Built By: Chris Stubbs & Dom Tag
Theme: Tesla Cybertruck
First Race Date: EMF Camp, 2022
Current Status: Active

Motor: 4x Hoverboard 6.5″ Hub Motors
ESC: 2x Hoverboard PCB
Battery 1: 48V 12S3P Li-Ion (2x 6S)
Gearbox: Direct hub motor

Hacky Racer Interviews: Chris with CYBR TRK


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.


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)

Other Features

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)


Swegway 1£30.00£309.31
Swegway 2£30.00
Wood for frame£50.00
12V reg£11.39
Pi enclosure£13.79
Motor drive enclosures£18.96
Throttle Arduino£3.19
Steering brackets£4.46
Steering column£3.25
Steering bolts£3.32
Steering wheel + pedals£7.59
Steering rod£2.80
Steering rod ends£9.31
Kill switchExcluded
Wood for bumpersExcluded
Battery 1Excluded
Battery boxExcluded
Lighting and control piExcluded
Brake kitExcluded
Brake standoffsExcluded


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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