I can’t remember when I first came across Allen Dong’s hand drawn directions for converting a chipper shredder into a bean thresher, but it was a long time ago. He has shared a large number of other designs over the years for small scale, DIY farm tools. His designs look, and are, straightforward to build, with mostly common, inexpensive or salvageable parts and without the need for overly special tools. The designs are very well thought out to serve their purpose, something that is not completely obvious without looking at the details and in some cases seeing Allen demonstrate the simplicity with which they work.
I felt very lucky to be at the OSU Small Scale Equipment Field Day last month where Allen was demonstrating his bean thresher, several winnowers and a hand operated screen, and a vacuum packer for storing seed. I took a few photos and I’ve put a link to them up on the photos page. Make sure to click on the thumbnails to get larger versions.