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#1
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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? |
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#2
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"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. |
#3
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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. |
#4
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"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. |
#5
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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. |
#6
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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. |
#7
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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. Some gardening required to reply via email. Words processed in a facility that contains nuts. |
#8
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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 |
#9
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"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. |
#10
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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 ) |
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