GIFT OF GIFT OF MECHANICAL ACHIEVEMENTS OF THE XIX. CENTURY. STE VEINS' Mechanical Catechism FOR STATIONARY AND MARINE ENGINEERS, FIREMEN ELECTRICIANS, MOTOR-MEN, ICE-MACHINE MEN AND MECHANICS IN GENERAL PRACTICAL KNOWLEDGE IN EVERY BRANCH OF MECHANICAL INDUSTRY Full Information on Water, Steam, Fire, Smoke, Electricity, Horse- Power, Refrigeration, Liquid Air. Exact Description of, and Directions for the Care of Boilers, Grates, Engines, Slide Valve, Safety Valves, Injectors, Pumps, Steam Gauges, Lubricators, Eccen- tric, Link Motion, Indicator, Ammonia Compressor. Brine and Direct Expansion Systems, Lathe, Tools, Dynamo, Batteries, Parallel and Series Wiring, Three- Wire System, Motors, Controller, Electric Heating, House Wiring, Traction Engine. Thorough Instruction in Calculation of Horse- Power, Pulley-Speed, Lathe-Gearing. Square Root. Leverage, Tensile Strength, etc. Introduction to Algebra. Systematic descriptions alternate with elaborate sets of Questions and An- swers in plainest English. Numerous tables and original diagrams make the book interesting as well as instructive. .. Valuable Recipes and Hints for all rff^ sorts of Emergencies, many of them especially selected for this work. OVER 240 SECTIONAL CUTS AND ILLUSTRATIONS BY . H. G. STEVENS, M.E.E. Copyright 1899, by WM. H. CHICAGO LAIRD & LEE TABLE OF CONTENTS The Alphabetical Index, pages 5-9, gives subjects in detail. PAGE WATER 11 STEAM*. 16 COMBUSTION AND FIRING.. 19 Locomotive firing 29 BOILERS 33 Rivets, Braces and Stays 33 Plant appliances 38 Boiler explosions 46 .Running a boiler 49 Steam heating 52 Smoke and chimney 53 Brickwork 54 Boiler testing 56 Boiler horse-power 57 Feed water heater 59 Tensile strength 60 SAFETY VALVES 62 INJECTORS 69 FEED PUMPS 73 STEAM GAUGES 89 LUBRICATORS... 91 THE ENGINE 96 Valve setting 97 Reversing 100 Lead and lap 102 Compound engines 104 Corliss electric engine stop 107 Hot air engine 109 Condensers 112 The eccentric 116 Dead centers 118 Lining the engine 120 Automatic governors 124 Balanced slide valve 133 Corliss engine and gear. 135 Vacuum dash pot 140 Review 141 Link motion 144 HORSEPOWER 146 INDICATOR 154 Pantograph 160 Review 162 PAGE COMPRESSED NON-VIB'R. AIR ENGINE 166 MISCELLANEOUS questions and answers 169 Mea.surements and cal- culations 175 MECHANICAL REFRIGER- ATION 180 Ammonia 182 Methods of refrigeration 185 Water examinations 195 Direct expansion system 197 Ammonia tests, etc 211 Review 219 LIQUID AIR 223 Liquid hydrogen 225 THE MACHINE SHOP 226 The lathe 228 Twist drill grinding 231 Polygonal nuts 233 RULES AND STANDARD NUMBERS 234 GENERAL USEFUL KNOWLEDGE 242 ELECTRICITY 249 Dynamo and attach- ments ?67 Varieties of dynamo 275 Management 279 Repairs 287 Measurements 290 Motors 297 Controllers 301 Electric locomotive 304 Electric heating 306 Motor connections 308 Electric wiring 309 THE ELEMENTS OF ALGE- BRA 318 THE TRACTION ENGINE.. 324 THE HAY STACKER 332 JOURNAL Box BABBITT- ING 335 INTRODUCTION Almost every day some new device is invented for saving labor or fuel or other material. Where so many brains, scientifically trained, and so many thousands of practiced eyes and hands combine to make human life more comfortable, by shifting an ever larger portion of the hard labor to the shoul- ders of Nature's hidden forces, it is not strange that the engineer and machinist finds greater and greater demands made on his intelligence and experience. A widely-known machinist delights in repeating to his friends his account of a little incident that will illustrate our point. He happened to enter the office of a large factory, where one of the firm jumped at him and hustled him into the engine- room, where the men tending the machinery were standing idle and puzzled. Something was wrong ! "Start her up," said the proprietor. The big engine made two or three revolutions, giving a thump at each turn as if the fly wheel was about to goto pieces. "Stop her!" the machinist said, took the key of shaft and fly-wheel out, filed it down one s&ty-fourth of an inch, and then drove it in place again and she started up without a thump. "Well, I declare," said the proprietor, "how much do I owe you?" "Twenty-five dollars and fifty cents." "What's that, sir $25.50 for twenty minutes of your time?" "No, sir ; 50 cents for my time and $25 for knowing just what to do. It's worth that much to you, I dare say, to get your men to work, isn't it?" The money was cheerfully paid. It's the PRACTICAL KNOWLEDGE that tells ; and to aid engineers and mechanics in general to do intelligent wor^ is, the-desrj^ and aim of C: O J. O V 1> THE AUTHOR. LIST OF ILLUSTRATIONS PAGE Cross Compound Engine. . 10 Ice Plant 10 Smoke prevention 25 Riveting 33,34,35 Gusset stay 36 Steam fittings 39 Globe valve 40 Water column 42 Safety alarm 43 Boiler water line 45 Straightway valve 50 Boiler setting 54, 55 Safety Pop and Muffler. .63, 64 Safety valve (lever) 68 Injector 70 Duplex pump 76 Check and gate valves. . .82, 83 Artesian pump 84 Pump governor 85 Deep well pump and plun- ger Steam Gauge Double and Triple feed lubricators 91,93 Common slide valve and movements 96, 98, 100 Tandem Comp'd Engine.. 106 Corliss electric engine stop 108 Hot air engine 110 Connecting rod and oilers Ill, 112 Concentric and eccentric. . 116 Direct and indirect mo- tion 117 Slotted stick 121 Engine lining . ..122 Automatic governors.. 125, 130 Balanced slide valve 133, 134 Corliss valve movements 135, 136, 137 Corliss cut-off gear 138 Vacuum dash pot 140 Ivink motion 144 Indicator 154,155 Indicator chart and dia- grams 156, 158, 159, 160 Pantograph 161 Air engine '. 167 Crank pin travel 169, 170 Dead center points 172 PAGE Ice machine 184, 186 Freezing tank 192 Ice can dumps 194 Compressor valve 197 Gas compressors 199, 201 Ammonia liquefier 203 Valves and fittings 207 Bye pass valve 208 Ammonia testing 211 Engineer's and machin- ist's tools 226,227 Lathe and tools 228, 230 Twist drill grinding... .231, 232 Area of circle. . . 234 Ventilation 243 Arc lamp 255 Incandescent lamp 261 Dynamo 268 Storage batteries 271, 272 Rheostat 272 Transformer and brush pointer 273 Alternating dynamo 276 Generator panel 279 Feeder panel 280 Chemical meter 295 Stationary motor 297 Carbon Brush Holders 298 Third rail motor trucks. . . 299 Street car motor suspen- sion and motor truck. 300, 301 Electric car controllers 302 Electric locomotive 304 Electric Heating and Cook- ing 307 Stationary motor connec- tions 308 Wire joints 314 Traction engine 324 Coal and water tank 325 Curve turning device 325 Compensating gear 326 Friction clutch fly wheel. . 326 Cross head 327 Tandem compound cylin- ders 329 Single eccentric reversing 330 Reversing rack 331 Hay stacker gearing. . . 332, 333 Hay stacker. 334 ALPHABETICAL INDEX NOTE : For Electrical Terms see, also, Dictionary, page 253. PAGE Absorption method, ice.. . . 185 Accidents by shafting 245 Accumu!ator 271 Air, a compound 13 ' chamber, Duty of. ... 83 ' Compressed engine.. 166 ' in combustion 19 Liquid 223 needed for fire 23 spaces in grates 20 Weight of 13 Alcohol expansion 18 Algebra, Elements of. 318 Alternating current 252 Ammonia 182 " Boiling points of 210 Charging 917 " compressors 184 " condenser ...188, 202 Discharging 219 " pump valve 197 tests 211 ' ' valve and fittings 207 Ampere 291 Ampere's Rule 252 Appliances of steamplant. 38 Area of circles 235 Artesian pump 84 Atmosphere, Weight of. . . 14 Automatic gov., side crank 124 self-contained. 129 Babbitting a journal 335 Balanced slide valve 133 Ball turning 229 Band saw mending 168 Barometer 14 Battery, Electric 271 " of boilers bl Belting, Cleaning of. 248 " horsepower 152 Boiler, The 33 construction 45 explosions 46 How to clean 49 " Safe pressure . . . 176 " setting 40,54 " testing 56 PAGE Boilers, Battefy of. 51 Boiling, Definition of 18 Boiling points of ammonia 210 Braces 35 Brine solutions, Table of . 195 " system 190 Brushes, Motor 298 Brush holder 273 B. T. U 293 Bye pass valve 207 Calculations, Engine 175 of coal in bin. 248 Pulley speed.. 239 Stay and bolt. 38 Capacity of pump 74 Carbonic acid 13 Care of electric plant 284 Casing for electric wire. . . 316 Cell, Daniell 274 " Gravity 274 Cement for steam pipes . . . 222 Charging ice machine 217 Check valve 81,83 Chimney 53 Circuit, Arrangement of. . 314 11 Short 312 Cleaning by steam 247 belts 248 / " rusty steel 247 Clearance 176 Closed coil 276 Clutch, Friction 326 Coal, Decomposition of. . . 21 ' How it burns 22 Coal-bin calculations .* . . 248 Cold storage temperature. 206 Color of flames 20 Combustion, Perfect 19 Commutator 270 Compensating Gear. 325 Compound engines 104, 328 Compressed air engine... 166 Compression method, ice.. 187 Compressor, Ammonia 197 Condensation, Ammonia.. 188 Condensers, Ammonia. 188, 202 Jet 114 INDEX Condensers, Open-air 204 Steam 112 Surface 113 Conductivity 310 Connecting rod 122 Connections, Electric 314 Constant potential service. 278 Continuous current 252 Controller 301 Converter 273 Cooking, E)lectric I . Corliss electric stop 107 Engine 135 Coulomb 291 Crankpin and crosshead travel 169 Crosshead at dead center. . 172 of engine 327 Current, Alternating 252 " Continuous 252 " Multiphase 252 Cut-out, Electric 316 Cylinder dimensions 328 Daniellcell 274 Dash pot 141 Dead center 118 Deep well plunger 87 " " pump 87 Diagram, Indicator 15ti Dictionary. Electrical 253 Differential gear 325 Dimensions of cylinders. . 328 Direct expansion system. . 190 Discharging Ammonia Pump 219 Distribution, Electric 314 Duplex gauge 90 Dyne 290 Dynamo and its parts 267 Care of. 279 " Efficiency of 293 Repairs of. 287 Running a 283 Varieties of 275 Eccentric 116 How to set an. .. 117 rod 9?' Single-revers- ing 100, 330 Efficiency of Dynamo 293 Electric locomotive 304 4 ' heating and cook- ing 306 11 measurements 290 Electric wiring 309 Electricity, Chemical and thermal 251 " Current and statical 250 Frictional and voltaic 250 Positive and negative .... 249 Elements of Algebra 318 Engine, The 96 Compound 104 with single valve. . . . 328 Compressed air . 166 Corliss 135 stop, Corliss elec. 107 Cross compound 105 crosshead 327 Electric 304 Hot-air pump'g. 109 Lining 120 measurements.. 175 pounding 119 Receiver .. 105 striking points.. 122 Tandem com- pound 105, 328 Traction 324 Erg 290 Expansion, Ammonia 188 system, Direct 190 Explosion of boilers 46 Feed of boilers 43 ' ' regulation 57 Fire, Care of 25 engine 83 Firing 19 Locomotive 29 Stages of 20 Fittings, Heater and boil'r 39 Flames, Color of 20 Length of 22 Foaming ' 50 Forced draught 22 Friction clutch 326 Friction in water pipe 238 Fuse, Safety, Boiler 42, 68 Electric.. 303, 308 Gaskets 51 Gas meter reading 243 Gauge, Comp'd ammonia. 90 Duplex 90 Steam , . 89 INDEX Gauge, Vacuum .89, 115 Gear, Differential 325 " Reversing 330 Gearing, Lathe 228 Stacker 332 Glass tube, How to cut 247 Governor, Automatic, side crank 124 ** Autorn., self- contained 129 " Pump, Autom.. 85 Graphite for steam-fitting. 246 Grate, Air spaces in 20 Gravity cell 274 Ground 812 Hard Water 195 Haystacker.... 334 Heat 174 " Latent 18, 175 " Utilized 23 Heater, Feed Water 59 Heating, Electric 306 Horse power 146 Belting 152 Boiler 150 Compound engine 150 Electric.. .. 292 Evapprat'n.. 57 for incand. lamp 293 u Heating sur- face 37, 148 " of traction engines . . 328 " of waterfall. 147 k ' of w a t e r - wheel 148 Rating of. . . 149 " Steam con- sumption. 149 " Tubular boiler 152 House Wiring 309 Hydrogen , Liquid 225 Ice Making 180 Incand. Lamp, H. P. for... 293 Indicator 154 card 159 " diagram chart .... 156 " examination 162 " with pantograph. 160 Induction 250 Injectors, Classes of 71 Injectors, Parts of 70 Size of. 73 Working of 69 Insulation. 311 testing 281 Inverse ratio 310 Iron and steel 61, 128 Joints, Electric 314 Journal babbitting 335 Kilowatt 148,261 Lamp sockets 317 Latent heat. . 18, 17o Lathe gearing 228 " tools 230 Law of Ohm 291 Lap and lead 102 Leather belting cleaned. 248 H. P 152 Leverage 241 " in safety valves .. 66 Lightning, What is 251 Lining an engine 120 Link motion 144 Liquid air 223 4 ' hydrogen 225 Lubricators, How to attach 94 How to clean. 95 " How to run.. 93 " Triple sight.. 93 Working of. . . 94 Machine shop 228 Magnetic field 250 Measures and weights 236 Measurements, Engine 175 ' " Electric.. . . 290 Chemical. 293 " Mechani- cal 296 Mending band saw 168 Meter, Gas 243 " Chemical.... *. 293 " Mechanical 296 Mineral water 196 Miner's inch 238 Miscellaneous Q. and A.. . . 169 Molecules 174 Motions, Direct and Indi- rect 117 of Crosshead.,169, 172 Motors, Stationary 297, 308 Third rail 298 " Surface Road 300 INDEX Motor Brushes . ....... 273, 298 Reversing ........... 308 M u.ffler, Safety Valve ...... 63 Multiphase current . , ..... 252 Multipliers, Standard ...... 235 Nitrogen ............... 13 Weight of. ...... 19 inches smaller in diameter than the cylinder of the engine. BOILERS Locomotive and Stationary Q. State the different classes and styles of boilers in use? A. There are three classes marine, stationary and locomotive and six styles marine, locomo r tive, upright, flue, tubular and water tube boilers. Q. How are the different classes fired? A. The marine, upright and locomotive (hang- ing fire-box) are fired internally, but the stationary boilers are mostly fired externally. RIVETS Q. Are boiler shells single or double riveted? A. The end seams are all single riveted. The longitudinal seams are single riveted for low pressure and double for high pressure. Q. Why are longitudinal seams double riveted and circular or end seams single riveted? A. Because the strain is greater on the sides 33 34 QUESTIONS AND ANSWERS than at the ends, as the steam pressure has more surface to work on. Q. What is the distance generally between rivets of a single, or double riveted boiler shell? A. Single rivets are generally 2% inches, and double rivets 2j^ inches apart. Q. What should the diameter of rivets be for any size sheet to make up the maximum shearing strength? A. The diameter should be equal to twice the thickness of plate to be riveted. Q. What is the usual distance between the edge of rivet hole and edge of sheet? A. The full thickness of rivet used. LAP JOINT RIVETING The following table indicates the various sizes, etc. , of rivets for plates of different thickness : SINGLE RIVETED LAP JOINT. DOUBLE RIVETED LAP JOINT. BOILERS THICK- DIAM- DIAM- STRENGTH IN % NESS ETER ETER OF PITCH. OF SOLID. PLATE. RIVET. HOLE. SINGLE. DOUBLE. SINGLE. DOUBLE. i in. 1 in- ijin. 2 in. 2| in. 0.66 0.77 ft " H " 1 " 2 T9 '' 2| " O.64 O.76 1* :: II ?:: it " aj " 2r' " 2J " 2| ;; 3 8 " 0.62 0.00 0.58 0.75 0.74 o.73 This table is applicable when steel rivets are used in steel plates, or iron rivets in iron -plates. When iron rivets are used in steel plates, both rivets and rivet holes should be larger by 1-16 of an inch. ^Wv SINGLE RIVETED BUTT JOINT. DOUBLE RIVETED BUTT JOINT. When plates thicker than ^ inch are used, the joint should be a butt joint with double fish plate. (See cuts.) BRACES AND STAY BOLTS Q. Where should braces be put in a fire*box boiler? A. On the crown sheet, in water leg, in dome and on all flat surfaces. Q. What kind of braces should be used? A. In the dome, crowfoot or solid braces; on flat surfaces and between water sheets, stay-bolts ; on the crown sheet, crown bars and stay-bolts ; in 36 QUESTIONS AND ANSWERS the boiler shell crown radial braces; and in corners gussets. Q. How is the load on a brace calculated? A. Multiply the supported area by the steam pressure and divide the product by the number of braces. The quotient gives the strain on each brace. The law allows not more than 6,000 Ibs. per sq. inch of cross section of brace. A round brace of i^ inch diameter has i sq. inch area in cross section. Q. How can it be known whether a brace is really carrying the intended load? A. If it does, it will give an even, clear sound when tapped with a hammer or the like. Q. How are braces put in properly? A. Have the brace about 1-16 of an inch short, heat it red hot in the center and put in place. It will shrink tight when it cools. Q. Why is the flue sheet thicker than the boiler shell sheets? A. Largely because it is weakened by the many BOILERS 37 flue holes cut in it, and it has to support the weight and sag of the flues. Q. Give the number of square feet of heating surface allowed to a horse-power in different types of boilers? A. For vertical 12 sq. feet, for horizontal tubular 15 sq. feet. Q. How is a boiler's horse-power determined? A. Add together all the areas, in sq. feet, of heating surface up to the fire line (shell, tubes, back head) ; subtract from this sum the cross section area of all the tubes and the area of the front head less the tubes, and divide the remainder by 15 if horizontal, by 12 if vertical. See .pages 148 and 153. Q. Give tonnage strain on the crown sheet of a fire-box? A. Multiply the length by breadth inches, divide by 12 for feet, multiply answer by steam gauge pressure and divide by 2,000. STAY-BOLTS Q. Explain the use of stay-bolts? A. They are used to strengthen flat surfaces in steam boilers. Q. State the surface of plate a stay-bolt must support? A. The support is represented by the area enclosed between four bolts. 38 QUESTIONS AND ANSWERS Q. How is the area between the four bolts found? A. By multiplying one distance by the other. The answer will be each bolt's support. Q. What pressure do the four bolts have to withstand? A. Multiply the area by highest boiler pressure. The product is the strain on cross sectional area. Q. State the strain on a single stay-bolt? A. It must not be over 6,000 Ibs. per sq. inch cross sectional area. Rule: Multiply cross sec- tional area of bolt by 6,000, divide by steam pressure and extract square root of quotient. (See under Miscellaneous, page 239. ) Q. In examining the inside of the boiler, what are some of the defects for which you would be on the lookout? A. For missing pins from the braces, slack braces, leaky socket bolts, defective riveting, defective heads to the rivets and for broken or loose stays. Q. Name some appliances necessary about a steam plant? A. A boiler and fittings, a pump or injector, piping for the feed water apparatus, steam pipes, globe valves, feed valves, feed water heater, steam trap, chimney and dampers, safety valve, check valve, the fire front containing the fire and pit, BOILERS 39 also flue doors, grate bars, and bearing bars, dead plates, man and hand hole plates, thimbles, water gauge cocks and glass gauge, blow-out cock, fusible plugs, steam gauge, fire tools, flue brush, gaskets and scaling tools, also hose for washing out the boiler, shovel, slice bar, rake, hoe, etc. STEAM FITTINGS Return Bend. Ffange Union." Close Pattern. Return Bend. Open Pattern. Pipes of y" bore have 27 threads to the inch; pipes of X or l /%" nave I8 pip es f 1 A or %" have 14; pipes of from i to 2" have \\ l / 2 ; larger ones, 8. CIpseMpple, LockflQt, Caft* Plug Q.__Name the principal features of the brick- work about a horizontal boiler? 40 QUESTIONS AND ANSWERS A. Binder bars, back stays, cleaning out doors, iron rollers and plates for the boiler lugs to rest on. Q. What is a globe, valve? A. It is a valve in a round or globe chamber, used on boilers, engines, etc. Q. What are thimbles on boilers? A. They are heavy castings riveted on the upper shell of the boiler with planed flanges to which are bolted the safety Globe Valve valve 3nd main steam pipe. Q. i s a horizontal boiler placed level on its saddles? A. No, it is given a slight tilt (i^ inch) toward the back, so all the water can be drained out through the blow-off. This also insures having always water at the end opposite the gauge cock. Q. How are the sizes found of steam, water and gas pipes? A. By measuring their inside diameters. Q. How do you find the size of a boiler tube, flue or gauge glass? A. By the outside diameter. Q. In taking charge of a new plant, what is the first thing to do? A. Look after the water and steam pipes, als the valves connected with them. BOILERS 41 Q. Does water become lighter or heavier in a boiler under steam pressure? A. It becomes lighter per cubic foot as its temperature increases. Q. State as near as practicable the^lace to tap an upright boiler for the lower gauge cock? A. Two thirds the distance between the two flue sheets, measuring from the bottom flue sheet. Q. Where would you place the lower gauge cock in a submerged tube vertical boiler? A. From 2^ to 4 inches above the top flue sheet, according to the size of the boiler, so that the top ends of the tubes would always be submerged. Q. Where is the water line of a horizontal tubular boiler? A. From one and a half to two inches above the tubes. Q. Where is the fire line? A. On outside of shell and in line with the upper row of tubes. Q. Where is the lower gauge cock in a hori- zontal tubular boiler? A. An inch and a half to two inches above the upper row of flues. Q. Where is the water pipe tapped in a boiler head for a water-combination column? Where is the steam pipe tapped, and what size of pipe is used for making the two connections? QUESTIONS AND ANSWERS A. The water pipe is generally tapped centrally between the two upper rows of flues and the shell of boiler. The steam pipe is tapped in the top of the shell or in the dome. The con- necting pipes should not be smaller than i % inch diameter. Q. How often would you blow out the gauge glass during the day? A. About four times, or as often as necessary. Q. Is a glass gauge always perfectly reliable? A. No. The gauge cocks must be tried even if a glass gauge is used. Q. Where is the safety plug usually placed in a water tube or flue boiler? A. In water tube boilers they are generally placed four inches above the bottom of the drum, and not in the tubes. In flue boilers it is some- times screwed in the top of one of the upper flues, but of late it is the custom to tap the crown of the TOP OF UPPER ROW OF FLUES TO WATER SPACE OF BOILER 8ETVKI THE TWO UPPER Of FLUES AND SHELL BOILERS 43 shell about 15 inches back of the dome and there insert a half -inch pipe, reaching to within 2^ of an inch of the flue line. The top of this pipe is tapped into a brass chamber, in the top of which the safety fuse plug is screwed in. Q. How does this arrangement work? A. When the water in the boiler falls below the lower end of the safety plug pipe (indicated by a dotted line in the cut), the dry steam enters it, passes into the chamber and fuses the plug, the steam escapes and gives warning. See also page 68. Q. At what temperature does the plug fuse, and what is it made of? A. It is made of Banca tin which fuses at 420 F. Q. What causes channeling and grooving in a boiler? A. They are caused by the mechanical action produced by unequal expansions and contractions. Q. Where would you feed water into a boiler to prevent grooving, etc. ? A. Feed near the water level of the boiler instead of near the bottom. Q. Which is the best arrangement of the feed pipe? 44 QUESTIONS AND ANSWERS A. It should enter the front head just above the tubes and a few inches away from the shell. It should then extend back to within a foot or so of the back head, then cross over and discharge on the opposite side, downward, between the tubes and shell. In this way the feed water becomes well heated before discharging into the boiler. Q. How large should a feed pipe be? A. According to the size of the boiler, from i to i^ inches. Q. How large should the blow-off pipe be? A. Ordinarily 2 to 2)4 inches diameter. Q. Where should the blow-off pipe be attached to the boiler? A. Underneath its back end. The shell should be re-enforced with a flange riveted on, and the pipe should be protected from the action of the flames and hot gases from the furnace by a fire brick stand. Q. Why is malleable iron used for the elbows in the fire? A. Cast iron ones would burn or break. Q. Is it dangerous to empty a boiler when the tubes or flues are hot? A. Yes ; and it is also dangerous to hastily fire up a boiler, because where the draught and com- bustion are sufficient for a white heat, the plates, no matter how good they may be, cannot with certainty resist the terrible heat. BOILERS 45 Q. State causes of defective circulation. A. It is caused by flues being too close together, scale thickening on them, and flues set zigzag. Q. What construction of a boiler would be con- sidered successful and economical? A. For a tubular boiler place the flues in vertical rows, leaving out the center row; good circulation is when water goes down in the center and rises at the sides where the heat strikes it. OOOOO OOO OOOOO OOO OOOOO OOO oooo oo Q. How much steam-space is there in a boiler? A. About % of the internal capacity. (In the cut the water surface is indicated by dotted lines, and the height of the steam space by b. ) Q. Give the space between the flues of a well- made boiler? A. The proper space should be half the diameter of the flue. (See the cut above.) Q. What amount of water in weight can be evaporated by one pound of good coal? 46 QUESTIONS AND ANSWERS A. The average is from six to ten pounds. Q. What waste of heat is there if 1-16 inch of scale is in the boiler? X A. Some of the best authorities claim from 10 to 15 per cent of fuel, and in this proportion upward according to thickness of scale. BOILER EXPLOSIONS Q. What causes a boiler to explode? A. It may be one or several of various causes. Defects in material or construction, or improper management account for most explosions. Q. What is the scientific explanation of an explosion? A. A boiler explodes when the pressure within exceeds its resisting power. Q. What decides a boiler's resistance? A. The strength of its weakest spot. It is there that an excessive pressure breaks through first. Q. Why are the parts surrounding the weakest spot affected? A. The break decreases their resisting power, while the shock and the sudden increase in the generation of steam manifold the pressure. Q. Does all the water instantly change to steam? A. No, but with a speed increasing at such a rapid rate that it seems instantaneous. BOILERS 47 Q. Is low water often a cause of explosion? A. Yes, when the engineer tries to fill the boiler quickly, instead of very slowly. If a large amount of cold water suddenly enters a hot boiler with a high pressure, too much of it^changes to steam, at once raising the pressure beyond the resistance of the boiler. Q. Is it proper, then, to feed water into a boiler when the water is out of sight? A. Under no circumstances. Q. What would you do? A. I should immediately draw the fire, if a light one ; if a heavy one, I should cover it over with wet ashes to deaden the heat. Q. Why not draw out a heavy fire? A. Because it would make more heat by raking. Q. What would you do if the water was too high in the boiler? A. Carefully open the blow-off and let out one gauge of water. Q. What injury and danger are caused by heavy scale in a boiler? A. The heat from the boiler plates is not com- municated to the water directly, but through the incrustation, a bad conductor. This necessitates an overheating of the plates, which deteriorates and weakens them rapidly. Q. What is a bagged or blistered boiler? 48 QUESTIONS AND ANSWERS A. A bag is a bulging out of the plate ; a blister is a bulging out not of the whole plate, but of the outer layer split from the inner. These defects are caused by too much sediment or scale. They weaken the boiler very much. Q. How are these defects remedied? A. By cutting the bagged or blistered piece out, and riveting a hard patch on the inside of the boiler. Q. Why on the inside? A. Because if put on the outside, the hole would form a pocket for sediment. Q. How would you find the safe working pres- sure of a boiler? A. Multiply twice the thickness of shell by the T. S. stamped on boiler plate and divide answer by 6 times diameter of shell in inches. If double riveted multiply by .70; if single, by .56. (Ans. in Ibs. of pressure gives the safe load, at which the safety valve is set.) Q. How is the safe working pressure found in cylindrical boilers? A. Multiply one-sixth of the lowest tensile strength by the shell's thickness (expressed in parts of an inch) at the thinnest part, and divide the product by the inside radius (half diameter) in inches. The answer will be the pressure allowable per square inch of surface for single riveted; if double riveted add 20 per cent. BOILERS 49 Q. Do these two rules give the same result? A. No, but they are both used by different engineers, and are both claimed to be service- able. Q. Which do you consider the safer, drilled or punched holes in boilers, for rivets, etc? A. Drilled holes. Q. Describe a good way of keeping a boiler clean? A. Every boiler should be supplied with a sur- face blow-off, as a large percentage of the foreign matter held in suspension in water rises at the boiling point and can then be blown off before it has had time to deposit on the surface and flues. If not blown off, the heavier particles will be attached b each other until they become sufficiently heavy to fall to the bottom, when they will be deposited 51 the form of scale, covering the whole internal surface of the boiler below the water line. Q. Where is the surface blow-off tapped? A. It is tapped in the crown of the boiler and its pipe is bent so as to lie even with 1:he average water level. When the valve is opened, the outrushing steam carries the surface water and any light matter floating on it along into the catch basin. This device is usually called the skimmer. Q. When is the proper time and how would 50 QUESTIONS AND ANSWERS you blow out a boiler for cleaning purposes? A. Allow the furnace and boiler to cool down, open blow-off so the water and mud will escape, then wash out with a hose. Scrape the flues if possible, pull out all the Straightway Blow-off Valve sediment and scale left on the bottom of the shell with a long-handled hoe through the hand hole of the boiler and thoroughly rinse with water. Q. Suppose a boiler was found badly corroded and pitted internally along the water line, and covered with a heavy deposit of sediment, baked on hard, what should be done? A. Get inside the boiler and thoroughly scrape the shsll, getting down to the sound plate, then with a stiff wire brush thoroughly oil or paint the corroded portion with red lead and boiled linseed oil, three coats. Q. What are the causes of * 'foaming"? A. Foaming comes from various causes, such as the mixing of water with steam, high water, irregular firing or feeding, impure or greasy water, too small steam space, dirty boiler, changing of water, etc. Q. How is it known when a boiler foams? BOILERS ' 51 A. It can be seen in the gauge glass by the water suddenly moving up and down, or by the sputtering at the gauge cock. Q. Can foaming be overcome? A. Yes, by partly closing large valves, opening fire doors and feeding water into boiler. Q. What is meant by a boiler's "priming"? A. Entrance of water together with steam into the steam pipe, caused by high water, narrow steam pipe and sudden opening of valve. Q. How would you remedy it? A. By opening the valve slowly, or lowering water in the boiler. Q. How would you gasket a steam joint so the gasket can always be taken out and replaced with- out injuring it? A. By rubbing a little graphite and oil between the face of the flanges and the gasket, both sides. Q. How would you remove a man or hand hole plate from a boiler? A. Simply loosen nut, remove brace (dog or crab), and turn the plate to narrow side and take out. Q. Why is a hand or man hole plate made oval instead of a true circle? A. So they can- be taken out and put in and new gaskets put on. Q. When you have a battery of two boilers or more and one boiler has 80 Ibs. steam pressure and 52 QUESTIONS AND ANSWERS the rest are cold, how would you proceed to con- nect them together? A. Simply fire up the cold boiler and raise steam pressure to equal the- one to which you wish to connect it. Never under any circumstances turn high into low pressure or hot into cold, because the sudden expansion may cause a serious rupture and may cost you your life. Q. What is the first thing you would do on entering the boiler room in the morning? A. See how much water is in the boiler by try- ing the gauge cocks, etc. Q. Then what would you do? A. Start a fire if I had one or two gauges of water. STEAM HEATING Q. How would you open a steam valve to supply steam to a building for heating in the morning? A. Open the valve slightly and wait until the pipe stops pounding, then gradually open a little more; it saves joints, gaskets, pipes, etc. When opening valves, make sure that the valve at the end of the return pipe is open until hot, then close it. Q. How is the amount of pipe required for properly heating a room calculated? A. By the following rules: BOILERS 53 One cub. foot of boiler to every 1,500 cub. feet of space. One H. P. of boiler to 40,000 cub. feet of space. One superficial foot of steam pipe to six superficial feet of glass in windows. One super- ficial foot of steam pipe to 100 sq. feet of wall, ceil- ing or roof. One sq. foot of steam pipe to 80 cub. feet of space. Q. How do you find the heating surface of a radiator? A. Multiply the total length of all the pipes by the outside circumference in inches, and divide by 144. The answers give the square feet. Q. Which is the best way to thaw out frozen steam pipes? A. By laying some old cloth or waste on the pipe and pouring on boiling water, the pipe can be thawed out in 10 minutes. SMOKE AND CHIMNEY Q. Would it be proper to have the chimney rough inside? A. No; it should be as smooth as can possibly be made, and the area a little larger towaitl the top than at the bottom (inside). Q. How much larger should the space be where the smoke or gases return through the flues than the grate surface? A. It should be one-fifth larger in area than the grate surface. 54 QUESTIONS AND ANSWERS Q. Where would you consider the proper place to close in against the sides of an externally fired boiler with brick (fire line)? A. About in line with the center of upper row of flues all along the full length outside of boiler. SIDE VIEW This cut shows the proper way of enclosing a boiler in brickwork. The figures give the dis- tances in inches. Q. Where does the greatest effect of the fire on the bottom of an externally fired horizontal boiler take place? A. Just back of the bridge wall. Q. From where is the height of a chimney measured? A- From the top of the grate. Q. What makes a chimney draw? BOILERS 55 A. The difference between the weight of the column of heated gases within and an equal column of cooler air without. Q. Upon what does the draught capacity of a chimney depend? END VIEW A. Upon its height, cross section area, and upon the temperature. Q. State the size of chimney necessary to fully relieve the tubes or flues of a boiler or boilers of smoke, and give height? A. The chimney should be one-fifth larger in area than all the tubes or flues combined, so as to afford an ample passage for all the gases. The top should project at least 10 feet above the high- est building in the immediate vicinity, to avoid all downward currents of the atmosphere. 