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bending aluminum - Page 3

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Posted by nicksanspam on December 15, 2007, 1:53 pm

Wow. How big were they?

I scored 4'x8" pieces from a $0 2'x50'x0.018" roll of Amerimax brown/white
roofing coil stock with a utility knife, then bent them to break, then
pounded them into a groove between 2 1x3s with a 1/2" copper pipe and
a rubber mallet, then removed the pipe, put some vinegar-smelling silicone
caulk in the aluminum groove, and pushed the pipe back into the groove,
with no rivets.

Why did you need to drill 5/8" holes in a 1" pipe? For headers, instead of Ts?

I've been trying to figure out how to make equal flows by squeezing one end
of each fin-pipe, without the usual extra reverse header, and wondering if
we can make a solar absorber out of thin steel electrical conduit with 1/2%
ACI-100 corrosion inhibitor in the water. Steel is a lot cheaper than copper,
but I guess we'd still have galvanic corrosion.


Posted by Jeff on December 15, 2007, 2:20 pm
nicksanspam@ece.villanova.edu wrote:

   14" wide. There are 4 pipes and there are 6 boxes 10' long. ~120 SF
of collector

   I've never seen the .018" stock where I live (Atlanta). I suppse I
could have ordered it. My experience with both Home Depot and Lowes is
they are bad at special orders, but I guess mail order is fine.

   At any rate, The surface cover I wanted unpainted as the emissivity
of solkote on aluminum is reduced. The instruction for painting is that
  you should see a bit of the substrate showing through...  Under most
typical conditions the selective coating makes a big difference. That
old t delta to the fourth really kicks in.

   Yes. One inch to 1/2" tees are hard to find and expensive. The joints
look good except for the  first several holes that were a bit oversized.

   Mike in NZ's suggestion as he builds them that way.

<cat involved here>

   I went to extreme lengths trying to make this without copper and in
the end decided it was trouble. You can google my old posts in this
group and others...


Posted by RicodJour on December 15, 2007, 5:20 pm
 On Dec 15, 8:53 am, nicksans...@ece.villanova.edu wrote:

I didn't know they were now selling scented caulking - if you had a
choice, vinegar was an odd one.  ;)

Why silicone caulking? It will slow the heat transfer between pipe and
sheet.  What's the reason you chose painted aluminum instead of mill


Posted by nicksanspam on December 15, 2007, 7:45 pm

There is more than one kind of silicone caulk. The common one that smells
like vinegar contains acetic acid that etches and bonds well to aluminum,
altho I suppose the paint prevents that. Maybe it etches copper too.

It speeds it up, compared to a small air gap. It's also a good glue.

So I wouldn't have to paint it.


Posted by RicodJour on December 16, 2007, 4:33 am
 On Dec 15, 2:45 pm, nicksans...@ece.villanova.edu wrote:

The common one(s)?  I've been in construction for thirty years and
never ran across a silicone caulk that didn't use acetic acid as the
crosslinking agent (responsible for the vinegar smell).  I know they
make silicone caulks that use ketoximes (sp?) for crosslinking, but
I've never encountered such an animal.  Where do you shop that you
have to avoid buying acetic-free silicone caulk?

True, and it slows it down compared to no air gap.  I know they use
silicone heat transfer compounds on electronic heat sinks, and that
some of them use aluminum oxide or other filler to aid in heat
transfer.  I'd be interested to see some results comparing a
reasonably tightly fitted aluminum jacket versus a reasonably tightly
fitted jacket with gaps filled with silicone.

Why not a black/white trim coil?


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