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



G

G.T.

Guest
[email protected] wrote:
> On Mon, 12 Feb 2007 18:37:47 -0800, "G.T." <[email protected]>
> wrote:
>
>> <[email protected]> wrote in message
>> news:p[email protected]
>>> On Mon, 12 Feb 2007 17:40:08 -0800, "G.T." <[email protected]>
>>> wrote:
>>>
>>>> <[email protected]> wrote in message
>>>> news:[email protected]
>>>>> On Mon, 12 Feb 2007 16:41:08 -0800, "G.T." <[email protected]>
>>>>> wrote:
>>>>>
>>>>>> <[email protected]> wrote in message
>>>>>> news:[email protected]
>>>>>>> On Mon, 12 Feb 2007 15:49:57 -0800, "G.T." <[email protected]>
>>>>>>> wrote:
>>>>>>>
>>>>>>>> "Ed Pirrero" <[email protected]> wrote in message
>>>>>>>> news:[email protected]
>>>>>>>>> On Feb 12, 3:02 pm, "G.T." <[email protected]> wrote:
>>>>>>>>>> "Ed Pirrero" <[email protected]> wrote in message
>>>>>>>>>>
>>>>>>>>>> news:[email protected]
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>> On Feb 12, 2:27 pm, "G.T." <[email protected]> wrote:
>>>>>>>>>>>> "Ed Pirrero" <[email protected]> wrote in message
>>>>>>>>>>>> news:[email protected]
>>>>>>>>>>>>> On Feb 11, 7:54 pm, Gary Young <[email protected]> wrote:
>>>>>>>>>>>>>> This is a variant of the
>>>>>>>>>>>>>> my-uncle-was-a-smoker-and-he-lived-until-95
>>>>>>>>>>>>>> argument.
>>>>>>>>>>>>> Except for the small details that smoking will most definitely
>>>>>>>>>>>>> cause
>>>>>>>>>>>>> some harm, and, so far, disk brakes have caused none due to
>>>>>>>>>>>>> the
>>>>>>>>>>>>> ejection force being present.
>>>>>>>>>>>> None? You're sure about that?
>>>>>>>>>>>> Greg
>>>>>>>>>>> The answer to both questions is in the part you trimmed.
>>>>>>>>>> "(Qualifier: if some harm has occurred, it certainly hasn't been
>>>>>>>>>> distinguished from user error.)"
>>>>>>>>>>
>>>>>>>>>> So now you're omniscient?
>>>>>>>>> Strawman.
>>>>>>>>>
>>>>>>>>> If you've got any, and I mean ANY, credible data that any of the
>>>>>>>>> incidents involving wheel ejection have been proven as disk-brake
>>>>>>>>> caused, go ahead and cite it.
>>>>>>>>>
>>>>>>>> It's sad that you and jb are such untrusting fools.
>>>>>>>>
>>>>>>>> "Missy's QR popped. She had definitely tightened it before the ride
>>>>>>>> as
>>>>>>>> she
>>>>>>>> was doing some goofy stuff. The Skareb had the lawyer lips intact.
>>>>>>>> [The]
>>>>>>>> XT skewer [was] really tight."
>>>>>>>>
>>>>>>>> "QR WAS done up - I had checked it at the top and had not stopped,
>>>>>>>> crashed
>>>>>>>> or clipped anything that may have undone it."
>>>>>>>>
>>>>>>>> Greg
>>>>>>> Dear Greg,
>>>>>>>
>>>>>>> For the rest of us fools, trusting or otherwise, could you add the
>>>>>>> missing citation?
>>>>>>>
>>>>>>> That is, who is saying that someone else's QR "popped"?
>>>>>>>
>>>>>>> And where can we find it--a web page, a magazine, a newspaper?
>>>>>>>
>>>>>> The first can be found by searching "missy giove wheel ejection" on
>>>>>> Google
>>>>>> and the other is on someone's site who y'all don't trust.
>>>>>>
>>>>>> Greg
>>>>> Dear Greg,
>>>>>
>>>>> Wouldn't it be common courtesy to just provide the links?
>>>> See below.
>>>>
>>>>> Your Google suggestion provides 42 places to look:
>>>>>
>>>>> http://www.google.com/search?as_q=m...as_dt=i&as_sitesearch=&as_rights=&safe=images
>>>>>
>>>>> See how easy it is?
>>>>>
>>>>> Why make it hard for people who are interested to look at whatever
>>>>> you're talking about? It gives the impression that whatever you're
>>>>> citing can't stand examination, which is scarcely your intent.
>>>> Because I don't believe that you, jb, or EP are interested or you would
>>>> have
>>>> found references to wheel ejections in the past.
>>>>
>>>> Greg
>>> Dear Greg,
>>>
>>> I'm asking where I can find what you quoted, which shows interest on
>>> my part.
>>>

>> Ok, my bad. When I searched just a little while ago this recounting was at
>> the top of the Google results:
>>
>> http://www.bikebiz.com/Missy-Gioves-QR-pops-open-
>>
>> Greg

