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).
Breakdown of wind resistance figures for various car components, based on wind-tunnel tests.
| Identifier | ExFiles\Box 160\2\ scan0038 | |
| Date | 1st February 1924 | |
| THE WIND RESISTANCE OF CARS+ I am indebted to Captain Malcolm Campbell for some very interesting figures relating to the wind resistance of cars. The tests which have resulted in the data set forth below were carried out by Messrs. Boulton and Paul, of Norwich, in their wind-tunnel, and were taken for the purpose of designing a new body for the record-breaking twelve-cylinder Sunbeam. The figures would, of course, be subject to some amount of modification in the case of a touring car; but they are nevertheless of extreme interest to every motorist, if only because they show how relatively small is the resistance opposed by the body, and what a high proportion of the whole lies to the account of axles and wheels. All the tests are taken at 100 foot seconds, at which the total ascertained drag was 111 pounds. The component parts contribute to this as under :- Per cent. % of total drag FRONT AXLE. Axle . . . . . . . . . . . . . . . . . . 9.0 Rod . . . . . . . . . . . . . . . . . . . 1.2 Front springs . . . . . . . . . . . . . 0.5 Fittings . . . . . . . . . . . . . . . . 0.3 11.0 EXPOSED PARTS CHASSIS FRAME. Front . . . . . . . . . . . . . . . . . . 2.9 Rear . . . . . . . . . . . . . . . . . . . 2.1 Sides . . . . . . . . . . . . . . . . . . 2.2 Exhaust manifolds . . . . . . . . . . . 1.9 Brake lever . . . . . . . . . . . . . . 1.6 10.7 BACK AXLE. Axle . . . . . . . . . . . . . . . . . . . 3.8 Rear springs . . . . . . . . . . . . . . 0.7 Fitting of springs on axle . . . . . . 3.1 Fitting of springs on chassis . . . . 3.7 11.1 FRONT WHEELS. Wheels . . . . . . . . . . . . . . . . . . 13.2 Interference of body and axle on front wheels . . . . . . . . . . . . 7.4 20.6 REAR WHEELS. Wheels . . . . . . . . . . . . . . . . . . 13.2 Brake drums . . . . . . . . . . . . . . . 6.7 Interference . . . . . . . . . . . . . . 2.6 22.5 BODY. Driver and wind-screen . . . . . . . . 19.9 . . . . . . . . . . . . . . . . . . . . . 4.2 24.1 ------ ------- 100.0 100.0 Rm.{William Robotham - Chief Engineer} | ||