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Re: [TCML] John Freau's streamer length equation

Terry,The toroid might be 30" x 10"?  In any case it's large enough.  Do you find that as you increase the input power from let's say, 3600 watts to 4500 watts that the spark length doesn't increase much?  If so that could be just a tuning issue, and you may need to tune outwards on the primary, although you probably did that already.  I assume you're using a variable speed rotary gap?  And if the capacitor is somewhat small that might limit the efficiency too.  If you're using a static gap, it might be power arcing at the higher power levels.  Also the transformer might be showing high losses at the higher power levels, or the ballast you're using could be wasting a lot of power (if so it will run very hot over time).  If you're using a resistive ballast that will burn up some power.  Then there's the possible power factor issue if you're not measuring true power but rather VA.  Those are just some things that come to mind.    All the best...   John  

-----Original Message-----
From: Terry Oxandale <toxandale@xxxxxxxxxxxxx>
To: tesla <tesla@xxxxxxxxxx>; Futuret <futuret@xxxxxxx>
Sent: Tue, Apr 14, 2020 7:46 pm
Subject: Re: [TCML] John Freau's streamer length equation

 Thanks John. The toroid is an OLD group buy from here years ago...thinking maybe 34" x 10" (stored in a crate right now). It looks like a stick with a large donut on top (6" diameter secondary). All the same, I'm still tweaking with caps and primaries to obtain a little more.

    On Tuesday, April 14, 2020, 05:07:59 PM CDT, Futuret via Tesla <tesla@xxxxxxxxxx> wrote:  
A large enough toroid diameter is needed to get the arcs to reach the full length.  Arcs tend to not be able to reach beyond 4 times the toroid diameter no matterhow much power you use.  (unless you use huge power such as in Bob Golka'sproject Tesla... something like that).  Also sometimes the VA input is a lot higherthan the wattage depending on the power factor.
John Freau

-----Original Message-----
From: Terry Oxandale <Toxandale@xxxxxxx>
To: Tesla Coil List <tesla@xxxxxxxxxx>
Sent: Mon, Apr 13, 2020 12:23 pm
Subject: Re: [TCML] John Freau's streamer length equation

I hope so (laughing). At 4500 input, I should be getting nearly 10' arcs, which I'm a long way from that (best was 82" point-to-point).

-----Original Message-----
From: Tesla <tesla-bounces@xxxxxxxxxx> On Behalf Of Steve White
Sent: Monday, April 13, 2020 9:39 AM
To: Tesla Coil List <tesla@xxxxxxxxxx>
Subject: **External Email** [TCML] John Freau's streamer length equation

I was wondering if John Freau's empirical streamer length equation applies equally well to both SGTCs and DRSSTCs? It seems to me that it would since both SGTCs and DRSSTCs both operate on the principal of feeding a rapidly repeating stream of CW pulses into the primary coil.

A related question involves how to measure the streamer length as predicted by the John Freau equation. Do you mentally straighten out the streamer removing all the bends and curves or do you just measure the straight-line length from start to finish with a straight line cutting through the bends and curves? My thinking is that you mentally straighten out the bends and curves into a straight line before making the measurement.

Here is John Freau's equation for spark gap coils for reference:

Length = 1.7 sqrt(input power)

where Length is in inches and input power is in watts.

Steve White
Cedar Rapids, Iowa

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