56 QUESTIONS AND ANSWERS BOILER TESTING Q. Is the hydraulic test or the hammer test better? and why? A. The hammer test is always reliable because a flawless metal gives a clear sound, and every part, inside and out, is examined by itself. In the hydraulic test a boiler may get strained, and when heated afterward, the expansion may bring out a leak. Government and insurance inspectors employ the hammer test. Q. How do you find a broken or loose stay or rivet? A. By holding a hammer against one side and striking the other side with another hammer. Any looseness can be discovered in this way by the feeling. Q. If tested by the hydraulic test how much pressure is sufficient to test the boiler so as to carry a certain amount of steam pressure? A. The hydraulic pressure test should be one- half more than the steam pressure to be carried, viz. : If steam pressure is to be 80 Ibs. the hydraulic test should be 120 Ibs. Q. What is it that ruptures a boiler? A. The pressure within it, and strains caused by unequal expansion and contraction. To avoid this trouble it is necessary to BOILERS 57 exercise great care in raising steam. The fire should be increased gradually and the boiler have at least four inches of water above the top row of flues so the temperature may be gradually raised. Q. Is it injurious to a boiler to open the fire doors often and suddenly cool the fire and sheets? A. Yes; it is very unsafe. FEED REGULATION Q. Suppose you had a battery of three boilers and the only valves near the boilers on the feed pipe were check valves, how would you feed the boilers evenly without using globe valves between the checks and boilers? A. First, fire the boilers evenly; second, keep the pumps running steady, and if one boiler should happen to receive more water than the others use the blow-off valve of that particular boiler and regulate the height by it. Q. Can uneven feeding be prevented? A. Yes, by partially closing the stop valves of the boiler or boilers with high water, and, if necessary, by opening the stop valves of the low water boilers a little more. BOILER HORSE-POWER Q. How can you find the amount of water evap- orated in a boiler? A. Take the mean between the widths of the 58 QUESTIONS AND ANSWERS two levels at the beginning and at the end of a space of 15 minutes, as indicated by the glass gauge. (See cut, pp. 42, 45.) Multiply the con- stant length of water surface with this mean width and multiply their product by 4. This gives the amount evaporated in cubic inches. Divid- ing the result by 1728, you get the answer in cubic feet. This test is not recommended, though used. Example: If the glass gauge shows a difference of one inch, we measure across the face of the boiler half an inch above the last level. If this measures 48 inches and the boiler is 14 feet long (=168 in.), we have 48X168=8064. Multiplied by 4=32,256 cub. in. per hour, or 18% cub. feet. Q. Can you know from the amount of water evaporated in one hour, how many horse-powers have been developed? A. Yes. Q. How many cubic feet of water evaporated in one hour equals a horse-power? A. One-half cubic foot, 3^ gallons or 864 cubic inches. Q. Then, in our example, how many horse- powers were indicated? A. Two times 18^, =37>< H. P. Q. How can you find the horse-power of a tubular boiler by the heating surface? A. First find the number of square inches of heating surface around boiler shell from fire line to . BOILERS m 59 fire line and in the flues; divide by 144 to get square feet; divide quotient by 15 if horizontal tubular, and by 12 if locomotive or vertical boiler to get H. P. FEED-WATER HEATER Q. How many types of feed- water heaters are there? A. Two. The open heater and the closed. Q. What is the difference between them? A. In an open heater the exhaust steam comes directly in contact with the feed -water, in a closed heater it does not. Q. What is the object of a feed - water heater? A. To save fuel by making use of the exhaust steam from the engine to heat the feed-water. Q. At what temperature will a heater deliver water to a boiler? A. That depends upon the type of heater and other conditions. A good heater of ample propor- tions should raise the temperature of the feed- water up to 200 F. , or higher. Q. What else is a heater good for besides heat- ing the feed-water? A. It also purifies the water by extracting the scale-producing matter, and also the mud. 60 QUESTIONS AND ANSWERS Q. In using an open heater is there any danger of flooding the cylinder, and if so, how? A. If there should be any stoppage of the out- flow of feed-water, it would flood the cylinder through the engine exhaust pipe, and perhaps cause a wreck. TENSILE STRENGTH The tensile strength of metals is the load that would break a bar of one inch area in cross sec- tion if applied in the direction of its length. For a test of the tensile strength of iron or steel boiler plates, narrow strips are sheared from plates selected at random from a pile of them rolled at the same time we will say the plates are steel and a quarter of an inch in thickness. These strips are at the middle reduced to a quarter of an inch each way (square). Suppose the testing machine pulls the first of 4 strips asunder at 3,999 Ibs. register, the second breaks at 4,001 Ibs. and the last two at exactly 4,000 Ibs. each. Adding these all together we have the sum of 16,000 Ibs., which, divided by 4, the number of strips tested, gives us 4,000 Ibs. as the mean breaking strain of a quarter square inch of sectional area of steel. Multiply this by the number of quarter square BOILERS 6 1 inches in i square in. and we have the tensile strength in i square in. of section. There being 1 6 quarter in. square in i square in. would give 16 times 4,ood, which equals 64,000 Ibs. for a bar having i square in. of sectional area, which would be about the average tensile strength of first quality steel. After tensile strength is found, all the plates are stamped T. S. in that particular batch, and under- neath stamp 64,000. Sheets not stamped should not be rated at more than 48,000 Ibs. T. S. STEEL AND IRON Q._What is steel? A. Steel is a variety of iron containing from one-half of one per cent to one and a half of one per cent of carbon. Q._What is iron? A Iron is a metal, the most abundant and the most important of all. It contains always impurities, such as magnesia, sulphur and phosphorus. It is hardly anywhere found native, but must be manufactured from ore. Cast z'rbn is brittle and hard. Wrought iron, obtained by puddling, is softer and malleable. Q. What are th principal advantages of steel over iron? A. Greater elasticity and hardness, which by tempering may be increased to any desired degree. 62 QUESTIONS AND ANSWERS POP AND LEVER SAFETY VALVES Q. Of what use are safety valves? A. They are to release the boiler automatically of all steam pressure above a certain point. Q. Are there more than one kind of safety valves? A. Yes the old lever and* the spiral spring safety valve. Q t When steam is heard issuing from a safety valve, does it signify danger? A. No; it is a signal of safety. It shows the valve is in working order and, if properly set and adjusted, it is a sure protection against trouble Q. How do you set a pop safety valve? A. In setting the valve shown on page 63, re. move the cap H., and turn the set bolt O up or down, to decrea se or increase the pressure. Q. How is the amount of reduction regulated? A. Remove the set screw D (Fig. i) from the lower part of the case M, insert a pointed instru- ment in the screw hole, and with it turn down (to the left) the set ring, increasing the amount of .loss, or up (to the right) for decreasing the amount. Then replace the set screw which holds the ring in position. SAFETY VALVE Fig. i V is the valve nut into which O is screwed. B is the valve. N is the upper cap over spring casing K inside casing M. S is the upper spring cap, R the lower. T is the testing lever, C the main casing, Ethe bolt bushing, F the bushing jam nut, A the guide for valve disc, J the guide for lower valve stem. Q. How large a loss is it usual to have? A. Three or four pounds. A valve can be set to lose less than half a pound in popping. Q. What new device is there for deadening the sound of the pop valve? A. The muffler attachment. (Fig. 2.) Q. How is the Muffler Valve adjusted? A. It can be adjusted on top without remov- ing from the dome. In order to adjust either the pressure or the blow-down, first remove the muffler I ; this exposes the compression screw G, adjustable nut M, crosshead L, locking latch O, and check nut H. By loosening the check nut H and screwing down the compression screw G, you increase the pressure, and the reverse for lessening the "pressure. (As .a general rule from 1-16 to % turn will change the pressure of valve five Ibs. 6 4 QUESTIONS AND ANSWERS ff either way. ) By raising the locking latch O and screwing down on the adjusting nut M one notch you will reduce the blow-down one pound, and the reverse increases it one pound. A base, A 1 valve seat, B valve, C spindle, D spring, E follower, F F 1 main casting, F 2 thread hub, G compression screw, H check nut, I muffler, J the regulating ring, J J 1 lugs on ring, K parallel rods, L cross-head, M adjusting nut, O locking latch. Q. Give proper size of safety valve for a boiler having 25 sq. feet of grate surface, allowing for 70 Ibs. pressure? A. For each foot of grate surface 22. 5 feet boiler heating surface is allowed ; 25 X 22. 5=562. 5. For the water in the boiler we allow 8.33 (the weight in Ibs. of one gallon), which, added to the given pressure, gives 78.33. 562.5 divided by 78.33 equals 7.18 sq. inches area, or a 3 -inch diameter. Q. How would you figure the pressure under a 3-inch safety valve with 75 Ibs. boiler pressure? A. Three times 3 equals 9 inches, times .7854 equals 7,068 area, times 75 equals 530.1 Ibs. Q. What is the United States government rule about the relative areas of grate and safety valve? SAFETY VALVE 65 A. One square inch area of lever safety valve to 2 square feet of grate surface. Q. State the general allowance among inspect- ors? A. One inch area of safety pop_valve to 3 square feet of grate surface. Q. Find area of a pop valve 3^ inches in diameter? (See table of areas, page 235.) A. Multiply diameter by itself and then by decimal .7854; answer is the area, less decimals. Q. When calculating the load on a safety valve, is allowance made for the atmospheric pressure on top of valve? A. No; because it is present everywhere, inside and outside the boiler, and may be left out of the calculation entirely. Q. Are the spring safety pops calculated when set? A. No: as a rule they are set by a test steam gauge. Q. What is done, if in such a test^the needle does not show true at 100 Ibs. pressure? A. It is pulled off the pin, and then put back in the right position. Q. What is meant by a strong or light needle? A. It is termed strong when at the test it shows less than the true pressure, and it is called light when it shows more. Q. What is it that keeps the face of the 66 QUESTIONS AND ANSWERS valve and the seat in line (opposite) and causes the rise and fall to be even and true? A. The valve spindle. Q. What is the point of contact? A. Where the valve and its seat meet. Q. At what angle is the edge of the valve and its seat beveled? A. At an angle of 45 degrees. Q. How is it known when the safety valve is in good working order? A. By the steam and gauge. Let the steam pressure rise enough to just move the safety no more and. note the correspondence between the gauge and safety valve. Q. Is there another way? A. Yes raising the valve by hand. Q. How do you find the exact place where to place the ball (weight) on the long lever of the safety valve? A. By applying the laws of leverage. (Page 241. ) Q. How do they apply in a safety valve? A. The bar holding down the valve is a lever of the third kind, the pivot representing the fulcrum, the valve representing the power, and the ball representing the weight. (See cut, page 68.) Q. Give the rule for calculating the distance from the fulcrum at which a given weight must be set to cause the valve to blow at any specified pressure. SAFETY VALVE 67 A. i. Multiply the area of the valve in square inches by the pressure in pounds per square inch. Call this product "number i." 2. Multiply the weight of the lever in pounds by the distance in inches of its center of gravity from the fulcrum; divide the product by the distance in inches from the center of the valve to the fulcrum ; add to the quotient the weight of the valve and spindle. Call this sum "number 2." 3. Divide the distance in inches from the center of valve to fulcrum by the weight of the ball in pounds, and call the quotient "number 3." 4. Subtract "number 2" from "number i," and multiply the difference by "number 3"; the prod- uct is the answer. Example: Given : diameter of valve 4 inches ; distance from fulcrum to center of valve 4 inches ; weight of lever 7 Ibs. ; distance from fulcrum to center of gravity of lever 15^ inches; weight of valve 3 Ibs. ; weight of ball 108.24 Ibs. Blowing- off pressure 75 Ibs. Area of 4" valves = 12.566 square inches 75 X 12.566 = 942.45 4 -f- 108.24 = .0369 942.45 30.125 =912.325 912.325 X .0369 = 35.66 inches. Ans. Q. How do you find the pressure at which a safety valve will blow off when the weight and ita position are known? 68 QUESTIONS AND ANSWERS A. Divide the fulcrum into the length of lever, multiply by weight of ball, add weight of lever, valve and stem and divide by ^ Q ^^ Q. How is the total weight of lever, valve and stem found? A. The easiest way is to tie the stem with a string to the lever and attach a spring (scale) balance to the lever and valve, directly over the center of the valve, and weigh them in place. AUTOMATIC EXTINCTION OF FIRE BY STEAM AT LOW WATER In this device, recently patented in Vienna, a pipe reaches through the top of the boiler down to low water mark, so that steam will enter it as soon as the water falls below the mark. In the upper end of the pipe a safety fuse is melted by the steam, opening connection with a second pipe, which leads into the fife-box, where the steam extinguishes the fire. The fuse being a ring between a conical valve and its seat, the valve can be screwed down on the valve seat, as soon as the fuse is melted out, and a new fuse put'in at any convenient time. INJECTORS 69 A whistle or bell is easily connected with the apparatus to give alarm. The air in the pipe first mentioned is exhausted through a stop-cock, after the boiler is heated. INJECTORS Q. What is an injector and its use? A. It is a substitute for a pump and is used in feeding a boiler with water. ^ Q. How is it that an injector forces water into a boiler against the pressure of the steam operating it? A. The water and steam mingling at the com- bining tube, the steam jet is condensed, con- verted into a water jet. This water jet has a much smaller cross section area than the steam jet had, and as the energy of the steam jet is retained entire, a greatly increased velocity results. Q. What forces the boiler check valve open? A. The pressure of the water in the delivery pipe. Q. State the velocity of steam passing through an inch pipe at 100 Ibs. pressure? A. Two thousand feet per second. Q. Where would you look for trouble if the injector stream broke and the same injector always before worked well? M N rc Tf xnvO l>00 O O - " ^ INJECTORS 7* A. At the water and steam supply. Q. Of what use is a steam nozzle? A. It is for the actuating steam jets to pass. Q. Where is the combining tube? A. In the casing of the injector where the steam and water mix. Q. Where is the delivery tube of an injector and what is its use? A. It is where the maximum velocity of the stream is attained, and the jet overcomes the back pressure from the boiler. Q. Are injectors divided into classes; if so, state how many? A. Yes; they are divided into two general classes, the lifting and non-lifting. Q. Can these two classes be subdivided? A. Yes ; they may be divided into six, namely, single tube, double tube, self-adjusting, restarting, open or closed overflow injectors. Q. Is it a good idea to turn on more steam after overflow has been shut off? A. No; it will cause the injector to break the stream. Q. State some of the principal causes that make an injector's stream break? A. ^Not enough water supply, straws, chips, mud, cinders, leaky joints, overheated water, bad strainers, corrosion in the injector casing and low steam pressure. 72 QUESTIONS AND ANSWERS Q. What rules are used for determining the proper size of an injector for different boilers? Rule i. For Vertical Tubular Boilers reduce all dimensions to inches and multiply the circum- ference of the fire box by its height above the grate ; multiply the combined circumference of all the tubes by their length ; next subtract from the area of the lower tube sheet, the area of all the tubes and add the remainder to the sum of the area of the tubes and shell and divide total by 144, and the quotient will be the number of square feet of heating surface. Rule 2. For Horizontal Tubular Boilers reduce all dimensions to inches and multiply two-thirds of the circumference of the shell by its length; multiply the length of the tubes by their combined circumference; next subtract from two-thirds of the area of both heads the combined area of the tubes and add the remainder to the sum of the tubes and shell, divide total by 144, etc. Rule 3. For Water Tube Boilers. Proceed to find the area of all heating surfaces exposed to the radiation of gases from the furnace of boiler, and if area is in inches, divide by 144, etc., as above. After finding the heating surface, as per rule i, 2 or 3, divide by 30 (see page 150) to get the horse power, and allow 10 gallons of water per hour for each horse power. FEED PUMPS 73 would be a short rule then? A. If H. P. is known, multiply number by 10 to find number of gals, of water the injector should deliver per hour. If H. P. is not known, multi- ply number of sq. feet of heating surface by 3. FEED PUMPS Q. Name Khe different kinds of pumps used flaily for boiler feeding, etc. ? A. Single action, with two valves, receiving and discharging; the double action, with two or more discharging valves. The latter receives and discharges water at both ends of water cylinder and has a steam cylinder attached to work the pump. The duplex is a combination of two double action pumps all cast together side by side. Q. What are the relative proportions of steam and water cylinders of feed pumps? A. The steam cylinder is 1-3 larger in diameter than the water cylinder. Q. In setting up a steam pump, how is it leveled? A. By leveling the discharge valve seat length- wise and crosswise. Q. Give rule to find area of a steam piston in connection with a pump? A. Multiply the area of water plunger by 2. Q. Of what are pump valves made? 74 QUESTIONS AND ANSWERS A. Hard or soft rubber, brass and sometimes vulcanized fiber and wood. Q. Can you give a short rule to find the sizes of steam pipes for cylinders? A. Divide the area of steam piston by 64 for steam pipe, and by 32 for exhaust. Divide the area of plunger by 3 for discharge pipe, and by 2 for suction pipe. Q. Suppose you had a duplex pump, size 8 in. water by 10 in. steam by 12 in. stroke and 3 in. diameter plunger rod, making 100 ft. piston travel per minute, how many gallons of water would the pump deliver, having full supply of water? A. First find the area of plunger face 8 times Sin. equals 64, multiplied by .7854 equals 50.2656, by 12 in. stroke equals 603.1872, by 4 cylinder ends equals 2412.7488 cubic in. Now subtract the cubic contents of 3 in. diameter plunger rod 12 in. stroke in one end of each water cylinder from the total cubic inches and divide by 231, which gives gallons for one stroke, 4 ends. This multiplied by 100 piston travel gives total. Three multiplied by 3 equals 9, by .7854 equals 7.0686, by 12 equals 85.032, by 2 equals 170.064, subtract from 2412.7488 equals 2242.6840, divided by 231 cubic inches in a gallon equals 9. 708 gals, one stroke, multiplied by 100 equals 970.8 gals, per minute. This rule holds good on other pumps. Q. Give quick rule to find quantity of water FEED PUMPS 75 pumped in one minute, pump making 100 ft. of piston speed per minute? A. Multiply the diameter of the water plunger by itself, then multiply the product by 4. Answer gives gallons for one pump ; if for two* pumps mul- tiply answer by 2 and so on. Q. How could the horse-power be found necessary to pump water to a given height? A. Multiply the total weight of water in pounds by the height in feet and divide by 16,500. This allows for water friction and steam loss. Q. How are the steam valves of duplex pumps set and adjusted? A. Remove the valve chest cover, place the rocker arm plumb (reach arm), then see how the valve on opposite cylinder is for lead ; if equal at both ends, the valve is set, if not, adjust the jamb nuts to suit. Do the same on the other pump. Q. Does the duplex pump exhaust its steam through the same port that it enters and thence through the cavity under the valve to the exhaust chamber as in the common slide-valve engine? A. No. It has a separate steam and exhaust port at each end. (See cut, page 76.) Q. How does it work? A. The piston covers and closes the exhaust before it reaches the end of its stroke, and the steam left in the cylinder acts as a cushion. At the end of stroke the steam valve opens and the 76 FEED PUMPS 77 * rce Chamber. " H'ndP Ive Guard. Ive Spring. iss Valve Plate. 1 livery Tee. Chamber. 1 G .2 tion Hand Plate. tofi Nut. nger Nut. am Ports, baust Ports. PQ 2 > & < < & s 3 W *e *. $ *$ $ So vo S, 3, 5 io * 6 00^ vj \O S Oi O c 1 1 5 s "O *^ 1 d 1 1 go jS M a c I 1 1 1 ">> *>* u u J s !* 8 jg c ca E 1 1 O d< 1 .2 I u 6 S 5 rt rt b c 3 v to bo c V T3 q i 3 cj i Q C/3 C/3 CA! ^ 6 S J 5 PH P* O M & ^ i * CA 13 00 t^ OH O + CA 3 16. Piston Tongue. 17. " Tongue Spring. 18. " Tongue Bracke 19. Rod Stuffing Bo3 20. Stuffing Box Glan 21. Steam Cylinder Foot. 22. Exhaust Outlet. 23. Piston Rod. 24. Valve Rod Head Pin. 25. Rod Link (long & short; 26. Long Lever. 37. Short Lever. 28. Rock Shaft Key. 29. Upper Rock Shaft. 30. Lower Rock Shaft. | 0) d 3 T3 1 o S3 1 S ^ 3 K | "o ^ fc S | 1 1 13 T3 11 8, s j? a pa 6* !> PH P4 tf P4 &H > > > C/3 tf) C/} J PH 2 fe S - CO ^ XO vd ^ 00 d - 9 -* /> 78 QUESTIONS AND ANSWERS live steam forces the piston back. The same at both ends. Q. Why does the piston with the long lever move in the same direction as the opposite valve, while the other piston with short lever and the opposite valve rod move in opposite directions to each other? A. The lever last mentioned (indirect motion) starts the opposite piston on the reverse stroke, and this piston on reaching the end of the stroke opens the valve for the other piston to reverse. Q. Why is this arrangement made so? A. Because it is necessary to secure the reversal of the pumps, which could not be done in any other way as simple. Q. What gives the most trouble about a pump? A. Leaks, in one way or another. Q. How large a vacuum can be maintained con veniently in a suction pipe? A. About 28 inches by gauge. Q. How large a vacuum should there be? A. There should be 3 or 4 more inches of vac- uum than feet of lift. Q. Suppose the suction-pipe was air-tight, and the vacuum was too low, what would generally be the cause? A. Leaky valves, or a leaky plunger, or a leaky Stuffing-box, or a cracked cylinder. FEED PUMPS 79 Q. What is the proper size of the suction-pipe? A. The full size of the opening in the pump. Q. Would a leaky water end of a pump cause any unnecessary waste of steam? A. Yes ; a pump would have to work~at greater speed to keep the boiler supplied with water, than otherwise required, and this means a waste of steam. Q. Upon investigation what would you find to be the trouble? A. The water end improperly packed or no packing. Q. Suppose the pump used a good deal of steam and still went very slowly, causing great friction, to what would you lay the trouble? A. To the, pump being packed too tightly. Q. How should the rings be fitted to prevent the friction? A. Cut the ring joints a little short to allow for expansion when wet or under pressure. Q. How would you try the pump to know that the packing is in good order? A. Close the delivery valve near the pump, let plunger make a stroke up and down. If then the pump stops of its own accord the plunger is well packed. Q. Is there any danger of bursting the pipe? A. No, for the pipe and valve should be able to withstand the pressure. 80 QUESTIONS AND ANSWERS Q. Is the pressure greater in the pipe than in the boiler; if so, what causes it? A. Yes, as there is more area in the steam cylinder. Q. How many valves has a duplex pump, and how many stories? A. The duplex pump has eight valves and two stories, four valves to each story, one story above the other. Larger pumps have more in proportion. Q. Where are the receiving valves located in a 3x4x6 inch duplex, also the discharge valves? A. The receiving or suction are the lower set and the discharge the upper set. Q. How would you partition off the valves in the water end of a double-acting pump? A. Place the partition between the suction valves only. Q. How many ports has each steam cylinder of a duplex pump? name them. A. There are five, namely, two steam, two exhaust and one outlet port to the atmosphere. Q. How wide are the steam, exhaust and out- let ports of a duplex pump 3x4x6 inches and how thick are the dividing ribs? A. The steam and exhaust ports are 7-16 of an inch, the outlet (in the center) is 9-16, and the ribs ^ inch each. Q. How long is the exhaust cavity in the middle of steam slide valve? FEED PUMPS 8l A. It is i and 9-16 inches long. Q. How long are the two faces at each end oi valve? A. They are each the same length as exhaust cavity. Q. How much lap has the valve at each end over the steam ports when in central position? A. Three-sixteenths of an inch. Q. How much lap has the exhaust? A. None; the valve just seals the two exhaust ports. Q. Why do large pumps have many small water valves? A. So the loss of water will not be so great in the rise and fall of the valves when the pump is working. Q. How is a vacuum created in a pump cylinder? A. There is not a real vacuum at any moment ; the water follows the piston as fast as it moves, driven by the 14.7 Ibs. per sq. in. pressure of the atmosphere. Q. To what height would the water follow, the piston? A. To the height of 33 feet. At this point the column of water in the pipe would have the same weight as a column of the atmosphere with the same cross section area. Q. Why is a check valve placed near the boiler? A. To prevent the water in the boiler from 82 QUESTIONS AND ANSWERS being forced back onto the pump at the end of each stroke. Q. What, if there were no check valve? ^Btil Check Valye. Horizontal Check Valve- A. The pump could be run, but the discharge valve would seat too hard and would wear out too soon. Q.--What is done when the check valve needs repairing? A. The gate valve between the check valve and the boiler is closed. Q. Are angle check valves and vertical check valves used with boilers? A. Rarely ; they are mostly used for connecting a steam heating system to the traps in the boiler room. Q. How much lift should a check valve have? A. Enough to give an area of opening, equal to the area of the feed pipe. Q. Is it well to give it a larger lift? Sectional. " Clip" Gate Valve FEED PUMPS 83 Angle Check Valve. Vertical Check Valve. A. No ; too much lift wears valve and seat Q. What is the use of the pet cock? A. If the pump is in good order, the pet cock will show full stream at forcing and weak at suc- tion. It shows tank or hydrant pressure both strokes, when receiving valve is held open by dirt, etc. It shows boiler pressure both strokes when check and discharge valves do not work properly. Q. What is the air chamber's duty? A. The elasticity of the air in it renders the pressure and flow practically uniform, notwith- standing the intermittent action of the force. It furnishes what in electricity would be called a constant potential service. It also renders the seating of the valves more even. Q. What are the features of a Fire Engiite? A. A fire engine consists essentially of a pair of single-action suction and force pumps. The boilers are tubular, of sufficient capacity to work the pumps 500 strokes per minute. The working pressure of steam is usually 80 to 100 Ibs. per square inch. THE ARTESIAN PUMP The engine part of the artesian pump shown in the cut, is a common ver- tical slide valve engine in its cylinder parts. The figures indicate the parts as follows: 1. Steam Cylinder. 2. Steam Cylinder Head. 4. Steam Piston Head. 5. Follower Head. 6. Inside Piston Ring. 7. Outside Piston Rings 8. Adjusting Screw. 9. Jam Nut. 10. Adjusting Spring. , 5 11. Cap Screws for Fol- lower. 12 A, B. Piston Rod. * 13. Brass Piston Rod Nuts. 14. Steam Slide Valve. 15. Steam Chest. 16. Steam Chest Cover. 17. Upper Stem Gland, 18. Lower Stem Gland. 19. Gland Studs. 20. Steam Valve Stem. 24. Stem Guide on Cylin- der. 25. Brass Jam Nut. 26. Brass Split Nut. 27. Brass Tappet Head. 28. Tappet Head Bolt. 29. Stem Link. 31. Fulcrum Bolt. 32. Stem Guide. 33. Stand. 34. Piston Rod Gland. 36. Swinging Arm. 38. Crosshead Link. 40. Crosshead with Bolts. 41. Crosshead Jam Nuts. 46. Suction Flange in the Base. 47. Discharge Flange. 48. Hinge Bolt and Nut. 65. Base Stuffing Box Gland. STEAM PUMP GOVERNOR DESCRIPTION. The upper wheel i jn yoke is the lock nut. Turn it to the left; then turn lower wheel 2 to the right, which raises and opens the double steam valve 8; when partly open, open the throttle valve and start the steam pump. Now close angle ^alve 4 and open globe valve 5. This lets the main water pressure on the piston 6 and spring 3 in brass water cylinder 7. Now regu- late by screwing up or down on wheel 2 until the water pressure gauge shows pressure desired to carry ; then set in place by turning wheel i to the right until up against bottom end of the piston rod. To OPERATE. In starting or stopping the pump do it with PUMP GOVERNOR the main steam throttle. Do not change the adjustment of the governor. In starting, close globe valve 5 and at the same time open angle valve 4. As soon as started, close angle valve 4, 86 PUMP GOVERNOR open globe valve 5 and pump will hold the pressure at which it is set. PACKING GOVERNOR, ETC. Pack the valve rod as light as you can and screw stuffing box nut down lightly with thumb and finger, just enough to stand the strain. Do not use wick packing, but some good sectional, square or round packing. To CLEAN AND OIL GOVERNOR. Once a month run the pump by the throttle, shut off both valves 4 and 5, then open union 9, take off water cylinder cap n, take out piston 6, also stem and steel spring 3, wipe out the cylinder 7, clean piston head 6, and oil them with some good oil that will not gum. If governor is kept clean and attention paid according to directions no trouble will arise. To CONNECT. Place governor between the steam chest and throttle valve so it will stand plumb; connect bottom outlet flange or screw with steam pipe on steam chest, then connect the boiler pipe to inlet, placing throttle in most convenient place. Use short nipples so as to place governor as close to steam chest as possible, To CONNECT WATER PART. Tap the discharge main or pipe, if horizontal, on the side for J^ inch pipe, run pipe up about a foot higher than top of pipework of governor, then over to it and down and connect to quarter-inch valve on top of pipe- work over governor. If for two governors on pumps discharging into same main tap, the same as PUMPS * 87 \0 for single governor and run up and over between governors, then put on a "T," and run to right and left till over pipework above each governor and connect. If the pulsation of pump is noticed it can be avoided by partly closing globe valve 5. Never connect close to air chamber. Insert a short piece of pipe in drip "T" 12 at bottom of brass cylinder to reach the floor. DOUBLE ACTION WATER PUMP WITH ROLLING VALVES (See page 88) A double action water pump, built in two pieces. A, the upper or main part, contains the delivery valves c,d, and the pump barrel c, which is made of a seamless drawn brass tube. (Fig. 2.) The lower part contains the chamber B, to which the suction pipe is connected, and the suction valves a, b. It is bolted to A by bolts e, f . The plunger, D, is provided with two reverse cup leathers. E, the plunger rod, passes through the stuffing box F. The downward stroke of D opens the two valves a and c, while it closes b and 4. The upward stroke acts in the opposite sense. The deep well plunger, Fig. i, consists of the brass pump cylinder A, the pump case B, the air barrel D, and the water pipe E connecting pump to stuffing box ; c is the suction valve, b the deliv- ery valve, f the suction strainer. 88 THE BOURDON STEAM SPRING GAUGE VIEW OF INNER PARTS DESCRIPTION. A brazed, tempered-brass tube, bent in an almost complete circle, has the open end attached to one arm of a siphon pipe, while its closed end is fastened to a lever. The steam pressure on the water, in the pipe and tube, tends to straighten the tube or spring (by pressing more against the outer curve than the inner), moving the lever, the long arm of which turns, with its toothed arch, the hand of the dial, indicating the pressure per sq. inch of boiler. Q. Why is water kept in the spring and siphon? A. A direct contact with steam would take the temper out of the tube. Q. How is a vacuum gauge constructed? 89 90 QUESTIONS AND ANSWERS A. It has a lighter spring and it acts in the reversed sense as the atmospheric pressure tends to bend it more, the less pressure there is inside, or in other words, the greater the suction. The dial plate is graduated to register 30 inches of vacuum to equalize 15 Ibs. of atmospheric pres- sure or a column of mercury of 36 inches. Q. Explain the compound ammonia gauge? A. It is the same ^style as a steam gauge, only the spring is of steel tubing and the graduation on the dial is to show both ways from zero mart . All figures above show pressure and all below show vacuum. Q. Why is the ammonia gauge spring made of steel instead of brass? A. Because the ammonia destroys brass, while steel is not affected by it. Q. Are there two springs in the compound ammonia gauge? A. -.-No; it is so named because it shows either vacuum or pressure on the same dial with the same needle. Q. What is a duplex gauge? A. It has two springs and two needles, one showing the excess pressure, and the other train pipe pressure. They are used on locomotives only. THE LUBRICATOR Q. Of what use is a lubricator? A. It supplies the valve, piston and cylinder with oil automatically after the drop feed is set. CONNECTION Q. How many different styles of lubricators are there in use? A. There are three single feed for stationary 91 92 QUESTIONS AND ANSWERS engines, double feed for compound and locomotive engines, and triple feed for triple expansion, and locomotive engines and air pump. Q. How does a lubricator do its work? , A. As seen in the cut, by the condensed water passing down the center water pipe from the con- dense chamber to the bottom of the oil reservoir, forcing the oil to the top and down the oil pipes to and through the feeder valves C, C. After passing the feeder valves, the oil floats up through the water in the sight feed glass and on reaching its surface is carried off horizontally through the choke plug (P) by steam from pipe E. Q. How is the lubricator attached to the system? A. Connect its top to the live steam pipe and the feed pipe further down. Q. What precaution should be had after attaching? A. The passages and connections of the lubri- cator should be blown out with steam. Q. How is a lubricator filled? A. Close all the feeder valves C, C, also the live steam connection, then open blow-out valve D, and fill through filler plug. Q. How is the feed stopped and started? A. By closing and opening the valves C, C. Q. Supposing the lubricator ran empty how would you refill it? THE LUBRICATOR 93 A. Close feeder valve C and live steam con- nection ; open blow-off D ; open filler plug and as the water passes out, fill in with oil. Q. After filling what do you do? A. First, close drip D, screw filler plug in Jtight, open live steam connection fully, then regulate oil flow with valves C, C. Q. Are the valves B, B ever closed? A. No, except when a feed glass is broken. Q.