Re: Testing caps (fwd)

---------- Forwarded message ----------
Date: Mon, 27 Jul 1998 07:54:49 -0400
From: Thomas McGahee <tom_mcgahee-at-sigmais-dot-com>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: Testing caps (fwd)

The PVC is fine. It is generally not worth all the extra hassle of
trying to *form* your own tubular coilform from acrylic/plexiglass.

True, plexiglass is *better* then PVC, but the difference in
actual operation of a 10" diameter coil will be so small that you
would probably not be able to notice it.

Spend your time making arcs, not going around in circles :)

As to testing the caps, you could try connecting them up to
the NST and a simple spark gap. Now, without a primary and
a secondary the caps would take a real battering, so I suggest
that you create a suitable 'load' for this thing. Why not
set it up as an induction heater? Where the Tesla primary would
usually go, place a work coil. Inside the work coil place
a decent sized piece of iron or steel, such as several large

The work coil should be a simple cylinder type solenoid wound
coil with a diameter from 3 to 5 inches. Make about 5 to 10
turns. Wire here could be something like solid #10 with
insulation. Wind it on any non-metallic form. 

When operating, keep the metal core material(s) centered, and
far enough away from the coil form that there is no arcing.
Make clearance at least 1/2".

Be aware that when you power this sucker up the core material
may get red hot. Take all necessary and prudent precautions
to make sure the core does not melt through anything or cause
a fire.

This is quicker than building a TC primary/secondary assembly,
and will provide enough load so that the caps don't get
battered unmercifully.

Hope this helps.
Fr. Tom McGahee

From: Tesla List <tesla-at-pupman-dot-com>
To: tesla-at-pupman-dot-com
Subject: Testing caps (fwd)
Date: Sunday, July 26, 1998 10:31 PM

---------- Forwarded message ----------
Date: Sun, 26 Jul 1998 11:11:14 -0700
From: Terry Perdue <terryp-at-halcyon-dot-com>
To: tesla-at-pupman-dot-com
Subject: Testing caps

I posted a message a few weeks ago about some oil-filled 10nF 80kvdc "xray
machine" caps I have, asking if they might be suitable for TC use. Several
people thought it was worth a try, but suggested a safety enclosure, in
case they overheated and exploded. My question is this: 

Is there a way I can test them for suitability before building the whole
system? I have a NST, and could fashion a temporary spark gap. I'd like to
run a minimal system long enough to give me confidence that these caps
will survive before going any further, as I'm not interested in rolling my
own cap. 

Two other questions: 

I had hoped to use 10" diam acrylic tubing for the secondary, but at
$40/ft, may have to use PVC. But I'm considering getting some sheet
acrylic and melting it around a form, possibly in half-cylinder sections,
then cementing them together. I've been pretty successful forming
plexiglas in this way in the past, and assume that it is the material of
choice. Has anyone tried this? (I'm assuming that the sheet stock is much
less expensive.) 

Finally, I think I read that if the spark gap is close enough to the
transformer, secondary RF suppression isn't necessary. Is there agreement
on this? 

Thanks for your comments.

Terry Perdue