Originally Posted by mrv

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!

Originally Posted by guy153

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.

Originally Posted by San Rensho

I don't believe the guy, the fork is pushed way back which it means he hit something really hard, head on. The bottom tube has the classic kink when a bike hits something head on. Ask me how I know, I hi t something head on and my bottom tube was badly kinked. If, the frame had "just fallen apart" while he was riding it, the bottom tube would not have been kinked and the forks would not have been pushed back.

Originally Posted by livedarklions

You don't know that. If the top tube weld fails and then he hits the front brake because he doesn't figure out what's going on, all kinds of crazy are going to happen to the fork and the bottom tube.

Originally Posted by San Rensho

I don't believe the guy, the fork is pushed way back which it means he hit something really hard, head on. The bottom tube has the classic kink when a bike hits something head on. Ask me how I know, I hi t something head on and my bottom tube was badly kinked. If, the frame had "just fallen apart" while he was riding it, the bottom tube would not have been kinked and the forks would not have been pushed back.

Originally Posted by unterhausen

The video you linked shows why it's not rupture. Steel doesn't fail in rupture like the bike in the op. It's clear that the frame failed in fatigue and then there was rupture at the bottom of the down tube. That's why there was bending there in the tube. The bending would have occurred a little further down the tube had it been in a crash. It might have been very low cycle fatigue from a large defect, there is no way to tell from here. Hitting a frame with a sledge pretty much tells nothing about the welds. It might be more common way to test a weld in thicker cross sections that are in plain strain loading. That is less ductile than a bike tube, even at the weld. I'm sure even some ineptly welded bike frames would pass the sledge test.

Originally Posted by San Rensho

But its not going to bend the front fork back like that. And assuming he lost control because the frame fell apart and then went head on into something, the fork would not bend back like that, there would be nothing to leverage the fork and apply a torque to it to bend it back.

Originally Posted by livedarklions

Have you done a lot of crash testing with a brake slam and a detached head tube? I'm not sure what you're looking at to determine the bend in the fork, none of the pictures I've seen make that clear, but even if you are right about the direction of the bend, how would you know where the fork was after the weld failure and what or who would land on it and with what force?

You're making a lot of absolute statements based on intuition about a situation you've never experienced.

Originally Posted by mr_bill

The fork is “bent” forward.




I know, east, west, front, back, easily confuse “experts.”

-mr. bill

Originally Posted by San Rensho

So how do you explain the fork being pushed back so far. And by the way, I have experienced this situation, kinking the down tube in a head on collision. What experience do you have with a head on crash, Mr. Know-it-all?

Look at the big picture, based on basic physics and mechanics FIRST, like torque and ****, before you obsess on metallurgic minutiae.

Originally Posted by mr_bill

The fork is “bent” forward.




I know, east, west, front, back, easily confuse “experts.”

-mr. bill

Originally Posted by San Rensho

Point taken, it is angled forward, but how do you explain the kink in the down tube, which is classic evidence of a hard head on hit. This is the mechanics. A hard head on crash will lever the head tube back, it will pull the top tube away from the head tube and compress the down tube, causing a kink in the down tube, which is what we see in this situation.

Originally Posted by livedarklions

You do understand that if a top weld goes first, there's going to be possible bending of the down tube as the head tube changes in orientation, right? The fact that it looks like the type of damage you'd see in a front-end doesn't prove anything except a possible coincidence, especially as there's now no other visual evidence of a front end--y'know, bent wheel or fork bent back.

It's pretty hilarious that you've now moved the goalposts. Just admit the photographic evidence doesn't actually prove anything and you'll feel a lot less defensive.

Originally Posted by San Rensho

Again, you dont understand basic physics. If the weld in the top tube fails first, the weight of the rider will pull the down tube OUT of the head tube, so again, no kink in the down tube. Obviously if the weld in the down tube fails again, there will be no kink.

I am man enough to admit I was incorrect, because some people that have posted here are really trying to understand and explain what happened. Part of that is to not be unreasonably stuck on a ridiculous position that you will never waver from, because you don't care about what happened, all you care about is being "right" in your mind. . You thin skin is showing. You are just on a crusade to double down and make any ad hominum, unscientific argument so you dont have to admit you are wrong. Sound like some who is president of the US?

Originally Posted by mr_bill

Now, assume the top didn’t fail first. Find me a picture of someone’s bike who crashed it into a barrier, slightly kinked the down tube, and had two complete joint failures, WITHOUT bending the fork. Still waiting and we are getting close to 100 replies....

-mr. bill

Originally Posted by livedarklions

My "crusade" is to say you don't have enough information to rule anything out. I'm being very clear that I don't know what actually happened. You're arguing that there can only be one possible cause for a kink in the down tube, which is clearly silly, and mr_bill has demonstrated that several times in this thread. If anything, I think he may be underestimating the complexity of the physics as we don't know if there were lateral forces occurring from panic swerving or whatever. I have no idea what a bike feels like when a weld snaps and neither do you, so I don't know how a person responds to what is probably some very confusing sensory input. .

Also, you apparently don't know what an ad hominem argument is. You're the one engaging in them.

Originally Posted by San Rensho

Obviuosly, you don't want to try to figure out the problem, you just want to "win" in your mind. Goodbye.

Originally Posted by livedarklions

See, now that's an ad hominem argument! Good for you giving the proper example.

How did Trump get into this?

Originally Posted by San Rensho

. . . . ,Trying to evade the issue, acting like a child in the playground "thats what you are, what am I", Hence you ad hominum comment, accusing me of doing it when I didn't, when you are then one that started made ad hominem arguments against me.

Don't worry, you win! You will respond to my post, I will not respond, I'm done trying to reason with small minds. So in your mind you will have the last word and therefore you win, right?

Originally Posted by San Rensho

Obviuosly, you don't want to try to figure out the problem, you just want to "win" in your mind. Goodbye.

Originally Posted by guy153

But the real problem is why did both the TT and the DT rupture in exactly the same way? Surely they didn't both have exactly the same welding defect?

Originally Posted by mr_bill

Now, assume the top didn’t fail first. Find me a picture of someone’s bike who crashed it into a barrier, slightly kinked the down tube, and had two complete joint failures, WITHOUT bending the fork.