Re: [TCML] largest secondary coil you'd drive with an NST

["Tim Meehan" <btmeehan@xxxxxxxxx>]

Thanks a lot for the info guys, that helps a lot - I heard someone mention
using concrete forms.  If I remember, those were made of very thick
cardboard?  Since I have heard several people talk about it - I imagine that
it is reasonably resistant to lighting on fire when it gets strikes?

I had been looking at a model rocketry site that sells fiberglass forms, and
even does custom work.  Would I be better off with cheaper PVC or concrete
forms, or would the lower loss tangent of fiberglass be worth something?
(granted, most of the loss tangent numbers I have seen are in the MHz or GHz
region, so kHz is probably not a problem with most materials)
(loss tangents)
http://www.rfcafe.com/references/electrical/dielectric_constants_strengths.htm

(fiberglass tubing)http://www.hawkmountain.ws/
and for the person interested in making something on their own:
http://www.giantleaprocketry.com/products_composites.asp



On Dec 14, 2007 7:02 AM, <FutureT@xxxxxxx> wrote:

>
> In a message dated 12/14/2007 4:05:01 A.M. US Eastern Standard Time,
> btmeehan@xxxxxxxxx writes:
>
> >I hate to ask this too - but what is the optimum aspect ratio for  a
> >secondary?  I've run JAVATC, and have built a feeble (but  pretty)
> classic
> >tesla before ... and have read but probably poorly  understood a few
> papers.
> >I think that I'm ready to build version two of  the static-gap,
> NST-powered,
> >properly filtered and protected  coil.  I just want to make sure that I
> learn
> >as much as possible  before I start purchasing things that probably won't
> >suit my  needs.
>
> ------------------------------------------------------------------------------
> -----------
>
>
>
>
> I don't think there's really an optimum.  If there is, it's not really
>  fully
> known
> yet.  The reason for this is because of the many variables  involved.
> Sometimes folks want a coil to be compact so it can be easily
>  transported.
> That may make a smaller narrower coil more desirable.  Others may  have
> plenty of space and opt for a wider coil which might have lower  losses
> since the same inductance can be obtained with fewer turns of thicker
> wire in a wider secondary.  Some folks like to parallel a few  NST's.
>  Such
> as coil can become rather powerful if 15/60 NST's are used with large
> capacitors, etc.  Certainly the coil size should have some  relationship
> to the input power.  A larger coil allows for upgrading the power  input
> over time.  Consider Gary Lau's 15/60 NST coil which uses around  a
> 6" x 26" secondary and gives I think 74" sparks.  Gary can  correct
> my memory if needed.  When I built my TT-42 coil, I was aiming  to
> build a compact portable coil.  The secondary is 4.2" x 19" or  so.
> I power it with a robust 12/30 NST and obtain 42" spark streamers.
> If I was using a 15/60 NST, I'd surely use a 6" dia secondary.
>
> John
>
>
>
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