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).
Analysis of saloon car performance based on wind tunnel data and various aerodynamic modifications.
| Identifier | ExFiles\Box 160\2\ scan0162 | |
| Date | 4th December 1933 | |
| -2- Ev.{Ivan Evernden - coachwork}1/KT.4.12.33. There is enough data here to predict the performance of any possible modification of the saloon car with considerable accuracy. We were able to predict the streamlined saloon's performance from the Wind Tunnel Data, and the known performance of the Standard Saloon. Certain interesting facts are indicated by the attached data sheet. (1) The "K" derived from the Tunnel Drag is about the same as obtained in the American Tests. The actual calculated vale of "K" based on the measured speed and horsepower of the two cars tested, is much higher. Even if the "K" be taken on the half mile speed, it is still much higher. Without an actual car's performance as a basis, the wind tunnel tests would not be of so great a value. (2) The Reflex Testing Method gives the highest drag but this appears to be anything from 20% to 35% too low. (3) As previously pointed out in Ev.{Ivan Evernden - coachwork}14/KT.27.6.33. changing of wings, screen angle, or tail length will make little difference to the performance of the standard saloon. The only front wings which are better than the standard are the Penhard and Cycle Type, and then the gain is small. (4) The complete filling in of the front of the car (tests 20 & 21) is the greatest in its effect, giving 3 M.P.H. to the lap speed. (5) The removal of the maximum overall width from the back, as in the case of the standard saloon to approx. the windscreen section on the streamlined saloon, coupled with a reduction in projected area of 17.5%, is the real cause for the latters enhanced performance. Of this we suggest that most of the improvement comes from the latter source as lap speeds of the standard saloon and the streamlined saloon are almost exactly inversely proportional to the projected area 86 x (23.4 / 19.025)^(1/2) = 94.5 (6) Cycle type front wings appear to add considerably to the drag as compared with no front wings, but the | ||