Is Aluminium alloy good for nothing?

Discussion in 'Cycling Equipment' started by sogood, Sep 29, 2006.

  1. sogood

    sogood New Member

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    Not to say that there aren't great Alu bike frames but pointing out that every company and bike store, and buyers (informed or not) are eyeing those carbon frames. For better or worse, it's clearly a trend that exists in today's market place. Carbon is being pushed as the ultimate material and their prices are falling. Even Cannondale, the major pusher of Alu frames is in Carbon. So yes, there's a definite trend there.
     


  2. sogood

    sogood New Member

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    My question is, apart from being cheaper at this time point, in what ways are Alu better than CF? Out there in the market place, it's as if Alu is a poor man's CF bike material. If you have the budget, then the prevailing suggestion is to go CF. This is the part I am trying to work out, to see if there's any counter reasons to go Alu rather than CF.
     
  3. Strid

    Strid New Member

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    Perhaps that

    http://www.cyclingforums.com/t367044.html

    isn't that unusual after all. Could have been a dangerous ride and a potential crash. They require more TLC and replacement.
     
  4. capwater

    capwater New Member

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    Carbon is good, but personally it is overrated as the ultimate frame material. It's the Lance effect. He rides a carbon frame, so Trek wants you to think you should as well. Big dollar marketing hype. It's not any better or worse. A note, CF price is actually going to increase as the aerospace industry is going to start using it big time thus driving up the prices, econ 101 supply and demand.
     
  5. BreezerBeliever

    BreezerBeliever New Member

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    The smoothest, fastest road frame I have ridden, the Cannondale Six13 (2005 model), is a combination of aluminum and carbon. Each material is situated to take advantage of its attributes. For instance. most of the rear triangle is CAAD 8 (aluminum) for efficient power transmission, while on my particular bike portions of the top tube, downtube and a small portion of the seat tube are carbon. This makes for a swift but comfortable ride. But I hardly notice a comfort difference when I switch to my all-aluminum R1000. Go figure. Also, most higher-end aluminum bikes come with a lot of carbon parts, like stems, seatposts, handlebars, etc. So these bikes are really neither fish not fowl, but they do fly.
     
  6. dhk2

    dhk2 Active Member

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    In terms of strength and stiffness to weight, believe well-designed frames of AL and CFRP will be close. Agree with you that CFRP is likely to dominate the mid-range bike market in the future as prices continue to drop due to the huge investments made in CF facilities in Taiwan and China. CFRP may well come to dominate the high-volume
    mid-range of the big brands, leaving Al to the smaller brands and custom builders.
     
  7. garage sale GT

    garage sale GT New Member

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    I am eyeing an Al frame with carbon fork and seatstays.

    The thing that worries me about carbon is I have heard that it can take a hit and not show any damage, but then just break completely on the next big hit. Does anyone have any (bike) experience with this? Or in other words, how bad does the bump have to be before replacement becomes a good idea?

    P.S. Strid: Minor detail, but be they soft, hard, brittle, resilient, etc....all grades of a given metal's alloys will have the same stiffness. So a 6061 frame differs from a 7005 frame only due to its geometry because they are both primarily Al. Same goes for 4130 vs 1010 steel.
     
  8. dhk2

    dhk2 Active Member

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    Regardless of the frame material, the fork is likely going to get the most loading from hittting something like a big pothole, high curb, or car. Would say your concern about hidden CF damage is valid for both forks and frames, but more critical on the forks. IAW, even if you have an al frame, you should be aware of the symptoms of possible failure of the CF fork.

    The LBS Trek dealer here has a big poster which warns customers not to ride a CF fork or frame that feels "loose", is making noises, or shows any evidence of damage. It says to bring the bike to the dealer for inspection if any of these symptoms of potential failure are noted. Certainly after a major accident or hit it would be smart to inspect both the CF and al parts of the frame.

    Believe real-world experience with millions of CF forks for at least the last decade has proven that a high-quality CF fork can be very tough. I ride a custom Al/CF rear frame, with a Reynolds Ouzo Pro fork. At 12K miles now, have no worries about the integrity of either the fork, frame or rear stays.
     
  9. allgoo19

    allgoo19 New Member

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    This simply tells me that Trek acknowledges CF parts break, so giving you a warning before it happens. If you read this negatively, Trek is saying "We are not liable for the breakage or your injuries because you were not paying attention to the warning sign."

    But here's a thing that contradict from what I have been hearing. CF, specially forks shows no sign visual or audible of any kind before they break, and it doesn't take a big impact to make it happen. It seems to be true, it doesn't happen very often but even if it happens on in a million, if it's to me, one too many.

