Page:International Library of Technology, Volume 93.djvu/125

 such engines are known as single-acting engines. In other forms work is done on both sides of the piston, and these are known as double-acting engines.

3. The construction of the single-acting engine is illustrated in Fig. 1, in which a is the cylinder; b, the piston;

c, the cylinder head; and d, the rotating shaft, known as the main, or crank-shaft. In order to convert the to-and-fro, or reciprocating, motion of the piston into a rotary motion of the crank, a connecting-rod e and a crank f are used. The connecting-rod is attached to the crank by means of the pin g y called the crankpin, and to the piston by means of the pin h, called the piston pin, or wristpin. The frame i supports the cylinder a and the main-shaft bearing j, and forms the rigid connection between them.

4. The construction of the double-acting engine is shown in Fig. 2, corresponding parts being represented by the same

letters as those used in Fig. 1. It will be seen that the principal points of difference between these two constructions are