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casette shifting, again



 
 
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  #11  
Old December 13th 18, 03:56 AM posted to rec.bicycles.tech
John B. Slocomb
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Posts: 805
Default casette shifting, again

On Wed, 12 Dec 2018 21:24:57 -0500, Frank Krygowski
wrote:

On 12/12/2018 5:29 PM, Theodore Heise wrote:
On Wed, 12 Dec 2018 17:15:45 -0500,
Frank Krygowski wrote:
On 12/12/2018 4:58 PM, Emanuel Berg wrote:
I thought the general problem was the cable loosed its
integrity or internal strength, so it got just a bit longer,
much like a bicycle chain, but enough to mess things up?

The cable itself is not going to get stretched with use, if
that's what you mean. That would require forces many, many
times larger than what's being applied in normal operation.


I think that's correct, and yet on my tandems I've sometimes seem
some changes in shifting that I attribute to change in cable
length--maybe more due to temperature changes than to actual
physical stretching. For example, when we go out on a very warm
day after having ridden in cold weather for a time, I often have
to tighten the adjuster just a smidge.


I think apparent increases in cable length are probably due to shifting
of position of the cable inside the housing, or wear of the housing
where the cable follows it through curves, or the end of the housing
settling further into a housing stop. Maybe the temperature change
triggers something like that?

As I've mentioned, my most frequent index shifting adjustment happens
with my folding bike, especially if its sat folded for a while. I've
learned it's easiest to just change the levers to friction mode for a
while, then re-try the index mode. Somehow, most of the misadjustment
corrects itself - I guess by the cables settling into their old
equilibrium position.

I'm pretty sure that if it were feasible to run the shift cable through
a straight, rigid tube all the way from shifter to derailleur, I'd never
see that problem.


If you are going to use rigid tubes why not a rod? Similar to the old
rod operated brakes. :-)

cheers,

John B.


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  #12  
Old December 15th 18, 05:17 AM posted to rec.bicycles.tech
[email protected]
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Posts: 16
Default casette shifting, again

Rod brakes: you mean like this? [1] It is a Flying Pigeon, which I won't bother saving.

Shifting: more snow, still works. The new cable did it. Only I don't know why. Also I don't know if this cable needs lubing. Next time, will investigate closer.

[1] http://user.it.uu.se/~embe8573/bike/...rear-brake.jpg
  #13  
Old December 15th 18, 06:34 AM posted to rec.bicycles.tech
John B. Slocomb
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Posts: 805
Default casette shifting, again

On Fri, 14 Dec 2018 20:17:29 -0800 (PST), wrote:

Rod brakes: you mean like this? [1] It is a Flying Pigeon, which I won't bother saving.

Shifting: more snow, still works. The new cable did it. Only I don't know why. Also I don't know if this cable needs lubing. Next time, will investigate closer.

[1]
http://user.it.uu.se/~embe8573/bike/...rear-brake.jpg

Sort of :-) When I lived in Japan all the bicycles had brakes similar
to that.

Actually they were pretty poor brakes mainly due to the design of the
brake arms and small brake pads but the linkage worked very well and
didn't stretch. Another problem was that the rims were chrome plated
steel which was pretty slippery.


cheers,

John B.


  #14  
Old December 15th 18, 02:50 PM posted to rec.bicycles.tech
AMuzi
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Posts: 13,447
Default casette shifting, again

On 12/14/2018 11:34 PM, John B. Slocomb wrote:
On Fri, 14 Dec 2018 20:17:29 -0800 (PST), wrote:

Rod brakes: you mean like this? [1] It is a Flying Pigeon, which I won't bother saving.

Shifting: more snow, still works. The new cable did it. Only I don't know why. Also I don't know if this cable needs lubing. Next time, will investigate closer.

[1]
http://user.it.uu.se/~embe8573/bike/...rear-brake.jpg

Sort of :-) When I lived in Japan all the bicycles had brakes similar
to that.

Actually they were pretty poor brakes mainly due to the design of the
brake arms and small brake pads but the linkage worked very well and
didn't stretch. Another problem was that the rims were chrome plated
steel which was pretty slippery.



For braking, pad size is a minor factor. It's all swept
area, CF and leverage. You're right that linkage is
efficient but the leverage is minimal and rubber on chromed
steel has a low CF, made worse by dried hard pads.

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


  #15  
Old December 15th 18, 07:30 PM posted to rec.bicycles.tech
Emanuel Berg[_3_]
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Posts: 32
Default casette shifting, again

AMuzi wrote:

For braking, pad size is a minor factor.
It's all swept area, CF and leverage.
You're right that linkage is efficient but
the leverage is minimal and rubber on chromed
steel has a low CF, made worse by dried
hard pads.


OK, so now it got complicated...

Swept area, should that be big or small for the
brake to be efficient? Small, right? As in disc
brakes where say a single degree of braking on
the small disc translates to a much larger
distance on the big wheel?

Or are disc brakes more efficient because of
material interaction and other technology
improvements alone?

And if the linkage on rod brakes is efficient,
how can leverage be minimal unless there is
something wrong with the levers, and they seem
pretty straightforward to me? Or is it the
shackle that is pulled onto the rim, as opposed
to squeezed into/around it, which is
more efficient?

Also, CF, is that some material
interaction property?

--
underground experts united
http://user.it.uu.se/~embe8573
  #16  
Old December 15th 18, 09:53 PM posted to rec.bicycles.tech
Frank Krygowski[_4_]
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Posts: 10,538
Default casette shifting, again

On 12/15/2018 1:30 PM, Emanuel Berg wrote:
AMuzi wrote:

For braking, pad size is a minor factor.
It's all swept area, CF and leverage.
You're right that linkage is efficient but
the leverage is minimal and rubber on chromed
steel has a low CF, made worse by dried
hard pads.


