|Is Lighter Safer? Story that quotes Ernesto Colnagno||BianchiAmber|
Mar 22, 2002 5:00 AM
|In the modern age where we have frames weighing in at under two pounds, Cycle Sport magazine publishes an article about Colnago. In the article, the respected Ernesto Colnago is quoted, "I like to sleep at night", on the reasons why he won't produce an aluminum frame under 2.6 pounds. Mr. Colnago is not a fan of aluminum, it needs to be said. However, it sounds like he is speaking up on a subject that most bicycle frame builders might be passing on and choosing technology over safety.|
Mar 22, 2002 5:43 AM
|I'm not so sure it's a matter of a frame outright breaking on the road causing a crash. It's more that with frame prices as high as they are, the customer deserves to get more than one season out of it.
The unfortunate fact is that aluminum does not have a long fatique life. If the frame is made strudy, it will have a jarring ride. If the frame is made lighter with thinner tubes, the ride will be fine but the frame may crack with time.
Sure some people get a good service life out of their super light Al frames. But the stasticists don't lie. If you take two identical Al frames, subject them to the same cyclic loading, one may crack and the other may not. Thus is the unpredictable nature of aluminum.
|Colnago a reluctant entry into aluminum?||Slipstream|
Mar 22, 2002 6:36 AM
|I read that quote too. I also read that Colnago started to build aluminum frames only because of the competition. |
Colnago is a superior frame designer and seems to work magic with whatever material he uses. He balances safety & cost with desired frame responsiveness. His frames may not be the lightest but you need to weigh factors other than weight when considering a frame. It seems that people want to use weight as a major determinant when comparing frames.
Any frame can fail, but aluminum and carbon--even titanium--may be prone to catastrophic failure. (I own a carbon C40 frame; I still like steel.)
So, maybe what Ernesto is saying is that you should choose a proven frame design & designer over an exotic (i.e. super light) frame???
|re: Is Lighter Safer? Story that quotes Ernesto Colnagno||DINOSAUR|
Mar 22, 2002 6:51 AM
|I read that article also. It was in the current addition of Cycle Sport Magazine and the statement was in a review about the Dream Plus. There was a debate on the VeloNews forum that turned sort of nasty. It is no secret that Ernesto Colnago prefers working with steel. Some feel that steel is the best material suited for a bicycle frame. Bottom line is probably cost. It cost less money to manufacturer an al frame than a light steel frame (such as foco). Colnagno and DeRosa are from the old world. Don't know is safety is an issue, the Klein on my frame weighs 2.7 pounds (per Klein specs). It's light and strong, I don't worry about frame failure, it just rides a tad too harsh for the kind of roads I ride. Probably would be great for some 24 year old kid.
It will be interesting to see what type of tubing they will be using for bicycle frames 10 years from now. How light can they get?
|re: Is Lighter Safer? Story that quotes Ernesto Colnagno||Galibier|
Mar 22, 2002 7:36 AM
|This thread raises several interesting points:
(1) "Statistics don't lie" -- aluminum frames are prone to failure, even after "one season." What statistics? In my 20 years of racing, I have seen carbon and titanium frames fail, including a carbon frame of my own. I have not yet seen a steel or aluminum frame fail. My statistics are that steel and aluminum are the most durable. What statistics are you referring to?
(2) "A sturdy aluminum frame creates a jarring ride." This claim overlooks the effect of frame geometry, tires, tire pressure, wheels, and fork contruction on a bike's ride. Together, the factors I listed have far more of an effect on a bike's ride than does the frame material.
(3) "It costs less to manufacture aluminum than steel." Says who? How much difference is there between the cost of bicycle-quality steel tubing and the cost of bicycle-quality aluminum tubing? My guess is the difference in tube cost, if any, is much less than the cost of design, assembly, painting, marketing, delivery, and sales.
My point is that people regurgitate truisms without actually evaluating them. Don't be fooled by myth, bias, and speculation masquerading as knowledge and wisdom.
Mar 22, 2002 8:22 AM
|It is a fact that aluminum is unpredicatable it terms of fatique durability. Fatique failures occur when a member is loaded-relaxed-loaded...ect. If you look at a fatique life plot of a tube in bending, an aluminum tubess will fail at random intervals. Compair this to steel or Ti for example, and the fatique life is very predicatable. Carbon is an unknown since the design and assembly quality is so critical.
To hedge against the unpredictable nature of these failures, many Al frame manufactures make the frame extra stout to reduce flex in the frame. By reducing the flex, stress in the tubes is less and thus the life is longer. Yes or course, tires and forks make a huge difference in ride quality of any frame - more so than material I think. But there clearly is less flex in some of the super oversize tubed Al frames these days.
Regarding building with Al, I'm not sure all the details but clearly cutting and mitering Al tubes is much easire than steel/Ti as is aligning the frame during assembly. The extra heat treat step for Al is extra cost there however.
