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

In article ,
jim beam wrote:

Tim McNamara wrote:
In article ,
jim beam wrote:

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.

Yes, the logical flaw is amazing. However, it's the glaring hole
in your classic red herring logic (or if you prefer, ignoratio
elenchi) that amazes.

that's just ****. focus on the facts.

I am, jim. And the fact is that you are a moron. You've made it
clearer and clearer and clearer with every post.

It is a false analogy. A bridge cannot be used without a
collapsing force

tim, this is why you have no dog in the hunt - you don't understand
the basics. /all/ bridges are used with collapsing force, just one
of lesser magnitude than the force that succeeds.

In a word, "duh." You are so engaged in proving me wrong that you don't
even bother to read and understand what I write.

and there is no way to design it otherwise,

that's the whole point big guy. but you /can/ determine the bounds,
and if you operate within bounds, you can call that "safe". see
above for magnitude.

but a disk brake can be easily designed to be used without an
ejection force.

can that same design withstand a defective q.r? if not, it has no
value.

Yes, it can. That's the point of the redesign. Are you even paying
attention?

repeated failure to recognize that fundamental point is a truly
extraordinary mental block.

ROTFL! Pot, kettle, black.

you don't get it tim.

You keep saying that. But you're wrong.

Tim McNamara wrote:
In article ,
jim beam wrote:

Tim McNamara wrote:
In article ,
jim beam wrote:

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.
Yes, the logical flaw is amazing. However, it's the glaring hole
in your classic red herring logic (or if you prefer, ignoratio
elenchi) that amazes.
that's just ****. focus on the facts.

I am, jim. And the fact is that you are a moron. You've made it
clearer and clearer and clearer with every post.

It is a false analogy. A bridge cannot be used without a
collapsing force
tim, this is why you have no dog in the hunt - you don't understand
the basics. /all/ bridges are used with collapsing force, just one
of lesser magnitude than the force that succeeds.

In a word, "duh." You are so engaged in proving me wrong that you don't
even bother to read and understand what I write.

"it is a false analogy"???


and there is no way to design it otherwise,
that's the whole point big guy. but you /can/ determine the bounds,
and if you operate within bounds, you can call that "safe". see
above for magnitude.

but a disk brake can be easily designed to be used without an
ejection force.
can that same design withstand a defective q.r? if not, it has no
value.

Yes, it can. That's the point of the redesign. Are you even paying
attention?

eh? you'd ride with a defective q.r.? that's bull.


repeated failure to recognize that fundamental point is a truly
extraordinary mental block.
ROTFL! Pot, kettle, black.
you don't get it tim.

You keep saying that. But you're wrong.

see above.

Tim McNamara wrote:
In article ,
jim beam wrote:

Tim McNamara wrote:
In article ,
jim beam wrote:

Tim McNamara wrote:
In article ,
jim beam wrote:

Tim McNamara wrote: snip crap

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.
LOL. Pot, kettle, black, dude. Jeez, you are such a riot to read.
that's just ****ing.

Yes. Just pointing out to you that ****ing is all you have left in this
argument.

er, i analyze facts. what do you do?


And I think you're- once again- just plain wrong.
you don't understand basic math tim.
LOL. Fortunately my puny math skills are adequate to the task.
so why can't you grasp the fact that if xy, y!x?

Because it has been demonstrated that y can be x. Your waffling
lunacy does not withstand this.

oh brother. if xy, y!x. don't you understand something so simple?
bleating about trying to find other values of x that might be less than
y is breathtakingly stupid.


It would seem, jim, that you are unable to comprehend the simple
fact that I can understand your position and still disagree with
it. You appear so convinced of your rightness, and so committed to
your conviction, that you can't see the forest for the trees.
no, you just won't accept that there's massive gaps in your
understanding - a gap of a size that you don't know what you don't
know.

Over and over and over you say this. You still can't conceive that
someone might possibly understand your position and *still* think that
you are a moron using insane troll logic.

see above tim. basic concepts.


I've been trying to cut you some slack and just figured that your
obvious personal vendetta against Jobst distorts your thinking. But you
know what? I was wrong. You're the idiot that you claim others are.

straw man.


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.
And yet he is a mechanical engineer, and you are not. Hmmm. In
fact, it appears that all the mechanical engineers in this thread
disagree with you. Hmmm.
and there's "mechanical engineers" that think castings are just as
good in tension as they are in compression. it's those kind of
"mechanical engineers" that are responsible for failures.

Or former metallurgists arrogant enough to be oblivious to the grievous
errors in their thinking, promoting a status quo that is flawed.

false conjecture. ad hominem. logical incongruity.

