Carlton Reid on QR safety

[jim beam]

James Annan wrote:
> Tony Raven wrote:
>
>
>> No one has yet commented on how the QR gets over the lawyers lips
>> without anyone noticing how loose the wheel has become in the forks
>> and the disc rubbing on the pads as the wheel flops from side to side.
>
>
> By Jove, Tony, I think you've got it! In 3 years of this "debate",
> no-one has yet mentioned this critical and obvious point! What were we
> all thinking of?
>
> Sheesh. That's a truly lame attempt at denial, even by your own standards.
>
> James

by jove, james, that's a really weak and pathetic denial of a pertinent
and obvious point! truly lame, even by your own standards.

 

[jim beam]

Michael Press wrote:
> In article <[email protected]>,
> Tony Raven <[email protected]> wrote:
>
>
>>Mike Causer wrote:
>>
>>>On Mon, 06 Feb 2006 04:12:58 +0000, Michael Press wrote:
>>>
>>>
>>>>You owe it to yourself to see for yourself. Jobst Brandt has already
>>>>posted a clear word picture of what is going on. The braking force of the
>>>>disk caliper on the disk generates a force. At the fork tips the braking
>>>>force translates into a force on the axle in the direction out of the fork
>>>>tips,
>>>
>>>This is correct if the caliper is behind the fork and the fork slots
>>>are vertical.
>>>
>>
>>Wrong. Provided the caliper is not mounted in line with the centre line
>>of the fork slot there will be a component of the force along the centre
>>line of the slot. If the caliper is behind the centre line the force
>>component will be out of the slot, in front and its into the slot.
>>
>>No one has yet commented on how the QR gets over the lawyers lips
>>without anyone noticing how loose the wheel has become in the forks and
>>the disc rubbing on the pads as the wheel flops from side to side.
>
>
> Loosening of the quick release nut from brake forces and
> rough terrain vibration. The quick release clamp is not
> designed for these conditions.
>
it's nylocked /and/ serrated, therefore it /is/ designed to resist
vibration.

 

[jim beam]

Tim McNamara wrote:
> Or you could just mount the caliper on the leading side of the fork
> and eliminate the need for the discussion entirely.

no tim, it's bad deployment of both fork material and caliper material.
compressive force [rear mounting] is much safer. which is why it's done.

 

[jim beam]

Mike Causer wrote:
> On Mon, 06 Feb 2006 19:32:45 +0000, jobst.brandt wrote:
>
>
>>>If you open your copy of Bicycling Science 3rd Ed to page 244, you will
>>>see that DGW shows the calculation of the maximum retardation possible
>>>for any bicycle configuration and that it depends on the position of the
>>>Centre of Mass. As the ejection force depends on the actual
>>>retardation, it should be clear that the maximum ejection force
>>>generated is directly dependent on the maximum retardation possible
>>>which is directly dependent on the rider position.
>>
>>That is for retardation of the bicycle and rider. It has nothing to do
>>with what is essential to the force on the dropout.
>
>
> So are you saying that this ejection force exists even if there is no
> braking? Or if it only exists under braking, that it does not vary with
> the amount of braking effort?
>
>
>
> Mike

heretic.

 

[jim beam]

Werehatrack wrote:
> On 06 Feb 2006 15:22:28 +0000 (GMT), David Damerell
> <[email protected]> wrote:
>
>
>>Quoting Andy H <[email protected]>:
>>
>>>If
>>>the design is inherently flawed why have we not all been maimed by our
>>>disk/qr problems?
>>
>>Hyperbole. A design can be unsafe relative to other designs without the
>>failure rate being such as to injure every user.
>
>
> The stated attitude, however, is at the root of the problem. To
> convince someone of a risk, it must be presented to them in terms that
> they can understand, and it must look like something that could
> actually be a problem *for them*. Thus far, I have to say that the
> evidence for wheel ejection as a problem for the average rider is much
> too thin to be compelling. One good, repeatable demo could change
> that. I doubt that anything else will.

indeed.

