Carlton Reid on QR safety

[David Martin]

Mike Causer wrote:
> On Mon, 06 Feb 2006 05:53:44 -0800, David Martin wrote:
>
> > Except that it is perfectly possible to set up a *stationary* bicycle such
> > that increases in rider weight will increase the ejection force.
>
> Sure, make the dropout point anywhere _above_ the horizontal.
>
>
> > As soon as the contact patch moves behind the
> > brake, the riders weight adds to the ejection force.
>
> As the contact patch moves either forward or backward from directly under
> the spindle the anti-ejection force due to weight of rider + bike will
> diminish until it becomes zero when the contact patch is horizontal with
> the spindle.

It is zero for a *stationary* bike when the contact point is under the
brake. As the patch moves behind the brake then the force becomes
negative (ie there is a pivot around the brake.)

Draw a line normal to the forces and plot on that line the force
applied to each point. That from the contact point is upward. That from
the brake is downward. The turning moment observed will show you that a
riders weight can provide an ejection force.


> As this force diminishes so does the braking power
> available, until it also becomes zero when contact patch is horizontal.

Indeed, but if the brake is binding than the available force is neither
here nor there as long as the rider is still staying behind the CoG.

...d

 

[Jay Beattie]

"James Annan" <[email protected]> wrote in message
news:[email protected]...
>
> Jay Beattie wrote:
> > James Annan wrote:
> > > Carlton Reid has a puff piece about a new "Secure QR
system" on bikebiz:
> > > <http://www.bikebiz.co.uk/daily-news/article.php?id=6427>
> > >
> > > While promoting this new mechanism as "safer" than the
existing system,
> > > he also insists that "industry experts say QRs are safe,
when used
> > > correctly".
> > >
> > > This assertion is backed up with a quote from "industry
expert" Bob
> > > Burns (actually Trek's *lawyer*), which is nothing more
than a
> > > boilerplate denial dating to a few years ago when the
QR/disk issue
> > > first surfaced.
> > >
> > > Strangely, alongside this there is no space in his article
for these
> > > quotes from people who actually have some relevant
engineering and
> > > technical experience:
> >
> > Gee, James, some pretty slick editing on your part,
>
> _MY_ part? Did you not realise that the bikebiz article was
written by
> Carlton Reid, not me?
>
>
> This is a _direct_ cut and paste, completely unedited, from the
middle
> of Carlton's article:
>
> ---
> [...] industry experts say QRs are safe, when used correctly.
>
> In 2003, Bob Burns, Trek's US-based General Counsel, told
BikeBiz.com:

The slick editing I am talking about is your post putting in the
bit about Bob Burns being Trek's *lawyer* and then leaving out
the part about how he has responded to your requests to look into
the problem (quote from Singletrack):

Trek's legal eagle in the USA has told BikeBiz.co.uk he will
"definitely talk to the relevant vendors and take a look at this
issue." What's needed are lab tests but even the proponent of the
wheel pop-out theory doesn't believe the supposed problem can
always be replicated away from the dirt. So, is it just a problem
with Ti skewers and badly-angled drop-outs, a problem easily
solved, or should bike trade execs be banging tech-heads together
to find out if the problem is more widespread?


Bob Burns, Trek's US-based General Counsel, has read the BikeBiz
story from earlier this week and has agreed to investigate
Annan's theory further. Trek is the first major company to agree
to such an undertaking.

Burns reports that the Trek warranty department has had no
reports of the kind of equipment failure described by Annan, the
Scottish climate research scientist, based in Japan.

However, Annan says the problem he describes is usually
mis-diagnosed as 'pilot error', in other words riders not
fastening their QRs correctly. Because of the mis-diagnosis risk,
Burns agreed to probe.

"Trek has not seen this, but [we] will be making inquiries of the
relevant component manufacturers," Burns told BikeBiz.co.uk.

"Virtually all 'defective quick release' claims that I have seen
relate to an improperly used quick release. Either the consumer
has ridden with the QR open; ridden with the QR losed like a wing
nut (rather than closing it over the cam); or ridden with
insufficient ightness to the adjusting nut to engage the cam. You
can generally determine this by examining the dropout surfaces,
which will show the marks left behind as a consequence of he
loose clamp force.

"We take great pains in our owner's manual to explain how to use
a QR, as do most good cycling books."

Annan says this is all well and good for rim-brake set-ups but QR
skewers may not be strong enough for disc-brake equipped bikes
pushed hard and fast by enthusiast riders.

(end quote)

The tone of your post is that there is some, sinister conspiracy.
You should give the complete story and disclose that Trek
actually listened to you. -- Jay Beattie.

 

[Werehatrack]

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.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

 

[[email protected]]

Mike Causer 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. The
> friction coefficient tyre-ground needs to be 0.65 or better. Higher
> friction won't gain any more retardation. At this point the whole
> of the weight of bike and rider is carried by the front axle,

Forget about the back wheel. I said that when the front wheel skids
on good traction (which my be rear wheel lift-off) the forces are
simply front wheel related and rider position etc. have no bearing.

Jobst Brandt

 

[Alex Rodriguez]

In article <[email protected]>,
[email protected] says...

>Holes in the current disks reduce surface area and do nothing positive
>for cooling. As I mentioned earlier, the holes seem to be a holdover
>from auto drum brake mystique.

