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  1. #1
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    Is my frame cracked? (Repost from General thread)

    I thought I'd repost this in the frame builders forum - you all might have some more insight into what this is, if not a crack.

    I was cleaning my 29er ti hardtail today, prepping it to be sold (I was hoping), when I noticed what looks like a crack at the underside of the weld where the headtube meets the downtube. None of the other weld transitions look like this on the frame, they are all smooth. Looking for some opinions - here are some pics:



    Also noticed these odd-ish looking welds at the seatstay-seattube junction - maybe not cracks but .....? I'm not sure. They are not rounded stacks like all the other welds.



    Here is a link to a few more pics:
    Is my frame cracked? - Imgur

  2. #2
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    if it's not cracked, it wants to be. Don't think the seat stay area is cracked, bead looks funny and there is some undercutting but that's water under the bridge at this point.

  3. #3
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    Novice opinion: Yes.

    Things that make me not say it's absolutely cracked: That's kind of an odd spot for a crack to start. And it could just be a sub par weld that has trapped dirt. If that's the case and it isn't a crack, that's where a crack WILL be soon enough. Is undercut the right term TIG experts?
    Last edited by G-reg; 03-12-2013 at 06:22 PM.
    Slowly slipping to retrogrouchyness

  4. #4
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    I've worked in an automotive structural / fatigue test lab for the last 20 years so have to look for this kind of thing every day. I'd say possible but very hard to tell from the photos. It is actually much more common to find cracks running through the weld rather than along the edge.

    If you can get it under a fairly regular microscope then it should be much clearer (but very hard to get focus right on curved parts).

    Dye penetrant inspection sprays would show that up quite well. Quite expensive as you'll need 3 cans (penetrant dye, cleaner and developer), especially when you only need a tiny amount.

    On first application of the dye, it will still be hard to tell (dye bleeds everywhere). However, if you keep cleaning off any dye (spraying small amounts of the cleaner onto a cloth - never directly onto the test piece) and reapplying developer (without adding any more dye) then a crack should keep bleeding dye if left for a little while. I've had success picking up tiny cracks in apparently ok parts where weeks / months later they have still been bleeding little red dots of dye in unusual places.

  5. #5
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    Well;

    I agree it is a bit of an odd place for one, but it sure looks like a crack to me. Too bad you can't pressurize it internally. Alternately, I would imagine the tubes are vented, so some thin oil drizzled down there would surely weep out if it were cracked. Any fluid for that matter.
    Most people ply the Well Trodden Path. A few seek a different way, and leave a Trail behind.
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  6. #6
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    Quote Originally Posted by mickuk View Post
    I've worked in an automotive structural / fatigue test lab for the last 20 years so have to look for this kind of thing every day. I'd say possible but very hard to tell from the photos. It is actually much more common to find cracks running through the weld rather than along the edge.
    I am pretty sure that with light tubing that any crack will almost always initiate along the edge of the weld and then often propagates into the weld. The exceptions are when the welder creates what amounts to a crack by some form of welding malpractice. With smooth, full penetration welds, the cracks start at the weakest point of highest stress concentration, which is at the edge of the weld. If you look at his link, there is evidence of undercutting, which would be a great way to start a crack there.

    Anecdotally, the places I have seen cracks, in order of how common they have been in my experience:
    1. Seat tube at BB
    2. Top tube at seat cluster
    3. DT at HT.
    4. chainstays
    So it's not particularly rare to see a crack at this location. Your experience may be different

  7. #7
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    I don't seem to have the strongest self-preservation streak, but if you decide to go ride it in the mean time, mark the ends with a fine Sharpie or something that you can remove. Check for propagation... often.

  8. #8
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    Have you ever hit anything with the bike? Like a tree or a large rock that stopped you in your tracks? I have seen cracks there before, but there were cracks on the top tube also that showed extreme flex in the head tube from the fork. In my professional experience as a welder, I have seen guys welding where the welder wasn't set right, moving too fast, and the metal surface being contaminated and the weld would actually flake up on one side of the weld. It looked 100% identical as in your picture. It isn't undercutting. If you have never jumped the frame too hard or wrecked it, I would say that it was a faulty weld, that had never had any penetration past the surface of the tube. Just my 2 cents.

