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).
Continuous running tests for a 20 HP Dynamo, investigating the effects of reversing polarity on the brush and commutator.
| Identifier | ExFiles\Box 50\5\ Scan193 | |
| Date | 30th June 1923 | |
| X4333 To R & E.{Mr Elliott - Chief Engineer} from EFC. c. CJ. & PN.{Mr Northey} c. EY. EP.{G. Eric Platford - Chief Quality Engineer} DA.{Bernard Day - Chassis Design} EFC1/T30.6.23. X.4383 - 20 H.P. DYNAMO - CONTINUOUS RUNNING - BRUSH & COMMUTATOR TESTS. X4333 Further to our EFC1/T27.6.23, we have now completed an amount of continuous running on the bench of two machines, changing the polarity roughly once every hour, with a view to determining whether there was any advantage in running with the polarity reversed from standard. There appears to be the slight advantage which would be expected, due to the equalisation on account of the fact that the positive brush for the same current generally presents a less good surface. With the standard polarity, the positive brush has to carry the largest current and with reversed polarity this has to carry a somewhat smaller current. It is doubtful at the moment if the improvement is sufficient to warrant the change, and further tests will be made on a machine running under continuously starting and stopping conditions, an arrangement for which we are at present preparing. EFC. | ||