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).
Modifications to the 'Japan' and 'Bensport' starter motors, specifically regarding the armature and carcass size.
| Identifier | ExFiles\Box 62\1\ scan0108 | |
| Date | 6th January 1933 | |
| Hs{Lord Ernest Hives - Chair}/Wst. x6134 BY/RD4/W.3.1.33. "JAPAN" AND "BENSPORT" STARTER MOTOR. Re :- Your proposal for 33-slot armature, and further proposal to increase the diameter 4¾" or 5". Confirming our conversation with you yesterday, it is now agreed that we shall proceed with the 33-slot armature and the 4¾" diameter carcase. We propose to share out this extra ¼" in the diameter by increasing the magnet case by .025" in thickness, the armature diameter by .100" and the pole tip by .025". The poles themselves have not been made .100 wider as you suggested, but .025" wider at the base and made from drawn bar thereby deleting the narrowing down due to the forging. The field winding strip is being wound on the flat and therefore, the semi-circular end of the pole has been deleted in favour of a flat end with smaller radii. These modifications greatly help the pole section. We attach hereto calculations showing the larger size armature strip which it is agreed to use, and also the flux density in the various parts of the magnetic circuit which now appear to be comparatively easy. We shall also instruct brushes having larger sectional area, to suit. BY/RD. RECEIVED JAN 6 1933 | ||