From Leonardo da Vinci, B Manuscript, f. 49r.
Removing material during excavation and in maintaining the canals.
The crane is mounted on a circular rotating base that moves above a platform with wheels. The boom with a loading pulley at the top is reinforced with four cross beams. There is a case at the back on the platform filled with stones, which serves as a counterweight. The rope is wrapped around a winch with a ratchet wheel blockage system for supporting the suspended load.
Dimensions: there are no quantitative references. The crane’s maximum dimensions can be calculated starting with the winch. In order for the laborers to easily operate the winch, it had to have the rotating axel positioned between 1 and 1.5 meters. Taking these measurements and comparing them to the drawing we can calculate the height and outreach capacity as around 6 – 7 meters.
Reconstruction: if this crane’s operation is initially clear, a series of problems emerge once one attempts to design it; it requires significant structural modifications in order to find a solution. Since it is necessary to avoid perforating the central vertical mount in order to pass the rope through, the crane should be mounted asymmetrically to the winch. Although the perforated mount causes rope friction on the internal surface of the hole, consequently causing heavy use of the same rope, it is possibly the most adherent solution to Leonardo’s drawing. The blocking system does not work because the asymmetrical gearing teeth were designed so as to stop rotating during lifting. The drawing of the rotating base is not clear and in order to be sufficiently solid it needs a doubling bracings structure to sustain the sliding wheels.