Mechanics Department J THE STEAM pCINE .INDICATOR AND ITS ; APPLIANCES. BEING A COMPREHENSIVE TREATISE FOR THE USE OF CONSTRUCTING, ERECTING AND OPERATING ENGINEERS, SUPERINTENDENTS, MASTER MECHANICS, AND STUDENTS, DESCRIBING IN A CLEAR AND CONCISE MANNER THE PRACTICAL APPLICATION AND USE OF THE STEAM ENGINE INDICATOR, WITH MANY ILLUSTRATIONS, RULES, TABLES, AND EXAMPLES FOR OBTAINING THE BEST RESULTS IN THE ECONOMICAL OPERATION OF ALL CLASSES OF STEAM, GAS AND AMMONIA ENGINES, TOGETHER WITH ORIGINAL AND CORRECT INFORMATION ON THE ADJUSTMENT OF VALVES AND VALVE MOTION, COMPUTING HORSE POWER OF DIAGRAMS, AND EXTENDED INSTRUCTIONS FOR ATTACHING THE INDICATOR. ITS CORRECT USE, MANAGEMENT AND CARE, DERIVED FROM THE AUTHOR'S PRACTICAL AND PROFESSIONAL EXPERIENCE, EXTENDING OVER MANY YEARS, IN THE CONSTRUCTION AND USE OF THE STEAM ENGINE INDICATOR, BY- WILLIAM HOUGHTALING. II THE AMERICAN INDUSTRIAL PUBLISHING CO., PUBLISHERS, BRIDGEPORT CONN., U. S. A. Engir- Library COPYRIGHT 1899 WILLIAM HOUGHTALING. ALL INTEREST AND RIGHTS RESERVED. DEDICATION. To the young Engineers of America, who by thoughtful and careful study ; are seeking to make their opportunities and overcome obstacles in the care and management of the Steam Engine; this volume is respectfully inscribed by THE AUTHOR. 35761 PREFACE. The preparation of this book has occupied most of the author's spare time for a number of years. Originally the matter was not intended for publication, but the manuscript has grown so large and complete, which consideration, combined with many repeated re- quests, has induced the writer to publish the matter in book form. Let every Engineer make his own Indicator book as he proceeds in his study and practice, and it will prove invaluable in after years. The present work has been compiled in this way, from data contin- ually obtained during the author's professional career, extending over a third of a century. The introduction of algebraical formules have been avoided. These are readily found in the many valuable mechanical Pocket- Books. The writer has endeavored to discuss the principle and use of the Indicator in as plain common sense words as the subject and the English language will admit of. Special attention has been given to the requirements of the young progressive student in Steam Engineering. The preparation of the following chapters has been a work of pleasure to the author, and if they prove beneficial to his fellow- workmen, he will be amply repaid. CHAPTER. BRIEF HISTORY OF THE INDICATOR, - ... I t PURPOSE OF THE INDICATOR, - II. DEFINITION OF TECHNICAL TERMS, - - III. CONSTRUCTION OF THE STEAM ENGINE INDICATOR, - IV. INDICATOR APPLIANCES, . V. INDICATOR APPLIANCES, CONTINUED, ... VI. INDICATOR REDUCING MOTION, . . . VII. DRUM STOP AND ELECTRICAL ATTACHMENT, ... VIII. CARE AND USE OF INDICATOR, ... IX. To TAKE DIAGRAMS, - ... X. INDICATOR DIAGRAM ., ... XL STUDY OF DIAGRAM::, - ... XII. LINES AND POINTS OF THE DIAGRAMS, . . XIII. ISOTHERMAL CURVE, - - . XIV. ADIABATIC CURVE AND POINT OF CUT-OFF, - - - XV. THE FOOT POUND AND MEASUREMENT OF DIAGRAM, - - XVI. EXPANSION OF STEAM, - . XVII. HYPERBOLIC LOGARITHMS, - - XVIII. THEORY OF ACTION OF STEAM EXPANSION IN CYLINDERS, * j XIX READING THE DIAGRAMS, - - XX. DIFFERENT METHODS OF COMPUTING WATER CONSUMPTION, - XXI. INDICATOR TESTING DEVICZ, - - XXII. PLANIMETERS, ... XXIII. COMPARISON DIAGRAMS FROM THROTTLING AND CUT-OFF ENGINES, XXIV. THE ECONOMY OF EXPANSION, .... XXV. THE POINT OF CUT-OFF, ... XXVI. BACK PRESSURE AND COMPRESSION, - - XXVII. COMBINING THE DIAGRAMS FROM COMPOUND ENGINES, - - XXVIII. DIAGRAMS FROM GAS AND OIL ENGINES AND AMMONIA COMPRESSORS, XXIX. MAKING CALORIMETER TESTS, .... XXX. MISCELLANEOUS DIAGRAMS, --..__ XXXI. ENGINE ECONOMY, - _ . . * XXXII. TABLES, XXXIIL CHAPTER I. BRIEF HISTORY OF THE INDICATOR. The idea embodied in this important and instructive little instrument, was originated by the celebrated James Watts dur- ing the latter part of the last century, at a very early period in the history of the steam engine, and it has since then in its improved forms, materially contributed to the perfection and efficiency of our modern steam engines , not only by enabling the engineer to ascertain the exact values of the forces from which the power is derived, but also by pointing out the pre- cise periods, in relation to the different parts of the stroke, at which these elements of power come into action. The original machine of Watts, consisted simply of a cylinder, about six inches long and one inch in diameter, in which there was a closely fitted piston ; and was attached to the engine cylinder by means of a suitable pipe, fitted with a valve to open or close communication between them. A long open coiled spring was used, of which one end was fastened to the piston, and the other to the cover of the indicator cylinder ; this spring resist- ed the pressure of the steam, in one direction, and also the pressure of the atmosphere in the other. 12 Steam Engine Indicator A pointer was connected to the piston, and moved directly with it and served to locate the atmospheric line, or zero ; and all motion of the pointer was above or below that point. There was no pajie^ \drum ^ i:he pointer merely indicating on a scale, the highest " and lowest pressure in the engine cylinder, measured front th^^tmospn^riG }ii?.e f ; An improvement on this instrument was made by adding a flat slide to which a sheet of paper was secured and giving it a coincident motion, on a re- duced scale, with the engine piston, by attaching a cord from it to the crosshead or some other moving part of the engine, and returning the same by means of a counterweight. The machine in this improved form, though crude in comparison and less compact in construction, was almost identical in prin- ciple of its operation, to the many different instruments now so extensively in use, and it enabled him to ascertain the exact mean effective steam pressure throughout the stroke, and also the proportion which the vacuum in the cylinder, at different parts of the stroke, bore to that in the condenser, in order to determine the dimensions of cylinder required for any given power, as also the relative proportion proper to be given to the steam and exhaust ports, of- the slow speed engines of his ex- periments. Having attained the objects, he left for succeeding engin- eers to devise, improve, and put into such a compact and por- table form, as to be easily applicable to steam engines of every description ; to such an extent as we find the modern indicator of to-day. One of the first to improve on the instrument of Watts, and nearly one-half a century later, was Wm. Macnaught of Glasgow, who constructed an instrument represented at one- quarter actual size in elevation, Fig 1 , i, and in plan, Fig. 2. Unlike the indicators of to-day, that have a parallel and multiplied movement of the pencil as compared with the pis- ton; in this instrument the movement of both are coincident, And Its Appliances. that is, whatever motion is imparted to the piston by the steam, the pencil moves precisely the same distance either way. As constructed in this way, the spiral spring op- posing the fof^Qf't-he steam against the pis- ton, is liable to disarrangement, and uneven- ness; o6,'8 ; ocQi;r^ J ofH^^g-?'^ter length of spring necessary to obtain cards of a conven- ient height for computation. Its consequent general adoption has led to many very important, and decided im- provements in the construction of the instru- ment, and very materially aided in elevating the standard of duty of steam engines, and also demonstrated the economy resulting from a liberal use of the expansive power of steam. From a glance at Figure i , it will be per- ceived that the Indicator is neither more nor less than a small single acting steam engine with the addition of a spiral spring on the op- posite side of the steam piston, to resist the force of the steam. The many treatises at the present day on the steam engine indicator, leaves little to be said in reference to the actual manipulation of the instrument in practice : and we now find almost all of the Stationary, Locomotive, Marine, and other engineers imbued with the necessity of un- derstanding the working of the indicator in all its details, not only in the interest of their employers, but particularly for their own personal benefit, in acquiring a knowledge of the intricate working of steam, or other operating forces, of their engines, in all their various details, and which becomes neces- sary to enable them to reach a place in the higher ranks of en- gineering science. FIG. 2. 14 Steam Engine Indicator The principal parts of an indicator, of the most complete construction, consists of an outside cylinder, or body, inside of which is secured an inner or working cylinder ; with a nicely fitting piston, 1 6; exactly 1 >h-half of a square inch in area, equal to about .7^8 9f'an mcli in v djameter, working therein. The pist^H&'i$*ir*Q^i3$$f&443 the working cylinder of the indicator, that at the pressures of from two to three hun- dred pounds per square inch, there is but a very small amount of steam that can pass by or through it ; but all indicators are subject to a certain amount of leakage of the piston, and for which ample means are always provided for its escape ; in or- der to avoid any unnecessary back pressure on the side of the piston opposite the steam pressure. Where the indicator is to be used for obtaining cards, from pressures ranging from four to six hundred pounds per square inch, it is advisable to use a reduced size of working cylinder and piston; the area of which, shall only be one-fourth of a square inch; equal to about .5641 of an inch in diameter, thus avoiding the use of indicator springs of a very high tension. The different sizes of the working cylinders, and their pistons, are made interchangeable in the indicator,, so that either can be removed at any time, and the other substituted. One end of the piston rod is connected to the piston, by a ball connected joint, and the opposite end to some part of a pencil mechanism, for producing a so-called parallel, or straight line movement of the pencil, up and down, in reference to the paper drum. The parallel motion is another beautiful and ingenious in- vention of Watts, as he applied it to steam engines, for the purpose of guiding the piston rod, back and forth in a straight line ; and without the intervention of any guides, or other means, for the purpose ; thereby eliminating friction to a great extent; with smooth working, and providing a mechanism that has since been used in various modified forms, and adapted, to. A nd Its Appliances, \ 5. a certain extent, to different kinds of machinery where a motion of this principle is desired. The parallel motion, as applied to his engines, was consid- ered by Watts, notwithstanding his other inventions, to be the one which gave him the greatest satisfaction and pride, as it performed its mission with the best practical results; even though not absolutely mathematically correct in some respects. In most of our modern indicators this principle of mechanism, for their pencil movement has been almost universally adopted in its various and possible modified forms, and constant efforts in this direction are being made, with a view of eliminating the slight inaccuracies that are known to exist in the original parallel motion ; particularly in the constant varying ratio of the movement, that exists between the piston and the extreme end of the system or the point at which the pencil is located. The parallel or straight line movement of the pencil is usually produced by a system of levers and links of definite lengths, and pivoted in such a manner that by any movement of the system, up or down, the end of the lever carrying the pencil is always expected to move in a straight line, and also in some exact ratio to the movement of the indicator piston. 1 6 Steam Engine Indicator CHAPTER II PURPOSE OF THE INDICATOR, The Steam Engine Indicator is an instrument originally designed for recording the varying pressure of steam in an en- gine cylinder ; at any, and all points during the revolution of the engine, and has subsequently been applied under many, and various other circumstances, wherever the record, and measure of an irregular pressure has been desired. The production of this record is the result of two motions, and is traced by the indicator pencil upon paper that is secured to a light cylinder, called the paper drum. To this drum is imparted a rotary oscillating motion upon its axis, at right angles to the motion of the pencil ; such mo- tion being derived from the cross head, or any part of the en- gine having a movement coincident with it. The motion of the pencil is produced by the varying pres- sures of steam acting against the indicator piston ; in opposi- tion to the strength of a spring of known tension. Conse- quently, an indicator properly attached too, and communicating with the interior of the cylinder of a steam engine in operation, and the drum given a motion (on a reduced scale) correspond- ing to that of the engine piston, will, (on bringing the pencil in contact with the paper upon the drum, during its oscilla- tion), trace the outline of an irregular figure upon the paper, which is usually known as, and called an Indicator Diagram, And Its Appliances. 17 an example of which is represented in Fig. 3, and shows the varying pressure acting against one side only of the piston, dur- FIG. 3. ing a revolution of the engine; and such pressures can be properly located, and correctly measured. The upper line C. D. E. F. of the diagram represents the force of the steam impelling the piston during its forward stroke ; while the back pressure line B. B. shows its retardation on the return stroke ; the average height of each being meas- ured, (by the scale of the spring), from the atmospheric line A. A. The difference between their average height, represents the Mean Effective Pressure, usually designated the M. E. P. of the diagram. The atmospheric line A. A, is also drawn by the indicator but at a time when steam communication between it, and the engine cylinder is closed ; and consequently subjecting both sides of the Indicator Piston to atmospheric pressure only. 1 8 S tea) n Engine Indicator To show the pressure on the other side of the engine pis- ton, another diagram must be taken from the opposite end of the cylinder. In most calculations of the diagrams, it becomes desirable to draw, by hand, additional lines, from and by which, the actual lines may be compared. First, the straight line V. V. is drawn to represent the ab- solute vacuum, or absence of all pressure. Second, the line V. O. represents the clearance volume, and is drawn at right angles, (or perpendicular), to the atmos- pheric line. Third, the line O. O. is drawn to show the full boiler pressure in order that it may be seen on the diagram how near that pressure has been realized. The different lines, and events of the stroke, as shown by the diagram during a revolution of the engine, and the name by which they are designated will be noted, and explained in a later chapter. Diagrams taken from different engines, and under vary- ing conditions, will present themselves in an almost endless variety of forms, depending entirely upon circumstances con- nected with the operation. The earlier forms of the instrument, (although the same in principle), were crudely constructed, the moving parts ex- ceedingly heavy ; inducing vibrations, sufficient to vitiate, and distort the diagrams ; also causing more or less tardiness at the different events of the stroke, such as admission of steam, point of cut-off, and also compression ; because of the heavy parts being unable to respond so promptly to change of pres- sure ; thereby making them unreliable, and imperfect in their action, to an extent depending upon the weight of the pencil mechanism, rapidity of rotative speed, and also suddenness of change of pressure ; and therefore preventing their being suc- cessfully adaptable, only to engines of very low rotative speeds.. And Its Appliances. 19 The prevalence of many high speed engines in use at the present time, renders the use of the old type of indicators al- most useless, and wholly unsuited for high speed, where any reliable results are expected, as many details which gave little trouble at low speed, seriously affect the results at the higher speeds. The present improved construction of some of the various modern indicators, in which perfection is attained as near as can be expected, consists principally in superior designs, sim- plified construction, a better adaptation of the pencil mechan- ism, also finer adjustment, convenience of manipulation, and especially extreme lightness of the moving parts, thereby practically eliminating the effects of inertia, and momentum of these parts. These qualities in any Indicator are absolutely indispensi- ble in order to secure accurate and reliable results from high speed engines. The information that may be derived from a careful and attentive application of the Indicator to engines of all descript- ions, is almost incalculable to the engineer ; because many facts are accurately determined by its use, that cannot be ob- tained in any other way, with any great degree of satisfaction or correctness ; consequently its use has enabled the engineer to discover many unforseen, and necessarily unknown defects ex- isting in the engine, that have formerly been veiled in mystery, and at the present time, its value is so universally recognized, and relied upon, that most manufacturers of high grade en- gines, make provision for its application; and do not consider their engines complete until the valves have been correctly ad- justed by the use, and assistance of the indicator, and set in such manner, as that the maximum efficiency of the engine shall have been attained. 2O Steam Engine Indicator CHAPTER III, DEFINITIONS OF TECHNICAL TERMS. The many terms, generally used in connection with the study of steam engineering, are all measurable ; each with reference to some established unit, and by which they are clear- ly defined, and their correctness recognized. Some of these are indispensible to the engineer, a few of which are briefly described, and explained as follows: The Unit of Work is equal in amount to the power required to lift one pound, one foot high, and is called the Foot Pound. The Unit of Heat, or Thermal unit, is the quantity of heat necessary to raise the temperature of one pound of water, one degree, or from 39 to 40 Fah. Also, one unit of heat is equal to 772 foot pounds or units of work. The Sensible Heat of any body, as Air, Water, or Steam, is the heat that is sensible to our touch, and in extent is as shown, and measured by the thermometer. Latent Heat of steam is the quantity of heat, (expressed in heat units), required to vaporize ivater, that has previously been heated to a temperature equal to the resulting steam, of vaporization. Specific Heat is the quantity of heat necessary to raise one unit of weight of the substance, through one degree of temper- ature, measured in thermal units. And Its Appliances. 2\ Saturated, or Dry Steam, is steam confined under pressure in contact with the water from which it is formed, and contains just sufficient heat to maintain the water in a state of steam, and will vary in pressure, and density corresponding to vary- ing temperatures. When saturated steam suffers any loss of heat, a condensa- tion of some of the steam also takes place. Superheated Steam is steam containing an excess of heat. If to saturated steam more heat be added, its temperature will increase, and the steam is said to be superheated, because its temperature will be greater than that. corresponding to satur- ated steam of the same pressure. This excess may be parted with, without condensation. Horse Power (H. P.) is the standard used for measuring the power of a steam engine, and is equal to lifting 33,000 pounds one foot high in one minute of time, or 550 pounds in one second, or any equivalent thereof in opposition to the force of gravity. Indicated Horse Poiuer, (I. H. P.) is the horse power of an engine as computed from the Indicator Diagram. If the mean area of the piston be multiplied by the mean effective pressure exerted against it, and also by its speed in feet per minute; this product on being divided by 33,000, will be the indicated horse power of the engine. Net Horse Power is the indicated horse power of an engine less the horse power which is consumed in overcoming its own friction. Boiler Pressure is the pressure above atmosphere, or the pressure as shown by a correct steam gauge. Initial Pressure is the pressure in the cylinder acting against the piston, at or near the commencement of the stroke of the engine. Absolute Pressure is the pressure of the steam calculated from absolute vacuum. 22 Steam Engine Indicator It is the pressure as shown by a steam gauge, with the pressure or weight of the atmosphere added thereto. Terminal Pressure is the pressure above the line of abso- lute vacuum that would exist in an engine cylinder, provided the release of the steam had not taken place until the end of the stroke had been reached. Usually the release happens earlier, and in such case its position may be located by continuing the expansion curve by hand from any point of release, to the end of the diagram. The terminal pressure must always be measured from the vacuum line ; consequently it is the absolute terminal pres- sure. Mean Effective Pressure (M. E. P.) is the average of all the varying pressures at different parts of the stroke, exerted against the engine piston to impel it forward ; less all the pressure that acts on the opposite side of the piston to retard its progress. Back Pressure Line, in a non-condensing engine, represents the loss that occurs, from the retardation of the escaping steam ; due to atmospheric or other pressure It is indicated on the diagram by its height above the at- mospheric line, and is expressed in pounds per square inch. On the diagram of a condensing engine it is indicated by its height above a line drawn by hand to represent the pres- sure in the condenser. Total Back Pressure is represented on the diagram by its height above the line of Absolute Vacuum. Initial Expansion is the fall of pressure along the steam line; which often happens in an engine cylinder, between ini- tial pressure, and the point at cut-off. Compression is a result caused by the action of the piston in compressing into the clearance space, all steam remaining in the cylinder after the exhaust valve closes. And Its Appliances. 23 Clearance is all of the space or waste room between the piston at the end of its stroke, and the face of the valve. Its volume or amount is usually expressed in its per cent- age of the piston displacement. Piston Displacement is the distance passed over by the piston in traversing a single stroke. Its volume is equal to the area of the piston in square inches, multiplied by the length of stroke, in inches, the pro- duct is the volume of displacement in cubic inches. Wire Drawing is a term sometimes applied to the action of steam, and arises in consequence of very restricted steam passages, also dilatory valve motion, thereby reducing more or less, the pressure in the engine cylinders, and usually consid- ered to be a loss in the matter of economy. Valve Lap is the excess of length of the valve at each end; (when at the middle of its stroke) over the extreme outer edge of the steam ports ; and is designed to serve as a cut-off valve within certain limits. Valve Lead is the amount of opening of the steam port, '(permitted by the valve) for the admission of steam to the cylinder, just before the piston arrives at the extreme end of its .stroke ; the entering steam thereby serving as a cushion for the reciprocating parts of the engine. Water or Steam Consumption is the amount of steam ac- counted for by the indicator, per horse power per hour ; and is & measure of the economy of the engine. Steam Engine Indicator CHAPTER IV. CONSTRUCTION OF THE INDICATOR. In the various constructions of the pencil mechanism at the present time, it may be said to be the essential difference between almost all indicators, and still further efforts are being made in this direction, in order to produce; ist, the nearest perfection to straight line movement of the pencil ; 2nd, equal ratio of movement between the pencil and the piston ; 3rd, in lightness of the moving parts, and by the latter effort, reducing the mo- mentum of these parts to a minimum, thereby produc- ing diagrams that may be considered reliable and ac- curate ; 4th, in the de- signing or arranging of all the parts so that they be most easily accessible and convenient for the oper- FIG. 5. ator when taking grams. dia- For our intent and purpose, it is not necessary to describe more than one of the various instruments in the market to-day, and we have in preference to all the others, selected the well known improved new style Tabor Indicator, as shown in Figs. And Its Appliances. 25 4, 5 and 6 as being the instrument more nearly fulfilling all of the conditions and requirements named ; and which are abso- lutely necessary for the production of the most accurate results in Indicator practice, including lightness of moving parts; thereby reducing momentum ; and also for ease and conven- ience to the operator in handling the instrument while taking diagrams. In order that the particular advantages of this instrument may be thoroughly understood, it is necessary that a brief de- scription of its construction, and ar- rangement of parts, should be given here. The principal and most important peculiarity of this instrument from all others, lies in the method em- ployed to communicate a straight line motion to the pencil, and at the same time of producing an exactly equal ratio of movement between the piston of the Indicator and the pencil ; both of which are perfectly FIG. 6. accomplished by means of a steel plate, through which there is a slot (as shown, full size, in Fig. 7), of such contour, or shape, as to exactly counteract the tend- ency to a radical movement of the pencil bar; this slotted plate is attached in an upright position on the swivel plate of the instrument, and upon which the whole pencil mechanism is self contained. The swivel plate is in turn secured to the cylinder cover of the instrument ; said cover serving as a cen- ter, upon which the entire pencil movement can be revolved in either direction, until it conies in contact with the paper drum. In order to make this slot in the plate available for the purpose, a small stud is secured on the pencil bar, upon which there is mounted a hardened steel roller, fitted so as to 26 Steam Engine Indicator travel in the slot from one extreme to the other; and in doing this, the pencil is caused to move in a straight line up and down the paper drum, and also in an exact ratio, throughout any and all parts of its movement, of exactly the distance moved by the indicator piston. The radial slot in the plate is an irregular curve and de- viates slightly from a true circle ; the irregularities existing in the curve, just compensating for the error that would occur in case a radial link was substituted, and corresponding in length to the average radius of the slot ; where one end of said link is pivoted to a stationary point and the other to some part of the pencil mechanism ; a method now employed in a number of the well known indicators at the present time, and the results are, that the lines made by the pencil, which are supposed to be straight, are not so, nor are the ratios of piston and pencil equal. A radial link, the end of which always moves in a true circle, is therefore not a success- ful substitute for accuracy, as compared with the irregular curve in the slot plate of the Tabor Indicator, as said slot which guides and controls I^very movement of the pencil being so formed is to give the most accurate results, in every FIG. 7. position the pencil bar may assume. There is another plate of exactly the same outline, as the slot plate (but without slot) and secured coincident with it ; the roll stud in the pencil bar projecting far enough through it to make contact with said plate, and serves to receive any pres- sure that may occur when the pencil is brought in contact with the paper drum in the act of taking diagrams ; and it also pre- vents the tortional strain that would otherwise come on the center and back links, thereby reducing the friction from this cause to a minimum. O o And Its Appliances. 27 These plates are provided with a projecting part on their lower ends, which are drilled and tapped to provide for a screw passing- through, to regulate the pressure of the pencil upon the paper drum, said screw coming in contact with a standard secured to the body of the instrument. A small up- right projection on the swivel plate, serves as a fulcrum for the lower end of the back link, the upper end being connected to one end of the pencil bar. The back and center links are made of a fine grade of steel as also the pencil bar, which is hardened and carefully drawn to a spring temper, highly polished and all given a blue finish. fi B The piston rod is of steel and made hollow in order ^- to reduce weight , its upper end is connected to the center link, and the lower is made solid and terminates in a ball ; this ball is provided with a universal cap and socket and to which, in turn the indicator piston is at- tached by means of a thumb nut. The piston rod is formed of three pieces ; the body, shanks and ball ; and upon the shank there is formed a col- lar as shown at A, Fig. 8, full size, a little larger in diam- eter than the body, and serves as a safety stop for the pencil movement, by coming in contact with the under side of the cylinder cover just before the pencil bar reaches its extreme height, thereby preventing any further movement of the piston rod, which would be likely to result in injury to the pencil movement in case of breakage of a spring when in use, or by a mistake of using too light a spring for the steam pressure. The piston is made very light of a hard bronze metal, truly turned, grooved on its periphery, to act as a water pack- ing, and lapped perfectly round and straight on its face to an exact size. On the projecting arm of the instrument is secured a steel center stud, extending to the top of the paper drum, and 28 Steam Engine Indicator around which all moving parts of the drum mechanism oscil- late. The spring case has a threaded hub and is permanently secured to the stud, and rests directly on the top surface of the arm and is secured thereto by a nut underneath. A flanged disc, or pulley, which carries the paper drum, has a projecting hub on both top and bottom, which insures a long and possible accurately fitting bearing on the stud, work- ing almost frictionless. There is a hook secured to the bottom hub, which engages one end of a plain flat spiral spring, while the other end of the spring connects to a similar hook in the spring case. A part formed on the disc, is made to come in contact with a stop se- cured to the projecting arm of the instrument and serves to always locate it in a positive position, when alone under the tension of the spring. The lower hub of the disc rests directly on the spring case, while the opposite hub is in contact with a knurled thumb nut, screwed and pinned to the central stud, just sufficient to give a slight amount of end motion to the disc. This thumb nut also serves as a convenient means of reg- ulating the tension of the spring, as by loosening the nut that secures the spring case to the arm of the instrument, said thumb nut can be turned in either direction until the desired tension is obtained, and then tightening the nut. The lower part of the disc is formed with a groove, wide enough to receive about two turns of the cord ; one end of the cord being made fast to, and encircling the groove, and the other attached to a pantograph, pendulous lever, or some sort of a reducing gear that has a movement generally derived from the motion of the engine crosshead, and which causes the disc to rotate in one direction ; the motion in the opposite direction is accomplished by the retraction of the spring connecting the disc with the spring case, and its oscillations are thereby made coincident with the movement of the engine piston. And Its Appliances. 29 1 The drum upon which the paper is placed in taking cards is a very light cylindrical tube, mounted on the disc, and moves in unison with it. It has a guide permanently secured on the inside, and which fits in corresponding recesses in the disc, in order to serve as a carrier, and also to locate it in its proper position in reference to the pencil bar, for either right X^^v or ^ e ^ h an d indicators. The JLJJl top is closed and fitted with a sleeve that provides a bear- ing in contact with the cen- tral stud, and which serves as a guide for it, and pre- vents any irregular motion at that point. A clip is attached XVI S- : r^L_x for securely holding the pa- ^^ ' ^ = v per, one leg of which is made shorter than the other to facilitate the matter of ad- justing the paper upon the drum. One end of a plate of suitable outline, shown in full size Fig. 9, and called the cord guide-base, is se- cured to the under side of the arm of the instrument by a nut for that purpose, and said plate can be turned in. any desired position parallel to it. The other end supports the cord-guide, which consists of a small grooved pulley mounted on a pin within the periphery of a circular disc, both being encircled by a clamp having a threaded stem, which projects through the plate, and is se- cured thereto in any desired position by a small thumb-nut, and the combination of the adjustment enables the cord to be correctly guided around the pulley and on to the flanged disc from any direction. FIG 9. 30 Steam Engine Indicator The cock tube is securely screwed in the body of the in- strument at the bottom, and the connection which secures the indicator to the cock is made with a single thread, and secures correct attachment at once without the annoyance of different trials, as is often necessary with connections made with two threads. The indicator cock has a stop, which limits its range in either direction to full open or closed, and also has holes pro- vided for the release of all steam that may remain between the indicator piston and cock, after operating. In taking cards where two indicators are being used, one on each end of the steam cylinder, the straight eocks shown in Fig. 14, Chapter 5, are all that is necessary for the production of cards from each on separate sheets, but in the case of only one indicator being used there is considerable trouble and annoyance, as well as time lost to the operator, in changing the instrument from one end of the cylinder to the other. All this may be entirely obviated by the use of the three-way cock shown in Fig. 10, this cock being interposed about midway of the steam cylinder in a line of pipe connecting the two straight cocks at the ends FIG. 10. r J _. 1-1 i ,1 of the cylinder. This three- way cock furnishes an easy and convenient means of taking cards from each end of the cylinder, and within a few seconds of each other; also on the same sheet of paper; and therefore admits at once of a ready comparison between the cards. At all other times than applying the indicator, the cocks near the cylinder should be kept closed. Fig. 1 1 is a sectional view of the three-way cock repre- sented in Fig. 10. And Its Appliances. A very simple and efficient cord attachment is shown in Fig. 12, providing a convenient and easy means of adjusting the length of the actuating cord between the reducing gear and the indicator, the hook that is fastened on the cord from indicator, con- necting in the hole at the end of the attachment. The springs are constructed o f two separate coils of wire of the finest grade of steel, the ends of each wire being shown in Fig. 13 ; and a correspond- FIG. 11. securely fastened to brass mountings, as said mountings are threaded on the inside ing threaded projection is formed on both cylinder cap and piston to receive them. The various denominations of the scale of the spring are made to meet all requirements of pres- sure, from zero to four hundred pounds per square inch, with the ordinary y 2 inch area piston. Where greater pressure is required to be indicated, such as the ex- cessive pressures frequently found in some of the gas and oil engines, it can be accomplished by the ( use of the smaller piston of V+ square inch area, men- tioned in a previous chapter. The coils are so at- tached to the mountings that the same length of wire is brought into action, whether under compression or extension, and are therefore correct for either pres- sure or vacuum. Indicator springs are usually constructed and FIG. 12. scaled with a view of their being used under a tem- perature due to the various steam pressures to which they may 32 Steam Engine Indicator be subjected, and called the hot scale of the spring", and for which they are supposed to be accurate, allowance in the con- struction having been made for the weakening, due to the effect of the heat of the steam or other hot vapor, and which would otherwise cause the spring to indicate too high a pressure ; therefore springs made for hot pressure are not accurate for cold, and consequently require a different scaling for cold and dead weight pressures. The spring in all indicators being the medium through which the pressures at all parts of the stroke of the engine are denoted o-n the card, it is necessar- ily important that it should be constructed with the greatest care and exactness to insure evenness and ac- curacy of motion to the indicator piston ; otherwise FIG, 13. the results from it are erroneous and of no practical value, notwitstanding the indicator itself might be all that could be desired for the work. The principal requisites for a reliable and correct spring are, that the wire should be of an exact size, and coiled on a special arbor of such a size that will give the proper tension to the spring for the different denominations. They should be evenly hardened and temper drawn uniformly all over, and in finishing should be made perfectly straight and true, and thereby reducing to a minimum all the chances of any side strain or buckling of the spring, which always tend to force the indicator piston against one side of the cylinder, and thereby creating a friction on the piston that will surely cause all results from it to be unreliable. The springs of the Tabor Indicator are made of different lengths, according to the denomination of the spring, the low pressure or light ones being the shorter, and from these continue to increase in length until the highest pressures have been reached. The principal object in making the springs of different lengths is that each may cause the pencil to mark the atmospheric line on And Its Appliances. 33 the paper drum in an exact position in reference to itself, so as to have an ample range of movement of the pencil either above or below the line for both pressure and vacuum. This varia- tion in the length of the spring obviates the annoyances and necessity of adjusting the length of the pencil connection to lo- cate the position of the atmospheric line in cases where all springs are of the same length, as in some makes of in- dicators. All indicator springs when in use are subject to what is sometimes called the lag of the spring ; that is, the lines marked on the paper drum by the pencil at a rising pressure (as compared with an accurate steam guage or mercury column) do not exactly coincide with the marks on the falling pressures as indicated by the gauge, as illustrated in Chapter XXII. This discrepancy is by some engineers attributed entirely to the friction of the piston against the sides of the cylinder, and which may be caused by some unevenness in the spring, or probably an imperfection in the alignment of the instrument, or both. Others have a theory that the whole of this discrepancy is not entirely on account of friction in the indicator, but that a portion of it is due to an inherent peculiarity in the spring itself, that will always prevent an absolute coincidence of the lines between a rising and falling pressure, and such peculiar- ity is entirely independent and regardless of friction that may occur in the indicator from any cause. Some special and carefully conducted tests, to determine the correctness of the latter theory, were made, we think, at the Stevens Institute and printed in the Stevens Indicator. The conclusions arrived at from these tests were that there was no difference in the marking between a rising and falling pres- sure that was due to any lag in the spring itself ; or, at least, no difference from such cause that would be appreciable in indicator measurements, and any discrepancy found in the 34 Steam Engine Indicator markings was altogether due to friction from some source in the indicator. A number of tests have been made by the writer, at differ- ent times within the last five years, on cold springs of various kinds, including springs both under compression and exten- sion, and also on round rods under tortional strains; as well as straight flat springs, which were secured at one end and weighed at the other. In all of these tests efforts were made, so far as possible, to eliminate friction, and in reference to the ones under extension, and especially the flat springs, of which we might say were completely devoid of friction, and still there appeared to be the same phenomena connected with them, as regards coincidence in the marking of lines, as is argued by some engineers in ref- erence to indicator springs. These observations, although not of an elaborate nature,, seem to indicate that there is a very slight discrepancy in the markings of all kinds of springs between a rising and falling- pressure, and might truly be called the lag of the spring. This- difference however being so slight, it is a question whether it is of sufficient importance as to be taken account of in indicator measurements of power. And Its Appliances. 35 CHAPTER V. INDICATOR APPLIANCES. It has been found advisable, in order to obtain the best results in indicator practice, to so construct the instrument that the piston shall have only a small amount of motion, and that the movement of the pencil shall bear a certain exact ratio to the movement of the piston. This ratio varies in different indicators ; in some, the pencil has four times, while others have five or six times the piston movement. This difference in ratio, as a general thing being a matter of selection, or convenience, of the makers in the designing of their indicators. One of the principal reasons for having the piston move but a short distance as compared with the pencil movement, is that a greater part of the friction between the piston and cylin- der, due to a long and rapid movement, is eliminated ; and consequently the results obtained from a short movement of the piston are much more accurate. By this it is not to be inferred that the shorter the piston movement the greater the accuracy ; as there are circumstances connected with the matter that prevents the realization of any theoretical conclusions, in reference to it; because the ratio between the piston might be made so great that the slightest loss motion in the piston connections would be so multiplied at the pencil as to vitiate all efforts to obtain correct results. 36 Steam Engine Indicator On the other hand, by making the ratio too small would tend toward the original principal ; where the piston and pencil had equal movement ; therefore, the best compromise between the two extremes becomes desirable, and an experience with different proportions seems to indicate that a pencil movement of five times that of the piston, is best adapted to average the imperfections that become involved in either a greater or less ratio. An important requisite, however, in this respect is, that whatever this ratio may be, is that the pencil shall move ex- actly that many times the distance moved by the piston throughout its entire range. This result has been perfectly accomplished in the Tabor Indicator through its specially de- signed pencil mechanism, which causes the pencil to move at any and every part of its travel of exactly five times the dis- tance moved by the piston, and this in connection with the straight line movement of the pencil, as well as the lightness of the moving parts and absence of friction always insures the accuracy of the diagram. Preparatory to taking indicator diagrams, it is well to see that the piping that connects the engine cylinder with the indicator has been properly done, and in the most convenient position to enable the operations to be performed successfully and with the least amount of anxiety and trouble to the opera- tor; The location of the indicator will, of course, depend somewhat upon the construction of the engine to which it may be applied, but the principal of its operation will always be the same in whatever position it may be placed. In the indicator piping on the side of horizontal engine cylinders, care should be taken that the holes for the pipe are drilled outside of the point reached by the extreme travel of the engine piston at each end of the cylinder. This precaution is taken to insure that the piston does not close, or even partly close, communication between the inside of the steam cylinder A nd Its Appliances. 37 and indicator piston ; which would result in showing, in many cases, a late initial pressure on the card, and otherwise cause it, to a certain extent, to be erroneous. It is also important, in all styles of engines, that these holes should be located as far from the steam ports of the engine as convenient, as there are instances in which a close proximity to said ports has to some extent influenced the pencil from indicating correctly, from the beginning of the stroke to the point of cut off ; this being due to the rapid inflowing of the steam through the ports and past the end of the pipe that communicates with the piston of the indicator ; thereby causing it to indicate a lower pressure than actually exists in the steam cylinder. The pipes, preferably of brass, should be as direct as pos- sible and without any unnecessary bends, and in cases where the regular straight indicator cock, shown in Fig. 14, is used at the centre, it is ad- visable to use straight way valves at the ends of the cylinder. There should be no appreciable dif- ference in the mean effective pressure, shown by the cards (under the same con- ditions), whether the indicator is located at the end or centre of the cylinder, that would be due to any difference in the length of pipe, within the limit of the length of the cylinder. A close com- FlG - T 4- parison of the card from the centre would only reveal a slight increase in the water consumption per horse-power over one taken at the end, and which is entirely due to the added clearance to the cylinder which would ensue from the greater length of pipe in use when the indicator is placed at the centre. The next matter of importance is in the selection of the best means of giving the paper drum an exact motion coincident 38 Steam Engine Indicator with the motion of the engine piston and cross head, on a suf- ficiently reduced scale, that will come within the limits of its motion ; this distance being limited by the stop formed on the disc (that carries the drum) for that purpose. This entire dis- tance is never utilized in practice, as there must always be a certain amount of allowance at each end of its motion, to guard against any accident that might occur by coming in contact with the stop. There are various devices for the purpose of giving motion to the paper drum ; an example of the most usual ones being shown here in the illustrations, some of which are theoretically correct, while others are only an approximation. The length of the card to be taken, as well as its height, depends some- what upon the speed or number of revolutions the engine may be running per minute. In the slow speeds a long and high card may be taken, whereas in the higher speeds a short and low diagram is necessary, in order to avoid as much as possible the effects of inertia of the paper drum, and also of the pencil movement. With the new style Tabor Indicator, diagrams can be taken five inches long and two and a half inches in height if desirable, but with the ordinary speeds up to 100, and from that to 200 revolutions per minute, a length of card of 4 inches in the first instance, and 3^ in the latter, will show well proportioned diagrams. As a guide in this matter it is recommended that with speeds up to 300 revolutions per minute the length of the card may be 3^ inches; of 400, 3 inches; of 500, 2^ inches; and of 600, about 2 inches long, which will insure reliable re- sults. The piston spring should also be of a higher tension (that is, a stronger spring), because, as the speed is increased, it becomes advisable to decrease the height of the diagram in about the same proportion as the length is shortened. Diagrams taken in these proportions seldom require any change of tension of the drum spring between the highest and A nd Its Appliances. 39 lowest speeds. The lazy tongs shown at about ^ actual size in Fig 1 . 1 5 is one of the appliances frequently used to obtain the necessary coincident motion (on a reduced scale) between the paper drum and cross head, and which it accomplishes in an accurate and satisfactory manner, provided the devise is well made and free from all lost motion in its many pivoted con- nections. It is usually pivoted at the end (B) by a stud and winged thumb-nut to a block of wood, or an angle iron, secured to the floor of the engine room or in some other convenient position, while the end (A) is fitted in a suitable piece secured to the cross-head of the engine. The actuating cord from the indicator is attached to the cord pin (E) on the cross bar (C D) ; said cross bar may be moved in different positions with relation to the centre (B), by changing the screws C and D, which hold it in place, but the cord pin (E) must always be placed in a line with the centres (A) and (B). The position of the cross bar C D, in relation to B, deter- mines the length of travel of the cord pin E, and consequently the length of the diagram. No special care is necessary to locate the position of B, in reference to the cross-head of the engine, so long as the devise works perfectly free throughout its range. One of the principal advantages of the Lazy Tongs over some of the other forms lies in its adaptability to the "various different conditions so often found in indicator practice. FIG. 15. 40 Steam Engine Indicator Fig. 1 6 represents one way of attaching it to an engine,, when the indicators are placed on the side of the cylinder. In this case it is worked in a .horizontal (or flat) position, one end is supported by a standard secured to the floor, and of sufficient FIG. 16. height to just bring the cord pin (E) on a level with the cord guide on the indicator ; consequently, in this case, the cord will run direct from the cord pin to the indicator.' They may also be used in a vertical position with equally good results, where the end B is attached to a low block or bracket secured to the floor, and directly below the engine cross-head. In this position it becomes necessary (in order to insure coincidence between the cross-head and paper drum) to use a small carrying pulley, over which the cord must pass from the cord pin, E, and thence to the indicator. Said pulley may be mounted on an additional suitable block that will admit of its being placed exactly on a level with, and a short distance from the cord pin, E. There are various other ways of applying the Lazy Tongs, as circumstances may require, which will suggest themselves. to the engineer, all depending entirely upon occurring condi- tions. Proportion of Lazy Tongs. In order to enable the engineer wishing to construct an accurate device similar to that shown in the illustration, the following data will need to be carefully observed to insure an accurate motion. /Ay Appliances. 41 The instrument is constructed principally of strips of thoroughly seasoned cherry wood about one and one-eighth (y&) inches wide, by three eighths (5/6) inch in thickness. The distance apart of the outer holes in the long strips is sixteen (16) inches, while the length of the short strips con- necting their ends are only one-half of that, or eight (8) inches between similar holes. In the cross bar C. D. there are eleven additional holes, one-half (^) of an inch apart, placed equidistant from each end, and are threaded to admit of the cord pin E, being screwed therein in its various positions on the cross bar. In one of each of the long and short strips are also eleven threaded holes, one-half (^) inch apart and exact duplicates of those in the cross bar C. D. and to which the cross bar is secured by screws in any desired position, as shown in the illustration. The pivoted joints are constructed of brass tubing about five-sixteenths (5-16) inch outside diameter, by three-sixteenths (3-16) inch inside, and of sufficient length to go through the joints and be riveted over iron washers on each end. This construction also provides a means of tightening the pivots in case they become loose from wear, by a further rivet- ing over of the tubing. There is also placed upon the pivot between each joint, two thin brass separating washers to prevent the strips of wood coming in contact with each other while in operation ; thereby obviating the friction that would otherwise take place. The studs A and B are shown one-half size in Fig. 17 and are made of round steel, seven-sixteenths (7-16) of an inch in diameter, and three and one-half (3)^) inches long. In the middle of their length is secured a collar three-quarters inch in diameter and one-quarter of an inch in thickness. Each of these studs on one side of the collar are made with nut and washer, and serve as pivots to connect the ends of the device. 