Flights of fancy

A new exhibition at the Science Museum in London focuses on the technical skills of Leonardo da Vinci. But, as Jerry Frank discovers, he was by no means the only `Renaissance man’

Five centuries ago Leonardo da Vinci (1453-1519), held by many to be the premier genius of the Renaissance, if not the millennium, turned his imagination to constructing a machine in which man could fly. Unlike dreamers before him, Leonardo drew on a highly developed study of mechanics as the basis of his design.

Of course, his man-powered flying machine never got further than the drawing board and it wasn’t until the start of this century that technology caught up with the dream of flight. But Leonardo’s drawings demonstrate a sophisticated knowledge of pulleys, cranks, toothed wheels, joints, transmission systems, high-strength axles and shock absorbers.

A life-size model of Leonardo’s pedal and pulley powered flying machine forms the centrepiece of a new exhibition at London’s Science Museum. The Art of Invention: Leonardo and the Renaissance Engineers charts the achievement of the artist-engineers of the Renaissance and shows the impact they have had on our cultural heritage, through drawings and working models in authentic materials. It shows how the flowering of the visual arts during the Renaissance went hand-in-hand with a flurry of technical innovation.

The exhibition’s central argument is that Leonardo was not a lone genius towering above his age, with an understanding of the physical world and technology 500 years ahead of his time, but was merely the most gifted exponent of a century-old tradition of artist-engineers.

Men such as Mariano di Iacopo, (1381-1458?) and Francesco di Giorgio (1439-1501) earned reputations in the city state of Siena for their public works, which revived classical technology, and through treatises setting out their inventions.

The exhibition’s curator, Professor Paolo Galluzzi explains: `The prime movers were mostly the artists (`artificers’ is a better term) who led the radical renewal of painting, sculpture and architecture during those decades. It is all too often forgotten that Renaissance artists were routinely involved in activities that we would define as engineering.

`Moreover, the celebrated artist’s workshops of the Renaissance had more in common with a bustling factory than with the modern cliche of an artist’s studio.’

Leonardo came to Florence as a teenager in the late 1460s to train as an artist-engineer at the workshop of Verrochio. His master had been commissioned to build a huge copper sphere to be placed on top of the lantern of the spectacular dome of the cathedral in Florence, begun 40 years earlier by Filippo Brunelleschi.

The apprentice was exposed to the world of machinery on the construction site and scaffolding around the dome. Built without the use of a wooden centring for masonry support, the dome was one of the most important architectural and engineering feats of the Renaissance.

Leonardo’s notebooks began to fill up with sketches of Brunelleschi’s machines – ingenious hoisting contraptions and powerful screws for lifting and placing large weights. It was here that he discovered his life-long passion for machines and their anatomy.

Where Leonardo stood out from his contemporaries, however, was in the way he investigated the laws that governed the physical world and formed the belief that mechanisms could be used to create an infinite variety of machines.

Dozens of his notebooks survive, crammed with half a century of drawings and notes. His illustrations minutely anatomised screws, springs, pulleys, flywheels, as well as toothed, pin gear and ratchet wheels and pinions. He also studied mechanisms like the crankshaft – used at the time to power machines such as lathes and pumps – and praised the efficiency with which it turned continuous rotary motion into reciprocral linear motion. He developed hoists that automatically released their loads when a counterweight touched the ground. And he explored techniques of reducing friction, pioneering the concept of the ball bearing race. He described an arrangement in which rotating spheres alternating with concave spindles, running in a horizontal circular track, supported a platform and allowed it to turn freely even when heavily loaded.

Leonardo also sought to demonstrate the analogy between the principles of the machine and the physical world. He regarded the human body as a mechanical instrument that created motion, the Earth as a vast organism governed by universal mechanical laws and buildings as organic structures composed of fully integrated parts.

The exhibition emphasises that Leonardo’s achievement may have been rooted in the Middle Ages tradition of the artist-engineer, but his drawings are informed by a modern view of science that marks the birth of modern technical draughtsmanship and design.

The Art of Invention: Leonardo and the Renaissance Engineers runs until April 24 at the Science Museum, Exhibition Road, South Kensington, London. It is open daily, 10am to 6pm. Further details on: 020 7942 4454/4455/4400.

How the worm turned

Leonardo was fascinated by screws and made extensive use of them. He sought to classify their different types, accurately determine their performance by geometrical methods and illustrate their potential applications in machines and mechanical operations.

He wrote in his manuscripts: `If the endless screw is made to turn with the aid of pinion mn and nut fs is firmly held in place in a way that allows its turning around, the turns of the nut will doubtless have great potency.’

Sienese engineers such as Francesco di Giorgio used the worm screw to transmit motion in powerful machines used to lift, raise and position heavy columns and obelisks.

Clocks ahead of their time

Leonardo designed this extremely complex mechanism to regulate the force of the spring concealed inside the cylindrical drum. The machine was intended to regulate the movement of large clocks and uses a range of basic mechanisms, including a toothed wheel, worm screw, a spring, a cone-shaped gear and a rack.

The crown wheel on the cylinder drives a winding cone-shaped gear. The top part of the shaft consists of a screw which drives down the cone-shaped gear. To keep the crown wheel and cone-gear continuously meshing, the worm screw engages with a toothed wheel. This drives a rack segment and shifts a horizontal slide attached to the cylindrical drum, pushing the drum to the right.

Leonardo: his genius was rooted in the tradition of the `artist-engineer’ which was already a century old

Military breakthroughs

Military systems and weaponry were a major preoccupation for Sienese engineers, most famously Mariano di Iacopo, known as Taccola. His studies of military technology focused on siege machines to breach the sophisticated fortress designs of the time. These included giant crossbows, articulated ladders and battering rams.

The trebuchet (pictured) hurled heavy stones to break down the defences of enemy fortresses and, according to Taccola’s drawing, would have stood at least 50 feet tall. A pivoting beam held a sling carrying the projectile with two stone-laden crates at the other end as counterweights. When the beam was released the weight of the crates catapulted the projectile through the air.

Water creates a power cut

Water was the main source of energy for Sienese engineers and the hydraulic saw mill was a widespread industrial machine from the 15th century onwards, being mainly used to cut large tree-trunks into planks.

Francesco di Giorgio, who was also interested in harnessing wind as a source of natural energy, undertook a painstaking analysis of hydraulic engines on mills. His detailed notes reveal he often performed his own operating tests on many of the systems illustrated.

His notes next to this accurate drawing give an elaborate explanation of the machine and stress that an abundant water supply would be needed to power the waterwheel that provides the power.