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).
Calibration requirements for speedometers on the India IV chassis.
| Identifier | ExFiles\Box 50\4\ Scan221 | |
| Date | 24th October 1928 | |
| X4308 Hs. {Lord Ernest Hives - Chair} BY {R.W. Bailey - Chief Engineer} /Cgh {W Clough} 4/N.24.10.28. INDIA IV. SPEEDOMETERS. ------------------------- With reference to the speedometers required for the above chassis when fitted with 11 x 50 ratio rear axle and 31 x 6" balloon tyres on 19" diameter rims, the gearing in the change speed gearbox as at present arranged will drive the speedometer at 782 revolutions per mile. The A.T. Speedometer Co. pointed out that they could not give us an instrument to suit this speed, and suggested that we should arrange to use instruments calibrated either for 765 or 800 revs. per mile. The nearest speed we could give is 743 or 821 revs. per mile by merely dropping or adding a tooth to one of the gears. It is impossible to obtain speeds nearer than this without making considerable alterations, therefore, the matter was taken up with the A.T. people, and they now inform us that they can supply us with an instrument calibrated for 776 instead of 782 as originally called for which would be within 1% and therefore within our limits. We understand you are ordering two sets of instruments for India IV. therefore, presume you will arrange for the speedometer to be calibrated at 776 revs. BY {R.W. Bailey - Chief Engineer} /Cgh. {W Clough} | ||