42 Steam Engine Indicator The opposite end of stud A is made either straight or tapering as occasion requires, to connect with the cross-head ; while the opposite end of stud B, is threaded, and provided with winged nut, for the purpose of attaching to the fulcrum, or to whatever the devise may be suspended ; as before mentioned. In order that the cross bar may not come in contact with the nut and washer of the stud B, when the de- vice is closed, the bar is elevated by means of two wooden washers, one FIG. 17. at each end, made of the same mate- rial as the strips, and the screws for securing the same are of sufficient length to reach through both, and screw into the drilled strips underneath. It is exceedingly important that all corresponding holes in the strips be layed out and drilled with extreme accuracy, and also the pivots made a close fit therein, to insure its perfect working at all points, from its closure to the full extension. In this construction of the Lazy Tongs, the location of the holes, their distance between centres, and the position of the cross bar in relation to the stud B, determines the ratio (that occurs in each case) in the amount of motion of the cord pin E, as compared with the amount of motion of the stud A. The holes being one-half inch apart, a change of the cross bar from one hole to the next, results in a change of motion of the cord pin E, of one-forty-eighth. For instance ; If the cross bar be secured in the holes that will bring.it nearest to the stud B, and if the cord pin E, there be placed in the hole that comes in line between the studs A and B, the reduction of motion of the cord pin will be three- forty-eighths, or one-sixteenth of that of the stud A ; in the second hole the reduction is four-forty-eighths, or one-twelfth ; in the third hole, it is five-forty-eighths ; in the fourth hole And Its Appliances. 43 it is six-forty-eighths, or one-eighths and so on, to the farthest holes from B, where the motion of the cord pin becomes thir- teen-forty-eighths of that of the stud A. From this it will be seen that each position of the cross bar has its own ratio of movement between the cord pin, and stud A, as above, whatever the length of stroke of the engine may be. In every position of the cross bar C. D. (if made according to directions), there is always one of its holes on an exact line between the centres of the studs A and B, and into which the cord-pin E, must always be placed in order that it may trove in an exact straight line parallel to the motion of the stud A. 44 Steam Engine Indicator CHAPTER VI. INDICATOR APPLIANCES CONTINUED. An accurate and simple form of pantagraph is shown in Fig. 1 8, in which the end, A, is connected with the engine cross-head by means of a pin or other suitable con- nection ; while the end, B, is pivoted to a bracket, C ; said bracket also serving as a support for the guide pulley, E, and upon which it may be adjusted at a level to coincide with the cord pin, D. The length of travel of the cord pin depends en- tirely upon the distance the cross-bar, F, may be placed in relation to the fulcrum, B. There is a slot in this cross bar which admits of an adjustment, and the securing of the cord pin, D, in any required position within the length of the vslot ; and in whatever position the cross bar may be placed, the cord pin must always be moved and secured by means of the thumb nut, on a line between the points A and B in order to insure an exact straight movement of the pin, D, and paral- lel with the engine cross-head. FIG. 18. And Its Appliances. 45 This instrument, like the Lazy Tongs, may be used in either a horizontal or vertical position ; it has a less number of pivoted connections and accomplishes equal accuracy ; but has not quite the same range of application under all circumstances. In all cases and with either instrument, where they are placed in a position requiring the use of a carrying pulley, care must be taken that said pulley, E, be located a short distance from the instrument, and in such position that the actuating cord will move parallel with A, from the cord pin, D, to the pulley, E, and thence in any desired direction to the Indicator. FIG. 19. Fig. 19 represents the pantagraph in its application to an engine cylinder, where the indicators are placed upon the side of the cylinder. In this case blocks of wood or iron is shown, secured to the floor, to serve as supports for the instrument, as well as the carrying pulleys ; this arrangement answers the purpose, but the bracket, C, is much more mechanical and con- venient. A simple method of obtaining the drum motion, and very frequently used by engineers (in the absence of a more accurate device), is the pendulous lever, A B, shown in Fig. 20, which consists of a strip of wood, about 4 inches wide, by ^ inches thick, and suspended from a bracket, G, which is secured to the ceiling or any overhead framing ; the lever being of suffi- cient length from its point of suspension, so that its lower end, 4 6 Steam Engine Indicator A, may connect to one end of the connecting bar, C, while the opposite end of said bar is attached to the engine cross-head, >j D. The length of the lever, A B, should be such that the end, A, should be as far below the line of movement of the cross-head, when on its center of travel, as it will be above the line at its extreme end of stroke. The cord pin, E, (to which one end of the indicator cord is at- tached), is located at such a dis- tance from the point of suspen- sion, B, as will rotate the paper drum, an amount that will give the FIG. 20. desired length of the diagram. In this device it is necessary to pass the cord from the pin, E, over the guide pulley, F, and thence ^ to the indicator. In connecting the ~ device, it is important that the cross- head, D, should be at its center of travel, when the lever, A B, is in a vertical position. This reducing motion may be easily and cheaply constructed and set up by any engineer, and will be found a con- venient means of giving motion to the paper drum; but although not mathe- matically correct, will give fair results. Fig. 21 shows another device, the same in principle, but instead of the cord pin there is substituted a segment of a circle, having its center at B, and with a radius necessary to give the paper drum the desired amount of motion. And Its Appliances. 47 In place of the connection, C, as in Fig. 20, the lower end of the lever at A is slotted and is worked by a stud, secured to the engine cross-head, D. Whenever this device can be placed in a direct line with the indicator, the guide pulley can be dis- pensed with, and the cord encircling the segment may be run from it directly to the indicator. As the relative length of the lever in this arrangement is constantly changing throughout its stroke, it is therefore as to the matter of accuracy about equal to Fig. 20. The plan of suspended lever, shown in Fig. 22, is an im- provement on the previous ones shown, and was proposed by \ Mr. Frank Richards in an article published in the American Machinist several years ago, in X which he gives a number ^ of modifications of the same principle, whereby perfect theoretical ac- curacy is attained. It consists of an ordinary suspended lever, with the lower end, A, slotted and driven by a pin se- cured to the engine cross- _ A head ; the end, B, being FIG. 22. pivoted to the bracket, G, which may be secured to the ceiling or some suitable frame work (or it may be used in a horizontal position if desired) ; the other element of the lever at C also being slotted, and giv- ing motion to a sliding bar, F, by means of a pin fastened to said bar, and working freely in the slot in the lever. The bar, F, slides in hangers secured in the same manner as the bracket, G, and in a line parallel to the line of the cross-head. The 48 Steam Engine Indicator cord, attached to the sliding bar, passing in a line over a suita- ble guide pulley and thence to the indicator. By this arrange- ment the relative length of the elements of the lever, A B, al- ways remains the same, and consequently insures coincidence and accuracy of the drum movement, throughout its entire range. The various different modifications of this principle, to at- tain accuracy of the drum motion, depends upon the use of the sliding bar, F, in each instance, and it is evident, as well as readily seen, that it makes no difference (so far as accuracy is concerned), whether the lever, A B, is slotted, or instead of the slots, we substitute two permanent pins in the lever, and have each pin work in slots formed in both sliding bar, F, and in a suitable slotted piece secured to the engine cross-head. Figs. 20, 21, and 22 show the position of the lever, A B, when engine cross-head is at the center of its stroke. In order to determine the proper distance (of the point on the lever to which the cord is attached), from the fulcrum, B, to take any desired length of card, it is necessary first to divide the stroke of the engine cross-head, in inches, by the desired length of the card required ; then divide the total length from center to center of the lever, A B, by that quotient, which will give the distance of the point in inches from the fulcrum, B, to the pin, E, or where the cord must be attached. For example, sup- pose the stroke of the cross-head to be 24 inches, the length of the lever, A B, between centres to be 48 inches ; and we desire to produce an indicator card 4 inches long ; then 24 inches di- vided by 4 inches, the length of the desired card, is equal to 6, and by dividing the length of the lever, A B, which is 48 inches by 6, gives us 8 inches, which is the proper distance from the fulcrum, B, to a point on the lever to which the cord must be attached to produce a card 4 inches in length. A slight discrepancy will sometimes appear in the length of cards, computed from any rules, owing to incorrect meas- urements, stretching of the cord, inertia of the paper drum, &c. And Its Appliances. 49 Fig. 23 shows another modification of the lever and slid- r* ing bar, F, in which the slots in the lever have been dispensed with, the lever being attached to the cross- head and bar F by means of the connections A H and C E. An important matter in this construction is that the lengths of the two connecting links must bear the same ratio to each other, as the ratio between the two elements of the lever, A B and B C ; there- Fio. 23. fore AB:BC::AH:CE. The pins on the cross-head and the sliding bar must be so located that lines drawn through the centres of the connections A H and C E, will be parallel with each other in any position >* the lever may assume. In ~~ the arrangement shown in Fig. 24 the fulcrum of the lever is at the pin, C, of the sliding bar, F, while the ends are each made in the form of a fork, the end, A, being moved by and sliding upon a pin secured to the cross-head, the end, B, moving on a pin fasten- FIG. ed to the bracket, G. In Figs. 23 and 24 the cross-head is represented at the extreme end of the stroke. Steam Engine Indicator These are modifications of Fig. 22, but without claiming any particular advantage for one over trie other. In all cases where this principle is accurately'applied, it will be found that the elements of the lever, A B, are always in a line at a right angle to the line of movement of the engine cross-head, at the time the cross-head is at the centre of its travel. The sliding bar principle may also be well adapted to en- gines where the end of the engine shaft is accessible. By in- serting a stud, A, in the end of the shaft, as shown in Fig. 25, at a proper distance from the centre, C, to give the desired length of card, and connecting it to a sliding bar, F, by means of a short connection, FIG. 25. A B, will insure a per- fect coincident motion of the engine cross-head on a reduced scale. The bar may be extended to any desired length to secure conven- ience in connecting with the indicator. A necessary requisite, to insure correctness by this arrangement, is that the length of the connection, A B, relative to the distance of the end, A, from the centre, C, must bear the same proportion that the main crank of the engine bears to its own connecting rod. It is not necessary in this case that the slide move parallel with the movement of the cross-head, as it may be moved in any desir- ed direction, but great care must be taken that stud A be placed in such position on the shaft that the sliding bar, F, will be on its extreme throw at the same exact time that the engine crank is at its extreme movement, and both at the same end of the stroke. Where the end of the shaft is not accessable, the same results may be accomplished by means of an eccentric placed in a convenient position on the shaft. A reducing arrangement, that gives good results at high speeds, is a plain lever swinging on a pin above (or it may be below) the cross-head, having a pin in the end which slides up A nd Its Appliances. 5 I and down in a slotted piece of metal fastened to the cross-head as shown in Fig. 26*. This method gives a fairly accurate motion. A segment of a' grooved pulley is fastened to the FIG. 28. upper end of the lever, and from this the cord extends to the indicator. The whole device should be made of wood as light as pos- sible, (consistent with strength), in order to reduce the inertia to a minimum. A heavy reducing gear on a high speed engine will wear very quickly and create inaccuracies in the diagram. When indicating High Speed Engines or Locomotives, the driving cord for hooking on the indicator should be continued beyond the loop, and fastened to a spring or an elastic band attached to the carrier pulley of the indicator. This band or spring is intended to always keep a tension on the driving cord, whether the indicator is in operation or not, and prevents entanglement and breakage of cord when the indicator is unhooked. The cut in Fig. 27 shows the arrangement as described, and which operates in a perfect satisfactory manner, as dia- grams can be taken with as little difficulty at high speeds, as on slow speed engines. 52 * Steam Engine Indicator The hook, A, on the indicator cord connects into the loop, B, on the driving cord when the indicator drum is in operation ; Fm. 27, the loop, B, is made long enough to be held with the hand when hooking on the indicator. To disconnect, merely catch the hook and hold it station- ary for a second, and the loop will come off. The rubber band then takes the motion and keeps the cord taut. Whatever arrangement is employed, it is desirable to avoid the use of long stretches of cord on account of its sagging and stretching. Small wire may be used to good advantage on vertical lengths except where the line passes over pulleys. Whatever the style of reducing motion that may be em- ployed for giving motion to the indicator drum, its accuracy can easily be tested, and ascertained in the following manner- Lay off a number of points on the cross-head guides, at say ^ , y, %> ^, s /% in. etc., of the stroke. Connect the Indicator with the reducing motion in the same manner as for taking diagrams. W T hen the cross-head And Its Appliances. 53 is on either dead centre, bring the pencil in contact with the paper on the drum and make a short vertical line. In the same manner make other lines on the paper, as the cross-head is moved to each successive eighth point on the guide. Then if the lines on the paper are exactly at eighths, the motion of the cross-head has been accurately reduced. These directions given for reducing motions are general ; some special cases require special modifications. T 54 Steam -Engine Indicator CHAPTER VII. INDICATOR REDUCING MOTION. There are a number of devices under different names, all designed for the purpose of giving the necessary accurate mo- tion to the paper drum; and each constructed on principles in which long swinging levers are dis- pensed with, the actuating cord from these devices being connected either directly to the engine cross- head, or to some moving part that has a motion in exact unison with it ; while another and separate cord connects the device with the indicator. If, in the act of operating the indi- cator with any of these 'devices, it becomes desir- ious of stopping the mo- F IG . 28. tion of the paper drum, it is necessary to disengage, or unhook, either one or the other of the cords that give it mo- tion ; a matter with some of them, requiring considerable And Its Appliances. 55 FIG. 29. practice to accomplish with ease and assurance especially on engine having high rotative speed. This operation of unhook- ing is usually performed on the cord connecting the device with the Indicator. Some of these attachments are constructed so as to be attached to the indicator by means of a bracket, adapted to the particular indicator to which it is to be applied ; while others are so made, that may be secured away from the in- dicator, to some part of the cylinder or engine framing by means of set screws or bolts; in many cases re- quiring considerable labor to secure them in a con- venient position. The particular Reducing Gear, of which we shall give a description in this article, is one that is constructed with and forms a complete part of the well known Tabor Indicator, as illustrated in Fig. 28. After securing the indicator in position on the pipe connecting with the engine cylinder, and attaching the end of the actuating cord to a stud screwed in the cross-head, the instrument may be used during the time of any experiment, without the necessity of connect- ing and disconnecting the actuating cord, in order to start or stop the motion of the per drum. The principal parts of this Reducing Gear consists of sup- porting base K, Fig. 29, with two short standards, B, and B 1 . The standard B 1 is fitted with a hardened steel center P, Fig. 30, which serves as a pivot bearing for the end of the worm shaft R, Fig. 31, and which receives the entire thrust of the shaft R, thus reducing the friction from that factor to a mini- mum ; the other bearing being in the standard B. The base Steam Engine Indicator FIG. 30. K is connected direct to the Indicator, upon the projecting arm that supports the paper drum B, and the teeth of the worm shaft, R, engage directly with the teeth on the drum car- rier g, thereby making a posi- tive connec- tion therewith, and forming a part of the In- dicator, (see FIG. 31. Fig. 2 8). To the base K, is also connected the spring case D, Fig. 32, permanently secured thereto, by means of screws passing through holes as shown in the spring case, and corresponding with holes tapped into the standard B, (as shown) of base K, and so located thereon that its centre shall be common with the center of the worm shaft R. Upon the worm shaft R, is secured by means of a set screw, the collar A, through which freely slides the clutch pin I, one end of which is securely fas- tened to the thumb piece U, by which the pin is operated. The whole mechanism of that part is shown complete in Fig. 33. The flanged pulley O, Fig. 34, rotates FIG. 32. freely and independently forward and back on the worm shaft R. It has its outer hub formed in the shape of a double cam clutch, with steel pins X, X, in- serted to prevent wear upon their faces, while the opposite side has a hole in which the pin A, of the spring case cover S, Fig. 35 engages. One end of the actuating cord is attached to the pulley O, (a hole being shown in the figure for that purpose) while the other is secured either to the engine cross-head ; a FIG. And Its Appliances. 57 FIG. 34. standard bolted to the same, or to any other part that has an exact similar movement, and should be connected from the pulley O, in a line parallel to the movement of the cross-head. The length of the actuating cord should be such, that when connected to the cross-head, at the commencement of the outward stroke of the engine, there should also be about six or seven turns of the cord encir- cling the pulley O, which will always in- sure the requisite amount of cord, and ob- viate the liability of breaking. Enclosed in the spring case D, Fig. 32, (not shown in the illustration) is a small plain Spiral Spring ; one end of which is secured to the spring case by means of a slot F, shown in the figure, while the other end connects with the hook C of the spring case cover S, Fig 35. This spring operates to return the pul- ley O, back to its starting point, after it has been revolved in one direction, by the outward movement of the engine cross- head ; therefore as this pulley O, has an independent rotating forward and back motion on the worm shaft, R, the necessity of unhooking the cord in order to stop the motion of the paper drum B, after the diagram has been taken, will be entirely overcome, as explained further on. The paper drum B, is rotated forward by means of the pulley O, through the worm shaft R, engaging with the teeth of the gear g, on the drum carrier ; and in the opposite direction by the action of its own retracting spring. On the top of the drum B, is a knurled thumb- piece, with a projecting pin on its under side, for the purpose of engaging with a similar pin, secured in the top of the drum, and is to be used by the operator when in the act of starting the drum ; for the purpose of moving it slightly for- ward before the clutch pin I, is pushed in engagement with FIG. 35. 58 Steam Engine Indicator the cam hub of the pulley O, thereby preventing the drum carrier from striking against its stop on the return motion. With this reducing gear the stopping of the drum motion becomes a very simple matter, and is accomplished by taking hold of the thumb piece U, and withdrawing the engagement between the clutch pin I and the clutch hub of the pulley O. The knurled thumb piece on the top of drum B, also fur- nishes another very convenient (and preferable) means of stop- ping the motion of the drum ; as by holding it so as to retard the motion of the drum on its return stroke, it will thereby cause the cam face of the pulley O, (which is constantly in mo- tion) to automatically force the clutch pin I out of contact with the clutch hub of the pulley O. The starting or stopping of the paper drum, at any time, will have no effect on the motion of the pulley O, which will continue to revolve independently while the engine is in motion. When desirous of starting the drum B, it will be necessary to again make the engagement be- tween the clutch pin I and the clutch hub of the pulley O, and which must be done by the combined means of the thumb piece U, and the thumb piece on top of drum B, as follows : The pulley O, being in constant motion ; with one hand take hold of the thumb piece on top of drunTB, and turn it in a direction from right to left, until it carries the drum and its carrier a short distance from its stop, (say about ^ inch). While holding the drum in this position, take hold of the thumb piece U, with the other hand and gently press it toward the clutch hub of the pulley O, and it will be foundth at when the engine cross-head arrives at its extreme inner stroke, that the engagement between the clutch pin I and the clutch hub of pulley O will ahvays take place at that particular point, and with the least amount of difficulty in the operation. The thumb pieces are so constructed that they may be readily held in the hand while running; therefore no difficulty is experienced in throwing the clutch pin in or out of gear. In And Its Appliances. 59 preparing to use this Reducing Gear, the first and very im- portant matter for consideration is in the selection of the pul- ley O, which shall be of such size in relation to the stroke of the engine as will give the requisite length of the Indicator Diagram. A ready and mental means of ascertaining this, is by divid- ing the length of the stroke of engine (in inches), by twelve, which will give the diameter (in inches), of the pulley O, that is, the stroke of the engine being 12 inches will require the pulley O to be one inch in diameter ; a stroke of 1 8 inches, i y 2 inch ; of 24 inches, 2 inch ; and of 36 inches a pulley of 3 inches in diameter, &c. ; and it is also well in this connection to bear in mind that for each complete revolution of the worm shaft R, there will a corresponding pencil line (when in con- tact), marked on the paper drum horizontally, about one inch in length ; consequently, two revolutions mark two inches ; three revolutions gives three inches, length of card, &c. It must be understood that this calculation of the size of pulley O, has reference to engines having low rotative speed, say up to 120 revolution per minute, and where a long card is desired ; but when the speed is increased from this to 500 or 600 revolutions per minute, the size of the pulley O will have to be in accordance with the recommendation (in chapter V) in reference to the height and length of diagram advisable, where the rotative speeds are gradually increased up to 600 revolutions per minute, and producing a card two inches in length. After selecting the pulley required, remove the clutch from the worm shaft R, by slacking the set screw shown in collar A, and place the pulley thereon, taking care that the pin-hole on the inner side of the pulley (not shown in cut), engages with the projecting pin A, of the spring case cover S, Fig. 35, then replace the clutch on the shaft as far as it will go and secure it firmly in place by the set screw in collar A. 60 Steam Engine Indicator Place the indicator in position, and attach the actuating cord as already described. The tension of the spring in the spring case D, must be sufficient at all times to just keep the cord taut, and this may be regulated by taking more or less extra turns of the cord around the pulley O, until it results in the desired tension. The alignment of the Indicator, in order to have the cord run evenly, is a matter to be observed ; and if upon starting the engine the cord should run unevenly on the pulley O, it may be entirely remedied by slacking the indicator connection a trifle, and turning the Indicator slightly in the necessary direc- tion until a perfect and uniform winding of the cord is ob- tained, and which can (by this means) always be accomplished. The peculiar construction of the angular teeth on the worm shaft R, and also on the drum carrier G, enables each to be- come the driver of the other ; that is, on the outward stroke of the engine, the drum carrier is driven by the worm shaft; while on the return or inward stroke, the worm shaft is driven by the drum carrier g, through the action of its retracting spring ; said spring always serving to return both of them back to their normal positions, at the extreme inner stroke of the cross-head, at each revolution while in operation. In the absence of a proper understanding of the principles of manipulating some of the various Reducing Motions in the market, some engineers that have had no particular experience with them, look upon all such devices as complicated and gener- ally troublesome to operate and are satisfied to continue the use of the more antiquated pantagraph and lever movements. In our own experience and that of engineers who have been using the positive Reducing Gear, described and illus- trated in this article, it may be said to have given entire satis- faction in all cases, and a return to any of the old methods, (after becoming familiar with this) could not be contem- plated under any circumstances. And Its Appliances. 61 CHAPTER VIII. DRUM STOP MOTION AND ELECTRICAL APPLIANCE. In using the different lever and pantagraph devices, that have been illustrated in a previous chapter (or any modifications of them), for the purpose of giving motion to the paper drum ; it becomes necessary with any and all of them to connect and disconnect the actuating cord leading from the device to the indicator, in order to start or stop the paper drum whenever necessary, for either adjusting or the removal of the paper from the drum. In slow speed engines, the matter of hooking and unhooking the actuating cord is of no great difficulty ; FIG. 36. but with engines of high rotative speed, it becomes more diffi- cult and requires much more skill and experience on the part of the operator to perform the operation successfully and with 62 Steam Engine Indicator ease. An efficient and very simple attachment, which may be adapted to different styles of indicators, for the purpose of starting and stopping the paper drum at all times without the necessity of unhooking the actuating cord, when used in con- nection with any of the pantagraph styles of reducing motion, is illustrated in Fig. 36, attached in this case to a Tabor Indi- cator ; and whereby the usual handling of the actuating cord (that otherwise becomes necessary), to stop the motion of the paper drum, is entirely obviated at any and all speeds. The device is shown in Fig. 37 detached from the indica- tor, and consists of an arm A, which may be secured to a part X of the indicator, by means of the set screw B. Up- FIG. 37. on the arm A, Fig. 37, is a slide C, which may be adjusted to any desired position on the arm and secured thereto by the knurled nut E and washer F. On the slide C is mounted the cord pulley D for the pur- pose of directing the. actuating cord (from any form of reduc- ing motion), around the said pulley and thence on to the paper drum carrier to the indicator. The method of determining the proper length of the actu- ating cord is as follows : set the slide C, to its extreme inner position on the arm A, and place the engine on its extreme outer stroke, then bring the cord from the drum carrier around the cord pulley D, and thence in the required direction to the point of attachment on the reducing motion, which will give the necessary length of the actuating cord. At any convenient position on the actuating cord and near the cord pulley D, there is superposed an elastic band, shown in Fig. 36, for the purpose of taking care of the slack of the cord, that will appear when the engine is in motion and the paper drum at rest. This slack is owing to the length of the actuating cord being And Its Appliances. 63 taken when the engine is at its extreme outer stroke ; conse- quently on its arrival at the inner stroke there is an amount of cord to be taken care of, equal to the presumed length of the indicator diagram, and the intervention of the elastic band is for that purpose only. While the slide C is at its inner position no motion will be transmitted to the paper drum ; but by moving the slide C out- ward upon the arm A, it will at once cause the paper drum to rotate forward and back, and the slide may be secured in any desired position on the arm by means of the knurled nut E, therefore in order to start, or stop, the motion of the paper drum at any time when the engine is in motion, it is only nec- essary to change the position of the slide C on the arm A, which is accomplished most satisfactorily, by means of the knurled nut E. To start the paper drum, move the slide outward on the arm and secure it by the nut E, and to stop, move it to its ex- treme inner position, the actuating cord continuing its usual motion during the time the engine is in motion. To Take Diagrams Simultaneously. In order to make com- plete and reliable tests of steam power from the various com- pound and multiple cylinder engines, or whenever it is desirous to take diagrams simultaneously from a number of steam cylin- ders (in which as many indicators are used), it becomes neces- sary to provide some sure means of operating the indicators, by which an operator can accomplish the object alone, without the aid of assistants and with the certainty that all diagrams taken at any particular stroke of the engine or engines, will all commence and leave off simultaneously with each other, and thereby dispensing otherwise with the number of attendants necessary to operate the different indicators at some decided upon signal ; a plan whereby an exact coincidence of the dia- gram at any particular stroke is very rarely obtained owing to the almost impossible concerted action between the operators. 64 Steam Engine Indicator The taking of diagrams from two or more cylinders at the same exact stroke of the engine or engines, may be accom- plished successfully in different ways that will oft-times, as oc- casion requires, suggest themselves to the engineer. An ar- rangement sometimes used with fair success, consists of a small reservoir of compressed air from which the pressure is com- municated to a small piston within a cylinder secured to each indicator ; one end of the piston rod being in contact with some part of the pencil mechanism, consequently any movement of the piston is communicated directly to the said mechanism, which results in a contact (when under pressure from the reser- voir), between the pencil and paper drum ; and a withdrawal of the pencil, (through the action of a spring) when the pres- sure is released. These small cylinders are connected to the reservoir by means of rubber tubing in which there is a cock for admitting and releasing the air pressure upon the piston. The operation of the device being about as follows : after seeing that the parts are properly connected, start the pencil mechan- ism of the indicators in motion, by opening the cock connected to each, then by opening the cock from the reservoir the pres- sure from that source (through the small piston and its rod), will force the pencil in contact with the paper drum and against the resistance of the spring. The time of contact between the pencil and paper drum is supposed to be during one complete revolution of the engine, unless an average card is desired from a number of revolutions. The instantaneous release of the air pressure against the small pistons, takes place in the act of closing the cock ; it being provided with an escape hole for that purpose, thereby admitting of the spring to at once move the pencil out of contact with the paper drum. In the absence of a reservoir of compressed air, the same results may be obtained in this device, by using a jet of steam through a small pipe leading from the boiler, steam pipe, or from any convenient place where a pressure of steam may be A nd Its Appliances. obtained. Other improvised means depending upon circumstan- ces and the ingenuity of the engineer, may be used to produce the desired result. The most successful, simple, and satisfactory results, may however, be ob- tained by the use of the electric current. A very neat and simple electrical attach- ment to enable an operator to produce diagrams, from any number of cylinders dur- ing the same stroke of the engine by simply pressing a button to close the electrical circuit is represented in Fig. 38, as attached (in connection with the reducing motion), to the well known Tabor In- dicator. The attachment consists of a specially constructed mag- net M, mounted on and secured to a support S, which encircles the body of the indicator, and is held in position by the clamp- ing screw E. Also secured to the support are the binding screws C and the spring D, these parts being shown sepa- rate from the indicator in Fig. 39- The stud B, Fig. 40, is screw- ed into the upright on the swivel plate that carries the pencil mechanism of the indi- cator and serves as a support Fia. 39. for the armature A, Fig. 41, and to which it is secured by a small set screw for that purpose ; therefore any movement of FIG. 38. 66 Steam Engine Indicator the armature A, in either direction, relative to the magnet M, produces a similar motion of the pencil (in the opposite direct- ion), to or from the paper drum of the indi- cator. The spring D, Fig. 39, is formed so as to hold the armature within the field of the mag- net, before the current is established, and also to quickly release it when the current from FlG< 41 * the battery is broken. The magnet M, consists of a FIG. 40. s } n gi e S p 00 i O f so ft iron, wound in the usual manner with insulated magnet wire, and enclosed by a soft iron shell, the combination thereof establishing the two poles of the magnet, when subjected to the effect of an electric current passing through the wire. The armature A is also constructed of a soft grade of iron and is finished to a diameter the same as the magnet shell, and is adjustable on the stud B, to exactly coin- cide with the magnet M. On the side facing the magnet are two small brass pins for the purpose of assisting in the instan- taneous release of the armature, from the magnet after the cur- rent is broken. This electrical device is easily attached or de- tached in a few seconds, and its connection with the indicator, does not in any way interfere with the usual manipulations of the operator, in adjusting the paper to, or removing it from the paper drum; changing of the springs in the instrument, or any minor operations that may become necessary, as the pencil mechanism is free to be revolved in any convenient position. It is represented in Fig. 38, as being attached to a Right- hand Indicator, but.it may be used on a Left-hand instrument with equal facility. The change from one to the other is easily and readily made in the following manner: first unscrew the cap (that carries the pencil mechanism), and take it complete from the indicator, then by loosening the clamping screw E, the support S may be readily removed, and it only remains to unscrew the magnet M, from the support S, and change the And Its Appliances. 67 location to directly the opposite side of the support and secure it in that position, by means of the small screws for that pur- pose. The binding screws, as well as the spring D, will also need reversing on the support S ; the parts all being provided with means by which it may (if necessary) be easily and readily accomplished. Replace the device on the indicator in a re- versed position and secure it by the clamping screw E. Where the circuit is short the device may be operated in connection with a single indicator, by any one of the well known batteries in the market, (either dry or liquid). In our own experience, and in all cases where such an ap- pliance is desired, and where accuracy is necessary, this simple electrical device seems to meet all requirements, being easily attached or detached, without any change in the mechanism of the indicator ; instantaneous in its action, and can be relied up- on at all times to give correct results, with the least amount of labor and anxiety to the operator. 68 Steam Rngine Indicator CHAPTER IX. CARE AND USE OF INDICATOR. Before attaching the indicator, open the cock and allow steam to blow through the pipes for the purpose of removing any scale or dirt that may remain in the pipe after fitting up ; as it is of the greatest importance that all parts of the indicator be kept in good working order, where a close degree of accu- racy is expected. The most important of these parts, are the cylinder and piston ; to which especial attention should be directed as to their condition ; because the accumulation of de- posit, or dirt of any description between their surfaces of con- tact, (however minute) will produce irregularities, and distor- tions in the diagram, to such an extent, as will render it almost impossibe to secure the information a diagram is intended to convey ; therefore it becomes very essential at frequent intervals to remove the piston from the cylinder ; (which can be done by simply unscrewing the cap upon which the whole mechanism is attached, and lifting from the instrument) and thoroughly clean both, by the use of cotton cloth, waste, or some other suitable material. This being accomplished, lubricate these parts with some good cylinder oil, and replace them again in the instrument. The pivots or joints of the pencil movement, should also be kept clean, and oiled occasionally with some light machine oil And Its Appliances. 69 that will not gum or become sticky ; a bottle of which usually accompanies the instruments of all makers. This should be used sparingly as a very small amount suffices for the purpose, and any surplus should be cleaned off. It is absolutely necessary that there be perfect freedom in the pencil mechanism ; (and when not subject to the action of a spring) the pencil bar on being raised to its highest position, should from its own weight, fall with the utmost freedom to its lowest position, and this requirement is very essential in order to insure correct diagrams. A further test of its correct- ness may also be made by again raising the pencil bar to its extreme height, and covering (with the thumb or finger) the hole through which the steam is admitted against the indicator piston ; and if the mechanism be not impeded in any way, ex- cept only by the air contained within the indicator cylinder, the pencil will descend slowly and uniformally until it reaches its lowest position. Should this be found otherwise than as stated, it may become necessary to disconnect the parts of the movements from the piston, and test each part separately until the cause of the trouble is located. The Paper Drum also requires attention, it being in constant motion, and subject to considerable wear; conse- quently should be examined from time to time, and the bearing cleaned, and thoroughly lubricated, using the same light machine oil, as for the pencil movement. With the ordinary paper on the drum the Siberian lead pencil about grade H. H. H. H. should be used in taking the diagrams ; the pencil being sharpened to a fine round point with a knife or fine file. A more satisfactory result of the tracings may be obtained by the use of a chemically prepared paper, (called metallic paper), upon the drum, and using a point made of common brass, or preferably silver wire suitably sharpened for the trac- ing point. 70 Steam Engine Indicator One sharpening of the metallic pencil will give good re- sults on a large number of diagrams, and the general character of the work will be much more satisfactory than with the lead pencil. The paper should be placed upon the drum in such a manner that it will be perfectly smooth. This may best be done by first folding one end, and slipping it under the longer clip ; then pass the paper around the drum and bring the loose end under the short clip ; taking the two ends thus located, between the thumb and finger, and with the other hand by a slight pressure at the top of the card, slide the whole down the drum ; the outer edge may then be folded back over the clip if needed. Adjust the stop screw so that the pencil will bear lightly on the paper, otherwise the friction between the pencil and card will cause the diagram to be irregular, and will not repre- sent the true action of the steam within the cylinder. Paper Drum Motion. The motion of the paper drum may be derived from various different parts of the engine, but what- ever point is selected, it is essential that the motion of the drum shall coincide in miniature, exactly with that of the en- gine piston, at every part of the stroke. Owing to the irregular motion of the engine piston, dur- ing the stroke, caused by the varying angularity of the con- necting rod, it is often uncertain, and difficult to select a point (other than the engine cross-head), that shall fulfill the exact conditions required ; but if such other point should be chosen, careful attention as to its location becomes necessary, in order that the motion resulting therefrom, may in no wise vitiate the diagram. The Cross- Head being directly connected to the piston rod, consequently moves at every part of the stroke, and under all circumstances in exact unison with the engine piston ; therefore, it is the part usually selected from which to obtain the motion of the drum ; as being the most direct, reliable, and A nd Its Appliances. 7 \ convenient for the purpose ; but the amount of its movement, (whatever that may be), must be reduced to suit the range of the paper drum, or the length of the diagram to be taken ; and this reduction must be in an exact proportion, throughout the stroke, to the movement of the cross-head. Where special reducing wheels are used for this purpose, a stud is generally screwed in the cross-head, of sufficient length, such as will cause the cord from the reducing wheel, when attached, to be in a direct and parallel line with its motion. It often happens that this plan cannot always be successfully accomplished, owing to the various different construction of engines ; hence in such cases a resort to the use of small carry- ing pulleys will be necessary. Carrying Pulleys. It is always desirable to avoid these pul- leys wherever possible, as their use are often detrimental ; in that they increase the tension on the cord ; cause the cord to become dirty from the oil used in lubricating the pulley; which will in a short time render it unfit for further use ; they also create a friction that becomes an additional tax upon the drum spring, and in many ways becomes a source of annoyance to the opera- tor. Nevertheless occasions often occur, where their use becomes indispensible, and in such cases they should be located at such points, as will suggest themselves to the ingenuity of the engineer, as best, for obtaining the desired re- sults. The style shown in Fig. 42 is universal and meets all requirements. Various devices, and methods for reducing FIG. 42. the amount of movement of the engine cross- head to any desired length of diagram, will be found repre- sented aud described in Chapters 5, 6 and 7. J2 Steam Engine Indicator The Indicator Cord. The usual manner of imparting- mo- tion from the engine cross-head to the drum, is through the medium of a hard braided linen cord ; and sometimes a metal- lic cord (such as fine piano wire), may be used to advantage in connection with it, under circumstances where an unusual length of cord is required. : , Cord of all kinds especially when new, is possessed of a certain amount of elasticity, of which it becomes necessary to re- move as near as possible, before using, in order to avoid any further stretch when in use ; so that coincidence of motion be- tween the cross-head, and the reduced motion of the paper drum shall be practically uniform. The most simple and ready method, and the plan usually adopted for removing this elasticity is by suspending the cord from one end, and attaching sufficient weights to the other ; allowing it to remain so suspended from 12 to 24 hours; or un- til it becomes apparent that any further stretching may result in injury to the cord. The cord that is intended especially for indicator work is; usually stretched by the manufacturers until its elasticity is eliminated, and therefore will not stretch, when in use under ordinary circumstances, to any extent that would seriously in- terfere with the accuracy of the diagrams. A simple, light, and exceedingly convenient cord adjust- er is represented in Fig. 12, Chapter IV, for adjusting the length of the cord between the indicator and reducing gear. The hook on the cord from the indicator, should be at- tached as close to the indicator as possible ; (to prevent any swaying of the cord), and connect into the ring of the cord ad- juster, while the small holes in the adjuster receive the cord from wherever the motion is derived. The Indicator Spring. The denomination of the spring to be used in any particular case, depends principally upon the boil- er pressure. A book usually accompanies most indicators,, And Its Appliances. 73, which, gives the necessary information, (either by a table di- rect, or by a computation rule), for the selection of the most suitable denomination of spring, for any given boiler pressure. In indicators which have a range of pencil movement of from 2^/2, to 3 inches in height, a 40 pound spring is a good standard for pressures between 80 and 90 pounds, and a 50 pound spring for boiler pressures from 100 to 120 pounds per square inch. Each indicator spring is numbered to correspond with the pressure per square inch required to compress it an extent, sufficient to cause a vertical movement of the pencil of exactly one inch. For example : In case a 50 spring, as shown in Fig. 13, Chapter IV, is used, a pressure of 50 pounds per square inch in the engine cylinder, will raise the pencil one inch, or a pressure of one pound will raise the pencil -fe of an inch ; the same rule applying to all other denomination of springs. After use, the spring ought never be allowed to remain in the instrument, but should at once be removed, and wiped perfect- ly dry ; otherwise it is liable in a very short time to become corroded and pitted to such an extent, as to render it quite in- accurate ; at the same time the inside of the indicator cylinder and piston, should also before laying away be made perfectly clean, and free from all moisture arising from condensed steam. Clean by means of cotton waste, or cloth, used in connec- tion with a wooden stick. -0 40 . 40 TO THE INCH 1 1 ' 1 ' 1 'I 1 80 FFT] 120 160 FIG. 43. Indicator Scales. For convenience and greatly facilitating the measuring of the diagrams, special boxwood scales, as shown in Fig. 43, are provided, upon which the inches are 74 Steam Engine Indicator divided into units ; each unit representing pounds pressure per square inch, corresponding to the number of the spring in use. The edge upon which the graduations are performed, is beviled, in order that the marking may be near the paper, and consequently be more readily observed ; hence their use will be found much more convenient, than the steel scales .sometimes in use. The Drum Spring. The tension on the drum spring illustrat- ed in Fig. 44, is a matter that depends upon the good judg- ment of the engineer, and should be just suffi- cient to keep the cord taut on the backward or inner stroke of the engine. The best re- sults are obtained where the highest tension FIG. 44. i s employed, consistent with good work. As the speed of the engine is increased, it is sometimes necessary to increase the tension on the drum spring to counteract the effect due to the inertia of the drum at the higher speed, and provisions are usually made on most indicators, and in- structions given whereby the tension on the spring may be varied to suit the higher speeds wherever necessary. And Its Appliances. 75 CHAPTER X. TO TAKE DIAGRAMS. The desired pressure spring being placed in the instru- ment, and the paper in place upon the drum, connect the cord from the indicator to whatever form of reducing motion there may be at hand, (thereby starting the drum in motion), then open the cock on the pipe communicating between the steam engine cylinder and the indicator piston, (which in turn starts the pencil movement) until a few revolutions of the engine have been made, or until the instrument is heated to a temper- ature due to the steam pressure present. During this motion, examine the pencil mechanism to see that it is moving freely, which may be ascertained by placing the finger directly against and over the top of the piston rod, and by following its motion up and down ; the presence of any grit between the indicator cylinder and its piston, can readily be detected. If such should be found to be the case it will be necessary to stop the motion of the indicator, and remove the pencil mechanism with the piston and thoroughly clean and oil, before again replacing in the indicator. Again set the Indicator in motion, and after a few revolutions of the engine have been made, swing the pencil until it comes in contact with the paper on the drum and hold it there during one complete revolution of the engine. Withdraw the pencil and close the indicator cock, and immediately return the pencil to the paper in order to trace the atmospheric line. This should always be done as soon as possible after tracing the card, so that 76 Steam Engine Indicator it may be drawn under about the same conditions (as to temperature, etc.) as when the card was taken. When power is to be measured, it is a good plan to keep the pencil in contact with the paper during a number of revol- utions of the engine ; and in measuring the diagram, to take a line most nearly representing the average. Diagrams should always be taken from both ends of the cylinder where correct conclusions are expected. Although a diagram from one end of the cylinder may prove satisfactory, it is not safe to infer that one from the opposite end will be equally so ; but on the contrary there will often be found a great difference between diagrams taken from each end of the cylinder, owing to the varying conditions of pressure, etc., usually found in practice. Very often this difference results from improper or uneven valve setting; wherein the period of opening or closing the valve, and also the point of cut-off differ at each end in relation to the stroke of the engine ; and may be partly due to rough and torturous steam passages. Sometimes the load may suddenly change during the in- terval between the taking of the first and second diagram, causing a disparity between them that might prove misleading, in that, it would give the appearance similar to that of an un- even valve adjustment, consequently after a careful consider- ation from a number of diagrams, it becomes a requisite of the engineer to use his best judgment in deciding the cause and applying the remedy for any irregular or unusal appear- ance of the diagram. This information can only be derived from a careful application of the indicator and a study of the diagrams. Where two indicators are used and placed at each end of the cylinder, the diagrams (if desired) may readily be taken simultaneously ; but in case of only one indicator at hand, it must be changed from one end of the cylinder to the other ; A) id Its Appliances. 