[TCML] Capacitor calculator?

[PAUL THOMPSON]

----- Original Message ----- 
From: "Quarkster" <quarkster at att.net>
To: "Tesla Coil Mailing List" <tesla at pupman.com>
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