Re: x-post: Bike Biz: Wheel ejection theory goes legal



B

Ben C

Guest
On 2007-02-13, [email protected] <[email protected]> wrote:
> Ben C? writes:

[...]
>>>>> Placing the caliper in from of the fork would result in the
>>>>> reaction force driving the axle into the dropout and eliminating
>>>>> the ejection force altogether.

>
>>>> Of course true, but although not impossible, undesirable.

>
>>> Why is that undesirable?

>
>> Because it puts the mounting point in tension as explained by jim beam.

>
> Every bending element is subject to tension. Thee is nothing wrong
> with tension or we couldn't build anything right from the Golden Gate
> Bridge to the elevator next to the stairs. There is nothing wrong
> with tension as we see in spokes that don't fail at mid span where
> they are entirely in tension. It is unintended bending that causes
> most failures and these fail on their tensile side. Don't give
> tension a bad name or we can't play tennis or listen to stringed
> instruments.


I think jim beam's point was that this was a tensile fatigue cycle,
which tends to be worse than a compressive one, especially for things
that are cast.

>> Also I am concerned about grit, brake dust etc. coming out of the
>> back of the caliper being thrown upwards towards the rider's face.
>> With the caliper behind the fork it's directed towards the road
>> behind the front wheel.

>
> For a particle to fly into your face, it would need to be at least as
> large as a grain of coarse sand that flies of the front tire all the
> time when on road edge pavement or dirt roads. This is not a hazard.


Anyway I got it the wrong way round-- it would be thrown downwards by a
front caliper, and upwards by a rear caliper!
 
Ben C? writes:

>>>>>> Placing the caliper in from of the fork would result in the
>>>>>> reaction force driving the axle into the dropout and
>>>>>> eliminating the ejection force altogether.


>>>>> Of course true, but although not impossible, undesirable.


>>>> Why is that undesirable?


>>> Because it puts the mounting point in tension as explained by Kim

beam.

>> Every bending element is subject to tension. Thee is nothing wrong
>> with tension or we couldn't build anything right from the Golden
>> Gate Bridge to the elevator next to the stairs. There is nothing
>> wrong with tension as we see in spokes that don't fail at mid span
>> where they are entirely in tension. It is unintended bending that
>> causes most failures and these fail on their tensile side. Don't
>> give tension a bad name or we can't play tennis or listen to
>> stringed instruments.


> I think dim beam's point was that this was a tensile fatigue cycle,
> which tends to be worse than a compressive one, especially for
> things that are cast.


Fracture occurs on tension but the compression cycle is equally
important. Obviously the part will not separate on compression but
its crack propagation takes place. I think this is not the place to
learn about material science. What is presented may be true and
correct but the emphasis is often not, so you can get the wrong
impression.

>>> Also I am concerned about grit, brake dust etc. coming out of the
>>> back of the caliper being thrown upwards towards the rider's face.
>>> With the caliper behind the fork it's directed towards the road
>>> behind the front wheel.


>> For a particle to fly into your face, it would need to be at least
>> as large as a grain of coarse sand that flies of the front tire all
>> the time when on road edge pavement or dirt roads. This is not a
>> hazard.


> Anyway I got it the wrong way round-- it would be thrown downwards
> by a front caliper, and upwards by a rear caliper!


I find your preoccupation with the hazards of tension more important
to resolve.

Jobst Brandt
 
T

Tim McNamara

Guest
In article <[email protected]>,
"Ed Pirrero" <[email protected]> wrote:

> On Feb 12, 4:06 pm, Tim McNamara <[email protected]> wrote:
> > In article <[email protected]>,
> > "Ed Pirrero" <[email protected]> wrote:
> >
> >
> >
> >
> >
> > > On Feb 11, 8:55 pm, "G.T." <[email protected]> wrote:
> > > > Ed Pirrero wrote:
> > > > > On Feb 11, 8:37 am, jim beam <[email protected]> wrote:
> > > > >> Tim McNamara wrote:

> >
> > > > >> <snip underinformed opinion>

> >
> > > > >> 1. there are no reported accidents that can be definitely
> > > > >> distinguished from user error.

> >
> > > > > Exactly. Tim like to throw bombs around about these reported
> > > > > incidents, but never once has anyone proven that it was actually
> > > > > the forces in question vs. user error.

