IoW - and new cogs

John Hearns said:

By fantastic forward planning (actually, just luck)
I have booked accomodation just outside Havenstreet, which is
one of the control points.
Looking forward to the weekend.
Say hello to the bloke dressed in black on the red+white compact
framed bike as you pass me on the hills.

Hmmm... is there some u.r.c. secret sign or handshake?

Those who also post on the Cycling Plus Forum have agreed to put some
yellow tape or ribbon on the handlebar stem.
We'll do the same.

We are riding down to Southampton [1] then Red Funnel to Cowes.

[1] Trains won't take the trice and they aren't running anyway, due to
the regular bank holiday engineering fiascos.

We'll be pegging out our little tents just outside Cowes - and use the
Travellers Joy at Northwood as an evening base (8 real ales to sample) :-))

As you are starting at Havenstreet and its an anticlockwise route is
more than likely you will be passing us.

John B

JohnB said:

John Hearns said:

By fantastic forward planning (actually, just luck)
I have booked accomodation just outside Havenstreet, which is
one of the control points.
Looking forward to the weekend.
Say hello to the bloke dressed in black on the red+white compact
framed bike as you pass me on the hills.

Hmmm... is there some u.r.c. secret sign or handshake?

Those who also post on the Cycling Plus Forum have agreed to put some
yellow tape or ribbon on the handlebar stem.
We'll do the same.

We are riding down to Southampton [1] then Red Funnel to Cowes.

[1] Trains won't take the trice and they aren't running anyway, due to
the regular bank holiday engineering fiascos.

We'll be pegging out our little tents just outside Cowes - and use the
Travellers Joy at Northwood as an evening base (8 real ales to sample) :-))

As you are starting at Havenstreet and its an anticlockwise route is
more than likely you will be passing us.

And we (Mrs. Hall and I) are starting either at Havenstreet or
Bembridge. We're riding our Pino and should be in the company of other
tandem riders. We're staying at a holiday village near the Wishing
Well pub.

Tim

John Hearns said:

I put a new cassette on my road bike on Sunday,
plus a new SRAM chain and one new chainwheel
(the smaller chainweel is the original - I guess
it should be changed too???)

No need unless it's so worn that it actually causes problems with the new
chain. A worn cog or chainring will not accelerate chain wear (it's only
the other way round that's the problem).

~PB

JohnB said:

John Hearns said:

By fantastic forward planning (actually, just luck)
I have booked accomodation just outside Havenstreet, which is
one of the control points.
Looking forward to the weekend.
Say hello to the bloke dressed in black on the red+white compact
framed bike as you pass me on the hills.

Hmmm... is there some u.r.c. secret sign or handshake?

Those who also post on the Cycling Plus Forum have agreed to put some
yellow tape or ribbon on the handlebar stem.
We'll do the same.

Yellow tape for me; red as well also means urc?

MartinM said:

JohnB said:

John Hearns wrote:

Quoted message said:

Quoted message said:

Quoted message said:

Looking forward to the weekend.

Hmmm... is there some u.r.c. secret sign or handshake?

Those who also post on the Cycling Plus Forum have agreed to put some
yellow tape or ribbon on the handlebar stem.
We'll do the same.

Yellow tape for me; red as well also means urc?

Fine with me.

Red and yellow then - although mine's likely to be on the flagpole ;-)

John B

JohnB said:

MartinM said:

JohnB said:

John Hearns wrote:

Quoted message said:

Quoted message said:

> Looking forward to the weekend.
>
> Hmmm... is there some u.r.c. secret sign or handshake?

Those who also post on the Cycling Plus Forum have agreed to put

some

Quoted message said:

Quoted message said:

Quoted message said:

yellow tape or ribbon on the handlebar stem.
We'll do the same.

Yellow tape for me; red as well also means urc?

Fine with me.

Red and yellow then - although mine's likely to be on the flagpole

;-)

anywhere as long as not in your back pocket, or you could come back
with more than a badge ;-)

Simon Brooke said:

Quoted message said:

A worn cog or chainring will not accelerate chain wear (it's
only the other way round that's the problem).

Are you sure?

I feel sure, but I stand to be corrected. I tried to explain last time
the subject came up (quite recently); there were no replies. It'd be nice
if we could get to the bottom of it this time to save us repeating the
same ping pong again......

Quoted message said:

I've always been told that worn cogs and chainrings
greatly accelerate chain wear - and, indeed, that's my experience.

