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Framebuilders Thinking about a custom frame? Lugged vs Fillet Brazed. Different Frame materials? Newvex or Pacenti Lugs? why get a custom Road, Mountain, or Track Frame? Got a question about framebuilding? Lets discuss framebuilding at it's finest.

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Old 03-10-07, 05:31 PM   #1
mrbike27
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carbon dangers

my neighbor nearly injured himself with his carbon fiber bike. he went trail riding with it and tried jumping a rock pile and flew off and the bike slammed into the ground. the frame busted literaly in two pieces. goes to show carbon fiber sucks. it was a $4785 bike
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Old 03-12-07, 02:17 PM   #2
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Sheesh, just goes to show that carbon fiber won't hold up to being smashed into rock piles. Tubular frames are for sissies. Real men ride frames made of solid iron RODS.
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Old 03-24-07, 11:48 AM   #3
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Lets put this in perspective.
An aluminum frame in the same crash would probably dent a tube on the rocks.
That dent is now a weak spot that can bend or fold later and cause much personal damage.
It's called crash damage and it happens to all materiel bikes at least to some extent.
It's just a part of riding. If a person is too afraid of crash damage then maybe they shouldn't ride.
It's not if we will ever crash, it's when and how bad.
Just my 2 cents
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Old 03-25-07, 08:56 PM   #4
charles vail
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CF ******* bike!

And a steel bike might have a dent in the tube or at worst a bent tube....certainly repairable and if a dent, it wouldn't affect the strength of the bike to any significant degree. Filling the dent with solder and sanding with some touch up paint or soldering a decorative "patch" plate, would be an easy fix plus make that place on the frame less likely to re-dent since it would be thicker.
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Old 03-25-07, 09:05 PM   #5
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Riding a c/f tandem with 14,000 miles on the odo. No problems.
Have broken 2 streel tandem frames and one steel tandem fork . . . and, no, we don't jump into a pile of rocks.
Anything will break/fatigue. Have you tried running your car into a brick wall and see if it holds up? We're betting on the wall!
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Old 03-26-07, 02:26 AM   #6
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Quote:
Originally Posted by mrbike27
my neighbor nearly injured himself with his carbon fiber bike. he went trail riding with it and tried jumping a rock pile and flew off and the bike slammed into the ground. the frame busted literaly in two pieces. goes to show carbon fiber sucks. it was a $4785 bike
Carbon is known for it's catastrophic failures. For all you guys who fealt it necessary to chime in against mrbike take a look at this: Bike accident/front wheel failure - how did it happen? Now tell me how much this bike was abused.

Tim
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Old 03-26-07, 07:08 AM   #7
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ZonaTandem is correct. Anything can fail from eventual fatigue. Hopefully, if the engineer/designer has done their job, the bike, be it any material will be designed to outlast the longest user of the frame.

Some of the current issues are not in the material but in the fact that the design is inappropriate for the use at hand. Light is right in most people’s minds and bike companies are responding by constantly pushing the envelope. Something has to give and this is usually durability. You can't have it all, even with Carbon. There is always a tradeoff between weight, durability and crash resistance.

So we all know that carbon works, There are literally millions of bicycles made of it, but I would say that if one want a carbon framed MTB that they have to realize that if the strength of the frame is exceeded then the failure mode will be different and in this case it was what we call catastrophic, which is a standard mode for Carbon. A similar, light steel bike or Ti one probably would not have separated but may have ended up with a dent or ripple which would have needed repair. A slightly heavier frame while not reducing this person’s actual performance may have fended off such a crash. One never really knows.

On the other hand, many carbon MTB frames actually weigh more than their metal counterparts and if carbon is not integral to the design (i.e. full suspension) then as a self taught engineer, I would say that for abusive MTB a steel or Ti frame is going to hold up better in the long run.

All the best,

Dave Bohm
Bohemian Bicycles
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Old 03-26-07, 12:04 PM   #8
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It's not the carbon so much as how it's used. Eggs have a reputation for great strength given the weight of the material in the shell. When they fail, though, failures tend to be catastrophic. If the egg were solid it would not be nearly so fragile.

A real world example are the earlier carbon fiber arrows for hunting. Acceptance was slow in some circles. One fear was that when they broke on a bone, that carbon shards would be hard to remove from the meat, and might injure diners. Well guess what design is now regarded as the most durable? One has to design with a given result in mind. If there is a reason for really durable bikes in carbon, I'm sure someone will figure them out.
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Old 03-26-07, 03:25 PM   #9
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If you side load aluminum, titanium, or even steel with enough force it will fail just as "catastrophically and dramatically as carbon. If you dent a main frame member it will weaken the member and should be inspected and repaired. Carbon fiber can be repaired. Even members that are completely broken in two if one has the technology or knows someone who does. It is not as easy as steel or aluminum but it can be done. No structural material is indestructible and one has to weigh how they plan on using their equipment. Repairs are a fact of life if you subject something to hard use. I fly a wing that has its main structural members made of carbon fiber. I regularly inspect it, as well as my aluminum tandem bike and my carbon fiber single. Everyone should give their frame a thorough visual examination periodically based on the amount of use.

