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new chain, slack



 
 
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  #11  
Old December 19th 17, 04:54 AM posted to rec.bicycles.tech
Emanuel Berg[_2_]
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Posts: 743
Default new chain, slack

avagadro wrote:

Riding over sand with factory lube wudnot
produce slack for miles


By the way you mean this figuratively?

Because isn't 5 miles ~= 8 km? I think I ride
that every day 365d/y

$ units '5 miles' km
* 8.04672
/ 0.12427424

--
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  #12  
Old December 19th 17, 05:33 AM posted to rec.bicycles.tech
Frank Krygowski[_4_]
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Posts: 5,847
Default new chain, slack

On 12/18/2017 7:55 AM, Emanuel Berg wrote:
Another issue is - when does chain wear occur?
Is it when pedalling forward or is it when
starting and stopping, including the
foot/coaster brake?

Here we assume "normal" usage


It's reasonable to assume that wear is proportional to the product of
contact pressure and velocity.

That would mean that stopping with a coaster brake would cause almost no
wear on the chain. You need motion between the parts in contact to have
wear.

If you're starting from a stop by applying extra torque to the cranks
(as is usual) you would get extra wear at that moment. But it's only
for a moment. I suspect it has little overall effect.


--
- Frank Krygowski
  #13  
Old December 19th 17, 06:05 AM posted to rec.bicycles.tech
Emanuel Berg[_2_]
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Posts: 743
Default new chain, slack

Frank Krygowski wrote:

If you're starting from a stop by applying
extra torque to the cranks (as is usual) you
would get extra wear at that moment. But it's
only for a moment. I suspect it has little
overall effect.


OK, so when and why does wear occur?

And how long should you be able to go before
the slack exposes you a fraud mechanic and/or
the owner of crooked gear?

--
underground experts united
http://user.it.uu.se/~embe8573
  #14  
Old December 19th 17, 11:20 AM posted to rec.bicycles.tech
[email protected]
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Posts: 6,374
Default new chain, slack

Worn sprockets

Plato ? slowly I turned ....

See utube on worn bicycle sproxkets or harris brown worn sprockets chain rings cassettes

Chain chain ring replacement
  #15  
Old December 19th 17, 02:33 PM posted to rec.bicycles.tech
AMuzi
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Posts: 9,384
Default new chain, slack

On 12/19/2017 12:05 AM, Emanuel Berg wrote:
Frank Krygowski wrote:

If you're starting from a stop by applying
extra torque to the cranks (as is usual) you
would get extra wear at that moment. But it's
only for a moment. I suspect it has little
overall effect.


OK, so when and why does wear occur?

And how long should you be able to go before
the slack exposes you a fraud mechanic and/or
the owner of crooked gear?


Take a couple of minutes to read Jobst Brandt's chain wear
analysis in the purple text box he

http://www.yellowjersey.org/3%2732.html

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971


  #16  
Old December 19th 17, 03:07 PM posted to rec.bicycles.tech
Frank Krygowski[_4_]
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Posts: 5,847
Default new chain, slack

On 12/19/2017 1:05 AM, Emanuel Berg wrote:
Frank Krygowski wrote:

If you're starting from a stop by applying
extra torque to the cranks (as is usual) you
would get extra wear at that moment. But it's
only for a moment. I suspect it has little
overall effect.


OK, so when and why does wear occur?


Chain wear happens inside the chain's pivots. The wear is on the pins,
the rollers and any surface between them.

The wear happens when the pivot is under tension and the two links
connected by that pivot are either bending or straightening.

And how long should you be able to go before
the slack exposes you a fraud mechanic and/or
the owner of crooked gear?


For derailleur bikes, many people recommend replacing a chain when it's
worn (or "stretched") so it's one half percent longer than when new.
(This is most easily measured with a ruler marked in inches. Do you have
one of those?) But for a bike with only one rear cog, I think can go
much longer.

I'd say if the chain on a single speed or hub gear bike doesn't skip
when you pedal your hardest, it's probably OK. We'll see if others disagree.

--
- Frank Krygowski
  #17  
Old December 19th 17, 04:14 PM posted to rec.bicycles.tech
David Scheidt
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Posts: 1,218
Default new chain, slack

Frank Krygowski wrote:
:On 12/19/2017 1:05 AM, Emanuel Berg wrote:
: Frank Krygowski wrote:
:
: If you're starting from a stop by applying
: extra torque to the cranks (as is usual) you
: would get extra wear at that moment. But it's
: only for a moment. I suspect it has little
: overall effect.
:
: OK, so when and why does wear occur?

:Chain wear happens inside the chain's pivots. The wear is on the pins,
:the rollers and any surface between them.

:The wear happens when the pivot is under tension and the two links
:connected by that pivot are either bending or straightening.

: And how long should you be able to go before
: the slack exposes you a fraud mechanic and/or
: the owner of crooked gear?

:For derailleur bikes, many people recommend replacing a chain when it's
:worn (or "stretched") so it's one half percent longer than when new.
This is most easily measured with a ruler marked in inches. Do you have
ne of those?) But for a bike with only one rear cog, I think can go
:much longer.

:I'd say if the chain on a single speed or hub gear bike doesn't skip
:when you pedal your hardest, it's probably OK. We'll see if others disagree.

The issue with going too much longer is that you wear the crank teeth
and rear cog teeth. They cost more, and are harder to change, than a
chain. Single speed and IGH bikes can use a wide chain, which will
lost a long time (particularly if fitted with a good chain guard/case.

