Auto-assembled, not yet reviewed

Legolas (open-source biped)

Cassie-inspired mini hobby-servo biped for learning RL locomotion, with full SolidWorks CAD and STLs.

Dormant. No upstream changes for two years or more. It may still build, but parts, firmware and docs may have drifted.

Last push to daviddoo02/Legolas-an-open-source-biped: 2024-05-04 (GitHub, checked 2026-10-01).

Repository activity

Reproducibility65/100Partial source coverage, unverifiedCADBOMWIREFWBUILDLICREPHow it is computed
Legolas (open-source biped) open-source 10-DoF biped robot, 3D render from CMU Mk 5.xml
simplified 3D · CMU Mk 5.xml

About Legolas (open-source biped)

Legolas is a mini bipedal robot by David Doan, inspired by Agility Robotics' Cassie, intended as an open platform for learning and applying reinforcement learning to legged locomotion. The hardware repository contains the SolidWorks CAD (V1/V2/V3 iterations, including a redundant right-leg mirror and a test bench) plus a complete set of printable STLs for V2, and a MuJoCo model of an older version (the other XML file is Agility Robotics' Cassie reference model). Actuation is low-cost hobby servos (8x 40 kg-cm and 2x 80 kg-cm) driven by a PCA9685 board from a Raspberry Pi 4, with an MPU6050 IMU and three ADS1115 ADCs, M4 connecting-rod / ball-joint linkages, and thrust bearings. The BOM is provided as linked Amazon parts rather than a costed table, and step-by-step assembly instructions are noted as a future addition. The control code lives in a separate Legolas_Controller repository. The repo was last updated in May 2024 and the assembly instructions were never published.

Licenses

Hardware
MIT
Software
MIT
Docs
Not published

Degrees of freedom

10 DoF legs 10

Breakdown source

Bipedsource

How to build Legolas (open-source biped)

5 steps

Steps marked Motari summary condense the linked source; follow the source for exact instructions. Upstream step marks a step taken from the linked guide.

  1. Get the CAD or STLs

    Clone the repo and either edit the SolidWorks V2/V3 parts or print the ready STLs in CAD/Legolas/V2/STLs.

    Motari summarygithub.com/daviddoo02/Legolas-an-open-source-biped

  2. Print the structural parts

    Print the STL files in CAD/Legolas/V2/STLs (thigh, foreleg, shin, foot, hip, main body, servo cover and shoe parts). The README lists 1 kg of 3D printing filament without naming a material. A V3 folder holds SolidWorks-only revisions of some parts.

    Motari summarygithub.com/daviddoo02/Legolas-an-open-source-biped

  3. Source electronics

    Order the 8x 40 kg + 2x 80 kg servos, Raspberry Pi 4, PCA9685, MPU6050, ADS1115 and linkage hardware from the linked Amazon parts.

    Upstream stepgithub.com/daviddoo02/Legolas-an-open-source-biped/blob/0457...

  4. Assemble the legs

    No assembly instructions are published: the README says they will be added in future updates. Use the SolidWorks assemblies as the reference for building the linkages from the ball joint rod ends and M4 threaded rod and for mounting the servos.

    Motari summarygithub.com/daviddoo02/Legolas-an-open-source-biped

  5. Run the controller

    Clone Legolas_Controller into a ROS Noetic workspace, build it with catkin_make and launch the walking gait demo, which plays a precomputed inverse-kinematics gait.

    Motari summarygithub.com/daviddoo02/Legolas-an-open-source-biped
Print timenot published
Assembly timenot published

Wiring, power and firmware are safety-relevant and shown for reference only. Check them against the source before building.

Legolas (open-source biped) bill of materials

13 rows

Cost to build

The sources do not publish a cost total. The rows below are what they list, without a sum.

Legolas (open-source biped) parts, as the source lists them. Prices are the source's, not checked against vendors.

