paging dr. woo...dr. woo to the er plz
- Thread starter jstuhlman
- Start date
Damn. He definitely cased the landing, but that snap sends chills. Can't believe he walked away from that ok.
Also, that guy following is a hero for not running him the F over.
Also, that guy following is a hero for not running him the F over.
I keep trying to look up the top of my screen to see ahead.
Not working too well, so I second 'Woos motion.
Seriously lucky on the miss, a part of a second faster and it would have been a train wreck. ....and ya, that sound - < shiver > ...
My crabon bars have about a dozen days on them, so maybe I will live the rest of this year...
Glad he was able to walk away, that looked like a stretcher ride for sure.
Not working too well, so I second 'Woos motion.
Seriously lucky on the miss, a part of a second faster and it would have been a train wreck. ....and ya, that sound - < shiver > ...
My crabon bars have about a dozen days on them, so maybe I will live the rest of this year...
Glad he was able to walk away, that looked like a stretcher ride for sure.
After the outcome, he might have been better off than getting full on ejected over the bars....
Clearly rode too much in the sun:
http://www.shockmansion.com/2017/09/15/60kph-road-rash/
http://www.shockmansion.com/2017/09/15/60kph-road-rash/
A rider crashed (cased badly) and broke a bike part that he bought used. Yawn. I continue riding my 4 year old Santa Cruz bars on my Nomad and 6+ year old Easton Havoc carbon bars on my V10. Can we get a materials engineer in here to explain that carbon doesn't fatigue? Solution to broken bike parts? Clear gaps and don't crash.
LOL, WHAT?
I've seen a few mentions that these and the renthal carbon bars should be avoided. anyone have an explanation?
Lulz what?
There's a handbook called "the Theory of Materials Failure" by Christensen. It has a whole chapter devoted to cascade failures in carbon fiber composites. Essentially, carbon doesn't fatigue in the conventional metal fatigue granularity way but what happens is that the fiber and glue matrix partially seperates on bending. The worrying thing about that, is that it ends up with a cascade shaped failure curve whereby the structure slowly drops in strength to a point, then rapidly loses its remaining strength as stresses become concentrated on the weakest point (localisation of bending moment).
Carbon is a great way to save weight but its not invincible.
Slid 20 yards on his penis LOL
i love laughing at matt crashing as much as anyone, and have done everything from watching him try to take out a huge berm with his face to cradle his snapped ankle in my hands...but in this case he cleared a drop he's cleared dozens of times before just fine and wrecked when his bars exploded...end of story
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Are you brought to us by Carl's Jr?
Casing is not crashing. And he also didn't case it.
But the day I can't case something on a bike because that's somehow outside the realm of what the bike can handle is the day riding it becomes pointless.
The idea that taking an impact while ON the fucking bike is somehow outside the realm of mountain biking makes you look like such an odd apologist for a shitty situation.
But hey good luck with those eastons. You're going to need it. Fortunately you don't seem to think getting off line, casing or overshooting a jump is part of mountainbiking so you should be all good.
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Composites Engineer here. The fibres themselves won't fatigue but as someone pointed out above the matrix material does if it's strained beyond yield. A degradation of mechanical properties is something that any decent design engineer working with composites will consider.
However, fatigue is completely irrelevant here. What is relevant is the atrocious standard of manufacturing of carbon fibre mountain bike handlebars, manufacturer wide and industry wide. There is not a single carbon handlebar that I've seen to date that I would be happy to put my faith in.
There are some answers to your question here I guess:
https://dirtmountainbike.com/features/interviews/steel-new-blueprint.html
"The carbon technology used for bikes, although I’m sure it’s plenty fit for purpose, is a bit more agricultural."
Basically, the bike industry is marketing crabonz as super high-tech technology, but what they are using is actually low-end compared to what's available for aerospace, etc. On the other hand, we probably don't need high-end carbon and the price that would come with it...
This. But I am a hack.
