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 development of an auto switch, detailing differences from the Midgley patents and subsequent improvements.
| Identifier | ExFiles\Box 59\1\ Scan339 | |
| Date | 9th December 1927 | |
| -7- Contd. as to what extent this proposed arrangement of auto switch would avoid the Midgley patents, giving the following differences :- (1) Much bigger resistance. (2) Different method of connection. (3) Resistance wound on core. (4) Rigid contacts. (5) Passing only headlamp current through series coil. It was at a slightly later date that we arrived at the fact that the series coil could be dispensed with together and the reduction of voltage of the system by the initial rush of current in switching off the lamps to throw the auto switch back on to contact, thus item (5) once becomes "the elimination of the headlamp series coil". In our EFC3/T30.11.27 we reported the results of bench tests with no series coil and that satisfaction was obtained. We then suggested the electrical arrangement of the complete distribution board with cutout and auto switch all contained. Dated 9.12.27, we wrote some Notes on the advantages of the R.R. electrical system incorporating the R.R. type of control switch, copy of which was circulated to those concerned. At a rather later date an improvement was made on the switch by the application of temperature compensation (i.e. for change of resistance with temperature of the | ||