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).
The results of tests on fourteen different ignition coils.
| Identifier | ExFiles\Box 164\5\ img406 | |
| Date | 6th February 1939 | |
| To Rm.{William Robotham - Chief Engineer} Rm{William Robotham - Chief Engineer}/WB.{Mr Brazier/Mr Bell}...6.2.39. Ignition Coils on 24.G.6. We have tested various coils for road performance, cold starting and maximum temperature, to find those which can be looked upon to give reliability in service. Fourteen coils in all have been tested. We give in the attached chart the maximum temperature attained, road performance, and time taken to start the car in the cold chamber at 6°F.{Mr Friese} The heat tests were taken under normal air temp. conditions, higher temperatures may therefore be expected during the hot weather. The tests however give a comparison between the various coils tried. The performance of the car was noted every 15 mins. until the coils reached maximum temp. To increase the tendency to misfire the gaps of the K.L.G.PLB.30X sparking plugs were increased to .040". We had considerable difficulty during the cold chamber tests to obtain anything like consistent results and comparable with those obtained on 28.G.6. twelve months previously. This we found was due to a weaker choke spring having been fitted, and which is at present on production. When we reverted to the stronger spring previously used, good starts were obtained on most of the coils. Summarised we find the R.R. standard coils, Bentley, P.III and Wraith as good as anything produced outside and favour their continued use. The Lucas sports is on a par with them in performance. If the hand choke control is to be continued, a stronger spring will be necessary to obtain good starts at the temperature tried. Rm{William Robotham - Chief Engineer}/W.Brazier. | ||