Sorry for the late reply, was away on holiday.
See attached a picture of a cross section of a downhill carbon bar of one of the "premier" leading brands. The cut was taken through the middle of the clamping section. If you need further explanation of why this is terrifying:
Beyond the manufacturing related issues above, bare in mind that, unless you go with very fancy materials, carbon fibre composites exhibit no ductile behaviour beyond yield. This means that when they yield, they do so with no bending/necking before they rupture and therefore no warning too. Based on this alone, I think they're an extremely poor choice for making handlebars out of as they're such a safety-critical component. You snap a chainstay/seatstay? Fair enough, you could probably still ride it out. You snap your bars and you roll the dice.
If you want to go light up front, go for Ti or something.
See attached a picture of a cross section of a downhill carbon bar of one of the "premier" leading brands. The cut was taken through the middle of the clamping section. If you need further explanation of why this is terrifying:
- The cross section isn't even close to round. The laminate thickness is varying by a huge percentage in places, most likely due to incomplete consolidation; this is the part of the process where the laminate is compressed to squeeze air and excess resin out to get your correct fibre volume fraction. Why is this important? Because a) the material properties (strength/stiffness) you designed the thing to work with depend on (now it's potentially weaker than you thought it was going to be) and b) see part two below.
- Voids. Lots of them. This is where you haven't got all of the air out during consolidation. These are stress concentrations and points of delamination waiting to happen.
- Hard to tell without actually checking all of the fibre angles, but it looks like they've used more than 4 plies pointing in the same direction and that the laminate isn't truly symmetric and balanced. I don't really have the time to go into detail as to why this is bad but it's poor design practice in composites.
Beyond the manufacturing related issues above, bare in mind that, unless you go with very fancy materials, carbon fibre composites exhibit no ductile behaviour beyond yield. This means that when they yield, they do so with no bending/necking before they rupture and therefore no warning too. Based on this alone, I think they're an extremely poor choice for making handlebars out of as they're such a safety-critical component. You snap a chainstay/seatstay? Fair enough, you could probably still ride it out. You snap your bars and you roll the dice.
If you want to go light up front, go for Ti or something.
Attachments
there is a great YT channel about that - great stuff:
https://www.youtube.com/channel/UCY9JUMYI54lLOHpb_zbIedQ
Great contribution Troy. I spent a lot of time following the youtube rabbit hole with this one. Even learned a thing or three.
Very useful explanation.
I am by no means a composites professional, but all the points you've listed should be without question implemented in the construction of every carbon piece out there. In terms of engineering the above statements should be common sense. Like a consistent diameter and no voids in the material should be very, very basic stuff that asolutely needs to be followed.
What dou you think about carbon frames, especially used in DH environment?
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Fify.
I've said it before and I'll say it again, most of these 'designers' in this industry couldn't cut it for a day in another manufacturing industry, esp aerospace. The amount of bullshit to sell bullshit is second to none. I know there's some solid engineers that do exist, but imo they are outliers. Some of the best CF stuff we have available would end up in the scrap bin at Boeing. That handle bar cross section is simply embarrassing and a strong tell of what's going on with manufacturing QA. Anyone remember the Yeti stays that pressed in to the touch? always a "bad batch" explanation, which brings up the 2nd issue: QA.
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So what qualifies someone to become a designer in the bike industry?
The Lizards are listening.
From what I've seen, saying you are is the biggest qualification. If you can make pretty pictures in some canned linkage software, that's worth a bsme, if you can make em in solidworks, a doctorate.
What you are saying makes me wonder why we don't see more broken frames and parts. Are they constructed with enough 'meat' that this doesn't matter or is the industry just lucky that not many ride their bikes hard enough?
I know in my local shop quite a few broken carbon frames are returned every year and from all manufacturers. Curious if anybody has a number on what percentage actually fails?
I know in my local shop quite a few broken carbon frames are returned every year and from all manufacturers. Curious if anybody has a number on what percentage actually fails?