Figure 3-23. - The parts of a piston.

examples of conditions that a piston must withstand at normal highway speed:

As the piston moves from the top of the cylinder to the bottom (or vice versa), it accelerates from a stop to a speed approximately 50 mph at midpoint, and then decelerates to a stop again. It does this approximately 80 times per second.

The piston is subjected to pressures on its head in excess of 1,000 psi.

The piston head is subjected to temperatures well above 600F.

The structural components of the pistons are the

HEAD, SKIRT, RING GROOVES, and LANDS (fig. 3-23); however, all pistons do not look like the typical one shown here. Some have differently shaped heads. Diesel engine pistons usually have more ring grooves and rings than the pistons of a gasoline engine. Some of these rings may be installed below as well as above the WRIST or PISTON PIN (fig. 3-24).

Figure 3-24. - Diesel piston assembly.