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).
Investigation into brush noise on 20/25 model dynamo brushes, referencing specified clearances.
| Identifier | ExFiles\Box 62\3\ scan0180 | |
| Date | 5th February 1931 | |
| RR 238 (150 BKS.) (OB 461-8-12-24) MP 306975 X6065. ROLLS-ROYCE LTD. INSTRUCTIONS. To: EFC Order No: AD 811. Customer's No: X 6065 Date: 5 Feb 1931 EFC 2/AD 26-1-31. 20/25 Dynamo Brushes. [Vertically written text] Brush noise. [Main text] Judging by the few complaints we receive both as to customers cars and from the Test dept, as well as in connection with experimental cars, the 20/25 dynamo brushes are reasonably quiet and free from sticking &c. We had cases of brushes chattering some years ago and found that this was aggravated by too much clearance between the brush holders and commutator. On this account we specified a clearance of .075" + .015" - .010" in the Production list which seems reasonable in amount and tolerance and we should want to accumulate a good deal of experience of quiet running with larger clearance if we are to depart from it in the Signed: (Cont'd) This Sheet must be filed on completion of the work. | ||