RE: Static gap behavior

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: C T <ct451-at-yahoo-dot-com> 

All the tables I came across that list break down
voltages mention either spherical electrodes or needle
point ones. I was just wondering how they compare with
cylinders. Jim Lux's suggestion of 70k/inch seems
about right.

I'll make a few more gaps at 0.06, .07 and .08" and
see which one works best. I've tried blowing air on it
with no improvement in performance but was unaware of
this behavior back then. It would be a pity to spoil
this motion of the arc in any case.

http://www.geocities-dot-com/ct451/minicoil.html

The major problem with the coil is in the top load
because I never got around to finishing a toroid for
it. Just a tray on top, however, is handy for
destroying unwanted electronics (laptop) from work.
I'm probably the only person in this list that works
for KPMG (yes I work with accountants) so I think I'm
safe to mention that I mainly built this small coil to
take to work when my manager went on a weeks vacation.

Chris


--- Tesla list <tesla-at-pupman-dot-com> wrote:
 > Original poster: "Lau, Gary" <gary.lau-at-hp-dot-com>
 >
 > Hi Chris:
 >
 > A 50 mil gap is not too small for a 4kV power
 > supply, that is what I use
 > with mine.  The arcing along the length of the gap
 > is consistent with what
 > I see on mine.  I've always thought it was strange
 > that the gap arc
 > wouldn't come to favor some point like one of the
 > ends, where there is an
 > edge, the temperature would be the highest and once
 > started, the
 > concentration of ionized gasses would be highest.
 > It's not clear what
 > "motivates" the arc to move from any one place to
 > another.  I'm just happy
 > that it does!
 >
 > There are tables that predict breakdown voltages
 > between various electrode
 > shapes (see
 >
http://hot-streamer-dot-com/TeslaCoils/Misc/SGapVolt.jpg),
 > but
 > there are so many variables that affect this, that
 > its better to just hook
 > up your NST to the gap and adjust it with no tank
 > circuit until it just
 > fires.
 >
 > Have you tried blowing air at the gap with a small
 > fan?  Beyond using the
 > correct cap size and getting the tuning and coupling
 > right, I've found that
 > top load size matters a lot!
 >
 > Gary Lau
 > MA, USA
 >
 >
 > Original poster: "C.T." <ct451-at-yahoo-dot-com>
 >
 > I'm using two horizontal 4.5" pieces of 1" copper
 > pipe as a gap on a small
 > coil running on a 4000/30 NST.
 > The gap is too small <0.05" apart and I only get
 > 6-7" streamers on the top
 > but I noticed a peculiar behavior while the coil is
 > running.
 > The actual spark  will only be ~3/4-1" along the
 > length of the pipe but it
 > starts on one end and slowly moves up length of the
 > pipes over a number of
 > cycles (or so it appears to the naked eye).
 > When it reaches the end it will either turn back and
 > come down the opposite
 > direction or jump to the other end and start moving
 > forward again.
 >
 > More ionized gasses at the side of the previous
 > spark or something I'd guess.
 > Is this normal behavior for this type of gaps or has
 > anyone observed the
 > same? How does this affect the performance of the
 > coil?
 >
 > Also I was wondering if there's a rule of thumb or a
 > table somewhere that
 > gives approximate breakdown voltages for gaps with
 > cylindrical electrodes.
 >
 > any input welcome,
 > Chris
 >
 >