(collisions reverberating)
- We've looked at the myths surrounding carbon fiber.
We've lifted the lid on aluminum.
We've investigated whether steel is in fact real; it was.
But, there is still a big gap in
the GCN Material Sciences Course.
And that, is titanium.
For a while, in the early '90s,
titanium was going to be the next big thing.
And to be fair, it briefly was,
but little by little it became eclipsed by carbon fiber.
Nevertheless though, it still has
a legion of super loyal fans, and quite right too.
So if you're not onboard the titanium train yet,
or perhaps more accurately, military aircraft or submarine,
what do you need to know?
(relaxed chill music)
Despite having the reputation that it's the preserve
of the Russian or American military,
which to be fair, it kind of was,
titanium is actually the ninth most common element
in the earth's crust.
And as well as using it to make bikes,
you can also find it in sun cream and paper,
to make it whiter.
Clearly though, what makes paper white
doesn't really help very much when you're making bikes,
other than perhaps drawing up your initial ideas,
and that is because it's titanium oxide
that's used in paper, whereas when we're making bikes
we need a titanium alloy.
The very first titanium bikes were actually though
made out of pure titanium, but they were very flexible
and they weren't very much good.
And it wasn't until a titanium alloy called 3AL/2.5V
that that changed, having blended in
3% aluminum and 2.5% vanadium.
The other common titanium alloy for bikes is 6AL/4V.
Both have a very high Young's modulus, which is
a measure of the stiffness of the material,
so they have a gPA of about 110
as opposed to, let's say 6061 aluminum,
which has a GPa about about 69.
And they also have a much higher yield strength,
so that is the point at which a material
stops returning to its original position
when a stress is removed.
So six-four titanium has an MPa of 1000,
whereas again 6061 aluminum has an MPa of just 270.
And what that means is that the material
won't deform or bend or buckle in a crash.
Three two-five actually has a lower yield strength
than six-four titanium, but then that's one of the reasons
why it is used almost exclusively in bike-building,
because six-four titanium is incredibly hard to work with.
It's more brittle and less ductile,
so forming it into simple shapes,
like, I don't know, tubes for a start,
is incredibly hard.
And actually most six-four titanium tubes
are rolled from sheet metal and then welded,
whereas three-2.5 tends to be seamless.
And so that actually gives a more consistent overall tube,
and therefore is better from a quality control perspective.
So in other words, basically, although on paper
the material properties of six-four titanium
might look better, it won't necessarily yield a better bike.
Titanium is renowned as being super light, but in fact,
as a material, it's actually 60% denser than aluminum.
However, given what we've just heard
about the other material properties,
you can still see why titanium frames
tend to come out slightly lighter than aluminum ones.
So, the best examples of each would be
about 1000 grams for a titanium frame
and about 1100 grams for aluminum.
So, 100 grams in it.
And the reason that difference is actually still quite small
is probably down to a measure of just how much easier it is
to work and manipulate aluminum,
and we we'll come on to that a little bit later on.
And we also have to bear in mind
that super light titanium frames
will also have exceedingly thin-walled tubing
as a result of that extra density.
And then when we compare it to steel,
titanium is as strong but 45% less dense.
And so that explains why titanium frames
are significantly lighter than steel.
That toughness in terms of material properties
does make titanium very difficult to work with,
as we've already touched on.
Fortunately though, much of that difficulty
is actually dealt with by the tube manufacturers themselves.
One of those things is that internally butted tubes
can't be made safely from titanium.
Basically the danger is that titanium can be overworked,
and then that would lead to a weakness in the material.
Now on the flip side, what you can do
is externally butt the tubing,
so instead of a mandrel working away inside the tube,
titanium is shaved off from the outside.
However that does rely heavily
on the straightness of the tubing in the first place,
because any imperfections in that
would also then be reflected in the wall thicknesses.
So, that's probably why this bike behind me (taps frame)
is made out of straight gauge titanium tubing.
Titanium is also a little bit trickier to weld
than steel or aluminum, and that's because
it's reactive to oxygen at higher temperatures,
meaning that when it is welded,
it needs to be done in an absence of that gas.
Now to be fair, all metals need to be
welded in an inert gas environment,
but titanium is particularly sensitive.
So to put it in context, if you're welding steel
an acceptable purge, so called,
needs to be about 1000 parts of oxygen per million,
whereas with titanium, it's just 10 parts per million.
So that is a little bit of challenge to a welder,
and if any oxygen does get into the weld,
then the titanium oxidizes.
Which, if you remember from earlier in the video,
is a very white, almost worthless white powder.
The technique then is to weld in an inert argon atmosphere,
so basically you pipe argon gas into the tubes,
and then externally to the weld as well,
but then that ensures that it's all nice and strong.
The last thing that can make titanium a bit tricky
is working.
So you see, we mentioned earlier
that aluminum can be engineered and manipulated
into all sorts of complicated shapes,
but with titanium, even bending
a simple S-bend chainstay, for example,
extreme care has to be taken you don't overwork the material
which can then lead to it becoming brittle
and therefore weak.
In order to avoid that, the titanium needs to be annealed,
which is where you heat it up and then
you allow it to cool down slowly in between
each incremental step of the process.
It's quite time consuming, labor intensive,
and it's another reason why titanium bikes
tend to be quite expensive.
Is it expensive though?
Well, yes compared to aluminum bikes.
But it's probably on a part with custom steel,
and significantly cheaper, you've got to say,
than top-end carbon fiber.
It is a boutique material, and so yes,
there is a boutique cost as well.
So the raw material is between $10 and $12 per kilo.
Finished tubes are between $100 to $120 per kilo.
But that puts it a little bit more than standard steel
and on a par with stainless steel.
But dare I say though, and because
it's not quite so fashionable at the moment
perhaps, in the cycling world,
there are some relative bargains to be had.
And to be fair, we've given you
an awful lot of information so far,
but we've not quite got to the nub yet
of why titanium has such a loyal following
and can be, frankly, so great.
You can get a custom titanium frame really quite easily
and it's going to be considerably lighter
than an equivalent custom steel frame,
so about 400 grams lighter.
I'd guess an average custom steel frame is about 1600 grams;
titanium could be about 1200 grams.
Which is pretty important if you are looking to build
a super light road bike.
Yes titanium is reactive, but your frame
is not going to corrode, not like steel,
not like aluminum; it is going to last.
And so for many people, the Ti bike is the keeper.
Beauty is very much in the eye of the beholder,
but I think titanium has undeniably a special something.
I mean look at the raw finish on this;
it's like it's glowing.
Ah, the ride quality, even harder to pin down
than aesthetics.
Now traditionally, titanium has a ride feel like no other.
But the boundaries between materials are blurring;
engineering is taking things to new places.
So steel can now be as stiff as aluminum;
aluminum can now be as forgiving as carbon fiber.
But titanium traditionally has always been about zing.
I heard it described back in the day
like a great titanium frame was trying to spring forward
and gain momentum off every bump or ripple in the road.
And that, to my mind, sounds pretty amazing.
Now unfortunately, I've literally never spent
any proper time on a titanium bike.
So at some point soon I hope to remedy that.
Well there is your Titanium 101.
Hopefully you can add it now as a material
that you know as much about as steel,
aluminum, and carbon fiber.
Please give this video a big thumbs up;
if nothing else you've been looking at some bike porn
for the last few minutes.
And if you want to watch one of those videos,
refresh your knowledge about the other materials,
why not check out the one about aluminum just down there.