Hesselman engine

[3][4] Most Hesselman engines were built during the 1930s and 1940s by firms in Sweden and the United States for use in both heavy vehicles and stationary industrial applications.

[1][4] During the engine's operating cycle, air is first drawn into the cylinder through an intake valve and given a rotary motion as a result of its tangential direction of entry.

The spark occurs at about 15 degrees before top dead-center after which the engine completes its power and exhaust strokes and the cycle began again.

Throttling of the engine is achieved by linked variation of air intake volume and duration of fuel injection.

[6] In the United States, Hesselman engines were built by the Waukesha Motor Company for both vehicular and industrial applications.