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, focusing on ballast resistance, magnetic saturation, and operating voltage.
| Identifier | WestWitteringFiles\I\October1922\ Scan61 | |
| Date | 28th October 1922 | |
| -4- Contd. what we should consider to be excessive, particularly in view of the fact of the smaller output available from the dynamo as compared with the 40/50. We do not mean that the reduction in the ballast resistance does not effect an improvement - there is a progressive improvement in reducing the ballast resistance, but in most cases the phenomenon is not eliminated, even though a ballast resistance of 1c" is used. It would rather point to the fact that the coil is already working near its point of magnetic saturation, so that an increase in the current at break is not accompanied by as much flux change at break as might be expected. This is also borne out by the fact that an increase of operating voltage to 16 did not, in the case tried, entirely eliminate the trouble. Though in the ordinary way the ignition will work on 8 volts, this being the voltage which is used in putting the coils through the specification of test, a reduction in the voltage on the chassis ignition system aggravated the phenomenon described. One or two other larger coils of different makes have been tried, particularly two 6-volt (normally) Remy coils, each with a ballast resistance mounted upon it, one of primary inductance suitable to six cylinder working, and one suitable to 12 cylinder working. Naturally it would be anticipated that these coils would work correctly on 12 volts with a certain amount of ballast (included in Contd. | ||