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Cybr trk profile.jpg
Built By Chris Stubbs and Dom Tag
Theme Tesla Cybertruck
First Race EMF 2022
Current Status Active
Motor 4x Hoverboard 6.5″ Hub Motors
ESC 2x Hoverboard PCB
Battery 48V 12S3P Li-Ion (2x 6S)
Gearbox Direct hub motor
Contact @emfroamer
View all Racer Profiles


Cybr trk rgb.jpeg

CYBR TRK started life in 2022 as the EMF Roamer; a publicly controlled, raspberry pi powered robot, that could roam the EMF site. This was a follow on project from the much smaller EMF Roamer in 2018. One of the main objectives was to also be as Hacky Racers legal as practical.

The theme is a loose caricature of the Tesla Cybertruck, rather than an original donor vehicle.



The chassis is constructed from wood, mostly decking frame offcuts, utilising recycled hoverboard components wherever possible. The front wheels are able to articulate using a hoverboard casting as a joint, in a crude suspension to keep 4 wheels on the ground.

The body is also constructed from a lightweight wooden frame, panelled with thin plywood. This is removable from the chassis to enable maintenance and transport.

Steering uses two M8 threaded tie rods to connect the pitman arm to the leading spindle arm. The steering column is 25mm electrical conduit with socket set couplings. No real thoughts were given to steering geometry (bad) as this was a retrofit from the fly-by-wire servo system.

Wooden chassis
Wooden body
Steering components


CYBR TRK utilises 4x 6.5″ 350W hoverboard motors, fitted with 4.10/3.50-5 tyres. Regenerative braking is extremely effective if configured correctly, however one motor has been fitted with a mechanical brake from a Xiaomi M365 scooter to comply with the rules.

Power is delivered to the motors using 2x original hoverboard PCBs running a fork of EFeru’s FOC firmware (links at the bottom). A higher current limit is applied to the rear motors to aid traction given the awful weight distribution. Throttle is applied in torque mode, controlled from a playstation racing pedals set via an Arduino.

Traction power is supplied by 2x custom 6S3P Samsung 30T 21700 Li-Ion battery packs, producing 48V total. Each pack contains a 40A continuous rated BMS. A second 6S4P set using reclaimed hoverboard 18650’s also exists for testing and running around, but does not perform well enough for racing. Block diagram of electrical configuration as configured for EMF Camp (local & remote mode)

Electrical block diagram

Other Features

Cybr trk trailer.jpg

A fold up trolley makes an effective trailer for running gear from the car park to the track!

Originally the car contained over 300 individually addressable RGB LEDs. It could produce an impressive RGB underglow, front headlight bar, and rear brake bar with animated indicators. This number has however declined as they were damaged in races and modifications.

When deployed as the EMF Roamer, the vehicle could be controlled by anyone using a web browser. This used a websockets connection for control, and jsmpeg for live video. A presentation was given at EMF with more information, but recordings could not be published. Presentation without audio available here.


A windscreen wiper motor was originally used as a steering actuator with a pot for feedback, all hooked up to an arduino PID controller. The setpoint could then either be fed from the steering wheel (an old playstation controller), or the Pi for remote control. Using the arduino also allowed current limiting and fault detection, to prevent fire if it gets jammed. Turns out as a neat trick, you can run a PID loop to control the servo angle, and a PID loop to control the max current, and just take the minimum output from either controller as the PWM drive! This was eventually removed in place of basic mechanical steering, at the request of Hacky Racers on safety and legality basis.

The Pi logs all hoverboard and arduino telemetry locally via MQTT/NodeRed/Grafana.


  • Fully Charged Live 2023
    • 1st place overall.
    • 2nd place race position.
    • 2nd place on Moxie points.
  • EMF Camp 2022
    • Beat slowest ever hacky racers lap (previously held by EMF Roamer in 2018)


Item Cost Total
Tyres £103.25 £371.15
Wood for frame/body £40.00
Control PCB £32.00
Swegway 1 £30.00
Swegway 2 £30.00
Chassis alu £20.00
Motor drive enclosures £18.96
Light bar £12.45
Paint £10.00
Bumper steel £10.00
Wire £10.00
Rod ends £9.31
Chair £8.00
Pedals £7.86
LED strip £5.60
Steering Wheel £5.00
12V reg £4.89
Steering brackets £4.46
Steering bolts £3.32
Steering column £3.25
Steering rod £2.80
Battery box Excluded
Brake kit Excluded
Brake standoffs Excluded
Kill switch Excluded
Bumpers Excluded
Batteries Excluded
Fuse Excluded


Tips over a lot.

BMS’s run extremely hot.

Happily pops 30A fuse if accelerating too hard/long.


Twitter Account @EmfFRoamer

The Hoverboard firmware, Arduino code, and CAD on GitHub

Remote control Pi code on GitHub

Chris’ website

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