IN T () i{()LI1 NGT -. S.lOCI( (i)N O iA1[IV'tYS,,&C.( B Y -' R - n I D 1: Y i.i 1 1 ) (' - P mn 1'n.1:- rp E 1) i-3- S u-I 1BAll -r T 0m I., On page 4, sixteenth line from bottom, the Aords: "Sli(Ies oel (. beel, p7a2e, &c.," should read:' SLIDES ON A LEVEL PLA4NEA, kc." Entered according to Adt of Congress, in the year 186Y,. By War. LoU. v-IRID E, In the Clerk's Office of the District Court of farvvlarlrd. IN x:: r7 z,-ea Ca C,.'. TL-_. sTI TO PROLLING STOCK ON RMALWAYS, &C. BY NYM. LOUGHRIDG~E Ba alt i n o 1 e: PRINTED BY SHERWOOD & CO. 1865. BERLIN, FREDERICK CO., MD., December, 1865. 5 J. Edgar Thomson, President Pennsylvania Central R. W. and othiers: GENTLEMEN:-I have made a series of experiments in accordance with my circular of Nov. 23, 1864, the results (in the main) of which are respectfully submitted for your consideration. I regret to report, that before I had concluded my main experiments, and sum up the results, I was taken sick, and that I have been confined to my house for nearly four months. Owing to this misfortune, I have not had sufficient strength to do justice to the important subjects which you entrusted me with. I therefore issue this, as my second report, with the understanding that I will, at the earliest possible period, send you my final report. In which I propose to discuss friction in its practical relation to curves, undulating tracks, elastic and non-elastic freight, high and low velocities, effects or resistance of air, and many other problems. Also the result of different metals rubbing together and the angle of friction for the same, with a number of valuable tables. I find the subject vei'y interesting and important, and worthy of a thorough investigation. In the meantimrne I will be pleased to have suggestions and friendly criticisrms made, as I am anxious to cover the whole ground of friction in its practical relations to Railways and Rolling Stoclk. I have finished my experiments on hand-brakes, and a power-brake, to enable the engineer to control the train for all practical purposes. Any company desiring to test a single car for the former, or train for the latter, ] am prepared to furnish them directions for either. The Northern Central Railway Company have adopted both, to whom I refer as to the utility and practicability of either. Respectfully, WM. LOUGHRIDGE. 4 PHILOSOPHICALLY CONSIDERED, I have no doubt that friction was designed, by the Great Architect of the universe in the economy of nature, as one of its most important laws, next to gravitation and cohesion. But for gravitation everything on the surface of the earth would fly into space by its centrifugal force. But for cohesion all bodies would separate as ropes of sand. But for friction it would be difficult for man or beast to exercise their physical powers to walk, and all bodies would, like particles of ice, slide into a confused mass. Friction is a natural law, and is governed by certain defiled rules, that are uniform and reliable under the same circumstances; which, to be understood, require, on the part of the philosopher and mechanic, careful study and practice, to enable them to fully comprehend its diversified changes and contingencies, or they will fall into fatal errors, when availing themselves of its advantages, or in attempting to avoid its resistance to power and tendency to heat and wear machinery. The tendency of gravitation and power is to put all bodies in motion. Friction always tendcs to destroy niotion, and bring bodies that are moving to a state of rest. Gravitation exerts its greatest power or force in a direct vertical line through the centre of gravity of the body to the centre of the earth. Friction exerts its greatest resistance to power or motion of a b-dcy, when the object slides on, a bevel plane or at right angles with the line of gravitation. Gravity attracts different materials with different degrees of force, in proportion to the solidity or quantity of matter of which they are composed. For example, platinum with a force of 1,379'31; gold 1,203'60; and cork with only 15 pounds to the cubic foot. Friction exerts a resistance to the motion of all bodies, when rubbing together, in proportion to the weight that presses them against each other. The smoothness of the surfaces in contact, the quality and quantity of the lubricant that -may be interposed between the rubbing surfaces, and numerous other contingencies. Weight, smoothness of surface, and lubricant, cannot be relied upon as a standard or unit for calculation. For one cubic foot of cork on cork will generate more friction than one cubic foot of ice on ice. But with the sabme material, weight, smooth ness of surface and lubricant, the resistance will be uniform, and can be relied upon for all practical punr'oses; but generally when a change is made in either, different coefficients of friction will ensue. I have made these comparisons to illustrate the truth that nature's laws, although diversified and prolific, they are always uniform and reliable in results under the same treatment; and that man, in availing himself of nature's bounties, must at least study nature, and confornm to nature's laws. Friction, in its practical relation to railways, is very comprehensive and variable under different circumstances; but is capable of being reduced to plain and unerring rules. It is plegnant with many contingencies, and a source of much controversy; but with an aim for truth, careful study and practical experience, we may be able to lay down valuable and reliable rudimental formula as a basis for future reflection and experiment, that will ultimately result in enabling every thioughtful railroad man to master the most minute laws of friction as it relates to his profession. "ROLLING STOCK." Rolling stock (as commonly called,) is nothing more than a compromise between frictionless rollers and a common sled; the wheels represent the frictionless part, and the brasses that rub on the journals, the sled. If the wheels were thirtythree inches in dciameter and the journals three inches, then for every revolution of the wheels and journals, the car rolls 103'672, and slides 9'4248 inches, or it rolls eleven times as fa-r as it slides, or in. rolling one hundred miles it slides eleven miles, consequently, it only requires oneeleventh part the force or power to move a car on wheels, and journals of the above proportions that would be required to move it on runners, on the primlciple or in the manner of a common sled. To move a car on the latter plan, when the surfaces of the rails were dry and rough, it would require a tractive force equal to the coefficient of friction between the vwheels and rails, or for convenience of calculation, say twentyb —five per cent. of the weight of the car; then, if the car -weighed 32,000 poulids or sixteen tons, a force of 8,000 pounds or four tons would be necessary to put the car in motion; but when on wheels and journals of the above proportion, the friction would be reduced eleven times, and 727' 2-10 pounds force will move the car, that is, when the sur 6 faces of the journals and bearings are in the same condition as the surfaces of the rails and whels, but when a lubricant is put in the journal boxes and between the rubbing surfaces, the friction will be reduced in proportion to the smoothness of the journals, and the quality and quantity of the oil, say for illustration, to ten per cent., then 290'8-10 pounds force would move the car, which. would be equal to 18-2-10 pounds for each ton on a basis of ten per cent. for friction with a three-inch journal, see annexed table for the coefficient of friction on different sized journals from one to 161- inches diameter, when you will observe that friction or a resistance to motion increases with an increase of the journal. Friction, in its practical relation to rolling stock, has several objectionable qualities, which. imay be classified under the following heads: Ist. Its resistance to power. Notwithstanding numnerous efforts have been made, no practical bearing, journal, or lubricant has yet been discovered that could induce friction to give Sower a free pass over any railway. It makes no distinction in rates on account of long journeys, but uniform'ily pro rates for all distances, and whether the trip is made slowly or quickly, it taxes power a certain per cent. per ton per mile, coummuting only on account of highly polished surfaces and a liberal supply of lubricants. With the exception of inclined planes, air, and the retarding effect arising from rolling the wheel on the rail, friction is the only resistance that prevents cars once in motion from perpetual motion. Therefore, the heavy expenditures for motive power for railways must be charged in the main to fricetion. 2d. Its tendency to abrade or wear machinery which is also charged by the ton per mile. All substances when rubbed together waste or wear away. In writing this manuscript with a leaden pencil, I discover that the abrasion of the lead is constant and uniform in proportion to the pressure on the paper. I also discover that the amount of lead which adheres to the paper is not only dependent upon the pressure I give it, but upon the hardness of tihe lead. From this experience it is fair to conclude that to avoid abrasion there are numerous contingencies which -must be taken into consideration. The diamond will not abrade or wear away by friction as rapidly as my leaden pencil, but time will wear both away. Therefore, it requires practical experience and judgment to select the material (all else being equal) that will wear the longest. Clean and highly polished surfaces and plenty of oil are the best remedies I know of to prevent abrasion. 