[TCML] Field expedient capacitors
Davetracer at aol.com
Davetracer at aol.com
Thu Dec 4 16:35:42 MST 2008
First, use bottles with good long necks. Corona beer bottles are excellent.
My suggestion, and what I've done for awhile, is to wrap each beer bottle in
aluminum foil on the outside. (Don't extend the aluminum wrapping up the
neck.) Leave a good foot of aluminum foil to crumple into a "wire". Use some
regular wire to hold the aluminum wrapping in place. I've tried various tapes,
glue, and whatnot, and this is a good "keep it simple" place.
If you want, that wire is "good enough" to make contact with the aluminum
foil, so after wrapping the aluminum foil, put a wrapping of, oh, 5 turns of
bare wire on it to hold it tight, then "tie off" the wire so it doesn't slip,
but don't cut the wire, then bring the wire out to a common connection, one
wire per bottle. I would say thick wire is better; the current through the
primary of the Tesla Coil is something else!
If you twist up the aluminum foil "tails" it boils down to the same thing.
I'm sure there will be a little electrolysis happening between the aluminum
foil and wire in the water, but most Tesla Coil runs are in the 30 second
range, and I've never observed a wire going "green", as I have in electrolysis
Don't be too clever on the inside of the bottles. I tend to run a bare wire
with a bolt on the end just for weight. Trim so that the insulation works
with the top of the corona bottle; don't drape a bare wire over the lip of the
I tend to use salt water and no oil at all. I've never had a bottle fail,
and I'm trying to keep things simple. Stop filling when you begin to go up the
neck of the bottles. Fill the bottles first and make sure they're physically
secured (any sort of packing the bottles into one unit helps), then fill the
container, hook up your wires, and go.
>From time to time, you'll need to add a little water.
A less reliable, but very quick, capacitor can be made up of 18" x 18" glass
or plastic (I was surprised to find that Home Depot doesn't cut glass
anymore). On each side, center up a 14 x 14 piece of aluminum foil. Run a wire
under the aluminum foil; bring out the wires on opposite sides. Tape it down.
Then pack the capacitors with like-sides together. About 3 of these kept a
12kv/60ma transformer happy. 4 was too much.
Primarily because of dielectric heating, you will get the occasional
punchthrough on these. There's several methods of fixing it, including putting glue
in the tiny hole, just cutting around the aluminum foil so it's not near the
hole, and so forth.
As I said, this is pretty field expedient but will get you running quickly
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