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).
Altering the Phantom II dynamo and two-rate charge scheme, considering 48-watt versus 60-watt headlamps.
| Identifier | ExFiles\Box 62\3\ scan0082 | |
| Date | 6th January 1931 | |
| Sgd. from EFC. C. to: PN.{Mr Northey} X6004. EFC1/AD6.1.31. X.6016. PHANTOM II DYNAMO AND TWO-RATE CHARGE SCHEME. X.6004. Further to our EFC2/AD3.1.31, during further discussion of the matter with E.{Mr Elliott - Chief Engineer} on Saturday last the following further points were arrived at :- It was then decided that the alteration to the system would be unlikely to make sufficient difference to enable the battery to keep up in winter Town running conditions. For this reason it was decided that we should make use of the 48 coil medium output dynamo which has a 2 m.p.h. earlier cutting in and can be arranged to give a peak output nearly as great as the 48 coil high output machine. Such a machine is therefore being prepared for use with this system on 58-GN. A further point that has been arrived at is the question of the power of the head lamps. Where there is a small surplus of current going into the battery, then, provided the battery is already fully charged, its terminal P.D. will rise and with it the P.D. of the system. The lamps will be brighter, but at the same time the generator output will be increased. If, on the other hand, there is a small discharge from the battery, the P.D. of the battery and the system will fall to a more normal value and the output of the generator will be correspondingly less. It may, therefore, quite easily happen that with 60 watt head lamps the resulting light may not actually be as good as the 48 watt head lamps taking at least 2 amperes of current less. The point has been partly confirmed by trying 48 watt bulbs on 58-GN in which case there is a surplus of charge running into the battery over quite a good range of speed. E.{Mr Elliott - Chief Engineer} has suggested that for this reason 48 watt bulbs should be considered standard instead of 60 watt bulbs until such time as we are able fully to supply 60 watt bulbs. Seeing that in the main we are at present likely to get as good a light from the 48 watt as from the 60 watt bulbs, this would appear to be a reasonable suggestion. EFC. | ||