Leonardo also put his eclectic genius to work in engineering: he designed all kinds of machinery as well as devices used for war and construction.

Da Vinci’s codices are an inexhaustible trove of insights into the master’s genius: they contain thousands of studies, diagrams, sketches, and designs for his machines, instruments, and devices of all kinds. Many are Leonardo’s original inventions, but there are also many attempts to improve on existing instruments as well as drawings of machines he observed, as is the case with the cranes. We do not know the intended use of all the machines: such as the motor cart, for many years considered a prototype for the automobile, but today thought to be a stage machine for the theatre. Other sketches however do come with detailed explanations of their purpose and mode of operation.

Throughout his life, Leonardo considered himself an inventor: as we read in the 1482 letter to Ludovico Sforza, he believed he was capable of building any kind of device necessary to protect the city and defeat the enemy in times of war. However, war machines were not his only inventions: he made plans to deviate the river Arno, designed musical instruments and theatre machinery, a knight automaton, motion transmission and measuring systems, hydraulic machines, flying machines and machines to dive into the depths of the sea.

In his letter to Duke Ludovico, Leonardo presents some of his inventions, describing several machines and especially his bridges, “Both light and strong at the same time […] easy and practical to remove and to put in place.” Many are the types of bridge designed by the Tuscan genius; among which was the “floating bridge resting on boats” (Codex Atlanticus, folio 857, 1480-1490), a boardwalk resting on boats or barrels that rotated thanks to a winch operated from land, enclosed in a recess dug for this purpose in the river bank, the opening of which was activated solely by the water current. Another example is the arched “revolving bridge” (Codex Atlanticus, folio 855, 1480-1490): built in a single span fixed to one of the two banks with a large vertical linchpin activated by a system of cords and winches, with a large chest as a counterweight, making it easy to maneuver. Leonardo also designed a “bridge with intermediate posts” and an “arched or speedy bridge,” a bridge intended mainly for military use, which could be put up and taken down quickly and was made of easily available materials.

Furthermore, Leonardo designed “covered, secure, and un-attackable carts,” predecessors of the modern tank. The idea of a heavy cart that could penetrate enemy lines was not new, but Leonardo’s design is one of the first (Codex Arundel, folio 1030). It is tortoise shaped, reinforced by metal plaques, armed with cannons all around, and equipped with an observation tower with which to keep an eye on the battlefield and aim the weapons. From his notes we know that the main problem that Leonardo faced was the cart’s movement – he discarded the idea of using horses and devised a system of cogs connected to the wheels and activated by the eight men inside.

Among the land war machines, the “scything cart” (Codex Arundel, folio 1030, 1487) appears in many drawings. A war machine driven by horses in which their movement activates wheels that in turn set in motion a system of rotating scythes. Nevertheless, Leonardo warns against the use of such a machine because it can bring damage not only to the enemy.

An extraordinary invention of Leonardo’s is the “aerial screw” (Codex Atlanticus, Manuscript B, folio 83 v., 1483-1486). Unlike many other designs (glider, flying machine, flapping-wing machine, parachute), the aerial screw is not an actual flying machine, but an object of study that leads Leonardo to theorize the tractive power of the screw centuries ahead of time (to the point that many consider it to be the forerunner of the modern helicopter). The machine, five meters in diameter, is made up of a wooden main body on a circular platform to which a vertical transmission shaft is connected. A helix-shaped linen structure is fastened to the shaft, its size decreasing in proportion with height, and is attached with wire to the circular base. Leonardo imagines the aerial screw to be powered by four men standing on the central platform, each pushing a beam causing the shaft to rotate activating the canvas helix, which was supposed to make the structure lift off the ground.