[EricVanWyk]

Ether - Thanks for compiling all those. It sparked a thought.

Theory:
Some Denso motors brushes are failing in such a way that too many windings can be active at the same time. This may be due to a winding-winding short, a brush deformation, or simple poor design. This state is limited to a limited portion of the rotary travel.

Direct Result:
While in this state, several things occur:
* Current increases: More windings means more mhos.
* Torque constant greatly decreases: Windings fight, reducing effectiveness. Imagine a shaft with a keyway in it: This is the extremely over simplified diagram of the torque constant vs angle that I'm imagining.*

Matching Symptoms:
* The motor will tend to lock into the keyway, given a load that is between the depth of the bore and the outer radius.
* Applying extra torque can pop it out.
* If the bore is deep enough (and it could be very deep), "smooth" current won't do anything.
* "Rough" current has the advantage of being little bursts of torque. This has the possibility of pushing a little harder momentarily (duty cycle <100). It also has the advantage of giving up, letting it roll the wrong way (out of the bore) and then charging forward over the valley.


Does this match up with other folks thoughts?

* Sorry for the weird bore analogy. Better wording of it would be appreciated.