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).
Temperature variation tests of an S.S. speedometer for a 40/50 HP vehicle.
| Identifier | ExFiles\Box 50\4\ Scan307 | |
| Date | 22th July 1929 | |
| By. {R.W. Bailey - Chief Engineer} from EFC. {E. Fowler Clarke - Electrical Engineer} c. Hs. {Lord Ernest Hives - Chair} X4308 EFC {E. Fowler Clarke - Electrical Engineer} 5/AD22.7.29. X.4308. UP-TO-DATE A.T. SPEEDOMETERS. 40/50 H.P. SPEEDOMETER. Further to our EFC {E. Fowler Clarke - Electrical Engineer} 4/AM7.7.29, we have now completed a test of another S.S. speedometer No.C.916-810 11/41 (N.B. In our previous report we put New PhantomCodename for PHANTOM I in error for S.S.) with results in accordance with the following table :- Temperature °C M.P.H. at 600 R.P.M. Corresponding drive revs. per mile for correct reading. 22.0 45.2 797 26.0 45.0 800 28.0 45.0 800 30.0 44.6 807 35.0 44.3 813 771 In this case it will be seen that the speedometer reads correctly in itself at almost exactly 30°C. namely 44.6 miles per hour at 600 r.p.m. and reads only 1.4% higher at 22°C. In view of the fact however, that this instrument would be driven on the car at 826 r.p.m. counted miles and speed reading at 30°C would be 2% high and the speed reading would become 3.4% high at 22°C. This particular instrument therefore, would no doubt be regarded as a very satisfactory example of what we require. Both instruments referred to have been returned to Stores. The summarised result of these tests is that we can regard the temperature variation on instruments now being supplied to us, as satisfactorily within the limits laid down by us, but that at the same time there appears to be a tendency for the absolute value of the speedometer readings to vary to a greater extent than we desire. In case it is considered necessary to write to the makers, the results given in this and our previous report, may be depended upon. Further similar results can be obtained if desired. EFC. {E. Fowler Clarke - Electrical Engineer} | ||