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Assembly Guide

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Timothy Yong edited this page Sep 18, 2026 · 19 revisions

Required STL Print List

STL part Qty Repo link
Supported Ball Bearing 24 Supported Ball Bearing.stl
Omni Wheel Core 2 Omni Wheel Core.stl
Bearing Inner Ring 4 Bearing Inner Ring.stl
Ball Retainer 4 Ball Retainer.stl
Roller 20 Roller.stl
Omni Wheel Frame 8 Omni Wheel Frame.stl
Hub Retaining Ring 4 Hub Retaining Ring.stl
Rear Base 1 Rear Base.stl
Main Base Bolt 4 Main Base Bolt.stl
Rear Drive Bolt 2 Rear Drive Bolt.stl
Rear Deadwheel Bracket 2 Rear Deadwheel Bracket.stl
Rear Wheel Nut 2 Rear Wheel Nut.stl
Servo Coupler 2 Servo Coupler.stl
Servo Clamp 2 Servo Clamp.stl
Servo Bracket Left 1 Servo Bracket Left.stl
Servo Bracket Right 1 Servo Bracket Right.stl
Arm Base 1 Arm Base.stl
Wheel Bearing Bracket Left 1 Wheel Bearing Bracket Left.stl
Wheel Bearing Bracket Right 1 Wheel Bearing Bracket Right.stl
Front Axle Halve 4 Front Axle Halve.stl
Front Drive Bolt 2 Front Drive Bolt v2.stl
Arm Retainer Pin Halve 8 Arm Retainer Pin Halve.stl
Arm Pin Half Bracket 4 Arm Pin Half Bracket.stl
Arm Pin Mini Bracket 4 Arm Pin Mini Bracket.stl
Arm Pin Bolt 4 Arm Pin Bolt.stl
ESP32 Mount 1 ESP32 Mount.stl
ESP32 Bolt 1 ESP32 Bolt.stl
Bus Adapter Bracket 1 Bus Adapter Bracket.stl
Bus Adapter Clamping Foot 2 Bus Adapter Clamping Foot.stl
Bus Adapter Clamp Bolt 1 Bus Adapter Clamp Bolt.stl
Bus Adapter Bracket Top 1 Bus Adapter Bracket Top.stl
Bus Adapter Bracket Bottom 1 Bus Adapter Bracket Bottom.stl
Bus Adapter Bracket Retainer 1 Bus Adapter Bracket Retainer.stl
Bus Adapter Retainer Bolt 1 Bus Adapter Retainer Bolt.stl
Battery Lock 1 Battery Lock.stl

Purchase the electronics in the sourcing table, then print the 3D parts from STL/ and follow the steps below.

Step 1 — Omni-directional ball bearing

Part Qty Notes
Ball bearing 12 Supported Ball Bearing.stl
Omniwheel core 2 Omni Wheel Core.stl
Bearing inner ring 2 Bearing Inner Ring.stl
Ball retainer 2 Ball Retainer.stl

Assembly

  1. Insert all six ball bearings onto the omniwheel core, then slide in the bearing inner ring.

    Step 1a

  2. Push the bearing inner ring against the balls while turning it so that the protruding circle faces up. Align the balls so they are spaced evenly at 60°.

    Step 1b

  3. Push the ball retainer into the balls until it snaps into place.

    Step 1c

  4. Repeat for the other side.

Step 2 — Omni-directional rollers

Part Qty Notes
Filament cut to 29 cm 4 Roller axle "shaft"
Roller 20 Roller.stl
Omniwheel frame side 8 Omni Wheel Frame.stl
Hub retaining ring 4 Hub Retaining Ring.stl

Assembly

  1. Slide five rollers onto a 29 cm filament, spacing them evenly.

    Step 2a

  2. Clamp the filament between two of the omniwheel frame sides.

    Step 2b

It may be helpful to place bits of CA (super glue) on each of the shafts so that the filament can stick to the omniwheel frame. You can also put a drop of CA right below the shaft so that the two frame halves stick together.