>
> Dear Greg,
>
> Now there's something to look at.
>
> Sorry, but it's not very credible as it stands.
>
> "Missy's QR popped. She had definitely tightened it before the ride as
> she was doing some goofy stuff."
>
> Does that mean that the speaker thinks that Missy must have tightened
> it because she was doing some goofy stuff and he assumes that she
> would have "definitely tightened" it?
>
> Or does it mean that he saw her tighten it before she went riding and
> began doing goofy stuff? Who watches another rider slapping a wheel
> into the fork? It's possible, but strange.
>
> "The Skareb had the lawyer lips intact. [The] XT skewer [was] really
> tight. I'd actually mentioned your story to Rick when we were leaving
> the office."
>
> How does he know how tight Missy's skewer was if she was the one who
> tightened it?
>
> You may not like such questions, but they're the ones that any lawyer
> or expert trying to reconstruct an accident would ask. Whatever Jobst
> may think about the principles, here's his timely comment in another
> current thread on plaintiffs and accident reconstruction:
>
> "I would like to have seen the bicycle [another bike, not Missy's]
> right after the incident. It has been my experience that
> reconstruction of what occurred is often easier than first
> indications. That has been so, in every case in which I was called to
> testify. That is to say, the event did not occur as plaintiff
> described."
>
> In these anecdotes mentioned in this thread, people insist that they
> had just definitely checked a really tight quick release because
> they'd been reading that the QR might pop open unexpectedly--and sure
> enough, the QR that had no previous history of popping open obligingly
> pops open on the ride.
>
> Isn't it odd that there's no history of Missy's QR popping open while
> she did "goofy stuff" in redwood forest rides with two friends, one of
> whom just read an article about QR's popping open?
>
> Maybe Missy's QR had been popping open all the time, but she just
> never mentioned it to friends? It could be, but it would be odd that
> she never mentioned such startling behavior.
>
> Maybe Missy had never previously ridden so goofily? It could be, but
> it seems unlikely that a world-class downhill rider suddenly exceeded
> all her previous efforts on a casual ride.
>
> Or maybe the other usual (and less flattering) explanations apply? "On
> Any Sunday" cruelly shows Malcom Smith, arguably that era's greatest
> desert racer, attacking the Widowmaker hill-climb on his Husqvarna
> with the cameras rolling and huge audience, only to sputter to an
> embarrassing stop because he forgot to turn his fuel tap on.
>
> Of course, there may be a more detailed article somewhere about
> Missy's QR that would lay the obvious questions to rest.
>
> And this story and every other story mentioned in this thread could be
> perfectly true and accurate.
>
> But the strange pattern of QR's that pop open as soon as someone hears
> they might do so raises reasonable doubts.
>
> So does the rest of the article that you quoted, which doesn't even
> mention the possibility that the QR might just not have been tightened
> as claimed afterward:
>
> "On One's Brant Richards is not convinced the 'Missy incident' is the
> Annan theory found in the field."
>
> "'We don't know how Missy's QR popped open. She could have caught it
> trailside on something. It might well have been tight, but might not
> have been locked over centre.'"
>
> "'It could have been incorrectly installed, with the clamping surface
> not sitting properly in the dropout, and have settled loose, then
> flopped open.'"
>
> "'The problem now is people are now suspecting an Annan-type QR/disc
> problem, not the fact that something else - several other things -
> could have happened!'"
>
> "'We have a rear disc mount on our singlespeed jump frames, and the
> relationship of the disc and dropout slot means that certain riders
> have noticed the wheel being moved backwards by the force of the disc
> brake due to the forces involved. This is only when the wheel is
> clamped in place by a chaintug - a device to stop the wheel moving
> forwards - which spreads the clamping force over a large area. Use of
> just a good old track nut usually stops this in its tracks.'"
>
> "'I therefore don't discount the fact that the physics and my
> experience show that a wheel can be shifted in the dropout under
> braking load. But I do discount that a correctly installed QR of a
> correct over-centre-clamp type lock won't come undone unless it's
> disturbed on the trail.'"
>
> "And Richards has a cheap solution:"
>
> "'Surely something as simple as zip tieing the QR in a closed position
> would stop all this. It's the bicycle equivalent of the axle nut split
> pin.'"
>
> http://www.bikebiz.com/Missy-Gioves-QR-pops-open-
>
> For anyone unfamiliar with axle nut split pins, front and rear
> motorcycle axles often (if not invariably) come with a hole drilled
> sideways through the threads and use a turret nut that allows a large
> cotter pin to be inserted and prevent the nut from unscrewing.
>
> The cotter pins rarely survive the first wheel removal, and the empty
> holes usually plug up with mud and even tiny rock fragments on trials
> machines.
>
> As for the notion that racers (and sincere amateurs) are somehow above
> simple mistakes, remember that during major surgery a nurse is
> required to count the instruments and sponges because experience (and
> x-rays) show that extraordinarily well-trained and dedicated surgeons
> keep leaving things inside patients.
>
> And despite this precaution, instruments and sponges still keep
> turning up inside patients.
>


Yep, you're right. Just like jb and EP, you're right, it's always the
user's fault. As a techie at work I should know that by now. It's
always the users fault.

