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  1. #1
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    Help with crack. I just want to prolong it for abit

    Hoping to get some advice.

    First off, I hve read as much as I can and know that repairing is not a long term solution. The fact is the replacment frame is delayed a month and I have a trip to North Carolina planed and just need to prolong this frame to last a week of riding.

    The local welding shop is pretty confident that they can weld it.



    As you can see it isnt critical. But when I sit on the saddle it does open up a little bit.

    If welding is a bad idea what about drilling small holes at the ends of the crack to remove the stress points.

    Thanks

  2. #2
    Big Gulps, Alright!
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    I would drill the ends before I would weld it.

    Check with the bike shop and make sure they don't need the old frame. Sometimes manufacturers want the defective frame back and modifying it could kill your warranty claim.

  3. #3
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    Is this aluminum that needs to be post welding heat treated back to T-4 or T-6 hardness?
    If so, that's a big deal.
    cheers
    andy walker

  4. #4
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    Quote Originally Posted by Berkley View Post
    I would drill the ends before I would weld it.

    Check with the bike shop and make sure they don't need the old frame. Sometimes manufacturers want the defective frame back and modifying it could kill your warranty claim.
    Thanks. The shop already has the claim processes. The shop has already taken the pictures. Under the circumstances I dont think it will be a problem.

    I will try the small holes first and test it out for a day and see if it grows.

  5. #5
    The cat's name is jake
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    I weld aluminum bikes, but I don't have a good answer for you. I don't usually like to gamble too much, but I'm going to offer an opinion that is based off of a gut feeling.

    If you insist on riding a cracked frame, I would weld it (assuming the area is thoroughly cleaned/degreased, crack ground out, then welded and left without grinding/sanding the top of the weld) and keep an eye on it. If you leave the crack, it will be easy for it to propagate. There aren't too many places on a bicycle frame that won't see a lot of periodic stress - the area with the crack in your case is no different. Just drilling holes isn't probably going to stop the crack in your case, as even the act of sitting down on the frame is opening up the crack more. That area will be weaker, but if done carefully, it won't be weaker across the entirety of that joint. Furthermore, once welded, it will most likely be stronger than it is in it's current cracked state. The adjacent areas should still remain in their heat treated state (assuming that the areas are kept from getting too warm), and the repaired area itself, while stressed, is not an unsupported area.

    If it were me, and I insisted on riding it, that's what I'd do.

    Good luck!

    -Peter

  6. #6
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    Thanks. As I said, it just needs to last the week. It may sound odd but I just want to ride my bike on this trip. I'm not into renting a bike or borrowing somthing. I really enjoy mine and just gathered up a bunch if parts for this trip.

    Thanks again for the advice. I am going to take it to the shop if I get home in time.

  7. #7
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    Help with crack. I just want to prolong it for abit

    I'd grind the crack out, drill the ends, weld it, then add small
    gussets to the little bit of seat tube that's exposed. Angle the gussets a bit to catch the sides of both tubes as much as possible.

    When welding aluminum and not heat treating/aging, it might as we'll be a hot glue gun joint in a high stress application. Add structure and use the weld to simply hold it
    In place.

  8. #8
    Big Gulps, Alright!
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    Side note: If you're looking to prolong crack, I hear marijuana is an excellent gateway drug.

  9. #9
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    if you weld that crack, I bet the seattube ID will go out of tolerance...you might just end up with a new problem (unless you have a seat tube reamer). Personally, I'd just buy a used bike or get a rental or something.
    whatever...

  10. #10
    A_A
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    You could do a composite repair. Look at how bamboo bikes are made and replicate that joint on your cracked frame. You will need to scuff the paint to get proper adhesion. I had a chainstay failure (broken completely through at the bottom bracket) on a cyclocross bike and I did this type of repair. I used the bike for a season for practice and a pit bike. Lots of good info on the interwebs regarding the proper resin, cloth and how to get good compaction on the joint.

  11. #11
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    I did something very similar on a 6061-T6 frame. Cracked along top toe of weld and had propagated out into the tube away from the weld before I caught it. Had it welded without any post heat treat. Got maybe another 50hrs out of it before it cracked again. Frame was a loss so it was worth a shot. Stop drilling it won't get you much, and honestly, that will more than likely last a couple weekends before it propagates considerable more, at least that was my experience.

    You a tall rider with a long post?

  12. #12
    Nemophilist
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    Adding a thought to Peter's always excellent advice;

    The fact that you will lose the hardness rating of the treated alloy in the general area of the repair might actually work in your favor in this specific case. Might, I say. And I would be inclined to make the weld more stout and substantial than "pretty."
    Most people ply the Well Trodden Path. A few seek a different way, and leave a Trail behind.
    - John Hajny, a.k.a. TrailMaker

  13. #13
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    No matter how stout you make the weld, without retreating the base metal, it will fatigue and crack again shortly.

  14. #14
    FBI tested, NSA approved!
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    For what it's worth, I don't think welding is the answer (not for a week). My suggestion would be to sand the area around the crack (including the full diameter of the seat tube, top tube and upper chain stays) and create a composite lug using fiberglass cloth tape and JB Weld. Wrap the tubes out two inches or so with JB saturated tape and create a good fillet looking joint then smooth and let cure for 24 hours. Cheaper than welding and IMO less apt to fail. I would watch your new frame closely, cracks like that can be atrributed to the welding process and if the new and old frame came off the same line with the same welding parameters, you could have similar issues in that or other joints. I'd be pretty concerned if my fork departed due to a weld-induced fatigue crack.
    The most expensive bike in the world is still cheaper than the cheapest open heart surgery.

  15. #15
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    How far is your seatpost inserted? Any shims?

  16. #16
    Randomhead
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    agree with the seatpost question. Are you getting all the support possible out of the seatpost? I know someone who rode a jb weld/fiberglass repair in that area for a while. Stop drilling is considered to be pretty pointless nowadays. Your hole quality will be bad, and cracks will reappear immediately, maybe more than what you had before. Welding is a dead loss.

  17. #17
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    I second the JB weld and fiberglass or DP420 or hysol adhesives if you have some.
    This and it's out of warranty right?
    If so, sand it down and make a big ole glue and cloth patch.
    cheers
    andy walker

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