Bending longeron

Lou wrote:
On Mar 5, 2:29 pm, Jerry Wass wrote:
J.Kahn wrote:
I need to make bends of about 30 degrees in a 3/4 x .049 longeron tube,
with a tight bend radius, no more than 3 inches. Can I do the bend hot
without wrinkling the tube by free bending or do I need a supporting die
of some kind? Anybody have any specific techniques?
John
--I bent some of the same tube by filling it with sand, bending it
around a 10" pulley that had been turned out inside to 3/8"
radius--Pulling it around with the inner race of a big ball brg that had
used 3/4" balls--this was pressed onto a smaller brg which was bolted to
a bar that pivoted on the center support of the pulley. BUT--
that's a 5" radius & you want 3"---might do it though..send ya a pic if
your interested. wass biplane at tds dot net

Can't you use a conduit bender?
Lou

Apparently you can but the radius I need is smaller than a conduit bender.

"J.Kahn" wrote

Apparently you can but the radius I need is smaller than a conduit bender.

Use that, then tweak it?
--
Jim in NC

J.Kahn wrote:

Dennis Fetters wrote:

Morgans wrote:

"J.Kahn" wrote in message
.. .

I need to make bends of about 30 degrees in a 3/4 x .049 longeron
tube, with a tight bend radius, no more than 3 inches. Can I do
the bend hot without wrinkling the tube by free bending or do I need
a supporting die of some kind? Anybody have any specific techniques?




Fill the tube with water and freeze it. Bend it with the ice inside,
this will help keep it from collapsing. It's better than trying to use
sand and cheaper than low temperature metals.



I'll experiment with that. Thanks. Doesn't the ice tend to crumble at
the bend and loose its ability to support the tube?

What about welding caps on the ends of the raw tube, one cap with a
treaded hole to take a plug, then filling with water that's had all the
air bubbles removed and plugging?

John

Yes it crumbles, but the ice expands inside the tube giving gripping
power, so the uncrumbled ice on either side of the bend holds the
crushed ice in place. Good luck

Morgans wrote:
"J.Kahn" wrote in message
.. .
I need to make bends of about 30 degrees in a 3/4 x .049 longeron tube,
with a tight bend radius, no more than 3 inches. Can I do the bend hot
without wrinkling the tube by free bending or do I need a supporting die of
some kind? Anybody have any specific techniques?

Good luck, without a die bender.

I have heard of some people bending tube by packing it, very tight, with
sand. I have never done it, personally.

We're only talking 30 degrees here guys. Sheesh!

Mark on either side of your 30 degrees. Heat the inside of the bend in
the area between the marks to a dull red, then each of you grab a side
and bend it into the hot area as if you were back peddling a canoe.
Don't add a lot of pressure. You're just "assisting" the torch heat.
Let it cool completely, and do it again if you don't have enough bend.

A standard hydraulic tubing bender for 3/4 OD tubing has a 3" radius
to tube centerline and says the minimum wall without flattening is
0.049 for "high strength" aluminum, or any for soft aluminum. If you
have a piece to try, head to your local hydraulic shop and ask them to
try.

With inner support, there is lots more capability, and as close as
this is, the spring will probably be enough.

On Mon, 05 Mar 2007 11:01:37 -0500, "J.Kahn"
wrote:

I need to make bends of about 30 degrees in a 3/4 x .049 longeron tube,
with a tight bend radius, no more than 3 inches. Can I do the bend hot
without wrinkling the tube by free bending or do I need a supporting die
of some kind? Anybody have any specific techniques?

John

On Mar 5, 9:01 am, "J.Kahn" wrote:
I need to make bends of about 30 degrees in a 3/4 x .049 longeron tube,
with a tight bend radius, no more than 3 inches. Can I do the bend hot
without wrinkling the tube by free bending or do I need a supporting die
of some kind? Anybody have any specific techniques?

John

This is easy to do with a torch. Secure the tube to your table, with
the horizontal tube tacked into place forward of the bend. Set your
torch with a neutral flame and heat to cherry red for about 2.5 inches
either side of the bend. Slowly bend to the desired dimension. If
your using a wood topped jig table, place a small piece of steel
between the tube and the table. Header wrap also works well to keep
from burning the table too much. If you're bending both the top and
bottom longeron you will have to alternately heat each tube at the
same time. If you're bending one tube alone, a conduit bender works
well. Practice with cheap conduit to get the hang of it first. Also
practice your bending with the torch on small scrap 4130 until you
feel confident with the process. If you go slowly, and don't over
heat, you will have a nice radius bend with no wrinkle.

Colin

http://www.jumprunenterprises.com

On Mar 5, 6:26 pm, "J.Kahn" wrote:
Dennis Fetters wrote:
Morgans wrote:
"J.Kahn" wrote in message
...

I need to make bends of about 30 degrees in a 3/4 x .049 longeron
tube, with a tight bend radius, no more than 3 inches. Can I do the
bend hot without wrinkling the tube by free bending or do I need a
supporting die of some kind? Anybody have any specific techniques?

