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:
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?

HAH! Gorramit, I got milk on my keyboard! Sonofabitch, that's funny!
Thanks jim, for brightening up my day!

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.

Geez louise, jim, you must not have passed algebra class in high school.
How many times can you have something so simple explained to you and
fail to grasp it? Good grief. Insane troll logic is all you have.

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.

Ah, yes. The standard bleating to which you have been reduced.

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.

Nah. Just pointing out that you've made yourself into an idiot through
unstinting effort.

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.

LOL. Just mirroring your own sad, flawed argumentation. And now here
you are again, throwing out terms you barely understand.

You've stated that you are a former metallurgist so- unless you were
lying- that's not a false conjecture. I'll give you the ad hominem,
since it was deliberate. And finally, you are promoting a flawed status
quo in fork design, which is an observation and thus would not have been
a "logical incongruity." You are oblivious to the grievous errors in
your thinking, which is also just an observation.

In article ,
jim beam wrote:

Tim McNamara wrote:
In article ,
jim beam wrote:

Tim McNamara wrote:
In article ,
jim beam wrote:

Tim McNamara wrote:
In article ,
wrote:

On Mon, 12 Feb 2007 17:27:57 -0600, Tim McNamara
wrote:

In article ,
wrote:

On Mon, 12 Feb 2007 09:19:17 -0600, Tim McNamara
wrote:

[snip]

In 40 years of riding bikes I've never seen a broken pivot
bolt on a front brake. That of course doesn't mean it
hasn't happened, just that I've never seen it. I don't
recall any reports of this in the newsgroups, either, but
that could be inaccurate as well. Carl could probably use
his prodigious Googling skills and find us some photos of
failed pivot bolts.
[snip]

Dear Tim,

No need to Google--the picture that you click on to see the
bicycle component failure museum shows a broken front brake
pivot bolt:

http://materials.open.ac.uk/mem/mem_ccf2.htm
Thanks! I can't to the larger version of the photos for some
reason. In the small version it almost looks like it was
sawed. Nice wear pattern on the brake shoes, too.

Interestingly, it only broke because of poor maintenance:

"This front brake assembly broke off under braking and
severely injured the cyclist. Poor maintenance had allowed
the brake bolt to loosen and allow the assembly to 'chatter'
when braking imposing cyclic loads instead of steady stress
on the fastening bolt."

In 40 years of riding, have you ever seen a disk brake eject
a front wheel?
Yes, I tested it on a couple of bikes with disk brakes to
verify the existence of the ejection force (which I didn't
believe at the time. It seemed like fearmongering and
handwaving to me. Oops.). Of course, I did leave the QR
undone at the time...
Dear Tim,

The pictures expand in Explorer 6, so possibly it's a Mac
problem.
Other pictures on other pages of that site work correctly on my
browser, just not that page. Odd.

It leaves a bad impression to say that yes, you've seen a disk
brake eject a front wheel . . .

And then add that it was only when the quick release was left
undone.

Maybe a would have helped?
I thought it was clear that the purpose of the experiment was
to verify the existence of the ejection force, not to test the
issue of retention.
and therein lies the cognitive brick wall. if you can't test
retention, you only have one side of the equation, and that's
worthless.
Ah, jim, you continue to grasp at straws.

I frankly didn't believe that any manufacturer would be unwise
enough to let a design with a flaw like that out of the
prototype stage, even if only for liability risk management. I
was astonished when the axle pushed out to the lawyer lips.
belief based engineering. how quaint.
Good grief, jim, you're getting delusional. Or you've lost
whatever reading abilities you had.

Since the problem is so easily rectified with one of several
simple design changes, there is no reason to apologize for the
design and defend it to the hilt like jim has done. Just fix
it.
i'm not defending it, i'm merely pointing out the teensy weensy
little inconvenient factoids like no verifiable cases of
ejection and retention force exceeding ejection force by a
considerable margin. you know, just like bridges support load
and planes fly in the face of potential destruction. what's
next, build a bridge to support 50x max load? 500x max load?
where do we stop?
It's a bad set of comparisons, as has been pointed out to you
over and over and over again. It's all you've got, it is a straw
and you might as well let it go because it won't save you from
drowning.
illogical nonsense.

"Am not!" "Are too!" Come on, jim, can't you do any better than
that?

You can design a fork to use with disk brakes without an ejection
force. It's damned near trivial to do so. You can't design a
bridge with infinite strength nor can you design a plane with
infinite fatigue life. You're trying to compare apples and
oranges. Time to stop reasoning by analogy and deal with the
controlling facts at hand.
trivialization of inconvenient truth.

LOL! You are a Usnenet classic, jim, and marching into troll-land
now.

so present fact! hint: supposition is not fact. ad hominem is not
fact. ignorance doesn't negate fact.

I've given you the facts, jim, over and over and over again. You can't
comprehend them, despite their simplicity. If I had any hope that
another recitation would help, I'd do it. The facts are self-evident
and you reject them.

Talking with you reveals the wisdom of Heinlen's advice: Never try to
teach a pig to sing; it wastes your time and it annoys the pig.

On Feb 15, 12:11 am, Ben C wrote:

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.

