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).
Article from 'MOTOR SPORT' magazine detailing the development and evolution of the 'Corniche' Bentley, focusing on aerodynamic improvements.
| Identifier | ExFiles\Box 160\5\ scan0350 | |
| Date | 1st August 1941 | |
| MOTOR SPORT 398 AUGUST, 1941 THE EVOLUTION OF THE "CORNICHE" BENTLEY Mr. W. A.{Mr Adams} Robotham, of Rolls-Royce, Ltd., describes the conception and development of one of Britain's most advanced high-performance cars IN 1931, when Rolls-Royce first took over the Bentley Company, some wind-tunnel tests were made on the first 3.5-litre saloon car. The results were illuminating, but not very helpful towards improving the top speed of a motor car which must suit the average Bentley customer. Briefly, it was found that small excrescences such as lamps, horns or mascots on the front of a car have little or no effect on its speed. Making drastic alterations to the front as a whole, cut down the drag considerably. The best shape appeared to be something on the lines of the Lancia. The main point about this design is that there are no sharp edges and the gap between the wings and the body is filled in. Unfortunately, in 1931, we particularly wished to retain the original Bentley appearance, and therefore any sweeping alterations to the radiator were out of the question. We found that, unless we altered the front, nothing we could do at the back made very much difference. With the altered front, however, a measurable improvement was obtained by a sweeping back and tail. When we had combined all the improvements (which produced an entirely unconventional-looking car), we got a figure of merit for this and then turned a model of the standard saloon back to front in the wind-tunnel. We were somewhat disgusted to find that a lower drag figure was produced than with our streamlined vehicle! Nothing further was done, therefore, to reduce the wind-resistance of the car sold to the public until just before the war. As soon as the Germans began to build their motor roads, it became evident that a vehicle designed for the winding lanes and congested main roads of Britain would have to be modified if it was to take advantage of this new road engineering. Before we started to design a car suitable for the autobahnen, therefore, we looked round to see if we could get any full-scale results which would be of value from cars that had already been built for private customers. We found that an enthusiast, the late Monsieur Embiricos, had, with the assistance of a French engineer, Monsieur Paulin, produced quite a practical streamlined Bentley, which seemed to be considerably faster than the standard product. In doing this he had taken liberties with the radiator, and this in no way resembled the standard Bentley. However, the tout ensemble was not altogether unpleasant. Mr. Embiricos very kindly agreed to lend us the car for experimental work, and we carried out a few minor modifications to improve the power-output of the engine and make the gear ratios more suitable for high speeds. When the modifications were complete, the car could be driven without excessive pinking on any No. 1 petrol available in England, and was free from detonation on Ethyl or any other premium spirit. The car was fitted with 6.5 in. by 19 in. tyres and geared to give the following road-speeds at 4,000 engine r.p.m.:— Overdrive = 127.5 m.p.h. Direct = 108 „ 2nd speed = 72 „ 1st speed = 45.5 „ The body was very light and the high first gear seemed quite practicable for starting and hill-climbing. Indeed, the car was so fast, tractable and economical that an extended continental tour was arranged, to demonstrate these virtues to representatives of the technical press. The car averaged 110.5 m.p.h. for five miles over German roads, under favourable conditions. It also gave the following consumptions at constant speed on the autobahnen:— 40 m.p.h. = 32 m.p.g. 60 „ = 26 „ 80 „ = 21 „ 90 „ = 17 „ To demonstrate that, in making this vehicle suitable for the German motor roads, it had not been spoilt for ordinary high-speed touring, some stretches were timed on the French roads between Paris and Metz. Montmirail to Chalons-sur-Marne was covered at an average speed of 76 m.p.h. and 60 m.p.h. was averaged over the 180 miles from Paris to Metz. At the conclusion of these road tests the car was taken to Montlhery and covered 107 miles in one hour, the fastest lap being at just over 110 m.p.h. These results were interesting and a few more modifications were made to the power plant. George Eyston then took the car round Brooklands and covered 114 miles in the hour. These results were just what we wanted technically, but we were not satisfied with the appearance of the car, and also it was a two-door saloon, with rather cramped luggage-space and rear passenger accommodation. Monsieur Paulin, therefore, Continued on page 415 Image Captions: The little "Aprilia" Lancia which suggested streamline form for the Bentley; this had its outcome in the "Corniche" Mk.{R. E. B. Meade-King} V 4.25-litre Bentley, pictured above LANCIA 1.7-litre | ||