3d. Its tendency to heat. The history of the Indian rubbing sticks together to excite them to a flame, is sufficient eivdence that this property of friction was understood long before the heating of car jounals and boxes on railways. The physical force necessary on the part of the Indian to develop the latent heat is evidence that the greater the pressure and velocity of the parts in contact the greater the tendency to heat. If the Indian had rubbed very broad surfaces together, and applied a thick coating of oil between them, he would have made-his supper on raw buffalo. The tendency to heat increases in proportion to the weight, velocity of the parts in contact, and depends in part upon the area of the surface and the quality of the oil, as well as care in keeping the boxes clean from dust and sand. Hot-boxes cause great inconvenience on railways, and are of frequent occurrence. The simple fact that a majority of boxes do not get hot, is proof positive that there is some defective mechanism in fitting the bearing of the others, or that there is a'want of a proper supply of oil. Every bearing when put on the journals should rest equally on all its parts, and should fit loosely between the flange and shoulder of the journal. I saw a stranger, on one occasion, trying to press a brass bearing that was too long, in between the flange and shoulder of the journal, when I remarked to him, " You will have a hot-box.'' "' WVhat for I have's a hot-box?" " For the reason that the brass has a less quantity of metal than the journal, consequently it will expand more rapidly, and by its expansion create friction and heat the box." He replied, ('Spansion-friction-und de devil. Ise been on tis railroad ten years, and I knows somting too." Before the train ran ten miles the box was in a flame, and before the train man could get the brass out, they had to cut part of the flange off the journal. I have not met the Dutchman since' to compare philosophy with ten years experience. I know of no better guide than to have convex and concave gauges, in principle, the same as the wire gauge, and a variety of sized bearings to suit the different sized journals. The journals are always wearing, whilst the pattern to cast the brasses from, remains the same. Consequently, brasses are often used that in the commencement have very little surface as a bearing; such' bearings must heat at high velocities. Friction is the only practicable means yet discovered as a fulcrum to pfull and retard trains, and it is equal with equal conditions in its effectiveness for both. It has also proved an effective safety valve in securing passengers and machinery from violent concussions, and governs power within certain and safe limits. I have no doubt if the mechanical wisdom of the world were assembled in convention for the purpose of superseding it, they would not suggest any means better adapted for the purpose. If its resistance to moving bodies or force was greatly increased, machinery would often be brought to sudden strains, and trains to a state of rest so quickly, as to cause a greater average injury to passengers and machinery than is now done by collisions. If cogs were constructed on the driving wheels and rails, or if it was practicable to cut file teeth on the tires of the driving and car wheels, by a careless application of steam to the engine, or too sudden an application of the brakes, the effect would be to loosen the rails from their fastenings, rack the machinery, throw passengers backwards when starting, and forward when stopping,. or from the platforms; so as to make the transportation of passengers impracticable and increase the loss of life ten-fold. 5Tilte is re'quisite to safely put cars and passengers in motion, as well as to bring them to a state of rest. Man's physical construction is such that he cannot.be moved with the quickness of the Falconer's arrow. Great ingenuity has been displayed to devise some means of increasing the adhesion of the wheels to the rails, but I venture the opinion that nature has made a provision of friction that will never be superseded by art. Friction limits the effects of power to pull and retard within certain safe bounds, regardless of the pressure of steam in the boiler, size of cylinders, or pressure on the brake-shoes, and I am sanguine it is not desirable to increase it. It would be very desirable and important to have the maximum firiction for pulling and retarding cars, always maintain at a uniform rate, but owing- to changes of surface on the rails by grease, &c., it varies from twelve to twenty per cent., I know of no better practical means to secure a uniform friction, than the common plan of sifting a thin coat'ng of fine sand on the rails. As an illustration to show 9 that a locomotive tractive capacity cannot be increased by enlarged cylinders and increased pressure of steam in the boiler beyond the coefficient of friction between the driving wheels and rails, or that the retarding effect on the train cannot be increased by pressure on the brake-shoes, beyond a point that will slide the car wheels. Suppose a man whose physical strength was four hundred pounds, attempted to lift a weight equal to his capacity, but when he had exerted two hundred pounds, the fullcrum on which he stood gave away, or that in attempting to pull a common dynamometer, so that the index should show four hundred pounds, and that to accomplish that object he would set his feet against a block of marble as a fulcrum, and th-at the friction between the marble and its support was only equal to two hundred pounds, then evidently, when the dynamometer or index showed two hundred pounds, the block of marble or fulcrum would slip, enabling him to exert but one-half his strength. Precisely the same principle is involved when the engine pulls, for the only fulcrum on which we depend for it to exert its power upon, is the adhesion of the driviiig wheels to the rails. Therefore, any increased pressure of steam in the boilers or area to the cylinders above that point is useless, and poor economy. WVhen a parallel rod breaks, it becomes necessary to take the opposite one off and run with one pair of driving wheels. All practical engineers know when this occurs that the locomotive loses one-half its tractive capacity, and that care must be observed in handling the throttle to prevent the wheels -from slipping. The reason is, that one-half the weight has been lost to the driving wheels, consequently the capacity of the cylinders and pressure of steam in the boiler, is too great for the weight on the drivers, and they slip before the full power of the motor can be exerted on the train, but if the same weight was put on the single pair of driving wheels, the tractive capacity of the locomotive would be equal to what it was before the parallel rods were taken off. Theoretically, with the same weiglht on the driving wheels, a locomotive will pull as much with one set of driving wheels as it will with any additional number, and if it does not practically, some other law or cause must be given to account- for the difference; for, under the same weight, an increase of surface or driving wheels will not increase friction or'the pulling capacity of' a locomotive, nor will an in 10 crease of bearings or journals, arising from an increase of drivers, increase the retarding effect on the engine, provided they are of the same diameter, and in all other respects equal to the single pair of journals, for the reason that each journal bears its proportion of the engine's weight. In facte-.three pair of driving wheels will reduce the friction on the journals as the wheels increase the aggregate Nweight of the locomotive, but do not by the weight increase the friction of the journals. From the above, it is fair to conclude, that when an engineer has to exercise care to prevent his driving wheel from slipping, that the area of the cylinder or prese sure of steam in the boiler is too great for the weight on the driving wheels. There is much truth in the common remark, that two locomotives of identically the same pattern, and built by the same builder, will often vary in their tractive capacity from one to twenty per cent. If these remarks are true, (I have no doubt of it,) there must be some cause for the difference, for if two locomotives are of exactly similar build, and in all other respects equal and under similar treatment, their pulling capacity will be as near in power as the oscillation of two pendulums of the same length will be in time at the same locality. Therefore, when not of equal capacity, it is proof positive, that they are not constructed or managed alike. I know of no machine that is more likely to vary in its power or pulling capacity than the locomotive, and there are certainly few that require more skill on the part of the mechanic to construct, or the engineer to manage. I could enumerate at least one hundred points connected with its construction, movements and management, that tend to effect its power, (I will confine myself to the leading ones,) and nine-tenths of them are chargeable to friction. The friction occasioned from sliding the pistons within the cylinders, the steam valves on their seats, the bearings on their journals, the eccentric straps on the eccentrics, the piston rods, valve rods, and pump-plungers through their respective packings, the cross-heads on their guides, the brasses within the connecting and parallel rods on thle crank pins, the rock, shaft and its pins, and bearings on the pins, &c., that connect it with the links and valve rods, the exhaust steam through contracted nozzles and forcing the water through the water-pipes, all tend to produce friction and retard the motion of the engine. Friction may be discussed