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).
Dynamo performance, battery overcharging risks, and potential solutions like thermostatic control.
| Identifier | ExFiles\Box 60\4\ Scan084 | |
| Date | 9th July 1931 | |
| X6099 PN.{Mr Northey}12/WT9.7.31. X6008 X6126 X6099 S/W. Hs{Lord Ernest Hives - Chair}/Pgt. Copy to R.{Sir Henry Royce} Sg.{Arthur F. Sidgreaves - MD} Mon F DA{Bernard Day - Chassis Design} Ry. Dynamo Performance. Referring to your Hs.{Lord Ernest Hives - Chair}1/AD7.7.31. It is not clear from the first par. in your memo whether you consider we are risking unwisely the reasonable upkeep of our batteries, or whether you consider we are giving undue serious consideration to the question of preventing overcharging. It certainly would appear from your statistics in respect of the 100 customers who have been given the improved output machine, that the dynamo now running on 25-EX should prove to be satisfactory for ordinary needs. With regard to the finer field-winding referred to, and the curve No. 2 on the chart (dated 1.7.31) attached to your memo, I can imagine the large output so well maintained would be extremely useful in certain cases, if not all, provided that there is a system of double switching, and some effective scheme could be made use of enabling a machine with this characteristic to cut in at say 10 m.p.h. instead of more like 14½, shown on the chart. I am aware that there is a system of thermostatic control in use quite a lot with American cars in respect of dynamo output, and it would appear not a very difficult thing to achieve, for a thermostatically controlled switch to be arranged to cut out some of the ampere-turns in the resistance or otherwise when the temperature of the machine rose beyond a pre-determined point. PN.{Mr Northey} RECEIVED 1931 JUL 10 HS{Lord Ernest Hives - Chair} | ||