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Re: [TCML] Dual identical FRANCE neon sign transformers (15000v 60mA each) in parallel

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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