04 Thingiverse: Threaded Servo Pulley (2 Oct 2013)

I've uploaded another thing to Thingiverse: http://www.thingiverse.com/thing:159208

This is a 25mm (working diameter) made to fit a Standard Nema 17 Stepper motor Shaft (5mm diameter with 4.5mm, 15mm long shaft cut-out).

This pulley should line up perfectly with the 25mm idler pulley to allow for perfectly parallel strings either side of the toper. 11mm maximum lateral travel should be fairly easy to contain. The version I uploaded to Thingiverse was made for 0.8mm string/cable so it provides a bit more margin on the sides.

As shown In the diagram above, the trucks will have a maximum vertical travel of 638mm which requires 8.12 revolutions to move the ruck through its full range. The hole for the nut to tie it to the shaft will have to be threaded though and should take M3 screws.

The other neat thing is that I initially drew the model in Sketchup. A friend of mine told me about OpenSCAD and after downloading it and familiarising myself for about 30 minutes, I was able to recreate the pulley in OpenSCAD. Awsome tool for parametric work. The OpenSCAD file is also available on thingiverse as part of the download.