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).
From R. to EFC. discussing ignition issues with platinum points at different engine speeds.
| Identifier | WestWitteringFiles\P\July1926-September1926\ Scan111 | |
| Date | 18th September 1926 | |
| TO EFC. FROM R.{Sir Henry Royce} ORIGINAL R4/M18.9.26. [Handwritten]: VX652 [Handwritten]: 21/9/26 re. PLATINUM POINTS. Naturally running the engine at slow speed the current at the time of breaking the circuit on the battery ignition must be rather high. The contact points on a magneto would not suffer from this disadvantage. It suggests that the ballast or other resistance is still further increased. The disadvantage of increasing the inductance of the winding is that it will not fire at high speed unless supplied with high voltage. We presume that the finer primary at present being standardised permits the engines to run up to their full speed of 3000 RPM. without missing fire, with 10 volts only. At the same time at slow speeds an effective ignition should be given when the voltage is as low as 8., but even this would only allow for one cell being run down and reversed. [Handwritten in margin]: Try on test engine Please let me know these two points, and whether we can increase the inductance or resistance, so as to still further reduce the current at the time of breaking. I also think it would be wise if the ignition were tested for a prolonged time at every conceivable speed that is likely to occur on the car, and the relative destruction of the platinums noted. This would tell us whether the destruction of the platinums is at the high or low speed. I anticipate at the moment it is at the low speed - i.e. slow break large current at the time of break. [Handwritten in margin]: Bench tests R.{Sir Henry Royce} | ||