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.
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>        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
>                                        jim
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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!
	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,