  9. #9
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    I'm not saying it isn't a crack - as you say, with thin wall it is could go either way - in or along the weld (or a combination of both).

    Using any kind of fluid as a penetrant is a good suggestion. Magnetic particle testing (used for ferrous metals not Ti!) often uses paraffin as the carrier as it flows well and evaporates quite slowly. So a dribble of that might be a good thing to try. If there is a crack it will keep reappearing even if the surface is repeatedly wiped dry (an undercut probably wouldn't do that). Also, a good local welding shop would probably have some dye penetrant sprays.

  10. #10
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    As I was typing, previously...

    I was thinking of how a frame would crack there. If it were from a large front wheel impact, the fork would surely have taken a beating. A rigid fork would surely have bent. Even with a suspension fork, it would also likely cause a buckle in the tubes - most likely the bottom of the DT - at the HT junction. We've likely all seen that.

    Saving a major front impact; too short an HT, with too large a brake rotor, with too many cycles, on too rough a terrain, with too hot an HAZ, or one to rapidly cooled. These are all possible contributors to a failure like this. Of course this is a classic frame crack. They will always crack at the foot of the weld first, going through the weld only when forces dictate, and/or a weak spot is found.
    Most people ply the Well Trodden Path. A few seek a different way, and leave a Trail behind.
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  11. #11
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    Hi guys i'm a newbie here... i know it's off topic but i do not know how to create a new thread.. i just bought a 26" epicon 2013 fork and saw that there is some oil not really sure on the adjustable air or something.. that does affect the performance of the fork or it's natural?

  12. #12
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    Quote Originally Posted by wheeljack87 View Post
    In my professional experience as a welder, I have seen guys welding where the welder wasn't set right, moving too fast, and the metal surface being contaminated and the weld would actually flake up on one side of the weld. It looked 100% identical as in your picture. It isn't undercutting.
    I think this is what happened. If you look at his third picture on Imagur, there is a chunk of the weld gone. And it's not gone the way you would expect a weld to crack either, you can see pristine metal underneath. I see undercutting on the seat stay joint, not sure I see any at the head tube.

  13. #13
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    Matt,

    I do not believe there is a crack.

    With titanium, it is common practice for all the joints to be fusion welded (no filler) to insure a completely welded structure with no voids. A second pass with filler is then placed overtop, using more heat, resulting in a wider puddle and inclusion of more tube surface area. This results in a smooth, feathered transition from tube to tube across the weld surface.

    What appears to have occurred with your frame is that the filler pass was run too cold or with too much filler material, resulting in the outside edges of the weld puddle cooling and leaving a vertical lip instead of a smooth transition to the adjoining tube. You can see how the edge of the lip follows the contour of the weld puddle. The welder then attempted to wash the pass again, but was unsuccessful in applying the correct torch angle and heat input...you can see a defined pass that pushes the weld to the superior portion of the bead but terminates short of the lower edge. This failed technique is present in both the HT and SS pictures.

    This does create a focus for stress, but will unlikely cause an issue with typical riding forces.

    It's amazing how much you can learn from looking at welds about the techniques applied by the fabricator...this is a good example of an issue that was not corrected.

    cheers,

    rody
    As requested by the MTBR gods, I am the voice of Groovy Cycleworks, check it out... http://www.groovycycleworks.com

  14. #14
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    Quote Originally Posted by Rody View Post
    Matt,

    I do not believe there is a crack.

    With titanium, it is common practice for all the joints to be fusion welded (no filler) to insure a completely welded structure with no voids. A second pass with filler is then placed overtop, using more heat, resulting in a wider puddle and inclusion of more tube surface area. This results in a smooth, feathered transition from tube to tube across the weld surface.

