Carlton Reid on QR safety

[Ian Blake]

On 14 Feb 2006 21:39:41 -0800, "Ed Pirrero" <[email protected]>
wrote:

>
>James Annan wrote:
>> Ed Pirrero wrote:
>>
>> >
>> > "Many" is not quantitative. Nor is it broken down by type or quality
>> > of data.
>> >
>> > Some guy said his QR slipped. OK.
>>
>> Do you think this sugggests a problem or is worthy of any
>> investigation?
>
>It may suggest user error, or it may suggest a deeper issue. It's hard
>to tell without "further investigation." Drawing a diagram and doing
>some simplified calculation is not the furthest that such investigation
>can be taken.
>

Ok. On the first occurrence of movement in the dropout I assumed
stupid me. I open the quick release reset my wheel and close the
quick release.

On several rides movement occurs again. You can assume I am immensely
stupid or that I notice that something is up. You can pretty sure
that I am paying attention to the way I close my QR. I do not have
weak hands. Although I don't do manual work I play the piano for
a hobby so my hand is possibly stronger than average.

Sometimes the problem would occur more than once on a single ride.
The problem continues so I think the X-Lite QR is not doing its job
properly. Swap in an old reliable Shimano QR. The problem was much
reduced in frequency but still occurred occasionally. This makes
sense the X-Lite had a short screw in lever for security which was
not as long as the standard Shimano lever. So the Shimano was
probably closed with greater force.

The user error hypothesis is credible for a single disastrous event
but is not believable for the multiple bloody annoying ****les I used
to suffer.

 

[[email protected]]

Ed Pirrero wrote:
> [email protected] wrote:
> > Ed Pirrero wrote:
> > >
> > >
> > > There is a force. Whether the force is sufficient to cause anything
> > > but consternation in engineering purists *has not yet been proven*.
> >
> > Rather, "has not been proven" to _your_ satisfaction (or jim beam's).
>
> When there are actual experiments (as opposed to drawings and
> calculations) I will consider those numbers to be the final word.

Fine.

In the world of design engineering, that standard is often considered
excessive, because it's not uncommon to design expensive, one-off
devices that _must_ work properly. For this reason, competent
engineers get good at examining free body diagrams, visualizing
directions of forces, considering things that might reasonably go
wrong, and making sure that there's metal to support critical forces -
not open slots and friction attachments.

BTW, engineers are also used to using large safety factors when serious
personal injury is a likely result of failure. A safety factor of two
(for example) is considered inadequate.

>
> > There will always
> > be people so welded to their own view that no amount of evidence and
> > logic will suffice.
>
> A lovely strawman. Knock it down!

You seem very confused about the definition of a "strawman argument."

> > > > There is a known mechanism for loosening
> > > > threaded fasteners, and there is no reason to presume that that
> > > > mechanism cannot apply to bicycles.
> > >
> > > Another presumption. It *might*. But *does it*? We don't know,
> > > because nobody has actually done any controlled testing.
> >
> > Our of curiosity, Ed, why do you think that well known mechanism for
> > loosening of industrial threaded fasteners would _not_ apply to
> > fasteners with far less locking power and far greater transverse loads?
>
> Who says they don't?
>
> Oh, that's right, another strawman.

Again, you seem very confused about that definition. Or alternately,
you're planning on using that word to avoid tough questions.

I gave a detailed explanation of the mechanism that tends to loosen
fasteners subjected to transverse cyclic forces. Quick release skewers
dealing with rear-mounted disk calipers are subject to such forces.
Which aspects of that phenomenon do _you_ think don't apply?

Or alternately, do you agree that everything I described _does_ apply
to those QR skewers? What's your judgement on the matter?

> But hey, *maybe*, since all the other fasteners on a bike seem to hold
> without the two anti-loosening strategies used commonly in QRs, it
> seems incredibly odd that MTBs don't routinely fall to pieces.

It may seem that way, if a person doesn't understand enough about
forces and threaded fasteners, I guess.


> Or maybe, just maybe, not everything is known about the system. It
> could be that James is 100% correct. I don't discount that possiblity,
> because I understand how hypotheses work. But it sure would be nice to
> see SOMETHING other than supposition and conjecture.

