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Obturator ring

From Wikipedia, the free encyclopedia

An obturator ring was a type of piston ring used in World War I aero engines for improved sealing in the presence of cylinder distortion.


The cylinders of rotary aircraft engines of World War I (engines with the crankshaft fixed to the airframe and rotating cylinders) were notoriously difficult to keep cool leading to thermal distortion. To keep the weight down they had very thin-wall (1.5 mm) steel cylinders.[1] Obturator rings, made of bronze in the early Gnome engines,[2] could flex to the shape of the cylinder. Wear on the rings was considerable. Engines needed to be overhauled about every 20 hours.[3] The reliability of Gnome engines license-built by The British Gnome and Le Rhone Engine Co. gave an overhaul life of about 80 hours mainly as a result using a special tool to roll the 'L' section obturator rings.[4] The problem of thermal distortion was effectively cured on the Bentley BR1 engine by using aluminium cylinders, for good thermal conductivity, with cast iron liners shrunk in.[5]

An 'L' section obturator ring is shown in Patent US 1378109A - "Obturator ring".[6]

See also


  1. ^ The Rotary Aero Engine, Andrew Nahum 1987, ISBN 1 900747 12 X, p.40
  2. ^ Aviation Engine Examiner, Major Victor W. Page, The Norman W. Henley Publishing Co., 2 West 45th Street, New York 1931, p.146
  3. ^ The Rotary Aero Engine, Andrew Nahum 1987, ISBN 1 900747 12 X, p.40
  4. ^ I Kept No Diary, Air Commodore F.R. Banks 1978, ISBN 0 9504543 9 7, p.63
  5. ^ The Rotary Aero Engine, Andrew Nahum 1987, ISBN 1 900747 12 X, p.27
  6. ^[bare URL PDF]

This page was last edited on 13 March 2022, at 18:07
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