Mtbr's 2016 Winter Biking GearReviews and Roundups

FAT BIKES

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  1. #1
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    aluminum welding for cracked frame?

    i've got a cracked 03 RM Switch Ltd. that's a year out of warranty. It blows, I know, so I've been sulking and feeling guilty about thrashing that baby for a few weeks, but now I just want to get back out on a ride! Anyone know anything about where I should go from here? Should I try to get in touch with a local framebuilder or could I just go with a general aluminum welder? I was referred by a local bike shop to talk to Frank the Welder at Sinister Bikes. Any idea on how long this welding would take or cost?

    Thanks, and thrash it hard!

  2. #2
    pronounced may-duh
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    I would go back to where you bought the bike or to the manufacture. Even out of the warantee period a good shop / bike company will make you a deal on a replacement frame. Remember it never hurts to ask.


    As for repair, I'm no expert but I would be wary of a repaired aluminium frame.

  3. #3
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    Aluminum can't be re-welded to its original strength like steel can. If you weld it, it will be barely any stronger than not, and you run the risk of a major breakage. I would just replace the frame rather than attempt to repair it.

  4. #4
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    Quote Originally Posted by somewhat_absent
    I was referred by a local bike shop to talk to Frank the Welder at Sinister Bikes. Any idea on how long this welding would take or cost?

    I agree with the guy who said you should talk to the manufacturer, warranty or not. Frank the Welder is legendary and should be able to fix your frame - although if it's 6061 the heat-treating might be a problem. I agree with the guy who said you should talk to the manufacturer, warranty or not. I'd get an estimate for both a replacement and a repair. The manufacturer may let you have a frame at cost,

  5. #5
    Lopen is sneller....
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    As above try and get a deal through your LBS or RMB. I have good experience with RMB...

    I had an aluminum chain stay re-welded and it's still holding up (about two years now). I would however not use that particular bike for anything else but XC and even then I'm worried it will leave me on the mountain some day.

    Good luck!

  6. #6
    those are Rollercams...
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    Another good reason to ride steel.

    I wouldn't take a chance with welding it, FTW's a master but he ain't a magician.

    Truly a wealth of useless information.


    http://blackdogadventureteam.blogspot.com/

  7. #7
    Tear it all out! SuperModerator
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    Pyrotek can do it, but it is probably cheaper to buy the parts from Rocky.

    Old article on Pinkbike about it:
    http://www.pinkbike.com/modules/news...leview&id=1117

  8. #8
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    theres not much to loose

  9. #9
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    Sorry, I'm a materials engineer and I can't help but to correct a couple things. Steel cannot be welded to it's original strength, there is always a heat effected zone. Post weld heat treatment is usually not required with steel, but the HAZ will have different structural properties than the parent metal.

    Heat treating AL isn't as hard as some make it out to be, especially with a swing arm that can fit into a home oven. 6061 heat treatment can be done in the 320 to 350 degree F range, 7000 series AL can be done much lower (room temp if you give it enough time but it is accelerated with temp). You would want to bring the 6061 down to T4 or even T0 after welding to balance the microstructure of the entire swing arm as much as possible, then bring it up to T6. Everything can be done with your oven and a bathtub. If you are married just make sure your wife isn't around with you use the kitchen and bathroom to fix your bike.

  10. #10
    AZ
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    Must be thread dredge week.

  11. #11
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    Dang, I need to get in the habit of checking the date of the OP not just the most recent post.

  12. #12
    Just a flesh wound
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    Quote Originally Posted by whydomylegshurt? View Post
    Sorry, I'm a materials engineer and I can't help but to correct a couple things. Steel cannot be welded to it's original strength, there is always a heat effected zone. Post weld heat treatment is usually not required with steel, but the HAZ will have different structural properties than the parent metal.

    Heat treating AL isn't as hard as some make it out to be, especially with a swing arm that can fit into a home oven. 6061 heat treatment can be done in the 320 to 350 degree F range, 7000 series AL can be done much lower (room temp if you give it enough time but it is accelerated with temp). You would want to bring the 6061 down to T4 or even T0 after welding to balance the microstructure of the entire swing arm as much as possible, then bring it up to T6. Everything can be done with your oven and a bathtub. If you are married just make sure your wife isn't around with you use the kitchen and bathroom to fix your bike.
    I had a Jekyll frame welded a few days ago. Cracked at the top tube to seat post weld. It is 6061 T6. I was going to bake it at 175 Celsius for 4 hours. Do I need to do anything else? Someone said I needed to heat the HAZ and quench it. Then artificial aging.
    My name is Chris and I ride a Prophet 650b with a Lefty.