Step 2b
Image attributed to @kitchencamaro

  1. Place the clamped frame onto the omniwheel core and secure it with the hub retaining ring.

    Step 2c

  2. Repeat Steps 2.1–2.3 for the other side of the omniwheel.

  3. Repeat for the other side of the robot.

Step 3 — Rear omni-wheel assembly

Part Qty Notes
Rear base 1 Rear Base.stl
Rear drive bolt 2 Rear Drive Bolt.stl
Rear deadwheel bracket 2 Rear Deadwheel Bracket.stl
Rear wheel nut 2 Rear Wheel Nut.stl
Omni wheel 2 From Steps 1–2

Assembly

  1. Connect the rear deadwheel bracket to the rear base with the rear drive bolt.

    Step 3a

  2. Slide the omni wheel onto the rear axle and tighten the rear wheel nut. Note that the pointy bits of the ball retainer should be facing outside, and the flat circular face of the ball retainer should be facing inside.

    Step 3b

  3. Repeat for the other side.

Step 4 — Traction wheel servo

Part Qty Notes
Feetech STS3215 servo (1/345) 2 From sourcing table
STS drive plate 2
Phillips screw 2
M3 × 5 mm screw 8
Servo coupler 2 Servo Coupler.stl
Servo clamp 2 Servo Clamp.stl
Servo bracket 1 each Left · Right
Arm base 1 Arm Base.stl
Main base bolt 2 Main Base Bolt v2.stl

Assembly

  1. Attach the STS drive plate to the Feetech STS3215 servo with the Phillips screw, then use the four M3 × 5 mm screws to bolt on the servo coupler.

    Step 4a

  2. Insert the Feetech servo assembly into the servo bracket.

    Step 4b

  3. Attach the servo clamp to the back of the servo using two of the servo's screws.

    Servo Clamp

  4. Place the arm base on top of the servo bracket. Run the main base bolt through the arm base and tighten it on the servo bracket.

    Step 4c

  5. Repeat for the other side.

Step 5 — Traction wheel bearing

Part Qty Notes
Ball bearing 12 Supported Ball Bearing.stl
Bearing inner ring 2 Bearing Inner Ring.stl
Wheel bearing bracket 1 each Left · Right
Ball retainer 2 Ball Retainer.stl

Assembly

  1. Insert all six ball bearings into the wheel bearing bracket, then slide in the bearing inner ring.

    Step 5a

  2. Push the bearing inner ring against the balls while turning it. Align the balls so they are spaced evenly at 60°.

    Step 5b

  3. Push the ball retainer into the balls until it snaps into place.

    Step 5c

  4. Repeat for the other side.

Step 6 — Front wheel assembly (VEX)

Part Qty Notes
Traction servo assembly 2 From Step 4
Traction wheel bearing 2 From Step 5
VEX shaft half 4 Front Axle Halve.stl
VEX Traction Wheel 2 VEX item 276-1497
Front drive bolt 2 Front Drive Bolt v2.stl
Main base bolt 2 Main Base Bolt v2.stl

Assembly

  1. Insert the VEX shaft half into the VEX Traction Wheel, then into the traction wheel bearing. Note that the pointy bits of the ball retainer should be facing outside, and the flat circular face of the ball retainer should be facing inside.

    Step 6a

  2. Align the axle end to face the servo coupler, then push the axle into the servo coupler until it clicks in place. Secure by locking the front drive bolt into the arm base side thread.

    Step 6b

  3. Repeat for the other side.

  4. Use two main base bolts to attach the rear base to the arm base.

    Step 6d

Step 7 — Mounting the SO101 arm

Build the follower arm per the official LeRobot SO-101 assembly guide (motor setup, joints, gripper).

Part Qty Notes
Arm retainer pin 8 Arm Retainer Pin Halve.stl
Arm pin half bracket 4 Arm Pin Half Bracket.stl
Arm pin mini bracket 4 Arm Pin Mini Bracket.stl
Arm pin bolt 4 Arm Pin Bolt.stl

Assembly

  1. For each joint that needs a mid-travel pose, connect that servo, select its ID in settings, and press Center Servo to drive it to position 2048 (no EEPROM write).

