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).
The necessary modifications for a large output 48 coil, 20 HP dynamo armature.
| Identifier | ExFiles\Box 62\3\ scan0031 | |
| Date | 26th February 1930 | |
| X.6005. Ry. from EFC. EFC1/AD26.2.30. 6005 X.5664. 48 COIL DYNAMO ARMATURE 20 HP. Further to our EFC6/AD5.2.36 we are now in a position to give you the necessary details for the large output type of 48 coil armature 20 HP. dynamo. (1) In regard to the provision of Mr. Brock's modification to the pole pieces of this machine, it is understood that Mr. Davis is preparing the necessary detail drawing. (2) In regard to the commutator position, we have confirmed that this is satisfactory in the same relative position to the armature as in the case of the medium output machine ten of which are already instructed. NB. We would point out here again that it is an advantage of the type of polar modification with which we are concerned, that the required resulting change of angular position of main brushes in relation to neutral points of the commutator is automatically effected by making the change of magnetic circuit reluctance in this manner, i.e. the neutral points on the commutator are advanced by such modification to an extent which is the automatic equivalent of retarding the main brushes by the desired amount. (3) (a) New control brush angle i.e. angle between main positive and control brushes is 125° in place of 123° on the other ten machines. (b) and (c) We are satisfied at the moment that no change of brush grade, brush bevel and shape of brush spring is required. Similar quantities in the case of the Phantom II machines are not yet finally fixed. We will give you the information in due course. EFC. | ||