Clerget
Encyclopedia
Clerget was the name given to a series of early rotary
aircraft engine
types of the World War I
era that were designed by Pierre Clerget. Manufactured in both France by Clerget-Blin
and Great Britain by Gwynne 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 engine
s and finally produced a H-16
engine before he died in 1943.
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 ring
s, called obturator ring
s. These were located below the 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.
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 direction of rotation was counter-clockwise as seen from the propeller-end of the engine. Between any two consecutive firing strokes, the engine turned through 80 degrees. Like many other rotary engine
s of the period they were made chiefly of steel, for strength and lightness.
80 hp (60 kW), seven-cylinder.
Clerget 9B
130 hp (97 kW), nine-cylinder.
Clerget 9Bf
140 hp (104 kW), nine-cylinder long stroke version of the Clerget 9B. The most numerous British production engine with 2,350 units being built.
Clerget 9Z 110 hp (82 kW), nine-cylinder. Redesigned with aluminium pistons, tubular connecting rods and revised valve gear.
Clerget 11Eb
200 hp (150 kW), 11-cylinder, single-row engine.
radial engine
s, the earliest were based on his rotary designs.
Clerget 9A
(1929) 100 hp (75 kW) Nine-cylinder, single row radial engine,
Clerget 14F-01
(1937) 14-cylinder, two-row radial engine, flown in a Potez 25
biplane.
known as the Type Transatlantique. It developed 2,000 hp (1,500 kW) through the use of four turbocharger
s.
Rotary engine
The rotary engine was an early type of internal-combustion engine, usually designed with an odd number of cylinders per row in a radial configuration, in which the crankshaft remained stationary and the entire cylinder block rotated around it...
aircraft engine
Aircraft engine
An aircraft engine is the component of the propulsion system for an aircraft that generates mechanical power. Aircraft engines are almost always either lightweight piston engines or gas turbines...
types of the World War I
World War I
World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...
era that were designed by Pierre Clerget. Manufactured in both France by Clerget-Blin
Clerget-Blin
Clerget-Blin was a French precision engineering company formed in 1913 by the engineer and inventor Pierre Clerget and industrialist Eugène Blin...
and Great Britain by Gwynne Limited
Gwynne (car)
Gwynne was an old established engineering company based in Chiswick, London, that made cars between 1922 and 1929. It was set up by Nevile Gwynne, brother of Rupert and Roland Gwynne....
, they were used on such aircraft as the Sopwith Camel
Sopwith Camel
The Sopwith Camel was a British First World War single-seat biplane fighter introduced on the Western Front in 1917. Manufactured by Sopwith Aviation Company, it had a short-coupled fuselage, heavy, powerful rotary engine, and concentrated fire from twin synchronized machine guns. Though difficult...
and Vickers Gunbus.
In the 1920s Pierre Clerget turned his attention to diesel
Diesel cycle
The Diesel cycle is the thermodynamic cycle which approximates the pressure and volume of the combustion chamber of the Diesel engine, invented by Rudolph Diesel in 1897. It is assumed to have constant pressure during the first part of the "combustion" phase...
radial engine
Radial engine
The radial engine is a reciprocating type internal combustion engine configuration in which the cylinders point outward from a central crankshaft like the spokes on a wheel...
s and finally produced a H-16
H engine
An H engine is an engine configuration in which the cylinders are aligned so that if viewed from the front, they appear to be in a vertical or horizontal letter H....
engine before he died in 1943.
Rotary engine development
What distinguished the Clerget rotary engine from its rivals (GnomeGnome et Rhône
Gnome et Rhône was a major French aircraft engine manufacturer. Between 1914 and 1918 they produced 25,000 of their 9-cylinder Delta and Le Rhône 110 hp rotary designs, while another 75,000 were produced by various licensees, powering the majority of aircraft in the first half of the war on...
and Le Rhône
Le Rhône
Le Rhône was the name given to a series of popular rotary aircraft engines produced in France by Société des Moteurs Le Rhône and the successor company of Gnome et Rhône. They powered a number of military aircraft types of the First World War...
