And I’m not advertising for Specialized:
Yeah but the Tarmac is UGLY!!! I’ll take a Roubaix any day though.
How did you find this? Seems like they’d want to keep a detailed description of their manufacturing process somewhat private.
Agreed, why do you think I’m keeping my options open on a new Road bike!!
I’m not sure I’m digging that tall head tube on the Roubaix though
It’s on the Specialized website. I’ve been doing a little research on a new bike and was on their site.
I think it’s pretty cool that they put this information out there for ‘us normal’ people. Good insight as to how carbon frames are made and put together.
I’ve been researching a new road bike, too. Damn it’s frustrating. What are you looking at?
'What are you looking at? "
Fed up with aluminum frames that rattle your fillings out. Carbon is too hyped up. Titanium too expensive. Steel is the best ride but is heavy.
Lemond has the OCVL/steel frames with a carbon/steel mix. The ride of steel but much lighter. I just bought a frame to replace my aluminiumTCR frame. Can’t wait to test it.
Before I get off on a lengthy bit of intellectual masturbation (hey, I’m admitting it), let me first say that on the whole I’m impressed by the paper. For depth and breadth of knowledge it is easily the equal of Craig Calfee’s composites white paper…which is getting a bit dated, last updated in ’02…and surpasses it in many (if not most) ways. I thoroughly recommend it to anyone who wants to know, in general, the “how and why” of composite bike frame manufacturing with a healthy dose of Composites 101 to boot. Now, that said, here’s my gripes:
-I hate this “aerospace grade” moniker that has been applied to certain level(s) of carbon fiber and IMHO misused by damn near everyone in the bike biz. I work in the aerospace industry and here’s the scoop: every modulus “grade” listed in the Specialized paper is aerospace grade. Every one is used by the aerospace industry. Specialized finally gets around to saying much the same thing back in the glossary of this paper. In fact, IM fiber (satellite grade? LOL) is the predominant carbon fiber for military aero applications by % weight of composite structure. If anything, the HM fiber “deserves” the space-grade tag…as it’s the satellite folks who really really need/appreciate the stiffness boost.
-RTM misconceptions:
First of all, RTM and prepreg properties are NOT the same. The USAF’s F-22 found this out the hard way. Here’s the skinny: RTM is very sensitive to variations in the weight of the dry fabric that goes into the mold unless you control that weight to the gnat’s patootie (very expensive to do…it means you reject a lot of material from the supplier unless it’s within a really tight window of acceptability). The mold fills up with resin regardless of whether or not your fiber is at the high or low end of the window. That means in the end you’ve got a pretty looking part that looks like all the other pretty parts from that mold but your fiber volume fraction (which is directly proportional to strength) could be all over the map.
Secondly, and somewhat related to the above, repeatably and reliably achievable fiber volume fractions with RTM are - on average - 5-10% lower than what you can get with prepreg. Simple physics at work here. Well, OK, really ugly fluid dynamics. To get Vf somewhere near prepreg levels you have to stuff so much fiber/fabric into that RTM mold that the resin - even at extremely low viscosity - has a really hard time flowing evenly and completely through the layup. It can be done, but it’s not cheap. In the end, and especially if you’re going to make a high rate of production with RTM, you take your weight or strength hit and go for something less than prepreg properties.
Finally, the bit about RTM being more successful for simpler parts is…simplistic. RTM’s chief benefit is repeatable dimensional control on all surfaces of the part. ALL surfaces of the part. Specialized’s bladder molding approach (pushing the layup out to the mold) gives them that kind of dimensional control only on the surface of the part you see. That’s not a bad thing: you don’t really care whether or not the interior of the tube has a glass-smooth finish, right? There are applications (esp in DoD aerospace) where you need (or just want) that fit & finish everywhere…and for different reasons. THAT is when RTM becomes attractive. NOT just when “simple stuff” is the goal.
-Thermoplastics: y’know, I’m mostly in agreement with Specialized on this one. I just think they should’ve owned up to their own place in the history of folks who tried it and gave up. Specialized has been there and done that too…and I’ve got one of their t-plastic MTB handlebars to prove it. FWIW, t-plastics are a bezotch to process and harder still to connect (bond) to anything else. IF you can make something that stands 100% alone (like my S-Works bar), t-plastics will kill everything else out there for damage tolerance and durability. Though heavy, the GT LTS frames that formed the t-plastic tube structure within aluminum lug skeletons were a really elegant solution to the joining issue.
-Galvanic corrosion: on the one hand they say they use a glass scrim layer as an isolation barrier. Then, in the Tarmac E5 description they only mention a conversion coat (alodine) on the aluminum and a layer of adhesive in the joint. Unless that layer of adhesive contains the scrim (which is possible, but they don’t say so), they’re a little out of synch here.
I was gonna say all that…
~Matt…note smiley faces for the sarcasim and humor impaired.
Not really sure at this point. Hell, I can’t decide if I want to go the Carbon way or Aluminum. I’m currently riding a stell LeMond and want something a little stiffer for climbing (the front end of my LeMond seems soft) and lighter.
Hey Carl
Thanks for the experts review and analysis. Since I assume you are a composities engineer, can you offer an opinion on the whole issue of vibration dampening or
whatever the proper term is? Seems like non CF mnfgs say there is no difference but I sure feel it in my Kestrel. What is it about CF that makes it absorb shock and vibration?
Thanks,
Mike
Mike-
Yes, that’s my dayjob (http://tinyurl.com/69lhe), but I’m not sufficiently versed on vibration damping characteristics to offer up anything resembling an expert opinion. I’ll say this though as a reasonable guess: the component of a composite frame that is likely responsible for damping is the matrix (resin)…not the fiber. Matrix materials are orders of magnitude less stiff than reinforcing fibers (carbon, kevlar, glass) and all the usual metallic alloys used in frame construction. That means they don’t resist bending/deformation very much by themselves. This is because the organic polymer chains that make them up are arranged in a rather more “loose” fashion than the close-packed atomic structure of metals. That lets them move (at an atomic scale) a lot more. They’ll suck up and dissipate more energy accordingly.
Or I could be all wrong 
The non-CF frame manufacturers are not really wrong, though. Metallic frames, and especially those that have been engineered to the nth degree of weight savings, just dissipate energy differently. Metals resonate, they “sing”…plastics don’t. Both are dissipating about the same amount of energy. And, even more importantly, and which has been pointed out by many others in many forums, a little wider tire and a little less air pressure makes orders of magnitude more difference than frame material differences ever will. That’s not to say you’re not noticing a difference with your Kestrel…but the chances that it’s solely due to the frame material are slim.