Parametric Timing Pulley v4

Updated 2017/10/03 to work in Customizer.

This OpenSCAD script makes many different types of pulleys for just about any sort of timing belt. This latest version adds support for shafts that have a flat, for multiple nut sizes based on the shaft diameter, adjustable flanges, and for making pulley sets, where the second one is based on a ratio of teeth from the first one. The prior version added support for any number of setscrews and allowed them to be at an angle. The original (By Erik de Bruijn) supported threaded shafts with a recess for a nut to hold the pulley in place, or an even number of set screws printed in a hub with a (capped) teardrop hole. The original works well with the Synchroflex(R) timing belt,1500Lx10Wmm from RS (order code 474-5892), spliced in half (to 5 mm width). Code from DJ Delore adds support for trapezoidal teeth and moves the flange to the bottom if there is only one.