a plug in the bottom, and washes the plates in situ with the hose. On the whole electricians are anxious to avoid all chance of leakage of the acid from the cells. Owing to the high acid density, the negatives do not last much longer than the positives. If stationary cells last six years-ten years are claimed sometimes-and batteries on locomotives almost as long, one year is considered a good age for automobile negatives. Simple volt-amperemeters are used on vehicles, not so far the many more or less complicated apparatus for indicating the remaining charge. The pure or mixed accumulator tramway service (exclusively or partly by batteries) has almost everywhere had to make room for the trolley and the per- fected conduit systems. Omnibus trams, however, are still run on two lines of the Pfälzer Railway (Bavarian Palatinate). Cars of 45 tons pull two trailers (total train weight, 110 tons) by means of 150 A.F.A. cells (German Tudor). of 80 kilo- grammes each. The battery weighs nearly 15 tons; the motor 4 tons. The cars make from 150 to 265 kilometres daily, at 45 kilometres per hour, and con- sume from 18 to 20 watt hours per ton kilometre. The cells are 420 by 700 by 340 millimetres. The battery efficiency is estimated at 65 per cent. The Siemens- Schuckert Werke started in 1904 two full-gauge accumulator cars on the line Dresden-Cossebaude. The two cars are coupled together, and are propelled by four motors and 386 cells of the Kölner Accumulatoren Werke. Accumulator loco- motives are used in many works (Chloride Battery Company, A.F.A. cars at the Kiel Shipbuilding Yards) and in coal mines. A Siemens shunting-engine has recently been put into service at the Oberhausen Railway junction. It weighs 27 tons-the battery, of five groups of 40 cells each, altogether 10 tons. The battery is charged once a day on a 110-volt circuit. Accumulator wagons and trucks for goods delivery have become popular in New York. Private accumulator carriages, for town service only, are coming to the front again. The "Electricia" cell of C. Contal (Paris), used by the Electromobile Company of London, is constructed on the lines above indicated. The two halves are riveted 720 SECTION VIII. together in the pasting, and triangular bars divide the face into 252 small squares, each perforated with a hole. The 17-plate standard cell of the Electromobile Com- pany has plates 220 by 103 by 3.5 millimetres; containers of ebonite (with two bottom ridges, 15 millimetres high); length 127, width 111, height 305 milli- metres; weight of cell complete, 11.6 kilogrammes (electrodes and connections, 8 kilogrammes); capacity at 30 amperes 150 ampere-hours, at 40 amperes = 135 ampere-hours, about 11 watt-hours per pound of battery. The ebonite covers consist of two pieces. A battery of 44 cells weighs 8 cwt., and is kept in an iron tray, lined with acid-proof compound, 3 ft. in. long, 2 ft. 14 in. wide, and 13 in. deep. The cells are charged in the tray, which is then raised by machinery and slung under the middle of the carriage. After being burned up, the cells receive three or four charges and discharges, and are then put into commission. In charging, the current density is first 1.5 amperes per square decimetre positive plate, and lowered gradually. The cells are always coupled in series--not in groups-and all discharged at the same rate, the Contal-Garnier motor (see Traction and Transmission, June, 1903) being provided with two armature windings and two commutators, and differential gearing. The batteries run about 48 miles, and may do 100 miles on one charge, and have done 4700 miles without renewals, 1200 miles a month without inter- changing batteries. The potential may go down to 1.7 volts in service. For car The "Fulmen" accumulators are essentially of the Faure type. lighting, ignition, telegraphy, and boats, Planté positives, a little heavier for equal capacity, are used, one type with gelatinised electrolyte. The automobile cells consist of two grids riveted together. The positive grid has many vertical, and a few horizontal, bars, giving high alveoles of small width; the negatives are provided with many square alveoles; there is a hole in each pellet. The Kriéger Electric Carriage Syndicate uses particularly the B21 "Fulmen " cells with 21 plates, in ebonite boxes, 178 by 112 by 250 millimetres, weighing complete 13 kilogrammes, for 176, 144, 134 ampere hours at 8, 4, 2 hours discharge rates. The B plates have all the same dimensions, only the length of the boxes changes with the number of plates. The cells are stored in two wooden boxes. The controllers for the two independent Kriéger motors and batteries allow of eight combinations; the average speed is 12 miles. The positives stand 2500 miles, the negatives 4000 miles; the cells are discharged down to 1.8 volts. The first charging lasts 18 hours at almost constant rate of 17 amperes; ordinary charging takes about seven hours. The City and Suburban Electric Carriage Company assembles 44 E P S cells of 11 plates with ribbed, perforated ebonite separators, in one tray of 2 ft. 5 in. by 2 ft. 5 in. by 12 in., weighing 10 cwt. The capacity of the battery is 120 ampere hours, and the ordinary discharge rate 35 amperes down to 1.7 volts per cell; driving a carriage of 28 cwt. complete with battery, 40 miles are done on one charge, 48 miles maximum; the battery is charged at 20-ampere rate on a 115-volt current. The specific gravity of the acid is corrected once a week; after 700 miles the cells are cleaned; the positives last about 3000, the negatives 5000 miles. The Industrial Storage Battery Syndicate (Elieson-Bobinski cells) uses plates of Planté type, consisting of horizontal lamellae, alternately corrugated and flat, burned to a central tube which takes up the expansion. The automobile cells for capacities of from 80 to 240 ampere hours contains 3, 5, or 7 plates only, the width varying from 13 to 4 in., length 7 or 8 in., height 12 or 14 in., weight 17, 261, or 29, 38 lb. complete with acid. The Gould Storage Battery Company, of New York, makes positives of pure lead prepared by a spinning process, so that twenty times the apparent surface is obtained, and forms only electro-chemically. Both electrodes are provided with ebonite separators. Non-Lead Cells; Alkali and Nickel-Iron Cells. Thallium, which resembles lead, is, according to L. Jonas (Zeitschrift für Electrochemie, 1903) not a promising metal for accumulators. Auer von Welsbach has used cero-sulphates in zinc-carbon storage-cells, relying on the high oxidising power of cerium salts. The various caustic alkali cells of Lalande-Chaperon and others combinations of zinc (or inagnesium, cadmium), alkali, and copper oxide— are more suitable for primary than for secondary batteries. Nickel electrodes have often been tried in alkali cells by Dun (1884), Jungner (1894), Edison, Laszcynski, Michalowski, and others. Nickel-iron cells have been constructed by Edison and by Jungner, cells containing silver or silver compounds by Jungner. The caustic alkali does not in these cells play the part of the sulphuric acid of the lead cells. It does not combine with the oxides of iron and nickel, forming the | STORAGE BATTERIES. 721 active material; does not or should not-attack the electrodes; and its average density does not change during the charge and the discharge; for this reason the capacity of the cell is not much affected by the rate of discharge. The density of the caustic alkali fluctuates considerably, however, near and in the electrodes. A nickel peroxide Ni O2 is unknown to chemists, and the so-called peroxide of Edison is, according to Zedner, a hydrated Ni2 O3. The cells of the Edison Storage Battery Company, of Glen Ridge, N.J., are built up of the following materials: Steel, especially nickel plated, making the grids and containers; nickel and iron oxides, to which graphite, etc., is added, as they are bad conductors; ebonite insulators, and a 20 per cent. solution of caustic potash in distilled water, density 1.190. Out of a plate 121 by 235 by 0.38 millimetres are punched 24 rectangular holes, in three horizontal and eight vertical rows, into each of which a pocket or box is fitted, 75 millimetres in height, 12.7 millimetres in width, 2 milli- metres in thickness. The little boxes consist of bottom and lid, both made of 0.076 millimetres steel strip, with flanged edges, corrugated, indented, and per- forated (about 5000 little holes per box), so as to attain the highest degree of elasticity. The pockets for the positives are filled-exact within 0.2 grain-with nickel peroxide, prepared by precipitating nickel nitrate with magnesia, and peroxidising the resulting hydroxide (which would swell in alkalies) by means of chlorine. Flakes of graphite are mixed with the oxide. The pockets for the negatives are charged with iron, reduced by the aid of hydrogen, and mixed, it is said, with graphite, or a paste of ammoniacal copper and mercury compounds. The boxes are fixed on the grid by means of hydraulic pressure. Boxes of the E18 cell contain 922 grammes of positive and 662 grammes of negative material each. The assembled plates are kept 1 millimetre apart by means of threaded, four- cornered ebonite rods. The container walls are also corrugated, except at the edges. The stamped top and bottom are soldered on. The top of the container has four openings, two stuffing-boxes for the terminals, a filling-hole closed by a spring lid, and a vent-hole with a gravity valve, lest carbon dioxide be absorbed from the air. The vent-hole is closed by a sheet of wire gauze, to prevent internal ignition of the mixture of hydrogen and oxygen evolved; and there is a diaphragm of steel underneath the gauge to break the small bubbles of alkali, and to keep the liquid in the cell. The cells stand in trays in hard rubber insulators. The following types are made:- Type. E 18 E 27 E 45 Number of Plates. Positive. Negative. 6 9 15 12 18 30 Capacity in Ampere-hours. 110 to 140 165 to 210 275 to 350 Charging Current. Amperes. 40 60 100 Weight. Complete. 12.5 lb. 5.7 kg. 17.5 lb. 8.0 kg. 30.0 lb. = 13.6 kg. = The normal charging time is always 3.75 hours. The dimensions over all, excluding trays, are also the same for the three types: Length, 5.1 in. (13 centi- metres), height, 13.2 in. (35.5 centimetres), volume, 175 cubic inches (2874 centi- metres). The capacity of the E type cell is about the same at 30 amperes (3.8 hours) and at 120 amperes (0.95 hours) discharge rates. At the former rate, the mean potential difference (down to 0.75 volts) is 1.234 volts, representing an output of 141 watt- hours, or 11.1 watt-hours per lb. At the 120-ampere discharge-rate, the mean potential difference is 1.04 volt, representing 118.5 watt-hours, or 9.38 watt-hours per pound. In these figures, the discharge is supposed to be stopped at 0.75 volt; the full capacity is higher-173 and 145 watt-hours at the two discharge-rates, yielding 13.7 and 11.5 watt-hours per pound, or 30.2 and 25.4 watt-hours per kilo- gramme respectively (Kennelly and Whiting). The independent laboratory and automobile tests by Janet, Hospitalier, Finzi, Hibbert, Fleming, and Joly, of 1903-1904, agreed as to the main features. The success is largely due to the perfect mechanical construction. The initial electro- motive force is uncertain, owing to the high polarisation. It depends upon the amount of occluded gas, and ranges between 1.35 and 1.65 volts. There is a rapid descent in the potential difference, lasting about one-tenth of the delivery period, a nearly steady gradient down to 1.2 volt, and a final rapid descent to 0.75 volt. The potential difference curve of the nickel electrode drops much more rapidly than that of the iron electrode. The resistance of the alkali decreases, like that of * 722 SECTION VIII. most electrolytes, with higher temperature at the rate of about 2 per cent. per degree Centigrade. The internal resistance of a discharging E18 cell is 0.0022 ohm down to the drop of the potential difference, increasing towards the end. It is little influenced by the rate of discharge. The watt-hour efficiency is not high- Hibbert's estimate is 56 per cent., Kennelly calculates 78 per cent. on 100 per cent. ampere-hour efficiency; but the ampere efficiency is itself low, in actual automobile work 75 per cent., owing to much gassing, which would reduce the watt-hour efficiency to 52.5 per cent. Heavy charges and discharges are borne remarkably well; the cells may be left discharged and on short circuit for considerable periods, and be discharged almost to zero. Local action, loss of material, and formation of sediment are insignificant, and there is no buckling. The gassing calls for a good valve, and occasional "topping-up" with distilled water. The following compara- tive data as to watts, watt-hours per kilogramme, and also discharge-rates, were given by Janet in 1903. Hospitalier (1903) found the bulk in cubic decimetres per kilowatt-hour: Contal, 13.7; Edison, 21.5. Contal. 2.0 2.8 5.0 7.4 σα MAMAMAMA 27.5 24.7 20.3 Density at 15 Deg. Cent. 1.000 1.015 1.030 1.045 1.060 1.085 1.100 1.110 1.125 1.140 1.155 1.170 1.185 1.200 1.210 33.4 32.7 29.5 22.3 1.220 1.230 1.240 Fulmen. 2.75 5.0 6.8 0 2.1 4.1 6.0 8.0 11.2 13.0 14.2 16.0 17.7 19.3 20.9 22.5 24.0 25.0 26.0 26.9 27.9 H2 SO4 Degrees Per Cent. Baumé. by Weight. 0.09 2.3 . 4.49 6.67 8.77 12.30 14.35 Blot-Fulmen. 15.71 17.66 19.61 21.55 25.47 25.40 27.32 28.58 29.84 31.11 32.28 A different type of Edison cells is now brought out. The Jungner cells, made in Norrköping, Sweden, and by the Kölner Accumulatoren-Werke, resemble the Edison cells in their general construction. Table 9.-Sulphuric Acid, Density and Percentage. (Lunge and Isler.) 1.9 3.4 5.0 One Litre Acid Con- tains Kg. H2 SO4. 0.001 0.023 0.046 0.071 0.093 0.133 0.158 19.0 17.1 15.2 0.175 0.199 0.223 0.248 0.275 0.301 0.328 0.346 0.364 0.382 0.400 Density at 3.95 9.9 14.6 27.7 15 Deg. Cent. 1.250 1.260 1.270 1.280 1.290 1.300 1.320 1.340 1.360 1.380 1.400 1.450 1.500 1.550 1.600 1.700 1.800 1.840 Edison. 26.3 25.7 23.9 20.0 28.8 29.7 30.6 31.5 32.4 33.3 35.0 36.6 38.2 39.8 41.2 44.8 48.1 H2 SO4 Degrees Per Cent. Baumé. 51.2 54.1 59.5 64.2 65.9 Discharge in Amperes. by Weight. 33.43 34.57 35.71 36.87 38.03 39.19 41.50 43.74 45.88 48.00 50.11 55.03 59.70 64.26 68.51 77.17 86.90 95.60 283 60 100 200 One Litre Acid Con- tains Kg. H2 SO4. 0.418 0.435 0.454 0.472 0.490 0.510 0.548 0.586. 0.624 0.662 0.702 0.789 0.896 0-996 1.096 1.312 1.564 1.759 To convert degrees Twaddell into density (water=1000), multiply by 5, and add 1000; thus: 35 deg. Tw.=5 × 35 + 1000=1175. To convert density (water-1000) into deg. Tw., subtract 1000 and divide by 5: density 1205=(1205-1000÷5=41 deg. Tw.) i1. STORAGE BATTERIES. 723 Percentage of Mono-hydrate. 2.88 5.22 5.77 6.45 7.31 8.45 H2SO4 per Cent. A 4.2 8.4 12.6 16.8 21.0 25.2 Table 10.-Freezing Points of Sulphuric Acid. (Pfaundler and Schnegg.) 29.4 33.6 37.8 42.0 1.0 2.5 5 10 15 20 25 30 35 40 50 60 75 Freezing Point. Degree Cent. In freezing, water crystallises, leaving concentrated acid in solution. Table 11.-Sulphuric Acid. Resistance in Ohms per Centimetre Cube. (Kohlrausch.) -1.11 -2.2 -2.43 -2.80 -3.3 -3.9 1.0382 1.0777 1.1177 1.1588 1.2088 Density at 18 Deg. Cent. 1.2439 1.3008 1.3332 1.3803 1.4298 1.008 1.016 1.033 1.070 1.100 1.140 1.180 1.220 1.260 1.310 1.400 Caustic Potash, KOH. 1 B 1.500 1.670 C 6.873 3.697 2.675 2.209 1.972 1.864 1.854 1.929 2.104 2.392 Percentage of Mono-hydrate. A = Per cent. of KOH or NaOH. B = Density at 15 deg. Cent. C = Resistance in ohms per centimetre cube at 18 deg. Cent. D = Diminution of resistance per deg. Cent. 10.0 12.25 15.8 22.27 D 1.88 1.87 1.89 1.94 2.00 2.10 2.22 2.37 2.58 2.84 31.2 35.25 Resistance at 18 Deg. Cent. A 2.5 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 42.0 22. 9.25 4.83 2.57 1.85 1.55 1.41 1.36 1.39 1.48 1.86 2.70 6.64 The minimum of the electric resistance lies near density 1.22. Table 12.-Caustic Potash and Caustic Soda. (Kohlrausch.) Freezing Point, Degree Cent. 5.0 - 6.7 - 9.8 1.1131 1.1700 1.2262 1.2823 1.3374 1.3907 1.4421 1.4615 -17.6 -57.1 -61.7 Diminution of Resistance per Deg. Cent. C 9.258 5.113 3.223 2.908 3.081 3.710 4.986 6.695 8.671 9.481 1.12 1.15 1.21 1.28 1.36 1.45 1.54 1.62 1.70 1.70 1.93 2.13 2.91 Caustic Soda, NaOH. B 1.0280 1.0568 D 1.95 2.02 2.18 2.50 3.01 3.70 4.50 5.54 6.52 6.92 Caustic Potash of about 29 per cent. conducts best; but it attacks iron at this concentration. SECTION IX. SURFACE AND CONDUIT SYSTEMS. SECTION IX. SURFACE AND CONDUIT SYSTEMS. SURFACE CONTACT SYSTEMS. General. Inventors have been hard at work for many years, endeavouring to design a surface contact system in which only that part of the track under the car would be alive. One of the first plans, and which at the time attracted a great deal of attention, is known as the Lineff system. A short experimental line was laid in London, and seemed to promise well. It was described and favourably reported on by Mr. Gisbert Kapp, but there the matter ended. It embodies an idea on which many similar systems have been worked out. The working or contact conductor is composed of a number of short sections of iron T-rails (the top of which is about level with the street surface), supported between the track rails on an insulating trough, containing throughout its entire length a continuous composite band of copper and iron, which is connected with the current generator, and is loosely supported on insulators beneath the bottom of the T contact rail. Beneath the car a large magnet is longitudinally hung, being of sufficient length to permit the iron rollers forming the poles to remain in contact with two of the contact sections. As the car proceeds, the As the car proceeds, the magnet, which is energised by the same current supplying the motors, causes that part of the strip or band beneath the magnet to be drawn up against the sections in contact with the rollers of the magnet, which also collect the current from the energising contact section. As the magnet comes in contact with the next section the band drops from the previously-connected section, but another portion is raised into connection with the new section; and in this way the raised portion of the band is kept moving along with the magnet under the car, connecting and disconnecting each section of the contact rail. A small battery is carried, to be used in energising the magnet in starting, or when the contact is lost. In other systems that have been devised, the switching is accomplished by means of numerous small plungers located beneath the sectional contacts, and caused to operate when under the influence of the car magnet. Mr. Schuckert designed a similar system, and laid down a trial line at the Frankfort Electrical Exhibition in 1891. It was not a success, and the line was eventually run by over- head conductors. In this system iron filings were used as a switching medium. These were placed in a conical receptacle beneath the contacts, and drawn up under the action of the magnet to the more confined portion of the receptacle, thereby connecting the terminals of the main and working conductors. Section rails and continuous-attracted contact slips have now been abandoned, and in their place a series of iron knobs has been adopted. Many such systems have come out within the last few years, and one which has been experimented with on the largest scale is that known as the Westinghouse enclosed conduit; of this a very fine working model has been exhibited in London, The Diatto System. (Figs. 1 to 3, pages 728 and 729.) Fig. 1 shows the arrangement of the system diagrammatically. At intervals in the street are placed boxes containing insulated porcelain cups C1, C2, C3, &c. These cups are partly filled with mercury, which is in permanent electrical connection with the feeder main F by means of a metal stud at the bottom of the cup. In these cups are dipped iron pius P1, P2, P3, &c., 80 propor- tioned that they displace a quantity of mercury, almost sufficient to float them. These cups and pins are directly under the surface buttons B1, B2, B3, &c., which are iron studs set in cover of the section boxes, and presenting their upper side to the street surface. The car carries a long electro-magnet M, normally energised by the line potential. The lower part of this magnet forms a metal shoe sufficient in length 728 SECTION IX. } to bridge two contact buttons at once. This shoe rubs upon the surface of the contact buttons B1, B2, B3, as the car moves along. If a battery were to be used to energise the first contact, and the car is to start, a local circuit is formed from the battery through the coils of the magnet M. This energises magnet M, and establishes a field force embracing contact B¹ and pin P¹. This draws pin Pl into contact with under side of the contact B1, which puts this contact in direct electrical connection with the feeder F. The current flows up through Pl, B1, and the long metal base of magnet M to the controller. The circuit through M is a shunt to the motor and battery circuits, and is connected outside of both controller and motors, so that the line potential immediately flows through and energises magnet M, although the motor circuit is not closed. This furnishes power to M, independently of the battery, to hold the pin Pl up against contact Bl. When the controller is closed the motors receive the line potential, Psz 24 576 1b3 bs P2 Feder Main Fig. 1. The Diatto Contact System. and the car moves along. Ground connections are made to the wheels or truck framing, the current returning to the station by the rail. When the car moves far enough for the left-hand extremity of M to cover the contact B2, then pin P2 is lifted, and an instant later, as the other end of M leaves the contact B1, Pl falls back into its original position, breaking contact with Bl. By letting the pin float in the mercury its weight is nearly all assumed by the mass of mercury, so that it does not require much magnetic effort to lift the pin. When, however, it has been brought into contact with B¹, the displaced mercury has resumed its normal posi- tion to a large extent, and very little of the weight of the pin is sustained by it, so that almost the whole weight of the pin is effective in falling by gravity away from the contact with B¹. If it is desired to stop, the motor circuit is, of course, thrown off as in ordinary practice, but the magnet M being energised in shunt with the motor circuit, still retains its magnetism, holding up whatever pins may be under it. This keeps the corresponding buttons alive, and ready to transmit current whenever the motor circuit is closed again. Figs. 2 and 3 show details of boxes and contacts. ·· 100000000 ·· 8 отот M Table 1.-Cost of Construction of the Diatto System per Kilometre of Single Track. (C. Julius.) (Based on French experience.) ·· Rails, 90 lb. per yard.. • Tie-bars, fish-plates, bolts and nuts, &c. Handling rails and waste Taking up setts, concrete foundations, 15 centimetres thick, and bonding and repairing.. Fixing 220 Diatto contact blocks Drainage Cable connecting-up contact blocks and junction boxes. Diatto boxes and apparatus Total per kilometre of track •• P1 ·· •• •• •• .. •• • • ·· •• .. • Francs. 19,000 3,000 1,500 18,000 10,700 30,000 .. 106,400 22,000 2,200 SURFACE AND CONDUIT SYSTEMS. 729 20翠 ​2 3 J (579) S P LY R S Figs. 2 and 3. The Diatto Contact System. 730 SECTION IX. Dolter Surface Contact System. This system utilises the ordinary contact studs and collecting skate. Each stud forms the upper part of a small watertight box, in which is suspended a bell- crank lever. The upper arm of this lever is of iron, and is capable of being mag- netically attracted by the iron block, when the block is magnetised by the skate. The skate is magnetised by the working current passing round electro-magnets, four small accumulators giving the necessary current when starting, &c. The 4 CELL'S BATTERY M כסנאסררב8 MOTOR MOTOR TO THE WHEELS ĮMAGNEȚ ME MAGNET „MAGNET HORSE? R SKATE ASAWW CONTACT: Boxes CIRCUIT CONTACT BOXESS From the Feeders ÖUND: Fig. 4. General Arrangement of Dolter Surface-Contact System. lower arm of the lever carries a piece of carbon, which is brought into contact with another carbon permanently attached to the underground feeders. Fig. 4 shows the general arrangement. The contact studs are placed about 6 yards apart. The car carries a small auxiliary skate at each end, which is grounded, so that if the switch fails to release, it is short-circuited, and a fuse blows, which entirely cuts it out of circuit. This it is claimed prevents the possibility of any stud being left "alive" after the car has passed. SURFACE AND CONDUIT SYSTEMS. 731 The Kingsland Surface-Contact System. (FIGS. 5 to 10, pages 731 to 733.) The principal feature of the Kingsland system is the use of a mechanical switch bolted to one of the tram rails, and having an operating lever or arm which is acted upon by a striker-bar or bars attached to the car. The lever is depressed a small distance by the operation of the striker, and returns automatically to its normal upright position immediately the striker has passed. There are two strikers attached to the car, one in a forward position and one at the rear. The first operation by the forward striker connects the stud with the main conductor and switches the current "on." The second operation by the rear striker switches the stud "off," and leaves it "dead." 311931) (842) ΤΟ Fig. 5. Section through Stud and Switch-Box (Kingsland System). In order to protect the switch-levers, and also to provide a channel or course for the strike-bars, a slot is formed alongside one of the tram rails by means of an outside or guard-rail. The slot thus formed at the surface of the road is ĝin. wide, and the tram rail together with the guard-rail forms a shallow conduit, the depth of the rail, along which the striker-bars can pass quite freely. Fig. 5 is a section through a stud and switch-box, showing the general arrange- ment of the outer or street-box, and the method of draining the same. There is a small bracket attached to the rail immediately over the switch-lever for the purpose of preventing the lever from being tampered with by means of a stick or anything passed down through the rail-slot. The striker-bars on the car are curved, so as to pass this bracket. D B C B B D الله... (845) Fig. 6. Switch-Commutator (Kingsland System); The electrical portion, or commutator, of the switch, is shown in Fig. 6. It consists of an outer case A, of insulating material, with two contact surfaces or plates D, D, to which the two conductors from the main and the stud respectively are connected. A centre revolving piece, C, consists of a body of insulating material, having embedded in it a metal ring connecting the three brush-holders B, B, B, carrying flexible copper contact brushes, which press against the inner circumference of the commutator box A. These three brushes are set at an angle of 120 deg. with each other, and the two contact plates D, D, are also set at the same angle. At every operation of the switch the centre portion is moved one-sixth of a revolution, so that the contact plates D, D, will be alternately connected and disconnected by 732 SECTION IX. two of the contact brushes. This will affect the alternate connection and dis- connection of the stud with the main cable. To avoid sparking within the switch itself, the distance between the front and rear striker bars is made slightly greater than the actual length of the skate. By this arrangement a stud is always in circuit before the skate actually touches it, and is not cut out of circuit until after the skate has left it. RAIL RAIL ST MAIN (844) STUD 28 730 с $2 Fig. 7. Arrangement of the Conductors (Kingsland System). For giving the requisite motion to the commutator, there is in the interior of the switch a double ratchet-wheel with teeth sloping in opposite directions. There are six of these teeth in each set, and each operation of the switch consists in moving the ratchet one step or tooth in either direction. This ratchet is directly connected to the commutator. The ratchet is operated from the switch lever by means of two pawls. The first striker bar on the car strikes the switch lever, and 8 29 ... 29/ STUD 28 302 +30 28 27 38 53 S³ (O) 28 STUD 730 B & 1 29 -28 27 (845) 9 Figs. 8 and 9. Details of Kingsland System. 27 1 moves the ratchet wheel the required distance, thereby putting the stud in circuit. After the striker bar has passed, the switch lever returns to its normal vertical position, ready for the operation of the second striker bar, which cuts out the stud. The return of the lever and pawls to their normal vertical position is accom- plished by means of an application of the principle of the screw. This is shown in Figs. 8 and 9. The three pieces, 27, 28, and 29, are shown in Fig. 9. The outside piece 27 SURFACE AND CONDUIT SYSTEMS. 733 is fixed to, and moves with, the spindle. The three curved ratchet-like teeth which it carries on one face are portions of a screw thread, and they engage with the corresponding teeth, on one face of the central piece 28. On the other face of 28 are similar teeth, but with the screw thread cut in the opposite direction, and these teeth engage with corresponding ones on the inner face of the piece 29. This latter piece, it will be observed, has three projections or lugs, 30, and these three lugs fit into corresponding grooves in the surrounding case. While the piece 27 turns with the spindle in either direction, the pieces 28 and 29 are free to move longitudinally along the spindle; but the piece 29 is prevented from revolving by the lugs, 30. 13 + UH 2. T ་ 10 10. TAMAA 11 12 (846) Fig. 10. Details of Striker (Kingsland System). By this arrangement, whichever way the spindle and screw clutch 27 is turned, a longitudinal motion will be imparted to 29 by the action of the screw threads on the intermediate piece 28. This motion is resisted by a spring, so that when the lever is released the force of the spring restores it to its normal position. At the completion of each movement of the commutator it is locked in position by means of a catch. The construction and mounting of the striker is shown in Fig. 10. It is carried by the axle-box, in order that it may be unaffected by the rise and fall of the car itself. An arm marked 2 is hinged below the axle box, so as to bring the striker in front of the wheel, and at the same time to permit of its accom- modating itself to curves on the line. At the end of this arm the striker 1 is attached by means of a special spring knuckle-joint, 9, 11, and passes straight down into the rail-slot. The "Paul" Surface Contact System. (FIGS. 11 to 13, pages 734 and 735.) The Paul sectional conductor system (formerly known as the Schuckert system, as Mr. G. Paul originally developed it for that firm) necessitates the installation of a row of contact studs in the centre of the track at distances depending upon the length of the cars (generally about 8 ft. or 10 ft. in the straight, or somewhat less in curves). These studs contain no moving parts, but consist simply of a block of hard granite, in which the hard steel contact piece is inserted. Each contact stud is connected with a separate contact switch by a cable. These switches are assembled together, in groups of about 30, in a cast-iron distribution box, which is sunk in the ground at the edge of the pavement, or in any other suitable position in the street. The distribution box is provided with a double cover and oil seal, which on the one hand permits the inspection of the switches at any time whilst the system is working, and on the other hand, prevents any dirt or moisture from entering the box. A section through one of these boxes is shown in Fig. 11. 734 SECTION IX. T In the distribution box the switches are arranged on a sort of switchboard, which is carried all round the box. Each switch is complete in itself, and arranged to clip into spring contacts so that it can easily be put into, or taken out of, 10 (1104) Mr 3 (1105) Fig. 11. Section through "Paul" Surface Contact Box. EC B J A a I d' Fig. 12. Switch, "Paul" Surface Contact System. the circuit, without making any wire connections. Each switch consists of four parallel electro-magnets united at the back, and so arranged that their centres form a rectangle. Two cores diagonally opposite one another are wound with the SURFACE AND CONDUIT SYSTEMS. 1386 735 RAIL RETURN PROJECTION OF STUD- ABOUT {"ABOVE ROAD LEVEL. RAIL RETURN AUTOMATIC EXCESS CURRENT CUT OUT (847) A HUNTS INTERCONNECTED WITH C. AND WITH SECOND GROUP PRE- -CEDING A (NOT SHOWN) MAIN SWITCH DRAW OFF RAW ON 》TO SAFETY DEVICES DRAW OFF. MOTOR B SKATE -DRAW ON kan diye kadar men de MAGNETO GENERATOR In C ĮSHUNTS INTERÇONNEC WITH A AND WITH GROUP DIRECTLY FOLLOWING D (NOT SHOWN) DRAW OFF ON 100 VECTED STUD D SHUNTS INTERCONNECTED with 8. ALSO WITH NEXT But one group. MAIN SWITCH DRAW OFF DRAW ON TO NEXT BUT ONE DRAW ON COIL TO NEXT BUT ONE DRAW OFF COIL IO NEXT DRAW ON COIL FOREXT DRAW OFF COIL Fig. 13. The "Paul" Surface Contact System. Coil Interlocking shown of two Sets of Shunts, one by full and one by broken line. ! 736 SECTION IX, pull-on coils, and the other two with the pull-off coils. The armature is, therefore, switched in and out electro-magnetically, and with the same force for either direction, see Fig. 12. All the coils of the apparatus are shunt-wound. The method of operation is as follows:-The current collector of the car bridges over the distances between three contact studs, and current flows through the stud to the shunt-winding of the switch, energising the pull-on coils, whereupon the armature is brought into the contact position. The shunt current, after leaving the two pull-on coils, is divided and flows at the same time to the pull-off coils of the second preceding, and second succeeding, switches, short-circuiting their pull-on coils, and cutting out the second preceding switch, and locking the second succeeding switch. The cycle of operations described is repeated each time the skate comes into contact with a stud. In Fig. 13 it will be seen that the car is receiving current from studs B and C. Besides this main current a shunt current is flowing through the draw-on coils, and also through the draw-off coils of the two switches on either side of B and C. Suppose the car is moving towards the right, i.e., towards stud D, as shown in Fig. 13, draw-off coil D is excited (from draw-on coil B), and is holding switch D open and short-circuiting its draw-on coil, through which, however, there is no current flowing. When the skate touches stud D, which it does before leaving stud B, the current flows through the short circuit, and also through draw-off coil B, short-circuiting draw-on coil B, and opening the switch. When the skate leaves stud B it breaks the current flowing through draw-on coil B, and consequently interrupts the current in draw-off coil D. This opens the short circuit on draw-on coil D, the switch is closed, and the stud connected to the main feeder. The cycle of operations is precisely similar, should the car travel in the opposite direction. The current collector consists of a linked chain, which is suspended beneath the car by a number of spiral springs arranged at equal distances from each other; the chain is also held by side adjustments which regulate its tension. If the current collector fails to make contact, or the circuit is cut-off for a moment at the power station, a special arrangement is devised whereby the car motors are connected as generators in such a manner as to excite the contact studs even when the car is moving at very low speed. When the car is standing, a small exciting dynamo inside the car is used to pick up the starting current. This system is claimed to provide absolute safety against live studs by employing a positive acting shunt-switch mechanism in connection with short- circuiting devices on the car and circuit-breaker on the line. The wear on the switches is stated to be negligible, as the apparatus works sparklessly. The "Paul" system is owned by Messrs. Witting, Eborall and Co., Limited. The "G. B." Surface-Contact System. (FIGS. 14 and 15, page 737.) This system of current distribution for traction purposes consists of a cable laid at a depth of about 12 in. below the track level, inside a glazed 5-in. stoneware pipe, the lengths forming which are connected together by a bituminous joint. The pipe, or conduit, is completely embedded in concrete. At the points where studs are located between the track rails, the conduit length is made with a box to contain the vertical stem of the stud, and is provided at these same points with an insulator on which the cable is carried. The insulator is mounted horizontally on a galvanised steel pin which emerges through the conduit wall on one side; the ends of the pins, which thus project outside the conduit, are joined together by a galvanised iron strip connected at intervals to the track rails, this ensuring the earthing of the system. The studs are with cast-iron heads, 24 in. by 10 in., which fit in recesses cut in the ordinary granite setts of the track, their top surface thus being level with the paving. The vertical part of the stud, the stem, is fork- shaped at the lower end and lined with brass; the fork contains the only moving part in connection with the electrical equipment of the track. It consists of à piece of galvanised iron, protected with copper, suspended by means of an insulated phosphor-bronze spring from the top of the fork, its action being limited by a brass pin, which fits in a slot, and is riveted in the jaws of the fork. A carbon contact block is provided at the lower end of the stem. The moving part is connected by copper leads to the main portion of the stud. The system acts as follows: When the magnet on the car passes over a stud, the moving part of the latter is magnetically attracted towards the cable, the carbon block comes in contact with the cable, and current is collected by the car (Fig. 14). When the SURFACE AND CONDUIT SYSTEMS. 737 car has run on, the spring in the stem above referred to withdraws the carbon from contact with the cable, and the stud is left dead (Fig. 15). Exhaustive experiments made with the springs, during which they were sub- mitted to the same number of extensions as would occur in a stud in a two-minutes service over a period of twenty years, have revealed no alteration in their elasticity. They are under no shock when in service, and as they are of phosphor- bronze, they are not liable to rust. The magnet is suspended rigidly from the car; the coils and the battery are so connected that when the motors are taking current, the current when small assists the battery in exciting the magnet, and when large also re-charges the battery. No special arrangements have to be made for battery charging. The collector consists of an iron chain with long specially. formed links. Each link is spring suspended, and one part of it projects into the pole of the magnet. When the collecting chain passes over a stud, the magnetic attraction causes the links immediately above it to move down into contact with it. 14 15 G (1103) ni 10 D CAST IRON GRANITE CONCRÉTE - Figs. 14 and 15. The "G. B." Surface-Contact System. The magnet is mounted about 2 in. above the road level. All ordinary cars can easily be adapted to the system. They can also be equipped both for this and for the overhead trolley system, and no stoppage is necessary for the change over. The working has been fully tested by the "G. B." Surface-Contact Company under service conditions with excellent results; the system is comparatively cheap in first cost, and economical in operation. This system is in operation on the Lincoln Corporation Tramways, the length of which is 12 mile, 1 mile being double and half a mile single track. The studs are fixed at 9 ft. centres throughout. The stud-heads measure 10 in. by 2½ in., and the conduit is 5 in. inside diameter. The depth of underside of conduit from rail level is 16 in. The galvanised iron wire conductor cable in the conduit is 14 in. in diameter. The average leakage test on line (just over three miles) is 0.3 amperes at 500 volts. The energy used to excite the collecting magnet, 11 amperes at 18 volts, at an average car speed of 8 miles per hour, works out at 11 x 18 8 × 1000 of 20 miles per hour, as this speed collection is absolutely continuous. Higher speeds are not obtainable from the motors, but presumably the limit of continuous collection has not been reached at 20 miles per hour. = 0.0247 units per car mile. Cars have been run at a measured speed The Lorain Surface-Contact System. This system is owned by the Lorain Steel Company, of Lorain (Ohio), and has been adopted by the Wolverhampton Municipal Electric Tramways. In this system, the underground cables lead to a brass lug fitted in an insulating socket at BB 738 SECTION IX. b. the lower part of a hollow granite block, and directly beneath an insulating- contact cup and an outside surface-plate. Above the lug connected to the supply cables is fitted a brass terminal moulded in the contact cup, and connected itself by a folded copper strip and a soft-iron plate to a carbon disc. The latter forms the live, movable, contact disc which normally rests on the copper strip at the bottom of the cup. The second brass terminal is moulded in the top part, or cover, of the insulating cup, and is connected direct below to a second, fixed, carbon disc. When the electro-magnets, carried underneath the car on both sides of a skate which slides over the surface-plate, pass over a stud, the soft-iron plate fitted under the movable carbon disc acts as an armature, and on rising brings the two carbon contacts together; the electric eírcuit is thus closed, the current being collected by the skate. When the car has moved on, the lower carbon disc drops by gravity with the soft-iron plate. OPEN Excavation Cement Granite paving laid Creosoted blocks Stoneware pipe That it is possible to successfully operate conduit electric roads there is no doubt. But, as compared to the overhead trolley system, there are several disadvantages. The first and greatest of these, and the one which more than all others has prevented general adoption, is the very heavy initial capital Table 3.-Approximate Cost of Conduit with Double Conductor per Single Mile of Track, as Proposed in England. Slot under Rail. (Waller and Manville.) ·· ·· .. General Remarks. ·· CONDUITS. Steel girder tramway rails . Wrought-iron fishplates Bolts and nuts Tie-bars Steel slot rails Wrought-iron fishplates Bolts and nuts Intermediate yokes Joint yokes ·· Hatch covers Bent roof plates Connecting plates Bolts and nuts for all yokes and connecting plates Labour, laying permanent way Insulation and suspension .. Conductors Royalty and various Feeders laid Bonding ·· .. ·· ·· ·· •• ·· .. ·· • •• .. •• ·· .. • •• ·· • ·· ·· ·· ·· .. ·· ·· ·· • .. .. ·· ·· • • • ·· £ s. d. 217 6 0 645 0 0 1760 0 0 52 16 0 88 0 0 324 2 2 ·· 6 18 2 3 15 0 26 12 10 403 12 7 10 4 6 8 0 0 282 17 1 102 2 10 Total 10,484 12 10 expenditure which is very difficult to determine, except when all the specia conditions of each individual case are known. In towns where water and gas pipes, sewers and drains, telephone, telegraph, and electric-light wires are crowded under the paving, a conduit may cost up to any amount. The writer has in mind one instance in America, where, to enable a conduit to be laid, the whole sewerage system of a town had to be practically relaid. Even supposing fairly favourable conditions, Tables 3, 4, and 6 show the probable minimum sum for which a conduit line could be constructed in England or America. 58.2 10 583 17 2 39 5 8 60 0 0 352 0 0 200 0 0 120 0 0 200 0 0 4800 0 0 140 0 0 Another great disadvantage of the conduit, as compared with the overhead system, lies in the fact that, should anything go wrong with the conductors, much more trouble is found in setting it right, the delay caused is greater, and the cost of repairs much heavier. SURFACE AND CONDUIT SYSTEMS. 739* Leakage on conduit lines is much greater and more difficult to prevent, and insulation troubles are very much more likely to arise. The conductors, being comparatively close to the roadway, are much more easily damaged; and inspection being difficult, small troubles are not detected until they have developed and caused serious breakdowns. One advantage a conduit possesses. viz., that while a double-trolley wire system is most undesirable, and the rails must be used for the return circuit, this is not true with a conduit system, and, therefore, all possible trouble from electrolysis is averted. With the present perfected method of bonding and return feeders, this last consideration is of no great importance. In the design of a conduit three special points must be borne in mind: 1. The conduit must be mechanically very strong, so as to maintain an equal width of slot at all times, and under all conditions. 2. All All parts of the conduit must be easily accessible, and insulators and con- ductors must be able to be inspected and renewed without taking up the roadway. The insulation must be of the very best. 3. The conduit should be designed to make the necessary excavation as shallow as possible. In doing this, however, care must be taken to allow the most ample drainage facilities, and manholes should be provided at frequent intervals to allow of cleaning the conduits. Table 4.-Total Cost per Mile of Single Track, Open-Conduit System, Second Avenue Railroad Company. (Compiled from the Diary of W. C. Gotshall.) Labour, digging trough, removing old track, repairing concrete, removing excess dirt, hauling all track-work, £1 10s. 11d. per linear foot Insulators, 5s. 8d. each Iron-work, excluding yokes, 7s. 4d. per linear foot Cost of iron, 224.7 tons at £5 48. Concrete, cubic yard per linear foot, 8s. 2d. per yard Haulage on yokes and iron-work .. Hard rain Condition of Weather During Test. "" "" Fairly dry day "" 93 "" ·· " "" "" It should be borne in mind that the items of cost of special track-work, feeder-ducts, paving, bonds, sewer connections, and temporary track, are not included in this estimate. The cost of concrete is put down at 8s. 2d. per cubic yard. This low cost is evidently an error of compilation. Other information in the pamphlet seems to prove that this cost should be from two and a-half to three times this amount. Table 5.-Insulation Resistance of Conductors in Conduit Line at Washington. "" ·· "" "" Very dry and cold 33 ·· ·· ·· .. Total, without paving The above total does not include cost of feeder-duct. Number of Circuit Tested. 1231NM INM ·· 1 ·· 2 ·· 3 ·· .. 8,300 8,000 5,200 ·· Insulation Resistance in Ohms of Positive Conductor. 19,500 18,100 10,900 36,800 29,100 27,600 .. 1,375 7 0 1,168 8 10 808 10 0 117 1 8 ..£11,841 17 1 .. .. ·· .. £ s. d. 8,173 0 0 199 9 7 Insulation Resistance in Ohms of Negative Conductor. 400 480 330 770 670 770 1250 830 910 • 740 SECTION IX. Table 6.—Estimated Cost of Single - Track Mile of Conduit Electric Tramways in England for Average Conditions. (December, 1900.) (A. N. Connett). Wheel rails, 90 lb., 141 tons per mile, at £7 Joints, 0.67 tons at £8 Slot rails, 66 lb., 105 tons at £8 Conductor rails, 28 lb., 44 tons at £8 Haulage, 290.67 tons at 4s. Bolts, Washers, keys, &c., 4.16 tons at £18.. Tie bars, 13.5 tons at £15 ·· ·· Feeder ducts Extras and contingencies .. ·· ·· ·· ** .. •• Insulators, complete with clip, 755 at 6s. 2d Cast yokes and insulator pit covers-yokes, 210 lb. each, spaced 3 ft. 6 in. centre to centre, 210 lb. by 1510 = 317,100 lb. =141.5 tons; insulator pit covers, 117 lb. each, 755 by 117-88,335 lb. =39 tons; total, 181.5 tons at £10 Haulage, 181.5 tons at 4s. Bonds ·· .. ·· ·· .. ·· Concrete for tube, 1 cement, 2 sand, 5 stone, 0.2 cubic yard, per 1 linear foot, 5280 by 0.2=1056 at 288. Concrete for paving, 1 cement, 3 sand, 6 stone, 0.10 yard, per I linear foot by 5280=528, 528 by £1 4s. Wood paving, 6373 square yards at 11s. Excavation, 2950 cubic yards at 5s... Sewer connections and manholes for same Platelaying, including average amount of special track work, 5280 at 3s. Temporary track (one track laid and repaved on side of street with turn-outs) at £1350 per mile of street, divided into two tracks for double track construction Special track work of cast steel construction, with hardened centres Obstructions (necessarily very indefinite). .. .. ·· .. 987 0 0 5 8 0 840 0 0 352 0 0 •• 74 18 0 202 10 0 : .. ** .. •• • .. .. 2184 8 0 58 2 0 277 8 0 232 16 0 1815 0 0 36 6 0 110 0 0 1478 8 0 633 12 0 3505 3 0 737 10 0 400 0 0 792 0 0 675 0 0 1128 0 0 1000·0 0 800 0 0 630 0 0 £16,493 13 0 According to Mr. Connett, where double conductors are used, it is always found that the insulation resistance of the negative conductor is far smaller than that of the positive, as shown in Table 5 of tests made by him on various sections of the Metropolitan Railway Company of Washington. It was found that if the leads were reversed the same phenomenon maintained. Deposit of moisture on the negative main is a quite common occurrence in conduits with bare copper strip for lighting work. On the Ninth Street line the insulators were never once cleaned during the first thirteen months of operation, and were necessarily dirty. Even under these conditions, the leak was too small to be worthy of notice. The leak across in clear weather is ampere, representing in 20 hours 3 kilowatt hours, which is produced for 12 lb. of coal, costing id. In very wet weather this leak will rise to 1 amperes ; but for 75 per cent. of the time the leak is easily maintained at the lower figure In August, the leak on the entire system of 22 miles was ampere. | SURFACE AND CONDUIT SYSTEMS. 741 Descriptions of Open-Conduit Systems. From the very inception of electric traction, inventors have been seeking to devise some method of doing away with the necessity of overhead wires. The first attempts were failures, electrically and mechanically, the trouble being that economy in the first cost was necessary to the promoters, and the conduits were much too shallow and badly drained. No shallow or cheap open-slot electrical conduit can ever be successful, in northern climates at least. Those who are most interested in electrical conduit construction admit that its first cost is such that it will be impossible for any except the great metropolitan roads to adopt it; for it must be remembered that the expensive feature of the cable system-the cable conduit itself-is joined to the most expensive feature of the electric system-the motors and power plant, thus making up a combined system far more expensive than either alone. The Siemens Conduit (Budapest). (FIG. 16, page 742.) Budapest was the first continental city to adopt a conduit system. The first line in this city was opened in 1889, and was designed and constructed by Messrs. Siemens and Halske of Berlin. At Budapest the channel is under one of the rails, and not in the centre of the road, as usual (Fig. 16). The conduit consists of cast- ings having flanges 18 centimetres (7 in.) placed every 1.2 metres (about 4 ft.), the space between forming a concrete conduit. The oval-shaped conduit has a clear width of 28 centimetres (11 in.), and a height of 33 centimetres (13 in.). The slot consists of two girder rails without inside flanges, and they are fastened to the conduit frame by wrought-iron angle pieces. The width of the slot is nominally 33 millimetres (15 in.). The total depth of the foundation below the rail top is 70 centimetres (27 in.). The conductors, both positive and negative, are made of angle-irons, secured by means of insulators fastened to the castings. They are sufficiently high above the bottom of the conduit, it is claimed, to be protected from the water collecting in the conduits, and are under cover, so that they cannot be harmed by anything falling through the slot. The water from the conduit is collected at the lowest points into settling boxes, from where it passes into sewers. The conductors are joined at intervals to feeders. The feeders are lead-covered armour-clad cables laid directly in the ground. The cost of track and conduit at Budapest per mile of single track was £7000 approximately, and of this track construction alone without conduit came to about £1500. As will be seen from the foregoing description, the circuit is double, and there is no return by the rails. Although the nominal width of the slot is 1 in., at points and crossings this width often exceeds 2 in. The pressure used on this line is 300 volts. The Waller-Manville Conduit. Messrs. Waller and Manville developed a system which permits of the con- ductor being put in and withdrawn from the conduit through the slot, thus obviating the necessity of breaking up the road when the conductor wants repairing or looking to. Its essential features are mechanical devices, permitting a flexible conductor to be used. The conductor being flexible, the supports can be placed at long intervals and in side openings to the conduit itself on large insulators. Removable covers are provided to the hatchways, giving access to the insu lators. In sharp curves, where it is necessary to attach the conductor to its support, freedom in the upward movement is allowed. A constant strain is main- tained upon the conductor by automatic appparatus at intervals. The collector is U-shaped, the conductor running in it. The collector lifts the conductor off the ordinary supports during its travel, and in the case of those supports to which the conductor is fixed, lifts the supports themselves. Berlin and Brussels. (FIGS. 17 and 18, page 743.) By the courtesy of the Union Company of Berlin (Thomson-Houston), we are enabled to give a fully-illustrated description of this conduit. It is a modified form of that designed by the General Electric Company of America, and laid in Lenox Avenue, New York. The chief difference consists in that, instead of having a special slot in the centre of the track, the conduit is built under the line of rails. Figs. 17 and 18 show how the conductors are suspended. These are steel of I section, and about 8 metres (26 ft.) in length. The yokes are cast iron, and are set on a concrete foundation 15 centimetres thick (about 6 in.), and 1.20 metres between centres (approximately 4 ft.). The width of the slot is 30 millimetres • 742 SECTION IX. Y Concrete Bons 3609.0 thick Vashis aure Set DO goog Fig. 16. The Siemens and Halske Conduit System. Ŀ SURFACE AND CONDUIT SYSTEMS. 743 (1.18 in.). On the slot side of the track two T rails are fixed to form the slot, and weigh 52 lb. per yard each. They are supported by the top of the yokes and bolted to them. The insulators are located between two yokes, and supported in a cast-iron box with a removable cover, which makes them accessible from the roadway. To 17 360.9.0. One 18 A i-600 .... Drainage to Sewer Figs. 17 and 18. The Berlin and Brussels Conduit Systems. prevent water getting to the insulators, they are protected by metal caps. The insulators are fixed in the cast-iron boxes in such a way that, after a couple of screws have been taken out, by giving the insulator half a turn, it can be removed. The drainage pits and manholes are put in every 40 metres (approximately 130 ft.), and connected to the drains. A trap is arranged so as not to allow water to flow back from the drains into the conduit, a pit being also provided to collect the mud. Third Avenue Main Line, New York. (FIGS. 19 to 25, pages 744 and 745.) Two types of electric conduit construction are employed: that for new con- struction, and that where the old cable conduit was to be retained. The chief features of the newer construction lie in the carrying of the rails upon a wooden 744 SECTION IX. 19 20 21 ---28 <24%*- - 2'9 % — — — x - 2'9 % — Ah lili_ Hi q- hale *418 -5- 70 -5'4- 5 Kan- hole 9 TH --294- · 5'- -2'4&- (564) Figs. 19 to 21. The Third Avenue Railway Conduit System, SURFACE AND CONDUIT SYSTEMS. 745 stringer, 5 in. wide by 6 in. high. This has been done to secure an easy riding track. The concrete is packed under and on the inside of this stringer, but not on the outside, where broken stone is used. This provides drainage and insures the dryness of the timber. The yokes are spaced 5 ft. apart, and are built up of three pieces riveted together, viz., a steel I-beam weighing 105 lb. and two cast-iron side pieces weighing 122 ĺb. each. The yokes rest on a continuous bed of 4 in. of concrete. The conduit between the yokes is of solid concrete. The wooden stringer is laid in 30-ft. lengths, and is of selected yellow pine, creosoted and planed to size. The slot rail is laid in 30-ft. lengths, is 7 in. high, and weighs 66 lb. per yard. The tie- 16 22 24 1/16" – 4:8/½' f I Beam 701bs per yard --+9:6~ -2:4% 23 (566) J Figs. 22 to 25. The Third Avenue Railway Conduit System. 225 rods between track rail and slot rail are spaced every 2 ft. 6 in., besides which there are the braces at every yoke, as illustrated. The track rail is laid in 60-ft. lengths, is 9 ft. high, and weighs 107 lb. per yard. It is of the Crimmins section, similar to that employed on the Metropolitan Street Railway. Insulator boxes are located every 15 ft. As shown in the diagram, they are hung on the slot rails, and can be slid either way, insuring facility in setting. When the structure is completed they are set in position. The conductor rail is of steel, "T" in section, and weighs 21 lb. per yard. In installing the conduit, a trench is first dug 35 in. deep, and the width of the road bed. The 4-in. concrete bed is then laid, after which all of the iron structure is erected complete before the concrete is filled in. In filling in the latter between the yokes, sheet-iron linings are used between them until the concrete is set. These linings, which are in two pieces, so that they can be slid through the slot, are held in position in the conduit by collapsible forms, which are also slipped through the slot and opened by a lever, pressing the lining in position against the yoke. Two of these are used between every yoke. The ducts for carrying the feeders are sometimes placed on the inside, between the tracks, and sometimes on the outside. A feeder vault is located every BB2 746 SECTION IX. ... 260 ft., and between each feeder vault there are two cleaning vaults. The manhole curbs of the cable vaults are kept small, viz., 20 in. by 20 in. Where the existing cable conduit is retained, a different type of construction has been adopted. New track rails have been laid, and provision made for installing conductors and insulators. The present height of the track rail is 7 in., and this height has been retained, as there is no change in the yokes. The rails weigh 104 lb. per yard, and are 7 in. deep. The original pulley carrying vaults, which are spaced every 35 ft., are undisturbed, and used for cleaning vaults. The feeder vaults are built under both tracks, and are 5 ft. wide and 24 ft. in. long inside, from one wall to the other. They are located every 400 ft. Siemens and Halske's Conduit at Berlin. (Figs. 26 to 29.) Figs. 26 to 29 show Messrs. Siemens and Halske's conduit at Berlin, which is very similar to the one installed at Budapest. The yokes are of cast iron, placed 49.2 in. apart. The conductors are of steel, T section, and are carried upon insulators fixed half way between the yokes. They are attached to the slot rails by small wrought-iron or cast-iron brackets, and are accessible through cast-iron hand-plates. The conduit is 13.4 in. wide and 17.7 in. deep. 26 Toma dun att dat ………………pe to a va qadar v 28 Section 48 0001 SECTION C. D 29 OS: 1:39 27 'Q SLCTION EF. To 589'σ 15 # 10 10 10 10 26 15 14 13 17 1 (099) Siemens and Halske System, Berlin. Figs. 26 to 29. SURFACE AND CONDUIT SYSTEMS. 747 Metropolitan Street Railway Company of New York. Fig. 30 shows the type of yoke adopted and the method employed for sup orting the insulators. It is very similar to that used by the Metropolitan I http 30 (851) • 00000 ·O.L Sul - .0.9 9.Dİ E -10.2. £6. admi12 (852) 31 :-$0,or 6"DRAIN PIPE Fig. 30 and 31, Metropolitan Street Railway Conduit 'System, New York. Street Railway of Washington, but the cross-section of the duct is more circular. It, however, differs considerably from the yokes used on the Lenox Avenue line. Fig. 31 shows a cross-section of straight track construction at manholes] 748 SECTION IX. Paris Conduit System. (Fies. 32 and 33.) The Paris conduit system is mainly of the side-slot type; but to avoid the difficulty experienced with such a system at points and crossings, at such places the slot is deflected to the centre of the track. Figs. 32 and 33 show the yokes used for the centre and side-slot respectively. £2 (854) INVI 1 "" Brussels 33 ·· •• New York Washington (later construction) Paris, centre slot side slot : 1440 K SECTION AT YOKE • 1440- [UIT --150- Fig. 32. Centre Slot Conduit; Paris, Lyons, Bordeaux, Nice. Fig. 33. Side-Slot Conduit, Paris. •• ㅏ ​·· YALL The side-slot yokes weigh 210 lb. each, and are spaced 3 ft. 6 in. apart. The following shows a comparison of the weight of the Paris construction with that of other lines:- -Ido· SECTION AT YOKE -780- • • • .. • •• ·152-*· ·· -176 ·· --200· Pounds per Foot of Track. 8888* 83 60 68 086-· 60 44 SURFACE AND CONDUIT SYSTEMS. 749 London County Council Conduit System. (FIGS. 34 to 56, pages 750 to 756.) The form of yoke (Fig. 34) is the design of Mr. A. N. Connett, the chief engineer of Messrs. J. G. White and Co., Limited. In general appearance, this yoke is not unlike that used for the side-slot conduit at Paris. Figs. 35 to 37 are a plan and a section of a single track. Fig. 38 illustrates an extended yoke. The yokes are spaced at intervals of 3 ft. 9 in. centres. The slot bars are Z bars weighing 61.5 lb. per yard. No fishplates are used in fixing these rails together; the ends rest directly on the yoke, and a true line is secured by means of a tie-bar pulling a large washer, 5 in. by 2 in. by in., hard up against the slot rail webs inside, the tie-bar passing through a half-hole in each rail end. Slot rail and track rail tie-bars are in the same vertical plane. One end of each bar is rigidly fixed to the yoke casting, thus securing perfect control of either track or slot-rail gauge. The chemical composition of the track rails allows a percentage of carbon from 0.4 to 0.5; manganese, from 0.7 to 1, sulphur and phosphorus, 0.08 (not more) and silicon 0.09 (not more). The drop tests required for the finished track rail are as follow: Track rails Slot rails .. Conductor bars Tie bars First blow Second blow The rail is placed on supports 3 ft. 6 in. apart, and the falling weight used is 1 ton. The tensile tests specified are indicated in the following Table : Table 7.—Tests of Track Material. ·· "" ·· ·· .. ·· ·· • · Tensile Strength in Tons per Square Inch. 38 35 20 30 Not Less Not More than than ·· • "" Drop. 7 ft. 20 ft. ·· 47 40 25 35 ·· .. The cast iron is specified to be cast from the best grey metal, and test-bars 2 in. by 1 in. section, cast at the same time as the metal is run, must bear a load of 30 cwt. at centre of 3 ft. span, and give a deflection or not less than 0.3 in. All castings have to be coated with preservative compound. The weight of the principal castings is as follows:- lb. Yokes (ordinary) 153 Cantilever yoke 124 184 258 288 .. ·· ·· "" "" Single insulator road-box frame and cover Double Sump pit frame and cover Plough hatch Insulator armouring clips and washers (per set) 9/11 Under the Board of Trade regulations, the line is divided into half-mile circuits or sections, each having its separate feeder. At the point of intersection there is a break in the conductor bars of about 2 ft., and the terminals are led to a switchboard erected in an enclosed support on the footpath. The switches enable the two circuits to be joined up in the event of any breakdown in the main leads from the power station to any one circuit. .. Per Cent. ·· Elongation not Less than 19000000 15 18 26 Deflection. in. to in. 2 in. to 3 in. .. ·· ·· .. Length be- tween Test Points in Inches. • .. ·· ·· 2 2 10 ·· ·· 144 13 750 SECTION IX. J 35 bat da se me m (856) 2 41 Đ -6 81 Gaugs rail % above hear 10-7-71 18 2 சூ SECTION AT YOKE rail. M fe z G H 34 36 部 ​VOĽNE 2 41 1- 4 81 Gauge ม เ R · ·-· -----} 14* ----2* ? i SECTION BETWEEN YOKES 2% K2% 2 41 منکر المال 12%- Asylater S HORIZONTAL SECTION A B PLAN OF SIngle track 'LONGITUDINAL SECTION MANHOLE Figs. 34 to 37. Conduit for London County Council (South London) Tramways. 37 -477 10% SURFACE AND CONDUIT SYSTEMS. 751 8 web 38 3100 (1106) DE 39 40 2 istot 2*4% 1300 (057 4:92 & " landed 704 8 Flow Slot rail above head of wheel rail. 8½ Track Gage 2.47 •· 6 ···· SECTION' C.D. 7 # London County Council Tramways. Fig. 38. Section of Extended Yoke. Fig. 39. Tramways Conduit. Fig. 40. Tramways Insulator. } 9% ہے۔ 400 752 SECTION IX. Figs. 39 and 40 are a section of the conduit, showing the conductor-bar insulators. The general arrangement of a section insulator is illustrated' in Figs. 41 to 43. The drainage system is shown by Figs. 44 to 46. At about 180-ft. intervals, 12-in. pipes have been laid under the permanent way at right angles to the rails, on a gradient of 1 in 10. These communicate with a sump, 3 ft. by 2 ft., formed at the side of the track, with an overflow pipe into the drains. The sump has a man- hole cover at the street level. 41 3.6 9:8 * 4:8% GAUGE -- 5.32-- 5:32 (1107) 134 2:56 2:56 0002 PLAN SECTION SECTION THROUGH A-B ---3.9 -*** 3.9 42 +-4:82 GAUGE----→→ MOROTROS PLAN ---- doplatin 88 1:8 Figs. 41 to 43. Arrangement of Section Insulator. The depth of metal at the bottom of the yoke is 6 in. The concrete foundation for the track rails is 8 in. thick. 3:3" ÁRATSTYD SMOON DEUXCOM * 1:6 και -3.0° SECTION THRO' C-D 43 The total depth from top of slot rails to bottom of yoke is 30 in., and the width is 26 in. The conduit chamber has a width of 14 in., and a depth of 17 in., below the bottom of the slot rails, in the centre. The contact face of the conductor bars is 34 in. wide, and they are supported 12 in. below the top of the slot rail, or 10 in. from the bottom of conduit, measuring to the centre of the conductor bar. The bars are placed 6 in. apart. The conductors bars have a conductivity of nearly 15 per cent. of Matthiessen's standard for pure copper. The insulators, shown in Figs. 39 and 40, are attached to the base of the slot rails. It will be seen that the conductor bar is fastened by means of a clip to SURFACE AND CONDUIT SYSTEMS. 1383 753 A (858) --- 44 MILLI 12 diam. Pipe Slope in 10 SECTION THRO˚A. A 45 PLAN. C.L C.L Yoke GE 10- · 10″- 3.0. لد سكسار 10 46 Figs. 44 to 46. Conduit for London County Council (South London) Tramways, II SECTION THRO′ 8.B 754 IX. SECTION a vertical steel bar, of which the upper end is corrugated, and cemented into a porcelain insulator. The insulator is cemented into a cast-iron box, which bolts on to the slot rail. .50 Figs. 47 to 50 show the method of supporting the plough from the truck framing, the ends of the two side-frames of one of the trucks having extensions formed for this purpose. This is built up of Z irons, bolted at each end to a casting attached to the truck, a projection on the top of the plough resting on the bottom 48 (850) A c d de vida de conta 5'9 8 5'9" T 1'9' 47 SECTION RA verde de de de pe ma ZAngles 8.3-24 Head of St, OA Enlarged SECTION BI Hod SECTION E.3 49 Figs. 47 to 50. London County Council Tramways; Plough and Truck Framing. Free Find flange of the Z irons. Small angle-iron prevents any tendency of the plough to lift. In the centre the bottom flange of the Z irons is cut away for a distance of 8 in., and replaced by a hinged flap, held in position by the bolt A (Fig. 50). This enables the plough to be removed from the car when required. The ends of the carrier slides have been left open, so that in the event of the plough taking the wrong path when going through points, it will eventually drop clear of the car altogether, thus avoiding strains and damage. Figs. 51 to 53 show the plough. The head is made of gun-metal, with a groove to take the two mild-steel plates which, bolted together, form the shank which passes through the slot. The conductors from the plough-shoes pass through grooves in the shank and head. The conductors are copper strip, insulated with rubber and tape, and vulcanised. The bottom part of the plough is of maple, prepared by immersion in a bath of special insulating compound. The plough-shoes are of soft cast iron. Each shoe is secured by a moveable link, and there is a powerful flat spring acting in an outward direction. The running distance between the shoes is 6 in., and the shoes rub against the rails with a pressure of about 6 lb. When free of the conductor rails, the shoes do not spread out to more than 7 in. apart. The fuses are of the flexible type, arranged to blow at about 150 amperes. When the complete plough is assembled, it is immersed in the special insulating compound for several hours. Figs. 54 to 56 show the method employed for moving the track-rail and slot- rail points. SURFACE AND CONDUIT SYSTEMS. 755 - 7"FROZE (860) 40%W1 51 6* H. *-... 1.75% --- 118 › qdo de pe mer du c kri a ta de cuadras d à des de la pre me v ………………. Ti" 53 --- 54 - de pe mama p 37 52 4' ----- ·q 18. 1'2 +2536° ------52- O OF ·89- Figs. 51 to 53. London County Council Tramcars; Details of Plough. 756 SECTION IX. 56 SECTION ON LINE C.D. > P.C. 100.0 °R. 66 PC_26.0.R. (1108) SECTION ON LINE A. 8. BG and s DI! ·D P.C.100 O`R Outline of Mechanism. Pit below surface shown by hatched edging ECTO TO RODOL RODOODIN 10 1 10 ||||||||||||| DODONDYEX- L Figs. 54 to 56, London County Council Tramways: Track-Rail and Slot-Rail Points, 54 55 Letve į 2. SECTION X. GENERAL TRACTION DATA, ROLLING STOCK, AND MOTORS. ,, SECTION X. GENERAL TRACTION DATA, ROLLING STOCK, AND MOTORS. GENERAL Definitions, &c. Velocity is the rate of change of position with respect to time, and is measured by the distance passed over in a given time. 8 For uniform velocity, v= or s=vt, where s is the space passed over in time t. • TRACTION DATA. t vm = If the velocity varies uniformly, and is v₁ at time t₁, and v2 at time t2, then the mean velocity vr + v2 2 The general expression for velocity at any time, however it may vary from d s time to time, is v d t • Hence S - Acceleration is rate of change of speed with respect to time, and is ex- d v pressed as dt d v dt If the velocity varies uniformly with respect to time, then v=kt where is a constant. a, the acceleration, where t = t2- t1. tą Sv - a = vdt. ย t Thus, if at time t₁ velocity = v₁, and at time to velocity is v2, then acceleration during time tɔ - t1 Hence acceleration is constant, and = k But for uniformly varying velocity. 8 ا. dkt d t 12 V1 V2 21 tą - t1 t where t = time taken for velocity to change from v₁ to v2. Hence for uniform acceleration, P *** V2 t da k. v1. vit m 2 1 *760 SECTION X. ! :or * Combining these two equations, we have 2 a 8 022 - vrs 2 t v22 — v2 t 8 = 2 a Also, since we have Substituting this value of v2 in equation 8 V2 — V1 t ·· =α, v2 = v1 + a t. If the body starts from rest, v₁ = zero and Ꭶ = 1 a 12. t2 • Acceleration is generally measured either in feet per second per second, or in miles per hour per second. An acceleration of one foot per second per second means that in one second the speed increases by one foot per second. The acceleration due to gravity, usually denoted by g, varies slightly with the latitude. The following are a few values :— ·· (2 v₁ + a t) t 2 = ₁₁t + 1 at². $ = (02 + v₁) E 2 England Philadelphia Paris When the only force acting upon a body is its weight, i.e., when it is falling freely, the acceleration is g. Hence, if a body is dropped, and falls s feet in t seconds, then the relation between 8 and t is given by equation: Also we know that .. 8 = Acceleration = 11912. .. 32.20 ft. per second per second. 32.16,, 32.18 and the speed attained will be v = gt. Since acceleration is the differential coefficient of speed with respect to time, and speed is the differential coefficient of space with respect to the same quantity, it follows that acceleration is the second differential coefficient of space with respect to time. = ds v = dt d d v d t (1/4) dt Force and Work.-A force is said to do work when it moves its point of application through any distance in its own direction, and the work done is measured as the product of the force into the distance through which it moves. E = ƒ F > "" "" If F is not constant, then for a short distance ds we have dE = Fds. or for the whole distance, Fds. 99 *** When a force does work on a body it gives it an amount of energy equal to the work done. Hence, if there is a constant force Facting through a distance s, the energy E developed will be given by equation E=FS. ord 8 = vdt. "" d2 s d t2 "" ROLLING STOCK AND MOTORS. 