New cap design (fwd)
From: Malcolm Watts [SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent: Sunday, August 09, 1998 5:28 PM
To: Tesla List
Subject: Re: New cap design (fwd)
> Date: Sat, 8 Aug 1998 16:50:48 -0400
> From: Thomas McGahee <tom_mcgahee-at-sigmais-dot-com>
> To: Tesla List <tesla-at-pupman-dot-com>
> Subject: Re: New cap design (fwd)
> The edge that is flipped over will be much thicker than the
> open side. As you roll it up you will find that the flipped
> side will gradually bulge. The effect is cumulative.
> Secondly, it has been my experience that when you try to
> roll such a beast up that you will experience a crinkling
> at the flipped edge.
> My experience with this method was that it produced more
> problems than it solved. The severity of the problem depends
> somewhat on the thickness of poly being rolled. It is
> much worse with thicker poly.
> Hope this helps.
> Fr. Tom McGahee
> > Date: Tue, 4 Aug 1998 02:39:28 -0500
> > From: Shaun <shaunobrien-at-geocities-dot-com>
> > To: Tesla List <tesla-at-pupman-dot-com>
> > Subject: New cap design
> > ello, everyone
> > While I was thinking. I came up with a diffrent way to make a rolled cap.
> instead of cutting all
> > the layers into sheets like we normally do. Why not make the poly 2 times as
> wide and fold it around
> > the plate? Corey Edmunds helped turn this idea into what it is now. There is
> a pic of the end view
> > of how the layers would be stacked at
> http://www.geocities-dot-com/SouthBeach/Pier/2756/newcap.jpg They
> > is only 1 disadvantage we saw at the time. That is trapped air in one end.
> Maybe with a strong pump
> > this would be overcome. Some of the advantages we saw to this design. Less
> poly needed to make a
> > cap, and more insulation around the plates. This would work really well for
> the extended plate
> > rolled cap design as the plates could go straight out of the sides
This is actually the design for a dry fired cap I published several
years ago. We too had problems with the differences in ROC of the
plastic causing crinkles etc. Two notes on this:
- considering that air is trapped inside the cap anyway, we have
found it makes no difference to the reliability of the cap if it is
run safely within its peak ratings
- It takes 2 - 3 people to roll them - two to hold the plastic in
place and one to do the actual rolling, usually kneeling on the
benchtop and applying arm numbing pressure to the roll while rolling
- The job is made much easier if a number of short lengths of
foil/plastic plates are rolled up rather than a single long one.
A final note - the caps age predictably with corona damage to
the plastic. We get about 1/2 an hour runtime from ours before they
give up. That is conditional on runs of a minute or less to prevent
the plastic heating too much.