LIBRARY OF CONGRESS, V Chap. Copyright No... Shelf.......:... i UNITED STATES OF AMERICA. >* H GO W > o u o A HANDBOOK OF ENGINEERING LABORATORY PRACTICE. BY r RICHARD ADDISON SMART, M.E., Associate Professor of Experimental Engineering, Purdue University. FIRS T EDITION. FIRST THOUSAND. <* i % • r/ y» <• NEW.Y0R.K*- / JOHN WILEY & SONS. London: CHAPMAN & HALL, Limited. 1898. 16845 Copyright, 1898, BY RICHARD A. SMART. ¥ ^ TWO COPIES RECEIVED. ROBERT DRUMMOND PRINTER, NEW YORK. 18 - . PREFACE THIS volume is intended primarily as a manual for the use of students in the routine of experimental wc>rk in Steam-engineering, Strength of Materials, anil Hydraulics. It may also serve in a limited way as a guide to those engineers in active service whose familiarity with the ordinary methods of testing is limited. The chief object in view has been to provide in convenient form such directions for the conduct of the various tests and experiments comprising the course as the student will need to enable him to take charge of and conduct the particular work assigned him in an intelligent manner and with little delay. With a large class of students beginning a variety of experiments at the same time it is essential that the directions be such as to make each student or group of students as nearly self-directive as possible. No attempt has been made, therefore, to preface the consideration of the subject from an experimental standpoint with an exposition of the theoretical con- siderations involved; it is assumed that the class-room work, which should be carried on in connection with VI PREFACE. that of the laboratory, will supply the theoretical in- struction. The methods of testing described under the various general heads are not intended to cover the subject in an exhaustive way. Only such tests have been described as may be carried on in connection with the complement of apparatus to be found in the better equipped laboratories of experimental engineering, and the methods explained are those which the author has found to be most easily employed in every-day prac- tice. Both the manner of arranging apparatus and the method of conducting the tests are capable of great variation to suit the needs of special investigations. Since the equipment of the majority of engineering laboratories does not permit all the students in a class to take up the course of experiments and tests in the same order, it becomes necessary to make the direc- tions for the various tests complete in themselves and avoid, so far as possible, reference to tests described in preceding sections. This necessitates the occasional repetition and duplication of directions which occur in the volume. Acknowledgment is hereby made of thanks due to Prof. W. F. M. Goss, for valuable assistance in the preparation of the volume; to Prof. W. Kendrick Hatt, who assisted in the preparation of the chapter on Strength of Materials; to Mr. C. H. Robertson, and to others who have aided in the completion of the work. R. A. SMART. Lafayette, Ind. Sept. i, 1S98. TABLE OF CONTENTS PAGE CHAPTER I. Introduction i CHAPTER II. Elementary Measurements 4 CHAPTER III. Measurement of Liquids 21 CHAPTER IV. Measurement of Gases 29 CHAPTER V. Measurement of Pressure 33 CHAPTER VI. Measurement of Temperature 40 CHAPTER VII. Calorimeters 47 vii Vlll TABLE OF CONTENTS. CHAPTER VIII. PAGE Measurement of Power 55 CHAPTER IX. Strength of Materials 70 CHAPTER X. Steam-boiler Testing 123 CHAPTER XI. The Steam-engine Indicator 139 CHAPTER XII. Steam-engine Testing 165 CHAPTER XIII. Testing of Hydraulic Machinery 224 CHAPTER XIV. Miscellaneous Tests 236 APPENDIX. Tables, etc 257 Index 277 ENGINEERING LABORATORY PRACTICE. CHAPTER I. INTRODUCTION. 1. The Laboratory Course. — The course in labo- ratory practice in Engineering is designed to familiar- ize the student with processes of investigation, to give experience in the conducting and reporting of experimental engineering work, to secure data which shall verify and supplement theoretical instruction, and to give a practical knowledge of the construction and management of machinery and apparatus. 2. Method of Instruction. — The method of in- struction should be such as will throw the investi- gator, as far as is practicable, on his own resources, giving only such directions as are necessary to facili- tate the work and secure uniformity of results. Since the working up of the data obtained is an extremely important part of the work, it is desirable that this be done under the immediate direction of the instructor. The time required to work up the data and prepare the report should be considered when grading the reports, in connection with the accuracy of the results and the proficiency shown in the con- 2 ENGINEERING LABORATORY PRACTICE. duct of the test and the management of the ap- paratus. It will be found convenient to record the dimensions and constants of the various pieces of laboratory apparatus in a book which may be kept at hand for convenient reference. This book will be referred to in what follows as the " Commonplace- book." 3. Care of Apparatus. — One mark of a good en- gineer is the care which he exercises in handling ma- chinery. While to the beginner the apparatus may all be new, a little care and close observation will en- able him to become familiar with its operation. The student should be held responsible for all apparatus, both large and small, which is placed in his charge and should see that small apparatus issued to him is returned immediately after the test. He should always leave such apparatus in good order. 4. Keeping the Records. — It is important that all original data be preserved. To this end, the record of observations should be kept on a prepared " Running Log" which may be handed in with the report. When the Running Log is kept by one man and the observations are taken by another, such observations should be handed to the log-keeper as soon as taken. In some cases it may be found convenient to have a number of logs, kept by different men. In such cases they should be signed, dated, and handed to the principal log-keeper immediately after the test. 5. Reports. — The reports should be made out in ink, except the portion which is made during the con- duct of the test. Where one experiment is assigned to two or more men, one report, bearing the signature of each man, should be handed in. INTRODUCTION. 3 6. Graphic Presentation of Results. — Reports of tests intended to show the relation of one variable factor to another should generally be accompanied by a curve, or set of curves, having the various values of the dependent variable as ordinates. The scale chosen should be such as to make the curve as large as will go on the piotting-paper furnished. It is generally best to connect the several points found by a straight line, instead of attempting to draw a smooth curve through them. The points from which the curve is located should be indicated by a suitable sign, and the scale of the ordinates and abscissae should be clearly indicated on their respective axes of coordinates. It may some- times be found desirable to plot several curves on one sheet to facilitate comparison. CHAPTER II. ELEMENTARY MEASUREMENTS. 7. Measurement of Time. — In the conduct of ordinary tests, such as those of engines, boilers, pumps, etc., the measurement of time should be made with the second-hand of a watch. In order to avoid confusion the second-hand should point to zero when the minute-hand is on the even minute ; otherwise the test might be started with the second-hand at zero and end with the minute-hand at zero, thus making an incorrect time-reading. In all important tests two or more watches should be made to correspond exactly, or their difference noted, before the test is begun, so that if one watch stops the time-reading may not be lost. Time-signals. — Signals are usually given by bell or whistle. The following is a convenient arrangement: thirty seconds before the time for taking observations three warning signals are given; ten seconds before the time two warning signals are given; and at the exact time one signal is given, at which the observa- tions are taken. Stops. — In case it is necessary to stop an engine-test between gongs, note the exact time that the stop is made and indicate the same on the Running Log. Note the time the engine starts again and ring the 4 ELEMENTARY MEASUREMENTS. 5 next gong at such a time after the start that the elapsed time between the previous gong and the stop, plus the elapsed time between the start and the sub- sequent gong, shall just equal the ordinary running time between gongs. 8. Measurement of Speed. Speed-counters. — The simplest instrument for the measurement of speed is 6 ENGINEERING LABORATORY PRACTICE. the speed-counter, one form of which is shown in Fig. i. They are made in many different forms, some with one and others with two dials. Those provided with rubber tips for contact with the shaft are especially recommended. When well made they are reliable for speeds as high as two or three thousand revolutions per minute. 9. Revolution-counters. — This instrument, shown in Fig. 2, is largely used where special accuracy is required or where it is desirable to make a more per- manent arrangement for speed measurement. The majority of such instruments are not accurate above 300 or 400 revolutions per minute. 10. Tachometers. — The tachometer is an instru- ment for measuring rate of speed. It is usually per- manently connected to the shaft or pulley whose speed is to be measured. An instrument of this type is the Boyer speed-recorder (Fig. 3), which is exten- sively used in railway service. The drum upon which the record-paper turns is actuated directly by the driving mechanism and moves in proportion to the distance passed over or to the number of revolutions. The pencil which produces the record is actuated by a rotary pump connected with the driving mechanism and so constructed as to raise the pencil an amount proportional to the rate of speed. The gage, which is in cord connection with the pencil-motion, gives a visible indication of the rate of speed. Fig. 3^ is a detail view of the drum mechanism. 11. Measurement of Areas. The Polar Planim- eter. — The planimeter is an instrument for finding the area of any plane figure. The form in common use was invented by Amsler and exhibited by him at ELEMENTARY MEASUREMENTS. Fig. 2.— Crosby Revolution-counter. Fig. 3. — Boyer Railway Speed-recorder. 8 ENGINEERING LABORATORY PRACTICE. the Paris Exhibition in 1867. It consists of an arm EP (Fig. 4) to which is pivoted a second arm EF Fig. 3a. — Details of Mechanism. carrying a record-wheel D and a tracing-point F. When in use the point P is fixed and the point F is Fig. 4. — Polar Planimeter. moved by hand around the outline of the figure whose area is desired, in the direction of the hands of a watch. The rotation of the record-wheel D is propor- tional to the area circumscribed, which is shown by ELEMENTARY MEASUREMENTS. 9 the graduations on the wheel to a given scale. The wheel may lie at D or on an extension of the arm EF, beyond the point E, the mathematical conditions being the same in either case. For the purpose of the following demonstration the position of the wheel will be assumed to be on the arm EF extended. 12. Theory of the Polar Planimeter.* Let r = oc (Fig. 5) ; r' = ob = radius of zero-circle ; m = og = og' = og" ; n = hg= tig' == h"g" = pi\ L = cg=c'g' = c"g"; j3 = angle ogc = opy = og r c' ; dd = angle coc f = gog ! = cac'. The values of r f , m y n y and L are constant for any given setting of the instrument. The zero-circle of the polar planimeter may be defined as the circle generated about the pole-point as a center, which when traced by the instrument will cause no movement of the record-wheel. In any irregularly shaped figure through which the zero-circle passes, the differential area (dA) may be taken as that portion of the figure outside the zero-circle and between two radial lines separated by the angle dd. That is, dA = bcc'e. By subtracting the triangle oeb from the triangle occ' we have dA = bcc'e = occ' — oeb. * The theory of the planimeter which is given herewith has been adapted from Carpenter's " Experimental Engineering" by C. H. Robertson, M.E., Instructor in Engineering Laboratory, Purdue University. 10 ENGINEERING LABORATORY PRACTICE. But r r r*d8 triangle occ r = cc' X — = rdO X — = « & 2 2 2 Fig. 5. In the same manner triangle oeb = r'Vfl 2 ; therefore rV0 r' *d0 r* - r" ak4 = = — — - 22 2 <#. . . (1) ELEMENTARY MEASUREMENTS. II In tracing the area bcc'e the record-wheel movement for be is equal and opposite to that for c'e\ eb, being on the zero-circle, causes no movement, and hence in tracing the area dA the only effective movement of the record-wheel is that for the side ee f . For this infinitesimal area the side cc r may be taken as the arc of a circle, in the tracing of which the angle ogc (= 0) remains constant. The path of the record-wheel will be hh'. The component of hh' which turns the record- wheel is shown geometrically by wv, drawn perpen- dicular to the bisector of the angle cad and midway on hh'. It may be considered as an arc of a circle about a as a center. While the tracer moves through the infinitely small distance ee' the corresponding differential record will be dR = wv = ai X dd. But ai = ap — ip = m cos fi — n ; therefore dR = (m cos j3 — n)dd (2) Now in the triangle ogc (pc) % = (ogY + (eg) 2 + (log XgeX cos /J), or r a = m* + V -f 2mL cos /? (3) In the triangle oh"c n the tracing-point c ,r is on the zero-circle and the plane of the record-wheel is radial ; hence c"h" is a right triangle and {oc"y = {c"g"+ g "h"f + x\ 12 ENGINEERING LABORATORY PRACTICE. or r" = (L + ny + x\ But x* = m % — « a ; therefore r' a = V + 2Z^ + ;*' + ^ a - rc a = U + m x -\-2Ln (4) Subtracting (4) from (3), we have r a — r /a = 2Z;# cos /3 — 2Ln, or = Z(/# cos f3 — n) (5) 2 Combining (5) and (1), we obtain dA = Z(*« cos /? — n)dO. ... (6) Now, substituting the value of dd as found in equa- tion (2), we obtain dA = LdR. Hence, integrating between the limits o and R, we have, since Z is constant, dA = Lf*dR\ A=LR. ...... (7) It is seen from equation (7) that the area is equal to the length of the arm from pivot to tracing-point, multiplied by the distance corresponding to the revo- lution of the record-wheel, and is independent of the other dimensions of the instrument. ELEMENTARY MEASUREMENTS. 1 3 It can readily be proven that the above demonstra- tion is true for areas not adjacent to the zero-circle or partly inside and out. 13. Area of the Zero-circle. — In case the exact area of the zero-circle is not known the following method may be employed to determine it: With a pair of compasses draw arcs of two concentric circles the radius of each of which is known to be greater than that of the zero-circle. For convenience let the arcs subtend an angle of 90 . Place the fixed pole of the planimeter at the center of the arcs, and with the tracing-point trace successively the periphery of the two arcs between their limiting radii, noting the re- spective readings on the record-wheel. Let the areas of the two sectors be a and a\ and the corresponding readings of the record-wheel be R and R\ Let the radius of the zero-circle be r'. Then, since the read- ing of the record-wheel is equal to the area outside of the zero-circle, we have a=-r' 2 + R and a' = -r" + R' f 4 4 and adding, we obtain -r ,a = a + a' - (R + R f ). ..... (8) 14. Adjustable Planimeter. — From equation (7) it will be seen that the area corresponding to one complete revolution of the record-wheel is equal to the length of the arm L multiplied by the circumference of the wheel, the unit of measurement being uniform. For instance, if the arm L is 5 inches long and the record-wheel has a circumference of 2 inches, one complete revolution will signify 10 square inches, and, 14 ENGINEERING LABORATORY PRACTICE. since the wheel is divided into ioo parts and a vernier is provided, the instrument will read to hundredths of a square inch. Now if the length of the arm L be changed to 0.775 inch, one revolution of the wheel will correspond to 1.55 square inches or 10 square cen- timeters and the instrument will read to hundredths of a square centimeter. Hence by changing the length of arm L the scale of the instrument can be changed. The ordinary form of instrument in use has a fixed arm and reads to hundredths of a square inch. An instrument is made, however, with an adjustable arm (Fig. 6). It may be made to read in different units, Fig. 6. — Adjustable Polar Planimeter. and can be set to read the M.E.P. of an indicator- diagram as follows: Calling / the height of the mean ordinate of the diagram and / the length of the diagram, then we have the area A =pl. From equation (7) we have A=LR; whence and k t l~ K ELEMENTARY MEASUREMENTS. 1 5 Now since the arm L is adjustable, we can make it equal to the length of the diagram /. We will then have /, the height of the mean ordinate, equal to the reading of the record-wheel, to the proper scale. 15. Directions for Use. — i. Handle the instrument with care, as it is liable to injury. 2. Wipe it off carefully before and after using. 3. See that the wheel revolves freely and the re- cording edge is smooth and bright. 4. Place the diagram to be evaluated on a smooth, level drawing-board, having first covered the latter with a sheet of smooth calendered paper. Fasten with thumb-tacks or pins. 5. Place the pole-point in such a position that when the tracing-point is near the geometrical center of the figure the two arms are approximately at right angles. 6. Trace in the direction of the hands of a watch. 16. Planimeter Exercise (a). — Read the theory of the planimeter (Sections 12 and 13) carefully. Find the area of the zero-circle by the method ex- plained in Section 13. Find the average error of the instrument as follows : Draw carefully three rectangles an inch square. Go over each several times and find the mean error of the instrument. Repeat with three figures of four square inches each. In the Report, give make and number of instrument, area of zero-circle, and aver- age per cent of error, including all readings and cal- culations made. Keep a record of results for use in the next experiment. 17. Planimeter Exercise {b). — Find the areas of figures on the blank furnished. The diameter of the record-wheel is inches. l6 ENGINEERING LABORATORY PRACTICE. Compute the length of arm Z, using one revolution of the wheel as a basis of computation. The arm m is inches in length. Compute length of arm n. In the Report give areas found ; also above dimen- sions, with formulae used and calculations in full. 18. Lineal Measurements. Micrometer Caliper. — This instrument is used for outside measurements only. The micrometer-screw has forty threads to the inch ; hence each revolution will advance it one fortieth (= 0.025) of an inch. The band surrounding the screw is divided into 25 parts, which allows the move- ment to be read to thousandths (^p) of an inch. The object to be measured is held between the measuring- points and the knurled handle turned until lightly touching the piece. Care should be taken not to exert too great a pressure, as this will strain the in- strument and vitiate the result. Take care to secure the same degree of pressure in all cases. 19. Vernier Caliper. — This instrument is used for both outside and inside measurement. For the former the scale is graduated in fortieths of an inch and the vernier reads to thousandths. In using the vernier read first the position of the zero-mark on the vernier relative to the scale. This will give tenths and quar- ters of tenths. Then by reading the number of the mark on the vernier nearest opposite a mark on the scale, that number, in thousandths of an inch, is added to the reading previously obtained to give the desired result. For example, suppose the zero-mark on the vernier to read three inches, four tenths and three spaces ELEMENTARY MEASUREMENTS. 17 =5 3.0 + 0.4 + (3 times j\ or 3 times 0.025 or °-°75) = 3.475. Then if mark number 1 1 on the vernier is nearest opposite a mark on the scale the complete reading is 3.475 + .011 = 3.486. For inside measurement add 0.25 of an inch to the vernier-reading. Never bring the jaws together while the piece to be measured is between them. If the distance is too great, remove the piece, decrease the distance, and apply again until the caliper will just slide over the surfaces to be measured. Great care should be taken not to strain the instrument by forcing it onto the piece. It is very delicately made and should be handled with care. 20. Sweet's Measuring-machine. — This machine is a micrometer caliper having a greater range than the one previously described. The micrometer-screw has a range of one inch, but the tail-piece may be set at distances of even inches from the zero position of the screw by means of distance-pieces. The instrument is furnished with a scale, graduated on its upper edge to read in sixteenths of an inch and on its lower edge to decimals of an inch. The graduated disk has two sets of graduations, that on the left corresponding to the upper scale and that on the right to the lower. The latter is read in the same manner as an ordinary micrometer, reading to thousandths directly. The former reads in binary fractions, the space between five figures corresponding to one thirty-second. The numbers are arranged as shown in Fig. 7. Beginning at o and following the line of chords to the right, the numbers are in regular 18 ENGINEERING LABORATORY PRACTICE. order, every fifth one being counted. Five complete revolutions corresponding to half the travel of the screw, or one half an inch, are necessary to pass the 16 divisions, thus making each division (= five spaces) correspond to one thirty-second of an inch. Since there are 40 small divisions between the successive 8 Fig. 7. numbers (as between 1 and 2), any desired fraction of a thirty-second can readily be obtained. The following is a portion of the directions accom- panying the instrument : " To measure objects larger than an inch bring the index-bar to zero, insert the proper distance-piece, and clamp the tail-spindle. Next bring the screw to exact contact with distance-piece, turning the latter to be sure it is held squarely between the measuring-points. When the friction slips leave the distance-piece held between the points while you see that the index-bar is adjusted as above; then proceed with the measure- ment. " The index-bar has been carefully set to correct the inaccuracy in the pitch of the screw. Do not alter it because it seems to give contrary readings. A little difference of temperature or an atom of grit will make noticeable change in the readings. ELEMENTARY MEASUREMENTS. 19 " The graduations of the circle upon the right of the central line indicate thousandths, and are read in connection with the scale upon the front edge of the index-bar. Those upon the left are numbered by thirty-seconds and the scale upon the back edge of the index-bar is used as a ' finder/ To set the machine at any desired thirty-second bring the central or ' read- ing line ' as near the place as can be done by means of the scale upon the index-bar. The number in- dicating the thirty-second will then be found near at hand. Bring this to the front edge of the bar. In measuring binary fractions of thirty-seconds always remember that upon this scale it requires five marks to count one." 21. Exercise with Measuring-instruments. — Read Sections 18, 19, and 20 on micrometer and vernier calipers. Measure the five pieces shown in Fig. 8 and make Report as indicated in the following blank form : REPORT ON MICROMETER AND VERNIER EXERCISE. Observer Date Measured with Micrometer. Vernier. Sweet's Micrometer. No. 1 A = No I C = No. 1 B = " 2C = 1 1 2 B = " 2 A = " 3 A = << 3 D = ■• 3 c = " 3 B = < < 3 D r = "4D = " 5 E = « 1 4 A = "4E = " 5 F = 1 1 4 B = " 5 L = " 5G = < 1 4 C = ■• 5H = < 1 5 A = " 5K = 11 5 B = u 5 C = • 1 5 D = c< 5 J = No. 4 F = 20 ENGINEERING LABORATORY PRACTICE. No. i. < No. >D No. 3. No. 4- ^-e— > 1 O F= Taper per inch m \\ 1 1 1 r3fc -B >*-C No. 5. Fig. 8. CHAPTER III. MEASUREMENT OF LIQUIDS. 22. Methods of Measuring Water. — The accurate measurement of large quantities of water is an im- portant factor in the testing of hydraulic and steam machinery. The methods of measurement in common use may be briefly summarized as follows: By the use of i. Weighing-barrels or tanks. 2. Orifices and nozzles. 3. Weirs. 4. Meters. The use of weighing-barrels in this connection does not warrant description here. 23. Formulae for Flow of Water through an Ori- fice. — The theoretical velocity of water flowing under any head is the same as the velocity attained by fall- ing through a distance equal to that head. If the head be represented by H and the resulting velocity by V y then V=V2gH. (1) Now if the issuing stream were of the same cross- sectional area as the orifice and flowed with the velocity due to its head, the rate of flow would be represented by the formula Q = FV2g-H, (2) 21 22 ENGINEERING LABORATORY PRACTICEc where Q is the rate of discharge in cubic feet per second, and F is the area of the orifice in square feet. With an orifice in a thin plate the conditions men- tioned above do not exist. The velocity of discharge is less than the theoretical velocity and the area of the stream is less than that of the orifice. It becomes necessary, then, to introduce into formula (2) a coefficient C y representing the ratio of the actual flow to the theoretical. The formula then becomes Q=CFV2gH. .... (3) 24. Determination of Coefficient of Discharge of an Orifice in a Thin Plate. — The coefficient C in formula (3), Section 23, is determined by experiment. It varies slightly with the form of the orifice and with the head. The apparatus required to make such a determination includes a suitably arranged stand-pipe to which the orifice may be attached and in which a given head of water can be maintained, and a cali- brated tank to receive the stream of water discharged. The quantity of water discharged in a given time under a given head may thus be measured directly and the coefficient computed by means of the formula. Specific Directions. — Run tests under six different heads, as may be specified by the instructor. Prepare Running Log and post observers in accordance with the following schedule of observations: — 1. Log and time — In charge. 2. Weight of water, 3. Head. Start the pump which supplies the stand-pipe, giv- ing attention to the lubricator and the cylinder-cocks. MEASUREMENT OF LIQUIDS. 23 Regulate the head of water in the stand-pipe by the pump-throttle. The length of each test is governed by the capacity of the tank into which the issuing stream is directed, and readings of time and quantity of water discharged should be taken at regular inter- vals of such a length that at least six (6) readings may be secured under each head. When the desired head has been secured, close the tank discharge-valve and note time. Take readings as explained above until the capacity of the tank is reached. Discharge the tank, change the head, and repeat. In case the several readings for any head do not show a steady flow, repeat the test under that head. The Report should be made out on the form shown below, and should be accompanied by the Running Log. 25. Form. FLOW OF WATER THROUGH A, Observers X Form of Orifice or Nozzle (Sketch). FORMULA. Date, Diameter, feet. Area, sq. feet. Number of Experi- ment. Head in Feet. Time in Seconds. Cubic Feet. Total. Cubic Feet per Second. Co- efficient of Dis- charge. Notes. Average. 24 ENGINEERING LABORATORY PRACTICE. 26. Calibration of an Orifice. — Orifices of various forms are often used to measure a constant flow of water. It is convenient in such cases to calibrate them, i.e., to determine the rate of discharge under different heads. For this purpose the issuing stream is directed into a weighing-barrel, while the head is kept constant, and the quantity of water discharged per second is noted. These results, obtained under different heads, are plotted in the form of a curve. Specific Directions. — Run tests under six different heads as may be specified by the instructor. Proceed as follows: Prepare the Running Log. Drain the weighing-barrel and start the flow of water, carefully regulating the same to secure the desired head. Set the poise on the platform-scale to read twenty (20) pounds in excess of the weight of the barrel when the stream is flowing and the discharge-valve is open. Begin the test by closing the discharge-valve and noting the time when the beam rises and the poise reading. Set the poise to read a little under the full weight of the barrel, and when the beam rises again note the time and the poise reading. The barrel may now be emptied, the head changed, and a new test begun. During each test keep the head constant by regulat- ing the supply-valve. The Report should be made out in accordance with the form shown below, and should be accompanied by a curve, carefully plotted on cross-section paper, using the various heads as abscissae and the flow in cubic feet per second as ordinates. MEASUREMENT OF LIQUIDS. 25 27. Form. FLOW OF WATER THROUGH A Observers < Form of Orifice or Nozzle (Sketch). Date Diameter, feet. Area, sq. feet.. Number of Experi- ment. Head in Feet. Time in Seconds. Pounds, Total. Pounds per Second. Cubic Feet per Second. Notes. 28. Determination of the Coefficient of Discharge of a Nozzle. — The rate of discharge from a properly designed nozzle approaches closely the theoretical rate. If the proper internal curvature of the nozzle is secured, there is no contraction of the area of the jet beyond the tip of the nozzle. The velocity of the jet is, however, reduced below the theoretical by fric- tion, and a coefficient must be introduced in formula (3), Section 23, to give the actual rate of discharge. To determine the value of the coefficient for a given nozzle under different heads proceed as explained under the " Specific Directions,' ' Section 24. 29. Formulae for Flow of Water over Weirs — The rate of flow of water over a rectangular overfall weir with complete and perfect contraction is given by Francis' formula as follows: Q = \CH\b-o.\nH))/2g, 26 ENGINEERING LABORATORY PRACTICE. where Q = flow in cubic feet per second; H = head in feet over weir from crest to surface of still water back of weir; b = breadth in feet at water-level; n = number of contractions, i.e., area of channel back of weir divided by area of wetted perimeter; C = a coefficient of discharge. In Section 186 is given a table of the value of the coefficient C for different heads and breadths. The formula for flow over a triangular overfall weir is 30. Measurement of Head. — Measurements of the head of water over a weir are usually made with a hook-gage. This instrument is placed on the up-stream side of the weir and a sufficient distance from it to avoid the effects of the surface-curve near the weir. It consists of a metal hook with a fine, sharp point, which may be raised or lowered to the level of the water and readings made of its position by a suitable scale. To take a reading the hook is lowered until the point is below the surface; it is then raised until the point just pierces the surface and a reading of the scale made. This reading when compared with that when the hook-point is level with the crest of the weir, called the zero-reading, will give the head over the weir. The zero-reading may be determined in several ways. In some cases it may be done with a spirit- level and straight-edge. Where this method cannot be used, a small quantity of water is allowed to flow MEASUREMENT OF LIQUIDS. 27 over the weir and the hook-gage read, at the same time measuring the depth of water over the crest with a thin and finely graduated scale. The hook is then lowered by the amount measured. Another method is to grease the edge of the weir and let the water stand as near the level of the crest as possible, then read the gage. 31. Water-meters. — Water-meters are liable to error from many sources and should therefore always be calibrated under the conditions with which they are to be used before their readings can safely be relied upon for experimental purposes. Among the many sources of error may be named change in temperature and head, the presence of dirt or air in the water, and the constant errors of calibration. 32. Calibration of Water-meters. — The calibrat- ing of a water-meter could be easily done if the per cent of error were constant for all rates of flow. Since this is not the case, it becomes necessary to calibrate for different rates. This may be accomplished with the aid of a tank of sufficient size, graduated in cubic feet. A pressure-gage should be placed in the supply- pipe between the meter and the valve, to register the head. Three observers are necessary for the work: one to take the meter-reading, one to take that on the tank, and the third to keep log and time. The opera- tion is as follows: Open the supply- and discharge- valves and allow the water to flow for a few minutes until the rate of flow, as shown on the pressure-gage, becomes steady; then close the discharge-valve, and as soon as water appears in the gage-glass on the tank, at a signal from the time-keeper, take simultaneous readings of the meter and tank. Repeat the readings 28 ENGINEERING LABORATORY PRACTICE. every minute until the tank is full. Empty the tank. Throttle the admission-valve a little so as to change the rate of flow and repeat. Make experiments at six different rates or pressures. The observations should be recorded on a Running Log, which should be made out to cover the following: 1. Time. 2. Pressure. 3. Tank-reading. 4. Temperature. The Report should be made out in the form shown below and should be accompanied by the original Running Log. 33. Form. REPORT ON CALIBRATION-TEST OF WATER-METER. Observers \ Date a. Number of test b. Duration of test, minutes c. Pressure of head, average d. Temperature of water, average e. Rate of discharge per minute by meter f. Rate of discharge per minute by tank g. Total volume by meter h. Total volume by tank 1. Total excess or deficiency in meter reading /. Per cent of error (-[- or — ) CHAPTER IV. MEASUREMENT OF GASES. 34. Methods. — The flow of gases may be measured by the following methods: 1. By flow through an orifice. 2. By determination of velocity. 3. By some form of meter. 35. Flow through an Orifice. — Where the flow of gas is at a constant rate, an orifice may be con- veniently employed in determining the rate of flow. Fig. 9 shows the arrangement of an orifice for this Fig. 9. — Arrangement of Orifice. purpose. At /, and / a are U-tubes for measuring the pressure before and after passing the orifice, and at t x is a thermometer for measuring the initial tem- perature. 36. Formula for Flow of Air through an Orifice. — The flow of air through an orifice can be computed 29 30 ENGINEERING LABORATORY PRACTICE. with the aid of the following, called Fliegner's formula:* P G = o.$2,oF^L=, when p x > 2p a ; G=i.o6oFJ Pa{p \ r A) when A<*Ai where /, is the absolute pressure in the reservoir, p a is the atmospheric pressure, T x is the absolute tempera- ture of the air in the reservoir in degrees Fahrenheit, G is the flow in pounds per second, and F the area of the orifice in square inches. 37. Formula for Flow of Steam through an Ori- fice. — The flow of steam through an orifice may be calculated by the following, called Napier's formula :f G=zF jo when A = <> r >lA; G = F 42 I 2 Pa \ WhCn A < 1A. The nomenclature is the same as in Fliegner's formula, just preceding. 38. Experiments on Flow of Steam. — The pur- pose of these experiments is to verify existing formulae for the flow of steam and to determine the change in the rate of flow under different conditions of pressure and moisture. The apparatus consists of an orifice of suitable dimensions (see Fig. 10) provided with gages, a condenser for measuring the steam, and two calorim- * See Peabody's "Thermodynamics," page 135. f Ibid., page 140. MEASUREMENT OF GASES. 31 eters for ascertaining the quality of the steam. The apparatus also includes a water-jacket for regulating the moisture of the inflowing steam to suit the desired conditions. Specific Directions, — To determine the change of rate of flow with change in the ratio of final to initial pressure, run a series of five tests with constant initial Fig. 10. and variable final pressure. The conditions should be as follows: For the first test, final pressure as low as obtainable. For the second test, final pressure to be 0.3 of difference between initial and atmosphere. For the third test, final pressure to be 0.5 of differ- ence between initial and atmosphere. For the fourth test, final pressure to be 0.7 of differ- ence between initial and atmosphere. For the fifth test, final pressure to be 0.9 of differ- ence between initial and atmosphere. Cooling-jacket to be cut out. Each test should be of 15 to 20 minutes duration, the conditions of the test to exist for five minutes before the first observation is taken. The following observations should be taken every two minutes: initial, intermediate, and final pressure. The following should be taken every four minutes: pressure and temperature in each calorimeter. The 32 ENGINEERING LABORATORY PRACTICE. weight of condensed steam should be taken once for the test, and the barometer read twice during the test. Use only enough cooling water on the condenser to condense the steam. Be sure that the pressure-gages are not subjected to a pressure beyond their range. The Report should include: i. Sketch and description of apparatus. 2. Sketch and dimensions of orifice. 3. Tabulated statement of results for each test. 4. A curve having ratio of final absolute pressure to initial absolute pressure for abscissae and flow of steam in pounds per hour for ordinates. In order to determine the effects of different per- centages of moisture in the steam repeat the above series, manipulating the cooling-jacket to secure in- creasing amounts of moisture in the steam. 39. Method by Determination of Velocities. — This method has a limited application, but may some- times be found convenient to employ. It involves the use of an instrument for determining the velocity of flow, such as an anemometer or Pitot tube. The velocity, thus determined, in connection with the cross-sectional area of the pipe or conduit, gives the rate of flow. CHAPTER V. MEASUREMENT OF PRESSURE. 40. Pressure-gages. — The most common instru- ment for the measurement of pressures in excess of a few pounds is the Bourdon gage (Fig. 11), which con- sists essentially of a curved tube, oval in cross-section, Fig. 11. — Bourdon Gage, having one end closed and the other in communication with the pressure to be measured. The tendency of an internal pressure is to make the cross-section round and thus straighten the tube. The motion produced serves to rotate a pointer by an amount proportional to the pressure. Such instruments may be used for pressures of either liquids or gases provided they are 33 34 ENGINEERING LABORATORY PRACTICE. not heated above 12 5 or 150 F., as excessive tem- perature will lengthen the levers and draw the spring temper of the tube. When used for steam-pressure, a siphon or trap should be used to prevent the steam from entering the gage. When making a selection of such a gage to measure a given pressure, it should be borne in mind that, since these gages are apt to be inaccurate at the lower points of their travel, the lowest total range should be chosen which is compatible with the pressure to be measured. 41. Vacuum-gages. — Bourdon gages of special design are used for the measurement of vacuo, movement of the pointer being obtained by means similar to that described for pressure-gages. They are generally graduated to read in inches of mercury below atmospheric pressure. 42. Calibration of Gages. — Method by Comparison with Standard. — In order to test the accuracy of pressure-gages they should be calibrated by being subjected to known pressures within their range and their error noted. In the method by comparison with standard the gage to be tested is placed in pipe- connection with a standard gage of known error and both subjected to pressure. This pressure may be of water, oil, or steam. If either oil or water be used, the pressure may be secured by a steam- or hand- pump. The difference between the readings of the two gages may then be noted and a table of correc- tions made for the gage under test. Specific Directions. — Before making the test see that the pump-lubricatcr is filled and started. Start the pump slowly and gradually increase its speed until the MEASUREMENT OF PRESSURE. 35 maximum pressure, depending upon the available steam-pressure, is reached. Stop the pump and read the gages. Allow the pressure to decrease by even five-pound steps as shown on the standard gage by manipulation of the outlet-valve. Take simultaneous readings of both gages at each pressure and enter the same on the form shown below. Check all readings once by repeating the test. In preparing the Report enter in the column headed " Actual Pressure " the corrected reading of the standard gage. The corrections, if there are such, will be found posted near the gage. In the column of ic Corrections ' enter the difference be- tween the corrected reading of the standard gage and the reading of the gage under test. These differences should be preceded by the minus or plus sign, accord- ing as the gage under test reads above or below the standard gage. 43. Form for CALIBRATION OF STEAM-GAGE BY COMPARISON WITH Make and number of gage Observer Date. . . Standard Gage. 6 u 3 CO en CD u Ph S3 < CD a O O fa* G •3 CD + u 1 *a u, O — U Standard Gage. cd' u 3 en en CD Ih 3 CD < CD* tfl O he •3 CD B 1 "O wCD J 15 U CD CD.O *-> -* u O *-» u en •a a 3 & a CD U U O V en C 3 O PL. d CD u u u Remarks. 36 ENGINEERING LABORATORY PRACTICE. 44. Calibration of Gages. — Method by Comparison with Crosby Gage-tester. — Gages may be calibrated by subjecting them to liquid pressure, the same pressure being made to sustain weights of known amount. The apparatus, shown in Fig. 12, consists of a cham- ber filled with oil, to which the gage is attached and Fig. 12. — Crosby Gage-tester. which terminates in a cylinder having a nicely fitting piston of one fifth of a square inch cross-sectional area. The piston is furnished at its upper end with a plat- form upon which accurate weights may be placed. The piston and platform together weigh one pound, and require therefore a pressure of five pounds per square inch (acting on the piston-area of \ of a square inch) to sustain them. In communication with the oil-chamber referred to is a reservoir fitted with an adjusting plunger which is operated by the hand- wheel shown on the right. This is used to force oil into the system as occasion demands in order to keep the platform and weights floating. MEASUREMENT OF PRESSURE. 