And some of us do not just "regurgitate truisms" as you say. I would be happy to send you some fatique life plots out of my old mechanics books if you would like to review them yourself. Also, check out the link below if you want some qualitative evidence of how Al frames are stiffer than some other materials. http://www.sheldonbrown.com/rinard/rinard_frametest.html
Please send me a fax number if you want the plots and I will get them together.
Mar 22, 2002 10:41 AM
|Thanks for the offer of the fatigue life plots, but I don't dispute the reports that aluminum has a finite fatigue life and may fail catastrophically and unpredictably. Assuming this is true, and to trot out another well-worn analogy, they still make airplanes out of aluminum -- the point being not that airplanes and bicycles are comparable, but that aluminum bicycle frames just have to be engineered to deal with aluminum's peculiarities. And a well-designed and built aluminum frame does just that, just like a well-designed and built steel, titanium, or carbon frame deals with the peculiarities of those materials. If it happens that a well-designed and built aluminum frame also happens to be quite stiff, well, I consider that a major bonus.
Mar 22, 2002 2:08 PM
|...we're talking about sub 2.6 lb. frames here. No doubt, frames made from thicker and heavier tubes will hold up better over time.|
|Safety, savety - Have anyone actually broken a road frame?||tz|
Mar 22, 2002 7:44 AM
|Did anyone have their frame fall apart from stress of road riding, not as a result of a crash?
It seems to me that in order to break a bicycle frame one has to deliberately cause it some significant damage.
Unfortunately, I haven't owned frames built of anything, but steel. Some of my bicycles were older than myself. Their frames showed no signs of weakness. That is why I am suspicious when people say that one frame is "safe" and other is not. I understand that different materials weigh/flex differently, but assuming no manufacturing flaws, a frame built of Al or Ti should last an eternity, since these metals don't oxidize, as iron alloys do.
I may be wrong, but I will be happy to hear opinions of experts.
|i've seen some broken road frames||colker|
Mar 22, 2002 7:59 AM
|one was made of foco.. the rider fell on the curb and seattube collapsed. |
thin aluminum frames. i wouldn't take an old (3yrs.) at speed down a mountain pass. call me paranoid.
Mar 22, 2002 8:29 AM
|I recently broke a 1996 Bianchi Eros frame from normal wear and tear. It's my rain bike and it cracked in the bottom bracket on a normal Sunday afternoon outing. It didn't create a safety problem but it certainly created a ridability problem. It's being replaced under warranty now.
I also have a friend who had a steel bike break at the bottom bracket-right chainstay junction. It was probably a bad weld and it was repaired under warranty.
Mar 22, 2002 8:33 AM
|Bianchi aluminum frames are known well for cracking around the bb portion. I haven't ever heard a steel bianchi doing that. How well did you treat the bike after the rain?|
Mar 22, 2002 9:21 AM
|I call it my rain bike but maybe I should call it the number two bike or something, I just can't think of a good expression. My primary is a Giant CFR which goes out on sprint nights, group rides, etc. I ride the Bianchi when I ride alone because even though it's noticeably heavier it's more comfortable and I'm not chasing anyone up a hill so it doesn't matter.
But to your question, my Italian Stallion (what my daughter named it) gets (got) treated pretty well and washed regularly. I'm not a fanatic about bike cleanliness but I do what I can to keep the mechanical stuff working well.
Actually, I was as surprised as anyone by the failure. The LBS guy wouldn't believe me when I described the problem. I told him the BB was moving way-to-much, enough to pull the chain off a cog and shift a gear. He examined it with a magnifying lens and found a crack in the bottom of the shell. It was a little tough to see with the naked eye but easy to see with a magnifying lens.
|Safety, savety - Have anyone actually broken a road frame?||binladen|
Mar 22, 2002 9:30 AM
|Broke a 2.2lb Giant TCR frame once and not from crashing. But the frame was so damn cheap, Giant could probably sell it for $150 if they did not have to sponsor a top pro team and do as much advertising as they do.|
Mar 22, 2002 9:37 AM
|Seen broken C'dale frames - very strong tri guy split his apart at the joint of the seat and top tubes. He was just riding along. ;-) Another buddy had his Specialized Allez carbon start to fail on a chainstay after many years of riding. A few Serotta ti bikes failed on the down tube where the cable bosses were welded. |
The big "if" in your statement is the assumption of zero manufacturing flaws. If everything were fully understood, desinged correctly and built exactly as designed then there wouldn't be any failures, but thngs don't work that way. Most steel frames lean towards the "over built" side of things while builders of aluminum and carbon are trying to shave weight and don't take the time or expense to do finite element analysis or fatigue life testing. Plus there's always the potential for failures at the welds and bonds due to workmanship. Wrecking is still the fastest way to destroy a frame.
Mar 22, 2002 9:59 AM
|Most receintly a friends GT road frame. Cracked through the seat tube at the bottom bracket. I've also seen broken Cannondales.