under natural and artificial heads; natural when arising from such causes as the weight of the boiler and mcachinery of the locomotive, and the bearings on the journals, the weight of the pistons when sliding within the cylinders, and all others resulting from weight or the effects of gravitation. Artificial when occasioned by setting out the packing rings within the cylinders, compressing the packing around the pump-plungers, &c. AS a general rule, the former is uniform under the same circumstances, but varies with the weight, the smooth condition of the surfaces, and the quality and quantity of the lubricant that may be interposed between the bearings. The latter depends very much upon the skill and judgment of the engineer who has control of the engine; in setting out the packing rings the pressure may be so intensified as to create sufficient friction to entirely resist the power of the steam, and in proportion to the pressure above a point which may be necessary to prevent the steam from blowing past the piston heads, so will the retarding effect be on the motor. Friction may be greatly increased by compressing the glands too hard upon the packing in the several stuffing boxes, keeping the brasses too tight on the crank pins, and when setting the packing rings by throwing the axis of the piston rods out of line with the axis of the cylinder. When the latter is done, the effect is to compress the piston-heads against the cylinders, the cross-heads against the guideplates, and the piston-rod against the packing in the stuffing boxes. The axle of the piston-rod should always work in a direct line from the cross-heads, through the axis of the stuffing boxes and cylinders. When constructing an engine, great care should be observed, to have the power to work in direct lines from the mover to the moved parts of the machine, and where bearings and journals are involved, that the axis of the journals should be at right angles with the line of power. I regard the above as sufficient to show the numerous contingencies upon which the tractive power of two engines of the same model depend. When of equal construction, the same model, weight on the drivers, &c., the one under the care of an expert and careful enlgineer, will do from ole to twenty per cent. more service than the other under inferior managemenct. But the engi.neer must not be held responsible for inferior construction or mechanism, nor can perfect mechanism be done without perfect lathes and tools. The above contingencies also ex 12 plain why an engine is more slunggish in its mnovements than the cars. When the throttle is closed, the cars invariably close up or overtake the engine. Cars with eight wheels have only eight points or bearings, generating friction, whilst the locomotive, with all its complicated machinery, has over fifty. The effects of friction on the locomotive- are diversified, and vary under different circumstances; when in a state of rest or drifting by momentumin, the friction arising from gravitation, setting the packi-ng rings, packing tlhe stuffing boxes, &c., resist the motion of the locomotive, but the instant that steam is applied to pull the train, additional friction accrues fronm iorcing the driving axles forward against the front part of the bearings, in proportion to the power or force which may be necessary to pull the train. If the force necessary to pull the train is equal to the weight on the driving wheels, then the friction will be exactly doubled on the bearings of' the driving journals, somewhat on the principle of driving a common wedge, that is, the iournal receives a rubbing at two points, on the top from gravitation, and on the front side from the pull of the train, the balance of the journals in thle train are effected conversely in the same way, but witlh a much less force, as the only pressure to resist power is that which may be necessary to overcolme the inertia or weiglht of the wheels and axle, but if the draw bars or couplings were fastened to the car boxes instead of the car beds, the entire resistance of the trucks and car beds would hang back on the bearings and increase the friction on the car journals the same as that of the driving wheel journals. When the engineer closes his trottle, and the bralkesmen apply the brakes, the car wheels adhere to the rails, and the momnentum of the engine, tender and cars press the car bearings iforward against the car journals, producing conversely the same effect upon the car journals that pulling does to the journals of the engine, lessening the pressure necessary to retard the wheels by the brakes inversely, as the diameter of the journals are to the wheels, and the'coefficient of the friction between the wheels and rails is to -the lubricated journals. THE ROADWAY. The relation that friction bears to the RoadNay is important and interesting. When the locomotive is pulling, 13 there is a constant tendency to cast the rails backward under the tender, equal to the force that is exerted upon the train, and when the brakes are applied to stop, a converse action takes place and the tendency is to carry the rails forward with the train. If frictionless rollers were constructed under the rails, this fact would be fully illustrated. WThen the rails lay on the cross ties, they are held to their place by friction, in addition to the fastenings from the spikes, equal to the coefficient of friction between the rails and cross-ties, which increases when the locomotive or cars rolls over the rails in proportion to the increased weight, showing that the locomotive and cars in passing over the rails carry, as it were, a temporary fastening with them from rail to rail; which is always equal to the power which the locomotive exerts when pulling, to cast the rails backwards or the tendency of the cars when thle wheels are sliding to drag the rails forward. ROLLING WHEELS ON THE RAILS. Coulomb and all other authorities which I have examined, allege "' that the reta-rding effect or resistance to motion produced from rolling a sphere or wheel on a level plane, is chargeable to friction." It is with extreme hesitation that I attempt to controvert this statement. I am not convinced that there is one particle of abrasion in rolling a perfect sphere on a smooth level plane. WVithout abrasion or rubbing, friction cannot be produced. In rolling a wheel back and ibrth upon a rail, the distance can be accurately measured, and it is a common practice to measure miles by the revolutions of the driving wheels. Consequently there can be no slipping of surfaces. There is, I admit, a resistance to force when a wheel is rolledcl upon a rail, or a sphere upon a plane, and I incline to the opinion that the resistance is occasioned by the indentation of the wheel into the rail. All hard metallic substances have more or less elasticity. WAThen the blacksmith striles his hammier on the face of the anvil, the hammer rebounds, showing that the hammer sinks into or compresses the steel on the face of the ham-mer and anvil. When a sphere or car wheel rests on a plane or rail, evidently weight creates the same indentation that percussion does; therefore, when a wheel rests on a rail, the bearing being almost a.nathematical point, the wheel sinks into the rail and the 14 face of the wheel becomes flattened, so that, when rolling, the point of the wheel that rests upon the plane is always nearer to the axis of the wheel than any other part. Consequently, the wheel has to compress the metal of the rail or rolls up an inclined plane, which causes a resistance to motion or a retarding effect, and in proportion to the woeiy7ht, so will the depth be that the plane or rail is compressed, and the face or periphery of the wheel flattened. This process (in my opinion) accounts for the splitting off of the sides of the rail. When the surface of the rail is very narrow and the weight on the wheels very heavy, the pressure is too great for the elasticity or cohesion of the iron; consequently, the metal is compressed beyond its retroactive capacity, and the particles of the metal, as it were, are driven or wedged apart or rolled out, and lose the power of cohesion and elasticity. Every metal has a certain limited capacity of elasticity that causes it to return to its original shape after being pressed or indented by percussion, the sanie in principle as ivory, but like steel springs when put under too much weight, will give way and never return to its original shape. If a train of cars were rolled on rails made of cast lead, evidently the wheels would sink into the rails and require more power to move the train than if placed on rails of hard. ened steel. Therefore it is evident that the resistance to motion will depend upon the weight as well as upon the hardness of the material on which the wheel or sphere rolls. MWhen car wheels are rolling rapidly on rails, the downward pressure from gravitation is the same as long as the plane is smooth and level, but the instant the'wheel comes to a point between the rails it fcds on the end of the next rail or strikes it with a greater force than is occasioned by pressure. Consequently, lamination occurs at the end of the rail more rapidly than at other points. 