I think some people give that advice or excuse out of ignorance (assuming
that it must work both ways round), others out of laziness or time-saving,
eg. from shop mechanics who'd rather just bung all new stuff on in one
operation than give existing sprockets/rings a chance with a new chain
first.

Of course worn chains greatly accelerate cog/chainring wear, but the other
way around? I think you may be mistaken about your experience.

I would be interested in a full explaination as to how a worn sprocket or
chainring can accelerate chain wear.

The only chain wear that matters is chain elongation, caused by wear to
the pins inside the chain, caused by normal useage as the links pivot,
accelerated by dirt and load (and perhaps lack of lubrication). How do
worn teeth increase wear to the chain's pins?

Chain pitch increases as the chain wears, but the actual chainring pitch
does not -- the teeth remain the same distance apart. A worn chain rides
higher on the teeth as the effective pitch /diameter/ increases due to the
pitch mismatch, but what difference does that make to how quickly a new
chain then wears on the same ring? I can't see how it makes any
difference to chain wear.

~PB

Simon Brooke said:

Are you sure? I've always been told that worn cogs and chainrings
greatly accelerate chain wear - and, indeed, that's my experience.

Chains wear internally by the pins and bushes wearing down. This is
accelerated by grit and dirt inside the links, usually washed in there
by oil applied to the outside. On a chainring or cog the chain is
stationary relative to the teeth so the only wear can be the outside of
the roller sliding on and off the teeth i.e. where it doesn't matter.
Even with worn teeth the pitch of the teeth does not change so no
different forces on the chain even.

There is a common fallacy that chains wear by stretching. They wear by
the pins becoming increasingly loose in the bushes.

--
Tony

"A facility for quotation covers the absence of original thought" Lord
Peter Wimsey (Dorothy L. Sayers)

Simon Brooke said:

A new chain on a worn sprocket engages fully with only one tooth at any
one time.

How do you work that out? The tooth pitch has not changed, only the
profile, which means each tooth still engages with each link with a gap
opening up between the back of the roller and the (non-load bearing)
front of the next tooth because the load surface has worn down.

--
Tony

"A facility for quotation covers the absence of original thought" Lord
Peter Wimsey (Dorothy L. Sayers)

in message <[email hidden]>, Tony Raven

(') said:

Simon Brooke said:

A new chain on a worn sprocket engages fully with only one tooth at
any one time.

How do you work that out? The tooth pitch has not changed, only the
profile, which means each tooth still engages with each link with a
gap opening up between the back of the roller and the (non-load
bearing) front of the next tooth because the load surface has worn
down.

Try it. The tooth pitch may not have changed, but where the roller sits
with respect to the radius of the sprocket has changed (as the chain
wears the roller rides further up the slope of the tooth, which is what
creates the distinctive sharks-fin hook on a very worn sprocket). So
the tooth-spacing effectively _widens_ as the sprocket wears, which is
a bit counter intuitive.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

Morning had broken, and I found when I looked that we had run out
of copper roove nails.

Simon Brooke said:

Try it. The tooth pitch may not have changed, but where the roller
sits with respect to the radius of the sprocket has changed (as the
chain wears the roller rides further up the slope of the tooth, which
is what creates the distinctive sharks-fin hook on a very worn
sprocket). So the tooth-spacing effectively _widens_ as the sprocket
wears, which is a bit counter intuitive.

Where does the *new* chain sit?

The old worn chain rides up because its pitch has increased and so that's
the only way it can mesh.

~PB

Simon Brooke said:

Try it. The tooth pitch may not have changed, but where the roller
sits with respect to the radius of the sprocket has changed (as the
chain wears the roller rides further up the slope of the tooth, which
is what creates the distinctive sharks-fin hook on a very worn
sprocket). So the tooth-spacing effectively _widens_ as the sprocket
wears, which is a bit counter intuitive.

The *new* chain will sit in exactly the same place on the old sprocket as
a new chain would on a new sprocket -- because there's nothing to stop it
from doing so and the chain is being pulled against the sprocket -- unless
so little tooth material remains that it can't hold the chain under load,
in which case it will skip over the teeth then sit back down again.