Everything breaks eventually, even steel frames. But the point of this whole discussion is superlight Al frames - sub 2.6 lbs. Colnago doesn't want to build them according to the article and I don't blame him.
|yes, wore it out..||dotkaye|
Mar 22, 2002 10:56 AM
|Tange Infinity steel tubing, made in Taiwan I think. Seattube cracked at the lug on the bottom bracket. Washed the bike after a long rain ride, noticed the crack. After next ride, it was an inch longer, so I stopped riding that frame.. I'm not particularly big (165lb) or strong, probably just a badly-made frame/lug job.|
|Only frame I ever snapped was Reynolds STEEL.||look271|
Mar 23, 2002 2:45 PM
|Just goes to show you, nothing lasts forever. And by the way, I was really JRA. No kidding.|
|Metallurgy for Cyclists--put the material where you need it.||Slipstream|
Mar 22, 2002 8:04 AM
|Excerpt from the article... |
The Search for Perfection
"To answer the question asked at the outset of this article, none of the materials described happen to be the perfect material to use - all have their advantages and disadvantages. Comparing and designing frames out of different materials is difficult because failure modes are so different. And welding, bonding, brazing, machining and finishing these materials are all accomplished differently. But the hardest part is wading through the bs from the marketing guys."
"What material properties are important in choosing bicycle frame material? First, there are three types of material properties:
*Physical - Density, color, electrical conductivity, magnetic permeability, and thermal expansion.
*Mechanical - Elongation, fatigue limit, hardness, stiffness, shear strength, tensile strength, and toughness.
*Chemical - Reactivity, corrosion resistance, electrochemical potential, irradiation resistance, resistance to acids, resistance to alkalis, and solubility."
"What we find is that aluminum (except for a couple of exceptions like the 5086 alloy) doesn't have an endurance limit. That means that even a minuscule load, if applied enough times, will eventually result in a fatigue failure. Kinda scary, don't you think? Steel and titanium are fine in this department, aluminum is not. Clearly, there are a lot of aluminum bikes out there. Are they all going to break? No, they're not."
"How do you design around this? Charles Teixeira, the Easton engineer who is responsible for the Varilite tubeset is a smart guy, and he knows materials. When he designs things, he pays attention to a few simple rules: One of them is to put the material where you need it. This is a very simple concept, but one that people seem to easily loose track of. The steel guys figured it out a century ago: butt the tubes."
"Well-designed butts can make your frame stronger and lighter. In fact, looking at what tube sizes have worked in steel is an excellent way to determine what properties are required for other materials. This is what Teixeira did in designing the excellent Varilite tubes, which came out in 1990 and were first used for Doug Bradbury's Manitou bikes. These were some of the first butted aluminum tubes to see wide use in the market."
"Trek had been doing a bonded aluminum bike with butted tubing for a few years previous to that, but widespread use didn't happen until the last couple of years. Klein and Cannondale got on the program a couple of years ago, and the Specialized M2 just got butted this year. '
"The Varilite tubes have extremely thick walls in the areas of high stress, and they taper down in the areas that handle less stress. In this way, stresses are dispersed in the tube, and the life of the structure is increased. It's not rocket science, just good design."
Mar 22, 2002 8:42 AM
|This discussion reminds me of post a long time ago. Somebody posted a website (below) which proved/refuted the merits of different materials. Pay particular attention to those frames that DIDN'T break.
Is the test acurate? Who knows. But it's an objective attempt, IMHO.
Mar 22, 2002 9:00 AM
|Aluminum alloys do fail predictably. That's why they replace parts on airplanes at regular intervals, because they know when it's going to fail. However, carbon fiber is different and fails very unpredictably.|
|re: cheap, light, strong pick two (nm)||cyclopathic|
Mar 22, 2002 8:08 PM
|If anyone read that article....||DINOSAUR|
Mar 23, 2002 7:37 AM
|Colnago's statement wasn't a bash against aluminum vs steel bikes. It was a one sentence liner in the whole review. Somehow this ended up into a big best tubing for bicycles debate. Cycle Sport actually have the Dream Plus high marks, stating that it was "a stripped-bare, sharpened tool, designed to win races, or in the very least place you in contention". It also states that Ernesto Colnago is not a fan of aluminum, he built his reputation on steel bikes that were strong, durable and built for riding long races. Read the article and see what he said...|
|That's why I always fly in a Carbon Fiber 747...||Me Dot Org|
Mar 23, 2002 1:18 PM
|...the ride is much smoother, too. Sure, it's a little more expensive, but worth it. I guess the downside is we don't show up on radar as well...
Hey, they make some plane parts from aluminum, some from titanium, some from composites...
Yes, there are many factors that influence ride quality, but I haven't noticed anyone coming out with aluminum forks or aluminum seat stays to put on Carbon fiber or steel bikes.