A very informative discussion of CF as a bike material.
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I have a degree in materials engineering and a Professional Engineering license in metallurgical engineering. For what it's worth, my road and gravel bikes are titanium frames. There is confusion between stiffness (modulus) and yield or tensile strength. At the end of the day, you ride what you prefer, not something to impress other people.
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I heard an interview with the guy who makes Starling MTBs (fillet brazed steel in his shed) and his day job is an aerospace engineer. He said most bike grade CF was over-specified because it's full of voids and other jank. Some of the high end frames will be better no doubt.
Certainly it used to be the case that very cheap CF frames were actually no lighter than good aluminium frames. I don't know if this is still true.
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This is interesting. I have a very short experience with a mid-range Bianch CF bike. And, it was that "thunk" that I interpreted as dead and hollow. I suspect, but don't know, that I would get used to that over time. I do like some of the CF designs. Aside from the "thunk" the thing that has kept off a CF bike is the cost.
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Oh, no. Material threads are a constant on the forum, although the disk/rim brake argument has taken over lately.
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My road rides are endurance rides of 100km and 200km mostly over chip seal roads. I like the vibration attenuation associated with titanium. I do have an aluminum frame bike which I use on my trainer. I have limited riding experience on carbon frame bikes, mostly rentals.
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The stiffest, most jarring ride I ever had was steel. The softest, most noodly ride I ever had was also steel.
It's not the material as much as it is how it's built.
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A friend was looking at a titanium Lynskey Helix and it was very stiff. My bike is a titanium VaMoots Moots. In addition to material of construction design would be important.
What I dont understand about carbon frame bikes is frame repairs. I really struggle with repairs restoring original properties. Load transfer through the fibers simply cant be the same when there is a discontinuity of matrix. I see people citing expert repairs. It just cant be the same.
What I dont understand about carbon frame bikes is frame repairs. I really struggle with repairs restoring original properties. Load transfer through the fibers simply cant be the same when there is a discontinuity of matrix. I see people citing expert repairs. It just cant be the same.
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What I dont understand about carbon frame bikes is frame repairs. I really struggle with repairs restoring original properties. Load transfer through the fibers simply cant be the same when there is a discontinuity of matrix. I see people citing expert repairs. It just cant be the same.
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Viathon Bicycles | R.1 Road Bike | Shimano 105 Equipped
I was looking at a BMC with 105 for about $2700. I suppose a CAAD12 is cheaper, but I'm sure there are other CF bikes out there in a similar price range.
Here is one for $1600.
2020 Polygon Strattos S7 Road Bike - Size: Large | Bikes Online (USA)
Here is one for $1100.
Save Up To 60% Off Shimano NEW Carbon Aero Road Bikes Motobecane Immortal Spirit with Shimano 22 Speed (bikesdirect.com)
Last edited by big john; 02-22-21 at 07:25 PM.
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A friend was looking at a titanium Lynskey Helix and it was very stiff. My bike is a titanium VaMoots Moots. In addition to material of construction design would be important.
What I dont understand about carbon frame bikes is frame repairs. I really struggle with repairs restoring original properties. Load transfer through the fibers simply cant be the same when there is a discontinuity of matrix. I see people citing expert repairs. It just cant be the same.
What I dont understand about carbon frame bikes is frame repairs. I really struggle with repairs restoring original properties. Load transfer through the fibers simply cant be the same when there is a discontinuity of matrix. I see people citing expert repairs. It just cant be the same.
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In any event, that particular design feature disappeared quickly for some reason, just as dark anodized rims had, a decade earlier.
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This is interesting. I have a very short experience with a mid-range Bianch CF bike. And, it was that "thunk" that I interpreted as dead and hollow. I suspect, but don't know, that I would get used to that over time. I do like some of the CF designs. Aside from the "thunk" the thing that has kept off a CF bike is the cost.
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Of the two of my bikes with aluminum forks, I bought one in 1995 and the other in 2005. Many tens of thousands of miles on both, and they're two of my favorite bikes. I suppose it's possible that the vibration-damping characteristics of aluminum forks, being between steel and carbon in that regard, might account for the enjoyable ride of those bikes, but I've always found tire pressure and wheelbase to be by far the major determinants of how bikes ride, nearly to the exclusion of other factors such as frame or fork material. (Although, come to think of it, I always disliked the way heavily loaded long-wheelbase steel touring frames tended to wallow around when standing and climbing.)
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It's certainly the case from any of the major manufacturers. I wouldn't be surprised if you could spend more on a bespoke frame from a builder, but I'd question if they were able to meaningfully improve upon the performance characteristics of the leading AL manufacturers with their hydroforming and alloys, etc.
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The problem is that you didn't go to engineering school and take materials science and statics...
With metal, the builder is limited to what is made commercially, diameter, wall thickness, and alloy. Not so with carbon/epoxy. Pretty easy to see why carbon is such a popular material.
With metal, the builder is limited to what is made commercially, diameter, wall thickness, and alloy. Not so with carbon/epoxy. Pretty easy to see why carbon is such a popular material.
