tight radius bends in conduit
 

http://users.goldengate.net/~dforeman/conduit/

Field-expedient tight bends in EMT for making stuff. Not pretty, but
it works.

Don Foreman writes:

http://users.goldengate.net/~dforeman/conduit/

Nice work, from another fan of EMT, the duct tape of metalworking.

On Tue, 02 Aug 2005 00:40:36 -0500, the opaque Don Foreman
clearly wrote:

http://users.goldengate.net/~dforeman/conduit/

Field-expedient tight bends in EMT for making stuff. Not pretty, but
it works.

Got structural integrity figs for that type of bend, Don? g

And shouldn't that last sentence read "Bondo and paint are the
amateur weldor's friends!"?


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On Tue, 02 Aug 2005 00:40:36 -0500, Don Foreman
wrote:

http://users.goldengate.net/~dforeman/conduit/

Field-expedient tight bends in EMT for making stuff. Not pretty, but
it works.
Nice job Don. Another method which works, and doesn't wrinkle the
metal, is to heat the area almost red or just till it starts being
red, and spray water on it. Do this a few times and the bend is very
controllable. I learned about this method in welding class. I saw it
being done at Lockheed Shipyard in Seattle before it closed. They were
using huge torches to heat 3 inch thick steel pie shaped sections.
These were being curved so they could be welded into a 1 half
spherical shape. It eventually was welded to the hull under the prow
of a ship. I'm sure you've seen an empty ship riding way out of the
water and there is this bulbous thing sticking out of the hull. Also,
we were shown a movie of the men who bent the legs to the Space Needle
using the same method. After seeing this I had to try it for myself
and have bent and straightened both mild steel and stainless steel.
Eric

On Tue, 02 Aug 2005 05:47:15 -0700, Larry Jaques
wrote:


Got structural integrity figs for that type of bend, Don? g

Not very strong with wrinkles, but if the gullets are filled with MIG
weld the bend is stiffer than the straight tube it was part of.

And shouldn't that last sentence read "Bondo and paint are the
amateur weldor's friends!"?

Well, I didn't want to admit that,but.... :)

On Tue, 02 Aug 2005 07:30:20 -0700, Eric R Snow
wrote:

On Tue, 02 Aug 2005 00:40:36 -0500, Don Foreman
wrote:

http://users.goldengate.net/~dforeman/conduit/

Field-expedient tight bends in EMT for making stuff. Not pretty, but
it works.
Nice job Don. Another method which works, and doesn't wrinkle the
metal, is to heat the area almost red or just till it starts being
red, and spray water on it. Do this a few times and the bend is very
controllable. I learned about this method in welding class. I saw it
being done at Lockheed Shipyard in Seattle before it closed. They were
using huge torches to heat 3 inch thick steel pie shaped sections.
These were being curved so they could be welded into a 1 half
spherical shape. It eventually was welded to the hull under the prow
of a ship. I'm sure you've seen an empty ship riding way out of the
water and there is this bulbous thing sticking out of the hull. Also,
we were shown a movie of the men who bent the legs to the Space Needle
using the same method. After seeing this I had to try it for myself
and have bent and straightened both mild steel and stainless steel.
Eric

I'll try that. Thanks!

Do you have it packed tightly with sand when you bend it?


Don Foreman wrote:
http://users.goldengate.net/~dforeman/conduit/

Field-expedient tight bends in EMT for making stuff. Not pretty, but
it works.

I have also used this method for tightening cross braces... works great!

Mark


"Eric R Snow" wrote in message
...
On Tue, 02 Aug 2005 00:40:36 -0500, Don Foreman
wrote:

http://users.goldengate.net/~dforeman/conduit/

Field-expedient tight bends in EMT for making stuff. Not pretty, but
it works.
Nice job Don. Another method which works, and doesn't wrinkle the
metal, is to heat the area almost red or just till it starts being
red, and spray water on it. Do this a few times and the bend is very
controllable. I learned about this method in welding class. I saw it
being done at Lockheed Shipyard in Seattle before it closed. They were
using huge torches to heat 3 inch thick steel pie shaped sections.
These were being curved so they could be welded into a 1 half
spherical shape. It eventually was welded to the hull under the prow
of a ship. I'm sure you've seen an empty ship riding way out of the
water and there is this bulbous thing sticking out of the hull. Also,
we were shown a movie of the men who bent the legs to the Space Needle
using the same method. After seeing this I had to try it for myself
and have bent and straightened both mild steel and stainless steel.
Eric

