thumb|upright=1.14|Preserved [[Clerget 9B rotary engine on display at the Pima Air & Space Museum]]
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 1910 to 1913 a series of, Clerget badged, inline-four and V8 aero-engines were manufactured and marketed by the Clément-Bayard automobile firm.
From 1912, Pierre Clerget focused his efforts on developing a series of rotary aircraft engines and founded a new company, Clerget-Blin in 1913. During World War I, more than 30,000 Clerget rotary engines were manufactured in France and the United Kingdom with the type powering many aircraft including the majority of Sopwith Camels.
Following the bankruptcy and liquidation of Clerget-Blin in 1920, Pierre Clerget joined the Service Technique de l'Aéronautique (STAé) where he specialised in the design of aircraft diesel engines up until his death in 1943.
The first Clerget engine designs
In 1895, at the age of 20, Pierre Clerget graduated with a diploma in mechanical engineering after attending evening classes that he began in 1892. During this period, he also maintained a small workshop within a larger engineering facility owned by his father. From 1895 to 1908, Clerget was primarily engaged with the design of engines for automobiles, buses, and trucks for a variety of customers in his native Dijon and in Paris. In 1901 he designed a relatively successful inline four-cylinder engine, some of which were sold to airship pioneers. The engine was used on several pioneering aircraft including the Coandă-1910 and the first Etrich Taube. Clerget also designed a similar, larger inline-four engine that produced . Both these engines were manufactured by Clément-Bayard. 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.
thumb|200 hp Clerget aircraft engine displayed at the London Science Museum
;Clerget 50 hp (4V)
:(1910) , , inline-four
;Clerget 100 hp (4W)
:(1910) , , inline-four
;Clerget 200 hp
:(1910) , , V8
Early Clerget engines on display
- A 50 hp Clerget engine is displayed at the Vienna Museum of Science and Technology.
- A 200 hp Clerget engine is displayed at the London Science Museum.
Rotary engine development (spark ignition)
thumb|Cylinder head of a Clerget 9J, showing the two valve rockers and the induction pipe from the rear of the engine
Beginning in 1911, Clerget's engines were built under an agreement with the firm Malicet et Blin with manufacturing outsourced to Clément-Bayard. 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. In 1913, Pierre Clerget founded a new company, Clerget-Blin with the industrialist Eugène Blin. More than 30,000 Clerget rotary engine were built during World War I and powered the majority of Sopwith Camel fighter aircraft flown by the Royal Flying Corps.
Design features
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.
Rotary engine types
Source:
;Clerget 7Z
:(1913) , seven-cylinder.
;Clerget 9A
:(1913) , nine-cylinder derivative of 7Z. (designation reused for radial)
;Clerget 9B
:(1915) , nine-cylinder. (designation reused for radial). Most numerous of the Clerget engines with 6,500 built in France and 5,200 manufactured, under licence, in the United Kingdom.
;Clerget 9Bf
:(1917) , nine-cylinder long stroke version of the Clerget 9B. 2,350 engines built with all production taking place in the United Kingdom.
;Clerget 9Z
:(1915) , nine-cylinder.
;Clerget 11Eb
:(1918) , 11-cylinder, single-row engine.
;Clerget 9J
:(1918) , nine-cylinder. Postwar development aimed at the light aircraft market. Redesigned with aluminium pistons, tubular connecting rods and revised valve gear.
Rotary engines on display
- 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
The Shuttleworth Collection based at Old Warden Aerodrome in the UK, operate an airworthy late production Sopwith Triplane (G-BOCK) fitted with an original 9B as well as an airworthy late production Sopwith Camel (G-BZSC) fitted with an original long-stroke 9Bf. These aircraft can be seen displaying at home air displays through the summer months.
X16 engine
;Clerget 16X
:An experimental 420 hp (310 kW) 16-cylinder, four-row X engine. (a lightweight high-silicon aluminium alloy).
Diesel radial engines
right|thumb|A Clerget 14F diesel aircraft engine preserved at the Conservatoire de l'Air et de l'Espace d’Aquitaine
Following the bankruptcy and liquidation of Clerget-Blin in 1920, Pierre Clerget joined the Service Technique de l'Aéronautique (STAé) as an engineer and remained there up until his death in 1943. During this period, Clerget primarily specialised in the study of aircraft diesel engines, particularly radial designs.
;Clerget 9B:(1930) nine-cylinder, single row radial engine.
;Clerget 9C: (1932) nine-cylinder, single row radial engine. Produced under licence by Hispano-Suiza as the Hispano-Suiza 9T
;Clerget 14D: (1933) 14-cylinder, twin-row radial engine.
;Clerget 14E: (1934) 14-cylinder, twin-row radial engine, flown in a Potez 25 biplane.
;Clerget 14F: (1934) 14-cylinder, twin-row radial engine, licensed to Hispano-Suiza and Panhard.
V16 diesel engine
Clerget's final engine design was a V-16 diesel engine designated as the Clerget 16H and known as the Type Transatlantique. It was projected to develop 2,000 hp (1,500 kW) through the use of four Rateau turbochargers. Development of the engine ended with outbreak of World War II and the subsequent occupation of France.