Atlas Shrugged

Just when I thought this thread can’t get anymore ridiculous! Thank you.

Kontact 

The weight of frames is the point of discussing strength to weight ratios on a bicycle forum. I haven't started a bunch of topics as much as I have tried to illustrate the same principles over and over from different examples to try and clarify what is going on. You're the one that brought welding formats into the discussion, which truly is off topic.

Specific to your claims, 7075 aluminum has a ratio of ultimate tensile strength to density of 188.
Pine, oriented with the grain, has ratio of 173
4130 steel has a ratio of 71
853/OX/S3 air hardening steel is 173
953 maraging steel is 256
3/2.5 Ti is 138
6/4 Ti is 264 (just edging out 953)
Carbon fiber epoxy composite 1200 to 2500
Pure carbon fiber 3200 for comparison (unusable)

All of these materials are appropriate for bicycles because they also have a relatively high ratio of flexibility (modulus) to weight, while many plastics do not. Which is why no one makes an aramid composite bike. It would be an unbreakable noodle. Or like riding a bike machined out of nylon.

So you can see from this 953 is the second strongest bike metal in use, which is why the lightest metal frames are 6/4. Which is unsurprising given the strength to weight ratio.

What is surprising is that bike grade steel, no matter how strong, runs into a limit in weight. 953 frames can hover just above 1000 grams, but so do weaker S3 framesets. The problem with both is that the steel has to be made so thin that it becomes fragile, and material has to be added for welding (butts). In contrast, materials with lower specific strength and lower densities - like 3/2.5 or aluminum alloy - can hang with the most advanced steels in weight because their more voluminous structure provides more wall thickness for chip protection and welding. That's why a butted 3/2.5 Merlin or Cannondale will be about the same weight as a 953 frame, and a 6/4 frame can be 25% lighter than either.

Wood is tremendously strong (which is why pines get to 268 feet, redwoods over 300), but the problem with wood for bike applications is that the very low density means the the compressive strength per square inch is pretty low. In other words, you can't thread or press a bearing into wood. So while you can make a frame of comparable weight to 4130 out of ash or hickory, you have to glue in higher density metals to allow you to clamp a seatpost, press in a bearing or thread a BB. Even though it has a specific strength up there with S3 steel.

Balsa wood has the same problem, but is even fluffier and soft. It is used in the core of wind turbine blades because it is good for a high volume application where it is surrounded by higher density material. But it is also very strong - stronger heat treated steel by weight. Often used with carbon fiber because they compliment each other.

Than we have carbon fiber composite - carbon fibers arranged like wood to have strength and stiffness in some directions, bonded together with an epoxy. The epoxy increases the density and lowers the tensile strength, but is necessary to give shape. You still don't want to thread carbon fiber, but it is hard enough to have BB cups pressed directly into it (at least most of the time). But it's overall strength to weight is close to 8 times that of 6/4 Ti, so why isn't it at least half as light as any metal frame? It has both the wood problem and the steel problem - it isn't great for attachment points, so those areas have to be reinforced. And it isn't very strong in thin sections, so it is difficult to get the tubes as thin as their structural strength would allow without them caving in at the first stone chip.


Ultimately, the need to attach stuff to a bike frame means that low density metal alloys - Ti, magnesium, aluminum - are the most efficient frame materials. They are coming closest to their maximum useful strength to weight ratios as finished products than either 953 or carbon fiber. But, the Aethos demonstrates that there is still much to be done with the way CF frames are designed to distribute forces and how they are assembled to avoid wasteful joint overlaps. That's why I predict we'll see a 400 gram CF frameset in the not-so-distant future. But I don't think we'll be able to go a lot lighter without bringing in another material to increase notch strength.


So far there hasn't been a debate. There has just been a discussion where everyone tries to get on the same page with the terms being used and their application.

Kontact 

My bad. Change all my comments to the de Haviland Mosquito, which was almost all wood, mainly birch and balsa, and one of the fastest and most capable planes of WWII.

tomato coupe

Still, what’s your point? The fact that wood was used in an 80 year old airplane in wartime footing doesn’t mean it’s a good material for airplanes or bikes today.

Maelochs

Actually, gross profit is unrelated to the cost or sale price (MSRP, we all know what that is worth)

Companies hide income, defer payments and reporting, pay off debt, loan cash or debt to other divisions of the same corporation ....

Generally markup on a general product is generally 300%. but really cheap stuff might have very low profit margin (no one gets rich selling bottles or bottle cages) and high-end stuff has a profit margin based on the perception of luxury .... an $18K bike doesn't seem like a "luxury" to a lot of serious riders, so i doubt the profit margin is that high .....

Generally mid-range, high-volume items get a biggish markup because you know, demand drives price .... You do know that, right?

