better sync motor mods (tests)

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>" <FutureT-at-aol-dot-com>

Hello all,

I did a test of the "V" cut idea for a squirrel cage rotor, but I did
not actually cut a V, but rather a concave shape, which I figured
might also be good.  The results were interesting, but inconclusive
because of the way I did the tests.

First I made the concave cuts (with a half-round file) on the 2.125"
diameter rotor armature.  It is a 3600 rpm motor (2.3A rated), so it
received 2 cuts.  This motor has no dead poles.  I made each cut
3/4" across.  So the cuts are rather narrow, at a little more than
1/3" the rotor diameter.  This I figured would be too small for best
results, but it was a starting point.  The concavity is about 1/8" deep
at the center of the cut.  This depth is the depth that would be 
reached with a normal flat cut which was about 1/2 the rotor diameter. 
My plan was that I would file the areas completely flat later, and 
compare the results.  Anyhow,  the 3/4" wide concavity caused the
motor to lock sync-ly (with a spark gap rotor attached) at 93 volts.
Vibration was negligable.

Next, I filed the area just a little, to make the cut 15/16" wide.
I wanted to see if the motor would get stronger or weaker.  I did
not use the concave method for this, I just filed flat across the
cusps of the concave area until the flat was 15/16" wide.  Of
course there was still the concave depression centered within the 
flat.  Well, I tested this with the spark gap rotor, and the motor 
locked at 98 volts.  The motor was getting weaker as I widened
the cut.  Vibration was still negligable.

I didn't do any more cutting, because I figured that if the motor
was already getting weaker, it will get even weaker if I do any
more cutting.  But I don't know if it would be stronger if it didn't
have the concave depression within the flat area.  I also don't
know how the original 3/4" concave cut would compare with a
3/4" flat cut, torque-wise.  It would have been better to make a 
3/4" flat cut first, then deepen it to form the concavity.

But this test suggests to me that a rather narrow cut may
be good, or maybe even best, but I can't be sure.  I don't know
if the concave aspect is making it better or worse.  Bottom line;
it's interesting... but more tests are needed.

Question;  has anyone made their flats only 1/3rd the rotor diameter
for a 3600 rpm motor, and did it work fine?

John Freau