Any engineers on board? Questions about my foray into modern carbon fiber...

[dd74]

I have the chance to pick up a Look 595 Ultra at a nice price. I haven't ridden carbon in 25 years. These days, I ride lugged steel and Ti. The prospective Look frame was used for one race season, and at that sparingly.

My concerns are the durability of modern carbon fiber to steel and/or titanium. Will this frame hold together on rough roads, or is it a plastic nuke bomb ready to shatter on the bumps and divots of Cahuenga Blvd?

Also, how will this compare in stiffness/responsiveness to steel and titanium?

I wanted to ask here instead of a cycling forum, for fear that my questions would be inundated with emotion and not necessarily fact.

Thx.

[enzo1]

Bicycle Frame Materials - Steel, Aluminum, Titanium and Carbon Fiber, by Sheldon Brown I have a cf love it,but have to be careful not to nick it!

[onewhippedpuppy]

I think Schumi does this as his day job, so I'll be basic (for fear that he's smart and I'm not). CF has excellent fatigue qualities, much better than steel, so in theory it should age better. However, it does not deal well with impact damage, which can significantly weaken it. I know nothing about bikes, but generally speaking it should be stiffer and lighter than a comparable steel bike.

[enzo1]

...... and a LOT better on the ass! actually it's the LIGHT weight, when comparable to steel, yes the steel does have fatigue but is cheaper, so you could buy 2or3 for the price of 1 CF

[dd74]

Originally Posted by enzo1

Bicycle Frame Materials - Steel, Aluminum, Titanium and Carbon Fiber, by Sheldon Brown I have a cf love it,but have to be careful not to nick it!

I'm familiar with Sheldon Brown (RIP) and his insights. But you say you have c/f. What type of riding do you do? And where? The "nick" factor is a concern to me. Are we talking impacts from rocks and/or gravel that are strong enough to dent a steel frame? I do know deep scratches can compromise the weave, but that's about it.

[enzo1]

bought steel bike, took it home, rode 10 miles for 7 days , took back"let mr try that CF" NEVER looked back, I have lots of potholes & rough stuff as well as smooth, kid i know wanted to try it out..... since it has no kickstand he dropped it on a concrete curb & nicked it, took to bike store and they used a coin ( quarter) , ran it down the chainstay tapping it and feeling or listening for a difference, it hadn't gotten into the actual fiber of the CF only the paint, this may sound funny but it's kinda like glass also unless you doit yourself, sending it off is hassle and $$ rocks and gravel would get paint on top(several coats) before CF

[enzo1]

YouTube - moldless vacuum bagging carbon fiber bicycle frame

[enzo1]

I have a entry level Trek CF, like it but next one will be a cervelo, this video shows the differences in technology...etc YouTube - Cyclo-CLUB Cervelo R3 Review

[look 171]

Hey DD,

I have had my look 171,"Jalabert special" for a long time now. I love that frame. Just look at my screen name. It still rides great. I have beaten the snot out of it. Crashed it a few times. Lucky no real damage done. I am a big fan of carbon especially the Look frames. Love the way they feel. I buy it in a heat beat. I just went out for a short ride Last week and was dead within the first 20 miles on my Look. I am actually looking at a carbon Torelli later today at a shop. Know anything about those?

BTW, buy the Look frame. I have gone over railroad tracks and huge pot holes on training rides trying to shake others off my tail. Yes, I had a few names called but that's the game is played. I am rough on bike equip. anyway, the frame will hold up fine. stone chip and dings are really no big deal. It wouldn't hurt it.

Have you ridden a mordern carbon before? You want to try my look?

[dd74]

I heard good things about Torelli. Yeah, the Look is very nice and will allow me into the c/f world with not too much $$$ worry. I already have a spare D/A group & wheels, so I'm set with components.

When I say "durability," I mean will this thing last in L.A. with all its junk roads. I do hear teams discard their c/f frames after Paris-Roubaix, as the bikes are basically beaten to pancakes. But I really don't see myself riding cobbles anytime soon.

What size frame do you ride? The Look I'm looking at is a 52cm, IIRC.

[look 171]

Yeah, I have met you once in those canyon drives. Yap, 52. It will hold up just fine in the roads around LA. I put in many hard and rough miles here. I have a Torelli alum with carbon stay frame that's got may be 1500 miles. Comes the kid, then I quit.

[Schumi]

Carbon composites aren't necessarily my day job per-se, but take up about 50% of my research here.

Carbon fiber products have changed a lot in the last 20 years, but it's not the actual carbon fibers that have changed. In fact, they have changed relatively little. The changes have happened in the theroset resin systems and the effect on layups that simulation has had. I'm highly doubting that many bike companies do much with finite element modelling on their layups, I'm sure it's mainly empirical testing.

Given a perfectly produced carbon fiber composite structure with a modern resin system that has been properly stressed (i.e. layer orientation management) , you can expect a carbon tube bike chassis to be about 3x as stiff as a typical aluminum chassis.

By weight alone, a bidirectional carbon tube will be just as stiff if not slightly stiffer than high grade 4130 steel. The advantage here is that you can make the bike much lighter, as the stength is far greater than aluminum or even titanium.