When something is perceives as a "status" luxury item, the profit margin skyrockets because people want to be able to brag about how rich they are. Most of the people I know or have met who own really pricey bikes are Not rich, just really into the latest, greatest .... a lot of them race, and some as pros, but in the kinds of races where the prize pool for the Pro 1-2-3 race might be $500 for the whole podium. Some might be getting their bikes subsidized, but most are on smaller teams and are responsible for their own gear.

Whatever. The people who think expensive bikes are too expensive are not going to care about the real figures, except to use them as ammunition to throw at others. The people who figure it is just business, might be mildly interested. The people who really don't care are reading another thread ... or out riding their bikes.

Kontact 

Since aluminum was also used in 80 year old warplanes, does that mean it isn't good for bikes?

But my point was about understanding material strengths, and that they frequently don't work like we think they work. Understanding the materials leads to understanding the limitations. Wood is an excellent way to understand some of the issues with carbon fiber, since they are both low density, oriented fiber materials.

tomato coupe

Your logic is bad — you’re trying to set up a false equivalency.

The statement 'A does not imply B' is not the same as 'A implies NOT B'.

PeteHski

One of the main reasons why the Aethos is so light is because they sacrificed aero efficiency for structural efficiency in their choice of tube profiles. I’m not sure there is much incentive to go even lighter unless they could maintain their target stiffness and durability. It may well prove to be too much compromise for relatively little overall weight saving.

A reduction in the UCI limit would probably provide more incentive for the industry to focus on lighter frames. The Aethos is a bit of a one-off experiment in optimising weight over aero in a high-end modern bike. It makes some sense for a dedicated climbing bike outside of UCI rules, but it is basically pointless otherwise. It’s main selling point is the “traditional” aesthetics for those who don’t value the aero gains.

Kontact 

I know that. I was just trying to express my frustration dealing with someone who acts like they can't understand the gist of anything. Totally pedantic.

"To date."

tomato coupe

It seems to me you're reacting negatively to being told you're in error, by intentionally making another error. Not a good long term solution ...

Kontact 

There will always be people, amateur racers or not, that enjoy having the lightest possible bike. That's the target market for the Aethos and similar. Other light bikes like the Factor O2 aren't aero or traditional looking.

Kontact 

I'm reacting negatively to a troll that makes an issue of when (not if) the Spruce Goose is was the largest airplane, in a thread about bikes, on a bike forum. And I'm reacting negatively to it because it was a) unnecessary and b) designed to to insult and belittle.

You are not a nice person. You're interactions with me have nothing to do with your enjoyment of our shared hobby, but a desire on your part to put someone down. It's gross. And it won't give you what you desire.

tomato coupe

You've played this card before. I asked a direct, relevant question after you took us down the Spruce Goose rabbit hole. Don't introduce non-bike topics to make your case, and then complain when someone comments on the fact that your information is false.

wolfchild

Next thread please: The actual cost to make a $ 300 gravel specific jersey.

livedarklions

worst
---+++++
thread
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ever

tomato coupe

^^^^ Should have been closed on day one ...

rydabent

Since when are you the dictator of what should be posted?
This is a legitimate question that a lot of people kind of want to know.

livedarklions

Transparently pointless response to a three day old post in a desperate attempt to bump an exhausted thread. Where did tomato coupe claim to be dictator? Since when are you the dictator of when people can post their opinion that a thread is crappy crap crap?

And there was already a thread on the EXACT SAME TOPIC open at the time you started this one. You even stole the $14,000 figure.

But since you bring it up, what was your purpose in starting this thread? Why is this information important? Are you learning anything from the responses? What? You want to keep the thread going? Say something worth discussing.

genejockey 

Are you new here?

Germany_chris

Here's the thing, I save for retirement, I save for emergencies, I keep money set aside for a couple of vacations every year, and I take my wife out whenever she wants. I have bikes that are rim brake, I have bikes that are disc, I've over spent on all of them based on the quality of the frame but I love them all. I'll leave Europe in 2024 and before I leave I'll buy either a Singer or Berthoud, and I'm sure I'll pay more for them than my other steel bikes...I grew up with parents that looked for "bang for the buck" with everything I hold onto things long enough to not care. My bikes live in the living room and computer room because so I can spend hours looking at them, they stimulate my creative juices and calm me at the same time.

livedarklions

Gotta say, getting nasty over wooden airplanes of WWII strikes me as a new low for BF.

Kontact 

Getting nasty seems to be the way you and you buddies prefer the forum.

Trakhak

"Fun, nasty fun!"

Eric F 

Having a low tolerance for false information and unjustified opinions is not the same thing, but I can see how it might seem that way to those with an agenda to push.

livedarklions

David is putting on the big suit.