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).
With a graph showing the horsepower required to overcome wind resistance at various road speeds.
| Identifier | ExFiles\Box 178\1\ img015 | |
| Date | 15th February 1926 | |
| - 3 - Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}/LG15.2.26. If on the other hand the car is originally travelling at 60 m.p.h. and a head wind of 10 m.p.h. again blows upon it, the extra H.P. necessary to keep the car going is 20 HP. In other words a 10 m.p.h. head wind at 60 m.p.h. has 3.3 times the effect of the same wind at 30 m.p.h. GRAPH II POWER OF WIND AT VARIOUS ROAD SPEEDS H.P. TO OVERCOME WIND RESISTANCE ROAD SPEED M.P.H. 30-40. 6 H.P. 60-70. 20 H.P. Hs{Lord Ernest Hives - Chair}/W.A. Robotham. | ||