What Size electric Motor for go Kart?
On our show, we like extreme tech. And, as far as we're concerned, racing go-karts at 90 mph with your butt half an inch off the ground certainly qualifies as extreme. With scary acceleration and speed, high-performance karts are as exhilarating as it gets in racing circles. But these track-only rides use two-stroke engines, which are notoriously dirty-one kart can spew as many pollutants as 100 cars.
We care about the environment and want to do our part, but still have a little fun. So we wondered: Could we create an electric kart that would outperform its noisy, gas-powered twin-and be just as thrilling?
Starting with two Tony Kart gas models, we converted one to electric in 12 hours flat. (We even amazed ourselves.) We used a 25-hp brushed DC (direct current) electric motor and an industrial controller from a golf cart, and then focused on four details that can trip up electric vehicles-torque curves, weight, batteries and cost. Cameras in tow, we headed out to Infineon Raceway in Sonoma, Calif. Race tracks, loud noises and burning rubber: just an average day on a MythBusters shoot.
Photograph by Mark Richards
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Adam: I had to create a link between the throttle pedal and the potentiometer, which is a mechanical device that tells the speed controller how much pressure is on the throttle pedal. The speed controller translates that signal to regulate how much amperage is sent to the motor-and that determines how fast the kart will go. Here, we're testing the linkage.
Photograph by Mark Richard
Jamie: Most manufacturers plan on using lithium-ion batteries in future hybrids and electric cars, but some current types can suffer from thermal runaway, or overheating, and catch fire. We avoided this by using lithium-iron-phosphate batteries from Thunder-Sky. They aren't as sensitive to temperature, but they do need to be kept under pressure. This bracket is part of a vice I'm building for the batteries. As they heat up, they can swell and crack the casing if they're not squeezed together. We used 28 batteries with a total of 110 volts. The kart can be charged to 80 percent in an hour and 100 percent overnight.