Sean H. Breheny wrote:
>Thanks again to all who responded, and thanks to Kat for the interesting link.
>
>Just as I had suspected (and as Morgan had recommended in the first place)
>splitting the commutation among high, low, and open (tristate) did the
>trick. My driver circuit now runs the motor almost dead on according to the
>specs (12v applied results in 250mA at 4500 rpm, the specs say it should
>draw exactly that amount of current and run at 4400 rpm).

WOW!
You probably have better drivers than they :)

Have you tested torque?

Simple method: attach a cylinder to the axis of known radius.  Mount he motor so axis is horizontal.
Then wind a wire (for larger motors a leather rope) some turns (seven use to be recommended) non-overlapping.
In one end of the wire hang a known weight so you get a known force.
Secure the other end on something nonmoving.
When cylinder is rotating the right way it wil try to lift the weight, and due to the many turns the force in the other end if the wire is negligible.


           _ secured wire end
           |
[MOTOR]-[///] Cylinder with wire wound around
         |
         |
        ###  Weight

Torque is simply radious times force of weight

Instead of weight you could use a weighing scale arranged some intelligent way.  I used a letter scale once, placed above engine and wire attached to letter plate lifting the wire)



...

Once upon a time i was thinking about converting an car engine generator to motor to drive a small electric vehicle.

Theese are three phase synchronous generators with electromagnet rotor.
-We then have the extra benefit of varying the magnet force: High for high torque; low for high speed (less back-EMF = no need for extreme voltages, better optimizing phase drivers for one voltage in th emiddle, and power supply can be direct battery)
(and of course it works nicely as electric generating brake)


>What a great resource the piclist is!

Agree

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