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 and potential improvements for J.2 and Bensport starter motors.
| Identifier | ExFiles\Box 62\1\ scan0096 | |
| Date | 28th November 1932 | |
| X6091 To E.{Mr Elliott - Chief Engineer} from Hs{Lord Ernest Hives - Chair}/Wst. c. Wor.{Arthur Wormald - General Works Manager} Sg.{Arthur F. Sidgreaves - MD} c. Ry. Hs{Lord Ernest Hives - Chair}/Wst.7/AD28.11.32. J.2 AND BENSPORT STARTER MOTORS X6134 We confirm our conversation this morning regarding the performance of the above motors. When the J.3 starter was designed, the same carcase was used as the 20/25 Bendix type motor whereas the design should have allowed for the fact that a sequence motor requires a little extra length of pole in order to accomodate the teazer winding as well as the main. In order to obtain proportionally the same electrical performance as the 4½" 20/25 motor the diameter should have been approx. 4¾" to 5". All our sequence starter motors on 40/50, Peregrine and J.2 turn the engine too slowly and we consider a move in the direction of immediately increasing the carcase diameter and reducing the length is considerably overdue. This would enable our motors to be working more nearly at their maximum B.H.P. point and will reduce the amount of current taken from the battery owing to the motor working more efficiently. These remarks refer more particularly to the J.2, Bensport and 40/50. Another proposal is to mount the starter motor rearwards alongside the clutch pit. This can possibly be effected with the proposed use of a separate gear box and would result in the motor being lifted higher, reducing the possibility of flood damage as well as giving much better scope for starter motor size etc. With the direct drive type of starter, our gear ratio is limited by the size of the flywheel so that unless some means can be effected of giving us a double reduction we must go to the larger diameter starter. For instance, a reduction in gear ratio of from 12 to 1 to 20 to 1 on the Peregrine would increase the engine speed 12% and result in a reduction of 35 amperes in the current taken from the battery. Hs{Lord Ernest Hives - Chair}/Wst. | ||