PC PASSENGER-BRAKE EQUIPMENT 277 



Maximum possible rate of rise of brake-pipe pressure, thus 

 insuring greater certainty of all brakes releasing when a release 

 is made. This is due to the fact that the brake pipe alone 

 has to be charged by the air that flows through the brake valve; 

 the pressure in the pressure chamber of the control valve is 

 restored by air from the emergency reservoir, which raises the 

 pressure at the same rate as brake-pipe pressure up to the 

 point of equalization (about 5 Ib. less than normal brake- 

 pipe pressure) of the emergency reservoir and the pressure 

 chamber. After equalization, the reservoir and the pressure 

 chamber are charged up to normal pressure from the brake 

 pipe; this insures a rapid and certain release of all brakes 

 and a rapid recharge and prompt response to succeeding 

 reductions that may be made. 



Greatly increased sensitiveness to release, due to the fact 

 that the rate of rise of brake-pipe pressure is much greater, 

 because only enough air to charge the brake pipe must flow 

 from the main reservoir through the brake valve to release 

 the brake. 



Means of eliminating the graduated release feature during the 

 transition period; if a PC equipment is used in a train of cars 

 not so equipped, the graduated -release feature can be quickly 

 and easily cut out. 



GENERAL ARRANGEMENT OF BRAKE 



Piping diagrams showing two methods of arrangement of the 

 PC equipment are shown in Figs. 1 and 2. Fig. 1 shows the 

 arrangement when the two brake cylinders point in opposite 

 directions, whereas Fig. 2 shows the arrangement when the 

 cylinders point in the same direction. The arrangement shown 

 in Fig. 1 permits of a simpler arrangement of the hand-brake 

 rigging; on the other hand, the arrangement shown in Fig. 2 

 brings, on some cars, the slack adjusters into a more conve- 

 nient position. The choice of arrangements, therefore, depends 

 largely on the construction of the underframing of the car and 

 on the location of the apparatus under the car. 



Two brake cylinders are used on each car. The service 

 cylinder is used in both service and emergency applications; 



