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).
Scale calibration data for a Bampost Rythn type A.T. Speedometer.
| Identifier | ExFiles\Box 59\2\ Scan275 | |
| Date | 14th November 1933 | |
| New Bampost Rythn type A.T. Speedometer Makers specific 795 R.P.M at 63 M.P.M. Thus 757 will be the Revs. per mile. Scale Calibration. R.P.M. OF DRIVE M.P.H. INDICATED FAST OR SLOW + - 18°C 30°C 65°C 18°C 30°C 65°C 130 137 131 10 -3.0% -8.5% -3.6% 260 270 293 20 -7.0% -7% -16% 397 400 391 30 -5% -5.3% -3.3% 523 528 512 40 -3.75% -4.5% -1.5% 647 650 628 50 -2.6% -3% -1.0% 771 768 743 60 -2% +1.5% +2% 881 878 850 70 - +1.7% +3.6% 999 997 953 80 +1.1% +1.25% +5.5% 1105 1105 1066 90 +2.5% +2.5% +6.1% 1220 1220 1177 100 +3.5% +3.5% +6.5% NB 14-11-33 | ||