77 In order to obtain diagrams from both, a matter requiring considerable time and trouble ; therefore it will be found most convenient in such case to place the indicator in connection with a three-way cock (previously described), at the middle of the cylinder, thereby admitting steam from each end, so that diagrams can be taken from either end of the cylinder, by simply turning the handle of the three-way cock to the required position. This arrangement greatly facilitates the labor, and it also enables the operator to produce diagrams from each end of the cylinder, upon the same sheet of paper, and in the short- est possible time ; it being very essential that the second diagram be taken as quickly as possible after the first, in order that the conditions of speed, load, and pressure may remain more nearly alike during the time occupied for both tracings. It is also more satisfactory to the engineer to take diagrams from both ends of the cylinder, upon the same paper as it en- ables him at once to make a discernable comparison of the pres- sures exerted on the opposite sides of the piston, throughout one revolution of the engine. After all required adjustments, that become necessary have been made, and a satisfactory diagram obtained, stop the motion of the drum and remove the paper therefrom. Make memorandum on the paper of as many of the facts, as may be required, such as the style of engine, where located, the diameter of cylinder, length of stroke, diameter of piston rod, the number of revolutions per minute, which end of cylinder, the scale of the spring, the vacuum in the condenser, the boiler pressure, the day and hour of tak- ing the diagram, and any other factors that may enter into, and become necessary for an accurate consideration and solu- tion of the diagrams. For convenience of writing in the data, and also for filing away for future reference, the paper used upon the drum is us- ually in the form of printed blanks of suitable dimensions to fit the drum of the indicator, for which they are designed, and 78 Steam Engine Indicator contain the heading of the different principal factors necessary for computing from the diagram, the horse power, water con- sumption, etc., of the engine. For very expert tests, these Diagram from ._ Diameter of Cylinder.. Boiler Gauge _.... _ _.. Engine at :,- Diameter, of Rod ; Stroke ; Clearance 'I8-. .; Time ; ad of CyllaOer..... ; Scale of Spring ; Vacuum Qauge ; Reaper minute .. ., .. f . /f.LfL ~ 1 l.HJ>. FIG. 45. blanks may be printed in various forms, to suit any required data necessary ; but the above as shown in Fig. 45 will be found sufficiently elaborate for any ordinary indicator practice. Oft And Its Appliances. 79, CHAPTER XL INDICATOR DIAGRAMS. The important and essential knowledge to be derived from, a careful investigation and study of indicator diagrams is in- valuable to the engineer, as they enable him to easily ascertain an*' establish various facts concerning the use of steam, that by any other method would prove complicated and unsatisfactory ; of which the following may be stated. First. It shows whether the valves of an engine are cor- rectly and evenly timed; and also serves as a guide in all necessary adjustments of the same that may be required, in order to insure the best distribution of the steam working with- in the cylinder ; and thereby securing the maximum economy, and efficiency of the engine. Second. The indicator power developed in the cylinder of an engine, may be determined ; also the quantity of power lost in various ways ; such as leakage of valves, back pressure, too early release, and incorrect adjustment of valves. Third. It indicates whether the steam ports, and passages are adequate in size, and a diagram taken from the steam chest, will also show whether the steam pipe and its connections are of sufficient size. Fourth. It indicates the condition of the valves and pis- ton in reference to leakage. Fifth. In connection with a feed water test, (showing the actual amount of steam consumed) the economy with which the engine works may be determined- 8o Steam Engine Indicator To ascertain with accuracy, each and every item of infor- mation here mentioned, it is absolutely essential that the dia- gram should truly represent the motion of the piston ; and also the pressure exerted on both sides of it, at every point of its stroke. The general features of a diagram, that indicates a proper distribution of the steam in an engine cylinder, is represented in Fig. 46, the attainment of which, (as near as possible) should be the endeavor of an engineer in setting the valves of FIG. 46. his engine. A. A. is the atmosphere line, and B. B. represent- ing boiler pressure. In this diagram the initial steam pressure, which is the highest pressure realized in the cylinder, is fully maintained up to the commencement of cut-off ; indicating ample size of steam pipes, ports, and other passages in the engine. The expansion curve is good, and the release of the steam is sufficiently early to secure a free exhaust, also low, and uni- form back pressure. The exhaust valve closes on the return stroke, in time to provide the necessary compression, (or cushion), and thereby A nd Its Appliances. 8 1 counteracting 1 in part the effects of enertia and momentum of the piston, cross head, and other reciprocating parts, at the end of the stroke. The admission of steam takes place promptly ; and projects the admission line to initial pressure at right angles (or per- pendicular) to the atmospheric line. These qualities in a diagram being an especial requisite tinder any circumstances, to insure an economical working engine. In practice however, there will be a great difference in the outline and appearance of the cards from different engines, and even from the same engine ; arising from numerous cir- cumstances and conditions connected with it. The diagram as before stated simply shows the pressure of steam existing in the cylinder at each part of the revolution of the engine, and it is the province of the engineer to determine whether these pressures at each and every point are the correct ones ; and if such is not the case to ascertain wherein the fault lies, that causes the error; then determine upon, and apply the remedy. It must be understood, that in a great majority of cases, the shape or outline of the diagram, depends principally upon the manner in which the steam is admitted to, and released from the engine cylinder. Therefore, by careful investigation and measurement of these outlines, and turning the varied information which they furnish to practical advantage, the real value of the indicator is readily made apparent. As a preliminary to the study of the diagrams, suppose we knew that at a certain part of the stroke the full boiler pressure should be realized ; now if this does not appear to be the case on the diagram there is evidently imperfections existing, either from an incorrect adjustment of the valves, or may be due to inadequate capacity of the steam pipes, and passages between 82 Steam Engine Indicator the boiler and engine cylinder; and almost invariably happens also with engines having insufficient, or extremely light loads. Adversely, the diagram may show toj great a pressure, at other certain points, when we know that there should be less in order that the demands for good economy and efficiency in the engine be obtained. This latter circumstance may also proceed partly from in- correct valve adjustment ; although it is principally caused by leakage through the admission valves after cut-off ; in combina- tion with the re-evaporation of steam previously condensed within the cylinder in the early part of the stroke. Any derangement of valve mechanism of the engine, such as incorrect position of the eccentric, on the shaft or an uneven adjustment in the length of the valve rods and connections, will in consequence, bs revealed in the diagram, by late admis- sion or release, by low initial, or high back pressure, also by absence of compression ; either of which in performing an equal amount of work will result in an increased consumption of steam. Consequently where discrepancies of any kind occurs, a thorough investigation, study, and reasoning of the diagram first becomes necessary, in order to intelligently locate the cause of the defect, and make changes, and corrections accord- ingly until the diagram shows a proper distribution of steam pressure throughout the stroke of the engine. And Its Appliances. 83 CHAPTER XII. STUDY OF DIAGRAMS. To the Steam Engine Indicator (it may be said), belongs the credit of furnishing a great part of the information that has enabled scientific engineers, (and others who have studied the subject) to apply intelligently and successfully, and has hereby contributed in a great measure to the present perfec- tion of our modern steam engines. The most correct and best means of obtaining a knowledge of the internal workings of the steam in a cylinder under differ- ent circumstances of loads and pressures is, by a careful study of what are designated as Indicator Diagrams. A diagram from one end of a steam engine cylinder shows the exact pressure acting upon the engine piston, at any and every part of its movement, during the time of one complete revolution on both forward and return stroke of the engine ; and to show a corresponding pressure on the other side of the piston, another diagram must be taken from the opposite end of the cylinder. The outline of the figure traced by the penci-1 upon the paper of the indicator drum, depends upon the variable pressure of steam in the cylinder, acting upon the engine piston, through- out one complete revolution of the engine, in combination with the horizontal length of the figure produced by the rota- tive motion of the paper drum. 84 Steam Engine Indicator If the steam be admitted to the cylinder at the commence- ment of the stroke and continued at a uniform pressure, and exhausted at the extreme end, and from thence returning to its beginning, it will have traced a figure on the paper, bearing a close approximation to a parallelogram, or rectangle. If the admission of steam had been cut off, after only a part of the stroke had been completed, (leaving the amount to expand to the end of the stroke) the diagram will assume a shape somewhat similar to that represented in Fig. 47. In the matter of n \ details these two rep- resentative forms may have innumerable modifications. We have selected Fig. 47 as exhibiting the essential features .and events (during the stroke of the en- H FIG. 47. gi ne )> f a well pro- portioned diagram, showing the action and pressures of steam that usually take place in the engine cylinder. This diagram shows that the admission of steam commences at A and con- tinues to the point C, where cut-off commences, and is com- plete at D ; the expansion is from D to E ; the exhaust begins to open at E and closes at G ; the back pressure is represented by the line from F to G, and continuing to A. The compres- sion of the steam remaining after the exhaust closes, begins at the point G, and ends at the admission line A, B ; this com- pression producing a continual increasing back pressure to the point A. The point T is where the expansion line would have reached provided the exhaust had remained closed to the end of the stroke, and is designated the Terminal Pressure. And Its Appliances. 85 The line H, I, represents the atmospheric line ; and the different events of the stroke, appearing on the diagram at various heights above the atmospheric line are measured from that line, in pounds pressure by a scale corresponding with the spring used, in producing the diagram ; and consequently the location of these points in reference to each other, becomes an index to the engineer, and serves as a guidance to him, in the study of engine performance and in the steam economy of engines. It is advisable in most cases to take the diagrams from both ends of the cylinder, on the same sheet of paper, as shown in Fig. 48, (by the use of the three-way cock, as recommended in a former chapter)in order to facilitate the matter of making a comparison between the diagrams from each end of the cylinder, more readily, and thus showing the varying pressure at dif- ferent events of the stroke, in both ends of FIG. 48. ^, ,. ., A . , the cylinder; such as Reproduction of an actual card taken from a 9^ in. x 9 J . Westinghouse engine 325 revolutions per minute. admission of S t 6 a m , point of cut-off, release, or opening of exhaust, closure of ex- haust, compression, etc., and thereby showing any errors or discrepancies in the adjustment of the valve, or valves, that regulates and controls the flow of steam to and from each end of the steam cylinder, and which thereby enables the engineer to arrive at correct conclusions in reference to faulty valve mo- tions and methods of correcting them ; which by any other way is a difficult task to accomplish, with any certainty, that the re- quirements of a correct valve motion are attained. 86 Steam Engine Indicator An Indicator Diagram is the result of two movements, which are at right angles to each other ; one of which is the rotation of the paper drum, forward and back, around its cen- tral stud, and is produced on a reduced scale, coincident with and by the movement of the engine cross-head, and thereby tracing a horizontal line on the paper drum, at any time a con- tact is made between the drum and pencil. The other is the vertical movement of the pencil, parallel to the axis of the drum and is produced by the steam pressure, acting on the piston of the indicator, and forcing it to a height proportionate to the pressure upon the piston ; consequently the length of the diagram represents the stroke of the engine on a reduced scale; while the vertical height at any given point, represents the pressure upon the Indicator piston, at a corresponding point in the stroke of the engine. The height to which the pencil will ascend, depends en- tirely on the pressure exerted upon the piston, and the denom- ination of the spring used, and is measured in pounds pressure per square inch, at any given point in the length of the diagram, by a scale, or rule, divided in a number of units per lineal inch, to correspond with the denomination of the spring. The denomination or number of any particular spring, is one that requires the same number of pounds pressure per square inch on the indicator piston, to compel the piston to move one inch in vertical height, against the resistance of said spring. By placing a spring in the indicator and connecting the cord so as to give motion to the paper drum, (and before admitting steam to the instrument) a horizontal line may be drawn, by bringing the pencil in contact with the paper on the drum. This line is called the atmospheric line, and from which, as a zero line, all pressures are measured in a vertical direction from the same, whether above or below the line. All And Its Appliances. 87 measurements above the atmospheric line represents positive pressure, while below the line, shows negative pressure. For each indicator spring, there is usually provided a special scale, or rule, for the different denominations. For example: A diagram that has been taken where a No. 40 spring was used in the indicator, (designated a 40 pound spring) should be measured by a scale that is divided in 40 parts to each lineal inch ; each division in vertical height, above the atmospheric line representing one pound pressure per square inch on the indicator piston. In the various computations and study of diagrams, for the purpose of ascertaining the Mean Effective Pressure on the Engine Piston; Horse Power; Steam Consumption, &c., and also for plotting the hyperbolic curve, it becomes necessary to establish what is called the vacuum line, or line of no pressure, which should be located parallel with the atmospheric line, and at a distance below it, equal to 14.7 pounds, by the scale corresponding with the scale of the spring with which the dia- gram was taken. Another and important factor pertaining to the same study, is the clearance line, which is drawn perpendicular to the, atmospheric line and located at the steam admission end of the diagram ; and at such distance from it, as will bear the same proportion to the length of the diagram, as the volume of the clearance space bears to the piston displacement ; or that vol- ume which is equal to the area of the steam cylinder multiplied by the stroke of the piston. The clearance is the amount of waste room between the steam valve and the engine piston when at its extreme end of the stroke, and which has to be filled with steam at initial pressure at each end of the cylinder, for every revolution of the engine. The required amount of steam for this purpose comes cither directly from the boiler, or, by the compression of the 88 Steam Engine Indicator 49 - steam that remains in the cylinder after an early closure of the exhaust valve, or from both combined. The amount of clear- ance varies in different styles of engines. In slow running engines, this variation usually amounts to from two to five per cent., whereas for high speeds it may reach from two or ten or twelve per cent., or even more. The finding of the ex- act amount of the clear- ance (in the absence of any data fiom the man- ufacturer of the en- gine), is often a diffi- cult matter, but may be roughly approximated in most cases, either by computation from measurements of the space between the valve and piston, when at its end of stroke ; or it may be accurately deter- mined, (where the valves and piston are tight) by filling the " space with water from a receptacle containing a quantity that has been previously weighed or measured, and its vol- ume ascertained. In many cases however this is not practicable, ElG> 50 ' and is almost impossible, with engines that have been in use and neglected until the valves and piston become leaky, and A nd Its Applia nces . 89 thereby preventing any chances of accuracy in the matter. Sometimes the only knowledge regarding the amount of clear- ance has to be obtained from the diagram itself. If this has well defined expansion and compression curves, the clearance line on the diagram may be closely determined, by a graphical method, from either curve ; as shown in Figs. 49 and 50 as follows; Select two points, (pref erably) . on the compression curve, Fig. 49, as far apart as possible, but within the limits of the true curve, and draw a line connecting the two points, which will represent one of the diagonals of a rec- tangle described on the curve, of which two sides are parallel to the atmospheric line. If now a diagonal be drawn through the opposite corners of the rectangle and extended to the vacuum line ; then a per- pendicular drawn from the point of intersection, will be the approximate clearance line : and the distance of this line from the end of the diagram, divided by the total length of the dia- gram will give the percentage of clearance in the engine. Another method of approximately as- certaining the clear- ance is shown in Fig. 5 1 , the results of which coincide exact- ly with Fig. 49, but is given as being rather more simple in its application. Draw the straight j line A. E. from a point ^ tr on the vacuum line ElG - 51 ' (as at A.) in a direc- tion as will cut the compression curve at two points B. and C. and continue it beyond the end of the diagram as at E. Now V 90 Steam Engine Indicator with a pair of dividers, set one leg on the point A. and adjust the other to point B. and with this distance so taken, place one point of the dividers on point C. and describe a line inter- secting the line A. E. at D. If a perpendicular be now drawn from the vacuum line through this intersection, then its distance from the end of the diagram will represent the clearance of the engine. The amount of clearance in an engine is an important fac- tor, and is always considered in the study of steam economy as a source of loss ; therefore in the designing of the various styles of engines, it has always been one of the principal in- tentions with engine designers, to construct them with a view of reducing the clearance to a minimum and thereby saving (in a measure) the amount of steam required to fill large clear- ance spaces. A reduction of clearance has an effect to produce a lower terminal pressure, for any given cut-off; and also greater mean effective pressure for a given terminal ; both of which are conducive to good economy. A loss takes place from the clearance, when the steam is exhausted at a higher pressure than the back pressure, or, that pressure which exists on the return stroke and consequently a reduction of clearance, also reduces this loss of steam, A ltd Its Appliances. 91 CHAPTER XIII. LINES AND POINTS OF THE DIAGRAMS. The diagram shown in Fig. 52, is presented in this chap- ter, to more fully designate by name the various lines, points, and curves, that in combination serves to make it complete, and also shows the lines dotted, that in most cases become nec- essary to be added by hand, in order to assist, and facilitate in all matters attending the accuracy of any calculations that may arise in reference to indicator diagrams. The following names are generally applied to the various lines and curves of the diagram. H. I. is the Atmospheric Line, and is traced by the indicator at a time when communication between the engine cylinder, and indicator piston is closed, and the atmosphere having free access to both sides of the piston of the indicator. V. V. is the Vacuum Line, drawn by hand in dotted lines, and represents the line of perfect vacuum or absence of all pressure. It is drawn i4 T V pounds, (by the scale of the spring with which the diagram is taken) below the atmospheric line ; that being the mean pressure at sea level. V. K. is the Clearance Line, shown drawn by hand in dotted lines, at such a distance from the end of the diagram, as will represent the total clearance or waste room between the 92 Steam Engine Indicator face of the valve, and the piston, when the engine is at either extreme end of the stroke. FIG. 52. Its distance from the diagram is usually reckoned in per cent, of the piston displacement, and in Fig. 52, shows about 4 per cent, of clearance. A. B. is the Admission Line, and its height above the at- mospheric line represents the pressure due to the admission of steam to the engine cylinder. It is usually very nearly perpendicular to the atmospheric line, for the reason that the admission of steam takes place very quickly, and at a time when the piston of the engine is moving very slowly, or nearly stationary. B. is the point of Initial Pressure and is the first pressure realized at the beginning of the stroke of the engine. B. C. D. is the Steam Line, and is traced during the time the steam is being admitted to the cylinder, or until cut-off takes place. And Its Appliances. 93 D. is the Absolute Point of cut-off and is the point where the valve closes and thereby prevents any further admission of steam to the engine cylinder. Owing to their peculiar formations, many diagrams do not show clearly, (from observation alone) the exact point. D. E. is the Expansion Curve, and represents the gradual fall of pressure due to the expansion of the steam remaining in the cylinder after cut-off takes place, and continuing to the end of the stroke. E. is the Point of Exhaust, and is located where the exhaust valve begins to open ; thereby releasing or exhausting the steam from the cylinder ; and like the point of cut-off, is some- times difficult of exact location. E. F. is the Exhaust Line, which descends suddenly and is traced during the interval that occurs, between the time the exhaust valve begins to open, and the end of the stroke. ff H z FIG. 53. In diagrams like Fig. 53, where the pressure has gradu- ally fallen during expansion, sufficiently low, to coincide with the return or back pressure, this line does not appear. And in diagrams like Fig. 54, where the expansion curve falls below the back pressure, before the end of the stroke, 94 Steam Engine Indicator (causing a partial vacuum in the cylinder thereby), the exhaust line is ascending until it agrees with, and merges into the back pressure line. FIG. 54. This action indicates a rapid flow of the steam from the exhaust pipe, back into the cylinder; thereby restoring the pressure lost through the expansion curve falling below the back pressure line, during the latter half of the stroke. F. G. is the Back Pressure Line, and represents the pres- sure opposing the piston on its return movement, and for this reason is called Back Pressure. In diagrams from non-condensing engines it either coincides with, or is above the atmospheric line ; while in condensing en- gine it is below the atmospheric line, at such a distance as cor- responds with the vacuum obtained in the engine cylinder ; and in either case it acts as back pressure. G. is the point of ExJiaust Closure, and is where the ex- haust valve closes ; thereby preventing the further escape of the steam from the cylinder. And Its Appliances. 95 Like the point of cut-off and exhaust, it cannot in all cases be located very exactly from observation ; on account of the change of pressure, due to a more or less gradual closing of the valve, which will cause its exact location to be rather undefined. G. A. is the Compression curve, and is a result of the rise in pressure due to the compression (from the return motion of the piston), of the steam remaining in the cylinder, after the exhaust valve closes. In cases where the exhaust remains open until the end of the stroke, this line does not appear on the diagram. T. is the point of Terminal Pressure, and is an indispensi- ble factor in many calculations pertaining to diagrams. It may be located by a continuation of the expansion curve from E, to the end of the diagram at T, as shown in Fig. 52, and its height above the line of perfect vacuum, V. V. repre- sents the absolute pressure that would exist at the end of the stroke ; providing the release of the steam in the cylinder does not take place earlier. This pressure is always measured from vacuum line V. V. hence it is the absolute Terminal Pressure. Initial Expansion, is the fall in pressure that takes place through expansion during the interval between the admission of steam, and absolute point of cut-off. It is represented in the diagram, Fig. 52, by the dotted line B. P. and is generally considered an undesirable feature, especially in automatic cut-off engines. T. i. and T. 2, in dotted lines, are made use of in calcula- tions connected with the water or steam consumption of the engine, per indicated horse power, as shown by the diagram ; and which will be referred to hereafter. The Mean Effective Pressure, as before noted, is the differ- ence between the average of all the varying pressures acting against the engine piston, in impelling it forward; and that of 96 Steam Engine Indicator all the average pressure which tends to retard its motion ; and is another indispensable factor in the computations of the dia- gram ; and is expressed thus: M. E. P. The point of cut-off is an important event in the stroke of the engine, and is located at a place on the diagram, wh'ere the steam valve absolutely closes; as at D, Fig. 52, and thereby prevents the further admission of steam to the cylinder during the stroke. With slow speed engines, and quick releasing gear, the point of cut-off will be fairly well defined ; but with the higher speeds, relative to the time, or period required from the com- mencement, to the absolute closure of the valve, it will enable the piston to travel a certain distance during that time, (more or less according to circumstances) and which will cause the steam line to be rounded off, to meet the expansion line, and consequently the point at which the valve actually closes, can only be approximately determined by noting the point at which the curve from the steam line changes and begins to concave inward; thence continuing on, to exhaust opening, thereby forming and completing the expansion curve. In many cases it is almost impossible to determine the point of cut-off even in this manner, owing to the various dis- torted formations of the lines of the diagram near this point. ftfc And Its Appliances. 97 CHAPTER XIV. ISOTHERMAL CURVE. A careful comparison and examination of the hyperbolic curve, with the expansion curve of a properly jacketed steam cylinder, with tight piston and valves, has demonstrated that the two curves conform with each other very nearly, in all re- spects ; therefore assuming 1 that the expansion line should be a hyperbolic curve, then the principle, upon which this curve is constructed, furnishes an easy and ready method of locating the theoretical point of cut-off, for any particular point select- ed on the expansion line of the actual diagram. The hyper- bola, sometimes called the Isothermal curve, is constructed on the principle established by Mariotte, in reference to the com- pression of gases, and known as the Mariotte law ; and is gen- erally expressed as follows : "The temperature remaining the same, the volume of a given mass of gas, is in inverse ratio to the pressure which it sustains. And this may be held to be substantially correct within a considerable range of pressure ; therefore according to this law, if steam of 100 pounds absolute initial pressure, per square inch, be admitted to a steam engine cylinder (ignor- ing clearance in the matter), during one-half of the stroke, and admission stopped at that point ; and allowing the volume at that pressure to expand during the balance of the stroke, the vol- ume will be doubled, with a reduction of pressure, of one-half, 98 Steam Engine Indicator or 50 pounds per square inch at the end of the stroke. If, in this example, the admission of steam had been stopped at one- quarter of the length of the stroke, the volume of that amount, of steam at half -stroke would have been doubled, but with a re- duced pressure of one-half, (or 50 pounds per square inch). At three-fourth stroke, the volume would be three times, at one-third pressure (or 33^ pounds), and at the end of the stroke, the volume would be increased four times, and result in a pressure of one-fourth initial (or 25 pounds per square inch), hence, the distance from the clearance line of a diagram, to any point on the expansion line, if multiplied by the pres- sure at such point, the product will be the same wherever loca- ted, and this fact furnishes a simple rule for determining any number of points through which the curve must pass, by tak- ing the .product of any point, (by such multiplication), as a constant number, and dividing it by other distances from the clearance for corresponding pressures, or by other pressures for distance from the clearance line. The properties of the hyperbola therefore enables us to locate points on the curve by an arithmetical method, described and represented in Fig. 55. > / First draw the absolute vacuum, or zero line V, at a distance equal to 14.7 pounds by the scale of the spring below, and parallel, with the atmospheric line H. I. Then locate the clearance line K, in accordance with the best data at hand, in. A nd Its Appliances. 99 reference to what its distance should be from the end of the diagram. Draw A, E, to represent the boiler pressure. Select the point of cut-off on the diagram (as near as possible from obser- vation, as at X), and draw a line through it, perpendicular to the vacuum line, and intersecting it at point 3, and the line A, E, at C, and this line is called the cut-off line. The point C, will then be the commencement of the hyperbolic, or theoreti- cal curve. The vertical height of the line 3, C, (above the zero line), represents the pressure of steam, at the point of cut- off C ; the diagram showing that pressure to be 100 pounds per square inch, (measured by the scale of the spring No. 80). The distance from the clearance line K, to cut-off line 3, C, will represent its volume. Divide this volume, or distance, into any convenient num- ber of equal parts, (it is shown divided into three parts in Fig. 55), then take the length of one such division, and (with a pair of dividers, or otherwise), commencing at the clearance line K, space on the vacuum line whatever number of these equal di- visions, that may be contained in the length of the diagram, and erect perpendicular lines (a little above the actual curve), from each division. These lines are designated as ordinates, and numbered consecutively i, 2, 3, 4, &c., beginning with the one nearest to the clearance line. It is immaterial whether the spacing comes out even with the end of the diagram ; but in cases where they do not, it is only necessary to make an ad- ditional spacing that will extend beyond the length of the dia- gram, (as shown in Fig. 55), and treat it the same as the other points. Now in order to utilize the properties of the hyperbola in laying out the theoretical curve, it will be necessary to draw short lines cutting the ordinates at the proper height, meas- ured vertically from the vacuum line ; so that if the pressure at anyordinate, be multiplied by the number representing the volume of the same ordinate, the product will always be the same, at IOO Steam Engine Indicator whatever point selected ; for example : Suppose on being meas- ured by the scale of the diagram, (No. 80) the height of the point of cut-off C, from the vacuum line V, be found to show an absolute pressure of 100 pounds per square inch ; with a vol- ume equal to three of the divisions, into which the diagram has been divided. Then 100 pounds multiplied by 3, equals 300; which will be our constant number, to be divided for all other pressures or volumes. Consequently the height at which the hy- perbola will cut any desired ordinate, may be found by dividing the constant 300, by the number of the ordinate; that is the height of ordinate 4, is found by dividing 300-1-4=75, and in the same manner the height of ordinate 5 is found by 300-^-5 = 60, or 300-^-6=50, &c., which will be the heights to be set off in divisions of the scale (each division representing pounds pressure), at the different ordinates. If so desired, the con- struction of the curve may be commenced either at the termi- nal pressure, or just before the point of release, and points lo- cated on the ordinates, in the opposite direction by the same method. In this case the terminal shows an absolute pressure of 25 pounds, per square inch; and having a volume of 12 di- visions; therefore 25 X 12 = 300, which if divided by the num- ber representing any other volume or ordinate, we have the same results for pressure as by the first method. Instead of using the height of the lines to represent pressure, they may just as well be considered to represent inches, and fractions of an inch, as follows : the vertical height of the point of cut-off C, from the zero line V, being ij^ inches, and on ordinate 3, therefore 3X i/^ = 3-75 inches, which is our constant number by this method. Hence 3.75^5 = . 75 of an inch, which will be the height of the point above the vacuum line, on ordinate 5, through which the curve will pass, and the heights of all other points may be found, by dividing the constant 3.75 inches, by the number representing each ordinate. The heights of all points must be measured from the vacuum line. A nd Its Appliances. IOI The location of the vacuum line may also be ascertained by dividing the ^pressure of the atmosphere, 14.7 pounds, by the scale of the spring, and the quotient will be in inches ; for example: 14.7-4-80 . 183 of an inch below the atmospher- ic line. This method of constructing the hyperbola, or isother- mal curve, as represented in Fig. 55, is intended to show more particularly, the principle upon which the curve is projected, rather than to lay any claim to simplicity. There are various geometrical methods, much more preferable, for projecting the theoretical curve ; all of which give about the same results, as the one described. ^ \ s*,3 i v One simple and convenient plan of doing; it, js represented FIG. 56. in Fig. 56, and is as follows: Draw the vacuum line V, Vi, parallel with the atmospheric line H, I ; at a distance below it representing 14.7 pounds, by the scale of the diagram; also draw A, E, parallel to the atmospheric line to represent the boiler pressure, erect the clearance line K, at a distance from the end of the diagram, that will represent the percentage of clearance in the engine ; said line being perpendicular to and cutting the vacuum line at V. Select any point on the actual curve, before commencement of the exhaust; as at B, and from that point draw a vertical line, cutting A, E, at E. From E, IO2 Steam Engine Indicator draw the diagonal E, V, and from B, draw a line parallel with the atmospheric line, intersecting the diagonal E, V, at D. From this intersection at D, erect a perpendicular cutting A, E, at the point C. Then C will be the theoretical point of cut- off, and D, C, is called the cut off line. From C, mark off any desired number of points on A, E, as i, 2, 3, 4, &c., and draw a perpendicular from each toward the atmospheric line ; also, from the same points, draw diagonals to the vacuum point V. At the intersection of the diagonals with the cut-off line D, E, draw horizontal lines to meet the perpendiculars from i, 2, 3, 4, &c., an4 the intersection of these lines are the points through which the theoretical curve must pass. This method, (as well/a? :ali:.0t)iers)i pfpGns.tr acting the hyperbolic curve is based on the assumption that the temperature of the steam, (or other medium) remains the same throughout its range of movement ; and also that the piston and valves are absolutely tight, as well as an absence of condensation, or any other dis- turbing influences. It is well known in indicator practice, that in taking dia- grams from a steam engine cylinder, we are subjected (at times) to all of the influences here mentioned. The temperature of the steam changes during the stroke, and usually we find the piston and valves, more or less leaky ; also initial condensation and re-evaporation takes place, (to a certain extent) all combin- ing to cause a departure of the actual (more or less) from the true theoretical curve. Therefore one of the objects, in con- structing the theoretical curve, is for the purpose of comparing and ascertaining the extent of this departure, where princi- pally located ; to study and find the cause of any discrepancies, so as to enable the engineer to apply the necessary means to correct, as nearly as possible, any disagreements that may ap- pear in the actual curve. In the construction of the theoretical curve, it has been assumed that the temperature of the steam remains the same A nd Its Appliances. 1 03 throughout the stroke ; whereas the temperature of the steam in an engine cylinder, gradually decreases from point of cut-off to the end of expansion. Hence, (all other conditions being perfect) temperature alone would result in a slight disagreement, and cause the actual curve at its terminal (with a giyen cut-off) to be a little below the theoretical. The re-evaporation of the steam condensed in the earlier part of the stroke, however, will later on, tend in a measure, to increase the pressure, there- by raising the actual expansion line to more nearly conform with the theoretical curve ; therefore as a general thing, a close approximation of the actual expansion curve, with the theoretical, may be taken as evidence of correct valve adjust- ment, and good practice. It is always advantageous to draw the true theoretical line on the diagram, in order that the ac- tual line may be compared with it. IO4 Steam Engine Indicator CHAPTER XV. ADIABATIC CURVE AND POINT OF CUT-OFF. The curve formed in accordance with the principles of the Mariotte law, depends for its correctness upon the condition that the temperature of the steam in the cylinder remains the same during the entire stroke ; and the curve that coincides with this law of expansion, is the Hyperbolic or Isothermal, in which it is assumed that the steam within a cylinder during expansion is of exactly the same temperature throughout the length of the diagram ; whereas the pressure from the point of cut-off, to the end, is continually changing, and any change in the pressure of steam, is always accompanied by a change of temperature ; therefore the application of this law to a dia- gram from a steam cylinder, would not be absolutely correct, because for any change in volume of the steam, the corres- ponding change that takes place in pressure, would be more than if the temperature had remained constant ; or more, than of a curve constructed in accordance with the Mariotte law. A method of improving this condition of temperature, and pres- sure, is by means of a steam jacket surrounding the cylinder, for transmitting heat from said jacket to the steam within the cylinder during expansion ; and thereby in a measure supply- ing the necessary heat for re-evaporation, and also for increas- ing the temperature, and consequently the pressure, thereby raising the actual line of diagram, in the latter part of the And Its Appliances. 105 stroke and thus causing it to very nearly conform to the Isoth- ermal or theoretical curve. In case of exposed cylinders, or where no provision is made for transmitting heat to the steam during the stroke, a curve may be drawn approximately, representing this curve of actual conditions; wherein, all changes of volume and tem- perature are accompanied by a change of pressure. This curve is called the Adiabatic ; as shown in Fig. 57, and may be, in fact, considered the true theoretical curve, and more nearly corres- ponding to the actual change of pressure that takes place, dur- ing expansion in an unjacketed steam cylinder. There is no absolute correct method of constructing the Adia- batic curve, because it is almost impossible to as- certain the exact amount of heat that has been imparted to the steam during the stroke of the engine ; therefore only an approximate curve can be drawn by, and with the aid of a table of the properties of saturated steam, but in any case, the projecting of this curve is more a problem for experts, rather than for the average engineer. Diagram Fig. 57, is presented to show the difference be- tween the two theoretical curves, as compared with the actual line of the diagram. The upper full line T, C, is the adiaba- tic, and T, B, shown in dotted lines, is the isothermal curve ; while the lower full line T, A, represents the line described by the indicator. If the top, (instead of the terminal) of the curve T, C, had been made to coincide with the theoretical point of cut-off B, the adiabatic would have fallen about two FIG. 57. 106 Steam Engine Indicator pounds per square inch below the theoretical curve at the ter- minal. In almost all diagrams however, from engines having tight pistons and valves, with properly jacketed cylinders, and wherever a high mean effective pressure, with a low terminal is obtained, thereby securing good efficiency and economy ; it is found in all such cases that the actual curve produced by the indicator, conforms very nearly with the Isothermal or theoret- ical curve. The fact of such agreement therefore must be due to a transmission of heat to the steam in the cylinder during expan- sion ; thus increasing the temperature and thereby producing a re-evaporation of a part of the steam condensed in the earlier part of the stroke. As the isothermal curve is very easily drawn and apparently correct enough for all practical purposes, it is therefore the curve now almost universally used by all classes of engineers, for the purpose of comparing with it, the lines of the actual diagram ; and where any considerable departure is found in the actual curve, all efforts are directed toward making such changes in the valve, and piston mechanism, as may be necessary to produce uniformity and a close coin- cidence of the actual line with the isothermal, and where they do so agree is generally considered an evidence of correct valve adjustment and efficiency of the engine. This presump- tion is no doubt nearly correct in most cases, with steam jacketed cylinders, and where the piston and valves are tight; but a close agreement must not always be taken as conclusive evidence of economical results; as we often find in practice some actual diagrams that coincide very nearly with the the- oretical ; but still upon investigation of the amount of steam used in the engine, they will be found to be deceptive and the opposite of economical conditions. This deception in many cases arises from a leaky condition of the piston and valves, rather than from any lack of proper adjustment in the timing of these parts; therefore any A nd Its Appliances. 1 07 decided disagreement of the actual curve from isothermal, gen- erally indicates a leakage of steam, either through the valves or piston or both ; and these may enter into combination, in such a manner, as to be very misleading. The consequences of a leaky steam valve are that it will always cause the actual curve of the diagram to be higher than it should be at the terminal from a given cut-off. The actual curve in Fig. 57, represents the effect on the diagram of a leaky steam valve. In this case the Isothermal (shown in dotted lines), has been started at the end of the expansion, for the purpose of showing how much more work might have been done by the steam, from the given terminal ; whereas if it had been drawn to coin- cide at the commencement, with the absolute point of cut-off, (that is, at the intersection of the actual curve with the line D, B,) it would have shown the expansion line of said curve considerably higlier than the theoretical at the terminal T ; this being due to the extra amount of steam entrained through the valve after cut-off and during expansion. If, in the present instance the piston had leaked just suf- ficient to cause the expansion line to coincide with the theoret- ical ; then the diagram might have been considered from obser- vation alone; as representing economy and good conditions in the engine ; when in fact the reverse of this in the case, owing to leaky condition of both of the parts named. Therefore in order to secure the most economical results in the steam en- gine, it is of the first importance, and absolutely necessary that the valves and piston, be practically tight, in order that all losses arising from this source shall be brought to a mini- munio A leaky steam valve will be less noticeable at the com- mencement, or in the earlier part of expansion, because of the slight difference of pressure at that part of the stroke, between the steam in the cylinder and that in the steam chest, but will become more apparent on the expansion line, as these pres- sures become more unbalanced in the latter part of the stroke. io8 Steam Engine Indicator Also a leaky piston will be indicated by a sudden falling away of the actual curve from the theoretical at the beginning of expansion, due to the difference in pressure between the opposite sides of the piston, but as the pressures become more equalized later in the stroke, this difference will finally dis- appear. If the valves and piston are absolutely tight, (thereby obviating all leakage) and also, if no re-evaporation takes place, then the theoretical curve drawn strictly in accordance with the principles of the Mariotte law, must necessarily be, at the point of release (from a given cut-off), higher than the ac- tual curve, principally on account of the increasing volume of the steam, thereby diminishing its heat, and consequently its pressure during expansion. But in indicator practice the re- verse of this is usually found, and in most cases the actual curve will be above the theoretical at the point of exhaust open- ing. This evident rise of pressure, in the latter part of the stroke, is claimed by some engineers to be due to a re-evapor- ation of the steam, that has lost a portion of its heat, and therefore condensed, by contact with the colder surface of the cylinder at the commencement and earlier part of the stroke ; said heat being again restored in the latter part of the stroke by transmission from the inner surface of the cylinder. It is construed by others to be due, more to defective and leaky steam valves than to re-evaporation. It may be due either to the latter, or to a leaky steam valve, or both com- bined, and therefore becomes a matter for consideration and judgment in most cases on the part of the engineer. The rise in pressure from re-evaporation a fane, would hardly cause the actual line to go much, if any, above the theoretical ; consequently a close agreement of the actual line of the dia- gram to this line, is all that can be expected, or desired under the circumstances. The location of the correct point of cut-off, on the diagram is another matter that requires considerable experience and A nd Its Appliances. 109 judgment in selecting the best point on the actual curve, to be used as a basis, with any of the various geometrical methods of construction, employed for locating the correct point of cut-off ; all of which give about the same results. One method of con- struction for locating the point, is repre- sented in Fig. 58, as follows: Draw the vacuum line V, V, parallel and below the atmospheric H, I, at a distance equal to 14.7 pounds by the scale of the spring. ir/ Draw the line A, E, also parallel and just the diagram. The clearance top of FIG. 58. touching, or near the being known, or de- termined by either of the methods previous- ly described erect the clearance line K, ac- cording; select any point on the expansion line, where it is known that the steam and exhaust valves are closed, as at D, and erect a perpendicular, intersecting the line A, E, at B; from B, draw the diagonal line to to the vacuum point V, and from D, draw a horizontal FIG. 59. I IO Steam Engine Indicator line cutting the diagonal B, V, at F. From F, erect a perpen- dicular intersecting the line A, E, at C. ThenC, is the correct point of cut-off ; or is where the further admission of steam to the cylinder must be stopped, in order that the expansion line shall pass through the selected point D. This diagram is rep- resented as having been taken from a single cylinder condens- ing engine, the steam valve having no apparent leakage, and the point D, as being selected belozv the atmospheric line. The diagram represented in Fig. 59, is taken from the same style of engine as Fig. 58 and the method of locating the point of cut-off is precisely the same. The only difference be- tween the diagrams, being in the location of the point selected on the expansion line. Here the point D is nearer the center of the curve, and above the atmospheric line, and gives the correct point of cut-off at C. The construction of the theor- etical curve on the diagram, in this case, indicates a consider- able leak in the steam valve. It is not necessary that the line A, E, be drawn at the extreme top, as in dia- grams where the valve is slow in closing, and thereby causing the curve of cut-off to be de- cidedly rounded, it may be better to draw the line through the abso- lute closure, as near as can be observed ; in or- der that the contrast ,may be more plain at that FTG. 60. Another very simple method of locating the point of cut- off, is represented in Fig. 60, and is as follows : Draw the vacuum and clearance lines the same as in the preceding And Its Appliances. ill figures ; also the line A, E, near the top, or through the noted point of cut-off. From V, draw the diagonal line at an angle of 45 degrees, with the vacuum line, and intersecting the line A, E, at B, drop a line from B, cutting the expansion line at D. Place one point of a pair of dividers at B, and with a radius equal to B, D, describe the arc D, C, cutting A, E, at C, then C will be the correct cut-off point. The drawing of the diagonal line will be more quickly done by the use of a 45 degree triangle, but in the absence of one, may be done by the method as shown in Fig. 60. Place one point of the divid- ers at V, and with any convenient radius describe the arc 1,2; then with the same radius, and from i and 2, draw short arcs, cutting each other at the point 3. From V, draw the diagonal through the intersection at 3, which will be the desired angle. 112 Steam Engine Indicator CHAPTER XVI. THE FOOT-POUND, AND MEASUREMENT OF DIAGRAMS. The foot pound is the unit of measurement in computing the power of steam engines and represents the force necessary to lift one pound, one foot high. The established standard of horse-power being 33,000 foot pounds or an equivalent amount of force, such as 1000 pounds lifted 33 feet; 500 pounds 66 feet; or 100 pounds lifted 330 feet in one minute. The horse power of a steam engine is therefore denoted by the number of pounds it is capable of raising to a given height in one min- ute. The usual and correct method of computing this is by multiplying the area of the piston (in square inches), by the mean effective pressure of the steam acting against the piston throughout the stroke, and also by the speed of the piston {in feet), per minute, and dividing the product of such multi- plication by 33,000, the quotient will be the indicated horse- power. For instance : Suppose we have an engine in which the piston area is 201 square inches, with a mean effective pressure of 30 pounds per square inch, and a piston speed of 450 feet per minute, then ^- = 82.22+ indicated horse-power. 33,000 The actual efficient horse-power will be somewhat less; de- pending upon the amount of friction in the engine. A ready and convenient method of calculating the horse-power from a A nd Its Appliances. 1 1 3 number of cards from the same engine, is for the engineer to first compute the horse-power of his engine at one pound mean effective pressure and using the number so found as a constant or multiplier for all other mean effective pressures. For illus- tration : Suppose as in the preceding example, the piston area to be 20 1 square inches, and piston speed 450 feet per minute, then -- = 2. 74+ which is the horse-power of the engine 33,000 at one pound mean effective pressure, and which may be used as a multiplier for all other mean effective pressures in the en- gine ; the product of the multiplication will be the total indicated horse-power. Hence the horse-power of the engine at one pound mean effective pressure as above being 2.744- therefore at 30 pounds it will be 30X2.74=82.20, or at 25 pounds mean effective pressure would be 25 X 2.74=68.50 in- dicated horse-power. The factors connected with the subject are therefore, as before stated, ist. The area of the piston (in square inches), which can be obtained from a table of the diameters and areas of circles, or may be computed by multi- plying the square of the diameter in inches by the decimal .7854; the product will be in square inches. 2nd. The speed of the piston (in feet), per minute and which may be found by multiplying twice the length of the stroke (in feet), by the number of revolutions of the crank, which will give the piston speed in feet per minute. 