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).
Material selection and design considerations for the Peregrine starter motor.
| Identifier | ExFiles\Box 62\1\ scan0079 | |
| Date | 1st November 1932 | |
| X6134 To By.{R.W. Bailey - Chief Engineer} from Hs{Lord Ernest Hives - Chair}/Wst. c. to E.{Mr Elliott - Chief Engineer} Hs{Lord Ernest Hives - Chair}/Wst.6/KT.1.11.32. PEREGRINE STARTER MOTOR. With reference to your BY.5/G.31.10.32. our reason for wishing to try Stalloy laminated pole pieces experimentally was that with this small motor the iron flux densities are higher due to the fact that the proportion of iron to copper is less than that in a large motor. When we experimented some time ago on the comparative merits of laminated and solid pole pieces it was in connection with, if we remember rightly, the old 40/50 6.00" diameter carcase motor where obviously the working flux densities must have been lower than any of our existing motors especially the Peregrine. Owing to the peculiar shape of the B.H. magnetisation curves of various irons the difference between two given samples of iron of different permeability is much more apparent at higher magnetisations. Thus a difference in permeability, which would not show any appreciable advantage on a large motor working at a low flux density, would show a considerable difference on a small motor working less efficiently at a higher flux density. In addition to what we have arrived at ourselves independently, we also observed that the Bosch Co. use laminated pole pieces on their smaller motors. It would be interesting to know the difference in manufacturing costs in making up the poles from stampings or machining them from drawn bar. We are endeavouring to obtain comparative magnetisation curves of our present standard armco iron as compared with Stalloy. Hs{Lord Ernest Hives - Chair}/Wst. | ||