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 discussing spark plug issues, testing methods, critical temperatures, and recommendations for B.G. type plugs.
| Identifier | ExFiles\Box 162\4\ img160 | |
| Date | 6th August 1936 guessed | |
| -2- (b) I can only suggest that you rig up some scheme in order to heat the nose end of the plug to a temperature consistent with running conditions, and then check it for electrical resistance or leakage. Submit new plugs to this test and also plugs which have shown signs of trouble in the engine and already have a deposit build up on the insulator. (c) The critical temperature appears to be around 650°C. and above this figure. (d) I think undoubtedly that the sparking plug voltage is raised when a plug has been operating in the presence of leaded fuel, and this is the reason why I have suggested using the B.G. type of four point gap. With this type there is plenty of surface for the spark to discharge from, and it reduces gap burning, which will also further tend to raise the voltage. If you have an engine which can be fitted with 18 mm. plugs of the short reach type I could let you have some B.G. plugs, about two years old, to try out. I am afraid I will be unable to visit you before commencing my holiday on the 7th August, but I hope to come to Derby immediately upon my return at the end of that month. With kind regards, Yours sincerely, (Sgd.) F.R.Banks. | ||