The problem that you see with people breaking carbon bikes is that the companies end up going lighter and lighter, fewer and fewer layers of carbon ... and the bike is still stiffer than an aluminum equivalent but prone to failure. The best advice here is really to just go with a trusted company that has experience here. Modern resin systems are incredibly tough, and any good manufactured should be using a prepreg resin system with adequate toughness and additives for UV resistance and galvanic corrosion resistance. Carbon in contact with aluminum (which is what the bearing bores will be made from most likely) caused a galvanic reaction. It is an incredibly slow galvanic reaction compared to what you normally think of, i.e. zinc and whatnot.. but it is there, and therefore the use of a bonding epoxy between the bearing bores and the carbon that resists that is necessary if you want to be riding the same bike for more than 5 years. Lotta guys out there making their own bikes aren't doing this.

Another issue is again with the bonding between the chassis and the bearing bores. A lot of failure come when the bores are bonded in improperly, usually because the carbon and aluminum interface surfaces are not prepped properly for a good bond as required by most epoxy systems (most use a Henkel product like Loctite Hysol 9460). This is another reason to stay away from the cheap stuff... since a lot of this stuff is hand made, you can't be sure how well they're prepping the stuff.

All the top bikes are surely prepreg laminates, but some of the small company stuff can be a traditional 'wet-layup' bike... starting with pure bi-directional fibers and wetting out by hand with a two part resin system (Aeropoxy or West Systems are common names). More sophisticated methods are by vacuum assisted resin transfer molding, or VARTM. The key to strength and stiffness with wet methods is an appropriate volume fraction, or amount of resin compared to amount of fiber, and also the resin distribution in the fibers. In most cases, a wet layup bike will not be able to be as light nor as stiff as an aerospace prepreg equivalent due to the inherent inaccuracies in the resin delivery system. The use of computational flow solvers in recent times have made manufacturing VARTM components with properties close to that of prepregs possible for a cheaper price, yet still... I doubt any bike companies are using such simulation. It's not something that is particularly easy.

I digress. The real thing you need to know is that a good quality bike from a solid reputable company should be able to perform just as flawlessly as any old steel or ti bike. It starts to come down to rider preference. The one thing about the carbon bikes is due to the stiffness increase, the natural frequency of the bike is several times greater than aluminum and the damping characteristics of the material are very different. On a fixed suspension road bike, this appears in the form of a slightly harsher, less damped ride. This would be barely noticeable to any joe schmoe, but an experienced rider will feel it.

Fatigue in the carbon itself is a non-issue. A correctly designed carbon fiber structure will literally never fatigue if the loads it sees are kept within design limits. A stress strain curve of a carbon laminate is nearly a straight line. There is not clear yielding and plastic deformation like any engineering metal exhibits. Fatigue in the resins used to be an issue, but not with any modern resin system. For bikes that are not painted, just clearcoated, be damn sure that the resin system has a UV inhibitor or else sunlight exposure over the years will age the resin (resulting in a yellow-hue to develop) and can weaker the outer surface slightly. This usually isn't a structual problem on say, carbon fiber formula car monocoques due to the sheer thickness of the material, the outer layer is all that is exposed. But on a road bike that has as little as 4 layers of fiber thick in some areas, the UV permeability can be a problem.



So, that's my technical opinions. It should be noted that I'm not a bike rider by any real means anymore, so there may be more that you would want to focus on when purchasing. Such as the price tag. And the color.

[dd74]

Whoa! Thanks, Schumi.

Yes, the frame is painted (black). And it comes from a leader in carbon fiber development for bicycles (Look). I examined it today, and other than typical scuffs due to the chain and cables (nothing too deep), the frame looks very good.

All I know is failure is not an option whilst descending Barham Boulevard.

[dd74]

Originally Posted by look 171

Comes the kid, then I quit.

...and when the kid grows up to be a self-feeder, no more excuses.

[slodave]

David, I have a client that rides all over the valley and over the hill sometimes. I believe he has at least one carbon bike. I have to give him a call in the next day or two and will ask what he thinks about eh roads as well, but I have not heard any complaints.

[dd74]

Originally Posted by slodave

David, I have a client that rides all over the valley and over the hill sometimes. I believe he has at least one carbon bike. I have to give him a call in the next day or two and will ask what he thinks about eh roads as well, but I have not heard any complaints.

Thanks Dave. That'd be great.

[Jim Bremner]

Get the newest Velonews and read up on their trip to the TIME factory.

Time builds their own carbon up from the strands. They do not lay it up wet, nor in sheets.

They use wax forms that they pull tubes of dry carbon over. After 5 to 8 layers are built up they pin the formed tubed to their lugs and insert them into the mold.

This mold is injected with the matrix, purging out all of the air just like bleeding a brake.

The wax is melted out in the next step.

All of their frames but 1 model are produced in France.
:: TIME :: Catalogue 2009 :: MODULES

[dd74]

Hi Jim,

I'm familiar with Time as well. However, what do you think of Look frames?

[Jim Bremner]

I'm biased. I'm the So-Cal Time rep.

[dd74]

Originally Posted by Jim Bremner

I'm biased. I'm the So-Cal Time rep.

LOL! Good man, you are. Okay, what in the Time lineup compares to the 595 Ultra? If you have a link to that frame, I'd love to check it out.

BTW: I wish I had earlier known you were the rep. I would have come down to check out the Time frames. They're very nice IMO.