Clerget aircraft engines
Clerget is the name given to aircraft engines designed by the French engineer Pierre Clerget(fr) in the first half of the 20th century. From 1912, Clerget focused his efforts on developing a series of rotary aircraft engines, which were widely used in French and British aircraft during World War I. More than 30,000 Clerget rotary engines were manufactured in France by Clerget-Blin and in Great Britain by Gwynnes Limited they were used on such aircraft as the Sopwith Camel and Vickers Gunbus.
In the 1920s Pierre Clerget turned his attention to diesel radial engines and finally produced a H-16 engine before he died in 1943.
Early Clerget engines
[edit]The first Clerget aero engine to enter series production was the 50 hp model of 1910. The engine was a water cooled inline-4 with aluminum pistons which produced 50 hp (37 kW) (40 hp (30 kW) when hot) for a weight of 73 kg (161 lb). The engine was used on several pioneering aircraft including the Coandă-1910 and the first Etrich Taube. Clerget also designed a second larger inline-4 producing 100 hp (75 kW). Both these engines were manufactured by Clément-Bayard.[1]: 106–110
In October 1910, at the Paris Air Show, Clément-Bayard showcased the powerful 200 hp Clerget water cooled V8 aero engine.[1]: 106–110 The engine weighed 290 kg (640 lb) which gave a power to weight ratio of only 0.515 kW/kg (0.313 hp/lb),[2] considered remarkable for its time period.[3] The engine featured a form of variable valve timing, utilising a camshaft that could be adjusted axially to engage different cam profiles. This allowed the opening period of the intake and exhaust valves to be optimised during flight.[1]: 118 [2] In 1912, a single 200 hp Clerget engine was fitted to the giant Voisin Icare Aero-Yacht.[1]: 110
Early Clerget engine types
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- 50 hp Clerget
- (1910) 50 hp (37 kW), inline 4
- 100 hp Clerget
- (1910) 100 hp (75 kW), inline 4
- 200 hp Clerget
- (1910) 200 hp (150 kW), V8
Early Clerget engines on display
[edit]- A 50 hp Clerget engine is displayed at the Vienna Museum of Science and Technology.[4]
- A 200 hp Clerget engine is displayed at the London Science Museum.[5]
Rotary engine development (spark ignition)
[edit]
From 1912, Pierre Clerget devoted himself to the design of rotary engines. Clerget's designs were successful, initially with the sports aircraft market and then with military customers. More than 30,000 Clerget rotary engine were built during World War I.[1]: 116
What distinguished the Clerget rotary engine from its rivals (Gnome and Le Rhône) was that the Clerget had normal intake and exhaust valves unlike the Gnome, and the connecting rod arrangement was much simpler than the Le Rhone. A source of failure among the Clerget engines were the special-purpose piston rings, called obturator rings. These were located below the gudgeon or wrist pin, to block heat transfer from the combustion area to the lower part of the cylinder and overcome their subsequent distortion. These rings were often made from brass and only had a lifespan of a few hours. The Clerget engines were considered reliable but they cost more per unit to produce than their rivals. Unlike other contemporary rotaries in which the ignition system was either switched on or off to provide a rudimentary form of engine speed control, the Clerget featured a throttle.
The Bentley BR1 and Bentley BR2 rotaries were designed as improvements of the Clerget, while sharing some of the earlier engine's distinctive design features.
Design features
[edit]The Clerget rotary engines were air-cooled with either seven, nine or eleven cylinders. They were fitted with a double thrust ball race, which enabled them to be used either as a pusher or as a tractor engine.
The engines worked on a four-stroke cycle. The chief points of difference from other rotary engines were:
- The connecting rods had a tubular section.
- The inlet and exhaust valves were mechanically operated by means of separate cams, tappets and rocker arms.
The direction of rotation was counter (anti)-clockwise as seen from the propeller-end of the engine. Like many other rotary engines of the period they were made chiefly of steel, for strength and lightness.
