Re: Spherical Capacitors

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Original poster: Jared E Dwarshuis <jdwarshui@xxxxxxxxx>

Just finished producing a set of top end capacitors using fiberglass
over inflated rubber balls. I used a cloth measuring tape and inflated
the balls until the circumference was correct.

 I used two layers of fiberglass with polyester resin and a tiny
amount of Bondo to smooth the seams.

You can use spray adhesive to hold the dry cloth to the sphere, this
saves a lot of time and allows two layers of cloth to be layed up at
once. (Dont do this trick for a boat repair!)

I used spray adhesive on the dull side of aluminum foil and burnished
it on the spheres when done.

The one warning: You cannot cover half of a sphere and then the other
half later. Temperature changes cause the ball to expand and contract
considerably.

Capacitance for sphere with second plate at infinity = 4 pi e R
          (R is in meters)

I suppose that this trick could work with truck inner tubes, but inner
tubes tend to inflate somewhat irregulary. Perhaps if a cloth envelope
was sewn around the tube to force uniformity?