If the wrist pin was free to move it would work out of the bosses enough so that the end would bear against the cylinder wall.
The wrist pin member is a simple cylindrical element that fits the bosses closely, and it may be either hollow or solid stock.
A typical connecting rod and its wrist pin are shown at Fig. 120.
The wrist pin can only be reached by the removal of the piston and connecting rod.
This makes a very positive lock and one that can be easily loosened when it is desired to remove the wrist pin.
The axle, probably square in cross section, turned only at the bearings and wrist pin.
Upon A-7a and A-5a engines a small tube supplies oil from connecting rod bearing directly upon the wrist pin.
The taper plugs would be screwed in deeper and the ends of the wrist pin expanded proportionately to take up the loss motion.
A good view of the wrist pin and connecting rod are also given.
It may have been cast in two parts, each with a crank arm, and then joined by the wrist pin, after the latter had been turned.