Carlton Reid on QR safety

How long would it take to *perform* the tests though?

Considerably less time than this thread has gone on for?

Ed Pirrero wrote:
wrote:
Ed Pirrero wrote:
wrote:

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.

This all sounds eerily familiar... remember the Nader thing? Ed, you
argued that one in *exactly* the opposite way.

--
Dave
dvt at psu dot edu

Ed Pirrero wrote:
wrote:

To develop a test to prove the obvious -
that these axles can slip dangerously under certain conditions
- would
take at least a week.

Actually, I thought up a test in my head in about thirty seconds. It
would actually require someone to do some real work, instead of tapping
on a keyboard, but I guess that's really the big impediment here,
right? Sheer laziness.

I'd like to read a description of that test, please.

--
Dave
dvt at psu dot edu

"Ed Pirrero" writes:

Tim McNamara wrote:

So in short, in your opinion laws of physics and facts of
engineering don't count.

My "emotional" investment is that there is a major flaw in the design
which creates a safety risk to the users, and that it is ethically
incumbent for the design to be rectified. That's it. The emotional
tonus in the discussion is coming from you and jim beam. If the pair
of you actually bothered to be rational rather than vitriolic, the
discussion would proceed reasonably.

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.

And yet you have offered no counter-analysis to the post I wrote which
summarized the forces involved- including the ones brought up by jim
beam in the course of the discussion- which showed the slim to
nonexistent margin of safety. Those calculations were based on real
world numbers, published measurements of pull-out resistance, and
minor things like the laws of physics. I didn't even have to appeal
to the issue of transverse cyclic forces to show that the problem
exists. And as was pointed out by another poster, I made an error
that understimated the magnitude of the problem.

In fact, you have offered no counter-analysis to anything at all. You
have only engaged in ad hominem and invective, demonstrated your
antiquated prejudices on a number of topics, dragged in red herrings
galore, and have failed to show anything approximating scientific
rigor in your own thinking. You've offered nothing positive to this
discussion- only spin, distortion and semantic games. I can only hope
that your contributions to chemistry are actually competent.

Mark Thompson
pleasegivegenerously@warmmail*_turn_up_the_heat_t o_reply*.com
writes:

How long would it take to *perform* the tests though?

Considerably less time than this thread has gone on for?

ROTFL!

Tim McNamara wrote:
Those calculations were based on real
world numbers, published measurements of pull-out resistance, and
minor things like the laws of physics.

Your calculations are all fine except that you keep considering pull out
forces in the absence of lawyers lips. Now most disk brake forks have
lawyers lips. With them the pull out forces are probably at least an
order of magnitude higher because you need to physically push them out
the way or stretch the skewer so it passes over them.

I didn't even have to appeal
to the issue of transverse cyclic forces to show that the problem
exists.

Only because you and everyone else keep ignoring the presence and
influence of the lawyers lips. If you include them you have to resort
to transverse cyclical forces and QR unscrewing or some other mechanism
to allow wheel ejection. That is the critical bit that everyone avoids
dealing with and has yet to show clear demonstration of a mechanism
preferring instead to rely on the post hoc fallacy that because a wheel
was lost it must have been ejected by the brakes. When the mechanism
can be demonstrated I will be persuaded but at present it's the elephant
in the room everyone is pretending is not there.

--
Tony

"The best way I know of to win an argument is to start by being in the
right."
- Lord Hailsham

Ed Pirrero wrote:
wrote:
Ed Pirrero wrote:


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.

That was the example you used.

I said that the necessity of dealing with one-off designs gives
engineers the skills to spot problems, such as the design problems
we're discussing..

Either you are unable to understand that simple, minor point, even
after clarification; or you are refusing to concede such an obvious
point. This has been your attitude regarding almost every detail in
this discussion.

This behavior satisfies me that you are not the least interested in
discussing this rationally. You're obstinately sticking to your
staked-out position despite any facts anyone brings to the table.

This must somehow make you feel intelligent. But as with the main
argument, the vast majority judges the evidence completely different
than you do.


I'm not even an engineer.

Yes. We know that very well.

Actually, I thought up a test in my head in about thirty seconds. It
would actually require someone to do some real work, instead of tapping
on a keyboard, but I guess that's really the big impediment here,
right? Sheer laziness.

Most of us see no need for a test, since we have sufficient evidence
already, plus adequate scientific explanations for phenomena already
observed.

_You_ feel there is a need for a test. Yet _you_ have not performed
that test. Sheer laziness!

....

Feel free to prove me wrong, if you dare.

:-) Prove you wrong to _your_ satisfaction? Impossible!

- Frank Krygowski

"James Annan" wrote in message
...
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...annondale.html

Do these calculations assume infinite traction and occupant
restraint? There is a point at which braking force will eject
the ride, and the ejection of the wheel will be irrelevant since
the rider already is airborne. I also wonder whether you can
generate those super high braking forces when your front wheel is
skidding down the road or sliding in soft dirt. In fact, most of
the hard braking on an MTB is on the rear wheel. Somebody should
rig a real bike with strain gauges or accelerometers (or whatever
the instrumentation should be) and find out what the real world
forces are. I had a broken frame case where we did that. Very
enlightening. -- Jay Beattie.

Jay Beattie wrote:
In fact, most of the hard braking on an MTB is on the rear wheel. ...
. -- Jay Beattie.


Dude! Most of you braking should be appled to the front wheel. If
you're jamming on the rear brake, you're not slowing you're slidding.

Oh and the rest of your post was wrong too.


Laters,


Marz

James Annan wrote:
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.

How do you know?

E.P.