Sand Muller Gearbox.

The most complicated part of a sand muller is easily the gearbox.  Welding spouts onto buckets isn't hard, but getting gear to mesh can be tricky.  I found that with some clever positioning, I could fit a lawn mower gearbox into a garage door opener system.  The rpm is still a bit high, but it is usable.

The main shaft goes to the small gear.  It meshed with the larger gear, which is mounted to the shaft of a lawn mower gearbox.  The output shaft from the gearbox goes through the existing bearing from the door opener.  The gears and gear box all came from the same self propulsion drive on a rusted out mower.