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 to Lodge Plugs Ltd. clarifying details about 14mm spark plugs and suggesting modifications for improved performance.
| Identifier | ExFiles\Box 162\6\ img365 | |
| Date | 26th April 1932 | |
| 84425. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}2/AD. April 26th, 1932. Messrs. Lodge Plugs, Ltd. Rugby. For the attention of MR. Bernard Hopps. Dear Sirs, With reference to your telephone call the other day re 14 mm. plugs. We think the heading of our last letter was confusing as the information given therein re 14 mm. plugs was meant to refer to 25 HP. and not the 40/50 car. Actually, the length from the C & A washer to the terminal should not be greater than on H.14. We think that one reason why the slow running has not been particularly good on the 14 mm. plugs is that they are rather badly pocketed in the head. Actually, the H.14 plug points are about .750 from the main combustion chamber. We know that pocketing the plug has a tendency to keep it cool but we feel that we might get better slow running if the A.14 was made into a long reach plug with the threaded portions somewhere near .70" long. The points could project .125" beyond this without any trouble and the cylinder head could be threaded for this length. The existing plug hole is threaded for 1/2" and the points can project beyond the end of the thread any distance that would be reasonable from the plug manufacturing point of view. Yours faithfully, FOR ROLLS-ROYCE LIMITED. | ||