Double Counterweights Elevator Crane
From Leonardo da Vinci, Codex Atlanticus, ff. 1012r,v.
Moving soil for digging canals.
Two cranes with parallel rotating arms carry the excavated material out of the work area. The system slides through the excavating area on runners. The counterweight that lifts the load is a mobile platform on which there are two oxen and a man.
Dimensions: Leonardo supplies the dimensions of the various parts of the crane in braccia (one braccio = 59.49 cm); pit depth: about 2.4m; crane height 4.8 m; Outreach capacity 4.5 m; counterweight elevator height: 1.80 m.
Reconstruction: the verbal descriptions refer to the right crane, whereas the variants shown in the left model make its purpose and operation unclear. The elevator bucket is hanging to a “rope sling”. Here again Leonardo’s drawing documents on paper an idea that geometrically portrays a potentially effective principle but that has not been verified from an engineering point of view.
The ramp of the elevator platform does not appear to have a structure that could sustain the weight of an ox. Moreover, the way that they are designed, without forestays or counterweights, could make the two cranes heavily unbalanced in front, causing them to overturn. An attempt to solve this problem can be found in the previously mentioned drawing of a beam perpendicular to the crane that is positioned on the riverbank. This element is also present in the same crane model drawn on the back of the same folio, which along with the double model analyzed here, gives an interesting example of the evolution of an idea.