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).
Letter detailing the results and calculations from wind tunnel tests on a car body.
| Identifier | ExFiles\Box 155\1\ scan0152 | |
| Date | 28th July 1934 | |
| COPY. x78 Alfriston, Edenbridge, Kent. 28th July, 1934. Dear Rm.{William Robotham - Chief Engineer}, You will be pleased to hear that we completed our Wind Tunnel Tests at 12.30 p.m. to-day. On Monday I have to call at Brooklands to collect the models and pick up the corrected figures, otherwise we shall not get them for some while as the person who does that work is away. We have taken photographs in the tunnel and also chalk templates of the final car. When we had done all that we proposed the drag had been reduced to .8740 lbs. The drag for the car in racing trim was, 1.072 if I recollect rightly. The reduction was 20% Taking the road wheel HP. at standard plus 30% this equals 92 + 27.6 = 119.6 H.P. The lap speed was 99.6 M.P.H. you say. T.R. = 1.25 x 30 = 37.5 lbs. ∴ H.P. due to windage = 109.6 H.P. Windage = (109.6 x 37.5) / 99.6 = 412 lbs./ At same speed with revised body, windage would be (412 x .8740) / 1.072 = 334 lbs. The projected areas are the same, and so are the H.P's. From appendix to Wind Tunnel tests Ev.{Ivan Evernden - coachwork}1/KT.4.12.33, V^3_2 = (V^2_1 x P_2 x 375) / R 1. = P.T.O. | ||