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Yesterday's GNATS meeting (fwd)



---------- Forwarded message ----------
Date: Mon, 27 Apr 1998 21:44:07 -0600 (MDT)
From: Chip Atkinson <chip-at-pupman-dot-com>
To: tesla-at-pupman-dot-com
Subject: Yesterday's GNATS meeting

Greetings all,

Yesterday was another meeting of the Greater Niwot Area Tesla Society.
Mike 
Hollingsworth came over and we fired up my 9" coil for the first time.  

This coil has about 1000 turns of 22ga wire around a thickwall pvc pipe. 
I believe that the coil form is 8" diameter pipe, but the o.d. is roughly
9".  We tried a couple toroids, different capacitor configurations,
different power levels, different gap settings and the effects of
different tunings.  We also had an oscilloscope running and watched the
wave forms when the coil was in and out of tune.

We also discovered that there are some situations where you actually get 
better performance when you let the smoke out.

Here are the details.  Mike came over and brought some goodies such as 
large magnets and an old variac that I'll have to play with.  We decided 
that we'd most like to play with the 9" coil that I had finished but 
never gotten working.  I recently acquired three rolled caps and put 
one of these into the circuit in parallel with the existing capacitor.
The new capacitance total is roughly 0.04 uF (0.025 + 0.017).  The
toroid is one that I had on my 4" coil, a 7x21 or so.  We got some
pretty decent sparks.  However, the problem is that I have several
space problems.  I have a garage door that I wish to keep alive, and a
garage that's suitable for a good 4" coil.  Therefore, we had to keep
the sparks pretty short and directed using a sharpened piece of wire
on the toroid.

Next we decided to try a series gap in series with the rotary.  This
didn't work too well, and we thought we'd try reducing the gap between
the stationary and moving electrodes in the rotary so there wouldn't
be too much total gap to bridge.  This didn't help too much either, so
the stationary and moving electrodes in the rotary so there wouldn't
be too much total gap to bridge.  This didn't help too much either, so
we started backing out the series gaps until there were none at all.
Now, with the reduced spacing of the rotary, the coil did much better
than it had.  Out with the stationary for now.

The next idea to try was adding another capacitor to give a total of
0.06uF.  We didn't notice much if any improvement, but we did notice
after a few seconds, that some smoke was starting to rise from
somewhere and there was an orangish colored light coming from the
rotary gap.  An immediate shutdown followed by an investigation
revealed that the rotary gap was chock full of smoke (the rotary is
totally enclosed in 1/2" lexan and 1" plexiglas).  After letting the
smoke out of the enclosure and removing an end of the enclosure, the
coil was back to its previous glory.

The other two things we tried were running the scope and a larger
toroid.  The scope was interesting.  With the coil in tune, we could
see the sort of dual hump damped wave profile.  When it was out of
tune, there were between 4 and 6 humps and a much shallower angle of
decreasing amplitude.  I took pictures and if they turn out, I'll send
them to someone for scanning and subsequent posting.

The larger toroid probably had a beneficial effect, but I can't say
for sure because it effectively decreased the distance between any
grounded object and the coil.  I was basically running an RF jacobs
ladder between a piece of grounded pipe and the toroid.

I guess the next thing is to put the coil outside and really throttle
it up to see what it's capable of.  Next I'll start fiddling with it
to see how I can increase the output.

Chip


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
 Chip Atkinson 
 http://www.pupman-dot-com 
 --- If I can't fix it, I can fix it so it can't be fixed --
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