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 for a 20 HP type, noting a lack of temperature compensation.
| Identifier | ExFiles\Box 50\4\ Scan191 | |
| Date | 17th April 1928 | |
| Y4308 EFC {E. Fowler Clarke - Electrical Engineer} 4/T17.4.28. To EY. From EFC. {E. Fowler Clarke - Electrical Engineer} c. EP. {G. Eric Platford - Chief Quality Engineer} CWB. c. Ey/Mtn. A.T. SPEEDOMETER - 20 H.P. TYPE. We have tested one of these instruments, No. B.167.N.740.11/50.. Corresponding to an axle ratio of 11/50, the correct indicated m.p.h. at 1600 r.p.m. should be 48.6, corresponding to 740 revs/mile. We found this instrument to read that amount at 21½°C. and to drop its reading down to 43.0 m.p.h. at 30°C, corresponding to a drop of from 51.0 m.p.h. at 18°C, i.e. a drop of 15.7% of its reading at 18°C. It will be seen from this that this 20 H.P. instrument is not temperature compensated in the same way as the latest Phantom instruments. The instrument has been handed to Ey/Mtn. EFC. {E. Fowler Clarke - Electrical Engineer} | ||