The rotary engine began with an improbable dream in the summer of 1919 by a 17-yearold German boy named Felix Wankel. In his dream he went to a concert in his own handmade car, remembering the boasting in the dream, he bragged to his friends about his new type of engine, half-turbine and half-reciprocated. When he woke up the following morning he was convinced that the dream was a premonition of the birth of a new type of gasoline engine. At the time Wankel had no fundamental knowledge about internal combustion engines but he believed that the engine could achieve four cycles while rotating. Wankels intuition triggered the birth of the rotary engine. .
In a rotary engine, the pressure of combustion is contained in a chamber formed by part of the housing and sealed in by one face of the triangular rotor, which is what the engine uses instead of pistons. The rotor follows a path that looks like something you would create with a spirograoh. This path keeps each of the three peaks of the rotor in contact with the housing, creating three separate volumes of gas. As the rotor moves around the chamber each of the three volumes alternately expands and contracts. The expansion and contraction draws air and fuel into the engine, compresses it and makes power as the gasses expand and then expels the exhaust. .
The rotary engine is an internal combustion engine, like the engine in a car, but it works in a completely different way then conventional piston engines. In a piston engine, the same volume of space alternately does four different jobs. A rotary engine does these same jobs, but each one happens in its own part of the housing. .
A few advantages of the rotary engine are that is is light weight and compact. It is smooth, and has and extended power stroke. There are also few moving parts, no valves, connecting rods, cams, or timing chains.