    I have been long skeptical of Aluminum frames (or any new material for that matter) the introduction of it in "80s, too whippy, too stiff etc. What I have been hearing lately is quite positive about Aluminum and I think the design engineering had improved quickly over the years. I think CF design is still in its infancy and still have a room to grow like Aluminum used to be. At this moment, I wouldn't say "It's been proven safe." specially when it's compared to other materials(yet). Eventually, all the negative factors will be worked out. After all, it seems to be working very well for F1 (or other open wheel race cars) chassis and its safety improved dramatically in the last ten years or so.
     
  10. bobbyOCR

    bobbyOCR New Member

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    The answer is no. Aluminium and carbon have different applications. A thin wall large diameter al tube will be have a better stiffness to weight ration thatn a carbon tube. Aluminium stays are currently lighter for the same stiffness than carbon stays (six13) The comfort in a ride can be dealt with simply by tyre pressure and tyre type. IMO, carbon is overrated (and still a better $:weight ratio than carbon for parts, eg a FSA RD200 bar and PRO xlt race stem combo (sub 350g)
     
  11. garage sale GT

    garage sale GT New Member

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    I am drawn to carbon because of its claimed ability to dampen road vibration; it seems a good idea to have an aluminum frame with carbon seatstays and fork.

    This may not be the best example. Race cars only need to last a season. Carbon is clearly strong enough; the problem is that it does not show fatigue.

    Airplanes use composite panels too, but the makers have sophisticated computer programs to predict when a part ought to be replaced.

    There is no analog for bikes. There is no way that a carbon part won't need replacement; the only question is when. Unlike steel, carbon (and Al for that matter) have no fatigue limit. Any amount of cyclic loading (vibration, pedaling, etc) will eventually result in fatigue failure. If a carbon fork is sufficiently overdesigned then it could conceivably last a hundred years or more but how do you tell where you're at?
     
  12. dhk2

    dhk2 Active Member

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    Most CF applications on aircraft have sophisticated inspection techniques to ensure safety. Scheduled replacement predictions aren't really sufficient for CF, because it doesn't have classical fatigue properties like metals.

    Most of us don't have access to ultrasonic or x-ray inspection equipment for our bikes. Trek has a campaign to inform customers that they need to be aware that CF forks and frames can be damaged. It tells them to bring the bike in for inspection immediately if they hear any creaking, feel looseness, or seen obvious signs of damage in the CF parts. Would say the same advice applies to forks/frames of any material.

    Your last paragraph seems biased against CF, IMO. Disagree that any small amount of cyclic loading will result in fatigue failure of CF, any more than steel or aluminum. After all, many CF forks and frames have been on the roads now for at least a decade, and riders aren't being thrown to the ground very often. A good CF fork which isn't subjected to bad roads, potholes, curbs, or crashing should last "forever"...at least as long as most of us care to ride the bike.

    Besides, "How do you tell where you're at?" with a steel fork? There's no way to assess cumulative damage leading to low-cycle fatigue failure unless you've had the critical stress areas of the fork instrumented thoughout it's life.

    Assuming I'm lucky enough to ride my bike 50K miles over the next ten years without a big crash, would bet that I'll never have to replace my Ouzo Pro fork. A CF fork (or frame) is just not something riders need to worry about.
     
  13. bobbyOCR

    bobbyOCR New Member

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    The thing about carbon's vibration dampening is only slightly true. A high modulus frame will be more unforgiving than an aluminium frame, because of its rigidity and brittleness. A low modulus frame will be comfortable (FLEXY) but FLEXY. That is what gives it its comfort. Certain designers can create a frame which is compliant in all the right areas, and stiff in all the right areas, all at the same time (cervelo R3). But many of these frames are very expensive. Cheap carbon is a huge waste of money, as alot of it is dyed glass fibre in lower end stuff, or carbon wrapped alloy. They have not progressed enough with carbon.
     
  14. toshi

    toshi New Member

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    +1.

    Besides, there are a number of pros who prefer and even like alu bikes. You don't need carbon to be a pro, and pros definitely do not need carbon.

    Sastre prefers his Cervelo Soloist Team. Danilo DiLuca rides an all alu Bianchi (http://www.cyclingnews.com/tech.php?id=tech/2006/features/liquigas).

    Carbon is just the hot material at the moment, and for good reason, but it is not ultimately superior to alu, no matter what marketers tell you.
     
  15. allgoo19

    allgoo19 New Member

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    I found this article interesting. It says

    == Composite materials are generally laminates, sheets of high-performance fibers, such as carbon, glass or Kevlar, embedded in a polymer resin matrix. Chou said that the traditional composite materials have inherent weaknesses because the matrix materials--plastics--surrounding the fibers are "strong, but far less strong than the fibers."

    This results in "weak spots in composites in the interface areas in the matrix materials, particularly where there are pockets of resin," Chou said.

