Yeah Titanium is not easy to weld..

I grew up on Long Island near where Grumman built F-14 Tomcat fighter jets for the U.S. Navy in the 1970's. A friend of mine worked on the production line and he tells me the titanium assemblies for their particular application can only be welded using a computer-controlled electron-beam welder. Apparently that method of welding does make quite a strong joint-- So strong in fact that the titanium load-bearing wing boxes on the F-14's swing wings has never had a failure during the fighter jet's service life (the Tomcat's motto: "...Anytime, baby!" yeah!).

I guess bicycle manufacturers can't be bothered to invest in electron beam welder tooling for making titanium frames. :p

It means really, that your alloy frame will become pitted and dull and crusty looking. It's very hard to make it go as far as the crusty stage, though. It's most dangerous at welds, because were the curve of the fish-scale is a tiny stress raiser. This, coupled with the preferential attack of reagents at zones of higher stress (it's called stress-corrosion cracking or SCC), will cause the weld strength to degrade, but worse, the toughness to drop substantially. Remember! Clean your frame regularly. It'll help you see corrosion sooner.

The part you're talking about is the variable-geometry anchor box. It's 6/4 Titanium alloy, and back then, in the '70's, titanium alloys were neither as clean, nor welding technologies as refined as they are today. A high end TIG torch can satifactorily purge the weld zone for bike frame assembly.

One of the reasons they've never had a failure on them is the enormous over-engineering of the joint system. That and the wing exits the body some inches from the axle through the wing root.

Pity they couldn't say the same for the powerplants :)

You could save even more time by not posting in this forum:D .

How strong is carbon compared to steel/aluminium when used as a bike frame? IE, what can stand more abuse?

I've always wondered this and I think it's a good question to ask in this situation.

Wow, I'm getting mad de ja vu right now...

That was a great post! One of the most informative I have ever seen on this forum.
Falanx, you have any comments on a frame (hardtail) that would last at least 10 years ridden in the slop of the great Pacific Northwest? Or is this question too open-ended?
By the way, I just put a post on scandium in the Al frames, but I haven't seen much on that here.

But Captain Crosschain, if I stopped posting I would miss the hilarious (in a pathetic kind of way) replies like yours.

A little video I found interesting comparing carbon, al, and ti tubing.

http://www.sicklines.com/2006/07/29/...y-of-titanium/

I wonder what steel would have done. I like how the aluminum one just folded.

Strictly speaking, you don't actually have to post in order to read replies. :love:

Neat video, but probably the least objective/conclusive test I've ever seen. He didn't tell us the grade of aluminum, the type of carbon, tube size, what bikes the tubes came from, etc, etc.

Scandium vs AL & TI?

No. This whole scandium thing is still confusing people :)

Go to Easton's website for a very good beginner's level explanation of what scandium is used for. Scandium is not used pure for any bike parts. It is an alloying ingredient in aluminium alloys. I repeat: scandium is an alloying ingredient in aluminium alloys, nothing more.

For those of you who don't weant to, Scandium is added to aluminium alloys for one reason and one reason alone. It does not make the tube appreciably stronger. It does not make the tube appreciably tougher. It does to weldments what has never been done in aluminium alloys before - it maintains a fine grain in the HAZ, a phenomenon that used to be restricted to steels only. Scandium vastly ******* the rate of grain growth in areas above the recystallization temperature of aluminium alloys. That is all it does, as far as you will be concerned.

What this means to the layman? The weld isn't brittle any more, and the solution treatment of the weld zone doesn't cause a massive, coarse precipitation there, while a fine one everywhere else. It means the metal in the weld is as strong as the metal in the tube, give or take work-hardening effects. This is an entirely new thing or aluminium alloys.


Carbon fibres at the scale you see in bike frames are approximately as strong as 853 (as supplied, not in the weld-zone) in tension. Their impact toughness in plain strain (what you commonly see in a Charpy impact test and what you will probably see most in failures) is about one fiftieth of that of an equal sized volume of stuctural, high-strength steel. Steel of the three is the toughest. Aluminium second, at about one third to one quarter that of steel.

If I didn't post how would I get to read his hilarious replies to MY posts?

Hey Hank, Love your picts - - but when it comes to your banter, maybe can get our mod to just create an "Argue with Hank" sticky :D

Who is forcing you to read posts that you don't like?

Does anyone other than Pete Fagerlin think "Hank Rearden" is amusing ?

Did Hank say something? I wasn't reading it . . . .

Yes.

As an objectivist, of course.

99% of conflict with him can be avoided with reading comprehension skills. Amusing since English is not, I predict, his first language.:)

Here is an amusing question related to the thread: Has anyone ever attempted to make frames out of ceramic material? :D How about magnesium? Why or why not?

You know Hank, you're alot like Raiyn used to be. The only difference is that Raiyn didn't just claim knowledge, he shared it. That was his one redeeming quality that was good enough to make him an asset to the community. Without it, he would have just been an abusive hack, much like you are.

You're not nearly as cool or as clever as you think you are. You're just obnoxious and annoying.

Magnesium frames exist. Dawes (responsible for Kirk's bloody catastrophe) and Merida, who are just outright lying to their customers, Zinn and Paketa are or have manufactured in magnesium alloy. I've written before on why I dislike magnesium intensely as a structural material, but it seems that certain bicycles companies, and a massive automobile are pressing ahead with integrating magnesium alloys into stuctural components.

Now, I can understand why a company may use Mg alloy for tubular bicycle frames, on the proviso that the frameset may last a few years at most. But the car consortium intends to make sub-frames and chassis parts from it. They will be exposed to road spray over many years. I bloody cringe.



As for ceramic? Carbon fibres are technically ceramic :) Well, not quite, but I can't see why the manufacture of fibre-reinforced composites using perhaps partially-stabilized zirconia couldn't be tried. Much tougher fibres than carbon fibre.

Doesn't Mg catch fire? Imagine a hot disc & a Mg frame...

So because I don't always take the time to share some basic, and easily obtainable, minutia, I"m a hack? Cool!

Here, you need this:

http://www.uab.edu/images/imedpub/Kleenex.jpg

If that doesn't work, try using the ignore function. You'll feel much better about yourself.

Not unless you've made a frame out of ribbon or powder. Or held a blowtorch to it.

Why does it seem like your job is more fun than mine is? :)

'Cause I get to play with powersaws, tonnes of liquid iron and my own budget?