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).
Analysis of potential ignition failures, suggesting changes to sparking plugs and coil insulation.
| Identifier | ExFiles\Box 45\4\ Scan075 | |
| Date | 13th November 1922 guessed | |
| Contd. -3- To EFC from n. compression pressure in this smaller engine is higher than in the 40/50. It is possible however that owing to a heated or oxidized condition of the sparking plug points, the margin of electromotive force is not high, and I suggest in the experiments that cooler working plugs are tried or plugs with platinum points, or that during experiments the points are cleaned from any oxidized effect. It will be noticed also that at the higher temperatures the ballast resistance has increased so that there are other phenomenon as well as the increased electro-static losses, which might account for the failure or might contribute towards the failure experienced. Apparently there would not be the advantage in reducing the external diameter of the coil when fitted in the stabalite cases, as when fitting a coil into the bakelite case. If it is found possible to satisfactorily use the bakelite cases I should suggest that we obtained some ebonite or stabalite tubing to fit over the coil before inserting it into the bakelite case. It would seem that the metal base that is at present located on the Coshawj and its 4 metal studs would contribute to the losses, suggesting that we remove the coil as far as possible from any metal work, and secure it by a central stud or tube through which passed the L.T. wires. Design will be sent. On further reading your report it would seem the the falling in insulatioN resistance with temperature is serious and might after all be the real cause of failure; separate insulation would prove this. R.{Sir Henry Royce} | ||