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 and regulator tests, comparing brush life and performance across different car models.
| Identifier | ExFiles\Box 168a\3\ img083 | |
| Date | 30th March 1939 | |
| -2- Car 6.B.IV. Dynamo, 48 coil (B.II and 25/30 standard). Regulator Output 16 amperes at 13.5 volts. Brush life 6,624 miles. Car 8.B.V. (First Test). Dynamo, 40 coil 36 slot (Wraith 'B' series). Regulator output 20 amperes at 13.5 volts. (Lucas say (Bentley V) we have since reduced the maximum limit to 19 amperes). Brush life 15,083 miles (2,766 in England). Car 8.B.V. (Second Test). Dynamo, above machine overhauled. Regulator, as above. Brush life, 12,607 miles. It will be seen from the above that any increase in load tends to shorten the life of the brushes, and that the new machine tends to counteract this effect. Present day heavier loads demand a higher output in order to keep the battery in a charged condition. Our only doubt in the new machine is in the life of the commutator, which has been cheapened by production, in that pressed copper segments and pressed mica insulations are used to cut out machining, and although we have had no failures on bench tests, it is possible that distortion and the rising of segments is occurring as a result of this, and thereby causing noise and additional brush wear. We are fully investigating this, and await with interest the return of the dynamo on 8.B.V. Although adding to production costs, it may be necessary to go back to the plain amber mica, and machine finish the 'Vee' in the commutator, in order to eliminate any steps between segments. To revert to the 48 coil machine would mean returning to the lower output regulator with all the complaints of undercharging that we had about a year ago. We have had a few complaints of brush sing on the new machine, this occurs after the car has been travelling for a | ||