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).
Gear ratios in relation to wind resistance and the fundamental laws of braking.
| Identifier | WestWitteringFiles\N\2October1925-December1925\ Scan43 | |
| Date | 12th June 1925 | |
| R.R. 493A (50 H) (D.D. 31, 12-6-25) J.H.D. EXPERIMENTAL REPORT. -6- Expl. No. REF Ho/Sm2/Ld121025 It is not generally realised that the outline of the car beneath the frame is of great importance with regard to wind resistance, a cushion of air tries to form between the car and the road, which can be eliminated by streamlining. Gear ratio: Owing to the huge wind resistance of the bodies, they carry, normal touring cars, are not geared for maximum speed but rather, lower. They are therefore rather over the peak of the power curve when all out on the road and lose perhaps 5% in H.P. This loss in H.P. can hardly be detected. The gain in acceleration, however, is appreciable. When the windage of the car is reduced considerably, 5 H.P. can make an appreciable difference in speed. A sports car may therefore benefit by a high axle ratio where a touring car would lose in acceleration, while the increase in maximum speed would not be detected. (5) BRAKING: Fundamental laws. Weight of car. Gradient. Distance, and time to rest. Windage. Rotating parts, and pedal pressure. Maximum rate of retardation. Personal comfort. Fundamental laws. (road surface); The rate at which a car can stop is not under the control of the designer. When the braking system has been arranged to give smooth and progress-ive action and to lock all four wheels (if required) with a reasonably light pedal pressure, the engineer has done everything possible, external conditions dictate the way in which contd:- | ||