Re: [TCML] secondary coil form

[Phillip Slawinski <pslawinski@xxxxxxxxx>]

Personally, I've had bad experience with foam core pipe.  I made some
secondaries from SCH40 foam-core pipe.  They were 3.5" x 12" windings on a
12.5" form.  I put a rather generous coating of epoxy on the outside of
them.  The first one I made failed during testing, due to internal arcing.
The arcing was from the middle of the secondary to the bottom.  By the way,
the coil was in tune when this happened.  I didn't want to throw this
secondary away, so I cleaned up the damage as best as I could, by scraping
out the charred sections, and then sanding it down.  After that was done, I
went one step further, and filled the secondary with oil.  The oil filling
was a disaster in it's own right, but that's a whole different story.  So
this repaired secondary seemed to work fine for about a year or so, and
then it broke down very spectacularly.  See here
http://www.flickr.com/photos/pslawinski/5043392786/in/set-72157623355704761/
This may be an edge case though, because I routinely push 5X the secondary
length out of that thing, so maybe the average coil isn't likely to see the
same level of stress.


A lot of low pressure pipe is actually a foam core with solid skins. Most
> ABS DWV (Drain, Waste, Vent aka sewer) is like this.  It's tough to tell,
> even if you saw it, because the foam looks the same, it's just
> significantly lower density.
>
> Over the years, several folks on the list have used various and sundry SDR
> type pipe, which is what I think you have, without problem.
>
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