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).
Wind tunnel testing of a car model to analyze aerodynamic drag and performance.
| Identifier | ExFiles\Box 160\2\ scan0130 | |
| Date | 27th June 1933 | |
| -3- longer tail, and having the Panhard wings. The lamps were removed, the space between the wings and the bonnet were filled in with a radius of plasticine, and by a similar means the space in front of the radiator was filled in until it was flush with the nose of the front wings. Both the wings and radiator were carried down to a level well below the chassis front horns. Attached is a photograph of the model as described. (To follow) From the attached table it will be seen that this change produced a reduction in the drag of 11.8% as compared with the same screen and tail with standard front wings. In fact the drag was nearly the same as that when no front wings were fitted. As a means of discovering whether with this frontal aspect the air was less disturbed, we tested the model as before but with a 17° screen and the shorter tail. It will be seen that the drag had increased, showing that screen and tail shape are of value if the air flow is steady over them. Reversed Car. At the suggestion of Rm.{William Robotham - Chief Engineer} we tested the model with a 45° screen and long tail, with no front wings, in reverse as it was agreed that the average car today would have a better maximum speed in reverse if geared as per forward speed. It will be seen that such a car would be capable of 104.5 M.P.H. with the present horse power at the road wheels. The Table. We give the drag of the model in the wind tunnel in an air stream of 70 ft. sec., (47.75 M.P.H.) and a corrected drag after the correction for the wind resistance of the wires and the spindle deflexion had been made. The lap speeds at Brooklands have been calculated from the relative wind tunnel drags, based on the fact that the Black Saloon, 1.B.3. (Model I. Test 4) lapped Brooklands at 89 M.P.H. with 91 HP. at the road wheels. Conclusions. (1) The shape of the standard saloon is very bad aerodynamically, and that no small change to the wings or body can effect any great improvement. | ||