Tim McNamara wrote:
In article ,
jim beam wrote:

Tim McNamara wrote:
In article ,
Ben C wrote:

On 2007-02-14, wrote:
On Feb 14, 3:48 am, Ben C wrote:
[...]
The point is that wheel ejection is a molehill of similar
proportions.
If you want to prove the front-mount-fatigue issue is of similar
importance to the bike wheel ejection issue, it should be easy
for you to do so. Just post here the tales of motorcycles losing
their front mount calipers due to fatigue.
If no such tales can be found that just proves that the motorcycle
designers made sufficiently strong or fatigue-resistant caliper
mounts to overcome the problem. I would expect the likes of Honda
to get that right whatever the basic design. It doesn't tell us
anything about the relative importances of fatigue and ejection.

My claim is that the fatigue hazard is entirely jim beam's
invention.
Yes, I also give jim beam the credit for pointing out the fatigue
hazard.
Pointing out the *presumed* fatigue hazard and then treating the
presumption as fact is more like it. There's no hard evidence to
support jim's claim that this is a hazard.
whoops, missed that peachy bit! now let me get this straight - a
presumed hazard cannot be taken as fact? is that correct? a
presumed hazard like disk ejection? i just want to be sure because
materials literature is full of data on casting fatigue behavior -
that's known to most people as "hard evidence".

The ejection force is a demonstrable fact. You've stipulated to that
already, unless you are (once again) changing your position.

the presumption is that it exceeds retention force!!! jeepers.

The
presumed catastrophic failures that you are treating as fact has not
been demonstrated.

but there's extensive lit on it! what more do you want?

Indeed, since perfectly workable forks with the
calipers in front exist, your claim seems rather specious.

on [a very small minority of] motorcycles with somewhat different
design. cheap lightweight castings are not the place for tension, for
reasons detailed in material lit at great length. and the angled fork
design is useless against a failed q.r!

Tim McNamara wrote:
In article ,
jim beam wrote:

wrote:
On Feb 14, 3:48 am, Ben C wrote:
On 2007-02-14, wrote:

But third (and perhaps easiest to understand) is that the
specific thing jim beam warns about - front mounting of disk
brakes - has been employed on multi-hundred-pound motorcycles for
many decades. The direct tensile stresses that come from such
mounting are small, and very easily accommodated. If they were
not, NHTSA and CPSC would have told you about it in the recall
documents for those motorcycles.
Noone's disputed that a front caliper is possible, but motorbikes
are not bicycles.
True. They're much more massive, travel at much higher speeds, and
impose much higher forces on their caliper attachements.

All the relative pros and cons are different, which makes it a
different optimization problem and we should not be surprised if
it has a different solution. Lots of motorbikes do have rear
calipers anyway.
Do you know of any motorcycle with a rear caliper and a quick
release front axle? I don't believe they exist. Every motorcycle
I've owned or seen had a through-axle. Thus, the hazard imposed by
a rear caliper was removed by other means.
conversely, why aren't /all/ motorcycles front caliper? idiot.

Who's the idiot, jim? Frank? Or you with your obstinate denial of
reality? If he's an idiot, you're a pathetic muppet.

Through axles. No QRs. Ejection force not an issue.

but you can already buy one. that's not a "design change"!!!


So yes, there's a grain of metallurgical truth in what j.b. says.
But the design proclamations he derives from it are nonsense.
He's making a mountain out of a molehill for reasons of his own.
The point is that wheel ejection is a molehill of similar
proportions.
If you want to prove the front-mount-fatigue issue is of similar
importance to the bike wheel ejection issue, it should be easy for
you to do so. Just post here the tales of motorcycles losing their
front mount calipers due to fatigue. Carl has posted several
examples of candidate motorcycles to check. If you find enough
such tales, I'll believe the hazards are similar.
post front wheel ejections where it's proven not to be user error!
idiot.

Post wheel ejections where it's proven to be user error! Muppet.

oh, wait, circular argument based on supposition. surely not part of
the research thesis is it?

[p.s. don't let lack of ejection data get in the way of that one tim.]


My claim is that the fatigue hazard is entirely jim beam's
invention.
i invented inferior fatigue properties for castings??? you don't
even know what a casting is! idiot.

You have an opportunity to prove me wrong.
no, you do that on your own. idiot.

ROTFL! jim, do you get spittle all over your keyboard when you are
posting this drivel?

eh? krygowski proves he knows nothing about castings and can't think
through a simple stress sense scenario correctly? but pointing that out
is drivel? get a grip on yourself man.

On 2007-02-15, Tim McNamara wrote:
[...]
The ejection force is a demonstrable fact.

Yes, but isn't the existence of a tensile fatigue cycle for a
front-mounted caliper also a demonstrable fact?

