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 L.S.P. Co. Ltd. discussing the performance, testing, and materials of spark plugs.
| Identifier | ExFiles\Box 162\6\ img018 | |
| Date | 8th December 1921 | |
| Page 2 L.S.P. Co. Ltd. Date 8. 12. 21 Messrs. Rolls-Royce Limited. hardly think that a higher temperature glaze was necessary. These plugs appear to have been worked at a very high temperature. As near as we can estimate we consider that the ends of the insulators have been at 1000° C. but even this temperature is a long way below the fusing point of the steatite itself, and we do not think it is possible at present to find a better material than this steatite that we manufacture, but we could omit the glaze at the sparking end of the insulator. The only difference this would have is that soot tends to cling to the unglazed surface rather more than to the glazed surface. We can also make the insulator at the sparking end a different shape which would keep the temperature lower, and if the plugs are to be used under similar conditions, such a shape would certainly be advisable, but in-as-much as we alter the shape to keep the temperature lower, we lose a certain amount of the ability to burn any soot away. We have tested all the six plugs here and they all fire correctly on our testing engine, but for our own information we have cut the plugs to pieces, and therefore enclose our credit note for them. We will shortly send you six more with a different shape insulator for you to test, and we propose to send some of them glazed and some unglazed. (Continued) | ||