Welding question: joining an inner sleeve

Please see the sketch at http://members.cox.net/mhorowit/cluster/
Using Oxyacetylene, how do I get the base molten without burning the
two pieces that form the 1/8" gap? Are "chill bars" the only choice?
MikeH

Michael Horowitz wrote:
Please see the sketch at http://members.cox.net/mhorowit/cluster/
Using Oxyacetylene, how do I get the base molten without burning the
two pieces that form the 1/8" gap? Are "chill bars" the only choice?
MikeH

If while playing with different heat settings you can't get the base
metal hot enough while not burning away the edges, you'll have to clamp
heat sinks to the upper parts.

However, you don't have to get the base completely molten to start a
weld. You get it just under molten, drop a molten bead on it, then heat
the bead itself until it fuses and blends with the underlying metal on
each surface, then start adding more rod to get the resulting puddle
nice and full with a nice fused feather edge all around, then start
moving. Putting down molten rod just before the base metal is molten
is the best way to weld exposed edges without burn back. You'll have to
carefully observe the edge of the puddle that is on the base material to
be sure it is blending and fusing.

The rod tip itself is key to controlling the amount of heat going into
the puddle. If an edge gets too hot and starts to burn away, don't back
right off, just back off a tiny bit while at the same time putting the
rod tip between the torch and the overheated edge and drop some rod
metal there. That gives a bit of breathing room while you adjust and go
back in. Mastering the technique of backing off just enough but not too
much makes a big difference because now you can stay in control while
doing a really tricky joint that is not tolerant of excess heat, and
when you get burn through's, you can pause to fill the hole and then
keep going without missing a beat.

John

On Wed, 19 Sep 2007 20:25:46 -0400, "J.Kahn"
wrote:

Michael Horowitz wrote:
Please see the sketch at http://members.cox.net/mhorowit/cluster/
Using Oxyacetylene, how do I get the base molten without burning the
two pieces that form the 1/8" gap? Are "chill bars" the only choice?
MikeH

If while playing with different heat settings you can't get the base
metal hot enough while not burning away the edges, you'll have to clamp
heat sinks to the upper parts.

However, you don't have to get the base completely molten to start a
weld. You get it just under molten, drop a molten bead on it, then heat
the bead itself until it fuses and blends with the underlying metal on
each surface, then start adding more rod to get the resulting puddle
nice and full with a nice fused feather edge all around, then start
moving. Putting down molten rod just before the base metal is molten
is the best way to weld exposed edges without burn back. You'll have to
carefully observe the edge of the puddle that is on the base material to
be sure it is blending and fusing.

The rod tip itself is key to controlling the amount of heat going into
the puddle. If an edge gets too hot and starts to burn away, don't back
right off, just back off a tiny bit while at the same time putting the
rod tip between the torch and the overheated edge and drop some rod
metal there. That gives a bit of breathing room while you adjust and go
back in. Mastering the technique of backing off just enough but not too
much makes a big difference because now you can stay in control while
doing a really tricky joint that is not tolerant of excess heat, and
when you get burn through's, you can pause to fill the hole and then
keep going without missing a beat.

John


This is tubing, right? Drill a couple of holes and rosette weld, or
plug weld the sleave in place. It is now doing it's job Now weld the
ends of the tubes together. If the weld penetrates into the
re-enforcement sleave, good. If it doesn't the sleave is still in
there providing extra strength to the joint (done properly, the joint
is almost strong enough with just 4 plug welds per end)

--
Posted via a free Usenet account from http://www.teranews.com

clare at snyder.on.ca wrote in news:r3k3f35vka26ss9jq6k80m2cr1ef67usun@
4ax.com:



This is tubing, right? Drill a couple of holes and rosette weld, or
plug weld the sleave in place. It is now doing it's job Now weld the
ends of the tubes together. If the weld penetrates into the
re-enforcement sleave, good. If it doesn't the sleave is still in
there providing extra strength to the joint (done properly, the joint
is almost strong enough with just 4 plug welds per end)


This makes sense to me, however, looking in my books, it's stated pretty
clearly that the inner tube should be welded to the outers.
there's a copy of that text he

http://www2.tech.purdue.edu/at/cours...Ac43-13-1B/CH4
_5.pdf

Now, it would seem to me that penetration of the inner tube would add very
little strength at all, particularly if it was a good snug fit. Am I
reading this wrong?

"Michael Horowitz" wrote in message
...
Please see the sketch at http://members.cox.net/mhorowit/cluster/
Using Oxyacetylene, how do I get the base molten without burning the
two pieces that form the 1/8" gap? Are "chill bars" the only choice?
MikeH

Will your situation allow you to increase the gap? Perhaps heating a little
slower and increasing the gap would work for you.

On Thu, 20 Sep 2007 04:46:45 +0000 (UTC), Fortunat1 wrote:

clare at snyder.on.ca wrote in news:r3k3f35vka26ss9jq6k80m2cr1ef67usun@
4ax.com:



This is tubing, right? Drill a couple of holes and rosette weld, or
plug weld the sleave in place. It is now doing it's job Now weld the
ends of the tubes together. If the weld penetrates into the
re-enforcement sleave, good. If it doesn't the sleave is still in
there providing extra strength to the joint (done properly, the joint
is almost strong enough with just 4 plug welds per end)


This makes sense to me, however, looking in my books, it's stated pretty
clearly that the inner tube should be welded to the outers.
there's a copy of that text he

http://www2.tech.purdue.edu/at/cours...Ac43-13-1B/CH4
_5.pdf

Now, it would seem to me that penetration of the inner tube would add very
little strength at all, particularly if it was a good snug fit. Am I
reading this wrong?

