Locomotive Testing . . AT • . PURDUE UNIVERSITY. i LAFAYETTE, INDIANA. 1894. r ?'ii> \Q OfQ-H I v / ^ v PRINCIPLES UNDERLYING THE PLAN OF MOUNTING. [ See Plate 1. 1 The plan of mounting a locomotive for experimental purposes, in its inception, involved (i) supporting wheels carried by shafts running in fixed bearings, to receive the locomotive drivers and to turn with them; (2) brakes which should have sufficient capacity to absorb con- tinuously the maximum power of the locomotive, and which should be mounted on the shafts of the supporting wheels; (3) a traction dynamo- meter of such form as would serve to indicate the horizontal moving force and at the same time allow but a slight horizontal motion of the engine on the supporting wheels. Assume an engine, thus mounted, to be running in forward motion the supporting wheels, the faces of which constitute the track, revolving freely in rolling contact with the drivers. The locomotive as a whole, being at rest, the track under it (the top of the supporting wheels) is forced to move backward. If now the supporting wheels be retarded in their motion, as for example by the action of friction brakes, the engine must as a result tend to move off them. If they be stopped, the drivers must stop or slip. Whether the resistance be great or small, the force which is transmitted from the driver to the supporting wheel to over- come the resistance, will reappear as a stress in the draw-bar which alone holds the locomotive to its place upon the supporting wheels. The dynamometer constitutes the fixed point with which the draw-bar connects and serves to measure stresses transmitted. It is evident from these considerations that the tractive power of such a locomotive may be increased or diminished by simply varying the resistance against which the supporting wheels turn, and that the readings of the traction dynamometer will always serve as a basis for calculating work done at the draw-bar. It was believed that a locomotive 4 thus mounted could be run either ahead or aback under any desired load and at any speed; that, while thus run, its performance could be determined with a degree of accuracy and completeness far excelling •that which it is possible to secure under ordinary conditions of the road; and that the whole apparatus would be extremely useful to students in steam engineering. It was not thought that every condition of the track would be perfectly met, but it was expected that the results ob- tained would prove valuable in extending a knowledge of locomotive performance. How far these conceptions were justifiable, the sequel will show. FROM A PHOTOGRAPH OF THE FIRST PLANT. THE DEVELOPMENT OF THE PLAN OF MOUNTING. The matter of having a locomotive mounted for the purpose of experiment was discussed at Purdue early in the year of 1890 and it was so well received that in May 1891 an order was given the Schenectady Locomotive Works for a 17" x 24" eight- wheeled engine. The details of the mounting were worked out during the two months following. In September the locomotive had been delivered and it was in operation before the close of the year. This plant, which is believed to be the first of its kind, is described in detail in a paper entitled “An Experimental Locomotive,” which was read before the American Society of Mechanical Engineers at the San Francisco meeting in May 1892. A second paper, “Tests of the Loco- motive at the Laboratory of Purdue University,” before the same society a year later, gives the result of twenty efficiency tests which were made during the winter of 1892-93. Besides the work involved by these elaborate tests, attention was given to various matters ol minor import- ance, among which may be mentioned the counterbalance problem. In the course of this latter work, the fact that a driver through the action of its counterbalance, will under certain conditions actually leave the track was demonstrated by passing a wire under the moving wheel; wires thus passed at high speed, came out with a portion of their length untouched by the wheel. It was also shown that a long pipe-connection for an indicator, such as is generally used in road tests, tends to enlarge the card given by the indicator, as the speed of the engine increases. During the latter part of 1893 a very complete series of fourteen efficiency tests were run. These were made under full throttle and some of them at high speeds, the indicator showing from 300 to 700 horse- power. The observed data obtained from these tests was of a very complete character and much was expected of it; but it was destined to serve no useful purpose. 