Alternative To Multiple Gears?

[metastable]

Found some videos of variable field motors online... seems to achieve the same desirable properties as continuously variable transmissions with reduced complexity.

With the stator inserted, one gets max torque per amp, and with the stator retracted, one gets max rpm per volt...

 

[metastable]

I ran a simulation of a BLDC vehicle that I tried to make similar to a Leaf (same drag coefficient, frontal area, loaded mass) and find with 80kW output the vehicle could reach ~126mph if geared appropriately, but the actual top speed with the gearing of a Leaf is around 90mph, which suggests the motor isn't power limited but rather rpm per volt limited at an estimated 25 rpm per volt (kv motor constant). To achieve 126mph with the available power the motor would need its kv constant to be adjustable from ~25kv to ~35kv at constant winding resistance...

But suppose the motor is wound for 10 kv, but adjustable to up to 35kv by pulling out the stator during operation at constant winding resistance (as opposed to fixed 25kv for 90mph top speed), we get more low end torque than before, and more high end top speed, without taking more current from the battery or putting more current through the motor... (see green vehicle thrust line, bottom left chart, red battery current line top left chart and blue motor current line top left chart)

^The final frame of the animation sets the motor constant at 35kv which is sufficient for the vehicle to reach 126mph given its wind drag and 80kw of motor output power.

The first frame of the animation sets the motor constant at 10kv which gives the most torque and acceleration for a given amount of heat production / loss but only 35mph top speed before pulling out the stator.