You mean like reports of front wheels popping out on hard application
of a rear-mounted disk brake?

Or you mean like multiple reports of QR skewers being carefully
adjusted and fastened, then becoming loose on their own after bumpy
braking with a rear mounded disk brake?

Or you mean standard engineering calculation techniques showing forces
in directions backwards from the original design intent of fork
dropouts?

Seems to me we have all those, and more.

I know it's insufficient to convince you. But frankly, I think it's
just because you've staked out your position so strongly that you now
require extreme (and expensive) levels of "proof." It's your
alternative to admitting you're wrong.

It's not an uncommon bit of psychology. In fact, we see it in the very
highest levels of government.

- Frank Krygowski

 

[Tim McNamara]

"Ed Pirrero" <[email protected]> writes:

> James Annan wrote:
>>
>> I'm just asking you to clarify what you mean by a "third party",
>> and what you might consider "verification".
>
> What difference does my opinion in this matter make? You don't have
> anything besides your *conjecture* on the subject.
>
> You made claims - claims you can't back up with anything except
> *your own personal conjecture*.

Ummm. Laws of physics don't count? Established facts of mechanical
engineering are not valid? Just checking.

 

[Tim McNamara]

"Ed Pirrero" <[email protected]> writes:

> Tim McNamara wrote:
>>
>> Then we only have your word and his, and neither of you is
>> credible.
>
> You making a judgement on scientific credibility is laughable.
> Here's a clue - the social "sciences" really aren't much about
> science. But hey, if it makes *you* feel more important, that's
> fine by me.

LOL. You know little about modern psychology, "Ed." Best if you
stick to topics you know something about. Whatever those might be.

 

[dvt]

Tim McNamara wrote:
> One thing I wondered about was instantaneous loading versus static
> loading, if those are the correct terms, which I have no idea how to
> calculate. I would think- but don't know- that a quick jam on the
> brake at 25 mph would result in a high sharp force compared to my more
> static force based on a .6 g deceleration. Would the magnitude of the
> force be raised with higher speeds, or just the time interval over
> which the load develops? My understanding of physics suggests the
> latter.

It is possible to generate more than 0.6g deceleration momentarily.
Others have written in this NG about the peak forces possible on rough
terrain. But I don't think many people ride that hard.

--
Dave
dvt at psu dot edu

 

[James Annan]

dvt wrote:

> Tim McNamara wrote:
>
>> One thing I wondered about was instantaneous loading versus static
>> loading, if those are the correct terms, which I have no idea how to
>> calculate. I would think- but don't know- that a quick jam on the
>> brake at 25 mph would result in a high sharp force compared to my more
>> static force based on a .6 g deceleration. Would the magnitude of the
>> force be raised with higher speeds, or just the time interval over
>> which the load develops? My understanding of physics suggests the
>> latter.
>
>
> It is possible to generate more than 0.6g deceleration momentarily.
> Others have written in this NG about the peak forces possible on rough
> terrain. But I don't think many people ride that hard.
>

The cannondale "tests" measured a peak 235 ft-pounds of braking torque
on the front wheel, fromw hich you can work out about 950N deceleration
and 3800N ejection force, far in excess of the ballpark estimates I and
others have produced based on a steady 0.6g braking.

http://www.ne.jp/asahi/julesandjames/home/disk_and_quick_release/cannondale.html

James
--
James Annan
see web pages for email
http://www.ne.jp/asahi/julesandjames/home/
http://julesandjames.blogspot.com/

 

[Tim McNamara]

dvt <[email protected]> writes:

> Tim McNamara wrote:
>> One thing I wondered about was instantaneous loading versus static
>> loading, if those are the correct terms, which I have no idea how
>> to calculate. I would think- but don't know- that a quick jam on
>> the brake at 25 mph would result in a high sharp force compared to
>> my more static force based on a .6 g deceleration. Would the
>> magnitude of the force be raised with higher speeds, or just the
>> time interval over which the load develops? My understanding of
>> physics suggests the latter.
>
> It is possible to generate more than 0.6g deceleration
> momentarily. Others have written in this NG about the peak forces
> possible on rough terrain. But I don't think many people ride that
> hard.

