Figure 3-21. - Wick seals.

Piston Assembly

Pistons (fig. 3-22) are usually made of an aluminum alloy. They are a sliding fit in the cylinders. This serves several purposes as follows:

Transmits the force of combustion to the crankshaft through the connecting rod.

Acts as a guide for the upper end of the connecting rod.

Serves as a carrier for the piston rings that are used to seal the compression in the cylinder.

The piston must withstand incredible punishment under temperature extremes. The following are

Figure 3-22. - Piston.