How do Jockey Wheels work?

A rather basic question I would have thought yet I have scoured the
internet, including Sheldon's site and the group FAQ and cannot find
an answer.

The first problem I have with answering this question myself is that I
cannot find a web reference or detailed picture showing what the parts
of the jockey wheel are called. If anyone can find such a reference
please post it here!

In the absence of this, I need to establish a language so that we here
know that we are all talking the same language! I need to define what
the Jockey Wheel parts are called, so here goes.

-----------

The JOCKEY WHEEL is made up of a

(usually plastic)IDLER PULLEY which takes the form of a moulded
plastic disc, with

IDLER PULLEY TEETH equally spaced around the outer circumference.

In the centre of the idler pulley there is a cylindrical hole that
goes right through and inside this fits the PULLEY BUSHING (usually
steel).

Encapsulating the pulley bushing are two PULLEY CAPs. These are
identical, but are installed as mirror images of each other. Each
pulley cap is a short cut off hollow cylinder, which is nevertheless
significantly larger than the diameter of the pulley bushing. The
exposed cut off outer edge of the pulley cap fits into a separate
cylindrical indentation in the pulley bushing.

The idler pulley, pulley bushing and pulley caps make up the JOCKEY
WHEEL ASSEMBLEY.

The PULLEY BOLT holds the jockey wheel assembley together. It fits
through a hole drilled in the centre of the nearside pulley bushing,
through the centre of the pulley bushing itself and finally through
the mirror image hole in the farside pulley bushing.

There is also a single washer in there on my particular jockey wheels
(Shimano STXrc) at least. I will call that the PULLEY BOLT WASHER

The pulley bolt also passes through the 'drop down dangly bit' (what
is the proper name for that?) of the derailleur and attaches the
jockey wheel to the derailleur assembly.

------------

OK are those definitions fine with everyone? Do they make sense?

Furthermore I know there are two different kinds of idler pulleys, an
'upper' kind and a 'lower' kind. Does anyone know the 'correct'
terms for those?

SNOOPY


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On Sat, 07 May 2005 17:07:59 +1200, (Snoopy) te**yson@caverock.*et.*z
(*is n) wrote:

The pulley bolt also passes through the 'drop down dangly bit' (what
is the proper name for that?)

The cage. ("Dangly bit"? Do you have cats?)

of the derailleur and attaches the
jockey wheel to the derailleur assembly.

------------

OK are those definitions fine with everyone?

Well, Shimano has their own set of terms in the exploded views that
they provide in the tech docs...

Do they make sense?

Making sense alone will be unpersuasive to the purists who believe
that The Word Of The Gods Is Sufficient, even when the results are
inconsistent, illogical, confusing, or not in a language they
understand. Otherwise, yes, your proposed terms do seem to make
sense, to me. (But I think you're going to swiftly discover that
there are more designs of jockey wheel setup than you thought.)

Furthermore I know there are two different kinds of idler pulleys, an
'upper' kind and a 'lower' kind. Does anyone know the 'correct'
terms for those?

As of last discussion, I believe the common jargon was "upper jockey
wheel" and "lower jockey wheel", oddly enough, though Shimano calls
the lower a "tension pulley" and the upper a "guide pulley".

Here's one of the Shimano exploded views:

http://cycle.shimano-eu.com/media/cy...9830494493.pdf

also accessible via

http://tinyurl.com/cj8gp


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Werehatrack wrote:

OK are those definitions fine with everyone?

Well, Shimano has their own set of terms in the exploded views that
they provide in the tech docs...

Yes, but Shimano is responsible for the execrable use of the term "brake
arch" so their credibility on English usage is dubious.

Do they make sense?

Making sense alone will be unpersuasive to the purists who believe
that The Word Of The Gods Is Sufficient, even when the results are
inconsistent, illogical, confusing, or not in a language they
understand. Otherwise, yes, your proposed terms do seem to make
sense, to me. (But I think you're going to swiftly discover that
there are more designs of jockey wheel setup than you thought.)

Furthermore I know there are two different kinds of idler pulleys, an
'upper' kind and a 'lower' kind. Does anyone know the 'correct'
terms for those?

Yes. Speaking ex cathedra, the upper one is the "jockey pulley" and the
lower one is the "tension pulley."

Sheldon "Cyclexicographer" Brown
+-----------------------------------------+
| Man invented language to satisfy his |
| deep need to complain. -- Lily Tomlin |
+-----------------------------------------+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com

On Sat, 07 May 2005 13:29:42 -0400, Sheldon Brown
wrote:

Werehatrack wrote:

OK are those definitions fine with everyone?