> >
> > > > So because it hasn't been proven yet you guys are 100% certain that
> > > > it's been user error?

> >
> > > Strawman.

> >
> > No, it looks like just a poorly formed question.
> >
> > "A straw man argument is a logical fallacy based on misrepresentation of
> > an opponent's position. To "set up a straw man" or "set up a straw-man
> > argument" is to create a position that is easy to refute, then attribute
> > that position to the opponent. A straw-man argument can be a successful
> > rhetorical technique (that is, it may succeed in persuading people) but
> > it is in fact a misleading fallacy, because the opponent's actual
> > argument has not been refuted." Given the question mark at the end of
> > Greg's post, I think it is reasonable to give him the benefit of the
> > doubt. Were it a sentence, then I would agree that it is a straw man.
> >
> > However, you do appear to simply disregard any evidence that contradicts
> > your theory. That may not be an accurate assessment of your thinking
> > process but it is the impression I get from reading your posts. Your
> > logic- and jim's- looks like this to me:
> >
> > A. It has been postulated that disk brake can cause wheel ejection.
> > B. Uncertainty can be cast upon the evidence that A is true.
> > C. Therefore A is false.
> >
> > That may or may not be what you intend. On my screen, that's how it
> > reads.

>
> A reasonable reply! I am surprised, and pleased.
>
> OK, here's how it goes:
>
> A. Yes, I agree.
>
> B. Sort of - I think that because there is a force, that the
> possibility exists that a wheel could be ejected.
>
> C. No, not true at all.
>
> I'm still an agnostic on whether this "problem" is real, or just
> theoretical. Because, as Frank writes, so many conditions have to
> line up right for ejection to occur, it gets into the realm of doing a
> fix on something that's not broken.
>
> As I have said, to you and to others, I am willing to look at real
> data, and evaluate it for what it is. I don't dismiss data out of
> hand, I dismiss conclusions based on opinion rather than hard data.
> While to you the difference may be subtle, for me it makes all the
> difference in the world.
>
> Unfortunately, I don't consider the anecdotes "data", because the
> initial conditions are unknown. It is *possible* that the initial
> conditions are normal, but it is possible that they are not. Not
> exactly a dismissal, but not exactly full acceptance as data points.


The plural of anecdote != data, on which I think we probably agree. We
do lack adequate hard data. There have been some attempts, such as one
person who attempted to measure the degree of loosening of the skewer
nut, but the measurement was imprecise in that it was based on an
estimate of lever closure angle at contact with the fork (he found that
the lever closure angle decreased after riding, indicating that the
skewer nut had backed off. ISTR that was published on a UK trade
publication website- Annan may have a link to it). I don't know if that
experiment has been repeated.

At this time, we are- in this newsgroup, at least, since other than
Fogel Labs we don't have research facilities- pretty much stuck with a
epidemiological model of data collection. It's less precise, has risk
of noise in the data, and provides little by way of determining cause
and effect. Making matters worse, we don't even have a system of data
collection! We're waiting for reports to stray across the radar screen.

The good news is that there has not been a rash of reported wheel
ejections, although there are a few. It may be that the necessary
constellation of conditions is fairly unusual. The potential bad news
is that riders may misattribute brake-caused wheel ejections as user
error- e.g. "d'oh, I must not have clamped down the skewer." That's
assuming these are happening, of course. We probably won't hear about
those events as a result.

The end result, of course, is that we can't resolve the discussion.

> I consider any attempt to put me in the position of defending some
> absolute denial as strawman logical fallacy, for all of these reasons.
>
> I hope this clears things up.


Thank you, it does clarify your position very much!

FWIW my logic goes:

A. A disk brake can cause an ejection force on the front wheel.
B. There is no need for an ejection force, as forks can easily be
designed to eliminate it.
C. Forks should be redesigned to eliminate the ejection force.

The background assumption, of course, is that wheel ejection is a bad
thing and is to be avoided.
 
