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).
Motor design calculations, torque requirements, and potential modifications.
| Identifier | WestWitteringFiles\Q\2April1927-June1927\ 139 | |
| Date | 2nd June 1927 guessed | |
| -3- Contd. (3) We use punched plated and no mica. (An experiment sometime ago on one of our 6" motors arranged like this showed very good results on brake test). A copy of a set of calculations is attached which represents what appears to us to be the most reasonable set of figures we can finally put together after careful consideration of all the information which we have. But as explained, the estimation of the ampere turns for the field is particularly only a rough estimate at the best. The torque of 1100 lb-inches assumed is supposed to be the maximum normal torque required to turn the engine under cold conditions, though it will be remembered that in the early stages of the arrangement of this motor, we took figures as high as 1900 lb-inches. There appears to us to be little doubt that this size of motor, as at present arranged, with the present ratio of 13 : 1, and with the characteristic of supply usually assumed, of 1 volt drop from 12 volts per 50 amperes, would not be able to turn against this torque, or what is the same thing, we doubt whether its stalling torque would exceed the necessary figure of 173 lb-inches. With the proposed arrangement of 116 conductors this will be more readily possible. As the result of this further consideration of the subject, we are not now necessarily so definitely of the opinion previously expressed, that the armature diameter should be smaller. Rather we feel that the carcase dia. should be bigger so as to keep the smaller ratio of armature to carcase which we think might help the special circumstances of | ||