Fill the tube with water and freeze it. Bend it with the ice inside,
this will help keep it from collapsing. It's better than trying to use
sand and cheaper than low temperature metals.

I'll experiment with that. Thanks. Doesn't the ice tend to crumble at
the bend and loose its ability to support the tube?

I'm sure it would crumble but the crumbled ice still won't compress.


What about welding caps on the ends of the raw tube, one cap with a
treaded hole to take a plug, then filling with water that's had all the
air bubbles removed and plugging?


That is similar to filling it with ice except the ice is it's own
plug
and in the process of freezing it will expand, expanding the tube
to a larger diameter, or maybe splitting it, whereas filling with
water may result in the volume lost by kinking the pipe at the bend
being made up for by expanding the diameter somewhere else.

Are you sure that a weldment isn't a better design approach?
I.e. cut wedges from the inside radius, bend it, weld it. If it
MUST be smooth grind the welds flush.

--

FF

wrote:
On Mar 5, 6:26 pm, "J.Kahn" wrote:

Dennis Fetters wrote:

Morgans wrote:

"J.Kahn" wrote in message
et...

I need to make bends of about 30 degrees in a 3/4 x .049 longeron
tube, with a tight bend radius, no more than 3 inches. Can I do the
bend hot without wrinkling the tube by free bending or do I need a
supporting die of some kind? Anybody have any specific techniques?

Fill the tube with water and freeze it. Bend it with the ice inside,
this will help keep it from collapsing. It's better than trying to use
sand and cheaper than low temperature metals.

I'll experiment with that. Thanks. Doesn't the ice tend to crumble at
the bend and loose its ability to support the tube?


I'm sure it would crumble but the crumbled ice still won't compress.


What about welding caps on the ends of the raw tube, one cap with a
treaded hole to take a plug, then filling with water that's had all the
air bubbles removed and plugging?



That is similar to filling it with ice except the ice is it's own
plug
and in the process of freezing it will expand, expanding the tube
to a larger diameter, or maybe splitting it, whereas filling with
water may result in the volume lost by kinking the pipe at the bend
being made up for by expanding the diameter somewhere else.

Are you sure that a weldment isn't a better design approach?
I.e. cut wedges from the inside radius, bend it, weld it. If it
MUST be smooth grind the welds flush.

--

FF

Well, shoot. I guess I need to stop using ice as a method of bending
tubing if it won't work. I wish I would have know that 30 years ago, I
would have not waited all my time bending tubes that way to keep them
from distorting.......

On Mar 13, 9:02 pm, Dennis Fetters
wrote:
wrote:
On Mar 5, 6:26 pm, "J.Kahn" wrote:

Dennis Fetters wrote:

Morgans wrote:

"J.Kahn" wrote in message
et...

I need to make bends of about 30 degrees in a 3/4 x .049 longeron
tube, with a tight bend radius, no more than 3 inches. Can I do the
bend hot without wrinkling the tube by free bending or do I need a
supporting die of some kind? Anybody have any specific techniques?

Fill the tube with water and freeze it. Bend it with the ice inside,
this will help keep it from collapsing. It's better than trying to use
sand and cheaper than low temperature metals.

I'll experiment with that. Thanks. Doesn't the ice tend to crumble at
the bend and loose its ability to support the tube?

I'm sure it would crumble but the crumbled ice still won't compress.

What about welding caps on the ends of the raw tube, one cap with a
treaded hole to take a plug, then filling with water that's had all the
air bubbles removed and plugging?

That is similar to filling it with ice except the ice is it's own
plug
and in the process of freezing it will expand, expanding the tube
to a larger diameter, or maybe splitting it, whereas filling with
water may result in the volume lost by kinking the pipe at the bend
being made up for by expanding the diameter somewhere else.

Are you sure that a weldment isn't a better design approach?
I.e. cut wedges from the inside radius, bend it, weld it. If it
MUST be smooth grind the welds flush.

--

FF

Well, shoot. I guess I need to stop using ice as a method of bending
tubing if it won't work. I wish I would have know that 30 years ago, I
would have not waited all my time bending tubes that way to keep them
from distorting.......

I didn't say it won't work, just pointed out that there might be some
problems with it for any specific application. Freezing water in
steel water pipes can burst them as many homeowners have
discovered.

--

FF

_said_

Dennis Fetters wrote:

Morgans wrote:

"J.Kahn" wrote: "A Whole Bunch of Stuff" from old posts.



Fred, you need to do some serious work on your trimming and snipping skills.

Most of those old, old posts and "so-and-so wrote's" could have, and should
have been trimmed "right out" of your reply.

As you are probably unaware, my name was in there as having "wrote"
something on your most recent post, but not one word on your post came from
any of my posts. I don't like (mostly on principle) being quoted when there
is nothing there I said.

I think you will understand, and will try harder, next time. :-)
--
Jim in NC