Yertle Quadruped

Yertle — A 3D Printed Quadrupedal Robot for Locomotion Research

Yertle is a 12-DOF quadruped robot designed for locomotion research. It fuses the leg geometry of the Kangal quadruped with the body geometry of SpotMicro, making most parts cross-compatible with the SpotMicro ecosystem.

Creator: Jerome Alexander Graves · License: MIT · Status: Work-in-progress (functional; ROS2 integration pending)

This Program is a learning entry point. The original firmware is C++ on an ESP32 with a Python GUI master controller — the orobot Program here exposes a stubbed JavaScript interface so you can explore the gait/command surface in-browser. To run on real hardware, follow the upstream build and flash instructions.

Mechanical

• 4 legs × 3 DOF (hip yaw + hip pitch + knee) = 12 servos total
• Leg extension: ~20 cm
• Mass: ~1.8 kg
• Frame: PLA or ABS, printable on a 150 × 150 mm bed (Ender 3 Pro tested)
• Print time: ~2 weeks (5–10 h/day on a single Ender 3 Pro)

3D-Printed Parts

This is the complete set of 21 unique parts: the four-piece outer Shell (Top, Bottom, Front, Back), the Frame (shoulder frames, servo mounts, body beams, electronics plate), and the Legs. Yertle is a 4-legged, 12-servo (3-DOF-per-leg) quadruped, so the leg and shoulder parts must be printed in multiples. Recommended material: PLA or ABS; a build plate of at least 150mm is needed for the larger parts.

Print quantities (per the upstream build guide):

Shell — Top Shell ×1, Bottom Shell ×1, Front Shell ×1, Back Shell ×1 (print these in a second color if you want a two-tone body).

Frame — Inner Shoulder Frame ×2, Outer Shoulder Frame ×2, Upper Shoulder Frame ×2, Lower Shoulder Frame ×2, Left Servo Mount ×2, Right Servo Mount ×2, Servo Mount Top Bracket ×4, Side Body Beam ×2, Electronics Mounting Plate ×1.

Legs (one set per leg, ×4 legs) — Femur ×4, Femur Servo Connector ×4, Inner Tibia ×4, Outer Tibia ×4, Short Link ×4, Long Link ×4, Left Shoulder ×2, Right Shoulder ×2.

Software Architecture

Master/slave over serial or UDP/WiFi:

• Slave (ESP32, C++/Arduino): servo control, sensor read, inverse kinematics, safety limits.
• Master (Python 3 GUI): gait generation, sensor fusion, ROS2 (todo). Runs on anything with WiFi + screen + Python 3.
• Simulation: Python-based built-in simulator; URDF available for Gazebo/Unity.

Build Cost

~$315–350 total (servos dominate at ~$200). See full BOM in the upstream Design/README.

Hardware Compatibility (BYOD)

Yertle is not an orobot-firmware-native build. It uses a custom ESP32 firmware. Running the orobot Program against real hardware requires bridging the orobot WebSocket protocol to Yertle's UDP master/slave protocol — a custom integration tracked under the orobot ESP32 BYOD effort.

Inspirations

• Kangal (leg design)
• SpotMicro (body geometry, parts compatibility)
• Open Quadruped

Links

• GitHub Repository
• STL Files
• Design/README & BOM
• ESP32 Firmware
• Python Master GUI
• URDF / Simulation

Extracted from commit 99c1f98 on 2026-04-27.