Re: This week is the week...need help on spark-gap spacing

To: tesla-at-poodle.pupman-dot-com
Subject: Re: This week is the week...need help on spark-gap spacing
From: Tesla List <tesla-at-stic-dot-net>
Date: Fri, 30 May 1997 22:32:29 -0500
Approved: tesla-at-stic-dot-net
Subject:  Re: This week is the week...need help on spark-gap spacing
  Date:  Fri, 30 May 1997 15:34:59 -0400 (EDT)
  From: Esondrmn-at-aol-dot-com
    To: tesla-at-pupman-dot-com


In a message dated 97-05-30 06:58:20 EDT, you write:

<< I am finally at the end of a three month endeavour and need help on
 setting
 my spark gaps.
 
 I have a 15KV 60mA neon, 15 turn 3/8" tubing primary with .0105 uF flat
 plate cap (freezer bags and aluminum foil), 1050 turn 6 " secondary
(#22
 AWG) and 24"x4" torroid. I am using a single forced-air gap.
 
 I have checked the resonant frequencies of my primary circuit with
 scope,
 sine generator and freq counter set up and have an incredibly high-Q
 primary. (deviating 5% from center frequency I almost lose the signal).
 I
 have made some 180uH protection chokes for the neon and have protection
 spark gaps made on the neon side. 
 
 Would someone please help me with a startup procedure for this? I
intend
 to
 mount the secondary tonight and find its resonant frequency and then
 match
 the primary to it before any startup.  
 
  I would assume I  should start with the protection gaps pretty wide
 open
 and a fairly narrow main spark gap and a low variac voltage. I then
 intend
 to slowly increase everthing until I am running at 110Vac on the
variac.
 What should I expect for approximate final gaps for the main spark gap
 and
 the protection gaps (just ball-park).
 
  Also, how can I best tune this ? I have heard of holding a discharge
 ball
 near the torroid and tuning, at low power, for maximum discharge
length.
 I
 am concerned about over/under coupling (my conical primary (30 degree
 rise)
 is 8.5" diameter on its center with an insulating plastic between it
and
 the
 secondar). THe base of the secondary winding is about even with the
base
 of
 the primary.
 
 Thanks alot for your help.
 Shawn
  >>
Shawn,

The physical geometry of your secondary and primary is almost exactly
the
same as mine.  I would start with the safety gaps set at about 1/2". 
For the
main gaps I would use a series of gaps to add up to about .15".  I think
my
static gaps that I used to use for up to 12kv 120ma was 6 gaps of .030"
each.
 Set the tap where you think it should be.  Place a small wire or other
sharp
object on the toroid and then suspend a ground wire (to the main RF
ground)
about 24" away.  Slowly bring up the variac voltage.  Arcs should break
out
with about 40 to 50% of variac full power.  Run it all the way up for
several
seconds and make sure there are no problems - like arcs where there
shouldn't
be.

The sparks should be hot and heavy to the ground at this point.  Now
slowly
move the ground farther away and retest.  Get it to the point where it
just
barely hits the ground wire at full power.  Now try going up and down
one
full turn on the primary and compare the results.  Once you find the
best
spot, try moving it up and down maybe one half turn.  Tune for best
sparks.
 When you get done and remove the wire on the toroid, the full power
best
tune spot will probably be about 1/2 turn farther out due to a more
intense
ion cloud around the toroid and effective more capacitance and thus
lower
frequency.  Set the safety gaps so they just ocassionally fire.  I think
mine
are set at about .50 to .65".

Keep us posted.

Ed Sonderman