78 ROUGH-AND-TUMBLE ENGINEERING 



a knock, which also appears in the wrist. Tighten the 

 11 and you will stop it. The piston rod may be keyed 

 in the cross-head, or it may be held in place by a nut. 

 The key is less liable to get loose, but should it work loose 

 a few times it may be necessary to replace it with a new 

 one. And this is one of the things that cause a bad break 

 when it works out or gets loose. If it gets loose it may 

 not come out, but it will not stand the strain very long 

 in this condition, and will break, allowing the piston to 

 come out of the cross-head, and you are certain to knock 

 out one cylinder head and possibly both of them. The 

 nut will do the same thing if allowed to come off. So 

 this is one of the connections that will claim your atten- 

 tion once in a while, but if you train your ear to detect 

 any unusual noise you will discover it as soon as it gives 

 the least in either key or nut. 



The cross-head loose in the guides will cause a knock. 

 If the cross-head is not provided for taking up this wear, 

 you can take off the guides and file them enough to allow 

 them to come up to the cross-head, but it is much better 

 to have them planed off, which insures the guides coming 

 up square against the cross-head and thus prevent any 

 heating or cutting. 



A knock caused by a loose fly-wheel will most likely 

 puzzle you more than anything else. So remember this 

 the wheel may apparently be tight, but should the key 

 be the least bit narrow for the groove in the shaft, it 



