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Chain stretch - actual tech.



 
 
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  #1  
Old February 21st 13, 07:35 AM posted to rec.bicycles.tech
James[_8_]
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Posts: 5,999
Default Chain stretch - actual tech.

I just came across this;

http://www.cantitoeroad.com/docs/con...ns_Stretch.pdf

I can't see whether the stretch was plastic or elastic. The length
doesn't appear to have been measured again with a 10kg load.

If it's plastic ... ouch! I hope it's not. I don't think it can be.

0.5% under 150 kg load. 39 tooth CR has a radius of about 79mm, and
175mm cranks gives a force multiplier of 2.2. A 75kg dude could easily
stretch a stretchy chain 0.5% just by standing on the pedals.

--
JS.
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  #2  
Old February 21st 13, 08:18 AM posted to rec.bicycles.tech
Jeff Liebermann
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Posts: 3,096
Default Chain stretch - actual tech.

On Thu, 21 Feb 2013 18:35:49 +1100, James
wrote:

I just came across this;
http://www.cantitoeroad.com/docs/con...ns_Stretch.pdf


I wish you wouldn't post interesting items just before I go to sleep.

I can't see whether the stretch was plastic or elastic. The length
doesn't appear to have been measured again with a 10kg load.


Yeah, that's what I was thinking. Are they measuring metal
deformation or are they measuring a spring.

If it's plastic ... ouch! I hope it's not. I don't think it can be.


It's not. My guess(tm) is that they took brand new chains, out of the
box, and ran the test. No breakin and a 10Kg preload is probably not
sufficient. The new chains will still have microscopic stamping and
machining defects that need to be worked out before such a test.

0.5% under 150 kg load. 39 tooth CR has a radius of about 79mm, and
175mm cranks gives a force multiplier of 2.2. A 75kg dude could easily
stretch a stretchy chain 0.5% just by standing on the pedals.


Ok, let's grind the numbers. The worst chain (KMC X 10 SL Gold)
failed with a total stretch of 2.15mm @ 150Kg. The test chains were
31 links long or about:
31 / 24 * 1ft * 30.48cm/ft = 39cm
Sanity check... the percent stretch should be:
2.15 / 39 * 100% = 5.5%
which agrees with the chart of test data.

According to conventional wisdom, a chain should be replaced when it
stretches 1/16" out of 24 links or 1ft. That:
0.0625" / 12" * 100% = 0.52%

So, by conventional wisdom, ALL the chains in the test should have
been immediately tossed because they had stretched up to 10 times the
acceptable limit for chain stretch. Something is wrong, very wrong
(hopefully not with my logic because I'm almost asleep at the
keyboard).

--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
  #3  
Old February 21st 13, 12:38 PM posted to rec.bicycles.tech
datakoll
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Posts: 7,793
Default Chain stretch - actual tech.

CHAINS wear elliptically uh egg shaped rollers.

If cleaned and lubed then hung....placing an empty tin of horsemeat under the chain off course...chain will elongate as garvity pulls rollers around seating large ends up: the larger end's steel wall thinner than the narrower end.
  #4  
Old February 21st 13, 12:45 PM posted to rec.bicycles.tech
thirty-six
external usenet poster
 
Posts: 10,049
Default Chain stretch - actual tech.

On Feb 21, 7:35*am, James wrote:
I just came across this;

http://www.cantitoeroad.com/docs/con...ns_Stretch.pdf

I can't see whether the stretch was plastic or elastic. *The length
doesn't appear to have been measured again with a 10kg load.

If it's plastic ... ouch! *I hope it's not. *I don't think it can be.

0.5% under 150 kg load. *39 tooth CR has a radius of about 79mm, and
175mm cranks gives a force multiplier of 2.2. *A 75kg dude could easily
stretch a stretchy chain 0.5% just by standing on the pedals.

--
JS.


I'm assuming it's elastic deformation. I've always liked the Connex
design as its the same proven design as the old Renold bicycle chains
and they never gave trouble. The exact conditions of service are hard
to pin down and it's best to go by proven designs. 1/8" bushed chain
isn't used on the track for fanciful reasons, it's used because it
works and doesn't break.
  #5  
Old February 21st 13, 12:58 PM posted to rec.bicycles.tech
thirty-six
external usenet poster
 
Posts: 10,049
Default Chain stretch - actual tech.

On Feb 21, 8:18*am, Jeff Liebermann wrote:
On Thu, 21 Feb 2013 18:35:49 +1100, James
wrote:

I just came across this;
http://www.cantitoeroad.com/docs/con...ns_Stretch.pdf


I wish you wouldn't post interesting items just before I go to sleep.

I can't see whether the stretch was plastic or elastic. *The length
doesn't appear to have been measured again with a 10kg load.