-r-What is to be done, when a glass breaks? A. Close valves C, Cand B, B; unscrew plug of top bracket, loosen packing nuts and remove old 94 QUESTIONS AND ANSWERS glass. Insert the new glass, and fasten nuts and valves, etc. Q. Is it well to reuse old gaskets? A. It is not. Q. Is there any difference between the single, double and triple lubricators? A. Not in principle or operation. Q. Do all lubricators work alike? A. No, the down feed lubricator dispenses with the water in the feed glass. Q. How much oil should be fed through a lubricator for an engine working heavily? A. That depends, of course, on the quality of the oil, and also, of course, on the condition of the engine. For heavy work 2-5 drops a minute, for light work 1-4 drops. Q. What care should be taken in filling a lubricator? A. No foreign matter must be allowed to get in. The opening in the feed nozzle is so small that almost anything would clog it. Q. How large is the opening? A. It is 3-32 of an inch. Q. How is the feed nozzle cleared of clogging matter? A. By shutting off the live steam connection, opening the blow-off and then opening the feed valve to allow the back pressure to pass through the opening. THE LUBRICATOR 95 O Q. How is the choke plug cleared of clogging matter? A. In the same way. The back pressure will force the matter into the feed glass. Q. How large is the opening in the choke plug? A. It is 3-64 of an inch. Q. How can it be decided whether this opening is of the right size? A. Start the engine. Then regulate the oil feed in the glass, counting the number of drops in one minute. Then shut the throttle of the engine and notice quickly whether the number of drops changes. The number will not change if the opening is of the proper size. Q. Is it harmful to use more oil than needed? A. Yes. It clogs up the exhaust pipe of the engine, decreasing its opening. The increase in pressure necessary for exhausting through a clogged exhaust pipe means larger coal consump- tion. Besides, it is a waste of oil. Q. Is it well to feed both valve-oil and engine- oil through a lubricator? . A. No. The mixing impairs the lubricating properties of the oils. Only valve-oil should be used for engine cylinders. THE ENGINE THE COMMON SLIDE VALVE DESCRIPTION. When the piston is at either end of the cylinder, the steam port at that end is open a fraction of an inch (lead) ; the steam enters and starts the piston on its travel, the port opening wide and admitting the steam freely. The valve travels in the opposite direction. When the piston has traveled ^ or so of its stroke (according to the lap on the valve) the slide closes the steam port, so that during the remainder of the stroke no more steam enters on that end of the cylinder. The steam present expands, therefore, as long as the piston keeps moving in the same direction. At the moment when the piston reaches the other end of the cylinder, the steam port there opens 96 THE ENGINE 97 slightly (lead), the entering steam pushes the piston back and the expanded steam on the other end of the piston escapes through the exhaust cavity of the valve, which at that moment con- nects the steam port with the exhaust port, and disconnects them again when only enough steam is left to serve as a compression at the point from which we started. The operation is the same at both ends of the cylinder. Q. How would you proceed to set a common slide valve? A. See that valve covers both steam ports equally, the crank pin at dead center, heavy side of eccentric up or at right angle with the crank pin, rocker arm plumb, at center of 'travel, and all connections close fit ; move the eccentric around on the shaft in direction engine is to run, until the valve has proper lead, say 1-16 of an inch, then tighten eccentric with set screws, turn crank pin to opposite dead center and see how the lead is at the opposite port. If equal the valve is set; if not, divide the difference by adjusting the length of the valve rod and readjusting the eccentric. Q. Is the common slide much used? A. Yes, in the cheaper forms of steam-engines, compressed-air engines, in some air-compressors, and in seme compressed-air ice machines. Q. How is the length of the valve stem and of the eccentric rod found? 98 THE ENGINE 99 t of Common Slide PPOSITE PAGE RRESPONDING PARTS Engine Showing Over or Eccentric Straps. " Rod. 4 Bushing. Valve Cross Head. " " " . Guide' Valve Stem. ~ J3 -d 3 . '3 . * s i o H a =g^ 5 ^ tiUfiS 3>fcbo *gW^^ ^liri!.?ili| w IIS sSo6^ ^ ^u^ 35'C&- -2.2 .o lli-'|Blfl|lll raiis ^M5yO- '5^'a s .2 ^c^o www- &c* J2 O O 5Oj>odOSO < M*00'^ ^^ ^oJviSifrJno^XSr, f ift ^ t^ CO OS O ^ (N 00 *' ift D 1> 00* O> O CD z = II <~0 - X *=* 0) OF NUMBERS AND ( rass. d - JdW qj PH J^ W j c *j ^ A *w C nfl a ca o re n a t= 0) = i M U - ^ S'^ ^ O ^ UO MPn "S3 _, .^a ^g jj ^ O.D^ ft tg^ JcO ^jOJ.5 ^fh*-h Ci.Pfl |ua 89 W a "g-o a P ts P c a a a a r^ RIGHT HAND ENGINE \J f ,_., LEFT HAND ENGINE _/ x t -V 3C 2 1 1 i : _^^~^ P f UJ S!HAFT LINE also the clearance between the piston and cylinder head when engine is at either dead center? A. By first finding the striking points, pushing the piston to one end of cylinder, then to the other, marking the crosshead and guide. After this is done find the full stroke of engine by measuring from center of shaft to center of crank pin. The distance found is one-half of stroke. The difference between full stroke and the tw# LINING, LEVELING AND SQUARING 123 striking points is full clearance for both ends. After this is known move the crosshead (with piston attached) back from striking point one-half of full clearance, which will give an equal clearance for both ends, viz. : Distance between striking points is 17% inches, stroke of engine 16 inches, full clearance i% inches; the half will be 3^ inch clearance at each end of cylinder. Then place the crank pin on same dead center at which the crosshead is placed and measure the length of rod with a tram from center of crank pin to center of crosshead (wrist) pin. Q. How are the guides put in line? A. For level, lay a straight edge across the two guides and caliper between it and the center line the whole length of the guides. For proper alignment across, caliper between the guide edges and the center line the whole length. Q. What do you do, after the guides are properly lined? A. Remove the line. Place the piston in the cylinder and place the crosshead on the piston, keying it on, or screwing it on as the case may be. Then line the piston rod by the guides for level and sideways at both ends of guides. Q. What do you do when the cylinder is worn so that the piston center is out of line. A. Put shims of tin under the spider between the lugs and bull ring, until the piston center is 124 AUTOMATIC SHAFT GOVERNOR central, then adjust the packing rings by the setting out or tension springs. Q. How do you line the crank pin with cylinder? A. Place the connecting rod on the crank pin, and key up the brasses until they hug the crank pin snugly. Then move the crank pin to one of the dead points, and measure with inside calipers how far the side of the brasses on the opposite end of the rod is from the guide. Then move the crank to the other dead center and measure the distance on the other end of the guide. If these two distances are the same, the crank pin is per- fectly in line. AUTOMATIC SHAFT GOVERNOR FOR SIDE CRANK ENGINE DESCRIPTION: In following cut, A indicates the hole in the tripod (a seat or instrument with three feet or arms) B, through which the engine shaft passes. The eccentric C is hung to the long arm of the tripod B by a stud and secured by a screw with washer. The hole through the eccentric is much larger than the shaft, which permits the center of the eccentric to shift across the shaft, thus varying its throw. The eccentric is supported and guided by a gibbed rebate fitting over a project- ing lip on the tripod. The dead wheel D is fitted loosely on the hub of the tripod so that it may FOR SIDE CRANK ENGINE 125 remain stationary while the tripod turns within it. The weights E, E are pivoted to the dead wheel by pins, fastened with set screws, and are con- nected with studs to the short arms of the tripod by the weight links F, F. The springs G, G are pivoted to the weights by their rods, and rest upon lugs on the arms of the dead wheel. They are precisely alike, acting together as one. . The weights and weight links, as well as the springs, are duplicated only to secure more perfect balance of the governor. The eccentric link H connects the eccentric with the rim of the dead wheel by pins, which are made tapering to provide means for taking up the wear. O, O, O, O, O represent oil holes in dead wheel. 126 AUTOMATIC SHAFT GOVERNOR To SET THE VALVE: The governor should set on the shaft so that the center of the long arm of the tripod, to which the eccentric arm is attached, is on the other side of the main shaft, directly opposite the crank pin, and keyed in that position. The steam valve that the governor controls should be adjusted to uncover the ports an equal distance on each end and should be set (while the weights are blocked out) as close to the rim of the dead wheel as the set-screw in the outer side of one of the weights will allow them to go. Place the engine crank pin on the inner dead center and allow the valve to just cover the steam port at the outer end of the cylinder ; that is, the outer end (edge) of the valve being line and line with the outside edge of the outer port. Turn the crank pin (or engine) in the direction it is to run (over or under) to the outer center, and the inner end of the valve should correspond in like manner with the outside edge of the inner port. If it does not, equalize the difference by the nuts on the valve rod. Roll the engine to the inner center again to be certain that the adjustment is right, and when this is accomplished the valve is correctly set. The governor should be so placed on the shaft that the eccentric is exactly in line with the valve crosshead pin and does not touch the side of the main shaft bearing. FOR SIDE CRANK ENGINE 127 MANAGEMENT AND CARE: All movements from the steam valve to the governor parts should be free, smooth, and without lost motion. To have the governor in order keep it clean and all pins and bearings well oiled. The cut shows five oil holes through the rim of the dead wheel, marked O. There are also two in the hub. These are closed with plugs which are removed when oiling. Use good oil and oil frequently. Should the governor work irregularly or fail to control the engine the cause will usually be found in some dry joint or place that binds. When there is a set screw on the inner side of the weight it is to limit the travel toward the hub, and should never be removed or disturbed. The . governor key should fit closely on the sides of the key way, but never on the top and bottom, to avoid springing the tripod hub and causing the dead wheel to bind. If governor should become gummed from bad oil, take out springs, first carefully measuring their length in position. This precaution is necessary so they may be replaced exactly in the same position. Take out one at a time to avoid disarrangement. Clean with kerosene, etc. Before tension is again put on the springs, move the dead wheel back and forth to see that there is no bind- ing in any of the working parts. To CHANGE SPEED by changing the tension of 128 AUTOMATIC SHAFT GOVERNOR the springs: To run faster, tighten; to run slower, loosen. Or move the weights. Never tighten the springs down so that their spirals touch each other. Never tighten or loosen the spring more than one inch beyond its set tension. If greater speed be desired than can be obtained from the springs and weights furnished with the governor, others should be ordered from engine builder. Be sure to mention speed desired. REVERSING governor and engine to run over or under: Remove the set-screw from the outer side of the weight. Disconnect the eccentric link H from the eccentric and from the rim of the dead wheel by removing the pins from the lugs b and d. Take hold of the rim of the dead wheel with a monkey-wrench and pull it around on the shaft . as far as it will go, in the direction the engine is to run, and again connect the eccentric with the rim of the dead wheel by inserting the eccentric link H into the other pair of lugs marked b. and d, using care in replacing the pins not to drive them so tight as to bind. Replace the set-screw in the outer side of the weight in exactly the same position as before. This reverses the governor and the engine is ready for service. HOW TO KNOW STEEL FROM IRON A drop of aqua fortis turns steel brown, and cast-iron black, while (wrought) iron is not affected. AUTOMATIC GOVERNOR FOR SELF- CONTAINED ENGINES SUCH AS DOUBLE CRANK DISC AND TWO PULLEY WHEELS, ONE EACH SIDE OF CRANK PIN DESCRIPTION: In the following cut, B is the eccentric, hung on the hub M of the band wheel by a pin, which is made tapering to provide means for taking up the wear. The hole through the eccentric is much larger than the shaft and per- mits the center of the eccentric to shift across the shaft, thus varying its throw. Piece C is the eccentric arm, which transmits the shift motion to the eccentric through the steel bands, or ribbons, which are fastened by clamps to the eccentric arms and by screws to the eccentric. The arm is securely fastened to a rocker shaft, which passes through one of the arms of the band wheel, and to which the spring crossheads D, D are also attached. The spring crossheads carry the weight bars I, I, weights G, G, and the spring rods J, J. The springs K, K are held by the spring rods and are precisely alike, acting together as one. The weights, as well as the springs, are duplicated only to secure more perfect balance of the governor. To SET THE VALVE: Governor should set on 129 130 AUTOMATIC GOVERNOR the shaft so that the center of the rocker shaft, to which the eccentric arm C is attached, is on the other side of the main shaft, directly opposite the crank pin, and keyed in that position. The steam valve controlled by the governor should be adjusted to uncover the ports an equal distance on each end and should be set while the weights are out as far as the stops will allow them to go. Place the engine on the "inner" center and allow the valve to just cover the steam port at the outer end of the cylinder so the outer end of the valve will be line and line with the outside edge FOR SELF-CONTAINED ENGINES 131 of the outer port. Turn the crank pin in the direc- tion it is to run to the "outer" center, and the inner end of the valve should correspond in like manner with the outside edge of the'inner port. If it does not, equalize the difference by the nuts on the valve rod. Roll the engine forward again to the "inner" center to be sure that the adjustment is right, and when this is accomplished the valve is set. MANAGEMENT AND CARE should be the same as for side crank engine governor. To CHANGE SPEED: Same as for side crank engine governor. The speed may also be changed by altering the positions of the weights on the bars. Sliding them toward the spring crossheads increases the speed, and in the opposite direction decreases it. Should a greater speed be desired than can be obtained from the springs and weights furnished with the governor, see instructions for speed changing on side crank engine governor. To REVERSE governor for running over or under: Remove the eccentric strap, then take out the key from the governor band wheel, slip the wheel out to the end of the shaft, remove the taper pin on which the eccentric swings, move the eccentric to the other hole in the hub, replace the taper pin in the eccentric, using care that it is not screwed in so tight as to bind, change the weight bars to the 132 AUTOMATIC GOVERNOR other ends of the spring crossheads, reversing their positions, loosen the nuts that hold the tension on the springs, being careful to measure the springs before removing the nuts, so as to replace them in exactly the same positions. After the springs are free from tension take out the small split pins that hold the ends of the spring rods in their places, remove both spring rods and turn them end for end, then replace the split pins. Before tension is again put on the springs, move the weight bars back and forth to see that there is no binding in any of the working parts. Also see that the eccentric travels its entire throw across the shaft, and that both of the lips strike the top plate that is bolted to the face of the wheel hub, back of the eccentric. Should the eccentric strike on one point and not on the other, loosen the clamps that hold the steel bands, or ribbons, move the eccentric just far enough to enable both points to touch, then refasten the clamps. Should the set-screws under the spring crosshead strike before the eccentric touches the stop, adjust them accordingly. Place the required tension on the springs, slip the wheel back to its place, drive in the key, replace the eccentric strap and the engine is ready to start. BALANCED SLIDE VALVE Q._What do the following cuts represent? A. The balanced slide valve of an automatic self-contained engine, protected from steam pressure by a hood. Q._ What does the first cut represent? A. It is the valve and seat with hood detached. Q.What does the second cut represent? A. A section through the valve and hood on the line A B, shown in the next cut. 133 134 QUESTIONS AND ANSWERS Q. What does the third cut represent? A. It is a perspective view of the valve and hood complete. B Q. How is the balancing of valve accomplished? A. The exposed ends of valves, being of equal area, balance each other. Q. How is the pressure counterbalanced? A. By recesses of equal area with the ports under the hood and over the valve. Q. What friction is there to overcome? A. The only friction is the weight of a very light valve. Q. How is a worn valve refitted? A. By scraping. Q. What is provided for the case of excessive pressure or water in the cylinder? A. The hood is set loose on the seat, and readily yields. Q. What guides the hood to its correct seat? A. The springs and studs. Q. What is the port action,, of the valve? A. It is that of any plain slide valve. Q. What quickens the opening and closing ot the ports? CORLISS ENGINE 135 A. The recesses in the hood over the valve. Q. What advantage has this valve? A. All the advantages of a perfectly balanced slide valve. CORLISS ENGINE The Corliss valve gear is a detachable gear. There are four valves two steam valves and two exhaust valves all connected to one center wrist plate. The wrist plate pin is connected to rocker arm by reach rod, and from there to eccentric by another rod. 1. Fly ball gov. 2. Gag pot. 3. Gov. stand. 3A. Bevel gear case. 4.4. Gov. rods. 5.5. Steam valves. 6,6. Exhaust valves. 7. Wrist and rocker con- necting rod. , 8. Dash pots and rods. 9. Eccentric rod. 10. Governor belt and pulleys. 11. Eccentric and strap. 12. Rocker arm. 13. Wrist plate. 14. Cylinder Bracket. 15. 15. Steam valve (adjust- ing) rods. 16. 16. Exhaust valve rods. TYPICAL CORLISS VALVE GEAR To SET VALVES, tal^e off the back caps or back heads of all four valve chambers. Guide lines will be found on the ends of the valves and chambers, as follows: On the steam valves, lines 136 CORLISS ENGINE indicating the working edges of the steam ports; on the exhaust valves and ports, guide lines for CORLISS VALVE OPENING OUT the purpose of setting them. As stated before, the wrist plate is centrally located between the four valve chambers on the valve gear side of the STEAM , WAY. cylinder. A well-defined line will be found on the bracket which is bolted to the cylinder, and CORLISS ENGINE 137 three lines on the hub of wrist plate, which, when they correspond with the single line on the bracket, show central position of the wrist plate, and the extremes of its throw or travel both ways. To ADJUST THE VALVC first unhook the reach or carrier rod connecting the wrist plate with rocker arm, then hold the wrist plate in its central position. The connecting rods between steam and exhaust valves and wrist plate are made with right' and left hand screw threads on their opposite ends, and provided with jamb nuts, so that by slacking the jamb nuts and turning the rods they can be lengthened or shortened as desired. By means of this adjustment set the steam valves so that they will have % inch lap for 10 inch diameter of 138 CORLISS ENGINE cylinder, and y% inch lap for 32 inch diameter of cylinder, and for intermediate diameters in pro- portion. FOR THE EXHAUST, set them with 1-16 inch lap for 10 inch bore, and y& inch lap for 32 inch bore on non-condensing engines, and nearly double this amount on condensing engines for good results. Lap on the steam and exhaust valves will be CORLISS KNOCK-OFF CAM D 1 S E N C AC I N G ,NQ STUD CUT OFF GEAR ,TCH SPRING shown by the lines on the valves being nearer the center of the cylinder than the lines on the valve chambers. Having made this adjustment of valves, the rods connecting the steam valve arm with the dash pot CORLISS ENGINE 139 should be adjusted by turning the wrist plate to its extremes of travel and adjusting the rod of each valve so that when it is down as far as it will go the square steel block or stud die on the valve arm will just clear the latch die on the'latch hook. If the rod is left too long the steam valve stem would likely be bent or broken ; if too short, the hook will not engage, and, consequently, the valve will not open. Having adjusted the valves as stated, hook the engine in, and, with the eccentric loose on shaft, turn it over and adjust the eccentric rod so that the wrist plate will have the correct extremes of travel, as marked on the wrist plate hub. If marks on wrist plate do not agree at each full throw with bracket marks, disconnect strap from eccentric rod and adjust the screw on stub end, as required, until marks do agree, both forward and backward; then place the crank on dead, center and turn the eccentric in direction engine is to run, until an opening of 1-32 or 1-16 is shown at steam valve, then throw crank pin on other (lead center to secure the desired lead in opposite motion. If lead is not the same, adjust by lengthening or shortening the connecting rods between the eccentric and wrist plate as the case may be. To ADJUST THE RODS connecting the cut-off or tripping cams with the governor, have the gov- 140 CORLISS ENGINE ernor at rest and the wrist plate at one extreme of its travel. Then adjust the rod connecting with the cut-off cam on the opposite steam valve, CORLISS VACUUM ENGINE DASH POT. LEATHER 'ACKiNQ so that the cam will clear the steel or latch die on the tail of the hook about 1-32 of an inch. Turn the wrist plate to the opposite extreme of travel and adjust the cams for the other valves in the same manner. CORLISS ENGINE 14! To EQUALIZE THE CUT-OFF and test its correct- ness, hook the engine in and block the governor up about halfway in the slot, which will bring it to its average position when running. Then turn the disc slowly in the direction which it is to run, and note the distance the crosshead has traveled from its extreme position at dead center when the cut-off cam trips or detaches the steam valve. Continue to turn the disc beyond the other dead center and note the distance of crosshead' s extreme travel when valve drops. If distance is the same the cut-off is equal ; if not, adjust either one or the other of the rods until the distance is the same. Q. Will the cut-off mechanism unhook when governor is down? A. No ; it keeps the valve hooked up full stroke. Q. Will the latch die hook on stud die of valve when dash pot rod is too short? A. No. Q. How long should the rod be? A. It should be long enough so when the plunger is at the bottom of dash pot the latch would hook over the latch stud (steel block) and the stud lie clear of the latch (hook). Q. What prevents the dash pot rod from break- ing or bending? 142 QUESTIONS AND ANSWERS A. The cushion of the plunger on air in the dash pot. Q. Have the plungers any packing to make them close fit? A. Yes; some have leather packing, others have piston rings. Q, How is the air regulated in the dash pot? A. By means of an air valve in the air opening by turning a screw in the escape hole. Q. What keeps the governor in regulation so it will not allow the engine to run away or be over- sensitive? A. A small oil reservoir on engine frame below governor, known as the gag pot. Q. What kind of oil is generally used in the gag pot? A. Kerosene oil. Q. How would you give the governor more freedom of motion? A. By removing one or more of the small screws in the piston plunger of gag pot. Q. How would you warm the cylinder of a Corliss engine before starting? A. By first blowing all the condensed water out of the steam pipe by means of the drip valve provided on the steam valve elbow or globe ; then open the steam valve a little to allow the valves and cylinder to become warm. Unhook rocker reach rod, and work valves with wrist plate by CORLISS ENGINE 143 nand with lever. The cylinder soon becomes warm and all water is expelled into the exhaust pipe, the exhaust drain cock having been left open to allow the condensed water to escape. Q. Would you then start the engine up lively? A. No. Let engine move slowly until satisfied all is right, then open throttle gradually until wide open. Q. Suppose the governor belt connection broke, would the engine run away? A. No; the trips or safeties would slip in between the latches and dies and prevent valves from opening or latches hooking on to latch dies. Q. Suppose the governor of a Corliss engine would allow the speed to fluctuate from one extreme to the other, where would you look for the trouble? A. The oil gag pot in connection with the governor will very probably be found to be empty, on inspection. Q. In the majority of cases where the governor gives trouble, what would you lay it to? A. Not getting proper oiling, being dirty, oil holes plugged and not good enough connection to the main shaft. Q. About how many oil holes has a Corliss governor, all told? A. From 10 to 13. LINK MOTION AND VALVE SETTING In the position of the link shown in the cut, the fralve has its shortest travel. The further removed the link is from the position shown, either upward or down, the longer is the valve's travel. V. Valve Stem. B. Link Block. L. Link. Ki 2. Link Blades. R. Radius. S. Shaft. a. Heaviest side of back- ward over eccentric. b. Heaviest side of forward under eccentric FOR VALVE SETTING in a stationary engine, 12x24 inches, place the valve central over the ports, the rocker arm plumb, the heavy side of the eccentric plumb over the shaft, and the crank pin at dead center. See that the eccentric blades are con- nected with the link and are in full gear, forward or backward. This will make the extreme travel .of the valve equal to the throw of the eccentrics. If a lead of 1-16 of an inch is desired, move the eccentric in the direction in which you want the engine to run, until your valve has the desired LINK MOTION AND VALVE SETTING 145 lead. Then fasten the eccentric, throw the crank pin on the opposite dead center and if the lead on the opposite port is then the same, the valve is set. If it is not, make adjustments. The above covers one motion. For tfce opposite motion reverse the link and go through the same operation for the other eccentric. For convenience an engineer should tram his valve-stem, so as to know the opening point either way without removing the valve chest cover. Q. Why is a link placed on an engine? A. Because it is the most convenient means for reversing an engine. It is almost a necessity where a valve has much steam lap, or where quick reversing is required. Q. Which way does the engine run when the link is fully down on the block? A. It would run under, toward the cylinder. Q. How would you reverse the engine in that case? A. By pushing it full up. Q. How can a single-eccentric engine be made to be easily reversible? A. By substituting a rocker arm with another rocker pin above the center of rock shaft. (See page 101.) 146 AREA OF STEAMPORT AREA OF STEAMPORT. The area of the steamport may be justly consid ered as the basis from which all other dimensions are derived in conformity with known laws. It makes a difference, whether the port is simply to admit the steam to the cylinder, or whether it is also to serve as exit or exhaust. In the latter case a small quantity of steam forces its way out with a constantly diminishing pressure and, therefore, the exhaust port must be larger than the steam port. Where the same port serves for both purposes, it must have the proper area for the exhaust, and is opened only partly for the admission of steam, which enters from the boiler with a practically constant velocity. NUMBER OF CRANK REVOLUTIONS FOR GIVEN STROKE AND PISTON SPEED. PISTON SPEED (feet per minute.) STROKE. 200 210 220 225 230 240 250 270 300 350 1 ft. 6 in. 67 70 73 75 76 80 83 90 100 116 1 " 8 " 60 63 66 68 70 72 75 81 90 105 1 " 10 " 55 57 60 61 63 66 68 74 82 96 2 " 6 " 40 42 44 45 46 48 50 54 60 70 3 " " 33 35 36 37 38 40 42 45 50 58 4 " " 25 26 27 28 29 30 31 34 38 44 5 " " 20 21 22 22 23 24 25 27 30 35 HORSE POWER Coal furnishes heat; heat converts water into steam; the steam drives the piston; the piston motion is converted into rotary motion by the con- necting rod and crank pin. The rotary motion is utilized for work. The amount of work that an engine can do is expressed in "horse-powers," the unit being determined as follows: The usual traveling gait of a horse hitched to a light sulky is about 5 miles an hour, or 440 feet per minute. If a spring scale be attached to the singletree we may note the amount of power the horse is exerting. Assuming this to be 75 Ibs. and the speed 440 feet, multiplied by 75 Ibs. equals 33,000 foot Ibs., which represents a horse-power. In applying this to a steam engine we first find the area of the face of piston head, multiply the answer by piston speed in feet per minute, and divide by 33,000; the answer will be the indicated horse -power. For the actual or effectual horse- power take 2-3 of the quotient. Example: Engine cylinder 12x24, speed 100 revolutions per minute, steam 80 Ibs., area of piston 113 square inches. Multiply 113 by 80, 14? 148 QUESTIONS AND ANSWERS equals 9,040 Ibs. pressure on piston face, by 400 feet piston travel per minute, equals 3,616,000, divided by 33,000 equals 109 N. H. P. full opening of valve, deduct 1-3 for cut-off, equals 72 2-3 actual h. p. For short cut-off one-half. The reduction is made for average pressure, condensa- tion, friction, etc. , and will be found quite correct in practice. Quick rules, such as are generally given for find- ing the H. P. of cylinders, waterfalls, water- wheels, etc., are useless. One "watt" is the 1-746 part of one horse power. One thousand watts or a "kilowatt" equals one and one-third horse power. The watt is the practical unit of electrical activity or power ; it is the rate of working in a circuit when E. M. F. is one volt and the current one ampere. (See elec- tricity. ) The best engines and boilers develop a horse power per hour by the consumption of 2 Ibs. of coal. But this is better than the average, and 3 Ibs. is more common. Q. How much heating surface is required to develop one horse power? A. It varies with the purpose of the plant. Steam for heating, etc 15 sq. ft. heating surface For plain throttle engine 15 ' For simple Corliss engine 12 ' For compound Corliss condensing. .10 ' Q. How many horse power will a boiler furnish HORSE POWER 149 for a plain slide valve engine, boiler having 1,500 square feet heating surface? A. One hundred H. P. Q. How much for simple Corliss engine, same boiler? A. One hundred and twenty-five H. P. Q. For compound engine? A. One hundred and fifty H. P. Q. Which would you consider the best basis in comparing boilers? A. Their evaporative efficiency. Q. Give consumption of steam per indicated horse power per hour for various engines? A. Plain slide valve engine 60 to 70 Ibs. High speed automatic engine. 30 to 50 " Simple Corliss engine 25 to 35 " Compound Corliss engine 15 to 20 Triple expansion engine 13 to 17 " An engine of the proper size and in good con- dition will yield one H. P. at the lowest consump- tion. Q. How would you determine the proper size or evaporating capacity of a boiler to supply steam for a given purpose? A. It is necessary to consider the number of pounds of dry steam actually required per hour at stated pressure. Q. What is the standard horse power rating for any steam boiler for common slide valve and Corliss engine? A. For plain slide valve engine the evaporation ISO QUESTIONS AND ANSWERS is 62*6 Ibs,, or one cubic foot of water per hour per horse power, and for the Corliss 31 X Ibs., or J^ cubic foot of water per hour per horse power. Q. How would you figure the horse power for a steam boiler of any size, if you wish to run a so- horse power engine for i hour, carrying 60 Ibs. of steam pressure? A. First multiply the pressure to be carried by time in minutes, 60, and divide by 30, the amount of water in pounds per horse power evaporated per hour. Q. How would you proceed to find the horse power of a compound condensing engine? A. The H. P. of a compound condensing, engine, of necessity, cannot amount to any more than the aggregate of the two powers produced in the two cylinders. Therefore the power developed in each cylinder must be calculated separately and the two results added. (See indicator, p. 154.) Q What is good working vacuum for a steam engine? A. From 22 inches upward, when the barometer stands at 30 inches. Q. Suppose the M. E. P. upon the piston is 40 Ibs. per sq. in., and the vacuum gauge stands at 22 inches (barometer at 30 in.), what would be the total on one side of the piston? A. 40 Ibs. per sq. inch, the M. E. P. Q. How is the horse power found of a non- HORSE POWER 151 condensing compound engine? A. By first finding the average area of both cylinders. This is done by finding the area of the high and the low pressure cylinders separately; then add them both together and divide by two. Q. How is the average mean effective pressure found? A. By finding each cylinder's mean effective pressure, then adding the two together and divid- ing by two. Q. After this is done, how would you proceed to find the gross H. P. ? A. Multiply the average area by the average mean effective pressure (see page 159), then by the piston travel per minute, and divide by 33,000. Answer will be H. P. Q. How do you increase the power of an engine. A. By increasing its speed. It is done: First, by increasing the boiler pressure, and, thereby, the M. E. P. on the piston. Second, by increasing the boiler pressure *and decreasing the outside lap of valve so as to cut off late" This method is not advisable. i bird, by increasing the leverage of the main shaft pulley by decreasing its diameter. Fourth, by increasing the speed of line shaft or the diameter of the driver pulley on line shaft, or by decreasing the diameter of pulley on main shaft. 152 QUESTIONS AND ANSWERS Q. Give the rule for finding the horse power of a belt's transmission ; also example? A. Multiply the width of the belt in feet by the number of hundred feet the belt has traveled in one minute. Example : Belt 2 feet wide run- ning 150 feet per minute 2 multiplied by 150 equals 300 h. p. Belting horse power of a belt equals velocity in feet per minute, multiplied by the width. One inch in length of single belt moving at 1,000 feet per minute per i inch width equals i h. p. For double belts of great length over large pulleys allow about 500 feet per minute per i inch of width per horse power. Power should be communicated through the lower running side of a belt, the upper side to carry the slack. The average breaking weight of a belt 3-16x1 inch, single leather, is 530 Ibs. ; three -ply rubber belt, 600 Ibs. The strength of a belt increases directly as to its width. The allowance for safety for rubber belts is ^ and for leather belts 1-16 (breaking weight) in lacing. Q. Can you give a short rule for finding the H. P. of tubular boilers, and are such rules of value? A. They are not. A short rule to find the horse power of a tubular boiler is : Multiply the square of diameter in eet by length and divide by constant .4. For flue boiler multiply diameter of shell in feet by length and divide by .4, or HORSE POWER IS3 multiply area of grate surface in square feet by i^. The answer gives the horse power. Table Giving Horse Power of Boilers of the Usual Sizes. Diameter Shell. Inches. "Srjti ffi Number Tubes. 5 . Ill Diameter Tubes.. Inches Heating Surface. Square feet. Horse Power 60 Ibs. Pressure. 72 72 72 72 18 16 16 15 70 90 112 112 18 16 16 15 4 3V2 3 3 1502 1472 1496 1400 100 98 99 93 60 60 60 00 18 17 16 16 65 65 65 80 18 17 16 16 XXX co co co co 1200 1148 1075 1088 80 76 72 72 54 54 54 54 18 17 16 16 50 50 50 60 18 17 16 16 3/2 3 1 A 3 951 900 795 832 63 60 53 55 CO 00 CO CO 16 16 15 14 40 49 49 49 16 16 15 14 3/2 3 3 3 683 684 642 600 46 46 43 .40 42 42 42 42 15 14 13 12 38 38 38 38 15 14 13 12 3 3 3 3 508 476 441 408 34 32 30 27 42 42 42 II 10 9 45 45 45 II IO 9 2K 2*4 2/2 390 355 320 26 24 22 THE INDICATOR Q. What is an indicator? A. It is an instrument which records the varia- tions of pressure during the length of one stroke. Q. Can you describe the instrument? A. A small cylinder of exactly % sq. inch inside diameter is connected to both ends of the steam cylinder, but steam is admitted from one end at a time only. In the small cylinder moves a piston, whose crosshead works a pair of light levers, the free end of which holds a pencil, which marks its path of motion on a paper clamped on a revolving I drum. Q. How is the stroke I of the instrument's pis ton regulated? A. By a spring of known tension. A set of such springs, each marked with the pressure for which it is intended, accompanies each instru- ment, as follows: For pressure up to 21 Ibs. per sq. inch use 15 Ib. spring. (I li tt 4 38 4. 