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 'The Motor' magazine detailing the high-speed performance and streamlined design of a special Bentley car.
| Identifier | ExFiles\Box 160\4\ scan0008 | |
| Date | 7th February 1939 | |
| The Motor 170 SOME MEN DELIGHT OLYMPIC DU FORM. A bird's-eye view of the Bentley, showing the beautiful streamlining which reduces the windage by 30-40 per cent. INTERNATIONAL rivalry in respect of really fast cars is as interesting as the political strivings of the nations producing them. If one were to think solely in terms of sports car races, the Italian and French constructors are facile princeps. Such events, however, by no means tell the whole story. Recent performances by British cars have demonstrated beyond doubt that on road and track we have 100 m.p.h. cars, and over, that will equal or surpass anything produced in Europe or the United States. Speeds of 100 m.p.h. or more are rare, for there are few engines on the market which can produce the needed 120 b.h.p. to overcome windage plus an additional 30-odd for chassis losses and tractive resistance. In the past two or three weeks the Bentley company have put up some performances on the Continent which show clearly what tremendous gains flow from fitting a really well-formed body in place of the conventional type. The Consequences of Streamlining This special Bentley has the characteristic downswept tail of the streamlined car, cowled-in lamps and a marked reduction of frontal area as compared with the normal chassis. It has, in addition, carefully arranged cowling underneath the works, this last being a vital point which is often overlooked. This care in detail is, indeed, characteristic of the vehicle, for the front wings are beautifully tapered, the rear wheels cowled over, and even such details as the door handles are flush-fitting to avoid setting up disturbance. One can estimate that a body of this type reduces the power required to overcome air resistance by something in the nature of 30 to 40 per cent., and the total power required, therefore, to achieve 100 m.p.h. drops from 150 to around 100 or 110. This is well inside the maximum output of the normal Bentley engine, but in order to demonstrate to the full the possibilities latent in the latest developments of fuel, as well as body A20 design, the Bentley company produced a modified piston giving a high com-pression ratio of 8 to 1. With the additional power so obtained, coupled to the low windage, the potential maximum of the car was in the region of 120 m.p.h. This, on the normal top gear ratio, would have been 5,100 r.p.m. and well over the peak speed of the engine. A specially high over-drive gear of 2.87 to 1 was, therefore, arranged, giving a maximum r.p.m. of 3,800 at 120 m.p.h. and a cruising r.p.m. of 3,200 at 100 m.p.h. These moderate speeds are impor-tant. They mean that the piston speed at 100 m.p.h. is only 2,350 ft. per minute and that it does not exceed 2,800 ft. at a maximum. These figures are strictly comparable with those at which aero engines are run for long periods without overhaul. With the equivalent standard of workmanship present in the Bentley engine, it follows that the car is not only capable of high speeds but also of maintaining them. The Practice of High Speeds The queries may arise in the minds of some readers: is there anywhere where speeds of 100 m.p.h. can be maintained continuously and, if so, do not such things as fuel consumption and tyre wear make them entirely uneconomic? Answering the first question, one may say that there are many parts of the Continent in which speeds of 80-90 m.p.h. can certainly be achieved with some frequency, and, for the moment at least, on the German system of Autobahnen even greater velocities are possible. So far as tyre wear is concerned, on the German roads I can say from experience that tread wear is by no means excessive; the roads are smooth and one has an almost entire absence of wheelspin. In answering the question of whether high speeds do not mean heavy fuel consumption, one can reply "No," if one has a well-streamlined type with high gearing such as the special Bentley. The consumption figures issued by the makers of the car indi-cate that 17 m.p.g. can be obtained at 90 m.p.h., a remarkably fine figure. It indicates that 75 b.h.p. only is required to drive the car at this speed in place of the 100-110 which one would normally allow. This Bentley car was recently subjected to a prolonged run on the Con-tinent, in the course of which it reached a sustained maximum of 112 m.p.h. over a distance of 4.2 miles, and has since then covered over 107 miles, one 100 M.P.H CREDIT. A pictu tyre on the Lagon ately after coverin miles at a running 90 m up, in the course of a on the Montlhéry track. Bentley Motors must be con lated on a remarkable te achievement. Similar cars c obtained to special order, and one wishes to purchase to-da {Bernard Day - Chassis Design} of to-morrow, all he has to square the bank manager a taxi to Conduit Street. Performances of an entirely nature, and reflecting great the makers concerned, were put up by a 12-cylinder Lagonda the pleasure of driving to Berlin. This car had been sold to a Par citizen some four or five months and I thought myself lucky wh was able to make arrangements borrow it. Here, I thought, chance of testing a car that in hard use all over the | ||