I discovered that there were people doing some really fun stuff using software to control machines, and that I didn't have to study or anything even remotely like it; just be clever. I have had to use vision systems to correct for the (very small) changes in shape of welded aluminum tooling fixtures over time in one very high precision manufacturing system. They should have been carved from a forged billet but even custom high dollar automation systems have a budget.
So, for the most part I agree with you 100% about metal. In spite of that, most of my bicycles are made of welded metal. However, not all of them are made from constant wall thickness drawn tubing. I believe that Lynskey forms some of their frame elements from sheets of Titanium, and I suspect that if they want to they can use variable thicknesses by working the sheet before it is welded into the frame element.
Another example in the bicycle world, the Finnish company Pole is machining some of their frames from a billet which allows them to use variable element thickness and an alloy which is not weldable, but those bikes cost as much as carbon fiber. They machine the main frame assembly in two pieces, then use an adhesive to bond them into the final assembly. I believe they do the same thing for the swing arm. I suspect that they chose this process because it was easier than low volume carbon fiber manufacturing in Finland.
Also, there are now processes which get lumped into the category of "additive manufacturing" which allow the mechanical designer to specify variable element thickness. Again they are not the cheapest. Atherton (formerly Robot) Bicycles is using additive technology to build custom frame lugs to which they bond carbon fiber tubes. My guess is that they could use steel or Titanium for the tubes if they wanted and that the use of carbon fiber tubes was to reduce weight and have a vibration damping material. Or maybe it was marketing.
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Another example in the bicycle world, the Finnish company Pole is machining some of their frames from a billet which allows them to use variable element thickness and an alloy which is not weldable, but those bikes cost as much as carbon fiber. They machine the main frame assembly in two pieces, then use an adhesive to bond them into the final assembly. I believe they do the same thing for the swing arm. I suspect that they chose this process because it was easier than low volume carbon fiber manufacturing in Finland.
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I started out in Mechanical Engineering probably a few years after you did, back when drawings were made with a drafting machine and a pencil. And mine were just plain ugly. But what I remember best was the "Materials and Processes" class where the instructor spent one day telling us why welding was a bad idea. Soon after I took that class I switched majors.
I discovered that there were people doing some really fun stuff using software to control machines, and that I didn't have to study or anything even remotely like it; just be clever. I have had to use vision systems to correct for the (very small) changes in shape of welded aluminum tooling fixtures over time in one very high precision manufacturing system. They should have been carved from a forged billet but even custom high dollar automation systems have a budget.
So, for the most part I agree with you 100% about metal. In spite of that, most of my bicycles are made of welded metal. However, not all of them are made from constant wall thickness drawn tubing. I believe that Lynskey forms some of their frame elements from sheets of Titanium, and I suspect that if they want to they can use variable thicknesses by working the sheet before it is welded into the frame element.
Another example in the bicycle world, the Finnish company Pole is machining some of their frames from a billet which allows them to use variable element thickness and an alloy which is not weldable, but those bikes cost as much as carbon fiber. They machine the main frame assembly in two pieces, then use an adhesive to bond them into the final assembly. I believe they do the same thing for the swing arm. I suspect that they chose this process because it was easier than low volume carbon fiber manufacturing in Finland.
Also, there are now processes which get lumped into the category of "additive manufacturing" which allow the mechanical designer to specify variable element thickness. Again they are not the cheapest. Atherton (formerly Robot) Bicycles is using additive technology to build custom frame lugs to which they bond carbon fiber tubes. My guess is that they could use steel or Titanium for the tubes if they wanted and that the use of carbon fiber tubes was to reduce weight and have a vibration damping material. Or maybe it was marketing.
I discovered that there were people doing some really fun stuff using software to control machines, and that I didn't have to study or anything even remotely like it; just be clever. I have had to use vision systems to correct for the (very small) changes in shape of welded aluminum tooling fixtures over time in one very high precision manufacturing system. They should have been carved from a forged billet but even custom high dollar automation systems have a budget.
So, for the most part I agree with you 100% about metal. In spite of that, most of my bicycles are made of welded metal. However, not all of them are made from constant wall thickness drawn tubing. I believe that Lynskey forms some of their frame elements from sheets of Titanium, and I suspect that if they want to they can use variable thicknesses by working the sheet before it is welded into the frame element.
Another example in the bicycle world, the Finnish company Pole is machining some of their frames from a billet which allows them to use variable element thickness and an alloy which is not weldable, but those bikes cost as much as carbon fiber. They machine the main frame assembly in two pieces, then use an adhesive to bond them into the final assembly. I believe they do the same thing for the swing arm. I suspect that they chose this process because it was easier than low volume carbon fiber manufacturing in Finland.
Also, there are now processes which get lumped into the category of "additive manufacturing" which allow the mechanical designer to specify variable element thickness. Again they are not the cheapest. Atherton (formerly Robot) Bicycles is using additive technology to build custom frame lugs to which they bond carbon fiber tubes. My guess is that they could use steel or Titanium for the tubes if they wanted and that the use of carbon fiber tubes was to reduce weight and have a vibration damping material. Or maybe it was marketing.
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Again, in the normal case I completely agree. Carbon fiber has lots of great properties and I don't understand why people disparage "plastic" as a material.