Re: New coiler- but with other experiences in electronics

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

Original poster: "Mark Fergerson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <mfergerson1-at-home-dot-com>

Tesla list wrote:
> 
> Original poster: "bdsabds sadgsdgsda by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <fdgahbdfhbfdb-at-juno-dot-com>
> 
> Hi, I've got some worries for the 4" coil I am building.  I dropped the
> coil on the way to the laquering table, and some of the turns of wire got
> bunched up. Is that all right? I have already  started laquering, but I
> hope it will not be a problem.

  You might want to try to save those turns and
use them at the top as suggested, but I'd chicken
out and cut them off. For me, rearranging the
entire system to deal with the new Ls and
consequent Fres is less stress than coping with
what I see as an inevitable failure mode down the
road. OTOH a lot of coilers seem to find that
pretty much all coils eventually develop one
failure mode or another (pushing the envelope
surely has nothing to do with it ;>)).

> ALso, not that I am, but why can't you wire the coil on a metal form? I
> do not see what the problem is.

  Um. Makes sense at first blush, more flux means
better power transfer, like in, um, power
transformers.

  Two problems, at least. A TC is basically a RF
transformer; visualize the core as an extra
winding comprising a single, thick, turn of iron
that has no terminals, a dead short. At 60 Hz the
iron takes power from the primary and stores it as
flux, then hands it off to the secondary. But the
conversion isn't perfect and some power is lost as
heat (iron makes a better resistor than
conductor). It's also frequency-dependent. It
isn't so bad at 60 Hz because the iron core has
the time to follow the field reversals. But at
typical TC frequencies iron's just too slow, and
the core turns most of its induced current into
heat, and has less left to hand off to the
secondary, so to speak.

  Also, you're trying to develop a large AC
potential across the secondary. A core'll look
like a near-short across the secondary and will
draw two arcs, one from the top of the coil to the
core, and one at the bottom. More heat.

  Not necessarily a silly idea BTW. If you read
any of Tesla's writings you'll find he tried
assorted metal cored transformer designs as he
experimented. As he worked with higher frequencies
(past a few hundred Hz) he was forced to go from
solid, to laminated, to built-ups (using fine iron
wire(s)) and eventually air (with thin wooden
supports). That's how we know, you see, he was
there first.

  So you're in good company.

> By the way, the form I am using for the toroid center is an old
> (smallish) bike wheel. It holds up much better than pie pans.

  I like it. Comes with a convenient mounting
bolt, pre-centered, even! Might make a really
_large_ ion motor with a spiked rim instead of a
smooth toroid surface?

  Mark L. Fergerson