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Freeing up stuck derailleur pantogram



 
 
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  #41  
Old February 9th 21, 08:11 PM posted to rec.bicycles.tech
Roger Merriman[_4_]
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Posts: 385
Default Freeing up stuck derailleur pantogram

Frank Krygowski wrote:
On 2/9/2021 8:44 AM, Roger Merriman wrote:
Frank Krygowski wrote:
On 2/4/2021 8:08 PM, News 2021 wrote:


Use a spring enough, and it will weaken.

Not necessarily, for any practical definition of "enough."

In fact, I'd say not usually.


I’d agree but I’ve certainly had bikes that the derailleur has become
sluggish, one was a old road bike with original kit and though it went
though the gears it was slow to do so.

And on the other end on my older MTB that is my commute bike that clocks up
the miles, And is rather a grandfather’s axe/brush I’ve also had to replace
the rear Derailleur few years back that just became sluggish.

In both cases where clean with fresh cables etc.


I think there may be many explanations for a "sluggish" derailleur
performance besides weakening springs. The first thing I'd check is
friction at the many moving points. In addition to the obvious hinges
and pivots, there can be less obvious, hidden friction points. I
mentioned the sliding contact between one derailleur's spring and an
inside surface of the derailleur. And I've dismantled old derailleurs
and found substances that were once grease, but now had the consistency
of wax.

In addition, cables can certainly have a dragging effect, sometimes from
hard-to-spot locations. I imagine changing a derailleur might
inadvertently improve alignment of the rear dropout's cable housing
loop, causing the new derailleur to be credited for something it didn't
do. Chain and sprocket condition can make a difference too.


In both cases all but the derailleur was changed, ie had fresh inner and
outers, due to the commute and the fact it’s a outside pet, cables don’t
last that long, maybe a year or so before they get sticky which can’t be
flushed out. They seem to shift fine covered in muck as is the habit with
uk winters, so I don’t really see the hinges being it.

I'm open to specific information on how a spring might weaken without
fracturing or partially cracking. (I mentioned the potential analogy
with vibrational stress relief.) But thinking about it in terms of
stress levels within the spring, material properties, metallurgical
structure etc. I don't know of a way it should happen, barring a design
that permits gross overload.

Thinking about it, I also have a old air pistol which is rather weak now,
it’s spring rather than air really, and after 70 or so years of plinking
cans it’s got a profile of a very fat pig jumping a big log!

Have you not sat on a old bed with sagging springs etc, nothing lasts for
ever.

Roger Merriman


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  #42  
Old February 10th 21, 05:45 AM posted to rec.bicycles.tech
pH
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Posts: 33
Default Freeing up stuck derailleur pantogram

On 2021-02-05, Jeff Liebermann wrote:

snip
https://www.ebay.co.uk/itm/Vintage-S...Cycle-Oil-Can-

227cc/274672630577?hash=item3ff3c3bb31:g:z-4AAOSw2w5gHUn4

Sewing machine and clock oils are usually based on common mineral oil.
The polymers in the oil are cracked into smaller lengths to give it a
lower viscosity. However, all petroleum based oils have the
irritating habit of attacking rubber seals and plastic parts. You
won't find that in a clock or sewing machine, both of which are mostly
metal on metal. So, the synthetic sewing machine substitutes are used
for those situations where the oil needs to touch rubber or plastic
(or possibly paint). What I like about all of them is that they act
the same whether hot, cold, wet, or dry.

For things with tight clearances which are stuck, try
Rock-N-Roll. It's unearthly in its penetration. I know this
sounds like a tout but it really is exceptional.


https://www.rocklube.com
I'll give it a try. Ummm... which version?
https://www.rocklube.com/products.html
I'll look at the MSDS sheet later. My guess(tm) is that it's mostly
mineral oil or a silicon based synthetic.

My favorite penetrating oil is Kroil, which is banned in the Peoples
Republic of California. I was somewhat involved in this mess:
https://ww2.arb.ca.gov/kano-laboratories-inc-settlement
I guess I shouldn't mention that I have a few unmarked cans of ozone
depleting Kroil left in my secret stash. No, you can't have any.
https://www.kroil.com


Hi Jeff.
I found a can of Kroil at my Mom's house. Man, it is odiferous and really
likes to travel.

I had to break my chain to get the derailleur off--had hoped I could avoid
that. Suntour XCD 7000.

All bad as new, now. Thanks for the tips

Note to Frank: This one had a cylindrical spring with a tang at each end, no
sliding part.

pH
  #43  
Old February 10th 21, 03:09 PM posted to rec.bicycles.tech
AMuzi
external usenet poster
 
Posts: 13,447
Default Freeing up stuck derailleur pantogram

On 2/9/2021 10:45 PM, pH wrote:
On 2021-02-05, Jeff Liebermann wrote:

snip
https://www.ebay.co.uk/itm/Vintage-S...Cycle-Oil-Can-

227cc/274672630577?hash=item3ff3c3bb31:g:z-4AAOSw2w5gHUn4

Sewing machine and clock oils are usually based on common mineral oil.
The polymers in the oil are cracked into smaller lengths to give it a
lower viscosity. However, all petroleum based oils have the
irritating habit of attacking rubber seals and plastic parts. You
won't find that in a clock or sewing machine, both of which are mostly
metal on metal. So, the synthetic sewing machine substitutes are used
for those situations where the oil needs to touch rubber or plastic
(or possibly paint). What I like about all of them is that they act
the same whether hot, cold, wet, or dry.

For things with tight clearances which are stuck, try
Rock-N-Roll. It's unearthly in its penetration. I know this
sounds like a tout but it really is exceptional.


https://www.rocklube.com
I'll give it a try. Ummm... which version?
https://www.rocklube.com/products.html
I'll look at the MSDS sheet later. My guess(tm) is that it's mostly
mineral oil or a silicon based synthetic.

My favorite penetrating oil is Kroil, which is banned in the Peoples
Republic of California. I was somewhat involved in this mess:
https://ww2.arb.ca.gov/kano-laboratories-inc-settlement
I guess I shouldn't mention that I have a few unmarked cans of ozone
depleting Kroil left in my secret stash. No, you can't have any.
https://www.kroil.com


Hi Jeff.
I found a can of Kroil at my Mom's house. Man, it is odiferous and really
likes to travel.

I had to break my chain to get the derailleur off--had hoped I could avoid
that. Suntour XCD 7000.

All bad as new, now. Thanks for the tips

Note to Frank: This one had a cylindrical spring with a tang at each end, no
sliding part.

pH


Suntour XCD rear changer? Just remove the lower pulley and
rotate the inner cage plate.

Yes, the pivot springs are cylindrical as you described.
Frank meant the body return spring.

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


 




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