Do frames go "dead" with age?

[mikeymustard]

@Yellow Saddle Are 5 and 7 not true?

Yes, the Bigfoot sneaks into your garage at night and pulls on them. He also lets down your tyres a bit

 

[Yellow Saddle]

@Yellow Saddle Are 5 and 7 not true?

No, for the same reason that frames don't go dead or soft.
Steel, continually strain-cycled at a point below yield does not yield. Put differently, no matter how many times you stretch steel below the point where it sets to a new length or shape, will not change shape. A practical example is a spring that does not soften with age. I have a few vintage watches and clocks in my collection, some are 120 years old, but the spring is still as good as the day it was coiled. Steel, for all intends and purposes, have an unlimited capacity in this way. Aluminium does not, that's whey alumiinium frames (think Cannondale) are designed to minimize flex. Even below alu's yield point, continuous stress cycles will fatigue the metal which then cracks. But it doesn't go soft or dies.

 

[mikeymustard]

@Yellow Saddle Are 5 and 7 not true?

Chains wear making the gaps bigger, so they seem stretched.
As far as cables are concerned, the initial 'stretch' is probably due to a combo of: spiral bound outer casing compressing and seating itself in the various stops a ferrules (modern indexing gear cables don't compress), plus pads and nipples bedding in; later 'stretch' is due to wearing of all components

 

[mikeymustard]

@Yellow Saddle but surely no.6 is true?

 

[mikeymustard]

(see http://www.ibiscycles.com/support/technical_articles/metallurgy_for_cyclists/the_basics/ )

thanks, interesting article

 

[Yellow Saddle]

Chains wear making the gaps bigger, so they seem stretched.
As far as cables are concerned, the initial 'stretch' is probably due to a combo of: spiral bound outer casing compressing and seating itself in the various stops a ferrules, plus pads and nipples bedding in; later 'stretch' is due to wearing of all components

Elongate is more apt than stretch when talking about wear in chains. A spiral bound outer casing will not compress under the conditions applicable to bicycle cables. The tension in cables is too low. The spiral is tightly bound and to get that to go tighter the compression has to take the steel into yield and there is just not enough space between the windings to overshoot the compression enough for that. No, cables don't compress nor do they stretch for equal but opposite reasons.

Myth no 6? Sorry, that should have been in my list of facts, not myths.

 

[mjr]

A spiral bound outer casing will not compress under the conditions applicable to bicycle cables. The tension in cables is too low. The spiral is tightly bound and to get that to go tighter the compression has to take the steel into yield and there is just not enough space between the windings to overshoot the compression enough for that.

Some outers are not a tight spiral inside, but have some gaps, so all the cable needs to do is compress the outer's metal into a solid spiral by compressing the plastic. I suspect another common source of "stretch" is cable clamps with insufficiently large grooves that flatten and straighten the inner cable's twist a bit, resulting in what seems like a slight "stretch" the first few times it's pulled to a stop. Both problems seem more common with cheaper parts IME and I expect you'd never sully your bikes with anything less than the best!

As for chains, you can keep typing elongating and elongation every time, but most will type "stretch"

 

[mikeymustard]

A spiral bound outer casing will not compress under the conditions applicable to bicycle cables.

So why do indexed gears need so called "compressionless" outers?

 

[Yellow Saddle]

Some outers are not a tight spiral inside, but have some gaps, so all the cable needs to do is compress the outer's metal into a solid spiral by compressing the plastic.

No. I'm yet to see a brake cable with gaps in the spiral. But even if there are gaps, the cable needs to compress beyond yield for the gaps to close permanently. Try it for yourself. Straighten a paper clip and attempt to put a 90 degree bend in it by folding it over the edge of a square table. You'll see that it doesn't stay at 90 degrees but springs back to say, 80. You have to overshoot. In a spiral there is no space for overshooting and if there is a gap after manufacturing, that gap will be there forever and a day.

I suspect another common source of "stretch" is cable clamps with insufficiently large grooves that flatten and straighten the inner cable's twist a bit, resulting in what seems like a slight "stretch" the first few times it's pulled to a stop. Both problems seem more common with cheaper parts IME and I expect you'd never sully your bikes with anything less than the best!