Greg

--
"All my time I spent in heaven
Revelries of dance and wine
Waking to the sound of laughter
Up I'd rise and kiss the sky" - The Mekons
 
B

Ben C

Guest
On 2007-02-11, [email protected] <[email protected]> wrote:
[...]
> I'd rather not go to the numbers because they are irrelevant. What is
> relevant is a coefficient of traction enough to cause an endo on solid
> pavement and that this can be as much as 1g considering the rider CG
> (belly button) can be on a 45° line from tire contact with the road.
>
> Half of that load is on each dropout pushing up and rearward at 45°.
> At the same time a downward force of the entire front wheel load times
> the ratio o f wheel diameter to disk diameter (up to 4x) is pulling
> one side of the wheel downward. Therefore, roughly 8x times the
> upward force on that one dropout.


This is correct, but I misunderstood it.

If we consider the direction of the net force on the front wheel, it's
[1, 0] from braking, [0, 1] from ground reaction, and [sin(theta),
-cos(theta)] * R/r from the disk. Not 2R/r.

We're assuming maximum braking here, and so the net torque on the wheel
is 0. The fact that the disk is only one side makes no difference to
that calculation.

Jobst's description is considering net force on the axle, which is
pushing the rider back along 45 degrees with both dropouts, but is
resisted at only one.

Correcting my calculations again, I get 34 degrees from vertical for Ben
Micklem's wheel (which is 54 degrees from the dropout exit angle), and
17 degrees from vertical for the wheel with the caliper at 3 o'clock.

I think the numbers do matter, particularly the difference in angle
between the direction of the ejection force and the exit direction
provided by the dropout. If the difference is > 45 degrees, it seems to
me the wheel would certainly not eject however large the magnitude of
the force. This is because the component pushing it out of the dropout
will be exceeded by the component burying it into the steel/aluminium of
the dropout.

function phi = ejection_angle(theta, R, r)
% theta is angle of caliper in radians, measured anticlockwise with 0 at 3
% o'clock. R is tyre radius, r is disk radius. phi is angle of ejection
% force from vertical in degrees.

% The caliper force. x +'ve is rearward, y -'ve is downward.
c = [sin(theta), -cos(theta)];

% Its magnitude is scaled by difference in radius between disk and tyre,
c *= R / r;

% Add the braking force and the contact force (friction coefficient is 1.0)
% to give the net force f on the wheel under braking.
f = c + [1, 0] + [0, 1];

% Work out that vector's direction from vertical
phi = atan(f(1) / f(2));
phi *= -360 / (2*pi);
endfunction

% Caliper at 2:30.
theta = (0.5 / 12) * 2*pi;
disp(ejection_angle(theta, 675.14, 160));

% Caliper at 3:00
disp(ejection_angle(0, 675.14, 160));
 
B

Ben C

Guest
On 2007-02-12, Tim McNamara <[email protected]> wrote:
> In article <[email protected]>,
> Ben C <[email protected]> wrote:

[...]
>> I think front mounted calipers is overkill, and has the drawback of
>> putting the mountings in tensile fatigue as you've explained.

>
> And yet it is done successfully on other vehicles, so that is a
> surmountable problem and a straw man raised by jim.


It was also interesting to read the reaction of Ben Micklem's frame
builder to the suggestion of front-mounting the caliper. They didn't
think it sounded like a good idea.

>> But moving the dropout angle forwards and the caliper upwards a bit,
>> as some designs already do-- wouldn't that solve the theoretical
>> and/or real problems?

>
> It could. Look at motorcycle disk brakes, which often place the caliper
> up tight against the fork leg. The caliper ends up nearly at the top of
> the disk. The vector of the reaction force from braking would be in a
> much more benign direction.


As I said in another thread, if the difference in direction is 45
degrees or better, I don't think you're going to get ejection. Unless my
calculations are still wrong (it's been known...) Ben Micklem has a 54
degree difference with a 2:30 caliper and 20 degree forwards dropout.
Should be perfectly safe.

> Placing the caliper in from of the fork would result in the reaction
> force driving the axle into the dropout and eliminating the ejection
> force altogether.


Of course true, but although not impossible, undesirable.

The 2007 range of "Ben C" mountain bikes will use rear calipers mounted
at 2:30 and slightly forward-opening dropouts. And no tapering on the
forks.
 
A

Andrew Lee

Guest
A Muzi wrote:
> p.s. - Jobst makes a good point about hub brakes (disc, drum whatever) on
> undersized/lightweight fork blades or stays. The occasional tinkerer
> discovers this with great surprise.


Imagine what would happen if someone Chalo-sized had to do hard braking on
this bike:

Skinny fork, brake calipers about 90 degrees from the dropout opening
http://www.hampsten.com/Tournesol/pop/commuteur05_pop.htm

No lawyer lips that I can see, but maybe they are really small
http://www.hampsten.com/Tournesol/pop/commuteur04_pop.htm

Hole midway up the fork on the brake side
http://www.hampsten.com/Tournesol/pop/commuteur02_pop.htm
 
M

Mike Causer

Guest
On Mon, 12 Feb 2007 23:27:33 -0600, Tim McNamara wrote:

> Other pictures on other pages of that site work correctly on my browser,
> just not that page. Odd.


