What broke? Carbon or Alu?

[hd reynolds]

Talk about being full of BS: you've presented zero science or deductive logic, but you have brought a lot of invective. You should take some engineering or science classes, so you can learn some science, reasoning, and empirical thought.

Are you talking about yourself? OIC your diablo's lover right?!!!

Maybe you should stop riding with just your seatpost. A seat would be more comfortable specially with that aero post.

 

[DiabloScott]

Any one using an aluminum steerer for sometime should examine theirs to avoid such failures, specially more so if involved in a crash.

Ditto for carbon fiber... in fact manufacturers usually include such a caveat with their carbon fiber components.

 

[RickF]

If I remember right the fork itself was not one of the high end products from Trek. It was something from their commuter range. This was used because it had a greater rake, improving comfort on the cobbles. There seems to be some confusion over the exact fork model. Trek gave some information that did not match up with post crash pictures.

I thought the Trek bikes used in Paris-Roubaix were Madone main triangle with Pilot rear triangle and fork.

 

[Insaneclimber]

No, and as I've said many times, the BS on this forum about fatigue is astounding.

All fatigue failures start with an incipient crack. Steel, titanium and aluminum will all fatigue in the same way (more or less) once the crack has started. Hincapie's steerer made of any of those materials would have broken in a similar manner. A steel or ti tube may have given a little more warning, that's all and maybe not even that (actually I'm not even aware of any ti steerer forks). A carbon tube probably would have shattered in the earlier crash to begin with - from some observation point I guess you can say that's better.

Do not fear the aluminum steerer! There's no way you'll ever see enough cycles to fatigue one without crash damage.

I think the fatigue will have started long befor the crack appears, i still can't believe anyone would use an aluminium steerer on a cobbled race. seems nuts to me. Iv crashed head on into a car befor with a full chromo fork and that didn't snap it just bent all the way back and put a nice hole in my shin.

 

[Insaneclimber]

Talk about being full of BS: you've presented zero science or deductive logic, but you have brought a lot of invective. You should take some engineering or science classes, so you can learn some science, reasoning, and empirical thought.

Seems obvious to me who's full of bull. aluminium is not a strong material it never will be and no matter how many times you say it is that wont change. we use it because it has an acceptable strength for the application. obviously some carbon fiber methods are stronger as is chromo and ti. and befor you call me a bs artist. I know this as fact because iv stood in a damn lab for weeks on end testing the damn stuff.

 

[DiabloScott]

I think the fatigue will have started long befor the crack appears

NO! The very definition of fatigue requires an initial crack. The crack can come from damage, a material flaw, or cyclical stresses but it always starts as a crack.

i still can't believe anyone would use an aluminium steerer on a cobbled race. seems nuts to me.

Thousands of racers on hundreds of cobbled races and ONE breaks AFTER it already was damaged in a crash... seems like a good history to me.

Iv crashed head on into a car befor with a full chromo fork and that didn't snap it just bent all the way back and put a nice hole in my shin.

That's not fatigue. Al, steel, and CF would probably all have reacted differently to your crash. The stresses there would probably have sheered a carbon fiber fork right off.

 

[alienator]

Seems obvious to me who's full of bull. aluminium is not a strong material it never will be and no matter how many times you say it is that wont change. we use it because it has an acceptable strength for the application. obviously some carbon fiber methods are stronger as is chromo and ti. and befor you call me a bs artist. I know this as fact because iv stood in a damn lab for weeks on end testing the damn stuff.

It's the design and construction that matters. Absolutes based on bulk material properties are useless because, lo and behold, materials are used in "applications".

 

[hd reynolds]

NO! The very definition of fatigue requires an initial crack. The crack can come from damage, a material flaw, or cyclical stresses but it always starts as a crack.



Thousands of racers on hundreds of cobbled races and ONE breaks AFTER it already was damaged in a crash... seems like a good history to me.



That's not fatigue. Al, steel, and CF would probably all have reacted differently to your crash. The stresses there would probably have sheered a carbon fiber fork right off.

Your argument is laughable and getting rediculous all the time.

 

[hd reynolds]

It's the design and construction that matters. Absolutes based on bulk material properties are useless because, lo and behold, materials are used in "applications".

Same as diablo... you bunch of novices are trying too hard on your case... just useless banter.

 

[ScienceIsCool]

NO! The very definition of fatigue requires an initial crack. The crack can come from damage, a material flaw, or cyclical stresses but it always starts as a crack.

Close, but I disagree on some major points. http://en.wikipedia.org/wiki/Fatigue_%28material%29 is a good place to start. What fatigue requires is an initial nucleation site, not a crack. Some materials such as aluminum intrisically have nucleation sites at the microscopic level. Others such as titanium and steel have very few nucleation sites, hence an apparent infinite fatigue life below a certain threshhold. However, all bets are off if the part is constructed with an inherent point of stress concentration (stress riser).

Typical stress risers in a steel frame are rust spots. Other stress risers are drilled parts - things like water bottle bosses. Chain stays usually do not stay below the infinite fatigue life stress limit and will eventually fail regardless of material.

Cyclical stresses are what cause the nucleation site to grow as the localized stresses exceed the material limit. They do not cause the crack. They cause the crack to grow from their microscopic level.

DiabloScott, it sounds like you have a lot of knowledge to offer in this debate, but your tone and confrontational manner are turning people off. It makes people defensive and they stop listening. Not that the rest of the people in this thread are doing much better...

<edit> HD_Reynolds is actually being the offensive one in this thread. Let's keep the rhetoric down and talk facts. BTW, I think bulk material properties are the whole point of this conversation </edit>

John Swanson
www.bikephysics.com

 

[DiabloScott]

DiabloScott, it sounds like you have a lot of knowledge to offer in this debate, but your tone and confrontational manner are turning people off. It makes people defensive and they stop listening. Not that the rest of the people in this thread are doing much better...

John Swanson
www.bikephysics.com

Cyclical stresses do cause the crack (unless it was already there), nucleation sites don't grow. All fatigue starts with a crack, if the nucleation sites never develop a crack you'll never have fatigue... just semantics there. You and I agree but you're afraid of calling BS when you read it.

I'm confronting the BS, not the authors of the BS, I've ignored dozens of personal attacks. Readers of this forum can decide if my (and your) explanations ring true or if they want to believe the ********.

Example: I think the fatigue will have started long befor the crack appears - that's not the statement of someone who understands fatigue... don't you agree? Maybe he meant "long before the crack is visible", that might make sense, because the fatigue starts as a small crack (even microscopic) and then the crack propagates with a speed governed by the size of the stresses and the material's toughness. But if he knew that he wouldn't have phrased it the way he did. In Hincapie's case, the first crash almost definitely created a crack or a gouge that developed into a crack over the next series of cobbled sections. Chances are really good the same or worse would have happened to a carbon steerer in the same crash. I advise everyone who's in a crash where the handlebars or fork get smacked to do a good inspection of their bike before they ride Paris-Roubaix... no matter what components they have.

Another: Your argument is laughable and getting rediculous all the time - no presentation of an alternate explanation, no reason why anyone should believe his side over ours... just trolling. Folks can believe those of us who obviously have some education and experience in this area or they can believe the posters who write poorly spelled, unsubstantiated statements, and respond with puerile name calling.