I get the picture and have heard that argument brought forward when I used to train people to change cables. That's not what happens because we can calculate the effect with a bit of trigonometry and it is absolutely negligible to plenty of decimals. Outers do however settle in ferrules if they are not correctly seated from the beginning. If you do everything by the book, there is no settlement of cable "stretch" (that hurt to get out) until the cable outer starts to display wear on the inside of curves. Like an oxbow curve in a river that grows to the outside of a curve, a cable inner wears on the inside of the curve through friction and fretting. This causes a relative change of length between the two. It is a relationship change, not a dimensional one in the sense of stretch.

As for chains, you can keep typing elongating and elongation every time, but most will type "stretch"

Sadly this is true. I suspect elongate will be written on my tombstone one day. As for not sullying my bike with rubbish cables. This is also true. Luckily the best cable is not the most expensive or fancy type and quality cable changed frequently makes a considerable difference in brake feel and indexing accuracy.

 

[Yellow Saddle]

So why do indexed gears need so called "compressionless" outers?

This is one of those misnomers of velo-speak. Rust-free is not the same as rust-proof and I suspect the use of rust-free in cutlery is a direct translation of the German rostfrei for stainless steel. It is just one of those wrong terms that we live with.

As for compressionless, it is meaningless. Does it mean that there is no compression in the outer or does it mean that the outer is compression proof?
Technically it is the former because gear housing is very un-compression proof if you get my drift. Gear housing is made from steel wire wound in a slack helix whereas true compression proof brake housing is wound from steel ribbon in a tight spiral.

I think it is one of those nonsense terms like Drive Side and Non-drive Side.

 

[mjr]

No. I'm yet to see a brake cable with gaps in the spiral.

Gear housing is made from steel wire wound in a slack helix whereas true compression proof brake housing is wound from steel ribbon in a tight spiral.

You don't remember shops that used to sell the same slack housing for both, then? Now I feel old...

 

[mikeymustard]

This is one of those misnomers of velo-speak

Ok, yeah I agree with you there, in fact I'm told "compressionless" outers can compress catastrophically if you put them on brakes!
Even the cable experts call it compression :
"Shift housing resists this flexing by using linear strands of wire that run the length of the housing parallel to the shift cable. These wires experience much lighter
loads, but are designed to keep the housing from compressing, resulting in clean, crisp shifting."
Jagwire's Tech Support Specialist Ben Oliver
http://m.pinkbike.com/news/To-The-Point-Shift-Cables-2013.html

 

[Yellow Saddle]

You don't remember shops that used to sell the same slack housing for both, then? Now I feel old...

I'll pretend that I don't. In those days my cables lasted the lifetime of the bicycle and I didn't know any better.

Just a note on "slack". I didn't mean that the (gear) housing is slack. It is indeed very stiff to prevent small radii. I meant a slack helix - a long slow helix as opposed to a tight coil.

 

[Yellow Saddle]

Ok, yeah I agree with you there, in fact I'm told "compressionless" outers can compress catastrophically if you put them on brakes!
Even the cable experts call it compression :
"Shift housing resists this flexing by using linear strands of wire that run the length of the housing parallel to the shift cable. These wires experience much lighter
loads, but are designed to keep the housing from compressing, resulting in clean, crisp shifting."
Jagwire's Tech Support Specialist Ben Oliver
http://m.pinkbike.com/news/To-The-Point-Shift-Cables-2013.html

I doubt Ben Oliver is the specialist his title suggest. Gear cable is under very little tension and I think the thick PVC plastic used in it is strong enough to prevent compression under those small loads. The linear strands are there to prevent tight radii which dramatically increase friction even for low-friction surfaces such as the plastic used on the outer's inner. We are not trying to prevent compression here, we are trying to make the very small movements introduced in the cable at the shifter, come out exactly as intended at the other end. This is critical in shifting with plenty of sprockets and small derailer movements. This is not critical in braking where another millimeter here or there makes no difference.

I have no doubt that if we could keep the gear cable straight from input to derailler we only need a plastic tube like that used on hydraulic hoses, without any supposedly compression-preventing steel.

 

[Yellow Saddle]

Ok, yeah I agree with you there, in fact I'm told "compressionless" outers can compress catastrophically if you put them on brakes!

This is not how they fail when used as brake housing. They fail by the inner cable popping out between the strands of outer wire. They herniate, if you like.