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).
Design and instructioning of a 56 coil 20/25 dynamo armature with modified slots and air gap.
| Identifier | ExFiles\Box 62\3\ scan0176 | |
| Date | 5th February 1931 | |
| To Ry. from EFC. C. E.{Mr Elliott - Chief Engineer} X.6106 56 COIL 20/25 DYNAMO ARMATURE WITH 18 SWG. CONDUCTORS. X.6076. In our EFC2/AD2.1.31 we gave our reasons for making the experiment of a P.2. dynamo armature with wider and deeper slots than normal to an extent sufficient to accommodate conductor wire of one gauge larger in section. This has been duly instructed by Ry/RD's dept. together with special pole pieces providing an air gap of .015" instead of the normal .022". Although we have not reached the stage of bench testing this arrangement, we are so confident of the result that we now wish to ask you to instruct an armature on similar lines for the 20/25 again with a special set of poles to give the minimum possible air gap mechanically which we believe is .012". In this 20/25 case the narrowing of the neck at the base of the tooth is relatively a little more pronounced than in the Phantom case, therefore this 20/25 armature will be the equivalent of carrying the principle a little further which is as we desire. We attach a sketch showing the relative dimensions of the old slots for 19 S.W.G. wire and the new slots for 18 S.W.G. wire. Will you please return this sketch in due course as we wish to keep it in our file. Will you please arrange for the instructioning of such a special armature and pole pieces at your early convenience. An interesting point is that we have all along noticed that output curves from the 20/25 dynamo have been somewhat more rounded and better maintained at speed than those of the 40/50, which we think may be due to the reluctance through the armature having been relatively greater than in the 40/50 case. EFC. | ||