Do a "view image", which will get the small picture with a URL like
http://materials.open.ac.uk/mem/images/images_cc/ccf7r.jpg
then take the "r" out of the name of the jpeg.
http://materials.open.ac.uk/mem/images/images_cc/ccf7.jpg


Something is borked in their javascript, which is completely unnecessary
for a simple link to a picture.


Mike
 
D

dvt

Guest
jim beam wrote:
> but the retention force exceeds payload by at least 3 times worst case
> scenario.


Worst case?

--
Dave
dvt at psu dot edu
 
M

Mike Causer

Guest
On Mon, 12 Feb 2007 16:23:21 -0600, Ben C wrote:

> Here is my working in the form of a GNU Octave script if anyone has the
> energy to check it.


I haven't gone through it thoroughly (downloading Octave now), but
there are a couple of assumptions that I think are incorrect:


> % Its magnitude is scaled by difference in radius between disk and tyre,
> % and multiplied again by 2 since the disk is only on one side of the axle.


This factor is only relevant when the weight of bike + rider is
included, which isn't part of this calculation. Instead of doubling the
braking load I think you should halve the gravitational load (when it's
used), and if you will grant some stiffness in the hub and axle that
transfers part of the braking load to the other side, reduce the braking
load by some percentage.


> % Add the braking force and the contact force (friction coefficient is 1.0)
> % to give the net force f on the wheel under braking.


Once the rear wheel has lifted a greater friction coefficient has no
effect, and I think you'll find that the actual value required for
maximum braking is between 0.6 and 0.65 (Wilson gives 0.56 but I think
he is assuming a crouched rider for his CoG location).

I have a program that allows some experiment with friction and CoG
position, but it's pretty crude and written in Awk, so I might rewrite
it in Octave as a way of learning something about Octave. If you want
to see the Awk version send me an email.



Mike
 
E

Ed Pirrero

Guest
On Feb 12, 4:06 pm, Tim McNamara <[email protected]> wrote:
> In article <[email protected]>,
> "Ed Pirrero" <[email protected]> wrote:
>
>
>
>
>
> > On Feb 11, 8:55 pm, "G.T." <[email protected]> wrote:
> > > Ed Pirrero wrote:
> > > > On Feb 11, 8:37 am, jim beam <[email protected]> wrote:
> > > >> Tim McNamara wrote:

>
> > > >> <snip underinformed opinion>

>
> > > >> 1. there are no reported accidents that can be definitely
> > > >> distinguished from user error.

>
> > > > Exactly. Tim like to throw bombs around about these reported
> > > > incidents, but never once has anyone proven that it was actually
> > > > the forces in question vs. user error.

>
> > > So because it hasn't been proven yet you guys are 100% certain that
> > > it's been user error?

>
> > Strawman.

>
> No, it looks like just a poorly formed question.
>
> "A straw man argument is a logical fallacy based on misrepresentation of
> an opponent's position. To "set up a straw man" or "set up a straw-man
> argument" is to create a position that is easy to refute, then attribute
> that position to the opponent. A straw-man argument can be a successful
> rhetorical technique (that is, it may succeed in persuading people) but
> it is in fact a misleading fallacy, because the opponent's actual
> argument has not been refuted." Given the question mark at the end of
> Greg's post, I think it is reasonable to give him the benefit of the
> doubt. Were it a sentence, then I would agree that it is a straw man.
>
> However, you do appear to simply disregard any evidence that contradicts
> your theory. That may not be an accurate assessment of your thinking
> process but it is the impression I get from reading your posts. Your
> logic- and jim's- looks like this to me:
>
> A. It has been postulated that disk brake can cause wheel ejection.
> B. Uncertainty can be cast upon the evidence that A is true.
> C. Therefore A is false.
>
> That may or may not be what you intend. On my screen, that's how it
> reads.


A reasonable reply! I am surprised, and pleased.

OK, here's how it goes:

A. Yes, I agree.

B. Sort of - I think that because there is a force, that the
possibility exists that a wheel could be ejected.

C. No, not true at all.

I'm still an agnostic on whether this "problem" is real, or just
theoretical. Because, as Frank writes, so many conditions have to
line up right for ejection to occur, it gets into the realm of doing a
fix on something that's not broken.

As I have said, to you and to others, I am willing to look at real
data, and evaluate it for what it is. I don't dismiss data out of
hand, I dismiss conclusions based on opinion rather than hard data.
While to you the difference may be subtle, for me it makes all the
difference in the world.

Unfortunately, I don't consider the anecdotes "data", because the
initial conditions are unknown. It is *possible* that the initial
conditions are normal, but it is possible that they are not. Not
exactly a dismissal, but not exactly full acceptance as data points.

I consider any attempt to put me in the position of defending some
absolute denial as strawman logical fallacy, for all of these reasons.

I hope this clears things up.

E.P.
 
