Ryan and dad (Larry) decided to build an electric Go-kart to learn more about math and physics, and have fun! Here we chronicle our experience.
Final cost: $964 (Go-kart kit, electrical, misc. hardware)
We began by drawing a few rough designs and coming up with a parts list (see picture below). We talked about how to steer. We talked about the concept of torque to get the thing going (if you sat on your RC car, would it still go?). And we talked about gear ratios; how a smaller gear can turn a larger one more easily, like on his bicycle.
After contemplating many trips to the hardware store, buying the wrong parts, we decided to purchase a Go-kart kit. Razor makes a nice electric Go-kart called the Ground Force ($280 on Amazon), but it is mostly assembled. Another option is the Road Rocket from GoKartsUSA.com for $531 base price.
Ordered the Road Rocket from GoKartsUSA.com. Included the chain guard option, but not the clutch (don't need one for an electric engine). Cost was $546.95 plus $113.28 shipping and handling for a total of $660.23.
This still leaves the engine, battery, electronics, etc. Looks like we could use replacement parts for the Razor Ground Force Go-Kart from Monster Scooter Parts. But we'll wait until we get the kit to figure out what kind of engine will work.
The Go-kart kit arrived today! View the unboxing video below.
Day 1 assembling the Go-kart. View the ready-to-start video below for a look at our work area.
We completed assembly and installation of the front wheels. Here's the final result for day 1.
|Here in Ryan's Recap, Ryan will share some of his observations, tips, and what he learned. “As we were working, I figured out that the longer the wrench, the more you can spin what you are screwing on or off with the same amount of force. I also learned how a ball bearing works; it is a ring that spins on metal balls. Lastly I learned that nylon is used to make bolts stay on better.”|
Finally found some more time to work on the GoKart (Day 2). Completed the steering assembly. Check out the progress video.
|“I learned that when you turn the steering wheel, it pushes some rods that turns the wheels. Even though you turn the steering wheel 90 degrees, the wheels turn less than 90 degrees. When you put the steering rod on you have to feed it through a rod that holds it in place. Plus the teeth on the steering column must face down or else the steering will be backwards.”|
Installed the brake assembly. Hard to say yet if it's in the right orientation. Hopefully we won't have to take it all apart later.
|“I learned that when you push on the brake pedal it pulls on the brake forcing it to expand. What this does is it stops the axle from spinning by pressing against it. It was hard to attach the brake because the rod wasn't easy to fit into place.”|
Installed the rear axle. Took a lot of wiggling and hammering, but we finally got it in there. Of course, judging by the warning nobody's gonna dare ride the thing. BTW, check out the new hammer! You can see the old wooden duct-taped one in previous entries.
|“The axle was extremely hard to put in. First of all there were many additional pieces that attached to the axle. It was also hard to assemble because on each side of the frame there were clamps to secure the axle and they were hard to get the axle through. We had to take them off to fit the axle through.”|
Finally figured out what we needed in terms of an electric motor. We went with the Razor GoKart motor (24V 250W with #25 chain sprocket) and accessories (2 12V batteries, charger, throttle, brake and controller). Total cost of $204 from Monster Scooter Parts, well, including a $45 red helmet (nice). In fact, we used it all as part of Ryan's science project, testing speed vs. voltage using a voltmeter and a bicycle speedometer (see picture).
Note: This motor comes with a #25 sprocket, but the GoKart comes with a #35 sprocket and chain. Unfortunately, there was no #35 sprocket for the motor shaft diameter, so had to get a shaft adapter and a #35 sprocket (from Grainger) for the engine. Sure hope this all works.
|“The motor goes really fast and shakes the table. The speed in miles per hour goes up faster than the electricity in volts.”|
Finally got the rear wheels on. The hard part was getting the brakes lined up so that the brake pads didn't rub against the brake drum. Eventually, we just sanded down the brake pads until they didn't rub. So, we now have a rolling gokart.
|“I learned that the back tires must me keyed to the axle and tightened on to the axle extremely tightly in order to stay on. Also I learned that the brake mechanism can sometimes not work if the hub doesn't fit onto the brake mechanism properly.”|
Brakes are connected, and seat is on. We are ready to roll. Check out the “exciting” video of Ryan rolling down the driveway.
|“The wheels didn't spin well because there was lots of friction and the axle didn't have a motor to speed it up. The steering is a little tight and the Kart doesn't turn very well. But it was good to get it out of the shed and ride it.”|
Mounted the electric motor and connected it to the drive sprocket with the chain. Piled all the electronics on the back for a test, but will have to tidy that up later. Ryan looks far too crazed for our first test. Will the motor be powerful enough to move the cart and Ryan? Yes! No room to go far in the shed, but it clearly had enough power. We'll post a video later when we get it out on the driveway (with a hopefully less crazed Ryan behind the wheel).
|“I learned that our electric motor was a lot faster than we expected it to be. I also learned how to use a chain breaker. I think the shed was a little too limited for our first test.”|
Success! We cabled the throttle to the pedal (after a few failed attempts) and velcro-ed the electrical in place (okay, and a little duct tape too). Below is a picture of the engine area. Also check out our first ride video! And a longer ride too. Thus ends our almost seven month journey. As Ryan put it in the long ride video, “This is cool.”
|“I learned that not following instructions does not pay off. I had
fun driving the kart in the driveway, it was very fast in straightaways. I was
very happy because we had finally finished, it was very difficult installing
the electric motor. We had to add a platform on the back to provide room for
the electrical components, and we also had to tape the wires down to keep them
away from the axle and the chain.
“What I learned about motors: In an electric motor you put electricity in one end and an axle which rotates at the other end which can drive a machine. How does electricity create movement? When electricity flows along a looped wire it creates a magnetic field. If that loop is near another magnet they will either attract or repel which is movement.
“The problem with creating movement this way is that the wire will eventually flip forcing the electricity to flow in the opposite direction causing the movement to reverse. In order to solve this you need two magnets one to push the axle halfway around and the other to push it the rest of the way creating a continuous cycle. This is how D.C. motors work.”