34 Book of Engineering 



on a tapering system to help the coal 



in its travel from back to front of the 



tender. 



But this would not operate satisfactorily 

 of itself, especially when we remember that 

 an engine must often run tender first for 

 some considerable distances. Hidden away 

 in the interior of the circular container is 

 a series of small engines, whose business 

 it is to work the coal forward so that the 

 fireman has always a supply within arm's 

 length. 



Unfortunately, the movement of the 

 train with its vibration tends to congeal 

 the fuel into a more or less solid mass, 

 and this factor had to be considered. 

 The clever designer of the self-trimming 

 tender got over his difficulty by making 

 the machinery hidden in the container 

 produce a complete turn round; that is 

 to say the container will rotate upon 

 steam being admitted to a certain valve. 

 This shakes up the coal and allows the 

 pushing forward screws to continue their 

 good work. 



