Ingenious devices designed to imitate the flight of birds
MODEL OF LEONARDO DA VINCI’S ORNITHOPTER. To obtain the up-and-down lapping motion Da Vinci arranged two arms, pivoted at the centre of a framework, with cords to be attached to legs. The act of stretching out the legs pulled the wings downwards; the arms, pushing upon a pair of rods, swept the wings up again into position for the next flap. There is no evidence to show that a full-sized example was ever built.
AN ornithopter, as the derivation of the name indicates, is a wing-flapping device designed to imitate the flight of a bird. The term applies equally to the early attachments of feathers to arms and legs, and to the more recent machines built by men in their various attempts to fly.
It was natural, after having watched and envied bird flight for countless years, that men should try to imitate the action of birds’ wings before looking elsewhere for a solution to the problem of flight. There are, therefore, many legends of attempted bird flight and many stories of ambitious men whose efforts ended in disaster.
Today we know, from a scientific study of the anatomy of birds, that it is impossible for any normal human being to lift himself from the ground by means of a wing-flapping machine in which his own muscles supply the motive power. A bird is able to fly only because of highly developed wing muscles. The experimenters of old did not appreciate this fact and they made scores of attempts to conquer the air with the help of ornithopters. The legend of Daedalus and Icarus is probably based on an ancient attempt at flapping-wing flight. Many ancient carvings and the generally accepted idea of an angel — a winged human body — indicate the lines of thought of past generations.
Leonardo da Vinci designed what must have been one of the oldest ornithopters, but there is no evidence to show whether it was ever built. To obtain the up-and-down flapping motion he arranged two arms, pivoted at the centre of a framework, with cords to be attached to legs. By the action of stretching out the legs, as in the breast stroke, a pair of cords pulled the wings downwards; the arms, pushing upon a pair of rods, swept the wings up again into position for the next flap.
In 1673 a French locksmith called Besnier designed an ornithopter on a different principle. It consisted of two light wooden poles, hinged to a harness over the shoulders. At either end of the two rods he fixed fabric, in the form of an inverted V, and tied the rear ends of the rods to his ankles. Thus by kicking downwards, first with one foot and then with the other, and by pulling the forward ends of the rods down again by his arms, he obtained a kind of double-oscillating movement (see the chapter “Flights of Fancy”).
In the years that followed many ornithopters were designed, but most of them included a form of parachute. This meant that the would-be aviator planned to jump from a height in the first place, and hoped to keep himself aloft by flapping. Many tried the device, and many perished.
Two French ornithopters were built between the years 1852 and 1857, the first by M. Breant, and the second by M. Le Bris; these devices embodied a mechanical return of the wings after a downstroke. Breant’s apparatus used elastic, Le Bris’ apparatus used springs. These ornithopters represented the first real attempts to add machinery to the old idea.
In 1866 another French inventor sought to improve upon Besnier’s invention of two centuries before, by arranging a system of cords to be operated in the same way as bicycle pedals. So the quest went on, until the latter half of the nineteenth century, when inventors began to think of using steam to help them into the air.
About this time, too, pioneers such as Percy Pilcher, Octave Chanute and Otto Lilienthal were experimenting with gliders. As their success was so marked, in comparison with all that had gone before, many who had been attempting flight by wing flapping machines turned to fixed-wing flight and used their ingenuity to devise means for obtaining motion. Thus fewer and fewer ornithopters were seen, and when wings moved at all they moved on the helicopter principle. Until quite recent years, however, inventors have tried to “fly like birds”.
Lawrence Hargrave, whose work with box kites was directly responsible for the early box-biplanes in Europe, made an intensive study of bird flight in his early years. In 1889, after having built many models, he produced a large ornithopter to put his theories to the test. Clement Ader, claimed by many to have been the first to fly in 1897, began his work by a study of bird flight. He built a manually-operated ornithopter.
Louis Bleriot built himself an engine-driven ornithopter in 1900, but when he started the engine it flapped so hard that it shook itself to pieces. Because all machines of this type were fundamentally unsound, and rewarded their creators with no useful results, few have been preserved. In the Science Museum South Kensington, London, is a compressed-air-driven replica of Hargrave’s ornithopter. This machine illustrates a sound attempt to overcome the greatest difficulty of all — the “figure of 8” movement of a bird’s wings. Hargrave was a careful and thorough workman; when he tackled a problem he did not leave it until he had examined every possibility of solving it. The fact that he discontinued his experiments along this line early in his career is proof that he was satisfied of the problem’s impracticability. The replica of his compressed-air-driven ornithopter embodies a link movement for obtaining the “figure of 8” sweep of wings peculiar to bird flight; this link is in itself an ingenious contrivance and far in advance of other ornithopter mechanism.
Mechanical Flapping
Another model ornithopter in the Science Museum represents the work of Major R. F. Moore, who spent many years studying the flight of birds and animals and trying to find some way of imitating it. Major Moore sought to obtain a natural flapping motion by representing the pectoral muscles by springs, carefully designed to operate for a given weight. To create the flapping power he used an electro-magnet, capable of attracting or repelling the wings; this, he intended, would be controlled by a hand switch, or by clockwork control governed by the “muscle” springs. At the first Aero Show held at Olympia, London, in 1909, several model ornithopters were exhibited. There was also a well-designed, full-sized machine built by Eugene De la Hault, a well-known Belgian aeronaut of the time. In this machine a petrol engine was connected to the wings instead of to a propeller, to produce a steady but vigorous flapping motion. It was one of the few ornithopters that worked. It is recorded that the inventor had succeeded in making several short flights in it, on one occasion reaching a height of over 25 feet.
Until fairly recently the remains of an ornithopter were to be seen in the rafters of a hangar at Brooklands Aerodrome. The name of its original creator is forgotten, but it is known that more than one enthusiast tried to make it work. Its main component was an old bicycle frame; an ingenious attachment between pedals and wings gave a simultaneous drive to wings and wheels. The would-be aviator “rode” the machine like a cycle, and attained a remarkably high ground speed — but never succeeded in rising into the air.
Two Chinese employed at the aerodrome showed particular interest in the contraption, and took amazing risks to make it work. Having seen that flight was impossible from the grassy surface of the aerodrome, they took the ornithopter to the top of the concrete banking of the motor track and pedalled downwards, only to crash at the bottom. The urge to build ornithopters is by no means dead. Almost every year paragraphs appear in the Press about machines of this type. Nearly always it is the bicycle idea, and in nearly every instance the inventor claims to have made short flights. Given a favourable wind, plenty of energy and forward speed, there is no reason why the machine should not hop about; but flights of any duration are a physical impossibility on an ornithopter which relies solely upon the power of the aviator.
LAWRENCE HARGRAVE’S ORNITHOPTER OF 1889 — of which a replica is illustrated here — was driven by compressed air. Hargrave’s ornithopter embodied a link movement for obtaining the “figure of 8” sweep of wings peculiar to bird flight. After Hargrave had devoted much time to the problem of building ornithopters he abandoned his investigations.
