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RE: argh -- poor output on TC #2

Hi Stan:

Your coil is similar to mine, except that you have three 15/60's and I use
only one.  Although my web page does not yet reflect this, I now use a 6" x
28" #22 secondary.  My comments interspersed below...

		Original Poster: Stan <sdarling-at-columbus.rr-dot-com> 

		Hello all, I have finished my TC #2.  This one is 30.5 in of
22AWG wound
		on 6" drain pipe.  Toroid is 6"x20".  Right now I'm using 3
15/60s and
		an EMMC at 22.5 nF.  Primary is .25" cu tubing spaced .25".
Using the
		original Victoreen ceramic gaps from my old coil, I get 45"+
which
		rapidly diminishes because (I'm assuming) of too much power
and
		overheating for those gaps.  So, I put together a 'blast
gap'.  I used
		some L-shaped pieces of aluminum and ran stainless bolts
through.  I
		epoxied an appropriate PVC reducer about .25" from the gap
and plugged
		my shopvac hose in.  In short, the gap was horrible--I'd say
20" of weak
		streamer.

		So my questions are:

		1) Anyone else used the Victoreen gaps at medium power
levels?  How good
		are they compared to other possibilities?  Why was my blast
gap giving
		such poor results or is it really that lousy of a gap?

I use a single gap, 0.34" wide, with air sucked through it.  See
http://people.ne.mediaone-dot-net/lau/tesla/tesla.htm

I wouldn't call three 15/60's "medium power".  A lot of heat will be
generated is a gap with that much power and the Victoreen gaps have no means
to dissipate that much heat.  I've seen but not actually used them though.

The arcing surfaces of your blown gap need to be smooth and blunt to prevent
premature breakdown due to formation of corona, and massive enough not to
get hot, which would generate hot ions and result in poor quenching.  How
wide is your gap?  If it's too narrow, the firing rate will be very high,
particularly with such a high current power supply and proportionately small
capacitor.

		2) How much would a SRSG help output? 45" seems poor given
the amount of
		power I'm dumping in.  What else would those with experience
with
		various gaps recommend?

With my one 15/60, static gap, and .02uF cap I get 60".  You should be able
to do much better with a static gap.
Bear in mind that if you switch to a sync RSG, you'll have to use a MUCH
larger cap to prevent it from charging to dangerously high voltages.  While
a static gap will guarantee that the firing voltage is limited to whatever
the gap is set to, the cap in a rotary gap system will charge to whatever
voltage can be attained in 8.33msec of charging. The smaller the cap, the
higher the voltage it will charge to, quite possibly higher than it's rated
for.  Your 22nF cap will certainly over-volt with three 15/60's charging it.

		3) I know for my 3 15/60's I should be using aroun 30nF to
be mains
		resonant.  Would I be better off removing one of the NST's
to get close
		to mains resonant with 22.5 nF?

Performance does not peak when the caps are mains-resonant.  In my case I've
found that 2X the mains-resonant cap is best.  I would recommend adding more
primary caps (easier and cheaper said than done, I know).  Alternately, try
using just one or two 15/60's.

		4) Would it be unusual for a coil like mine to have a large
tuning
		range?  It seems quite content from about 9.5 turns up to
11.  My old
		coil had maybe a 1/2 turn range where output seemed to peak.

Mine is not too critical either, there are usually two taps a turn apart
that perform about the same.

		I have noticed that this coil also seems much less drawn to
typical
		strike objects.  For example, it seems happy to have its
streamers go an
		extra 6" to hit wooden shelving than to hit a grounded wire
with a
		pointy tip.

Streamers are not as smart as we might think.  I think most of their
direction is random.  If they happen to connect to a grounded target, that's
fine, but they're equally happy (likely) to go off into nowhere.

		Am I missing something?  I know I'll probably never match
the efficiency
		of aces like Terry but this is pretty bad!

I think your system would also benefit from a larger topload, especially if
you do end up using a larger primary capacitor.

		Help! :)

		-Stan
		
Regards, Gary Lau
Waltham, MA USA