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 a spark plug manufacturer regarding the examination and suggested modification of a 765-A plug.
| Identifier | ExFiles\Box 162\4\ img044 | |
| Date | 5th May 1934 | |
| 8198B. PHONE: PUTNEY 2671-2-3-4. TELEGRAMS: KAELGEE PHONE LONDON CONTRACTORS TO THE ADMIRALTY, WAR OFFICE, AIR MINISTRY & FOREIGN GOVERNMENTS CODES USED: { A B C 5TH EDITION, WESTERN UNION K.L.G. Sparking Plugs Limited MOTOR TRADE ASSOCIATION MAKERS OF JIGS AND PRECISION TOOLS SOLE MANUFACTURERS OF K.L.G. SPARKING PLUGS SOCIETY OF BRITISH AIRCRAFT CONSTRUCTORS S.B.A.C ROBINHOOD ENGINEERING WORKS PUTNEY VALE . LONDON . S.W.15 IN YOUR REPLY PLEASE REFER TO TECHNICAL DEPT AND QUOTE REFERENCE CMC/MEN. 5th May, 1934. Messrs. Rolls-Royce, Ltd., Derby. Gentlemen, For the attention of H.E. West, Esq. We have now made a very careful examination of the 765-A plug which Mr. West handed to the Writer in London last week. We are pleased to tell you that we can find nothing wrong in this plug and we have, therefore, had it repolished and cleaned up so that it is in perfectly good state for further use. However, in view of Mr. West's statement that some suspicion of trouble with these plugs has arisen we have examined the design carefully and have come to the conclusion that it is just possible that when the gaps become very wide occasional sparking may take place from the end of the copper sleeve to the inside wall of the body. The distance between these parts is, in our experience, adequate, but there is very little margin of safety and we have in the past had instances of sparking taking place at this point in other plugs even when this distance is considerably in excess of the width of the spark gap. In order to provide a larger factor of safety, we suggest cutting away the wall of the body at this point to a small extent and we are sending herewith a section of a plug so cut. We shall be very grateful if you will examine this as, subject to your approval, we should like to make up a set of twelve of these plugs so that they may be given a test on the road. | ||