Sure. 0.9*SQRT [900 watts (based off of a 15/60NST)] = 27 pF. A good rule
of thumb is a toroid equals 1 pF per inch of diameter, so you want a 27
inch diameter toroidal top load for longest spark, or some combination of
top loads that adds up to less than or equal to 27 pF.
On Mon, Feb 17, 2014 at 8:16 PM, Kuba Anglin <kubaanglin@xxxxxxxxx> wrote:
> Can you tell me the optimum sized toroid I should have?
>
>
> On Mon, Feb 17, 2014 at 4:15 PM, Scott Bogard <sdbogard@xxxxxxxxx> wrote:
>
> > Hi Kuba,
> > One other thing to consider, if you lower the air pressure in there
> > with a vacuum pump, the pump MUST be disconnected when the coil is
> running,
> > and it must be valved off with a GLASS or PLASTIC valve. Otherwise the
> > entire cavity can become ionized, and an electrically conductive trail
> will
> > travel to your vacuum pump, and all your tank energy will go straight to
> > ground, through you pump. You will cook the pump, perhaps sooner, or
> > perhaps later. I work with plasma balls and such, I use a grounded metal
> > gas manifold to prevent this, anytime you are live filling it will try to
> > escape to your pump potentially. If you are worried about Ozone, run the
> > coil outside, or build a sucker or blower gap, and vent the exhaust
> > outside, don't try to contain it, because then a leak can result in
> lethal
> > levels of it escaping. Higher pressure in the gap is better as it will
> > encourage the arc to extinguish, which is paramount for coil performance.
> > Also I didn't look at your top load design, but I know Tesla map
> > recommends top load size based on quarter wave, which has been proven to
> be
> > nonsense. I love Tesla map and use it regularly, but size your top load
> > using this formula. C in pf=A*SQRT[input watts] (A=0.5-0.9, higher
> gives
> > longer sparks, lower gives multiple healthy streamers). This WILL result
> > in a top load that looks too big, but modern experimentation shows a "too
> > big" top load is the best for making big sparks. Just some food for
> > thought, have fun experimenting!
> >
> > Scott Bogard.
> >
> >
> > On Mon, Feb 17, 2014 at 4:23 AM, Kuba Anglin <kubaanglin@xxxxxxxxx>
> wrote:
> >
> > > Thanks for your response,
> > >
> > > Sorry I was not very clear on my spark gap design. Here is a rough
> > rendered
> > > image of what it will look like. A vacuum pump will suck the air from
> the
> > > tube to lessen the air resistance for greater control over the spark
> gap
> > > and limit ozone production for obvious reasons.
> > > http://s29.postimg.org/t4o3jgapz/spark_gap.jpg What do you think? Is
> it
> > > worth the benefits?
> > >
> > > Thanks,
> > > Kuba Anglin
> > >
> > >
> > > On Sun, Feb 16, 2014 at 6:46 PM, Gary Lau <glau1024@xxxxxxxxx> wrote:
> > >
> > > > Hi Kuba,
> > > >
> > > > There's nothing wrong with adding a sphere atop a toroid. However,
> the
> > > > incremental capacitance of the sphere, assuming your image is to
> scale,
> > > > will be rather small, as the shape of the toroid will shield the
> field
> > > from
> > > > the sphere. I think just adding an extra primary turn would probably
> > > have
> > > > a greater impact at lowering Fres than the added sphere.
> > > >
> > > > If you're shooting for the maximum spark length, I think the size of
> > your
> > > > toroid needs to be up'ed considerably. With my 15/60 NST, I use a
> 7x30
> > > > primary toroid with a smaller corona ring toroid spaced beneath it,
> to
> > > gain
> > > > additional height for the main toroid. With top loads, bigger is
> > > _always_
> > > > better.
> > > >
> > > > I didn't completely understand the geometry of your gap. I don't
> think
> > > > there's any good reason to try to contain the gap arc. PVC, and
> > > > particularly rubber (!), will suffer rapidly from exposure to the UV
> > > > radiation of the gap. I think the gap will generate the same amount
> of
> > > > ozone whether or not it's contained, assuming that the air is
> > circulated
> > > > and not sealed, and you DO want good circulation. And in any
> > > > well-performing coil, the sound from the top load sparks will be much
> > > > louder than the sound of the gap, so no point in trying to muffle it.
> > I
> > > > would recommend a sucker gap - it's been widely tested and is easy to
> > > > construct and adjust. See http://www.laushaus.com/tesla/onegap.htm
> > > >
> > > > Hope this helps,
> > > >
> > > > Regards, Gary Lau
> > > > MA, USA
> > > >
> > > >
> > > >
> > > >
> > > > On Sun, Feb 16, 2014 at 8:03 PM, Kuba Anglin <kubaanglin@xxxxxxxxx>
> > > wrote:
> > > >
> > > > > Hello,
> > > > >
> > > > > I have been working on a Tesla coil design for the past month now
> and
> > > am
> > > > > about ready to order the parts.
> > > > >
> > > > > My main questions:
> > > > >
> > > > > -Are there any issues with my design?
> > > > > -Is it OK to have a toroid and a sphere as the top load? I am only
> > > doing
> > > > > this because these two pieces equal the required capacitance level
> of
> > > > > around 29pF (see the TeslaMap image for more info).
> > > > > -I was planning on creating a vacuum static spark gap by putting
> the
> > > > > electrodes inside a PVC pipe sealed with rubber sheets and lexan
> > board.
> > > > The
> > > > > vacuum pump would suck out the air to limit resistance caused by
> the
> > > air,
> > > > > lessen ozone production, and reduce noise. Does this sound like a
> > good
> > > > > idea?
> > > > >
> > > > > I have added a 3D render of my design and a filled out TeslaMap
> > page. I
> > > > > will be phasing two NSTs to achieve the right amperage. Check the
> > > > TeslaMap
> > > > > attachment for more specific specs.
> > > > >
> > > > > 3D render link: http://s13.postimg.org/q9tpxzsjb/Tesla_Coil.jpg
> > > > > TeslaMap link: http://s9.postimg.org/t0ss08wmn/Tesla_Map_Page.jpg
> > > > >
> > > > > Here is my parts list:
> > > > >
> > > > > Secondary Coil6.625" PVC Pipe 3'22 AWG Magnet Wire 5lbs wound 34"
> > > > > highToroid
> > > > > 18" x 4.5" + Sphere 7" diameterPrimary Coil3/8" Copper Tubing 60'
> 11
> > > > > turns1/2"
> > > > > Copper tubing 10' strike railBase(2X) 15 KVA 60mA Transformer(2X)
> 1"
> > > > Brass
> > > > > Electrode
> > > > > 72 Capacitors (.15uF 2kV each) 4 strings of 18(2X) Brass Bolt
> > > > >
> > > > > Thanks,
> > > > > Kuba Anglin
> > > > > _______________________________________________
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