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Re: Here are my current specks: Was I give up!
On 22 Aug 00, at 11:38, Tesla list wrote:
> 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.
Stop. That should be 8.85nF (8,850pF) for resonant charging
from the mains.
> 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.
Recheck all that based on the capacitance I just gave. If it
turns out that C is about right regardless, you're about right
in that dept.
> Primary is #14 wire, about 40 windings with lots of bare spots for tapping.
Diameter? Height? Type of winding (helical, flat etc.)?
Boring details but essential.
> Secondary is a 3" PVC pipe covered with 24 inches of #29 wire.
Taking a stab at guessing the insulation thickness of the
wire, that sounds like around 2000 turns. Correct? Pse confirm
before I can do further calcs.
> 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.
Those chokes sound like a recipe for NST disaster. I'd rewire
the primary circuit to the simplest form possible - gap across
the transformer and from there the primary series'd with the
cap/s. The chokes do NOT isolate the system from 60Hz mains.
In theory they're supposed to isolate the transformer from
high frequency transients generated by the gap but I'd expect
them to cause more strife than they cure.
> 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
> One person here said given what I had, I should not have trouble getting 30"
> 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.
I wonder if the transformer is still OK? Too soon to judge
> 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.
That sounds like progressive detuning of the system as primary
capacitance is altered.
> 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
My #1 suspect is the cap followed by the transformer.
> 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.
We need much more data to calculate what your system is doing.
I've asked for the relevant bits above. Also, please reiterate
what type and size of terminal.
> 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.
The "electrolyte" should in fact be dielectric or insulating
fluid. What dielectric (e.g. glass, plastic) are you using
between the plates?
> 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
Before you do a thing, post the specs asked for and let us do
> 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.
I know this isn't exactly related, but later today I will have
a couple of jpgs available for viewing of my upgraded work
coil in action. The original can be seen on Bert Pool's
website. BTW - the wire size is 0.56mm, not 0.1mm.
Significant mods which have increased performance are an
improved transformer, a much larger top terminal, 50% more
primary inductance which greatly decreased primary losses and
some air through the gap which is now necessary to prevent
power arcs. Does someone on the list have a place where the
pictures could be posted for viewing? Please email me offlist.