RE: Designing BIG Secondary Coil

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

Original poster: "Dave Hartwick by way of Terry Fritz <twftesla-at-qwest-dot-net>" <ddhartwick-at-earthlink-dot-net>

John,
I'm minutes away from rearranging things in the basement to maximize the
limited area, but with the current setup, measurement is easy since I rarely
get free-air streamers and get rather "power arcs" to nearby fixed metallic
objects--30"-40".

In my experience, which is disproportional to what I actually know, racing
arc and breakdown have not occurred unless the system is overcoupled. My
thinking is to elevate a 30ish inch toroid above my proposed short fat coil
by perhaps a foot. Any larger toroid will start to eat up horizontal room.
I do see that electrostatic shadowing may not be adequate for such an
arrangement, but it's an interesting problem and worth a shot.
I note that Tesla's Wardenclyffe coil had the topload elevated above the
magnifier coil by a substantial distance. But, that WAS Tesla....

Once one is geared up with wire and forms and a jig, churning out a
secondary for possibly dubious experiments is not terribly traumatic. I do
have a fairly standard 10" sec that I'll realistically never be able to
fully utilize, so maybe I'll just chop it in half and try that for starters.
Dave




Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<FutureT-at-aol-dot-com>

Dave,

If the coil is too short for a given bang size, sparks may run
along the full length of the secondary, or break it down at
various places as you mention.  This is much less likely to
occur at a high breakrate, since a smaller bang size can
be used for a given sparklength.   Can you even measure
the sparklengths accurately in your basement?  Certainly
sparks up to 3X or 4X the length of the resonator or longer can
be produced without a problem, especially at higher breakrates.

Yeah, I'm not able to fire coils outdoors here either, which is
a bummer.

I've always had the idea that the secondary diameter should
be related to the spark length and toroid size.  You want the
toroid to dominate the secondary diameter by 3X or 4X for
best results I think.  For all I know, maybe it's not really that
important though.  I haven't really done a whole lot of tests
of that.

Then there's the issue of how to get the longest sparks from
a physically small coil, which is related to the above.

John


>
> John,
> I assume you are referring to inter-turn insulation breakdown. As I was
> telling the good Dr. R, I was thinking about a ~12" x 24", wound with
> something like #20 wire. The hope is fitting max perf in my vertically
> challenged basement (7'); though what is the point? This new 4" x 24" sec
is
> already overwhelming the area. An exercise in efficiency, I suppose.
>
> I envy the boys that are able to fire outside, which is unthinkable in my
> classically suburbian environs.
> Dave
>