Re: spark gaps

To: tesla-at-pupman-dot-com
Subject: Re: spark gaps
From: Richard Hull <hullr-at-whitlock-dot-com>
Date: Thu, 17 Oct 1996 10:20:23 -0700
Tesla List wrote:
> 
> >From mhammer-at-midwest-dot-netWed Oct 16 23:00:56 1996
> Date: Wed, 16 Oct 1996 19:39:16 -0500 (CDT)
> From: Mike Hammer <mhammer-at-midwest-dot-net>
> To: tesla-at-pupman-dot-com
> Subject: spark gaps
> 
> Hello all,
> 
> In my never ending quest for more power and longer spark
> I have come to a bottleneck. I believe the gap is now my limiting factor.
> Running at about 1.2 KVA I notice that as I run the variac up towards
> maximum the spark output actually decreases slightly. I believe that the
> gap may not be quenching well as I turn the power up.
> 
> I have built an 8 electrode cylinder gap similar to the design
> from the funet archives. The 7 gaps are set at .025 inch for a total of .175
> inch.
> I used 3/4 inch copper tubing and a piece of 4 inch PVC to house it.
> A small muffin fan provides air for cooling. (I'm a use what I got kind of guy).
> 
> Questions.
> 
> 1. Would a larger version (bigger, longer electrodes) of the cylinder gap
>    provide better perfromance?



Not likely, but try a larger surfaced gap.  R. Hull


> 
> 2. Do I need more than 7 gaps to adequately quench my neon bank? (12kv-at-100ma)
>    Or another set of gaps in parallel with the first?




Definitely not!  It sound like you are at "the rope limit".  R. Hull



> 
> 3. I have seen references to vacuum gaps in the archives but very few details.
>    Could somebody who has built one give some details and what kind of results
>    were obtained.




The details are.... put the series gaps in a box or plenum so that no air 
can get in except by straining through the "teeth" of the gap.  Next, 
mount a vacuum cleaner blower assembly to the box in such a manner that 
cool outside air must be sucked through the working gaps into the box and 
exhaust from the blower.  We show several of these during construction 
and operation on our video tape reports.  The results were excellent.

R. Hull



> 
> 4. The message I get from the list archives is that rotary gaps are not
>    for neons. The message is loud and clear that using a rotary on a neon
>    is inviting transformer failure. Why? What is it that promotes a failure?
>    I'm not likely to build a rotary anytime soon but would like to know just
>    the same.



The rotary forces a break rate!!!!  Most beginners run the things at 
countless billions of breaks per second!  Somehow or other, they find the 
20,000 rpm motors and put 24 studs on a 6" diameter wheel and hum the 
thing up.  This shortens the lifetime of a neon sign by about 10,000% 
over just shorting the ouputs together, plugging it in and walking away.

The series static gap allows the, naturally weak, neon transformer to 
supply energy and quench the spark in its own good time and at levels 
relatively comfortable to its natural desire to squelch the output 
voltage.  This avoids any ill timed interupts and reflections from the 
tank.  Still, the transformer is doomed!

R. Hull, TCBOR

 
> 
> Any input appreciated.
> 
> Mike Hammer
> mhammer-at-midwest-dot-net