From Leonardo da Vinci, B Manuscript, f.49v.
Removing material in the pit and maintaining the canals.
This crane is the same concept as the one designed on the front of the same folio yet differs from it essentially because it was constructed with two opposing loading boom which are operated using the same winch and operated alternatively: one loads and the other unloads. The crane is mounted on a rotating platform that is moved manually with handles placed around the outside of the platform. A winch is attached to the crane making it possible to move it. On the platform, at the base of the mounts that hold up the arms of the two cranes, there are two cases positioned for ballasting the machine and making it more stable during lifting.
Dimensions: Leonardo did not furnish any measurements, but if we use the winch as a reference, which must be moved by an arm, we can theorize that its rotating axel was about 1.5 meters from the platform. Taking this into consideration, we can thus hypothesize the overall height of the crane to be between 5 and 6 meters, for a moving diameter of about 3 meters.
Reconstruction: a very unclear element is the rotating base, which shows only four wheels. In the single arm model (B Manuscript, f.49r), this crane had a much more solid base, regardless of a presumably smaller load. It is not clear how the axles of the wheels can cross since they are at the same height; in the reconstruction the axles are placed at different heights, consequently alternating the radius of the wheels.