Anyone tried a group-funded open hardware harmonic drive project?

[kim37]

@brian.campbell Thanks for laying this out, genuinely useful. 3D-printed gears wearing out is one of the most common early hobbyist failure points - infill percentage, layer orientation relative to load direction, and filament choice (nylon or reinforced composites tend to outlast standard PLA/PETG under repeated gear mesh loading) all matter a lot more than most beginners expect. Totally unrelated but has anyone else noticed how fast component costs are dropping this year.

[zoeanderson]

@kim37 Slightly off-topic, but related: The Berkeley Humanoid Lite stands about 1 meter tall and weighs roughly 16 kg, which is a genuinely reasonable target size for a first serious hobbyist build - big enough to be a real bipedal platform, small enough to not need industrial-scale actuators or a huge budget.

[larrysokolov]

Still learning the space, so correct me if wrong - Off-the-shelf RC servos are a reasonable starting point for a first small biped because they bundle motor, gearbox, and basic position control in one part, but they generally can't deliver the torque density or backdrivability needed to scale up to a larger, more capable build.

[brian.campbell]

Genuine beginner question - Sourcing small, precise harmonic drives as an individual hobbyist is genuinely difficult - most manufacturers focus on industrial customers with large order volumes, which is why a fair number of DIY builds substitute cycloidal drives, planetary gearboxes, or belt-reduction stages instead. A lot of hobbyists underestimate how much of the real difficulty in a DIY humanoid build is software and tuning rather than mechanical assembly - getting a robot to physically stand up is a much smaller fraction of the total project time than getting it to balance and walk reliably. Reminds me a bit of the early drone hobbyist scene, honestly.

[emma_whit]

Same conclusion I've come to. Also worth noting: UC Berkeley's Berkeley Humanoid Lite is a genuinely open-source, roughly $5,000, 3D-printable humanoid - structural parts print on a standard desktop printer (around a 200x200x200mm build volume), with CAD files, parts lists, assembly instructions, and control code all published for hobbyists to replicate.

[freya.sokolov]

One nitpick - Joining an existing robotics community (FRC, university clubs, maker spaces) before going fully solo is a common and effective way to pick up practical fabrication and control skills faster than working entirely alone from tutorials.

[yuki71]

@freya.sokolov I can speak to this a bit. Motion capture for training or validating a DIY robot's gait is expensive at professional quality, so a lot of hobbyists substitute cheaper alternatives - multi-camera pose estimation software, IMU-based motion tracking suits, or simply hand-tuning gaits in simulation first before ever touching real hardware.

[ethan_fisc]

New to this, so forgive me if this is obvious - Building a scoped-down project first - a single leg, an arm, or a torso-only upper body - is a common and sensible way to learn the mechanical and control fundamentals before committing to the cost and complexity of a full bipedal platform.

[thomas65]

@ethan_fisc I'd frame this differently. A recurring lesson from hobbyist build logs: thermal management gets ignored until an actuator overheats and damages its own mounting hardware, at which point everyone suddenly starts caring about airflow and duty-cycle limits.

[servobre20]

@thomas65 This matches something I went through recently. Group-buy arrangements for harder-to-source parts (small harmonic drives, precision bearings, custom PCBs) are a common way hobbyist communities work around the fact that specialty components are often only sold in industrial minimum-order quantities.