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.
| Identifier | ExFiles\Box 160\2\ scan0198 | |
| Date | 28th July 1934 | |
| Copy for files Alfriston. Edenbridge. Kent Sat. 28th July / 34 Dear Ru. You will be pleased to hear that we completed our Wind Tunnel Tests at 12:30pm today. On Monday I have to call at Brooklands to collect the models & pick up the corrected figures, otherwise we shall not get the job done while as the person who does that work is away. We have taken photographs in the tunnel, & 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 HP The lap speed was 99.6. M.P.H. you say. T.R = 1.25 x 30 = 37.5 lbs. HP due to T.R at 99.6 MPH = 10 HP. ∴ H.P. due to windage = 109.6 HP. Windage = (109.6 x 375) / 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, & so are the H.P.s. From Appendix to Wind Tunnel Tests EV{Ivan Evernden - coachwork}1/KT.9.12.33 V₂³ = (V₁² x P₂ x 375) / R₁. = (99.6² x 119.6 x 375) / 334 = 110. M.P.H. You will realise that this is only a rough shot & full report & complete data & predicted speeds will follow. EV{Ivan Evernden - coachwork} | ||