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Re: [TCML] Capacitor calculator?



----- Original Message ----- From: "Quarkster" <quarkster@xxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Thursday, September 17, 2009 2:39 PM
Subject: Re: [TCML] Capacitor calculator?


Paul -

How well did the metal Leyden jars work?

Regards,
Herr Zapp

If you mean metal jars laminated with dielectric, not so well. I tried layering on plastics of various kinds, shellacked paper, neoprene (!) and even liquid tool grip rubber. I then put a layer of metal foil on the outside of that. This worked, but feebly. I suspect the integrity, smoothness, and dielectric strength of the coatings was not the best. My dream was to find metal and dielectric cylinders that fit neatly and naturally into each other. The closest I came was 16 oz peroxide bottles and 12 oz soda cans. Lemonade canisters are best, but they require heat to soften the plastic to allow the can to fit.

I tried a lot of metal fillings. Two of the most interesting were copper scrubber pads and copper clad BB shot. I put 2-3 scrubber pads in a 500ml HDPE wide mouth vitamin bottle (the sort called in the industry a "packer" bottle). I used a length of 10 gauge copper wire inserted in the mesh and connected to a brass top terminal. The outside of the jar got the usual aluminum tape. These usually gave me about 150 to 200 pF. The same bottle 2/3rds full of BBs was good for 250-300pF. These were pretty heavy. Using BBs does allow to vary the capacitance at will by mounting the jar sideways with interruptions in the exterior coating. By rotating the jar (and the BBs inside) you can vary the capacitance. This is more useful in crystal radio experiments though.

I tried the usual 5 gallon bucket jar. My results were inconsistent. I got a lot of arcing and perforation of the dielectric, which on a jar that big was rather, um, exciting. I think a better grade of plastic would give better results, but once I fixed on the soda can design I haven't gone back to the big bucket.

Paul

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