Thanks for the info Dave!
So if I have only 24" long 6" diameter PVC pipe to work with, I keep
reading that you need 2-3" on both ends of the pipe that I wont have then.
I'm assuming for the bottom end of he secondary pipe I would need to raise
it up 2-3" with a wooden block or other material BUT I am using 1" high
HDPE 12" long strips to hold the 50' of 1/4" refrigerator tubing, I would
assume I wouldn't have to raise the secondary only 1" then to make it even
with the 1" high HDPE strips. If it is raised only 1" I was thinking of
using PVC cement to attach it to the 1" high wooden block. I would then
attach the wooden block to the base with L brackets (non metal if I can
find them - but don't think it would matter).
At the top of the 24" secondary (assuming almost the entire 24" length is
wire wound - or 23 to 23.5"), I would make it only about 23.5" and save the
last 0.5 inch to attach some way a torroid. BTW: is a large sphere any
better than a large torroid on this 6" diameter (24 " tall pipe) wound 23
or 23.5" of 26 gauge wire?
I would like to use what I have already purchased but if I absolutely have
to have a longer 6" diameter, I think Menards has 10' lengths I saw online
but another expense for just being a few inches short with what I have at
24" already.
Another idea - since Lowes sells the 24" (6" diameter) pipe. what about
buying another 24" (6" diameter) pipe and using PVC cement them together
for 48" (6" diameter) and use a hacksaw to saw it down to maybe 30" or so,
Does that sound reasonable?
Thanks!
Tim
On Sun, Feb 22, 2015 at 5:22 PM, David Rieben <drieben@xxxxxxx> wrote:
> I'd think that 6" would be a pretty optimal secondary diameter for a ~2
> kVA Tesla coil. If you can't find a sufficient length of it at Lowe's of
> Home Depot (try asking them if they have it or can get it, if you can't
> find it), I would try a local plumbing or irrigation supply. #26 AWG wire
> would be pushing the envelope in wire thinness for a coil this size, but it
> would work. And a 24" secondary winding length would be sufficient for this
> power level, assuming that you topped it with a properly sized toroid
> topload (~6"x 24"). You could probably get away with a 4" diameter coil,
> but 6" would be better and would likely give you longer sparks with a given
> amount of power throughput, compared to a 4" coil. So, in conclusion, I
> would aim for a 6" (or even 8") diameter by 24-26" winding length of about
> #24 AWG magnet wire (or 30" to 32" long for an 8" diameter form) for my
> finished secondary. If the PVC doesn't pan out, you can also use one of
> those cardboard
> concrete former tubes. Lowe's and HD both carry these in 8" and 12"
> diameter by 48" long. The 4:1 to 5:1 is a good aspect range to aim for but
> it isn't really that critical, so long as you keep your dimensions within
> reason ( >3:1 and < 7:1 would probably be just fine). If you go the
> cardboard concrete former tube route, you'd just need to make sure that you
> completely evacuated any stray moisture from it (heat it or place it out in
> the sun for several hours on a warm, dry day) and then soak and coat it
> with several coats of polyurethane spar varnish (to keep moisture out), as
> cardboard is notorious for soaking in atmospheric moisture, especially in
> humid ambient conditions.
>
> David
>
>
> On Sunday, February 22, 2015 1:44 PM, Tim Gilmore <tdg8934@xxxxxxxxx>
> wrote:
>
>
>
> I went to Lowes and found a greenish 6" pvc? Tube BUT it's only 24" and
> the only 6" pipe they carry. Also went to Home Depot and bought a 4"
> standard pvc whitish tube but only 24". They do carry longer 4" pipe but it
> would need to be cut from a 5' length.
>
> Since I'm using 2 15000v 60mA NST I'm thinking I will need to use the 6"
> pipe but for 1200 turns Ill need 26 gauge for 22" but leaves me with a
> 3.5:1 ratio. Is this good enough not being at 4:1 or 5:1 ratios - or is it
> better to just use the more common 4" pipe (2' or buy a taller one) with
> the 2 NSTs?
>
> Thanks, Tim
>
> > On Feb 21, 2015, at 3:22 PM, Futuret via Tesla <tesla@xxxxxxxxxx> wrote:
> >
> >
> > Tim,
> >
> > The secondary does not need to be as tall as the spark is long. For
> example
> > my TT-42 coil has an 18" tall secondary and gives 42" sparks. However
> sparks
> > are more likely to arc down from the toroid and strike the primary if
> the secondary
> > is too short. I often place a smaller toroid below the main toroid to
> raise up
> > the main toroid some to keep sparks away from the primary. The length
> > of the sparks has a lot to do with the current in the arc and the growth
> > of sparks over successive gap firings. It seems to me that a high spark
> > gap break rate coil could tolerate a smaller secondary than a low break
> > rate coil for a given input power, because the "bang size" (joules per
> > gap firing) is lower in the high break rate coil. As far as I know no
> one
> > has ever really researched this. It was the next thing on my list but
> > I never got around to it. I usually prefer low break rate though
> because it can
> > be more efficient in the sense of producing longer sparks for a given
> > input power in a properly designed coil. High break rate has it's good
> > points too though.
> >
> > Generally speaking, when the power is increased, the coil is made larger
> > in proportion. If you use 4 times the power, then the coil should be
> twice
> > as large in all proportions including the toroid (assuming the coil was
> sized
> > correctly in the first case).... square law sizing concept. As you said,
> > the wire should generally be somewhat thicker for higher powers.
> >
> > The 22 gauge plastic insulation wire will work, but may result in the use
> > of fewer primary turns, which increases the spark gap losses somewhat
> > due to the non-linearity of the arc resistance. Plastic insulated wire
> will
> > also run at a higher frequency which generally results in shorter sparks
> > also. Generally the magnet wire is a better choice. Very large coils
> > may better tolerate the plastic insulated wire however.
> >
> > Cheers,
> > John
> >
> >
> > All,
> >
> > If I use both 15kv/60mA NSTs (yes they were identical and phased the same
> > with my jacobs ladder - bigger flame spark), then the sparks could be 4-5
> > feet in length so shouldn't the secondarys also be 4-5 feet tall. All of
> > the designs I see are about 2 feet for the secondarys but are wider in
> > diameter like 4" to 6" or more. This doesn't make sense to me. Why go
> wider
> > in diameter and not taller in the secondary? I would think you would want
> > thicker wire like 22 or 20 gauge wire and not 24 or 26 gauge. Also does
> it
> > have to be magnet wire. Radio Shack 22 gauge wire has plastic like
> > insulation. Is that ok?
> >
> > Thanks,
> >
> >
> >
> >
> >
> >
> >
> > _______________________________________________
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> > Tesla@xxxxxxxxxx
> > http://www.pupman.com/mailman/listinfo/tesla
>
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