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10 tests and suddenly...RRRAAAATTTTT!!!

Subject:  10 tests and suddenly...RRRAAAATTTTT!!!
  Date:  Sun, 11 May 1997 03:42:01 +0200
  From:  tesla <tesla-at-ixx.se>
    To:  tesla-at-pupman-dot-com


Hi all.

Just returned from my test site and now i believe i can't stop doing
this 
anymore. Yep, just got my coil working after 9 or so miserably 
unsuccessful testruns. Here's the specs :

Primary : 10 turns of 0,8mm coppertubing and 1cm spacing 
           Angle : 5%

Secondary : 1000 turns of 0,6mm enamled copperwire 
             Height : 60cm
             Diameter : 16.5mm (0,4mm walled PVC pipe)

Cap : Homerolled poly cap. 29,3nF approx. capable of 20kV pulse 
        (Very overdimensioned!! Just in case)

Transformer(s) : 6 4kV/45mA transformers wired in series and paralell
                 for a total output of 8kV/135mA. About 1,08kVA

Other : Toroid - Dia : 70cm x 11,5cm covered with aluminumfoil
         Spark gap : R.Q with 7 electrodes and 12V high speed fan.

I gotta tell you i really didn't think i would ever get this thing to
work.
The first 1-7 times we struggled with different configurations with my
two
saltwater caps. We tried large capacitance and small and we probably
tried
all combinations in wiring the components together. What happened was
nothing!
We didn't even get corona in the caps. 
 
So the next 2 times i tried to wind new primaries and that did seem to
help
somewhat. We got some sparks hitting the secondary from the
primary.(Lyckily 
it was only to a bad solder that has now been fixed and insulated)
And we actually got the thing to burn two times at different places.
At those two times we got some puny 3" thin blue sparks from the toroid
to 
a grounded lifting jack. We got soo happy that something at all happened
that 
it took us about 5 seconds to notice the little forest fire at the back
of 
the coil. No harm to the coil though, just minor burns to two of the
primary
plexi holders.

Oh well, at the last session we actually got a different sound in the
spark
gap
and some nice corona clouds appeared at the bottom of the coil. I think
i did some sort of happy dance and shouted "-It works!". Well, i
shouldn't
have
done that, the next second a white hot arc shot up from the 4'th or 5'th
turn
on the primary to the secondary. I turned off power really fast!
No harm still done to the coil. Some new fresh polyurethane to the
bottom
af the
secondary and it was set to dry until the next session.
The next time we didn't get any results at all. I saw the problem wich
seemed
to reside in the saltwater caps. Small yellow and blue sparks were
surrounding
all my bottles. This sessioen ended rapidly and i said to myself -"What
i need
is a good cap!"
My disappointment was HUGE! (Well, i was sorta happy that we got some
sort of 
oscillation in the tank circuit on the previous session)

Now don't think that i haven't done any calculations or do things the
"Edison"
way from the beginning, even though it may look so. Every piece of the
coil
is calculated and measured as according to all formulas and
specifications.

So tonight we set up the stuff as usual and plugged my new cap in. On
the 
first run we got many many white arcs 8" long to the same grounded
lifting
jack.
I was IMPRESSED, but this was only the beginning.
We tried to pull the grounding target further away. At about 11" there
were
only few sparks flying so we thought for a moment and decided to add
more
turns 
to the primary. The problem was that there were no space to add any
turns
outward,
so we figured that we probably wouldn't get any sparks hitting the
strike
rail.
Said and done the strike rail now became another turn in the primary and
we
also
added another turn between the outer "real" primary turn and the strike
rail.
With this new configuration i just tried for fun to see if any sparks
would 
emanate without any grounded target. The lifting jack was about 4 feet
away
at this time.
I went to the variac and cranked it up when
suddenly......KKKKRRRRRAAATTTT.
Some really fat purple and white arcs jumped around the toroid and some
shot of to the lifting jack. I was STUNNED! 3-4 footers continously!!

Now this might not seem very impressive to some of you experienced guys
but
to 
me, with all my failed tests this is a real big leap forward.
I'm off to coiling heaven. Nothing(except power) will stop me now. I'm
hooked!
It sure is one thing to see pictures of a running coil and experience it
live!
The sound it produces is really agressive.

Well, all things must come to an end. After experimenting around with
light
bulbs
and other things one(or more) of the transformers died ending my fun
abruptly.
I didn't do any more tuning to it since i reached the limit . I might
have 
gotten even longer sparks if i had more primary turns. What i know is
that it
sure isn't tuned to its optimal point.
But i don't care, i have three newly renovated polepigs waiting to be
used.
Two 2kVA and one 4.5kVA so i can go up in power successive.

I won't bore you anymore with this but instead i've got a question
regarding the
cap.
Why is it that the capacitance recommended by different programs and
even the
"hand" calculated values are way too big?? The only way to get it near
the 
"correct" value is dividing it by two.
I think i must agree with Richard Hull here. Theory and practice are two
very different things, yet one can't live without the other.

I'm off rebuilding things, see you later.....   =)

//Matt