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).
Tests on electrical coils comparing heating at different voltages and performance under high temperatures.
| Identifier | ExFiles\Box 69\1\ scan0124 | |
| Date | 6th July 1928 | |
| EFC3/T6.7.28. -3- Contd. each case, but again the temperature attained when running is greater than that attained when standing on contact. It will appear, therefore, that in the use of the combination of double ballast and coarser primary coil, we have the condition of the very minimum of heating for any arrangement we have used, and it appears to be a useful feature that the heating when standing on contact on 12 volts is actually less than the heating when running on the 17.5 volts, to which the system attains when charging is in progress. Other tests were also made on these two coils with a view to discovering whether the old phenomenon of weakness resulting from the material of the case was present. Quoting from my assistant's report, the nature of results of these tests are as follows :- "(b) Tests in an electric oven at various temperatures, the coil being screwed down to an earthed metal plate to approximate engine conditions. These tests consisted of raising the coil (connected up to a distributor as in (a) to different temperatures up to 100°C. and observing the maximum gap which could be inserted in series with the main H.T. supply without causing irregular firing of the distributor on 5.5 mm. three-point gaps. (c) Direct leakage effects on the coil performance by placing an earthed metal sheath round the outside of the coil case. The effect was observed by running the coil normally at 17.5 volts for 2 hours, thus allowing the coil to warm up, and then ascertaining the amount of series gap that could be inserted without causing misfiring on the H.T. gaps set to 5.5 mm. Contd. | ||