compareeHub

YOU CAN 3D PRINT THIS OPEN-SOURCE ROBOT DOG WITH CYCLOIDAL GEARBOXES

A 3D-printed robot dog with custom cycloidal gearboxes that walks like the Boston Dynamics one, for the cost of the motors.

by James Bruton

FULL CAD BOM FIRMWARE DOCS

RoboticsOpen-hardware

Built withTeensy3D printing

difficulty
●●●●●
time
weeks
license
MIT
repo
repo ACTIVE488 stars

WHAT YOU’LL NEED

Videos
1
Jump to section

COMPAREE VERDICT

openDog V3 is James Bruton's third iteration of a DIY quadruped robot. The mechanical design is the real achievement here: custom 3D-printed cycloidal gearboxes, each built up from dozens of small bearings and steel pins, that give it a smooth, powerful gait. Apart from motors, bearings, carbon tube and fasteners, the structure prints in PLA on an ordinary FDM printer. A Teensy 4.1 runs the kinematics and talks to six ODrive 3.6 controllers, which handle closed-loop control of the twelve motors with AS5047P encoders. The hardest part is not the printing — it is tuning twelve motors to walk without tearing themselves apart. The motors and ODrives are the big expense, and the robot runs from a high-drain 6S LiPo that has to deliver serious current. If one leg behaves differently from the others, you are in for hours of tuning and mechanical adjustment. The documentation is a BOM, CAD, code and a long YouTube build series rather than a written manual — expect weeks of assembly, wiring and debugging before it walks. If you have built multi-motor robots before and have the tools and patience for iterative tuning, this is one of the best open quadruped designs available. If you have not, the gap between 'it printed' and 'it walks' will eat your month.

GOOD TO KNOW

  • —MIT license — commercial use allowed.
  • —CAD is published as STEP files only: the full robot model (zipped STEP), the toleranced cycloidal drive internals, the foot and foot mould, the remote and assembly jigs. There are no ready-made STL files, so you export the printable parts from the STEP models yourself.
  • —Teensy 4.1 code (Arduino IDE) for the dog and remote, including inverse kinematics and ODrive setup; no wiring diagram.
  • —BOM with part numbers and example suppliers; assembly is shown in the YouTube build series rather than a written guide.
  • —No PCB files — this is motors, controllers, and mechanical parts.
  • —BOM lists twelve 9225-size 90 KV brushless motors and six ODrive 3.6 controllers with AS5047P encoders — both can be expensive or hard to find today.

Parts to buy

9 items

From our check of the build. Exact quantities and part numbers are in the creator’s BOM.

  • Twelve 9225 90 KV brushless motorsFind
  • Six ODrive 3.6 controllersFind
  • Twelve AS5047P encodersFind
  • Teensy 4.1 (plus a Teensy LC for the remote)Find
  • MPU6050 IMUFind
  • NRF24L01 radiosFind
  • 6S high-drain LiPo plus a small 2S packFind
  • 28 mm carbon fibre tubeFind
  • HTD belts and several hundred bearingsFind

BUILDS OF THE WEEK

Five open-source builds worth your weekend, every week.

Checked like this one: what’s really in the repo, what it costs, how hard it is. One email, unsubscribe anytime.

Can I build this?

PrintFull frame, leg assemblies and twelve cycloidal drive sets, all in PLA — large parts at about 15% infill, 3 perimeters and 0.3 mm layers, cycloidal drive internals at 4 perimeters and 30-40% infill. The creator gives no total print time; expect many days of printer time.
BuyTwelve 9225 90 KV brushless motors, six ODrive 3.6 controllers, twelve AS5047P encoders, a Teensy 4.1 (plus a Teensy LC for the remote), MPU6050 IMU, NRF24L01 radios, a 6S high-drain LiPo plus a small 2S pack, 28 mm carbon fibre tube, HTD belts and several hundred bearings.
ToolsFDM printer (Prusa/Ender size or larger), hex keys, soldering iron, bench PSU, basic motor tuning knowledge.
SkillsAdvanced — you need to wire and tune twelve motors, understand PID loops, and debug mechanical binding. Not a first robotics project.
TimeWeeks — many days of printing, then assembly, wiring and encoder calibration, and tuning it to walk is open-ended.
CostHigh — twelve 9225 brushless motors and six ODrive 3.6 controllers dominate, plus twelve AS5047P encoders, several hundred bearings (the creator paid about 70 dollars for 400 of the small ones), a 6S high-drain LiPo and filament. The BOM gives no total; price the motors and controllers first.
SafetyA 6S high-drain LiPo powers the motors — use a proper balance charger and charge it in a fire-safe place. Powerful motors can pinch or crush fingers during testing; keep the e-stop within reach. No mains voltage, but high-current DC can arc and burn.

Build at your own risk. Projects involve tools, electronics and sometimes mains voltage — follow the creator’s safety notes.

Videos

Robot Dog V3 - 3D Printed & Open Source #1

James Bruton's official openDog V3 build series is linked from the README — start with 'Robot Dog V3 - 3D Printed & Open Source #1'.

