Carlton Reid on QR safety

[James Annan]

jim beam wrote:


>
>
> what lunacy. "can't be operated correctly" applies to every single tool
> any human touches. kitchen knives cut off fingers - do you want to
> "redesign" those too? how about 2-wheel bikes? we can fall off those
> if we can't balance them correctly.

In fact, all of these tools can be operated quite correctly.

However, there are no instructions as to how to operate a QR so that it
withstands the load of a disk brake, nor design standards to ensure that
it can do so at all.

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

 

[James Annan]

jim beam wrote:

>
> tim, what exactly is a "large force"? it can only be "large" relative
> to its application, which as stated before and which you seem completely
> unable to grasp, is not the case. the fundamental problem with annan's
> chicken little story, and by which you seem to be completely bamboozled,
> is that:
>
> 1. ejection incidence is effectively zero and cannot be distinguished
> from operator error.
>
> 2. therefore there has to be a difference between reality and the #'s
> annan wants to use for his alarm.
>
> 3. we've calculated here what those #'s are.
>
> 4. howat's [limited] testing backs those #'s up.
>
> 5. those #'s blow annan's boat out of the water.
>
> end of story.


I ggues this is the "repeat a lie often enough, and everyone will know
you're a moron" strategy.

http://www.ne.jp/asahi/julesandjames/home/disk_and_quick_release/QRReport1.pdf

The Howat numbers are an order of magnitude lower than your risible
"calculation" of the retention ability of a QR that you made up
previously. They are similar to (often lower than) the estimated
ejection force.

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

 

[Johnny Sunset aka Tom Sherman]

"jim beam" who? wrote:
> ...
> oh, and since you obviously missed it countless times before, the reason
> for /not/ front mounting a caliper is FATIGUE. cast alloys such as
> those in forks and calipers ARE NOT GOOD IN TENSILE FATIGUE. that's a
> pretty fundamental omission from someone that seems to feel qualified to
> lecture on what comprises good engineering design.

Gee, the fork manufacturers could simply increase the size of the
protrusion that the disc brake caliper bolt threads into and the wall
thickness of the fork tubing in this area so the stresses from braking
are below those that will cause fatigue failure within the expected
lifespan of the fork (with a standard factor of safety). That is what
an ENGINEER would do.

A (former?) material scientist with an ax to grind [1] apparently has a
different approach.

[1] Note Jobst Brandt is in general agreement with James Annan.

--
Tom Sherman

 

[[email protected]]

Tim McNamara wrote:
> jim beam <[email protected]> writes:
>
> > it's not kerfuffle - but sure seems to be something you're having a
> > hard time understanding!!! IF THE RETENTION FORCE EXCEEDS THE
> > "EJECTION" FORCE, THE WHEEL WILL REMAIN FASTENED TOT THE BIKE.
> > PERIOD.
> >
>
> Now you're shouting. You can be wrong louder, but that doesn't make
> you any more correct.

Look on the good side, Tim. "jim beam" has finally found his
shift key!

Now if we can teach him to use it correctly... ;-)

- Frank Krygowski

 

[Johnny Sunset aka Tom Sherman]

Sheldon Brown wrote:
> Exactly how many angels can dance on the head of a pin again?

Is the pin steel, aluminium alloy, titanium/titanium alloy or carbon
fiber reinforced composite?

--
Tom Sherman

 

[[email protected]]

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).
>From what I've seen, any issue outside purely theoretical mathematics
cannot be proven to the satisfaction of _everyone_. There will always
be people so welded to their own view that no amount of evidence and
logic will suffice.


> > 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?
Can you identify any specific mechanical reason, or is it just another
"you can't prove it" thing?

- Frank Krygowski

 

[Luke]

In article <[email protected]>, Benjamin Lewis
<[email protected]> wrote:

> Tony Raven wrote:
>
> > I'm not saying that at all. I am saying that the proponents need to
> > demonstrate that a properly done up QR will loosen to the point where
> > even the lawyers lips secondary retention devices will not restrain the
> > wheel against the ejection force.
>
> Axle slippage is a brake system failure, regardless of whether lawyer lips
> prevent wheel ejection or not.

<snip>

I agree. Regardless of where one stands on this issue, a scenario
whereby the LLs' retain the wheel after the QR cannot certainly
qualifies as a failure - i.e., the QR has *failed* to secure the front
wheel. How can a scenario that results in loss of control and,
possibly, damage to bike and rider be regarded otherwise?