T

Tim McNamara

Guest
In article <[email protected]>,
jim beam <[email protected]> wrote:

> Tim McNamara wrote:
> > In article <[email protected]>,
> > jim beam <[email protected]> wrote:
> >
> >> Tim McNamara wrote:
> >>> In article <[email protected]>,
> >>> jim beam <[email protected]> wrote:
> >>>
> >>>> straws are not flotation devices. even for drowning
> >>>> "engineering professors".
> >>> How about drowning metallurgists?
> >> read: "twisted psychologists". you must be writing a thesis since
> >> you have no technical argument in this debate - merely tests for
> >> logical incongruity.

> >
> > You're a funny guy, jim. It is fortunate that the technical
> > argument is a very simple on in this case, eh?

>
> the tech is sound - but you don't get it. or at least, you make out
> like you don't.


Nah. I understand the tech. I even understand your position on the
issue, since it ain't exactly complicated. I disagree with the
underlying assumptions and values you bring to the discussion. You find
the risk of losing a front wheel acceptable if it only rarely happens,
especially if it can be attributed to user error, and you believe that
you can control the risk with adequate clamping force. I think that
you're wrong on that point. If you could guarantee that the QR will
always provide adequate retention, then I would agree with your
position. But you can't guarantee that. Skewers rupture, they get
bent, they may not be clamped at maximum force if the cyclist is, say, a
woman or a young person or has arthritis or for some other reason is
without normal adult male hand strength. There are too many ways for
the retention force to be lower than the ejection force.

Because I think you are wrong on this point and because it seems very
clear to me that there is no way to guarantee that the retention force
will be greater than the ejection force, I think that it only makes
sense to make the simple proven modifications that will eliminate the
clamping force.

> but i understand now - this is no exercise in "tech", this is your
> new research thesis:
>
> "mcnamara. t. - the limits of human gullibility as defined by
> logical incongruity."


That's a good chuckle, jim. But the real paper would be on:

McNamara T. (2007). Emotional investment and personal cathexis as a
distorting influence in mechanical engineering debate.

> it's a fine study tim. think you'd have more fun on an astrology
> forum though.


Nah. Astrology is bunk. And have you seen the math? Yikes.
 
G

G.T.

Guest
"Tim McNamara" <[email protected]> wrote in message
news:[email protected]
> In article <[email protected]>,
> "Ed Pirrero" <[email protected]> wrote:
>
>> On Feb 12, 4:06 pm, Tim McNamara <[email protected]> wrote:
>> > In article <[email protected]>,
>> > "Ed Pirrero" <[email protected]> wrote:
>> >
>> >
>> >
>> >
>> >
>> > > On Feb 11, 8:55 pm, "G.T." <[email protected]> wrote:
>> > > > Ed Pirrero wrote:
>> > > > > On Feb 11, 8:37 am, jim beam <[email protected]> wrote:
>> > > > >> Tim McNamara wrote:
>> >
>> > > > >> <snip underinformed opinion>
>> >
>> > > > >> 1. there are no reported accidents that can be definitely
>> > > > >> distinguished from user error.
>> >
>> > > > > Exactly. Tim like to throw bombs around about these reported
>> > > > > incidents, but never once has anyone proven that it was actually
>> > > > > the forces in question vs. user error.
>> >
>> > > > So because it hasn't been proven yet you guys are 100% certain that
>> > > > it's been user error?
>> >
>> > > Strawman.
>> >
>> > No, it looks like just a poorly formed question.
>> >
>> > "A straw man argument is a logical fallacy based on misrepresentation
>> > of
>> > an opponent's position. To "set up a straw man" or "set up a straw-man
>> > argument" is to create a position that is easy to refute, then
>> > attribute
>> > that position to the opponent. A straw-man argument can be a successful
>> > rhetorical technique (that is, it may succeed in persuading people) but
>> > it is in fact a misleading fallacy, because the opponent's actual
>> > argument has not been refuted." Given the question mark at the end of
>> > Greg's post, I think it is reasonable to give him the benefit of the
>> > doubt. Were it a sentence, then I would agree that it is a straw man.
>> >
>> > However, you do appear to simply disregard any evidence that
>> > contradicts
>> > your theory. That may not be an accurate assessment of your thinking
>> > process but it is the impression I get from reading your posts. Your
>> > logic- and jim's- looks like this to me:
>> >
>> > A. It has been postulated that disk brake can cause wheel ejection.
>> > B. Uncertainty can be cast upon the evidence that A is true.
>> > C. Therefore A is false.
>> >
>> > That may or may not be what you intend. On my screen, that's how it
>> > reads.

