Ed Anderson wrote:
Hi Paul,
As you know, the BurnsStainless bent aluminum tubing is
annealed
to
"O"
condition before bending - leaving it somewhat softer than
desired
for
our
applications. See extract below, it appears that by sticking it
into a
regular electric (not microwave) and baking it for 8 hours you
can
get
it
back to T-6 condition. (hate to think what the electicity cost
would
be).
I think I may try that with my intake manifold just to see.
Ed Anderson
Jim Millett, president of U.S. Light Aircraft Corp., told us
something
that
illustrates the peculiarities one can encounter in the field of
heat
treating aluminum. He suggests taking a small piece of 6061-T6
sheet
and
trying to bend it with your hands. You will find it to be very
strong
and
springy. Then heat it to 950 degrees. This could be done in a
pottery
kiln
or by using a propane torch to heat it evenly until the surface
turns
gray.
Then immerse it in cold water. This is what is called "solution
heat
treatment." The sample is now in the 6061-0 condition, the last
"0"
meaning
that it has been annealed to dead soft and easily bent
condition.
Then
bake
it in a kitchen oven at 350 degrees for eight hours. This is
called
"precipitation hardening" and the sample is now back to the
6061-T6
condition and just as strong as it originally was.
Ed Anderson
Matthews, NC
RV-6A N494BW
eanderson@carolina.rr.com
Funny you should mention that now. I am about to pick up about 120
bends
from the
bender and take them over to the heat treater.
How does it feel in the O condition. Can you easily bend or dent
the
.058
scrap?
BTW the legs on those bends look very long. What did Burns charge
you for those bends? I assume you are going to cut them off around
17 inches.
Paul Lamar
The O condition is soft, fairly easy to ding. They have probably
age
hardened a tad since I've had them a while. I forget the exact
price,
but
it was somewhere around $27 each. Yes, I am going to cut them off
at
around
8-9 inches up. I am going to leave the length of the secondary
about
what I
have now as it gives me great torque around 5300 rpm (on cold
mornings
can
get 5800-5900 as I overpower and stall the prop). However, the
primary
loop
will be shorter to try to get a little more power in the higher rpm
range.
Attached are some photos of the tubes and flange as well as the
ported
casting. I need to see if that brazing rod will build out a flange
around
the bolt hole along the edge. Then cook it for 8 hours {:>)
Ed
David Barker wrote:
If I rememeber my limited metalurgy correctly, I think the hardening
Aluminum to T-6 takes 8-11 hours at ~900 degrees F not 350 degrees.
Dave Barker
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