Repairing a well-rusted cluster?

I could use some brainstorming on how to approach the rusted cluster
shown at http://members.cox.net/mhorowit/cluster/ - Thanks, Mike

Michael Horowitz wrote:
I could use some brainstorming on how to approach the rusted cluster
shown at http://members.cox.net/mhorowit/cluster/ - Thanks, Mike

You're going to have to cut the cluster out and fabricate a new one that
you splice in with truncated sleeve and rosette weld repairs per AC43.

1. Make a bracing fixture to hold the fuselage in alignment in the area
of the repair.
2. Cut the cluster out about 12" out on each tube or as far as you have
to go to get unrusted metal..
3. Do a splice repair on the longeron tube with truncated sleeves per
the standard method, temporarily tacked in place.
4. Prepare and fit the diagonal tubes to duplicate the original cluster
and tack them them with splice sleeves at each junction with the old tubing.
5. When everything is fitted peachy keen weld 'er up.

John

While we're on the subject, I have a question about Rosette welds. With the
specified hole size in realtion to the thickness of the metal, I have a
hard time getting the metal underneath to heat up enough to melt before I
blow away the metal on top. I have preheated the innner piece as much as
possible and this does produce better results, but It's still a bit hit and
miss. Is there a trick? Smaller tip? Bigger?

On Wed, 19 Sep 2007 17:23:13 +0000 (UTC), Fortunat1 wrote:


While we're on the subject, I have a question about Rosette welds. With the
specified hole size in realtion to the thickness of the metal, I have a
hard time getting the metal underneath to heat up enough to melt before I
blow away the metal on top. I have preheated the innner piece as much as
possible and this does produce better results, but It's still a bit hit and
miss. Is there a trick? Smaller tip? Bigger?

This is first cousin to the posting I just made concerning welding an
inner sleeve. Unfortunately, the solution is probably different.

What I was shown was to drill an 1/8" hole in the top layer, aim the
flame at the inner piece and let the 1/8" hole melt back. by the time
the hole increases to 1/4", the inner piece will have formed a
puddle. Give her a try on some scrap; I tried it with two pieces of
sheetmetal and it worked. - Mike

Michael Horowitz wrote in
:

On Wed, 19 Sep 2007 17:23:13 +0000 (UTC), Fortunat1 wrote:


While we're on the subject, I have a question about Rosette welds.
With the specified hole size in realtion to the thickness of the
metal, I have a hard time getting the metal underneath to heat up
enough to melt before I blow away the metal on top. I have preheated
the innner piece as much as possible and this does produce better
results, but It's still a bit hit and miss. Is there a trick? Smaller
tip? Bigger?

This is first cousin to the posting I just made concerning welding an
inner sleeve. Unfortunately, the solution is probably different.

What I was shown was to drill an 1/8" hole in the top layer, aim the
flame at the inner piece and let the 1/8" hole melt back. by the time
the hole increases to 1/4", the inner piece will have formed a
puddle. Give her a try on some scrap; I tried it with two pieces of
sheetmetal and it worked. - Mike



Yes, I've tried a few pieces and had mixed results. You've certainly
answered one question that was banging around in my head and that was "can
you allow the hole on the top piece to expand?" Apparently you can.
A bigger problem for me is one of the parts I have to make is a compression
tube with a solid plug in the end. Actually Ii have to make 12 of them. The
plans call for fixing this plug in the tube end (3/4 .035 tube) with a pair
of rosettes. I've tried this and actually found it easier than the blind
plug thing by heating the plug where it's exposed and then zapping in the
rosette while it's hot. I'm finding the blind rosettes a lot more difficult
but I don't seem to be doing anything too wrong so it muct just come down
to practice!

"Fortunat1" wrote in message
...

While we're on the subject, I have a question about Rosette welds. With
the
specified hole size in realtion to the thickness of the metal, I have a
hard time getting the metal underneath to heat up enough to melt before I
blow away the metal on top. I have preheated the innner piece as much as
possible and this does produce better results, but It's still a bit hit
and
miss. Is there a trick? Smaller tip? Bigger?

