Re: [TCML] Spark Length Measurement Techniques

[mddeming@xxxxxxx]

Hi Gary, All,

I would have to agree with you on this, Providing an intermittant conductive path would have to produce somewhat better results than a straight shot through open air. Of course, it wouldn't matter if everyone used the same technique, for then it would be a comparable, if artificial number.(Like octane ratings for gasoline, or milage ratings for cars). In a larger sense though, all TC discharges are an atmospheric phenomenon and are therefore a function of voltage, power, geometry, temperature, pressure, humidity, air quality and movement. The last 5 of these are not characteristics of the coil, although they do affect spark length. Therefore it's unlikely to make measurements under identical conditions. 
This does bring up an idea for a possibly interesting display. What would happen if instead of a strin of nails, an air hose were used to blow little puffs of metallic dust into the air?near the torroid of an operating coil? Of course, it might ignite the cloud, but that would be spectacular too! ;^))
?

Matt D.


-----Original Message-----
From: Lau, Gary <Gary.Lau@xxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Wed, 20 May 2009 8:31 am
Subject: RE: [TCML] Spark Length Measurement Techniques



This technique may be useful to gauge relative performance of the same coil with 
the same measurement technique to assist with tuning, but I'm not sure the 
results are comparable to anyone else's coil measured in a conventional manner.  
Just as the breakdown voltage of a multi-segment spark gap ten times 25 mils 
will be very different than a single 0.25" gap (a seldom-mentioned truth!), I 
suspect the same would be true with topload discharges.

I would also question whether the presence of nails conducting the discharge 
current might increase the capacitance-to-ground of the streamer and result in 
tuning to a lower frequency than if the nail segments were not present.

Regards, Gary Lau
MA, USA

> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of Dave Leddon
> Sent: Tuesday, May 19, 2009 7:02 PM
> To: Tesla Coil Mailing List
> Subject: Re: [TCML] Spark Length Measurement Techniques
> 
> Here's a scheme that I use to tune a coil to it's maximum spark
> length which also yields an accurate measure the length achieved.  I
> tape a nylon weed-wacker line to the toroid and attach the opposite
> end to a vertical support about 20 feet from the coil.  Suspended
> from the line are about 20 movable wooden dowels each pierced by
> small nails at the lower end with the nail furthest from the coil
> being grounded.  An arc from a breakout point on the toroid will jump
> from nail to nail to reach ground and so you just keep increasing the
> dowel spacing an readjusting the coil until the arc cannot reliable
> span the distance.  Once the coil is tuned to achieve a maximum spark
> length, all one has to do is measure the span and subtract the total
> length of the nails.
> 
> Here's a picture this setup taken at Greg Leyh's Nevada Lightning
> Laboratory last summer:
> http://www.teslacoiling.com/firingthegap.jpg
> 
> Dave

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