Carbon rip off (vs Aluminium)

[_Daemon_]

Well I guess then the whole bike industry is wrong and it's just all a money making scheme and there is no point in having a carbon fork on a alu frame to absorb road vibrations...etc.

Right off to go buy a full steel frame cause it's just as good as carbon!

 

[Skillie]

www.cyclingnews.com

review of the pinarello F4:13

 

The flipside to this, of course, is that the bike does not feel very forgiving. My experience is that, in general, a stiff carbon bike will still be more comfortable than a stiff aluminium bike. Carbon frames and forks generally damp a bit more vibration, while remaining fairly stiff and light. However, of all the test bikes I've had the pleasure to ride in the past few years, this was the most demanding physically. I didn't feel as though I'd been put through the ringer or left jarred by the experience after a ride, but my hands and arms did let me know that they were doing a bit more than usual to soak up the bumps.

[Christie]

Daemon, I am in agreement with JB on this. Carbon does have the potential to have more structural damping than aluminium. But stuctural damping is very small (1% to 5% typically), and for structural damping to happen, there must be elastic stress. Elastic stress is the result of deflection. Verical deflection is very small on a road bike, so a small amount of damping of a small deflection = a very very small effect.

 

Vertical deflection of tires & saddle (due to much lower stiffness) is much more than the frame deflection, and will have a much bigger impact on ride comfort.

 

Carbon can also have less structural damping, depending on how it was designed. I've measured some high modulus carbon structures that had less damping than the same stucture from either steel or aluminium. Carbon does not equal more damping.

 

Now, to contradict myself. Some carbon frames do feel different to metal frames. This "feel" is hard to quantify. I suspect that our senses are accute enough to observe a small difference in vibration at certain frequencies. This is why carbon feels less tingly than aluminium (also described as dead). Also, some frame manufacturers have come up with ways to increase the vertical deflection of a frame without compromizing the lateral stiffness. (like thin seatstays on Cervelo R3) so in theory, these frames should be able to damp a bit more, in an academic sense, when comparing bikes with same wheels, same tires @ same pressure, same saddle etc, but made from different materials with the same frame geometry. I do believe that the damping effect of the frame is small, and marketing (like the SDS shock damping system sticker on my Scott's top tube) plays this up for more than it is worth, increasing the placebo. Some examples of why I also think it is more placebo: Boonen rode Raubaix on alu, he did not complai about getting beaten up by the frame. Hunter, Soler & the rest of TBL rode the TDF on bikes with alu rear ends, that did not stop them from out performing riders on full carbon frames.

 

I spoke to some cycling friends about a this a month ago, about getting some frames into a structure testing lab & measuring the damping, stiffness etc, but they looked me with  bored expressions, left to get more

drinks muttering something about Dilbert getting out of hand... (perhaps Supercycling will be interested   

[greatwhite]

 

Further ammo against this vibration argument is the huge damper every bicycle comes with - your body. I once saw a bike gadget salesman demonstrate a damper for handlebars. It was a piece of rubber he inserted - each into one one end of the bar. He dropped the bar and it didn't resonate. He then took the rubber out' date=' dropped the bar and it resonated audibly. I then took the undampened bar, hit is agains the counter and made it resonate. Simply by touching it with a finger, could I stop the resonation. Now imagine how well you dampen it when both hads are clutched around the bar, not to mention the tape, brakes bells and whistles you have on your handlebar.

 

Remember, the resonance of a body is determined by the largest component of the body. A light handlebar cannot resonate when it is dominated by a  pair of heavy arms. Likewise, a silly piece of plastic in a bike's frame cannot stop it from vibrating, the frame is bigger than the plastic. The frame stops vibrating because your body is damping it.

 

 

[/quote']

 

Yeah, the body is the heaviest item in the system, its also by far the softest and has great damping ability. I think the issue here though, is that you don't want the vibration transmitted to the body in the first place. Vibration absorbed by the rider causes fatigue (physiolgical type as opposed to the mechanical type) .

[Johan Bornman]

I switched from a carbon bar to an aluminium one on my mtb recently and could feel a big difference in the amount of trail vibrations.

 

Care to explain that one Johan?

 

For the first time your posts are really not making sense. I find it ridiculous that you think that different materials would not have a different feel to them or absorb shock differently.

 

So if I make a frame from pvc piping it's going to rid the same as all the steel' date=' carbon and ali frames out there....? That's what your logic iplies....that material makes no difference.

 

I think not. Why don't you guys all do some googling and back up your statements with facts so we can settle this....?

 

 

 

[/quote']

 

Firstly, I don't want to try and explain your perceptions. That'll be impossible. I do know that people perceive acoustic feedback differently. A tyre with a specific sound is preferred over another with a different sound and people will always tell you because it is more supple or use some other undefineable term.

 

But lets talk about two terms you use:

 

1) Shock Absorbtion

2) Vibration.