3rd. The force or mean effective pressure of the steam, acting upon the piston during the time. The product of all three being divided by 33,000, the standard unit of horse-power. The indicator in most cases is used principally for deter- mining the horse-power ; but by the aid of its record made on the card, the impelling force against the piston at all periods of the stroke, is made visible, and thereby furnishes an index of the work performed, and enables the engineer to study in- telligently many other important matters connected with the Steam Engine Indicator S*0 problem of steam economy. In order to determine the horse- power of an engine, it first becomes necessary to ascertain from the diagram, the mean effective pressure of the steam acting upon the piston during the stroke of the engine. The finding of the mean effective pressure is rapidly and easily accom- plished by the use of the Planimeter, an instrument especially adapted for the purpose ; but when an instrument of this kind is not at hand, this pressure may be approximately determined by means of a number of lines drawn through the diagram as. represented in Fig. 61, and is as follows : Di- vide the diagram into any number of equal parts, and draw lines (called ordinates), through each division and perpendicular to the atmospheric line ; thus dividing the dia- gram into a number of small areas. The mean effective pressure may now be found by meas- uring the height of each line, in pounds, by a scale corresponding with the scale of the spring with which the diagram was taken ; then by adding the pressures so found at each division and dividing their com- bined sum by the number of divisions into which the diagram has been divided, will give the mean effective pressure in pounds per square inch. The diagram, Fig. 61, is shown (by the ordinates in full line), to be divided into ten equal parts; consequently ten would be the divisor for the combined sum of the ordinates in this case; for example: The combined length of the ordinates measured in pounds by the scale of the. FIG. 61. A nd Its Appliances. 115 spring (50) is 428 and this divided by the number of divisions as 428^- 10=42.8 pounds mean effective pressure. Where greater accuracy is desired, or where the outlines of the diagram are very irregular, it may be advisable to sub- divide as shown in dotted lines, making twenty divisions, and consequently dividing their combined sum by twenty. In dia- grams where this irregularity exists only in a part of its length, it is sufficient (at that part alone), to sub-divide on each side of the line or lines, for which the pressure is required ; and measure the pressure on each sub-division ; add together and divide their sum by two (2) ; the quotient will be the pres- sure sought on the full division line as shown at the top of the diagram in Fig. 61. In place of measuring the heights of the ordinates, (in pounds) by the scale of the spring, each may just as well be measured in inches. If the sum of their combined length be multiplied by the scale of the spring, and divided by the num- ber of ordinates, the quotient will be the mean effective pres- sure in pounds per square inch, acting against the piston throughout the stroke. For example : The combined length of the ordinates measured in inches'^ 8.56, then 8.56 X SO-T- 10= 42.8 pounds mean effective pressure, the same as before. An- other convenient method, which has the merit of simplicity may be staten as follows : If we draw the number of ordinates in the length of the diagram equal to the number correspond- ing with the denomination of the spring, then the combined length of the ordinates in incJies will be the mean effective pressure in pounds per square inch. For example : Suppose in the diagram, Fig. 61, the spring to be a 50 and that the length of the diagram be divided into the same number (50) of equal parts, then each inch of the combined length of the ordinates would represent one pound mean effective pressure. If it had been divided into twenty-five (25) parts, then each inch would represent two (2) pounds mean effective pressure, etc., and in 1 1 6 Steam Engine Indicator any case by dividing the number representing the denomina- tion of the spring by the number of division in the length of the diagram ; the quotient will be the multiplier for the combined length of the ordinates in inches, and the product of such mul- tiplication will be in pounds mean effective pressure. For in- stance : The combined length of the ten divisions in the dia- gram, Fig. 61, is 8.56 inches, and the scale of the spring is 50, therefore 50-^10=5 and 8.56x5 42.8 pounds mean effective pressure, the result being precisely the same as by the other methods. In working out the diagrams it is advisable to make the divisions as numerous as convenient, which tends to more accurate results, and particularly so where the outline of the diagram is very irregular. In cases where a scale of the spring is not at hand, a con- venient method of finding the combined length of the ordinates is by taking a narrow strip of paper and marking on it the height of each division, commencing at No. i. Mark its length on the paper, then place the mark made at the top of No. i on the bottom of No. 2 and mark the top of No. 2, and so on successively to the end of the diagram, then measuring their total combined length in inches which being multiplied by the number of spring, and divided by the number of divisions, will give the mean effective pressure, in pounds, per square inch, or, in place of measuring with a strip of paper, it may be as correctly done by drawing a straight line of sufficient length to contain the combined length of the ordinates, and with a pair of dividers set to the length of each different ordinate suc- cessively; commencing at No. i, and transferring the length of each upon the line. The mean effective pressure may then be found from the total length in inches after all the measurements of the ordinates have been transferred to the line, by either of the two latter methods of computation. The diagram, Fig. 62, represents the effect in a non-con- densing engine of cutting off the steam at a very early part of \ And Its Appliances. 117 the stroke, and shows the expansion line crossing and running below the atmospheric line for the greater part of the stroke. This result is a general thing brought about in diagrams from an engine having insufficient load. In this case the diagram is composed of two distinct parts, and must be treated as such in computing the horse-power of the engine. All ordinates above the atmospheric line, or between the actual boundary line of the diagram and before crossing the line of back, or counter pressure, will k represent positive pres- sure, while all ordinates ^vkj ii i i . I . i i . below the back pressure ^-*- ' ' ' I y line and between bound- - p- ary line will be negative, FIG. 62. and the combined length of the latter must be deducted from the former, in order to. as- certain the mean effective pressure. For example : Suppose the scale of the spring to be 40, and the combined length of the ordinates of positive pressure to be 4.05 inches while the combined length of the lines of negative pressure is 1.65 inches, then the difference will be 4.051.65 = 2.4 inches. The number of divisions of the diagram (20) being just one- half of the scale of the spring (40), it is only necessary to mul- tiply the difference in the length of the lines by two ; that is 2.4X2 = 4.8 pounds mean effective pressure throughout the stroke. An indicator diagram like Fig. 62 always indicates a loss of efficiency and measures should at once be taken to rem- edy the evil. In the matter of the computation of diagrams for mean effective pressure alone, it may here be well to state, that 1 1 8 Steam Engine Indicator neither the atmospheric, vacuum, or clearance lines become factors in the case ; therefore we have only to deal with the lengths of ordinates witliin the actual boundary line of the diagram, And Its Appliances. 119 CHAPTER XVII. EXPANSION OF STEAM. The expansion of steam in the cylinder of an engine per- forming work coincides very nearly with the principle of the law pertaining to gases, and know as the Mariotte law ; (as before noted in Chapter XIV) wherein the pressure varies in- versely as the volume; the temperature remaining the same. Upon opening communication (at any observed pressure of steam) between a boiler, and the cylinder of a steam engine, a corresponding pressure of steam will be exerted against the piston, and unless the steam be either condensed, or discharged from the cylinder, the same pressure will continue to act upon the piston ; even after the valve has been closed that commun- icates with the boiler, and this pressure will continue so long as the volume and temperature remains unchanged. If steam is supplied from a boiler to move a piston altern- ately in a cylinder, and the valve for admission of steam re- mains open during the full stroke of the piston, then the cylinder will be filled with steam at each stroke of the piston, of a pressure nearly equal to that of the boiler ; and is conse- quently exhausted also at nearly the same density. The parallelogram or rectangle shown in dotted lines b, d, vi, v, of Fig. 63 represents a theoretical indicator diagram from a condensing engine under such conditions; the line I2O Steam Engine Indicator v, vi being the line of absolute vacuum, and b, d, the boiler pressure. Assume an indicator to be attached to the cylinder of such an engine, and the drum carrying the paper be given a recip- rocating motion to coincide (on a reduced scale) with the mo- tion of the engine piston ; then if before admitting steam to the indicator piston, (and while the drum is in motion,) the f l X X X K / V 7 1 1 1 rv 4 ? / f ? : i ^ FIG. 63. indicator pencil be brought in contact, with the drum, a hori- zontal line a, ai, (called the atmospheric line) will be traced upon the paper; in length, proportioned to the stroke of the engine piston ; and also during this time, the pressure of the atmospheric will have free access to both sides of the indicator piston. If communication be now suddenly opened between the steam cylinder, and indicator, at a time when the pencil is at the point a, the pencil will ascend, and trace upon the paper And Its Appliances. 121 the vertical line a, b, to a certain height, depending upon the pressure of the steam, and also upon the strength or scale of the indicator spring in use ; and this height will represent the pressure per square inch of the steam within the engine cylinder. Assuming now that the engine piston had just commenced to move from left to right, and the admission of steam, con- tinues until the completion of the stroke ; the pencil will have traced the line b, d, representing in this case the mean'pres- sure of the steam throughout the stroke. If at the point d, the valve for the admission of steam be closed, and this volume of steam be suddenly condensed by being exhausted into the condenser, (thereby creating a vac- uum) the pencil will descend, and trace the line d, vi, and consequently on the return stroke follow along the line vi, v, to the commencement ; thus describing a parallelogram of which the horizontal line v, v r , would represent a portion of the stroke of the piston, and the vertical line v, b, would rep- resent the total steam pressure in pounds per sqaure inch act- ing upon the piston ; therefore the area of this parallelogram would represent pounds pressure, multiplied by the distance in feet moved through by the piston in a single stroke. The theoretical diagram here described is one that never occurs absolutely in indicator practice ; for the reason that the varying circumstances arising in the use of steam, would always preclude the possibility of obtaining such a result ; therefore it is only drawn for the purpose of making a comparison of effi- ciency, between it, and the actual diagram, taken as near as possible under the same conditions. In the foregoing, steam is supposed to be admitted to the cylinder, during the entire length of stroke of the piston; without any attempt to employ and utilize the benefits to be derived from the expansive properties of the steam. 122 Steam Engine Indicator The diagram in full line of the same figure, show approxi- mately the outline of an actual diagram, (in practice) as the re- sult of such an adjustment of valves, (as herein described) as would admit steam at one end, and exhaust at the other, alter- nately during the entire length of each stroke of the piston. It will be observed that the actual diagram may deviate to a considerable extent, from the theoretical, in accordance wi'.h various circumstances. r / A. j ^ ? <* j FIG. 64. For instance, the boiler pressure may not be fully real- ized ; also the interval of time that must elapse between the point of commencement of opening, or closing of the valves, and the absolute accomplishment of the same, will produce a wire drawing effect of the steam, and will invariably cause the corners of the diagram to be, more or less, rounded off, as shown in the diagram. The location of the line representing the back pressure on the return stroke, will depend upon the degree of vacuum And Its Appliances. 123 maintained in the condenser, and this will usually be found in most diagrams, to be from three to five pounds above the line v, vi, of absolute vacuum. The production of diagrams like the one shown in Fig. 63 are only not desirable, but the reverse of economical, and such results can only be entertained where the desire is to ob- tain the greatest possible power, from a given size of engine, without regard to the highest economy. In order to save steam, or to better realize the econ- omy, and efficiency of a given amount of steam to a greater degree, its admission to the cylinder must be stop- ped, or cut-off after the piston has moved only a portion of the stroke ; and as the piston continues to move along the cylinder (thereby increasing the volume of the steam so con- fined and allowing it to act expansively), its pressure from the point of cut-off will gradually diminish to the end of the stroke, and in such proportion as corresponds to its increased volume. Suppose we have a boiler under a steam pressure of 60 pounds per square inch, to which we add the pressure of the atmosphere (say 15 pounds), making a total of 60-1-15 = 75 pounds per square inch absolute pressure. Now if this steam be admitted to the cylinder of an engine, and the admission stopped after the piston had traveled one- half of its length of stroke, as represented by b, c, Fig. 64, it will have performed a certain amount of work, which may be represented in foot-pounds; the amount being the product of the total pressure in pounds acting upon the piston, multi- plied by the distance in feet it has passed over. If this steam, before being discharged from the cylinder is allowed to expand to double its volume, thereby forcing the piston to the end of the stroke, an additional amount of work will have been performed with this same amount of steam, and 124 Steam Engine Icdicator result in effecting a decided economy in the engine ; as this excess of work has been obtained through utilizing the expan- sion of the steam. In this case the steam was expanded to twice its volume at the termination of the stroke of the piston, with a pressure of 37/4 pounds per square inch, or just one-half what it was at half stroke. In Fig. 64, suppose the stroke of the piston to be 4 feet and this length divided into eight equal parts, i, 2, 3, etc., each part or volume representing six inches, or one-half foot of the stroke ; then if the piston be acted upon by an absolute pressure of steam (as before stated), of 75 pounds per square inch at the beginning, and continued to the fourth division, (as at c), equal to one-half of the stroke, it will have performed an amount of work which may be represented by the mean pressure (75 pounds) multiplied by 4, (75X4)=3OO foot pounds of work for each square inch of the area of the piston. If the admission of steam be stopped or cut-off, after the piston has arrived at half stroke, this volume of steam in the cylinder will expand ; and its pressure will gradually diminish to the end of the stroke ; and the indicator pencil will trace the curve line c, g, and when the exhaust valve opens (assum- ing for the time a perfect vacuum in the condenser), it will de- scend to the point vi. In the diagram, Fig. 64, there is only one-half as much steam admitted into the cylinder during the stroke, as in the case of diagram Fig. 63, but it will be readily observed by a comparison of the diagrams, that the area of the former is greatly in excess of half that of Fig. 63, in fact, by actual com- putation, (the rule for which will appear later on) its area will be found to be about .846 of that of Fig. 63, and with a mean pressure of 63.49 pounds per square inch during the en- tire stroke ; (eight divisions) therefore the work done by the steam in the first-half of the stroke being represented by And Its Appliances. 125 75X4=300, the amount during the whole stroke will be 507.92 300=207.92 . . 1 63.49X8=507.92, hence j ^ = 693, equivalent 300 3^^ to a gain of power of about 69.3 per cent. This has been obtained through utilizing the expansion of half the quantity of steam that would be employed during the stroke of an engine represented by the theoretical diagram Fig. 63. "~^v f i \ . \ \ J \ ^s^. \ 1 x^ \ \ ^-^^ \ *** , S gj x ul \ \ \ \* \^ / ^ N * *. J 4 ? i y ir' FIG. 65. Fig. 65 is a further illustration of a diagram in which the admission of steam is cut off at one-fourth, and expanded the balance of the stroke. In this case the amount of steam used is only one-fourth of that at full stroke, but the total area of the diagram is over .58 of the full theoretical diagram; and which is equal to a mean pressure of 44.74 pounds per square inch throughout the entire stroke, (the total initial pressure as stated being 75 pounds per square inch.) 126 Steam Engine Indicator Consequently the work done during the first quarter (one- fourth) of the stroke is represented by 75 x 2= 150, and during the entire stroke by 44.74x8=357.92, therefore =1.38 equivalent to a gain of 138. per cent In making calculations for pressure of steam after it has been expanded, it is the total pressure that must be considered, and which is reckoned from absolute vacuum. Consequently the extra amount of force thus obtained, and utilized in impelling the piston the balance of the stroke, may be considered theoretically as just so much gain, over the single effect of the same amount of steam ; as none of this additional pressure would have been realized upon the piston, if the stroke had terminated at the point where the steam was cut-off. From this theoretical gain however, there are certain losses that must be deducted ; such as friction of the engine during expansion ; the loss of temperature caused by the grad- ual reduction of pressure of the expanding steam ; and this loss is further increased by the abstraction of heat from the cylinder during the return stroke ; thereby producing a com- paratively cooling effect on the interior walls of the cylinder and also the piston. This, as a consequence, necessitates a greater condensation of the steam, (in the earlier part of the following stroke) be- fore the temperature of the cylinder is again restored to that of the entering or initial steam. In practice these losses prevent the full theoretical economy that might be obtained ; therefore in order that the maximum gain from expansion may be realized, they must be reduced to a minimum. The usual means employed for their prevention, is by some system of cylinder covering or jacketing, also superheat- ing ; to obviate the matter of condensation ; this also in And Its Appliances. 127 connection with the best methods of reducing the friction to a minimum. The economy that may be derived from the expansion of steam, when used under different conditions, is an import- tant consideration, and requires ability and good judgment (of the engineer) in arriving at the best means for realizing all ^expected or desired results. The greatest gain from expansion is generally secured in Condensing Engines, but the application of a condenser however should be judiciously made, as with loads already too light, it would be of little value, and the results disappointing. tir 128 Steam Engine Indicator CHAPTER XVIII HYPERBOLIC LOGARITHMS. In the absence of an indicator, the Mean Effective Pres- 'sure of the expanding steam in a cylinder, and the power of the engine from a given pressure of steam, and point of cut-off may be approximately ascertained, and the average pressure , per square inch that will be exerted against the engine piston, during the stroke can be estimated, by means of the table No. i , of Hyperbolic Logarithms ; which are calculated for expan- sion according to the Mariotte law. The Hyperbolic Logarithms as found in the table, is the product of the common logarithm multiplied by 2.302585 ; and .adversely the common logarithm is the product of the hyper- bolic logarithm multiplied by 0.43429448. The table referred to, contains the hyperbolic logarithm of numbers up to 39, which are considered sufficient for applica- tion to steam expansion. The rule, and method of calculating the Mean Pressure by the use of the table is as f ollows : Rule. To the total length of the stroke of the engine pis- ton, (in inches) add the clearance in the cylinder at one end (also in inches) divide this sum by the length of the stroke at which the steam is cut-off, added to the same clearance ; and the quotient will express the ratio or number of expansions. And Its Appliances. 129 Find in the table the logarithm of whatever number is nearest to that of the quotient, to which add i . The sum is tJie ratio of t lie gain. Multiply the ratio thus obtained by the absolute pressure of steam as it enters the cylinder, and divide the product by the relative expansion; the quotient is the mean pressure required. No. Loga- rithms. No. Loga- rithms. No. Loga- rithms. No. Loga- rithms. 0.0 0.00000 4.0 1.38629 7.0 1.94591 10 2.30258 1.1 0.0^530 4.1 1.41096 7.1 1.96006 11 2.39589 1.3 0.18213 4.2 1.43505 7.2 1.97406 12 2.48491 1.3 0.26234 43 1.45859 7.3 1.98787 13 2.56494 1.4 0.33646 4.4 1.48161 7.4 2.00149 14 2.63906 1.5 0.40505 4.5 1.50408 7.5 2.01490 15 2.70805 1.6 0.46998 4.6 .52603 7.6 2.02816 16 2.77259 1.7 0.53063 4.7 .54753 7.7 2.04115 17 2.83321 1.8 0.58776 48 .56859 7.8 2.05415 18 2.89037 1.9 0.64181 4.9 .58922 7.9 2.06690 19 2.94444 2.0 0.69315 50 .60944 8.0 2.07944 20 2.99573 2.1 0.74190 5.1 62922 8.1 2.09190 21 3.04452 2.2 0.78843 5.2 64865 8.2 2.10418 22 3.09104 2.3 0.83287 5.3 .66770 8.3 2.11632 23 3.13549 2.4 0.87544 5.4 .68633 8.4 2.12830 24 3.17805 2.5 0.91629 5.5 .70475 8.5 2.14007 25 3.21888 2.6 0.95548 5.6 .72276 8.6 2.15082 26 3.25810 2.7 0.99323 5.7 .74046 8.7 2.16338 27 3.29584 2.8 .02962 5.8 .75785 8.8 2.17482 28 3.33220 2.9 .06473 5.9 .77495 8.9 2.18615 29 3.36730 3.0 .09861 6.0 1.79175 9.0 2.19722 30 3.40120 3.1 .13140 6.1 1.80827 9.1 2.20837 31 3.43399 3.2 .16314 6.2 1.82545 9.2 2.21932 32 3.46574 3.3 1.19594 6.3 1.84055 9.3 2.23014 33 3.49651 3.4 1.22373 6.4 1.85629 9.4 2.24085 34 3.52636 3.5 1.25276 6.5 1.87180 9.5 2.25129 35 3.55535 3.6 1 28090 6.6 1.88658 9.6 2.26191 36 3.58352 3.7 1.30834 6.7 1.90218 9.7 2.27228 37 3.61092 3.8 1.33046 6.8 1.91689 9.8 2.28255 38 3.63759 3.9 1.36099 6.9 1.93149 9.9 2.29171 39 3.66356 TABLE No. 1, For example. Suppose steam of 100 pounds absolute pres- sure per square inch, be admitted to the cylinder of an engine, at the beginning of the stroke (ignoring clearance for the 130 Steam Engine Indicator present), and admission stopped after one-fifth (1-5) of the stroke had been completed, and the steam allowed to gradually expand to the end of the stroke. Then in accordance with the principle of the law, in ref- erence to the expansion of gases, the volume of steam in this case, on being continually increased, will consequently suffer a corresponding reduction in pressure. At 2-5 of the stroke the volume will be double, and the pressure reduced to y 2 of the initial, or to 50 pounds per square inch; at 3-5 to y or 33^ pounds; at 4-5 to j or 25 pounds, and at 5-5 or the whole stroke the volume is increased 5 times, with a reduction of pressure of 1-5 initial or to 20 pounds pres- sure per square inch at the termination of the stroke. Now what we desire to ascertain in such a case, is the average pressure during the entire stroke or, what pressure acting uniformally throughout the stroke will perform an equivalent amount of work. This may be calculated very readily by the use of the Table No. i, in connection with the Rule. Suppose in the foregoing example, the stroke of the piston to be 60 inches, and the admission of steam be stopped after the piston had ad- vanced 12 inches and expansion continuing to the end of the stroke ; then by the Rule f 5 the ratio of expansion. This ratio of expansion (5) will be found in the table No. i, under the head of numbers, and directly opposite (to the right) will be found its hyperbolic logarithm 1.609, to which add i. the sum of which i.-|-i.6o9=2.6o9 the ratio of gain. Multiply 2.609 by the initial pressure of steam entering the cylinder, and divide the product by (5) the ratio of expan- T ^OO N^ T OO sion : hence - =52.18 which represents in pounds per square inch, the average or Mean Pressure that would be ex- erted uniformally against the piston during the entire stroke of the engine. If the stroke of the engine piston in the above And Its Appliances. 1 3 1 example had been 48 inches, the steam cut-off, after the piston had advanced 12 inches, and the absolute initial pressure of the entering steam be 80 pounds per square inch, then ^ = 4 equal the ratio of expansion; the logarithm of which is 1.386 and represents the ratio of the gain. i. + 1.386x80 2.386x80 Hence ! 2 - 2 - =47-72 which would ex- 4 4 press the Mean Pressure in pounds per square inch impelling the engine piston during the entire stroke. In computing the above examples for the Mean Pressure, the effect of the clearance in the cylinder, has been purposely neglected, in order that the calculation might be presented in a more simple manner. In the case of the latter example, suppose the percentage of clearance to have been such as to add two (2) inches in length to each end of the cylinder; then 48+2=50 inches, the length of stroke with the clearance at one end added ; and by adding the same clearance to the distance of cut-off, 12+2= 14 inches, therefore -^=3.57 the ratio of expansion in this case. From the table No. i, we find the nearest number to this ratio of expansion is 3.55 the logarithm of which is 1.267 to which add i. then i.+ 1.267= 2. 267 an d - = 50.80 which represents the Mean Pressure per square inch, when computed with the clearance included, instead of 47.72 as before ; an in- crease of 3.08 pounds per square inch. As all calculations of this kind are generally made for ap- proximate results or comparisons only, it is in most cases un- necessary to take the clearance into consideration, unless it should be unusually large, or unless the cut-off should take place very early in the stroke; either of which, or both com- bined would in a measure cause a variation in the final re- sults. 132 Steam Engine Indicator This indifference, relative to the clearance in the calcula- tions proceeds from the fact that the full boiler pressure is never fully realized in the cylinder ; and also on account of a falling of pressure that often takes place in the cylinder before cut-off ; and it may be assumed that what will be gained by clearance, is about offset by the failure of the steam to fulfill the conditions required. Portion of stroke at which steam is cut off. Grade or ratio of expansion Hyperbolic logarithm Mean pres- fSEE I ff X P % To, or 0.1 10.0 2.302 3.302 230.0 J , or 0.125 8.0 2.079 3.079 208.0 |, or 0.166 6.0 1.791 2.791 179.0 T 2 o, or 0.2 5.0 1.609 2.609 161.0 I , or 0.25 4.0 1.386 2.386 139.0 ft-, or 0.3 3.33 1.203 2.203 120.0 I , or 0.333 3.0 1.099 2.099 110.0 | , or 0.375 2.66 0.978 1.978 97.8 T 4 o", or 0.4 2.5 0.916 1.916 91.6 i, or 0.5 2.0 0.693 1.693 69.3 A, or 0.6 1.666 0.507 1.507 50.7 f , or 0.625 1.6 0.47 1.47 47.0 | , or 0.666 1.5 0.405 1.405 40.5 T \, or 0.7 1.42 0.351 1.351 35.1 } , or 0.75 1.33 0.285 1.285 22.3 T 8 o, or 0.8 1.25 0.223 1.223 20.5 I , or 0.875 1.143 0.131 1.131 13.1 A, or 0.9 1.11 0.104 1.104 10.4 TABLE No. 2. It must be understood that the Mean Pressure as estimated in the preceeding examples, is the absolute pressure, measured from the line of perfect vacuum. In non-condensing engines under good conditions, the average back pressure will be from one to two pounds above A nd Its Appliances. 1 3 3 the atmosphere, or about 16 pounds absolute; and which must be deducted from the results obtained. The remainder will be the average, or Mean Effective Pressure. In condensing engines the back pressure will average from about 4^ to $ pounds irrespective of the atmosphere, being a loss through imperfect vacuum ; and which must also be de- ducted in this case, in order to obtain the Mean Effective Pres- sure. In either case the exact amount of back pressure to be deducted will vary ; and such variation will depend mostly up- on circumstances, and local conditions. The theoretical economy of using steam expansively is given in Table No 2, which contains the hyperbolic logarithm for numbers running from 10, the grade, or ratio of expansion, representing o. i, or i-io cut-off, to i.n, representing 0.9, or 9-10 cut-off, and which may be considered of sufficient range for application to the expansion of steam in engines for all practical purposes. The first column L represents the portion of stroke at which steam is cut-off, the second G the grade, or ratio of ex- pansion, the third X the hyperbolic logarithm of the number or grade of expansion ; the fourth, the mean pressure of steam during the whole stroke, and the fifth column the percentage of gain in power. T/ie per cent of gam by expansion is obtained by multiply- ing the logaritlim of the number of expansions by 100. In the Table no deductions are made for a reduction of the temperature of the steam during expansion, nor for any loss through back pressure. In expansion, the same relative advantages occur, as given in the table whatever may be the initial pressure of the steam. The results, in reference to the percentage of gain as shown by the table, is as before stated, theoretical, as from the 134 Steam Engine Indicator resistance to expansion of the back pressure in a cylinder, and from the loss of temperature of the steam by cooling, and also from the friction of the steam passages, these results in practice are very materially reduced. The pressure of the atmosphere is always included in cal- culating the expansion ; therefore must be deducted from the results in all non-condensing engines. CONSTANTS FOR FINDING THE AVERAGE PRESSURE IN THE CYLINDER WITH ANY PRESSURE OF STEAM. Percentage of the stroke at which steam is cut off. Constant. Percentage of the stroke at which steam is cut off. Constant. Percentage of the stroke at which steam is cut off. Constant. Percentage of the stroke at which steam is cut off. Constant. l/o 0560 21/ 5377 41/ 7758 61/o 9114 2 0982 22 5529 42 7841 62 9162 3 1321 23 5679 43 7920 63 9200 4 1688 24 5823 44 8010 64 9264 5 1998 25 5967 45 8088 65 9298 6 2288 26 6102 46 8164 66 9340 7 2563 27 6237 47 8235 67 9385 8 2821 28 6365 48 8318 68 9427 9 3067 29 6484 49 8396 69 9461 10 3302 30 6612 50 8466 70 9496 11 3527 31 6726 51 8536 71 9531 12 3743 32 6842 52 8592 72 9588 13 3952 33 6958 53' 8660 73 9595 14 4152 34 -7066 54 8722 74 9620 15 4345 35 7172 55 8779 75 9638 16 4532 36 7276 56 8846 80 -9784 17 4712 37 7378 57 8904 85 9878 18 4885 38 7477 58 8962 ( 90 9945 19 5055 39 7567 59 9002 95 9960 20 5219 40 7665 60 9062 100 1-0000 TABLE No. 3. In condensing engines a deduction must be made for im- perfect vacuum ; usually amounting to, from 2^ to 3 pounds per square inch. The Table No. 3 contains constants for finding the average pressure in the cylinder, for any percentage of the stroke (from And Its Appliances. 135 i to 100) at which the steam is cut-off, and on account of its simplicity, will be found in many cases more convenient in finding- the average pressure on the piston throughout the stroke (from a given initial), than by the ordinary method of using hyperbolic logarithm. The rule by which to use the constants is as follows: Multiply tjie constant opposite the known per cent of cut-off, by the total pressure of the steam entering the cylinder ; the product will be the total average pressure on the piston. AVERAGE PRESSURE OF STEAM IN THE CYLINDER WITH VAR- IOUS INITIAL PRESSURES AND DIFFERENT RATES OF EXPANSION. Initiar pressure above atmos- phere in Ibs. per sq. inch. Percentage of the stroke at which steam is cut off. 10 ) 15 20 25 30 35 40 45 50 60 Average pressure >n Ibs. per square inch during the whole stroke. 40 18'1 23-8 28'6 32'8 36-6 39-3 421 444 46-5 49-9 45 . 19-8 262 31-0 35-8 39-2 430 46-0 48-6 507 54-4 50 21-5 28-3 338 387 43-0 465 49-9 52-6 55-0 59-0 - 55 23-2 30-5 36-4 417 46-2 50-2 53-5 56-7 59-1 63-3 60 24-7 32-6 39-0 44'8 49'5 53-7 57-4 60-8 63-4 68-0 65 26-4 34-8 417 47-7 52-9 573 61 1 64-8 67-5 725 70 28 : 37-0 44-1 50-6 56-1 60-9 65-0 68-8 71-8 77-0 75 297 39-2 46-9 537 59-4 64-3 68'8 72-9 76-0 81-5 "80 31-3 41'4 494 56-6 62-8 68-0 727 76-9 80-2 86-0 85 33-0 435 52-0 59-6 66-0 71-5 76-5 80-9 84-4 90-6 90 347 45-7 547 62-7 69-5 75-0 ,80-3 84-9 88-7 95 : 3 95 363 47-9 57-5 65-9 73-0 78-6 84 1 89-0 930 100-0 100 38-0 500 59'9 68-7 76-0 82-2 88-0 93-0 97-3 104-5 110 41-3 54-5 65-0 74-6 82-6 893 95-7 101-0 105-6 113-0 120 447 58-8 701 80-5 89-3 96-5 103-3 109-1 114-0 1221 130 48-0 63-1 75-3 86-5 96-0 103-8 111-0 117-2 122-5 131-3 140 51-2 67'5 807 92-5 102-6 111-0 118-6 125:3 131-0 140-4 150 54-6 71-9 85-9 98-5 109-3 118-0 1263 133-4 139-5 1495 160" 57-9 76-2 91-1 104-5 116-0 125-2 134-0 141-5 148-0 15S-5 170 61-2 80-6 96-3 110-5 122-6 1324 141-8 149-7 1565 167-5 180 64'5 85-0 101-5 116-5 1293 1397 149-5 157-9 165-0 176-6 190 67-9 893 1067 122-5 136-0 146-5 157-3 166-0 1735 185-7 200 71-1 937 11 2^0 128-5 142-6 154-0 165-0 174-0 182-0 1 194-8 TABLE No. 4. From this total, subtract the average back pressure, (which will be about five pounds in condensing engines, and in i 36 Steam Engine Indicator non-condensing engines it will be from one to two above the atmosphere, or about sixteen pounds total), the remainder will in either case be the average, or mean effective pressure. Table No. 4 gives the average pressure of steam in the cylinder of an engine for the various initial pressures, above the atmosphere in pounds per square inch, and at different rates of expansion. In the above table, no allowance is made for back pres- sure and compression, therefore their effect must be subtracted from the above average pressures in order to ascertain the mean effective pressure on the piston. In non-condensing engines, working under favorable con- ditions, the average back pressure will be from i. to 2. pounds above the atmosphere or ordinarily a total of about 16 pounds per square inch ; this amount varies according to location, or elevation above the sea level. In condensing engines the back pressure will average about 5 pounds, irrespective of atmospheric pressure. And Its Appliances. 13/r CHAPTER XIX. THEORY OF ACTION OF STEAM EXPANSION IN CYLINDERS. There are three conditions of the steam cylinder, within which the action of the steam is differently influenced, as follows : i st. The outer surface may be bare or unprotected by any covering whatever and wholly exposed to the surrounding medium. 2d. It may be covered by some non-conducting material, such as felt or asbestos, and this in turn protected by a cover- ing of wood or iron on the outside. 3d. It may be so constructed than an annular chamber may be formed on the outside, to be filled with steam from the steam chest, steam pipe, or from any convenient place where the steam is, of at least, the same temperature as the entering 1 steam driving the piston. In some cases the cylinder heads are also cast with a chamber for containing steam ; this is called steam jacketing, and the jacket itself is also covered with a non-conducting material. Therefore an explanation of the generally accepted theory of cylinder condensation may be of assistance to many, and lead to a better understanding of the action of steam within the cylinder of an engine while in operation, and also explain the cause of such condensation ; which invariably occurs, more or less, in all steam engine cylinders, 138 Steam Engine Indicator The action of steam in an unjacketed or exposed non-con- densing 1 engine cylinder is about as follows : As the entering steam at the commencement of the stroke, is of a much higher temperature than the metal parts, with which it comes in con- tact; (that is the interior surface of the cylinder, piston, and cylinder head;) consequently a portion of this steam is con- densed in heating up these parts, to the temperature of the entering steam. As the piston moves forward uncovering fresh surfaces of the cylinder, the condensation continues until after the admis- sion valve closes, or until cut-off takes place. This condensation is deposited in form of moisture upon the interior walls of the cylinder, also the piston and cylinder head; but does not become apparent on the steam line of the diagram, because the place of that condensed, is supplied from the steam chest, during the admission of steam. After cut-off the steam then commences to expand, and both pressure and temperature begin to diminish in a corres- pondingly degree ; and unless the steam is cut-off very early in the stroke but little further condensation takes place ; (although fresh surfaces of the cylinder that are cooler than the steam, continued to be uncovered as the piston advances) for the reason that as soon as the temperature of the steam commences to fall, through expansion, the head, piston, and walls of the cylinder, (already heated to the temperature of the initial steam,) begins to impart a portion of their heat to the expand- ing steam, and thus prevent further condensation (to any great extent) taking place. As represented at A in diagram Fig. 66. As the piston continues to advance, the expansion is carried still further and in consequence, the temperature, as well as pressure, is correspondingly lowered. During this time the higher temperature existing in the cylinder walls, piston and head, has been gradually imparted to the steam condensed in the early part of the stroke, causing And Its Appliances. 139 a re-evaporation of this moisture and thereby raising the ter- minal pressure in the cylinder. Also shown in Diagram 66 at B. When the piston arrives at or near the end of the stroke, the exhaust valve opens, and both pressure and temperature of the steam immediately falls to an extent corresponding to the pressure and temperature of steam at atmospheric or back pressure. As the metal has still a higher temperature than the ex- haust, any remaining water is therefore re-evaporated during FIG. 66. the return stroke, by absorbing heat from the cylinder walls, piston, and head, thereby still further reducing their tem- perature ; and this extraction of heat has to be restored to these parts again at the expense of the entering steam for the next forward stroke of the engine. In a very early cut-off in unjacketed cylinders the steam suffers further condensation for some distance after the admis- sion valve closes, owing to the cooler portions of the cylinder surface which are being exposed (by the advance of the piston,) having to be heated by the comparatively small volume of steam confined within the cylinder after cut-off, and the consequence 140 Steam Engine Indicator is that the pressure falls for some distance in a much greater ratio, than that due to expansion alone. As the piston ad- vances however, and the expansion continues, the pressure falls, and consequently the temperature of the steam becomes less than that of the interior surface of the cylinder, and other parts ; thereby causing a re-evaporation of the moisture which has been deposited upon their surface during the earlier part of the stroke. The volume of steam present, being thus in- FIG 67. creased by this re-evaporation, the pressure also becomes higher, resulting in a rise of the expansion line during the latter part of the stroke. Therefore the effect of this action on the expansion curve of an actual diagram, with an early cut-off, is to cause it at first to fall considerably below, (just after cut-off) and subsequently to rise above the true theoretical curve toward the end of the stroke. The expansion line of Fig. 67, represents the partial in- creased effects of cylinder condensation, that is due to an early cut-off, showing the falling below at a point A, and rise above at B, of the actual from the theoretical curve drawn in dotted line from the point of cut-off C. And Its Appliances. 141 The theoretical curve D, B, is drawn in dotted line from the point at which the exhaust valve opens, and represents the additional work that might be done by the steam at the ter- minal pressure ; provided condensation were prevented. This deviation from the true curve is greatly increased by water held in suspension or entrained in the steam. It is therefore important that the initial steam be prac- tically free from moisture. The mutation of heat back and forth, (which occurs at every stroke) between the steam, and the interior surface of the cylinder as well as the cylinder head and piston, take place very quickly, and effects the metal of these parts to a slight depth only ; as there is not sufficient time for it to penetrate very deeply, especially in high speed engines. Steam Jacketed Cylinders. The action which takes place in a steam jacketed cylinder of a condensing engine is some what different ; as the following description will indicate : In such cases the jacket is arranged to be supplied con- stantly with direct steam (either through the steam chest, or steam pipe) of the same temperature and pressure as the initial steam entering the cylinder ; consequently the alternate heat- ing, and cooling of the metal that occurs in an unjacketed cyl- inder, will in a great measure in this case be prevented ; hence, comparatively no initial condensation takes place, and the steam will enter the cylinder without apparent loss. The piston itself being partially under the same conditions as before, will tend continuously to condense a very small por- tion of the steam; but this condensation, (in the act of form- ing) will at once be re- evaporated ; therefore no actual conden- sation takes place during expansion, as the quantity of heat that disappears in doing work is steadily supplied by the cylinder walls. 142 Steam Engine Indicator The walls in turn absorb heat from the steam in the jacket^ thereby condensing a portion of the steam, but the jacket being constantly supplied with direct steam, maintains the cylinder at nearly a uniform temperature. When the exhaust valve opens, and communication is made with the condenser, (there being no water or moisture to re-evaporate,) a further expansion of the steam occurs ; there- by lowering both pressure and temperature. This exhaust steam being comparatively dry, receives and parts with heat slowly, and therefore does not absorb as much heat from the cylinder walls when expanding into the con- denser, as the wet steam from an unjacketed non-condensing cylinder ; as in the former case. Although the steam jacket supplies the heat necessary to prevent condensation, and also to heat up the cylinder, from a temperature corresponding to the exhaust, to that of the initial or entering steam ; yet this quantity of heat is much less than that which is extracted by wet steam from the walls of cylinders that are unjacketed, consequently the actual gain effected by the use of a steam jacket on a cylinder, is, the difference of saving, between the prevention of condensation in the cylinder during the first part of the stroke, and the loss that occurs in heating the exhaust steam during the return stroke ; and this gain may in many cases be very slight, as the saving depends principally upon the fact that steam absorbs heat much slower than water. In preventing this condensation in the cylinder, the heat abstracted from the steam jacket, transfers all liquefaction or condensation of the steam to the jacket ; and on this account some engineers at the present time, questions its utility in the matter of economy, (also considering first-cost) and claim that the condensation, and waste of steam in the jacket, is more than that lost or wasted in unjacketed cylinders ; the excess And Its Appliances. 143 being due to increased condensing, and radiating surface of the jacket, above that of the steam cylinder. The diagram represented in Fig. 68 is from a steam jack- eted cylinder and it will be seen that the actual curve agrees very closely to the Isothermal. In reference to the efficiency of the jacket however, all re- sults depend in a great measure upon its proper construction, and appliances ; and also in providing means for the removal of all air and water arising from condensation ; and utilizing FIG. 68. such water, as fast as formed by returning it to the boiler ; thereby preventing the accumulation of either in the jacket. In addition to this and to insure the best efficiency it is absolutely essential that the jacket be constantly supplied with dry steam of a temperature fully as high as that of the initial working steam entering the steam cylinder, and in all cases (more especially in engines with early cut-off, and consequently high expansion). Where the details referred to, are strictly observed and carried out, the result must evidently tend more or less to 144 Steam Engine Indicator better economy and efficiency in engines, by the use of the steam jacket. On the contrary, if wet steam, or steam containing a large proportion of moisture be introduced into a steam jacketed en- gine cylinder in the beginning of the stroke, a result will fol- low, which will be the opposite of economy, and end in con- siderable loss, this loss arising from the large quantity of heat abstracted from the jacket during the stroke, for the evapora- tion of this water or mois.ture that has entered the cylinder. Therefore to insure that the economy and efficiency which is expected from the use of the steam jacket be realized, it is very essential that all the requirements before mentioned for its proper performance, should be assured, otherwise the jacket may be quite ineffectual ; its theoretical efficiency wholly destroyed, and its utility consequently questioned. In a great majority of cases at the present time, cylinder jacketing is accomplished in accordance with the second con- dition mentioned ; viz, that of thoroughly covering the whole of the exterior surface of the cylinder, and steam chest, with some non-conducting material as felt, wool, or asbestos, and secured thereto by an extra covering of wood or iron ; com- pletely enveloping the whole. This combination of covering where suitably applied, ap- pears to give general satisfaction, as many builders of our best modern engines testify ; by the almost exclusive use of some suitable material for cylinder jacketing, on this prin- ciple. Also in many cases where engine cylinders are covered and protected in the manner just described, and having steam tight valves, and piston, it is frequently found that the expan- sion line of the diagrams therefrom, agree very nearly with the isothermal or true theoretical curve as represented in Fig. 69. And Its Appliances. 145 Therefore it is readily seen from the diagrams Fig. 68 and Fig. 69 the advantages to be derived by either of the latter conditions or methods of cylinder jacketing, to secure the greater economy, and efficiency in the engine ; above that of one from an exposed or unprotected steam cylinder with an FIG. 69. Dearly cut-off as represented in the diagram Fig. 67. In order to obtain Indicator diagrams that shall be accurate exponents, and represent the true action of steam expansion within the cylinder, it is absolutely essential that the valves, and piston of the engine be practically steam tight ; and also that the In- dicator itself have perfect and unimpeded freedom of move- ment in all its parts, when under pressure and temperature of the steam present. The exact measure of the tension, or in other words, the strength of the spring used, is also of great importance; as the accuracy of all computations based upon the form of the diagram, for obtaining the Mean Effective Pressure, acting against the piston depends upon the correct- ness of the spring ;. therefore its accuracy should be determined and established, (by comparison with a correct steam guage), before any elaborate tests are anticipated. This may be ac- complished in a satisfactory manner by means of the simple Indicator spring testing device represented and described in Fig. 84, Chapter XXII. 146 $ 'tea in Engine Indicator CHAPTER XX. READING THE DIAGRAM. The principal and most positive information to be derived from the reading of an actual indicator diagram, is, the meas- ure of the force or pressure in the cylinder, acting upon the oppOvSite sides of the piston, at any and all points, during one complete revolution of the engine ; hence the actual card, as compared with the theoretical diagram, (under similar con- ditions) indicates the efficiency and economy of the engine ; and all other information must also be acquired through ex- ceedingly careful consideration, and reasoning in the study of the diagrams ; and conclusions arrived at, therefrom in accord- ance with an exercise of the best judgment of the engineer. The figures traced by the pencil will vary in outline in different engines, and also from the same engine under vary- ing conditions, due to a number of causes ; as leakage of valves, condensation and re-evaporation of the condensed steam in the cylinder, construction and the adjustment of valves, condi- tion of the steam, etc. These effects will be more apparent along the expansion curve especially ; and as a consequence the actual curve will very rarely coincide exactly with the true theoretical curve. Therefore it is very essential that all cards traced by the indicator should accurately represent the duty performed by the engine ; as the accuracy of all such investigations depends entirely upon the correctness of the diagrams. And Its Appliances. 147 Upon an examination of the steam expansion curve of in- dicator diagrams it will be found (almost invariably), that the Terminal pressure is relatively too. high (from a given cut-off), as compared with the true theoretical curve ; the amount in- creasing as the ratio of expansion increases : as shown in Fig. 70. B FIG. 70. This result may be due to either of two causes, or to both combined. i st. To leaky steam or admission valves, through which the steam is enabled to pass into the cylinder, after the closure of such valve ; or in other words, after the point at which cut- off is supposed to have taken place ; and thereby producing a higher terminal, than would otherwise appear with steam tight valves. 2nd. To a re-evaporation of the entering steam that is condensed in the earlier part of the stroke, through coming in contact with the interior walls of the cylinder, which have been cooled to a temperature corresponding to the lower pressure of the escaping steam, during its exhaust. 148 Steam Engine Indicator In some cases however the expansion curve of the actual diagram will be found falling below the true or theoretical curve throughout its entire length ; as shown in Fig. 70, evi- dently due, to leaky piston, and exhaust valves; this, also in connection with exposed or unjacketed steam cylinders. But it frequently happens that cards are found wherein the expansion curve coincides very nearly with the isothermal or theoretical, although they have been taken from engines in which both valves and piston are known to leak badly. In such cases the leakage through the admission valve after closing is just sufficient to restore the steam lost through a leaky piston, and the result under such circumstances, are that the two curves will be a very near approach to each other. Such cards from observation alone has the appearance of good efficiency and economy in the engine ; when in fact the opposite of this prevails, and an extravagant loss and waste of steam is the consequence ; all arising from a leaky condition of these parts. The loss of steam from this cause, and also from cylinder condensation is not accounted for by the indicator, hence does not appear in the diagrams, and is only made apparent by a comparison of the water consumption per horse power (as com- puted from the diagram), with the actual amount of water that has been supplied to the boiler. An important matter to be ascertained in reference to all indicators ; is, whether the vertical or admission line on the diagram, made by the pencil (when in contact with the paper on the drum) is exactly perpendicular to the atmospheric, or horizontal line, that is made by the pencil, when in contact with the drum while rotating. A leaning of the admission line either forward or back, thereby causing it to be out of square with horizontal line, tends to be misleading in reference to the proper adjustment of the valves, especially if a fault of this kind exists in the And Its Appliances. 149 instrument, and not previously known. This fact may easily be determined at any time before placing the spring in the instru- ment, by simply placing the paper upon the drum the same as FIG. 71. for taking diagrams, and bring the pencil in contact with it ; then cause the drum to rotate once back and forth by means of the cord attached to the indicator, thereby making a hori- FIG. 72. zontal line on the paper ; then mark a perpendicular to this by raising the pencil by hand to its extreme height, Remove the 150 Steam Engine Indicator paper from the drum, and compare its correctness with any ordinary square or right angle triangle at hand, as shown in Fig. 71. Any inclination or leaning of the admission line in indicator diagrams, either forward or back, as in Fig. 72 and Fig. 73, is usually constructed and considered to be an im- proper adjustment of the valves. For example. In reviewing the diagram represented in Fig. 72 ; from the fact of a leaning forward of the admission line, the time of opening of the valve for steam admission, would ordinarily be assumed to be too late, or indicating in- sufficient lead ; and in consequence the piston has advanced a portion of the stroke, (as shown at A), before the initial pres- sure has reached its highest point ; resulting to a certain de- gree, in a loss of power, and efficiency in the engine. Again suppose in a diagram the results are as represented in Fig. 73, where the admission line inclines outward; this FIG. 73. might indicate either a too early opening of the steam valve, thereby admitting steam in the cylinder before the piston had completed the stroke ; or a too early closing of the exhaust at that end of the cylinder, thus causing excessive compression ; either of which would also cause a loss of efficiency and power. A nd Its Appliances. 