Titanium Frames

"Around Australia Recumbent Style" <[email hidden]> wrote in
message "]news:[email hidden]...

Quoted message said:

Greetings all. I read the other Titanium thread with much
interest and then started to

ask

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a few questions of people who I thought would know how
good a "Ti" frame would be.

I was told by one person that Titanium frames have a
propensity to crack

due

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to metal fatigue. This was supposed to be from the lack of
give in the

very

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rigid frame. He also said that pro riders don't really
care if the frame cracks because they can just chuck it
away and get another.

Anyone had any experiences with this, or know of anyone
who has had this problem?

Thanks in advance.

Andrew

My el cheapo radioactive chinese Ti mountain bike frame has
been going fine for about two years now. (Ab)Used several
times a week for long rides in the bush. My two ti road
bikes are going well too.

geo.net.aumartys bikes.htmOpen ↗

Marty

Around Australia Recumbent Style:

Quoted message said:

I was told by one person that Titanium frames have a
propensity to crack due to metal fatigue. This was
supposed to be from the lack of give in the very
rigid frame.

This is nonsense. Look up the fatigue strength of titanium
versus aluminium, and see that the former has the advantage.

A frame that is well made will be durable regardless of the
metal used. A frame made of titanium will have a longer
fatigue life over an _equivalent_ aluminum frame. However,
for a reasonably sized Al frame (ie not stupid light),
you're likely looking at a life of hundreds of thousands of
cycles, if not in the millions, the point being that
extending fatigue life beyond this is most likely not a
significant consideration. Many, if not most, aluminium
frames last hundreds of thousands of kms, lifetimes for
many riders.

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He also said that pro riders don't really care if the
frame cracks because they can just chuck it away and get
another.

Maybe so, but this has nothing to do with what material the
frames are made of, but more of the money involved in
sponsorships.

Enter this person in a tall stories contest; he might serve
a useful purpose there.

"Jose Rizal" <_@_._> wrote in message
"]news:[email hidden]...

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Around Australia Recumbent Style:

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This is nonsense. Look up the fatigue strength of
titanium versus

aluminium, and see that the former has the advantage.

Actually, that's only one part or a very complex problem.
But put simply, neither Aluminium or Titanium has a fatigue
limit. That is, one day after X number of cycles, the
material WILL break. Steel has a fatigue limit. But this all
is irrelevant, since it's the design of the frame (wall
thickness, design, joining etc) that is the biggest factor
in how long a frame of any metrial will last, and that
frame's characteristics. The material it's made out of is
just one part of the design.

Cheers Gemma

Gemma Kernich:

Quoted message said:

"Jose Rizal" <_@_._> wrote in message news:mkQkc.1061$a47-
[email hidden]...

Quoted message said:

Around Australia Recumbent Style:

Quoted message said:

This is nonsense. Look up the fatigue strength of
titanium versus

aluminium, and see that the former has the advantage.

Actually, that's only one part or a very complex problem.
But put simply, neither Aluminium or Titanium has a
fatigue limit. That is, one day after X number of cycles,
the material WILL break. Steel has a fatigue limit.

Nope, both titanium and steel have fatigue limits, Al does
not.

Quoted message said:

But this all is irrelevant, since it's the design of the
frame (wall thickness, design, joining etc) that is the
biggest factor in how long a frame of any metrial will
last, and that frame's characteristics. The material it's
made out of is just one part of the design.

Fatigue limit (or lack of) is not irrelevant, since in good
designs it is what defines the frame tube sizes for each
material, such that either the fatigue limit is not reached
in steel and Ti frames, or the fatigue life of the Al frame
is of reasonable length.

Since there isn't much of a variance in most frame designs,
the triangle front and rear being the most common, it's not
a complex thing to do to design frame tubes of sufficient
gauge using different metals to allow for durability.

"Jose Rizal" <_@_._> wrote in message
"]news:[email hidden]...

Quoted message said:

Gemma Kernich:

Quoted message said:

"Jose Rizal" <_@_._> wrote in message news:mkQkc.1061$a-
[email hidden]...

Quoted message said:

Around Australia Recumbent Style:

> This is nonsense. Look up the fatigue strength of
> titanium versus
aluminium, and see that the former has the advantage.

Actually, that's only one part or a very complex
problem. But put

simply,

Quoted message said:

Quoted message said:

neither Aluminium or Titanium has a fatigue limit. That
is, one day

after X

Quoted message said:

Quoted message said:

number of cycles, the material WILL break. Steel has a
fatigue limit.

Nope, both titanium and steel have fatigue limits, Al
does not.