3I Y E X P E R I 3 E N T S. During my experience in introducing my Brake, I have spent considerable time at the principal machine shops of twenty of the leading railways in diflerent sections of the country; this necessarily brought me into frequent controversy with master mechanics, master car builders, and many of the best mechanics in the country, on the general laws of machines, &c. I found a great difference of opinion amongst leading mechanics, as regards the construction of machines, 15 rolling stock, and the laws governing the movements of the same. Owing to this diversity of opinion, and a desire to acquaint myself with the subject in which I felt most interested, I was induced to search for some practical authorities on these subjects, and I was truly disappointed in not being able to find any authority on the laws of friction, in its practical relation to rolling stock on railways. To a person engaged in improving the present system of retarding trains by brakes, a thorough knowledge of these laws are absolutely indispensable. KInowing of no person willing to give the subject a practical investigation,, with a full sense of my inability to do it justice, I determined to undertake it myself, hoping the result might prove beneficial to the general public and railway interests of the country. Believing a solution of the subject would benefit railway companies much more than myself, I felt justified in asking them to pay the expenses of the experiments as an equivalent to loss of time on my part; therefore, the following Circular was sent to two hundred railway companies; but twenty companies, whose names are annexed, became a party to the expense to the extent of the conditions of the Circular, making a fund of only two thousand dollars, three thousand less than the sum originally estimasted by me as necessary to do the subject justice; owing to this deficiency, I have omitted a number of problems, and confined my expenditures to the leading fulndamental laws of friction. I onmitted, for the present, equi:ping the ten cars mentioned in my Circular, as I wished to avail myself of any new discoveries that might develop themselves during my experiments. I feel justified in saying I am now much better prepared to equip trains with brakes than at any previous period; I have finished my combinations in all respects, and have no more experiments to make. To companies who are desirous of equipping their trains with the best means to retard them, I am willing to guarantee a system that will give at least thirty per cent. greater average safety than those now in general use for either the hand or engineer's brake. 16 A PIROPOSITlON TO THE BAIL COM PANIES OF THE UNITED STATES, BY WILLIAM LOUGHRIDGE, Of Weverton, Washington County, Od., TO ENTER INTO A SERIES OF EXPERIMENTS TO DISCOVER ALL THE LAWS OF FRICTION, &C., RELATING TO THE RETARDING OF RAILWAY TRAINS BY BRAKES. — Q — The undersigned are of the opinion that valuable results will accrue from the experiments AMr. Loughridge proposes to make, and recommend that they be made. THOMAS A. SCOTT, C. M. LEWIS, Vice-President Pa. B. R. Co. Ilas. of AT., N. C. B. RW. JOHN P. LAIRD, T. PERKINS, Sufpt. Ji. _P. & M. Pa. R. R. C. -A. of., B. & 0. BR. WEVERTON, Washington County, l3fd., November 23d, 1864. To the Officers of all the Raitroad Companies in the United States: GENTLEMEN:-After ten years constant application in perfecting a mode of applying all the Brakes in a train of cars from the locomotive by the Engineer, I feel justified in presenting to your consideration my last improvement, lately adopted by the Northern Central Railway, and now running upon that road on a train of five (5) cars. Before I send detailed drawings of my plan to the companies who have adopted my brake, I propose to make a series of experiments to discover all the laws of friction governing the retarding of trains by equipping a train of ten cars, to be controlled by the Engineer or Brakesman, in such a manner as in my judgment will secure the greatest safety to trains, and economy to Railroad Companies. The want of reliable rules to govern the power applied to Brakes in proportion to the weight of car, has been a great disadvantage to the working of Brakes. Owing to that deficiency, most of cars. are so equipped, that either the wheels slide and become flattened, or the power is so small that the Brakesman cannot produce one-half the effective retarding power upon the train. I discover that upon most of the roads in this country, very little attention is paid to the length of levers in proportion to the weight of the car. But they rely upon the judgment of the Brakesman to apply the exact required power. As the physical strength of men differs, the result cannot be otherwise than the slidcing of wheels, or the want of proper control of the train.. I am very sanguine that the result of the experiment I propose will clearly demonstrate the inefficiency of the present general mode of equipping cars with Brakes. First — I propose equipping ten (10) cars to be controlled by the Engineer or Brakeman, in such a manner that the full retarding power will be obtained, and the sliding of wheels obviated. Second.-To ascertain what proportion of the weight of the car applied to the Brakes will slide'the wheels on a dry, wet, lubricated and sanded rail. TFzird.-What length of lever, or advantage of leverage, a Brakeman should have to do good braking without sliding wheels on cars of different weights. Fourth.-What number of pounds pressure on the wheels are required, to slide them with cast iron, wrought iron, chilled iron, wooden endwise, or parallel with the grain, leather, or other substance usually used as a brake-shoe. Fifth.-How many pounds retarding power a car will produce, at different velocities, per ton, when the brakes are applied at one-fourth, one-half, three-fourths, and at sufficient power to slide the wheels. Sixth.-Within what time and distance a car or train can be brought to a state of rest at different velocities. Seventh.-At what rate of speed a car will pass the different points within the distance that is required to bring it to a state of rest, or whether it is the converse of a falling body. Eightho — Whether the retarding power of the car is practically effected in any way by changing the brake-shoe to different points on the periphery of the wheel. Ninth.-Whether a clog-shoe, the size of a common brakeshoe, will increase the retarding effect on the car by placing it under the wheel. Tenth.-''" The angle offrictionr" for rolling stock when the brakes are fully applied. Eleventh.-All other problems relating to the subject that 2 18 may occur to me, or that may be suggested by the officers of the companies who patronize the experiments. I am, yours respectfully, VWILLIA1M1 LOUGHRIDGE. -- O- } We, the undersigned, agree to pay our slaare of the expenses necessary to make the annexed experiments, provided the sum required of our company shall not exceed one hundred ($100) dollars': 1. J. EDGAR THOIS/ TSON President Pennesylvania ailroad. 2. DEAN RICH:!OND, President 2ew York, Central Railroad. 3. JOHN iW. GARRETT, P2residcnt Batibmovre and Ohio aidlroad. 4. J. M. TAYLOR JOHNSON, President Central t. W. of New JTersey. 5. W. H. OSBORN, President Illinois Central Railroad. 6. S. S. L'HOINiEDIEU, President Cgncininati, ]Yamilton and Dayton _?ai- road. 7. W. Hi. CLEMgIENT, President Little NMiaimzi Railroad. S. H. C. LORD, President zndianoplis and Cincinnati Railroad. 9. AUGUSTUS BREWSTER, President Norwich and Worcester Railway. 10. Mi. L. SYKES, President Southerm lichigan C a$iway. 11. J. H. STURGEONN, Pres. f& Gen. Su2't N. itissvouri aitway. 12. C. M1~INOT, General Su-perintendcnt New Yorlk and Erie Railway. 13. J. N. DUBARRY, General Sziperintendent 2ortthern Central R~ailway. 14. Ri. S. VAN RE NSELAER, General Superlinten,dent Camden and RArwboy Railway. 15. C. G. HAMMOND, Gen. Sup't Chicago e. Quincy Railway. 16. G. A. NICOLLS, GeCn. Sup't Philadelhia e( Readivg Railway. 17. H. F. KENNIEY, Superintendent Philadelpcba, W'iii n,7vgton and Baltimore RTaiway. 18. J. H. HOYT', Sn? erinteetdent N2ew Yorok and 7 ew Iavsen Railway. 19. E. B. PHILLIPS, Siqp't Boston W Worcester Railway. 20. J AS. D. ALsOP, Receiver Ohio anzd Mississippi a'ilroad. 19 It will be observed that, in the above Circular, ten propositions are laid down for investigation; I will give the results in the order in which they stand: 1st. I have perfected a plan that effectually prevents the engineer or brakesman from sliding wheels, yet they can graduate the power from the minumum to the maximum retarding effect on the train. The device weighs the power and stops the winding of the chain beyond the desired pressure on the brakes. 2nd. The investigation of this important problem was the iost prolonged and interesting of the whole series; it is the key to regulate the leverage for the brakesman at the hand brake, or the power of steam, &c., used by the engineer. I discover that when the friction of the brake-shoe is equal to that of the rail, the p2ressure of each shoe against each wheel must be equal to the pressure of ecach wheel upon the rail, less the.friction of the journals. When a car stands upon its wheels, there is nothing to prevent force from putting it in motion, or revolving the wheels, except the resistance of the friction of the journals. Therefore, to cause the wheels to slide on the rails, a counter resistance must be applied to some other part of the face of the wheel, that will be equal to the coefficient of friction between the rails and the wheels, when the force and resistance will be equal, and the wheels will slide or cease to revolve. Therefore, if an eight wheel car weighs 32,000 pounds, each wheel will bear 4,000 pounds upon the rail, and it will require the samne pressure upon each brake-shoe to prevent the revolution of the wheels. When a material is used for a shoe that has a less coefficient of ffriction than the rail, the pressure upon the shoes must be increased in proportion to the difference. For example, if ice had sufficient cohesiveness to bear the pressure, it is evident it would be entirely unsuited for a brake-shoe, as the friction it affords is so insignificant that the