151 Most types of indicators after their being in use for a length of time, are liable to certain defects, or disarrangement more or less in their pencil movement ; (and these defects some- times appears in new instruments) and which prevents the ini- tial pressure or vertical line as traced upon the paper, from be- ing at a right angle or perpendicular to the atmospheric line ; and in such case the instrument is usually designated as out of square. As a consequence, the admission line at either end of the diagram, will be inclined to the perpendicular, as appears by FIG. 74. the dotted lines A, A, in the diagrams Fig. 74, and which may be wholly due to such incorrectness in the indicator as stated ; notwithstanding the valve adjustment of the engine may be practically all that can be desired. This discrepancy very often arises from careless handling, and from culpable neglect, and abuse of the instrument in var- ious ways. Where a defect of this description exists in the in- strument, it is generally advisable to send it at once to the maker, to insure that the necessary correction be properly and satisfactorily accomplished. 152 Steam, Rjigine Indicator CHAPTER XXI. DIFFERENT METHODS OF COMPUTING THE AMOUNT OF STEAM ACCOUNTED FOR BY THE INDICATOR. If the number of cubic feet occupied by the steam in an engine cylinder, and the pressure it exerts against the piston at any point of the stroke be known, the number of pounds which the steam weighs may be computed. The weight of the steam at any point, less the weight re- maining in the cylinder at compression, is the weight account- ed for by the indicator. The weight accounted for on one stroke,- multiplied by the number of strokes per hour, and divided by the indicated horse power, is the amount of steam accounted for, per indi- cated horse power per hour. This computation requires a knowledge of the volume of the clearance space in the cylinder; that is, the cylindrical space between the cylinder head and the piston, when the pir- ton is at the end of its stroke, and also includes the volume of the steam ports and passages which conducts the steam from the admission valve to the cylinder, and also from the cylinder to the exhaust valve. The water consumption of an engine (as stated in another chapter) is the measure of its economy, but the exact amount is not determinable from the diagram, because that gives the pressure of steam only. And Its Appliances; 155 Of the water that has been carried over with the steam, or of the steam that has been condensed by coming in contact with the comparatively cold surfaces of the cylinder, the dia- gram gives no record. We know however, that the amount of steam accounted for by the indicator has at least passed through the cylinder ; and in fact, we know that sometimes a much larger amount has been used. One method of ascertaining the amount accounted for by an indicator is to calculate the piston displacement, plus the clearance space for a given time, in cubic feet, up to a certain point in the stroke before the exhaust opens, and multiply this volume by the weight of a cubic foot of steam of the absolute pressure at this point. 3J f . FN \JB FIG. 75. This method is described in the diagram Fig. 75 and is as follows: Draw the vacuum line V. V., and the clearance line D. and select some point on the expansion curve, as at C- where it is known that both the steam and exhaust valve are closed and wherever it is possible, have this point C. at a j 54 Stt'aj/i Engine Indicator distance from the end of the diagram equal to the clearance dis- tance D. Where this can be done, then the volume to point C., in- cluding clearance, will just equal the piston displacement which is the area of the piston multiplied by the length of stroke. Where this cannot be done, then find volume to point C, including clearance, which if multiplied by the weight of a cubic foot of steam of the absolute pressure at the point se- lected will give the weight of the steam contained in the cylin- der at such point. The volume at point C may be found as follows : Assume the cylinder of an engine to be 12 inches in diam- eter, (113.09 square inches in area) with a stroke of piston of 30 inches running 90 revolutions per minute ; the area of pis- ton rod being 6.18 inches; the clearance being five per cent, and the scale of the spring 40. From the area of the cylinder, deduct one-half the area of the piston rod (6. 18-^-2 = 3.09 inches) hence ; 1 13.093.09= 1 10 square inches as the mean area of the piston. The total piston displacement per stroke therefore will be, the mean area of piston in inches multiplied by length of stroke, also in inches, 110x30=3300 cubic inches per single stroke of the engine. The displacement to the selected point C, may then be ascertained, by multiplying the total displacement, (3300 cubic inches) by the distance that point C, is from the initial end of the diagram, or from line E, and dividing this product by the total length of the diagram, or line A, B, for example: The length of the line C, E, is 3.56 inches, and the length of A, B, is 3.75 inches, therefore ?i- - = 3132.8, cubic inches. To this must be added five per cent, for clearance, or 3300X .05= 165. then 3 132.8+ 165 = 3297.8 cubicinches occupied A nd Its Appliances . 155 by steam at point C. The engine running 90 revolutions per minute consequently makes 90x2x60=10800 single strokes per hour; therefore the displacement per hour is 32 9 7.8X 10800 =2Q6lIcubicfeet . 1728 Now with the scale of the spring, (40) with which the dia- gram was taken, measure the absolute pressure from the va- cuum line to point C, and opposite this pressure in the Table No. 8 of properties of saturated steam will be found the weight of a cubic foot of steam at that pressure. The absolute pressure at point C, is 26 pounds and the weight of a cubic foot of steam at this pressure is .065, hence the weight of steam at this point per hour is 2061 1 X .065 = - 1339.71 pounds. From this amount however the steam saved by compression caused by the closing of the exhaust valve before the end of the stroke, must be deducted ; the remainder being the actual consumption of steam as accounted for by the indicator. The process by which to ascertain the amount of this de- duction is as follows : From the selected point C, draw a line parallel with the vacuum line to E, intersecting the compression curve at point F. ; multiply the accounted consumption by the distance from C to F, and divide this by the distance from C. to E. The length of the line from C. to F. is 3.32 inches, and that of the line from C. to E. is 3.56 inches, hence 339-/ 5i2r 1249,39 pounds of steam exhausted per hour, corrected for both clearance and compression. The Mean Effective Pressure of the above diagram (measured by Plani- meter) being 37.5 pounds per square inch, the Horse Power is -^L 45 56.25, hence the steam accounted for per 33000 1249 39 horse power per hour will be ?^r = 22 - 21 pounds. 156 Steam Kngine Indicator A somewhat simpler method of determining the same re- sult, is to continue the expansion curve of the diagram in its gradual descent, to the end of the stroke, and by that means locate the terminal pressure as at T, Fig. 76. FIG. 76. This point may be found according to the method des- cribed for constructing the theoretical curve as explained in Fig, 56 Chapter XIV, or may be traced by hand from the point of exhaust opening on the expansion curve, to the completion of the stroke ; and -which will be sufficiently near in cases where no great accuracy is desired. The process by calculation is to find the total mean dis- placement of the piston for the whole stroke, plus the clearance in cubic feet per hour. Multiply this by the weight of a cubic foot of steam at the terminal pressure T, and divide this product by the Indicated Horse Power. The quotient is the number of pounds of steam entering the cylinder per horse power per hour. For example : Assum- ing the engine data to be the same as in the preceeding A nd Its Appliances. 157 example ; therefore the mean piston displacement per single stroke in this case will be 3465 cubic inches; which if multi- plied by 10800 the number of single strokes per hour, and di- vide by (1728) the number of cubic inches in a cubic foot, the quotient will be the total piston displacement in cubic feet per 3465 X 10800 . . hour, that is, ** * - = 21656. 1 728 The absolute terminal pressure being 2 5 pounds per square inch, the weight of a cubic foot of steam at that pressure, ac- cording to the table is .063 pound; therefore 2i656x.o63 = 1364.32 pounds, which divided by the indicated horsepower of the diagram (56.25) is equal 1353.50-^-56.25 = 24.25 the num- ber of pounds of steam entering the cylinder per horse power per hour. And this would also be the actual amount of steam ex- hausted, were it not for the fact that it is exhausted above va- cuum from which the pressure is calculated ; also a portion of it is saved in the clearance space upon the return of the piston, and this saving is still further increased by the closure of the exhaust valve before the end of the stroke ; therefore the actual indicated consumption will be minus this amount. This correction may be made as follows : From the terminal pressure T, draw a line T 2, parallel with the vacuum line, thereby intersecting the compression curve at i, at which point the quantity of steam exhausted from the clearance has been restored, and the consumption will be as much less than the rule shows, as the line T. i. is shorter than the line T. 2. or the length of the diagram. Consequently to find the corrected rate, multiply the result as found by the rule (24.25) by the length of the T. i. = 3.47 inches, and divide by the length of the line T. 2 = 3.75 inches, hence - ^-^-=22.43 pounds per Indicated Horse Power per hour ; the corrected rate for both clearance and compression. 158 Steam Engine Indicator The volume of the cylinder, and the number of strokes being factors in the computation of the amount of steam ac- counted for in any given time, and the same also being factors in the calculation of power developed, consequently for this reason it is not necessary to take these quantities into consid- eration, when only the amount accounted for per horse power per hour is desired. The above fact provides another, and much more simple method of computing the rate of water consumption ; in which the piston displacement is not required, and which is indepen- dent of any knowledge of the size or speed of the engine ; the diagram alone being sufficient ; but it is necessary however to know the mean effective pressure. This rate may be found by the following rule : Divide the constant number 859375 by the volume of steam at the ter- minal pressure, and by the mean effective pressure. The quotient will be the w r ater consumption per horse power per hour uncorrected for compression and clearance. This correction is made in the same manner as that given in the previous method. This constant 859375 is the number of pounds of water that would be used in one hour by an engine developing one horse power, if run by water, (instead of stean?) at one pound pressure per square inch. The process is based on the following considerations : A standard horse power is 33000 pounds raised one foot per min- ute, or 33000 foot pounds, which is 33000X60=1,980,000 foot pounds per hour, or i,98o,ooox 12 = 23,760,000 inch pounds per hour. The latter number of pounds on being raised one inch per hour, requires the same expenditure of energy, as to lift 33000 pounds one foot per minute; each being the equiva- lent of the other. Now suppose the engine to be run by water, (instead of steam) at one pound pressure per square inch, and the number And Its Appliances. '59 of cubic inches in a pound of distilled water being 27.648 then 2 3, 760, 000-^-27, 648 =8 5 93 7 5 which is the desired constant, and which is the number of pounds of water per indicated horse power per hour that would be consumed by an engine driven by water, (instead of steam) at one pound mean effect- ive pressure. Example: Assume the diagram shown in Fig. 77, to be one from an engine of 12 inches, diameter of cylinder, and 24 \ \ \ FIG. 77. inches stroke running 100 revolutions per minute, the scale of the spring 40. The mean effective pressure of the diagram is found to be 42 pounds per square inch, when measured either by ordinates or by planimeter. The absolute terminal pressure T. V, is 28 'pounds, and the volume at that pressure (as given in table No. 8) is 883, that is one cubic inch of water at a temperature of 60 de- grees, makes 883 cubic feet of steam at 28 pounds pressure per square inch. 160 Steam Engine Indicator Hence by the rule the rate of water consumption will be oo 23.17 of water per indicated horse power per hour. But in this case some steam is saved by the closure of the exhaust valve before the end of the stroke, while some is ivasted by exhausting from the clearance at a pressure greater than the back pressure, and the above calculation so far makes no allowance for either. This allowance for compression and clearance may be cal- culated by the following method : Locate the point T on the diagram where the expansion line would have terminated, provided the steam had not been released until the end of the stroke. Draw the line T. 2, parallel with the atmospheric line A. A, which will intersect the compression curve at i, at which point the quantity of steam exhausted from the clearance has been restored ; therefore the consumption will be as much less than the rule shows, as the line T. i. is shorter than the line T. 2, or the length of the diagram. Multiply the result obtained by the rule, by the length of the line T. i, and divide the product by the length of the line T. 2 ; the result will be the rate of consumption corrected for both clearance and compression. Example: The length of line T. i, is 3.47 inches, and the length of line T. 2, is 3.75 inches. The rate of consump- tion obtained by the rule is 23.17, hence 2317x3.47-^3.75 = - 21.43 pounds; the corrected rate per indicated horse power per hour. This latter method is most generally employed by engin- eers in charge of plants, as it gives a very close approximation, and is very much more convenient than computations made from the steam displacement of the cylinder. Where diagrams are taken that have only a small amount of compression, the line T. i, will not intersect the compression A nd Its Appliances . 1 6 1 curve ; as in Fig. 78. In such cases it is necessary in order to find the length of the line T. i, to continue the curve from the FIG. 78. end of the diagram, (being guided by the eye) upward in about its natural direction, and far enough beyond the end of the di :gram, as to be intersected by the line T. i, which is always drawn parallel with the atmospheric line, as shown by the dotted lines in Fig. 78. The line T. i, will therefore be lengthened, but whatever may be its length, it is always the multiplier in making the cor- rections, while T. 2, is always the divisor, and represents the length of the diagram. In this case the result obtained by the rule is increased, because the multiplier T. i, is longer than T. 2. In diagrams like Fig. 79 where there is no compression, the proper position for point i ^on the terminal pressure line may be found as follows : First draw the vacuum line V, and locate the clearance line C, in accordance with the best data at hand ; then draw the terminal pressure line extending from 1 62 Steam Engine Indicator T. to C, which will intersect the end of the diagram at point 2, and from point 2, draw a diagonal line to the intersection of clearance line with the vacuum line ; (see 2 V). FIG. 79. This diagonal will intersect a continuation of the back pressure line at F, directly under the proper place for point i, on the terminal. In this case as in Fig. 78, the result ob- tained from the rule will be increased, because the multiplier (distance T. i.) is longer than T. 2 in the correction. A knowledge of existing clearance is necessary, as such diagrams give no information in regard to it. But the expan- sion curve of a cut-off diagram however, does furnish the in- formation necessary to arrive at approximately at the volume of clearance, unless the curve is very irregular in its forma- tion. Diagram Fig. 50 illustrates the method of establishing the clearance line by means of the expansion curve. The diagram Fig. 80 illustrates one process of locating the point i, (T. i.) in the terminal line, when this line is be- low the atmospheric line, and consequently below any part of the compression curve defined on the diagram. A nd Its Appliances 1 6 3 Locate the terminal line by drawing from T, (the terminal pressure) a line parallel with the atmospheric line and intersecting the end of the diagram at 2. Select any point in the compression curve as at D. lr FIG. 80. From that point draw a line perpendicular to the atmos- pheric line to terminal line as at F. Then from V where the clearance line intersects the vacuum line, draw a diagonal line through point F, to point E, (same height as point D.) then a line drawn perpendicular to the atmospheric line, from E, will intersect the terminal line at the proper place for point i. The process will be recognized the same in principle as that used for finding a point in the isothermal expansion curve. The water consumption computed for diagram Fig. 80 is as follows : The mean effective pressure as measured by planimeter is 2^8 pounds per square inch, and the terminal pressure is 7 pounds absolute. 164 Steam Engine Indicator The volume for 7 pounds as given in the Table No. 8, is 3300, hence 8 59 375 = pounds uncorrected for com- pression. 3300x2.125 Line T. i, is 2.60 inches long, and lineT. 2C(or the whole length of diagram) is 3.75 inches, hence 122.5x2.60^-3.75 = 84.93 pounds per indicator horse power per hour, the correct rate. Diagrams similar to Fig. 80 are wasteful of steam, and are usually obtained from engines having insufficient load, and a comparison of the water consumption, (as computed) with that of diagrams taken from moderately loaded engines will at once make apparent the economy of the latter, as against the extrav- agant waste of the former. Probably no other single condition is so detrimental to good economy as an engine over large for its work, as a too light load necessitates an early cut off ; the expansion and con- sequent fall of temperature becomes excessive, and hence in- ternal condensation appears to the fullest extent. In the computation for water consumption of these dia- grams it must be understood that the rates as calculated are theoretical, and assumes perfect conditions, such as dry steam, entire absence of loss from leakage, condensation, etc. The diagram shows only the minimum amount of steam that has been consumed by the engine to do a given amount of work, and there are many reasons why this consumption of water as shown by the indicator should be less than the actual amount. It is considered that the percentage of loss in a modern and properly constructed steam plant is fully twenty per cent. ; and taking the engine alone, is at least ten per cent, and this may be still further increased by condensation, and also where considerable leakage occurs, etc., so that it is safe to add at least 10 per cent, to the indicated consumption to closely ap- proximate the actual consumption. A nd Its Appliances . 165 The loss from water that is carried over with the steam is chargeable to the boiler, and not to the engine. The unindicated loss will also be greatest at light loads. With steam at 80 pounds pressure, and a mean effective pres- sure of from about 40 to 45 pounds, (corresponding to about one-fourth cut-off), will give the least loss. Very short cut-off gives an increased loss. The steam used in the low pressure cylinders of compound engines, first passes through the high pressure cylinder ; hence the water consumption as computed for the high pressure cylinder, (corrected for compression") will be the measure of consumption for the whole engine. This amount is to be divided by the horse power of the whole engine for the consumption per indicated horse power per hour. The consumption may also be computed from the low pressure cylinders in the same manner as for the high pres- sure cylinder , but which will be found to disagree with the former owing to some loss between the cylinders. It will also be found that if no other steam is admitted to the low pressure cylinders, except what has already passed through the high pressure cylinder, that the water consump- tion will appear greatest when calculated from the high pres- sure, and will gradually become less from each successive cylinder: therefore it is a good plan, and of interest to meas- ure the consumption from each and all of the cylinders, and compare the results. The differences may be considered as fair measures of the loss in transmission between the cylinders. Another method is here given for calculating the water consumption by constant, and which is also independent of any knowledge, (except the mean effective pressure) of the size or speed of the engine ; and which may be easily and accurately determined from the diagram, for both cut-off, and release by 1 66 Steam Engine Indicator means of, and the use of the formula : i, X (proportional volume at cut-off X weight of steam) minus, (proportional vol- ume at compression X weight of steam) = number of pounds of steam accounted for at cut-off, per indicated horse power per hour. Or, by the formula : M p X (proportional volume at release X by weight of steam) minus, (proportional volume at compression X weight of steam) = number of pounds of steam accounted for at release per indicated horse power per hour. The following is the explanation of the above formula M. E. P. is the mean effective pressure. In compound, triple and quadriple expansion engines, this is the sum of two or more quantities. One is the M. E. P. of the cylinder under consideration, as for instance, the high pressure cylinder, and the others are the M. E. P. in the other cylinders referred to the high pres- sure cylinder. The proportional volume at cut-off is the percentage of the stroke computed at cut-off, (as at D. Fig. 81) added to the per- centage of clearance, and this is to be multiplied by the weight of one cubic foot of steam at the cut-off pressure. TJie proportional 'volume at compression is the percentage of the return stroke uncompleted at compression added to the percentage of clearance, and this is to be multiplied by the weight of one cubic foot of steam at the pressure where com- pression begins. Tlie proportional volume at release is the percentage of the stroke completed at release added to the percentage of clearance, and this is to be multiplied by the weight of one cubic foot of steam at the pressure where release is taken. The constant 13750 is the volume of steam in cubic feet per hour required by an engine without clearance to develop A nd Its Appliances. 1 67 one horse power when working with one pound pressure per square inch and without expansion. This quantity will be less in proportion to the increase of average pressure ; there- fore it is divided by the mean effective pressure (M. E. P.) of the diagram. The quantity will also be increased in proportion to the percentage of clearance, and decreased by the quantity of steam saved by compression. The points of cut-off, release, and compression referred to are shown respectively at D. E. and F. in the diagram Fig. 81. FIG. 81. The pressures at these points must be the absolute pres- sure, taken from zero or a perfect vacuum, which is 14.7 pounds below the atmosphere when the barometer indicates 29.92 inches. Where great accuracy is desired, the height of the barom- eter should be observed, when the diagrams are taken in order that the atmospheric pressure which it shows should be used in such cases. 1 68 Steam Engine Indicator The pressure of the atmosphere as shown by the barome- ter in inches of mercury should be multiplied by 0.491 to re- duce it to pounds per square inch. The requisite data for computing the amount of steam ac- counted for, from the diagram Fig. 81 is as follows: The pro- portion of stroke completed at cut-off D, is thirty-hundredths, (.30) and the absolute pressure of steam per square inch at that point is eighty-three (83) pounds The weight of a cubic foot of such steam is .1967 pounds. The proportion of stroke completed at release E, is ninety- hundredths (.90) and the absolute pressure thirty (30) pounds. The weight of a cubic foot of such steam is .0755 pounds. The proportion of the return stroke uncompleted at com- pression F. is ten-hundredths (.10) the absolute pressure is sixteen (16) pounds, and the weight of a cubic foot of this steam is .0413 pounds. The clearance of the engine equals .02 per cent. The mean effective pressure on the piston is forty (40) pounds per square inch. Hence by this method the amount of steam accounted for at cut-off will be _?Zl_x(. 30+. 02). 1967= - 4 (. io-{-.O2).O4i3 343. 75 X .0579 19.90 poundsof steam or water per indicated horse power per hour. The amount of steam accounted for at release will be : 40 pounds of steam per hour. Suppose in the engine to which these calculations ap- ply, an actual feed water test gave a consumption of thirty (30) pounds of water per indicated horse power per hour; then the percentage of feed water accounted for at cut-off is 9 '9 .663 and at release !--==. 739, 30 30 And Its Appliances. 169 The formula for release may be simplified in cases where there is a sufficient amount of compression, by locating the compression point at such a height on the compression curve as will make that pressure and the release pressure equal, as shown in diagram Fig. 82. The formula then becomes M p p (percentage of stroke completed at release, minus percentage uncompleted at com pression) multiplied by the weight of a cubic foot of steam at release pressure, thus, \ ^ (.90 .io(.o755 20.62 pounds, M. h<. r. the effect of clearance disappearing. The quantity in the parenthesis is the proportion which the distance (1) between the points in Fig. 82 bears to the whole length of the diagram FIG. 82. or to L. That is the proportion 1 release formula. L The calculation of the quantity M. E. P. may be facilitated by reference to following Table No. 5, This applies only to the in these formulas Steam Engine Indicator QUANTITY OF STEAM ACCOUNTED FOR BY INDICATOR. M.E.P. Ibs. 13750 M.E.P. M.E.P. Ibs. 13750 M.E.P. M E.P. Ita. 13750 M.E.P M.E.P. Ibs. 13750 M.E.P. IO. 1375-0 36.5 376.8 66. 208.3 119. "5-5 10.5 .309.6 37- 37J 6 67. 205.2 120. 114-5 II. "5 I25O.O 1195.6 i: 5 366 7 361.9 68. 69.' 202 .'2 199.3 12 1 '. 122, 113.6 112. 7 12. 1145.8 38.5 357-2 70, 196 4 '123 in. 7 12.5 IIOO.O 39 352.6 71- 193.7 124. 1 10 8 13 1057 7 39-5 348 2 72. 191 o 125. no o 13-5 1008. 6 40. 343 8 73 188 4 126. f9- r 14- 982 i 40.5 339-6 74- 185.8 127. V io8 2 '4-5 948.2 41- 335 4 75- 183 3 128. 107 4 15 916.7 41-5 33i 4 76. 180.9 129. 106.5 5-5 .887 o 42. 77 1/8.6 I 3 0. 105^7. 16. 859-4 42 5 323-6 78. 176.3 104.9 165 833.4 43 319 8 79- 174.1 132! 104 i 17, 808.8 43-5 316 o So. I7I.9 133. 103 3 17-5 785-8 4V ' 312.6 81. 169.8 102.6 18. 763 9 44-^ 309.0 82. 167.7 135- 101.8 18.5 743-2 45. 305-6 83- 165 7 1 3 6. KM. I 19. 723-7 302.2 84- 163.7 '37- 100.3 19-5 705 * 46. 298.9 85- 161.8 138. 99-6 20. ' 687.5 46.5 295 6 86. 159-9 139- 98.9 20 5 670.8 47- 292.6 87. 158.0 140. 98.2 St. 654.8 47 5 289.4 88, 156.2 141. 97-5 21.5 639.6 48- 286.5 ^89. !54-5 142. 968 22, 625.0 48.5 283 6 90. 152.8 143' 96.1 23'* 611.2 597-8 49 49 5 280.6 277.8 91. 92- 151.1 149.4 144. f 45' 95-4 94 8 2 3 ^ 585-2 50. 275.0 93- 147.8 140. 94.1 24, 572-9 5-5 272 3 94- 146 3 147. 93-5. 24-5 561 2 5' 269 6 95- 144.7 148. ,92-9 25. 550.0 51 .5 267 o 96- 143 2 149. '92.2 S: 5 539 2 528 9 52. 52-5 264 4 261.9 97- 98. I4I.8 140 3 150. 91.6 91.0 26.5 518.8 53 259-4 99- 138.9 ^152; 90,4 27. 509 3 53-5 257 o 100. 137-5 153- 89.8 27 5 500 o 54- 254-6 101. 136.1 89.2 28. 491 i 54 5 252 3 102. 134-8 155'- 88.7 28.5 482,4 55 250 o I0 3- 133-4 156. 88.1 29. 474 l 55 5 247.7 104. 132.2 157- 87-5 29 5 466/2 56. 245-5 I0 5- 130.9 158. 87.0 3 458.3 56.5 242.4 106. 129.7 159- 86,4 30.5 450 8 57- 241.2 107. 128 5 160. 85.9 443-5 57-5 239-1 108. 127-3 161. 85.4- 3i-5 436-6 58. 237 i 109. 126.1 162. 84.8 ,32- 429 7 58.5 235-1 lio. 125.0 163. 84-3 32 5 423.0 59 233-1. in. 123.8 164. 83.8 33- 33-5 416.7 410.4 231.1 229.2 112. 113. 122 7 121 6 S: 83-3 82.8 34- 34-5 404.5 398,6 61! 62. 225 4 221 7 114 120 6 119.5 IS: 82.3 81.8 392.9 63: 218.3 116 118 5 169. 81.3 35-5 387-4 64 214.9 117. "7-5 170. 80.8 36- 381.9 65- 211. 5 118 116.5 80.4 And Its Appliances. 171 QUANTITY OF STEAM ACCOUNTED FOR BY INDICATOR.-Continued. M.E.P. Ibs. 13750 M.E.P. Ibs. 13750 M.E.P. Ibs. 13750 M.E.P. Ibs. 13750 M.E.P. 172. 79-9 93- 71.2 213. 64.5 233, 59-0 173- 79-4 194. 70 8 214. 64 2 234. 58.7 174. 79 o 195 . 70-5 215. 63 9 235. 58.5 '75- 78 5 196. 70.1 216. 63 6 2 3 6. 582 1 7 6. 78.1 197. 69.7 217. 63.3 237- 58.0 177. 77-6 198. 69.4 218. 63.0 238. 57-7 I 7 8. 77-2 199. 69.0 219. 62.7 239- 57-5 179. 76.8 200. 68.7 220. 62 5 240 57-2 180. 181. 76-3 75-9 201. 202. 68.4 68.0 <22I. 222-. 62.2 61.9 . 2 4 I. 242. 57-0 56-8 182. 75-5 203. 67.7 223 61 6 243- 56.5 183. 75- 1 204 67 4 22 4 . 61 3 244- 56.3 184. 185. 74 7 74-3 3: 67.0 66.7 225. 226. 61.1 60.8 245. 246. 56.1 55-8 1 86. 73 9 207. 664 227 605 247. 556 187. 73 5 208 66.1 228. 60.3 248. 55 4 188. 209. 65-7 229. 60 o 249. 55-2 189. 72 7 210. 65.4 230. 59 7 250 55-0 190. 72-3 211. JS-J 23L 59-5 251. 54-7 191- 71.9 212. 64.8 232. 59-2 252. 54-5 192. 71.6 The foregoing table gives the result of the division for each half pound mean effective pressure, between 10 and 60, and for each pound between 60 and 252. It is a good plan to compute the steam accounted for, at both cut-off and the release points of the diagram ; because if the expansion curve should deviate much from the isothermal a very different result is shown at one point from that shown at the other. In many cases the extent of the loss occasioned by cylin- der condensation and leakage is indicated in a more truthful manner at the cut-off than at release. The constant 13750 may also be employed in a somewhat similar manner for computing the steam consumption of an engine, by the following method. Select any point as at D. on the expansion curve, Fig. 83, and draw a line from it, and parallel with the vacuum line, 172 Steam Engine Indicator until it intersects the .compression line at C, then with the scale of the spring, (measuring from vacuum to the height of this line above) find the pressure of steam at such height ; then from Table No. 8, find the weight of a cubic foot of steam at that pressure. FIG. 83. Multiply 13750 by this weight of steam per cubic foot, and by the distance in inches, between the points C. and D. Di- vide the product by the mean effective pressure multiplied by the distance A. A. or the extreme length of the diagram. The result will be the number of pounds of steam con- sumed per indicated horse power per hour as shown by the diagram. For example : Suppose the whole length of the diagram to be 3.75 inches, and the distance between the points C. and D, 3.10 inches, the scale of the spring 40, and the mean effect- ive pressure 39 pounds per square inch, the pressure from va- cuum to line C. D. being 30 pounds. The weight of a cubic foot of this steam as shown by the table No. 8 is .0755 pounds.. A nd Its Appliances . 173 Therefore I375 x '755X 3- IO =22 pounds consumption per 39X3-75 indicated horse power per hour. The use of the constant number 13750 is based on the fol- lowing considerations : If a piston one square inch in area moves twelve inches, it will do work equal to one foot potmd for each pound pressure of steam per square inch. That is, every twelve cubic inches of piston displacement represents one foot pound of work at one pound mean effective pressure ; and as twelve cubic inches is equal to T } of a cubic foot, the piston must sweep a volume of 33QQQX o _ j 375Q cu ki c f eel per horse power per hour, when 144 the mean pressure equals unity ; therefore as the volume of steam used per horse power per hour varies inversely as the mean effective pressure and if the weight of a cubic foot of steam at the release pressure be designated by W, and the mean effective pressure by M. E. P. we have the formula, ^~^ X W the number of pounds of water consumed per indicated horse power per hour, exclusive of waste by condens- ation and leakage ; and also makes no allowance for clearance and compression. 174 Steam Engine Indicator CHAPTER XXII. INDICATOR TESTING DEVICE. In indicator practice it is frequently found that the initial pressure in the steam cylinder, as shown by the indicator dia- gram, will in some cases be from five to ten or twelve pounds less pressure per square inch, than the pressure in the boiler, as indicated by the steam guage. This discrepancy in pressure between the indicator and steam guage may arise from various causes ; such as inadequate size of steam pipe, also torturous and rough passages, non- covered or unprotected pipes, incorrect valve setting, tardy valve motion, etc. ; all or any of which tend to cause an appar- ent difference of pressure between the indicator and steam gauge. Where such differences do exist in these pressures, the fault is generally supposed at first thought, to lie with the in- dicator, when in fact it may be due to any of the causes named ; or may be due to the incorrectness of the steam gauge itself. Therefore it becomes important that means be taken to ascertain how near the gauge and indicator agree in denoting the steam pressure, in order that the amount of pressure lost between the boiler and engine may be determined. And Its Appliances. 175 For making such comparative tests the arrangement illus- trated in Fig. 84, is easily constructed, not very expensive, and is well adapted for the purpose. It may be connected directly with the steam space of the boiler, or may be attached to the steam pipe in any convenient, position. FIG. 84. In making a comparative test when the device is attached to the steam pipe (as shown) it is best that it be done at a time when the engine is at rest, and the throttle valve closed in or- der to avoid any fluctuations of pressure that otherwise might exist in the pipe. 176 Steam Engine Indicator In the matter of construction the Chamber C. should be of such size as to contain a considerable volume of steam, and such chamber may consist of an ordinary four inch cross fitting, with the inlet and outlets reduced to suit the size of pipe em- ployed. V Steam is admitted to the system through a i inch pipe, and controlled by the globe valve A, and discharged as occa- sion requires, through the ij^ inch pipe by the valve D. This pipe is made larger in order to facilitate the discharge of the volume of steam under pressure in the chamber, as quickly as possible. The top is tapped to suit the indicator cock I, which is us- ually made of a size corresponding to ]/ 2 inch pipe fittings. The bent pipe U, leading to the steam guage G, may be of y^ inch pipe. The bend in the guage pipe should be extended downward at least four or five feet below the center of the four inch cross fitting; thereby securing a sufficient column of water to insure against overheating of the gauge above the existing medium, or atmosphere. Before preparations for any tests are made, it will be advisable to partly fill the gauge pipe with water ; which can be readily accomplished by disconnecting the gauge G, and pouring water into the pipe until it stands in both legs of the pipe about as high as the center of the chamber C. In preparing to make a test, attach the indicator contain- ing its spring, and also steam guage, in the manner shown in the illustration, and secure a piece of paper in the usual way to the drum of the indicator. Close the discharge valve D, and open the indicator cock I, also open communication between indicator, and gauge, by means of cock F. Now by gradually admitting steam to the chamber by the valve A, there will be a simultaneous advance movement of both the indicator pencil, and gauge hand, and which will And Its Appliances. 177 continue as the steam is admitted until the desired limit of the in- dicator spring has been reached. This is a preliminary oper- ation for the purpose of warming up the indicator preparatory to making the card. After the indicator and its spring has been thoroughly warmed, first close the valve A, and then open the valve D, thus discharging the steam from the chamber, through the open pipe into the atmosphere ; and thus lowering the pres- sure, and causing the indicator pencil and gauge hand to return each to their normal positions. Now with one hand, bring the indicator pencil in contact with the paper on the drum ; and by means of the cord E, (with the other hand) cause the drum to rotate a small amount, which in consequence results in tracing a line upon the paper, and which represents the zero or atmospheric line. Then close the discharge valve D, and slowly admit steam to the chamber through the valve A, and continue until the observed reading of the steam gauge denotes, say ten pounds pressure per square inch. Just at this point mark another line on the paper by the same means, (by hand) as employed in tracing the atmospheric line. Continue to mark the corresponding lines on the paper for each successive ten pounds movement of the gauge hand (from observation) until the pressure limit of the indicator spring has been reached. Close the admission valve A, and discharge the steam re- maining in the chamber through the valve D. Remove the paper from the drum, and compare the mark- ing with a rule or scale, on which the divisions coincide with pounds pressure per square inch, according to the denomination of the indicator spring used. Supposing a forty pound spring is to be used in the indi- cator, and assuming both the steam gauge and spring as 178 Steam Engine Indicator correct ; then the marking would appear as shown at A in the illustration Fig. 85 for each ten pounds on the gauge, succes- sively from zero to eighty pounds pressure per square inch. But in many cases they do not agree so uniformly, as shown in the figure from the fact than steam gauges, and also indica- tor springs vary more at some pressures, than at others; hence, such a test enables the operator to observe the true ac- tion of the spring; also at what part of the marking the great- est variations (if any) occur, and shows that some springs although correct in some parts of their compression, are incor- rect in other parts ; and also that either gauge or spring may show light at some pressure and heavy at another. If the spring registers the greater pressure according to its scale it is light, and if less it is heavy, provided the steam gauge is correct. This device is easily manipulated to mark a descending, as well as an ascending pressure, and on the same paper, and may be accomplished by a very gradual releasing of the pres- sure in the chamber, after the extreme height (to which the indicator spring should be subjected) has been reached, and in again marking the paper, upon the descent of the pencil, from the same readings of the gauge as was done in the ascending pressure. A comparison of this kind is both interesting and instruc- tive, as it furnishes the means for observing the various phe- nomina connected with springs in general, and in their appli- cation to different purposes. In a test of this description, and where friction exists in the indicator, it is found that a variation or lack of coincidence more or less, appears in the lines so marked ; that is, a differ- ence between the lines marked when the pencil is rising and those marked when the pencil is under falling pressure ; the latter failing (particularly at the higher pressures) to drop suf- ficiently low, as to meet the lines marked during a rising A nd Its Appliances. 179 pressure : A corresponding pressure always being denoted by the steam gauge at each marking up or down. This lack of coincidence, gradually decreases from the higher pressures downward until the zero line has been reached, and where the lines again agree. This is shown at B, Fig. 85, and the column marked up, is the rising, and that marked down the falling pressure. The fact of their disagreement is caused principally to undue friction in some part of the indicator, and might also be Up Down 70 60 50 40 30 ?0 10 ou 70 60 50 40 30 30 10 -w 70 60 56 40 30 ao. 10 - Fia. 85. partly due under some circumstances to lost motion in the pen- cil mechanism. Consequently the elimination of friction in the indicator to a minimum, is a matter greatly to be desired ; it being an im- portant requirement in all indicators, in order to insure accu- racy in the diagrams. Although an indicator, upon inspection may appear satis- factory in all respects when cold, it may become the reverse of this when in operation and subjected to a high temperature of steam ; this, application of heat, and circumstances causing i8o Steam Engine Indicator unequal expansion of the metals of which the indicator cyl- inder is composed. The expansion that takes place upon being- heated, varies in the different parts of the indicator; generally increasing the size of the piston to a greater extent than it does the sur- rounding metal ; and thereby involves a liability of the indica- tor piston to become sufficiently increased in size as to bind in the cylinder; thus creating excessive friction, but which may obviously be eliminated by a slight reduction in the size of the piston. Another source of friction which often happens, arises from springs of imperfect construction, or out of true, causing when under tension, a lateral or side pressure against the cylinder. Either of these faults results in an interrupted or broken action in the movement of the pencil, and which is fatal to the accuracy of the instrument, therefore in order that perfect freedom of action, and that smoothness and accuracy in the pencil movement be attained, it is indispensible that friction in the instrument be reduced to the lowest degree possible. By the use of this device an amount of interesting and varied information may be obtained, pertaining to the condi- tion and action of springs, the variations in pressure for equal movement of the pencil, in showing the difference between a rising and falling pressure when undue friction is present, and also as a means of observing inaccuracies that may appear in any part of the mechanism connected with the indicator. In many cases errors arise from excessive friction of the indicator piston, caused by scale or grit of any description being carried from the pipes and other connections leading to it. If such should b2 suspected it will likely be detected (where slow speeds prevail) either by close observation of the pencil in its movement up and down, or by placing the finger And Its Appliances. 181 at the top of the indicator piston rod, and gently follow it in its downward movement. As a matter of course the remedy is to remove the piston and clean. Sometimes with new indicators and clean pistons an un- usual amount of piston friction shows itself in the diagram by a series of very definite serrations on the expansion line just after cut-off, as shown in Fig. 86 the horizontal portion of the serrations indicating a disposition of the piston to hang at each of these positions in its descent. FIG. 86. In some cases of this kind it may be necessary to very slightly reduce the size of the piston by means of a fine crocus paper, or by oiling, and allowing it to run a short time, having first disconnected the pencil movement. With springs of a higher tension, that is, with stronger springs, the serrations resulting from the friction of a tightly fitting piston, will not be so apparent, and will be less defined, than with the lighter springs. However the difference in results on the diagram between a tight piston, and one fit- ting freely, will be, that with the former the various events of the stroke such as cut-off release, and compression, will occur 1 82 Steam Engine Indicator latter in the stroke, owing to the tardy response of the piston to the variations of steam pressure. The fricton of a tightly fitting piston therefore will cause the initial pressure to be less, but the pressure along the expan- sion, and also the back pressure line, (on account of its tardi- ness) will be greater, than with the more freely moving piston. However the area of diagrams from each may not differ greatly; because the loss of initial pressure is partially com- pensated in the formation of the expansion line ; owing to a tardy piston. Occasionally the mean effective pressure in each may not differ materially, still in most diagrams that have been taken with an indicator in which the piston was too tightly fitted, the diagrams have been found to be unreliable, inaccurate, and misleading. The piston friction on an indicator may be approximately determined in the following manner : First allow the instru- ment (by a few working strokes) to become heated to a temper- ature coinciding with the steam pressure present ; then after closing communication with the engine cylinder, gently depress the pencil lever (by hand) just sufficient to slightly ex- tend the spring, and then allow it to slowly return to rest. While in this position a horizontal line is drawn on the diagram. The pencil lever is next raised and the spring slightly com- pressed, and then again allowed to come to rest and another line drawn as before. The distance or space between the lines so marked is a measure of the sum of the total frictional resistance in both directions, and assuming the pencil movement without friction, then the whole of the error so measured is attributable to pis- ton friction. Careful attention to the lubrication of the piston, and pen- cil movements will conduce to smooth running, and to a certain And Its Appliances. 183 extent, will prevent the tendency to stick or bind in the cylinder. Clean cylinder oil will be found a far superior lubricant for the piston, than the limped oil used for the pencil move- ments. f I * 4 184 Steam Engine Indicator CHAPTER XXIII. PLANIMETERS. Where considerable care and attention is used the mean effective pressure of diagrams may be computed with a close approximation to accuracy, by the use and method of ordinates, as before described, 4 but the operation is usually attended with considerable anxiety, and also becomes otherwise a rather tedi- ous operation in various ways with more or less liability of error. Therefore, where the mean effective pressure of a large number of diagrams is desired, and where greater accuracy is required, time and labor may be greatly facilitated by the use of an instrument termed a Planimeter, constructed and used for the purpose of correctly measuring the area of any irregular figure regardless of its outline. There are various forms of this instrument, some of which are so constructed that by moving the tracing point over the entire outline of a diagram, its area may be read from a graduated index wheel, its move- ment being relative to some fixed or zero point. There are others in which the reading is taken from the movement of a blank wheel, traversing a graduated scale, and the result is ascertained by noting the coincidence on the scale of some particular line corresponding to the edge of the wheel that has been selected, and made to coincide with a zero point of the scale; when commencing to trace the diagram. The instrument shown and illustrated in Fig. 87 is one of the former, with a graduated index wheel and vernier and And Its Appliances. represents the well known Coffin Averaging Planimeter in position on its board ; and which was especially designed and adapted to the purpose of measuring the mean effective pres- sure of indicator diagrams. With this instrument no calcula- t i o n s whatever are required to ascertain the av- erage pressure or mean height o f the diagram, throughout the stroke of the en- gine, and it may also be applied, when desired, for m e a suring the areas of any, and all other irregu- lar figures. It is especially valua- ble where a large number of dia- grams have to be measured for area or mean effective pressure, either or both of which may be ascertained at all times (without any adjustment of the instrument), by a single passage of the tracing point around the outline of the figure. In consideration of the accuracy attained and the ease with which it is manipulated makes its use desirable in all cases in a single as well as in a number of diagrams, as the chances of error in making calculations are entirely eliminated. 