Phase resistance, "Motor resistance", stall torque

[apullin]

Hey folks. I was just hoping that you could help me sort out a couple of quick calculations. Seeing as I can't seem to figure this out easily, I've decided that I will be sitting in on the motor design class next semester to freshen up my knowledge

Nonetheless, I have a Scorpion 4025-16 motor, as seen here: http://www.scorpionsystem.com/catalog/motors/s40/S-4025-16/

Their website reports the "motor resistance" as 0.034 ohms, and that the motor is wound in a Delta configuration. Measuring between two phases with a multimeter, I get 0.2 ohm, but perhaps I'm doing it wrong? What's the definition of phase resistance and motor resistance?

This is all for the purpose of determining the stall torque of this wee little motor, or a similar one, for the application of using it as a starter motor for a very small engine. I'm interested in the "motor resistance" to determine what voltage I'll need to push a given current through the motor at a given speed. I know the actual develop-able stall torque is a function of the controller algorithm for brushless control, but I'm just looking at the numbers for now.

If someone wanted to sanity check this for me, I'd be very grateful:
Kv = 330 rpm / volt , so Kt = 1352.4 / Kv (in oz-in / A) = 4.098 oz-in/A = 0.0213 ft-lbs/A.
So if I push 75 A (the continuous rating) through it at stall, T = 1.6 ft-lbs.

 

[amberwolf]

Measuring between two phases with a multimeter, I get 0.2 ohm, but perhaps I'm doing it wrong?

What are you measuring *with*? A regular multimeter probably isn't anywhere near sensitive enough to read correctly at those levels.

 

[regmeister]

deleted

 

[apullin]

Aha, I got hold of a proper micro-ohm meter, and sure enough, it reads as 34 milliOhms between two leads, which tells me that that is indeed the resistance of the two windings in series in parallel with the other winding. Neat. Now to find some donor gears and 1-way bearing from a motorcycle to complete this starter mechanism.