Yeah, that's what I was thinking. *Are they measuring metal
deformation or are they measuring a spring.

If it's plastic ... ouch! *I hope it's not. *I don't think it can be..


It's not. *My guess(tm) is that they took brand new chains, out of the
box, and ran the test. *No breakin and a 10Kg preload is probably not
sufficient. *The new chains will still have microscopic stamping and
machining defects that need to be worked out before such a test.

0.5% under 150 kg load. *39 tooth CR has a radius of about 79mm, and
175mm cranks gives a force multiplier of 2.2. *A 75kg dude could easily
stretch a stretchy chain 0.5% just by standing on the pedals.


Ok, let's grind the numbers. *The worst chain (KMC X 10 SL Gold)
failed with a total stretch of 2.15mm @ 150Kg. *The test chains were
31 links long or about:
* 31 / 24 * 1ft * 30.48cm/ft = 39cm
Sanity check... the percent stretch should be:
* 2.15 / 39 * 100% = 5.5%
which agrees with the chart of test data.

According to conventional wisdom, a chain should be replaced when it
stretches 1/16" out of 24 links or 1ft. *That:
* 0.0625" / 12" * 100% = 0.52%


2% stretch is recommended as the limit by Wipperman (but perhaps not
strictly apply with silly small teeth on modern multi-sprocket
bikes). For 99% of the time all the chains will be below that level
of elongation taking both wear and active load into account.


So, by conventional wisdom, ALL the chains in the test should have
been immediately tossed because they had stretched up to 10 times the
acceptable limit for chain stretch. *Something is wrong, very wrong
(hopefully not with my logic because I'm almost asleep at the
keyboard).


I'll not be loading the chain of my "racing" bike with a consistent
load of 150kg anytime soon.

It's more realistic to measure the load at which one can sustain (for
at least 10 minutes) with purely nasal breathing.
  #6  
Old February 21st 13, 01:55 PM posted to rec.bicycles.tech
datakoll
external usenet poster
 
Posts: 7,793
Default Chain stretch - actual tech.

On Thursday, I discovered the hung chain measuremt addcidently with 2-3 used/repaired chains measured horizonatally on the chain board then hung allowing lube drying.

Off course when remeasured 3-4 days later using Epic at prob 100 degrees on thinner cleaned chains, chains meassured disappointingly longer and waaaay over spec.

I imagine this is the more exact chain measure procedure with a steel guide hung downward with chain...no discurbing !

also a useful visual on chain materials
  #7  
Old February 21st 13, 03:11 PM posted to rec.bicycles.tech
Jay Beattie
external usenet poster
 
Posts: 4,322
Default Chain stretch - actual tech.

On Feb 21, 12:18*am, Jeff Liebermann wrote:
On Thu, 21 Feb 2013 18:35:49 +1100, James
wrote:

I just came across this;
http://www.cantitoeroad.com/docs/con...ns_Stretch.pdf


I wish you wouldn't post interesting items just before I go to sleep.

I can't see whether the stretch was plastic or elastic. *The length
doesn't appear to have been measured again with a 10kg load.


Yeah, that's what I was thinking. *Are they measuring metal
deformation or are they measuring a spring.

If it's plastic ... ouch! *I hope it's not. *I don't think it can be..


It's not. *My guess(tm) is that they took brand new chains, out of the
box, and ran the test. *No breakin and a 10Kg preload is probably not
sufficient. *The new chains will still have microscopic stamping and
machining defects that need to be worked out before such a test.

0.5% under 150 kg load. *39 tooth CR has a radius of about 79mm, and
175mm cranks gives a force multiplier of 2.2. *A 75kg dude could easily
stretch a stretchy chain 0.5% just by standing on the pedals.


Ok, let's grind the numbers. *The worst chain (KMC X 10 SL Gold)
failed with a total stretch of 2.15mm @ 150Kg. *The test chains were
31 links long or about:
* 31 / 24 * 1ft * 30.48cm/ft = 39cm
Sanity check... the percent stretch should be:
* 2.15 / 39 * 100% = 5.5%
which agrees with the chart of test data.

According to conventional wisdom, a chain should be replaced when it
stretches 1/16" out of 24 links or 1ft. *That:
* 0.0625" / 12" * 100% = 0.52%

So, by conventional wisdom, ALL the chains in the test should have
been immediately tossed because they had stretched up to 10 times the
acceptable limit for chain stretch. *Something is wrong, very wrong
(hopefully not with my logic because I'm almost asleep at the
keyboard).


Or we're talking about elastic and not plastic deformation. I've
never measured chain elongation while riding hard. Maybe the
unsupported section of my old SRAM chain is flexing like a giant
rubber band! I'm probably wasting enough watts to light a small city!

