Freeing up stuck derailleur pantogram

Trying out slrn...hope I can get it to work okay.

My old SunTour XCPro was getting old and tired, the jockey wheels (idler
sprockets?) were worn down and annoyingly, it would not shift into 6th gear
on the freewheel (SunTour Ultra 6 or Winner pro, something like that).

I put on an old XCD out of my junk box (complete w/ red bullseye type
pulleys) and life was good again.

BUT...it did not take long before the darn thing gummed up and would not
shift back down to smaller cogs *at all*. This was about over the course of
a month. I've not put many miles on this year so far, so it's been in the
garage and it's been rainy and I'm only a few miles from the coast as the
crow flies...but....still.

I released the cable and confirmed that the thing was frozen up. A few
drops of oil has set things mostly to right on the pivots...but really..

Q; Should I have used oil or something lighter?
Q: What about simply a propane torch?
Q: Should I pry the joints apart ever so slightly of the pantogram assembly
to loosen things up?

It still won't go onto the smallest cog...just like the old one.

I've never really had this problem pop up like this which is why I ask if I
should pry at the joints or something.

pH in Aptos

On Thu, 04 Feb 2021 07:01:27 +0000, D. Pureheart Steinbruner scribed:

Trying out slrn...hope I can get it to work okay.

My old SunTour XCPro was getting old and tired,

Is it spring return?
IME, the sprigs wear out and I found myself needing to do mainteance/
cening a lot more.

On 2/4/2021 1:01 AM, D. Pureheart Steinbruner wrote:
Trying out slrn...hope I can get it to work okay.

My old SunTour XCPro was getting old and tired, the jockey wheels (idler
sprockets?) were worn down and annoyingly, it would not shift into 6th gear
on the freewheel (SunTour Ultra 6 or Winner pro, something like that).

I put on an old XCD out of my junk box (complete w/ red bullseye type
pulleys) and life was good again.

BUT...it did not take long before the darn thing gummed up and would not
shift back down to smaller cogs *at all*. This was about over the course of
a month. I've not put many miles on this year so far, so it's been in the
garage and it's been rainy and I'm only a few miles from the coast as the
crow flies...but....still.

I released the cable and confirmed that the thing was frozen up. A few
drops of oil has set things mostly to right on the pivots...but really..

Q; Should I have used oil or something lighter?
Q: What about simply a propane torch?
Q: Should I pry the joints apart ever so slightly of the pantogram assembly
to loosen things up?

It still won't go onto the smallest cog...just like the old one.

I've never really had this problem pop up like this which is why I ask if I
should pry at the joints or something.

pH in Aptos


Replacing the rollers in your XC Pro is a good path too.

Good for you to disconnect the gear wire so as to identify
an actual body problem. After sitting around for 30 years it
could be corrosion in the pivots or maybe just dried
lubricant. Oil is fine, every year or more depending on
ambient crud and frequency of use. For recalcitrant body
pivots try Rock-N-Roll it's especially effective in those.

Do not use heat and do not try to prise open the pivots.

If you have compressed air available, lubricate and work the
pivots at the bench, spray out, repeat until there's no more
crud escaping then oil well, wipe and re install. I would
assume given your area that you have dried lubricant in
there and not sal****er corrosion which means a complete
victory is very likely with small effort.

If your XCD body shows pavement scars from being smashed and
does not respond to clean/lube, then I would go with the XC Pro.

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

On 2/4/2021 4:24 AM, News 2021 wrote:
On Thu, 04 Feb 2021 07:01:27 +0000, D. Pureheart Steinbruner scribed:

Trying out slrn...hope I can get it to work okay.

My old SunTour XCPro was getting old and tired,

Is it spring return?
IME, the sprigs wear out and I found myself needing to do mainteance/
cening a lot more.



IME steel springs do not wear out.
They do get overly tensioned until the end snaps off which
is 'user error' not 'product failure'. Pivots corrode,
clearances go both over(wear) and under(rust) spec but
springs do not 'wear out'.

Fatigue failure in normal use is almost unknown.

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

On 2/4/2021 10:17 AM, AMuzi wrote:
On 2/4/2021 1:01 AM, D. Pureheart Steinbruner wrote:
Trying out slrn...hope I can get it to work okay.

