Obturator ring

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.

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.

[1] 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.

[3] Clerget rotary aircraft engines also used obturator rings which were prone to overheating and seizure.

[4] Le Rhône and Bentley BR1/BR2 rotary engines used cylinder liners and were sealed using conventional piston rings rather than obturator rings.