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).
Performance of a standard starter motor with a specific field coil arrangement.
| Identifier | WestWitteringFiles\G\September1921\ Scan42 | |
| Date | 8th September 1921 | |
| ORIGINAL To R.{Sir Henry Royce} A & E.{Mr Elliott - Chief Engineer} from EPC. c. to CJ. & FN. c. to Hy.{Tom Haldenby - Plant Engineer} & Da.{Bernard Day - Chassis Design} c. to Rg.{Mr Rowledge} & EP.{G. Eric Platford - Chief Quality Engineer} c. to R.R. of America Inc. EPCB/T8.9.21. X.4399 - R.R. STANDARD STARTER MOTOR WITH FIELD COILS TWO SERIES TWO PARALLEL. With reference to the proposed standardisation of the two series two parallel arrangement of field winding for the R.R. standard starter motor, and further to our report EPCI/T18.7.21 giving a comparison of the relative performance of this arrangement with the standard arrangement, we would like to make it clear that this comparison only holds exactly when the volt-ampere characteristic of the supply of current to the motor is in accordance with our assumed characteristic, namely, 1 volt drop from 12 volts for every 50 amperes of current taken. The volt-ampere characteristic of the supply to the motor on the car may approximate to this when the battery is in a fully charged condition, but usually it is likely that the characteristic will be worse. If we imagine the characteristic of the supply to be progressively improved, a motor with low resistance windings will show up increasingly better as compared with a motor with windings of high resistance. Likewise, if the supply characteristic is made progressively worse, there may come a time when the low resistance motor shows up to no advantage in performance (judging the performance by the rate at which the engine is turned), and carrying matters further, we think we are right in saying, although we have not proved this, that on Contd. | ||