THE VALVE-GEAR 



95 



tram points should now measure the exact distance be- 

 tween the two marks and when applied should be nearly 

 parallel to the piston-rod, as shown in Fig. 30. In the 

 same manner, a mark should be made at any convenient 

 place on the frame near the crank-disc, a scratch made on 

 the disc (which should come across the face of the disc), 

 and a light prick-punch mark made on the disc, so that the 

 tram measures the exact distance between the marks, as 

 shown in Fig. 29. Next, 



turn the engine until the _ rr -^- rr- 



cross-head comes back 

 to the same place, but 

 with the crank-pin on 

 the other side of the 

 dead-center, holding the 

 tram with one point in 

 the mark on the frame, near the guides, and the other so 

 that it will drop into the cross-head prick-punch mark 

 when it comes to the right place. Next, place one leg of 

 the tram in the other mark on the frame and make 

 a scratch on the disc as before, to locate the second mark 

 on the rim of the crank-disc. When this is done, find 

 the mid-point between the two marks (which are tem- 

 porary), on the disc, with a pair of dividers, mark it 

 clearly, and then destroy the two original marks. The 

 other dead-center is found in the same rmnner. Now 

 when the crank-disc is turned around until the tram point 



FIG. 30. TRAM ON CKOSS-HEAD. 