The OEM Porsche rotors are actually cast that way. With holes.

Much less prone to cracking than rotors which are cast solid and
drilled later.

My Audis have calipers mounted in front on the front wheels, and in
the rear on the rear wheels.

E.P.

In article ,
jim beam wrote:

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.
look it up. tables for fatigue strength in castings. it's been
posted here before.

And, of course he neglects
to mention that existing brake caliper bolts and their mounts are
not loaded only in compression.
caliper bolts are mounted in shear. bolts are not cast.

This varies with the design of the mounts,
of course, as there are several in use.
no, /all/ caliper bolts are in shear.

Hayes makes something like 13
different adapters for their brakes!
and /all/ the caliper bolts are in shear.

So then there's no problem with mounting the brake in front of the
fork leg, as all those motorcycle brakes prove.

eh? it's raining wednesday, so i'll paint the house blue? do you
even know what shear /is/???

Yup. Note, however that I was talking about the bolts *and* their
mounts. You decided to overlook what the post was actually about-
again- to serve yourself.

Unless you really wanted to claim that the mounts are loaded in shear?

your cognitive myopia is downright scary.

LOL! In the land of the blind, the myopic man is king. LOL!

In article ,
Mike Causer wrote:

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.

Oh dear. Mike, Mike, MIke. Don't introduce actual observed facts into
the discussion. What fun is that? ;-)

Of course you're quite right. I too spent some time looking at these
brakes in bike shops a while back, which made the glaring errors in
jim's arguments all the more obvious.

in article , Tim McNamara at
wrote on 15/2/07 15:22:

In article ,
Ben C wrote:
Front calipers on bicycles are rare.

Front *disk* calipers on bicycles are nonexistant.

The Cotic Roadrat's roadhog fork has them:
http://www.cotic.co.uk/product/roadrat.html

On 2007-02-15, Tim McNamara wrote:
In article ,
Ben C wrote:
[...]
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.

And I say wonderful! I am glad that there has been no rash of these
failures. But I am concerned that there have been partial failures-
loosening of the QR- that would confirm the analysis and which we simply
don;t hear about because the rider assumes user error as the culprit.
After all, we have all had the lore drilled into us that QRs only fail
because of user error. But that was before suspension forks and disk
brakes put unforeseen stresses on QRs.

I actually think that the cry of the anti-ejectionists that "the QR was
probably loose" works against them-- if people can't be counted on to do
up their QRs properly, which they can't, then it follows that the
ejection force is at least a potential problem.

Front calipers on bicycles are rare.

Front *disk* calipers on bicycles are nonexistant.

Not non-existent, a link was posted in this thread or a similar one to
one bicycle with a front disk caliper, although I can't now find it.

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

Unless you are hiding evidence of tensile fatigue problems in disk rbake
bicycle forks, that issue is simply untested. jim may be right, he may
be wrong. Until prototypes are made tested and examined we don't know.

There is no proposed mount design to consider.

Except for the one indicated in the link in the post which I can't find
alluded to above.

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

On a minority of motorbikes.

But in use none the less, which demonstrates the validity of the design.

Noone ever disputed that the design could be made to work. The problem
is one of optimization, and the details and hence the solution are
different in the motorbike case.

As I've said, 2:30 caliper and front-facing dropouts are what I'm
putting on the next disk-equipped MTB I design.

On 2007-02-15, Ben Micklem wrote:
in article , Tim McNamara at
wrote on 15/2/07 15:22:

In article ,
Ben C wrote:
Front calipers on bicycles are rare.

Front *disk* calipers on bicycles are nonexistant.

The Cotic Roadrat's roadhog fork has them:
http://www.cotic.co.uk/product/roadrat.html

Thanks, that's the one I was just trying to find.

On Thu, 15 Feb 2007 09:22:38 -0600, Tim McNamara wrote:

Front *disk* calipers on bicycles are nonexistant.

I wouldn't be so sure. If you look at "Richards' 21st Century Bicycle
Book", published in 2000, the section on brakes includes a drawing of a
caliper mounted in front of the axle, albeit at the back of the bike. And
there was a reference recently to a current production bike with front
mounted front calipers.


On a minority of motorbikes.

But in use none the less, which demonstrates the validity of the design.

As evidenced by the /majority/ of motorbikes in my garage. Two with front
calipers and one with rear calipers.



Mike

Ben C? writes:

[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.

As you say, you have an advanced education so finding the material
should be no problem.

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.

I'm sorry your schooling was at the mercy of such untalented teachers.
This was not my experience and I hold those professors memories in
high esteem. My respect for them grew as I became able to gauge their
skills against what I encountered in engineering, putting to use what
they taught. I cannot imagine "opinionated, egotistical, informative
and full of **** as the best usenet cranks" having any place in
education. When I hear such tales, it makes me feel I lead a charmed
life throughout my education beginning with kindergarten. A young
person should not be expected to separate true from false in
authoritative lectures in his learning years.

It's the same in life, when a person lies to you he cannot be believed
in anything he says that you don't already know. Somehow, this
concept eludes some people, especially public figures who depend on
people who do not understand the finality of lying.

Jobst Brandt