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Re: motor winder in dallas

Original poster: "Steve White by way of Terry Fritz <twftesla-at-uswest-dot-net>" <slwhite-at-zeus.ia-dot-net>

The rotor that I made is 10" in diameter and 1/2" thick and is made from
G10. I started by rough-cutting the rotor on a bandsaw. I had heard a lot of
horror stories about how difficult it was to work with this material and
after having worked with it I think they are exaggerated somewhat. It took
me about 20 minutes to rough-cut the rotor. The saw blade may have been
dulled, but if it was I didn't notice it. If done carefully, the
rough-cutting should get you within 1/16" of round. The next step is to
assemble the rotor and hub into the final assembly as it will be used on the
RSG. Then mount the assembly to your RSG motor shaft. I used a Stock Drive
Products timing belt pulley for my hub and I highly recommend it. It is made
from stainless steel and is machined on a lathe so that there is no
measureable run-out laterally or longitudinally. It is crucial that you do
the final machining with the rotor assembly mounted on the motor as it will
be used. Next, I fashioned a jig for my rotary die grinder (hereafter
referred to as RDG). A RDG is like a large Dremel tool. You could probably
use a Dremel tool in place of the RDG. The purpose of the jig is to provide
a means for holding the RDG cutting tool against the rotor edge without the
RDG being able to move.  To achieve precision roundness, the RDG must be
able to be locked down where it will not move. Essentially, you are
fashioning a poor man's lathe. My jig was fiendishly simple. I just took a
piece of 2x4 wood and drilled a hole through it so that I could jam my RDG
into the hole. I could then clamp down the 2x4 with C clamps against the
base plate of my RSG assembly. At this point you need to install a tungsten
carbide cutter into the RDG. These are widely available from Dremel, E-Bay,
and tool stores. The tungsten carbide is necessary to cut the G10. Now you
simply rotate the rotor by hand until you find the low spot on the
circumference. Place the cutting tool against the rotor edge (RDG shaft
parallel with RSG motor shaft). Clamp down the RDG jig. The cutting tool is
now positioned at the low spot of the rotor and the RDG is clamped down. You
are now ready to cut. Turn on the RDG and slowly rotate the RSG rotor by
hand against the cutting tool. Keep going until you do a complete rotation
of the rotor. When you are down, the rotor should be within a few mils of
perfectly round. A final cosmetic step is to turn remove the RDG and start
the RSG motor. Hold some fine grit sandpaper against the rotor edge for a
minute and you will end up with a rotor edge that is extremely smooth and
not rough.

I should mention that I initially tried methods where I tried to machine the
rotor by running the RSG motor at full speed (3600 RPM on my system). I then
reasoned that if I held the cutting tool against the rotor edge while the
RSG motor was running, that it would naturally machine down to a perfect
circle. This never worked because the rotor was so out of balance from the
rough cut that the vibration would shake the cutting tool while it was
cutting thus never allowing a perfect circle to be achieved. I also tried
coarse-grit sandpaper with no better result. The key to achieving the
perfectly round rotor is to do the maching with all components assembled and
turning the rotor by hand so that no vibration is induced.

I hope that this long-winded explanation is helpful.

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Wednesday, May 16, 2001 5:28 PM
Subject: Re: motor winder in dallas

> Original poster: "mpf by way of Terry Fritz <twftesla-at-uswest-dot-net>"
> Please share your technique with the list!
> Thanks,
> Michael
> ----- Original Message -----
> From: Tesla list <tesla-at-pupman-dot-com>
> To: <tesla-at-pupman-dot-com>
> Sent: Wednesday, May 16, 2001 9:58 AM
> Subject: Re: motor winder in dallas
> > Original poster: "Steve White by way of Terry Fritz
> <slwhite-at-zeus.ia-dot-net>
> >
> > Dear Dan,
> >
> > I made my own 1/2" G10 rotor with nothing more than a band saw to rough
> cut
> > the rotor and a rotary die grinder (like a big Dremel tool) with a
> tungsten
> > carbide cutter for fine machining. I almost gave up trying to get the
> rotor
> > perfectly round and almost took it to a machine shop, but I was
> > and eventually thought of a way to do this myself. The rotor turned out
> very
> > well and I would estimate is within a few mils of being perfectly round.
> If
> > you are interested in my technique I can tell you about it.