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).
Suggesting an experiment to improve 20 HP dynamo commutation and discussing its noisiness and current density.
| Identifier | ExFiles\Box 50\5\ Scan188 | |
| Date | 19th June 1923 | |
| To R.{Sir Henry Royce} from EFC. c. CJ. Hy.{Tom Haldenby - Plant Engineer} X4383 EFC3/T19.6.23. X.4383 - 20 H.P. DYNAMO - COMMUTATION. It is suggested that commutation might be better if the armature slots were skewed half a pitch only, in place of a whole pitch. Would you consider an experiment on these lines to be worth while ? Regarding its effect on the noisyness of the machine, in spite of the skewed slots and tapered pole pieces, we do not seem to be entirely free from this trouble, the machine prepared for 4-C.II car just taken to you, though apparently quite silent on the bench, being rather bad on the car in this respect. We shall be in a position early next week to give you results of continuous running bench tests on a 20 H.P. dynamo doing the equivalent of 5,000 miles on the road at each of the three speeds, 1750, 2,500 and 3500 R.P.M. The current density on the positive brush of the 20 H.P. dynamo with the present (increased) output we think rather high, namely, about 60 amperes per sq.inch. On the 40/50 Lucas machines the maximum current density which occurs on the control brush at high speeds is about 46 amps. per sq.inch. On the same basis of positive brush current on the E.A.C. dynamo as on the 20 H.P., the density would be 54 amperes per sq.inch. EFC. | ||