Jockey wheels - Page 2

> Alan Walker wrote:
> >
> >>Bicycle derailleurs have two small wheels on the chain tension cage. They are normally called
> >>"jockey wheels" in the bicycle world. In my experience, wheels performing a similar function in
> >>other types of machinery are usually called "idler wheels" or "tension wheels".
> >>
> >>Am I correct about the usage in general engineering? If so, why a different term for the bicycle
> >>industry? Is the term "jockey wheel" used in other industries?
>
> Paul Kopit wrote:
>
> > The top one is sometimes referred to as the derailleur pulley and I think the bottom one is the
> > jocky.

"Sheldon Brown" <CaptBike@sheldonbrown.com> wrote in message
news:3F668371.4050007@sheldonbrown.com...
> I've always understood the term "jockey pulley" to refer to the upper pulley. This is because it
> "jockeys" or guides the chain from sprocket to sprocket. It isn't used in other industries because
> derailers are not used in other industries.
>
> The lower is called the "tension pulley."
>
> Sheldon "Cyclexicographer" Brown

Hmmm. I find "upper" and "lower" pulley sufficient.

Do you really say "jockey pulley" when writing service with a non-afficionado?

--
Andrew Muzi, who also likes "crank bearing assembly" instead of "BB" www.yellowjersey.org Open every
day since 1 April, 1971

Carl Fogel writes:

>>> I've always understood the term "jockey pulley" to refer to the upper pulley.

>>> The lower is called the "tension pulley."

>> I don't use the term for either wheel because it is undefined. I find it used to refer to either
>> of the two idler wheels. Idler is in contrast to drive sprockets, since some early derailleurs
>> used sprockets for these wheels. In many derailleurs they are identical parts as they were in all
>> the early ones by Campagnolo, Huret, Simplex and others.

>> Avoid vague jargon (AVJ)!

> Is there any mechanical difference between the two pulleys? That is, might one be expected to
> handle a different load?

It depends on the included angle between entry and exit of the chain, and its tension. Since tension
is the same, only the angle between the two chain lines has a differentiating effect. That would be
T * sin A = idler load.

> I'm curious because I recently replaced a badly worn pair on a Schwinn LeTour by robbing parts
> from spare LeTours that I bought for that purpose and for visiting friends to ride.

The wear has more to do with side loads and chain pitch. A worn chain widens the round recesses in
the idler.

> To my surprise, the upper and lower 10-tooth plastic pulleys are different parts. One is stamped
> on both sides "SHIMANO NARROW" and has a noticeably narrower profile. The other is stamped
> "SHIMANO CENTERON G-PULLEY NARROW" and has a thicker shoulder extending to the base of the worn
> plastic teeth.

I am not familiar with these parts. I can't say what that is about.

> Below are crude illustrations of the upper halves of each pulley with a tooth on top. Only the
> tooth is worn, not the other parts.

> | _|_
> / \ | |
> / \ | |
> / \ / \
> | | | |
> ------------ -----------

> narrow g-pulley

> Obviously, Shimano thought that there was some functional difference. The only thing that I can
> think of is that the lower pulley where the chain arrives from the front gears might be
> blockier and thicker without causing any trouble, but the pulley where the chain exits to the
> rear cogs might somehow profit from being narrower to allow the chain to flex sideways without
> wearing the pulley?

> Regrettably, I paid no attention when removing the pulleys on three different LeTours, so I don't
> know which pulley was upper or lower.

I don't think it makes any difference, knowing how fast these things wear. The old wobbly pulley was
designed to help people pre-shift before starting to pedal, they bing unable to pedal and shift at
the same time. That was before brake/shift levers.

Jobst Brandt jobst.brandt@stanfordalumni.org

On 16 Sep 2003 15:42:48 -0700, carlfogel@comcast.net (Carl Fogel) wrote:

>
>Below are crude illustrations of the upper halves of each pulley with a tooth on top. Only the
>tooth is worn, not the other parts.
>
> | _|_
> / \ | |
> / \ | |
> / \ / \
> | | | |
>------------ -----------
>
> narrow g-pulley
>
>Obviously, Shimano thought that there was some functional difference. The only thing that I can
>think of is that the lower pulley where the chain arrives from the front gears might be
>blockier and thicker without causing any trouble, but the pulley where the chain exits to the
>rear cogs might somehow profit from being narrower to allow the chain to flex sideways without
>wearing the pulley?
>
>Regrettably, I paid no attention when removing the pulleys on three different LeTours, so I don't
>know which pulley was upper or lower.