Luke

 

[Michael Press]

In article
<[email protected]>,
Mark McNeill <[email protected]> wrote:

> Response to Tony Raven:
> > On a normal nut the ratio of nut diameter to thread diameter is a lot
> > lower than the QR nut so ease of tightening and releasing will be
> > misleading as the turning leverage is much greater on the QR nut.
>
> That's all very well; but it doesn't address the point I was making, or
> at any rate *thought* I was making.
>
>
> > No I don't but the onus is on those proposing that they behave
> > differently to show it to be so.
>
> Yes indeed.
>
> I'm not an engineer [and those who think that only engineers should post
> opinions on this matter may here allow their attention to wander ;-)],
> but it doesn't seem to me at all unlikely firstly that some QRs may be
> liable to loosening under prolonged/severe vibration, even when the
> manufacturer's instructions are followed, and secondly that the force
> acting on a brake disk may eject a loosened wheel.
>
> I can see the chain of reasoning; but there seems for the moment to be a
> dearth of real-world measurement and observation, and not only on the
> "plaintiffs'" side. As you say, it's up to them to make their case: but
> on the other hand there's surely an onus on designers and manufacturers
> to ensure that their products are safe, which requires an understanding
> of all the forces involved. If I was in the population at risk, I'd
> definitely be curious to see evidence that they do. ;-)

From what you understand of the theory, consider this
proposed experiment.

Take a bicycle equipped with a disc caliper mounted on the
back of the fork. Loosen the quick release clamp until it
is barely engaged. Walk the bicycle at a brisk pace, then
apply the front brake.

--
Michael Press

 

[Michael Press]

In article <[email protected]>,
Sheldon Brown <[email protected]> wrote:

> Exactly how many angels can dance on the head of a pin again?

Can we neglect the space taken by the orchestra?

--
Michael Press

 

[Tim McNamara]

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

> Tim McNamara wrote:
>> "Ed Pirrero" <[email protected]> writes:
>>
>> > Hoist on your own petard...
>>
>> LOL. Like politicians, you think that declaring victory means that
>> you have won.
>
> Actually, all you have to do to prove me wrong is quote where I
> compared anyone to Ralph Nader. That's *your* claim.
>
> Prove it, or shut up.

Surely you're not this much of a pissant, Ed? Without cross-polluting
the thread with extensive rehashed material, here are two quotes from
you courtesy of Google's archives:

Fri, Feb 10 2006 1:49 pm
> I am reminded every time these threads come up about Ralph Nader and
> the Corvair, "unsafe at any speed."

Fri, Feb 10 2006 8:03 pm:
> "Unsafe at any speed," right, Tim?

The words are yours, the reference is yours. In the first quote you
were comparing the people finding these faults to Ralph Nader. In the
second, following closely on the heels of the previous post, you
attempted to apply that to me.

Feel free to check Google's archives for yourself. You're the one who
is lying, Ed. Or you're suffering from some memory deficit that means
you can't remember what you've written just a few days ago.

We done playing these games now, Ed? Or do you want to try a few more
squirms and lies?

 

[Tim McNamara]

[email protected] writes:

> Tim McNamara wrote:
>> jim beam <[email protected]> writes:
>>
>> > it's not kerfuffle - but sure seems to be something you're having
>> > a hard time understanding!!! IF THE RETENTION FORCE EXCEEDS THE
>> > "EJECTION" FORCE, THE WHEEL WILL REMAIN FASTENED TOT THE BIKE.
>> > PERIOD.
>>
>> Now you're shouting. You can be wrong louder, but that doesn't
>> make you any more correct.
>
> Look on the good side, Tim. "jim beam" has finally found his
> shift key!

ROTFL!

> Now if we can teach him to use it correctly... ;-)

 

[Luke]

In article <[email protected]>, Tony Raven
<[email protected]> wrote:

> >
> > How does this bear on the subject? The bikes in question were not
> > fitted with disc brakes so configured to transmit a considerable
> > ejection force to a wheel fastened by QR and vertical drops (to my
> > knowledge). The court didn't rule on the integrity of such a system vis
> > rear mounted disc brake calipers. There is no mention of disk brakes at
> > all[1].
>
> Correct, no disk brakes involved at all. But clear evidence of wheel
> loss and serious injury due to an ejection force (gravity) in the
> direction of the drop-out opening and failure of the retention
> mechanisms to retain the wheel against the ejection force. Design flaw
> or not design flaw?

Are you being facetious? Alright, I'll play. Yes, the court decided
that in the *concerned cases* the liberation of the front wheel was not
a result of a design flaw and that the vendors were not responsible.

The attorney for the plaintiffs stated, "Most of the families who
purchased the bikes had no idea there was a quick-release feature and
some did not get manuals instructing them how to adjust the
mechanism..." In short, the plaintiffs' ignorance and misuse of the
QRs were at fault.

