What is "fretting?"
LewW
denotes some sort of metal damage. For example, there is a current
thread about fretting at the pedal/crank interface.
Would someone please explain what "fretting" is?
Thanks,
Lew
Fritz M
> Would someone please explain what "fretting" is?
I just found this; hope this helps:
http://www.google.com/search?hl=en&lr=&c2coff=1&oi=defmore&q=define:fretting
RFM
Bill Sornson
Sic BS
Jasper Janssen
When two bits of material are connected together nearly-inflexibly and get
constantly changing loads (which describes many parts of bikes perfectly),
they will move just a tiny invisible little bit lots and lots of times, so
over time some material will be worn away.
Jasper
jobst....@stanfordalumni.org
The term is often used in a social context where someone worries about
some event but does nothing about it other than complain that it is
so.
Fretting in metals is similar, there being no visible motion but much
action. It is micro motion, often in the range of metal elasticity,
between seemingly intimately bound parts. Typically, gears pressed
onto splined shafts fret and cause rouge in their interface. It is
generally a motion below visible detection and is often not planned
for by designers. High forces and low speeds on bicycles are fraught
with fretting problems.
Aluminum crank/square taper steel spindle interfaces fret, eroding the
steel spindle and leaving traces of rouge.
Pedal shaft/crank attachments fret, eroding crank faces and damaging
threads. Fretting motion is what would unscrew pedals if their
threads were not left and right handed as they are.
Quill stems fret in steertubes generating rouge until corrosion locks
an aluminum stem solid into the steertube.
Knurled jam nuts on QR axles eat into dropouts from fretting such that
the wheel does not want to drop out when the QR is opened.
Clicking spoke nipples give witness to fretting in spoke nipple/rim
interfaces but do so mainly once rust develops in the eyelet. To
prevent clicking eyelets have often been made of stainless steel.
Head bearings develop dimples from ball bearing fretting while on long
coasting descents that require no steering motions that would to
replenish lubricant as the fork crown articulates fore and aft through
vibration angles. Dimples in cup and cone are galling pull-outs that
leave a matte finish unlike a Brinell dimple that is spherical and
shiny. This type of failure is common on cars shipped by train over
long distances. The differential and wheel bearings fret into galling
and can often be heard on BMW's as they shhhhhhhh past on the road.
I'm sure there are other examples.
MSA
>
>>Would someone please explain what "fretting" is?
>
>
Not sure what it means but they do say it's not allowed in swimming pools.
--
Mark
_____________________________________________
Deja Moo - The feeling that you've heard this bull before
Luns Tee
Crossed spokes fret against each other at their crossings with
every wheel revolution, as the passing wheel load compresses first one
spoke then the other. The relative change of lengths causes the spokes to
slide against each other, eroding the spokes at their points of
contact. The resulting notching is readily apparent on a well-used
wheel when grasping spoke pairs and squeezing them to slide against
each other, this notching not present on a freshly built wheel with new
spokes.
-Luns
jim beam
other. in the pedal context, it's no big deal.
jim beam
what garbage. you've clearly never opened a text book since the 50's,
the time at which this kind of auto bearing damage /used/ to occur.
today, similar vehicles shipped in exactly the same way survive the
exact same journey cross country with no problem whatsoever. why?
better bearing metallurgy, better lube technology. honestly jobst, you
really do need to get a grip on this ridiculous paranoia of yours. way
you write, anyone would think the world was conspiring against you. but
you're the savior of the world sent to save us from evil bmw, right? or
is it suv's. i forget which.
and on the subject of headsets, has your "fretting" model ever managed
to explain indexing after a single blow [like a crash] yet?
Michael Dart
> Worrying about greased tapirs.
>
> Sic BS
I so love a good "call back". ;^D
Mike
jobst....@stanfordalumni.org
> Worrying about greased tapirs.
> Sic BS
Zog The Undeniable
> Worrying about greased tapirs.
I think all this talk of tapirs is rather nebulous:
Paul Smith
Hope this helps
"LewW" <l...@worthem.com> wrote in message
news:1116269908....@g47g2000cwa.googlegroups.com...
Chalo
Bill Sornson wrote:
>
> Worrying about greased tapirs.
>
> Sic BS
They seem like they'd be at least as worrisome to catch as greased
pigs:
http://www.helgeroe.com/Album/Bolivia/252_5209.JPG
Chalo
Jasper Janssen
>and on the subject of headsets, has your "fretting" model ever managed
>to explain indexing after a single blow [like a crash] yet?
Does bearing indexing necessarily have to have the same cause on every
occurence?
Jasper
jobst....@stanfordalumni.org
>> and on the subject of headsets, has your "fretting" model ever
>> managed to explain indexing after a single blow [like a crash] yet?
> Does bearing indexing necessarily have to have the same cause on
> every occurence?
No one has demonstrated that dimples in reasonable head bearings can
be caused by any mechanism other than fretting. It takes a massive
direct blow with a hammer on the bearing laid on an anvil to make a
visible mark on head bearing races. Beating on the underside of a
junk bicycle fork crown will not cause dimples. For those of us who
used steel cottered cranks, the exercise of pounding directly on the
BB spindle to seat cotters with a steel hammer was done often. The
absence of dimples on the spindle and cups should have raised
questions long ago on how a front tire can impart sufficient force to
cause head bearing indexing.
http://www.sheldonbrown.com/brandt/indexed-steering.html
As mentioned in the above article, the dimples are matte and oval, and
are found mainly in the fore and aft quadrant of head bearings. It is
in this area where fretting motion of a fork acts as the fork crown
oscillates with tiny in line vibration of the front axle. That there
are dimples in the upper race can also not be explained by impact.
I find this interesting because it is similar to years of people
placing the cause of spoke failure on momentary overload instead of
fatigue failures. That goes for many other failures on bicycles as
well. It should occur to riders that these failures do not occur the
first time the bicycle is subjected to a rough ride. It takes many
incidents of mostly average loading to build up cyclic failures.
jim beam
that's possibly the most astute question anyone's ever asked in the
whole headset debate - no of course not. there are two mechanisms, true
brinelling & false brinelling, what jobst calls "fretting".
true brinelling is that arising from overload, typically something like
impact. even though the bearing races are are made of very hard steel,
they still have the ability to plastically deform under load. [it was
interesting reading the recent thread on replacing cartridge bearings
for a suntour hub a few days ago - several contributors took the trouble
to warn of the dangers when fitting the replacement bearing, to avoid
loading the inner race to prevent damage.] the deformation is exactly
like that seen in brinnel hardness testing, an easily googleable term.
false brinelling is commonly associated with things like shipping damage
where a bearing is assembled but improperly greased & unloaded. the
lack of [pre]load allows relative sliding movement between the rolling
elements, which is concentrated in one spot and may eventually lead to wear.
so, it /is/ possible for a headset bearing to "fret", but for a well
lubed, properly adjusted headset, it is most unlikely. indeed, the
solution for shipping damage to bearings [the bigger ones] is to either
pre-load them or ship disassembled. my first experience of an indexed
headset was after crashing into the back of a car with a new bike. the
crash was sufficient to bend the fork slightly, but index the head set
significantly - immediately noticeable. i took it for examination at my
metallurgy lab where i was an undergrad at the time.
one caveat: if a headset /is/ brinelled with impact, it /is/ possible
for it to subsequently "fret" if it continues to be ridden. when
resting in the impact dimples, the bearing elements are no longer
preloaded as they were before, so relative sliding motion can occur.
one could therefore possibly draw the wrong conclusion about
origination, but for someone that's taken more than a cursory glance at
the subject, that confusion should not arise.
jim beam
> Jasper Janssen writes:
>
>
>>>and on the subject of headsets, has your "fretting" model ever
>>>managed to explain indexing after a single blow [like a crash] yet?
>
>
>>Does bearing indexing necessarily have to have the same cause on
>>every occurence?
>
>
> No one has demonstrated that dimples in reasonable head bearings can
> be caused by any mechanism other than fretting. It takes a massive
> direct blow with a hammer on the bearing laid on an anvil to make a
> visible mark on head bearing races.
er, carl fogel beat his against a straw mat & got brinelling.
> Beating on the underside of a
> junk bicycle fork crown will not cause dimples.
er, i beat mine against a perfectly good fork crown & got brinelling.
we both posted our results jobst. your inability to accept our evidence
is plain spite. your inability to open a book on the subject is plain
asinine.
> For those of us who
> used steel cottered cranks, the exercise of pounding directly on the
> BB spindle to seat cotters with a steel hammer was done often. The
> absence of dimples on the spindle and cups should have raised
> questions long ago on how a front tire can impart sufficient force to
> cause head bearing indexing.
jobst, when i turn the spindle on a brand new, fresh out of the box,
unbuilt shimano 105 hub & feel roughness in the rotation, exactly how
much aspherodicity of bearing ball is causing that? it's certainly not
visible, but very much detectable by feel. you're trying to argue that
because a dimple can't be "seen" with the naked eye on a dirty greased
up bearing, that it therefore can't exist? you're living in a twisted
myopic world of your own ridiculous design.
>
> http://www.sheldonbrown.com/brandt/indexed-steering.html
>
> As mentioned in the above article, the dimples are matte and oval, and
> are found mainly in the fore and aft quadrant of head bearings. It is
> in this area where fretting motion of a fork acts as the fork crown
> oscillates with tiny in line vibration of the front axle. That there
> are dimples in the upper race can also not be explained by impact.
>
> I find this interesting because it is similar to years of people
> placing the cause of spoke failure on momentary overload instead of
> fatigue failures. That goes for many other failures on bicycles as
> well. It should occur to riders that these failures do not occur the
> first time the bicycle is subjected to a rough ride. It takes many
> incidents of mostly average loading to build up cyclic failures.
>
> Jobst....@stanfordalumni.org
you can stick to the same old stories based on "selected data" as long
as you want jobst, but as long as you do, you'll never have any
credibility. go to a library. publish hard data points like your own
spoke tensions. stop fudging.
diann...@yahoo.com
> I find this interesting because it is similar to years of people
> placing the cause of spoke failure on momentary overload instead of
> fatigue failures.
I understand journalists aren't technical writers, but I wonder what
cause might be attributed to Basso's broken spokes in this year's Giro?
http://www.cyclingnews.com/road/2005/giro05/?id=results/giro0510
jobst....@stanfordalumni.org
>> I find this interesting because it is similar to years of people
>> placing the cause of spoke failure on momentary overload instead of
>> fatigue failures.
> I understand journalists aren't technical writers, but I wonder what
> cause might be attributed to Basso's broken spokes in this year's
> Giro?
http://www.cyclingnews.com/road/2005/giro05/?id=results/giro0510
That one may have been obvious for folks on the scene. I can imagine
that in the rough, a foreign object got in the wheel and ripped a
spoke. This was not caused by bumpy terrain.
Donald Gillies
handlebars held straight is pure speculation.
In my informal survey of 12 steel bicycles with mostly campy headset -
almost all of them 30 years old, indexed headsets are highly
correlated with long head tubes, 23.5", 24.5", etc., and reynolds 531
tubing, which implies that possibly it's more likely that indexed
headsets are a result of heavier riders and/or flexion in the head
tubes.
Jobst's _explanation_ for fretting (not the mechanism, but the cause)
is imho entirely speculation.
- Don Gillies
San Diego, CA
Alfred Ryder
(snip)
> Head bearings develop dimples from ball bearing fretting while on long
> coasting descents that require no steering motions that would to
> replenish lubricant as the fork crown articulates fore and aft through
> vibration angles. Dimples in cup and cone are galling pull-outs that
> leave a matte finish unlike a Brinell dimple that is spherical and
> shiny. This type of failure is common on cars shipped by train over
> long distances. The differential and wheel bearings fret into galling
> and can often be heard on BMW's as they shhhhhhhh past on the road.
>
> I'm sure there are other examples.
