174 



CONTINUOUS EATr.WAY BRAKES. 



brakes, complying with Loth " a " and " b " of tho require- 

 ments as regards their action. 



Definition of " Brake." — If we doflno a brake mechanism 

 in its widest and most general sense, wo might define it 

 to bo a mechanism designed for tho purpose of dispersing, 

 absorbing, or transforming the kinetic energy of a train. 



Furthermore, it will be found that, as regards tho classi- 

 fication of — ■ 



SECTIONAL BRAKES, 



they may bo classified according to tho manner in which 

 the kinetic energy of the train is dispersed, and the form 

 of instrument directly employed in its dispersion. Thus 

 we have Block brakes, Slipper brakes, and Clip brakes ; also 

 Pump brakes. Fan brakes, and Sand brakes. ■ It will bo 

 sufficient to indicate the method of dispersing the kinetic 

 energy of the train in one, or two, or three of the brakes 

 just named. 



In the case of the "Block" brake, the friction set up 

 between the wheel tires and the blocks, which are pressed 

 against them by suitable gearing in the vans, generates 

 a large amount of heat, in whicli form the kinetic energy 

 of the train disai)pears. 



In the case of the " Slipper " brake, by moans of suitable 

 gearing, the weight of the brake van is transferred from 

 the wheels to a " slip])cr," whcro the previous rolling 

 friction of the wheels on the rails is altered to a sliding 

 one, and an increased amount of the train's energy is 

 absorbed in overcoming tho extra IVictional resistance thus 

 set up. 



In the case of tho "Clip" brake, by means of suitable 

 gearing, a " clip " is made to grip tho rails ; and the frictional 

 resistance set up between it and the rail, and also the 

 molecular stresses set up in the parts of the brake me- 



