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).
Development of new spark plugs by the Flint Company and the American Bosch Co.
| Identifier | ExFiles\Box 33\3\ Scan067 | |
| Date | 22th May 1920 | |
| OY3/G22.5.20. May 22nd. 1920. To - Mr. F.H. Royce - 2. (a) That the Flint Company is making us special plugs to suit our requirements with reference to drawings of the engine particulars of the speeds, compression pressures, etc. They imagine that their engineers will be able to give us a plug very suitable to our requirements. (b) The American Bosch Co. is just developing a new type of spark plug having three points on the body of the plug and a central electrode on a similar principle to the Lodge plug except that three earthed electrodes are separate wires pushed into the body of the plug instead of ring swaged in as on the Lodge. The electrodes of this plug are of excellent section, especially the central electrode, which is 1/8" dia. After over twelve months' experiment with one of the foremost porcelain makers in this country, they have evolved a material which is similar to the old "pot" insulator, except that it is rather finer in appearance and which is claimed to have the highest insulating heat resisting qualities of anything so far evolved. This plug is only just in production, and at present is only in the standard American 7/8" size. As soon as 18 m/m plugs are produced, we will send a set to England for test. With regard to the material of electrodes, the standard metal used here is 97% nickel and approximately 3% chromium. I have not seen the exact analysis, but understand this is the standard S.A.E. material. OY. | ||