Quoted message said:

But this all is irrelevant, since it's the design of the
frame (wall thickness, design, joining etc) that is the
biggest factor in how long a frame of any metrial will
last, and that frame's characteristics. The material
it's made out of is just one part of the design.

Fatigue limit (or lack of) is not irrelevant, since in
good designs it is what defines the frame tube sizes for
each material, such that either the fatigue limit is not
reached in steel and Ti frames, or the fatigue life of the
Al frame is of reasonable length.

Since there isn't much of a variance in most frame
designs, the triangle front and rear being the most
common, it's not a complex thing to do to design frame
tubes of sufficient gauge using different metals to allow
for durability.

So why do we see so many cracked Aluminium frames?

Marty

"Marty Wallace" <[email hidden]> wrote in message
"]news:[email hidden]...

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"Jose Rizal" <_@_._> wrote in message news:3U%kc.2364$8S1-
[email hidden]...

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Gemma Kernich:

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"Jose Rizal" <_@_._> wrote in message news:mkQkc.1061-
[email hidden]...
> Around Australia Recumbent Style:
>
> > This is nonsense. Look up the fatigue strength of
> > titanium versus
> aluminium, and see that the former has the
> advantage.
>
Actually, that's only one part or a very complex
problem. But put

simply,

Quoted message said:

Quoted message said:

neither Aluminium or Titanium has a fatigue limit.
That is, one day

after X

Quoted message said:

Quoted message said:

number of cycles, the material WILL break. Steel has a
fatigue limit.

Nope, both titanium and steel have fatigue limits, Al
does not.

Quoted message said:

But this all is irrelevant, since it's the design of
the frame (wall thickness, design, joining etc) that
is the biggest factor in how long

a

Quoted message said:

Quoted message said:

Quoted message said:

frame of any metrial will last, and that frame's
characteristics. The material it's made out of is just
one part of the design.

Fatigue limit (or lack of) is not irrelevant, since in
good designs it is what defines the frame tube sizes for
each material, such that either the fatigue limit is not
reached in steel and Ti frames, or the fatigue life of
the Al frame is of reasonable length.

Since there isn't much of a variance in most frame
designs, the triangle front and rear being the most
common, it's not a complex thing to do to design frame
tubes of sufficient gauge using different metals to
allow for durability.

So why do we see so many cracked Aluminium frames?

Because of exactly what Jose said (sort of) - as frames
_aren't_ necessarily designed for durability!! I have seen
quite a few broken frames in my time...., cracked seat
tubes, down tubes, stays... still waiting for a fork to
fail! Look around at all the expensive frames that only have
a one-year warranty - it's engineering for other things,
lightness and the marketing value mainly I'd say. And
apologies to Jose, I did get the fatigue limit [censored]-about,
now I remember why I didn't do mech eng 😉 It's Al and
Magnesium I was thinking of (anyone own a Merida Mag? 😉
Cheers Gemma

The issue of fatigue is an interesting one. I think all materials for bike frame manufacture could crack under fatigue type loading.

But let's examine the loading required to initiate fatigue. First of all materials have elastic and plastic deformation zones.

The elastic zone is where the material can be loaded (to say 10kN) then unloaded, without a change a change in any dimension.

If you go past the elastic limit of the material it will deform and it will not return to it's original dimensions or shape. This is a good property of say Al & Fe, because we can sometimes detect parts are fatiguing before they break!

The other component that can dramatically assist fatigue is a stress concentrator. If you a nick or a scratch in the material at the right place that fatigue wants occur, it will hasten the process 10 fold.

powinc

Marty Wallace:

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"Jose Rizal" <_@_._> wrote in message

Quoted message said:

Quoted message said:

Since there isn't much of a variance in most frame
designs, the triangle front and rear being the most
common, it's not a complex thing to do to design frame
tubes of sufficient gauge using different metals to
allow for durability.

So why do we see so many cracked Aluminium frames?

Several things: poor welding techniques (cheap), inadequate
post-welding heat treatment (cheap), undersized frame tube
thickness (for that stupid-light feel). I also believe (but
haven't got empirical evidence of) that Al alloys like the
7000 series are more prone to stress-corrosion fractures
once their usually anodized surfaces are breached by
scratches and the like. You can glean a hint of this when
manufacturers like Race Face warn on stress corrosion and
taking off anodization on their cranks, and looking at the
properties of the higher series aluminium alloys. HOWEVER,
how much more likely stress corrosion is to happen in these
alloys once the anodizing is breached is anybody's guess, or
if it is really much of a concern at all.

powinc:

Quoted message said:

The issue of fatigue is an interesting one. I think all
materials for bike frame manufacture could crack under
fatigue type loading.

