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).
Schemes to improve dynamo output and battery charging on Phantom II and 25HP cars.
| Identifier | WestWitteringFiles\U\2January1930-September1930\ Scan106 | |
| Date | 6th May 1930 | |
| EFC. BY.{R.W. Bailey - Chief Engineer} ) FROM R.{Sir Henry Royce} E.{Mr Elliott - Chief Engineer} HS.{Lord Ernest Hives - Chair} ) (At Le CanadelHenry Royce's French residence.) C. to SG.{Arthur F. Sidgreaves - MD} WOR.{Arthur Wormald - General Works Manager} DA.{Bernard Day - Chassis Design} C. to GY. Mr. BROCK. ORIGINAL R1/M6.5.30. CAR WORK - PHANTOM 2. & 25HP. DYNAMO OUTPUT. x8780 Mr. Elliott's suggestion of extra output from the dynamo when headlamps are on appears to be extremely useful providing the dynamo will not overheat. The scheme should be tried on several customers' cars who are complaining. It should be tested out for standardisation without delay, because in any case it seems preferable to have the arrangement that has been schemed to embody the idea. Also we have now come to the conclusion that the reduced output at high speeds is not an advantage, or has been overdone in the past. Brock's scheme of getting a more level characteristic curve of output is very clever but one thinks it may be done somewhat more simply. I had however thought that there was any difficulty in altering the curve in the way desired, but probably I am mistaken. Have you tried the control brush rather further back, which would increase the output perhaps too much at slow speed. We should then increase the air gap until this was the desired amount, when I believe it would be found to be more constant for different speeds. The reason the current falls with speed seems to be that with the reduced exitation the armature cross magnetisation is relatively greater. A stiffer field altogether would, one thinks, result in less control by the control brush, also a greater span for the field circuit should also result in less control effect. It is just possible that my suggestion has the same effect as Mr. Brock's, and if so, it would be simpler and better in many ways, especially for silence and cost. This same idea may explain the difference between Lucas and RR. dynamos. Small machines always have less armature reaction because their fields and air gaps are relatively larger, or conversely their armatures are less in dia. Undoubtedly the extra resistance should be in the field circuit, and the arrangement as far as I have examined it has resulted in better than present standard, with very little trouble or expense of extra parts. Though this will be a great improvement, making some allowance between summer and winter, much daylight and night work, and also saving the battery from heavy charging current and in some cases overcharging, we still require some more satisfactory way of knowing the state of the battery charge, and in some cases a garage charging equipment, of which I have not yet seen a model. The problem is quite simple when continuous current is available, but when alternate current is used for lighting the garage a rectifier is needed. The charge could be a very small one for a long period (dribbling charge), or if more convenient say about half normal for a few hours while cleaning the car. If I remember rightly our switchbox connection socket is arranged so that the polarity of the charge cannot get wrongly connected by the plug - i.e. the poles are marked and one leg is larger than the other. I agree to go ahead with increased dynamo output when headlights switched on, and much more constant dynamo output with speed. R.{Sir Henry Royce} | ||