A screw-propelled vehicle is a land or amphibious vehicle designed to cope with difficult snow and ice or mud and swamp.
source/image: Junkyard – Origin of Creativity
Such vehicles are distinguished by being moved by the rotation of one or more auger-like cylinders fitted with a helical flange that engages with the medium through or over which the vehicle is moving./wikipedia
Modern vehicles called Amphirols and other similar vehicles have specialised uses.The weight of the vehicle is typically borne by one or more pairs of large flanged cylinders; sometimes a single flanged cylinder is used with additional stabilising skis.
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These cylinders each have a helical spiral flange like the thread of a screw. On each matched pair of cylinders, one will have its flange running clockwise and the other counter-clockwise.The counter-rotations cancel out so that the vehicle moves forwards (or backwards) along the axis of rotation.