 

Shock absorbsion happens when the bike hits a bump and some compliance (flexibility ifyou like) somewhere in the bike takes the edge off the bump by giving way somewere. The modern double-diamond frame we use, make with the tubes we use (carbon or steel or alu), doesn't bend perceptibly. A triangle is just too stiff to bend in the lateral plane. The horizontal plane doesn't come to play here, that's the flex you see at the BB when pedaling hard. That has nothing to do with shock absorbtion.

 

The only compliance (of note, I'm not talking about the 0.2mm in whe wheels and the small amount the fork sags) in a bicycle ahppens in the tyres, on the saddle, on the soles of your feet and in your hands. The rest is for all intents and purposes, completely rigid.

 

Vibration.

 

A vibration is a resonance at one or other frequency. A land rover shaking along on a rutted road is not a vibration. That's just shaking. A Land rover driving along on a corrugated road does vibrate, as does a bike going over a buzz strip on modern yellow lines.

 

Riding a bike on the road doesn't cause a vibration. There is some shaking and rattling going on, but no vibration. Try it this afternoon and tell me what frequency you think your bike vibrates at. Middle C is 256HZ, use that as a reference.

 

Thus, with no vibration, there cannot be any damping. That's my point. Some of the shaking and bumps are absorbed by the tyre, which easily gives you 10mm of compliance.

 

Now for your PVC tube argument. PVC tube - lets say thin ones like used in electrical conduit, easily buckles (bending) and therefore the diamond frame will not be perfectly stiff, there will be compliance in there and it will absorb shock. However, the tubes our bikes are built from are far, far stiffer than that and therefore don't bend. But, if the frame was made from stiff PVC, then it would be the same as another bike, albeit with different accoustic feedback. It will make a different sound as things rattle against it.

 

Lots of people have said that their frames are better than the previous one that cost less, but no-one has yet explained by what mechanism. I'm eager to hear those explanations.

 

 

 

 

 

 

Johan Bornman2007-11-19 03:12:21

[Skillie]

ons gaan mekaar tog nie oortuig nie.

 

hier iets wat ek gegoogle het.

 

Carbon as a material is pretty amazing. Basically, it?s similar to a piece of cloth impregnated with glue. There are lots of different thread variations out there, but the molecular carbon basis is the same. Differences can be how the carbon is made, how they are actually assembling or ?laying up? the frame and who is assembling them. Some carbon frames can take up to 48 hours to hand lay. The size and shape of the tubes are determined by the manufacturer. Because carbon is a fabric, it can be formed into virtually any shape. This allows manufacturers to create some wild shapes in the tubes. This is one of the ways each manufacturer can differentiate their products and add stiffness or compliance where a common tube couldn?t.

The ride characteristics of a carbon frame are determined by the manufacturer?s geometry and how they lay the carbon fiber cloth. Different directions and different amounts of carbon can create a completely different ride. One thing that is generally said about carbon is that gives an almost ?air? type quality to the ride. This ?air? feel is the carbon dampening high frequency road vibration. This doesn?t necessarily mean the frame is soft like titanium. In fact, it?s generally the opposite, but the vibration from the road doesn?t make it through the frame to the rider. A good example of this would be to take a tube and smack it on a square edge. Unlike a steel, titanium or aluminum tube that would ring through your hand, the vibration in the carbon tube is deadened.

 

[Johan Bornman]

Cut cut cut......

 

' date=' some frame manufacturers have come up with ways to increase the vertical deflection of a frame without compromizing the lateral stiffness. (like thin seatstays on Cervelo R3) so in theory, these frames should be able to damp a bit more,cut cut cut

 

[/quote']

 

Does anyone have a photo of these seatstays. I'd like to have a good look at this and see if it makes sense. I remember the Cannondale CAAD4s had an hourglass seatstay for supposedly the same reason, but they are completely incompressible. Marketing hype. I so like them though, because they remind me of other aesthetically pleasing curves.

 

I spoke to some cycling friends about a this a month ago' date=' about getting some frames into a structure testing lab & measuring the damping, stiffness etc, but they looked me with  bored expressions, left to get more

drinks muttering something about Dilbert getting out of hand... (perhaps Supercycling will be interested   

[/quote']

 

Now you are talking. Lets do it. There are pleny of freak compliant carbon bikes here on the Hub we can use to defy physics and become famous.....

[MAESTRO's]

Well I guess then the whole bike industry is wrong and it's just all a money making scheme and there is no point in having a carbon fork on a alu frame to absorb road vibrations...etc.
Right off to go buy a full steel frame cause it's just as good as carbon!

 

Daemon, you hit the nail on the head!!!

 

I have ridden many a bike, including a Colnago C40, Pinarello Paris Alu Pinarello Dogma and a Paris Carbon. All are awesome rides, especially the Dogma with the ONDA FPX fork. These bikes are all plenty stiff, but my two favourites is my current Pegoretti steel frame, with a Reynolds carbon fork and a Eddy M MX Leader with steel fork. What these two bikes have that the others do not is that magical softer ride ......thats it. Steel absorbes more vibration than Allu. CF or magnesium (dogma)

 

Daemon, check your PM's    

[_Daemon_]

 

Well I guess then the whole bike industry is wrong and it's just all a money making scheme and there is no point in having a carbon fork on a alu frame to absorb road vibrations...etc.

