15-2 ROUGH-AND TUMBLE ENGINEER 



find by careful measurement, a point on the wheel G 

 exactly midway between C and I 7 . If the engine is now 

 turned until the points of m just fit into the niarkb 



B and G, the engine will be on dead center. The other 

 dead center should now be found by an exactly similar 

 process. 



DIRECTION FOR SETTING A PLAIN SLID: 



1. Sec that the set screw in the eccentric is set tightly ; 

 then turn the engine fly wheel completely around, and <>!> 

 serve if the valve uncovers one port as much as it does 

 the other. If not, adjust the valve on its stem until it 

 does. 



2. Put the engine on dead center by means of the 

 trams; then turn the eccentric in the direction the engine 

 is to run until it shows the correct amount of lead 

 about one-thirty-second of an inch on the side nearest 

 the piston. 



3. Secure the eccentric in this position and place the 

 engine on the other dead center and see if the lead is the 

 same. 



4. If the lead is not the same, correct one-half of 

 the error by moving the valve on its stem and the other 

 half by moving the eccentric. The valve will now he 

 correctly set. 



5. If the measurements in item No. i were accurately 

 made, the correction noted in item No. 4 will not be 

 necessary. 



