Subject: APPROPRIATE CAP...?
From: richard.quick-at-slug-dot-org (Richard Quick)
Date: Mon, 30 Jan 1995 22:06:00 GMT
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> From: Dan Kline <KLINEDA-at-UNIVSCVM.CSD.SCAROLINA.EDU>
> Subject: Appropriate Cap...?
> To: Richard Quick <RICHARD.QUICK-at-SLUG.ST-LOUIS.MO.US>
DK> Dear Richard,
DK> I wanted to ask you this personally, so please excuse me for
DK> writing uninvited, ok? (I just didn't want to take up Tesla-
DK> list bandwidth with it)
No problem with writing uninvited, and as for the bandwidth...
I thought that's what it's there for!
DK> I don't have the best of memories, but it seems to me that
DK> back in '87, '88, or '89, someone named Richard Quick sent a
DK> letter to Popular Electronics or Radio Electronics with a
DK> picture of what he called "a medium-sized coil." There was a
DK> white band around the secondary that was "used for measure-
DK> ment purposes only", and the picture had been taken outside
DK> and the scenery looked western. If this was you, I think
DK> that maybe you can give me some advice about whether or not
DK> I'm going to have to build a capacitor or not.
I am sorry, it was not me. But I forwarded your post (and a copy
of this reply) into the group so that maybe someone will
recognize either the capacitor, or the article.
DK> It seems that the capacitor-bank used on that coil was made
DK> up of exactly the same type of capacitor I want to use on my
DK> next coil. The kind I'm "speaking" of had heavy aluminum
DK> end-plates, the body is covered with brown kraft-type paper,
DK> the capacitance was .02 microF, and the voltage rating was
DK> 120 kV. I got it from Fair Radio Sales a few years ago.
DK> Does this ring a bell?
No, not me. Anybody else?
DK> Anyway, if you are familiar with that particular capacitor,
DK> can you tell me of the appropriateness of it's use for a
DK> Tesla-coil? Will it work ok? It has in the past, but only in
DK> the old-style configurations. I will be doing new style on
DK> this next coil, which is why I'm asking about this
DK> capacitor. Thanks for any info!
If the cap worked on your previous coil, and you were happy with
the performance, it will work quite well with the high inductance
secondary and large primary. I can always tell from the color of
the secondary spark if the capacitor in the tank circuit has high
enough Q. If the spark was thick, white, and violent, with little
or no violet or purple-blue color; it was pulsing well. Violet,
blue, purple, or reddish spark (or hues) tell me the cap is not
DK> Also while I've got you here, :) I had a very small system
DK> that ran on 270 W, with glass cap bank, and cylindrical
DK> primary. The secondary was 3.5 inches dia. and 12 inches
DK> tall. I could get about a 7-8 inch spark out of it. Not too
DK> bad for a small system. Then I took your advice...
DK> First, I pounded a 5 foot, copper pipe into the ground and
DK> connected it to the system with 6-gauge stranded wire,
DK> rubber covered.
That's what I call rebuilding from the "ground up"! Bravo!
DK> I put 450 W into the system, made a toroid, added turns to
DK> the primary, retuned and fired it up. I was getting double
DK> forked sparks about 16 inches long! I was totally amazed
DK> right up until the secondary burned up! :) I had wound on
DK> PVC with only polyurethane top-coats, using 24-gauge wire.
DK> Also, the primary was only 8" in diameter. The next coil
DK> will incorporate your designs and should be fairly
DK> spectacular! You really know what you are talking about!
DK> Thanks! Dan <klineda-at-univscvm.csd.scarolina.edu>
Thank you for the very nice complement. Your basic data shows
that using just some of the more important points that I have
covered, your efficiencies have really improved: your spark
length exceeded the length of the secondary coil by 25% (16 inch
spark vs 12 inch long coil form); the secondary spark has more
current (split forks); the original setup required 33.75 watts
per inch of spark, but the reconfigured coil produced a hotter,
longer spark with only 28.2 watts per inch. Not bad for a small
coil! If the coil had been properly capped, with no holes drilled
and the wire never entering into the coil form, it would have
held up without breaking down or burning up. Sorry about the loss
of the coil, but it made a real show case for the design theory.
... If all else fails... Throw another megavolt across it!
___ Blue Wave/QWK v2.12