 

[jim beam]

James Annan wrote:
> Werehatrack wrote:
>
>>On 5 Feb 2006 22:47:12 -0800, "James Annan"
>><[email protected]> wrote:
>>
>>
>>>Werehatrack wrote:
>>>
>>>
>>>>It is very hard to convince people that a problem is both real *and
>>>>serious* when you don't have anything but math and a few isolated
>>>>phenomena to offer as evidence. That the problem is real they may
>>>>accept if they are math-literate, but since nearly everything has risk
>>>>of one sort or another, it's also necessary to convince them that the
>>>>problem is serious enough (not just in terms of potential harm should
>>>>it occur, but more specifically in terms of the potential for the harm
>>>>to come *to them* at all) before they will be persuaded that action is
>>>>warranted or necessary. The paucity of demonstrated failures speaks
>>>>volumes to the masses.
>>>
>>>Do you think that Shimano were wrong to recall their brake cables?
>>>
>>>http://www.bikebiz.com/daily-news/article.php?id=4933
>>>
>>>----
>>>A statement from Shimano said:
>>>
>>>"It is possible that the tensile strength of the joint between the
>>>cable and the cable end (nipple) may not meet Shimano's usual standards
>>>and that therefore the nipple, when under stress during application of
>>>the brake, could pull loose or detach from the cable. This could lead
>>>to brake failure.
>>>
>>>"Shimano is not aware of any case in which the nipple has separated
>>
>>>from one of these cables during use on a bicycle."
>>
>>>----
>>>
>>>Note that not only was there not a single injury as a result of this
>>>fault, there wasn't even a single failure in use. Numerous recalls are
>>>made on a similar basis - this was just the first I googled. I question
>>>whether you are aware of the relevant laws on the matter.
>>
>>This was an example of a readily replicatable and demonstrated
>>shortcoming in a product. Shimano acted correctly even though no
>>in-service failures were on record.
>
>
> Why would they do any testing? There were no reported failures, right?
>
> Just like in the case of disk brakes - except in this case there
> actually are several reported cases, which have all been brushed off by
> the manufacturers - except for the ones who paid off a plaintiff.
>
>
> James
>

so james, are you able to differentiate between someone that doesn't
operate their qr correctly [user error] and design flaw? no? are you
going to keep on ignoring the FACT that correctly fastened qr's retain
wheels with a significant safety margin? [also ignoring the efficacy of
lawyer lips of course.] until you can, you're simply the lunatic the
industry is going to ignore.

 

[[email protected]]

Benjamin Lewis writes:

>>>> I am not questioning the direction of the load, what I _am_
>>>> questioning is its magnitude in relation to the other loads
>>>> present. To find the value of the ejection force and the value
>>>> of the retaining forces we need to know the geometry of the whole
>>>> bike and rider.

>>> I don't see why. All that is required is what I stated, the ratio
>>> of disk diameter to tire OD and the position of the caliper. The
>>> fore that the caliper puts on the fork relative to the wheel is as
>>> I stated, only caliper location is the matter at hand.

>> Except that there is a maximum force that be generated in this way,
>> and to find the maximum we need to consider the factors I've
>> mentioned.

>> Assuming a conventional upright bike, with wheelbase a little over
>> 1 metre, the maximum braking effort is found when the back wheel
>> lifts, at which point the retardation will be about 0.65g.

> You don't think you can momentarily spike the braking force above
> that without doing an endo?

Use your imagination. The rider is descending a bumpy trail, causing
intermittent lift-off. When he lands, the wheel skids and he bounces
again. Anyone who has some trail experience has heard and seen this
effect. It does not involve and end-over.

> (I don't know if you can, or by how much, but the point seems to
> have been neglected).

If you stop averaging for the bicycle, you'll see that fairly high
forces are absorbed. This is just like the people who cannot
visualize that a spoked wheel regularly gets peak loads that are as
much as four time the average load. That's why crummy wheels need
spoke prep.

Jobst Brandt

 

[jim beam]

[email protected] wrote:
> Benjamin Lewis writes:
>
>
>>>>>I am not questioning the direction of the load, what I _am_
>>>>>questioning is its magnitude in relation to the other loads
>>>>>present. To find the value of the ejection force and the value
>>>>>of the retaining forces we need to know the geometry of the whole
>>>>>bike and rider.
>
>
>>>>I don't see why. All that is required is what I stated, the ratio
>>>>of disk diameter to tire OD and the position of the caliper. The
>>>>fore that the caliper puts on the fork relative to the wheel is as
>>>>I stated, only caliper location is the matter at hand.
>
>
>>>Except that there is a maximum force that be generated in this way,
>>>and to find the maximum we need to consider the factors I've
>>>mentioned.
>
>
>>>Assuming a conventional upright bike, with wheelbase a little over
>>>1 metre, the maximum braking effort is found when the back wheel
>>>lifts, at which point the retardation will be about 0.65g.
>
>
>>You don't think you can momentarily spike the braking force above
>>that without doing an endo?
>
>
> Use your imagination. The rider is descending a bumpy trail, causing
> intermittent lift-off. When he lands, the wheel skids and he bounces
> again. Anyone who has some trail experience has heard and seen this
> effect. It does not involve and end-over.

