Model of a Lifting Screw, Model of a screw sleeve between stern and stern, with part of the keel and the rear apostles. The screw light device consists of a loose frame with a screw that can be hoisted up and down in the sleeve on a rope that runs over a disc at the top of the screw sleeve and a disc in the screw frame. The screw is a Mangin screw, a four-blade propeller, composed of two two-blade screws that can be set in parallel for lifting. For this purpose, the shaft of the rear propeller, which runs through the shaft of the front propeller, is provided with a slot at the rear, which must be placed in a vertical position to enable the propeller to be lifted, the rails over which the slot runs immediately blocks the screw in the vertical position. The front screw is then in horizontal position. Of these, the propeller shaft has two intersecting slots on the front, which fit over the same rail: halfway between lines A and B, this rail is interrupted, so that the screw can be turned here. The vertical rails against the stern and the stern over which the screw frame moves are provided with teeth, this includes catches of the screw window that prevent slipping back. The catches can be held back by pulling on two ropes, so that the screw window can be lowered. 1:10 scale (derived)., Petrus van der Loo, Netherlands, 1857, wood (plant material), rope, model: h 61.5 cm × w 36 cm × d 22.5 cm packaging capsule: h 65.5 cm × w 40.5 cm × d 25.5 cm

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