>
Last year I replaced by head bearings which had developed dimples in the cup
and cone. I did not spend any time wondering how they got there since I felt
it was obvious. Like many phenomena, it is more complex than I realized.
But here is, I think, another example of the phenomenon. When I was in high
school, the local fad was to take a quarter (quarters were soft with a
relatively high silver content then) and a spoon and, holding the quarter
between finger and thumb, hit it with the convex part of the spoon. After
hours of tapping the edge of the coin, the edge would begin to spread out.
And after many, many hours, it would spread out enough so that, when the
center was drilled out, it became a silver ring for the finger. Although a
lot of us walked around school taping our quarters, I never saw anyone
actually keep it up long enough to finish.
It was the many little taps that made the metal "flow". There is no way that
a few heavy blows could do the same thing. And I am not sure this is the
same as "fretting".
Chalo
>
> But here is, I think, another example of the phenomenon. When
> I was in high school, the local fad was to take a quarter
> (quarters were soft with a relatively high silver content
> then) and a spoon and, holding the quarter between finger and
> thumb, hit it with the convex part of the spoon. After hours
> of tapping the edge of the coin, the edge would begin to
> spread out. And after many, many hours, it would spread out
> enough so that, when the center was drilled out, it became a
> silver ring for the finger. Although a lot of us walked
> around school taping our quarters, I never saw anyone
> actually keep it up long enough to finish.
>
> It was the many little taps that made the metal "flow". There
> is no way that a few heavy blows could do the same thing. And
> I am not sure this is the same as "fretting".
An interesting analogy, but it doesn't apply to the bearing surfaces at
issue. In order for metal to be displaced as you describe, there must
be local stresses (e.g, a the point of contact between spoon and
quarter) in excess of the material's yield stress. There are no such
local stresses in a ball bearing in normal use; if there were, it
wouldn't function as a bearing.
The question being disputed here is whether _abnormal_ loads that are
possible to apply to a headset in a bicycle can surpass the local yield
stress of the bearing race.
My thinking is that true brinelling in an installed headset may be
possible, because manufacturers push the limits of cheapness in their
parts. If a properly hardened bearing race made of conventional
bearing materials can never exhibit brinelling as used, then why not
cut costs by using lesser materials or simpler manufacturing processes?
The limit of how much this reasoning can be extended is determined by
the magnitudes of the forces most bikes are exposed to, most of the
time.
It would not surprise me if a headset bearing surface that had been
cost-engineered (to a lower hardness than one would be likely to find
in an industrial bearing) could be damaged by an anomalous overload--
like a top race tightened to locknut torque, a wheel-breaking pothole
impact, or a sharp blow to the underside of the fork crown-- that could
still occur while the headset was installed in a frame.
But it is quite plain to observe that most instances of headset
"brinelling" are the result of fretting damage after lubrication
failure.
Chalo Colina
jobst....@stanfordalumni.org
That is not fretting. Each of these blows was causing plastic
deformation, however small, and I guess the added up as you describe,
although I can't imagine anyone doing that successfully.
Fretting is friction induced micro-welding and breaking of these
welds. It is not causing deformation but rather erosion by tearing
out tiny bits of metal. These are hardened steel bearing races and
harder steel bearing balls of which we speak.
jobst....@stanfordalumni.org
> Jobst's belief that fretting occurs from long downhill rides with
> the handlebars held straight is pure speculation.
> In my informal survey of 12 steel bicycles with mostly Campy headset
> - almost all of them 30 years old, indexed headsets are highly
> correlated with long head tubes, 23.5", 24.5", etc., and Reynolds
> 531 tubing, which implies that possibly it's more likely that
> indexed headsets are a result of heavier riders and/or flexion in
> the head tubes.
When you say "heavy riders" what criterion are you using. As far as I
can detect, many of the regulars who post to this group are over
230lbs. My bicycle regularly suffered from indexed steering until
Shimano introduced the spherical swivel under the head bearing as I
described. Besides, I'm' certainly around 180lbs. Do I qualify for
the heavy rider syndrome in this day of heavies in the USA?
There have been enough 21" frames with indexed steering in the days of
such Italian frames to demonstrate that it is not only tall bicycles
that suffer this damage. However, if only tall bicycles suffered from
this, what do you propose is the mechanism?
> Jobst's _explanation_ for fretting (not the mechanism, but the
> cause) is IMHO entirely speculation.
Please explain how these dimples occur if it is not fretting, a common
mechanism for damaging rolling element bearings.
jim beam
you're such a joke jobst. deformation occurs in one metal system, but
not another??? utterly ridiculous.
>
> Fretting is friction induced micro-welding and breaking of these
> welds. It is not causing deformation but rather erosion by tearing
> out tiny bits of metal.
that /is/ a description of fretting, but it's pure guesswork on your
part that it's occuring if you can't grasp the fact that even hardened
metals plastically deform.
> These are hardened steel bearing races and
> harder steel bearing balls of which we speak.
that plastically deform when overloaded.
Chalo
> > edge would begin to spread out. And after many, many hours, it
> > would spread out enough so that, when the center was drilled out,
> > it became a silver ring for the finger.
>
> deformation, however small, and I guess the added up as you describe,
> although I can't imagine anyone doing that successfully.
It has been done. I have not only seen rings made from 90% silver
half-dollars, I have seen laminated quarters turned into little
barrel-shaped webbed rings by having been trapped inside a tumble dryer
for years.
The spoon method is probably most appropriate for OCD sufferers-- it
takes a *long* time to finish.
Chalo Colina
carl...@comcast.net
Dear Alfred,
I promptly decided that you were a nutcase with a coin
fetish and even said so to several other people.
Then I decided to look up your ridiculous idea:
D'oh!
http://forgedunderthemountain.com/FUTMPG3.html
Nice pictures that show the result that you have in mind.
They cheat and use a hammer, but the gentle repeated tapping
is emphasized
Thanks for the odd information and the lesson in the dangers
of dismissing odd ideas out of hand.
Carl Fogel
Donald Gillies
>> Jobst's _explanation_ for fretting (not the mechanism, but the
>> cause) is IMHO entirely speculation.
>Please explain how these dimples occur if it is not fretting, a common
>mechanism for damaging rolling element bearings.
Jobst, you are not understanding my point or you would not be
complaining. i never disagreed that dimples were from "fretting". in
fact, i made a point to use "indexing" in the rest of my message so as
not get into the fretting/brinneling war.
but you are way off base to go beyond the type of damage and suppose
that it is caused by a certain style of riding. you in fact make the
same error here that you made in your book when you claim that MA2
rims are some of the best ever made. you confused YOUR riding style
with the AVERAGE riding style and then made value judgements based on
your erroneous belief that YOU ARE AVERAGE which you are most
certainly not. For example, I have heard people say that you descend
like a maniac, and in your book you made a value judgement that
durable rim sidewalls are important because otherwise they wear out.
I'd like to know how many people in this country have ever experienced
a sidewall wear-out in their lifetimes vs. how many have experienced
an out of round or pretzled rim, and I think you'd find that the
latter beat the former by an order of magnitude or more. In the big
scheme of things sidewall wearouts are a secondary consideration for
most riders.
Similarly now, you have taken one of your riding styles (I presume)
which is long downhill coasting events, perhaps in the swiss alps or
wherever, and correlated a headset "indexing" event with a ride that
had some long straight downhills, and drawn the wrong conclusion, once
again, based on your riding style, which is not average.
jobst....@stanfordalumni.org
>>> Jobst's _explanation_ for fretting (not the mechanism, but the
>>> cause) is IMHO entirely speculation.
>> Please explain how these dimples occur if it is not fretting, a
>> common mechanism for damaging rolling element bearings.
> Jobst, you are not understanding my point or you would not be
> complaining. i never disagreed that dimples were from "fretting".
> in fact, i made a point to use "indexing" in the rest of my message
> so as not get into the fretting/brinneling war.
Well that's part of the problem. You should say what side of the
fence you are on so that the discussion can progress. As you see,
with things up in the air, definitions are lacking.
> but you are way off base to go beyond the type of damage and suppose
> that it is caused by a certain style of riding.
I have no "style of riding" in mind but rather longer durations of
vibratory micro-motion that is caused from riding straight ahead. You
will notice that the dimples are oriented straight ahead. On top of
that, as I mentioned, automotive steering mechanisms suffered from
this endlessly leading to patents for Saginaw, Gemmer, Ross and other
steering gears that attempted to either randomize the load point or
make it insensitive to this wear.
> you in fact make the same error here that you made in your book when
> you claim that MA2 rims are some of the best ever made. you
> confused YOUR riding style with the AVERAGE riding style and then
> made value judgements based on your erroneous belief that YOU ARE
> AVERAGE which you are most certainly not.
You are harping on an invalid issue. This claim is from the
popularity of the MA-2 rim here and abroad in every bicycle shop I
entered. Tourists and racers used them and before that the tubular
variety of socketed rims from Mavic. If you haven't been there you
cannot assess that widespread use.
> For example, I have heard people say that you descend like a maniac,
> and in your book you made a value judgement that durable rim
> sidewalls are important because otherwise they wear out. I'd like
> to know how many people in this country have ever experienced a
> sidewall wear-out in their lifetimes vs. how many have experienced
> an out of round or pretzled rim, and I think you'd find that the
> latter beat the former by an order of magnitude or more.
You apparently haven't had contact with all the wheels people build
and replace rims for exactly the reason of sidewall wear-out. Today,
people cast off wheels so often that they never wear much. It's a
fashion business now, not a utility one.
> In the big scheme of things sidewall wearouts are a secondary
> consideration for most riders.
So what. Most riders are not the one who suffer a crash from sidewall
failure. As you may have seen we recently had a whole thread from
people who had sidewall failures.
> Similarly now, you have taken one of your riding styles (I presume)
> which is long downhill coasting events, perhaps in the swiss alps or
> wherever, and correlated a headset "indexing" event with a ride that
> had some long straight downhills, and drawn the wrong conclusion, once
> again, based on your riding style, which is not average.
I think you are scraping the bottom of the barrel with this "riding
style" perspective. It doesn't wash.
Peter Cole
>
> but you are way off base to go beyond the type of damage and suppose
> that it is caused by a certain style of riding. you in fact make the
> same error here that you made in your book when you claim that MA2
> rims are some of the best ever made. you confused YOUR riding style
> with the AVERAGE riding style and then made value judgements based on
> your erroneous belief that YOU ARE AVERAGE which you are most
> certainly not. For example, I have heard people say that you descend
> like a maniac, and in your book you made a value judgement that
> durable rim sidewalls are important because otherwise they wear out.
> I'd like to know how many people in this country have ever experienced
> a sidewall wear-out in their lifetimes vs. how many have experienced
> an out of round or pretzled rim, and I think you'd find that the
> latter beat the former by an order of magnitude or more. In the big
> scheme of things sidewall wearouts are a secondary consideration for
> most riders.
Rims wear out from riding in the rain, speed has nothing to do with it.
Out of round rims come from improper build, pretzels come from crashes.
If you ride in the rain, well built, uncrashed rims will die from
sidewall wear. It's not unusual for some riders to wear out a rim in a
year or less. That's how mine die, although it takes more than a year.
carl...@comcast.net
jobst....@stanfordalumni.org wrote:
[snip]
>You will notice that the dimples are oriented straight ahead.
[snip]
Dear Jobst,
So are the vast majority of impacts, major and minor, in
road bicycling.
Carl Fogel
carl...@comcast.net
jobst....@stanfordalumni.org wrote:
[snip]
>Please explain how these dimples occur if it is not fretting, a common
>mechanism for damaging rolling element bearings.
