Re: Cap Size

In a message dated 96-07-27 23:06:33 EDT, you write:

>Hi all:  
>I've got my coil back in action with four banked 15kv neons at 30 ma
>apiece.  I'm using my old plate-glass-and-foil 90 lb cap which, when I
>first designed it, was 0.02 + or -.  The gap puts out a mighty roar
>indeed, and judging from the temperature of the line cord (from a
>microwave oven), it's drawing in the neighborhood of 18 to 20 amps.
>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.
>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?  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.  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!
>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!
>Thanks again.


It sounds like you have built a nice system.  I don't recall the specs on
your primary, secondary and ground.  You might post them.  It sounds like you
need a better spark gap.   I would recommend the cylindrical gap as described
at the ftp site.  I have built two of these.  One works great for the amount
of power you are using.  The large copper pipe gives lots of surface area and
the fan helps keep things cool.  A series of gaps works better than one or
two.  Mine have seven copper pipe sections for seven gaps of .030 each.  Once
you build a gap like this it sounds like the higher operating primary voltage
will destroy your capacitor.  I would suggest a commercial cap about this
time.  In order to maximize your system, I think you need a larger toroid.
 Make one out of six inch dia. plastic corrugated drain pipe, covered in foil
tape - probably 24 to 30" in diameter.

Good luck,

Ed Sonderman