E

Ed Pirrero

Guest
On Feb 12, 3:49 pm, "G.T." <[email protected]> wrote:
> "Ed Pirrero" <[email protected]> wrote in message
>
> news:[email protected]
>
>
>
>
>
> > On Feb 12, 3:02 pm, "G.T." <[email protected]> wrote:
> >> "Ed Pirrero" <[email protected]> wrote in message

>
> >>news:[email protected]

>
> >> > On Feb 12, 2:27 pm, "G.T." <[email protected]> wrote:
> >> >> "Ed Pirrero" <[email protected]> wrote in message

>
> >> >>news:[email protected]

>
> >> >> > On Feb 11, 7:54 pm, Gary Young <[email protected]> wrote:

>
> >> >> >> This is a variant of the
> >> >> >> my-uncle-was-a-smoker-and-he-lived-until-95
> >> >> >> argument.

>
> >> >> > Except for the small details that smoking will most definitely cause
> >> >> > some harm, and, so far, disk brakes have caused none due to the
> >> >> > ejection force being present.

>
> >> >> None? You're sure about that?

>
> >> >> Greg

>
> >> > The answer to both questions is in the part you trimmed.

>
> >> "(Qualifier: if some harm has occurred, it certainly hasn't been
> >> distinguished from user error.)"

>
> >> So now you're omniscient?

>
> > Strawman.

>
> > If you've got any, and I mean ANY, credible data that any of the
> > incidents involving wheel ejection have been proven as disk-brake
> > caused, go ahead and cite it.

>
> It's sad that you and jb are such untrusting fools.


Logical fallacy - ad hominem.

E.P.
 
B

Ben C

Guest
On 2007-02-13, Mike Causer <[email protected]> wrote:
> On Mon, 12 Feb 2007 16:23:21 -0600, Ben C wrote:
>
>> Here is my working in the form of a GNU Octave script if anyone has the
>> energy to check it.

>
> I haven't gone through it thoroughly (downloading Octave now), but
> there are a couple of assumptions that I think are incorrect:
>
>
>> % Its magnitude is scaled by difference in radius between disk and tyre,
>> % and multiplied again by 2 since the disk is only on one side of the axle.

>
> This factor is only relevant when the weight of bike + rider is
> included, which isn't part of this calculation.


Yes, exactly right, and I realized this and pointed it out in an earlier
post. You need to get rid of the factor of two.

> Instead of doubling the braking load I think you should halve the
> gravitational load (when it's used), and if you will grant some
> stiffness in the hub and axle that transfers part of the braking load
> to the other side, reduce the braking load by some percentage.


I'm just considering the forces on the wheel: road force (horizontally
backwards), ground reaction force (vertically upwards, same magnitude--
friction coefficient of 1.0), and caliper force. Add those three up and
you get the net force on the wheel. Then you can see if its direction is
within 45 degrees of the way out.

The caliper force is computed so as to give zero net torque on the
wheel.

Now I'm thinking there's another error there. Ground reaction force
should not be included, as it is opposed by the weight of the rider/bike
pushing down on the wheel. This means I'm right back to my original
version of the calcuation (no ground reaction force or factor of two)
and I get 27 degrees from vertical for the caliper at 2:30 (which is 47
deg from the dropout if the dropout is 20 deg forwards), and 13 deg from
vertical for caliper at 3:00 (or 14 deg if the disk/rim ratio is exactly
4 instead of 4.2).

>> % Add the braking force and the contact force (friction coefficient is 1.0)
>> % to give the net force f on the wheel under braking.

>
> Once the rear wheel has lifted a greater friction coefficient has no
> effect, and I think you'll find that the actual value required for
> maximum braking is between 0.6 and 0.65 (Wilson gives 0.56 but I think
> he is assuming a crouched rider for his CoG location).


1.0 was meant to be sort of "worst case", although actually the friction
coefficient can get slightly higher than 1.0.

> I have a program that allows some experiment with friction and CoG
> position, but it's pretty crude and written in Awk, so I might rewrite
> it in Octave as a way of learning something about Octave. If you want
> to see the Awk version send me an email.


I might do that. Thanks for looking through my version.
 
E

Ed Pirrero

Guest
On Feb 12, 8:58 pm, Tim McNamara <[email protected]> wrote:
> In article <[email protected]>,
> "Ed Pirrero" <[email protected]> wrote:
>
>
>
>
>
> > On Feb 12, 3:02 pm, "G.T." <[email protected]> wrote:
> > > "Ed Pirrero" <[email protected]> wrote in message

>
> > >news:[email protected]

>
> > > > On Feb 12, 2:27 pm, "G.T." <[email protected]> wrote:
> > > >> "Ed Pirrero" <[email protected]> wrote in message

>
> > > >>news:[email protected]

>
> > > >> > On Feb 11, 7:54 pm, Gary Young <[email protected]> wrote:

>
> > > >> >> This is a variant of the
> > > >> >> my-uncle-was-a-smoker-and-he-lived-until-95 argument.

>
> > > >> > Except for the small details that smoking will most definitely
> > > >> > cause some harm, and, so far, disk brakes have caused none due
> > > >> > to the ejection force being present.

>
> > > >> None? You're sure about that?

>
> > > >> Greg

>
> > > > The answer to both questions is in the part you trimmed.

>
> > > "(Qualifier: if some harm has occurred, it certainly hasn't been
> > > distinguished from user error.)"