Legolas (open-source biped) bill of materials
PartQtySpecSourceConfidence
40 kg-cm hobby servomain leg actuators
8high-torque digital servo, waterproof
Amazon (generic)price not listedREADME.md line 55
high
80 kg-cm hobby servohigh-load joints
2digital high-torque servo
Amazon (GoolRC)price not listedREADME.md line 56
high
Raspberry Pi 4onboard controller
1quad-core SBC
Amazonprice not listedREADME.md line 53
high
PCA9685 servo driver16-channel PWM driver
1I2C PWM servo board
Amazonprice not listedREADME.md line 54
high
MPU6050 IMU6-axis accel/gyro
1I2C IMU
Amazonprice not listedREADME.md line 57
high
ADS1115 ADCThe controller code reads the 10 servo potentiometers through three ADS1115 boards; the README gives no quantity
3I2C 4-channel ADC
Amazonprice not listedREADME.md line 58
high
M4 ball-joint rod ends + threaded rodlinkage hardware
1M4 rod ends, M4 threaded rod
Amazonprice not listedREADME.md lines 48-49
med
Thrust bearingsListed in the README; placement not stated upstream
1thrust bearing set
Amazonprice not listedREADME.md line 47
med
3D printing filament + fastener kit1 kg filament + M2-M5 bolts/locknuts
11 kg of 3D printing filament (material not named upstream); assorted metric hardware
Amazonprice not listedREADME.md lines 44-46
med
Jumper wireselectronics wiring
1breadboard jumper wire assortment
Amazon / Elegooprice not listedREADME.md line 59
med
Power DIY connectorpower harness connector
1DIY power connector
Amazonprice not listedREADME.md line 60
med
USB-C connectorelectronics connector
1USB-C connector module
Amazonprice not listedREADME.md line 61
med
4-to-1 wire connectorelectronics connector
14-to-1 wire connector
Amazonprice not listedREADME.md line 62
med

Rows from the source's own parts list 3

README.md@045709emarkdown

Source rowQtyPrice and vendorLine
main body printed material and linkage hardware
1 kg filament; other quantities not enumerated
Amazon-linked partsno price listed
L44
controller, servo driver, servos, IMU, and ADC
8 40 kg servos; 2 80 kg servos; single linked boards unless otherwise noted
Amazon-linked partsno price listed
L53
electronics wiring and connector accessories
single linked line items; quantities not enumerated
Amazon-linked partsno price listed
L59

Legolas (open-source biped) source files

8 files

Files stay in the upstream repository under their own licenses; these links open them there. The 3D model on this page is Motari's conversion of the file named under Simulation.

Legolas (open-source biped) in simulation

Robot description files a simulator or CAD tool can load, linked at the commit they were found.

The 3D specimen on this page is converted from Mujoco xml/Working Mk 5 - Old model - Demo only/CMU Mk 5.xml at 045709e.

Builds of Legolas (open-source biped)

0 reviewed

No reviewed builds of Legolas (open-source biped) yet.

A build log records the evidence (photos, a video, your repository), what the build cost, how long it took and what you changed. Each one is checked by Motari (until a maintainer claims this page) before it shows here, and reviewed builds count toward the reproducibility score.

Sources and provenance

Sources

Last push to daviddoo02/Legolas-an-open-source-biped: 2024-05-04 (checked 2026-10-01)

How this page was made

Assembled from public sources on 2026-06-04, not yet reviewed by the maintainer. Each figure links to where it is stated; a value the sources do not state reads "not published". Last source review: README 045709e source materials parsed.

Original files stay intact and separately licensed; Motari adds only the summary on this page. Maintainer? Request a correction or removal.

Badge for the README

Maintain Legolas (open-source biped)? Show its reproducibility score in the project's README. The badge links back to this page and updates with the score.

Badge: reproducibility 65/100

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Not fully met yet: bom evidence (partial), wiring diagram (partial), build instructions (partial). The score is read from the project's own sources, so publishing what is missing is what raises it. A score of 90 or more needs a reviewed build. How the score is computed