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Re: [TCML] party cup capacitors



Leyden jars were my introduction to the high voltage hobby. I built a lot of them, made of different found objects, foil, metal tape, etc. My ultimate design (so far) is based on soda cans and drink mix canisters:

http://www.instructables.com/id/Leyden-Jar-Battery-for-Tesla-Coils/

The canisters are polypropylene. With proper preparation, you can insert an aluminum soda can, coat the outside with foil tape, and make a pretty good capacitor. The first ones I made were before I started coiling. I charged them from a Wimshurst machine, and they were pretty scary. They hissed menacingly from corona loss; in the earliest version I did not insulate the top of the can with a thick layer of wax. When they arced over they emitted thick, loud, hot sparks which were more intimidating than the arcs produced by my other HV equipment. Spark coils and later Tesla coils make bright, continuous discharges which can be pretty and fascinating to watch. The soda can Leyden jar was like a poisonous creature ready to bite. I never took a direct jolt from them, but I have been stung by residual charges.

Anyway, the soda can design works pretty well. It's cheap, though bulkier than this party cup design. No oil, no liquid makes it light too. My small tabletop coils are modular so that I can swap out components for comparison, and I definitely see a difference in performance between my jars and commercial caps. (I use Soviet made ceramic doorknob caps made for HV radio. They work very well). I would estimate the doorknobs are 30 to 50% more efficient. On the other hand, I have never burned out any of my Leyden jars, and I have destroyed a small bucket full of commercial caps. None of the Soviet doorknobs--they're tough.

Paul
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