Re: 15" coil project

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

Original poster: "Barton B. Anderson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <tesla123-at-pacbell-dot-net>

Hi Brett,

I agree with John's comments throughout. One thing to keep in mind is that
you will
be in uncharted waters. I don't know any coilers who have built a large
secondary
with high turns and small wire size. I myself retired a 12" pig coil the
past year
and built a smaller 8.5" coil using 1700 turns of 24awg. I haven't ran this
coil
yet. It's waiting for the trigger gap I'm buiding at the moment.

Regarding the primary: I think you'll be ok on the size considering the
number of
turns and the voltage distribution on those turns. As a matter of fact,
this might
be a good recipe for large coils as it will keep the primary somewhat compact.

Best of luck,
Bart

Tesla list wrote:

> Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<FutureT-at-aol-dot-com>
>
> In a message dated 10/20/01 9:27:43 PM Eastern Daylight Time,
> tesla-at-pupman-dot-com writes:
>
> > I also don't want the arcs to be fainter and not as
> >  bright due to a decrease in current to both the
> >  primary and secondary.
>
> Brett,
>
> Well it's a trade off between gap losses and pri/sec losses.
> I'd probably use 20awg wire, since the wide diameter will
> help to give a high inductance.  You should still be able to
> get about 1400 turns which should be enough.  You can
> try the 22awg if you're daring.   For the primary maybe the
> 3/8" copper tubing is preferable.  The break rate matters too,
> because a low break rate requires a larger cap, which tends
> to decrease the surge impedance, and forces the use of
> thinner wire in a sense.  Low break rate seems to the best
> anyway, but high breakrate is OK too I guess. My feeling is
> that you will not lose any performance by using 1400 turns
> of 20awg, and you'll probably gain performance compared
> to using a thicker wire such as 16awg, or 14awg, etc.
> You'll probably get 10 people telling you that large coils need
> real thick wire, that lots of turns are only good for small coils,
> etc.  Needless to say, I don't agree, but I can't really prove it
> since I've never built a very large coil.  In my view, a coil should
> tend to scale up evenly in almost every way, aspect ratio,
> toroid size, wire sizes, etc, etc.  Some people have reported
> that they built a big coil using thick wire, and it gives good
> performance, so therefore thick wire is best.  I never could
> understand their logic, since they never did a comparison
> with thinner wire.  This sounds like a nice project you're planning.
>
> Cheers,
> John Freau

--
Barton B. Anderson
http://www.classictesla-dot-com