Nice idea (tu)
What are the advantages of this design vs. the other column types?
What are you going to use for the vertical rods?
You could use 6 bearings vs. the 8 on the carriages, reducing the total count from 24 to 18.
I think it will be more forgiving of geometric imperfections.
Have you included a spring to allow two of the bearings to float?
You could also use one bushing-ball bearing on one shaft, and 2 ball bearings on the other to prevent rotation of the carriage.
What are the advantages of this design vs. the other column types?
What are you going to use for the vertical rods?
You could use 6 bearings vs. the 8 on the carriages, reducing the total count from 24 to 18.
I think it will be more forgiving of geometric imperfections.
Have you included a spring to allow two of the bearings to float?
You could also use one bushing-ball bearing on one shaft, and 2 ball bearings on the other to prevent rotation of the carriage.