4' 44 4 2 Q 1 94 1 143 30 50 154 THE INDICATOR 155 Q. What makes the indicator card revolve^ A. A carefully adjusted cord, indirectly con nected to the crosshead of the engine. Q. How do the pencil tracings on the paper convey information? A. For an in tell i- , gent read- ing of the diagram one should compare it with the line the pencil perfect con- Q. How would trace under ditions. would you con- struct such a perfect line? A. Assuming an engine to have a 32" stroke, 60 Ibs. steam (gauge pressure), vacuum 12 Ibs., cutting off at 8", exhaust release 2" from end of stroke, and compression (exhaust closure) 5" from com- pletion of stroke, I should lay off these figures on a "cross-section" sheet. (Fig. i shows the cross-section in the margin only, to give a clearer cut. Only the principal lines are drawn all across. ) Mark off 32 spaces, each to represent i" of stroke, horizontally, calling the starting point at the left o and the end at the right 32. Mark off '56 THE INDICATOR vertically 25 spaces, each to represent 3 Ibs. of pressure. The upper limit of the fifth space (starting from the o point first mentioned) will JNfinD RELEASE LINE NOISSIMOV imssn XUH JLL \ I I, I FIG. I then be atmospheric line (3x5=15), 5 spaces further will be the 15 -Ib. steam pressure line, and so on, the last line representing the 6o-lb. pressure. THE INDICATOR 157 Steam enters in our case during % of the stroke, therefore, we make the "steam line" 8 spaces long on the 60 -Ib. line, starting from the o vertical. At the end of the steam line the supply is cut off, expansion begins and pressure is reduced, first rapidly, then more and more slowly (in an inverse ratio to the volume; at point 1 6 the volume has been doubled and the pressure halved). This gives an evenly curved line down to the intersection of the vertical 30 (2 from end of stroke) with the horizontal indicating 6 Ibs. of pressure (2 spaces above the atmospheric line). At this point (point of release) the release (exhaust) valve should open, and the pressure sink again rapidly down to nothing (atmospheric line) and below, represented by a short, sharp curve between the verticals 30 and 32 and a straight line along the vertical 32, 4 spaces to the exhaust line (release line, or vacuum , line). The engine piston travels then 27 inches in the opposite direction, while the exhaust valve' keeps open (exhaust line) to the "point of compression" where the not exhausted steam begins to be com- pressed until during the last 5 inches of the piston's travel the pressure is gradually brought up to atmospheric pressure. The "compression line" representing this is an upward curve ending at the intersection of the atmospheric line and the '5* QUESTIONS AND ANSWERS zero vertical. At this point steam is admitted, raising the pressure instantly to 60 Ibs., shown on the diagram by a straight line along the vertical zero up to the 6o-lb. horizontal. This completes the diagram. Q. Does the diagram taken on engines deviate much from this model just described? and if so, why? A. There are great deviations, caused by v leaks, wrong lead, late fv valves, light load >v with heavy com- pression, etc. 60 ATMOSPHERE LINE. FIG. 2 (The broken lines in the cut give examples of diagrams indicating imperfections in the cylinder or valves, while the outline is a nearly perfect specimen of diagram above atmospheric line ) Q. What is the purpose of an indicator card? A. It serves as a guide in setting the valves, as a help (in connection with a feed-water test for steam -consumption) in determining the economy with which an. engine works, and especially for finding the MEAN EFFECTIVE PRESSURE of an engine. Q. How do you figure the M. E. P. from an indicator card? THE INDICATOR 159 A. Divide the extreme length of the diagram in 10 equal spaces vertically by 9 dotted lines (Fig. 2), and divide each space into vertical halves by full lines. The length of these 10 vertical lines (ordinates) inside the diagram indicates the M. E. P. for each space. Add these 10 lengths together, and divide their sum in inches by 10. Multiply the quotient by the scale of the spring used in the indicator, and the product will be the M. E. P. throughout the stroke. Many engineers mark the ordinates only, in Fig. 3 the dotted lines marked O. The broken line G shows a lazy valve opening. Notice that the ordi- nates are measured from the atmospheric line, not from the vacuum . ^ line. f FIG. 3 Q. Why do you multiply by the scale of the spring? A. Because one inch of height in the diagram represents the amount of pressure indicated on the spring, two inches the double, etc. Q. Is there a quick way of figuring the M. E. P.? i6o QUESTIONS AND ANSWERS A. Yes. Make a rough sketch of a diagram and divide the length of it into 10 equal spaces; allow for the first four spaces (to cut-off) the full pressure as per gauge, say 100 Ibs. each, divide their sum, 400, by 5, the number of the next space, 100 100 100 100 80 ORD1NATES 66.4 57.1 allowing the quotient, 80, for the fifth space; then divide the same sum, 400, by 6 and allow this quotient for the sixth space, and so on, to the last space. Add all these figures together, and divide by 10 and proceed as above. (See cut.) Q. Is this a very accurate way? A. No, but it will answer for a rough figuring under ordinary circumstances. Q. How is the PANTOGRAPH used in connection with the indicator? A. One end of it (C) is. fixed to the crosshead, the other (D) is made stationary by a fixed stake THE INDICATOR 161 placed in line with the crosshead socket at mid- stroke. A peg (F) is placed in one of the holes on the adjustable strip G, so as to be on the line between the two points C and D, and at such distance from C that the cord connecting it with the indicator drum will be parallel with the guides. The peg will not move as fast as the piston head, but it moves at exactfy the same ratio, giving an accurate diagram. (See cuta) 162 QUESTIONS AND ANSWERS INDICATOR EXAMINATION Q. Can any one use the indicator intelligently? A. No, only one who has had experience with engines, who possesses power of observation, and who is familiar with measurements and calcula- tions. Q. What length can a diagram be? A. As long as the circumference of the drum. Q. What do the length and the height of the diagram represent? A. The length represents the length of the stroke. The diagram is one inch high for every 15 or 20, etc., Ibs. pressure, according to the spring scale. Q. If the 30 Ibs. spring is used and the diagram is 2^ inches high, what does this indicate? A. It would indicate that the greatest pressure during the stroke (steam line) was 2 l /% times 30 Ibs. Q. Would the 15 Ibs. spring answer in this case? A. No. The pressure would be 63^ Ibs., while the 1 5 Ibs. spring is not able to act under a pressure of more than 21 Ibs. Q. Explain the steam line? A. It runs. from the place of admission to begin- ning of cut-off. Q. Where is the exhaust liner THE INDICATOR 163 A. It begins at the point of exhaust or release. Q. Which is the expansion line? A. It is the curved line between the cut-off and the point of exhaust. Q. What is the vacuum line? A. A straight line, laid out by measuring down from the atmospheric line a distance equal to pres- sure of atmosphere, as shown by the barometer. Q. Does this line indicate a real vacuum? A. No, it indicates a reduction of the atmos- pheric pressure. Q. What points does an indicator card show? A. The high and low pressure, cut-off and lead, exhaust point and atmospheric point. Q. How does the steam line show on a card when steam is wire drawn? A. It falls as the piston advances. Q. What is meant by wire di awing? A. It is reducing the pressure by choking. Q. When should the atmospheric line be taken on the card by indicator? A. Immediately after the card has been taken. Q._Why? A. Because the spring in cooling will change the position of the pencil point. Q. How is the atmospheric line drawn? A. By holding the pencil lightly against the card, taking care not to get it out of its true posi- tion, and then revolving the drum with the hand. 164 QUESTIONS AND ANSWERS Q. What is an ordinate? A. It is the length of a line showing the height of a point above a level or line. Q. How many ordinates are marked on a diagram? A. You may mark any number. The larger the number the more accurate will be the result. Ten is the number usually taken for ordinary purposes. Q. Where do you place the ordinates? A. In the middle of the ten equal spaces into which I divide the diagram. Q. What does each single ordinate show? A. It indicates the mean effective pressure during the time in which the pencil passes across the space, in the middle of which the ordinate lies. Q. What is meant by "mean"? A. If the pressure was 60 Ibs. on entering a space and ran down evenly to 55 Ibs. on leaving the space, 57^ Ibs. would be the half-way between the two, or the "mean,'* which may be safely called the pressure all across the space. Q. After the card has been properly laid out, what should be done? A. Measure the combined length of all the ordinates, divide their sum by the number of ordinates, and multiply the quotient by the figure on the spring scale in use. THE INDICATOR 165 Q. How do you "add" the ordinates? A. By laying them off in one continuous straight line on a cardboard, then measuring their total length in inches. Q. Suppose the total length of the ten ordinates were 8 inches and the spring used was a 50 scale, how would you proceed? A. The eight inches and 10 ordinates equals eight-tenths, or . 8, multiplied by 50 scale equals 40 pound mean effective pressure in the cylinder of engine. Q. Does the indicator allow for all friction, etc.? A. Yes. Q. How are the ordinates measured, when the expansion line drops below the atmospheric line? A. The sum of the lengths below the atmos- pheric line is subtracted from the sum of those above. Otherwise the calculation is the same. Q. What does the scale number on an indicator card mean? t A. It indicates what pressure will lift the pencil point one inch. (See cut, page 156.) Q. What is meant by mean effective pressure? A. It means the average pressure of steam in the cylinder during one stroke, minus the back pressure. THE COMPRESSED NON-VIBRATING AIR OR STEAM ENGINE CAN BE USED TO PROPEL HORSELESS CARRIAGES, YACHTS, MOTOR WAGONS, ETC. The growing demand for a small engine, more particularly for traction and marine work, simple in construction and operation, economical, non- vibrating, light weight, yet strong and compact, and reversible by simply shifting the valves, has resulted in the perfection of an engine far in advance of anything heretofore made for the purpose. One of the more essential requirements for the above purposes is : Sufficient strength to start a given load from a standstill, \vhich must be greater than the force necessary to overcome ordinary obstacles when in motion. The "compressed air engine" develops extreme power for its weight and the space it occupies. It also dispenses with all vibration, which heretofore has been the great trouble in locomotion of horse- less carriages, etc. DESCRIPTION: The cylinder, as seen in follow- ing cut, has 2 ports, 3 pistons, i stuffing box, i crosshead and slide for same and connecting rods to a double crank arm shaft. No cylinder heads. This construction makes no difference in the 166 THE COMPRESSED NON-VIBRATING AIR OR STEAM ENGINE A A, Bedplate; B B, Double Cranks and Shafts; C C, Cylinder; D D, 3 pistons; E E, Center Piston Rod and Connecting Rod; F Fi F2 FS, Four Connecting Rods; I, Eccentric; J, Eccentric Rod; K, Engine Tube Frame. The steam chest does not show, being behind the cylinder. 167 l68 NON-VIBRATING AIR OR STEAM ENGINE action, but it does in the results obtained. The two outside pistons are fastened together so as to move in the same direction, and are connected to one side of the crank shaft. The center piston, acting between these two, is connected centrally between two cranks and always moves in the opposite direction from the two outside pistons. It travels between the two ports, first meeting the lower piston at lower port, then reversing and meeting the upper piston at the upper port, the two outside pistons always traveling outside of the two ports, thus answering the purpose of the two cylinder heads, which are simply converted into movable heads or pistons. In a starting pull, the same charge of steam or air acting on both pistons at the same time gives twice the power at starting and a double expansion for the balance of the stroke. The ports and exhaust are the same in construction and opera- tion as standard makes of engines on the market, . MENDING A BAND SAW Bevel both ends of the saw the length of two teeth. Fasten the saw in brazing - clamps, with the backs against the shoulders. Wet the joint with solder fluid (or with a lump of borax rubbed into a creamy paste with a teaspoonful of water on a slate). Put a piece of silver solder of the shape of joint in the joint, and clamp with tongs heated to a light red heat. As soon as the solder fuses, blacken the tongs with water (taking care not to get any water on the saw), release tongs and smooth the joint by hammering and draw-filing. MISCELLANEOUS QUESTIONS AND ANSWERS ON THE ENGINE TRAVEL OF CRANK PIN AND CROSSHEAD Q. Do crank pin and crosshead travel at an even gait during one revolution of the disc? A. They do not. The diagram shows (i) that the crosshead travels only a very short distance while the crank pin moves 15 degrees (}4 of 90, a quarter revolution) upward from the dead center ; (2) that the distance traveled by the crosslaead increases in each of the 5 following spaces, each of them corresponding to the crank pin's travel of 1 5 degrees (6xi 5 = 90) ; (3) that the crosshead has traveled more than one-half of its stroke (the half- way point is indicated by a dotted line in the cut), when the crank pin has traveled 90, or % revolu- tion. 169 170 MISCELLANEOUS QUESTIONS AND ANSWERS 17] d PI a 4-> n CJ 6 1 o "o t mparing indicates 8 1 to 1 CD 111 CD t/2 O O S 1 ., besides the level. n3 a CD S 2 c g }-l bo *c 1^5. 7S 1 "5 S Cj 1 a "rt .S ^ 'o .S ^ ts 4> Q I 1 bJD 8 CJ i g *-M O CD P s 1 1 1 _g si EH 2 o .S 2 ^ | o i O CJ " s ^ ^ g i 1 1 M J o S ^ ^ .S ^ o 00^ g *s i ed p ffi 1-i * CD B ^H CD . fX, ^_> a; ^ H to CD s .S 2 <1 5 4j C fl-.l* ^ G 2 Q 1 CD ^H CJ E .d the distance th of stroke in ^ rcumference o i highest eleva CD .g O t g CD .S ) passes below :d the central ] ess than half "c P Efl 8 G rterit moved he second quai ;_ "~" ^0 'S ^H ^3 CD i s rt 1 S-> 1 cr .H c "TV "c ^C IH r^ "S 4 to 'd 4>J _C 'c PH tie difference is p travels arounc 3 M ided semicircle, PQ P c 1 lent of highest el he semicircle ha the crosshead i ^ 4J -4- t* >rH CD "S 5 I'l r ^ aj CD C +-> -M CD o b/ 1 ^C ' C HH CO <~ -(- O 5 'rt P "cr "c 4J .S Vr j_i *"* r^ "- 1 .S T! CJ IM rQ "C^ "o ff CD T^H 4_ S M CD" o tc Er CD r5 3 8 C 8 C ' S ,! 'o ^ JH S o CD 5 |M j3 v: P *d cj oi < .s r ^ '7. "5 T3 'd' Cl *"* & 5 3 a 1 8 ^ ,. , c^ b CJ H g & t3 CJ s *0 ^0 1 Si? 'O 9 1' Q CD" ^ o c < p c J 4*1 1 rf 2 jfi IH CJ t^ c/^ Al CJ cu to 8 S CJ CD | 1 1 3 & .9 0) s 172 MISCELLANEOUS Q. Is a heavy disc or a fly wheel of service in this connection? A. Yes, it serves to make the speed in a revolu- tion more even, so that the shaft revolves steadily, while the unevenness of motion is put on the piston. Q. What other purpose does a fly wheel serve? A. It serves to overcome the dead centers, where the piston can neither push nor pull. Q. Does a crosshead stand still at dead center points? A. No. The crosshead center could stand still only if the crank pin moved around it as the center. The following cut shows how the reality differs from such a case. H, Hi are the positions of the crosshead pin center when the crank pin center is at D, Di. The circle shows the real movement of crank pin ; the two curves indicate the circles in which the crank pin would have to travel as long as the crosshead stood still. QUESTIONS AND ANSWERS 173 The movement near the dead centers is com- paratively slow, but as the crank pin does not stand still at the dead center, but is moving either toward it or away from it, the crosshead, moving with it, does not stand still either. The dead center is an imaginary point, having no dimen- sions; thus it cannot be said that the crank pin center remains at the dead center point any time, or that it takes the crosshead any time to change its direction of stroke. Q. Can you illustrate this fact? A. Yes. The pendulum of a clock does not stand still at either end of its arc of oscillation. No time intervenes between the end of one year or month or hour and the beginning of the next. Q. Do the connecting rod brasses wear the crank pin evenly all around? A. No, in running "over" only one-half of the circumference of the crank pin is pushed and pulled, while in running under it is the other naif. (In the full page cut the half affected in running "under" is shaded; the half affected in running "over," the direction indicated by the arrows, is not shaded.) Q. Why are horizontal engines (stationary) generally run over and not under? A. So the thrust will be downward upon the foundation rather than up against the caps of the boxes and the upper guides. 174 MISCELLANEOUS Q. How much farther does the crank pin travel than the crosshead each revolution? A. One-half farther. The crosshead moves twice the diameter of the disc (back and forth), while the crank pin travels around the circum- ference (= 3.1416 times the diameter); 3 is more than 2 by half. Q. Does a crank pin have a tendency to flatten on one side, or on both sides, traveling in one direction? A. Simply on one side. The push and pull of the rod is on one-half of the pin only, as the pin turns with the crank, wheel or disc. HEAT Q. Is heat a substance? A. No. Scientists say now it is the energy of molecular action. Q. What are molecules? A. The smallest possible parts into which any substance can be divided without losing its chemical identity. Q. What is meant by "absolute zero"? A. The absolute cessation of molecular action. Q. When heat is applied from outside to a substance, what are the effects? A. The substance increases in temperature, changes its volume^ and, at certain degrees of temperature, changes its form. (See page 180.) QUESTIONS AND ANSWERS 175 Q. What is meant by "latent heat"? A. In expanding, gases take heat from their surroundings. This amount of heat does not increase the temperature of the expanding gas, and is therefore not measurable by the ther- mometer. Any heat expended in this or a similar way, and not "sensible," or "noticeable to the feeling," is called latent heat. Q. How is sensible heat measured? A. By means of a thermometer. Q. How is a thermometer constructed and graduated? A. A glass tube with bulb at closed end is partly filled with mercury, and heated until the mercury overflows. Then the open end is closed by fusing, and when cooled, the bulb is placed in melting ice and the point to which the mercury falls is marked the freezing point, 32 deg. Then place it in boiling water which is exposed to the open air and when the mercury rises to its full height, mark it 212 deg., or boiling point. The distance between the two points is 180 deg. . Q. What causes the mercury to rise and fall? A. Expansion and contraction. MEASUREMENTS AND CALCULATIONS Q. Give a general rule for determining the sizes of piston rods for steam engines? A. They should be 1-6 the diameter of the piston-head. t 1 76 MISCELLANEOUS Q. Does this rule answer for all-sized cylinders? A. No ; only sizes ranging from 4 inches up to 28-inch cylinders. For sizes above 28 inches the piston rods are smaller in proportion. Q. Suppose there were 2 pounds of steam in the cylinder, how much pressure would there be between the 'piston head face, valve face and cylinder head? Explain by rule? A. Rule: First find the area of piston and multiply by pressure in cylinder. Q. What is the meaning of the term "clear- ance" in an engine cylinder? A. The unoccupied space between the valve face, cylinder head and piston head at each end of the stroke. Q. Which end of the cylinder has the most power? A. The end without the piston rod. Q. Explain why so? A. Because the steam has more square inches to act upon in the end without the piston rod. Q. How would you know the safe pressure to carry in a boiler }& inch steel, 42 inches diameter, and 50,000 Ibs. tensile strength? A. First multiply thickness of shell by full tensile strength and divide by half the diameter (radius), and divide by 6, which gives the safe pressure allowed by U. S. if welded. If boiler shell is double riveted multiply by .70 (== 70 per QUESTIONS AND ANSWERS 177 cent), in single riveted multiply by .56 (= .56 per cent). Q. What is understood by a unit? A. The basis of measurements, such as the day for measurements of time; the dollar for money; the atmosphere (14.7 Ibs. per sq. inch) for pressure; the caloric (heat required for raising temperature of one Ib. of water one degree) for heating; the horse-power (33,000 Ibs. raised one foot high) for energy; the volt for electromotive force, etc. Q. What is a "thermal unit"? A. The amount of heat found necessary to raise or lower a pound of water i degree (Fahr.) of temperature. Q. What is meant by positive and negative heat? A. The former means the work of actual heat- ing , the latter means the work done in cooling. Q. How is the weight of the atmosphere found? A. By the barometer. Q. How does it show? A. Air, being a substance, has weight. The atmosphere surrounding the earth presses at sea level with an average weight of 14. 7 Ibs. per sq. inch. This atmospheric pressure balances a column of mercury, in the vacuum arm of a siphon, of about 30 inches height. As the air rises (when heated, as in summer over a sandy plain) 178 MISCELLANEOUS or sinks (when cold or heavy with moisture), we have lower or higher pressure and the barometer indicates this by the lower or higher position of the top of the mercury column in the vacuum tube. For better indication the scale is generally attached to the open arm, which is made very narrow so as to show greater differences. Q. How much does the whole atmosphere weigh? A. It is estimated at five trillions of tons, the weight of a solid leaden ball of 60 miles diameter. Q. How large should the stack be in proportion to the area of the tubes or flues combined of a stationary boiler? A. The stack should be about 25 per cent, or # larger in area to do good work. Q. How many square feet of heating surface is generally allowed to i square foot of grate surface? A. From 22.5 to 40 square feet. Q. Suppose the area of a valve is known, how is the diameter found? A. Divide the area by .7854 and extract square root answer equals diameter. Q. How is the radius (half diameter) found when area is known? A. Divide area by 3.1416 and extract square root answer equals radius. Q. How is the linear dimension of a square found from the area? QUESTIONS AND ANSWERS 179 A. It is its square root. (See page 239.) Q. How much will i cubic inch of cold water expand when changing to steam? A. About 1728 times, or into i cubic foot. Q. How large should the diameter of a pump cylinder (plunger) be to deliver 324 gallons of water per minute, traveling 100 piston speed? A. Divide 324 by constant 4, equals 81; from this extract the square root answer equals 9 inches, diameter of plunger. Q. What size should the steam cylinder be as compared with the pump cylinder? A. One-third larger in diameter. In the case mentioned, it should be 12 inches. Q. How much of the steam generated in a boiler is allowed for consumption in the engine? A. One-half only. With the usual average of 70 Ibs. steam and the feed water at the temper- ature of 100 P., each 15 square feet of heating surface of the boiler will evaporate 30 Ibs. of water per hour. The engine should, therefore, consume only 15 Ibs. of water per hour for every 15 square feet of boiler-heating surface. Q. What if the boiler is not capable of gener- ating double the amount of steam consumed by the engine? A. The boiler will be overworked, which means shortness of life, many repairs, a great waste of labor and fuel, and much annoyance. MECHANICAL REFRIGERATION AND ICE MAKING THE SCIENTIFIC PRINCIPLE It is a well known fact that metals expand or contract as they are heated or cooled. Many other substances have the same quality, and it is a scientific truth, applying to all substances ca- pable of expansion, that a change of volume implies either an absorption of heat from, or a loss of heat to> the surroundings. Different substances have their extremes of volume at different temperatures. It is by no means so, that any substance will keep decreas- ing in volume indefinitely as its temperature decreases, or that its volume will keep increasing with increasing heat. Water, for instance, occupies the smallest space at 39.2 F. (the temperature found at the bottom of deep lakes), and has its extreme expansion at 212.8 F. (when it boils, or, in other words, when it changes from the liquid condition to the gaseous). Below 39.2 F. water expands with decreasing temperature (this is why ice floats and bursts pipes); and it cannot be heated beyond 212.8 F., except 180 REFRIGERATION AND ICE MAKING l8l in a closed vessel, which serves to compress the steam into a smaller volume. From the above it will be understood that Gases when compressed yield heat to, and when expanding absorb heat from, their surroundings. THE APPLICATION OF THE PRINCIPLE A gas which will rapidly increase its volume when surrounded by a very low temperature, taking the heat it needs for expansion from the surroundings, will, therefore, create around it a very cold region. Scientists have frozen water in a bottle placed in a fire. The bottle was wrapped in woollen rags soaked in ether or chloroform, which evaporate so rapidly that they draw heat enough from the water in the bottle-to freeze it. Common air can be reduced to a liquid by the alternate application of enormous pressure and of cooling. Liquid air boils at 312 below o F., a 'tem- perature almost inconceivable. Undoubtedly, liquid air will become a mighty agent in the hand of man before long. (See page 223.) Such a gas is, also, anhydrous ammonia, which boils under ordinary atmospheric pressure at 28.5 below zero F. By compressing it in strong steel tanks it is kept in a liquid condition, and is 182 QUESTIONS AND ANSWERS sold that way. From this tank (drum) it passes as a gas (vapor), feeding into a pump, which com- presses it again. In this condition it enters the evaporating coils, in which it is allowed to expand rapidly. In this rapid expansion a con- sumption of heat is necessary, and the required heat is taken from the brine in which the coils are immersed. Then the expanded vapor is exhausted into a condensing tank, the evaporating coils receive a new charge of condensed vapor from the pump, and the operation is repeated. In this way the brine is kept at the desired low temperature. The brine cannot solidify (freeze) on account of the salt it holds in solution. Q. What is mechanical refrigeration? A. It is produced by the evaporation of a volatile liquid which boils at a low temperature, and which by means of evaporating coils, a con- denser and a gas compressor, is brought under the control of the operator. AMMONIA Q. What does the name "anhydrous" ammonia mean? A. "Anhydrous" means "free from water" or "dry." Q. What is ammonia, and where is it found? A. It is a gas composed of i part of nitrogen and 3 parts hydrogen. It can be obtained from REFRIGERATION AND ICfi MAKING 183 the air, from sal-ammoniac, nitrogenous con- stituents of plants and animals by process of distillation. As a matter of fact, there are very few substances free from it. At present almost all the sal-ammoniac and ammonia liquors are prepared from ammoniacal liquid, a by-product obtained in the manufacture of coal gas and coke. Q. What are the properties of ammonia? A. Pure ammonia liquid is colorless, having a peculiar alkaline odor and caustic taste. It turns red litmus paper blue. Its boiling point depends on its purity, and is about 28^ deg. F. below zero at atmospheric pressure. The purer the liquid the lower its boiling point. Compared with water, its weight or specific gravity at 32 deg. F. is about fo of water, or 0.625. One cubic foot of liquid ammonia weighs 39.73 Ibs., i gallon weighs 5.3 Ibs. One pound of the liquid at 32 deg. will occupy 21.017 cubic feet of space when evaporated at atmospheric pressure. The specific heat of ammonia gas (heat required to raise one unit of it one degree of temperature, as compared with the heat required for the same weight of water, =i. ) is o. 50836. Its latent heat of evapora- tion, as determined by the highest authorities, is not far from 560 thermal units at 32 degrees. Q. What is a "refrigerant"? A. Anything that cools, such as ammonia known as anhydrous or dry ammonia. 184 QUESTIONS AND ANSWERS Q. What is the ammonia condenser? A. It is that part of the apparatus in which the gas is cooled and changed to a liquid. Q. How is the water changed into ice'r A. By a system of evaporating coils in which the liquid ammonia is expanded into gas, thereby cooling the space around by absorption of the heat. ICE MACHINE. BEAM PATTERN -CORLISS ENQINE.V Q. At what degree does pure anhydrous ammonia boil? A. At from 28^ to 40 deg. below zero. (See table of boiling points, page 210.) Q. What advantage does this give? A. Ammonia can be kept at its boiling point without any artificial" heat, which is not possible with water. Q. Is ammonia the most serviceable of all refrigerants? A. Yes, it has many advantages over other refrigerants. ABSORPTION AND COMPRESSION METHODS 185 Q. Which standard is applied to the amount of ammonia consumed in producing cold, weight or volume? A. Weight. x Q. Is ammonia inflammable and explosive? A. It is not inflammable, and is, therefore, not explosive in the sense in which gunpowder is explosive; but at any temperature above 28.5 below zero F. it is expansive like dry steam, and is, therefore, dangerous. Q. Has ammonia any corrosive effect on steel or iron? A. No; but on brass it eats. Q. Has it any effect when mixed with water on the machinery or piping? A. No. ABSORPTION METHOD AND COMPRES- SION METHOD Q. Can you describe the absorption method or system? A. Yes, but it is very little used now. , The gas, instead of being compressed by mechanical means, is obtained from a 26 per cent solution of ammonia in water, heated in 'a boiler or still, until the ammoniacal gas is driven off. This gas then goes through the cycle of operations as described, until, having done its work of refrigeration, it is conveyed into the absorber. i86 QUESTIONS AND ANSWERS Here the gas is brought in contact with the water, called the mother liquid, from which it was originally extracted in the still, this water in the meantime having gone through an elaborate proc- ess of cooling. The cool mother liquid rapidly absorbs the gas and forms again a strong solution ABSORPTION AND COMPRESSION METHODS 187 of ammonia. This solution is returned to the still by means of a pump and is ready again to go through the same cycle (round) of operations. Q. Name the parts of an absorption apparatus? A. Generator, ammonia pump, absorber, con- densing tank, weak liquor tank, equalizer, freez- ing tank, cooling tank and receiver for ammonia. Q. What is the absorption system based upon? A. The chemical law which allows ammonia to boil into gas at 28.5 deg. below zero, while water is not affected until 212 deg. is reached. By this the ammonia and water are capable of being separated and made to perform continuous duty. Q. Is the compression system based on the same difference? A. No, because anhydrous ammonia is used in this system. ("Anhydrous" means without water.} Q. Why is it called a compression system? A. Because it consists of alternate compression and expansion of the refrigerant. Q. What are the different operations in this system? A. There are three, namely, ist, compression of the gas; 2d, condensation of the gas and a withdrawal of the heat caused by compression; 3d, expansion of the gas and absorption by it of the heat from the surrounding objects. Q. Explain process of compression? A. The refrigerating agent (anhydrous am- l88 QUESTIONS AND ANSWERS monia) is furnished in heavy iron drums and allowed to enter, through connecting coils, the induction pipe in the compression pump, from whence it is drawn into the cylinders, where it is compressed to a pressure varying from 125 to 175 Ibs. per sq. inch. This variation of pressure is regulated by the temperature of the condens- ing water. This compression produces, by a largely increased friction of the gas molecules (small particles), intense heat. Q. Does the pump get hot? A. Yes, cold water is kept flowing around it, to cool it. Q. Explain process of condensation? A. The compressed gas is then allowed to enter the system of pipes known as the condenser, over which cold water is kept constantly flowing (see cut, page 203). The cold water absorbs the heat generated in the process of compression. The gas is thus cooled in its flow through the great lengths of pipe, until it finally cools to below 28. 5 F. , when it collects in the receiver as a liquid. Q. Explain process of expansion? A. The liquefied ammonia, through a siphon, now slowly enters the expansion or evaporating coils, which are brought in contact with, or in close proximity to the objects to be cooled. As it enters these coils the high pressure before men- tioned is reduced, and the ammonia immediately ABSORPTION AND COMPRESSION METHODS 189 re-expands into the gaseous condition, absorbing the heat necessary for this process from the pipes and through them from the surroundings. Wher- ever two bodies of different temperature are brought in contact, the hotter wiU impart its heat to the colder until the temperatures are equalized. Q. After having thus accomplished its cooling work, where does the gas go? A. It is returned to the compressor, there to again begin afresh the cycle of operations, namely, compression, condensation and expansion. Q. Is there any loss of ammonia during each operation? A. Yes, very small. Q. How often can ammonia be used in the manner just described? A. Times without number. Q. What is absolutely necessary to render these three operations continuous? A. Each separate part of the machine (appa- ratus) must be suitably connected. (See testing and charging. ) Q. State the main points as to all appliances and machinery about a refrigerating plant? A. Good order and cleanliness should be prac- ticed, also pump and valve tightly packed. Q. What gives the greatest trouble about an artificial ice plant? A. Leakage. BRINE SYSTEM AND DIRECT EXPAN- SION SYSTEM Q. In what different ways is refrigeration done? A. For lesser degrees of cooling, as for brew- eries, living-rooms, etc., the brine system is sufficient, in which the brine after being cooled by the ammonia is pumped through the pipes. For very low temperature, as needed in cold storage, direct expansion is used, allowing the gas to expand in the pipes, which are placed in the cool- ing rooms. Q. Which of the two systems is more expensive? A. The direct expansion system, both because of the large amount of specially made pipe required, and because the whole plant must be in operation day and night, to supply liquid ammonia for expansion. Q. What advantage has the brine system over the direct expansion in ordinary conditions? A. Ordinary piping may be used, and the large body of brine suffices to maintain the temperature desired in the rooms for a considerable length of time by merely operating the brine circulating pump, it very frequently being only necessary to operate the compressor in the daytime to maintain the temperature during the entire twenty-four hours. Q. Describe the process of circulation in the brine system? 