THE STEAM LOCOMOTIVE 



the engineer in order to apply the brakes let out the 

 air in the train pipe instead of forcing air into it, a 

 ** triple valve" on each car performing the work of 

 operating the brake cylinder automatically. 



The advantage of this system over the older one is 

 obvious. Whereas the detachment of a portion of the 

 train, or a leak in any part of the air brake system 

 heretofore had left the engineer helpless, exactly the 

 reverse condition was produced in the new system. 

 Any leakage of air, either from a break or a defect, 

 caused every brake on the entire train to be applied 

 to the wheels and brought the train to a stop. More- 

 over, with the new system it was now possible to equip 

 each car with a valve which would lessen the pressure 

 of air in the train pipe so that the train could be brought 

 to a stop by the trainmen in the rear or intermediate 

 coaches as readily as by the engineer. 



This system worked perfectly on passenger trains; 

 but on long freight trains the resistance to the passage 

 of the escaping air through the train tube was so great 

 that if an emergency required the full force of the brake 

 to be applied suddenly, the brakes of the rear cars did 

 not come into use until several seconds after those of 

 the forward cars. The result was that the momentum 

 of the rear cars caused them to strike the forward cars 

 with great violence. But Mr. Westinghouse overcame 

 this defect by an ingenious use of the triple valve mech- 

 anism of each car, whereby the application of the 

 emergency brake by the engineer caused the air in the 

 train pipe on each car to be discharged simultaneously 

 into the brake cylinder. In this manner the discharge 



TOL. VII. — lO [ 145 ] 