1 86 Steam Engine Indicator The parts of this instrument being permanently secured in- sures it always ready for use, without the necessary adjustment to length of diagram, etc., required by some other makes, in order to ascertain areas and average pressures, and which gives only the readings of one or the other separately. This instru- ment measures the area and average pressure or mean height of any diagram or figure at the same operation, however ir- regular, or whatever its shape may be, just as quickly and accurately as if it were some regular figure, such as a square or rectangle. The Coffin Averaging Instrument proper consists of an arm fitted at one end with a tracing point O, and at the other with a hardened steel guide pin (not shown in the cut), the centre of which is common with the centre of the weight Q. Upon this arm is also mounted a graduated index wheel and spindle, delicately poised on hardened steel centres, thereby reducing friction to a minimum. The axis of said wheel being parallel to a line drawn from the centre of a guide pin to the tracing point. In close proximity to the wheel there is per- manently secured to the arm a graduated vernier scale and used in connection with the graduations of the wheel, thereby enabling the readings to be readily observed in small fraction- al parts of a square inch. The distance between the centres of the guide pin and the tracing point of the arm is assumed to represent the length of one side of a rectangle, while the circumference of the graduated wheel represents its component or height, and if the terms of these two factors be in inches, the product of their multiplication will be the area of the rectangle of such dimensions in square inches. For example : In this instrument the distance between the guide pin and tracing point is six and one-quarter (6.25) inches, and the cir- cumference of the wheel two and four-tenths (2.4). correspond- ing to a diameter of about .764 part of an inch, then 6.25x2.4 is equal to fifteen square inches, which will be the area of a And Its Appliances 187 rectangle, where one of its dimensions coincides in length with the distance between the guide pin and tracing point, and the other with the circumference of the graduated wheel. The circumference of the wheel is therefore divided into fifteen (15) main divisions, each division representing one square inch area of the rectangle. Each of the main divisions are sub-divided into five (5) equal parts, each one representing one-fifth (1-5) or twenty hundredths of a square inch. The vernier scale is composed of ten ( i o) divisions, their combined linear distance being just equal to nine (9) subdivisions of the wheel. Therefore, as each subdivision on the wheel represents one-fifth (1-5) or twenty hundredths (20) then, accordingly the divisions of the vernier will represent eighteen hundredths (18) a difference of two hundredths (.02), consequently the vernier enables the sub- divisions to be read to one-fiftieth (1-50) or two hundredths (.02) of a square inch. Accompanying the instrument is a nicely finished mahog- any board, upon which it is mounted when in use, and an especially prepared blank card is firmly secured to the board upon which the Index Wheel travels. There is also fitted to the board a metal grooved guide I in which the guide pin slides being secured therein by the weight Q. The Clips C and K are for the purpose of securing the card to be measured in the most easy and convenient position for the operator. The angle clip C is fixed permanently to the board with its inner edge in a direct line with the centre of the groove in the guide I. The clip K is secured to a slide that is moveable in order that it may be adjusted to any length of card. The guide I is secured by a suitable thumb screw on the under side of the board; said guide is shown in the cut with its end projecting beyond the board, which is its proper position when in use. The guide may, if desired, be reversed on the board which will bring its end even with the same, and affords a better 1 88 Steam Engine Indicator opportunity of packing or laying away when not in use. In pre- paring to use the instrument the indicator card is first placed un- der the clips C and K which are so made as to admit of its be- ing inserted underneath and adjusted in the proper position, that is, with the extreme left hand end of the diagram coincid- ing with the perpendicular edge of the clip C, while the atmos- pheric line is placed near to and parallel with the horizontal edge of the clip. The movable slide carrying the clip K is then adjusted, until the edge of the clip just touches the right hand end of the diagram, the presure of the clips upon the paper serving to secure it firmly while the work upon it is be- ing performed. The slide to which the clip K is secured, is fitted so that only a slight pressure of the thumb or finger is required to move it in either direction. The mean effective pressure of an indicator diagram being one of the principal factors in the computation of power of steam engines, hence this particular location of the diagram upon the board (as represented in the cut) is only necessary where the finding of this quantity is desired. Otherwise, in cases where only the area of the diagram or other irregular figure is needed, it may be placed in any desired position with- out reference to any point, and the area read directly from the graduated wheel. The instrument is then arranged upon the board with its guide pin inserted in the groove of the guide I, and secured therein by the weight Q. The tracing point O is then moved to the extreme right hand end of the diagram, where the line is in contact with the clip K (as shown at D). Here make a slight indentation in the paper, by pressing the thumb against the top of the tracing point ; this gives the start- ing point from which to trace around the diagram The zero mark of the graduated wheel is then turned and made to exactly coincide with the zero mark on the vernier. In commencing operations the direction in which the diagram should be followed by the tracing point is ; first along the back A nd Its Appliances, 1 89 pressure and compression lines, thence returning by way of the expansion curve to the starting point. The only object in tracing in this direction being that the main divisions on the wheel are numbered towards the left from the zero mark, and consequently in this direction any movement of the wheel is recorded in regular order, as i, 2, 3, etc., whereas, if the diagram is traced in the opposite direction, the reading will be the re- verse of this, as 14, 13, 12, etc., and, although the circumfer- ential movement of the wheel would be precisely the same in either case, the only consequence of tracing the diagram in the latter direction would be the inconvenience of reading the areas. In the measurement of indicator diagrams, for mean effec- tive pressure, no attention whatever need be given to reading the areas. After the tracing point has made a complete circuit and again reached the starting point, it is then moved upward along the edge of the clip K until the zero mark of both the wheel and vernier coincide. Another slight indentation is then made at this point, (as shown in the cut at A). The dis- tance between these two indentations (D and A) represents the average height of the card, and also, if this is measured with a scale corresponding in pounds to the denomination of the spring with which the diagram was taken the said measure- ment will be the mean effective pressure of the diagram in pounds per square inch, according to the spring and scale used. Where two diagrams are taken on the same card it is ad- visable to measure and find the average pressure separately ; for the purpose of comparison with each other. By the use of this instrument all imperfections or irregularities whatever in the outline of the diagrams whether to be added or subtracted, are accounted for, and the final results given exact. For in- stance, where a loop is formed in the diagram (as in Fig. 62) caused by the expansion line crossing the atmospheric line early in the stroke, and running below to the end, thereby 190 Steam Engine Indicator dividing the diagram into two distinct parts, its outline should be traced in the same manner as is done in any well formed diagram, as the principle upon which the instrument is con- structed, enables it to perform the operation of addition or sub- traction with the greatest exactness and will consequently sub- tract the effect of the said loop from the positive part of the diagram and the reading of the instrument after the diagram has been traced, will give the net average pressure per square inch throughout the stroke. Where the instrument is used to measure the area of any figure, it is only necessary to select a starting point. Adjust the zero marks on the wheel and vernier to coincide, and trace around the outline of the figure, then its correct area will be found from an observation of the number of main divisions, and subdivisions of the wheel that have passed beyond the zero mark on the vernier. For example : Suppose upon noting the number of main divisions of the wheel that have passed the zero mark of the vernier, we find the largest figure to be three (3) which will represent inches, and the number of sub-divisions that have also passed the zero mark of the vernier, to be four (4), each subdivision representing one-fifth (1-5) or twenty-hundredths (.20) of a square inch, and the number of the division on the verneir which exactly coincides with a division on the wheel to be two (2), each representing two-hundredths (.02) of a square inch, therefore the reading taken from the instrument in this position will be 3+(4x.2o)-{-(2x.O2)=3.84 square inches, as the area of figure. This instrument being of careful and delicate construction, should be handled with the greatest care and kept perfectly free from any matter that might interfere with the movement of the wheel ; thereby insuring accurate results. To a great many users of the Averager or Planimeter, shown and described in Fig. 87, it may be considered a fact that the reason and principle upon which its accuracy is based, And Its Appliances. 191 in the measurement of the area of any irregular figure, is, to a certain extent, shrouded in mystery ; but nevertheless it is well-known that a comparison of its readings, taken from figures of known areas, prove its reliability and correctness, and can under all circumstances be depended upon for correct results ; hence, a study of the theory of its operation may be interesting to many. The manipulation of the instrument being easily per- formed, as before described, and its theory quite simple, we shall endeavor to make clear and explain why, by simply passing the tracing point around the outline of a given figure, its exact area will be denoted on the registering wheel. In attempting this we shall leave out, wherever possible, the use of the higher mathematics usually employed in connection with a discussion of the subject, and also shall first consider the instrument in its application to the measurement of areas, and which consideration will also apply in principle to all other planimeters. Although the principle is simple, still it is necessary for the reader not conversant with it, to follow closely the explanation in order to become familiar with the peculiar movements and actions of the registering wheel. In Fig. 88 the outline A, Ai, C, D and A3, is supposed for our purpose to represent an indicator diagram, the expan- sion curve being shown in dotted lines. The point A on the diagram is selected as the starting point from which to trace and consider the figure. Probably a better idea may be had, by first confining our study of the subject to a part of the diagram ; that is, the area of the square inclosed by the lines A, Ai, A2 and A3. The line Ai-Bi represents the arm of the instrument, and shows its position after the tracing point has been moved horizontally away from the starting point A to the position at Ai. This line (Ai-Bi) may be assumed to be a small round rod, the end (Bi) being guided to always move in a straight line, as shown by dotted line from Bi to 63 ; while 1 92 Steam Engine Indicator the end (Ai) carrying the tracing- point is free to be moved in any direction, and to any point of the diagram. This arm or rod is also shown here as the axis of the registering wheel W, and is represented in this way for the purpose of simplifying matters in the way of its demonstration, and because the final results of the registering wheel W, in having its axis coincident with the arm Ai-Bi, will be precisely the same as though its axis was located at a distance from, and parallel to, a line drawn between the tracing point Ai and guide pen at Bi ; (this latter construction being that of the instrument repre- sented in Fig. 87). In the diagram the four positions of the registering wheel are shown at Wo, W, Wi and W2, when the tracing point is respectively at each corner of the square or rectangle A, Ai, A2 and A3. Suppose the tracer to be at the starting point A the arm then coinciding with line A-B, and the registering wheel at Wo ; now, any movement at the tracing point up or down on that line will simply cause the wheel to slide in the same direction, but without causing any rotation of it, because its axis is coincident or parallel to said line ; hence, any move- ment of the wheel in a direction parallel to its axis will not cause rotation. If, now, the tracing point be moved to the right, in a hori- zontal direction, until the arm is in the position Ai-Bi, then the wheel has moved from Wo to W, and has revolved a certain distance at its periphery ; the amount depending upon the degree of the angle formed by its departure from the starting pointer line A-B ; but, any consideration of the amount of this movement, as a factor in the case, is wholly unnecessary, because all motion imparted to the wheel by its departure from the line A-B is always exactly cancelled (in whatever direction it may return) on arriving at the starting point. Now, consider the action of the wheel in an assumed down- ward movement of the arm, from its position Ai-Bi to a And Its Appliances. 193 position A2-B2, then the area swept over by the arm is the space Ai-Bi, A2-B2, which is exactly equal in area to that [of the square, or rectangle A, A i , A2 and A3 , because they both have the same base, and between the same parallels. The result of this move- ment of the arm will cause the register- ing wheel to move from W along the dotted line to the position Wi. The wheel being in contact with the paper, and the direction of its movement from W to Wi, at an angle with its axis, will consequently cause it to revolve while being moved downward to Wi, and the amount of this motion at its periphery will be re- presented by the line W-N, which is the sine of the angle W, Wi, N, with Wi-W as the radius of the circle ; consequently, by knowing this angle, the length of its sine can be found from a table of sines, in which their lengths are given for any angle, the radius being unity. Suppose, for example, the angle formed between the arm A2-B2, and the vertical line of movement of the wheel from W to W i , to be one of 18^3 degrees, and that the vertical distance traversed by the wheel to be two (2) inches ; then from a table we find the sine for that angle to be . 32 in terms of inches, at unity. Therefore, if this be multiplied by the verti- cal movement, two (2) inches (-3 2 X 2= .64 in.), this product being the length of the line W-N. FIG. 88. 194 Steam Engine Indicator The rotary motion, therefore, that has been imparted to the periphery of the wheel (by being in contact with the paper over which it runs), in moving from W to Wi, is equal to the length of the line W-N, and the final result in the readings are precisely the same as though the wheel was first rolled in the direction of its rotation upon the line W-N, and then without rolling moved down the line A2-B2, coincident with its axis to Wi ; hence, this distance (W-N) if multiplied by the length of the arm Ai-Bi (W-Nx Ai-Bi), is equal to the area of the space passed over by the arm, and is also equal to the square or rectangle A, Ai, A.2 and A3, for the reason before stated, both having the. same base, and between the same parallels. Suppose now the tracing point to be moved from its posi- tion A2 to A3 ; in doing this the wheel will have moved from its position Wi to W2, and revolved at its periphery an amount exactly equal to that which it revolved in being moved from A to A i. Therefore, as the wheel has revolved through the same angle in both cases, but the motion being in opposite directions, will thereby cancel each other, and, as a conse- quence, leave no positive results on the registering wheel. In moving upward from A3 to the starting point at A, the wheel will not revolve, because this movement is parallel to its axis. From a careful consideration and study of the matter, the following facts may be deducted and readily observed: ist. That all movements of the tracing point that are in a direction parallel to the axis of the wheel, will not cause it any revolu- tion. 2d. That all revolution of the wheel caused by a de- parture of the tracer from the starting point A, will be exactly cancelled on its return to that point. 3. That the only perma- nent record remaining on the wheel (after tracing the diagram), is derived entirely from vertical movements of the tracer rela- tive to the starting point A, the amount of its revolution depending upon the angle formed by the arm with the line And Its Appliances. 195 A-B, together with the vertical distance passed over by the tracer. 4th. That the amount of revolution of the wheel is always equal to the sige of the angle (formed by its axis with the direction of its movement), multiplied by the distance of its vertical movement. It also becomes evident that any departure of the tracer Ai from the starting point A, is pro- portioned to the sige of the angle so formed, multiplied by the length of the arm Ai-Bi. Supposing this angle to be one of iS;/} degrees (the same as the previous example), the sige of which at unity is .32 inches, and the length of the arm Ai-Bi to be 6.25 inches, then (.32x6.25 = 2 inches), the dis- tance of the tracer's departure from A. This product, then, if multiplied by any vertical movement of the tracer, is equal to the area corresponding to such movement. If in place of moving the tracer to A i it had been stopped at the point 4, and moved down the line to 5, and thence through A3 to the starting point A, the area of this rectangle recorded on the wheel would be just one-half that of A, Ai, A2 and A3, because this angle is proportionately one-half of the former, thereby making it more acute, and consequently its sine would also be only one-half. The effective rotary mo- tion of the wheel in this case is derived entirely fronvits verti- cal movement along the line from 4 to 5. Therefore by apply- ing the rule (A i.Bi X sine of angle X vertical movement = area), it will be found that the area of the latter is only one- half that of the larger rectangle. We may now consider the whole of the diagram. Fig. 88, including the dotted curve line Ai, C. ; and in doing so it must be understood that whatever has been said in reference to the larger rectangles, is equally true of any, and all, others that may be inscribed within its extreme outline ; (however numer- ous, whatever their size, and wherever located). If in addi- tion to the larger rectangles we inscribe smaller ones, num- bered 1.2, and 3 in the diagram, and from the starting point 196 Steam Engine Indicator A, carry the tracer around their extreme outline, so as to in- clude their measurements; it will be found on returning to the starting point, that the reading on the wheel will be increased by an amount just equal to the combined areas of the smaller rectangles 1-2 and 3, (over the readings taken from the larger ones contained in the square A-Ai-A2 and A3 :) and such read- ing will be approximately the area of the diagram. Other additional smaller rectangles may still be inscribed in the spaces adjacent to the dotted curved line ; (said space yet remaining unaccounted for in the reading;) And if these smaller rectangles should be made sufficiently numerous, and measured separately, by passing the tracer, in turn, around the extreme outline of each, without removing from the paper, the wheel would mechanically add the area of these rectangles together, and on the return of the tracer to the starting point A, the reading of their combined sum would be exactly equal to the area of the whole diagram ; and which will also be equiv- alent to the reading that would appear on the wheel after pass- ing the tracer around the outline of the diagram, including the curved line Ai, C. Therefore it will be seen that as the horizontal movements of the tracer, over the lines of any rectangle, cancel each other, while only verticle movements relative to the starting point A, leave any permanent record on the wheel, the results will be precisely the same as though the tracer had simply moved over the actual extreme outline of the diagram As the area of any rectangles or parallelogram, is equal to the product of its length multiplied by its vertical height, it is readily seen, that after passing the tracer once around the out- line of any figure, (regular or irregular;) its exact area will be denoted by the number of divisions of the wheel that have passed the zero mark on the vernier ; consequently the neces- sary height of a rectangle of the same length, to contain the same area may be determined by moving the tracer upward along the clip K. until the same number of divisions have returned ; and the zero marks on the wheel, and vernier again coincide, A nd Its Appliances. 1 97 (as mentioned in the description of the instrument in Fig. 87), which point will be the average height of a parallelogram, con- taining exactly the same area as the figure traced. Therefore in case the figure traced be an indicator diagram, such point must be its average height, because it is the height of a rec- tangle of the same length, and same area as the diagram. Con- sequently if this average height be measured by the scale of the spring with which the diagram was taken, the units of the scale will show the mean effective pressure in pounds per square inch throughout the stroke of the engine without any compu- tation whatever. The number of parts into which the circumference of the wheel may be divided; can be 10-15-20 or any other convenient number; the only requisite being, that the circumference of the registering wheel shall be so proportioned that one com- plete revolution on its axis, would cause it to roll over the paper an amount, such, that if this distance was multiplied by the length of the tracer arm, that their product will be equal to the area of a rectangle containing exactly some whole number of square inches; (suppose for example fifteen:) now if the cir- cumference of the wheel be graduated into the same number of divisions, and numbered accordingly from one to fifteen, then each division on the wheel will represent one square inch ; and the area of any figure, after the tracing point has passed around its outline, will be indicated in square inches, according to the number of divisions of the wheel that have passed a given point. We again mention the necessity of handling the instrument with great care in order to obtain the most accurate results , never allowing the contact edge of the registering wheel to become indented in the least, keep perfect- ly free from rust or deposit of any kind, and a good plan, is to pass a thin piece of paper between the wheel and vernier to remove any particles of dust that may accumulate and destroy the free action of the wheel ; see that the spindle runs easily, and freely between the centres, and practically without end and play ; and care must also be taken to prevent the tracer arm from getting bent or in anyway out of shape. 198 Steam Engine Indicator The Amslcr Polar Planimeter. Illustrated in Fig. 89 is another device for measuring diagrams : This instru- ment does not give the mean effective pressure directly, but it determines the area of the diagram, and from this area the mean effective pressure is computed in the manner described. It con- sists of the two arms, A and D, and the measuring wheel, C. To operate it, a piece of smooth, hard paper is laid on the table, and the instrument placed upon it, with the needle point, A, pressed into the board. This point serves as a centre about which the apparatus is Fie. 89. turned. The indicator card is laid under the tracer, B, and held either by tacks, which fasten it to the table, or what is quite sufficient, by the pressure of the fingers. The tracing point is set on the line of the diagram say near the middle of the steam line and a slight indentation made in the paper, to serve as a starting A nd Its Appliances. 1 99 point. The graduated wheel is set at the zero mark. The tracer is then moved over the line of the diagram in the di- rection of motion of the hands of a watch, finally making a complete circuit, and returning to the starting mark. The number of divisions and fractions of a division shown on the wheel at the point opposite the stationary zero mark, indi- cates the area of the diagram traced. The wheel has ten main graduations, each of which represents one square inch of area. Each main division is subdivided ten times, and each subdi- vision represents one-tenth of a square inch of area. A stationary vernier scale E is placed beside the graduated edge of the wheel, and serves to indicate the smaller fractions, viz., hundredths. To read the vernier, the eye is run along the stationary scale till a line of division is found which is just opposite a division on the wheel. The number of the division on the vernier, reckoned from the zero mark, is the number of hundredths sought. If, for example, the reading of the area is two main divisions on the wheel, and four of the subdivisions and the line of coincidence on the vernier is number seven reckoned from zero, the area sought is 2.47 sq. in. To reduce this to mean effective pressure, two perpen- dicular lines are drawn, one through each terminal point of the diagram, and the length of the diagram is measured by measuring the distance between these two perpendiculars. Suppose this distance is 3.78 in., and suppose the number of the spring employed is No. 40. Then the mean effective pres- sure is found by dividing 40 by 3.78 and multiplying the result by 2.47. Making this computation the mean effective pressure sought is 26. 13 Ibs. per sq. in. In working the Polar Planimeter, care must be observed to place the diagram so that the two arms are not brought too near each other at one end of the course, nor yet carried too far apart of the other end. At a point midway between the two extremes the two arms should lie about perpendicular to each other. 2OO Steam Engine Indicator As an example of the manner of computing the horse- power of an engine, suppose an engine has a cylinder 1 5 inches in diameter, a piston rod 2^ inches in diameter, a stroke of 2)^ feet, running at a speed of 135 revolutions per minute. Suppose the indicator diagrams show a mean effective pressure of 36 Ibs. per square inch, this being the average of the indi- cations at the two ends. The area of the cylinder to be used is the net area obtained by deducting one-half the area of the rod. The area of a cylinder 15 inch in diameter is 176.71 square inches. One-half the area of a rod 2}4 inches in diameter 2.45 square inches. The net area to be used in the computation is 176.71 2.45174.26 square inches. The speed in feet per minute is 135x2^x2 = 675 feet. The horse-power developed, therefore, is 36x174-26x675 4,234,518 =. 125.3 " * 33,000 33,ooo That is M. E. P. net area of cylinder in sq. ins. pistonspeed in feet 33,ooo when the engine has more than one cylinder, the power de- veloped in each cylinder is computed in the manner given, and the results added together. i And Its Appliances. 201 CHAPTER XXIV. COMPARISON OF DIAGRAMS FROM THROTTLING AND CUT-OFF ENGINES. The following diagrams in this chapter were taken from, what originally was, (when new) a pair of side by side non- L FIG. 90. FIG. 91. condensing throttling engines, and connected to the crank shaft at right angles, or quartering. 2O2 Si cam Engine Indicator After running in this manner for some time it was deemed advisable, and also as an experiment, to convert the valve motion of one of the pair into a special automatic cut-off valve gear in order to use the steam expansively on one engine, and throttling on the other. This alteration of the engine being completed, the dia- grams both in Fig. 90 and Fig. 91 in connection, were taken to show the extreme range of this new valve gear. FIG. 92. FIG. 93- The diagrams from Fig. 92 to Fig. 103 inclusive, are fac- similas of diagrams taken in pairs, after this alteration had been made on the engine ; having one cylinder throttling, and the other with automatic valve gear, and were taken to illus- trate the difference in the two systems of government at diff- erent loads ; the data of the engine being as follows : And Its Appliances. 203 AUTOMATIC ENGINE Dia. of Cylinder, i5 T 3 g- in. " " Piston Rod, 2^5 " Length of Stroke, 42 " Revolutions per min. 60 Piston speed " " 420' THROTTLING ENGINE Dia. of Cylinder, 15^3 in. " " Piston Rod, 2% " Length of Stroke, 42 " Revolutions per min. 60 Piston speed " " 420' Scale of Spring, 40 Scale of Spring, 40 Thus giving a value of the engine constant on the auto- matic side of 2.275, and of the throttling side 2.334, indicated horse power, for each pound of mean effective pressure, at a .speed of 60 revolutions per minute. /Co //,"/? VV.C FIG. 94. FIG. 95. In calculating the horse power from the diagrams, the factor that has been used to represent speed has been the actual number of revolutions of the engine, at the time each diagram was taken. 204 Steam Engine Indicator The mean effective pressure was obtained by the use of a planimeter, and the steam or water consumption, computed by the formula that is ' by dividin & the A T pM E P constant 859375, by the volume of the steam at absolute term- inal pressure, multiplied by the mean effective pressure in pounds per square inch of the diagram ; the quotient being the number of pounds of steam or water consumed per hour per each indicated horse power developed by the engine. FIG. 96. FIG. 97. In the latter calculation however, no allowance has been made for compression and clearance ; the rule for making such allowance or correction being described in Fig. 77, Chapter XXI. These diagrams were selected from a large number, with two objects in view ; first to show the different forms or outlines of the pressure areas between the automatic, and throttling And Its Appliances. 205 system of governing, from pairs of diagrams of approximately the same horse power ; and second, to show the relative rates of water or steam consumption of each, in pounds per horse power per hour. In addition the diagrams from the automatic side also show that the minimum amount of steam consumption (and we. FIG. 98. FIG. 99. consequently the greatest economy) occurs in diagrams No. 5, Figs. 100 and 101, where the cut-off takes place at about twenty-two hundredths of the stroke, corresponding to about 4.57 ratio of expansion, and to very nearly the generally con- sidered most economical point of cut-off in automatic engines working at a steam pressure of from 60 to 75 pounds pressure per square inch. 2O6 Stcain Engine Indicator By reference to the diagrams from either the automatic or throttling engine it will be observed that a gradual decrease in the water consumption takes place as the power developed by the engine increases, or, as in case of the automatic engine, when the cut-off takes place later in the stroke. The minimum consumption appears to have been reached FIG. 100. FIG. 101. in either case, in the diagrams Nos. 5, and it will be seen that in all diagrams on either side whether developing more or less power, that an increase in the rate of water consumption in- varibly takes place. In these diagrams the economy of the automatic cut-off engine, over that of the ordinary throttling system is very And Its Appliances. 207 fairly exhibited, and shows the relative economy that might be expected from the automatic, under ordinary circumstances, over that of the throttling system of regulation. The outlines of the various diagrams of each system are fair representations of what ought to be expected from an en- gine with properly designed valve gear, and with evenly and accurate adjustments of the same. FIG. 102. FIG. 103. It must be understood that the diagrams here presented are not intended, or claimed, as representing the highest effi- ciency and economy obtainable, but are only given from actual ordinary practice, in order to be able to make an interesting comparison between the two systems of regulation. 208 Steam Engine Indicator CHAPTER XXV. ECONOMY OF EXPANSION. As regards the economy of expansion it will be found by reference to the Table No. 8 on the properties of saturated steam that the weight of a given volume of steam varies very nearly in proportion to its pressure that is, a cubic foot of steam at 60 pounds pressure weighs approximately twice as much as the same volume at 30 pounds pressure. A given weight of steam represents the same weight of water that must be evaporated to produce it, consequently the lower the terminal pressure at the end of the stroke in a given cylinder the less will be the amount of water exhausted as steam ; and as the measure of the work done in the cylinder by the steam, is proportional to the mean effective pressure, it becomes evident that economy in the use of steam in an en- gine, consists in getting a high mean effective pressure, in connection with a low terminal pressure. This can only be accomplished by cutting off the supply of steam, at a time when the piston has only completed a part of its stroke, and by that means obtain an additional amount of work from the expanding steam to the end of the stroke. Suppose in a steam cylinder using steam at 100 pounds ab- solute pressure, be cut off when the piston had moved one- fourth of its stroke, than the mean pressure calculated accord- ing to the rule in Chapter 1 8 will be almost 60 pounds ; and And Its Appliances. 209 this is obtained by using only one-quarter of a cylinder full of steam ; whereas if the entire cylinder had been filled the mean pressure would have been only 100 pounds, and at an expend- iture of four times the quantity of steam used when cutting off at one-quarter stroke. This indicates the direction in which a saving is effected ; but in practice however, condensation in the cylinder, and other causes prevent this full theoretical gain from expansion being realized ; at the sanie time however the gain from this source is an important one. Therefore from what has been said in this connection it would be natural to expect, in considering diagrams from first- class cut-off engines, to find the initial pressure of the diagram high, as compared with the boiler pressure, also with straight or fairly straight steam lines, and sharp cut-off ; because these all tend to bring about both high mean effective, and low terminal pressure ; also whatever tends to make the terminal pressure higher than it should be, represents waste of steam. Economy of High Pressure. It is a well established fact that the use of steam of a high pressure tends to greater economy in the engine ; the reason for which is simply as follows : Suppose in this case an engine working without expansion, and in order to simplify the matter, assume that there is no clearance. Assume also the engine to be working non-con- densing, with an absolute back pressure of 1 5 pounds, or three- tenths above the atmosphere. If steam of 20 pounds absolute pressure is used in the cyl- inder, the mean effective pressure on the piston is 2015=5 pounds. If the piston has a total displacement of one cubic foot, then we are using one cubic foot of steam, of a pressure of 20 pounds at each single stroke of the piston. In the Table No. 8 on the properties of saturated steam, the weight of a cubic foot of steam of this pressure is found to 2io Steam Engi)ie Indicator be .0511 pound, and the heat units per pound 1183.5; hence the cubic foot of steam from which the mean effective pressure of 5 pounds has been obtained, contained 1 183.5 X .051 1 = 60.47 heat units. Now instead of steam of 20 pounds pressure, suppose steam of 100 pounds absolute pressure be used: Then the mean effective pressure would be 100 15 = 85 pounds. The weight of a cubic foot of steam of 100 pounds pressure is .2330 pounds and one pound contains 1213.8 heat units. Then as before 12 I3.8X .2330=282.8 heat units used. In the first case 60.47 heat units have been used, equal to- 60.47-^5= i2 v . 09 heat units for each pound mean effective pressure; whereas in the second case 282.8-^-85 = 3.32 heat units for each pound mean effective pressure have been used. This great difference and discrepancy in the two instances, arises from the fact that the greater part of the total heat of the steam still remains in it at the pressure of the exhaust, (i 5 pounds) and all of this heat is entirely lost with the exhaust steam. The only heat that can be converted into useful work, is the quantity that is added above exhaust pressure ; therefore it becomes apparent that a greater per cent of the total heat can be made available, as the pressure increases. From this it must be clearly understood, that a large pro- portion of the heat that enters into the steam used in a steam en- gine is requisite in order to raise it to the pressure at exhaust ; (15 pounds), a pressure at which no work can be utilized from it, The diagram Fig. 104 fairly illustrates the economy of the use of high pressure steam in a cut-off engine. The full lines of the figure represents an actual diagram, and above it the shaded portion has been drawn by hand to- show precisely as if the whole of the diagram had been taken at a higher steam pressure. And Its Appliances. 21 1 The pressure of the steam at the end of the stroke, or after having performed all of tJie work there is in it, is not changed ; as the terminal pressure T remains the same : hence we conclude that as far as we can judge by the diagram, the work represented by the shaded portion could be done without additional expense. This is on the assumption that steam expands according to the Mariotte law, but if the result were calculated from Table FIG. 104. No. 8 (properties of saturated steam) it would be somewhat different, but we have no positive assurance that it would be any more correct ; therefore for all practical purposes, this presentation of the subject should prove acceptable. There is a point however where it is the reverse of econom- ical to run at very high pressures, and that is when the load on the engine is so light, and cut-off so short, that the steam expands below the atmosphere, and thereby forming a long loop in the diagram as illustrated in Fig. 54 and 62. 212 Steam Engine Indicator In such cases the engine is running" a portion of each stroke on the momentum of the moving parts. Where this occurs it is better to reduce the boiler pressure until expansion shall come quite down to, but not below the at- mosphere. In 'such an instance a considerable advantage is realized by reducing the speed of the engine ; as the resistance of the atmos- phere must be overcome in running an underloaded, as well as in a heavily loaded engine ; therefore by reducing the speed this factor is made less, and on lightly loaded engines becomes a considerable percentage of the total power; this percentage decreasing in extent as the engine is more heavily loaded. In connection with losses from having under loaded en- gines, is the fact also, that the friction of the engine, conden- sation, etc., are all present almost regardless of the load, and always appear in a greater proportion in light, than in heavy loads; therefore the final expense is decreased when running at" a slower speed ; as there is a better opportunity to secure a later cut-off, since the power being the same, with reduced speed, the mean effective pressure must be proportionally in- creased. A nd Its Appliances. 2 1 3 CHAPTER XXVI. THE POINT OF CUT-OFF. It must not be understood, (in reference to steam expan- sion) that the higher the grade or ratio of expansion, the greater is the economy, because, quite the reverse may often happen, as the results in practice are greatly modified in vari- ous ways by other considerations. Consequently the most economical point of cut-off will vary in different types of engines, in accordance with the special conditions, and circumstances to which each may be subjected ; such as high or low initial pressure, condensation of steam in the cylinder, different methods of jacketing and superheating, amount of back pressure and compression, incor- rect adjustment of the valves, also a size of engine that is not adapted to the work, etc. ; any or all of which necessitates a change more or less of the point of cut-off, in accordance with any particular condition, in order that the greatest efficiency of the engine may be realized. Initial Pressure. In engines with an early cut-off, and where a higJi rate of expansion prevails, the mean or average pressure throughout the stroke must necessarily be low ; and a low mean pressure, for a given power necessitates the use of a larger engine. Also a high rate of expansion leads to a low terminal pres- sure, and to expel the steam from the cylinder after it has 2 1 4 Steam Engine Indicator performed its work, will require from one to three pounds pressure above the atmosphere ; therefore if the rate of ex- pansion be such that the terminal pressure falls below this, the expansion is excessive, and the reverse of advantageous. In non-condensing engines the lowest possible terminal pressure coincides with the pressure of the atmosphere, or about I4 T V pounds per square inch absolute; but 18 pounds may be considered as the lowest pressure to which steam can be expanded to advantage ; and where the exhaust passages are small and torturous, or where the exhaust steam contains considerable moisture, a still higher terminal pressure will be more economical. In condensing engines, the temperature in the condenser is usually about 100 degree Fah., and which corresponds to a pressure of very nearly one pound to the square inch ; but the presence of air in the condenser generally prevents the pres- sure falling below two pounds per square inch. From three to four pounds is the more usual and may be considered as the lowest advantageous final pressure, to secure the best economy. The highest advantageous rates of expan- sion with jacketed cylinders appear in practice to be between tivelve and sixteen ; but in unjacketed or exposed cylinders, the limit of advantageous expansion is much below the lowest of the rates mentioned. The principal cause of the discrepancy between the theo- retical, and actual economy, is in the amount of heat lost in changing the water (by condensation or otherwise) in the cylin- der, to the condition of steam ; most of this heat passing out with the exhaust steam, either into the condenser or the atmos- phere. It has been fairly well demonstrated by frequent tests, that the most favorable point of cut-off, in a simple non-con- densing engine, is usually about one-fourth stroke, when using steam of from 80 to 90 pounds per square inch initial pressure. And Its Appliances. 2 1 5 Where the cut-off is earlier than this a greater per cent of loss is induced through cylinder condensation ; and where the cut-off takes place later in the stroke there is also an increase of loss, from the fact that the steam is exhausted and lost while yet at a considerable pressure. FIG. 105o Fig. 105 is a fair representation of an indicator diagram from an engine working under the favorable conditions men- tioned. The results of some recent experiments on a 17 by 30 inch stroke non-condensing double valve engine by Prof. J. E. Denton, to determine the relation of steam consumption to point of cut-off is illustrated by the graphical diagram Fig. 106. The line A. B. represents the stroke of the engine, which is equally divided into tenths and twentieths, to denote the various points of cut-off in fractions of the stroke, or periods of admission of steam to the cylinder. From each of these fractional parts of the stroke perpen- dicular lines are erected, and also above these points are hori- zontal lines laid off 1-5 of an inch apart; each representing 4 216 Steam Engine Indicator pounds, or a scale of 20 pounds per inch ; being the actual pounds of water used per horse power per hour. Through these lines three curves are plotted, being the result of experiments at various points of cut-off, and boiler pressure by which the change in the rate of water consump- tion, corresponding to changes in point of cut-off, (as well as changes in boiler pressure) are readily observed. 0.1 O.8 0.3 0.8 O.tf 1.00 * 0.5 0.6 FIG. 106. The three curves shown in the diagram corresponds to 90, 60, and 30 pounds boiler pressure respectively per square inch, and the curves were constructed by locating points as a result of tests in each case at different rates of cut-off. It will be clearly seen that the curve corresponding to 90 pounds per square inch boiler pressure and the steam cut-off at l^, or -ffc of the stroke gave the best results, and represents a water con- sumption of about 26 pounds per horse power per hour ; that for A mi Its Appliances. 217 60 pounds pressure, cut-off at T %- of the stroke a consumption of about 32^2 pounds, and that for 30 pounds pressure, cut-off at _4_5_ o f the stroke; corresponds to a consumption of 43 pounds of water per indicated horse power per hour. For a short distance on either side of these points of cut- off, the amount of water consumption is only slightly increased and the economy is practically the same, but in case of very early or very late cut-off the amount of water consumed is considerably increased ; the relation of economy to cut- off being well represented by these experiments in the diagram. In some similar experiments with a small (7x14) Buckeye automatic non-condensing engine, with a boiler pressure of 75 pounds, the same experimenter has found the best rate of con- sumption to be 30 pounds of water at about % cut-off; and while the most favorable point of cut-off is the same in small as in large engines, the matter of economical use of steam is in favor of the larger engine and high pressure. It should be understood that these results were deduced from refined tests, extending over a considerable period, the engines. being in perfect condition as to leakage, etc., and the steam collected, condensed and carefully weighed after the work was performed, thus eliminating errors as far as possible. The steam was also practically free from moisture, as, in the tests of Fig. 106 it contained less than one per cent. From these and other similar tests we are enabled to form- ulate the following approximate rule for best cut-of. Divide 100 by 42 times the square root of the initial pres- sure and the quotient will represent the most favorable point of cut-off, expressed in fractions of the stroke. The initial pressure must be reckoned from a vacuum for condensing and from the atmosphere for non-condensing engines. 2 1 8 Steam Engine Indicator In a test for ascertaining the economy of engines, it is very ^f 1 * important that the quality of the steam used, or in other words the amount of moisture it contains, be determined. This quantity may be approximately found by making what is known as a calorimeter test, as explained in Chapter XXX. There are a number of instruments of varied construction and principle, on the market for this purpose, with full and complete instructions for their use. In the absence of such, a test, no accurate conception of the amount of steam actually used by the engine to produce a horse power per hour, can be obtained, for the steam may con- tain a large amount of ineffective moisture in the form of spray, which can only be detected either by an application of the calorimeter, or by collecting and weighing the exhaust. The generally acknowledged economy, that has been at- tained in the steam engine within the last thirty years, (esti- mate between thirty and forty per cent.) may be considered due, principally to the employment of multiple cylinder engines in connection with the best modern method of jacketing: also an increase of steam pressure, and superheating the steam ; -either or all of which (when judiciously made use of) tends to better efficiency, and more economical results. \w And Its Appliances. 219 CHAPTER XXVII BACK PRESSURE AND COMPRESSION. Back Pressure may be considered as one of the most serious losses in an engine, and represents the power expended in ex- pelling the exhaust steam, and in compressing steam into the clearance spaces, and is usually called the loss from back pres- sure, for it must be clearly understood that the direct steam does work in expelling the exhaust from the engine, as well as in driving the machinery to which the engine is connected. The whole of the back pressure cannot be removed, but a large proportion of the present losses would be avoided, if the clearance spaces were reduced to the smallest practical dimensions. The following diagrams Figs. 107 to 1 10 will serve to illus- trate the economy to be derived where small clearances prevail. The diagrams referred to, are theoretical, but in each case the assumed clearances (Fig. 107 being seven per cent, and Fig. 109 bsing only two per cent.) are exactly with many of those found in different makes of slow speed engines. To obtain the maximum economical results with an engine at any given cut-off, compression should be carried up to, or very nearly the initial pressure of the cylinder. Where the clearances are large however, this is not always possible, especially with condensing engines, and without much consideration of the subject many builders of engines adjust the valve so that compression begins at about' seven- eighths of the stroke. 22O Steam Engine Indicator In the diagrams the various compression lines are shown, and the results compared. The initial pressure is 100 pounds above zero in all, and the cut-off takes place at one-quarter stroke in each, so that when compression is carried up to initial pressure, the same quantity of steam, practically, is used per stroke in each engine irrespective of clearance, but the net power developed under those circumstances will differ very materially. The exhaust lines in the non-condensing diagrams are 0.3 pounds above atmosphere or 1 5 pounds above zero, and in the condensing diagrams 3.5 pounds above zero, or 11.2 pounds below atmosphere. FIG. 107. THEORETICAL DIAGRAM WITH 7 PER CENT CLEARANCE. In Fig. 107 the solid lines represent diagrams from a non- condensing engine with compression A to initial pressure, and also compression B to 50 pounds, or one-half the initial pres- sure. The dotted lines represent the back pressure lines of dia- grams from a condensing engine, A i, represents compression to initial pressure; B i, compression to 50 pounds, and C, compression to 14 pounds. A nd Its Appliances. 221 The initial pressure of theoretical diagram Fig. 107 is 100 pounds above zero ; cut-off one-quarter stroke ; terminal pres- sure 30 pounds above zero, back pressure non-condensing, 15 pounds and condensing 3.5 pounds above zero. From these diagrams the Available Power may be ascer- tained, which includes the amount absorbed in driving the engine as well as the effective power, and is usually designated the Indicator Horse Power, and written I. H. P. This is not the total power derived from the steam, but the I. H. P. must be known in order to ascertain the loss. The total power diagram of Fig. '107 is shown by the full lines in Fig. 108 and is determined as follows : During a single stroke of the engine piston, the indicator on that side where the steam is admitted will trace the upper line only of the dia- gram, the lower line being zero. The pressure of steam during that stroke being measured from the zero line (by the scale of the spring) consequently the total power exerted by the steam is proportional to the area enclosed between the zero line and the upper line of the dia- gram. If an indicator be placed in communication with the other side of the piston during the same stroke it will make the lower line only, or the back pressure line, (represented by the dotted lines in Fig. 108) of the indicator diagram. This line also in connection with the zero line forms another diagram, and the area enclosed between these lines, represents the power necessary to expel the exhaust steam during the first part of the stroke, and to compress steam into the clearance spaces during the latter part. The full lines of the diagram Fig. 108 show the total power exerted by the steam, and the dotted lines show back pressure from exhaust, and compression, or the resistance 222 Steam Engine Indicator which the direct steam must overcome before any useful work can be accomplished. The difference between the two is the power that must be expended before any is available for running the engine or driving the machinery and is a total loss. FIG. 108. It is evident at a glance of the diagram Fig. 108 that this loss is a large proportion of the total power and every means that will tend to reduce this loss should be adopted. As before mentioned the whole of this cannot be avoided, because it is impossible to obtain a perfect vacuum in an engine cylinder ; however the back pressure should be as low as pos- sible, bearing in mind that the clearance spaces should be filled with steam compressed (as near as possible) to the initial pres- sure at the end of the stroke. In the case of condensing engines having large clearances, this latter condition is difficult of attainment, and if strictly carried out would probably entail so much loss from increased back pressure as to off-set any gain from high compression. This points to the benefit of small clearances with which compression may be carried to any desired pressure. In Fig; 107 the mean effective pressure of the non-con- densing diagram compressed to initial pressure, (as line A), is A nd Its Appliances. 223 41.6 pounds, while the average pressure of the total power diagram Fig. 108 is 64 pounds, or about 54 per cento greater than the available power. In this case the only way of reducing the back pressure is. to commence compression later in the stroke as shown by line B. The effect of this however, is a loss from low compression, as this is only carried to 50 pounds, and also from increased condensation. By comparing the results from the two diagrams it will be found that the latter has a mean effective pressure of 47 pounds, making a gain in pressure of about 1 3 per cent over that of the former but there would be 14 per cent more steam necessary to fill clearance spaces, and the condensation would be increased more than 4 per cent., making a loss of 5 per cent, by not compressing to initial pressure. If this engine was condensing it would be practically im- possible to compress to initial pressure as in order to do so, it would be necessary to begin compression at the commencement of the stroke with a pressure of 6. 5 pounds, above zero (line A i), therefore 8.2 pounds would be the maximum vacuum that *jv could be obtained in the cylinder ; consequently the highest pressure to which compression can be carried practically in this case is one-half the initial pressure or 50 pounds above zero (line B i). The mean effective pressure of this diagram is 54.3 Ibs. and the total power diagram as shown in Fig. 108 is 64 pounds or about 18 per cent, greater; however there would be 14 per cent, more steam required than when compressing to initial pressure, and condensation would be increased fully 4 per cent. If compression did not commence until later in the stroke and only carried up to 14 pounds (line C), the mean effective pressure would be 59.6 pounds or 9.8 per cent, more than the previous diagram, but over 24 per cent, more steam would be required than if compression were carried to initial pressure,. 224 Steam Engine Indicator and the extra condensation would amount to 6.9 per cent, or a loss of 3 per cent, over the previous diagram with greater com- pression. Comparing the later diagram (line C), with the total power it will be seen that the total power is but 7.5 per cent, greater, and it is this near approach to the total diagram, that makes the condensing engine so much more economical than the non- condensing, and a moderately well loaded engine gives better results than one lightly loaded, as in the case of a lightly loaded engine, the waste power remains the same, and conse- quently the percentage of loss increases ; although both the total, and available power are less. In the first diagram the steam developed over 3 horse- power to make 2 horse power available, or a loss of 35 per cent. In some very lightly loaded engines, the steam develops over 3 horse power to make i horse power available, or a loss of 70 per cent. FIG. 109. THEORETICAL DIAGRAM WITH 2 PER CENT CLEARANCE. Initial pressure 100 pounds above zero: cut-off, one-quar- ter stroke ; terminal pressure 30 pounds above zero ; back pressure non-condensing 15 pounds and condensing 3.5 pounds above zero. In Fig. 109 as in Fig. 107 the full lines represent And Its Appliances. 22$ diagrams from a non-condensing engine with compression A to initial pressure, and compression B to 50 pounds above zero. The dotted lines represent the back pressure lines of con- densing diagrams, with compression A i, to initial pressure, also compression B i, to 50 pounds pressure and compression C to 14 pounds above zero; therefore the two diagrams Figs. 107 and 109 are identical in all respects except in their amount of clearance. The total power diagram of Fig. 109 is shown in full lines in Fig. 1 10, and the back pressures and the compression curves are shown by the dotted lines A, A i, B, B i, and C. The mean effective pressure being determined in the same manner as in the previous diagrams. In Fig. 109 the mean effective pressure of the non-con- densing diagram compressing to initial pressure (line A) is 44 pounds and the average pressure of the total power diagram Fig. 1 10 is 60.8 pounds or about 38.5 per cent greater than the available power. This is quite a loss, but it is a decided improvement over the percentage of loss shown by the diagram with large clear- ance, as in Fig. 107. If in this case the compression had been carried to 50 pounds only, (line B), the mean effective pressure would have been 45.6 pounds or 3.6 per cent, greater pressure, but there would be over 4 per cent, more steam required to fill the clear- ance spaces, and the condensation would be increased over 3 per cent., making a loss of about 3. 