OP
Very cool! The tines are just made from regular steel, or do any of the parts need to be hardened?
Your dead right, the only reason that i didn't go for a similar design was that I could not get the impellers cheap enough in Australia, so I just turned them out of some hard box timber. Milled the slots in the vice with a router, and machined the centre hole with a metal lathe and boring bar. To finish off any rough spots I then used car body filler, then sanded back to speck with 500 grit sandpaper in the wood lathe. Now that it has sort of run in, they do run quite well.There was a thread about a seeder on TBN few years back. I forgot the details but the guy used outboard engine water pump impellers for seed metering. I could imagine that they would require much smaller torque to turn due to small diameter.