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Thread: Scandium

  1. #1
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    Scandium

    I heard this bike dealer talkin about Scandium saying that a SC frame
    will lose its stiffness within one season of riding.I am thinking about buying a
    Scott team issue SC(oh so light 1250 g.) frame and would like some opinions on the subject..

  2. #2
    Baliw
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    Quote Originally Posted by Phoo
    I heard this bike dealer talkin about Scandium saying that a SC frame
    will lose its stiffness within one season of riding.
    Horsesh!t. File that in the same brown folder as "Al gives a harsher ride than steel", "Steel is more supple/compliant", "I can feel the difference between Al and steel and Ti".

    What ScaMdium will do for you is lighten your wallet unnecessarily, because it's an "aerospace" metal used for "ballistic missiles". Oh, and file the latter under the same brown folder as above.

  3. #3
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    Quote Originally Posted by steve3
    Any superlight race specific frame will loosen up, scandium or not. It's the nature of metal.

    If you build a stronger frame, it will loosen less, but any superlight and underbuilt frame will loosen more, regardless of material.
    Nonsense. "Loosen up"? Metal doesn't "loosen", whatever the crap that means. Frames don't "loosen" either, since they're rigid structures that are WELDED together. There are no joints that can "loosen", they can only break.

  4. #4
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    Quote Originally Posted by Juramentado
    Nonsense. "Loosen up"? Metal doesn't "loosen", whatever the crap that means. Frames don't "loosen" either, since they're rigid structures that are WELDED together. There are no joints that can "loosen", they can only break.
    This is a common misconception. Metals are not eternal, and will change over time as they are repeatedly loaded and unloaded, or left loaded for a long time (even with small stresses much lower than their yield stress). The two main forms of metal failure due to small loads are fatigue and creep, both of which involve stresses lower than the yield stress of the material so they will not cause immediate failure.

    Fatigue is the processes of creating dislocations within a metal's structure due to repeated (typically in the range of >10^3) loadings that result in stress (engineering stress is defined as load divided by initial area). Dislocations are interruptions to a material's crystal structure, forming numerous tiny grains of uniform lattice within the metal, and dislocations make a metal harder and stronger, but also less ductile (= more brittle). Dislocations may be caused by impurities in the metal (carbon atomics dissolved in iron makes steel, for example) or through cold working of the metal, which "breaks" the grains, and makes them smaller (the newly formed grain boundaries act like dislocations).

    These stesses are usually small, and won't cause failure immediately. However, if you inflict your material to enough of these small stresses you will create lots of dislocations, which will in turn make more tiny "cracks" (invisible to the naked eye) formed from the grain boundaries. Brittle failure (which means it will fail suddenly, and without much notice) will then occur when the tensile load applied to the piece is sufficient to break the smaller remaining crosssectional area. This is the cause of sudden unexpected failures (and why aircraft wings are inspected so rigorously , look up the DeHavilland Comet for a good case study on why fatigue is important).

    There is also a property of some BCC crystal structures (steel being the most common) and HCP structures (titanium) that has a "fatigue limit". This means that if you keep your applied stress under this limit stress fatigue won't occur for those metals. If you exceed that limit fatigue will still occur. Aluminum has a FCC structure, and it has no fatigue limit. This means that for any stress it will eventually fail after a long number of cycles.

    Fatigue is also proportional to the magnitude of the stress, so if you keep it lower (even if it's in the fatigue region) you can subject it to more cycles. At .9(yield) you will only get a very low number of loading cycles (say, 100) but at .1(yield) you can get very high amounts (say, 10^6). Larger parts also resist fatigue for a given load better, since the stress (which is responsible for fatigue) is lower due to the bigger crossectional area.

    Creep is the process of loading a part with a constant load and letting it sit for a long time. The part will plastically deform, depending on how long you leave it loaded and what the stress in it is. The creep is caused mostly from dislocation movement. For bikes, this probably doesn't come up as much (unless you sit on your bike nonstop for months, heh), but it is a change of a metal without breaking it. You can do a little test of this yourself by getting some solder wire and hanging a weight from it and watching it stretch slowly over time.

    In either of these cases the material's crystal structure is being changed, and in doing so you change its material properties (ie, making it looser/tighter, or changing dimensions). If you've ever been bending sheet metal with a hammer and it gets harder to keep bending after a while you're observing this directly. You can check this phenomenon with a paperclip if you're doubtful too (by bending it back and forth you fatigue it, and with each bend you make going back gets a little harder, up until a point).

  5. #5
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    Quote Originally Posted by Durundal
    This is a common misconception. Metals are not eternal, and will change over time as they are repeatedly loaded and unloaded, or left loaded for a long time (even with small stresses much lower than their yield stress).
    You don't even know enough to distinguish between types of metals and their different properties. Yield stress is not the only determinant of fatigue onset. Metals which don't have fatigue limits such as Al accumulate loads and result in eventual failure, whereas metals such as steel, when loaded below its fatigue limit will NEVER fail, regardless of number of cycles of load.

