Welding An Aluminum Rim

I have a Campy rim made of Aluminum. The rim was originally joined
together by way of a metal sleeve which slots together both ends and is
glued together making the hoop. About a year ago I hit a pot hole and
the rim split apart at this metal sleeve. The metal sleeve is
irreparable, but the rim is still good. I was wondering if it's
feasible to have a welder weld the rim seam together and have the weld
ground down smooth and flat to the braking surface. Can this be done
and would this wheel be safe to ride on?

"Kenny" wrote: (clip) I was wondering if it's feasible to have a welder
weld the rim seam together and have the weld ground down smooth and flat to
the braking surface and would this wheel be safe to ride on?
^^^^^^^^^^^^^^^^
I suggest posting to sci.engr.joining.welding. There are some real experts
there. I have been welding for years, but by no means consider myself an
expert. But I have my doubts. You have several problems to overcome: loss
of strength in the aluminum from the welding heat, perfect alignment of the
ends of the rim, distortion of the metal around the weld, removal of the
excess weld bead on the braking surfaces, adequate preservation of the
surfacre where the bead fits inside the rim. These challenges would involve
so much time and skill that, even if it can be done, the cost would likely
exceed the cost of a new rim.

Kenny wrote:

I have a Campy rim made of Aluminum. The rim was originally joined
together by way of a metal sleeve which slots together both ends and is
glued together making the hoop. About a year ago I hit a pot hole and
the rim split apart at this metal sleeve. The metal sleeve is
irreparable, but the rim is still good. I was wondering if it's
feasible to have a welder weld the rim seam together and have the weld
ground down smooth and flat to the braking surface. Can this be done
and would this wheel be safe to ride on?

Are you sure the metal "sleeve" or tongue is beyond repair? No glue is
normally required, as rims are under a HUGE compressive stress when
built up. In the days before machined rims it was common for
wheelbuilders to have to manipulate this joint a little before
tensioning the wheel, otherwise there would be a little lip to catch the
brake pads.

I wouldn't weld it. The chances of doing so without weakening the
metal, and getting the end result flat, are minimal.

"Zog The Undeniable" wrote: (clip) Are you sure the metal "sleeve" or
tongue is beyond repair? No glue is normally required, as rims are under a
HUGE compressive stress when built up. (clip)
^^^^^^^^^^^^^^
After reading Zog's post, I think it could be repairable by welding. I
would build the wheel, relying on the spoke tension toclose and hold the
joint in position. Then take it to a welder and have him make a couple of
very small TIG welds, just enough to keep it from ever slipping sidewise.
Do not weld the braking surface. I think you will wind up with a usable
wheel.

Kenny wrote:
I have a Campy rim made of Aluminum. The rim was originally joined
together by way of a metal sleeve which slots together both ends and is
glued together making the hoop. About a year ago I hit a pot hole and
the rim split apart at this metal sleeve. The metal sleeve is
irreparable, but the rim is still good. I was wondering if it's
feasible to have a welder weld the rim seam together and have the weld
ground down smooth and flat to the braking surface. Can this be done
and would this wheel be safe to ride on?

rims welded at the factory are resistance welded. ie. local electrical
heating followed by mechanical pressure to "smudge" the two hot surfaces
together. this means lower temperatures and less recrystallization.
tig is an entirely different process involving a molten weld pool &
greater heat. if as suggested by leo, you have a couple of small spots
holding the seam toether, you can probably get away with it, but i
wouldn't assign a high probability of the welds lasting.

Kenny Post writes:

I have a Campy rim made of Aluminum. The rim was originally joined
together by way of a metal sleeve which slots together both ends and
is glued together making the hoop. About a year ago I hit a pot
hole and the rim split apart at this metal sleeve. The metal sleeve
is irreparable, but the rim is still good. I was wondering if it's
feasible to have a welder weld the rim seam together and have the
weld ground down smooth and flat to the braking surface. Can this
be done and would this wheel be safe to ride on?

Don't mess with the welding. This is not something that can be done
other than by resistance welding in a fixtured machine and with a
slight oversize of the hoop that gets slightly shorter in the process.

