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 the Lodge Sparking Plug Company Limited regarding the failure analysis of experimental Model SM plugs.
| Identifier | ExFiles\Box 79\1\ scan0107 | |
| Date | 1st July 1918 | |
| X6.01 The Lodge Sparking Plug Company Limited. Rugby. Telegrams: "Lodge Rugby" Telephone: Rugby 235. UNDER GOVERNMENT CONTROL. Messrs. Rolls-Royce, Ltd. Nightingale Road D E R B Y YOUR REF OUR REF AML/FB Date 1 July 1918 [STAMPED: JUL 2 1918] For the attention of Mr. Hives Dear Sirs, We have now safely received the 4 Model SM experimental plugs which you very kindly tested for us, and we have examined their condition in conjunction with your report. We have come to the conclusion that the failure of these experimental plugs with detachable pins is all explained by the pins coming loose. The moment the pins came loose there would be a blow-pipe effect which would be quite sufficient to account for the fusing of the mica, the cracking of the steatite insulator, and the loosening of the nickel sparking point, this latter being due to the very high temperature reached by the end of the copper pin. We quite agree with your suggestion that the pins came loose owing to the expansion of the metal between the internal screw and the gas-tight seating on the outside of the insulator, and we shall see that this fault is corrected in future plugs of this design. [Logos on left margin]: THE SOCIETY OF MOTOR MANUFACTURERS & TRADERS THE CYCLE AND MOTOR CYCLE MANUFACTURERS AND TRADERS UNION LIMITED. FOUNDED 1890. INCORPORATED 1910. THE MOTOR TRADE ASSOCIATION S.B.A.C THE SOCIETY OF BRITISH AIRCRAFT CONSTRUCTORS ENGINEERING EMPLOYERS' FEDERATION 1896 | ||