Gnome Monosoupape

Early Gnome rotary engines like the Gnome Omega, Lambda and Delta used an arrangement of valves in order to eliminate pushrods that operated during the inlet phase of the combustion cycle on more conventional engines. Instead, a single exhaust valve on the cylinder head was operated by a pushrod that opened the valve when the pressure dropped at the end of the power stroke. A pressure-operated inlet valve, which was balanced by a counterweight to equalize the centrifugal forces, was placed in the centre of the piston crown, where it opened to allow the fuel–air charge to enter from the engine's central crankcase. The use of automatic intake valves in the piston crown had several drawbacks. The engine's volumetric efficiency was low because the inlet valve opened later and closed sooner than the ideal timing that could have been achieved with actuated valves. The inlet valves were also a source of poor reliability and high maintenance, as they easily became unbalanced and gummed up. The valves also performed poorly at higher altitudes. ==Design==

In 1913, the Gnome motor company introduced the new Monosoupape series, which eliminated the troublesome inlet valve, replacing it with piston-controlled transfer ports similar to those found in a two-stroke engine. The charge was an overly rich fuel-air mixture, which was acquired through the hollow crankshaft. Air entered through scoops at the back of the crankshaft. Fuel was continuously injected by a fuel nozzle on the end of a fuel line, also entering the crankcase through the hollow crankshaft. The nozzle was in the proximity of, and aimed at, the inside base of the cylinder where the transfer ports were located. The fuel nozzle was stationary with the crankshaft, and the cylinders rotated into position in turn. The compression stroke was conventional. However, Monosoupape engines used less lubricating oil, and weighed slightly less, than earlier Gnome series engines with intake valves in the piston crown. ==Variants==

;Gnome Monosoupape 7 Type A :Seven-cylinder rotary engine, . Bore and stroke: . ;Gnome Monosoupape 9 Type B-2 :Nine-cylinder rotary engine, . Bore and stroke: . This variant was produced under licence in the United Kingdom and the United States. ;Gnome Monosoupape 11 Type C :An 11-cylinder version, . ;Gnome Monosoupape 18 Type C :An 18-cylinder version, . ;Gnome Monosoupape 9 Type N :(1917) nine-cylinder rotary engine, larger diameter crankcase than the B-2, 150 or 160 hp (112 or 119 kW), increasing capacity to . Bore and stroke: . ;Gnome Monosoupape 9 Type R :180 hp nine-cylinder rotary engine, development of 9N with same stroke. ==Applications==

Monosoupape 7 Type A • Avro 504 • Avro 511 • Bristol-Coanda G.B.75 • Sopwith Pup • Voisin L Monosoupape 9 Type B • Avro 504 • Airco DH.2 • Airco DH.5 • Blackburn Scout • Blackburn Twin Blackburn • Blackburn Triplane • Bristol-Coanda T.B.8 • Bristol Scout • FBA Type B Flying boat • Nieuport IV • Royal Aircraft Factory B.E.8 • Royal Aircraft Factory F.E.8 • Short S.80 • Short Type C • Sopwith Sociable • Sopwith Type 807 Folder Seaplane • Sopwith Two-Seat Scout • Sopwith Schneider • Sopwith Pup • Sopwith F.1 Camel • Thomas-Morse S-4 • Vickers Gunbus (FB.2, 3, 5, 6 and 7) • Vickers F.B.12 • Vickers F.B 19 Bullet Monosoupape 9 Type N • Morane-Saulnier AI • Nieuport 28 • Orenco B • Sopwith Camel ==Engines on display==

• A nine-cylinder Monosoupape engine is on public display at the Royal Air Force Museum London. • A nine-cylinder Monosoupape engine is on public display at the Aerospace Museum of California. • A seven-cylinder Monosoupape engine is on display at Solent Sky. • One Monosoupape built by Peter Hooker - England is on display at the Museo Nacional de Aeronáutica - Morón, Argentina. It is used during exhibitions to explain the rotary engines systems as it shows its operative internal parts. • There is a restored B-2 Monosoupape on display at the New England Air Museum, Bradley Int'l Airport, Windsor Locks, CT, USA. • TAVAS in Australia have two Monosoupape 9 Type Ns • An original (unrestored) running nine-cylinder Monosoupape engine is on public display at the South Australian Aviation Museum. • A nine-cylinder Monosoupape engine is on public display at the Musée aéronautique et spatial Safran. • The Imperial War Museum has a Gnome Monosoupape B-2. • The Shuttleworth Collection has a Gnome Monosoupape B-2 which is used at airshow events. ==Specifications (Monosoupape 9 Type B-2)==