Tesla List wrote:
> >From richard.quick-at-slug-dot-orgWed Aug 14 21:24:24 1996
> Date: Tue, 13 Aug 1996 02:39:00 GMT
> From: Richard Quick <richard.quick-at-slug-dot-org>
> To: tesla-at-poodle.pupman-dot-com
> Subject: Re: help
> > Now drill a small hole each end of the PVC about 1/2 inch
> > from the top and bottom. Shove one end of the wire thru one
> > of the holes and leave about a foot of wire on the inside.
> > Take some tape and put it over the wire so you don't pull it
> > out like some dummy I know did (me). Now comes the winding...
> Don't ever make this mistake. I learned the hard way. Drilling
> holes and introducing wire inside of the coil form are lethal
> errors. While the coil may function fine with a CW or solid state
> driver system, when properly excited in a Tesla tank circuit the
> coil will fail internally. Now with this "candlestick" design
> advocated by the author you will never be able to properly couple
> the coil to a Tesla tank circuit (due to the high aspect ratio)
> IF you could if would short out through the inside of the tube.
> Richard Quick
> ... Quoting Brent Turner:
> > Richard -
> > Couldn't help but jump in here a sec -
> > Every coil I have built using the 'pass-the-wire-through-the-hole
> > technique seems to work fine!!! One coil has a winding length of only
> > 13", and would toss out 14" sparks religiously. Even my large 3.5KVa
> > coil uses this method...it's secondary has a winding length of about
> > 25", and throws a really hot 65" spark!!!!! (I did cheat a bit with
> > this coil though by placing two plexiglass insulator disks internally
> > on the secondary coil form. (10" dia, grey PVC ducting)
> Even baffles do not work when you max out a coil design and are putting
> out 3 to 3.5 times the winding length in spark discharge. This is not
> really a sound practice IMHO.
> > Try putting a blob of RTV around the wire on the inside of the
> > coil form.
> Been there. Done that. I have blown out baffles. Blown through RTV
> sealant (layered even), blown through coil form sidewalls. When you
> squeeze a bunch of inductance into a fairly small unit volume of
> coil form the resonator geometry becomes quite potent. The problem
> then becomes one of redesigning the construction to prevent internal
> breakdowns while removing the need for internal baffles.
> Quite simply: while you have not had this problem, many others have.
> The best solution I have found was the one Richard Hull suggested:
> Never allow the wire inside the coil form. Since adopting this
> method I have had zero secondary failures. I have not had any
> complaints from any others who build with this construction tip.
> Ed Sonderman has a 22 inch long secondary winding, has good photos
> out here showing 72 inch point to point strikes: no baffles.
> RTV silicone sealant produces high concentrations of acetic acid
> vapor during the curing process. When used to seal baffles inside
> of a secondary coil form the trapped gas ionizes readily. I did
> this once with a clear plastic coil form and you could see the
> glow from the inside of the coil when the system was energized,
> prior to the big glow that ended the short life of this coil.
> The baffles failed.
> > Besides, there's little difference between arcing from the top
> > winding to the bottom on the inside OR outside.
> I don't know about that... When they fail internally the coil
> forms are generally arc scored and the coil is ruined. When they
> fail externally I just put a larger toroid on the top and fire
> again with no apparent harm done.
> Richard Quick
> ... If all else fails... Throw another megavolt across it!
> ___ Blue Wave/QWK v2.12
On the bulkheads, I drilled a very, very tiny hole to vent the
fumes and air pressure. Sealed it with a dap of RTV when everything
else cured. I routinely get 65" hot sparks out of this coil with no
problems once I got it in tune. Bill Wysock also uses the 'drill-a-hole'
technique without problems.
I definately agree that when you are pushing 3x spark lengths, things
get weird really fast...guess I haven't gotten to that point yet. Lack
of $$$$ among other things...!
One idea that did pop up is to place the holes on opposite sides,
instead of on top of each other.
I have seen a fried coil form where the form itself broke down - the
arc jumped across the windings, not from the top wire hole to the
bottom - admittedly, there was a tuning problem; I think a cap blew
and instantly shifted the primary frequency. (fascinating, but not
On another note - does Richard Hull or any of you 'hard-core'
coilers have any sort of documentation on the design of maggies? I
would very much like to try and place a resonant coil on top of my
insulated pedestal stand in place of myself to see if I can obtain