I finally had a chance to give this another go, and I didnt' need to build a fixture after all.
Turns out it was as easy as pulling the covers of a hubmotor, almost: Pry up a little (millimeter or less at a time) and insert shims until I could stack washers in there, then nuts, then bigger things, at equally-spaced points around the edge, until it was high enough to be able to put my feet on two opposing corners of the base, and grasp the edges of the "rim" on the hub, then pull straight up in one smooth but very difficult motion and it came off.
The very hardest part was the first centimeter or so, because of friction with the actual hub/axle it is normally bolted to inside the motor. After that, it was a lot easier, so the magnets werent' quite as strong as I had feared.
Putting it back on might be interesting
but it is at least off for the moment, allowing internal access.
Nice long magnets, very wide stator. I expect that means there are less end-turn losses, because there is less end length vs width parallel to the magnets?
I already know it's cabable of a lot of torque even at low voltages, as it's designed to run on 24V, along with another separately-controlled motor, to haul a large person (potentially 3-400lbs or more, plus the powerchair's weight) around. That means lots of stops and starts, sometimes running for up to several miles at a time, able to do some pretty severe inclines (whatever the chair can do without tipping over), etc.
It does not use three halls. It has a pair of them, probably Honeywell SS495A, if I am reading them right.
on an electronics board that I can't quite read most of the markings on. I cannot read the ones on the chip; they're too small and faint (but they are there, if I can get sufficient magnification and lighting).
These are detecting fields on a small magnetic encoder ring within the hub/axle's end. Dunno how the fields are setup on the magnet ring. (which is the gray plasticky looking ring just on the inside of the aluminum hub I"m holding in hand)
Really glad I was given the circlip tool a few years ago; it has been invaluable in situations like this:
So to use this with an ebike controller, I'll have to install halls in the stator. Hopefully I can install them in an equivalent spacing to that of one of my hubmotors, based on number of stator teeth vs diameter, or something like that. I have no idea how this motor is wound (phase pattern) other than that it is done as Terminated Wye. Thick winding, though.
Phase ends are circled in green, terminations in red.
Now to find a bit of time to locate some hall sensors that still work, in some other object I don't need, like an old floppy drive or laser-printer mirror-scanner board, salvage them, and start playing with phase/hall combos and hall positions on this motor, to see if I can get it to run on an ebike controller.
If I can, then I can also use this motor to power a super-hauler of a cargo bike, able to easily pull extremely heavy loads. Or, perhaps, a bike that can pull off-the-line really hard and get to speed very fast.
(assuming I can set up a battery pack that can supply the necessary current, and modify a controller to handle that).