The Sopwith Dolphin, a restored First World War aircraft on display at the United Kingdom’s Royal Air Force (RAF) Museum in Hendon, England features a new set of extension springs manufactured by Lee Spring for use on the replica Lewis guns. The assistance and support for this restoration was facilitated by Lee Spring, Europe, headquartered in Wokingham, Berkshire, United Kingdom.

The single seat fighting aircraft served operationally from January 1918 to July 1919. At its peak, the Sopwith Dolphin equipped five RAF Squadrons during World War One, primarily in France along with a handful on home defense duties in the UK. A total of 1,778 Sopwith Dolphins were built in Britain but the model was declared obsolete in 1921.

“We believe that our Dolphin is now the only one in existence,” says John Stoyles, part of a team who restored the Dolphin now on display in the Claude Graham-White building at the RAF Museum Hendon. 

Restoration started in 1968 and was completed in early 2012 after 11 years at the RAF Museum in Cosford, England. The restoration includes some original parts from different Dolphin aircraft but any unavailable parts were primarily manufactured using original Sopwith Aviation (the manufacturer) drawings.

“The Sopwith Dolphin was the first four gun fighter, having two Vickers machine guns (pointing forwards) and two Lewis guns inclined on the top of the aircraft,” says John, revealing that Lee Spring provided two new music wire extension springs for use in the Lewis gun mechanism. “The original specified spring was 5/16 o/d, 2 1/4" long 20g steel wire, but the Lee Spring replacements were very similar and did the job admirably.”

Helical extension springs are loaded in tension and feature hooks or loops to allow a pull force to be applied. Usually, extension springs are attached at both ends to other components which, when they move apart, the spring tries to bring them together again.

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