Steel bike failure. Is this manufacturing or something else?
#51
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To me, it looks like brittle welds as a result of improper set up and temperature control.
My project car is a Jaguar E-Type which has a complex front frame that is brazed together. Anyone who knows anything about these frames knows that they can only be properly repaired by someone very knowledgeable about temperature control and brazing the specific alloy. People have repaired them without proper temperature control and have ended up having catastrophic failures.
My project car is a Jaguar E-Type which has a complex front frame that is brazed together. Anyone who knows anything about these frames knows that they can only be properly repaired by someone very knowledgeable about temperature control and brazing the specific alloy. People have repaired them without proper temperature control and have ended up having catastrophic failures.
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This is why I will not risk my life on an archaic steel frame. Modern carbon fiber is so much stronger than anything that was available 20 years ago. It should be against the law to sell these inferior, weaker frames.
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I would love to get my hands on this thing and put it under a microscope. I think it's consistent with a fatigue failure from a weld defect. Maybe it saw some hard use. Makes me want to go inspect the welds on my macho macho man disc (3M)
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The welds actually look really good and it's failed in the heat affected zone just outside them with a very clean brittle fracture exactly the same on both tubes. There is some deformation of the down tube but very little. When I've tried destruction-testing welds on cromoly bike tubes before the whole tube can be completely folded over and flattened before anything fails. My suspicion is that the actual tubes are not cromoly, either the wrong tubes have been supplied or used, or maybe even they're from a batch of cromoly that wasn't made properly.
See also this video (at about 10:57 if you can bear to watch) for the expected failure mode:
See also this video (at about 10:57 if you can bear to watch) for the expected failure mode:
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The prevailing wisdom in the bike industry during the days of steel frames was if you have the telltale ripples on the top-and down-tubes, the bike was in an accident and the failure is not the result of a manufacturing defect. If there is no ripple on the underside of the top-tube then it possibly let go because of a manufacturing defect.
My guess is that the head tube was separated from the top tube before the accident, or as a result of a less serious hit (went through a sewer grate turned the wrong way, for instance), and when the top tube and head tube was completely separated, the down tube held on for a bit, and was deformed before it let go completely.
My guess is that the head tube was separated from the top tube before the accident, or as a result of a less serious hit (went through a sewer grate turned the wrong way, for instance), and when the top tube and head tube was completely separated, the down tube held on for a bit, and was deformed before it let go completely.
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I think it was mutant termites that eat metal.
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It's true that cracking open like that is consistent with fatigue but the thing is it was practically a new bike. Fatigue failures tend to appear after after several tens of thousands of km. I think because it was such clean breaks on both tubes, exactly the same, that the wrong or a defective alloy was supplied. There's no way it should fail like that.
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That image doesn't seem to show a weld failure, but a tube failure just behind the weld. Maybe embrittlement? Cooling too quickly?
From millerwelds.com:
"Note that if the tubing is below 60 degrees F, use a small propone torch to heat the base metal to up to 300 degrees F. Otherwise, the metal could cool too quickly and become brittle. Welding cold metal may also promote hydrogen cracking, so that’s another reason to preheat 4130 if it’s cold."
From millerwelds.com:
"Note that if the tubing is below 60 degrees F, use a small propone torch to heat the base metal to up to 300 degrees F. Otherwise, the metal could cool too quickly and become brittle. Welding cold metal may also promote hydrogen cracking, so that’s another reason to preheat 4130 if it’s cold."
Agree that it's the tube that's failed and not the weld. I think the bike company should be checking who exactly in China they got thir "612 select" cromoly from.
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My guess is that the head tube was separated from the top tube before the accident, or as a result of a less serious hit (went through a sewer grate turned the wrong way, for instance), and when the top tube and head tube was completely separated, the down tube held on for a bit, and was deformed before it let go completely.
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The question is which came first. Before a multi-million settlement, one could try building a frame with the HT welded to the DT, but not welded to the TT. Then see if one can get the same DT bend. I'm not sure the above bend could happen without a significant crash with both welds intact.
The round tube is 0.8mm wall 4130 cromoly from an old Trek 520 (whose frame failed elsewhere). I've welded it onto some 1.6mm wall mild steel square tube using ER-70S2 filler wire.
