It's always cycloids with me lately, isn't it?
This is my second attempt at making a gearbox which fits motors from a crashed RC heli, the first which works acceptably: Note I do not say fly as much as "whirl its blades around alarmingly". Unlike my previous attempts it has no preferred direction of rotation. It cannot be backdriven -- if you try and let the motor freewheel, it will just seize!
Four 4.5mm balls are used to join the wobbling gear to the output plate. A bunch more are used in a thrust bearing as shown in the cutaway view.
Name Last modified Size DescriptionApache Server at burningsmell.org Port 80
Parent Directory - heli-cam.stl 01-Jun-2016 17:33 86K Tiny Eccentric Cam heli-lbox.stl 01-Jun-2016 17:33 2.1M All Parts Except Cam heli.jpg 01-Jun-2016 17:33 142K 10:1 Helicopter Gearbox heli-gbx5.scad 09-Jan-2017 21:44 13K Complete Source Code