Weak Force Press

Huntsville, Alabama

Specializing in Technical History

The Care of the
100 h.p. Monosoupape Engine
9-Cylinder Type B2

Rotary engines comprised about 80% of the engines used in World War I. This was in spite of their arcane construction. The crankshaft was bolted to the airframe and everything else (cylinders, pistons, crankcase, propeller) rotated around the fixed crankshaft. Rotaries were popular for a time because they offered two distinct advantages over contemporary engines: 1) low weight for the amount of power they produced, and 2) low vibration.

Laurent Seguin and his brother Louis, of the Societe des Moteurs Gnome, introduced the first of the aviation rotaries at the Paris Air Show of 1908. This first Gnome was a 50-hp 7-cylinder engine with its intake valves in the piston crowns. Gnome engines developed rapidly into 80 and 100 hp 9-cylinder versions. A 160 hp 14-cylinder two-row held the world speed record before World War I. Gnomes was widely licensed and copied.

The Seguin brothers realized that having an intake valve in the piston was hurting the engine’s reliability and causing maintenance nightmares. To remedy this situation, they introduced the Gnome Monosoupape, meaning “single valve” in 1912. The troublesome automatic intake valve was eliminated in favor of a ring of transfer ports near the base of the cylinder that were uncovered when the piston reached the bottom of its stroke.

This maintenance manual covers the Gnome 100 hp Type B2 Engine and contains all the information you will need to operate and overhaul your Gnome Monosoupape.

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