Revolving crane

This revolving crane with two arms, which had probably been seen by Leonardo on many construction sites, near stone quarries or at canal excavation works, not only lifted weights but could also rotate, thereby allowing for the fast transfer of materials from one site to another. The drawing also shows how the function of the two arms is essentially that of counterbalancing each other: while one was loaded with a block of stone that had just been cut, the other would unload the previous block. The platform would then rotate so as to reverse the position of the two arms. The crane could be towed for short distances.