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).
Noisy 20 HP dynamo, diagnosing the cause as the positive brush holder and recommending its replacement.
| Identifier | ExFiles\Box 47\4\ Scan199 | |
| Date | 1st September 1924 | |
| V 4318 To BY.{R.W. Bailey - Chief Engineer} from EFC. EFC1/T1.9.24. X.4383. 20 HP. DYNAMO No.848. EX CHASSIS GAK.60 With reference to your EY4/H26.8.24, as stated the positive brush is particularly noisy. It is considered that the brush holder should be replaced. As regards electrical noise generally on this machine, this is rather masked by the noisy positive brush, but so far as we can judge there does not seem to be anything out of the way and we doubt if it is really more noisy electrically than many other machines that have been turned out. You will already appreciate that we do not consider a noise test on the bench is of much value, and the only thing we can do, if it is really thought that this dynamo is specially electrically noisy, is to put it on one of our cars for a noise trial, after the positive brush holder has been replaced. The precise reason why the positive brush is noisy is that the face of the brush holder against which the brush should be held jointly by the pressure of the spring and the drag of the commutator, is not plane, but presents a slightly convex surface to the corresponding face of the brush, enabling the brush to roll a little on this face, with changes in the relative values of those two forces. A minor reason is that the bottom of the holder is .090" from the commutator, whereas it should be .075". We return the machine and shall be glad to do this subsequently, if you so desire. WDA | ||