so jobst, on my ride this sunday, i descended three sections of rocky
trail that were so steep, even hard braking at the skid threshold could
not prevent rapid acceleration. these were hard rock bumpy rock, no
loose surface to reduce tire friction. now, given that my qr was
exactly as tight after this ride as it was before, with not even
slippage evident, can you please explain to me how exactly ejection
force is spiking beyond retention force "descending a bumpy trail"? how
about the fact that i've never experienced slippage or ejection in the 3
years i've ridden disk brakes? you can answer from your own extensive
experience actually riding disk braked mountain bikes, right?

>
>
>>(I don't know if you can, or by how much, but the point seems to
>>have been neglected).
>
>
> If you stop averaging for the bicycle, you'll see that fairly high
> forces are absorbed. This is just like the people who cannot
> visualize that a spoked wheel regularly gets peak loads that are as
> much as four time the average load. That's why crummy wheels need
> spoke prep.

red herring.

>
> Jobst Brandt

 

[G.T.]

jim beam wrote:
> [email protected] wrote:
>
>> Benjamin Lewis writes:
>>
>>
>>>>>> I am not questioning the direction of the load, what I _am_
>>>>>> questioning is its magnitude in relation to the other loads
>>>>>> present. To find the value of the ejection force and the value
>>>>>> of the retaining forces we need to know the geometry of the whole
>>>>>> bike and rider.
>>
>>
>>
>>>>> I don't see why. All that is required is what I stated, the ratio
>>>>> of disk diameter to tire OD and the position of the caliper. The
>>>>> fore that the caliper puts on the fork relative to the wheel is as
>>>>> I stated, only caliper location is the matter at hand.
>>
>>
>>
>>>> Except that there is a maximum force that be generated in this way,
>>>> and to find the maximum we need to consider the factors I've
>>>> mentioned.
>>
>>
>>
>>>> Assuming a conventional upright bike, with wheelbase a little over
>>>> 1 metre, the maximum braking effort is found when the back wheel
>>>> lifts, at which point the retardation will be about 0.65g.
>>
>>
>>
>>> You don't think you can momentarily spike the braking force above
>>> that without doing an endo?
>>
>>
>>
>> Use your imagination. The rider is descending a bumpy trail, causing
>> intermittent lift-off. When he lands, the wheel skids and he bounces
>> again. Anyone who has some trail experience has heard and seen this
>> effect. It does not involve and end-over.
>
>
> so jobst, on my ride this sunday, i descended three sections of rocky
> trail that were so steep,

Get back to us when you descend something for more than 30 seconds.

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

 

[James Annan]

jim beam wrote:

> until you can, you're simply the lunatic the
> industry is going to ignore.

It's not me they have to worry about, it's the injured riders seeking
compensation. But if they are happy to pay anyone off who gets as far
as serving a writ, this could go on a long time. Especially since the
journalists have apparently decided that their readers don't need to
hear about it.

James

 

[Luns Tee]

In article <[email protected]>,
jim beam <[email protected]> wrote:
>Tim McNamara wrote:
>> Or you could just mount the caliper on the leading side of the fork
>> and eliminate the need for the discussion entirely.
>
>no tim, it's bad deployment of both fork material and caliper material.
> compressive force [rear mounting] is much safer. which is why it's done.

Two questions.
1) What is the distance between the brake disc and the caliper mount
2) How thick is the caliper mount on an MTB fork?