Racers and those into "xtreme" riding, yes. But those are a tiny
minority. I remain concerned about folks like kids or the disabled or
the target market for Co-Motion's "big person" bike, who might be
attracted to disk brakes for the low lever effort, but whom also might
not close the QRs tight enough due to hand strength or unfamiliarity.
Tourists with a large load might be another market of concern. A 150
lbs MTB racer, OTOH, might stay below the margin of safety in terms of
the ejection force.

 

[Ed Pirrero]

Tim McNamara wrote:
> "Ed Pirrero" <[email protected]> writes:
>
> > Tim McNamara wrote:
> >>
> >> Then we only have your word and his, and neither of you is
> >> credible.
> >
> > You making a judgement on scientific credibility is laughable.
> > Here's a clue - the social "sciences" really aren't much about
> > science. But hey, if it makes *you* feel more important, that's
> > fine by me.
>
> LOL. You know little about modern psychology, "Ed."

It's not a hard science, and never will be. Chemistry is, and always
will be.

Sorry that the facts don't coincide with your opinions.

E.P.

 

[Ed Pirrero]

Tim McNamara wrote:
> "Ed Pirrero" <[email protected]> writes:
>
> > James Annan wrote:
> >>
> >> I'm just asking you to clarify what you mean by a "third party",
> >> and what you might consider "verification".
> >
> > What difference does my opinion in this matter make? You don't have
> > anything besides your *conjecture* on the subject.
> >
> > You made claims - claims you can't back up with anything except
> > *your own personal conjecture*.
>
> Ummm. Laws of physics don't count? Established facts of mechanical
> engineering are not valid? Just checking.

They count and are valid. But they do not provide *verification* that
James' claims are caused as he suggests.

Now, do *you* have some data, other than conjecture and speculation,
that somehow clarifies these incidents? No?

Just checking.

E.P.

 

[Ed Pirrero]

James Annan wrote:
> Ed Pirrero wrote:
> > James Annan wrote:
> > > Ed Pirrero wrote:
> > >
> > > >
> > > > "Many" is not quantitative. Nor is it broken down by type or quality
> > > > of data.
> > > >
> > > > Some guy said his QR slipped. OK.
> > >
> > > Do you think this sugggests a problem or is worthy of any
> > > investigation?
> >
> > It may suggest user error, or it may suggest a deeper issue. It's hard
> > to tell without "further investigation."
>
> Do you think the manufacturer, when informed of the problem, should
> undertake this "further investigation"?

Sure. And if they find something, they should, *as a result of testing
the system*, act upon the knowledge generated

If no actions are taken, it could actually mean that they found the
problem to be overstated. Or they decided to settle any lawsuits. Or
they decided you were just another kook, and round-filed your letters.

Or maybe they aren't responsible to respond to every crank who thinks
that there's some safety issue. Do you think you are the only one who
ever writes to a company saying their products are unsafe? And even if
you are 100% right, that doesn't mean that bike makers can separate
your voice from the kooky noise.

In the end, we're still no closer to experimental determination of the
forces involved.

But it doesn't matter what *I* think. I'm just one guy, and a sceptic
to boot.

E.P.

 

[Ed Pirrero]

James Annan wrote:
> Ed Pirrero wrote:
> > [email protected] wrote:
> > > Ed Pirrero wrote:
> > > >
> > > >
> > > > There is a force. Whether the force is sufficient to cause anything
> > > > but consternation in engineering purists *has not yet been proven*.
> > >
> > > Rather, "has not been proven" to _your_ satisfaction (or jim beam's).
> >
> > When there are actual experiments (as opposed to drawings and
> > calculations) I will consider those numbers to be the final word.
>
> But:
>
> Ben Cooper's experiments don't count
> Velotech.de's experiments don't count.
> Dave Gray and Brant Richards' own personal experiences don't count
> Journalists describing repeated skewer loosening on a new,
> manufacturer-supplied test bike don't count

I don't see too many measurements of the actual forces involved here.
The descriptions of QR loosening are exceedingly difficult to separate
from the normal noise of user error. Do you believe that loose QRs
only happen on disk-brake bikes?