Well, Shimano has their own set of terms in the exploded views that
they provide in the tech docs...

Yes, but Shimano is responsible for the execrable use of the term "brake
arch" so their credibility on English usage is dubious.

Furthermore I know there are two different kinds of idler pulleys, an
'upper' kind and a 'lower' kind. Does anyone know the 'correct'
terms for those?

Yes. Speaking ex cathedra, the upper one is the "jockey pulley" and the
lower one is the "tension pulley."


At the risk of offending the greatest Cyclexicographer of all time,
I'll go with the common gravity orientated (and in brackets Shimano)
definitions of:

Lower (tension) Pulley and
Upper (guide) Pulley

I do this because the phrase 'jockey wheels' has come to mean both
pullies (perhaps dating from the time both were in fact identical?) so
I find it unclear to refer to only the top pulley as a 'jockey
pulley'.

I have edited 'Werehatrack''s reference drawing by taking out
extraneous information aand putting on some definitions of my own.

You can see the modified artwork he

http://img.villagephotos.com/p/2005-...derailleur.gif

Now my Upper (guide) Pulley doesn't have any 'pulley seal rings' like
the one shown (why do some Upper (guide) Pulleys have them and some
not), but hopefully that doesn't matter! If I take out my 'Upper
guide Pulley' sit it on the table and remove one of my pulley caps, I
see my 'pulley bearing' is contained within another metal bearing (you
can kind of see that on the drawing).

By contrast the pulley bearing of the Lower (tension) Pulley Wheel
sits straight inside a hole bored in the plastic to suit.

The upper guide pulley bearing looks to be designed to move 'back and
forth' by a tiny amount. My best guess at measuring the back and
forth play is less than 1mm. However, when a derailleur changes gear
the guide pulley is indexed from side to side (not back and forth).

So my question is how can such a tiny amount of play, in what seems to
be the wrong direction, make a difference? Just how does this Upper
(guide) Jockey Wheel work?

SNOOPY


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On Sun, 08 May 2005 14:29:14 +1200, (Snoopy) te**yson@caverock.*et.*z
(*is n) wrote:

The upper guide pulley bearing looks to be designed to move 'back and
forth' by a tiny amount.

Correct.

My best guess at measuring the back and
forth play is less than 1mm. However, when a derailleur changes gear
the guide pulley is indexed from side to side (not back and forth).

Yes.

So my question is how can such a tiny amount of play, in what seems to
be the wrong direction, make a difference? Just how does this Upper
(guide) Jockey Wheel work?

While the indexed motion for each change of gears is by a fixed
amount, it is often the case that the rest position is just a trifle
off from the ideal alignment for any given gear. To keep the chain
from being pushed out of line (and perhaps start hunting between two
gears), a little lateral play in the upper pulley is designed in; this
allows it to seek a rest position which is aligned with the
freewheel/cassette sprocket. If this play was not included,
derailleur adjustment would be *much* touchier.


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On Sun, 08 May 2005 05:29:40 GMT, Werehatrack
wrote:

On Sun, 08 May 2005 14:29:14 +1200, (Snoopy) te**yson@caverock.*et.*z
(*is n) wrote:

The upper guide pulley bearing looks to be designed to move 'back and
forth' by a tiny amount.

Correct.

My best guess at measuring the back and
forth play is less than 1mm. However, when a derailleur changes gear
the guide pulley is indexed from side to side (not back and forth).

Yes.

So my question is how can such a tiny amount of play, in what seems to
be the wrong direction, make a difference? Just how does this Upper
(guide) Jockey Wheel work?

While the indexed motion for each change of gears is by a fixed
amount, it is often the case that the rest position is just a trifle
off....


off- in what direction?


from the ideal alignment for any given gear.


To keep the chain
from being pushed out of line (and perhaps start hunting between two
gears), a little lateral play in the upper pulley is designed in;


Did you see my web picture, that includes the way I am describing the
movement in different directions?

http://img.villagephotos.com/p/2005-...derailleur.gif

I am not sure what you mean by 'lateral play' in this context, but *I*
take it to mean 'side to side' play as in the diagram. The upper
guide pulley looks to be designed to go 'back and forth'. That is
where the freedom of movement is *not* 'side to side'.

I agree that to have 'side to side' play would be logical. So why
isn't the upper guide pulley (apparently) not designed to have it?
This is what is puzzling me.

