I had 2 bid sacks of sunflower seeds from last summer, that I just could not make clean enough - there was a lot of duct, debris, empty seeds, broken seeds, small stones. I was looking on internet to buy a winnowing machine, small and cheap enough so that for my use one day a year it would not be a big burden.
China makes them, cheap - just $100 a piece, but to ship it over they ask for additional $400 - not worth it...
And then I found a website where a man was explaining and showing DIY little machine to do small batches of seeds. He published the drawings for this little machine in here. Many people already built similar ones and say good words about it. It looked so ridiculously easy to build, that we just built it in half a day, only spending $10 on good smooth wood planks. The rest was just from scrap materials.
I could not believe it would clean my sunflower seeds until I turned the shopvac on... To my utter surprise it worked like a charm, separating good seeds from the debris in no time. I only spent 15 minutes to clean the whole sack of seeds. That was so amazing! Big Thank you goes to that British guy who invested his own time to design and test it, and publish it so people can use it !