Discussion. American Locomotives and Rolling Stock

AMERICIN LOCOMOTIVES AND ROLLING STOCK. ' 385 l@. COLBURNconsidered the subject already well worn-indeed almost threadbare. There were but few engineers who had studied the peculiarities of American rolling stock, with reference to their own practice, who were not already familiar with it in all its de- tails. Many members of the Institution had visited the States, and had examined the question there for themselves. Beyond this, there was Captain Gakon's ample report upon American railways, accompanied by what might almost be called working drawings of every variety of rolling stock.' After that came 'Rh. Neilson's Paper before the Institution of Engineers in Scotland ;'? and since then there had been almost continuous publications of everything of interest on the other side of the Atlantic with reference to this subject. Although he had not been in the States himself for eight years, he was in constant communication with railway engineers and managers there. Most of the statements in the Paper, which might lead to some discussion, were matters within his personal knowledge: inother cases hehad derived his information from numerous printed andwritten documents sentto him by the managers of the leading lines in the States. Mr. HEMANSdirected attention to the fact that, on a length of railway of 42,000 miles in America, the whole train service was performed by fifteen thousand locomotives; and as far as could be judged,those engines were smaller and less powerful thanin England, where a length of 15,000 miles was served by ten thousand engines. Though a comparison of this nature would be modified by the qualityof the service-such as an increased number of trains and greater speed-still it was almost as 2 to l, and to that extent was in favour of the American engines. He had calculated the resistance of the train, in the experiments made by Mr. Colburn on the Erie railroad, where a gross loadof 1,572 tons had been taken up a gradient of 1 in 880. This was certainly a very extraordinary result. Taking the friction of the load at 8 Ibs. per ton-whch was the accepted ratio in England, -the friction of the engine at llilbs. per ton, of t,he tender at 12 lbs. per ton, and the effectof gravity on this gradient 2& Ibs. per ton, and adding these to the load, a tractive force of 16,826 lbs. would be arrived at, which, when divided, would give a coefficient of adhesion of a little over 24. In other words, an engine on four wheels would be able to go up a iess gradient than 1 in 3. On the Delaware division of' the Erie railroad, the same engine had taken up a gradient 3 miles long, of 1 in 117, a gross load of 514 tons; this would produce a resistance of 14,156 lbs., or a co- ~ -- 1 Vide " Report to the Lords of the Cnn~nitteeof Privy Couucil for Trade ant1 Foreign Plantations, on the Railways of tllo United States." By Ccpt:\in Dougln~ Galton, RE. Folio. Lond., 1857. Vide Trsns. Inst. Civ. Enx. $cot., vul. i. p. 11 F). I18w-e:). N.s.] 2 (1 Minutes of the Proceedings of the Institution of Civil Engineers 1869.28:385-439. 386 AMERICAN LOCOMOTIVES AND ROLLING STOCK. eficient of adhesion of 2-8 ; so that the engine alone would run up a less gradient than 1in3. Assuming that there was some mistake, and thatonly @h of the adhesion given was available, the resistance would be 6 lbs. per ton, including the resistance of gravity ; and if it were kth, the resistance would be 5 *4lbs. per ton only, of which nearly one-half would be due to gravity. Even if an error had crept into the report of the experiment, he thought there was still much to be considered with regard tothe resistance of rolling stock in Ame- rica, as there it seemed to be very much reduced, compared wit,h the 8 lbs. per ton which wasassumed in England. He believed the use of the double bogies to every wagon, which was apparently universal in America, of central buffers and drawbars, instead of side-coupling and close-coupledbuffers, and moreover, of the closed oil-box, by which the dirt in the common railway grease was avoided,-had greatly reduced the resist'ance to railway trains, and ought to induce a careful study of improvements for rolling stock. He disapproved of t'he stereotyped make of English locomotives and rolling stock, and of the enormous weights placed upon a singlepair of wheels. He had been informed of instances in which a weight of 18 tons had been put upon a single pair of wheels. These weights were very injurious to the permanent way. The practice of distributing the weight of the locomotive on a larger number of wheels was indispensable in America, where the permanent way was not very durable, and must lead to greater