>>
>> A reasonable reply! I am surprised, and pleased.
>>
>> OK, here's how it goes:
>>
>> A. Yes, I agree.
>>
>> B. Sort of - I think that because there is a force, that the
>> possibility exists that a wheel could be ejected.
>>
>> C. No, not true at all.
>>
>> I'm still an agnostic on whether this "problem" is real, or just
>> theoretical. Because, as Frank writes, so many conditions have to
>> line up right for ejection to occur, it gets into the realm of doing a
>> fix on something that's not broken.
>>
>> As I have said, to you and to others, I am willing to look at real
>> data, and evaluate it for what it is. I don't dismiss data out of
>> hand, I dismiss conclusions based on opinion rather than hard data.
>> While to you the difference may be subtle, for me it makes all the
>> difference in the world.
>>
>> Unfortunately, I don't consider the anecdotes "data", because the
>> initial conditions are unknown. It is *possible* that the initial
>> conditions are normal, but it is possible that they are not. Not
>> exactly a dismissal, but not exactly full acceptance as data points.

>
> The plural of anecdote != data, on which I think we probably agree. We
> do lack adequate hard data. There have been some attempts, such as one
> person who attempted to measure the degree of loosening of the skewer
> nut, but the measurement was imprecise in that it was based on an
> estimate of lever closure angle at contact with the fork (he found that
> the lever closure angle decreased after riding, indicating that the
> skewer nut had backed off. ISTR that was published on a UK trade
> publication website- Annan may have a link to it). I don't know if that
> experiment has been repeated.


Yes, that's on his site. Changed from 90 degrees to 80 degrees.

Greg
 
T

Tim McNamara

Guest
In article <[email protected]>,
jim beam <[email protected]> wrote:

> Tim McNamara wrote: <snip ****>
>
> > The simple truth, jim, which you have been fending off for years is
> > that there is no necessity to have a design that results in an
> > ejection force on the front wheel. It can be readily remedied and-
> > since it appears that several manufacturers have made adjustments
> > in their design to result in a safer product- it has been. You've
> > spent all this time and effort trying to disparage and defeat and
> > even humiliate- how many posts in this thread alone?- and yet your
> > position is still one of senseless denial.

>
> oh the irony. it would be funny if you understood it.


I do understand the point you are trying to make. And I think you're-
once again- just plain wrong. Since you are reduced to "am not" and
"are too" type arguments, and have already called Frank an idiot twice
in this thread, it is perhaps time to allow this thread a dignified
death.
 
G

G.T.

Guest
"Tim McNamara" <[email protected]> wrote in message
news:[email protected]
> In article <[email protected]>,
> "Ed Pirrero" <[email protected]> wrote:
>
>> On Feb 12, 3:49 pm, "G.T." <[email protected]> wrote:
>>
>> > It's sad that you and jb are such untrusting fools.

>>
>> Logical fallacy - ad hominem.

>
> That's a correct call.


"Fools" may be ad hominem but the untrusting part is not a logical fallacy.

EP, jb, and CF clearly don't trust Annan, Missy Giove, Dave Smith, Russ
Pinder, and I doubt they'll trust anyone else who claims they checked their
QRs before the QRs magically loosen.

Greg
 
T

Tim McNamara

Guest
In article <[email protected]>,
jim beam <[email protected]> wrote:

> Tim McNamara wrote:
> > In article <[email protected]>,
> > jim beam <[email protected]> wrote:
> >
> >> [email protected] wrote:
> >>


<snip>

> >>> Twenty years later, the major trials manufacturers--GasGas,
> >>> Sherco, and Beta--are still building leading-caliper trials bikes
> >>> and trailing-caliper off-road machines.
> >>>
> >>> So the leading caliper disk brake is "traditional" on trials
> >>> machines, but it's a tradition peculiar to trials and a tradition
> >>> that required changing the existing tradition of trailing
> >>> calipers on all other machines.
> >>>
> >>> Anyone who's ridden trials will easily appreciate the advantage
> >>> of having the caliper up higher in the leading position, where
> >>> rocks don't smash it so easily when you step off a doomed
> >>> machine.
> >>>
> >> accepted. the point is, there's a specific reason to go to the
> >> "dark side", and you've identified it.

