All About Engines

The Modern Reciprocating Engine T47 An additional advantage of the multiple-cylinder engine is that it is more easily balanced (see pages 109-116). In this respect three cylinders are better than two, and four are better than three. Whether more than two cylinders are desirable depends upon the pressure. For moderate pressures and moderate powers there is no need to go to additional expense for a third or fourth cylinder. But for the most powerful engines, using steam at 180 lb. to 225 lb. on the square inch, triple or quadruple expansion is fully justified and regularly employed. And in order to secure the advantages of four cranks over three in regard to balancing, and at the same time to avoid the construction of very large cylinders, triple-expan- sion engines are frequently supplied with two L.P. cylinders. If these are placed at the ends, with the h.p. and i.p. between them, the problem of balancing assumes its simplest form.