37 Specific Directions. — Open the cock connecting the gage with the oil-cylinder and screw in the plunger until the piston and platform have risen two or three inches above the lowest position. Twirl the platform to avoid a false reading due to piston friction, and take a reading of the gage, recording the same, together with the actual pressure (five pounds), in the proper columns on the form shown above. Add successive weights by five-pound steps and take corresponding readings, twirling the platform each time while taking the reading. Continue up to the limit of the gage and repeat, to check the results. In preparing the Report, leave the columns headed li Standard Gage " blank. In the column of " Correc- tions " enter the difference between the actual pres- sure and the reading of the gage under test. These differences should be preceded by the minus or plus sign, according as the gage-reading is greater or less than the actual pressure. 45. Correction of Gages. — If an error appears as a result of calibration it may generally be corrected. If the error is a constant one, the hand may be removed with a needle-jack and moved an amount corresponding to the error. If the error is an increas- ing or diminishing one, it can be corrected by chang- ing the length of the levers which operate the pointer. It is generally desirable to set the gage to read cor- rectly at the pressure under which it will be most fre- quently used, especially if it is to register a constant pressure, as that of a boiler. In such a case, the gage should be subjected to the desired pressure and the needle placed to indicate the same on the dial. 46. Manometers. — For the measurement of small 38 ENGINEERING LABORATORY PRACTICE. pressures or vacuo the U-tube manometer is in com- mon use. It consists usually of a U-shaped tube of glass, partially filled with mercury or water and pro- Fig. 13. — Bristol Recording Pressure-gage. vided with a scale for reading the difference of level of the liquid in the two legs. One branch of the tube is connected with the pressure or vacuum to be measured, and the other is open to the atmosphere. MEASUREMENT OF PRESSURE. 39 The difference of level of the liquid in the two branches, measured in inches, multiplied by the weight of a cubic inch of the liquid gives the pressure in pounds per square inch above or below atmos- phere.* In reading the height of mercury columns, read the level at the top of the meniscus or con- vexity; in reading a water-column, read the bottom of the meniscus. 47. Bristol Recording-gage. — This gage, one form of which is shown in Fig. 13, is so arranged that the pressure or vacuum actuates a pen which leaves a continuous record on a revolving disk of paper. The disk is operated by clockwork. The instrument is of special value in recording the fluctuation of pressures subject to considerable variation. It is a valuable adjunct in making tests of boilers, the record obtained more nearly representing the average pressure than is possible with periodic observations. * The weight of a cubic inch of mercury at 6o° F. is 0.490 pounds ; of water at 6o° F. 0.0360 pounds. CHAPTER VI. MEASUREMENT OF TEMPERATURE. 48. Mercurial Thermometers. — Measurements of temperature are usually made by means of mercurial thermometers, which depend for action on the expan- sion of mercury in a bulb and capillary tube when subjected to heat. Mercurial thermometers when used in engineering work should frequently be tested for accuracy, as they are liable to error from many sources, such as variable diameter of bore, permanent change of volume of bulb from use, etc. Great care should be exercised in handling, to reduce breakage and damage to a mini- mum. 49. Rules for Care of Thermometers. — The fol- lowing rules should be observed in connection with the use of mercurial thermometers: 1. Keep the thermometer in its case when not in use. 2. Exercise care in inserting and removing from the thermometer-cup. 3. See that there is no water in the cup before inserting thermometer. 4. Keep the cup filled with heavy oil, and wrap the stem with waste at the mouth of the cup to avoid contact with the metal. 40 MEASUREMENT OF TEMPERATURE. 41 5. Be sure that the range of the thermometer is high enough for the temperature to which it will be exposed. 6. Do not carry the thermometer wrong end up. 7. Return the thermometer to its own case when through using. 50. Calibration of Thermometers. — Method by Comparison with Standard. — In order to test the accuracy of thermometers, they should be subjected to known temperatures and their errors noted. This may be done by comparing their readings with those of a standard thermometer whose error is known. Specific Directions. — Place the thermometer to be calibrated and the standard in adjacent cups of the same depth in the testing-drum. Allow steam to run through the drum for a few minutes to warm it up, then throttle the discharge until a pressure of five pounds is maintained upon the gage. Allow the mercury in the thermometer to come to rest (five to ten minutes) and take simultaneous readings of the two thermometers, removing them from their tubes only far enough to bring the mercury to view, and taking the readings as quickly as possible to avoid the cooling effects due to partial removal from the tubes. Close the discharge-valve again until the pressure is raised to ten pounds, and repeat. Carry the pressure by five-pound steps up to the limit of pressure, and descend in the same manner. Be sure that time is allowed for the mercury to come to rest before reading. Read Section 49 before beginning the test. Report on the form shown below, omitting the columns headed " Steam-gage " and the barometer reading. 42 ENGINEERING LABORATORY PRACTICE. 51. Form for CALIBRATION OF THERMOMETER BY COMPARISON WITH Thermometer checked : Distinguishing mark Range of scale . Range of test . . . Scale Observers Date No. Standard Thermome- ter. Steam- gage. 6 u P u a; a a u H CALORIMETERS. 49 The formula is derived in the following manner: Let p x = boiler-pressure, absolute; p^ = pressure in calorimeter, absolute; t s = temperature in calorimeter; r, and q x = heats of vaporization and of the liquid corresponding to p x \ A, and / 2 = total heat and temperature corresponding to / a ; C p = specific heat of steam ; x x = quality of steam required. Then the heat in a pound of steam flowing to the orifice will be and that in a pound of steam in the chamber b> after passing through the orifice, will be, assuming that all the moisture is reevaporated, K + C/t. - Q. Now, assuming that no heat is lost or converted into work during the transformation, these two quan- tities must be equal. Whence *fx + 9i = K + C,(t, - t,), . r K + Clt, - /,) - q x .. x x - 60. Limitations of the Throttling Calorimeter. — It is apparent, on consideration of the foregoing formulae, that if the entering steam contains too great a percentage of moisture, it may fail to superheat on passing through the orifice. This, then, is the limit- ing condition under which the calorimeter can be used. 50 ENGINEERING LABORATORY PRACTICE. The point at which superheating ceases varies ordi- narily from about 3 per cent with low steam-pressures to 7 per cent at very high pressures. The precise limit under any given pressure varies slightly with the pressure in the calorimeter. 61. Use of the Throttling Calorimeter. — Care should be taken in placing a calorimeter that a fair sample of steam is obtained. To this end the calo- rimeter-pipe should extend well into the steam-pipe and should be provided with perforations inside the steam-pipe. The A. S. M. E. recommends that the calorimeter-pipe be \ inch in size, that it extend into the steam-pipe to within £ inch of the opposite wall, that the inner end be plugged, and that it be provided with not less than twenty ^-inch holes distributed along and around its length, no hole being closer than \ inch to the inner end. The instrument should be well wrapped with hair-felt or asbestos, to prevent radiation. It should be started at least ten minutes before the first observation is to be made, to allow the conditions to become settled. A pressure of 4 or 5 pounds should constantly be maintained by manipulat- ing the discharge-valve. The thermometer should be put in place after the instrument is started and removed at the end of the test. Never close the dis- charge-valve without first shutting off the calorimeter- gage. The observations to be taken are pressure of steam in pipe, pressure and temperature of steam in calorimeter, and barometric pressure. The report should be kept on the calorimeter form shown below. In testing a small boiler the calorimeter may be shut off part of the time in order to avoid the waste of a large quantity of steam. In making a combined CALORIMETERS. 51 engine- and boiler-test when the water is measured before entering the boiler, the length of time which the calorimeter is in action should be carefully noted, in order to calculate the weight of steam lost, as ex- plained in Section 37. 62. Form for Calorimeter Test. TEST FOR DETERMINING THE QUALITY OF STEAM by use of Throttling Calorimeter No Tests made in connection with No Made by Date In 1 u u £} 3 2 — ze/^ This formula assumes that the constant of the in- strument is zero and that there is no radiation. The preliminary heating of the barrel, as explained above, makes the calibration-constant a negligible quantity, and if the test is of short duration it is customary to disregard the radiation. 66. Calorimeter Exercise. — The apparatus con- sists of three calorimeters of different types connected to the same steam-supply and with the same manner of attachment. A suitable water-jacket is provided to govern the quality of the steam supplied. The different instruments used are: 1. A throttling calorimeter. 2. A separating calorimeter. 3. A barrel calorimeter. Three observers are needed, one for each calorim- eter. Run simultaneous tests, adapting the time of observations on Nos. 1 and 2 to that which will be convenient for the barrel calorimeter. Run three tests, changing the quality of steam each time by means of the water-jacket on the steam-pipe. Let the observers change positions so that each will run a test on each calorimeter. In the Report present a copy of all running logs, table of calculated results arranged for convenient comparison, and a curve of the quality of steam shown by each calorimeter based upon a straight line repre- senting dry steam. For formula and directions con- cerning each calorimeter, see Sections 59 to 65. CHAPTER VIII. MEASUREMENT OF POWER. 67. Classification. — Machines for the measurement of power may be divided into two general classes: those which absorb the power measured, called absorption-dynamometers; and those which form a connecting link in the transmission of the power to be measured, called transmission-dynamometers. 68. Absorption - dynamometers. The Prony Brake. — The form of absorption-dynamometer in most common use is the Prony brake, of which there are many varieties. One of the simplest forms, which may be taken for illustration, consists of a rope placed over or wrapped around a pulley which receives the power to be measured. The rope is provided with adjustable weights, and the friction induced by the revolution of the pulley is such as to sustain the weighted end of the rope against gravity. An increase of load is obtained by adding more weights, which causes the rope to bear on the pulley with greater force, thus increasing the friction. Since it is difficult to obtain the weight which will just be thus sustained, it is customary to attach a spring-balance to the other end of the rope as a compensating device, as in Fig. 15. The lower end of the balance is attached to some fixed point. 55 56 ENGINEERING LABORATORY PRACTICE. The power absorbed by such a brake is given by the following formula: 2 7tm( W — w) H.r . = , 33OOO where r is the radius of the wheel plus half the diameter of the rope in feet, n is the revolutions per Fig. 15.— Rope Prony Brake. minute, W is the weight on the tight side of the rope and w is the weight on the slack side as shown on the spring-balance. A common modification of the rope-brake is the substitution of a steel band or bands for the rope. This band has attached to it at intervals of a few inches blocks of hard wood which bear on the wheel and form the rubbing medium. Another form of Prony brake is shown in Fig. 16. The parts lettered a and b are of hard wood, and the load is obtained by tightening the hand-wheel k. The load is measured by a platform-scale which registers the retarding MEASUREMENT OF POWER. 57 force at the radius r. Since the scale sustains not only the downward pressure due to the revolution of the pulley, but also the weight of the brake-arm itself, this latter amount must be ascertained and deducted from the reading of the scale to determine the power Fig. 16. — Block Prony Brake. given off by the pulley. By making W equal to the reading of the scale and w the weight of the brake-arm at the radius r, the above formula will apply to this form of brake. By slight modifications the same formula may be made to apply to all forms of the Prony brake. 69. Special Forms of Prony Brakes. — In the Purdue Laboratory are several special forms of brakes, two of which will be here described. Pipe-brake. — This is a form of Prony brake in which four f-inch iron pipes are substituted for the rope. These pipes run in grooves turned in a wooden band bolted to the fly-wheel. A system of reducing- levers is introduced on the tight side to weigh the load, and a large spring-balance is employed to measure the back pull. This spring-balance is connected to an equalizing device by which the pull on all the pipes is maintained alike and the balance registers the pull on 58 ENGINEERING LABORATORY PRACTICE. a single pipe. Water is circulated through the pipes to carry off the heat generated. In operating the brake, determine the load under which it is desired to run the engine and place enough weights on the scale-pan to equal this load. After the engine is started, tighten the hand-wheel on the slack side until the lever rises and floats at its middle posi- tion. The formula for horse-power is (3# — 4b -f- c)2 7trn H.P, 33000 where a is the weight on scale-pan not including weight of pan, b is the back pull as shown by the cor- rected spring-balance reading, r is the effective brake- arm, n is the revolutions per minute, and c is the unbalanced weight of scale-pan, lever, links, pipe, etc. The value of the constant quantities may be found in the Commonplace-book. Band-brake. — In this brake the power is absorbed by a steel band running on a heavy wooden pulley. The band is surrounded by a strip of muslin which receives and distributes a spray of water for cooling purposes. The wooden lever to which the ends of the band are attached rests upon platform-scales, and the load is applied by means of a hand-wheel which tightens the band on the pulley. The directions for management of the pipe-brake apply in a general way to this brake. The formula in Section 68 may be used by making the item w equal the unbalanced weight of the lever-arm and connections. The value of the brake-constants may be found in the Commonplace- book. MEASUREMENT OF POWER. 59 70. Transmission-dynamometers. — A form of transmission-dynamometer which may be easily and cheaply constructed has been devised by Prof. W. F. M. Goss. It is shown diagrammatieally in Fig. 17. This dynamometer consists of a differential lever by which the difference in tension of the two sides of a belt is determined. This lever is pivoted to a fixed a 00 s \d Fig. 17. — Belt Transmission-dynamometer. point and carries the pulleys b and c. It is pro- vided with a scale-pan s, and a combined dash-pot and counterweight d. The power transmitted by the belt is measured by the speed in feet per minute at which it runs multiplied by the difference in tension of the two sides, as shown on the dynamometer. The force tending to raise the left end of the lever is twice 6o ENGINEERING LABORATORY PRACTICE. the tension t x of the tight side of the belt; that tend- ing to raise the right side is twice the tension / a in the slack side. Hence the resultant movement tending to produce rotation of the lever is twice the difference in tension of the two sides of the belt, acting on an arm bo (= oc) equal to the distance from the fulcrum of the lever to the center of the pulley supported by it. Since the lever-arm of the scale-pan ao is twice the above, a weight on the pan equal to the difference in tension of the belt will balance the lever. The belt speed is known from the revolutions per minute of the driven pulley and its circumference in feet. The formula for horse-power is ndnw H.P. = , 33000 where d is the diameter of the driven pulley plus the thickness of the belt in feet, n is its revolutions per minute, and w is the weight in pounds necessary to balance the lever. The observer in charge should keep such a weight on the scale-pan as will cause the lever-arm to move evenly between the stops. 71. Efficiency of Screws. — The screw is one of the elementary mechanical forces and one that forms an essential part of a great variety of mechanisms. The efficiency of the screw may be defined as the ratio of the work done upon the screw to lift a given load through a certain height, to the work done by the screw in lifting. This ratio varies for different loads lifted. The factors in the first member of the ratio are the distance passed through by the moving force, expressed in any convenient unit, and the mean force exerted in pounds. The factors in the second member MEASUREMENT OF POWER. 6l of the ratio are the load lifted in pounds and the height through which it is raised. In order to determine the efficiency of the screw the following test may be made : The apparatus con- sists of a jack-screw fitted w T ith a lever of convenient length, say 36 inches, and a spring-balance at the end of the lever. The jack-screw is placed on the table of a testing-machine, which serves to register the load. Specific Directions. — Place the jack-screw to be tested on the center of the testing-machine table, with a block of hard wood above and below it. Balance the poise-lever and run the movable head down until in contact with the screw. Place the poise at the one- thousand-pound mark and run the head down until the poise-lever rises and remains in balance. Back the screw down and then run it up by means of the lever and spring-balance, and note the reading on the balance the instant the poise-lever rises. Be careful to exert the pull at right angles to a vertical plane through the lever-arm. Now move the poise to the two-thousand-pound mark, run the movable head down until this load is balanced, and repeat the test. Make six tests at one-thousand-pound steps, and repeat the observations once or twice under each load. At each test note the number of full threads exposed to view. In calculating the efficiency of the screw the de- termination may be based upon one complete revolu- tion of the screw. Although only momentary condi- tions are observed, these conditions may be assumed to hold true for a complete revolution. Suppose the height through which the screw is raised be equal to the pitch (p) of the screw in inches, or one revolution. 62 ENGINEERING LABORATORY PRACTICE. Let the load lifted be W pounds and the correspond- ing pull on the balance be P. Then the work done by the operator at the end of the lever-arm in raising the load, expressed in inch-pounds, will be 2n X 36 X P. The work given out by the jack in moving the load will be p\V. The efficiency in per cent is therefore pW 100 £ — ^ ^. 27T X 36 X^ The Report should be made out on the form shown below. 72. Form for EFFICIENCY TEST OF SCREW. Made by Date, Outside diameter of thread in inches Pitch " " " " Form of thread. . . . Effective length of hand-bar used in inches Load under which efficiency was obtained Work which the screw would do in one revolution, in inch- pounds Pull on lever in pounds Work which would be done upon the screw in one revo- lution, in inch-pounds.... Efficiency 1 2.3 4 Notes; MEASUREMENT OF POWER. 63 73. Efficiency of Hoists. — This test is conducted for the purpose of determining the relation between the work put into a chain-hoist on the hand-chain, and that given out by the hoist in lifting the load. The method consists in putting a definite load on the hoist and noting the stress or weight on the hand-chain necessary to keep the load moving upward; that is, the weight on the hand-chain necessary to keep the load moving after it has been started by hand, since the friction at starting is much greater than that after the load is in motion. Specific Directions. — In calculating the efficiency, the following factors are necessary: the value of the load raised, the weight on the hand-chain required to raise it, and the ratio of the velocity of the hand-chain to that of the load-chain. With the Weston differ- ential hoist, this velocity-ratio is equal to 2AL -f- (AL - AK\ Fig. 18. Fig. 18. But since the circumference is proportional to the radius, we may employ the number of link-pockets for our unit of measure: the velocity-ratio may therefore be found by subtracting the number of pockets in the small wheel from the number in the large wheel and dividing this difference into twice the number in the large wheel. With other forms of hoists, the ratio 64 ENGINEERING LABORATORY PRACTICE. may be determined by experiment. Tie a piece of string on a link of the load chain opposite some fixed part of the hoist and put a similar piece on the hand- chain. Move the former a considerable distance and observe the corresponding movement of the hand- chain. Repeat several times and calculate the velo- city-ratio from the mean of the observations. This ratio should be expressed in the form of a fraction, the denominator being I. The weight lifted, in pounds, may be taken as a unit representing the work done; the stress in pounds on the hand-chain, multiplied by the fraction repre- senting the velocity-ratio, will measure the correspond- ing work put into the hoist. The efficiency in per cent is equal to 100 times the work delivered by the hoist divided by the work supplied. Make determinations in both hoisting and lowering with six loads, increasing by one-hundred-pound steps, and report on the form shown below. The last item on the report, " Ratio of work done by falling load to work done on hand-chain in lower- ing, " is not expressed as an efficiency, since the chief purpose of the hoist is to raise and not to lower the load. It should be expressed as a ratio thus: \ \ x\ the work done on the hand-chain being taken as the I. Note. — The weight of the scale-pans should be in- cluded as a part of the load. MEASUREMENT OF POWER. 65 74. Form for TEST OF HOIST. Made by Date, VELOCITY-RATIO Load lifted in pounds Stress on hand-chain in pounds. Work put into the machine Efficiency in hoisting Stress on hand-chain necessary to lower Work done in lowering Ratio of work done by falling load to work done on hand- chain in lowering 123456 Notes: 75. Belt Testing. — Belts are tested to determine the power which they will transmit under different conditions of tension, speed, and load, and the coeffi- cient of friction between them and the pulley. The apparatus should be so arranged that the belt may be run under different initial tensions and the power absorbed by some form of brake. Specific Directions. — Run four tests of twenty minutes each, with initial tensions of 20, 40, 60, and 80 pounds per inch width of belt. Let the brake load be as large as can be carried with a slip of not to exceed 3 per cent. Observe: 1. Time. 2. Revolutions of driving-pulley. 3. Revolutions of driven pulley. 4. Initial tension (when at rest). 5. Total tension (in motion). 66 ENGINEERING LABORATORY PRACTICE. 6. Net load on brake. The Report should include, in addition to a copy of the Running Log, the following items: a. Kind of belt. b. Width and thickness. c. Condition of belt. d. Rough or smooth side to pulley. e. Diameter of driving-pulley, inches. /. Diameter of driven pulley, inches. g. Length of brake-arm, inches. h. Initial tension, per inch of width. t. Speed of belt, in feet per second. j. Slip, in per cent. k. Tension on tight side, T x . I. Tension on slack side, T^. m. Horse-power of belt. n. Equivalent horse-power at ioo feet per second. The per cent of slip is found as follows: Let r be the actual revolutions of the driven pulley, and r, the calculated revolutions without allowing for slip. Then the per cent of slip will be r, — r ioo— . The values of T x and 7^ are found as follows: The total tension on the belt is composed of the sum of the tensions on the two sides or item 5 = 7^ -f- 7!,. If T x and 7", are equal, no motion of the belt will result. If 7", be greater than 7!,, then motion will result and power will be transmitted proportional to that differ- ence. This is expressed by the following formula: T T J item y *- 2 - (item/) MEASUREMENT OF POWER. 67 from which, with the relationship expressed above, the values of T i and T 2 can be found. 76. Belt Slippage. — A knowledge of the slippage of belts is of importance when selecting sizes for pulleys, since it is evident that if this slip is neglected the driven pulley will fail to reach the intended speed. Specific -Directions. — The apparatus required to de- termine the per cent of slip consists of two speed- counters and a gong or whistle for signals. An ob- server with a counter in hand should be stationed at each shaft connected by the belt, while a third keeps time and log. Upon signal, the counters are applied simultaneously to each of the shafts and the revolutions taken for a given interval of time (two minutes), which is ended by a second signal. From the known diameters of the two pulleys calculate the number of revolutions which the driven would make in the interval covered by the observation, provided there were no slip, and let this be called r t . Let the observed revolutions of the driven pulley be r 2 . Then r, — r 2 will represent the slip, and the per cent of slip will be r, — r„ 100 -. Several observations should be made and the results averaged. The Report should include width, thick- ness, and kind of belt, diameter of driver and driven pulleys; also the following: (a) revolutions of driver and driven per minute for each observation, and mean; {b) speed of belt in feet per second ; (c) revolutions which driven should make if no slip, average ; (d) slip in revolutions per minute, average; {e) per cent of slip, average. In connection with the report, solve the following: 68 ENGINEERING LABORATORY PRACTICE. Problem. — A main shaft running at the rate of 200 R.P.M. carries a driving-pulley 48 inches in diameter. What should be the diameter of the driven pulley in order that it may run at 300 R.P.M., there being no slip ? What should be its diameter if there is to be 3 per cent of slip ? 77. Tests of Paper Friction Wheels.— The use of paper wheels for the transmission of power is being rapidly extended, and a knowledge of their capac- ity and wearing qualities is correspondingly valu- able.* For the investigation of this subject a machine is in use in the Purdue Laboratory which consists of a paper pulley, driving a secondary shaft which is fitted with a Prony brake. The paper pulley is held against its follower by means of a bell-crank lever and weights. The experiments may be conducted according to the following : Specific Directions. — {a) Note lengths of lever-arm, diameters of pulleys, etc., unbalanced weight of levers, brake, etc. (b) Place on the scale-pan sufficient weights to make a normal pressure between pulleys of 75 pounds per inch of width. Place a light load on the brake and take simultaneous speed-readings of both pulleys, noting slip from known diameters of the two pulleys. Increase the brake-load to make about 5 per cent of slip, and repeat. Make tests with two intermediate brake-loads. (c) Change the normal pressure to 120 pounds and again to 140 and 160 pounds per inch of width, and repeat as under (b). (d) Report should cover all measurements and constants, tabulated logs of each test, giving time, * See paper on " Paper Friction Wheels," Trans. A. S. M. E., vol. xviii. p. 102. MEASUREMENT" OF POWER. 69 speeds, brake-load, and normal pressure; a tabulated statement of results of each test giving normal pres- sure, horse-power transmitted, slip and coefficient of friction; and four curves showing relation of horse- power transmitted to normal pressure with constant slip, relation of horse-power to slip with constant pressure, and relation of coefficient of friction to slip with normal pressure constant, and to normal pressure with slip constant. The coefficient of friction in this case is the ratio of the tangential pull to the total normal pressure, and is calculated as follows: Let r be the effective brake- arm, r, be the radius of the driven pulley, p the net brake-pull, P the normal pressure per inch of width, and w the width of the narrower pulley in inches. Then the coefficient of friction is /= pr r x pr Pw ~ Pr.W Caution. — Wipe off surfaces of driver and follower with piece of perfectly clean waste, and see that bear- ings are oiled before starting. CHAPTER IX. STRENGTH OF MATERIALS. 78. Testing-machines. — Machines for the testing of materials may be said, in general, to consist of (1) a power system by which stress is applied to the specimen, and (2) a weighing system by which the stress applied is measured. The power system may consist of a train of gears or an hydraulic cylinder, either of which may be operated by power or by "land. The weighing system usually consists of a system of levers and a poise by which the stress is balanced as on an ordinary pair of scales. An exception to this is the Emery Testing-machine, in which an hydraulic head and scale take the place of the system of levers commonly employed. In some Continental machines a mercury column is used to measure the stress. The usual form of testing-machine is that in which the load is applied through a train of gears and screws operated by power, and the stress is measured by a system of levers. They are of the vertical type, in which the tensional and compressional specimens are held in a vertical position. The vertical screws con- nected with the power system operate a movable head, to which the lower end of the tension specimen is 70 STRENGTH OF MATERIALS. 71 connected. The upper end of the specimen is con- nected to the upper head which is a part of the weighing system and rigidly connected with the table of the machine, the latter resting in turn on the lever system. In compressional tests the specimen is placed directly between the movable head and the table. 79. Riehle Screw-power Testing-machines. — In Fig. 19 is shown a Riehle Testing-machine of 300,000 lbs. capacity. As shown in the cut, it is arranged for either tensional, compressional, or trans- verse tests. The screws s, s are operated by power through a system of gears shown under the frame of the machine. The speed of the screws is controlled and their motion reversed at will, by manipu'ation of the three levers, l lf / 2 , / 3 , located in a position near the poise-lever, convenient to the operator. These screws operate the movable head b. The upper head a is connected with the table t which rests on the system of levers e, f. g, h. Along the last lever, k, the poise p is made to travel by the hand-wheel w. The lever h is balanced by the adjustable counterpoise c. The head a may be raised or lowered to accommodate different lengths of specimens. For adjusting the machine four different speeds are provided, for both upward and downward movement. These are secured by manipulation of levers /„ / 2 , and / 3 . For testing, two speeds are provided, using levers l l9 / 2 , and handle i. Specimens may be tested in tension up to 6 feet in length, with an allowance for a total elongation of 3 feet. In Fig. 20 is shown in perspective the Riehle patent high-faced wedge for flat specimens. The 72 ENGINEERING LABORATORY PRACTICE. serrated surface is slightly convex, and grips the speci- men first on a line parallel to its axis. As the wedge- Fig. 19. — Riehle 300,000-pouND Testing-machine. teeth sink into the specimen a hold is received over its entire width. It is claimed that by the use of this device a more centrally applied stress is secured. STRENGTH OF MATERIALS. 73 Fig. 21 shows a plan of the arrangement with the specimen D in place. The curvature of the faces of the wedges cc is exaggerated to render the action Fig. 20. — Riehle Patent High-faced Wedge. Fig. 21. — Arrangement of Wedges. more easily understood. For round specimens, wedges are provided with V grooves of different sizes, into which the specimen fits. 80. Riehle 100,000-lb. Testing-machine. — In Fig. 22 is shown a form of Riehle machine having a capacity of 100,000 lbs. The general arrangement is that usually employed. It differs from the previous example principally in the use of a fixed upper head. The machine shown in the cut is provided with a special form of automatic poise which adjusts itself to balance the increasing loads. The poise-lever is in the form of a screw, and the poise is a nut which is revolved on the screw by means of a train of gears and a splined rod back of the poise-lever and parallel with it. This is well shown by the detail view. The splined rod is driven by a belt operated from the driving-mechanism of the machine, and its motion is 74 ENGINEERING LABORATORY PRACTICE. controlled by an electromagnetic clutch carried on the back end of the poise-lever. The poise-lever is connected at its outer end to an auxiliary lever which carries at its free end two contact-points which operate the electromagnetic clutch. The operation is as follows: As a load is applied to the specimen, the poise-lever rises and the auxiliary lever falls, ^O^ N\©V» o\ ^0\8», Fig. 22. — Riehle ioo,ooo-pound Testing machine. making contact with the lower contact-point. This energizes one side of the clutch, which, through the rod and gears, moves the poise-weight along the poise-lever until the latter is balanced and, falling, breaks the electric contact. If for any reason the load should decrease, contact would be made at the upper contact-point, the other side of the clutch would be energized, and the poise would be moved backward until a balance was secured. In later STRENGTH OF MATERIALS. 75 designs provision is made for adjusting the speed of travel of the poise to the size of the test-piece. 81. Olsen ioo,ooo-lb. Testing-machine. — A de- sign of testing-machine of 100,000 lbs. capacity, made by Tinius Olsen & Co., is shown in Fig. 23. The Fig. 23. — Olsen ioo,ooo-pound Testing-machine. machine differs from those already described in the arrangement of the driving mechanism and the weigh- ing levers. Four straining-screws are employed, in- stead of two as in the Riehle machine. The poise- lever is fitted with a vernier-dial at its back end, which is graduated to 10 pounds. Several adjusting 76 ENGINEERING LABORATORY PRACTICE. speeds are obtained by manipulation of the two levers shown, and the slowest testing-speed is controlled by the hand-wheel, which throws a pair of grooved fric- tion-wheels into action. Fig. 24. — Riehle Hydraulic Testing-machine. 82. Riehle Hydraulic Testing-machine. — Testing- machines are made by Riehle Brothers in which the STRENGTH OF MATERIALS. 77 power is applied by hydraulic pressure. The train of gears, which forms the power-system in the usual design of machine, is replaced by an hydraulic cylinder connected to the movable head. Fig. 24 shows a Riehle hydraulic machine of 50,000 lbs. capacity. This type of machine may be conveniently used for stresses not exceeding the above-mentioned capacity. For stresses above that amount the leakage of the hydraulic cylinder renders the action of the machine unsatisfactory. As shown by the cut, the pump is situated on the table of the machine between the upright columns and the poise-system. The pump is operated by a handle which may be detached when not in use. Attached to the pump is a small check-valve controlled by a lever, which when opened allows the oil to fiow from the hydraulic cylinder back to the pump. This allows the large counterweight to raise the plunger with the attached movable head to its normal position after the breaking of a specimen. 83. Emery Testing-machine. — One of the most accurate forms of testing-machines made is the Emery Hydraulic Testing-machine, made by Wm. Sellers & Company. The following description is given by the makers : The essential peculiarity of the Emery testing- machine is the method by which the stress produced upon the piece tested is conveyed to the scale and accurately weighed by mechanism that is entirely fric- tionless, and hence responds to the same increment of load regardless of the amount of strain upon the specimen. This result is accomplished by receiving the load upon a fiat closed cylinder called the 78 ENGINEERING LABORATORY PRACTICE. " hydraulic support." The general scheme is indi- cated in Fig. 25, which shows merely the relation of the parts, no attention being paid to proportion. The depth of the hydraulic-support cylinder A is exceedingly small. The end is closed to prevent the escape of the contained fluid by a thin sheet of metal, b y upon which rests a piston, c, considerably smaller than the internal diameter of the cylinder; this piston is secured to the cylinder by thin flexible fixing-plates, dd, which permit a very small movement in the direc- tion of the axis of the cylinder while rigidly securing it against any lateral movement. This longitudinal movement of the piston from no load to full load is not more than .003 inch, and as there is no hydraulic packing and no sliding, there is no friction beyond that of the fluid. This hydraulic chamber is connected by a pipe e, with a smaller but similar chamber B, placed in the scale; the piston c f of this latter cham- ber acts through the block H against the first lever C of the scale, which thus receives a fraction of the load upon the piston c determined by the relation between the areas of the two hydraulic cylinders A and B. The scale-body is a rigid cast-iron frame carrying the steel scale-levers, all the supports and connections of which are thin, flexible plates of steel firmly secured to the levers and their supports, and having a sufficient exposure between their fixed ends that the amount of bending due to the movement of the levers shall be well within the elastic limit of the material. The long arm of the lever C is coupled by the bar D with the short arm of the poise-frame lever E\ the long arm of this lever carries all the standard weights of the scale, and the method of putting them on or taking them STRENGTH OF MATERIALS. 79 80 ENGINEERING LABORATORY PRACTICE. off, without handling, is peculiar to the Emery sys- tem. Suspended from this lever E at suitable inter- vals by thin fulcrum-plates are " poise-frames " N> consisting of an upper cross-head >S and a lower cross- head T, united by three vertical bars disposed at equal intervals about the cross-heads. These bars are provided on their faces with short projecting brackets V, having a horizontal surface and a bevelled surface corresponding with similar surfaces formed on the weights k, which are short cylinders or rings with bevelled edges; the weights are carried by the flat surfaces and centered by the bevelled surfaces. A " weight-frame/* M, for carrying the weights when not in use, of similar construction, has its three verti- cal bracketed bars alternating with the bars of the poise-frame; this weight-frame is guided, and is raised and lowered in a vertical line without touching the poise-frame, by a rock-shaft and a hand-lever coupled to the rod projecting from the cross-head R. The brackets on the weight-frame bars are differently spaced from those on the poise-frame, and when the weight- frame is at the top of its stroke it carries all of the weights clear of the poise-frame; a small move- ment downwards transfers one weight to the poise- frame, the bevelled surfaces on the brackets centering the weight if it becomes displaced sideways by a too sudden movement. A further movement transfers another, and so on ; that is, the movement of the weight-frame in either direction transfers the weights singly and successively from one frame to the other; the weights f and g are shown carried by the poise- frame, j and k by the weight-frame, while h is being transferred from one to the other. STRENGTH OF MATERIALS. 8 1 The operating hand-lever is provided with a notched segment, into which a click-spring plays so that the operator feels when he has moved the lever the right distance to transfer a weight to or from the poise- frame without having to watch the indicator as formerly, and the arrangement of the six bars sur- rounds the weights by a cage that effectually prevents any displacement and consequent interruption of the test, as sometimes occurred when the weights rested on simple shelves secured only by short-pointed pins. There is hence no necessity for opening the glass case that encloses this part of the scale, and the weights are never exposed to any risk of alteration. The weights in the first poise-frame have a value of ioo pounds, the next frame carries weights of a value of ten times as much, or iooo pounds, the next 10,000 pounds, and so on; and the readings are summed up by a series of segments connected to the several operating shafts and provided with figures denoting the number of weights on each poise-frame. A hori- zontal slot in a vertical plate near the upper left-hand corner of the scale is so placed that the reading of the figures shown through this slot denotes the number of pounds pressure applied to the specimen. The final lever of the scale is an indicator-needle/ 7 , which has a movement at its point of if to 2 inches, and this movement, calculated from the mechanical ratios of the hydraulic chambers and of the levers in the scale, is not less than 300,000 times the movement of the piston c in the first hydraulic chamber, and may on large machines be 6,000,000 times as much. The transfer of fluid from one chamber to the other is almost imperceptible, and while it takes force to move 82 ENGINEERING LABORATORY PRACTICE. the metal sheets and to bend the steel fulcrums, yet this force is all returned as the various parts resume their position of equilibrium, the needle returning to 3 u < i o H w W H >< W W o Q Q > H O o u o W I M 6 STRENGTH OF MATERIALS. 