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).
Dynamo output variations related to brush gear, bedding, and reversed rotation.
| Identifier | WestWitteringFiles\V\2January1931-April1931\ Scan034 | |
| Date | 3rd February 1931 guessed | |
| -3- LPCS/AM3.2.31 contd. The phenomenon appears to be bound up with the general design of the machine and the grade of brush material rather than in inaccuracies of the brush gear -- Our attempts to overcome it so far as seem necessary or desirable are in the direction of altering the brush grade and in altering the output characteristics of the machines in the direction of later cutting in and higher output by the inclusion of more than normal reluctance in the magnetic circuit. It has been noted that any modification of this kind has, in general, a beneficial effect on commutation. A definite test has established that the output of a machine is the same when brush bedding is O.K. and brush angles are the same even if the grade of the brushes be changed within reasonable limits (say from the Carbon Z. to Morganite E.G.2.). (2b) Subsement variation of output. As referred to in the last paragraph above, it is outside our experience that there is any variation of output apart from the original drop, arising from the effects of vibration, road shocks etc. It has to be remembered that dynamo output is greatly subject to variation as a result of varying dynamo temperature and operating voltage. There is also a slight hysteresis effect which results in the peak output when the speed is being reduced being a little less than that when the speed is being increased. It is assumed in this that brush holders are remaining firm and that their dimensions and limits are in accordance with the original specification, in short, that no variation of bedding is possible as a result of original brush gear inaccuracies. (3) Alteration of output caused by reversed rotation. We have satisfied ourselves by actual test that no alteration of output occurs as a result of backward/running in the absence of brush gear dynamo inaccuracies and defective brush bedding. Actual tests on both a 40/50 dynamo on a car and a 20/25 dynamo on the bench showed no alteration whatever in the peak output as a result of running the dynamo backwards. | ||