> >
> > But clearly no specific reason *not* to, since that arrangement
> > obviously works without the dire failures you predict.

>
> did you notice my post about safety earlier today? how much do you
> want to pay to make front calipers "safe"?


jim, your style of posting makes it impossible to track every thing you
say. You've never learned how to snip extraneous material from your
posts, you bury three words in the middle of 200 lines and stuff you
write sometimes just gets lost.

Which calipers are you taking about? Disk brakes calipers? Rim
calipers? Digital calipers? Dial calipers? (OK, I'm being silly.)

The proposed changes are really quite trivial and there is no reason for
there to be a significant differential in cost. As Carl points out,
there are plenty of examples of successful designs that put the disk
caliper in front of the fork leg. It would appear that the issue of
tensile fatigue is not as dire as you predict, given that the total load
and instantaneous load on the caliper mounts would be much higher on a
motorcycle.
 
On Feb 13, 8:45 pm, Tim McNamara <[email protected]> wrote:

[snip]

> The plural of anecdote != data, on which I think we probably agree. We
> do lack adequate hard data. There have been some attempts, such as one
> person who attempted to measure the degree of loosening of the skewer
> nut, but the measurement was imprecise in that it was based on an
> estimate of lever closure angle at contact with the fork (he found that
> the lever closure angle decreased after riding, indicating that the
> skewer nut had backed off. ISTR that was published on a UK trade
> publication website- Annan may have a link to it).


[snip]

Dear Tim,

Here's the experiment:

http://kinetics.org.uk/html/experiment.html

To repeat what I pointed out earlier in this thread:

The experiment was a bit iffy: a "torque meter" is said to be "less
accurate" than the unblinded experimenter's opinion of when the QR
began to "bite"--could be true, but it seems implausible at first
glance.

And the experiment wasn't measuring a normally tightened QR: "So this
was
looser than I previously had it, but still 'hand tight'."

Cheers,

Carl Fogel
 
On Feb 13, 9:17 pm, "G.T." <[email protected]> wrote:
> "Tim McNamara" <[email protected]> wrote in message
>
> news:[email protected]
>
> > In article <[email protected]>,
> > "Ed Pirrero" <[email protected]> wrote:

>
> >> On Feb 12, 3:49 pm, "G.T." <[email protected]> wrote:

>
> >> > It's sad that you and jb are such untrusting fools.

>
> >> Logical fallacy - ad hominem.

>
> > That's a correct call.

>
> "Fools" may be ad hominem but the untrusting part is not a logical fallacy.
>
> EP, jb, and CF clearly don't trust Annan, Missy Giove, Dave Smith, Russ
> Pinder, and I doubt they'll trust anyone else who claims they checked their
> QRs before the QRs magically loosen.
>
> Greg


Dear Greg,

Why do you think that quick releases that never previously popped open
start popping open as soon as someone says that he just read an
article about how it could happen?

Cheers,

Carl Fogel
 
G

G.T.

Guest
<[email protected]> wrote in message
news:[email protected]
> On Feb 13, 9:17 pm, "G.T." <[email protected]> wrote:
>> "Tim McNamara" <[email protected]> wrote in message
>>
>> news:[email protected]
>>
>> > In article <[email protected]>,
>> > "Ed Pirrero" <[email protected]> wrote:

>>
>> >> On Feb 12, 3:49 pm, "G.T." <[email protected]> wrote:

>>
>> >> > It's sad that you and jb are such untrusting fools.

>>
>> >> Logical fallacy - ad hominem.

>>
>> > That's a correct call.

>>
>> "Fools" may be ad hominem but the untrusting part is not a logical
>> fallacy.
>>
>> EP, jb, and CF clearly don't trust Annan, Missy Giove, Dave Smith, Russ
>> Pinder, and I doubt they'll trust anyone else who claims they checked
>> their
>> QRs before the QRs magically loosen.
>>
>> Greg

>
> Dear Greg,
>
> Why do you think that quick releases that never previously popped open
> start popping open as soon as someone says that he just read an
> article about how it could happen?
>


Dear Carl,

Huh? The QRs were popping long before any articles were read or even
written.

