Gas-Engines and Producer-Gas Plants / A Practice Treatise Setting Forth the Principles of Gas-Engines and Producer Design, the Selection and Installation of an Engine, Conditions of Perfect Operation, Producer-Gas Engines and Their Possibilities, the Care of Gas-Engines and Producer-Gas Plants, with a Chapter on Volatile Hydrocarbon and Oil Engines

by Rodolphe Edgard Mathot

The number of these rings ought not to be less than four or five, arranged at the rear of the piston. It is to be observed that makers of good engines use as many as 8 to 10 rings in the pistons of fair-sized motors.

Piston-rings of gray pig-iron can be adjusted with the greatest nicety in such a manner that, by means of tongues fitting in their grooves, they are held from turning in the latter, whereby their openings are prevented from registering and allowing the passage of gas. As a general rule, a large number of rings may be considered a distinguishing feature of a well-built engine. In order to prevent a too rapid wear of the cylinder, several German manufacturers finish off the front of the piston with bronze or anti-friction metal in engines of more than 40 to 50 horse-power. It is to be observed, however, that this expedient is not applicable to motors the cylinders of which are comparatively cold; otherwise the bronze or anti-friction metal will deteriorate.

Arrangement of the Cylinder.—The cylinder shell or liner, in which the piston travels, and the water-jacket

should preferably be made in separate pieces and not cast of the same metal, in order to permit a free expansion (Figs. 22 and 23). If for want of care or of proper lubrication, which frequently occurs in gas-engines, the cylinder should be injured by grinding, it can be easily renewed, without the loss of all the connecting parts.

Fig. 22.—Head, jacket and liner of cylinder, cast in one piece.

Fig. 23.—Cylinder with independent liner and head.

For the same reason, the cylinder and its casing should be independent of the frame. In many horizontal engines, the cylinders overhang the frame throughout the entire length, by reason of the joining of their

front portions with the frames. Although such a construction is attended with no serious consequences in small engines, nevertheless in large engines it is exceedingly harmful. Indeed, in most modern single-acting engines, the pistons are directly connected with the crank-shaft by the piston-rod, without any intermediate connecting-rod or cross-head. The vertical reaction of the motive effort on the piston is, therefore, taken up entirely by the thrust of the cylinder, which is also vertical (Fig. 24). This thrust, acting against an unsupported part, may cause fractures; at any rate, it entails a rapid deterioration of the cylinder joint.