Re: Capacitor Container Failure

In a message dated 3/18/99 2:01:26 AM Pacific Standard Time, tesla-at-pupman-dot-com

- el snippo -
>  The failure turned out to be a hairline crack in the side of the lower
>  end cap.  The crack extends 1.5" vertically from the base.  It doesn't
>  appear to go along the bottom of the endcap, but the paint may be
>  obscuring it.  I am puzzled by this failure.  This doesn't seem to be a
>  highly stressed area.  Being on the side, it is twice and thick as
>  anywhere else and definitely didn't see the stresses during vacuum
>  degassing that the bottom did.  My only guess is that the PVC cement
>  softened it and somehow weakened it.  The coil (6" sec, 12KV, 120ma, 50"
>  arcs)  has been run  5 times and the caps are only a couple of months
>  old.
>  Has anyone ever seen a rolled LDPE cap with a PVC container fail in this
>  manner before?  Is painting PVC considered a bad practice?  Are there
>  some crazy PVC glue dynamics that I need to be aware of?
>  --
>  Ross Overstreet

I have a couple of these, built almost exactly as you describe.  Having no
vacuum pump, I have never stressed them that way.  I left mine standard pvc
white and did not paint them.  They have not leaked in about two years.

After reading Bob Volk's response: - my end caps originally came with some
kind of rubber seals glued into them which I removed before using.  They were
embarrassingly expensive at about $10.00 each and quite thick.

Ed Sonderman