87 pipe, depending upon the direction in which the strain is to be exerted upon the specimen. The weighing- and straining-heads are mounted on a suitable frame or bed and are held together by heavy straining-screws. In Fig. 27 is shown a special form of Emery machine of 30,000 pounds capacity for weighing the tractive force of locomotives on shop testing-plants. The draw-bar of the locomotive is connected to the draw-bar of the weighing-head, and the latter thus receives the stress due to the tractive force. The weighing-head is provided with mechanism for pro- ducing an initial stress upon the draw-bar in either direction. This initial tension for the machine illus- trated is equal to about 25,000 pounds, and operates to push the draw-bar ahead when the locomotive is running forward and the reverse when it is running backward. A special form of scale is used in which the levers are provided with sliding-weights, as in an ordinary pair of scales, instead of the arrangement shown in Fig. 25. Provision is made for raising or lowering the weighing-head to accommodate different heights of draw-bar. 84. Riehle Wire-tester. — A very convenient form of wire-tester is shown in Fig. 28. The power is applied by a hand-wheel which gives motion to one pair of grips through the medium of a nut and splined collar. The other pair of grips is attached to an ac- curate spring-balance, reading to 600 pounds. The needle of the balance is so arranged that it remains at the highest point reached, after fracture takes place. Provision is made for taking up the recoil after fracture, to prevent injury to the balance. The 88 ENGINEERING LABORATORY PRACTICE. machine is arranged for quick adjustment to accom modate different lengths of specimens. X I CO 6 85. Olsen Cement-testing Machine. — A special form of machine for testing cement is shown in Fig. 29. The specimen is held between two shackles and STRENGTH OF MATERIALS. 8 9 the power is applied slowly by means of a hand-wheel. A system of levers weighs the load to which the specimen is subjected, the poise being conveniently moved by means of a small hand-wheel and endless cord. Fig. 29. — Olsen Cement Testing-machine. 86. Accessory Testing Appliances. Riehle-Yale Extensometer. — In order to determine the elastic 90 ENGINEERING LABORATORY PRACTICE. limit and modulus of elasticity, it is necessary to know the rate of deformation of the specimen as Fig. 30. — Riehle-Yale Extensometer. stress is applied. For this purpose, use is made of an instrument known as an Extensometer, one form of STRENGTH OF MATERIALS. 91 which is shown in Fig. 30. This form is usually used in tensional tests, but may also be used to a limited extent in compressional tests. The instrument con- sists of a pair of clamps, each fitted with three sharp- pointed thumb-screws, by which they may be fastened to the specimen. A distance-piece or spacer is so arranged that the clamps will be exactly 8 inches apart. This distance-piece is removed as soon as the instrument is in place and before the stress is applied. The upper clamp carries two rods fitted at their lower ends with adjustable contact-points. The lower clamp is fitted with two micrometer-screws, reading to ten- thousandths of an inch, by which the elongation is measured. Electrical connection is made, as shown, with a battery and bell. The ringing of the bell announces the completion of the circuits at the points P and P r as the micrometer-screws are raised to measure the elongation of the specimen. By this means a uniform pressure of contact is secured. 87. Autographic Recording Apparatus. The Henning Portable Recorder. — The Autographic Re- corder is an instrument for producing stress-strain diagrams or curves showing the variation of strain with stress. One of the newer forms of autographic recorders is the Henning Portable Recorder, shown in Fig* 3 1 - The drum is attached by means of cord and pulleys to the poise, and revolves in proportion to the increasing stress. A proper reduction of the length of travel of the poise is made. The stretch of the specimen actuates the pencil-lever, the movement of the latter being ten times the elongation of the speci- men up to elastic limit. After that point is reached the pencil-lever strikes a stop and is then raised bodily 9 2 ENGINEERING LABORATORY PRACTICE. with its carriage, giving a record directly proportional to the elongation. The instrument can be applied to Fig. 31. — Henning Portable Recorder. specimens from £ inch in diameter to 2 by if inches in cross-section. It can be used for compression as well as extension, and may be used for gage-lengths of 6, 8, 10, and 12 inches. The wedges must be blocked STRENGTH OF MATERIALS. 93 up when the instrument is kept on the specimen to the point of rupture. 88. Deflectometer. — This instrument, Fig. 32, may be used to record the contraction of short specimens under compressional stress or the deflection of speci- Fig. 32. — Deflectometer. mens under transverse stress. The cut shows the manner of arranging the instrument and renders further explanation unnecessary. 89. Laying off Gage. — As is explained later, speci- mens in tension are sometimes marked for a length of 8 inches in one-inch lengths, preparatory to testing. The instrument shown in Fig. 33 is conveniently iiiiiSiniVillP^liiillliPii! llilRlEHDE 40 .30 2 ^Jjll'l'l ■■||||l|ll , m'||"1'""lllllllllllll:!lllHllmi r\X\T\Tvr\j\j Fig. 33. — Riehle Laying-off Gage. arranged to assist in marking the specimen. At one end of the gage is a per-cent scale, arranged to read directly the per cent of elongation in 8 inches after fracture, 90. Methods of Testing. Tension. — Materials are tested in tension to determine, among others, the following properties, viz.: Ultimate Strength, Elastic Limit, Moduli of Elasticity and Resilience, Percen- 94 ENGINEERING LABORATORY PRACTICE. tage of Elongation, and Reduction of Cross-sectional Area. 91. Definitions. — Ultimate Strength. — The ulti- mate strength may be defined as the maximum stress borne by the specimen per square inch of original area. Elastic Limit. — Considerable confusion exists in the definition of the elastic limit. The term is used to indicate three different points: (1) The unit-stress beyond which a portion of the deformation remains permanent after the load has been released. (2) The unit-stress at which the deformation ceases to be proportional to the load applied, i.e., the " pro- portional elastic limit." (3) The point in the stress-strain diagram where the deformation increases rapidly without any increase in the load, or the unit-stress corresponding to the scale-beam load when the beam, which has been kept balanced, " drops' ' suddenly. The detection of the first elastic limit involves a release of the load, and presents many practical difficulties. Indeed any load produces a slight set. The second elastic limit is the elastic limit ordinarily determined when an extensometer is used. With the ordinary material encountered it is not very de- finite, especially when very delicate measurements are made. The third or " apparent " elastic limit, that measured in commercial testing, and by best usage called the " yield-point, " is most easily fixed, and most valuable. In determining the yield-point, the student will do well to check the scale-beam indica- tion by using a pair of dividers as follows; STRENGTH OF MATERIALS. 95 Space the dividers eight inches, and put one leg in the lower gage-mark. Chalk the surface of the speci- men around the upper gage-mark. As the test pro- gresses swing the upper end of the divider to mark a line on the chalked surface. The space between these lines will widen rapidly at the yield-point. Note also that just above the yield-point the specimen begins to scale. The following definition of apparent elastic limit has been proposed by Prof. J. B. Johnson:* The apparent elastic limit is the point on the stress- diagram of any material, in any kind of test, at which the rate of deformation is 50 per cent greater than it is at the origin. Modulus of Elasticity. — This is the number express- ing the ratio of the stress per square inch to the deformation per inch accompanying that stress, within the elastic limit. Thus if P equal any increase of stress per square inch, and d is the total increase of deformation under that load, per inch of length, ex- pressed in inches, then the modulus of elasticity E = P/d. We may, in determining this modulus, use for d the average deformation per inch corresponding to successive increments of load of impounds per square inch, these deformations being observed between cer- tain specific limits. Modulus of Resilience. — The modulus of resilience is the amount of work, in foot-pounds, done on a cubic inch of the specimen up to elastic limit. It is * " Materials of Construction," by J. B. Johnson. John Wiley & Sons. 9 6 ENGINEERING LABORATORY PRACTICE. equal to one half the load per square inch at elastic limit multiplied by the total elongation in feet, per inch of length up to elastic limit; or to the square of the load at elastic limit divided by twenty-four times the value of E. Percentage of Elongation. — This is the ratio of the total elongation of the specimen to its original length, measured between two gage-marks, usually placed 8 inches apart. It is a measure of the ductility of the material. Reduction of Cross-sectional Area. — This is the ratio of the smallest area after fracture to the original area of the specimen. 92. Form of Specimens for Tension. — Forms of specimen conforming closely to those recommended as standard by the French Commission are shown in Fig. 34. They are arranged so that the per cent of elon- -i-d- V 8d- ^E*Sff ■Ad? -4-6- > Wb 9V~M- KVfT ih Fig. 34.* — Standard Forms of Specimens for Tension. gation shall be the same, for the same material, when different lengths of specimen are used. It will be seen that the recommended relation between gage-length and cross-sectional dimensions is, for round speci- mens, /= Sd, * Reproduced from Johnson's " Materials of Construction," STRENGTH OF MATERIALS. 97 and for square specimens / = 9 Vbi. For cast iron and for some other materials special forms of specimens are used in place of those men- tioned above. The specimens should be prepared with great care. The machining should be done in such a manner that the material is not torn or otherwise weakened, and it is recommended that all machined surfaces be finished by filing. When a sheared specimen is straightened, this straightening must be done cold. 93. Method of Testing for Ultimate Strength. — This test is the one commonly employed in commer- cial testing to determine the characteristics of metals in tension. For purposes of comparison it serves as a fair indication of the quality of the material. Specific Directions. — The specimen should first be examined for cracks and flaws, as these may seriously affect the results of the test. Such defects should be noted on the report. The specimen should then be carefully measured in all dimensions, reading the dimensions of the cross-section to the thousandth of an inch, and making the record on the blank form. If the length of the specimen will permit, marks should be made upon it an inch apart for a space of eight inches. The outside marks are called gage-marks. This is done with a laying-off gage, and is for the purpose of determining the elongation after rupture. Balance the machine on which the test is to be made, first noting that the four check-nuts at the corners of the table are only loosely screwed down. 98 ENGINEERING LABORATORY PRACTICE. After balancing the machine, the specimen should be carefully placed between the wedges, care being taken to have it centrally and vertically located. The wedges should be oiled on the back with heavy oil before being placed in position. Start the machine at a slow rate of speed and keep it running continuously until fracture occurs. Note the time of starting the test and the time when frac- ture occurs. The test should last from five to ten minutes. The scale-beam should be kept floating at all times during the test. When operating machines fitted with a hand-poise, take care not to run the poise out beyond the point necessary to float the beam, and do not run it back when the beam falls for any reason, unless the maximum stress has been reached and it is desired to find the load at the point of rupture. In such a case be sure to note the maximum load before moving the poise back. The following points should be noted: 1. Time of starting test. 2. Load on specimen when the beam first falls. This is called the yield-point, and occurs at from 50 to 75 per cent of the maximum load. Do not confuse this with drop of the beam due to slipping of the wedges. 3. Maximum load. 4. Load at rupture. 5. Time of rupture. After rupture occurs, stop the machine, remove the specimen, clean and return the wedges to their proper place. Leave the testing-machine in good order. Place the fractured ends of the specimen carefully STRENGTH OF MATERIALS. 99 together, measure the elongation in eight inches, and determine the per cent of elongation. With a vernier caliper determine as closely as possible the minimum area of the fracture. In the case of the more ductile metals a rapid pull- ing out occurs near the point of fracture just before breaking. When this occurs the measured amount of elongation will vary in the same material, according as the fracture is between or near the gage-marks. If the fracture were just midway between the gage- marks, nearly all of the elongation would fall between those marks, and the measured elongation would be a maximum. But if the fracture should occur near a gage-mark, much of the elongation would fall outside of the marks, and the measured elongation would be less than in the previous case, To correct for this variation, an " equivalent elongation " may be calcu- lated by the following method: Suppose the specimen to be divided into x equal spaces between gage-marks, and that the fracture is y spaces from the nearest gage-mark. Mark two points, A and B (Fig. 35), on the long piece at y and \x I B DC Fig. 35. spaces, respectively, from the fracture. Place the pieces carefully together and measure from the gage- mark on the short piece to point A. This distance plus twice the measured distance fromyi to B should be taken as the final length of the specimen, and minus the original length, is called the equivalent elonga- tion. In some specifications it is required that the IOO ENGINEERING LABORATORY PRACTICE. fracture shall occur within the middle third of the length. The fracture should be carefully examined and pro- nounced either coarse or fine, and in metals either fibrous, granular, crystalline, or silky. It should also be noted as plane, oblique, cup-shaped, half-cup, or irregular. Tie the two pieces of the broken specimen together, attach a card on which is noted the kind of material, and the principal results of the test and place in the case provided for the purpose. The Report should be made out on the blank form for " Tensional Tests," and should include the fol- lowing items: Kind of material, sketch of specimen, dimensions of cross-section, area of cross-section, dis^ tance between gage-marks, time of test, yield-point, maximum stress, ultimate strength, reduction of area, percentage of elongation (actual), equivalent elonga- tion, sketch of fracture, character of fracture, notes. 94, Determination of Elastic Limit by the Exten- someter. — In the determination of the elastic limit by the extensometer, the test is conducted in sub- stantially the same manner as that prescribed for find- ing the ultimate strength, except that instead of a continuous application of stress from start to the point of rupture the stress is applied in definite incre- ments, and after the application of each increment the test is stopped and a measurement made of the deformation. For this purpose an extensometer, a description of one form of which is given in Section 86, is used. These measurements are continued until shortly after the elastic limit is reached, when the instrument is removed and the stress applied con- tinuously up to the point of rupture. STRENGTH OF MATERIALS. IOI Specific Directions. — Prepare the specimen and place in the testing-machine as directed in Section 93. From the known properties of the material under test, determine approximately the probable load per square inch at elastic limit, and reduce this to the corresponding actual load. Divide this actual load into twenty (20) equal increments and enter them in tabular form on the extensometer log. Place a load corresponding to one increment on the specimen and then place the extensometer in position. In adjusting, be sure that the clamps are concentric with the specimen and that the axes of the microm- eter-screws are parallel with and equidistant from it. In tightening the adjusting-screws be careful not to overstrain them. See that the contact surfaces are clean and the electric circuit in order. In attaching the wires to the extensometer, so arrange them that there will be no tension in them tending to pull the instrument out of line. Now take a zero-reading. This is done in the fol- lowing manner: Place the micrometer on one side at zero and move the upper contact piece until contact is made as shown by the ringing of the bell. Now back the upper screw off, and again bring it down until the bell just begins to ring. Then back the micrometer away from the upper contact point. Repeat the operation on the opposite side. Apply the second increment of stress to the speci- men and take a reading of the extensometer, this time having the upper contact pieces in their original posi- tion and making contact by means of the micrometer- screws. Repeat this process as rapidly as practicable until the sudden increase in the rate of deformation 102 ENGINEERING LABORATORY PRACTICE. indicates that the elastic limit has been passed. Remove the extensometer, and finish the test as pro- vided in Section 93, under the head of Ultimate Strength. The Report should be made out on the blank form for tensional tests, and should be accompanied by the extensometer log and a stress-strain diagram (see Section 95). The items called for in addition to those given for tests of ultimate strength are: Elastic limit, modulus of elasticity, and modulus of resilience. Calculate the modulus of elasticity between the limits of 8000 and 18,000 lbs. stress per square inch. 95. Stress-strain Diagrams. — The stress-strain diagram is a curve, the ordinates of which represent the stress on the specimen in pounds per square inch and the abscissae represent the corresponding total deformation per inch of length. From an inspection of this diagram the behavior of the material under stress, and in a general way its characteristics, may be deter- mined. For most materials the diagram will be nearly a straight line up to the elastic limit. In Fig. 36 is shown a typical diagram in two scales for wrought iron. In case the diagram is plotted from the results of an extensometer test, it can only be drawn to a point a little beyond the elastic limit. Such a scale should be chosen as will exhibit to best advantage the char- acteristics of the curve. Make the even thousands come at the heavy division-lines on the coordinate paper. See to it that the diagram can be read easily. To determine the modulus of elasticity, E y from the strain-diagram, proceed as follows: From the abscissa representing an elongation of .001 inch per inch of STRENGTH OF MATERIALS. 103 specimen, erect an ordinate to intersect the line drawn from the origin parallel to the straight part of the stress-strain curve. Find the stress corresponding to / f 1 z hi Q. Z O H < O Z O _J Id HONI 3uvn is s y3 J SON nod Q 6 3 83 s 3§ z © 10 © © rt pi h I en W H to the point of intersection. This multiplied by 1000 will give E. To find the point on the diagram corresponding to the yield-point (Section 91) draw to the stress-strain curve a tangent which has an inclination 50 per cent 104 ENGINEERING LABORATORY PRACTICE. greater than the straight line from the origin to the elastic limit. The point of tangency will be the yield-point. 96. Autographic Records. — Many forms of instru- ments have been devised for autographically produc- ing a stress-strain diagram during the progress of the test. One of these, the Henning Portable Recorder, is described in Section 87. In the majority of designs two movements are provided: one a drum-movement, attached to the weighing-poise and revolving in pro- portion to the outward movement of the latter; and the second a pencil-movement, connected in some manner with the specimen and moving in proportion to the deformation of the latter. In the best designs two rates of pencil-movement are provided. Up to elastic limit the movement is magnified to render the characteristics of that part of the curve more easily seen. After elastic limit the rate of movement is much slower, in order that the latter part of the curve may be kept within reasonable limits. 97. Methods of Testing in Compression. — Ma- terials are tested in compression to determine their crushing strength and strength to resist bending; also at times their elastic limits, and, if ductile, their plastic limits. Short specimens, those whose length is less than five diameters, usually fail by crushing or flowing. Long specimens usually fail by bending toward the side of least resistance. 98. Short Specimens. — The materials may be divided into two general classes, in accordance with their behavior when subjected, in short specimens, to compressional stress. In the first classification are the plastic materials, such as wrought iron, soft steel, STRENGTH OF MATERIALS. 10$ copper, the alloys, etc., which fail by flowing. After the elastic limit is passed, further compression results in an increase of the cross-sectional area under a con- tinually increasing load. For such materials there are two fixed points independent of shape of specimen, i.e., the elastic limit and the plastic limit. It has been found that the elastic limit of these materials is nearly the same as their elastic limit in tension, and for this reason and in view of the difficulty of measur- ing the deformation of short specimens, compressional tests upon them are seldom made. The second classification embraces the brittle ma- terials, such as stone, brick, wood, cement, cast iron, etc., which fail by crushing due to the shearing on definite angles. With these materials the ultimate strength is easily determined. Preparing the Specimen. — If the material be metal, the specimen should preferably be turned and the ends faced up carefully to insure that they are plane and perpendicular to the axis of the specimen. If the ma- terial be of stone, cement, or some similar substance, the specimen is usually cubical in form; and the bear- ing-surfaces should be made as nearly plane and parallel as possible by grinding, and should then be bedded in a thin layer of plaster of paris. Sized paper should be put between the specimen and the plaster of paris bed to prevent absorption of water by the specimen. To secure a true bed, the plaster is allowed to set for about ten minutes while the specimen is on the table of the testing-machine, the movable head being run down in contact with the upper layer of the bed. The use of pasteboard or lead liners is not recom- mended. 106 ENGINEERING LABORATORY PRACTICE. Specific Directions. — Prepare the specimen as di- rected above. Measure all dimensions and record on the blank report-sheet furnished. Balance the testing- machine with the specimen on the table. Apply the stress continuously until rupture occurs, or, in the case of the plastic materials, until the amount of deforma- tion is quite marked. In the case of stone, cement, etc., if the specimen begins to spall or flake off before rupture occurs, note the load when such action begins. Avoid injury from flying fragments. Take the time of starting and stopping the test. If the conditions of the test are proper, but little spalling will occur. The specimen will break suddenly, and the interior cone or pyramid will be evident. The Report should include the following items: Kind of material, sketch of specimen, dimensions of cross-section, area of cross-section, height, time of test, maximum stress, ultimate strength, sketch of specimen after test, notes. When a compressometer is used, a stress-strain diagram should be constructed. 99. Long Specimens or Columns in Compression. — A specimen of length greater than ten diameters usually fails by bending toward its side of least resist- ance. The maximum strength of an ideal or perfect column, centrally loaded, must be taken as the load obtained by multiplying the area of cross-section by the elastic limit of the material, a result independent of the length. The unavoidable imperfections of material and of workmanship and the difficulty of centering the load will, however, produce some bend- ing before this maximum load is reached. When the column is once bent, the deflection increases rapidly, and the material on the concave side STRENGTH OF MATERIALS. 107 of the column is subjected to the twofold stress due (1) to the direct compression of the load, and (2) to the bending produced by the load acting with a lever- arm about the neutral axis of the section. The column will completely fail at the point where this twofold stress exceeds the crushing-strength of the material. This load at failure depends on (1) the strength of the material of the column; (2) the value of E\ (3) the character of the ends, whether square or round; (4) the condition of application of the load, whether eccentric or not; and (5) on the ratio of the length / of the column to its radius of gyration r. In the case of very long columns {l/r > 150) the maximum load is that which will hold the column at any given deflection, and which, when allowed to con- tinue acting, will so increase the deflection as to cause failure. This breaking load is given by the equation P = uEI -T- /, where P= total load at point of flexure; E = modulus of elasticity; /= moment of inertia; / == length of specimen at point of flexure in inches; and u = a constant. This equation is known as Euler's formula, and the values of u are 4 and I for square and round ends, respectively. The specimens used ordinarily will not be long enough to come under this head. For the ordinary length of specimen the load on the scale-beam will 108 ENGINEERING LABORATORY PRACTICE. increase with an increasing deflection of the column until the twofold stress, mentioned above, will exceed the crushing strength of the material. At this point the maximum load is indicated, and after this the scale-beam drops off with increasing deflection. For all ordinary cases this load is given by the Rankine-Gordon formula, or by some one of the other well-known formulae (as, for instance, Prof. J. B. Johnson's parabolic formula) which are intended to represent the results of experiments on columns. It is necessary in testing columns to define as accu- rately as possible the condition of the ends. They should be either completely fixed or perfectly free to turn. The first condition is difficult to obtain. The second condition may be obtained by the use of clamps with attached knife-edges, the column being so fitted to the clamps that the neutral plane, when the column is unstrained, coincides with a plane joining the knife- edges. The perfection of the adjustment may be tested with moderate loads. Specific Directions. — The aim of the laboratory ex- periments with columns is to fix in the student's mind the behavior of columns of varying lengths. Select a piece of 2 X 4-inch wooden scantling and cut it into lengths of 86.7, 57.8, 43.35, 21.67, arj d 6 inches. Stretch a fine wire along the length of the specimen in the plane of the neutral axis. Test these pieces in compression with round ends, noting at suitable inter- vals of loading the lateral deflection at the neutral plane from the wire stretched along the column, and the maximum load. The deflection may be read from a small scale fixed to the center of the column. In STRENGTH OF MATERIALS. 109 the case of the 6-inch specimen use the compressom- eter. Plot the results as a curve showing the relation between /-— r and maximum scale-beam load for the different columns. Compare the results of experi- ments with the values derived by calculation from various formulae supplied by the instructor. 100. Cross-bending Tests. — Cross-bending tests are used to determine, in case of brittle materials like cast iron, the modulus of rupture and the resilience, and in case of ductile materials like wrought iron and soft steel, the elastic limit and modulus of elasticity. Other tests on springs, rails, rail-joints, etc., deter- mine the stiffness, i.e., the deflection at given loads, the elastic limit, and, in some cases, the ultimate strength. Tests on composite structures, like brake- beams, truck-bolsters, etc., are made to determine the stiffness, the elastic limit, and manner of failure, Specific Directions. — In preparing a specimen for test (supposing the specimen to be a prismatic beam) stretch a fine copper or steel wire between two pins which are driven directly above the points of support on the line of intersection of the neutral plane with the side of the beam. A suitable weight should be hung on the wire to keep it taut. Fix a micrometer on the beam so as to read the deflection of the neutral plane below the fixed wire. Connect the micrometer in circuit so that the contact of the micrometer with the wire is indicated by the ringing of an electric bell consequent on the completion of the circuit. In case of large wooden beams, a polished steel scale may be attached to the side of the beam at mid-span, and the deflection read by eye to hundredths IIO ENGINEERING LABORATORY PRACTICE. of an inch, taking care to avoid parallax by reading when the wire is in coincidence with its image on the polished surface. The deflection should not be read with reference to any part of the frame of the ma- chine. The specimen must be protected if necessary from the indentation of the knife-edges by the use of bearing-plates. Measure the beam in all dimensions and length of span. Place the beam so that one principal axis of inertia of the section shall be horizontal. Compute, for the case of a prismatic beam, the probable center load at the elastic limit from the formula le where R is the value of the elastic limit in tension, 7* the moment of inertia, / the length of span in inches, and e the distance in inches from the neutral axis to the outermost fiber. Divide this load into ten equal parts, and apply these part loads successively as in- crements to the center of the specimen, endeavoring to read the deflection without stopping the test. Note the load at rupture and manner of failure. Note any side buckling. In some cases the load may be released after each increment in order to determine the set. The Report should include a diagram whose abscissae are the deflections, and whose ordinates are the loads at the center. The results derived should be, when possible to obtain them, stress in outer fiber at elastic limit, modulus of rupture, modulus of elas- ticity, and resilience- STRENGTH OF MATERIALS. Ill The modulus of rupture is the value of R as com- puted from the formula In consequence of the tendency to equalization of the stress over the cross-section above the elastic limit and of the failure of Hooke's law, the value of R determined from this formula (which is based on Hooke's law) will in some cases be greater than the ultimate strength of the material in tension of steel. The elastic limit in flexure will be fixed by the elastic limit of the outer fiber, and can be computed by the formula given above, assuming that a small longitudinal bar in the surface of the beam behaves just as it would if tested by itself in tension. The elastic limit in flexure will, however, be greater than in tension for the case of square or flat plates of steel. The ultimate resilience of a brittle material (where the elastic limit is near the ultimate strength) will be P being the load at the center, and d the deflection at that load. E is computed from the formula E = 48 dr 101. Cement-testing. — The usual tests applied to cement are those for tensile strength, fineness, soundness, time of initial and final set, and crushing strength. 112 ENGINEERING LABORATORY PRACTICE. Specific Directions. — The work will include tests on two Portland cements and two natural cements. In order to obtain uniform and representative results for the tensile strength great care must be exercised to observe the following directions: (i) Portland Cement. — (a) Neat Tests. — Arrange moulds, oiled inside, on a non-absorptive plane sur- face. Take i£ pounds of cement and 25 per cent of water at 70° F. Mix water and cement thoroughly, using enough water to make a stiff plastic mixture, and work mixture at least three minutes. Put mix- ture in moulds, pressing it firmly in moulds with thumbs, but do not pound the briquette. Strike off both surfaces of briquette with trowel. Set the moulds away on a non-absorptive surface in a damp atmosphere. Except for one-day tests they should be kept in moist air 24 hours and then put under water. The student will return on the following day to immerse the briquettes, writing with lead-pencil the number of the series on each briquette. (b) 2-to-i Mortar Tests. — Take some of the labora- tory sand and sift it through Nos. 20 and 30 sieves. Use 1 pound of what passes No. 20 and is held on No. 30, with \ pound of cement. Mix thoroughly and add 15 per cent of water. Work at least 4 minutes. Fill moulds to overflowing and pound down mortar with flat side of trow T el, beginning at sides of briquette. These briquettes are disposed of as in (I, a). (2) Natural Cement. — Take 1^ pounds of cement and 30 per cent of water and mix briquettes as di- rected in (1, a). Do not allow the cement to assume initial set before filling the moulds. Then take J STRENGTH OF MATERIALS. 113 pound of cement and f pound of sand and mix as in (1, b). These briquettes may be immersed in water a few hours after hardening. (3) Concrete. — Concrete should be a compact mass as free as possible from pores or open spaces. The materials — broken stone, or gravel, and sand — are bound together by the cement. The proportion of the three different materials should be selected so that the sand practically fills the voids in the gravel or broken stone and the cement fills the voids in the sand. Rather more than this quantity of cement should be used to allow for imperfect mixing. Fill a box holding one cubic foot with gravel. Shake down well and strike off level. Weigh box and contents. Then pour water on gravel until the water rises to the surface. Weigh again and calculate the percentage of voids in the gravel. Then determine the weight of a solid cubic foot of sand. Supposing the weight of a solid cubic foot of sand to be 165 pounds, calculate the per cent of voids in the sand. Now make a mixture of gravel, sand, and Portland cement, with minimum amount of water, using enough cement to fill the voids. Directions for mixing will be supplied by the instructor. Make three 4-inch cubes, and allow them to set in air one day and in water 2J days. Test in com- pression after 28 days. Make another series with the proportion 1 sand, 3 gravel, 1 cement, and test as before. Report all data obtained, and report the character of gravel and sand supplied, noting whether or not the surface of the gravel was clean and whether the sand was sharp and free from clay or loam, 114 ENGINEERING LABORATORY PRACTICE. For Fineness. — If any time remains determine the fineness of grinding by sifting £ pound of cement through the three sieves Nos. 50, 80, and 100, weigh- ing the residue which remains on each. For Constancy of Volume or "Soundness." — Make on a slab of glass two thin-edged briquettes, 3 inches in diameter and \ inch thick, of stiff plastic consist- ency. After thorough setting put one cake under water and examine it from day to day to detect any radial cracks or changes of form. Do not confuse these with the irregular surface-checks which appear when the cement is mixed too wet. For Portland cements a more severe test is the heat test, conducted as follows: expose a pat of neat cement, after setting, to the action of steam for several hours, then place it in boiling water for three hours more. Perhaps the best test for soundness is the boiling test, as follows: Make two balls \\ to 2 inches in diameter and allow them to set in damp air for 24 hours. Place these in a beaker filled with water and bring to boiling-point in 30 minutes. Boil for three hours. The test-pieces are examined after slow cool- ing. They should not show cracks nor should they warp. In case of natural cements these tests are not so satisfactory. This test is made to detect the presence of free lime, the future slaking of which will destroy the work into which such cement enters. Time of Setting. — Mix pats similar to those for the test for soundness. When a needle T ^ inch in diameter loaded with \ pound ceases to penetrate the entire mass, setting is said to have begun. When a STRENGTH OF MATERIALS. 1 1 5 needle -^ inch in diameter loaded with I pound will not penetrate the mass at all, setting is said to be complete. The time of complete setting may roughly be determined by the fact that the cement offers con- siderable resistance to indentation with the finger-nail. After One Week, — Test briquettes in tension as soon as taken from water, noting the breaking-load in the laboratory record. Apply stress at the rate of 400 pounds per minute. Insert pieces of rubber bands between briquette and edges of grips in order to obtain break in center of briquette. Crushing Strength. — It is not usual to make com- pression tests in America. The results in tension vary directly with those in compression, so that the tensile strength is a satisfactory index of the value of the cement in compression. The student will make one 2-inch cube of each series mentioned and test in com- pression after one week as directed in Section 98. 102. Wire Rope in Tension. — Preparation of Speci- men. — In preparing specimens of wire rope for tension tests the chief difficulty is to so hold the ends that the strain may come equally on all parts of the cross-section and a break in the middle of the specimen length may occur. By the use of very long conical wedges, working in steel bushings, satisfactory results may be obtained; the wedges grip the rope as a whole. Or an artificial socket may be made in the steel bushing as follows: Bind the specimen with wire about six inches from the ends, to prevent unwinding, and wind the inter- vening length with cord to keep the strands in place. Slip the bushing over the ends. Unwind the strands down to the binding-wire; cut out the hemp core if Il6 ENGINEERING LABORATORY PRACTICE. necessary, and turn each separate wire back on itself toward the center to form a conical head, which may be drawn into the bushing so that it may assume the proper shape. The head should be boiled in caustic soda to remove grease, then washed in hot water, dipped in chloride of zinc and afterwards in molten solder. The head is then drawn into the bush- ing and melted Babbitt metal poured around it. For cables of small strength lead may be used in place of Babbitt. A method of testing which gives satis- factory results is that in which a number of the wires are tested individually to determine the uniformity of the rope. 103. Rattler Test for Paving-bricks. — Paving- bricks are tested for durability by placing them in a rattler of suitable form and noting the amount of wear when revolved at a given rate of speed. The results from the machine give a true index of the essential properties of paving-bricks, namely: toughness and vitrification. The machine should be constructed according to the dimensions recommended by the National Brick Manufacturers' Association. The charge should be the number of bricks nearest to 10 per cent of the volume of the cylinder of the rattler. At times a mixed charge of brick and foundry shot is used. It is found that the diameter of 28 inches and a charge of 10 per cent of the volume will give the maxi- mum wear. The wear of a brick during the first part of a test is due to the chipping of each brick into a rounded mass; after that the wear proceeds steadily. The test should continue long enough to include the effect of the wear beyond the chipping stage; 2000 STRENGTH OF MATERIALS. 117 revolutions will accomplish this purpose. It is found that beyond a minimum of 18 inches the length of the rattling-chamber makes no difference in the proportion of wear when the per cent of charge is the same, and that, within limits, the rate of revolution makes little difference ; 24 to 36 R.P.M. may be used. A machine is in use in the Purdue Laboratory which conforms closely to the dimensions given above. It differs from the ordinary tumbler in the provision for inserting brick in the end, thus avoiding the neces- sity of removing a slat. The special experimental work will be assigned to the student by the instructor. 104. Impact Tests.— The method of conducting impact tests has not been standardized, nor is there any uniformity in the construction of machinery for such tests. The difficulty in such tests is to so arrange the impact that the entire energy of the blow may be used in deforming the specimen. Part of the energy may disappear in: (1) Deforming the specimen locally at the point of impact. The loss of energy depends on the relative inertia of the moving weight and the specimen, and on the velocity of impact. (2) In moving the abutments, which may not be rigid and will absorb energy (3) A small amount of energy may disappear in vibration. It may be said in general that impact must result from the fall of a large weight through a small dis- tance, and that the abutments must be solid, or of such character that a known amount of energy will be absorbed. The specimen must be broken with a single blow. Il8 ENGINEERING LABORATORY PRACTICE. The experimental work assigned will consist of experiments on longitudinal impact of wire specimens. As no standard form of impact machine has yet been prescribed, a machine has been designed for use in the Purdue Laboratory which meets the requirements mentioned. The apparatus consists principally of a framework of two upright posts bridged over at a cer- tain height above the floor, a lifting mechanism to raise the weight and the specimen, and a revolving drum on which the record of the motion of the weight is taken. The specimen is attached at its upper end to a cast-iron cross-head which slides on ways fastened to the posts; to its lower end is attached the weight. The specimen with cross-head and weight attached is raised to a certain height, and in falling the cross- head strikes a cross-piece on the frame which arrests its motion suddenly. The specimen sustains the im- pact due to the continued motion of the weight. The weight consists of a cylindrical casting of 845 pounds with hollow center to receive the bushing or grip. The apparatus is used in the following manner: Specific Directions. — Take a specimen of Norway iron T 5 ¥ inch in diameter and about 10 feet long and mark it off in one-foot lengths. Measure its diam- eter. Run one end through the cylindrical weight and fasten the wire in the steel bushing with the conical wedges. Drive the wedges in tight. Draw the bushing up inside the cast-iron cylinder until it bears against the interior shoulder. Pass the upper end of the wire through the cross-bridge into the upper bushing. Drive the upper wedges. Release the weight so that it is supported by the STRENGTH OF MATERIALS. II 9 bridge through the specimen and the upper steel bushing. Allow the pencil, attached to the weight, to mark the zero-line on the drum. Then arrange the pencil so that it will be sure to trip at the proper time. Attach the tongs to the upper bushing and lift the weight, specimen and upper bushing about 8 feet. Wind up the propelling-cord on the drum and at a signal from the operator release the drum. When Fig. 37. the small weight whose descent turns the drum strikes the floor, the vibrating tuning-fork is turned on the drum and the tongs released. The weight descends and fracture of the specimen occurs; the pencil, shot out at the proper time, marks a record on the drum. Repeat the test on another specimen. The drum-record will be about as shown by Fig. 37. The energy expended in breaking the specimen will be J TdX where GX = J* TdX + \M{y? - vf) 9 120 ENGINEERING LABORATORY PRACTICE. in which G = weight of hammer; T= tension in specimen; X == total elongation; M = mass of G\ v x = final velocity; z> = initial velocity. Divide this energy, in foot-pounds, by the volume of the wire in cubic inches and the ultimate resilience Fig. 38. in foot-pounds per cubic inch will result. Determine the time of impact given by the horizontal projection of ab. Compare the elongation measured on the specimen with the elongation recorded on the drum. Measure the diameter of contracted area. Determine the velocity of the drum from the tuning-fork record. From the known masses and the curve ab construct n stress-strain diagram for the specimen as in Fig. 38. Divide ac into ten parts, and erect ordinates to meet the curve in points p y /, etc. Find the successive velocities at these points graphically, i.e., lay off STRENGTH OF MATERIALS. 