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).
Bentley's performance issues due to high wind resistance and the need for more streamlined bodywork.
| Identifier | ExFiles\Box 161\1\ scan0029 | |
| Date | 21th August 1937 | |
| Sg.{Arthur F. Sidgreaves - MD} from Rm.{William Robotham - Chief Engineer} c. Hs.{Lord Ernest Hives - Chair} c. Hy.{Tom Haldenby - Plant Engineer} c. Da.{Bernard Day - Chassis Design} c. Sr. c. Ev.{Ivan Evernden - coachwork} File 1330 Rm.{William Robotham - Chief Engineer}6/AP.21.8.37 BENTLEY WIND RESISTANCE. During our recent tests in France, Sr. pointed out that the Bentley was not as fast as the Bugattis, De la{L. A. Archer} Hayes, Talbots, etc. with which it was competing directly in the sports car class. We agreed, but in reply emphasised that English conditions were steadily making maximum speed of less importance, while increased acceleration was becoming more and more desirable. One is forced to admit that on the Continent the reverse state of affairs exists, owing to the magnificent auto stradas and motor roads which have been constructed. With an overdrive fitted, top speed becomes almost entirely a matter of the wind resistance of the car. Our products, owing to their necessarily conservative appearance, are about as bad as any we know for lack of streamlining. As an example, we recently had the Oldsmobile on Brooklands. Its frontal area is very much the same as the 25/30. It actually has a wider front seat. The engine is a 3½ litre side valve and certainly develops no more H.P. than our 4¼ litre O.H.V. unit and yet the Oldsmobile laps Brooklands at 79½ MPH. against a 25/30. lap speed of 73½ MPH. As wind resistance varies as the square of the speed, this indicates that the Olds. has 15% less windage than the 25/30. Another simple test it will be remembered was conducted when we were doing some wind tunnel work on Bentley bodies. It showed that the standard Bentley would go 15 MPH. with the present engine if it was driven backwards. FASTER When we have got on top of our present programme, we shall have to devote some attention to this subject if only to improve acceleration and reduce petrol consumption (Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}16/KW. 6.4.36 attached). In the meantime, however, it seems to us a pity that Sr. cannot help himself and provide us with some information, by building bodies having less windage where customers are willing to pay for them and enjoy the unconventional appearance. continued | ||