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).
Comparing different armature slot configurations to reduce noise for Phantom and 20 HP models.
| Identifier | ExFiles\Box 68\4\ scan0288 | |
| Date | 21th February 1929 | |
| X5663 BY.{R.W. Bailey - Chief Engineer} from EFC. c. to BY/RD. EFC4/LG21.2.29. X.5664 INTERMEDIATE OUTPUT ARMATURE. X.5663 As referred to in our EFC1/LG20.2.29 we have now looked closely into the matter of an intermediate output armature and the following is the result : Originally we had an odd number of slots and sections in the armature and noise trouble was the result. When we adopted an even even number (28) the noise trouble almost completely disappeared. The value of an even number e.g. 26 in the reduction of the noise is rather problematical and we are of the opinion we should keep off such a number. Therefore, the possible numbers of slots and sections are 32 and 24. With 32 slots we should have 3 turns per coil or 6 turns per section, making 384 conductors in all whilst with 24 slots we should have 4 turns per coil or 8 turns per section again making 384 conductors in all. In the Phantom armature the conductor sizes would be .056" dia. for the 24 slot case and .048" dia. for the 32 slot case and in the 20 HP. armature they would be .048" dia. for the 24 slot case and .040" dia. for the 32 slot case. We are of the opinion from a comparison of the two cases, that the 24 slot case (both Phantom and 20 HP.) is the one to be chosen for the following reasons : Contd :- | ||