~PB

in message <[email hidden]>, Pete Biggs

(') said:

Simon Brooke said:

Try it. The tooth pitch may not have changed, but where the roller
sits with respect to the radius of the sprocket has changed (as the
chain wears the roller rides further up the slope of the tooth, which
is what creates the distinctive sharks-fin hook on a very worn
sprocket). So the tooth-spacing effectively _widens_ as the sprocket
wears, which is a bit counter intuitive.

Where does the *new* chain sit?

The one engaged roller, as I described. Where the other rollers sit is
irrelevant as they aren't taking any load - there's no metal for them
to engage against. This must be the case because, as the inter-dental
gaps have widened if I'm right that the engaged roller is offset
radially, only a stretched chain could engage against every tooth.

Quoted message said:

The old worn chain rides up because its pitch has increased and so
that's the only way it can mesh.

It rides up because the profile of the tooth becomes increasingly
ramped.

At least, this is what I believe. I think I've got a really trashed
drivetrain on one of the bikes I'm cannibalising for a project, so if
you like I'll test the hypothesis. If not I may beg a really trashed
sprocket out of the LBS junk bin just to see.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

;; I'll have a proper rant later, when I get the time.

Simon Brooke said:

Quoted message said:

Where does the *new* chain sit?

The one engaged roller, as I described. Where the other rollers sit is
irrelevant as they aren't taking any load - there's no metal for them
to engage against.

Regardless of if and how well links engage with the teeth, the pins in the
"other" links are still taking load from the tension in the chain from
pedaling force, which too is unaffected by the number of links fully
engaging. This causes wear as the links pivot as they travel around the
sprockets.

I'm not happy about the "new chain on a worn sprocket engages fully with
only one tooth at any one time" statement, but I can't see how that would
make a difference anyway. What difference does it make to total wear if x
load is concentrated on one link at a time instead of x/6 load applied to
six links at a time?

Quoted message said:

This must be the case because, as the inter-dental
gaps have widened if I'm right that the engaged roller is offset
radially, only a stretched chain could engage against every tooth.

The chain doesn't have to *fully* engage with any teeth at all. Just
engaging with part of the teeth is usually enough, and that will happen
when there is still enough unworn material left at the *base* of the teeth
for the rollers to push against. In fact large chainrings can be in a
terrible-looking state and still work like this. Before the slopes get
too bad, rollers can drive without riding up by a significant amount.

See the picture 2/3 of the way down www.sheldonbrown.com/chains.html --
Material remains at the base of the teeth where a new chain would sit.

The example there is probably too worn to work with a new chain but one
not quite so bad would. The point is that there's still something there
where needed for the rollers to pull against without the roller needing to
ride up very much, let alone "fully engage". Therefore I think load is
spread over several teeth/links instead of all going on one.

Quoted message said:

Quoted message said:

The old worn chain rides up because its pitch has increased and so
that's the only way it can mesh.

Quoted message said:

It rides up because the profile of the tooth becomes increasingly
ramped.

An old chain wouldn't stay down even if the teeth were not worn. That's
why a worn out chain skips on a new sprocket. And the ramping is caused
by a loaded chain with an increased pitch.

However, after re-reading www.sheldonbrown.com/chains.html , I think I
have to accept that a new chain does ride up moderately worn teeth a bit
as well, causing the rollers to roll more, possibly increasing wear to the
innards (?)....Note that the article talks about chains with bushings on
this point, when most chains nowadays are bushingless. (It also
concentrates on rear sprockets and not front chainrings, which tend to be
larger).

I don't know how much difference that makes to this point and whether any
extra wear is enough to count as "great", as in "greatly accelerate chain
wear" as you put it. Apologies for saying there is no increase in wear at
all, if I'm wrong. Anyway, that's a different cause for the wear than
what your theory says, Simon :-)

Quoted message said:

At least, this is what I believe. I think I've got a really trashed
drivetrain on one of the bikes I'm cannibalising for a project, so if
you like I'll test the hypothesis. If not I may beg a really trashed
sprocket out of the LBS junk bin just to see.

It would be easier to see affects using a trashed large front chainring
instead of rear a sprocket. Unfortunately I binned my worst one ever (and
the crank it fitted as well). Lets see if theory sorts us out first.

Calling Sheldon Brown.... ;-)

~PB

Pete Biggs said:

I'm not happy about the "new chain on a worn sprocket engages fully
with only one tooth at any one time" statement, but I can't see how
that would make a difference anyway. What difference does it make to
total wear if x load is concentrated on one link at a time instead of
x/6 load applied to six links at a time?