economy in wear and tear, and in the maintenance of the road. The limit to the distribution of weight by increasing the number of wheels must depend on thelength of the wheel-base. Even if great weights could be drawn by locomotives without injury to t.he permanent way, he believed the present rolling stock and locomotives would require considerable modification. Mr. Fairlie's engine afforded the means of greatly diminishingthe friction and weightupon individual wheels on a small wheel-base, while the tractive power of the locomotive was increased. It had been too much the habit to drive over all lines, whether main lines or small branches, the same stereotyped form of heavy locomotives and rolling stock. Where the traffic was enormous and ever-flowing, heavy engines and rolling stock might be suitable ; but in such countries as Ireland, where the traffic was small, it was a wasteful expenditure to employ engines of 40 tons weight for drawing five or six carriages and a luggage-van, and but few passengers ; and it was quite time to reduce the needless expenditure by which the profits had been sndlowed up. Mr. W. BRIDGESADAMS remarked that a bogie was a short truck with a vertical pivot, allowing it to swivel beneath a superin- cumbent, load. The earliest type was to be found in the timber- trucks of the railway. In carrying large sticks of timber, it was impossible to construct EL wagon long enough for the purpose, EO Minutes of the Proceedings of the Institution of Civil Engineers 1869.28:385-439. AiUERICAN LOCOMOTIVES AND ROLLING STOCK. 387 the timber wasplaced on two trucks far apart ; but it wassoon found that, under such circumstances, the impediment to free running caused the vehicles to run off the line. And so saddles mere placed in the centre of each truck, each with a vertical pivot, and the timber being laid on the saddles, the trucks were free to move round the curves. Thus,then, the bogie system resolved itself into vehicles with short wheel-bases instead of long ones. The drawing in Mr. Chapman's patent showed a bogie applied to the hind end of an engine, evidently originating in the perch-bolt and wheel-plate of the ordinary road-carriage, but with four wheels instead of two, and the guidance by the rails instead of the pole. But short wheel-bases ' wabbled,' thoughrunning with less resistance than long ones. The long bases, with greater steadiness, involved greater friction without being quite steady. So passenger carriages were screwed tightly together, and converted more or less into sledges, to increase the steadiness, but with the result of convert- ing oscillation into vibration and grinding friction. Goods and coal trains, on t'he contrary, mereloose-coupled, for the simple reason that otherwise their resistance would be so great as to overpower the haulage ; and their sinuous motion showed how the wheel3 strove to follow the path of least friction over theirregular surfaces and incessant short curvatures of the rails. There was a proportion of length to breadth ; i.e., the distance between the axles, andthe width of gauge, andthe former must be more or less in excess of the latter. The earlier bogies were made with the wheels nearly close together; and the result com- monly was, especially when running fast, that the bogie dragged or sledged, and the wheels recoiled from the contact with the outer rail, and took positions abnormal to the curves. To correct this, it became needful to lengthen the bogies. But under all conditions, whether a short or a long wheel-base, it was proved that, with rigidly fixed axles, even when truly parallel, and at a right angle with the centrallongitudinal line of the vehicle, the leading wheel- flange on curves got forced against the outer rail, and the trailing wheel-5ange against the inner rail, and this placed the vehicle in B diagonal position. And the longer the vehicle, and the sharper the curve, the greater was the grinding and vibration. In Eng- land, there was a remarkable sample of vehicle, in which the breadth of the gauge exceeded the distance between the axles. It was the horse-box of the Great Western railway. Originally these vehicles were of great length, to contain many horses, which were expected to journey quietly side by side. But they would not stand trans- versely to therails ; and so the eight-wheel horse-boxes were cut in two, resulting in a &feet coupling with a 7-feet gauge. There was then nothing in theprinciple of the.bogie other than thatof a short truck, which, unsteady in itself, bad the unsteadiness partially neu- 2cz Minutes of the Proceedings of the Institution of Civil Engineers 1869.28:385-439.

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