More builds like this

All projects
You can build an open-source underwater research robot for 850 dollarsRoboticsMUR: an open-source underwater robot for research and explorationRoboticsdRehmFlight — DIY VTOL flight controller (Teensy)Robotics

Gallery

opengraph.githubassets.com
img.youtube.com
img.youtube.com
img.youtube.com

Start here

Navigation into the creator’s own docs — we don’t rewrite the guide, we route you to the source.

  1. 1.Read the README and BOM in the repo, then watch the openDog V3 YouTube playlist (Check motor and controller availability before printing — the exact models may be hard to source.)
  2. 2.Print one leg assembly as a test(Validate fit and gearbox tolerances before committing to the full frame.)
  3. 3.Order motors, ODrive controllers, and bearings(The motors and ODrives are the big expense — price them before anything else, and verify ODrive 3.6 availability and firmware compatibility.)
  4. 4.Print the frame and remaining parts(The creator gives no total print time or filament weight; with twelve cycloidal drives plus the frame and legs in PLA, expect many days of printer time.)
  5. 5.Assemble and wire, then tune one leg at a time(Do not power all twelve motors until each leg has been tested individually.)

Resources

Documentation, files and community threads for this build — we link straight to the original sources and never rehost the creator’s files.

KNOWN ISSUES

  • The build uses six ODrive 3.6 boards, which are discontinued in favour of newer ODrive models — check availability and firmware compatibility before you commit.
  • The 9225 90 KV motors in the BOM are not always in stock, and substituting a different motor means re-checking the motor mounts and re-tuning the control loop.
  • The cycloidal gearboxes are assembled from printed parts plus hundreds of small bearings, steel pins and nylon spacers — print the internals with 4 perimeters and 30–40% infill as the creator does, or they will bind or develop backlash.
  • Tuning twelve motors to walk without oscillating or binding takes days, not hours — budget time for PID tweaking and mechanical adjustment.
  • The main 6S LiPo must be a high-drain pack (the creator uses 60C) with a proper balance charger — a weak pack will sag and brown out when all twelve motors load up.
  • If you skip the leg-by-leg testing and power everything at once, a wiring mistake or short can destroy an ODrive board — the most expensive part to replace.

Can I use cheaper motor controllers instead of ODrive?

You need closed-loop control with position feedback, which most cheap ESCs do not provide. ODrive is expensive but purpose-built for this. Alternatives like VESC or custom STM32 boards exist but require firmware porting.

How long does the full print take?

The creator does not give a total print time. Everything is PLA — the large parts at about 15% infill, 3 perimeters and 0.3 mm layers, the cycloidal drive internals at 4 perimeters and 30-40% infill — and with twelve gearboxes plus the frame and legs, expect many days of printer time.

Will it walk on carpet or outdoors?

The repo does not document surfaces. The creator's videos show it walking and climbing over obstacles indoors; the printed parts are PLA and not weatherproof, so outdoor use is at your own risk.

What is the hardest part of the build?

Getting it to walk. There is no written assembly guide, so the mechanical build follows the CAD and James Bruton's YouTube series, and then every AS5047 encoder has to be configured and offset-calibrated in the ODrive tool, the default joint offsets in the code adjusted to your build, and the gains tuned so twelve motors coordinate without oscillating or binding.

Community builds

No community builds yet — be the first, we feature the best ones.

Discussion1

FROM THE COMPAREE TEAM

Twelve brushless motors, twelve printed cycloidal drives and an encoder calibration for every joint before it walks — what would you use it for once it is running?

CompareeTEAM2mo agoedited

Practical notes from our verification: the repo contains a STEP and zipped CAD model, Arduino code for the Teensy 4.1 and the remote, and a BOM spreadsheet the author describes as probably complete. There is no step-by-step assembly guide or wiring diagram in the repo — the build is documented in James Bruton's openDog V3 YouTube playlist, linked at the top of the README. The drive train is twelve 9225 90 KV brushless motors on six ODrive 3.6 controllers with AS5047 encoders, powered by a 6S LiPo, and the printed cycloidal drives use 384 internal bearings in total, so availability of the ODrive 3.6 and the motors is the first thing to check. Before it moves, every encoder has to be configured and offset-calibrated as described in the ODrive documentation, and the default joint offsets in the code need adjusting to your build. The parts are printed in PLA, with the cycloidal drive internals at higher infill. This is not a weekend project, and the motors and controllers are the bulk of the cost. Correction (4 October 2026): we re-checked this page line by line against the project's own repository, documentation and videos, and fixed errors in earlier versions.

James Bruton

James Bruton is a maker and YouTuber (XRobots) known for building large 3D-printed robots. openDog started in 2018 as an experiment in DIY quadruped locomotion and is now on its third version, with printed cycloidal gearboxes and full inverse kinematics.

GitHub

Star the project on GitHub

DISCLAIMER

  • Comparee is not the author of the projects featured here. All rights to each project belong to its creator — every page links to the original source, and we never host creators’ files.
  • Information is provided without warranty and may become outdated as projects evolve. Prices are indicative bands only — always check the creator’s parts list for current costs.
  • Building and operating any project is at your own responsibility. Protective equipment, safe workshop practice and compliance with local regulations are the builder’s responsibility.
GitHub repo