121 length mn proportional to u, the velocity of the drum, and draw from m lines parallel to tangents at p, p\ etc. These parallels to the tangents will cut off from no lengths which, taken to scale, are the velocities of the weight at/, p' , etc. Lay these velocities off on the ordinates a'p' , a"p" , A v etc. The acceleration at any point p is -r-, and should be computed. Then if T is the tension in the specimen, T= G + Mp, where / is the acceleration. Compute the successive values of T and lay these off from the axis of elongation ad along d n e" , etc. Join the points with a curve, and determine the work done, or resilience, as measured by the area between the " load-elongation curve," and axis ad. Test two similar specimens in the 300,000-lb. Riehle machine as directed in Sections 93 and 102. Report comparison of results in impact and tension as to ultimate stress, total elongation, elongation in that foot containing ruptured section, and total resilience. 105. Cold-bending Test. — The following test is often prescribed for boiler and similar material: The material shall bend double without showing cracks or flaws, both while cold and after being heated to a cherry red and cooled in water at 8o° F. The specimen may be partly bent in a vise and afterwards closed down flat in a testing-machine. In case an interior radius is specified, an auxiliary plate must be dressed to this radius and inserted. The 122 ENGINEERING LABORATORY PRACTICE. specimen should bend without initial cracks or rough- ness which will start larger cracks. Rivet-metal is commonly tested by cold bending at a nicked section. The bar should have one deep nick, not a number of successive shallow nicks. The test indicates the toughness of the material. 106. Drifting Tests. — In the drifting test a hole is punched or drilled near the edge of a plate and then enlarged by a drift-pin. This test, like the cold bend, indicates the ductility of the metal. CHAPTER X. STEAM-BOILER TESTING. 107. Objects of the Test. — Among the objects commonly sought in testing boilers are the following: To determine the capacity and efficiency of a given boiler under a given set of conditions, to determine the change of efficiency of a boiler under different conditions, and to determine the amount of coal and water necessary to supply a given engine with steam. The method employed in making the tests will vary in its details to suit the particular object in view. The general principles underlying the various methods are, however, much the same. 108. Comparison of Tests under Different Condi- tions. — The evaporative or commercial efficiency of any given boiler under a given set of conditions is usually expressed as the number of pounds of water evaporated per pound of dry coal. If the conditions of operation remain the same, this forms a just basis for the comparison of different boilers. If, however, the conditions of operation, such as the steam-pressure or the feed-temperature, are not the same, this basis of comparison is not suitable, since it requires more heat- units to evaporate a pound of water at the higher steam-pressure or the lower feed-temperature. To secure a fair basis of comparison under all con- 123 124 ENGINEERING LABORATORY PRACTICE. ditions, it is customary to reduce the actual evapora- tion per pound of dry coal to an equivalent evaporation per pound of dry coal from a feed-temperature of 2 12° F. into steam at the same temperature, i.e., at atmospheric pressure. This is commonly called the equivalent evaporation "from and at 212 F." 109. Horse-power of Boilers. — The accepted defi- nition of a boiler horse-power is the evaporation of 30 pounds of water per hour from a feed-temperature of 100 F. into steam at 70 pounds pressure. This is equivalent to the evaporation of 34^- pounds per hour from and at 212 F. 110. Boiler Efficiencies. — The efficiency of a boiler is usually expressed as the ratio of the heat supplied the boiler in the form of coal to that delivered by the boiler in the form of steam. This evidently includes both the efficiency of the boiler proper and that of the furnace. Properly speaking, the efficien- cy of the boiler is the ratio of the heat supplied as coal minus that lost in the ash, cinders, and waste gases to the heat delivered in the steam. The efficiency of the furnace is, then, the ratio of the heat supplied as coal to that absorbed by the boiler. In finding either of these efficiencies, determination must be made of the heating value of the coal and of the temperature and chemical composition of the waste gases. Such determinations are only undertaken in connection with the more elaborate tests of boilers. in. Determination of Heating Value of Fuels. — The determination of the heating-value of fuel is made by burning a known weight of the material and measuring the heat evolved. The method of burning must be such as to produce perfect combustion. The STEAM-BOILER TESTING. 125 fuel may be burned in air or in the presence of oxygen or some oxide. The measurement of heat is usually made by absorbing it in a known weight of water and noting the resulting rise in temperature. From this and the constants of the apparatus employed, the heat produced can be determined. For determining the heating-value of coal, the in- struments used are known as coal-calorimeters. They are made in a variety of forms, for description of which the reader is referred to the various papers and arti- cles on the subject.* In selecting the sample of coal care should be taken to insure a representative sample. A good method of procedure is to draw off a shovel- ful from time to time during the conduct of the test, the intervals being such as to secure a sample weigh- ing from 75 to 100 pounds. Immediately upon the clo&e of the test this should be broken up to about egg size, carefully mixed and quartered. The quarter selected should then be broken to nut size and again mixed and quartered. The final quarter should be broken to pea size, and placed in an air-tight jar to await the calorimetric determination. 112. Flue-gas Analysis. — In order to ascertain the degree of perfection attained in the combustion of fuel, recourse is had to the analysis of the flue-gases, the results of which serve to indicate the character of the combustion. The method of obtaining the sample and of analyzing the gases may be found by reference to the existing works upon the subject. f * Trans. A. S. M. E,, vol. xiv, p. 8r6 and vol. xvi, p. 1040. Car- penter's i4 Experimental Engineering," Chap. 14. f Hempel's " Method of Gas Analysis," Trans. A. S. M. E., vol. VI., p. 786. Carpenter's " Experimental Engineering," Chap. 14. 126 ENGINEERING LABORATORY PRACTICE. 113. Graphical Logs. — The graphical log is useful in determining the constancy of the conditions under which the test was made. It is plotted from the running log of the test, taking time as the abscissae and the various observed quantities as the ordinates, using a suitable scale for each. In case the test is made in connection with an engine test, the graphical log may be made to include the observations for both. 114. Methods of Testing Boilers — Following is the code of rules for testing boilers prescribed by the American Society of Mechanical Engineers, adopted at their 1884 meeting: * CODE OF RULES FOR BOILER TESTS. PRELIMINARIES TO A TEST. I. In preparing for and conducting trials of steam- boilers the specific object of the proposed trial should be clearly defined and steadily kept in view. II. Measure and record the dimensions, position, etc., of grate- and heating-surfaces, flues and chim- neys, proportion of air-space in the grate-surface, kind of draught, natural or forced. III. Put tlie boiler in good condition. Have heating- surface clean inside and out, grate-bars and sides of furnace free from clinkers, dust and ashes removed from back connections, leaks in masonry stopped, and all obstructions to draught removed. See that the damper will open to full extent, that it may be closed when desired. Test for leaks in masonry by firing a little smoky fuel and immediately closing damper. The smoke will then escape through the leaks. * Trans. A. S. M, E., vol. vi, p. 676. STEAM-BOILER TESTING. 12J IV. Have an understanding ivith the parties in whose interest the test is to be made as to the char- acter of the coal to be used. The coal must be dry, or, if wet, a sample must be dried carefully and a determination of the amount of moisture in the coal made, and the calculation of the results of the test corrected accordingly. Wherever possible, the test should be made with standard coal of a known quality. For that portion of the country east of the Allegheny Mountains good anthracite egg coal or Cumberland semi-bituminous coal may be taken as the standard for making tests. West of the Allegheny Mountains and east of the Missouri River Pittsburg lump coal may be used.* V. In all important tests a sample of coal should be selected for chemical analysis. VI. Establish the correctness of all apparatus used in the test for weighing and measuring. These are: 1. Scales for weighing coal, ashes, and water. 2. Tanks, or water-meters for measuring water. Water-meters, as a rule should only be used as a check on other measurements. For accurate work, the water should be weighed or measured in a tank. 3. Thermometers and pyrometers for taking tem- peratures of air, steam, feed-water, waste gases, etc. 4. Pressure-gages, draught-gages, etc. VII. Before beginning a test, the boiler and chim- ney should be thoroughly heated to their usual work- ing temperature. If the boiler is new, it should be * These coals are selected because they are about the only coals which contain the essentials of excellence of quality, adaptability to various kinds of furnaces, grates, boilers, and methods of firing, and wide distribution and general accessibility in the markets, 128 ENGINEERING LABORATORY PRACTICE. in continuous use at least a week before testing, so as to dry the mortar thoroughly and heat the walls. VIII. Before beginning a test, the boiler and con- nections should be free from leaks, and all water connections, including blow- and extra feed-pipes, should be disconnected or stopped with blank flanges, except the particular pipe through which water is to be fed to the boiler during the trial. In locations where the reliability of the power is so important that an extra feed-pipe must be kept in position, and in general when for any other reason water-pipes other than the feed-pipes cannot be disconnected, such pipes may be drilled so as to leave openings in their lower sides, which should be kept open throughout the test as a means of detecting leaks, or accidental or unauthorized opening of valves. During the test the blow-off pipe should remain exposed. If an injector is used it must receive steam directly from the boiler being tested, and not from a steam- pipe or from any other boiler. See that the steam-pipe is so arranged that water of condensation cannot run back into the boiler. If the steam-pipe has such an inclination that the water of condensation from" any portion of the steam-pipe system may run back into the boiler, it must be trapped so as to prevent this water getting into the boiler without being measured. STARTING AND STOPPING A TEST. A test should last at least ten hours of continuous running, and twenty-four hours whenever practicable. The conditions of the boiler and furnace in all respects should be, as nearly as possible, the same at the end STEAM-BOILER TESTING. 1 29 as at the beginning of the test. The steam-pressure should be the same, the water-level the same, the fire upon the grates should be the same in quantity and condition, and the walls, flues, etc., should be of the same temperature. To secure as near an approxima- tion to exact uniformity as possible in conditions of the fire and in temperatures of the walls and flues, the following method of starting and stopping a test should be adopted: X. Standard Method. — Steam being raised to the working pressure, remove rapidly all fire from the grate, close the damper, clean the ash-pit, and as quickly as possible start a new fire with weighed wood and coal, noting the time of starting the test and the height of the water-level while the water is in a quiescent state, just before lighting the fire. At the end of the test remove the whole fire, clean the grates and ash-pit, and note the water-level when the water is in a quiescent state; record the time of hauling the fire as the end of the test. The water- level should be as nearly as possible the same as at the beginning of the test. If it is not the same, a correction should be made by computation, and not by operating pump after test is completed. It will generally be necessary to regulate the discharge of steam from the boiler tested by means of the stop- valve for a time while fires are being hauled at the beginning and at the end of the test, in order to keep the steam-pressure in the boiler at those times up to the average during the test. XI. Alternate Method. — Instead of the standard method above described, the following may be em- ployed where local conditions render it necessary: 130 ENGINEERING LABORATORY PRACTICE. At the regular time for slicing and cleaning fires have them burned rather low, as is usual before cleaning, and then thoroughly cleaned; note the amount of coal left on the grate as nearly as it can be estimated; note the pressure of steam and the height of the water-level — which should be at the medium height to be carried throughout the test — at the same time; and note this time as the time of starting the test. Fresh coal which has been weighed should now be fired. The ash-pits should be cleaned at once after starting. Before the end of the test the fires should be burned low, just as before the start, and the fires cleaned in such a manner as to leave the same amount of fire, and in the same condition, on the grates as at the start. The water-level and steam-pressure should be brought to the same point as at the start, and the time of the ending of the test should be noted just before fresh coal is fired. DURING THE TEST. XII. Keep the Conditions Uniform. — The boiler should be run continuously, without stopping for meal-times or for rise or fall of pressure of steam due to change of demand for steam. The draught being adjusted to the rate of evaporation or combustion desired before the test is begun, it should be retained constant during the test by means of the damper. If the boiler is not connected to the same steam- pipe with other boilers, an extra outlet for steam with valve in same should be provided, so that in case the pressure should rise to that at which the safety-valve is set, it may be reduced to the desired point by opening the extra outlet without checking the fires. STEAM-BOILER TESTING. I3I If the boiler is connected to a main steam-pipe with other boilers, the safety-valve on the boiler being tested should be set a few pounds higher than those of the other boilers, so that in case of a rise in pressure the other boilers may blow off, and the pressure be reduced by closing their dampers, allowing the damper of the boiler being tested to remain open, and firing as usual. All conditions should be kept as nearly uniform as possible, such as force of draught, pressure of steam, and height of water. The time of cleaning the fires will depend upon the character of the fuel, the rapidity of combustion, and the kind of grates. When very good coal is used and the combustion not too rapid, a ten-hour test may be run without any cleaning of the grates other than just before the beginning and just before the end of the test. But in case the grates have to be cleaned during the test, the intervals between one cleaning and another should be uniform. XIII. Keeping the Records. — The coal should be weighed and delivered to the fireman in equal por- tions, each sufficient for about one hour's run, and a fresh portion should not be delivered until the previous one has all been fired. The time required to consume each portion should be noted, the time being recorded at the instant of firing the first of each new portion. It is desirable that at the same time the amount of water fed into the boiler should be accurately noted and recorded, including the height of the water in the boiler, and the average pressure of steam and tem- perature of feed during the time. By thus recording the amount of water evaporated by successive portions 132 ENGINEERING LABORATORY PRACTICE. of coal, the record of the test may be divided into several divisions, if desired, at the end of the test, to discover the degree of uniformity of combustion, evaporation, and economy at different stages of the test. XIV. Priming Tests. — In all tests in which accuracy of results is important, calorimeter tests should be made of the percentage of moisture in the steam or of the degree of superheating. At least ten such tests should be made during the trial of the boiler, or so many as to reduce the probable average error to less than one per cent, and the final records of the boiler-test corrected according to the average results of the calorimeter tests. On account of the difficulty of securing accuracy in these tests the greatest care should be taken in the measurements of weights and temperatures. The thermometers should be accurate to within a tenth of a degree, and the scales on which the water is weighed to within one-hundredth of a pound. ANALYSIS OF GASES — MEASUREMENT OF AIR-SUPPLY, ETC. XV. In tests for purposes of scientific research, in which the determination of all the variables entering into the tests is desired, certain observations should be made which are in general not necessary in tests for commercial purposes. These are the measurement of the air-supply, the determination of its contained moisture, the measurement and analysis of the flue- gases, the determination of the amount of heat lost by radiation, of the amount of infiltration of air through the setting, the direct determination by calorimeter experiments of the absolute heating value of the fuel, STEAM-BOILER TESTING. 133 and (by condensation of all the steam made by the boiler) of the total heat imparted to the water. The analysis of the flue-gases is an especially valu- able method of determining the relative value of different methods of firing, or of different kinds of furnaces. In making these analyses great care should be taken to procure average samples — since the com- position is apt to vary at different points of the flue, — and the analyses should be intrusted only to a thoroughly competent chemist, who is provided with complete and accurate apparatus. As the determinations of the other variables men- tioned above are not likely to be undertaken except by engineers of high scientific attainments, and as apparatus for making them is likely to be improved in the course of scientific research, it is not deemed advisable to include in this code any specific directions for making them. RECORD OF THE TEST. XVI. A "log" of the properly-prepared blanks, follows : test should be kept on containing headings as Pressures. Temperatures. Fuel. Feed-water. u ^j Time. u • 5P < S 9 V a u ho a J2 b£ C u u ill V •a S B od en s u ■ rt u X H J H -) 134 ENGINEERING LABORATORY PRACTICE, REPORTING THE TRIAL. XVII. The final results should be recorded upon a properly prepared blank, and should include as many of the following items as are adapted for the specific object for which the trial is made. The items marked with a * may be omitted for ordinary trials, but are desirable for comparison with similar data from other sources. RESULTS OF THE TRIALS OF A BOILER AT TO DETERMINE i. Date of trial 2. Duration of trial DIMENSIONS AND PROPORTIONS. (Leave space for complete description.) 3. Grate-surface. . . .wide. . . .long. . . .area 4. Water-heating surface 5. Superheating-surface 6. Ratio of water-heating to grate-surface AVERAGE PRESSURES. 7. Steam-pressure in boiler, by gage *8. Absolute steam-pressure .. *9. Atmospheric pressure, per barometer.. 10. Force of draught in inches of water AVERAGE TEMPERATURES. *n. Of external air *I2. Of fire-room *I3- Of steam 14. Of escaping gases 15. Of feed-water * See reference in paragraph preceding table. STEAM-BOILER TESTING. 135 FUEL. f 16. Total amount of coal consumed 17. Moisture in coal 18. Dry coal consumed 19. Total refuse, dry- • ■ .pounds = 20. Total combustible (dry weight of coal, Item 18, less refuse, Item 19) , . . *2i. Dry coal consumed per hour *22. Combustible consumed per hour RESULTS OF CALORIMETRIC TESTS. 23. Quality of steam, dry steam being taken as unity 24. Percentage of moisture in steam 25. Number of degrees superheated WATER. 26. Total weight of water pumped into boiler and apparently evaporated^: 27. Water actually evaporated, corrected for quality of steam § 28. Equivalent water evaporated into dry steam from and at 212 F.§ *29. Equivalent total heat derived from fuel in British thermal units § 30. Equivalent water evaporated into dry steam from and at 212 F. per hour ECONOMIC EVAPORATION. 31. Water actually evaporated per pound of dry coal, from actual pressure and tem- perature § 32. Equivalent water evaporated per pound of dry coal from and at 212 F.§ 33. Equivalent water evaporated per pound of combustible from and at 212 F.§ lbs. per cent lbs. per cent lbs. lbs. lbs. per cent deg. lbs. lbs. lbs. B. T. U lbs. lbs. lbs. lbs. * See reference in paragraph preceding- table. + Including equivalent of wood used in lighting fire. One pound of wood equals 0.4 pound coal. Not including unburnt coal withdrawn from fire at end of test. X Corrected for inequality of water-level and of steam-pressure at beginning and end of test. § The following shows how some of the items in the above table are derived from others: Item 27 = item 26 X item 23; Item 28 = item 27 X factor of evaporation; 136 ENGINEERING LABORATORY PRACTICE. COMMERCIAL EVAPORATION. 34. Equivalent water evaporated per pound of dry coal with one sixth refuse, at 70 pounds gage-pressure, from temperature of ioo° F. = Item 33 multiplied by 0.7249. RATE OF COMBUSTION. 35- * 3 6. *37- *38. 39- Dry coal actually burned per square foot of grate-surface per hour f Consumption of ^| Per sq. ft. of grate- surface Per sq. ft. of water- heating surface . . . Per sq. ft. of least area for draught . . dry coal per | hour. Coal as- I sumed with ' one sixth ref use.f RATE OF EVAPORATION. Water evaporated from and at 212 F. sq. ft. of heating-surface per hour.. " Water evapor- per ^40. f 42. ated per hr. from tem- perature of 100 F. into steam of 70 lbs. gage- pressure. f Per sq. ft. of grate- surface Per sq. ft. of water- heating surface Per sq. ft. of least area for draught. . . . lbs. lbs. lbs. lbs. lbs. lbs. lbs. lbs. lbs. Factor of evaporation = H 965-7 H and h being respectively the total heat-units in steam of the average observed pressure and in water of the average observed temperature of feed, as obtained from tables of the properties of steam and water; Item 29 = item 27 X (H - A); Item 31 = item 27 -r- item 18; Item 32 = item 28 -+- item 18 or = item 31 X factor of evaporation; Item 33 = item 28 -7- item 20 or = item 32 -=- (per cent 100 — item 19); Items 36 to 38. First term = item 22 X f ; Items 40 to 42. First term = item 39 X o. , A . item qo Item 43 = item 29 X 0.00003 or = — ; 34s , _ difference of items 43 and 44 item 44 * See note *, p. 134. + See note §, p. 135. STEAM-BOILER TESTING. »37 COMMERCIAL HORSE-POWER. 43. On basis of thirty pounds of water per hour evaporated from temperature of ioo° F. into steam of 70 pounds gage- pressure (=34^ lbs., from and at 2i2°)f. 44. Horse-power, builders' rating at. . . .sq. ft. per horse-power 45. Per cent developed above, or below, rat- ingf t See note §, p. 135. 115. Abbreviated Directions. — Apparatus, — Tanks and scales for weighing water, scales for weighing coal, calorimeter, barometer, thermometers for tem- perature of room, feed-water, and waste gases. Method. — Calibrate all apparatus. Prepare blank logs and post observers. Note Rules VII and IX before starting. Start by standard or alternate methods, Rules X and XI. Take readings of time, boiler-pressure, barometer, draught, temperature in smoke-box, quality of steam, pounds water supplied, pounds water lost by calorimeter, leakage, etc., pounds coal fired, per cent of moisture in coal, pounds dry ash. Observe Rules XII, XIII, and XIV during the test. Make test ten hours long if possible, mak- ing running observations every ten minutes. If possible keep coal and water record so that quantities may be computed for each hour. Dry a sample of coal, not less than 50 pounds, in order to determine per cent of moisture. If using standard method of starting and stopping, dump the grates at end of test and weigh all the ash, minus any unburned coal, which I38 ENGINEERING LABORATORY PRACTICE. should be removed, weighed, and the weight deducted from the total amount of coal fired. If using the alternate method, do not dump the grates until the ash is removed and weighed, and do not weigh back any unburned coal found on grate or in ash. Report. — Make report on forms given and submit a graphical log (Section 113) of the test. For method of working up the test and calculating the various desired results, see Section 161. The method of conducting special boiler-tests is given under separate heading (Sees. 160 and 162). CHAPTER XL THE STEAM-ENGINE INDICATOR. 116. General Description. — The steam-engine in- dicator is an instrument used for recording the pressure on the engine-piston at each point of its stroke. It consists of the following elements: The Cylinder and Piston, the former in pipe connec- tion with one end of the engine-cylinder in such a manner that the pressures in the latter are received by the indicator-piston. The Indicator-spring, attached to the piston and opposing the force of the steam-pressure, allowing a limited motion, proportional to that pressure. The Pencil-motion, by which the motion of the piston is multiplied, the resultant motion of the pencil being a straight line. The Drum, which gives motion to a card in direct proportion to the motion of the engine-piston, but of a total length usually not exceeding four inches. The drum is actuated by a cord of braided linen and its motion is controlled by a spring, the tension of which may be varied to suit the speed. 117. The Crosby Indicator. — A sectional view of the Crosby indicator is shown in Fig. 39. The prin^ cipal parts are a piston, 8, moving within the cylinder, 139 140 ENGINEERING LABORATORY PRACTICE. 4, and connected with the pencil-lever, 16, by means of a piston-rod, 10, swivel-head, II, and link, 14. The pencil mechanism, by which the pencil, 23, is Fig. 39. — The Crosby Indicator. caused to move in a straight line, consists of a system of links mounted on a sleeve, 3. The motion of the piston is resisted by a spring fastened at its lower end to the piston by means of a ball-joint and at its upper end to a cap, 2, which forms the upper cylinder-head. The drum, 24, drum-spring, 31, and connected parts are easily understood by reference to the cut. THE STEAM-ENGINE INDICATOR. 141 To remove the piston and pencil mechanism from the indicator, unscrew the cap, 2, and lift the cap, sleeve, 3, and connected parts from the indicator. To insert the spring ', unscrew the piston and piston- rod from the swivel-head, holding the cap, 2, from turning. Take the socket-wrench from the cover of the indicator-box, slip it over the piston-rod, and unscrew the latter from the piston. Now with the piston-rod still in the socket of the wrench slip the spring over the piston-rod until the bead of the spring rests in the concave end of the rod ; then invert the piston and pass the transverse wire of the spring through the slotted portion of the piston-socket and screw the piston-rod firmly into place. The lower piston-screw, 9, should be loosened slightly before this last operation and afterwards set up against the bead lightly to prevent lost motion, but not enough to prevent the bead from turning. Caution. — In the under side of the shoulder of the piston-rod B y Fig. 40, is an annular channel formed Fig. 40. to receive the upper edge of the socket on the piston A. When attaching the piston to the rod always screw the piston-rod onto the socket as far as it will go; that is, until the upper end of the socket, 142 ENGINEERING LABORATORY PRACTICE. d , is brought firmly against the bottom of the annular channel, b*, in the piston-rod. This insures correct alignment of the piston within the cylinder. Having the spring and piston together, hold the sleeve and pencil-motion in an upright position, slip the piston-rod up over the threaded portion of the swivel-head, II, Fig. 39, until the threads on the upper head of the spring engage those on the cap, 2, and screw the spring firmly onto the cap. Now allow the cap to turn and screw the piston-rod onto the swivel-head until the top of the rod is nearly flush with the shoulder on the swivel-head. The piston may now be inserted in the cylinder and the cap screwed into place. To change the location of the atmosphere- line y un- screw the cap and remove the piston, and pencil- movement. Unscrew the piston-rod from the swivel- head to raise the atmosphere-line and the reverse to lower it. One turn will change the position of the pencil •§• of an inch. To change the drum tension y remove the drum, lift the knurled nut at the top of the drum spring from its square seat, turn in the direction required, and re- place. 118. The Tabor Indicator. — The special feature of the Tabor indicator is the means employed to secure a straight-line motion for the pencil. This is secured by means of a curved slot, fastened to the cylinder- cap, in which travels a roller attached to the pencil- lever (Fig. 41). The method of fastening the piston, rod, and spring together differs from that employed in the Crosby indicator in that the point of flexibility THE STEAM-ENGINE INDICATOR. H3 occurs, not between the spring and the piston, but between the piston and the rod. To remove the piston and pencil mechanism from the indicator, unscrew the cylinder-cap and lift it with the connected parts from the indicator. To insert the springy unscrew the small nut under the piston from the piston-rod and remove the piston. Fig. 41. — The Tabor Indicator. Slip the spring over the piston-rod, the end marked T uppermost, and screw it to the cap; then screw the piston to the lower end of the spring. Now move the pencil-motion down until the lower end of the piston- rod enters the piston and the square shoulder enters the square socket provided in the piston. Holding it 144 ENGINEERING LABORATORY PRACTICE. in this position, replace the small nut below the piston, screwing it firmly home. The piston may now be replaced in the cylinder and the cap screwed in place. To change the drum tension, remove the drum, drive out the small taper-pin which holds the knurled nut and unscrew the latter. Now grasp the drum-carriage firmly, lift it clear of the stops, turn in the required direction, and lower into place. Do not loose hold of it or the spring will rapidly uncoil and become detached. Replace the nut, taper-pin, and drum. 119. Choice of Spring. — Such a spring should be used that the maximum pressure to which it will be subjected is not greater than one and three quarter times the scale of the spring. Following is a table of the scale of spring to be used with different steam- pressures: Steam-pressure (gage). Scale of Spring. 40 30 60 40 80 50 IOO 60 140 80 175 IOO 2IO 120 250 150 120. Use of the Indicator. — The indicator is one of the most delicate and costly instruments which the engineer uses in ordinary practice. It requires careful handling and a thorough knowledge of its construction and operation in order to secure accurate results and prevent damage to itself. Before the Test. — Remove the indicator carefully from its box, handling it so far as possible by the THE STEAM-ENGINE INDICATOR. 145 cylinder. Never handle an indicator by the drum, as this is loose in most makes and comes off readily. Lift the pencil up and down slowly to see that it is perfectly free. Remove the pencil-motion and piston by unscrewing the knurled nut at the top of the cylinder. Thoroughly clean all working parts. Insert the spring in the pencil-motion as explained in Sections 117 and 118. Cover the piston with a thin coat of heavy oil and replace in the cylinder. See that the moving parts of the drum and pencil-motion are lubricated with watchmaker's oil. After blowing out the cock with steam, attach the indicator to the engine, and adjust the guide-pulleys so that when the cord is attached to the reducing- motion it will be parallel to the motion of the indi- cator-rig or, if a brumbo pulley is used, will be tangent to it. Adjust the cord so that the drum will not strike either stop when the cord is attached to the rig. If a hook is used on the drum-cord a convenient mode of attaching it to the cord is to pass the end of the latter through the eye of the hook and then make two half-hitches around the shank. This hitch may be easily untied by slipping it over the end of the hook. If the drum tension needs altering it may be changed as explained in Sections 117 and 118. Taking the Card. — Place the blank card on the drum so that both ends will be under the clips and not project out from the drum. By so doing the card will be less liable to come loose and will lie flat when taken. See that the pencil is firmly placed and sharp. For very accurate work a brass point should be used in connection with iA metallic paper/' Taking the loop of cord attached to the reducing-rig in one hand, I46 ENGINEERING LABORATORY PRACTICE. pull the drum-cord out to the end of its travel several times and then attach to the loop. Adjust the pencil- pressure to give a fine line. Open the cock half-way and allow steam to blow through the relief for two or three revolutions, then open full and draw the dia- gram. Close the cock, draw the atmosphere-line, and unhook the drum, taking care not to let it snap back against the stop. Remove the card and examine to see if there are any irregularities in the diagram. If these appear call the attention of the instructor to them. They may be due to disarrangement of parts or grit in the indicator-cylinder. If the latter, the piston should be removed, the cylinder blown out, and the piston oiled and returned. This should be done occasionally on all engine-tests. If the indicator is used on a gas-engine the piston should always be removed from its cylinder when not actually in use, as it is liable to be overheated if left on the engine between cards. After the Test. — Remove the indicator immediately, using waste to prevent burning the hands. Remove the piston and spring and clean all parts thoroughly. Oil the piston and working parts and put together without the spring. 121. Errors of the Indicator. — The two most fruit- ful sources of error in the mechanism of the indicator are the pencil-motion and the spring. To test the former, place a card on the drum and draw the atmos- phere-line. With the spring out place the pencil in contact with the paper and raise it up to the full height of its travel. Repeat at several different points on the card, holding the drum firmly in each THE STEAM-ENGINE INDICATOR, H7 position. Test the perpendicularity of the lines with a triangle and straight-edge. 122. Testing Indicator-springs. — Indicator-springs are often tested under hydraulic pressure and even by pressure exerted by a rod upon the under side of the piston, the lower end of the rod resting on suitable scaler. Most satisfactory results, however, may be obtained by a test under steam-pressure, in which case the conditions of the test are similar to the conditions of actual use, but it has generally been found difficult to maintain a constant pressure and to accurately deter- mine its value. A steam-gage is too sluggish in action to properly serve in this connection. A method of testing has been devised by Prof. W. F. M. Goss which overcomes these difficulties. The apparatus consists of a steam-drum having a pressure-regulating valve which responds to change in volume rather than to change in pressure, the pressure remaining constant at any point desired. The details of the arrangement are shown by Fig. 42. a rh rTU if ■ B Ad i ■$= Fig. 42. — Indicator-testing Apparatus, As is clearly shown by this sketch, a piston of known area is arranged to receive the pressure in the drum, against which it is held by standard weights placed upon the holder at its upper end. The piston I48 ENGINEERING LABORATORY PRACTICE. is free to move between stops, and as it rises it in- creases the area of port-opening through which the steam within the drum is allowed to escape. The piston therefore serves as a means of controlling and weighing the pressure within the drum. The area of the piston is one fifth of a square inch. The piston with weight-holder weighs one pound. A pressure of five pounds per square inch may therefore be maintained with no weights upon the holder. The weights to be used are those supplied with the Crosby Gage-tester. The value of these weights (which is stamped upon them) is five times their actual weight. Specific Directions. — Attach the indicator (or indi- cators) by means of the usual indicator-cocks. Open wide the discharge-valve D (Fig. 42). Have no weights upon the weight-holder, place one hand on it, and gradually open the steam-supply valve, 5. Thoroughly warm the steam-drum, allowing the weight-holder to rise under pressure of the hand. Observe the amount of motion which the weight-holder has, so that in the work to follow it may not be allowed to strike against its stops. Load the weight- holder with the desired weight and adjust the steam- supply valve, if necessary. Open and close the in- dicator-cock several times; finally leave it open; twirl the weight-holder, and make the record on the indi- cator-card by revolving the drum by hand. Be sure that on the ascending scale the pencil rises to the pressure and on the descending scale falls to the pres- sure, since one object of the test is to discover any lost motion or friction which may exist. There should be one observer to manipulate the THE STEAM-ENGINE INDICATOR. 149 testing apparatus and one for each indicator to be tested. The Record, — Before putting the paper on the indicator-drum draw upon it two parallel vertical lines about a quarter of an inch apart (a and b y Fig. 43)- When testing with differences of pressure on the ascending scale, make lines by means of the indicator toward the right, beginning with the left vertical; when the differences of pressure are on the descending scale, make lines toward the left, beginning with the right vertical. For springs under thirty pounds to the inch make 25 20 e IS / k — ? O 10 ft i 1 5 Atmosphere Line a b Fig. 43. a record for every five pounds change in pressure; for springs above thirty pounds, for every ten pounds change in pressure. Care should be taken that the spring is not subjected to a greater pressure than it is made to stand (see Section 119). Take several cards; then remove and clean the indicators. With a scale corresponding to that of the spring, measure the pressures from the atmosphere-line up to the several lines drawn, and record the same on their respective lines. The Report should be made out on the blank form given below. Paste the card to the report sheet. 150 ENGINEERING LABORATORY PRACTICE. 123. Form for CALIBRATION OF INDICATOR-SPRING NO.... IN CONNECTION WITH INDICATOR No. Observers X SCALE OF SPRING Date, No. Actual Pres- sure. Reading. Error. Up. Down. Up. Down. Remarks. Attach card here. 124. The Indicator-diagram. — The diagram drawn by the steam-engine indicator furnishes the means for determining the action of the valve, for analyzing the action of the steam in the cylinders, and for determin- ing the power developed. In Fig. 44 is shown a typical diagram taken from a locomotive at speed. #Adm, Fig. 44. The Point of Admission, a, is the point at which the valve opens for the admission of steam to the cylinder. The Steam line, from a to c~o, is the line drawn during the time when the steam is passing into the cylinder. The Point of Cut-off, c-o, is the point at which the THE STEAM-ENGINE INDICATOR. 