The Howat paper is about the closest thing to real data gathering that
I've seen. I've not seen Velotech's article in English, so I can't
comment.

You obviously don't feel that Cannondale's test was acceptable - so if
you have high standards, why am I not allowed the same thing? Or is
only the data that supports your position valid?

> What actually would count?

Real testing of the forces involved. Since I have mentioned this
standard to you about 20 times, I'm going to stop repeating myself now,
and just say "Google is your friend" when you ask this question again.
Not if, but when.

E.P.

 

[Ed Pirrero]

[email protected] wrote:
> Ed Pirrero wrote:
> > [email protected] wrote:
> > > Ed Pirrero wrote:
> > > >
> > > >
> > > > There is a force. Whether the force is sufficient to cause anything
> > > > but consternation in engineering purists *has not yet been proven*.
> > >
> > > Rather, "has not been proven" to _your_ satisfaction (or jim beam's).
> >
> > When there are actual experiments (as opposed to drawings and
> > calculations) I will consider those numbers to be the final word.
>
> Fine.
>
> In the world of design engineering, that standard is often considered
> excessive, because it's not uncommon to design expensive, one-off
> devices that _must_ work properly.

These are not one-off designs. The raw materials to make the tests are
trivially inexpensive for the manufacturers of the items in question.

But when there is a question of safety of design, doing some small
amount of destructive testing can completely answer questions without
being excessively expensive.

I am completely will to accept the hypothesis and the estimated forces
as a first step. But the question of lack of even the vaguest
anecdotal evidence that the issue rises out of statistical noise begs
to be answered. We don't know even if there's a higher incidence of
loose QRs among disk brake bikes vs. rim brake bikes. Maybe there is -
maybe the incidence is high enough to be alarming to even the
staunchest supporter of the current design. But nobody knows.

> > > There will always
> > > be people so welded to their own view that no amount of evidence and
> > > logic will suffice.
> >
> > A lovely strawman. Knock it down!
>
> You seem very confused about the definition of a "strawman argument."

Actually, I'm quite clear. You are implying that I am welded to my own
view, and that no amount of evidence and logic will suffice.

Since this is not true, it is indeed a strawman, used to rhetorically
paint an unflattering mind-set picture - a misstating of your
opponent's position to gain advantage in a discussion.

If you were not implying that about me, then that bit was not clear
from your writing.

> > > > Another presumption. It *might*. But *does it*? We don't know,
> > > > because nobody has actually done any controlled testing.
> > >
> > > Our of curiosity, Ed, why do you think that well known mechanism for
> > > loosening of industrial threaded fasteners would _not_ apply to
> > > fasteners with far less locking power and far greater transverse loads?
> >
> > Who says they don't?
> >
> > Oh, that's right, another strawman.
>
> Again, you seem very confused about that definition.

Actually, it is you who are confused. Again, you state clearly that I
have a particular position - a position that I don't actually have, in
order to paint a rhetorical picture.

Instead of building strawmen and knocking them down, why not address
what I'm actually trying to discuss? Don't tell your audience that I
don't believe in fastener unscrewing, because that's just not true.
Instead, figure out how much greater the incidence of QR loosening is
on disk-brake bikes. If you don't know what the data happen to be,
just say so.

At least that's honest.

>
> > Or maybe, just maybe, not everything is known about the system. It
> > could be that James is 100% correct. I don't discount that possiblity,
> > because I understand how hypotheses work. But it sure would be nice to
> > see SOMETHING other than supposition and conjecture.
>
> You mean like reports of front wheels popping out on hard application
> of a rear-mounted disk brake?

Reports? I've only seen conjecture on a couple of incidents where what
really happened is still unknown.

If there are others, I haven't read about them. Of which incidents are
you speaking?

> Or you mean like multiple reports of QR skewers being carefully
> adjusted and fastened, then becoming loose on their own after bumpy
> braking with a rear mounded disk brake?

