Michel engine

The Michel engine was an unusual form of opposed-piston engine. It was unique in that its cylinders, instead of being open-ended cylinders containing two pistons, were instead joined in a Y-shape and had three pistons working within them.

These engines were produced by Hermann Michel of the Michel Engine Company of Kiel, Germany, in the 1920s and 1930s. A US patent application was filed in 1921 and granted in 1926.

This Michel engine should not be confused with the contemporary Michell engine, which was a swashplate engine.

The Michel engine was a two-stroke diesel engine, of piston-ported opposed-piston design. Its unusual feature was that rather than two pistons sharing a cylinder, the cylinders here were Y shaped and contained three pistons. The two upper pistons controlled the inlet ports, with the one lower piston controlling the exhaust ports. Having two inlet (scavenge air) pistons to one exhaust piston provided good scavenging and efficient combustion. The engine was water-cooled.

Early versions of the Michel engine were cam engines. These do not use a crankshaft in the conventional sense, but instead have a shaped cam. The pistons or their connecting rods have cam followers that slide over the surface of this cam. Although most cams use rotary motion to generate a linear motion, this 'crankshaft' use is also possible, where the linear motion of the pistons is used to drive the rotary motion of the cam and the engine's output shaft.

Cam engines have all been unsuccessful so far, although the idea enjoyed some popularity in the mid-20th century, amongst inventors if not engineers. A similar idea was the swashplate engine, an axial form of cam engine. Although the forces in a cam engine are often greater and the frictional losses are high, they can also allow the use of larger bearing surfaces than a conventional crankshaft. Before the development of high performance bearing materials, the cam and swashplate engines appeared to offer some advantages.

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Wikipedia