I like biochar to be crushed: from my reading and experience it is best to have it in relatively uniform pieces, sizes ranging from a dime to a grain of rice. So, I filled two sono-tubes with concrete and suspended a concrete form pin in the center of each with a jig. Then, with a diamond bit grinder wheel on the angle grinder I made a bunch of dust, cutting grooves and planing down the faces of the grinder wheels. Then, big thanks to Brien, I welded up a frame and mounting points for the wheels, the bearings, the old motor and the hopper supports. Scrounged up a chain and matching sprockets, and spent a few days with different chain and sprocket combinations until the speed and durability were up to snuff. Brien had the genius idea to use motorcycle chain when I was thinking V-belt, and good thing he did because it works great now.