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Gnome et Rhône

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Gnome et Rhône
Company typePrivate
IndustryAircraft engines manufacturing
Founded1905
FounderLouis Seguin, Laurent Seguin
FateNationalized and merged into Snecma in 1945
Headquarters
France
Area served
Worldwide (licensed production)
ProductsAircraft engines, motorcycles, bicycles

Gnome et Rhône stood as a prominent French manufacturer of aircraft engines. Between 1914 and 1918, the company produced 25,000 units of their 9-cylinder rotary engines, including the Gnome Delta and the Le Rhône 110 hp models, with an additional 75,000 engines manufactured under licensing agreements. These powerplants equipped the majority of Allied aircraft during World War I and were also installed in German planes built by Motorenfabrik Oberursel.

Following the war, the firm developed a new engine series inspired by the Bristol Jupiter. This led to the creation of the twin-row Gnome-Rhône 14K Mistral Major, a radial engine delivering around 1,000 horsepower. This model gained widespread international licensing and saw extensive use throughout World War II. The company supplied engines to the German Luftwaffe, producing both original and licensed German designs. Precision bombing campaigns targeted their factories, ultimately removing their manufacturing capabilities from wartime operations.

In 1945, Gnome et Rhône was nationalized and integrated into Snecma. The brand briefly continued in the production of motorcycles and bicycles thereafter.

Gnome

In 1895, engineer Louis Seguin obtained a license from the German firm Motorenfabrik Oberursel to produce the Gnom gas engine. Marketed under the name Gnome, this was a single-cylinder stationary engine designed for industrial applications, generating approximately 4 horsepower. Its distinctive valve arrangement included a rod-operated exhaust valve alongside an intake valve concealed within the piston head.

On June 6, 1905, Louis Seguin and his brother Laurent established Société Des Moteurs Gnome with the goal of manufacturing automobile engines. They soon pioneered one of the earliest dedicated aircraft engines: the seven-cylinder rotary Gnome Omega introduced in 1909, which delivered 50 horsepower while weighing only 75 kilograms. Over 1,700 units were produced in France, complemented by licensed manufacturing in Germany, Sweden, Britain, the United States, and Russia. The Omega powered landmark flights such as Henry Farman's Farman III and was instrumental in achieving the first seaplane flight with the Fabre Hydravion in 1910, cementing France's position as a leader in aviation.

Gnome engines were notable for their innovative fuel delivery system that eliminated external piping. Initial versions featured two valves—one positioned in the cylinder head and another embedded within the piston—that opened via counterweights to admit fuel mixture during piston descent. Due to maintenance difficulties with this setup, subsequent models adopted the Gnome Monosoupape (single-valve) system. This design utilized one exhaust valve supplemented by ports exposed when the piston moved downward to allow fuel intake.

The engine line expanded with more powerful variants: starting with the 80 hp Gnome Lambda in 1911, followed by the nine-cylinder 100 hp Gnome Delta in 1914 which incorporated the Monosoupape principle. A larger fourteen-cylinder two-row Double Lambda delivering 160 hp was produced in limited numbers but influenced Germany’s Oberursel U.III engine used briefly on early Fokker fighter aircraft. In 1918, Gnome launched the nine-cylinder Monosoupape Type-N rated at 160 hp, which powered models such as the Nieuport 28.

Le Rhône

Louis Verdet designed a compact rotary engine in 1910 and subsequently introduced a more successful seven-cylinder model known as the 7C in 1912, generating 70 horsepower from a weight of 90 kilograms. That same year he founded Société des Moteurs Le Rhône, soon releasing the nine-cylinder Le Rhône 9C producing 80 horsepower (60 kW). Unlike Gnome’s designs, Le Rhône engines featured copper intake manifold pipes along with conventional intake and exhaust valves. These engines were extensively licensed; notably, the 110 hp Le Rhone 9J was manufactured under license in Germany by Oberursel as the Ur.II, as well as in the United States by Union Switch & Signal Company, with additional production taking place in Austria, Britain, and Sweden.

Gnome et Rhône

Following a period of intense rivalry, Gnome merged with Le Rhône on 12 January 1915, creating the Société des Moteurs Gnome et Rhône. Their efforts centered on enhancing the 9C design, increasing output to approximately in the 1917 Le Rhône 9J and reaching in the rarer 9R model. The 1917 double-row Le Rhône 18E, derived from the 9R components, encountered cooling difficulties and never entered active service.

After 1916, Gnome rotary engines lost favor for frontline aircraft due to their limited power improvements compared to liquid-cooled V-8s and more advanced rotaries like the Clerget 9Bf. The Monosoupape 9N marked their pinnacle but was predominantly used in training aircraft. The 9C and 9J engines found widespread application in French and British forces and were licensed to Germany’s Oberursel company, which labeled Gnome-based engines with a U prefix and those based on Le Rhône with Ur.

The Inter-War years

Following World War I, the company expanded into various sectors including automobile chassis and engine production (notably for Rolland-Pilain and Pic-Pic), diesel engines through Ansaldo, as well as manufacturing refrigerators, sewing machines, and jackhammers. In 1920, they introduced their inaugural motorcycle, the Gnome et Rhône 500 cc, which continued production under the "Gnome Rhone" brand into the early 1950s.