But let's examine the loading required to initiate
fatigue. First of all materials have elastic and plastic
deformation zones.

The elastic zone is where the material can be loaded (to
say 10kN) then unloaded, without a change a change in any
dimension.

If you go past the elastic limit of the material it will
deform and it will not return to it's original
dimensions or shape. This is a good property of say Al &
Fe, because we can sometimes detect parts are fatiguing
before they break!

What you mention has to do with tensile strength and modulus
of elasticity, and while it has some bearing on fatigue,
it's a different mechanism.

Al can be cyclic loaded within the elastic zone and yet its
fatigue life is still shortened because it does not have a
fatigue limit. You won't see any permanent deformations and
yet it will still fail after a certain number of loads.
Steel and Ti can also be cyclic loaded within their elastic
zones but if their fatigue limits are reached, they will
fail eventually.

Gemma Kernich:

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now I remember why I didn't do mech eng 😉

It's all good though!

"Jose Rizal" <_@_._> wrote in message
"]news:[email hidden]...

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Gemma Kernich:

Quoted message said:

now I remember why I didn't do mech eng 😉

It's all good though!

I went down the civil eng path. I also remember the
"Engineering Materials" subjects were always after lunch
on a cheap beer Wednesday or something like that...
*grin* Gemma

On Mon, 3 May 2004 10:57:47 +0930, "Gemma Kernich" <[email hidden]>

Quoted message said:

"Jose Rizal" <_@_._> wrote in message news:0H9lc.1821$a47.-
[email hidden]...

Quoted message said:

Gemma Kernich:

Quoted message said:

now I remember why I didn't do mech eng 😉

It's all good though!

I went down the civil eng path. I also remember the
"Engineering Materials" subjects were always after lunch on
a cheap beer Wednesday or something like that... *grin*

Well I *did* do mech eng (and civil, electrical, etc.) and I
can't remember the details of most of this stuff. It was a
long time ago and I went straight into the software
development after uni. But I'm enjoying reading the posts,
so thank you to the experts.

PS, There's an interesting article on carbon fibre by Raoul
Luescher in the Q & A section of May June 2004 Bicycling
Australia. Raoul has posted here in the past.

--
Regards. Richard.

Thank You everyone for your input, most of which went
straight over my head at the same altitude as the Space
Shuttle, but I think I get the engineering drift.

Nice bikes Marty. I think I might have to try those Chinese
Ti frames after all.

Regards and safe travels,

Andrew

"Around Australia Recumbent Style"
<[email hidden]> wrote in message news:zaKkc.6750$TT.506@news-
server.bigpond.net.au...

Quoted message said:

Greetings all. I read the other Titanium thread with much
interest and then started to

ask

Quoted message said:

a few questions of people who I thought would know how
good a "Ti" frame would be.

I was told by one person that Titanium frames have a
propensity to crack

due

Quoted message said:

to metal fatigue. This was supposed to be from the lack of
give in the

very

Quoted message said:

rigid frame. He also said that pro riders don't really
care if the frame cracks because they can just chuck it
away and get another.

Anyone had any experiences with this, or know of anyone
who has had this problem?

Thanks in advance.

Andrew

"Marty Wallace" <[email hidden]> wrote in news:4094bef3$0$27645
[email hidden]:

Quoted message said:

So why do we see so many cracked Aluminium frames?

Because aluminium is now far and away the most common frame
material. When it was steel, you used to see plenty of
cracked steel frames.

"John Stevenson" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

"Marty Wallace" <[email hidden]> wrote in
news:4094bef3$0$27645 [email hidden]:

Quoted message said:

So why do we see so many cracked Aluminium frames?

Because aluminium is now far and away the most common
frame material. When it was steel, you used to see plenty
of cracked steel frames.

I disagree with that. I've been riding for a long time and
steel frames never cracked at the rate that I see aluminium
ones failing. As a matter of fact, I've never personally
seen a steel frame fail.

Marty

"Marty Wallace" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

"John Stevenson" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

"Marty Wallace" <[email hidden]> wrote in
news:4094bef3$0$27645
[email hidden]:

Quoted message said:

So why do we see so many cracked Aluminium frames?

Because aluminium is now far and away the most common
frame material.

When

Quoted message said:

Quoted message said:

it was steel, you used to see plenty of cracked steel
frames.

I disagree with that. I've been riding for a long time and
steel frames never cracked at the

rate

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that I see aluminium ones failing. As a matter of fact,
I've never personally seen a steel frame fail.

I've had two steel frames and three Al frames crack (but
I've ridden more Al frames than steel). I do have a
Titanium frame now, but it's only done about 500 km so way
too early to tell.

Jeff