Chain wear measurement

In article ,
"Jay Beattie" wrote:

[...]

Perching a ruling on a dirty chain is hardly accurate either -- I
wonder what the error rate is in the usual $.39 wood ruler. Not
that I am sold on the expensive Park tool, either -- although it
is kind of fun and looks more technical than a ruler (even my
steel ruler).

No need to wonder.
I compared a dial caliper (0.01" ticks) with an engineer's
scale. They agree to the limit of observation. I compared
the engineer's scale with two steel desk rulers, a wooden
desk ruler, a steel tape measure, a roofer's square, a
machinist's square, a draftsman's tee square, and a 4 foot
builders ruler.

The wooden desk ruler is off by 0.01" over 12".
The steel tape measure is off by 0.01" over 12".
The tee square is off by 0.02" over 12".
The 4 foot builders ruler is off by 0.03" over 12" all
along its length.
The other scales showed no deviation from the engineer's
scale.

[...]

--
Michael Press

wrote:
On Mon, 15 Aug 2005 15:08:11 +0100, "Pete Biggs"
wrote:

[snip]


Park CC-2 can hardly be inserted into a new Campagnolo C9 chain to get a
zero reading but reads 0.25% for a new SRAM PC59. Does the average tech
realise that? Do you call that consistent?

~PB


Dear Pete,

It sounds as if the tool is consistent, while the two brands
of chain are surprisingly different in how they would fit on
a sprocket.

http://www.parktool.com/tools/CC_2BIG.shtml

Do these chains fit sprockets very differently? Are their
rollers different sizes?

Curiously,

Carl Fogel

1. sram come "pre-stretched". they're essentially an after-market chain
and as such more likely to be fitted onto previously used cogs so a
little over-spec makes them fit better.

2. a little over-spec means a little less time before replacement! good
for business.

Old Crow writes:

1. sram come "pre-stretched". they're essentially an after-market
chain and as such more likely to be fitted onto previously used cogs
so a little over-spec makes them fit better.

I have a box full of SRAM chains and none show any visible deviation
from 1/2" pitch over their length, all pins lining up with 1/2" marks
on a steel rule. Where do you get this information and have you
verified it or is this just some more myth and lore?

2. a little over-spec means a little less time before replacement!
good for business.

That sounds like libel to me.

Jobst Brandt

On Tue, 16 Aug 2005 05:09:59 GMT,
wrote:

Old Crow writes:

1. sram come "pre-stretched". they're essentially an after-market
chain and as such more likely to be fitted onto previously used cogs
so a little over-spec makes them fit better.

I have a box full of SRAM chains and none show any visible deviation
from 1/2" pitch over their length, all pins lining up with 1/2" marks
on a steel rule. Where do you get this information and have you
verified it or is this just some more myth and lore?

2. a little over-spec means a little less time before replacement!
good for business.

That sounds like libel to me.

Jobst Brandt

Dear Pete, Jim, and Jobst,

I admit that I'm startled by the idea of a half-inch chain
that isn't half-inch.

But Pete is saying that the same Park chain measurement tool
will barely fit into a new Campy chain, but gives a 0.25%
wear indicator on a new SRAM chain:

"Park CC-2 can hardly be inserted into a new Campagnolo C9
chain to get a zero reading but reads 0.25% for a new SRAM
PC59."

http://www.parktool.com/tools/CC_2BIG.shtml

It may take a few new chains, a micrometer, a Park tool, and
so forth to clear this up.

If anyone has a new chain that's shorter than a new SRAM
chain, even by just a thousandth of an inch per link,
hanging the new chains (110 links or so) from the same nail
against a wall should show a noticeable difference.

If it's a matter of new rollers being a tiny bit smaller,
that wouldn't affect the half-inch pitch, but it would
presumably make the chain fit a bit differently onto a
sprocket. Determining that would take a micrometer or some
manufacturer's detailed specifications.

Carl Fogel

On Mon, 15 Aug 2005 21:00:48 -0700, jim beam
wrote:

1. sram come "pre-stretched".

You're kidding, right?

JT

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In article ,
wrote:
If it's a matter of new rollers being a tiny bit smaller,
that wouldn't affect the half-inch pitch, but it would
presumably make the chain fit a bit differently onto a
sprocket. Determining that would take a micrometer or some
manufacturer's detailed specifications.

Roller wear isn't so much a matter of the rollers being
smaller on the outside, but more of clearance between the roller and
the bushing it spins on (or the bulges on the inner link plates on
bushingless chains). On the other hand, for analyzing the effect of
roller wear on how the chain meshes with sprockets, it's handy to
translate this clearance into an reduction in the diameter of a
clearance-free roller.

I agree though that roller wear does affect how the chain
fits the sprocket, but how it changes is rather subtle. On one hand,
Jobst's picture of rings hanging on nails is a good one, but on the
other hand, the forces experienced by all the rollers around a sprocket
aren't uniform in direction the way gravity on the hanging rings is.

I think what matters to the sprocket is the roller pitch,
this being ever so slightly different from the pin pitch, the rollers
being pushed outwards relative to the pins to live on a slightly larger
diameter circle. The 'exchange rate' of roller wear to pitch wear is
tricky, and I need to think about it some more, but offhand I can see it
depending on tooth shape and sprocket size. Pitch wear is more important
for larger sprockets, with the geometry for a few successive links
looking very much like the rings on nails picture. For smaller
sprockets, the relative importance of roller wear increases, but I'm
not sure yet if it ever gets to the point of actually mattering.

