346 BRAKE CYLINDERS 



The force exerted in a brake cylinder is found by multiplying 

 the area of the piston, in square inches, by the pressure per 

 square inch in the cylinder. Thus, if the piston has an area 

 of 154 sq. in., it will develop a force of 154X50 = 7,700 Ib. 

 under a 50-lb. pressure. 



The area of a piston may be found by multiplying the 

 diameter of the piston, in inches, by the diameter and by 11, 

 and dividing by 14. Thus, the area of a 10-in. piston is 



= 78? sq. in. nearly. Another, and slightly more 



accurate, method of calculating the area of a piston is to multi- 

 ply the diameter, in inches, by the diameter, and by .7854. 



FILLING BLOCKS 



When cars already equipped with the standard apparatus 

 (schedule PM) are to be changed over to the new equipment 

 (schedule LN) and when the foundation brake-gear design 

 permits, it may be desirable to leave the old (type M) brake 

 cylinder in position on the car instead of repla- 

 cing it by a new (type N) cylinder. This can be 

 accomplished by the use of a filling block, shown 

 in the accompanying illustration, one face of 

 which fits the seat on the brake cylinder, while 

 the other face is a suitable seat for the triple 

 valve to be used. When a filler block is used, 

 an extra gasket suitable for the triple valve 

 employed, is required. The piece numbers of the different 

 filling blocks are: Filling block for changing from P-l to L-l 

 triple valve, 9,361; filling block for changing from P-2 to 

 L-2 triple valves, 9,357; filling block for changing from P-2 

 to L-3 triple valves, 13,006. 



COVER-PLATES 



When making the change from the standard (PM) to the 

 new (LN) schedule, if it is found possible to leave the old 

 (type M) brake cylinder in place on the car, but impracticable 

 to use a filling block, the triple valve can be mounted on a 



