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).
Specifications for a new 40/50 HP dynamo armature with a larger output and higher cutting-in speed.
| Identifier | ExFiles\Box 68\4\ scan0073 | |
| Date | 28th March 1928 | |
| X8664 To BY.{R.W. Bailey - Chief Engineer} from EFC. c. BY/RD. EFC3/T28.3.28. 40/50 H.P DYNAMO ARMATURE FOR LARGER OUTPUT WITH HIGHER CUTTING-IN SPEED. we have now carefully considered this matter and have decided that what we require is an armature with 26 slots, 52 coils or commutator segments, three turns per coil, 312 conductors, 12 conductors per slot. One coil will be a lap coil as in our present 28 slot armature. The step or winding pitch in slots will be 6 (1 to 7). The conductor will be of 17 S.W.G. (.056") in place of 18 as at present. In working out the case we have allowed the insulation of the conductors and the slot to be exactly as given in your print D.70974, i.e. the alterations to the dimensions of the slot are precisely those resulting from the alteration in the number and diameter of the conductors. A rough winding diagram will be shown to Mr. Davis as a guide in the instructioning of this job. In the first instance we think only one armature should be instructed, in which case the slots will naturally be milled, the skewing of the slots being the same as we have on present standard. We expect this armature to give a cutting-in speed about 35% higher than a present standard, and an output about 53% higher. We think the present commutator dia. and brush contact area will satisfactorily agree with this, but this remains to be proved. This armature should take precedence over the 20 H.P. armature which we are also asking you to instruct in our EFC4/T28.3.28. EFC. | ||