metal fatigue

[Doc]

Last year the axle of my BB broke(Shimano BB UN-51) can I attribute this to fabrication vice or to
metal fatigue? Do metal fatigue exist? I have an old cro-mo touring frame with many thousands
miles,is this frame will break one day by metal fatigue? I saw some alu frames broke,is
steel(cro-mo) will do the same with time? In a century,could I ride this old friend without risk?
Other question:is the metal (frame) becomming more soft with time? Thanks. Doc.

 

[Ted Bennett]

In article <[email protected]>, "Doc" <[email protected]> wrote:

> Last year the axle of my BB broke(Shimano BB UN-51) can I attribute this to fabrication vice or to
> metal fatigue?

Oui.

> Do metal fatigue exist?

Oui.

> I have an old cro-mo touring frame with many thousands miles,is this frame will break one day by
> metal fatigue?

Not unless the load exceeds the fatigue limit. It is unlikely.

> I saw some alu frames broke,is steel(cro-mo) will do the same with time?

Aluminum has no fatigue limit, so every load cycle contributes to eventual failure. Most aluminum
frames are well-designed, so that failure was likely due to poor construction, either defective
welding or heat treatment.

> In a century,could I ride this old friend without risk?

Almst certainly, but there is risk in everything we do.

> Other question:is the metal (frame) becomming more soft with time?

Non, absolument.

> Thanks. Doc.

Ce n'est rien.

--
Ted Bennett Portland OR

 

[David L. Johnso]

On Sat, 05 Apr 2003 17:03:19 +0000, Doc wrote:

> Last year the axle of my BB broke(Shimano BB UN-51) can I attribute this to fabrication vice or to
> metal fatigue?

Unless it was fairly new, and from the model number it probably wasn't, I'd vote for fatigue.

> Do metal fatigue exist?

Try an experiment. Find a paper clip. Bend it back and forth many times.

> I have an old cro-mo touring frame with many thousands miles,is this frame will break one day by
> metal fatigue?

Probably not. If it was well-designed, it won't fatigue significantly.

> I saw some alu frames broke,is steel(cro-mo) will do the same with time? In a century,could I ride
>this old friend without risk?

In a century, if you are still riding, I would be impressed.

> Other question:is the metal (frame) becomming more soft with time? Thanks. Doc.

Troll!

--

David L. Johnson

__o | To announce that there must be no criticism of the president, or _`\(,_ | that we are to
stand by the president right or wrong, is not (_)/ (_) | only unpatriotic and servile, but is
morally treasonable to the American public. --Theodore Roosevelt

 

[...Who Cares]

Why don't ya just buy a new bike?

To your exact specs. Just imagine the joy you would have riding it instead of your other
piece of junk.

You can afford it.

Go on -DO IT

"Doc" <[email protected]> wrote in message news:[email protected]...
> Last year the axle of my BB broke(Shimano BB UN-51) can I attribute this
to
> fabrication vice or to metal fatigue? Do metal fatigue exist? I have an old cro-mo touring frame
> with many thousands miles,is this frame will
break
> one day by metal fatigue? I saw some alu frames broke,is steel(cro-mo)
will
> do the same with time? In a century,could I ride this old friend without risk? Other question:is
> the metal (frame) becomming more soft with time? Thanks. Doc.

 

[Bruce Jackson]

"Doc" <[email protected]> wrote in message news:<[email protected]>...

Hitting just a few of the points

> Last year the axle of my BB broke(Shimano BB UN-51) can I attribute this to fabrication vice or to
> metal fatigue?

In years past bottom bracket spindles did break eventually. With modern cartridge bottom brackets
this is rare. Since modern cartridge BBs are cheap and can not be serviced they are discarded long
before there should be any danger of the spindle breaking.

The spindles in the older bottom brackets did usually last many tens of thousands of miles before
failure though.

I'm of the opinion that your bottom bracket was defective.

> Do metal fatigue exist? I have an old cro-mo touring frame with many thousands miles,is this frame
> will break one day by metal fatigue?

Bicycles are built to last many thousands of miles. For the most part when steel frames fail they do
not do so catastrophically; they give some warning and even when they do fail they often do not dump
you to the ground. The steel frame that I broke creeked for months before the seat stay finally
broke. Several riders I know broke their downtube near the bottom bracket because the builder
overheated the tubes. None of these cases resulted in injury to the cyclist. Breaking a BB or pedal
spindle, crank arm, or stem often does produce injury.

If your frame is well built it should last as long as you care to ride it, if it isn't well built it
should still last a long time and isn't likely to maim you when it does fail.

> I saw some alu frames broke,is steel(cro-mo) will do the same with time? In a century,could I ride
> this old friend without risk?

Other posters ansered this.

> Other question:is the metal (frame) becomming more soft with time? Thanks. Doc.

Steel does not change its stiffness over time. It maintains the same stiffness until almost the
point of failure.

best, Bruce
--
Bruce Jackson - Sr. Systems Programmer - DMSP, a M/A/R/C Group company

 

[Ted Bennett]

"...who cares" <[email protected]37.freeserve.co.uk> wrote:

> Why don't ya just buy a new bike?
>
> To your exact specs. Just imagine the joy you would have riding it instead of your other piece
> of junk.
>
> You can afford it.
>
> Go on -DO IT

These are odd comments, to say the least. To buy an entire new bicycle because one part broke is
foolishness.

How do you know that bike is " piece of junk"?

--
Ted Bennett Portland OR