    Quote Originally Posted by Durundal
    The two main forms of metal failure due to small loads are fatigue and creep, both of which involve stresses lower than the yield stress of the material so they will not cause immediate failure.
    I suggest you read up more on these concepts, much much more, before you try your hand at applying them in the case of bike frames.

    Quote Originally Posted by Durundal
    Fatigue is the processes of creating dislocations within a metal's structure due to repeated (typically in the range of >10^3) loadings that result in stress.
    Fatigue is what occurs after a metal is subjected to loads beyond the fatigue limit for those metals that have them, such as steel, or accumulated loads for those metals that don't have them (such as Al). The indicator for fatigue is an initiating crack. There are NO TYPICAL number of cycles to fatigue; these are dependent on the metals involved and their sizes. For certain metals, if the loads are below the fatigue limit, fatigue NEVER HAPPENS while for those metals such as Al, fatigue damage occurs after x number of cycles, x depending on the size of the component and the load magnitude.

    Quote Originally Posted by Durundal
    Dislocations are interruptions to <>
    Reciting passages from sources doesn't add to your arguments when you don't understand them.

    Quote Originally Posted by Durundal
    These stesses are usually small, and won't cause failure immediately. However, if you inflict your material to enough of these small stresses you will create lots of dislocations, which will in turn make more tiny "cracks" (invisible to the naked eye) formed from the grain boundaries. Brittle failure (which means it will fail suddenly, and without much notice) will then occur when the tensile load applied to the piece is sufficient to break the smaller remaining crosssectional area. This is the cause of sudden unexpected failures (and why aircraft wings are inspected so rigorously , look up the DeHavilland Comet for a good case study on why fatigue is important).
    Next time you quote passages from a pop science source such as http://www.sciencedaily.com/encyclop...igue__material_

    be sure to read up and understand the basics of the underlying principles behind the article subject. What you typed above may be true for Al and its alloys, but it certainly DOES NOT APPLY to all metals.

    Quote Originally Posted by Durundal
    There is also a property of some BCC crystal structures (steel being the most common) and HCP structures (titanium) that has a "fatigue limit". This means that if you keep your applied stress under this limit stress fatigue won't occur for those metals. If you exceed that limit fatigue will still occur. Aluminum has a FCC structure, and it has no fatigue limit. This means that for any stress it will eventually fail after a long number of cycles.
    Yes, so WTF are you carrying on about then?

    Quote Originally Posted by Durundal
    Fatigue is also proportional to the magnitude of the stress, so if you keep it lower (even if it's in the fatigue region) you can subject it to more cycles. At .9(yield) you will only get a very low number of loading cycles (say, 100) but at .1(yield) you can get very high amounts (say, 10^6). Larger parts also resist fatigue for a given load better, since the stress (which is responsible for fatigue) is lower due to the bigger crossectional area.
    These are meaningless figures. You CANNOT TYPIFY fatigue across the range of metals in existence, you have to consider the EXACT composition of the alloy. Your figures are nonsensical.

    Quote Originally Posted by Durundal
    Creep is the process of loading a part with a constant load and letting it sit for a long time. The part will plastically deform, depending on how long you leave it loaded and what the stress in it is. The creep is caused mostly from dislocation movement. For bikes, this probably doesn't come up as much (unless you sit on your bike nonstop for months, heh), but it is a change of a metal without breaking it.
    You're now digging yourself a larger hole. Creep is only a consideration when the continuous stress applied to the metal is done so at ELEVATED temperatures. For aluminum alloys these temperatures are above at least 100-150 degrees Celsius, for steel alloys even higher, so unless you ride your bike in an oven and get the metal to be that hot, you won't get a budge from the frame.

    Quote Originally Posted by Durundal
    You can do a little test of this yourself by getting some solder wire and hanging a weight from it and watching it stretch slowly over time.
    And so now you're saying solder wire is the same as Al, steel, Ti, and all other metals. Jeezazz....

    Quote Originally Posted by Durundal
    In either of these cases the material's crystal structure is being changed, and in doing so you change its material properties (ie, making it looser/tighter, or changing dimensions).
    Can't be more incorrect, see above. Making a metal "looser/tighter"? WTF does this mean? Changing dimensions? Bone up on your materials properties before you make such pronouncements.

    Quote Originally Posted by Durundal
    If you've ever been bending sheet metal with a hammer and it gets harder to keep bending after a while you're observing this directly.
    But you were talking about creep, which happens with a constant load at elevated temperatures on a metal component, now you're saying bending and cyclic impact loading a metal is the same case. You're trying alright, but not succeeding..

    Quote Originally Posted by Durundal
    You can check this phenomenon with a paperclip if you're doubtful too (by bending it back and forth you fatigue it, and with each bend you make going back gets a little harder, up until a point).
    Which has what to do with creep, and what to do with bike frames?

    ZILCH.

    You've stumbled badly by over-reaching your comprehension of physical phenomena in metals.

  6. #6
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    Quote Originally Posted by steve3
    You're right and I'm wrong.
    You recognize that at least.

