Different mounting hight of the same stator

[qv_]

If you read this on page http://aircraft-world.com/prod_datasheets/cdmotor.htm
"We have since leared that having them protrude from the bell by ~1.0mm gives a small increase in effciency"

My question is:

1- Is this because better flux or
2- less friction.

I have on my APEX test different mounting hights for the stator on the statorholder.
If I mount the stator "all the way down" I got Io 0,67A and if I mount it 0.8mm upp the Io is 0,63A.
The eta is allsaw 1-2% better and a small dec of Rm with 2,5%

Background:
The magnets are centerd around the stator by it's magnetic force.
If you mount the stator "all the way down" the can on the APEX cdr will hit the bearing and probebly inc the friction.
If you mount the stator 1 mm upp on the statorholder the can allsaw inc the distans to the statorholder with 1 mm.
You can easy fell this because you can now press the can 1mm down and it will go back when you release the presure.

/jan

[David T]

The metal bell increases flux. By having the magnets protrude they will be reducing flux. My guess is they found a 'sweet spot' for that particular setup that increased efficiency.

[olmod]

Makes me wonder what are the wind details ? perhaps by reducing the number of turns one might get the same effect without offsetting the magnets , cheers :) nice kit arent they.