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 on an A.T. Speedometer No. A728, detailing accuracy over a temperature range.
| Identifier | ExFiles\Box 50\4\ Scan296 | |
| Date | 30th May 1929 | |
| HS {Lord Ernest Hives - Chair} 44308 30.5.29. X.4308. A.T. SPEEDOMETER NO. A728 C800 14/52. The above speedometer has been tested at 600 r.p.m. exactly over the temperature range 20°C to 33°C for accuracy of speed needle indication. At this speed the correct reading corresponding to a drive ratio of 800 revs. per mile is 45 miles per hour. The actually observed indications were as follows :- Temp (°C) M.P.H. at 600 r.p.m. 20.0 46.0 23.0 45.1 25.0 44.7 28.2 44.0 30.5 43.9 33.0 43.6 showing a correct reading at a temperature slightly over 23°C and a % fall of reading from 20°C to 33°C of 5.2 which is more than it should be according to previous negotiations with the makers. At 33°C a reading was also taken at an exact speed of 1200 r.p.m. This was found to be 87.6, whereas the correct reading at this speed at 800 revs. per mile should be 90.0 m.p.h. The scale proportionality however, is thus shown to be good. EFC. {E. Fowler Clarke - Electrical Engineer} | ||