Capacitor survey

I think most coilers would agree that the most troublesome component in a
coil would be the capacitor.  Unless you have the big bucks to blow on a
commercial unit, the alternative is to build one and hope that it lasts.
Too often, after a laborious and expensive construction project, one's
cap ends up as just so much smelly. oily, burnt, expensive, useless poly
and flashing, and we wonder "where did I go wrong?"  It would be nice if
we could all learn by other's successes and failures.

I would like to propose and volunteer to organize a survey of home-built
capacitors.  I would like to focus upon sheet-plastic dielectric units,
both rolled and flat plate, rather than saltwater/bottles, which are
difficult to quantify.  

Please help!

Below is a survey form, filled out with the details on my (failed) unit
as an example.  Please delete my data and add yours, and return it to me
at lau-at-hdecad.enet.dec-dot-com.  If you'be built several different units,
please make a copy of the form for each one.  I promise to post the
compiled results on my web site and announce this on this list.  Since I
don't plan on performing any digestion or analysis on this data, it would
probably be too large for a post to this List, unless our Moderator feels
otherwise?  <<<<Large posts can overwhelm the server system so large files
are best to post elsewhere and tell us were to look. - Terry>>>>

Gary Lau
Waltham, MA USA


Your name, email address:
Gary Lau, lau-at-hdecad.enet.dec-dot-com

Final disposition of capacitor: (continues to work great, or failed)

Nature of failure (or N/A):
One unit suffered a dielectric puncture at the edge of the foil plates.
There was no evidence of a margin arc-over.

Failure conditions (or how much run-time on surviving units):
Ran coil for approx 7 continuous minutes prior to failure.  Caps felt
slightly warm over edges of foil plates prior to failure.  Had several
successful, shorter runs prior to failing run.

Power supply:           
15KV/60mA NST

Gaps (include total gap distance if static):                   
Static, single segment, vacuum motor air-quenched, 0.36 inch total gap

Dielectric material:    
.04 inch LDPE from Cadillac Plastics

Oil/vacuum used?:             
Pumped down with vacuum pump, back-filled with laxative-grade mineral oil.

Number of cap units (if series connected), dielectric thickness per unit:
2, one layer 0.04 inch LDPE per unit

Total dielectric thickness across all units:
0.08 inch

Dielectric edge margin:
1.50 inches

Capacitor details and other misc notes:  
0.01 uF total series value over two identical units.  Each unit measured
0.02 uF.  Used extended foil rolled construction using household aluminum
foil.  See http://people.ne.mediaone-dot-net/lau/tesla/capacitor.htm for
complete details.