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).
Gear ratio compromises for a damper speed control unit on the Bensport gearbox speedometer drive.
| Identifier | ExFiles\Box 178\3\ img261 | |
| Date | 1st July 1932 | |
| P. FROM HDY.{William Hardy} Copy to - HS.{Lord Ernest Hives - Chair} BENSPORT SPEEDOMETER DRIVE. We are providing for a damper speed control unit on the Bensport gearbox, and the combined drive for this and the speedometer involves us in a compromise in the speeds. We can arrange for a gear ratio between speedometer and engine of .215, which will give approximately 640 revs. per mile against the 810 of Phantom and 25HP. The maximum revs. per minute of the speedometer will be about the same as on the Phantom. The above appears to us to be unlikely to present any difficulties. There will be slight loss of accuracy at the lowest speeds perhaps compared with our standard instruments. We should prefer to run the speedometer however still slower, say .143 engine speed, giving 430 revs. per mile, and a maximum RPM. 2/3rds. of that of the Phantom. Would you kindly let us know, after enquiring of the makers if necessary, whether this lower speed will be too low for the necessary sensitiveness of the instrument over its whole range. HDY.{William Hardy} | ||