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 ignition coil performance, discussing issues with ballast resistance, current draw, and potential misfiring in Goshawk engines.
| Identifier | WestWitteringFiles\I\October1922\ Scan64 | |
| Date | 28th October 1923 | |
| EFCH/T28.10.23. -7- Contd. result having been experienced with two coils. with 30" of ballast they are not immune. The Goshawk coils on the other hand are not immune with the 10" ballast. The actual current taken by the 40/50 coil with 20" ballast would be about 1.8 amperes as against about 1 ampere for the standard 40/50 arrangement, so the efficiency would be low. To summarize the whole position it appears to us that all these experiments show that in the size of coil we have adopted we have very little margin for untoward conditions. When all the circumstances which affect results are favourable we have a coil, the power of which is capable of performing the ignition operation of the Goshawk engine under all conditions of running. When, however, this is not the case, there seems a possibility that under the most adverse conditions of running some failure of the nature of misfiring will occur. In pre-Goshawk days we had even felt this in connection with the 40/50, but it appears now to be a little more aggravated owing to the requirements of the Goshawk being a little more exacting. It might be possible, without increasing the size of the coil, to increase its power by giving the core a larger cross sectional area. There would appear to be an optimum size of core for a given size of coil which would store up the largest magnetic energy available for the spark at break. Contd. | ||