Re: Backwards primary?

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

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

Tesla list wrote:
> 
> Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <acmq-at-compuland-dot-com.br>
> 
> Tesla list wrote:
> >
> > Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> <Beans45601-at-aol-dot-com>
> >
> > I was wondering, Would it help anything if you made a primary that,
> instead of
> > starting at the primary and going up, it went from the secondary down? I
> am not
> > sure if i said it right, but, i think you get the idea. It seems that it
> would
> > cut down on the primary strikes...
> 
> If this is equivalent to wind the primary in a different direction,
> no difference at all.

  I think the OP was referring to
solenoidal coils, and meant:

(cross-section views, P=primary
windings, s=secondary windings)

    s s
    s s
    s s
    s s
    s s
  P     P
  P     P

  rather than the "standard":

    s s
    s s
    s s
  P s s P
  P s s P

  which would indeed help reduce P/s
strikes by getting more of the primary
out of the secondary's electrical field.

  Other than drastically reducing k, I
see no problems. ;>)

> > Also, it is possible to wind your secondary
> > and take out the pipe? What would be the pros of doing this?
> 
> You will obtain a more fragile secondary, after a lot of work.
> No measurable advantage, unless your form is very, very, lossy.

  Comparing Tesla's larger coils and
modern "hobby" coils, he had much less
in the way of "foreign materials"
within/near his coils, partly because
they were so large his support
structures had to be rather minimalist
hence the "wire fence" appearance.

  While his construction techniques
minimize the effects of said materials
on the properties of the coils (possible
benefit), I can't imagine scaling them
down to common "hobby coil" sizes simply
because we'd have to use chopsticks or
similar; strength and deviation from
circularity of the windings would become
issues. The latter would seriously
complicate mathematical modeling not to
mention providing increased-curvature
hot spots which would increase the
likelihood of unintended strikes.

  As for his smaller demonstration
coils, I believe he'd prefer more modern
materials (e.g. plastics, transformer
oils) over the stuff he used (wood,
phenolic, organic insulating fluids
etc.) and would be quite satisfied to
compromise overall "purity of
properties" for strength.

  Mark L. Fergerson