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).
Results and conclusions of aerodynamic smoke tests on a car model, focusing on screens and tails.
| Identifier | ExFiles\Box 160\2\ scan0129 | |
| Date | 27th June 1933 | |
| -2- EV.{Ivan Evernden - coachwork}14/KT.27.6.33. Screens & Tails. (Group 2). Generally speaking there was no gain by any increased angle of screen, in combination with either tail, with any of the standard front wings. Smoke Tests. In view of these rather disconcerting results we decided to restore the model to its original condition representing the green car saloon 2.B.4. and to pass chemical smoke through the tunnel and to observe the behaviour of the air currents around the car. The following features were recorded. (1) The majority of the air stream at a point about two inches in front of the car became deflected sideways and upwards and did not come into contact with the car again. All of the body appeared to be in a backwash of eddy currents and not in the main stream. (2) Such air as did pass close to the car's surface appeared to be accelerated through the gap between the front wings and the bonnet and radiator. (3) Much air appeared to pass under the car and was expelled in a state of violent turbulence from beneath the petrol tank and rear wings. Conclusions Reached at this Stage. (1) It was evident that the front wings and radiator were setting the air into a state of turbulence, that it was no wonder that any improved screen angle or tail shape produced no beneficial results. In fact, the longer tail produced an increased drag in some tests due to its increased skin resistance (2) The fact that the air was crowding through the spaces between the wings and bonnet indicated that the re-entrant angle was a bad feature. (3) Because of the passage of air under the car being great and turbulent, a loss in this direction was indicated, which could be dealt with by either an undershield, or preventing its entry under the front of the car. Subsequent Tests resulting from Observations. The model was fitted up with the 350 screen and | ||