190 DIRECT EXPANSION SYSTEM 1 9! A. It is done by a special pump known as the brine circulating pump, which forces it through the pipes arranged in the rooms to be cooled, from which it returns to the re -cooling tank and is used continually over and oveiv again. Q. Is the brine circulation independent of the gas? A. Yes. Q. Where and when do they come in contact? A. In the brine tank only. Q. Explain how this is done? A. The cold ammonia gas extracts the heat from the brine as it flows through the tank in the circulation pipes. Q. Do the two circulating systems come any nearer than that just mentioned? A. No. Q. What is the brine tank in an ICE-MAKING PLANT? A. It consists of one or more salt water tanks, in which the evaporating coils of pipe are sub- merged, and the liquid ammonia is allowed to expand within, where it assumes its original gaseous condition and in so doing absorbs the heat from the brine, lowering the temperature to any degree required. Q. How is the brine tank arranged for making ice? A. It is a covered tank with many openings to *H S S 3 192 DIRECT EXPANSION SYSTEM 193 admit galvanized sheet iron tanks to hold distilled water for freezing into blocks of clear ice. (See opposite page; for model ice plant, see page 10.) Q. How long will it take the water in the galvanized tanks to freeze a cake of the usuaj size, 11x22x45 inches? A. It is according to the temperature of the brine. Q. If the brine is cooled to 14 deg. above zero, how long would it take? A. About 60 hours. Q. Why does it take so long? A. Ice is a bad conductor; the ice forming first on the six surfaces communicates the cold very slowly to the water within. Q. Is it a good plan to freeze the water quickly? A. No; if frozen too quickly it will not be transparent, but cloudy. Q. What is meant by the agitator and its use? A. It is a centrifugal (rotary) pump used for drawing the brine from the bottom of one end of the tank and discharging it in the other end at the top, thereby securing uniform freezing by con- tinual circulation of the bath. Q. How is the ice cake taken from the mold? A. By running hot water over the can and dumping it. (See cuts of Eclipse thawing ap- paratus, next page. ) MOULD HOLDER. "~1 JPRIQMT POSITION. | Wooden Dump ECLIPSE AUTOMATIC THAWING APPARATUS AND CAN DUMP. 194 WATER EXAMINATIONS 195 TABLE OF BRINE SOLUTIONS (Chloride of Sodium, Common Salt) Percentage of Salt by Weight Degrees by Salo- meterat 60 P F Specific Gravity at 60 F.. . , Weight of Gallon One Pounds of Salt in One Gallon Pounds of Water in One Gallon Pounds of Water in One Cubic Foot... Freezing Point in Degrees F 5 90 1 037 8 65 432 8 218 25 4 1 037 8 95 895 8 055 62 172 61 465 60 253 ! 59 134 57 408 55 695 18 6 |12 2 20 WATER EXAMINATIONS FOR HARD WATER, ETC. Particles suspended in the water may be detected by filling a tall glass cylinder and placing same on a clean piece of white paper and looking down through the water. All waters are known* as hard or soft, and in many cases hard water may be made soft and the air and gases be expelled by boiling, in which case it is called temporary or removable hardness. If unaffected by boiling it is called permanent hardness, and nothing short of distillation or boiling into steam and condensing the vapor will remove the cause. 196 QUESTIONS AND ANSWERS Q. What is it that makes watef hard, and how much of it is present? A. Eight grains of mineral matter (carbonate of lime, etc. ) or more in a gallon of water make it hard. Q. How is the quality of hardness particularly noticeable? A. When soap is used, the harder the water, the less effect has the soap, because the mineral matter neutralizes so much of it. SIMPLE RULES FOR ASCERTAINING THE QUALITY OF SO-CALLED MINERAL WATERS Water which will turn blue litmus paper red before boiling, but not after boiling, is carbonated (contains carbonic acid). The blue color can be restored by warming. If it has a sickening odor, giving a black sedi- ment, acetate of lead, it is sulphurous (containing sulphureted hydrogen). If it gives blue settlings with yellow or red prussiate of potash by adding a few drops of hydrochloric acid, it is chalytate (carbonate of iron). If it restores blue color to litmus paper after boiling, it is alkaline. If it has none of the foregoing properties in a marked degree and leaves a large residue after boiling, it is saline water (containing salts). THE APPARATUS USED IN THE BRINE AND IN THE DIRECT EXPAN- SION SYSTEMS THE PUMP VALVE The induction or suction valve is shown closed, the piston being on its upward stroke. Surround- ing the upper portion of the valve stem is se'en a coiled spring which raises the valve, holding it firmly upon its seat , as shown above and in sec- tional view of compressor, page 199. As the piston commences its downward stroke the pressure of the gas in chamber D opens the valve and the cylinder commences to fill. 197 198 REFRIGERATION Below A in Fig. i is seen a small passageway connecting the gas inlet space on the right with a small chamber on its left formed by the ring B on the valve stem and the bore of the valve cage. This passage opens a little above the bottom of the chamber, and when the valve is fully opened the ring B covers the passage, and the gas in the lower portion of the chamber, unable to escape, forms an elastic cushion, which prevents any strain on the valve stem and holds the valve in perfect equilibrium. The downward stroke being complete, the incoming gas no longer presses open the valve and by the combined action of the spring and the imprisoned cushioning gas it is instantly seated. The discharge valve is side by side with the induction valve, and works in the opposite sense. The requirements of a good pump are: To instantly admit the gas to the cylinder, filling it full at each downward stroke of the piston; to expel (discharge) the entire contents of the pump through the outlet valve K, Fig. 2, which opens as soon as the cylinder pressure overcomes the combined force of the valve-spring and of the pressure in the condenser beyond the valve Valves, of ample area, durable in construction and reliable in action, must be supplied. A ' piston is required that is perfectly tight, yet 199 2OO THE APPARATUS working freely, and a stuffing box for the piston rod in which the packing can be readily adjusted while in operation. The stroke of the piston is accurately gauged so as to reach within a hair's breadth of the upper cylinder head in order to force all the gas out. Just above the lowest position of the upper face of the piston head there is a ring of 8 openings in the cylinder wall, connecting with the induction chamber D. Through these holes, whose total area equals that of the induction valve, the gas enters at the lowest position of the piston head, thus securing a complete filling of the cylinder, after the induction valve has closed. For the induction valve, as shown by the indicator, admits only about three-fourths of the desired amount of pressure, because, with the spring tension, this is enough to balance the pressure in the induction chamber. As the piston rises again, it closes the ring of 8 openings, until it passes beyond them, when the gas enters once more through them to fill the vacuum under the piston. In the downward stroke, when the piston closes these openings, the remaining gas under it is pressed through small openings (shown white in the cut) at the bottom of the cylinder into the closed chamber N, whence it issues again at the beginning of the upward stroke, working like a cushion. PURGING VALVE AMMONIA COMPRESSION PUMP 202 THE APPARATUS USED THE STUFFING OR PACKING BOX The leakage of ammonia, even if so slight as to cause but little expense, is always an annoyance. Confined as it is in the pipe system, in endless coils without the possibility of escape, the only portions of the plant needing careful attention, to guard against leaks, are the stuffing boxes B, Fig. 2, of the compression pump piston rods A. The stuffing box is of unusual depth, but with whatever care it is designed, engineers are aware that frequent attention is required in all machines to keep the packing set up enough to prevent leakage, and still not so much as to induce heat- ing and the consequent cutting of the rods. The stuffing box is under perfect control of the engineer at all times. Its geared gland Ci, Fig. 2, connects with a short rod F. Turning the handle F will tighten or loosen the packing. The engineer can regulate the pressure upon the packing while the pump is in motion. To guard against the leakage of ammonia, in addition to the very long stuffing box already mentioned, a lubricating chamber with oil pipe G is attached for lubricating the piston rod within the packing. THE AMMONIA CONDENSER The ammonia leaving the compression- pumps hot, compressed, but still gaseous reaches the condenser, which consists wholly of piping and IN REFRIGERATION 203 should be conveniently located on the roof of the building. The condenser should be divided into two parts, namely, the preliminary condenser and the liquefier, as shown in the illustration on this page. The gas when discharged from the compressor AMMONIA UQUEFICR WITH PRELIMINARY CONDENSER. passes into a trap where oil. and other foreign matters are deposited ; from the trap it passes into the preliminary condenser (3), which is located a little lower than the bottom of the liquefier. After being cooled to a considerable extent in the pre- liminary condenser the gas passes through another oil trap (i), which thoroughly eliminates even the 2O4 THE APPARATUS USED slightest trace of oil still remaining in the am- monia. When it is remembered that the ammonia supply ought to do its work for a long period of time in the performance of the never-ending cycle of operations, and that all foreign substances act injuriously on both gas and machinery, it is apparent that it is of the most vital importance to keep the gas absolutely free from all impurities. This the additional oil trap successfully accom- plishes. Thus, completely purified, the gas passes out to the liquefier (2), where it is cooled to a liquid. The condensing pipes are cooled by water. In the open air system the water drips on the top coils and from them down on the lower ones, until it reaches the shallow tank in which the prelimi- nary condensing coils are immersed. Thus the water is hottest when it meets the hottest gases. A waste pipe carries the overflow of hot water to the steam condenser. In another cooling system, the condensing pipes are entirely submerged in a water tank, the water flowing in at the bottom and running out near its surface. The work' of condensing can, therefore, not be divided up as in the open air system. The divided form of condenser possesses marked advantages and is a great improvement over the old method of arrangement. The warmest water IN REFRIGERATION 205 meets the hottest gas, and, as it has already per- formed duty on the liquefier, it is used on the preliminary condenser, Without expense. All the coils should be made from extra heavy special drawn pipe, bent cold, "and finished coils, which should be tester 1 under many times the pressure they will ever be subjected to in actual use. The liquid ammonia flows into the receiver, where it is ready to perform the work of cooling either by expanding into coils in tanks or by expanding into coils in rooms to be cooled. THE EXPANSION COILS The ammonia, which left the compression pumps and entered the condenser as a gas through a large pipe, now leaves the condenser in a pipe from one-half to one inch in diameter, and enters the third division of the system, there again to expand into its original gaseous condition. And it is while expanding to this gaseous condition that the ammonia absorbs the heat from the sur- rounding objects ere it returns to the compressor to be again compressed. SOLDER AND SOLDERING FLUID Bar solder: i Ib. block tin, ^lb. lead. Glazing solder: i Ib. block tin, i Ib. lead. Plumbing solder: i Ib. block tin, 2 Ibs. lead. For a good soldering fluid, drop small zinc strips into i oz. of muriatic acid until the bubbles cease to rise, then add # teaspoonful of sal ammoniac. COLD STORAGE TEMPERATURES ARTICLES. Fahr. ARTICLES. Fahr. FRUITS. Apples 32-3^ CANNED GOODS. Sardines . 35_40 Hun an as !M Fruits (Nuts in shell) 35-40 36 Meats * 35 40 Cranberries 33-36 Cantaloupes 40 Dates Figs etc 50-55 BUTTER EGGS, ETC Fruits dried 35-40 Grapes 34-36 18 20 Lemons 33 36 Oranges 34-36 Eggs 31 Peaches Pears, Watermelons . MEATS. Brined 34 36 | 34-36 38 LIQUIDS. Beer, Ale, Porter, etc. Cider 33 30 Beef, fresh 33 36 Beef, dried 36-40 Wines 40 45 Calves 32-33 Hams, Bibs, Shoulders (not brined) .. . 20 Hogs 29-32 FLOUR AND MEAL. Lard 38 Buckwheat, \\ r heat Livers 20-30 Flour 36 40 Sheep, Lambs 32 Corn Meal , Oats 36-40 Ox-tails 30 Sausage Casings Tenderloins, Butts,etc. VEGETABLES. 20 33 MISCELLANEOUS. Furs, Woolens, Cigars, etc 35 Asparagus, Carrots . . . Cabbage, Celery 34-35 34-35 36-^40 Honey, Maple Syrup, Sugar 40-45 Dried Beans, Corn, Hops Oils 40 35 Onions, Parsnips FISH. Fresh Fish 34-35 20 Poultry, dressed, iced. ,, dry picked... scalded Game Poultry to freeze 28-30 26-28 20 15 18 Dried Fish 36 Game after frozen 25-28 Oysters in shell 30-35 Oysters in tubs 25 206 BYE PASS VALVE AMMONIA VALVES AND FITTINGS i. Expansion valve. 207 2. Ninety-degree angle valve. 3. Cross valve. 4. Return bend. 5. Ammonia tank valve. 6. Forty-five-degree angle valve. 7. Coupling. 8. Joint cross. 9. Liquid valve. 10. Ninety -degree angle purger valve. 11. Union loop. BYE PASS VALVE ON THE DOUBLE AMMONIA GAS PUMP Through the bye pass the ammonia can be readily exhausted from any part of the system and may be stored in any other part temporarily until the repairs or examinations are made. By the peculiar arrangement of pipes and valves the action of the compressor and pump can 208 BYE PASS VALVE be reversed and the gas pumped from the con- denser, storing it in the brine tank. In each case, after the examination of any part, the air can be exhausted therefrom and charge of ammonia reintroduced without the admixture of air. Ammonia Blinder Ammonia A. B, Ammonia Pumps. Ai, A2, Discharge Stop Valves. Bi,B2, Suction Stop Valres. T > 2, 3. 4, 5, 6, Bye Pass Valves. M, D, Main Discharge Pipe M, S, Main Suction Pipe. 7, 8, 9, Bye Pass Pipes. 10, Plunger Valve. DESCRIPTION: A, B, compressor pumps; Ai, A2, main discharge stop-valves; Bi, B2, main suction stop-valves; i , 2, 3, 4, 5, 6, bye pass valves; M, D, main discharge pipe; M, S, main suction pipe; 7, 8, Q, bye pass pipes. How TO OPERATE: To exhaust gas from pump BYE PASS VALVE 209 ^ all bye pass valves should be closed to begi a with; close main stop-valve Bi, B2 and Aa; open bye pass valves 2 and 3 ; then by running pump slowly the contents of pump B can be exhausted ; then close valve 4 and remove" bonnet. After closing bonnet, air can be removed in same way, previously shutting main stop-valve Ai and ex- pelling the air through purging valve on pump- head; close all bye pass valves when done and open main stop-valve. To EXHAUST PUMP A Proceed in same manner, using the opposite set of valves. To EQUALIZE PRESSURE between condenser and brine tanks Open stop-valve Ai or A2 and bye pass valves i and 2, also 5 and 6, thus forming passage direct from main discharge to main suction pipe. To EXHAUST CONDENSER and store gas in brine tank All valves closed to begin with. Open stop-valve Ai on pump A, bye pass valves i and 4, opening communication to pump suction B; expel gas by opening bye pass valves 2 and 5, thus discharging into main suction pipe, kun pumps slowly by using opposite set of valves (either pump may be used), the mode of operation being simply that one pump is used to exhaust the gas through the bye pass from the discharge ; while the other forces it through the other naif oC bye pass into the suction pipe. BOILING POINT OF AMMONIA PRESSURE. S Boiling Point Fahr. Latent Heat. PRESSURE. Boiling Point Latent Heat. K- 'os Absolute. o O 4.01 Absolute. 0) SB 1 43.30 579.7 58.00 28.9 537.6 11.00 3.70 39 579.1 59.41 44.71 30.0 536.9 12.31 2.39 35 576.7 60.00 45.30 30.6 536.5 13.00 1.70 -32.7 575.3 61.50 46.80 32.0 535.7 14.13 0.57 30 573.7 62.00 47.30 32.3 535.5 14.70 4J3.00 28.5 572.3 63.00 48.30 33.0 535.0 15.00 -J-0.30 -27.8 571.7 64.00 49.30 33.7 534.6 16.17 1.47 25 570.7 65.93 51.23 35.0 533.8 16.71 2.01 22 568.9 67.00 52.30 35.8 533.3 17.00 2.30 21.8 568.7 69.00 54.30 37.2 532.4 18.45 3.75 20 567.7 71.00 56.30 38.6 531.5 19.00 4.30 18.9 567.0 73.00 58.30 40.0 530.6 20.99 6.29 -15 564.6 74.07 59.37 41.0 530.0 JJ.27 6.57 13 563.4 75.00 60.30 41.5 529.7 22.10 7.40 12 562.8 76.00 61.30 42.2 529.2 J2.93 8.23 11 562.2 78.00 63.30 43.4 528.5 23.77 9.07 10 561.6 80.66 65.96 45.0 527.5 24.56 9.86 9 561.0 88.96 74.26 50.0 524.3 25.32 10.62 8 560.4 92.00 77.30 51.4 523.4 20.08 11.38 7 559.8 95.00 80.30 53.2 522.3 26.84 12.14 6 559.2 97.93 83.23 55.0 521.1 27.57 12.87 5 558.5 100.00 85.30 56.1 520.4 28.09 13.39 4 557.9 104.84 90.14 59.0 518.6 28.64 13.94 3 557.3 1 107.60 92.90 60.0 517.9 29.17 14.47 2 556.7 110.00 95.30 61.1 517.2 29.70 15.06 1 556.1 115.00 100.30 63.5 515.7 30.37 15.67 Hh zero) 555.5 118.03 103.33 65.0 515.3 31.00 16.30 -J-1.4 554.6 119.70 105.00 66.0 514.8 A FEW TESTS FOR AMMONIA Ammonia liquid for use in refrigerating machines should be absolutely pure. It* should be tested. The various tests to which it should be subjected are: For water, for specific gravity, for inflam- mable gases, and for boiling point. TEST FOR WATER As shown in the engraving, screw into the ammonia flask a piece of bent ^4-inch pipe, which will allow a small bottle to be placed so as CLASSTUBE 'JOBBER I to receive the discharge from it. This test bottle should be of thin glass with wide neck, so that quarter-inch pipe can pass readily into it, and of about 200 cubic centimeters capacity equals 1.69 gills or a 6% ounce bottle. Put the wrench on the valve and tap it gently with a hammer. Fill the bottle about one-third full and throw sample out tti 212 AMMONIA TESTS in order to purge (clean) valve, pipe and bottle. Quickly wipe off the moisture that has accumu- lated on the pipe, replace the bottle and open valve gently, filling it about half-full. This last operation should not occupy more than one minute. Remove the bottle at once and insert in its neck a stopper with a vent hole for the escape of the gas. A rubber stopper with a glass tube is the best, but a rough wooden stopper loosely put in will answer the purpose. Procure a piece of solid iron that should not weigh less than 8 Ibs. , pour a little water on this and place the bottle on the wet place. The ammonia will at once begin to boil and in warm weather will soon evaporate. If any residuum, pour it out gently, counting the drops carefully. Sixteen drops are about equal to one cubic centimeter, and if the sample taken amounted to 100 cubic centimeters, sixteen drops of residuum shows one per cent impurities (adulteration), and 20 drops i# per cent. Care is necessary in the drawing of the sample, as a very little moisture in the bottle, or in the pipe, or a brief exposure to the atmosphere will at once affect its purity. TEST FOR SPECIFIC GRAVITY The specific gravities of aqua ammonia by the Beaume scale are given in the following table. AMMONIA TESTS 213 By drawing off some of the liquid in the tall test tube generally provided by ice-machine builders, the Beaume hydrometer may be inserted and the specific gravity read upon the scale. If water is present, the liquid will show a density pro- portionate to the percentage of water present. TABLE OF SPECIFIC GRAVITIES AND PERCENTAGE OF AMMONIA (CARIUS) Degrees Specific Percent- Degrees Specific Percent- Beaume. Gravity. age. Beaume.. Gravity. age. 10 1.000 0. 21 .9271 19.4 11 .9929 1.8 22 .921 21.4 12 .9859 3.3 23 .915 23.4 13 .979 5. 24 .909 25.3 14 .9722 6.7 . 25 .9032 27.7 15 .9655 8.4 26* .8974 30.1 16 .9589 10. 27 .8917 32.5 17 .9523 11.9 28 .886 35.2 18 .9459 13.7 29 .8805 19 .9395 15.5 30 .875 20 .9333 17.4 * Called by the trade 29} per cent. Specific Gravity of pure anhydrous ammonia is .623 TEST FOR INFLAMMABLE GASES Take a pail of water, submerge the bent pipe therein, open the valve on flask slightly and allow a small quantity of gas to flow into the water. If inflammable gases are present they will rise in bubbles to the surface of the water and may be removed by igniting the bubbles by means of a lighted match or candle. As water has a strong affinity for ammonia it will be readily absorbed, 214 TESTING REFRIGERATING MACHINERY while air or other gases will show only in the form of bubbles. TEST FOR BOILING POINT OF ANHYDROUS AMMONIA By inserting the special low temperature stand- ardized chemical thermometer into liquid drawn into the 6^ oz. test glass jar, readings can be obtained through the side of the jar without removing the instrument. Hold the thermometer in such a position that only the bulb is immersed. This test will give you the boiling point of ammonia at atmospheric pressure and it is well to know that the state of the barometer affects the temperature of the boiling point. With the barometer at 29.92 inches the boiling point should not be above 28.6 deg. below zero and may be much lower, depending upon purity of sample. If the ammonia is impure the boiling point, is raised in proportion. TESTING THE REFRIGERATING MACHINERY PRESSURE TEST. It is important before introduc- ing the charge of gas into the machine system to carefully test every part of the apparatus and make it thoroughly tight under at least 300 Ibs. air pres- sure, which pressure may be obtained by working the ammonia compressor (pump) and allowing free air to flow into suction side of pump by open- ing special valves generally provided for the TESTING REFRIGERATING MACHINERY 215 purpose, the entire system being thus filled with compressed air at the desired pressure. While this pressure is being maintained a search is instituted for leaks, every pipe, joint and square inch of surface being scrupulously noted. One method is to cover all surfaces with a thick lather of soap, leaks showing themselves by formation ' of soap bubbles. In the case of condenser and brine tank coils, the tanks are allowed to fill with water, the bubbles of air escaping through the water locating the leak. It is important that the apparatus be thoroughly tig it, and, as a few joints are to be made when new plants are put in, it is necessary to go over the entire surface of the system to be sure. While the machine is engaged in pumping air into the system advantage should always be taken of this opportunity to purge (clean) the system of all dirt and moisture. To do this properly, valves are provided so the apparatus may be blown out by sections, removing valve covers (bonnets), loosening joints for this purpose, so that it is positively known that each pipe, valve and space is strictly clean and purged of all dirt and traces of moisture. A final test may then be had by pumping air pressure of 300 Ibs. into the entire system and allowing the apparatus to stand for some hours, estimating the leakage, if any, by noting the 2l6 TESTING REFRIGERATING MACHINERY degrees of pressure as shown by the pressure gauge connected to system. The air pressure will shrink somewhat at first, by reason of losing heat gained during compression by the pumps. As soon as the air parts with its heat and returns to its normal temperature, the gauge will come to a standstill and remain at a fixed point (depending upon the barometer and upon the temperature of the room), if the system is tight. Never charge a system until it is well cleansed, purged and absolutely tight. VACUUM TEST After having tested the system with a pressure of 300 Ibs. of compressed air, the air must be exhausted from the entire system, by working the pumps and discharging the air through valves provided therefor (located generally on the pump domes). When the escape of air ceases and the compound or vacuum gauges show a full vacuum, it is well to close all outlets and allow the machinery and system to stand for some time, to test the capacity of the apparatus to withstand external pressure without leakage. In some cases it has been discovered that parts while tight from internal pressure, owing to loose particles lodging over leaks and acting as plugs to prevent escape, give way and disclose the leakage when sub- jected to an external pressure. INTRODUCING THE CHARGE OF AMMONIA Place the ammonia flask (tatok) on small plat form scales, in order to weigh the contents and know positively when flask is exhausted. Con- nect the flask to the charging valve, the gauge still showing a vacuum, close the expansion valve in main liquid pipe connecting receiver to brine tanks; then open valve on ammonia flask and allow the liquid to be exhausted into the system. The machinery may be run all this time at a slow speed, with both discharge and suction hand stop valves wide open. As one flask is exhausted, place another on the scales and continue until the liquid receiver is shown to be partly full by the glass gauge thereof. Then shut the charging valve and open and regulate the main expansion valve. The machine is then sufficiently charged to do work, as shown by the pressure gauges and gradual cooling of the brine and frosting of expansion pipe leading to brine tank coils. While the system is being charged water is allowed to flow on the condenser, and time dili- gently employed in searching further for leaks, which can readily be detected by sense of smell, ^ach joint being again gone over. 2l8 QUESTIONS AND ANSWERS Q. Why are the joints and whole system again gone over after having withstood the two tests, 300 Ibs. air pressure and lowest vacuum? A. Because ammonia in itself is a great dis- solvent and eventually it will purge and scour the entire system clean to the metal surfaces. Q. Where does the loose foreign matter go? A. It is caught in the separators and inter- cepters provided for this purpose. Q. Is ammonia a lubricant? A. Yes, slightly. Q. Has it any effect on iron or steel? A. None whatever. Q. Has it any effect on brass, copper, etc.? A. Yes, it eats and corrodes them. AIR IN THE SYSTEM Q. What causes air to get in the system? A. Negligence in regulating the expansion valve, needlessly pumping a vacuum on the brine tank, leaky piston rods, also taking the apparatus apart and not expelling the air before the re- introduction of the anhydrous ammonia gas. Q. How is the pressure of air in system in con- siderable quantity readily noticed? A. By the intermittent action of the expansion valve and singing noise, rise of condensing pres- sure, loss of efficiency in the condenser, etc. Q. What means are provided for the escape of DISCHARGING AMMONIA 219 the imprisoned air to restore the apparatus to its normal condition of pressure and efficiency? A. The purging (cleaning) valves on the con- denser or the bye pass. (See description of bye pass on pumps, pages 208 and 20*9. ) TAKING THE AMMONIA OUT OF THE APPARATUS Q. How can ammonia be taken out of the sys- tem of an ice machine without losing any of it? A. If the plant is of ordinary construction and of compression (liquefying gas by gas pump) design, connect the liquid receiver by its bottom connection to the empty shipping tank and allow the gas to flow into the tank, being sure to have ^the tank on a scale to weigh the quantity you put in. Do not allow more to be placed in the tank than was originally in it when shipped. In other words, the tank must not be filled with liquid to more than five-eighths of its cubic contents. This is one of the most dangerous pieces of work that a refrigerating engineer is called on to do, and on the first trial the chances are ,about even that he will burst the compressor, blow the receiving tank up and possibly blow his own head off. QUESTIONS AND ANSWERS IN REVIEW Q. How is the compressor pump cylinder kept cool? A. It is incased with a water jacket through 220 QUESTIONS AND ANSWERS which cold water is constantly circulated (see J, Fig. 2, page 199). Q. What causes the heat in the pump? A. The compression of the gas. Q. What kind of oil should be used in the com- pressor, if used at all? % A. Oil generally known as "the perfection ammonia pump oil," or the cold test "zero oil," which is especially manufactured, and which stands a very low degree of cold without volatiliz- ing. Sometimes the best paraffine oil is used, and again a clear West Virginia crude oil. These oils when subjected to a low temperature should not freeze. Never inject oil directly into the compressor, and use sparingly in the stuffing box. Q. What is an oil separator used for? A. It is to eliminate the small quantity of oil from the ammonia gas in its passage from the compressor to the condenser. Q. Is the ammonia gas, when exhausted, in- flammable? A. Yes, sometimes, if the oil traps have not absorbed the oil which the gas carries off from the hot pump. Q. Is ammonia dangerous to handle? A. It is, because when condensed to a liquid it is under an enormous pressure, which may cause great destruction when suddenly released. IN REVIEW 221 Q. What advantage has the bye pass valve? A. By means of it the ammonia can be ex- hausted from any part of the machine that may need repairing. Q. What is an ammonia receiver, and where is it placed? A. It is a tank to store liquefied ammonia, and is placed between the condenser and expan- sion valve (see condenser). Q. What do the pipes in a cold storage room with a very low temperature contain? A. They contain ammonia gas. Q. What do the pipes used in a hotel for cool- ing living rooms contain? A. They contain brine. Q. What does a gas need for expansion and how does it get what it needs? A. It needs heat and takes it from the sur- roundings. Q. But what, if the surroundings have no heat? A. Heat means any degree of temperature. Taking heat from surroundings means lowering their temperature. Taking heat from cold sur- roundings means making them still colder. Q. In which three forms does matter exist? A. Solid, liquid and gaseous. Q. Does iron exist in these three forms? A. We can liquefy it by melting it in great 222 QUESTIONS AND ANSWERS heat, and it is affirmed that iron exists in gaseous form in the sun. Q. How can this be known? A. "Spectral analysis" reveals the fact Q. Why does ice float? A. Because ice is lighter than water at any temperature. Q._What makes it lighter? A. Expansion. A pound of ice has more volume than a pound of water. Q. Whst would happen, if ice were denser and therefore heavier than water at any temperature? A. In severe winters the deepest lakes would freeze solid down to the bottom. Q. Does ice keep on expanding, the colder it grows? A. No, there is a point at which it begins to contract again. Q. Why does it not keep the same volume? A. Because change of temperature is impos- sible without change of volume. Q. Is that a law of nature? A. It is a truth established by sufficient obser- vation, that one never occurs without the other. A STEAM AND WATER-PIPE CEMENT that will set under water, is made of 2 Ibs. ground Paris white, 5 Ibs. ground lithage, X lb. fine yel- low ochre, ^4 z - hemp cut up small. Mix well with linseed oil to the consistence of putty ,and use at once. LIQUID AIR, THE COMING FORCE Water freezes at 32 above zero. Mercury in a thermometer freezes solid at 40-42 below zero. The alcohol in a spirit thermometer freezes at 200 below. Air becomes a liquid at 312 below zero. Eight hundred cubic feet of free air are con- densed into one cubic foot of liquid air. One pint of liquid air weighs one pound, like water. By the aid of a so-horse-power steam air pump ordinary air is compressed until it becomes red- hot. ** Then it is cooled in submerged pipes, and is further compressed until the pressure is regis- tered at thousands of pounds to the square inch. More cooling is done, and more pressure applied, until, finally, the air liquefies. It oozes through the steel of the pipe in the shape of a milky vapor and trickles down into the receptacle below. As there is a difference of 344 between the temperatures of ice and liquid air, it will be under- stood why liquid air boils furiously even when placed on a block of ice. A hand thrust into this liquid, in appearance like water, would be destroyed in 10 seconds, but if drawn out again instantly, the moisture of the skin freezing to ice would be protection enough. The feeling at touching the liquid is like that of iron at white heat. 223 224 LIQUID AIR, THE COMING FORCE Like quicksilver, liquid air does not adhere. If poured over silk, it will leave no stain. When boiling, the vapor of liquid air, being nothing but highly-compressed air, sinks to the ground. If water is poured into liquid air it turns to ice instantly, and of such a low temperature that it will not melt near a red-hot stove for a long time. A stick of arc light carbon, heated to 2,000 degrees above zero, thrust into liquid air, causes the oxygen in it to burn with a dazzling bright flame. A teaspoonful of liquid air in a closed vessel, if lighted, explodes with tremendous force, jarring the ground like an earthquake. The expansive power of liquid air is about 20 times greater than that of steam. Ten years ago it cost about $2,000 to produce i gallon of liquid air. To-day, so Prof. Chas. E. Tripler, of New York, states, it can be manu- factured at the cost of 3 or 4 cents a gallon, at the rate of 40 or 50 gallons a day. Some of the uses to which this uncanny sub- stance can be put are as follows: A steam engine horse-power is now figured at $36.00 a year expense ; by the use of liquid air it should not be more than about $7.00. The resistance in electric wires is entirely over- come, if submerged in liquid air. The intense cold knits the molecules of metal so closely that LIQUID AIR AND HYDROGEN 225 it becomes a perfect conductor, without any leakage. A pocket flask full of liquid air will furnish free air for submarine apparatus for hours. It furnishes a clean, dry cold, at any desired temperature, for refrigerators, hospitals, engine rooms, etc. If used in propelling steamships, there would be no heat in the furnace room, and little need of a furnace. Guns using liquid air as an explosive would never get hot. Liquid air sprayed on dangerous wounds arrests blood poisoning instantly, as by a miracle. Malig- nant cancers have been cured by one drop of the liquid. All pulmonary and throat diseases, hay fever, asthma, diphtheria, grip and all fevers yield to a spray of liquid air. LIQUID HYDROGEN In the spring of 1898, Prof. Dewar, of the British Royal Institution, succeeded in liquefying the most volatile of all gases, hydrogen. Liquid hydrogen is colorless, transparent, and of only one-fourteenth of the density of water. It is so cold that it freezes and solidifies air and oxygen instantly. In a closed tube brought in contact with it, the air freezes into a small lump, leaving the tube a vacuum. 226 THE MACHINE SHOP TOOLS 227 THE MACHINE SHOP One of the things by which a mechanic is known, is the way he keeps his tools. It makes no difference whether he works in a small shop or in one of the great establishments, every mechanic should be inflexible in following these TWO RULES: 1. Every tool should have its exact place, and should be in that place when not in actual use. 2. Every tool should be in good order and ready for use. A mechanic with whom the constant observation of these rules has grown to^ be a habit, is worth three others to his employer, and saves himself a great amount of annoyance, loss and worry. LATHE GEARING To gear a lathe to cut any number of threads when no gear plate is attached to lathe bead art THE MACHINE SHOP 229 block, simply find the run of gears belonging to the lathe to know if odd or even number of teeth are on gears. Multiply the number of threads to be cut to the inch by any small number from 3 up to 6 that will bring the answer even with one of the gears on hand. Say 10 threads are to be cut 4 times 10 equals 40. Place this gear on lead screw of lathe. Multiply the same number (4) by the number of threads per inch on your lead screw, say 6. 6x4= 24. Place 24 tooth gear on spindle, and connect by suitable intermediate. TURNING A BALL There are expensive machines for turning balls, but common lathes will produce perfect spheres. Turn the piece first on centers, using the calipers to get it approximately near the shape; then cut off the centers. Make a cup in a chuckblock of hardwood, to hold a small section of the ball, and for the center use a blunt wood center with a concave piece of copper. Put the work in. the chuclt so as to take the first cut around it in the direction of its former centers, or axis. Cut lightly and a very narrow ribbon all around; then change the chuck so as to cut the second ribbon at right angles with the first, with the same depth of cutting. Then the third 230 THE MACHINE SHOP LATHE TOOLS 1. Half Diamond Point. 2. Diamond Point for steer and iron, left hand. 3. Diamond Point for steel and iron, right hand. 4. Heavy Diamond Point for Cast Iron. 5. Right Side Tool, bent. 6. Left Side Tool, bent. 7. Right Side Tool. 8. Left Side Tool. 9. Inside Thread Tool. 10. Inside Turning (Bor- ing) Tool. 11. Bent Thread Tool. 12. Thread Tool, straight. 