steerer tube fatigue and fatality

Discuss light weight issues concerning road bikes & parts.
mattr
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by mattr

And?
A certain number/amount/volume of voids and inclusions etc will be allowed for in the material data used in the original design.

Same with working in metals, the basic design data is taken from sample materials, which include all the faults/void/inclusions/whatevers you'll get in the bulk material.
The issues arise when you get the issue in a highly stressed area or loads of them, which is partially what i was talking about the bike industry doing less stupid things these days......

If you want to actually go completely "void free" we'll be looking at higher than aerospace levels of processing and inspection during manufacture. And then inspection during servicing as well.

That'll slim down the market for new bikes.

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sugarkane
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by sugarkane

User Name wrote:This carbon tech guru has been getting lots of views on Youtube lately.

"voids in the fork steerers are not isolated to one brand. Here is a small sample."
https://twitter.com/raoul_luescher

Image



who do you think @whodesigns is :lol:

mattr wrote:And?
A certain number/amount/volume of voids and inclusions etc will be allowed for in the material data used in the original design.

Same with working in metals, the basic design data is taken from sample materials, which include all the faults/void/inclusions/whatevers you'll get in the bulk material.
The issues arise when you get the issue in a highly stressed area or loads of them, which is partially what i was talking about the bike industry doing less stupid things these days......

If you want to actually go completely "void free" we'll be looking at higher than aerospace levels of processing and inspection during manufacture. And then inspection during servicing as well.

That'll slim down the market for new bikes.


you do know that that Raoul was a composites engineer over at boeing... :roll:

by Weenie


mattr
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by mattr

Yes. I can read. :roll:

It's not as simple as all voids are bad.

joec
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by joec

yeah, thats fine, bit it seems that little is done in the way of checking for issues during manufacturing bu most manufacturers, fine at the to end you can generally have pretty high confidence n the product, but lower down the cost scale?

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kgt
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by kgt

I would like to see sections of forks by Colnago, Time, Parlee, Cipollini etc. in comparison.

joec
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by joec

me too,

I'd especially like to see the storck stilletto fork.

darnellrm
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by darnellrm

I really question how much flex / fatigue a steerer tube actually has, since it is rigidly supported by a bearing at each end. I see the crown area and the unsupported section above the top bearing as critical areas, but the center, not so much so.

Thought by some of you engineer types?

mattr
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by mattr

It's not rigidly supported by the bearing, its fairly near to a pivot for the levels of deflection you see in a steerer (not much these days with CF and massively oversize steerers.)

So a lot of fatigue, relatively.

The new EN standards cover this to some degree.

wingguy
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by wingguy

joec wrote:yeah, thats fine, bit it seems that little is done in the way of checking for issues during manufacturing bu most manufacturers, fine at the to end you can generally have pretty high confidence n the product, but lower down the cost scale?

Lower down the cost scale how often are you hearing about people crashing because their steerer breaks?

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cyclespeed
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by cyclespeed

The (fairly basic!) destruction testing I did on my Sworks fork (before I chopped it up!) shows how incredibly strong they are around the crown area (presumably the most stressed area in the case of a frontal impact).
The force required to snap the fork there would be enormous.
I've also tried to deform/break steerer offcuts in the vice to no avail.

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mpulsiv
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by mpulsiv

This is getting more visibility on daily basis https://cyclingtips.com/2016/12/after-t ... rk-failure


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Racing is a three-dimensional high-speed chess game, involving hundreds of pieces on the board.

:arrow: CBA = Chronic Bike Addiction
:arrow: OCD = Obsessive Cycling Disorder

AJS914
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by AJS914

Click bait articles.

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mpulsiv
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by mpulsiv

AJS914 wrote:Click bait articles.


http://www.cyclingtips.com is one of the most most reputable source in cycling arena.

You do realize that 95% of people on WW forum are far from intelligent, randomizers with nothing but personal opinions and no credibility.
Racing is a three-dimensional high-speed chess game, involving hundreds of pieces on the board.

:arrow: CBA = Chronic Bike Addiction
:arrow: OCD = Obsessive Cycling Disorder

joec
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by joec

wingguy wrote:
joec wrote:yeah, thats fine, bit it seems that little is done in the way of checking for issues during manufacturing bu most manufacturers, fine at the to end you can generally have pretty high confidence n the product, but lower down the cost scale?

Lower down the cost scale how often are you hearing about people crashing because their steerer breaks?


this isnt about how often its happened, its about how often it may happen. as already discussed a perfectly aid up fork will have a basicly infinet fatigue life, trouble is there are layup issues wth even the top forks, and these dont seem to be going through a decent enough QC for defects IMO, add to that we are now starting to see carbon forks on cheaper bikes, and the possibility of faliures becoming more common i the coming years starts to become a concern.

dont get me wrong, carbons great, but a bit of thought about its application is warrented, if a frame lets go, then generally its not going to be a big issue, but a fork, well that a different matter.

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kgt
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by kgt

This carbon fork failure danger is exaggerated IMHO. A carbon handlebar can break much more easily with the same carastrophic results. Maybe one of the reasons many pros still prefer alu bars.

by Weenie


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