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).
Letter to S. Smith & Sons Ltd. regarding noise issues with the chassis lighting dynamo.
| Identifier | ExFiles\Box 3\5\ 05-page115 | |
| Date | 30th August 1919 | |
| X. 295. EFC3/T. 30th August 1919. Messrs. S. Smith & Sons Ltd., 179-185 Great Portland Street, London, W.1. Dear Sirs, X 3014 X 295 CHASSIS LIGHTING DYNAMO. Thank you for your letter of the 27th inst. On our present standard dynamo, we are having great difficulty in eliminating completely (1) bearing noise, (2) magnetic hum, at a certain speed, and we are insisting with the Makers that everything shall be done to get rid of these objectionable qualities. We go to a very great length to eliminate noise on our engine, so that any noise from the dynamo is very apparent. Such noise might not appear on the bench test of the dynamo where the dynamo is rigidly clamped down, but when in position on the car, the undershield acts to some extent as a sounding box causing such noise to be re-inforced. We are giving you this information in the hope that in any dynamos you submit to us, these points will have due consideration. We consider, for instance, that a dynamo must be fitted with Hoffmann bearings and that these should not be just any Hoffmann bearings, but must be specially selected for quietness, also that all possible steps should be taken, e.g. the use of skewed armature slots or tapered pole pieces, to eliminate the magnetic hum. It might even be worth while going to the length of rigging the dynamo up for a bench test on a sort of hollow box which is not quite rigid, and which will act as a sounding box. We shall be writing you again later as regards our visit, but for the time being we cannot fix this. Yours faithfully, | ||