Alternator GO Kart

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.

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Step 1: Finding Your Materials

One hard point is where you find your materials and best would be for free.

  • Scrapyard
    • 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
    1. 4 Wheel lawnmower wheels and front assemly
    2. 1" square tubing roughly 200 inches
    3. Old car alternator
    4. 4x 12v 11ah atv batteries (you could use more or less any 12v batteries)
    5. A speed controller for an ebike from ebike (1000w)
    6. Chains and sprockets with sprocket hub
    7. 7/8 inch drive shaft because the 4 lawnmower tire were to small
    8. 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

I expected that part to be the easiest but it wasnt. I tried to bind the driveshaft together with the alternator with a sprocket chain system. So I "keyed" the drive shaft with an angle grinder and patience and drilled holes in the shaft of the alternator so the hub could be screwed into place. then i made a mounting plate out of angle iron for the alternator and made spacers out of remaining 1" square tubing. To get tension I put washers between the tubings and tensed up the chain. Be prepared to dull some drill bits and you better have sharp ones. It took me 2 hours to get through the metal with dull drills. After that was done the chain ripped apart because the connecting link wasnt secured so i tried it again and now it finally worked yaaayyy!!!!! So I aligned everything and tried it out and i found out that one of the scrapyard tires couldnt hold air anymore and i ramkeyed them so i couldnt disassamble anything.

Step 4: General Safety Concerns

  1. 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.
  2. The batteries together have enough power to fry you keep your hands away
  3. Even tho kids really wanna ride it, dont it goes pretty fast if there is no real weight on it
  4. The batteries I had didnt have enough Ah which led to me being stuck at the bottom of a hill
  5. The motor gets hot, after a 10 min drive its gonna be hot
  6. Get a seperate battery for the field coil otherwise the speedcontroller cuts out.

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