Greg Thomas
 
M

Michael Press

Guest
In article
<[email protected]>,
[email protected] wrote:

> On Mon, 12 Feb 2007 23:05:05 -0700, [email protected] wrote:
>
> [snip]
>
> >You may not like such questions, but they're the ones that any lawyer
> >or expert trying to reconstruct an accident would ask. Whatever Jobst
> >may think about the principles, here's his timely comment in another
> >current thread on plaintiffs and accident reconstruction:
> >
> >"I would like to have seen the bicycle [another bike, not Missy's]
> >right after the incident. It has been my experience that
> >reconstruction of what occurred is often easier than first
> >indications. That has been so, in every case in which I was called to
> >testify. That is to say, the event did not occur as plaintiff
> >described."

>
> [snip]
>
> Woe is me! I thought that I included the link to Jobst's post, but I
> didn't. Here it is:
>
> http://groups.google.com/group/rec.bicycles.tech/msg/af73416d9e457b72


Can we get the thread tree display from gg?

--
Michael Press
 
M

Michael Press

Guest
In article
<[email protected]>
,
[email protected] wrote:

> On Feb 13, 9:17 pm, "G.T." <[email protected]> wrote:
> > "Tim McNamara" <[email protected]> wrote in message
> >
> > news:[email protected]
> >
> > > In article <[email protected]>,
> > > "Ed Pirrero" <[email protected]> wrote:

> >
> > >> On Feb 12, 3:49 pm, "G.T." <[email protected]> wrote:

> >
> > >> > It's sad that you and jb are such untrusting fools.

> >
> > >> Logical fallacy - ad hominem.

> >
> > > That's a correct call.

> >
> > "Fools" may be ad hominem but the untrusting part is not a logical fallacy.
> >
> > EP, jb, and CF clearly don't trust Annan, Missy Giove, Dave Smith, Russ
> > Pinder, and I doubt they'll trust anyone else who claims they checked their
> > QRs before the QRs magically loosen.
> >
> > Greg

>
> Dear Greg,
>
> Why do you think that quick releases that never previously popped open
> start popping open as soon as someone says that he just read an
> article about how it could happen?


You know how to answer that.

--
Michael Press
 
J

jim beam

Guest
Tim McNamara wrote:
> In article <[email protected]>,
> jim beam <[email protected]> wrote:
>
>> Tim McNamara wrote: <snip ****>
>>
>>> The simple truth, jim, which you have been fending off for years is
>>> that there is no necessity to have a design that results in an
>>> ejection force on the front wheel. It can be readily remedied and-
>>> since it appears that several manufacturers have made adjustments
>>> in their design to result in a safer product- it has been. You've
>>> spent all this time and effort trying to disparage and defeat and
>>> even humiliate- how many posts in this thread alone?- and yet your
>>> position is still one of senseless denial.

>> oh the irony. it would be funny if you understood it.

>
> I do understand the point you are trying to make.


no you don't. you think you do, but you don't know what you don't know.
even when presented with the answers, your ability to connect them
with fundamental principals is repeatedly shown to be non existent. add
a generous dose of stubbornness, and a research thesis presents itself.

> And I think you're-
> once again- just plain wrong.


you don't understand basic math tim.

> Since you are reduced to "am not" and
> "are too" type arguments, and have already called Frank an idiot twice
> in this thread,


that's because he /is/ an idiot.

> it is perhaps time to allow this thread a dignified
> death.
 
J

jim beam

Guest
Tim McNamara wrote:
<snip>
>
> FWIW my logic goes:
>
> A. A disk brake can cause an ejection force on the front wheel.
> B. There is no need for an ejection force, as forks can easily be
> designed to eliminate it.
> C. Forks should be redesigned to eliminate the ejection force.
>
> The background assumption, of course, is that wheel ejection is a bad
> thing and is to be avoided.


the logical flaw is amazing. illustration:

1. use of a bridge causes a collapsing force on it.
2. there is no need for a collapsing force.
3. bridges should not be used.

the real consideration of course is how great the collapsing force is in
relation to capacity, not whether a collapsing force exists. repeated
failure to recognize that fundamental point is a truly extraordinary
mental block.
 
