More of a clean shiny texture...
A smoother spline... (if that's what you used for the outer shape, smooth is nice)
Smaller bearings...
Better placement of the ball bearings... ( they do not touch the inner ring )
Overall it is a good attempt and a well made proto type...
Don't give up...
You only fail if you stop trying... =)

N A wrote:

a little failure

don't try and mimmc reality you are gonna fail

see don't even try to get something real like this