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).
Cost and accuracy implications of a proposal for standardized speedometer drives with a common gearbox.
| Identifier | ExFiles\Box 165\2\ img162 | |
| Date | 26th February 1938 | |
| 60651 Det. c. Rm.{William Robotham - Chief Engineer} c. BY/RD. DA{Bernard Day - Chassis Design}/Hdy.{William Hardy}1/G.26.2.38. RC.{R. Childs} This seems to be the correct course. Rm{William Robotham - Chief Engineer} B.111, SPEEDOMETER DRIVES. B.50 and WRAITH, WITH A COMMON GEARBOX. With reference to the proposal to save cost on the speedometer by arranging the driving gears on all cars to give the same revolutions per mile, the scheme we have just issued (P.D.115) is not suitable for this arrangement as the teeth are much too coarse. An extra pair of spiral gears appears to be necessary, and in this case there will be extra cost on the gearbox, which, if the costs of the pieces on our standard boxes are gone by, may amount to 25/-. We understand that of the reduction of price recently secured on the speedometer, only 5/- is likely to be due to our undertaking to standardise the revolutions per mile for all speedometers. Therefore, if this is so, from the point of view of cost, it will be best to retain our present arrangement. The present arrangement also gives the greatest accuracy, as whatever error is present in the gearing must sometimes be added to the errors due to tyre variation and to the speedometer. We do not think that it would be practicable to provide gearing which would always give within 2% of the standard speed. DA{Bernard Day - Chassis Design}/Hdy.{William Hardy} | ||