From Leonardo da Vinci, Codex Atlanticus, f. 4r.
Counterweights elevator system (saliscendi) with integrated flywheel.
The crane has a rectangular tetrahedron shape that slides along the runners thanks to a screw traction system. The two crane arms are mounted on the same axle and can rotate 180° alternately lifting and lowering the two cases: one loads and the other unloads. This synchronized lifting and lowering operation (saliscendi) is performed with a rope, which by passing through a large “pulley-flywheel” in the middle of the rectangular structure connects the two elevator buckets.
Dimensions: if we take the spades for excavating portrayed in the drawing, which were approximately 1 – 1.20 meters, as a point of reference, we can imagine this enormous machine about 8-9 meters high and 6 meters wide with a large pulley-flywheel of about 2.5 meters in diameter.
Reconstruction: from the drawing it is not clear where the ropes pass to arrive at the wrapping hub; also, the counterweight elevator motor could not work according to the way the carriers are drawn, both in the pit being loaded. The idea that the latch is put into motion only by the laborers who climb into the empty carrier is not plausible due to the weight of the load to be lifted. Even if it were only 50 cubic centimeters – a measurement obtained in proportion to the dimensions of the spade – this would be more than 500 kg. The principle of the saliscendi could work if either a carrier that lifts a maximum 100-120 kg of soil were built, or if there were an additional hypothesis for envisioning the “pulley-flywheel” as a tread wheel similar to the one in the Vitruvian cranes. Since the crane has two independent arms, the wheel inside the structure can be considered a tread-motor capable of operating simultaneously. Another problem with the drawing is the depiction of the digging area. It appears to be too wide, greater than the length of the crane’s arms, which impedes them from carrying the carriers to the riverbanks.