BRAKES. The Westinghouse Quick-Action Brake.—In 1S86 a practical test was made upon a train of 50 freight cars, to determine the applicability of existing brake ap paratus to such a train service. This test was made upon the Chicago, Burlington & Quincy Railroad, under the direction of the Iklaster Car-Builders' Association. It established the fact that, when the brakes were applied from the locomotive with full force, the reduction of air pressure in the train brake-pipe progressed gradually from the forward to the rear part of the train, causing the application of the brake upon the fiftieth car seventeen seconds later than that upon the first car. The retarding effect of the brakes applied to the forward ears, accumulating as it passed backward toward the nnretarded rear of the train, was to close up the space between consecutive cars (due to lost motion in the couplings and compression of the draw-springs), and to produce severe and injurious shocks upon the rear cars and their lading.
It became evident that, to avoid such shocks and to give satisfactory results in this class of railway service, the application of the brakes upon successive cars must occur at such a rapid rate that no considerable retarding effect of the brakes shall be produced upon the for ward part of the train before the brakes are in action at the rear end of the train. ments made by the Westinghouse Air-Brake Co., in the development of the quick-action brake, demonstrated that, with the closed coupling between cars and springs of such elasticity as those commonly employed in the draft-gear of freight-cars, shocks at time rear end of the train, of such magnitude as to injure cattle. could not be prevented, if the interval of time between the applications of succeeding brakes exceeded -05 second; or the brake upon the fiftieth ear must be applied not later than about 2'5 seconds after the application of that upon the first car. These conditions are fulfilled by the quick-action automatic brake, by the use of which the brakes upon 50 freight-cars may be successively applied in 2.25 seconds, or with an interval between the applications of succeeding brakes of but -045 second.
The controlling element in this system is is discharge of air from the train brake-pipe at each car, by the operation of the triple valve, to cause the operation of the triple valve upon the next succeeding, car ; that is, a quick discharge of air from the train-brake pipe (either through the engineer's brake-valve, by the engineer, or at any point in the train), causing the nearest triple valve to operate, the others are successively operated by repeated discharges of air from the train brake-pipe, each triple valve responding to the discharge through the next preceding. The length of the main train brake-pipe, upon a train of 50 freight-cars. is L900 ft. The remarkable results attained, in the application of the quick-action automatic brake, will he appreciated when it is remembered that the elasticity of dry atmospheric air permits the propagation of an impulse or vibration, under the most favorable ciremnstances, only at the rate of 1,090 ft. per second. Sounil—a most perfect example—reptires 11 seconds to travel unimpeded through the atmosphere a distance of 1.900 ft. Yet the quick-action brakes are applied by an impulse which actuates a piece of mechanism, which in turn pro duces a second impulse. which actuates a second piece of mechanism, and so the impulse is forty-nine times and caused to travel 1,900 ft., against the retarding influences of a comparatively small pipe, having a sinuous course and a vast number of irregular shapes and sharp turns, in the inconceivably short time of less than 21 seconds, or with a velocity SO per (alit of that of sound. Such results have been attained through a slight modification of the triple valve of the plain automatic brake (IT which name the former Westinghouse ant otuatic brake is now known), with the addition of a few supplementary parts. These modifieat ions are such that they alter in no respect the fnnetions performed by the triple valve of the plain automatic brake, and the additional parts operate only when a quick stop of the train is requ i red.