Toni Clark uses a twin v belt from Gates! I was thinking cog belt about the size of the old sunbeam electric lawnmowers. ½ in belt is too heavy maybe 3/8 in belt might work. Or use the same belts Toni uses and turn the parts out of aluminum. Maybe time to invest in a small lathe! The chain drive is too big a small standard sprocket is 16 tooth and is about 2” and a 45 tooth is 5”. The prop shaft will have to be at least 4” away from the crank, and the chain is heavy. I think this contraption will be heavy enough mad of aluminum.