As has been discussed here in the past, once the rim is tightly
spoked, it won't even need an alignment insert to operate under load,
the compression forces are great enough to keep the rim aligned.
Since this alignment is not there when you start spoking the wheel,
you either need an external guide, such as a C-clamp and pressure
plates both laterally and radially to hold the rim flush. Once
complete, a tight wheel puts insufficient shear stress on the cross
section to go out of alignment.

This was made clear in the days of tubular rims that were all aligned
with inserts of varying precision and often required a bit of lateral
shoving to avoid having a step in the brake surface. Many of these
rims were not held together. That is they could be manually pulled
apart before spoking.

If your rim s truly undamaged, build it up again as I described. On
the other hand, I can't imagine damaging the insert without bending
the rim.

On 8 Apr 2005 08:05:44 -0700, "Kenny" wrote:

I have a Campy rim made of Aluminum. The rim was originally joined
together by way of a metal sleeve which slots together both ends and is
glued together making the hoop. About a year ago I hit a pot hole and
the rim split apart at this metal sleeve. The metal sleeve is
irreparable, but the rim is still good. I was wondering if it's
feasible to have a welder weld the rim seam together and have the weld
ground down smooth and flat to the braking surface. Can this be done
and would this wheel be safe to ride on?

If you weld that joint, you're going to end up with an undersize rim.
I'd fabricate a replacement for the insert and lightly repoke the
wheel; if it can be made to run reasonably true at a low tension, then
I'd call it a suitable candidate for finishing the job and taking it
to full in-service tension. I suspect, however, that you will
discover that it's bent; I can't imagine that the rim would have been
able to fail in a manner that damaged the insert and left the hoop
unscathed. My expectation is that this rim will be found to be junk.
--
Typoes are a feature, not a bug.
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Words processed in a facility that contains nuts.

No way of welding that rim. Welded rims are done via flash welding, an
autogenous process (no filler material) similar to bandsaw welding.
Each end is held in a copper chuck and current is run through the rim.
The ends are then forced together and the current takes the shorter
path, through the joint instead of the rim. This heats the joint to
the point of melting and the fusion pressure forces the excess material
from the joint. The current ceases and the resultant heat affected zone
is tiny.

Even the best GTAW (TIG) welder will make a heat affected zone 4 times
the thickness. It will be ugly and unsafe.

Pin the joint.


--
Weisse Luft

"Leo Lichtman" wrote in message
...

"Zog The Undeniable" wrote: (clip) Are you sure the metal "sleeve" or
tongue is beyond repair? No glue is normally required, as rims are under
a HUGE compressive stress when built up. (clip)
^^^^^^^^^^^^^^
After reading Zog's post, I think it could be repairable by welding. I
would build the wheel, relying on the spoke tension toclose and hold the
joint in position. Then take it to a welder and have him make a couple of
very small TIG welds, just enough to keep it from ever slipping sidewise.
Do not weld the braking surface. I think you will wind up with a usable
wheel.

The "sleeve" does nothing but hold the rim in alignment prior to the spoking
process. In many cases it's nothing more than a block of aluminum.

There are some 32 holes of so in the rim and the spoke is under about 150
lbs of tension. 32 * 150 is 4800 lbs. Do you suppose at "sleeve" is going to
withstand any sort of misalignment forces that would put the ends of the rim
apart?

Welding aluminum is a sure way to simply destroy the rim. Most rim materials
aresilicon alloys which don't weld well and become brittle at welds.

But if that's what you think you can get away with go right ahead.

On 2005-04-08, Kenny wrote:

I have a Campy rim made of Aluminum. The rim was originally joined
together by way of a metal sleeve which slots together both ends and is
glued together making the hoop. About a year ago I hit a pot hole and
the rim split apart at this metal sleeve. The metal sleeve is
irreparable, but the rim is still good. I was wondering if it's
feasible to have a welder weld the rim seam together and have the weld
ground down smooth and flat to the braking surface. Can this be done
and would this wheel be safe to ride on?

No; don't do it. Pinned rims are generally made from alloys that shouldn't
be welded. Just spring for a new rim...

--

-John )