THE 



97 



amination of these marks will show whether it has or has 

 not. If it has slipped, the trouble may be corrected by 

 loosening the set-screws and rotating it around the shaft 

 until the marks correspond. An eccentric is liable to slip 

 when it becomes hot from running without oil and this 

 tendency in such cases is sometimes strong enough to 

 draw over or even shear off the points of the set screws 

 which secure the eccentric. 



Besides the marks on the eccentric, there are marks 

 on the valve-stem and its stuffing-box, in order to make 

 apparent any change in the length of the valve-rod or the 

 eccentric-rod. To use these marks, however, one should 

 have one of the Company's valve-rod trams. This is 

 shorter than the one used on the crank-disc and measures 

 exactly four and three-sixteenths inches between points. 

 It is used as shown in Fig. 31. There are two marks on 

 the valve-stem and they 

 should be on top. When 

 the reverse lever is at the 

 rear end of the quadrant, 

 (i. e., the road motion), 

 and the engine is placed 

 on one of its dead centers, 

 the valve-rod tram should 

 drop into one of the marks, 

 and when the engine is placed on its other dead-center, 

 the tram should drop into the other mark. If the tram 



7 



FIG. 31. TRAM ON VALVE-STEM. 



