obturator ring
{{Short description|Part of aero engines}}
{{Other uses|Obturator (disambiguation){{!}}Obturator}}
An obturator ring was a type of piston ring used in the early rotary engines of some World War I fighter aircraft for improved sealing in the presence of cylinder distortion.
Purpose
The cylinders of rotary aircraft engines (engines with the crankshaft fixed to the airframe and rotating cylinders) suffered from uneven cylinder cooling as the side facing the direction of rotation received more cooling air which lead to thermal distortion. To keep weight down the cylinders on rotary engines had very thin-walls (1.5 mm)The Rotary Aero Engine, Andrew Nahum 1987, {{ISBN|1 900747 12 X}}, p.40 and some had no cylinder liners. On engine types without cylinder liners, obturator rings, made of bronze in the early Gnome engines,Aviation Engine Examiner, Major Victor W. Page, The Norman W. Henley Publishing Co., 2 West 45th Street, New York 1931, p.146 were fitted as these were soft enough to not damage cylinder walls and could flex to the shape of the cylinder.
In operation wear on the rings was considerable. Engines needed to be overhauled about every 20 hours. The reliability of Gnome engines license-built by The British Gnome and Le Rhone Engine Co. was improved with an overhaul life of about 80 hours being achieved, mainly as a result using a special tool to roll the 'L' section obturator rings.I Kept No Diary, Air Commodore F.R. Banks 1978, {{ISBN|0 9504543 9 7}}, p.63 Clerget rotary aircraft engines also used obturator rings which were prone to overheating and seizure.{{Cite book| title=My life and my cars|last=Bentley|first=Walter Owen|date=1969|publisher=A S Barnes|chapter= 5 - Aero Engines|language=en|isbn=978-0498073427}}
Le Rhône and Bentley BR1/BR2 rotary engines used cylinder liners and were sealed using conventional piston rings rather than obturator rings.{{cite book |author= |date=1919|chapter=Chapter II - The 80 and 110 Horsepower LeRhone Motor|title=Rotary Engines|location=United States|publisher=The War Department}}{{Cite book |last=Lumsden |first=Alec |title=British Piston Engines and their Aircraft |date=2002 |publisher=Airlife Publishing |isbn=1853102946 |pages=88 |language=en}}
See also
References
{{Reflist}}
External links
[https://patentimages.storage.googleapis.com/31/ba/4e/d0d1dff885aaff/US1378109.pdf An 'L' section obturator ring is shown in Patent US 1378109A - "Obturator ring".]
{{Aircraft piston engine components}}