Frame Raised by Four Screws
A large braced structure lifted by four screws, with a strong platform built beneath it
The note beside the large figure states that four screws raise this 'castle' (a large frame or tower), and that once it is raised a strong platform is built beneath it. The drawing shows a big frame with crossed diagonal bracing, a circular drum and a vertical threaded screw column serving as the lifting mechanism. The text is written in Leonardo's mirror-script.
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Four screws raise the frame, then a platform is set beneath
Four screws lift the large frame ('castello'); once it has been raised, a strong platform is built underneath to support it. The device serves to raise and hold a heavy structure on site.
Braced hoist with drum and screw column
The mechanism is a large frame stiffened by crossed diagonals, carrying a circular drum and a vertical threaded screw column. The screws provide the lift described in the note.