"Eric R Snow" wrote in message
...
On Tue, 02 Aug 2005 00:40:36 -0500, Don Foreman
wrote:

http://users.goldengate.net/~dforeman/conduit/

Field-expedient tight bends in EMT for making stuff. Not pretty, but
it works.
Nice job Don. Another method which works, and doesn't wrinkle the
metal, is to heat the area almost red or just till it starts being
red, and spray water on it. Do this a few times and the bend is very
controllable. I learned about this method in welding class. I saw it
being done at Lockheed Shipyard in Seattle before it closed. They were
using huge torches to heat 3 inch thick steel pie shaped sections.
These were being curved so they could be welded into a 1 half
spherical shape. It eventually was welded to the hull under the prow
of a ship. I'm sure you've seen an empty ship riding way out of the
water and there is this bulbous thing sticking out of the hull. Also,
we were shown a movie of the men who bent the legs to the Space Needle
using the same method. After seeing this I had to try it for myself
and have bent and straightened both mild steel and stainless steel.
Eric

Could you provide a few more details? I am assuming you spray a small
quantity of water on the inside of the curve to be bent, correct?

Jerry

Don,
You will find that the wrinkle bends whould be limited to 15 degrees each.
To do a 90 you should have six wrinkles. I first stumbled on to this
procedure in an old Union Carbide gas welding textbook. The procedure works
with any size pipe and if you follow the 15 degree rule there is no
appreciable reduction in cross sectional area so fluids are not restricted.
On really big pipe a com-a-long is needed to maintain bending force as you
heat the pie section.
As you mention cooling off after each heat is necessary so that you can
locate the wrinkle accurately.
Randy

"Don Foreman" wrote in message
...
http://users.goldengate.net/~dforeman/conduit/

Field-expedient tight bends in EMT for making stuff. Not pretty, but
it works.

"Randy Zimmerman" wrote in message
news:Q01Ie.100937$5V4.49675@pd7tw3no...
Don,
You will find that the wrinkle bends whould be limited to 15 degrees
each.
To do a 90 you should have six wrinkles. I first stumbled on to
this
procedure in an old Union Carbide gas welding textbook. The
procedure works
with any size pipe and if you follow the 15 degree rule there is no
appreciable reduction in cross sectional area so fluids are not
restricted.
On really big pipe a com-a-long is needed to maintain bending force
as you
heat the pie section.
As you mention cooling off after each heat is necessary so that
you can
locate the wrinkle accurately.
Randy


I have a "Copper and Brass Pipe and Tube Bending Handbook", published
in 1954 by the Copper & Brass Research Association, that has 8 pages
of text, tables, and photos devoted to the subject of wrinkle bending.
Maybe I'll scan them and post to my personal page...

On Tue, 2 Aug 2005 16:25:40 -0700, "M" mark@maxmachinedotcom wrote:



I have also used this method for tightening cross braces... works great!

Mark
I never thought of that. It sounds like it could be a great way in
some situations.
Eric

"Eric R Snow" wrote in message
.. .
On Tue, 02 Aug 2005 00:40:36 -0500, Don Foreman
wrote:

http://users.goldengate.net/~dforeman/conduit/

Field-expedient tight bends in EMT for making stuff. Not pretty, but
it works.
Nice job Don. Another method which works, and doesn't wrinkle the
metal, is to heat the area almost red or just till it starts being
red, and spray water on it. Do this a few times and the bend is very
controllable. I learned about this method in welding class. I saw it
being done at Lockheed Shipyard in Seattle before it closed. They were
using huge torches to heat 3 inch thick steel pie shaped sections.
These were being curved so they could be welded into a 1 half
spherical shape. It eventually was welded to the hull under the prow
of a ship. I'm sure you've seen an empty ship riding way out of the
water and there is this bulbous thing sticking out of the hull. Also,
we were shown a movie of the men who bent the legs to the Space Needle
using the same method. After seeing this I had to try it for myself
and have bent and straightened both mild steel and stainless steel.
Eric

On Wed, 03 Aug 2005 00:03:02 GMT, "Jerry Foster"
wrote:


