Video can be found here: https://www.youtube.com/watch?v=8sq4pHdSXYM

STL and Editable Fusion 360 source files can be found here: https://bbprojects.technology/collections/stl-fusion-360-source-files/products/3d-printable-high-torque-servo-gear-reduction-files

I've created a Universal Motion Controller to control the position on this servo. More info can be found here: https://www.thingiverse.com/thing:4245315

This servo/gear reduction uses mostly 3D-printed parts. The servo uses a 775 36V 9000rpm brushed DC-motor wich is driven by a BTS7960B motor driver wich is controlled by an arduino mega 2560. The stall torque of the servo is about 55kg/cm wich is about 5.39 Nm. the peak current is about 18 amps when using a 6s LIPO battery (about 22-24V). the reduction ratio is 1:30. I originally wanted to use some 20mm ball bearings for the outputshaft but they didn't arrive in time so I ended up using two 20mm holes and a lot of lubrication. For the intend of filming the internals of the servo for possible faillures, I printed some collored gears and lasercut a 5 mm acrylic lid. Unfortunatly I didn't get to film any awsome footage of gears exploding because they were far to strong ;-). Even at a peak torque of 54kg/cm they didn't show the slightest form of flexing or cracks. The two middle gears (blue and red one) use a stainless steel shaft of 6mm diameter. The holes of the gears are designed at 6.2mm diameter so they would fit nicely around the 6mm shaft but some additional filing/sanding might be required. The same might has to be done for the 20mm shaft holes.

I uploaded the dxf of the lid so people with a laser cutter can cut the lid out of transparant acrylic.

Video can be found here: https://www.youtube.com/watch?v=8sq4pHdSXYM

More info can be found here: https://hackaday.io/project/162855-3d-printable-high-torque-servogear-reduction

Components used:

1 × 775 Motor DC 12V-36V 3500-9000RPM Motor Large Torque High Power Motor
link: https://www.banggood.com/775-Gear-Motor-DC-12V-36V-3500-9000RPM-Motor-Large-Torque-High-power-Motor-p-1091058.html?rmmds=search&cur_warehouse=CN

1 × Arduino nano V3
link: https://www.banggood.com/Geekcreit-ATmega328P-Nano-V3-Module-Improved-Version-With-USB-Cable-Development-Board-For-Arduino-p-933647.html?p=E01411629100201406T1&custlinkid=255135

1 × L298N motor driver
link: https://www.banggood.com/Wholesale-Dual-H-Bridge-DC-Stepper-Motor-Drive-Controller-Board-Module-Arduino-L298N-p-42826.html?p=E01411629100201406T1&custlinkid=255131

1 × Heat shrinks
link: https://www.banggood.com/328pcs-Heat-Shrink-Tubing-Insulation-Electrical-Shrinkable-Tube-Sleeve-Cable-21-p-1362019.html?p=E01411629100201406T1&custlinkid=669227

2 × stainless steel shaft
dimensions: 6mm diameter, 70mm lenght

2 × M5 bolt and nut
dimension: 40mm lenght

1 × 20mm steel tube
dimension: 125mm lenght

2 × screws 15mm lenght
dimension: 4.5mm diameter, 15mm lenght

5 × screws 35mm lenght
dimension: 4.5mm diameter, 35mm lenght

Recommended Tools:

3D-printer: https://www.banggood.com/Creality-3D-Ender-3-Pro-V-slot-Prusa-I3-DIY-3D-Printer-Kit-p-1346320.html?p=E01411629100201406T1&custlinkid=677427

Paypal: https://paypal.me/BrockenBrian

Feel free to take a look at my other designs:

3D printable antweight battlebot: Bulldog: https://www.thingiverse.com/thing:4623536
SpaceX inspired edf rocket: https://www.thingiverse.com/thing:4606751
3D printed high torque servo/gearbox version 2: https://www.thingiverse.com/thing:4547703
UMC - Universal motion controller: https://www.thingiverse.com/thing:4245315
3D-printable Davinci catapult gift card: https://www.thingiverse.com/thing:4067668
Arduino controlled photogrammetry 3D-scanner: https://www.thingiverse.com/thing:3958326
Fully 3D-printable turntable: https://www.thingiverse.com/thing:3723618
RC FPV tank rover: https://www.thingiverse.com/thing:3587738
Fully 3D-printable wind-up car gift card: https://www.thingiverse.com/thing:3308710
3D-printable High torque servo/gear reduction: https://www.thingiverse.com/thing:3292860
'BOOM box' high voltage capacitor bank case: https://www.thingiverse.com/thing:2980012
Subby the interactive youtube subscriber robot: https://www.thingiverse.com/thing:2928254
robot hand || bionic hand prosthesis prototype: https://www.thingiverse.com/thing:2838239
3D-printable linear actuator: https://www.thingiverse.com/thing:2783959
Mini 3D-printable crossbow: https://www.thingiverse.com/thing:2710472
8 legged spider robot: https://www.thingiverse.com/thing:2470882
best 3D-printable bearing: https://www.thingiverse.com/thing:2349065

Have a nice day!