Black plastic stuff and Nathan's coil...
Subject: Black plastic stuff and Nathan's coil...
From: Terry Fritz <twftesla-at-uswest-dot-net>
Date: Sat, 08 Jan 2000 17:06:47 -0700
Thanks to the United States Postal Service, Nathan got is cap this
afternoon and his check with a piece of the "evil" black polyethylene came
to me too. The HP34401 could not read any resistance across it. The stuff
has a waxy heavy feel to it. I took a bit of it and fried it with the blow
torch. After the poly burned off, the residue was able to get white hot
without further damage. I assume that is carbon. In general, this
definitely looks like a carbon impregnated material to me. It reminds me
of the black carbon plastic anti-static bags you used to see. It is the
exact stuff used under rocks and tree bark in lawns and such. If you rub
it hard on paper, it leaves black streaks. It has a very gritty feel and
is filled with impure things. According to Starrett, it is 4.3 mils thick
(4.3 thousandths of an American inch that be ;-))
I then blasted it with the HV power supply. The arc traveled along it's
surface which was a bit of a surprise. The arcs were definitely drawn to
the material but it was hard to say if that was just due to the dielectric
properties attracting the arc. I didn't have the stuff to test breakdown
at all handy...
I don't think this stuff is blatantly conductive. The carbon bits are
probably each encased in the plastic, sort of insulating each bit. I can't
imagine what this material would do in a capacitor but it would be no
surprise that the loss would be enormous but the material would not
breakdown. Perhaps it was acting like a true artificial dielectric where
energy goes in but does not come out (like a stealth fighter. Maybe you
only need to wrap a plan in this stuff ;-))). Apparently, it will hold off
the voltage so it would still be a capacitor that would have tuning points
and all that. It just appears to have very high loss. Nathan probably
didn't run it long enough, and it was in oil, but I bet the cap was heating
at a very high rate.
I have not heard back from Nathan yet on the results, but I am pretty sure
we nailed this problem ;-)) Yeah!!
Thanks again to the Post Office!!! I mailed it next day Saturday delivery
but I never though it would go from here to there through all the planes
and trucks (and government cars apparently ;-)) to our little towns and
then make residential delivery in 28 hours for only $15. Perhaps the tax
payers paid the other $5000 dollars to get it there ;-))
Hoping Nathan's coil works now.... This has really been fun!!
BTW- yesterday at work, some techs came to me asking about a similar thing
with black Krylon spray paint (I was afraid to ask the "why" part ;-)).
They did similar testing and found that it also was made from carbon black.
Soooo... Avoid all black materials in Tesla coils unless you are super
sure they are ok (it is not easy to know). I prefer water clear materials
where I can "see" that there is nothing in it...