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).
Letter requesting the properties of dynamo brushes previously submitted for testing by British Carbons.
| Identifier | ExFiles\Box 62\3\ scan0225 | |
| Date | 6th May 1931 | |
| X6066. Hs{Lord Ernest Hives - Chair}/CAP1/AD. 6th May, 1931. Messrs. British Carbons, Crowther St.{Capt. P. R. Strong} Bradford. Dear Sirs, Some time ago you submitted for test, samples of your brushes suitable in dimensions for our car dynamos. We should now be pleased if you would supply us with values for the following properties of those brushes. (1) Grade of brush, i.e. whether graphite or carbon etc. (2) Specific resistance in ohms per inch cube. (3) Coefficient of friction. (4) Normal current density in amperes per sq. inch. (5) Contact drop, in volts, at normal current density. (6) Maximum speed, in feet perminute, at which commutator may run. We should also be pleased to have similar information concerning any other grade of brush which you can recommend. Thanking you, Yours faithfully, FOR ROLLS-ROYCE LIMITED. | ||