I would think that you need less heat and more patience. I'm not the
world's greatest gas welder, but until someone else that is comes along and
says something, I'll give it a shot.

I think you need much less heat. If you concentrate the heat on the inner
tube, and get a molten puddle going, you can then make the rose shape in a
pattern around a point in the middle of the hole.

It does not take that much heat to get the puddle going. If you concentrate
a small flame on the middle, the rod will slowly melt into the puddle. If
it isn't kinda' slow, your flame is too big, or too hot. A good molten
puddle filling in the hole will get the outsides of the outer tube's hole
molten, and blend into the rose.

Does that make sense to you?
--
Jim in NC

"Morgans" wrote in
:


"Fortunat1" wrote in message
...

While we're on the subject, I have a question about Rosette welds.
With the
specified hole size in realtion to the thickness of the metal, I have
a hard time getting the metal underneath to heat up enough to melt
before I blow away the metal on top. I have preheated the innner
piece as much as possible and this does produce better results, but
It's still a bit hit and
miss. Is there a trick? Smaller tip? Bigger?

I would think that you need less heat and more patience. I'm not the
world's greatest gas welder, but until someone else that is comes
along and says something, I'll give it a shot.

I think you need much less heat. If you concentrate the heat on the
inner tube, and get a molten puddle going, you can then make the rose
shape in a pattern around a point in the middle of the hole.

It does not take that much heat to get the puddle going. If you
concentrate a small flame on the middle, the rod will slowly melt into
the puddle. If it isn't kinda' slow, your flame is too big, or too
hot. A good molten puddle filling in the hole will get the outsides
of the outer tube's hole molten, and blend into the rose.

Does that make sense to you?

Not only makes sense. It seems to work just fine.
Not so much the less heat, but the more patience part. One of the
problems I was having was I tended to chicken out when the edges of the
outer tube started getting soggy. This time I just ignored that and went
in as close as possible to the base tube and held it there until I
started getting one big puddle. At that point I started a circle with
the rod and voila!

Thanks!

"Michael Horowitz" wrote in message
...
I could use some brainstorming on how to approach the rusted cluster
shown at http://members.cox.net/mhorowit/cluster/ - Thanks, Mike

Wow, you don't ask too much, do you!

What a mess. Like the other said, secure the location of the tubes, cut off
at good part and splice (or replace the whole tube, for the diagonal and
uprights) and fit it up to make a new cluster. Not any other choice, that I
am aware of.
--
Jim in NC

On Sun, 16 Sep 2007 15:04:11 -0400, "Morgans"
wrote:


"Michael Horowitz" wrote in message
.. .
I could use some brainstorming on how to approach the rusted cluster
shown at http://members.cox.net/mhorowit/cluster/ - Thanks, Mike

Wow, you don't ask too much, do you!

What a mess. Like the other said, secure the location of the tubes, cut off
at good part and splice (or replace the whole tube, for the diagonal and
uprights) and fit it up to make a new cluster. Not any other choice, that I
am aware of.

You definitely need to cut that one out and start over. With rust that
bad at the cluster, I'd be checking all the tubes, particularly that
lower longeron pretty closely a ways in either direction!!!

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

John has given you some good advice, in my opinion.

When the corrosion is this bad you have to take the possibility of
internal rusting into account.

I've a hunch the cluster is suffering from a quickie repair made in
the distant past, which would cause me to distrust the other welds
associated with that cluster.

Take special pains with your jigging before doing any cutting. The
usual procedure is to create a tack-welded secondary structure with
good triangulation so that cutting away the rotten stuff will not
disturb the alignment. Another method (for those who know how) is
bondo, bailing wire and wooden struts. A third is to affix the
structure to the hangar floor. The need for special care at this
stage is because the welding needed to do the repair will introduce
some distortion. Establish good trammel points before doing any
cutting.

I've found that when the corrosion is this bad the MORE of the
existing structure you cut away, the LESS chance of ending up with a
'crank' structure.

-R.S.Hoover