SNOOPY



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Snoopy *is n wrote:
On Sun, 08 May 2005 05:29:40 GMT, Werehatrack
wrote:


On Sun, 08 May 2005 14:29:14 +1200, (Snoopy) te**yson@caverock.*et.*z
(*is n) wrote:


The upper guide pulley bearing looks to be designed to move 'back and
forth' by a tiny amount.

Correct.


My best guess at measuring the back and
forth play is less than 1mm. However, when a derailleur changes gear
the guide pulley is indexed from side to side (not back and forth).

Yes.


So my question is how can such a tiny amount of play, in what seems to
be the wrong direction, make a difference? Just how does this Upper
(guide) Jockey Wheel work?

While the indexed motion for each change of gears is by a fixed
amount, it is often the case that the rest position is just a trifle
off....



off- in what direction?


from the ideal alignment for any given gear.


To keep the chain

from being pushed out of line (and perhaps start hunting between two

gears), a little lateral play in the upper pulley is designed in;



Did you see my web picture, that includes the way I am describing the
movement in different directions?

http://img.villagephotos.com/p/2005-...derailleur.gif

I am not sure what you mean by 'lateral play' in this context, but *I*
take it to mean 'side to side' play as in the diagram. The upper
guide pulley looks to be designed to go 'back and forth'. That is
where the freedom of movement is *not* 'side to side'.

I agree that to have 'side to side' play would be logical. So why
isn't the upper guide pulley (apparently) not designed to have it?
This is what is puzzling me.

SNOOPY





What gives you the impression that the upper pulley is 'designed' to go
'back and forth'? My upper pulleys have some lateral (side to side)
play, not 'back and forth'. It sounds if you have a worn out bearing.

Lou
--
Posted by news://news.nb.nu

On Sun, 08 May 2005 09:51:59 +0200, Lou Holtman
wrote:

Snoopy *is n wrote:
On Sun, 08 May 2005 05:29:40 GMT, Werehatrack
wrote:

I am not sure what you mean by 'lateral play' in this context, but *I*
take it to mean 'side to side' play as in the diagram. The upper
guide pulley looks to be designed to go 'back and forth'. That is
where the freedom of movement is *not* 'side to side'.

I agree that to have 'side to side' play would be logical. So why
isn't the upper guide pulley (apparently) not designed to have it?
This is what is puzzling me.

What gives you the impression that the upper pulley is 'designed' to go
'back and forth'?


I have removed my upper guide pulley from my derailleur.

I have removed the pulley caps from both sides of the pulley.

When I take hold of the pulley and lift it upwards holding the pulley
teeth in opposing fingers the pulley bearing has a natural tendancy to
'fall out' (remain on the table surface).

This is not surprising. I observe a clearance between the outer
circumference of the pulley bearing and the steel lined 'hole' in the
centre of the upper guide pulley. The clearance between the outer
circumference of the pulley bearing and the inner circumference of the
upper guide pulley is what gives me about 1mm of 'back and forth'
movement.

Normally the upper guide pulley is held inside the derailleur cage.
It is a tight fit and no side to side movement is possible.

That is why I say the upper guide pulley is *designed* to go back and
forth.


My upper pulleys have some lateral (side to side)
play, not 'back and forth'.


My first observation is that I cannot see that it is *possible*, using
the design in the picture and as described, to eliminate back and
forth movement.

I will add another separate observation here. If I

1/take the upper guide wheel assembly AND
2/hold it in one hand between my thumb and opposing finger (one each
on opposing pulley caps) THEN
3/I am able to move the upper guide wheel by turning it slightly about
the 'up down' axis (**).

[(**) Before you think I am doing something bizarre here, I am using
the Right Hand rule to describe the twisting motion I am performing.
Point your thumb in the direction of the up-down axis. The way your
fingers wrap around the axis is the direction of movement.]

That means the upper guide wheel can be made to kind of 'laterally
wobble' (not a good description which is why I gave the more detailed
description above). I suppose that is a *kind* of side to side
movement. But it is not the kind of side to side movement I had in
mind. Designing a gear system this way means the gears on the cluster
and the upper guide wheel can be mostly out of vertical alignment.

Would that arrangement not be far *less durable* than an old fashioned
friction system where the jockey wheels and the rear gear cluster have
to be aligned manually, by ear?


It sounds if you have a worn out bearing.


I have never heard of having an upper guide pulley that has a worn out
internal bearing. Usually the outer circumference pulley teeth have
gone long before that might become a problem! Of course that doesn't
mean my upper guide pulley bearing isn't worn. But it was operating
just fine when I took it off the bike and it seems to move freely when
off. Is there a 'wear test' that you can suggest?

