Well hello there, this is not really a how to but more a share of informations. So to start out: My name is AJ, I'm an exchange student from germany in the US. I made the Go kart in an effort for an application at the MIT. I wanted to make a follower car that could carry atleast 150 pounds and would have been controlled by raspberry pi. But because of problems in my hostfamily I had to literally abandon the project. I still learned an incredible amount and i want to share that knowledge in the hope of making it easier for the next person to make one.
Step 1: Finding Your Materials
One hard point is where you find your materials and best would be for free.
- I got my wheels, wheel mounts, motor, cables and various other parts from the scrapyard. You could also get everything from the scrapyard if you would find the right stuff.
- Hardware shops
- I had the luck that I lived in a very small city at first so i got the local hardware store to sponsor me for the last few components
- If you have a welding shop nearby then it would also be woth going dumbster diving in their metal bin
- Materials I used
- 4 Wheel lawnmower wheels and front assemly
- 1" square tubing roughly 200 inches
- Old car alternator
- 4x 12v 11ah atv batteries (you could use more or less any 12v batteries)
- A speed controller for an ebike from ebike (1000w)
- Chains and sprockets with sprocket hub
- 7/8 inch drive shaft because the 4 lawnmower tire were to small
- Pillow bearings for the back axel
- As I already said I was very lucky to have the hardware shop and the local car shop helping me because otherwise i would have paid more than the 150 bucks i paid.
Step 2: Motor(Alternator)
Every alternator can be rewired to be a motor. What you basically have to do is take off the connector assembly and rewire the wires coming out of the alternator.
Austiwawa made a pretty nice video about it and also went over the basic steps on how to do it.
Basically you get 6 wires out of the alternator (most of the time) and the 2 brushes.
First you have to ensure that you have a a way to put power on the 2 brushes directly. you might end up to open up the plastic around the brushes and solder directlyto the graphite springs. To put them back into place i recommend instamorph or some other plastic that is shapable with hot water. Then you check the 6 main wires for resistance and determine the coils and wire them in a y or delta config. The three resulting wires are your motor wires that go to the speed controller.
- One big problem I experienced was I disassembled the whole alternator and reassembled it to see how it looks in the inside. In the process one of the bearings started to grind once every revolution. I "fixed" that by hitting the shaft with a hammer twice after that it was smooth again.
- Another problem you might experience is that everything is setup and it should work but the motor is just making funny noises and doesnt spin up.
- That could be the speed controller: Some speed controllers require a hall sensor which an alternator doesnt have. If they cant detect the hall sensor they try the motor for a second but give up and dont do anything in the end. --> buy diffrent speed controller
- Loose wiring: The copper leads from the Alternator are fairly thick and have a coating to prevent shorts, if your solder iron isnt hot enough you wont have a good connection
- If it still doesnt work check your wiring and ask in the comments maybe i can help.
Step 3: Motor Mounting
Step 4: General Safety Concerns
- The motor kicks. Means the if you pass the thottle threshold it goes forward pretty fast so you better have a suffiecent chair i didnt i only had a board and that wasnt good enough.
- The batteries together have enough power to fry you keep your hands away
- Even tho kids really wanna ride it, dont it goes pretty fast if there is no real weight on it
- The batteries I had didnt have enough Ah which led to me being stuck at the bottom of a hill
- The motor gets hot, after a 10 min drive its gonna be hot
- Get a seperate battery for the field coil otherwise the speedcontroller cuts out.