Re: 15" coil project

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

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