It is your life and health you are protecting.

Happy riding all
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Old 03-28-07, 02:08 PM   #10
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Quote:
Originally Posted by cs1
Carbon is known for it's catastrophic failures. For all you guys who fealt it necessary to chime in against mrbike take a look at this: Bike accident/front wheel failure - how did it happen? Now tell me how much this bike was abused.
If you read through the entire thread, the OP seems to eventually admit operator error may be cause of failure. His original post makes it sound as if a carbon fork spontaneously sheared in half through both legs.
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Old 03-28-07, 02:28 PM   #11
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Obvious troll. Sounds like your neighbor needs to learn how to ride.

Quote:
Originally Posted by mrbike27
my neighbor nearly injured himself with his carbon fiber bike. he went trail riding with it and tried jumping a rock pile and flew off and the bike slammed into the ground. the frame busted literaly in two pieces. goes to show carbon fiber sucks. it was a $4785 bike
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Old 03-28-07, 05:27 PM   #12
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It might be worth mentioning here that some steels are much tougher than others. 'Aircraft grade chromoly' is commonly used in bikes. There are much tougher grades of steel. Some of the more aggressive and abusive mountain bikers who have routinely dented and damaged and replaced frames (including various steel frames), will comment on how beautifully 853 holds up. The paint may get chipped, over and over, with impacts on rocks, but the tubing stays fine. They repaint, and are amazed at how well the frames hold up.

For this kind of riding (or similar abuse, or potential abuse), one of these ultra-strong steels would probably be a good choice.
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Old 04-04-07, 09:59 AM   #13
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Quote:
Originally Posted by zonatandem
Riding a c/f tandem with 14,000 miles on the odo. No problems.
Have broken 2 streel tandem frames and one steel tandem fork . . . and, no, we don't jump into a pile of rocks.
Anything will break/fatigue. Have you tried running your car into a brick wall and see if it holds up? We're betting on the wall!
Forget that refined iron crap, bricks are real. Bash anything into o pile of rocks hard enough and it'll break. I'll bet a $50 Walmart bike could be fixed or replaced for $50, does that make it better?
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Old 04-04-07, 08:09 PM   #14
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Quote:
Originally Posted by jccaclimber
Forget that refined iron crap, bricks are real. Bash anything into o pile of rocks hard enough and it'll break. I'll bet a $50 Walmart bike could be fixed or replaced for $50, does that make it better?
On the contrary, carbon fiber if it doesn't break right away, will suffer micro cracking and fail at some unexpected time, usually in a catastrophic manner. Steel on the other hand will usually only dent or bend. It would take repeated extreme bending before steel would crack and break. What causes steel bikes to fail from fatigue cracking is poor design ( inadequate thickness at stress points) or poor welding/brazing, not the material. Carbon fiber while very strong and light will definately not stand up to abrasions, nicks, scratches, gouges or impacts without suffering damage to its structure (even if not immediately visiable) that will lead to unexpected failure.
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Old 04-04-07, 11:23 PM   #15
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Again, blanket black & white, all-or-nothing, yes/no blanket statements. Let's add some number to your assertions like:

"Steel on the other hand will usually only dent or bend. It would take repeated extreme bending before steel would crack and break. "

What thickness of steel tubing? Material? At what load levels and bending amounts? Compared to what thickness of CF tubing?

Carbon fiber while very strong and light will definately not stand up to abrasions, nicks, scratches, gouges or impacts without suffering damage to its structure (even if not immediately visiable) that will lead to unexpected failure.

What kind of CF? What kind of construction? What if you made the CF frame of exactly the same weight as steel? What if the CF frame as 90% the weight of steel? How about 80%? 70%?
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Old 04-05-07, 10:18 AM   #16
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Quote:
Originally Posted by seeker333
If you read through the entire thread, the OP seems to eventually admit operator error may be cause of failure. His original post makes it sound as if a carbon fork spontaneously sheared in half through both legs.
We're not talking about operator error. We are talking about what happens to carbon when it fails compared to other materials. Steel would have bent. Carbon looks like it exploded.

Tim
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Old 04-05-07, 01:00 PM   #17
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Ever see what happens to a 0.5-lb steel fork when it hits the pavement after a wheel falls off??? You have to equalize the various factors if you want to narrow the comparison down to only materials comparison.
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Old 04-07-07, 09:03 PM   #18
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Just wanted to let you guys know that there are parts of the Space Shuttle that are built out of carbon fiber that haven't failed yet.
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Old 04-07-07, 09:42 PM   #19
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Originally Posted by bellweatherman
Just wanted to let you guys know that there are parts of the Space Shuttle that are built out of carbon fiber that haven't failed yet.
Um, Don't know how serious this post was but of course the loss of the Space shuttle Columbia was due to a catastophic failiure of the leading edge of the wing which was a piece of Carbon-Carbon RCC tile. Carbon is an excellent refractory material but lacks impact resistance. The SR-71 dealt with heating very similar to the Shuttle at a lower intensity and used Titanium for this purpose and never once failed. There were better the day they retired them then when they were new.

