https://www.dropbox.com/s/i8wi9xaafn4atps/2015-04-01%2013.59.17.jpg?dl=0

Was really fun to make. We designed the buckets in Solid edge and had one 3d printed. I then made a couple of silicone moulds of the 3d print and we resin cast 20-odd buckets for the turbine. The hub the attach to was laser cut out of steel which is /awesome/.

Once it was mounted properly in a frame with bearings and what not it span really nicely. We got 6,801 RPM running it with compressed air, and around 4k with water (using a spear valve I designed and built out-of pvc plumbing parts :D )

Is the idea of the part open bucket to make sure they're totally empty when they come back round?

No, gravity will take care of that. The open section is so that the next bucket on the wheel doesn't impinge on the water jet. Best efficiency is to have the jet perpendicular to the bucket, so the slot gives a clear path to the bucket you're actually aiming at.