And how many incidents of bikes with rim brakes have had the same thing
happen?

> Or you mean standard engineering calculation techniques showing forces
> in directions backwards from the original design intent of fork
> dropouts?

That's part of the original hypothesis, and isn't more convincing upon
multiple repetition.

> I know it's insufficient to convince you

As I have stated on multiple occasions.

> But frankly, I think it's
> just because you've staked out your position so strongly that you now
> require extreme (and expensive) levels of "proof."

Yet another strawman. Imbuing me with some sort of attitude that I
just don't have. But hey, they are fun to knock down...

Yes, the experiments will take time and effort. But they are hardly
extreme, and should not be too expensive. Even you could design an
experiment to generate some preliminary data that could be used as a
basis for further refining of the hypothesis and subsequent
experiments. Ooops, can't reveal any more of the super-secret idea
code-named "The Scientific Method."

> It's your
> alternative to admitting you're wrong.

Actually, that's the pay-off for this poorly-crafted strawman - that
somehow the goalposts move with each succeeding data set, so why bother
generating any more data? "Nothing will ever satisfy you." Hogwash,
and double ********.

But that position does let you off the hook very nicely, while allowing
you to throw up your hands in exasperation. Clever, in a high-school
sort of way.

I have stated, multiple times, that if the testing data shows I'm
wrong, you all will get a public apology. Because, unlike our fearless
leaders, I actually do take responsibility for my positions. But I'm
not going to repeat that again - next time I'll just say "google is
your friend".

E.P.

 

[Ed Pirrero]

David Damerell wrote:
> Quoting Ed Pirrero <[email protected]>:
> [Who, of course, is no more of a chemist than I am...]

LOL. That's a good troll. I'll have to remember that one.

E.P.

 

[James Annan]

Ed Pirrero wrote:
> James Annan wrote:
> > Ed Pirrero wrote:
> > > James Annan wrote:
> > > > Ed Pirrero wrote:
> > > >
> > > > >
> > > > > "Many" is not quantitative. Nor is it broken down by type or quality
> > > > > of data.
> > > > >
> > > > > Some guy said his QR slipped. OK.
> > > >
> > > > Do you think this sugggests a problem or is worthy of any
> > > > investigation?
> > >
> > > It may suggest user error, or it may suggest a deeper issue. It's hard
> > > to tell without "further investigation."
> >
> > Do you think the manufacturer, when informed of the problem, should
> > undertake this "further investigation"?
>
> Sure.

Well, they haven't.

James

 

[A Muzi]

(Alias jim beam no caps)
>>>>> no, the over-center was not an original feature - the old straight
>>>>> lever campy qr's tighten all the way to the stop.

([email protected])
>>>> You should take one of those apart. The original design clearly
>>>> goes 'over center' to lock.

>> Old Crow writes:
>>> i did. it functioned as i described. i wouldn't use it because of
>>> that.

> [email protected] wrote:
>> That's too bad, because even without taking it apart the over center
>> feature is detectable both by inspection and manual action. I
>> wouldn't be riding those original QR's if that were not the case. You
>> are trying hard to avoid any credibility, if there was any.

jim beam wrote:
> just like your assertion that the traction cable on san francisco cable
> cars are wound with longitudinal strands rather than helical strands,
> you're wrong on this one jobst. regrettably, i've sold the hub so i
> can't prove it to you, but i would if it still had it.

The cam in the new ones is exactly the same shape as the one
you had and the originals 80+ years ago. Campagnolo wheel
quick release cams all lock over center. Take any
Campagnolo skewer apart if you doubt it. It's the essence of
the patent on his #1 product.

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

 

[A Muzi]

-Rolled thread on brake bolts?-
jim beam wrote:
> eh? like this?
> http://www.flickr.com/photos/38636024@N00/99524699/

The Shimano bolt referenced is indeed rolled. That is not at
all common to our industry.

I pulled one of those Shimano bolts and a loupe. It is also
the only brake bolt here without a center pip for turning.