151 valve is just closed, the admission of steam ceases, and expansion begins. The Expansion- curve, from c—o to r, is the line drawn while the steam is expanding behind the piston. The Point of Release, r, is the point at which the valve opens communication with the exhaust-port and the steam is released from the cylinder. The Exhaust-line, from r to c, is the line drawn while steam is being exhausted from the cylinder. The lower portion is also called the Back-pressure Line. The Point of Compression, c, is the point at which the valve closes communication with the exhaust-port and the steam retained in the cylinder begins to com- press. The Compression-curve ', from c to a, is the line drawn while compression is taking place. The Initial Pressure is measured from the atmos- phere-line to the highest point of the steam-line. Do not confuse this with a high point sometimes appear- ing just at the beginning of the stroke, due to inertia of the moving parts of the indicator. The Least Back-pressure is measured from the atmos- phere-line to the lowest point of the back-pressure line. The Events of Stroke are the points of admission, cut-off, release, and compression. The Per Cent of Stroke at the different events is the distance of the piston from its initial or admission end when the event occurs, expressed as a per cent of the total length of stroke. 125. Locating the Events of Stroke. — The loca- tion of the events of stroke, especially for cards taken 152 ENGINEERING LABORATORY PRACTICE. at high speed, requires much care and considerable skill. In locating, for instance, the point of cut-off, the best method is to follow with the eye up the expansion-curve until the point is reached at which the reverse curve begins. This point may be taken as the point of cut-off. Similarly, for release, follow down the expansion-curve until the point is reached at which the reverse curve leading to the back-pressure line begins. This is the point of release. When determining these points for the purpose of finding the weights of steam, it is essential that the valve be entirely closed at the points located. It will therefore be found more accurate, when doubt exists as to the precise location of the point, to locate it too far on the expansion-curve rather than the reverse. Do not continue the expansion or compression curves up and down, as shown in Fig. 45. This is a common method of locating the events, but is apt to obscure the real point sought. Fig. 45. 126. Determining the Per Cents of Stroke. When the events are located, draw ordinates through them and at the ends of the card. Make a scale somewhat longer than the longest card, about an eighth of an inch, and divide it into one hundred parts. If this scale be placed so that the ends exactly coincide with the end ordinates, the percentage of THE STEAM-ENGINE INDICATOR. 153 stroke may be read directly for each event and prop- erly recorded on the corresponding ordinate. All per- cents should be taken from the admission-end of the card. 127. Mean Effective Pressure. — The mean effec- tive pressure for one end of the engine is the average pressure during the forward stroke on that end, minus the average pressure during the return stroke. As shown by the card, it is the average length of all the ordinates intercepted between the upper and lower lines of the card, multiplied by the scale of the spring. For rough approximations the M.E.P. may be deter- mined from the following formula, neglecting clear- ance and compression: M.E.P. = (* + hyp, log .£)/>-*/> R. where R is the ratio of expansion or the piston-dis- placement divided by the volume at cut-off, P 1 is the initial pressure, and P 2 the back-pressure, absolute. The results thus obtained will always be greater than the actual values. 128. Mean Effective Pressure by the Method of Ordinates. — First, by use of two triangles draw ordinates at each end of each diagram, perpendicular to the atmosphere-line. Next construct on a piece of paper a scale of ten equal parts such that the sum of the parts will be a little greater than the length of any of the diagrams. To use this scale place it obliquely across the card in such a position that the first and last division points will fall on the end ordi- nates already drawn. Make points on the card oppo- site each division on the scale, and afterwards draw 1 54 ENGINEERING LABORATORY PRACTICE. ordinates through each of these points. If this work be properly done, each diagram will be divided into ten vertical sections of equal width (Fig. 46). It remains rHNCO-^lOO I. CO © 3 £3 Fig. 46. to obtain the average height of these sections which, since the sections constitute the card, may be accepted as the average height of the card. Lay off on a strip of paper having a straight edge (Fig. 47) the effective Fig. 47. height of the card as observed on the first ordinate, that is, lay off ab (Fig. 46) on the paper strip as a l b x ; add to this the height of the last ordinate cd> as b l d l \ and then take half the distance a l d l as a new starting point e, and add the effective length of all the other ordinates making yg* = eg\ hi = g l i\ etc., until all the intermediate ordinates are taken off. When this is accomplished the distance measured on the strip from a 1 to the last point is approximately the sum of the THE STEAM-ENGINE INDICATOR. 1 55 height of the vertical slices, and this distance divided by ten (there being ten spaces) will give the average height of the card. This average height in inches multiplied by the scale of the spring gives the M.E.P. of the card. The reason that half the sum of the first and last ordinates is taken will appear when it is remembered that the result sought is the average height of the ten spaces and not of eleven lines. In other words, the first and eleventh ordinates are con- sidered as the same line, a condition which can be illustrated by rolling up the card until they coincide. 129. Mean Effective Pressure by the Planimeter. — The usual method of finding M.E.P. is to measure the area of the card with a planimeter (see Sections 1 1 and 15) and divide the area thus found by the length parallel to the atmosphere-line. The quotient, which is the height of the mean ordinate in inches, is multi- plied by the scale of the spring to give the M.E.P. The length of the card is found as follows: Place a straight-edge on the card coincident with the atmos- phere-line, and with a triangle draw ordinates at each end of the card. The length can now be measured to hundredths of an inch, holding the scale parallel to the atmosphere-line. 130. Condensed Directions for working up Cards. — 1st. Locate the events of stroke, admission, cut-off, release, and compression, with great care on all cards. Be sure that the last three are well on their respective hyperbolic curves. In this connection it should be remembered that when doubt exists as to the exact location of, for instance, the point of cut-off, much less error in calculating the weight of steam at that point will result from locating the point too late than 156 ENGINEERING LABORATORY PRACTICE, the reverse, since after cut-off occurs the change in weight is very slight compared with the change immediately preceding cut-off. Do not attempt to continue the expansion and compression curves up and down as in Fig. 45, as this is apt to obscure the real location of the event. Submit some of your first work to the instructor before proceeding. 2d. Draw ordinates through the points located with a fine hard pencil or, if metallic paper is used, with a brass point. Draw them perpendicular to the atmosphere-line and about two inches long. 3d. Draw end ordinates, locating them with great care. 4th. Find areas with the planimeter. These should be checked by two men to within one per cent and Fig. 48. the two readings averaged. Use a smooth board covered with a sheet of foolscap to run the planimeter on, and see that the record-wheel does not mount the card. Do not dig the tracing-point of the planimeter into the card and thus destroy its outline. In case the card is dim, make fine pencil-points about i inch apart around its outline before tracing with the planimeter. Enter the result as shown in Fig. 48. THE STEAM-ENGINE INDICATOR. I 57 5th. Measure the length of the card parallel to the atmosphere-line, reading to hundredths of an inch. This need not be checked. 6th. Calculate the M.E.P. to two places of deci- mals. Do not use a slide-rule for this work. This calculation must be checked. In figuring M.E.P., it will be found more accurate to multiply the area by the scale of spring and then divide by the length. This method should be followed. Do not figure on the back of the card. 7th. Measure pressures at cut-off, release, compres- sion, and find initial and least back-pressures. These should all be taken from the atmosphere-line, and the results should be marked on each ordinate as shown in Fig. 48. The initial pressure is generally taken as the highest point on the card unless there are indica- tions that the highest pressure is due to excessive compression, indicator inertia, or some cause other than initial steam-pressure. 8th. Measure per cents of stroke at the same points and enter on the proper ordinate. These should be read to one place of decimals. 131. Calculations from the Card. Horse-power. — The work developed in the cylinder of the engine is the product of two factors. The first may be called the total mean effective pressure, and is the product of the M.E.P. and the net area of the cylinder in square inches. The second is the distance through which the foregoing pressure is exerted per minute or the product of the length of stroke in feet by the number of effective strokes per minute. The first factor is expressed in pounds, the second in feet per minute, and the product, foot-pounds per minute, I58 ENGINEERING LABORATORY PRACTICE. may be reduced to the equivalent horse-power by dividing by 33,000. To determine the horse-power of the ordinary steam-engine, find the M.E.P. of the cards as ex- plained in Section 128 or 129. Average this M.E.P. for each end of the cylinder and apply each value in the following formula: PLAN H.P 33000' where P is the M.E.P., L the length of stroke in feet, A the net area of the cylinder (on the end in question) in square inches, and N the revolutions per minute. This will give the horse-power on each end of the cylinder. The total indicated horse-power of the engine is the sum of that for the two ends. 132. Use of the Engine Constant. — When the horse-power of the engine is to be found under a number of different conditions, the calculation may be simplified by the use of the engine constant. This is a factor which is determined for each end of the cylinder and is composed of the constant factors of the usual horse-power formula as follows: ^ . LA Engine constant = 33000 The horse-power is now found for each end of the cylinder by multiplying together the engine constant for that end, the M.E.P. for that end, and the R.P.M. 133. Weights of Steam from the Card. — In find- ing the steam-consumption from the card and in tracing the action of the steam in the cylinder it is THE STEAM-Ex\GINE INDICATOR. 1 59 necessary to find the weight of steam in the cylinder at the different events of stroke. The weight of steam at any point, as for instance at cut-off, is found from the indicator-card on the assumption that the cylinder is full of steam that is dry and saturated. The factors in the calculation are, first, the volume in cubic feet of the space filled with steam at the point of cut-off, and second the w T eight of a cubic foot of steam at the pressure existing at cut-off. To determine the first factor, find the per cent of stroke at cut-off and add the per cent of clearance for the cylinder-end under consideration. These are both expressed as per cents of the piston-displacement, and hence if their sum be multiplied by the piston-dis- placement in cubic feet, the result will be the volume of steam at cut-off. The weight of a cubic foot of steam at the absolute pressure of cut-off may be found from the Steam Tables, section 182. This, multiplied by the volume, will give the weight of steam at cut-off by indicator. The weights of steam at the other events of the stroke may be found in a similar manner. It will be seen that inasmuch as a portion of the steam in the cylinder is not dry and saturated, but has been condensed and exists as water, the weights of steam shown by indicator will be in error to this extent. 134. Reevaporation. — As the steam enters the cylinder during the period of admission a portion of it is condensed by coming in contact with the cooler walls and the retained steam. After cut-off occurs the temperature of the expanding steam falls below that of the cylinder-walls and a portion of the mois- 6o ENGINEERING LABORATORY PRACTICE. ture is reevaporated. The amount of this reevapora- tion per stroke during expansion is determined by subtracting the weight of steam at cut-off from that at release. The reevaporation per revolution is the sum of the weights per stroke for each end. 135- Clearance from the Card. — Two methods of determining clearance from the indicator-card are given below. The methods are both approximate, since they are based upon the assumption that the expansion and compression curves are hyperbolic curves. Since the compression-curve is generally nearer an hyperbola than the expansion-curve, it is preferably used for this work. First Method, — Select two points a and b, Fig. 49, on the expansion or compression curve, and draw o 9 f No Pressure Line Fig. 49. vertical and horizontal lines through each, forming a parallelogram having the line joining the points for a diagonal. Then the point at which the other diagonal produced intersects the line of no pressure will also mark its intersection with the clearance-line. The distance og in per cent of the whole length of the card is the per cent of clearance. Second Method. — Draw a line cd through the expan- sion or compression curve, Lay off ec equal to df. THE STEAM-ENGINE INDICATOR. I'M Draw through e, a line perpendicular to the atmos- phere-line. This will' be the clearance-line. 136. Method of Combining Indicator-cards. — In comparing the performance of a compound or multi- cylinder engine with that of a simple engine, it is sometimes found helpful to combine the cards from the different cylinders of the former, plotting them to the same scale of pressure and volume. The follow- ing method, although open to some criticism, is frequently used. The description will apply to the case of a compound receiver engine, but may readily be modified to suit any combination of cylinders. The necessary data are: Simultaneous cards from the same end of each cylinder. Ratio of piston-displacement for the ends from which the cards were taken (expressed as a whole number). Per cent of clearance for each cylinder for the end from which cards were taken. Scale of spring of cards. Barometric pressure. Divide the cards into 10 equal spaces by means of ordinates drawn perpendicular to the atmosphere-line. Measure and record the pressures at both top and bottom of the card on each ordinate. On a piece of coordinate paper assume ten half- inch spaces, as from F to G> Fig. 50, to represent the low-pressure piston-displacement. Assume an atmosphere-line I-J and construct the low-pressure card, using a scale of 20 pounds to the inch. Draw the Line of No Pressure, HG, at a distance below the atmosphere-line equivalent to the barometric pressure. l62 ENGINEERING LABORATORY PRACTICE, At the admission-end of the low-pressure card lay off a distance FH to represent the clearance-volume of the low-pressure cylinder. At the point //erect the Line of No Volume, HK. •Cut-off % Clearance H.P L.P. Piston Displacement H.P L.P. Ratio of H.P. to L.P.area= Ratio of H.P. to corrected L.P. M.BJP. from the original cards= Ratio of sum of areas of combined cards to area A B C D E A. H F G Fig. 50. From HK lay off KA to represent the high-pressure clearance-volume. The scale of volumes should be the same as that used for the low-pressure card, viz. : L.P. displacement 1 small division 100 THE STEAM-ENGINE INDICATOR. 163 From A lay off AL equal to the high-pressure dis- placement, or equal to distance FG -f- cylinder-ratio. Now construct the high-pressure card, using the same scale of pressure and volume as given above. Through the point of cut-off of the high-pressure cylinder draw an hyperbola with the lines of no pres- sure and no volume as axes. Draw the straight lines AB and CD, thus completing the theoretical card ABCDEA. From the original cards determine the mean effec- tive pressure. Multiply the low-pressure M.E.P. by the cylinder-ratio. The ratio of the high-pressure M.E.P. to the corrected low-pressure M.E.P. stu the ratio of the work done by the H.P. and L.P. cylinders. It should be equal to the ratio of the areas of the combined cards. Fill out the items as shown on Fig. 50. The original cards, pasted to a blank sheet, should accom- pany the report. 137. Exercise. Calculations from an Indicator- card. — The student will be provided with a blank form on which are an indicator-card and a list of items to be filled out. The first step is to carefully locate the events of stroke, cut-off, release, and compression, as explained in Section 125. Now measure the pressures at the several events and find the per cents of stroke (Section 126). Measure the area of the card with the planimeter (Section 130, Item 4) and determine the clearance (Section 135). The various calculations may now be made and entered in the proper place. 164 ENGINEERING LABORATORY PRACTICE. In calculating M.E.P., see Section 129; Weights of steam, " 133; Horse-power, " " 131; Reevaporation, M i6i ? item 5 ; Steam-consumption," 161, item 11. CHAPTER XII. STEAM-ENGINE TESTING. 138. Classification of Tests. — Tests of the steam- engine may be classified as follows: To determine whether the valves are correctly set, to measure the indicated and brake horse-power, to determine the friction of the mechanism, to determine the steam- consumption or commercial efficiency, and to investi- gate cylinder losses and the interchange of heat between the working-fluid and the cylinder-walls. 139. Valve-setting. — The economical use of steam in the steam-engine depends in a large measure upon its proper distribution in the cylinder. This requires careful setting of the valve or valves and adjustment of the valve-gear, which may be accomplished in one of two ways: first, by measurements taken directly from the valve and valve-seat in different relative positions, and second by use of the indicator. Thus the valves of Corliss engines and those having a complicated valve-gear are generally adjusted by taking a card from each end of the cylinder, using a slow speed and a light spring in order that the events of the stroke may be plainly marked. The valve connections may then be changed until the events are correctly placed. The method by use of the indicator is the more accurate for high-speed engines and when the valves 165 l66 ENGINEERING LABORATORY PRACTICE. are not easily accessible, rendering actual measure- ment difficult. For low-speed engines, the method by measurement is to be preferred, as giving more accu- rate results. 140. General Definitions. — The Head End is the end of the cylinder farthest from the crank. The Crank End is the end of the cylinder nearest the crank. Steam-lap is the distance in inches which the valve moves from its mid-position to its position when the admission of steam to the cylinder begins, as shown in Fig. 51. The steam-lap is sometimes called outside lap, in the case of a valve taking steam on the outside. Exhaust-lap is the distance in inches which the valve moves from its mid-position to its position when the release of steam from the cylinder begins, as shown in Fig. 51. In the case of a valve taking steam on the outside, the exhaust-lap is sometimes called inside lap. It may become equal to zero or become negative, in which latter case it is termed exhaust or inside clearance. Lead is the amount in inches by which the valve uncovers the steam-port when the crank is on the dead-center. The Events of the Stroke, admission, cut-off, release, and compression, may each be expressed as the dis- tance from the position of the piston when the eveni: takes place, to the end of the cylinder at which admis- sion occurred or by the fraction representing the per- centage of this distance to the full stroke. All head- end events should be measured from the head end of the cylinder and all crank-end events should be meas- ured from the crank end, as shown on Fig. 44. STEAM-ENGINE TESTING. 167 Equal Cut-off represents the condition when the per cent of cut-off for the head end of the cylinder is equal to the per cent of cut-off for the crank end. Steam Lap Steam Lap Exhaust Lap ^•Exhaust Lap Fig. 51. Equal Lead represents the condition when the amount of lead on the head-end center is equal to that on the crank-end center. 141. Specific Directions (for slide-valve engines). — To Set for Equal Cut-off, — The valve must first be so placed on its stem that its travel will be equal on 1 68 ENGINEERING LABORATORY PRACTICE. both sides of the mid-position. To do this, move the engine (or turn the eccentric on the shaft) until the valve reaches one extreme point of its travel, and measure the amount by which the open port is un- covered. Then place the valve at the opposite extremity of its travel and take similar measurements of the other port. If the measurements do not agree, correct by moving the valve on its stem away from the port having the least opening, by an amount equal to one half of the difference between the meas- urements. Repeat the entire operation until correct. The motion of the valve is now symmetrical with the ports, and it remains to so fix the eccentric on the shaft that the motion will bear the required relation to the motion of the piston, i.e., will cut off the steam on each end of the cylinder after the piston has travelled equal distances from the ends of the stroke. To do this, place the cross-head at the required per cent of stroke at which cut-off is to take place, as shown by marks on the guide, and move the eccentric on the shaft, turning it in the direction in which the engine is to run, until the valve is just cutting off the steam from the end of the cylinder from which the piston is travelling. Now fasten the eccentric in this position and turn the engine over until the piston has travelled the same distance in the other direction. If the valve is now just cutting off the steam from the opposite end of the cylinder, the setting is correct. If the valve fails to cut off, or has travelled too far, move it upon its stem until one half the error is cor- rected and then turn the eccentric on the shaft to correct the other half, that is, until the valve just cuts off. Now turn the engine to its first position and STEAM-ENGINE TESTING. 169 note the location of the valve. If not cutting off, correct as for the other end. Repeat this process until the desired result is obtained. After setting the valve to the required performance as explained above, fill out the tabular statement on the form shown below. The per cent of stroke at release and compression can be obtained by reference to the valve and valve-seat plan, found in the Common- place-book. From the results obtained, construct the theoretical indicator-card (Fig. 52), assuming 100 Cut Initial Pressure 100^ Back Pressure 5 Scale of Spring 50*" -Adm. Adm. xComp. Comp. Fig. 52. pounds initial steam-pressure and five pounds back- pressure, using a scale of 50 pounds to the inch and making the card four inches long. To Set for Equal Lead. — The valve must first be so placed on its stem that its travel will be equal on both sides of the mid-position, as explained in the first paragraph of Section 141. Then put the engine on the head-end center and move the eccentric on its shaft in the direction which the engine is to run, until the head-end port is open by the amount of the lead and any further motion of the valve in the same direction will open the port wider. Fix the eccentric at this point. Turn the engine over to the opposite dead-point and note if the lead on 170 ENGINEERING LABORATORY PRACTICE. the crank end is the same. If it is not, divide the error into two parts and correct one half by moving the valve on its stem and the other half by slipping the eccentric. Repeat until correct. After setting the valve to the required performance, fill out the tabular statement on the form shown below. The per cent of stroke at release and com- pression can be obtained by reference to the valve and valve-seat plan, found in the Commonplace-book. From the results obtained, construct the theoretical indicator-card (Fig. 52), assuming 100 pounds initial steam-pressure and five pounds back-pressure, using a scale of 50 pounds to the inch and making the card four inches long. 142. Form for VALVE-SETTING. Directions: Date Mr will set valve of engine to give ; engine to run (Signed) Instructor. Report : Having complied with the foregoing directions I hav^ohtained results which are as follows : Per cent of admission. . . . 11 " cut-off 11 V " release M H " compression .. Lead in inches Head End. Crank End. (Signed) , [Attach card (or cards) to this space by pasting at the upper edge only.] STEAM-ENGINE TESTING. 171 143. Valve-setting by Indicator. — In many cases it is impossible or inconvenient to set valves by measurement on account of their inaccessibility or for other reasons. In such cases recourse is had to the indicator-card, from which an approximate determina- tion of the events of the stroke may be made. Let it be required to set the valve of an engine to give 75 per cent cut-off on each end of the cylinder, the engine to run over, and let it be assumed that the valve travel has been equalized, i.e., made symmetrical on both sides of the mid-position. The process consists in taking an indicator-card from each end of the cylinder with the engine under a medium load, using as light a spring in the indicator as is compatible with the steam-pressure. If the cut-off shown by the cards is not that desired, make such change in the angular advance of the eccentric or the length of the rod as will correct the error, and repeat until the desired result is obtained. Specific Directions. — Read Sections 120 and 148 on the use of the indicator and on the care of the engine. Having the indicator in place and lubricator and oil- cups filled, start the engine and bring slowly up to speed and conditions of load desired. After the engine has been running a short time, take an indi- cator-card for each end and locate cut-off as explained in Section 125. If it is not at the required per cent of stroke, stop the engine and shift the eccentric on the shaft the amount deemed necessary to correct the error. Re- peat until correct. Stop the engine, shut off lubricator and oil-cups, 172 ENGINEERING LABORATORY PRACTICE. remove and clean the indicator, and leave the engine in good condition. Measure the valve-travel and find the ratio of the length of the crank to that of the connecting-rod. In the Report state the method of procedure, the number of adjustments made, and present the last card taken, with all events located and per cents of stroke entered at the respective places. Draw on the report sheet a Zeuner diagram, assuming the same cut-off as that for which the valve was set. The valve and seat dimensions may be found in the Commonplace-book. Compare the per cents of re- lease, compression, and admission shown by the valve- diagram and by the indicator-card. 144. Steam-distribution of Locomotive Link- motion. — The Stephenson link-motion is in almost universal use in this country for locomotive valve-gears. Since the economy of the machine is, in a measure, dependent on the steam-distribution, the design of a link-motion which will give a suitable distribution at all cut-offs is a matter of importance in locomotive design. The object of this experiment is to investigate the distribution of steam given by a link-motion of pro- portions similar to those used in locomotive practice. The apparatus consists of a model link-motion, so constructed that it can be set to the dimensions of the valve-gear of any locomotive in regular service. Specific Directions. — The experiment consists in placing the reverse-lever in different positions and noting the per cents of stroke at which the several events occur. The events to be determined are (1) admission, (2) cut-off, (3) release, and (4) compression for each end of the cylinder and each notch of the STEAM-ENGINE TESTING. 173 reverse-lever, forward and back. The events are determined with reference to the per cent of piston travel accomplished when they take place. To this end the piston is provided with a scale graduated in 100 parts. All events for the head end are said to take place when the piston is at certain per cents of its travel from the head end, whether the piston is moving from or to the head end (see Fig. 44). Note that when the crank is uppermost and moving toward the cylinder the model is " running forward/' Commence at the longest cut-off, running forward, and proceed with each notch in turn as far as time will permit. Be careful to reverse the motion of the model when the reverse-lever passes the center notch. The Report should correspond to the following form: 145. Form. REPORT ON STEAM-DISTRIBUTION OF LOCOMOTIVE LINK-MOTION. Observers < Date Head End. Crank End. Number of Notch. Adm. Cut. Rel. Comp, Adm. Cut. Rel. Comp. 146. Indicated Horse-power. — The factors in the indicated horse-power of an engine are the size of the cylinder, the revolutions per minute, and the mean 174 ENGINEERING LABORATORY PRACTICE. effective pressure on the piston. Its determination involves the taking of indicator-cards and simultaneous readings of the speed for a sufficient length of time to secure observations showing the average performance of the engine. From the data thus secured the indi- cated power may be calculated. Specific Directions, — This test should be conducted by two men, one taking indicator-cards and the other speed readings. These positions may be interchanged half-way through the test. The accessory apparatus needed is an indicator, a speed-counter, and a whistle. Prepare the blank log-sheet according to the form shown below. Before the test it will not be necessary to rule up more than the portion headed Running Log, leaving space for the other data as shown. Before the test read carefully Sections 120 and 148 on the use of the indicator and the care of the engine. Make the test forty-five minutes in duration, and take cards every five minutes. The speed-reading should be taken, beginning with the signal for the card and continuing for one minute. After the test find the dimensions of the engine from the Commonplace-book. Calculate the M.E.P. from the cards by the method of ordinates as explained in Section 128. Find the indicated horse-power as explained in Section 131, using the average M.E.P. of the cards from each end. Under the head of minimum and maximum horse- power, enter the horse-power shown by the cards having respectively the lowest and highest average M.E.P. for the two ends. Make out the report in the form shown below and accompany it with an average card, pasting the same to the report. STEAM-ENGINE TESTING. 147. Form of REPORT ON INDICATED HORSE-POWER 175 OF A Observers \ Date, CONSTANTS OF THE ENGINE. Dia. of cylinder in. Area of piston, H. E. Dia. of piston-rod in. C. E. Length of stroke ft. RUNNING LOG. sq. in. sq. in. Number. Time. R. P. M. M. E. P. Remarks. H. E. C. E. Total Average. . . . Average I. H. P. Max. I. H. P. Min. I. H. P. H. E. C. E. Total. 148. Care of the Steam-engine. — The following are brief directions for the operation and care of the steam-engine. They are applicable in a general way to the ordinary types of stationary engines. 1. Inspect the engine, piping, etc., carefully, to see that the plant is in good order. 2. Fill lubricator with cylinder-oil and oil-cups 176 ENGINEERING LABORATORY PRACTICE. with engine-oil, and adjust the feed to the required amount. Oil around where necessary. 3. If condensing-engine, start air-pump and turn on cooling water to condenser. 4. Open cylinder and pipe-drains. 5. Start engine slowly and bring gradually up to speed. Shut drain-cocks. 6. Apply the load gradually as desired. 7. During the run watch lubricator and oil-cups. Feel the bearings occasionally. Use only enough cooling water to properly condense the steam. 8. After the run, remove the load gradually, stop engine and air-pump. Shut off condenser cooling water and stop lubricator and oil-cups. Open drains. Clean the plant thoroughly. Lubricators. — In Fig. 53 is shown a sectional view of a sight-feed lubricator. The top and side connec- tions lead to the steam-pipe, the latter at a point nearest the engine. Steam enters the upper connec- tion, is condensed, and as water flows through the small curved pipe to the bottom of the large chamber, which is filled with oil. The oil thus displaced enters the top of the second small pipe, flows downward by the regulating-valve, rises through the glass, which is filled with water, and reaches the main steam-pipe through the side connection. In filling the lubricator it is necessary to shut off the regulating-valve and the valve in the upper connection. The oil-chamber may then be drained and filled. The left-hand glass serves to indicate the level of oil in the chamber. If the sight-feed glass becomes clogged with oil, it may be cleaned by shutting the feed-regulating valve and opening the small valve immediately to the right of STEAM-ENGINE TESTING. 177 "5enior ,, S.F,Lubricator. theLunkenheimerCo. Cin,,Ohio. FlG. 53. — LUNKENHEIMER LUBRICATOR. 1 7 8 ENGINEERING LABORATORY PRACTICE. the latter. Steam will then blow through from the main steam-pipe and clean the glass. On closing the small valve allow the glass to fill with water of con- densation before opening the feed-valve. In Fig. 54 is shown a lubricator of another make. This instrument is fitted with a condensing-bulb A2, Fig. 54. — Detroit Lubricator. the latter being provided with a valve A4. between it and the body of the lubricator. In filling the oil- chamber this intermediate valve is closed, thus retain- ing the water of condensation in the condensing-bulb. STEAM-ENGINE TESTING. 179 149. Friction of the Mechanism. — All the power developed in the cylinder of the steam-engine re- appears at the brake-wheel except that absorbed by the friction of the mechanism. The purpose of this test is to determine the ratio between this frictional horse-power (F.H.P.) and the indicated horse-power (I.H.P.). The method consists in taking simultaneous observations of the indicated and brake horse-powers under the conditions of running for which the friction is desired. In case it is impossible to fit the engine with a brake, the friction of the engine may be found when the engine is running light by observing the I.H.P. under no load. This, however, does not represent the friction when the engine is under load, since that quantity varies somewhat under different conditions of running. Specific Directions. — Run twelve tests, the first to be under no load, the twelfth to be under the maxi- mum load, and the remainder to be under loads dis- tributed between the first and twelfth. The tests should be four minutes in duration, witn cards and observations every two minutes. The auxiliary apparatus needed is an indicator, a speed-counter, and a whistle. Prepare a Running Log in accordance with the following form : RUNNING LOG. Test No. No. of Gong-. _,. No. of Time. Card> Steam pressure. R.P.M Brake Load. M. E.P. H. E. C. E. i8o ENGINEERING LABORATORY PRACTICE. Before the test read Section 120 on the use of the indicator and Section 148 on the care of the engine. Start the engine slowly under no load, and after the proper conditions are obtained take a few preliminary cards before commencing the test. The Report should include the Running Log, sample cards, a statement of the dimensions and constants of the engine, and the calculated results. It should be made out in accordance with the form given below. The directions for finding M.E.P. are given in Section 129; for I.H.P. in Section 131 ; for B.H.P. in Section 68 et seq. The formula for mechanical efficiency is B.H.P. 100 X TjOV Accompany the report by two curves, one showing the relation between F.H.P. and I.H.P. ; the other, the relation between mechanical efficiency and I.H.P. These should be plotted on a single sheet of plotting- paper. 150. Form of REPORT ON FRICTION TEST OF Observers I Dia. of cylinder in. Dia. of piston-rod in. Length of stroke ft. SUMMARY OF RESULTS Date. Area of piston, H. E sq. in, C. E sq. in. No. of Test. I 2 3 4 etc. Steam- pressure. R. P. M. I.H.P. B. H. P. F. H. P. Mechanical Efficiency. STEAM-ENGINE TESTING. l8l 151. Commercial Efficiency. — The commercial effi- ciency of the steam-engine is usually expressed as the number of pounds of dry steam used per I.H.P. per hour, or sometimes per B,H.P. per hour. To deter- mine this quantity it is necessary to run the engine under the conditions which it is desired to investigate and measure the I.H.P. and the water-consumption. To this end the engine must be fitted with an accurate indicator reducing-motion, and the indicators, prefer- ably one for each end of the cylinder, should be placed as close to the cylinder as possible to avoid the errors due to long connections. An absorption-dynamometer should be provided to absorb and measure the work done by the engine. The steam-consumption is preferably obtained by leading the exhaust-steam to a surface condenser, where it may be collected as water and weighed. The condenser may or may not be fitted with an air-pump. A calorimeter of some approved form, such as the throttling calorimeter, should be provided to determine the quality of steam used (see Section 59). This should be located as close to the engine as possible. In case the accessory apparatus, such as gages, thermometers, indicator- springs, and weighing-barrels, have not previously been calibrated, this must be carefully done before the test, keeping record of all results. Specific Directions. — Observers will be needed for the test in accordance with the following schedule: 1. Log and time ) . , ur b , r > in charge. 2. Weight of steam ) 3. Indicator, head end. 4. Indicator, crank end. 5. Speed and load. 1 82 ENGINEERING LABORATORY PRACTICE. 6. Miscellaneous observations. Secure the following accessory apparatus: Two in- dicators with springs to suit steam-pressure (see Sec- tion 119), indicator-cards, one speed-counter, one whistle, one 212 F. thermometer, and one 400 F. thermometer if a throttling calorimeter is used. Prepare the blank Running Log, making provision for the following items: 1. Time. 2. R.P.M. 3. Brake load. 4. Back pull on brake (if any). 5 . Steam-pressure. 6. Vacuum (if any). 7. Barometric pressure. 8. Pressure in calorimeter. 9. Temperature in calorimeter. 10. Temperature of room. 11. Weight of condensed steam. The test should be from one hour to one hour and a half long, depending upon the constancy of the running conditions. Observations and cards should be taken every five minutes. Before the test, read Section 120 on the use of the indicator and Section 148 on the care of the engine. Having the indicators in place and observers posted, start the engine and secure the desired running conditions. Start the test by taking time, cards and observations and commenc- ing the weighing of water. During the test keep all running conditions" as constant as possible. Watch the lubricator and oil- cups. Keep only sufficient cooling water on the con- denser to prevent the condensed steam from vaporiz- STEAM-ENGINE TESTING. 183 ing as it emerges. After the test, stop the engine, shut off the cooling water from the condenser, stop the lu- bricator and oil-cups, remove and clean the indicators, collect all logs and cards, and see that the former are dated and signed with the initials of the observer. Report. — The Report should be accompanied by the Running Log or Logs, and all cards taken. It should include the following items: CONSTANTS OF THE ENGINE. Clearance (both ends). Kind of brake. Brake constants. Make of condenser. Make and numbers of in dicators. Scale of spring. Type of engine. Make of engine. Size of cylinder. Diameter of piston-rod. Area of piston (both ends) Piston-displacements. Engine constants. Duration of test. Steam-pressure. R.P.M. Brake load, net. Vacuum. OBSERVED DATA. Averages. Barometer. Pressure in calorimeter. Temp, in calorimeter. Temperature of room. Wt. of cond. steam (total) CALCULATED DATA. Mean effective pressure. H.E. and C.E. (Section 129). Indicated horse-power. H.E. and C.E. (Section 131)- Indicated horse-power, total. Brake horse-power (Section 68). 1 84 ENGINEERING LABORATORY PRACTICE. Frictional horse-power (Section 161, item 19). F.H.P. in per cent of I.H.P. Ratio of B.H.P. to I.H.P. Quality of steam (Section 59). Pounds of dry steam per I.H.P. per hour, by tank (Section 161, item 12). * Pounds of dry steam per I.H.P. per hour by in- dicator (Section 161, item 11). * Clearance from the card (Section 135). In case no calorimeter is available, the steam may be assumed to be 98 per cent dry if the distance from boiler to engine is not great and the steam-pipe is well covered. 152. Investigation of Cylinder Losses. — In more extended investigations of steam-engine performance than that described in the preceding section, it is cus- tomary to make an analysis of the action of the steam in the cylinder, with a view to discovering the losses occasioned by changes of condition of the steam, inter- change of heat between the steam and the cylinder- walls and kindred causes. One method of making a complete investigation of such losses is known as Hirn's Analysis. f Another method is the Entropy Temperature Analysis.;}; In order to determine the change in condition of the steam during different parts of the cycle, the * Calculate the weights of steam for this item for a pair of sample cards whose combined M.E.P. corresponds most nearly to the average for the test. The clearance is found from the same cards. f See Peabody's "Thermodynamics of the Steam-engine," page 185. X " Entropy Temperature Analysis of Steam-engine Efficiencies," by Reeve. STEAM-ENGINE TESTING. 1 85 following items must be added to the " Calculated Data ' ' as given in Section 151. Absolute pressure at cut-off, head and crank end (average of all cards). Absolute pressure at release, head and crank end (average). Absolute pressure at compression, head and crank end (average). Per cent of stroke at cut-off, head and crank end (average). Per cent of stroke at release, head and crank end (average). Per cent of stroke at compression, head and crank end (average). Weight of steam per revolution at cut-off (Section 161, item 2). Weight of steam per revolution at release (Section 161, item 3). Weight of steam per revolution at compression (Section 161, item 4). Reevaporation per revolution (Section 161, item 5). Reevaporation per I.JH.P. per hour (Section 161, item 6). Weight of steam per revolution by tank (Section 161, item 7). Weight of mixture in cylinder per revolution, maxi- mum (Section 161, item 8). Per cent of mixture accounted as steam at cut-off (Section 161, item 9). Per cent of mixture accounted as steam at release (Section 161, item 10). In case it is desired to use Hirn's Analysis, the 186 ENGINEERING LABORATORY PRACTICE. following observations will need to be added to the Running Log, as given in Section 151 : Weight of cooling water. Initial temperature of cooling water. Final temperature of cooling water. Temperature of condensed steam. 