Leonardo da Vinci:Body as Machine and Machine as Body

  • Update:2011-12-01
  • Martin Kemp
  • Source: Zhuangshi

The “Uccello”
The great prize for Leonardo the engineer was flight – the making of the uccello, the “great bird”, on which he set such store. Anymore who could master the skies could indeed claim to have become a “second nature” in the world. The ambition to fly had mythological roots, with the ancient inventor Daedalus, who tragically sacrificed himself in the quest. A similar fate befell a 16th-century aviator at the court of James V in Scotland. For his part, Leonardo recommended that his machine be tested over a lake by a flyer equipped with a life belt in the form of inflated wine-skins.

It was Deadalus’s more successful exploits and general renown that had lead Carlo Marsuppini, the humanist Chancellor of Florence, to compare Filippo Brunelleshci’s renowned machines with those of his ancient predecessor. Amongst the mediaevalphilosophers, Roger Bacon, whose quest for a universal science was a source of inspiration for Leonardo, was famed for his desire to create man-powered flight. Leonardo was well aware of the immortality that awaited him if he succeeded in soaring into the air: “the great bird will take its first flight on the back of the great Swan [i.e. from the slopes of Monte Cecceri near Fiesole] filling the universe with stupor, filling all writings with it fame, and bringing eternal glory to the place of its birth”. He was equally alert to the potential for derision if he failed in full public gaze. He writes at one point that he should test a trial wing on the roof of the Corte Vecchia away from the side that was overlooked by the workmen constructing the crossing dome of the cathedral. In all respects, the activity was best kept secret until he could unveil his uccello with assured success and to universal acclaim.

The foundations as always lay in nature, in this case very directly. Birds and bats showed that it could be done, and demonstrated the means to that end. This is not to say that Leonardo considered following the legendary precedent of Daedalus by attaching feathery bird’s wings to his arms in the hope of flapping aloft. He knew from the first that power-to-weight ratio was a problem. He knew enough about anatomy to understand the human arm was not built for flapping with a power equivalent to that of a bird’s wing. Characteristically, he embarked on researches into the flight of birds, since he needed to understand the principles on which he could proceed, if he were to succeed in creating analogous results using only human power. In his earliest sustained attempts to design an ornithopter in the years before 1490, he conceives wing designs with skeletons closely inspired by those of flying creatures, but he attempts to bring other human muscle groups into play, particularly those of the legs (fig.16). Perhaps his pedalling feet could amplify his arm and chest muscles sufficiently to achieve the desired lift. The wings themselves use assemblages of wooden bones, rope tendons, and leather ligaments to achieve the sinuous motion created by the “hand” of the bird’s wing. The vision was beautiful, but he came to realise that none of his cherished schemes would work in the required way.

16. Scheme for the Mechanism of a Flying Machine, Paris, Institut de France, MS B 74v.

In the second major phase of his assault on this problem when he was back in Florence, he took a different tack. The small codex in Turin devoted to the flight of birds and dated 1505, shows that he renewed his studies of birds gliding in the thermals high above the Tuscan hills – particularly of the great birds of prey who circle without flapping as they survey the ground below for potential victims. He made sketches of the vortices of air below the concave palm of a bird’s wing, worked out what the shifts of the bird’s centre of gravity might accomplish, and how small motions of the wings and tail could achieve great things. He now adopted the strategy of active gliding, in which whatever motions were given to the wings and tail were directed at controlling the pitch, banking and path of the glide rather than achieving unaided lift-off. The wing design was still based on those he had observed in nature, in terms of principles and general disposition rather than precise imitation. The aviator, probably with a tail to help with steering and stability, was to hang below the wings using his centre of gravity to control the flight as best he could. He wrote optimistically that
A bird is an instrument working according to mathematical law. It lies within the power of man to make this instrument in all its motions, but without the full scope of its powers; but this limitation only applies with respect to balancing itself. Accordingly we may say that such an instrument fabricated by man lacks nothing but the soul of man.

Although he knew nothing about aerofoil design in the modern sense, and had only a tentative grasp of the different pressures exerted by compressed and rarefied air, his consultation of nature’s engineering did ensure that he was on more or less the right track. One of his wing designs (fig.17) has been built by Skysport of Bedfordshire in England and tested by Judy Leden (world hang-glider champion), with triumphant success. The key feature of this design, laconically but clearly drawn and labelled by Leonardo, is that the cloth (panno) covering the upper layer of the wing was to be wrapped over the leading edge and secured well back on the lower side. Together with the shape and structural integrity of the wing’s skeleton, this formation resulted in sufficient lift to secure a flight that exceeded the first attempts by the Wright brothers in 1900. There is no evidence that Leonardo himself actually built this wing design, let alone launched it from a Tuscan hillside in a way comparable to its maiden flight on the Sussex downs in 2003. His sheer inventiveness often presented him with so many alternatives as to paralyse his choice. But the pious recreation of his design does show that his insights as to how the human inventor might proceed were valid, even if in this case he got the right result for the wrong reasons – at least in terms of the physics at his disposal.. He was indeed close to realising his uccello, at least as a gliding bird.

17. Wing and Mechanism for a Flying Machine, Milam, Biblioteca Ambrosiana, 858r.

The notions of human and animal bodies as machines and machines as kinds of body were to enjoy long histories. Descartes argued that animals were mere automata, while increasingly ingenious constructions of mechanised animals and humans succeeded in performing animate tricks in a remarkable way. A duck invented by Vaucanson in 18th-century Paris even digested grain in a “chemical” stomach. Perhaps inevitably, the question of L’homme machine became a major bone of philosophical and theological contention. The idea that a mechanical device might actually achieve something equivalent to a super-human also has a long history – rendered more urgent by the advent of computers and the contentious field of artificial intelligence. Some fragmentary designs sugget that he might even have been thinking of a kind of man-automaton. In any event, in his general vision of the body-machine, Leonardo demonstrated an unerring intuition as to where some of the very biggest issues of human intellectual endeavour were to lie. It was not the only field in which he manifested such intuition.

 

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