Cracked frame
08-10-16 | 02:07 PM
#1
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Cracked frame
Hello
I am posting a photo of my first frame and its catastrophic failure, in the hopes of avoiding the same mistake with the next one.
Down tube is True temper 31,8mm 0.7,0.5,0.7 HOX3TT2
The crack shape is identical on the other side of the downtube.
Any comments/observations much appreciated.
I am posting a photo of my first frame and its catastrophic failure, in the hopes of avoiding the same mistake with the next one.
Down tube is True temper 31,8mm 0.7,0.5,0.7 HOX3TT2
The crack shape is identical on the other side of the downtube.
Any comments/observations much appreciated.
08-10-16 | 02:22 PM
#2
Senior Member
Joined: Apr 2009
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From: New Rochelle, NY
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
Are you the builder?
If so, it might be (just a possibility among others) the result of overheating, or overly quick cooling when brazed.
Thin walled tubing cools very quickly (by steel standards) and rapid cooling can render many alloys more brittle than otherwise.
Of course, there might be other possibilities such as stress risers from a prior non-catastrophic collision, though I see no obvious evidence of an upset.
It's hard to draw a conclusion from a photo, and often the best clues lay elsewhere, like the fork, or toptube, neither of which were shown.
If so, it might be (just a possibility among others) the result of overheating, or overly quick cooling when brazed.
Thin walled tubing cools very quickly (by steel standards) and rapid cooling can render many alloys more brittle than otherwise.
Of course, there might be other possibilities such as stress risers from a prior non-catastrophic collision, though I see no obvious evidence of an upset.
It's hard to draw a conclusion from a photo, and often the best clues lay elsewhere, like the fork, or toptube, neither of which were shown.
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FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
08-10-16 | 02:46 PM
#3
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Thanks for the reply, yes I'm the builder, valid point about the rapid cooling, It was welded in a semi-open shop, so even a cool breeze could make the difference I guess.
It was involved in two major collisions as well that actually bent the front disc.
It was involved in two major collisions as well that actually bent the front disc.
08-10-16 | 03:06 PM
#4
Senior Member
Joined: Apr 2009
Posts: 39,897
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From: New Rochelle, NY
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
Other possible causes are misalignment when built leaving residual stress in the tube, ie. you brazed the D/T first then pulled the head in to meet a slightly short top tube. There's also the perverse irony that a thin larger diameter tube may be more prone to cracking than bending when over stressed.
Those are all possible contributing factors, but my money is on heating/cooling issues compounded by the rough service. Possibly either alone might have been OK, but the combo took it's tool.
__________________
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
08-10-16 | 06:05 PM
#5
Randomhead
Joined: Aug 2008
Posts: 25,930
Likes: 4,825
From: Happy Valley, Pennsylvania
the split is a little weird. It probably started at the edge of the heat affected zone somewhere near the bottom of the tube. Likely due to overheating. Lucky it didn't get much bigger, would have been a big boom.
That is a very ambitious material for a first frame. I would use some much thicker Verus next time
That is a very ambitious material for a first frame. I would use some much thicker Verus next time
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