6 On the 23d of January, 1894 the Engineering Laboratory was burned. All experimental data which had not been published, went up in smoke, and the locomotive went down in the wreck. The fire entailed a heavy burden of labor and expense. But with the new responsibilities which it brought, there came also, new opportunities. All details of the mounting mechanism were most carefully reviewed, and every fragment of experience was made to serve a useful purpose in the design of a new plant. The damaged locomotive was extracted from the ruin and delivered to the P. C. C. & St. L. R. R. Co., at Indianapolis for repairs. Though but four months have passed since the fire, the new work is now complete and the reconstructed engine is in position. The following pages will serve to indicate the character of the new plant. FROM A PHOTOGRAPH AFTER THE FIRE. THE NEW PLANT. A comparison of Plates I. and II. with the published drawings of the original plant, to which reference has already been made will disclose important changes. The new plant as shown by the accompanying plates, occupies a building especially planned to receive it, and it is arranged for the accommodation of any locomotive, either steam or electric. The dotted outline in Plate I. is to the scale of the University’s locomo- tive “Schenectady.” THE WHEEL FOUNDATION. By reference to Plates I. and II. it will be seen that there is provided a wheel foundation of nearly twenty-five feet in length. This is more than sufficient to include the driving-wheel base of any standard eight, ten, or twelve-wheeled engine. For engines having six wheels coupled, a third supporting axle will be added to those shown, and for engines having eight wheels coupled, four new axles having wheels of smaller diameter than those shown, will be used. The wheel foundation carries cast-iron bed-plates to which are secured pedestals for the support of the axle boxes. The lower flanges of the pedestals are slotted, and the bed-plates have threaded holes spaced along their length. By these means, the pedestals may be ad- justed to any position along the length of the foundation. The boxes in use at present, are plain babbitted shaft bearings, and between each bearing and its pedestal, a wooden cushion is inserted. A bearing has been designed for use in some special experiments, which provides for the suspension of the axle from springs, but this bearing has not yet been used. The outer edges of the wheel foundation are topped by timbers to which the brake cases are anchored. The brakes which absorb the power of the engine, are the ones which were used in the original plant. They are constructed upon a principle developed by Professor Geo. I. Alden, and their capacity and wearing qualities are beyond question. 8 The load upon them is controled by varying the pressure of water which circulates through them and carries away the heat. The water pressure acts upon stationary copper plates which are forced against a moving cast iron disc thereby creating friction. No provision is made for determining the load upon each brake, but the loads may be equalizedjby equalizing the flow and pressure of the cooling water. The sum of these loads plus the friction of the axles in their boxes, makes up the sum total of work to be done; this work must be given out from the locomotive drivers. It all reappears in the form of draw-bar stress and its value is shown by the traction dynamometer. An elaborate system of piping (not shown on plates) provides for the circulation of the cooling water for the brakes, at whatever point along the length of the foundation they may be located. THE TRACTION DYNAMOMETER. The vibrating character of the stresses to be measured, makes the design of the traction dynamometer a matter of some difficulty. The dynamometer of the original plant consisted of an inexpensive system of levers attached to a heavy frame work of wood, the vibrations being controled by dashpots. In the present construction, wood as a support is entirely abandoned and a massive brick pier, well stayed with iron rods, has been substituted. The dynamometer itself consists of the weighing head of an Emery testing machine, the hydraulic support of which is capable not only of transmitting the stress it receives, but also of withstanding the rapid vibrations which the drawbar transmits to it. The apparatus is of 30,000 pounds capacity. In view of the enormous force which a locomotive is capable of exerting, it would appear at first sight, that an error of 50 or even 100 pounds in the determination of draw-bar stresses would be of slight consequence, and that great accuracy in this matter is not required. Under some conditions this conclusion is correct but under others it is far from true. The work done at the draw-bar is the product of the force exerted, multiplied by the space passed over; if the force exerted be great and the speed low, a small error in the draw-bar stress is not a matter of great importance; but if the reverse conditions exist, if the speed be high and the draw-bar stress low, then it is absolutly necessary that the draw-bar stress be determined with great accuracy. Moreover, 9 high speeds necessarily involve low draw-bar stress. A locomotive which at ten miles an hour may pull 12,000 pounds, will have difficulty when running sixty miles per hour, in maintaining a pull of 2,500 pounds. These conditions have prompted the Purdue authorities to make ex- traordinary efforts to secure accurate measurements at the draw-bar, and they serve as a sufficient justification of the heavy expenditure involved in the purchase of the Emery machine. As is well known, the arrangement of the hydraulic support of the Emery testing machine, permits the weighing scale to be at any con- venient distance from the point where the stresses are received. Plates I. and II. show only the receiving end of the apparatus. The draw-bar connects with this apparatus