>
>Jobst....@stanfordalumni.org
Dear Jobst,
While searching for posts about the number of bearings in a
headset, I stumbled across a 1997 post from you about
dimpled headsets that included this intriguing calculation:
"It is not at all a bumpy descent problem and not one of
pushing aside grease, but rather one of penetrating the
boundary layer between ball and race. The bearing is not
lubricated by the grease as such, but rather the oil that
the grease exudes. This is a film no thicker than a few
micro-inches (10^-6). It takes a ball rotation of less
than a degree to replenish this film, a steering motion of
1/10 of that, the ratio of ball to bearing diameter being
about 1:10."
http://groups-beta.google.com/group/rec.bicycles.tech/msg/2d541ce44398f645
The explanation makes sense, but I was startled by how tiny
a handlebar movement seemed to be needed to prevent headset
dimpling by fretting--less than 1/10 of less than one
degree.
Curious, I slapped a tape measure across my touring bike's
handlebars and found that its modest antlers have a 17 inch
spread--8.5 inches to either side of the headset.
A tenth of a degree on a 17-inch diameter circle is about
0.015 inches, less than the thickness of a sheet of copier
paper.
Even coasting down the smoothest, straightest road, the ends
of the handlebars constantly swivel considerably more than
0.015 inches. (At a modest 30 mph, a bike covers 44 feet of
road surface per second--a 0.1 degree change of course
amounts to only 0.92 inches in 44 feet. Few people can shoot
1-inch groups with .22 target rife at 50 feet from a
standing position.)
It sounds as if the very road vibration that the fretting
theory of dimpled headsets relies on to micro-weld and then
tear apart the balls and races would be ample to replenish
the protective oil film.
Was your 1997 calculation wrong about the necessary steering
motion? Or am I missing something crucial about the fretting
theory?
Carl Fogel
Benjamin Lewis
> Even coasting down the smoothest, straightest road, the ends
> of the handlebars constantly swivel considerably more than
> 0.015 inches.
How much do they swivel?
> (At a modest 30 mph, a bike covers 44 feet of
> road surface per second--a 0.1 degree change of course
> amounts to only 0.92 inches in 44 feet. Few people can shoot
> 1-inch groups with .22 target rife at 50 feet from a
> standing position.)
Why is this a good comparison? You don't steer with your hands when
coasting downhill, and you don't even give indication in your rifle example
of how fast the angle is changing, which is of course important in the case
of coasting on a bike.
--
Benjamin Lewis
Although the moon is smaller than the earth, it is farther away.
carl...@comcast.net
<bcl...@cs.sfu.ca> wrote:
>carl...@comcast.net wrote:
>
>> Even coasting down the smoothest, straightest road, the ends
>> of the handlebars constantly swivel considerably more than
>> 0.015 inches.
>
>How much do they swivel?
>
>> (At a modest 30 mph, a bike covers 44 feet of
>> road surface per second--a 0.1 degree change of course
>> amounts to only 0.92 inches in 44 feet. Few people can shoot
>> 1-inch groups with .22 target rife at 50 feet from a
>> standing position.)
>
>Why is this a good comparison? You don't steer with your hands when
>coasting downhill, and you don't even give indication in your rifle example
>of how fast the angle is changing, which is of course important in the case
>of coasting on a bike.
Dear Benjamin,
It seems unlikely that any rider can lean on a pair of
17-inch-wide handlebars and coast downhill on an ordinary
paved road without the ends of the handlebars swivelling
constantly back and forth more than 0.015 inches.
That's roughly 1/64th of an inch, the thickness of a fifteen
human hairs or a sheet of paper. The bumps on a well paved
road are considerably larger than that, and the effect is
magnified at ends of the bars. How steady can any rider hold
the handlebars against the buzz of road vibration?
Riders are unconsciously making endless small corrections,
(even when riding no-hands) much larger than a tenth of less
than one degree of steering motion, which is the 0.015 inch
movement said to be sufficient to replenish the protective
oil layer under a headset bearing.
One easy way to demonstrate this is to try to hold one side
of your front tire within an inch of a highway stripe for 44
feet at 30 mph (one second).
A more difficult demonstration is to find a 30 mph roll-out
through a convenient puddle at the bottom of a hill after a
rain. The tracks on the dry pavement past the puddle will
vary rather more than an inch to both sides side of the
initial line every 44 feet.
(For those who lack surveyor's equipment, a peep-sight rifle
is a handy tool, but pick a deserted road--bystanders tend
be easily alarmed. Because our muscles are shakier than we
like to think, sighting steadily even on an inch-wide target
at 50 feet with a 24-inch sight radius (easier than a
17-inch handlebar) is so hard that you'll quickly realize
why surveyors use tripod rests and cross-haired telescopic
sights.)
Closer at hand, pick up your keyboard, which is conveniently
about the width of touring handlebars. Brace its middle
against a corner of your desk, extending your arms in
roughly a bicycling posture. Do the ends of the keyboard
move more than the thickness of a sheet of paper?
Now imagine that instead of your nicely padded and
presumably motionless chair, you're rolling on 100 psi tires
on an unsuspended bicycle on ordinary asphalt at 30 mph.
The gyroscopic effect of the wheel does smooth things out at
higher speeds, but all sorts of tiny corrections are
guaranteed by the lack of any suspension beyond the highly
inflated tires on a contraption jointed roughly in the
middle of a 40-inch wheelbase with a center of gravity about
40 inches about the center of gravity.
As a final thought experiment, ponder how long it would take
for you to fall at 30 mph if the ends of the bars were
leashed to the frame with only one-tenth of less than one
degree of freedom. (Actually, just welding a single rod from
the seat post to the end of one handlebar would probably
still allow more than that much swivel, given the joint of
the headset and the flex of the frame.)
In short, I think that the handlebars on any bicycle rolling
"straight" down a normal road swivel constantly in tiny arcs
that are considerably greater than the width of the terminal
letters of the two following words on a 1280-pixel-wide,
12.5-inch screen line:
Carl Fogel
Benjamin Lewis
> In short, I think that the handlebars on any bicycle rolling "straight"
> down a normal road swivel constantly in tiny arcs that are considerably
> greater than the width of the terminal letters of the two following words
> on a 1280-pixel-wide, 12.5-inch screen line:
What do you think is the period of these oscillations? How long a time is
required for fretting to start?
jim beam
> carl...@comcast.net wrote:
>
>
>>Even coasting down the smoothest, straightest road, the ends
>>of the handlebars constantly swivel considerably more than
>>0.015 inches.
>
>
> How much do they swivel?
>
>
>>(At a modest 30 mph, a bike covers 44 feet of
>>road surface per second--a 0.1 degree change of course
>>amounts to only 0.92 inches in 44 feet. Few people can shoot
>>1-inch groups with .22 target rife at 50 feet from a
>>standing position.)
>
>
> Why is this a good comparison? You don't steer with your hands when
> coasting downhill, and you don't even give indication in your rifle example
> of how fast the angle is changing, which is of course important in the case
> of coasting on a bike.
>
Benjamin Lewis
Because it might be slower than the length of time it takes fretting to
start.
jim beam
if it's less than the lube replenishment period in a system like this.
Ed
>I'd like to know how many people in this country have ever experienced
>a sidewall wear-out in their lifetimes vs. how many have experienced
>an out of round or pretzled rim
Good point. I never knew sidewalls could wear out until I started reading this
newsgroup. But I live in a flat part of the country and do not intentionally
ride in the rain. And I have pretzled a rim.
Benjamin Lewis
I have no idea how long either of these times are, which is why I was
asking. I wouldn't be at all surprised if it were less.
carl...@comcast.net
<bcl...@cs.sfu.ca> wrote:
>jim beam wrote:
>
>> Benjamin Lewis wrote:
>>> jim beam wrote:
>>>> Benjamin Lewis wrote:
>>>>> Why is this a good comparison? You don't steer with your hands when
>>>>> coasting downhill, and you don't even give indication in your rifle
>>>>> example of how fast the angle is changing, which is of course
>>>>> important in the case of coasting on a bike.
>>>>
>>>> why is the rate of angle change important?
>>> Because it might be slower than the length of time it takes fretting to
>>> start.
>>>
>> what length of time "might" that be? i don't know, but i'd be surprised
>> if it's less than the lube replenishment period in a system like this.
>
>I have no idea how long either of these times are, which is why I was
>asking. I wouldn't be at all surprised if it were less.
Dear Benjamin,
Asking about both times sounds sensible.
The time for replenishing the squashed-out oil is probably
the time for a single roll in any direction of one tenth of
one degree, corresponding to the length of time for the
outside of the handlebar to move 0.015 inches. That is, a
single roll to a new patch of oily surface is all that's
needed.
Figuring out how long it takes a small bearing to move less
than 0.01 degrees would require first knowing how the
bearing's circumference and dividing that by 3600.
A 1/4" bearing has a circumference of 0.7854 inches, so 0.1
degrees of movement (1/3600th) means a roll of 0.000218
inches.
A 3/16" bearing has a cirumference of 0.5890 inches, so 0.1
degrees of movement (1/3600th) means a roll of 0.000163
inches.
A 5/32" bearing has a circumference of 0.4909 inches, so 0.1
degrees of movement (1/3600th) means a roll of 0.000136
inches.
(For comparison, a human hair is about 0.001000 inches, five
times the size of the largest movement above.)
Of course, another factor is how long it takes for the ball
to penetrate the protective oil layer. Given the viscosity
of oil, it seems likely that this will be longer than the
ball will sit still and move less than 0.0002 inches, just
from ordinary handlebar vibration due to road buzz.
That leads to the related question of how fast the
handlebars are moving back and forth. The accelerometer
tests from Specialized measure vibrations between the axle
and the handlebars up to at least 600 Hz:
http://www.specialized.com/OA_MEDIA/pdf/Witchcraft.pdf
Copies mailed to me from Specialized were clear enough to
see that the horizontal scale on those two lower graphs runs
0, 100, 200, 300, 400, 500, 600 Hz, while the vertical scale
is log, going down 1, 0.1, 0.01, 0.001, 0.0001.
(Regrettably, there was no further improvement in
legibility, but a new scanner and a related set of graphs
may prove to be of interest.)
Anyway, those are some of the figures that I can see, though
they're not enough to answer the question directly. However,
the fretting theory itself seems to insist that ordinary
riding is sufficient to stop the balls from penetrating the
oil, micro-welding to the race, and tearing loose. So the
fretting theory itself predicts that the steering motion
from merely turning the pedals on the flats is enough to
make a difference--which suggests a very slow penetration
time.
The jiggling of a rider's hands on the bars while coasting
down a normal road at 30 mph is far more than the tenth of
less than one degree predicted to be enough for
replenishment. The vibrations are measured in hundreds of
Hertz (cycles per second), so they're orders of magnitude
faster than any pedal cadence measure in rpm.
I still waver on the matter and hope to hear more, but I
have to side with Jim Beam on which time is likely to be
faster. Until someone comes up with an explanation that goes
against these kinds of figures, I expect the headset balls
to roll back and forth 0.1 degrees on a normal road far more
rapidly than they penetrate the oil--if they didn't, they'd
fret themselves during any kind of riding, not just downhill
coasting.
Carl Fogel
Tom Ace
> That there
> are dimples in the upper race can also not be explained by impact.
What about the cases where only the lower race has dimples?
I remember that around 1980, one of the mail-order houses
(probably Bikecology or Nashbar (originally Bike Warehouse))
included in their catalog a replacement bottom half of a
headset, for riders who had detented steering due to dimples
in the lower race of their Campi headsets. I know that the
marketing of a part by no means guarantees that it solves
a real problem--but around that time, my Campi Record road
headset (#1039) developed dimples in the bottom half only,
and I doubt I was the only rider with that experience.
I replaced the bottom half with Stronglight roller bearing
parts and never had the problem thereafter.
Tom Ace
LewW
Jim and Jobst, I fret over the rancor between you two. I wish you would
kiss and make up. How about a hug?
Lew
Mark Janeba
> For example, [...] in your [Jobst'] book you made a value judgement that
> durable rim sidewalls are important because otherwise they wear out.