"Eric R Snow" wrote in message
.. .
On Tue, 02 Aug 2005 00:40:36 -0500, Don Foreman
wrote:

http://users.goldengate.net/~dforeman/conduit/

Field-expedient tight bends in EMT for making stuff. Not pretty, but
it works.
Nice job Don. Another method which works, and doesn't wrinkle the
metal, is to heat the area almost red or just till it starts being
red, and spray water on it. Do this a few times and the bend is very
controllable. I learned about this method in welding class. I saw it
being done at Lockheed Shipyard in Seattle before it closed. They were
using huge torches to heat 3 inch thick steel pie shaped sections.
These were being curved so they could be welded into a 1 half
spherical shape. It eventually was welded to the hull under the prow
of a ship. I'm sure you've seen an empty ship riding way out of the
water and there is this bulbous thing sticking out of the hull. Also,
we were shown a movie of the men who bent the legs to the Space Needle
using the same method. After seeing this I had to try it for myself
and have bent and straightened both mild steel and stainless steel.
Eric

Could you provide a few more details? I am assuming you spray a small
quantity of water on the inside of the curve to be bent, correct?

Jerry

Greetings Jerry,
What happens is that the heated metal expands. Since the hot metal is
plastic it will move as far as it can, which is where the metal is too
cool to deform. Then when the hot area is cooled the space between the
molecules shrinks and the metal contracts. If left to cool slowly the
displaced metal will move back into it's original shape. But rapid
cooling prevents this so instead the metal shrinks. So rapid cooling
is important. The metal you are shrinking must be able to go through
these hot and cold cycles without damage. So mild steel is a good
candidate for this process. It takes practice but not that much and
once mastered it can be real useful. Another place this method is used
is with removing dents from sheet metal, as in auto bodies. Big dents
in an auto body stretch the metal and to avoid using bondo to fill the
depression heat shrinking the area is sometimes used to fix these
dents. I've done it with a torch and a wet rag. Sheet metal is so thin
that a wet rag can cool the area fast enough.
ERS

On Tue, 2 Aug 2005 16:25:40 -0700, M mark@maxmachinedotcom wrote:


I have also used this method for tightening cross braces... works great!

Silly question - don't the tight bends in EMT make it a bitch to pull
wire through it?

It is very important to understand that you do not cool the red area. If
you have spray mist or wet rags you cool the area surrounding the red
section keeping as large a temperature gradient as possible. The larger the
temperature difference the larger the forces are on the plastic red area.
You chase the perimeter of the red until it disappears. At that point there
is no more plastic movement .
In our local area a huge pipe bender is being set up that will heat by
induction using massive amounts of electrical power and at the same time
water spray mist is applied. This is for large pipe over two feet diameter
from what I understand.
Or.... you can build a 3000 ton horizontal press that pushes the pipe. We
built one for a customer over a year ago,.
Randy

"Eric R Snow" wrote in message
...

Greetings Jerry,
What happens is that the heated metal expands. Since the hot metal is
plastic it will move as far as it can, which is where the metal is too
cool to deform. Then when the hot area is cooled the space between the
molecules shrinks and the metal contracts. If left to cool slowly the
displaced metal will move back into it's original shape. But rapid
cooling prevents this so instead the metal shrinks. So rapid cooling
is important. The metal you are shrinking must be able to go through
these hot and cold cycles without damage. So mild steel is a good
candidate for this process. It takes practice but not that much and
once mastered it can be real useful. Another place this method is used
is with removing dents from sheet metal, as in auto bodies. Big dents
in an auto body stretch the metal and to avoid using bondo to fill the
depression heat shrinking the area is sometimes used to fix these
dents. I've done it with a torch and a wet rag. Sheet metal is so thin
that a wet rag can cool the area fast enough.
ERS

I'd be interested.
Karl

"Rick" wrote in message
et...

"Randy Zimmerman" wrote in message
news:Q01Ie.100937$5V4.49675@pd7tw3no...
Don,
You will find that the wrinkle bends whould be limited to 15 degrees
each.
To do a 90 you should have six wrinkles. I first stumbled on to
this
procedure in an old Union Carbide gas welding textbook. The
procedure works
with any size pipe and if you follow the 15 degree rule there is no
appreciable reduction in cross sectional area so fluids are not
restricted.
On really big pipe a com-a-long is needed to maintain bending force
as you
heat the pie section.
As you mention cooling off after each heat is necessary so that
you can
locate the wrinkle accurately.
Randy


I have a "Copper and Brass Pipe and Tube Bending Handbook", published
in 1954 by the Copper & Brass Research Association, that has 8 pages
of text, tables, and photos devoted to the subject of wrinkle bending.
Maybe I'll scan them and post to my personal page...