My old SunTour XCPro was getting old and tired, the jockey wheels (idler
sprockets?) were worn down and annoyingly, it would not shift into 6th
gear
on the freewheel (SunTour Ultra 6 or Winner pro, something like that).

I put on an old XCD out of my junk box (complete w/ red bullseye type
pulleys) and life was good again.

BUT...it did not take long before the darn thing gummed up and would not
shift back down to smaller cogs *at all*.Â* This was about over the
course of
a month.Â* I've not put many miles on this year so far, so it's been in
the
garage and it's been rainy and I'm only a few miles from the coast as the
crow flies...but....still.

I released the cable and confirmed that the thing was frozen up.Â* A few
drops of oil has set things mostly to right on the pivots...but really..

Q; Should I have used oil or something lighter?
Q: What about simply a propane torch?
Q: Should I pry the joints apart ever so slightly of the pantogram
assembly
to loosen things up?

It still won't go onto the smallest cog...just like the old one.

I've never really had this problem pop up like this which is why I ask
if I
should pry at the joints or something.

pH in Aptos


Replacing the rollers in your XC Pro is a good path too.

Good for you to disconnect the gear wire so as to identify an actual
body problem. After sitting around for 30 years it could be corrosion in
the pivots or maybe just dried lubricant.Â* Oil is fine, every year or
more depending on ambient crud and frequency of use. For recalcitrant
body pivots try Rock-N-Roll it's especially effective in those.

Do not use heat and do not try to prise open the pivots.

I strongly agree!

If you have compressed air available, lubricate and work the pivots at
the bench, spray out, repeat until there's no more crud escaping then
oil well, wipe and re install. I would assume given your area that you
have dried lubricant in there and not sal****er corrosion which means a
complete victory is very likely with small effort.

If your XCD body shows pavement scars from being smashed and does not
respond to clean/lube, then I would go with the XC Pro.

I'd spend some time moving the derailleur body by hand, carefully
feeling and looking to see if I could spot the source of friction. And
yes, I'd flush every moveable joint repeatedly with penetrating oil (I
like PB Blaster) then lube with light oil.

On at least some SunTour derailleurs (like the Superbe Pro on one of my
bikes) the main spring ends in a sort of loop that has sliding contact
with the inner surface of a parallelogram arm. That sliding contact can
get sticky and hamper shifting to smaller cogs. Be sure it's nice and slick.

--
- Frank Krygowski

On Thu, 04 Feb 2021 09:21:30 -0600, AMuzi scribed:

On 2/4/2021 4:24 AM, News 2021 wrote:
On Thu, 04 Feb 2021 07:01:27 +0000, D. Pureheart Steinbruner scribed:

Trying out slrn...hope I can get it to work okay.

My old SunTour XCPro was getting old and tired,

Is it spring return?
IME, the sprigs wear out and I found myself needing to do mainteance/
cening a lot more.



IME steel springs do not wear out.

Okay, I'll collect up my collection of old, tired springs and post them
to you for a good talking too.

They do get overly tensioned until the end snaps off which is 'user
error' not 'product failure'.

Please explain how that happens in a deraileur, front and back. where the
limits are set by the construction.

Fatigue failure in normal use is almost unknown.

Wow, you have limited life experence.

On 2/4/2021 5:19 PM, News 2021 wrote:
On Thu, 04 Feb 2021 09:21:30 -0600, AMuzi scribed:

On 2/4/2021 4:24 AM, News 2021 wrote:
On Thu, 04 Feb 2021 07:01:27 +0000, D. Pureheart Steinbruner scribed:

Trying out slrn...hope I can get it to work okay.

My old SunTour XCPro was getting old and tired,

Is it spring return?
IME, the sprigs wear out and I found myself needing to do mainteance/
cening a lot more.



IME steel springs do not wear out.

Okay, I'll collect up my collection of old, tired springs and post them
to you for a good talking too.

They do get overly tensioned until the end snaps off which is 'user
error' not 'product failure'.

Please explain how that happens in a deraileur, front and back. where the
limits are set by the construction.

Fatigue failure in normal use is almost unknown.

Wow, you have limited life experence.


If or when one exceeds the elastic limits[1] a spring will
be deformed or fail:
https://www.engineeringtoolbox.com/h...nt-d_1853.html

Until that point springs to not 'wear out' or 'weaken'.

