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).
Development and performance improvements of the New Peregrine Starter Motor.
| Identifier | ExFiles\Box 62\1\ scan0069 | |
| Date | 22th October 1932 | |
| X6134. R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/Wst. c. Ss.{S. Smith} Wor.{Arthur Wormald - General Works Manager} c. E.{Mr Elliott - Chief Engineer} De. c. By.{R.W. Bailey - Chief Engineer} Hdy.{William Hardy} Hs{Lord Ernest Hives - Chair}/Wst.5/KT. 22.10.32. NEW PEREGRINE STARTER MOTOR. It will be remembered that the original motor with a carcase diameter of 3.750" gave a very poor torque speed characteristic, and it was decided to increase the size of the motor to 4" in order to gain the extra power. The first 4" motor produced had exactly the same number of armature conductors as the original one, advantage only being taken of the extra iron in the magnetic circuit. It was found, however, on test that this motor gave a very poor torque speed performance with hardly any increase in power over the 3.750" diameter carcase motor. After considerable thought on the matter we decided that these small motors must obviously work at a very much higher flux density than the larger motors we have usually been associated with, and therefore we revised our calculations on the basis of allowing a much higher magnetisation. This reduced the number of conductors necessary in the armature considerably and to prove our theory we had another armature made up with only half the number of conductors as previously. As the conductors were of the same cross sectional area we gained a considerable increase in the cross sectional area of the iron in the armature teeth, thus improving the magnetisation characteristic of the iron at this point. This motor on test gave an extraordinary increase in power, the stalling torque being approx. 30% better, and the efficiency correspondingly higher. Comparison of this motor with the little Bosch is very satisfactory and we can see our way now to still further improve this motor in a number of items, such that we hope to eventually have a motor on the Peregrine which will be even better for its size than the Bosch. The reason we state this lies in the fact that we consider our arrangement of winding the main field and teaser on each of the four poles of the motor is a better scheme than the Bosch who put the main winding on two of the poles and the teaser winding on the other two. We are particularly anxious to improve the speed of this motor for a given torque, owing to the fact that on the Bensport using a supercharger it is necessary | ||