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).
Technical memo discussing the late cutting in point of the dynamo on post-war cars.
| Identifier | ExFiles\Box 36\4\ scan 158 | |
| Date | 25th October 1920 | |
| x3014b To EWT. from EFC. EFC5/T25.10.20. X.3014b. RE ELECTRICAL EQUIPMENT ON POST-WAR CARS. X.516. X.3770. X.3654. In answer to your EWTHJC/G22.10.20, our remarks on this letter Oy2/G7.10.20, of Mr.Olley are as follows :- We are well aware that the particular dynamo which we fit to the cars is late in cutting in point, as compared with other dynamos which we know. Further that the cutouts vary a good deal in cutting in point and are generally definitely later than they should be in the hot condition. Thus, although the dynamo itself is somewhat late as compared with other machines, this may be made to appear worse by the fact that the cutout does not connect the battery to the dynamo quite as early as it should, particularly in the hot condition. The highest possible speed at which the dynamo must be run to balance the battery corresponding to hot condition of dynamo and fully charged condition of battery at 13.6 volts, is 725 R.P.M., the ratio of dynamo drive being 1.565. It will be found that this speed corresponds to 14 M.P.H. assuming no belt slip. The lateness of the cutout might make the cutting in point in the extreme worst condition as high as 18 M.P.H., but certainly no later than this. It should be expected that if the dynamo belt is not slipping, the cutting in speed should never exceed 18 M.P.H. and probably lie between 12 and 16 or 17 M.P.H. according to circumstances. Contd. | ||