153. Method of Measuring Clearance. — The clear- ance of a steam-engine cylinder is all of the clear space between the piston and the face of the valve, when the piston is at the beginning of its stroke. It is usually expressed as a per cent of the piston-dis- placement, and should be found for each end of the cylinder. The piston-displacement for each end is the area of the piston on that end in square feet, multiplied by the length of the stroke in feet. The method of determining the clearance consists in placing the engine on center and filling the clear- ance-space with water, noting the weight required to fill. Knowing the temperature of the water, the volume can then be found. This volume divided by the piston-displacement for that end and multiplied by 100 will give the per cent of clearance for the cylinder end under consideration. The process of getting the water into the cylinder depends largely upon the construction of the engine. It must be poured in at the highest point of the cylinder in order to avoid entrapping air in the clearance-space. For a plain slide-valve engine, with the valve-box on the side, it may usually be poured in through the indicator-cocks. In such a case it will be necessary to disconnect the valve-rod and adjust the valve to cover the ports, clamping it in place. A block of wood with STEAM-ENGINE TESTING. 1 87 a rubber gasket may be used instead of the valve. For a slide-valve engine with the valve on top it is best to remove the valve-box cover and valve, and pour in through the port. For a Corliss engine, remove the steam-valves and use the ports thus exposed. In general an examination of the engine will suggest the course to be followed. Specific Directions. — Provide two cans of water, a and b, weigh each carefully and note the temperature. With a fill the clearance-space as rapidly as possible and note the time occupied in filling. Then with b pour in to replace that lost by leakage, maintaining the level for one minute from the time the original filling was completed. Weigh both cans and note the weight of water used. The weight used from can a will represent the weight required to fill the clearance-space, subject to the following correction: One half the amount used from can b, multiplied by the time in minutes occupied in the original filling, may be assumed to have leaked out during the original filling, and this amount is to be subtracted as a correction from the weight used from can a. From the corrected weight thus obtained and the temperature, the volume may be calculated. If the correction to be made is large, the result will be only approximately correct. In such a case it may be well to attempt to stop the leakage, which is usually between the piston and the cylinder, by oiling the cylinder thoroughly with a heavy oil. It is often thought necessary that the engine be warmed up by steam before the clearance is obtained, that working conditions may be had, but it is doubtful if such a precaution is necessary. 1 88 ENGINEERING LABORATORY PRACTICE. 154. Advanced Work in Steam-engine Testing. — Effect of Load on Economy. — To determine the most economical load for a given speed and steam- pressure, run a series of five tests at a constant speed and steam-pressure to be assigned by the instructor. For the first test let the load be zero. For the fifth test, let the load be as large as can be carried under the assigned conditions, and let the intermediate tests be under intermediate loads. The directions will assume that a condenser is employed to measure the water-consumption. All tests should be of 30 minutes' duration, the conditions to be maintained for 15 minutes before the test begins, and the test to be conducted and worked up in all respects as explained in Section 151. The Report should include: 1. A statement of the purpose of the tests. 2. A brief description of the plant. 3. A statement of constant conditions. 4. A copy of all calibrations, measurements, and observed data. 5. A tabulated statement of calculated results. 6. Curves showing the following relations: {a) Indicated and brake horse-power with per cent of cut-off (if an automatic cut-off engine). {U) Pounds of steam per I.H.P. per hour with indi- cated and B.H.P. 7. Conclusions as to the most efficient load under the conditions. 8. Sample cards. Effect of Different Steam-pressures on Economy. — To determine the effect of different steam-pressures on the economy of a steam-engine, run a series of five tests STEAM-ENGINE TESTING. 1 89 at constant speed and two-thirds load under steam- pressures ranging from 60 to 200 pounds pressure. Make all tests 30 minutes in duration, and let the conditions be maintained for at least 15 minutes before the test is begun. The tests should be con- ducted and worked up as described in Section 151. The Report should include the following: 1. A statement of the purpose of the tests. 2. A brief description of the plant. 3. A statement of the constant conditions. 4. A copy of all calibrations, measurements, and observed data. 5. A tabulated statement of calculated data. 6. Curves showing the following relations: (a) Indicated and brake horse-power with steam- pressure. (b) Steam-consumption with steam-pressure. 155. Tests of Compound Engines. — The purpose of, and methods employed in, compound engine- testing are similar to those relating to the simple engine. Read the introductory portion of Section 151. Specific Directions. — Observers will be needed for the test in accordance with the following schedule: 1. Log and time ) . , m b t r m charge. 2. Weight of steam ) 3. Indicators, high-pressure, head and crank. 4. Indicators, low-pressure, head and crank. 5. Revolutions, pressures, and miscellaneous obser- vations. 6. Brake load. Secure the following accessory apparatus: Four indicators with springs to suit steam-pressure (see I90 ENGINEERING LABORATORY PRACTICE. Section 119), indicator-cards, whistle, thermometers for temperature of room, and calorimeter. Prepare the blank Running Log to cover the fol- lowing items: 1. Time. 2. Counter or R.P.M. 3. Brake load. 4. Steam-pressure. 5. Pressure in receiver. 6. Vacuum. 7. Barometer. 8. Pressure in calorimeter. 9. Temperature in calorimeter. 10. Temperature of room. 1 j. Weight of condensed steam. Conduct the test as specified in Section 151. The Report should cover: 1. Constants of the engine. 2. Running logs, averaged. 3. Tabulated data from cards showing M.E.P. and pressures and per cents of stroke at the different events (see Section 130). 4. Calculated data. Indicated horse-power, H.P., L.P., and total. Brake horse-power. Frictional horse-power. F.H.P. in percent of I.H.P. Ratio of B.H.P. to I.H.P. Quality of steam. Pounds of dry steam per I.H.P. per hour by tank. Number of expansions in H.P.C. Number of expansions in L.P.C. Total number of expansions, STEAM-ENGINE TESTING. I9I Ratio of work done in H.P.C. to that in L.P.C. Ratio of maximum pressure on H.P. and L.P. pistons. Initial pressures, H.P.C. and L.P.C. Final pressures, H.P.C. and L.P.C. Drop in pressure, H.P. final to L.P. initial. Weight of steam at cut-off, H.P.C. per revolu- tion. Weight of steam at release, H.P.C. per revolu- tion. Weight of steam at cut-off, L.P.C. per revolu- tion. Weight of steam at release, L.P.C. per revolu- tion. Reevaporation during expansion, H.P.C. Reevaporation during expansion, L.P.C. Condensation (or reevaporation) between cut-off H.P.C. and cut-off L.P.C. 5. Present a representative set of cards. 6. Take head-end cards from same set (item 5) and plot to same scale of pressures and volumes (see Section 136). 156. Directions for Equalizing the Work of a Compound Engine. — The work done by the cylinders of a compound engine should be equally distributed between the two cylinders. This condition will be realized when the mean effective pressures are in- versely proportional to the areas of the cylinders, the length of stroke being the same. The method of equalizing the work is as follows: Take simultaneous cards from both cylinders and determine the average M.E.P. If the ratio between them is not inversely proportional to the cylinder 192 ENGINEERING LABORATORY PRACTICE. areas, and it is found, for instance, that the M.E.P. of the L.P. cylinder is too small, shorten the cut-off on the L.P. cylinder. This will increase the back- pressure on the H.P. cylinder and increase the initial pressure of the L.P. cylinder. Take another set of cards, and if not correct, repeat the process. In reporting results give: 1. A statement of the result to be accomplished. 2. A tabulated statement as below: M. E. P.— H. P. C. M. E. P.-L. P. C. Ratio of M.E.P. in H. P. C. H. E. C. E. Ave. H. E C. E. Ave. to that in L. P. C. Eng. as found. ist change.. . . 2d change. . . . Etc. 3. A statement of the maximum piston-pressures after equalization. 157. Locomotive Testing. — Tests of locomotives are of two general kinds, those made on the road under conditions of actual service and those made on specially devised testing plants, where the engine may be placed under conditions similar to those mQt with in road service. For all tests involving an accurate determination of the engine and boiler per- formance the shop test is to be preferred, since by that method all conditions may be maintained with great constancy, a feature impossible with road tests. The method of conducting the tests on the road varies according to the purpose for which the test is made, but for all ordinary road tests the following method, recommended by the American Society of STEAM-ENGINE TESTING. I93 Mechanical Engineers,* is standard. The code pro- vides for both road and shop tests. 158. A. S. M. E. Standard Method of Testing Locomotives. I. Preparations for Test, and Location of Instruments. f A. The locomotive should be put in good condition preparatory to the test. The boiler and tubes should be tight, and both the interior and exterior surfaces should be clean, and if possible free from scale. There should be no lost motion in the valve-gear, and the valves should be set properly. No change in the engines should be allowed during the progress of a series of tests, unless so ordered for the pur- poses of the trial. A glass water-gage should be fitted to the boiler, if not already provided. A rod should be attached to the reversing-lever and carried forward to the front end of the boiler, where a graduated scale is provided and suitably marked, so that the position of the reversing-lever can be seen at a glance by the person taking indicator-diagrams. The throttle-valve lever should be provided with a scale to show the degree of opening of the throttle. B. The valves and pistons should be tested for leakage with the engine at rest. The steam-valve can be tried by setting the engine so that the valve on one side will be at the center of its throw, in which * Transactions of the American Society of Mechanical En- gineers, vol. xiv, p. 1312. f The directions here given apply largely to both shop and road tests, but especially to the latter. 194 ENGINEERING LABORATORY PRACTICE, position both ports are usually covered, and pulling open the throttle-valve, blocking the drivers if there is a tendency for the engine to be set in motion. Leakage of the valve, if any occurs, will show itself by escaping at the smoke-stack, or at the open drain- cocks. The tightness of the piston may be tested by setting the engine so that it takes steam, blocking the drivers, and opening the throttle-valve. This should be tried first on one cylinder anJ then on the other, and if desired, it may be tried with the pistons at various points in the stroke. The leakage, if any occurs, will be shown either at the top of the smoke- stack or at the open drain-cock. C. The following instruments should be verified or calibrated: Steam-gages, draught-gage, pyrometer, thermometers for calorimeter and feed-water, water- meter, tank, revolution-counter, indicator-springs, dynamometer-springs, and dynamometer recording mechanism. The radiation loss on the steam-calo- rimeter should be determined or the normal readings ascertained;* and the quantity of steam which passes through the instrument in a given time should be measured. D. The quantities of steam consumed by the air- pump, the blower, and the whistle, under conditions of common use, should be determined, thereby obtaining data by which to correct for the steam thus used. This can best be determined for each one by observing the fall of water in the gage-glass when no steam is drawn from the boiler for any other purpose, the quantity being computed from the data thus * Transactions A. S. M. E., vol. xi, p. 793. STEAM-ENGINE TESTING. 195 found, and the dimensions of the boiler. The leakage of the boiler should also be found, using the same method. E. To facilitate the measurement of coal and the determination of the quantity used during any desired period of the run, it is desirable to provide a sufficient number of sacks of a size holding a weight of, say, 100 pounds, and weigh the coal into these sacks pre- paratory to starting on the test. If desired, the sacks may be numbered, to facilitate the accuracy of record. F. The instruments and other apparatus that should be provided, and their locations, are as follows: To facilitate the work of operating the indicators and reading the instruments at the front end, the smoke-box should be surrounded with a wooden fence, or" pilot-box, " as it may be called, resting on the top of the cow-catcher and extending back far enough to enclose also the sides of the cylinders. This box is floored over, and the enclosure thus pro- vided forms a convenient place for the accommodation of the assistants at this end of the locomotive, and it affords them some measure of protection against wind and rain, as also the jolting and vibrations due to rapid travel. A special steam-gage with a long siphon is to be used for registering the boiler-pressure. It can best be located on the left-hand side of the cab. The indicator apparatus which is most suitable con- sists of a three-way cock for the attachment of the indicators, and some form of pantograph motion for the driving-rig. The pipes leading from the cock to the cylinder should be three-fourths inch diameter inside, and they should connect into the side of the I96 ENGINEERING LABORATORY PRACTICE,, cylinder rather than into the two heads. The indi- cator should also be piped so that a steam chest diagram can be drawn by it. Sharp bends in the pipe should be avoided, and they should be well covered, to intercept radiation. The three-way cock should be provided with a clamp rigidly secured to the cylinder, and thus overcome any tendency of the indicators to move longitudinally with reference to the driving-rig. Absolute rigidity is highly essential in this particular. In both of these the reduced motion is transmitted to the indicator through a light rod, working horizontally. By this means a cord eight or ten inches in length is sufficient for connec- tion to the indicator. Care should be taken to set the instrument in such a position that the cord-pin in the end of the rod travels in a direction pointing to the groove in the paper drum. Pantograph motions arranged as noted are preferable to the common pendulum and quadrant reducing mechanism, with its long stretch of cord. A draught-gage consisting of a U tube containing water, properly graduated in inches, should be con- nected to the smoke-box and attached to the side of the pilot-box. A pyrometer for showing the temperature of the escaping gases should be used in a position below the tip of the exhaust-nozzles. The calorimeter should be attached either to the steam-dome at a point close to the throttle-opening, or to the steam-passage in the saddle-casting on one side, according as it is desired to obtain the character of the steam at one point or the other. The former location is preferred by the committee. A perforated STEAM-ENGINE TESTING. I97 half-inch pipe should be used for sampling and con- veying the steam to the calorimeter-pipe. For descriptions of various forms of calorimeters which are adapted to locomotive use, see Trans. A. S. M. E., vol. X. p. 327, vol. XI. p. 790, vol. XII. p. 825. The water-meter should be attached to the suction- pipe of the injector, and located at a point where it can be conveniently read when the locomotive is running. It should be provided with a check-valve to prevent hot water from flowing back through it from the injector, and a strainer to intercept foreign material. To measure the depth of the water in the tank, a metallic float should be used, carrying a vertical tube which slides upon a graduated rod, the lower end of which rests upon the bottom of the tank. This should be placed at the center of gravity of the water-space. If the desired location cannot be used, provision should be made for ascertaining the level or inclination of the tank. The best device for this pur- pose is a plumb-line of a certain known length, pro- vided at the bottom with a double horizontal scale, having one set of divisions parallel to the side of the tank and the other set at right angles to it. From the readings on these scales referred to the length of the line the level of the tank in both directions can be ascertained. A similar device should be attached to the boiler to correct for the variation in its inclina- tion. The plumb-line may be conveniently attached for this purpose at some point near the front end. The revolution-counter should be placed near the front end of the engine in plain view from the pilot- box. It is operated through a belt from the driver shaft. This recommendation applies to that form of I98 ENGINEERING LABORATORY PRACTICE. counter which shows at a glance the exact speed in revolutions per minute. A stroke-counter should be provided for showing the number of strokes made by the air-pump. Electric connection should be made between the dynamometer-car and the pilot-box, so that dynamom- eter records and indicator-diagrams may be taken simultaneously. Another provision is a speaking-tube leading from the dynamometer-car to the locomotive- cab, and one also to the pilot-box. G. It is needless, except for a complete record of directions for preparatory work, to call attention to the desirability of having the test, especially the road test, made under the supervision of a competent person, who is not only familiar with the details of testing, but also with the proper method of firing and mechanical operation of the locomotive. This is a most important factor, for it is only the clear-headed and able experimenter who is likely to obtain satis- factory work in this most difficult department of engineering tests. In the matter of assistants, the conductor of the test is best able to judge as to the number required, the various duties of the different men, and the manner of taking records. A good test can be made with eight (8) assistants, distributed in the manner indicated in the following list, which gives their duties: Two (2) cab assistants, who note the reading of the steam-gage and the water-meter, the position of the throttle-valve and reversing-lever, the height of water in the tank, the height of water in the glass water-gage, the level of the tank, the number of times the whistle is blown, the length of time the safety-valve blows, STEAM-ENGINE TESTING. I99 the length of time the blower is in action, the reading of the air-pump counter, the temperature of the feed- water in the tank, the time of starting and stopping the injector, the time of opening and closing the throttle-valve, and the number of sacks of coal used. These two observers have previously checked the weights of coal placed in the sacks. Three (3) pilot-box assistants, one of whom reads the pyrometer, the draught-gage, the steam-chest gage, the revolution-counter, and marks on the indi- cator-diagrams the time, position of reversing-lever, steam-chest pressure, and revolutions per minute. He also takes the levels of the boiler at stopping- places. The other two observers are stationed at the cylinders and manipulate the indicators, one being employed on each side. One (1) calorimeter assistant, who reads the calo- rimeter thermometers, and the gages connected with the instrument, if these are employed. Two (2) dynamometer-car assistants, who record time of each start and stop, time of passing each station and each mile-post, time of taking each indicator-diagram as obtained from signals of the indicator men ; and all these readings are marked so far as possible on the dynamometer-paper. One of these men also assists the cab observer in reading the tank-depth and its levels at stopping-places. These men also keep a record of the direction and force of the wind, and the temperature of the atmosphere. An additional assistant is required if the gases are sampled and analyzed. H. It is of paramount importance, after the com- plete preparatory work has been accomplished, that the locomotive be subjected to a preliminary run, of 200 ENGINEERING LABORATORY PRACTICE. sufficient duration to make a fair trial of the testing apparatus, and to give the various assistants an oppor- tunity to become trained in their duties. II. Shop Test. A . Preparation and Location of Instruments. In preparing for a shop test the preparations described in Section I should be followed so far as the nature of the test requires. When run as a stationary engine the locomotive is not circumscribed by the conditions of road service, and many provisions re- quired on the road are unnecessary. It is unnecessary to determine the quantity of steam consumed by the whistle and air-pump, for these are not brought into use on the shop test ; and no occasion exists for finding the quantity lost at the safety-valve, for on the con- tinuous shop run the steam-pressure can be maintained at a uniform point, and blowing-off readily prevented. It is unnecessary to use sacks for the convenient measure of coal, because the coal can be readily weighed up in lots as fast as needed for the test. It is unnecessary to provide a 4< pilot-box," and no fixed location of the instruments is required, as on the road test. The feed-water may be weighed before it is supplied to the tank, and the tank may be used in this case as a reservoir, the float showing its depth. The meter would thus be unnecessary as the principal instrument of measurement, but a meter is in all cases useful as a check upon this most important element in the data. The long indicator-pipes required on the road test may be dispensed with, and one indi- cator applied close to each end of the cylinder, a practice much to be preferred to the use of a three- way cock and the single indicator. The dynamom- STEAM-ENGINE TESTING. 201 eter-car is not required, but its equivalent should be provided, consisting of a dynamometer which registers the pull on the draw-bar, in the same manner as the device used on the road. The number of assistants required on a shop test is less than that needed for a road test. A good test can be made with four (4) assistants distributed as follows: One (1) assistant for operating indicators. One (1) assistant for measuring water. Two (2) assistants for general observations and coal measurement. If the gases are sampled and analyzed, one more assistant is required. B. Conditions of Test. The test should be continued for a run of at least two (2) hours from the time normal conditions have been established. At the close of the test the water height in the boiler and the height of water in the tank should be the same as at the beginning, or proper corrections made for any differences which may exist. The fire-box and ash-pit are then cleaned, and such unburnt coal as may be contained in the refuse is separated, weighed, and deducted from the total weight of coal fired. The balance of the refuse is weighed, as also the cinders removed from the smoke- box. During the progress of the test samples of the various charges of coal should be obtained, and at its close a final sample of these should be selected, dried, and subjected to chemical analysis and calorimeter test. The weight of the sample is taken before and 202 ENGINEERING LABORATORY PRACTICE. after drying, to ascertain the amount of moisture contained in the fuel. C. The Data and Results. The data and results of the shop test can best be arranged in the manner indicated in Table No. I. Table No. 1. DATA AND RESULTS OF SHOP TEST ON ENGINE, MADE 189 GENERAL DIMENSIONS, ETC., To be accompanied by a complete description, with drawings and full dimensions. 1. Kind of engine 2. Size and clearance of cylinders 3. Area of heating-surface 4. Area of grate-surface 5. Diameter of exhaust-nozzles TOTAL QUANTITIES. 6. Duration 7. Weight of dry coal burned, including 0.4J weight of wood 8. Weight of water evaporated corrected for moisture in the steam 9. Weight of ashes and refuse from ash-pan. 10. Weight of cinders from smoke-box 11. Percentage of ash, as found by calorim- eter test I per cent. 12. Total heat of combustion per lb. coal as found by calorimeter test B. T. U. POWER DATA. 13. Mean effective pressure, high-pressure cylinders 14. Mean effective pressure, low-pressure cylinders 15. Average revolutions per minute 16. Indicated horse-power, high pressure cylinders 17. Indicated horse-power, low-pressure cylinders 18. Indicated horse-power, whole engine. .. . 19. Pull on draw-bar 20. Dynamometer horse-power Whole Run. STEAM-ENGINE TESTING. Table No. 1 — Continued. 203 21. AVERAGES OF OBSERVATIONS. Average boiler-pressure lbs. lbs. deg. in. deg. deg. per cent. per cent. lbs. lbs. lbs. lbs. lbs. lbs. lbs. lbs. lbs. lbs. lbs. lbs. lbs. Whole Run. 22. Average steam-chest pressure 23. 24. 25. 26. 27. Average temperature of smoke-box Average draught-suction Average temperature of feed-water Average temperature of atmosphere Average percentage of moisture in the steam 28. Maximum percentage of moisture in the steam 29. 30. HOURLY QUANTITIES. Weight of dry coal burned per hour Weight of dry coal burned per hour per sq. ft. of grate-surface 31. Weight of coal burned per hour per sq. ft. of heating-surface 32. 33- Weight of water evaporated per hour. . . . Equivalent weight of water evaporated per hour with feeding- water at 100 and pressure at 70 lbs 34- Equivalent weight of water from 100 at 70 lbs. evaporated per sq. ft. of heating- snrfflrp PRINCIPAL RESULTS, COMPLETE ENGINE AND BOILER. 35. Coal consumed per I.H.P. per hour 36. Coal consumed per dynamometer horse- nnwer ner hour 37. 38. Weight of "standard coal" consumed per I.H.P. per hour Weight of "standard coal" consumed per dynamometer horse-power per hour 39- 40. BOILER RESULTS. Water evaporated per lb. of coal Equivalent evaporation per lb. of coal from and at 21 2° 41. Equivalent evaporation per lb. of com- bustible from and at 212 204 ENGINEERING LABORATORY PRACTICE. Table No. 1 — Continued. CYLINDER DATA. 42. Mean initial pressure above atmosphere. . . 43- 44. 45. 46. 47- 48. 49- lbs. Cut-off pressure above zero Release pressure above zero Compression pressure above zero., Lowest back-pressure above or be- low atmosphere Proportion of forward stroke com- pleted at cut-off Proportion of forward stroke com- pleted at release Proportion of return stroke uncom pleted at compression lbs. lbs. lbs. lbs. lbs. lbs. lbs. H.P. Cyl. L.P. Cyl. CYLINDER RESULTS. 5L 52. Total water consumed per indicated horse power per hour corrected for moisture in steam lbs. Water consumed per I. H.P. per hour by cylinders alone (from line 51, less all measured losses) lbs. 55. 56 53. Steam accounted for by indicators at cut-off 54. Steam accounted for by indicators at release Proportion of feed-water used by cylinders (line 52) accounted for at cut-off Proportion of feed-water used by cylinders accounted for at re- lease lbs. lbs. lbs. lbs. H.P. Cyl. L.P. Cyl. So far as these are in common with the data and results obtained on the road test, the forms used on both kinds of test are identical. Reports should give copy of a set of sample indi- cator-diagrams, also combined diagram (in case of multi-expansion engine), and a chart showing graphi- cally the principal data. STEAM-ENGINE TESTING. 205 III. The Road Test. A . Preparation and Location of Instruments. The preparations required for the road test, and the proper location of instruments for the purpose, are fully described in Section I, and repetition is unnecessary. B. The Dynamometer-car . With a suitable dynamometer-car the force required to move the train, or the pull upon the draw-bar, is registered upon a strip of paper travelling at a definite rate per mile. The scale upon which this diagram is drawn should be as large as is possible within reason- able limits; a scale of \ inch per iooo pounds pull being suitable, as the maximum registered pull rarely exceeds 30,000 pounds. The height of the diagram should be measured from a base-line drawn upon the paper by a stationary pen, so located that when no force is exerted upon the draw-bar the base-line should coincide with zero pull. The apparatus should be arranged to make a record of time-marks in connection with the curve showing the pull. A chronometer should be provided, having an electric circuit-breaker, by means of which a mark is made on the dynamometer-paper every five (5) secunds. A better apparatus may be used in which a continuous speed-curve is traced upon the paper parallel to the curve of pull. The ordinates of this curve, measured from a base-line, give the speeds desired. The location of mile-posts and other points along the route should be fixed upon the dynamometer- paper by employing an additional pen, and operating 206 ENGINEERING LABORATORY PRACTICE. it by means of electric press-buttons, which are placed at convenient points in the car. As already noted, a similar device should be pro- vided for marking upon the dynamometer-paper the time of taking indicator-diagrams. The rate of travel of the paper per mile should be such that one inch measured upon the diagrams repre- sents ioo feet for short-distance work, and for long- distance work % inch or J inch should be used to represent ioo feet of track. The driving mechanism for the paper should be so arranged that it can be changed to give these proportions. It is necessary to have all the registering-pens located upon the same transverse line at a right angle with the direction of the movement of the paper, in order that simultane- ous data may be recorded. C. Method of Conducting the Road Test, The locomotive having been brought to the train, the steam-pressure being at or near the working- point, the fire being clean and in good condition, though not over 4 to 6 inches thick, the ash-pan being also clean, observations are taken, say five (5) minutes before starting-time, of the thickness and condition of the fire, the height of water in the boiler, the depth in the tank, the levels, the water-meter, and the air- pump counter; and thereafter the regular observations are carried forward, and coal is fired from the weighed sacks. Indicator-diagrams should be taken as frequently as possible, the intervals between them not being over two minutes. Other regular observations should be taken at close STEAM-ENGINE TESTING. 207 intervals. Calorimeter readings, when taken, should be continued for at least five (5) minutes at one- minute intervals. At water stations careful records should be obtained of water heights and levels of boiler and tank. As the end of the route is approached, the fire should be burned down so as to leave the same amount and the same condition as at the start. When the end is finally reached, the fire should be raked, and its condition carefully noted. If it differs from that which obtained at the beginning, an estimated allowance must be made for such difference. At the close of the test the height of water in the boiler should be the same as at the beginning, or if not, the difference, corrected for inclination of the boiler, should be allowed for. During the process of weighing the coal into sacks numerous samples should be obtained, and a final sample cf these selected. This is to be dried and subjected to chemical analysis and calorimeter test. The sample is weighed before and after drying, and data obtained for determining the weight of dry coal used during the test. The duration of the road test is the length of time which the throttle- valve is open. D. The Data and Results. The data and results of the road test may be tabulated in a form corresponding in general with that recommended for the shop test; viz., Table No. 1. 159. Locomotive-testing Plants. — The first plant for testing locomotives * was established at Purdue *A second locomotive-testing plant has been built by the 208 ENGINEERING LABORATORY PRACTICE. University in 1891. The plant was designed by Prof. W. F. M. Goss, and consists, in its elements, of a locomotive, mounted on supporting wheels (see Fron- tispiece) in such a way that it can be run under its own steam at speeds equal to those attained in actual service and under loads commensurate with its capac- ity. The load is supplied by four hydraulic friction- brakes of a type devised by Professor Geo. I. Alden, which are keyed on to the shafts of the supporting wheels and interpose a resistance to their motion. Work is thus furnished the locomotive, not in putting a section of track behind it, but in moving the top of the supporting wheels backward, a condition pre- cisely similar in its effect to the load furnished by a train on the road. The maximum capacity of the four brakes is 800 horse-power. The first effect of the retarding action of the brakes to the motion of the supporting wheels is the ten- dency of the locomotive to move forward with a force proportional to the retarding action. This forward tendency is opposed by the draw-bar which alone holds the locomotive on the supporting wheels and which is attached to an Emery dynamometer of 30,000 pounds capacity, made by Wm. Sellers & Co. (Fig. 27), which serves to measure the draw-bar pull. Thus the load, and consequently the speed, are very readily controlled by varying the amount of water flowing to the brakes. The locomotive is fired with coal in the usual way, and is operated from the cab in a manner precisely similar to that employed on the road. Chicago and Northwestern Railway at their Chicago shops. The general arrangement is similar to that employed in the Purdue plant. STEAM-ENGINE TESTING. 209 The plant as originally built was destroyed by fire on January 23, 1894. It was immediately rebuilt in a new location with many added improvements, among which may be mentioned the provision for test- ing any locomotive built, up to eight wheels coupled. The locomotive originally purchased for use on the plant was sold to the Michigan Central Railway in June, 1897, and a new machine, known as Schenectady No. 2, was purchased in its stead. The following are its principal dimensions: GENERAL DIMENSIONS. Gage 4 '8J".. Fuel Bituminous coal. Weight in working order 107,200 lbs. Weight on drivers 65,700 lbs. Wheel-base, driving 8' 6". Wheel-base, total 23' 6". CYLINDERS. Diameter of cylinders — simple 16"; compound, 16" and 30", Stroke of piston 24". Diameter of piston-rods 2}". Size of steam-ports 18" X if". Size of exhaust-ports 18" X 3". Size of bridges if". VALVES. Kind Allen-Richardson. Maximum travel . 6". Outside lap i|". Inside lap Line and line. WHEELS AND JOURNALS. Diameter of drivers, outside tires.. . . 69". Diameter and length of driving-jour- nal 7i"X8i". BOILER. Style Extended wagon-top. Outside diameter of first ring 52". Working pressure 250 lbs. Thickness of plates f", f", 9/16", and |". Grate-surface . 17 sq. ft. Heating-surface 1322 sq. ft. 2IO ENGINEERING LABORATORY PRACTICE. 160. Method of Testing. — The method of testing employed at Purdue is briefly as follows: The test on the boiler is conducted according to the alternate method prescribed by the A. S. M. E. The duration of the test is, except for very slow speeds, sufficient to give a total run of ioo miles. The water supplied the injectors is measured in carefully-calibrated barrels. The coal is weighed out to the fireman as needed. Two indicator-cards are taken on each cylinder and one on the right steam-chest. The cord- connections are short and the reducing-motion accu- rate. The draw-bar pull is measured by an Emery hydraulic dynamometer. The speed is measured by a revolution-counter and checked by a Boyer speed- recorder. The boiler and dry-pipe pressures are regis- tered by carefully-calibrated gages, the former being checked by a Bristol recording-gage. The draught is measured by draught-gages and checked by a Bristol gage. A Bristol gage is also employed to record the exhaust-pressure. The quality of the steam is deter- mined by a throttling-calorimeter on the dome, made in accordance with the recommendations of the Com- mittee on Locomotive Testing of the A. S. M. E. The temperature of the smoke-box gases is deter- mined by two methods, the first making use of a Le Chatelier pyrometer, and the second employing the copper-ball calorimeter described in Section 56. A special device is employed to measure the amount of cinders thrown out of the stack. Observers. — The plant is manned by a force con- sisting of one supervisor, one fireman, one assistant fireman, two brake-tenders, and observers to the num- ber of ten. The duties of the latter are as follows: STEAM-ENGINE TESTING. 211 a. Log and time. b. Right-head indicator, Boyer recorder, Bristol gages, barometer and temperature of room. c. Right-crank indicator and dry-pipe pressure. d. Left-head indicator and draft. e. Left-crank indicator, steam-pressure, and calo- rimeter. /. Steam-chest indicator, counter, and brake-pres- sures. g. Weight and temperature of feed-water. h. Weight of coal. i. Dynamometer. j. Temperature of waste gases and weight of stack- cinders. The following are the observations taken during the test : Time. Counter. Dynamometer. Brake-pressures. Boiler-pressure. Dry-pipe pressure. Barometer. Pressure in calorimeter. Temperature in calorimeter. Temperature of room. Temperature of waste gases by calorimeter. Temperature of waste gases by pyrometer. Draft, gross. Draft, net. Weight of water delivered to injectors. Overflow loss from injectors. Temperature of feed. 212 ENGINEERING LABORATORY PRACTICE. Height of water in boiler. Minutes injectors were in action. Loss of steam by calorimeter. Position of engine on supporting wheels. Weight of coal fired. Weight of stack-cinders. During the test samples of waste gases and coal are taken for analysis. After the test the weight of cinders in the smoke-box and of the ash is found and a determination of surface-moisture in the coal is made. (See Sec. in.) 161. Method of Working Up Locomotive Tests. — The method of working up herein described includes those items usually found in the report of an engine and boiler test, with the addition of certain others relating only to the locomotive. The data from the tests are preserved in the form of indicator-cards and running logs, accompanied usually by samples of the coal, ash, cinders, and smoke-box gases. Analyses of the samples are made according to the purpose for which the test was run. The results of the analyses are not included in the following calculations. The Running, Water, and Coal Logs should first be averaged and all necessary corrections, such as those due to errors of gages, etc., applied. In averaging the columns carry the average to two places of deci- mals. Then transfer the results to the Summary- sheet. The cards, except those from the steam-chest, should be treated as explained in Section 130. After the factors are determined and marked on the cards, transfer them to the Card Log. Add and average the columns and enter the results in pencil. In averaging STEAM-ENGINE TESTING. 21 3 columns carry the average to two places of decimals, except on the Per-cent Log, where they should be car- ried to three places of decimals. This should be checked. Then transfer to the Summary-sheet. Fill in all items on the several logs before commenc- ing calculation on the Summary-sheet. In calculating volumes at the several events of stroke use the piston-displacements as given in the 4< Commonplace-book " to four places of decimals and express the volumes to four places. In using the steam tables'* carry all interpolations to the number of decimal places given in the table. In calculating weights of steam, carry the result to four places of decimals. In calculating horse-power use the H.P. constant to five places of decimals and carry the result to two places. The calculated results appearing on the Summary- sheet are derived as follows: 1. Indicated horse-pozver is the product of the R.P.M., the indicated horse-power constant, and the M.E.P., the last two being for the cylinder-end in question. The total I. H.P. is the sum of the I. H.P. for the four ends. 2. Weight of steam per revolution at cut-off is the sum of the weights (per stroke) for each end at cut- off. The weight for one end is found by multiplying the weight of a cubic foot of steam at the absolute pressure of cut-off by the product of the piston-dis- placement for that end in cubic feet into the sum of the per cent of cut-off plus the clearance on that end. (See Sec. 133). * See Peabody's " Tables of Saturated Steam." 214 ENGINEERING LABORATORY PRACTICE. 3. Weight of steam per revolution at release is the sum of the weights for each end at release. 4. Weight of steam per revolution at compression is the sum of the weights for each end at compression. 5. Reevaporation per revolution is the difference between the weight of steam per revolution at release (3) and the weight of steam per revolution at cut- off (2). In case the reevaporation is negative, change the item to read " Condensation/ ' 6. Reevaporation per horse-power per hour is the product of the reevaporation per revolution (5) and the average revolutions per hour, divided by the total horse-power. 7. Weight of steam per revolution by tank is the quotient of the total weight of steam used by the engine by the total number of revolutions for the test. 8. Weight of mixture in cylinder per revolution is the sum of the weight of steam per revolution by tank (7) and the weight of steam per revolution at com- pression (4). 9. Per cent of mixture accounted as steam at cut-off is one hundred times the weight of steam per revolu- tion at cut-off (2) divided by the weight of mixture in cylinder per revolution (8). 10. Per cent of mixture accounted as steam at release is one hundred times the weight of steam per revolu- tion at release (3) divided by the weight of mixture in cylinder per revolution (8). 1 1 . Pounds of steam per I. H. P. per hour by indicator is the weight of steam per revolution at release (3) minus the weight of steam per revolution at compres- sion (4) multiplied by the revolutions per hour and divided by the I.H.P. STEAM-ENGINE TESTING. 