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).
Considerations for A.T. speedometers, focusing on the factors affecting the drive mechanism.
| Identifier | ExFiles\Box 59\2\ Scan052 | |
| Date | 9th August 1930 | |
| X4308 To R.{Sir Henry Royce} from EFC. c. Sg.{Arthur F. Sidgreaves - MD} c. Wor.{Arthur Wormald - General Works Manager} E.{Mr Elliott - Chief Engineer} c. Da.{Bernard Day - Chassis Design} Ey. PN.{Mr Northey} EFC1/AM 9.8.30. X.4308. A.T. SPEEDOMETERS. The consideration of A.T. speedometers falls rather naturally into two portions which we feel should be considered in the main as quite distinct one from the other. The Drive. The revolutions per car mile of the road wheels from which the speedometer drive is taken is a quantity, the dependence of which upon :- (1) Tyre size (2) Degree of inflation (3) Speed and also perhaps (4) Nature of road surface is studied with the object of knowing the maximum variations of this quantity due to the several causes cited. The revolutions per car mile of the actual speedometer drive is arranged to be greater than this in a definite proportion by the use of suitable gearing providing a fixed speed ratio. The absolute minimum number of speedometer drive revolutions per car mile occurs with the largest size of | ||