LUBRICATION AND ADJUSTMENT OF BEARINGS. 43 



the top. Shims made of sheet-iron of the proper thickness 

 must now be inserted. These should be put in on both sides 

 of the brasses so as to not change the length of the rod, and 

 make it necessary to re-divide the clearance. 



It is best to take off the connecting-rod when the engine 

 is cold ; if it be taken off when the boiler is under steam pres- 

 sure, and the throttle should accidentally be left open, or 

 should leak, the piston may be driven through the cylinder 

 with force enough to do serious damage. 



To Divide the Clearance. The clearance of an engine 

 is the cubical contents of the port, from the face of the valve 

 to the cylinder, including the space between the piston and 

 the cylinder head when the engine is on dead-center. To 

 divide the clearance, loosen the clamp bolt and the jam nut 

 on the piston rod and unscrew the rod from the cross-head 

 until the piston strikes the cylinder-head as the crank passes 

 the head dead-center ; then screw in the rod until the piston 

 strikes the other cylinder head as the engine passes the other 

 dead-center carefully counting the number of turns of the 

 rod. Now unscrew the rod half the number of turns counted 

 and the clearance will be divided. Tighten the clamp bolt 

 and the jam nut. 



The Shoes of the Cross-Head are adjusted by loosening 

 the four cap screws, (E), and screwing up the four set 

 screws, (F), to force the shoes against the guides. This 

 will leave a space between the shoes and cross-head into, 

 which sheet-iron shims should be inserted. If these shims 



