Re Second change for longer sparks (fwd)

---------- Forwarded message ----------
Date: Wed, 15 Jul 98 10:09:55 EDT
From: Gary Lau  15-Jul-1998 0954 <lau-at-hdecad.ENET.dec-dot-com>
To: tesla-at-pupman-dot-com
Subject: Re Second change for longer sparks

>From: Marco Denicolai <marco-at-vistacom.fi>
>After using a bigger toroid and getting improvements:
>air streamers from 20" to 31"
>streamers to grounded point from 20" to 24"
>I have reduced my RQ spark gap gaps from 0.0275" to about 0.007". This was
>mechanically not so easy and I ended up with a clearance between 0.005" and
>0.01" (about) different between different sections. Not good...
>Before I was using two series of 0.0275" gaps in parallel. Now I could use
>a single series of 10 gaps and have the safety gap strike intermittently. I
>tested with this setup and I didn't notice any improvement (or worsening) of
>the streamers. Spark gap sound was intermittent as with the old gaps.
>Then I started reducing the number of gaps until I was using 5 gaps. The spark
>gap sound was then almost continuous and I got longer streamers! About 35" to a
>grounded point and over 40" into air.
>My problems:
>- the gap gets extremely hot very quickly
>- some of the gap sections get filled with some black stuff (cupper oxide?)
>- I don't quite understand what is going on!
>Please, help me to figure out what I am doing...
>- I suppose I have just increased the spark gap breakout repetition rate as well
>as I have fed the primary with less voltage. Higher discharge rate seems to be
>better for longer sparks than higher voltage. Am I right?
>- Higher repetition rate stresses more the spark gap that gets really hot. Is
>that the way it should work or what should I do?
>- My ideas (also after reading the list mails) about the relation between:
>   - spark lenght
>   - primary voltage at gap breakout
>   - breakout repetition rate (60 Hz, 120 Hz, more?)
>   - spark gap quenching
>are VERY confused. Could please someone give a brief (or long if he can)
>explanation about the above factor interaction?

A little more info is required.  What kind of power supply are you using?
A simple gap arrangement like you describe is fine for small-medium
coils, but not so good for high current multi-KW jobs.  Also, do you have
any air flow over your gaps?  The fact that they're getting hot indicates
poor quenching, consistent with RQ-style gaps without airflow.

Gary Lau
Waltham, MA USA