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 analysis of a motor's design, focusing on magnetic flux, torque, and a comparison with a post-war Bosch motor unit.
| Identifier | WestWitteringFiles\Q\2April1927-June1927\ 97 | |
| Date | 10th May 1927 guessed | |
| -3- Contd. than in the other case. It would appear that the difficulty in the design of this unit is to produce sufficient magnetic flux to set up a large longitudinal pull without at the same time setting up too much rotational torque. The large torque at zero moderate speed causes the motor to attain a moderate speed very quickly. As the motor appears to us, we think that too much length of pole core, and therefore field winding space, has been sacrificed in getting an armature of a certain size, and that conditions would be better if the size of the armature were reduced. The teazer winding occupies space on the pole cores which is not being used in normal running and therefore the pole cores should be relatively deeper than in an ordinary motor. We think this is largely the reason why we have not been able to get such good efficiency from this motor on the brake test as on our standard 6" motor at present on the Phantom. We have carefully compared the post-war Bosch motor unit, and we find that whereas the external carcase diameter of the Bosch is very nearly the same as our own, viz. 5.000", its armature diameter is 2.750" as against our 3.100". The armature active length of the Bosch is 2.800" as against our 2.750". On the Bosch, although the machine is 4-pole from the iron point of view, two opposite poles are energized with similar polarity by the main current, and the other two opposite poles similarly with the teazer current, the space Contd. | ||