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Re: Spark gap not firing
Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>" <Tesla729-at-cs-dot-com>
In a message dated 2/2/01 8:45:06 PM Pacific Standard Time, tesla-at-pupman-dot-com
built a foil stack capacitor composed of five aluminum flashing plates that
were 5" x 7" sandwiched in between them was a rubberized adhesive coating
which I do not know the exact K value for. The rubber adhesive was four
across and covered the length of the aluminum plate, giving a capacitor area
4" x 7". The rubber layers is about 1/64" of an inch across. >>
I would say that your cap is shorting your NST out. You say that the aluminum
plates are 5" x 7" but your rubber adhesive strip is only 4" wide, if I'm
standing you correctly. The dielectric MUST must exceed all deminsions of
the conductor plates or the HV will easily arc around the egdes of the dielec-
tric or worse yet, the foil plates will lay on each other where they overlap
dielectric and completely short out the transformer. You need at least a 1"
clearance of dielectric on all sides of the conductive plates, i.e.- 6" x 6"
tive plates need at least 8" x 8" dielectric plates between them.
Also, you will definitely need a dielectirc thicker than 1/64" for a Tesla
capacitor. And it will need to be oil-filled and vacuumed down or it will
fail. In my opinion, if you can afford it, you need to buy some of Terry's
sonic .056 uFD MMC caps and build your cap from that. I think this would
save you a lot of headache in building your capacitor. I've successfully built
homemade caps that would hold a charge and give a visible spark discharge,
but I have never successfully built one that was suitable for Tesla service.
Some people have, but most them had skills and facilities that are beyond
the average hobbiest reach. And in the long run, it would probably be a lot
cheaper for you to buy the MMCs than to buy the polyethylene sheets and
alum. flashing and then it fail on you anyway :-(
My $.02 worth,