13. Roughing Tool. 14. Cutting-off Tool. 15. Water Finishing Tool. 16. Round Nose Tool. NOTE: Set the cutting edge a little above the axis, or it will not cut properly, and may be drawn under and broken off. TWIST DRILL GRINDING 231 ribbon half-way between the first two, and so on, until the whole surface is covered. The right angle need not be measured except with the eye. Finish the ball with a hand tool, or scraper. TWIST DRILL GRINDING The cutting edges of a drill must have a proper and uniform angle with the longitudinal axis of the drill (Fig. i); the two edges must be straight and exactly of the same length ; and the lips must be sufficiently backed off (Fig. 6). Q. What is the proper angle to which a drill should be ground? A. 59 degrees. (See Fig. i.) Q. What is the result of an improper angle? A. A lesser angle gives a longer edge, likely to hook and to produce a crooked and irregu- lar hole. A larger angle gives too short, an edge to do the work easily. Q. Where is the longitudinal axis of the drill? A. It is at the intersection of the two longitu- Fig. i 232 QUESTIONS AND ANSWERS dinal planes indicated by the scribing (center line) along the middle of the two grooves. Q. Of what importance is this axis? A. The cutting edges must be at equal dis- tances from it, and also at the right distance to get the proper angle of point. Q. What is this point? A. It is the part where the two edges of the lips are run together in the center. If the cutting edges are too far from the axis the angle point does not cut; if too near, it cuts too rank. Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 2 shows the proper proportions. In Fig. 3 the edge is too near the center line, and in Fig. 4 it is too far from it. Q. What is clearance? THE MACHINE SHOP 233 A. The amount which is champered off back from the cutting edge. Fig. 5 shows how the clearance is determined as well as the height of the cutting lips, which should be equal, as stated before. Q. What, if there is not sufficient clearance? A. The drill will not cut, and under force wfli split or break. Fig. 6 shows the rear of lip removed. Q. How would you start a drill? A. By hand, in order to see first how it works. If it cuts well, the chips will show a clean cutting surface. Q. Does a good drill in the ^ "line cut small chips? A. In cast metal, yes; but in wrought metal, it will cut a curled shaving sometimes very long. Q. Why are the two grooves shallower near the shank than near the point? A. The center is made , thicker toward the shank for strength. As the drill wears short, the center must be thinned out by grinding, care being taken to remove an equal amount of stock on each side and so keep the point central. * POLYGONAL NUTS A 4 sided nut is called square. AS " " " " a Pentagon A 6 " " " " " Hexagon. A 7 " " " " " Heptagon. An 8 " " " " an Octagon. RULES AND STANDARD NUMBERS DIAMETER, CIRCUMFERENCE AND AREA In a circle of one inch diameter describe 16 radii at equal distances (Fig. i). The spaces FIG. I. between them and the 16 parts of the circum- ference may be arranged in a double row (Fig. 2). The circle area is thus divided up into 16 parts, 8 of which are placed in nearly a straight line on each side of the row. By actual measurement the width of this row is % inch and the length i.57o8 /x (allowing a trifle for the difference between the 8 little curves and a straight line). Therefore cir- ) _o v 1 WW cumference f ' Area =1.5708" X Yz" Difference of) areas of circle V= sum of 4 corners (Fig. 1) and square ) = 3.1416" = 0.7854 sq. inch. = 0.2146 sq. inch. RULES AND STANDARD NUMBERS 235 STANDARD MULTIPLIERS 1. For the area of a circle, multiply square of diameter by 7854 2. For the circumference of a circle, mul- tiply diameter by 3. 1416 3. For the diameter of a circle, multiply circumference by ,. 31831 4. For the surface of a ball, multiply square of diameter by 3. 1416 5. For the cubic inches in ball, multiply cube of diameter by 5236 6. For the cubic contents of a cylinder, multiply the area by the length. 7. For the pressure in Ibs. per sq. inch in a column of water, multiply its height in feet by , 434 AREA OF CIRCLES DlAM. AREA DlAM. AREA DlAM. AREA DlAM. AREA % 0.6013 13 132.73 36 IOI7.8 71 3959-2 I 0.7854 14 153-93 37 1075.2 72 407L5 # 1.767 I4# 165.13 4i 1320.2 76 4536.4 2 3-I4I i6# 205.97 45 1590.4 80 5026.5 X 3-976 18 254.46 46 1661.9 81 5153-0 X 4.908 K 268.80 47 1734-9 82 5281.0 * 5-939 19 283.52 48 1809.5 83 5410.6 3 7.068 # 298.64 49 1885.7 .84 5541-7 X 8.295 20 3I4-I6 50 1963.5 85 5674.5 % 9.621 X 330.06 5i 2042. 8 86 5808.8 X 11.044 21 346. 36 52 2123.7 87 5944-6 4 12.566 tf 363-05 53 2206. I 88 6082. i K 15.904 22 380.13 54 2290.2 89 6221.1 5 I9-635 V2 397.60 55 2375-8 90 6361.7 Q. What difference is there between 3 square feet and 3 feet square? 236 QUESTIONS AND ANSWERS A. The first means 3 squares, each one foot square; the second is 9 squares, each one foot square, arranged in 3 rows of 3 squares each. Q. Is there any difference between one square foot and one foot square? A. No. WEIGHTS AND MEASURES Q. How many square inches in a square foot? A. 12 times 12, or 144. Q. How many cubic inches in a cubic foot? A. 12 times 12 times 12, or 1728. Q. How many cubic inches in a gallon, in a cubic foot, in a bushel? A. 231 in a gallon; 1,728 in a cubic foot; 2,150 in a bushel. Q. How many gallons in a cubic foot of water? A. Tfa gallons. Q. How many cubic inches in one pound of water at 60 F.? A. 27.71 cubic inches. Q. How do you figure the gallons contained in a barrel? A. Add together the two diameters (in inches) of the barrel at head and bung, and divide the sum by 2, which gives the mean diameter. Multi- ply the square of this diameter by .7854, which gives the area of the mean diameter circle in sq. inches. Multiply this area by the length of the WEIGHTS AND MEASURES 237 barrel in inches, to get the cubic contents in cubic inches, and divide the product by 231 to get the gallons. Example: A barrel 40 inches long, 19 inches diameter at the head, 25 inches diameter at the bung. 19 + 25 = 44 44-f-2 = 22 22 X 22 = 484 484 X .7854 = 380 380 X 40 = 15200 15200 -H 231 = 65.9 gall Q. How much does a cubic inch of water weigh? A. It weighs .0361 of a pound, or .577 of an ounce. Q. What is the weight of a gallon, a cubic foot of water? A. A gallon weighs 8^ Ibs. K a cubic foot 62 K Ibs. Q. What is the weight of a column of water, one inch sq. and 2.309 feet high, the temperature at 60 F.? A. One pound. Q. What is the weight of a column of water, one inch sq. and one foot high? A. It weighs .434 Ibs. * Q. How much does a cubic inch of mercury weigh? A. It weighs .49 of a pound. Q. How much does a column of mercury one inch sq. and 30 inches high, weigh? A. 14.7 Ibs. 238 QUESTIONS AND ANSWERS Q. What is meant by a miner's inch? A. It is approximately equal to a supply of 12 gallons per minute. Q. In what relation does the friction of water in pipes stand to the velocity of flow? A. It increases with the square of velocity. If the velocity increases 4 times, the friction increases 16 times. Q. In what relation does the capacity of pipes stand to their diameter? A. It increases with its square. Doubling the diameter increases the capacity four times. Q. How much water is consumed in obtaining one nominal horse power in heating buildings, etc. ? A. One cubic foot. Q. How much for engine purposes? A. One-half cubic foot. Q. How much heating surface is allowed for one nominal H. P. in boilers? A. 15 sq. feet for horizontal, and 12 sq. feet for vertical. Q. How do you find the H. P. required to elevate water to a given height? A. Multiply the total weight of water in Ibs. with the height in feet and divide the product by 33,000. Then allow 25 per cent for water friction and 25 per cent for steam loss, in all 50 per cent, or one-half, which is the same as dividing by 16,500 instead of by 33,000. WEIGHTS AND MEASURES 239 Q. How do you find the total amount of pres- sure exerted by a pump, and how the resistance? A. The area of the sleam piston, multiplied by the steam pressure, gives the pressure. The area of the water piston, multiplied by the water pressure per sq. in. , gives the resistance. Q. If pressure and resistance' are the same, does the pump work? A. No, there must be a margin of from 30 to 50 per cent steam pressure according to the re- quired speed. PULLEY SPEED CALCULATION Driven pulley revolutions are found by multiply- ing the diameter of the driver by its number of revolutions and dividing by the diameter of the driven. Diameter of driving pulley is found by multiply- ing the diameter of the driven by the number of revolutions it shall make and dividing the answer by revolutions of driver per minute. Diameter of driven pulley that should make a certain number of revolutions is found by multiply- ing the diameter of the driver by its number of revolutions and dividing [by the revolutions the driven should make. SQUARE ROOT Q. How is the square root of a number found? A. i st Separate the number into periods of 240 WEIGHTS AND MEASURES two figures each, beginning at the right hand or digit space. 2d Find the greatest number whose square is contained in the period on the left; this will be the first figure in the root. 3d Subtract the square of this figure from the period on the left, and to the remainder annex the next period of two figures to form a dividend. 4th Divide this dividend, leaving out the last single figure on the right, by double the part of root already found, annex the answer to that part and also to the divisor, then multiply the divisor thus completed by the figure of the root last obtained and subtract the product from the dividend. 5th If there are any more periods to be brought down continue the operation in the same manner as before. Note If a cipher occurs in the root, annex a cipher to the trial divisor and another to the dividend, and proceed as before. EXAMPLES : 18,66,24 | 432 Sq. Root. .0,00,36 | .006 Sq. Root. 16 * 00 | 00 249 00 862 | 1724 006 | 0036 1724 0036 LEVERAGE Q. Name the three points in, a lever. A. Force, weight and fulcrum. Q. If the fulcrum is between the force and weight, what kind of a lever would it be? A. A lever of the first kind. Q. If the weight is between the force and the fulcrum, what kind would it be? A. A lever of the second kind. Q. When the force is between the weight and the fulcrum, what kind would it be? A. It is a lever of the third kind. Q. State how the proportions of a lever of the first kind are found? A. By dividing the length of that end of the lever between fulcrum and weight into the length of the opposite end. Example: If length of lever between fulcrum and weight is 6 inches and the other 1 8 inches the lever is said to be 3 to i, and a weight equal to 3 times the force applied at force may be lifted at weight by pulling down at force. Q. How do you figure the lever of the second kind? A. By dividing the length of the end of lever between the fulcrum and weight into the total 242 USEFUL KNOWLEDGE length of the lever. Example : If length of lever between fulcrum and weight is 6 inches and the other 24 inches the lever is said to be 4 to i, and a weight may be lifted at weight equal to 4 times the force applied. Q. What are the lever proportions of third kind? A. They are found by dividing total length of lever into the length of the end between fulcrum and force. Example: If total length of lever is 30 inches and the length between weight and force 24 inches, the lever is said to be an 8-10 to i, and a weight equal to 8-10 of the force applied at force may be lifted at weight. GENERAL USEFUL KNOWLEDGE AIR PURIFIER FOR ENGINE ROOM AND MACHINE SHOP The contrivance consists of a tubular casing adapted for insertion in a circular opening in the roof of a building or the deck of a vessel. Inside of the casing a sleeve is so supported as to leave an air-passage between the casing and the sleeve. Mounted in the sleeve is a tube provided internally with a spider or frame, and at its upper end with a rotatable ingress tube. This ingress tube likewise has a spider or frame on which a rod is centrally pivoted. The upper end of the casing is inclosed USEFUL KNOWLEDGE 243 by a hood formed with a conical end, through which the ingress tube passes. With the conical end of the hood an ingress tube is connected which communi- cates with the interior of the hood. These ingress and egress tubes are curved in opposite directions, and are*mounted to swing in such a manner that the ingress tube shall constantly present its opening to the wind. The ingress tube continually forces a column of air downward through the building, and the egress tube permits all warm or vitiated air to escape. Any vacuum formed by ventilation, it is said, will be immediately filled by the air pressed into the cold tube entering a room at the bottom. The ventilator at the rear or leeward of the hood con- stitutes an air-passage, creating a vacuum below and drawing up the warm air. HOW TO READ A GAS METER The right hand dial of the three used for actual measurement, records the number of feet by hundreds, up to 1,000, the center dial the number of thousands up to 10,000, and the left hand one the number in tens of thousands up to 100,000. Thus, if the hands have passed the 5, 6 and 7 figures on these dials the amount consumed is 76,500, etc. THERMOMETERS COMPARATIVE SCALES. Reau- Centi- Fahr^ mur, grade, enheit BULBS FOR CONVERSION. % 80*. 100. 212. 76 7* 68 95 90 85 203 194 185 Abbreviations: F. = Fahrenheit, C = Centigrade, R. = Reaumur 63.1 78.9 174 60 75 167 56 70 158 62 65 149 48 60 140 44 55 131 42.2 52.8 127 40 50 122 36 45 113 .33.8 42.2 108 To Convert 32 40 104 29.3 36.7 98 F. to C., subtract 32 and multiply 88 85.8 35 32.2 95 90 remainder by f . 24 21.3 30 26.7 86 80 F. toR., subtract 32 and multiply 20 16 25 20 77 68 remainder by f . 12.4 10.2 15.3 12.8 60 55 C. to F. , multiply by f and add 32. 8 10 50 5.8 7.2 45 R. to F. , multiply by f and add 32. 4 5 41 1.3 1.7 35 32 C. to R., multiply by j. 0.9 4 1.1 5 30 23 R. to C., multiply by f 5.3 6.7 20 -8 -10 14 9.8 12.2 10 12 15 5 14.2 17.8 16 -20 4 20 25 13 24 -30 22 28 35 31 32 -40 40 244 USEFUL KNOWLEDGE 245 STOPPING WITH A HEAVY FIRE When it becomes necessary to stop an engine with a heavy fire in the furnace, place a layer of fresh coal on the fire, shut the damper and start the injector or pump for the purpose of keeping up the circulation in the boiler. TO PREVENT ACCIDENT BY THE SHAFTING While the shafts are in motion, it is strictly pro- hibited: a. To approach them with waste or rags, in order to clean them. b. To climb upon a ladder or other convenience in order to clean a shaft. These parts of the machinery must be cleaned by means of a long-handled brush only, and while standing upon the floor. The workmen charged with these or other func- tions about the shafting must wear jackets with tight sleeves, and closely buttoned up ; they must wear neither aprons nor neckties with loose ends. Driving pulleys, couplings and bearings are to be cleaned only when at rest. > This labor should, in general, be performed only after the close of the day's work. If per- formed during the time of an accidental idleness of the machinery, or during the time of rest, or in the morning before the commencement of work, the engineer in charge is to be informed. 246 USEFUL KNOWLEDGE GRAPHITE IN STEAM-FITTING The value of graphite in making joints cannot be overestimated. Indestructible under all changes of temperature, a perfect lubricant and an anti- incrustator, any joint can be made up perfectly tight with it and can be taken apart years after as easily as put together. Rubber or metal gaskets, when previously smeared with it, will last almost any length of time, and will leave the surface perfectly clean and bright. Few engineers put to sea without a good supply of this valuable mineral, while it seems to be almost overlooked on shore. HOW TO OVERCOME VIBRATION How to put the smith shop in an upper story without having the working on the anvils jar the building, has been a problem that has frequently given manufacturers trouble. A mechanical engineer ' says it may be safely done by placing a good heavy foundation of sheet lead on the floor, and on that putting a good thickness of rubber belting. Another person who is interested in the problem has tried the experiment, with some success, of placing the block, not on the floor, but on the joist direct, making a cement floor up to the block, and over the wooden floor, reaching back beyond the reach of sparks. It is sometimes said that black- smith shops never burn, but they keep right on USEFUL KNOWLEDGE 247 burning in spite of theory, and cement floors ought to be helpful in guarding against fires. STEAM AS A CLEANSING AGENT For cleaning greasy machinery nothing can be found that is more useful than steam. A steam hose attached to the boiler can be made to do better work in a few minutes than any one is able to do in hours of close application. The principal advantages of steam are, that it will penetrate where an instrument will not enter, and where anything else would be ineffectual to accomplish the desired result. Journal boxes with oil cellars will get filthy in time, and are difficult to clean in the ordinary way ; but, if they can be removed, or are in a favorable place, so that steam can be used, it is a veritable play work to rid them of any adhering substance. What is especially satis- factory in the use of steam, is that it does not add to the filth. Water and oil spread the foul matter, and thus make an additional amount of work. MIXTURE FOR CLEANSING RUSTY STEEL Tin putty, 10 parts; prepared buckshorn, 8 parts; spirits of wine, 25 parts. Mix to a paste. Rub on the part to be cleaned and wipe off with blotting paper. HOW TO CUT A GLASS GAUGE TUBE Take a three-cornered file and wet it, hold tube in left hand with thumb and index finger at the 248 USEFUL KNOWLEDGE place where you wish to cut, saw it quickly two or three times with the edge of the file ; then take tube in both hands, both thumbs being on the opposite side to the mark and about an inch apart, then try to bend the glass, using the thumbs as fulcrums. Too much bearing surface in a journal is some- times worse than too little. Steel hardened in water loses in strength but hardening in oi] increases its strength, and adds to its toughness. RULE for roughly figuring on the coal in a bin or box Multiply the length of the bin or box with its width and the product by the height of the coal in feet. Multiply the result by 54 for, fine anthracite coal or by 50 for bituminous. The answer will be in pounds. , Divide by 2,000 to get tons. If a leather belt is oil-soaked, sift Fuller's earth (a mixture of clay and silicious matter) or pre- pared chalk on its face, and after a while remove it by scraping with a sharp edged stick. A little damp salt applied to the pulley side of a leather belt roughens it and prevents slipping. Oil is injurious to rubber belts, but when a rub- ber belt slips on account of dust and dryness, a little boiled linseed oil lightly applied on the pul- ley side of the belt will remove the trouble. ELECTRICAL MACHINERY ELECTRICITY Q. What is electricity? A. Electricity is the name for the cause of a large and important class of phenomena in nature, such as attraction and repulsion, heating, luminous and magnetic effects, chemical decomposition, etc. Q. Is it a fluid? , A. It probably is not. Nobody knows exactly what it is. It is now supposed to be a quality, possessed to some degree by all or most substances, consisting in a peculiar movement or arrangement of the molecules. Q. Is electricity a newly discovered power? A. Its most simple effects were noticed by a Greek, Thales, in the sixth century before Christ. He observed that amber, when rubbed with silk, attracted light bodies, like bits of bran, cork and the like. (The Greek for amber is electron, hence the term electricity. ) Q. What is meant by positive and negative electricity? A. It is found that glass rubbed with silk attracts, while the silk repels. Sealing wax rubbed with silk repels, while the silk attracts. 249 250 QUESTIONS AND ANSWERS The vitreous (glass) electricity is called positive, the resinous (wax) electricity is called negative. Q. Is electricity always due to friction? A. No, we have frictional (or statical) and voltaic (or current) electricity. The statical is so called because it is at rest. Q. Which of the two is used in arts and mechanics? A. The voltaic. Q. How is it produced? A. Either by a voltaic battery, or by revolving a coil of wire in the magnetic field between the poles of a steel magnet (electro-magnet), or by in- ducing the current by the action of another current or magnet. Q. What is induction? Q. The process of creating electric properties in a body through the influence of a neighbouring body, having those properties. Q. What is an electro-magnetic field? A. The space traversed by the lines of magnetic force produced by an electro-magnet. Q. What is the principal difference between statical and current electricity? A. Current electricity has little electro-motive force, but is very large in quantity. It has little power to overcome resistance (of a non-conductor), but it can do a great amount of work. Statical electricity has the opposite qualities. ELECTRICITY 251 Q. What causes lightning? A. It is supposed that lightning is due to the high potential created by the union of many minute water-drops into larger ones and the accompanying immense decrease of surface. What produces the atmospheric electricity, is unknown. Q. What is current electricity mostly used for? A. For producing the electric light, for. elec- tro-plating and for the transmission of energy. Q. Is this manner of transmission of energy inexpensive? A. Yes. It may be transmitted over miles of wire, which could be done in no other way, and some dynamos transform as high as 90 per cent of the mechanical energy used in revolving the armature into the energy of the electric current. Q. What is chemical and thermal electricity? A. Chemical electricity is produced by chemical action ; thermal is produced by the application of heat to an arrangement of metallic plates. Q. Does electricity pass through all substances? A. No. Some materials, like rubber, mica and fiber, offer such high resistance that the current will take some other path. They are called non- conductors and are used for insulating conductors. Q. What are the principal subjects considered under the head of current electricity? A. They are the effects of the current in caus- ing chemical decomposition in electrolysis and 252 QUESTIONS AND ANSWERS electro-metallurgy ; in producing heat and light in a resisting medium ; in the production of induced currents in a coil of wire; the measurement of electro-motive force (unit: one volt), of resistance (unit: one ohm), of the force of a current (unit: one ampere), and of working power (unit: one watt). Q. How many kinds of current are dis- tinguished? A. Three continuous, alternating and multi- phase. The continuous current is a constant flow from the positive pole, as in chemical electricity. The alternating current is produced by a rotation of the two legs of a magnet opposite an armature, or, in modern machines, by a rotation of an armature between the two poles of a magnet. The multiphase current results from combining 3 or more alternating currents, with phases displaced with respect to each other ; has definite direction of flow. Q. Can you detect the nature of a current? A. Yes. A magnetic needle introduced into a continuous current will assume a fixed position; in an alternating current it will swing from side to side ; and with a multiphase it will revolve. Q. How can it be determined which is the north or positive pole in an electro-magnet? A. According to "Ampere's Rule," the experi- menter considers himself to be swimming head foremost with the current, along the wire, always ELECTRICITY 253 facing the iron core ; then the north-seeking pole will always be at his left hand. Q. What other way is the positive or negative pole found? A. First saturate a piece <> white blotting paper with a solution of potassium iodide diluted in a glass of water, parts i to 4. Place the blot- ting paper on one of the brushes, then hook one end of a piece of insulated wire, the ends of which are bare, to the switch and place the other end on the blotter where it touches the brush, and if it is the positive pole or brush the blotter on the under side will turn a brownish color; if it is the negative or south pole it will not affect it. ELECTRICAL TERMS Accumulator, or Secondary Battery An ap- paratus for storing electrical energy produced by another apparatus. Alternate Current Dynamo A dynamo in which the current rapidly alternates or reverses its direction from positive to negative. Ammeter, or Ampere Meter An instrument for measuring the rate at which a current passes through a conductor. Ampere The unit by which the flow of current is measured so called after Ampere, a French scientist 254 ELECTRICAL TERMS Ampere Hour A current of one ampere flowing for one hour. When multiplied by the pressure in volts it gives the consumption of electrical energy in Watt-hours, 1,000 of which form the B. T. U. (Kilowatt). Ampere's Rule for rinding the direction of a current A magnetic needle, if placed near a current of electricity flowing from the observer who is facing the needle, is deflected to his left. Anode The positive terminal of an electric source, in opposition to Kathode, the negative terminal. Arc The bow of light produced by the electric current flowing between two carbon points (electrodes) which are slightly separated. Arc Lamp A device for regulating and feeding the carbons of an electric arc, so that as the car- bons are consumed the distance between them or the length of the arc is continually preserved. Armature That portion of a dynamo which revolves between the magnets and in which the electric currents are induced. Automobile Machines that move automatically through electricity or any other force. Bare Conductors Electric wires or conductors with no covering or insulation. Batteries, Primary A set of cells for generating electric currents by chemical action. ELECTRICAL TERMS 2 55 Bitumen InsulationA prepared bitumen com- pound used for covering or insulating electric conductors. Board of Trade Unit (B. T. U.) A measurement of electrical energy decided upon by the Board f of Trade for the public supply companies to base their charges upon. It is equal to 1,000 Watt- hours, or about the amount of electrical energy consumed by seventeen i6-candle-power lamps burning for one hour. Brush of Dynamo An arrange- ment of copper wires, gauze or strips soldered together at one end, for collecting the current from the commutator of a dynamo. Buckling A bending and dis- placement of the plates of an accumulator, caused usually by dis- charging the current too rapidly. Cables, Electric Usually applied to electric conductors, consisting of stranded wires, to dis- tinguish them from single wires. Calibration Standardizing or correcting of any instrument to the standard value, such as volt- meter, ammeter, etc. 256 ELECTRICAL TERMS Candle, The Standard A spermaceti wax candle, burning 120 grains per hour, taken as the standard of reference for measuring the lumi- nosity, or candle power of any light. Carbons For arc lamps, rods, or pencils, gen- erally made from powdered gas-coke, hardened into shape by baking, and used for the electric arc. Casing, Wood A covering or sheath of wood, generally containing two grooves, used for the protection of insulated wires. Cathode The negative terminal of an electric source. See Anode. Cell A box or other receptacle containing the elements and solutions necessary for the produc- tion of storage of electrical energy. A number of such cells are termed a battery. Change Over Switch A switch for changing electrical connections from one source of supply to another. Charging Filling or storing an accumulator with electrical energy. Circuit A system of metallic or other conduct- ing bodies placed in continuous contact and capable of conveying an electric current. Commutator Bars of copper and sheets of isinglass to separate them, which form the ends of the armature coils, and from which the current is collected. ELECTRICAL TERMS 257 Conductivity The facility offered to the pass- age of electric currents through a substance. Conductor A substance through which elec- tricity will pass, but applied principally to those in which v.ery little resistance is offered to the passage of a current, such as copper wire. Continuous Current A current from a dynamo or battery which does not vary in direction and flows continuously. Controller An automatic magnetic regulator for a dynamo-electric machine. Converter The inverted transformer or induction coil, used on alternating current systems. Coulomb The unit of electrical quantity. That quantity of electricity which would pass in one second through a resistance of one ohm with a pressure of one volt. Current, Electric The flow of electricity through any conductor. Creeping A leakage of electricity over the surface of an insulating body, caused by a film of moisture and dirt, or deposit from evaporation, forming a conductor. Dielectric Another term for insulator. Diaphragm A plate or sheet securely fixed at its edges, as a drum head, and capable of being set in vibration, like a telephone diaphragm. Dimmer A choking coil employed on trans- x$8 ELECTRICAL TERMS former circuits to regulate the potential. Used ir theaters to turn the lights up or down. Distributing Board A board from which branch wires or cables are led to various positions from main conductor. Dynamo A machine for producing electricity by transforming mechanical work into electrical energy. Earth or Ground Term used to denote the leakage of electricity (short circuit). Earth Return A circuit in which the earth forms part of the conducting path. It is usually formed by connecting the ends of an insulated line, either to gas or water pipes, or to metal plates buried in the earth. Electric Motor A machine similar to a dynamo, but used for conveying electrical energy into mechanical power. Electrical Energy The capacity of electricity for doing work, whether for electric lighting or for power or traction purposes. It is directly pro- portionate to the amount of current and its pres- sure. Thus by multiplying the flow of current in amperes by the pressure in volts the amount of electrical energy is obtained in watts. Electricity, Thermal Produced by the applica- tion of heat to an arrangement of metal bodies. Electrodes The two terminals forming thr positive and negative poles in a battery. ELECTRICAL TERMS 259 Electrolier A device for suspending a group of incandescent lamps ; the equivalent of chandelier, gasalier, etc. Electrolysis The process of chemically separat- ing the component parts of any substance by means of electricity. Electrolyte Any substance capable of under- going a chemical dissolution by an electric current. Electro-Magnet A bar of soft iron temporarily magnetized by the influence of an electric current passing through a wire encircling it. Electro-Metallurgy The science or process of electrically decomposing solutions or salts of metals. Electro-Motive Force (usually written E. M. F. ) The cause of the transfer of electricity, and therefore the force which supplies the pressure to an electric current. Electro-Plating The depositing of metals by means of electricity upon the surface of another metal or other substance. Field, Electro-Magnetic The space trayersed by the lines of magnetic force produced by an electro-magnet. Filament of an Incandescent Lamp The thread- like substance composed usually of vegetable matter (such as bamboo, cotton, paper, etc.), which by the application of intense heat has been carbonized 260 ELECTRICAL TERMS Forming Plates The operation of bringing the plates of accumulators into proper chemical con- dition. Galvanic Electricity Produced by chemical action ; so termed after Galvani. Galvanometer An instrument used in testing, for showing the flow of an electric current. Glow A white, bright heat. Henry The practical unit of self-induction. A secohm or quadrant. Horse-Power To find the power of engine required to run a dynamo, multiply voltage by amperes, then multiply the answer by number of lights lit and divide by 746. Answer in Watts. Hour Lamp A service of electric current which will maintain one electric lamp one hour. Incandescent Lamp A glass bulb or globe from which the air has been exhausted, contain- ing a carbonized filament which comes to a white glow on the passage of an electric current. Induced Current Electricity produced by the influence that one magnetic or electrified body has on another not in contact with it. Induction The influence that one magnetic or electrified body has over another produced by a dynamo. Installation Plant. Insulation The non-conducting substance ap- ELECTRICAL TERMS 261 plied to the surface of an electrical conductor to prevent leakage. Insulator Any non-conducting material, such as gutta-percha, india- rubber, china, glass, oko- nite, etc. Jablochkoff The in-, ventor of the Jablochkoff ] candle, an arrangement * of carbons placed side by side, and separated by a suitable non-con- ducting substance, such as kaolin, and used to form an electric arc. Kaolin The finest of china clay. Kathode See Cathode. Kilowatt 1,000 Watts. Mains Copper cables or other means used for the purpose of conveying electricity, chiefly applied to the larger conductors INCANDESCENT LAMP AND SWITCH SOCKET. or cables. Megohm A unit of resistance; equal to one million ohms. Meter, Electric An instrument for measuring the amount of electrical energy used. L#2 ELECTRICAL TERMb Milliampere The one- thousandth part of aa ampere. Motor Any machine which may be used for imparting mechanical power. A dynamo running the reverse way. Negative See Positive. Non-Conductor Any substance which resists the passage of electricity, chiefly applied to those in which this quality is strongly marked. Ohm The unit by which the resistance offered to the passage of an electric current is measured ; the legal ohm is the resistance offered by a column of pure mercury, 106 centimeters in length and i millimeter square in cross-section ; or the resist- ance offered by a copper wire 32 gauge, 10 ft. long (from Dr. G. S. Ohm). Okonite Composition of tape and rubber mixed, to wrap joints, to insulate, etc. Parallel Wiring Term used to express the sys- tem of electrical distribution, in which each lamp has its individual flow and return wires, no current passing through two lamps in series. Permanent Magnet A piece of steel or loadstone containing enduring magnetic force, and requiring no electric current to mag- netize it. Photometer An instrument for measuring th^ Intensity of light. Pilot Lamp A test lamp frequently used in th ELECTRICAL TERMS 263 engine-room, serving to denote the E. M. F. of the current from the dynamo. Plugs, Safety-Fuse The movable portion of the safety-fuse, containing the fusible wire. Plugs, Shoe The movable ^portion of a shoe or small attachment, to which are attached the flexible wires in connection with the portable lamp. Poles General term to express the positive and negative conductors in electricity, or the north and south extremities of a magnet. Positive and Negative Terms used to dis- tinguish the polarity of wires in an electric circuit; the flow is termed the positive pole, and the return the negative. Potential As heat tends to equalize between two bodies of different temperature, so electricity tends to equalize between two points of different potential. As the difference in level between two water reservoirs connected by a pipe determines the velocity of the equalizing process, so the difference of potential determines the electro- motive force of the equalizing' electric current. Another determining part is the resistance of the connecting conductor; as the diameter of the connecting pipe and friction are for the two water reservoirs. Primary Cables and Wires In an electrical system of distribution where high pressure cur- rent is transformed to low pressure, all cables and 264 ELECTRICAL TERMS devices conveying the high -pressure current are termed primary. Resistance The opposition afforded by any substance to the passage of electricity. Resistance Coil A coil of wire used for creating a certain desired resistance to the passage of a current. Rheostat An instrument consisting of one or more resistance coils for varying the resistance in an electrical circuit. Rocker An attachment on the bearing of a dynamo to permit of the adjusting of the brushes. Safety Fuse, or Cut-Out A device for auto- matically stopping the flow of electricity in case of accidents or defects in the conductors ; a single- pole safety fuse controls only one wire, a double- pole controls both the positive and negative. Scaling in Accumulators The formation of a deposit upon the plates which prevents the acid from acting upon them. Secondary Wires The low-pressure coils in a transformer, which are acted upon by the primary or high-pressure wires. Series, Electro-motive An arrangement of the metals, so that each is positive with reference to those which follow in the list, and negative to those which