I believe the proportion in which Rohloff and Park's chain
measuring devices combine roller and pitch wear are completely arbitrary
though, and I'm not at all convinced they're any better (or even as
good) a measure as simple ruler measurement.

-Luns

wrote:
I admit that I'm startled by the idea of a half-inch chain
that isn't half-inch.

But Pete is saying that the same Park chain measurement tool
will barely fit into a new Campy chain, but gives a 0.25%
wear indicator on a new SRAM chain:

"Park CC-2 can hardly be inserted into a new Campagnolo C9
chain to get a zero reading but reads 0.25% for a new SRAM
PC59."

http://www.parktool.com/tools/CC_2BIG.shtml

It may take a few new chains, a micrometer, a Park tool, and
so forth to clear this up.

That would be good to do. Note that I'm not the only one to notice the
difference. There have been questions here before from posters who
couldn't figure out how to use their CC-2... because it can only be
/forced/ into a new Campag C9 chain. Park says "play" varies between
different makes of chain.

If anyone has a new chain that's shorter than a new SRAM
chain, even by just a thousandth of an inch per link,
hanging the new chains (110 links or so) from the same nail
against a wall should show a noticeable difference.

If it's a matter of new rollers being a tiny bit smaller,
that wouldn't affect the half-inch pitch, but it would
presumably make the chain fit a bit differently onto a
sprocket. Determining that would take a micrometer or some
manufacturer's detailed specifications.

Ditto. Cheap caliper + average eyeballs + cheap brain leaves me unable to
measure to more precision than 0.1mm or so.

~PB

wrote:
Old Crow writes:


1. sram come "pre-stretched". they're essentially an after-market
chain and as such more likely to be fitted onto previously used cogs
so a little over-spec makes them fit better.


I have a box full of SRAM chains and none show any visible deviation
from 1/2" pitch over their length, all pins lining up with 1/2" marks
on a steel rule. Where do you get this information and have you
verified it or is this just some more myth and lore?

do you own /any/ measuring instruments or not? you can't tell us the
tension on your spokes and now you can't get a set of calipers inside a
length of chain?

it's called "manufacturing tolerance" - as you would now if you'd
actually worked in any form of production environment. a box of the
same chain with the same tolerance says /nothing/. variance between
different types of chain tells you everything. measuring anything with
some old wooden ruler you found at the bottom of your old school bag is
just a joke.

"hi, nasa? my name's jobst brandt and i'm here to calibrate your
measuring instruments. yes, i have my old wooden ruler - it won't take
a second. thanks, i can find my own way out."



2. a little over-spec means a little less time before replacement!
good for business.


That sounds like libel to me.

eh? you are the most spectacular goddamned hypocrite. you blithely
slander and bull**** your way all over the net, utterly "free" to
masquerade opinion as fact, yet you can't acknowledge standard
manufacturing practice? oh, wait, you never /worked/ in a production
environment? sorry, my bad.


Jobst Brandt

wrote:
On Tue, 16 Aug 2005 05:09:59 GMT,
wrote:


Old Crow writes:


1. sram come "pre-stretched". they're essentially an after-market
chain and as such more likely to be fitted onto previously used cogs
so a little over-spec makes them fit better.

I have a box full of SRAM chains and none show any visible deviation

from 1/2" pitch over their length, all pins lining up with 1/2" marks

on a steel rule. Where do you get this information and have you
verified it or is this just some more myth and lore?


2. a little over-spec means a little less time before replacement!
good for business.

That sounds like libel to me.

Jobst Brandt


Dear Pete, Jim, and Jobst,

I admit that I'm startled by the idea of a half-inch chain
that isn't half-inch.

But Pete is saying that the same Park chain measurement tool
will barely fit into a new Campy chain, but gives a 0.25%
wear indicator on a new SRAM chain:

"Park CC-2 can hardly be inserted into a new Campagnolo C9
chain to get a zero reading but reads 0.25% for a new SRAM
PC59."

http://www.parktool.com/tools/CC_2BIG.shtml

It may take a few new chains, a micrometer, a Park tool, and
so forth to clear this up.

If anyone has a new chain that's shorter than a new SRAM
chain, even by just a thousandth of an inch per link,
hanging the new chains (110 links or so) from the same nail
against a wall should show a noticeable difference.

If it's a matter of new rollers being a tiny bit smaller,
that wouldn't affect the half-inch pitch, but it would
presumably make the chain fit a bit differently onto a
sprocket. Determining that would take a micrometer or some
manufacturer's detailed specifications.

Carl Fogel

carl, i have several different brands of new-in-box chain and a decent
dial caliper. i'll make some measurements for you tonight. it's an
exercise i've already done before, but i'll repeat for the record.

In article .com,
says...

I have a friend who has a new cheap chain hanging on a finishing nail
in the garage. When he cleans the chain, he puts it on the finishing
nail on top of the new chain. Easy to see that the old chain has
"stretched". Very dramatic when you look at the total "stretch" over a
4.5 foot chain. New chains are cheaper than chain checking tools.
$7.99 for a cheap chain at Nashbar compared to $9.95 for the Park chain
checking tool. And of course the truely frugal could just have his
replacement chain hanging in the garage and use it to check for chain
wear. And then install it when the old one is "stretched". Then get a
new replacement chain and repeat. No need to squander money on a $0.39
wood ruler.

It's not that hard to use a ruler. The other nice thing about a ruler is that
you can put it to other uses besides checking chains.
-------------
Alex