Model of a Lifting Screw

Model of a screw casing between the sternpost and the rudderpost, with a section of the keel and the sternpost. The screw lifting device consists of a loose frame with a screw, which can be raised and lowered in the casing by a rope running over a pulley at the top of the screw casing and a pulley in the screw frame. The screw is a Mangin screw, a four-bladed propeller, composed of two two-bladed screws that can be set in parallel for lifting. The screw is disengaged by pulling the shaft into the ship. The vertical rails against the sternpost and the rudderpost over which the screw frame moves are provided with teeth; into these fall pallets of the screw frame that prevent it from sliding back. The pallets can be held back, allowing the screw frame to descend. Beams against the posts hold the screw frame down and must be removed for lifting. Scale 1:10 (estimate).