Then, from the answers, answer these questions:

1) What turning moment does the force of braking generate as
it's transmitted across this distance
2) What forces must be present in the caliper mount to support
this moment

-Luns

 

[Clive George]

"Michael Press" <[email protected]> wrote in message
news:[email protected]...
> In article
> <[email protected]>,
> "Clive George" <[email protected]> wrote:
>
>> "Michael Press" <[email protected]> wrote in message
>> news:[email protected]...
>>
>> >> > Please comment upon the force diagram for front disc brakes.
>> >>
>> >> I am neither a physicist nor engineer; many here are.
>> >>
>> >> I will leave comments to those more qualified.
>> >
>> > You owe it to yourself to see for yourself.
>>
>> Micheal, you seem to be confusing comment with understanding.
>> Understanding
>> the force diagram is easy enough. Being able to comment on it in a useful
>> manner, especially without repeating what has already been said, is
>> entirely
>> different.
>>
>> Or do you feel "me too" is an acceptably useful post?
>
> Some folks are adamant that there is not a problem; but
> never address the force diagram, and its consequences.

You might want to read what Helen wrote a little more carefully then, rather
than just leaping in in the manner in which you did.

> Being able to comment upon it in a useful manner is a
> prerequisite to productively entering this discussion.

Bollocks. Maybe the physics is all you're interested in, but there are other
ramifications - eg user interface, legal, and the one which Helen raised,
which is the perception of the problem.

cheers,
clive

 

[Tony Raven]

[email protected] wrote:
>
> I've seen several beginning bicyclists misuse a quick release and
> showed them the correct method of fastening the wheel. So I think
> that bicyclists should welcome a simplification of the current design.
>

Not just beginners. I put the following page up two years ago
http://www.cycling.raven-family.com/Dropouts/QR.htm

--
Tony

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

 

[Tony Raven]

Michael Press wrote:
> In article <[email protected]>,
> Tony Raven <[email protected]> wrote:
>>
>> No one has yet commented on how the QR gets over the lawyers lips
>> without anyone noticing how loose the wheel has become in the forks and
>> the disc rubbing on the pads as the wheel flops from side to side.
>
> Loosening of the quick release nut from brake forces and
> rough terrain vibration. The quick release clamp is not
> designed for these conditions.
>

Try it. Undo your quick release until it just releases over the lawyers
lips and then do it up just enough to marginally retain the axle. Go
test ride the bike carefully. Then tell me that it is not very obvious
that the QR is undone. I know, I've forgotten to do up the QR on
occasions when setting off and I have never got more than a few yard
before it is very obvious something is wrong.

--
Tony

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

 

[Tony Raven]

jim beam wrote:
>
> it's nylocked /and/ serrated, therefore it /is/ designed to resist
> vibration.

As recommended as two of the three ways to prevent vibration loosening
in the Bolt Science website that JA uses as the basis for his vibration
loosening theory. That bit always seems to be glossed over for some reason.

--
Tony

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

 

[James Annan]

Tony Raven wrote:

> Michael Press wrote:
>
>> In article <[email protected]>,
>> Tony Raven <[email protected]> wrote:
>>
>>>
>>> No one has yet commented on how the QR gets over the lawyers lips
>>> without anyone noticing how loose the wheel has become in the forks
>>> and the disc rubbing on the pads as the wheel flops from side to side.
>>
>>
>> Loosening of the quick release nut from brake forces and rough terrain
>> vibration. The quick release clamp is not designed for these conditions.
>>
>
> Try it. Undo your quick release until it just releases over the lawyers
> lips and then do it up just enough to marginally retain the axle. Go
> test ride the bike carefully. Then tell me that it is not very obvious
> that the QR is undone. I know, I've forgotten to do up the QR on
> occasions when setting off and I have never got more than a few yard
> before it is very obvious something is wrong.

So what? Even you can't deny that this wheel loss actually happens. Some
of the people have noticed their front wheel coming loose. Some of them
lost the wheel before they could stop. So what's your point?

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

 

[David Damerell]

Quoting Tony Raven <[email protected]>:
>Try it. Undo your quick release until it just releases over the lawyers
>lips and then do it up just enough to marginally retain the axle. Go
>test ride the bike carefully. Then tell me that it is not very obvious
>that the QR is undone.

OK, I will; the local chavs periodically undo front QRs, so - back when I
had a front QR hub - I've found myself riding with a loose one once or
twice (lucky me, I don't have a disc brake). No, it's not necessarily
obvious; and that's on smooth flat pavement, not rattling about like crazy
down a hill offroad. The axle is retained in its normal position in the
dropouts by the weight of the rider.
--
David Damerell <[email protected]> Kill the tomato!
Today is First Monday, February.

