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YOU CAN BUILD A REAL TRANSFORMER YOU CAN RIDE

A ride-on car that unfolds itself into a standing robot and folds back into a car, built so you can actually sit on it.

by James Bruton

FULL CAD BOM FIRMWARE DOCS

RoboticsWorkshop

Built withArduinoTeensy3D printing

difficulty
●●●●●
time
several weekends
license
MIT
repo
repo ACTIVE3 stars

WHAT YOU’LL NEED

Videos
1
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COMPAREE VERDICT

This is a car you sit on and drive, which unfolds itself into a standing robot about the size of a person at the press of a button and folds back again. James Bruton built it because most real-life Transformers have no room left for a passenger, so he rides on it like a kid's Power Wheels car instead. The repo has the full CAD assembly as a single STEP file (packed in a 7z archive) and the Arduino sketch under the MIT licence, but there is no parts list and no written instructions; the video is your guide, and James names the main parts as he goes. It is a serious build: 16 motors (2 RC servos, 8 Dynamixel servos and 6 geared DC motors with magnetic encoders), plus two hoverboard wheels for driving, an aluminium extrusion frame and two LiPo batteries. The Dynamixels will dominate your budget; James calls them quite expensive. The hardest part is the motion, not the printing: the six leg joints are DC motors turned into servos with encoders and PID control, and the panels have to move in the right order so they do not crash into each other. Also know the weak spot James found himself: with his e-bike motor controllers the rear wheels free-wheel, so it has no brakes and steering does not really work. If you have built multi-actuator robots before and you are happy to write your own parts list from a video, this is a great project to learn from.

GOOD TO KNOW

  • —The repo contains one STEP assembly (in a 7z archive) and one Arduino sketch.
  • —There is no parts list, no written build guide and no wiring diagram.
  • —The YouTube video is the build log, with James explaining the main parts as he uses them.
  • —MIT licence allows commercial use.
  • —16 motors: 2 RC servos, 8 Dynamixel servos, 6 DC brushed motors with encoder feedback. Two hoverboard wheels do the driving.
  • —Repo last updated in June 2025, when the video came out.

Parts to buy

12 items

From our check of the build. Exact quantities and part numbers are in the creator’s BOM.

  • 16 motorsFind
  • AS5047 magnetic encoders with magnetsFind
  • 6 BTS7960 motor driversFind
  • TeensyFind
  • Dynamixel shieldFind
  • 6 V regulatorsFind
  • Two 3S LiPo batteriesFind
  • Emergency stop and relayFind
  • Front castersFind
  • Aluminium T-slot extrusionFind
  • 20 mm and 8 mm steel shaftFind
  • BearingsFind

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Can I build this?

PrintA lot of 3D-printed structural parts: joint plates, large gears, the body, limbs and hinge assemblies, plus wheel arches and the head. The STEP file is one assembly, so you will need to split it into printable parts.
Buy16 motors (2 RC servos, 8 Dynamixel servos, 6 Gimson Robotics gear motors), AS5047 magnetic encoders with magnets, 6 BTS7960 motor drivers, a Teensy, a Dynamixel shield, 6 V regulators, two 3S LiPo batteries, an emergency stop and relay, two 10-inch hoverboard wheels with two e-bike motor controllers and thumb throttles, front casters, aluminium T-slot extrusion, 20 mm and 8 mm steel shaft, bearings, shaft collars, M5 T-nuts and foam board for the panels.
ToolsA 3D printer with a large build volume (James used a long-bed printer with a 1.2 mm nozzle for the big parts), 7-Zip or similar to unpack the CAD, CAD software that opens STEP files, a soldering iron, a multimeter, tools to cut aluminium extrusion and steel shaft, and hand tools.
SkillsAdvanced: multi-actuator robotics, motor control with encoders and PID, Dynamixel servos, and mechanical design. You need to be comfortable reverse-engineering a build from video and writing your own parts list.
TimeSeveral weekends at least. James does not give a build time, but there are many large prints, a metal frame, 16 motors to wire, and the transformation sequence to tune.
Cost$$$. The eight Dynamixel servos are the single largest cost, then the six gear motors, the hoverboard wheels, the batteries and a lot of filament and aluminium extrusion. James does not give a total.
SafetyRuns on two 3S LiPo batteries, so charge and store them properly; James's build has an emergency stop that cuts power through a relay. The main risk is mechanical: the leg joints are geared down so far they are very hard to move by hand, so keep fingers out while it transforms and test without sitting on it first. It has no brakes.