761 or Hence But where M = the mass of the body From this we have Hence or at any instant the rate of change of energy with respect to time is the product. of force into velocity. The kinetic energy of a body, or energy due to its velocity v is expressed by and E dt dE= Født, Fv, d E d t Hence the mass of a body M Substituting in equation (1), since body started from rest. Hence E = dE d v - d E dt M M » where W is the weight of the body. W g M v2 2 where α = acceleration. In practical use, M is expressed in terms of the weight, and "a" in increments. of velocity (either miles per hour or feet or metres per second). We have seen that M v d v dt F= M F8= d v d t = Ma (1) Hence, with a body of mass M and weight W, the acceleration g produced when no other force besides gravity is acting, is g = W M Fv F = M × α, or a = F = M α W F= ******** a, or a g When a body of mass M moves with velocity v, it has a certain amount of energy. This energy is equal to the amount of work done in bringing the body to this speed from rest. If F is the force acting, and 8 is the distance traversed before speed v is attained. then work done = F's. But o+oot= 8=0+00 2 M v2 2 W v2 29 • М' Μυ t 2/2 Mox ut. Μυ t F M t FXg W 762 SECTION X. 1 61 60 < LOO 3 4 6 7 8 9 10 11 12 B 14 15 20 25 30 35 40 45 50 55 60 88 176 264 352 440 528 616 704 792 880 968 1056 1144 1232 1320 1760 2200 2640 3080 3520 3960 4400 4840 5280 Table 1.-Conversion Table for Miles per Hour, Feet per Second, &c. 1.47 2.93 4.40 5.87 7.33 8.80 10.27 11.73 13.20 14.67 16.13 17.60 19.07 20.53 22.00 29.33 36.67 44.00 51.33 58.67 66.00 73.33 80.67 88.00 0.4469 0.8938 1.3407 1.7876 2.2345 2.6814 3.1283 3.5752 4.0221 4.4630 4 915 5.3628 5.8097 6.2566 6,7035 8.9380 11.1725 13.4070 15.6415 17.8760 20.1105 22.3450 24.5795 26.8140 2.237 4.474 6.711 8.948 11.185 13.422 15.659 17.896 20.133 22.370 24.607 26.844 29.081 31.319 33.556 44.741 55.926 67.111 78.296 89.482 100.667 111.862 123.037 134.222 196.86 393.72 590.58 787.44 984.30 1181.16 1378.02 1574.88 1771.74 1968.60 2165.46 2362.32 2559.18 2756.04 2952.90 3937.20 4921.50 5905.80 6890.10 7874.40 8858.70 9843.00 10827.30 11811.60 3.281 6.562 9.843 13.120 16.400 19.680 22.96 26.24 29.52 32.81 36.09 39.37 42.65 45.93 49.21 65.62 82.02 98.43 114.80 131.20 147.60 164.00 180.40 196.80 .01136 .02273 .03409 .04545 .05682 .06818 .07954 .09091 .10227 .11364 .12500 .13636 .14773 .15909 .17045 .22727 .28409 .34091 .39773 .45454 .51136 .56818 .62500 .68182 .00508 .01016 .01524 .02032 .02540 .03048 .03556 .01064 .04572 .05080 .05588 .06096 .06604 .07112 .07620 .10160 .12700 .15240 .17780 .20320 .22860. .25400 .27940 .30480 Feet Per Second to Miles per Hour. 0.6818 1.3636 2.0454 2.7272 3.4091 4.0909 4.7727 5.4545 6.1363 6.8181 7.4999 8.1817 8.8635 9.5453 10.2271 13.6362 17.0452 20.4543 23.9633 27.2724 30.7814 34.0905 37.5995 40.9086 Feet Per Second to Metres per Second. 0.3048 0.6096 0.9144 1.2192 1.5240 1.8288 2.1336 2.4384 2.7432 3.0480 3.3529 3.6576 3.9624 4.2672 4.5720 6.0960 7.6200 9.1440 10.6680 12.1920 13.7160 15.2400 16.7640 18.2880 1 ROLLING STOCK AND STOCK AND MOTORS. 763 The acceleration due to gravity is generally expressed in feet per second per second, and its value is then 32.2 (in England). If expressed in miles per hour per second its value is 32.2 × 0.682. Hence in equation, and ton If W = Then Hence α = FX g 20 w = 2240 W, a = Fx gx .682 W F = force in pounds. W = weight of body in pounds. weight of body in tons of 2240 lb. each. F = ft. per = 102.1 lb. F× g × .682 2240 W · = 0.00979 miles per hour per second. wx a .00979 second per F W second. miles per hour per second. miles per hour or 102.1 x Wα. F W = 102.1 a. Thus to obtain an acceleration of 1 mile per hour per second, the pull per F (四​) per second. To obtain an acceleration of 1 metre per second per second, the pull per ton = 45.63 lb. In the case of any train in motion, there are a series of forces acting upon it. Each force considered separately will tend to produce a certain acceleration, the magnitude of which will depend upon the weight of the train and the magnitude of the force. The acceleration will be positive or negative, according to the direction of the force tending to produce it. The algebraical sum (i.e., taking positive and negative signs into account) of these accelerations will be the resultant acceleration. Thus, if we have a series of forces acting, F', F". F"", &c., they will tend to pro- duce on a mass M accelerations which we may call a', a", a”” respectively, i.e., F' = Ma' F" = Ma" F"" = Ma"!! Hence ΣFM Za, or resultant force = mass X resultant acceleration. = Hence the acceleration of any train depends on the resultant of all the forces acting upon it. Approximate Calculation of the Motion of Trains. (FIG. 1, page 766. The general problem to be solved in the preliminary investigation of an electric railway is what size of motor will best suit the conditions of the service which is required. This problem is usually solved by "trial and error" methods; and though other, and perhaps more scientific, means can be employed, they have little, if any, practical advantage over the first. Thus the usual practice is to investigate several motors of different sizes, and see which one will best fulfil the requirements of the case under consideration. As a general rule, the distance between stopping-places is fixed, the weight of the train can be approximated to without any sensible error, and a certain schedule time of running is required, allowing for stops at stations of a given duration. 764 SECTION X. The problem, then, is to find a motor equipment which will do the necessary work in the prescribed time. In many cases a definite rate of acceleration is tentatively agreed upon, the rate for frequent stoppages ranging from one mile per hour per second upwards. For the purposes of preliminary calculation with continuous-current motors, operating with series-parallel control, the acceleration is generally assumed constant up to the moment when the motors are in full parallel, with all resistance cut out; and though this is not what actually happens, the results obtained from the assumption are quite accurate enough for most purposes. In other words, the motors are assumed to exert a uniform tractive effort at a steadily-increasing speed. For any given rate of uniform acceleration, the tractive effort necessary will depend upon three things :— 8 (a) The weight of the train. (b) The various forces opposing motion on a level line, and spoken of collec- tively as "tractive resistance. (c) The gradient, which may either assist or resist the tractive effort of the motors. Of these three, "a" is known or can be assumed with sufficient accuracy, and "c" will merely decrease or increase the resistance to traction by a definite amount, depending on the slope of the gradient. The amount by which the resistance per ton is increased or decreased is 22.4 lb. for every 1 per cent. of grade. The tractive resistance is a force which may truly be said to obey no universal law, and its value can only be approximated to. It varies according to the speed, but is at the same time a function of so many other varying conditions that no simple rule can be considered as a means of estimating its value. In most calculations it is usually assumed to be a constant resistance of from 10 lb. to 12 lb. per ton weight of the train, if the line is fairly straight, the value being increased if curves are being dealt with. Making the above assumptions, and taking the tractive resistance as 12 lb. per ton, the tractive effort required for any given rate of acceleration can easily be calculated. On a level track, the pull per ton required for an acceleration of one mile per hour per second is 102.1 lb., exclusive of friction, or 114.1 lb. if we include friction. On an up-grade of, say, 1 per cent., the force per ton would be 1 114.1 + × 2240 lb. or 136.5 lb. Multiplying this by the number of tons in the 100 weight of the train, gives the total tractive effort required to be exerted by the motors. The performance of a train is usually graphically represented by plotting the speed, distance, &c., against the time, in the form of curves, the time-values being taken as abscissæ. By plotting such curves, it is easy to see how long the acceleration must continue in order to cover a given distance in a given time. The run of a train may be divided into three main periods: first, the period of acceleration; secondly, the period of coasting, or running at maximum speed; and lastly, the period of braking. The considerations which chiefly affect the size of a motor to be employed are the rate of acceleration and the maximum speed required. The motor must be capable of exerting the torque necessary for the required acceleration at a speed somewhat below the maximum running speed. If the run is sufficiently long, the motors will attain a maximum speed greater than that at the moment of going into full parallel; but up to that moment the torque, and therefore the accelera- tion, is assumed to be practically constant. As soon, however, as the motors are connected straight across the line, with no resistance in series, the speed increases at a much slower rate, both the torque and the acceleration falling off. The maximum output of the motor is reached at the end of the period of constant or uniform acceleration. After that, the speed of the motors tends to rise until their torque just equals the tractive resistance plus or minus the effect of the gradient. The usual method of making a preliminary investigation of an electric railway is thus somewhat as follows:- A certain rate of acceleration is taken-say, one mile per hour per second-and it is further assumed, tentatively, that the period of constant acceleration shall continue until the speed has reached 30 miles per hour; i.e., it continues for 30 seconds. For a level track, the pull per ton to produce an acceleration of one mile per hour per second is 114.1 lb., allowing 12 lb. per ton tractive resistance, ROLLING STOCK AND MOTORS. 765 Hence, if this pull is to be exerted at a speed of 30 miles an hour, the horse-power required per ton of train :- 114.1 × 30 × 5280 9.3 horse-power. 33,000 × 60 Multiplying this by the number of tons in the weight of the train gives the maximum total horse-power required; and further dividing by the number of motors to be used, gives the maximum horse-power output per motor. Having thus obtained some idea of the size of the motor which will be required, the characteristic curves of various motors are consulted, until a motor is found which will give the required output at 30 miles per hour. Assume for example a train weighing 100 tons. Then the maximum horse- power is 930 horse-power, or, say, 116 horse-power per motor, with eight motors on the train. The Dick, Kerr 4 A motor, a curve of which is shown further on, gives 120 horse-power, at 32 miles per hour, when operating on a 625-volt circuit, and is therefore somewhat larger than is required. Assuming, however, that this motor is to be fitted to the train, an approximate speed time curve can easily be plotted for the performance of the train. The total force required in accelerating at the rate of one mile per hour per second is 114.1 x 100 or 11,410 lb., which works out at 1426 lb. per motor. The steady rate of acceleration will go on up to a speed of 32 miles per hour, as will be seen from the characteristic curves of this motor. As soon as this speed has been reached the rate of acceleration will diminish, and the speed will rise with increasing slowness, up to the time that power is shut off, and coasting or braking commences. With this particular motor, which is larger than would be required, the speed would become very high eventually, if the run were long enough. Using the characteristic curves of the above motor, the speed-time curve can evidently be plotted showing the performance of the train during the time the energy is applied. If coasting is indulged in, the graphical representation of this will be a line which is nearly straight, and only slightly inclined towards the abscissa, since the frictional resistance of 12 lb. per ton will be the only force tending to reduce the speed. The line representing braking will also be approxi- mately straight, and very nearly twice as steep as the line of uniform acceleration, only in the opposite direction. Fig. 1, page 766, shows such a speed-time curve plotted. Up to the point marked A the acceleration is constant, and from then onwards the line gradually slopes off, or curls over, until a speed of 45 miles an hour is reached, 50 minutes after starting. The exact shape of the curve between A and B is not very easy to calculate; but for cases where the distances between stops is small, it is not long enough to make its precise shape of any great importance. It can be drawn in "by eye" near enough for all practical purposes. The line from B to Crepresents "coasting," during which the speed is assumed to fall at the rate of, approximately, one-tenth of a mile per hour per second. When the point C has been reached the brakes are put on, the rate of retardation being taken as two miles per hour per second, and the train brought to a stop at the time indicated by the point at which the line "CD," or braking line, cuts the abscissa, in this case, 120 seconds after starting. Since the curve thus plotted represents the change of speed with reference to time, the space covered by the train will be represented by the area enclosed by the time-speed curve. Hence, to find the distance traversed the area of the curve can be measured by a planimeter. But a better method is to plot a separate distance-time curve. This can be easily done by taking intervals of, say, 10 seconds, and assuming that the average speed during that time was the mean between the speed at the beginning and the speed at the end. OE is a distance curve plotted in this way, from which it will be seen that a distance of 5450 ft. was run by the train before stopping. By cutting off power at B' or B" instead of B, and applying the brakes at the points C' or C", as the case may be, it is evident that a smaller or larger distance can be covered in the same time as was taken in the original run. Similarly, by adjust- ment of the moments of cutting off power and applying the brakes, the same distance could be covered in more or less time. The dotted curves O E' and O E" are the distance curves obtained by accelerating up to B' and B" respectively. Thus by the above means a very complete investigation of the probable performance of the train can be made. Variations can also be introduced by alterations of the gear ratio of the motor. The power consumed can be approximated in the following way: Up to 766 SECTION X. 16 miles per hour the motors are in series, and the current is assumed to be constant, while from 16 miles per hour up to 32 miles per hour the motors are in parallel, the current being likewise constant, and just double what it was for the motors in series. Looking at the curves of the motor, we see that at 32 miles per hour the current consumption is about 180 amperes per motor, or 1440 amperes for the complete train. Hence, up to 16 miles per hour the current consumption will be 720 amperes. From the point A to the point B the current will gradually fall off, reaching at B the value of 100 amperes per motor (800 amperes per train), this being the current corresponding to a speed of 45 miles per hour. At this speed current is supposed to have been shut off, so that the curve F G H K L represents by its area the current taken in the run. Multiplying this by the voltage of the supply gives the kilowatt expended. The above calculations have all been made in English units, but for rapid approximations the metric system is somewhat simpler if the following values are given to the different quantities :- Amperes per train(8motors) 1500 6000 60 5000 50 4000 Feet Bestage aut 1000 may sad song in pads (1109) 19 Từ G Current RS MI Distan E' H E Time P-CS Wit B" -- I D 0 10 20 30 40 50 60 70 80 90 100 110 120 130 Time in Seconds Fig. 1. Time-Speed, Distance and Power Curves, for Train Weighing 100 Tons, on Level Track, Line Voltage 625. To produce an acceleration of 1 centimetre per second per second, a force of 1 kilogramme per ton is required on a level track, exclusive of track resistance. A gradient of 1 millimetre rise in a metre is equivalent to a force of 1 kilo- gramme per ton. Tractive resistance = 5 kilogrammes per ton. In the above, the ton has been taken as equivalent to 1000 kilogrammes. Forces Acting Upon a Train. There are several forces acting upon a train in motion :- 1. The tractive effort of the motors. 2. The gradient (if any) which may or may not oppose the motion of the car or train. 3. The inertia of the train considered as a body moving in a straight line, and consequently opposing any change of uniform motion in that direction. 4. The inertia of the rotating parts of the train (motors, wheels, gearing, &c.), the moment of inertia of which also opposes any change from uniform motion. 5. The ordinary tractive resistance on a straight line. 6. The additional resistance due to curves. No. 1 2 3 4 5 6 7 8 9 10 11 12 R = tractive resistance in pounds per ton (2,240 lb.). V = velocity in miles per hour. W = weight of engine and tender in tons (2,240 lb). Authority. Clark "" "" ?? Harding Gooch ·· Henderson Wellington " "" : : "De Monte Alto ·· ·· "} .. : : : : .. : ·· : : ·· .. ▸ • Table 2.-Formulæ for Train Resistance. (Aspinall, Proc. Inst. C.E.) ·· 6 + V2 240 + 6 + Value of R. V2 171 V2 V 8+ 6 + 240 √2 114 2+V2 12 + + 6 (1 600 V2 x 0.0025 A 1+ W 20 10) 6 + 3 (V − 10) 10 V 3.36 + 4.48 + 6.72 + X - V2 193.5 V2 116 V2 94.7 V2 100.8 V2 72.3 W (w + ) } W 20 = weight of carriages in tons (2,240 lb.). = A area of front of train in square feet, L = length of train in feet. Whole train. Carriages only. Whole train-narrow gauge. Engine and tender. Carriages only. Carriages only. Conditions. 20 loaded box cars 40 empty 20 loaded flat cars 40 empty, "" "3 "" Up to 30 miles per hour. ROLLING STOCK AND MOTORS. 767. 1 : 4 768 X. SECTION No. 13 14 15 16 17 18 19 20 21 22 23 * ***** & 24 27 28 29 30 " Blood 25 Sinclair 26 Dodd 31 32 Wellington "" Searles Chanute Ricour Gerry Horton Forney Authority. "" "" Lundie West Clayton .. .. • ·· Barnes Baldwin Company ·· ·· ·· ·· .. ·· "" ·· .. : : • • ·· · .. .. : ·· : : : : : : : •• : Table 2.-Formula for Train Resistance (Continued). ** • Value of R. 1 162 4.48 +0.0056 V2 + 0.46 4.48 + 5.4 + 0.006 V² + V2 พ 0.0006 V2 W2 W + w 0.3 V2 5.6 + 0.008 V2 + W 4.48 + 0.0902 V V2 4.48 + 178.5 8 + 0.006 V2 V2 4.48 + 152.6 4.48 + 0.179 V 0.56 V 3.36 + 3 1.68 + 0.224 V 4.48 +0.168 V + 0.336 2 + 0.5 V 2 + 0.24 V 12.5 +0.224 V 20.16+ 0.224 V 7.84 +0.224 V A 4.48 + 1.12 V ( 0.24 + V V2 5 ·+. 15 246 6.5 + 0.16 V V1.8 W + w 20) 14 35 + W + w Engine and train. Carriages only. Whole train. Passenger cars. T (47 to 77 miles per hour). Whole train. Engine. Carriages. Conditions. Oil lubrication. 1 1 ! T 1 f 1 ROLLING STOCK AND MOTORS. 769 CC No. 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 Clayton Pettigrew Deeley Wolff >> "" "" "" "" "" Eastern Railway of France Authority. Barbier "> ·· Laboriette "" "" " ·· .. "" Du Bousquet ·· "" "" "" "" ·· 4. •• : .. ,, "" : "" "" "I :: : : : Table 2.-Formulæ for Train Resistance-(Continued). : 3 3 Value of R. 6.5 +0.005 V2 9 +0.007 V2 V2 3+ 290 V2 250 3+ 'V + 12 (V+12) V2 + V + 3 300 0.305 V + 5.24 2.24 + - 0.305 V+ 4.1 3.96 +0.18 V 4.032 + 0.289 V + 0.28 4.032 + 0.289 V + 0.194 4.032 + 0.505 V + 0.129 3.22 +0.00492 V2 0.2497 V V2 190 W 89.2 8.51 +3.24 V (¹ V2 W V2 V2 178.5 3.58 +1.658 V (1.609 V +50 1000 3.58 +1.644 V W V2 W 1.609 V + 10 1000 .609 V+30 1000 10) 30) Grease lubrication. 111 Train only. w = 102.6 tons. w= 185 tons. 20 to 31 miles 31 to 40 43 to 50 " Conditions. "" 7.5 to 20 miles per hour. per hour. "" "" Four-wheeled coaches. Bogie coaches. Locomotive and tender. ▬▬▬▬▬▬▬▬▬ No. 51 52 53 54 285008J::J 55 56 57 59 60 61 62 63 64 Aspinall : "" "" "" "" Authority. Fink ·· .. : .. "" •• : ·· •• Eastern Railway of France ·· : ·· • .. " ·· Northern of France Railway Desdouits Von Roehl " ·· Table 2.-Formulæ for Train Resistance-(Continued). ·· •• .. ·· Value of R. v% 58.7 vš 2.5 + 2.5 + 2.5 + 2.5 + 2.5 + 65.82 y! 73.05 Vš 80 Vš 50.8 +0.0278 L W 0.316 V5.245 4.09 +0.316 V 5.6+0.00579 V2 8.39 +0.0087 V2 3.248+0.00463 V2 3.355+ 0.00405 V2 3.355+0.0925 V 0.0112 +0.000001965 V3 0.0056+0.000001965 V3 M 88 5 bogie coaches and dynamo-meter car. 10 15 20 19 Conditions. "" " "> "} "} Unfavourable conditions. Goods train of at least 30 wagons. V = 0 to 50 miles per hour. "9 V = 19 to 63 Locomotives. Trains only. * " Oil axle boxes. General formula, bogie coaches, oil axle boxes. Complete formula. Reduced formula generally sufficient. Favourable conditions. 1 770 SECTION X. 1 1 L 1 ROLLING STOCK AND MOTORS. 771 With regard to 4, the inertia of the rotating parts may be considered as an increase of the linear inertia. Mr. Storer recommends 10 per cent. as the allowance to be made, and this may be taken as substantially correct in the majority of cases. It is convenient if all forces acting are measured in pounds per ton of total weight. The pull that the motor can give at any speed is known from experiment. The effect of gradient depends on the slope. The resistance of curves depends on the degree of curvature. It is usual to assume this resistance as equivalent to from 0.8 lb. to 1.0 lb. per ton per degree of curvature. (See Table 12, page 33, for relation between curve expressed in degrees and radius in feet.) The ordinary tractive resistance on a straight line differs considerably, according to circumstances. Table 2, page 767, gives a large number of formulæ for calculating this resistance. In the case of high-speed work, the braking force usually reckoned on is 168 lb. per ton. This is total braking force, and includes the frictional resistances of bearings and rails, and also any additional resistances due to curvature. The characteristic curves of the motors figure largely in the plotting of speed- time curves. Usually these curves give the values between the current input at a given pressure, and (a) the tractive effort or pull, (b) the speed, (c) the efficiency. Train Resistance. The friction between the driving wheels and rails which prevents them from slipping, and enables them to propel the train, is a static, or merely resisting friction as distinguished from dynamic friction, or that in which motion takes place between the surfaces in contact, with resulting destruction of energy. Its cause is an interlocking of the roughnesses or projecting fibres of the surfaces in contact, as cogs might interlock. That this is true of all friction between metallic surfaces, under the most favourable circumstances, was shown by experiments of Mr. Beauchamp Tower. No error can arise from assuming that the resistance of the wheels to slipping is sensibly constant at all speeds. When slipping has once begun, the conditions are very different. 1. The coefficient of static friction between rail and wheel is not sensibly affected by the speed. 2. It is greatly affected by the weight, increasing rapidly therewith. 3. It is greatly affected by the condition of the surfaces as regards moisture, even when the eye can detect no difference; and by other causes which can rarely be determined. 4. It is greatest when the rails are dry or very wet; slight moisture or frost have the most injurious effect. 5. The coefficient of sliding friction is much less than static friction, and is affected by speed, being inversely proportional thereto. At the instant when slipping begins, the velocity of the rubbing surfaces being very small, it is sensibly the same as static friction: as the speed increases, it falls rapidly until it is barely to the static friction. Measuring Train Resistance. There are two methods of measuring train resistance: one by observing it as a function of the retardation or acceleration, and the other by measurement direct as the resistance pull. The first can be applied in three different ways: -- 1. By bringing the train to a given speed, then coasting and measuring the dis- tance till a full stop is reached, and then calculating the average train resistance. 2. By bringing the train to a known speed, and measuring the reduction in velocity at stated intervals until it comes to a standstill. 3. By calculation from the acceleration or retardation due to gravity, on a down or up-grade. In the second method, which consists in measuring the resistance pull, three different means may be adopted to obtain this: by the use of a dynamometer, by calculation from indicator cards of the steam locomotive, or by calculation from the power curves of an electric motor. The dynamometer and indicator have been used with good results. 772 SECTION. X. Subdivision of Train Resistance. Subdivision of train resistance may be made as follows:- 1. The journal friction, between journal and bearing. 2. The rolling friction proper, between wheel and rail. Both these together are commonly included, both in this volume and else- where, under the general name of rolling friction, and their aggregate only has been determined with approximate exactness. 3. The "velocity resistances;" and experiment seems to agree with the requirements of theory, that they should vary as the square of the velocity. These latter can be divided as follows: a. Atmospheric head and tail resistance, including the head resistance of the locomotive and of the front car above the tender, and that resulting from the suction of the last car. b. Atmospheric side resistance, including that between the successive cars. 4. Additional rolling and journal friction, resulting from oscillation and concussion. An additional resistance is the stopping and starting resistance, and finally grade resistance, which is sensibly the same rate per cent. of the total weight of the train as the rate per cent. of the grade: 22.4 lb. per ton for each 1 per cent. of grade. Brake friction. The average retarding efficiency of brakes may be considered as from 10 to 14 per cent. of the load on the brake wheels in passenger service, with air brakes, and from 24 to 5 per cent. with hand and driven brakes on heavy freight trains. The safe pressure on the brake shoes is not much over two-thirds of the load on the wheels. — " >> "" (W. B. Potter.) Tractive effort necessary to overcome rolling friction of rail, and air resistance (approximate) compiled from numerous tests- 15-ton car, up to 25 miles per hour, 25 lb. per ton (2000 lb.) 15 50 50 "" 39 25 25 20 "" "" 25 50 25 "" "" 25 "" 25 - "" "" "" 100-ton train,, 15 "" 59 "" "" Heavy-freight train 6 to 10 These figures considerably increased by snow or dirt on track- weight on driving wheels total tractive effort Tractive coefficient "" "" "" "" · "" "" •• ·· "" ·· "" "" state of rails. For general train work-coefficient should not be less than 6. The following Table is based on a series of tests: Tractive coefficient. "" per cent. 28 20 15 "" "" and is largely dependent on Dry rail.. Thoroughly wet rail Greasy moist rail Ice and snow may make coefficient even lower, and increase rolling friction. Sanded. per cent. 28 25 25 Comparison of Steam and Electric Haulage. A comparison of the actual results obtained on the elevated electric railways of Chicago, and on the Metropolitan and District line in London, shows that the maximum speed of 25 miles an hour is obtained in 10 seconds with electric traction, but that it takes 33 seconds to do it with steam locomotives-the electrically-pro- pelled train could do a distance of 1880 ft. in 66 seconds; with steam it would take 93 seconds, or nearly half as much time again. If, in the case of electric traction, the power is cut off the moment the maximum speed of 25 miles an hour is obtained, and the train allowed to coast before the brakes are put on, the distance considered would be done in 76 seconds. The steam-driven train even then would take more than 25 per cent. longer to do the same distance. Steam locomotives use but very little less coal and water when they are stand- ing still than when they are running, and are much less economical, consuming, as they do in America, from 5 lb to 6 lb. of coal per indicated horse-power. On main- line English roads 3 lb. to 4 lb. are consumed, not including stand-bys and firing-up; and taking an average power of 400 horse-power per locomotive, and a train plus engine weighing 250 tons, at a speed of 40 miles an hour, we get for the most economical rate about 0.65 lb. of coal per ton-mile. A properly-designed electric station with large units would never consume more than 2 lb. of coal ROLLING STOCK AND MOTORS. 773 per indicated horse-power hour, or 2.65 lb. of coal per kilowatt hour, or Board of Trade unit at the switchboard; and engines of the size of 4000 to 6000 horse-power would be guaranteed to consume not more than 12 lb. of steam per indicated horse- power hour. Comparing, again, the coal consumption per train mile on large English main- line railways, which varies from 35 lb. to 58 lb. of coal per train mile, we get a coal consumption of from 0.146 lb. to 2.32 lb. per ton-mile. Importance of Rapid Acceleration. Practical experience with electrically-driven motor cars, or locomotives on the experimental track of the General Electric Company, at Schenectady, has proved that it is perfectly feasible to attain a speed of 30 miles an hour 10 seconds after starting from a standstill. The most important point is to attain a high average speed, and to keep the maximum speed attained as low as possible, as by so doing less power is required in Speed in Miles per Hour. 40 35 30 We 70 • 5. 19 Metres per Second 60 Feet Per Second 18 17 55 16 15 14 25 上​臼​. - 73 12 10 209 30 8 6 19 لها -50· 4 40 533 75 20 310 0 10 Meat politary Cont extin 20 My pr Liverpool Overhead B. B Barme itan Dist Steam to. 30 La Metro evate abchmy eam Bu def (Ste Gala an The ini, tompex Quing Troans 50 Trandey 60 Agro E 40 Time in Fig. 2. Acceleration Curves of Steam and Electric Railways. Seconds NA 10 1 1 80 " 80 1110 100 braking the train, and also less power is required to run the train. The time from starting to the moment when the brakes are put on should be, at least, from four to six times that required for stopping the train, so as to allow for errors in judgment on the part of the driver, and also to enable him to make up lost time. On the Manhattan Elevated Railway, in New York, the trains which are drawn by steam locomotives take 20 seconds to attain a speed of 14 miles an hour. Fig. 2 shows the different accelerations obtained on various steam and electric lines. Time and Power used in Acceleration. A much larger current will be required to attain a rapid acceleration than to attain a slow one, but the current will be required during a much shorter time, and the total energy supplied will be less in the case of rapid than of slow acceleration. This fact must not be lost sight of when calculating the feeders for such a system, 774 X. SECTION Bailway Company. ·· Manhattan Elevated.. Special Test General Electric Co. Special Test General Electric Co. Special Test General Electric Co. ·· Table 3.-Accelerations in Use on Some American Railways. (Swinburne and Cooper.) .. Remarks. Cars. Weight of Train in Net Tous. (Tons of 2000 Lb.) of Number Grade. per ton friction. sec. lb. sec. Metropolitan Elevated | Electric (15 lb.) | 2 44 L 10 158 40 Lake Street Elevated.. Electric (15 lb.) 2 44 L 10 121 40 Alley Elevated.. Steam (15 lb.) 3 10 121 40 72 L 4 116 L 10 86 40 Illinois Central Steam (15 lb.) Steam (15 lb.) | | 95 10 80 40 Electric (20 lb.) 1 Electric (20 lb.) | 1 Electric (20 lb ) | 1 'I 6 Tractive Effort per Net Tons. (Tons of 2000 Lb.) Maximum for Given Time. 9 L Average for Total Time. lb. 91 75.2 87.4 71 25 L 10 282 20 186 L 10 264 20 199 10 163 20 126 09 Average Acceleration per Second in Miles per Hour. 10 Seconds. .75 Average Acceleration in Metres per Second. ² .8170.365 3.0 2.8 1.61 1.64 0.73 1.22 0.555 12.2 1.22 0.555 12.2 90 0.335 Speed Miles per Hour. Distance Run in Feet. Average Acceleration per Second in Miles per Hour. 1.34 1.25 0.73 16.4 120 1.12 & 2 2 3 3 90 1.02 8.17 60 7.5 55 20 Seconds. 0.5 0.455 .975 0.435 Average Acceleration in Metres per Second. 2 30.0 220 1.9 28.0 206| 2.05 16.4 120||1.22 .715❘ 0.32 .675 0.3 30 Seconds. Speed Miles per Hour. | Distance Run in Feet. Average Acceleration per Second in Miles per Hour. 0.85 38 556 0.92 41 600 0.545 24.5 360 22.5 330 1.00 0.45 30.0 660 20.5 300 .773 0.345 23.2510 19.5 285 .80 14.3 210 13.5 199 Average Acceleration in Metres per Second. 2 Speed Miles per Hour. Distance Run in Feet. per Second in Miles Ave¹age Acceleration per Hour. Cat .87 0.39 .69 0.31 0.36 24.0540 .715 0.32 .683 0.305 |20.5450 .64 .583 0.26 17.5 386 .52 40 Seconds. - pa K in Metres per Second. 2 Average Acceleration Speed Miles per Hour. Distance Run in Feet. 34.8 1020 27.6 870 28.6 840 0.285 25.6 750 0.23 21.0 615 K Maj V ROLLING STOCK AND MOTORS. 775 and the train service should be arranged in such a way that as few trains as possible start together. The more rapid the acceleration the larger will the motors have to be, and, therefore, there will be a limit above which it will not be advantageous to push the rapidity of acceleration. In new tunnel lines it is an advantage to have the stations built with a down-grade for the trains to start, so as to help the motors and reduce the current required at starting; and similarly to have an up-grade when nearing the station, so as to reduce the amount of power required in braking. By properly choosing these gradients, it is found that a total economy of from 40 to 50 per cent. in the total power required by a train may be made. Table 4.-Speed, Weight, and Tractive Effort on Various Lines. Railway Company. Metropolitan Electric Elevated, Chicago Lake Street Electric Elevated, Chicago Alley Electric Elevated, Chicago Illinois Central Electric, Chicago Manhattan Electric Elevated, New York.. ·· ·· Number of Cars. Weight of Trains in Pounds. 2 Tractive Effort per Ton. Maximum Average for Given for Total Time. Time. sec. lb. sec. Ib. 10 177 40 88,000 107 2 88,000 10 135 40 84 3 144,000 10 135 40 98 4 300,000 10 95 40 79 4 190,000 10 40 67 5888 Maximum Speed in Miles per Hour. 34.8 27.6 28.6 25.60 21.00 Distance Run. ft. 1020 870 840 750 615 With a complete train composed of one motor-car and two passenger cars, weighing complete 148,000 lb., a maximum horizontal effort of 9750 lb. was required in acceleration, the maximum current was 780 amperes at 500 volts, the maximum speed attained was 32 miles an hour, and the time taken to attain the speed was 34 seconds, the motor-car being equipped with two 200 horse-power motors. In an experiment with a train composed of one motor-car and one trailer car, weighing 57 tons, with an average distance between stations of 4280 ft., a maximum speed of 37 miles was attained, the average speed being 17 miles an hour, the power required being 0.067 Board of Trade units per ton mile. In another case, with a train composed of one motor-car, equipped with two 125 horse-power motors, and one trailer car, the total weight of train being 103,000 lb., a maximum speed of 31 miles an hour was attained in 37 seconds, the maximum current being 500 amperes, and the maximum horizontal effort required to attain acceleration 5640 lb. In a series of tests made on the Nantasket Beach line, it was found that with a heavy motor-car, 51 ft. in length over all, carrying 100 passengers, weighing 31 tons, on an average distance of 2980 ft. between stations, a maximum speed of 40 miles an hour was attained; the average speed being 18 miles per hour, and the power required being 0.098 Board of Trade units per ton mile. Liverpool Overhead Railway. (FIG. 3, page 776.) Experiments were made with a new equipment to ascertain what acceleration could be obtained, and Messrs. Dick Kerr and Co., Limited, guaranteed to run the whole distance-including 16 stops of 12 seconds each-in 20.9 minutes, thus raising the schedule speed to nearly 19 miles an hour. The weight of train, including 154 passengers, was 55 tons. Fig. 3 shows the acceleration curves obtained, and also the speed and power curves. The maximum acceleration was 4.2 ft. per second per second, or nearly 3 miles per hour per second, the average acceleration being well over 1 mile per hour per second, thus enabling the train to cover the 2110 ft. between the stations in slightly over one minute, including starting and stopping. During the acceleration of the train in the series position of the controller, each motor carries 300 amperes. 776 SECTION X. The retardation or negative acceleration reached 4.75 ft. per second per second. Trains running at high schedule speeds with frequent stops may consume 120 to 150 watt-hours per ton mile. With infrequent stops, 90 to 100 watt-hours per ton mile would be required. The consumption in the experiments recorded above was 137 watt-hours per ton mile, or about 6.35 kilowatts per train mile. The following Table compares the old and new systems. Mean speed in miles per hour Number of stops Mean time at stations in seconds ·· Mean distance between stations in yard Watt-hours per ton-mile Acceleration in feet per second second Recardation in feet per second per second per 60 5 45 45 $40 4 35 3.5 30 MILES PER HOUR. AMPERES & VOLTS. 8 {26_-26} ·26|| 2 1581.5 2010 1 5005 on of 800205 700 1.5 600 2 6002·5 400™ 300 3.5 2004 1004.5 0 6 12 TOXTETH| DOCK. 6 18 12 18 ·· AMPERES VOLTS "" Extreme width Wheel base ACCELERATION 24 80 26 42 48 54 60 166 22 TIME IN SECONDS. BRUNSWICK DOCK TOTAL WEIGHT TRAIN (2 MOTOR CARS & TRAILERS)-55.52 TONS. EQUIPMENT-2,100 HP. MOTORS PER MOTOR CAR Diameter of wheels Width of tyres Weight ** Gauge.. Overall height above rail level length, buffer to buffer .. SPEED! ACCELERATION CURVES. Fig. 3. Liverpool Overhead Railway. 4. .. 24 30 36 42 48 54 TIME IN SECONDS. .. ·· With the previous equipment the trains ran 144 train miles per hour; with the w method they will do 216. Also the original five minutes headway between trains will be reduced to 3 minutes. : ELECTRIC LOCOMOTIVES. Table 5.-City and South London Railway. LEADING DIMENSIONS OF ELECTRIC LOCOMOTIVE. •• • : 2110 FEET • ·· • Old System. New System. 12 19 16 16 11 11 729 729 110 137 1.6 3.0 3.0 4.8 • • •• • ·· ·· ·· ·· AKING ·· .. .. · 60 66 72 •• •• ft. in. 4 8 8 5 14 0 6 10 6 0 2 3 0 42 10 to 13 tons. ROLLING STOCK AND MOTORS. 777 North-Eastern Railway Electric Goods Locomotives. (FIGS. 4 to 6, pages 778 and 779.) These locomotives are of the double-bogie type, and weigh 50 tons each. Each of the four axles is driven by a G. E. 55-type 2-turn armature, driving through single-reduction gearing having a ratio of 3.28. The principal dimensions are given below:- Gauge.. Length over central cab headstocks buffers Pivotal centres of trucks.. Wheel base of trucks Width over cab side soles all "" "} Diameter of wheels "" ·· "" •• .. ·· ·· axles at centre journals • • •• ·· Height from rails to top of cab.. floor .. .. ·· ► .. ·· ·· • ·· ·· ·· ·· ·· .. ·· • .. .. ·· ·· ·· ·· • ·· • ·· ·· ·· ·· ·· ·· •• ·· •• ▼ ft. in. 4 8 9 01 35 0 37 11 20 6 6 6 7 61 7 108 8 8 9 4 32 3 0 11 0 63/ 0 6 0 10 "" Length of journals.. Figs. 4 to 6, pages 778 and 779, show different views of the locomotive. The trucks are of the steel-plate frame type, built in accordance with English railway practice. A specially heavy design of brake-gear is employed, blocks being fitted to each side of each wheel, and the whole gear made heavy enough to be operated by air pressure. The wheels are of the cast-steel disc type, fitted with rolled-steel tyres 5 in. wide by 24 in. deep on the tread, held on by retaining rings, supplemented by eight set screws. The Sprague-Thomson-Houston system of control is employed, arrangements being made for driving the locomotive from either end of the cab, which is fitted in duplicate with master controller, air brake, sand and whistle valves. The air brake is of the quick-acting pattern, the compressed air being supplied by means of a British Thomson-Houston electrically-driven compressor of the C. P. 14 type. The locomotive is fitted with a sliding-bow trolley, as well as the ordinary shoe collectors, for use with a third rail conductor. The bow can be lowered, when not in use, by turning a hand-wheel inside the cab. Each locomotive, when operating on a 600-volt circuit, is capable of handling a 300-ton train on the level at a speed of 14 miles an hour, and can start with a train of 150 tons up a grade of 1 in 27, under all conditions of weather, running up the grade at a speed of 9 to 10 miles per hour. These locomotives were supplied to the railway company by the British Thomson-Houston Company, the trucks and bodies being built by the Brush Electrical Engineering Company. American Electric Locomotives. There are certain classes of service in connection with steam railroads, electric railways, and industrial transportation systems, in which the advantages of the electric locomotive and the economies to be obtained by its adoption are at once apparent. In Table 6 are shown the results of a few cases recently investigated by the General Electric Company of America. In this table the cost of operation is expressed in cost per engine mile as well as in cost per 1000-ton miles. The costs of steam operation are in every case taken from records upon the steam road in question, or have been estimated as closely as possible from what records can be obtained. The costs of electric operation are derived from records of existing electric locomotives, and from a study of the service conditions to which they would be subjected in each particular case. In this table Road "A" refers to a road using locomotives for "pushers" over a heavy grade, and the second column shows the economy which could be obtained by substituting electric locomotives for steam over the short section on which these pushers are operated. Road "B" is a road handling general freight over a section in which a good deal of traffic originates, so that the service demands a great proportion of switching and short runs. Road "C" is a road handling ore over a section with heavy loads in one direction, and empty trains in the other. CC ** C C2 778 SECTION X. G Scale of Feet Sand EUZELE onl foll QUHE Contac Frame INVILLE MWLEA 11 North-Eastern Railway Goods Locomotive, DO DE COPCO DUG Mus པ་1 IL Contactor Frame Fig. 4. Elevation. Reverse (ale) Fig. 5. Plan. Air Res }}}} 4 ROLLING STOCK AND MOTORS. 779 100s +=+=+ In oo LEP(-) [H]' {0} -------- 47522 ###} များ لمان O O 1112. 15 4.82 Gauge· Fig. 6. Bogie Truck for the North-Eastern Railway Goods Locomotive. 1 T 780 SECTION X. Table 6.-Comparison of Steam and Electric Locomotive Operation of Trains. Road A. Length of road Character of service Trains-daily number-total Locomotives-weight-total Weight on drivers Number-total Number in daily service Daily mileage-regular ** >> >> "" Cost of coal per ton Average number cars weight trailing load "" D ·· Fuel Power Engine crew ·· ·· ·· .. .. Daily number 1000 ton miles—gross Operating expense per engine mile- • switching. per locomotive Fuel Power Engine crew .. Maintenance and repair Round house and inspection Oil, waste, and supplies Total Depreciation Total per engine mile Operating Expense per 1000 ton miles- ·· .. •• .. Maintenance and repair Round house and inspection Oil, waste, and supplies Total Depreciation Total per 1000 ton mile •• .. • ·· ·· ·· ❤ ·· ·· · .. •• ·· ·· ·· ·· ·· .. .. .. ·· ·· .. . .. • ·· Steam Operation. 15.4 Pusher. 20 40-60 275-600 145 86 23 18.8 455 560 54.4 $1.26 288 $0.0852 .1058 .0883 .0168 .0084 .3045 .0518 .3563 30.30 .3770 .3140 .0599 .0295 1.0834 .1820 1.1654 Electric Operation. 15.4 Pusher. 20 40-60 275-600 85 85 12 10 455 560 102 $1.26 261 .0422 .0651 .0243 .0014 .1330 .0500 .1830 .1640 2530 .0945 .0055 .5170 .1950 .7120 Steam Operation. 34.5 Gen. Frt. 8-20 240-690 130 70 43 39 1150 450 41 $1.87 1109 $0.1620 .1310 .1010 .0339 .0092 .4371 .0680 .5051 .2340 .1895 .1460 Road B. .0477 .0133 .6305 .0985 .7290 Electric Operation. 34.5 Gen. Frt. 8-20 240-690 90 90 27 24 1150 450 67 $1.87 1047 $0.1400 .0488 .0258 .0020 .2166 .1265 3.431 .2150 .0747 .0396 .0052 .3345 .1940 .5285 Steam Operation. Road C. 113 Ore 44 30.4 2070-547 130 80 35 30 5000 160 $3.25 7155 $0.1665 .0620 .0524 .0090 .0038 .2937 .0293 .3230 .1165 .0434 .0367 .0063 .0026 .2055 .0205 .2260 Electric Operation. 113 Ore 44 30.4 2070-547 80 80 20 18 5000 278 $3.25 6896 $0.0903 .0398 .0250 p .0020 .1571 .0453 .2024 .0655 .0285 .0181 .0015 .1136 .0328 .1464 ROLLING STOCK AND MOTORS. 781 Table 7.-Performance of Some Electric Locomotives. Name. Baltimore and Ohio loco- motive, 1896 Baltimore and Ohio loco- motive, 1903 Buffalo and Lockport loco- motive Mediterranean Railway locomotive Bush Terminal Company locomotive G. E. Co. 30-ton yard loco- motive .. G. E. Co. 40-ton yard loco- motive ·· Voltage at which Operated. •• Grade on which train is to operate given in per cent. Note.-Resistance per ton of train due to grade is 20 G; e.g., resistance per ton due to grade on a 2 per cent. grade is 20 × 2 = 40 .. Resistance per ton of train due to friction.. Draw-bar pull exerted at locomotive draw- bar to maintain train at constant speed.. Weight of locomotive in tons of 2000 lb. Weight of entire train Horizontal effort necessary at rail head to move train at a constant speed ·· ·· Watt hours' input per train mile (see E) Speed of train in miles per hour ·· Amperes used by locomotives Volts at motor terminals •• Load Handled on the Level. • Tractive effort exerted by locomotive drivers at rail head Horse-power developed at locomotive draw- bar at constant speed Horse-power developed by locomotive at rail head tons amp. m.p.h. amp. tons m.p.h. amp. m.p.h. 625 1900 12 1800 625 3000 2200 13 900 1400 10 1600 500 450 500 14 250 200 11 500 500 1000 24 600 230 21 500 600 640 330 300 11 250 500 600 7 380 230 6 250 700 1200 12 540 350 9 .. •• Kilowatts used by locomotive as useful work in moving train ·· Starting Current. ·· Data Required by the General Electric Company for Electric Locomotives. Data. Symbol. How to be obtained. Weight of load to be hauled by locomotive in tons of 2000 lb. WI Conditions of problem ·· ·· Efficiency of locomotive (may be ordinarily assumed at 80 per cent.) Acceleration of train in feet per second per second Acceleration of train in miles per hour per second ·· •• .. ·· •• ·· Final Speed on Level. .. ·· 14 G F D We Wt H Wa S Running Current at Final Speed. T H Pl HPt KWE A V E Af Am Load Handled on 1 per cent. Grade. |||||| 11 11 11 **** #1 Final Speed on 1 per cent. Grade. # 11 Running Current at Final Speed on Free Running Grade. Speed of Loco- motive Alone. 24 450 24 800 39 1 375 TX S Conditions of problem Friction curve W1 (F + 20 G) 5D (approximate) We + W1 Wt (F+ 20 G) 2H E 375 2TS 1000 440 16 900 25 1 KWE V X A T-H 62 Wt T-H 91 Wt Conditions of problem or characteristic curves Characteristic curves DX S Characteristic curve Characteristic assumed, 500 curve, k 782 SECTION X. Name. Table 8.-Principal Features of some Electric Locomotives. (General Electric Company, New York.) Cayadutta locomotive Baltimore and Ohio locomo- tive, 1896 ·· Paris-Orleans locomotive Mediterranean Railway locomo- tive St. Louis and Belleville locomo- tive Bush Terminal Company loco- tive New York Central and Hudson River Railroad.. 96 each unit.. 80 Do. do. 1903* complete locomotive 160 Hoboken Railway locomotive.. Buffalo and Lockport locomo- tive .. Weight in Tons. .. .. 3 888 35 ·· ·· 36 55 38 50 50 93 ** • ft. in.! Weight of locomotive (80 tons per unit) Number of units Type of motor Rating of each motor at 625 volts Gearing 4 8 4 84 Number of Motors. Horse-power of each Motor. Volts on Line. Gauge. Diameter of Wheels. Length Overall. 4 8 8 4 • 4 4 8 4 .. ·· 4 • • 4 4 .. ·· 4 4 4 4 * The Baltimore and Ohio Locomotive, 1903, is composed of two similar units coupled together and operated as one. Table 9.-Principal Features of Baltimore and Ohio Electric Locomotive, 1903. .. 125 500 40 360 300 62 35 200 625 42 29 • • Rigid frame. Number of motors (4 per unit) Number of driving wheels (8 per unit.) Weight on driving wheels (80 tons per unit).. Total tractive effort for two units at full load on motors.. Total tractive effort at starting up, assuming 25 per cent. tractive co-efficient Gauge.. Diameter of driving wheels Length over all (for 1 unit, 29 ft. 7 in.)" Wheel base of each unit ·· ·· 200 625 42 58 7 9 5 13 8 140 500 40 ·· 75 500 36 225 575 49 34 10 150 500 42 150 500 33 150 500 33 550 625 44 37 3 10 2 13 11 I .. .. Extreme width over cab roof Extreme width outside of third-rail shoe supports.. Height to top of cab Height to top of bell Motor axle bearings Journal bearings .. ·· .. ·· .. ·· ·· .. ·· ·· in. ft. in. ft. in. ft. in. ·· ·· ·· •• ·· .. .. ·· ·· •• ·· . 0 7 ·· ·· Width Overall. | .. .. I 80,000 lb. 4 ft. 8 in. 42 in. ·· .. 58 ft. 7 in. 14 ft. 6 in. 9 ft. 5 in. -- 9 5 13 11 9 513 8 Height to Top of Cab. 160 tons 2 GE-65-B 200 H.P. 81/19 8 16 160 tons 70,000 lb. 12 6 10 ft. 7 in. 13 ft. 8 in. 14 ft. 9 in. 14 in. by 8 in. .. 12 in. by 6 in. ROLLING STOCK AND MOTORS. 783 New York Central Electric Locomotive. Total weight Weight on drivers Number of driving wheels Number of pony trucks OLOLOLOL Fig. 7. New York Central Electric Locomotive. Fig. 7 is a view of the New York Central electric locomotive, with a longi. tudinal section through the motors. ·· •* • Length over buffer platforms Extreme width Height to top of cab Total wheel base Wheel base of drivers Diameter of drivers Diameter of pony wheels. Diameter of driving axles Normal rated horse-power of locomotive .. • • .. .. Maximum power Normal draw-bar pull Maximum starting draw-bar pull Speed with 500-ton train .. Voltage of current supply Normal full load current.. Maximum full load current Number of driving motors Type of motor Rating of each motor • • ·· • • .. • ·· .. • • • • •• .. ·· ·· .. ·· ·· •• ·· .. • ·· .. .. ·· ·· ·· .. ·· ·· ·· .. •• ·· ·· ·· •• •• • .. ·· · .. .. ·· .. ·· .. .. • ·· .. • ·· .. ·· • • 945 95 tons 67 tons 8 2 37 ft. 10 ft. 14 ft. 4 in. 27 ft. 13 ft. 44 in. 36 in. 8.5 in. 2200 3000 H.P. 20,400 lb. 32,000 lb. 60 m.h.p. 600 3050 amp. 4300 amp. 4 GE 84-A 550 H.P. 1113 CONDUCTOR RAILS. (FIGS. 8 to 16, pages 784 and 785.) It is more economical to use a large rail, as the expense of equipping a road with it, compared to a small rail reinforced with feeders, is less. It is also advisable to use specially soft steel for the third rail, in consequence of its being low in carbon, which materially increases its conductivity. Particular attention should be given to the design of the ear for holding the rail in order to relieve the insulators of all undue strains, and the insulators should permit of perfect freedom to the rail in regard to expansion, irregularities of track construction, depression of ties, &c. Third Rail Shoes :-For collecting current to the car or locomotive numerous designs of third-rail shoes, essentially alike in principle, have been developed. The main contact runners are usually supported by links, and so designed that the shoe rests upon the third rail by gravity alone. The links are slotted, which allows the contact runners or shoes to take any inequalities in the heights of the rails. Provision is made for the adjustment, to counteract wear in the journals, turning down of the truck wheels, &c. The shoes, being of cast iron, have their bottom surface thoroughly chilled, which materially increases their life. 784 SECTION X. • a Third rail. b Power feeder. c Light feeder. d Signal wires. e Telephone wire. ✰ Test wire. a z ·500 10 -375- 73,0 -375- 08 ·OOL··· ON IRON SLEEPERS. 11 ·570· ON WOOD SLEEPERS. 9 -75..... 300 -1300 ···150· Figs. 8 to 11. Third Rail for Berlin, Elevated Railroad. (Siemens and Halske,) ··· 189·· 14 15 16 875 " 144 143 12 • 4 NOU Z N MIZ OUTREA La 101 8 M 20 N 2 O WHEN 1870 ... CENA -10-2 15 FLORE 13 28′to yauga lina ne-pie · _89-114 ཁ/- བ་ " 14 · Track Rail-meme 30 ft. Lengths 3rd Rail—80 ft, or 60 ft Guard Channel -10-2 H a la plana ph date ap " 29 ft. 11) Lengths -8'114 ወ 100 ·· 7) Palem • 180 Em në 'n¼¡nų įn [218 1218 | 2144; PLAN O „‚9.1°. 1474 QU ZUO N J | Akk Top of third rai is above top of running rail 1434/1444 hisww! Third Rail Systems. Figs. 12 and 13. Third-Rail Insulator, Berlin Elevated Railroad. (Siemens and Halske.) Fig. 14. Suggested Height of Rail and Guard, and Spacing of Supports. Figs. 15 and 16. Plan and Elevation of Contact and Protected Third Rail.. (General Electric Company, America.) 786 SECTION X. | Per cent. 0.09 Third Rail Composition:- Carbon .. Manganese Phosphorus Sulphur 0.044 0.088 0.08 ·· This rail had a resistance of 12.9 ohms per cubic centimetre, or 7.25 times that of commercial copper. 17 i • _1:4″ .. · · ·· For the best practice the proportions of the above substances should not exceed the following: Per cent. 0.15 Manganese Carbon .. Phosphorus 0.12 0.10 Sulphur 0.05 For such a rail the resistance is, as above, about seven or eight times that of commercial copper. Figs. 8 to 16 show various arrangements of third rails and current collectors. * .. SLEEPER •• Figs. 17 and 18. Doulton Insulators. 2-4/4 ·· 2-4/4. •• Conductor Rail Insulators. (FIGS. 17 to 19.) Fig. 17 shows Doulton's patent rail insulator. It consists of a pedestal of porcelain or stoneware resting upon the rail-tie, and secured thereto by exterior clips. It is recessed at the top to receive a depending stud attached to the rail-chair. The illustration shows an insulator fitted with a chair for a rail of rectangular section. This type of insulator is also supplied with fittings for rails of other sections, e.g., flanged or channel sections. .. : ·· 7114 R 18 *1/16 Fig. 19. Metropolitan District Track. Fig. 18 shows another type manufactured by Doulton, as adopted by the Underground Electric Railways Company of London for the Metropolitan District Railway and connections. Fig. 19 is a view of the Metropolitan District track, showing the third rail insulator in place. HEAVY ELECTRIC TRACTION. (FIGS. 20 to 23, pages 790 to 792.) Figs. 20 to 23, pages 790 to 792, show the general arrangement of trains on some of the principal electric railways in existence, and the seating accommo- dation afforded in the various cars. Table 10.—Electric Railway Rolling Stock, built by the Brush Electrical Engineering Company, Limited. SHOWING THE ADVANTAGE GAINED BY THE BRUSH ALL-STEEL CONSTRUCTION. Type of car Material used in construction "", "" "" Extreme length over buffers "" "1 "" Name of Railway. "" " "" "" "" "" >> "" >> "" "} Extreme width of body "} ,, over posts inside >> "" ** "" "" " "" .. over platformıs of platforms of body inside of end doorway of side doorway of platform trances "" of gangway Height from rail to outside roof "" >> passenger inside motorman's cab of luggage com- partment ·· ·· ·· .. ·· ·· ·· compartment 38 6 ·· en- ·· rail to underside sole- bar floor to ceiling of clerestory floor to lower ventila- tor rail Central London Railway. trailer wood and steel ft. in. 46 3 45 ∞ 3 39 ∞ ∞ ∞ ∞ 8 8 8 6 6 2 N MO MO 3 3 0 2 10 51 0 enlady 時時​越 ​9 1 7 5 6 5 3 motor wood and steel ft. in. 50 8 49 Great Northern and City Railway Company. —A∞∞ M 9 4 40 8 37 2 2 10 9 8 3 CO LO 00 : 6 12 5 2 11 4 31 6 0 22 କ୍ଷ 5644 11 2 8 4 7 1 trailer wood and steel ft. in. 50 8 49 4 40 8 40 2 ¯¯∞ ∞ M 9 9 8 3 : 2 2 12 2 60 1000 2 11 5 0 364 "C 11 8 4 7 1 } motor all steel ft. in. 50 3 49 4 3 8 9 6 9 41 37 "" 9 ochek 424 ✪ 000 N N 9 IS 10 12 3 8 7 9 2 9 asco ma pro 2 6 4/2/2 1/1 69 0 trailer all ft. 50 49 aa∞∞ N 9 4 3 9 41 0 40 7 8 steel in. 2 ma com o 2 2 12 3 3 8 7 6 2 10 : + ** Hot in 23 0 Metropolitan District Railway Company. motor wood and steel ft. in. 49 6 48 Co A com 3 45 34 Co 3 8727 aC CO 8 8 12 61 34 111 3 0000000 22 10 40 30 -R-N-K 2 10 5 5/2 101 8 3 7 1 trailer wood and steel ft. in. 49 61 48 94 3 61 1 42 41 8727 OC 3 I Jand 3 10 81 10 5 10 2 53 2 5 -- 34 12 31 2 8 7 1 Great Northern, Piccadilly, and Brompton Railway. trailer all steel }al ft. 49 49 3 41 40 00 00 00 00 8 8 8 3 629 1 in. 10 1층 ​101% 4곱 ​91 D∞IO 9 8 1 0 3 SO LO LO cekzo 5 5 ROLLING STOCK AND MOTORS. 2 101 1 3}} 7 6 6 4 1897 i Table 10.-Electric Railway Rolling Stock, built by the Brush Electrical Engineering Co., Ltd.—Continued. Type of car • Height of platform entrances of side doorway "" of end doorway " Centre to centre of bolsters Type of bolster >> Name of Railway. "" truck "" >> truck bolster "" Wheel base of motor truck. of trail truck Diameter of wheel "" "" "" ·· axle ·· ܼܝ journal Length of journal Lubrication of journal ·· •• • ·· ·· ·· ·· ·· Weight of body and underframe each motor truck "" each trail truck "" " electrical equipment Weight per seated passenger, less · electrical equipment Number of passengers seated Central London Railway. trailer ft. in. 6 44 29 6 box girder pressed steel with swing bolster pressed steel 0 5 31 in. at centre 5 2 4 in. at wheel seat 0 3 0 6 oil and pad t. c. q. 11 15 0 3 • 0 0 828 lb. 48 Great Northern and City Railway Company. motor ft. in. 6 1 6 0 6 3 34 6 bar truss cast steel side frames with swing holster built 6 3 0 6 t. 13 4 9 1 0 c. q. 11 0 0 0 • 5 0 832 lb. 58 ft. 6 6 6 trailer 34 6 bar truss cast steel side frames with swing bolster built t. = 6 3 in. 1 0 3 53 to 4§ in. 4/ 8 11 0 0 но oil 0 c. q. 16 0 3 9 0 0 1 0 675 lb. 62 motor in. 3 3 6 4 34 6 box girder cast steel side frames with swing ft. 6 6 bolster built 6 3 t. 10 4 9 1 0 6 65?: : : 0 800 q. 10 0 690 lb. 60 0 0 5 0 trailer ft. 6 6 6 3 4 34 6 box girder cast steel side frames with steel bolster built 6 ♡ ♡ 3 0 0 mo in. 3 ·· 5 to 4§ in. 0 1 0 oil t. C. q. 10 10 0 4. 8 3 9 0 1 0 644 lb. 64 Metropolitan District Railway Company. motor ft. in. 6 3 6 3 6 3 33 10 bar truss cast steel side frame with swing bolster built 6 3 0 0 0 6 ܚ 0 7 9 oil t. c. q. 12 8 0 4 17 0 1031 lb. 48 trailer ft. in. 6 3 6 3 6 3 33 10 bar truss 10 2 5 + M.C.B. diamond frame oak and steel cast steel 0 6 0 3 0 = = = oil t. c. q. 11 1 3 1 7 3 9 2 Great Northern, Piccadilly, and Brompton Railway. trailer 33 to 4 in. 3 to 4 in. 673 lb. 60 ft. 6 6 6 33 0 cast steel 10 2 5 in. 6 10 G 3 0 500191 0 6 oil 7 t. C. q. 5 0 2 16 0 572 lb. 62 788 SECTION X. " : I ! 1 ROLLING STOCK AND MOTORS. 789 Table 11.—Length of Track and Route of Some Electric Railways. Name of Line. City and South London Railway Liverpool Overhead Railway City and Waterloo Railway Central London Railway. Great Northern and City.. Mersey Tunnel Liverpool and Southport.. · • one •• North Eastern Railway Metropolitan, London Metropolitan District, London Underground Electric Railways, London .. • • ·· Manhattan Elevated, New York Brooklyn Rapid Transit, New York Interborough Rapid Transit, New York Boston Elevated, New York Chicago South Side Elevated Lake Street Elevated .. ·· Length of Route. Length of Track (single). • 23.5 miles miles D.C. 6.13 12.26 3rd rail| 500) 6.5 13.0 550 1.5 3.0 500 6.25 12.5 500 3.33 500 insulated 4.65 600 600 track and 4th rail track 550 550 insulated 550 6.66 9.3 47 37.5 82.0 W .. Metropolitan West Side Elevated Wilkesbarres and Hazelton, Pa. Paris Metropolitan.. 10.78 21.56 Berlin Elevated and Underground 6.23 12.46 Paris-Versailles (Oest) Berlin-Gross Lichterfelde.. 11.0 24.0 6.0 12.0 37.54 75.08 37.63 117.14 37.0 87.73 21.0 56.0 7.77 15.54 8.56 18.62 7.5 18.62 18.64 37.28 26.2 27.0 Method of Opera- tion. >> "" "" "" "" "" "" "" * A "" "" "" "" :: "" "" "" "" "" "" Voltage on Con- ductor. "" 59 550 500 500 5001 500 .. .. or Track Rail Insulated Return. 500 700 500 550 track "" "" >> "" 99 track "" track "" "" "" "" 19 "" track eight per Yard of Track Rails. M ·· lb. lb 80 40 5641.5 87 46.7 100 85 80 86 100 76 : ·· 90 80 86 100 86 100 100 90 .. Weight per Yard of Third Rail. •• 85 85 90 60-80 30 80 95 80 105 79 58 .. 82 82 Coaches for Rapid Handling of Crowds. A system which practically combines the advantages of all other previous arrangements is that employed on the Illinois Central Railway. The coaches are provided with cross seats with a longitudinal corridor to permit of the even distribution of the passengers. Side doors are used to render the process of loading and unloading as speedy as possible, there being as many doors on each side as there are compartments in the coach. The doors are not of the old swinging type used on steam lines, but are of the sliding type, and are operated preferably by pneumatic power, but can also be worked by hand. In either case, man can lock and unlock, open and close all the doors of one coach simultaneously. If desired, he need not open the doors after unlocking them, but leave this to be done by the passengers themselves. By the above means, the doors can all be closed simultaneously before the train starts, and are not unlocked until the train stops again, hence there is no chance of anyone boarding or leaving the car whilst in motion. Sliding doors also have the advantage of being safer than swinging doors, as in the event of any of them not being properly locked, they do not fly open if a passenger leans against them, as would be the case with swinging doors. There is no risk of injury to passengers during the closing of the doors, since though the motion is rapid at first the final closing is slow and safe. Also, as the doors slide into the walls of the car, they are opened without occupying any additional room, and with the complete absence of risks either to passengers in the train or on the platform. 2 790 SECTION X. In connection with the design of carriages, it is interesting to note that at the time of the Chicago World's Fair, the New York Railway Company built a large number of railway coaches with side entrances, some of them double; and by this means they found it possible to load and unload 100 passengers in ten seconds; and on one occasion five trains, each carrying 1000 passengers, were unloaded on the # KİMİ,GAİPALI B A LUGGAGE 1 A LUGGAGE 'B__18-8QQmb=_61-8″ @ PROPOSED MOTOR CAR (TO SEAT 73) HAMBURG RAILWAY 59:0″ 1ST CLASS MOTOR CAR (TO SEAT 48) A. Sliding Door B. Swing Door 59.0" 3RD CLASS Motor Car (TO SEAT 50) A 58' 6*___. 1ST CLASS TRAILER CAR (TO SEAT 60) A 58:6 A A 3RD CLASS TRAILER CAR(TO SEAT 64) MERSEY RAILWAY Fig. 20. Seating Accommodation of Various Carriages. 1118 same platform within four minutes. The total number of passengers carried in the day on which this record was made was 509,000. It is of great importance for high rates of speed that the cars should be very strongly built, not only with respect to the flooring, but also as to walls and roof; since in event of the derailment or any similar accident, the consequences to the passengers depend very largely upon the rigidity of the car. ROLLING STOCK AND MOTORS. 791 i j MOTOR LUGGAGE B #annaðinnand MOTOR CAR ( TO SEAT 69) H A. Sliding Door B. Swing Door JU IA JUU 1 / 10 11111111 60:02 TRAILER CAR (TO SEAT 66) LANCASHIRE & YORKSHIRE Railway ILWA # A 7:795m-25:6% Trailer Car (TO SEAT 26) PARIS METROPOLITAN Electric Railway [A A A A A A TRAILER CAR(TO SEAT 88) ப A -2·9m 1:104 Trailer Car(to Seat 100) ILLINOIS CENTRAL RAILWAY A 49-103 MOTOR CAR (TO SEAT 48) UT S 10 L 49-10 TRAILER CAR TO SEAT 525- LONDON UNDERGROUND ELECTRIC RAILWAY 149:6 רוון A -> 12:7m=41:8". TRAILER CARITO SEAT 44) BERLIN ELEVATED Railway Fig. 21. Seating Accommodation of Various Carriages. _8:70 *23 8 • B 9:4 LONDON UNDERGELECTRY. LANCASHIRE & YORKSHIRE RY MOTOR CAR MOTOR CAR ILLINOIS CENTRAL RAILWAY TRAILER CAR X Fig. 22. Fig. 23. 2016. LUGGAGE A __24+ 10%. .__. A 10.6 1 • 11:66 14:336* *** 22 39 MOTOR CAR (TO SEAT 48) MANHATTAN ELEVATED RAILWAY www.ww and 40:8 49:6 9:4 12-8+ HAMBURG RAILWAY MOTOR CAR MOTOR CAR (TO SEAT 58) GREAT NORTHERN & CITY RAILWAY B 56:6* IST CLASS MOTOR CAR (TO SEAT 48.) A. Sliding Door B. Swing Door NORTH EASTERN RAILWAY MOTOR CAR DUF 1мг 56:6″ K 3RD CLASS TRAILER CAR(TO SEAT 70) NORTH EASTERN RAILWAY K- B 240: B I I I 10:6 13:10. ✰. 1119 Heavy Electric Traction. Outside Dimensions of Various Carriages. Seating Accommodation of Various Carriages. 19:6 12:26 1116 1 | ROLLING 793 STOCK AND MOTORS. Table 12.-Weight, Dimensions, and Seating Capacity of some Electric Trains. Name of Line. City and South London Liverpoool Overhead Waterloo and City Central London Great Northern and City Mersey Tunnel Liverpool and Southport Manhattan Elevated, New York Brooklyn Rapid Transit Boston Elevated Metropolitan, W. Side Elevated Paris Metropolitan Berlin Elevated and Under- •• ·· ·· ·· Number of Cars in Train. ground Wilkesbarre and Hazleton, Pa. Berlin Gross Lichterfelde 0 2233 1-2 1-3 2 2 North-Eastern 2 Metropolitan, London 2 4 Metropolitan District, London 3 4 48 Underground Electric Railways of London 111 3 4 1244 ∞ H OD ANNOHO HON tomatico Maximum Seating Capacity. 212 68 272 94 120 308 114 114 456 84 96 648 54 58 108 116 788 50 64 292 100 128 1584 69 66 270 138 132 540 186 96 & 136 140 372 47 57 42 1 48&68 70 00 00 00 00 00 00 0 1-2 3-6 48 4 48 4-5 0· 48 4 2 48 50 292 ****S A NN NO 1 44 34 136 60 154 228 324 394 2 48 50 244 240 52 304 52 352 52 352 38 .. 31 31 248 39 Maximum Combined Seating and Standing Capacity. 44 122 38 74 58 206 ** ****** 229 76 104 704 100 584 100 488 480 : Weight, Exclusive of Passengers. 62 496 88 (244 76 1.10 78 298 tons loco. 13 16.85 27 23 40 36.5 29 104 608 36 104 1704 36 36 25.5 29.5 23.75 14.75 17 8.5 12.75 21.13 37.5 42.25 35.5 Trailer Car. 21 17 17 tons 9 12.3 18 15.5 121 20 200 19.5 131 17 .. Total 13 Train. Weight per Seat, Exclusive of Passengers. tons lb. lb. lb. 49 593 807 46.0 798 460 677 90 1062 707 884 724 1227 1660 774 1147 1635 683 1005 80 140 176 Motor Car. • } ·· 1353 955 1680 732 1032 1680 732 1120 • ·· 672 964 : : : Total Overall Length. 50.3 176 1680 732 1120 137.5 1055 48 106 1190 582 974 147.5 1376 38.5 1210 1376 46.5 86 1228 614 776 ft. } loco. 32 14 45 46 46 49.5 59 60 56.5 50.3 50.3 29 55 1214 650 1009 41.7 37.52210 2210 120. 63.3 Car. Total ft. ft. 142 45 46 46 135 184 322 49.7 347.3 9.3 59.6 296.88.6 60 240 9.85 56.5 169.5 9.0 50.3 301.8 8.67 |50.3| 352.18.67 50.3| 352.18.07 284 46 8.6 235.5 232 .. ·· Overall Width of Cars. Train. ·· 29 ft. ·· Kad 41.7 125.17.4 8.5 WE : 794 SECTION X. THREE - PHASE (FIGS. 24 to 26, pages 796 to 799.) Polyphase, especially three-phase, motors have found practical application ever since the now historic three-phase power transmission from Lauffen to Frankfort, during the International Electric Exhibition of 1891. It was left to Messrs. Brown, Boveri and Co., of Baden, Switzerland, first to suggest, and finally successfully carry out, the practical equipment of the first commercial three-phase electric tramway, at Lugano, in 1894. RAILWAYS. The reason for equipping this line with three-phase motors were that there was water-power at Maroggia-12 kilometres (7 miles) from Lugano-which was utilised to light the latter town. A tramway was wanted along the lake front at Lugano, to connect the various hotels. Owing to the distance, it was out of the question to generate continuous current at Maroggia, and the expense of installing and operating a converter station at Lugano was too great to be considered. The first railway to be equipped with three-phase motors was the Burgdorf- Thun line, also installed by Messrs. Brown, Boveri and Co., and opened in July, 1899. The reason for equipping lines hitherto on the three-phase system would seem to be that in all cases the current is generated by free water power, the current being transmitted at high tensions-10,000 to 20,000 volts. In all the lines installed by Messrs. Brown, Boveri and Co., the potential in any one phase of the contact line does not exceed 750 volts, the current from the feeders being transformed down to this pressure in static transformers situated along the line. Messrs. Ganz and Co. have departed from this practice, and are using 3000 volts on their system on the Lecco-Sondrio line. Messrs. Siemens and Halske, and the Allgemeine Elektricitäts Gesellschaft of Berlin, have used 10,000 volts on the experimental military railway between Berlin and Zossen. The majority of three-phase railways in existence are mountain lines. The Lugano three-phase line was built and partly equipped by Messrs. Brown, Boveri and Co., of Baden, Switzerland, and by the Oerlikon Company, who have favoured the system for some of the steep gradient and mountain railways of Switzerland. Water power is the prime mover, and a 300 horse-power turbine drives a 150 horse-power generator at 600 revolutions. The 5000-volt current, generated about 8 miles from Lugano, is reduced at that place to 400 volts, the pressure at which it is delivered to the 12-pole 20 horse-power motor fitted to each This is but a very light line, the speed on which is about 9 miles an hour; the cars weigh 6½ tons, and the motor is geared in the ratio of 1 to 4. car. The Jungfrau Mountain Railway, built also by Messrs. Brown, Boveri and Co., is a metre-gauge line, on which trains holding 80 passengers are carried at a speed of 54 miles an hour. This is a true mountain railway, with a maximum (rack- worked) gradient of 25 per cent. It has been in complete and successful operation since April, 1899. The Evian-les-Bains Railway was equipped by Messrs. Ganz and Co. It is only 330 yards long, and has a maximum gradient of 10.2 per cent., on which is a curve of 49 ft. radius. The rolling stock consists of one car, holding 14 persons, and the speed is about 6 miles per hour. The Stansstad-Engelberg is another mountain railway electrically equipped by Brown, Boveri & Co. In its length of less than 13 miles there is 1 mile of rack. The speed on this latter is about 3 miles, and elsewhere about 12 miles an hour. The locomotives weigh 14 tons, and are each provided with two 35 horse-power motors, working on a 650-volt circuit. The Gornergrat Mountain Railway (Brown, Boveri and Co.) runs from Zermatt to Gornergrat, a distance of 5 miles; part of this is a rack line. The maximum speed is 4 miles an hour, with trains of one locomotive, and two carriages that carry 110 passengers. Fig. 24, page 796, show the rolling stock used in the Lecco-Sondrio three- phase railway, of which further particulars are given in Table 14, page 797. Figs. 25 and 26, pages 798 and 799, illustrates the electric connection on the motor cars and locomotives of the Burgdorf-Thun Electric Railway. ROLLING STOCK AND MOTORS. 795 Name. Zermatt-Gorner- grat Jungfrau Stans sta đ- Engelberg Burgdorf-Thun Valtellina ·· } Zossen (Berlin).. Date Opened. Length in Miles. 1899 14 1899 25 1898 5.7 3 ft. 3 in. Rack 1 in 5 1898 2.2 13 ft. 3 in. Rack 1 in 4 Adhesion 3ft. 3 in. 1 in 20 Rack 1 in 4 : : 67 Gauge. 14 4 ft. 8 in. Table 13.-Three-Phase Electric Railways. 4 ft. 8 in. Maximum Gradient. 4 ft. 8 in. 1 in 40 1 in 185 per Hour. Speed Miles 4.35 12.5 3 Passenger 22.5 Goods 11.2 Passenger 42 Goods 20 102 Motor- Locomotives Cars. or Horse-Power per Train. Locomotive 180 40 Locomotive 200 38 Motor-Car 105 Locomotive 150 Motor-Car 240 Locomotive 300 }} Motor-Car Locomotive Motor-Car 600} Periods per Second. 3,000 40 Trolley - line Voltage. 15 540 500 750 40 750 3,000 Transmission Voltage. 5,400 7,000 5,300 16,000 20,000 50 10,000 10,000 Remarks. Braking on down gradient by return- ing energy to line. Ditto About 1 mile of rack; braking on down gradient by return- ing energy to line. Generators 4000 volts; step-up transformers. to "Cascade" starting and braking. Re- turns energy line when braking at speeds above half speed. Step-down trans- formers on the train. Braking by separately exciting and short - circuit- ing the motors and by reversing mo- tors. Experimental military railway. (High speed). 196 SECTION X. dra Daddad Upd SHUDDE 調 ​8707 *** Part D MEAN SEAN dan mandate de de dette kan omba má o te mbeten de me the grade de MAA ADA pla Steve a statute to a de Pada o te tagad map 1°1 日​一日 ​dar LOGO moment a 4-dmete ******* bulacan a dat d 11300 19080 **** a non è que 18, 180 ID!! $70 Spag THE AREWE 1a.mall *** 2500 ****** Fig. 24, Side Elevation, Plan and Section of Motor Car, (Lecco-Sondrio Railway.) 20 *** *** ={ # 38 -~~-~- - **** · ·2700 wanaume m ROLLING STOCK AND MOTORS. 797 Table 14.-Particulars of Rolling Stock on the Lecco-Sondrio Line. Complete weight of motor car Weight of one motor truck, with wheels and axles, but without motors Weight of car body Total weight of one motor complete Weight of one complete trolley Weight of one water rheostat, complete, filled with liquid Distance between king-pins of trucks Wheel-base of truck Length of car over dashboards Length of car over buffers Width of car over all Diameter of wheels Gauge Height from top of rail to top of car Diameter of car axles ·· ·· ·· •• .. Number of axles Distance between axles Length between buffers Number of motors Normal seating capacity of car Maximum seating capacity of car ·· .. ·· .. .. ·· · • • .. • ·· Total dead-weight of locomotive Weight of electric equipment Weight of each motor Speed per hour ·· •• ·· · · · .. ·· ·· ·· ·· ·· .. .. .. ·· Figs. 25 and 26 show the electrical connections employed in the case of the motor cars and locomotives on the Burgdorf-Thun line, of which Tables 15 and 16 give further details. Table 15.