Rotary engine types
[edit]- Clerget 7Y
- (1912) 45 kW (60 hp), seven-cylinder.
- Clerget 7Z
- (1913) 60 kW (80 hp), seven-cylinder.
- Clerget 9A
- (1913) 82 kW (110 hp), nine-cylinder derivative of 7Z. (designation reused for radial)
- Clerget 9B
- (1915) 97 kW (130 hp), nine-cylinder. (designation reused for radial)
- Clerget 9Bf
- (1915) 104 kW (139 hp), nine-cylinder long stroke version of the Clerget 9B. The most numerous British production engine with 2,350 units being built.
- Clerget 9J
- (1917) 82 kW (110 hp), nine-cylinder. Redesigned with aluminium pistons, tubular connecting rods and revised valve gear.
- Clerget 9Z
- (1915) 82 kW (110 hp), nine-cylinder.
- Clerget 11Eb
- (1918) 150 kW (200 hp), 11-cylinder, single-row engine.
Rotary engines on display
[edit]- A locally-built Clerget 9B of 1917 is displayed at the Museum of Lincolnshire Life.
- A preserved Clerget 9B engine is on public display at the Fleet Air Arm Museum, RNAS Yeovilton.
Operational rotary engines
[edit]The Shuttleworth Collection based at Old Warden Aerodrome in the UK, operate an airworthy late production Sopwith Triplane (G-BOCK)[6] fitted with an original 9B as well as an airworthy late production Sopwith Camel (G-BZSC)[7] fitted with an original long-stroke 9Bf. These aircraft can be seen displaying at home air displays through the summer months.
Radial 'X' engines
[edit]- Clerget 16X
- A 420 hp (310 kW) 16-cylinder, four-row X engine.
Diesel radial engines
[edit]
In the 1920s Pierre Clerget designed static diesel radial engines, the earliest were based on his rotary designs.
- Clerget 9A
- (1929) 100 hp (75 kW) nine-cylinder, single row radial engine.[8]
- Clerget 9B
- Clerget 9C
- Produced under licence by Hispano-Suiza as the Hispano-Suiza 9T
- Clerget 14F-01
- (1937) 14-cylinder, two-row radial engine, flown in a Potez 25 biplane.
- Clerget 14F-02
- Clerget 14Fcs
16H engine
[edit]Clerget's final engine design was a V-16 designated Clerget 16H and known as the Type Transatlantique. It developed 2,000 hp (1,500 kW) through the use of four Rateau turbochargers.
See also
[edit]References
[edit]- ^ a b c d e Hartmann, Gérard (2004). Pierre Clerget (1875-1943): Un motoriste de génie [Pierre Clerget (1875–1943): A Genius Engine Designer] (in French). Editions de l'Officine. ISBN 978-2914614641.
- ^ a b Angle, Glenn D. (1921). Airplane Engine Encyclopedia. Dayton, Ohio, USA: The Otterbein Press. p. 122.
- ^ "Aerial Motors at the Salon". Flight. 2 (45). United Kingdom: 903. 5 November 1910.
- ^ "Clerget 50 hp, Vienna Museum of Science and Technology".
- ^ "200 hp Clerget, Science Museum Group: Collection". London.
- ^ The Shuttleworth Collection - Sopwith Triplane Retrieved: 21 August 2018
- ^ The Shuttleworth Collection - Sopwith Camel Retrieved: 21 August 2018
- ^ Grey, C.G., ed. (1931). Jane's all the World's Aircraft 1931. London: Sampson Low, Marston & company, ltd. p. 42d.
- "Air Board" Technical Notes issued by Controller Technical Department for persons holding an official position in His Majesty's Service dated 1918
- Gunston, Bill (1986). World Encyclopedia of Aero Engines. Wellingborough: Patrick Stephens. pp. 44–45.
- Clerget Aero Engines: Instructions and List of Parts. Camden Miniature Steam Services. 2001 [1917]. ISBN 0-9536523-1-9.
External links
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