Bending 6061-t6 tubing..again
Kenneth Chandler
You might remember the first post ..and If you do PLEASE HELP
ME!!!!
The methods most suggested was to fill the tube with sand and bend
away..
Another suggestion was to add water to the sand and freeze the tube then
bend..Okay.
Now maybe It was the material I was bending.(6061-t6 .065 wall 2"o.d..)
the bend Is only 30 degrees So I loaded up the tube with wet sand
,packed It fairly tight
set the mandrel tube bender up (it's hydraulic) made three strokes and
BAM split the tube In two...
So any new Ideas will help
Thanks for all the input
Ken
James Lloyd
with sand but not to tightly packed and then bent it while using a
little heat from a propane torch.You see, it is not hard to stretch The
outer radius, It is hard to shrink the inner.I hope That this helps.
Richard Lamb
I've bent a whole lot of 6061-T6 tube.
I've never used the "pack it with something" trick
anthough I've HEARD of it all my life.
But the tail and cabanse of my parasol use 1" dia 6061-T6
tube, and I've learned how to bend the stuff reliably.
Only a few detail items worth note:
1) you MUST use the correct bender.
you will NOT get good results from a conduit bender.
2) wall thickness less than .049 is hopeless.
.049 works ok, .058 a lot better.
(and I bend .125 wall for a main gear part)
3) my bender is a hand operated GEARED device that pulls
the tube around a 12 inch dia mandrel.
That gives a 6" radius.
Even hydraulic tools that don't use a full mandrel,
and keep the tube in tension during the operation
can't do a decent job. Too much interior side buckling.
4 thru 9) No, you can NOT improve the "bendability" of thin
wall stuff by putting another tube inside.
Ask me how I know.
10) for beest results, see item 1 and 3...
ta...
--
Richard Lamb
email: lam...@flash.net
web: http://www.flash.net/~lamb01
brian whatcott
Hmmm...that's bad news: looks like you can have a nice bend if you are
happy with 6061-O, or you can have a nice expensive bend if you want
6061-t6.
You choose.
Either 1) Buy the -O condition, bend it and take it to a shop for the
-t6 heat treat. (-t4 would probably bend OK, but I don't see it in ASP
cat.Pazmany's Construction book said the heat treat is not expensive,
but that was many years ago....)
Or 2) Skip the heat treat and leave it weak.
Brian Whatcott Altus OK
<in...@intellisys.net>
Eureka!
Richard Lamb
It's bench mounted.
It has a 12 inch ring mandrel with a big bolt
in the center for a pivot pin.
A flip-over latch holds the butt end of the tube
while you crank the wheel around however far you
want to bend the tube.
The tube is literally streached around the curve.
Last price I saw on the net was less than $200.
(no, sorry, no adr)
Not much help today, am I?
Bruce A. Frank
day job we bend 2" .065" 6061 T-6 every once in a while. The bending
shoes fit tightly and we wax the aluminum slightly (lubrication). In 30º
there is almost never any shrinkage of diameter. Why not 6061-0?
--
Bruce A. Frank, Editor "Ford 3.8L Engine and V-6 STOL
BAF...@worldnet.att.net Homebuilt Aircraft Newsletter"
| Publishing interesting material|
| on all aspects of alternative |
| engines and homebuilt aircraft.|
*------------------------------**----*
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welding
0 0
Kenneth Chandler
I knew I could count on the group for some more ideas..I guess the 6061-0
would be a better choice..what about 2024 T3 same O.D thicker wall.... .095??
Any thoughts??
Thanks
Ken
Kelly
>
> Thanks guy's
> I knew I could count on the group for some more ideas..I guess the 6061-0
> would be a better choice..what about 2024 T3 same O.D thicker wall.... .095??
> Any thoughts??
> Thanks
> Ken
>
different types, some that can be bent, and some that can't. What you
want is 6061 wrought (or drawn) seemless. -K
David A Donnora
I'm no expert either but I have to agree with bruce I've bent a lot of
thin wall exhaust tube and if it was dry (no lube) it would either make a
sloppy looking bend or rip the tubing not sure if it helps .
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Rich Shankland
news:3A915472...@sympatico.ca...
Thanks guy's
I knew I could count on the group for some more ideas..I guess the 6061-0
would be a better choice..what about 2024 T3 same O.D thicker wall....
.095??
Any thoughts??
Thanks
Ken
Start with aluminum in the alloy and hardness which you want in the finished
part. Thicker wall tubing is usually easier to bend without flattening or
wrinkling than thinner wall.
Outline the area to be bent using a felt tip pen. Light an oxyacetlyene
torch with just the acetylene turned on. Pass it over the area, depositing a
layer of soot on the metal. Then add oxygen, adjusting it to a neutral
flame. Heat the area gently, until the soot burns off. Keep the torch
moving - it is easy to melt through the aluminum. I recommend practicing on
some scrap first.
If you want to get fancy, you can buy some "Tempstick" - a crayon which
melts and marks at a specific temperature. You'll need look up the correct
temperature to annealing aluminum. Another way of detecting the proper
temperature is to pull the flame off the piece momentarily and try to mark
the aluminum with a splinter of fir or other softwood. When it marks, you're
just right. You're also about 50 degrees shy of melting the aluminum! It's
touchy, so never let the torch sit still.
