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 battery and starter motor performance, comparing expected values to actual measurements under cold and hot conditions.
| Identifier | WestWitteringFiles\H\March1922\ Scan37 | |
| Date | 13th February 1922 | |
| Contd. -3- EFC2/T13.2.22. In the R.R. case, we consider, as stated at various times previously, that the battery characteristic and cables should be such that with the battery not too low in its state of charge, the voltage at the motor terminals should not be less than 12.00 by an amount greater than 1 volt per 50 amperes of current taken. According to this limit, in the cold case when the motor took 120 amperes, the voltage should not be less than 9.6, whereas actually the voltage was only 8.48. The loss due to the cable should not exceed 1 volt drop per 200 amperes - actually it is about 1 volt drop per 120 amperes. Again in the hot case, the motor voltage ought to be 10.76, whereas it was only 9.56. The drop in the cables should only be .31 ohm - actually it was .55 ohm. In the C.A.V. case, the cable resistances are well within our limit, so that the characteristic of supply to the motor is also within the limit. By rearranging the starter motor on the 40/50 car, with larger battery, larger cables, and R.R. standard starter motor but arranged with field coils two series two parallel, it is highly probable that owing to the more lively start we shall secure, the total number of ampere-minutes consumed in starting the engine will actually be less than at present. Admittedly, this argument would not continue to hold indefinitely, but we are of the opinion that as at Contd. | ||