By the early 1920s, rotary engines were considered outdated. In 1921, Gnome et Rhône acquired licensing rights for the successful Bristol Jupiter, marking their re-entry into aircraft engine manufacturing under Paul-Louis Weiller’s direction starting in 1922. The Jupiter-inspired 9A model achieved strong sales. Additionally, they licensed Bristol’s smaller Bristol Titan engine in 1926 while Bristol incorporated Gnome’s Farman-style reduction gearing into their designs.

In pursuit of autonomy from licensing dependencies, Gnome developed the K-series beginning in 1927 using Titan-based mechanics: the five-cylinder Gnome-Rhône 5K Titan delivering 260 hp (190 kW), the seven-cylinder Gnome-Rhône 7K Titan Major rated at 370 hp (270 kW), and the nine-cylinder Gnome-Rhône 9K Mistral producing 550 hp (405 kW). These variants were identified by a three-letter code indicating series type, rotation direction, and charging method. By 1930, having produced over 6,000 units, Gnome had become France’s leading engine manufacturer.

To satisfy increasing power requirements, they introduced the two-row Gnome-Rhône 14K Mistral Major in 1929 with two banks of seven cylinders generating 625 hp (460 kW). By 1933, enhanced supercharging elevated output beyond 1,000 hp (750 kW), establishing it as a globally licensed success.

Moving away from multi-engine K-series concepts, development focused on the larger Gnome-Rhône 18L, which combined two rows of nine cylinders to yield 1,400 hp (1,030 kW). However, due to an unfavorable power-to-weight ratio, this project was abandoned in 1939. The more compact Gnome-Rhône 14M Mars replaced earlier Mistral models by offering a high power-to-size ratio and powered aircraft such as the Potez 631.

The widely adopted Gnome-Rhône 14N, launched in 1936, delivered up to 1,210 hp (890 kW) with an improved power-to-weight balance. Its updated naming system indicated rotation direction through odd or even numbers. This engine series powered French bombers and fighters including the Bloch MB.210 and MB.152 models but saw limited licensing abroad due to escalating geopolitical tensions.

The pre-war advancement was represented by the Gnome-Rhône 14R, introduced in 1939 with takeoff power nearing 1,600 hp (1,161 kW) achieved by raising RPM levels. Despite these capabilities, contemporary British and German engines had already surpassed such performance benchmarks.

Following France’s defeat in 1940, Gnome et Rhône was compelled to manufacture the German BMW 801 engine under license. Their own designs like the14M and14N were utilized sparingly on German aircraft including the Henschel Hs129B and Messerschmitt Me323. Production fell significantly short of German expectations—only about8,500 engines had been produced by May1944 compared to a target of25,000. Allied bombing raids in1944 heavily damaged facilities located at Gennevilliers and Limoges.

Post-war recovery proved challenging; Gnome et Rhône briefly shifted to producing M4 Sherman tanks for France before being nationalized on29 May1945 as Société Nationale d'Etude et de Construction de Moteurs d'Aviation (SNECMA). This new entity continued manufacturing existing engine lines such as the14N and14R series while also developing new models like the14U.

Licensed Variants and International Production

The 14K engine stood out as a premier powerplant of its time and was extensively licensed worldwide. In Poland, it served as the power source for export fighter models such as the PZL P.24. In Romania, it equipped several Polish-origin PZL fighters before becoming the main engine for the IAR 80 aircraft. Yugoslavia manufactured the 7K, 9K, and 14N-0 versions under license at Industrija motora Rakovica.

Italian manufacturers Isotta Fraschini and Piaggio obtained licenses to produce the engine, creating the K.14 and P.XI respectively, which powered various pre-war export aircraft. Hungary's Manfred Weiss also produced a licensed version known as the WM K-14, which powered their adaptations of the Reggiane Re.2000 fighter (MAVAG Heja "Hawk") and the Weiss WM 21 Sólyom.

The British firm Alvis secured licenses for both the 14K and 18L models but did not commence production before World War II concluded. Following the war, Alvis developed the 9-cylinder Alvis 501 Leonides and the 14-cylinder Alvis 701 Leonides Major, with the latter primarily utilized in helicopter engines.

In the Soviet Union, the Tumansky OKB produced close to 500 units of the 14K under license, designated as the M-85.

Gnome

Le Rhône

Interwar Period

World War II

Motorcycles

Beginning in the 1920s, Gnome et Rhône diversified their production into bicycles and motorcycles, creating popular and elegant machines. They founded the Société Française des Moteurs ABC in Paris to manufacture the Granville Bradshaw-designed ABC motorcycle, producing it until 1924. Bradshaw's initial design featured a 400cc engine that was later enlarged to 493cc, with approximately 3,000 units built. Subsequently, the company developed proprietary motorcycle models featuring single-cylinder and flat-twin engines that remained in production through World War II. Notable models included:

  • 3CV Type Junior ()
  • 4CV Major ()
  • 4CV Super Major ()
  • 5CV Type D.5 ()
  • 5CV Type C.V.2 ()
  • 5CV Type V.2 ()
  • Type X ()

See also

References

  • Aircraft Piston Engines: A Historical Overview, Herschel Smith, Sunflower University Press, 1981

External links

  • Gnome – features an animated demonstration of the Gnome valve mechanism>
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