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).
The failures and performance summary of a 36 slot dynamo.
| Identifier | ExFiles\Box 168a\3\ img082 | |
| Date | 30th March 1934 | |
| 6142 To By.{R.W. Bailey - Chief Engineer} c. to Mx.{John H Maddocks - Chief Proving Officer} c. to By/RD. RM{William Robotham - Chief Engineer}/RC.{R. Childs}18/JH.30.3.34 re 36 slot dynamo. Two consecutive failures of a dynamo of the above type running on 3.B.V. in France, called for an investigation as to the reliability of the new type machine. Both these failures were the result of a brush wearing right down, followed by continued running on load without replacement. Warning of a worn out brush is given by erratic charging and vibration of the cut-out. If running is continued for any length of time in this condition, arcing will tend to overheat the commutator, especially at high speeds, and melt the solder of the commutator bar connections. In the above tests the dynamo failed in the first instant after 15,033 miles (2,766 in England) and in the second test after 12,357 miles. From the above, we can expect a brush life of at least 12,000 miles, probably 15,000 under normal conditions. A summary of dynamo performance on cars run in France during the last two years is as follows :- Car 26.G.VI. Dynamo 48 coil (Bentley 11 and 25/30 standard). Regulator output :- 14 amperes at 13.2 volts. Brush life :- 17,000 miles. Car 3.B.IV. Dynamo as above. Regulator as above. Brush life :- 11,356 miles. The brushes used on this test were of a grade EG12 material, which is considered by the Makers, better able to cope with sparking conditions and should have given better wear than the above. | ||