Gary very good insight into the rotary spark. Gap to big or not firing
properly would explain the variac blowing fuse after fuse just passed where
it starts to fire. Thays my second spark gap sorry third. First was a bench
grinder with a 4 inch solid rubber body mount from a vehicle with four even
spaced hole drilled and 2 pieces of wire ran around opposite sides of the
back and everything wrapped in electrical tape on top of that actual seemed
to work well then second was a six inch lexan disc I ground round on the
bench grinder and mounted on a hand grinder. Eventually the disc shattered
and I realized that was way to unsafe so I took a wire wheel cup and cut
off all the wires which I will never do again seeing how I'm still getting
jabbed from them in random clean cloths I put on they just seem to travel
everywhere even have the missus curse me every now and again when she gets
one. So third Idea which worked really well but was already starting to get
loose from vibration was an 8 cylinder distributor cap mounted on the
grinder wheel with fixed and adjustable oil burner ignitor insulated points
on either side of it for the pick up but the grinder makes me nervous after
seeing the lexan shatter and gimme a good slice across a finger. I also
where safety glasses when anything is running. So that's when I came up
with the bench grinder fan wheel idea because the benchgrinder is heavier
and easier to secure plus im only looking a 3500 rpm versus an unstable
10,000rpm. What do you think k about removing the fan wheel an installing
distributor cap on that? The point are heavy duty and so of designed for a
similar purpose minus the 3500 rpm?
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Valid until: Feb 23, 2021
On Sun, Feb 21, 2021, 7:35 PM Gary Lau <glau1024@xxxxxxxxx> wrote:
> I have no experience with X-ray transformers, and I also don't recall
> hearing of any success stories using such to power a TC.
>
> The construction of your rotary spark gap is concerning. The flying copper
> wire electrodes woven into the plastic fan are going to get hot, melt the
> wheel, and go flying off. Sorry to be the Debbie Downer!
>
> The mechanical tolerances of the gap electrodes look large, and I worry
> about a break-rate too infrequent or irregular to guarantee a bang every
> mains half-cycle. If the break-rate is too infrequent, the transformer
> will draw crazy-high current.
>
> I would advise you to abandon the X-Ray power supply in favor of a simple
> NST, and build an MMC capacitor and start off with a static spark gap.
> While I admire a just-try-it willingness to experiment, TC's don't fare
> well with just throwing spare parts at them and hoping it will work. You'll
> just have to do the math.
>
> Gary Lau
> MA, USA
>
> On Sun, Feb 21, 2021 at 3:29 PM Lux, Jim <jim@xxxxxxxxxxxxx> wrote:
>
> > On 2/20/21 3:50 PM, Curt Wilson wrote:
> > > My names Curt and I've been trying to get a tesla coil up and running
> > for a
> > > while now. I've used multiple power supplys such as four mots wired in
> > > series parralell with a center tap ground but they did not last
> probably
> > > due to being used for fractal wood burning prior. I have tried NST's
> but
> > > they had the gcfi on them and only worked for the first few minutes. So
> > now
> > > I've moved onto a cathode/anode 80 kva x-ray transformer that feeds
> > through
> > > a bucket capacitor and into a bench grinder with a 6inch plastic fan
> > wheel
> > > that I wove solid copper wire through four of the fins and have a oil
> > > burner point on with side for the pick ups. My primary coil is 9/16" x
> > 1/8"
> > > solid copper ribbon with 1"spacing between coils and my current
> secondary
> > > is 4.5" pvc with two recycled 34 guage magnet wire soldered together
> and
> > my
> > > top load is two old chevy hubcaps hot glued together. I'm running a
> 30amp
> > > variac 125v ac to regulated 125v ac and I can't get past about 30v with
> > out
> > > the fuse blowing. Just when the rotary gap starts to fire the fuse
> blows.
> > > I've tried a mot with secondary shorted between the transformer and the
> > > variac but it didn't seem to make a difference and I've tried a250 watt
> > > 15ohm resistor first where the mot was then tried it between the
> > > transformer and the primary. Both places it just heated up and would
> not
> > > allow any spark at the gap. Any help with the wiring on the transformer
> > or
> > > variac or suggestions would be greatly appreciated! Thanks in advance.
> > > https://photos.app.goo.gl/nPS9fMg36375yAXi8
> > > _______________________________________________
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> > > Tesla@xxxxxxxxxxxxxxxxxx
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> > >
> >
> > What is your X-ray transformer output voltage? Most Xray transformers
> > have *very* high output voltage compared to what's practical for most
> > home built TCs.
> >
> > Xray - 75-120kV isn't unusual. Neon Sign Transformer (NST) or Pole
> > Transformer are 12-15 kV.
> >
> >
> > So you should be looking at feeding your Xray with around 10-20VAC.
> >
> > A real issue is that Xray transformers don't have any current limiting,
> > so you'll need a ballast to limit the current (just like pole-pig
> designs).
> >
> > Does your Xray transformer have rectifiers?
> >
> >
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> > Tesla@xxxxxxxxxxxxxxxxxx
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> >
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