Fw: A *DRY* TESLA COIL CAPACITOR
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>
> 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
> > 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,
> > setting. I'm sure it would be difficult, but if a process could
> > and mastered it would make a very convenient capacitor. Is there
> > drawback to using epoxy (i.e. RF losses)? Talk to you later.
> > - Owen -
> > owen-at-iosphere-dot-net
> > http://www.iosphere-dot-net/~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
> 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
> because I am still mulling over the ramifications of some of the
> design elements. (So MANY thoughts and not enough time to try
> any of them. It is *so* frustrating to me not to be able to
> 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
> will have four sides and a bottom, but NO TOP (yet). Assemble the
> 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.
> has to be determined experimentally.)
> This will squeeze the poly and plates flat and drive out all air
> the capacitor itself. Now fill the plexiglass box with epoxy up to
> the point where it fills the spaces between the strips of plywood
> a depth of almost 3/4 inches.
> At this point the capacitor is air-free. After the epoxy sets you
> 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
> heavy wires or in some other way, such as via bolts through the
> 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
> experimentation comes into play. I would begin by trying the idea
> 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
> 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
> 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
> 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
> pressure to be transmitted to the top plastic plate (and therefore
> 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
> When pressure is released as the press is removed, there may be
> 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
> these ideas and run with them.
> Hope this helps someone out there.
> Fr. Tom McGahee