On Thu, 04 Aug 2005 01:26:43 GMT, "Randy Zimmerman"
wrote:

It is very important to understand that you do not cool the red area. If
you have spray mist or wet rags you cool the area surrounding the red
section keeping as large a temperature gradient as possible. The larger the
temperature difference the larger the forces are on the plastic red area.
You chase the perimeter of the red until it disappears. At that point there
is no more plastic movement .
In our local area a huge pipe bender is being set up that will heat by
induction using massive amounts of electrical power and at the same time
water spray mist is applied. This is for large pipe over two feet diameter
from what I understand.
Or.... you can build a 3000 ton horizontal press that pushes the pipe. We
built one for a customer over a year ago,.
Randy

Randy,
When I learned this water was applied to the red area. And stuff
shrank right up. This is what I was taught: The red area, as it cools,
draws the metal in toward the cooled area. I will try your method
however, because it always pays to know as much as possible.
Thanks,
Eric
"Eric R Snow" wrote in message
.. .

Greetings Jerry,
What happens is that the heated metal expands. Since the hot metal is
plastic it will move as far as it can, which is where the metal is too
cool to deform. Then when the hot area is cooled the space between the
molecules shrinks and the metal contracts. If left to cool slowly the
displaced metal will move back into it's original shape. But rapid
cooling prevents this so instead the metal shrinks. So rapid cooling
is important. The metal you are shrinking must be able to go through
these hot and cold cycles without damage. So mild steel is a good
candidate for this process. It takes practice but not that much and
once mastered it can be real useful. Another place this method is used
is with removing dents from sheet metal, as in auto bodies. Big dents
in an auto body stretch the metal and to avoid using bondo to fill the
depression heat shrinking the area is sometimes used to fix these
dents. I've done it with a torch and a wet rag. Sheet metal is so thin
that a wet rag can cool the area fast enough.
ERS

"Karl Vorwerk" wrote in message
...
I'd be interested.
Karl

"Rick" wrote in message
et...
I have a "Copper and Brass Pipe and Tube Bending Handbook",
published
in 1954 by the Copper & Brass Research Association, that has 8
pages
of text, tables, and photos devoted to the subject of wrinkle
bending.
Maybe I'll scan them and post to my personal page...


OK. I've scanned the entire bending handbook (30 pages) in jpg. I'll
upload it as time allows then post a link. It covers hand, machine,
and wrinkle bending.

Each scan is about 300K though (scanned at 150 dpi) so it's going to
take me a while to upload on a dialup..

If you can picture the shrinkage action the only upsetting that happens is
the red metal. The cool metal surrounding it is preventing the red from
expanding so it upsets/swells. When you cool that area around the red the
cooling metal fights the expanding red area increasing the upsetting. Once
the whole area is black the metal is cooling and contracting but the
shrinkage effect is lost..
I have bent one inch plate heating it to a red on one side and spraying air
/water mist at the same time on the other side. It will take a kink out
right fast.
Randy

"Eric R Snow" wrote in message
...
Randy,
When I learned this water was applied to the red area. And stuff
shrank right up. This is what I was taught: The red area, as it cools,
draws the metal in toward the cooled area. I will try your method
however, because it always pays to know as much as possible.
Thanks,

On Fri, 05 Aug 2005 04:00:50 GMT, "Randy Zimmerman"
wrote:

If you can picture the shrinkage action the only upsetting that happens is
the red metal. The cool metal surrounding it is preventing the red from
expanding so it upsets/swells. When you cool that area around the red the
cooling metal fights the expanding red area increasing the upsetting. Once
the whole area is black the metal is cooling and contracting but the
shrinkage effect is lost..
I have bent one inch plate heating it to a red on one side and spraying air
/water mist at the same time on the other side. It will take a kink out
right fast.
Randy

Randy,
I did exactly that method on the back blade for my tractor. My
neighbor was dubious, but it worked great.
Eric
"Eric R Snow" wrote in message
.. .
Randy,
When I learned this water was applied to the red area. And stuff
shrank right up. This is what I was taught: The red area, as it cools,
draws the metal in toward the cooled area. I will try your method
however, because it always pays to know as much as possible.
Thanks,

"Rick" wrote in message
.net...

"Karl Vorwerk" wrote in message
...
I'd be interested.
Karl


Posted in JPG at http://home.tir.com/~artemus/Bending%20Tube/