-Details of Burgdorf-Thun Motor Cars. 16 50 4 Number of places, second class Number of places, first class Number of axles on each car Distance from centre to centre of bogie wheels Distance from centre to centre of bogies Length between buffers 86, in. 31 ft. 2 in. Number of motors Power of each motor.. Tension at terminals of motors Number of revolutions of motors per minute ·· Speed of travel of car per hour Ratio of reducing-speed gear Total dead-weight of car Weight of electric equipment Nett weight of car Weight of each motor .. .. ·· .. .. •• ·· ·· • ·· •• .. • .. •• • .. • ·· ·· · • · Power of each motor Tension at terminals of motors Number of revolutions of motors per minute .. ·· ·· ·· 53,660 kgs. (53.6 tons) 7,500 (7.5 tons) (16.5 tons) (3.8 tons) (357 lb.) ·· 16,500 3,800 162 • ·· "" 11.5 metres 2.5 18.1 19.17 2.7 1.17 1.435 3.485 .150 "" "" 30 passengers 40 passengers ·· ·· .. ·· ·· ·· ** ·· ·· · 453 (997 lb.) (37.8 ft.) (8.2 ft.) * - • Table 16.-Details of Electric Locomotives on the Burgdorf-Thun Railway. •• ·· ·· "" "" "" "" .. .. · "" "" • "" "" • "" >> ·· ·· ·· (59.9 ft.) (62.9 ft.) (8.9 ft.) (3.84 ft.) (4 ft. 8 in.) (11.43 ft.) (9.32 in.) ·· .. 53 ft. 5 in. 4 60 horse-power 750 volts 600 22.35 miles 1 32 tons 10 "" 22 "" 30 cwt. 2 10 ft. 3% in 25 ft. 7 in. 2 150 horse-power 750 volts 300 29.6 tons 10 tons 4 tons 11.18 or 22.35 miles 798 SECTION X. ! Co (877) SWITCH CONTROLLER OTOR BOW COLLECTORS ====== COMPRESSOR MOTOR FUSES A 20120 RAILS RESISTI 3 LIGHTING ARRESTER SWITCHES FOR HEATING, LIGHTING A FUSES NEATING COILS 0000 1000000 FUSEB R/HEAT SWITCH RETURN CONTACT Fig. 25, Electrical Connections of Motor Car. a 福 ​56510 (Burgdorf-Thun Railway.) ROLLING STOCK AND MOTORS. 799 あ ​(872) Bow COLLECTORS AMP MET SWITCH “COMP. matö CONTROLLER.1.84 RAIL a mind RESISTANCE FUSES MOTOR # VOLT METER AUTOMATIC SWITCH| MOTOR 2. # OMPRE MOTOR RETURN CONTACT Fig. 26. Diagram of Electrical Connections on Locomotive. jót TRANSFORMERS CONTROLLER 2: (Burgdorf-Thun Railway.) 800 SECTION X. Power Consumed per Car Mile. In working out the power required in the power station, it is necessary to know the amount consumed per car-mile run. In this connection, in Table 17, for which we are indebted to the courtesy of Professor Mengarini, of Rome, a very interesting series of figures is set forth, which shows that for lines having at least ten motor cars, even with heavy gradients of 1: 10, an allowance of one Board of Trade unit per car-mile is quite safe in estimating the quantity of power which will be required a point which is of very great interest where, as in many instances, the power is not generated by the tramway company, but is bought from a lighting or power station, and a guarantee of an annual minimum consumption has to be given. Number of Cars Running. Table 17.-Average Power Consumption on Electric Line, Maximum Grade 1.10. AVERAGE SPEED, 8 MILES PER HOUR. ENG COI CÓ CÓ CÓ CÓ C 20 21:00 1 2 3 4 6 7 8 8.3 8.2 8.8 $ 9 Number of Days Test Lasted. 4413 5 4 5 31 31 31 29 B. T. Units per Car Mile. 2.185 1.585 1.008 1.116 1.147 1.068 1.034 0.992 1.034 1.075 1.046 .! Current consumption on 10 per cent. grade, 50 to 70 amperes at 500 volts. Maximum gradient, 1:10. Sharpest curve, 48 ft. radius. Car Energy Curves. (FIGS. 27 and 28, page 801.) These curves are based partly upon calculations and partly upon experimental results. They are intended to serve as a guide in laying out new installations, or in raising the speed upon existing systems. Curve Fig. 27 is plotted for double-truck cars using two motors, or single-truck cars using one motor, i.e., half the axles driving the car. Curve Fig. 28 is plotted for double-truck cars using four motors, or single truck cars using two motors, i.e., all the axles driving. As an example of the difference in the energy consumed per car under the two conditions, consider a schedule speed of eleven miles per hour, and six stops per mile. The curves show that when all the axles are driving, the average energy consumed is 16 kilowatts per car as against 20 kilowatts when only half the axles are driving. The difference is due to the superior acceleration which can be obtained when all the axles are driving, and is accentuated when the car has to operate under adverse circumstances, such as very icy weather, &c. Both sets of curves are made out for schedule speeds of from six to twenty miles per hour, including stops averaging eight seconds each, and the energy values given are at the car axle, and do not include any line losses, which would raise the result from 10 to 15 per cent. above that given by che curves. The curves are also plotted for level track; and where the road is hilly another 10 to 15 per cent. must be added on. For specially hilly routes containing long and severe grades, the curves are not suitable-such problems should be treated as special cases. The curves are plotted for a 12-ton car, but as the energy consumed is directly proportional to the weight of the car, they can easily be used for cars of any weight, with very little calculation. To obtain the average energy consumption per car necessitates a very intimate knowledge of the local conditions governing the operation of the road. In nearly ROLLING STOCK AND MOTORS. 801 MILE. PER STOPS MILE PER 14 (869) STOPS 18 12 71 10 8 2 13 12 11 10 → ∞ ~ S → ❤ 2 0 (869) 2 4 2 4 6 6 CAR ENERGY CURVES. 12 TON CAR: 120 LBS. PER TON ACC, INCLUDING 15 LBS.PER TON FRICTION; 150LBS.PER TON BRAKE. 17 7 27 8 10 12 14 AVERAGE 28 19M.PH 6 8 10 12 14 16 18 20 22 24 26 28 30 32 AVERAGE KILO-WATTS. JOM PH n KILOWATTS. 12 -72 13 ÇAR ENERGY | CURVĖS. 12 TON CAR:160 LBS PER TON ACC.INCLUD -ING 15 LBS.PER TON FRICTION; 150LBS. PER TON BRAKE. 8 14 -74 15 16 181200 1947 18 19 -B0 16 18 20 22 24 26 28 30 32 34 36 38 Figs. 27 and 28. Car Energy Curves (see page 800). 122 DD 802 SECTION X, every case, the schedule speed during "rush" hours is low, and there are many stops, but when the traffic is lighter, the speed is considerably greater, and there are but few stops, especially in outlying districts. Hence the traffic throughout the day should be divided into classes, and the average energy consumption per car determined for each class. Then the average of these class averages may be taken as the energy consumption of the car throughout the day. Kind of Car. Trailer Motor car.. "" "" Motor car with gears or armature Motor car.. .. Minutes Apart or Headway. 1234H LO 5 6 8 10 15 20 30 Table 18.-Traction Co-efficients. -- 6 50 33 25 20 17 14 13 10 7 5 842272="« Horse-power on axle = Weight of car in tons x tractive force in pounds × speed in feet per minute 44 Grade. Numerous experiments have proved that for the English climate and grooved rails a tractive power of 30 lb. per ton is necessary. For speeds below 10 miles an hour, the effect of the wind may be disregarded, and the following formula used for the level : 33,000 For gradients the lifting power must be added, which is given by : Weight of car in pounds x grade in per cent. x speed in feet per minute 33.000 29 p.c. 5.95 5.97 2.53 17 14 12 5.97 5.95 100 86 75 67 60 38 33 22 25 11 Mr. Tresca proved that the groove in the rail was the direct cause of a large portion of the resistance to traction. 9 Table 19.-Number of Cars on Ten Miles of Track, Various Speeds and Headways. 6 4 Co Speed in Miles per Hour. lb. lb. 4.11 6,270 400 7.81 16,872 1,119 11.10❘ 16,872 533 | FERERE 7.23 16,135 1,036 | 8.14 16,300 1,056 19 Weight of Car. 15 Average Speed in Miles per Hour. 7 」「 8 」 。 「 10 「 12 「 16 | 20 | 25 「 3 30 14 13 13 11 11 10 9 8 5 4 3 Dynamometer Pull. 743200 8 8.2 -∞∞+~~ 30 20 15 12 10 Equivalent on Level. 8 lb. 26.4 112 106.21 6 73 85 ORTROONCOLO O DO QU 50 25 17 13 10 40 20 13 PRO-NOD HBGH Coefficient of Track Pull per Ton on Level. 10 lb. 98 14.95 14.70 8 7 6 2 1 9.85 11.75 Track wet "" 840000+H~~~- Remarks. 30 Track dry 15 10 6 5 2 1 24 12 *д∞HO OS QI QI - H ROBHMB 0 0 I m d 8 99 6 ** 5 2 2 1 1 20 10 7 5 4 3 3 3 2 1 1 1 J ROLLING STOCK AND MOTORS. 803 Table 20.-Tractive Resistance on City and South London Electric Railway. (P. V. McMahon.) Starting resistance on level.. Speed, 2 miles per hour 4 "" "" "" "" 6 8 10 "} Passengers inside ,, outside total "" >> >> " Brill truck) Depth of sill Thickness of floor "" of car Ditto at ends of car ·· .. ·· • · Length of body outside Gauge .. From rail to under side of sill (with · .. ·· Height from floor to ceiling at centre Thickness of roof ·· "" "" and seats From rail to roof outside at centre.. to top of seat to walking passage at sides ·· • ·· •• .. • CARS AND CAR BODIES. The electric car must have a strong underframe, with cross-timbers so arranged that portions of the floor may be removed to give access to the motors. The roof of an electric car has also to be constructed with a view to great strength, so as to be able to support the trolley and its stand. Besides the actual weight of the trolley, the increased speed and lurching, and the leverage exerted on the base of the trolley, due to the pressure of the trolley wheel against the overhead wire, requires the top frame of an electric car to be far stronger and heavier than on either horse, cable, or steam cars. See Figs. 29 to 32, page 804. For cleaning tracks after a heavy snowfall, specially-built snow sweepers have been developed. Two types of these are generally used: the first is used on country roads or extremely wide thoroughfares. It consists of an extra heavy truck, carrying two large circular wire brooms, set on a slant on each side of the car. A 50 horse-power motor is used to drive the brooms, and besides this motor, the car is furnished with the usual pair of 25 horse-power motors to drive the car itself along the road. Behind the brooms the ordinary snow-scrapers are usually provided. .. For cities having crowded streets, and where large accumulations of snow are never permitted to remain in the streets, a different kind of snow plough is used. This consists simply of an extremely heavy car, furnished with a pair of powerful motors driving it, and provided with scrapers, which scrape the snow from the centre of the track and deposit it on each side. With such an apparatus it is not possible to remove more than 2 in. or 3 in. of snow at a time. .. Table 21.-Some Dimensions of Double-Deck Single-Truck Cars. (Railway World.) •• ·· • "Standard" with Garden Seats. 22 34 56 ft. in. 16 0 4 81 2 11 0 5 007 6 9 0 4 .. 9 9 ·· 1 .. 1 1 .. .. .. ·· 42.0 lb. per ton. 18.0 13.5 10.2 12.3 13.3 Type. Special Low with Garden Seats. 22 34 56 ft. in. 16 0 4 84 2 11 0 0 03 6 2 0 4 1 "" "" "" "" "" 9 2 1 22 24 46 Knifeboard Seat Car. ft. in. 16 0 Bez 4 81 181478 2 0 51 0 6 9 0 44 9 9 8 4 9 0 804 SECTION X. ; 29 B 513 A-Trap Door. B-Crown Piece. G-Longitude: 30 512 K. $15 189 5.8.6.4 H TT D. Knee, E- Ribs. F-Sills. (side) F. M 377 SHOWING FRAMING. Hauste Platform Knee Light Rail A Belt Rail A Figs. 29 to 32. FLOOR FRAME FOR ELECTRIC CAR. IN Truse Rod Ribs -M A A M: G-Middle Bearer K-Corner Pillar. H-Crossing. L-Intermediate. JªEnd Crossing. Short Bearer. S&B-Spring Box Bearer. N-Short Tie Rod. G 0-Tie Rod. TRUSS ROD END PLATFORM SILLS. G HA **-1 SHOWING BODY COMPLETE. Corner Iron Toorpillar +K 32 Iron Moulding B Guard Rail with Iron mould! on face END ELEV HALF IN FRAME Construction of Car Bodies. 31 ROLLING STOCK AND MOTORS. 805 Table 22.-Double-Deck Car Bodies. (Railway World.) The principal dimensions suitable for mounting on a single 4-wheel truck, for 3 ft. 6 in., 4 ft., and 4 ft. 8 in. gauge are as follows: C'auge Passengers inside .. outside total >> "" "" Length of body inside outside "" "" "" Width over all .. over platforms of each platform. over fenders .. .. •• "" "" • ·· .. ·· over side pillars Height from floor to ceiling at centre. Approximate weight of body only Type of staircase Length over corner pillars platforms ·· ·· • •• " overall Width over side-sills posts overall "" Clear height inside at centre Overall height from rail.. • · ·· • ft. in. 3 6 22 28 50 .. ft. in. 15 4 16 0 26 0 5 0 27 0 6 3 6 0 6 9 3 tons Reversed ft. in. 4 0 22 30 52 ft. in. 15 4 •• 16 26 0 0 5 0 0 6 € 27 6 3 6 9 3 tons R. Preston Double-Service Car. (FIGS. 33 to 35, page 806.) Figs. 33 to 35, page 806, show a recent type of car which has been brought out and patented by the Electric Railway and Tramway Carriage Works of Preston. This is a single-deck car, which can be employed either as a closed car for winter service, or as a car which is practically open for summer use. This end has been obtained by the simple device of bringing the Monitor sashes down to the side of the car as shown in the figure, and thus providing sufficient space to push up both the lower sashes out of the way when it is desired to use the car as an open one. The noticeable feature is that the sashes are not removed for storage, neither do they drop into pockets. The serious objections to the latter method of con- struction and disposal of the sash are that the pockets take up valuable room in the wall of the car, while also becoming receptacles for dirt and refuse. The car can be altered to an open car in the space of a few minutes. The sashes are in two sections, held in the usual way between the posts by a pair of grooves on each post, into which the trunnions on the sash fit. When it is necessary to raise the sash, the lower one, after it has been raised a short distance, automatically engages the upper sash, and, carrying the latter along into the roof of the car, deposits it in a pocket, and slides upwards till it drops over a switch, with which it is held in place, and at the same time prevented from moving or dropping. The following are the chief dimensions of a car of this type standard gauge, seating 32 passengers :- ·· ·· ft. in. 4 8 .. ·· ft. in. 15 4 16 0 22 34 56 26 0 5 0 27 0 7 0 6 9 6 9 33 tons R. ·· • ft. in. 4 83 18 25 43 ft. in 13 13 14 2 24 3 5 3 25 8 7 0 6 9 6 6 Ordinary 8 8 ft. in. 20 8 30 3 31 11 8/ 0 11 7 10 10 10 The Electric Railway and Tramway Carriage Works Combination Car. (FIGS. 36 to 38, page 807.) Figs. 36 to 38, page 807, illustrate a combined opened and closed single-deck car designed by the above company to meet the demand for a single-deck car which should provide accommodation for both inside and outside passengers. The car illustrated has a seating capacity of 20 passengers outside, and is mounted on maximum traction bogies. Smaller cars of this type are also constructed for mounting on four-wheel trucks. * 806 SECTION X. 33 35 Collapsible Gate 183.111/2 辩 ​A your Erg ·6'Q' 18:7″ 27:10". JU Seats trimmed Rattan with Reversible Backs H ΠΠΙΠ 250 1.24 g 40:9 -..311/2 1120 8.0% 6.4 7:10 7.8 1/2″ 6.872 48½ Goæge 34 CA Figs. 33 to 35. Preston Double- Service Car. ROLLING STOCK AND MOTORS. 807 E=R 9:6 4.0 ! 03 36 20:6" Centres of Pwetal Points „16′10″ 3510″ " 2:6. Figs. 36 to 38. Preston Combination Car. 1/21 10:10½" 37 [6:9 38 6:5″ 808 SECTION X. Top-seat motor car, single truck.. Bogie motor car Top-seat open motor car, single Single deck, single truck ** Table 23.-Leading Dimensions of Car Bodies Manufactured by the Electric Railway and Tramways Carriage Works, Preston. >> >> " Open motor car, single truck Combination car, Combination bogie car "" >> "" "" "" .. Semi-convertible car, single truck Top-seat single truck .. .. •• : " .. : ·· : : ·· Gauge. ft. in. 3 6 3 6 3 3 4 8 3 6 3 6 4 8 4 8 4 83 4 85 4 72 { Length of Length Body Over Over Fenders. Corner Posts. ft. in. 16 0 23 6 16 0 20 0 18 0 over platform } 00 12 8 16 0 18 7 16 0 16 0 ft. in. 28 6 34 11 26 9 29 0 28 0 29 0 30 0 36 0 27 10 27 6 27 6 Length of Plat- forms. ft. in. 5 9 5 0 5 0 4 0 4 6 ·· 8 2 9 6 3 11 5 3 5 3 Width Over Sills. ft. in. 5 5 : 5 10 6 0 5 7층 ​6 0 6 5 7 8 6 0 6 0 Width Over Window Belts. ft. in. 6 3 6 0 6 9 6 9 7 6 6 1 6 6 6 9 8 03 6 7 6 9 Width Over Roof. ft. in. • .. ·· : ·· 6 4 6 9 8 4 ·· : Clear Height Seating Inside Capa- city. at Centre. ft. in. 6 9 6 9 6 6 7 8 710 7 10 6 9 6 9 48 72 58 28 28 40 34 46 28 58 ROLLING STOCK AND MOTORS. 809 D D² Table 24.-Principal Dimensions of Standard Open and Closed Cars used in Fourteen Large Cities in the United States. City and Name of Company Baltimore-United Railways and Electric Company Boston Elevated Railway Company Buffalo Railway Company Chicago City Railway Company Cleveland Electric Railway Company Denver City Tramway Company San Francisco-United Railroads .. Detroit-United Railway Company.. Indianapolis Traction and Terminal Company Milwaukee Electric Railway and Light Company Minneapolis-Twin City Rapid Transit Company Philadelphia Rapid Transit Company Pittsburg Railways Company St. Louis Transit Company ·· ·· : : : : · Single, Double, or Maximum Traction Trucks. M. T. M. T. and double double "" "" "" >> "" "" "" "" single double " Length of Body. 2000008 * ft. 28 ***** Closed and Semi-Convertible Cars. 33 in. 00000+ 6 4 ~ 2 OOHOH 0 0 1 0 19 11 30 0 California type 38 0 33 41 Length Over All. ***88* ft. in. 38 33 40 48 43 41 O382 O 45 0 6 41 0 45 0 41 OONOO∞∞ 5 ft. and 6 ft. side entrance, 5 ft. 2 in. 6 ft. 6 in. and 5 ft. 6 in. 6 0 5 0 5 3 4 6 4 5 5 6 6 two side entrances, 2 8 8 3ft. 6 in. and 7 ft. 0 25 38 0 30 0 -les 42 8 39 44 Length of Platforms. in. 0 4 0 4 3 6 5 ft. 154 Width of Car Width of Car Body at Body at Belt Sills. ft. in. 7 6 6 8 7 8 8 8 6 6 7 31 8 8 8 8 7 1 4 1 6 7 1-ko-ka-ica 8 6 8 2 9 1 ft. in. SOONON 277∞∞∞ ∞ ∞ ∞ ∞ ∞ ∞ 1 00 Rail. Floor. 8 7 10 6 8 8 8 8 8 2 1 7513NO 2 Height Side Top Rail from 6 8 9 '0 ft. in. (CO LOCO LO co co • 5 6 5 6 57 5 10 5 10 5 6 0 Edo no∞o hoo I 6 0 2 5 9 5 10 72 6 0 810 X. SECTION Table 24.-Principal Dimensions of Standard Open and Closed Cars used in Fourteen Large Cities in the United States.-(Continued.) City and Name of Company. Baltimore-United Railways and Electric Company Boston Elevated Railway Company.. Buffalo Railway Company Chicago City Railway Company Cleveland Electric Railway Company San Francisco-United Railroads St. Louis Transit Company ·· Denver City Tramway Company Detroit-United Railway Company. Indianapolis Traction and Terminal Company Milwaukee Electric Railway and Light Company Minneapolis-Twin City Rapid Transit Company Philadelphia Rapid Transit Company Pittsburgh Railways Company ·· ·· ·· ·· * Same cars summer and winter. .. .. .. .. ·· :: .. ·· Height of Step from Rail. in. 15 16 16 16 17 14 149 17 from Step to Plat- Height form. 14 142 13 13 131 12 2 steps 17 and 13 in. 2 steps 11 and 12 in. 13 12 .. 16 2 steps 18 in. 153 16 15 .. 13 12 Closed and Semi-Convertible Cars. 13 2 steps of 12 in. 13 Height Riser from Platform to Car Floor. in. 72 7 8 10 3 10 9 5 8 8 10 none 13 Cross or Side Seats. side ,, "" cross side Seating Capa- city. cross side "" cross outside side inside cross 46 |||21,760 34 24,660 40 40,180 52 | 48,000 34 | 28,000 cross side and cross 43 52 44 Weight Com- plete Without Passengers. 48 34,000 32,000 "1 cross side & 14 cross 52 | 43,000 40 | 32,000 30 17,100 50 |||32,600 44 33,500 50 40,000 + The long closed semi-convertible car is also used in summer. Kind of Brakes. hand >> straight air air hand straight air storage air alr hand straight air "" magnetic straight air wheel & track storage air Open Cars. Single, Double, or Maximum Traction Trucks. M. T. single, M. T. and double double double + single M. T. * single double || Weight without motors. ROLLING STOCK AND MOTORS. 811 Table 24.-Principal Dimensions of Standard Open and Closed Cars used in Fourteen Large Cities in the United States. (Continued.) City and Name of Company. Baltimore-United Railways and Electric Company Boston Elevated Railway Company.. Buffalo Railway Company Chicago City Railway Company Cleveland Electric Railway Company Denver City Tramway Company ·· ·· ·· Same cars summer and winter. •• ·· Detroit-United Railway Company. Indianapolis Traction and Terminal Company Milwaukee Electric Railway and Light Company Minneapolis-Twin City Rapid Transit Company Philadelphia Rapid Transit Company Pittsburg Railways Company San Francisco-United Railroads St. Louis Transit Company ·· ·· ·· ·· .. ·· •• All. ft. in. ft. 38 9 29 34 42 4 2 11 * 43 0 +34 5 * +41 6 24 3 34 2 Width Over All. * * in. 7 10 7 6 7 6 8 9 8 †7 10 $8 7 7 * 2 * 31/ 10 10 * Height Side Top Rail from Floor. ft. 6 5 5 5 6 in. 1 5 5 7 * 1 +5 $57 8 Open Cars. Height Run- ning Board from Rail. in. 18 19 19 $12 2 steps 138 * +18 * 17 to Height from Running Board Number Floor. in 16 15 16 $12 * 12 ** +16 16 * of † The long closed semi-convertible car is also used in summer. car in summer. § Two 12-in. steps. || Weight without motors. Benches. 2424* 12 12 14 14 * * *** * Capacity. Seating 11 848** 45 60 84 * * +12 +60 +18,000 * * * 60 || ||23,100 15,080 22,073 34,924 air and hand * 11 55 Weight Com- plete With- out Passen- gers. $26 152 $26,500 * * • 40,000 ** * * of Kind Brakes. hand hand hand hand * * + hand ‡ hand magnetic + Also uses semi-convertible *: 812 SECTION X. Table 25.-Double-Deck Car Bodies. (Railway World.) The principal dimensions suitable for mounting on two 4-wheel maximum traction trucks for 3 ft. 6 in., 4 ft., and 4 ft. 8 in. gauge are as follows: Gauge Passengers inside "" outside total.. 19 "9 Length of body inside .. outside "" " "> "" Width over all "" over platforms of each platform over fenders ·· ·· Length of Body. ft. in. 14 0 14 6 15 6 16 0 16 6 17 0 17 6 18 0 18 6 19 6 22 () 22 6 • ·· · 24 0 26 0 27 0 28 6 30 0 31 6 34 0 35 6 •• only Type of staircase, Reversed .. ·· side pillars.. Height from rail to underside of channel sole Height from rail to platform floor Height from floor to ceiling at centre ·· Approximate weight of body tons .. Length of Platform. •• ft. in. 4 0 4 0 4 0 4 0 4. 0 4 0 4 0 4 6 4 6 4 6 5 0 5 0 5 0 5 0 5 6 5 6 6 0 6 0 6 0 6 0 ·· .. ·· •• .. .. ·· ft. in. 3 6 32 33 65 ft. in. 22 10 23 6 33 6 5 0 34 6 6 0 59 2 2 22 2 0 20 6 8 69 Width. ft. in. ft. in. ft. in. ft. in. ft. in. 40 4 8 4 8 3 6 30 30 30 30 34 38 42 64 68 72 ft. in. 6 0 6 0 6 0 6 0 6 0 6 0 6 0 6 3 6 3 ft. in. 21 4 6 3 6 6 6 6 6 6 6 6 6 9 12444 44 R. R. R. 6 9 7 0 7 0 7 0 7 0 22 0 32 0 5 0 33 0 6 3 6 0 ft. in. 21 4 22 0 32 0 .5 0 33 0 6 6 6 3 22 20 69 40 30 36 66 16 16 21 22 22 22 24 24 26 26 30 30 32 34 36 38 ft. in. 21 4 40 42 46 48 22 0 32 6 5 3 ft. in. 21 4 22 0 32 0 5 0 33 6 33 0 6 6 70 6 3 6 9 2 2 22 20 20 6 9 6 9 42 12 12 R 42 R. R. Ꭱ. NOTE.-The car given in the fourth column is fitted with vestibule ends, hence the increased weight and length of the platform. The widths given are those usually allowed: these may have to be reduced for special narrow streets to suit the requirements of the Board of Trade. The width for the narrow gauge may sometimes be the same as for the standard gauge, depending on local conditions. Table 26.-Car Dimensions and Passenger Capacity. ***5228 46 76 29 29 ft. in. 20 4 29 29 33 33 37 41 41 45 45 49 49 53 57 57 21 0 31 0 5 0 32 6 70 6 9 2 2 20 69 ft. in. 4 8 ft. in. 22 10 Passengers Passengers Total Number Outside. of Passengers. Inside. 23 6 33 6 5 0 35 0 7 0 6 9 2 2 2 0 6 8 CESSNEY 41 41 46 47 34 46 80 51 51 53 53 59 225FF2758* 95 103 115 R. The Brush Electrical Engineering Company's Cars. Figs. 39 to 42, page 813, give an example of a car which is built by the Brush Electrical Engineering Company, and is much used throughout the country. ROLLING STOCK AND MOTORS. 813 39 40 5′3″ (890) J 1 6'ot 27-97-16′ 3 × × × × × × × × × × × × × × × X XXX X X X X X X X X X X X X X X X X Y RA XX XXX To seat 22 inside X X X X X X X X X X X X X X X X X X X X X X X X XX XXX <--1.'8' T பூய ALY 4.8'½ Gauge To seat 34 outside Figs. 39 to 42. Double-Deck Motor Car. (Brush Electrical Engineering Company.) L ·6′0″½ 21 41 42 814 SECTION X. TRUCKS. Comparison of Four-wheel and Bogie-Cars. The multiplication of the carrying units or the increased frequency of their circulation is the most convenient ideal for a dense traffic; and if, in addition to this multiplication of units, by the device of attaching a trailer to each motor car the carrying capacity of the unit itself can be momentarily increased by 50 per cent. (bringing it up to over one-and-a-half times the capacity of a double-truck car), to meet the requirements of the morning and afternoon maxima, all that is possible will have been done to meet the requirements of the traffic in question. The cost of working a single-truck car service with added trailer at the periods of maximum traffic is not greatly in excess of that of a double-truck car service. "" "" Table 27.-Weights of Various French Trucks. Name. French Thomson-Houston (Postel Vinay) Desouche David (Paris) Société Alsacienne (Belfort) Franco-Belge Table 28,-Longest Wheel Base on German Light Railways. Radius of curve in metres feet Mean wheel base in metres feet 25 40 82 131 1.4 1.8 50 75 100 125 150 180 164 246 328 410 492 590 2.0 2.5 2.9 3.3 3.6 3.9 6.56 8.2 9.5 10.8 11.8 12.8 4.6 5.9 "" ·· ·· ·· • ·· Weight in Pounds Standard Gauge, including Wheels and Axles, but without Motors. 5940 5720 4900 3690 ·· ·· ·· •• .. ** Trucks-General. The modern electric-car bodies carried on four wheels are seldom shorter than 18 ft. over the end panels, and reach 22 ft., exclusive of the platforms. The whole length of the car over the platforms is from 30 ft. to 32 ft. This increase of nearly 25 per cent. in the length and more than 25 per cent. in the weight of the bodies has been accompanied by an increase of only about 20 per cent. in the wheel-base of the trucks. A long and rigid spring-base is an absolute necessity. The wheel-base cannot be lengthened much over 7 ft. or 7 ft.; on this account a long spring-base must serve the purpose of an increased wheel-base. To obtain easy riding, it is necessary that all the springs should be sufficiently light to obviate vertical motion in the car body. Some makers constructed the side frames of the truck in one piece, by bolting heavy centre-bars to the pedestals. Others forge the side frames of the truck, and weld the whole together into one piece. A motor truck comprises many parts, the most important of which are the side frames, springs, wheels, axles, boxes, bearings, motor bearings and suspension, sandboxes, brakes, and safety appliances. The following are the essential con- ditions which must be fulfilled by a truck in order that it may be suitable for electric traction :- 1. The truck must be as light as possible, consistently with rigidity and strength. 2. It must be thoroughly braced, so as to keep it stiff and square, without having to depend in any way on the car body. The strains on a motor car in rounding curves, and when passing a change of gradient, are extremely severe : much more so than with horse-cars, where the horses pull the car round on curves, and go slower at a change of gradient. 3. The journal-boxes must be self-lubricating, must require but little attention, and must be dust-proof. 4. The brake action must be simple, effective, and easily adjustable; and the brake shoes must admit of being replaced at a moment's notice, and must be mounted in such a way as not to be influenced by the vertical motion of the car. 5. The truck must be constructed in such a manner as to render access easy to ROLLING STOCK AND MOTORS. 815 all parts; and to admit of motors, wheels and axles, journal-boxes, brake-gear, and other parts being easily removed, without having to dismember the truck. Cross-strains on bolts should be avoided as much as possible. 6. The car body must be attached to the truck in such a manner as to be readily removed on loosening a few bolts. 7. Springs must be arranged so as to render the running of the car as smooth when empty as when fully loaded, and to prevent the pitching and rolling motion to which street cars are so liable on sharp curves and rough roads. This is a highly important point, not only for the comfort of the passengers, but also to prevent rapid deterioration of the car wiring and car bodies; deterioration of the wiring is likely to cause grave results to the motors by producing short circuits. 8. An appropriate choice of wheels is most important. Track. Table 29.-Dimensions of Peckham Standard Trucks. (FIGS. 43 and 44, page 816.) Gauge ft. in. 3 0 3 0 3 0 3 3 3 3 2000 cookbook.com CD COO 3 6 3 6 3 6 4 0 4 0 4 0 4 0 4 8 4 84 4 81 4 8 2~~~~~ Nɔ ɖɔ ɖɔ ɖɔ 03 03 03 03 03 03 H HEE Wheel Wheel Gauge. Base. ft. in. 3 3 3 3 3 A 4 4 ft. in. 117 5 6 6 0 114 11- 6 6 5 6 6 0 6 6 7 0 5 6 6 0 6 6 7 0 5 6 6 0 6 6 7 0 5 6 6 0 6 6 7 0 117 11 400x-0001-0000/2000|0|05|00 B 11 ∞ ∞ ∞ ∞ с Length Over Axle- Boxes. ft. in. 5 8 5 5 5 11 5 11 5 11 5 11 6 2 6 6 6 6 6 6 2 6 2 7 8 8 -777 ∞ ∞ ∞ ∞ ~~~~ 2 8 8 8 D C. to C. of Side Frames. ft. in. 4 6 4 6 4 6 4 98 4 93 4 4 5 0 5 0 5 5 0 5 6 5 6 5 6 5 6 6 2 6 2 6 6 anka-ka E Length of Top Bar. ft. in. 13 1 13 7 14 1 13 1 13 7 14 1 14 7 13 1 13 7 14 1 14 7 13 1 137 14 1 14 7 13 1 13 7 14 1 14 7 The Brush Single Truck. (FIGS. 45 and 46, page 817.) F G Dia- Dia- meter of meter of Wheels. Axle. in. 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 in. 33 330 ∞∞∞∞ COPROPRU The frame is solid steel, supported on journal boxes by eight laminated springs. The car body is carried on eight long-movement coil springs, and four three- quarter extension elliptic springs, and the motor is supported on an independent spring base. The oscillation of the car body is prevented by the spring distribution. The four-coil springs nearest the ends, and the three-quarter elliptic springs, support the car body when empty. In addition to this, a spiral check-spring is placed at each corner of the truck to take the back-lash. The brakes are supported on coil springs, which prevent their communicating any shock to the car body. The journals have large wearing surfaces. The journal box holds a large store of lubricant, and is entirely dust-proof. The bearings are made of the best anti-friction metal. 816 SECTION · X, . 44 Host++e 19819 $553) 43 WILDORA B Figs. 43 and 44. Peckham Standard Truck. (HTEN : ! ROLLING STOCK AND MOTORS. 817 45 46 ...1.7 -2.64 * ∙11.14.- 6.0. _Y.. --101 10年 ​-- O 2.04 Figs. 45 and 46. Standard Single Track, Type A, Brush Company, O · - · 1. 7. ' - - - 818 SECTION X. Brill No. 21-E. Truck. (FIGS. 47 to 49, page 819.) The axle-box frame consists of two side-bars and two end cross-bars, secured at the corners by eight 1-in. bolts. The side-bars of axle-box frame are forgings made up from muck-bar billets, 4 in. square, forged into shape, forming a single integral piece each side of truck. The side-bar is a continuous solid forging. The yoke is formed out of the solid, and so welded that the grain in the iron is preserved. The end cross-bars are of solid wrought-iron, 7-in. thick by 3-in. face, with 6-in. right-angle foot bent at each end, by which feet they are securely bolted by J-in. bolts to side-bars, to make a continuous axle-box frame. In addition to these end cross-pieces, diagonal braces are bolted tightly into truck frame. These diagonal braces extend entirely across the truck frame, from truck side-bars diagonally across centre, and are so arranged as not to interfere with the motors. The journal boxes at the lower edges have wings formed in the casting, extending 6 in. outside of the wall of the journal boxes. These wings are recessed for a 34-in. long spiral spring, on which the axle-box frame rests. The top plates are of wrought iron down" at point of contact with springs. in. thick by 24 in. wide, and are "set The spring posts are of machinery steel, 14 in. round, having the ends shouldered with 1 in. shank, tapered. The lower end of spring post is shouldered in similar manner as top, and all spring posts are connected by a tie bar, which is made of 14 in. double thick hydraulic pipe, having wrought-iron ends, 2 in. by & in., welded on to receive the spring posts. The truck has two independent sets of springs, viz., the journal-box cushion springs, and the car-carrying springs. The journal box cushion springs are 3 in. lông by 4 in. outside diameter, and have a capacity of 5,500 lbs. each, with 1 in. movement. These springs to rest in recesses in wings of journal boxes, one each side. The car-carrying springs are divided into two classes, and are of different capacities. The spiral springs are located one on each side of yoke, 10 in. each side of centre. They are 7 in. long, 44 in. outside diameter, with capacity of 2500 lb. -each, with 2-in. movement. The semi-elliptic springs are located on drop-forged spring seats on end of side-bar. They are 36 in. long, having seven plates, 3 in. by in. steel, and have a capacity of 3000 lb., with 24-in. movement. They are secured to spring seat on axle-box frame by 5-in. round "U" bolts straddling the spring, having nuts and lock washers. The ends of the semi-elliptic springs bear against malleable iron guide-and-wear caps, which are flanged at the sides only. Table 30.-Standard Dimensions for Brill No. 21-E Trucks. GAUGE. A B D L it. in. ft. in. ft. in. ft. in. ft. in. ft. in. ft. in. ft. in. 3 0 5 03 4 10 5 7 5 5 3 33 3 6 5 43 5 2 4 0 4 8 M in. 16 5 1 4 108.5 8 5 11 N 5 5 ♡♡ Là có có ổ đi LOKO-KOKO CELO 5 10 5 8 6 5 6 6 0 in. 199 5 5 91 6 6 6 0 in. 263 J.-Diameter of axle. 6 E 7 6 0 15 7 14 6 6 16 1 15 0 0 16 7 15 6 7 6 17 1 16 0 P in. F 10 G R in. 15 H in. 30 33 | | I in. 251 268 S | in. 36 K.-Diameter of journal. J K ft. in. ft. in. 0 3 0 3 0 4 0 3 11 T in. 20 ROLLING STOCK AND MOTORS. 819 © 191 Chang 47 Om O (893) O • D B › www doggi s -A F 48 M -Gauge K Figs. 47 to 49. Brill No. 21-E Truck. 2010 A Cross from OD-100 : • OOHOO 820 SECTION X. Table 31.-Weight of Brill Trucks. Name of Truck. 21 E Maximum Traction (each bogie) 27 G (each bogie) Weight in Pounds, Standard Gauge, without Motors, but with Wheels and Axles. Minimum mean radius of curve, feet Maximum length of wheel base, feet ·· .. .. •• •• Four-wheel Trucks. In the rigid four-wheel truck, where the wheel-base is naturally restricted, it is of the greatest importance to have an arrangement whereby the car body is supported as far outside the wheel-base as possible; and to diminish as much as may be, by the judicious use of springs, the destructive effect of jolting, both upon the car body and upon the motor equipment. As the length of the car body grows, the difficulty increases of supporting it properly at the ends. The resistance offered by any truss to bending varies directly as the cube of its depth. Beyond 27 in., or at most 30 in., every inch that the car platform is raised above the level of the street makes it so much the more difficult for ingress and egress. This is the limit in height to which the car body can be raised. This problem has been solved by the use of extension rods. A second bridge truss is constructed by employing the extension rod as a lower member, and the car sill as an upper member; and this truss is supported flexibly upon the main trunk truss. The truss extension-rods are carried below and around its lower member, and are stayed to the car sill by bolts passing through the truck pedestals and end springs. The angle of the truss extension-rods has not been changed in any way to secure a longer support; but as they are dropped bodily lower, they give a wider base of support to the car body than would otherwise be possible. By this method it has been found practicable to carry upon single trucks, with a wheel-base of only 7 ft., cars as long as 35 ft. The sharpest curve is naturally a primary factor in determining the greatest length of wheel-base. The following are the maximum lengths of wheel-base advisable for curves of the radius given :- ·· 4400 3200 4600 25 30 40 50 60 6 6 7 7 78 It is possible to use a wheel-base of 6 ft. on a curve of 25 ft. mean radius, or a wheel-base of 7 ft. on a curve of 30 ft. mean radius, without danger of running off the rails, provided the latter are laid exactly to gauge and are protected with guard rails. Maximum-Traction Trucks. (FIGS. 50 to 55, pages 821 and 822.) With the double truck and bogie equipment the next question that comes up is the number and distribution of the motors. If the weight of the car is equally distributed on the four axles, and there is a motor on each axle, that is to say, four motors in all, then the starting torque, which can be exerted before skidding takes place, is equal to the total adhesion of the truck. But if, on account of the total power required, or for other reasons, only two motors are employed, then the relative distribution of the weight becomes of the highest importance; because, if the weight is equally distributed on all the four axles, only half the total adhesion of the truck is available for starting. The distribution must therefore be such that the greater part of the weight is carried by the axle to which the motor gears. Trucks of this kind are called maximum-traction trucks. In all bogie trucks, whether of maximum or of equal traction, the car body must be free to swivel round its point of support with minimum friction. With this view the motion of rubbing surfaces relatively to each other must be as small as possible, and all dirt must be excluded from them. "Swing Bolster" Maximum-Traction Truck. To reduce the height of a car body, the truck wheels "swing" between the car sills. The wheels of this truck are 30 in. or 33 in., to give sufficient clearance between the track and the motor, and the small wheels (18 in. or 20 in.) swivel beneath the car sills. To relieve the truck wheels and car body from side thrusts when rounding curves, and obviate the necessity of adding weight to the small wheels to prevent them from jumping the track, this truck is constructed with a Centre Bearing "C Spring Bolster " This bolster is located as near the driving wheels as possible, ROLLING STOCK AND MOTORS. 821 50 ! (891) D O O " 2·3/2 4'0 O O 1′ 8 ½ 51 52 O 27½ -- 20 ·48½ Garrge-- Figs. 50 to 52. Standard Maximum Traction Truck. Type B, Brush Company. ...... 8:5 822 SECTION X. 53 54 1 NAU --24 …………… – 48. ···· 2.0. -91 Doub muut 110k". P ·174. ש 18] A vide CTOC. OF SIDE FRAMES. -5°Ð´ -I.L I CARS... 134 +2 01. 55 Figs. 53 to 55. Peckham Maximum Traction Truck, Birkenhead Corporation Tramways, ROLLING STOCK AND MOTORS. 823 and supported upon springs between two transverse transom-bars, secured in pockets to both the side frames of the truck. These transom-bars act as a guide for the bolster, preventing it from moving longitudinally with the car. The spring plank upon which the elliptic and spiral springs supporting the bolster rest, is hung by four links from the transom-bars, so as to raise the side of the car body towards which the bolster moves when striking a curve. The end spiral springs supporting the bolster being directly underneath the side-bearing plates, admits of a slight rocking motion, which adds greatly to the easy riding of the car, as it permits the wheels on one side of the truck to rise independently of the car body. In order that the driving wheels may occupy the least possible distance between the car sills, it is necessary to bring the centre upon which the car swings near the centre of the driving axle. A segmental swivel-plate with arms extending towards the driving-axle is secured to both the body and truck bolsters, the upper and lower plates being connected by a "King" pin, which serves to fix the centre of the swing. This point is adjusted, ordinarily, about 6 in. from the centre of the axle, but can be changed as desired, so as to make the swing more or less. These swivel-plates are made with male and female connections, the lower plate having the projection to fit into the upper, so that, without having the addition of the "king" pin, this truck would swing to the correct centre. As these swivel-plates cover each other, excepting when the truck is rounding a curve, the surfaces are protected from dust and grit. The lower circular plate is provided with an oil-well for lubricating the same. The following advantages are claimed by the makers :- 1. The centre bearing "Swing Bolster" relieves the car body, as well as the wheels and track from the strains incident to rigid side bearings, and by relieving the strain on the flanges of the small wheels, prevents them from jumping the track. 2. By arranging the motor outside the driving wheels, and the weight of the car body upon the swing bolster near the driving wheels, a larger percentage of traction is obtained on the driving wheels than can be obtained from any other arrangement without danger of derailment. 3. The pivotal bearing of the truck is so arranged that it is near the axle, and gives a short swing to the driving wheels, enabling them to swing between sills of narrow cars. 4. The arrangement of the brake connections is such, that the pressure of the shoes can be applied to the large or driving wheels, and to the small or pilot wheels, in proportion to the weight they carry. This prevents sliding and flatten- ing of wheels. 5. The brakes of the driving wheels are constructed upon the "Gravity” principle, thus doing away with the use of links or movable parts. This arrange- ment necessitates but four wearing parts in the brake rigging as compared with 24, when the shoes are in links, and does away with the kicking of brakes, and also the noise and rattling incident to links. 6. The application of the weight of the car body and load is such that no arrangement of springs is necessary over the small wheels to keep them on the track, thereby increasing the traction on the large or driving wheels at least 10 per cent. Table 32.-Dimensions of Swivel Trucks. Wheel base (recommended) Height of truck bolster with 30-in. wheels, empty car body.. 33 "" "" "" from" bottom of car sills to track, with 30-in. wheels "" "" "" "" "" "" "" "" "" "" "" ?? 33 Width between car sills required (for swing of wheels) on a 40 ft. radius curve For a car 25 ft. over end panels 30 "" "" "" >> "" "" "" "" >> >> "" " "" ** This is for 24 tread of wheels. Wider treads would require pro- portionately wider distances between sills. 35 40 "" >> "" ·· 99 "" "" "" ► ·· .. ·· · ·· ·· ·· ·· •• ·· ·· 4 ft. 6 in. 24 } 26 0 27 29 1 5 6 0 6 "" "" "" 6 "" 5 9 **** "} -20 "" 11 Q 1 **** " "> - "" "" "9 824 SECTION X. T The Brill No. 27-G. Truck. (FIGS. 56 to 58, page 825.) The weight of the car is, in this truck, taken on the centre plate. The motor is placed outside the axle. This increases the tractive power, and enables the wheel-base to be reduced to 4 ft. The truck belongs to the equalised swing motion type. The body of the car is so suspended that the truck may quickly move sideways, as at the entrance to a curve, without communicating a shock to the car. The "27-G" truck differs from the maximum traction in drawing from the centre by a bolster, but, like it, has a considerable excess of weight on the driving axle, due to the weight of the motor acting as leverage to increase the downward thrust or weight on driving axle. The wheels, however, are all of the same size. The points of support are distributed, relative to the weight carried by the truck frame, to prevent kicking up under the action of the brakes. Figs. 56 to 58, page 825, shows the 27-G Brill type truck, as manufactured by the Electric Railway and Tramways Carriage Works, Preston. Table 33.-Brill No. 27-G Truck. Gauge. ft. 3 2009 HELO LO LO in. 0 3 0 5 3 Centres of Frame. ft. gauploa in. 4 10 4 109 5 5 5 81 289122 91 5 11 6 23 6 2 Radius of Rub Plates. ·· ft. 1 1 1 1 ~~~~ 2 2 2 2 in. 321 Gà L có đi đi Timesharesher 57% 632 đi đ extreet resto Width Over All.* ft. in. 5 7 5 81 5 6 6 6 77 11 Diameter of wheel Distance from track to under side of body bolster; car empty Distance between hubs, variable. 62 .. 418 아 ​O Length of Axles.* ft. in. 5 58 5 5 6 6 6 6 10 6 *When it is necessary to use a longer axle on account of wide tread wheels, the width over all will be increased proportionally. 99 33 Dimensions of Axles and Journals for Brill 27-G Trucks. in. in. in. in. Diameter of axle Diameter of journal LIT 4 33 31 41 41 3 3급 ​3급 ​Standard wheel base, 4 ft. ; it may be increased if necessary. in. in. in. 28 30 33 26 27 47 71 28/ 101 Motor supports are arranged to suit style of motor. If only one motor is to be used, the end angle iron can be made straight if so desired. Allow 11 in. for distance between car body bolster and bottom of truck bolster. The Brill Maximum Traction Truck. (FIGS. 59 to 61, page 826.) Each side bar is of solid cast steel, made entirely in one piece. The lower part of each yoke below the journal box is fitted for receiving tie bars. Extreme ends of side bar are cast so as to receive the end cross T-iron. Side bars are firmly held together on the inner side of the yoke near the small wheel journal box, by heavy bar iron bolted to side bar, and extending across to opposite side bar. From this cross iron is suspended the brake arrangement for the small wheels. On it is also placed the compression-device. The compression-device consists of a plunger supported by a large spiral spring, and held in position by malleable iron casting, bolted to the cross-bar of truck, and so arranged with set nuts on the underside of plunger head that the weight from the downward pressure of the compression-device plate on the car body may be increased or lessened, as may be required by the conditions under which the truck is operated, and the weight which may be desired on the small wheels. ROLLING STOCK AND MOTORS. 825 Figs. 56 to 58. Brill 27-G Truck. O ver .0; Milan and dad Quak HHOLD 65 5 42. 9:9 4-8½ 4'-0" 58 " 3'-11" ·东盛 ​10% www 99 [CD3 MANA 21:62 29. 826 SECTION X. The arrangement for attaching the truck to the car body consists of a king- bolt or pull-iron, attached to the framing of the body at the outer end of the truck towards the platform of the car, which bolt projects through a radial casting fitted to the outer end of the truck. This radial casting is so designed that the radiation of the truck between the rub plates under the car allows full swing of the king-bolt within this radial casting, and at the same time fits neatly, without any undue lost motion. The weight of the load is carried on the side bars of truck, 124 in. back of the centre of the driving axle, and rests on two rub plates, one on each side bar, which are supported on large spiral springs held in position 1-8" + 5:94 627 2'÷1½" -Il*-* Pivotal Point 3:2216" autom 4-0". 3′11″ Mishri O 1123 59 690 61 Figs. 59 to 61. Brill Maximum Traction Truck. by spring posts fitted to the rub plates, and extending downwardly through the upper arm of the cast-steel side bar, the large spiral springs, and also the lower main section of side bar. The rub plates at their outer edge are fitted with a wearing piece, arranged to bear upon the angle plates under the car body. The tops of rub plates are fitted with grease cavities. The truck is fitted with link-suspended brake arrangement, so arranged that the pressure on the large and small wheels will be exerted in accordance with the weight on each wheel. Figs. 59 to 61, above, show the Brill Maximum Traction Truck, as manu- factured by the Electric Railways and Tramways Carriage Works, Preston. ROLLING STOCK AND MOTORS. 827 Gauge. Table 34.-Brill Eureka Maximum Traction Truck. Centres Radius of Centres of BrakeRods.* of Frame. ft. in. CD CD CD > 5 5 5 6 6 "" pony "" 109 2 11 NNNY að að að a 100 — 10|0D LOkao vatao 1122 25 "" "" " ·· Angle Plates. ft. in. .. .. 2 818 ·· Length over all Width over side-frames Width over axle-boxes Wheel diameter Wheel-base.. 2 91 2 101 3 3 3 3 3 WOOHEM LO ————7—1000-100-100 444 journals 39 ·· · • ft. in. 3 11 4 4 3 •• ·· **పొగిడే 2 .. 3 11 Brill Eureka Maximum Traction Truck Axles and Journals. Diameter motor axle 3321 5 ww 2 3 10 5 5호 ​co að MHHk Haa 3½ Width Over All. ft. in. LO LO LO CO6677 polo echte 7 5 81 ·· 5 5 11 .. 58 * This dimension is variable. When the gauge is less than 4 ft. 8 in., the brake rods are frequently placed outside the wheels. The width over all will be proportionately increased when it is necessary to use longer axles on account of wide tread wheels, short radius curves, or long cars. The distance between hubs is variable. Distance from centre of axle to channel iron, 31 in. It must be increased when the radiation of the truck on curves would cause the motor, or motor supports, to strike the channel iron. Distance from centre of axle to bottom of sill is 11 in., with the weight of the empty car body. Diameter of driving wheel can be made 30 in. or 33 in. Table 35.-Dimensions of Central London Railway Motor Trucks. (FIGS. 62 to 64, page 828.) Axle diameter in centre, wheel seats and motor bearings Diameter of axle journals Length of axle journals.. Length of Axle. ft. in. 5 59 61 99 5 5 6 6 6 4 31/1 42 37 4/1 31 32 These dimensions 3 when roller bear- ings are used. 6 6 10 6 101 3手 ​47 71 ft. in. 9 6 7 2 10 00000 0 0 0 8 The Mountain and Gibson 21-E. Truck. (FIGS. 65 and 66, page 829.) Figs. 65 and 66, on page 829, illustrate the 21-E. trucks built by Messrs. Mountain and Gibson, of Bury. These trucks, like those manufactured by the Brush Company, are throughout of British manufacture. Manhattan Elevated Motor Trucks. (FIG. 67, page 830.) These motor trucks were supplied, part by the American Car and Foundry Company, and part by the Wason Car Company, upon specifications of the Manhattan Railway Company. They are of the swing bolster type, with 6 ft. wheel-base. The frame is rectangular, and made of angle-iron 4 in. by 3 in. by § in., 14.6 lb. per foot. The transoms are made of 10 in. channels, 30 lb. per foot, connected to the truck frame by -in. steel gusset plates, securely riveted and bolted as shown. The bolsters are open-hearth steel plates 8 in. wide by 2 in. thick, placed flatwise and fastened together, as shown in the section. The steel has a tensile strength of 60,000 lb. per square inch, and an elongation of 22 per cent. in 8 in. The spring- plank is made of an 8-in. channel, 13.75 lb. per foot, with an oak plank fitted to the 828 SECTION X. 6.5. Brake puit 2000ền con 887 4 ) nan DaRQUES I HONEY 63 Da i da se on - mo sa të pa Panda-dija te v 00: 56 62 ------ sen ---- 36 ------- medê thì la de a ta ar pun pan de ve bag cada ve * A DOG § 16 van de on to age de ne te da de la can be (HA - OTO O 64 Half the trucks to have this pull-rod on the night and half on the left 2. MENG t www Figs. 62 to 64. Motor Truck for Rolling Stock, Central London Railway. . : ROLLING STOCK AND MOTORS. 829 4-* __3′0″ 6:10" Overafk»> 5:8″. _73 4:8/2 Gauge BOH 16-0* 6-6″Wheelbase C.L.Motor Suspension 197 2/2 2- 1124 Figs. 65 and 66. Mountain and Gibson Truck. 2-10 830 SECTION X. Fig 67. 4- Rea's Ent Motor Truck for Manhattan Elevated Railway. οοοο -½ll~· 868 · Rivets swyl-anʊqı¡m-X:22 -491 -75. Steel Casting - -19 34% Wheel -for £3,50 niên nên -48+ • 1.Pipe pod MALIron Casting X Turned bolt ijd. finished is Bt fange of [ -15 Steel Casting ---- " **** Top of Track. "1 TI -30% a fatal |+3| -Jan: 34:19|2j| Nolster I ם W rol Iron In $48% of axle "" トピー ​" Car Floor оо -10%~ TM = KEK ¼ bafely atwap 22 " 154. *Trent Eud -->> " 27% to top of rail without pass. id.--- Cast steel | madaru Ky 484- SAD- ・サイコー ​• -8036- Ho! H lolis 600, through ← pedosnta ´¯σ ROLLING STOCK AND MOTORS. 831 channel. The pedestals for the journal boxes are of cast steel, and the equaliser bars are of steel 1 in. by 6 in. in section. The journal boxes are of malleable iron. The journal brasses used are of phosphor bronze lined with babbitt. The phosphor bronze employed follows the Manhattan composition, viz.: 77 per cent. copper, 8 per cent. tin, and 15 per cent. lead. The babbitt is made up of 12.50 per cent. tin, 1.25 per cent, copper, 16 per cent. antimony, and 70.25 per cent. lead. Master Car-Builders' Journal Box. (FIG. 68.) Fig. 68 shows a section through the Master Car-Builders' standard journal box for inter-urban service. This form allows for the automatic alignment of the brass and the journal by means of the circular form of the top of the wedge. -6¼4″ -55/8" (899) Fig. 68. Master Car-Builders' Journal Box. Thrust surfaces are provided at both ends of journal, which avoids the tendency to spread the side frames which exist when the end motion is only taken up by one side frame at a time. Interborough Rapid Transit, New York. Two types of trucks are being built, one for the motor end, the other for the trailer end of the car. The following are the principal dimensions of the trucks :- Motor Truck. "" Gauge of truck Distance between backs of wheel flanges Height of truck centre plate above rail, car body loaded with 15,000 lb. Height of truck side bearings above rail, car body loaded Wheel base of truck Weight on centre plate with car body loaded, about Side frames, wrought-iron forged Pedestals, wrought-iron forged Centre transom, steel channel Truck bolster.. "" • ·· .. ·· .. gear seat wheel seat .. 8". Journal 44×8" ·7'014 over all! •• •• Equalising bars, wrought-iron Centre plate, cast steel Spring plank, wrought-iron Bolster springs, elliptic, length Equalising springs, double coil, outside dimen- sions Wheels, cast-steel, spoke centre, steel tyred, diameter. Tyres, tread M.C.B. standard • Axles, diameter at centre.. ·· 4/16 ·· · ·· ·· ·· ·· • ·· .. ·· "" "" Journals Journal Boxes, malleable iron, M.C. B. standard • 4 ft. 8 in. 4 ft. 53 in. 30 in. 34 in. 6 ft. 8 in. 27,000 lb. 24 in. by 4 in. cast steel 1 in. by 3 in. 30 in. 47 in. by 7 in. 332 in. 2ğ in. by 5 in. 6 in. 713 in. 7 in. 5 in. by 9 in. Trailer Truck, 4 ft. 8 in. 4 ft. 5 in. 30 in. 34 in. 5 ft. 6 in. 1 in. by 3 in. wood and iron = white oak 32 in. 3ğ in. by 6 in. 30 in. 24 in. by 51 in. 42 in. 53 in. 44 in. by 8 in 832 SECTION X, X. AXLES AND WHEELS. Car Axles. (Master Mechanics' Association.) As a rule, very little trouble is experienced with hammered steel or cold-drawn steel axles; cold-rolled axles usually spring out of line when the keyway is cut, as cutting into one side relieves the initial tension of the metal. Some master mechanics prefer wrought iron because it is fibrous in structure, but as the fibrous structure is caused by the presence of impurities (slag, &c.) in the metal, this does not seem to be a good argument, It is hard to secure a good quality of wrought iron, because of the difficulty of keeping steel from becoming mixed with the scrap from which the iron is forged. As many of the street car axles are reported to have broken just inside the hub, or in the journal, a table (see Table 36) has been prepared to show the relative strengths of the American Master Car-Builders' standard axles for freight cars of different capacities, and a number of street-car axles. In estimating the load per axle for the street cars, the figures for a crowded car have been taken, and perhaps that is as fair as to take the freight cars as loaded up to their full capacity. In general, cars of either kind are not run fully loaded at all times. As the strength of the axle varies as the cube of the diameter, the cube of the diameter divided by the moment to which it is subjected will give a measure of the strength; what is called in the table the "relative strength" is the quotient so found multiplied by 1000. It will be noted that the four street-car axles, under the conditions assumed, are subjected to relatively heavier stresses than are the M. C. B. axles for freight cars. Street cars make from four to eight times the average daily mileage of freight cars on steam roads, though the speed is less, and there would seem to be no reason for not making the axles at least relatively as strong as those used under freight cars. The question of the size and chemical composition of car axles has assumed great importance since the introduction of electric traction. The difficulty in designing car axles for electric traction lies in the fact that it is impossible to calculate with any certainty the total stress to which they will be subjected in actual service. The bending moment and the torque can, of course, be estimated very closely, but these two stresses are not nearly so destructive as the hammer blows which are experienced when passing over bad rail joints, or any other inequalities in the track. The fact that a considerable portion of the weight of the motor is carried on the axle does not affect materially the moment to which the axle is subjected, but the weight being, to a large extent not spring- borne, makes the effect of shocks more severe. The requisite size depends not only on the weight of the car-body and motors, but also on the speed of running, since the higher the speed the greater the shocks which the axle has to stand. The correct dimensions for any particular service can only be obtained by a method of trial and error, combined with past experience. It is certainly better to be on the large side, and a diameter of 4 in. is none too large for any car axle. Carbon Phosphorus Sulphur Silicon .. Manganese The greatest care should be taken to see that Siemens-Martin steel is used, and the chemical compositions should not vary beyond the following limits :- ·· 0.24 to 0.37 per cent. "" 0.047 0.06 0.059 0.06 0.2 per cent. 1.00 "" "" "; "" The Great Western Railway Company specify that the tensile strength of the steel used for axles should be at least 35 tons to the square inch, with an elongation of 25 per cent. The standard practice in Germany calls for Siemens-Martin steel, having a tensile strength of at least 39 tons to the square inch. Some old American trucks which had been running in this country for twenty-seven years had the axles tested, when the tensile strength was found to be 28 tons to the square inch. The specification issued by the Manhattan Elevated Company calls for a tensile strength of 26.6 tons per square inch, with an elongation of 22 per cent. in a length of 8 in. ❤ ROLLING STOCK 833 STOCK AND AND MOTORS. Axle. Table 36.-Comparison of Various Axles. M.C.B. 40,000 lb. M.C.B. 60,000 lb. M.C.B. 80,000 lb. 1 2 3 4 W 10,500 13,750 8,000 8,000 lb. 8,000 10 8,000 8,000 A in. "" "" B с in. 3.5 8.5 4 9.125 4.5 3.375 4.25 in. in. 4.875 3.75 5.5 4.25 6.375 5 4 4.56 4.56 3.75 5.875 3.875 3.75 4.69 4.375 3.625 3 Centre to centre of journals Length of journals Diameter of journals wheel-seat .. D 3.5 3.25 3.25 "" at centre of axle Relative Relative Strength Strength at C. of Journal. ·· 1.449 1.866 2.075 2.062 1.429 • 1.121 1.266 The great majority of steel axles that fail in street railway service break at a square corner or the fracture starts in the key. In some instances it has been found that the cracks started at tool marks in a fillet. (FIG. 71, page 836.) Main Details of Specification of Carriage Steel Disc Wheels, Axles and Tyres, for the London, Brighton, and South Coast Railway. ·· 1.882 1.829 2.020 1.300 Axles.-Axles to be made from the best mild Siemens open-hearth steel- forgings, and to stand a tensile strain of from 32 to 35 tons per square inch, with 30 per cent. elongation. Journals to be reduced in forging from the solid, and not turned down. The axles must be turned exactly to the gauges and the drawings supplied, so as to be interchangeable; wheel-seat to be turned parallel, and without keyway. The axles must also stand a weight of one ton dropped 20 ft.; the axle being upon supports 3 ft. 6 in. apart, the weight to be dropped five times, and after each test the axle to be turned over. Upon the completion of these tests the axle must be tested until fractured. .940 One axle in every forty, selected by the inspector, must be tested thus at the works of the manufacturer. 1.107 .771 Few broken in last 3 years. About 20 per cent. break each year. 31 per cent break each year. Remarks. 6 ft. 3 in. 8 in. "" 4 51 in. 4 "" Wheel Centres.-To be of solid wrought iron, Kitson's patent, made in exact accordance with the gauges and drawings supplied, and pressed on the axles with a hydraulic pressure of not less than 60 tons, care being taken that each wheel is set equidistant from the centre of each journal. The boss, disc, rim, and flange on rim to be forged solid in one piece, The inside edge of the hole in boss forming the wheel-seat to be slightly rounded, and the flange of rim to be grooved and turned to 3 ft. 4 in. diameter to the form shown on drawing; and drilled to receive bolts of retaining rings. The retaining rings to be secured to the rim of the wheel by eighteen bolts § in. in diameter. All bolts to be tightly driven in, and the ends to be riveted. Wood. To have wood liner of dry and well-seasoned Moulmein teak between tyre and rim of wheel centre, with holes drilled to suit retaining rings. Thickness of wood to be such that it may be tightly embraced by the retaining ring. EE } 834 SECTION X. Tyres.-Tyres to be solid rolled of the best mild Siemens-Martin steel, turned and bored to the drawing and gauges supplied, and tightly forced on the wood liner after the wheel has been placed on the axle. The tyres must be recessed for receiving the retaining rings, which run entirely round the wheel, as shown on drawing. Retaining rings and bolts to be made of the best Staffordshire iron. The tyres must stand a tensile strain of 35 tons per square inch, with 25 per cent. elongation, and to stand being compressed by hydraulic pressure 6 in. without fracture; also to stand without fracture a weight of one ton falling 20 ft. One tyre out of every forty to be tested thus in the presence of the inspector. Diameter of tyre on tread Thickness of tyre on tread Breadth of tyre on tread Distance between tyres.. Deflection 99 "" Guarantee. Each axle to be stamped with the maker's name, away from the centre of the axle; the tyres also to be stamped with the date and maker's name ; and any tyres or axles failing before they have run 12 months, must be replaced by the contractor. Balancing. The wheels must be carefully balanced, so that, when completed, and the journals of the axles are placed upon horizontal straight edges, the wheels will remain at rest in any position; and when placed in balance and driven at 600 revolutions per minute, they will run quite smoothly, and without vibration. "" Data of some Axle Tests. The ends of the axle tested, rested on rigid supports 6 ft. 6 in. apart. Pressure was applied at the centre to bend axle out of line, varying amounts, the pressure taken off, and the axle allowed to spring back. The deflection and permanent set were recorded on a scale. Test No. 1.—Applied to a 33 in. diameter cold rolled steel axle, Griffin special quality. "" "" >> ·· ·· •• -#-## ·· .. . •• 1 ARONCH in. : "> "" "" "" "" Test No. 2.—Similar to test No. 1, but applied to American Master Car Builders' standard steel axle, for 50,000 pounds capacity cars. Diameter at centre of axle 44 in. Deflection 1 in. "" Permanent set " "" ·· "" ft. in. 3 7호 ​0 21 0 5 4 5 Permanent set ** "" · •• ·· .. · ▸ • 1 "" Test No. 3.-Sufficient pressure was brought to bear to deflect the axle 1 in. the first time, and pressure was then released and the axle allowed to spring back. Applied to Griffin special cold rolled axle, 4 in. in diameter. Deflection Permanent set in. 1 in. Test No. 4. Similar to test No. 3, but applied to a Master Car Builders' standard steel axle for 50,000 pounds capacity cars. Diameter at centre of axle 44 in. Deflection 1 in. Permanent set +8 in. Test No. 5.-Applied to Griffin special cold rolled steel axle, 4 in. in diameter, 6 ft. 5 in. long. This axle was bent cold under the hydraulic press until the ends were brought together. No defects of any kind appeared. The special feature of this test was that it was made on exactly the same quality axle as was subjected to the tests for bending and deflection, indicating that the strength and toughness of the axle were equal to its elasticity. A sample of a similar quality axle was exhibited which had made a mileage of 120,000 miles with less than one thirty-second of an inch wear. • None ·· "" "" ¿ in. .. None in. 18 18 "" ROLLING STOCK AND MOTORS. 835 Various Tests Specified for Car Wheels. Austro-Hungarian State Railway Specifications. Wheel placed upright on heavy iron bed plate 48 in. in diameter, 8 in. in thickness, weighing 3060 lb., resting on stone foundation 5 ft. deep. Weight of 475 lb. dropped from varying heights, commencing at 1 metre (3 ft. 3 in.), and increasing by metres to 6 metres (19 ft. 8 in.), wheel being required to stand eight blows without breaking in two or more pieces. Belgian State Railway Specifications for Steel-Tired Wheels. Wheel placed upright on heavy iron and stone foundation (same as Austro- Hungarian) Weight of 2200 lb. dropped from varying heights, beginning at metre (1 ft. 7 in.), and increasing by metres. Wheel required to stand five blows without breaking in pieces. German State Railway Specifications. Wheel placed in horizontal position on wooden blocks supported by heavy iron and stone foundation, the hub having been carefully bored to receive conical steel sections, with interior steel wedge having a taper of 1 in 20, all machined and accurately fitted. Wedge driven home by dropping weight of 440 lb. from varying heights, com- mencing at 1 metres (about 5 ft.), increasing by metre to 4 metres (13 ft. 1 in.), the object being to burst the wheel. Specifications require the wheel to stand six blows in succession without bursting. Pennsylvania Railroad Thermal Test. "Wheel laid flange down in the sand, and channel-way 1 in. wide and 4 in. deep, moulded with green sand around the wheel. The tread of wheel must form one side of this and the flange part of the bottom. Channel-way filled to the top with molten cast iron. Two minutes later an examination of plates to be made. Wheel to be accepted must not be broken in pieces, and cracks, if any, must not extend through tread.” Master Car Builders' Standard Test for American Railroads. Wheel placed in horizontal position on heavy iron and stone foundation. Weight of 140 lb. dropped from height of 12 ft. on hub. The requirements under this test vary in the case of different railways, but the maximum requirement is that of the Pennsylvania Railroad, which calls for twelve blows from a height of 12 ft. Steel-Tyred Wheels. (FIGS. 70 to 74, pages 836 and 837.) Figs. 70 and 72 show a steel-tyred wheel as used on the Continent. The tyre is of steel and shrunk on, being held in position by set screws. 865 840 830 Table 37.-Dimensions of Steel-Tyred Wheels. Diameter Diameter Diameter Weight of in Milli- in Milli- metres metres over Inside Tyre in Milli- metres. Wheel with- out Tyre in Kilo- grammes. over Flanges. Tread. 830 800 800 725 725 725 59 57 75 Weight of Steel Tyre in Kilo- grammes. 77 49 54 Weight of Steel Axle for Standard Gauge in Kilo- grammes. 91 88 118 Weight of One Axle and Wheels Com- plete in Kilo- grammes. ށ 361 304 376 Most city tramways in Europe used car-wheels with steel tyres shrunk on to a separate centre, which is usually of wrought iron. Fig. 73 shows the construction of the standard wheel used by the Brussels tramways. The weight of this wheel is about 374 lb., the diameter is 30 in. at the tread, and 31.38 in. at the flange. A few companies on the Continent use chilled iron wheels; the street railway in Milan is one of them. The largest user is the city of Budapesth. Fig. 74 shows a section of the wheel used. 836 SECTION X. 1 < 69 71 555. 505 # 54 + -160- H Section A.B. -60 -640- W 18881 70 72 5 8 Cers of Bear" 40 (૬૦) * 6. 3 -0% M--~4:25 1 - - - 4. 8. -60. Figs. 69 to 72. --------5- 32. 16 .67 F J B † -610 不 ​.640. -47%2 735 -762 8%% +-+ Axles and Wheels. 30 or 33: **** ROLLING STOCK AND MOTORS. 837 73 (900) ***19 M40€ 74 Fig. 73. Standard Brussels Wheel. Fig. 74. Section of Wheel used at Budapesth. Wheel Tests. Results obtained from some Tests of Griffin Special Quality Car Wheels. Austro-Hungary State Railway Drop Test. Diameter of wheel 38 in., weight 860 pounds; cracked at ninth blow, and broke in two pieces at twenty-second blow. German State Railway Bursting Test. Diameter of wheel 33 in., weight 650 pounds; cracked through hub at four- teenth blow, and broken in two pieces at the sixteenth blow. Pennsylvania Railroad Dist. Thermal Test. Diameter of wheel 33 in., weight 560 pounds; after a two-minute test no failure of any kind was developed, only a slight skin fracture in the front plate of wheel, in. deep and 4 in. long. The special and most important conditions which wheels have to fulfil may be briefly stated as follows: Wheels broken must show clear grey iron, free from blow holes. The chill must not vary in depth more than in. from the standard depth specified all round the tread of the wheel. The wheel must have no flats, and be absolutely cylindrical. The tread and body of the wheel must be smooth and free from sand, slag, or blow holes, or deep and irregular wrinkles. It has been found necessary on street railways to slightly cone the tread of the wheel, and in order that the wheels may remain on the rails it is necessary to provide them with a flange, which, to minimise friction, must have its side form a considerable angle with the side of the rail. In practice, this angle varies between 20 deg. and 35 deg. Practice has shown that the depth of flange first used on street car wheels, which attained a maximum of 14 in., was a mistake; and at present flanges of from in. to in. deep are used. Owing to the use of the step rail, flanges in America are generally much thicker than in this country, where the grooved rail is universal. It is necessary that the axles be perfectly parallel, and that the line connecting the centre of the journals be perpendicular to the axis of the axles. If these conditions are not filled, both track and wheels will suffer, and sharp flanges result. The cast iron of which chilled wheels are made in America has some remark- able properties. Tests of some of the best American car wheels have shown tensile strengths of from 35,000 lb. to 40,000 lb. per square inch. This cast iron is found to take impressions from blows of a hammer in exactly the same way that a piece of wrought iron would. Pieces of this iron have actually been hammered into plates. On railroads the mileage of a wheel often attains 100,000 miles; whereas, on street railways 80,000 miles is a maximum figure, occasionally reached. Flat wheels caused by a bad use of the brake are a source of much trouble, but can be avoided by careful handling of the brakes. A small flat on a wheel, of course, encourages the formation of a layer because, when the brake is set, the tendency 838 SECTION X. of the wheel naturally is to stop on the flat already formed. Enormous differences between wheels of various makers have been found, graduating up from averages of 10,000 miles to 70,000 miles, and in some cases to nearly 80,000 miles per wheel. No road can afford to buy anything but first-class wheels by recognised and reliable manufacturers. On English roads chilled wheels have also been used successfully, the average mileage of a wheel reaching 30,000 miles. Steel-tyred wheels similar to those adopted on European railroads are in current use on many tramways on this side of the Atlantic, and it seems as if they might find adoption in America. For cast-iron chilled wheels special iron is required. Cast-steel wheels have been used to some extent, but their price is much higher, and their advantages only slightly greater than those of the cheaper cast-iron chilled wheels. Wrought-iron wheels with steel tyres have proved very efficient on railroads. They are claimed to be more durable than chilled wheels, owing to their greater elasticity. They admit of the use of interchangeable hardened steel tyres, and also the steel tyres can be turned down if flats are formed. In this style of wheel the rim is rolled in a special form of rolling mill; the spokes are often elliptical in shape, and are cut into lengths as they come from the rolling mill. The hub is formed by forcing a piece of heated iron on die. The different parts of the wheel are then assembled, and heated in a special furnace to a white heat. It is then placed in a die, and a steam hammer is brought down on the die, thus causing the rim, spokes, and hub to be firmly welded together. The wheel, when removed from the die, is cleaned, bored, and finished on the lathe, and is then ready to receive the steel tyre. It is claimed that the life which may be expected from steel tvres is 200,000 miles. TROLLEYS. Standard American Trolley. (FIGS. 75 and 76.) In Fig. 75, if T represents the projection of a trolley pole on a plane parallel to the track, and a the greatest angle which the trolley wire can make d ROOF 2738.A OF CAR Fig. 76. T 525 α Fig. 75. Trolley Wheel. OAK Car Framing for Trolley Pole. ROLLING STOCK AND MOTORS. 839 with the direction of the projected trolley pole, we see that d, the greatest distance of the centre of the track from the trolley wire, cannot exceed d = √ T² - (T cos a)2 as given by the above formula. As T is generally about 10 ft. (the trolley measur- ing usually about 12 ft.), and a is approximately 20 deg., we find that this gives for d the approximate length of 3 ft. 6 in., that is to say, the distance of the trolley wire to the centre of the track (if the trolley pole is, as in America, on the centre of the car) must not exceed 3 ft. 6 in., or else the trolley wheel will leave the wire. This distance is in practice never attained, from 2 ft. to 24 ft. being the maximum ever allowed. West End Trolley Wheel. (FIGS. 77 to 80, pages 839 and 840.) When the earlier form of trolley wheel was used, the flange dropped off when the groove which receives the trolley wore through to the outside. By using the West End Trolley Wheel, this difficulty is entirely obviated by means of ribs which serve to hold the flange in position, after the sparking of the wheel indicates that it is worn through and therefore should be discarded. This warning is timely, for the wheel may be used after the flange is cut through by the trolley wire, long enough to get to the car house, where a new wheel can be put in. With the old form of brass wheel, when the flange wore through and dropped off, the car was disabled, and had to be pulled to the car house, or removed from the track. Top of Trolley Standarddpoint. of Trolley Pole. (509) or, finally, we get B D D.