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).
Page of mathematical formulae for calculating the revolutions and deflection of a speedometer drive.
| Identifier | ExFiles\Box 59\2\ Scan124 | |
| Date | 23th March 1931 guessed | |
| -4- The revolutions per minute of the speedometer drive :- N = GRS/60 = G/60 (R_oS - bs{A J. Barnes - Assistant Manager}^2) G being the fixed gear ratio of speedometer drive revs. to wheel revs. The deflection of the indicating pointer reckoned in divisions on any proportional miles per hour scale is :- d = cN{Mr Chamberain} (c being a constant) = cG/60 (R_oS - bs{A J. Barnes - Assistant Manager}^2) In the absence of any speed effect of the tyres the deflection :- d_o = cG/60 . R_oS whence S = 60/cG . d_o/R_o and cG/60 .bs{A J. Barnes - Assistant Manager}^2 = 60/cG .b d_o^2/R_o^2 and finally d = d_o - 60b/(cGR_o^2) . d_o^2 = d_o - kd_o^2 (k being yet another constant) | ||