Summary I tried many pulley designs but finally I did my own designs and I think they do their job pretty well. Instructions You can use a M3 screw and M4 nuts at both sides, you will see how they fit. You can see it in the many picture. There are two models: Simetric parts meant to glue each other. It is a little bit smaller. Two different parts to attach to each other. It is not recommended, but a little bit of glue will avoid separate each other after spinning many times.