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).
Test report for an A.T. Speedometer allotted to a 10,000-mile test chassis, detailing temperature-based reading variations.
| Identifier | ExFiles\Box 59\2\ Scan018 | |
| Date | 18th February 1930 | |
| X4308 18.2.30. X.4308. A.T. SPEEDOMETER NO. C.561 740. 11/50. ALLOTTED TO 10,000 MILE TEST CHASSIS 14-GIV. This instrument has been tested for spindle revolutions per counter mile and found to give the figure 742.6. Driven at 600 r.p.m. it has been adjusted to give the following readings in miles per hour at temperatures quoted :- Temperature oC. Miles per hour at 600 r.p.m. 20.0 50.2 23.0 49.9 25.0 49.7 30.0 49.4 32.0 49.3 For internal correctness of the instrument the readings should be 48.5 miles per hour at 600 r.p.m. On the car the instrument will be driven at 750 revs. per mile at which the correct miles per hour at 600 r.p.m. are 48.0. The instrument will therefore read mileages 1.0% high, the speed indications cold 4.5% high and speed indications hot 2.5% high. It is intended that the instrument be again subject to laboratory test after the completion of the 10,000 miles to ascertain if any loss of eddy current drag has occurred. [Handwritten initials: EFC] EFC. | ||