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    In 1917 the Sopwith Camel airframe cost £874 and the Clerget engine that powered it cost £907. The fact that the power unit usually cost more than the airframe is not always recognized.
    The Clerget had neither the peculiar intake arrangements of the Gnome nor the strange connecting rods of the Le Rhône. Its valves were actuated by conventional rocker arms from two pushrods per cylinder—these constituting a recognition feature. Clergets were made in 110 hp and 130 hp models, however, the 130 hp may have been a little overdeveloped, since it was subject to overheating. It used a special type of piston ring, called an obdurator ring, below the wrist pin to block heat transfer from the combustion area to the lower part of the cylinder. When this ring broke, as it was prone to do, the cylinder turned blue from the heat—a blue color meant that the steel had been heated to 600°F (316°C). Clergets were generally very well engineered except for this problem—those made in England by Gwynne being especially excellent.


Clerget Rotary Engine (Type 9) - France

Date: ----------------- 1916
Cylinders: ------------ 9
Configuration: -------- Rotary, Air cooled
Horsepower: ---------- 110 (82 kw)
R.P.M.: --------------- 1,200
Bore and Stroke: ----- 4.7 in. (120 mm) x 5.9 in. (150 mm)
Displacement:--------- 931 cu. in. (15.3 liters)
Weight: --------------- 295 lbs. (134 kg)

Clerget Rotary Engine (Type 9B) - France

Date: ----------------- 1917
Cylinders: ------------ 9
Configuration: -------- Rotary, Air cooled
Horsepower: ---------- 130 (96 kw)
R.P.M.: --------------- 1,250
Bore and Stroke: ----- 4.7 in. (120 mm) x 6.3 in. (160 mm)
Displacement:--------- 992 cu. in. (16.3 liters)
Weight: --------------- 381 lbs. (173 kg)

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Created December 23, 2009. Updated October 12, 2013.