 

[jim beam]

James Annan wrote:
> Tony Raven wrote:
>
>> Michael Press wrote:
>>
>>> In article <[email protected]>,
>>> Tony Raven <[email protected]> wrote:
>>>
>>>>
>>>> No one has yet commented on how the QR gets over the lawyers lips
>>>> without anyone noticing how loose the wheel has become in the forks
>>>> and the disc rubbing on the pads as the wheel flops from side to side.
>>>
>>>
>>>
>>> Loosening of the quick release nut from brake forces and rough
>>> terrain vibration. The quick release clamp is not designed for these
>>> conditions.
>>>
>>
>> Try it. Undo your quick release until it just releases over the
>> lawyers lips and then do it up just enough to marginally retain the
>> axle. Go test ride the bike carefully. Then tell me that it is not
>> very obvious that the QR is undone. I know, I've forgotten to do up
>> the QR on occasions when setting off and I have never got more than a
>> few yard before it is very obvious something is wrong.
>
>
> So what? Even you can't deny that this wheel loss actually happens.

i'll deny it for you james. wheel loss CANNOT happen on a fork with
lawyer lips. sorry to point out something so fundamentally obvious and
painful for you, but reality has to slap you in the face some day.

> Some
> of the people have noticed their front wheel coming loose. Some of them
> lost the wheel before they could stop. So what's your point?
>
> James

 

[jim beam]

G.T. wrote:
> jim beam wrote:
>
>> [email protected] wrote:
>>
>>> Benjamin Lewis writes:
>>>
>>>
>>>>>>> I am not questioning the direction of the load, what I _am_
>>>>>>> questioning is its magnitude in relation to the other loads
>>>>>>> present. To find the value of the ejection force and the value
>>>>>>> of the retaining forces we need to know the geometry of the whole
>>>>>>> bike and rider.
>>>
>>>
>>>
>>>
>>>>>> I don't see why. All that is required is what I stated, the ratio
>>>>>> of disk diameter to tire OD and the position of the caliper. The
>>>>>> fore that the caliper puts on the fork relative to the wheel is as
>>>>>> I stated, only caliper location is the matter at hand.
>>>
>>>
>>>
>>>
>>>>> Except that there is a maximum force that be generated in this way,
>>>>> and to find the maximum we need to consider the factors I've
>>>>> mentioned.
>>>
>>>
>>>
>>>
>>>>> Assuming a conventional upright bike, with wheelbase a little over
>>>>> 1 metre, the maximum braking effort is found when the back wheel
>>>>> lifts, at which point the retardation will be about 0.65g.
>>>
>>>
>>>
>>>
>>>> You don't think you can momentarily spike the braking force above
>>>> that without doing an endo?
>>>
>>>
>>>
>>>
>>> Use your imagination. The rider is descending a bumpy trail, causing
>>> intermittent lift-off. When he lands, the wheel skids and he bounces
>>> again. Anyone who has some trail experience has heard and seen this
>>> effect. It does not involve and end-over.
>>
>>
>>
>> so jobst, on my ride this sunday, i descended three sections of rocky
>> trail that were so steep,
>
>
> Get back to us when you descend something for more than 30 seconds.
>
> Greg
>
eh? how does that effect grade or braking magnitude???

 

[jim beam]

Luns Tee wrote:
> In article <[email protected]>,
> jim beam <[email protected]> wrote:
>
>>Tim McNamara wrote:
>>
>>>Or you could just mount the caliper on the leading side of the fork
>>>and eliminate the need for the discussion entirely.
>>
>>no tim, it's bad deployment of both fork material and caliper material.
>> compressive force [rear mounting] is much safer. which is why it's done.
>
>
> Two questions.
> 1) What is the distance between the brake disc and the caliper mount
> 2) How thick is the caliper mount on an MTB fork?
>
> Then, from the answers, answer these questions:
>
> 1) What turning moment does the force of braking generate as
> it's transmitted across this distance
> 2) What forces must be present in the caliper mount to support
> this moment
>
> -Luns

aha! logic!!! excellent!

i started going down that road in the carbon seat post thread recently,
but no one seemed interested in talking sense...

in brief,

1. the disk tab is roughly 1/3rd the distance from the axle of the brake
bosses.
2. there is one primary tab, which is thiner than one brake boss.

numbers are back in that thread.