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RE: [TCML] Spark Gap Tests
Cole,
I agree with Gary, since all of the things he mentioned have proven true, countless times. Of course, there is the fact that, for a low-power coil, heating of the spark gap will be of little concern, especially with such a large conductor of heat as a doorknob (great thermal mass and a fair amount of surface area).
As for concern with toxic fumes from stainless steel, aren't the nitrates from the ionisation of air toxic, as well? Just keep runs short and you shouldn't have a problem - it's not like you're working in a coal mine.
As for Gary's assessment that 'tungsten is best', I would have to respectfully disagree, on some accounts. In low-power applications, copper offers a greater surface for gap conduction, which means a more-regular break-rate when not using a rotary gap, and is more conductive - electrically and thermally - than tungsten. If you could manage to find some copper of any sort - if we're talking less than 1.5KW of power - it should be up to the task, given it's of sufficient thermal mass and thickness.
In practice, copper pipe works quite well. Two bars in parallel, with a fan blowing on them from the side, the top, or what have you.
Best of luck,
- Christopher
> Date: Sun, 29 May 2011 23:31:03 -0400
> Subject: Re: [TCML] Spark Gap Tests
> From: glau1024@xxxxxxxxx
> To: tesla@xxxxxxxxxx
>
> Cabinet knobs are good for safety gaps, which by definition, do not
> (hopefully) fire frequently. But for a main spark gap, there's a couple of
> problems.
>
> The material - stainless steel - is not optimal. It's a poor conductor of
> heat, which means that the metal at the point of arcing will get hot
> locally. This will affect the breakdown voltage. I also have heard reports
> that stainless steel generates toxic fumes if it gets that hot, but I can't
> confirm that. Copper or brass are better, tungsten is best, though the
> available tungsten shapes are limited. Note also that cheap cabinet knows
> look like brass, but are in fact brass-plated zinc alloy.
>
> The other problem is the shape. With spherical or similar shapes, the arc
> will occur at one and only one point on the surface, and that point will get
> hot and the metal there will quickly erode. It's better to have two
> parallel pipes so that the arc occurs across the length of the electrodes.
>
> Regards, Gary Lau
> MA, USA
>
> On Sun, May 29, 2011 at 9:10 PM, Cole Awesome-Jordan <
> jordancole@xxxxxxxxxxxxxxxxxxx> wrote:
>
> > Hi, recently i picked up two stainless steel cabinet knobs and they are
> > coated in a lacker this does make the spark (just from a transformer not
> > hooked to a MMC) behave oddly but it doesnt stop it. Has any else tried to
> > use cabinet knobs for a spark gap before?
> >
> > Thanks
> >
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