Starting from the top down, original design. I'm redoing the top roller since it was having serious problems, which I'll describe later.
The top is made of two steel mixing bowls taped together with aluminium tape. It's connected with a wire to a screen wire patch (aluminium). The screen comb is attached to the top of the main PVC shaft, and is very close (but not touching!) to the neoprene belt.
The upper roller the belt goes over is a piece of PVC pipe wrapped in aluminium tape (to make it be conductive), and spins on a smaller piece of PVC pipe which goes through a couple holes in the top of the main PVC shaft.
The lower roller is plastic, and is directly connected to the motor's shaft.
The base is designed to be expandable, it is made of wood, screws, some metal supports, and can have parts replaced relatively easily, as well as cardboard inserted in some spots to more precisely set the belt's angle up (to make sure the top and bottom rollers are as close to perpendicular as possible).
The lower shaft (which doubles as the lower roller) extends out in both directions, through two bearings. Two small pieces copper pipe with 1/2" ID and very thin walls are on both outside walls of the base, superglued on (to stop the shaft from shifting while it's spinning). There is a drill bit glued inside one end of the PVC bottom roller, which a handheld electric drill can easily be attached to.