> I'd like to know how many people in this country have ever experienced
> a sidewall wear-out in their lifetimes vs. how many have experienced
> an out of round or pretzled rim, and I think you'd find that the
> latter beat the former by an order of magnitude or more. In the big
> scheme of things sidewall wearouts are a secondary consideration for
> most riders.
Ahh, but Don, you're in sunny (? maybe not this year) Southern
California. I'm in wet Western Oregon, and I've had a sidewall wearout,
as has a friend when he lived here.
I'm sure what you say is true for low-rain areas; when I lived in a
low-rain area, I would have agreed with you. No longer, I've learned
the hard way. Fortunately I was moving slowly when the sidewall peeled
off and jammed in the brakes, locking the rear wheel.
Now I pay attention to the conditions of the rim sidewalls on bikes that
get ridden lots in the rain.
Mark Janeba
carl...@comcast.net
wrote:
Dear Lew,
I doubt that you'll make a dent in their relationship
without using an electron microscope to see if the dimples
in the mysterious Mona-Lisa smiles of the races show erosion
or compression (or both).
Amusingly, like most of our squabbles here, it doesn't
matter which damage theory is correct, since there's no cure
except to replace the enigmatic ball bearings with tapered
roller bearings.
But it's lots of fun to wonder.
Carl Fogel
Benjamin Lewis
> The time for replenishing the squashed-out oil is probably the time for a
> single roll in any direction of one tenth of one degree, corresponding to
> the length of time for the outside of the handlebar to move 0.015
> inches. That is, a single roll to a new patch of oily surface is all
> that's needed.
>
> Figuring out how long it takes a small bearing to move less than 0.01
> degrees would require first knowing how the bearing's circumference and
> dividing that by 3600.
[...]
> Of course, another factor is how long it takes for the ball to penetrate
> the protective oil layer. Given the viscosity of oil, it seems likely
> that this will be longer than the ball will sit still and move less than
> 0.0002 inches, just from ordinary handlebar vibration due to road buzz.
>
> That leads to the related question of how fast the handlebars are moving
> back and forth. The accelerometer tests from Specialized measure
> vibrations between the axle and the handlebars up to at least 600 Hz:
>
> http://www.specialized.com/OA_MEDIA/pdf/Witchcraft.pdf
Do these vibrations cause horizontal steering movement? How much?
[...]
> Anyway, those are some of the figures that I can see, though they're not
> enough to answer the question directly. However, the fretting theory
> itself seems to insist that ordinary riding is sufficient to stop the
> balls from penetrating the oil, micro-welding to the race, and tearing
> loose. So the fretting theory itself predicts that the steering motion
> from merely turning the pedals on the flats is enough to make a
> difference--which suggests a very slow penetration time.
>
> The jiggling of a rider's hands on the bars while coasting down a normal
> road at 30 mph is far more than the tenth of less than one degree
> predicted to be enough for replenishment. The vibrations are measured in
> hundreds of Hertz (cycles per second), so they're orders of magnitude
> faster than any pedal cadence measure in rpm.
>
> I still waver on the matter and hope to hear more, but I have to side
> with Jim Beam on which time is likely to be faster. Until someone comes
> up with an explanation that goes against these kinds of figures, I expect
> the headset balls to roll back and forth 0.1 degrees on a normal road far
> more rapidly than they penetrate the oil--if they didn't, they'd fret
> themselves during any kind of riding, not just downhill coasting.
I'm not sure what you're suggesting. Are you arguing that fretting does
not happen (in spite of pretty clear evidence, IMO), or merely that it is
not more likely to happen during downhill coasting than in other types of
riding?
My intuitions are that a) fretting is a somewhat marginal event whether
downhill coasting or not, or we'd see it occur much more rapidly, and that
b) it is most likely to occur during periods of minimal steering, and
downhill coasting seems to me to be the best candidate.
jobst....@stanfordalumni.org
>> Please explain how these dimples occur if it is not fretting, a
>> common mechanism for damaging rolling element bearings.
> While searching for posts about the number of bearings in a headset,
http://groups-beta.google.com/group/rec.bicycles.tech/msg/2d541ce44398f645
It isn't smoothness of surface but speed and not having a disturbing
grip on the bars. Classically, tucked in coasting down HWY1 to Santa
Cruz at 50+mph with wind causes no steering motions that you can see.
I have the hands on the stem and take pleasure in riding ON the 3"
wide edge stripe on the side of the road. Meanwhile the fork crown is
vibrating and because it is a Shimano pre-loaded angular contact
bearing, these motions are taken up by the spherical seat under the
ball bearing, something inherited from needle bearing headsets that
indexed worse than ball bearings.
> It sounds as if the very road vibration that the fretting theory of
> dimpled headsets relies on to micro-weld and then tear apart the
> balls and races would be ample to replenish the protective oil film.
The tear apart occurs in the range of ball fretting rotations, there
is no excursion outside of the elastic contact zone of the ball. That
is why the bearing fails.
> Was your 1997 calculation wrong about the necessary steering motion?
> Or am I missing something crucial about the fretting theory?
No.
jobst....@stanfordalumni.org
>>> Even coasting down the smoothest, straightest road, the ends of
>>> the handlebars constantly swivel considerably more than 0.015
>>> inches.
>>How much do they swivel?
>>> (At a modest 30 mph, a bike covers 44 feet of road surface per
>>> second--a 0.1 degree change of course amounts to only 0.92 inches
>>> in 44 feet. Few people can shoot 1-inch groups with .22 target
>>> rife at 50 feet from a standing position.)
>> Why is this a good comparison? You don't steer with your hands
>> when coasting downhill, and you don't even give indication in your
>> rifle example of how fast the angle is changing, which is of course
>> important in the case of coasting on a bike.
> It seems unlikely that any rider can lean on a pair of 17-inch-wide
> handlebars and coast downhill on an ordinary paved road without the
> ends of the handlebars swivelling constantly back and forth more
> than 0.015 inches.
I don't know where you get these dimensions but bumps on pavement
surfaces do not induce steering. At high speeds such steering motions
are essentially impossible unless you are striking your bars with your
fist. What I see here is that you are trying to nullify the
definition and common occurrence of fretting that was dug up by
posters to this subject. The definitions are there, accept it. As I
mentioned, automotive steering gears were classic places where such
problem existed.
> That's roughly 1/64th of an inch, the thickness of a fifteen
> human hairs or a sheet of paper. The bumps on a well paved
> road are considerably larger than that, and the effect is
> magnified at ends of the bars. How steady can any rider hold
> the handlebars against the buzz of road vibration?
I don't know where you are measuring, with angles and distances mixed.
By getting diverted into minutia, you are losing track of the issue.
> Riders are unconsciously making endless small corrections, (even
> when riding no-hands) much larger than a tenth of less than one
> degree of steering motion, which is the 0.015 inch movement said to
> be sufficient to replenish the protective oil layer under a headset
> bearing.
That's what gets repeated often but these people apparently never
descend at speeds over 30mph where you have a hard time guessing
where any steering corrections are being made. As I said, I often
coast downhill riding in the width of the 3" wide edge stripe just for
the hell o9f it, just as I usually cut between pairs of Botts dots on
double yellow line marked roads. That's a slot of 2" taken at an
angle.
> One easy way to demonstrate this is to try to hold one side of your
> front tire within an inch of a highway stripe for 44 feet at 30 mph
> (one second).
I do that for a 1/4 mile at least but that doesn't mean you need to do
that to avoid steering motions. Most people take a random azimuth to
road striping when coasting on empty roads and follow an equally
straight course, only on that is not parallel to any prescribed line.
> A More difficult demonstration is to find a 30 mph roll-out through
> a convenient puddle at the bottom of a hill after a rain. The
> tracks on the dry pavement past the puddle will vary rather more
> than an inch to both sides side of the initial line every 44 feet.
I don't get it. What is this about and what does it prove?
> (For those who lack surveyor's equipment, a peep-sight rifle is a
> handy tool, but pick a deserted road--bystanders tend be easily
> alarmed. Because our muscles are shakier than we like to think,
> sighting steadily even on an inch-wide target at 50 feet with a
> 24-inch sight radius (easier than a 17-inch handlebar) is so hard
> that you'll quickly realize why surveyors use tripod rests and
> cross-haired telescopic sights.)
How does the NRA keep getting into bicycle steering gears?
> Closer at hand, pick up your keyboard, which is conveniently about
> the width of touring handlebars. Brace its middle against a corner
> of your desk, extending your arms in roughly a bicycling posture.
> Do the ends of the keyboard move more than the thickness of a sheet
> of paper?
This sounds like some office exerciser routine. I've heard other
things one should pick up and do lifting motions.
As I said, you don't steer when you descend fast, It's mainly no-hands
control that takes over even with hands on the bars.
jobst....@stanfordalumni.org
> The time for replenishing the squashed-out oil is probably the time
> for a single roll in any direction of one tenth of one degree,
> corresponding to the length of time for the outside of the handlebar
> to move 0.015 inches. That is, a single roll to a new patch of oily
> surface is all that's needed.
> Figuring out how long it takes a small bearing to move less than
> 0.01 degrees would require first knowing how the bearing's
> circumference and dividing that by 3600.
> A 1/4" bearing has a circumference of 0.7854 inches, so 0.1 degrees
> of movement (1/3600th) means a roll of 0.000218 inches.
More important is the elastic contact patch of such a bearing ball in
its races and how much of a ball rotation is required to expose all of
that area to surrounding lubricating oil. That is where the angular
computation takes place. Handlebars are not part of this.
> A 3/16" bearing has a cirumference of 0.5890 inches, so 0.1 degrees
> of movement (1/3600th) means a roll of 0.000163 inches.
So? How large is the contact area under normal loading? That is
where the angle arises.
> A 5/32" bearing has a circumference of 0.4909 inches, so 0.1 degrees
> of movement (1/3600th) means a roll of 0.000136 inches.
> (For comparison, a human hair is about 0.001000 inches, five times
> the size of the largest movement above.)
And I suppose a rifling land has a width as well but lets get back to
bicycles and bearings.
> Of course, another factor is how long it takes for the ball to
> penetrate the protective oil layer. Given the viscosity of oil, it
> seems likely that this will be longer than the ball will sit still
> and move less than 0.0002 inches, just from ordinary handlebar
> vibration due to road buzz.
That probably takes a few seconds but I haven't given that much
thought because fretting damage occurs and many different riders have
reported it, ones that descend fast as well as more careful riders.
> That leads to the related question of how fast the handlebars are
> moving back and forth. The accelerometer tests from Specialized
> measure vibrations between the axle and the handlebars up to at
> least 600 Hz:
http://www.specialized.com/OA_MEDIA/pdf/Witchcraft.pdf
These are all pointless diversions. If you want to do a quantitative
analysis of this, I suggest you do that in the privacy of your own
laboratory and return with th results. Public research at the KBD
doesn't cut it.
jobst....@stanfordalumni.org
What about it? I just mentioned that I observed head bearings that
had upper bearing damage to underscore that it doesn't require impact.
That some bearings are not affected doesn't change that.
jobst....@stanfordalumni.org
> Jim and Jobst, I fret over the rancor between you two. I wish you
> would kiss and make up. How about a hug?
Please cite where I posted with rancor. I think you are seeing
someone else's writing. In fact those who take greatest offense when
I describe some mechanical phenomena are usually ones who volunteer
that they are perpetrators of the practice I describe. I don't ask
for volunteers to raise their hands and say "Hey, that's me!" but they
do it anyway, somehow believing I identified them by name. That's
where I see rancor.
jobst....@stanfordalumni.org
>> I thank everyone who responded.
>> Jim and Jobst, I fret over the rancor between you two. I wish you
>> would kiss and make up. How about a hug?
> I doubt that you'll make a dent in their relationship without using
> an electron microscope to see if the dimples in the mysterious
> Mona-Lisa smiles of the races show erosion or compression (or both).