However, this thread involves components used and installed as per
design specifications; and ejection forces that render your 'gravity'
ejection force insignificant. That you won't make these distinctions
and imply that the Walmart verdict testifies to the integrity of the
vertical dropout/QR/rear mounted Disc Brake design strikes me as
disingenuous.

Why introduce irrelevancies into the debate?

Luke






But that you regard tha apply those conclusions to this argument
strikes me as disingenuous.

 

[[email protected]]

Your comment gave me an idea for a simple experiment. I went out to the
garage, lifted the front wheel of my mountain bike, gave the front
wheel a sharp spin, and, still holding the bike up, slammed on the disk
brake, stopping the wheel violently. Repeated several times, then
opened quick release. No motion that I could detect. Now for the good
part. If I loosen the quick release so that the clamping action begins
at 45 degrees from closed, instead of the usual 80 degrees from closed
for this quick release, and redo the stop-spin cycle, the front wheel
does in fact move in the dropouts.

I can tell that the wheel has moved by listening when I open the quick
release. If the wheel has moved, the front fork will fall back into
place when the clamping force is removed. I checked to make sure that
this is a valid test for motion by clamping the quick release with the
bicycle held up, so that the wheel is suspended by the lawyer lips, and
then unclamping. I hear the same click when the wheel drops. But if I
clamp with the weight of the bicycle on the fork I don't hear the
click. If I don't go through the spin-stop cycles, I don't hear the
click. I'm not ready to machine reference surfaces on the fork dropout
so that I can measure with the dial calipers.

So I've given you all an experiment which you can repeat in the privacy
of your own homes. The question then becomes one of scale. Do the
forces that you can exert while riding down a steep rocky slope also
have the potential to cause this kind of motion? Possibly. So now
realize that for a bike with disk brakes, the lawyer lips are a part of
the primary retention system and are no longer just a safety feature.
(Don't file these off.)

When and if the time comes to replace the fork I'll purchase a
replacement from a manufacturer who has made design changes which
rectify the problem. (Marzocchi appears to be using a forward angle on
some of their fork dropouts this year.)

 

[A Muzi]

>>> Mike Causer wrote:
>>>> They could both be right. It is a fact that QRs were designed long
>> before
>>>> disk-braked bikes came along,

>> "jim beam" <[email protected]> wrote in message
>>> but qr's have evolved with their application. over-center cam locking,
>>> serrated faces, thread lock...

> jtaylor wrote:
>> The "over-centre cam locking", in particular, is what makes a QR a QR.

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

You should take one of those apart. The original design
clearly goes 'over center' to lock.

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

 

[jim beam]

A Muzi wrote:
>>>> Mike Causer wrote:
>>>>
>>>>> They could both be right. It is a fact that QRs were designed long
>>>
>>> before
>>>
>>>>> disk-braked bikes came along,
>
>
>>> "jim beam" <[email protected]> wrote in message
>>>
>>>> but qr's have evolved with their application. over-center cam locking,
>>>> serrated faces, thread lock...
>
>
>> jtaylor wrote:
>>
>>> The "over-centre cam locking", in particular, is what makes a QR a QR.
>
>
> jim beam wrote:
>
>> no, the over-center was not an original feature - the old straight
>> lever campy qr's tighten all the way to the stop.
>
>
> You should take one of those apart. The original design clearly goes
> 'over center' to lock.
>
i did. it functioned as i described. i wouldn't use it because of that.

 

[A Muzi]

> jtaylor wrote:
>> Hey jim - found those BROKEN brake bolts yet?
>> You've decided they are unsafe - show us the evidence...

jim beam wrote:
> i've told you before, answer my questions and i will. what are you
> afraid of?

1.)The overwhelming bulk of brake center bolts have cut
threads and
2.)failure is virtually unknown - even after being bent from
hitting the downtube in a crash.

Does anyone seriously dispute either statement?

If I recall, Mr Beam asserted that brake bolts have rolled
threads (which is a good idea, I suppose, but in the
world we actually live in, they don't) and hasn't yet had
either the opportunity to look at brake bolts closely or the
grace to walk away from his hasty statement. Did I miss
anything?

I looked at vintage and modern brake bolts a few weeks ago
but tonight I shot a photo of a brand new Campagnolo Chorus
caliper:

http://www.yellowjersey.org/photosfromthepast/CHRCALIP.JPG

Note that in the profile shot, the thread is clearly smaller
than (cut from ) the body of the bolt. Rolled threads are
raised above the base diameter.

