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).
Suggesting design improvements for a 56 coil P.2. dynamo armature using 17 S.W.G. conductors.
| Identifier | ExFiles\Box 62\3\ scan0081 | |
| Date | 1st January 1931 | |
| X6076. To By.{R.W. Bailey - Chief Engineer} from EFC. c. E.{Mr Elliott - Chief Engineer} EFC2/AD2.1.31. X.6076. 56 COIL P.2. DYNAMO ARMATURE WITH 17 S.W.G. CONDUCTORS. We know from experience of the results on the output capabilities of dynamos with different variations of windings and magnetic circuits, that the general result of increasing the reluctance of the magnetic circuit is, coeteris paribus, a raising of the speed of cutting in together with the raising of the peak output and the tail end of the output curve. We have recently proved, that subject to re-correction of the brush positions, the same result practically is brought about by making this increase by means of increasing the air gap concentrically as by taking off the poles in the manner that has been our practice. It has occurred to us that an equally similar result should surely be produced if the increase of reluctance takes place by removing iron from the armature teeth instead of removing iron from the pole pieces, which at once gives us the further advantage of providing more space for copper conductors. It is true that from the point of view of design of an ordinary shunt wound machine, the size of teeth (in relation to slots) thus resulting may appear wrong. A battery controlled generator, however, which is required to give an output not increasing with speed, is a different proposition and may easily become a justification for abnormalities in the tooth and slot design. Our definite suggestion is to produce a 56 coil armature with slots sufficiently widened and deepened to take 17 S.W.G. copper conductors in place of 18 S.W.G. the number and arrangement remaining as before. It is understood that there is already in existance a milling cutter (used to cut the slots in the higher output 56 coil 3 turn per coil machine) which would be capable of cutting these slots to the necessary depth. Will you please arrange to have such an experimental armature instructed as we consider the possibilities of such an armature are sufficiently attractive to render this step of value. EFC. | ||