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adjustable gap
Subject: adjustable gap
Date: Tue, 17 Jun 1997 15:56:07 -0700
From: gene lambert <tesla-at-cyberverse-dot-com>
Organization: Tesla Electric, LTD
To: Tesla List <tesla-at-pupman-dot-com>
CC: tesla-at-poodle.pupman-dot-com
References: 1
Tesla List wrote:
>
> Subject: Fw: A *DRY* TESLA COIL CAPACITOR
> Date: Tue, 17 Jun 1997 08:29:25 -0400
> From: "Thomas McGahee" <tom_mcgahee-at-sigmais-dot-com>
> To: <tesla-at-pupman-dot-com>
>
> ----------
> > From: Thomas McGahee <tom_mcgahee-at-sigmais-dot-com>
> > To: Owen Lawrence <owen-at-iosphere-dot-net>
> > Cc: tesla-at-pupman-dot-com
> > Subject: Re: A *DRY* TESLA COIL CAPACITOR
> > Date: Friday, June 13, 1997 5:03 PM
> >
> >
> >
> > ----------
> > > From: Owen Lawrence <owen-at-iosphere-dot-net>
> > > To: tom_mcgahee-at-sigmais-dot-com
> > > Subject: A *DRY* TESLA COIL CAPACITOR
> > > Date: Friday, June 13, 1997 9:49 AM
> > >
> > > > A *DRY* TESLA COIL CAPACITOR
> > >
> > > Without getting into thoughts about how difficult it would be to
> > construct,
> > > why not use epoxy rather than spar varnish? Get the kind that
> > takes at
> > > least a day to set. You wouldn't have to worry about it drying,
> > just
> > > setting. I'm sure it would be difficult, but if a process could
> be
> > devised
> > > and mastered it would make a very convenient capacitor. Is there
> > any
> > > drawback to using epoxy (i.e. RF losses)? Talk to you later.
> > >
> > > - Owen -
> > >
> > > owen-at-iosphere-dot-net
> > > http://www.iosphere-dot-net/~owen
> >
> > Owen,
> > First, if properly made there would be NO epoxy at all between the
> > poly layers since the pressure would have squeezed it out. The
> trick
> > is to make it so that no air is ever ably to sneak back IN!
> >
> > This gets us into the topic of encapsulated dry capacitors. Yes, I
> > have some definite ideas along these lines. I haven't shared them
> yet
> > because I am still mulling over the ramifications of some of the
> > design elements. (So MANY thoughts and not enough time to try
> hardly
> > any of them. It is *so* frustrating to me not to be able to
> actually
> > try these ideas out immediately!!
> >
> > OK, imagine that you want to manufacture say a .01 mfd 15KV AC RMS
> > poly capacitor, and you have access to a press. (or a reasonable
> > facsimile thereof). Let's say that you determine you can build the
> > basic capacitor itself so that the size is 8" x 10" x 4".
> >
> > Further assume that the poly plates are 8" x 8" (the ends of the
> > metal plates accounts for the other 2"). Build a box from 1/4"
> > plexiglass that has INSIDE dimensions of 8.5" x 10.5" x 5". This
> box
> > will have four sides and a bottom, but NO TOP (yet). Assemble the
> DRY
> > capacitor inside the case such that it is centered. Place a 8" x 8"
> > 1/4" thick piece of plexiglass over the top of the capacitor such
> > that it lines up with the underlying poly. On top of this place
> > several strips of 8" x 1" x 3/4" thick plywood such that there are
> > spaces at least 1" wide. On top of this place a sheet of 8" x 8" x
> > 3/4" plywood. Place this entire assembly into an overhead press.
> > Bring the press to bear and increase the force to a value such that
> > the pressure is high but not enough to fracture the plexiglass.
> (This
> > has to be determined experimentally.)
> >
> > This will squeeze the poly and plates flat and drive out all air
> from
> > the capacitor itself. Now fill the plexiglass box with epoxy up to
> > the point where it fills the spaces between the strips of plywood
> do
> > a depth of almost 3/4 inches.
> >
> > At this point the capacitor is air-free. After the epoxy sets you
> can
> > remove the tension slowly, and if we are lucky the assembly will
> > hold. Now you can pour in some more epoxy if you want, so that the
> > box is totally filled with epoxy at the top.
> >
> > Oh yeah, I assume that the electrical connections are coming out
> via
> > heavy wires or in some other way, such as via bolts through the
> side.
> >
> > Not having every attempted to build a capacitor under pressure, I
> > don't know what all the "gotcha's" will be. That is where the
> actual
> > experimentation comes into play. I would begin by trying the idea
> out
> > on a small scale first. Maybe make a .005 mfd at 12KV AC RMS or
> > something like that.
> >
> > ***
> > The key elements in the design above are that pressure is not
> applied
> > to the walls of the case, but only to the base via the press. Once
> > pressure is applied a liquid is introduced. (Keep bubbles to a
> > minimum around the edges of the capacitor.) Once the liquid hardens
> > the pressure is released and a final topping off of the structure
> can
> > be executed if desired. No oil is required, as PRESSURE is used to
> > drive all air out, and this pressure is not taken away until the
> > capacitor is completely surrounded by an encapsulating medium that
> > also provides structural rigidity.
> >
> > RTV Silicone and other such things may ALSO be appropriate
> materials,
> > but the details of manufacture will only be known once actual
> > experimentation can be performed.
> >
> > Please note that the purpose of the thin strips of wood are to
> allow
> > pressure to be transmitted to the top plastic plate (and therefore
> to
> > the cap) and still get the encapsulating medium to engulf enough of
> > the TOP section such that when pressure is removed there are
> > encircling sections of the epoxy in place to keep the assembly
> > intact.
> >
> > When pressure is released as the press is removed, there may be
> major
> > distortion of the plexiglass. I just don't know exactly what will
> > actually happen without experimentation. And I can't do any such
> > thing until probably early September. So maybe someone else can
> take
> > these ideas and run with them.
> >
> > Hope this helps someone out there.
> > Fr. Tom McGahee
Thomas:
I, (and perhaps others), have been trying to contact you about the
adjustable gap you so kindly offered plans for. Could you send me copies
via email? I tried to emial you for a week, and it always came back.
thank you,
Gene Lambert
tesla-at-cyberverse-dot-com