OK, is this over yet?
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

 

[jim beam]

Tim McNamara wrote:
<snip drivel>
>
>
> I see. And that situation is insurmountable? The designers are
> incompetent to deal with that? Good heavens. Might as well go back
> to V-brakes, dude. Oh wait, those are mounted on the front too- no
> doubt there are millions of them being ripped off of forks even as we
> speak.

oh dear. sorry tim, zero points. do the math on the force at the brake
bosses compared to a disk tab. look at the comparative size differences
too and use that to estimate stress. then look at an s-n chart.

 

[A Muzi]

> jtaylor wrote:
>> How many BROKEN brake bolts have you seen?

jim beam wrote:
> more than you evidently - the kid that'll call names but won't fight.
> come on, be a man. come out to the parking lot and answer my questions.

Oh, come on.

In spite of some childish banter, brake bolts are
overwhelmingly cut, not rolled. Anyone with a magnifying
glass and a caliper can verify that.

And failure is virtually unknown. Ask any bike mechanic.
Bent? sure. Damaged threads? sure. Vise grip marks? sure.
Broken? Can't recall the last time I saw one - it's been a
long while.

Here's a new Chorus caliper for those of you who do not have
a bike handy:
http://www.yellowjersey.org/photosfromthepast/CHRCALIP.JPG

Can we drop this now?
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

 

[jim beam]

Johnny Sunset aka Tom Sherman wrote:
> "jim beam" who? wrote:
>
>>...
>>oh, and since you obviously missed it countless times before, the reason
>>for /not/ front mounting a caliper is FATIGUE. cast alloys such as
>>those in forks and calipers ARE NOT GOOD IN TENSILE FATIGUE. that's a
>>pretty fundamental omission from someone that seems to feel qualified to
>>lecture on what comprises good engineering design.
>
>
> Gee, the fork manufacturers could simply increase the size of the
> protrusion that the disc brake caliper bolt threads into and the wall
> thickness of the fork tubing in this area so the stresses from braking
> are below those that will cause fatigue failure within the expected
> lifespan of the fork (with a standard factor of safety). That is what
> an ENGINEER would do.

why would they do that? it's not just the fork material, it's the
caliper material as well. it's pointless to increase the sprung mass
when one can simply ensure loading is compressive, not tensile, as
engineers through out the bicycle and motorcycle industries are now doing.

>
> A (former?) material scientist with an ax to grind [1] apparently has a
> different approach.

it's not different - go look in a motorcycle show room some time.

>
> [1] Note Jobst Brandt is in general agreement with James Annan.
>

brandt agrees that annan's force calculation is substantially correct,
as do i. but brandt fell for the same hocus pocus most others are
falling for - the vital omission of the retention force from the
equation, and the fact that if retention exceeds "ejection" force, the
wheel's going to stay put. which is of course what we see from the
experience of millions of rider-hours of usage.

 

[jim beam]

Michael Press wrote:
> In article
> <[email protected]>,
> Mark McNeill <[email protected]> wrote:
>
>
>>Response to Tony Raven:
>>
>>>On a normal nut the ratio of nut diameter to thread diameter is a lot
>>>lower than the QR nut so ease of tightening and releasing will be
>>>misleading as the turning leverage is much greater on the QR nut.
>>
>>That's all very well; but it doesn't address the point I was making, or
>>at any rate *thought* I was making.
>>
>>
>>
>>>No I don't but the onus is on those proposing that they behave
>>>differently to show it to be so.
>>
>>Yes indeed.
>>
>>I'm not an engineer [and those who think that only engineers should post
>>opinions on this matter may here allow their attention to wander ;-)],
>>but it doesn't seem to me at all unlikely firstly that some QRs may be
>>liable to loosening under prolonged/severe vibration, even when the
>>manufacturer's instructions are followed, and secondly that the force
>>acting on a brake disk may eject a loosened wheel.
>>
>>I can see the chain of reasoning; but there seems for the moment to be a
>>dearth of real-world measurement and observation, and not only on the
>>"plaintiffs'" side. As you say, it's up to them to make their case: but
>>on the other hand there's surely an onus on designers and manufacturers
>>to ensure that their products are safe, which requires an understanding
>>of all the forces involved. If I was in the population at risk, I'd
>>definitely be curious to see evidence that they do. ;-)
>
>
> From what you understand of the theory, consider this
> proposed experiment.
>
> Take a bicycle equipped with a disc caliper mounted on the
> back of the fork. Loosen the quick release clamp until it
> is barely engaged. Walk the bicycle at a brisk pace, then
> apply the front brake.
>
michael, why are you ignoring my post on this challenge? i did this
yesterday. the fork was retained by the lawyer lips. were you
expecting anything else to happen? if so, why?