> Amusingly, like most of our squabbles here, it doesn't matter which
> damage theory is correct, since there's no cure except to replace
> the enigmatic ball bearings with tapered roller bearings.
I disagree. There are several head bearings that are fairly immune to
this syndrome and I have mentioned them often. Of course if you don't
believe fretting has anything to do with this than you wouldn't buy
one of these bearings and continue to conjecture on minutia between
fact and fiction.
> But it's lots of fun to wonder.
That's the problem. Stop wondering and become familiar with the
solution to this problem offer4ed by manufacturers.
Joe Riel
> Ahh, but Don, you're in sunny (? maybe not this year) Southern
> California. I'm in wet Western Oregon, and I've had a sidewall
> wearout, as has a friend when he lived here.
I live in San Diego and have worn out rims. It might not rain much,
but because I was riding (commuting) regardless, and down a fairly
long descent, it took its toll. Virtually all the rim wear occurred
in the rainy season.
Joe
carl...@comcast.net
jobst....@stanfordalumni.org wrote:
carl...@comcast.net wrote:
[snip]
>> One easy way to demonstrate this is to try to hold one side of your
>> front tire within an inch of a highway stripe for 44 feet at 30 mph
>> (one second).
>
>I do that for a 1/4 mile at least
[snip]
Dear Jobst,
I'd be glad to host a picture of the right side of your tire
track staying within an inch of the left side of a solid
road stripe at 30 mph for . . .
Let's see, how about a tenth of your claim of 1/4 mile?
That would be 132 feet, three seconds at 30 mph.
Perhaps you could mount a videocam on your handlebar or
frame, aimed down at your front tire.
Or a car could follow as you zoom through a puddle or some
paint and film the result--the paint would make things
clearer than a 24 or 30 frame per second video.
I really would like to know if it's true, so I look forward
to some truly impressive pictures.
Carl Fogel
carl...@comcast.net
Dear Jobst,
If you're ever short of time, you could tighten up that
familiar post by just quoting Shakespeare:
I thank my God for my humility.
--R. III
Incidentally, there's a difference between describing a
mechanical phenomena and describing your theory about a
mechanical phenomena.
Carl Fogel
jtaylor
<carl...@comcast.net> wrote in message
news:ko35919juhsuu17bl...@4ax.com...
> Dear Jobst,
>
> I'd be glad to host a picture of the right side of your tire
> track staying within an inch of the left side of a solid
> road stripe at 30 mph for . . .
>
> Let's see, how about a tenth of your claim of 1/4 mile?
>
> That would be 132 feet, three seconds at 30 mph.
>
> Perhaps you could mount a videocam on your handlebar or
> frame, aimed down at your front tire.
>
> Or a car could follow as you zoom through a puddle or some
> paint and film the result--the paint would make things
> clearer than a 24 or 30 frame per second video.
>
> I really would like to know if it's true, so I look forward
> to some truly impressive pictures.
>
That's no so hard - in earlier days (before the ten-speed boom) I've seen
kids ride railway tracks.
It's a bit tricky when they come off, but not scary enough that they didn't
go do it again and again untill they could do 200 metres or so...
jtaylor
<jobst....@stanfordalumni.org> wrote in message
news:j0tke.1771$W51....@typhoon.sonic.net...
>
> > Was your 1997 calculation wrong about the necessary steering motion?
> > Or am I missing something crucial about the fretting theory?
>
> No.
No to one, the other, or both?
Peter Cole
> Dear Jobst,
>
> If you're ever short of time, you could tighten up that
> familiar post by just quoting Shakespeare:
>
> I thank my God for my humility.
> --R. III
>
> Incidentally, there's a difference between describing a
> mechanical phenomena and describing your theory about a
> mechanical phenomena.
>
> Carl Fogel
From m-w.com:
"usage: Phenomena has been in occasional use as a singular for more than
400 years and its plural phenomenas for more than 350. Our evidence
shows that it is primarily a speech form used by poets, critics, and
professors, among others, but one that sometimes turns up in edited
prose <the Borgia were, in modern terms, a media phenomena --
Economist>. It is etymologically no more irregular than stamina, agenda,
and candelabra, but it has nowhere near the frequency of use that they
have, and while they are standard, phenomena is still rather borderline."
Tom Ace
> > What about the cases where only the lower race has dimples?
[...]
>
> What about it? I just mentioned that I observed head bearings that
> had upper bearing damage to underscore that it doesn't require
> impact. That some bearings are not affected doesn't change that.
So far so good. But I would also like to understand what
is going on in cases where the dimples appear only in the
bottom race.
Are lower-race pits always a result of lubrication failure
and fretting (exacerbated by the role the lower race plays
in bearing the rider's weight), or is another mechanism
sometimes the culprit?
Tom Ace
jobst....@stanfordalumni.org
>>> One easy way to demonstrate this is to try to hold one side of
>>> your front tire within an inch of a highway stripe for 44 feet at
>>> 30 mph (one second).
>> I do that for a 1/4 mile at least
> I'd be glad to host a picture of the right side of your tire track
> staying within an inch of the left side of a solid road stripe at 30
> mph for...
> Let's see, how about a tenth of your claim of 1/4 mile?
> That would be 132 feet, three seconds at 30 mph.
Just because you can't do that, don't assume others can't either.
Locally, coasting down HWY84 toward La Honda as well as down the half
mile descents of HWY1 on the coast staying within a 3" stripe is
trivial at 30-50mph if there isn't a cross wind. Next time you coast
down a smooth highway with your hands on the stem try it. It's easy.
> Perhaps you could mount a videocam on your handlebar or frame, aimed
> down at your front tire.
There must be some riders around your neck of the woods who can coast
on a 3" wide road-edge stripe without difficulty. Get a demo.
> Or a car could follow as you zoom through a puddle or some paint and
> film the result--the paint would make things clearer than a 24 or 30
> frame per second video.
> I really would like to know if it's true, so I look forward to some
> truly impressive pictures.
All I seem to hear from your side is "liar, liar, pants on fire..."
You are getting close to insultingly incredulous.
jobst....@stanfordalumni.org
>>> What about the cases where only the lower race has dimples?
>> What about it? I just mentioned that I observed head bearings that
>> had upper bearing damage to underscore that it doesn't require
>> impact. That some bearings are not affected doesn't change that.
> So far so good. But I would also like to understand what is going
> on in cases where the dimples appear only in the bottom race.
> Are lower-race pits always a result of lubrication failure and
> fretting (exacerbated by the role the lower race plays in bearing
> the rider's weight), or is another mechanism sometimes the culprit?
Yes and upper race indexing probably occurs mainly with head bearings
that are adjusted on the low clearance side and remain in contact
during oscillations. You can imagine that if there is even a 0.0001"
or so of lift-off, that lubrication can be replenished.
carl...@comcast.net
Dear Jobst,
More pictures, less boasting. I didn't say within a 3"
strip. I said the right side of your 1-inch tire staying
within 1 inch of the left side of the stripe.
Just do it, to use your phrase, and show us the pictures.
A stripe of paint from your tires 132 feet long on a 30 mph
downhill, with no more than an inch of daylight between it
and the highway stripe, and no new paint on the stripe.
Incredulously,
Carl Fogel
data...@yahoo.com
improved lubrication.
http://www.google.com/search?hl=en&lr=&c2coff=1&oi=defmore&q=define:f...
And off course known to the state of california
and finish lime! whew... smelss like...
the drive in!!
data...@yahoo.com
less can be said of his critics
Donald Gillies
>In article <d6pktu$2du$1...@cascade.cs.ubc.ca>, Donald Gillies says...
>>I'd like to know how many people in this country have ever experienced
>>a sidewall wear-out in their lifetimes vs. how many have experienced
>>an out of round or pretzled rim
>Good point. I never knew sidewalls could wear out until I started reading this
>newsgroup. But I live in a flat part of the country and do not intentionally
>ride in the rain. And I have pretzled a rim.
Jobst lives in the Peninsula of the Bay Area which is a highly UNUSUAL
place no matter what people tell you. 80% of the population in this
country has severe winters and potholes, and imho potholes and poor
road conditions are the most common cause of rim failure, but in jobst
experience, potholes don't exist so potholes don't matter.
- Don Gillies
San Diego, CA
Donald Gillies
recommend a type of rims than you can recommend a "best color". All
you guys keep debating what is the best color, do it to you're blue in
the face.
I grew up in Rainy central Illinois, which like 85% of the country has
frost and potholes and sewer gratings and I lost ALL but one rim to
potholes and one to pretzling in a slide and NONE to sidewall
wearout. I rode in the rain all year long, and in the ice too.
Now that I live in California imho the worst rims are mavic's - why ?
here's stupidity personified : my sidewalls got practically destroyed
by my 1998 Ultegra brake pads which incidentally squeeled like crazy.
MA2's ?? they'd be destroyed too !! Now do you understand how
sophomoric the "best rims" argument can be ??
Now Jobst is trying to do the same thing with headset wearout -
proffering that one riding style causes failure, so parts that
withstand that one riding style are best. I won't stand for such
foolishness. I won't.
Bruce Graham
carl...@comcast.net says...
Carl
This does sound dangerous with my skill levels but maybe not too hard.
Is it only my small mind that amuses itself with pedalling on the white
line side marker? If you can stay on while pedalling, would it not be
easier when coasting?
Bruce
jim beam
carl...@comcast.net
Gillies) wrote:
Dear Don,
No one would accuse me of worshipping Jobst blindly, but I
really have to say that I'd be astonished if Jobst has no
experience with the effects of severe winters or with
potholes.
There are rumors that Jobst ventures into the Sierras, and I
could swear that I've seen pictures of someone resembling
him wandering around spring snowbanks in Alpine passes.
Incidentally, severe winters are not the only cause of
potholes:
"Florida roads were ranked third worst for potholes and poor
repair in a recent study of roads in 38 states and
Washington, D.C., by the Surface Transportation Policy
Project, a non-profit coalition of 175 local and national
transportation policy groups. . . . pothole problems often
are caused by freezing and thawing weather patterns or, as
in Florida's case, heavy traffic and rapid population
growth."
http://pr.tennessee.edu/news/sept97/potholes.htm
Carl Fogel
carl...@comcast.net
Dear Bruce,
To clarify the point that keeps getting lost, yes, a rider
can keep his front tire on a 3-inch wide highway stripe at
30 mph. (But that wasn't what I was saying--read on.)
If we generously allow a 1-inch tire to stray to either side
of a 3-inch highway stripe until the whole tire is just
barely still in contact with the 3-inch stripe, then
the tire has a 4-inch center range of movement, meaning that
its center can move left or right 2 inches from the center
of the stripe:
----------1---------2---------3---------4---------5
012345678901234567890123456789012345678901234567890
| TTTTTTTTTT |
TTTTTTTTTT| |
| |TTTTTTTTTT
<----------------4" range---------------->
of center movement
(Sorry, but you have to imagine that the |'s are zero-width
edges. ASCII art is crude--and probably shows up wrong on
some displays. You can draw a better picture with a ruler.)
If we're more restricitve and insist that no part of a
1-inch tire can stray beyond the edges of the 3-inch highway
stripe, then the 1-inch tire has a total range of center
movement of only 2 inches, meaning that it's center can move
left or right only full inch from the center of the stripe:
----------1---------2---------3---------4---------5
012345678901234567890123456789012345678901234567890
| TTTTTTTTTT |
|TTTTTTTTTT |
| TTTTTTTTT|
| |
<-----2" range----->
of center movement
But that's not what I wrote or meant.
I'm saying that I don't think that a rider can keep one edge
of his front tire within 1 inch of one side of a highway
stripe, which means only a 1/2-inch of tire movement left or
right:
----------0----------1---------2---------3---------4
----------01234567890123456789012345678901234567890
| |
TTTTTTTTTT | |
TTTTTTTTTTT| |
| |
<--------->
1" range
of center movement
See how much narrower what I was saying is? I'm talking
about a 1-inch range of movement, not a 2 or 4 inch range.