) was that the Clerget had normal intake and exhaust valves
Poppet valve
A poppet valve is a valve consisting of a hole, usually round or oval, and a tapered plug, usually a disk shape on the end of a shaft also called a valve stem. The shaft guides the plug portion by sliding through a valve guide...
unlike the Gnome, and the connecting rod
Connecting rod
In a reciprocating piston engine, the connecting rod or conrod connects the piston to the crank or crankshaft. Together with the crank, they form a simple mechanism that converts linear motion into rotating motion....
arrangement was much simpler than the Le Rhone. A source of failure among the Clerget engines were the special-purpose piston ring
Piston ring
A piston ring is a split ring that fits into a groove on the outer diameter of a piston in a reciprocating engine such as an internal combustion engine or steam engine.The three main functions of piston rings in reciprocating engines are:...
s, called obturator ring
Obturator ring
Obturator rings are a specific type of piston ring used in World War I aero engines to compensate for warping of the cylinders.-Purpose:The rotary aircraft engines of World War I were notoriously difficult to keep cool when operating...
s. These were located below the 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
Ignition system
An ignition system is a system for igniting a fuel-air mixture. Ignition systems are well known in the field of internal combustion engines such as those used in petrol engines used to power the majority of motor vehicles, but they are also used in many other applications such as in oil-fired and...
was either switched on or off to provide a rudimentary form of engine speed control, the Clerget featured a throttle
Throttle
A throttle is the mechanism by which the flow of a fluid is managed by constriction or obstruction. An engine's power can be increased or decreased by the restriction of inlet gases , but usually decreased. The term throttle has come to refer, informally and incorrectly, to any mechanism by which...
.
The Bentley BR1
Bentley BR1
-See also:...
and Bentley BR2
Bentley BR2
-See also:-Bibliography:* Gunston, Bill. World Encyclopedia of Aero Engines. Cambridge, England. Patrick Stephens Limited, 1989. ISBN 1-85260-163-9*Jane's Fighting Aircraft of World War I. London. Studio Editions Ltd, 1993. ISBN 1-85170-347-0...
rotaries were designed as improvements of the Clerget, while sharing some of the earlier engine's distinctive design features.
Design features
The Clerget rotary engines were air-cooledAir-cooled engine
Air-cooled engines rely on the circulation of air directly over hot parts of the engine to cool them.-Introduction:Most modern internal combustion engines are cooled by a closed circuit carrying liquid coolant through channels in the engine block and cylinder head, where the coolant absorbs heat,...
with either seven, nine or eleven cylinders. They were fitted with a double thrust ball race
Thrust bearing
A thrust bearing is a particular type of rotary bearing. Like other bearings they permit rotation between parts, but they are designed to support a high axial load while doing this.Thrust bearings come in several varieties....
, which enabled them to be used either as a pusher
Pusher configuration
In a craft with a pusher configuration the propeller are mounted behind their respective engine. According to Bill Gunston, a "pusher propeller" is one mounted behind engine so that drive shaft is in compression...
or as a tractor
Tractor configuration
thumb|right|[[Evektor-Aerotechnik|Aerotechnik EV97A Eurostar]], a tractor configuration aircraft, being pulled into position by its pilot for refuelling....
engine.
The engines worked on a four-stroke cycle. The chief points of difference from other rotary engines were:
- The pistons were of an aluminium alloyAluminium alloyAluminium alloys are alloys in which aluminium is the predominant metal. The typical alloying elements are copper, magnesium, manganese, silicon and zinc. There are two principal classifications, namely casting alloys and wrought alloys, both of which are further subdivided into the categories...
. - The connecting rods had a tubular section.
