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Re: [TCML] tesla coil blowers



True. The spark leaves an ionized trail that has to be blown away so the next spark can punch through virgin air. If you have no airflow the arc is just like the arc from an NST.

---Carl







On 11/26/2011 2:13 PM, Carl Noggle wrote:
You're right. The pressure at the Paschen minimum is what is in a thyratron, OMs lower than atmospheric.

---Carl



The relationship between air pressure, electrode gap spacing and breakdown voltage is well documented by Paschen's law/curve. The breakdown voltage does reduce with pressure to a point but then increases again when the pressure is further reduced. These low pressures are probably much lower than a normal blower could achieve (Wikipedia cites an example of 10^-3 atmospheres). The probability of a random free ion being pressent to start the breakdown is increased by the quantity of air flowing through the spark gap which would also lend it's self to lower breakdown voltage.
  - David


________________________________
From: Carl Noggle<cn@xxxxx>
To: Tesla Coil Mailing List<tesla@xxxxxxxxxx>
Sent: Saturday, 26 November 2011 4:06 PM
Subject: Re: [TCML] tesla coil blowers

Hey---Sounds like a reasonable theory. There should be a gap length for
max performance corresponding to each blower speed.  I'll check it on
mine--it's an annular blower gap.  I'll report findings.

---Carl




Though no one asked, I'll offer my theory. The air between the electrodes in a sucker gap is at a lower pressure than the surrounding atmospheric
air.  As the pressure is reduced, the breakdown voltage of the gap is
reduced.  A lower breakdown voltage delivers smaller bangs, and lower
performance. Just a theory though - I haven't run my sucker gap in many
years and I haven't personally witnessed this.

Regards, Gary Lau
MA, USA

On Fri, Nov 25, 2011 at 6:29 PM, Jonathan Peakall<jpeakall@xxxxxxxxxxxx>wrote:

I found with my sucker gap that too much vac actually decreased
performance. There was a sweet spot somewhere around the 20-30% power mark,
as Gary describes.

Jonathan

----- Original Message ----- From: "Carl Noggle"<cn@xxxxx>
To: "Tesla Coil Mailing List"<tesla@xxxxxxxxxx>
Sent: Friday, November 25, 2011 8:04 AM
Subject: Re: [TCML] tesla coil blowers


   Thanks, Gary--after 20 years of running my coil I never thought of
that. Probably make for longer motor life, too, although in that time I have only had to replace it once. Still, I had egg on my face in the middle of a show. A small step-down autotransformer would work well, too.

---Carl


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In a nutshell it blows out the ionized air making the gap more reliable and accurate. I use a squirrelcage fan on a 1/2 hp big old motor. Never heard the pressure thing, true the pressure changes slightly with the movement of the air, (think airfoil) but I say that if they make the gap better its because the moving air does not allow the gap space to be heated. Think (jacob's ladder)

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