Imagine standing and balancing with one foot ahead of the
other on a 4-inch wide board, about the width of an adult
shoe--you can do this.
Now imagine doing the same thing with a 2-inch wide
board--that's trickier.
Now try a 1-inch wide board. This is why few of us are
tightrope walkers.
Bicycle tires continually curve to maintain balance. In a
"straight" line, the curves are tiny--but the curving track
is more than an inch wide over 44 feet on ordinary pavement
at 30 mph, which is one second, which arose from the long
forgotten point that a 0.1 degree angle, more than enough to
replenish the lubrication of a headset bearing, ends up 0.92
inches wide in 44 feet.
An understandable comment is that riders can easily hit a
single tiny target with the front tire at 30 mph. Drop a
shiny dime on the ground, come back, and you should be able
to hit it with your front tire.
But this is point accuracy, not lengthwise accuracy.
Dab 26 colored toothpicks with glue and stick them an inch
to one side and parallel to a highway stripe at 5-foot
intervals on some reasonably straight downhill, about 132
feet and about 3 seconds at 30 mph. (I can't think of a
cheaper test, as long as you remember to lay the toothpicks
flat.)
Now give yourself plenty of time to get rolling and try to
hit all 26 colored toothpicks.
I don't think that you'll hit all 26 toothpicks, even with
the guide of the white highway stripe next to them.
If you don't, then the center of your 1-inch tire was moving
more than an inch, side-to-side.
(Dimes would be 70% easier to hit than toothpicks, since
they'd turn the 1-inch wide acceptable weave into 1.7
inches--see how small these things are?)
As baseball outfielders know, the easiest way to catch a fly
ball is to take a curving approach--we can control how
tightly we curve better than we can stay on a straight line
if all we have to do is hit a point.
And that's how we hit a single toothpick at 30 mph--we're
already heading close to it, so we just curve a tiny bit and
nail it.
But that curve sends us off-course for the next toothpick in
the straight line--not that we have time to react to 26
toothpicks 5 feet apart in only 3 seconds--they're zipping
past at almost 10 toothpicks per second.
A wiggling curve pattern in which the tire can weave only
half an inch left or right from dead straight doesn't offer
much balance--that's what I'm talking about, allowing no
more than an inch of daylight between tire and stripe and
not letting the tire edge drift over the stripe.
A wiggling curve pattern in which the tire can weave an inch
left or right is obviously at least twice as good for
balancing, though still not much--that may be what some
people are talking about, keeping an inch-wide tire entirely
on a 3-inch wide stripe.
A wiggling curve pattern in which the tire can weave two
inches left or right is at least 4 times as good for
balancing--this may be what most people are talking about,
keeping at least one edge of an inch-wide tire touching a
highway stripe.
I may still be impressed by someone, but I suspect that it
will take a hell of a smooth downhill and fantastic balance
for an inch-wide high-pressure tire on a rigid-frame bicycle
not to weave more than half an inch left or right.
Carl Fogel
Bruce Graham
carl...@comcast.net says...
> I may still be impressed by someone, but I suspect that it
> will take a hell of a smooth downhill and fantastic balance
> for an inch-wide high-pressure tire on a rigid-frame bicycle
> not to weave more than half an inch left or right.
>
>
thread in detail to see if that is what Jobst claimed. If we were
investigating aviation accidents, we would have to do this, but I'm happy
to cut him a bit of slack in the interest of colourful language here.
cheers
Bruce G
Luns Tee
<carl...@comcast.net> wrote:
>At a modest 30 mph, a bike covers 44 feet of
>road surface per second--a 0.1 degree change of course
>amounts to only 0.92 inches in 44 feet.
Hold it right there, Carl. You're assembling numbers in a way
that does not reflect what actually happens. This value of 0.92 inches
is meaningless, and does not relate one bit to a steering angle of 0.1
degrees. This number is for a STRAIGHT line relative to some reference
line on the road. A bicycle travelling a straight line has a steering
angle of zero. You can be on a straight line trajectory 20 degrees to
the road with no substantial steering angle.
The angle that the handlebars have turned affect the _curvature_
of the bicycle's path. The angle the bicycle is travelling at is not the
angle of the handlebars, it's the running sum (the integral) of this
curvature.
Try again. Here's a hint: if your calculation doesn't include
the wheelbase, then you don't have a meaningful representation of
what's going on.
-Luns
Peter Cole
> I grew up in Rainy central Illinois, which like 85% of the country has
> frost and potholes and sewer gratings and I lost ALL but one rim to
> potholes and one to pretzling in a slide and NONE to sidewall
> wearout. I rode in the rain all year long, and in the ice too.
Sounds more like a operator issue than a rim issue.
>
> Now that I live in California imho the worst rims are mavic's - why ?
> here's stupidity personified : my sidewalls got practically destroyed
> by my 1998 Ultegra brake pads which incidentally squeeled like crazy.
> MA2's ?? they'd be destroyed too !! Now do you understand how
> sophomoric the "best rims" argument can be ??
Sounds more like a pad issue than a rim issue.
jim beam
it's not just a pad issue - it's a shimano design issue. shimano, this
era at any rate, have the pads toes from the factory, and they're toed
front end in so any grit on the rim gets trapped within the front/rear
gap. cool stop pads have a scraper lip which addresses this issue by
touching at the rear first stopping grit progressing under as the brake
is applied, but at the expense of pad thickness. campy brakes, [and now
the current generation of high end shimanos] have orbital pad mountings
that allow the pads to be set parallel with the rim. this pretty much
alleviates the problem and is what i do to my campy bikes. i hardly
ever have embedding issues, even with stock pads. for the "toe in
advocates", there's never been any braking problems from ignoring toe
that i've ever been able to determine.
Tom Nakashima
<carl...@comcast.net> wrote in message
news:m06791l9fv2hrk9hf...@4ax.com...
The straightness of a painted line on the road is greater than .500" over 10
ft. so how do you expect one to follow it within 1.000"
-tom
Donald Gillies
>Donald Gillies wrote:
Exactly. The best rim might depend more on the operator or brake pads
than on a particular rim quality. You get an "A".
- Don
Zog The Undeniable
> In the big
> scheme of things sidewall wearouts are a secondary consideration for
> most riders.
As you live in California, maybe that's true. In rainy, muddy, icy
Britain rims wear out in as little as two seasons. The rear one goes
first because it's constantly bathed in gritty water by the front wheel.
Zog The Undeniable
> I'd be glad to host a picture of the right side of your tire
> track staying within an inch of the left side of a solid
> road stripe at 30 mph for . . .
Where possible, I ride on the white lines in TTs. They're smoother than
the asphalt. A couple of weeks ago in an open TT I was riding at 30mph
with a roaring tailwind (the return leg into the wind was hell).
Jose Rizal
> Peter Cole wrote:
>
>> Donald Gillies wrote:
>>> Now that I live in California imho the worst rims are mavic's - why ?
>>> here's stupidity personified : my sidewalls got practically destroyed
>>> by my 1998 Ultegra brake pads which incidentally squeeled like crazy.
>>> MA2's ?? they'd be destroyed too !! Now do you understand how
>>> sophomoric the "best rims" argument can be ??
>>
>>
>>
>> Sounds more like a pad issue than a rim issue.
>
>
> it's not just a pad issue - it's a shimano design issue. shimano, this
> era at any rate, have the pads toes from the factory, and they're toed
> front end in so any grit on the rim gets trapped within the front/rear
> gap.
Nonsense. Shimano pads don't have built-in toe, they're mere
flat-surfaced pads that are adjusted by the bike assembler at the
caliper; Shimano brake assemblies aren't usable out of the box without
any adjustments. It's the assembler that toes in pads.
> cool stop pads have a scraper lip which addresses this issue by
> touching at the rear first stopping grit progressing under as the brake
> is applied, but at the expense of pad thickness.
The scraper lip of Koolstops last all of a few tens of miles of hard
use, the pads afterwards becoming just simple straight-surfaced pads for
most of their lives. These aren't magical by any means.
> campy brakes, [and now
> the current generation of high end shimanos] have orbital pad mountings
> that allow the pads to be set parallel with the rim.
Shimano calipers and pads have always had this adjustability.
> this pretty much
> alleviates the problem and is what i do to my campy bikes.
What problem, wear? You're a magician if you think you've found the
solution to rim wear.
> i hardly
> ever have embedding issues, even with stock pads.
This is a related, but different issue to wear.
> for the "toe in
> advocates", there's never been any braking problems from ignoring toe
> that i've ever been able to determine.
Maybe because you hardly ride at all... most squealing and shuddering
problems from rim brakes are directly attributable to pad positioning
relative to the rim.
Tom Nakashima
"Jose Rizal" <_@_._> wrote in message
news:505le.7693$M36....@newsread1.news.atl.earthlink.net...
>
> What problem, wear? You're a magician if you think you've found the
> solution to rim wear.
Actually I may have. I've found the Kool Stop Continental pads don't wear
the rim as much as other brake pads, including the Kool Stop Salmon Colored
replacements. At $5.95 a pair it's worth a try. They squeal a bit at first
until you hit the first rain which will surface the brake pads to the rim.
http://harriscyclery.net/site/itemdetails.cfm?ID=479 the link to the Kool
Stop Continental pads.
-tom
carl...@comcast.net
Dear Luns,
I agree that the width of a tenth of less than one degree at
44 feet (0.92 inches) is not the same as what a movement of
the same angle of the handlebars would describe over the
same distance.
But since the bars are vibrating back and forth when viewed
from above considerably more than 0.1 degrees, it seems like
a reasonable approach to a neglected detail.
The theory, as I understand it, is that the handlebars don't
move enough on long downhills to move the ball bearings
enough to keep them lubricated. This seemed reasonable,
until I stumbled over Jobst's post (quoted well up this
thread) that stated that a ball bearing rotation of less
than one tenth of one degree is enough to replenish the
lubrication.
One-tenth of one degree of a 17-inch diameter circle
(roughly the size of a pair of touring handlebars) amounts
to the end of the handlebar moving 0.015 inches--less than
the thickness of a sheet of copier paper.
The path of the front wheel rolling in a "straight" line is
actually a series of small, constant correcting curves:
----------------
/\/\/\/\/\/\/\/\/
------------------
as oppose to the single simplified curve:
-----------------
/
----------------
(Imagine the single / stretching from left to right, and the
numerous /\/\/'s not nearly so sharply angled. ASCII art and
the scale don't make it easy.)
The running sum approach is indeed what's involved, but it
would be just as inaccurate unless we figured out how many
actual curves were involved.
I can't even get most of these guys to see that I'm talking
about the center of the tire weaving only an inch or less,
much less to wonder whether their handlebars rotate the
thickness of a sheet of paper (0.1 degrees, which would
produce a curve considerably greater than 1 inch over 44
feet for a bicycle wheelbase--if not constantly corrected).
Carl Fogel
carl...@comcast.net
Dear Tom,
Actually, I don't expect any bicyclist to ride that
straight.
I agree with you that even highway painting crews can't make
lines that straight using 4-wheeled vehicles at low speeds,
though they do a pretty good job.
I don't think that anyone can lay down a line in advance,
whether of paint or toothpicks, that the center of the front
tire will then follow without diverging more than half an
inch at 30 mph over 132 feet.
I think that the front tire is constantly being corrected by
tiny (and unconscious) steering movements as it rolls over
the bumps (which are small on decent pavement, but are
hitting 100 psi tires on a sold frame bicycle at 300 mph).
Another approach would be to ponder how far anyone can ride
a bicycle in a straight line with its stem welded solid to
the frame. That would prevent any handlebar steering
movement beyond the flex of the frame tubing.
