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).
Ignition troubles, improvements in A.C. insulator materials, and spark plug developments.
| Identifier | ExFiles\Box 158\5\ scan0070 | |
| Date | 25th April 1940 | |
| Rm{William Robotham - Chief Engineer} - 6. Serial No.102. OY.3/D/pr.25.40. on the ignition trouble caused by lead, but that now A.C. are getting results. The A.C. insulator material (Siemens - A.C. - Sphinx aluminum oxide base) is claimed to be physically stronger and more satisfactory than the Battelle Institute magnesium oxide base material, and has got rid of the "green glass" breakdown of the old A.C. silica-base material. The new 10 m/m plugs have got rid of the old trouble of carbon-loading which was due to insufficient clearances between insulator and shell. Cadillac will stay with the 10 m/m plug. They cannot over-heat the insulators on the latest A.C. plugs, due to improved thermal conductivity. I should see Critchfield of Delco Remy, who has promised Chevrolet for 1941 a coil which can run regularly on .050" spark gap with lean mixtures. OY. Copy to Lessells. 2 extra copies Hm.{Capt. W. Hallam - Head Repairs} | ||