The official assembly guide is marked incomplete and leaves screw counts as a TODO, so builders lean on the CAD, the Tnkr guide and Discord.
Open Duck Mini is a roughly 42 cm tall walking robot modeled on Disney's BDX droid, built from 3D-printed parts and 14 Feetech serial bus servos. It runs walking policies trained with reinforcement learning in simulation on a Raspberry Pi Zero 2W, driven by a gamepad. Pollen Robotics later released the related commercial Microduck.
At a glance
| Parts cost | $400 project · The README says the full parts list should come in under $400. The parts list sheet totals 398 EUR including about 20 EUR of filament source ↗ |
|---|---|
| Difficulty | 3/5 Intermediate · Printed parts and off-the-shelf servos, but needs soldering, a 2S battery build, servo calibration and some comfort with RL policy tooling. |
| Build time | Not stated |
| Tools needed | 3D printer (PLA at 15% infill, about 500 g per the parts list, plus TPU for the foot soles), soldering, heat-set insert tool, blue threadlocker |
| Motors | 14x Feetech STS3215 7.4V serial bus servos, plus 2 small 9g servos for the antennas |
| Controller | Raspberry Pi Zero 2W with a Waveshare bus servo adapter |
| Sensors | BNO055 IMU, foot contact switches; camera, microphone and speaker in the optional expression package |
| Published | ✓ Parts list✓ CAD/STL✓ Assembly guide✓ Wiring✓ Software✗ Video GitHub README + markdown guides (print, motor setup, assembly), Google Sheets parts list, Onshape CAD, third-party Tnkr guide, Chinese Feishu wiki |
| Activity | Last update 2026-01-31 · 4,177 GitHub stars · Discord linked from README; 539 forks |
| Kits | A parts and electronics kit is listed at $600 on the Tnkr page |
Licenses
| Design files | Apache-2.0 (same repo-wide LICENSE covers the STL files in print/; the Onshape CAD has no separate license statement) source ↗ |
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| Code | Apache-2.0 (repo-wide LICENSE) source ↗ |
| Documentation | Apache-2.0 (same repo-wide LICENSE, no separate docs or media license) source ↗ |
Builder notes
Practical points from the project's issue tracker, forum and docs, each linked to its source.
- The maintainer's TODO list for a next version flags a neck part that breaks often, a BMS that causes too many problems and is hard to get in some regions, and missing screw counts in the docs. source ↗
- The parts list note to buy the 7.4V (19 kg.cm) STS3215 points retailers to the 1:345 C001 variant. Builders with that variant report joints that cannot reach the speeds the walking policy asks for, and the thread has no official answer on whether a faster gear ratio is intended. source ↗
- The 1 W eye LEDs pull more current than a Raspberry Pi GPIO pin can supply. The suggested fix is driving them through a small N-channel MOSFET from the 5V rail. source ↗
- A screw head on the roll motor bracket rubs against the roll-to-pitch part. The maintainer confirmed it and said the part tends to wear its own clearance slot. source ↗
- The assembly guide is marked incomplete, and the page on going from Onshape to a MuJoCo model is flagged as outdated. Training has moved to a separate Open_Duck_Playground repo. source ↗
Other bipeds plans
- Otto DIY · $60–$70 · difficulty 1/5
- ODRI Bolt biped · $4,700 (2022) · difficulty 5/5