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PostPosted: Tue Feb 13, 2007 3:31 pm 
Concours Judge
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My Almega was obviously very seldomly moved. All original parts, no wear on tyres, rims or whatsoever. Bright paint, zero chips. Though the frame developed cracks everywhere.

I heard a Roox post snap when standing in the livingroom.

I undertood alloy does age by time, as does titanium. Steel doesn't. Aluminium will eventually snap sooner or later, but it will.

"Aluminium is real" doesn't rhyme to me 8)


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PostPosted: Tue Feb 13, 2007 4:20 pm 
Retro Guru

Joined: Fri Apr 28, 2006 8:42 pm
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To avoid further confusion too, you should stop saying "alloy" when you mean "aluminium".

An alloy is a combination of metals - for example 531 is Manganese, Molybdenum and Steel. It's a steel and it's an alloy.


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PostPosted: Tue Feb 13, 2007 4:26 pm 
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terryhfs wrote:
To avoid further confusion too, you should stop saying "alloy" when you mean "aluminium".


Does/did anyone make a bike frame out of pure / 1xxx aluminium?

Tis true that a lot of people say alloy when they mean aluminium alloy though... "alloy wheels" for example; Steel's an alloy...!

Quote:
An alloy is a combination of metals - for example 531 is Manganese, Molybdenum and Steel. It's a steel and it's an alloy.


Strictly speaking, steel isn't a metal itself... Alloys don't have to be all metal though. Don't know about anyone else, but I'm confusing myself! :lol:


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PostPosted: Tue Feb 13, 2007 10:59 pm 
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Elev12k wrote:
My Almega was obviously very seldomly moved. All original parts, no wear on tyres, rims or whatsoever. Bright paint, zero chips. Though the frame developed cracks everywhere.

I heard a Roox post snap when standing in the livingroom.

I undertood alloy does age by time, as does titanium. Steel doesn't. Aluminium will eventually snap sooner or later, but it will.

"Aluminium is real" doesn't rhyme to me 8)


Ok as Industrial design engineer I learned it all, but unfortunately it slipped away after designing toys, trainers for elderly and earplugs.

I will give you a tip: don't buy aluminium frames! especcially the old nice once because they will break, especcially when they have nice collours and the more beautiful the frame is the easier they brake!

ok hope the prices of nice aluminium frames will go down a bit now :lol:

That Almega frame must have been of a low alloy degree (like the grisleys) from the 4000 series, cheap. they don't need to be precipitated. Their precipetation hardening already occurs at room temperature, if this process continues for too long there is (translated from dutch) grain growth, the etnic-minority-atoms don't stay in their patern but can slightly move around deteriorating the mechanical properties by grouping just as minorities tend to do in real live. This in combination with a pre stressed frame could cause cracks when just sitting around I guess.

As for the higher quality frames precipitation takes place at a much higher temperature, so if you don't leave your bike in a car cooking in the sun you will be fine. still natural aging continues at a very very slow pass. I never got any info on what time span we must think about, but with airplanes serving for 40years I think my aluminium bikes will outlive me

As for the fatigue, a well engineered frame ensures the strains remain within the fatigue stress boundries, the material will not be streched that far that it will enter this fatigue strain.

Final note: I am NOT a material EXPERT!! just had to learn a little about the terms and stuff to be able to communicate with an material expert. So hope someone can support me. To give you a clue, my book: "Material science and engineering, an introduction" (!) is over 800 pages (at A4 small print, and not that many pictures!) There are maybe four pages about the precipitation of aluminium alloys and not a sentence about long term ageing!


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PostPosted: Tue Feb 13, 2007 11:09 pm 
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Ziggy wrote:

Does/did anyone make a bike frame out of pure / 1xxx aluminium?



thats food industry alloy. 99% AL, with the yield strength of say a strong syrop and tensile strength of 90MPa, that against for example the 570MPa of 7075


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PostPosted: Tue Feb 13, 2007 11:16 pm 
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Location: No brakes? Way to commit soldier.
Its quite simply nonsense to say "don't buy old aluminium frames, they will break" as there are so many factors to be taken into account.


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PostPosted: Tue Feb 13, 2007 11:24 pm 
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Russell wrote:
Its quite simply nonsense to say "don't buy old aluminium frames, they will break" as there are so many factors to be taken into account.


shit caught!@# hoped to get the prices of Kleins down :roll:


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PostPosted: Tue Feb 13, 2007 11:27 pm 
Klein Guru / BOTM Winner

Joined: Fri May 05, 2006 6:06 pm
Posts: 984
Location: Houston TX
Russell wrote:
Its quite simply nonsense to say "don't buy old aluminium frames, they will break" as there are so many factors to be taken into account.


i think Wytze forgot the :wink: after that statement :wink:

but i agree with him, especially those crappy old Klein frames have a lifespan of max. 10 years so no one (except me) should anymore buy pre-1996 Kleins! they are dangerous! :wink: :wink:

but more seriously, there has been written soooo much about this topic by experts and non-experts (like me) that it might help to do a google search...

cheers, carsten


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PostPosted: Tue Feb 13, 2007 11:43 pm 
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Jez,

1.) does aluminum's material properties change with the passing of time???

The short answer is yes

2.) Will this change impact my 10 year old NOS Klein frame?

The short answer is no.

3.) Is aluminum the ideal material for a bicycle frame?

The short answer...maybe

The longer but still not so involved answer...AL that is used for bicycle frames has an engineered "life" of around 3-4 years. This takes into account post manufacture irregularities, fatigue life, and general abuse.

More importantly, manufacturers have realized that the majority of consumers will rotate/purchase a new high end bicycle in less time. This allows for high performance features (light weight) at the expense of longevity. Post production, the frame only has to last long enough to secure another confident purchase.

So, where does this leave the vintage collector? We can appreciate the beauty of retro AL, but know that if you ride it hard, it WILL fail eventually.

cheers,

rody


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PostPosted: Tue Feb 13, 2007 11:47 pm 
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Wahey! Rody to the rescue!

So it DOES degrade in time then


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