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).
Test results concerning the voltage and amperage of the dynamo and distribution box for 20 HP and 40/50 HP models under various conditions.
| Identifier | ExFiles\Box 165\6\ img026 | |
| Date | 28th June 1926 | |
| Contd. -2- EFC3/T28.6.26. Beyond the tabulated speeds above the voltage at the distribution box would rise above 18.0 in each case. There is, however, a minimum value of the external conductance which is capable of preventing the voltage at the distribution box from rising above 18.0 in any circumstances. This was found to be .865 mho in the 20 HP. case, corresponding to an ampere output of 15.6, and in the 40/50 HP. case, 1.00 mho, this corresponding to an ampere output of 18.0. + As a matter of interest corresponding figures for the hot condition were found to be for the 20 HP. .66 mho, corresponding to 12.0 amperes output, and for the 40/50 HP. .70 mho, corresponding to 12.6 amperes output. + A further test taken with the dynamos cold was to find the dynamo speed and chassis m.p.h. at which, with no external load, the field current would reach six amperes (this current considered to be the fusing current of the - field wire). For the 20 HP. machine this was found to be .875 r.p.m. at 12.0 m.p.h. and the corresponding voltage at the distribution box was found to be 22.8. For the 40/50 HP. this was found to be 2900 r.p.m. at 17.2 chassis m.p.h. the corresponding voltage at the distribution box being 29.7. From the above results it will be seen that though it would not be impossible to drive the car with all lights on, at a moderate speed, without a battery, and in the case of a driver who was aware of the possibilities, nevertheless | ||