48V 3-phase AC motor?!?!?
 

Okay, this strikes me as the holy grail - 3-phase AC motors of less than 208 volt. I don't know if there are any commercial manufacturers of these, though.

This guy apparently made his own:

Rudolf Czernoch's 1997 Cagiva

Small enough to fit on a bike with 48V of batteries and it goes 120mph!?

Okay, so making an A/C controller is not THAT hard - we could open-source one in a matter of a couple months. This dude made his own motor, though... how the hell do you do that? If it was 72V it may open more doors, or even a 144v for cars... AC motors don't seem to come in anything but 120v 1-phase or 208/240/480/640v 3-phase. I want options! I envy this guy's bike - he can go super fast and he has a 50mile max range... i only need to go 50km/day. I want.

The easiest way is to rewind an existing motor. To keep power output similiar, use more turns of smaller conductor magnet wire for higher voltages, or less turns of thicker wire for lower voltages.

Course you could machine everything from scratch too, then add wire.

Thanks, dcb. Sounds like I shouldn't do that because i've never taken a motor apart. However, if i DID do that, what factors am i looking at for determining how many turns and what size of wire? Presumably, i'd want far more amps to go through it to generate the same power - so the motor makes the same torque.

In other news... Looks like Kelly sells 3-phase AC hub motors that are rated at lower voltages like 48-72. HHHHmmmmm!!!!! Unfortunately, doing some rough calculation on their rated RPM, I wouldn't be able to spin one up to 80km/h - i hope I"m wrong, though.

Not a ton of technical info, but Frank's theworkshop.ca site documents a small DC motor rewind as part of his dirt bike conversion project:

Suzuki RM125 Electric Conversion - Part 4

Thanks, that was interesting to see. Not something i'd get into as a first step in motor fun.

It would be fun to see how cheaply and effectively one could build their own electric motor. Maybe after I run out of things to design for the chassis I will take a field trip to the library and get me an edumucation on it ;)

There's always the option of stepping it up and then converting it to AC. The Prius uses that approach.

I have a 3 phase 72 volt motor on my electric bicycle, you can get the motor, controller and everything other then the batteries for $800 from Electric Bike Parts for Crystalyte Hub Motors & Conversion Kits

I thought the prius had a very high voltage pack so no step-up was needed?

What's the wattage on your 72v bike? Are you actually running it at 72v? How fast is it? Does it have the juice to be used on the back wheel of a small motorcycle with intended top speed of 80km/h? What's your shortcoming? Batts, controller or motor?

Hey Matt, this link might help with some of those questions ;)