What You Need to Know About Leonardo da Vinci's Giant Crossbow

The giant crossbow is a type of shooting weapon created by Leonardo da Vinci, whose drawings are found in the Codex Atlanticus. Never built by its designer, it was instead manufactured on a 1:1 scale. Da Vinci's original idea, as described in the drawings, was to build a giant crossbow to increase the range of the dart. It was used to shoot bombs and stones and was primarily used for intimidation. The bow was made of thin wood, on six wheels, 27 meters in diameter and consisted of 39 distinct parts.

Leonardo da Vinci's Invention

The creation of the giant crossbow design is linked to Ludovico Sforza, an Italian Renaissance prince, wishing to expand and evolve both his army and the Milan region. He then wanted to update the current treatise on military engineering by Roberto Valturio. Leonardo da Vinci responded by writing a letter to Sforza including a number of innovative machine designs, including the giant crossbow. He also emphasized his engineering expertise in his letter, probably knowing that Sforza was hiring military engineers at the time.

Although there is no exact date for the drawing of the giant crossbow, it is thought to have been completed between 1483 and the early 1490s. Generally, several scholars agree that Leonardo da Vinci finished the illustration in Milan. Some believe he came to Milan to seek work as a painter, then heard about Sforza's military wishes upon arrival. As for others, they suggest that the main reason was to work for Sforza.

While some think that Leonardo designed the giant crossbow for his own amusement, the context surrounding this invention suggests that the giant crossbow was intended to be a dangerous weapon that could please his employer Ludovico Sforza. The inspiration for such a weapon likely stems from the fact that Leonardo grew up in 15th century Italy, meaning he witnessed the ongoing war between the city-states of his region. As a result, he devoted a great deal of time and effort to inventions that could protect his fellow citizens, but also greatly harm the enemy. The giant crossbow supports this theory with the enormous size of the planned weapon intended to invoke panic and fear in his enemies to drive them away. However, it would still have the ability to cause enormous damage and injury if it had been built.

The Design of the Giant Crossbow

Long before Leonardo da Vinci's design, the crossbow already existed. However, his design made the weapon more advanced, which is why the giant crossbow stands out as important. If a crossbow is built with a narrower stock and a conical bolt adjusting the nocking of the arrows, it greatly improves the airflow of the bow and the drag on the arrows. This allows the crossbow to function more efficiently and have more accurate aiming. These ideas were featured in Leonardo's design, and came from him alone.

The mathematics he used to design his giant crossbow invention were very advanced despite currently known inaccuracies with today's knowledge of design and geometry. However, Leonardo da Vinci was the first modern engineer to attempt to apply the geometric mathematics of the laws of motion to machine design. The proportional techniques he used in every aspect of the design are the other mathematical marvel noted in the giant crossbow design.

Mechanically, the stock of the rapid-fire crossbow was divided into two stacked wooden pieces fastened together at the front by a hinge and secured in place at the rear by a spring latch. Wedged inside the tiller, a pair of interconnected folding levers hold the lower half of the tiller to a sliding plank that rests on the upper half of the tiller between the two metal prongs, identical in mechanical concept to the Gastraphetes, containing the rolling nut and spring trigger at the rear of the plank. Meanwhile, the lower half of the stock contained the trigger. By pressing a switch on the side of the stock to release the latch, the user folds the lower half of the stock downwards. Meanwhile, the interconnected levers push the sliding plank forward until the rolling nut held in place by the tension of the trigger spring catches the bowstring. By pushing the lower half of the placed tiller back, the latch locks the lower and upper halves of the tiller together. When a bolt is loaded onto the giant crossbow and aimed, the trigger is pulled to compress the spring and release the string from the rolling nut to propel the bolt.

In 2013, after the construction of a prototype, the first working model was released in 2015 during a demonstration at the Castello Sforzesco in Milan. The giant crossbow model allows for precision shooting and is equipped with a rapid internal spanning device, non-existent in most modern crossbows.