Re: Variable capacitor for tinkering with

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

Original poster: "Sundog by way of Terry Fritz <twftesla-at-qwest-dot-net>" <sundog-at-timeship-dot-net>

Hi All, Greg!

It was the simplicity of it that made me shake my head and think, "Nah, it
can't be *THAT* easy...."  But my DMM and crude lashup in the kitchen sink
says the thing works, a single bottle giving me a sizeable increase in
capacitance. (.3nf to 1.2nf)

The notion of bottles breaking in TC service...I haven't used SW caps
extensively.  I do know glass is a lossy dielectric, and my tube coil runs
at ~400khz.  So I'm expecting a bit of heat (even the panasonic MMC gets
warm after extended runs at 1kw).  Plus with the capacitor at it's lowest
capacitance setting (the bottom of the bottle about 1/8" below the water's
surface), it's carrying the full current on only a thin band of glass.  I
don't worry about the bottle breaking, I have plenty of spares (and ones to
make spares, come to think of it).
Only bottle I lost in TC duty was because it flashed over (foil outside the
glass to ground) and got hot.

 Also, I won't be adjusting the full capacitance of the tank cap like that,
I'll only be aiming for ~10% of the tank cap to be variable. So a single
bottle will work for my 833 powered coil.  I need to get the tube coil
running though :)


Shad



----- Original Message -----
From: Tesla list <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Sunday, September 16, 2001 6:59 PM
Subject: Re: Variable capacitor for tinkering with


> Original poster: "Gregory Hunter by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <ghunter31014-at-yahoo-dot-com>
>
> I think it is a neat idea--brilliant in it's
> simplicity. BTW, where did this notion come from that
> beer bottles get hot and crack in Tesla coil service?
> I've been running a bank of them for months at pole
> pig power levels (up to 7200VA), and I've never
> cracked one. I've never noticed one warm above room
> temperature even on extended runs. Obviously, all
> glass is not alike (I assume there are many different
> recipes for glass), and Miller Geniune Draft bottles
> seem indestructable. If your beer bottle caps get hot
> or crack, you're using the wrong kind of bottle.
>
> Greg
>
> http://hot-streamer-dot-com/greg
>
> --- Tesla list <tesla-at-pupman-dot-com> wrote:
> > Original poster: "Sundog by way of Terry Fritz
> > <twftesla-at-qwest-dot-net>" <sundog-at-timeship-dot-net>
> >
> > Hi All!
> >
> >    It's been a hectic week for me (the attacks shut
> > down all flights, and the
> > business I work for relies heavily on FedEx to fly
> > our packages everywhere, so
> > we had a ton of irate customers), plus that bit of
> > really nasty weather that
> > rolled through earlier this week.
> >
> >  I had an idea for a cheap, easy to make variable
> > cap, but dismissed it as "Too
> > cheezy."  The idea kept rolling around in my head,
> > and I finally gave in to it
> > and told my buddy Dave about it.  He really liked
> > it, so I guess I'll give it a
> > whirl.
> >
> >   I'm needing a variable cap for my VTTC.  I like
> > the idea of a pre-made unit,
> > but I'm usually pretty limited on spendable funds.
> > My idea is to make a good
> > 'ole SW bucket cap with a dozen beer bottles (in
> > good supply here), and put
> > them in a basket in the 5 gal bucket.  To chance the
> > capacitance, simply lift
> > the basket to raise the caps further out of the SW
> > in the bucket.  Of course
> > using fishing line of something else non-conductive,
> > so I can change it as it's
> > running.
> >
> >    I figured that I'd bust a few bottles, they'd get
> > hot, be lossy, and so on,
> > but here's why I like the idea.
> >   #1.  Cheap!   I have lots on hand.
> >  #2.   Easy to repair.  Bottle pops, oopsie, drop in
> > a new one.
> >  #3.  No PVC container full of HV oil to house a
> > normal variable cap leaking
> > all over, and HV oil has *always* leaked out of my
> > PVC containers.
> >   #4. It's just so rediculous it has to work! :))
> >
> >   I'll do some measurements later on today and post
> > my results, time
> > providing.  My VTTC is in shambles at the moment, so
> > I probably won't be able
> > to give it a go on the coil.  Sure, this is no real
> > replacement for a quality
> > component, but at least the only thing I'll have to
> > buy is a new 5 gal bucket
> > ($2-3 at Home depot).  The rest (bottles, salt, etc)
> > I have on hand.  High
> > tech, no.  Lossy? yes. Silly-looking, you betcha!
> > But it should work, and let
> > me play more with my VTTC when I get it back up &
> > running! :)
> >
> >
> >
> >                         Caio!
> >
> >
> >     Shad
> >  Comments?
> >
> >
> >
>
>
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