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

 

[Tim McNamara]

"Ed Pirrero" <[email protected]> writes:

> Tim McNamara wrote:
>> "Ed Pirrero" <[email protected]> writes:
>>
>> > Tim McNamara wrote:
>> >>
>> >> Then we only have your word and his, and neither of you is
>> >> credible.
>> >
>> > You making a judgement on scientific credibility is laughable.
>> > Here's a clue - the social "sciences" really aren't much about
>> > science. But hey, if it makes *you* feel more important, that's
>> > fine by me.
>>
>> LOL. You know little about modern psychology, "Ed."
>
> It's not a hard science, and never will be. Chemistry is, and
> always will be.

Psychology covers a far more complicated field of knowledge than
chemistry, "Ed." Perhaps you should learn something about it rather
than just putting more of your rank prejudices on display.

> Sorry that the facts don't coincide with your opinions.

Still showing your ignorance, "Ed." LOL.

 

[Tim McNamara]

"Ed Pirrero" <[email protected]> writes:

> Tim McNamara wrote:
>> "Ed Pirrero" <[email protected]> writes:
>>
>> > James Annan wrote:
>> >>
>> >> I'm just asking you to clarify what you mean by a "third party",
>> >> and what you might consider "verification".
>> >
>> > What difference does my opinion in this matter make? You don't
>> > have anything besides your *conjecture* on the subject.
>> >
>> > You made claims - claims you can't back up with anything except
>> > *your own personal conjecture*.
>>
>> Ummm. Laws of physics don't count? Established facts of
>> mechanical engineering are not valid? Just checking.
>
> They count and are valid. But they do not provide *verification*
> that James' claims are caused as he suggests.

So in short, in your opinion laws of physics and facts of engineering
don't count. Yah, typical ******** from someone talking out of his
field. As I recall, it was chemists who came up with cold fusion,
too.
>
> Now, do *you* have some data, other than conjecture and speculation,
> that somehow clarifies these incidents? No?
>
> Just checking.
>
> E.P.

 

[[email protected]]

Ed Pirrero wrote:
> [email protected] wrote:
> > Ed Pirrero wrote:
> > > [email protected] wrote:
> > > > Ed Pirrero wrote:
> > > > >
> > > > >
> > > > > There is a force. Whether the force is sufficient to cause anything
> > > > > but consternation in engineering purists *has not yet been proven*.
> > > >
> > > > Rather, "has not been proven" to _your_ satisfaction (or jim beam's).
> > >
> > > When there are actual experiments (as opposed to drawings and
> > > calculations) I will consider those numbers to be the final word.
> >
> > Fine.
> >
> > In the world of design engineering, that standard is often considered
> > excessive, because it's not uncommon to design expensive, one-off
> > devices that _must_ work properly.
>
> These are not one-off designs. The raw materials to make the tests are
> trivially inexpensive for the manufacturers of the items in question.

I didn't say they were one-off designs. I said that engineers have to
have the skills to evaluate one-off designs. Those same skills can be
used in other situations to obviate the need for tests, when bad design
becomes obvious, as it has in this case.

In many cases, it comes down to a judgement about most efficient use of
resources. Is it easier to set up carefully controlled lab tests to
verify an obvious problem, or is it easier to simply and easily fix it?
In this case, the fixes are trivially easy.

>
> But when there is a question of safety of design, doing some small
> amount of destructive testing can completely answer questions without
> being excessively expensive.

I can draw up a revised dropout design, or a revised disk caliper
mount, in less than an hour. To develop a test to prove the obvious -
that these axles can slip dangerously under certain conditions - would
take at least a week. IMO, the only reason a company wouldn't do the
easy re-design would be the complications coming from our liability
system - an admission of liability on the forks & brakes on the market.


> > > > There will always
> > > > be people so welded to their own view that no amount of evidence and
> > > > logic will suffice.
> > >
> > > A lovely strawman. Knock it down!
> >
> > You seem very confused about the definition of a "strawman argument."
>
> Actually, I'm quite clear. You are implying that I am welded to my own
> view, and that no amount of evidence and logic will suffice.

Yes, I believe that's true. But that wasn't a strawman argument. You
don't understand the definition of the term.