precede. In dilute sulphuric acid the order is zinc, lead, iron, copper, silver, platinum, carbon. ELECTRICAL TERMS 265 Series Wiring Where the positive pole of each cell is connected to the negative pole of the next cell. In the multiple arc, all the positive poles are wired to one post and all the negative ones to another. Short Circuit A term used to express any metallic or other connection formed accidentally between a positive and negative wire, by which the current may take a short cut, instead of com- pleting its journey through the lamp, motor, etc. Sunbeam-LampsIncandescent lamps of high candle power. Switch An arrangement for breaking or com- pleting an electric circuit. Telpherage A system of overhead transporta- tion of goods by means of cars running between two steel rails top and bottom of car from which an electric current is obtained to work motors fixed on one or more of the cars. Tension The same for electricity, as pressure for steam. Terminal Attachment screw, by which a cur-, rent enters or leaves any electrical apparatus or conductor. Thermo-Pile A combination of certain metals coupled together so as to produce electricity by the application of heat. Three-Wire System A system of distribution in which two dynamos and three wires are so 266 ELECTRICAL TERMS connected that the third wire serves as flow and return to the other two wires. Besides a consider- able saving in the cost of the cables, a constant potential service results. Transformer An instrument for reducing or transforming a high pressure current to a low one, or the reverse. Transmission of Power The operation of conveying or transmitting power from one point to another. Turbine A machine for utilizing the force or fall of running water. Two or Three-Way Switch A switch having two or three contact pieces attached to con- ductors, which by means of a movable handle permits the current to be sent into either con- ductor. Unit, Board of Trade. See B. T. U. Unit, of Current. One Ampere. Unit, of Electrical Energy. One Watt. Unit, of Pressure. One Volt. Unit, of Resistance. One Ohm. Volt The unit by which the electro-motive force or pressure of current is measured. It is the E. M. F. that will cause a current of one ampere to flow against a resistance of one Ohm. The volt is based on the product of one Daniell cell. Named after Volta, an Italian scientist and inventor of the Voltaic column. . ' ' THE DYNAMO AND ITS PARTS 267 Volt-Meter The instrument for measuring the pressure or E. M. F. of a current. Vulcanized India Rubber India rubber, treated with suphur, etc., to preserve and make it hard. To combine india rubber with sulphur % by heat. Watt, The The unit by which electrical work is measured. It is equal to the current of one ampere flowing at a pressure of one volt. The amount of energy is found by multiplying the amount of current by its voltage pressure. For instance, a current of 10 amperes with a pressure of 100 volts, represents 1,000 Watts. See B. T. U. Wire, Flexible A conductor composed of a large number of fine wires stranded together, so making it flexible. Wires, Electric Small conductors, other than the mains. THE DYNAMO AND ITS PARTS AND ATTACHMENTS Q. What is a dynamo? A. The dynamo, or better, the dynamo-electric machine, converts energy (motion of piston and disc) into electricity by the aid of the permanent magnetism present in certain iron portions. The electricity generated then reacts on the iron, heightening its magnetism; the increased mag- netism again p'roduces more powerful electrical 268 QUESTIONS AND ANSWERS effects, and so on, until a limit is reached. The limit depends partly on the velocity of motion partly on the quality and proportions of the iron and wire in the dynamo, and partly on the resistance throughout the circuit. Q. What are the parts of a dynamo? A. An electro-magnet M, M, M, which is made of two columns of soft iron, encircled by coils of insulated copper wire, and which are united together by cross pieces top and bottom. THE DYNAMO AND ITS PARTS 269 Between the poles or magnet revolves the armature A, which consists of a number of coils of insulated wire wound around an iron core. The ends of each coil are connected to copper strips (segments, or bars) plaped side by side, forming a cylinder known as the commutator C, from which the current is collected. Generally two sets of so-called brushes or collectors B are fixed upon the rocker (yoke) D, which remains stationary, unless it is necessary to adjust the position of the brushes around on the commutator. (See pages 273, 285.) Attached to these brushes, one set being positive and the other negative, are cables E, E, conveying the two main currents (positive and negative) generated to the switch at the top (side) of dynamo, by means of which con- nection can be made with the main supply cables. An attachment F, F to convey the current to the electro-magnet is at the top of the two magnet coils. G is the driving pulley. The armature should be kept up to the proper speed found stamped on field plate. The speed is known by a speed indicator and timepiece. > Com- mutator should be kept quite clean and bright by wiping it occasionally with a rag when running. If necessary it may be cleaned with sandpaper before starting for regular run, the brushes being raised off the commutator. The brushes for service must be set firmly in 270 QUESTIONS AND ANSWERS their holders and rest well on the commutator so as to make good contact. They must be set exactly opposite each other and no brush wires (if made so) left straggling. The rocker yoke holding the brushes should be moved up or down, so as to adjust them to the neutral point, according to the amount of current the dynamo is supplying. When properly adjusted there should be no sparking. Q. What is a commutator? A. It consists of a number of metal cylinder segments insulated from each other by mica. Q. What is the exact function of the com- mutator? A. It serves to rectify, or send in one direction, the vibrations or opposing currents created by the alternate passing of each pole of the armature before the north and south pole of the magnets. Q. How is it done? A. It is done in different ways. In some sys- tems, springs, sliding over the half cylinders, are so arranged that they always are one in positive, and the other in negative condition. In other systems the armature is rotated so rapidly (1,600 revolutions per minute, and more) that the waves of current succeed each other at such short inter- vals, that they appear like a steady current, no break in continuity being perceptible to ordinary tests. THE DYNAMO AND ITS PARTS 271 Q. Does this rapid magnetization and demag- netization produce heat? A. Yes, overheating of the dynamo is a draw- back of this system of commutation. h 2LECTIUCAL POWER 6T08AOB ACCUluULATOa CELLS. Q. What is the accumulator? A. It is a battery of cells in which the electrical power is stored. It is also called a secondary battery. * Q. What is such a battery used for? A. The wet battery (large cut) is used for storing electricity to maintain a limited number of lights after the dynamo has been shut down. The dry accumulator (small cut) is used for automobile vehicles, small lamps, etc. 272 QUESTIONS AND ANSWERS ELECTRIC CYCLE LAMP AND ACCUMULATOR. fOCKET ELECTK1C ACCUMU- ELECTRIC HAND L6.US tATOR. ACCUMULATOR. Q. What is a rheostat? A. It is an instrument for regulating or adjust- ing a circuit, so that any required degree of resist- ance may be maintained; a resistance coil. Q. Give an ex- ample of the way in which the rheostat is used? See cut l^T A. When the dy- namo is first speeded to proper speed it shows a dull light and through the rheostat or controller the voltage is raised up to no, the proper voltage for incandescent lamps. Q. What is a transformer? A. It is used for tapping a low voltage circuit into a high voltage circuit, as in connecting an incandescent- lamp to an arc light circuit. Q. What is a "step up" transformer? THE DYNAMO AND ITS PARTS 273 A. It is used for the reverse, getting high voltage from a low voltage circuit. Q. On what principle are transformers based? A. On greater or lesser resistance. Q. What is a converter? A. The inverted trans- former, or induction coil, used on alternating current sys- tems. Q. Are the same brushes used for dynamos and motors? c A. No. The motor brushes are almost exclusively compressed carbon ; on the dynamo copper plates or wires are used. Q. How are the pointer and scale used? A. They are attached to the rocker stud, and serve to secure a sparkless position of * the brushes by adjusting the arrow to the scale every 274 QUESTIONS AND ANSWERS time the load (number of lamps in circuit) is changed. Q. What is a Daniell cell? A. A zinc plate immersed in dilute sulphuric acid contained in a porous vessel, outside of which is a perforated copper plate surrounded by a solution of copper sulphate. The action is as follows: The reaction between the zinc and sul- phuric acid produces zinc sulphate and hydrogen. The latter, however, instead of collecting on the copper plate, unites with the copper sulphate, forming sulphuric acid and metallic copper. The former goes to keep up the supply of acid in the inner vessel and the latter is deposited on the copper plate. The consumption of copper sul- phate is made good by a supply of crystals in a receptacle at the top. Q. What is a gravity cell? A. It is a modification of the Daniell cell, in which the porous vessel is done away with. The two liquids are separated by their specific gravities ; the copper sulphate surrounds the copper plate at the bottom, and the zinc sulphate surrounds the zinc plate at the top. HOW TO MAKE TRACING-PAPER Place your sheets of double-crown tissue paper in one smooth pile, and apply to the top sheet a mixture of mastic varnish and oil of turpentine, equal parts in bulk, using a flat brush, 2 inches broad. Hang each sheet, when coated, over a line to dry. You may trace on this paper with ink. VARIETIES OF THE DYNAMO Q. How would you classify dynamo-electric machines in general? A. In generators and motors. A generator is a machine for the conversion of mechanical energy into electrical energy, by means of magneto- electric induction. A motor is a machine for the conversion of electrical energy into mechanical energy by means of magneto-electric induction. Q. Why are there so many different generators? A. Some are more economical for certain pur- poses ; some give a constant potential, others give a constant current, etc. Q. What is a magneto-electric machine? A. It is similar to a dynamo, except that the fields are permanent magnets instead of electro- magnets. Q. What is a compound dynamo machine? A. One whose fields are wound with two coils, one of large wire, being in series with the arma- ture, the other of smaller wire in parallel with the armature. This arrangement makes the-dynamo self-regulating. Q. What is a multipolar dynamo? A. A bi-polar dynamo has only one pair of field magnets, a multipolar one has more than one pair. 275 276 QUESTIONS AND ANSWERS Q. What is an alternating current dynamo? A. A dynamo without a commutator. The fields are usually separately excited, as a direct current is required for their excitation. ELWELL-PARKER ALTERNATE CURRENT DYNAMO,' Q. What is meant by "separately excited"? A. The field coils receive the current for their excitation from some source other than their own armature. Q. What is meant by closed-coil? A. The coils are connected continuously to- gether in a closed circuit, being attached to VARIETIES ,OF THE DYNAMO 277 successive bars of the commutator, as in the Gramme and most direct-current dynamos. When not connected continuously, although at- tached to successive bars of the commutator, as in the Brush or T. H. arc dynamo, they are termed open-coil. Q. What is shunt? A. A dynamo so constructed that the entire current must pass through the field coils, is called a series dynamo; where an additional path (external circuit) is provided, so that only a por- tion of the current passes through the field coils, this parallel connection is called shunt. The fields are "wound in shunt with the outside circuit." Q. What is meant by short-shunt? A. When the shunt coils of the fields of a com- pound dynamo are connected to the brushes of the machine, not to the binding posts or external circuit as in the long-shunt. Q. What is a "shunt and separately-excited" dynamo? A. It is compound- wound, one field coil, receiv- ing current from the armature, the other from a separate source. Q. How many kinds of series dynamos are there? A. Three, all compound, as follows: i. Series and magneto, in which the circuit of 278 QUESTIONS AND ANSWERS a magneto machine is connected in series with its armature and fields. 2. Series and separately-excited, in which the fields have two circuits, one in series with the fields and external circuit, the other being sepa- rately excited, used to maintain constant potential at the terminals. 3. Series and shunt, one of the field coils of which is in series with the armature and outside circuit, the other in shunt with the armature. Q. What is meant by synchronizing? A. Modifying the phase of two alternating cur- rent dynamos so that they may be connected in parallel. Q. What is the three-wire system? A. A combination of Edison's for the distribu- tion of electric current for constant potential service, in which three wires are used instead of two, one being a neutral wire. Two dynamos are employed. Q. What is constant potential service? A. An even flow of current. In a water pump the air chamber similarly renders the pressure and flow even or constant. See Potential, p. 263. Q. What is the difference between a dynamo and a motor? A. The dynamo converts mechanical work into an electric current, which the motor then converts back into, or uses in, mechanical work. MANAGEMENT AND CARE OF A DYNAMO THE PLANT Q. -What rules should be observed in placing a dynamo? A It should be placed in a Veil-lighted, clean, cool and dry place, and so that it is easily access- ible from all sides. Q. What should not lie near a dynamo? Generator Panel: Front, Side and Back Views. A. Iron, steel, bolts, nails, tools of any descrip- tion, or waste, filings or dust, as they may be attracted by the powerful magnetism or the cur- rent of air created by the revolving armature. 279 280 QUESTIONS AND ANSWERS Q. Where should the switch-board and fuse blocks be? A. Like the engine, they should be so near the dynamo that the whole plant can be taken t Feeder Panel : Front, Side and Back Views. in at one glance, but so far apart that there is no danger of a short circuit. Q. Of what should the bases of all cut-outs, switches, lightning arrestors, etc., be made? A. Marble, slate, or porcelain. Q. How should connections be made? A. Soldered and thoroughly insulated. Q. What kind of wire should be used in damp places? ^ Rubber-covered wirea- THE CARE OF A DYNAMO Q. Would you use metal staples in electric light or power work? A. No. Use porcelain insulators. Q. What is an insulator? A. It is a non-conductor, preventing the cur- rent from leaving the wire. (See page 312.) Q. In cleat work, what kind would be best to use? A. Those with V-shaped grooves; they clamp firmly. Q. How many cleats should be used to turn a corner or angle, and why? A. Two, to make it neat and workman-like. Q. Would it be safe and proper to use a bare wire in any part of the wiring throughout a build- ing? A No. All wires should be properly insulated. Q. How do you test the insulation of a wire. to see whether it affords the required resistance? A. It should be tested to not less than 250 Megohms per mile in dry places and 600 Meg- ohms per mile in damp places. The test must be taken with an electro-motive force of not letfs than loo volts after the insulated cables have been in water at 60 degrees Fahrenheit for 24 hours, and with one minute's electrification. Q. What should be put in a line, between the cut-out switch and the street where the wire entered the building? 282 QUESTIONS AND ANSWERS A. Loops of wire known as drip loops. Q. What style of belting should be used for a dynamo or motor? A. It should be a light double, endless and rivetless one. Q. Why should the belt be endless and not laced? . A. Because every time the laced joint passed over the dynamo pulley the lights would fluctuate (flicker). Q. If the belt is endless, how is the slack taken up? A. Nearly all dynamos and motors are provided with a frame and belt-tightening apparatus com- prised of one center or two side screws and foundation slides on which the dynamo rests; with these the dynamo or motor can be forced back and the belt tightened. Q. How much should a belt be tightened? A. Enough to prevent extreme slipping. STARTING THE DYNAMO Q. What should be done every day before starting a dynamo? A. The dynamo tender should examine the binding posts, the commutator and brushes, also see that the contacts are clean and firmly tight- ened by the set screws. Any dust and dirt should be most carefully removed with soft rags and a THE CARE OF A DYNAMO 283 bellows, as they cause the majority of all the troubles and annoyances. Q. What rules should be observed in starting the dynamo? A. Always start the machine to running with the main switch open and the brushes raised from the commutator, so all the working parts can be seen ; be sure that the rheostat is at zero. Then drop the brushes on the commutator, then see that the voltage is correct on volt-meter. If the brushes spark, rock the brush holder quadrant forward or backward around the commutator until a sparkless place is found, then close the main switch. When running drop a little oil on tjie end of finger and rub in the palm of hand, then pass the finger gently over the commutator lengthwise. Q. How high would you cause the volt-meter needle to rise? A. The proper voltage for incandescent lights is no volts. If run up to 115, there is danger of burning out the filaments. Q. What rules must be observed in disconnect- ing the dynamo? A. In disconnecting the dynamo after it has been used for charging the accumulators or supply- ing lights, etc., the engine should be eased down, dynamo switch opened, and the brushes raised from the commutator to cool, also to be free in case the armature was turned the reverse way. 284 QUESTIONS AND ANSWERS The copper brushes should be fil^d to one bevel, also kept clean and free from oil, copper dust, etc. RUNNING THE PLANT Q. How and when would you test the circuit? A. It should be tested every day for grounds, by means of the detector, galvanometer or a mag- neto bell. Q. If there was a ground, how would you locate it? A. By disconnecting the circuit in different places, and testing each section separately until located. Q. Give various reasons for excessive sparking of commutator and brushes of a dynamo or motor? A. Poor condition of the brushes and holders ; faulty adjustment of brushes ; surface of the com- mutator rough or covered with dirt and grease; the insulation of one field magnet coil injured and the coil short-circuited in itself. If one magnet is excited more than the other, one brush will spark more than the opposite one, in the same way as if improperly adjusted. Two or more segments of commutator short- circuited. Dynamo or motor overloaded. Overloading will also cause considerable heating of the armature and fields. Overloading of the dynamo, or motor, THE CARE OF A DYNAMO 285 may be caused by poor insulation of the external circuit, thus causing a considerable amount of current to escape froirf one pole to the other. Grounding of the external wires, which fre- quently happens in rainy weather. In arc lighting, lamps may be fed by too strong a current ; in incandescent lighting, too many lamps may be put on the leads. Q. Name the different causes of the eating away of the" segments of a commutator? A. Too much tension, too much contact sur- face, brushes not set properly, or not far enough around on the commutator. Q. What will cause flat spots on the face of commutator? A. Badly soldered armature wire connections, also soft spots in the copper segments. Q. How would you know when brushes have not enough contact or pressure on commutator? A. By a peculiar snapping noise. Q. What is the effect of a brush being too long, or pressing too hard? A. It will cut the commutator, emitting strong spattering sparks. Q. How can the brushes be made to press harder or lighter on the commutator? A. By adjusting the brush holders. Q. How are brushes moved on commutator? A. By the yoke (quadrant). (See page 273.) 286 QUESTIONS AND ANSWERS Q. Why are they moved around on the com- mutator, and when? A. When more or fewer amperes of electricity are necessary for lights, power, etc. Q. How are the different kinds of brushes adjusted? A. Practically all alike. They should be set at a bevel of 45 to the commutator. Each brush should cover at least one segment and two insula- tions to make the current as nearly continuous as possible. Copper wire or copper leaf brushes are filed to a 45 bevel and the commutator wears them to a concave. Carbon brushes are concaved by putting coarse sandpaper on the commutator, rough side up, and by drawing it to and fro. Q. Where should the brushes be set? A. At neutral (opposite) points. Q. How would you make a copper brush? A. Cut the strips the width of the opening in the -brush holder, and take so many of them that the brush will pass through the holder easily, and solder them together at one end. The same for wire, gauze and other copper brushes. Q. How thick should a carbon brush be? A. One-half thicker than the commutator bar to make it strong enough. Q. Is it safe to touch the two opposite brushes (positive and negative) at any time while running? THE CARE OF A DYNAMO 287 A. No, for if the motor or dynamo be grounded (short-circuited) the full voltage would be received and cause either paralysis or death. Q. When a motor or dynamo becomes very hot, to what would you lay the trouble? A. It being overloaded, or poor connections. Q. How can stationary motors be reversed? A. By changing (crossing) the wires on the yoke or fields, also reversing the brushes. Q. Suppose the twine covering the armature wires near the commutator segments happened to unravel while running, what would you do? A. Open switch and after motor or dynamo has stopped remove the remaining twine. Q. Would it not interfere with the machine? A. No. It is there to keep out as much dust as possible from in between the armature wires. REPAIRS Q. What causes the insulation of one or more coils around the armature to char and crumble off? A. Excessive heat caused by short circuit, poor connections, overloading, and cotton waste, etc., being attracted at the end of the dynamo and pressed between the armature and pole pieces. Q. In what way will the waste injure the armature? A. By scaling off the insulation from the wire in some places or bursting the metal bands encir- cling the armature. 288 QUESTIONS AND ANSWERS Q. Do these injuries extend below the outside / layer of wire? A. Sometimes, but not very often. Q. Can the wires be insulated without being taken to a repair shop? A. Yes, by carefully lifting one wire at a time just high enough to wrap it with silk tape, and thus insulate it. Q. What causes the field magnet to short- circuit and burn the insulation? A. By getting parts of the field wire in contact with the iron core. Q. What should be done in such trouble? A. Unwind the wire until the damaged part is reached, and after insulating it properly, it should be wound back on the cores. Q. How are field magnets wound and un- wound? A. By placing the field horizontally between the two centers of a turning lathe. Q. What would you do after having wrapped and insulated all the injured parts of an armature? A. Drive the wires back into their positions by means of a hard wood block and hammer, after which give them two or three good coatings of shellac varnish. Q. If the injury was below the outside layer, what should be done? A. Take the armature to a regular shop and let THE CARE OF A DYNAMO 289 them do the repairing, as they have the proper tools to do the work. Q. Suppose you had to replace an old com- mutator with a new one, how would you proceed to do it? A. Take the armature out from between the poles, and place the two ends of the shaft on wooden horses. Mark the wires leading from the armature to the commutator by attaching little tags with numbers, to make sure of the proper place of each wire after taking off the commutator. Then disconnect these wires from the correspond- ing copper bar of the commutator, either by unscrewing the set screw, or unsoldering the con- nections by means of a hot soldering iron. After this is done remove the commutator, clean the shaft and connections and put the new com- mutator carefully in its proper position, and connect the armature wires in proper turn to the corresponding copper bars of the commutator by means of set screws, or hard soldering. Great care must be taken not to short-circuit any part of the commutator with drops of solder. Q. Why do electrical engineers and linemen wear rubber gloves and rubber soles? A. Because rubber, like glass, is a non-con- ductor of electricity. Live wires should never be touched without one or the other, as instant death may occur. MEASUREMENTS OF ELECTRICITY Q. What is a dyne? A. The unit of force. The force which, in one second, can impart a velocity of one centimeter per second to a mass of one gramme. Q. Why are these terms not given in U. S. measurements, such as ounces and inches? A. Because scientists all over the world use the decimal system, and electricity has been developed by scientists exclusively. Q. What is an erg? A. The work done in moving a body through a distance of one centimeter with the force of one dyne. A dyne centimeter. Ten million ergs = one joule. The joule is the practical C. G. S. unit of electrical energy or work. (C. G. S. = cen- timeter gramme second. ) Q. What is a watt? A. The unit of -electric work or power, equal to one joule per second. One H. P. = 746 watts. The number of watts is numerically equal to the product of the current passing, times the voltage which produces that current. i volt times i ampere = i watt ; 3 volts times 3 amperes 9 watts, etc. A kilowatt is 1,000 watts. 290 MEASUREMENTS OF ELECTRICITY 291 Q. What is a coulomb? A. The unit of electrical quantity. That quantity of electricity which would pass in one second through a resistance of one ohm with a pressure (force) of one volt. * ^ Q. What is an ampere? A. The unit of electric current. That rate of flow which would transmit one coulomb per second. Q. What is an ampere-hour? A. The equal of one ampere flowing for one hour, or 3,600 coulombs. Q. What is an ohm? A. The practical unit of electrical resistance. A resistance through which an electric current of one ampere will flow under a pressure of one volt. The legal ohm, now internationally adopted, equals the resistance of a column of mercury 106 centimeters in length, having an area of cross- section of one square millimeter, at o C., or 32 F. A section of wire having a resistance equal to the legal ohm is used as a "standard oh*m." 1000 feet of T \j-inch copper wire has a resistance of very nearly one ohm ; a mile of common iron telegraph wire has a resistance of about 13 ohms. A megohm = one million ohms. Q. What is the Law of Ohm? A. The strength of a continuous current (C) 292 QUESTIONS AND ANSWERS is directly proportional to the electro-motive force (E) in the circuit, and inversely proportional to the resistance (R) in it. It is, therefore, the e. m. f. divided by the resistance. C =~ ; E = C X ff R. R; R = -. C Q. What is a volt? A. The practical unit of electric pressure, or electro-motive force. The pressure required to move one ampere against one ohm. The volt is based on the product of one Daniell cell. Q. What similarity is there between electrical terms and steam terms? A. The volts may be compared to pounds of steam pressure; the resistance to friction; the wire to the pipe ; the coulomb to the quantity of steam passing through the pipes; the ampere to the rate at which the steam passes; the watt to the amount of work performed (H. P. ). Q. What difference do you make between "force" and "power"? A. In common language, they are used as equivalents, but in science the following distinc- tion is made : Force is the cause of a change, such as from rest to motion, or in condition, etc. ; power is the rate of the expenditure of energy. Electricity, steam, gravity, expansion, etc., are forces; we speak of horse-power, candle-power, gross and net power, etc. MEASUREMENTS OF ELECTRICITY 293 Q. How much of a H. P. is required to main- tain a steady light for a i6-candle-power incandes- cent lamp? A. About one-tenth, or 10 lamps to a H. P. Q. How many volts for an arc light? A. 220. Q. Can arc lights and incandescent be run on the same circuit? A. Yes, by the use of the transformer. Q. How is the efficiency of a dynamo deter- mined? A. By dividing the electrical energy produced by the mechanical energy expended in driving the dynamo. Q. How do you arrive at the amount of elec- trical power spent? A. By multiplying the amount of current by its pressure. For example, a current of 10 amperes with a pressure of 100 volts represents 1,000 watts (i kilowatt). A current of 20 amperes with a pressure of 50 volts represents the same power (1,000 watts). Q. What is meant by the B. T. U.? A. It means the consumption of electrical energy of one thousand watts in one hour. Q. How are the electric currents measured? A. Either chemically or mechanically. Q. Explain the chemical system? A. It is based on the simple fact that one 294 QUESTIONS AND ANSWERS ampere of electricity will deposit from sulphate of zinc, under standard conditions, a definite weight of metal. This type of meter is a small electro- plating battery through which a certain proportion of the current is carried the proportion being accurately determined by the relative sizes of the meter wires and the shunts with the result that one of the two plates is decreased and the other increased in weight, according to the amount of current consumed. Q. Where and how is the meter placed? A. It should be placed in a clean, dry place and connected to the inside service with moisture- proof wire. It must always be protected by a service cut-out ; never placed between the cut-out and the street service. It should be in a place not likely to freeze, also where the inspector can have easy access to it. The meter should be screwed fast to a well-seasoned board, not less than i inch thick and well-covered with asphal- tum against the wall. Never place more lights on a meter than it is intended to carry. Q. What test is made, and how is it made? A. It is necessary to find the positive clips and mark them. For this two things must be known : Which side of meter is connected to street, and which of the two outside wires is positive. The first is found by tracing the conductors or opening the circuit. MEASUREMENTS OF ELECTRICITY 295 The second, by testing with a blotting paper saturated with a solution of potassium iodide. With the moistened paper in hand press it against the upper and middle binding posts. A brown mark will appear where the paper .Meter Fed on Right Side. (See cuts A and B.) *A" When top post gives brown mark, right hand clips are positive. "B" When middle post gives brown mark, left hand clips are positive. Meter Fed on Left Side. (See cuts C and D.) "C" When top post gives brown mark, left hand clips -are positive. "D" When middle post gives brown mark, right hand clips are positive. 127 + CIJPS A. + CUPS B. + CLIPS C. + CLIPS D. *LAMP > touched the positive post. By following rule the positive clips can be determined. The clips are 296 MEASUREMENTS OF ELECTRICITY at the top of meter and the chemical bottles set under them. If the center wire is not brought into the meter, the lowest post must be used for the middle in using foregoing rules. All positive clips should be carefully marked. The positive plate can be known by it being next to the head of the bolts which bolt the two plates together. Sometimes the positive plate has a tag attached, which prevents mistakes. Q. Explain the mechanical meter? A. Of these there are many varieties, those most in use being the Thompson- Houston watt meter and the Westinghouse or Schallenberg ampere meter, both of which are small motors driven faster or slower as the demand for current is greater or less, and communicating their action to a train of wheels with dials like those of a gas meter, so that they may be verified by burning a given number of lamps for an hour and compar- ing the dials at the beginning and end of the time. The meter record is taken usually once a month, and the bills are based upon these records with as much certainty as though electricity were visible. THE MOTOR AND CONTROLLER Q. -What is an electric motor? A. The reverse of the dynamo, used for con- verting electricity into mechanical work. Q.^-When is the work of an electric motor at its maximum? [ELECTRIC- MOTOR. A. According to the "law of Jacobi," when the counter E. M. F. is equal to half the E. M. F. expended on the motor, or the impressed E. M. F. Q. What are stationary motors used for? A. For running elevators, machinery, dyna- mos, etc. Q. Where does a stationary motor get its power from? 297 298 THE MOTOR AND CONTROLLER A. From a dynamo, or generally from a three- wire system set of dynamos. Q. What voltage, amperes and speed has a 15 H. P. motor? A. Generally 220 voltage, and any amount of amperes it may need and 1,600 speed per minute. Q. What different systems of using electricity for traction are in use? A. The overhead trolley,, the underground trolley, the storage battery and third-rail systems. Q. How are the brushes set on the commutator of a car or engine motor? A. Directly against the commutator and op- posite, instead of aslant as on stationary motors. Q.What voltage and H. P. are the motors of elevated roads? Railway Motor. THIRD RAIL SYSTEM WITH SLIDING FEEDER SHOE IZ3 Eli] EBl DEJ SIDE VIEW OF MOTOR TRUCKS 300 QUESTIONS AND ANSWERS A. Generally 2,000 volt type and 100 H. P. Q. How many are usually placed under a car? A. Two one at each end of car, so as to avoid the need of a turn table. Q. What system is generally used? A. The third-rail system. (See page 299.) Q. Can the car be run in both directions from either end? A. Yes, by reversing the motor through the controller box. Q. How is the electric current transmitted from the third rail to the controller and motor? A. By a shoe sliding on the third rail. The shoe may be raised from the rail by a short ful- crum lever in the controller room, thus breaking the circuit. Diagram of Method of Suspension. Q. How is the motor of a surface trolley car suspended and geared to the wheels? THE MOTOR AND CONTROLLER 301 A. It is suspended with springs and a frame between the wheels and truck. Railway Motor. The armature axle is geared to the wheel so that the armature pinion turns about four times to a single turn of the wheels. THE CONTROLLER Q. What is a controller and its duty? A. It consists of two switches (see cut, page 302), each having its own separate operation to perform. The controlling cylinder (switch) No. 2 proper is used simply to make the different com- binations required to obtain the proper regulation of the speed of the car. The second switch, or small handle, is also of a cylindrical form, but is used for either breaking the circuit or reversing the motor, either forward or back. Q. Can a controller be compared to a rh'eostat? A. Yes, its function of controlling the speed of the car can be compared to the working of the rheostat in increasing or decreasing the resistance. Q. Will switch No. i of the controller cut off the current if moved? 