Rusty is the resident expert on failures on these things so a couple of
questions for him.
Were the connections on the end tanks welded on?
Yes,
they were TIG welded. I packed a heat sink compound all around the area
when welding, and did all the welding in short spurts, so as not to overheat the
tank. See pic that shows one of the fittings. Please keep the
laughter to a minimum Ed K :-)
I'm wondering if
the heat may have weakened the furnace brazed joints there since the failures
were always on the ends (I think).
The first core that leaked, was on the end without the
fitting, however, that end was dented when I got the core. When it
leaked, I got concerned about the strength of the tanks, and did all
sorts of pressure testing at various locations. Unfortunately, I
didn't consider (and no one else mentioned) the possibility that pulsations
in the pressure were causing the joint to fatigue and fail.
Ultimately, I concluded that the first failure (on the ground, during test
runs) was due to the damage the core had received in shipping. This was a
bad conclusion. As I recall, it had run for 30 hours or so, but then
developed a slow leak. The pic shows the dented section, and oil speckled
on the exhaust pipe. This was the first
failure.
I noticed there is an
aluminum strap welded to the end tanks from top to bottom on some Harris
cores. Did yours have this? I am wondering if they are to resist the
expansion force trying to split the tank segments apart.
Nope,
I haven't seen such a strap.
I have built a test evap core cooler with bonded plates on the
ends tied together with threaded rod. This serves two purposes. It
resists the expansion forces and provides a thicker plate to drill & tap for
AN fittings (no welding required). Even with all the added hardware
it only weighs 5 1/2 lbs.
I
still have one of the 5 cores that you see in the pic. One
of the ends is dented, much like the core that failed, so I would never
want anyone using it. If you would like to do some destructive testing on
it, it's yours, for the low, low price of nothing.
The Fluidyne I was looking at
was 12 lbs (and still would not fit in the space available). Weight is so
important to me that I place a value of $100 per pound on weight savings.
For example, the 12 pounds I saved with aluminum landing gear cost an
extra $1200.00.
The
weight I saved by using an evap core over a real oil cooler cost about
$3000 in aircraft recovery, and engine rebuild. I also have the priceless memory of smoke in the
cockpit, and oil on the canopy, as I glided for the Navy field (exactly 53 weeks
ago today).
If the
Fluidyne won't fit, hopefully, Ed K can build you a suitable cooler, and you'll
give up on the evap core. Otherwise, I'm going to have to call
Laura :-)
Cheers,
Rusty
(I'll do it, really, I will <g>)