It took some time, but our boy Thom created a winnower prototype that works like a charm! Built from simple PVC tube and a blower, Thom played with the tube diameter and air velocity until he dialed in the perfect airflow. Next step is to create a human powered way (hand or pedal) to provide the constant airflow (no easy task...too much air blows the seed out the top, too little does not winnow the material).
This is what threshed material looked like prior:
This is the remaining chaff:
And this is the winnowed seed:
Thom Rules!!!