The exact date is not known. The drawing is in the Codex Atlanticus, a collection of his works dating from 1478 to 1519 - this is the nearest we can get to the date of the design.
About 1482 Leonardo entered the service of the duke of Milan, Ludovico Sforza, having written the duke an astonishing letter in which he stated that he could build portable bridges; that he knew the techniques of constructing bombardments and of making cannons; that he could build ships as well as armored vehicles, catapults, and other war machines; and that he could execute sculpture in marble, bronze, and clay. He served as principal engineer in the duke's numerous military enterprises and was active also as an architect.
Comments
The exact date is not known. The drawing is in the Codex Atlanticus, a collection of his works dating from 1478 to 1519 - this is the nearest we can get to the date of the design.
http://www.hucbald.ramst.ca/articles/leonardo_cata...
http://www.wired.com/culture/education/news/2007/0...
About 1482 Leonardo entered the service of the duke of Milan, Ludovico Sforza, having written the duke an astonishing letter in which he stated that he could build portable bridges; that he knew the techniques of constructing bombardments and of making cannons; that he could build ships as well as armored vehicles, catapults, and other war machines; and that he could execute sculpture in marble, bronze, and clay. He served as principal engineer in the duke's numerous military enterprises and was active also as an architect.