[Ari423]

Team 423 used VexPro 3.25" VersaWheels one next to each other as an intake last year. The gap between the treaded parts of the wheels is .370" which is the perfect size to hold in 3/8" poly cord (I think it was 3/8 but it may have been one size smaller). They occasionally would walk into the next groove over if they got a lot of side force but for the most part they worked like a charm. On the other end, we used a piece of PVC tube with slices of a larger PVC tube screwed into it to create grooves. If you don't have access to a lathe or 3D printer, PVC tubing is very versatile and you can find it in almost any hardware store.