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).
Specifications and test results for a starter motor, including component weights and electrical resistances.
| Identifier | ExFiles\Box 34\3\ Scan143 | |
| Date | 22th March 1918 | |
| R.R. 235A (500 T) (S.D. 408. 26-4-17.) Bm. 2/156/13. -2- EFC3/T22.3.18. Contd. C.M. 4 morganite, these being the same material as used on the Lucas motor. We have several sets of experimental brushes for the R.R. starter motor of different materials, and the comparison of these will form the subject of a separate experiment. We are now arranging to carry though brake tests of the R.R. starter motor with the other two types of armature and curves for these will be issued in due course. The area of each (of the four) brush contact surface is .4 sq.ins. and the weight of the motor without armature is 23 lbs. 13 ozs. Weight of 17 slot armature = 11 lbs. 4½ ozs. " " 24 " " = 10 lbs. 13 ozs. " " 45 " " = 10 lbs. 11 ozs. We measured the following resistances with the following results:- Average resistance from brush terminal to brush terminal. .0157 ohm cold. Resistance of armature from com: segment to com: segment 90o away. .0119 ohm cold. Resistance of field winding is .021 ohm. (This resistance being composed of the four field coils in series. This figure we have carefully confirmed). The comparison of the watts consumed by the field winding of this motor with similar quantities for the Lucas and C.A.V. motors. all at their points of maximum efficiency that this quantity is about twice as great in the R.R. case as in either of the other cases. It would appear therefore, | ||