    What appears to have occurred with your frame is that the filler pass was run too cold or with too much filler material, resulting in the outside edges of the weld puddle cooling and leaving a vertical lip instead of a smooth transition to the adjoining tube. You can see how the edge of the lip follows the contour of the weld puddle. The welder then attempted to wash the pass again, but was unsuccessful in applying the correct torch angle and heat input...you can see a defined pass that pushes the weld to the superior portion of the bead but terminates short of the lower edge. This failed technique is present in both the HT and SS pictures.

    This does create a focus for stress, but will unlikely cause an issue with typical riding forces.

    It's amazing how much you can learn from looking at welds about the techniques applied by the fabricator...this is a good example of an issue that was not corrected.

    cheers,

    rody
    What this guy says, trumps most.
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  15. #15
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    Thanks for all the input guys! A lot of different opinions, but it sounds like it may not be cracked. I'm going to try some light oil in the crack to see if it seeps through and out the vent hole in the head tube.

  16. #16
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    Quote Originally Posted by TrailMaker View Post
    As I was typing, previously...

    I was thinking of how a frame would crack there. If it were from a large front wheel impact, the fork would surely have taken a beating. A rigid fork would surely have bent. Even with a suspension fork, it would also likely cause a buckle in the tubes - most likely the bottom of the DT - at the HT junction. We've likely all seen that.

    Saving a major front impact; too short an HT, with too large a brake rotor, with too many cycles, on too rough a terrain, with too hot an HAZ, or one to rapidly cooled. These are all possible contributors to a failure like this. Of course this is a classic frame crack. They will always crack at the foot of the weld first, going through the weld only when forces dictate, and/or a weak spot is found.
    Now that you mention it - I did at one time take a nasty fall resulting in a broken collar bone. Basically, landed way to far forward. I don't remember seeing damage at the time, and the fork has been fine since. I rode the bike for another season after this occurred.

  17. #17
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    Not a crack but it is a pressure separation where the welding was done. Did you do some jumps on it?

  18. #18
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    Well;

    I would think that if it were some form of welding anomaly, that some other portion of some weld somewhere else would look the same. No other weld in the proximity looks like that. I'm no one's idea of a TIG God, and I didn't stay at a Holiday Inn Express last night, but I still think it's a crack. It just walks too much like a duck...
    Most people ply the Well Trodden Path. A few seek a different way, and leave a Trail behind.
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  19. #19
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    Quote Originally Posted by TrailMaker View Post
    Well;

    I would think that if it were some form of welding anomaly, that some other portion of some weld somewhere else would look the same. No other weld in the proximity looks like that. I'm no one's idea of a TIG God, and I didn't stay at a Holiday Inn Express last night, but I still think it's a crack. It just walks too much like a duck...
    TM,

    Thanks for the opportunity to explain welding technique a bit more for the benefit of all forum members.

    There is evidence of a wash pass over the filler pass on all the welds. A close look at each of the bead patterns clearly illustrates two definative outer margins; one from the filler pass that is fairly well defined and a second outer margin from the wash pass, just superior, that has a fuzzy/less defined edge. This is most prominent in areas where the torch angle varied from a nice 45-90 degree attitude.

    The "welding anomaly", in the form of a defined edge, is due to inconsistant torch angle. As the operator moves the torch into the acute angle of the HT joint, he is reaching his torch in rather than keeping it perpendicular to the base. This action lays the electrode down, reducing it's ability to penetrate the base as efficiently with the same amperage. This results in less heat input to the base, thus the cooler bead that does not flow out and the resultant defined edge.

    The same action is present on the seat stays, only this time he did not rotate his wrist around to maintain constant torch angle. As the torch reaches around the joint, laying down, and the tube falls away, the arc must work harder to maintain good heat input. Take a close look at the weld bead. Instead of the typical "stack of dimes" the trailing edge is wavy and fuzzy, evidence of poor position and a wandering arc. The same phenominon occurs; with less heat the new bead does not wash out the filler edge into new material, leaving two defined outer margins. Had the operator kept a constant torch angle and rotated around the joint, we would have seen a nice defined bead with feathered edges.