The 'G-Pulley' is for the upper/jockey and the other is for the lower/tension. That is Shimano's
system and designation.

I haven't looked for a while, but the 'G-pulley' used to have a certain amount of 'float,' lateral
movement. This was either to help with shifting, or to allow a small amount of slop in alignment of
the derailleur. Maybe someone else knows the technical reason.

I never swapped the two on older derailleurs to see if their position made any difference in
shifting or noise. And I do not know if newer shifting/indexing makes this difference moot.

On 17 Sep 2003 03:10:32 GMT, Peter Moylan <peter@seagoon.newcastle.edu.au> wrote:
> Rick Onanian <spamsink@cox.net> wrote:
>> Lots of things sound cool lately. Learning C++, teacher introduced the "destructor", and I was
>> rather impressed with that term.
>
> If you're learning C++, you'll be even more impressed once you get to the definition of "friend".

I got that the same day, but it wasn't nearly as exciting.

I'd have more fun as a Destructor than a Friend.

--
Rick "The Friendly Destructor" Onanian

Rick Onanian <spamsink@cox.net> writes:

> On 17 Sep 2003 03:10:32 GMT, Peter Moylan <peter@seagoon.newcastle.edu.au> wrote:
>
> > Rick Onanian <spamsink@cox.net> wrote:
> >> Lots of things sound cool lately. Learning C++, teacher introduced the "destructor", and I was
> >> rather impressed with that term.
> >
> > If you're learning C++, you'll be even more impressed once you get to the definition of
> > "friend".
>
> I got that the same day, but it wasn't nearly as exciting.

Not even the fact that a friend has full access to your private member?

--
Evan Kirshenbaum +------------------------------------ HP Laboratories |Ye knowe ek, that in forme
of speche 1501 Page Mill Road, 1U, MS 1141 | is chaunge Palo Alto, CA 94304 |Withinne a thousand
yer, and wordes
| tho
kirshenbaum@hpl.hp.com |That hadden prys now wonder nyce and
(650)857-7572 | straunge |Us thenketh hem, and yet they spake
http://www.kirshenbaum.net/ | hem so
| Chaucer

On Wed, 17 Sep 2003 01:37:53 UTC, Rick Onanian <spamsink@cox.net> wrote:

> How long does a linear accelerator have to be in order to be useful?

Long enought that when they build it they have to worry about the curvature of the Earth.

--
John Varela

Dan Daniel writes:

>> Below are crude illustrations of the upper halves of each pulley with a tooth on top. Only the
>> tooth is worn, not the other parts.

>> | _|_
>> / \ | |
>> / \ | |
>> / \ / \
>> | | | |
>> ------------ -----------

>> narrow g-pulley

>> Obviously, Shimano thought that there was some functional difference. The only thing that I can
>> think of is that the lower pulley where the chain arrives from the front gears might be blockier
>> and thicker without causing any trouble, but the pulley where the chain exits to the rear cogs
>> might somehow profit from being narrower to allow the chain to flex sideways without wearing the
>> pulley?

>> Regrettably, I paid no attention when removing the pulleys on three different LeTours, so I don't
>> know which pulley was upper or lower.

> The 'G-Pulley' is for the upper/jockey and the other is for the lower/tension. That is Shimano's
> system and designation.

These designations don't come out of Shimano engineering but rather from their USA contacts who are
no more savant than the average wreck.bike contributor, many of whom prefer bicycle jargon to plain
English. The more bicycle jargon the more exclusive the club.

> I haven't looked for a while, but the 'G-pulley' used to have a certain amount of 'float,' lateral
> movement. This was either to help with shifting, or to allow a small amount of slop in alignment
> of the derailleur. Maybe someone else knows the technical reason.

As I mentioned, this arose back in the days before integrated brake and shift mechanisms. It allowed
riders to pre-shift while not pedaling. Many riders cannot pedal without both hands on the bars.

Jobst Brandt jobst.brandt@stanfordalumni.org

about 2 miles, -tom

"John Varela" <javnews@earthlink.net> wrote in message
news:ZKRm3c4Ddl7U-pn2-dgHw7ZiYNYPo@d...on1.Level3.net...
> On Wed, 17 Sep 2003 01:37:53 UTC, Rick Onanian <spamsink@cox.net> wrote:
>
> > How long does a linear accelerator have to be in order to be useful?