You've stipulated to that already, unless you are (once again)
changing your position. The presumed catastrophic failures that you
are treating as fact has not been demonstrated.

There's precious little evidence of catastrophic failures due to
_either_ demonstrable fact (ejection force or tensile fatigue).

Back to your "absence of evidence != evidence of absence" idea-- we
would expect to see frequent ejections, if they are a problem, since
rear calipers are out there in the wild in their tens of thousands.
Front calipers on bicycles are rare.

There is more evidence that ejection is not a problem in practice than
there is that tensile fatigue is not a problem.

Indeed, since perfectly workable forks with the calipers in front
exist.

On a minority of motorbikes.

On 2007-02-15, wrote:
[...]
Dear Frank & Ben,

To clarify things, disk brakes first appeared on large, heavy street
motorcycles--and were originally mounted with high leading calipers by
Honda.

In ten years or less, the industry (including Honda) had switched to
overwhelmingly to low trailing calipers.

The only modern leading calipers that I know of are found on trials
machines, where the high leading position helps avoid damaging
calipers when the bikes are dropped to one side or the other in rocks,
a routine hazard.

Trials machines are not designed or certified for road use and
nowadays weigh under 170 pounds. Their braking can be quite savage at
low speeds in stunt-riding maneuvers, with the contact patches at
absurd angles.

I don't know why all other machines switched to low trailing calipers
after the first high leading calipers, but I doubt that it had
anything to do with failures. More likely, the lower trailing caliper
improves handling at normal speeds--the motorcycle calipers and disks
are much larger and heavier than what's found on bicycles.

Possibly there are aerodynamic advantages as well.

[...]
Any RBT poster interested in such things should stop by a motorcycle
shop or just peek at a parked machine and see how much thicker,
heavier, and stronger motorcycle parts are.

I have been getting funny looks recently as I scrutinize the caliper
placement of every parked vehicle I walk past. All the motorbikes I've
seen had them low and rear.

Most cars I saw had them front mounted, but some were rear mounted.

I saw a couple of Porsche 911s with cross-drilled discs. Grrr.

On 2007-02-15, jim beam wrote:
[...]
question: in a situation where there is a known risk, but another known
benefit with a certain design, then what happens? example: most modern
cars have negative scrub radius for their steering. it's "safe" because
it tends to counteract the steering effect of a front tire flat at speed
thereby allowing an unskilled driver more chance of retaining control
and bringing the vehicle to a halt in a controlled manner. but the
danger is that it makes steering feel light [and therefore "safe"] when
braking /through/ corners, thereby encouraging that unsafe habit.

I used to drive a Mini which I believe had a zero scrub radius. I braked
deep into corners (risk of a spin but the technique, once mastered,
neutralized understeer and I felt allowed you to carry more speed
through the corners). The car felt good doing that, I didn't notice the
steering getting heavy or uncertain, although perhaps I was just used to
it.

I read in a book at the time that negative scrub radius made steering
slightly vague around the centre position, but made motorway/freeway
driving easier as constant steering correction was not required. I
thought that was the purpose of it.

The Mini was designed in 1959 (before motorways), had very precise
steering (low-geared, light, and the steering wheel was connected
directly to the rack with no UJs in between), but did require more
correction when cruising on motorways than the average 1980s shopping
car.

physics will tell you that braking through corners is a bad thing, and
positive scrub makes braking through feel heavy and uncertain, thereby
discouraging that kind of bad behavior. how might a legal test be
applied to that?

On 2007-02-14, wrote:
On Feb 14, 3:11 am, Ben C wrote:

[J.B.] I think this is not the place to learn about material science.

It's better than nothing.

Actually, it goes beyond that. This is also not the place to learn
about mechanical design to resist fatigue failure, and that's really
what we're discussing at the moment. j.b. appears to know something
about metallurgy, but he knows too little about mechanical design.
It's principles are by no means obvious.

So explain them, or suggest a link.

You won't learn them here, and certainly not from jim beam.

In my salad days I attended a top university myself, and learnt many
things there. Almost to a man the tutors were as opinionated,
egotistical, informative and full of **** as the best usenet cranks. The
learning process consisted of filtering and thinking for yourself, no
different to r.b.t. or life in general.

On Wed, 14 Feb 2007 19:26:56 -0800, jim beam wrote:

no, /all/ caliper bolts are in shear.

Except for the maybe 50% that aren't. Data obtained by examining the
attachment of every disc brake on the stock of new bikes in Moon's Cycle
Centre, Newmarket, England, yesterday afternoon.

What I saw removed any doubts about front mounting, the weediness of some
of the rear mounted setups has further convinced me that the load, and
service life, would be very easily handled with a properly made front
attachment.


Mike