CONTINUOUS RAILWAY BRAKES. 195 



Comparing now tJio " Westingliouso " automatic prossnro 

 brake with the " Steel & Mclnnes " pressure automatic 

 brake, and assuming the same diameter of cylinder, 8 inches, 

 the same maximum piston travel G cubic inches, and the 

 auxiliary reservoir 1,800 cubic inches capacity, and the 

 train-pipo capacity to each carriage 284 cubic inches, the 

 volume swept through by the brake-piston when the brakes 

 are full on being 300 cubic inches, we shall find that, 

 whereas it was necessary for a full application of the 

 brake (differential pressure) to discharge 884 cubic inches 

 of air on each coach, it is onljr necessary to discharge 40 

 cubic inches in the " Westinghouse " brake to fully apply 

 the brakes. It is evident that the " Westinghouse " can 

 be applied faster, taken "off" faster, and that it is more 

 economical in the use of air. 



Though the amounts of air which have to bo discharged 

 in the " Steel & Mclnnes " and the " Westinghouse " 

 are for a full application of the braises, the actual amounts 

 used in working the brakes are only as 2^ to 1. 



The next brake is Barker's Hydraulic Brake. 



Bakkeu's IIydkaulic Brake. 



In Barker's brake a force-pump on the engine forces 

 Water along a continuous brake-pipe to an " accunnilator " 

 placed on each coach. The water is under the pressure of 

 a very powerful coiled spring, placed under compression 

 '>y a piston which the entering water forces forward. 



A slide valve, carried in the piston in the auxiliary piston- 

 valve, is placed in a condition of unstable oquilibrium by 

 the pressure of water in the train-pipe on one side, acting 

 against a coiled spring on the piston-valve rod, as seen in 

 the wall diagram. 



In certain positions the auxiliary piston valve opens a 



