PC PASSENGER-BRAKE EQUIPMENT 276 



vertically in the air. The magnitude of the energy that must 

 be destroyed in stopping the train running at a speed of 70 mi. 

 per hr. is too great to grasp without a special effort. But to 

 give an idea of the magnitude, it may be said that if a person 

 were to count 150 in each minute, or 90,000 in 10 hr., he would 

 have to count 10 hr. a day at this rate for about 3,189 da., or 

 every day for about 8| yr., to count the number of foot-pounds 

 of energy to be destroyed in stopping the train running at a 

 speed of 70 mi. per hr., or 287,017,500. This energy, if con- 

 verted into heat, would produce 268,917 units of heat, an 

 amount sufficient to raise 2,598 Ib. (311 gal.) of water from 

 70 F. to the boiling point, or to raise the temperature of 16 T. 

 of iron 100 F. 



To destroy, within a distance of less than 1,200 ft. and with- 

 out endangering the safety of the passengers and equipment, 

 the enormous energy stored up in modern trains of heavy cars 

 moving at high speeds, requires a brake of high maximum 

 emergency stopping power; to perform the ordinary service 

 functions and to provide the automatic safety and protective 

 features necessary for a service of this kind, requires a very 

 flexible and efficient service stopping power. It was to provide 

 a brake that would fulfil these requirements that the PC pas- 

 senger equipment was designed and introduced into service. 



FUNCTIONS AND FEATURES OF BRAKE 



In the PC passenger equipment, the triple valve is replaced 

 by a valve known as a control valve, which performs several 

 new functions in the manipulation of the brakes. The features 

 of the brake, as well as its functions, are as follows: 



Graduated release and quick recharge, which are obtained in a 

 manner similar to that of the type L triple valve. The emer- 

 gency reservoir furnishes the air necessary, for obtaining the 

 graduated release and for assisting in recharging. 



Certainty and uniformity of service action, which are obtained 

 by so designing the parts of the control valve that the feed- 

 grooves are closed on the slightest brake-pipe reduction. The 

 design is such that the differential necessary to move the parts 



