Hit-and-miss engine

A hit-and-miss engine is a type of four-stroke internal combustion engine that is controlled by a governor to operate a set speed. It was conceived in the late 19th century and produced by various companies from the 1890s through approximately the 1940s. The name comes from the speed control on these engines: they are designed to fire ("hit") only when operating at or below a set speed, and to cycle without firing ("miss") when they exceed their set speed. This is as compared to the "throttle governed" method of speed control. The sound made when the engine is running without a load is a distinctive "POP whoosh whoosh whoosh whoosh POP" as the engine fires and then coasts until the speed decreases and it fires again to maintain its average speed.

Many engine manufacturers made hit-and-miss engines during their peak use—from approximately 1910 through the early 1930s when more modern designs began to replace them. Some of the largest engine manufacturers were Stover, Hercules, International Harvester (McCormick Deering), John Deere and Fairbanks Morse.

A hit-and-miss engine is a type of flywheel engine. A flywheel engine is an engine that has a large flywheel or set of flywheels connected to the crankshaft. The flywheels maintain engine speed during engine cycles that do not produce driving mechanical forces. The flywheels store energy on the combustion stroke and supply the stored energy to the mechanical load on the other three strokes of the piston. When these engines were designed technology was not nearly as advanced as today and all parts were made very large. A typical 6 horsepower (4.5 kW) engine weighs approximately 1000 pounds (454 kg). Typically, the engine material was mainly cast iron and all significant engine parts cast from it. Small functional pieces are made of steel and machined to perform their function.

The fuel system of a hit-and-miss engine consists of a fuel tank, fuel line, check valve and fuel mixer. The fuel tank most typically holds gasoline but many users would start the engines with gasoline and then switch over to a cheaper fuel such as kerosene or diesel . The fuel line connects the fuel tank to the mixer. Along the fuel line, a check valve keeps the fuel from running back to the tank between combustion strokes. The mixer creates the correct fuel-air mixture by means of a needle valve attached to a weighted or spring-loaded piston usually in conjunction with an oil-damped dashpot.

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