This LEGO Great Ball Contraption (GBC) module uses a true Double Helix Archimedes Screw to transport the balls. It uses slides (6 x 12 x 8 studs, 11267) for its screw. It works very reliably and does not jam. There are some more photos in my Flickr album.
I am an Associate Professor (Reader) at the HIT Lab NZ, University of Canterbury.