brianallan

So my buddy broke his carbon bars today! He hit a ditch, the bars snapped, he got all scraped up! The bars are somewhat old, purchased in 99, been on several bikes (non of which were installed with a torque wrench). The brand is LB or something? They're no longer in business. My friend has one of their seat-posts though and i think he might be purchasing a new one after today.

enjoy!

jiiiim

wow! thank you now my carbon fear just shot over the moon!

mlts22 

Great, you got me scared stiff again about carbon now. First, the seatpost fracture a week or so ago, now handlebars shearing off where the stem grabs the bar.

Slight digression: What brand of bars are going in the now-sheared place of the carbon ones? I have no clue which brands are the pack leaders. I've heard good things about Race Face, Bontrager, and some others, but haven't heard of any brand that just "owns" the market, like Thomson does seatposts or Phil Wood arguably does hubs.

LowCel 

It happens from time to time. However, hearing about a seven year old bar that has been mounted and remounted over and over again on different bikes with no torque wrench really shouldn't scare anyone off.

RIC0

I agree, carbon technology has come a long way since 99, better material, crush points added in the center of them, etc, etc.

Riles

if one snaps, is it going to be any worse than comming off at speed over an intact bar ??

I'm thinking not & everyone who rides an MTB is having a few bad falls a season anyway... so why worry.

apclassic9

A carbon bar made in 99 probably doesn't have the UV protective coating on it that a newer one would... which is to say that the one from 99 probably should have been replaced in '01 or '02....

C Law

Bingo.

rushguy

yeah.........it must have began to melt. That is, if it was in the sun too long.

ed 

There's definately a difference between LP composites from '99 and today's Easton CNT Zyvex crizzap.

The new CNT XC bar has "Highest impact strength of any ATB riser bar ".

Don't take that statement the wrong way. The EA90 is not stronger than the Easton Havoc.

Over time, the Havoc will handle more abuse. As far as impact, carbon is strong.


Carbon nanotubes have been called “the strongest fiber that will ever be made”. Nanotubes have a strength-to-weight ratio orders of magnitude greater than steel.


I am just saying don't let that picture of an LP composite bar that's 7 years old scare you away from carbon. I wouldn't ride aluminum for 7 years either.

Check out Eastons stuff if you wonder about carbon. It's the Bizzomb.

mcoine

Could you please provide the units for the y axis.

Brian

I'm still sticking with titanium. But I've got CF heasdset spacers.

jiiiim

PSI

jk i'm an ass

dutret

Thats the strength of a single nanotube right not the strength of the nanotube enchanced final product?


MPa*mL/g would make sense but I don't think thats what that is.

John Galt

yeah...

khuon

Just to expound upon this, BMC and Easton uses MWNT (multiwall nanotube) "enhanced" high-modulus CF for the frame, fork, handlebars and seatpost. This is essentially "doped" CF whereby a CNT additive is injected into the resin. While this isn't a pure nanotech CF structure it is dramatically stronger than standard CF prepregs. The CNT-enhanced CF that Easton and BMC uses is about a hundred times stronger than aluminum 7005 and ten times stronger than traditional ultrahigh modulus CF. The material is strong and abrasion resitant enough that the entire headtube of the BMC bikes including headset faces can be made with it instead of relying on a steel or aluminum insert as in traditional CF frames. The BMC bikes also use full CNT dropouts instead of metal ones.

The real breakthrough will be a pure SWNT (single-wall nanotube) CF frame whereby the entire structure is made of NT-CF. This is still fairly difficult to manufacture. The manufacture of large-scale pure MWNT structures have just started becoming possible and SWNT is closely following in its footsteps. The aerospace industry has been developing this technology for the last 15 or so years but it's really coming along.

From a materials comparison standpoint:

khuon

That's the seamline on the cosmetic weave outer layer. It says nothing about the quality of the underlying layers.

John Galt

You're wrong.

That is not a cosmetic defect. The cracks penetrated quite deeply in fact.

DirtPedalerB

I'd guess the strength numbers go down substantially when it is chipped in a small place.

That fracture in the 1st pic looks like someone cut it cleanly.. I had imagined it would string or splinter out.

khuon

Okay. I thought you were pointing at the seamlines. I have a similar looking visual effect on my CT2 and have verified (using both the vasoline+UV light and laser beam method) that it isn't a crack.

khuon

Yes. The strength of a notched CF specimen goes down dramatically when compared to unnotched. There are several ways to make CF less notch and abrasion sensitive however.

DirtPedalerB

That sounds like borderline paranoia. Unless of course you have some vasoline and lasers around the house, which is just weird.

free_pizza

arent petroleum based products and carbon a bad mix?

khuon

Doesn't everyone have some vasoline?

As for lasers, a simple laser pointer will do. Just shine it through... tangentially cutting across the cross section of the CF to see how deep a gouge or crack actually is. You should see a marked refraction at the surfaces of the notch.

khuon

Vasoline is not especially harmful to CF. Some people even use it in their molds to keep the CF from sticking.