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RE: spark gap/ primary coil

Original poster: "Hooper, Christopher AZ" <christopher.az.hooper@xxxxxxxxx>

Hi Michael,

Here is a little spark gap that worked well for me. I still use this and
it just keeps ripping along. I ran this coil at the Teslathon (W.W.T
2006) and pumped big sparks for a static spark gap @


-----Original Message-----
From: Tesla list [mailto:tesla@xxxxxxxxxx]
Sent: Wednesday, February 22, 2006 9:48 AM
To: tesla@xxxxxxxxxx
Subject: Re: spark gap/ primary coil

Original poster: "David Rieben" <drieben@xxxxxxxxxxxxxxx>

Hi Michael,

Welcome to the list and to coiling ;^) First of all, you are NOT
going to be delveloping 6000 kV (that's 6 megavolts!) with your
coil nor is anyone else on this list for that matter! 600 kV would
be a closer guestimate although that's still probably high by a fac-
tor of 2 or 3 for an average sized NST driven, spark gap coil.
The alternating currents in the tens or hundreds of kHz can pro-
duce spark lengths vs voltage that are much higher than the
standard DC sphere spark vs voltage rating.

The 1/4" copper tubing should not be that expensive at your
local home improvement store's (Home Depot or Lowes) plumb-
ing department. I would think that you should be able to obtain
(2) 50 ft rolls of it for under $50. I think most knowlegable coil-
ers are going to tell you that coax cable is NOT a good choice
for the primary coil conductor. In operation, it will carry some
very high peak currents (in the hundreds of amps) and the fine
outer braiding of standard coax cable is not suitable for carrying
these immense currents. OTOH, copper tubing is indeed well
suited for this purpose and is the usual conductor of choice for
most coilers' primary coils. Also, as you said, the bare copper
tubing renders multiple tuning much simper than with insulated

Good luck with your coil,
David Rieben

----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Wednesday, February 22, 2006 8:57 AM
Subject: spark gap/ primary coil

>Original poster: "Michael Ong" <omenowner725@xxxxxxxxxxx>
>hello, i am planing to use a TCBOR style spark gap but was wondering
>what the advantage was of having it in the circular PVC pipe instead
>of just a flat sheet of plastic with large fans blowing across it.
>it seems like construction would be difficult to get the spacing
>correct inside a tube like that. also, my coil is going to be a
>6000kv  with a secondary of 4.25" diameter  1700 30 awg wire (22
>inches tall) for the pirmary using 1/4" copper tubing 1/4" spacing
>in a flat spiral my java tc simulations say that i will need about
>52 feet of copper (18 turns). I dont think i want to spend the $100+
>on just the pirmary so i am thinking about going with coax cable. my
>question then is: is there a way to adjust the pirmary easily using
>coax? or is the easy shorting clip used on the copper tubing the
>reason why most use that?
>thanks again for all your help, its really getting me through my
>first tesla coil experience.