I think that the bike would end up nowhere near the initial
intended line, proving that small steering movement are
occurring at the bearings. In fact, I think that the rider
would fall rather more quickly than he might expect.
Unfortunately, I doubt that I can lure anyone into
attempting more than one test run at 30 mph on a bike with
its front end welded solid.
But I'm willing to be proved wrong. Someone could roll
through a puddle or some paint, lay down a 132 foot track on
a shoulder, well away from any wobbly highway stripe, and
use surveyor's equipment to show how beautifully straight it
is.
But I think that a string line will show that the track of
the tire wanders even more without the guide of a nearby
line to let the rider correct it--that is, the "straight"
line on a shoulder would tend to curve back and forth even
more.
Carl Fogel
Luns Tee
<carl...@comcast.net> wrote:
>The path of the front wheel rolling in a "straight" line is
>actually a series of small, constant correcting curves:
>
>----------------
>/\/\/\/\/\/\/\/\/
>------------------
There are undulations, but let's keep in mind how they come
about. The bicycle is inherently stable and able to remain upright even
without a rider on it. Its trajectory won't necessarily be a straight
line, but depending on the initial conditions will be some simple arc -
it's not oscillatory.
The rider observes the difference between the curve the bicycle
is taking, and the direction intended. Small amounts of curvature take
longer to grow to being observable, so it's not unreasonable to
approximate the behaviour as happening at discrete intervals. These
intervals are long, so it's reasonable to look at how far a single
bend can get in the time you'd expect it takes a rider to notice and
correct it.
>The running sum approach is indeed what's involved, but it
>would be just as inaccurate unless we figured out how many
>actual curves were involved.
Approach this from the other side - instead of trying to guess
some curvature and decide whether a 0.1 degree steering angle fits or
not, take the 0.1 degree steering angle (and wheelbase: typically around
110cm) amd see what curve you can get from that. The decide whether
what comes out is reasonable or not. You've tried this already,
estimating the curve as a straight line at a 0.1 degree angle, but a
straight line is not a curve.
>I can't even get most of these guys to see that I'm talking
>about the center of the tire weaving only an inch or less,
The problem is that the evidence you're demanding people
demonstrate is overconstrained. The trajectory you want demonstrated
restricts both the angle _and_ the starting position, but what's being
argued is only the one of these two. It's like arguing that darts
never hit a 1cm horizontal strip on a dartboard, then demanding
somebody show you a bullseye to prove otherwise: you're excluding too
much.
A more direct analogy, albeit on a different time scale would
be objects in free-fall. I claim that a ball tossed in the air will stay
in a range of heights of less than 2cm for the 0.1 seconds around its
peak height. Your reasoning is to not believe this claim unless
somebody can demonstrate tossing a ball in the air _and_ have it stay
within 2cm of the ceiling for 0.1 seconds. One can keep tossing balls
in the air all day long, each time either not coming close enough to
the ceiling, or bouncing off of it, either way not demonstrate what
you're seeking. Yet with every toss that doesn't hit the ceiling, the
hovering within 2cm happens for 0.1seconds all the same.
>0.1 degrees, which would produce a curve considerably greater than 1
>inch over 44 feet for a bicycle wheelbase
So by your own admission, your 1" strip is too narrow a
constraint.
-Luns
jim beam
> jim beam wrote:
>
>> Peter Cole wrote:
>>
>>> Donald Gillies wrote:
>
>
>>>> Now that I live in California imho the worst rims are mavic's - why ?
>>>> here's stupidity personified : my sidewalls got practically destroyed
>>>> by my 1998 Ultegra brake pads which incidentally squeeled like crazy.
>>>> MA2's ?? they'd be destroyed too !! Now do you understand how
>>>> sophomoric the "best rims" argument can be ??
>>>
>>>
>>>
>>>
>>> Sounds more like a pad issue than a rim issue.
>>
>>
>>
>> it's not just a pad issue - it's a shimano design issue. shimano,
>> this era at any rate, have the pads toes from the factory, and they're
>> toed front end in so any grit on the rim gets trapped within the
>> front/rear gap.
>
>
> Nonsense. Shimano pads don't have built-in toe, they're mere
> flat-surfaced pads that are adjusted by the bike assembler at the
> caliper; Shimano brake assemblies aren't usable out of the box without
> any adjustments. It's the assembler that toes in pads.
jose, with respect, shimano 7700, 6600 & 5500 calipers are all toed out
of the box. you should check one some time.
>
>> cool stop pads have a scraper lip which addresses this issue by
>> touching at the rear first stopping grit progressing under as the
>> brake is applied, but at the expense of pad thickness.
>
>
> The scraper lip of Koolstops last all of a few tens of miles of hard
> use, the pads afterwards becoming just simple straight-surfaced pads for
> most of their lives. These aren't magical by any means.
sorry, but they have a void behind the lip. that means there's no
pressure on the lip & they /do/ last the life of the pad. you've
evidently never used them. i have.
>
>> campy brakes, [and now the current generation of high end shimanos]
>> have orbital pad mountings that allow the pads to be set parallel with
>> the rim.
>
>
> Shimano calipers and pads have always had this adjustability.
the above cited calipers are not adjustable unless you physically bend
the caliper arms - somehting that you should /never/ do for fatigue
initiation reasons.
>
>> this pretty much alleviates the problem and is what i do to my campy
>> bikes.
>
>
> What problem, wear? You're a magician if you think you've found the
> solution to rim wear.
don't put words in my mouth. i was referring to grit embedding. thanks
for paying attention.
>
>> i hardly ever have embedding issues, even with stock pads.
>
>
> This is a related, but different issue to wear.
>
>> for the "toe in advocates", there's never been any braking problems
>> from ignoring toe that i've ever been able to determine.
>
>
> Maybe because you hardly ride at all... most squealing and shuddering
> problems from rim brakes are directly attributable to pad positioning
> relative to the rim.
busted. i don't own a single bike. i never ride. i've never worn out
rims. i've never brinelled a bearing. i have no idea about fatigue. i
can't do simple leverage calcs recognizing the principle of equilibrium.
and i have absolutely /no/ clue about how microstructure affects
material properties. no siree bob.
jim beam
which is why ceramic rims were invented.
jobst....@stanfordalumni.org
>> What problem, wear? You're a magician if you think you've found
>> the solution to rim wear.
> Actually I may have. I've found the Kool Stop Continental pads
> don't wear the rim as much as other brake pads, including the Kool
> Stop Salmon Colored replacements. At $5.95 a pair it's worth a
> try. They squeal a bit at first until you hit the first rain which
> will surface the brake pads to the rim.
http://harriscyclery.net/site/itemdetails.cfm?ID=479
> the link to the Kool Stop Continental pads.
Not only do rims still wear with these pads but the pads wear out as
well. I have a bag of about 40 worn-to-the-metal Kool-Stop
Continental brake pads that go with the pile of worn out rims. The
reason this is interesting is that prior to switching to these pads,
about 20 years ago, rims got chewed up much faster by pads that
developed embedded cutting tools of road grit and aluminum oxide.
Don't over-sell the product and above all, talking to Kool-Stop has
not built confidence in their technology. I think they stumbled onto
this compound because they don't recognize its superiority while
making composite brake pads that have a mix with poorer materials.
I've tried to talk to them at trade shows and am not reassured.
jobst....@stanfordalumni.org
> I agree that the width of a tenth of less than one degree at 44 feet
> (0.92 inches) is not the same as what a movement of the same angle
> of the handlebars would describe over the same distance.
> But since the bars are vibrating back and forth when viewed from
> above considerably more than 0.1 degrees, it seems like a reasonable
> approach to a neglected detail.
> The theory, as I understand it, is that the handlebars don't move
> enough on long downhills to move the ball bearings enough to keep
> them lubricated. This seemed reasonable, until I stumbled over
> Jobst's post (quoted well up this thread) that stated that a ball
> bearing rotation of less than one tenth of one degree is enough to
> replenish the lubrication.
I don't see where handlebars naturally oscillate in steering motion
and I don't believe I said 1/10 of a degree of ball bearing rotation.
As I explained, if you know the load you can derive the contact area
of a ball in the race and this defines the angle that must be exceeded
to replenish lubrication.
In any case, this is so much sophistry. As people have cited from
reliable texts, fretting damage is a common occurrence in ball
bearings, I have seen it in automotive steering gears, wheel bearings
and differential bearings. Arguing over how straight a bicyclist can
coast down a hill is getting off the fairway and deep into the rough.
> One-tenth of one degree of a 17-inch diameter circle (roughly the
> size of a pair of touring handlebars) amounts to the end of the
> handlebar moving 0.015 inches--less than the thickness of a sheet of
> copier paper.
Common copier paper is 0.003" thick.
> The path of the front wheel rolling in a "straight" line is actually
> a series of small, constant correcting curves: as oppose to the
> single simplified curve:
This is entirely theory while in practice long sections of road are
covered in a path without corrections, one that doesn't necessarily
follow any pre-painted lines. That one can coast on a long straight
course is borne out by the occurrence of fretting damage to head
bearings that have all the characteristics of such damage... and the
occurrence of which has been almost eliminated by compound head
bearings with a swivel plate.
jim beam
> Carl Fogel writes:
>
>
>>I agree that the width of a tenth of less than one degree at 44 feet
>>(0.92 inches) is not the same as what a movement of the same angle
>>of the handlebars would describe over the same distance.
>
>
>>But since the bars are vibrating back and forth when viewed from
>>above considerably more than 0.1 degrees, it seems like a reasonable
>>approach to a neglected detail.
>
>
>>The theory, as I understand it, is that the handlebars don't move
>>enough on long downhills to move the ball bearings enough to keep
>>them lubricated. This seemed reasonable, until I stumbled over
>>Jobst's post (quoted well up this thread) that stated that a ball
>>bearing rotation of less than one tenth of one degree is enough to
>>replenish the lubrication.
>
>
> I don't see where handlebars naturally oscillate in steering motion
> and I don't believe I said 1/10 of a degree of ball bearing rotation.
> As I explained, if you know the load you can derive the contact area
> of a ball in the race and this defines the angle that must be exceeded
> to replenish lubrication.
>
> In any case, this is so much sophistry. As people have cited from
> reliable texts, fretting damage is a common occurrence in ball
> bearings
your texts date from the 50's jobst. get to a library and open
something published later than 1980 will you? metallurgy has advanced
since you were a boy. lubrication technology has advanced since you
were a boy. machine precision has advanced since you were a boy.
that's why manufacturers can ship cars around the globe without ruining
their bearings, /unlike/ when you were a boy.
>, I have seen it in automotive steering gears, wheel bearings
> and differential bearings.
you don't seem to know the difference between true brinelling & false
brinelling, so all you're seeing is what you /want/ to see. just like
you "see" gyroscopic stabilization in bike steering.
> Arguing over how straight a bicyclist can
> coast down a hill is getting off the fairway and deep into the rough.
>
>
>>One-tenth of one degree of a 17-inch diameter circle (roughly the
>>size of a pair of touring handlebars) amounts to the end of the
>>handlebar moving 0.015 inches--less than the thickness of a sheet of
>>copier paper.
>
>
> Common copier paper is 0.003" thick.
>
>
>>The path of the front wheel rolling in a "straight" line is actually
>>a series of small, constant correcting curves: as oppose to the
>>single simplified curve:
>
>
> This is entirely theory while in practice long sections of road are
> covered in a path without corrections, one that doesn't necessarily
> follow any pre-painted lines. That one can coast on a long straight
> course is borne out by the occurrence of fretting damage to head
> bearings that have all the characteristics of such damage... and the
> occurrence of which has been almost eliminated by compound head
> bearings with a swivel plate.
what a crock. you don't know what "fretting" damage is given that you
assert repeatedly that bike headsets cannot be true brinelled, despite
hard evidence to the contrary. you're just twisting facts in a vain
effort to fake credibility with the unitinitated. as for the
survivability of modern bearings, the bearing races have the same
angular contacts with the balls as ever before, but the metallurgy, the
lubrication, the precision and the sealing technologies have all
advanced. the evidence is right in front of you jobst, but you're
screaming denial. why? what does it achieve? embrace reality and move
forward 5 decades or so.