302 QUESTIONS AND ANSWERS A. Yes, the slightest movement cuts the cur- rent entirely off. Q. How many notches has the current switch? Name them? A. Three go ahead, back up, center cut-out. Q. How is the resistance provided on an elec- tric controller? A. A considerable amount of resistance is pro- vided in the shape of bands, ringers or strips of iron or nickel steel. Q. How is this resistance subdivided? THE MOTOR AND CONTROLLER 303 A. Into a considerable number of parts so that it can be cut down gradually. Q. How many notches has a controller dial plate, and what is their purpose? A. Generally 7, and they are there to indicate the increase of speed gradually -and uniformly by continually lowering the resistance of circuit. Q. When the motorman moves the large handle No. 2 around on the dial (notch plate), what does it do? A. It connects a coil of wire on the motor with trolley (feeder) wire each notch it is moved. Q. Suppose the controller handle No. 2 stood in the seventh notch and the current switch No. i was suddenly turned on, what would be the result? A. The fuse strips would blow, or melt. Q. What are cut-out plugs or strips? A. They are fusible wire and are used to save overcharged or heated wires from melting. Q. To what could the above be compared so as to be easily understood? A. To an attempt at starting a steam engine suddenly at full speed instead of gradually turn- ing on the steam with throttle. Q. Compare the principle of controller box and coils of motor with the steam engine? A. It is the same as placing the reverse lever in center notch so valve equally covers both steam ports, then opening the steam valve full, this 304 BALDWIN AND WESTINGHOUSE acting as the current switch, and the reverse lever as the controller switch. When ready to start drop the reverse lever or controller down one notch ; if more steam or current is required drop it another notch, and so on until the full power or current is passing into cylinder or motor coils (fields). THE BALDWIN AND WESTIXGHOUSE ELECTRIC ENGINE has solved the problem of a locomotive running 120 miles an hour. In appearance this new wonder does not betray its qualities. The motors are incased, so that hardly any mechanism is in sight. The electric headlight and the pilot alone disclose its character as a motor car or locomotive. The locomotive weighs 150,000 Ibs. and is 37 feet long over the pilot The frame is made of lo-inch rolled steel chan- nels, covered by a one-half inch rolled steel plate over the entire floor, giving enormous strength to resist blows in collisions, etc. This frame is carried on two trucks, with all the modern devices of springs, for swinging motion ELECTRIC ENGINE 305 and free movement. The trucks are built very strong and they are of the swiveling type, so they may go around any curve passable for an ordinary freight car. The geared connection between the axles and the electric motors permits'* of any gear ratio desired. The driving wheels may be connected by par- allel rods for pulling heavy trains, as such rods would not permit one pair of wheels to slip with- out the other. The motors are directly beneath the car floor, between the two trucks, and are "iron-clad" con- sequent pole motors. They are entirely encased in thin steel shells, so as to be protected from all injury under normal conditions of service. The armatures are laminated, being made up of thin slotted discs of steel. 'In the slots the armature wires are placed. The commutators are of the best forged copper with mica insulation. The motors have the highest grade of insulation. Power is furnished by the third-rail system. At both ends is a controller. The path ' of the current may be divided so as to pass to both motors independently, or it may be sent through one motor to the other. The braking system has some unique features. The compressed air-brake is used. The engineer's 306 HEATING AND COOKING valve is of the standard Westinghouse type. When the handle of the brake valve is put at "emergency" for a sudden stop, pneumatic action breaks the circuit at the same time as it applies the brakes. A special reversing switch acts on the motors. The automatic air-pump is driven by electricity, its special motor being directly con- nected and without gear. The interior of this locomotive is that of an observation car, and very handsome. Our 120 miles an hour locomotive is ready for us, but we are not quite ready for it. Before we can risk flying across the country at such speed, all grade crossings must be abolished and the whole present R. R. signal system must be changed. Signals are now about a mile apart, while the new locomotive cannot stop within less than one and a half miles of clear way. ELECTRICITY FOR HEATING. To fit heating and cooking utensils for the use of electricity, a thin film of enamel or cement is spread over the outer saucepan, griddle, kettle or heater. Then iron, platinum or other high resistance wire is laid zigzag over it, with copper wire connections made to the two ends; and more of the cement or enamel is spread over the wires so as to com- pletely embed them. When enamel is used the apparatus is put in a kiln and burnt on similar to the ordinary iron cooking utensils. In both BY ELECTRICITY 307 methods the film of enamel or cement insulating the heating wires is put on so thin and is so good a conductor of heat that the heat generated by the electricity is rapidly conveyed to the utensil ClflDDLE to be heated. Electricity can thus be sent through the wires without fear of overheating them. This would not be possible if they were exposed to the air, which does not conduct heat, but radiates it. 308 STATIONARY MOTOR AND CONNECTIONS To start motor, quickly throw in switch 4. Then move rheostat-handle 3, slowly over the arc, until stopped by magnet to, which holds it while motor runs. The nearer the handle approaches the mag- net, the larger a number of high-resistance wire coils in the rheostat box transmit the current, which has full flow when handle reaches magnet. To stop motor, throw switch 4 out, and move handle 3 off the arc. The motor, i, in the cut is series wound, one pole connected with two .binding posts of revers- ing switch, 2 ; the other pole connects with handle, 3. 5, 5 1 are safety-fuses, 6 is the volt-meter, 7 the ampere-meter, which at 8 connects with rheostat graduation arc. Fuse 5 1 connects with third binding post on switch, 2. By throwing lever, 9, to the left, the direction of the current, and with it the motion of the motor, is reversed. ELECTRIC WIRING CONDUCTIVITY No part or particle of any substance on earth can ever get lost. It may change its form, but it cannot get away from the earth. There is now exactly as much water on earth as there was one thousand years ago, not even one drop more or less, while there is, of course, a constant change in its distribution over the globe, in the proportions of its three forms (gas, liquid, ice), and in its combinations with other substances. Heat con- sumed in expansion, etc., is called "latent heat." So, also, electricity, like any other force, cannot get lost, but it may change its form. When an electric current meets resistance its quantity is decreased, and the difference can be indirectly but accurately measured by the increased temperature of the resisting substance. Current electricity not transmitted is converted into heat. The several metals vary as much in their power of transmitting electric currents (conductivity) as they do in other respects. Silver and 'copper possess the greatest conductivity, tin and lead the smallest. The same fact may be stated thus : Tin and lead offer the greatest resistance to an electric current, silver and copper the least. Any sub- stance that offers great resistance is called a bad 309 310 ELECTRIC WIRING conductor ; the less the resistance (or, the greater the conductivity), the better a conductor is the substance. Conductivity is nearly zero for glass, sulphur, resin ; it is very low for most liquids and for gases. It varies not only with varying temperature, but also with varying tension, torsion, or pressure. It stands in proportion to the cross-section area of the conductor (wire). The following table shows at a glance that in the list of the metals named the heat evolved by an electric current increases in the inverse ratio as the conductivity decreases. The conductivity of gold is z / z of that of copper, the heat evolved is I or i^ times that of copper. The conductivity of tin is *4 of that of copper, the heat evolved is 6 times as large: Conver- Conduct- sion ing to heat. power. Silver 6 to 120 Copper 6 to 120 Gold 9 to 80 Zinc 18 to 40 Conver- Conduct- sion ing to heat. power. Platinum... 30 to 24 Iron 30 to 24 Tin 36 to 20 Lead 72 to 10 Silver wire conducts 120 units out of 126, losing 6; iron wire conducts 24 out of 54, losing 30; lead conducts 10 out of 82, losing 72. Silver, copper and gold are excellent for con- ducting strong currents; platinum and iron are used where very light currents are- required, as in telegraphing; lead is used where great resist- ELECTRIC WIRING 311 ance is desirable to check too strong a current, as in safety-fuses ; platinum is used in incandescent lamps because its expansion in heat is equal to that of glass ; zinc and tin find minor employment, as stated further on. For traction and electric lighting very strong currents are needed, and the conductors are, there- fore, made of copper wire of a size proportionate to the rate of flow desired, gold and silver being excluded by their costliness. Copper can be procured in sufficient quantity, is therefore cheap enough, and is very durable and flexible. The purer copper is the better. The law does not allow an alloy containing less that 96 per cent of pure copper for electrical purposes. Copper that has become brittle from some cause can be made soft again (annealed) by heating it dark cherry and plunging into cold water. INSULATION As dry air is a non-conductor, bare copper wires will conduct a strong electric current without losing any of it (without leakage). This is why telegraph, arc light and trolley wires a,re left without a covering. Moist air, all wet substances and water, are excellent conductors, and by one of the principal laws of electricity an electric current returns to its source by the easiest possible path, or along the line of least resistance. 312 ELECTRIC WIRING The ground, whether earth or lake or sea, is always ready to serve as the easiest and shortest path back to the source, and in order to have the current flow through all the wires of the circuit in undiminished force, and to provide against any portion of it taking a short circuit, the wires exposed to possible dampness, contact with water, or the like, are insulated, that is, they are covered with a dampness-proof, water-proof, non-con- ducting material. Such materials are glass, ebonite, paraffin, shellac, india rubber, gutta percha, sulphur, silk, porcelain, etc Some of these are suitable in some places and conditions, and others in others. Iron and porcelain are used for supporting bare wires. For telegraph cables gutta percha is used, which, however, is easily affected by heat, and cannot be used for insulating electric light wires carrying a large voltage. Instead, a fibrous matter (jute and the like), steeped in a resinous or bituminous compound, is used. India rubber (vulcanized to make it harder and more durable) is considered the best insulator for house wiring. To prevent decomposition of the rubber by the copper, the copper wire is usually ccj. . ~ which also makes soldering the joints easier. Then a cover of india rubber is put on, then a second cover of vulcanized india rubber. The third covering consists of india-rubber-coated ELECTRIC WIRING 313 tape ( okonite ), and over this tarred flax is braided and coated with a preservative compound. When the wire is so insulated, the electric cur- rent finds it easier to travel the length of it foi thousands of miles than to escape through the insulation, one-sixteenth or one-eighth of an inch thick. But remember, wherever the insulation is faulty or injured, admitting water or contact with any other good conductor, there the current escapes and returns by the shortest route to the source. Aside from the loss in lighting power, such defects are frequently the cause of disastrous conflagrations or of death. House wiring should be entrusted to experienced, skillful and con- scientious men only. For test of insulation, see page 281. SIZE OF WIR,E Two considerations determine the proper size of wire to be used in a circuit: The wire must be thick enough to carry an electric current of the desired voltage at the desired rate of flow, and on the other hand, to avoid unnecessary expense, it must not be thicker than necessary. If the wire is too thin, a portion of the current is converted into heat (see page 309), and the hot wire becomes a source of great danger. The fire insurance inspectors insist on this point, and rightly so. Of course, the light furnished by too thin a wire is very poor. 314 ELECTRIC WIRING CONNECTIONS A joint or connection must be solid, that is, it must not offer any more resistance than the wire itself, and must, therefore, be made with the utmost care. The second requirement is, it must be damp proof. The strands of copper are first cleaned by scrap- ing, then interlapped or scarfed, another wire is wound around the joint (especially in the case of Joints. large cables), and the whole is soldered. This gives a so-called hard joint. Then insulation is put on with equal care, first india rubber, and then okonite (india rubber tape), making a solid and dampness-proof insulation. ARRANGEMENT OF CIRCUITS The plan for the wiring of a building should be given great care and skill, requiring much experi- ence. v First, find the point at which the main circuit from the dynamo or supply-wire will be most conveniently divided up into a number of smaller circuits. A fault is easily located in a small circuit and cannot disturb the service except in its own circuit. A "central distribution board" is erected, and from this a small special circuit leads ELECTRIC WIRING 315 to each lamp, or, in a large building, cables run to a number of branch distribution boards, with which then the lamps are connected. It is best to connect each lamp with the distribu- tion board by two wires (parallel wiring). If all the lamps are strung along one common circuit (series wiring), all the lamps will be affected by any little irregularity, and the distribution of cur- rent is uneven. These disadvantages far outweigh the saving in the* first expense of installation. PLACING THE WIRES The greatest care should be taken to keep the wires absolutely free from dampness or water, since they establish at once a short circuit (earth, ground, leakage), and a portion or all of the electric current returns by the nearest path (by wall or pipe, or the like, and the ground) to the source. Another great cause of annoyance to be guarded against, is a short circuit by leakage from one wire to another through defective insulation, crossed wires, etc. The electric current, finding its way through dry dust, lint, rubbish, or wooden parts, heats them to the point of ignition, and a fire is the result. In placing the wires, neatness of appearance, safety from leakage, and protection from fire are the three points to be kept in mind. 316 ELECTRIC WIRING Wires without casings should be 6 inches apart for mains, and 2% inches for smaller sizes. Metal or glass tubing is a good protection against gnawing rats or mice, but insurance inspectors do not look upon them with favor for high-voltage circuits. The most serviceable casings are of well- seasoned hard wood, grooved. The fillets sepa- rating the grooves should be i% inches in width for mains, i inch for main branches, y 2 inch for smaller branches. The inside of wood casings should be painted with a fire-proof paint or com- pound, and the wires packed in with asbestos or silicate cotton. For chandeliers twin wires are generally used. They should be handled very carefully, and properly protected with cut-outs. CUT-OUTS What the safety-valve is for the boiler, the cut- out or safety-fuse is for the electric circuit. It consists of a short lead or tin wire of a siae propor- tionate to the greatest quantity of current required for the circuit. If the current increases beyond that point, the tin or lead wire, unable to transmit more than so much of the current, converts the excess into heat and melts (is blown), thus break- ing the circuit. The cut-out is a guarantee, therefore, against overloading the wire from any cause, short circuit, ELECTRIC WIRING 317 crossing wires, or negligence of dynamo attendant. The best place for the cut-outs is on the distribu- tion board, where the small circuits are connected to the mains. The circuits can thus be easily disconnected by removing the safety-fuse. For special purposes cut-outs are"" placed wherever desirable. THE SOCKETS Incandescent lamps receive the current from contact pieces in the socket of the "shoe," or ' 'plug, " or in a socket swinging on the circuit wires. Such plugs are frequently distributed along the walls of the rooms, for the sake of attaching a portable lamp to either one of them, wherever it may become desirable. This is a great con- venience. The socket is either a screw socket or a "bayo- net" socket. The latter is simply pushed in and turned around one-eighth, to make connection with the circuit. In the screw socket connection does not take place until the lamp is screwed in as far as it will go. To avoid the handling of the lamps when the current is to be turned on or off, a key or switch is provided. This key should never be placed any- where between full-off and full-on, not even for a moment, because in a partial connection the con- tact pieces will get heated and grave consequences may result at once or later on. THE ELEMENTS OF ALGEBRA BY PROF. O. H. L, SCHWETZKY Q. What is arithmetic? A. The science of numbers, or the science of numerical equivalents. Q. What does it teach? A. It teaches how to calculate or compute quantities by the means of numbers. Q. What is algebra? A. Sir Isaac Newton called it "universal arithmetic," meaning by this term, that algebra teaches the rules which apply to any and all numbers. Q. What is one of the principal differences between arithmetic and algebra? A. In arithmetic we have only 10 characters with which to work: o, i, 2, 3, 4, 5, 6, 7, 8, 9 and which, besides, have a limited meaning, variable by position only. In algebra, quantities of every kind may be denoted by any characters whatever. Q. -What are the characters mostly used in algebra? A. The known quantities in each case are generally denoted by the first letters of the 318 THE ELEMENTS OF ALGEBRA 319 alphabet, a, b, c y etc. , and the unknown quantities to be found are represented by the last letters of the alphabet, z,y, x, w, etc. Q. What do these characters represent? A. They represent any number chosen. If we assume a to represent-g, and b to repre- sent 3, then a-|-b=i2; and in a + b = c we would put c = 12, In a b = c we would have c = 6 ; inaXb = c, c would be =27; in a-r-b = c, c would be = 3- In a -r- b = c -5- x, x is the required answer, a, b and c being known quantities. Q. What signs are used in arithmetic? A. Plus (-(-) for addition, minus ( ) for sub- traction, times (X) for multiplication, by (-*-) for division, and equals (=) to show equality. Q. What signs are used in algebra? A. )-, and =, as in arithmetic. The X is rarely used. Instead of a X b the form a b is em- a ployed, or a . b . Instead of a -r- b we write e- Q. Name another difference. A. In arithmetic any operation that is readily performed is at once executed and the result 'sub- stituted, as 10 for 7 + 3, 3 for 10 7, 21 for 3X7, 7 for 21-7-3; but in algebra this is not done : a -\- b is called a sum ; a b is a quantity equal to the excess of a over b ; a b is a product ; r- is a quotient ; (a + b) (c + d) is the product of the two sums 320 QUESTIONS AND ANSWERS a -f- b and c + d ; a (b -\- c) is the product of a and the sum b + c ; a ( J is the product of a and the quotient , etc. c Q. Explain the use of the parenthesis, (), further? A. It means that the term enclosed in the parenthesis is to be treated as one quantity. If a = 9, b = 8, c 4, and d 3, then (a+b) (c+d) =(9 + 8) (4 + 3) = 17 X 7=H9; a(b + c) = 9 X 12 = 108 ; a ( J = 9 X 2 = 1 8. Q. Are there no definite numbers used in algebra? A. Yes. a-|-ais written 2 a; ab + ab-}-ab = 3 ab, etc. The definite numbers in this case are called numerical coefficients, or for short, co- efficients. a X a is written a a or a 2 , which is read ' ' a square." a X a X a is written a 3 , which is read "a cube," etc. In this case the figure indicates how many times a quantity is to be multiplied by itself, and is called the exponent. Q. In what relation does a stand to a 2 ? A. It is the square root of a 2 . Q. What is the meaning of a ^ "t" if"-* J A. That depends on the definite numbers to be substituted for the characters. If all the + quan- tities (positive quantities), a+(-?J + 6ac added THE ELEMENTS OF ALGEBRA 32! together give a larger quantity than the quanti- ties (negative quantities), b + 2 ab -j- d added to- gether, then the answer is positive, otherwise it will be negative. Q. How can a quantity be negative? A. In the case of bookkeeping it would mean that there is that much deficit or loss ; in traveling it would indicate that distance back of a certain point instead of forward; on a thermometer or steam gauge it would indicate so many degrees below zero instead of above, etc. Plus means "above zero," or "more than nothing," minus means " below zero," or " less than nothing." Q. What is the difference between a b + c and a (b + c) ? A. In the first case b is to be subtracted from the sum of a and c ; in the second case the sum of b and c is to be subtracted from a. The difference becomes clear by substituting definite numbers: 20 9+4 = 15; 20 (9 + 4) = 7- Q. What is the meaning of a (b + c) = a b c? A. It means that additions and subtractions may be performed in any order. We may either subtract the sum b+c from a, or we may subtract first b from a and then subtract c from the remainder. The result is the same. Q. Can you further illustrate the meaning of the minus sign ? 322 QUESTIONS AND ANSWERS A. i. a-|-b = c b a + 2/b = c Taking b away on one side is the same as adding +b, because -f-b b o. To keep the two terms at the sides of the = sign of the same value, we must add -|- b at the other side, too, which gives 2 b. 2. a ( b) = ab This signifies that " multiplication by a negative quantity" ( b) means "starting from the zero point in the opposite direction." If John has $500 assets, and Frank has ten times as much liabilities, he owes $5000. Also: If John owes $500, ( a), and Frank owes ten (b) times as much, he owes ( a) b = ab, or $5000. 3. (-a)(-b) = +ab This is the reverse of the above (2). The same principle applies. If John is $500 short, and Fred has ten times as large an amount of cash on hand, he has $5,000. Expressed as a rule, this simple truth presents itself as follows: Minus multiplied by minus produces plus, or, in other words, the product of 2 negative factors is positive. Q. Can you further illustrate this rule? A. i. A rich man said to his son: "I will make you the owner of a fortune 8 times as large as your present indebtedness." The son con- THE ELEMENTS OF ALGEBRA 323 fessed that he owed at that moment $7,000. To make good his promise, the father had to pay the debt and give his son $56,000 besides. 2. One ship sailed 200 miles due east from a port, while another steamed 3 times as far due west. They were consequently 800 miles apart, one being 200, and the other 600 miles, from the port, in opposite directions. 3. An open siphon, one arm o'f which had a five times larger inside area of cross-section than the other, was provided with a scale, and filled with water to the zero point of the scale. A piston was introduced in the wider arm, and pressed down, until the water surface in this wider arm stood at 3 inches below zero. Where was the surface in the other, smaller arm? Ans. ( 3) ( 5) = -f- 15. Q. What is the meaning of a( j = ? A. It means that multiplications and divisions may be performed in any order. Q. What advantage does algebra give? A. It gives short characters instead of long numbers, and tedious multiplications, etc., are avoided, as no such operations need to be executed, except in the answer, where the given values are substituted. THE TRACTION ENGINE A traction engine is a locomotive for common roads, and by throwing the driving wheels out of gear is converted into a stationary engine. As a traction engine it is steered by a worm gearing, which turns a winding shaft, on which a chain is wound and unwound, drawing one or the other front wheel back, according to the direction in which the engine is to run. The engineer steers by turning a hand-wheel controlling the worm gearing. The driving wheels have V-shaped projections on their rims to prevent slipping. They get their motion through differential or compensating gears from the engine. (See cut page 326.) The motion of the engine is reversed through a special device, a single eccentric reversing gear, or through a reversing rack. (See pages 330, 331). THE TRACTION ENGINE 325 Coal and water are carried in the combination tank. For turning the curves of a road one of the drivers is loose on the shaft, so that it may run a longer or shorter distance than the other driver, without straining the axle or connections. For running on a straight road, the loose driver is made solid with the shaft by inserting the key A into slot B. As a stationary engine (the drivers being thrown out of gear), the pulley- A. face fly-wheel (or a friction clutch wheel, see page 326), fur- nishes the power by means of a belt. The rear axles and brackets of all good traction engines are placed back of the firebox, so that the* weight will be well distributed between the fore and aft wheels. Short axles riveted to the sides of the firebox are very dangerous. DIFFERENTIAL OR COMPENSATING GEAR The differential or compensating gear is arranged as seen in the cut: A is a large bevel THE TRACTION ENGINE wheel (loosely set on the axle), carrying three pinions, B, so distributed over it that they together engage the ground wheel by meshing either with C or D, ac- cording as the engine is to travel forward or b a c k- ward. C is bolted to the main drive- wheel ; D is keyed on t h e axle. A gets its motion from the engine through the in- clined shaft and the bevel pinion, E. FRICTION-CLUTCH FLY-WHEEL The fly-wheel of a traction engine must allow of being thrown in and out of gear easily. One of the most convenient de- vices for this purpose is the friction clutch shown in the cut. The wheel has diam- etrically placed a driving- arm, A, to which is cast a sleeve, B, surrounding the axle of the wheel. The end of B carries the pinion C, keyed to it at D. Both ends of the driv- ing arm A Have a cast- iron shoe, E, loosely bolted to them. The bolts are solid with A. These shoes are hollow and rilled W T i t h hard - wood blocks with a surface curved to correspond exactly with the inside surface of the wheel rim, THE TRACTION ENGINE 327 turned true. The free ends of the shoes are pro- vided with a toggle-joint (or turn buckle joint), G, G, by which the wood is pressed firmly against the wheel rim, when the fly-wheel is to be engaged. The toggle-joint is worked by throwing the collar F, which loosely fits around the sleeve B, toward the wheel. This is done by means of a lever within easy reach of the engineer, but not shown in the cut. CROSS-HEAD A is the piston rod with threaded end. B is the piston lock-nut, C is the cross-head frame. D, D are the slide blocks, E,E are the cap screws which hold the slippers (slides), D, D, to the cross-head frame. F, F are the adjusting screws for taking up the wear of the slides. This is done (about once a year) by slightly slacking out the bolts E, E, and screwing in the screws F, F, until the lost motion is taken up. G is the small end of the con- necting rod containing the brasses, adjustable by means of a screw bolt, H, engaging with a beveled block in the strap, said bolt being locked in position by jam-nut K. The cross-head pin, L, can be removed by unscrewing the nut from the pin and driving the pin out of the cross-head frame by means of a hammer and a wooden block. 328 THE TRACTION ENGINE DIMENSIONS AND HORSE-POWER OF TRACTION ENGINES Their speed is about 250 revolutions a minute. Ten-inch Stroke Simple High-Pressure Engine. Ten-inch-Stroke Compound Tandem. Horse Diameter Horse Diameter in inches. Power. in inches. Power. HighP.Cyl. L/ow P. Cyl. 9 7X 12 $X 8X 12 8X 15 6^ 9 15 9 20 7 10 20 10 25 7% n TANDEM COMPOUND CYLINDERS AND VALVE MOTION The Tandem Compound Traction Engine does not differ much from the plain single cylinder engine, in operation, or in the care it requires. Where the work (load) amounts to the full horse- power capacity of the engine, the tandem com- pound is economical, otherwise it is wasteful. The accompanying cut shows the very simple and compact arrangement of the two cylinders (one high and one low pressure) and the slide valve. The cylinders are cast separately and bolted together at U. The partition R is cylinder head for both cylinders, is held in place by jam bolts (Y), and at S the piston rod passes through its center. The packing is metallic ^and does not need adjustment or renewal. One piston rod carries the two pistons, A, B. By unbolting at U, U, the interior of the two cylinders is reached easily. Only on the larger or "low pressure" cylinder is there a steam chest, valve seat, etc. In order to connect with both cylinders, the slide valve and seat are arranged as follows : Steam for the boiler enters through H into X, a chamber formed by the hood enclosing the slide valve. This hood and the slide valve proper are one casting, and move THE TRACTION ENGINE 329 together in the steam chest, M. The passages I, I communicate with M. From X the live steam passes through L into E in the high-pressure cylinder. At the end of the stroke, X and K com- municate and live steam enters from X through K (see dotted lines) into D at the other end of the high-pressure cylinder, reversing the piston motion. The expanded staam in E exhausts through L into the receiving chamber, M, and from there passes through I and N into G in the low-pressure cylinder. The steam expanded in D exhausts through K into M, and passes from there through I, P into F. P and N finally carry the steam exhausted from the low-pressure cylinder off through O. Port J in M serves to admit live steam to facilitate starting the engine. After starting, it is closed. The low-pressure cylinder must be larger than the high-pressure cylinder, because the expanded steam, exhausting from the latter into the former, is so much weaker than live steam that it requires more piston area 'to work on, to furnish the same pressure as the live steam exerts on the smaller piston area. The proportion of the areas is closely culiulated by experts; roughly it maybe said to be 1:2. See table, page 328, For more explicit information on compound and pther engines see pages 96, 104 and 133. 330 THE TRACTION ENGINE Some engineers have asked why the valve was not worked directly by the piston rod, by means of a lever of the proper kind and proportion. (See leverage, page 241.) In the beginning the valve was worked in that crude way, and, at the very first, by hand. The necessity of economy, how- ever, in the consumption of steam has led to the devising of eccentrics, link motion, compound engine, single eccentric, etc. SINGLE ECCENTRIC, VALVE AND ENGINE REVERSING GEAR For general information about the eccentric, see page 116; link motion, page 144. A traction engine must necessarily have the most simple possible attachments. A very simple and ingenious valve and reversing gear is shown in the cut. There is only one eccentric. To the eccentric strap, which carries the valve rod, a roller is pivoted a little above the valve rod pin. The roller runs in a guide, the position of which is regulated by the re- verse lever, to which it is connected by a "reach rod." Chang- ing the angle of the guide reverses the en- gine, or it may simply shorten or lengthen the travel of the valve and thereby change the point at which the steam is "cut off." Besides its extreme simplicity, this device has the further great advantage that it makes the lead of the valve "constant," that is to say, the lead does not vary with the travel, as it does in link motion. The valve gives a quick, full opening at exactly THE TRACTION ENGINE 331 the right moment, admitting steam promptly at the dead points. Also, it cuts off quickly, giv- ing quick expansion. To reverse, the lever is thrown back to the furthest notch on the quadrant. To stop, the lever is placed in the center notch. By holding the lever between the center notch and one of the other notches, the stroke of the slide valve may be set at any aesired length short of its extreme travel. This is done by economical engineers, when the load is light The whole gear is so simple and durable that no skill is required to run it, or to replace and adjust it. The eccentric has its center almost directly opposite the crank pin, so that the roller will stand exactly over the center of the guide, when the engine is at either dead center. This renders it easy to find the correct position of the eccentric. To set the valve, the eccentric rod is then adjusted so as to give equal lead at both ends of the valve. REVERSING RACK For throwing the eccentric into the reverse position, the reversing rack shown in the accom- panying cut is used on simple or single cylinder engines. Where the eccentric is cut away in the cut, the arrow shows the reversing rack. 332 THE TRACTION ENGINE STACKER GEARING ANDi TURNTABLE A, A is the upper frame; B, B is the lower frame. C is the lower frame chair bracket, with a central hub, and the pocket D, in which a collar turns, that is attached to the upper frame chair bracket E. The center gear shaft turns in the lower frame hub and in the upper frame collar, and is geared below (miter gear F) to the main shaft, G, driven by pulley H, and above (miter gear I, K) to the sprocket wheel shaft L. M is the shaft box. N is the bracket for the pin which, by means of the lever O, serves to clutch the three- wheel gear P, P, P, with the main shaft G, around which it fits loosely. When so engaged the pinion Q at the other end of the sleeve engages pinion R and the shaft S, at the other end of which there is THE TRACTION ENGINE 333 a bevel spur wheel, T, driving U and V in opposite directions. The reversing spool, W, serves to throw shaft X into gear with either U or V. W is worked by means of the lever Y. Z is a universal joint, enabling shaft a and worm b to be thrown out of gear with the turntable d by the lever c. The turntable d is attached to A, A, pivots around the central shaft in the collar in D, and has a ball- bearing, E, E, attached to the lower frame. The shaft L drives the working shaft /"by means of the sprocket wheels g, g, h, h. The three pulleys on shaft/ drive the different parts by belting. Lever O starts or stops the stacker; lever c starts or stops the turntable d; lever Y controls the direction in which d turns. When the turn- table is thrown out of gear the stacker may be swung around by hand. 334 THE TRACTION ENGINE THE STACKER The cuts show a straw stacker, both folded and in operation. The folding and unfolding are done by hand or steam power. A carrier, 24 feet long, delivers the straw from the hopper of the threshing ma- chin e to the stacker. The stacker carries the straw to the desired height and dumps it on the stack. The mechanism of the turntable, reversing gear, etc., are fully described on pages 332, 333. JOURNAL-BOX BABBITTING 335 *.-? "a V u Standard Babbitts M u P. ^; c3g a o a a a ^ * U H N H High Speed Babbitt... IO 16 ^ 70 IOO Medium or Common... 4 6 QO IOO Machinery Bearings... 8 12 IOC Muntz Metal . 60 /in IOO German Silver 33 '/ 20 I/ IOO White Brass IO IO 80 IOO Fine Yellow Brass 66 34 IOO Gun Metal for Valves, etc 90 IO IOO Journal Brasses for Rods etc 80 17^ 2 // IOO In melting babbitt metal care must be taken not to burn it by overheating. Melt a part first in small chunks, and add remainder gradually. As soon as all melted, remove from fire and skim off the dirt. If heated beyond the melting point the softer components evaporate and leave the mass in a pasty condition. When about to babbitt a journal wrap one thickness of common writing-paper smoothly around the bearing, fastening it in place with twine wound around in a regular spiral line three- sixteenths of an inch apart. The paper keeps the babbitt from getting chilled by the journal. It will, therefore, have a fine surface, and will also fit just right without any scraping. The twine leaves nice oil grooves. Before pouring the metal through the t>il-hole, make sure the journal is level and in central posi- tion. By means of two pasteboard rings fitting the journal, the ends of the box are closed, using putty or soft clay. A high funnel of clay^ is made around the oil-hole to facilitate the pouring in of the babbitt, and to increase the pressure, so as to have the babbitt fill the box perfectly. 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