Electric Go-Kart
Electric Go-Kart
Duration: 3.5 weeks (130+ hours)
Approximate cost: $380
Construction: Mild Steel chassis, heavy-duty cart wheels, plastic school chair…from my high school, other components in Steel and Aluminium.
Operation: Power developed by two brushed DC 36v 750W (1HP) motors, power supplied by 3 Lead-acid batteries in series, providing 3kWh of power. Power managed by a 4-Quadrant PWM motor controller, with custom trimming. Braking from regenerative brakes and mountain bike disk brakes on independent rear axles. 240v batter charger converts outlet supply power to charge battery. Ackermann un-powered front steering. Drivetrain uses chain and sprocket with 1:12 torque step up.
I had great rapport with my high-school technology teachers; I was grateful when they permitted me to keep and use for myself many components of an electric wooden go kart that had been started by a club of students some years earlier. In 2016, I inherited a (poorly constructed) wooden frame, the loose motors and a broken motor controller, along with a few other small components.
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This project began with deconstruction of what I had been given. Following this, I developed a design for the frame that could accommodate all the required systems and used less than 6m of 30mm mild steel square tube – the only length within budget. This was a roundabout exercise in balancing use of material across interdependent parts of the frame, all at once. With this design completed, I set to repairing the motor controller. I knew it didn’t work, I had tried it, but it also has literally hundreds of components, most of which I was very unfamiliar the function of at the time. I suspected a blown trace or failed component, so I tested them all in turn to see whether they had continuity or performed as expected. I narrowed down the probably issue to a single blown trace. I replaced it with a wire bridge and voila! Good as new.
Welding the frame took a long time, no thanks to owning the cheapest stick welder on the market. Once I had done this and attached ancillary mounts, I painted the frame – it’s marvelous what paint can do to hide amateur welds. I fabricated the electrical circuits and the kart was immediately functional. I trimmed the settings on the motor controller to give maximum regenerative braking (Wikipedia article on regen braking) without overloading the drivetrain with torque (sometimes the chain would slide over teeth on the drive sprocket when it was set too firmly). Acceleration was tuned so that the measured current to the motors would not exceed the maximum rating for the motor controller (160 amps). So, a relatively simple build, and an exercise in employing purchased components (primarily) to produce results.
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It has a top speed of about 19mph and a battery life of many miles – I’ve never actually had it run out, even after whole days of having fun in it. At my little sister’s request, I built a chariot style trailer which it can tow – believe me it’s quite a sight in my neighborhood!