I used three pieces of 3/4" plywood for both 'wheels' and once I achieved a basic pulley shape to accomodate the tube, I added two piecees (per wheel) of steel to brace the wood and bolted them on the top and bottom.  Next I'll add the base and larger center bolts and a lever and a few small brackets to hold the tube in place.  Could work, who knows ?  The sand and heat might be enough to be a success.