74 SCIENCE OF SUCCESSFUL THRESHING. 



piston-rod, as shown in Fig. 23. 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. 22. 



Next, turn the engine until the 

 cross-head comes back to the 

 same place, but with the crank- 

 pin on the other side of the 



dead-center, holding the tram 

 FIG. 24. 



TRAM ON CROSS-HEAD. 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 temporary), 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 manner. Now 

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

 drops into one of the marks on it, the engine will be 

 on either of its dead-centers. With engines, on which the 

 crank-disc is not easily reached, the prick-punch marks for 

 the tram are usually located on the fly-wheel rim. They were 

 so placed on "Case" center-crank engines. 