New materials such as zirconium diboride may hold promise as being a replacement for RCC and have better reliability.

Honestly, The Shuttle is not a good example for this. It is a 40 year old design. Much of the choices made in its construction were as much politically motivated and done for the cool factor as anything else and if the leading edge had been backed with Titanium or Inconel, there may have been a chance for that crew to still be alive.

Carbon bikes are generally reliable. What scares me is that they are much more open to construction errors and poor engineering than metal materials.

Dave Bohm
Bohemian Bicycles
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Old 04-08-07, 02:38 AM   #20
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Quote:
Originally Posted by DannoXYZ
Ever see what happens to a 0.5-lb steel fork when it hits the pavement after a wheel falls off??? You have to equalize the various factors if you want to narrow the comparison down to only materials comparison.
No. Actually, I've never seen a steel fork that light. My Reynolds 753 bike doesn't have a fork anywhere near that light.


Tim
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Old 04-08-07, 09:05 AM   #21
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engineering marvels

Quote:
Originally Posted by DannoXYZ
Again, blanket black & white, all-or-nothing, yes/no blanket statements. Let's add some number to your assertions like:

"Steel on the other hand will usually only dent or bend. It would take repeated extreme bending before steel would crack and break. "

What thickness of steel tubing? Material? At what load levels and bending amounts? Compared to what thickness of CF tubing?

Carbon fiber while very strong and light will definately not stand up to abrasions, nicks, scratches, gouges or impacts without suffering damage to its structure (even if not immediately visiable) that will lead to unexpected failure.

What kind of CF? What kind of construction? What if you made the CF frame of exactly the same weight as steel? What if the CF frame as 90% the weight of steel? How about 80%? 70%?
Just referring to the common guages and thicknesses currently in use for bicycles. I suppose you could design CF with thicker walls (making it heavier) and introduce other materials into the matrix that might give it some more toughness. Of course we already have a material like that! Steel remains the best material for bicycle building especially when you consider the common componentry available and the generous clearances that result when using it for practical use machines.

Nearly all bicycle manufacturers have shorter warranties on CF products and weight limits for their use. Most authorities don't reccomend using CF for heavy riders or for off the beaten path touring. CF cloth and epoxy is a wonderfull combination that solves some of the problems of weight and stiffness although the whole weight thing is a little overblown IMHO and........its still just fabric and glue! Steel has enjoyed a 1000 years of development and over 100 years of use in bicycle frame construction and it remains the best material for alot of good reasons. Yes these are blanket statements but they are true in a general sort of way.
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Old 04-08-07, 10:12 AM   #22
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Quote:
Originally Posted by dbohemian
Um, Don't know how serious this post was but of course the loss of the Space shuttle Columbia was due to a catastophic failiure of the leading edge of the wing which was a piece of Carbon-Carbon RCC tile. Carbon is an excellent refractory material but lacks impact resistance. The SR-71 dealt with heating very similar to the Shuttle at a lower intensity and used Titanium for this purpose and never once failed. There were better the day they retired them then when they were new.

New materials such as zirconium diboride may hold promise as being a replacement for RCC and have better reliability.

Honestly, The Shuttle is not a good example for this. It is a 40 year old design. Much of the choices made in its construction were as much politically motivated and done for the cool factor as anything else and if the leading edge had been backed with Titanium or Inconel, there may have been a chance for that crew to still be alive.

Carbon bikes are generally reliable. What scares me is that they are much more open to construction errors and poor engineering than metal materials.

Dave Bohm
Bohemian Bicycles


Really?! Maybe I am wrong, but I thought it was determined that it was a failure in the plastic O-rings that held the steel SRB (solid rocket booster) plates together. The O-rings couldn't handle the heat that was transmitted from the SRB plates upon entry into the atmosphere. Maybe, they should've used carbon?

"Several engineers—most notably Roger Boisjoly, who had voiced similar concerns previously—expressed their concern about the effect of the temperature on the resilience of the rubber O-rings that sealed the joints of the SRBs. They argued that if the O-rings were colder than 53 °F (approximately 11.7 °C), there was no guarantee the O-rings would seal properly. They also argued that the cold overnight temperatures would almost certainly result in SRB temperatures below their redline of 40 °F. However, they were overruled by Morton Thiokol management, who recommended that the launch proceed as scheduled.[4]"
more can be read here: http://en.wikipedia.org/wiki/Space_S...enger_disaster
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Old 04-08-07, 11:43 AM   #23
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Respectfully,

1. The Space Shuttle Challenger (1986) failed when an o-ring allowed hot gases to penetrate the main tank.
2. The Space Shuttle Columbia (2003) failed when a piece of foam punctured the wings carbon leading edge and the heat of re-entry caused the craft to disintegrate.

Dave
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Old 04-11-07, 08:51 PM   #24
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Touche Dave!
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Old 04-11-07, 09:03 PM   #25
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My Spinergy disintegrated when my kickstand was pushed into the spokes. Eff carbon!

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