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Re: Coil design questions.
to: Travis
The 60 ma drive current will give you much better performance as the cap
won't be starving for recharge current. If you have to stick with the 30
ma drive, then reduce your cap to around .005 or .006 MFD and use primary
turns on your primary inductor to acheive resonance. At the 6 inch dia I
would strongly suggest a flat spiral primary as an inverted cone would
begin to produce overcoupling and forced resonance which can lead to
problems especially with neon sign transformer (NST) powered systems. If
you have the means to check the coeff. of coupling shoot for a value
between 0.18 and 0.20 which seems to work very well with small and medium
size systems.
DR.RESONANCE-at-next-wave-dot-net
----------
> From: Tesla List <tesla-at-pupman-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Coil design questions.
> Date: Tuesday, December 01, 1998 4:20 PM
>
> Original Poster: Travis Tabbal <bigboss-at-inquo-dot-net>
>
> I have built one coil from a book and got pitiful performance. After
> reading here and on varrious websites I think I have enough info to start
> again. I did just about everything wrong the first time so any info here
> that can save me time/money would be appreacted.
>
> The plan.
>
> 6" dia 24" long PVC Secondary wound with 22 AWG for 888 turns. PVC
sanded,
> dried, and treated.
>
> Inverse conical primary from 1/4" copper tube starting at 8" with .200
> spacing and 30 degree slant.
>
> Rolled poly cap(s) WinTesla says .0108 mfd should do it.
> I was planning on using the design from the list archive page.
>
> 15kv 30ma Neon
>
> RQ Style static series gap
>
> 6A Varriac
>
> Topload of about 14 pf.
>
> -----
>
> Now, this seems to fit, I was planning on using one rolled poly cap of
the
> design listed which with 90 mil poly should give me .0100 mfd according
to
> the docs, I was thinking to build two of them right off just in case. The
> doc states that it will handle a coil with input of 15KV.
>
> For the poly, I think 90 mil is the way I should go. Are 3 30 mil layers
> prefferable to a 60 and a 30 or otherwise?
>
> For the oil soaking does layering oil soaked paper in with the poly
sheets
> help? If I do so that will affect the thickness of the dielectric. Is
> replacing a poly sheet to compensate a good idea? I'm leaning against
> this and would preffer to just parallel 2 of them if I do add the
> paper. "better safe then sorry".
>
> I don't have a vacuum pump and would preffer not to buy one. I can let
> them sit for a while before use and plan to break them in with the NST
and
> varriac. I would preffer not to have them explode. :)
>
> If the vacuum is that important any idea on where I can obtain a cheep
> pump?
>
> Any ideas where the primary will tune? I found a good price on a 50ft
roll
> of copper tube and don't mind using the whole thing if I need it. The
> calcs I have from WinTesla and the spreadsheet on the archive page think
I
> can get 12-14 turns starting from 8 in.
>
> For the topload, I was thinking of using the duct wrapped in foil method.
> But the copper spheres mentioned on the list today calc to a higher
> capacitance for a 6" then the torriod that I was planning. And it would
> look cooler and be eaiser to work with. Is there a prefference on sphere
> vs. torriod for this?
>
> The transformer/cap match equations seem to think I want 60ma for this
> size cap. Can I get by with 30 or should I go up to 60? I don't mind
> limited performance for the first runs and I allready have the 30 ma
> transformer from my previous efforts. Any estimates on performance either
> way? Would putting another 30 in parallel overload my varriac? Do I need
> PFC on this thing? :)
>
> For hookup wire I would like to use the 8 AWG power cable I use in my
car.
> It's very flexable and is made from thousands of tiny strands. I am
> concerned about the insulation. Has anyone used simmiliar cable for the
> connections on a coil? I would like to use it in the caps too, so
> breakdown is important. Is encasing it in poly tubing a workable way to
> prevent problems? I believe it's made by "Monster Cable".
>
> For oil filling the caps I found a local jobber I can get Shell Diala AX
> from for what seems to be a reasonable price ($25/5 gal). Is there any
> problem using this oil in a cap? I've read on the list that it is a good
> oil, I just didn't see anything saying what for. They tell me it's a
> transformer oil, which seems to fit the requirement. Any idea how much
oil
> I need for 2 caps?
>
> For the neon protection network I need caps, where can I get some? :)
What
> exactly do I need for this? I found a doc thinking that the LC filter was
> prefferable to RC. I don't really know and don't want to start a debate.
> Any pointers? I need to keep the cost reasonable so please keep that in
> mind. :)
>
> Thanks if you got this far, I'm a bit new and thought I should ask all
the
> questions I could think up in one message rather then flood the list with
> posts over the next week. :)
>
> Any thoughts on my proposed system would be welcome, even to say I'm an
> absolute idiot. :) If you do that please provide somewhere to look for
> more info though! :)
>
> Saftey tips are great too, after shocking myself on the primary of my
last
> coil I'm pretty carefull now though. ;) I think I'll build a box for the
> primary circuit this time.
>
> Thanks!!
>
> Travis
>