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 to Lodge Plugs Ltd. detailing engine testing results and feedback on their spark plugs.
| Identifier | ExFiles\Box 162\6\ img187 | |
| Date | 21th November 1932 | |
| 84475. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}12/AD. November 21st, 1932. Messrs. Lodge Plugs Ltd. Rugby. For the attention of Mr. Hopps. Dear Mr. Hopps, I have just had a week in France running on your 14 mm. plugs. The engine in which they have been used is an unsupercharged job of 6 : 1 compression ratio. Some of the fuels could certainly only be described as poor. We find that your HD.{Mr Hayward/Mr Huddy}15 plug is just on the verge of pre-ignition under Continental conditions of sustained all-out running. We think that this is a very excellent state of affairs but we should like to have some plug intermediate between it and the X.306 in case we wish to raise our compression ratio slightly. The fault we have to find with the HD.{Mr Hayward/Mr Huddy}15s is that it only requires a slight amount of carbon from an over-rich mixture to cause it to miss rather badly. To quote an actual case. We had a weak mixture range on the carburetter from 30 to 50 M.P.H. We carefully cleaned the plugs and there was little or no misfiring or spitting back at these speeds. We then ran 100 miles with a definitely over-rich top mixture and the plug started missing again. We took the precaution of setting them to .015 gap before we started the test. When we dismantled the plugs, as one would expect, the film of carbon was quite light. | ||