  2. Mount the base of the SO101 follower arm to the chassis. Insert all four arm retainer pins all the way into the holes.

    Step 7a

  3. Insert the arm pin half bracket on one of the pins on the bottom of the chassis and rotate it until it reaches the back.

    Step 7b

  4. Push the arm pin mini bracket into place and fasten using the arm pin bolt.

    Step 7c

  5. Repeat 7.3 and 7.4 for all pins.

Step 8 — Configuring left and right motors

The two Feetech STS3215 traction-wheel servos ship with the factory ID. Each must be set to ID 7 (left) and ID 8 (right) before the robot is wired up. Use the SO101 Driver board (not the LCD board) and keep the two jumpers on B until the end of this section.

  1. Plug a USB-C cable from your computer into the SO101 Driver board.
  2. Plug in the barrel jack (battery / bench power) to the Driver Board.
  3. Go to https://timrobot.github.io/SOBle/ on Google Chrome. Accept all permissions.
  4. Connect to the Driver board's port on the upper right hand corner by clicking on the Leader Port dropdown and selecting the proper port.
WebUI Interface Leader Port
  1. Click on the settings button on the lower right hand corner.
WebUI Interface Settings
  1. Left motor only — plug the left servo into the driver bus, select 7 on the dropdown, Flash Servo, then unplug the left motor when the script says it succeeded.
Flash ServoID 7
  1. Right motor only — plug the right servo into the driver bus, select 8 on the dropdown, Flash Servo, then unplug the left motor when the script says it succeeded.
Flash ServoID 8
  1. Unplug all power — disconnect the barrel jack and the USB-C cable from the SO101 Driver board.
  2. Wire J2 (servo 2) to the left traction motor.
  3. Wire the left traction motor to the right traction motor.
  4. Wire the right traction motor to J1 (servo 1).

Step 9 — Clone SOBle and flash firmware

ESP32-S3 LCD board

If the board is already on the robot, do not power the robot. The SO101 Driver board may be damaged if the robot is powered without a shared ground.

  1. Clone the SOBle repository on your laptop:

    git clone https://github.com/timrobot/SOBle.git

  2. Plug a USB-C cable from your computer to the LCD board.

  3. Flash firmware — Open esp32/So101-Platform/ in the Arduino IDE (or your usual ESP32 toolchain). Add the esp32 boards library from the boards manager and GFX_Library_for_Arduino from the Library Manager.

  4. Apply the patch — before uploading, run from the repo (required for the Waveshare LCD on ESP32 core 4.x):

    cd SOBle/esp32
./patches/apply.sh

  5. On the port, select the ESP32-S3 Dev Module board type, click on the connected serial port, and upload the sketch. It should take around one minute.

  6. Unplug the USB-C cable from the LCD board.

Step 10 — Preparing the cables and LCD pins

  1. Insert the barrel connector and UBEC power wires into the XT60 female screw terminal, as shown in the diagram.

    Step 10a

  2. Optional. If you are planning to use the Raspi camera or you have hooked jumpers, you will have to do this. Be warned that this step is irreversible:

    1. Remove the header from the end of the UBEC.
    2. Insert the power wires into the USB-C female screw terminal, as shown in the diagram.
    Step 10b

  3. Solder the header pins onto the LCD board's right side. (You may skip this step if you are using hooked jumpers.)

    Step 10c

Step 11 — Mounting the Electronics

Part Qty Notes
LCD (ESP32-S3) 1 From Step 9
ESP32 Mount 1 ESP32 Mount.stl
M2 × 6 mm screw 4 From sourcing table
Rear base 1 From Step 3
ESP32 bolt 1 ESP32 Bolt.stl
Bus adapter 1 Bus Adapter Bracket.stl
Bus adapter clamping foot 2 Bus Adapter Clamping Foot.stl
Bus adapter clamp bolt 1 Bus Adapter Clamp Bolt.stl
Bus adapter bracket top 1 Bus Adapter Bracket Top.stl
Bus adapter bracket bottom 1 Bus Adapter Bracket Bottom.stl
SO101 Driver board 1 From SO101 follower arm
Bus adapter bracket retainer 1 Bus Adapter Bracket Retainer.stl
Bus adapter retainer bolt 1 Bus Adapter Retainer Bolt.stl

