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).
Recommendations for improving the Bensport starter motor by increasing power.
| Identifier | ExFiles\Box 62\1\ scan0118 | |
| Date | 7th February 1933 | |
| X6134 To E.{Mr Elliott - Chief Engineer} from Hs{Lord Ernest Hives - Chair}/Wst. c. By.{R.W. Bailey - Chief Engineer} Wor.{Arthur Wormald - General Works Manager} c. Sg.{Arthur F. Sidgreaves - MD} Hs{Lord Ernest Hives - Chair}/Wst.6/KT. 7.2.33. BENSPORT STARTER MOTOR. If we fit the existing 20/25 starter motor to the Bensport it will be necessary for the power of this motor to be improved. It has been proved that with the Bensport high compression engine, starting under cold condition is extremely difficult. Increasing the gear ratio with this motor will not give as much increase of engine speed, as the B.H.P. torque curve is rather flat. Additionally much mechanical difficulty is introduced when an attempt is made to alter the ratio. We feel that with this size of motor, considerable increase in power could be effected by rearrangement of design. On the Peregrine starter motor we are actually gaining .1 B.H.P. over the maximum BHP. (.8) developed by the 20/25 starter motor. As the 20/25 motor is 1/2" extra diameter than the Peregrine, it should be possible to effect a considerable increase in max. BHP. without alteration to external design. A rearrangement of the windings for increased power is much more attractive, and would involve less expense. Our recommendations for alteration to the motor XX based on our experience with the Peregrine motor are as follows :- (a) Increase the armature core length by .375" (b) Increase armature diameter to 3.000". (c) Machine the armature for 33 slots and wind on one turn per coil of D.71710 strip, as XX has already been arranged for the new Japan motor. The iron circuit will be slightly better than the Japan owing to the diameter being slightly larger. (d) Reduce pole core length to suit armature diameter and increase core length to suit armature increased core length. | ||