(old) OpenSCAD: bevel gears (v16) (please check v25)

This is based on / beruht auf: 
Bibliothek für Evolventen-Zahnräder, Schnecken und Zahnstangen
Autor :   Dr Jörg Janssen
Stand :   29. Oktober 2018
Version :  2.3
Lizenz :   Creative Commons - Attribution, Non Commercial, Share Alike
Thingiverse: https://www.thingiverse.com/thing:1604369

It contains modules to build bevel gears (Kegelräder) and differentials in OpenSCAD. 

It also features a very flexible tube() module (called "Rohr()") which has chamfers, tapers, min/max radius, sector, facets, and a box() module with chamfers and more (this is updated in v17 over the rudimentary box() in v16).

Plus a set of more rudimentary modules that ease the typing work much like macros in other environments.

updates for basic files: https://www.printables.com/model/1381670-openscad-basic-modules-and-planetary-gears-v19-add