Me neither and how does it actually work? One link in six engages and
pulls the cog round? So one engages, goes all the way round, lets go and
the sixth link along picks up at the start and carries on round with the
five in between doing nothing?

Even then how does it increase wear because for one revolution it may
take six times the load and six times the wear but unless the number of
teeth and number of links is exactly synchronised, next time round it
will take no load and no wear so will average out over multiple
revolutions of the chain.

--
Tony

"A facility for quotation covers the absence of original thought" Lord
Peter Wimsey (Dorothy L. Sayers)

Pete Biggs said:

What difference does it make to total wear if x
load is concentrated on one link at a time instead of x/6 load applied to
six links at a time?

Only makes a difference if wear is not linear with respect to load. If it
was quadratic (which it may be - Joe?) then it will wear faster.

...d

in message <[email hidden]>, Tony Raven

(') said:

Pete Biggs said:

I'm not happy about the "new chain on a worn sprocket engages fully
with only one tooth at any one time" statement, but I can't see how
that would make a difference anyway. What difference does it make to
total wear if x load is concentrated on one link at a time instead of
x/6 load applied to six links at a time?

Me neither and how does it actually work? One link in six engages and
pulls the cog round? So one engages, goes all the way round, lets go
and the sixth link along picks up at the start and carries on round
with the five in between doing nothing?

My assumption is each tooth grabs a link, but as soon as the next tooth
grabs a link all the strain comes off the previous one. This assumption
is of course testable... I've just phoned my LBS and asked them if
they've got a really worn sprocket in the scrap bin.

"Yes, I think so. Why do you want it?"

"There's some discussion on the Internet about whether worn sprockets
wear new chains."

"Yes, of course they do."

"Well, that's what I think, but other people are saying it makes no
difference."

"Well, they're wrong."

So I'll pick it up this afternoon and play with it tonight to see what
happens.

The experimental method I propose is as follows:

(i) clamp sprocket in the vice

(ii) drape new chain over sprocket

(iii) Attach shock-cord to the pulling side of the chain to simulate
load

If my hypothesis is correct the link on the second engaged tooth away
from the load will be slack and capable of being moved radially of the
order of half a millimetre. Would you agree this proposed experiment
would be conclusive? If not, what experimental method would you
propose?

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/
; ... of course nothing said here will be taken notice of by
; the W3C. The official place to be ignored is on www-style or
; www-html. -- George Lund

Simon Brooke said:

The experimental method I propose is as follows:

(i) clamp sprocket in the vice

(ii) drape new chain over sprocket

(iii) Attach shock-cord to the pulling side of the chain to simulate
load

If my hypothesis is correct the link on the second engaged tooth away
from the load will be slack and capable of being moved radially of the
order of half a millimetre. Would you agree this proposed experiment
would be conclusive?

I don't know. Would you mind if I x-posted this to rec.bicycles.tech?

~PB

Simon Brooke said:

My assumption is each tooth grabs a link, but as soon as the next tooth
grabs a link all the strain comes off the previous one. This assumption
is of course testable...

It still wouldn't make any difference because a link is now only engaged
for a fraction of the time it would be on an unworn sprocket. So
unless, as someone else pointed out, wear is superlinear with load, it
will average out at x times the load for 1/x times the time = the same wear.

I've just phoned my LBS and asked them if

Quoted message said:

they've got a really worn sprocket in the scrap bin.

"Yes, I think so. Why do you want it?"

"There's some discussion on the Internet about whether worn sprockets
wear new chains."

"Yes, of course they do."

"Well, that's what I think, but other people are saying it makes no
difference."

"Well, they're wrong."

It won't be the first time an LBS has got it wrong especially with why
sell a chain when you can sell a chain and sprocket cluster.

Quoted message said:

If my hypothesis is correct the link on the second engaged tooth away
from the load will be slack and capable of being moved radially of the
order of half a millimetre. Would you agree this proposed experiment
would be conclusive? If not, what experimental method would you
propose?

It says nothing at all about wear unless you can show that the load-time
product for the chain is much greater for a worn cog than an unworn one.
And I can't see any mechanism for that to happen from what you have
described. Indeed if the load-time product is greater then the work
done for the same movement of the wheel would go up proportionately and
you would find yourself riding a very sluggish and hard work bike.

--
Tony

"A facility for quotation covers the absence of original thought" Lord
Peter Wimsey (Dorothy L. Sayers)