i have wondered why the archimedies screw isnt used as much. glad an upgraded version is going the rounds.,(reply>), I think the general problem with archimedes screw is the same as with Wankel engine: sealing the moving surfaces is just too damn hard in practice. You either have too much friction, too much leaking or too short lifetime for the seals.,(reply>), The main use I can think of is for dredging bodies of water.