    The reason the balance of the weld does not share the defined edge with crack like similarities is that it is easier to reach with proper torch angle and heat input.

    You are right, this baby is quacking like a duck, just not for the obvious conclusion.


    To the OP...obviously all we have is conjecture based on a few pics over 1's and 0's, a first person examination with penetrating dye is the best way to resolve your query.

    cheers,

    rody
    As requested by the MTBR gods, I am the voice of Groovy Cycleworks, check it out... http://www.groovycycleworks.com

  20. #20
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    Well heck;

    It is a thrill to have my ignorance be a catalyst for learning!

    That is great information, to be sure. I myself have not gotten good enough that I can roll my wrist around a tube, try as I might. However, I have welded enough and have enough power of observation to understand exactly what you are saying because I have experienced it. Fortunately for me, I'm guessing that ChroMo is more forgiving than Ti. I'm a metal gluer. It'll hold, most likely, if not win any beauty contests.

    I still think it's a crack, though.
    Most people ply the Well Trodden Path. A few seek a different way, and leave a Trail behind.
    - John Hajny, a.k.a. TrailMaker

  21. #21
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    Quote Originally Posted by mattgVT View Post
    Thanks for all the input guys! A lot of different opinions, but it sounds like it may not be cracked. I'm going to try some light oil in the crack to see if it seeps through and out the vent hole in the head tube.
    Hey;

    I'd remove the BB and dribble it down from that end. I assume the vent hole from DT to HT is reasonably centered so a small amount of oil would not make its way out the vent into the HT. I would keep the frame at an angle to facilitate the ends of this test.
    Most people ply the Well Trodden Path. A few seek a different way, and leave a Trail behind.
    - John Hajny, a.k.a. TrailMaker

  22. #22
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    That is a crack, and it is caused by fatigue.... simple.
    The appearance of the weld is caused by welding into the tighter sections (sections with a greater total of thickness) without turning the amps up, there is nothing wrong with the welding that would cause this, just simple fatigue.
    I bet anyone the owner/owners have done plenty of miles on this baby. she is just getting old.

    I would not ride it, just hang it up and remember all the fun that it gave you

  23. #23
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    Well, it looks like the frame is cracked. I let some liquid wrench pool around the area and it eventually made it's way through and out the vent in the head tube.

    RIP

    Thanks for the input.

  24. #24
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    Quote Originally Posted by mattgVT View Post
    Well, it looks like the frame is cracked. I let some liquid wrench pool around the area and it eventually made it's way through and out the vent in the head tube. RIP. Thanks for the input.
    To be clear;

    You ran your test from outside, and it ended up inside? Unless I'm reading it wrong, that is what you are describing. I'm not sure how you would even do that, successfully.

    --------------------------------------------------------------------------------------------------

    OK;

    Now, I may be opening myself up yet again to the rebuke of the knowledgeable, but is not Ti repairable? I can imagine that filleting out a weld area like this "simply is not done," but why would you not? Are there substantive reasons why this cannot be repaired, and fairly easily?
    Most people ply the Well Trodden Path. A few seek a different way, and leave a Trail behind.
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  25. #25
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    Quote Originally Posted by TrailMaker View Post
    To be clear;

    You ran your test from outside, and it ended up inside? Unless I'm reading it wrong, that is what you are describing. I'm not sure how you would even do that, successfully.

    --------------------------------------------------------------------------------------------------

    OK;

    Now, I may be opening myself up yet again to the rebuke of the knowledgeable, but is not Ti repairable? I can imagine that filleting out a weld area like this "simply is not done," but why would you not? Are there substantive reasons why this cannot be repaired, and fairly easily?
    I just used some tape around the top/head/downtube to create a pool for the liquid to sit in. I used my stand to position the frame with the head tube pointed down. Some found its way inside. I'm pretty sure I could get it repaired, I may do that at some point.

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