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).
Investigations into the Midgley unit and a temperature-related snag with the auto switch system's shunt coil.
| Identifier | WestWitteringFiles\R\2December1927-February1928\ Scan159 | |
| Date | 9th February 1928 | |
| EFC2/T9.2.28. -4- Contd. As indicated in EFC5/T5.12.27, we did make further investigations of the Midgley unit in order to get more familiar with the working of same, in the light of our new experiences. Without reporting the details of these tests, we may say that the results are such as to suitably substantiate the advantages of the RR. auto switch system as set out in our Notes dated Dec. 9th last on the advantages of the RR. electrical system incorporating the RR. type of auto charge control switch. As a result of auto switch testing on the road we did arrive at a result which might be considered a slight snag, and that is due to the variation in the resistance of the shunt coil with temperature. According to the setting of the instrument it would not be impossible to have a condition where the auto switch would operate with a fully charged battery when things are cold, and will never operate when everything is hot, because it is possible for the shunt coil to heat up with the application of increasing voltage to such an extent that the voltage necessary to operate it may be more than that same voltage by which it is heated, i.e. the ~~operating~~ heating voltage may never catch up with the (same) ~~heating~~ operating voltage within a reasonable voltage of the system at which we want the switch to operate - although the switch will operate cold if it so happens that the battery has not been much used. This however is a question of adjustment and can be ruled out entirely by adjusting the switch to work at a lower voltage than would otherwise be the case. (Contd) | ||