- Px sin. B (1) P-YL2-H² L.= struα (2) (3) Fig. 77. Diagram of Extreme Angles for Trolley Pole. If this breakdown occur in a crowded thoroughfare, or in an out-of-the-way place where it is not easy to obtain assistance, as is often the case, the awkward- ness of the situation and the annoyance resulting from it are obviously great. This wheel is a practical and tried device. A very large number are now in use. They are economical, both in first cost and length of life. The wheel as made to run on single O wire weighs 2 lb. 6 oz. In practice (Figs. 77 to 80) the angle a with a swivelling trolley should not exceed 30 deg., and the angle ẞ 45 deg. The formulæ (1 to 3), see Fig. 77, there- fore become: 1 Mala D= PX √2 P = √ L2 - H2 L = 2 × H, ➡ Px • 1 1.4142 D= 1.22 x H L = 2H H = = P X 0.707 Trolley Wheet × L, or if we vary the angle a, keeping ẞ equal to 45 deg., we have D= 1.22 x H Η sin a L = H 840 SECTION X. 78 $10 Side elevation with Trolley in vertical plane parallet to centre line of Car. α 80 Plan with Trolley in vertical plane forming angle with centre line of cay ہے ALDA -1 100 ]‒‒‒‒‒-----¶¶¤ 11110000 10 11/1 Q 100 79 D H Back elevation with Trolley in vertical plane parallel to car axles. Figs. 78 to 80. General Arrangement of Car and Trolley. : ROLLING STOCK AND MOTORS. 841 Deg. 10 12 14 16 18 20 22 24 26 27 28 Table 38.-Natural Sines of Angles 10 deg. to 60 deg. Sine. .174 .208 242 .276 .309 .342 .375 .407 .438 .454 .469 Deg. Sine. 29 .485 30 .500 31 32 33 34 35 36 37 8588 38 39 .515 .530 .545 .559 .574 .588 .602 .616 .629 Deg. Sine. 40 .643 41 .656 42 .669 43 .682 44 .695 45 .707 46 .719 47 .731 48 .743 49 .755 50 .766 •• Deflection of pole, 13 ft. 6 in. long 2 in. at butt, tapering to 1 in. at point. Weight of pole 27 lb. .. .. Table 39.-Weight of Top Seat Trolley Standards. (Dawson's Patent.) * Deg. 51 52 53 54 55 56 .. 58881 ·· 57 59 Trolley head and wheel Annealed steel trolley base Swivel part, cable and springs Trolley pole, 13 ft. 6 in. long, insulated Trolley wheel Table 40.-Tests on Standard Trolley Poles. Weight loaded at end of pole. 20, 30, 40, 50, 60, 70, 80, 100, 125 lb. } set. 60 lb. 6 140 to 150 100 25 2 Deflection of pole 13 ft. 6 in. long in. O.D. at 1 in. at point. Weight of pole (10, 144, 19, 23, 28, 33, 38 in. 27 lb. Sine. .777 .788 .799 .809 .819 .829 .839 .848 .857 .866 4, 7, 101, 15, 20, 25, 31, 36, 40 in. Blackwell Enclosed Trolley. (FIG. 81, page 842.) In this trolley the pressure of the wheel against the wire is maintained by a helical spring in compression, which is enclosed within the trolley standard. The rotating portion of the standard is within the stationary part, and has two bearings, one near the top and the other at the bottom. The upper is a ball- bearing, and supports the weight of the moving part. The lower is a plain cylindrical bearing, which merely prevents lateral motion. The pole socket is pivoted to the swivelling portion, so that it can turn in a vertical plane. To give the requisite pressnre between trolley wheel and line, a rod in the interior of the swivelling portion is attached to the tailpiece of the socket, the rod being pulled down by the action of a helical spring. The spring encircles the rod, being compressed between a nut on the end of the latter and the top of the swivelling portion. In action, as the spring becomes compressed and the force it exerts becomes greater, its leverage on the pole decreases so as to maintain the moment of the spring about the pivot constant. Hence the pressure of the trolley wheel against the wire does not vary with elevation of the latter, the equalisation being almost perfect, between 35 deg. and 50 deg. angle of pole with the ground. The socket is provided with maximum and minimum depression stops, and there is also a stop which prevents the trolley making more than one complete revolution. The cable from the trolley-head, on leaving the base of the pole, is brought down to the base of the standard through the interior of the hollow tension rod. A bonnet covers the tailpiece of the pole socket, and prevents the access of water, dirt, &c., to the internal mechanism of the trolley. E E2 842 SECTION X. 1 801. poland pulledral St the Fig. 81. The Blackwell Enclosed Spring Trolley. 15 ROLLING STOCK STOCK AND AND MOTORS. 843 喵 ​Ground Terminal The Dick, Kerr Double-Deck Trolley. (FIG. 82.) Fig. 82, below, shows the Dick, Kerr trolley as used for double-deck cars. The standard is of cast steel, and supports the lower half of the ball-race upon INS Rubber Tubing Flexible Cable Tin Tube over Babbitt Bush #125 Fig. 82. Dick, Kerr Double-Deck Trolley. which the swivel fulcrum revolves. The two ball-races are made of malleable cast iron. The requisite pressure between the trolley wheel and wire is obtained 844 SECTION X. ¡ TRA by means of a spring in compression, which tends to raise the trolley arm, the pivot above which the trolley pole moves being situated on the side of the standard away from the wheel. This construction enables the interior of the trolley to be most efficiently protected against the intrusion of wet. The details of the design are clearly shown in the drawing, Fig. 82. The Dick, Kerr Single-Deck Trolley. (FIG. 83.) Fig. 83, below, shows the type of trolley employed by the above firm for single-deck cars, and an examination of the drawing will show the method of operation. The trolley base is of cast steel, with the swivel post either cast with it, or screwed in tight and riveted over. The swivel fulcrum swings about this 222222012 2:703532 A 10% * ZZZ ZZZZZ ZZZZZZzzzzzzzËS 2017 7 7 7 7 7 7 7 Section through Pole Bracket PA k.43/8" 10M 10/8" JO A 1 C 1126 Fig. 83. Dick, Kerr Single-Deck Trolley. pivot on ball-bearings at the top and bottom. It will be seen that the trolley pole is pressed upwards by means of two compresssion springs, acting in "series," and merely separated by a collar between them. In this way, if the spring becomes defective, the half that is at fault can be replaced at approximately half the expense that would be incurred if the spring were in one piece. Siemens Sliding Bow. (FIG. 84, page 845). The first use which has been made of the sliding bow on an important scale was at Hanover and Dresden. The first construction of the bow in 1893 had an iron contact piece which wore the line very much, as a good contact was only to be produced by pressing the rather heavy contact bow strongly against the contact wire. This defect, however, was discovered before much injury was done to the overhead construction, and the iron contact piece was replaced by a brass bar covered with white metal. The wear of the line was then no longer noticeable, and only the contact piece, which can easily be replaced, suffered from wearing. A still greater improve- ment was made when the contact wire was lubricated by means of a furrowed aluminium contact bar, by which means also all noise was suppressed. Aluminium has been chosen in order to decrease the swinging weight, and consequently to diminish the contact pressure. A contact piece covered with composition will last about two weeks, after which time the cover must be renewed. ~ An aluminium piece will last from six to eight weeks (about 8000 car kilometre). The cost of maintenance of both contact pieces is about the same, being about 0.07 pfg. per car kilometre. ROLLING STOCK AND MOTORS. 845 (904) Fig. 84. Siemens Sliding Bow. : 846 SECTION X. Blackwell Standard Trolley Head. (FIGS. 85 to 88.) Figs. 85 to 88 on this page, show Messrs. R. W. Blackwell and Co.'s standard trolley head for use on swivelling trolley. The rubbing surfaces, through which 87 GU TIIN 88 (903) Marsour SEC.THRO.A.A. ------ O Ta TIN VÀ * G* « que não me we 85 * ** ** * TIRES THE 86 A Figs. 85 to 88. Blackwell Standard Trolley Head. the current passes, are bushed with graphite. The construction is such that, by removing a pin the wheel and harp can be taken out without removing the rest of the head from the pole. Trolley for Lecco-Sondrio Three-Phase Railway. (FIGS. 89 to 91, page 847.) The type of current collector used on the Lecco-Sondrio Three-Phase Railway is shown in Figs. 89 to 91, page 847. It is composed of two siliceous bronze hollow rollers, each revolving on hard steel ball-bearings, separated by a fixed cylinder of wood of the same diameter (76 millimetres). The rollers are 24 milli- metres thick. The ball-races are insulated, and carry no current. The coned con- tinuation of the collector does not revolve, and is mounted on a wooden or other insulating spindle. This spindle carries a steel tube, to which the ball-races are attached. The current is brought from the rollers by annular carbon blocks, which are pressed by spiral springs against a copper collar fixed at the end of each roller. A piece of flexible copper cord takes the current to the two pairs of trolley poles which serve to support the rollers at either end. Insulating caps are fixed to the ends of the conical prolongations of the rollers, which are supported by a vertical stud, free to slide up and down in a slot formed in the small casting into which the two trolley poles fit. This casting has attached to it two coil springs, forming an angle of about 45 deg. with the stud to which they are connected. These springs constantly tend to press up either end of the roller in a vertical plane, the casting to which the springs are attached in their turn being held up by the spiral springs at the bottom of the trolley. The weight of the roller is 12 kilogrammes (27.5 lb.), and, to run satisfactorily, it has to be pressed against the trolley wires with an upward pressure of 15 kilogrammes (33 lb.). The trolley poles on either side of the roller are connected below to a solid casting, hinged on a cast-iron base, supported on metal caps fixed on the top of ROLLING STOCK AND MOTORS. 847 porcelain insulators. Two spiral springs lift each pair of trolley poles up to the trolley wire, as in ordinary practice. The peculiar feature in this trolley is that the springs, instead of being solidly fixed at one end to the base casting, are con- nected to two short horizontal levers which form the end of a piston-rod working 89 06 ***** **** USUZ · ***** *** • ******* 515 ***kanag didates ↑ Vande – hood of 91 ----2750. ·832. app _(506) Figs. 89 to 91. Details of Electric Trolley on the Lecco-Sondrio (Ganz) Three-Phase Railway. horizontally in a cylinder which is part of the base casting. This piston is operated by compressed air, and the springs are brought into action and held in position by this means. Should the trolley rise above a predetermined height, a valve is automatically opened, which releases the air and lets the trolley down. 848 SECTION X. CAR WIRING. for use. Cables complete with suitable taps for connecting controllers, resistance, and motors for the shunt-method of control, are preferably purchased made up ready These cables are manufactured in lengths of 30 ft., 32 ft., 34 ft., and 36 ft. Two cables are required for double motor cars, each containing seven wires. In addition, a separate ground wire is required. Each wire in the cable is composed of seven strands of small tinned wire, to make it flexible and not easily broken. Two-way connectors should be used in connecting taps to motor leads, and soldered to the latter. In ordinary cases the required length of cable will be 6 ft. longer than the over-all length of a closed car, and 4 ft. longer than the over-all length of an open car, measured in both cases from dasher to dasher. On a closed car four 2-in. holes should be bored through the car floor under the seats, one as near each corner of the car as possible. On one side of the car four §-in. holes should be bored in a line and 4 in. apart, to receive the taps from the cable to the leads of motor No. 1. The exact location of these holes depends on the type of motor used. The distance from the centre of the axle to the centre of this group of holes should be about 24 ft. On the same side of the car, and in the same line, four other §-in. holes should be bored 4 in. apart, to receive the taps from the cable to the resistance boxes. On the other side of the car, three §-in. holes, in a line and 4 in. apart, should be bored to receive the taps from the cable to the leads of motor No. 2; and on the same side of car, and in the same line, five other §-in. holes, 4 in. apart, should be bored to receive the taps for the trolley, resistance, and shunt for motor No. 2. Each set of holes must be on the proper side of the car, and at such a distance from side sills as to be out of the way of wheel throw. Measuring about 38 in. from the brake staff, and a suitable distance inside the dash rail, an oval hole, 5 in. by 24 in., should be cut in each platform to receive the cables. To Find Length of Cables Required for Car Wiring. (FIGS. 92 and 93, page 849.) Following dimensions measured on car required :- For cable Y: d, f, g, a (distance from where cable laid under seats of car to centre of No. 2 motor), b, c (distances from where cable fixed under car seats to terminals of resistance). For cable X: H, I, J, K (distance from where cable fixed under car seats to centre of No. 1 motor), p, r (distances from where cable fixed under car seats to terminals of corresponding resistance). Length from trolley base to canopy switch at one end of car, from there back to the other end of car to other canopy switch, then to side, and down car to lightning arrester (for this + L. S. W. G. 2000 Meg. braided cable generally used). Length of ground wire shown in figures in dotted lines from controller to con- troller, including taps to motor frame (for this a piece of bare trolley wire may be used, or a bare copper wire not smaller than No. 2 B. W. G.). Length of tap from cable Y to lightning arrester. If no choking coil sent with arrester, allow 8 ft. extra length to be wound round a 2-in. wooden cylinder 6 in. long. Directions. The length of each cable is measured to the end of the canvas hose, which should reach to the bottom of the controller, and wires emerging from the cables and connecting within the controller are in excess of this length. If the car body has been built, a convenient way for measuring lengths of cable is to lay a small rope in proposed position of the cables; on this mark the position where the taps should emerge, and measure their needed length; then remove_rope, lay it in straight line, and measure the several portions of the length, and fill in same on a diagram. These dimensions to be filled in on the cables X and Y are for purpose of locating position of taps and their length. Allow 3 in. extra for any corner around which cable has to be bent. The leads on these made-up cables will have two extra coverings of insulated braid for their better protection. This is used in order to avoid rubber tubing, the best of which deteriorates, and should not be used. Each car should be provided with a lightning arrester and choking coil on the trolley wire side; as the series field coils of the motors are in most cases sufficient to prevent any damage from the ground side of the circuit. The ROLLING STOCK AND AND MOTORS. 849 lightning arrester should be placed in a position where it will be protected from mud and water thrown by the wheels. 92 CableY www KATANYAAN PONTIA RORS To Lightging Arrester, WE Jaya alim punain 7 To Groand ghtning Arrester Box To Ground 由​上​腔​相​付​在 ​Form K2 poweQS WAY;" ใช่ Jam o 3-4 I ON Removable Bars NAKON ASSEZON DO ---II *- : // : 2015 Cable x Trolley Base 93 (540, Figs. 92 and 93. Laying out Wiring for Car. CON 03 The kicking coil consists of ten turns of the main circuit wire wound about a wooden core, 2 in. in diameter and 6 in. in length. It should be connected between the lightning arrester and the controller. Car Lightning Arresters. The Wurts non-arcing railway lightning arrester consists of two brass elec- trodes separated by in. of insulation, into which narrow grooves have been burnt. On the top of this a tightly-fitting insulating cover is fixed. The principles on which this arrester is based are: (1) That experiment has shown that a static discharge will jump over a non- conducting surface more easily than through an equal air space, and that a carbon groove over the non-conducting surface very much facilitates the discharge. 5 850 SECTION X. { (2) That an arc, in order to be maintained, must be fed by the vapours of the electrodes, and that, if these fumes are prevented, the arcing will not take place. The passage of an electric spark acrose an air gap is so instantaneous that it, so to speak, bursts through the air: but a pencil mark across a piece of ground glass will very much facilitate the passage of the electrical discharge, although it will intercept the passage of a current. The resistance between the two conducting surfaces of the lightning arrester is over 50,000 ohms, so that it is not a cause of leakage. CAR LIGHTING. (FIGS. 94 to 97, pages 850 and 851.) The car is lighted by one or more groups of five incandescent lamps, put in series on the motor circuit, and provided with a fuse and cut-off switch. TROLLEY Farrah d α Doors. NONE → 222244 545 Fig. 94. Diagram of Car Wiring. Fig. 94 is a diagram showing wiring for 5 lamps; Figs. 95 to 96 are similar diagrams for 5 and 10 light cars; and Fig. 97 shows the wiring for lamps on Bradford cars. It has been estimated that the cost of heating cars by means of coke or oil stoves in America amounts to about 8d. per car per day of 18 hours. These stoves are, of course, a source of danger from fire if not carefully attended to, both during the day and before leaving the cars at night. Gas and oil stoves have also been tried. The direct mode of transforming electricity into heat is now largely employed. In a comparatively mild climate like ours, the cost of electric heating would probably not be greater than that of heating by any other means. This is due to care in regulating the heat, and turning it on and off at will. As great a radiating a surface as possible should be given to the heaters, and they should be placed low down and near the doors of the car. The following table gives the results of tests made by the Atlantic Avenue Electric Railway Company, of Brooklyn, in the early part of 1894. Table 41.-Showing Electric Power Consumed in Heating Electric Cars. Cars. Windows. HEATING. Electric Car Heaters. 222222 Contents. Temperature. 850 850 808 913 1012 1012 Outside. cubic feet. deg. Fahr. 28 ∞78078800 RAIL m 28 36 28 Average in Cars. deg. Fahr. 55 39 49 52 46 54 Electrical Power Consumed. watts. 2295 2325 2180 2745 3038 3160 ROLLING STOCK 851 STOCK AND AND MOTORS. 95 97 WW VAY V Wiring of receptacle box Tra Switch Switch Fuße Wiring of receptacle box Ground (546)* Ney Platform Switch Nº2 } Switch TqNº1 Motor mearest fuse (538.) Trolley зуб Ground Switc Trolley 18 Ground Receptacle box with Contact stem in position Diagram of Car Receptacle box with. Contact stem in position Car Fuse For Power Circuits FUSE Switch SILL OF CAR. Platform Switch No! Lightning Arrester Choke co11 To trolley wire in canvas hose Figs. 95 to 97. Electric Lighting of Cars. Earth Connection an moter Fig. 95. Wiring for Five-Light Car. Fig. 96. Wiring for Ten-Light Car. Fig. 97. Light Wiring for Cars at Bradford. 852 SECTION X. 7 The American Electric Heater. (FIG. 98.) The whole consists of a steel frame with pins projecting on either side, on which are supported grooved porcelain insulators. The coil consists of spirally- wound wire. Through the centre of the spiral a stout asbestos cord is run, of just sufficient length to fasten at one end of the heater to an insulator, and extend to the other end when tightly drawn. This cord of predetermined length is straightened out, and the coil, which, when wound, is considerably shorter than the cord, is stretched so as to be of equal length, thus giving uniform spacing to the spiral. The whole is then placed in position, the ends being fastened round the end porcelain insulators. A rubber-covered wire, connected by making a good mechanical joint and then by soldering to each end of the coil, completes the construction of the electric circuit. Fuse box These heaters and frame having two independently placed side, and one on the other of the frame, are placed in cases. wires are conducted through porcelain bushed holes in the cases. struction there are two independent circuits in each heater. divisions of heat, one coil has twice the resistance of the other, consequently using half the current of the lower resistance coil. Motor Switch i AB 'TwoN° / Switches Aon, Boff-Low Bon. A OFF - Medium Hest A & B on - Full Heat Trolley Base To Motors coils, one on one The leading-out With this con- To get three (536) To Earth Fig. 98. Diagram of Wiring for Car Heating. "Wire B&S "10 Wire 8 & S For four-heater equipments the heaters are connected in series, using on one series of coils 3 amperes at 500 volts, and on the other 5 amperes. For the low heat, the high resistance coil is turned on. For the medium heat the high resist- ance coil is off, and the low resistance on, and for maximum heat both series are on. By this arrangement, whenever any current is on at all, every heater is in service, distributing heat throughout its entire length. This is a very important feature in street-car work. It has been the practice to place the coils, instead of parallel as in this case throughout the heater, to practically cut each heater in halves, having in one end one coil and in the other the other, with the result that but small area was at work when part of the load was on (as compared to its entire length), and a discharge of hot air is produced from a small area when only mild temperatures are required. The concentration of heat for car heating is the thing to be avoided. This will be evident upon a very brief consideration of the subject. One important element in car heaters to ensure their durability is that they should be long lengths of wire of large diameter, so as to provide the largest possible area of radiating surface per watt or free heat unit. The smaller the wire and the hotter it is compelled to run, the greater the expansion aud contraction, and the shorter its life. As will be noted, there are three divisions of heat-equal distribution for each division. ROLLING STOCK AND MOTORS. 853 For cut-outs are furnished what is known in America as the "D and W" non- arcing, non-explosive, fusible cut-out. The switches are made entirely of slate and metal, and of two types. One, a single pole, quick-break switch, two of which are designed to be used, one on each circuit; and the other style, a combination arranged to control the two circuits, to give the three divisions of heat. This switch has a single lever, double break, positive snap switch, and carries an indicator showing what degree of heat is on. The lever works through an arc of about 70 deg., and the operating switch is automatic when the lever reaches a certain point in its course, so that it is inde- pendent of the control of the operator after the handle has passed the tripping point. All heaters have a maximum watt capacity of about 1000 to 1200 each. They can be arranged for any less amount as a maximum. The number of square feet of heating surface of wire or superficial area of the wire constituting the coils in the heater, is from 1.8 to 4.56 square feet. CONTROLLING. Controller Location and Erection. In the Standard car equipment one controller is placed on each platform on the side opposite the brake handle, in such a position that the controller spindle and the brake staff shall not be less than 36 in., or more than 40 in. apart. The exact position depends somewhat on the location of the sills sustaining the plat- form. The feet of the controller are designed to allow a slight rocking with the spring of the dasher. Two -in. bolts secure the feet to the platform. An adjustable angle-iron is furnished, to be used in securing the controller to the dash rail. Where wires are on top of roof, they need not be covered with canvas or moulding. Floor wiring may be done after the car is built. Main Cut-out and Motor-Switch. On closed cars the main fuse or cut-out should be placed on the outside of the platform-sill under one corner of the car. It is not good practice to place it under the seats, or on either platform. It should be so secured to the car that the cover will hang vertical and swing_upward. This will bring the trolley and motor terminals on the outer side. The method of support may be either a backboard or an angle-iron. The main cut-out or motor switch is always in duplicate, and is worked from each platform, being generally put just over the motor-man's head, so as to be easily reached by him. The current is always turned off here, whenever the motor-man leaves his car. The use of circuit-breakers on cars, under such severe conditions as emergency reversals, may be recommended. Dick, Kerr Controllers. The controller is of the usual series-parallel type. The controller is designed for fastening to the dasher of the car platform, and consists of a strong cast-iron frame supporting two vertical cylinders, upon which are mounted the contact rings, by means of which the different combinations are made through stationary fingers held against the cylinders by spring pressure. One of these cylinders controls the power and speed of the car, the other is for reversing the direction of motion. The whole mechanism of the controller is protected by a heavy sheet-iron cover, hinged on the frame, and held closed by two strong clips insulated on the inside by sheet asbestos. The top of the controller case consists of a brass cover, through which the spindles of the cylinders project to receive the handles. This cover is waterproof, and embodies a dial plate, by means of which the position of the cylinders can readily be seen. The cylinders are interlocked in such a manner that the operating or driving handle cannot be moved unless the reversing handle be either at the "forward "reverse" positions; nor can the reverse handle be moved unless the operating handle be at the "off" position. or Means are provided in the controller allowing of either motor being entirely cut out of service, and the car driven by the other. Between each of the contact fingers of the power cylinder a solenoid is placed 854 SECTION X. ▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬ ---- so that the connection is broken in a strong magnetic field, thus avoiding any burning effect which might otherwise take place. These solenoids are supported by a hinged frame, which can be swung back to allow of thorough inspection of the contacts and cylinder. By a special movement of one of the controlling handles, the motors can be converted into generators, with the result that a powerful braking action is applied to the car. "" "" :) Form K14.. K15.. K16.. K21.. "" "" >> "" "" Type of Controller. Table 42.-British Thomson-Houston Controllers Forms K and L. (Figs. 99 to 101, pages 854 and 855.) L2 L3 L4 ·· L6 L7 .. RI .. (692) * •• .. •• Motors for which Designed. No. 4442 2 4 4 4 4 R2. R1-R2 5.24 ohms. R 2 - R3 = 1.25 R3-R4 = .81 R4 R5 = .34 H.P. 75 125 125 50 125 160 75 175 175 "" "" "" .. ·· .. Number of Resistance Points in Series. 99 .. R3 6 › co co mɔ mA 00 TO 00 00 1O 1O 1O 2 M CO DO LO LO .. 6 6 8 3 PR 112 PR 113 2 4 6 8 10 12 4 6 8 10 12 high rig 3 5 7 3 5 79 8 Number of Resistance Points in Parallel. 8 5 5 5 3 6 Resistances Approximate at 70 deg. Cent. 3 5 5 R4 R5 Total Number of Points. R 17.64 ohms total. R 2 = 2.40 R 3 = 1.15 R 4 = .34 R5= .0 >> "" "" "" 13 13 13 9 8 16 8 15 15 Brush Company's Controllers. Figs. 102 and 103, page 856, show the Brush Company's controller diagram for two motors and two series-parallel controllers, with emergency brake. ROLLING STOCK AND MOTORS. 855 Nº OUT A2 Con.No1 AA2 AI AAI N'OUT (907) CABLE AA2 A2 100 Connect field leads E &F as stamped on motors and motor diagrams To secure proper position of Reversing Handles armature connections must be as below AA2 9990 GROUND AA2 AAI AI A2 Controller AAL N°2. T Ri R2 R3 Ra Rs 19 15 E ||||| Grounded to Frame 19 101 Forward Emergency Grounded to shaft Ꮳ Blow-out Magnet •AI Az ◆AA, CALE Rs Fi Ra Ra Re Ri RS R4 R3 R2R1 MINT #11 H T ●F2 AA2 ●A2 15 ¿Reverse Emergency Grounded to shaft A, Leads and taps from cables to be connected as they are marked WE, NOM Figs. 100 and 101. Diagram of K 10 Controller. (British Thomson-Houston Company, Limited.) 856 SECTION X. 103 *HA 102 SERIES PARALLEL 5 6 7 SEE CONTROLLER TERMINAL|BDARD FORWARD BACKWARD ➡ EMERGENC FRO No I CUT OUT A 13 N VT OU! POWER 6 NOTCH I OFF TROLLEY 2007 W A www www. W ww www www. ww SOLENOIDS www www WW www www M AWY MA ww w EMERGENCY STOP CAR толк •HITI- HOS ብ lan EU BUNDLE Annam RHEOSTATS CPU- Vo ·TTEND GROUND WIRE IN CAR BUNDLE GROUND GROUND WIRE N CUT OUT -- A) Inte No ? CUT OUT LIN3D834} # AZİ OBVM NOVD FORWARD PARALLEL (208) Figs. 102 and 103. Controller Diagram for Two Motors and Two Series-Parallel Controllers, with Emergency Brake. (Brush Electrical Engineering Company, Limited.) ROLLING STOCK AND MOTORS. 857 Dick, Kerr Controllers for Double and Quadruple Motor Equipments. (FIGS. 104 and 105, pages 858 and 859.) Fig. 104, page 858, shows the wiring diagram of the Dick, Kerr D.B.-1 Form E controller for two motors. This form of control embodies a rheostatic brake with several notches, which range in steps from short-circuiting the motors as generators through the whole of the resistances to a dead short circuit. An automatic device called a run-back preventer is also supplied, which checks the car should it attempt to run backwards on a gradient. Fig. 105, page 859, illustrates the form of wiring employed with the Q.E.-1 Form A controller for quadruple equipments. This controller is provided with five series notches and four parallel notches. The Sprague Thomson-Houston Multiple-Unit Train-Control System. (Fig. 106, page 860.) The system consists of two general parts: first, a number of electrically- operated switches called contactors, and an electrically-operated reverse-switch, called the reverser, constituting a series-parallel controller for the motors on each motor-car, which effects the different combinations of the motors and varies the resistance in series with them. • Second, a master controller or controllers located at one end or one at each end of each motor-car in the motor-man's compartment, and controlling the contactors on all motor-cars in the train. A cable connected to each master- controller and to the contactors runs the entire length of the train, with suitable couplers for making the necesssary connections between cars. The main motor current does not pass through either the master-controller or the train-control cable, these parts carrying only the current which operates the contactors. Each motor-car collects its own motor current from the line by means of its contact device (collector shoes or trolley), and the current for operating the contactors of all motor-cars in the train is drawn from the collecting device through the master-controller on the car from which the train is operated. Thus the move- ment of this controller sends current to the contactors, which are wired in parallel to the train cable, insuring simultaneous movement of all contactors on the train. The synchronous action of the motor controllers of all cars simultaneously with the movement of the master-controller handle insures similar resistance connections and motor combinations on all the cars at all times. The position of the master-controller handle indicates to the operator the exact position of all the motor controllers on all the cars. The rate of movement of the motor controllers, and consequently the amount of current taken by all of the motors, is under his immediate control, just as it is with ordinary hand-operated controllers. The motor-man is able, at will, almost immediately to utilise the full power of the motors in either direction in an emergency. In case the supply of power to the train is momentarily interrupted for any reason, the contactors all open the motor circuits, but the motor and resistance connections which were in effect immediately preceding such interruptions are instantly re-set upon the restoration of power, provided the master-controller position is unchanged. The interruption of current to the motors in the off position of the master- controller is insured by providing three separate contactors connected in series, any of which is capable of opening the circuit. If the train breaks in two, the current is automatically and instantly cut off from the motors on that part of the train which is not under the control of the motor-man, while his ability to control the front part of the train would not be affected. When the master controller is returned to the off position, both positive and negative connections are cut off from the operating coils of important contactors, and none of the train wires in the train-line cable remain in circuit. For reversing the motors the master-controller is provided with a separate reversing handle, and a mechanical locking device prevents this handle from being thrown unless the main handle is in the off position. Moving this reverse handle either forward or backward, makes connections for throwing the electrically- operated reverse switch either "forward" or "reverse.' This main reversing switch is electrically interlocked, so that it cannot be thrown when the motors are in circuit. The operating circuit is so arranged that, unless the reverse switch on any car is thrown in the direction indicated by the master-controller reverse handle in use, SOLENOID CIRCUITI BREAKER 100-200 AMPS! IMPO CONTROULER NO I CONTROLLER NºĮ, -➖➖➖➖➖HE OFF R3 R2 080-00- RESISTANCE TYPE B FORM E I COIL 10 COILS N° 45 *40 DOBIERKUJE R2 PI TIKA JĮ VULT | II COILS N! 45 BOX Nº 5 TYPE- DBI CONTROLLER FORM-E BOX N° 2 BOX Nº1 NOIS 6 COILS Nº 45 -BRAKE 5 6 74-POWER MOTOR Noi GROUNDED TO CONTR. FRAME LL. ___? MC-III) 133 SLOBBL LIGHTNING ARRESTER B R CHOKE COIL CE BRAKE SHOE wwwwwwwwwww CIRCUIT BREAKER RESISTANCE DOUBLE DKG A EQUIPMENT ELECTRIC BRAKE "RUN BACK PREVENTER' R$ MOTOR No 2 AAI === 1 +1 RESISTANCE TYPE B FORM E. BOX N° 3 # COILS Nº 40 AUXILIARY RESISTANCE FR3 BRAKE SHOE RS 9 COILS N° 45 TROLLEY LIGHTNING ARRESTER, 2 COILS N° 40 BOX N°4 CHOKE COIL -401D FF 24 AA 2 GROUNDED TO MOTOR FRAME CONTROLLER Nº 2 CIRCUIT BREAKER ว 1 CIRCUIT BREAKER 100-200 AMPS CONTROLLER Nº 2 1127 *B-BBEE Fig. 104. Wiring Diagram of Dick, Kerr Type D. B.-1 E Controller. 32 - - - - - - ------ FI FFI -------- AZ อย 858 SECTION X. 1 | ROLLING STOCK AND MOTORS. 859 SOLENOID #1 11 11 |||||||||||||| -SWITCH, Nº 2 } 1 CONTROLLER No I MOTOR NOI MOTOR N° 2 CONTROLLER NO I LIGHTNING ARRESTER 3 COILS N8 30 ". " " TYPE QEI CONTROLLER FORM A. 12 TURNS CHOKE COIL # L AA2 6 COILS 480 9 COILS Họ 30 MOTOR NO I CONTR. FRAME GROUNDED HERE QUADRUPLE EMERGENCY EQUIPMENT BRAKE THE SHORT SYSTEM CANOPY SWITCH N°2 PRS RE R2 RI AAI 6 COILS No 40 3 COILS N° 30 RESISTANCE TYPE B FORM B COILS N°30 LIGHTNING ARRESTER MOTOR N? 2 FF2 A2 GERA TROLLEY mw MOTOR CHOKE GOIL MOTOR Nº 3 FF3 AA3 RESISTANCE OFF4 MOTOR! N° 4 AA4 10 CIRCUIT BREAKER COO TO 300 AMP! MOTOR N? 4 I GROUNDED TO MOTOR FRAME L Fig. 105. Wiring Diagram of Dick, Kerr Q.E.-1 A Controller. " CONTROLLER t N° 2 A50 CIRCUIT BREAKER CONTROLLER Nº 2 R3 R2 RI BARENÉ F21 420 AA213-- AAID- AID- FFID FF21 F3 AA3 --A3 A4. ·444; 1128 I $1 860 SECTION X. OROMO OMODON Owoody fo OPOROW σloodby CONTROL COUPLER SOCKETS COUPLER O REVERSE CYLINDER AUTILIARY CONTACTS] LOCK NAGNET = MOTOR CIRCUIT SWITCH CONTROL GIRCUIT SWITCH FUSE 0449-A CONTROLLER REVERSE FORWARD BLOW OUT COIL €16 FUSE THIRD RAIL SHOE OPERATING COIL 12 AUXILIARY BLOW OUR GOIL [IZLI 15182 [4]| • clin 61 31 BLOW OUT COIL Finney RUNNING POINTS - RESISTANCE POINTS CONTROL CUT OUT SWITCH AND FUSES CONNECTION BOX No I 99999 AMAĞ LA 02 AAI RZ TË 13|23||33|32|32|47 CONTROL GIRCUIT RHEOSTAT Lamar w Lumori Mr R2 W R3 ԱՄ 31 R4 5162 13382. 162 151 Ailan R6 ՆՈՐ 4. R7 ||6 2||12|77 7}|| SW FM Z212/ www EM RUNNING POINTS RESISTANCE POINTS CONTROL CIRCUIT SWITCH CONNECTION BOX N° 2 99999 REVERSE CYLINDER AUXILIARY CONTACTS J LOCK MAGNETI Low COIL AA2 FUSE FRONT END OF REVERSER BOX ◊ ENERGIZED 8 ENERGIZED LAY RT OPERATING COIL C-1D-A CONTROLLER REVERSE WEZ TO Fig. 106. Connection of Sprague-Thomson Train Controller. 8 FORWARD AUXILIARY JBLOW OUT COIL THIRD RAIL SHOE OMO»Ð¸ OPCON CHORO Q₂OOO₂ GROPON O+ODOLY CONTROL COUPLER SOCKETS COUPLER 1/29 ROLLING STOCK AND MOTORS. 861 it will be impossible to operate the contactors on that car so as to get any current in the motors on that particular car. A cut-out switch is provided on each car, so that in an emergency all of the contactors on that car may be disconnected from the control circuit. The control operating current at 550 volts line potential is about 2.5 amperes per car for an equipment of two 160 horse-power motors, or four 80 horse-power motors, and the total weight of the control apparatus for this equipment is approximately 2200 lb. Fig. 106, page 860,(shows the connections. Ganz "Cascade" Method of Control used on Lecco-Sondrio Three-Phase; Railway. (FIGS. 107 to 109, pages 861 to 863.) V. This method, besides regulating the speed, ensures a large starting torque, but is only feasible when motors are used in pairs. At starting, the two motors- Ⅲ Troller Trolley Cami" Barth Stafor SORVALL ndary AM Staigh Primary Water Rheostat Rotor Secondary Rotor Primary n z I MONE (910) Fig. 107. Diagrams of Connections for Running Motors in Cascade. (Lecco-Sondrio Railway Speed Control.) F. 862 SECTION X. Trodey Trolley Reversing Switch Transformer for lighting healing & compressino Stator Secondary 19/11 Water Khu ostat Robor Rotor Stator Primary Short arcuiting! device Controller Water Breastat Sturt arayiting dence Cortiabiler Primary Rotor Stator Secondary Rotor Stator J Trolley Fig. 108. Diagram of Connections and Switching Gear for Motor Car. Trolley Lightning. Arresters Heversing Switch ! } ! : ! i ROLLING STOCK AND MOTORS. 863 which need not be the same in power or construction-are connected as follows: The stator of the first motor is switched directly on the line, the collector rings on its rotor are in turn connected to the stator of the second motor, and the stator of the second motor is connected to a non-inductive resistance. The motors thus connected will start with a large torque, but their maximum theoretical speed cannot exceed one-half of that one of the motors directly connected across the line. When motors are connected thus in cascade at half speed, the slip of the rotor of the primary will be 50 per cent., and the cycles will be half the number of those supplied to the stator of the primary motor. The action of the primary on the secondary motor will be to tend to induce it to rotate at synchronous speed and frequency. At half speed the frequency in the secondary will be half that in the primary. The speed of the rotor is proportional to the number of cycles, all being equal. Therefore, up to half speed two motors could be in cascade. This would not be possible above half speed, as then the difference between the cycles induced in the rotor of the primary motor would be less than half frequency, and if this were connected to the secondary motor, would drive it at less than half speed, and hence, instead of acceleration, there would be retardation. Trolley Wire. Stator of Primary Motor: [6106X) High tension, auto- •matic reversing switch. Fig. 109. Connection of High-Tension Reversing Switch. The four running positions, shown in Fig. 107. They are: Trolley Wire 1. Stator of primary on line. of secondary on water rheostat. Earth commencing with the one referred to above, are Rotor of primary on stator of secondary. Rotor Rotor of primary on stator of secondary. Rotor Rotor of primary on water rheostat. Secondary 2. Stator of primary on line. of secondary short-circuited. 3. Stator of primary on line. motor cut out. 4. Stator of primary on line. Rotor of primary short-circuited. At high periodicities this method has serious disadvantages, owing to the large self-induction which is added by the stator of the second motor to the rotor of the first motor; this, of course, greatly reduces the torque of the latter. The rotor winding of the first motor must be of fairly high resistance, in order to limit the current inflow and increase the electromotive force at the stator of the second motor, and if both motors are to be capable of running in parallel across the line, the ratio of the stator to the rotor windings must be unity. cascade' Fig. 108 shows the connections of motors and controllers for working on this line. Fig. 109 shows the connections of the high-tension combined reversing switch and circuit breaker. The switch consists of six copper plungers, which, when lowered, fit into an equal number of copper cylinders, in a similar manner to the high-tension oil switches used by the General Electric Company, of America, in the 96th Street Power Station of the Metropolitan Street Railway Company of New York. By rotating the switch through 60 deg., the connections shown are changed from the full to the dotted lines. This changes the position of two of the phases, and the motor is reversed. The six points of interruption are con- "C "3 864 SECTION X. tained in long porcelain tubes fastened to the iron case, while the parts which serve to close the circuits are mounted vertically on a circular insulated disc, attached to a metallic rod capable of being moved upwards and downwards. The lift of this switch when wide open is about 8 in.; there being six plungers, each phase is broken in two places, in series with each other. Raworth's System of Automatic Regenerative Control for Traction, (FIGS. 110 to 112, pages 864 and 865.) The principal feature is the use of motors with shunt-field instead of series- field windings. One of the advantages claimed for this is the ease of manipulation obtained by regulation of the field circuit, independently of the armature circuit. The armature current automatically adjusts itself to suit the load; thus, if the controller be fixed for any speed, the car will travel approximately at that speed irrespective of grade, the current varying according to the load. DEVONPORT & DISTRICT TRAMWAYS. DIAGRAM OF CURRENT CONSUMPTION & REGENERATION UP AND DOWN A GRADE OF I IN 12 X Indicates Current returned to line Direction of running Amperes 1 75 60 $ 45 30 15 O Bottom of grade Zero Line X Top of grade X- 75 60 45 30 15 O 15 30 45 45 60 60 75 75 Direction of running ← Current recovered-50 per cent of current consumed Weight of Car-9 tons Diagram of Current Consumed and Regenerated. 15 30 Amperes 1130 Fig. 110. For the motors in actual service the shunt coils are designed for regulating the speed of the cars from about four miles per hour to the maximum speed required, and also for braking purposes below this speed. The series coils are provided for emergency braking in the event of the trolley leaving the line or of current failing. The lowest regenerative speed corresponds approximately with the speed of ordinary series motors when both are in series and all resistance cut out. The principal advantages claimed for this system are:- (a) Regeneration of energy by the motors acting as generators in descending gradients, and in braking; (b) Improved control in speed regulation: (c) Mechanical braking reduced to a minimum, and the wear considerably decreased. (d) The wear of wheels in braking avoided and their life extended. Tests made on the hilly lines of Devonport by means of recording wattmeters, show a saving in energy of 31.30 per cent. On some of the gradients as much as 54 per cent. of the energy consumed in ascending was recovered in descending. These results were obtained from tests made under the supervision of the officials of the Brush Electrical Engineering Company. A three months' test on the Birmingham Tramways showed that the consumption of electrical energy was reduced from 1.24 to 0.97 per car mile, as measured at the switchboard. Fig. 110 shows proportion of energy consumed and regenerated, on a gradient of 1 in 12. ROLLING STOCK AND MOTORS. 865 Kilo -watts In Fig. 111 below, the consumption and recovery of energy is shown respectively in accelerating to full speed, and then braking to 4 miles per hour. About 50 per cent. of the energy used in acceleration is recovered. AUTOMATIC REGENERATION CONTROL SYSTEM. DIAGRAM OF BRAKING EFFECTS TAKEN BY RECORDING WATTMETER ON A 9 TON CAR. Diagram No1. Diagram No2. Diagram No 3. 50 40 30 9 90 9 20 10 20 30 40 sol S.6.1 S.L.2 101 0 Direction of running 10 101 20 20 30 30 40 40 50 50 Diagram No1 shows Regeneration in reducing speed in 10 seconds 2 5 "1 " " " " " 3 Front "Zero Kine 7S 6157 S.L.S 50 40 30 20 CONTROLLER N9 I #1 " " 3 " " "} " Curves above zero line show energy consumed in starting and accelerating to full speed 13 miles per hour Curves below zero line show energy recovered in braking speed to 4 miles per hour. Fig. 111. Diagram of Braking Effects (Raworth). DIAGRAM SHOWING ARRANGEMENT OF ARMATURES AND FIELDS. Zero line S Shaunt Fields coupled in series A Armature " F Series Fields E Earth Connection S 6000002 A F Back REFERENCE S.LI Off position P.L.I | Off position S.L2 Full speed P.L.2 Braking position S.L.3 First speed position | P.L.3 1st Starting S.L.4 Slow speed S.L.5 Emergency Brake P.L.4 Running position resistance contact " S 00000 " “Q0000- F "I "" E Fid CONTROLLER Nº 2 50 40 30 Back 20 10 Ant Zero line "" B 1132 (131 P.L.4 Front Fig. 112. Controller Diagram (Raworth). Wheels and brakes last longer. At Devonport brake-blocks have run 25,000 miles, as against 1000 miles. At Gravesend brake-blocks run about 20,000 miles. Fig. 112 shows the type of controller used in the simple series method of FF 866 SECTION X. control. The handles have a forward and backward motion, corresponding respectively to increase or decrease of speed. The handle A on one side controls the field circuit, and the handle B on the other side controls the armature circuit. Increase of speed is obtained by moving the speed handle A forward over the speed regulating rheostat contacts, and to reduce speed the handle is pulled backwards. When the handle is pulled right back, the series field-winding is put in circuit with the armature. Reversing switches can be fitted to this type of controller. The The construction and operation of the regenerative series-parallel controller is very similar to that of the ordinary series-parallel system, the interlocking_of the reversing and power barrels being carried out in a similar manner. regulation of the armature and shunt circuits is done on the power barrel. For speed regulation, eight different steps are provided for variation of the shunt field. The change from series to parallel and vice versa is, under ordinary conditions, not noticeable by the passengers. The Johnson-Lundell Regenerative System. (FIGS. 113 to 115, page 867.) Fundamentally, the system is based upon the universally accepted principle of effecting speed variation in electric traction by series-paralleling the motor circuits. The circuits are paralleled twice, thus necessitating the employment of four instead of two armature circuits. It is immaterial whether these four circuits are in four separate motor units or, as in the present instance, in two motors, each of whose armatures have their coils divided and fitted with two independent com- mutators. By means of double series-paralleling in combination with strong magnetic fields, the usual main-circuit resistances are dispensed with. checking the rush of current, and obtaining the speed regulation called for by each series-parallel circuit change, an ample range of field variation has been developed. In order that the changes of field strength shall the more perfectly synchronise with the series-parallel changes of the motor circuits, the laminated form of field magnet has been adopted instead of the usual solid casting. For By means of a method devised by Dr. Lang, the field windings of the motors are made to do duty as series windings when the motors are acting as motors, and as compound windings when they are acting as regenerators, the whole of the copper being usefully employed in each case. This is effected by suitably grouping the several field coils in the requisite series or parallel relation by means of a special device. This device, which has for its sole function this determination of the motor characteristic, is termed a "field changer," and is made to act auto- matically by means of a solenoid, so arranged as to oscillate the contact cylinder with which the device is fitted against the retractile force of a clock-spring. The spring holds the cylinder normally in the position which gives to the equipment its series or motor characteristic. When it is oscillated from this position by the action of the solenoid, the equipment is given its compound or regenerative characteristic. The solenoid operating the field changer is controlled through contacts in the platform controllers, which are operated by means of thumb pressure upon a lever fixed in the controller handle. In the operation of the platform controller the various changes of the circuits and of the field strength which are effected by the forward movement of the controller handle, for the purpose of accelerating, are, of course, made in the reverse order when the handle is moved backward, but are without effect if the equipment is left in its series relation. If, however, the equipment is given its compound relation, through the operation of the field changer, these changes of circuit and field strength cause the motors to develop a braking effort, step by step, as the handle is moved back- wards, in the same graduated way as they developed the accelerating effort when the handle was moved forward. The changes in the circuits are shown diagram- matically in Figs. 113 and 114. The compounding is so proportioned as to effect a graduated braking effort. The series ampere turns, acting in opposition to the shunt ampere turns, tend to decrease the braking capacity as the armature current rises, thus preventing an excessive braking effort and securing the essential smoothness in operation. The desired braking effort for each controller position is effected by varying the shunt ampere turns by means of resistances; extra contact fingers on the platform controllers control these resistances. The extra fingers are brought into circuit by means of the field changer, those effecting the changes of field strength for accelerating purposes being cut out at the same time and by the same means. The motors are of the usual four-pole type, and are suspended in the usual manner. They weigh 2100 lb. and develop 371 horse-power each-railway rating. OFF 84 °°° Ü 1100 NOTCH HOLE mim NOTCH 7 STARTING NOTCH I NOTCH 2 oo NOTCH 3 NOTCH 9 NOTCH 9 NOTCH 9 NOTCH 8 00 direct 11 Винни 1000 113 NOTCH 5 114 NOTCH 6 NOTCH 7 0000 Armature Circuits wwwww Fixed Series Turns NOTCH 6 NOTCH 5 NOTCH 4 NOTCH DIAGRAM FOR SERIES COMPOUND SYSTEM. ACCELERATION. Convertible Turns in Parallel for Series Excitation 1133 Figs. 113 and 114. 1. 11 10000 1 NOTCH 8 NOTCH 9 NOTCH 3 NOTCH 2 Снимилии NOTCH I STARTING Tood Diverting Resistance Starting Resistance Shunt Resistance Johnson-Lundell Regenerative System. 09 NOTCH DIAGRAM FOR SERIES COMPOUND SYSTEM. REGENERATION. -www-www.Convertible Turns in Series for Shunt Excitation 1134 Fig. 115. Johnson-Lundell Regenerative Brake. 868 SECTION X. They are, as has been indicated, fitted with armatures having divided windings and two commutators. The field magnets are of the laminated type instead of the usual solid castings; these are supplied with both series and shunt windings, which are, however, so proportioned as to require but little more winding space than is usually allowed for series winding alone. It is claimed by the inventors that they can be accommodated in the standard traction motor. The platform controllers are of the standard series-parallel type, and differ there- from only in that they are fitted with the additional contacts required for double series-paralleling the circuits, and have fitted into their handles a button lever-switch for operating the contacts which control the field changer. The automatic controller or field changer is located underneath the car in an accessible position between the motors. It is electrically connected with, and controlled from, both the platform controllers. As the economic braking function of the regenerative motors ceases when the car speed falls to about one mile per hour, it then becomes necessary to bring into action a mechanical or other braking method, to complete the arrest of the car, and to hold it when on a grade. Obviously this substitution of the mechanical for the regenerative system must take place automatically, since no driver could possibly time the exhaustion of the one and introduce the other with such nicety as to prevent either an overlapping of the braking factors, and a consequent loss of regeneration, or a non-braking interval with its liability to dangerous acceleration. To fulfil these requirements a special device has been invented by Mr. E. H. Johnson. This arrangement is scarcely a brake, but rather a method of applying the kinetic energy of the car to whatever system of niechanical brakes there may be employed. It is equally applicable to wheel shoes or track slippers. Fig. 115 shows its application to the ordinary wheel-shoe system of a standard four-wheel tram-car, the entire braking mechanism of which is retained, and may, in addition to the special control to which it is subjected, be operated by hand in the usual way. To the end of the regular braking lever there are attached two stout steel-wire cables. These are led to one of the axles, and there attached to the respective ends of a specially-designed resilient spiral friction band, which band is given about five turns around the car axle. Normally, this band is by its own resilience maintained in open form, and therefore free of the axle, and hence inoperative; but should a pull be exerted upon its two ends, and its resilience thus overcome, it will wind up on the axle and exert a pull upon one or the other of the brake-lever cables, according to the direction of the axle rotation. The value of this pull will be the friction value of the five turns of the band derived from the pull or drag that is being exerted by the weight, or other force, employed to over- come its resilience, and initiate its winding action. Whatever excess this force may have over and above that required to overcome the spiral resilience becomes a drag on the "free" end of the spiral, and determines the value of the pull on the brake lever. The form of force now employed for exerting this initial pull and subsequent drag is a weight; attached to this weight is a pulley, and around this pulley a small steel cable, the ends of which are attached to the respective ends of the spiral band. The weight is at the same time the plunger of a solenoid, which latter performs the office of holding it in suspense, thus supplying the potentially- energised factor. The solenoid is governed by contacts in the platform controllers. These are so located as to cause the weight to be lifted in advance of the starting moment of the motors, and then maintained in suspense until the controller is again returned to the "off" position, or, until through some other happening the equipment becomes deprived of its electric power; in which event the solenoid, of course, loses its energising force and its plunger falls, thereby applying the brakes. MOTOR S. Power Curves. (FIGS. 116 and 117, page 869.) For convenience in quickly ascertaining the horse-power required to propel a ar of known weight under known conditions of speed and grade, see Fig. 117. The quantities which the various lines represent are marked on the diagram. The left-hand portion of the lower horizontal line represents the speed in miles per hour; the right-hand portion of same line, the horse-power per car; the oblique lines in left-hand side, the per cent. grade as marked on each line; the oblique lines on right-hand side, the weight of car as marked; the vertical line in centre represents the horse-power per ton. Suppose it is required to find the horse-power needed to operate a 15-ton car at 20 miles per hour on a 5 per cent. grade. Referring to the lower left-hand horizontal line we find the point that represents a speed of 20 miles per hour; following the vertical line from this point until it ROLLING STOCK AND MOTORS. 869 42 (492) Diameter of Wheels. 892 100 30 10% 116 28 124 11 B% 25 76 34 30 MILES PER HOUR. Figs. 116 and 117. 1078 2 009 Miles per Hour Amacore Speed Gear Ratio. Azle Speca and Miles pe. Hopi. Azle Speed] | COVIJOLOMBI GRADE 20 jhana no ch WESTINGHOUSE CURVES oF APPROXIMATE POWER OF MOTORS REQUIRED TO OPERATE GARS UNDER GIVEN GONDITION OF SPEED aan GRADE 101 H.P PER TON bear Ratio to\ STON CAR BiL 10: J 3 50 ? § Armature Spard Revolutions per Minute. Vito 4. I to 5. 100 ION 008 20 [0001 XON BAR 20 ron of SO TOK CA Voo 160 117 HP CER CAR Power and Speed Diagrams for Electric Traction. Joon 200 260 870 SECTION X. intersects the oblique line representing 5 per cent. grade, and then following the horizontal line to the right, we find that it crosses the central vertical line at the point whose value is 6.5, which shows that it requires 6.5 horse-power per ton to propel a car at 20 miles per hour on a 5 per cent. grade. Multiplying 6.5 by 15, which is the weight of the car in tons, we find that 97.5 horse-power are required. The same result may be directly obtained by continuing along the horizontal line until it intersects the oblique line representing a 15-ton car, and then dropping vertically to the lower horizontal line which shows the horse-power per car. The result (97.5) is the total horse-power required; therefore, if the car is to be equipped with two motors, the capacity of each should be one-half the total horse-power. In the case mentioned, two 50 horse-power motors would fill the requirements. Suspension of Motors. (FIGS. 118 to 123, pages 870 to 872.) There are three principal ways in which the motors can be suspended from the trucks; they are known as "nose" (Figs. 118 and 119) and "side-bar" (Figs. 120 and 121), and "centre" suspension (Figs. 122 and 123). In the first method, one end of the motor rests on the axle through its bearings, while the other is hung from 118 119 497 cr Key H Finish. #3 ½ Deep 10%... • · Minimum Guage 42†- Ο zing home can cle AJ A to C C iz **** DOO WA # * * ---- ·Finish Ü 13 Figs. 118 and 119. "Nose" Suspension of Electric Motor. G. E. 800. K ROLLING STOCK AND MOTORS. 871 the truck by a cross-bar and springs. An advantage claimed for this method is that the gearing wears more evenly. In "side-bar" suspension the weight is nearly all taken off the axles, a side frame resting entirely on springs carrying 120 121 ..!!!! 67% 316 14' -1932 10: b -- 9¾½... Centre of Truck Centre of Motor 22/16- is/....d 19% 2 lug 13% long -13/2-1 .13/ •*!! رو . TAJDT Figs. 120 and 121. "Side-Bar" Suspension of Electric Motor. (G. E. 800.). 33 r. the motor by two lugs, one on either side, which are so placed that the motor is suspended from its centre of gravity. This plan has not proved as successful as was anticipated; and the first, or "nose" suspension, is still much in use. 872 SECTION X. ; ! 122 -카를 ​123 MAIS /H]}}}) www GADU } th __718-.. (498) Figs. 122 and 123. J 6.7.….. #{}£]*j€¥¥¥¥S $92 Centre of Moter G --- 10 * .9%. SO Doo- Swing of 15/16 ---- +62. 42° Minimum Gauge Cover ·4:7% · 197...... •Ha HP 134.. KLIPIN ACHIEVE "Central" Suspension of Electric Motors. A Red paper and oiled cotton for body, pinion end. B Irish linen dressing, pinion end. C Oiled pressboard over coils, pinion end. D Japan pressboard between outer and inner turns of coils. E Outside clamp for coils, pinion ends. F Hickory top stick. Repairs. Repair Parts of Railway Motor Armature of the G.E. Type. 38. G End clip for binding wire. H Red paper band under binding wire. I Oiled asbestos and oiled pressboard between leads and ends of coil. J Japan pressboard between outer and inner turns of coils. ROLLING STOCK AND MOTORS. 873 124 K Red paper and oiled cotton for body, commutator end. L Mica slot insulation. -8 E M Oiled asbestos behind commutator. N Acme tape 1 in. wide. O Pressboard strip for commutator. CY- F P Irish linen dressing, commutator end. R Pressboard head over leads. D G H Ena ring Bead ring UPPETTAR LIST ANN JULIATO TELEE BL GE-800 COMMUTATOR (472) 125 མལ་ •Outer mica cones ·-Inner mica cones M mico collar under segment Cap Clamping ring. -Shell 126 Binding wire is .045 in. tinned steel. T -S Figs. 124 to 126. Repair Parts of Railway Motor Armature. S Oiled cotton strip over leads at end of slot. T Oiled pressboard between long and short leads. U Japanned canvas between leads. -R GE-1000 COMMUTATOR. P :a > HORSE POWER FRACTIVE EFFORT SPEED: MOTORS IN SERIES "" SPEED Efficiency Horse Power Effort Tractive " 60 34 50 "" 20 Speed Motor in Series 10 20 30 40 Amperes AXLE SPEED (REVS PER MINUTE) ← MILES PER HOUR ARME = 70 Speat WHEELS 30° DIA. 60 80 H 70 80 X 11.25 X 53.75 48 80 148 44 BRAVE HORSE POWER AT MOTOR PINION 140 136 116 32.14 28 Brake Horse Rower at Car Axle § 24 ខ 20 Š 12 13 18 1135 Fig. 128. Characteristic Curves of the Brush 1002 B Motor. ROLLING 875 STOCK AND MOTORS. Designation. Name of Motor. No. 3 No. 12 No. 12 A No. 38 B Vo. 56 Table 43.-Westinghouse Railway Motors. (Figs. 129 to 146, pages 876 to 879.) Ilorse- Speed at Power. Full Load. 20-25-30 25-30 25-30 50 20 General Data Reduction Ratio. Gearing. Pin. Gear. 8888 300 3.45 18 525-715 4.86 14 68 510-550-685 4.86 14. 68 520 2.42 24 50 370 3.56 18 64 4.86 14 68 62 Number of Poles. Number of Field Coils. 4 4 4 4 4 4 1 4 4 4 Slots in Armature. Commutator Bars. Number of Bands. 95 We do this a hit a 47 95 22 93 13 47 93 14 2270 6 2340 : ུཆེ 45135 : Complete with Gears. : lb. 2800 •• Weight. Armature Complete. Ib. : : 360 525 720 Gears and Casing. Ib. in. in. 12 ·· Commutator Pinion Bearing. Bearing. .. htt 2 350 2 325 23 rithm to maintainin 31 in. in. 2 5%/ 25 6 21 6 2 6 84 14 4-11-16 53 Dimensions. 6 6 : Diameter of Armature. Length of Armature. in. in. 11% 15 11ğ 131 14 81 : : 876 SECTION X. De Pomerodeta O ghetto put the a changin vragen Tag Y Last Armature I I ·· "" AD Type of Motor. Rated horse-power Axle diameter in inches Standard gear reduction Total weight of motor in pounds Minimum gauge · • 132 Figs. 129 to 132. Westinghouse Railway Motor. Type 12 A. Table 44.-British-Thomson Houston Traction Motors. • • • Commutator wearing length depth "" Bearing length pinion end commutator end Clearance with 30 in. wheels: Between motor frame and top of rails Between gear case and track, with maximum gear reduction ·· .. ·· .. 129 130 ·· *199 TOP OF RAIL. VTITT TOP OF RAIL STTTTT 4-turn 6-turn SURPANDER GE 52. G E 54. GE 58. | G E 60. 3-turn 1725 488* 23 in. in. 73 in. 6 in. (The Davey 1830 488* 31 in. in. 73 in. 6 in. 4-turn 131 13666 6-turn 4-turn 393 in. 3 in. & in. 73 in. 6 in. 23 in. 23 in. 6-turn 27 | 20.5 30.3 37.5 28 27 | 19.8 40 | 35 32-4 33-4 33-4 32-41 4.78:14.78:1 4.6:1 & 4.78:14.6:1 & 33-4 3.94: 1 2150 3.94 1 2385 48 31 in. in. 8 in. 6 in. 1665 36 23 in. in. 73 in. 5g in. 43 in. 34 in. 43 in. 31 in. 3 in. 31 in. * Special armature shaft and lining will permit 48 in. gauge. 3-turn 4-turn M firm smo GE 67. 3 in. 2 in. Smog overfæri,d 118- ROLLING STOCK AND MOTORS. 877 135 133 1J To me so m *E* CENTER LINE OF "MOTOR & TRUCK Ba TOP VALM - CREBLE SEGMENEAME An Ad Map en dan agama 44 AM to சணி 134 +37 136 » Men » so wi TEP VIEW - NOSE SUSPENSION. CENTER LINE MATOR & TRUCK, TOS OF BON A SU ADA EUR ENO NEW - CRIBLE SBMNSOR LUOGANS DE 1879 39987=22&W. (480) QORNOWN IHRE LE V07 108 Type 38 B. Figs. 133 to 136. Westinghouse Railway Motor. 878 SECTION X. 137 138 Cross + Cross benn 6830 Abe • ¿ -24%" 1 Top View Cradle dusp mefor and trubi}|| *** To suit truck - FRONT View of GRADLE TOP VIEW Near SuspenIT 梅县 ​din sang. à den i mig Got a cute & Co » Sunda Te suit trúek - 139 140 141 सकत FRONT NEW Asar Suspension -rice. END VIEW Nose Suspension ... Anton END NEW Cradle Sus PITKINN Figs. 137 to 141. The Westinghouse No. 56 Tramway Motor. • HI -Dimanalare of Kay 1x 15″ long For 38" to 5'shafts NOTES All parts shown in det and dash (... are la be furnished by truck Bulders. The mater 'la odapted receive an arte of any damater from 3f" to 5"; the sizes most frequently used are 4*and of and Merefor gears and aste boerings fe these dramatera are COM sidered as stock sizes 1 : 142 143 Met de qui per t ±±±1919 19 13.66*.. జీవరంటే TXlESKEY 26... ·13·66·· 5418 5615 Do 144 A in. 3,3% 42 g 427 6. 7,32 ♡ Length of Collar. THOLS in. 3 4 + 108 11% Diameter of Axle and Bore of Collar. in. in. 3 x 3 x 3 x 32 x Cl Koixa 19.7- SEASHOON "" 99 "" 99 |------ -18 Figs. 142 to 146. Westinghouse No. 49 Street Car Motor. Gauge Distance Between of Truck. Hubs. G M in. 4818 ft. in. 4 8 4 10 5 0 5015 52,78 5 5 Key. in. ----- To soT TRACK in. 26.66 in. X 5 × 1 x 1 x 5 15% "" "" "" " Det var det betekent shah alam di dekade a dark JOE-HETEN HOUSE THE HERMITE ---she was dit at man v Remarks. B in. 72 Centre-line of motor on centre-line of truck. 82 9 E in. ang dro að ve de m "" >> "" "" F in. PR 19/1855 146 Inoodlot 145 ******* è ou no m 39 " "" "" FORECASATIEM G in. } $ 880 SECTION X. 148 3'0 TT ✡ か ​+62-624-222" (913) 1.2 147 Cen, of Arm Ceru of Truck Ground Terminal 7'8 12 ½ — +63- $1 149 this dimension to suit truck ... ♡ kzémble CA. +-5%/ --1'2½- FINISHED " 7'3 + M -7.2 3 - + 4:55 4.2 2.1 13 mán ( da toplo važna, 481 Std Gange-- shan Figs. 147 to 150. No. 100 A Motor. (Dick, Kerr and Co.) + \FINISHED - 10 5 150 ROLLING STOCK AND 881 MOTORS. Efficiency 8 Miles pr hour Horse Power Lbs.Hor Eff. at Car Wheel 90 80 32 60 70 28 28 30 20 10 50 20 20 |1000 40 16 16 800 100 36 36 1800 80 Per cent. Efficiency Miles pr. hour 70 60 90 60 24 24 |1200| 12 8 20 10 65 55 50 50 40 32 1600 30 30 2000 8 20 1400 12 600 4 400 Horse Power Lbs Hor.Effort at Car Wheel 200 200 4000 180 3600| 45 120 2400 160 3200 40 35 80 1600 140 2800 2.5 40 100 |2000 20 60 1200 800 400 60 3-A-4 RY. MOTOR 500 VOLTS DIAMETER OF CAR WHEEL - 30" GEAR RATIO |69/15 – 4·6/|| ARMATURE SPEED M.P.H/O194 4 TURN ARMATURE TEST THROUGH GEAR Efficiency including Gear losses) 20 30 151 100 120 Horse Power Horizontal Effort 152 Speed फे Amperes Efficiency (including DK 4 A R.Y. MOTOR 625 VOLTS DIAMETER OF CAR WHEEL 42″ GEAR RATIO 43/22 : 1.95/1 ARMATURE SPEED-M.P.H/0838 ONE TURN ARMATURE BRAKE TEST THROUGH GEAR ing Gear losses Horse Power hour & 75° C. Rise|for one Horizontal Effect 140 160 180 200 Amperes 75°C. Rise for one hover Speed 220 240 260 * 280 300 Dick, Kerr Railway Motor. Fig. 151. Characteristic Curve of 3 A Railway Motor. Fig. 152. Characteristic Curve of 4 A Railway Motor. 49 1136 1137 882 SECTION X. Miles prhour 88 Efficiency & HorsePower Lbs.Hot.Eff 8 at Car Wheel 100 90 36 80 70 28 28 1400 60 24 24 1200 50 20 20 40 16 9 10 Efficiency per cent. Miles pr how 100 30 12 12 600 90 32 32 1600 20 8 8. [400 80 50 30 36 20 10 36 1800 40 16 20 12000 1165 32 32 12 8 00 4 70 28 28 1400 4 60 24 24 1200 1000 800 Horse Power ~Lbs Hor. Effort 18 at far Wheel 200 36 1800 16 2000 1600 20 11000 800 12 600 8 400 4 200 10 DK-6-A RY. MOTOR sbo VOLTS DIAMETER OF CAR WHEEL – 30″ GEAR RATIO 71/14 5.07/1 ARNATURE SPEEĎ M.R.H/-D176 4 TURN ARMATURE CALCULATED CURVES Efficiency including Gear losses से 153 20 Horse Power E Horizontal Effor 154 Amperes 25 A R.Y. MOTO R 500 VOLTS DIAMETER OF CAR WHEELE 30" GEAR RATIO PI/14 $.07/1 ARMATURE SPEED-M.P.H/•0176 4 TURN ARMATURE BRAKE TEST THROUGH GEAR AFTER ONE HOUR RỤN ÁT 45 AMP. Efficiency (including Gear tosses) J Horse Power Amperes Speed 75°C.Rise for one hour Horizontal Effort 60 Speed 75°C.Rise for one hour 10 Dick, Kerr Railway Motor. Fig. 153. Characteristic Curve of 6 A Railway Motor. Fig. 154. Characteristic_Curve of 25 A Railway Motor. 80 80 #138 #39 ROLLING STOCK AND MOTORS. 883 Liverpool Overhead Railway. (FIG. 155.) The following diagram, Fig. 155, gives the characteristic curves of the motor used on the Liverpool Overhead Railway. (See page 775 ante.) 100 0 200 4000 190 3800 5 180 3600| 170 3400 90 8 SPEED IN MILES PER HOUR EFFICIENCY %. 8 150 3000 2800 13032600 6020 120 2400 110 2200 25 100 2000 in 90th 1800- 80 1600 70 1400 235 602 1200 50 1000 40 800 600 400- 200 100 70 10 160.3200} C 15:140 ∞ 30 40 10 45 0 50 30 20 10 0 · (867) 0 10 30 50 Name of Motor. Rated horse-power Axle diameter, in inches Ratio of gear reduction Total weight of motor pounds Number of teeth in pinion Total field turns Slots in armature Conductors per slot Number of commutator bars Diameter of armature in inches.. ·· CHARACTERISTIC CURVES BY BRAKE TEST WHEELS 33 GEAR RATIO 2,79 70 ). .. in •• · Length of armature in inches Minimum gauge 70 100 H.P. MOTOR. SPEED HORSE/POWER HORIZONTAL EFFÖRT 90 Fig. 155. Table 45. Data on the British Thomson-Houston Company's Type G. E. Traction Motors. (FIGS. 156 to 173.) EFFICIENCY 1725 14 626 29 12 87 bo d. bo d. 60° d. 18° 0. d. BEARINGS AIR TEMPERATURE 28 d. RESISTANCE AT 201GT FIELD 0192 OHMS ARMATURE '0606 OHL 8. TOTAL MOTOR-15] OHMS. 110 130 150 170 190 210 230 250 270 300 AMPERES. EFFICIENCY CURVES. Liverpool Overhead Railway. TEMPERATURE RISE 'AT END OF ONE HOUR DELIVERING TODE.PAT ARMATURE SHAFT. 1725 14 742 29 18 87 COMMUTATOR. İRISE ARMATURE FIELD GE 52 GE 52 G E 54 G E 58 G E 58 G E 60 G E 60 G E 67 2G E 54 G € 58 G 60 G E 60 G 4-T 6-T 3-T 4-T 6-T 4-T 6-T 3-T Arm. Arm. Arm. Arm. Arm. Arm. Arm. Arm. 1830 14 514 29 12 115 27 27 20.5 30.3 37.5 28 33-4 33-4 32-4 3-4 33-4 4.78-1 4.78-1 4.78-1 3.94-1 3.94-1 4.78-1 4.78-1 3.94-1 33-4 19.8 40 3-4 38-41 11 11 9 9 9 488* 485* 485* . 11.5 14.5 6.5 393 2150 2150 1665 1665 17 17 14 14 578 702 598 686 33 33 12 18 18 99 99 111 111 37 12 365898 14.5 13.75 13.75 6.5 4.5 4.5 36 3932 36 2385 17 442 37 9 111 14.5 8.5 48 * Special armature shaft and lining will permit 48 in. gauge. The curves from some of the various types of motors manufactured by the British Thomson-Houston Company are shown in Figs. 165 to 173, pages 886 to 889. Efficiency, speed, and tractive effort curves, as well as thermal characteristic curves, are given for several motors. These curves are of special interest, when the current used by cars at various speeds and under various conditions has to be ascertained. 884 SECTION X. in S EW_WID 158 156 210= S(477) 52 181 +28+28++ 876 817/20 8 →→ 01 2218- *9,8 45 10 Gada µ---- 12 1/2 --- 7 Ground G *minal 14 Bolts Armatu --------- şli độ đ Center !10 8 Bið bitte Diễ JORGE BE 17 * 11/16 - 11/13 2110 51 Bolls & X3 "| [1 For electric brake Jattachment +632 8 O 47/ ↓ Miz 1/2 Center of Axle 318; 102 33 […] 108 $£ 102 1 - 10 157 GIMITAN 262 13½ Figs. 156 to 158. Brit`sh Thomson-Houston Company's Rai way Motor. Type GE 52. Yoke Suspension. ¡ ROLLING STOCK AND MOTORS. 885 1.59 Dom Youp 161 (476) (476) 611 + G joko 1 25. 9- O A vana kun v 518- 11 8 - - - -|-- - - 11 3 ---- 2Ground Terminal 12 14% 68 +21 --11· © -08-+ en. of Truck Boits 16/ 岩 ​Bolts ---14- ---- -25 15- -263- ---18 × 5 L TH སྙུ+; سے # 11 -/-/o 10 [m]mp Center of Axle -NO IN niq 160 *114 3 nio V A 14--T 4/2 -321 12" 143 14.166- 1.1.38 +-143/3 La 12호 ​12호 ​Figs. 159 to 161. British Thomson-Houston Railway Motor. Type G E 51 B. 886 SECTION X. 164 (4784) 182 [mm] -5 -10%/ 8' 13% 10h EL 08 8 5元​/斤 ​7/16 -36″ Minimum Gauge 17" 5%-8 Ystyks For Electric Brake Attachment. M ···5%½- ·10' Mo 01:05 GOYART TOP ju... 77/4 ...... 87/½.... Imm efficiency Hour Miles per • 5 8 8 2 8 2 2 8 8 8 per cent 100 50 2000 90 45 1800 80 40 1800 à ~ ~ & & 70 35 1400 lbs tractive effort 60 30 1200 60 25 1000 800 40 20 30 15 10 600 20 10 400 O 200 0 0 (489) 165 163 12/2 ∙11- Eff 14½ 12. |-- Tractive Effort active Effort Speed Speed 10 20 30 40 50 60 10 80 90 100 110 Amperes. 42% Approje 63-4% .f... Da vi da je Figs. 162 to 165, British Thomson- Houston Railway Motors. Type G. E. 60 Yoke Suspension. Diameter of driving wheels, 33 in Armature, 4 turns. Field spools, 143 turns. Pinion for dotted curve, 22 teeth. Pinion for full curve, 17 teeth. Gear for dotted curve, 62 teeth. Gear for full curve, 67 teeth. Ratio for dotted curve, 1:2.82. Ratio for full curve, 1:3.44. For two motors for dotted curve, speed on level, 32 miles per hour with 10 ton car. For two motors on full curve, speed on level, 25 miles per hour with 10 ton car. ROLLING STOCK AND MOTORS. 