AIR BRAKE 



119 



AIR CELLS 



on fools who thought they could "stop trains 

 with wind." Fortunately, however, Andrew 

 Carnegie and several of his friends were willing 

 to bear the expense of an actual test, and in 

 October, 1868, the first train equipped with the 

 Westinghouse air brake ran from Pittsburgh 

 to Steubenville, Ohio, a distance of forty-three 

 miles. The experiment was entirely successful, 

 and proved that a train could be stopped 

 within its own length. The old-fashioned hand 

 brakes are still used in sections where traffic 

 is light and every train has only a few cars, 

 but on all the great railway systems of the 

 world the Westinghouse automatic air brake is 

 used. It has also been adapted for use on elec- 

 tric railways, the power being furnished by an 

 electric motor instead of by a steam engine. 



triple valve automatically slides so that the 

 auxiliary reservoir is placed in connection with 

 the brake. If, for any reason, the pressure in 

 the train pipe ceases, the train comes to a stop. 

 When the engineer wishes to apply the 

 brakes, he throws the handle of the air brake 

 valve to a specified position, thus permitting 

 the air in the train pipe to escape into the open 

 air. The escape of the air lowers the pressure 

 in the train pipe, and the triple valve, respond- 

 ing to the higher pressure in the auxiliary reser- 

 voir, slides back, thus opening an aperture 

 through which the air in the auxiliary or car 

 reservoir reaches the brake cylinder. The 

 pressure of the air forces the piston of the 

 brake cylinder forward, and the piston in turn, 

 through proper levers, presses the brake shoes 



DETAILS OF AIR BRAKE MECHANISM 



(a) Hose and coupling 



(b) Brake pipe 



(c) Pull rod to brake beam 



(d) Cylinder levers 



(e) Emerging reservoir 

 (/ Service reservoir 

 (g) Brake cylinder 



Its Operation. The air brake in use to-day is 

 a great improvement over the first one used in 

 1868, but the principle is the same. Some of 

 tin steam in the engine works an air pump, 

 which compresses air in a reservoir under a 

 pressure of eighty to ninety pounds per square 

 inch. From this central reservoir in the loco- 

 motive, pipes run under the cars the enim 

 th of the train, the connection between the 

 cars being made by rubber tubing. Attached 

 he bottom of each car is a secondary or 

 liary reservoir; this receives the compressed 

 through a device called the triple valve, 

 winch is the automatic feature of the entire 

 system. So long as the air pressure continues 

 he train pipe, the triple valve remains in 

 position so that the air pressure is exerted in 

 iary reservoir but not on the brake; if 

 pressure is reduced or entirely removed, tin 



(fc) Conductor's valve 

 (i) Hose and Coupling 

 (>) Centrifugal dirt collector 

 (fc) Battery and switch 

 (f) Universal valve with electric magnet 

 (in) Auxiliary reservoir 

 (n) Train pipe to engineer's cab 



against the wheels. When the engineer wishes 

 to release the brakes he turns the valve in the 

 locomotive so that air rushes from the central 

 reservoir through the train pipe. The pressure 

 thus increases on the triple valve, which is 

 forced back, thus opening an aperture through 

 which the compressed air in the brake cylinder 

 escapes into the open air. Inside the cylinder 

 is a coiled spring, which then reacts and forces 

 tin- brake piston back to its normal position. 

 The brakes are thus released. The valve in the 

 locomotive may be turned so that the brakes 

 operate either slowly or suddenly. Sec WEST- 

 INGHOUSE, GEORGE; LOCOMOTIVE. CJLM. 



AIR CELLS, small cavities, either in plants 

 or animals, which contain only air, and exist 

 for the sake of giving buoyancy. Water plants 

 which float upon the surface, such as water 

 lilies, have them in abundance, and arc held up 



