Car-coufilings.—To connect the cars of a train with one another and with the engine, a coupling of some form must be employed. The simplest form of this device, the link and coupling-pin attached to a draw-bar, is in common use in the United States. In Europe there is employed a more rigid form of coupling, a view of which is shown in Figure This is the so-called "screw-coupling," consisting of a right- and left-handed screw shackle, by which a coupling- can be made as rigid as may be desired. The draw-bar, passing beneath the car-frame, is connected to a spring- of some form, which lessens the jolt of the sudden starting of the train. When the train stops, each car, by reason of its momentum, tends to push up against the one in front of it, and in case of sudden stoppag,e for any reason the shock of the cars butting against one another would severely strain the inelastic frame of these vehicles, were it not that each car is provided with elastic buffers to receive these frequent shocks. Both these devices—buffing- and drawing-springs—are made sufficiently clear in Fig ure 7. Figures 8 and 9 exhibit modifications of the buffer-spring, the first (fig. 8) having a special spring of hardened steel and the second (fig. 9) one of rubber, in Nybich rubber rings alternating with brass disks form an air-cushion which yields with the slightest pressure. As an additional precaution against the breaking of a coupling, gnard-chains, which ordi narily hang slack, are sometimes provided between the cars. These chains are of somewhat doubtful utility, as the shock that would break the ordi nary coupling would be more than likely to snap the chains.
Serftiv-coztfilings.—In order to effect the coupling of the cars by the devices here described, the train-hands must step between the cars—a prac tice that is attended with much danger, and that is accountable for more fatal accidents than any other single cause. To avoid this danger, many devices have been proposed for coupling cars from the platform and by appliances working automatically. Some of these are exceedingly ingeni ous, and to some extent have been utilized. The want of uniformity in the construction of cars, especially those for freight service, has thus far proved a great hindrance to the general adoption of safety-devices of this kind. On Plate 31 (figs. 4-6)is shown the Janney coupling, adopted by the Pennsylvania Railroad, and in g-eneral use on other American railways.
Brakes.—To stop a train at stations or elsewhere, to diminish its speed in descending a grade, or to bring it quickly to a stop in case of danger, some form of brake mechanism is necessary. It is a mistake to suppose that the ideally perfect brake is one that will bring a moving train to a standstill instantaneously. Such a mechanism would be utterly unavail able even were it possible to realize it in practice. It must be borne in mind that the vis viz.er of the moving car cannot be overcome without the expenditure of a corresponding opposing force. If the wheels of the 1110V ing car are arrested suddenly, the entire train will slide upon the rails until friction brings it to rest; or if sliding be prevented, the result will be a shock substantially like that caused by the collision of two trains, with the same destructive effect upon cars, passengers, and freight. The efficient brake,
therefore, is the one that will stop the train quickly, but not instantly.
ihria-brakes.—The ordinary hand-brake (once universally in use, but now discarded on nearly all passenger-trains in American railway practice in favor of the far more efficient power-brake) is commonly placed upon both ends of the car, and is operated by the guard or brakeman from the car-platform or the roof. It acts on the principle of applying pressure by means of a brake-block of wood or iron to the periphery of the wheels. For this purpose a brake-wheel or lever is placed on the front and rear platform, by the rotation of which a chain is wound up or a combination of rods, levers, etc., is actuated, by means of which the brake-blocks are forcibly pressed against the wheels. One form of the hand-brake is shown on Plate 3o (jig. 11). The operative mechanism is sometimes a screw, but more commonly a chain the tension of which is maintained by the inter vention of a pawl and ratchet. The forms of braking devices are nearly as numerous as those of car-couplings. The subject may be disposed of, how ever, by the statement that the most perfect system yet devised is the con tinuous brake applied by the engine-driver from his cab. Several plans of this order have been proposed, the actuating power being compressed air, vacuum (atmospheric pressure), and fluid pressure.
continuous-brake system worked by compressed air, devised and perfected by George Westinghonk, Jr., of Pittsburg, Pa., has been by far the most successful, and is now everywhere in use in the United States on passenger-trains, and is rapidly being introduced on Euro pean roads. One of the special merits of the Westinghouse system is that it is not only continuous—that is, capable of being operated from a single point throughout the entire train—but also automatic. Normally, the pressure of the air in a continuous pipe and reservoirs beneath each car of the train keeps the brakes off. When it is desired to apply the brakes, the air-pressure imist be reduced, when a valve of peculiar construction is brought into action and effects the application of the brake. To release the brakes, the engine-driver must restore the pressure in the brake-pipe. From this explanation it will be observed that in the event of an accident by which the brake-pipe is broken—as, for example, by the parting of one or several cars of a train—the escape of the air would reduce the pressure, and the brakes would be applied at once, automatically. The efficiency of the air-brake may be duly estimated by considering that, with its use, a train travelling at the highest attainable speed may be stopped within its ONVI1 length. Its general adoption by railway managers has contributed more to the safety of railway travel than any other single invention.