(2) Connecting Rod and Crankshaft. The upanddown movement of the
piston is called reciprocating motion. This reciprocating motion must be
changed to rotary motion to propel the vehicle. The change is accomplished by
the crankshaft and a connecting rod which connects the piston (Figure 13) and
the crankshaft. The connecting rod is attached to the piston by a piston pin
or "wrist pin". The pin passes through the bearing and surfaces in the piston
and connecting rod. The lower end of the connecting rod is attached to the
crankpin on the crankshaft. As the piston moves up and down in the cylinder,
the upper end of the connecting rod moves up and down with it.
Figure 13. Piston, Connecting Rod, and Piston Pin.