887 LEŠ TRACTIVE EFFORT 166 GE. 58-6TURN-500 VOLTS GEAR RATIO0-3-94. WHEELS 30. Calculated for 5 Gear and Friction loss at Full load and 75°C. 2400 2200 22 2000 20 હૂ હૈ મૈં… । LBS PER HOUR 1600 1400 $99800! 600 400 200 167 • 18 9 Q 0 (693) 110 H.P. OUTPUT O 100 80 AMPERES 8 8 90 45 70 40 30 20 10 O 168 50 $25 30 25 20 4 H.P. OUTPUT 2 55 M 50 AMPERES 35 30 ~ 35 70 20 15 10 01 5 80 60 8 9 8 9 50 20 10 EFFICIENCY TRACTIVE EFFORT 20 30 40 50 AMPERES (694) SPEED AMPERESE 60 70 80 90 HPOUTPUT € 100 90 80 ARMATURE RATING 70 89 50 40 30 20 GE-58 RAILWAY MOTOR. 4 TURN ARMATURE-500 VOLTS. Thermal Characteristic Curves: 10 % EFFICIENCY TIME IN HOURS GE=60 RAILWAY MOTOR. FIELD RATING. 6 TURN ARMATURE - 500 VOLTS · 30 WHEELS-GEAR RATIO 4.78 Thermal Characteristic Curves. Figs. 166 to 168. Characteristic Carves of British Thomson- Houston Motors. H.P.OUTPUT AMPERES 2 TIME IN HOURS * 1 2400 2200 ਸਪੈਕਟਰਜੀ ਅਨਮਤ MILES PER HOUR(30 WHEELS). POUNDS TRACTIVE EFFORT (30° WHEELS). 20002 25 100 1800 1400 GE-58-500 VOLT RAILWAY MOTOR. 4 TURN ARMATURE - 3.94 GEAR RATIO 30" WHEELS. CHARACTERISTIC CURVES ON 250 & 500 VOLTS. 160030280 7000 PER CENT EFFICIENCY. 400 90 1200 1560 200 70 800 10 40 30 600 5 20 10 50 THERMAL CAPACITY RATED LOAD] 75°C RISE IHOUR RUN EFFICIENCY 500 VOLTS EPTICIENCY 250 VOLTS 2504500 VOLTS TRACTIVE EFFORT SPEED 500 VOLTS SPEED 250 VOLTS 5 HOURS RUN. 0 10 20 30 40 50 60 70 80 90 100 110 AMPERES. THERMAL CAPACITY CURVE SHOWS Nº OF HOURS (915) RUN AT ANY GIVEN LOAD WITH 75° C.RISE. Figs. 169 to 171. Characteristic Curves of British Thomson-Houston Railway Motors. G.E: 62 MOTOR. ITTTTT 1900 4 TURN ARMATURE-500 VOLTS 30″WHEELS-GEAR RATI0478 1800 1700 CHARACTERISTIC ČURVES 1600 20005- [23] 1500 301 POUNDS TRACTIVE EFFORT (ON 30°WHEELS) ဒွိ ငွ ဒွိ န္ဟ င္ငံ MILES PER HOUR (ON 30° WHEELS PER CENT EFFICIENCY || உ + 140028 1300 1200 od 221 1000 20 100 900 800 500 261 300 200 100 • 181 201 801 @ 、。。 su O (691) 888 ? 30 170 SPEED TRACTIVE EFFORT EFFICIENCY 30 40 50 60 70 80 90 100 AMPERES. 171 4 TURN ARMATURE-500 VOLTS. THERMAL CHARACTERISTIC CURVES. Curve showing Time in hours dur ing which,motor will deliver any given BHP.throughits gearing orpass given current with a temperature rise not exceeding 75°C. 80 H.P. OUTPUT 35 70 30 60 25 20 AMPERES d. 15 30 101 20 (690) *FIELD RATING H.P. OUTPUT 2 J TIME IN HOURS ARNATURE LRATING 5 Pounds Tractive Effort 4800 4400 4000 40 3200 2800 2400 3600 36 90 2000 1600 1200 800 48 400 44 Miles per Hour 32 28 20 16 8 GE-66-A RAILWAY MOTOR TURN ARMATURE GEAR RATIO 71/18 – 3 94-36″ WHEELS-550 VOLTS 100 * Efficiency 80 70 60 50 12 301 40 20 101 EFFICIENCY OURVE INcludes gear & FRICTION LOSSES & IS BASED ON A COPPER TEMPERATURE OF 751 c. Cork Loss %C² R Friction 20 40 60 Efficiency Tracti Font Speed 100 120 140 160 180 200 220 240 Amperes 172 Figs. 172 and 173. Characteristic Curves of British Thomson-Houston Railway Motors. 1140 173 Miles Per Hour 6000 50 5000 Pounds Tractive ♪ Effort 404000 30 3000 20 2000 10 1000 O GE-69-B RAILWAY MOTOR I TURN ARMATURE GEAR RATIO+64/19 – 3·37. 38" WHEELS. 550 VOLTS EFFICIENCY CURVE INCLUDES GEAR & FRICTION LOSSES & IS BASED ON A COPPER TEMPERATURE OF 75ºC. 100 % Efficiency 90 70 60 50 40 30 20 10 O % Core Loss Gear Friction Lass % Efficienc 100 240 300 Amperes racti Effort Speed 400 V%C²R Loss 500 (141 890 ¿ SECTION X. 1: 176 (916) S.O. o AMPERES & TORQUE IN MT. KGS. • 8 & EFFICIENCY. 1200 ≥ 1100+ * €1000 100 800 90- 1800 80 700 70 600 60 50050 Fig. 177. 400 40% 800 80 200 20 100 10 (917) E To JISIK İPAPEELSEIM* 5 174 10 tapi pe • 15 • CL.of Armatures C.L.Of Truck 20 P 25 SIEMENS & HALSKE TRACTION WOTOR DÜ4U. 500 VOLT. 175 * P * * Figs. 174 to 176. Siemens and Halske Traction Motor. (Table 47, page 892.) 80 EFFICIENCY CURRENT TORQUE REVO. PER MIN, →→ 36 10. UBERRIM!! RATED B.H.P. Characteristic Curves of Siemens and Halske Motor. ROLLING STOCK AND MOTORS. 891 D 14/8.5 s g D 14/15 L g D 14/15 8 D 14/20 г. Type. D 14/20 s g D 17/18 L C D 17/18 L g D 17/18 s c D 17/18 s C D 17/24 L c D 17/24 8 D 17/30 L D 17/30 s D 17/30 19 20 21 22 23 24 25 26 27 28 c D 19/30 " Table 46.-Siemens and Halske Traction Motors. 2500 2000 n la MILES PER HOUR ON 30 WHEEL. HORIZONTAL EFFORT ON 30'WHEEL IN LBS. :: L P V ? ? *Ľ C 1000 800 OOGI (690) .2 Fig. 178. Rated Brake Horse Power. 8.5 13 19 19 22 20 22 22 27 27 27 I~~~~~*** 85 42 39 48 52 68 Revolutions Volts per at Minute. Terminals. 19 810 560 690 540 700 520 520 770 770 530 570 430 580 800 SPEED 570 720 CURVES OF MOTOR EHT.52: (500 VOLTS) EFFICIENCY EFFECTIVE HORSE-POWER 500 500 500 500 500 500 500 500 50 AMPERES 500 500 500 500 500 750 GO 600 750 HORIZONTAL EFFORT ON 30 WHEEL 70 Minimum Gauge. 81 mm. 450 560 560 900 900 685 900 685 900 1000 1000 1435 1435 1435 1435 1435 90 Weight including Gears and Gear-Case. 100 900 925 900 925 900 925 1200 1200 1560 1560 1560 kg. 385 600 600 1750 1750 100 08 08 OL OP ON or 20 59 OF 20 PERCENTAGE EFFICIENCY EFFECTIVE HORSE POWER 10 : Characteristic Curves of Messrs. Witting, Eborall and Co.'s Railway Motor. Type E. H. T. 52. 892 SECTION X. T Ww ***. {me}} 179 3.0" +--+- 11%___ 1.1 - 180 fact ہ۔ KURKAT B |700|79 500150 500 50 jo la MILES PILA HOUR CoefficiencyM7% #KAMING I & K 8 R US 60 125 50 JO 90 & 15-420) 25 10 (698) 10 EFFICIENCY DEVI PER NINUTE RAILWAY MOTOR TYPE EH& TESTED AT SOOVOLTS TORQUE IN POUNDFEET. 30 60 70 80 90 100 110 ANPERES EFFICIENCY MILES PLA HOUR. DRAW BAR PULL RAILWAY MOTOR TYPE E33 TESTED AT 500 VOLTS WHEELS 30 INSI 10 20 30 40 50 GO AMPEPEN 182 70 80 90 100 110 181 Figs. 179 to 182. Messrs. Witting, Eborall and Co.'s Railway Motor. Type E. H. INTAN BAR PULL 2 ROLLING STOCK AND MOTORS. 893 Table 47. Siemens and Halske Motors. (FIGS. 174 to 177, page 890.) Motor. b d f h g i q. k 1 m p 8 t D 14/20 750 c D 17/18 800 c D 17/24 800 900 324 686 590 275 390 255 15 118 257 257 375 | 290 375 290 473 450 267 830 348 718 615 325 420 290 40 107 293 298 400 315 | 350 | 320 | 487 | 420 | 263 900 348 750 615 325 470 325 10 100 300 303 400 315 375 320 470 450 315 D 17/30 800 |1240 348 | 772 | 560 324 450 282 5 | 110 | 310 | 314 | 400 | 315 | 540 | 310 | 660 | 630 | 353 | 85: c D 19/30 850 1240 396 825 605 345 495 270 40 110 335 335 445 345 490 345 695 590 410 80 1 100 90 80 70 60 50 Bruce Peebles Tramway Motors. (FIG. 183.) Fig. 183 gives a complete performance curve for Messrs. Bruce Peebles standard 25 to 30 horse-power motor, which illustrates quite well the characteristics of all their machines, except, of course, that the larger motors are slightly more efficient. 40 30 20 10 2.5 0 20 IS 10 a 5 30 20 C 10 1000 800 600 400 200 Efficiency Miles per Hour Horse Power | 0 Bounds Hor Effårt Dimensions in Millimetres. 0 TRACTION MOTOR SIZE T 25 Efly, without Gear 50 Horizontal Effort Speed Horse Power CURVES BASED ON 30″ WHEEL 600 VOLTS GEAR RATIO 88/14 Amperes r 60 *****8 1142 Fig. 183. Characteristic Curve of Bruce Peebles T 25 Railway Motor. The motors are of the usual construction, totally enclosed in steel case, which is horizontally divided, with laminated poles bolted to the case; while the armature is of the ventilated type, the ventilation ducts in it registering with corresponding ducts in the laminated poles. The armature is further designed specially small to reduce momentum. The chief mechanical feature about the motors is that the bearings are not attached to either the upper or the lower field casing, but are held in a separate housing, which is clamped between the upper and lower field casings when these are bolted up. A further mechanical feature of interest is that oil ring lubrication of a special form has been adopted for the armature bearings, with, it is stated, most satisfac- tory results. 894 SECTION X. 184 800 _455. 380 HD56 840 JET 120. Hall ·-310· .300. 001 -650 901 185 580 -310 -800- 482. -932- ·-390 — — - .-605- - 342- [800 -750 720· to p -304- € 10 kn + • — — da v s 2/17 27. -304! Df -645). -1200. -275, -225 90 186 Figs. 184 to 186. Oerlikon Company's Railway Motors. --1460– RAZ. 1400 (ID y035. OLL 066 535—— ROLLING STOCK AND MOTORS. 895 1 Table 48.-Motors Constructed by the Oerlikon Company. (FIGS. 184 to 186, page 894.) Drawbar Pull in Pounds at 9.4 miles an hour. 440 661 882 1322 Type. E.Z. 6 E.Z. 7 E.Z. 8 2107 175- 475-←► 487 Rated Horse- Power 705- 10 15 to 18 20 30 "" "" 0010989985 Lo 25 40 $80. + Efficiency at Rated Load, including Gearing. 300 730- per cent. 78 80 HOOD! 82 84 433 -1,200 Total Weight in Pounds, including Gearing. 1764 2050 2424 3500 <160 1,730 1,210- 1,360-- Revolu- tions of Speed Armature | Reduc- tion. per Minute. 1.050 450 450 400 350 + 1:5 1:5 1 : 4.2 1:4 Fig. 187. Brown and Boveri Railway Motor. (See Table 49, page 896.) 896 SECTION X. Table 49.-Brown and Boveri Three-Phase Traction Motors. (FIG. 187, page 895.) Power of motor in horse-power Gauge of line for which suitable Weight of motor in kilogrammes Speed of motor, revolutions per min. Full load efficiency ·· " ·· · • ·· .. ·· Table] 50.-Ganz and Co.'s Three-Phase Motors, Lecco-Sondrio Railway. Current per primary motor at 150 brake horse-power starting "" "" Starting current per motor car (total weight of train, 84 to 90 tons) .. ·· Type I. 13-19 1 metre 700 400 84 per cent. Efficiency of primary motor at full load Power factor of primary motor at full load, 150 brake horse-power Power factor of primary motor at starting half-load "" 25 "" mum torque when concatenated Power factor when braking Weight of rotor "" stator Air gap (distance between rotor and stator) Diameter of rotor Horizontal pull with 1170 millimetres wheel at 300 revolu- tions, 3000 volts, 15 cycles, per primary motor.. Horizontal pull with one primary and one secondary motor concatenated (150 revolutions) Play between car axle and sleeve on which rotor is fixed.. Bearing in which rotor turns ·· and secondary motors at maxi- .. Type II. 35 1 metre 970 485 86 per cent. .. .. • ·· • ·· • ·· ·· ·· ·· .. ·· ·· 26 amperes 40 "" 70 to 90 278 28 Type III. 60 1.345 1500 600 90 per cent. 90 per cent. 90 91 80 70 "" 69 "" "" "" "" "" "" 1100 kgs. (2420 lb.) 2700 (5940 2 mm. (in.) 800 (31.5 in.) 11 "" 1000 kgs. (2200 lb.) 1800 "" (3960 ,,) 2 in. 6 in. long by 12 in diameter. The primary motors have six poles, and are rated to develop 150 brake horse- power each at 300 revolutions per minute, 3000 volts and 15 cycles per second. Their maximum torque is about four or five times their normal torque. The ratio of transformation in the primary motor is 10 to 1, and in the secondary motor 1 to 1. Since the stator of the primary is always on the line, the current of magnetisation is always constant, and amounts to 6 or 7 amperes at 3000 volts. BRAKES. In actual practice brake ratios vary widely, but taking as an average 1: 100 between the handle and shoe, we find that the handle must move 25 in. for each 1 in. movement of the shoes. With a 2 in. slack the handle must make almost two complete revolutions, in addition to taking up slack before the shoe touches the wheel. With more powerful quick-acting brakes, both the flatting and the general wear of wheels have been reduced. The explanation appears to be that with a power brake the greatest pressure is applied when the wheels and car are moving most rapidly, and when there is the least danger of skidding. Brakes acting on the rim of the wheel must be worked by very powerful levers. The brake-blocks are usually of cast-iron, and made in such a way as to be easily replaceable by the removal of a wedge. Means must also be provided for easily and rapidly taking up the wear of the brake-blockɛ. ROLLING STOCK AND MOTORS. 897 Table 51.-Brake-Shoe Tests. Wear of Brake Type of Brake Shoe. Shoes during Tests. Chilled cast-iron brake shoes Composite cast and wrought-iron brake shoes Steel brake shoes .. Ib. 96.69 37.63 4.53 to 10.22 { Wear of Wheels Relative Dis- expressed by tance run Reduction after Brake Circumference. Applied. of in. ft. 2.81 1834 2.34 1.15 to 2.97 Average pressure on brake shoes, 40 lb. per square inch. made of chilled cast-iron. 1905 2482 to 3561 Resistance offered by Brakes. lb. 2439 2356 1773 to 2077 Wheels of car tested These tests were made in running by gravity on a uniform descent of 80 ft. to the mile, with three cars weighing approximately 130,000 lb. Brakes were only used on the foremost cars, and in each test the cars were run down one mile and then the brake put on. From this Table it would seem that the wear of cast-iron brake blocks is the most rapid, but at the same time they appear to have the greatest retarding power. In the wear of the wheels no important difference seems to exist. Brakes and wheels are a function one of the other, and one or other, or both must wear. It is preferable to wear out brake shoes rather than wheels, and that must be taken into consideration. It is fairly accurate to say that, on an average, brake shoes last 5000 car miles, and chilled wheels 30,000 car miles without renewal. The average weight of a brake shoe may be taken as 21 lb. when new, of which 9 lb. remain when the blocks are discarded, giving a wear of 12 lb. Taking the value of the cast iron thus burnt or ground down at 1d. a pound, and the average annual car mileage of a car at 29,000 miles, the annual value of the brake shoes worn out amounts to just over 2s. 3d. per annum per car. The brakes must be quick acting, and a few turns of the driver's handle should suffice to put them hard on. To allow easier manipulation of the brake handles, they are connected to the spindle by means of a ratchet arrangement, which enables the driver to pull the brakes up tight at the most convenient position of the handle. Gravity Brake Gear, This brake was designed expressly for use with single trucks, and has been adopted by the Metropolitan Street Railway of New York City. When the brake upon the car is released by the motor-man, the weight of the break beams, with brake-heads attached, will release the brake shoe from the wheel without requiring release springs. To accomplish this, the brake guide attached to the side frames and supporting the brake beams is constructed on an incline. This brake does away with the use of four pull-back springs, and requires less power to operate it, and the brake shoes can be released from the wheels more quickly and surely than by release springs, which are not always to be depended upon. Power Brakes. The principal conditions to be filled by a power brake are as follows: 1. Time required for applying the brake blocks to wheels to be reduced to a minimum. 2. Pressure between blocks and wheels to be constant, and never to exceed & designed maximum. 3. The release of the blocks to be complete, and practically instantaneous when pressure is taken off. 4. The friction between the surfaces of wheels and rails to be always rolling and not rubbing. G G 898 SECTION X. Track Brakes. (Fig. 188.) Fig. 188 show a form of track brake supplied by Messrs. R. W. Blackwell and Company, Limited. The drawing shows the working sufficiently clearly, without requiring any further explanation- Z (920) t 918. 13 HH i E P EVO AMO Fig. 188. Track Brake. Westinghouse Magnetic Brake. (Newell Patents.) (FIG. 189.) The brake proper comprises: (1) a double track-shoe of peculiar construction, combined with a powerful electro-magnet which, when energised by current, produced by the car motors acting as generators, is strongly attracted to and grips the rail by magnetic force; (2) brake heads and shoes of the ordinary type acting directly on the wheels, and constituting a wheel-brake of great power and efficiency; (3) sundry castings and forgings for simultaneously transmitting the ownward pull and resultant drag of the magnetic track-brake into lateral pressure upon the wheels. M HH Fig. 189. Westinghouse Magnetic Brake. - GRAND ● ROLLING STOCK AND MOTORS. 899 Fig. 189 illustrates the general arrangement of the brake, and the method of attaching brake mechanism to truck and suspending shoes over track rails. When the brake is applied the magnets are energised by current supplied by the car motors acting as generators, and the track shoes are strongly attracted towards the rails. This brings into play three distinct braking actions— 1. Friction between track-brake shoes and rails. 2. Braking effect on wheels by means of the mechanism provided for that purpose. 3. A positive braking effect on the car axles, due to the load on the motors running as generators to supply current. There is also a certain increase of the pressure between wheels and track, due to downward pull of magnets. The brake-shoe pressure is automatically regulated by the condition of the rail surface. If the rail be dry and sandy, the drag of the track-shoes and the con- sequent thrust upon the levers applying the brakes to the wheels are great; if the rail be wet or greasy, the drag of the track-shoes is lessened in inverse proportion to the frictional resistance between them and the rail, thus automatically decreas- ing the corresponding brake-shoe pressure on the wheels. The lever connections between the electro-magnet and the wheel-brake blocks are adjusted to give correctly-proportioned braking effects at the track-rail and on the wheels, so that no greater brake pressure can be applied to the wheels than they can withstand without skidding. The brake is thus adjusted to suit tran- cars of any weight, and to suit the limiting gradient of any tramway. British Thomson-Houston Electro-Magnetic Track Brakes. (FIG. 190.) This device consists of suitable electro-magnets, which are mounted in proximity to the track, and which, when energised by current, are drawn into contact with the rails. The current is generated by the motors acting as generators, and the braking action is obtained both by the drag of the electro-magnets on the rails and by the direct retardation of the wheels, due to the motors acting as generators. CHAMUTE C Dood 114.3 Fig. 190. British Thomson-Houston Brake Diagram, showing Attachment of Brake to Maximum Traction Truck. The brake consists of a properly-designed cast-steel shoe suspended from a bracket fastened to the side of the car truck. This bracket is well ribbed and braced, and is provided with heavy lugs which take the thrust through cast-steel links in compression. The bracket is formed to act as the seat for two compression springs which support the brake proper by wrought-iron eye-bolts. These springs keep the brake shoe free from the track when it is not in use. The brake shoe itself consists of a substantial steel casting, with a cored recess, into which the magnetising coil is placed. A brass cap or cover is placed over this coil, and so fitted as to form a watertight protection. 900 SECTION X. A steel core extends through the coil providing two magnetic circuits, each of which is completed by the section of rail immediately under the brake shoe. The terminals of the magnetising coil consists of well insulated flexible wires brought out through bushed holes in the top of the cast-steel frame of the shoe. They consist of two wires in duplicate, and are of sufficient length to extend from the end of the coil winding to the car underframing without a joint. Each shoe is provided with wearing plates for contact with the rails. These plates are steel castings, held in place by machined bolts so placed that the plates may be renewed without removing the brake shoe from the truck. Christensen Air Brake. (FIG. 191, page 901.) There are two systems of this brake; first, the straight-air system, suitable for trains of four cars or less; and second, the automatic system, suited to long trains. In the present state of the application of electric propulsion, the automatic system is only advantageous in a few exceptional cases. The straight-air system consists of an ample quantity of compressed air stored under proper pressure in a reservoir or reservoirs, usually of about 10 cubic feet capacity, located upon the car; which air can be admitted to and released from the brake cylinder, the piston-rod of which is connected with the brake levers in such a way as not to interfere with the manual operation of the brakes in the usual manner. The admission to and release of air from the brake cylinder is accomplished by means of a valve which is under the hand of the motor-man, and is so constructed that he can control the amount of pressure exerted upon the brake blocks, either admitting instantly the whole pressure contained in the reservoir or a portion thereof, and in the latter case diminish or increase the amount as demanded. The maximum pressure which it is desirable to exert being the amount which is equivalent to the traction existing between the wheels and the rails, a greater pressure than this will result in skidding or locking the wheels, which will not secure as quick a stop as if the proper amount only is supplied, and will result in causing flat wheels. The amount of pressure which it is possible for the motor-man to apply to the blocks is therefore scientifically adjusted to be, as near as possible, equivalent to the amount of traction existing in each case. This is attained by a proper proportionment between the pressure in the reservoir, the size of the brake cylinder, and the arrangement of the brake levers; and when so proportioned it is impossible for the motor-man to over-brake his car; and yet he is at all times prepared to make an instantaneous application of just the proper amount of pressure to make the quickest possible stop depending upon wheel traction. There are two methods of obtaining the desired amount of compressed air required, first by means of a compressor placed upon the axle and operated by the rotation thereof. In this form an eccentric, provided with a sleeve, is dowel-pinned on the axle, and tramsmits a reciprocating motion to a single-acting plunger, operating in a cylinder which forms part of an air-tight casing, which is mounted upon the sleeve of the eccentric, and together with it forms a complete protection from dust for all moving parts, as well as supplying a reservoir, which, being partially filled with oil, provides direct lubrication throughout. The governor performs its office of regulating the amount of pressure in the reservoir by creating a full opening from the discharge pipe, before its entry to the reservoir, to the atmosphere as soon as the predetermined maximum is reached, and closing the said opening again when the pressure in the reservoir has fallen to the predetermined minimum. This opening and closing is positive and complete, overcoming the objection existing in all governors depending upon the pressure of the air against a spring for operation, namely, when near both limits of maximum and minimum they operate partially by each pulsation caused by the movement of the piston, which causes undue wear on the governor as well as unnecessary strain on the compressor. The axle compressor has proved unsatisfactory for the speeds usually required on electric tramways, and is now almost completely discarded in favour of the motor-driven compressor. In the motor-driven type, the compressed air is supplied by a compressor driven by a motor receiving its current from the same source as the propelling motors. The combined motor and compressor has the following qualities to recommend it for the service: it is compact, all parts are easily accessible for removal and repairs, it requires no attention from the motor-man while in ROLLING STOCK AND MOTORS. 901 (889) H 191. Fig. 191. The Christensen Brake. 2 MAIN RESERVOIR MOTOR COMPRESSOR 217.72 BRAKE CYLINDE JUXILIAR A ERVOIR. 52& 902 SECTION X. Į service, but will remain in service for at least six months without the necessity of overhauling of any kind. It is noiseless in operation. In general construction it has two cylinders, with single-acting plunger pistons fitted with an im- proved form of packing ring, and with steel case hardened and ground wrist pins. The connecting rods are operated by a steel crank-shaft, with cranks 180 deg. apart. The crank-shaft is extended at one end beyond the main bearing, to receive the gear wheel which engages with a pinion on the armature shaft. The base of the motor forms a top cover for the pump base. The gears are also enclosed in a suitable casing. At the gear end the armature shaft revolves in an extra long bronze bearing. It will be seen that the interior of the pump is completely enclosed, and that the compressor base forms a dustproof reservoir, which, being partially filled with oil, furnishes lubrication for all moving parts of both compressor and motor, with the exception of the armature shaft hearing at the commutator end, which bearing is oiled from the small reservoir for the purpose provided. This reservoir wants filling once in two or three days, and the main reservoir requires replenishing once in several weeks; and these two points being attended to, there is no further care required for lubrication. The suction and discharge valves consist of a cold-drawn steel cup, and are practically indestructible. They are identical in size and shape, and are interchangeable, and they are the only moving part of the valve arrangement. Electric Switch Controller for Air Compressor. (FIGS. 192 and 193, page 903.) Figs. 192 and 193 show the arrangement of the wiring of the controller switch, which cuts out the motor compressor when the pressure in the main reservoir rises to 80 lb., and cuts it in again when the pressure falls to 70 lb. Fig. 192 represents the switch open, the pressure being 80 lb. When this pressure falls to 70 lb. the pressure gauge moves the hand over to the stop marked 70, and completes the circuit around the solenoid C. This sucks in the core E, breaking the contact BB, and closing the motor circuit through the switch F. At the same time, the electromagnet D becomes excited and tends to withdraw E, but is resisted by the solenoid C. This state of affairs (shown in Fig. 193) continues until the compressor has raised the pressure to 80 lb. When this happens, the hand makes contact with stop marked 80, and shunts the current passing round C. As the current round D remains the same as before, E returns to its original position and throws the switch F open, cutting out the motor and withdrawing the insulation from between the contacts BB. The switch thus returns to its original condition, ready to cut in when the pressure again falls to 70 lb. Triple Valve for Christensen Air Brake. (FIG. 194, page 904.) Fig. 194 shows a sectional view of the quick-acting automatic triple valve used in the Christensen Air Brake. This valve has several functions, viz.: To admit compressed air from the train-pipe to the auxiliary reservoir. To cut off connection between train-pipe and auxiliary reservoir, and connect up the latter to the brake cylinder, when train-pipe pressure falls 5 lb. or 6 lb. In service application of the brakes to cut off connection between auxiliary reservoir and brake cylinder, when the pressure in the former has been lowered to the same as that in the train-pipe. To establish connection between brake cylinder and atmosphere in releasing, by introducing a higher pressure in the train-pipe than in the auxiliary reservoir. To connect up train-pipe and brake cylinder in an emergency stop, by reducing train-pipe pressure by 10 lb. or 12 lb., the connection being considerably larger than the ordinary connection between brake cylinder and auxiliary reservoir. To cut off connection between train-pipe and brake cylinder as soon as the pressures in the two become equal; and, as soon as this is the case, to equalise the pressure between auxiliary reservoir and brake cylinder. After an emergency application to release the brake by restoring the pressure in the train pipe, so that it is greater than the equalised pressure between brake cylinder and auxiliary reservoir. All the joints of this triple valve are vertical, and the possibility of the lodg- ment of moisture thereby reduced to a minimum. ROLLING STOCK AND MOTORS. 903 192 193 Ad: Insulation Solenoid D D P | | | | E Insulation E B Solenoid C B с Trolley L Trolley Motor Fuse 70 Gauge Fuse Motor DJNEN Crea Greynd Figs. 192 and 193. Switch Controller for Air Compressor used in Christensen Brake. 904 SECTION X. To Auxiliary Reservoir Tu Brake Cylinder. |||||]] Fig. 194. Christensen Brake; Three-way Valve. Train Pipe ROLLING STOCK AND MOTORS. 905 Engineer's Valve for Christensen Automatic Air Brakes. (FIG. 195, page 906.) This valve is designed particularly for trains with automatic air brakes, where six or eight cars are coupled together, and is provided with an automatic train- pipe feed mechanism, by means of which the pressure in the train-pipe is kept at 70 lb., irrespective of any higher pressure which may exist in the main reservoir. With the handle in "release and running" position, air can pass from the main reservoir pipe up through the centre of the rotary plug and into the train-pipe. The central opening is provided with a valve attached to a diaphragm, and held open by a spring. When the pressure in the train-pipe rises to 70 lb., this diaphragm moves and closes the valve down upon its seat, and so cuts off the supply of air to the train-pipe. In making a service stop with this valve, the handle is moved into the "service" position, and about 5 lb. or 6 lb. of pressure allowed to escape from the train-pipe, which sets the brakes. The handle is then moved to either "lap" position, which keeps the brakes on, or the "release and running" position. In the former position all the ports in the rotary plug are covered, and the handle can be removed from the valve. As soon as the pressure falls below 70 lb. in the train-pipe, and the handle is put into "release and running" position, the valve in the central opening in the rotary plug opens, and the train-pipe is once more charged up to 70 lb The Westinghouse Air Brake. (FIGS. 196 and 197, pages 907 and 908.) The Westinghouse brake, as fitted to motor cars and trailers, is identical-in all respects with the type in use on all railways, for engines and carriages The only difference is that the steel air reservoirs, in. in thickness, are generally of smaller proportions than those in use for steam on railways, ranging on tramways from 4 in. to 10 in. in diameter. It is usual on Westinghouse installations to provide a charging equipment at the power stations for the supply of compressed air (pressure being from 80 lb. to 120 lb. per square inch). This system of providing air has been followed up till now on the City and South London and the Liverpool Overhead Railway, and on many other lines in America and Europe; motor com- pressors are now, however, being fitted on the trains themselves. The air is delivered on the brake cylinders through reducing valves at 50 lb. pressure and the minimum limit is fixed at 40 lb. Special compressors may be worked off the axles. The comparison as to cost of a charging station and motor compressors on each unit is distinctly in favour of the former, although the independent system is coming more and more into favour. This is probably due to the unavoidable delays involved in bringing the cars up to the charging station when the reservoirs are exhausted. These are usually proportioned so as to supply sufficient air for 80 stops. On a small system, where the number of units running is limited to eight, the relative cost of charging station equipment to motor compressor equipment per unit is as 791 to 115%. With a greater number of running units the cost of the charging station is not proportionately increased. Both Westinghouse and Christensen brakes are plenum brakes, the vacuuin brakes being unsuitable to electric traction owing to the greater necessity of economising space and weight than on steam railways. Motor Car.-Storage reservoir is charged to high pressure to suit require- ments, and is connected to a small main reservoir of ordinary working pressure, which is maintained by the reducing valve placed between them. A special brake valve is required to suit the working conditions: it has three legs, as shown on sketch, one connected to main reservoir, one to non-auto pipe, and the other, with cock attached, is connected to auto-pipe; the passage into pipe is a very small hole for feeding only. The two outer legs of brake valve are connected in the usual manner for working the non-auto brake, and the middle leg with cock has been so arranged that when handle is moved towards the right hand, and at right angles, the air is exhausted from auto-pipe, thus applying the brake on trailer car; this would only be used should non-auto hose have burst, or some other defect rendering the non-auto brake useless. G G2 906 SECTION X. Weservan Pipe WIEM Release or direct Exhaus Train adid Reservp Pipe [Main] Reservor Lading Emergency Felcase & Ryoning: Left Hand. 30; -Exha der Service Scop O Right Hand Service stap Trein, Pipe Lap Train Pipe! Release Aaming. Kmecgency Fig. 195. Christensen Brake; Engineer's Valve. ROLLING STOCK AND MOTORS. 907 Trailer Car.-The trailer car is fitted with auto- and non-auto brakes; auto- matic action on motor car is not required, as it would set up a resistance on motors which is not desirable until current is switched off. It will be observed that the two couplings on trailer car of auto-pipe have valves which are perforated: this is required in case the cars should break away, thus applying the brake. Emergency cocks are fitted on both motor and trailer cars, for the use of the conductors should working conditions require it. Pressue reducing Valve Auxiliary Reservoir Red Coupling Brake Valve Emergency Cock Stop Cock *Coupling with Walve perforated Red Coupling MOTOR CAR. Storage Reservoir "" "" Main Pipe (non Aatomatic) Electric "" Main Pipe (Automatic). Emergency Cock TRAILER GAR.. Main pipe (Automatic) Auxiliary Reservoir Main Pipe(Non automatic) 4 c "" "" Brake Cyl.T "" (708.) Fig. 196. Westinghouse Brake on Motor and Trailer Cars. Brake Tests. To calculate the braking power required for a car, the following figures taken from the Street Railway Journal are useful: Table 52.-Energy Stored in Cars at Different Speeds. lb. ft. lb. Horse-car and load, 10,000 6 miles per hour, 12,025 10,000 8 23,000 10,000 10 20,000 15 20,000 20 33,000 150,000 278,000 "" "" Brake Cyl** "" * Release Valve Emergency "" Special Triple Valve Stop Cock Stop Cock Emergency Cock โ "" Brake Vatre "" Red Coupling "" "" Coupling withh Mible perforated Bed Coupling 908 SECTION X. PRESSURE GAUN RELEASE VALVE #IRON P} NYBDRIVERS BRAKE VALVE RELEASE PRESSUREŇ| GAUGES HO TO HAND BRAKE 10×15 AUXILIARY RÉSERVOIR´ SPINDLER MN95 DRIVERS BRAKE VALVE Kat TUXILLA plan to DRAIN PLUG 10 › Vegan e arsimaman de cette a DWS CYLINDER K VALYK MAIN RESERVOIR (CAPACITY 10 CUB 1 Pag St J MAIN PIPE, IRON PIPE/ MAIN RESERVOIR ··· PIPE K ŢIKON PIPE 2 MP, ELECTRIC AIR PUMP → 2 HP. ELECTRIC AIR PUMP, Nº5DRIVER'S BRAKE VALI FALCRUM ROD TO NAND BRAKE SPINDLE A'S DRIVERS BRAKE VALVE RAREISURE GAUGES `RELEASE VALVE~~~) « PRESSURE GAUGES (PRESSURE GAUBE -RELEASE VALVE ¿IRON PIPE Į IRON MPE ¿RON MAE (702) Fig. 197. Arrangement of Westinghouse Automatic Brake Connected to Hand Brake. ŞNOS DRIVERS BRAKE VALVE PRESSURE GAUGE ROLLING STOCK AND MOTORS. 909 MISCELLANEOUS DETAILS. Safety Guards. A Safety guards are to prevent people getting under the wheels of the cars. The greater proportion of recorded accidents is due, not to the effects of persons being knocked down, but to the wheels running over them after they have fallen. The motor-man, by means of powerful brakes as well as by reversing the motors, can bring a car from a high rate of speed to a stop in a very short distance. Therefore, people who come into collision with a car do so for the most part when the car is travelling slowly, and are not greatly damaged by the collision itself. Some device is therefore required which will either push the person off the track, if he falls down, or pick him up before he comes in contact with the wheels. Á very large amount of ingenuity has been shown in constructing such devices, the greater part of them being large, cumbrous, and most unsightly. Some are like huge fishing-nets hung in front of the car, and let down by the motor driver in case of necessity. This arrangement is a mistake, as in case of probable collision the driver has all he can do to stop the car. Others stretch out some distance in front of the car an inch or so above the ground, and are often the cause of the accidents they are meant to prevent; as people crossing the street misjudge their distance, or overlook the fender entirely, and are consequently tripped up. It seems preferable to leave the front of the car entirely free of all obstructions, and to provide a sort of scoop underneath each platform to pick up people who may fall under the car. A fender should under no circumstances be rigid. It must have a large amount of spring, so that it can be carried close to the ground, and also because, if it is stiff and strikes a prostrate person, it is liable to go over and crush him. There are, of course, many types of fenders in use. Platform Fist The Tidswell Life Guard. (FIGS. 198 and 199.) Figs. 198 and 199 show the Tidswell life guard, which has been adopted on the new cars of the London County Council. It consists of a gate A, which by a suit- B 199 198 | Platform Joist CB Figs. 198 and 199. Tidswell Life Guard. E 910 SECTION X. 1 able apparatus is connected to a catch C, which holds up by the rods B the scoop D. Any obstruction striking the gate releases the catch, and the scoop falls to the level of the ground, the dotted line showing the position of the guard when in operation. A spring E is attached to the scoop, so as to quicken the action of dropping. The crank F is placed on the top of the platform, so that the motor- man, by pressing it down, may release the scoop in the same way as if it were operated by an obstruction coming against the gate. Fig. 199 is a front view of the guard, which is constructed of light wooden laths screwed on to an iron framework. 1: SECTION XI. EFFICIENCY, MAINTENANCE, DEPRE- CIATION, AND COST OF POWER. 5 SECTION XI. EFFICIENCY, MAINTENANCE, DEPRECIATION, AND COST OF POWER. GENERAL. - It is practically impossible to ascertain accurately at each instant the mechanical efficiency of an electric tramway system or its component parts. This. depends upon their load, speed, and many other factors, which are constantly varying. The only figure which can approximately be obtained is the average efficiency, or, in other words, the ratio of the actual horse-power exerted on the wheels of the car, to the indicated horse-power at the steam engine. In discussing this question, however, we must not lose sight of the fact that, in many instances, the mechanical efficiency is not the most important point to be considered, the main desideratum being to work most economically with the least depreciation and great flexibility. The electric motor is no prime mover. It only serves to transform the electrical energy which it receives into motion. The initial power, from either fuel or water, has to pass through several different transformations, and naturally sustains. losses. The various points of loss may be tabulated as follows:- Power-House. Boilers or turbines. Steam engines or turbines. Line. Feeders. Gearing. Loss in friction of truck bearings. Return circuit. The following Table gives the appropriate efficiencies of the various parts of the system. Table 1.-Giving Approximate Efficiencies of the Various Parts of Electric System. .. .. ·· .. Water wheels Turbines Pressure engine Steam engines Mechanical efficiency of dynamos Overhead line and feeders Motors, including gear.. Single reduction gear Accumulators in central stations Rotary transformers Stationary alternating-current transformers Return circuit In a fairly large plant a total efficiency of from 50 to 65 per cent. may be obtained, if the greatest care in the design and operation of the line is taken. "" "" Railway generators can be designed so as to give a very nearly constant efficiency at all loads. The efficiency of a well-designed 1000 horse-power railway generator remains from one-quarter load to full load practically constant within ·· .. .. .. •• ·· • ·· · -- .. · ·· ·· ·· Overhead line. Controlling devices. Motors. ·· ·· Per Cent. .. ·· .. ·· ·· .. 40 Dynamos. • • • .. 30 to 70 75 70 80 85 70 90 70 90 94 98 ; "" Per Cent. 75 80 85 95 95 95 85 95 86 96 97 99 "" "" "" "" "" >" "" "" per cent. Minimum efficiencies under various loads of the different parts of an equipment. are generally called for in specifications and guaranteed by contractors. 914 SECTION XI. In nearly every case the tests specified include the measurement of the power obtained, its cost, and the quantity of fuel required. This entails careful measure- ment of the quantity of water, fuel, and steam used, and the determination of their quantities, as well as the various wastes which take place. To determine the actual value of a steam engine, a comparison of the average continuous cost with the average value of the power supplied for useful work is necessary. Fuel or Heat Energy Supplied. Although in traction plants the engines cannot usually be worked at their full load constantly, and are therefore not run as economically as they might be, yet they generally have to work for very long hours, which is distinctly in their favour as compared with electric-lighting stations. To run engines and keep boilers warm and deliver power for 24 hours, 3 lb. of coal per Board of Trade unit are required approximately; whereas, if the boilers are kept warm and run the plants for only 3 hours per day, about 7 lb. per unit are necessary; and to keep boilers warm and pressure up without furnishing steam, requires approximately 10 per cent. of the coal consumption that would be required to deliver steam to the engines. a = α Depreciation. r (1 + r) n (1+r)n-1 where a = Rate of Depreciation Capital C - r = Interest n-Number of years in which capital is to be written off. A sum of £100 is to be written off in 15 years, with interest at 3 per cent. ; then 0.035 x 1.673 α = 100 = 100 0.035 (1+0.035)15 (1 + 0.035)15 – 1 0.673 a = 8.5. This is the case when the value of the old material is = 0. If the ratio of the value of the old material to that of the new b, then r [(1 + r)n -b] (1 + r)n 1 A sum of £100 is to be written off in 15 years, with interest at 3 per cent. ; the old material has 12 per cent. of the value of the new; we have then 0.035 [(1 + 0.035)15 0.1251 0.035 (1.673-0.125) a = 100 (1 + 0.035)15 1 1.673-1 a = 8.05. = 100 a = C (at the end of the year). a = c r [1 + r)n - 1-b] (at the beginning of the year). (1 + r)n − 1 Payment a to be made at the end of each year, in order to possess the sum 8 at the end of n years. a = s go • << (1 + r)n − 1 If it be required to have £100 in hand at the end of three years, with 3 per cent. interest, the annual payment a = 100. 0.035 (1.035)3-1 a = 32.1. Under the same conditions as above, but after two years, 1000.035 0.109 a = s. a = 49.3. Payment a to be made at the beginning of each year, in order to possess the sum S at the end of n years. * (1 + r) n + 1 —(1 + r) EFFICIENCY, MAINTENANCE, AND DEPRECIATION: 915 Table 2.-Sinking Fund. Showing percentage to be set aside yearly, invested at 3, 31, 31, 4, 4 and 5 per cent., to redeem capital in a given number of years. Years. 5 10 12 15 20 21 25 30 35 ***CORS 40 42 45 50 60 70 80 3 Per Cent. "" 18.83 8.72 7.04 5.37 3.72 3.48 2.74 2.10 1.65 1.32 1.21 1.07 0.88 0.61 0.43 0.31 ," "" "" 31 Per Cent. 18.74 8.62 6.94 5.27 3.62 3.39 2.65 2.01 1.57 1.25 1.14 1.01 0.82 5 years 22.2 21.8 21.3 20.8 20.3 10 11.5 11.2 "" 12.1 11.9 8.6 11.7 8.4 15 8.7 "" 20 7.1 7.0 6.9 30 5.5 5.5 40 4.7 4.7 50 4.3 4.3 0.55 0.38 0.27 ·· ·· • Table 3.-Rate of Depreciation, with Interest at Three-and- a-half per Cent. Annually. Ratio of Value of Old Material to that of New. To be Written Off in Op.c. 2 p.c. 5 p.c. 7 p.c. 10 p. c. 12 p.c. 15 p. c. 20 p.c. 30 p. c. 40 p.c. 50 p.c. White oak and chestnut oak Chestnut Black locust** Cherry, black walnut, locust Elm Red and black oaks.. Ash, beech, and maple Redwood •• Cypress and red cedar Tamarack Longleaf pine Hemlock Spruce.. ·· ·· ·· 3/1/2 Per Cent. When the old material has no value, with interest at 5 per cent., the annual depreciation is for payment in 5 years, 22.03 per cent. 10 12.39 99 "" "" "" 39 39 ·· 18.64 8.52 6.84 5.18 3.53 3.30 2.56 1.93 1.49 1.18 1.07 0.94 0.76 0.50 0 34 0.23 8.3 8.2 19.9 19.4 18.5 16.6 14.7 12.9 11.0 10.8 10.4 9.5 8.7 7.8 8.0 7.9 7.7 7.1 6.6 6.1 6.4 6.0 5.7 5.2 5.1 4.9 6.8 6.7 6.6 6.5 5.3 5.4 5.4 5.3 5.3 4.7 4.5 4.7 4.6 4.6 4.6 4.2 4.3 4.2 4.1 4.0 4.0 3.9 4.2 4.2 4.2 • Table 4.-Durability of Railroad Sleepers, from a Report of the United States Department of Agriculture. •• ·· ·· ·· : .. .. .. .. • ·· !! : Ad ·· 4 Per Cent. ·· 18.46 8.32 6.65 4.99 3.35 3.12 2.40 1.78 1.35 •• 1.05 0.95 0.82 0.65 0.42 0.27 0.18 •• • · ·· 4.5 4.5 4.1 4.1 ·· -- ·· • • • .. 41 5 Per Cent. Per Cent. ·· ·· 18.28 8.14 6.47 4.81 3.19 2.96 2.24 1.64 1.23 0.93 0.84 0.72 0.56 0.35 0.22 0.14 ·· • ·· .. ·· •• .. .. ·· .. ·· ·· · 18.09 7.95 6.28 4.63 3.02 2.79 2.09 1.50 1.10 0.82 0.73 0.62 0.47 0.28 0.16 0.10 ·· .. • 4 .. Years. 8 8 10 7 6 to 7 4 5 4 "" 12 10 7 to 8 6 4 to 6 5 916 SECTION XI. Table 5.-Approximate Life of Various Parts of Well-Installed and Maintained Plant. Track Overhead line Buildings Cables Tram or railway motors Stationary motors ·· ? Slow-speed steam engines Boilers, pumps, piping, &c. Slow-speed dynamos of modern design Power plant High-tension feeders. Sub-stations Trolley wire (high-tension) Car equipment * Track-work Bonding .. ·· ·· ·· ·· ·· ·· Name. ·· .. .. Stationary transformers Accumulators in central stations Trolley line Poles ·· Buildings Water turbines Boilers Dynamos and engines Large slow-speed steam engines direct-driven plants "" ·· ·· Feeder cables Lighting and current meters Cars ·· Albany and Hudson Schenectady Northern Ohio Traction Company • ·· ·· Table 6.-Maintenance of High-Tension Single-Phase Traction Plant. ·· ·· .. Repair-shop and test-room fittings Motors Rotary transformers Spare parts .. ** • ·· ·· • ·· • •• ·· ·· ·· ·· Table 7.-Approximate Rates of Depreciation to be Allowed in Per Cent. of Capital Cost. .. • -- • • ·· •• .. ·· .. .. ·· .. .. .. .. .. .. • •• 10 to 15 years "" "" 15 20 Practically indefinite, .. ·· • .. •• ·· .. .. ·· ·· 20 to 40 15 30 15 35 ·· 10 20 10 15 10 35 say 50 years .. ·· "" "2 "" "" • d. 1.0 0.6 0.35 "" 5 8 5 10 00 LO LO LO *:*: 9 4 2 8 5 12 LO 00 5 •• Per Per Cent. Cent. 21 to 3 7 10 10 6 8 8 ·· 1/1 7 6 4 ·· Motor-Car Trucks and Cars. • " "" **** Per Cent. 3 5 4 1 12 "" "" "" "" " "" "" "" "" "" "" "" "" "" "" PHOTONDON 11 6 4 5 10 71 15 "" On remaining capital expenditure incurred Accidents and insurance should be put down as from 0.75 per cent. to 2.25 per cent. of the gross receipts. Taking the interest rate at 5 per cent., and supposing the entire plant must be entirely renewed at the end of twenty years, 3 per cent. on the original outlay must be set aside each year to do this. Table 8.-Cost of Maintenance per Motor-Car Mile on some American Lines. 8 10 2 10 10 6 Electrical Equipment. d. 0.5 0.5 0.25 | EFFICIENCY, MAINTENANCE, AND DEPRECIATION. 917 Table 9.-Maintenance Cost per Ton-Mile for some American Railways. Name of Line. ·· d. d. .0354 .0177 Albany and Hudson Railway Niagara Falls International Traction Company* .0095 .00784 Schenectady Street Railway Companyt Cleveland, Painesville and Eastern Railway Company Rockford and Janesville Railway Company...0078 •• در Maintenance per Ton-Mile. Car-bodies and Trucks. ·· • * Average mileage per car per day, 325 miles. t "" 33. "" 275 Cars and motors inspected once a day. Electrical Equipment. .. .01277.00732.00495 Overhead Equipment. Car Bodies- Including painting, upholstering, and all work of any description on the car bodies, excepting the daily cleaning. ·· .0554 .00594 |.0061 d. 19 Trucks- All labour and material on trucks, with the exception of brake- shoes .. ·· Air Brakes- All labour and material on brake mechanisms, including renewals of brake-shoes Air-Compressors and Governors— Table 10.-Cost of Maintenance of Electrical Equipment. Pence per motor-car per mile. Total works cost per unit generated Cost of repairs .. Coal consumed per B.O.T. unit generated.. All costs of renewals, including labour and material of every description • ·· m.p.h. tons 28 24 31 ·· Multiple-Unit Controlling Apparatus— Covering all labour and material on complete control equipment.. •• Maximum Speed. •• .. 45 50 45 45 .2 Weight of Car. 0.236d. 0.029d. 2.4 lb. 25 26 .0625 .015 .077 Motors- The above, it should be understood, covers the maintenance of a two-motor equipment, representing two 125 horse-power motors, one set of thirteen con- tactors, one reverse, two master-controllers, with the necessary wiring, switches, couplers, &c. .071 .055 The air-brake of this equipment is assumed to have a capacity of 20 cubic feet per minute. Table 11.-Recent American Costs of Large Steam-Turbine Operated Station. LOAD FACTOR, 30 To 40 PER Cent. K ; 918 SECTION XI. Table 12.-Depreciation Allowed on some British Electric Tramway Lines in per Cent. of Capital Involved. Name. Bolton .. Glasgow .. ·· Track. per cent. 6.8 8.7 Electric Equip. Buildings. Station ment. Plant. per cent. 5.0 3.3 Trains per day run in each direction Average weight of train "" Cost of Operation : Table 13.-Cost of Working Electrically Invalides Line of Western Railway of France. ·· Total Train Mileage in 1903 : speed, including stops, miles per hour .. per cent. per cent. 3.0 2.5 5.0 Trains hauled by electric locomotives motor-cars Ton-miles hauled by electric locomotives* motor-cars t "" "" Average energy consumed at power-house per train-mile Average energy consumed at sub-station per train- mile .. Average energy consumed at power-house per ton- mile .. ·· Average energy consumed at sub-station per ton- mile ·· ·· Train staff and drivers, per train-mile Electric energy Grease, oil, waste, &c. Maintenance and repair-locomotives and motor- cars Maintenance and repair-working conductor Works cost at power-station per unit generated Power- Rolling Total Stock. Average. ·· .. ·· ·· .. .. • • ·· •• ·· ·· Total average energy consumed at generating- station, per train-mile Line pressure in conductor-rail…. Average maximum starting current Works cost per unit generated.. ·· • * In this figure the weight of the locomotive is omitted. + In this figure the weight of the motor-cars is included. Cost of maintenance per mile per annum of third rail, £45. • •• per cent. 10.0 7.5 Table 14.—Cost of Working Paris-Orleans Railway Electrically. Average mileage in round figure run per annum : Per locomotive hauling trains Per locomotive shunting .. Average running speed, miles per hour Maximum authorised speed, miles per hour.. Average weight of train hauled Total average energy consumed at generating- station, per ton-mile.. ·· - 29 74 tons 16.4 to 18.8 188,230 miles 39,923 14,344,800 2,898,300 10,343 B. O. T. units 7,242 d. 1.622 8.343 0.294 105 watt-hours 74 2.503 1.205 per cent. 4.61 5.63 "? "" 13.967 0.5952 12,400 miles 2,800 16.5 to 21.3 "" 31 150 tons 65.11 watt-hours 9973 B. O. T. units 600 volts 800 to 900 amperes 0.387d. EFFICIENCY, MAINTENANCE, AND DEPRECIATION. 919 Table 14.-Cost of Working Paris-Orleans Railway Electri-. Cost per Train-mile : Depôt charges Train staff Electrical energy Oil, grease, waste, &c. General Maintenance and repair Hull Leeds Place. ·· Blackpool and Fleetwood 1904 1904 1904 Cork Dublin Birkenhead Bournemouth Cardiff 1905 1905 1905 Glasgow (May) 1905 Huddersfield ·· .. ·· ·· Portsmouth .. Reading Sheffield ·· ·· Steam engines Auxiliary engines Exciter engines Boilers •• ·· Newcastle-on-Tyne. .. Total per train mile .. Table 15.-Cost per Unit in some Traction Stations. •• • • •• .. ·· .. • Year Ended December. 1905 1905 1904 ·· ·· .. cally.-(Continued.) .. · Items. .. · ·· •• ·· Three-phase generators Auxiliary generators Exciter generators Static transformers Rotary converters and boosters Buildings, including smokestack .. Number of Units Used. d. .35 .32 8,054,279 .25 2,276,901 .29 1,738,483 .71 .24 6,534,783 20,268,407 .12 901,910 961,788 .01 .03 .05 .04 .04 .02 1905 3,185,640 .15 .01 3,853,114 .26 .03 11,503,188 .16 .03 7,757,885 .16 .02 3,019,955 1905 .33 .06 1905 1,020,400 .43 .03 1905 10,781,227 .20 .04 .. .. ·· .. : •• .. • • • Coal and Other Fuel. .. •• Oil, Waste, Table 16.-Cost of Glasgow Power Station, Four 2500-Kilowatt Generators and Five Sub-Stations with Rotary Converters. •• 40 •• ** d. .08 .. .. .. ·· and Stores. • Costs Per Unit. Wages and Salaries. .. d. 0.2558 d. .26 .12 .13 .20 .19 4.8128 6.3196 0.1502 0.0776 1.1587 12.7747 .12 .11 .08 .09 .07 .13 .11 .25 .08 Repairs and Mainten- ance. Works Costs. .28 .10 .05 .06 .08 .01 .05 .05 .08 .03 .05 .04 .04 .13 Total in Pounds. £ 104,000 9,000 3,100 21,300 25,700 .55 .46 .60 1.02 .41 .30 5,300 1,700 20,000 39,200 45,000 .29 .46 .29 .36 .54 .75 .45 Power Pur- chase Costs. d. l'ounds per Kilowatt. £ s. d. 10 8 0 0 18 0. 0 6 0, 2 2 0 2 11 0· 0 10 0· 0 4 0 2 0 0 3 18 0 4 10 0 920 SECTION XI. Name. Aberdeen Ayr Birkenhead Blackpool Bolton Bournemouth Bradford Brighton Burnley Burton-upon-Trent….. Bury Cardiff Carlisle Trams Co. Chester .. Colchester Darlington Darwen Dover Dundee East Ham Farnworth Glasgow Gloucester Halifax Ilford Ipswich Keighley ·· ·· Table 17.-Operating Expenses of some Traction Plants Period Covered and Year of Working. 1904-5, 5th 1904-5, 3rd 1904-5, 4th 1904-5, 1904-5, 5th 1904-5, 3rd 1904-5, 6th 1904-5, 3rd 1904-5, 3rd 1904-5, 2nd 1904-5, 1st 1904-5, 2nd 1904, 4th 1904-5, 1st 1904-5, 1st 1904-5, 1st 1904-5, 4th 1904-5, 6th 1904-5, 4th 1904-5, 3rd 1903-4, 2nd 1904-5, 6th 1904-5, 11mo. 1904-5, 6th 1904-5, 2nd 1904-5, 1st 1904-5, 1st Length as Single Track in Miles. 27.75 7.65 23.57 21.25 40.14 25.00 95.26 17.11 19.65 8.64 24.13 32.62 9.00 4.76 8.33 8.89 7.22 4.50 23.24 12.25 7.35 147.52 12.52 48.20 11.35 14.87 5.83 Gauge. ft. in. 4 83 167 4 8 33 4 83 110 4 8 81 4 8 3 6 + 0 3 6 4 0 3 6 4 8: SI 6 3 6 3 6 3 6 4 0 3 6 4 103 168 47 38 40 18 10 43 13 8! 164 19 115 50 1000 50 173 60 70 42 -3-3 30 00 00 8/ Population Served, in Thousands. Length of Traffic Day, in Hours. 85 4 7 3 6 3 6 4 85 3 6 4 0 55 175 63 324 126 160 52 16 106 13 | 100 19 86 92 18 112 19 81 15 98 16 88 19 112 18 111 120 83 19 of Car- Day per IS 16 14 15 Number Miles per Car. 93 92 92 82 75 64 18 85 18 $3 16 110 83 14 20 80 18 109 18 67 18 106 Number of Car- Hours per Day. Average Speed per Hour in Miles. 728 7.50 130 8.00 7.01 511 • 954 7.25 589 6.33 1945 6.86 496 5.96 420 6.50 208 6.85 7.50 1235 7.50 Maximum Board of Trade Speed. Traffic Ex- Details of Expenses per Car-Mile. Repairs and Maintenance. 203 7.50 352 5.79 34 7.00 penses. General Ex- penses. d. d. d. d. 12 3.09 .86 .45 .19 .06 12 2.20 1.12.18 14 3.49 .78.51 .09 .10 .02 |2.65 | 1.53.55 14 2.57 .58 .31 12 3.19 .90.29 .09 .09 12 3.19 3.19 .96 .33 .17 12 3.32 .98 .31 .09 12 3.23.89.50 | .05 9 2.90 1.06.05.15 2.41 .65 14 3.01 3.01.86 .86.41 2.51 .75 10 2.101.10.03 12 2.52 .84 .06 .16 .03 S2 8.00 155] 6.12 151 6.60 12 2.26 .53 •• • .11 .97.37 .82.53 9.00 10 2.76 1.13.13 .34 .11 •• 390 6.50 6.00 7178 7.40 232 6.50 673 7.24 .06 121 6.25 8 2.84 .65 481 6.47 12 2.68 10 B.12 4.38 .60 .07 .08 .06 16 2.91 1.05 .33 .08 12 2.60 .74.07 .14 14 2.74 1.22 .73 12 2.97 .78 .24 9 3.53 .63 .08 9 2.65 .93 .01 .02 .01 .04 .04 : d. .02 .02 .20 .05 .08 .11 .17 .10 .03 .Q2 .11 .08 .04 .02 .01 .07 d. .49 .49 .21 1.09 .98 1.13 .93 .89 68828:2939: ESI 1.15 .77 .49 .43 .21 73 .48 .44 .28 d. .01 .01 .01 ·· .03 .03 .01 .04 .02 .02 ·· .01 M Total. d. 1.16 .76 .81 1.77 1.38 1.68 1.53 1.35 1.22 .94 .22 1.59 .33 .32 .71 .30 1.69 1.33 1.21 1.45 .70 .92 .43 1.70 .78 .65 .43 ** EFFICIENCY, MAINTENANCE, AND DEPRECIATION. 921 Name. Kilmarnock Kingston-upon-Hull Kirkcaldy Lancaster Leeds Liverpool London Co. Council. Manchester Nelson ·· ·· ·· .. Newcastle-on-Tyne. Nottingham Oldham Portsmouth Preston Rochdale Salford Sheffield · ·· ·· ·· .. Southampton Southport Stockport Sunderland .. .. .. ·· Wallasey Walsall Warrington West Ham Wolverhampton ·· .. ·· .. .. Table 17.-Operating Expenses of some Traction Plants (Continued). Period Covered and Year of Working. 1904-5, 1st 1904-5, 5th 1904-5, 2nd 1904-5, 2nd 1904-5, 7th 1904, 6th 1904-5, 2nd 1904-5, 3rd 1904-5, 2nd 1904-5, 3rd 1904-5, 4th 1904-5, 2nd 1904-5, 3rd 1904-5, 6mo. 1904-5, 2nd 1904-5, 3rd 1904-5, 5th 1904-5, 5th 1904-5, 4th 1903-4, 3rd 1904-5, 4th 1904-5, 3rd 1904, 1st 1904-5, 3rd 1904-5, 1st 1904-5, 3rd Length as Single Track in Miles. 5.53 27.19 7.50 4.82 89.14 103.00 98.00 146.19 3.68 54.52 30.12 Gauge. 16.74 10.76 11.50 19.54 11.85 17.09 9.05 17.03 20.00 ft. in. 4 8$ 4 8 3 6 4 8 4 83 4 8 4 4 4 0 4 8 4 8 8 4 7 4 84 34.11 28.50 16.30 17.22 4 70.75 4 65.75 4 4 8 HAHA Population Served, in Thousands. Length of Traffic Day, in Hours. 3 6 36 251 750 42 LEKLERLE CHE02:29:003700 14 18 34 15 44 14 450 15 765 19 300 240 150 16 200 115 86 300 433 110 18 32 4 110 4 83 166 4 822 60 3 6 4 24 20 18 17 15 17 16 15 19 18 80 13 81 300 96 17 18 16 of Car- Car- Miles per Day per Hours per Day. Number of Car. Number 93 114 7.12 99 1169 9.00 64 77 107 825 6.00 98 8.00 2763 7.04 5000 7.50 4037 8.00 84 93 97 5704 7.00 94 108 7.00 1815 7.00 100 : : 103 95 114 106 76 53 109 79 93 91 92 106 89 Average Speed per Hour, in Miles. ·· 705 6.44 990 8.00 ·· Details of Expenses per Car-Mile. Repairs and Maintenance. Maximum Board of Trade Speed. Traffic Ex- penses. General Ex- penses. Electrical Equip- ment. d. d. d. d. 12 2.45 .81 .11 .04 .22 .02 .09 •• 14 2.33 .51 .38 12 2.26 .67 .07 10 2.79 1.02 .07 .04 14 2.82 60.97 .11 14 2.85 1.02 .50 12 3.49 .79 .32 14 3.13 1.00 .16 10 2.34 .51 14 3.81 1.13 .44 12 3.011.03.23 10 2.76 .71.12 10 3.11 1.01 .19 .10 .10 .03 .12 .09 .28 8.00 12 297 6.00 14 3.55 .92 .04 .13 12 2.82 .70 .24 .14 7.50 6.33 12 3.62 .13 .82 .38 .95 .76 .11 7.50 210 6.70 10 2.92 10 2.56 .95 .15 .13 828 2.78 .67 .05 .01 12 2.83.82 .07 .82.07.08 10 3.25 .90.12 .23 371 7.00 221 7.00 14 2,76 .99 .37 8.00 10 2.57 1.14 .25 .03 .20 544 6.67 12 3.74 1.18 338 6.50 12 2.56 .78 .18 .16 K Buildings - pue | d88888E :ಮತಃ : | 8 82 d. .03 .34 .03 1.25 .01 .01 .06 .07 .04 tures. Rolling Stock. .02 .02 .01 .01 .02 .03 .06 .02 .01 .07 .34 .30 .50 .84 .49 .58 .26 .58 .50 .69 .43 1.00 .59 .72 .56 .56 .12 .40 .60 .40 .46 .50 .43 Miscella- neous Equip. ment. d. .. • + 28: åk: : 22: 2) : : R: KRER: Total. d. .52 1.88 .44 .42 1.64 1.51 .99 .87 .54 1.25 .88 1.11 .72 1.19 .99 1.25 1.45 .86 .18 .58 1.01 .85 .85 .73 .84 922 SECTION XI. : Name. Aberdeen Birkenhead.. Blackpool Bolton Bournemouth Bury Cardiff Carlisle Chester Colchester Darlington Darwen Dover Dundee East Ham Farnworth Glasgow Gloucester Bradford Brighton Burnley Burton-on-Trent ·· Halifax Ilford .. Kirkcaldy Lancaster .. Leeds.. Liverpool L.C.C. ·· ·· Salford Sheffield ·· .. ·· ·· ·· ·· •• .. Ipswich Keighley Kilmarnock.. ·· ·· .. .. • .. Manchester .. Nelson 1st 1st 4th 6th 4th 3rd 2nd 6th 1st 6th 2nd 1st 1st 1st Kingston-upon-Hull 5th 2nd 2nd 7th 6th 2nd 2nd 2nd 2nd 4 81 Southampton Southport Stockport Sunderland. Wallasey Walsall Warrington.. West Ham Wigan Wolverhampton ·· ·· • • •• ·· •• .. • • • • • Newcastle-on-Tyne Nottingham Oldham Portsmouth • • • • ❤ · • . -- · • • Year of Operation. • 5th 3rd 4th 19th 5th 2nd 6th 3rd 3rd 1st 1st 2nd 4th 2nd 5th 5th 3rd 2nd 4th 3rd Gauge. 1st 3rd 4th 4 8 3rd 4 8 3rd 4 73 2nd 4 8 4 8 4 81 4 8 4 81 4 84 4 81 3 6 483 4 81 4 8 36 1st 3rd 3rd ft. in. 4 8 4 8 4 8 4 83 481 36 40 3 6 4 0 3 6 4 8 4 8 3 6 3 6 3 6 3 6 4 0 3 6 48 4 8 4 81 4 7 3 6 3 6 481 3 6 4 0 4 8 4 81 36 4 81 4 84 4 4 8 4 8 40 Population Served in Thousands. 167 33 110 55 175 63 324 126 160 52 103 168 47 38 40 48 40 43 164 115 50 1000 50 173 60 70 42 36 251 34 44 450 765 750 42 300 240 150 200 300 433 110 32 110 166 60 80 81 300 61 96 Table 18.-Particulars of Some Number of Times Popula- tion Carried Per Annum. 104 108 101 132 115 167 145 90 63 75 40 144 62 55 70 54 55 66 71 124 31 196 71 101 93 82 26 25 108 107 28 142 152 169 43 143 115 90 98 131 148 84 123 28 93 119 56 54 52 108 80 Length of Route Reduced to Single Track. Capital Per Mile of Single Track. 3.68 54.52 Car Miles Run in Thousands. 27.75 7.65 23.57 21.25 40.14 25.00 95.26 17.11 19.65 9,455 8.64 10,634 24.13 8,938 32.62 21,395 2,770 360 9.00 11,243 4.76 13,797 272 8.33 7,067 325 8.89 8,088 307 7.22 10,988 239 4.50 9,300 283 23.24 11,484 933 12.25 12,431 864 7.35 147.52 5,945 243 18,732 17,944 12.52 9,983 449 48.20 7,679 1,541 11.35 561 14.87 5.83 5.53 27.19 7.50 4.82 89.14 103.00 98.00 146.19 12,808 1,618 10,287 366 14,884 | 1,310 12,887 835 13,213 | 2,161 12,678 1,122 9,245 5,053 15,967 1,153 1,227 454 509 30.12 34.11 12,860 1,506 28.50 21,247 1,975 70.75 65.75 16.74 9,022❘ 4,885 16,737 | 6,050 11,233 1,108 10.76 11,011 11.50 12,198 19.54 14,624 11.85 11,462 427 606 1,496 779 17.09 632 9.05 403 17.03 20.87 20.00 8,764 10,877 1,693 19,341 12,003 810 Passengers Carried in Thousands. 1,237 714 17,143 3,579 11,146 7,247 20,215 10,058 47,108 11,321 12,377 7,532 692 6,804❘ 1,637 7,464 120 14,371 2,911 11,829 432 7,535 195 13,274 7,121 64,224 18,604 12,666 116,643 26,722 14,081 164,819 126,901 11,005 14,123 9,052 206 20,559 4,326 18,170 | 2,549 10,037 3,878 4,065 24,134 2,935 2,096 2,801 2,167 2,211 2,853 11,642 13,690 1,532 195,768 3,547 17,679 5,585 5,694 1,091 907 27,103 3,633 1,252 1,793 43,070 27,518 13,466 19,625 89,214 63,952 9,295 3,877 3,171 15,364 7,143 4,514 4,418 15,774 6,601 7,667 EFFICIENCY, MAINTENANCE, AND DEPRECIATION. 923 Tramways in the United Kingdom. Ch £ d. 10.46 10.46 10.59 2504 9.78 9.89 | 1937 8.50 10.08 4070 p. c. 8.17 d. 1.13 1.30 5.27 1.73 0.67 6.03 1.33 1.81 8.35 1.47 1.10 6.15 1.36 1.08 7.19 60 1.80 1.03 7.54 70 1.57 1.50 8.01 76 1.94 1.56 8.36 75 1.35 1.37 6.77 1.15 1.33 1.45 5.20 1.04 1.56 0.42 6.43 5.26 0.83 1.05 0.92 1.75 5.14 0.97 1.31 1.50 6.04 0.92 1.12 1.75 5.06 1.24 8.41 ·· 0.94 4.82 1.12 2.75 7.91 0.91 4.86 1.70 1.33 7.13 0.64 5.39 1.10 1.75 7.32 1.30 0.50 6.33 2.86 1.17 5.68 13.55 0.93 4.88 4.31 0.91 3.77 1.13 0.30 5.22 1.15 1.25 5.21 1.94 1.50 8.56 5.49 1.00 5.66 4.53 1.03 1.50 6.08 6.79 0.99 4.20 0.98 4.81 1.15 1.50 6.54 2.47 1.02 **4.01 0.98 2.00 5.87 2.59 0.94 3.78 1.13 1.25 5.20 11.85 1.00 4.72 1.27 0.46 5.33 3.04 0.78 3.37 1.33 1.50 5.36 79 1.17 1.94 6.50 11.86 5.50 0.87 4.23 1.10 5.06 9.51 1.11 5.38 8.62 0.97 13.79 1.19 116 55 7.25 66 1.14 1.51 0.31 1.57 5.27 1.22 5.00 5.23 0.81 3.39 8.14 ·· 1.33 1.49 2.00 6.99 64 5.13 73 0.86 6.19 1.66 0.41 7.01 4.92 66 1.25 6.83 59 1.66 1.50 7.08 72 1.52 4.58 4.84 0.54 5.66 44 4.51 0.92 1.41 1.49 6.62 70 1.72 0.45 6.49 67 1.18 2.13 7.83 72 5.69 6.54 1.07 9.60 1.08 5.04 1.17 8.70 1.17 11.88 1.28 7.16 0.90 7.41 1.27 5.32 6.04 1.08 4.37 4.68 1.40 3.63 8.79 1.00 4.23 10.32 1.28 5.16 5.82 1.33 4.60 6.16 0.90 4.56 7.76 0.84 5.65 4.60 1.28 5.55 1.15 4.18 1.58 62 68 1.12 1.50 6.04 1.30 1.29 5.31 1.12 1.88 6.37 1.59 1.63 7.75 1.11 1.76 63 66 6.57 69 1.23 1.60 6.52 63 1.06 1.60 66 7.34 7.97 6.55 9.04 6.34 7.24 7.81 7.86 8.25 4.58 6.23 5.92 5.26 5.32 2.76 5.62 6.76 3.43 5.37 5.43 6.40 7.92 8.68 13.97 2248 10.63 2368 8.90 12.05 2211 9.35 10.63 9.32 10.88 2347 9.82 10.48 2915 8.18 10.57 2768 8.54 9.49 2068 8.00 9.21 808 8.71 9.69 3195 8.16 7.13 1133 7.71 8.39 3688 8.62 8.79 1600 7.06 6.69 937 9.24 12.68 1596 10.03 9.84 | 2500 12.47 11.49 1895 15.80 10.49 10.49 2992 6.32 7.55 1019 10.91 10.23 5253 7.89 7.43 901 11.47 11.61 | 1542 9.95 10.05 2019 8.22 8.11 1568 6.60 6.81 796 7.22 7.26 644 9.30❘ 4143 9.31 8.40 6.77 1567 6.40 5.62 941 9.11 10.15 3302 9.59 10.80 5251 11.70 11.63 6775 8.99 10.73 4299 8.68 7.07❘ 1650 9.95 10.96 3547 10.79 11.89 | 4123 8.95 10.58 1925 9.94 12.45 3358 8.00 10.29❘ 2963 10.57 9.63 3564 8.39 11.03 2976 9.07 10.06 1628 5.23 7.55❘ 1619 10.20 10.34 3290 9.17 11.94 | 3221 7.14 9.66 1458 10.95 10.05 | 1834 12.75 10.90 3731 9.24 12.68 1673 9.40 11.05 1834 7.14 d. 0.97 1.00 1.16 1.60 1.13 1.32 1.14 1.06 1.32 1.08 d. 5.11 4.08 5.08 5.95 4.53 5.77 5.68 5.65 5.34 4.90 3.28 5.46 3.59 3.52 4.07 3.09 5.58 1.25 0.92 .. d. 6.53 + =Surplus = Deficit. p. c. 60 53 60 60 58 71 58 66 73 TORE |IRUNRF55 || 18 70 NOON. 8888 £ 13,408+ 3,932+ 1,893+ 3,345+ 15,541+ 5,467+ 15,930+ 322- 1,182+ 557+ 570+ 21+ 232+ 1,334+ 2,629- 92- << 5,340+ 2,612+ 1,780- 271,590+ 1,661- 990+ 2,325+ 822- 1,166 - 3,180- 75,430+ 81,326+ 119,693+ 35+ 11,936+ 20,182+ 7,826- 21,246+ 15,440+ 17,327+ 3,302+ 341- 630 - 5,736+ 6,501+ 2,269+ 450+ 9,762+ 4,983+ 924 SECTION XI. ! ¡* Table 19.—Cost of Engines erected and of Piping (Steam, Water, Drips, and Exhaust), for some Modern Power Plants, 120 lb. to 150 lb. Steam Pressure. Number and Capacity of Steam Units. Four vertical cross-compound slow-speed condensing, direct connected, 500 kilowatts Four vertical cross-compound condensing, slow speed, direct connected, 500 kilowatts Six vertical cross-compound con- densing slow-speed direct con- nected, 500 kilowatts Two horizontal cross-compound condensing, direct connected, 400 kilowatts Two tandem compound con- densing, direct connected, 200 kilowatts ·· .. .. ·· Type and Num- ber of Boilers. • Water tube Water tube Water tube Maximum traction trucks per set Ordinary bogie trucks per set.. Standard four-wheel truck Extra long truck.. Top-seat car bodies Single-deck car bodies Double motor equipment, including resistances and controllers ·· Water tube, three boilers ·· Single car motor, 15 to 50 horse-power Set of complete made-up cables for trolleys and motors.. Automatic car cut-outs, each.. Main motor switch Resistances, sets of three per car Top-seat car swivel trolley Swivelling trolley for single-deck car Ordinary straight under - running trolley for single-deck car.. Life-guards or car fenders, per set Automatic air brake equipment per motor car Electric brakes, per set... Controllers, each ·· ·· Cost of Engines Erected. •• વા 17,000 16,500 17,500 5,800 •• Cost of all Pipe- work Erected. £ 5500 £250 0 210 0 4980 4580 1680 3100 Table 20.-Approximate Cost of Trucks, Car Bodies and Trollies, and Equipments, &c. 200 0 0 75 0 0 12 0 0 400 1 10 0 7 0 0 "" £130 0 0 125 0 0 70 0 0 75 0 0 0 to £300 0 0 0 265 0 0 "" "" "" "" Cost of Steam Engine Erected per Kilowatt. "" £ s. 8 10 8 5 5 16 "" £20 0 0 15 10 0 "" 7 5 280 0 0 120 0 0 15 0 0 5 0 0 • 2 10 0 800 6 10 0 £10 0 0 to £25 0 0 £200 0 0 £20 0 0 to £30 0 0 20 0 0 30 0 0 Kilowatt Cost of Piping Erected. per £ s. 2 12 2 10 1 7 2 8 7 15 EFFICIENCY, MAINTENANCE, AND DEPRECIATION. 925 Table 21.-Cost of Track Laying, Bonding, and Overhead Line Construction. Cost per mile of single track, 4-ft. 84-in. gauge, 100-lb. rails, wood paving :- Excavation Concrete foundation . Rails, fishplates and bolts, tie bars Labour of plate laying Wood-paving blocks delivered Labour and material for laying paving Contingencies, watching, and lighting ·· .. Double trolley wire on side brackets span wire .. centre brackets side brackets span wire .. "" "9 Single trolley "" Total per mile of single track Bonding one mile single track, with two 8-in. flexible 4/0 bonds "" "" "" Bonding one mile double track, with two 8-in. flexible 4/0 bonds, and necessary cross bonding Bonding one single track, with two 34-in Chicago bonds Bonding one mile double track, with two 34-in. Chicago bonds, and cross bonding Bonding points, with 4/0 solid crown bonds Bonding one crossing, with 4/0 solid crown bonds .. "" .. •• .. .. " ·· .. • Table 23.—Approximate Cost of Parts Cost of railway generator per kilowatt three-phase machinery per kilowatt steam plant complete, engines, boilers, all accessories for high-speed engines Cost of steam plant complete for Corliss "" "" engines .. Horizontal return tubular boilers per horse- power (30 lb. of water evaporated) Water-tube boilers for high-pressure per horse-power .. ·· Table 22.-Cost per Mile of Overhead Construction with Three- Section Tubular Poles, Standard Brackets, Bars, &c., and 1/0 Trolley Wire. .. Lancashire boilers for high pressure per ·· horse-power ·· Cost of Corliss engine, including piping and foundations per horse-power Cost of lightly-built engine-house per horse- •• Cost of feed pumps and injectors per horse- power Cost of corrugated iron power station, approximate, per superficial foot.. Surface condenser, including air and cir- culating pumps when steam driven per kilowatt ► Ditto, electrically driven per kilowatt Evaporative condenser, "including air, cir- culating pumps, and fans, per kilowatt.. Ejector condenser, including circulating pumps per kilowatt Cooling towers, including fan ·· •• ·· • • ·· ·· •• • ·· .. ·· 13 £ s. d. 345 0 0 725 0 0 1360 0 0 308 0 0 2526 0 0 " 440 0 0 609 0 0 6313 0 0 £ 120 to 150 "" 280 340 130 160 £ 1000 to 1200 1200 1500 1100 1300 900 1050 1100 1350 300 350 200 "" 200 £9 to 11 Composing Power Plant. £6 0 0 to £10 0 0 7 0 0 10 0 0 19 >> "" 15 2 0 0 3 to 4 3 10 0 5 to 8 100 0 7 6 0 6 0 "" 99 "" "" £2 0 0 to £2 10 0 2 5 0 300 £2 10 0 1 5 0 1 10 0 926 SECTION XI. Table 24-Approximate Cost of Steam Turbo-Generator Plant, including Erection (exclusive of Condensers). 100 kilowatt sets 250 500 750 1000 5000 "J "" >> ·· "" "" ·· "" "1 "" Name of Company. "" ·· "" -- : Cleveland and Durham County Electric Power Company Clyde Valley Electrical Power Company •• : County of Durham Electric Power Supply Company Derbyshire and Nottinghamshire Electric Power Company.. Gloucestershire Electric Power Company Lancashire Electric Power Coin- pany Midland Electric Corporation for Power Distribution Newcastle-upon-Tyne Electric .. Table 25,-Data of Electric Power Distribution Companies. -- Supply Company North Metropolitan Electrical Power Distribution Company Shannon Water and Electrical Power Company South Wales Electrical Power Distribution Company Yorkshire Electric Power Syn- dicate .. .. ·· .. .. Per Kilowatt. £9 0 0 to £11 0 0 7 0 0 7 10 0 6 5 0 7 0 0 5 15 0 5 10 0 3 10 0 1,000,000 333,000 | 1,333,000 900,000 300,000 1,200,000 500,000 166,000 666,000 1,800,000 600,000 2,400,000 250,000 83,000 333,000 3,000,000 1,000,000 4,000,000 200,000 500,000 166,000 666,000 500,000 360,000 325 166,000 666,000 120,000 480,000 1800 750,000 250,000 1,000,000 1034 2,000,000 666,666 2,666,666 1800 •·. ·· "" 820 735 250 1575 326 1000 90 ** "" "" "" : .. 1,000,000 .. : 6 15 0 6 5 0 4 0 0 ·· .. 1,000,000 1 7 3 1 4 2 4 I 2 3 1 3 *N The cost per kilowatt installed, taking into consideration the expenses connected with securing the concession and the cost of land, buildings, as well as all the rights of way, cables and machinery, do not differ materially in different countries. The only exception to this may be found in some plants installed in the wilder portions of America and the Colonies, these plants for the most part, being merely temporary. In The total efficiency of an electric-power plant and system of distribution-that is, the ratio of the power actually supplied to the consumer to that produced at the station switchboard-depends on the amount of copper laid in the street. calculating this amount, what we will call the load factor-that is the ratio between what the station could supply if all the plant was running at its rated capacity twenty-four hours a day, and the actual output-must never be lost sight of. The depreciation, maintenance, interest on capital spent, and sinking fund of feeders must be balanced against. the value of the power wasted in transmission. Only in properly balancing these two factors will a really economical result be reached. Each case must be most carefully and separately considered. The following figures have been worked out for a station of about 2000 kilowatts capacity, with coal costing about 10s. a ton. EFFICIENCY, MAINTENANCE, AND DEPRECIATION. 927 Table 26.-Load Factor and Cost per Unit. Total Cost per Unit Generated. Load Factor in per Cent. 10 15 20 25 30 35 40 45 50 60 70 90 .. · • •• ·· Metropolitan Companies Provincial Companies .. Metropolitan Local Authorities ·· Provincial Local Authori ties ·· ·· "" "" "" •• "" • >> ·· "" "" ·· ·· ·· .. 1,000 units or less per month 1,000 units up to 2,000 3,000 5,000 10,000 20,000 40,000 80,000 : • d. 1.045 1.176 1.315 1.06 • "" • "" • "" "" >> :: The above costs do not include interest or sinking fund, but they do include maintenance and repairs in the generating station. These figures agree very closely with the results which have been given by various authorities, and they are based on the actual results obtained in existing stations, which is the only safe way of obtaining approximately correct results. 2,000 units per month. 3,000 5,000 10,000 20,000 40,000 80,000 200,000 "" Table 27.-Average Cost of Production in British Electric Lighting Stations, per Unit Sold. "" d. .113 .138 .121 .113 ·· •• .. •• .. •• • Coal and Oil, Waste, Wages of Repairs and Works otherFuel. Water, Stores. Workmen. Maintenance. Cost. d. .308 .569 .381 .265 Cost of Power. Società Lombarda per Distributione di Energia Elettrica. Formed in 1897 at Padermo on the Adda, twenty-five miles from Milan; total station capacity, 13,000- horse-power; partly used in the district for various purposes, and partly trans- mitted to Milan, there used by the Società Edison for lighting and tramways. Average cost £6 per electrical horse-power per year for constant use. Cusset Electrical Power Station.-Situated on the Rhone, fifteen miles above Lyons; founded in 1892; power installed, 20,000 horse-power; £500,000 expended on hydraulic work alone. Lachine Rapids Electric Power.