BRAKE CYLINDERS 



345 



If the rule for the capacity of a cylinder is applied for a 

 piston travel of 1 in., the number of cubic inches the capacity 

 of a brake cylinder will change for each inch increase or decrease 

 of piston travel, is numerically equal to the area of the cyl- 

 inder. For example, the capacity of an 8-in. cylinder will 

 change 50 j cu. in. for every 1 in. of change in the piston travel; 

 that of a 10-in. cylinder will change 78j cu. in.; that of a 12-in. 

 cylinder, 113 cu. in.; and so on. 



FORCE EXERTED IN BRAKE CYLINDER 



The total allowable braking force should not be exceeded 

 when an emergency application of the brakes is made, since 

 at such times it is especially important that no wheels slide, 



FORCE EXERTED IN BRAKE CYLINDER 



as a sliding wheel exerts but little retarding force. For this 

 reason, the braking power is calculated on the assumption 

 that, in an emergency application, 60 Ib. pressure is obtained 

 in the brake cylinder with a quick-action brake, and 50 Ib. 

 with a plain triple. 



The total force, in pounds, that a brake cylinder will develop 

 when subjected to 50 and 60 Ib. pressure per sq. in. has been 

 calculated for several sizes of cylinders; the results are given in 

 the accompanying table. 