I thought the holes were there to attract all the weight weenies. At
interbike there was a company selling custom brake rotors with all sorts
of cut outs.
-------------
Alex

 

[Mike Causer]

On Mon, 06 Feb 2006 14:00:36 +0000, Tony Raven 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.

OK, my comment is a special case of your general case. However as the
majority of drop-outs are pretty close to vertical I hope it's a
simplification we can live with.



> 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.

I thought somebody did, but maybe that was in another of the interminable
threads about this. If I ever got a bike with lawyer lips I'd grind the
damn things off anyway.


Mike

 

[Mike Causer]

On Mon, 06 Feb 2006 17:26:40 +0000, jobst.brandt wrote:

> Forget about the back wheel. I said that when the front wheel skids on
> good traction (which my be rear wheel lift-off) the forces are simply
> front wheel related and rider position etc. have no bearing.

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.

(If you only have the 2nd Edition it's page 197.)


Mike

 

[[email protected]]

Mike Causer writes:

>> Forget about the back wheel. I said that when the front wheel
>> skids on good traction (which my be rear wheel lift-off) the forces
>> are simply front wheel related and rider position etc. have no
>> bearing.

> 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.

Jobst Brandt

 

[Mike Causer]

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

 

[James Annan]

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

 

[James Annan]

Jay Beattie wrote:

> The tone of your post is that there is some, sinister conspiracy.
> You should give the complete story and disclose that Trek
> actually listened to you. -- Jay Beattie.

I don't believe that Trek ever did any testing - they certainly never
published any results.

I do know that Cannondale did some utterly hopeless, most likely
deliberately fraudulent "tests" and would not reveal the details except
through a Freedom of Information request:

http://www.ne.jp/asahi/julesandjames/home/disk_and_quick_release/cannondale.html

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

 

[James Annan]

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

 

[[email protected]]

Mike Causer writes:

>>> 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?

I think the situation has been stated in plain English. If the wheel
stops, regardless of how heavy the rider and bicycle is, the force is
related as stated. It is dependent only on the load on the axle. You
don't need to know anything about the handlebar height, the seat
position or the weight of the rider. That is all contained in the
axle load and that the wheel is stopped from rotating by the brake.
That could be a skid or the beginning of an end-over.

The separation force is the wheel to disk diameter ratio times the
axle load in a direction tangent to the disk at the caliper.

Axle load is a downward force while the caliper force acts upward if
it is behind the axle. However, its force acts only on one end of the
axle in a direction tangent to the disk at the caliper. In addition a
horizontal skid force acts horizontally to the rear and is equal to
the axle load for events of interest. None of these parameters are
modified by other frame considerations.

Jobst Brandt

 

[Tim McNamara]

Mike Causer <[email protected]> writes:

> On Mon, 06 Feb 2006 04:21:25 +0000, jobst.brandt wrote:
>
>> Yes but that was not an issue. Porsche, in an effort to circumvent
>> patents by Girling and Dunlop, designed a peripherally supported
>> disk with an inside grasping caliper. This was soon dumped and
>> work continued with ATE-Dunlop.
>
> IIRC some aircraft brakes use this layout. Possibly because they
> can get the maximum disk diameter for overall package size. You and
> I were in competition then, because I used to design brakes at
> Girling in the early 1970s.

My Volvo splits the difference, with Girling at one end and ATE at the
other. Never have been sure why.

 

[Tim McNamara]

Or you could just mount the caliper on the leading side of the fork
and eliminate the need for the discussion entirely.

 

[Michael Press]

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

--
Michael Press

 

[Michael Press]

In article
<[email protected]
lid>,
Mike Causer <[email protected]> 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.
>
>
> > and this force is opposed only by the clamping of a quick release
> > on the fork tips.
>
> Incorrect. There is the weight of the bike and rider as well.

The weight of the bike is there. True. Braking force plus
vibrations of rough trails where the amount of rider
weight taken up at the axle-fork tip interface varies
wildly means that the quick-release clamp frets and the QR
nut loosens through fretting. Many riders have reported
consistent loosening or QR nuts. The nut loosens, and soon
there is not even that holding the wheel in the fork tips.

--
Michael Press

 

[Michael Press]

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.

--
Michael Press

 

[[email protected]]

Michael Halliwell writes:

>> Anyways, I think that checking the front quick release before each
>> ride might be a good idea. In fact, I think I'll go check it right
>> now...

> You mean, like most manufacturers recommend before each ride in
> their owners manuals?

> What a novel concept!

That is "novel" if you mean that literally, as in "new". In the many
years I have ridden bikes with QR hubs, I have not done that and also
never found a loose QR when taking a wheel out for, for instance
repairing a flat on the road. Maybe the QR's of today are no good and
open themselves, as John Howard claimed in his now famous testimony
that brought us lawyer lips.

This is all so reminiscent of AUDI unwanted acceleration, that was an
old story long before because AARP folks driving Cadillacs had a
history of stepping on the gas when they meant the brake... so today
we must push the brake pedal before engaging the automatic
transmission. Not a bad idea, but useless for drivers with good
habits.

Jobst Brandt

 

[Benjamin Lewis]

Mike Causer wrote:

> On Mon, 06 Feb 2006 04:05:23 +0000, jobst.brandt wrote:
>
>>> 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?

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

--
Benjamin Lewis

Now is the time for all good men to come to.
-- Walt Kelly