Check out the strange and magical inner workings of the Gnome Monosoupape aircraft engine of World War I in this fascinating digital animation.

To modern eyes, the Gnome rotary aircraft engine of World War I must be one of the craziest machines ever conceived by human minds. The Gnome superficially resembles a conventional radial aircraft engine, but there is a crucial difference. Here, the crankshaft is fixed to the airframe and the crankcase and cylinders rotate, driving the propeller. Wait, there’s more: there is no throttle as such; instead, engine speed is controlled by cutting the ignition in and out. And there is no conventional intake valve mechanism either, but on the exhaust side alone. On that basis, this variety of the Gnome was commonly known as the Monosoupape, French for “single-valve.”

Despite its seemingly bizarre design, the Gnome was actually was one of the most effective aircraft engines of the first World War, manufactured under license by both sides in the conflict, and there were other rotary engine makers as well. To help us understand the mysteries of the Gnome’s inner workings, Pierre Jansen of the Netherlands produced this stunning digital animation of the Gnome 9-B2, a 9-cylinder model of 1916 that developed 100 hp but weighed only 303 lbs. (Which points to one of the rotary’s multiple attributes, a superior power/weight ratio.) Once the assembly is completed, at around the 8:48 mark the four-stroke operating cycle is demonstrated. Enjoy the video.