From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Letter from Imperial Airways concerning the performance and oiling issues of 'Wizard' spark plugs.
| Identifier | ExFiles\Box 58\2\ Scan266 | |
| Date | 9th December 1935 | |
| Handwritten notes: E/BN{W.O. Bentley / Mr Barrington} B Please note and return when convenient S6000. WTP HS{Lord Ernest Hives - Chair}/Wst broken a valve head but was not satisfactory for High Duty Engines. Bn{W.O. Bentley / Mr Barrington} Printed and typed text: IMPERIAL AIRWAYS LTD AIR PORT OF LONDON CROYDON Telephone: CROYDON 4422 (10 lines) Telegrams: FLYING, CROYDON Codes: BENTLEYS & I.A.T.A. Ref: ES/JWS/MOD/11,140 9 December 1935 H.E.West Esq., Messrs. Rolls-Royce Limited, Derby Dear Mr. West, In reply to your letter of the 7th December, reference: Hs{Lord Ernest Hives - Chair}/Wst.5/MA, the "Wizard" plug is used as standard on the large aircraft of our fleet, engined with Jupiters, Servals and Jaguars. The "Wizard" plug is removed for cleaning at 200 to 250 hours, as compared with 15 to 20 hours for other types of plugs - therefore it is difficult to compare the "Wizard" with other plugs insofar as electrical failures are concerned. Nevertheless, it is reasonable to assume that, as the "Wizard" plugs remain in the engines ten times as long as the ordinary plugs, they are less prone to electrical failures. With regard to your question re the ability of the "Wizard" plug to function where a lot of oil is present, it was just this feature which caused us to turn our attention to the problem of designing a plug, with the result that the "Wizard" plug was evolved. It is a fact, however, that no plug yet made will fire an explosive mixture while the firing points are submerged in oil and this is, unfortunately, what happens in the lower cylinders of some radial engines. On many occasions I have removed a "Wizard" plug, which was oiled up in the lower cylinder of a radial, placed it in a cylinder, the plugs of which have been firing, and the oiled-up "Wizard" has always functioned correctly. Our problem now is to prevent oil reaching the combustion chambers in large quantities and this is being ameliorated by the fitting of high pressure scraper rings. One of the difficulties we have to face is the | ||