This design contains two coaxial counter rotating toroidal propeller one within other. It looks mesmerizing when both turns.

This is %100 printed version. I strongly recommend bearing version for smoother rotation. You can see design here. 

ASSEMBLY

It's very easy to assemble.

1. Take the Hub (orange)
2. Put outer propeller as shown (yellow)
3. One washer (grey) (not push too back so propeller can rotate freely)
4. Now inner propeller (purple)
5. One more washer (same as before)
6. Sun on the hexagon socket (yellow)

Hub has special design so there is one part in it (print in place) that can freely rotate. And thanks to 3D printing miracle, it's not come off and rotate smooth as feather (very tight tolerance).

Now it's time for rod which is stackable. You can use many rod to reach to starts with adding each other.

As final step, you can use this clamp to attach your windmill. To do that, just assemble the root part (small rod).

NOTE: In V2, stopper feature on axle has been longer due to clashing while rotating.