Do aluminum frames wear out?

Buy a titanium frame. Doesn't corrode, not brittle like alumnium.

There is a good article on the advantages/disadvantages of frame materials
at:

http://www.exploratorium.edu/cycling/frames1.html






"Chris Hansen" wrote in message
om...
Hello,

I've talked to two people who have said aluminum frames wear out. One
said that after about 8 years they kind of go "dead" and lose the feel
they once had. Another talked about how he broke the bottom bracket
out of an old aluminum frame.

Does anyone know anything about this? If you plan to keep a bike for
longer than 10 years is it better not to get aluminum?

In article ,
says...
On Wed, 24 Mar 2004 20:04:16 GMT, Cipher
wrote:

Here's something to read on the subject:

http://www.ihpva.org/com/PracticalIn...materials.html

Good site. He neglects titanium, though. The homebuilder committed
to welding aluminum already has a MIG or TIG setup, and in my
experience, 6Al-4V Titanium is easier to weld than aluminum, and
stiffness-to-weight, there is no contest.
A vast difference between steel and aluminum was explained to me by an
ME friend thusly: After a million flexural cycles on a steel
structure, it can be considered to have unlimited life; After a
million flexural cycles on an aluminum structure, it can be considered
to have Zero remaining flexural life. (I do not know the rationale for
this, nor the mechanisms, etc. BUT: Do airframe components "time
out"? There are plenty of commercial aircraft flying after decades of
use. But they are not 6061-T6, I do not think.)

They are also routinely inspected for cracks every so many cycles (one
takeoff and one landing being a cycle). Remember the Hawaiian 737 a few
years ago where the top half of the fuselage ripped off, and then
inspection found fatigue cracks?

--
Dave Kerber
Fight spam: remove the ns_ from the return address before replying!

REAL programmers write self-modifying code.

On Wed, 24 Mar 2004 23:17:35 GMT, "Peter Cole"
wrote:

(I do not know the rationale for
this, nor the mechanisms, etc. BUT: Do airframe components "time
out"? There are plenty of commercial aircraft flying after decades of
use. But they are not 6061-T6, I do not think.)

I wouldn't take any chances, refuse to fly anything but steel planes!

That Soviet Foxbat that defected to Japan was. We thought it was
titanium like ours, till someone noticed that it was starting to rust
out like an old Chevy. Which proves that if you put a big enough
engine on an anvil, it might fly.
Likewise, if you can pedal hard enough, long enough, it probably does
not matter what something weighs. Growing up, the neighborhood Rich
Kid has one of those Schwinns that had everything; A generator,
lights, an electric horn built into the tank, tons of chrome.
Everyone liked to look at it, and nobody rode it more than once.

Obviously the material has "a lot" to do with longevity. I'ts just not the
be-all and end-all of longevity.

An old engineering saying goes: "There are not bad materials, only bad
applications"

Try building an origami bike frame and see
what happens.

I see no reason why you couldn't build a bike out of properly engineered
cardboard tubes which would at least be marginally functional.

After all, there's a reason nearly all cars are made of steel,
whereas fiberglass and other metals are somewhat rare.

Yes, cost. A typical automobile manufacturer can price their vehicles by the
pound and get a pretty close estimate to their actual production costs.

High-end vehicles are often carbon fiber these days.


Chris Neary


"Science, freedom, beauty, adventu what more could
you ask of life? Bicycling combined all the elements I
loved" - Adapted from a quotation by Charles Lindbergh

Easier to mass produce.
Cheaper.
Doesn't "dent".

Surely "doesn't dent" is a part of "longevity," isn't it?

My wife rode for years on a Cannondale with big dent in the top tube before
we donated it. Some woman in Team In Training is probably still using it.



Chris Neary


"Science, freedom, beauty, adventu what more could
you ask of life? Bicycling combined all the elements I
loved" - Adapted from a quotation by Charles Lindbergh

On Wed, 24 Mar 2004 10:42:25 -0800, Chris Hansen wrote:

Hello,

I've talked to two people who have said aluminum frames wear out. One
said that after about 8 years they kind of go "dead" and lose the feel
they once had. Another talked about how he broke the bottom bracket
out of an old aluminum frame.

Can I guess that these two people are maybe trying to sell you something
other than an aluminum frame?

A well-made frame of any material should last for many years. A
poorly-made one (I*almost wrote "cheap", but there is little if any
relationship to price) will break sooner. It's not so much the material
as the workmanship, and design.