-Power installed, 12,000 horse-power; small consumers for lighting purposes, 5d. per Board of Trade unit; for continuous power use £6 13s. 2d. per electrical horse-power per annum; for small consumers £17 148. Od. per electrical horse-power per annum. •• Table 28.-Rates Charged to Ordinary Consumers by the Cataract Power and Conduit Company. ·· ·· · •• ·· .. d. .90 to 1.00 .78 .85 .56 .70 .45 .55 .40 .50 .45 .35 .33 .30 .28 .25 .24 .23 "" ·· 22 • "" "" "" "" • >" "" "" "" "" d. .372 .327 .353 .281 .42 .40 .38 .34 .30 .30 .. ·· .. • .. ·· d. 1.855 2.20 2.13 1.885 Per Unit. 1d. 0.75d. 0.60d. 0:50d. 0.40d. 0.375d. 0.35d. 0.33d. 0.32d. 928 SECTION XI. } t + Table 29.-Mileage of Tramways in America, and Number of Cars, During Seven Years, 1897 to 1903. Electric Horse Cable Steam Mileage. Total miles Number of Cars. Electric Horse Cable Steam ·· Year. ·· Total cars 1896 1897 1898 1899 1900 1901 ·· .. ·· 52 64 81 92 102 132 ·· .. ·· .. 1897. 1898. 14,300 960 16,300 670 540 460 470 540 16,270 17,970 Cars. Cars. 39,748 45,785 5,177 3,123 5,199 4,701 2,653 2,541 52,777 56,150 22.30 21.12 19.98 18.99 18.47 18.55 Name of Line. South-Side Elevated, Chicago City and South London Manhattan Elevated ·· ·· Table 29, compiled from official data, shows the increase of electric traction in America during seven years, and the figures there given are probably too small. Table 30, taken from Mr. Garcke's Manual of Electrical Undertakings, is very interesting; it shows how the initial cost is subdivided in the case of British electric-lighting plants. •• Table 30.-Per Cent. of Capital Spent on Various Parts of Lighting Plant in Great Britain. (E. Garcke.) 36.7C 35.9 37.0 36.2 37.36 35.91 1899. 20,000 500 400 500 21,400 Cars. 10 1900. 1901. 20,051 22,818 332 370 330 241 460 439 6.1 37.5 51,000 57,221 3,000 1,556 4,200 3,517 2,000 2,853 60,200 65,147 21,211 Cars. Cars. 32.16 35.15 34.24 35.72 35.28 34.60 3.17 3.35 4.38 4.50 4.72 4.96 23,830 26,192 Cars. 64,848 1,411 1,643 3,205 71,107 1902. 1903. 25,592 | 29,212 297 Table 31.—Passengers Carried and Receipts per Mile of Route. Miles of Passengers Carried Route. per Mile of Route. 3,450,000 2,725,000 6,670,000 209 94 1.39 1.18 1.27 1.35 1.53 1.48 260 151 79 29,702 Cars. £ 37,600 22,300 71,500 Capital Spent on Provisional Order, &c. 3.11 3.28 2.48 2.06 2.24 2.23 Receipts per Mile of Route. EFFICIENCY, MAINTENANCE, AND DEPRECIATION. 929 Table 32.-Results Obtained by Electrification of Branches of New York, New Haven, and Hartford Railroad. Name of Line and Length. Stamford to New Canaan- 8 miles of single track Hartford to Bristol miles of single track Berlin to New Britain-3 miles 16.6 of double track Braintree to Cohasset-11.5 miles of double track Nantasket Junction to Pem- berton-6.9 miles of double track ·· ·· ·· Items. .. Type of Conductor. Overhead trolley Third rail Gross receipts in dollars Operating expenses in dollars Net earnings in dollars.. Passengers carried Ratio of operating expenses to receipts .. "" .. "" Overhead trolley The trains on these lines consist of from two to five cars, and run at a schedule speed of 30 miles an hour, with a maximum of 45 miles an hour. On the average there is one stop every two miles. The motor cars weigh 45 tons each, and seat 60 passengers. •• Table 33.-Manhattan Elevated Railway Results of Electrification. .. ·· .. ·· .. Repairs and maintenance of motor-cars Repairs to car bodies.. Annual Passenger Traffic. When After Operated Electrifi- by Steam. cation. ·· 98,300 184,728 83 367,695 1,060,617 189 267,936 341,207 30 304,292 · Steam Operation Electric Operation Results for Six Results for Six Months Ended 31st March, Months Ended 30th September, 1902. 1903. Increase in revenue due to electric traction, 28 per cent. Average distance travelled per passenger carried, 4 miles. Increase in schedule speed of trains, 25 per cent. (Extract from Colonel Yorke's Report.) Manhattan Elevated when operated by steam: Maximum headway of train, 57 seconds. Average distance between stations, 575 yards. Average schedule speed of stopping trains, 13 to 14 miles per hour. When operating electrically in crowded hours the trains used are made up of four motor cars and two trailers, which in other hours split up into two trains of three cars, two motors and one trailer. Track rail, 80 lb. per yard. Pressure on third rail, 600 volts. Sharpest curve, 90 ft. radius; maximum grade, 1.50. Conductor rail, 80 lb. per yard. 4,857,256 2,935,685 1,921,521 108,164,184 51.19 per cent. Table 34.- Cost per Ton-Mile of Train on the North-Western Elevated of Chicago. · 702,419 131 Per Cent. Increase. •• 6,441,437 2,819,764 3,621,673 125,548,740 42.02 per cent. •• d. 0.0036 0.0045 H H .. •• 930 SECTION XI. Table 35.-Cost of Locomotive Power per Train-Mile on the Metropolitan District (*). Fuel Wages Oil, waste, and stores Water .. Repairs and renewals Total ·· .. •• Fuel per ton-mile Wages ** .. ·· Average speed, from 11 to 13 miles an hour. Average acceleration, 6 in. per second, per second. Average weight of locomotive, 45 tons. Oil, waste, and stores Water Repairs and renewals .. NAME. •* Capital Traction Company,} Boston Elevated Railroad Company* Montreal Street Railway Com- pany* United Railway and Electric Company of Baltimore* International Railway Com- pany, Buffalo.. Brooklyn Rapid Transit Company* Columbus Railway Company* * These figures are based on an engine mileage of 1,010,689 miles, the useful train mileage being only 542,765. Table 36.-Cost per Ton-Mile on Metropolitan District, when Operated by Steam, of useful Train Load, Weighing Empty 90 Tons, Without Locomotive. • Average Distance Apart of Fixed Stop- ping Places (if any). yards 200 ·· 170 : 120 None · 163 .. Urban Route from End to End of City, and Passing through Centre. ·· Total per ton-mile .. Table 37.-Speeds of Electric Tramcars in America. (Association of Municipal Tramway Managers.) Average Speed, in- cluding Stops. 6.2 (in city) 8 ·· 10 (a) 10 6.87 9 (on all routes) 6 (in centre of city) 8.13 Purely Suburban Route (if any). • 11.45 18 to 20 • 15 23 11.26 21.32 .. • •• 16.67 ·· • .. d. 4.150 3.330 0.258 0.506 1.895 10.139 .. miles per hr. miles per hr. miles per hr. 12 in city 9 (in city) 15 outside .. d. 0.0461 0.0370 0.0029 0.0056 0.0211 0.1127 Maximum Speed Attained on System. 18 25 (in country) 45 21.32 12 to 15 Average * Speed at which cars may travel is regulated by police or local authorities. (a) Between streets, and does not include time taken at stopping-places. 22.80 EFFICIENCY, MAINTENANCE, AND DEPRECIATION. 931 Glasgow Corporation Ayr Corporation Brighton Corporation Sheffield Corporation Name of Tramway. Bradford Corporation Halifax Corporation Aberdeen Corporation Dover Corporation Cardiff Corporation Oldhain Corporation Birkenhead Corporation Blackburn Corporation Sunderland Corporation Dundee Corporation East Ham District Council ·· ·· ❤ ·· Newcastle Corporation Huddersfield Corporation Liverpool Corporation Manchester Corporation Average .. ::: : ·· ·· ·· ·· Table 38, Speeds of Electric Tramcars in Great Britain. (Association of Municipal Tramway Managers.) ·· •• ·· ·· ·· ·· ·· .. .. ·· ·· · :: ·· ·· ·· : .. ·· ·· · ::: • ·· .. ·· .. ·· : : : ·· .. ·· : ·· ·· ** ·· .. ·· ·· .. ·· •• .. ·· .. .. DD ·· Average Distance between Fixed Stopping Places (if any). yards. 200 160 220 215 173 227 220 None 250 None 200 200 220 200 235 150 200 205 Urban Route from End to End of City, and Pass- ing Through Centre. miles per hour. 6.42 7.5 1 7.2 Average Speed, including Stops. 7.3 (a) 7.12 (a) 6.2 (a) 7.15 6.27 6.0 6.23 6.6 7.2 6.73 6.0 6.28 7.0 (a) 6.41 6.71 6.68 (a) Route is from centre of city to suburban terminus. (b) Route is not purely suburban; streets are continuously used for heavy traffic, Purely Suburban Route (if any). miles per hour. 6.196 6.7 (b) 8.0 7.22 7.02 1 932 SECTION XI. NAME. Table 39-Speeds of Electric Tramcars on the Continent. (Union Internationale Permanente de Tramways.) Aachner Light Railway Company Strassburg Street Railway Company Solinger Light Railway Company German Street Railway Company of Dresden Dresden Street Railway Frankfurt-on-Maine Corporation Street Rail- ·· .. way Street Railway Company of Brunswick Breslau Street Railway Company Street Railway Company of Hamburg Barmen-Elberfeld Tramways Erfurt Electric Street Railway Bergish Light Railway Company, Elberfeld Stettin Street Railway Company Cologne Corporation Street Railway UM ·· ·· ·· ·· · (a) Nuremburg-Furth Street Railway Co. Hanover Street Railway ·· Great Leipzig Street Railway (a) Zwickau Electricity Supply and Street Railway Company .. .. Average Distance between Fixed Stop- ping Places (if any). yards 327 (town) 547 (subs) 200 262 380 to 440 310 275 to 330 219 217 164 200 to 242 173 217 to 434 205 (town) 507 (subs.)) 380 Average Speed in- cluding Stops. On Route Running Through an Urban Dis- trict & into the City. 8 (town route) miles per hr. mls. p. hr. miles per hr. 6.8 (town route) 11.2 12.4 .. 7.4 7.5 6.7 7.5 7, 6.5, 6 ·· .. 6.8* 7.5 On Purely Suburban Route. 6.5 8.5 7.7 9.1 9.6 .. ·· 10.6 9.2* 11.7 Maximum Speed Attained on System. 11.5 10.0 9.4 (town) 12.4 (subs.) 16.2 16.8 12.5 15.6 9.3 15.0 11.2 9.3 15.5 9.3 11.5 16.4 12.4 11.2 18.6 REMARKS. Intend to apply for a maximum speed of 18.6 miles per hour. Time-tables made out for an average speed of 7.5 miles per hour. 15.6 miles per hour allowed *Not including stops. EFFICIENCY, MAINTENANCE, AND DEPRECIATION. 933 Lodz Electric Street Railway Company (a) Crefeld Street Railway Munich Tramways Company, Limited Siemens and Halske, Limited, Berlin Leipzig Electric Street Railway Great Berlin Street Railway Company Magdeburg Street Railway Company Bern Street Railways Zurich Street Railways Brussels Tramways Brussels Mutual Tramways Company (a) Galatz (a) Dunkerque ·· .. •• • ·· • .. ·· .. .. National Society of Local Railways in Belgium ·· Liége Tramway Society, Limited Société Anonyme d'Entreprise Barcelona (a) Générale de Travaux, Liége Nicolareff (a) Tramway Union of France ·· General Omnibus Company, Paris The General Parisian Tramways Company Parisian Eastern Tramway Company Reims Tramway Company Omnibus and Tramways Company, of Lyons Turin Tramways ·· Town City of Prague electric railways Copenhagen Tramway Company Riga Street Railway Company, Limited Average O D ·· Florence Tramways Street Railways of the Canton of Basle .. ·· .. · • 317 191 330 to 440 340 230 to 330 273 206 ·· : 327 273 219 109 to 328 218 225 220 271 to 327 220 274 61 6.5 6.6 7.7 7.5* 7.2 7.7 6.8 7.2 6.5 7 (in town) 8 7.7 8 (all routes) ·· 6 6.8 6.2 8.4 7.5 7.6* 7.5 9.3 (max.) 7.5 ( 7.1*' 6.5 7.2 :00:00:100 9.5 8 7.5 •• 9.1 8.75 (out- side town) ·· 8 : ·· • 11.2 max. 9.6 11.2 ·· 12.5 15.6 12.5 15.5 15.6 15.5 11.2 18.6 9 9.7 18.6 10 8 12.42 15.5 15.5 10 15.3 10 12.5 8.7 12.5 15.5 15.6 12.5 12 13 * From a suburb through the town to another suburb. Average speed, 10 per cent. less than the maximum speed allowed. } All regulations agree to an average speed of 7.5 miles per hour, including stops, in urban districts, and 18.8 miles per hour in suburban districts. Maximum speed allowed 12.5 miles per hour. If furnished with ordinary brake power. If furnished with a continuous brake. Max. speed allowed, 15.5 miles per hour. Max. speed allowed, 12.5 miles per hour. * 6.7 from one end of town to the other. Average speed fixed at 7.5 miles per hour * From a suburb through the town to another suburb. N.B.-In all cases, with the exception of those places marked (a) there is a regulation stipulating the rate of speed at which electric cars may travel; in most cases this regulation is issued by the police authorities. ! 934 SECTION XI. Table 40.-Receipts per Passenger on Steam and Electric Lines. d. 1.78 } Metropolitan Railway Metropolitan District Railway East London Railway North London Railway Central London Railway City and South London Railway London, Brighton, and South Coast Suburban System (estimated) .. ·· • • .. ·· ·· • • • 1.84 1.47 0.93 1.90 1.87 2.0 SECTION XII. TRANSMISSION OF POWER. TRANSMISSION OF POWER. Cost of Power Generated from Falling Water. (J. B. C. Kershaw, F.I.C.) The aggregate amount of power at the present date generated from falling water forms no inconsiderable portion of the total power utilised in manufacturing industries. Two years ago it was estimated by Mr. Kershaw to be between 236,000 and 350,000 horse-power. Table 1.-Estimated and Actual Costs and Charges for Water per Electrical Horse-Power Year or 8760 Hours. (J. B. C. Kershaw, F.I.C.) Country and Place. Norway Canada (Lachine Rapids).. Scotland (Foyers) Switzerland .. Austria (Meran) SECTION XII. Norway (Sarpsfos).. United States (Massena) Italy Sweden ·· ·· "" •• ·· ·· .. Japan (Kyoto) Canada (Lachine Rapids).. France United States (Niagara) .. ·· ·· "" "" Switzerland (Schaffhausen) (Zurich) Germany (Rheinfelden) Japan (Kyoto) Canada (Montreal). United States (Utah) Canada (Montreal) United States (Buffalo) ·· ·· ·· ·· ·· ·· ·· Cost or Charge. £ s. d. 1 0 0 1 5 5 1 10 0 1 19 0 2 7 6 2 7 6 2 10 0 2 16 0 138. to £3 £ s. d. 3 6 0 3 11 9 3 16 7 3 19 7 4 6 7 4 13 4 5 0 1 5 10 6 6 0 0 6 8 0 6 13 2 12 10 0 17 14 0 25 11 0 Remarks. Average of actual costs at small power stations. Estimated cost when 20,000 horse-power is developed. Operating costs only. Lowest charge recorded. Charge to Carbide Company for 2,000 horse-power. Average charge to carbide factories. Lowest proposed charge. Average operating costs. Estimates by Carlsen. Charge to large users. Present cost of power. General estimate of costs. Charge to large consumers. Average charge for whole of power. Charge for Niagara power in Buffalo. Charge to large consumers. "" "" ** "" "" "" "" small large over an 80-mile transmission line. to small consumers. "" " for Niagara power to small con- sumers in Buffalo. H H2 938 SECTION XII. The cost of power is considerably raised by transmission. Niagara power at Buffalo costs £4 13s. 1d. per electrical horse-power year, as compared with £3 198. 7d. at Niagara. The power from Lachine Rapids costs £6 13s. 2d. per electrical horse-power year in Montreal, whereas the present costs at the generating station are only £3 11s. 9d. In Utah the charge to mines on an 80-mile transmission line is £12 108. per electrical horse-power year; the cost of this power at Provo is probably not one- fourth of this amount. Table 2.-Capital Outlay upon Water-Power Developments. Place. Vallorbes Hte. Savoie Massena Hte. Savoie Italy Rheinfelden France Hte. Savoie Zurich Canada (Lachine Rapids) Interlacken Lyons · Water Steam ·· ·· ·· Source of Power. Gas (blast furnace) Gas (producer) Location. ·· · Upper Savoy Department Isère Upper Savoy .. .. .. ·· • ·· .. .. .. ·· Gross Horse-Power. 3,000 8,500 75,000 4,000 Average 16,000 1,000 300 25,300 6,600 ? 11,900 Lowest Estimated Cost. £ s. d. 1 5 5 H4+LO 4 18 8 1 7 5 0 0 Capital Outllay. Horse- Power. £ 10,400 36,400 381,800 28,000 * This does not include cost of dynamos. Table 3.-Comparative Costs of Electric Power. Lowest Recorded Costs per Electrical Horse-Power Year of 8760 Hours. 8500 4000 300 Outlay 225,000 24,000 9,000 760,000 ? 1,000,000 Country. Canada England Germany England Outlay per Horse-Power. Height of Fall. £ 8. d. 3 9 4 5 5 1 7 0 12 0 metres 140 100 2 14 1 0 0 24 30 30 30 34 Lowest Actual Cost. 0 0 10 0 0 84 0 0 £ s. d. 1 19 0 4 17 7 3 Lunge. 7* | Janet. 10 0* | Janet. 0 3* Electrical energy, generated by falling water, is costing more at Rheinfelden, at Zürich, and at Buffalo, than it would cost in South Lancashire, if generated by steam power in large units; and the margin between the actual charge for water power at Niagara, and the estimated cost of steam power in large generating stations in South Lancashire, is only 12s. 1d. per electrical horse-power year. Table 4.-Water Power Development Schemes in France. Total. Authority. £ 36,400 28,000 9,000 0 Minet. 0* | Janet. 9 Bignami. Wallbank. J. W. Hall. J. W. Hall Country. Capital Outlay. C Switzerland. United States. £ 4 7 Per Horse-Power at Turbine Shaft. $500 30 0 0700 d. TRANSMISSION OF POWER. 939 Size of Cables. 3- 7/18 3- 7/16 3- 7/14 3-19/16 Size of Cables. 3- 7/18 3- 7/16 3- 7/14 3-19/16 Table 5.-Comparison of Cost of Overhead and Underground Mains. (Addenbrook.) OVERHEAD MAINS.-THREE-PHASE CABLES. (On the basis of 1 per cent. loss per mile.) Particulars of the Conductors. Section of Cables in Square Inches. 3 .01292 3 .02299 3 .03588 3 .06247 Particulars of the Conductors. Section of Cables in Square Inches. 3 .01292 3 .02299 3 .03588 3 .06247 Weight per Mile. Weight per Mile. Carrying Capacity in Kilowatts at the Following Voltages. lb. 3× 266 3× 468 3x 730 3 x 1270 6000 81 143 222 382 8000 152 254 394 680 81 143 222 382 10,000 12,000 £ lb. 3x 266 £ 245 230 52/- 3× 468 259 275 290 36/3 3x 730 301 316 332 27/- 3 x 1270 402 418 433 21/- UNDERGROUND MAINS.-THREE-PHASE CABLES. (On the basis of 1 per cent. loss per mile.) 225 400 615 1060 Carrying Capacity in Kilowatts at the Following Voltages. 6000 8000 10,000 152 254 394 680 225 323 545 887 1526 400 615 1060 12,000 Capital Cost of Line Complete per Mile, allowing 45 Poles per Mile at the Following Voltages. 323 545 887 1526 6000 £ 211 8000 6000 £ 490 520 545 760 10,000 Cost of Main Complete Laid and Jointed at the Following Voltages. 8000 £ 540 635 660 858 12,000❘ 6000 £ 260 305 347 448 £ 678 725 772 957 10,000 12,000 Capital Cost of Line Complete per Kilowatt Conveyed per Mile at the Following Voltages. £ 800 870 950 1050 8000 6000 120/- 73/- 49/- 40/- 30/- 21/8 16/- 12/4 8000 10,000 12,000 Cost of Line Complete per Kilowatt Conveyed per Mile at the Following Voltages. 71/- 50/- 34/- 25/- 22/- 14/6 10/9 8/2 16/– 11/3 7/10 5/10 60/- 36/- 25/- 18/- 10,000 12,000 49/6 32/- 21/- 13/9 . : 940 SECTION XII. Insulators and Pins. Porcelain is much stronger mechanically than glass, and can be chipped without cracking the whole insulator. Glass is cheap, and also its dielectric strength is greater. Porcelain must necessarily depend on the strength of the outer coating or glaze for its insulating qualities. If this becomes cracked by extremes of heat or cold, moisture working in will cause a puncture of the insulator in time. There appears to be little practical difference in the working of porcelain and glass. Both give excellent results. Glass shows any defects to the eye, and testing is unnecessary. The defects in porcelain are not visible, and tests at high voltage with plenty of transformer capacity are absolutely necessary. It is admitted that the static effect of the current tends to dispel moisture, what- ever the type of insulator. At Provo, with 40,000 volts and a grounded neutral, glass insulators are used. The leakage towards ground must be considerable; it is impossible to operate a telephone line on the same poles. On the 33,000-volt line into Los Angeles the neutral is also grounded, but the telephone line is perfectly satisfactory. Porcelain insulators of about the same diameter as the glass used on the Provo line (about 7 in.) are employed on this line. When insulators are broken the result is a burned pin, but the leakage rarely produces a short-circuit on the line. Wooden pins boiled in paraffin or linseed oil are commonly used, though on the 33,000-volt Los-Angeles line iron pins are giving satisfaction. The insulator should be high enough from the cross-arm, so that the distance from the edge of the insulator to the cross-arm is more than the distance in from the edge of the insulator to the pin. The design of insulators for 60,000 volts for the two large plants now going in near San Francisco is radically different from that heretofore followed. The size of insulator required to avoid a high- voltage discharge over the surface of the insulator at 60,000 volts in all kinds of weather led to the use of a large umbrella of porcelain, 12 in. in diameter, mounted with a sulphur-joint on to a very high, long, single-petticoat_glass-insulator 12-in. high, with a sulphur-joint between the porcelain and glass. Porcelain was selected for the umbrella because of its mechanical strength. These insulators, before being put on the lines of the Standard Electric Company of California, are tested at Oakland with 120,000 volts between tie-wire and centre of pin. At this voltage they do not puncture, but a rattling discharge takes place over the surface of the insulator clear around the edges of the umbrella and petticoat to a wire placed in the centre of the pin. This voltage will jump 12 in. between points in open-air. Testing High-Tension Porcelain Insulators. (FIG. 1, page 941.) High-tension porcelain insulators are usually tested at three times their working pressure. In making these tests only one set of transformers should be used to step up to the highest pressure required, and the reactance should be as low as possible, the reason for this being that a set of transformers in series gives poor regulation, and makes it very uncertain as to what actual pressure has been applied. Porcelain insulators to be satisfactory must be absolutely non-absorbent to moisture. To test this the insulators are broken up into small pieces and kept in a dry place for a considerable time, after which they are carefully weighed and then immersed in water for at least twenty-four hours. They should be then dried in blotting-paper and the weight taken, which should not exceed that which was taken immediately after drying. Disruptive pressure tests can be taken by putting the insulator in salt water, filling the pin-hole also with salt water, and applying pressure between the two liquids. The length for which the test pressure is applied varies. All insulators to be used should be tested, and the usual method is to test a considerable number at one time, when it is usually found that some insulators give way, the rule then is to keep on the test for another fifteen or twenty minutes after the last insulator has given way. Insulators should also be tested as regards surface leakage, by applying pressure between the pin-hole and a conductor fixed to the top on which the wires are supported whilst they are under a sprinkler. Where insulators are built of more than one piece, each part should be able to withstand pressure greater than it would have to stand when actually put together. Practice has shown that wooden pins should not be used, as they easily become charred, and iron pins should always be employed. In making the test under a sprinkler above referred to, care should be taken that water is applied from the nozzle at a pressure of from 40 lb. to 60 lb. to the square inch, and sprayed at an angle of about 30 deg. from the horizontal. Besides electrical tests referred to, insulators should also be submitted to mechanical tests based on the conditions under which they will be employed. TRANSMISSION OF POWER. 941 Thickness of Porcelain in m/m 10 - Number of Plants. 11 (1163.) 444 9 8 7 6 5 4 3 2 10 20 30 40 50 60 70 80 90 Pressure in Thousands of Volts 1 Fig. 1 shows the pressure at which various thicknesses of "Hermesdorfer” porcelain is broken down. Regulation of Transmission Lines. This is an important question; knowing the probable power factor of the load, the line drop may be calculated, thus determining the amount of regulation which must be applied. If there are several sub-stations at different distances from the generating station to be supplied, the regulation to be allowed in each sub-station should be calculated. The charging current of the line has an important bearing on the regulation of the system. There are two methods of determining the effect of the capacity current of a line on the voltage of the receiver. In the one most commonly used the line capacity is assumed to be concentrated at one point, or for longer lines the capacity is divided into several parts, and these several capacities are connected across the line at various points. The pressures consumed over the line are then added geometrically to the receiver pressure. Transmission Voltage. Table 6. Data of some American Power Transmission Lines. C Length of Line in Miles. Max. Min. 19 12,000 4,600 25 9 7 16,000 14,500 31 24,000 20,000 60 27,000 25,000 46 34,000 30,000 83 60,000 40,000 101 Max. Min. 35 Range of Power Factor. 29 60 80 to 100 7 80 97 107 80 90 16.6 80 90 90 95 65 100 108 Distance between Conductors in Inches. "" "" "" "" "" 100 Max. Min. 36 40 48 14 18 26 18 24 42 Height Lowest Standard Conductor Length is above the Ground in Feet. "" "" "" of Span in Feet. 88888888 18 to 40 80 to 125 15 125 15 27 90 140 25 35 90 130 19 27100 130 19,, 30 100,, 180 "" 32 80 >> 99 "" "" 942 SECTION XII. Name of Transmission. Bay Counties Power Co. Lauffen, Frankfort (Germany) Los Angeles, Cal. Redlands, Sacramento, Cal. Missouri River Power Co. Telluride, Utah Kalamazoo, Mich. Tacoma, Wash. Ogden, Salt Lake City, Utah Fresno, Cal. Bland, N.M. ·· ·· West Kootenay, B.C. Newcastle, Sacramento, Cal. ·· San Antonio, San Bernardino, Cal. St. Paul, Minn. ·· Spiez-Thun, Burgdorf, Berne Meran-Bozen Milan, Italy Folsom, Sacramento Bakersfield, Cal. Redlands, Cal. Paderno, Milan Niagara Falls, Buffalo.. •• Butte City, Montana Nice, Italy Blue Lake, Cal. ·· ·· .. .. ·· ·· ·· ·· ·· .. • • ·· Table 7-Data of Some Existing Power Transmissions. : .. : ·· Transmitted Distance in Miles. 142 106 83 80 65 55 46 45 40 35 31 30 29 28 28 26 25 25 221 22 21 21 21 2223 21 20 20 Brake Horse- Power De- livered. 30,000 generated 300 3,000 4,000 5,700 1,000 2,000 1,340 5,000 1,400 800 2,000 1,000 160 4,000 5,400 6,000 4,000 1,200 1,000 12,000 10,000 4,000 2,670 1,800 Pressure in Volts. At Generator } 2,400 300 750 750 550 800 2,300 2,300 2,300 700 605 1,100 500 1,100 800 4,000 3,600 13,000 800 550 2,500 13,500 340 800 5,500 1,000 On Line. 40,000 30,000 33,000 30,000 50,000 40,000 40,000 13,000 15,000 11,000 17,300 20,000 15,000 10,000 30,000 16,000 10,000 13,000 11,000 10,000 10,000 13,500 11,000 15,000 26,000 5,500 12,000 System of Transmission. 3 phase 2 3 2 "" 3 "" >> "" "" "" "" "" "" "" 2 and 3 phase Single phase 3 phase "" " "" "" "> "" "" "" "" "" >> 2 and 3 phase of Cycles per Number Second. 84 88:8888888: :892 :888** 60 25 50 50 60 60 60 60 60 60 60 60 40 40 60 60 50 40 25 60 25 .. Allgemeine Elektricitäts-Gesellschaft, Berlin, Maschinenfabrik Oerlikon General Electric Co., Schenectady "" "" "" Westinghouse Co. General Electric Co., Schenectady " "" " Name of Makers. "" "" "" Westinghouse 99 "" "" >> "" "" "" "" "" General Electric Co., Schenectady Brown and Boveri Ganz and Co., Budapest General Electric Co., Schenectady "} >> >> >> "" "" "" "" "" "" "" Brown and Boveri Westinghouse and General Electric Company General Electric Co., Schenectady Stanley Electric Company "" TRANSMISSION OF POWER. 943 Name of Transmission. Kinderhook, N.Y. Mechanicville, N.Y. Teluride Santa Cruz, Cal.. Tivoli, Rome, Italy Lowell, Michigan Three Rivers, Canada Lindsay, Ont. Cordova, Argentine Republic Bogota, Colombia Republic Hochfelden, Oerlikon Hiromura, Japan Lowell, Nashua, N.H. Salem, N.C. •• Montreal, Canada Bulack, Oerlikon Portland, Ore. Little Cotton Wood, Salt Lake City, Utah N. Gorham, Me. Big Cotton Wood, Salt Lake City, .. ·· ·· ·· ·· ·· ·· ·· .. Table 8.-Data of Some Existing Power Transmissions-(continued). .. .. ·· ·· ·· • .. • • .. • .. Utah Varese, Italy Soulanges Canal, Canada Bodie, Cal. Zufikon-Zürich, Switzerland La Goule, St. Etienne, France Les Clees-Yverden, Switzerland Victoria, Goldstream, B.C. Trenton, Canada ·· ·· ·· ·· ·· ·· ·· ·· .. .. ·· •• Transmitted Distance Brake Horse- Power De- in Miles. livered. 18 3,000 18&14 7,000 1,600 400 18 18 18 18 17 17 16 15 15 15 15 15 15 14 14 14 14 14 14 ; 14 13 12 124 124 12 12 2,000 270 800 535 1,500 1,400 900 1,000 550 1,000 20,000 400 2,500 3,000 1,670 675 1,000 704 160 1,300 2,000 1,800 960 735 Pressure in Volts. At Generator. On Line. 12,000 12,000 500 1,100 5,500 1,000 2,000 605 700 6,700 500 1,150 330 10,000 12,000 86 6,000 500 10,000 525 5,000 2,400 3,500 5,000 5,000 5,000 700 2,500 12,000 12,000 11,600 11,000 5,500 10,000 12,000 11,000 10,000 6,700 13,000 11,500 3,500 10,000 12,000 13,000 6,000 15,000 10,000 10,000 5,000 2,400 3,500 5,000 5,000 5,000 10,000 2,500 System of Transmission. 3-phase 2 and 3 phase Single phase 2-phase "" "" " " "" "" 3 "" 2 3 "" "" "" "" "" 2 and 3-phase 3-phase 2200 Number of Cycles per Second. 25 38 .. :882 :88: :08 60 60 50 60 30 48 33 88800: 848 8: 60 60 "" >> "" single-phase 3-phase single-phase 50 50 3-phase "" "* 45 60 50 60 60 Name of Makers. General Electric Co., Schenectady. >> Westinghouse Company. Ganz and Co., Budapest. Stanley Company. "" General Electric Co., Schenectady. Maschinenfabrik Oerlikon." Brown and Boveri. General Electric Co., Schenectady. "" "" Stanley Company. "" Maschinenfabrik Oerlikon. General Electric Co., Schenectady. "" Westinghouse Company. General Electric Co., Schenectady. "" Co. Francaise Thomson-Houston. General Electric Co., Schenectady. Westinghouse Company. Maschinenfabrik Oerlikon. "" " General Electric Co., Schenectady. " 944 SECTION XII. Electric Power Transmission Section. For three-phase power transmission the conductors are generally placed so as to form the apexes of an equilateral triangle; the following figures give the spacing usually adopted for such conductors at various pressures. Pressure between Conductors between Conductors Volts. 15,000 20,000 25,000 80,000 50,000 Voltage. 11,000 12,000 16,000 22,000 25,000 30,000 34,000 40,000 45,000 50,000 A in. 20 24 26 30 36 40 42 48 60 72 .. (1164) .. ·· ·· L---D ·· • Table 9.-Showing some Relative Positions of Insulators for Different Pressures. (FIG. 2.) B in. 44 46 54 60 60 60 72 88NN** 宣 ​72 K- ←-----B 1 Distances in Inches. с in. 24 84 84 ·· ·· - .. Distance Inches. 20 KC --* 30 35 40 60 28 30 30 36 36 40 48 54 60 A D in. 20 20 24 30 36 40 42 48 60 72 2 Porcelain as an Insulating Material for High-Tension Work. If porcelain is not properly vitrified, it does not possess any great insulating properties, even when perfectly dry. Thoroughly vitrified porcelain possesses great insulating strength. The properties required of an electrical insulator for high-tension transmission work are, that it should possess a high efficiency as a non-conductor, and that it should be sufficiently strong mechanically to resist the strain of wiring, and the hard treatment to which such insulators are sometimes subjected. The composition of the porcelain is of great importance. According to TRANSMISSION OF POWER. 945 Mr. A. S. Watts, a moderately high proportion of S i O2 and A120g gives a good strong porcelain, but that not over one Al2O3, and 6.2 Si O₂ should be used. Tests go to show that all specimens which exhibit a high electrical resistance contain a high proportion of silica and a low proportion of alumina. The composition of a good porcelain is as follows: 0.5 to 0.8 20{0.8 to 1.0 A 4203 } 4.2 to 6.2 S i O2. 0.5 to 0.2 Insulators on High Tension Transmission Line of the Bay Counties Power Company. (FIGS. 3 to 5.) (Standard Electric Company). 3 4 19271 33 263. ====> Za hand (928) 1 I 3 ક 6 Fig. 3. Details of Insulator for 40,000 volts. showing manner of Tying Line Wire. Cross-Arm for High-Tension Transmission. Fig. 4. Fig. 5. View of Insulator, Details of Pole and Figs. 3 and 4 show the insulator. It is a two-part insulator, the upper portion being of porcelain and the lower of glass. The two parts are cemented together with cement composed of sulphur and sharp sand in about equal parts. 946 SECTION XII. I i ! The insulator pins used by the Standard Electric Company are made from eucalyptus, or blue-gum wood, specially seasoned, and are soaked in hot oil. The largest diameter of the pin is 24 in., tapering to 24 in. at the upper shoulder. The diameter at the base of the thread is 7 in., and 1 in. as the top. There are four threads to the inch. The overall length of the pin is 167 in. Fig. 4 shows the manner of fixing the wire to the insulators. Fig. 5 shows the insulators mounted on the pole and cross-arm. Table 10.-Hermsdorf High-Tension Porcelain Insulators. (FIG. 6.) Maximum Diameter in Millimetres. · 160 175 190 205 220 235 210 210 255 300 Total Height in Millimetres. 185 200 220 232 255 270 220 220 240 265 (1165.) Weight in Kilogrammes. 1925 2300 2900 3125 4150 4800 3350 3775 5400 7250 6 Working Pressure. volts. 37,000 41,000 46,000 50,000 55,000 60,000 48,000 50,000 60,000 70,000 * Test Pressure. volts. 65,000 70,000 75,000 85,000 90,000 95,000 85,000 85,000 100,000 100,000 50,000-Volt Transmission of the Missouri River Power Company. (FIGS. 7 and 8, page 947.) The pole line is 65 miles long. The line consists of two lines of poles about 50 ft. apart. The cables are arranged on the poles in the form of an equilateral triangle, the sides of which measure 78 in. (Fig. 7). Each line consists of three 7-strand copper cables, each cable having a sectional area of about 106,000 circ. mils. The cables are transposed five times in the whole length of line. The distance between consecutive poles is 110 ft. Fig. 8 shows one of the insulators. A glass sleeve is fitted over the wooden pin below the insulator, to keep the pin as dry as possible. Paderno-Milan Transmission. (FIG. 9, page 947.) Fig. 9 shows the type of porcelain insulator used on this line. The number of wires used is 18; that is, 9 wires per pole, it being a double- pole line. The poles are of iron, and are spaced 60 metres (196 ft.) apart. The distance between the wires is 60 centimetres (23.6 in.), and the diameter of the wire is 9 millimetres (35 in.). The pressure on the line is 15,000 volts. TRANSMISSION OF POWER. 947 (930) 7 180 94 6·6- Figs. 7 and 8. Arrangement of Transmission Conductors, and Section of Insulator. -98- 10 10 8 (991) Fig. 9. Insulator used on Paderno-Milan Transmission Line K----67----X POWER TRANSMISSION IN FACTORIES. Power Required to Drive Shafting. (Fig. 10, page 948.) Professor Kennedy gives the loss of power in shafting to be 22 per cent. of the indicated horse-power of the engine; Mr. Crompton gives 32 per cent.; and Sir T. Richardson found that it varied from 25 per cent. to 70 per cent., with an average of 43 per cent. At Messrs. Furness, Westgarth and Co,'s engine works, at Middlesbrough, the loss was about 50 per cent. for the whole works. In several different factories in Cleveland, Ohio, Mr. C. H. Benjamin found the loss to vary from 50 to 80 per cent. At Bristol Wagon Works it varies from 22 to 57 per cent. 948 SECTION XII. Experiment made by C. E. Hodgkin Shafting 24 in. diameter, 82 ft. long, supported by ten bearings, each 7 in. long, and running at 500 revolutions per minute, driven by a motor giving 15 brake horse-power running at 1025 revolutions. Motor running light required, 1.45 horse- power (1080 watts); when driving shafting only 3.85 horse-power (2870 watts), or an addition of 2.4 horse-power; and when driving 13 idle belts, a total supply of 3742 watts was required, or an addition of 1.17 horse-power for 13 belts. 50 40 30 20 10 HORSE POWER 0 (710) 7 TIME 8 USEFUL WORK ING ESTIMATED FRICTION LOSS IN ENGINE 12 1 M. USEFUL WORK POWER LOST BY FRICTION. SHAFTING 2 ESTIMATED FRICTION LOSS IN ENGINE 11 10 A. M. (54 HOURS) Graphic Illustration of Friction Losses from Tests made by Croeker. 10. 5 4 3 P.M. (4 HOURS) Mr. Langdon gives the following particulars of a test made at the Midland Railway works at Derby :- Some fifteen tools are driven from one main shaft, 98 ft. long, 2 in. in diameter, which has twelve bearings 48 in. long. The shaft is driven by an electric motor running at 500 revolutions. To drive the shafting alone, quite free from all belting, at 110 revolutions, required 272 watts; to drive it with nineteen belts, free from the tools, 518 watts; with the addition of the counter-shafting, 794 watts. At the Baldwin locomotive works, out of 2500 horse-power only 500 reaches the machines, or a loss of 80 per cent. in shafting, &c.; but this is probably an exceptional case, and a fair average figure would be 40 per cent. The following figures give actual results obtained from numerous tests to determine the actual power required to operate shafting, and also that necessary to drive machinery. For a very complete series of tests of power absorbed by motors driving different classes of machinery, the reader is referred to Mr. Selby-Bigge's paper read before the Iron and Steel Institute, Newcastle-on-Tyne meeting, 1902, and published in Engineering, vol. lxxiv., page 488, and vol. lxxv., page 71. TRANSMISSION OF POWER. 949 Table 11.-Power Absorbed by Shafting and Machinery. (Flather.) Name of Firm. Lane and Bodley J. A. Fay and Co. Union Iron Works Frontier Iron and Brass Works ·· ·· ·· Taylor Manufacturing Co. Baldwin Locomotive Works W. Sellers and Co. (one department) Pond Machine Tool Co. Pratt and Whitney Co. Browne and Sharpe Co. Yale and Towne Company Ferracuts Machine Co. T. B. Woods' Son Bridgeport Forge Company Singer Manufacturing Co. Howe Manufacturing Co. Worcester M. S. Company Hartford Nicholson File Company.. •• ·· .. .. ·· .. ·· .. Descrition. Nature of Work. Engines and wood-work- ing machinery. Wood-working machinery Engines, mining "" Marine engines, &c. Automatic engines Locomotives Heavy machinery Machine tools "" "" "" "" Cranes and locks Presses and dies Pulleys and shafting Heavy forging Sewing machines "" Machine screws 39 "" Files, &c. Average • Flax card.. .. Drawing frame of 156 slivers, per sliver Combing machine Rolling frame, 330 spindles, per 100 spindles Spinning frame (dry), 1480 spindles, per 100 spindles Spinning frame (wet), 2080 spindles, per 100 spindles .. .. ·· ·· .. .. ·· ·· ·· ·· .. .. ·· ·· • • • ·· .. .. • • • • ·· 58 400 400 25 95 2500 At Work. 102 180 120 230 135 35 12 150 1300 350 40 1.42 0.0794 0.151 2.434 2.515 1.613 400 350 346.4 Horse-Power. I Horse-Power. 55555 15 95 8 - 2000 500 11 67 11 75 Table 12.-Power Required by Various Tools. HORSE-POWER REQUIRED TO DRIVE THE MACHINES OF A FLAX MILL. (Cugnot.) } 1 41 61 75 105 85 305 17 100 300 Empty. 2.1 0.0934 0.555 2.627 3.21 2.24 68 24 ·· Henthorne gives as a result of fifty-five tests in New England 26 per cent. loss in belting and shafting, while Flather contends that his experience shows such losses to reach an average of about 40 per cent. of total power developed. The mean of the tests taken on 108 shops, by Fessenden, gives the average loss through friction as 69 per cent., while Gibbs, in a series of tests, found the average to be 52 per cent. 1 48 818 4119588 15 23 32 80 40 31 50 25 38.6 Efficiency of the Machines. per cent. 32 15 75 7.3 21.6 19 950 SECTION XII. I Table 13.-Direct-Driven Boring Mills, Working on Cast Iron. Size. 2007∞∞∞ONN ft. in. 4 5 6 6 8 8 8 10 12 12 0 10 to 16 ft. 14 0 in. 14 to 20 ft. 25 0 Size. 8 146678 £300000 £300000 ft. in. 0 0 0 0 12 0 12 0 10to 16 ft. 14 0in. 14to 20 ft. 25 Oin. Size in Inches. 38983 36 60 84 120 120 120 Diameter of Work in Inches. 2 2 47.0 28.0 8.0 57.3 60.0 85.5 Number of Cutting Tools. 1 84.5 54.0 70.0 12.5 96.0 73.0 21.5 172.0 220.0 25.7 34.0 59.0 Number of Cutting Tools. Diameter Number of Work in of Cutting Inches. Tools. 53.0 30.0 40.0 84.0 123.0 84.0 98.0 132.0 109.0 PPP- 2112~~~-~-~~-~~ Size of Cut in Inches. 4 × 1 & 4 × 1 Heavy rough ~~~~H~~~~~~~ 2 2 1 2 2 2 2 2 Size of Cuts. XX **** XX cut Running light fx f Running light 18.0 Running light 18.0 Table 14.-Direct-Driven Boring Mills, Working on Steel. Cutting Speed in Feet per Minute. Horse-Power Required to Drive Machine. ਤੇਲ X X X X X X *** in. and × "" "" *2006/20~+<*~* Cutting Speed in Feet per Minute, Material. "" >> "" ** "" 39 "" in. and "" रु १७ "; Size of Cuts. "" "" "" "" "" ནི, "" 18 "1 if x to do you do no Do not X : : XXXX :x :×× ____ co XX 29.1 S 7.0 18.0 CI 7.0 18.2 2.4 16.0 CI 6.6 3.1 3.6 XXXX 1414180 XXXXX Bojan m100-1 сокоди aojou anjeu aojta adjo Cutting Speed in Feet per Minute. 1000000 1000 LO|OO|~[X=# 24.6 17.6 20.9 27.3 31.4 25.3 34.9 35.3 25.5 17.9 Table 15.-Belt-Driven Planers, Working on Steel and Cast Iron. Horse-power Required to Drive 32.1 35.8 19.9 23.7 23.0 Rates of cutting speed to return speed 25.2 21.4 19.3 18.1 18.8 21.7 23.1 10.3 18.3 19.7 32.6 34.7 17.2 19.1 20.0 19.4 20.1 25.5 Horse-Power Required to Drive Machine. 2.7 2.9 2.0 = 1.3. 4.7 2.9 3.0 3.6 3.7 3.4 6.5 3.4 4.3 2.4 2.4 4.8 Cutting Reversing Return Reversing Stroke. to Return. Stroke. to Cut. 7.6 4.9 4.8 5.6 4.9 6.9 2.0 4.8 6.5 6.6 3.3 4.4 4.5 7.2 4.8 4.2 5.0 4.8 7.1 9.2 17.8 20.3 20.0 5.8 14 TRANSMISSION OF POWER. 951 Size in Inches. 120 120 Size in Inches. Table 16,-Direct-Driven Planer Working on Cast Iron. Cutting Speed in Horse-power Required to Drive Feet per Cutting Reversing Return Reversing Minute. Stroke. to Return. Stroke. to Cut. 12 12 12 18 18 24 60 3000000000 48 48 48 Number of Cutting Tools. 2 How Driven, DD ** "" "" "" "" BD PBD PDD ?? Ratio of cutting speed to return speed = 1.3. Table 17.-Direct- and Belt-Driven Slotters. Tool. 200 lb. Compact hammer ·· 72 in. Lathe 1 × } & { × } Running light Air Compressor Milling Machine Cold Saw Size of Cut in Inches. ·· Size of Cut in Inches. 7 ft. radial drill 8 ft. 36 in. drill." 30 in. drill (with tap- ping attachment) 26 in. drill to 32X 16X 18x 18X 42 in. rotary planer X11 X light ·· • jan makan majan DD = Direct-driven. PDD Portable direct-driven. Cutting Speed in Feet per Minute, 12.0 12.5 "" 13.5 10.0 "" "" 20.0 How Driven. 21.0 21.0 Belted D. Driv. Belted 7.25 Direct Driven Direct Driven Belted Direct Driven 18.0 18.0 Direct Driven Portable key-seater Belted Material CI CI MI S CI S CI B D = Belt-driven. P B D = Portable belt-driven. Table 18.—Horse-Power Required for Miscellaneous Tools. "" Material. Cast Iron "" "" Tool Steel Laminated Iron Tool Steel ·· Cast Iron 11.3 3.6 Cutting Reversing Return Reversing Stroke. to Return. Stroke. to Cut. Tool Steel Heavy Steel T Rail Cast Iron Cast Iron 23.8 24.4 1.8 1.0 1.7 1.2 1.1 3.5 7.2 4.4 4.75 1.3 } Horse-power Required to Drive 1.6 1.1 1.8 2.3 1.1 1.1 21.1 5.3 8.8 8.8 4.4 4.2 99 1.4 Class of Work. 7 "" M Drilling 3 in. hole "" "" 1 1.5 0.7 0.4 0.9 12.0 4.6 2.7 2.7 "" "" "" "" 7 Starting hammer Striking 245 blows per minute in. x 3 in. cut. Speed 36.4 ft. per of work 11.9 11.7 minute Diameter 37 in. Pumping against 80 lb. pressure 3 in. x in. cut. Fastest speed Feed in. per minute in. x 18 in. cut. Speed 39.7 ft. per minute Feed 2 in. per minute in. x 1 in. cut. Cutting Stroke Return Stroke 1.5 0.8 1.6 0.7 1.0 9.1 5.0 2.7 2.7 Horse- Power to Drive. 2.5 2.1 1.3 1.4 1.3 11.3 7.9. 3.6 15.3 1.2 2.3 8.6 2.0 1.5- 952 SECTION XII. : • The following table shows the approximate horse-power required to drive machines. The figures given indicate the horse-power required by the machines themselves, exclusive of shafting or gearing :- Table 19.-Power Required to Drive Various Machines. ÆRATED WATER, &c., PLANT, Bottle-washing machines-capacity 1000 dozen per day Double bottle-washing machine-capacity 100 dozen per hour Filling and corking apparatus-capacity 100 dozen per hour Soda-water machines-producing capacity 700 dozen per day 99 "" "" 1200 50,000 "" "" 99 AUTOMATIC ELECTRIC SIGNS. Sign consisting of 78 8-candle-power lamps.. BOOKBINDING AND BOX-MAKING PLANT. "" "" .. ·· "" "" "" ·· "" "" ·· ·· ·· "" .. Box-corner cutting machines Combined scoring, bending, and grooving machines-31 to 50 in. between side gauges.. 14 in. board-scoring machine 26 in. "" 42 in. "" "" .. • .. Box mangle Hydro-extractor-26 in. to 32 in. Ironing machine-width of ironing roller, 100 in. Wringing machines .. •• .. .. .. .. DENTAL SURGERY APPLIANCES. Wire-stitching and binding machines to stitch up to in. thick BRUSH-MAKING MACHINERY (see Wood-Working Machinery). CARPET-BEATING PLANT. Beater-taking carpet 6 yards wide .. Tumbler carpet beater-to beat 120 yards Willowing machine-for teasing cotton and woollen flocks CYCLE-MAKING AND REPAIRING. Automatic capstan lathe.. Dental engines FOUNDERS. Blower-to pass 2300 cubic feet of air per minute, at 1 lb. pressure per square inch Five-ton travelling crane (single motor) Sand-mixing plant.. •• Three emery wheels, two shaking boxes, drilling machine, and grindstone ·· LAUNDRY MACHINERY. ·· ·· ·· ·· .. .. "" "" ·· .. ·· ·· Amateur's lathe Drilling machine-for up to 2 in. holes Engineer's grindstone-4 ft. in diameter 6 ft. planing machine .. Sliding surface and screw-cutting lathe-7 in. centres •• •·· ·· LETTERPRESs and Lithographic Printing PlanT. Guillotine cutting machine-26 in. to 32 in. wide 38 in. to 44 in. wide "" Ink grinding mills-rolls 12 in. by 8 in. 18 in. 10 in. "" "" "" 24 in. 12 in. "" "" " Letterpress cylinder machines-demy, double crown .. .. -double demy and quad crown " Linotype (type setting) machines Lithographic machines-demy, double demy, quad royal Paper-glazing machines-to roll 27 in. to 36 in. wide Platen machines—foolscap folio, crown folio, and demy folio METAL WORKING MACHINERY, .. • ⇓⇓ .. • • ·· ·· • 4 : ·· .. • ·· ·· •• • Horse-power. 1 .. ·· ·· • : .. .. ·· • • .. •• •• ·· * 1 12 21 3 to 5 23 k 2 PŘ 1 11 13 1429 3 } ***** NAKANAN " 6 6 6 1 궇 ​to 초 ​20 3 3 to | p 1 to 3 "" et 1 3 4 5 1 -de enfer *** 322 "" "" LO O 3 LO CO 5 - 0"""" 2 5 6 457 -ลง to to 1 3 1 3 11 I TRANSMISSION OF POWER. 953 Glazing calendar-paper 80 in. wide Paper machines Rag engines.. Rotary cutting machine "" "" "" "" • To move 1,000 to 1,500 cubic feet of air per minute 2,000 3,000 3,000 6,000 6,000,, 9,000 20,000,, 45,000 "" "" "" .. "" PACKING-CASE MAKING MACHINERY (see Wood-Working Machinery). UMBRELLA AND STICK-MAKING PLANT. Eight lathes and eight sewing-machines (combined) VENTILATING FANS. Portable desk, ventilating fans, and motor (combined)-suitable for offices, &c. ·· .. "" "" "" "" 16 in. 6 in. Combined roller-feed timber and deal frames- To saw logs 16 in. in diameter by 25 ft. long 42 in. 45 ft. "" Tenoning machine.. "" "" "" "" PAPER-MAKING PLANT. ·· ·· ·· "" "" "" "" "" "" "" "" "" by 6 in. thick Log-sawing machines for trees up to 4 ft. diameter 6 ft. "" "" .. Automatic powder weighing machine Boot-polishing machines.. Cake and whisking machines Coffee-roasting machine "" .. WOOD-WORKING MACHINERY. Band saw machine-to saw 16 in. to 22 in. deep Combined band saw machine and saw bench-to saw 9 in. deep planing and moulding machine, for flooring and matchboarding- For planks up to 9 in. wide by 3 in. thick "" ·· ·· "" Dovetailing machines-to dovetail up to 15 in. to 36 in. wide by 14 in. thick "" Cutting machine Dough brakes Dough-kneading machines- sack "" "" "" "" 12. ·· Rack circular saw bench- Saws up to 42 in. in diameter, to saw 16 in. deep 78 in. 33 in. .. Four-cutter general joiner-to saw 9 in. deep, to plane 9 in. wide by 3 in. thick ·· •• Fret-saw machine to cut up to 8 in. deep Joiners' and box-maker's cross-cut saw bench, to cross-cut 24 in. wide 1 11 2 3 4 ·· ·· ·· "" "" Rounding machine-to round up to 14 in. in diameter 3 in. .. ·· "" "" "" "" "" Moulding-iron grinders, saw-sharpening machines, and sand-papering machines Pattern-makers' lathe ·· · • • • ·· MISCELLANEOUS TRADES. ·· ·· ·· ·· ** Rack-feed timber frames-logs 16 in. 'in diameter by 25 ft. long 36 in. 40 ft. "" .. Rip saw-cutting speed 9000 ft. per minute, ripping hard wood 6 in. thick at 10 ft. per minute Roller-feed timber frames-for logs 23 in. in diameter by 25 ft. long •• 30 in. 35 ft. "" .. "" ·· ·· Combined blending and sifting machine Crane-worked by friction wheels, 10 cwt., 60 ft. per minute 10 cwt., 90 ft. ·· ·· ·· ·· •• .. • ·· ·· :: " .. ·· .. ·· ·· •• .. ·· ·· .. ·· •• ·· •• · .. .. ·· · ·· •• ·· .. ·· ·· ·· .. •• .. ·· •• ·· ** ·· · ·· .. :: · •• .. • •• •• .. ·· ·· :: ·· · 15 to 30 25 30. 15 35 1 4 57 3 12 LO 1 5 10 2 5 14 4 == 1 1 } Ha C10 pond jonk 211 -- 4 ma 5 6 46 888 "" " "" 11 "" 1 1 " 3 },, 1 "" " to 1 5 "" "" "" ♥ ♥ ♥ ♥ "" "" "" " 99 "" 183 :::: 0 :: 1100-1400 " "" "" "" 4 15 "" to : : : : : +2: 5 to 6 8 34 6. 8 2: 4. 14 6 commit phot 1 1 5 7 1 3. B 16. 5 12. م مدرسه 9. 1 NOÌN 14 3 2 2 2 4. 5 2 6 2 to 6 69 954 SECTION XII. • • Goods hoist-worked by gearing, 10 cwt., 60 ft. per minute Jewellers' plant Organ blowing Pressure blowers for foundry work Press pump Sack cleaner. .. .. .. Watchmakers' plant Woodburn disintegrator •• • Light.. Working Two 12-in. Lathes-Light Drill-14-in. spindle, 6-in. stroke Saddlers' sewing machine Sewing machines .. Sausage machines Shafting 24 in. in diameter, per 100 ft. at 120 revolutions Sifting and dressing machine Stuff-folding machines and cutting machines Sugar mills ·· Mr. Raworth has given the following figures: Wood Planer (12-in. cutter) :— ·· Light.. Drilling 1-in. hole .. • Power Metal removed Time occupied ·· ·· ·· Cutter running light Cutter and bed running Cutter take cut 3 cuts to in. on 3 in. pine.. Circular Saw-10 in. in diameter: Running light Cutting 3-in. pine ·· Band Saw-wheel, 28 in. in diameter; saw, & in. :- Running light Cutting Grindstone-4 ft. in diameter, 7 in. wide Lathe-2 ft. 6 in. centres: ·· ·· ·· • ·· .. .. • ủ •• ·· ·· .. ·· · ·· .. •• •• .. .. ·· .. .. ·· •• ·· • .. .. •• •• • • :: ·· • .. :: .. •• .. from Power Metal cut Time occupied being an average of 275 watts per ounce of metal removed per minute. driven by motor direct :— ·· 41 5 ·· Average 143 watts per ounce per minute. 1 1 to 2 3 1 ++++*+ 玄​圣女 ​03 རྣཊྛུུསྶ༠=S ; :+S ||1=400 coke Mr. Langdon gives the following experimental results :- To drive a 9 in. screw-cutting lathe No. 1 light, while all other machines and belts are at rest clear of the shafting, requires 381 watts; and the power absorbed when the machine was loaded, that is, when the tool was turning down a bar of gun-metal at the rate of 1.1 ounce per minute, was only 545 watts; or the lathe running light consumed 381 watts, and the work done 164 watts, or at the rate of 495 watts per ounce of metal removed per minute. By gearing an electric motor of low efficiency direct to the same lathe, and setting it to precisely the same description of work, the power consumed was at the rate of 214 watts per ounce per minute. In each case the greatest care was taken to insure equality in the cutting power, shape, and cut of the tool, and one cut only was made. The work dealt with by the same No. 1 lathe when making three cuts simul- taneously, each of the same character as the previous single cut, gave the follow- ing results, when driven by belting :— 1007 2290 968 1738 164 768 1200 318 19 3 Net Watts 1078 1188 1738 404 818 1188 watts 9.75 ounces 2.25 minutes 1 to 616 watts 9.75 ounces 2.25 minutes LM 1 3 to 6 76 1 - mky 1 When Multiplying the watts by the time occupied in doing the work in each case, the relative value is found to be :- One cut. By belting, 2207; by motor, 769 Ratio Three cuts. By belting, 2675; 3 to 1 by motor, 1386 Ratio 2 to 1 TRANSMISSION OF POWER. 955 Electric Distribution of Power in Factories. The arrangements adopted must be in each case carefully considered, as the possible economies can be very easily swallowed up in losses, due to interest, &c., upon the capital spent. • A good method is to group together machines which are similar in character, and that usually run simultaneously, and drive them by a single motor, reserving for independent driving the larger machines. In an engineer's workshop the larger tools often stand idle for long periods; and so it may be less expensive to provide interest upon the extra cost involved in the motor and switch, than to pay for driving the countershaft continuously, whether fully loaded or not. Tests made at Messrs. Bennett's Works, Manchester, by Messrs. Lacey, Clirehugh, and Sillar. :11 " 1898. Date Oct. 4 "" 99 "" "" "" "" "" * "" "" "" "" "" Table 20.-Details of Power Required to Drive a 24-In. Saw Frame. "" 5 44 LO LO LO LO LO LO HHHHH~~ MI 1212~H~TH&SHIQ3+ Number of Trial. 6 6 6 6 1 1 1 5 2 777 1 5 3 1 1 Number of Log. 1 1 4 4 Number of Saws. 12 1 12 17 12 12 11 13 21 14 14 15 15 28 28 28 28- Size and Character of each Log. ft. in. 27 21 15 10 in. 8 x 16 deep. 6 x 16 "" 13 9 3 x 17 20 0 × 17 31 3 x 17 24 3 X 15 17 0 X 16 17 3 x 16 16 0 X 22 16 6 × 23 16 0 × 23 13 8 × 22 6 x 16 3 x 16 0 X 14 3 x 18 "" "" "3 "" 99 "" "" " "" "" "" 19 99 "" Birch .. " "" 91 "" "} Pitch Pine Am. Ash "" "" 99 Yellow Pine "" "" "" British Thermal Unit for each Log. 14.8 13.7 11.1 13.3 8.8 4.77 4.3 13.6 15.1 10.5 8.1 7.7 17.6 16.4 20.6 Power required to start machine = 23 horse-power. Machine running light = 9.75 " Cutting each Log. Time min. 63 50 51 49 35 22 ANCINE :20000 19 42 41 32 29 48 58 Horse-Power for each Log. 19 22.21 17.6 21.8 20.4 17.4 18.3 26.2 19.3 20.7 20.6 21.1 27.4 29.1 27.4 28.6 Advantages of Electrical Transmission. Advantages of electrical transmission are thus stated by Mr. Raworth :— 1. Absence of overhead shafting and belts, which ordinarily require special construction of workshops, and interfere with the arrangement of machines. 2. Saving of time in repairing belts. 3. Easy application of power to special appliances, such as boring bars for large cylinders, and key seating tools for flywheels. 4. Facility of working overtime on even one machine, without any increase in the cost of power. 5. Increase of output. 6. Moreover, it is found with a constant speed that a higher speed may be adopted for the tools, which results in a still higher output of work. At Messrs. Richardson's works, where electric driving was adopted, the speed of the tools was increased by an average of 20 per cent., with a corresponding increase of output. In a rail-rolling mill in the United States, it is stated that the work hitherto done by 6000 hands with separate engines can now be accomplished by 4000 hands with electric power. 956 SECTION XII. www. Table 21.-Horse-Power Required for Woollen Mill Machinery. (Hartig.) Description. Washing machine, two cylinders Centrifugal pump for this machine Hydro-extractor Burring machine.. Scutcher, continuous feed Opening machine Scribbler card, 40 in. wide Intermediate card, 40 in. wide Finishing 99 ·· One spindle, spinning doubling ·· Brushing ?? • Loom, 7.45 ft. wide Scouring machine, for two pieces Fulling mill, one cylinder, ·· ·· .. • ·· across one cylinder two cylinders ·· ·· "" .. Sizing and warping machine (without ventilator) ·· ·· .. .. nouveautés Fulling mill, three cylinders, for cloth "" Double fulling mill, for nouveautés cloth Single fulling stock, two stamps, (Dobbs) Double fulling stock, two stamps, (Spranger's) Gig (Laineur), single, without spreader double Machine for dressing the reverse side, "" .. · ·· for •• ·· with cylinders Machine for dressing the reverse side, with eccentrics Wringing machine, lengthwise "" "" " ·· ·· .. ·· .. · Ordinary Speed in Revolutions per Minute. revolutions 35 300 1000 to 1200 350 500 "" 300 350 to 450 110 2500 1100 17 40 to 45 40 100 45 110 100 45 blows 125 116 revolutions 90 100 100 100 650 1000 250 250 Horse-Power. At Empty. Work. h.p. .75 1.47 199251:8 .005 :: AE89 89 92 = 2222 .13 .19 .17 .71 .30 .16 .53 .43 .19 .20 .11 .17 .52 .37 h.p. .223 .77 1.20 1.77 .66 .95 .58 .43 .0027 .006 .071 .113 .50 2.54 1.59 2.74 3.40 3.26 1.64 1.99 73 1.38 2.03 2.45 .61 .31 1.03 Efficiency of the Machines. per cent. 118528981 39 17 55 40 36 13 IIN ***N 74 93 89 73 91 95 78 74 28 * *** 74 86 94 93 14 22 64 1 SECTION XIII. ALTERNATING CURRENT TRACTION. 4 SECTION XIII. ALTERNATING CURRENT TRACTION. GENERAL. "This much is certain-that alternating-current traction in some form is highly desirable for much of the future railway work; that it has already made progress enough to deserve serious consideration and to ensure future growth; and finally, that if the large experiments now under way turn out well, alternating- current motors will be pushed into very extensive use both in new work and in the re-equipment of systems in which direct-current traction has been forced beyond its economical limits.”—(Dr. Louis Bell.) There can be no doubt as to the reliability and suitability of the direct-current system for all purposes, no matter what the maximum speed to be obtained, or how high the desired rate of acceleration, or how heavy the weight of train to be hauled may be. But from a financial, and from the ordinary railway man's point of view, it possesses serious disadvantages when compared to the alternating- current system. It necessitates, in order to comply with the Board of Trade's regulations, not only a third rail, but in most cases a fourth rail as well; and if it is to be used on an extended system, all current has to be generated in the shape of high-tension polyphase currents, which have then to be transformed first to low- tension alternating currents, then to direct currents, and finally distributed by means of low-tension conductors. The capital cost of a complete direct-current third-rail system, with high- tension three-phase transmission and rotary converter sub-stations, is much greater than that of an equivalent single-phase system, and the operating costs are larger than in the case of a three-phase one. Some of the main items of the former are the cost of the additional current which has to be generated in the station, owing to the loss in transformation, as well as additional costs involved in operating and maintaining rotary sub-stations, and interest on the greater capital involved. It has been held by some that the cost of overhead construction used with single-phase high-tension railways is greater than the cost of installing the third and fourth rail, but such statements do not bear careful examination; and, as far as Great Britain is concerned, where a fourth as well as a third rail, is in most cases practically a necessity, it will be found that the cost involved by such a construction, and by the necessary inter-connection between the different rails which must be effected, is, if anything, larger than the very best and most solidly- designed overhead construction. Even if the expense of construction and operation were of little importance, there is another reason which militates seriously against the adoption of direct current and third rail by the main-line railways of Europe for long-distance service. The bulk of European railway engineers are opposed to the introduction of the third rail, and, without going into the merits of this opposition, it will suffice to state that if a third rail were essential to the use of electricity, it is very proble- matical whether electricity would ever be introduced on a serious scale by most of our railways. As long as there is a system which, while obviating the use of a third rail, possesses the following principal characteristics, it will be adopted by the railways in preference to the direct-current one, necessitating a third or fourth rail. The characteristics are:- Rapid acceleration from starting to maximum speed. Reserve power and speed for making up lost time. Simplicity and efficiency of equipment and economy in power consumption. Ease of extension and adaptability to run over existing systems. 960 SECTION XIII. I 1 SINGLE-PHASE MOTORS. Broadly speaking, there are at the present moment on the market two definite types of single-phase motors. The one designed, built, and advocated by the Westinghouse, Siemens-Schuckert and General Electric companies, may be called for the sake of briefness, the "plain series motor." This motor has been brought to a great state of perfection by the Westinghouse Company, and the general results obtained by its use seem to be excellent, and appear to be in every way satisfactory. The other type of single-phase motor may be broadly called the compensated repulsion type. The most satisfactory example of this type, up to the present, is the Winter-Eichberg motor, manufactured by the Allgemeine Elektricitäts Gesellschaft, the rights for which, in Great Britain, are owned by the British Thomson-Houston Company, who are the joint contractors with the Allgemeine Elektricitäts Gesellschaft, for the electrification of the London, Brighton and South Coast Railway. A motor, much on the same lines, has also been put on the market recently by Messrs. Lahmeyer. The Plain Series Motor (FIGS. 1 and 2.) This motor (Fig. 1) as its name implies, is an adaptation of the direct-current series motor, the alterations and additions being of a nature to reduce sparking at SIMPLE SERIES MOTOR F A 1 WINTER EICHBERG ว COMPENSATed RepulsION MOTOR. Field 2 3 Exuter brushes Short circuiting brushes Exciter Transformer. munting Autotransformer. COMPENSATED SERIES MOTOR. အင်္ဂါ အပ်ချုပ် I 꾸 ​ 1144 the commutator. As is well known, any ordinary series motor can be operated with single-phase current, and it is on this principle that Messrs. Deri and Lamme and Dr. Finzi started, having been followed by the General Electric Company of America and by Messrs. Siemens-Schuckert. The various devices which have been adopted for decreasing the sparking may be roughly divided into two categories, namely, the compensated coil method and the use of resistance in the armature circuit between the armature coils and the commutator. The compensated coils may consist of short-circuited windings on the stator, which was the arrangement first adopted by Deri some seven years ago, or an I с D E D A PAÑA. A. Main Transformer. B. Exciting Transformer. C. Stator Winding. R. 5 A D. E. Reversing Switch. 1, 2, 3, 4, 5. Contactors. Resistance. Ground Trolley 2 P 6 Fig. 4. Winter-Eichberg Four-Motor Single-Phase Equipment. Motor Equipment with Regenerator shown_thus • First braking position; first braking 6 is closed; second braking 7 is closed. Rotor Winding. Position of Controller. I. II. III. IV. V. с D E D 5-1 5 - 2 5-3 O 1150. Contactors Closed. 4-2 4-3 ALTERNATING CURRENT TRACTION. 961 ,: 1 II 962 SECTION XIII. additional shunt coil on the stator, which, in combination with the resistances between the armature windings and the commutator bars, is that which has been successfully adopted by Siemens-Schuckert. The Westinghouse Company im- proved the resistances by dividing them in such a way that each resistance only remains in circuit during the time that the commutator bar to which it is attached is covered by the brush. The Westinghouse Company has further introduced a compensated or neutralised winding, which is in series with the armature, and is reversed when the armature is reversed. In the case of the compensating shunt- winding mentioned, it would appear that to make it in any way satisfactory, some regulation of this winding is necessary, so as to insure the compensating field remaining always at right angles to the main field at all loads and speeds. Diagrammatically these arrangements as regards compensating are shown in Fig. 2. The Compensated Repulsion Motor. (FIGS. 3 and 4, pages 960 and 961.) Having briefly examined the connection and construction of the series motor, we will now as briefly investigate the compensated repulsion motor; a diagram of the connections is given in Fig. 3. It will be seen from this diagram that the construction and connections of this motor are totally different from the plain series motor. The field winding can be entirely separated from the armature winding, and it is therefore possible, if it is wished, to wind the field in such a way that high-tension currents can be directly employed to excite it. The only low-tension current required to be taken from the line would then be that supplied to the exciting brushes on the armature. In many instances it is preferable to use low-tension motors, in which case all the current required by the motors has to be transformed from the high pressure to the maximum low pressure usable just as in the case of the plain series motor. If high-pressure windings to the stator or field are adopted, only a comparatively small portion of the current-namely, that required for the exciter brushes-has to be transformed, In the case of low-tension motors series-parallel controllers are used, the rotors being generally kept permanently in series; while the stators are first started in series, and later on are put in parallel. The connections as proposed to be used on the London, Brighton, and South-Coast Railway are shown in Fig. 4. Characteristics of the Single-Phase Equipment. (FIGS. 5 and 6, pages 963 and 694.) Before describing some of the single-phase motors which have been made on this side of the Atlantic, it may not be out of place to see how far the single-phase motor is suitable for operating suburban trains; as there still appear to be many engineers who are of the opinion that, while single-phase traction may with advantage be used for long interurban roads and over those lines where rapid acceleration is not of primary importance, it is not suitable for handling suburban traffic, where rapid acceleration is of vital importance. In this connection the decision of the officers and directors of the Brighton Railway Company to adopt the single-phase system of haulage, after most careful investigation, is of great im- portance; especially as the conditions which the railway company required to be fulfilled were probably among the most stringent that have ever been issued, and the guarantees which are required from the tenderers were of the most far-reaching character, and every guarantee given had to be based upon actual experimental results. Figs. 5 and 6 are two diagrams which have been compiled from experimental data; both show the running of a three-car train through a distance of 1225 meters on a level and straight track. Each train was composed of two motor-cars and one trailer-car, and was propelled by eight motors. The only difference was that one train was operated by direct current and the other by single-phase current. The comparative weight and the result obtained are given below: Direct Current. Weight of three-car train including 220 passengers •• Add for revolving motors Gear ratio Average power factor Watt hours per ton kilometer Efficiency .. • •• ·· .. 110 tons 9 per cent. 1 to 3.5 44.6 72.8 per cent Single-Phase. 117 tons 11 per cent. 1 to 3.7 0.85 {(41.3) if regenerating 72 per cent. ALTERNATING CURRENT TRACTION. 963 But the curves of the performance of the two trains show far more than would be apparent from the above table, and clearly demonstrate the advantage of the use of a properly designed single-phase motor as regards acceleration. From them it will be seen that whereas with a direct-current motor it took 44.11 seconds to reach a speed of 34 miles per hour, with a single-phase motor equipment 34 miles per hour were reached in 32-11 seconds. The curves also show that in the case of a direct-current motor the acceleration is only fairly constant for about half the total period of acceleration, after which it rapidly falls off; whereas, in the case of Speed in Miles per Mour Milo Voll Amperes 36 38 40 8 * X 16 18 20 22 24 26 23 30 N 3 * 8 9 + O 1131 8-28 70 7:55 Kilowatt 7-65 24-52 Time in Seconds. 487 .61 2 Time in Seconds. ALTERNATING MOTOR CURVE CONTINUOUS CURRENT # SHOWN THUS 15 35 15-08 1146 Fig. 5. Comparative Curves of Alternating and Continuous-Current Motors. the single-phase motor the acceleration is practically constant throughout the whole period of acceleration. Fig. 6 gives efficiency, speed and power-factor curves of the W. E. I. single-phase motor used in this test. The dark lines indicate the different transformer ratios employed to obtain the different speeds. The diagrams given for the direct-current train were calculated for eight GE 66 motors, manufactured by the Allgemeine Elektricitäts Gesellschaft. The single-phase diagram includes eight W. E. I. Winter-Eichberg motors. It will be seen that the maximum kilowatt is somewhat greater in the case of a single-phase than in direct-current; but it will be observed that this maximum comes at a later stage than in the case of the direct-current, and that the result of it is a higher rate of acceleration. The diagram clearly proves that the single- phase motor is eminently suitable for heavy traffic and rapid acceleration, or, in other words, for handling suburban trains. 964 SECTION XIII.* : Mi Kg. 1500 4200 1100 1000 900 800 700 600 $00 400 300 200 Power Factor 100 29 B : 0.4 1001 * Km. per hour. ad 50% az 80% 45 40 $5 30 25 20 16 10 Efficiency In $ including gearing 10% 60% 2 50% W W.E. I.MOTOR. 6000 Volt 25 Cycles 18 10 10 12 .12 Efficiency 194. M. amp 16 16 15% Fig. 6. 19 13/1 [127 Speed in Kmk's her Hayr 12. 10 94 13% Power Factor 14%, * ~ 18 20 22 24 £4 VA K9 Draw bar Aulin 22 2 24 26 24 %, 28 20 so amp. 30 1147. The Westinghouse Single-Phase System. (FIGS. 7 and 8, pages 965 and 966.) The car equipment, which is shown in Fig. 7, consists essentially of trolley circuit-breaker, main auto-transformer, induction regulator (or hand-controller), reverse switch, motor cut-out switch, and motors. With the induction regulator control, the regulator reverse switch and circuit-breaker are operated by com- pressed air from the brake system of the car, controlled by a master-switch through electro-magnetic valves. The induction regulator consists essentially of a transformer whose primary core and winding can be moved relatively to the secondary. In the position for starting up the motor, the regulator generates maximum voltage opposing the voltage of the main auto-transformer; when the primary is moved through 180 deg. from this position, the voltage aids that of the transformer. With the winding in an intermediate position, the voltage of the secondary is zero. The motor is started up with the regulator in the first position, and the regulator is then gradually moved until it takes up the second position mentioned, where its voltage is a maximum and aids the auto-transformer. This is the full speed position. ALTERNATING CURRENT TRACTION. 965 With hand control the motors are connected successively to different taps on the main auto-transformer. A motor voltage of 250 volts at full speed is adopted, regardless of the voltage on the trolley. Lighting the car is managed by a small auxiliary transformer reducing the TROLLEY HO 1000 2> 0000 Չ www..... 0000 d 0000 e RAIL d=Field of motors. c=Reversing switch. ƒ=Equalising transformer. Fig. 7. Diagram of Connections in Car for Westinghouse Single-phase System. a=Auto-transformer. b=Induction regulator. e=Armature. pressure to about 50 volts, and this transformer also supplies a series alternating- current motor for operating the air compressor. Usually the motors are connected permanently in parallel, which allows the use of a simple reverse switch. The motors weigh approximately the same as direct-current motors of the same capacity, and the regulator and transformer for a four-motor equipment 996 SECTION XIII. .! measured by thermometer. carry at standard voltage for one hour, with a temperature rise of 75 deg. Cent., from that of a direct-current motor. The rating of the motor is the load it will The external appearance is similar to that of direct-current motors. The entire magnetic part of the field is laminated. The armature is not essentially different LIGHTING TRANSFORMER “FUSE BLOCK мий Family www wwwwwww $ CIRCUIT BREAKER Fummer I 1000 M5 MISER.CO 8-342 #25 CABLE -408 V. TRIPPING COIL -1080 V, www 1C 20 BC 408 V. 9-842 #25 CABLE T1, *12 WIRE 3-942 CHANGING SW. 3-342 #25 CABLE #12 WIRE 61 +17 CABLE PAT.K.8784 M3 M4 M6 M 7 RAEV.RES HP. NIVW/ MAIN AUTO 3-342 25 CABLE PAT.K. 8794 MB SWITCH 1284 GROUND INDUCTION ~REGULATOR 2-25922 CABLE PÁT.K. 6794 WITH THE FOLLOWING. VOLTAGES IMPRESSED ON| LEADS. 1 - 8 --- 1100 V, 2-8--- 1050 V. 8-8---1000 4-8- V. 955 V. 5-8--- 400 V. -STYLE 1389 L.A. ∞∞ ∞ a 300 will be obtained from 6 - 8 and 280 from 7 – 8. 2-259 #22 CABLE 8-842 #26 CABLE 3-342 #25 CABLE 19 #21 CABLE 50 2-342 #25 1/2 2/2 12/24 50 A2+ A MOTOR CUT OUT 1234 2-342 #25 19 #21 #12 WIRE elle 0000 #21 19 #21 19 1921 2-342 #25 www. B3 1294 BALANCING COIL F3+ elle -82 {[F4+ REVERSE SWITCH FOR. Fa REV. FOR. REV. 2-342 #25 A3+ 1A3- 1A4- 0% TA4+ A3+ 2-342 #25 96% OPE-G 3-342 #25 Cable CANOPY SWITCH MB ! Fig. 8. Diagram of Controller and Motor Connections for Westinghouse Single-phase System. 8-342 #25 CABLE MOTOR CUT OUT. 1. Motors all in. 2. Motors 1 & 2 out. 3. Motorn 3 & 4 out. 4. Balancing Coil out. Motors are being built in standard sizes of 50, 75, 100, and 150 horse-power. equipment of equal capacity. everything included, weighs about 15 per cent. more than a direct-current together weigh about the same as a single motor. The complete equipment, ALTERNATING CURRENT TRACTION. 