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Aviation History
1964
1964 - 0269.PDF
Air-Cu*hion Vehicles FLIGHT International supplement. 30 January 1964 A RACING ACV . . . boosted in this way would certainly be fast, but incredibly noisy and dan- gerous too! A more serious and sensible approach to the power problem would be to make the fullest use of current motor car transmission systems. In Project 1 two sleeved-down Mini Minor power units, with gearboxes emptied of sur- plus gears, would fill the bill admirably; Project 2 could use the lj-litre trans- verse engine/transmission unit that BMC are bound to produce within the near future; and Project 3 could use a Corsair GT engine and the standard gearbox locked in the most suitable gear. The tail-rotor drives of any small helicopter could be adapted to handle propulsion if a separate propeller were required. The Problem of Control Precise con- trol characteristics have never been the strongest feature of ACVs. The trouble is, of course, that although they float in the air the cushion which supports them is strongly influenced by the surface immediately beneath it. The ACV cannot control itself as effectively as an aircraft because it cannot bank; and the moment it tries to control itself by direct contact with the surface many of its advantages are lost. The racing ACV will probably be better off than the commercial ACV because it will have a much better power : weight ratio. It will have more thrust to force its lower mass in whichever direction the driver chooses. Control, however, will need to be of such a high standard that the designer The author's Project Three, in model form,compared with a BRM l^-litre V-8 racing car. The ACV would be powered by oCorsair GT engine with a single axial lift fan will have to think of something rather more scientific than sheer brute force. If he wants to make use of friction with surface, there is no reason why he should not do so, except that he will be creating extra drag, weight and compli- cation. If air-jet controls could be made to react powerfully off the surface this would be a rather neater solution. Surprisingly, perhaps, the biggest con- trol problems seem to occur at medium and low speeds. At high speeds the aerodynamics controls become reas- onably effective and the inertia of the vehicle smothers any small forces that try to influence the vehicle's direction. At low speeds, however, the vehicle becomes about as manageable as a balloon. Power and thrust are needed to counteract wind and slopes, and power to introduce a change of direction. Unfortunately, the propeller develops only a fraction of its potential power at low speeds, and this is why the ACV has always had sloppy low-speed handling qualities and poor hill-climbing ability. If anybody can find a way of using the vehicle's full power at low speeds with the effectiveness of wheeled drive, but without making physical contact with the surface, then the problem will be solved. The old dream of a reaction motor that works within itself on itself, on the lines of a gyroscope, would be the perfect solution if it could ever come true. Again, if the air could be made to "grip" the surface then many of the problems of hill-climbing and control would be overcome. A Light and Rigid Structure One of the most pleasing aspects of the racing ACV is the huge variety of layouts and design techniques that all seem equally suitable. There is an enormous number, for example, of very promising methods of construction. Project No 1 would probably be served best by a space- frame backbone with the engines slung on outriggers. The rest of the structure, including the ducting, could be very lightly built in aluminium or glass-fibre. Project 2 might also make use of a backbone, though the offset cockpit might cause a few asymmetric stress problems that would be hard to solve without incurring a weight penalty. A spaceframe box in the centre of the vehicle to contain the petrol tank, engine and cockpit, with outriggers for the fans, might be more efficient. Project 3 would require a different technique from the other two because the fan separates the engine from the cockpit. As these weight masses are so far apart it would probably be easiest to route the stresses throughout the structure rather than try to localize them with a spaceframe. Such a monocoque structure would be difficult 12 and expensive to build, but would be light in weight and would offer the best resistance to minor bumps. However, the sheer permanence of a monocoque structure would make it extremely difficult to incorporate modifications to the internal airflow passages. The racing ACV could borrow many of the sports-racing cars streamlining techniques, but would differ in one very important aspect. Whereas car bodies have to be designed to produce a neutral or negative lift component, the ACV would benefit enormously from a balanced amount of positive lift. Very careful calculations would be necessary to ensure that the vehicle did not flip on to its back if jolted to an excessive angle of attack, or bounce itself clear of its air cushion with dis- astrous results when returning to earth. The racing ACV would seem to offer a very real challenge to the ingenuity of both the aircraft designer and the racing car designer, overlapping as it does into both of their highly specialized arts. There seem to be no clear-cut solutions to any of the many problems, so won- derful opportunities are offered to the inventive and imaginative mind. Small, powerful, noisy and spec- tacular grand prix ACVs could attract the vast crowds of spectators who, in paying to watch them race, would be helping to finance the development of docile and economical machines for their own ultimate use. What better reason for a full-blooded racing ACV? POSTSCRIPT Since this article was written I have had an opportunity to talk at length with Owen Maddock, former chief designer of the Cooper Car Co Ltd, to compare our ideas on the subject. We agreed entirely on the nature of the problems to be overcome; but, more important, we agreed that a new form of drive and propulsion was necessary before these machines could be raced safely and efficiently on a track. We examined several new and different ideas, some of which seemed very promising and worth taking beyond the pure conjecture stage. We then decided to approach Stirling Moss to find out how a racing motorist would feel about driving one of these machines —assuming, of course, that it could be con- trolled reasonably well. We were delighted to find him extremely enthusiastic about the whole idea; nearly all racing drivers, he remarked, like to have a go at something really new. With one or two obvious excep- tions, he thought, ACV racing would be welcomed by manufacturers and the many other people connected with motor racing. This very favourable reaction from a professional was enormously encouraging, and Mr Maddock and myself are now con- sidering the possibility of finding enough financial support to put our ideas into prac- tice by designing and building m prototype- Well, what other way is there of starting the ball rolling ?
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