brlakesman could not exert sufficient power to slide -the wheels without a greatly increased leverage and loss of time. Or if the friction of the rail and wheel was only equal to ice on ice, then some other mode of stopping trains would have to be resorted to. W~hen the rail is wet, greasy, or sanded, the retarding effect will change in proportion to the coefficient of fiiction that thie different conditions of the rail afford, but the required pressure on the brakes will not change in the same ratio, because w hen the rail is wet or greasy, the wheel, in rolling upon the rail5- accuinulates on its face the water or oil which 20 is upon the rail, and conveys it to tlhe shoe when the brakes are applied; then, if the quantity of the oil between the shoe and wheel is equal to that between the wheel and rail, the pressure or power to be exerted by the brakesman would be the same; but the retarding effect upon the car always changes in proportion as the coefficient of friction between the rail and wheel. As the shoe becomes heated and dry, and -also scrapes the grease from the wheel, it is fair to coincide with practical brakesmen who allege it requires much less physical strength to slide the wheels when the brakes are slippery than when dry and clean. When stoppin g at stations and for other ordinary purposes, if the track is wet and greasy, the brakes must be applied farther from the stopping place; in case of danger, sand should be strewn upon the rails, which increases the friction nearly equal to a dry clean rail, regardless of the condition of its surface. 3rd. To arrive at a correct point for calculation, it becomes necessary to know the power or force that a brakesman exerts at the brake windlass. With tile piresent hand-brake system, there is no means of regulating the power or pressure applied to the brakes, except a ]man's strength; and, as a general rule, the advantage of leverage which he requires is shortened to prevent the strongest brakesmen from sliding wheels. With a view to determine the capacity of brakesmen for hand-brakes, I had a local platform cdnstructed, and hand windlass, in all respects similar to the hand windlass on the platform of a passenger car, except that I keyed on the chain barrel where the chain usually folds, a lever, in length equal to one-half the diameter of the brake-wvheel, so as to determine the exact power a brakesman, in the position he'usually stands, can exert without any advantage of leverage. I thel attached a dynamometer to the chain that usually folds on the chain barrel, then selected seven regular brakesmen, who exerted their full strength on the brake windlass, when the indicator showed the following remarkable difference of power or capacity in the brakesmen:. A exerted a power of 320 lbs. B' " 304 C C L6'' CL as 288 C' D " CC, 272 (6 E CC CC CC C 226 6 F' " C 192 C G, a new beginner, 160 ( Making an average of 251 pounds. 21 To a discriminating, practical railway man, the above table of results will clearly show the imperfections of' the present hand-brake system; and the difficulty of regulating the leverage of cars so as to secure a uniform pressure on the brakes, and retarding effect on the train. As previously shown, the p)ressure on the brakes must be proportionate to the weight of the car, and the leverage regulated to prevent the strongest brakesmlan from sliding wheels. Therefore, if A, with a force of 320 pounds, cannot slide wheels, G, with only one-half his strength, cannot produce more than fifty per cent. retarding effect on the car; clearly showing that, with the present system, the effective retarding power on trains varies proportional to the expertness or physical strength of the brakesman. Assuming that the leverage of all the cars was regulated proportional to the weight of the cars, then if the capacity of A was adapted to apply the brakes to a car weighing 40,000 pounds, G would be suited to brake a car weighing only 20,000 pounds. Therefore, if the capacity of A, (320 pounds,) is taken as a unit for calculation, the leverage or advantage of power must be regulated so as to enable the brakesman to exert a power in pounds upon the centre of each brake beam equal to double the weight of each wheel upon the rail; then deduct twenty per cent. from that sum to prevent the wheels from sliding, when you have eighty per cent. effective retarding power on the car, provided the brakes are constructed-to equalize the pressure on all the wheels of the car. But with G as brakesman, you have forty per cent. A little care in selecting brakesmen would remedy this evil to a great extent. 4th. If wrought iron brake-shoes require a pressure equal to the weight of the wheels on the rail, then the pressure on each of the other materials must be increased or diminished in proportion, as the coefficient of friction of each material is more or less than wrought iron. For example, the coefficient of friction of dog-wood is eight per cent., and butternut twelve, (see test of western woods,) then it would require one-third greater pressure on a dog-wood shoe than one of butter-nut to produce the same retarding effect on the car. 5th. As the resistance of friction is equal at all velocities, and the retarding effect proportional to the pressure on the brakes, the retardl.ng effect on the car will be equal to the pressure on the brakes. 6th. This problem has also been omitted for the present. 22 The following, ho wever, may prove of equal value, as showing how quickly a train may be brought to a state of rest at different velocities; the trials were public with my Engineer' s Brake, and the decisions were given by able railroad officers appointed for that purpose: Time stopDistance run pins in When running at a speed of 56 miles to the hour, the in feet. seconds. tlrain was brought to a state of rest froin the. point - _. where the signal was given, in ) 624 16 2d speed of train 32 miles per hour............................. 408 16 3d cc "c i' 32 "' "' "......................... 412 1 6 4th " 24 " "'....................... 250 16 5th " " " 50 " "...........................21 21 6th " "' 50 l " " Hand Brakes............ 117__ 51 When I made the last stop, I w as convinced the power was not fully applied; and as the friction wheels was greasy, I could not increase it, consequently the train ran 97 feet farther at 50 miles than at 56 nmiles speed, but the time of stopping was also increased 5 seconds. At the same trial with the hand brakes, at a speed of 50 miles per hour, the train ran 1,817 feet, and required 51 seconds time to stop. It is a truth worthy of notice, that where the brlakes are applied to produce the maximum e'ffect, that the timue in stopping is always unifobrm, regardless of speed. The only philosophical solution. I amn prepared to give in relation to this truth is that of the pendulumn oscillating different distances within the same time. To those who are not familiar with this principle of the pendulum, the following experinent will prove interesting: Drive a tack or pin to the ceiling or at any point suitable, then take a plummet and line, and fasten the line so that the centre of the plu mmet will be 39'1013 inches from the point of suspension, then give the plummet an oscillating m.otion, the same as the pendulum of' a clock, and you will discover it will beat seconds with your watch, regardless of the distance it vibrates back and forth. As the plummet is elevated within its arc or gyration, the force of gravity increases sufficiently to force it back thiough the greater distance within the same time. It is fair to assume that the same principle is involved in stopping trains, and that increased momentum forces the train more rapidly through the distance that is required to bring it to a state of rest. 23 7th. This problen was not tested, but I incline to the opinion that it partakes of the nature of projectiles, or the converse of a alling body. 8th. Whe7n the power or force bears on the brake-shoe in a dtirect line from the centre of the shoe to the axis of the axle, the resistance to the motion of the wheel will be equal, regardless of the point on which the brake-shoe is applied. The retarding effect on the car, however, does not depend upon the kind of shoe or where it is applied to the wheel, but solely upon the coefficient of friction between the wheel and rail. All that is required to produce the maximum effect is to bring the wheel nearly to a sliding point, regardless of the means of doing it. 9th. As surface does not increase friction, a clog-shoe will not produce a greater retarding effect than the small point of the wheel that rests on the rail, provided the friction of its material is not greater than the chilled wheel. 