@Erlkoenig BTW, does it make sense in the 2020s (or even the 2000s or the 2010s) for anyone to buy a titanium frame? IIUC this was fashionable at the height of steel frame — because they have all the virtues of steel minus the rust. But why would anyone prefer Ti today over carbon? Is it just that it may last longer?
The idea of acquiring or keeping nuclear weapons as a deterrent, but also being committed to never using them reminded me of this scene: https://youtu.be/zgUvwcU6P7I?si=MG-vRLy309AA3ufP
@Sam7919 It's much more robust than CF, which is also good for carrying luggage. I.e. a titanium fork or seatpost can easily carry high loads. More scratch resistant. Also looks damn good
Making CF frames requires a lot of manual work with toxic materials, and many (not all) manufacturers do this in low-wage countries with low labour&environmental protection. Working with titanium isn't as dangerous, but it does require a lot of energy in production. High-quality titanium frames basically last forever (unless you get in a bad crash) while CF does slowly degrade with use and UV exposure
Materials may seem easy to recycle on the first glance, but are not because of additives or alloys. Example aluminium, different alloys of it are nearly impossible to distinguish in recycling. Separation into elemental metals is prohibitively expensive.
Otoh even though titanium can be recycled there probably isn't much infrastructure for that, and it's difficult to repair, while there are actually quite a few CF repair shows now.
Recycling by melting may require more primary energy than a non recyclable material. Example glass jars.
Titanium is rare enough that mining it and processing the ore might require so much primary energy and cause enough harm that even if recycled it longer lived other materials would have less impact. I don't know that. It is something to consider though.
Carbon composite production is not much different from other plastics. Martin impact is probably at the oil well and refinery. It might be such a cheap material that even with single use and perhaps shorter service life it might have a smaller footprint.
To find out, one would have to do a full analysis of all these frame materials.
Also depends on the type of bike: When road riding you don't usually crash, so a CF frame will last a long time, but for off-road riding crashes are part of the fun, so a CF frame will have a limit lifetime
@PaulH Everything there is subtle. There is a difference between committing not to use them and not having the intention to use them, ever, UNLESS X. Oddly, the X also needs to remain unspecified.
In current conflicts luckily nuclear weapons (of any kind) are not usable weapons. The US bombed a distant country, but if you are eyeing conquering a land, the last thing you’d want is to contaminate the land you want to conquer.
We might approach a situation where a country simply wants to secure its own survival. Strategic bombing can be used for this, as you don't want to conquer the land
Not currently. But perhaps in 10 years, if Putin/his successors decide to make good on his promise to bring central Europe under his control, after the Trump/his successor has left the NATO and ceased support for the Ukraine as promised. Strategic bombing, i.e. the act of using nuclear weapons to terminate your opponents' ability to wage war, might be Europe's last recourse.
@Erlkoenig (to quote Paul H), this reminds me of the difference between ballroom tango and Argentine tango. The former is to impress others. The latter is to give joy to oneself.
Now the question is: does titanium give its rider joy (exceeding carbon)?
@Sam7919 this is not a concern preventing the use of tactical nukes. (a) a power would nuke in the enemies rear to hit logistics, ground lines of communication, and special assets. (b) a power that's not all that concerned with the health of their populace will accept a slight increase in cancer rates in a newly gained territory they might otherwise not have. It really is political consequences and nuclear deterrence that keeps nuclear powers from a limited use of tactical nukes.
@Criggie I still want to understand how carbon’s vibration damping yet strength work (engineering.stackexchange.com/q/61663/36266). A truss, properly designed, would simulate these two contradictory features. Then the question is whether Ti has the same dual benefits, and to what degree.
@Sam7919 CF parts also have trusses and similar shapes, it works just the same way
The "secret" of CF is that it gives the designer great freedom to achieve all kinds of different properties. The most desired property is lightweight, but it can also have flexibility, dampening, strength. Also there is great freedom in the shapes that can be manufactured, including making very thin structures. This allows for making voluminous structures without increasing weight much (with thin walls), which is critical for aerodynamics (an aerobike made of AL would be possible but very heavy)
Also, one layer of CF is only strong in one direction but is lighter than a piece of AL that has the same strength in this direction. Metals have the same strength in all directions, but you usually don't need this, so with CF you only add strength in the directions you need, saving weight by not adding strength for other directions. A piece of CF that is strong in all directions is probably just as heavy as an equivalent AL piece, but more expensive, and therefore not made in practice
This effectively makes CF "better" than all metals. It's quite an amazing material. Ti and steel are similar, Ti is "just" lighter and rust-proof. Both are flexible (like a regular spring) but have little dampening properties (that's why proper suspension also has air or oil dampeners). You could probably make a CF bike that's as strong as a Ti bike, but it would probably also be just as expensive without looking as good 😉
Carbon consists of very thin fibers. They are very flexible but almost impossible to strech or tear. The fibers are woven into mats very much like fabric (causing the famous checkerboard pattern). These mats are soft much like fabric, but virtually impossible to stretch/tear. They are cut into pieces which are then glued (using epoxy) in several layers around the desired shape (e.g. a tube or something complex) or inside a mold. It's critical that there is a certain distance between the mats.
The layers work like the both sides of an I-beam (steel), with something in between to keep the distance. If you use an I-beam to hold up a bridge, the weight attempts to bend the lower band and squeeze the upper one, due to the "standoff" in between. Since steel doesn't tear easily, the beam keeps its shape (mostly). Same with the layers of carbon mats. The "standoff" can be plastic, foam, AL honeycomb or other CF structures.
As you see the shape of the CF part is absolutely critical to its strength, which is why designers spend a lot of work with CAD and simulation software to achieve the perfect shape.
Here and here are a few pictures of manufacturing a CF chassis for a formula student race car
On the far right you can barely see the special honeycomb that sits between the layers of CF, which acts like the middle part of the I-beam
Although small/simple parts don't have a standoff like that
@Erlkoenig Carbon still has a higher specific strength than aluminum, so there are some benefits, but it's nowhere near as dramatic as when you can utilize its best properties. A good example is carbon cranks. They're not THAT much lighter than alu ones because cranks see load in pretty much every direction
@Erlkoenig Air is not a good damper...the oil does all the work. The air is the spring 😉. Also, metals like magnesium have good internal damping, which is part of the reason why most suspension forks have magnesium lowers