Now to test it... To get it into this state I had to really whale on the cromoly chainstay with a 1kg hammer. As you can see it's deformed considerably, with plenty of ripples, and still nothing has actually broken. I think this is roughly what's supposed to happen. Not that it just snap right behind the weld.
Last edited by guy153; 12-21-19 at 02:59 AM.
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The steel looks really thin to me. I have no expertise in this whatsoever other than having seen much thicker steel on bike frames, but isn't there a ratio between the radius of the tube and the thickness of the tube wall for a certain type of steel?
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The thickness looks about right. Cromoly bike tubes are usually 0.8mm or 0.9mm at the ends which that probably is. The ratio you might be talking about is 50:1 diameter to wall thickness which is a good rule of thumb to avoid "beer canning". The diameter of that top tube is either 25.4mm or 28.6mm which means a ratio of about 30:1 which is fine. The thicker steel you've seen may have been at the top of the seat tube, but it's often thicker or reinforced up there because you're clamping the seat post in.
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Steel is Reel! - if designed and manufactured properly.....
I find this thread fascinating:
1. I had a low speed MTB incident in the '90s where I kinked the top tube / down tube, but did not crash. It was a light weight Jamis Dakota - no bent fork or wheel problems.
2. I t-boned another racer who was sliding across the ground in front of me during a criterium, sending me knee caps over coffee cups resulting in a kinked top tube and down tube - no bent fork, no wheel problems. An early '90s Japanese built Schwinn Paramount
3. Back in August of this year I crashed in a very poorly marked construction zone, resulting in a cracked aluminum rim, a bent steel fork, and me going tibias over tea kettle, landing on my shoulder & side of my head. My helmet did it's job, but my co-riders were generally freaking out. (what was kinda weird was I bent my NITTO bars and sprained my thumb, but opposite sides... weird...and my tire didn't flat, but the rim cracked - let's hear it for inner tubes! )
- - the GUNNAR CrossHairs frame was (is) fine (brand freaking new! like i'd been riding it a week!!!) . No tube kinks. No cracked paint. No frame mis-alignment (checked out by my local bike shop and me with my engineering degree that I bought 25 years ago....)
- - I talked to the construction company. I am not the litigious sort, so we settled on $500 for me to go away. That covered my bike parts replacement (mostly), but not my e-room visit.
Hopefully someone will stumble upon how the whole thing with the All City was resolved and post it here.
My vote is a manufacturing defect. It sure looks like the welds failed. But do you want to take the opinion of someone who keeps crashing bikes?!
ciao!
1. I had a low speed MTB incident in the '90s where I kinked the top tube / down tube, but did not crash. It was a light weight Jamis Dakota - no bent fork or wheel problems.
2. I t-boned another racer who was sliding across the ground in front of me during a criterium, sending me knee caps over coffee cups resulting in a kinked top tube and down tube - no bent fork, no wheel problems. An early '90s Japanese built Schwinn Paramount
3. Back in August of this year I crashed in a very poorly marked construction zone, resulting in a cracked aluminum rim, a bent steel fork, and me going tibias over tea kettle, landing on my shoulder & side of my head. My helmet did it's job, but my co-riders were generally freaking out. (what was kinda weird was I bent my NITTO bars and sprained my thumb, but opposite sides... weird...and my tire didn't flat, but the rim cracked - let's hear it for inner tubes! )
- - the GUNNAR CrossHairs frame was (is) fine (brand freaking new! like i'd been riding it a week!!!) . No tube kinks. No cracked paint. No frame mis-alignment (checked out by my local bike shop and me with my engineering degree that I bought 25 years ago....)
- - I talked to the construction company. I am not the litigious sort, so we settled on $500 for me to go away. That covered my bike parts replacement (mostly), but not my e-room visit.
Hopefully someone will stumble upon how the whole thing with the All City was resolved and post it here.
My vote is a manufacturing defect. It sure looks like the welds failed. But do you want to take the opinion of someone who keeps crashing bikes?!
ciao!
#75
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Incidents like these are pretty rare. It shouldn't dissuade one from buying a steel bike and probably shouldn't dissuade one from All City.
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