--
sig 22
  #18  
Old December 20th 17, 01:21 AM posted to rec.bicycles.tech
James[_8_]
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Posts: 5,711
Default new chain, slack

On 18/12/17 08:43, Emanuel Berg wrote:
It seems after putting on a new chain, it turns
really slack after only 2-3 weeks. When you
then restraighten it, it remains tight
considerably longer. Is this so or does
intuition play a trick on me? In general, how
many bike hours does a chain last?


2-3 weeks seems like only a short amount of time under "normal"
conditions. There are too many variables to quantify exactly "how long".

Is it possible the rear axle nuts were simply not done up quite tight
enough and the axle slipped forward in the drop out slots?

I'd expect at least 2000-6000km from a new chain to wear 1%, depending
on the conditions and the rider. The Wippermann chain test shows more
than a 3:1 wear rate from the best to worst chains they tested. (36 to
114 hours of their abusive test.)

http://www.cantitoeroad.com/Wipperma...ained_b_2.html

Standard bicycle chains measure 1/2 inch from pin centre to pin centre.
There are something close to 100 half links or 50 inches of chain, so 1%
is one half link or 1/2 inches of wear. That would mean the rear wheel
would need to be moved 1/4 inches rearward to take up the slack from a
worn out chain.

(Actual number of links or half links depends on the length of chain
stays and the crank and hub gear diameters.)

--
JS
  #19  
Old December 20th 17, 02:20 AM posted to rec.bicycles.tech
Frank Krygowski[_4_]
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Posts: 5,847
Default new chain, slack

On 12/19/2017 8:21 PM, James wrote:
On 18/12/17 08:43, Emanuel Berg wrote:
It seems after putting on a new chain, it turns
really slack after only 2-3 weeks. When you
then restraighten it, it remains tight
considerably longer. Is this so or does
intuition play a trick on me? In general, how
many bike hours does a chain last?


2-3 weeks seems like only a short amount of time under "normal"
conditions.* There are too many variables to quantify exactly "how long".

Is it possible the rear axle nuts were simply not done up quite tight
enough and the axle slipped forward in the drop out slots?

I'd expect at least 2000-6000km from a new chain to wear 1%, depending
on the conditions and the rider.* The Wippermann chain test shows more
than a 3:1 wear rate from the best to worst chains they tested.* (36 to
114 hours of their abusive test.)

http://www.cantitoeroad.com/Wipperma...ained_b_2.html

Standard bicycle chains measure 1/2 inch from pin centre to pin centre.
There are something close to 100 half links or 50 inches of chain, so 1%
is one half link or 1/2 inches of wear.* That would mean the rear wheel
would need to be moved 1/4 inches rearward to take up the slack from a
worn out chain.

(Actual number of links or half links depends on the length of chain
stays and the crank and hub gear diameters.)


Another factor: The geometry of the situation means it takes only a tiny
change in length (or position of the axle relative to the cranks) to
generate a noticeable amount of slack.

This has a couple possible implications. Here's one: sprockets
(especially chainrings on less expensive bikes) are seldom perfectly
round. Usually you can notice the change in tension (i.e. change in
visible slack) as you turn the cranks with the bike on a stand. I
suppose it's possible that the first estimate of chain "tightness"
happened with the chain on a high spot, the next one on a low spot.

Conversely, if someone installed a chain and happened to have it at a
low spot on the sprocket, then bolted the rear axle in place, the
crank's high spot might over-tension the chain. It might even have
enough leverage to pull the axle forward when a properly adjusted chain
would never do so. Or the over-tensioned chain might wear more quickly,
I suppose. (I learned about this problem in a related way back in my
pre-BMW days, when my motorcycles had drive chains.)

Finally, no matter what the situation, it seems the chain must have some
microscopic roughness - peaks and valleys - on mating parts. The peaks
would tend to wear off in the beginning generating at least some
clearance. Once the peaks wore, further wear would be much slower. This
is partly why engines are (or were) supposed to be carefully "run in" or
"broken in" when new.


--
- Frank Krygowski
  #20  
Old December 20th 17, 12:01 PM posted to rec.bicycles.tech
[email protected]
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Posts: 220
Default new chain, slack

On Tuesday, December 19, 2017 at 4:07:53 PM UTC+1, Frank Krygowski wrote:
On 12/19/2017 1:05 AM, Emanuel Berg wrote:
Frank Krygowski wrote:

If you're starting from a stop by applying
extra torque to the cranks (as is usual) you
would get extra wear at that moment. But it's
only for a moment. I suspect it has little
overall effect.


OK, so when and why does wear occur?


Chain wear happens inside the chain's pivots. The wear is on the pins,
the rollers and any surface between them.

The wear happens when the pivot is under tension and the two links
connected by that pivot are either bending or straightening.

And how long should you be able to go before
the slack exposes you a fraud mechanic and/or
the owner of crooked gear?


For derailleur bikes, many people recommend replacing a chain when it's
worn (or "stretched") so it's one half percent longer than when new.
(This is most easily measured with a ruler marked in inches. Do you have
one of those?) But for a bike with only one rear cog, I think can go
much longer.

I'd say if the chain on a single speed or hub gear bike doesn't skip
when you pedal your hardest, it's probably OK. We'll see if others disagree.


On a single speed you have the same wear criteria as with derailleur system if you want to replace the chain without replacing the cog or chainring. If you accept that you have to replace the cog and/or chainring when you replace the chain than you can go on until you can't tension the chain anymore or the teeth are completely gone.

Lou
 




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