I designed and built it myself with the help of my dad. It is made from a recycled 55 gallon steel drum with sheet rubber glued to the inside. Stainless steel rubber coated paddles rotate inside the drum and rub the hulls from the grain. These paddles are bicycle powered and spin at 100-120 rpm while an electric fan blow the chaff out of the drum. Further winnowing and hand picking is required to separate the remainder of the chaff and a few kernels that make it through with their husks in place.