OK, so now it got complicated...

Swept area, should that be big or small for the
brake to be efficient? Small, right? As in disc
brakes where say a single degree of braking on
the small disc translates to a much larger
distance on the big wheel?

Or are disc brakes more efficient because of
material interaction and other technology
improvements alone?

And if the linkage on rod brakes is efficient,
how can leverage be minimal unless there is
something wrong with the levers, and they seem
pretty straightforward to me? Or is it the
shackle that is pulled onto the rim, as opposed
to squeezed into/around it, which is
more efficient?

Also, CF, is that some material
interaction property?


Emanuel, with all due respect, you should spend the winter reading a
physics book or two. Or three. Skip the parts on electricity, atomic
physics, etc. Concentrate on forces, motion, work, energy etc. - the
parts that apply to bicycles.

I say that because words like "efficient" have carefully defined
technical meanings, and you tend to mis-apply them. "Leverage" is
perhaps less technical, but probably better expressed as "mechanical
advantage." And look up "swept area" for brakes (you can google it). By
CF, Andrew meant Coefficient of Friction. It's most often abbreviated
with the Greek letter "mu" which is hard to type into these discussions.

Really, you need more foundation in basic mechanics and physics. It will
allow you to understand the relevant mechanisms and to phrase your
questions much more clearly. This study will be well worth your time,
and will save the rest of us time as well.

--
- Frank Krygowski
  #17  
Old December 15th 18, 10:04 PM posted to rec.bicycles.tech
Emanuel Berg[_3_]
external usenet poster
 
Posts: 32
Default casette shifting, again

Frank Krygowski wrote:

Emanuel, with all due respect, you should
spend the winter reading a physics book or
two. Or three. Skip the parts on electricity,
atomic physics, etc. Concentrate on forces,
motion, work, energy etc. - the parts that
apply to bicycles. [...]


Blah blah blah, you have told me this at least
a dozen times by now. Probably because it is
easier to be didactic/demeaning than to
actually answer the questions.

--
underground experts united
http://user.it.uu.se/~embe8573
  #18  
Old December 15th 18, 10:34 PM posted to rec.bicycles.tech
AMuzi
external usenet poster
 
Posts: 13,447
Default casette shifting, again

On 12/15/2018 3:04 PM, Emanuel Berg wrote:
Frank Krygowski wrote:

Emanuel, with all due respect, you should
spend the winter reading a physics book or
two. Or three. Skip the parts on electricity,
atomic physics, etc. Concentrate on forces,
motion, work, energy etc. - the parts that
apply to bicycles. [...]


Blah blah blah, you have told me this at least
a dozen times by now. Probably because it is
easier to be didactic/demeaning than to
actually answer the questions.


Sincerely, Frank's advice is excellent. Visit a used book
store and find a basic physics textbook. It's well worth a
few Krona and a few hours of your time, if only to posit
questions here!


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


  #19  
Old December 15th 18, 10:59 PM posted to rec.bicycles.tech
AMuzi
external usenet poster
 
Posts: 13,447
Default casette shifting, again

On 12/15/2018 3:04 PM, Emanuel Berg wrote:
Frank Krygowski wrote:

Emanuel, with all due respect, you should
spend the winter reading a physics book or
two. Or three. Skip the parts on electricity,
atomic physics, etc. Concentrate on forces,
motion, work, energy etc. - the parts that
apply to bicycles. [...]


Blah blah blah, you have told me this at least
a dozen times by now. Probably because it is
easier to be didactic/demeaning than to
actually answer the questions.


more.

I left school without having slept through even one physics
class. My reference work here is a 1955 high school textbook
for $1 (9 Kr). I don't know all of even that, but I
understand the world well enough to know that this headline
last week:

https://www.dailymail.co.uk/sciencet...soon-2022.html

was completely ridiculous. The chamber pressures are in the
same range, but not power, not even within a magnitude*!
Power is work over time. Without some grasp of the actual
world, you would not have laughed aloud when reading the
headline, etc.

*A typical 120mm tank round is 7.5 kilos of depleted uranium
moving at 1700 m/s. The new 6.8 rifle typically moves 7.5
grams at 850 m/s. That's why you need basic physics.

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


  #20  
Old December 15th 18, 11:01 PM posted to rec.bicycles.tech
Emanuel Berg[_3_]
external usenet poster
 
Posts: 32
Default casette shifting, again

AMuzi wrote:

Blah blah blah, you have told me this at
least a dozen times by now. Probably because
it is easier to be didactic/demeaning than
to actually answer the questions.

Sincerely, Frank's advice is excellent.
Visit a used book store and find a basic
physics textbook. It's well worth a few Krona
and a few hours of your time, if only to
posit questions here!


I spent 6 years, 7 months, and 12 days at the
university. My degree project [1] is 153 pages.
I solved the same problem five other guys did
at two North-American universities. I don't
have to prove to anyone I can read and
understand whatever I put my mind to.

In fact, this has nothing to do with any of
this. This is the bike culture which for
whatever insane reason is snobbish
beyond belief.

You can all try this out for yourself.
Install Emacs, use it until you run into
a problem, then go to gnu.emacs.help and ask
about it. If you get the answer "you are not
using the terminology correctly, go read
a book, then come back" please show it to me,
as, in all my years in computing, I've never
ever seen that.

[1] http://user.it.uu.se/~embe8573/hs-li...ort/report.pdf

--
underground experts united
http://user.it.uu.se/~embe8573
 




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