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 explaining the horsepower required to overcome wind resistance at various speeds.
| Identifier | WestWitteringFiles\O\2January1926-March1926\ Scan105 | |
| Date | 15th February 1926 guessed | |
| contd :- -3- to maintain the road speed of 30 m.p.h. is only 6 HP. 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. [Text on Graph] POWER OF WIND AT VARIOUS ROAD SPEEDS GRAPH II H.P. TO OVERCOME WIND RESISTANCE. 30-40, 6 H.P. 60-70, 20 H.P. ROAD SPEED M.P.H. [Bottom Right] Hs{Lord Ernest Hives - Chair}/W. A.{Mr Adams} Robotham. | ||