RE: Small TC experiments

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

Original poster: "Lau, Gary by way of Terry Fritz <twftesla-at-uswest-dot-net>" <Gary.Lau-at-compaq-dot-com>

Thank you for sharing this!  It's not often we have the time for such a
controlled set of re-builds and measurements.  I think the second set of
comparisons where the tank cap was kept constant and the secondary (gauge
and turns) and primary (turns) were varied offers further evidence that
higher primary inductances will result in lower primary currents, which
result in correspondingly lower gap losses.  Varying the primary cap size is
another set of tradeoffs...

On a different tangent, I've also always to build a very small coil and have
pulled a small transformer out of a bug zapper to power it.  It's marked
3kV/9mA (or was it 4Kv?).  Clearly small by most standards, but I love to
challenge conventions.  Has anyone else made a TC powered by such a
transformer?

Regards, Gary Lau
Waltham, MA USA


Original poster: "Peter Lawrence <Peter.Lawrence-at-Eng.Sun-dot-com>

I like minature things. I've been experimenting with a small TC, 3.5x10" 
secondary, for quite a long time (years...).

Last weekend I decided to rewind some of my secondaries (there are some
advantages to not coating them!...)

I had these three, all on the same size 3.5x12" tubes
	450 turns #24 wire
	570 turns #26 wire
	667 turns #28 wire

I always got the best sparks from the #28 coil.  That had a lot to do with
uping the the primary Cap at the same time, and getting up to a "resonance" 
sized cap with the #28 coil, putting more energy per charge into the primary
circuit.

I had always wondered where the progression would end. Last weekend I
unwound
the #24 and #26 and rewound them so now I have (again all on 3.5x12" tubes)

	667 turns #28 wire		(6"-diam 7-T, 9.6nF, primary)
	990 turns #30 wire		(6"-diam 10-T, 9.6nF, primary)
	1320 turns #32 wire		(6"-diam 13-T, 9.6nF, primary)

and now the #32 coil seems to get the best sparks.  This time it is with
the same resonance-sized cap in all cases.

So I still don't know where the progression will end! Guess I'll just have
to try #34 wire too! (#36 may be getting a little to fragile to handle!)


I suspect that many of the old recommendations (large aspect ratio for small
TCs, dont use thin wire, etc) are mostly myth..., then again I haven't been
able to up the input power to what I want to yet...


-Pete Lawrence.

(ps, I get ~7" hot point-to-point sparks, and 8~10 inch streamers w/ 6-20
NST
and the #32 coil (~5" with #24 coil, ~6" with #28 coil), and want to try a
7.5-25 and a 9-30 NST to see how things scale, and how that compares with 
J.Freau's and others inches-per-kWatt spark length equations, so far even 
with these radical coils I'm still pretty far off JF's eqn, and they're 
only at about 4x my torroid's minor diameter, not the 10x that JF says is 
possible...)