Right off to go buy a full steel frame cause it's just as good as carbon!

 

Daemon' date=' you hit the nail on the head!!!

 

I have ridden many a bike, including a Colnago C40, Pinarello Paris Alu Pinarello Dogma and a Paris Carbon. All are awesome rides, especially the Dogma with the ONDA FPX fork. These bikes are all plenty stiff, but my two favourites is my current Pegoretti steel frame, with a Reynolds carbon fork and a Eddy M MX Leader with steel fork. What these two bikes have that the others do not is that magical softer ride ......thats it. Steel absorbes more vibration than Allu. CF or magnesium (dogma)

 

Daemon, check your PM's    

[/quote']

 

Yup friend of mine got a old steel Lemond frame....what a pleasure to ride, sooooooooo smooth!

 

Got no messages.

 

[Johan Bornman]

ons gaan mekaar tog nie oortuig nie.

 

hier iets wat ek gegoogle het.

 The ride characteristics of a carbon frame are determined by the manufacturer?s geometry and how they lay the carbon fiber cloth. Different directions and different amounts of carbon can create a completely different ride. One thing that is generally said about carbon is that gives an almost ?air? type quality to the ride. This ?air? feel is the carbon dampening high frequency road vibration. This doesn?t necessarily mean the frame is soft like titanium. In fact' date=' it?s generally the opposite, but the vibration from the road doesn?t make it through the frame to the rider. A good example of this would be to take a tube and smack it on a square edge. Unlike a steel, titanium or aluminum tube that would ring through your hand, the vibration in the carbon tube is deadened.

 

[/quote']

 

You read it on the Internet, it must be true.

[Skillie]

nee johan, darem nie so dom nie.

dit is net nog n opinie, soos almal hul opinies gee

[Johan Bornman]

Several of you disagree with me, but I suggest you guys come up with a unified story in order not to contradict yourselves.

To quote one post: "A good example of this would be to take a tube and smack it on a square edge. Unlike a steel, titanium or aluminum tube that would ring through your hand, the vibration in the carbon tube is deadened. "

 

To quote another post: "Yup friend of mine got a old steel Lemond frame....what a pleasure to ride, sooooooooo smooth".

 

How does this work?

Johan Bornman2007-11-19 03:40:08

[_Daemon_]

 

Several of you disagree with me' date=' but I suggest you guys come up with a unified story in order not to contradict yourselves.

To quote one post: "A good example of this would be to take a tube and smack it on a square edge. Unlike a steel, titanium or aluminum tube that would ring through your hand, the vibration in the carbon tube is deadened. "

 

To quote another post: "Yup friend of mine got a old steel Lemond frame....what a pleasure to ride, sooooooooo smooth".

 

How does this work?

[/quote']

 

People have different opinions, and not everyone will agree with you...that's life get over it.

The steel lemond is a smooth ride...some carbon frames do absord vibrations more for me....but frankly, I don't care what you think, it's about what works best for me as a cyclist, and so far a carbon frames makes me feel less tired on rougher surfaces and I love the smooth feel of the lemond frame, and my little alu frame flexes all over the place, but still feels rougher on bad surfaces than the carbon frame, that's sooo much stiffer.

 

 

[Johan Bornman]

nee johan' date=' darem nie so dom nie.

dit is net nog n opinie, soos almal hul opinies gee

[/quote']

 

Ek moes seker maar 'n smaailie daar gebruik het. Kom ek sit gou hierdie een in

 

Ek wens net mense wil nie goed soos Air Quality Ride skryf nie. Dis 'n betekenlose term. Verder, ek sal graag wil sien hoe die skrywer van daai storie vir ons wys hoe die verskillende orientasie van koolstofvesel in verskillende fietse 'n verskil maak. Hy skryf dit asof die verskil sal wees soos 'n Mercedes S klas teenoor 'n 1984 City Golf.

 

Soos ek se, mense lees te veel baaiesukkel tydskrifte. Die goed tas hulle dinkvermoee aan 

 

JB

[Skillie]

ek ry net fiets om dit te geniet, en nie veel belang in al die hoe ha en "regte" maak fiets nie.

op growwe teerpad voel my rug net baie gemakliker met n carbon frame as met aluminium.

dis my opinie, en dit werk vir my, so ek is happy daarmee.

maar ek stem saam johan, dat bemarking n groot rol in alles wat met fietse te doen het speel.

[Christie]

The only way to resolve this debate is to measure. (Dilbert is looking very happy ) It will take some accelerometers, a modal hammer, a signal amplifier & some vibration analysis software, & some frames to measure. Oh yes, some money to pay for using the equipment, & some tough bouncers to hold all the unhappy bike companies at bay.

 

pic of the Cervelo R3, with very thin seatstays:

http://www.cervelo.com/models/2008/thumbnail/2008-R3.png