what would happen if you turn the strew clockwise and you also rotated the cylinder anticlockwise?,(reply>), Those directions would result in no transport of anything at all. Look at the screw, and the scoops. The directions need to be reversed from what you said to have any effect. If you turn both the screw and the cylinder in the proper directions but kept everything else the same, it would transport the same amount as before because the scoops are the same size, and delivering material to the screw at the same rate as before.,(reply>), The stuff will move up twice as fast,(reply>), same thing as if you hold a piece of wood and rotate it opposite a rotating screw, it goes twice as fast,(reply>), Probably the same as turning the cylinder twice as fast?