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Re: Caps: Stacked vs Rolled

Subject:  Re: Caps: Stacked vs Rolled
  Date:   Fri, 11 Apr 1997 11:51:26 -0400 (EDT)
  From:   Esondrmn-at-aol-dot-com
    To:   tesla-at-pupman-dot-com


In a message dated 97-04-10 18:47:17 EDT, you write:

<< 556 cascade controll circuit. I am now using a 10kv furnace trans
with a
 small quick and dirty cap which I think works pretty well for the 15
 minutes of careful craftsmanship that went into it. I can only run the
 unit at about 30 on the big-ol-variac, but its a start and tons o fun
 with purple glowing from the cap and a 2 inch sparc. 
 
 ANYWAY..
 I am now determined to manufacture a serious capacitor and would like
to
 post my current design thoughts and would ask if this seems sound;
 
 I have read some comentary that smaller caps in par. discharge quicker
 that larger caps (Fr. McGahee), My interpretation of this is that the
 same plate area will discharge quicker when divided into a greater
 number of smaller units, this is the first reason I have decided to go
 with a stacked design. The second is flexibility, I think a stacked
 design lends itself to an adjustable set up.
 
 I intend to obtain several sheets of .05 copper, and have these sheared
 to 5" x 6.5", then take these to a machine shop buddy of mine (arent
 they great?) and have him stack-em, clamp-em and rabbit out 1.5" x 4.1"
 or so with an eighth inch round on that inside corner. This should
leave
 me with 25sq inches per plate face. Im thinking about 30 plates.
 These would be alternated and placed in a custom plexi box. For
 dielectric Ill be using 3 or 4 sheets of polyetheline between each
 plate. I havent settled on a thickness yet (hey, I'm still designing)
 But all will be mounted and clamped, filled with a good transformer oil
 and topped off with a half inch of parafin. (Do these things get hot?
 Ive seen no mention of running temps for caps) 
 The tabs will then be fixed so that two buss bars can be attached to a
 variable number of plates.
 
 I am a strong believer in versatility and already have 4 secondaries of
 varying sizes im playing with. 
 
 As they say there is nothing new under the sun, and Im sure this has
 been tried. Am I doomed or does this seem a good path to pursue?
  >>
Chris,

I have only built rolled poly caps, but your construction plans sound ok
to
me.  I would definitley submerge it in oil.  I have found that the
dielectric
thickness needs to be greater than described in some plans for the
rolled
poly caps.  I am convinced that .062 poly should be rated for maximum 9
kv AC
in Tesla coil operation.  Three layers of .030 should work well for your
caps.  The last rolled cap that I made I used two layers of .062.  This
gets
quite stiff and is difficult to roll, but should be pretty bullit proof.

Ed Sonderman