967 • At full load the power-factor is approximately 90 per cent or more. power-factor at starting is low. The The car now in operation at Pittsburg, Pa., is equipped with four single- phase motors, as well as the necessary controlling and regulating apparatus. Fig. 8 gives a diagram of the controller and motor connections for four motors. The motors are connected up in pairs, each pair being connected with the two fields and two armatures in series respectively. A balancing transformer is connected across the two pairs of armatures, and the point of connection of the armatures is joined to the middle point of the transformer winding. This equalises the voltage of the armatures. A master-controller on each platform controls all operating switches; it consists essentially of a metal drum made in one casting, with contact points arranged to give the proper combinations, rubbing against stationary contact fingers. All the switches are of the drum type. The main and reversing switches are operated pneumatically, and controlled by magnet valves. The motor cut-out switch is hand-operated. The controlling mechanism is operated by current from a storage battery. By bringing out a few loops from the secondary of the main transformer, the same car can be operated from different trolley voltages without change in equipment. Winter-Eichberg Motor. (FIGS. 9 to 11, pages 967 and 968.) This motor is illustrated in Figs. 9 to 11, on pages 967 and 968. It consists of a rotor or revolving armature and fixed stator or field magnets. The winding of the stator is similar in form to that of ordinary induction-motors and generators, and has no salient poles. The field-winding is laid in slots. The rotor has a commutator and two pairs of brushes which are electrically 90 deg. apart. The first pair of brushes coincide with the axis of the magnetic-field, and are short- circuited. The second set are electrically 90 deg. from the former, and are called -1435- BACK VIEW. | Fig. 9. Motor for Winter-Eichberg Spindlersfeld Line, Manufactured by Allgemeine Elektricitäts-Gesellschaft Company. + exciting-brushes. They are connected to the secondary of a transformer, the primary of which is in series with the high-tension stator or field-winding. The voltage of the exciting current can be regulated by varying the number of coils connected; in other words, by varying the transforming ratio. The use of this transformer enables a very high pressure to be used in the fields, whilst a low pressure can be used in the armature-winding, and hence obviates the difficulties which would arise if a high pressure in the fields necessitated the same pressure to be used in the armature, as is the case with the series-wound alternating-current motor. 968 SECTION XIII. 邋 ​+ The current which flows in the armature sets up a magnetic field at right angles to the magnetic field produced by the stator or field winding. As the current supplied is alternating, a transformer action takes place between the field and the armature winding. The field produces an electromotive force in the -730- Fig. 11. 505 420 SIDE ELEVATION. Fig. 10. Motor for Winter-Eichberg Spindlersfeld Line, Manufactured by Allgemeine Elektricitäts-Gesellschaft Company. - plang dapa 1052 1269- PLAN. -335- a Motor for Winter-Eichberg Spindlersfeld Line, Allgemeine Elektricitäts-Gesellschaft Company. armature winding, which causes a current to flow through the short-circuited pair of brushes on the commutator. This current, in combination with that produced by the armature revolving in the magnetic field, causes a torque in the same direction as that due to the latter, the value of the torque varying with the field strength and the current in the armature. When the armature is in motion, its ALTERNATING CURRENT TRACTION. 969 conductors cut the magnetic field, and an electromotive force is generated which decreases the effective electromotive force on the secondary or armature winding. Thus, as the speed increases the secondary current decreases, and the torque is reduced. An additional torque is obtained at an increased speed by increasing the electromotive force of the armature excitation. The reversal of the direction of running is obtained exactly as in a direct- current series-wound motor, by reversing the direction of the current either in armature or field, and this is obtained by reversing the switch on the secondary of the transformer which excites the armature. This motor, therefore, acts in a very similar manner to the ordinary direct-current traction motor, but with the added VØ www YY -F 1. Fig. 12. Connections of Winter-Eichberg Motor. effect due to the transformer action which takes place between the field and the armature. The connections of the motor are shown diagrammatically in Fig. 12. As will be seen, the high-tension current, at a pressure of 6000 volts in this case, comes through the primary of a transformer into the field or stator of the motor, and from there back by the track rails; the secondary of the transformer is connected to two brushes resting on the commutator of the armature or rotor of the motor, which are electrically at 90 deg. to the axis of the principal magnetic field, which is produced by the stator. The armature is wound in very much the same way as an ordinary continuous-current series traction-motor, except that the voltage between the commutator segments is kept very low, and thus a larger number of commutator segments are needed than in an ordinary continuous-current motor. The commutator is short-circuited by a pair of brushes on the axis ☀ of the main field. I 12 970 SECTION XIII. The secondary of the transformer has five connections, by which the ratio which exists between the primary and the secondary can be varied. By this means the voltage of the compensating or armature exciting current can be varied. The effect of increasing the pressure of the armature exciting current is to shift the speed, torque, efficiency, and power-factor curves. For a given ratio of transformation a certain torque, which corresponds to the greatest efficiency of the motor will be reached, at a given speed of the armature. If the ratio of transforma- tion is decreased, that is to say, if the armature exciting voltage is increased, the same torque and efficiency will be reached, at a greater speed of the armature. In other words, the arrangement enables a nearly constant torque to be obtained, with high efficiency and high power-factor at five different speeds. The result of this is, that more favourable acceleration curves are obtained than could be with continuous- current traction motors. Thus, with continuous-current motors, the acceleration, which is very large at starting, rapidly decreases as the speed of the car increases; and therefore, in order to obtain an average acceleration of, say 18 in. per second per second during the whole period, it is necessary, at the very commencement, to reach an acceleration which may be as high as 4 ft. per second per second, and this causes a correspondingly large starting current. In an Allgemeine Elektricitäts Gesellschaft single-phase motor, the acceleration could be kept very nearly constant during the whole period of acceleration, and therefore the very large starting current necessary with continuous-current motors, will not be required to the same extent where alternating-current motors are used. Characteristic curves of this motor, giving the speed, tractive effort, efficiency, and power-factor, are given in Fig. 6, page 964. Each of the curves is numbered, the numbers corresponding to a given position of the secondary transformer switch, that is to say, a given excitation electromotive force. At When the motors are stopped, the secondary circuit of the transformer is opened. The primary then acts as a choking coil, and very little or no energy is wasted in the stator of the motor; and for this reason it is not necessary to open the high-tension circuit in ordinary running; if trains have to stop a very long time, the high-tension circuit can be opened by means of a special switch. starting no energy has to be wasted in resistances, as is the case with con- tinuous-current motors. The energy being in the form of wattless current at starting, causes the power factor to be low, but only for a very short period, and it rises rapidly as speed increases, and can be arranged so that at between 10 and 15 miles an hour the power factor is above 0.7; and in fact, in making calculations for a complete system with a large number of trains operating, it will probably be found that the average power factor for the whole system will be between 0.8 and 0.9, or quite as good as the power factor obtained where rotary converters are used, as on the Central London and Lancashire and Yorkshire. The controller methods used are similar to those illustrated in the diagram, Fig. 23, on page 983, which shows the controller connections. The controller is similar in appearance and construction to the master-controller used in the multiple-unit system of the General Electric Company of America, where continuous currents are used, and similar to the system adopted on the Central London and the City and Great Northern, and the North-Eastern Railways. A separate controller is supplied for reversing. The magnetic switches are installed on the side of the car, where they are easily accessible, and they are operated by low-tension current supplied from a special small auxiliary transformer, which supplies current for lighting as well as for operating the motor-driven air compressor operating the brakes. A resistance is put on the cars, but is only used to short-circuit the armatures of the motors when braking; and when this connection is made through the controller, the motors act exactly as continuous- current motors do. Before the car can be started the reversing switch has to be in the forwards position, and the high-tension circuit-breaker must be closed. Current is then supplied to the electromagnets which operate the switch controller, the handle can then be moved and the various switches closed as required. The handle of the master-controller is supplied with a button which always has to be kept pressed down by the motor-man; should he leave go of this handle, two things will happen: firstly, the current will be cut off from the electro- magnetic switches by the rising up of the button, and therefore the secondary circuit of the transformer opened, and the motor brought to a standstill; and, secondly, the controller handle will go back to the off position, will also put on the air-brakes, therefore any accident to the motor-man will cause immediate stoppage of the train. Should the motor-man release his handle, or take his thumb off the button whilst running, it will be necessary for him to start again from the begin- ning, and therefore no damage will be done to the motor. ALTERNATING CURRENT TRACTION. 971 5mm Dmr. ·1,5· Fig. 13. Overhead Construction used on the Spindlersfeld Single-phase Railway. T 972 SECTION XIII. The trolley is raised and lowered from the wire by means of compressed air.. The high-tension circuit-breakers and wiring are entirely enclosed in fireproof casing, which can only be got at when the trolley is down, as the door is locked when the trolley is up and cannot be opened until the trolley is down; and this is immediately connected to earth, so that even should some accident happen to the high-tension wire connected with the trolley, no damage can be done by handling the high-tension conductors as they are earthed; the current and the voltage dealt with by the master and reversing controllers are all very small, and no high-tension current can by any means be got at, either by the drivers, conductors or passengers. Fig. 13 shows the type of overhead construction employed on this line. Single-Phase Motor of the General Electric Company of America. (FIGS. 14 to 19, pages 972 to 977.) The alternating-current motor, as developed by the General Electric Company and installed on the Ballston line, is of the "compensated" type, so named on account of the character of the field winding, which fully neutralises or com- pensates for the armature reaction. Both the compensated motors are adapted for Lbs.Tractive Effort M.P.H % Efficiency GEA 604 COMPENSATED RY. MOTOR CHARACTER)STIC CURVES GEAR RATIO 71/19−3·74 DIAN.OF WHEELS 34 IN. AC 200 VOLTS 25 CYCLES 1300 1200 1100 50 1000 100 17 900 90 Power Factor Flee Effy Effy includ 40 800 80 FY 700 70 30 600 60 500 50 20 400 40 300 30 10 200 20 100 10 Q B 10 160 200 Amperes Practive Effort 240 280 320 46! Fig. 14. Characteristic Curves of the G. E. A. Single-phase Motor. operation on the 2000-volt alternating-current trolley between the cities and the standard 600-volt direct-current trolley in Schenectady. This ability of the com- pensated-motor equipments to run over tracks equipped with either alternating- current or direct-current trolley makes their field of application very broad, as the cars can secure all the benefit of running over existing city tracks, without in any way sacrificing their running qualities upon suburban sections equipped with alternating-current trolley. The compensated motor is essentially a variable-speed motor, differing in this respect from the multiphase induction motor, whose constant speed characteristics proved so serious a handicap to its successful adoption in railway work. The speed torque characteristic of the compensated motor is very similar to that of the direct-current series motor, while its commutating qualities and method of control prove equally satisfactory. ALTERNATING CURRENT TRACTION. 973 Fig. 14a. Volts 450 400 350 Amperes 3 6 6 2 2 2 2.8 Miles per Hout 36 44 |500) 40 400 32 28 1100- 50-1000-100 900-90 40 800 80 700 70 30 600 60 300 24 20 200 16 [100] 8 4 M.P.H. 500-50 20-400-40 300 30 10 200-20 100 10 LBS.TRACTIVE EFFORT. % EFFICIENCY. 1500- 1400 1300 1200 G.EA 604 COMPENSATED RY MOTOR. CHARACTERISTIC CURVES. GEAR RATIO7/19-3-74 DIAM. OF WHEELS 34IN. 0 40 (1175) b.c. 250 VOLTS. EFFICIENCY INCLUDING Voltage -81 ELECTEERIGYENCY GEAR & FRICTION. 80 120 160 200 240 280 AMPERES. Speed TRACTIVE EFFORT Characteristic Curves of the G. E. A. Continuous- Current Motor. Gurr Tent SPEED SPEED TIME CURVE A.C. RUNNING 4 | GEA 604 COMPENSATED RY.MOTORS TOTAL WEIGHT OF CAR] 31.55 TONS LENGTH OF İRUN 16 MILES GEAR RATIO] 3:74 DIAM OF WHEELS 34 IN. 100 120 140 Second's 1 160 T 180 200 (158 Fig. 15. Speed Time Curve of the G. E. A. Single-phase Motor. 974 SECTION XIII. : 650 $600 550 VOLTS 400- AMPERES 500, 40 ******** MILES PER HOUR 44 36 32 30024 SWITCH 28 2002 16 hnwr 100 8 12 Arrant PROM COMMUTATING huww SPEED TIME CURVE D.C. RUNNING. 4 G.E.A 604 COMPENSATED RY MOTORS. TOTAL WEIGHT OF CAR 31.55 TONS. LENGTH OF RUN 1.6 MILES GEAR RATIO 3.74. bwww Fig. 15a. Speed Time Curve of the G. E. A. Continuous-Current Motor. MOTOR CONNECTIONS FOR 4 AC MOTORS 'USED ON BOTH AC AND DC SERVICE First Series DC First Series AC brow ww SPEED! 0 20 40 60 80 100 120 140 160 180 200 SECONDS. (1174) AMPERES! мито Immommc нит OMLAR чита Full Series DC www ти www лишь питомни First Parallel DC DIAM OF WHEELS 34IN, www www Ommy чтоб нито Damo WW VOLTS Full Parallel DC hraww bra Full Series AC hannn huviv ww www mm Omma www www tomma Omma ww лит First Parallel AC лит Oman O лит Omma Full Parallel AC Omma G INTERMEDIATE STEPS CUT OUT SECTIONS OF RESISTANCE Fig. 16. Motor Connections for Four Alternating-Current Motors. ALTERNATING CURRENT TRACTION. 975 On the Ballston division of Schenectady Railway, advantage is taken of the ability of the compensated motor to operate with either alternating or direct- current. TRACK AND LINE. The Ballston division is 15.5 miles in length, including 3.9 miles of city running in Schenectady over tracks equipped with direct-current trolley. INCOMING LINE ·SCONNECTING SWITCHES LIGHTNING ARRESTERS FORMX O P. OIL SW. S P.ST GROUND S P.S.T SWITCH FORM K S.P DIL SW FORM K D. P. OIL SWITCH| * CURRENT TRANSFORMERS 22000 V. BUS 回 ​AMMETER TRIP COIL SWITCHES OIL COOLED TRANS ECUR TRANS. 22000 V.AUX. BUS. LIGHTNING ARRESTER TH SPS.T.SW. S.P.S.T.SW. £9 OUTGOING LINE + 2200 V. BUS. 回 ​100 BAMNETER HANNETER TRIP COIL TRIP COIL CUR TRANS. CUR TRANS. SECTION INSULATOR Two trolleys in series One trolley and double track Two trolleys and double track Double track alone t2,5 AMMETERS RIP COIL LIGHTNING ARRESTER FUTURE TRANS. 00 · TRANSMISSION LING DISCONNECTING SWITCHES LIGHTNING ARRESTERS TROLLEY • •• INCOMING LINE .. LIGHT IN MRRESTERS FORM'K”| D.P. OIL SW. HH KAMMETER TRİP COIL GUR. TRANS. GROUND S.P. S.T.† †SWITCHES S.P.S.T. SWITCH 22000 V. BUS, FORM"K". S.P. OIL SW. 22000 AUX. V.BUS OIL COOLED TRAMS. 2200 V.MUS. HBAHMETER HEMMETER TRIP COIL CUR TRANS. TRIP COIL CUR TRANS. LIGHTNING LIGHTRING ARRESTER ARRESTER S.P.S.T.SW. S.P.S.T.SW. FUTURE TRANS. SECTION INSULATOR INTERMEDIATE SUB-STATION TERMINAL SUB-STATION Fig. 17. Power Distribution System for Single-phase Railway; Single-phase Transmission, Double Track." (General Electric Company of America.) COMPARATIVE ALTERNATING-CURRENT and Direct-CURRENT RESISTANCE OF TROLLEY AND TRACK PER MILE OF CIRCUIT. Direct-Current Alternating-Current Ratio Resistance. Resistance. Direct-Current. .318 .167 .417 .259 .155 1.31 1.55 1.76 .088 .0174 .114 6.55 With the alternating-current system, using a trolley and track return, there is an inductive drop in the trolley and rails, with an additional loss in the latter case due to eddy currents and hysteresis. Measurements made upon the Ballston line indicate an apparent track resistance of 6.55 times the ohmic resistance. The resistance of the alternating-current trolley wire is somewhat reduced by the steel catenary in parallel with it. The alternating-current trolley wires are 5 ft. apart, and 16.5 ft. above track; while the four 75.0-lb. track rails are tied together every 1500 ft. The increased resistance with alternating current is a serious factor in low-voltage alternating-current city systems; but since the compensated motor operates perfectly with the direct current of our city systems, no general necessity exists for a low-voltage alternating-current trolley. ·· 1159 976 SECTION XIII. carried on the car. mechanical construction to a direct-current railway-motor armature. throughout the range of operation. This type of motor is so designed that at the pensates for the armature reaction, so that power factors are relatively high fed from the 400-volt secondary of an 80-kilowatt air-blast step-down transformer, motors are wound for 200 volts, are permanently connected two in series, and are The distributed character of the field winding fully com- These DISCONNECTING SWITCHES INCOMING LINE LIGHTNING ARRESTEA GROUND FORM*K' OIL SWITCH HHH S P. S.T AMMETERS HD CURRENT 22000 V. BUSSES GROUND ETJAMMETER TRIP COIL CUR TRANS SWITCHES TRANSFORMERS FORMX OIL SW. S.P.S.T. SWITCHES 22000 V. AUX. BUSSES W HHHÉÉÉTRIP OUTGOING LINE AWW.VA LIGHTNING ARRESTERS S.P.S.T 2200 V. TWO PHASE BUS • TRANSFORMERS FODILS TRANS. wwwwwww wwwwwww B SWITCHES B EXAMMETER FOTAMMETER STRİP COIL COBTRIP COIL CUR TRANS. CUR TRANS. SWITCHES لود SECTION INSULATOR INTERMEDIATE SUB STATION 00 DISCONNECTING, SWITCHES TRANSMISSION LINE LIGHTNING ARRESTERS TROLLEY INGOMING LINE FORM K. MAMMETER OIL SWITCHHHH TRIP COIL S.P.S.T 22000 V. BUSSES S P. S. T. GUR. TRANS 22000 V. AUX BUSSES SWITCHES TRANSFORMERS SWITCHES S. P.S.T. ཀeNMe TRANSFORMERS www wwwww! VAFF S.P.S. T. SWITCH 2200 V. TWO PHASE BUS. [ANNETERĮ LIGHTNING RRESTERS SWITCHES A SECTION INSULATOR Fig. 18. Power Distribution System for Single-phase Transmission, Single Track, (General Electric Company of America.) AMMETER TERMINAL SUB STATION B 1 1160 induction motor, and an armature provided with a commutator similar in general annular laminated iron field, with a distributed winding similar to that of an The General Electric alternating-current compensated motor consists of an Compensated Motor. ! ALTERNATING CURRENT TRACTION. 977 free running speed of the car, which is the condition most frequently met with in suburban work, the power factor and efficiency are nearly at their maximum values. A high power factor is desirable, as it reduces the capacity and cost of the AC Fuses Jazzy buivay617 |AC| Oil Switches [DC] 30 -ˇˇˇˇˇˇˇˇˇˇ- Main Transformer Kicking Co// "Um DC Fuse 594617 G Lightning Arrester AC AC DC Commuţaţing Switch OC Reverse 3-4 PJDMJOJ Run Points Heoters imma www TYBAN HHIHI $$seler HHIHI HH[M] Pump Motor KE 陳潔 ​Governor ww HILD Hi! Brown Que -G fum FOXOTOXOTO Compensator OLOR TO Ora ora 2010 20 20+ Main Fuse www Sofia b= 8763 0104 Uşa ~ww W www www. QAAE www FFR W -WW>> wwww 1157 Fig. 19. Car-Wiring for K.-28 Controllers, with Four G. E. A.-604 Motors. For Altering and Direct- Current Operation. (General Electric Company of America.) generating and distributing systems, and more especially effects a material' improvement in the regulation of the alternating-current generators. Unlike a direct-current system, which has a practically constant potential at the sub-station bus-bars, irrespective of the load, the drop in an alternating-current railway 978 SECTION XIII. system is culminative up to and including generator and engine regulation. It is desirable, therefore, to maintain as good a power factor as is consistent with good motor design, in order to limit the total drop of the system to a reasonable amount. A set of motor characteristics is shown for both alternating-current and direct-current running in Figs. 14 and 14a, on pages 972 and 973. It will be noted that the speed torque characteristics for alternating-current running are equal to direct-current running in meeting the requirements of railway work. Unlike the multiphase induction motor, with its practically constant speed characteristic, the compensated alternating - current motor varies its speed with the load, and is thus better adapted to operate trains over an irregular profile. The commutation of the compensated motor is equally satis factory when running alternating-current or direct-current; and this good commutation is secured by careful electrical and mechanical design, without resorting to high-resistance leads or other expedients liable to give trouble in case of sustained heavy overloads. Comparative Operation on Alternating and Direct-Current. It is instructive to compare the performance of the compensated motor equip- ment when operated with alternating-current and direct-current. A set of speed- time runs is shown in Figs. 15 and 15A, on pages 973 and 974, taken over the same stretch of track with alternating-current and repeated with direct-current. The direct-current time speed and ampere curves are typical, and require no particular comment. The alternating-current run, taken under exactly similar conditions over the same track, illustrates what can be expected from series-parallel control with compensated motors. The rate of acceleration is somewhat lower in the alternating-current run, hence requiring the application of power up to the moment of braking. The shape of the speed-time curve is also characteristic of alternating-current motor work, that is, a comparatively short time on the con- troller, with a large amount of motor-curve acceleration. The short period of fractional voltage running of alternating-current motors makes the method of their control of secondary importance, and largely minimises the economy of potential control over series-parallel control. All speed-time runs taken on the Ballston line were made over a distance of 1.6 miles on tangent level track, at an average speed of 32 miles an hour, or a schedule speed of 29.5 miles per hour, including 15-second stops. The compensated motor equipment has thus demonstrated its ability to make as high schedule speed as any suburban road now operating direct-current equipment under like conditions. The following constants apply to both sets of runs :- Comparative Alternating-Current and Direct-Current Runs. Direct-Current. 1.6 miles 31.55 tons 180 seconds 229 amperes 606 98 86.3 32 miles per hour 29.5 Current. ·· Length of run Weight of car Time ·· Average current power on Average voltage Kilo-volt-amperes full-speed on ·· ·· • ·· · .. level Volt-ampere hours per ton mile of given run Average speed Schedule speed including fifteen- second stops ·· ·· ·· • Alternating-Current. 1.6 miles 31.55 tons 180 seconds 346 amperes 425 110 125.5 32 miles per hour 29.5 The The lower volt ampere-hours per ton mile of the direct-current run are partly due to the better efficiency and power factor of the compensated motor when run with direct current, and partly due to the somewhat higher rate of acceleration, permitting some coasting and resulting in a more efficient speed time curve. difference in kilo-volt amperes alternating-current and direct-current depends upon the length of the run, and the values approach each other more nearly the longer the run. It will be noted that the compensated motors run the car at practically the same speed with 200 volts per motor alternating-current and -300 volts direct-current. This uniform speed is obtained by series-parallelling the fields, as shown in diagram of connections. ALTERNATING CURRENT TRACTION. 979 Siemens-Schuckert Single-phase Motor. (FIG. 20, page 980.) This Company have a line running at Ober-Ammergau which appears to be very successful. The single-phase current is generated at 5000 volts, and at a frequency of 163 cycles per second, and is fed direct into the line at this pressure, the return being earthed. The total drop in volts when two trains are at the end of the line furthest from the power station is only 6 per cent. The overhead wire is mostly single, but there are some experimental lengths of catenary suspension, comprising one steel catenary and two copper wires. Some of the poles are provided with horn lightning arresters, which carry out their functions very well. The district is subjected to extremes of weather, the violent thunderstorms of the summer giving place to heavy snowstorms and intense cold in the winter, when the temperature falls as low as 30 deg. Cent. Hence the overhead line had to be very carefully and strongly erected. It was at first found that the snow tended to short-circuit the lightning arresters, whilst the lubricant of the motor and car axles often froze; but these troubles have been successfully overcome. The motor coaches are mounted on three axles, and are divided into four sections, namely, second class, third class, post and luggage, and driver's compartments. Their net weight, fully equipped, is 26 tons. They are lighted by means of batteries under the car bodies, and electrically heated by radiators in the secondary circuit. The brakes are worked by compressed air, provided by axle-driven compressors. The collecting apparatus comprises two bows mounted on the top of each car on frames which are insulated from the roof. The bows are held up by springs, and are pulled into position by an air cylinder, which is fed from the brake reservoir, and controlled by the driver. The high-pressure current is taken past a horn lightning arrester through a choking coil and fuse on the roof, and passes thence to an automatic circuit-breaker under the car body. This switch is mechanically closed by the first operation of the controller CB, and is provided with two electro-magnetic trip devices; one of these is in series with the primary of the transformer Tp, and operates as a maximum cut-out. The other trip device is controlled by a local battery and switch in the driver's cab, and enables the driver to open the main high-tension switch. Each motor is provided with one transformer, which is suspended under the car body, enclosed in an iron oil tank, which is ribbed outside. The secondary coil of the transformer Ts is con- nected at various points to the controller C B, which is provided with a magnetic blow-out M, and is taken thence to the reversing switches R R and the motors M₁ and M2, the main current passing through an ammeter shunt, to which are con- nected two ammeters Am. The reversing switches have, as will be seen, three positions. The two extreme positions are for backward and forward running respectively, whilst the centre position is for taking the cars into the car-shed, where a special low-pressure overhead trolley line is provided. For this purpose, when the cars arrive at this point, the switches Sw are closed, and low-pressure trolleys LT are put into operation. The transformer reduces from 5000 volts to 260 volts, and the barrel controller switches this voltage step by step on the motors. Each car is provided with two 80 horse-power motors, which are geared to the two axles of the coach through single reduction-gear, having a ratio of 1 to 5.2, the running-wheels having a diameter of 800 millimetres (31 in.). These motors enable the car to maintain a normal full speed of 40 kilometres (25 miles) per hour when running either by itself or with a trailer. The two motors are always in parallel; they are of the 10-pole single-phase commutator type, and are built to a patent design of Messrs. Siemens-Schuckert, which includes special windings for reducing the sparking. The Oerlikon Company's System of Current Collection. (FIG. 21, page 981.) The collector is of the bow type, and consists essentially of a light curved metallic rod, the convex side of which makes sliding contact with the conductor. One end of the rod is unattached, and the other is free to rotate about an axis parallel to the direction of motion of the car. The point of connection of the rod is also capable of being moved a certain amount more or less horizontally in a direction at right angles to the length of the car. The necessary pressure between the collector and the wire is obtained by LT Ž UQUO M R MAIHEE lo la -30 0; 0; to jo to P 00 00 |||| wwwwwww D J CB TR mum I p DOW Diagram of Connections. Fig. 20, Siemens-Schuckert Ober-Ammergau Line. Зда 5.00 Ma Sw Sw 1151 m. LT 980 SECTION XIII. - [ T } ALTERNATING CURRENT TRACTION. 981 means of a clock-spring, which tends to rotate the metallic rod about its pivot. When the weight of the rod acts in conjunction with the force of the spring, the latter is exerting its minimum effect, being in the most uncoiled position. But when the weight of the rod tends to counteract the effect of the spring, the spring is most tightly coiled up, and thus exerts its most powerful torque. By this means a very uniform pressure is obtained throughout the whole range of posi- tions. The collector, by its rotation, automatically adapts itself to any change in position of the conductor. The lateral movement, which is only required in B H A.. 3150 4650 550 ᎡᎥ t 950 800 2000 2300 Ra li १ 800 dashālmssonsden v vlád 4300 Fig. 21. Oerlikon Current Collector. special cases, can also be made automatic if desired. The motor-man can at any time lift the collector out of contact with the wire. According to the position of the overhead wire, the rod rubs on the top side, or bottom of the wire. The normal state of affairs is to have the wire running to one side of the track, with the metallic rod making rubbing contact on the top of the wire. There is a wide range of positions which the collector can assume even without making use of the lateral motion, which would still further extend its range. In tunnels and similar situations the wire can be situated directly over the track; in which case the collector acts just like one of the ordinary bow type. Fig. 21 shows the collector and its method of working. Besides its great flexibility, the design embodies several other valuable features. The contact-rod is very light, weighing less than 34 lb., and it is easily replaceable. The last feature makes it possible to cover it with some composition softer than copper, and thus to minimise the wear on the aerial line; should the collector-rod catch in the overhead work, it is so slight that it would be the rod which would be damaged, and not the overhead construction. •** 982 SECTION XIII. The Stubaithal Railway. (FIG. 22.) (Allgemeine Elektricitäts- Gesellschaft Company). The electrical equipment of the motor carriages consists of four Winter- Eichberg motors, of a capacity of 40 horse-power at a 1-hour rating. The four motors are arranged in two parallel groups. The stator windings of both motors. in each group are in parallel, and in series with a regulating auto-transformer, to the secondary terminals of which are connected the two armatures of each motor group, which are arranged in series. The ratio of the regulating transformers is altered by means of the controller. In addition to the regulation effected by the auto-transformer, the primary pressure leading to the motors can also be changed. The controllers are of the same size and appearance as those used on tram-cars, and have six steps. On the first three steps a pressure of 400 volts primary is given to the motors; on the T $75 Folty mããão Rotor Whyhe لا Main transformer и Regulating exciting trabsfärmer Whin 1145. Oil circuit breaker -400 volts Trolley my wire Lightning arrester 2500 volts 42 periods *Stator Circuit breaker Rail & earth Fig. 22. Stubaithal Railway. Diagram of Motor Connections. following three steps the primary pressure is 525 volts. All the different steps correspond with different taps of the regulating transformers. Any step can be used continuously. The controller is provided with cut-outs, which can be brought into use if a breakdown of any motor occurs. As may be seen from Fig. 22, the equipment is protected by a lightning arrester. The alternating-current at 2500 volts is led to the car by the bow current collector, and reaches the main transformer through an oil-switch and a high-tension fuse H S. The primary winding of the main transformer is earthed on one side. The transformer produces 525 volts secondary, and has also a 400-volt tapping terminal. The connection of the regulation transformer RT of the stator windings S, and of the armature windings A, can be seen from the accompanying diagram. In order to ensure the protection of cars from falling wires in the event of damage to the overhead conductors, metallic earthed bars are arranged on the roof. ALTERNATING CURRENT TRACTION. 983 Backward W P Mulber K THE Forward 4 3 2 H S M Positions for Braking 1098 21 Q ••• W Le JOU R2 77 a -OR R₂ E α Pilot Lamp b G Forward A Backward Forward #y Backward Fig. 23, Diagram of Connections, Swedish State Railways, M Positions for Braking 1098755- 1152 jar 984 SECTION XIII. The time required for the whole journey is about one hour, and the speed of travel on level is about 25 kilometres per hour. The speed along 45 per cent. of the whole length of the track is 18 to 20 kilometres per hour. The energy consumed during four months' working of the Stubaithal Railway amounted to an average of 70 watt-hours per ton kilometre, measured at the feeding-point, and therefore including the losses in the secondary conductors and in the overhead conductor. The mechanical power required was calculated on the basis of exact measurements of the train resistance, and found to be 48 watt-hours per ton kilometre. The total efficiency is therefore 68 per cent. Swedish State Railways. Single-phase Installation. (FIGS. 23 to 25, pages 983 to 985.) The multiple unit train is made of two motor cars and two trailers, equipped by the Allgemeine Elektricitäts-Gesellschaft. Each of the former carries two 120 horse-power Winter-Eichberg 51 single-phase motors. A diagram of the 'connections of this motor is shown in Fig. 23. As will be seen, the stators are arranged to use the line potential. This is one of the principal points of advantage claimed by the manufacturers for this machine. The stator circuit is non-induc- tive, and its apparent resistance varies directly with the speed. In series with the stator field is the primary of a transformer from whose secondary the rotor operating current is taken. To produce a variation in torque it is usually the practice to take current for the rotor from different taps on the secondary of this tranformer. In addition to this circuit, and its set of brushes, the motor has another set of brushes which are set at 90 deg. from the first set, and are short- -circuited, as shown. This circuit receives its current by transformer action from the stator coils upon which it reacts, and thus produces the effect of the insertion -of resistance in the stator circuit. - To Power Station A, S S N ケ ​115.3. Fig. 24. Wiring Connections of Section Insulator. The controller connections of the motor are shown in Fig. 23. This diagram is particularly interesting, because several of the manufacturers of single-phase apparatus have announced that the multiple-unit system has been or can be adapted to the control of the single-phase motors, but no complete diagram of the connections or description of the methods to be employed have been published. The Allgemeine Elektricitäts Gesellschaft, as is well known, controls the general electric patents in Germany, and several other continental countries of Europe; so that its multiple-unit control system is that using electrical contactors, and what is known here as the Sprague General Electric System, or a modification of it. In the diagram, Fig. 23, the rotors of the car motors, with their short-cir- cuiting coils, are shown at A, and the stators at F. The high-tension circuit starts from the collector A, and is carried to the change-over switch E, operated by contactors 2 and 8. This switch, as shown by the developed diagram of the controller at the right of the diagram, first connects the rotor field in series, but when notch 4 on the controller is reached it connects them in parallel. From the rotor fields the high-tension circuit leads to earth. Taking up now the con- troller circuit assume the circuit-breaker closed, and the reverser handle on the forward notch. Then the contactors closed are 2, which connects the stator coils in series 9, which closes the reversing switch for forward running and 7. Step 1 on the controller operates contactors 3 and 6, by which the rotors are connected to the first tap on the transformer. On steps 2 and 3 contactor 3 is dropped, and first 4 and then 5 are thrown in, giving the full series position. Step 4 is not a running point, as contactor R6 is open; while the stator fields are changed from series to parallel at E through contactor 8. Steps 5, 6, and 7 on the controller ALTERNATING CURRENT TRACTION. 985 then gradually increase the voltage in the rotor. The reversing switch is operated by contactors 0 and 9, 9 being for forward and 0 for backward. Current collector Single-phase current is used for operating the contactors. Air pressure is employed to actuate the current collectors. 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The motors are geared 1: 4.26 to give a speed of 45 kilometres (28 miles) an hour, but can also carry gears in the ratio of 1:2.96 to secure a speed of 65 kilometres (40 miles) an hour. 986 SECTION XIII. The locomotive furnished by the Siemens-Schuckert Works has a weight of 36 tons, and is intended for freight trains with speed up to 45 kilometres (28 miles) per hour on a level road, and about 24 kilometres (15 miles) per hour on grades of 1 per cent. By changing the ratio of gearing, it is intended to increase the speed later on to 65 kilometres (40 miles) per hour. The locomotive has three driving axles, each being driven by a compensated series motor of similar design to those used on the Murnau-Oberammergau single-phase road. The normal capacity of the 320-volt 25-cycle motors is 110 horse-power; and with the ratio of gearing 1 to 5, which is used at present, the maximum tractive effort of the three motors is 6000 kilogrammes (13,200 lb.) at the wheels. In the front of the loco- motive a transformer is placed, with a normal capacity of 300 K.V.A., the primary of which consists of a series of windings, the connections of which may be changed so that the voltage supplied to the primary may be varied between 5000 volts and 20,000 volts. One of the chief purposes of the tests is to find the highest voltage with which a safe and satisfactory traction service can be maintained. The voltage of the secondary of the transformer can be varied between 160 volts and 320 volts. A controller contains ten positions, of which the first one is intended for very slow speed, and a special device for blowing out magnetically the spark due to the short-circuiting of coils. The motors are artificially cooled with air. The loco- motive has two aluminium bows for taking off the current from the trolley wire. Fig. 25 shows the electrical connections. At stations special precautions have been taken to break the circuit in the trolley wire at the station, and for a distance on each side. The wiring details of this section insulator is shown in Fig. 24. The two switches S, each of which controls one section, can be operated by hand, or in such connection with the semaphores that the current is cut off when the semaphore is set for a stop. The other switches, such as A, which cuts off current from the station rails, and the emergency short-circuiting device N, are only operated by hand. Single-phase Direct-Current Locomotive for the New York, New Haven, and Hartford Railroad. (Westinghouse Company.) (FIGS. 26 to 30, pages 987 and 988.) The New Haven locomotive at the Pittsburg Works is the largest which has yet been constructed for single-phase operation. The armature winding is closed on itself, and is not directly connected to the commutator, but is indirectly connected to it through resistance leads. The armature, in one sense, may be considered as a transformer with a lead brought out from each coil to a contact-piece, the various contact-pieces being assembled together to form a commutator. The brush, in passing from one contact to another, short-circuits an intermediate coil, just as in the case of a transformer under similar conditions. The function of the preventative coils or leads is to reduce to a rather low value the short-circuit current caused when the brush passes from one commutator bar to the next. The active armature winding consists of several coils per slot, with one turn per coil. The coils are made of form-wound strap, and are inserted in the slots from the top. Fibre wedges are used for holding the coils in place in the body of the armature, while binding wires serve for supporting the ends of the winding. There are several brushes per holder, and both the brushes and holders resemble closely those used in direct-current work. The brushes have a thickness of in. and are pressed against the commutator by means of a coiled spring. Field. The field winding is arranged in two circuits, namely, the main field coils, which are placed around projecting poles on the field core and produce the active field flux, and the compensating field coils, which are placed in slots in the projecting pole-faces and serve for opposing the armature magnetomotive force, and thus of neutralising the reactance of the armature. Each pole is provided with a number of slots for containing the neutralising coils, which remain at all times electrically in series in the armature circuit, whether the machine is operated by direct-current or alternating-current. The neutralising coils are mechanically so arranged on the core that the active field coils can be removed without disturbing the other coils. Although during normal direct current operation the field coils receive twice as much current per armature per ampere as during alternating current, and, therefore, in effect the coils of each motor are arranged in two groups, which are placed in series for direct-current and in parallel for alternating-current, the active field coils of each motor are in reality joined · ALTERNATING CURRENT TRACTION. 987 permanently in series, and only two leads pass from the field frame for this purpose. Two motors are operated as a unit, and the separate field circuits for these motors are placed in series or in parallel as desired, according to the current used. Special precautions are taken to insure that both the gravitational force of the motor on the axle and torsional force of the armature on the drivers should be transmitted through elastic mediums on account of the effect which the great 26 Miles per Ebur R 18 8 8 8 10 Eff and X.P.H. 90 18 80) R 70 Co 30 40 801 20 10 Horas Power 100 Kilowatts & Amperes 1200 1000 200 800 Volts-DC 48 Wheel A Time to Rise 15°from 25°C B- H * Efficiency 1900 400 600 800 Amperos Pields in Multiple Kłowąska • pare Borsć, Power Trac • " Tractive Effort M.P.H. São Võlts VA Pields in Multiple Time Tem 1000 Amperes per Motor Morr Fields in Multiple Effort Tima Minutes Tractive Effort per Motor 4500 Curves for Typica) Eun on Direct Current Watt Hours per Tồn Mila, Train & Locomotive Squire Boot Mean Square Amperes per Motor 871 Balancing Speed in Miles per Hour ---- Motors in’Beries 1500 20 "|Locomotiva] + 20400 1200 1400 1000 1800 2000 10000 CHARACTERISTIC Curves of 20Hp GEARLESS MOTOR OPerating ON 200 VOLTS, DIRECT CURRENT 180 12000 140 Tinie, Minutes 100 aboo 4000 60 20 Power Factor Efficiency & K.P.A. |Horse Power 90 80! 70 60 800 80. 40 8 30 10 90 100 Miled per Hour 8 00 18 400 401 30 200 10 & Amperes, Kilowatts 1200 1000 800 20 400 3 27 | Ampà.-1 Kwin elts. 2-Cycles Tractive Effort Speed K.F H Hores Ime to Rise ☎"Ir 1000 Efficiency Power/Pector Minutes ower XP.B. Amperes CURVES OF 10HP GEARLESS CHARACTERISTIC MOTOR OPERATING ON 235 VOLTS, ALTERNATING CURRENT Watt Hours per Ton-Mție, Train & Lo Square Root Mean Square Amperes per Balancing Speed in Miles per Hour- Motors in Beries-Parallel II 1500 • Tractive Entort per Motor 1500 •Locomotive 40.1 645 6 ་ 18000 180 8000 BONUS BUIL 18000 100] 100 3 20 113.5 TYPICAL RUN OF LOCOMOTIVE ON DIRECT CURRENT WITH MOTOR-GROUPS IN PARALLEL 29 TYPICAL RUN OF LOCOMOTIVE ON DIRECT CURRENT WITH MOTOR-GROUPS IN SERIES 28 weight of the motor equipment would produce at high speed. The problem of suspension, as exemplified in these motors, was much more difficult than that encountered in gearless motors intended solely for direct-current work, by reason of the fact that one of the prime essentials in the construction of single-phase motors is that the air-gap must remain constant; while with certain direct-con- nected motors of the bi-polar type, it has been found possible to allow the mechanical position of the armature in the field structure to vary between wide limits. 988 SECTION XIII. The hollow shaft of the armature is constructed in two halves. These two halves are alike, and each is provided with an end disc, on which project seven hollow pins. Each half is forced, by hydraulic pressure, into the ends of the hollow armature spider, and is securely keyed in place. The field structure of each motor is mechanically connected to its armature structure through two bearings, which ensure that the armature will remain at all times concentric to the field poles. The central portions of these two bearings are formed on the hollow cast-steel shaft of the armature, and the external portions are composed of split-bronze bearings, which fit snugly into the field housings. The weight of the entire motor, therefore, may be carried by the armature shaft or by the field structure, according to the relative values of the upward pressures exerted on these members. The axle of the locomotive passes through the armature quill, and when actually concentric with it there is a clearance of about § in. on all sides between the axle and the inside of the shaft. This allows a slight movement of the Miles per Hour 70 60 50 40 30 20 10 Kilowatts & Amperes 1600 1400 1200 1000 800 600 400 200 Total Weight of Locomotive and Train=289 Tons. mper Apparent KW Real K.W Speed M.P.H. Minutes 3 1156. Fig. 30. armature, in respect of the axle required by the flexible suspension of the motor, which is about to be described. On each end of the locomotive axle is mounted a 62-in. driving wheel, in the hub of which are formed seven circular pockets, which contain helical springs for assisting in carrying the weight of the motor, and for transmitting the torque from the armature. Into each of these pockets there projects one of the hollow pins on the end of the armature shaft. Each pin is surrounded by a spring placed between the outer circumference of the pin and the inner circumference of the pocket This pin is arranged so as to tend to hold the pin concentric with the pocket, and it resists yieldingly to any gravitational or torsional force for a total movement of in. The spring is of unusual form: its turns are progressively eccentric. Thus an end view of the spring would show an inner radius and an outer radius differing from each other by in. greater than the thickness of the stock from which the spring is built. The convolution of the spring first touches the outer circumference, then passes inwardly, and gradually approaches the inner circumference, which is reached by the end of the second turn; it then gradually passes from the inner to the outer circumference, which latter is reached until the end of the fourth turn, and so on to the end of the spring. Between the outer circumference of the spring and the inner circumference of the pocket is fitted a sheet-iron tube, and a similar tube is placed between the spring and the tube. These tubes and the spring form a unit which may be taken intact from the pocket when the outer end ALTERNATING CURRENT TRACTION. 989 cap is removed. On account of their mechanical form and their position in the pockets, these springs cannot be stretched beyond their elastic limit; and, since each pocket is provided with adequate lubrication, it is expected that they will stand the most severe wear, and will last indefinitely. They are capable of sustaining the whole weight of the motor, but they will normally be used solely for transmitting the torque to the drivers. Each pin contains a hollow space, in which is placed an additional pocket, which serves for receiving the end thrust of the motor against the driver. The frame from which the motor is suspended is distinct from the truck, and the swinging of the locomotive can have no effect on the motor; and it would seem that it was not possible for the motor to deliver other than a cushioned blow to the rails. Recent observations show that, even when travelling at a speed of 40 miles per hour over an exceedingly rough track, the motor was not subjected to excessive vibrations, and the locomotive rolled smoothly. The backward torque of the field structure is transmitted to the truck through rods which permit a certain amount of vertical or horizontal motion. Figs. 26 to 30, pages 987 and 988, show the performance of the motors considered separately, and the locomotive as a whole. Fig. 26 gives the calculated performance curves of the motors on direct-current of 300 volts per motor, while Fig. 27 gives the performance curves of the machines on 25-cycle current at 235 volts per motor. These two curves indicate that the motors are excellent direct-current machines, and that they operate on alternating current at a good power factor, and a satisfactory efficiency. The curves of Fig. 28 show a typical run of the locomotive on direct-current, the motors remaining always in series; while Fig. 29 shows a typical direct-current run with the motors operated in series- parallel. The effect of shunting the field coils with the motors in series will be noted from the sudden increase in the amperes taken by the motors just before they increase in acceleration while operating without resistance. With the shunted field coils the series connection of the motors would allow a maximum speed of 45 miles per hour under the assumed load; while with the motors in parallel, without shunted field coils, the maximum speed obtained on a level track would be 64 miles per hour, as indicated in Fig. 29. The curves of Fig. 30 were obtained during an acceleration test of the locomotive on alternating current. The current and power consumption correspond very closely to the pre-deter- mined values. The line upon which the locomotive has been tested is not well adapted to high-speed work, on account of the numerous sharp curves which exist. But, in spite of these adverse conditions, the locomotive has been operated at speed above 60 miles per hour without difficulty. Result Tests with a 50,000-Volt Single-phase Oerlikon Loco- motive in Switzerland. (FIGS. 31 and 32, page 990.) The Seebach-Wettingen Railway in Switzerland has been in operation since January 16th, 1905. It is a part of the railroad system owned by the Government, from which the Oerlikon machine works received permission more than a year ago to equip a section of track between Seebach and Wettingen, a distance of over 15 miles. Up to the present, the electrification has been carried from Seebach only as far as Affoltern, a distance of 2.4 miles, and the tests mentioned below have been conducted upon this section of track. Experiments have been conducted with two types of locomotives: the company was using a Ward-Leonard converter locomotive, which took single-phase current at 14,000 volts from the trolley wire, and had also just finished the electric locomo- tive equipped with series-commutating single-phase motors. Before describing the details of the new locomotive, it may be of interest to present the following data covering the amount of work done by each of the locomotives during the period indicated. Record of Work Done. Day trips were made.. Trips made Train kilometre made on test divi- .. .. sion, including switching.. Gross ton-kilometre carried.. Converter Locomo- tive. January 16th to October 1st, 1905. 164 1,442 4,850 496,000 Single-phase Locomo- tive. October 1st to December 1st, 1905. 51 304 997 135,209 990 SECTION XIII. After passing an automatic circuit high-tension breaker, which is located under the roof, and which can also be actuated either mechanically or pneumati- cally, from the motor-man's compartment, the current passes to a pair cf air-cooled transformers placed in the middle of the locomotive. All of the high-tension wiring is placed in micanite tubes, which are of such insulating strength that they Trolley Resistance having res. half 300 Volt Note:- Besides windings shown there is a Compensator which can either work short-circuited or can be hut in series with the main current. sudunian Venty induction Earth Fig. 31. Diagram of Connections of Oerlikon Motor. [fotos 0000 ww 100 at Hteraindly Powerfactor Efficiency Revolution 180 250 P& 1148. Fig. 32. Oerlikon 200-Volt Single-phase Motor. Transformer 200 Dou 1149. may be touched with impunity. These transformers reduce the voltage from 15,000 to 750, and each has a full load capacity of 200 K.V.A. The return circuit of the high-tension circuit is through the locomotive truck and the rails. REM Two systems of control have been installed for experimental purposes. One is the tap method, and 21 taps are used from the 750-volt secondary, which would give a difference in potential between consecutive taps of 37.5 volts. The outside ALTERNATING CURRENT TRACTION. 991 taps also lead to an induction regulator of the usual type, which is controlled from the motor-man's cab through a hand-wheel by means of a shaft and worm gear. One of these controllers will be used in the final equipment. It will be so arranged that it can be operated electrically from the motor-man's stand. From the controllers the current passes to the motor switches, and thence to the motors, which are of 200 horse-power each, at 650 revolutions per minute. They are of the series-commutator type, and each has 8 poles, with additional "interpoles" for compensation. Each motor is mounted in the middle of its four-wheel trucks, and the power is transmitted through gearing to a driving-shaft, which is connected to the wheels by side rods. The total weight of the locomotive is 43 metric tons (946,000 lb.); body and trucks, 23,500 kilogrammes (91,700 lb.); electric equipment and brake apparatus, 19,500 kilogrammes (42,900 lb.); motor, without the gearing, 3380 kilogrammes. (7436 lb.); induction regulator, with base-plate and gearing, 4000 kilogrammes (8800 lb.); speed regulator, with oil receptacle, 310 kilogrammes (682 lb.). This locomotive drew loads weighing 200 tons at 30 kilometres speed on curves up to 8 per cent., without appreciable sparking at the commutator. The starting current when the motors are connected in series is about 1000 amperes, and is about 780 amperes when the locomotive is running on an 8 per cent. grade at 27 kilometres an hour, with the motors taking 450 volts. ་ 3 APPENDIX. 串 ​K K CONVERSION TABLES FOR WEIGHTS drachms 1-RELATION BETWEEN ENGLISH AND METRIC UNITS. in. 1 2 OZ. 1 = .0625 16 1 16 256 = 7168 28672 = 1792 448 28 112 4 573440 = 35840 = 2240 = 80 www magkak ⠀ ⠀ --- grains 1 24 480 5760 138 11 11 11 12 = 36 72 = 6 198 = 16 660 7920 = 63360 = 5280 www AND MEASURES. S APPENDIX. Table I.-Avoirdupois Weight. qrs. lb. tons = .0039 = .000139.000035 = .00000174 = ******** || || || = .0625 = .00223 = .000558 = .000028 1 = .0357 1 = .333 dwts. .04167 1 20 240 1 2 51 220 1760 cwts. OZi. .00208 .05 1 12 = .00893 = .000447 = .25 = .0125 = .05 = 1 = Table 2.-Troy Weight. 110 880 20 1 || | || || 7000 grains troy = 1 lb. avoirdupois. 175 lb. troy = 144 lb. avoirdupois. Pounds avoirdupois × 1.2153 = pounds troy. Pounds troy × .82286 = pounds avoirdupois. Table 3.-Long Measure. ft. yards fathoms poles furlongs miles .083 = .02778 = .0139 = .005 = .000126 = .0000158 = = .1667 = .0606 = .00151 = .0001894 = = .00454 = .000568 .5 = .182 .1 = .364 = .0091 = .001136 231 = .003125 = .125 1 lb. .0001736 .004167 .0833 1 || || 1 = .025 40 320 1- 00 8 11 11 || || || || French grammes. 1.771846 = 453.59 28.34954 French grammes. 12,700 50,802 1,016,048 .0648 1.555 = 31.1035 = 373.242 French metres. .0254 .3048 .9144 1.8287 5.0291 201.16 = 1609.315 996 APPENDIX. Table 4.-Conversion Table for French and English Measures of Length. Number. 12345 CO. 6 7 8 9 10 11 12 13 14 15 16 212272****7; 18 19 20 23 24 25 26 Metres to Feet. 3.281 6.562 9.843 13.12 16.40 19.68 22.96 26.24 29.52 32.81 36.09 39.37 42.65 45.93 49.21 52.49 55.78 59.06 62.34 65.62 68.90 72.18 75.46 78.74 82.02 85.30 88.58 91.87 95.15 98.43 28 29 30 31 101.7 32 104.9 33 108.2 34 111.5 35 114.8 36 118.1 37 121.3 38 124.6 39 127.9 40 131.2 41 134.5 42 137.8 43 141.0 44 144.3 45 147.6 46 150.9 47 154.2 48 157.4 49 160.7 50 164.0 Centi- Feet to Metres Metres. to .305 .394 .610 .787 .914 1.181 1.219 1.575 1.524 1.969 1.829 2.362 2.134 2.756 2.438 3.150 2.743 3.543 3.94 4.33 4.72 5.12 5.51 5.91 6.30 6.69 7.09 7.48 7.87 8.27 8.66 9.06 9.45 9.84 10.24 10.63 11.02 8.84 11.42 9.14 11.81 9.45 12.21 9.75 12.60 10.06 12.99 10.36 13.39 10.67 13.78 10.97 14.17 11.28 14.57 11.58 14.96 11.89 15.35 12.19 15.75 12.50 16.14 12.80 16.54 13.11 16.93 13.41 17.32 13.71 17.72 14.02 18.11 14.32 18.50 14.63 18.90 14.93 15.24 3.05 3.35 Inches to Centi- Inches. metres. 3.66 3.96 4.27 4.57 4.38 5.18 5.49 5.79 6.10 6.40 6.71 7.01 7.31 7.62 7.92 8.23 8.53 Number. 2.540 5.080 52 7.620 53 51 167.3 15.54 15.85 170.6 173.8 20.08 129.5 20.47 132.0 20.87 134.6 16.15 10.16 54 177.1 16.46 21.26 137.1 12.70 16.76 21.65 139.7 15.24 17.07 22.05 142.2 17.78 17.37 22.44 144.7 20.32 17.68 22.84 147.3 58 22.85 59 17.98 23.23 149.8 25.40 60 18.29 23.62 152.4 27.94 61 18.59 24.02 154.9 18.90 24.41 157.4 24.80 160.0 25.20 162.5 25.59 165.1 25.98 167.6 116.8 119.3 121.9 19.29 124.4 19.69 127.0 Centi- Inches Metres Feet to metres to to Feet. Metres. to Centi- Inches. metres. 55 56 180.4 183.7 57 187.0 190.2 193.5 196.8 200.1 30.48 62 203.4 33.02 63 206.7 18.90 35.56 64 209.9 19.51 213.2 38.10 19.81 65 40.64 66 216.5 20.12 219.8 20.42 43.18 67 45.72 68 223.1 20.73 48.26 69 226.3 21.03 50.80 70 229.6 21.34 71 232.9 21.64 21.94 22.25 28.74 185.4 22.55 29.13 187.9 22.86 29.53 190.5 23.16 29.92 193.0 23.47 30.32 195.5 30.71 198.1 31.10 200.6 31.50 203.2 31.89 205.7 32.28 208.2 210.8 32.68 33.07 213.3 33.47 215.9 33.86 218.4 34.25 220.9 34.65 CIJELJINIILUSI 53.34 236.2 55.88 72 58.42 73 239.5 60.96 74 242.7 75 246.0 63.50 66.04 76 249.3 68.58 77 252.6 71.12 78 255.9 73.66 79 259.1 76.20 80 78.74 81 81.28 82 83.82 86.36 84 83 272.3 275.6 88.90 85 278.8 91.44 86 282.1 93.98 87 285.4 96.52 88 288.7 99.06 89 101.6 292.0 90 295.2 91 298.5 92 301.8 104.1 106.6 109.2 93 305.1 111.7 94 308.4 114.3 311.6 314.9 318.2 23.77 24.08 262.4 24.38 265.7 24.69 269.0 24.99 95 96 97 98 321.5 99 324.8 100 328.1 26.38 170.1 26.77 172.7 27.17 175.2 177.8 27.56 27.95 180.3 28.35 182.8 25.30 25.60 25.91 26.21 26.52 26.82 223.5 27.13 35.04 226.0 27.43 35.43 27.73 35.83 228.5 231.1 28.04 36.22 233.6 36.62 236.2 28.34 28.65 37.01 238.7 28.95 37.40 241.2 29.26 37.80 243.8 246.3 29.56 38.19 38.58 248.9 38.98 251.4 39.37 253.9 29.87 30.17 30.48 TABLES FOR WEIGHTS AND MEASURES. 997 100 1076 110 1184 120 1292 130 1399 140 1507 150 1615 160 1722 170 1830 180 190 Table 5.-Conversion Table for French and English Areas. 1938 2045 200 2153 210 2261 220 2368 230 2476 240 2583 250 2691 260 2799 270 2906 3014 3122 280 290 300 3229 310 3337 320 3445 330 3552 340 3660 350 3768 360 3875 370 3983 380 4090 390 4198 400 4306 410 4413 420 4521 430 4629 440 4736 450 4844 460 4952 470 5059 480 5167 490 5275 500 5382 510 5490 520 5597 530 5705 540 5813 550 5920 9.3 10.2 11.1 12.1 13.0 13.9 14.9 15.8 16.7 17.6 18.6 19.5 20.4 21.4 22.3 23.2 24.1 25.1 26.0 26.9 27.9 28.8 29.7 30.7 31.6 32.5 33.4 34.4 35.3 36.2 37.2 38.1 39.0 39.9 40.9 41.8 42.7 43.7 44.6 45.5 46.4 47.4 48.3 49.2 50.2 51.1 15.5 17.1 18.6 20.2 21.7 23.3 24.8 26.4 27.9 29.5 31.0 32.6 34.1 35.7 37.2 38.8 40.3 41.9 43.4 45.0 46.5 48.1 49.6 51.2 52.7 54.3 55.8 57.1 58.9 645.1 709.6 774.2 838.7 560 6,028 52.0 570 6,136 53.0 580 6,243 590 6,351 903.2 600 6,459 967.7 610 6,566 1032.0 620 6,674 1097.0 630 6,782 79.1 80.6 82.2 83.7 85.3 1161.0 1226.0 640 650 1290.0 660 1355.0 670 7,212 1419.0 680 7,320 1484.0 690 7,427 1548.0 700 7,535 1613.0 710 7,643 1677.0 720 1742.0 730 1806.0 740 1871.0 750 8,073 1935.0 760 8,181 2000.0 770 8,289 2064.0 780 2129.0 790 8,396 8,504 2193.0 2258.0 810 2322.0 820 800 8,611 8,719 8,827 2387.0 830 8,934 2452.0 840 9,042 2516.0 850 9,160 2581.0 860 9,257 2645.0 870 9,365 2710.0 880 9,473 2774.0 890 9,580 2839.0 900 9,688 2903.0 910 9,796 2968.0 920 9,903 3032.0 60.5 62.0 63.6 65.1 66.7 68.2 69.8 71.3 72.9 74.4 3097.0 3161.0 76.0 77.5 3226.0 3290.0 3355.0 3419.0 3484.0 3548.0 6,889 6,997 7,104 7,750 7,858 7,966 930 10,011 940 10,118 950 | 10,226 960❘ 10,334 970 10,441 980 | 10,549 990 10,657 1000 | 10,764 53.9 54.8 55.7 56.7 57.6 58 5 59.5 60.4 61.3 62.2 63.2 64.1 86.8 88.4 89.9 91.5 93.0 94.6 96.1 97.7 99.2 100.8 102.3 103.9 105.4 107.0 108.5 110.1 111.6 113.2 114.7 65.0 66.0 66.9 67.8 68.7 69.7 116.3 70.6 117.8 71.5 119.4 72.5 120.9 73.4 122.5 74.3 124.0 75.3 125.6 76.2 127.1 77.1 128.7 78.0 130.2 79.0 131.8 79.9 133.3 80.8 134.9 81.7 136.4 82.7 83.6 84.5 141.1 85.5 142.6 86.4 144.2 87.3 145.7 88.3 147.3 89.2 148.8 90.1 150.4 91.0 151.9 92.0 153.5 92.9 155.0 138.0 139.5 3613 3677 3742 3806 3871 3935 4000 4064 4129 4193 4258 4322 4387 4451 4516 4580 4645 4709 4774 4839 4903 4968 5032 5097 5161 5226 5290 5355 5419 5484 5548 5613 5677 5742 5806 5871 5935 6000 6064 6129 6193 6258 6322 6387 6452 998 APPENDIX. pints gals. pecks 1 = .125 = .0625 8 = 16 = 64 = 1 6360 < ALD 1 ∞ ∞ 512 = 64 2560 = 320 6120 = 610 = 2 4 2 8 5 = .5 = "" 1 4 32 160 320 Cube feet Table 6.-Measure of Capacity. bushels qrs. wey last .01562 = .00195= .00039 = .000195 = = .125 = .0156 = .00312 = .00156 = .25 = .03125= .00625 = .00312 = .125 = .025 = .0125 = .2 = 1.341 2.681 4.022 5.363 6.703 6 8.044 7 9.384 8 10.725 9 12.065 10 13.406 11 14.747 12 16.087 13 17.428 14 18.768 10.4 15 20.109 11.2 16 21.450 11.9 17 22.790 12.7 18 24.131 13.4 19 25.471 14.2 20 26.812 14.9 21 28.153 15.7 22 29.493 16.4 23 30.834 17.2 24 32.174 17.9 25 33.515 18.6 26 34.856 19.4 27 36.196 20.1 28 37.537 29 38.877 20.9 21.6 30 40.218 22.4 31 41.559 23.1 32 42.899 23.9 33 44.240 24.6 34 45.580 25.4 35 46.921 26.1 36 48.261 26.9 37 49.602 27.6 Kilowatts Horse- to Horse- Power to Power. Kilowatts. .746 1 ∞ 1.49 2.24 2.98 3.73 4.48 5.22 5.97 6.71 8 7.46 8.21 8.95 9.70 40 80 = x .78 = bushels. inches x .00045 = Table 7.- Conversion of Horse-Power into Kilowatts and Kilowatts into Horse-Power. 1 gallon in wine, ale, or dry measure=2774 cube inches=0.16 cube feet. 1 >> of distilled water weighs 10 lb. Cube feet X 6.2355 = inches x .003607 = gallons. 99 "" 1 bushel = 2218.19 cube inches = 1.28 cube foot. 1 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 NOASCNIJ58588°F~~~ 63 64 65 66 67 68 69 70 71 72 1 = 5 10 73 74 "" Kilowatts Horse- to Horse- Power to Power. Kilowatts. 50.943 52.283 53.624 54.965 56.305 57.646 58.986 60.327 61.667 63.008 1 2 64.349 65.689 67.030 68.371 69.711 71.052 72.392 73.733 75.074 76.414 77.755 79.095 80.436 81.777 83.117 84.458 85.798 87.139 88.480 89.820 91.161 92.501 93.842 95.183 96.523 97.864 99.204 28.3 29.1 29.8 30.6 31.3 32.1 32.8 33.6 34.3 35.1 35.8 36.5 37.3 38.0 38.8 39.5 40.3 41.0 41.8 42.5 43.3 44.0 44.8 45.5 46.2 47.0 47.7 48.5 49.2 50.0 50.7 51.5 52.2 53.0 53.7 54.5 55.2 M 75 76 77 78 ******** 79 80 81 cube feet .02 .1604 = .3208 = .1 = 10.264 290.625 .5 = 51.319 = 1453.126 1 =102.64 = 2906.25 1.283 = 82 83 84 85 86 87 88 89 90 91 92 93 94 98 99 100 200 300 400 500 11 108.588 109.929 111.269 112.610 113.951 115.292 116.632 117.973 119.313 120.654 121.995 123.335 124.676 126.016 95 127.357 96 128.698 97 130.038 131.379 132.719 134.060 268.120 litres 100.545 101.886 103.226 104.567 105.907 107.248 .5676 4.543 9.082 36.3282 Kilowatts Horse- to Horse- Power to Power. Kilowatts. 402.18 536.24 670.30 600 804.36 700 938.42 800 1072.48 900 1206.54 1000 | 1340.60 55.9 56.7 57.4 58.2 58.9 59.7 60.4 61.2 61.9 62.7 63.4 64.2 64.9 65.6 66.4 67.1 67.9 68.6 69.4 70.1 70.9 71.6 72.4 73.1 73.8 74.6 149.0 224.0 298.0 373.0 448.0 522.0 597.0 671.0 746.0 TABLES FOR WEIGHTS AND MEASURES. 999 French. 1234 10 CO 2 00 5 6 7 8 9 10 11 12 13 14 15 18 19 20 Table 8.-French Horse-Powers Converted into English. ~I~RENCHEZZZZZEUGOVOGAwwFoot-Pounds. 3 11 13 14 15 16 18 20 English. 16 17 16.8 17.8 18.7 19.7 25 .986 21 22 1.97 2.96 3.94 4.93 5.92 6.90 7.89 8.88 9.86 10.8 11.8 12.8 13.8 14.8 15.8 Kilogramme- Metres. .1383 .2766 .4149 .5532 · .6915 .8298 .9681 1.1064 1.2447 1.3830 1.5213 23 24 25 26 27 1.6596 1.7979 1.9362 2.0745 2.2128 2.3511 2.4894 2.6277 2.7660 2.9043 3.0426 3.1809 3.3192 3.4575 *****28♫ 29 30 31 32 33 34 35 36 37 38 1588888 39 40 20.7 21.7 22.7 23.7 English. 24.7 25.6 26.6 27.6 28.6 29.6 30.6 31.6 32.6 33.5 34.5 35.5 36.5 37.5 38.5 39.5 Foot-Pounds. 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 French. 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 888 59 Kilogramme. Metres. 3.5958 3.7341 3.8724 4.0107 4.1490 4.2873 4.4256 4.5639 4.7022 4.8405 4.9788 5.1171 5.2554 5.3937 5.5320 5.6703 5.8086 5.9469 6.0852 English. 6.2235 6.3618 6.5001 6.6384 6.7767 6.9150 40.4 41.4 42.4 43.4 44.4 45.4 46.4 47.3 48.3 49.3 50.3 51.3 52.3 53.3 54.2 55.2 56.2 57.2 58.2 59.2 Foot-Pounds. Table 9.-Foot-Pounds and Kilogramme-Metres. 51 52 53 54 55 56 57 58 59 60 61 62 63 31585882ENRER 64 65 66 67 68 69 70 71 72 73 74 2382 French. 75 61 62 63 64 65 66 67 68 69 70 71 72 CIJIIHFJZHJ882; 73 74 75 76 77 78 79 80 Kilogramme- Metres. 7.0533 7.1916 7.3299 7.4682 7.6065 7.7448 7.8831 8.0214 8.1597 8.2980 8.4363 8.5746 8.7129 8.8512 8.9895 9.1278 9.2661 9.4044 9.5427 9.6810 9.8193 9.9576 10.0959 English. 10.2342 10.3725 60.2 61.2 62.1 63.1 64.1 65.1 66.1 67.1 68.1 69.0 70.0 71.0 72.0 73.0 74.0 75.0 76.0 76.9 77.9 78.9 spund 400 fo¯****************** 76 78 79 83 84 85 86 88 90 92 93 96 98 *******∞∞∞ French. 100 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 English. 79.9 80.9 81.9 82.8 83.8 84.8 85.8 86.8 87.8 88.8 89.8 90.7 91.7 92.7 93.7 94.7 95.7 96.7 97.6 98.6 Kilogramme- Metres. 10.5108 10.6491 10.7874 10.9257 11.0640 11.2023 11.3406 11.4789 11.6172 11.7555 11.8938 12.0321 12.1704 12.3087 12.4470 12.5853 12.7236 12.8619 13.0002 13.1385 13.2768 13.4151 13.5534 13.6917 13.8300 1000 APPENDIX. 103 50 > "" "" "" "" "" "" "" "" " "" Alternators, Advantages of, 466 "" "" "" "" "" on some American Railways, 774 Time and Power used in, 773 Traction Motors, 759 "" "" >> "" "" "" "" INDEX. "" " "" Metropolitan New York, 474 Multiphase, 467 Oerlikon, Three-Phase, 485 Specification of Revolving Field, 465 Star and Delta Grouping, 466 Westinghouse Standard, High-Speed, Engine-Type, 481 Aluminium Conductors, Price of, 121 "1 Resistance and Losses in Return Circuits, 1015 Resistance of Conductors with, 119 Allgemeine Elektricitäts Gesellschaft, 480 Brown, Boveri and Co., 485 British Thomson-Houston Standard Three-Phase, 483 Connections of Westinghouse Two- and Three-Phase, 474 Dick, Kerr and Co., 476 Efficiency of some, 471 for Railway Work, 483 in Parallel, 463, 473 for Electric Conductors, 121 American Blower Company's Induced Draught System, 381 Corliss Engines, Ratio of Cylinders of, 165 "1 Electric Heater, 852 "" "" "" Electric Locomotives, 777 Electric Tramcar Speeds, 930 Open and Closed Cars, Leading Dimensions of, 809 Power Transmission Lines, 941 1018 INDEX. American Rail Steel Qualities, 17 " "" ", در "" "" "" "" Railways, Acceleration on Some, 774 Railways, Maintenance of, 916, 917 Safety Valves, 398 Standard Slow-Speed Tramway Engines, 164 Standard Trolley, 838 Stoker, 307 "" "" "9 "" Anchor and Splicing Ear Combined, 76 Chairs, 23 "" "" Ear, 76 Joints, 23 "" Anchors per Mile of Track, 21 Anderson's Double Pull-Off, 79 Angle Diagram for Trolley Pole, 839 of Points, Determination of, 25 Archbutt-Deeley Water-Softener, 332 Area Units, French and English, 997 Armature Cores, 424 "J Hub, Dick Kerr and Co., 423 Reaction, 413 Repair Parts, Railway Motor, 872 Windings, 419 T Railway Rails, 19 T Rail Steel Track, 10 Tramway Rails, S Tramways, Mileage and Cars, 928 "" "" Armour for Underground Cables, 125 Armoured Cables, 100 Ash, Composition of, 387 Ashbin Refuse, 301 Ashmore, Benson and Pease Batteries, 717 Askham Brothers, Points and Crossings, 25 Asphalte Roadways, 50 Astaki, or Petroleum Refuse, 403 Austro-Hungarian Railway, Wheel Specification and Test, 835, 837 Automatic Regenerative Control, Raworth System, 864 Automobile, MV Exide Type, Chloride Cell, 716 Avoirdupois Weight, 995 Axle Steel, 832 Tests, 834 "" Axles and Wheels, 832 Babcock and Wilcox Boilers, Draught Required, 390 Chain Grate Stoker, 314 "" "" "" "" Patent Water-Softener, 330 Superheater, 348 " "" Water-Tube Boiler, 274 Balancer Panel, Three-Wire, Switchboards, 557 Ballast, Depth of, 7 Baltimore and Ohio Electric Locomotives, 782 Barrel Calorimeter, 342 Batteries. See Storage Batteries, 707 Bay Counties Power Companie's Insulators, 945 Bearings of Dynamo, 430 Behrend Accumulatoren Werke's Batteries, 718 Belgian State Railway Wheel Specific, 835 Belliss Steam Engine, 169 Belt and Bucket Conveyor Combined, 322 Conveyors, 315 "" Bennis Mechanical Stoker, 308 Bergtheil and Young's Flexible Coupling, 632 Berlin Conduit Tramways, 741-746 " "" "" Elevated and Underground Railway, 789 Elevated, Third Rail, 784 Lichterfelde Railway, 789 ! 1 Į ť INDEX. 1019 "9 "" Berryman Feed-Water Heater, 341 Bituminous Fuel-Producer Plant, 661 Blackwell Enclosed Trolley, 841 Frogs and Crossings, 78 Improved Junction Box, 109 Standard Trolley Lead, 846 Blast-Furnace Gas, 663 Blind Switch, 25 "" Blow-off Cocks, 300 Board of Trade Regulations and Tests, Switchboards, 559 Regulations for Guard Rails, 95 Rules for Safety Valves, 298 "" "" "" "" 99 "" " "" "" "" "" "" "" "" "" >> "" "" Unit, Coal Required per, 914 "" "" Unit, Cost per, in some Traction Stations, 919 Bogie Truck for North-Eastern Railway Electric Locomotive, 779 Boiler Scale, Analyses of, 329 Boilers, Accessories, 299 "" American, Cylindrical Type, 283 Babcock and Wilcox, 274, 278, 279 Breaking Stresses of Plates, 259 "" Bryan Donkin on Efficiency and Coal Consumption, 284 Butt Straps, 259 Calorimetric Tests, 342 Chimneys, 371 Choice of Type and Location, 251 Classification of, 252 "" "" "" "" "" ?? "" "" "" "" "" "" "" " "" "" "" "" "" "" "" 99 "" "" "" "7 19 99 99 " 19 "" "" " . "" "" Rules for Strength of Steam Pipes, 188 Rules for Welded Wrought-Iron Steam Pipes, 187 Unit, 409 Coal Consumption and Efficiency, 284 Coal Conveyors for, 315 Combustion, Rate of, 363 Composite Lancashire and Tubular, 273 Cornish, 267 Corrosion of, 327 Cost of, 925 Cylindrical American Type, 283 Cylindrical Shells and Internal Pressure, 260 Cylindrical, Two-Storey, 274 Diameter of Rivets, 259 Draught Area of Smoke Tubes, 257 Economiser with, 341 Efficiency and Coal Consumption, 284 Efficiency and Heating Surface, 287 Elephant, 271 Energy Available in Event of Explosion, 283 English Unit of Evaporation, 254 Evaporation Factors, 255 Evaporation Formulas, 255 Feed-Heaters for, 337 Feed-Pumps, 350 Fire-Grates and Furnaces, 289 Fired with Liquid Fuel, 402 Flat-Plate Rules, 260 Flue Areas, 256 Flues for Lancashire and Cornish, 289 Fox and Purves' Furnace Tubes, 263 Fraser, Dry-Brick, 280 Fuel for, 348 Furnace Flue Formulæ, 262 Furnace for Burning Wood, 399 Galloway, 270 Gauges and Cocks, 299 Grate Area per Horse-Power, 256 Heating Surface and Efficiency, 287 Heating Surface and Grate Area, 255 Heating Surface Measurement, 255 "" "" " "" "" "" "" 1020 Boilers, Heating Surface per Horse-Power, 251, 256 Heating-Surface Total, 256 Heating-Surface Values, 257 "" " "" "" "" "" "" "" "" "" "" "" "" >> " "" "" "" "" "" "" "" "" " "" "" "" "" "" "" "" "" >> "" "" "" "" " "" "" • "" "" 4 در " "" Horse-Power of, 253 Horse-Power of, Nominal, English, 287 Hydraulic Tests, 264 Incrustation of, 327 Injectors, 350 Internal Pressure in Cylindrical Shells, 260 Lancashire, 264 Locomotive Type, Evaporative Power, 280 Main Features in Designing, 251 "" "" "" "" Manholes, 292 Marine, 270 Material for Cylindrical Shells, 260 Measures of Efficiency of, 254 Mechanical Draught, 372 Mechanical Stokers for, 307 Plates for Flanging, 261 Plates, Strength of, 264 Portable Engine, 281 Pumps and Piping, Life of, 916 Refuse Destructors, 301 Weight of, 288 "" Bolton Tramway Depreciation, 918 Bolts, Nuts, and Washers per Mile of Track, 21 Their Current Carrying Capacity, 618 "" Bonding and Return Circuit, 51 Cost of, 925 INDEX. Return Large Smoke-Tube, 283 Riveting, 258, 259 Riveted Joints, 259 Safety-Valves, 292 Scale in, 327 Setting, 288 Shell-Plate Formulæ, 260 Smoke Tubes, Draught Area of, 257 Smoke Tubes, Heating Surface of, 258 Smoke Tubes, Length of, 258 Stacks, 361 Stay Girders, 263 Stays, Loads Allowed on, 263 Stays, Material for, 262 Stirling, 276, 280 Strength of Joints, 259 Superheaters for, 347 Bonds, Chicago "Crown," 54 Temperatures of Brick Setting, 289 Tests at Shoreditch by Kincaid, Waller, Manville and Dawson, 277 Tube Plates, 264 Types for Traction Work, 252 Water and Coal Required per Indicated Horse-Power, 253 Water for, 355 Water-Softeners for, 330 "Chicago" Rail, 52 Columbia, 54 Comparison of Resistance of Various, 60 Crown, 53 Edison-Brown Plastic, 59, 61 Formulæ for Ascertaining Weight, 54, 57 Miscellaneous, 58 Neptune, 57 Results of Tests, 54 Weight of, 52 Boring Mills, Power for Driving, 950 Boosters, 438 of Points and Crossings, 63 + INDEX, 1021 Boosters, Reversible-Switchboards, 552 Storage Batteries, 711 "" Boston Elevated, New York, 789 "" "" Bow, Siemens Sliding, 844 Box Fuse, the Ferranti, 578 Box's Experiments, 178 Brackets, 86 Brake Gear, Gravity, 897 Brake-Shoes, Average Pressure on, 897 "" Average Weight of, 897 Chilled Cast-iron, 897 "" "" Composite, Cast, and Wrought-iron, 897 Steel, 897 "" Tests, 897 "" Brake Tests, 907 Brakes, 896 "" Breaking-down Voltage-Feeders, 120 Load of Aluminium Wire, 121 Bricks, English, Varieties of, 694 Test of, 693 Weight of, 693 "" "" Brickwork, 693 Brill Trucks, 818 British Insulated Wire Co.'s and Callender's Conduits, 102 Lighting Plants, Capital Spent on, 928 Standard Sections, Tramway Material, 12 Tramcars, Speeds of, 931 Tramways, Particulars of, 922 "" "" "" "" British Thomson-Houston Air Blast Transformers, 508 Controllers, 854 >> "" Elevated Rail Steel Specification, 17 Insulators, 74 "" "" " 59 + "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" Bronze Metal Feeder Plug, 74 Brooklyn Rapid Transit, New York, 789 "" "" Brown, Boveri and Co.'s Alternators, 485 Railway Motor, 895 "" Brown, Coal, Furnace for, 291 Bruce-Peebles Tramway Motors, 893 Brush Company's Cars, 812 Controllers, 854 "" "" "" "" "" "" "" "" Distance-Controlled Switch, 531 Electro-Magnetic Track Brake, 899 Feeder Regulators, 498 Junction Boxes, 109 Polyphase Induction Meter, 604 Magnetic Blow-Out Circuit-Breaker, 567 Oil-Break Switches, 533 Rotary Converters, Starting, 494, 495 Round Type Polyphase Meter, 605 Standard Three-Phase Alternators, 483 Switch-Gear, 530 Traction Motors, 876, 883 Strain and Globe Insulators, Combined, 76 Strain Insulator, 74 Electric Railway Rolling Stock, 787 Single Truck, 815 39 Traction Motors, Curves of, 874 "" Brushes, Carbon and Copper, Compared, 424 of Dynamos, 421 "" Brush-holder, Dick, Kerr and Co., 422, 425 Brussels Conduit Tramways, 741 Bruun's Automatic Water-Softener, 337 Bucket Angles, 201 Conveyors, 316 "" Buffalo and Lockport Electric Locomotive, 782 Railroad Rail-Steel Specification, 17 Buildings, 685, 1022 INDEX. 