Steel molecules - do they get tired?

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Mick F
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Re: Steel molecules - do they get tired?

Postby Mick F » 1 Aug 2020, 4:59pm

Trying to cast my mind back to school.
Elements, compounds and mixtures.

From what I remember, a mixture is something you can separate by various means, but a compound is a combination of elements that cannot be separated.

So .......... if steel is a mixture, it must be that you can remove the carbon atoms from the iron atoms as they are not chemically bonded.
Mick F. Cornwall

Jdsk
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Re: Steel molecules - do they get tired?

Postby Jdsk » 1 Aug 2020, 5:05pm

Mick F wrote:From what I remember, a mixture is something you can separate by various means, but a compound is a combination of elements that cannot be separated.

No, unless you restrict that definition to particular means of separation.
https://en.wikipedia.org/wiki/Chemical_compound

Jonathan

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Re: Steel molecules - do they get tired?

Postby al_yrpal » 1 Aug 2020, 5:27pm

All the stuff about Molecules is irrelevant. To widen the spacing you have got to take the steel frame past its elastic limit and permanently deform the material. As I said earlier this could weaken the material slightly. This is all well known basic Engineering Strength of Materials taught in the first year of an Engineering Degree.
However long you hold a material like steel under stress within its elastic limit it will just spring back into shape immediately the stress is discontinued. That is how springs work. It doesnt get tired.
If the material is at high temperatures it may creep. Lead can creep at ambient temperature. Aluminium will creep under stress at 200 degrees C. A problem for supersonic aircraft like Concorde.

Al
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Mick F
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Re: Steel molecules - do they get tired?

Postby Mick F » 1 Aug 2020, 7:10pm

al_yrpal wrote:However long you hold a material like steel under stress within its elastic limit it will just spring back into shape immediately the stress is discontinued. That is how springs work. It doesnt get tired.

Tell that to a clock that's had its spring wound tight for years without running.
Mick F. Cornwall

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simonineaston
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Re: Steel molecules - do they get tired?

Postby simonineaston » 1 Aug 2020, 8:36pm

I've read all your replies - a brilliant read! Thanks. What I've actually done is to have a word or two with the piece of metal concerned. I've put it to the piece that I'd respectfully appreciate it if it were to adopt a slightly wider posture from now on and tomorrow morning I'm going to see if my words have fallen on deaf ears, or else, if they have born fruit... talk about mixing my metaphores!! Hope springs eternal.
ttfn, Simon in Easton
(currently enjoying a Moulton TSR & a nano Brompton...)

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Re: Steel molecules - do they get tired?

Postby Jdsk » 1 Aug 2020, 8:43pm

simonineaston wrote:Hope springs eternal.

ISWYDT

: - )

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Re: Steel molecules - do they get tired?

Postby OldLimey » 1 Aug 2020, 9:14pm

I never use the proper terms because I'm usually wrong, so rather than say 'molecules,' I would say 'thingies.' Do steel thingies get tired? Thingies can be anything you like.

I've seen video where a guy used threaded rod with nuts and washers in between the dropouts to spread them. He seemed satisfied with what he did.

I've seen advice to lay the bike down and pull up on the chainstay, one side at a time because both chainstays may not have the same tensile strength. But surely, to be able to pull up on one chainstay, you'd have to put your foot on the other one. That's hardly any different to using the threaded rod. I think the threaded rod will give you more control, and you would have to spread them a bit wider than your OLN to allow for them springing back.

Just one word of caution: Never spread the chainstays on an aluminum or carbon fiber frame.
If I knew how to ride a bike, properly, I'd do it every time

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Re: Steel molecules - do they get tired?

Postby simonineaston » 1 Aug 2020, 9:28pm

Never spread the chainstays on an aluminum or carbon fiber frame.
Those things are not proper metal - I have seen them... one is made from old frying pans and the other, from stiffened air. I do not believe in either of them.
ttfn, Simon in Easton
(currently enjoying a Moulton TSR & a nano Brompton...)

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Re: Steel molecules - do they get tired?

Postby Brucey » 1 Aug 2020, 9:41pm

OldLimey wrote:
I've seen advice to lay the bike down and pull up on the chainstay, one side at a time because both chainstays may not have the same tensile strength. But surely, to be able to pull up on one chainstay, you'd have to put your foot on the other one.....


foot on the down tube/seat lug/BB means you can bend one side at a time. It is much the fastest way of doing it.

cheers
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Re: Steel molecules - do they get tired?

Postby francovendee » 2 Aug 2020, 7:43am

Mick F wrote:
al_yrpal wrote:However long you hold a material like steel under stress within its elastic limit it will just spring back into shape immediately the stress is discontinued. That is how springs work. It doesnt get tired.

Tell that to a clock that's had its spring wound tight for years without running.

Leaf springs on old cars drop or loose their curve. Is this because they have been over stressed or just got tired?

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Re: Steel molecules - do they get tired?

Postby Bonefishblues » 2 Aug 2020, 7:51am

francovendee wrote:
Mick F wrote:
al_yrpal wrote:However long you hold a material like steel under stress within its elastic limit it will just spring back into shape immediately the stress is discontinued. That is how springs work. It doesnt get tired.

Tell that to a clock that's had its spring wound tight for years without running.

Leaf springs on old cars drop or loose their curve. Is this because they have been over stressed or just got tired?

As do car springs, also.

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Re: Steel molecules - do they get tired?

Postby al_yrpal » 2 Aug 2020, 7:58am

francovendee wrote:
Mick F wrote:
al_yrpal wrote:However long you hold a material like steel under stress within its elastic limit it will just spring back into shape immediately the stress is discontinued. That is how springs work. It doesnt get tired.

Tell that to a clock that's had its spring wound tight for years without running.

Leaf springs on old cars drop or loose their curve. Is this because they have been over stressed or just got tired?


Some materials work harden and I guess something like a leaf spring can suffer from metal fatigue and possibly creep.

https://idcspring.com/spring-lose-tensi ... ompressed/

Al
Touring on a bicycle is a great way to explore and appreciate the countryside and towns you pass through. Make a difference...

David9694
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Re: Steel molecules - do they get tired?

Postby David9694 » 2 Aug 2020, 8:27am

No, they get fatigued. My grade for O level Chemistry was so bad that those who missed the exam did better. Anyway, only elements have molecules.

I haven’t found the method you’re using to be very effective. I have a butcher’s block and the drawers when opened are just the right shape to shove in a drop out and support It. Then it’s bear down on the head end, swapping over dropouts as you go until you reach the desired width.

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Re: Steel molecules - do they get tired?

Postby Jdsk » 2 Aug 2020, 9:02am

David9694 wrote:Anyway, only elements have molecules.

What does that mean? I can't think of any way of interpreting it that isn't wrong.

Jonathan

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Re: Steel molecules - do they get tired?

Postby Jdsk » 2 Aug 2020, 9:08am

Most metal vehicle springs, whether leaf or coil or torsion bar, outlast the vehicle. Some break first.

Other suspension components such as shock absorbers, bushes and blocks wear out and cause drop.

But there's a whole industry that makes money out of replacing springs. Some of this is good practice, such as heavily loaded springs on commercial vehicles. A lot of it is fashion, and there are lots of enthusiasts who'll pay for them... easy to swap, cheap, change the ride height, pretend it's a racing car....

Jonathan