Parametric Herringbone and Helical Gears

Ever since my friend Mike B. showed me a herringbone gear that he had printed from rhys-jones' Herringbone Geared Extruder blueprints, I've been interested in making my own. What would be really useful, I thought, would be a parametric version of this type of gear--then we could build custom gear sizes for robot parts, or whatever project we have going. So here is my attempt at using OpenSCAD to generate parametric herringbone gears.

It's a work in progress, but I hope this might be useful