>
> > > So now you're omniscient?

>
> > Strawman.

>
> > If you've got any, and I mean ANY, credible data that any of the
> > incidents involving wheel ejection have been proven as disk-brake
> > caused, go ahead and cite it.

>
> Define "credible." As far as I can tell, you consider no report
> credible that contradicts your theory.- Hide quoted text -


Credible includes where the initial conditions are known and verified.

"Somebody said so" isn't data, Tim. Never has been, never will be.

E.P.
 
G

G.T.

Guest
Ed Pirrero wrote:
> On Feb 12, 8:58 pm, Tim McNamara <[email protected]> wrote:
>> In article <[email protected]>,
>> "Ed Pirrero" <[email protected]> wrote:
>>
>>
>>
>>
>>
>>> On Feb 12, 3:02 pm, "G.T." <[email protected]> wrote:
>>>> "Ed Pirrero" <[email protected]> wrote in message
>>>> news:[email protected]
>>>>> On Feb 12, 2:27 pm, "G.T." <[email protected]> wrote:
>>>>>> "Ed Pirrero" <[email protected]> wrote in message
>>>>>> news:[email protected]
>>>>>>> On Feb 11, 7:54 pm, Gary Young <[email protected]> wrote:
>>>>>>>> This is a variant of the
>>>>>>>> my-uncle-was-a-smoker-and-he-lived-until-95 argument.
>>>>>>> Except for the small details that smoking will most definitely
>>>>>>> cause some harm, and, so far, disk brakes have caused none due
>>>>>>> to the ejection force being present.
>>>>>> None? You're sure about that?
>>>>>> Greg
>>>>> The answer to both questions is in the part you trimmed.
>>>> "(Qualifier: if some harm has occurred, it certainly hasn't been
>>>> distinguished from user error.)"
>>>> So now you're omniscient?
>>> Strawman.
>>> If you've got any, and I mean ANY, credible data that any of the
>>> incidents involving wheel ejection have been proven as disk-brake
>>> caused, go ahead and cite it.

>> Define "credible." As far as I can tell, you consider no report
>> credible that contradicts your theory.- Hide quoted text -

>
> Credible includes where the initial conditions are known and verified.
>
> "Somebody said so" isn't data, Tim. Never has been, never will be.
>


So you need, what, 17.5 people including the Pope to check that
someone's QR was tight before you'll believe any of these people?

Greg

--
"All my time I spent in heaven
Revelries of dance and wine
Waking to the sound of laughter
Up I'd rise and kiss the sky" - The Mekons
 
E

Ed Pirrero

Guest
On Feb 13, 9:24 am, "G.T." <[email protected]> wrote:
> Ed Pirrero wrote:
> > On Feb 12, 8:58 pm, Tim McNamara <[email protected]> wrote:
> >> In article <[email protected]>,
> >> "Ed Pirrero" <[email protected]> wrote:

>
> >>> On Feb 12, 3:02 pm, "G.T." <[email protected]> wrote:
> >>>> "Ed Pirrero" <[email protected]> wrote in message
> >>>>news:[email protected]
> >>>>> On Feb 12, 2:27 pm, "G.T." <[email protected]> wrote:
> >>>>>> "Ed Pirrero" <[email protected]> wrote in message
> >>>>>>news:[email protected]
> >>>>>>> On Feb 11, 7:54 pm, Gary Young <[email protected]> wrote:
> >>>>>>>> This is a variant of the
> >>>>>>>> my-uncle-was-a-smoker-and-he-lived-until-95 argument.
> >>>>>>> Except for the small details that smoking will most definitely
> >>>>>>> cause some harm, and, so far, disk brakes have caused none due
> >>>>>>> to the ejection force being present.
> >>>>>> None? You're sure about that?
> >>>>>> Greg
> >>>>> The answer to both questions is in the part you trimmed.
> >>>> "(Qualifier: if some harm has occurred, it certainly hasn't been
> >>>> distinguished from user error.)"
> >>>> So now you're omniscient?
> >>> Strawman.
> >>> If you've got any, and I mean ANY, credible data that any of the
> >>> incidents involving wheel ejection have been proven as disk-brake
> >>> caused, go ahead and cite it.
> >> Define "credible." As far as I can tell, you consider no report
> >> credible that contradicts your theory.- Hide quoted text -

>
> > Credible includes where the initial conditions are known and verified.

>
> > "Somebody said so" isn't data, Tim. Never has been, never will be.

>
> So you need, what, 17.5 people including the Pope to check that
> someone's QR was tight before you'll believe any of these people?


Greg, I realize that you're now just after some sort of pissing match.

That's fine - I'm not going to play. Have the last word, if you'd
like.

E.P.
 
Ben C? writes:

> As I said in another thread, if the difference in direction is 45
> degrees or better, I don't think you're going to get ejection.
> Unless my calculations are still wrong (it's been known...) Ben
> Micklem has a 54 degree difference with a 2:30 caliper and 20 degree
> forwards dropout. Should be perfectly safe.


>> Placing the caliper in from of the fork would result in the
>> reaction force driving the axle into the dropout and eliminating
>> the ejection force altogether.


