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).
Analysis of dynamo performance and electrical load requirements for various chassis models.
| Identifier | ExFiles\Box 60\3\ Scan214 | |
| Date | 17th March 1933 | |
| -2- Cont'd.{John DeLooze - Company Secretary} Instrument board lights (4 watt) .75 ampere. Battery ignition 1.25 ampere. ___________ Total 14.5 amperes. If it is assumed that the car will not be driven faster than say 60 M.P.H. with the windscreen wiper in operation we have to balance at speeds above 60 M.P.H. a continuous load of 13 amperes and 14.5 amperes at speeds below 60 M.P.H. The dynamo fitted to this customer's car must therefore be capable of delivering 13 amperes continuously at say 13 volts at speeds above 60 M.P.H. without failure. The maximum dynamo speeds for our chassis are approximately as follows:- 40/50HP. - 5250 R.P.M. Bensport. - 4500 R.P.M. 20/25HP. - 5000 R.P.M. Peregrine. - 5000 R.P.M. The commutator sparking on each dynamo in question must therefore be reasonable at the above speeds and loading. Previously the third brush dynamo only delivered about 8 amperes at the maximum speeds quoted above hence although there was a debit of 5 amperes the commutator sparking was better. In the case of customer (b). we assume his maximum continuous discharge load will be only 10.5 amperes assuming that he uses the legal 36 watt headlamp bulbs. The conditions are thus much easier as regards commutation at high speeds etc., but the dynamo cutting in speed must be earlier. In the case of customer (c) we assume that his maximum continuous discharge load will be the same as (b) but his battery will be in a lower state of charge due to the continuous use of the starter hence his dynamo must be capable of giving a high rate of charge without overheating. In order to completely satisfy all conditions of running therefore our vibrator controlled dynamo must be capable of giving a high rate of charge when required at low battery voltages without dangerously overheating, have a relatively early cutting in speed and must be capable of balancing the continuous discharge load at high speeds without failure. | ||