[regarding QRs loosening under the lateral forces imposed by the disk,
just as industrial fasteners loosen under lateral forces:]
> > > > > Another presumption. It *might*. But *does it*? We don't know,
> > > > > because nobody has actually done any controlled testing.
> > > >
> > > > Our of curiosity, Ed, why do you think that well known mechanism for
> > > > loosening of industrial threaded fasteners would _not_ apply to
> > > > fasteners with far less locking power and far greater transverse loads?
> > >
> > > Who says they don't?
> > >
> > > Oh, that's right, another strawman.
> >
> > Again, you seem very confused about that definition.
>
> Actually, it is you who are confused. Again, you state clearly that I
> have a particular position - a position that I don't actually have, in
> order to paint a rhetorical picture.

1) The mechanism of such loosening is well known. 2) This situation
has all the earmarks of the physics that loosens such fasteners. 3)
You implied QRs might not loosen here, despite all those earmarks. 4)
I asked why you believed they might not - that is, what might prevent
it.

Again, that does _not_ fit the definition of a strawman... unless you
want to pretend you didn't mean "They might not." All I'm asking for
is the counter-mechanism you envision "might" be operating to prevent
loosening.


> > > Or maybe, just maybe, not everything is known about the system. It
> > > could be that James is 100% correct. I don't discount that possiblity,
> > > because I understand how hypotheses work. But it sure would be nice to
> > > see SOMETHING other than supposition and conjecture.
> >
> > You mean like reports of front wheels popping out on hard application
> > of a rear-mounted disk brake?
>
> Reports? I've only seen conjecture on a couple of incidents where what
> really happened is still unknown.

The point is, the wheels popped out. They were reported. That makes
them "reports."


> > Or you mean like multiple reports of QR skewers being carefully
> > adjusted and fastened, then becoming loose on their own after bumpy
> > braking with a rear mounded disk brake?
>
> And how many incidents of bikes with rim brakes have had the same thing
> happen?

Zero, AFAIK. If you pretend otherwise, say so. If not, quit asking
distracting, hypothetical and irrelevant questions. Meanwhile, you
asked for something other than conjecture, and I'm giving it to you.


>
> > Or you mean standard engineering calculation techniques showing forces
> > in directions backwards from the original design intent of fork
> > dropouts?
>
> That's part of the original hypothesis, and isn't more convincing upon
> multiple repetition.

Again, "convincing" depends on the background knowledge of the reader.
Some people just won't understand, and thus won't be convinced. But
this is a technical discussion, not a jury trial, so the votes of those
with less understanding count for less. (I notice that many of the
people arguing against you are engineers.)


> > But frankly, I think it's
> > just because you've staked out your position so strongly that you now
> > require extreme (and expensive) levels of "proof."
>
> Yet another strawman. Imbuing me with some sort of attitude that I
> just don't have. But hey, they are fun to knock down...

Wow! Talk about ignoring the evidence! But then, one's own
faults are easy to ignore.

"O wad some Pow'r the giftie gie us
To see ourseles as others see us!"
- Robert Burns

- Frank Krygowski

 

[Ed Pirrero]

Tim McNamara wrote:
> "Ed Pirrero" <[email protected]> writes:
>
> > Tim McNamara wrote:
> >> "Ed Pirrero" <[email protected]> writes:
> >>
> >> > James Annan wrote:
> >> >>
> >> >> I'm just asking you to clarify what you mean by a "third party",
> >> >> and what you might consider "verification".
> >> >
> >> > What difference does my opinion in this matter make? You don't
> >> > have anything besides your *conjecture* on the subject.
> >> >
> >> > You made claims - claims you can't back up with anything except
> >> > *your own personal conjecture*.
> >>
> >> Ummm. Laws of physics don't count? Established facts of
> >> mechanical engineering are not valid? Just checking.
> >
> > They count and are valid. But they do not provide *verification*
> > that James' claims are caused as he suggests.
>
> So in short, in your opinion laws of physics and facts of engineering
> don't count.

No, in short, you're so emotionally invested in the subject that you
can't help but construct logical fallacies to attempt to sway folks to
your position.

Pathetic.

E.P.