The rapid fire crossbow (in Italian Balestra veloce) is a crossbow project with a fast, lever-action, spanning mechanism build inside the crossbow's tiller. It was designed by Leonardo da Vinci around 1485 and was drawn on sheets 143r, 153r and 155r of the Codex Atlanticus. However there is no evidence that it was ever made or used in Leonardo's time, or had any effect on military history.
Mechanically, the rapid fire crossbow's tiller was split into two stacked wooden pieces held together at the front by a hinge and held in place at the back by a spring-loaded latch.[better source needed] Sandwiched inside the tiller, a pair of interconnected folding levers attach the lower half of the tiller to a sliding plank sitting on the top half of the tiller between the two metal prods, similar in mechanical concept to the Gastraphetes, that contained the rolling nut and spring-loaded sear at the back of the plank. Meanwhile, the bottom half of the tiller contained the trigger. Upon pressing a switch on the side of the tiller to release the latch, the user can then fold the bottom half of the tiller down. At the same time, the interconnected levers then push the sliding plank forward until the drawstring is caught by the rolling nut, which is held secure by the sear's spring tension. Upon pushing the bottom half of the tiller back into place, the latch locks the upper and lower halves of the tiller back together.[better source needed] After a bolt is loaded on the crossbow and aimed, the trigger is then pulled to compress the sear's spring and enable the rolling nut to release the drawstring to propel the bolt.
After a prototype built in 2013, the first working model was released on 24 June 2015 during a demonstration at the Castello Sforzesco in Milan. The working replica was the culmination of a study conducted by Edoardo Zanon of the Leonardo3 study center in respect of the processing and assembly techniques available at the time of Leonardo. The model allows precision shooting and is equipped with a fast internal spanning mechanism, non-existent even in most modern crossbows. The working model built is on display at the museum Leonardo – The World of Leonardo in Piazza della Scala, Milan, Italy.