High-speed performance, including a graph of road wheel horsepower versus speed.
| Identifier | ExFiles\Box 160\2\ scan0059 | |
| Date | 12th June 1925 | |
| R.R. 493A (50 H) (D.D. 31, 12-6-25) J.H.D. EXPERIMENTAL REPORT. -9- Expl. No. REF: Hs {Lord Ernest Hives - Chair} /Rm {William Robotham - Chief Engineer} 2/LG121025 [GRAPH] Y-Axis: Road Wheel H.P. X-Axis: Road Speed M.P.H. Key: A B = Loss in max. speed due to under-gearing - (1.5 m.p.h.) C D = Loss in max. speed due to silencer. (2.25 m.p.h.) [/GRAPH] (4) HIGH SPEED PERFORMANCE Windage. With a normal touring car, a large increase in engine power will only produce a very small increase in max. speed due to the rapid increase in wind resistance. A good example of this is the New PhantomCodename for PHANTOM I and Silver Ghost1907 40/50 historic RAC 15,000 miles trial cars. The former has 33% more power but a max. speed less than 10% greater than the latter. Exhausts. In the same way, a free exhaust (cutout), though it effects an appreciable gain in horse power, increases the max. speed but little. The main function of a cutout is to improve the high speed acceleration which it undoubtedly does. Projected car area. Streamlining. It should be remembered in considering a sporting car body that figures for the projected windage area of the car do not mean very much. It is possible to reduce the wind resistance of a given projected area 50% by careful streamlining. This was actually accomplished on The Thomas Special car this year. It is not generally contd:- | ||
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).