Practical Hand Book of Gas, Oil and Steam Engines / Stationary, Marine, Traction; Gas Burners, Oil Burners, Etc.; Farm, Traction, Automobile, Locomotive; A simple, practical and comprehensive book on the construction, operation and repair of all kinds of engines. Dealing with the various parts in detail and the various types of engines and also the use of different kinds of fuel.

by John B. Rathbun

(127) Hit and Miss Governing.

When the speed of an engine is held constant for varying loads by missing explosions on the light loads and increasing the number for heavy loads, the governing system is said to be of the “hit and miss type.” The mixture remains constant in quantity and quality in this type of engine. A hit and miss governor allows only enough charges to be fired to keep the speed constant.

When the load falls off, with a natural tendency on the part of the engine to increase its speed, the governor cuts out the next explosion by holding the exhaust valve open and the inlet closed, thus preventing fresh mixture from being drawn into the cylinder. With an increase in load, the governor allows the valves to follow their regular cycle with the result that a greater or less number are fired in succession. Hit and miss governing is very economical for only full charges of the most perfect mixture are fired, and with short exhaust pipes the scavenging is much better than with other forms of governing. The principal difficulty with this system is that the regulation is not as perfect as with some other types.