> Of course true, but although not impossible, undesirable.


Why is that undesirable? I believe it is entirely aesthetics. I see
no technical reason for not doing so. Caliper behind the strut is
much like recessed rim brake anchor nuts (even on the back side of the
fork crown), it looks more "cool".

> The 2007 range of "Ben C" mountain bikes will use rear calipers
> mounted at 2:30 and slightly forward-opening dropouts. And no
> tapering on the forks.


Instead of calculating, I think more would be gained by observing the
reactions on a bicycle by taking out the QR skewer to observe how the
axle moves when someone else pushes the bicycle forward and applies
the disk brake. This does not require a rider to sit on the bicycle,
just pushing it forward will do, the forces being proportional
regardless of load.

Jobst Brandt
 
E

Ed Pirrero

Guest
On Feb 13, 11:49 am, [email protected] wrote:
> Ben C? writes:
> > As I said in another thread, if the difference in direction is 45
> > degrees or better, I don't think you're going to get ejection.
> > Unless my calculations are still wrong (it's been known...) Ben
> > Micklem has a 54 degree difference with a 2:30 caliper and 20 degree
> > forwards dropout. Should be perfectly safe.
> >> Placing the caliper in from of the fork would result in the
> >> reaction force driving the axle into the dropout and eliminating
> >> the ejection force altogether.

> > Of course true, but although not impossible, undesirable.

>
> Why is that undesirable? I believe it is entirely aesthetics.


But you don't *know* that. So far, this is merely conjecture. Oddly,
others have presented this as fact.

> I see
> no technical reason for not doing so.


Which means what? That there is no technical reason for doing so?

Another conjecture.

> Caliper behind the strut is
> much like recessed rim brake anchor nuts (even on the back side of the
> fork crown), it looks more "cool".


Opinion based on conjecture.

> > The 2007 range of "Ben C" mountain bikes will use rear calipers
> > mounted at 2:30 and slightly forward-opening dropouts. And no
> > tapering on the forks.

>
> Instead of calculating, I think more would be gained by observing the
> reactions on a bicycle by taking out the QR skewer to observe how the
> axle moves when someone else pushes the bicycle forward and applies
> the disk brake.


And exactly what does this prove, aside from the fact that the
ejection force exists?

Everyone who is involved in this discussion, and for the last few of
these discussions, already agrees that the force exists, and its
approximate magnitude.

What is to be gained, Jobst? How does it change the discussion at
all?

(Anyone want to take bets on how these last two questions will be
studiously avoided?)

E.P.
 
B

Ben C

Guest
On 2007-02-13, [email protected] <[email protected]> wrote:
> Ben C? writes:
>
>> As I said in another thread, if the difference in direction is 45
>> degrees or better, I don't think you're going to get ejection.
>> Unless my calculations are still wrong (it's been known...) Ben
>> Micklem has a 54 degree difference with a 2:30 caliper and 20 degree
>> forwards dropout. Should be perfectly safe.

>
>>> Placing the caliper in from of the fork would result in the
>>> reaction force driving the axle into the dropout and eliminating
>>> the ejection force altogether.

>
>> Of course true, but although not impossible, undesirable.

>
> Why is that undesirable?


Because it puts the mounting point in tension as explained by jim beam.

Also I am concerned about grit, brake dust etc. coming out of the back
of the caliper being thrown upwards towards the rider's face. With the
caliper behind the fork it's directed towards the road behind the front
wheel.
 
Ed Pirrero writes:

>>> As I said in another thread, if the difference in direction is 45
>>> degrees or better, I don't think you're going to get ejection.
>>> Unless my calculations are still wrong (it's been known...) Ben
>>> Micklem has a 54 degree difference with a 2:30 caliper and 20
>>> degree forwards dropout. Should be perfectly safe.


>>>> Placing the caliper in from of the fork would result in the
>>>> reaction force driving the axle into the dropout and eliminating
>>>> the ejection force altogether.


>>> Of course true, but although not impossible, undesirable.


>> Why is that undesirable? I believe it is entirely aesthetics.


> But you don't *know* that. So far, this is merely conjecture.
> Oddly, others have presented this as fact.


Well, I didn't present it as fact. Now what?

>> I see no technical reason for not doing so.


> Which means what? That there is no technical reason for doing so?


> Another conjecture.


Why are you so argumentative. You seem to take my posting as a
personal injury. Instead of "another conjecture" you might propose an
alternative. As you see, what I wrote, I put forth as opinion, not
fact as you seem to assume.

>> Caliper behind the strut is much like recessed rim brake anchor
>> nuts (even on the back side of the fork crown), it looks more
>> "cool".


> Opinion based on conjecture.


>>> The 2007 range of "Ben C" mountain bikes will use rear calipers
>>> mounted at 2:30 and slightly forward-opening dropouts. And no
>>> tapering on the forks.


>> Instead of calculating, I think more would be gained by observing
>> the reactions on a bicycle by taking out the QR skewer to observe
>> how the axle moves when someone else pushes the bicycle forward and
>> applies the disk brake.


> And exactly what does this prove, aside from the fact that the
> ejection force exists?