21 5 12. Pounds of steam per I.H.P. per hour by tank is the weight of steam used by the engine per hour divided by the I.H.P. 13. Distance equivalent to total revolutions is the product of the total number of revolutions by the cir- cumference of the drivers in feet divided by the number of feet per mile. 14. Mites per hour is the total miles (13) divided by the duration of the test in hours. 15. Dynamometer horse-power is found by multiply- ing the tractive horse-power constant (circumference of drivers in feet divided by 33000) by the average dynamometer-reading in pounds and by the R.P.M. 16. Friction of engine in H.P. is the difference between the I.H.P. and the dynamometer H.P. (15). 17. Friction of engine in per cent of I.H.P. is one hundred times the friction H.P. (16) divided by the I.H.P. 18. Dynamometer work in foot-tons per pound of steam by tank is found by dividing the distance run in miles (13) by the total weight of steam by tank and multiplying the result by 5280, giving the distance run in feet on one pound of steam by tank. This distance multiplied by the dynamometer-reading in pounds and divided by 2000, the number of pounds per ton, gives the desired result. 19. Dynamometer ivork ill foot-tons per pound of dry coal is found as above, using total weight of coal in place of steam. 20. Equivalent weight of train in tons is found by dividing the corrected dynamometer-reading in pounds by the number of pounds assumed to be necessary to draw one ton (see Section 185). 2l6 ENGINEERING LABORATORY PRACTICE. 2 I . Equivalent number of loaded cars is the total weight of train (20) divided by 33, the assumed weight in tons of a loaded car. 22. Equivalent ton-miles is the product of the weight of train in tons (20) and the total miles run (13). 23. Pounds of coal per EH. P. per hour is the total pounds of dry coal fired divided by the product of the I.H.P. and the duration of the test in hours. 24. Pounds of standard coal per EH, P. per hour. Standard coal is by definition a coal containing 12,500 B.T.U. per pound. Therefore pounds stand- ard coal is to pounds actual coal (23) as the number of B.T.U. in a pound of actual coal is to 12,500. 25. Pounds of coal per EH. P. per hour per square foot of" grate-surface is found by dividing the pounds of dry coal per I.H.P. per hour (23) by the area of the grate-surface in square feet. 26. Pounds of coal per dynamometer H.P. per hour is the total weight of dry coal per hour divided by the dynamometer H.P. (15). 27. Pounds of coal per mile run is found by dividing the total pounds of dry coal by the total miles run (13)- 28. Pounds of coal per ton-mile is the total pounds of dry coal divided by the product of the number of tons (20) and the total miles run (13) or by item (22). 29. Pounds of water evaporated per hour is found by dividing the total pounds of water delivered to the boiler by the duration of the test in hours. 30. Pounds of water evaporated per pound of dry coal is found by dividing the total pounds of water evaporated by the total pounds of coal fired. 3 1 . Equivalent evaporation from and at 212 F. per STEAM-ENGINE TESTING. 2lJ pound of dry coal is found by multiplying the actual evaporation (30) by the quotient obtained by dividing the B.T.U. per pound of water evaporated (34) by 965.8, which is the number of B.T.U. per pound of water evaporated from and at 212 F. 32. Equivalent evaporation from ioo° E. into steam at jo pounds pressure is found by multiplying the actual evaporation (30) by the quotient obtained by dividing the B.T.U. per pound of water evaporated (34) by 1 1 10.2, which is the B.T.U. per pound of water evaporated under the above conditions. 33. Equivalent evaporation from ioo° F. into steam at Jo pounds, per square foot of heating- surface is item (32) divided by the area of the heating-surface in square feet. 34. B. T. U. per pound of water evaporated, or B.T.U. required to evaporate one pound of water under the conditions of the test, is represented by the expression x x r x + q x — q„ the value of which is found as follows: If the boiler-pressure is p x and the tem- perature of the feed-water is / 2 , then the heat neces- sary to raise a pound of water from temperature /, up to and into steam at pressure/, will be q 19 which is the heat of the liquid at pressure/,, minus q„ which is the heat of the liquid at the temperature / 2 , plus.*", per cent of r lf the heat required to vaporize one pound of water at the pressure/,, where x x is equal to (1 minus the per cent of moisture in steam). (For values of r,, q 19 and q^ see steam tables.) 35. B.T.U. taken up by boiler per minute is the B.T.U. per pound of water (34) times the pounds of water evaporated per minute. 36. B. T. U. taken up by boiler per pound of dry 2l8 ENGINEERING LABORATORY PRACTICE. coal is 60 times the B.T.U. taken up by boiler per minute (35) divided by the pounds of dry coal fired per hour. 37. B.T.U. taken up by boiler per pound of combus- tible is found by multiplying item (36) by the ratio of coal to combustible. 38. B.T.U. per I. H. P. per minute is the B.T.U. taken up by boiler per minute (35) divided by the I.H.P. 39. Pounds of coal per square foot of grate -surface per hour is the pounds of dry coal per hour divided by the area of the grate-surface in square feet. 40. I.H.P. per square foot of grate -surface is the total I.H.P. divided by the grate-surface in square feet. 41. Horse-power of boiler is found by multiplying the B.T.U. per pound of water (34) by the pounds of water evaporated per hour and dividing by (30 X 1 1 10.2), a H. P. being by definition equivalent to the evaporation of 30 pounds of water per hour at 100 F. into steam at 70 pounds pressure. 162. Test of Combined Engine and Boiler. — This test, embodying the elements of tests of large steam- plants, gives the student practice which will fit him to conduct the more elaborate tests. The plant con- sists of a small combined engine and boiler, the former provided with friction-brake and indicator-rig and the latter with calibrated feed-barrels and platform scales for weighing coal. A convenient arrangement of feed- barrels is to provide two barrels, one of which receives the supply through a suitable valve. This barrel is provided with a discharge-valve and an overflow-pipe and is calibrated to the top of the overflow. The STEAM-ENGINE TESTING. 219 second barrel fitted, with a gage-glass, is placed under the first barrel and receives its discharge. This barrel supplies the boiler. Since the plant is small, the method of conducting the test should be the Alternate Method prescribed by the American Society of Mechanical Engineers. Specific Directions. — Two students will be assigned to this test. On the day of the test they will be assigned two assistants, to whom they may detail such observations as they choose. The necessary accessory apparatus is an indicator, speed-counter, thermometers for feed- and room-temperature, and a whistle. In making preparations to start the test the following order of procedure should be observed : 1. Secure the accessory apparatus mentioned above. 2. Prepare blank log. 3. Assign observers according to the schedule given below. 4. Place the indicator in position; fill oil-cups and lubricator, the former with engine-oil, the latter with valve-oil. 5. Determine upon brake load to be carried. 6. Weigh out a box of coal, broken to proper size. 7. Start the test as directed below. The following list of assignments is recommended: 1. Log, time, and misc. observations , in charge. 2. rireman ) 3. Cards, brake load, and weight of coal. 4. Speed and weight of water. The Log should contain the following items: 1. Time. 2. R.P.M. 3. Brake load. 220 ENGINEERING LABORATORY PRACTICE. 4. Boiler-pressure. 5. Barometer. 6. Temperature of feed. 7. Temperature of room. 8. Pounds of water delivered to boiler. 9. Pounds of water lost from boiler (leakage and other loss). 10. Pounds of dry coal fired. Having the apparatus in good working order, indi- cator in place, brake adjusted, oil-cups filled, and steam at the working pressure, start the engine, open- ing the throttle wide after a few minutes' run, and adjust the brake load to the amount previously deter- mined upon. Start the test by taking the time, placing the marker on the w r ater-level in boiler and in lower feed-barrel, and taking all observations except cards. The fireman should begin to fire from weighed coal and should note the depth and general condition of the fire, so that they may be duplicated at the end of the test. He should clean the ash-pan immediately after the start. The feed-measurer should, imme- diately after the start, fill the upper barrel to the point of overflow before beginning to replenish the lower barrel. During the test he should be careful to drain the upper barrel thoroughly before closing the drain- valve. The test should be from two to four hours in dura- tion. Observations should be taken every ten minutes and cards every fifteen minutes, the first to be taken five minutes after the start. Keep all conditions as constant as possible during the test. Watch the lubrication carefully and add a little water to the brake-wheel from time to time to supply that lost by STEAM-ENGINE TESTING. 221 evaporation. The fireman should seek to maintain an even steam-pressure and depth of fire and to keep the injector running continuously if possible. Just before the close of the test see that the con- dition of the fire is the same as at the start and regu- late the injector so that in the remaining minutes the water in the boiler will reach the initial level. Have the level in the lower feed-barrel slightly below the initial level. Stop the test by taking all observations except speed and shutting down the engine. Bring the water-level in the lower feed-barrel back to the starting-point and note the fraction of the contents of the upper barrel which has been used. Start the in- jector and fill the boiler to the third gage-cock. Clean the ash-pan and weigh the ash collected. Rake down the fire left on the grate into the ash-pan. Return all wrenches and oil-cans to their proper places, fill the feed-barrels, and leave the engine, boiler, and surroundings in good order. The Report should cover the following: Constants. Date of test. Name of maker of engine. Diameter of cylinder. Stroke of piston. Diameter of piston-rod. H.E. Engine-constant Radius of brake-arm. Weight of brake-arm. Diameter of boiler. Number of tubes. Diameter of tubes. 222 ENGINEERING LABORATORY PRACTICE. Length of tubes. Distance from grate to lower tube-sheet. Area of grate-surface. Area of heating-surface. Ratio of grate- to heating-surface. Running Log. — In addition to the items given on page 219 under this head the following: Quality of steam (assumed 98 per cent dry). Pounds of water delivered to engine (see note on page 223). Kind of coal. Pounds of ash. Calculated Results. — a. M.E.P. H.E C. E Average b. Indicated horse-power. H.E C.E Total c. Brake horse-power. d. Frictional horse-power. e. Same in per cent of I.H.P. /. Pounds dry steam per I.H.P. hour by tank (Section 161, item 12). g. Pounds of coal per I.H.P. hour (Section 161, item 23). h. Pounds of water evaporated per pound of coal (Section 161, item 30). i. Equivalent evaporation from and at 212 F. (Section 161, item 31). j. Horse-power of boiler (Section 161, item 41). The Report should be accompanied by a sample pair of cards. The directions for working up the cards for M.E.P. and horse-power will be found in Sections 129 and STEAM-ENGINE TESTING. 223 The item pounds of water delivered to engine is the pounds delivered to boiler, as shown by the Running Log, minus the loss by leakage and through the calo- rimeter, if one be used. CHAPTER XIII. TESTING OF HYDRAULIC MACHINERY. 163. Tests of Steam-pumps. — The methods of arranging for and conducting tests of steam-pumps vary with the design of the plant and the data which it is desired to obtain. The method here described applies to a comparatively small plant fitted with a condenser.* Both the steam- and water-cylinders of the pump should be fitted with indicators. If the pump is of the ordinary direct-connected type without fly-wheel, provision should be made to make regular observa- tions of the length of stroke. This may easily be accomplished by fastening a pencil to the cross-head and preparing a board with strips of tough paper of suitable length so that the pencil may draw a line on the paper equal in length to the stroke. Provision must be made for measuring the quantity of water delivered and of regulating and determining the suc- tion- and delivery-heads. The measurement of the water delivered may be accomplished by allowing it to flow over a suitable weir or through an orifice the coefficients of discharge of which are known. Specific Directions. — The number of observers *For directions for conducting elaborate tests see report of committee of A. S. M. E., Trans., vol. xn. p. 530. 224 TESTING OF HYDRAULIC MACHINERY. 225 needed is eight and they should be distributed as follows: 1. Los: and time ) . . ■r^ 1 1 1 r in charge. 2. Discharge-head ) 3. Speed and length of stroke. 4. Quantity of water delivered (hook-gage). 5. Indicators, steam end. 6. Indicators, water end. 7. Weight of condensed steam. 8. Miscellaneous observations. The Log should be made out to include the fol- lowing observations: 1. Time. 2. Speed (double strokes per minute). 3. Length of stroke. 4. Steam-pressure. 5. Barometer. 6. Delivery-head. 7. Suction-head. 8. Temperature of discharge. 9. Temperature of room. 10. Volume of water discharged (hook-gage). 11. Weight of condensed steam. The test should be at least an hour long, with obser- vations every five minutes. The conditions of the test should be maintained for fifteen or twenty minutes before the test commences. Consult the instructor for conditions of head and speed. Observe the usual precautions in starting the test. Maintain all conditions as nearly constant as possible during the test. The Report should include, beside a copy of the Running Log, the following items: 226 ENGINEERING LABORATORY PRACTICE. Kind of pump. Name of maker. Dimensions and constants, a. Duration of test b. Speed (double strokes per minute), average. c. Boiler-pressure, average. d. Delivery-head, average. e. Suction-head, average. f. Total head, average. g. Temperature of delivery, average. h. Cubic feet of water delivered per second. i. Gallons delivered per 24 hours. j. Horse-power delivered as shown by water pumped. k. Indicated horse-power, steam-cylinder. /. Indicated horse-power, water-cylinder. m. Mechanical efficiency, (item / -f- item k) X 100. 11. Ratio of I.H.P. (water end) to delivered H.P., (item 7-7- item /) X 100. 0. Steam per I.H.P. per hour. /. Duty. q. Slip in per cent of total volume swept through. r. Sample cards. The slip is found by deducting the volume of water pumped in a given time from the volume swept through by the pump-plunger in the same time. The duty is the number of foot-pounds of work delivered by the pump per 1,000,000 B.T.U. supplied. Calculate the heat supplied from the amount of steam used by the pump and the heat per pound of steam at boiler-pressure, assuming 2 per cent of moisture. 164. Advanced Work on Steam-pumps. — To de- termine the relation between duty and head with TESTING OF HYDRAULIC MACHINERY. 227 constant steam-pressure, run a series of three tests at constant steam-pressure and throttle-opening and with varying heads. To determine the relation between duty and steam- pressure, run a series of three tests at constant head and throttle-opening and with steam-pressures rang- ing from 80 to 150 pounds. Let the tests be conducted and worked up as speci- fied in the preceding section. The Report should include a statement of the purpose of the tests, a description of the plant, a statement of the constant conditions, a copy of all observed and calculated data, a comparison of results in tabular and graphic form, and conclusions. 165. Tests of Centrifugal Pumps. — The test in- volves the measurement and comparison of the power supplied the pump and that delivered by the pump. The former quantity may be measured by some form of transmission-dynamometer (see Section 70). The delivered power is computed from the quantity of water delivered and the total head against which the pump works. Specific Directions. — Provide a suitable dynamom- eter to measure the power supplied, means for con- trolling and measuring the head, and a weir-tank to measure the quantity of water delivered. The aux- iliary apparatus needed is a whistle, two speed- counters, and a thermometer. Prepare a Running Log with the following headings : 1. Time. 2. Discharge-head. 3. Suction-head. 4. Dynamometer- reading. 228 ENGINEERING LABORATORY PRACTICE. 5. Cubic feet of water delivered (hook-gage). 6. Speed of pump. 7. Speed of dynamometer. 8. Temperature of water. The Log should cover the above observations, to- gether with the discharge-pressure and the position of the discharge-valve, indicated by the number of turns it is open. The test should be from one hour to one hour and a half in duration, with observations every five minutes. The conditions of the test should be main- tained for ten minutes before the test commences. For conditions of head consult the instructor. The Report should include, beside a copy of the Running Log, the following items: a. Duration of test. b. Total head. c. Average speed of pump. d. Position of gate-valve. e. Average temperature of water. f. Cubic feet of water pumped per second. g. Gallons pumped per hour. //. Horse-power delivered by pump. i. Horse-power supplied. j\ Efficiency of pump. In case a line of counter-shafting is interposed between the dynamometer and the pump the pump- belt should be thrown off and a friction test made of the power absorbed by the counter-shafting. This should be subtracted from the horse-power as shown by the dynamometer to find that absorbed by the pump (item i). In calculating the horse-power de- livered by the pump (item k) notice should be taken TESTING OF HYDRAULIC MACHINERY. 229 of the temperature of the water as affecting its specific weight. 166. Advanced Work on Centrifugal Pumps. — To investigate the relation of the efficiency of the pump to the head, run a series of three tests, the first to be under as low a head as can be obtained, the third to be under as high a head as can be obtained, and the second to be under a head midway between the first and third. The tests should be twenty to thirty minutes in duration, the conditions to be maintained for ten minutes before the test begins. The Report should include a statement of the pur- pose of the tests, sketch and description of apparatus, a statement of constant conditions, a copy of all observed and calculated data (as per Section 165), a comparison of results, including a curve showing rela- tion between efficiency and total head, and conclusions as to the head at which maximum efficiency is obtained and the delivery of the pump at that head. 167. Tests of Turbine-wheels . — The method of testing prescribed in this section applies to turbine- wheels belonging to the classification known as re- action turbines, in which the system of piping in which the wheel is located is filled completely from high level to low level with water. The test involves the measurement and comparison of the power sup- plied and that delivered. In Fig. 55 is shown a well-known form of turbine- wheel with housings. Specific Directions. — The power supplied is deter- mined from a consideration of the quantity of water used by the wheel and the head under which it 230 ENGINEERING LABORATORY PRACTICE, operates. Provision should be made in the plant for controlling and measuring the head and a weir-tank Fig. 55. — Leffel Turbine-wheel and Housing. provided to measure the quantity of water used. The delivered power is measured by a suitable Prony brake. The auxiliary apparatus needed is a whistle, a speed counter, and a thermometer. Make out the Running Log to cover the following observations: 1. Time. 2. Head. 3. Speed. 4. Brake load. 5. Hook-gage. TESTING OF HYDRAULIC MACHINERY. 23 1 6. Temperature of water. 7. Gate-opening. The test should be from forty-five minutes to one hour in duration, with observations every five minutes, the conditions of the test to be maintained for ten minutes before the test begins. For conditions of head and load consult the instructor. The Report should include, beside a copy of the Running Log, the following: a. Duration of test. b. Average total head. c. Average speed. d. Cubic feet of water used per second. e. Pounds of water per minute. /. Horse-power supplied. g. Horse-power delivered. h. Mechanical efficiency. t. Velocity of water due to head. j. Velocity of periphery of wheel. Since the turbine receives not only the effect of the pressure-head, measured from the center of the wheel to the level of water in the head-race, but also that of the suction-head, measured from the center of the wheel to the level of water in the tail-race, the total head (item b) is the difference of level between the head-race and the tail-race. In calculating the pounds of water discharged per minute (item e) notice should be taken of the tem- perature of the water as affecting its specific weight. 168. Advanced Work on Turbines.— To investi- gate the relation of head and speed to efficiency, run three series of tests, the first to be at a low head, the third at a high head, and the second intermediate. 232 ENGINEERING LABORATORY PRACTICE. Each series should consist of three tests at different brake loads. Each test should be of from 20 to 30 minutes' dura- tion, conditions to be maintained for 10 minutes pre- vious to each test. The Report should include a statement of the pur- pose of the tests, a sketch and description of the plant, a statement of the constant conditions, a copy of all observed and calculated data (as per Section 167), a comparison of results, including curves showing the relation of efficiency to speed with constant head and to head with constant speed, and conclusions as to conditions of speed and head giving maximum effi- ciency. 169. Tests of Impulse-wheels. The Pelton Wheel. — The Pelton water-wheel consists of a series of buckets of special form, secured to the periphery of a wheel, and receiving the impact of a jet of water. Fig. 56. — Pelton Bucket. The form of the bucket is shown in Fig. 56, from which it is seen that the jet on striking the bucket is divided by the central rib into two portions, each branch being diverted on curves designed to secure TESTING OF HYDRAULIC MACHINERY. 233 the maximum efficiency of the jet. Fig. 57 shows the wheel with housing removed. r -\ ^Ir . <^yp|r •tit:;;' . f : '■'-■■' - si 1 ' --"' <: ' w o o — w o C Ratio of explosions to revolutions. e. Sequence of explosions. f. Ratio of gas to air in the explosive mixture. g. Mean effective pressure. h. Maximum pressure. i. Indicated horse-power. j Brake horse- power. k. Frictional horse-power. /. Cubic feet of gas per I.H.P. per hour. As subjects for advanced study the following 2 3 8 ENGINEERING LABORATORY PRACTICE. changes may be investigated : change of efficiency with load, speed, temperature of jacket, and gas mixture. 172. Tests of Air-compressors. — The extended use of compressed air for the transmission of power and its exclusive use for special purposes, such as the air-brake, gives frequent occasion for the testing of air-compressing plants of various kinds. These tests Throttle Compressor - 1 Air Valve Small Receiver — Orifice Exhaust Cooling Water Condenser Condensed Steam Fig. 58. — Arrangement of Compressor Plant. are usually to determine the volume of air delivered per pound of steam at various pressures of delivery and the pounds of steam consumed per horse-power of work delivered. To give practice in the testing of compressors working under different conditions, this MISCELLANEOUS TESTS. 239 test may be run either as a continuous test, the condi- tions being those under which compressed-air power- plants operate, or as an intermittent test, representing the working conditions of an air-brake pump. The plant consists of the compressor, a surface-condenser which receives the exhaust-steam, a large main receiver into which the air-cylinder discharges, and an auxiliary receiver into which the main receiver leads and which contains an orifice of known diameter for measuring the discharge of air. In Fig. 58 is shown an arrange- ment of piping which has been used in the Purdue laboratory with satisfactory results. Specific Directions : Continuous Test. — This test should be conducted by two men, to whom two assist- ants are assigned. The following is a recommended assignment of observers: 1. Log and time ) . 2. Weight of condensed steam ; ^ 3. Speed. 4. Miscellaneous observations. The Running Log should be drawn up to contain the following items: 1. Time. 2 . Steam-pressure. 3. Main-receiver pressure. 4. Auxiliary-receiver pressure. 5. Barometer. 6. Speed of compressor (double strokes). 7. Temperature in auxiliary receiver. 8. Temperature of room. 9. Weight of condensed steam. In case a speed-recorder is not attached it may be found convenient to keep the record of speed on a 240 ENGINEERING LABORATORY PRACTICE. separate log-sheet, the observer detailed to count the same making a mark for each double stroke. The speed should be counted continuously for five minutes at a time, beginning at intervals ten minutes apart. The accessory apparatus needed for the test is a thermometer and a whistle. The test should be one hour in duration and observations should be taken every five minutes. Conduct the test as follows: Carefully inspect the piping and see that all valves are suitably placed. See that the lubricator is filled and adjusted. Having the Running Log prepared and observers posted, start the compressor and turn cooling water on the condenser, regulating the supply-valve to obtain the amount necessary to prevent the escape of uncondensed steam. See that the weighing-tanks are empty and the dis- charge-valve open. Secure the desired pressure of delivery in the main receiver by manipulation of the valve between the main and the auxiliary receiver and keep it constant during the test. Start the test by noting the time, taking all obser- vations, closing the weighing-tank drain-valve, and noting the water-level as shown by the float or gage- glass on the tank. Keep all conditions constant dur- ing the test. Specific Directions : Intermittent Test, — This test should be conducted by two men with two assistants. The following is a recommended assignment of ob- servers : 1. Log and time ) . 2. Weight of condensed steam ; ^3. Speed. 4. Miscellaneous observations. MISCELLANEOUS TESTS. 24I The Running Log should be drawn up to cover the following items: 1. Time of starting compressor. 2. Time of stopping compressor. 3. Steam-pressure. 4. Main-receiver pressure, maximum. 5. Main-receiver pressure, minimum. 6. Auxiliary-receiver pressure. 7. Barometer. 8. Speed of compressor (double strokes). 9. Temperature of auxiliary receiver, ■io. Temperature of room. 11. Weight of condensed steam. The test should be one hour in duration, and obser- vations should be taken at the time of starting and stopping the compressor, except in the case of items 3, 6, and 9, which should be taken at intervals while the compressor is at work. The speed (item 6) is determined by counting the number of double strokes for the interval during which the^ compressor is run- ning. Conduct the test as follows: Carefully inspect the piping and see that all valves are suitably placed. See that the lubricator is filled and adjusted. Having the Running Log prepared and observers posted, start the compressor and turn cooling water on the condenser, regulating the supply-valve to obtain the amount necessary to prevent the escape of uncon- densed steam. See that the weighing-tank is empty and its discharge-valve open. With the throttle-valve wide open, regulate the auxiliary-receiver pressure to give a main-receiver pressure of five pounds in excess of the maximum pressure determined upon. This 242 ENGINEERING LABORATORY PRACTICE. auxiliary-receiver pressure should be constantly main- tained throughout the test by manipulation of the main-receiver discharge-valve. Now stop the com- pressor and allow the main-receiver pressure to fall. When the pressure has fallen to the predetermined minimum the compressor should be started with wide- open throttle and the test considered as commenced. The method of procedure now is to allow the com- pressor to raise the main-receiver pressure to the pre- determined maximum, then shut down quickly and allow the pressure to fall to the minimum, always keeping the auxiliary-receiver pressure constant. Then start the compressor and repeat the process throughout the test. The test is to be stopped when, after shutting down the compressor, the main-receiver pressure has fallen to the minimum. Report of Compressor Test. — The Report should include the following: a. Weight of air escaping per second, in pounds. G = o.5 3 oF^ when A > 2 A > • ■ • (0 G= i.o6oF^/ P ^ P ' t A) when /,<*>.. ( 2 ) where A is the mean pressure in the small receiver in pounds per square inch absolute, p a the barometric pressure in pounds per square inch, T, the absolute temperature of the air in the small receiver in degrees Fahrenheit, and F the area of the orifice in square inches. Use formula (i) or (2) according as A may be greater or less than 2p a . MISCELLANEOUS TESTS. 243 b. Pounds compressed per minute, P=GX 60 (3) c. Total weight compressed, P y = P X no. of minutes of entire test. . (4) d. Volume of one pound of atmospheric air in cubic feet, 53-227; ,. '•"^ST' (5) where T a is the absolute temperature of the room in degrees Fahrenheit. e. Volume compressed per second, V=V a xG (6) f. Total volume compressed, V 1 — V X no. of seconds of entire test. . (7) g. Work done in compressing one pound of air in foot-pounds, where n = 1.4, and p^ is the mean pressure in the main reservoir in pounds per square inch absolute. h. Horse-power, Wx P H - p - = l^ • • • • (9) H.P. = *** fht . . (,o) 33000 X no. minutes that J compressor was working 244 ENGINEERING LABORATORY PRACTICE. Formula (9) should be used for continuous and formula (10) for intermittent running. i. Steam per H. P. per hour steam per hour in lbs. = - H.P. " " * ' ^ II ' j. Air compressed per pound of steam in pounds .... (12) total steam in lbs. k. Volume of air compressed per pound of steam V total steam in lbs, (13) /. Volume of standard air compressed per pound of steam = I2.3QOQ X ,. ^ 1 ^ — TT~ • • ( l 4) Jy y total steam in lbs. v ^' m. Ratio of volume of air compressed to volume swept by piston = V l -^ (volume swept by pistons < in one stroke X total number of strokes) . . . (15) C X no. of strokes The value of the constant C in formula (15) may be had by reference to the laboratory Commonplace- book. The volume of standard air, that is, air at 32 F. and under atmospheric pressure as given by formula (14), will serve as a basis of comparison between differ- ent tests. The constant 12.3909 is derived from formula (5), making T = 32 -\- 460.7 and/ a = 14.7. MISCELLANEOUS TESTS. 245 173. Advanced Work on Air-compressors. — To determine the efficiency under different pressures of delivery, run a series of four tests under constant steam-pressure. Let the conditions be as follows: 1st. Continuous running with air-pressure as high as pump will deliver. 4th. Continuous running with air-pressure as low as can be had without using more steam than can be readily condensed. 2d and 3d. Continuous running with air-pressure intermediate between that of 1st and 4th tests. All tests should be of 30 minutes' duration, and the conditions should be maintained for ic minutes before beginning the test. They should be conducted and worked up as explained in Section 172. The Report should include a statement of the pur- pose of the test, a sketch and description of the plant, a statement of the constant conditions, a copy of the Running Log, a tabulated summary statement of the calculated results, and a comparison of results, includ- ing curves showing the relation of horse-power, steam per horse-power-hour, cubic feet of air pumped per second and per pound of steam to pressure of delivery. To determine the efficiency under different steam- pressures, run a series of three tests under constant pressure of delivery and with steam-pressures of 60, 120, and 180 pounds. Conduct the tests and make the report as described above. 174. Tests of Injectors. — Description. — The injec- tor is an instrument in common use for delivering feed-water to boilers. It is used very generally on locomotive boilers and to a considerable extent in 246 ENGINEERING LABORATORY PRACTICE. small stationary plants. It is made in two general classes, lifting and non-lifting. In the former class the water-supply is below the level of the injector and work is done in raising the water, in addition to that required to deliver against a pressure. In the latter class the water is delivered to the injector under more or less pressure. The lifting injectors may be further divided into single- and double-tube injectors. In Fig. 59 is shown a sectional view of the Metropolitan double-tube locomotive injector. Pipe-connection is made at A with the steam-supply, at B with the water-supply, and at C with the delivery-pipe. D is the overflow. The tubes E are termed the lifting and combin- ing tubes and their function is to lift the water from the source to the forcing-tubes F, which deliver it against the desired pressure. Fig. 60 is a sectional view of the Sellers self-acting injector of 1887, a single-tube injector. At 19, 23, iga and 29 are, respectively, the connections for the steam-supply, water-supply, delivery, and overflow. The single set of tubes 3-2-1 performs the function both of lifting and forcing. Operation of the Injector. — The method of starting the injectors described above, which applies in a general way to many injectors now on the market, is as follows: Open steam and water-supply valves wide. Pull starting-lever back a short distance until water appears at the overflow and then continue the move- ment steadily as far as the lever will go (Metropoli- tan); or pull the starting-lever back steadily as far as it will go (Sellers). MISCELLANEOUS TESTS. 247 248 ENGINEERING LABORATORY PRACTICE. tO* MISCELLANEOUS TESTS. 249 Regulate the rate of delivery by the water-supply valve. Method of Testing. — The testing-plant consists of two tanks mounted on scales or fitted with calibrated gage-glasses. The injector draws from one and de- livers into the other. In order to begin the test with a flying start, provision is made by which the injector may be started prior to the commencement of the test, drawing from the supply-tank and delivering into a by-pass fitted with a suitable swinging nozzle. The initial level is maintained in the supply-tank by an inlet-pipe controlled by a quick-acting valve whose handle is connected with the swinging nozzle. When the test is begun the supply-valve is closed and at the same time the swinging nozzle turns the delivery from the by-pass into the delivery-tank. Provision is made for producing and measuring the head against which the injector is to work and for measuring the temperatures of supply and de- livery. Specific Directions. — Determine upon the steam- pressure, pressure of delivery, temperature of supply, and rate of delivery under which the test will be made by consultation with the instructor. Prepare the Running Log, making provision for the following list of observations: 1. Time. 2. Steam-pressure. 3. Delivery-pressure. 4. Barometric pressure. 5. Temperature of supply. 6. Temperature of delivery 7. Temperature of room. 250 ENGINEERING LABORATORY PRACTICE. 8. Reading of supply-tank. 9. Reading of delivery-tank. The duration of the test is governed by the capacity of the supply-tank, and will vary with the rate of delivery. Having the discharge-tank empty, the supply-tank full, and the regulating-valve on discharge-pipe wide open, start the injector, allowing the delivery to flow into the by-pass. Open the supply-tank inlet a sufficient amount to maintain a constant water-level in the supply-tank. When the desired conditions are obtained start the test by shutting off the supply- valve, turning the delivery into the delivery-tank and taking all observations. Take observations at regular intervals during the test and keep all conditions con- stant. To close the test, stop the injector. The following is a form of Report to be used in connection with the injector test: TEST OF INJECTOR. Observers \ Date, Make of injector Number and style Size of connections: steam in.; water in.; dis- charge in. Diameter (minimum) of lifting-tube. .. .in. ; forcing-tube. .. .in. a. Duration of test b. Steam-pressure (average), pounds gage, /> t c. Delivery-pressure (average), pounds gage, / 2 d. Delivery-head (average), feet, h x e. Suction-head (average), feet, h- 2 f. Temperature of supply (average), /j g. Temperature of delivery (average), 2" 2 h. Pounds water supplied per hour, W\ MISCELLANEOUS TESTS. 2$ I i. Pounds water delivered per hour, Wi /. Cubic feet of water delivered per hour, c k. Wet steam per hour, zu k /. Dry steam per hour, w 2 m. Water delivered per pound wet steam, pounds n. Water delivered per pound dry steam, pounds o. Velocity of discharge, feet per second, v /. Energy delivered, raising injection-water, B.T.U. per hr q. Energy delivered, heating injection-water, B.T.U. per hr r. Energy delivered, velocity of discharge, B.T.U. per hr s. Total energy delivered, B.T.U. per hour t. Energy supplied, B.T. U. per hour u. Thermal efficiency v. Horse-power w. Dry steam per horse-power per hour, pounds The wet steam per hour, w 1 = W^ — W x . The dry steam per hour, w^ = x 1 w l , where x x is the per cent of dry steam. If this is not measured assume 98 per cent. The water delivered per pound of wet steam = W^ The water delivered per pound of dry steam = W q -f- w 2 . The velocity of discharge, c X 144 v = 3600 X (area discharge end in sq. in.)' The energy of raising injection-water = [WJJi x -\-h^ + wji^ + 77%. The energy of heating injection-water = W x (q 2 — q x ), where q x and q 2 correspond to t x and t % . The energy of discharge = Wj? -f- (2g X 778). The total energy delivered = item / -f- item q -\- item r. 252 ENGINEERING LABORATORY PRACTICE. The energy supplied = w l (x 1 r l -f- q x — q^) y where r, and q x correspond to /, , and q 2 corresponds to / 2 . -T-i i i m • item s lhe thermal efficiency = ioo X • J item / Tll . w x {K + h % ) + w x h x The horse-power == -p . v 6o X 33°oo The dry steam per horse-power per hour = ze/ 9 -f- item v, 175. Advanced Work on Injectors. — As topics for advanced study of injectors the following are sug- gested : 1. Effect of steam-pressure on efficiency and capacity. Run a series of five tests under the following con- ditions: steam-pressures of 60, 80, 100, 150, and 200 pounds; rate of discharge minimum, mean, or maxi- mum ; feed-temperature constant and delivery-pressure equal to steam-pressure. 2. Effect of temperature of feed on efficiency and capacity. Run a series of five tests under the following condi- tions: feed-temperatures of 50, 80, no, 140, and maximum; steam-pressure constant; mean rate of delivery and delivery-pressure equal to steam-pres- sure. 3. Effect of delivery-pressure on efficiency. Run a series of three tests under the following con- ditions: delivery-pressure 75 and 100 per cent of steam-pressure and maximum; mean rate of delivery; steam-pressure and feed-temperature constant. 4. Maximum starting and working temperatures. Make an experimental investigation under different steam-pressures. MISCELLANEOUS TESTS. 253 5. Overflow loss under different steam-pressures. 6. Restarting conditions. These tests (except under heads 4, 5, and 6) should be run and worked up as described in Section 174. The Report should include a statement of the purpose of the tests, a sketch and description of the plant, a statement of the conditions of the tests, a copy of all observed and calculated data, comparisons of results accompanied by curves, and conclusions. 176. Tests of Steam-turbines. The De Laval Turbine. — The De Laval steam-turbine consists of a wheel provided with buckets, against which act jets of steam delivered from suitable nozzles. The wheel is ELEVATION I Turl n Turbine Wheel •' ',' }j 2 • PLAN Fig. 61. — De Laval Steam-turbine. Arrangement of Wheel and Nozzle. mounted upon a shaft carrying a small pinion which meshes with a large gear on the driving-shaft, thus 254 ENGINEERING LABORATORY PRACTICE. reducing the speed at which the power is delivered. The speed is regulated by a throttling-governor. In Fig. 6 1 is shown the arrangement of nozzle and wheel, and in Fig. 62 are shown dimensioned drawings of the moving parts of a 10-horse-power turbine. The form of the nozzle is such that the steam in passing through is expanded to atmospheric pressure, while its velocity is correspondingly increased. The energy in the steam is thereby converted into the form most available for impact on the wheel. In the 10-horse-power turbine there are four nozzles, two of which are provided with stop-valves. Nozzles of different sizes are provided for use with different steam-pressures, as follows: No. 1. No. 2. No. 3. No. 4. For 100 lbs. (7 kgm.)) 5 x7.1mm. 5X7-10101. R] . . use nozzles marked f (with stopper). (with stopper). 5 x 7 ' x mm ' oiina. I3 olbs.( 9 . 2 kgm.)[ (^sto^er). (with re^spindle). 4 X 6.3 mm. 4 X 6.3 mm. x 4 olbs.( 9 .8kgm.)[ (w ^ h 6 st ; m p m r , (1 &&5£> 4X6.3 mm. 4 X 6.3 mm. x8olbs.( I2 .7k g m.)f ^£5^ ik&S*. 3.7X6mm. Blind. When using the regulating-spindle with 130 pounds pressure observe the following directions: On the spindle nearest the wheel is the mark 09^; here the hand must point when the nozzle is used with 130 pounds pressure. To shut off the nozzle entirely, the hand should point to mark 5. On the socket of the nozzle and also on the box of the turbine is the mark 1, showing where the socket and nozzle should be placed. In fitting the turbine for testing it should be provided with a suitable brake, and should be in pipe-connection with a surface-condenser. MISCELLANEOUS TESTS. 255 ,1* ft^h w Section 1 5 lip if w H C/) ■J w Q fa o C/2 ►J s w Q O t-H 256 ENGINEERING LABORATORY PRACTICE. Specific Directions. — Run three tests at constant steam-pressure and different brake loads to determine the variation in economy. The auxiliary apparatus needed includes a speed-counter and a whistle. The tests should be of 30 minutes' duration, with observations at five-minute intervals, the turbine to run at least 20 minutes before the first test is com- menced, and to run under load conditions of the test for five minutes before taking observations. The observations are as follows: 1. Initial steam-pressure. 2. Pressure below governor- valve. 