Assembly

  1. Place the LCD onto the ESP32 Mount and insert four M2×6 mm screws.

    Step 11a

  2. Slide the ESP32 Mount onto the rear base and secure with the ESP32 bolt.

    Step 11b

  3. Secure the clamp feet to the bus adapter with the bus adapter clamp bolt.

    Step 11c

  4. Clamp the top and bottom bus adapter brackets onto the SO101 Driver board.

    Step 11d

  5. Insert the top and bottom bus adapter brackets into the bus adapter, slide on the bus adapter bracket retainer, and secure with the bus adapter retainer bolt.

    Step 11e

  6. Slide the bus adapter into the back of the SO101 arm.

Step 12 — Wiring the arm UART and power

  1. Move the two jumpers on the SO101 Driver board from B to A.

  2. Attach the TX/RX jumper headers (or hooks) to the LCB board's right side (Diagram A), and then wire them to the SO101 Driver board (Diagram B).

    Diagram A — UART wiring Diagram B — driver wiring

  3. LCD connection options:

    Configuration Instructions
    No Raspi camera, UBEC header Plug the header into the right side of the LCD board (as shown).
    No Raspi camera, UBEC USB-C Use a USB-C to USB-C cable from the UBEC to the LCD board.
    With Raspi camera Use a USB-C → µ-USB cable from the UBEC to the Raspi PWR. Use a µ-USB → USB-C cable from Raspi USB to the LCD board. (See Raspi camera attachment (optional) for camera assembly.)

  4. Plug the barrel connector into the SO101 Driver board.

  5. Insert the 7.4 V battery into the battery cage and secure it with the battery lock (Battery Lock.stl).

Step 13 — Controlling the robot

  1. Plug the leader arm into your PC or Mac.
  2. Plug the XT60 male connector into the battery's XT60 female socket. This will power the robot.

WebUI

  1. Go to Google Chrome and enable all Bluetooth/BLE flags.
  2. Go to https://timrobot.github.io/SOBle/. Read the robot name on the OLED. Type it in the search bar and press Connect.
  3. Control the robot using WASD and the leader arm.

Python Script

WARNING: When you start the example below, the follower arm on the robot will immediately engage to match the joint mapping in your config file. Keep hands clear of the arm and make sure it has room to move before running.

  1. Pip install the library if you have not already:

    pip install "soble @ git+https://github.com/timrobot/SOBle.git@master"

  2. Read the robot name on the OLED. Then, on your PC or Mac:

    cd examples
python soble-app.py -p /dev/tty.usbmodem575E0032081 -n Capybara -c config.json
    • -p — Leader port (Linux e.g. /dev/ttyACM0, Windows e.g. COM3, macOS e.g. /dev/tty.usbmodem575E0032081)
    • -n — Robot name (e.g. Capybara)
    • -c — Config file — leader/follower joint limits (see config.json)

  3. Control the robot using WASD and the leader arm.

Raspi camera attachment (optional)

If you plan to add the Raspi camera attachment, print SO-ARM101_IMX708_wrist_mount.stl and mount it on the gripper as shown:

Camera mount

  1. Camera to Pi — Connect the Arducam IMX708 camera module to the Raspberry Pi Zero 2 W camera port.

  2. Mount Pi + camera — Secure the camera and Pi Zero 2 W to the cam mount.

  3. SD card — Flash an SD card with Raspberry Pi OS. Setup the WiFi if you require video streaming.

  4. AprilTag service — Boot the Pi, copy the SOBle/raspi tree onto it, and run:

    bash install-detect-atags-service.sh

    (from SOBle/raspi/). Then shut the Pi down.

Optional: Display an AprilTag such as this tag16h5 example on your phone — with the Raspi camera attached, you should see the tag detected in the UI.

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