ENGINE No. 77. 



Elevator Engine, 8" x 10." 



This is introduced as a curiosity, and at the same time it 

 reveals the wasteful character of this class of engine. There 

 is an absence of expansion and exceedingly high back pressure, 

 both of which are required by the exigencies of the service and 

 type of valve mechanism which that service necessitates. This 

 diagram also illustrates the effect of improper location of the 

 indicator on the cylinder. In this case it was placed at a short 

 distance from the end of the stroke, so that the piston ring 

 covered the hole until it had moved a certain distance on the 

 forward stroke. The hump on the diagram is caused by this 

 defective location. 



The diagram was taken on an upward trip. 



ENGINE No. 77 



298 



