The Wankel engine

General of  Wankel's rotary engine

The German engineer Felix Wankel, inventor of a rotary engine that will be used in race cars, is born on August 13, 1902, in Lahr, Germany.

Wankel reportedly came up with the basic idea for a new type of internal combustion gasoline engine when he was only 17 years old. In 1924, Wankel set up a small laboratory where he began the research and development of his dream engine, which would be able to attain intake, compression, combustion and exhaust, all while rotating. He brought his knowledge of rotary valves to his work with the German Aeronautical Research Establishment during World War II, and to a leading German motorcycle company, NSU Motorenwerk AG, beginning in 1951. Wankel completed his first design of a rotary-piston engine in 1954, and the first unit was tested in 1957.

In other internal-combustion engines, moving pistons did the work of getting the combustion process started; in the Wankel rotary engine, an orbiting rotor in the shape of a curved equilateral triangle served this purpose. Fewer moving parts created a smoothly performing engine that was lightweight, compact, low-cost and required fewer repairs. After NSU officially announced the completion of the Wankel rotary engine in late 1959, some 100 companies around the world rushed to propose partnerships that would get the engine inside their products. Mazda, the Japanese automaker, signed a formal contract with NSU in July 1961, after receiving approval from the Japanese government.

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Principle of  Wankel's rotary engine


alte Ausführung (2 Zündkerzen pro Scheibe) Wankel’s rotary engine is an internal combustion engine which uses the same principle of converting pressure into rotating motion, but without the vibrations and mechanical stress at high rotational speeds of the piston engine. Dr. Felix Wankel and his colleagues obtained the engine’s housing design by completing the following steps: they first fixed an outer-toothed gear on a white sheet and interlocked it with a larger inner-toothed gear; with the ration between the two gears being 2:3. Next, they attached an arm with a pen on the outside of the larger inner-toothed gear. When turning the inner-toothed gear on the small gear, the pen generated a cocoon-shaped trochoid curve.

The Wankel engine works in the same 4-stroke cycle as the reciprocating piston engine, with the central rotor successively executing the four processes of intake, compression, ignition (combustion) and exhaust inside the trochoid chamber. So, although both types of engines rely on the expansion pressure created by the combustion of the fuel-air mixture, the difference between them derives from the way they harness it to


transform it into mechanical force. In a rotary combustion engine, this expansion pressure is applied to the flank of the rotor. Because of the rotor’s triangular shape, the inside space of the housing will always be divided in three working chambers. This is fundamentally different from the piston engine, where the four processes take place within each cylinder.


Prinzip des Kreiskolbenmotors


a Kolben, b Innenverzahnung, c Zahnrad, d Gehäuse, e Motorwelle, f Exzenter, g Kolbenmittelpunkt, h Einlaßöffnung, i Auslaßöffnung