  13. #13
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    Hopefull Fix

    ]Just got my frame back from the welder. Going to try to get alittle more out of it. I had him install another support tube to add extra strength to the weakened old crack site. Check the pic. Hope it holds. (for my sake)
    Attached Thumbnails Attached Thumbnails aluminum welding for cracked frame?-bikefix2.jpg  

    aluminum welding for cracked frame?-bike-fix.jpg  


  14. #14
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    New question here. Complete Newbie in need of advice

    Hi everyone

    Have been following the forums for a while V interesting. I have a question? My son has just bought a used kona king kikapu frame cos he wants to build a bike from scratch. The frame has been welded right up front where the frame meets forks/handlebar joint. Weld looks clean but he has been told not to risk using it by a guy in a bike store because it is an AL frame and so can't be welded safely. Is this true? and if not how do we check if the weld has been done well? Seller just says he thinks it is fine but will refund purchase price if we are not happy. Son would rather keep frame if possible but will take advice as he obviously doesn't want to build an unsafe bike or sell on an unsafe frame

    Any advice gratefully received

  15. #15
    AZ
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    Quote Originally Posted by mtbjac View Post
    Hi everyone

    Have been following the forums for a while V interesting. I have a question? My son has just bought a used kona king kikapu frame cos he wants to build a bike from scratch. The frame has been welded right up front where the frame meets forks/handlebar joint. Weld looks clean but he has been told not to risk using it by a guy in a bike store because it is an AL frame and so can't be welded safely. Is this true? and if not how do we check if the weld has been done well? Seller just says he thinks it is fine but will refund purchase price if we are not happy. Son would rather keep frame if possible but will take advice as he obviously doesn't want to build an unsafe bike or sell on an unsafe frame

    Any advice gratefully received


    Since the weld is of unknown "pedigree" I wouldn't take the risk. My two cents.

  16. #16
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    Has reapir held up ?

    Quote Originally Posted by archman99 View Post
    ]Just got my frame back from the welder. Going to try to get alittle more out of it. I had him install another support tube to add extra strength to the weakened old crack site. Check the pic. Hope it holds. (for my sake)
    Hey has the weld repair on your bike held up? Please let me know I have a nice frame i want to get repaired thanks.

  17. #17
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    lasted for about 10 rides

    Quote Originally Posted by sil2222 View Post
    Hey has the weld repair on your bike held up? Please let me know I have a nice frame i want to get repaired thanks.
    It lasted for about 10 rides. I had a major failure when I was clearing a fallen tree. I was lucky i did not get hurt. It was ugly . It broke in 3 places like a ripped open pop can.Long walk back. If you can afford it. I would buy a new frame.
    My KHS frame was about 8 years old when I repaired it. That probably had something to do with the major failure.
    Good luck.

    Arch

  18. #18
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    Wouldn't even consider riding it since the welded area is the worst possible place for a failure.

  19. #19
    Randomhead
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    a pointer to this thread should be added to the faq since "can I get my aluminum bike fixed" is such a common question

  20. #20
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    Quote Originally Posted by unterhausen View Post
    a pointer to this thread should be added to the faq since "can I get my aluminum bike fixed" is such a common question
    Agreed, it's a common enough question.

  21. #21
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    I just finished putting my FSR XC back together. The chainstay completely broke and I had it welded. Looks good. So far, a ride around the parking lot, bouncing the suspension seems to be solid. I have to wait till next weekend to really test it. I'll post back with deets. Oh yeah, I made it a 69'r too. Should be fun.

  22. #22
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    Took the bike for a ride today. (Welded chainstay) So far, it passes the novice to advanced novice test. Next week, intermediate to advanced full blown throw down break it test.

  23. #23
    Randomhead
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    doubt it would break in a few rides. Who welded it? Please report back in a year/and or at failure

  24. #24
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    The biggest difference between steel and aluminum is that steel can be designed for an unlimited fatigue life, where aluminum is always destined to fail at some point. Whether that point is within the life of the part is another question. That is why aluminum frames have to be so stiff, if they flexed as much as steel they would fail very quickly.

    So if your aluminum frame has cracked, it was not designed/built properly or it suffered a major load which yielded the material causing a stress riser which eventually led to failure.

    Bottom line -replace a broken aluminum frame with a better one.

  25. #25
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    A little bit of history on this break. It did not occur under "Normal" wear and tear. I beat the balls off this bike. The bearings in the pivot completely fell apart and it snapped in half. So I went to HD, got some bolts and "There, I fixed it"
    I didn't plan for it to last too many rides so I went and put a 29r fork n wheel on it to play. Maybe keep it for urban rides. After three light rides, the chainstay snapped. I knew it was going to happen but I started really liking the 69r setup. So I welded up all the parts and tightened up the suspension. I'll ride it some more and If I keep it, I'll get the right parts.
    I like having the "rolls over everything" of a 29r and the speed of a 26r.
    I need more rides to be sure though.

    I'm in S Florida and went to a local guy.
    I think he did good work, looks solid. We'll see.
    Attached Thumbnails Attached Thumbnails aluminum welding for cracked frame?-dsc00348.jpg  


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