You're quoting a very general section. If you could cite the specific
sub-paragraph it might help - Mike

Michael Horowitz wrote in
:

On Thu, 20 Sep 2007 04:46:45 +0000 (UTC), Fortunat1 wrote:

clare at snyder.on.ca wrote in
news:r3k3f35vka26ss9jq6k80m2cr1ef67usun@ 4ax.com:



This is tubing, right? Drill a couple of holes and rosette weld, or
plug weld the sleave in place. It is now doing it's job Now weld the
ends of the tubes together. If the weld penetrates into the
re-enforcement sleave, good. If it doesn't the sleave is still in
there providing extra strength to the joint (done properly, the
joint is almost strong enough with just 4 plug welds per end)


This makes sense to me, however, looking in my books, it's stated
pretty clearly that the inner tube should be welded to the outers.
there's a copy of that text he

http://www2.tech.purdue.edu/at/cours...Links/Ac43-13-
1B
/CH4 _5.pdf

Now, it would seem to me that penetration of the inner tube would add
very little strength at all, particularly if it was a good snug fit.
Am I reading this wrong?

You're quoting a very general section. If you could cite the specific
sub-paragraph it might help - Mike



Sorry. Scroll down to 4-84.
There's a whole section on the type of repairs you're talking about.
4-84 specifically mentions including the innner tube into the weld. It
seems to me that the weld area would be at least as strong without
welding across the inner tube like that. If you weld a doubler on the
end of a strap, for instance, you don't lap weld across the widthe of
the strap where the thickness steps down, you only edge weld around the
outside perimeter. That would indicate to me that welding across a piece
of tubing, unneccesarily, only puts stress risers around the weld. If
it's a snug fit, you've got to have at least the same strength there you
had with the original tube.

"Fortunat1" wrote

Sorry. Scroll down to 4-84.
There's a whole section on the type of repairs you're talking about.
4-84 specifically mentions including the innner tube into the weld. It
seems to me that the weld area would be at least as strong without
welding across the inner tube like that. If you weld a doubler on the
end of a strap, for instance, you don't lap weld across the widthe of
the strap where the thickness steps down, you only edge weld around the
outside perimeter. That would indicate to me that welding across a piece
of tubing, unneccesarily, only puts stress risers around the weld. If
it's a snug fit, you've got to have at least the same strength there you
had with the original tube.

The repairs detailed in the "acceptable repairs" publication are time tested
and true. There have been tube and fabric planes being repaired in this
manner, for a very long time.

I would tend to believe that if it is outlined in a certain way, then there
is a good reason for it. As far as stress risers, gas welding done
correctly will not create them.
--
Jim in NC

Fortunat1 wrote:
clare at snyder.on.ca wrote in news:r3k3f35vka26ss9jq6k80m2cr1ef67usun@
4ax.com:


This is tubing, right? Drill a couple of holes and rosette weld, or
plug weld the sleave in place. It is now doing it's job Now weld the
ends of the tubes together. If the weld penetrates into the
re-enforcement sleave, good. If it doesn't the sleave is still in
there providing extra strength to the joint (done properly, the joint
is almost strong enough with just 4 plug welds per end)


This makes sense to me, however, looking in my books, it's stated pretty
clearly that the inner tube should be welded to the outers.
there's a copy of that text he

http://www2.tech.purdue.edu/at/cours...Ac43-13-1B/CH4
_5.pdf

Now, it would seem to me that penetration of the inner tube would add very
little strength at all, particularly if it was a good snug fit. Am I
reading this wrong?


I believe that you have to effectively have a full lap joint weld
between each outer tube and inner tube, AND the joint must be a
truncated cut and not just straight across in order to have sufficient
weld cross section since it's essential that the weld zone be much
stronger than the virgin metal up the tube.

The rosette welds done further up don't contribute that much strength
and are mostly (I believe) to prevent the inner tube from having an
unsupported length that allows "wiggling" of the inner tube in the outer
tube under stress. possibly leading to cracks in the main weld.

John

"J.Kahn" wrote in
:

Fortunat1 wrote:
clare at snyder.on.ca wrote in
news:r3k3f35vka26ss9jq6k80m2cr1ef67usun@ 4ax.com:


This is tubing, right? Drill a couple of holes and rosette weld, or
plug weld the sleave in place. It is now doing it's job Now weld the
ends of the tubes together. If the weld penetrates into the
re-enforcement sleave, good. If it doesn't the sleave is still in
there providing extra strength to the joint (done properly, the
joint is almost strong enough with just 4 plug welds per end)


This makes sense to me, however, looking in my books, it's stated
pretty clearly that the inner tube should be welded to the outers.
there's a copy of that text he

http://www2.tech.purdue.edu/at/cours...Links/Ac43-13-
1
B/CH4 _5.pdf

Now, it would seem to me that penetration of the inner tube would add
very little strength at all, particularly if it was a good snug fit.
Am I reading this wrong?


I believe that you have to effectively have a full lap joint weld
between each outer tube and inner tube, AND the joint must be a
truncated cut and not just straight across in order to have sufficient
weld cross section since it's essential that the weld zone be much
stronger than the virgin metal up the tube.

The rosette welds done further up don't contribute that much strength
and are mostly (I believe) to prevent the inner tube from having an
unsupported length that allows "wiggling" of the inner tube in the
outer tube under stress. possibly leading to cracks in the main weld.


OK, I can buy all of that, but I don't know exactly what you mean by
truncated. Are you talking about the profile of the edges of the outer
tube, or do you mean the outer tube must be cut diaganally?