Build at your own risk. Projects involve tools, electronics and sometimes mains voltage — follow the creator’s safety notes.

Videos

I built a Real Transformer I can Ride on21:16

The full build log with voiceover (June 2025). James explains the joints, motors, encoders, wiring and code as he goes, but there is no written parts list, so pause and take notes.

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Start here

Navigation into the creator’s own docs — we don’t rewrite the guide, we route you to the source.

  1. 1.Watch the video and make your own parts list (Pause whenever James names a motor, driver or bracket and write down the model.)
  2. 2.Download the CAD assembly (One STEP file packed in a 7z archive in the CAD folder. You will need to split it into printable parts.)
  3. 3.Source the motors before you print anything(Eight Dynamixel servos are the expensive part. If you cannot get them, the project stops.)
  4. 4.Build and tune one leg joint before the whole frame(James built and tested a single joint first: gear motor, printed gears, magnetic encoder and PID code. A joint that binds or drifts will multiply across all six.)

Resources

Documentation, files and community threads for this build — we link straight to the original sources and never rehost the creator’s files.

KNOWN ISSUES

  • There is no parts list. You will watch the video and write down every motor, driver and piece of hardware James mentions. Plan your first evening for that.
  • Eight Dynamixel servos are not cheap; James calls them quite expensive, and his came from Robotis. Check availability and price before you commit.
  • The CAD is one STEP assembly inside a 7z archive. You cannot just slice and print: you need to split it into parts and decide how to print each one.
  • The panels, head, bonnet and shoulders have to move in the right order or they collide. James calls fitting it all together a hard challenge, so expect a lot of tuning.
  • It has no brakes. James found that with his e-bike motor controllers one wheel just free-wheels, so differential steering did not work. Plan for proper brakes or different controllers.
  • The code is one sketch of about 700 lines with comments, but there is no separate documentation. You will read it to understand the transformation sequence.

Is there a parts list?

Not a written one. The repo has the CAD and the code only. James names the main parts in the video as he builds: Gimson Robotics gear motors, AS5047 magnetic encoders, BTS7960 motor drivers, a Teensy, Dynamixel servos, hoverboard wheels and e-bike motor controllers.

Can I use cheaper servos instead of Dynamixels?

Partly. James ran out of Dynamixels himself and used cheap 270-degree hobby servos, geared down 2:1, to move the bonnet. The arms, shoulders and head use geared Dynamixels driven in position mode over their own bus, so replacing those means rewriting that part of the code and checking the torque.

How big are the printed parts?

Big. James printed the chunkiest structural parts on a long-bed printer with a 1.2 mm nozzle and the detail parts on a smaller printer. It is not all plastic: the frame is aluminium T-slot extrusion and steel shafts held together by printed plates, and the body panels are partly foam board.

How do you drive and transform it?

You sit on it and drive with two thumb throttles that control the two rear hoverboard wheels. The transformation is started with a button; there is a short delay so you can step back. It does not walk, and it cannot drive while standing up.

Is it strong enough for an adult?

James, an adult, rides it himself. Before adding the motors he sat on the folded legs to test them: the hinged pieces close onto end stops, and those carry the weight.

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Discussion1

FROM THE COMPAREE TEAM

Sixteen motors, no parts list and no brakes. What is the first thing you would add or test before sitting on it?

CompareeTEAM4d agoedited

Practical notes from our verification: the repo contains exactly what the README says, one STEP assembly file and the Arduino code, last updated in June 2025. There is no parts list, wiring diagram or written guide, so the video is the build log; its description lists the 16 motors: 2 RC servos, 8 Dynamixel servos and 6 DC motors with encoder feedback. In the video James steers it with two thumb throttles and points out that it has no brakes.

James Bruton

James Bruton is a British maker who builds robots, walking machines and other big mechanical projects on his YouTube channel and publishes the CAD and code on GitHub as XRobots. He built this one because most real-life Transformers have the car full of robot, with no room left for a passenger.

GitHub

Star the project on GitHub

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  • Comparee is not the author of the projects featured here. All rights to each project belong to its creator — every page links to the original source, and we never host creators’ files.
  • Information is provided without warranty and may become outdated as projects evolve. Prices are indicative bands only — always check the creator’s parts list for current costs.
  • Building and operating any project is at your own responsibility. Protective equipment, safe workshop practice and compliance with local regulations are the builder’s responsibility.
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