About this 3D model

UPDATE I added a version for use with a standard 608 bearing 3d printed bearing to use with a 1/2 inch wood dowel and 1/4 inch steel bearing balls which are pretty cheap to buy. You would need to print at least 4 and maybe dedicate a center portion of the shelf to use these. The idea is to use a half inch dowel with a printed bearing on each end and slide it onto the 1x2. place the spools on top of the rod and you are done.