Double Flag Crane
From Leonardo da Vinci, Madrid Codex I, f. 96r.
Load and unload materials in canals and harbors.
As it was designed this crane seems to be operated by an arm. The power reduction system is a mobile pulley but the crane can easily be equipped with a winch.
There are two parallel independent cranes with horizontal arms capable of rotating each one around its own vertical axis. Bracings reinforce the structure.
Dimensions: there are no details that give us the dimensions. From the drawing we understand that the relationship between the diameter of the pulley and the arm movement radius of the crane is 1 and 15. If we envision a pulley 30 cm in diameter, the crane’s arm radius would be 4.5 meters.
Reconstruction: the two cranes have the same dimensions therefore they can rotate parallel to one another or alternately but not cross.