On 17 Sep 2003 09:59:16 -0700, Evan Kirshenbaum <kirshenbaum@hpl.hp.com> wrote:
>> I got that the same day, but it wasn't nearly as exciting.
>
> Not even the fact that a friend has full access to your private member?

Okay, I'll concede that point, but I already have someone who has full access to my private member;
OTOH, I have yet to build anything called a destructor.

So, let's destroy something already! It's inappropriate to access private members here anyway.

--
Rick "Maybe We Should Destroy This Thread" Onanian

Alan Walker <walker@netcon.net.au> wrote in message
news:5cb9c6e4.0309151607.402fd26f@posting.google.com...
> Bicycle derailleurs have two small wheels on the chain tension cage. They are normally called
> "jockey wheels" in the bicycle world. In my experience, wheels performing a similar function in
> other types of machinery are usually called "idler wheels" or "tension wheels".
>
> Am I correct about the usage in general engineering? If so, why a different term for the bicycle
> industry? Is the term "jockey wheel" used in other industries?
>
> Perhaps I should consult "The Dancing Chain"!
>
> AW

How about: They are called jockey wheels because that's what they do -- move and jockey the chain
over to the next gear wheel, up or down, when the lever on the handlbars is moved?

As for other industries, I don't know.

Cheers, Sage

the basic overwait deore from Nbar has different wheels top and bottom so sez the labeling.I took
their word for it. like they spent the dough on it right? i'm very pleaed with boat trailer bearing
grease applied frequently which is a sufficient conclusion based on suffiecient experience that this
lube is sufficiently necessary for the reasonabley prudent rider who isn't droolingover a set of
sealed bearing aluminum wheels which are as Hegel once said empirically unproven firsthand.

Rick Onanian <spamsink@cox.net> wrote:
>On 17 Sep 2003 03:10:32 GMT, Peter Moylan <peter@seagoon.newcastle.edu.au> wrote:
>> Rick Onanian <spamsink@cox.net> wrote:
>>> Lots of things sound cool lately. Learning C++, teacher introduced the "destructor", and I was
>>> rather impressed with that term.
>>
>> If you're learning C++, you'll be even more impressed once you get to the definition of "friend".
>
>I got that the same day, but it wasn't nearly as exciting.
>
>I'd have more fun as a Destructor than a Friend.

Even though a friend is defined as someone who is allowed to see your private parts?

With the help of a friend, you can be a constructor.

--
Peter Moylan Peter.Moylan@newcastle.edu.au http://eepjm.newcastle.edu.au (OS/2 and eCS information
and software)

Carl Fogel wrote:
>

> To my surprise, the upper and lower 10-tooth plastic pulleys are different parts. One is stamped
> on both sides "SHIMANO NARROW" and has a noticeably narrower profile. The other is stamped
> "SHIMANO CENTERON G-PULLEY NARROW" and has a thicker shoulder extending to the base of the worn
> plastic teeth.

The CENTERON is the slop pulley and is the upper one (the guide pulley). It has slop so any
inaccuracy of the indexing can be slopped out and the chain won't make much noise against the cogs.

I'm really sorry about the sloppy vague jargon. Wait, no I'm not.

"Skitt" <skitt99@comcast.net> wrote:

> Rick Onanian wrote:
>> Skitt wrote:
>
>>>> I don't know what a linear accelerator is, but it sure sounds cool. What is it?
>>>
>>> Type the phrase into the box provided by MWCD10 at www.m-w.com and you'll find out.
>>
>> So, it's a particle accelerator that doesn't go in circles? How long does a linear accelerator
>> have to be in order to be useful?
>
> Gosh, I wouldn't know. The one at Stanford is two miles long.

The one in the Netherlands is used for medical purposes, so they probably don't need TeV
energy levels -- they want to cure people, not annihilate them. I suspect it's a bit less than
2 miles long.

--
Ray Heindl (remove the X to reply)

jobst.brandt@stanfordalumni.org wrote:
> Carl Fogel writes:
<snip>
>>Is there any mechanical difference between the two pulleys? That is, might one be expected to
>>handle a different load?
>
>
> It depends on the included angle between entry and exit of the chain, and its tension. Since
> tension is the same, only the angle between the two chain lines has a differentiating effect. That
> would be T * sin A = idler load.
>
<snip>

2T * cos (A/2) = idler load, if A is the included angle between chains, and (180 deg. - A) is the
chain wrap angle. Load is zero for the case of 0 deg. chain wrap and 2T for 180 deg. of wrap.

Dave Lehnen