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).
Technical memorandum discussing design modifications for a starter motor, including changes to the armature and winding.
| Identifier | WestWitteringFiles\Q\2April1927-June1927\ 138 | |
| Date | 2nd June 1927 guessed | |
| -2- Contd. Where conditions are very much easier, as in the case of the 20 HP. starter motor (only ½" smaller in carcase dia. and no teazer winding) it was not/difficult matter to arrange the quantities of the motor on paper fairly consistently, and also to appreciate on test very nearly the estimated figures of performance. In the present case, however, owing to the more saturated condition of the magnetic circuit for the performance demanded of it, it is possible for the original estimation of the quantities, and particularly that of the field winding required, to vary considerably. So much so in fact that the best arrangement of the field winding can really only be a question of test. In carefully reconsidering the whole matter, the conclusion has now been arrived at that we should depart from the 41 tooth armature with single turn per coil, and adopt a 29 tooth armature (as used on the 20 HP.) with 116 conductors and two turns per coil. We find this to give the easier magnetic circuit through the teeth apparently so necessary for the present special circumstances. A print D.71371 of the arrangement of the slots, teeth and conductors, is attached. To help to relieve the situation it is suggested that (1) The banding wires be omitted (we do this on the Phantom dynamo so there would appear no reason for not adopting it on the motor). (2) The polar embrace be increased to 76%, thus taking in 5½ tooth pitches per pole, in place of 5. | ||