Re: My second coil attempt, advice?

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Yurtle Turtle <yurtle_t@xxxxxxxxx>

I'm sure you'll get lotsa advise, but the biggest
thing I see is the AWG14 in your tank circuit. It's
fine to use smaller conductors from your transformer
to the tank, but once your spark gap conducts, you
want really big conductors involved. Consider using
1/4" tubing if you have any left. Forget about
insulation; just run your conductors with lotsa space.

Your primary has .75" spacing between turns? Is that
center to center, or clear space? In any event, unless
you're using higher than usual voltage, most folks use
the tubing diameter for the clear space, or twice the
diameter for the center to center diminsion.

As to your gap, bolts filed to a point are not the
best configuration. Consider a sucker gap like this:

http://www.hot-streamer.com/adam/shopvac_gap.jpg

I've run it with a fair amount of pig power before. It
took over 20 kVA to melt it.



Good luck
Adam

--- Tesla list <tesla@xxxxxxxxxx> wrote:

> Original poster: "Scott Bogard"
> <teslas-intern@xxxxxxxxxxx>
>
> Hello all,
>      I am a relative newbie to the list, and I have
> recently finished
> my second Tesla coil (60Hz AC system), and the
> output is Ok (strikes
> 38 in, and streamers about 5 ft tops) but I have
> seen very similar
> coils put out as much as 8 ft or more.
>      Here are the specs,
>      Power supply:  6 MOT stack, center tapped
> ground (~12kV out 120V
> in ?? amps, I don't have the tools to actually
> measure this) no
> variac, full power or nothing.
>
>      Ballast: 1 MOT (shorted of course).
>
>      Tank capacitor:  75nf Maxwell, tested at 81nf
> (so the label says anyway).
>
>      RF filter:  ohmite resister 50 ohm "chokes"
> filled with 4
> welding rods for "inductance" and some ceramic
> capacitors about 600pf
> (I don't know if it works or not, but there isn't
> much interferance
> on our TV unlike my old (smaller) coil) and safty
> gaps to ground (I
> don't use a mains ground at all, I use a seperate
> peg in the ground
> from the RF ground for the MOTs and safety gaps).
>
>      Secondary: 6in PVC 22AWG wound 31 in (+-1160
> turns) three super
> thick (uneven) coats of polyurethane.
>
>      RF ground: copper pipe pounded in about 1.5 ft
> (the ground may
> still be frozen down there).
>
>      Top load:  2 aluminum flex duct toroids covered
> in foil tape,
> 3in*15 and 7in*21 (I tried a large 11.75*42, but got
> no streamers
> breakout with it connected).
>
>      Primary:  1/4in copper (refridgerator) tubing,
> spaced .75in
> apart with an 8in hole in the middle for the
> secondary.  Tapped
> between turns 7 and 8, and sits just a hair below
> the first secondary
> winding (no racing arcs yet, moving it downward
> lowers the
> performance, moving it up changes nothing).
>
>      Wiring: tank circuit-14AWG rated at 15kV, other
> wire-whatever I
> had lying around (18AWG 20kV, some house wire, and
> some 22AWG magnet
> wire, run through polyethylene tubing for
> insulation).
>
>      Spark gap: (probably my performance killer)
> single blower static
> gap, two brass bolts filed roughly to points (I use
> pointed contacts,
> because smooth rounded contacts on my first smaler
> coil, instantly
> gave me terrible (really really bad) racing sparks,
> and the pointed
> ones gave fairly smooth nice operation,) currantly
> .75cm or just
> between 1/4 and 1/2 in. seems to give best results.
> My saftey gaps
> are set much narrower than this, but they have
> rounded contacts and never fire.
>
>      I am building a synch rotary, but it will be
> some time until it
> is ready, I do however have a much stronger blower
> on the way (the
> currant one is lousey compared to the one that is
> coming).  The
> output is Ok but somwhat inconsistant (I am running
> it outside, and
> it is very moist here right now with snow melt and
> rain) sometimes it
> will strike the strike rail 38in away while two
> additional long
> streamers fly out in the air, and then a second
> later all you will
> see is one tiny streamer 2.5 feet long or so, and it
> does everything
> in between totally randomly.  Aside from building my
> rotary gap, is
> there anything I can do to tweak just a little more
> output out of the
> thing (a breakout point reduces the output, but
> makes it easier to
> see as it doesn't move around the toroids).  Thank
> you much
> Scott Bogard.
>
>
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