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 Ethyl Export Corporation discussing sparking plug issues and recommendations.
| Identifier | ExFiles\Box 150\1\ scan0151 | |
| Date | 29th July 1936 | |
| CABLEGRAMS: ETHYLPORT, LONDON. 61282. TELEGRAMS: ETHYLPORT, SOWEST. ETHYL EXPORT CORPORATION Incorporated in the State of Delaware, U.S.A. with limited liability. THAMES HOUSE, MILLBANK LONDON, S.W.1 Telephone: VICTORIA 1441 Head Office: 135 EAST 42ND STREET NEW YORK, U.S.A 29th July, 1936. H.{Arthur M. Hanbury - Head Complaints} E.{Mr Elliott - Chief Engineer} West Esq., Experimental Department, Messrs. Rolls-Royce Ltd., Nightingale Road, DERBY. 86001B. Dear West, Very many thanks for your letter of the 28th July. I hope you had a good holiday despite the weather. As a matter of fact I have only just returned from the States and have been rather busy clearing up and writing my American report. With regard to this vexed question of sparking plugs, I will endeavour to answer your questionnaire as well as I can. (a) It is rather difficult to give a direct answer here because there are two problems involved. If you use a short blunt nosed insulator it will virtually be a cool running plug, and when idling may allow a certain type of deposit to pile up rather quickly. Immediately upon subjecting the engine to more load this deposit will probably become an electrical conductor as it heats up, whereas it is a fairly good insulator when cool. I would say, however, that the short nosed insulator and the cool running plug generally would be more satisfactory than the K.L.G.850 type, that is to say if it does not suffer from over oiling. Also, I would suggest sparking points of heavy construction and similar to the four point B.G. aviation plug. (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 | ||