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 memorandum discussing the dynamo output and two-rate charge scheme for various vehicles.
| Identifier | ExFiles\Box 163\6\ img114 | |
| Date | 3rd January 1931 | |
| X6016 To R.{Sir Henry Royce} from EFC. To Sg.{Arthur F. Sidgreaves - MD} c. By.{R.W. Bailey - Chief Engineer} E.{Mr Elliott - Chief Engineer} c. PN.{Mr Northey} Wor.{Arthur Wormald - General Works Manager} EFCl/AD3.1.31. X.6084. P.2. DYNAMO OUTPUT AND TWO-RATE X.6016. CHARGE SCHEME. Refs. R2/M23.12.30 and SC21/E31.12.30. We agree that the suggestion contained in our EFCl/ADl.2.12.30 is somewhat complicated. We cannot understand the statement that 18-EX cuts in at 13 m.p.h. and is charging constantly at 10 amperes at very slow speeds. The dynamo in itself is of exactly the same type as the one on Sg{Arthur F. Sidgreaves - MD}'s car which, when in a hot condition, attains a terminal P.D. of 14.0 volts at a road speed of 15 m.p.h., this would be about the speed at which the cut-out is first operated with no dynamo field resistance inserted. With a field resistance such as was originally arranged on Sg{Arthur F. Sidgreaves - MD}'s car, this first cutting in point would be raised to slightly over 19 m.p.h. At 25 m.p.h. a small charge of 3 to 4 amperes was given to the battery. The only difference between the system on 18-EX from that on 58-GN is in the fact that the latter was originally fitted with a resistance of rather high value. 18-EX as sent away was fitted with an intermediate value resistance but a range of resistances was provided so that variations might be tried out. When everything is cold somewhat lower cutting in speeds than those quoted might be noted. An output curve of the 48 coil machine at 80°C. and at 14.0 terminal voltage was exhibited on a blue print attached to our EFC2/AD9.12.30 (Curve No.II). When the dynamo is cold both the cutting in point and the output would be somewhat improved. An output of 10 amperes could not be reached at least until 21 m.p.h. The equipment fitted to 58-GN was one of six sets which had been produced for trials cars in further confirmation of the satisfactoriness of the system, as indicated by the 10,000 mile test on 23-EX. It was for that reason that no particular selection was made of a resistance better suited to Town running conditions. | ||