Revolving crane

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Working model after Leonardo da Vinci, Codex Atlanticus (BAM), fol. 965r

The revolving crane was at least 20 meters high. It was likely used to build the dome's oculus and to position the heavy stone and marble blocks of the closing octagonal ring forming the lantern base. The crane's vertical shaft, guided by a long rudder, could rotate 360?. The load and counterweight were shifted simultaneously (in divergent or convergent mode) to keep the crane in constant balance on its vertical shaft. The wheel at the foot of the shaft helped reduce the friction caused by the rotation on the base platform. The load was raised or lowered by means of a vertical screw fitted with three turnbuckles to keep the load on a level plane. The crane required four teams of workmen: one to rotate the crane, two to turn the screws for the radial displacement of the load and counterweight, and one to operate the vertical screw. In the drawings of the crane by Leonardo and Bonaccorso, the load being raised is a marble block of the lantern.

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