CAUSES THAT LEAD TO BROKEN CYLINDER-HEADS.
The causes which most commonly lead the piston to smash out cylinder-heads, are broken cross-heads, broken piston-rods, and broken main-rods. A main crank-pin or wrist-pin breaking, is almost certain to leave one end of the cylinder a wreck. These may be termed the major causes for breaking out cylinder-heads; but there are numerous minor causes, which are scarcely less destructive. A piston-rod key begins to work loose. It is hammered down occasionally, which does not improve its fit; and some day it jumps out altogether, letting the piston go on a voyage of discovery. A machinist of the careless sort has been examining a piston’s packing, and, in screwing up the follower-bolts, one of them gets a twist too much. Drilling out a follower-bolt is a troublesome operation, so Mr. Careless lets it go. On the road this head drops out, and a broken cylinder-head is the consequence. One of the worst causes of breakage to a cylinder that I have ever seen, was caused by the packing-ring of the piston catching in the steam-passage. Part of the ring broke off, and wedged itself between the advancing piston and the cylinder. The wedge split the cylinder open, and the remainder of the piston acted like a pulverizer upon the fragment of the cylinder.