Yonder Robotics · 2025–2026
Rotating Base
The rotating base carries everything above it. A CM-AKE60 motor with an integrated ODrive encoder drives a 6.75:1 compound reduction (belt first stage, planetary second), giving closed-loop position control of the whole arm's yaw.
Rotating about a fixed sun
Rotation happens around a fixed sun gear with a driven planet carrier, using a custom water-jetted 5052 aluminum sun gear and ABS thermoplastic structural parts. The compound reduction splits the work between a belt stage and the planetary, which keeps the motor small and the backlash manageable.
A $35 bearing doing a precision job
Structure is water-jetted 0.25" 5052 plate. The skeletal lattice pattern is mass removal, not decoration. The main bearing is an off-the-shelf McMaster-Carr turntable bearing, repurposed as a preloaded precision base bearing for thirty-five dollars.
Buying the bearing rather than making it is what let the rest of the base be custom.
Cable management as a mechanism
A custom e-chain system routes every cable through the rotating joint, enabling continuous 360° rotation without wires winding up. I developed it and then handed it to another team member to finish.
The base interfaces directly with the shoulder motor module and the arm structure above it.
Yonder Robotics