There are just as many people who tell you that a steel frame will go
"soft" on you. I wouldn't know, my steel bike is only 30 years old.
Maybe eventually it will go soft. I know I will.

--

David L. Johnson

__o | It doesn't get any easier, you just go faster. --Greg LeMond
_`\(,_ |
(_)/ (_) |

On Wed, 24 Mar 2004 21:57:55 +0000, TopCounsel wrote:

It's a mistake to think material has anything to do with longevity.
^^^^^^^^
I think you mean "everything".

Obviously the material has "a lot" to do with longevity. I'ts just not the
be-all and end-all of longevity. Try building an origami bike frame and see
what happens. After all, there's a reason nearly all cars are made of steel,
whereas fiberglass and other metals are somewhat rare.

But that reason has to do more with cost of manufacture than anything else.

--

David L. Johnson

__o | The lottery is a tax on those who fail to understand mathematics.
_`\(,_ |
(_)/ (_) |

Chris Hansen wrote:

Hello,

I've talked to two people who have said aluminum frames wear out. One
said that after about 8 years they kind of go "dead" and lose the feel
they once had. Another talked about how he broke the bottom bracket
out of an old aluminum frame.

Does anyone know anything about this? If you plan to keep a bike for
longer than 10 years is it better not to get aluminum?

What will you use instead? Steel?

Are your handlebars steel? How about your stem? Your rims? Your
cranks? Your brakes? Your hubs? Your seatpost?

On all my bikes, all those components made of aluminum. On my favorite
bike, the frame is aluminum too. It was made in 1986. Last summer, it
took me coast to coast, fully loaded.

The bit about frames "going dead" is absolute nonsense. And FWIW, most
common thinking on aluminum's fatigue life is nonsense, too.

It's possible to buy a too-light, disposable aluminum frame, and you may
see it fail in a couple years - or a couple months. But that can
happen, and has happened, with steel frames, titanium frames, carbon
fiber frames, magnesium frames, etc etc.

--
-------------+
Frank Krygowski [To reply, omit what's between "at" and "cc"]

Cipher wrote:

Here's something to read on the subject:

http://www.ihpva.org/com/PracticalIn...materials.html

Well, it's not too bad.

I probably shouldn't feel this way, but I get skeptical about the
knowledge of anyone who can't spell "Chromium Mollybenduim" [sic]. Or
who gives no hint that it's actually a type of steel.


--
-------------+
Frank Krygowski [To reply, omit what's between "at" and "cc"]

Methuselah wrote:

A vast difference between steel and aluminum was explained to me by an
ME friend thusly: After a million flexural cycles on a steel
structure, it can be considered to have unlimited life; After a
million flexural cycles on an aluminum structure, it can be considered
to have Zero remaining flexural life.

Your Mechanical Engineer friend was grossly simplifying. Either that,
or you remembered things a bit wrong.

Fatigue life depends on the number of cycles of stress, and on the level
of that stress, as well as the metal properties. Obviously, some
alloys are better than others.

You can certainly flex a steel sample and cause fatigue failure in far
fewer than a million cycles. All you need to do is provide a high
enough stress level. Think of bending a coat hanger wire back and forth
a few dozen times.

What your friend was probably referring to is this: with steels, it's
possible to have an infinite fatigue life, IF you keep the stress level
of each cycle low enough - below what's called the "endurance limit."
IOW, if you bend a steel part back and forth, but never exceed (say)
10,000 psi, the steel part will _never_ crack due to fatigue.

On the other hand, aluminum alloys do not have an endurance limit. No
matter how low the stress you apply, if you bend things back and forth
enough times, the aluminum part will fatigue - someday. Eventually.

The question is, when? The lower the stress (just as with steel) the
longer the fatigue will take. Keep the stress down low enough, and your
bike frame may fatigue while your great-grandchild is riding it in an
antique parade, but not before then.

Do airframe components "time out"?

For what it's worth, time has nothing to do with it - assuming you're
not corroding it badly during the intervening years. It's all based on
the number of stress cycles, and the level of stress in those cycles.

The frame of a bike generally carries fairly low stresses. It's well
triangulated, and most riding is done at low levels of exertion. I
think that, unless you're a Keirin racer, or you buy a bonded aluminum
frame with bad joint bonds, your aluminum frame will last a long, long
time. Mine certainly has.

--
-------------+
Frank Krygowski [To reply, omit what's between "at" and "cc"]