Another slack chain question

AASHTA

http://www.sheldonbrown.com/chains.html#stretch

Is'nt it just a combination of the wear leading to the chain sitting 'further in' on both chain ring and sprocket. Together with rivet wear, allowing the plates to pull further apart.

Yes, chains get longer but how would the plate actually stretch - what is it, rubber?

If each pin/link hole gets larger by 0.1mm just through wear and tear then across the whole chain it makes a much longer chain.

So the issue is with the word stretch, nobody is saying they don't get longer.

I let my chain slowly go slack and every week or so I reset the wheel - I don't bother with tugs as this weekly check forces me to tune up/check out the drive chain.

^ this. Plus stick an old tennis ball between the wheel and the seat tube. Roll the wheel to trap the ball and give you some good tension, but not too tight as stated here.

Yes, chains get longer but how would the plate actually stretch - what is it, rubber?

if it was just the inner bushings and pins, it wouldn't get two whole links longer?

Mirages are rare, and hallucinations don't occur that often either,

but mis understandings are common. I'd say the chance of the actual plates stretching is minimal, the pins waring and hole and bushings wearing is another matter. This gives the sames visual effect when two chains are hung up next to each other.

if it was just the inner bushings and pins, it wouldn't get two whole links longer?

Your chains are gaining links with age?

ha, I change them every 8 months or so.

well, if there are 150 links, at each pin getting 0.1mm bigger, that is 30mm extra, so yeah.

mdcc_tester has done a post about it somewhere, basically, the torque involved are not enough to stretch metal.

From Wickipedia:

The effect of wear on a roller chain is to increase the pitch (spacing of the links), causing the chain to grow longer. Note that this is due to wear at the pivoting pins and bushes, not from actual stretching of the metal (as does happen to some flexible steel components such as the hand-brake cable of a motor vehicle).

Yesterday, after putting up with my wheel slipping forward for a couple of weeks I put a chain tug back on my bike. Wound it up til it was tight, then let it off half a turn.

Perfect.

Silent drivetrain, easier to pedal.

Im no mechanical engineer but the the center to center distances from to pin to pin seem larger in an old chain and i think that will mean stretch.
when i have the time ill use a caliper to measure this distance and if possible the diameters of the pins.

related to this.
Which do you think it´s the main cause of having two different chain tensión places of the cranks?

Cog and chain wheel in different planes?
misalignment of the chain wheel with respect of the spider of the cranks?
bended chainring?

i observed that this effect is greater when using a wear out/strecht chain.

[QUOTE=arregi;1324442]Im no mechanical engineer but the the center to center distances from to pin to pin seem larger in an old chain and i think that will mean stretch.
/QUOTE]

that's because they are. the effective pitch of the chain increases, which wears the chainring and cog to fit the new pitch, but it is not due to the link plates stretching.

ok. got it.
pins are further apart but because the holes grow wider.

i disagree.
the pins and bushes wear yes, and the bushes end up loose on the worn pins. but they are internal and would not make the outside longer.

misalignment of the chain wheel with respect of the spider of the cranks?

I'm guessing this^

i disagree.
the pins and bushes wear yes, and the bushes end up loose on the worn pins. but they are internal and would not make the outside longer.

the length of the link doesn't increase but the centre to centre distance of the pins does, increasing the pitch.

i disagree.
the pins and bushes wear yes, and the bushes end up loose on the worn pins. but they are internal and would not make the outside longer.

But if the chain sits further in on the chainring and sprocket then it will effectivly seem longer.

If the chain is longer when examined off the bike. Then I call rivet wear. But its a separate effect.

So therefore, a chain DOES stretch with use and time.

The chain being made up of several parts, and wear between these parts causes the chain to become longer.

The plates are not the chain, but only part of the chain. These plates (apparently) do not stretch, but its the wear that occurs to the pins, bushings, and rollers that cause the "stretch" that is witnessed.

Would this be correct?

My reasoning is that a plate is not a chain, just as an engine is not a car. One part of a thing should not be referred to as if it is the whole mechanism?

I'd rep you oldtimer, but you have to do a funny first.

@GA2G, wear is not stretch, it wear.

gagz, stretches

Maybe its the understanding of the word "stretch", that may be confusing me, or others?

When an object is a given length, and remains that length when no other forces/factors are applied to it (heat, torque, etc), it remains its given length. But when an object increases in length, due to external forces/factors ....isn't this known as "stretching"?

I'm aware that the plates remain of fixed dimensions, but if referring to the before-and-after dimensions of a chain, couldn't the increase in overall length be called "stretch"?

"Wear" is what occurs to the indivual parts of the chain, but the overall effect is lengthening.

Yes murtleflaps, I do stretch, quite a bit. ;)