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 output improvements for the Phantom II and 25 HP models.
| Identifier | ExFiles\Box 163\6\ img039 | |
| Date | 6th May 1930 | |
| X 6016 EFC. By } FROM R.{Sir Henry Royce} E.{Mr Elliott - Chief Engineer} Hs.{Lord Ernest Hives - Chair} } (At Le CanadelHenry Royce's French residence) R1/M6.5.30. X8780 X 6016 c. to Sg.{Arthur F. Sidgreaves - MD} Wor.{Arthur Wormald - General Works Manager} Da.{Bernard Day - Chassis Design} c. to OV. Mr. Brock. CAR WORK - PHANTOM 2. & 25 HP. DYNAMO OUTPUT. 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. Mr. 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 never 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 excitation 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. | ||