Re: [TCML] Acrylic Covers

[Phillip Slawinski <pslawinski@xxxxxxxxx>]

On Thu, Apr 22, 2010 at 09:29, William Noble <william_b_noble@xxxxxxx>wrote:

>
> some of the info below just can't be true - in particular, whatever
> dielectric effect adding material around the coil has is not dependent on
> the existance of an airgap - the effect may be insignificant, but if you do
> the math, you will see that for these situations the existance of a gap
> doesn't matter.  What is true is that if there is an air gap, you can have
> all the normal effects of air taking place in that gap.
>

If there is an air gap between the secondary and acrylic cover nothing stops
it from flashing over end to end.  Also nothing stops corona from forming in
the gap.  No math is required to figure that one out. That said, the tube
may serve to lessen the chance of a primary to secondary flash over, but
certainly not secondary to secondary flash over.


>
> > Date: Thu, 22 Apr 2010 09:01:26 -0500
> > Subject: Re: [TCML] Acrylic Covers
> > From: pslawinski@xxxxxxxxx
> > To: tesla@xxxxxxxxxx
> >
> > On Thu, Apr 22, 2010 at 08:40, Brandon Garretson <
> garretsontech@xxxxxxxxx>wrote:
> >
> > > I am nearing the completion of the second incarnation of my 4” Tesla
> Coil.
> > > After a good deal of time spent polishing and cleaning the copper
> > > primary I got the idea of installing an acrylic disk over it in order
> > > to help protect it from dust, fingerprints, falling objects, idiots,
> > > etc…
> > >
> >
> > That's a good idea. I incorporate this on all my flat primaries now. It
> > helps smooth the e-field around the primary to a limited degree, as well
> as
> > providing protection to the finish of the copper.
> >
> >
> > > In searching the archives, I read about this being done before but
> > > found nothing regarding its effect on the device.
> > > I also found an acrylic tube that slides perfectly over the secondary
> > > coil leaving an eighth of an inch clearance between the windings and
> > > the ID of the tube.
> > >
> >
> > If there is ANY air between the tube and the secondary windings the
> tube's
> > only function will be aesthetic. If you would like it to provide
> electrical
> > protection to the secondary you will need to fill the space between the
> tube
> > and the windings with oil or epoxy. If you don't already have the tube
> I'd
> > suggest looking into using epoxy, it would probably be cheaper, and when
> > applied properly provides a glass-like finish that is very resistant to
> > racing sparks and flash over.
> >
> >
> > > Aesthetically it is all very pleasing, but will that much plastic have
> > > a measurable impact on the performance of the coil?
> > >
> >
> > If you take the steps mentioned above you would be able to push the coil
> > harder without having to worry about flash overs or racing sparks.
> >
> >
> > > It looks as though it may help prevent racing arcs due to the lack of
> > > any direct path of air between the primary and secondary but I cannot
> > > figure out in what way (if any) it might adversely affect the
> > > relationship between L1 and L2.
> > >
> >
> > There should be no effect. You can adjust for any coupling changes you
> > might have due to the inner diameter of the primary accommodating the
> > secondary form.
> >
> >
> > > The acrylic over the primary would be .25” and the wall thickness of
> > > the tube over the secondary .125” for a total of .375" (3/8").
> > > Has anyone experimented with this before or is it common knowledge
> > > that this is just too much dielectric?
> > >
> >
> > Too much? Hardly.
> >
> >
> > >
> > > Thanks!
> > >
> > > Brandon from Jersey
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