3. Exhaust-pressure. 4. Barometer. 5. Brake load, net. 6. Speed. 7. Weight of condensed steam. After determining the desired brake loads under which the tests are to run calculate from known dimensions of the brake the weight which must be carried on the scale to secure the required power. The Report should fully state conditions of test, giving number and size of nozzles used, and shou'd include a brief statement of arrangement of plant, a tabulated Running Log, and the following calculated results: a. Brake H.P. b. Weight of steam per H.P. per hour. As subjects for advanced study, investigate the change of efficiency with change of steam-pressure and the effect of varying the number of nozzles in use. APPENDIX. 177. Circumferences and Areas of Circles. 1 TO 400 ADVANCING BY 10THS FROM 1 TO 50. (Abridged from Carpenter's "Experimental Engineering.") Diam. Circum. Area. Diam. Circum. 20.106 Area. Diam. Circum. 37-071 Area. 1.0 3.142 .7854 6.4 32.170 11. 8 109.36 1.1 3-456 •9503 6.5 20.420 33-183 11. 9 37-385 in. 22 1.2 3-77Q 1.1310 6.6 20.735 34.212 12.0 37-699 113. 10 *-3 4.804 1.3273 6.7 21 .049 35-257 12. 1 38.013 114.99 1.4 4.398 1-5394 6.8 21.363 36.317 12.2 38.327 116.90 i-5 4.712 1.7672 6.9 21.677 37-393 12.3 38.642 118.82 1.6 5.027 2.0106 70 21.991 38.485 12.4 38.956 120.76 1.7 5.241 2.2698 7- 1 22 . 305 39-592 12.5 39.270 122.72 1.8 5-655 2-5447 7-2 22.619 40.715 12.6 39.584 124.69 1.9 5-969 2-8353 7-3 22.934 41.854 12.7 39.898 126.68 2.0 6.283 3.1416 7-4 23.248 43.008 12.8 40.212 128.68 2.1 6-597 3-4636 7-5 23.562 44-179 12.9 40.527 130.70 2.2 6.912 38013 7-6 23.876 45-365 i3.o 40.841 132.73 2-3 7.226 4.1548 7-7 24.190 46.566 13. 1 41-155 T34.78 2.4 7-54o 4.5239 7 .8 24 • 504 47-7 8 4 13.2 41.469 136.85 2.5 7.854 4.9087 l' 9 24.819 49.oi7 13-3 41-783 138.93 2.6 8.168 5.3093 8.0 25.133 50.266 13-4 42.097 141.03 2.7 8.482 5.7250 8.1 25.447 5T.530 i3-5 42.412 i43- T 4 2.8 8.797 6.1575 8.2 25.761 52.810 13.6 42.726 145-27 2.9 9. in 6 . 6052 8.3 26.075 54.106 13-7 43.040 147.41 3.0 9-425 7.0686 8.4 26.389 55.4i8 13.8 43-354 149-57 3-i 9-739 7-5477 8.5 26 . 704 56.745 13-9 43.668 I5I-75 3-2 10.053 8.0425 8.6 27.018 58.088 14.O 43.982 153-94 3-3 10.367 8.553o 8-7 27-332 59-447 14. 1 44.296 156.15 3-4 to. 681 0.0792 8.8 27.646 60.821 14.2 44.611 158.37 3-5 10.996 9. 62 1 1 8.9 27.960 62.211 14-3 44-9*5 160.61 3-6 11. 310 10.179 9.0 28.274 63.617 14.4 45.239 162.86 3-7 11 .624 10.752 9.1 28.588 65-039 14.5 45-553 165.13 3.8 xi. 938 11. 341 9.2 28.903 66.476 14.6 45.867 167.42 3-9 12.252 11.946 9-3 29.217 67.929 14.7 46.181 169.72 4.0 12.566 12.566 9.4 29-53 1 69.398 14.8 46.496 172.03 4.1 12.881 13.203 9-5 29.845 70.882 14.9 46.810 174-37 4.2 ^•IQS 13.854 9.6 30.159 72.382 15 O 47.124 176.72 4-3 x 3-509 14.522 9-7 30.473 73.898 i5-i 47.438 179.08 4.4 13.823 *S-SOS 9.8 30.788 75-43° 15 2 47-752 181.46 4-5 H-I37 15.904 9-9 31 . 102 76.977 15-3 48.066 183.85 4.6 M-45 1 16.619 10. 31.416 78 • 540 15.4 48.381 186.27 ♦ •7 H.765 17.349 10. 1 3 » • 73o 80.119 15-5 48.695 188.69 4.8 15.080 18.096 10.2 32.044 81.713 15.6 49 . 009 191.13 4-9 1 5-394 18.857 10.3 32.358 83.323 15-7 49.323 193-59 50 15.708 19.635 10.4 32.673 84-949 15.8 49-637 196.07 5.i 16.022 20.428 10.5 32.987 86 . 590 15.9 49-951 198.56 5-2 16.336 21.237 10.6 33-3QI 88.247 16.O 50.265 201 .06 5-3 16.650 22.062 10.7 33-6i5 89.920 16. 1 50.580 203.58 5-4 16.965 22.902 10.8 33.929 91 .609 16.2 50.894 206. 12 5-5 17.279 23-758 10.9 34-243 93-3*3 16.3 51.208 208 . 67 5.6 J 7.593 24.630 II. 34.558 95-033 16.4 51.522 211.24 5-7 17.90? 25.518 II . I 34.872 96.769 16.5 51.836 213.83 5.8 18.: - 26.421 IT. 2 35.T86 98.520 16.6 52.150 216.42 5-9 18.535 27.340 "•3 35-500 100.29 16.7 52.465 219.04 6.0 18.850 28.274 11,4 35.8i4 102.07 16.8 52.779 221.67 6.1 19.164 29.225 "•5 36.128 103.87 16.9 53-093 224.32 6.2 19.478 30.191 11. 6 36.442 105.68 17.O 53.407 226.98 6.3 19.792 31-173 11. 7 36.757 107.51 17. 1 53-721 229.66 257 258 ENGINEERING LABORATORY PRACTICE. CIRCUMFERENCES AND AREAS OF CIRCLES Diam. Circum. | 17.2 54-035 17-3 54.350 17.4 54.664 17 5 54-978 17.6 55-292 17.7 55.606 17.8 55-92Q 17.9 56 235 18.O 56.549 18. 1 56.863 18.2 57.177 18.3 57-491 18.4 57-805 18.5 58.119 18.6 58.434 18.7 58 748 18.8 59.062 18.9 59.376 19.0 59.690 19. 1 60 . 004 19.2 60.319 19-3 60.633 1 19.4 60.947 | 19-5 61.261 1 19.6 6i.575 19.7 61.889 19.8 62.204 19.9 62.^18 20.O 62.832 20. 1 63.146 20.2 63.460 20.3 63-774 20.4 64.088 20.5 64.403 20.6 64.717 20.7 65-031 20.8 65-345 20.9 65-659 21.0 65.973 21 .1 66.288 21.2 66 . 602 21.3 66.916 21.4 67.230 21.5 67-544 21.6 67.858 21.7 68.173 21.8 68.487 21.9 68.801 22.0 69.115 22.1 69.429 22.2 69-743 22.3 70.058 1 22.4 70.372 ! 22.5 70.686 22.6 71 .000 22.7 7I-3I4 22.8 71.268 22.9 71.942 23.0 72.257 23.I 72.571 1 232.35 235.06 237-79 240.53 243.29 246.06 248.85 251-65 254-47 257.30 260.16 263.02 265.90 268.80 271 .72 274-65 277-59 280.55 283.53 286.52 289.53 292-55 295-59 298.65 301 .72 304.81 307.91 3 IX -o3 314.16 3*7- 3 1 320.47 323.66 326.85 330.06 333-29 336.54 339.8o 343-07 346.36 349.67 352.99 356.33 359-68 363-05 366.44 369.84 373-25 376.69 380. 13 383.60 387-08 39o.57 394.08 397-6i 401.15 404.71 408 . 28 411.87 415.48 419.10 Diam. 23.2 23-3 23-4 23-5 23.6 23-7 23.8 23.9 24.O 24.1 24.2 24-3 24.4 24-5 24.6 24.7 24.8 24.9 25.O 25.1 25.2 25-3 25.4 25-5 25.6 25-7 25.8 25-9 26.O 26.1 26.2 26.3 26.4 26.5 26.6 26.7 26.8 26.9 27.O 27.1 27.2 27-3 27.4 27-5 27.6 27.7 27.8 27.9 28.O 28. T 28.2 28.3 28.4 28.5 28.6 28.7 28.8 28.9 29 o 29.1 Circum. 72.885 73-199 73-5I3 73.827 74.142 74-456 74.770 75.084 75 398 75-712 76.027 76.341 76.655 76.969 77-283 77-597 77-9" 78.226 78 . 540 78.854 79.168 79.482 79.796 80. in 80.425 80.739 81.053 81.367 81.681 81.996 82.310 82.624 82.938 83.252 83.566 83.881 84.195 84.509 84.823 85.137 85.451 85.765 86.080 86.394 86.708 87.022 87.336 87.650 87.965 88.279 88-593 88.907 89.221 89-535 89.850 90 . 1 64 90.478 90.792 91.106 91.420 Area. 422.73 426.39 430.05 433 • 74 437-44 44i-i5 444-88 448.63 452 .39 456.17 459.96 463.77 467.60 47^-44 475-29 479.16 483-05 486.96 490.87 494.81 498.76 502 . 73 506.71 510.71 5H-72 518.75 522.79 526.85 530.93 535 .02 539-13 543-25 547.39 55L55 555.72 559-90 564.10 568.32 572.56 576.80 581.07 585.35 589.65 593.96 598.29 602 . 63 606.99 611.36 6i5-75 620.16 624.58 629.02 633-47 637.94 642.42 646.93 651.44 655-97 660.52 665.08 Diam. Circum. 29.2 91-735 29-3 92.049 29.4 92.363 29.5 92.677 29.6 92.991 29.7 93 • 305 29.8 93.619 29.9 93-934 300 94-248 30.1 94.562 30.2 94.876 30.3 95.190 30.4 95-505 30.5 95.819 30.6 96.133 30.7 96.447 30.8 96.761 30.9 97.075 3io 97-389 31-1 97.704 31.2 98.018 3i.3 98.332 3*-4 98.646 3'-5 98.960 31.6 99.274 3i-7 99.588 31-8 99.903 31.9 100.22 32-0 100.53 32.1 100.85 32.2 101.16 32.3 101.47 32 4 101.79 32.5 102.10 32.6 102.42 32.7 102.73 32.8 103.04 ^2.9 103.36 33 -o 103.67 33-1 103.99 33-2 10^.30 33-3 104 . 62 33-4 104.93 33-5 105 . 24 33-6 105.56 33-7 105.87 33-8 106. 19 33 9 106.50 34 106.81 34-1 107.13 34-2 107.44 34-3 107.76 34-4 108.07 34-5 108.38 34-6 108.70 34-7 109.01 34-8 x °9-33 34-9 109.64 35 109.96 35-i 110.27 Aiea. 669.66 674.26 678.87 683.49 688.13 692.70 697-47 702.15 706.86 711.58 716.32 721.07 725.83 730.62 735-42 740.23 745.o6 749-91 754-77 759-65 764.54 769.45 774-37 779.31 784.27 789.24 794-23 799.23 8°4 • 25 809.28 8i4-33 819.40 824.48 829.58 834.69 839.82 844.96 850.12 855-30 860 . 49 865 . 70 870.92 876.16 881.41 886.68 891.97 897.27 9°2 • 59 907.92 913.27 918.63 924.01 929.41 934-82 940.25 945.69 951.15 956.62 962. 11 967.62 APPENDIX. 259 CIRCUMFERENCES AND AREAS OF CIRCLES. Diam. Circum. 110.58 Area. Diam. Circum. 129 43 Area. Diam. Circum. Area. 35-2 973-14 41.2 T 333-i7 47-2 148.28 1749.74 35-3 110.90 978.68 4*. 3 129-75 1339.65 47-3 148.60 1757-16 35-4 in. 21 984.23 4T.4 130.06 1346.14 47-4 148.91 1764.60 35-5 in. 53 989.80 4i-5 130.38 1352.65 47.5 149-23 1772.05 35-6 in. 84 995-38 41.6 130.69 i359-i8 47 6 149-54 1779.52 35-7 112. 15 1000.98 41.7 1 3 1 . 00 1365.72 47-7 M9 85 1787.01 35.8 112.47 1006.60 41.8 131.32 1372.28 47.8 150.17 i794-5i 35-9 112.78 1012.23 41.9 13^63 1378.85 47-9 150.48 1802.03 360 113. 10 1017.88 42. 131.95 1385-44 48.O 150.80 1809.56 36.1 "3-4 x 1023.54 42.1 132.26 1392.05 48.1 151-11 1817.11 36.2 "3-73 1029.22 42 .2 ^2^58 1398.67 48.2 151.42 1824.67 36.3 114.04 1034.91 42.3 132.89 1405.31 48.3 I5I-74 1832.25 364 "4-35 1040.62 133.20 141 1 .96 48.4 152.05 1839.84 36.5 114.67 1046.35 , 42-5 J 33-52 1418.63 48.5 1 5-2 -37 1847.45 36.6 T14.98 1052.09 42.6 133.83 1425.31 48.6 152.68 1855.08 3 6 «7 II5-30 1057.84 | 42.7 x 34-i5 1432.01 48.7 153-00 1862.72 36.8 115. 61 1063.62 j 42.8 134.46 1438.72 48.8 153-3 1 1870.38 3 6 -9 115.92 1069.41 1 42.9 134-77 M45-45 48.9 153.62 1878.05 37 116.24 1075.21 43 135-09- 1452.20 49.O 153-94 1885.74 37-i 116.55 108 1 .03 43-1 i35.4o 1458.96 49.1 154.25 1893.45 37 2 116.87 1086.87 43-2 x 35-72 I465-74 49-2 154.57 1901 .17 37-3 117. 18 1092.72 43-3 136.03 1472.54 49-3 154-88 1908.90 37-4 117.50 1098.58 43-4 136.35 1479-34 49-4 155-I9 1916.65 37-5 117. 81 1104.47 43-5 136.66 1486.17 49-5 155.51 1924.42 37-6 118. 12 1110.36 43 6 136.97 1493.01 49 6 155-82 1932.21 37-7 118.44 1116.28 43-7 T 37>29 1499.87 49-7 156.14 1940.00 37.8 118.75 1122.21 43-8 137.60 1506 74 49 8 156.45 1947.82 37-9 119.07 1128.15 j 43.9 137.92 1513-63 49-9 156.77 1955.65 380 119.38 1134.11 , 44 138.23 1520.53 50.0 157.08 1963.50 38.1 119.69 1140.09 44.1 138.54 I527.45 51 160.22 2042 . 82 38.2 120.01 1146.08 44.2 138.86 1534-39 52 163.36 2123.72 38.3 120.32 1152.09 44-3 J 39'i7 1541.34 53 166.50 2206.19 38.4 120.64 1158.12 44.4 139-49 1548.30 54 169.64 2290.22 38.5 120.95 1164.16 44-5 139.80 I555-28 55 172.79 2375.83 38.6 121.27 1 1 70. 21 44.6 140.12 1562.28 56 175-93 2463.01 38.7 121.58 1176.28 44-7 140.43 1569.30 57 179.07 2551-76 38.8 121.89 1182.37 44-8 140.74 1576.33 58 182.21 2642.08 38 9 122.21 1188.47 44.9 141.06 I583.37 59 185-35 2733.97 39 122.52 1*94-59 45.0 Mi- 37 i59o.43 60 188.50 2827.44 39-i 122.84 1200.72 45-i 141.69 I597-5I 61 191.64 2922.47 39-2 123.15 1206.87 45-2 142.00 1 604 . 60 62 194.78 3019.07 39-3 123.46 1213.04 45-3 142.31 1611.71 63 197.92 3117.25 39-4 123.78 1219.22 45-4 142.63 1618.83 64 201.06 3216.99 39-5 124.09 1225.42 45-5 142.94 1625.97 65 204 . 20 3318.31 39<6 124.41 1231.63 45-6 143.26 1633.13 66 207.34 3421.19 39-7 124.72 1237.86 45-7 x 43-57 1640.30 67 210.49 3525.65 39-8 125.04 1244.10 45-8 143 88 1647.48 68 213.63 3631-68 39-9 125.35 1250.36 45-9 144.20 1654.68 69 216.77 3739-28 40 O 125.66 1256.64 46 O I 44-5i 1661 .90 70 219.91 3848.45 40. 1 125.98 1262.93 46.1 144.83 1669.14 71 223.05 3959.19 40.2 126.29 1269.23 j 46.2 145.14 1676.39 72 226.19 4071.50 4o-3 126.61 1275.56 j 46.3 145.46 1683.65 73 229.34 4185-39 40.4 126.92 1281.90 46.4 M5-77 1690.93 74 232.48 4300.84 40-5 127.23 1288.25 46.5 146.08 1698.23 75 235.62 4417.86 40.6 127.55 1294.62 46.6 146 40 170504 76 238.76 4536.46 40.7 127.86 1301.00 46.7 146.71 1712.87 77 241.90 4656.63 40.8 128.18 1307-41 46.8 M7.03 1720.21 78 245.04 4778.36 40.9 128.49 1313.82 46.9 M7-34 1727.57 79 248.19 490 t .67 41.-O 128.81 1320.25 47 M7-65 1 734 -94 80 251.33 5026.55 41. 1 129.12 1326.70 47.1 M7-97 1742.34 81 | 254.47 5153-00 260 ENGINEERING LABORATORY PRACTICE. CIRCUMFERENCES AND AREAS OF CIRCLES. Diam. 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 IOO 101 102 103 104 105 106 107 108 109 no in 112 "3 114 "5 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 *34 135 136 137 138 139 140 141 Circum 257.61 260.75 263.89 267.04 270.18 273-3 2 276.46 279.60 282.74 285.88 289.03 292.17 295 -3 1 298.45 301.59 304.73 307.88 311.02 314.16 317.30 320.44 323-58 326.73 329.87 333-OI 336.15 339.29 342.43 345.58 348.72 351.86 355- 00 358.14 361.28 364.42 367.57 370. 7 1 373-85 376.99 380.13 383-27 386.42 389.56 392.70 395.84 398.98 402.12 405.27 408.41 4H-55 414.69 417-83 420.97 424.12 427.26 430.40 433-54 436.68 439.82 442.96 Area. Diam. 5281.02 142 5410.61 J 43 554*-77 144 5674-50 M5 5808.80 146 5944.68 147 6082.12 148 6221. 14 149 6361.73 150 6503.88 *5 l 6647.61 152 6792.91 153 6939.78 154 7088.22 155 7238.23 156 7389.81 157 7542.96 158 7697.69 159 7853.98 160 8011.85 161 8171.28 162 8332.29 163 8494.87 164 8659.01 165 8824.73 166 8992.02 167 9160.88 168 933 I -3 2 169 9503.32 170 9676.89 171 9852.03 172 10028.75 173 10207.03 J 74 T0386.89 J75 10568.32 176 10751.32 177 10935.88 178 11 122.02 179 1 1309- 73 180 11499.01 181 11689.87 182 11882.29 183 12076.28 184 12271.85 185 12468.98 186 12667.69 187 12867.96 188 1 3069. 8 1 189 13273.23 190 13478.22 191 13684.78 192 13892. 91 193 14102.61 194 14313.88 195 14526.72 196 14741.14 197 14957.12 198 15174.68 190 T 5393-8o 200 15614.50 201 Circum 446.11 449.25 452-39 455-53 458.67 461.81 464.96 468.10 471.24 474-38 477.52 480.66 483.81 486.95 490.09 493-23 496.37 499-51 502.65 505.80 508.94 512.08 515-22 518.36 521.50 524-65 52779 530.93 534.07 537-21 540.35 543.5o 546.64 549.78 552.92 556.06 559- 20 562.35 56S-49 568.63 571-77 574-91 578.05 581.19 584.34 587.48 590.62 593.76 596.90 600 . 04 603.19 606.33 609.47 612.61 6i5.75 618.89 622.04 625.18 628.32 631.46 Area. Diam. 15836.77 202 16060.61 203 16286.02 204 16513.00 205 16741.55 206 16971.67 207 17203.36 208 17436.62 209 17671 .46 210 17907.86 211 18145.84 212 18385.39 213 18626.50 214 18869.19 215 i9"3-45 216 19359.28 217 19606.68 218 19855.65 219 20106.19 220 20358. 31 221 20611.99 222 20867.24 223 21124.07 224 21382.46 225 21642.43 226 21903.97 227 22167.08 228 22431.76 229 22698.01 230 22965.83 231 23235.22 232 23506.18 233 23778.71 234 24052.82 235 24328.49 236 24605 . 74 237 24884.56 238 25164.94 239 25446.90 240 25730.43 241 26015.53 242 26302.20 243 26590.44 244 26880.25 245 27171.63 246 27464.59 247 27759.11 248 28055.21 249 28352.87 250 28652.11 25 1 28952.92 252 29255-30 253 29559.25 254 29864.77 255 30171.86 256 30480.52 257 30790.75 258 31102.55 259 3i4i5.93 260 3'73o.87 261 Circum. 634.60 637-74 64c. 88 644.03 647.17 650.31 653-45 656.59 659-73 662.88 666.02 669.16 672.30 675-44 678.58 681.73 684.87 688.01 691.15 694.29 697.43 700.58 703 . 72 706.86 710.00 7I3.H 716.28 719.42 722.57 725 -7 1 728.85 731.99 735.13 738.27 741.42 744-56 747.70 750.84 753-98 757-12 760.27 763-4* 766.55 769.69 772.83 775-97 779-n 782.26 785.40 788.54 791.68 794.82 797.96 801. 1 1 804.25 807.39 810.53 813.67 816.81 819.96 Area. 32047.39 32365.47 32685.13 33006.36 33329-16 33653-53 33979-47 34306.98 34636.06 34966.71 35298.94 35632.73 35968.09 36305.03 36643-54 36983.61 37325-26 37668.48 38013.27 38359.63 38707.56 39057.07 39408.14 39760.78 40115.00 40470.78 40828.14 41187.07 4 x 547-56 41909.63 42273.27 42638.48 43005.26 43373-6i 43743-54 44115.03 44488.09 44862.73 45238.93 45616.71 45996.06 46376.98 46759.47 47H3-52 47529.16 47916.36 48305.13. 48695.47 49087.39 49480.87 49875.92 50272.55 50670.75 51070.52 5r47 T -85 51874.76 52279.24 52685.29 53092.92 53502.11 APPENDIX. 26l CIRCUMFERENCES AND AREAS OF CIRCLES. Diam. Circum. Area. Diam. 309 Circum. 97o-75 Area. Diam. Circum. 1115.27 Area. 262 823.10 53912.87 74990 . 60 355 98979.80 263 826.24 54325.21 3io 973-89 75476.76 356 1118.41 99538.22 264 829.38 54739.11 3" 977.04 75964.50 357 "21.55 100098.21 265 832.52 55 I 54-59 312 980.18 76453.80 358 1124.69 100659.77 266 835.66 5557i-6i 313 983-32 76944.67 359 1127.83 101222.90 267 838.81 55990.25 3*4 986.46 77437-12 360 1130.97 101787.60 268 841.95 56410.44 3*5 989.60 77931.13 361 1134.11 102353.87 269 845.09 56832.20 316 992.74 78426.72 362 1137.26 102921.72 270 848.23 57 2 55-53 3i7 995-88 78923.88 363 1140.40 103491-13 271 851-37 57680.43 318 999.03 79422.60 364 "43-54 104062.12 272 854.51 58106.90 3i9 1002.17 79922.90 365 t 146. 68 1C4634.67 273 857-65 58534-94 320 1005.31 80424.77 366 1149.82 105208.80 274 860.80 58964-55 321 1008.45 80928.21 367 1152.96 105784.49 275 863.94 59395-74 322 1011 .59 81433.22 368 1156.11 106361.76 276 867.08 59828.49 323 1014.73 81939.80 36Q "59-25 106940.60 277 870.22 60262.82 324 1017.88 82447.96 370 1162.39 107521 .01 278 873-36 60698.71 325 1021.02 82957.68 37i "65.53 108102.99 279 876.50 61136.18 326 1024.16 83468.98 372 1168.67 108686.54 280 879.65 61575.22 327 1027.30 83981.84 373 1171.81 109271.66 281 882.79 62015.82 328 1030.44 84496.28 374 1174.96 109858.35 282 88593 62458.00 329 1033.58 85012.28 375 1178.10 110446.62 283 889.07 62901.75 330 1036.73 85529.86 376 1181.24 111036.45 284 892.21 63347.07 33 1 1039.87 86049.01 377 1184.38 1 1 1627. 86 285 895-35 63793.97 332 1043.01 86569.73 378 1187.52 112220.83 286 898.50 64242.43 333 1046.15 87092.02 379 1190.66 112815.38 287 901 . 64 64692.46 334 1049.29 87615.88 380 1193.81 113411.49 288 904.78 65144.07 335 1052.43 88141.31 381 1196.95 1 14009. 18 289 907.92 65597.24 336 1055.58 88668.31 382 1200.09 114608.44 290 911.06 66051.99 337 1058.72 89196.88 383 1203.23 115209.27 291 914.20 66508 . 30 338 1061.86 89727.03 384 1206.37 115811.67 292 9I7-35 66966.19 339 1065.00 90258.74 385 1209.51 116415.64 293 920.49 67425.65 340 1068.14 90792.03 386 1212.65 117021 .18 294 923.63 67886.68 34i 1071.28 91326.88 387 1215 .80 117628.30 295 926.77 68349.28 342 1074.42 91863.31 388 1218.94 118236.98 296 929.91 68813.45 343 1077.57 92401.31 389 1222.08 118847.24 297 933 05 69279.19 344 1080.71 92940.88 390 1225.22 119459.06 298 936.19 69746.50 345 1083.85 93482.02 39i 1228.36 120072.46 299 939-34 70215.38 346 1086.99 94024.73 392 1231.50 120687.42 300 942.48 70685.83 347 1090.13 94569.01 393 1234-65 121303.96 301 945.62 71157.86 348 1093.27 95114.86 394 1237.79 121922.07 302 948.76 71631.45 349 1096.42 95662.28 395 1240.93 122541.75 303 951.90 72106.62 350 1099 . 56 96211 .28 396 1244.07 123163.00 304 955-04 72583 36 35* 1102.70 96761.84 397 1247.21 123785.82 305 958. 19 73061 .66 35 2 1105.84 973*3-97 398 1250.35 124410.21 306 961.33 7354L54 353 1108.98 97867.68 399 1253.50 125036.17 3°7 964.47 74022.99 354 III2.I2 98422.96 400 1256 .64 125663.71 308 967.61 74506.01 1 262 ENGINEERING LABORATORY PRACTICE. 178. Decimal Equivalents. 8ths and i6ths. 32ds. 6 4 ths. I Decimals. 8ths and i6ths. 32ds. 64ths. Decimals. I 015625 9/16 18 36 .5625 I 2 03125 37 .578125 3 046875 19 38 •59375 I/I6 2 4 0625 39 609375 5 078125 5/8 20 40 .625 3 6 09375 41 .640625 7 109375 21 42 .65625 1/8 4 8 125 43 .671875 9 140625 11/16 22 44 .6875 5 10 15625 45 .703125 11 I7I875 23 46 .71875 3/16 6 12 1875 47 •734375 13 203125 3/4 24 48 • 75 7 14 21875 49 .765625 15 234375 25 50 .78125 i/4 8 16 25 5i .796875 17 265625 13/16 26 52 .8125 9 18 28125 53 .828125 19 296875 27 54 .84375 5/i6 10 20 3125 55 .859375 21 328125 7/8 28 56 .875 11 22 34375 57 .890625 23 359375 29 58 .90625 3/8 12 24 375 59 .92 875 25 390625 15/16 30 60 •9375 13 26 40625 61 •953125 27 421875 31 62 .96875 7/16 14 28 4375 63 .984375 29 453125 1 32 64 1. 00 15 30 3i 46875 484375 1/2 16 17 32 33 34 35 5 515625 53125 .546875 APPENDIX. 263 179. Weights of Various Materials. Material. Cast iron Wrought iron . Soft steel Hard steel Brass Lead Copper — cast. . Copper — sheet. Mercury Zinc Tin Timber Stone Brick Mortar Water Approx Sp. Gravity, •4 2.2 1.6 7-1 7-7 7.9 7.7 8.4' 14 8-7 8.9 3.6 7-1 7 3 to .8 to 2 8 to 2.1 1-5 1 Pounds per Cubic Inch. .2607 .281 .285 .278 .304 .410 .315 .322 .490 •253 .263 .0144 to .0289 .079 to .101 0578 to .0752 .0544 .036 Pounds per Cubic Foot. 450 486 493 480 525 709 543 555 847 437 458 25 to 50 137 to 175 100 to 130 94 62.4 Cubic Feet per Ton (2000). 4.44 4.II 4.06 4 17 3.81 2.82 3.68 3.60 2.36 4.58 4-37 80 to 40 14.6 to 11 4 20 to 15.4 21.3 32.0 264 ENGINEERING LABORATORY PRACTICE. 180. Weight of Water. Tempera- Weight per Tempera- Weight per Tempera- Weight per ture. Cubic Foot. ture. Cubic Foot. ture. Cubic Foot. Fahr. Pounds. Fahr. Pounds. Fahr. Pounds. 32 62.42 122 61.70 168 60.81 40 62.42 124 61.67 170 60.77 45 62.42 120 61.63 172 60.73 5o 62.41 128 61.60 174 60.68 55 62.39 130 61.56 176 60.64 60 62.37 132 61.52 178 60.59 65 62.34 134 61.49 180 60.55 70 62.31 136 61.45 182 60.50 75 62.27 138 61.41 184 60.46 80 62.23 140 61.37 186 60.41 85 62.18 142 61.34 188 60.37 90 62.13 144 61.30 190 60.32 95 62.04 146 61.26 192 60.27 100 62.02 148 61.22 194 6o.22 102 62.OO I50 61.18 196 60.17 104 61.97 152 61.14 198 60.12 106 61.95 154 61.IO 200 60.07 108 61.92 156 61.06 202 60.02 no 61.89 158 61.02 204 59.97 112 61.86 160 60.98 206 59.92 114 61.83 l62 60.94 208 59.87 116 61.80 164 60.90 2IO 59.82 118 61.77 166 60.85 212 59-76 120 61.74 COMPARISON OF HEADS. One foot of water at 50 F. = 62.41 pounds per sq. ft. One foot of water at 50 F. One foot of water at 50 F. One pound per sq. ft. at 50 F. One pound per sq. in. at 50 F. One inch of mercury at 32 F. One atmosphere of 29.92 in, of mer. 0.4334 pounds P er s q« in- 0.8845 in. mercury at 32 F. 0.01602 feet of water. 2.308 feet of water. 1. 130 feet of water. 33.80 feet of water. APPENDIX. 265 181. Melting-points of Metals. Mercury — 38 F. Tin 442 F. Bismuth 497 F. Lead 612 F. Zinc 773 F. Antimony 8io° F. Brass 1869 F. Silver 1874 F. Copper 1995° F. Gold 2016 F. Iron, cast 2780 F. Platinum 3280 F. 266 ENGINEERING LABORATORY PRACTICE. 182. Properties of Saturated Steam. (Abridged from Kent.) Vacuum- gage. Inches of Mercury. Absolute Pressure. Lbs. per Sq. In. Tempera- ture. Fahrenheit. Heat of the Liquid. Heat of Vaporiza- tion. r. Weight of 1 Cu. Ft. in Pounds. 29.74 .089 32 O IO9I.7 .OOO30 29.67 .122 40 . 8 I086. I .00040 29.56 .176 50 18 IO79.2 .OOO58 29.40 •254 60 28.01 1072.2 .OOO82 29.19 •359 70 38.02 IO65.3 .OOII5 28.90 .502 . 80 48.04 1058.3 .OOI58 28.51 .692 90 58.06 I05L3 .OO213 28.OO •943 IOO 68.08 IO44.4 .00286 27.88 I I02. 1 70.09 IO43.O .OO299 25.85 2 126.3 94.44 1026.0 .OO577 23.83 3 141. 6 109.9 IOI5.3 .00848 21.78 4 I53.I 121. 4 IOO7.2 .OIII2 19.74 5 162.3 130.7 IOOO.7 .OI372 17.70 6 170. 1 138.6 995.2 .01631 15.67 7 176.9 145.4 990.5 .01887 13.63 8 182.9 155.5 986.2 .02140 II.60 9 188.3 156.9 982.4 .02391 9.56 10 193.2 161. 9 979.O .02641 7.52 11 197.8 166.5 975.8 .02889 5.49 12 202.0 170.7 972.8 .03136 3-45 13 205.9 174.7 970.O .03381 1. 41 14 209.6 178.4 967.4 .03625 Gage-pres- sure. Lbs. 14.7 212.0 180.9 965.7 .03794 per Sq. In. O.304 15 213.0 181. 9 905.0 .03868 1-3 16 216.3 185.3 962.7 .O4IIO 2.3 17 219.4 188.4 960.5 .04352 3.3 18 222.4 I9I-4 958.3 .04592 4-3 19 225.2 194-3 956.3 .04831 5.3 20 227.9 197.0 954-4 .05070 6.3 21 230.5 199.7 952.6 .05308 7-3 22 233-o 202.2 950.8 .05545 8.3 23 235.4 204.7 949.1 .05782 9-3 24 237.8 207.0 947-4 .06018 APPENDIX. PROPERTIES OF SATURATED STEAM. 26j Gage- pressure. Lbs. per Sq. In. Absolute Pressure. Lbs. per Sq. In. Tempera- ture. Fahrenheit. Heat of the Liquid. Heat of Vaporiza- tion. r. Weight of 1 Cu. Ft. in Pounds. IO.3 25 240.O 209.3 945-8 .06252 H-3 26 242.2 211. 5 944.3 .06487 12.3 27 244-3 213.7 942.8 .06721 13.3 28 246.3 215.7 941.3 .06955 14.3 29 248.3 217.8 939-9 .07188 15.3 30 250.2 219.7 938.9 .07420 16.3 31 252.1 221.6 937-2 .07652 17-3 32 254.0 223.5 935-9 .07884 18.3 33 255.7 225.3 934.6 .08115 19.3 34 257.5 227.1 933-4 .08346 20.3 35 259.2 228.8 932.2 .08576 21.3 36 260.8 23O.5 93I.O .08806 22.3 37 262.5 232.1 929.8 .09035 23.3 38 264.0 233.8 928.7 .09264 24.3 39 265.6 235.4 927.6 .09493 25.3 40 267.1 236.9 926.5 .09721 26.3 41 268.6 238.5 925.4 •09949 27.3 42 270.1 24O.O 924.4 .IOI8 28.3 43 271.5 24I.4 923.3 .IO40 29.3 44 272.9 242.9 922.3 .1063 30.3 45 274-3 244.3 921.3 .IO86 3i-3 46 275.7 245.7 920.4 .1108 32.3 47 277.0 247.O 919.4 .1131 33-3 48 278.3 248.4 918.5 •1153 34-3 49 279.6 249.7 917.5 .1176 35-3 50 280.9 25I.O 916.6 .II98 36.3 5i 282.1 252.2 915.7 .1221 37-3 52 283.3 253.5 914.9 .1243 38.3 53 284.5 254.7 914 O .1266 39-3 54 285.7 256.O 913. 1 .1288 40.3 55 286.9 257.2 912.3 .1311 41.3 56 288.1 258.3 9*1-5 .1333 42.3 57 289.1 259.5 910.6 .1355 43-3 58 290.3 260.7 909.8 .1377 44-3 59 291.4 261.8 909.0 .I4OO 45-3 60 292.5 262.9 908.2 .1422 268 ENGINEERING LABORATORY PRACTICE. PROPERTIES OF SATURATED STEAM Gage- pressure. Lbs. per Sq. In. Absolute Pressure. Lbs. per Sq. In. Tempera- ture. Fahrenheit. Heat of the Liquid. Heat of Vaporiza- tion. r. Weight of 1 Cu. Ft. in Pounds. 46.3 6l 293.6 264.0 907.5 .1444 47.3 62 294.7 265.1 906.7 .1466 48.3 63 295.7 266.2 905.9 .1488 49-3 64 296.8 267.2 905.2 .1511 50.3 65 297.8 268.3 904.5 .1533 51.3 66 298.8 269.3 903.7 .1555 52.3 67 299.8 270.4 903.O •1577 53-3 68 300.8 271.4 902.3 .1599 54-3 69 301.8 272.4 9OI.6 .1621 55-3 70 302.7 273.4 9OO.9 .1643 56.3 71 303.7 274.4 900.2 -1665 57.3 72 304.6 275.3 899.5 .1687 58.3 73 305.6 276.3 898.9 .1709 59-3 74 306.5 277.2 898.2 .1731 60.3 75 307.4 278.2 897.5 .1753 61.3 76 308.3 279- 1 896.9 .1775 62.3 77 309.2 280.0 896.2 •1797 63-3 78 310.1 280.9 895.6 .1819 64.3 79 310.9 281.8 895.O .1840 65.3 80 311. 8 282.7 894.3 .1862 66.3 81 312.7 283.6 893.7 .1884 67.3 82 313.5 284.5 893.I .1906 68.3 83 314.4 285.3 892.5 .1928 69.3 84 315.2 286.2 89I.9 .1950 70.3 85 316.0 287.0 89I.3 .1971 71.3 86 316.8 287.9 890.7 .1993 72.3 87 317.7 288.7 89O.I .2015 73-3 88 3i8.5 289.5 889.5 .2036 74-3 89 319.3 290.4 888.9 .2058 75.3 90 320.0 291.2 888.4 .2080 76.3 *9i 320.8 292.0 887.8 .2102 77.3 92 321.6 292.8 887.2 .2123 78.3 93 322.4 293.6 886.7 .2145 79-3 94 323.1 294.4 886.1 .2166 80.3 95 323.9 295.1 885.6 .2188 81.3 96 324.6 295.9 885.0 .22IO APPENDIX. PROPERTIES OF SATURATED STEAM. 269 Gage- pressure. Lbs. per Sq. In. Absolute Pressure. Lbs. per Sq. In. Tempera- ture. Fahrenheit. Heat of the Liquid. Heat of Vaporiza- tion. r. Weight of 1 Cu. Ft. in Pounds. 82.3 97 325.4 296.7 884.5 .2231 83.3 98 326.1 297.4 884.O .2253 84.3 99 326.8 298.2 883.4 .2274 85.3 100 327.6 298.9 882.9 .2296 86.3 IOI 328.3 299.7 882.4 .2317 87.3 102 329.O 300.4 881.9 .2339 88.3 103 329.7 301. 1 881.4 .2360 89.3 104 330.4 30I.9 880.8 .2382 90.3 105 33I-I 302.6 880.3 .2403 91-3 106 331.8. 303.3 879.8 .2425 92.3 107 332.5 304.O 879.3 .2446 93.3 108 333-2 304.7 878.8 .2467 94-3 109 333-9 305.4 878.3 .2489 95.3 no 334-5 306.I 877.9 .2510 96.3 III 335.2 306.8 877.4 .2531 97.3 112 335-9 307.5 876.9 .2553 98.3 113 336.5 308.2 876.4 .2574 99-3 114 337.2 308.8 875.9 .2596 100.3 115 337-8 309.5 875.5 .2617 101.3 Il6 338.5 310.2 875.0 .2638 102.3 117 339-1 3I0.8 874.5 .2660 103.3 Il8 339-7 311. 5 874.1 .2681 104.3 119 340.4 312. 1 873.6 .2703 105.3 I20 341-0 312.8 873.2 .2724 106.3 121 341.6 3I3.4 872.7 .2745 107.3 122 342.2 314.1 872.3 .2766 108.3 123 342.9 3I4.7 87I.8 .2788 109.3 124 343-5 315.3 871.4 .2809 1 10. 3 125 344-1 316.0 870.9 .2830 in- 3 j 126 344.7 316.6 870.5 .2851 112.3 127 345-3 317.2 87O.O .2872 113. 3 128 345-9 317.8 869.6 .2894 II4-3 129 346.5 318.4 869.2 .2915 115.3 I30 347.1 319-1 868.7 .2936 116.3 131 347-6 319.7 868.3 .2957 117. 3 132 348.2 320.3 867.9 .2978 270 ENGINEERING LABORATORY PRACTICE, PROPERTIES OF SATURATED STEAM. Gage- pressure. Lbs. per Sq. In. Absolute Pressure. Lbs. per Sq. In. Tempera- ture. Fahrenheit. Heat of the Liquid. Heat of Vaporiza- tion. r. Weight of 1 Cu. Ft. in Pounds. 118. 3 133 348.8 320.8 867.5 .3000 "9-3 134 349-4 321.5 867.O .3021 120.3 135 350.0 322.1 866.6 .3042 121. 3 136 350.5 322.6 866.2 .3063 122.3 137 351. 1 323.2 865.8 .3084 123.3 138 351.8 323.8 865.4 .3105 124.3 139 352.2 324-4 865.0 .3126 125.3 140 352-8 325.0 864.6 .3147 126.3 141 353-3 325.5 864.2 .3169 127.3 142 353-9 326.1 863.8 .3190 128.3 143 354-4 326.7 863.4 .3211 129.3 144 355-o 327.2 863.0 .3232 130.3 145 355-5 327.8 862.6 .3253 I3I-3 146 356.o 328.4 862.2 .3274 1323 147 356.6 328.9 861.8 .3295 133-3 148 357-1 329.5 861.4 .3316 134-3 149 357-6 330.0 861.0 •3337 135.3 150 358.2 330.6 860.6 .3358 136.3 151 358.7 331-1 860.2 •3379 137-3 152 359-2 331.6 859-9 .3400 138.3 153 359-7 332 2 859-5 .3421 139-3 154 360.2 332.7 859.1 -3442 140.3 155 360.7 333-2 858.7 .3463 141. 3 156 361.3 333.8 858.4 .3483 142.3 157 361.8 334-3 858.0 .3504 143-3 158 362.3 334.8 857.6 •3525 144-3 159 362.8 335.3 857.2 .3546 145-3 160 363-3 335-9 856.9 .3567 146.3 161 363.8 336.4 856.5 .3588 147-3 162 364.3 336.9 856.1 .3609 148.3 163 364.8 337-4 855-8 .3630 149-3 164 365-3 337-9 855.4 .3650 150.3 165 365.7 338.4 855.1 .3671 151. 3 166 366.2 338.9 854.7 .3692 152.3 167 366.7 339-4 854.4 .3713 153.3 168 367.2 339-9 854.0 •3734 154-3 169 367.7 340.4 853.6 •3754 APPENDIX. PROPERTIES OF SATURATED STEAM. 27I Gage- pressure. Lbs. per Sq. In. Absolute Pressure. Lbs. per Sq. In. Tempera- ture. Fahrenheit. Heat of the Liquid. 9- Heat of Vaporiza- tion. r. Weight of 1 Cu. Ft. in Pounds. 155.3 170 368.2 340.9 853.3 •3775 156.3 171 368.6 341-4 852.9 .3796 157.3 172 369.I 341.9 852.6 o8l7 158.3 173 369.6 342.4 852.3 .3838 159-3 174 370.0 342.9 851.9 .3858 160.3 175 370.5 343-4 851.6 .3879 l6l. 3 176 37I.O 343-9 851.2 .3900 162.3 177 371-4 344-3 850.9 .3921 163.3 178 371-9 344-8 850.5 •3942 164.3 179 372.4 345-3 850.2 .3962 165.3 180 372.8 345.8 849.9 .3983 166.3 181 373-3 346.3 849.5 .4004 167.3 182 373-7 346.7 849.2 •4025 168.3 183 374-2 347-2 848.9 .4046 169.3 184 374-6 347.7 848.5 .4066 170.3 185 375-1 348.1 848.2 .4087 171. 3 186 375-5 348.6 847.9 .4108 172.3 1S7 375-9 349.1 847.6 .4129 173-3 188 376.4 349-5 847.2 .4150 174-3 189 376.9 35o.o 846.9 .4170 175.3 190 377.3 350.4 846.6 .4191 176.3 191 377-7 350.9 846.3 .4212 177-3 192 378.2 351-3 845.9 •4233 178.3 193 378.6 351.8 845.6 .4254 179-3 194 379 352.2 845.3 .4275 180.3 195 379-5 352.7 845.O .4296 181. 3 196 380.0 353-1 844.7 .4317 182.3 197 380.3 353-6 844.4 •4337 183.3 198 3807 354-0 844.I .4358 184.3 199 381.2 354-4 843.7 •4379 185.3 200 381.6 354-9 843.4 .4400 186.3 201 382.0 355-3 843.I .4420 187.3 202 382.4 355-8 842.8 .4441 188.3 203 382.8 356.2 842.5 .4462 189.3 204 383.2 356.6 842.2 .4482 190.3 205 383.7 357-1 841.9 .4503 272 ENGINEERING LABORATORY PRACTICE, PROPERTIES OF SATURATED STEAM. Gage- pressure. Lbs. per Sq. In. Absolute Pressure. Lbs. per Sq. In. Tempera- ture. Fahrenheit. Heat of the Liquid. Heat of Vaporiza- tion. r. Weight of 1 Cu. Ft. in Pounds. 191. 3 206 384.I 357-5 84I.6 .4523 192.3 207 384.5 357.9 841.3 •4544 193-3 208 384.9 358.3 84I.O .4564 194.3 209 385.3 358.8 84O.7 .4585 195.3 2IO 385.7 359-2 84O.4 .4605 196.3 211 386.1 359.6 840.I .4626 197.3 212 386.5 360.O 839-8 .4646 198.3 213 386.9 360.4 839.5 .4667 199.3 214 387.3 360.9 8392 .4687 200.3 215 387.7 361.3 838.9 .4707 201.3 2l6 388.1 361.7 838.6 .4728 202.3 217 388.5 362.1 838.3 .4748 203.3 218 388.9 362.5 838.I .4768 204.3 219 389.3 362.9 837.8 .4788 205.3 220 389.7 363-2 837.6 .4808 APPENDIX. 273 183. Comparison of Fahrenheit and Centigrade Thermometer Scales. u +j u j u ^j u ^j In • u ^j A c •fi a J3 c c .C c -C c ' tt V rt V a V "r5 Prony 55 Brick, rattler test for paving 1.16. Bristol recording pressure-gage, the 39 C Calculations from the indicator-card, clearance. . o « 160 , exercise. 163 , horse-power 157 , reevaporation , ... 159 , weight of steam 158 Calibration of gages, method by comparison with gage-tester 36 , method by comparison with standard 34 , form for 35 an orifice . 24 , form for 25 thermometers, method by comp. with standard.... 41 , method by comp. with steam-pres- sure 42 , form for 42 water-meters 27 , form for 28 Caliper, the micrometer 16 , the vernier 16 Calorimeters, coal 124 , steam, barrel 52 , Carpenter separating, 51 INDEX. 579 PAGE Calorimeters, steam, Carpenter separating, use of 52 , exercise with 54 , Peabody throttling 47 , form for 51 , limitations of 49 , use of 50 Card, the indicator 150 Care of apparatus 2 the steam-engine . . .. 175 Carpenter separating calorimeter 51 Cement-testing in machine, Olsen 88 Centrifugal pumps, tests of . . . , , 227 Choice of indicator-springs 144 Circumferences and areas of circles, table. . . - 257 Clearance from the indicator-card 160 of the steam-engine, method of measuring 186 Coefficient of discharge through a nozzle 25 an orifice 22 of rectangular weirs, table 275 Cold-bending tests of materials 121 Combined engine and boiler, test of 218 Combining indicator-cards , • 161 Commercial efficiency of the steam-engine 181 Commonplace-book 2 Comparison of heads of water, table. 264 F. and C. thermometer-scales, table 273 Compound engines, equalizing the work of 191 , tests of 189 Compressional tests of materials 104 , long specimens 106 , short specimens 104 Compressors, tests of air 238 Concrete, tests of » 113 Constant, the engine 158 Copper ball pyrometer, the 45 Correction of gages 37 Crosby indicator, the 139 Cross bending tests of materials 109 Cylinder losses of the steam engine , <, . . . 184 280 INDEX. D PAGE Decimal equivalents, table 262 Deflectometer 93 De Laval steam-turbine, the 253 Detroit lubricator, the 178 Diagram, the indicator (see Indicator card). Diagrams, autographic 104 , stress-strain 102 Directions for use of the planimeter 15 Drifting tests of materials 122 Dynamometers, absorption 55 , Emery locomotive 87 , transmission 58 E Efficiency of boilers 124 the furnace 1 24 hoists 63 screws 60 the steam-engine, commercial 181 Elasticity, modulus of, definition of 95 Elastic limit, definition of c . 94 , determination of „ 100 Elongation, equivalent 99 , per cent of, definition of 96 Emery hydraulic testing-machine 77 locomotive dynamometer 87 Engine and boiler, test of combined 218 , gas, tests of 236 , steam, care of 175 , clearance of, method of measuring 186 , commercial efficiency of 181 , compound, tests of 189 , constant, use of 158 , cylinder losses of 184 , friction test of, 1 79 , horse-power of 157 -testing 165 Equalizing the work of a compound engine 191 INDEX. 28l PAGE Equivalent elongation 90, evaporation, definition of 123 Errors of the indicator. . . 146 Exercise, calculations from an indicator-card 163 with measuring-instruments 19 with the planimeter, (a) 15 . w 15 with steam-calorimeters, 54 Experiments with flow of steam through an orifice 30 Extensometer, Riehle Yale, the 89 use of the 100 F Flow of gases, measurement of 29 steam, experiments on. 30 , formulae for 30 water over weirs, formulae for 25 through orifices, formulae for 21 Flue-gas analysis 1 25 Form for boiler tests 134 calibration of gages .... 35 thermometers 42 water-meters 28 efficiency tests of hoists 65 screws 62 exercise with measuring-instruments 19 experiment on stem-immersion of thermometers 44 flow of water 23 friction test of the steam-engine 180 indicated horse-power test 175 indicator-spring testing 1 50 locomotive link-motion experiment 173 locomotive-testing 202 throttling-calorimeter 51 valve-setting 170 of specimen for tension tests 96 Formulae for flow of air 29 steam 30 water through an orifice 21 over weirs 25 282 INDEX. PAGE Friction test of the steam-engine 1 79 , form for 180 Fuel calorimeters 124 , heating value of. ... . 124 Gage, hook 26 , laying-off 93 , pressure 33 , Bristol recording 39 , calibration of, by comparison with standard 34 gage- tester. ... 36 , form for 35 , correction of 37 , vacuum. 34 Gas-engines, tests of 236 Gases, measurement of 29 Graphical logs of boiler tests 126 Graphic presentation of results 3 H Head over weirs, measurement of 26 Heads of water, comparison of, table 264 Heating value of fuels 1 24 Henning portable recorder, the 91 Hoists, efficiency of , 63 , form for 65 Hook-gage, the 26 Horse-power of boilers 124 the steam-engine 157 test, indicated 173 , form for 175 Hydraulic dynamometer, Emery 87 machinery, testing of 224 testing-machine, Emery. 77 , Riehle 76 I Impact tests of materials 117 Impulse-wheels, advanced work on 235 INDEX. 283 PAGE Impulse-wheels, tests of 232 Indicator-card, the : 150 , calculations from 157 , condensed directions for working up 155 , determining per cents of stroke 152 , locating events of stroke. . 151 , M. E. P. of 153 , M. E. P. by method of ordinates 153 , M. E. P. by planimeter . 155 diagram, (see Indicator-card), springs, method of testing.. 147 , form for 150 , steam-engine, the 139 , choice of spring for 144 , Crosby. -...- 139 , errors of. 146 , Tabor 142 , use of , 144 , valve-setting by 171 Indicated horse-power test 173 , form for 175 Inertia, moments of, table 247 Injectors, advanced work on 252 , Metropolitan 246 , Sellers 246 , tests of 245 Investigation of cylinder losses of the steam-engine 184 K Keeping the records 2 L Lap, definition of 166 Laying-off gage 93 Lead, definition of 166 Le Chatelier pyrometer, the 45 Leftel turbine-wheel, the 229 Lineal measurement 16 Link-motion, steam distribution of 1 72 284 INDEX. PAGE Locomotive dynamometer. 87 link-motion, steam distribution of 172 -testing 192 , A. S. M, E. standard method of 193 -testing plants 207 , methods of testing 210 tests, method of conducting. . » 210 , method of working up 212 , tractive force of, table 2 74 Long specimens in compression, tests of 106 Lubricators , 176 Lunkenheimer lubricator, the 177 M Manometers 37 Materials, strength of 70 , weights of, table 263 Mean effective pressure of the indicator-card 153 by method of ordinates 153 by planimeter 155 Measuring-instruments, exercise with 19 -machine, Sweet's. 17 water, methods of , . 21 Measurement of areas t 6 gases 29 head over weirs 26 length 16 liquids 21 power 55 pressure 33 speed 5 temperature 40 time 4 Melting-points of metals, table 265 Mercurial thermometers 40 Metals, melting-points of, table. 265 Meters, water 27 , calibration of 27 , form for 28 Method of combining indicator-cards 161 INDEX. 285 PAGE Method of instruction 1 measuring clearance of the steam-engine 186 gases . . 29 liquids 21 testing boilers 126 in compression 104 in tension 93 for ultimate strength 97 for elastic limit 100 locomotives 210 , A. S. M. E 193 working up locomotive tests 212 Metropolitan injector, the 246 Micrometer caliper, the 16 Miscellaneous tests 236 Modulus of elasticity, definition of • 95 resilience, definition of 95 Moments of inertia, table 274 N Nozzle, coefficients of discharge of 25 O Olsen 100, 000- pound testing-machine 15 Orifice, calibration of 24 , form for. 25 , determination of coefficient of discharge of 22 , formulae for flow of air through an 29 steam through an 30 water through an 21 P Paper friction-wheels, tests of , 68 Paving-brick, rattler test for 116 Peabody throttling calorimeter, the 47 Pelton wheel, advanced work on 235 , tests of 232 Per cent of elongation, definition of ........... 96 286 INDEX. PAGE Pipe brake. 57 Pitot tube for measuring flow of gases 32 Planimeter, adjustable ........ 13 , area of the zero-circle. 13 , directions for use of. 15 , exercise with, (a) 15 >(*) 15 , polar, the 6 , theory of 9 Plants, locomotive-testing , 207 Pressure-gages 33 , calibration of 34 , measurement of 33 Prony brake, the . . ... 55 , special forms of ..... . 57 Properties of saturated steam, table 266 Pumps, centrifugal, advanced work on 229 , tests of. .... . 227 , steam, advanced work on 226 , tests of 224 Pyrometers, copper-ball 45 , Le Chatelier. . . 45 R Rattler test for paving-brick 116 Records, autographic 104 , keeping the 2 Reduction of area, definition of 96 Reevaporation from the indicator-card 159 Reports 2 Resilience, modulus of, definition of 95 Revolution-counters 6 Riehle hydraulic testing-machine 76 patent high-faced wedge. 71 100,000-pound testing-machine 73 300,000-pound testing-machine 71 Rise and fall of mercurial thermometers, rate of 43 Rules for care of thermometers 40 use of the indicator 144 INDEX. 287 S PAGE Screws, efficiency test of , 60 , form for 62 Sellers injector, the 246 Separating calorimeter 51 , use of 52 Short specimens in compression 104 Slide-valve engines, valve-setting for 168 Slippage of belts 67 Specimens for tension tests, form of 96 wire rope in tension 115 Speed-counters 5 , measurement of 5 -recorder, the Boyer 5 Springs, indicator, choice of 144 , method of testing 147 Standard method of testing boilers, A. S. M. E 126 locomotives, A. S. M. E 193 Steam-boiler testing. 123 distribution of locomotive link-motion 172 , form for 173 -engine, care of 175 , clearance of 186 , commercial efficiency of 181 , cylinder losses of 184 , friction test of 179 indicator, the 139 testing 165 , advanced work in 188 , experiments on flow of 30 , formulae for flow of 30 , properties of saturated, table 266 pumps, tests of 224 turbines, tests of 253 , the De Laval 253 Stem-immersion of mercurial thermometers, experiment on 44 Stops, method of making 4 Strength of materials 70 Stress-strain diagrams 102 Sweet's measuring-machine , . . , . . , 17 288 INDEX. T PAGE Table of circumferences and areas of circles 257 coefficients of discharge of rectangular weirs 275 decimal equivalents 262 Fahrenheit and centigrade thermometer-scales 273 melting-points of metals 265 moments of inertia „ . 274 properties of saturated steam . . 266 tractive force of locomotives 274 weights of various materials 263 water. 264 Tabor indicator, the 142 Tachometers . 6 Temperature, measurement of 40 Tension tests of materials , 93 , form of specimen for , 96 Testing indicator-springs 147 , form for 150 -machines 70 , brick 116 , Emery hydraulic 77 , impact 117 , Olsen cement 88 , Olsen 100,000-pound 75 , Riehle hydraulic 76 , Riehle 100,000- pound 73 , Riehl& 300,000-pound 71 , Riehle wire 87 of hydraulic machinery 224 of steam-boilers , 123 of steam-engines 165 -plants, locomotive 207 Tests of air-compressors 238 belts 65 cement Ill centrifugal pumps 227 combined engine and boiler 218 compound engines , 189 erficiency of hoists 63 screws. ........... , f .... . 60 INDEX. 289 PAGE Tests of gas-engines , 236 impulse-wheels 232 indicated horse-power 173 injectors 245 locomotives 192 materials by cold-bending. ...» . . . 121 by drifting 122 in compression 104 in cross-bending 109 in impact 117 in tension k 93 paving-brick 116 steam-engines, compound 189 , efficiency 181 , friction 1 79 steam-pumps 224 steam-turbines 253 turbine- wheels 229 wire rope 115 Theory of the planimeter 9 Thermometers, calibration of, by comparison with standard. ..... 41 steam-pressure 42 , form for 42 , comparison of scales, table 273 , effect of stem-immersion 44 , mercurial 40 , rate of rise and fall 43 , rules for care of 40 Throttling calorimeter, the , 47 , form for 51 , limitations of 49 , use of 50 Time, measurement of 4 -signals 4 Tractive force of locomotives, table 274 Transmission-dynamometers 58 Transverse tests of materials 109 Turbines, steam, tests of 253 , the De Laval 253 Turbine- wheels, tests of 229 , advanced work on 231 290 INDEX. U . PAGE Ultimate strength, definition of 94 , method of testing for 97 U-tubes, use of 37 V Vacuum-gages 34 Valve-setting 165 by indicator. . . . 171 , form for 170 , general definitions 166 , specific directions for 167 Velocity, flow of gases by method of 32 Vernier caliper, the 16 W Water, comparison of heads of, table ,. , 264 , formulae for flow of, over weirs 25 , through orifices 21 -meters, calibration of 27 , form for 28 , methods of measuring 21 , weights of, table 264 Wedge, Riehle patent high-faced 71 Weights of materials, table 263 steam from the indicator-diagram 158 water, table 264 Weirs, formulae for flow of water over 25 , measurement of head over 26 , coefficients of discharge of, table 275 Wire rope, preparation of specimens 115 , tests of, in impact 117 -testing machine, Riehle 87 Working up indicator-cards, directions for 157 locomotive tests, directions for „ 212 Y Yield-point, definition of 94 Z Zero-circle of the planimeter 13 Zero-reading of the hook-gage 26 SHORT-TITLE CATALOGUE OF THE PUBLICATIONS OF JOHN WILEY & SONS, New York. 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