by a ball joint which leaves its outer end free to respond to the movement of the locomotive on its springs. A threaded sleeve allows the draw-bar to be lengthened or shortened for a final adjustment of the locomotive to its position upon the supporting wheels; and, finally, to meet the proportions of different locomotives, pro- vision is made for a vertical adjustment of the entire head of the machine upon its frame. THE SUPERSTRUCTURE. Plates III. and IV. show the arrangement of floors. The “visitors’ floor” (Plate IV.) and the fixed floors adjoining, are at the level of the rail. The open space over the wheel foundation is of such dimensions as will easily accommodate an engine having a long driving-wheel base, moveable or temporary floors being used to fill in about each different engine, as may be found convenient. The temporary flooring shown, is that employed for the Purdue Locomotive. The level of the “tender floor” is at a sufficient height above the rail to serve as a platform from which to fire. At the rear, is a run-way leading to the coal room, the floor of which is somewhat lower than the tender floor. A platform scale is set flush with the floor at the head of the run-way. During tests the scale is used for weighing the coal which is delivered to the fireman. The feed-water tank, from which the injectors draw their supply, is shown in the lower right-hand corner of Plate IV. Above this supply tank, are two small calibrated tanks so arranged that one may be filled while the other is discharging. o The steam pump shown on the visitors’ floor is for the purpose of supplying water under pressure, to the friction brakes which load the engine. The conditions under which the engine is operated are at all times within the control of a single person whose place is just at the right of the steps leading to the tender floor. From this position he can see the throttle and reverse lever, and observe all that goes on in the cab. At his right is the dynamometer scale-case wherein is shown the load at the draw-bar; in front are the gages giving the water pressure on the brakes; and under his hand are the valves controling the circulation of water through the brakes. No attempt has been made in these drawings to show small accessory apparatus, neither does it seem necessary to give an enumeration. THE BUILDING. Plate V. presents several views of the locomotive building. The entrance door, which opens upon the visitors’ floor, is shown in the south elevation. It is approached from the general laboratory, 150 feet away. The north and west elevations show the roof construction, whereby the upper end of the locomotive stack is made to stand outside of the building. The roof sections shown may be entirely removed, and a door in the cross-wall, which extends between the removable roof and the main roof, provides ample height for the admission of the locomotive to the building. A window in this door (Plate IV.) serves to give the fire- man a clear view of the top of the locomotive stack from his place in the cab, a condition which is essential to good work in firing. Above the stack is a pipe to convey the smoke clear of the building* To meet a change in the location of the stack, this pipe may be moved to any posi- tion along the length of the removable roof. It is proposed to embody in this pipe, a simple form of cinder trap which will catch and hold the sparks thrown out by the locomotive. The plan of the building ( Plate V.) shows the arrangement of tracks for the locomotive, and, of those used for supplying coal. I I THE PURDUE RAILROAD. In the process of establishing the first plant, it was necessary to move the 85000-pound locomotive, “Schenectady,” across wheat fields and pastures, for a distance of one and a quarter miles. Now Purdue has a track of its own connecting the locomotive laboratory with the railroads of the country. Locomotives may now be received and delivered with- out difficulty. For example, when the University engine was re- turned after being repaired at Indianapolis, it was put under its own steam and backed in on the Purdue track, directly to its place over the supporting wheels of the testing plant. The track will also serve to bring in supplies of every sort. ALDEN FRICTION BRAKE. (one-half OF CAEE REMOVED./ Wooi'Roo'm THE BALDWIN FOUR-CYLINDER COMPOUND. The general engineering laboratory of the University, as a building, is quite distinct from the plant which has thus far been described, but it also offers some important facilities for locomotive testing. In this laboratory will be the engines of a 9^ and r6 by 18 Vouclain compound locomotive. These engines will be fitted with a fixed frame similar to that of a stationary engine, and will be mounted upon a foundation. Steam will be supplied them from the laboratory boilers, their exhaust will be piped to a Wheeler condenser, and they will be run under the load of a friction brake. This apparatus will furnish opportunities for a careful experimental study of this type of compound engine, and also of some of the questions affecting other forms of compound locomotives. FLOOR PLAN OF THE ENGINEERING LABORATORY. < J Plh Locomotive Laboratory. PLATE III Purdue University. Locomotive Laboratory. PLATE IV Purdue University. ■Nor\H X\«v