-- Jay Beattie.
  #8  
Old February 21st 13, 05:13 PM posted to rec.bicycles.tech
Jeff Liebermann
external usenet poster
 
Posts: 3,096
Default Chain stretch - actual tech.

On Thu, 21 Feb 2013 04:58:52 -0800 (PST), thirty-six
wrote:

According to conventional wisdom, a chain should be replaced when it
stretches 1/16" out of 24 links or 1ft. *That:
* 0.0625" / 12" * 100% = 0.52%


This author recommends 0.52%
http://www.kronowit.com/bicycling/chainstretch.html
which agrees with
http://www.sheldonbrown.com/chains.html
"If the rivet is 1/16" past the mark, you should replace
the chain, but the sprockets are probably undamaged."

Again, it's uncertain if the measured deformation is permanent
(plastic) or temporary (elastic).

I'm beginning to wonder if the test is really a measurement of how
much force it takes to squeeze the lubricant out of the bushings.
31 links should be:
31 * 0.500in/link * 25.4mm/in = 393.7mm
If the chains were packed with grease or wax, the initial 10Kg load
should be less than 393.7mm. However, they're all greater, which
eliminates that theory. Oh well.

2% stretch is recommended as the limit by Wipperman (but perhaps not
strictly apply with silly small teeth on modern multi-sprocket
bikes). For 99% of the time all the chains will be below that level
of elongation taking both wear and active load into account.


It's Wippermann with 2 n's at the end. Having a similar last name
makes me rather sensitive to such creative spelling.

2% seems rather high, unless the sprocket teeth are correspondingly
worn.

Wippermann tool, which seems to be a go/no-go test, without any
measurements:
http://www.cantitoeroad.com/chain-wear-indicator-stainless-steel-wippermann

When they sponsored a chain wear test, a run-in test was performed
before making measurements. However, there's no indication that they
did that in this static test.
http://www.youtube.com/watch?v=RGjcD8xEu8o
The chains were considered to have failed at 1% elongation.

I'll not be loading the chain of my "racing" bike with a consistent
load of 150kg anytime soon.

It's more realistic to measure the load at which one can sustain (for
at least 10 minutes) with purely nasal breathing.


I would prefer to see a range of loads extending to well beyond what a
human could possibly produce so I can see where the curve is going. I
also would like to see deformation IN BOTH DIRECTIONS forming
something like the usual stress/strain hysteresis curve. That is used
to show both plastic and elastic deformation. Three data points is
not sufficient to generate a meaningful trend line or hysteresis
curve. In addition, it would be nice to be sure that they were
measuring chain stretch and not lubricant compression, which would
require a solvent bath to remove the lube before testing.

--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
  #9  
Old February 21st 13, 07:37 PM posted to rec.bicycles.tech
davethedave[_2_]
external usenet poster
 
Posts: 602
Default Chain stretch - actual tech.

On Thu, 21 Feb 2013 18:35:49 +1100, James wrote:

I just came across this;

http://www.cantitoeroad.com/docs/con...ns_Stretch.pdf

I can't see whether the stretch was plastic or elastic. The length
doesn't appear to have been measured again with a 10kg load.

If it's plastic ... ouch! I hope it's not. I don't think it can be.

0.5% under 150 kg load. 39 tooth CR has a radius of about 79mm, and
175mm cranks gives a force multiplier of 2.2. A 75kg dude could easily
stretch a stretchy chain 0.5% just by standing on the pedals.


Wow! Manufacturer in manufacturer funded, manufacturer conducted research
proves our **** doesn't stink shocker!
--
davethedave
  #10  
Old February 21st 13, 09:31 PM posted to rec.bicycles.tech
James[_8_]
external usenet poster
 
Posts: 5,999
Default Chain stretch - actual tech.

On 22/02/13 06:37, davethedave wrote:
On Thu, 21 Feb 2013 18:35:49 +1100, James wrote:

I just came across this;

http://www.cantitoeroad.com/docs/con...ns_Stretch.pdf

I can't see whether the stretch was plastic or elastic. The length
doesn't appear to have been measured again with a 10kg load.

If it's plastic ... ouch! I hope it's not. I don't think it can be.

0.5% under 150 kg load. 39 tooth CR has a radius of about 79mm, and
175mm cranks gives a force multiplier of 2.2. A 75kg dude could easily
stretch a stretchy chain 0.5% just by standing on the pedals.


Wow! Manufacturer in manufacturer funded, manufacturer conducted research
proves our **** doesn't stink shocker!


It's right up there with a certain bicycle light manufacturer, eh?

Still, when it's the only test around... Or are there independent chain
tests available that you know of?

--
JS.
 




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