The Sopwith Dolphin, a restored First World War aircraft now on show at RAF Museum Hendon, features a new set of extension springs manufactured by Lee Spring for use on the replica Lewis guns.
The single-seat fighting aircraft served operationally from January 1918 to July 1919. At its peak, the Sopwith Dolphin equipped five RAF Squadrons, mainly in France with a handful on home defence duties during the First World War. A total of 1778 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 RAF Museum Cosford. The restoration includes some original parts from different Dolphin aircraft, but any unavailable parts were primarily manufactured using original Sopwith Aviation (the manufacturer) drawings.
Revealing that Lee Spring provided two new music wire extension springs for use in the Lewis gun mechanism, John says: "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. 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.
Chris Petts, Managing Director at Lee Spring, Europe, says: "This is a truly unique application. It is another example of how varied the applications of Lee Spring are, and we are delighted to be part of such an historic restoration project."
For more information about springs from Lee Spring, visit their website at www.leespring.co.uk, or to learn more about the Sopwith Dolphin go to www.rafmuseum.org.uk/research/collections/sopwith-dolphin-5fi/.