How to Make a Custom Electric Go-Kart and Brushless DC Motor

This Instructable details the design and fabrication of my electric go-kart. However, the principles and methods I used can be applied to similar vehicles.

Eli-Kart grew out of an interest of mine to create a simple, reliable, personal electric vehicle that would be practical off the racetrack. By using an electric motor and running everything off batteries, Eli-Kart doesn’t add directly to air pollution (so I don't feel bad using it indoors). Unlike most go-karts, it only has three wheels: two in the front and one in the back. At the expense of a little cornering speed, Eli-Kart has decent ground clearance and extra space for another passenger or extra cargo.

I began to design to formulate ideas for an electric go-kart around the beginning of my senior year in college. I was able to devote a good deal of time to the project in my last semester by working on the project as my undergrad thesis. In my design and analysis, I used computational tools to aid my calculations.  These tools allow for realistic simulations of a variety of conditions.  I used these to double-check things such as shaft yielding and aerodynamics, along with motor torque and magnetic flux for my motor.

Step 1: CAD

Eli-Kart existed on my computer in Solidworks long before it had a physical form.  I spent a lot of time doing virtual tinkering and fine tuning the design.  I've found that the more time you spend on the computer, the less time you spend actually building it.  Attached are some final renderings I generated just before I began building.

You may have noticed the motor in the renderings is different from the custom motor I designed. This is because I originally designed Eli-Kart to be used with a commercially available brushless motor. In the vein of similar EV power systems, it was about a 3kW peak hobby aircraft motor. However, it was relatively simple to devise a new mounting system for my new motor.

The motor design I came up with much later.  I based everything off of motor parts I found online, which I'll get into later.  I attached some pictures of the motor for the Solidworks file as well.

Comments

[ben_k]

The kart looks great! How stable is it cornering at speed, with three wheels and a relatively high center of gravity? Also, how does the performance of your custom motor compare to the aircraft (turnigy?) motor?

[elidavis]

Thanks! Stability is an issue, and I would recommend going with either a lower center of gravity or 4 wheels instead of neglecting both. One wheel drive is very convenient though so it's a tradeoff. With no passenger, its not too bad if you keep your weight over the front wheels, but Eli-Kart is really not made for lateral g's.

Mostly because the motor is much bigger (5" diameter and 5" long compared to probably 2.5" by 2.5") it produces about 6 times as much torque per amp. Given that, it spins 6 times slower. I'm only running it at the same voltage (40V), but since it spins slower I can probably run the motor at a much higher voltage (I'm hoping for around 100V or so). Again, I haven't pushed it but it should be able to sustain about twice the current of the hobby motor. Together that's probably at least 4x the power output if you have the right batteries/controller.

[mjb134]

Good kart. I'm only 13 and I'm about to finish my first kart and post an Instructable about how I built it. Mine will hopefully have a faster gas motor. I will scrounge the junkyard for one. The wheels will be a larger set of off road tires in rear of the kart. The front tires will be smaller off roads too. How much thrust does your motor deliver to propel it? Mine is not finished yet.

[reverbflange]

Sorry for the simple question, but how fast does it go? Very cool!

[elidavis]

Just uploaded a video of Eli-Kart being tested! The steering was a bit loose so he didn't want to hit top speed, but you can see the acceleration pretty well.

http://youtu.be/kAGa7U7URYo

[elidavis]

It goes about 20mph tops and has good acceleration with the hobby motor. I should make a drag race video and add it to the end :)

[tbarber4]

I think it looks like you have made a pretty awesome and fun kart. For stability you could simply add some casters to the back corners. I think either swivel casters or no swivel casters would work. The non swivel casters would require a little closer alignment, but with your skills you could get it done easily. You get the simplicity of the single wheel drive and the stability of having wheels at all four corners.

[ride on toy dude]

What if you made it a one seater with a much bigger rear wheel. Then lowered the chassis for better stability. Basically and electric Can-Am spidyr. Then with the bigger wheel for better traction and a lower center of gravity for better handling. It would be so cool.

[jonpersonals]

I like your idea.. A larger 20" ? wheel will be much more stable since the center of gravity at this wheel will be well below a small wheel, and now will be much more stable and the cornering is much better. Of course the heavy parts must be mounted as low as possible, like a Can AM car.
Added bonus of your larger wheel is a much smother ride. A 20" H D bike tire/wheel should be great , dont you think? It seems you can use the stock gears too ,cheap and good too? A 55 or 65 chain wheel can be bolted up easily th th e last large gear if you wanted to drop the gear ratio .
I made one of these 3 wheelers many years ago and used a wide front track and a 24"? bicycle wheel at the rear . . I did use rubber mounted smaller wheels as out riggers on the rear, but rairly needed or used them .
I ues 3 battries and manually swithed the voltage from all batts in parellel for hills or starting and then 2 in parellel and one series ect till all were in series for high speed and level ground. A switchis easy to make use silver dimes for contacts is great.

[rondust]

LOL there goes my kids electric battery scooter.
Cut up the chassis rear end for the motor and wheel and battery, only need a second front wheel and platform.
Steering column, handle bars already there, speed control and brakes too.
Could put free wheeling caster wheels each side of platform rear, cheap stability.
Great idea for the younger kids - GOOD job.

[elidavis]

Thanks! Kids seem to love it when they see me driving around.