Along with pictures which you will be able to see in the gallery, as work progresses and the design changes, I will be uploading dated zip files with the latest FreeCad and stl files for printing all parts on a 3D printer.  I use Creality Ender 3.   Minimal print bed dimensions you need are about 200x200 mm.  

Print everything with 0.3mm layers.  Print shafts and hips with a brim.  One of the gears (driveGear) requires supports.  I do not have any ABS however it might be best to print gears with disk breaks out of ABS since they might get warm.  Be careful, I've heard ABS shrinks a bit.

If you decide to print a non-final design, there are two problems that need to be fixed. Gears do not have a 45 degree miter.  (Use untested gears from BreakerOne_gears_2020-05-27.zip )  Second, when two hips are put together, hips' shafts do not align on the central gears the way I want them.

Each leg requires the following number of part copies: 1 hip, 2 femurs, 1 tibia, 2 driveGears, 3 endGears, 4 bearingGears, 1 of each shafts.  holeTransferPattern can be used to mark holes on the 3.5" Hard Drive plates.  Hip is about a 3.5 hour print, gearbox body is about 3 hours,  femur is about 1.5 hours and the rest of the parts are under an hour each.  All miter gears have a 1.3 mm module.  All involute gears also have a 1.3 mm module.

I use a 22 mm hole saw to clean up all bearing holes before inserting bearings.  Sand all 3D printed shafts with sandpaper.  File the brim with a file.  Holes of all gears need some filing with a small round or flat file.  Clean up the pin holes with a 2 mm drill bit and screw holes with a 4 mm bit.