Ok, maybe I'll kick off a controversey here, but maybe we can learn something.
I've built a couple electric gokarts now, and I've done a fair bit of research on motors. I wanna go fast. DC motors seem to dominate the DIY EV world, but the commercial attempts seem to favor 3 phase AC induction motors. From what I can tell, 3PAC motors (I made the designation up for the purposes of this discussion) are a far more robust and simple design. (Ever take one apart?) I understand how they work, more or less, and I have a handle on why the controllers for 3PAC motors are so complicated and expensive. 3PAC motors tend to also be more efficient, IIRC, and they can have a much broader torque range. In short, they're capable of being hands-down better than comparable DC motors. It's possible to design an EV with a 3PAC motor that requires no transmission, and I think that's cool.
What I don't understand is why a 3PAC motor is so much more expensive than a comparable DC motor. The 3PAC doesn't need brushes and generally has less to worry about wearing out. My favorite 3PAC motor is the Brusa ASM810, or whatever it's part number is now. It's rated 40 HP for one hour and 87 peak. It's about 13.5" in diameter, 10" long, and weighs around 150 lbs. It's end-stackable, so if you need more power, add motors. Very cool concept. But Geez Louise, it costs over $15,000, and the recommended controller is over $25,000. It's cool, alright, but not that cool.
Ok, I have a small machine shop in my basement. What I've been thinking is how hard can it be to build a comparable motor? I'd need a bigger lathe to turn the motor housing. I don't have a source for the silicon steel sheet for the stator core, and I don't have a way to punch the plates out. Well, I should be able to get a stator core out of an existing motor, right? I can ditch the heavy steel housing and replace it with aluminum to lighten things up and facilitate cooling. The housing could even be built with water passages for cooling. And although it's a slow, tedious process, it's possible to wind a motor by hand.
I know that some thought goes into making a motor, with things like current densities, core losses, saturation, and balancing of the moving bits. It's not exactly trivial, but that $15,000 number makes it sound a bit, well, "NASA". Am I really this ignorant?
So does anybody out there "hot rod" electric motors, or know someone who does? Gear heads everywhere have been building and modifying infernal (sic) combustion engines since forever. Is this another budding area of interest to anyone?