You can also install a Motorbike, Car, and Truck alternator on a single motor. One trick I do to charge batteries early game is a single Frame with a V-twin or 1-cylinder motor, all three alternators, controls, and a small fuel tank. No wheels. Start it up, get out of the way of the smoke (or use an extra frame and a muffler) and wait 30 minutes. Car battery charged with smaller gasoline consumption than using a single alternator.
Hopefully this isn’t considered an exploit, because each alternator saps power to provide the charging force, it’s just a cool way to use available components in a specific way. It would probably suck to drive a scooter or motorbike with all three alternators.