Lawrence Harris via EV wrote:
I was thinking it might be more interesting if they put the rotor on
a lead screw and allowed the positioning of the magnets w.r.t. the
coils to be adjusted.  Would provide something like field weakening
on a permanent magnet motor.

There is a style of induction motor that does this. A classic single-phase induction motor requires a trade-off in rotor resistance. You can design the rotor for high starting torque, or high running torque; but not both.

So they made one with two rotors. One optimized for high starting torque, the other for high running torque. They are mounted on the same shaft, end-to-end. There is a spring that pushes the high-torque rotor into the stator when the motor is off. When you power the motor, the high-torque rotor provides the torque needed to start the load. But then, the stator's magnetic field acts like a solenoid, to compress the spring and pull the high-efficiency rotor into the stator. This type of motor got used in millions of home appliances.
Whether we or our politicians know it or not, Nature is party to all
our deals and decisions, and she has more votes, a longer memory,
and a sterner sense of justice than we do. -- Wendell Berry
Lee Hart, 814 8th Ave N, Sartell MN 56377,
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