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).
Results of tests on a new 20/25 dynamo, proposing different field resistances for summer and winter charging.
| Identifier | ExFiles\Box 163\6\ img190 | |
| Date | 8th July 1932 | |
| Y6016 E.{Mr Elliott - Chief Engineer} From Hs{Lord Ernest Hives - Chair}/Wst. c. Pa.{Mr Paterson} Sg.{Arthur F. Sidgreaves - MD} c. Wor.{Arthur Wormald - General Works Manager} BY.{R.W. Bailey - Chief Engineer} Hs{Lord Ernest Hives - Chair}/Wst.9/MA. 8.7.32. 20/25 DYNAMO CHARGE. We have now completed tests on the new 20/25 dynamo with the two proposed field resistances for Summer and Winter charging and we attach herewith curves showing the charge :- (1) With no resistance, for night headlight running. (2) With one stage of resistance suitable for winter day charging or side and tail lamp running Summer or Winter. (3) With a second stage of resistance for Summer day charge only. This scheme of cutting down the charge in the Summer will be necessary with this larger output machine in order to avoid damaging the 20/25 battery which is smaller in capacity than the 40/50. We still have to consider the cutting in point for summer day running which is still inevitably high. It appears to us that we have to choose either to overcharge the battery in the Summer time in order to keep the dynamo cutting in point early, or to protect the battery by inserting field resistances which necessarily make the cutting in point later. This of course is one of the fundamental disadvantages of any charge scheme as compared with a vibrator regulator scheme where the cutting in point remains constant for all charge conditions. We have no two immediate alternatives for present 20/25 production :- | ||