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).
Windage and acceleration tests of the New Phantom (10-EX car) at Brooklands.
| Identifier | ExFiles\Box 29\3\ Scan150 | |
| Date | 30th November 1925 | |
| R.R. 408a (50 SH) (D.D. 31. 12-6-25) J.H.U. EXPERIMENTAL REPORT. Expl. No. REF. Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}/LG30.11.25. BROOKLANDS TESTS - NEW PHANTOMCodename for PHANTOM I. We have carried out our standard windage and acceleration tests on 10-EX car, a high compression (5.2 : 1) engine fitted to a sporting body. Considering that the car was fitted with a 17-tooth axle and weighed nearly 2¾ tons, when carrying two passengers and xxx instruments ready for test, its acceleration was remarkably good. The car was run throughout the tests on a 50/50 petrol/benzol mixture to reduce detonation. When using full throttle below 25 m.p.h. it was necessary to retard the ignition to avoid this phenomenon, otherwise the car was singularly free from torque reaction or vibrations. We experienced no difficulty in obtaining the benzol mixture on our run down or on the return journey. Graph 1. This shews the road wheel H.P. of the car measured on the dynamometer before and after the test, and the H.P. to drive the car calculated from our windage tests on the track. The wind resistance of a car is a very difficult thing to measure accurately. In this case our figures are obviously somewhat high because if correct the car would not exceed 76 m.p.h. Actually, from our acceleration figures it should do 78 m.p.h. and the best timed lap was 79.2 m.p.h. The best lap speed is usually higher than our other figures which are all averages. The difficulty in measuring windage is due to the fact that at very high speeds, where the wind resistance is most important, the vibration contd :- | ||