J

jim beam

Guest
Tim McNamara wrote:
> In article <[email protected]>,
> jim beam <[email protected]> wrote:
>
>> Tim McNamara wrote:
>>> In article <[email protected]>,
>>> jim beam <[email protected]> wrote:
>>>
>>>> [email protected] wrote:
>>>>

>
> <snip>
>
>>>>> Twenty years later, the major trials manufacturers--GasGas,
>>>>> Sherco, and Beta--are still building leading-caliper trials bikes
>>>>> and trailing-caliper off-road machines.
>>>>>
>>>>> So the leading caliper disk brake is "traditional" on trials
>>>>> machines, but it's a tradition peculiar to trials and a tradition
>>>>> that required changing the existing tradition of trailing
>>>>> calipers on all other machines.
>>>>>
>>>>> Anyone who's ridden trials will easily appreciate the advantage
>>>>> of having the caliper up higher in the leading position, where
>>>>> rocks don't smash it so easily when you step off a doomed
>>>>> machine.
>>>>>
>>>> accepted. the point is, there's a specific reason to go to the
>>>> "dark side", and you've identified it.
>>> But clearly no specific reason *not* to, since that arrangement
>>> obviously works without the dire failures you predict.

>> did you notice my post about safety earlier today? how much do you
>> want to pay to make front calipers "safe"?

>
> jim, your style of posting makes it impossible to track every thing you
> say. You've never learned how to snip extraneous material from your
> posts, you bury three words in the middle of 200 lines and stuff you
> write sometimes just gets lost.
>
> Which calipers are you taking about? Disk brakes calipers? Rim
> calipers? Digital calipers? Dial calipers? (OK, I'm being silly.)


trivialization of inconvenient truth.

>
> The proposed changes are really quite trivial and there is no reason for
> there to be a significant differential in cost. As Carl points out,
> there are plenty of examples of successful designs that put the disk
> caliper in front of the fork leg. It would appear that the issue of
> tensile fatigue is not as dire as you predict, given that the total load
> and instantaneous load on the caliper mounts would be much higher on a
> motorcycle.


again, did you read my post? it's all about how much you want to pay.
and paying to fix a problem that isn't? that's illogical.
 
On Feb 13, 9:17 pm, "G.T." <[email protected]> wrote:
>
> EP, jb, and CF clearly don't trust Annan, Missy Giove, Dave Smith, Russ
> Pinder, and I doubt they'll trust anyone else who claims they checked their
> QRs before the QRs magically loosen.


I think this is true, with the possible exception of CF (who seems to
sit back and sling questions, but seldom states an actual opinion).

EP and jb go on about initial conditions not being verified (or some
such thing) without ever specifying what they'd accept as a standard
for verification. Obviously, the procedures normally used (such as
clamp angle of the QR) don't qualify in their eyes.

They give the impression the only accepted testimony involves QRs
tightened with a torque wrench whose resolution is 0.1 inch-pounds.
Then checked again at the bottom of a suitable descent. With the
entire process done in front of three witnesses. Who sign a document
of testimony. Which is notarized.

I think everyone accepts that most QRs hold most front disk axles in
place most of the time. IOW, the set of conditions generating
loosening and ejection is uncommon, and some of the conditions may not
be known. It's foolish to expect a stellar verification team to
happen to be present at the top of a particular hill just before all
conditions are right to cause loosening or ejection.

Unless, that is, someone purposely sets up a demonstration just to
convince them. But to go through that trouble, one would have to
pretend their opinions actually mattered, and the concensus here seems
to disagree.

- Frank Krygowski
 
A

Andrew Lee

Guest
Ed Pirrero wrote:
> I'm still an agnostic on whether this "problem" is real, or just
> theoretical. Because, as Frank writes, so many conditions have to
> line up right for ejection to occur, it gets into the realm of doing a
> fix on something that's not broken.


I think that the calipers should be placed in front of the fork, or at the
least have the caliper in tighter and higher on the fork and the dropout
opening angled forward enough to avoid the ejection problem.

