Bicycle Mechanics - Cracked aluminum frame, able to fix by welding?
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Hi, I have an aluminum Klein Quantum frame and recently, the derraileur hanger cracked. It did not break off, but is cracked on one side. I was wondering if there were any forms of welding the hanger back together would be possible, (its not a replaceable hanger), so, if anyone has some feedback, that would be helpful.
Yes, there are, but they will be difficult to do in a small repair. Have you talked to a decent frame builder, or perhaps a welder? Have you called Klein?
11-07-02, 01:28 PM
A good welding shop should have a TIG machine, which is probably the method most appropriate for an aluminum bike frame. Also, check with your LBS to see if they can recommend anyone in your area who can perform such a repair.
11-07-02, 01:32 PM
hah....good one byron
11-07-02, 08:23 PM
Yes, your hanger can be repaired. I done a few broken hangers on aluminum frames. I think Kline bikes are built with 7000 series alum. 7000 series can be allowed to air cool without any big loss of strength. You will have to remove the paint from the area, any paint sucked into the weld puddle will weaken the weld. I still don't know why any frame builder would build an aluminum frame without a replaceable hanger. Its not a huge job, should only take an hour or so. (hard to say without seeing it) Most weld shops would charge $50 or so, some more some less. You will need to strip down the frame. And after repairing the hanger you may need to realign the hanger.
There may be another way... Take a look at www.exposales.net they sell an aluminum brazing rod. It melts at 735* and flows into the gain of the base metal (alum melts around 1100*) A propane torch would work well. The rod is called HTS-735. I have not used it myself, but I have seen a few things repaired with it. I would not use this to repair a high stress aera such as a cracked headtube, but it should work on a hanger. the rod has a tensile rating of 45,000 psi and shear of 31,000 psi.
thanks for the reply, would any welding shop beable to do this? WHat did you mean by strip down? take off all the parts? thanks for this info
11-07-02, 08:57 PM
You'll have to take off any parts near the hanger. The brake should be far enough away that the heat won't hurt it. If you have a chainstay protector I'd take it off too.
I would just call around to some of the welding shops and see if they can weld aluminum.
11-07-02, 09:36 PM
and take off all the paint in the region. so it doesnt burn, or fall into the weld.
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