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

[resonance@xxxxxxxxxxxx]

They are called Sonotubes and available from local concrete supply
companies.  Just call any concrete contractor in your phone book and ask
him where he buys his Sonotubes.

They are thick cardboard and work very well.  I used one with a coil with
a 9 ft spark and it's still being used daily in a museum for the past 21
years.

Be sure to coat outside and inside with 3-4 coats glyptal of Dolph's AC-43
for best results.  Prior to winding.

Dr. Resonance


> 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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Dr. Resonance

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