Steel molecules - do they get tired?

General cycling advice ( NOT technical ! )
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simonineaston
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Steel molecules - do they get tired?

Postby simonineaston » 1 Aug 2020, 10:47am

My rear drop-outs are slightly too narrow for my new hub - the dropouts are exactly 131mm apart at rest - the hub has an OLN measurement of exactly 135mm. I am using a piece of threaded stock to gently increase the gap between the dropouts. At the moment they are spread out to about 140mm, in the fond aniticpation that, unstressed, they will rest at 134mm.
Do you think that if I leave them spread out to 140mm for ages, the molecules in the metal will "get used to it" and stay there?? Or are they made of sterner stuff?
(As you have hopefully worked out, I'm not being entirely serious...)
ttfn, Simon in Easton
(currently enjoying a Moulton TSR & a nano Brompton...)

Jdsk
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Re: Steel molecules - do they get tired?

Postby Jdsk » 1 Aug 2020, 12:42pm

I know where the molecules are going...

“That is a very serious defalcation,” he said, “but all the same I will tell you the size of it. Everything is composed of small particles of itself, and they are flying around in concentric circles and arcs and segments and innumerable other geometrical figures too numerous to mention collectively, never standing still or resting but spinning away and darting hither and thither and back again, all the time on the go. These diminutive gentlemen are called atoms. Do you follow me intelligently?”

https://www.laphamsquarterly.org/comedy/flann-obrien-splits-atom

Jonathan

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al_yrpal
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Re: Steel molecules - do they get tired?

Postby al_yrpal » 1 Aug 2020, 1:11pm

No, its all to do with the elastic limit of the material and whether this has been exceeded. You will have to exceed the elastic limit to cause pernanent deformation and that will inevitably weaken it.

Here is information for steel....

https://www.cmrp.com/blog/faq/analysis- ... steel.html

Al
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freeflow
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Re: Steel molecules - do they get tired?

Postby freeflow » 1 Aug 2020, 1:12pm

There is no such thing as a steel molecule.

tim-b
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Re: Steel molecules - do they get tired?

Postby tim-b » 1 Aug 2020, 1:32pm

Hi
No, they don't get tired but you might have have alkynes of trouble
Regards
tim-b
~~~~¯\(ツ)/¯~~~~

PaulaT
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Re: Steel molecules - do they get tired?

Postby PaulaT » 1 Aug 2020, 1:44pm

freeflow wrote:There is no such thing as a steel molecule.


Totally correct.

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Re: Steel molecules - do they get tired?

Postby Vorpal » 1 Aug 2020, 2:02pm

simonineaston wrote:My rear drop-outs are slightly too narrow for my new hub - the dropouts are exactly 131mm apart at rest - the hub has an OLN measurement of exactly 135mm. I am using a piece of threaded stock to gently increase the gap between the dropouts. At the moment they are spread out to about 140mm, in the fond aniticpation that, unstressed, they will rest at 134mm.
Do you think that if I leave them spread out to 140mm for ages, the molecules in the metal will "get used to it" and stay there?? Or are they made of sterner stuff?
(As you have hopefully worked out, I'm not being entirely serious...)

What Al said.

If it were me, I wouldn't bother with the threaded stock.

You either need to get the frame spread (or do it yourself; there are a couple of threads on here about that), or use it as is. Unless the hub would have a problem with the little bit of inward pressure this would exert, the only problem with the use-as-is approach is getting it in and out if you have to repair a puncture by the side of the road.

If it were me, I'd probably try it without any frame modification.
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Bmblbzzz
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Re: Steel molecules - do they get tired?

Postby Bmblbzzz » 1 Aug 2020, 2:19pm

Nothing tires Bike of Steel -- except Kryptonite. So be careful what lock you use.

Jdsk
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Re: Steel molecules - do they get tired?

Postby Jdsk » 1 Aug 2020, 2:30pm

freeflow wrote:There is no such thing as a steel molecule.

I doubt if we're disagreeing about what steel is, but I find "steel molecules" a convenient and useful term.

Jonathan

freeflow
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Re: Steel molecules - do they get tired?

Postby freeflow » 1 Aug 2020, 4:43pm

More convenient than just 'steel'

Jdsk
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Re: Steel molecules - do they get tired?

Postby Jdsk » 1 Aug 2020, 4:45pm

If the aim is to explain the properties of the material, definitely.

Jonathan

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531colin
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Re: Steel molecules - do they get tired?

Postby 531colin » 1 Aug 2020, 4:47pm

simonineaston wrote:My rear drop-outs are slightly too narrow for my new hub - the dropouts are exactly 131mm apart at rest - the hub has an OLN measurement of exactly 135mm. I am using a piece of threaded stock to gently increase the gap between the dropouts. At the moment they are spread out to about 140mm, in the fond aniticpation that, unstressed, they will rest at 134mm.
Do you think that if I leave them spread out to 140mm for ages, the molecules in the metal will "get used to it" and stay there?? Or are they made of sterner stuff?
(As you have hopefully worked out, I'm not being entirely serious...)


You are unlikely to get a symmetrical increase in the OLN like that. Even if the right chainstay isn't dented to clear the chainwheel, the stays won't necessarily be exactly the same stiffness.
Put the frame on a concrete floor, supported by blocks of wood, so that you can stand on (say) the BB and the seat cluster. Pull up on one dropout until you feel it "yield"...ie you go past the elastic limit. Measure the increase in the OLN ....when you have gone from 131 to (say) 133, turn the frame over and repeat, aiming for (in this example) 135.

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

Postby Mick F » 1 Aug 2020, 4:47pm

Molecule.
molecule
noun Chemistry
a group of atoms bonded together, representing the smallest fundamental unit of a chemical compound that can take part in a chemical reaction.


Are we saying that steel isn't a compound?
Iron is an element Fe
Carbon is an element C

Steel is a combination of iron and carbon, is it not? :?:
Mick F. Cornwall

Jdsk
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Re: Steel molecules - do they get tired?

Postby Jdsk » 1 Aug 2020, 4:52pm

Steel is a mixture. And an alloy. It isn't a compound.

Some steels contains species other than iron and carbon.

Some of the components are monoatomic, others aren't.

...

And with all of those being true, and presumably, undisputed there's still a question of usage over "steel molecules".

Jonathan

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

Postby Mick F » 1 Aug 2020, 4:54pm

As for the OP question, I think you need to consider elasticity.
I've altered the rear ends of three bikes over recent years.

First was Mrs Mick F's bike, a Mixte frame with 120oln that I spread to 130oln
Next was my Moulton which came with a compromise of 132mm that drove me mad! :shock: So I squeezed it down to 130mm.
Third was our daughter's bike at 120mm that I spread to 130mm.

All done with a threaded bar, nuts and washers. The main thing to do, is to take the steel way beyond the elastic limit so it springs back to where you want it.

Do it by trial and error, but it's frightening how much you have to go before it springs to where you want it.
Mick F. Cornwall