    As a result, defects, including tiny microcracks, can occur. Over time, those microcracks can threaten the integrity of the composite ==

    And there maybe more reliable way to detect it using carbon nanotube mixed (not for the strength but for detection purpose) into it in the future.

    In other words, the current methods available are not quite perfect yet.
     
  16. dhk2

    dhk2 Active Member

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    Voids and defects in bonding can be a problem in CF manufacturing, but quality controls on production, test "coupons" as well as NDT inspection procedures have been around a long time now. Would think most CF manufacturers are doing both NDT and destructive testing on a sample of each production lot to ensure quality. Bottom line for me is that you shouldn't have to worry about voids or debonding in quality CF frames.

    Even with perfect quality though, the microcracks you mention can appear from severe repeated loading or flexing of the frame. When these cracks grow into debonded areas, they "threaten the integrity of the composite"....I like that wording :)

    Speaking of CF failures, just saw a racer buddy at the Trek dealer today. He had his second warranty replacement Trek CF frame in for a new BB. The original and first replacements broke from too much hard racing and training over the past decade. He explained Trek wised up this last time; told him this was the last freebie, that they don't warranty frames against fatigue and aren't in business to furnish free frames for life to racers.

    Not a CF scare story at all; this guy understands that every lightweight frame will break eventually if ridden hard and says he's happy that he's more than gotten his money's worth from the Trek.
     
  17. Buffalo Dude

    Buffalo Dude New Member

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    There's no reason that you couldn't calculate when any CF or Al part would fail, the limiting factor is cost. Fatigue analysis is a basic part of any engineer's curiculum. Well, mechanical engineers at least. The cost to comission engineers and the computing power necessary usually limits how much companies invest in research.

    Most companies will make decisions based on what will typically happen. All parts have a finite lifespan, even steel. Well, I suppose a part could have an infinite lifespan, but then you overdesigned it and now it probably costs too much/weighs too much/etc.

    The point is that you can design parts that will never fail and that are "perfect" in terms of manufacturing flaws. It's just that few, if any, people could afford it, and may not even want it because something costing half as much might not last as long, but will last longer than the intended service life. Let's not forget that the fastest cars in the world rely heavily on CF, but cost 7+ figures. To me, it's mostly about preference, and unless you're part of the elite 2% of the sport most of it is marketing hype.
     
  18. sogood

    sogood New Member

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    Isn't that the whole issue? CF is marketed as being lightweight, so the tendency is to reduce material as much as possible. I can't see how well a CF component would sell if it's markedly heavier than a comparable alloy part.

    Been doing some shopping recently for a bar and stem combo. I note that many CF components are of similar weight (within 10s of grams) to premium alloy components that's 30-40% cheaper.
     
  19. Bro Deal

    Bro Deal New Member

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    That has nothing to do with the material properties of AL vs. Carbon. Aluminum frames have become a commodity. They were first pioneered by Klein and then made for a more reasonable price by Cannondale. In the latter half of the nineties, welded AL frames began to be made by anyone with a TIG welding machine. You can now buy a frame for a hundred bucks. You can probably get such a frame from the Chinese OEM for thirty or forty dollars.

    The first defense for AL was to add a carbon rear triangle, promote it with some marketing bullshit about road buzz damping, and jack up the price because the frame was now high tech. This did not work too well because it turned out that for all but the most rock bottom AL frame manufacturing using a prefabbed carbon back end is actually cheaper than using an AL backend when labor costs are accounted for. The end result was that carbon back ends showed up on all the low end AL frames.

    Now manufacturers like Cannondale are being forced to go to carbon because they can still get a premium for their frames even though they are mass manufactured. Most companies do their actual frame manufacturing in Asia and their costs of goods is very low. The high tech marketting B.S. surrounding carbon still works so they can charge a high price. Being able to charge more with reduced costs of goods is a nice trick.

    I have frames made from AL, carbon, steel, and titanium. My favorite is my ti bike because it is made by the company I consider to be the best titanium craftsmen on the planet. But aside from geometry differences I cannot honestly attribute any differences to the frame material. Maybe I just have dull senses but I think the tales of road buzz damping and reviews describing frames as "stiff but comfotable" are a load of crap.

    I tend to think that the real difference people claim they can feel is actually just differences in the sound bikes make when you hit something. Big tubed AL makes a harsh sound, but I don't think that actually translates to lack of comfort. I have never done a hundred miles on my AL bike and thought, "Gee, I am so beat up I wish I would have used my carbon or titanium one." Fact is that when I am in form I can click off a hundred miles without thinking about it and I feel just as comfortable at mile 90 as I did at mile 10--aside from leg fatigue if I am hammering.
     
  20. Bro Deal

    Bro Deal New Member

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    Too bad Trek forgot to show one of those to George Hincapie.

    Yeah, yeah, yeah. The steer tube was AL, but still...
     
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