Peter Cole
>>>Now that I live in California imho the worst rims are mavic's - why ?
>>>here's stupidity personified : my sidewalls got practically destroyed
>>>by my 1998 Ultegra brake pads which incidentally squeeled like crazy.
>>>MA2's ?? they'd be destroyed too !! Now do you understand how
>>>sophomoric the "best rims" argument can be ??
>
>
>>Sounds more like a pad issue than a rim issue.
>
>
> Exactly. The best rim might depend more on the operator or brake pads
> than on a particular rim quality. You get an "A".
Soft pads wear out rims quickly in the rain. Of course the thinner the
rim sidewalls, the faster the rim wears out, all other things being
equal. I don't understand the point you're trying to make. First it
seems that you claim rims don't wear out, then an anecdote about crappy
pads.
I don't know if anyone could accurately estimate how many rims are lost
to impact damage vs. sidewall wear. From the postings here it seems like
sidewall wear is pretty common. That has also been my experience. I'd
like a rim that had an extra 0.5mm or so in the sidewall, especially
since replacement rims cost about the same as whole wheels.
frkr...@yahoo.com
jim beam wrote:
> jobst....@stanfordalumni.org wrote:
> >
> >
> > In any case, this is so much sophistry. As people have cited from
> > reliable texts, fretting damage is a common occurrence in ball
> > bearings
>
> your texts date from the 50's jobst. get to a library and open
> something published later than 1980 will you? metallurgy has advanced
> since you were a boy. lubrication technology has advanced since you
> were a boy. machine precision has advanced since you were a boy.
> that's why manufacturers can ship cars around the globe without ruining
> their bearings, /unlike/ when you were a boy.
> >
> > This is entirely theory while in practice long sections of road are
> > covered in a path without corrections, one that doesn't necessarily
> > follow any pre-painted lines. That one can coast on a long straight
> > course is borne out by the occurrence of fretting damage to head
> > bearings that have all the characteristics of such damage... and the
> > occurrence of which has been almost eliminated by compound head
> > bearings with a swivel plate.
>
> what a crock. you don't know what "fretting" damage is given that you
> assert repeatedly that bike headsets cannot be true brinelled, despite
> hard evidence to the contrary. you're just twisting facts in a vain
> effort to fake credibility with the unitinitated. as for the
> survivability of modern bearings, the bearing races have the same
> angular contacts with the balls as ever before, but the metallurgy, the
> lubrication, the precision and the sealing technologies have all
> advanced.
This is from today's website for Timken, Inc. Look about halfway down
the page to find their illustrations of true brinelling and false
brinelling.
I may be wrong, but I don't think this was on the 1950s version of
their web page. ;-)
I won't say that headsets _cannot_ suffer true brinelling. But I think
it's very clear that they (and bearings in similar service) can suffer
false brinelling.
Oh, and a related point on handlebar movement: I've got a 1972 BMW
motorcycle I ride occasionally. It has an adjustable friction damper
for the steering - a big knob at the top of the headset. These bikes
had some problems with high speed wobble, so it's useful to dial in
some steering friction when on the freeway.
I've confirmed by experiment that I can, indeed, ride that motorcycle
for at least a quarter mile on a straight freeway with the steering
locked down all the way. It was just a curiosity thing, and I'm
certainly not going to try to see exactly how far I can ride that way,
but it made it clear to me that steering motions aren't always
necessary for balance.
- Frank Krygowski
Peter Cole
>>
>>> cool stop pads have a scraper lip which addresses this issue by
>>> touching at the rear first stopping grit progressing under as the
>>> brake is applied, but at the expense of pad thickness.
>>
>>
>>
>> The scraper lip of Koolstops last all of a few tens of miles of hard
>> use, the pads afterwards becoming just simple straight-surfaced pads
>> for most of their lives. These aren't magical by any means.
>
>
> sorry, but they have a void behind the lip. that means there's no
> pressure on the lip & they /do/ last the life of the pad. you've
> evidently never used them. i have.
First, it's Kool Stop or Kool-Stop (in case anyone wants to Google).
I'm not sure which model you're referring to, I can't see one on their
web site with a "lip", they do have a patented "plow tip" on some
models. I don't see the "void" you refer to, perhaps you could give the
model.
In my experience with Kool Stop, Shimano, Ritchey, Tektro and other
pads, no matter what the pad surface profile, it wears flat to match the
rim. I've also found that regardless of toe-in or toe-out, the embedded
grit seems evenly distributed over the pad surface. It's easy to spot,
as it's highlighted by the surrounding aluminum shavings. I think the
idea of reducing grit entrapment with pad shape or installation angle
works better in theory than practice. The hardness of the compound seems
to be the determinant. If you do rainy pace line rides you can hear the
difference. Coming to a stop sign my brakes will make the typical gritty
scraping sound for a few seconds, then quiet down, other brakes keep
scraping away.
Tom Nakashima
<frkr...@yahoo.com> wrote in message
news:1117116080.8...@g49g2000cwa.googlegroups.com...
>
> Oh, and a related point on handlebar movement: I've got a 1972 BMW
> motorcycle I ride occasionally. It has an adjustable friction damper
> for the steering - a big knob at the top of the headset. These bikes
> had some problems with high speed wobble, so it's useful to dial in
> some steering friction when on the freeway.
>
1966 R69 and 1970 R75/5
-tom
Peter Cole
>
> This is from today's website for Timken, Inc. Look about halfway down
> the page to find their illustrations of true brinelling and false
> brinelling.
>
> I may be wrong, but I don't think this was on the 1950s version of
> their web page. ;-)
>
> http://tinyurl.com/83jrv
>
>
> I won't say that headsets _cannot_ suffer true brinelling. But I think
> it's very clear that they (and bearings in similar service) can suffer
> false brinelling.
I don't understand how the loads sufficient for true brinelling could be
transmitted through the tires.
Tom Nakashima
<carl...@comcast.net> wrote in message
news:qtt99110m3ir2rk22...@4ax.com...
> But I'm willing to be proved wrong. Someone could roll
> through a puddle or some paint, lay down a 132 foot track on
> a shoulder, well away from any wobbly highway stripe, and
> use surveyor's equipment to show how beautifully straight it
> is.
>
> But I think that a string line will show that the track of
> the tire wanders even more without the guide of a nearby
> line to let the rider correct it--that is, the "straight"
> line on a shoulder would tend to curve back and forth even
> more.
>
> Carl Fogel
I don't know if this comes close but I used to watch my Dad bowl years
ago...great bowler btw. He was a lefty so the lanes were not has heavily
used and early Sunday morning to boot when we probably should have been in
church. The distance from the foul line to the head pin is 60 ft. The
weight of the ball is 16 lbs. and the speed of the ball is approx. 15 mph.
We were always the 1st ones there, so there was fresh oil on the lanes.
Once after his first throw after the ball return, I remember measuring the
track of the oil on the ball which was less than .100" of an inch. Pretty
awesome.
-tom
Jose Rizal
> Jose Rizal wrote:
>
>> jim beam wrote:
>>>
>>> it's not just a pad issue - it's a shimano design issue. shimano,
>>> this era at any rate, have the pads toes from the factory, and
>>> they're toed front end in so any grit on the rim gets trapped within
>>> the front/rear gap.
>>
>> Nonsense. Shimano pads don't have built-in toe, they're mere
>> flat-surfaced pads that are adjusted by the bike assembler at the
>> caliper; Shimano brake assemblies aren't usable out of the box without
>> any adjustments. It's the assembler that toes in pads.
>
> jose, with respect, shimano 7700, 6600 & 5500 calipers are all toed out
> of the box. you should check one some time.
What absolute garbage. There's nothing in the Shimano instructions to
say that these should stay toed in. You've obviously never handled nor
used these brakes before, because they absolutely have toe-in
adjustability. You only needed to check the instructions -
http://cycle.shimano-eu.com/media/cycling/techdocs/en/bikecomponents/BR/SI-br6600_v2_m56577569830537941.pdf
Now stop making things up.
>> The scraper lip of Koolstops last all of a few tens of miles of hard
>> use, the pads afterwards becoming just simple straight-surfaced pads
>> for most of their lives. These aren't magical by any means.
>
> sorry, but they have a void behind the lip. that means there's no
> pressure on the lip & they /do/ last the life of the pad. you've
> evidently never used them. i have.
I suggest you buy and use some of these pads, because just checking them
out on the Kool Stop website obviously doesn't give you an accurate view
of how these are actually used.
There's no pressure on the lip? How do you then contend that this lip
scrapes the dirt from the rim if there is no pressure on it, despite the
fact that your brake lever pushes the whole pad into the rim with enough
force to stop the bike? It's quite obvious you've never even handled
one of these pads. If you still claim that the protrusion that acts as
a scraper in Kool Stops do not wear out faster than the rest of the pad,
despite the fact that it touches the rim first if positioned
appropriately, then there is little hope for getting you out of your
fantasy world.
>> Shimano calipers and pads have always had this adjustability.
>
> the above cited calipers are not adjustable unless you physically bend
> the caliper arms - somehting that you should /never/ do for fatigue
> initiation reasons.
Absolute rubbish. Go see these at your LBS. Easier yet, go see the
website above.
>>> for the "toe in advocates", there's never been any braking problems
>>> from ignoring toe that i've ever been able to determine.
>>
>> Maybe because you hardly ride at all... most squealing and shuddering
>> problems from rim brakes are directly attributable to pad positioning
>> relative to the rim.
>
> busted. i don't own a single bike. i never ride. i've never worn out
> rims.
Boo-hoo.....
> i've never brinelled a bearing.
Oh, I think you have, by hammering on one in a vise. Now go out and
ride, and try to do the same thing with just your weight on your bike.
Do 5, 6ft jumps on concrete even, and produce some pictures.
> i have no idea about fatigue.
At last.
> i
> can't do simple leverage calcs recognizing the principle of equilibrium.
Keep going.
> and i have absolutely /no/ clue about how microstructure affects
> material properties. no siree bob.
Thanks jim.
Jose Rizal
> "Jose Rizal" <_@_._> wrote in message
> news:505le.7693$M36....@newsread1.news.atl.earthlink.net...
>
>>What problem, wear? You're a magician if you think you've found the
>>solution to rim wear.
>
> Actually I may have. I've found the Kool Stop Continental pads don't wear
> the rim as much as other brake pads, including the Kool Stop Salmon Colored
> replacements.
The critical phrase here is "don't wear the rim _as_much_as_ other brake
pads". Any brake pad wears out rims.
Tom Nakashima
"Jose Rizal" <_@_._> wrote in message
One magician told me disk brakes won't wear out the sides of a rim.
-tom
Jose Rizal
> "Jose Rizal" <_@_._> wrote in message
>>
>>pads". Any brake pad wears out rims.
>
> One magician told me disk brakes won't wear out the sides of a rim.
> -tom
They will if you apply them to the rim.
carl...@comcast.net
Dear Tom,
I like it! If nothing else, I never wondered how fast a
bowling ball rolls.
But a single bowling ball is far denser than a pair of wire
spoke wheels connected by a hinged frame, and an oiled
wooden alley is rather smoother than the typical pavement
next to the noticeably smoother highway paint stripe.
Am I right in thinking that hard-core bowling also requires
that the lane not be heavily oiled? I seem to recall that a
little extra oil somehow tends to give an unfair advantage,
the bowler's version of a spitball.
Not, of course, that going early for freshly oiled lanes
means that the Nakashima family was doing anything
underhan--
Er, well, all bowling is underhanded, but you know what I
didn't mean. You just preferred to play on the equivalent of
a freshly mowed infield.
Carl Fogel