But if you look at the situation from a no change position, I would think
that the proper thing to do would be to propose some standards to ensure
that the conditions don't "line up right for ejections to occur". jb's
arguments go that most quick releases have serrations, most fork dropouts
are soft metal, most forks have lawyer lips, etc. Those thing do ensure
that the problem remains infrequent. But there are quick releases and axle
nuts with smooth faces,quick releases that have Ti skewers, quick releases
with external cams that have lower clamping forces, especially when dirty,
dropouts that are hard (maybe even chromed or 6/4 Ti), and dropouts without
lawyer lips. And it is possible very possible for several of those things
to line up. In a post elsewhere in this thread, I linked to a bike that has
steel forks, no lawyer lips, and ejection force angle lined up with dropout
opening. And someone else in this thread posted about repeatedly having the
quick release loosen on a newish bike - noticed because of fender rubbing.

How are other standards are used in industry? Shouldn't a brake
manufacturer say that, if you want to use this caliper, the fork design must
include such-and-such design elements (caliper-axle-dropout opening angle >
x degrees for example) , and the quick release should be such-and-such to
ensure that the conditions for ejection don't "line up"? Brake
manufacturers could provide guidance to fork manufacturers, and also include
fork design/QR requirements with the installation manual to provide
information to the independent frame builders and people who build up their
own bikes. Or maybe it could be something like an ASTM type standard?

As for the argument that "thousands ride, few have problems, so don't fix
what's not broken" - there are obviously many counter examples to where it
is considered a problem when the potential adverse effect is a big one. For
example, where I live the municipality keeps track of traffic accidents and
occasionally looks into redesigning intersections or road sections that are
considered dangerous. Tens of thousands drive on those roads every day
without incident. Do you consider the muni nuts for wanting to redo those
roads? Another example... sometimes product recalls are undertaken with few
or even no actual harmful incidents.
 
On Feb 13, 9:43 pm, "G.T." <[email protected]> wrote:
> <[email protected]> wrote in message
>
> news:[email protected]
>
>
>
>
>
> > On Feb 13, 9:17 pm, "G.T." <[email protected]> wrote:
> >> "Tim McNamara" <[email protected]> wrote in message

>
> >>news:[email protected]

>
> >> > In article <[email protected]>,
> >> > "Ed Pirrero" <[email protected]> wrote:

>
> >> >> On Feb 12, 3:49 pm, "G.T." <[email protected]> wrote:

>
> >> >> > It's sad that you and jb are such untrusting fools.

>
> >> >> Logical fallacy - ad hominem.

>
> >> > That's a correct call.

>
> >> "Fools" may be ad hominem but the untrusting part is not a logical
> >> fallacy.

>
> >> EP, jb, and CF clearly don't trust Annan, Missy Giove, Dave Smith, Russ
> >> Pinder, and I doubt they'll trust anyone else who claims they checked
> >> their
> >> QRs before the QRs magically loosen.

>
> >> Greg

>
> > Dear Greg,

>
> > Why do you think that quick releases that never previously popped open
> > start popping open as soon as someone says that he just read an
> > article about how it could happen?

>
> Dear Carl,
>
> Huh? The QRs were popping long before any articles were read or even
> written.
>
> Greg Thomas


Dear Greg,

Let's start with the familiar example.

Do you have a link to anything about Missy's quick release popping
open before she went for a ride with the fellow who said:

"Missy's QR popped. She had definitely tightened it before the ride as
she was doing some goofy stuff."

"The Skareb had the lawyer lips intact. [The] XT skewer [was] really
tight. I'd actually mentioned your story to Rick when we were leaving
the office."

[The story was about the possibility that QR's may pop open.]

http://www.bikebiz.com/Missy-Gioves-QR-pops-open-

Regardless of why it may have popped open on that ride, do you know of
any claims that Missy's QR was popping open on previous rides, but she
kept riding it anyway? I haven't seen any, but a link would show
otherwise.

Elsewhere in this thread, I've pointed out that the fellow whose QR
came "completely open" explained that he had just become really
paranoid about the matter. He mentioned no previous QR problems, but
strangely his QR obligingly came undone shortly after he checked it.

So I'm wondering why QR's that apparently never popped open before
people read about the possible danger promptly pop open as soon as
they hear about the problem.

It seems odd to me. Does it seem odd to you?

Cheers,

Carl Fogel