- The inlet and exhaust valves were mechanically operated by means of separate camCamA cam is a rotating or sliding piece in a mechanical linkage used especially in transforming rotary motion into linear motion or vice-versa. It is often a part of a rotating wheel or shaft that strikes a lever at one or more points on its circular path...
s, tappetTappetA tappet is the noise made by a worn cam follower, however the term is widely used to represent the cam follower itself. In mechanical engineering it is a projection which imparts a linear motion to some other component within an assembly...
s and rocker armRocker armGenerally referred to within the internal combustion engine of automotive, marine, motorcycle and reciprocating aviation engines, the rocker arm is a reciprocating lever that conveys radial movement from the cam lobe into linear movement at the poppet valve to open it...
s.
The direction of rotation was counter-clockwise as seen from the propeller-end of the engine. Between any two consecutive firing strokes, the engine turned through 80 degrees. Like many other rotary engine
Rotary engine
The rotary engine was an early type of internal-combustion engine, usually designed with an odd number of cylinders per row in a radial configuration, in which the crankshaft remained stationary and the entire cylinder block rotated around it...
s of the period they were made chiefly of steel, for strength and lightness.
Rotary engine types
Clerget 7Z80 hp (60 kW), seven-cylinder.
Clerget 9B
130 hp (97 kW), nine-cylinder.
Clerget 9Bf
140 hp (104 kW), nine-cylinder long stroke version of the Clerget 9B. The most numerous British production engine with 2,350 units being built.
Clerget 9Z 110 hp (82 kW), nine-cylinder. Redesigned with aluminium pistons, tubular connecting rods and revised valve gear.
Clerget 11Eb
200 hp (150 kW), 11-cylinder, single-row engine.
Rotary engines on display
- A locally-built Clerget 9B of 1917 is displayed at the Museum of Lincolnshire LifeMuseum of Lincolnshire LifeThe Museum of Lincolnshire Life is a museum in Lincoln, Lincolnshire, in the UK. The museum collection is a varied social history that reflects and celebrates the culture of Lincolnshire and its people from 1750 to the present day...
. - A preserved Clerget 9B engine is on public display at the Fleet Air Arm MuseumFleet Air Arm MuseumThe Fleet Air Arm Museum is located north of Yeovil, and south of Bristol. It has an extensive collection of military and civilian aircraft, as well as models of Royal Navy ships, especially aircraft carriers. Some of the museum has interactive displays...
, RNAS Yeovilton.
Diesel radial engines
In the 1920s Pierre Clerget designed static dieselDiesel cycle
The Diesel cycle is the thermodynamic cycle which approximates the pressure and volume of the combustion chamber of the Diesel engine, invented by Rudolph Diesel in 1897. It is assumed to have constant pressure during the first part of the "combustion" phase...
radial engine
Radial engine
The radial engine is a reciprocating type internal combustion engine configuration in which the cylinders point outward from a central crankshaft like the spokes on a wheel...
s, the earliest were based on his rotary designs.
Clerget 9A
(1929) 100 hp (75 kW) Nine-cylinder, single row radial engine,
Clerget 14F-01
(1937) 14-cylinder, two-row radial engine, flown in a Potez 25
Potez 25
|-See also:*Aerial operations in the Chaco War-References:Heinonen, Timo Heinonen: Thulinista Hornetiin, Keski-Suomen ilmailumuseon julkaisuja 3, 1992. ISBN 951-95688-2-4.-External links:* *...
biplane.
H-16 engine
Clerget's final engine design was an H-16H engine
An H engine is an engine configuration in which the cylinders are aligned so that if viewed from the front, they appear to be in a vertical or horizontal letter H....
known as the Type Transatlantique. It developed 2,000 hp (1,500 kW) through the use of four turbocharger
Turbocharger
A turbocharger, or turbo , from the Greek "τύρβη" is a centrifugal compressor powered by a turbine that is driven by an engine's exhaust gases. Its benefit lies with the compressor increasing the mass of air entering the engine , thereby resulting in greater performance...
s.