10th. The angle of friction for rolling stock or cars on wheels, is the same as that of a common. sled, for the same reason as given to the ninth problem. This varies from 12 to 25 per cent., and depends upon the clean or greasy condition of the rail. -1th. It will be observed t1hat I have discussed a number of problems in addition to the above. I have had no suggest'ios from others except the following practical letter from Joseph Potts, Esq., General 3Ianager of the Philadelphia and Erie Railway. Owing to its pertinence and brevity of expression, I take the liberty of inserting it in this report. I had h hoped to receive from others similar encouragemnent.' our circular received. I see thae our President, Mr. Thomapson, has already subscribed. The information you propose toobtain is much needed; I would suggest that you add to your sixth proposi;ion the words C and on different grades.' The practical result is to so apply the knowledge you gain as to enable the engineer or any. brakesman of ordinary strength to apply so many pounds and no ~more to each wheel, as secures the fnll retarding effect without sliding wheels. Nothing bu't a self-regulating application will answer. No man's judgment can be trained to sufficient accuracy. In compliance with the above request I will give my views upon the relation friction bears to rolling stock on grades, under the separate heading of 24 INCLINED PLANES. I quote the following laws relating to the subject from Scribner's valuable Engineers' and Mechanics' Companion, page 104. When a power acts on a body on an inclined plane, so as to keep that body at rest; then the weight, the power and the pressure on the plane, will be as the length, the height and the base of the plane when the power acts parallel to the plane, that is, The weight will be as the plane; The power will be as the height; The pressure on the plane will be as the base. These properties give rise to the following: General principle. As the length of the plane is to the height or angle of inclination, so is the weight to the power. The length and height of an inclined plane being known, to find the weight that a given power will support upon the plane. The time of describing the whole length of an inclined plane, is to the time of falling freely through its height as the length of the plane to its height.-Olrnsted's Philoso2phy. RBule-Multiply the power by the length of the plane, and divide the product by the height; the quotient is thIe weight that the power will support. Examples.-Let the length of an inclined plane be 30 yards, and its height 4 yards, require the weight that a power of 50 pounds will support upon the plane. 50 multiplied by 30 divided by 4, equals 375 pounds. Let the length of an inclined plane be 5,280 feet, (one mile,) and its height 1,320 feet, (one-fourth of a mile,) require the weight that a power of 8,000 pounds will support upon the plane. 5,280 multiplied by 8,000 divided by 1,320, equals 32,000. Let the length of an inclined plane be 5,280 feet, (one mile,) and its height 660 feet, (one-eighth of a mile,) require the weight that a power of 8,000 pounds will support upon the plane. 5,280 multiplied by 8,000, divided by 660, equals 64,000. The above examples show that if a plane is one mile long, 5,280 feet, and has an elevation of one-fourth of a mile, 1,320 feet, that if a car weighing 32,000 pounds with three inch lubricated journals was placed upon the plane, it would re 25 quire 8,000 pounds resistance, or one-fourth the weight of the car to prevent its descending the grade, less the friction of the journals, which is computed in table A at 290 pounds, which, with 7,710 pounds, would make the force and resistance equal, when the car would remain at rest until an additional force was applied to move it down the grade. It will make no difference whether the resistance consists in hanging a weiglht of 7,710 pounds in addition' to the 290 pounds of resistance of friction of the journals, to a cord extending from the car over a frictionless pulley to the weight, or whether the brakes are applied so as to create a resistance of friction, between the wheels and rails equal to 8,000 pounds, then the resistance of friction from the brakes being equal to the weight and friction of the journals, the car would remain in a state of rest when the weight was removed, but the moment the brakesman would relieve the brakes of one-half the pressure, the car would descend the plane impelled by a force of gravity equal to 8,000. pounds and resisted by friction equal to 4,000 pounds. The force of gravity and the resistance of friction remaining the same, regardless of increased velocity. Therefore the impelling force on the car would be double the resistance, and it would increase in velocity until it met with sufficient resistance of air to bring it to a uniform velocity, at which it would move forever, provided the plane was endless and the machinery, &c., endured as at the start. The above calculation is based upon the presumption that the resistance of friction is the same in descending grades as it is upon a level plane, which is not the case. Friction is alwaocys at itbs mcaximum when the body slides at lright anytes with the line of gravitation. There would be very little friction if a body was sliding down a plane at an elevation of eighty-five degrees. It will be observed from the above, that a grade of 1,320 feet to the mile, is the angle of friction for a car when its wheels are locked, and assuming the friction estimated at twenty-five per cent. in table A, as correct. Then, as friction increases in proportion to weight, it is evident it would prove the angle of friction for cars of differen, weights. Therefore, as gravity acts upon bodies in proportion to their quantity of matter, the force on a car weighing 32,000 pounds on such a plane would be 8,000 pounds, and oni a car of half the weight 4,000 pounds, and the resistance of friction of both would be proportional to their weig't. Therefore if the coefficient of friction of each 26 czar remains the same, their velocity in descending grades would be equal, provided they presented equal surfaces to the air. A train of cars weighing 100 tons moved upon a level grade, with a constant force equal to 1,894 pounds, would give the train a velocity equal to its descent upon a grade of 100 feet to the mile by the force of gravity. 5,280 multiplied by 1,894, divided by 100, equals 99,993 lbs.; the weigh-t nearly that 1,894 pounds will balance on an inclined plane of 100 feet to the mile. Therefore if tle trains are to be stopped within equal distances when the brakes are equally applied to both, the steam power of the train on the level grade must continue whilst stopping, to equal the force of gravity on the train descending the grade. When ascending the same grade a converse effect -takes place, and the force of steamn or 1,894 pounds tractive power would be required for the ascending train to stop within equal distances under the same conditions of weight, resistance, &c. Withw equal conditions equal forces will give equal velocities, and equal resistances will bring moving bodies to a state of rest withlin equal distances. Th-erefore, when a train ascends or descends a grade, -the force of gravity must be added or deducted to determine the distance a train will run in comnparison with a level grade after the brakes are applied. CAR BRAKIES. Next in importance to a complete and reliable locomotive, such as will at all times enable the engineer to comply with the conditions of the. tine table, stands a perfectly reliable and uniform means of retarding trains. I am. compelled to say that the general mode adopted in the United States, so far as it has come under my observation, (aRd I have seen it in twenty States,) is grossly defective, and would not, under a fair investigation, afford a greater average than fifty per cent. retarding power without' sliding wheels. When, if properly constructed, at least eighty per cenlt. should be the minimum average resistance. I allude to the defectiveness of the comnlon hand-bralie, but if brought into comparison with an efficient brake under the control of the engineer, the latter would, if the time of application be considered, afford at least two hundred per cent. greater average safety in case of emergency than tle present slow and unreliable hand-brlake system. As early as 1832, the question of placing the control of the brakes of the entire trainin the hands of the engineer was brought before the English Parliament by George Stevenson. He gave as his opinion before that honorable body, that "' if such a device could be practically applied, it would be infinitely superior to having a brakesman to each car in the train." During the same period (1832 and 1833) he made several efforts to accomplish the purpose on the Buffer principle, but failed to get his plan adopted. Since then the best etalent of' the worldc has been enogaged on different plans and systems to accomplish the saimne end, and vast sums of money have been expended -with a prodigal liberality by railway companies and individuals, but owing to a defectiveness in their plans, or a want of perseverance to pursue the subject until they became familiar with all its contingencies, the general railway management of the world have not universally adopted any special plan. It seems supererogatory for ile to offer an argument in favor of placing the control of the brakes in the hands of the engineer, as every practically experienced railway officer knows that the engineer is the first, in almost every case, to receive and communicate notice of any danger, or when it is important, to quickly stop the train. The Engineer, from the position he occupies, is the " confidence man of the train," and when he sees great danger he has not only all the impulses of self-preservation to induce himn to use all the means placed at his disposal, but lie feels the sacred responslbility of having in his charge the safety of' every passenger, also a comillendable pride in saving his locomotive and train, Fromn a long experience as fireman, -then engineer, and the acquired daring that the p0sition he occupies in always confronting danger inculcates, males him unquestionably the most reliable iaan on the train, to act quickly, cooly, and reliably in an emergency; therefore, it is poor economy to refuse him every practical safeguard. If he has no means at his disposal except to reverse his engine and apply the brakes to the tender, he must resort to the slow process of signalling the brakesman, which will require on an average twelve second's time before the brakesnman gets to the brake windlass and fully apply the brakes. A train running thirty