1 .. Buildings, Approximate Cost, 685 ** "" "" "" "" "" Limes, Mortar and Cements, 689 Paints, 704 Piles, 689 "" Plaster, 696 Regulations Roofs, 697 "" "" "" Slope of Drains, 688 Stone Masonry, 695 "" Wall Construction, 685 "" Wall Thicknesses, 688 "" Burgdorf-Thun Three-Phase Railway, 795 to 799 99 "" "" Burnt Ballast, 691 Bursting Strength of Tubes, 189 Burton Level Crossing, 28 " Bush Terminal Company's Electric Locomotive, 782 Bye-pass System of Steam Piping, 184 Bearing Power of Soils, 686 Brickwork, 693 Columns, Posts and Floors, 703 Excavator's Memoranda, 687 Foundations, 686 Life of, 916 Cable - Charging Gear, the Ferranti, 584 Connectors, 620 Laying, 99 "" "" Socket Table, 619 "" Thimble Table, 619 "" " " Cables, Concentric Underground, 129 Electric, Life of, 916 "" "" in London and Provinces, 685 "" "" "" Callender-Webber Conduit, 102 Internal Wiring, 128 Single-Core Underground, 128 Test of High-Tension, 142 Three-Core Underground, 129 Various Types of, 99 Callender's and British Insulated Wire Company's Conduits, 102: Calorific Value of Refuse, 302 Calorimeter, Barrel, 342 "" "" Coil, 343 for Determining Calorific Power of Coal, 387 Peabody's, 344 Tests, 342 Capacity, Alternating-Current Circuit, 449 and Output-Storage Batteries, 709 Measures, 998 "" "" Cap and Cone Insulator, 79 Capital Outlay in Water Power, 938 "" Spent in British Lighting Plants, 928 Car and Trolley Arrangements, 840 Car Axles, 832 London, Brighton Railways Specification for, 833 Steel for, 832 Tests of, 834 Car Bodies, Cost of, 924 Leading Dimensions of, 808 Car Dimensions and Passenger Capacity, 812 ,, Energy Curves, 800 ,, Framing for Trolley Pole, 838 Heating, 850 "" ,, Lighting, 850 "" "7 Cars and Car-bodies, 803 Lightning Arresters, 849 Wiring, 848 INDEX. 1023 Cars, Comparison of Various, 833 "" Energy Stored in, at Different Speeds, 907 Open and Closed in America, Leading Dimensions of, 809; Carbon Brushes, 421, 424 "" Carbonate Waters, 327 Cardew Type of Hot-Wire Measuring Instruments, 588 Carriages, Dimensions and Seating Accommodation, 790, Carriages for Rapid Handling of Crowds, 789 Cascade, Gant, Method of Control, 861 Cast-Iron Joint Boxes, 100 Steam Pipes, Thickness of, 187 "" Cataract Power and Conduit Company, Rates of, 927 Caustic Alkali Cells, 720 Potash and Soda, Storage Batteries, 723 Cayadutta Electric Locomotive, 782 "" Cells for Automobiles, &c., Storage Batteries, 723 "" for Motor-Cars and Launches, Storage Batteries, 712 Cement for Pavements, 49 Cements, 689 Central London Railway, 789 "" 19 66 "" Centre Bearing Rail for Tramways, 9 Cero-Sulphates in Zinc-Carbon Celís, 720 Chain-Grate Stoker, Babcock and Wilcox, 314 Chairs, Great Western Railway, 6 "" "" London and South-Western Railway, 5 Midland Railway, 6 Chemical Composition, American Rails, 17 British Rails, 12, 17 German Rails, 17 "" "1 "" "" "" >> Chicago" Rail Bond, 52 "" "" South-Side Elevated Railway, 789 Storage Battery Company's Cells, 7191 Chicago North-Western Elevated, Cost per Ton Mile, 929 Chimneys, 361 "" "" Batter of Shaft, 366 Brick Lining, 367 Brickwork Base, 366 Caps, 368 "" "" Cavity and Lining, 366 Dimensions of, 360 Draught-Power of, 363 Firebrick Lining, 366 Foundation, Bolts for, 370 Foundations for, 370, 372 Foundations, Working Loads on, 372 "" "" "" "" "" "" "" "" "" "" "" ** 99 "9 "" "2 "" "" "" "> Pollock Company, 371 Properties of, 365 Relation of Area to Length of Flues, 361 Riter Conley Company, 371 Shafts, Regulations, 367 Size of, 362 Stability of, 364, 365 Steel, 361, 371 Wind Velocity and Pressure, 369 "" Chloride Electric Storage Company's Batteries, 714 Christensen Air-Brake, 900 Motor-Trucks, 827 Rolling Stock, 787 Transformers, 510 "" "" Its Influence on Conductivity of Steel, 51 Interior of, 366 Iron and Steel, 370 Lightning, Protection Against, 369 Main Flue, Proportions, 363 Circuit-Breaker, British Thomson-Houston Magnetic Blow-out, 567 Cowan-Andrews Reverse Current, 570 I. T. E., 568 1024 'INDEX. City and South London Railway Electric Locomotives, 77 Track, 789 Tractive Resistance on, 803 "" "" >" "" City' and Waterloo Railway, 789 "" Roads Tramway Track, 7, 11 Clamps, Overhead Line, 76 Coaches for Rapid Handling of Crowds, 789 Coal Ash, Composition of, 387 "" "" "" "" "" "" "" >" "" "" 79 " "" Combustion, Air Required, 669 Consumption of Steam Engines in Tramway Power-Stations, 170 Composition, Weight, &c., of, 387 Conveyors, 315 American, Average Composition of, 398 Bituminous, Yield of, 668 Calorific Power of, 387 Classes of, 384, 386 Handling Plant, Data on, 326 "" 39 Products of Distillation of, 667 Required per Board of Trade Unit, 914 Space Occupied per Ton, 667 Stores, 667 "" "" Coals, Theoretical Heating Value of, 394 Cockrill-Doulton Tiles, 103 Cockerill Gas Engine, 638 Coil Calorimeter, 343 Coke-Oven Gas, 663 Columbia Bonds, 54 Columns, Posts and Floors-Buildings, 703 Combination Car, Preston, 805 Combustion, 388 " "" Determination of the Caking of, 667 Distillation of Cannel, 668 Gas Composition, 668 Gas Production, 666 "" "" Air Required for, 389 by Induced Draught, 379 Commercial Value of Fuel, 397 Commutator, Dick Kerr and Co., 423 Compactum Feed-Water Heater, 337 Composition and Tests of Rails, 16, 17 Compound Engines, 159 Reaction Turbine, 230, 242 29 "" ور ❤ Compounding, Advantages of, 159 Compression, 159 Concrete, 692 for Pavements, 49 Foundations, Hamburg Tramways, 11 Condensation Cylinder, 159 "" در in Cylinders, Loss of Steam by, 347 in Long Steam Pipes, 193 Condensers, 174 "" Reaction Turbines, Three-Section, 243 Steam Turbines, Their Theory, 214 Wound Dynamo, 418 Evaporative, 178 Conductivity of Metals for Feeders, 119 Steel, Influence of Chemical Composition in, 51 Conductor Rail Insulators, 786 Rails, 783 Conductors, Copper, British Standards for, 130 Dimensions and Characteristics of, 138 Table of Equivalents, 138 " 99 Conduit Systems, 727, 738 Conduits, British Insulated Wire Company's and Callender's, 102 Callender-Webber, 102 "" "" Cost of, 738 Doulton, 99 INDEX. 1025 Conduits, National Conduit Company's System, 102 Sykes', 105 "" Ventilated Manhole, 103 Conical Steel Tramway Poles, 86 Connecting-up and Regulating Storage Batteries, 711 Constant Potential Machine, 417 Constants, Hysteretic, 414 Consumers Rates, Cataract Power and Conduit Company, 927 Consumption and Pressure of Slow-Speed Steam Engines, 166 of Power for Car-Heating, 850 of Power per Car-Mile, 800 "" Contal" Electricia" Cell, 719 Continental Tramcars, Speeds of, 932 Continuous-Current Dynamos, Classification of, 418 Rail, 63 Control, Ganz Cascade Method of, 861 "" Johnson-Lundell Regenerative System, 866 Raworth Automatic Regenerative Method of, 864 Controllers, British Thomson-Houston, 854 Brush Company's, 854 "" Diagram, British Thomson-Houston, 855 Diagram, Brush Company's, 856 Dick, Kerr and Co.'s, 853, 857 Location and Erection, 853 ** "" Main Cut-out and Motor Switch, 853 "" Wiring Diagram, Dick, Kerr Controllers, 858, 85 Controlling of Cars, 853 "" Conversion Tables for Weights and Measures, 995 Conveyor, Cost and Maintenance, 323 "" "" Conveyors, 315 Cooling Plant, 175 Towers, Cost of, 925 39 Copper and Carbon Brushes Compared, 424 Conductors, British Standards for, 130 for Feed-Wire, Amount of, 118 "" 3. "" "" 99 "" 12 >> "" "" 19 "" Wire Strands, 133 "" 99 Wire, Temperature Corrections, 130 Wire, Tensile Strength of, 68 Cork Tie-Rod, 23 "" "" Corliss Compound Condensing Engines, 163 Cornish Boiler, 267 "" 19 "" "" Corrugated Iron Roofing, 703 Cost and Quantities, Permanent Way on Metallic Sleepers, 49 Track Construction, 48 99 " Speeds, 322 "" "" Cost of Construction of Tramway Track, 46 "" "" " " Compensating Device, 318 for Single, Two- and Three-Phase Lines, 456 Steam Pipes, Factor of Safety of, 188 Wire, Dimensions for, 132 · Electric Power, Comparative, 938 Engines, &c., for some Modern Power Plants, 924 Generators, &c., Glasgow Power Station, 919 Gas Engines and Plant, 671 Light Railways and Tramways, 45 Light Railways in Different Countries, 45 Overhead and Underground Mains, 939 Overhead Line Construction, 925 Parts Forming Power Plants, 925 Power, 927 Power in Various Plants, 913 Products in British Lighting Stations, 927 Track Laying, Binding, &c., 925 Trucks, Car Bodies, &c., 924 Water Power, per Electric Horse-power, 937 Working Invalides Line, Paris, Electrically, 918 Working Paris-Orleans Lines Electrically, 918 ** LL (* My 1026 INDEX. : Cost per Ton-Mile, Chicago Elevated, 929 Ton-Mile, Metropolitan District, 930 Train-Mile, Metropolitan District, 930 Unit and Load Factor, 927 "" "" "" "" Unit in some Traction Stations, 919 County Council Conduit System, 749 Country Roads Tramway Track, 7, 11 Cowan-Andrews' Discriminating Devices, 571 Reverse Currents Circuit-Breaker, 570 Indicating Device, 572 Cowan E. H. T. Switch Gear, 540 Crankshafts, 171 Creosoted Blocks for Pavements, 49 Critical Current of Series Dynamos, 415 Crompton Wiring Coil Instruments, 590 Cross-Arm, High-Tension Transmission, 945 Section of Wire, Calculation of, 121 Ties per Mile of Track, 20 Crossings, Points, &c., 24 Crossley Gas Engines, 639 Gas Producers, 658 "" "" "" Crossley's Magneto-ignition, Gas Engines, 628 Crossovers, 36 Crown Bonds, 53 Current Density, Calculation of Most Economical, 116 Transmission, Alternating, 456 "" Currents, Types of Multiphase, 465 Curtis Steam Turbine, 244 "" 99 "" 19 "" "" 11 ** "? " "" 19 99 "" "" "" "" "" "" "" "" "" 11 "" " "" "" "" "" "" "" Curve Crosses, 25 Curves, 32 "" "" "" "" "" >> "" Laying Out, 40 "" Middle Ordinates on 10-ft. Chords, 33 "" "" "" " Cylinder Condensation, 159 "9 "" Diameters and Areas, 355 Diameter Diagrams, 156 Ratios, 162, 163 Cylinders and Steam-Pipe Sizes, 186 Cylindrical Two-Storey Boiler, 274 Damper Regulators, 382 Dawson Drain Rail, 44 Dead-weight Safety Valves, 294 De Laval Steam Turbine, 204 Radius Corresponding to Curve, Expressed in Degrees, 33. Super-elevation of Outer Rail on, 42 Widening Gauge on, 42 "" "" " 59 "" Admission Valves, 247 Bearings, 246 Buckets and Nozzles, 247 Clearances, 247 Condenser Gear, 247 Construction, 246 Emergency Governor, 247 Governor, 247 "" Oil Supply, 247 Size of, 248 79 งา : Bearings, 210 Buckets, 207 Efficiency, 210, 212 Flow through Nozzle, 209 Governor, 210 Nozzle, 206 Pinions, 208 Shaft, 208 Steam Consumption of, 230. INDEX. 1027 De Laval Steam Turbine, Wheel Construction, 206 Wheel Speeds, 204, 212 "" Delta and Star Grouping, 466 Demerbe Rail, 11, 12 Denver City Rail Steel Specification, 17 Track, with Brick Paving, 10 Depreciation Formula, 914 ?? of Plants, 913 "" "" "" "" of Plant in Per Cent. of Capital, 916 on British Electric Tramways, 918 Rate, Interest at 3½ Per Cent., 915 Desrumaux Water Softener, 335 Destructor Furnaces, 301 Deutz Double-acting Gas Engine, 652 Gas Engine, 638 22 Suction-gas Plant, 663 "" Diatto Surface-contact System, 727 Dick, Kerr Air-Blast Transformers, 510 Alternators, 476 Controllers, 853, 857 "" "" "" "" "" "" "" "" "" "" "} >> "" "" Differentials and Integrals, 1004 Dielectric Thickness, Paper or Jute, 125 Diesel Oil Engine, 681 Dimensions of Various Carriages, 790 Direct-coupled Dynamos, Power of Engine Required for, 426 Discriminating Devices for Alternating-Current Circuits, Cowan-Andrews', 571 Distribution of Alternating Currents, 456 District Railway, London, 789 Dolter Surface-Contact System, 730 Double-deck Car Bodies, 805, 812 Single-Truck Car Dimensions, 803 Double Line Cost, Light Railways, 45 Double-Service Car, Preston, 805 Doulton-Cockrill Tiles, 103 Doulton Conduits, 99 Insulators, 786 Down-Draught Furnace, Hawley's, 311 D. P. Batteries, 716 Drain Box, 46 Rails, 44 "" "" Details of Generator, 422, 423 Double-Deck Trolley, 843 8-Pole Generator, 440, 442, 443 Equipment for Liverpool Overhead Railway, 775 Generator, Connections of, 429 High-tension Switches, 542 Natural-draught Transformers, 503 Oil-cooled Transformers, 514 Railway Motors, 880 Single-deck Trolley, 884 12-Pole Generator, 440, 442, 443 "" "" Drainage of Tramways, 45, 47 Draining of Steam Pipes, 187 Drains, Slope of, 688 Draught, Forced, 377 "" "" Induced, and Steel-Plate Fans, 373 Mechanical, 372 Required for Efficient Combustion, 372 Required under Babcock and Wilcox Boilers, 390 "" Drop in Alternating-Current Circuit, 451 Dryness of Steam, 342 Dujardin-Planté Battery Company, 716 Duntley Cells-Storage Batteries, 719 Durability of Rails, 23 Sleepers, 915 Dust Fuel, 404 Furnace, 291 1 1028 INDEX. Į } ' ل Dynamometer-Type Wattmeters, 593. Dynamos, A. E. G. Continuous-Current E G Type, 448 Armature Cores, 424 " "" "" >> "" 39 ** "" "" "> "" "" "" ** "" "" 99 "" >> ** "" 25 J2 "" "" "" "" "" "> " "" ** "" "" "3 >> >> "" "" 31 19 "" "" "" "" >> "" "" "" "" "" Armature Windings, 419 Bearings, 430 B. T. H., for Railways, Connections of, 42 Brushes for, 421, 424 Carbon Brushes, 421, 424 Characteristic Curves, 414 Commutator, 421 Compound-wound, 418 Compound-wound, Belt, Rope, Generators, 448 Connections, 418 Connections of Dick, Kerr and Co.'s, 429 Continuous-Current, B. T, H., Direct-Connected, 439, 441 Continuous-Current, B. T. H. Railway Generators, 437 Continuous-Current, Classification of, 418 Continuous-Current, for Railway Work, Performance and Rating, 431 Continuous-Current, Slow-Speed, A. E. G., 431, 434 Continuous-Current, Westinghouse Engine Type, 444, 445, 446 Cost per Kilowatt, 925, 926 Critical Current of Series, 415 Curves of Various, 432 Details of, 421 Dick, Kerr and Co., Details of, 422, 423 Dick, Kerr and Co.'s 12- and 8-Pole Generators, 440, 442, 443 Direct-connected Railway Generator, Specification for, 427 Efficiency and Losses in, 413 Efficiency Formulas, 415 Field Magnets, 421 Field of, 421 Electromotive Force Produced by a, 418 External Characteristics of, 415 for Railways, their Principal Features, 420 for Traction Work, 419 Friction between Commutator and Brushes, 425 Insulating Materials, 426 Insulation of, 421, 425 Life of, 916 Limitations of Output of, 419 Oerlikon Railway Generators, 448 Power of Engine Required for Direct-coupled, 426 Railway Generator, Specification for, 427 Running and Care of, 427 Running Temperature, 419 or Direct-Driven Ganz Railway Ears, Anchor, 76 Self-Regulating, External Characteristic of, 417 Series-Wound, 417 Shunt, Characteristics of, 416 Shunt-Wound, 417 Siemens and Halske Railway Generators, 446 Sparkless Running, 419 Windings and Connections, 418 Anchor and Splicing Combined, 76 Feeder, 76 Mechanical, 76 ?? "" Soldering of, 94 Spliced, 76 "" Straight Line, 76 "" Easement Curves, 40 Ebbw Vale Company's Steel Sleepers, 6 Economiser, Green's, 339 INDEX. 1029 Economiser, Tests With and Without, 341 Edison-Brown Plastic Bonds, 59, 61 Edison Storage Battery Company's Cells, 721 Efficiency and Losses in Diagrams, 413 Formulæ for Dynamos, 415 19 ** Internal, of a Compound Turbine, 215 Mechanical, of Dynamos, 913 "" "" ". "" >> "" "" ** "" "" "" ** "" "" "" "" "" "" "" "" " "" "" "" >> "" "" " ;; "" " در "" "" "" "" "" "" "" Ejector Condensers, 174 Electric and Steam Haulage Compared, 772 "" "" ?? of Accumulators in Central Stations, 913 of Electric Tramway Systems, 913 of Motors, including Gear, 913 of Overhead Line and Feeders, 913 of Perfect Heat Engine, 147 of Plants, 913 of Pressure Engines, 913 of Railway Generator, 913 of Return Circuit, 913 of Rotary Transformers, 913 of Single Reduction Gear, 913 of Stationary Alternating-Current Transformers, 913 of Steam Engine, 150, 913 of Storage Batteries, 709 of Three-phase Generators, 471 of Turbines, 913 of Underspeeded Turbines, 218 of Water-Wheels, 913 and Steam Locomotive Operation of Trains, 780 Generators, 409 Heating of Cars, 850 Lighting of Cars, 850 Locomotives, 776 Locomotives, Data Required by General Electric Company, 781 Locomotives, Performance of Some, 781 Locomotives, Principal Features of Some, 782 Motors, 868 Plants, Gas-Driven, Consumption and Costs, 672 Power, Comparative Costs of, 938 Power Storage Company's Batteries, 714 Power Storage Company's Cells, 712 Railway and Tramway Carriage Works' Cars, 805 Rolling Stock, by the Brush Company, 787 Railway Tracks and Routes, 789 Spark Ignition, Gas Engines, 625 Switch Controller, Christensen Air Brake, 902 Traction, Heavy, 786 Tramcar Speeds in America, 930 Tramcar Speeds, Great Britain, 931 Tramcar Speeds, Continent, 932 Tramway and Motor Omnibus, 1008 Trams, Weight, Dimensions, and Seating Capacity, 793 Units, 409, 410, 411 "" Electrical Company's Switch Gear, 533 Equipment, Maintenance Cost of, 917 Transmission, Advantages of, 955 Electrically-welded Joints, 64 "" "" Electrolytic Corrosion of Boilers, 329 Electro-Magnetic Track Brake, British Thomson-Houston, 899 Electromotive Force in Alternating-Current Circuit, 452 Produced by a Dynamo, 418 Storage Batteries, 707 "" "" "" " Electrostatic Type of Measuring Instruments, 589 Elephant Boilers, 271, 283 Elieson-Bobinski Cells, 720 Elliott Brothers' Alternating-Current Instruments, 591 "" "" Board of Trade Panel, 561 Three-Phase Feeder-Panel, 548 1030 INDEX. Elliott Brothers' Three-Phase Wattmeter Connections, 600 Enclosed Trolley, the Blackwell, 841 Energy Curves, 800 "? Engine House, Cost of, 925 Engineer's Valve, Christensen Air Brake, 905 Engines, &c., Cost of, for some Modern Power Plants, 924 Entropy, 147 "" "" E. P. S. Batteries, 714 Cells for Large Power Stations, Storage Batteries, 712 Evaporative Condensers, 178 ,, Evaporative Power of Town Refuse, 302 Everett, Edgcumbe and Co.'s Measuring Instruments, 588 Power-Factor Indicator, 606 "" "" "" "" "" "" Evershed Patent Ohmmeter, 611 Excavation for Pavements, 49 Work, 687 " "" Stored in Cars at Different Speeds, 907 "" "" Exhaust and Steam Pipes, Dimensions of, 180 Exide M V Chloride Cell for Automobiles, 716 Expansion Curves, 154 Joints for Steam Pipes, 191 External Characteristics of Dynamos, 415 "" Temperature, Diagram, 151 "" Factories, Power Transmission in, 947, 955 Falk Cast Weld, 63 Joints, Conductivity Rests on, 66 "" Fans for Forced Combustion, 380 "J 19 "" " "" "" "" "" 19 "" Resistances Insulation Indicators, 612 Synchroniser, 608 "" "" "" "" 29 Characteristic of Self-regulating Dynamo, 417 Feed-Check Valve, Hopkinson's, 301 Feed-Heaters, 337 Feed Pumps, Air Vessels, 350 and Injectors, 350 Capacity of, 351 Diameter of Suction and Delivery Pipes, 350 General Directions for, 351 Induced Draught Capacity Table for, 373 "" "" "" 99 "1 >> "" "" Feed-Water Tanks, 359 Wire Insulator, 76 Power Required to Raise Water, 351 Power Required to Work, 351 Sinclair Variable Stroke, 354 "" Feeder Car, 76 Plug, Bronze Metal, 74 "" Regulators, British Thomson-Houston, 498 Feeders, 99 "" Size of Steam Cylinder, 350 Speed of, 350 Steam Consumed in Working, 351 Weir Differential, 354 Weir Direct-acting, 353 Worthington Standard, 352 Amount of Copper for, 118 Breaking-Down Voltage, 120 British Standard Sizes of Stranded Conductors, 123 Calculation of Comparative Cross-Section, 121 Conductivity of Metals, 119 Cross-Section of, to Transmit 100 Horse-Power, 122 Current Density, 116 Determination of Size of, 114 Dielectric Thickness, 125 Formulæ for, 122 INDEX. 1031 Feeders, Insulation Resistance of Various Substances, 120 Lord Kelvin's Law, 116 "1 99 99 ** "" "" "" '"" "" Felten and Guilleaume Joint Box, 101 Ferranti Box Fuse, 578 Cable-Charging Gear, 584 High-Tension Switchboard, 545 Indicating Wattmeter, 602 Integrating Wattmeter, 599 Maximum Current Time-Limit Relay, 573 "" " Oil Fuse, 576 Protective Resistance for Electrostatic Voltmeters, 589 Field Magnets, 421 Filter, Pulsometer Engineering Company's Torrent, 336 Fire-bars, 290 ,, Bridges of Steam Boilers, 290 Split, 290 "" Grates and Furnaces, 289 "" Fishbolts and Nuts, 15, 16 Protection of Duplicate, 574 Resistance of Current with Alternating-Currents, 119 Rubber Dielectric and Lead Sheathing, 127 Throw-Over Arrangement, 110 "" London and South-Western Railway, 5 Fishplate, Standard, 4 Fishplates per Mile of Track, 20 Fleming's Hand Rule, 413 Floors of Buildings, 703 Flow of Steam in Pipes, 181 Flues, Amount of Gas in, 361 Fluids, Heat of, 145 Flywheels, 172 Footpaths and Floors, Concrete, 50 Foot-Pounds and Kilogrammetres, 999, 1000 Force and Work, Traction Motors, 760 Forced Draught with Warm Air, 377 Forces Acting Upon a Train, 766 Formation, Storage Batteries, 709 Foundations of Buildings, 686 Four-Wheel and Bogie Cars Compared, 814 Trucks, 820 "" "" Dry-Back Boilers, 280, 282 France and Water-Power Development, 938 French Trucks, Weight of Various, 814 Frequency, 450, 451 Friction in Pipes, 357 Frogs, Tool for Putting up, 76 "" "" Fuel, 384 "" "" "" " 39 "" Analyses of, 385 Coal, 384 Commercial Value of, 397 Dust, 404 and Heat Energy per Board of Trade Unit, 914 Liquid, 400 Straw, 405 Testing, 388 "" Wood, 398 "" "Fulmen " Accumulators, 720 "" "" and Crossings, Trolley Wire, 76, 78 "" Cell Charge or Discharge, 708 Furnaces and Fire-grates, 289 Furnace for Burning Dust Fuel, 291 Lignite, 291 Saw-mill Refuse, 291 Wood, 399 "" "" Fuses, Switchboards, 576 Fusible Wires for Cut-outs, 616 Fusing Point of Tin and Lead Alloys, 106 1032 INDEX. Gallons into Litres, 1002 Galloway Boilers, 270 Galvanised Steel Span-Wires, 69 Ganz Cascade Method of Control, 861 Railway Generators, 448 99 Three-phase Motors, Lecco-Sondrio Railway, 896 Trolley, Lecco-Sondrio Three-Phase Railway, 846 Gas and Coal, 666 "" 19 Composition, 663, 665 Consumption and Cost, 671 "" "" "" Driven and Steam-Driven Stations Compared, 673, 678 Electric Plant, Consumption and Costs, 672 Gas Engines, 623 27 "" "" "" "" " "" "" " "" "" "" "" "" "" "" "1 "" "" "" "" "" Gas in Flues, Amount of, 361 "" "" "" "" "" "" ** "" Compression, 630 Cockerill, Deutz, and Körting Compared, 638 Cooling Water, 630 Cost of Coal-Gas Works, 630 Pipes, Diameter and Discharge, 669 Producers, 654 "" " Gases of Combustion, Analysis of, 390 Gasholders, 670 Gauge Cocks, 299 "" "" " "" Couplers for Direct Driving, 631 Crossley, 639 Measurement of Track, 24 Widening, American Practice, 44 Widening or Curves, 42 Wire, Comparison Table, 131 33 Gauges in Millimetres, Wire, 142 Usual, of Tramways, 24 Gay-Lussac's Law, Gas Production, 666 G. B. Surface-contact system, 736 "" General Electric Company's Conductor Rail, 785 "" Depreciation and Maintenance, 630 Deutz Double-acting, 652 Efficiencies, 629 Explosive Mixtures, 629 Fuel Consumption of, 671 Gas Consumption, 630 Governing, 630 Körting, 636 Natural Gas Consumption, 630 Nuremberg, 648 Oechelhaeuser, 647 "Premier," 642 Pressure-initial and Mean Effective, 630 "" Producers, 654 Temperature, 630 Valves of, Their Working, 624 Westinghouse, 633 Data Required by, for Electric Laws, 781 Single-phase Motors, 972, 976 Generator Connections, Westinghouse Two- and Three-phase, 475 Generators. See Dynamos. "" "" " Advantages of Polyphase, 466 Allgemeine-Elektricitäts Gesellschaft Alternators, 480 Alternating-Current, 464 Alternators for Railway Work, 483 British Thomson-Houston Three-phase, 483 Brown, Boveri and Co's. Single and Multiphase, 485 Connections of Westinghouse Two- and Three-phase, 474 Cost of, Glasgow Power Station, 919 Dick, Kerr Alternators, 476 Efficiency of some Three-Phase, 471 Metropolitan, New York, 474 Oerlikon Three-Phase, 485 INDEX. 1033 Generators, Synchronisers for Three-Phase, 471 Westinghouse Alternators, 481 "" Geneva Tramway Section, 12 German State Railway, Wheel Specification and Test, 835, 837 Glasgow Power Station, Cost of Generators, &c., 919 Tramway Depreciation, 918 "" Globe Frog Pull-Off, 76 "" 39 "" "" Gould Storage Batteries, 720 Granite Tests, 50 Gravity Brake Gear, 897 Great Northern and City Railway, 789 Green's Economiser, 339 Griffin Car Wheel Tests, 837 Ground, Bearing Power of, 686 Grooved Girder Tramway Rails, 8 Guard Rail for Tramways, 9 Wire, 69, 95 "" "" >> "" "" 99 >> 95 "" Guards, Safety-Rolling Stock, 909 Guernsey Stations, Generating Costs, 674 Guide Blades and Bucket Angles, 201 "" " Guard-Wire Insulator, 76 Insulator, 76 Strain Insulator, 74 Goldschmidt Process of Rail-Welding, 65 Haarmann Rail, 17, 18 Hadfield's Standard Cross-overs, 36 Easement Curves, 40 Equilateral Turnouts, 34 Lateral Turnouts, 37 99 "" "" "" "" "" "" "" Halifax Tie Rod, 22 Hamburg Tramways, 11 Hangers for Guard Wire, 76 Hardness of Water, 327 "" "" Hart Accumulator Company's Batteries, 717 Haulage, Steam and Electric Compared, 772 Hawley Down-draught Furnace, 311 Heat, Loss of, 358 Headways and Speeds on Track, 802 "" Heat Availabe at Each Stage, Steam Turbine, 244 Available in a Compound Turbine, 217 Conducting Power of Covering Materials, 192 Rolling Stock, 787 Piccadilly, and Brompton Railway Rolling Stock, 787 Railway Rails, 3, 4 ,, Hangers, 76 Insulator, 76 "" "" "" Temperatures, Unit of, 145 Units Available in Superheated Steam-Turbines, 229 Heating of Cars, 850 Engine, Efficiency of Perfect, 147 Latent, 147 Loss from Steam Pipes, 193 Loss in Uncovered and Covered Steam Pipes, 191, 192 Mechanical Equivalent of, 145 Sensible, 147 Specific, 145 Specific of Superheated Steam, 146 390 Power of Refuse, 303 Power of Wood, 399 Value of Coals, 394 Value of Petroleum and Coal, 401 "" "" Heavy Electric Traction, 786 Heel Plates, 32 LL2 1034 INDEX. Heinz Accumulators Storage Batteries, 718 Hermsdorf High-Tension Porcelain Insulators, 946 Heyl and Paterson Coal Conveyor, 320 Highfield Booster, 553 High-Tension Insulators, 940 "" Hoboken Railway Electric Locomotive, 782 Holden's System of Burning Liquid Fuel, 403 Holden and Brooke's Grease and Oil Separator, 336 Holing of Rails for Fishes and Bolts, &c., 15, 16 Hopkinson's Accessible Feed-check Valve, 301 Patent "Absolute " Water Gauge, 299 Hoppenstedt Coupling, 633 Horse-power, French into English, 999 into Kilowatts, 998 Hot-tube Ignition, Gas Engines, 625 Hot-wire Type of Measuring Instruments, 588 Howden's System of Forced Draught, 377 Hydraulic Damper Regulators, 382 Hysteretic Constants for Various Materials, 414 Hysteresis Loss in Various Metals, 414 Ignition Methods, Gas Engines, 623 Illinois Central Railway Management, 789 Impedance, 449, 451 "" and Reactance for Various Circuits, 461 Imperial Standard Wire Gauge, 70 Impulse and Pressure Wheels, 201 ** Impurities Storage Batteries, 708 Incrustation and Čorrosion of Boilers, 327 Indicated Horse-power of an Engine, 159 Indicator Diagram, 153 Theoretical, 155 "" "" Induced Draught, 372 "" "" " "9 "" Inductance, 449 Induction Troubles, Overhead Line, 98 "" "" "" Influence of Chemical Composition on Conductivity of Steel, 51 Injector, Rules for Finding Size of, 354 Injectors, 350 Instruments, Measuring-Switchboards, 586 Insulating Materials, Quality of Various, 426 Insulation of Dynamos, 421, 425 Resistance of "Etna" Insulators, 81 "" Resistance of Various Substances, 120 "1 "" 99 "" "" Insulators and Line Material, 72 "" Simple, Turbines of the Allgemeine-Elektricitäts Gesellschaft, 213 Steam Turbines, 204 "" ** Forced Combustion by, 379 System of American Blower Company, 381 "" "" "" "" Type of Measuring Instruments, 591 Type Wattmeters, 594 Testing Instruments, 611 and Pins, 940 Berlin Elevated Third Rail, 785 Boston, 74 Brass Cap Feed-wire, 76 Bronze Metal Feeder Plug, 74 Brooklyn and Globe Combined, 76 Brooklyn Strain, 74 1 Cap and Cone, 79 Double Brooklyn Strain, 74 for Conductor Rails, 786 Globe, 74, 76 Globe Guard Wire, 76 Guard-Wire Hangers, 76 Heavy Terminal, 76 1 INDEX. 1035 I Insulators, J. A., 74 "" "" King Turnbuckle, 76 Positions for Different Pressures, 944 Straight Under-running Section, 76 Tests for Tensile Strength, 80 "West-End" Bracket-Arm Hanger, 74 "West-End" Bridge, 74 "West-End" Car House, 74 "West-End" Double Pull-off, 74 West-End" Insulating Bolt, 74 "West-End" Single Pull-off, 74 "West-End" Straight Line, 74 Integrals and Differentials, 1004 Interborough Rapid Transit, New York, 789, 831 Internal Efficiency of a Compound Turbine, 215 Wiring Cables, 568 >> ** "" "" Invalides, Paris, Line, Cost of Working Electrically, 918 I. T. E. Circuit Breakers, 568 "" "" "" "" 39 "" "C "" " “J. A.” Insulators, 74 Johnson-Lundell Regenerative System of Control, 866 Johnson and Phillips Accumulator Switchboard, 562 Joint Boxes, Cast-Iron, 100 Joints, Falk Cast Weld, 63, 64 "" Goldschmidt Process, 65 Movable Rail, 25 Welded Electrically, 64 Jones' Underfeed Stoker, 310, 312 " "" Journal Box, Master Car-Builders', 831 Junction Boxes, 108 " "} "" "" Street Pillar Connections, 111 Jungfrau Three-Phase Railway, 795 Jungner Cells, Storage Batteries, 722 Jute and Paper Dielectric Thickness, 125 "" "" Blackwell Improved, 109 British Thomson-Houston, 109 Connections of, 107 Keene's Cement, 691 Kelvin Engine-room Wattmeter, 602 Multi-cellular Electrostatic Voltmeter, 590 Parallelling Voltmeter, 564 * Kelvin's Law, 116 Keys, Oak, for Rail Fastening, 5 Kilogrammetres and Foot-pounds, 990, 1000 Kilowatt in Power Stations, Cost of, 925, 926 Kilowatts into Horse-power, 998 Kincaid, Waller, Manville and Dawson Boiler Tests, 277 King Insulated Turnbuckle, 76 Kingsland Surface Contact System, 731 Klein's Central Jet-Condensing Plant, 177 CC Koker" Stoker, 311 Kölner Accumulatoren Werke, Gottfried Hagen, 718 Körting Gas Engines, 636 Lag and Lead in Alternating-Current Circuits, 450, 463 Lake Street Elevated Railway, 789 Lancashire and Tubular Boiler Combined, 273 Boiler, 264, 281 "" Lead and Armour for Underground Cables, 125 1036 INDEX. | Lead and Tin Alloys, Fusing Point of, 106 Cells, Storage Batteries, 707 "" Sheathed Dock Coiled Armoured Cable, 100 Sheathing, Feeders, 127 "" 99 Leads of Crossings, 32 Letheroid, Insulation Strength of, 426 Lecco-Sondrio Three-Phase Railway, Ganz Cascade Method, 861 "" Ganz Motors, 896 Motor Car, 796, 797 Trolley, 846 "" "" "" Ledward's Evaporative Condenser, 178 Lehmann-Mann Accumulators, 718 Leitner Cells-Storage Batteries, 717 Length of Some Electric Trains, 793 Level Crossing-Burton, 28 Lever Safety-valve, Rule for Calculating Load on, 293 Life of Rails, 24 "" " "" Lignite, 400 "" "" Light Power Plant, Load Diagram of, 173 Railways, Cost of, 45 39 Lighting of Cars, 850 "" "" Plants, British, Capital Spent on, 928 Stations, Cost per Unit Sold, 927 Two-wire, Feeder Panel-Switchboards, 559 Three-wire, Feeder Panel-Switchboards, 558 Reversible Booster Panel-Switchboards, 556 Lightning Arresters, 113, 579 "" for Cars, 849 99 99 Furnace for, 291 "" Lime and Cement Mortar, Strength of, 691 Limes, Mortar and Cements, 689 Line Constants for Polyphase Power Transmission, 460 Liquid Fuels, 400 Litres into Gallons, 1002 Liverpool and Southport Railway, 789 Overhead Railway, 775, 789 Overhead Motor Curves, 883 "" "" Lloyd's Rules for Safety Valves, 298 Load Diagram of Street Light Power Plant, 173 Factor and Cost per Unit, 927 "" "" on Lever Safety-valve, Rule for Calculating, 293 Lock Armoured Single Cable, 100 Locomotives, Electric, 776 Principal Features of Some, 782 London and South-Western Railway Rails, &c., 4 "" "" Long Distance High-tension Power Transmission, 458 Measures, 995, 996 "" Lorain Surface-contact System, 737 Brighton, and South-Coast Railway Axle Specification, 833 County Council Conduit System, 749 "" Losses in Dynamos, 413 "" Loss Due to Hysteresis in Various Metals, 414 of Power in Shafting, 947 Electric Tramway Systems, 913 "" Return Circuits, Alternating Currents, 1013 Low-water Detector and Alarmı, 301 Lubricants, Data on, 196 Lumford Plates-Storage Batteries, 716 Machine-Tool Drives, 947 Machines, Power Required for Various, 952 Magnetic Brake, Westinghouse, 898 Track Brake, British Thomson-Houston, 899 Maintenance Cost of Electrical Equipment, 917 of High-Tension Single-phase Traction Plant, 916 INDEX. 1037 1 1 Maintenance of Plants, 913 per Motor-Car Mile on American Lines, 916 per Ton-Mile for American Railways, 917 Magnetic Flux, 412 "" Units, 409, 410, 411 Magneto-ignition, Crossley's, Gas Engines, 628 Magnetomotive Force, 413 "" "" Main Thoroughfares Tramway Track, 7, 11 Majert Plates-Storage Batteries, 718 Manhattan Elevated Railway, New York, 789 Motor Trucks, 827 Results, 929 "" Manholes, 106, 292 "" "" Ventilated, 103 "" Manufacture of Storage Batteries, 710 Marine Boilers, 270 "" Master Car-Builders' Journal Box, 831 Wheel Test, 835 Maximum Traction Trucks, 820 Mean Effective Pressures, 154 Measurement of Power in Circuits, 592 Measuring Instruments-Switchboards, 586 Mechanical Draught, 372, 377 "" "" "" "" >> "" "" Mediterranean Railway Electric Locomotive, 782 Meldrum and Clayton's Patent Sprinkling Stoker, 313 Meldrum's Refuse Destructor, 304 "" System of Forced Draught, 378 Mensuration, 1005 Mersey Tunnel, 789 Metal Work per Mile of Track, 20 "" Ears, 76 Equivalent of Heat, 145 Stokers, 307 "" Metallic Sleepers, Permanent Wagon, Quantities and Cost, 49 Metric Units and English, 995, 996 Metropolitan-District, Cost per Ton- and Train-Mile, 930 District Railway Rolling Stock, 787 District Track, 786 New York Generators, 474 Railway, London, 789 West Side Elevated Railway, 789 Midland Railway Rails, 3, 4 Milford-on-Sea Electricity Supply Company, Log Sheet, 676 Missouri River Power Company's 50,000-volt Transmission, 946 Moisture in Steam, Determination of, 346 Mond Gas Producer, 655 Money Tables, 1007 Mortar, 689 Motion of Trains, Calculation of, 763 Motor Dynamos, 438 Motor Generators and Rotary Converters, 486 Motor Omnibus and Electric Tramway, 1008 Motors, Electric. See Traction Motors, 759, 868 Stationary, Life of, 916 "" Mountain and Gibson Trucks, 827 Moving Coil Type of Measuring Instruments, 590 33 Nalder Brothers and Thompson's Measuring Instruments, 588 Ohmmeter, 612 National Conduit Company's Automatic Accumulator Switch, 575 System, 102 "" "" "" Negative Booster Connections, 439 Neptune Bonds, 57 Neuilly Company's Pollak Cells, 718 Neumühl, Morian and Co., Batteries, 718 1038 INDEX. "" " Newbigging's Rule, Scrubbers and Washers, 666 New York Central Electric Locomotive, 782 Metropolitan Generators, 474 Metropolitan Street Railway Company, 747 Newhaven and Hartford Railway Electrification, 929 Single-phase Motors, 986 Third-Avenue Main Line, 743 North-Eastern Railway, 789 " Electric Locomotives, 777 North-Western Elevated, Chicago, Cost per Ton-Mile, 929 Nuremberg Gas Engines, 648 Oak Key, London and North-Western Railway, 5 Midland Railway, 5 Oak Trenail, London and South-Western Railway, 5 Ober-Ammergau Line Single-phase Motors, 979 Oechelhauser Gas Engines, 647 Oerlikon Company's Railway Motors, 894 Current Collection, Single-phase Motors, 979 Locomotive, Tests of a 50,000-Volt, 989 Motor Generators, Efficiency of, 490 Railway Generators, 448 "" "" "" "" Three-Phase Generators, 485 Ohmmeters, 611 "" Oil Fuse, the Ferranti, 576 Omnibus, Motor, and Electric Tramway, 1008 Operating Expenses of Traction Plants, 920 Output and Capacity, Storage Batteries, 709 Overhead and Underground Mains, Cost of, 939 Overhead Line, Bracket Arms, 86 Construction, Cost of, 925 "" "" "" "" " "" "" "" "" 29 "" "" "" 19 " "" "" "" "" " "" 99 "" Splicing Sleeve, 79 Suspenders, 92 ་ English Conical Steel Tramway Poles, 86 Erection, 93 Flexible Suspensions, 91 Galvanised Steel Span Wires, 69 Guard Wires, 95 Induction Troubles, 98 Insulators and Line Material, 72 Life of, 916 List of Tools for Line Erection, 98 Material Used in Construction, 73 Sag on Span Wire, 71 Sag in Trolley Wire, 70 Soldering Ears, 94 Specification of Material, 73 Switch, 94 Tensile Strength of Copper Wire for, 68 Trolley Wire Lengths, Joints, 72 Trolley Wire Tensile Test, 69 Tubular Tramway Poles, 85 Wire-Stretching Device, 80 Wooden Poles for, 83 Paderno-Milan Transmission, 946 Paints for Buildings, 704 Paper or Jute, Dielectric Thickness, 125 Paralleling Continuous-Current Generators, 564 Paris Conduit System, 748 Metropolitan Railway, 789 " "" "" "" Parian Cement, 691 -Orléans Electric Locomotive, 782 Line, Cost of Working Electrically, 918 Versailles Electric Railway, 789 ! . 1 ; Parsons Steam Turbine, 235 "" "? "" " ** "" "" "" "" "" "" "" 7 "" "" 39 "" "" Balancing, 235 Bearings, 237 Blade, 238 Buckets, 237 Casing, 237 Drum, 235 Efficiency, 240 Foundations, 240 Glands, 237 Governor, 238 Starting Up and Running, 240 Thrust Blocks, 239 Weight and Space, 240 "" "" "" "" "" "" "" "" "" Partridge's Patent Sparklet Fuse, 577 Passengers Carried and Receipts per Mile, 928, 933 INDEX. Paul Surface-contact System, 733 Pavements, 49 Peabody's Throttling Calorimeter, 344 Peat, 400 Peckham Standard Trucks, 815 Pennsylvania Railroad, Specification for Petroleum Products, 199 Wheel Thermal Test, 835, 837 Periodicity, 450, 451 Permanent Way on Metallic Sleepers, Quantities and Cost, 49 Pescetto Cells-Storage Batteries, 718 Petroleum as Fuel, 401 Oils Against Boiler Corrosion, 328 Products, Pennsylvania Railroad, Specifications, 199 Refuse, or Astaki, 403 "" "" "" Pflüger Negatives Storage Batteries, 718 Philadelphia Step-rail Track Section, 9 Piles, 689 Pins and Insulators, 940 Pipe Bends, 100 "" "" ** Hangers and Brackets, 193 Steam Covering, 191 Pipes, Friction in, 357 "" "" "" Gas Service, 669 Steam, Data on, 183 Piston Speed, 163 Plane Triangles, 1003 Composition, Dr. Angus Smith, 360 Compound, P. and B., 360 & "" Planes, Belt-driven, Power for Driving, 950 Direct-driven, Power for Driving, 951 Planté-Faure Plates Storage Batteries, 717 Plaster for Buildings, 696 of Paris, 691 "" Plate Conveyors, 316 Points and Crossings, Method of Bonding, 63 Crossings, &c., 24 Pole and Cross-arm, High-tension Transmission, 945 Planting and Raking, 82 "" Sizes, Weights and Strains on, 83 Poles and Pole Straps, 76 "" Steel, 86, 87 "" Pollak Cells-Storage Batteries, 718 Polyphase Generators, Advantages of, 466 "" Power Transmission, Current and Pressure, 462 Power Transmission, Data on Lines for, 460 Pop Safety Valves, 296 Porcelain as Insulating Material, High-tension, 944 High-tension Insulated Tests, 940 "" Portable Engine Boilers, 281 Portland Cement, 690 Posts and Floors-Buildings, 703 1039 N 1040 INDEX. Power and Speed Curves, Traction Motors, 868 Brakes, 897 >> 31 ** "" " "" ** ** 11 ?? >" "2 >> "" ** ** "" "" "Premier" Gas Engines, 642 Pressure and Consumption of Slow-Speed Steam Engines, 166 Compounded Steam Turbines, 215 ** ** Gauges, 299 "" Consumption per Car-mile, 800 Consumption for Car Heating, 850 Cost, 927 Cost, Generated from Falling Water, 937 Distribution Companies, Data on, 926 Factor in Alternating-Current Circuits, 452, 466 Factor Indicators, 605 Loss in Shafting, 947 Plant Cost, Details of, 925 Plants, Cost of Engines for some Modern, 924 Required for Various Tools and Machines, 951 Stations, Steam Engines for, 165 Stations, Tramway, Consumption of Steam Engines, 170 Transmission, 937 Transmission, Electrical, 456, 458 Transmission in Factories, 947, 955 Lines, 941 "" Pressures, Mean Effective, 154 "" or Reaction Turbines, 202 Tables, 1001 Wheels, 201 Preston Combination Car, 805 Double-service Car, 805 Most Economical Terminal Absolute, for Compound Corliss Condensing Engines, 163 Priming, 342 Pritchett and Gold Accumulators, 718 Producers, Gas, 654 Protective Devices-Switchboards, 566 Pull-off, Anderson's Double, 79 Pulsometer Engineering Company's Torrent Filter, 366 Push-plate Conveyor, 322 Quantity and Cost, Permanent Wagon Metallic Sleepers, 49 Track Construction, 48 99 Raffard Flexible Coupling, 632 Rail Bonds, 52 "" Continuous, 63 Fastenings, 5 "" 19 " *1 "" ** "" *3 Rails, Drain, 44 77 ** Joint, Standard, 4 Steel, Qualities, 17 Tests, 16, 24 Welder, Connections of, 63 Welding, 63 Great Northern Railway, 3, 4 ** London and South-Western Railway, 4 13 Midland Railway, 3, 4 >> Simple Formulæ for, 20 *3 ** ** "3 "" Railway Cost, 45 >> Standard American Tramway, 8 Standard Sections, 4 Wear of, 24 Weight per Mile, 20 Generators 99 >> 11 Connections of British Thomson-Houston, 428 Continuous-current British Thomson-Houston, 437 Dimensions of Ganz, 448 INDEX. 1041 Railway Generators, Performance and Rating of Continuous-cnrrent, 431 Principal Features of, 420 "" ** Specification for Direct-connected, 427 "" 39 Motor Armature, Repair Parts of, 872 Rolling Stock, Electric, by the Brush Company, 787 Sleepers, their Durability, 915 Steel Sleepers, 6 Railways, Alternators for, 483 " "" "" "" "} " "" Rake of Poles, 82 Rapid Handling of Crowds, Coaches for, 789 Rateau 500 Electric Horse-power Turbo-dynamo, 219 Steam Turbine, 220 99 "" "" "C "" 22 "" "" >> "" "", "" Light, Their Cost, 45 Light Working Expenses, 45 Rotary Converters for, 488 Three-phase, 794 "" " "" "" "" "" >> "" "" "" "" "" "} "" "" "" "" "" "" "" "" "" "" "" Rates to Consumers, Cataract Power and Conduit Company, 927 Raworth System of Automatic Regenerative Control, 864 Reactance, 450 and Impedance for Various Circuits, 461 Reaction Turbines, 202 "" "" Compound, 230 "" "" Speed Flow from Guide Blades, 233 Reaction Turbines, Speed of Bucket, 233 Stage Efficiency of a, 232 Velocity Diagram, 230 Receipts per Mile and Passengers Carried, 928 per Passenger, Steam and Electric Lines, 933 Receiver and Woolf Engines, 160 "" "" Refuse, Destructors, 301 "" Capacity, Two-Cylinder Compound Engine, 162 Recovery, Storage Batteries, 708 Reducing Valves, 195 Buckets, 221, 222 Design of a, 224 Diaphragms, 222 Disc Friction and Losses by Fan Action, 222 Internal Efficiency, 224 Leakage Losses, 222 Steam Consumption, 224 Trial Data of a 500 Horse-power, 225 Velocity Diagram, 221 Wheel Construction, 220 Evaporative Power of, 302 Regulating Storage Batteries, 711 Regulation of Transmission Lines, 941 Regulations for Polyphase Circuits, Westinghouse-Stillwell, 500 Reissner's Rule, Scrubbers and Washers, 666 Repair Parts of Railway Motor Armature, 872 Residue, Solid, in Water, 328 Resistance, Insulation of Various Substances, 120 "" "9 "" "" "} "" Resonant" Circuit, 451 in Return Circuits, Alternating Currents, 1013 of Converters with Alternating Circuits, 119 of Trains, 766-772 "" Return Circuit Alternating Currents, Losses and Resistance in, 1013 and Bonding, 51 Reversible Boosters, Switchboards, 552 Rheostats, 613 Riedler-Stumpf Steam Turbine, 213 "" ** "} "" of Wire for Polyphase Power Transmission, 460 of Wire in Relation to Frequency and Power Factor, 459 Virtual, Alternating-Current Circuit, 452 "" "" 33 Buckets, 214 Nozzle, 214 Shaft, 214 Wheel Construction, 213 1042 INDEX. Ring System of Steam Piping, 184 Riveted Steel Steam Pipes, 187 Roadways, Asphalte, 50 Rolling Stock, 759 "" ** "" "" "" "" Roman Cement, 691 Roofs of Buildings, 697 Rotary Converters and Motor Generators, 486 "" 39 "" by the Brush Company, 787 Cost, Light Railways, 45 Safety Guards, 909 "" "" "" for Railway Work, 488 Impressed, Counter, and Impedance Electromotive Force in, 490 Maximum Output with Given Line Impedance, 491 Proportion of Compounding in, 492 Regulation of Electromotive Force, 491 Starting, 492 Westinghouse, 494, 497 Rubber Dielectric-Feeders, 127 Ruberoid Roofing, 697 "" "" "" Safety Guards, Rolling Stock, 909 Safety Valves, 292 "" "" British Thomson-Houston, 494, 495 Dick, Kerr and Co., 496 Difficulty with Parallel-connected, 494 "" "" 99 "" "" ** "" Sag in Trolley Wire, 70 Sag on Span Wire, 71 Saturated Steam, 146 33 and Fire-grate Areas, 297 B▼ Properties of, 146, 148 Sawdust as Fuel, 405 Saw-Frame, 24-in., Power to Drive, 955 Scale in Boilers, 327 Scale-making Material, Solubility of, 329 Scarfed Joint, Continental Track, 10 Schmidt Superheater, 348 Areas, Minimum Allowed by Board of Trade, 297 Board of Trade Rules for, 298 for High Steam and Low Water, 296 in America, Dimensions of, 298 Lloyds' Rules for, 298 Springs, Size of Steel for, 294 Schulz Plates, Storage Batteries, 718 Schweizer Accumulatoren Werkes Batteries, 718 Screw Threads of Pipes, 190 Scrubbers and Washers, 666 Scum Cocks, 300 "" Seating Accommodation of Various Carriages, 799 Capacity of some Electric Trains, 793 Self-Discharge, Storage Batteries, 708 ,, Induction, 449 Separator, Holden and Brooke's, 336 Series-wound Dynamo, 417 Service Pipes, 666 Shaft, Pull on, Due to Displacement of Armature, 172 Shafting, Power Required to Drive, 947 Shaw Non-Arcing Arrester, 584 "" Shoreditch Refuse Destructors, 303 Vestry Boiler Tests, 277 Shunt Dynamos, Characteristics of, 416 Shunt-wound Dynamo, 417 -Siemens Conduit, Berlin, 746 Conduit, Budapest, 741 Gas, 655 -Schuckert, Single-phase Motors, 979, 985 ་ INDEX. 1043 Siemens Sliding Bow, 844 >> Synchroniser for Three-Phase Generators, 472 Siemens and Halske Lightning Arrester, 579 Measuring Instruments, 588 Railway Generators, 446 Traction Motors, 890, 893 "" "" "" "" "" Sinclair Variable-stroke Feed Pump, 354 Single-phase Allgemeine Elektricitäts-Gesellschaft, 963, 967, 282 "" Car Connections, Westinghouse, 965 Car Controller, Westinghouse, 966 Curves Compared with Continuous, 963 Equipment, Characteristics of, 961 General Electric Company, America, 972, 976 Generator Panel - Switchboards, 550 Motors, 960 Motors, Compensated Repulsion, 960, 962 Motors, Compensated Series, 060 Motors, Plain Series, 960 "" " "" "" "" "2 "" "" "" "" "" >> "" "" ** 19 "" > "" "" > > "" Motors, Simple Series, 960 Motors, Track and Trolley Resistance, 975 Motors, Winter-Eichberg, 960, 967, 969 New York, New Haven Railroad, 986 Ober-Ammergau Line, 979 Oerlikon Company's Current Collection, 979 Oerlikon Locomotive Tests of a 50,000-Volt, 989 Operations, Compared with Direct-current 978 Overhead Construction, 971 Resistance of Trolley and Track, 975 Runs, Compared with Direct-current, 979 Siemens-Schuckert System, 979, 985 Spindlersfeld Line, 967 "" "" Stubaithal Railway, 982 Swedish State Railways, 983 Traction Plant Maintenance, 916 Trolley and Track Resistance, 975 Single-phase Westinghouse, 964, 986 Single-truck Double-deck Car Dimensions, 803 Sinking Fund, 915 "" Size of Feeders, Determination of, 114 Skin Effect in Álternating-current Circuit, 453 Sleepers, Different Woods, their Durability, 915 "" Metallic, Quantity and Cost of Permanent Way on, 49 per Mile of Track, 20 Spacing of, 7 Steel, 6 "" "" Slope of Various Soils, Natural Angle of, 687 Slotters, Direct- and Belt-driven, Power for, 951 Smoke Prevention, 389 Soda, Employment of, in Feed-water, 337 Soft-iron Type of Measuring Instruments, 587 Soldering Iron, Trolley Wire, 76 of Ears, 94 Solders, Composition of, 108 Solid Residue in Water, 328 Span Wire Sag, 71 "" Wires, Galvanised Steel, 69 Spark Ignition, Gas Engines, 625 Sparklet Fuse, Partridge's Patent, 577 Speed Table, Traction Motors, 762 Traction Motors, 759 "" Speeds, Electric Tramcars, America, 930 "" Electric Tramcars, Continent, 932 Electric Tramcars, Great Britain, 931 and Headways on Track, 802 "" "" Spike, London and Great Western Railway, 5 Spindlersfeld Line, Single-phase Motors, 967 Splicer Ear, 76 1044 INDEX. Splicing Sleeve, Overhead Line, 79 Sprague, Thomson-Houston Multiple-unit System, 857 Spring-loaded Safety Valves, 295 Square and Surface Measure, 1000 St. Gallen Tramways, 11 St. Louis and Belleville Electric Locomotive, 782 Stacks. See Chimneys. "" Standard American Trolley, 838 Trolley Pole Tests, 841 Stansstad-Engelberg Three-phase Railway, 795 Star and Delta Grouping, 466 Starting Polyphase Induction Motors, 565 Steam and Electric Haulage Compared, 772 and Electric Locomotive Operation of Trains, 780 and Exhaust Pipes, Dimensions of, 180 and Gas-driven Stations Compared, 673 Boilers, 251 "" "" "" "" "" "" >> "" "" Steam Engines, 145 Collecting Pipes, 300 Consumption of Engines in Tramway Power Stations, 170 Consumption of Slow-speed Condensing Engines, 166 Determination of Moisture in, 346 Dryness of, 342 "" "" "" "" "" "" "" "" "" "" " "" "" "" ** "" "> "" >> "" "" "" "" "" "" " "" "" "" "" "" "" 19 "" "" Belliss, 169 Compound Corliss Condensing, 163 Compounding, 159 Consumption of, in Tramway Power Stations, 170 Cylinder Ratios, 162 Cylinders and Steam-pipe Sizes, 186 :: Economical Results, 171 Efficiency, 150 Steam Expansion Curves, 154 Flow of, in Pipes, 181 "" Loop, 355 "" "" Mean Pressure of, in Engines of Different Types, 158 Steam Pipes, Cast-iron, Thickness of, 187 Copper, 188, 189 Covering, 191 for Electrical Power Stations, 165 High-speed, 167 Ideal Diagrams, 161 Indicated Horse-power of, 159 Life of, 916 Mean Effective Pressure and Steam Consumption of Slow Speed, 166 Piston Speed, 163 Ratio of Cylinders, American Corliss, 165 Receiver Capacity, 162 Single, Compound, and Triple-expansion Compared, 160 Standard American Tramway, 164 Willans High-speed, 167 Woolf and Receiver Types, 160 Data on, 183 Draining, 187 Expansion Joints, 191 Flanges and Brackets, 193 Linear Expansion of Material, 190 Ranges, 187 Riveted Steel, 187 Steam Piping, 179 Sizes of, for Stationary Engines, 186 Strength, Board of Trade Rules, 188 Strength of Materials Used for, 188 Thickness of Copper, 190 Welded Wrought-iron, 187 Wire-wound, 189 By-pass System, 184 Ring System, 184 INDEX. 1045 Steam Plant, Cost of, 925 Separators, 195 Turbine Operated Station, America, Costs of, 917 Steam Turbines, 201 - 39 29 "" "" "J "" "" >> "" "" "" " "" "" "" 19 "" "" Steam Valves, 194 Reducing, 195 Steel, Conductivity and Chemical Composition of, 51 Poles, Sizes, Weights, and Deflections, 87 Sleepers, 6 "" Track Construction, American, 13 Tramway Poles, 86 Steel-tyred Wheels, 835 "" Step-rail Track Section, 9 "" "" "" "" Step Tramway Rails, 8 Stillwell Regulators for Polyphase Circuits, 500 Stirling Water-tube Boiler, 276 Stokers, Mechanical, 307 >> Stone Block Pavement, 50 豐 ​Masonry, 695 99 Stop and Throttle Valves, Area through, 185 Storage Batteries, 707 "" "" 99 " "" "" *99 "" "" "" 99 1 "" "" "" "" >> >" * Comparative Efficiency of Impulse and Reaction, 231 Compartment Compounded, 218 Compound Reaction Turbine, 230 Curtis, 244 "" "" "" "" De Laval, 204 Giving 2000 Indicated Horse-power at 35 Revolutions per Second, Proportions for, 243 Heat Units Available in Superheated Steam, 229 Parsons, 235 Riedler-Stumpf, 213 Stage Efficiency of Reaction, 232 Theory of the Compound, 214 Westinghouse-Parsons, 240 Working with Superheated Steam, 226 19 " +9 "" Accumulator Industries, Limited, 717 Accumulatoren Fabrik, 718 Alkali and Nickel-iron Cells, 720 Ashmore, Benson, and Pease Batteries, 717 Behrend Accumulatoren Werke, 718 Capacity and Output, 709 Caustic Potash and Soda, 723 Cells for Motor Cars and Launches, 712 Chloride Electric Storage Company, 714 Connecting-up and Regulating, 711 Contal "Electricia" Cell, 719 Dujardin-Planté Battery Company, 716 Edison, 721 Efficiency, 709 Electromotive Force, 707 Elieson-Bobinski Cells, 720 E. P. S. Cells for Large Power Stations, 712 E. P. S. Company's Batteries, 714 Formation, 709 "Fulmen" Accumulators, 720 Fulmen Cell Charge and Discharge, 708 Gould Company's, 720 Hart Accumulator Company's, 717 Heinz Accumulators, 718 Jungner Cells, 722 Kölner Accumulatoren-Werke Gottfried Hagen, 718 Leitner Cells, 717 Lumford Plates, 716 Majert Plates, 718 Manufacture of, 710 Neumühl, Morian and Co., 718 Non-lead Cells, 720 1046 INDEX. [ Storage Batteries, Pescetto Cells, 718 " "" "" "" "" "" "" "" >> "" 1: "" ". "" "" "" "" "" "" Straight Line Ear, 76 Strains on Poles, 83 " "" >> " Strands of Copper Wire, 133 Stranded Conductors, British Standard Sizes, 123 Straw as Fuel, 405 Street Pillar Connections, 111 "" "" ** "" "" Stretching Device, Overhead Line, 80 Stubaithal Railway Single-phase Motors, 982 Sulphate Waters, 328 "" "> "" Sulphating, Storage Batteries, 709 Sulphur, Removing of, from Gas, 665 Sulphuric Acid, Storage Batteries, 722, 723 Superheated Steam, 146 "" " ** Superheaters, 347 Surface-contact and Conduit Systems, 727 Surface Measure, 1000 Suspenders for Overhead Line, 92 Suspension of Traction Motors, 870 Suspensions, Flexible, for Overhead Line, 91 Swansea Tie-Rod, 22 Swedish State Railways Single-phase Motors, 983 Swinburne Induction Type of Measuring Instruments, 591 "Swing Bolster" Maximum-traction Truck, 820 Swinging Conveyor, 322 Switch Controller, Christensen Air-brake, 902 Switch of Overhead Line, 94 Switchboards, 527 Plüger Negatives, 718 Planté-Faure Plates, 717 Pollak Cells, 718 Portable Cells, 719 Pritchett and Gold Batteries, 718 Recovery, Self-discharge, Impurities, 708 Schulz, Witten, Plates, 718 Schweizer Accumulatoren Werkes, 718 Sulphating, 709 Sulphuric Acid for, 722, 723 Treatment of, 710 Tudor Cells, 713, 714 Willard Battery Company's, 718 "3 "" Economy of, 347, 348 Engines, 152 Accumulator Board, 562 Air-gap of Converters, 580 Automatic Protective Devices, 566 Board of Trade Panel, 560 Board of Trade Regulations for Tramways, 559 Board of Trade Tests, 559 Bolts, Current Capacity of, 618 British Thomson-Houston Distance Controlled Switch, 531 British Thomson-Houston Magnetic Blow-out Circuit-breaker, 567 British Thomson-Houston Oil-break Switches, 533 British Thomson-Houston Switch-Gear, 530 Cable Connectors, 620 Cable Sockets, 617 Cable Thimbles, 619 Classification, 529 Cotton Covering on Wires, Allowances for, 616 Cowan-Andrews Discriminating Devices for Alternating-current Circuits, 571 Cowan-Andrews Reverse-current Circuit Breaker for Continuous Currents, 570 Cowan-Andrews Reverse current Indicating Device, 572 Cowan Extra High-tension Switch-gear, 540 Current Density Allowed under Various Conditions, 618 Dick, Kerr Extra High-tension Switches, 542 INDEX. 1047 " Switchboards, Electrical Company's Switch-gear, 533 "" Electrical Errors of Instruments, 586 Elliott Alternate-current Instruments, 591 Elliott Three-phase Feeder Panel, 548 Extra High-tension, 529 Ferranti Box Fuse, 578 Ferranti Cable-charging Gear, 584 Ferranti High-tension Board, Cellular Type, 545 Ferranti Maximum-current Time-limit Relay, 573 Ferranti Oil Fuse, 576 Ferranti Protective Resistance for Electrostatic Voltmeters, 589 Fuses, 576 Fusible Wires for Cut-outs, 616 Highfield Boosting System, 553 High-tension Boards, 544 Instruments, Types of, 587 I. T. E. Circuit-breaker, 568 Kelvin Paralleling Voltmeter, 564 Lightning Arresters, 579 Load Panel, 562 Location, 529 "" "1 "" "" "" "" " "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" 99 "" "" >" "" "" "" "" "" "" "" "" "" " "" "" "" "" 9" "" "" "" " >> "" "" "" "" "" >> "" "" 99 "" "" "" "" "" ** 99 "" "" Low-tension, with Gear, 546 Materials of Construction, 527 Measurement of Power in Circuits, 592 Measuring Instruments, 586 Motor-Gear for Extra High-tension Switch, 532 N. C. S. Automatic Accumulator Switch, 575 Ohmmeters, 611 O K Oil-break Switch, 532 Paralleling Continuous-current Generators, 564 Partridge's Patent Sparklet Fuse, 577 Polyphase Meters, 604 Power Consumption of Instruments, 587 Power-Factor Indicators, 605 Protection of Duplicate Feeders, 574 Protective Devices, 566 Resistance and Insulation Indicators, 612 Reversible Boosters, 552 Reversible Traction Booster Panel, 554 Rheostats, 613 Shaw Non-arcing Arrester, 584 Siemens and Halske Lightning Arrester, 579 Single-phase Generator Panel, 550 Spark Gap of Arresters, 580 Sparklet Fuse, Partridge's, 577 Starting Polyphase Induction Motors, 565 Station Panel, 562 Switch-gear Diagrams, 546 Synchronisers, 608 Synchronising Alternators, 563 Synchronous Motor-generator Panel, 549 Synchus Copes, 610 Tank Arrester, Westinghouse, 583 Three-phase Feeder Panel, 548 Three-phase Generator Panel, 547 Three-wire Balancer Panel, 557 Three-wire Lighting Feeder Panel, 558 Three-wire Reversible Lighting Booster Panel, 556 Traction Feeder Panel, 552 Traction Generator Panel, 551 Two-wire Lighting Feeder Panel, 559 Wattmeter Types and Connections, 592 Westinghouse Electrically-operated Field Rheostats and Switches, 539 Westinghouse Lightning Arrester, 582 Westinghouse Remote Controlled Board, 537 Wire Gauges in Common Use, 620 Wire Tables, 614 1048 INDEX. 1 : Switchboards, Wurts' Lightning Arrester, 582 Switches, 24 Swivel Trucks, 823 Sykes' Troughs and Conduits, 105 Synchronisers, 608 "" for Three-phase Generators, 471 Synchronising Arrangements in Alternating-current Circuits, 470 Gear, Switchboards, 563 19 Synchronous Motor-generator Panel, Switchboards, 549 Synchroscopes, 610 Tanks, Capacity of, 334-360 99 Contents of in Gallons, 359 Feed Water, 359 "" "" Weight of Wrought-iron, 360 Tannate of Soda Compound, 328 Tar Extractor, Crossley's Centrifugal, 662 Pavement, 50 "" Telegraph and Telephone Wires, 121 Temperatures, Absolute, 145 "" "" "" Temperley Transporter, 324 Terminal Insulator, 76 Overhead Line, 76 Tests, Brake, 907 "" "" "" "" "" "" Brake-shoe, 897 for British Tramway Rails, 16 for Tensile Strength of Insulators, 80 of Granite for Pavements, 50 High-tension Cables, 142 Porcelain Insulators, 940 Thallium in Storage Batteries, 720 Theoretical Indicator Diagram, 155 Thermometers Compared, 1006 Third Rail for Berlin Elevated Railway, 784 Shoes, 783 "" Thomson Wattméter, 602 Corrections for Copper Wire, 130 Entropy Diagram, 151 of Combustion, 390 Thomson-Houston Electro-Magnetic Track Brake, 899 Threading of Pipes, 191 > Three-phase Feeder Panel-Switchboards, 548 Generator Panel Switchboards, 547 Generators, Efficiency of some, 471 Power Transmission, 944 Railways, 794 "" "" "" System, Measurement of Power in, 467 Traction Motors, Ganz and Company's 896 Throttle and Stop Valves, Area through, 185 Throw-over Arrangement for Feeders, 110 Tidswell Life Guard, 909 Tie-bar, 15, 16 per Mile of Track, 21 "" Tie-rods, 22, 23 Tiling, 693 Time-limit Relay, Ferranti's, 573 Tin and Lead Alloys, Fusing Point of, 106 Ton-Mile Cost, Metropolitan District, 930 North-Western Elevated, Chicago, 929 Tongue Switch, 24 39 "" 7 Tools for Overhead Line Erection, 98 "" Power Required for Various, 947-951 Top Seat Trolley Standards, Weight of, 841 Torrent Filter, 336 Tower Wagon for Line Erection,93 INDEX. 1049 Track and Route of some Electric Railways, 789 Brakes, 898 Laying, Cost of, 925 Life of, 916 "" ""> "" "" "" ?? Construction-Quantity and Cost, 48 for English Tramways, 7, 11 Section-Philadelphia Step Rail, 9 of Metropolitan District, 786 " with Brick Paving, Denver, 10 "" Traction, Alternating and Continuous Currents Compared, 959 Data, 759 11 Coefficients, 802 "" "" Traction Motors, 868 " Feeder Panel-Switchboards, 552 Generator Panel-Switchboards, 551 Heavy Electric, 786 "" "" "" "" "" "" "" "" "" "" "" "" >> "" "" "" "" "? "" British Thomson-Houston, 876 Brown, Boveri and Co., 895 Bruce, Peebles, 893 Brush Company, Curves of, 874 Dick, Kerr and Co., 880 Formulas for, 759 Ganz and Co., 826 Life of, 916 Witting, Eborall and Co., 891 Traction Plants, Operating Expenses of, 920 *" 19 Reversible Booster Panel, 554 Work, Dynamos for, 419 Tractive Effort, American Lines, 775 Tractive Resistance on City and South London Railway, 803 Train Acceleration, American Lines, 774 "1 Mile Cost, Metropolitan District, 930 Motion, Calculation of, 763 19 19 Resistance, Calculation of, 766-772 Train Speed, American Lines, 775 Train Weight, American Lines, 775 "" "" Trains, Electric, Weight, Dimensions, and Seating Capacity, 793 Tramway Cost, 45 " "" "" 95 "" " "" "" "" "" "" "" "9 "" Liverpool Overhead, Curves of, 883 Oerlikon Company, 894 Power Curves, 868 Repair Parts for, 872 Siemens and Halske, 890 Speed Diagrams, 869 Suspension of, 870 Westinghouse, 875 Curves, Crossings, and Points, 31 Drainage, 45-47 Material, British Standard Sections, 12-16 Material, Rail Tests, 16 Material, Standard Wheel Flange, 14 Poles, English Conical Steel, 86 Poles, Tubular, 85 Track in City Roads, 7, 11 Track in Country Roads, 7, 11 Track in Main Thoroughfare, 7, 11 Usual Gauges, 24 Works, Weights of Material, 22 " Tramways in America, Mileage and Cars, 928 in United Kingdom, Particulars of, 922 Transformers, 500 Rails, American, 8, 9 Steam Engines, 168 Track, British, 7, 11 Track, Cost of Construction, 46 Air-blast, 506 Air-cooled, 503 1050 INDEX. Transformers, British Thomson-Houston Air-blast, 508 Central London Railway, 510 >> "" 29 55 "" "" "" "" ** "" "" "" >" " "" "" "" "1 ?? "" "" >> *** > "" "" "" ?? "" "" "" "" "" "" "" "" "" Witting and Eborall, Natural Draught, 503 Transmission Lines, 941 "" *9 Regulation of, 941 >> of Power, 937 Transporter, the Temperley, 324 Treatment of Storage Batteries, 710 Triangles, Solution of Plane, 1003 Trigonometrical Formulæ, 1003 Triple Valve, Christensen Air-brake, 902 Trolleys, 838 and Equipments, Cost of, 924 Trolley Arrangement on Car, 840 Pole, Car Framing for, 838 "" >" "" 39 "" "1 >" Standards, Weight of, 841 Trolley-wire Frogs and Crossings, 76, 78 "I "" Troy Weight, 995 'Trucks, 814 Connections for Polyphase Transformation, 515 Connections for Starting Motors, 515 Connections for Three-phase, 523 Connections with Converters, 517, 522 Constructive Details of, 502 "" Dick, Kerr Air-blast, 510 Dick, Kerr Natural Draught, 503 Dick, Kerr Oil-cooled, 514 Efficiency, 501 Grouping Single-phase, for Polyphase Transformations, 518 Heating and Current Density in, 502 Insulation, 501 Losses in, 501 "1 Magnetic Fatigue or Ageing, 502 Power Factor, 502 Oil-cooled, 510 Oil-cooled, with Water Circulation, 515 Polyphase, 523 Specification for, 502 Ventilators for Air-blast, 509 Westinghouse Air-blast, 506 Westinghouse Air-cooled, 503 Westinghouse Oil-cooled, 510 Westinghouse Self-cooling, 513 Pole, Diagram of Extreme Angles for, 839 Pole Tests, 841 Lengths, Joints, Spacing of Supports, 72 Sag, 70 Soldering-iron, 76 Tensile Test, 69 Birkenhead Corporation Tramways, 822 Brill Eureka Maximum Traction, 827 Brill Maximum Traction, 824 Brill, No. 21 E, 818 Brill, No. 27 G, 824 Brill, Weight of, 820 Brush, Maximum Traction, 821 Brush, Single, 815 Central London Railway Motor, 827 Comparison of Four-wheel and Bogie Cars, 814 Cost of, 924 Four-wheel, 820 General, 814 Interborough Rapid Transit, New York, 831 Journal-box, Master Car-builders', 831 Longest Wheel-base on German Light Railways, 814 Manhattan Elevated Motor, 827 Maximum Traction, 820 S: INDEX. 1051 Trucks, Mountain and Gibson's, 827 "" "" "" "" "" Tubes, Bursting Strength of, 189 Tubular and Lancashire Boiler Combined, 273 Tramway Poles, 85 Tudor Cells. Storage Batteries, 713, 714 Turbine-operated Station, America, Costs of, 917 Turbines. See Steam, Parsons, De Laval, &c., Turbines. Turbo-dynamos, Cost of, 926 Turnouts, 34, 37 Twin City Rapid Transit Rail Steel Specification, 17 Two- and Three-phase Circuits, Measurement of Power in, 468 Tyres for Car Wheels, 834 Underfeed Stoker, Jones, 310 Underground and Overhead Mains, Cost of, 939 Cables, 125 "" Electric Railways, London, 789 Under-running Section Insulator, 76 "" Trolley-wire Frogs and Crossings, 76 United Kingdom Tramways, Particulars of, 922 Railroad Rail Steel Specification, 17 Unit Cost and Load Factor, 927 "" "" Units, Electrical and Magnetic, 409, 410, 411 Valtellina Three-phase Railway, 795 Valves, Steam, 194 "" "" Velocity Diagram for Reaction Turbine, 230 Traction Motors, 759 Ventilated Manhole, 103 Ventilators for Air-blast Transformers, 509 Vicars' Mechanical Stoker, 308 Vignoles Railway Rails, America, 19 "" Peckham Maximum Traction, 822 Peckham Standard, Dimensions of, 815 "Swing Bolster," Maximum Traction, 820 Swivel, Dimensions of, 823 99 Weight of Various French, 814 Rail Steel Track, America, 10 "" Virtual Electromotive Force in Alternating-Current Circuit, 452 Resistance, Alternating-Current Circuit, 452 Volume Tables, 1002 "" Waller-Manville Conduit, 741 Walls of Warehouses, Stores, Factories and Stables, 685 Thicknesses of, 688 "" Water for Boilers, Analyses of, 329 "" "" "} "" Cost per, in some Traction Stations, 919 The Board of Trade, 409 >> "" Flow Through Pipes, 355, Guages, 299 Hardness, 327 Power, Capital Outlay Upon, 938 , Power, Cost of, 937 "" Power, Development in France, 938 Specific Heat of, 145 Troubles in Boilers, 330 Useful Data for, 355 "" C Charges, per Electric Horse-power, 937 Cooling Arrangements, 175 Discharge and Speeds due to Heads, 356, 358 Expansion and Weight of, 356 1052 INDEX. Water Softener, Archbutt-Deeley, 332 "" 19 "" "" * Water-tube Boiler, Babcock and Wilcox, 274 Washers and Scrubbers, 666 Wattmeters, Dynamometer Type, 593 "" "" "" " "" "" "" "" "" "" Wear of Rails, 24 Weber Rail Joint, 18 Weights and Measure Tables, 995 Weight of Different Woods, 82 Poles, 83 "" of some Electric Trains, 793 Weir Differential Feed Pump, 354 Direct-acting Feed Pump, 354 Weld, Falk Cast, 63, 64 "" Welded Joints, Electrical, 64 Goldschmidt Process, 65 "" 99 Welding of Rails, 63 Welsh Anthracite, Analysis of, 669 "West End" Bracket-arm Hanger, 74 Bridge Insulator, 74 Car-house Insulator, 74 Double Pull-off, 74 Insulating Bolt, 74 Single Pull-off, 74 "" "" "" "" 29 Straight-line Insulator, 74 Trolley Wheel, 839 "" Westinghouse Air-blast Transformers, 506 Air-brake, 905 "" "" "" "" "" "" 99 "" >" "" "" "" Babcock and Wilcox Patent, 330 Bruun's Automatic, 337 Desrumaux, 335 "" "" "" "" "" "" Elliott Brothers Three-phase, Connections of, 600 Ferranti Indicating, 602 Ferranti Integrating, 599 for Three-phase Unbalanced Loads, 599 Induction Type, 594 Kelvin's Engine-room, 602 Method of Connecting, 594 Thomson's, 602 Westinghouse Polyphase Switchboard, Integrating, 597 >> "" " "" Air-cooled Transformers, 503 Alternators, Connections of, 474 Continuous-current Dynamos, 444, 445, 446 Extra High-tension Three-phase Switch, 538 Electrically-operated Rheostats and Switches, 539 Gas Engines, 633 Lightning Arresters, 582 Weston Type of Measuring Instruments, 590 Wheels and Axles, 832 Magnetic-brake, 898 Oil-cooled Transformers, 510 Parsons Turbine, 240 Polyphase Switchboard Integrating Wattmeter, 597 Power-factor Meters, 607 Westinghouse Railway Motors, 875 Remote Controlled Board, 537 Rotary Converters-Starting, 494, 497 Self-cooling Transformers, 513 Single-phase Motors, 964, 986 Standard, High-speed, Engine-type Alternators, 481 Stillwell Regulations for Polyphase Circuits, 500 Synchroscopes, 610 Wheel-base, Longest, on German Light Railways, 814 Square, for Gauging Curved Tracks, 43 Wheel Centres, 833 Flange, Standard, British Tramways, 14 Tests, 834, 835 "" " Wheeler's Patent Feed-water Heater, 339 INDEX. 1053 Wilkesbarres and Maxelton Railway, Pa., 789 Willans Central-valve High-speed Engine, 167 Efficiency, 151 Willard Battery Company Cells, 718 Winter Eichberg Single-phase Motors, 960, 967, 969 Wire Gauge, Comparison Table, 131 Imperial Standard, 70 in Millimetres, 142 "" Wire-splicing Sleeve, 79 Stretching Device, 80 "" Tables, 614 Wiring for the Heating of Cars, 852 for the Lighting of Cars, 851 Formulæ, 457 "" of Electric Cars, 848 "" "" "" "" "9 Witting-Eborall Natural Draught Transformers, 503 and Co.'s Railway Motors, 891 Wood's Frogs and Crossings, 78 Wood, Analyses of, 399 as Fuel, 398 "" for Poles, 82 "" Heating Power of Soft, 399 Pavements, Specification for, 49 Sleepers, their Durability, 915 Weight, Strength, &c. of, 399, 702 Woolf and Receiver Engines, 160 Woollen Mill Machinery, Power to Drive, 956 Woodward's Patent Furnace, 314 Work and Force, Traction Motors, 760 Working Expenses of Light Railways, 45 of Traction Plants, 920 Worthington Cooling Tower, 176 Standard Feed Pump, 352 Wurts' Lightning Arrester, 582 Wyatt's Rule, Scrubbers and Washers, 666 "" Zermatt-Gornergrat Three-phase Railway, 795 Zodel Flexible Coupling, 632 Zossen, Berlin, Three-phase Railway, 795 INDEX TO ADVERTISEMENTS. Babcock & Wilcox, Ltd., 17 Bennis & Co., Ltd., Ed., 19 Blackwell & Co., Ltd., Robert W., 4 Booth & Bros., Ltd., Joseph, 14 British Insulated and Helsby Cables, Ltd., 6 Broughton Copper Co., Ltd., The, 10 Brush Electrical Engineering Co., Ltd., 3 Clarke, Chapman & Co., Ltd., 22 Davey, Paxman & Co., Ltd., 11 Dennis & Co., W. F., 9 Dick, Kerr & Co., Ltd., 25 Edwards' Air-Pump Syndicate, Ltd., 23 Electric Construction Company, Ltd., 21 "Electric Machine Design," (Parshall and Hobart), 5 Engineering,' "G. B." Surface Contact Company, 12 Hadfield's Steel Foundry Co., Ltd., 13 Lancashire Dynamo & Motor Co., Ltd., 12 Magnolia Anti-Friction Metal Co. of Great Britain, Ltd., 20 Phosphor Bronze Co., Ltd., 7 Schäffer and Budenberg, Ltd., 18 "Sir Henry Bessemer, F. R.S." An Autobiography, 13 Tudor Accumulator Co., Ltd., 16 United Asbestos Co., Ltd., 15 Weir, Ltd., G. & J., 24 Western Electric Co., 8 66 19 PRINTED AT THE BEDFORD PRESS, 20 AND 21, BEDFORDBURY, STRAND, LONDON, W.C. Advertisements. 21 ՈՑ։ E.AC.HC. THE ELECTRIC CONSTRUCTION COMPANY LTD OPPY E.C.C. MANUFACTURERS OF EVERY DESCRIPTION OF ELECTRICAL PLANT. POLYPHASE CONTINUOUS CURRENT GENERATORS TO 5000 BP MOTORS FOR ALL PURPOSES TRANSFORMERS ALTERNATING & CONTINUOUS ROTARY CONVERTORS AND SWITCHBOARDS. CONTRACTORS FOR QUEWAYS, TRAWAYS POWER HOUSES. DON & STEEL WORKS, COLLIERIES, & ALL KINDS OF FACTORIES BUSHBURY ENGINEERING WORKS. WOLVERHAMPTON. 00 21110 Ab. 1 LONDON AND WOLVERHAMPTON. 22 Advertisements. CLARKE, CHAPMAN & CO., LIMITED, GENERAL and ELECTRICAL ENGINEERS, GATESHEAD. ALSO CONTRACTORS TO BRITISH AND FOREIGN GOVERNMENTS. SLOW-SPEED DIRECT-ACTING FEED PUMPS — is WATER-TUBE BOILERS. "WOODESON'S PATENTS." SIMPLEX OR TANDEM COMPOUND TYPES, AS SUPPLIED MANY POWER STATIONS. ("WOODESON'S PATENTS") High Efficiency. Low Steam Consumption. ALL TUBES STRAIGHT AND OF EQUAL LENGTH. -MAKERS OF MAXIMUM STEAM RELEASE. MINIMUM DEPOSITS. EASY ACCESS TO ALL PARTS FOR CLEANING OR RENEWALS. Tele. Adr.: "CYCLOPS," GATESHEAD. OF 014 900 'Phones: 1070 & 1073 Nat. ; 137 P.O. ENQUIRIES SOLICITED. Advertisements. 23 THE EDWARDS PATENT AIR PUMP FOR Surface, Evaporative, and Jet Condensers. NO FOOT OR BUCKET VALVES. FITTED TO MORE THAN 300 OF THE Leading Electric Lighting and Traction Stations IN ALL PARTS OF THE WORLD. SPECIALLY SUITABLE FOR THE HIGH VACUUM REQUIRED FOR STEAM TURBINES. FOR ILLUSTRATED PAMPHLET AND FULL PARTICULARS, APPLY TO The EDWARDS AIR PUMP SYNDICATE, Ltd., 3 & 5, CROWN COURT, OLD BROAD STREET, LONDON, E.C. Telegrams: "MANAGEMENT, LONDON." Telephone No.: 2369 LONDON WALL. 24 Advertisements. HIGH VACUUM CONDENSING PLANTS WEIR C THE WEIR SYSTEM. Steam and Electrically-Driven Installations.. Fitted to over 520,000 I.H.P. *** WEIR ON WEIR INDEPENDENT AIR PUMPS. *** DIRECT-ACTING FEED PUMPS. Simple and Compound-Standard Stock Sizes. *** DIRECT-ACTING CIRCULATING PUMPS. G. & J. WEIR, Ltd., CATHCART, GLASGOW. Contacements 25 PRESTON, Lancs. UNIVERSITY OF MICHIGAN DI 3 9015 01302 7415 LIMITED, ABCHURCH YARD, CANNON ST., LONDON, E.C. Co., S KILMARNOCK, N.B. Motors for Crane and Hoist Work. THE experience gained in Tramway and heavy power work has enabled us to design a motor which is particularly well adapted for cranes, hoists, and purposes where the performance of the motor is heavy yet intermittent. It is efficient over a wide range of load, and has been designed to meet over-loads up to 50 per cent. The motors are constructed with or without counter shaft bearings, and can be supplied with a special magnetic brake. BARAN •* C