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).
Conclusions from an investigation into engine misfiring, ruling out spark plugs and lead deposits as the cause.
| Identifier | ExFiles\Box 150\1\ scan0182 | |
| Date | 31th August 1936 guessed | |
| 3. Conclusions. It is a well established fact that lead deposits found on sparking plugs are non-conductors at temperatures below 650°C; above this temperature fusion occurs and the deposits will become conductive. On cooling, however, cold deposits would probably also have a high resistance. In this case, from the results of the examination, it is difficult to believe that the plugs themselves, or the lead deposits, have been the cause of the misfiring complained about. The fact that the plug break down resistance was in every case equal to, or in excess of, the break down voltage required for Air Ministry test purposes, indicates that the plugs should have fired perfectly satisfactorily in the engine. This is substantiated by the pressure tests. Furthermore, from the chemical examination, there is no evidence at all of fusion, which is the only condition which would lead to the insulation resistance of the plug being diminished. In view of these two findings it can only be suggested that misfiring was due to some other cause disconnected with sparking plugs, wuch as the general electrical system or perhaps even carburation. Hossell | ||