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).
Insufficient dynamo output on the 20/25 Chassis and proposed solutions.
| Identifier | ExFiles\Box 163\6\ img192 | |
| Date | 21th July 1932 | |
| X6076 To R.{Sir Henry Royce} from E.{Mr Elliott - Chief Engineer} E.1/HP.9.7132. c.c. Sg.{Arthur F. Sidgreaves - MD} Sor. TN. Hs.{Lord Ernest Hives - Chair} By.{R.W. Bailey - Chief Engineer} re Battery Charging 20/25 Chassis. It has been generally realised for some time that the dynamo output on the 20/25 is insufficient for satisfactory operation under all conditions of service, and that in this respect the 20/25 is inferior to the Phantom, particularly as regards the road speeds at which the dynamo commences to register a charge. A number of attempts have been made to improve the output, but until recently any improvement in cutting in was attended by added loss of output at high speed, and this led to the suggestion to use the P.II dynamo on the smaller chassis with some suitable safeguard to prevent battery overcharging. We have looked into this matter as desired and find that the larger dynamo can be comfortably accommodated on the 20/25 crankcase, in fact the existing casting can be bored to fit the larger carcase, as is shown on the blueprint LeC.3130 attached. It is however necessary to modify the exhaust manifold and downtake pipe to obtain the necessary clearance. LeC.3130 shows the existing type so modified, but the sliding gland design of exhaust is due to be standardised, and could be altered before adoption. The scheme proposed for taking care of the charge is to use two stages of resistance inserted in the field circuit, giving two rates of charge as well as full charge, instead of having full charge, reduced charge, and no charge. The present no charge position of the ignition switch would be replaced by a Summer daylight running | ||