The metal will be soft enough to bend. Within a few days after annealing, it
will regain most of it's original temper. I don't recommend this technique
for critical structural parts, but I used it for years at the shipyards,
bending aluminum tubing for piping in Destroyer Escorts.
--
Rich Shankland
The Banjo:
". . . the war-drum of the White Man round the world!" R. Kipling
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Richard Lamb
It's not tempered (duh!)
Heat treating might cause some warpage.
--
highflyer
>
> Thanks guy's
> I knew I could count on the group for some more ideas..I guess the 6061-0
> would be a better choice..what about 2024 T3 same O.D thicker wall.... .095??
> Any thoughts??
> Thanks
> Ken
2024 T3 is already hardened. 2024 in general work hardens quickly. I
have formed 2024 with a hammer and shot bag for repairs on compound
curve surfaces. It doesn't have to be worked much before it cracks
and it doesn't like to stretch much.
Aluminum doesn't heat treat like steel. With steel you heat it hot
enough
to cause the crystal structure to change and then quench it to freeze
that
structure. Subsequent tempering will change some of the hard brittle
structure back to the soft but tough structure, allowing intermediate
levels of hardness and toughness.
Aluminum hardens be a combination of working and aging. High strength
aluminum rivets used to be made from an age hardening alloy. They were
called "icebox" rivets, because you had to anneal them before you drove
them. Since the "aging" process in aluminum proceeds more slowly at
lower temperatures and faster at higher temperatures, they would store
the rivets in a dry ice cooler after annealing so they would still be
reasonably soft when they were driven. Otherwise the heads would all
crack and the rivet would have to be drilled out and replaced. They
allowed about a half an hour at "room temperature" before you had to
stop using them and have them annealed again.
To bend any metal, you have to exceed the structural limit so the metal
permanently deforms. There will be some "springback" as it attempts to
return to its undeformed shape. When you bend a tube or bar of metal,
the metal on the inside of the curve, closer to the center of curvature
than the nuetral line of the shape, will attempt to compress. The metal
outside the nuetral line will have to fail in tension and stretch.
With a hydraulic bender, that consists of a couple of rollers that are
fixed and a hydraulic jack with a curved mandrel head on it, forces it
to yield by pushing on the inside of the tube. As a result, the
tendency is for the inside portion to fail in compression before the
outside fails in tension. The compression failure mode of something
loaded in compression can be either a thickening of the material, which
is what you want, or a buckling and crumpleing, which you do NOT want.
What determines the mode is the relative size of the part. Euler,
the mathematician established what is called the "Euler Column Length"
which is the crossover point between the two failure modes. It is
a length in the stress area of about fifty times the minimum dimension
of the compression loaded part. That tells us that "thin wall" tubes
will tend to fail in buckling when they are loaded in compression.
Bracing the surface will shorten the effective "column length" and help
to prevent the buckling failure. That is why you see "jury struts" on
airplane wing struts. The length of the strut exceeds the Euler length,
so you put a brace strut in the center to effectively shorten the column
length. This is what you were attempting when you filled the tube with
sand.
The other way to avoid this problem is to use a bender that forces the
failure that allows the bend to appear mostly as tension. The tube
may draw down slightly in diameter when it fails in tension, but it
cannot buckle! A buckle causes a sudden and drastic reduction in
strength. A tension failure causes a slight and gradual reduction in
strength. Hence, they developed tube benders that PULL the tube around
a mandrel to bend it and control the bend so that all of the deformation
is taken outside the nuetral axis in tension mode. No buckling.
The yield strength of most metals goes down sharply when the metals are
heated. That is why cylinder head temperature is important and why the
cylinders for a diesel are so much heavier than the cylinders for a
gasoline engine. What you do when you heat the metal to bend it, is
heat it enough for the metals yield strength to be compromised enough
that you can deform it with less force. :-)
How about that. I gave you all Metallurgy 101 without EVER telling you
how you can bend that tube without it buckling! :-)
--
HighFlyer
Highflight Aviation Services
Richard Lamb
Uh, can I quote you on that?
>
> How about that. I gave you all Metallurgy 101 without EVER telling you
> how you can bend that tube without it buckling! :-)
>
> --
> HighFlyer
> Highflight Aviation Services
Yes you did.
Robin du Bois
are you going to verify its integrity? I know nothing about bending tubes,
quite a lot about what happens when they break. Best luck.
"Kenneth Chandler" <kenneth....@sympatico.ca> wrote in message
news:3A90610D...@sympatico.ca...
Mitsuko LeClere
If you want to bend it you have to aneal it locally:
Use a black feltpen and put marks all over the area to be bent.
Heat this area with a propane torch large one) and when the marks
turn brownish quench the heated area in cold water.
Now you can bend it with the metod you tried.
Bending will restore some hardness.
Dan LeClere
Kenneth Chandler wrote in message <3A90610D...@sympatico.ca>...