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).
The bench re-testing of an A.T. Speedometer B.563 which showed unsteady readings.
| Identifier | ExFiles\Box 50\4\ Scan254 | |
| Date | 10th December 1928 | |
| Hs. {Lord Ernest Hives - Chair} from EFC. {E. Fowler Clarke - Electrical Engineer} Cr. {Mr Cra???ster / Mr Chichester} Hs {Lord Ernest Hives - Chair} /HEL. X4308 EFC {E. Fowler Clarke - Electrical Engineer} 2/T10.12.28. A.T. SPEEDOMETER B.563. 800. 14/52 WITH SMALL TYPE DIAL. HS {Lord Ernest Hives - Chair} /AJL1/LG7.12.28. This speedometer has now been re-tested on our bench. With the 14/52 axle ratio and standard tyres, when the car is doing 45 m.p.h. the speedometer drive speed is 600 r.p.m. Previous to putting this instrument on the car we found that the reading at 16°C to be 47.2 m.p.h., corresponding to a reading at 30°C of almost exactly 45 m.p.h, representing an increased reading at 16°C of nearly 5% (positive error). On now re-testing this instrument at 600 r.p.m. exactly we find the reading at 16°C to be unsteady between 40.7 and 43.7 m.p.h. showing that the reading has materially altered. The previous test showed the reading to be quite steady. There is no variation in the drive which is by means of a synchronous motor on the Corporation Mains. We do not know the exact reason of this alteration but we are returning the instrument to the makers for their remarks. EFC. {E. Fowler Clarke - Electrical Engineer} EFC. {E. Fowler Clarke - Electrical Engineer} | ||