I liked the model as posted by @3DMK which was based on the model of Dalpek. But after printing I found that I do not like the bearing construction between the two big rotors. It was to fragile to my opinion. And I was not able to print the big rotors on my ender3. So I have scaled the rotor by approx. 90% and created my own bearing construction.

Most has a quite rigid fit but a bit of glue is recommended. Mounting instructions:

• First mount/glue the axle through the rotor.
• Fit the bearing within the bearing housing, should be a thight fit
• Slide the axle through the bearing assemly
• Slide/Glue the axle closing ring over the axle to fix the bearing position on the axle
• Slide the complete assembly into the housing.

Repeat the same procedure for the other side.

Parts required:

• Rotor left side
• Rotor right side
• Housing (pay attention to orientation, side with internal support layer should be down. Support only required underneath the extension) (On request I have also uploaded a version without internal support layer)
• 2 x bearing housing
• 2 x axle 
• 2 x axle closing ring