Re: Here are my current specks

["Paul Mathus" <pmathus-at-learningco-dot-com> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Garry,

You can test your nst by seeing if you can draw an arc from each HV lead to
the 
case, which should be grounded.  Be very careful doing this, do not hold
the HV 
leads with your hand.

Have you checked for corrosion on the spark gap?  I don't know about Al, but 
brass corrodes quickly, which could account for your story of good output at 
first, then worse and worse.  Check your doorknobs for corrosion, and sand it 
off with some sandpaper if there is some.  Better yet, use copper tubes
instead.
They will still corrode, but not as quickly as brass. 

paul

______________________________ Reply Separator
_________________________________
Subject: Here are my current specks: Was I give up!
Author:  "Tesla list" <tesla-at-pupman-dot-com> at INTERNET
Date:    8/22/00 12:19 PM


Original poster: "Garry F." <garryfre-at-pacbell-dot-net> 
     
     
Ok, I read a lot of replies and lots of people asked what my coil 
configuration was.
     
Ok, here it is. As I mentioned before, I built it according to plans from 
sciencefirst-dot-com but
     
it did not work as advertized (Oh what a surprise).
     
NST is the same in all cases 9,000 volt at 30 MilliAmps
     
Given this NST, I caculate the Impedance as being 300,000 ohms
     
I caculate that I need an .088pf capacitor or since I have two in series, I 
will need two about
176uf each.
     
My current caps are aluminum flashing stacked with two 12mm sheets of poly 
between them. The plates
are such that there is 6.5 inches of overlap. the sheets are 4" wide so I 
caculate an area per plate
of 26 square inches.
     
Using the formula I saw in Brent Turner's book and given the thickness, I 
calculate that I need
35 sheets.
     
Primary is #14 wire, about 40 windings with lots of bare spots for tapping. 
Secondary is a 3" PVC pipe covered with 24 inches of #29 wire.
     
There are three chokes composed of #29 wire wrapped over a half inch thick 
dowel. The length of the
windings are all 3.5" each. One choke on each high voltage lead from the NST 
between the spark gap
and the NST. The caps are in series with the primary winding and the other 
end goes to one side of
the spark gaps. This isolates the primary from the rest of the circuit as 
far as the 60 cycle current
is concerned. The primary is center tapped in the center after tuning 
through a third choke with the
same configuration as the other two.
     
My best performance was off a spark gap composed of flashing rolled up at 
the ends that was mounted in
a 4" PVC joint with a muffin fan on top.
     
I had about 12-14" sparks and similar streamers off this with a 2" X 8" 
commercial spun aluminum
toroid.
     
One person here said given what I had, I should not have trouble getting 30" 
sparks.
     
In each case where I had a degradation of performance when I tried to change 
the spark gap I
observed a drastic loss in performance. In each case, I tried different 
things to make the new
spark gap to work even romotely as well as the original all failed. Attempts 
to revert to the
original gap design mentioned above resulted in performance that was not 
quite what I had before
I tried to change it. Over a period of several attempts the output of the 
coil seemed to deminish as
each attempt to successfully resulted in failure and attempts to revert, 
ended up in more failure.
     
Finally, I tried two brass doorknobs. Flat surface area inside the same PVC 
joint with the same fan.
Result was a significant improvement in performance to the tune of 16" 
sparks. The best yet!!
     
The next morning, I turned it on and the gap would only fire sporatically. 
So, I closed the gap a bit
and by the time I got some reliable firing the sparks were quite a bit 
weaker. They were thinner and
much shorter, with less bang and noise from the toroid.
     
The spark gap too sounded different. It had a rat tat tat sound that was 
noticeably slower and only
half of normal volume. Before the failure, the spark gap was quite loud with 
a rapid sound similar to
a chainsaw.
     
I tore open the caps that had 17 plates each - According to the 
calculations, I need 35 plates each
because they are in series but I noted that the more plates I added the 
weaker the system seemed to
become. I inspected each plate carefully, and there was NO sign of any break 
through the electrolyte.
     
After trying to work with it today and tune it more and trying to increase 
the number of plates I got
some better performance but the gap simply does not have the loud BANG it 
had before, tho the frequency
seems back to normal. The spark length is about 8" but are half as loud, and 
only half as thick as they
were before. Streamers are also thinner but more of them, the streamer 
length is only 3 or 4 inches max
compared to 15" or so streamers the night before they failed.
     
It does not seem to make sense to me that the closer I come to the supposed 
35 plates each cap, the
less performance there is. There is something wrong but I don't know what it 
is.
     
Can someone confirm the above calculations for me? I am prone to error to a 
most astonishing degree
and I don't trust my calculations any farther than I can throw a fully 
loaded and operating washing
machine! I transpose figures, I fail to see stuff that is right in front of 
my face and am capable
of great overvation and the next I can act like I never had an eye or a 
braincell to my name.
     
My guess as to what is wrong is that the NST has fried partially and I am 
not getting the current
I should be getting out of it.
     
The second guess is that somehow the ozone had rendered the electrolyte in 
the caps as conductive
but it is hard for me to believe that this can happen over night.
     
As for getting a new neon sign transformer, this is rather problematic as 
the only shop that has any was
recently bought by "Newbies" who said themselves that they do not have a 
clue of what the value
of anything they have in their inventory and seemed understandably reluctant 
to sell or give away any
used items.
     
You should know that I live in an Apartment. There are no garages. So, I 
have nothing but hand tools at
my disposal and I must eyeball things to make sure they are parallel as best 
I can. I'm not terribly
accurate due to a history of near blindness that was left untreated so long 
as a child that my depth
perception is only 10% of normal. I do what I can, but having even a table 
saw is totally out of the
question in this apartment.
     
I wish I could hope that I havent' forgotten anything but I know for certain 
that I have.
     
It never fails. At least I got a nice video of my tesla coil operating well 
and frying some nasty
meat bees before it died or became severely ill.
     
My next step, is to start stripping off a plate on each cap, and 
reassembling and retuning and trying
it out until I either note a decrease or a plateau in performance. I think I 
need LESS plates not more
     
I used to use doorknob caps. Boy those things created some lovely output. I 
wish I could get my hands
on some of those. Sure they wern't the best but they beat the stuffins out 
of whatever other
failed caps I tried.
     
I would appreciate any help. I thank you all. I note that nobody flamed me. 
This I bet would never
happen in any discussion group as most other groups are more like a pack of 
wolves that jump another
when one of them go down. I am most impressed with the kind and never harsh 
replies I got from this
group. You should all be proud.