The bit my brain can't quite grasp, having watched the video - is the internal screw actually necessary? wouldn't the scoops at the bottom pulling material in force material up the tube anyway?,(reply>), the scoops of the bottom of the tube push the material inward and thus force it up the ramp 'screw", without the screw there would be no upward motion the material would just get packed into the center of the bottom of the tube