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Re: Cap Size
>From: Stephen G Stanton <ulflyer-at-juno-dot-com>
>To: tesla-at-pupman-dot-com
>Subject: Cap Size
>
>Hi all:
>
>I believe I have the coil in resonance. I don't really have a toroid;
>rather, it's two 10" salad bowls tackwelded together at the bead. I get
>a wonderful writhing display of corona off the bowls, especially at the
>bead, and can draw out about a 14" arc at will. Despite my best
>efforts, I can't get more, and yet, from what I am reading, with the 120
>ma or so going in, I should be getting much longer discharges.
>
------------ include old message ----------------------
>Everyone,
>
>
> I hooked up one side of the 15Kv 60ma "bad" unit in place of my Xeon
>starter xformer and immediatly had 1' sparks break out from my 28" by 4"
>torroid! My little starter xformer would never do that.
>
>
> Specs:
>
> primary: 15.5 turns inverted cone 1/4" copper tubing.
> 11.75" inside diameter
> 41" outside diameter
> 30 degreee rise.
> 124 uH measured inductance.
>
> cap: 0.0137 uF measured
> 10" by 96" rolled flashing and 0.060" polyethylene
> in transformer oil.
> I'm a little woried about blowing this with 15Kv.
>
> Fo 122KHz
>
> spark gap: three 3/8" by 1 1/2" carriage bolts. I will build an
> RQ cylinder gap today!
>
>
> Secondary: two polyethylene trash cans glued together 7.5" to
> 8" to 7.5" 20 5/8" long.
> wound with 22 A.W.G. magnet wire. 2 coats of water
> based polyurethane over it. Oops!
>
> 33.4 mH measured inductance.
> 238Khz self resonant frequency => 13.5pF self
> capacitance
> 133Khz resonant with 28" by 4" torroid => 30pF
> torroid capacitance.
> note: the torroid was
> measured on the coil which was sitting
> on the floor of the garage.
>
>
>Any thoughts? comments? At this level of Power, 7.5Kv 60ma, what size sparks
>are reasonable?
>
>
> jim
>
> ps.
> I mispelled tesla and this message bounced. Since then, I've built
>RQ's gap and got a (measured, straight line distance) spark of 20".
>
> I can't say more power anymore. I have to say MORE
>ROOM!
>
> jim
-------------------end include-----------------------------
I almost doubled my spark length 1' to 20" by changing from 3 bolts in
series to a 7 (I think) cylindrical gap.
Before warned thought, you may blow you cap with the higher primary
voltages generated.
>I was in the process of building my own a-la the 5 gallon bucket of oil
>and hundreds of baggies and foil, but I opted instead to go for the
>ready made variety -- seemed more cost-effective to me. I took the
>plunge with the group purchase, but when it fell apart, I had second
>thoughts. Now I'm wondering if I should go for the commercial cap to
>see if it will improve the discharge. Am I on the right track, or is
>this a matter of not having the right toroid, or perhaps cleaning up the
>corona leakage?
remove the "ring" and use Al tape to smooth out the edge.
> Or, is it the gap? I'm only using a simple series gap
>with 1/4-20 brass bolts, which seems to work nicely, but nowhere near as
>complex as the series gaps I've seen posted by Richard Quick.
The cylindrical gap quenches much more rapidly than a simple gap.
Which means much less power lost in it's arc.
> As I open
>the gap, the discharge increases, but then I get ominous green flashes
>from the cap. By past experience, this presages a punchthrough of the
>plate glass and then -- dismantle and cut and paste to fit around the
>shattered parts!
>
Try a rolled cap. When you blow it, you will know how to repair it.
I've smoked 3 so far and will spend part of today rebuilding them.
>Any advice at this point would be much appreciated. I very much enjoy
>the postings on this net, and of course am enthralled by watching my
>coil do its thing in darkness!
>
Stephen,
Your glass cap has a very high loss factor, you toroid has a
sharp edge and you gap is not quenching rapidly enough. The last 2
should be easy to remedy. The cap will just take a little effort.
Try air blowing your gap with compressed air throught a hole drilled
in 1 electrode and peening over the lip of the bowl.
Good luck,
jim