miles per hour passes over forty-four feet of rail per second, or 528 feet within twelve seconds; and generally, when hand-brakes are used, runs about fifteen hundred feet at thirty miles per hour. With an efficient means in the hands of the engineer 28 to apply all the brakes, four hundred feet on a level grade is always a safe distance within which to stop the train, without injury to passengers. After a long practical experience, I am convinced that the safety of the passengers, train-men, and train, depend very much upon a well-regulated engineer's brake; but to be efficient, it must be well constructed, and have reasonable attention, as well as the locomotive, when it can always be relied upon to stop the train for all purposes. I know of no part of the machinery about rolling stock that is constructed more indifferently than brakes generally. The rattling of some of them is nearly sufficient to signal a station. HANGlNG BRAKES. There is quite a diversity of opinion as to the best mode of hanging brakes. I have seen them on top of the wheels, outside of the trucks, inside of the trucks, on one side of the trucks, so as to bear on only two wheels of the four; clogshoes to throw on the rail, and grippers to press on each side of the rail. Sometimes the brake-shoes were hung low, so as to nearly touch the rail, and again so high as to rub the truck frames, each party claiming some peculiar merit in his particular mode. All parts of the periphery of the wheel being equi-distant from its axis, the brake-shoe must act on the wheel lever equally; therefore, there is no advantage in one part over the other as long as the power acts in direct lines from the shoe to the centre of the axle. In hanging the brakes on top of the wheel the shoe requires to be kept too far from the wheel to allow for the vibration of the sprincgs, and when the springs break the brakes fall on the wheels, unless the fulcrum is put in the boxes, which interferes with the pedestals. On the whole, owing to room, &c., a proposition to put the brakes on top of the wheels, with the present mode of trucks, should not be entertained for a moment. I have known gentlemen to contend that braking on top of the wheel tended to press the wheel on the rail and increase the retarding effect. I generally reminded them of the story of the man lifting himself up by the handles of a tub, when standing within it. Brakes hung outside of the truck are, in my opinion, at their proper place. They are easily shod or taken down for repairs, and the inspector can see any defects at a glance. Wlhen hung between the trucks they are very difficult to put up and take down, 29 and the power applied to the brakes always tend to spread the wheels, which, with the weight of the car body, tends to weaken the truck, especially when the cord or straps of iron that hold the pedestals together break. Brakes applied to one side of the truck and to only one pair of wheels, create a tortional strain on the axle equal to one-fourth the weight of the car, or the resistance of the friction, and tend to loosen the wheels on the axle with thie same strain. Clogshoes to be pressed on the rail instead of the wheels I have seen tested, the shock which they give to the train in their application, independent of the inconvenience of applying and usirg them, renders the plan entirely impracticable. I witnessed a trial of them in the West, when the track was strewn with the firagments the first trial. The idea Of using grippers on each side of the rail is unfeasible. Several persons have recommended placing independent wheels on the axle, inside of the car wheel, so as to obviate the wear of the car wheel. This would be impracticable and useless, as the rubbing of the shoes on the wheels is a decided advantage, for it tends to keep the surface even, as the weak or flat places on the wheel is never touched by the brake-shoe, as it passes over them, and abrades only on the higher or outer part of the shell or chill. The best point that I have discovered for hanging the brake beams, is to have the centre of the beam four inches below -the axis of the car axle. When the beain is hung level with the axle, the pressure tends to " rock " over the brasses and close the wheels together, which increases the distance that the brakesman must wind up his chain. Hanging brakes to the bodies of cars is objectionable, as when the car turns on heavy curves it presses the shoes laterly against the flanges of the wheels, costing considerable power. Care should also be oblserved when hanging the brake-bealn- to the truck so as to prevent the shoes rubbing the flanges when too much lateral play takes place in the journals. WVhen the brake-beams are hung to the trucks, they should be fastened so that the shoe when new barely touches the face of the wheel. They are frequently hung away froml the face of the wheel, as much as two inches, so that gravity shall assist the springs to keep them away from the wheels. In many cases springs are dispensed with and gravity alone depended upon to keep the shoes from slamming against the wheels, If the beams are allowed to swing back and forth without any interruptions from springs, the wear 30 on the shoes and retarding effect on the car is equal to having them hung close to the wheels. It is poor economy to dis pense with springts or to depanol upon gravity to keep brake-shoes away from the wheels. B rake-shoes should always be hung parallel with the face of the wheel. This is one of the most difficult problems relating to -the whole subject, from the fact that when the springs bearing the truck yields or gives way, it lowers the brake-shoe from its original relation to the circum-ference of thle wheel, but if the springs under the truck maintain their original set, there is no difficulty in keeping the concave shoe parallel with the convex face of the wheel, provided proper means are used to hang the brakes. The heavy levers and connecting rods that fulcrate in the levers, tend to throw t1he shoe inwardly at the top, and causes the shoes to wear or rub the wheels, cos-ting in the aggregate a serious loss of power. The brake-beams should, when hung to the truck framie, balance perfectlyT, and the fulcrum on which the beam pivots, should be at the top of the shoe, or its equivalent, to prevent the beam f~rom turning or rolling, but when the lever sets some six inches inside the beam, this is nearly impossible when running on undulating tracks. BR3AKE-SHOES. To judge from the variety of materials I have seen used for brake-shoes, there is certainly a great diversity of opinion on that subject. The following are the principal ma'terials used. Wrought iron, cast iron, chilled iron, wood parallel with the grain, wood endwise, old (junk) rope, and leather. All else being equal, I would prefer wrought iron for a brake-shoe, as it wears longer and gives a more uniform friction than most other material. You can base your calculations for leverage for the brakesman or for a power brake with more certainty, as the coefficient of friction of the wrought iron rail and wrought iron shoe are generally about the same. Cast iron makes a very good shoe, and is decidedly more convenien t to attach to th1e brakes, anfd when worn out the remnant can be cast over, but the metal frequently changes from a soft surface to a chill which changes the friction and necessarily the power to be applied by the brakesnan. Chilled shoes possess no advantage over cast iron except in wear, and as the chill does not exceed one quarter inch in depth, when the chill is worn off the soft 31 metal changes the relation of friction. Wooden shoes may do very well -for roads that have no grades, but they are so variable in the friction they afford, that the power changes as r arch as 33 per cent. (see butternut and red beach of western woods) in the degree of friction, creating a great liability to slide wheels, and they frequently burn out on level roads, Wood endwise has no advantage, and is liable to split unless very heavy, which makes them unworthy of consideration. Old (junk) rope is too inconvenient to apply for a brake-shoe; leathler is too scarce for general use, and has no advantage. The only question as to the best brakeshoe is, to select a material that is uniform in friction, one theat is cheap and can be quickly put on and taken off the brako-beanms, tlius saving time, and that can be fastened with per-,ect security to prevent its falling on the track; then adopt it and avoid having several materials for shoes. Suppose the coefficient of butternut to be fifteen and wrouoght iron ten, then the brakesrman would apply one-third more power for wrought iron than he would for butternut, when the result would be the same in retarding tihe car. T1he great object in brakes is to have a uniform retarding effect on the car, to do this the pressure on the brakes and friction of the shoes imust be uniformly graduated to the weight of the car, or the wheels will slide. The power applied to.the brakes should always act directly on the centre of the shoe, otherwise the shoe will wvear off -faster on one end than the other, (examine your worn out shoes.) If' the centre of the shoe is in the centre of the blake beam, the power should also act direct to the centre of the a xle. SURFACES. in 1832 and 1833 M. l NorLn, of the French Academny of Science, during a series of experiments, under the patronage of the Frle'ch Government, confirmed the truth of Coulomb's theory that friction does not increase with an increase of surra.ce, and this truth is generally conceded by the ablest civil engineers in the world. Notwithstanding this fact, I hiave had frequent warm controversies witlh practical nen upon the subject, and