This is a 4:1 stackable Planetary Gearbox, designed with just enough slack in the system to mean it should work perfectly first time. I've printed a few other such gearboxes from here on Thingiverse and couldn't get them to work because the tolerances were too high... this shouldn't be a problem here. Stackable means you can print two or more gearboxes and insert them into each other, increasing the overall output ratio, ie 4:1, 16:1, 64:1, etc. I've included printing instructions (though it is a VERY easy print - no supports required) and the video below demonstrates how things are easily fitted together.
WANT TO TIP?
My design for these planetary gears was inspired by a build by PCGEAR https://www.thingiverse.com/thing:3047454 and whilst mine was a completely separate build, I still feel that if you're good enough to want to give a tip, it should go to him. If I hadn't seen and tried his version, I would have never made my own. So my thanks go to PCGEAR for the inspiration.
JUST ONE STIPULATION... if you feature this in a YouTube video, please name me as the Creator and provide a Link to this file AND to my follow my YouTube Channel.
I took this 3D printed gearbox and converted it to aluminium using Lost PLA Casting.