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).
Urgent memo discussing design challenges with the Sequence Starter Motor No. 2B with tapered armature, particularly its tight electric and magnetic circuits.
| Identifier | ExFiles\Box 64\2\ scan0166 | |
| Date | 30th June 1928 | |
| X7625B To BY.{R.W. Bailey - Chief Engineer} from EFC. c. BY/RD. URGENT MEMO. EFCL/T30.6.28. X7625B SEQUENCE STARTER MOTOR NO. 2B SCHEME WITH TAPERED ARMATURE. The size and general arrangement of this motor are such that the electric and magnetic circuits are very difficult to get sufficiently right to permit of a reasonable efficiency and performance, so much so that, it will be remembered, we had previously advocated (and R.{Sir Henry Royce} has to some extent responded to our suggestion) some change in the fundamental dimensions of the motor. Latterly, however, Mr. Royce would not further consider this but decided that we must continue with the 5" dia. carcase and the same length of armature. (It may be remembered that he had previously suggested either increasing the carcase to 5 1/2" dia. or to lengthen the armature somewhat). On the 20 H.P. motor (4 1/2" dia. carcase) we made one set of calculations only, made the motor to those calculations, and realised on bench test almost the exact performance indicated by those calculations. This resulted from the fact that the electric and magnetic circuits were comparatively easy and therefore much more amenable to calculation. In the present case this is not so; both magnetic and electric circuits are so tight that it is impossible to arrange the motor by calculation and realise even approximately the result which might be indicated. In particular it is impossible to specify with any degree of confidence the most suitable number of turns for the field winding. This being so, it is must essential that in this motor we must take every possible care to keep | ||