> Everyone who is involved in this discussion, and for the last few of
> these discussions, already agrees that the force exists, and its
> approximate magnitude.


> What is to be gained, Jobst? How does it change the discussion at
> all?


> (Anyone want to take bets on how these last two questions will be
> studiously avoided?)


How does your "conjecture" response "change the discussion at all"?

The direction of the ejection force and an optimum angle for dropout
slot has not been determined. My suggestion was aimed at resolving
that issue.

Jobst Brandt
 
Ben C? writes:

>>> As I said in another thread, if the difference in direction is 45
>>> degrees or better, I don't think you're going to get ejection.
>>> Unless my calculations are still wrong (it's been known...) Ben
>>> Micklem has a 54 degree difference with a 2:30 caliper and 20
>>> degree forwards dropout. Should be perfectly safe.


>>>> Placing the caliper in from of the fork would result in the
>>>> reaction force driving the axle into the dropout and eliminating
>>>> the ejection force altogether.


>>> Of course true, but although not impossible, undesirable.


>> Why is that undesirable?


> Because it puts the mounting point in tension as explained by jim beam.


Every bending element is subject to tension. Thee is nothing wrong
with tension or we couldn't build anything right from the Golden Gate
Bridge to the elevator next to the stairs. There is nothing wrong
with tension as we see in spokes that don't fail at mid span where
they are entirely in tension. It is unintended bending that causes
most failures and these fail on their tensile side. Don't give
tension a bad name or we can't play tennis or listen to stringed
instruments.

> Also I am concerned about grit, brake dust etc. coming out of the
> back of the caliper being thrown upwards towards the rider's face.
> With the caliper behind the fork it's directed towards the road
> behind the front wheel.


For a particle to fly into your face, it would need to be at least as
large as a grain of coarse sand that flies of the front tire all the
time when on road edge pavement or dirt roads. This is not a hazard.

Jobst Brandt
 
M

Mike Causer

Guest
On Tue, 13 Feb 2007 14:35:54 -0600, Ben C wrote:

> Also I am concerned about grit, brake dust etc. coming out of the back
> of the caliper being thrown upwards towards the rider's face. With the
> caliper behind the fork it's directed towards the road behind the front
> wheel.


Only if you're riding backwards surely? What little dust comes out is
going to follow the rotation of the disc and come out forwards.


Mike
 
E

Ed Pirrero

Guest
On Feb 13, 12:50 pm, [email protected] wrote:
> Ed Pirrero writes:
> >>> As I said in another thread, if the difference in direction is 45
> >>> degrees or better, I don't think you're going to get ejection.
> >>> Unless my calculations are still wrong (it's been known...) Ben
> >>> Micklem has a 54 degree difference with a 2:30 caliper and 20
> >>> degree forwards dropout. Should be perfectly safe.
> >>>> Placing the caliper in from of the fork would result in the
> >>>> reaction force driving the axle into the dropout and eliminating
> >>>> the ejection force altogether.
> >>> Of course true, but although not impossible, undesirable.
> >> Why is that undesirable? I believe it is entirely aesthetics.

> > But you don't *know* that. So far, this is merely conjecture.
> > Oddly, others have presented this as fact.

>
> Well, I didn't present it as fact. Now what?


If you're offering technical explanations, why bring your opinion of
positioning into it? What do they have to do with anything?

> >> I see no technical reason for not doing so.

> > Which means what? That there is no technical reason for doing so?
> > Another conjecture.

>
> Why are you so argumentative.


Now you're being evasive. Answer the question if you are able, or if
not, say "I don't know." It's really quite simple.

But attacking me is an easy way to avoid the question, right?

[strawman snipped]

> >> Caliper behind the strut is much like recessed rim brake anchor
> >> nuts (even on the back side of the fork crown), it looks more
> >> "cool".

> > Opinion based on conjecture.
> >>> The 2007 range of "Ben C" mountain bikes will use rear calipers
> >>> mounted at 2:30 and slightly forward-opening dropouts. And no
> >>> tapering on the forks.
> >> Instead of calculating, I think more would be gained by observing
> >> the reactions on a bicycle by taking out the QR skewer to observe
> >> how the axle moves when someone else pushes the bicycle forward and
> >> applies the disk brake.

> > And exactly what does this prove, aside from the fact that the
> > ejection force exists?
> > Everyone who is involved in this discussion, and for the last few of
> > these discussions, already agrees that the force exists, and its
> > approximate magnitude.
> > What is to be gained, Jobst? How does it change the discussion at
> > all?
> > (Anyone want to take bets on how these last two questions will be
> > studiously avoided?)

>
> How does your "conjecture" response "change the discussion at all"?


Another evasion. Not like I predicted it or anything...

> The direction of the ejection force and an optimum angle for dropout
> slot has not been determined. My suggestion was aimed at resolving
> that issue.


"That issue" was resolved long ago. Let me repeat: the direction and
magnitude of the braking forces due to disk brakes is already agreed
upon by most everybody, and certainly everyone participating in this
particular thread.

Bringing it up (again) does nothing to resolve any of the remaining
issues. So why bring it up as a solution? It's an answer to a
question, for this thread at least, no one has asked.

E.P.
 

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