@randall
that is exactly what we wanted to do, but such bearings seem to be very expensive

@John Nurre.
Thanks a lot for pointing the headset bearing solution.
I can't really figure how to fix the bearing to the boxes but I will try to find a cast off headset and make some experiments today.

@bluerover.
I did not understand this part:
"eccentric to both the lower and central boxes is driven by gears or a belt from the inner of the lower shafts"
I am really interested to know how this kinetic sculpture is working. May I ask you a sketch or an image of your "copy"?

@PierArg
I already own strong steppers, I 'm on a 3d simulation I will post here to get further help.

Thanks everyone, I really appreciate getting some advice from you