The Westinghouse non-automatic or "straight" air-brake, patented in 1869, consists in its simplest form of a direct-acting, steam-driven air-pump, carried on the locomotive, which forces compressed air into a reservoir, usually placed under the foot-plate of the locomotive. From this reservoir a pipe is led through the engine cab, where it is fitted with a three-way cock, to the rear of the locomotive tender, where it terminates in a flexible hose, on the end of which is a coupling. The coaches are furnished with a similar pipe, having hose and coupling at each end, which communicates with one end of a cylinder containing a piston, to the rod of which the brake-rods and levers are connected. The application of the brakes is effected by the engine-driver turning the three-way cock, so that compressed air flows through the pipe and, acting against one side of the brake-cylinder piston, applies the brake-shoes to the wheels by the movement of this piston and the rods and levers connected to it. To release the brakes the three-way cock is turned to cut off communication between the main reservoir and the train-pipe, and to open a port permitting the escape of the compressed air in the train-pipe and brake-cylinders. This brake was soon found defective and inadequate in many ways. An appreciable time was required for the air to flow through the pipes from the locomotive to the car-cylinders, and this time increased quickly with the length of the trains. Still more objectionable, however, was the fact that on detached coaches the air-brakes could not be applied, the result being sometimes serious collisions between the front and rear portions of the train.
[Illustration: FIG. 1.--Westinghouse Air-Brake.
Section through Triple-Valve and Brake-Cylinder.]