SNOOPY










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Snoopy *is n wrote:
On Sun, 08 May 2005 09:51:59 +0200, Lou Holtman
wrote:


Snoopy *is n wrote:

On Sun, 08 May 2005 05:29:40 GMT, Werehatrack
wrote:

I am not sure what you mean by 'lateral play' in this context, but *I*
take it to mean 'side to side' play as in the diagram. The upper
guide pulley looks to be designed to go 'back and forth'. That is
where the freedom of movement is *not* 'side to side'.

I agree that to have 'side to side' play would be logical. So why
isn't the upper guide pulley (apparently) not designed to have it?
This is what is puzzling me.


What gives you the impression that the upper pulley is 'designed' to go
'back and forth'?



I have removed my upper guide pulley from my derailleur.

I have removed the pulley caps from both sides of the pulley.

When I take hold of the pulley and lift it upwards holding the pulley
teeth in opposing fingers the pulley bearing has a natural tendancy to
'fall out' (remain on the table surface).

This is not surprising. I observe a clearance between the outer
circumference of the pulley bearing and the steel lined 'hole' in the
centre of the upper guide pulley. The clearance between the outer
circumference of the pulley bearing and the inner circumference of the
upper guide pulley is what gives me about 1mm of 'back and forth'
movement.

That is way too much. In front of me lies a upper pulley of my spare
(brand new) Veloce rear derailleur. The outer diameter of the bolt
measures 4.95 mm and the inner diameter of the inner bushing measures 5
mm, leaving a 0.05 mm radial play.


Normally the upper guide pulley is held inside the derailleur cage.
It is a tight fit and no side to side movement is possible.

That is not true (in my case). The inner bushing (pulley bushing in your
drawing) is a little bit wider than de outer bushing and/or the plastic
pulley so when the bolt is tightened body cage plates are not squeezed
against the pulley leaving some side to side movement.

That is why I say the upper guide pulley is *designed* to go back and
forth.


It is not, because it has no purpose



My upper pulleys have some lateral (side to side)
play, not 'back and forth'.



My first observation is that I cannot see that it is *possible*, using
the design in the picture and as described, to eliminate back and
forth movement.

Take one apart. You see.


I will add another separate observation here. If I

1/take the upper guide wheel assembly AND
2/hold it in one hand between my thumb and opposing finger (one each
on opposing pulley caps) THEN
3/I am able to move the upper guide wheel by turning it slightly about
the 'up down' axis (**).

I can't.


[(**) Before you think I am doing something bizarre here, I am using
the Right Hand rule to describe the twisting motion I am performing.
Point your thumb in the direction of the up-down axis. The way your
fingers wrap around the axis is the direction of movement.]

That means the upper guide wheel can be made to kind of 'laterally
wobble' (not a good description which is why I gave the more detailed
description above). I suppose that is a *kind* of side to side
movement. But it is not the kind of side to side movement I had in
mind. Designing a gear system this way means the gears on the cluster
and the upper guide wheel can be mostly out of vertical alignment.

How old are your pulleys?

Would that arrangement not be far *less durable* than an old fashioned
friction system where the jockey wheels and the rear gear cluster have
to be aligned manually, by ear?

I don't know.



It sounds if you have a worn out bearing.



I have never heard of having an upper guide pulley that has a worn out
internal bearing.


I did. I know of someone who's pulley developed so much wobble that he
was not able to adjust his rear derailleur correctly. He replaced the
jockey wheel and after that everything was fine.

Lou
--
Posted by news://news.nb.nu

Snoopy *is n wrote:



I have never heard of having an upper guide pulley that has a worn out
internal bearing. Usually the outer circumference pulley teeth have
gone long before that might become a problem! Of course that doesn't
mean my upper guide pulley bearing isn't worn. But it was operating
just fine when I took it off the bike and it seems to move freely when
off. Is there a 'wear test' that you can suggest?

You're over complicating this. The upper pulley is meant to be sloppy.
Once the chain is on the sprocket, you don't want any lateral pulley
force, that just creates friction. You can replace the pulley with an
after-market one with no slop, it will work fine, but shifting has to be
perfectly adjusted or you'll get noise from pulley rub. It can be
helpful to get a little more life out of an old derailer with worn
pivots by using a slop-less pulley, but such pulleys often cost more
than some derailers. Indexed shifting seems to continue to work well
even after the pulleys are very worn.