they evinced much surprise that I should undertake to defend such a philosophy. On. one oceasion, a-ier a spirited discussion wit' an able rail-road oficer upon this subject, we determined to decide the question in a practical -wvay, and selected twe valve plates; the one 32 was laid down with its broad surface upwards, vwhich was 18 inches square, the other of the same dimensions and one inch thick; therefore the broad surflces each contained 324 inches, whilst the surface on the edge contained but 18 inches or one-eighteenth the surface of the face. We first placed the two broad surfaces together and drew the top plate over the other with a spring balance, which showed the coefficient of friction between the two broad surfaces to be seven pounds; we then turned the plate upon its edge, and to the astonishment of my friend, the resistance or friction was exactly the same. Now if any of my readers doubts this theory, they can malke similar experiments, when they will also be convinced of the truth of Coulomb's theory, but they must be careful that the suriaces are equally polished and lubricated, and of the same material; although different materials sometimes have the same coefficient of friction, generally they produce very different results, (see test of western woods.) Take two cars of the same weight, say 32,000 pounds each, place the one on runners, in the manner of a common sled, and the other on eight wheels, in the usual way, with the wheels locked to prevent them from revolving; then take a dynamometer and pull them both on the rail, and the resistance will be the same, say 8,000 pounds. In this casethe wheels resting as they do on a surface not exceeding one square inch, willcreate as much friction as the runners having 240 times'the surface. Will the retardinzy eqect on a car e be the same wwhe the wheels slide as wlhe they merely revolve? Evidently on a dry clean rail, the nearer a wheel approaches a sliding point on the principle of the sled, the greater the retarding effect. And I do not doubt when it slides the maximum friction is produced. VWhen the rail has greasy matter on it in spots, the moment the wheel slides it collects the grease, and lubricates the whole surface of the rail; whereas, when the wheel revolves, it has all the parts that are clean to adhere to, creating a greater retarding effect than if the wheels were to slide on the rail. Upon this principle a locomotive having three pair of drivers, has an advantage over one pair, as when one pair rest on greasy spots, the others may rest on clean parts of the rail. 33 MECHANICAL POWERS. The pressure on the brake-shoe being greater than the capacity of the brakesman, it becomes necessary to use some one of the mechanical powers to enable him to apply the required force on the brakes. The lever, the pulley, the inclined plane, the wedge, the screw, the toggle joint, cog gearing, and almost every form into which the mechanical powers can be turned, have been used to apply brakes. There being no gai~n offorce by mecharnicaipowers, and great loss by some of them, it is important to select those belt adopted to the construction of the trucks. The toggle joint, owing to its sudden change of power when' the shoes wear away, miakesit totally unsuiited for the purpose. The screw absorbs power rapidly by friction, and is slow when the brakes are to be relieved; avoid its use. The wedge generates too much friction. The inclined plane, either in its simple form, or as a cone for the chain to fold upon the chain barrel, is unfit'for use, as it changes the relation of power when the shoes wear and lost motion occurs, often requiring six inches more fold of chain. The lever has ~ decidedly the preference in power and convenience. The single pulley next, which is convenient when levers cannot be readily substituted. Cog gearing is a waste of labor, as the present plan of folding the chain upon a chain windlass is much simpler and'of equal power. There are great difficulties in applying brakes with'the plain lever now in general use, which but few practical: menfully appreciate. To avoid breaking off the break windlass, it becomes necessary to set them on the platformns right and left, about twenty inches fronm the centre of the car; then to avoid the buffer the levers have to be set at an angle from the centre of the brake beam to meet the direct line ifrom the lever to the brake windlass. Then the connecting rod that passes from one lever to the other, runs at at angle; again, the rod that passes from the top of the lever of the first truck, to the same point in the lever in the second truck, has also to pass at an angle, and so on until the connections between the two brake windlasess are made; consequently, when power is applied to either hand-brake, the effect is to twist the rods and levers, simply because the power don't act in direct lines, but travels in zig-zag lines, causing much lost motion, 34 and strain to the levers and their connections, and delay in applying the brakes. There being a great disparity between the power of the brakesman and the pressure required on each brake-beam, it becomes necessary to give the brakesman an advantage of leverage equal to the difference; consequently, we take A. (see table) as a standard, and have 320 pounds as a unit of power when a sixteen-inch brake wheel is used. Then if the chain barrel gives, say six times leverage, we have 320 multiplied by 61-, equals 2,000 pounds on the top of the lever; then if an advantage of fdur to one is given in the lever that sets in the brake-beams, we have 2,000 pounds multiplied by four, equals 8,000 pounds in the contre of each brake-beam, and 4,000 on each brake-shoe, the power necessary for a car weighing 32,000 pounds; then deducting twenty per cent. from the power required on the centre of' each brake-beam, and you have 6,334 pounds the actual power required on the centre of each brake-beam to avoid sliding wheels for a car of the above weight. This would require the lever in the trucks to be shortened on the lon g end one-fifth or about 5- inches, and gives the following dimensions, nearly, for all the brake apparatus: Brake wheel, 16 inches diameter. " shaft, 1-4 " Chain, to fold on the brake shaft, i and I1 wide. Rod, that connects with the chain, -i. Lever, 7 inches between the two first holes, and 22j for the other, 21 by i- in centre or middle hole. The other connecting rods and levers should correspond in power proportionally. These dimensions must be changed proportionally to suit the weight of heavier or lighter cars. [A] TABLE sholclig tlheorelically the power required to pull an eilght-wheeled car, of thirtl-t'ree inciee dinceleer eacih, weighing, zhen loaded, thirly-two thousandpoun poz cds, with journals of various dianeters, from one to sixteen intches. Also, philosophically accouznting for the advantages in econonzmy of friction gained by the use of wheels and joutrnals, insteatd of sech devices cas woald slide the body to be moved upon the principie, or in the manner of a simp2.le sled. The journsals and bearings being smooth and lubri- I w I I' c,5:' cated rubbing surfaces, the coefficient of friction, ac-: ~ a, o The ratio (in proprtion to respective diameters of cording to Morin, would be 8 per cent. —say, howreve, F~ P4 z4 journals and wheels) ofthe riction upon thejournals 10 per cent. —instead of- 25, as calculated in the last zK w R vto that upon the periphery of the wheels —the coeffi- column, being the coefficient for the wheel slisidmg on - " F~.ci; cient of friction for the surf.tces in contact being the the rail, and you have _ a p same. Per centage of friction onl a 0 r a c the journals taken in con- o O z~:Z; W; Z Z;;, SUBDIICxtD INTO3 nection with the true co- Power in pounds required z, i i Ha a a Per centage of friction on I[Power in poui!ds required efficient for smooth sur- to pull the car constructed a- iz awn journals as compared withll to pull car with journals faces comparel witla the ihewit smootl anldlublricated Ea 1 Z. < i w ~ t;hat upon the surfaces on constructed withl such rub- friction upon the wheels jjournals. ag the wheels when sliding. bing surfaces. when sliding. _ __ _ o-7 1 33 25 pr. t. 32,00 8,000.0303 242.4.012) 96 9 6.0 2'.'. 1'.0606 484.8.0242 [ 193.9 12.1 3.'.'. " j o.0909 727.2 -.0363 290.S 18.2 4.' ". i.1212 969.. 3.0485 387.8 24.3 5.. " ".1515 1212.1.0606 484-8 30.3 6.. ".1818 1454.5.0729 581.7 36.4 7 " " " " -.2121 1696.9.0848 678. 42.4 8..'. "; " " 2424 1939.3.0969 775.6 48.5 g9.(.. I 218 t;.2727 2181.7.1096 872.6 5 4.6 10 "c'.3030 2424 2.1212 969. 60.6 11 I.333 2666.6.1333 1066 6 1 (6.6 12 ". ".'.3636 2909.0.1454 1163.5 72.7 13 i t 3939 3151.4.1576 1260.5 78.8 14 I" " "'.4242 3393.8.1697 1357.4 84.8 15 1 " "..4545 36:36.3 1818. 1454.4 90.9 16 " "'.4848 3878.7.1939 1551.4 96 9 16 t. "' " 5000 4000 2000 1600 100. SUPERiIC NIAL EXPERIMENTS WITH DIFFERENT WS'"VTERN WOODS ON WROUGHT IRON. 13MATERIAT, AT REST, WEIGIWT OF MATERIAL, WEIGHT TIME PASSING I Wrought Tron. In Motimn —In pounds. In lbs. and oz. on ne Foot. Elm, with double we:ght.............. 200 20 3 minutes. Elm...10..................................... I00 10 3 Poplar........................................ 100 IQ16 3' White Aslh....... 100 - i 3 White Pine 1i 0 11 3l " Butternut. 100 1 12, 3 C Bass XWFood 1.......I 00 10 I 3' Black Walnut.100. 3............ T0 9 8 Red Beach..........................! 3 Yellow Pine................................... I. 0I I 3 " White Oak....... 0.........................., 8 3 1 Hickory....................................... 10. 1 3 10010 Cherryy............. o. 100 i 1. 31 Red Maple............................. 100 i 3 3 " Dog Wood........................ 100 8 3 __..._._ _. _,_ ____.,,__, 3 =