5 per cent, by the lower compression. With the condensing diagram Fig. 109 it will be seen that compression may be carried to initial pressure, (line A) and the mean effective pressure in this case would be 52.8 pounds. If the compression had been carried to 50 pounds only, (line B), the mean effective pressure would have been 56 226 Steam Engine Indicator pounds, or an increase of 6 per cent, in the pressure ; but as an off-set, over 4 per cent, more steam would be required to fill the clearance space, and the condensation would be increased more than 3 per cent., leaving a loss of i per cent. If the compression had been still lower, (line C), the mean effective pressure would have been 57.5 pounds, or an increase of 8 per cent, in the pressure ; but there would be 7 per cent. more steam required to fill the clearances, and condensation would be increased over 5 per cent., making a loss of 4 per cent, by the low compression. Comparing the results obtained from the two diagrams, the vSaving effected by an engine having small clearance will readily be seen, and as this has such an important bearing on the economy of the engine, small clearances should be strictly insisted upon. There are many slow speed engines in use at present hav- ing less than 3 per cent, clearance, and this amount should therefore be the maximum allowed in slow speed engines, either simple or compound. FIG. 110. Full lines show theoretical diagram of total pressure exerted by the steam. A nd Its Appliances . . 227 Dotted lines show back pressure from exhaust and com- pression, or the resistance which the direct steam must over- come, before any useful work can be accomplished. COMPARISON OF RESULTS. Non-Condensing 'Diagrams. Clearance ..... , . . TJf ..... 2% Cut-Off ......... 2si ..... 25% Terminal Pressure ..... 3olbs. above zero 26-slbs. above zero. Back " M.E.P. M.E.P. Compression to Initial pressure and Gain compared with using equal quantities of steam larger clearance. per stroke in both engines . . . 4i'6lbs. . . . 44lbs. 5-8$ Loss by Compressing to solbs pressure in place of full Com- pression .......... 5^ ..... 3-5$ 7-3$ Condensing Diagrams. Clearance ......... 7$ ..... 2% Cut-Off ..... ..... 25^ ..... 25$ Terminal Pressure ...... 3olbs. above zero 26 -slbs. above zero. Back " ....... 3'5lbs. " " 3'Slbs. Gain compared with larger clearance. Compression to Initial pressure . 8% Loss by Compressing to solbs. pressure in place of full Com- pression ......... 6% \% 13$ Loss by Compression to i4.1bs. pressure in place of full Com- pression . ... ." .... 9^ 4 # 13$ In Compound Engines the greater economy will be obtained when expansion is carried down to the back pressure in each cylinder, except the last, and Compression is carried up to In- itial pressure in all ; with no drop or free expansion between the cylinders. 228 Steam Engine Indicator CHAPTER XXVIII. COMBINING DIAGRAMS FROM COMPOUND ENGINES. Compound engines, for almost all purposes are now com- ing into more general use each year ; but in the use of the in- dicator upon them, both cylinders are treated as simple engines, the power of each being added together. The diagrams from both cylinders can be taken with the same denomination of spring if desired, but usually a compar- atively light spring is used on the low pressure in order that the dimensions or area of the diagram may be increased. The compound engine with receiver, is as two engines, one high pressure non-condensing, and the other a low pres- sure condensing engine, but from the fact that the same steam is used in both cylinders, the action of the steam must be con- sidered as if used in a single engine, and the diagrams from each cylinder must be combined, to form an equivalent simple one. Before making combinations of diagrams from the high and low pressure cylinders of compound engines, the object of combining them should be first understood. There are certain losses in single or non-compound en- gines which are corrected to a great extent by compounding, but this in turn introduces other losses which it is desirable to reduce to the least possible amount. And Its Appliances. 22 g These losses are between the two cylinders, and consists of, condensation in the passages, pipes, and receiver (if one be used), friction in the steam ports and pipes, and expansion of the steam that takes place between the two cylinders without doing useful work. The extent of these losses can be shown by combining the diagrams from the two cylinders and drawing in the hyper- bolic curve. This curve should just touch the expansion line 'of the high pressure diagram at a point where the exhaust from the cylinder begins, and the space between the curve and both diagrams below this point, and also the space between the two diagrams, represent the loss between the two cylinders. To correctly combine the two diagrams, the clearance in each cylinder should be known and accounted for, as well as the piston displacement, and the relative length of the two diagrams when combined, is as the ratio of the total volume of the cylinders, that is; the piston displacement plus the clear- ance at one end. To do this, a base line may be taken if desired and divided into two parts, which have the same relation to each other in length, as the total volume of the cylinders. The short por- tion of the line will represent the small or high pressure cylin- der, and on this length the diagram from this cylinder is con- structed from the lowest pressure, and on the longer portion of the line the diagram from the large cylinder is laid out. It is best however to decide on the total length of the low pressure diagram first, and a length that can be easily divided into 100 parts will be found most convenient, as percentages of this length can then be easily measured; for example, 10 inches for a scale of tenths, or 12 j4 inches for a scale of eighths. The combination diagram, Fig. 113, was drawn 12^ inches long, and photo reduced to the length shown. It now becomes necessary to decide on the scale of the spring to which the two diagrams are to be plotted ; usually it 230 Steam Engine Indicator will be found most convenient for this to take the scale of the low pressure diagram ; then draw in the atmospheric, and va- FIG. 111. *l *i 3j 4j f\ t\ ^ FIG. 112. cuum lines, and erect perpendiculars at the two extremes of the combination, diagram, one of which is the clearance line. All measurements of distance should be made from the clearance line, and all measurements of pressure from the And Its Appliances. 231 atmospheric line. Now divide each, original diagram into any desired number of equal parts, 10 being a good number. Find the volume of the piston displacement of the low pressure cylinder, to which add the volume of the clearance ; the total length of the diagram represents this total volume. Divide the clearance by the total volume, and the quotient will be the percentage this clearance bears-to the whole length. FIG. 113. . .-_ Set off this distance from the clearance line, and divide the remainder (representing the piston displacement) into the same number of parts that the original diagram is divided into. , If the scale selected is the same as that of the original dia- gram, simply transfer the pressures directly with a pair of di- viders from the lines on the original diagram to the corres- ponding lines on the combination ; then draw in the connecting 232 Steam Engine Indicator portions of the diagram, and the result will be an elongated diagram from the low pressure cylinder or as if it had been taken with the same spring as before, but with a proportion- ately enlarged paper drum. Now find the total volume of the high pressure cylinder, and divide it by the total volume of the low pressure cylinder, and the quotient is the percentage of length of the diagram, which should be measured from the clearance line. Divide the clearance volume of the high pressure cylinder by the total volume of the low pressure cylinder and measure off the percentage of length, as before, from the line. Divide the remaining length of the high pressure diagram (representing the piston displacement) into the same number of parts as the original diagram, and transfer the pressures from the lines on the original diagram to the corresponding lines on the combination and to the new scale of pressures. If the original high pressure diagram was taken with a 40 spring, and the combination diagram made to a scale of 10 Ibs. per inch, then the new diagram will be four times as high as before, although it may be shorter. Next draw in the hyperbolic curve ; (a method of doing this is given, on page 101, Fig. 56) and the two diagrams thus combined will form a single one. The process of combining indicator diagrams from com- pound engines is both interesting, and instructive to the en- gineer in various ways, and usually attended with most satis- factory results. Diagram Fig. 113 is a combination of the diagrams Figs. 1 1 1 and 112, and were taken from a tandem compound engine. In order to make the foregoing explanation more clearly understood, diagrams Figs, in, 112 and 113 have the con- struction lines shown, and the necessary calculations are given below. Fig. 113 was drawn 12^ inches long over all and re- duced by photo engraving process to its present length. A nd Its Appliances. 23$ Diameter of H. P. Cylinder - - 30 in. " L. P, " - 50 in. Stroke of Pistons 72 in. Diam. of Piston-rod, both Cylinders 6^ in. Volume of High Pressure Cylinder (706-86 30-68) X 72 = 48685 cubic inches. Clearance volume = 2545 " " Total volume 51230 Volume of Low Pressure Cylinder (1963-50 30-68) X 72= 139163 cubic inches. Clearance volume = 7673 " " Total volume 146836 Total length of L.P. card, 12^ inches, or 100 eights; scale 10. Length of L.P. clearance, marked A on diagram, - 146836 = 5*22$ of total length or -jj--!--^ in. The remainder of the length, representing the piston displacement, is divided into 10 parts, the same as original diagram, and the pressures trans- ferred to the corresponding lines. Total length of H.P. card, or B+C on diagram, 5I23 X IO 146836 = 34-89$, or 4ff in. Length of H.P. clearance, marked B on 2545 X 100 diagram, J = 1-73^, or V in., leaving the distance 140830 marked C, representing the piston displacement, which is di- vided to correspond with the original diagram, and the pres- sures transferred either with scales or dividers ; in the latter case each distance must be multiplied four times. Draw in the connecting portions of the diagrams, taking care to follow the contour of the original as closely as possible ; and finally the hyperbolic curve is drawn in. 234 Steam Engine Indicator CHAPTER XXIX. DIAGRAMS FROM GAS AND OIL ENGINES AND AMMONIA COMPRESSORS. In the last few years the large increase in the number of gas and oil engines in use for all kinds of manufacturing enter- prises both at home and abroad, has been most remarkable, and their number and power are still increasing each year, so that now these motors are in competition with steam engines in almost all progressive countries. The fact that both gas and oil engines now run with greater regularity than in the past is principally due to im- proved and better governing arrangements. The portability of small oil engines renders them very convenient for use in country towns, and other places where gas is not made. A greater part of these motors work with the four-cycle, and with lift valves. Gas engines are in most cases single acting and single cyl- inder, except for the largest powers, when two cylinders are generally used. The charge is usually fired either by tube ignition, or by an electric current. The piston speed usually varies from 500 to 700 feet per minute, and the clearance volumes of the cylin- der are much larger than in steam engines, usually from 20 to 50 per cent, of the piston displacement, against from 3 to 8 per cent, in steam engines. And Its Appliances. 235 When considering that in -the employment of gas engines no fuel is being consumed when the engine is not in- actual operation, it is evident that they form economical motors when small powers are required, and will soon come into more ex- tensive use as affording a cheap, and efficient motive power in a great number of places where the use of steam is difficult or impossible. Owing to the greatly increased initial pressure in the cyl- inders of these engines, (being principally due to the explosive mixture employed therein) specially designed indicators have been constructed to better meet the requirements necessary, and provide means for indicating pressures ranging from 300 to 600 or more pounds pressure per square inch. This is accomplished by making provision in the construc- tion of the instrument, whereby a piston can be used of a small- er size than the piston of one-half square inch in area, as ord- inarily used in most makes of indicators. This smaller piston is usually made one-quarter inch square in area, or one-half that of the former, and which when in use results in doubling the readings or amount of pressure, as when used with the same denomination of spring in con- nection with the larger piston. Fig. 114 represents the manner of con- struction in combining the half and quarter inch area piston in one in- strument, as applied to the Tabor Indicator, whereby the use of the one-half inch piston for low pres- sures, or in which the quarter inch piston may be used for the very high FIG. 114. - pressures often attained in some oil and gas engines. Either of these pistons may be used 236 Steam Engine Indicator independently as desired, without any change whatever either in the spring or any part of the instrument. In the illustration the half inch piston is not shown ; but instead the quarter inch piston is represented attached to the spring in position for operation. The body A. of the instrument is shown partly in section in order that the location of the parts may be readily observed. B. is the piston cylinder in which the half inch piston works, and which is srcewed at its lower end into the body A. C. is the piston cylinder in which the quarter inch piston works, and is formed in the upper end of the tube G. D. is the quarter inch piston, and is sufficiently elongated as to reach and work in the cylinder C. Its upper end is threaded and screws into the mounting of the indicator spring. It is made in the form of a shell, and the pencil mechanism is. secured to it by means of the extended thumb-nut E. F. is. the usual connection for securing the indicator to the cock. H., I. and J. are respectively the cylinder cap, swivel plate and piston rod. In addition to obtaining the most accurate results from high pressures by the use of the smaller size of piston, this combined indicator has another advantage in that it requires a less number of springs for any given range of pressure. For example : A 50 spring may be used in connection with the larger piston to 120 pounds pressure per square inch, but by substituting the smaller piston, pressures may be indicated to 240 pounds with the same denomination of spring ; a range that would otherwise require two springs ; thereby doubling the range of the instrument with a single spring. Figs. 1 15 to 1 1 8 inclusive represent diagrams taken from the Springfield Gas and Gasolene engines. Fig. 115 is from a 7^ inch diameter of cylinder by 14 inches stroke, running 200 revolutions per minute, with scale of spring 120. And Its Appliances. 237 Fig. 116 is from a 13 inch diameter of cylinder by 24 inches stroke, running 160 revolutions per minute, with the scale of spring 120. FIG. 115. Each of the above may be considered as ideal cards in every respect. Figs. 117 and 118 are from gasolene engines FIG. 116. presented simply for the purpose of showing some bad cards. Fig. 117, shows the effect of late ignition, while Fig. 118, 238 Steam Engine Indicator shows also late ignition, and a stratified condition of the charge. This is indicated by the waiving expansion line, each waiving being an independent explosion or combustion. FIG. 117. These two latter cards were taken expressly for the pur- pose of showing these very things. Fig. 1 19 represents a pair of superimposed indicator diagrams taken from a 20 by 2 6 inch steam cylinder, driving a double-acting ammonia compressor from a Buffalo Refrigerating plant, making 26 revolutions per minute, and are ideal diagrams in almost every respect. How- ever where the speed of the engine is slow, as in refrigerating machines they are only what might be expected, as the exist- FIG. 118. ing conditions are generally favorable for the production of good diagrams ; because a longer interval of time is given to the steam to pass through the steam ports and fill the cylinder And Its Appliances. 239 nearly to boiler pressure at the commencement ' of the stroke, and thus continue to the point of cut- off ; and where the steam admission is regulated by an automatic system of valve gears (such as in this case) we find the cut-off well defined, the ex- SCALE, 40 LBS. PER Steam Pressure , .75 Ibs. Revolutions ..26 per rain. Indicated Horee Power *.0 'Bottom end. Steam Cylinder, .. .20W FIG. 119. pansion line all that could be desired, and the back pressure line nearly straight. Figs. 1 20 and 121 represents diagrams taken from the gas or ammonia cylinder which is 15 inches in diameter by 26 inch 8CALK, 80 LB8. TER 8 scale of spring 40. FIG. 182. Fig. 132 was taken from an automatic slow speed engine. Diameter of cylinder 20 inches, dia. of rod 3 inches, stroke 48 inches making 63 revolutions per minute, 63 Ibs. boiler pressure, scale of spring 32. And Its Appliances. 259 J 33 an( 3- 134 were taken from the same pair of en- gines as the comparative diagrams represented in Chapter XXIV., the data of the engine being the same as there given. FIG. 133. In this case the horse power developed being greater than those in the previous chapter. FIG. 134. The horse power developed by the automatic Fig. 133, being 86.26 while that of the throttling engine, Fig. 134, is 87.06. The mean effective pressure of each is 38 Ibs. 260 Steam Engine Indicator Figs. 135 and 136 were taken from a side by side double Wheeloclt engine, cylinder 18 in. X48 in. stroke, running 54 revolutions per minute, boiler pressure 90 Ibs., the cranks con- Fio. 135. nected at right angles or quartering. The M. E. P. of Fig. 135 being 32.2 Ibs., and developing 101.75 horse power while the M. E. P. of Fig. 1 36 is 31.8 and developing 101.44 horse power. FIG. 136. Figs. 137 and 138 are diagrams from a Ball & Wood com- pound, high pressure cylinder 13 inches, and low pressure And Its Appliances* 261 cylinder 20^ inches by 15 inch stroke, running 270 revolu- tions per minute, boiler pressure 145 Ibs. Scale of H. P. cyl. 80, and L. P. cyl. 20. FIG. 137. FIG. 138. Figs. 139 and 140 are diagrams from a 14 in. x 14 In. Fitch- burg engine, revolutions 154 per minute. Boiler pressure 75 Ibs., by gauge. Scale 60. Fig. 139 shows the condition of the 262 Steam Engine Indicator engine when the indicator was first applied. Fig. 140 shows the improvement made, an increase of about 40 per cent, in FIG. 139. FIG. 140. mean effective pressure. The cuts are full size, and the load on the engine was 200 incandescent lamps of 16 c. p., and 39 arc lamps, nominally 2000 c. p. FIG. 141. Fig, 141 are diagrams taken from both ends of a 13 in. x 13 And Its Appliances. in. Armington & Sims engine, 250 revolutions per minute Gauge pressure 85 Ibs., and scale 50. FIG. 142. FIG. 143. Figs. 142 and 143 are diagrams taken from a Watts, Cam- bell tandem compound H. P. cylinder 18 inches, and low. 264 Steam Engine Indicator pressure cylinder 32 inches by 42 inches, stroke running 100 revolutions per minute. Boiler pressure 120 Ibs. Scale H. P. 60, and L. P. 10. FIG. 144. Figs. 144 and 145 were taken from a 7 in. x 12 in. Buckeye engine. The former was taken as found running, as per data on card. The latter was taken after the proper equalizing of the valve connections had been made. FIG. 145. Figs. 146 and 147 are diagrams from the high pressure cylinder of a Providence tandem compound engine, taken before and after adjusting. Diameter of cylinder 12 inches. A nd Its Appliances. 265 Stroke 22 inches, revolutions per minute 175. Boiler pressure 1 20 Ibs. Scale 60. FIG. 146. The improvement in Fig. 147 consisted *in advancing the eccentric on the shaft, and equalizing the valve connections. FIG. 147. Figs. 148 and 149 are diagrams from a Corliss condensing' engine, with data affixed thereto. The improvement in Fig. 266 Steam Engine Indicator 149 consisted of the same treatment as that given in the two preceeding diagrams. FOUND RUNNJAJG Rev. 54. Press. JO&. Initial Dress. 63. IIG. 148. H Pressure 94- Ibs. *>csvle- 5o. Initial press. 84. FIG. 149. The diagrams Fig. 150 were taken from a Porter- Allen condensing engine, 13 inches diameter of cylinder, by 24 in- ches stroke, 200 revolutions per minute. Boiler pressure 80 Ibs. Vacuum 20 inches. And Its Appliances. 267 Diagrams, Fig. 151, were taken from a 14 x 24 x 14 inches Westinghouse compound engine, boiler pressure 120 Ibs. Scale of Spring 60. FIG. 150. Fig. 152 shows a pair of diagrams (Photo reduced in size) taken from a compound tandem jacketed Corliss engine. Diameter of H. Pressure cylinder 16^ inches and L. Pressure FIG. 151. cylinder 32 inches; stroke 54 inches, revolutions per minute 59. Boiler pressure 108 Ibs. 268 Steam Engine Indicator These diagrams shows the action of the steam while pass- ing through both cylinders, and it will be observed that the steam expanded from an initial pressure of 121 Ibs. to 30 Ibs. in the first cylinder, with an additional expansion in the second, or low pressure cylinder to 8 Ibs., thus giving a range of temperature between 341 deg. and 182 degrees, a change of 159 degrees. It is very evident that any attempt to get the same range of expansion from a single cylinder as obtained in this pair, would be attended with serious loss from condensa- tion ; hence, as higher steam pressures are used, and the num- ber of expansions increased, more cylinders are added in order FIG. 152. to keep the range of temperature in each cylinder within economical limits. Triple and Quadruple expansion engines are simply the results of high steam pressure, and more liberal expansion. The engines from wnich these diagrams were taken belong to the slow or medium speed type. In reference to indicator cards in general it will be seen that in many cases their lines do not reach that degree of excel- lence as shown in Fig. 152. The fault is often due to bad valve setting or poor valve construction, and it may sometimes be due to the indicator itself, either of which may cause the steam line to be wavy from And Its Appliances. 269 start to finish. The usual reason assigned, however, is the presence of water, which comes in such volume that its inertia 92. FIG. 153. B.- -carries the indicator piston too far ; but the chances are that if water passes in such quantities to the indicator, the engine will 270 Steam Engine Indicator not escape some disaster, and as nothing unusual happens when: such cards are taken it is fair to assume some of these irregu- larities are due to other causes than water; one of which may be considered, and what appear to be the most logical cause. Diagrams Figs. 153 and 154 were taken from high speed engines, both taken at a speed of 350 revolutions per minute. The steam and expansion lines on Fig. 153 are all that can be desired; but the lines of Fig. 154 are quite irregular. On each diagram a circle is drawn to represent the travel of the crank pin. The element of time must be considered, and the influence it has on the indicator piston, spring, and pencil movement. All of the parts have weight, and conse- quently inertia. If the pencil movement is relatively slow, the inertia, or tendency to go too far, is slight and our diagram will be comparatively free from wave lines : on the contrary where the movement is rapid, or performed in an unusually short time, the inertia will be great and a diagram with irregular lines will be the result, as shown in Fig. 154. The valve motion of an engine influences this time, and in the cases of Figs. 153 and 1 54 there is enough difference in the valve motion to account for all the difference in the lines of the diagram. By referring to the diagrams it will be seen in Fig. 153 that the indicator piston begins its upward motion at a point marked A on the exhaust line : at this time the crank is at A on the circle. If the compression line is followed it will be seen that when the indicator pencil arrives at the point B it has reached its limit of upward travel, and the crank has passed on to its point B through 92 deg. of the circle, or more than one- fourth of its entire travel. Here then is a high-speed engine so far as relative speed is concerned, but an easy speed for indicating ; because the large clearance, and early compression makes the movement of the indicator so gradual, that severe inertia shocks are elim- inated. And Its Appliances. 271 Diagram Fig. i 54 is lettered the same but there is a decided difference in the location of the letters. In this case compres- sion did not commence until the stroke was nearly finished, and only rose a few pounds. Ninety per cent, of the upward movement of the indicator pencil is represented by a nearly vertical line, showing that this motion occurred while the crank was passing through a very small part of its travel, that is, from A to B on the circle. If the difference- in the spaces between the points A and B on the two crank circles be compared they will give a fair idea of the difference in the velocities of the pencil movement when these diagrams were taken. The difference is the measure of the disturbance, and in Fig. 153 will be found all the conditions which insure a smooth card, while Fig. 154 is decidedly the reverse. In indicator practice we occasionally get cards from slower running engines which show all the irregularities found in cards from high-speed engines : but an analysis of the diagram will probably show that the indicator has had but little help from compression, and the steam admission was very quick. Most of the excellent diagrams taken from high-speed engines, and published in the catalogues of indicator and engine makers, are usually from compression engines ; that is, the type which has large clearance and early compression. The diagram Fig. 1 5 5 is from a pump-cylinder scale 40, and the different lines represent all that can be desired ; as the nearest approach to a rectangle in a pump diagram, the better practice it represents. The line A is the atmospheric line, and the distance from that to the lower line represent the suction, which may be more or less, according to the height the water is lifted, and also to the freedom with which it passes to the pump. The upper line represents the pressure against the plunger or piston necessary to force the water out, and this pressure is due, and 272 Sceam Engine Indicator proportionate to the height to which the water is forced, and also to the friction it encounters in passing from the pump. Commencing at the right hand lower corner of the dia- gram, (the cylinder being full of. water) and the piston begins to move, the pressure instantly rises to about 75 pounds above atmosphere, and continues at a uniform pressure to the end of the stroke, showing that there was no shock due to starting the water-column, and that the passage of the water from the pump- FIG. 155. cylinder was practically without resistance. If the cylinder is not filled with water, the line at the right will not be vertical. At the commencement of the return stroke the pressure instantly fell to 8^ pounds below atmosphere, the degree of vacuum necessary to lift the water The lower or suction- line is about as regular as the upper or discharge line showing with what freedom the water passes through the suction-valves. Such a diagram as this shows an absence of shock to the pump, and that a cylinder full of water is discharged at each single .stroke. And Its Appliances. 273 Fig. 156 is a specimen of diagram which is often taken from pumps, and shows that enormous shocks take place to the parts as well as only partially filling .the cylinder with water. This often happens in practice under circumstances, that cannot always be avoided, but in all cases our endeavors should aim to have the lines of a pump-diagram that will enclose a rectangular figure, and as such, it may be assumed that the operations of the pump must be satisfactory. If the construc- tion of the pump is such that torturous passages exist, causing undue friction of the water getting into or out of the cylinder FIG. 156. the shocks will be greater at some parts of the stroke than at others, and this will be shown by corresponding inclinations of the suction and discharge lines. Shocks and jars and inter- mittent action will be shown by abrupt irregularities in the lines as in Fig. 156. Fig- J 57 represent diagrams taken from the steam cylinder of a Marsh pump working on a suction lift of 24 feet. By means of a deflecting valve, the exhausting end of the steam cylinder can, when desired, be placed in open communication with the suction chamber of the pump. The effect of this connection is to extend the vacuum existing in 274 Steam Engine Indioatcr the suction pipe to the exhaust side of the steam piston. To illustrate the value of this device as claimed for it, is the object of the above card. The full lines were traced with the steam exhausting- directly into the atmosphere. The lever for operating the deflecting valve was then thrown over, thereby turning the ex- haust steam into the suction, and the indicator pencil again applied to the same card, thus tracing the dotted outline. WITH FXHAURT FT^AV OUT. WITH EXHAUST TUHNrp IN. ecALr or urr.itic co. L VACUUM LINE 11 POUNDS. ,.........----...-..- ----.^.. FIG. 157. From this it is apparent that the steam represented by the area enclosed between the upper full line, and the upper par- allel dotted line is just that much gain, for every stroke of the piston, (in this case nearly 25 per cent.), and it will be further noticeable that the total area enclosed by the dotted lines, ex- ceeds the figure enclosed by the full lines to a considerable degree, consequently, there is more power to perform the work, with a smaller expenditure of force, and with the labor a constant factor, the speed of the pump is increased, and a greater amount of water delivered. A nd Its Appliances. 275 CHAPTER XXXII. ENGINE ECONOMY. In considering the matter of steam economy in the engine alone, it must be understood that the Mean Effective Pressure of the steam acting against the piston for a given time, represents the exact measure or exponent of the work performed by the engine in such time, and is consequently an important factor in all calculations pertaining to engine performance. The Terminal Pressure, or that pressure of steam which would exist in the cylinder, provided the exhaust valve re- mained closed to the end of the stroke, is the corresponding measure or exponent of the consumption of steam or water by the engine, or the cost of the power, and is also an indispensible factor in the calculation of the diagram. But almost invariably in all makes of engines, the exhaust valve opens, and releases the steam before the piston reaches the end of its stroke ; and in such cases the Terminal Pressure, is found by continuing the expansion curve in its gradually descending direction (by hand) to the end of the diagram, and measuring from that point to the vacuum line by the scale of the diagram, as shown at T. V., Fig. 77, page 159. From the conclusions conceded in reference to the Mean Effective and Terminal Pressures, it is evident that the maxi- mum economy will result when the mean effective pressure is greatest relatively to the terminal pressure ; therefore if by any means the former can be increased without a corresponding 276 Steam Engine Indicator increase in the latter, or anything that will decrease the latter without correspondingly decreasing the former, must result in improving the economy of the engine. In non-condensing engines, therefore it would appear that the maximum economy with a given boiler pressure is theor- etically obtained when the full pressure is admitted to the cyl- inder and continued to such point of cut-off, as that the degree of resulting expansion may be such that at the end of the stroke, the terminal pressure has fallen to, or nearly to, atmospheric pressure. The attainment of this economy in practice will depend somewhat upon conditions, and the construction of the engine ; such as possessing a free exhast for the steam, in combination with the least possible loss from clearance, friction, leakage and condensation. Hence under favorable conditions it is possible to expand the steam until there is no more work in it, and no greater economy can be expected with a given initial pressure of steam ; unless by the aid of a condenser. With a given load, and boiler pressure, the best theoret- ical economy is obtained, when the cut-off takes place as early in the stroke, as is consistent with obtaining the average pres- sure in the cylinder to do the necessary work, and at the same time maintain the required speed of engine. The measure of the economy of .the engine alone, therefore is the number of pounds of water which passes through the cylinder in the shape of steam per hour, for each indicated horse power developed. The actual amount of water thus consumed appears in three conditions ; and consists in part of the steam that begins to suffer condensation immediately upon leaving the boiler : due to coming in contact with the comparatively cooler steam passages, and which is further increased upon striking the in- ternal surfaces of the cylinder ; part is condensed in the act of A nd Its Appliances . 277 transforming heat into work ; that is, in giving- motion to the piston, and part in that discharged from the cylinder as ex- haust steam. The portion condensed in the act of changing heat into work is the only one of value ; as this quantity (namely, that exhausted and that whose heat is converted into work,) is the amount of water, or steam accounted for by the indicator, and is a measure of the performance of an engine, and when com- pared with the performance of the best, it shows the economy with which the engine works. The steam lost in internal condensation is not at all accounted for by the indicator. Hence the total amount of loss from this source is really the difference between the water actually pumped into the boiler, and that accounted for by the indicator. Tests. It is a very simple matter in testing a plant com- prising an engine and boilers, to ascertain the economy of the plant, as a iv/iolc, as theie is usually but little to determine beyond the quantity of fuel consumed, and the horse power developed ; but to ascertain the economy and the losses, aris- ing from each of the various parts of a plant, (such as the engines, boilers, heaters, economizers, pipes, etc.), requires close attention to all the several points to insure accurate results. Where tests of the latter kind are made the following par- ticulars and data should be recorded : First. The total weight of water supplied to the boiler. Second. The quantity of water drained from the separ- ator, (if one be used) which includes the water carried along with the steam ; (known as priming and for which the boiler alone is responsible) also the condensation in pipes. Third. The percentage of moisture in the steam that is being supplied to the engine. This may be determined by 278 Steam Engine Indicator means of what is called a calorimeter test, the method of its operation being described in Chapter XXX. From these amounts the weight of steam (or water) passing through the engine, per hour may be ascertained, and dividing this weight by the horse power developed will give the weight of steam used per horse power per hour. If this amount is very high it will probably be due to leakage, and if such should be the case it will be detected more quickly by this than by any other method. Fourth. The total weight of coal burned in the furnace. If this weight is small in comparison with the weight of water pumped into the boiler, showing a large evaporation per pound of coal, it will probably be found that the boiler primes. If the opposite of this is the case, it may be due to a poor quality of coal, improper firing, poor draft, etc., either of which will cause the final results to be disappointing, Fifth, The temperature of the feed water before and after passing through the heater ; this shows the efficiency of the heater. In a non-condensing engine the heating of the feed water by the exhaust steam should always be taken advantage of, as in this way a saving of coal will be effected of from 10 to 15 per cent., depending upon the efficiency of the heater and manner of connecting. To realize .the full economy from heating the feed water, it should not enter the boiler at a temperature less than 210 de- grees Fah. and besides, at this temperature it also obviates the strain on the boiler, that arises from feeding cooler water. In a condensing engine however there is but little gain from the use of a heater over that of feeding the boiler direct from the hot-well ; provided the temperature of the hot-well is not unnecessarily low ; excepting under circumstances where the water used for condensing purposes is unfit for feeding the boiler on account of salt, lime, and other substances held in A nd Its Appliances . 279 solution, and which causes such water to be deleterious in its action upon the interior surface of the boiler. In the latter case therefore, a slight economy may be de- rived from the use of a heater ; as by its use the fresh water selected for feeding the boiler may have its temperature con- siderably increased above that of the hot- well while passing through the pipes of the heater on its way to the boiler ; and a somewhat further gain is effected, which consists in lessening the amount of water requisite to supply the condenser ; due to the heater condensing a portion of the exhaust steam in its passage through it. In all steam plants there is considerable loss of heat from radiation, by the boiler and setting, and a large percentage of the fuel burned simply replaces the heat radiated from this source, such heat being conveyed away by the air passing over them, without doing any useful work in the way of forming steam ; and a further amount is also wasted by the radiation from the pipes, etc., between the boiler and engine, this latter causing the condensation of steam in the pipes. In order to have a test of this description complete, it is necessary that the amount of these losses from radiation be ascertained, as the heat radiated from the boiler and setting should not be charged against the steam formed ; the loss also from condensation in the pipes is an uncertain quantity and often much larger than supposed. One plan of ascertaining the amount of each of these losses is, after the engine has been stopped, to keep the nor- mal pressure of steam on the boiler for several hours, taking care to keep the water in the boiler, (as near as possible,) at the ordinary level, and the engine stop valve must be tightly closed to prevent any escape of steam or water through it. The amount of fuel burned, and also the quantity of water pumped into the boiler during this radiation test, should be carefully weighed, and at the end of the test the water of 280 Steam Engine Indicator condensation must be drained from the engine steam pipe, and all other pipes connected directly with the steam space of the boiler, and this total amount also carefully weighed and noted. If during this test it is found that more water has been supplied to the boiler than that collected from the drains, the difference is evidently due to leakage ; therefore, when taking account of the steam passing through the engine in a power test, this leakage should be allowed for. Hence, to ascertain the exact evaporation per pound of coal, it is necessary that the amount of coal burned, and water used per hour during the radiation test, be deducted from the. coal and water used per hour during the power test. The difference in the amount of coal, shown by this sub- traction, is the actual amount that is consumed in forming steam only; while the difference in the amount of water used, shows the exact amount of water that has been formed into steam by this quantity of coal. Therefore, in power tests where the amount of coal con- sumed is the measure of the engine's performance, (as is fre- quently the case,) the quantity of coal remaining (after deduct- ing the amount used in the radiation test,) is the correct amount chargeable against the engine. In making the radiation test, every precaution should be taken that will tend to burn the coal to the best advantage ; the draft openings for the furnace, and also the back damper, should be carefully adjusted, so as to just maintain the pres- sure of steam required, and also to prevent an excess of air from conveying any large amount of heat up th chimney. In the absence of an accurate water metre for measuring the quantity of water forced into the boiler during a test, a very satisfactory arrangement may be substituted, consisting of two barrels or casks, in connection with an ordinary plat- form weighing scales. A nd Its Appliances. 2 8 1 One of these barrels is placed upon scales, and together elevated above the second barrel, which for convenience, should be somewhat the larger. The feed water is drawn into and carefully weighed in the upper barrel, and then run off into the lower one, from which it is pumped into the boiler. Another and somewhat more convenient method of testing is sometimes resorted to, but which gives approximate results only. In this operation the feed water is brought to a given point near the upper part of the gauge glass, and then shut off, and the test made by observing the rate at which the water boils away. The height of the water in the glass at the beginning, and at the end of the test being carefully observed and noted. The weight of the water evaporated and supplied to the engine can then be calculated from the cubical volume that it occupied in the boiler, always bearing in mind that the weight of a given volume of water varies with its temperature. (See table No 9). To insure greater accuracy, tests made by this method can be repeated a number of times, and the results averaged. Feed water tests, made by measuring all of the water sup- plied to the boiler, are of no positive value unless leakage of water from the boiler (if any exist) be deducted therefrom ; hence, particular attention should always be given to this fact, and the leakage determined as before described. A better and more accurate way than either of the above methods for ascertaining the weight of steam consumed by an en- gine, is to use a Surface Condenser, in which all of the steam passing through the engine is condensed, and the resulting water saved and weighed; and the only correction needed is to deduct the per cent, of moisture contained in the steam supplied, which may be determined by a Calorimetric test. 282 Steam Engine Indicator A portion of the steam required by an engine may also be found by calculation from the diagram. A method of making this calculation is given in Chapter XXL Engine economy includes everything that enters into cost of maintenance, and operation, and the problem with the en- gineer in charge of engines and boilers, is how to get the best possible results from such machinery as comes under his direc- tion. The value of his services depends largely upon his ability in this direction, and an important part of his education is how best to accomplish the most desired and economical re- sults. Economy to him consists in keeping the fuel account as low as possible for the power developed, having few repairs, little loss (through accidents or otherwise) from stoppages, and also having the least possible loss from wear and tear or de- terioration. The cost of fuel is always an important matter, but some- times it happens of more importance that there be no com- pulsory stoppage of the engine or that the speed be very regular. It is the province of the engineer to study this in any par- ticular instance and govern himself according to circumstances and observation, and take measures to obviate or remove (if possible) whatever may be detrimental to good economy. In reference to fuel economy it frequently happens that the engineer has to contend with defective conditions, or under such adverse circumstances, as will render the attainment of good economy impossible. A condition very unfavorable to fuel economy of non -con- densing engines exists in cases where the expansion line of the indicator diagram falls below the pressure of the atmos- phere early in the stroke (as shown in Fig. 62). or in other And Its Appliances. 283 words, where the engine is too large for its work, necessitating an early cut-off, and in consequence, greater loss from con- densation. The reason of this increased loss through condensation, is owing to the interior walls of the cylinder becoming cooled to a lower temperature during expansion and exhaust, and in consequence, a considerable portion of the entering steam at the beginning of the stroke is condensed ; due to parting with its latent heat in order to restore the temperature of the in- terior exposed surface of the cylinder. In an engine with a light load, the steam thus condensed is a larger proportion of the total steam used, than in one more heavily loaded. Another reason why poor economy is gener- ally the rule where light loads prevail, is that a part of the work done in the cylinder of a steam engine is in overcoming the friction of the moving parts; and this friction docs not in- crease proportionately fast as the load is increased, the friction sometimes being nearly as great with light running, or no load, as with the engine fairly well loaded. In a non-condensing engine the useless work of moving the piston against the pressure of the atmosphere must always be done, besides some additional back pressure, although this will not increase as fast in proportion as the mean effective pressure is increased. In a condensing engine the piston has always to be moved against pressure due to imperfect vacuum, besides a certain amount of back pressure also. Owing to various conditions and circumstances, connected with the sub- ject, the exact loss from condensation cannot be ascertained very closely by calculation ; therefore it cannot be told just what the mean effective pressure on an engine piston should be y to realize the best economy in fuel consumption. Experiments to determine the relation of steam consump- tion to point of cut-off, under different pressures of steam in a non-condensing engine will be found described in Chapter XXVI. 284 Steam Engine Indicator CHAPTER XXXIII. The following tables (No. 6) apply both to exhaust steam heaters and economizers where, what would otherwise be, waste heat is utilized for heating the feed water. The percentage of saving given is the saving in the amount of heat required to generate a certain quantity of steam. The saving in fuel depends on other conditions, and may be more than given above. If, for instance, a boiler is too small to steam easily without a feed-water heater, the application of a heater will make a much greater saving in fuel than the per- centage given in the table : but if the boiler steams easily with- out a heater, the addition of a heater will save about the same per cent, of fuel as given in the tables. It is assumed in each case that the addition of an exhaust steam heater does not im- pair the vacuum on a condensing engine, or increase the back pressure on a non-condensing engine, and that the addition of an economizer does not impede the draught. A heater maybe applied to the exhaust pipe of a condensing engine that will, without impairing the vacuum, heat the feed- water from the temperature of the hot well (about 1 00) to 165 or 170, a saving of about 6 per cent., then passing it through an economizer, should raise the temperature another 100 (from 170 to 270), making a further saving of about 10 per cent. In non-condensing engines an exhaust steam heater will heat the feed- water from 62 to 210, a saving of 12.9 per cent. An economizer will heat the feed-water to from 220 to 320, according to the temperature of the waste gases, and also- the temperature of the water entering the economizer. A nd Its Appliances. 285 After heating the water, care should be taken that it stays liot until it enters the boiler. If, for instance, the water is heated in an economizer to 270, and then in passing through the pipes to the boiler it cools down 10, to 260, there is a loss of i. 06 per cent., the greater portion of which might be saved by carefully protecting the pipes. The temperature of the feed water, before and after passing through the economizer, and the temperature of the gases both sides of it, will show whether the economizer is efficient or not. If the temperature of the water leaving the economizer gradually lowers while the average temperature of the escap- ing gases gradually increases, it indicates a scaling up of the economizer, which at once requires attention. Also if the quantity of fuel increases gradually, it may possibly be due to air leaks in the setting or scaling either in the boiler, or econ- omizer, and should be remedied. 286 Steam Engine Indicator TABLE No. 6. Saving effected by the use of Feed-Water Heaters in the generation of steam of 100 Ibs. guage pressure or 115 Ibs. total pressure. Temp. from which the water is heated or cooled. Temperature of the Water entering Boiler. 32 85 | 40 | 43 ) 50 | 55 | 60" | 62 65 > \ 70 | 73 80 | 88' Percentage of gain.(-H or Jos? ( ) by heating or cooling the water. 32 00 25 67 110 1-52 1-94 2-36 -f 2-53 + 2-79 + 3-21 + 3-63 + 4-05 + 4-47 35 -25 00 42 85 1-27 1-69 2-12 2-29 2-54 2-96 3-39 3-81 4-23 40 67 -42 00 43 85 1-28 1-70 1-87 2-13 2-55 2-98 3-40 3-83 45 1-10 85 -43 -00 43 85 1-28 145 1-71 2-13 2-56 2-99 3-41 50 1-52 1-27 85 43 00 43 86 1-03 1-29 1-71 2-14 2-57 3-OO 55 1-94 1-69 1-28 85 -43 00 43 60 86 1-29 1-72 2-15 2-58 60 2-36 212 1-70 1-28 "86 -43 00 17 43 86 1-30 1-73 2-16 62 2'53 2-29 1-87 1-45 1-03 60 -17 00 26 69 1-13 1-56 199 65 279 2-54 2-13 1-71 1-29 86 43 -26 00 43 87 1-30 1-74 70 3-21 2-96 2'55 2-13 1-71 1-29 86 69 -43 00 44 87 1-31 75 3-63 3-39 2-98 2-56 2-14 1-72 130 1-13 87 -44 00 44 88 80 4-05 3-81 3-40 2-99 2-57 2-15 1-73 1-56 1-30 87 -44 00 44 85 4-47 4-23 3-83 3-41 3-00 2-58 2-16 1-99 1-74 1-31 88 -44 00 90 4-90 4-66 4-26 3-85 3-44 3-02 2-60 2-43 2-18 1-75 132 89 -45 95 5-33 5-09 4-68 4-28 3-87 3-45 3-04 2-87 2-61 2-19 1-76 1-33 89 100 575 5-51 5-11 4-70 4-30 3-88 3-47 3-30 3-05 2-63 2-20 1-77 1-33 110 6-59 6-36 5-96 5-56 5-15 4-74 4-33 4-17 3-92 3-50 3-07 2-65 2-22 120 7-44 7-20 6-81 641 6-01 5-60 5-20 5-03 4-79 4-37 3-95 3-53 3-10 130 8-29 8-06 7-67 727 6-88 6-47 6-07 5-91 5-66 5-25 4-34 4-42 4-00 140 914 8-80 8-52 8-13 7-73 7-33 6-93 6-77 6-53 6-12 5-71 5-30 4-88 150 9-99 976 9-38 899 8-60 8-20 7-81 7-65 7-41 7-00 6-60 619 5-77 160 10-84 10-61 10-23 9-85 9-46 9-07 8-68 8-52 8-29 7-89 748 707 6-66 170 11-68 11-46 11-08 10-70 10-32 9-93 9-55 9-39 9-15 8-76 8-36 7-95 755 180 1254 12-31 '11 94 11-57 11-19 10-80 10-42 10-26 10-03 9-64 9-24 8-84 8-44 190 13-39 13-17 12-80 12-43 12-05 11-6711-29 11-14 10-91 10-52 10-13 9-73 9-33 200 14-24 14-02 13-66 1329 12-92 12-54-12-17 12-01 11-79 11-40 1101 10-62 10-23 210 15-10 14-89 14-53 14-16 13-79 13-42 13-05 12-90 12-67 12-29 11-91 1152 11 13 212 15-27 15-06 14-69 1433 13-96 13-59 1322 13-07 12-85 12-47 12-08 11-69 11 3f> 220 15-96 15-74 15-38 15-02 14-66 14-29 13-92 13-77 1355 13-17 12-79 12-41 12-02 230 16-81 16-60 16-24 15-89 15-52 15-16 14-79 14-65 1442 14*05 13-68 1330 12-91 240 17-66 17-45 17-10 16-75 16-39 16-03 15-67 15-52 1530 14-93 14-56 14-18 13-81 250 260 18-52 19-38 18-32 19-18 17-97 1883 17-62 1849 17-26 18-14 16-91 17-78 1655 17-43 16-41 [16- 19 17*29170; 1582 16-71 15-45 16-35 15-08 16-98 14-71 15-61 270 20-24 20-03 19-69 19-35 19-01 18-66 18-31 18-17 1793 1759 17-2316-87 16-50 280 21-09 20-89 20-55 20-21 19-87 19-52 19-18 19-04 18-83 18-47 18-1217-76 17-39 290 21-95 21-75 21-42 21-08 20-75 20-40 20-06 19-9219-71 19-36 19-01 18-65 18*30 300 22-80 22-61 22-28 21-95 21-61 21-27 20-93 20-80'20-59 2025 19- JO 19-54 19-19 310 o20 23-67 24-52 23-47 24-32 23-14 22-82 2400123-68 22-49 23-35 22-15 23-02 21-82 22-69 21-68 21 4S 22:56 22'35 21-14 22-02 20-7920-44 21-67 I 21'33 20-00 20-98, And Its Appliances. 28.7 TABLE No. 6. CONTINUED. Saving effected by the use of Feed- Water Heaters in the generation of steam of 100 Ibs. guage pressure or 115 Ibs. total pressure. Temp, from which the water is heated or cooled. Temperature of the Water entering BoMer. 90 ) 93 100 | 110-' 120" 130 | 140 [ 150 160 | 170j 3217- 2OI.I .i 3931-4 222.2 | 2585.4 180.2 3229-5 201.4 .1 3945-2 222.6 I 2596.7 180.6 3242.2 201.8 7X 'i 3959-2 223. I 2608. iSr. _. 3254-8 202.2 .i 3973-1 2234 | 2619.4 181.4 , : 3267-5 202.6 .i 3987.1 223.8 3. 2630.7 I8l.$ 3280.1 203. .f 4001.1 224.2 5* 2642 I 182.2 3292.8 203.4 .1 4015.2 224.6 2653.4 182.6 1 3305-5 203.8 .* 4029.2 225. 2664.9 183. 65- 33i8.3 204.2 f 4043-3 225.4 2676.3 183-3 3331- 204.5 .1 4057. 225.8 2687.8 183.8 ,. 3343-9 205. 72. 407J.5 226.2 2699.3 184.1 .. 3356.7 205.3 .i 4085.6 226.5 2710.9 184.6 t . 3369-6 205.8 .i 4099.8 227. 2722.4 184.9 \ 3382.4 206. i .1 4114. 227-3 59 2734- 185.4 3395-3 206.6 .4 4128.2 227.7 \- 2745-5 185-7 ,j 3408.2 206.9 4 4142.5 228.1 2757-2 186.1 66.' 3421.2 207.3 .1 4156.8 228.5 j- 2768.8 186.5 .\ 3434-1 207.7 4 4171. 228.9 2780.5 186.9 34472 208.1 73- 4185.4 229.3 { 2792.2 187-3 346o.i 208.5 .1 4199.7 229.7 | 2803.9 187.7 3473-2 208.9 .i 4214.1 230.1 ^ 2815.6 188.1 3486.3 209.3 .f 4228.5 230.5 60 2827.4 188.5 3499-4 209.7 i 4242-9 230.9 i 2839.2 188.8 3512.5 2IO. .1 4257-3 23I-3 0. 4 2851. 189-3 67. 3525-6 210.5 .f 4271.8 231.7 2862.8 189.6 .* 3538.8 210.8 .1 4286.3 232. 2874.8 190.1 3552. 211.3 74- 4300.8 232.5 2886.6 190.4 3565.2 211. 6 .1 43I5-3 232.8 2898.5 190.9 3578.5 212. 1 .i 4329.9 233.2 2910.6 191.2 3591-7 212.4 .1 4344-5 233-6 61 2922.5 191.6 3605- 212.8 .i 4359-2 234- 1 2934-4 192. 36iS.3 213.2 f 4373-8 2344 i 2946.5 192.4 68. 363I-7 213.6 .t 4388.5 234-8 1 2958.5 192.8 .f 3645- 214. .1 4403. i 235-2 I 2970.6 193-2 j. 3658.4 214.4 75- 4417.9 235-6 | 2982.6 193-6 f 3671.8 214.8 .* 4432.6 236. 