    Quote Originally Posted by steve3
    Live in your vacuum where any object you see is already in its most elemental form and it's not composed of smaller components.
    Ah, okay, why don't you outline your fantasy.. err, theory on how metal alloys get "loose" with loading? First define WTF you mean by "loose", then be sure to include basic principles of physical metallurgy in your argument, apply it to the case of bike frames, and quote your references.

  7. #7
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    Allrighty then...

    So if I go and buy the mother&/#& Scandium frame, will it last for a longer or shorter
    period of time than a light weight aluminum frame ???

  8. #8
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    Quote Originally Posted by Phoo
    Allrighty then...

    So if I go and buy the mother&/#& Scandium frame, will it last for a longer or shorter
    period of time than a light weight aluminum frame ???
    PM Nino in the 'Save some weight' forum. He has a Scott Scandium HT that he uses alot and likes alot.

  9. #9
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    Quote Originally Posted by steve3
    Wow, you're really pathetic (in addition to being wrong).
    Stevo, that's the worst dodge I've seen in a while here. Just state your theory of metal "loosening", back it up with basic principles of metallurgy, state some examples and quote your references.

    Quote Originally Posted by steve3
    Anger management does wonders. Try it.
    Since you don't exhibit any intelligence nor knowledge in any of your posts here, why should anyone think this advice is not meaningless sh!t?

  10. #10
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    Quote Originally Posted by Phoo
    Allrighty then...

    So if I go and buy the mother&/#& Scandium frame, will it last for a longer or shorter
    period of time than a light weight aluminum frame ???
    This question is very difficult to answer quantitatively, since fatigue life is dependent on the metal, the cyclic loading frequency and magnitude, welding standard, appropriate heat treatment, AND the dimensions of the components. In general, "light-weight frame" (ie "stupid-light") is to be avoided if you're not a pro with stacks of sponsorship money and unconcerned about durability. By the way, when people refer to Scandium frames, they really mean Scandium-reinforced ALUMINUM frames. The main advantage of the addition of Scandium is improvement in strength, allowing for lighter structures. However, this does not translate directly into improvement in FATIGUE life.

    If you want a simplistic comparison of two frames, both identical in tubing sizes and geometry, one Al-Scandium alloy and one 7000 series Al alloy, both subjected to the same loadings and everything else equal, it's safe to say that there may likely be a noticeable difference in fatigue life between both, based on metal properties alone. This is because the stronger Scandium-alloyed Al will now be "over-built" for the purpose, ie the Scandium tubing of the same thickness as the Al 7000 alloy is able to withstand higher loadings for the same fatigue life; but this is ONLY IF the Sc tube is the same size as the Al tube. Since the selling point of Sc frames is the lighter weight due to thinner tubes than equivalent Al frames, this advantage is lost. Your frame will not necessarily last longer or shorter, and the only way to find out exactly is by determining the factors stated in the first paragraph above.

    Pile on top of that the significantly higehr cost of Scandium frames, and you're left to decide if you're being sold swampland or not.

  11. #11
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    I hate it when people use personal insults in a pathetic attempt to "win" an argument (at least in their mind - you're not fooling anyone). If you're right, it's not that hard to prove . This isn't a school yard. If you don't have something intelligent to say, just admit you're wrong, prove otherwise, or STFU

  12. #12
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    Quote Originally Posted by steve3
    Wow, in addition to being stupid, you're contradictory.
    Wow, your stupidity and inability to read, let alone comprehend, the simplest of concepts has made you one of the biggest fools in these fora.

    You're rapidly descending the rungs, keep it up!

    "Just state your theory of metal "loosening", back it up with basic principles of metallurgy, state some examples and quote your references."

  13. #13
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    Who is this "Steve3"?

    Quote Originally Posted by steve3
    Wow, in addition to being stupid, you're contradictory.
    And why is he such a blithering idiot?

  14. #14
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    Quote Originally Posted by Phoo
    I heard this bike dealer talkin about Scandium saying that a SC frame
    will lose its stiffness within one season of riding.I am thinking about buying a
    Scott team issue SC(oh so light 1250 g.) frame and would like some opinions on the subject..

    hi man, you cant go wrong with this frame, its the lightest production mtb frame avaliable and one of the stiffest too, as tested by those rocketscience freeks germans. ask nino, he have all the tests. its the frame of choice of most pro riders here and i never saw anyone badmouthing this frames and never heard about frame breakages, fails, or anything like that. the only downside is the cost.

    but remember, this frame is designed for xc, its very,very fast in singletracks and accelerates like a rocketship.

    by the way, this frame in size medium weights 1.170grms. and contact nino, he have a brand new 2004 frame for sale.

    hey
    ho
    lets go!

  15. #15
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    Wow 1.170 grms that is light, or is the in kg?
    When it rains it pours.

  16. #16
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    Quote Originally Posted by boris the blade
    Wow 1.170 grms that is light, or is the in kg?
    in kg off course. or 2,57lbs if you prefer.

    if you want real weights of almost all bike parts avaliable, check out weightweenies.starbike.net, great site with lots of usefull stuff.
    hey
    ho
    lets go!

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