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Re: Refining 10kv -at- 23ma

Subject:     Re: Refining 10kv -at- 23ma
      Date:  Fri, 23 May 1997 09:52:11 +0000
      From:  Chris Gardner <gchristo-at-clt.mindspring-dot-com>
        To:  Tesla List <tesla-at-pupman-dot-com>
References:  1


Tristan wrote:
 >
> 
> Good job on your small coil! Can't tell you your at a good efficiency or
> not, but i can say your eff. is better than mine. My first coil uses two
> OBIT's in parallel, .01uF salt water caps, 1/4" coper tubing
> primary(cylinderical), 22awg mag wire round a 3.5" diam for 15", using 4"
> diameter stovepiping ellbows for about 1.25 feet across toroid. I get about
> 5 to 6 inch good discharge and can see corona out to about 8 or 9 inches.
> The funny thing about this setup is that it doesn't discharge unless there
> is a ground in proximity to it. Any suggestions? With another setup I use a
> small sphere about .5 feet diameter and .07 uF caps and get about 5" of
> discharge into the air without giving it any ground. I would appreciate any
> suggestions and I would like to know how you made your caps and how much
> they cost.
> 
> Tristan Stewart,CET
> (Ohio)

I followed the advice of the wonderful post on primary geometries that
suggested that inverted spirals were slightly more efficient than
cylinders.

It sounds like you did the same thing I did at first and stuck to large
a toroid on the top, I tried one that big and got no where, the size of
the toroid necesitated tuning out on the primary further than I had
windings. Ive used three toroids this coil, the first (toroidette) is a
steel chain ring, approximately 2" by 1/4" which works better than I bet
most would think, but it dosent hold enough, next was the teenage mutant
ninja turtle figure inner tube, a plastic toroid, covered in al tape,
about 4" by 1" which worked better, but I was still getting discharges
all over the place, Last, and best, was a piece of aluminum dryer duct
approx 4" in diameter, closed into as tight a circle as it would allow,
about 1 foot, stapled together and simply placed on a cut out pie pan
and placed on top of the coil. To my mind, for this coil, its about
perfect. I get one nice streamer which popped my primary at one point,
which is how I know I got 11".

as for the cap, approximate cost? ummm..... 14 bucks, mabye..

"The ice cream sandwich special"

two pieces of 1/4 or 3/8 glass, 7"x9"
one roll of .006 poly (heavy duty drop cloth stuff from Home Despot)
one roll of heavy duty Aluminum Foil
about a foot of half or 3\4 copper pipe
a couple of Eckerds sized containers of Mineral Oil
one tupperware container big enough to place glass plates in bottom,
with room to spare on the ends

before using glass be sure you have sanded ALL the edges with silicon
carbide sand paper, so it dosent cut you or whatever you use to bind
this thing up.

...start cuttin... 150 sheets of poly, same size as glass, 7x9
16 sheets of Aluminum 5" by the width of the roll, about 16 inches I
think
...start stackin... (this can be messy, so be prepared)  lay out first
sheet of glass, and lay on first sheet of Al, before placing any Al in
stack, round off the corners on one end, place it on the other piece of
glass and smooth it out with a dowell, then place on the stack with 1"
to spare on three sides, use a brush to sparingly paint on mineral oil
on all of the Al, out to the edge of the glass or poly. then stack 10
sheets of poly with a dolop of Mineral oil in the middle of each sheet
as you add it. Alternate you aluminum plates, and straighten the whole
affair from time to time.
Finish off with the other piece of glass. Clamp the whole thing, which
should cause lots of oozing. Bind the sandwich with some heavy nylon
string or such, striving to get it as tight as possible, you will
probably want to roll up the excess Al and temporarily clip it while you
do this. This thickness of glass is pretty tough at this size, so be
careful, but dont be shy, you want the distance between plates to get as
close to .060 as you can.
once your done cut two lengths of pipe to about 6.5 inches, sand them up
to make nice clean contact, solder some short lengths (5 inches or so)
of  #6 or #8 wire to the ends, and roll up the aluminum on each end of
the sandwich. I then placed a standard office paper binder clip on the
middle of each roll for good measure.
Place the whole thing in the tupperware, connect your wires through the
lid however you care, cover the sandwich in oil in the container,  seal,
and go for it man.

the surface area of the plates, 5x7 times sixteen plates at .060 poly
calculates to .004 ufd and the voltage rating is plenty for an Oil
burner. I prefer the stacked for two reasons 1) I agree with Fr. Mgahee
that many smaller plates dischage quicker than fewer larger plates and
2) if and when you blow this puppy, it just hisses and bubbles, it wont
do that grenade trick.

Also you could use heavy plexi or some other plastic for the outside of
the "sandwich" and drill it and use some kind of non conducting
mechanical connections to clamp it together, but I prefer the heavy
glass because its very rigid, and will clamp it all together much more
evenly.

Hope this helps, Im newer at this than most.