1 2994.8 194. '* 3685.3 215.2 i 4447.4 236.4 A nd Its Applian ces . 293 TABLE No. 7o CONTINUED. Areas and Circumferences of Circles from 1-64 to 4 inches in diameter varying by sixteenths; and from 4 inches to 100 inches, varying by one-eighth inch. Diam. Area Circum. Diam. Area Circum. Diam. Area Circum. in in Square in in in Square in in in Square in Inches. Inches. Inches. Inches. Inches. Inches. Inches. Inches. Inches. 75-1 4462. 1 236.7 824 5297-I 258. 88.| 6203.6 279-2 4477- 237-2 i "4 53I3.3 258.4 8 9 . 6&I. I 279.6 4 4491.8 237-5 3. 8 5329-4 258.8 4 6238.6 280. 3 A 4506.7 238. I 5345-6 259.2 i * 4 6256.1 280.4 I 4521-5 238.3 1 5361.8 259.6 6273.6 280.8 7 6. 4536-5 238-8 3 "4 5378.1 260. .i 6291.2 281.2 4 4551-4 239- r 4 5394-3 260.4 '5 6308.8 281.6 4566.4 239-5 83- 5410.6 260.8 i 4 6326.4 282. 1 4581-3 239-9 .* 5426.9 26l.l 4 6344. 282.3 $ 4596-3 240.3 T 5443-3 261.5 90. 6361.7 282.7 4 4611.3 240./ % 5459-6 261.9 4 6379-4 283.1 4 4626.4 24I.I 4 54/6- 262.3 1 4 6397-I 283.5 f 4641.5 24I-5-. A 8 5492.4 262.7 4 6414-8 283.9 11; 4656.6 241.9 . .f 5508.8 263.1 | 6432.6 284.3 i ' 4671-7 242.2 I 5525.3 263.5 I 6450.4 284.7 4686.9 242.7 S 4 . 554^.8 263.9 4 6468.2 285.1 . j 4702. i 243- 4 5558.3 264.3 'H 6486. 285.5 ! 4/17-3 243-5 JL 4 5574-8 264.7 91. 6503.9 285.9 f 4732-5 243-8 559 1 -3 265." 4 6521.7 286.3 .j 4747-8 244-3 I 5607-9 265.5 6539.7 286.7 .1 4763.- 244-6 5624-5 265.8 i 6557.6 287.1 7 8. 4778.4 245- 4 5641.2 266.2 i 6575.5 287.5 .4 4793-7 245-4 I 5657:8 266.6 i 6593-5 287.8 | 4809. 245-8 85. 5674.5 267.. .2 6611.5 288.2 4 4824.4 246.2 \ 5691.2 267.4 4 6629.5 288.6 4839.8 246.6 5707.9 267.8 92. 6647.6 28 9 . 1 4855-2 247- 4 5724.6. 268.2 1 6665.7 289.4 ,| 4870.8 247-4 .1 574J-5 268.6 6683.8 289.8 8 4886.1 247-7 i .5758.2 268.9 4 6701.9 290.2 79- 4901.7 248.2 2 5775-1 269.4 i 6/20. 1 290.6 4 4917.2 248.5 8 5791-9 269.7 1 6738.2 2 9 I. i 4 4932.7 249- 86. .5808.8 270.2 6756.4 291.4 I 4948.3 249-3 .4 .5825-7 270.5 i" 6774.7 291.8 4963-9 249.8 :i 5842-6 271. 93 'i 6792.9 292.2 1 4979-5 250.1 .3 5859.5 271.3 6811.1 292.6 . 4995-2 250.5 i 58/6.5 271.7 6829.5 293. .* 5010.8 250-9 K 5S93-5 272.1 4 6847.8 293-4 SO. ' 5026.5 251-3 .a 5910.6 272.5 2 6866. i 293-7 4 5042.2 251:7 .2 5927.6 272.9 .1 6884.5 294.1 i 5058. 252.1 87. 5944-7 273-3 4 6902.9 294-5 4 5073.7 252.5 i 5961-7 273-7 -1 6921.3 294-9 1 5089.6 252-9 4 5978.9 274. i 94- 6939.8 295-3 f 5105.4 253-3 3 5996. 274-4 f 6958.2 295-7 4 5121.2 253-7 ^ 6013.2 274-9 6976.7 296.1 I 5^37-1 254-1 f 6030.4 275-2 .1 6995-2 296.5 81. 5I53-. 254-5 2 6047.6 275-7 1 7013.8 296.9 4 5168.9 254-9 8 6064.8 276. i 7032.3 297.3 ? 5184.9 255-3 88. 6082.1 276.5 a 7051. 297.7 1 5200.8 255-6 i 6099.4 276.8- f 7069.5 298.1 .1 5216.8 256. 6116.7 277.2 95- 7088.2 298.5 8 5232.8 256-4 6134. 277.6 7106.9 298.8 .i 5248.9 256.8 i 6151.4 278. .J- 7125.6 299.2 8 5264.9 257.2 1 6168.8 278.4 f 7144.3 299.6 82. 5281. 257-6 2 6186.2 278.8 i 7163- 300. 2 9 4 Steam Engine Indicator TABLE No. 7. CONTINUED. Areas and Circumferences of Circles from 1-64 104 inches in diameter, varying by sixteenths; and from 4 inches to 100 inches, varying by one-eighth inch. Dia in IiicTi tn. es. Area in Square Inches. Circum. in Inches. Diam. in Inches. Area in Square Inches. Circum. in Inches. Diam. in Inches. Area in Square Inches.. Circum. in Inches. 951 1 7l8l.8 300:4 97 | 7408.8 305.1 98 i 7639-4 309.8 j | ; 720O.6 300.8 7428. 305.5 7658.9 310.2 7219.4 301.2 7447-. 305.9 i 7678.2 310.6 9 6. 7238.2 301.6 J 7466.2 306.3 99 7697J 3". i 7257.1 302. | 7485.3 306.7 77I7.I 3II-4 . . 7276. 302.4 | 7504.5 307.1 A 7736.6 3II.8 7294.9 302.8 ^ 7523.7 307.5 3 7756.1 312.2 73I3-8 303.2 98 7543. 307.9 7775-6 312.6 7332-8 303.5 7562.2 308.3 7795-2 313. 7351.8 303.9 | 7581.5 308.7 | 7814.8 3'34 g 7370.7. 304.3 7600.8 309. I 7834.3 313-8 97, 7389.8 304.7 * 7620. 1 3094 100. 7854. 3U2 If the areas of larger circles are required, they will be found by the following : RULE Multiply the square of the diameter in inches, by the decimal 0.7854, and the product will be the area in square inches ; or, multiply half the circumference by half the diam- eter. If the circumference of a larger circle is wanted, and having the diameter, the rule is as follows: RULE As 7 is to 22, so is the diameter to the circumfer- ence, or diameter multiplied by 3.1416 equal circumference. And Its Appliances. 295 TABLE No. 8. The properties of Saturated Steam. rtlESSURB PER SQUARE INCH. Temp- erature ,in Fahrenheit Degrees. NUMBER o* BRITISH THERMAL UNITS IN ONE POUND FROM ZERO (FAHRENHEIT). Weight of One Cubic Foot of Steam . in Decimals of a Pound. Number of Cubic Feet of Steam from One Cubic Foot of. Water. Total- Pressure iu Pounds from u Vacuum Pressure in Pounds as Shown by Steam Gauge. Number of Units of Heat in Water. Number of Units of Heat Required for Evaporation, Called Latent Heat. Total Number of Units of Heat Contained in Steam. \ 102. 102.086 1042.964 1145.050 .0030 20620.0 2 126.266 126.440 1026.010 1152.450 .0058 10720.0 3 141.622 141.877 1015.254 1157.131 .0085 7326.0 4 153.070 153.396 1007.229 1160.625 .0112 5600.0 5 162.330 162.722 1000.727 1163.449 .0137 4535.0 6 170.123 170.577 995.249 1165.826 .0165 3814.0 7 176.910 177.425 990.471 1167.896 .0189 3300.0 "8 182.910 183.481 986.245 1169.726 ;0214 2910.0 g 188.316 188.941 982.434 1171.375 .0239 2607.0- 16 193.240 193.919 978.958 1172.877 .0264 2360.0 11 19t.768 198.496 975.762 1174.258 .0289 -2157.0 12 201.960 202.737 972.800 1175.537 .n3l3 1988.0 13 205.885 206.709 970 025 1176.734 .0337 1846.0 14 209.560 210.428 967.427 1177.855 .0362 1722.0 14.7 212.000 212900 965700 1178.600 .03797 1644.0 15 .304 213.025 213.939 964.973 1178.912 .0:187 1612.0 16 1.304 216.296 217.252 962.657 1179.909 .0413 1514.0 17 2.304 219.410 220.409 960.450 1180.859 .0437 1427.0 18 3.304 222.378 223.419 958.345 1181.764 .0462 1350.6 19 4.304 225.203 226.285 956.343 11 82.628 .0487 1282.1 20 5.304 227.917 229.039 954.415 1183:454 .0511 1220.3 21 6.304 230.515 231.676 .952.570 1184.246 .0536 1164.4- 22 7.304 233.017 234.218 950.791 1185.009 .0561 1113.5 23 8.304 235.432 236.672 949.072 1185.744 .0585 1066.9 24 9.304 237.752 239.029 947.424 1186.453 .0610 J024.1 23 10.304 240.000 241.314 945.825 1187.139 .0634 984.8.' 26 11.304 242.175 243.526 944.277 1187.803 .0658 948.4 27 12.304 244.284 24.5.671 942.775 1188.446 .0683 914.6. 28 13.304 246.326 247.748 941.321 1189.069 .0707 883.2 29 14.304 248.310 249.769 939.905 1189.674 .0731 854.0 30 15.304 250.245 251.738 938.925 1190.263 .0755 826.'8 31 16.304 252.122 253.648 937.1878 1190.8358 .0779 801.2 32 17.304 253.952 255.512 935.8818 1191.3938 .0803 777.2 33 18.304 255.735 257.329 934.6088 1191.9378 .0827 754.7 34 19.304 257.476 259.103 933.3658 1192.4688 .0851 733.5 35 20.304 259.176 260.835 932.1523 1192.9873 .0875 713.4 36 21.304 260.835 262.527 930.9668 1193.4938 .0>99 694.5 37 22.304 262.458 264.182 929.8068 1193.9888 .0922 676.6 38 23.304 264.045 265.801 928.6718 1194.4728 .0946 659.7 39 24.304 265.599 267.386 927.5608 1194.9468 .0970 643.6 40 25.304 267.120 268.938 926.4728 1195.4108 .0994 628.2 41 26.304 268.611 270.460 925.4058 1195.8658 .1017 613.4 42 27.304 270.073 27-1.954 924.3578 1196.3118 .1041- 699.3 43 28.304 271.507 273.417 923.33J3 1196.7493 .1064 586.1 44 29.304 272.915 574.855 922.3238 1197.1788 .1088 573.7 45 30.304 274.296 276.266 921.3343 1197.6003 .1111 561.8 46 31.304 275.652 277.651 920.3632 1198.0142 .1134 550.4 47 32.304 276.986 .279.016 919.4052 1198.4212 .1158 539.5 43 33.304 278.297 280.355 91&4662 1198.8212 .1181 529.0 49 34.304 279.585 281.672 917.5422 1199.2142 .1204 518.6 50 35.304 280.854 282.969 916.6316 1199.6006 .1227 508.5 51 36.304 282.099 284.243 915.7377 1199.9807- .1251 499.1 52 37.304 283.326 285.499 914.8557 1200.3547 .1274 490.1 296 Steam Engine Indicator TABLE No. 8. CONTINUED. The Properties of Saturated Steam, PRESSURE PER SQUARE INCH. Temp- erature in Fahrenheit Degrees. NUMBER OF BRITISH THERMAL UNITS IN ONE POUND FROM ZERO (FAHRENHEIT). Weight of One Cubic Foot of Steam in Decimals of a Pound. Number of Cubic Feet of Steam from One Cubic Foot of Water. Total Pressure in Pounds from a Vacuum Pressure in Pounds as Shown by Steam Gauge. Number of Units of Heat in Water. Number of Units of Heat Required for Evaporation, Called Latent Heat. Total Number of Units of Heat Contained in Steam. 53 38.304 284.534 286.736 913.9871 1200.7231 .1297 481.4 54 39.304 285.724 287.952 913.1340 1201.0860 .1320 472.9 55 40.304 286.897 289.153 912.2906 1201.4436 .1343 464.7 56 41.304 288.052 290.335 911.4611 1201.7961 .1366 457.0 57 42.304 289.112 291.503 910.6407 1202.1437 .1388 449.6- 58 43.304 290.316 292.654 909.8325 1202.4865 .1411 442.4 59 44.304 291.425 293.790 909.0346 1202.8246 .1434 435.S 60 45.304 292.520 294.911 908.2472 1203.1582 ,1457 428.5 61 46.304 293.598 296.016 907.4713 1203.4873 .14793 422.0 62 47.304 294.663 297.108 906.7042 1203.8122 .15021 415.6 63 48.304 295.714 298.185 905.9477 1204.1329 .15248 409.4 64 49.304 296.752 299.249 905.2005 1204.4495 .15471 403.5 65 50.304 297.777 300.300 904.4621 1204.7621 .15697 397.7 66 51.304 298.789 301.338 903.7327 1205.07U7 .15921 3921 67 52.304 299.789 302.364 903.0116 1205.3756 .16147 386.6 68 53.304 300.776 303.377 902.2999 120-1.6769 .16372 381.3 69 54.304 301.753 304.380 901.5947 1205.9747 .16598 376.1 70 55.304 302.718 305.370 900.8991 1206.2691 .16817 371.2 71 56.304 303.673 306.350 900.2101 1206.5601 .170^8 366.4 72 57.304 304.617 307.320 899.5280 1200.8480 .1725'.) 361.7 73 58.304 305.551 308.279 898.8537 1207.1327 .17481 357.1 74 59.304 306.474 309.228 898.1863 1207.4143 .17704 352.6 75 60.304 307.388 310.166 897.52^9 1207.6929 .17923 348.3 76 61.304 308.290 311.092 896.8764 1 207.9684 .18142 34-4.1 77 62.304 309.184 312.011 896.2301 1208.2411 .18360 340.0 78 63.304 310.069 312.920 895.5910 1208.5110 .18579 336.0 79 64.304 310.945 313.821 894.9571 r-'OS.778l .18797 332.1 80 65.304 311.812 314.712 894.3304 1209.0424 .19015 328.3 81 66.304 312.670 315.595 893.7092 lL'09.3042 .19232 324.6 82 67.304 313.520 316.468 893.0954 1209.5634 .19454 320.9 83 68.304 314.3(51 317.333 892.4871 1209.8201 .19674 317.3 84 69.304 315.195 318.190 891.8843 12 10.0743 .19887 313.9 85 70.304 316.021 319.040 891.2862 1210.3262 .20105 310.5 86 71.304 316.839 319.882 890.6938 1210.5758 .20321 307.2 87 72304 317.650 320.717 890.1061 1210.8231 .20535 304.0 88 73.304 318.453 321.543 889.5251 1211.0681 .20753 300.8 89 74.3U4 319.249 322.362 888.9490 1211.3110 .20970 297.7 90 75.304 320.039 323.176 888.3758 1211.5518 .21183 294.7 91 76.304 320.821 323.981 K87.8094 1211.7904 .21303 291.8 92 77.304 321.597 324.781 887.2460 1212.0270 .21608 288.9 93 78.304 322.C66 325.572 886.6896 1212.2616 .21829 286.1- 94 79.304 323.128 326.358 886.1362 1212.4942 .2204"> 283.3 95 80.304 323.884 327.136 885.5887 1212.-7247 .22247 280.6 96 81.304 324.634 327.909 885.0444 1212.9534 .'22455 278.0 97 82.304 325.378 328.675 884.5052 1213.1802 .22667 275.4 98 83.304 326.114 329.433 883.9721' 1213.4051 .22883 272.8 99 84.304 326.845 330.186 883.4421 1213.6281 .23095 270.3 100 85.304 327.571 330.935 882.9144 1213.8494 .23302 267.9 101 86.304 328.291 331.678 882.3909 12I4.U689 .23510 265.5 102 87.304 329.005 332.414 881.8727 1214.28b7 .23717 263.2 103 88.304 329,714 333.145 881.3577 1214.5027 .23925 260.9 104 89.304 330.416 333.869 880.8481 1214.7171 .24132 258.7 105 90.304 331.113 ,334.587 880.3429 1214.9299 .24340 256.5 Its Appliances. TABLE No. 8. CONTINUED. The Properties of Saturated Steam. PRESSURE PER SQUARE INCH. Temp- erature in Fahrenheit Degrees. NUMBER OF BRITISH THERMAL UNITS IN ONE POUND FROM ZERO (FAHRENHEIT). Weight of On Cubic Foot of Steam in Decimals of a Pound. Number of... ' Cubic Feet of Steam from One Cubic Foot of Water. Total Pressure in Pounds from a Vacuum Pressure in Founds as Shown by Steam Gauge. Number of Units of Heat in> Water. Number of Fiats of Heat Required for Evaporation, Called Latent Heat. Total Number of Units of Heat Contained in Steam. 106 91.304 331.805 335.301 879.8400 1215.1410 .24547 254.3 107 92.304 332.492 336.009 879.8416 -1215.3506 .24754 252.2 108 93.304 333.174 336.714 878.8447 1215.5587 .24961 250.1 109 94.304 333.851 337.411 878.3542 1215.7652 .25168 248.0 110 95.304 334.523 338.105 877.8653 1215.9703 .25376 246.0 111 96.304 335.191 338.795 877.3789 1216.1739 .25582 244.0 112 97.304 335.854 339.479 876.8970 1216.3760 .25788 242.0 113 98.304 336.511 340.157 876.4198 1216.5768 .25994 240.1 114 99.304 337 165 340.832 875.9442 1216.7762 .26199 238.2 115 100.304 337.814 341.502 875.4721 1216.9741 .26405 236.3 116 101.304 338.459 342.169 875.0018 1217.1708 .26611 234.5 117 102.304 339.100 342.831 874.5352 1217.3662 .26816 232.7 118 103.304 339.736 343/488 874.0722 1217.5602 .27020 231.0 119 104.304 340.30.S :;44.i4i .873.5120 1217.7530 .27224 229.3 120 105.304 34U.995 b44.789 873.1555 1217.9445 .27428 227.6 121 106.304 341.618 345.432 872.7027 1218.1347 .27028 226.0 122 107.304 342.238 346.073 872.2508 1218.3238 .27828 224.4 123 108.304 342.854 346.709 871.8027 1218.5117 .28027 222.8 124 109.304 343.466 347.343 871.3553 1218.6983 .28227 221.2 125 110.304 344.074 347.972 870.9118 1218.&838 .28426 219.7 126 111.304 344.678 348.596 870.4721 1219.0681 .28625 218.2 127 112.304 345.279 349.217 870.0342 1219,2512 .28824 216.7 128 113.304 345.876 349.833 869.5983 1219.4333 .29023 215.2 129 114.304 346.459 350.448 869.1663 1219.6143 .29222 213.7 130 115.304 347.059 351.059 868.7351 1219.7941 .29420 212.3 131 U6.304 347.644 351.665 868-3079' 1219.9729 .29618 210.9 132 117.304 348.2^7 352.267 867.8836 1220.1506 .29816 209.5 133 118.304 348.806 352.867 867.4601 1220.3271 .30013 208.1 134 119.304 349.382 353.463 867.0397 1220.5027 .30209 206.7 135 120.304 349.954 354.055 866.6223 1220.6773 .30405 205.4 136 121.304 350.523 354.644 866.2068 1320.8508 .30601 204.1 137 122.304 351.089 355.230 866.7934 1221.0234 .30796 202.8 138 123.304 351.752 355.813 865.3820 1221.1950 .30990 201.5 139 124.304 352.211 356.392 864.9735 1221.3655 .31186 200.2 140 125.304 352.767 356.969 864.5661 1221.5351 .31386 199.0 141 126.304 353.319 357.541 864.1627 1221.7037 .31587 197.8 142 127.304 353.869 358.110 863.7613 1221.8713 .31788 196.6 143 128.304 354.416 358.677 863.3611 1222.0381 .31990 195.4 144 129.304 354.960 350.240 862.9640 1222.2040 .32190 194.2 145 130.304 355.501 359.801 862.5679 122 .'.3689 .32391 193.0 146 131.304 356.039 360.359 862.1740 1222.5330 .32592 191.9 147 132.304 356.574 360.913 861.7832 1222.6962 .32794 190.8 148 133.304 357.106 361.465 861.3934 1222.8584 .32995 189.7 149 134.304 357.635 362.013 861.U068 1223.0198 .33196 188.6 150 135.304 358.161 3t>2.559 860.6213 1223.1803 .33400 187.5 151 136.304 358.683 363.100 8bU2399 1223.3399 .33580 186.4 152 137.304 359.203 363.640 859.8588 1223.4988 .33761 185.3 153 138.304 359.721 364.177 859.4799 1223.6569 .33942 184.3 154 139.304 360.236 364.711 859.1031 1223.8141 .34123 183.3 155 140.304 360.749 365.243 858.7276 1223.9706 -.34304 182.3 156 141.304 361.260 36-3.773 858.3533 1224.1263 .34485 181.3 157 1-42.304 361.768 366.300 857.9811' 1224.281 1 .34666 1S0.3 158 143.304 362.273 366.824 857.6112 1224.4352 .34847 1 79.3 Steam Engine Indicator TABLE No. 8. CONTINUED. The Properties of Saturated Steam. PRESSURE PER SQUARE INCH. Temp- erature in Fahrenheit Degrees. NUMBER OF BRITISH THERMAL UMTS IN ONE POUND FROM ZERO (FAHRENHEIT). Weight of One Cubic Foot of Steam in Decimals of a Pound. Number of Cubic Feet of Steam from One Cubic Foot of Water. Yotal Pressure in Pounds from a Vacuum Pressure in Pounds as Shown by Steam Gauge. Number of Units of Heat in Water. Number of. Units of Heat Required for Evaporation, Called Latent Heat. Total Number of Units of Heat Contained in Steam. 159 144.304 362.776 367.347 857.2415 1224.5885 .35028 178.3 160 145.304 363.277 367.867 856.8740 1224.7410 .35209 177.3 161 146.304 363.774 368.383 856.5099 1224.8929 .35397 176.4 162 147.304 364.270 368.898 856.1461 1225.0441 .35585 175.5 163 148.3t>4 364.764 369.410 855.7846 1225.1946 .35773 174.6 164 149.304 365.255 369.920 855.4243 1225.3443 .35961 173.7 165 150.304 365.744 370.428 855.0654 1225.4934 .36149 172.8 166 151.304 366.232 370.934 854.7077 1225.6417 .36337 171.9 107 152.304 366.717 371.438 854.3514 1225.7894 .36525 171.0 168 L53.304 367.199 371.939 853.9974 1225.9364 .36714 170.1 169 154.304 367.680 372.437 853.6456 1226.0826 .36903 169.2 170 155.304 368.158 372.934 853.2942 1226.2282 .37092 168.4 171 156304 368.632 373.427 852.9461 1226.3731 .37272 167.6 172 157.304 369.105 373.918 852.5995 1226.5 175 .37452 166.8 173 15S.304 369.576 374.408 852.2533 1226.6613 .37632 166.0 174 159.304 370.045 374.895 851.9094 1226.8044 .37812 165.2 17-> 160.304 370.512 375.380 851.5670 1226.9470 .37992 164.4 176 161.3U4 370.978 375.865 851.2239 1227.0889 .38172 163.6 177 162.304 371.442 376.347 850.8833 1227.2303 .38353 162.8 178 163.304 371.904 376.827 850.5441 1227.3711 .38534 162.0 179 164.304 372.364 377.305 - 850.2062 1227.5112 .38715 161.2 180 165.304 372.822 377.781 849.8698 1227.6508 .38895 160.4 181 166.304 373.275 378.255 849.5347 1227.7897 .39077 159.7 182 167.304 373.731 378.727 849.201 1 1227.9281 .39259 159.0 183 168.304 374.183 379.197 848.8689 1228.0659 .39441 158.3 184 169 304. 374.633 279.665 848.5380 1228.2030 .39624 157.6 185 170.304 375.081 380.131 848.2086 1228.3396 .39807 156.9 186 171.304 375.527 380.595 847.8805 1228.4755 .39990 156.2 187 172304 375.971 381.056 847.5549 1228.6109 .40173 155.5 188 173.304 376.413 381.516 847.2297 1228.7457 .40356 154.8 189 174.304 376.853 381.974 846.9058 1228.8798 .40539 154.1 190 175.304 377.291 382.429 846.5844 1229.0134 .40722 153.4 191 176.304 377.727 382.883 846.2633 1229.1463 .40899 152.7 192 177.304 378.161 383.335 845.9437 * 1229.2787 .41076 152.0 193 178.304 378.593 383.785 845.6256 1229.4106 .41253 151.3 194 179.304 379.023 384.233 845.3089 1229.5419 .41430 150.7 195 180.304 379.452 384.679 844.9938 1229.6728 .41607 150.1 196 181.304 379.979 385.123 844.6801 1229.8031 .41784 149.5 197 182.304 380.305 385.567 844.3660 1229.9330 .41962 148.9- 198 183.304 380.729 386.008 844.0543 1230.0623 .42140 148.3 199 184.304 381.152 386.449 843.7422 1230.1912 .42318 147.7 200 185.304 381.573 386.887 843.4326 123031% .42496 147.1 2Q1 186.304 381.992 387.324 843.1234 1230.4474 .42667 146.5 202 187.304 382.410 387.760 842.8148 1230.5748 .42838 145.9 203 188.304 382.827 388.194 842.5076 1230.7016 .43009 145.3 204 189.304 383.242 388.627 842.2010 1230.8280 .43180 144.7 205 190.304 383.655 389.057 841.8969 1230.9539 .43351 144.1 206 191.304 384 066 389.485 841.5942 1231.0792 .43523 143.5 207 192.304 384.475 389.912 841.2921 1231.2041 .43695 142.9 208 193.304 384.883 390.337 840.9914 1231.3284 .43866 142.3 209 194.304 385.288 390.759 840.6933 1231.4523 .44039 141.8 210 195.304 385.671 391.179 840.3967 1231.5757 .4421 1 141.3 And its Appliances. 2 99 TABLE No. 9. The Properties of Water from 32 to 212 Fahrenheit. ELASTIC FORCE. Tem- perature in Fah- renheit Degrees. NUMBER OF BRITISH THERMAL UNITS IN ONE POUND FROM ZERO (FAHRENHEIT). Weight of One Cubic Foot of Vapor in Decimals of a Pound. Number cf Cubic Feet cf Steam from One Cubic- Foot of Water. Ja Pounds on the Square Inch. 1 11 1 nches of Mercury. Number of Units of Heat in Water Number of Units of Heat Required for Evaporation, Called Latent Heat. Total Number of Units of Heat Contained in Vapor. .089 .1811 32 32.000 1091.700 1123.700 .00030 208,080 .092 .1884 33 33.000 1091.005 1 124.005 .00030 200,480 .090 .1960 34 34.000 .1090.310 1124.310 .00031 193,180 .100 .2039 35 35.000 1089.615 1124.615 :00032 186,180 .104 .2121 36 36.000 1088.920 1124.920 .00033 179,380 .108 .2205 37 37.000 1088.225 1125.225 .00034 172,780 .112 .2292 38 38.000 1087.530 1125.530 .00036 166,380 ".117 .2382 39 39.001 1086.834 1125.835 .00038 160,230 .122 .2476 40 40.001 1086.139 1126.140 .00040 154.330 .127 .2573 41 41.001 1085.444 1126.445 .00042 148,620 .132 .2673 42 42.001 1084.749 1126.750 .COO 13 143,220 .137 .2777 43 43.001 1084.054 1127.055 .00045 138,070 .142 .2884 44 44.002 1083.358 1127.360 .00047 133,120 .147 .2994 45 45.002 1082.663 1127.665 .00049 128,370 .152 .3109 46 46.002 1081.968 1127.970 .C0050 123,840 .158 .3228 47 47.002 1081.273 1128.275 .00052 119,610 .164 .3351 48 48.003 1080.577 1 128.580 .00054 115,490 .170 .3478 49 49.003 1079.882 1128.885 .00056 111,470 .176 .3608 50 50.003 1079.187 1129.190 .00058 107,630 .1S3 .3743 51 51.004 1078.491 1 129.495 .00060 103,930 .190 .3883 52 52.004 1077.796 1129.800 .00062 100,330 .197 .4028 53 53.005 1077.100 1130.105 .00065 96,930 .205 .4177 54 54.005 1076.405 1130.410 .00067 93,680 .212 .4332 55 55.006 1075.709 1130.715 .00069 90,540 .220 .4492 56 56.006 1075.014 1131.020 .00071 87,500 .228 .4656 57 57.007 1074.318 1131.325 .00073 84,560 .236 .4825 58 58.007 1073.623 1131.630 .00076 81,740 .245 .5000 59 59.008 1072.927 1131.935 .00079 79,020 .254 .5180 60 60.009 1072.231 1 132.240 .00082 76,370 .263 .5367 61 61.010 1071.535 1132.545 .00085 73,810 .273 .5560 62 62.011 1070.839 1132.850 .00088 71,330 .1-32 .5758 63 63.012 1070.143 1133.155 .00091 68,940 .292 .5962 64 64.013 1069.447 1133.460 .00094 66,630 ."02 .6173 65 65.014 1068.751 1133.765 .00097 64,420 .313 .6391 66 66.015 1068.055 ] 134.070 .00100 62,290 304 .6615 67 67.016 1067.359 1134.375 .00103 60,280 !335 .6846 68 68.018 1066.662 1134.680 .00107 58,340 .347 .7084 69 69.019 1065.966 1134.985 .00111 56,470 ,359 .7330 70 70.020 1065.270 1135.290 .00115 54,660 .372 .7583 71 71.021 1064.574 1135.595 -.00119 52,910 -.385 .7844 72 72.023 1063.877 1135.900 .00123 51,210 r .398 .8114. 73 73.024 1063.181 1136.205 .00127 49,570 .411 .8391 74 74.026 1062.484 1136.510 .00131 48,000 .425 .8676 75 75.027 1061.788 1136.815 .00135 46,510 .440 .8969 76 76.029 1061.091 1137.120 .00139 45,060 .455 .9271 77 77.030 1060.395 1137.425 .00143 43,650 .470 .9583 78 78.032 1059.698 1137.730 .00148 42,280 .4sa .9905 79 79.034 1059.001 1138.035 .00153 40,960 .502 1 .023 80 80.036 1058.304 1138.340 .00158 39,690 .518 1.056 81 81.037 1057.608 1138.645 .00163 38,480 ;535 1.091 82 82.039 1056.91 1 1138.950 .00168 37,320 300 Steam Engine Indicator TABLE No. 9. CONTINUED. The Properties of Water from 32 to 212 Fahrenheit. ELASTIC FORCE. Tem- perature in Fah- renheit Degrees. NUMBER OF BRITISH THERMAL UNITS IN ONE POUND FROM ZERO (FAHRENHEIT). Weight of One Cubic Foot of Vapor in Decimals of a Pound. Number of Cubic Feet of S tea in rom O.ne cubic Foot of \N ater. In Pounds on the Square Inch. Iii Inches of Mercury. Number of Units of Keat in Water. Number of Units of Heat Required for Evaporation, Called Latent Heat. Total Number of Units of Heat Contained in Vapor. .553 1.127 83 83.041 1056.214 1139.255 .00173 36,1 'JO .571 1.163 84 84.043 1055.517 1139.560 .00178 S5,100 .590 1.201 85 85.045 1054.820 11C9.865 .00183 34,050' .609 1:240 86 86.047 1054.123 1140.170 .00189 33,030 .629 1.281 87 87.049 1053.426 1140.475 .00195 32,050 ,650 1.323 88 88.051 1052.729 1140.780 -.00201 31,100 .671 1.366 89 89.053 1052.032 1141.085 .00207 30,180 .692 1.410 90 90.055 1051.335 1141.390 .00213 29,290 .715 1.454 91 91.057 1050.638 1141.695 .00219 28,430 .738 1.500 92 92.059 1049.941 1142.000 .00226 27,600 .761 1.548 93 93.061 1049.244 1142.305 .00233 26,800 .785 1.597 94 94.063 1048.547 1142.610 , .00240 26,020 ,809 1.647 95 95.065 1047.850 1142.915 .00247 25,270 .834 1.698 96 96.0C8 1047.152 1143.220 .00254 24,540 .860 1.751 97 97.071 1046.454 1143.525 .00262 23,830 .887 1.805 98 98.074 1045.756 1143.830 .00270 23,140 .914 1.861 99 99.077 1045.058 1144.135 .C0278 22,470 .943 1.918 100 100.080 1044.360 1144.440 .00286 21,830 .972 1.977 101 101.083 1043.662 1144.745 .00294 21,210 1.001 2.037 102 102.086 1042.904 1145.050 .00302 20,620 1.031 2.099 103 103.089 1042.206 1145.355 .00311 20,050 1.062 2.163 104 104.092 1041. f -68 1145.660 .00320 19,500 1.094 2.227 105 105.095 1040.870 1145.965 .OC330 18,970 1.126 2^293 1C6 106.098 1040.172 1146.270 .00340 18,460 1.159 2.361 107 107.101 1039.474 1143.575 .00350 17,960 1.193 2.431 108 108.104 1038.776 1143.880 .00360 17,470 1.229 2.503 109 109.107 1038.078 1147.185 .00370 16,990 1.265 2.577 110 110.110 1037.380 1147.490 .00380 16,520 1.302 2.653 111 111.113 1036.682 1147.795 .00390 16,070 1.341 2.731 112 112.117 1035.983 1148.100 .00400 15,640 1.381 2.810 113 113.121 1035.284 1148.405 .00410 15,220 1.421 2.892 114 114.125 1034.585 1148.710 .00421 14,820 1.462 2.976 115 115.129 1033.886 1149.015 .00433 14,430 1.504 3.061 116 116.133 1033.187 1149.320 .00445 14,050 1.547 3.149 117 117.137 1032.488 1149.625 .00457 13,080 1.591 3.239 118 118.141 1031.789 1149.930 .00470 13,320 1.636 3.331 119 119.145 1031.090 1150.235 .00483 12,970 1.682 3.425 120 120.149 1030.391 1150.540 .00496 12,630 1.730 3.522 121 121.153 1029.692 1150.845 .00508 12,300 1.779 3.621 122 122.157 1028.993 1151.150 .00521 11,980 1.828 3.723 123 123.161 1028.294- 1151.455 .00535 11,670 1.879 3.826 124 124.165 1027.595 1151.760 .00549 11,370 1.931 3.933 125 125.169 1026.896 1152.065 .00563 11,080 1.984 4.042 126 126.173 1026.197 1152.370 .00578 10,800 2.039 4.153 127 127.177 1025.498 1152.675 .00593 10,530 2.096 4.267 128 128.182 1024.798 1152.980 .00608 10,265 2.154 4.384 129 129.187 1024.098 1153.285 .00624 10,010 2.213 4.503 130 130.192 1023.398 1153.590 .00640 9,760' 2.273 4.625 131 131.197 1022.698 1153.895 .00656 9,516 2.335 4.750 132 132.202 1021.998 1154.200 .00673 9,276 2.398 4.878 133 133.207 1021.298 1154.505 .00690 9,046 And its Appliances 301 TABLE No 9. CONTINUED. The Properties of Water from 32 to 212 Fahrenheit. ELASTIC FORCE. lem- perature in Fah- renheit Degrees NUMBER OF BRITISH THERMAL UNITS IN ONE POU.ND FROM ZERO (FAHRENHEIT). Weight Oi One Cubic Foot of Vapor in Decimals of a Pound. Number of Cubic Feet of Steam , from Ono Cubic Foot of V ater. In Pounds on the Square Inch. In Inches of Mercury. Number of Units of Heat in Water. Number of Units yf Heat Kequired tor Evaporation, Called Latent Heat, Total Number of Units of Heat Contained in Vapor. 2.461 5.009 134 134.212 1020.598 1154.810 .00707 8,826 2.526 5.143 135 135.217 1019.898 1155.115 .00725 8,611 2.594 5.280 136 136.222 1019.198 1155.420 .00743 8,401 2.663 5.420 137 137.227 1018.498 1 155.725 .00761 8,191 2.732 5.563 138 138.223 1017.797 1156.030 ,00780 7,991 2.803 5.709 139 139.239 1017.096 1156.335 .00799 7,798 2.876 5.858 140 140.245 1016.395 1156.640 .00819 7.613 2.952 6.011 141 141.251 1015.694 1156.945 .00839 7,433 3.029 6.167 142 142.257 1014.993 1157.250 .00860 7,258 3.108 6.327 143 143.263 1014.292 1157.555 .00881 7,088 3.188 6.490 144 144.269 1013.591 1157.860 .00903 6,920 3.270 6.657 145 145.275 1012.890 1158.165 .00925 6,755 3.353 6.827 146 146.281 1012.189 1158.470 .00948 6,595 3.438 7.001 147 147.287 1011.488 1158.775 .00971 6,440 3.526 7.179 148 148.293 1010.787 1159.080 .00993 6,290 3.615 7.361 149 149.299 1010.086 1159.385 .01016 6,144 3.707 7.547 150 150.305 1009.385 1159.690 .01040 6,004 3.801 7.736 151 151.311 1008.684 1159.995 .01064 5,867 3.896 7.929 152 152.318 1007.982 1160.300 .01089 5,734 3.992 8.127 153 153.325 1007.280 1160.605 .01114 5,604 4.090 8.329 154 154.332 1006.578 1160.910 .01140 5,477 4.191 8.535 155 155.339 1005.876 1161.215 .01167 5,353 4.295 8.745 156 156.346 1005.174 1161.520 .01194 5,232 4.400 8.959 157 157.353 1004.472 1161.825 .01222 5,114 4.507 9.178 158 158.360 1003.770 1162.120 .01250 5,000 4.617 9.401 159 159.367 1003.068 1162.435 .01279 4,888 4.729 9.629 160 160.374 1002.366 1162.740 .01308 4,779 4.843 9.861 161 161.381 1001.664 1163.045 ..01338 4,673 4.960 10.098 162 162.389 1000.961 1163.350 .01368 4,569 5.079 10.340 163 163.397 1000.258 1163.655 .01399 4,467 5.200 10.588 164 164.405 999.555 1163.960 .01430 4,368 6.324 10.840 165 165.413 998.852 1164.265 .01462 4,271 5451 11.097 166 166.421 998.149 1164.570 .01495 4,177 5.580 11.359 167 167.429 997.446 1164.875 .01528 4,085 5.711 11.627 168 168.437 996.743 1165.180 .01562 3,996 5.845 11.900 169 169.445 996.040 1165.485 .01596 3,910 6.981 12.178 170 170.453 995.337 1165.790 .01631 3,826 6.120 12.461 171 171.461 994.634 1166.095 .01667 3,744 6.262 12.750 172 172.470 993.930 1166.400 .01704 3,664 6.408 13.045 173 173.479 993.226 1166.705 .01741 3,586 6.555 13.345 174 174.488 992.522 1167.010 ..01779' 3,510 6.704 13.651 175 175.497 991.818 1167.315 .01817 3,436 6.857 13.963 176 176.506 991.114 1167.620' .01855 3,365 7.013 14.281 177 177.515 990.410 1167.925 .01894 3,295 7.172 14.605 178 178.524 989.706 1 168.230 .01934 3,226 7.335 14.935 179 179.533 989.002 1168.535 .01975 3,159 7.500 15.271 180 180.542 988.298 1168.840 .02017 3,093 7.668 15.614 181 181.551 987.594 1169.145 .02060 3,029 7.841 15.963 182 182.561 986.889 1169.450 .02104 2,966 8.016 16.318 183 183.571 986.184 1169.755 .02148 2,905- 8.194 16.680 184 184.581 985.479. 1170.060 .02193 2,846 302 Steam Engine Indicator TABLE No. 9. CONTINUED. The Properties of Water from 32 to 212 Fahrenheit. ELASTIC FORCE. Tem- NUMBER OF BRITISH THERMAL UNITS IN ONE PODND FROM ZERO (FAHRENHEIT). Weight of One Cubic Number *f Cubic IP' d perature Number Number of Total V;UU1O Foot of Feet of on the In Inches of in Fah- renheit Of Units of Heat in Units of Heat Required for Evaporation, Number of Units of Heat Vapor in Decimals Steam rom One Cubic 4 c Mercury. Degrees. Called Contained of a Foot of Inch. Water. Latent Heat. in Vapor. Pound. Water. 8.375 17.049 . 185 185.591 984.774 1170.365 .02238 2.789 8.558 17.425 186 186.601 984.069 1170.670 .02284 2^33 8.745 17.807 187 187.611 983.364 1170.975 .02331 2,678 8.936 18.196 188 188.621 982.659 1171.280 .02379 2,624 9.132 18.593 189 189.632 981.953 1171.585 .02428 2,571 9.330 18.997 190 190.643 981.247 1171.890 .02470 2,519 9.532 19.408 191 191.654 980.541 1172.195 .02529 2,469 9.738 19.827 192 192.665 979.835 " 1172.500 .02580 2,420 9.947 20.253 193 193.676 979.129 1172.805 .02632 2,372 10.160 20.687 194 194.686 978.424 1173.110 .02685 2,325 10.377 21.129 195 195.697 977.718 1173.415 .02740 2,279 10.597 21.579 196 196.708 977.012 1173.720 .02796 2,234 10.822 22.036 197 197.719 976.306 1174.025 .02853 2,190 11.051 22.502 198 198.730 975.600 1174.330 .02910 2,147 11.284 22.976 199 199.741 974.894 1174.635 .02967 2,105 11.521 23.458 200 200.753 974.187 1174.940 .03025 2,064 11.761 23.948 201 201.765 973.480 1175.245 .03083 2,024 12.006 24.446 202 202.777 972.773 1175.550 .031-12 1,985 12.255 24.953 203 203.789 972.066 1175.855 .03201 1,953 12.508 25.468 204 204.801 971.359 1176.160 .03261 1,916 12.766 25.992 205 205.813 970.652 1176.465 .03323 1,880 13.028 26.525 206 206.825 969.945 1176.770 .03386 1,844 13.295 27.067 207 207.837 969.238 1177.075 .03450 1,809 13.568 27.619 208 208.849 968.531 1177.380 .03516 1,775 13.843 28.180 209 209.861 967.824 1177.685 .03584 1,741 14.122 28.751 210 210.874 967.116 1177.990 .03654 1,708 14.406 29.332 211 211.887 966.408 1178.295 .03725 1,676 14.700 29.9218 212 212.900 965.700 1178.600 .03797 1,644 IN3DKX. PAGE A Absolute icforination from diagram, - 79 " pressure, ----- 21 Action of steam in cylinder, theory of - 137 " " li " jacketed cylinders, -141 Actual curves, ------ 105 Adiabatic curve, - ... I0 5 Adjuster for indicator cord, - - 31-72 Admission line, ------ 92 " " late, 150 " correctness of - - - i_;8 ' " method of determining the correctness of, 149-151 Amsler polar planimeter, - 198 meau effective pressure from, 198 Application of indicator, - - - - 35 Areas and circumferences of circles, 289 Areas of large circles, finding 294 Atmospheric line, - 75-91 " " tracing, - - - 75 Averager for measuring diagrams, - - 185 Available power, - 221 PAGE - 244. - 248 - 255 22-23-87 - 88 Back pressure, - - - - - . - 219 " cause- of excessive, - - 219 in condensing and non- condensing engines, 220-2-7 " loss from, - ... 219 total 22 " line, - 22-94 Blanks, example of printed, 78 Boiler pressure, ------ 21 Boilers, testing, - 277 Calculating water consumption by con- stant, 165 Care and use of indicator, - - 68 Carrying pulleys, - - 71 Calorimeter tests, manner of making, - 248 " rule, for computing, - 251 Calorimeters, differer.t kinds, - Calorimeter, description of barrel, Trof. Carpenter's, Clearance, - " estimating, " percent. ..... 23 " the effect of 219 line. ...... 87 " locating, ... - 88 Close agreement of the actual with the isothermal in jacketed cylinders, 143 Coffin averager, ..... 1^5 " construction of, - - 186 " " finding the mean effect- ive pressure with - 188 principle of operation of the ... 190-197 Compression, ------ 22 " and clearance, - - .?.-<) " . curve, - - - -." - 95 Comparison of diagrams from throttling and cut-off engines, - - - ?oi Comparison of results between large and small clearance, .. . . 227 Condensing engine diagrams, - 266-267 Condensing and non-condensing dia- g ams compared, - ... 227 Condensation in cylinders, - - - 138 loss from - 142 Condenser, effect of adding - 214 " pressure in - - 214 Condensation in unjacketed cylinders, - 139 Cock, three way ----- 30 " section of three way 31 Cord, indicator, ----- 72 " adjuster ------ 31 " stretching of the - - - - 72 Computing horse po\ver, - 112 Computing steam accounted for by the in-'icator, different methods of 152-157 Combining diagrams, methoJ of - 229-233 Irom compound engines, - - 228 304 Index. PAGE Compound condensing engines, dia- grams from, .... 261-268 Curves, theoretical or isothermal - - 97 " agreement of actual and theo- retical expansion, ... 106 Cut-off, the point of - - - - 93-213 " locating the point of - - 108-111 " the best point to - - - - 214 Data necessary, 77 " how to preserve 77 Description of indicator, i^ Device, indicator testing, - - - - 175 Diagrams, indicator - - - - - 16 the information to be derived from - 79-82 " from Marsh steam pump, - 274 combining, - - - - 228 Diagram, essential features of a well- formed ----- 84 lines and points of the 91 Diagrams, to take simultancusly ( 3 the outline of - - - 83 engine underloaded - - 117 not desirable - 123 reidingthe .... 146 Diagram representing the economy of high pressure - - - - 211 Diagram showing the most favorable point of cut-off - 216 Diagram from a steam jacketed cylin- der, - 143 Diagrams from both euds of a cylinder, 85 Diagram, good features of a - - 80 Diagrams, measuring a large number of 185 Diagram, mmes of the lines of the 91-95 .Diagrams, study of - - - - -83 method of taking 75 from pumps, - 272-273 Diagram averager - 185 Diagrams from various engines, - 258-267 Diagrams to show the effect between large and small clearance, - 219226 Diagrams from fteani cylinder and ammonia compressor, - - 239-240 Diagrams from gas engines, - - - 241 " from oil engines, ... 242 miscellaneous, 2 8-267 Directions for indicating, ... 75 Driving gear for fndicator, 54 Drum motion, testing accuracy of - 52 Drum stop motion, - ... 61-62 Drum spring, 74 E PAGK Economy in the use of steam - 282 " of expansion, - - 123-125-208 " heating feed water, - - 284 " high pressure, ... 209 " steam engine ... - 275 Engines, testing 282 " compound ----- 267 " comparison of diagrams from throttling and cut-off - 202-207 Essential features of diagrams, - - 84 Exhaust-closure, - .... 94 Exhaust-closure, early and late, - - 219 Exhaust, heat lost at .... 210 Exhaust-line, .... , - 93 Exhaust-valve, leaky - - - - 148 Expansion of steam, - - - - 119 " line or curve, - 93 ratio of ----- 130 " initial - 22 " curve, peculiarities of 83 line, and leaky valves, - - 147 curve, agreement of actual and theoretical - 143-145 curve, geometrical method of finding points in the - 101 Experiments to determine the most favorable point of cut-off, - - 215 Feed-water, economy of heating - - 284 Feed-water accounted for by the indi- cator, ...... 152 Footpound, - - - - - -112 Friction, effects of ----- 179 " of indicator piston - - - 181 " " " " how to de- termine ----- 182 G Gases, Mariotte law concerning - 97 Gas engines, diagrams from - 240-241 Gauge or boiler pressure, 21 Guide or carrying pulleys, - 71 Guide pulleys, disadvantages of .. 71 Gas and oil engine diagrams - - 234 II Heat lost, - 214 " available .... - 210 " latent .... 20 44 1 cf of f* ViailQf - - 210 " sensible .... - - 20 Index. 30$ PAGE Heat units .=._-. 2 o High pressure, economy of 209 High speed diagram compared with moderate speed, ... 267-268 High ?peed engines, manner of using the cord o-.i ..... 51 Holes in cylinder, position for indi- cator, 36-37 Hooking the cords, 51 Horse power, elements of ... 112 " " finding the - - 112 " for one pound mean effective pressure, - - 113 " " indicated 21 " " net 21 " " factors for .... 113 " byordiuates ... 114 Hyperbolic logarithms, - - - - 128 curve ..... 97 " logarithms, table of - - 129 I Indicator, brief history of the n Watts' original - - - n " construction of n " McNaught 12 description of - 13 " pirts of ----- 14 " size of piston of 14 " purpose of the 16 " care required in the use of - 68 Tabor .... 24-25 construction of parts of - 24-30 oiling the - 68-183 " scales .... 73-87 springs .... 32-33-34 to use 73 '' appliances, cuts of - - 44-53 " electrical appliance - - 65 testing devise, ... j-^ " construction of 176 manner of using 176 information de- rived from - 1 80 reducing gear, 54 ' parts of - 55-57 1 directions for using - 58^60 " cord -...._ 72 " adjuster - 31 driving gear - . - - 5^ how to attach the 75 piston, the effects of momen- tum of PAGE Indicators, using one or two - - 30-77 Indicator diagrams, the production of 17-86 explanation of 17-18-19 " cylinder, warming up - - 75 " card, proportionate length of 38 diagrams from various engines 257 " piston, effects of a tightly fitting ..... !8 2 Initial expansion, ..... 55 Initial pressure, .... 92-213 Isothermal curve^ ..... 97 " locating points on the 98 " geometrical method for constructing the 101 Jacketing, cylinder, Latent heat, - - - 20 Lazy tongs, 39~4O " " proportion of - - 40-41-42 Leakage - - - - 79 Leaky Valves, detecting by the indicator 106 Length of diagrams, - - 38 Levers, reducing - 46-49 Locating clearance line on diagram, 88 " point of cut-off - - 108-111 Long indicator pipes, - - 37 Management and care of indicator, - 63 Mariotte law of gases, - - - 97 Manner of taking diagrams, - - 75 Marsh steam pump diagrams, - - 274 Mean effective pressure, - - 22-95 computing - 117 " " '* measuring by ordinates the 114 Mean effective pressure, horse power for one pound, - 113 Mean pressure of expanding steam, the rule for finding the - - 130-131 Measuring diagrams, - - - 114 Memoranda of diagrams, making - 77 Method of indicating a steam engine - 75 " " computing horse power, 113-114 Moisture in steam, - - - - 244 Motion, Watts' parallel - - 14 " straight line - - 15 " drum - 16-70 Movement of pencil, - - - 16 306 Index. O PAGE -243 68-183 Oilengines, operation of - Oil engine diagrams, Oiling the indicator, - Ordinates, horse power by - JU " different methods of measur- ing the - 116-117 Paper-drum, Pautagraph " adjusting the - Parallel motion, Watts Parallel or straight Hue motion, - Pencil, adjusting the Pencil movement, proportioning of Pendulum reducing gear, - Piping for indicators, . Planimeters, " Amsler polar PlanimeteY, measuring mean tffect pr-ssure by the Point of cut-off, " " exhaust, - Pressure, ab-olute - back " boiler " initial - " mean effective - " of expanding steam " of expanding steam, rule finding the " terminal - " total back " lor indicator springs - Priming, extent of Printed blanks, Pulleys, carrying - Pump diagrams, - B Ratio of expansion, - T 3 Reducing levers, - - 47 Reducing gears, different kinds of 50-53 Re-evaporation, - - - - 138 Resistance to motion of the piston of a steam engine, - 219 Rule for finding the mean pressure of expanding steam, - - 16 44-45 - 45 - 14 - 15 69-70 :5-36 47-49 - 36 - 184 - 198 ive - 184 93-213 - 93 21-22 - 219 21 21 22-95 - 1^3 for 130-131 - 22 - 22 - 73 - 244 - 78 - 71 272-273 Safe pressure for indicator springs, Saturated steam, PAGE Scales, indicator - - - - 73 Seusib e heat, - - - -20 Serrated line.s of the diagram, - - 181 Specific heat, - - - - 20. Spring-;, how maikt d, - - - 73 Spring t> use. proper - - - 73 Springfield gas engine diagrams, 237-238 Steam, d r y - - - - - 21 " expansion of 119 11 li ic - - - - 92 " exhau ted per hour, - - 152 " line, straight - 209 " per horse power per hour - 152 " jacketed cylinders, diagrams from - - - 14? " pressure of expanding - - 123 '" pipe, large and small, - - 79 *' pressure, working with hiyh a. >d low, - - 208 " properties of saturated - - 295 " saved in clearance, - - IQJ " buperheated, - - --21 " or water consumption, - 2$ ' admission of - - 84 " connections for indicators, - 3> " in cylinders, (action of) - - i 57 " accounted for by the indicator, - 152 " valve, leaky - - 79 Tabor indicator, - 24-25 " with reducing motion andpaits, - 54-57 i " with electrical attach- ment - - -65 with combined pistons, 255 Table of hyperbolic logarithms - - i2j " showing the theoretical economy of using steam expansively, - 132 " of constants for finding the average pressure with any pressure of steam, - 134 *' of average pressure of steam in the cylinder with different rates of expansion, - - - - '35 " quantity of steam accounted for by the indicator. - 170-171 " slowing saving effected by the use of feed-water heateis, - - 286 " areas and circumferences of circles 2^ " properties of saturated steam, - 2 95 " properties of water, - - 2 99 Technical terms. - - 20-21-22-23 Terminal pressure, - - 95- I 47- 2 75 Index. 307 PAGE - 147 - 147 - 277 277 279 102 Terminal pressure, cause of high - " " theoretical - - Tests, different methods of making - " what should be noted in making, Testing engines and boilers, - - Theoretical curve, object of drawing the " " points from which to draw the - - 98 " " reasons for establish- ing the - - 103 Theoretical diagram, - 120 economy of expansion, 126-133 Three-way cock, - 30 u Underloaded engines, - - 116-212 Unit of heat, " - - 20 " " work, - - - - 20 Uses to which the indicator may be applied, - . 79 Vacuum-line, establishing Valves, adjusting " detecting leaky Valve lap, " lead, ... " gear, incorrect, w Watts' original indicator, . " parallel motion, Water consumption, making allowance for 41 per horse power per hour Wiredrawing - Work and heat - " in the two ends of the cylinder " the unit of Zero line, PAGE ' 8 7 - 80 - 79 - 23 - 23 - 82 ii 14 164 152 23 210 83 20 ADVERTISEMENTS. A dvert isemen ts . THE CONSOLIDATED SAFETY VALVE GO, MANUFACTURERS 'OF 50LID NICKEL 54FETY VALVES, WATER RELIEF VALVES, CYLINDER RELIEF VALVES. OFFICE 1 M> SALESROOMS: 85, 87, 89 LIBERTY STREET, - - NEW YORK. Advertisements. N. L. HAYDEN, Pres. J. N. DERBY, Vice-Pres. M. LUSCOMB, Secy, and Treas. THE HAYDEN & DERBY M'PG. Co., SOLE MANUFACTURERS METROPOLITAN INJECTORS Send for Catalogue. HIGH GRADE. RELIABLE. DURABLE. METROPOLITAN AUTOMATIC INJECTOR. H. D. ELECTORS DELIVERY ^SUCTION Oo**v EYING H/IQUIDS or* OFFICE AND SALESROOMS: No. 85, 87, 89, LIBERTY STREET, - NEW YORK A dvertisements. THE ASHGROFT MANUFACTURING GO, MANUFACTURERS OF THE THBOQ ENGINE Coffin Averagers, Amsler Planimeters, Lazy Tongs and Pantographs, Carrying Pulleys, Three Way Cocks, Straight Cocks, etc., etc. OFFICE AND SALESROOMS : 85, 87, 89 LIBERTY STREET, - NEW YORK. Advertisements. THE QUEEN MERCURIAL PYROMETER For Stack Temperatures. Sensitive and Accurate. THE QUEEN FEED WATER THERMOMETER. STANDARD THERMOMETERS For All Mechanical Purposes. QUEEN * CO., INC., Electrical 1 Scientific Instrument Works, 1010 CHESTNUT STREET, PHILADELPHIA, PA. Ill I MOST HI silt lltl.r GAR High Grade Packings Elastic Ring:, Sectional, Spiral and Special Water Packings for Steam, Water, Gas, Ammonia, etc. Waterproof Hydraulic Packing. High Pressure Packing. THE GA^IOCK PACKING @. NONE GENUINE NEW YORK ^^SS^^ PlTTSBURG BOSTON ^JiBliBS^fefc CLEVELAND CHICAGO ^^|| m^ DENVER PHILADELPHIA ST. LOUIS WITHOUT IT. MAIN OFFICES AND FACTORIES: IMtMYRA, X. Y. ROME. GA. Advertisements. Established 1865, by Frederick Keppy. 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Being a comprehensive treatise for the use of Constructing, Erecting and Operating Engineers, Superintendents, Master Mechanics, Students, etc., describing in a clear and concise manner the Practical Application and Use of the Steam Engine Indicator, with many Illustrations, Rules, Tables and Examples for obtaining the best results in the Economical Operation of all classes of Steam, Gas and Am- monia Engines together with original and correct information on the Adjustment of Valves and Valve Motion, Computing Horse Power of Diagrams, and extended instructions for Attaching the Indicator. Its Correct Use, Management atid Care, derived from the author's practical and pro- fessional experience extending over many years, in the Construction and Use of the Steam En- gine Indicator, by WILLIAM HOUGHTALING. 300 pages, nearly 150 engravings, 20 full page tables, handsomely bound in silk cloth PRICE $2.OO MODERN EXAMINATIONS Off STEAM ENGINEERS, by W. H. WAKEMAN. Size 6x9. inches, 272 pages, clotn. Contains 300 quest ions with answers, likely to be asked when you take an examination for License. This book has been especially written for Engineers and Hiremen who are preparing to take an examination for U. S. Government or State License, and gives in a plain practical way just what you must know before you can hope to obtain a license. PRICE $2. STEAM BOILER CARE AND MANAGEMENT, by FREDERICK KEPPY, M. E- Being useful, common sense information on the Practical and Safe Operation of Steam Boilers on Land and Sea. Intended for the Use of Engineers, Firemen and Steam Users. Pamphlet, 48 pages, size 6x9 inches. PRICE 25 Cents. HANDBOOK OF CORLISS STEAM ENGINES, by F. W. FHILT.ITTO. JR. , describing in a comprehensive manner the Erection of Steam Engines, the Adjustment of Corliss Valve Gear and the Care and Management of Corliss Steam Engines ; with full page illustrations and complete descriptions of the leading Corliss Engines Illustrated by 64 original engravings, 224 pages, handsomely bound in green silk cloth. PRICE $1.0O. PRACTICAL GUIDE FOR FIREMEN, or Instructions and Suggestions for the Care and Management of Steam Boilers, Pumps. Injectors, etc., by W. H. W \KEMAN. This book is purely an elementary treatise and is intended to give the Duties of the Firemen, or the one in charge of a Steam Plant, in as simple and concise a manner as possible, and to furnish all the information required to enable them to take charge cf, and operate a Steam Plant successfully and economically. 80 pages, 4x6^ inches, 14 illustrations, cloth. PRICE 75 Cents. TUB ENGINEER'S MANUAL. Containing a vast amount of practical information which comes into daily use in the Boiler and Engine Room The works treats on Engines and Boilers, Pumps and Pumping Machinery, together with Safety Valves. Injectors, Steam Appliances, etc. Also contains valuable Rules and Tables, necessary for use of Engineers and Firemen. Second edition, 121110, cloth, postpaid. PRICE 5O Cents. THE DESTRUCTION" OF STEAM BOILER3. Being a practical treatiseon the Destruction of Steam Boilers from the Effects cf Incrustation and Corrosion, with Simple Methods for Pre- venting the same etc By W. H. WAKEMAN. Pamphlet 6x9 inches, illustrated PRICE 25 Cts. REFRIGERATION AND ICE MAKING AND REFRIGERATING MACHINERY. Being a practical treatise on the Construction, Operation and the Care and Management of Refriger- ating Machinery. By W. H. WAKEMAN. Pamphlet 6x9 inches, fully illustrated. Numerous valuable tables, etc. PRICE 25 Cents. REFRIGERATING MACHINERY, by GEORGP: RICHMOND. M. E Containing the gen- eral principles of Refrigerating and Ice Makine Machinery. A small book with a large amount of useful information. Pamphlet form, 7x10 inches. PRICE 2O Cents. DYNAMOS, by F. S HUNTING. Being a practical explanation of the Construction, Oper- ation, Maintenance, Care and Management of Dynamos. 161110, paper, 26 illustrations. PRICE 25 Cents. AMERICAN ENGINEERING is owned, edited and published by Engineers, working En- gineers write the leading articles. Its editor, W. H. Wakeman. the well known Engineer and Mechanical writer, needs no introduction at cur hands and should be a sufficient guarantee that the reading matter will not be excelled by any publication of its class. Published monthly at the low price of 50 cents per year. Sample Copies Free. Any of the above books will be sent by mail postpaid on receipt of price or the entire ten books and one year's subscription to AMERICAN ENGINEERING, will be sent on receipt of $6 25 The American Industrial Publishing Co., .S A. A dvertisements. HAND BOOK OF CORLISS STEAM ENGINES DESCRIBING IN A COMPREHENSIVE MANNER The Erection of Steam Engines, The Adjustment of Corliss Valve Gear and the Care and Management of Corliss Steam Engines. By FRA.NK WILLIAM SHILLITTO, Jr. Illustrated by 64 New and Original En- gravings, prepared expressly for this work. In One Volume 16mo. 224 Pages. Cloth, 31.OO. Cloth, pocket-book form with red edges, $1.5O. Russia Leather, pocket-book form, gilt edges, $2.OO. A thoroughly practical treatise on the Corliss Engine, covering every necessary point in re- gard to this class of engines from the preparation of foundations to the proper care and manage- ment and operation after they are set up ready for running. Part I contains eight chapters on Setting Up Engines, giving full instructions on Preparing Foundations, Reference Lines for Lo- cating the Engine, Templates, Placing Main Parts in Position, Lining and Levelling, Assembling the Moving Main Parts, etc., etc. Part II contains 21 chapters on Valves and Valve Gears, fully explaining how to set them ; Dash Pot Rods, the Eccentric, Rocker Arm, Reach Rod, Centering the Engine, Setting the Eccentric, Adjusting the Governor, Indicator Diagrams, a Few Pointers from the Author's Experience, the Double Ported Valve and Long Range Cut Off, Tables and Memoranda, and complete descriptions of the leading types of Corliss Engines, with full page illustrations of same. Large descriptive circular will be sent free on application. COMMENTS OF THE MECHANICAL PRESS. The work should prove particularly valuable to engineers without experience in Corliss -engine work. Electrical World. The book is recommended as being well worth the price to any engineer not already well posted on these subjects. National Engineer. The book will be found particularly useful to young engineers who wish to become thor- oughly familiar with Corliss valve gear and its adjustment. Home Study. The language is clear, and the cuts are well chosen, and the book should be of value to an erecting man as well as to the engineer in charge of engines of this type. Power. The book should prove a useful one to any erector or operator of Corliss engines. It is plainly and clearly written and the illustrations are well chosen. American Machinist. A modest little treatise on how to set and run a Corliss engine, with more solid meat in it than is often found in many larger volumes. Mining and Scientific Press, San Francisco, Cal. The language is clear and concise and free from unnecessary technicalities * * * The work should be of value to many others than the younger engineers, whose advancement and welfare is its main purpose. Tradesman. The matter is well arranged, is compact and to the point, and is illustrated whenever illus- trations will assist in elucidating the subject matter in hand. American Miller. This book i-5 by a practical man * * * It cannot be doubted that every engineer would be the gainer b}' learning so much of this branch of the business as is contained in this little book. The chapter on valve adjustment will be valuable to mechanic and engineer alike Machinery, J\'ew York. This is a splendid elementary treatise on the Corliss engine, giving the practical man in the engine room as well as the student in engineering a good working knowledge of the Corliss engine and how to manage and take care of it. The book is well printed, illustrated and bound, and contains a very complete index. Electrical Engineer. The book will be found of great value to old engineers as well as younger ones. It should rind a place in every mechanic's library. Engineer's List. It is a book which no engineer should wish to be without. The Engineer. THE AMERICAN INDUSTRIAL PUBLISHING CO., BRIDGEPORT, CONN., U. S. A. Advertisements. Universally acknowledged by engineers as the best and most complete book on the subject. Recognized both by Applicants and Ex- aminers as the standard work in examinations. 1O,OOO copies sold. Third edition now ready. THEN STUDY THE Modern Examinations of Steam Engineers. By W. H. WAKEMAN. 53 Chapters of Reading Matter fully ANSWERING 300 PRACTICAL QUESTIONS about Engines, Boilers. Safety Valves, Belting, Shafting, Steam Heating, etc., etc. A GOOD BOOK OF REFERENCE Fully Indexed and Illustrated. Just the thing to have at hand -when you -want to find something in a hurry. Size 6x8 inches, 272 pages, handsomely bound in cloth. PRICE, $2.00, POSTPAID. THIS book has been especially written for Engineers, Firemen and all others who are preparing to take an examination for U. S. Government or State license where such licenses are required, and give in a plain, practical way just what you must know before you can hope to obtain a license It is divided into 53 chapters, which, after giving a general outline of the requirements for the several classes of licenses, take up the various parts of the steam plant which are treated from a practical standpoint. Beginning with the steam engine, the valves are first discussed and the following twelve chapters explain in a clear manner the various parts of an engine, how they should be designed, adjusted, etc., and also the vaiious types of engines. This part of the book contains num- erous numerical examples of the calculations of various- parts, horse-power, weifht of fly-wheels, and other es- sential factors of an engine, which puts the subject be- fore the reader in a manner that is easily undei stood. Under the subject of boilers, the safe working pres- sure, strength of seams, bracing and other requirements are treated and mathematical examples are given. After covering the subject of piping, exhaust steam heating, strength of materials and other allied subjects, the book concludes with 300 practi- cal questions in regard to the matter contained in the text, with references to the pages where the answers are to be found. THE AMERICAN INDUSTRIAL, PUBLISHING CO., PUBLISHER?, BOOKSELLERS AND IMPORTERS, BRIDGEPORT, - - CONN., U. S. A. UNIVERSITY OF CALIFORNIA LIBRARY BERKELEY Return to desk from which borrowed. This book is DUE on the last date stamped below. JAN 26 NOV 3 - 1949 OCT 24! LD 21-100m-9,'47(A5702sl6)476 YC 33279 7357G1 Engineering Library UNIVERSITY OF CALIFORNIA LIBRARY