[1]Easily accomplished by running a gear changer into the
spokes at speed, as many here have discovered.
--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

On Thu, 04 Feb 2021 17:55:31 -0600, AMuzi scribed:

If or when one exceeds the elastic limits[1] a spring will be deformed
or fail:

That is taking the extreme example and is not disputed.

https://www.engineeringtoolbox.com/h...ring-constant-
d_1853.html

I've read that sort of stuff plenty of times before. it is all design
principles.


Until that point springs to not 'wear out' or 'weaken'.

Use a spring enough, and it will weaken.

Springs have a life time of a limited number of cycles. that is because
every extension of a spring is stressing and changing the metal/material.
Most bicyclists will experience this deformation/change in cable controls
when the cable stretches. It isn't so obvious in springs because the
metallurgy and their 'construction' is tweaked to cater for it. It may
require sensitive instruments to measure it, but it does happen.

It may be missed by anyone who follows fashion and changes components
with the breeze, but keep stuff long enough and you see it hapenng.




[1]Easily accomplished by running a gear changer into the spokes at
speed, as many here have discovereD.

What about the front derauiller?

On 2/4/2021 6:55 PM, AMuzi wrote:
On 2/4/2021 5:19 PM, News 2021 wrote:
On Thu, 04 Feb 2021 09:21:30 -0600, AMuzi scribed:

Fatigue failure in normal use is almost unknown.

Wow, you have limited life experence.


If or when one exceeds the elastic limits[1] a spring will be deformed
or fail:
https://www.engineeringtoolbox.com/h...nt-d_1853.html


Until that point springs to not 'wear out' or 'weaken'.

[1]Easily accomplished by running a gear changer into the spokes at
speed, as many here have discovered.

We can discuss.

A spring properly designed for a given application should not "wear out"
or "weaken." That's by definition of "properly designed." The spring
metal should not exceed its elastic (yield) limit. More to the point, it
also should not exceed it's fatigue endurance limit. But problems can
and do occur.

I broke a cage rotation spring on a SunTour derailleur many years ago.
That's a coil spring would of square cross section wire, with a 90
degree tang on the end that slid into a slot. The tang snapped off the
coil. Instead of replacing the spring or derailleur, I just took out the
spring and bent a new tang. I think that derailleur is still working on
my utility bike - maybe because my bend was not as sharp as the
original, so the stress concentration factor was less.

But I've come across other broken springs. A coil spring broke on my
mom's Ford Taurus many, many years ago. (It became part of the pile of
broken mechanical parts I used for class illustrations.) I broke a
torsion bar (which is a type of spring) on a Honda Civic, and used it in
class as well. Now in both those cases, it's possible (or likely?) that
the initial problem was corrosion attacking the spring steel and
generating stress risers; but they were certainly broken.

Also, while I haven't experienced it, I've wondered about the myriad
stories about cars with sagging springs. Yes, it seems the only way a
suspension spring should sag is if its yield strength is exceeded, and
that should be impossible with good design. But are all those tales
false? I don't know.

I presented this as a question to a metallurgy professor I know (who,
incidentally, is also a bicyclist). I had just read an article
describing Vibrational Stress Relief, which was new to me. (It's still
sort of a fringe process.) The article surmised that VSR worked by
inducing microscopic yielding in the areas of a casting, weldment, etc.
that had the highest residual stresses. I wondered if this same
mechanism might cause dimensional changes in auto leaf springs.
Unfortunately, my metallurgist friend had never heard of VSR and didn't
know the answer. And neither do I; but it seems like an interesting
possibility.


--
- Frank Krygowski

On 2021-02-04, AMuzi wrote:
On 2/4/2021 4:24 AM, News 2021 wrote:
On Thu, 04 Feb 2021 07:01:27 +0000, D. Pureheart Steinbruner scribed:

Trying out slrn...hope I can get it to work okay.

My old SunTour XCPro was getting old and tired,

Is it spring return?
IME, the sprigs wear out and I found myself needing to do mainteance/
cening a lot more.



IME steel springs do not wear out.
They do get overly tensioned until the end snaps off which
is 'user error' not 'product failure'. Pivots corrode,
clearances go both over(wear) and under(rust) spec but
springs do not 'wear out'.

Well, the heck of it is that it worked perfectly well at first and only had
to sit a few weeks in my garage to freeze up.
While it's mostly functional just wondered what is preferred lube or maybe
propane torch *then* lube.

pH




Fatigue failure in normal use is almost unknown.