I'm not sure I quite understand the utility either, especially because you now have to have at least TWO friction reducing bearing surfaces instead of one.<br><br>Traditional screw: fixed tube with a bearing/bushing between the moving screw and stationary tube.<br><br>Olds screw: fixed screw with a bearing/bushing between it and the moving tube (to guarantee alignment) AND a bearing/bushing between the tube and whatever the device is attached to.<br><br>The Olds version also can't really "clear" it's own path as it pulls material from the sides rather than in front. This also means the "collecting" end MUST be larger in diameter than the tube as a whole in order to "scrape/scoop" material into it.<br><br>I would also think this would generate more static electricity since you'd have more surface area "sliding" through the material (both the inner AND outer surfaces of the tube are spinning as well as the material moving over the screw)<br><br>The main advantage that MAY occur is a reduction in wear on the screw, though you'd trade that for greater wear on the tube, but the tube is a simpler piece to construct.<br><br>Drive input location seems to be the major (perhaps only) advantage I can think of, except possible patent avoidance.