Re: Somewhat of a newbie..

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

Original poster: "Gregory Hunter by way of Terry Fritz <twftesla-at-qwest-dot-net>" <ghunter31014-at-yahoo-dot-com>

Ben,

A 12oz beer bottle or wine cooler bottle is good for
750-900pF.  A six pack of 12oz bottles is very close
to .005uF.  These figures will get you to within one
turn of the calculated primary tap point if you are
using one of the popular Tesla coil calculator
programs.  I've measured scores of bottles and I've
built hundreds of saltwater caps--trust me on this
one.  My own beer bottle cap has a measured
capacitance of 81nF using 98 Miller Geniune Draft
bottles in parallel.

BTW, I've used both very expensive Fluke meters, and
very cheap Chinese meters.  In side-by-side
comparison, expensive and cheap meters were in near
perfect agreement as to the capacitance of a bottle. 
You can get a junky Chinese DMM with cap function for
around $35 and put an end to the guesswork.

I think you have a couple of vacuum caps there.  If
I'm right the dielectric is actually a very "hard"
vacuum.  12pF is pretty useless for Tesla coil work,
but if they are vacuum variables, you might be able to
use them as Tesla coil tank circuit "trimmers" for
fine tuning.

Regards,

Greg
http://hot-streamer-dot-com/greg

--- Tesla list <tesla-at-pupman-dot-com> wrote:
> Original poster: "spoonMAN by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <spoonman534-at-yahoo-dot-com>
> 
> Anyway, my question
> involves capicitors.. I started out using saltwater
> caps
> made from beer bottles.. but I realized that I had
> no way
> of knowing how much capacitance I had.. is there any
> way to
> test them or is there some general default value per
> bottle? I also ordered 4 caps vacuum sealed in a
> glass
> envelope rated 12pF -at- 30kV each .. they're
> absolutely
> beautiful.. each one is about the diameter of a soup
> can
> and about 8 inches long.. will these work in coiling
> applications? > 
> Thanks for any help!
> 
> Ben McMillen
> 
> 
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