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 tractive resistance of a car and the expected increase in speed from an increase in power.
| Identifier | ExFiles\Box 183\M22\ img180 | |
| Date | 1st February 1924 | |
| R.R. 403 A (40 H) (SL 42 12-7-23). J.H.D. EXPERIMENTAL REPORT. Expl. No. 4578 6 EX REF: He/Rm{William Robotham - Chief Engineer}/LGS. 2. 24. INCREASE OF SPEED TO BE EXPECTED FROM A NEW INCREASE IN POWER The tractive resistance of a car consists of two main factors, a constant which may roughly be said to consist of the bearing friction, tyre rolling resistances etc. and a factor which varies as the square of the velocity which is mainly due to the wind resisting frontal area of the car. At high speeds, by far the most important factor is therefore the nature and dimensions of the frontal area of the body. In an ordinary touring body with big wings, the tractive resistance increases enormously at speeds above 60 m.p.h. the extent of this increase is shewn on the attached graph compiled from tests taken 26.2.23 on 6.EX car, a car with very fairly sporting outlines. The method of plotting the curve above 60 m.p.h. at which speed we cannot measure the tractive resistance practically, is shewn and we should say the result is a very fair approximation of actual conditions. ------------------------- | ||