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 describing the speed control of a motor and a method for determining vibration frequency.
| Identifier | ExFiles\Box 53\1\ Scan067 | |
| Date | 20th February 1928 guessed | |
| - 2 - The second trick is the speed control of the motor. This is done roughly by a rheostat, but the fine adjustment which makes the object appear to move slowly either forward or backward, is done by a screw-adjusted friction brake on the motor-spindle. 3000 cycles per minute is about top speed, but objects moving much faster are readily seen as stationary by choosing a sub-multiple of the actual speed. The frequency of a vibration is readily arrived at by finding the two neighbouring frequencies at which the objective appears stationary. Thus if an object appears stationary under 2000 flashes per minute and also 3000 flashes per minute, it is actually moving at 6000 cycles per minute I believe Derby Exp. Dept. would find this device of extraordinary use. Very truly yours, MO r {Sir Henry Royce} / [Stamped in red ink] COPY | ||