Brake, AIR

or ATMOSPHERIC. Device for putting on or off, by the use of compre ed air, the brakes which retard the motion of a railway train. An air-pump on the locomotive compre es air into a reservoir (usually under the foot-plate), and from there a pipe may carry the air to the cars of the train and to cylinders under each car. This pipe is made continuous by rubber hose connections at each end of each car. The engine driver by opening a valve in the engine-cab can allow pre ure from the main reservoir to pa into the pipe, and so to the brake-cylinders of the cars, and by acting on the movable pistons in these cylinders the air-pre ure applies the brakes.