Carlton Reid on QR safety

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

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

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

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/

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...annondale.html

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

Werehatrack wrote:
On 5 Feb 2006 22:47:12 -0800, "James Annan"
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

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.

The statement above by the Trek Man shows that Trek is aware of
a general problem with the usability of the current quick release
system, but the statement seems to me that the analysis was
done with the conclusion in mind.

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.

I ride very rough, rocky terrain, up to 20 percent grade, on my
full-suspension mountain bike with disc brakes. Since I became
aware of James Annan's alarming posts I have checked my QR's
and once found the front much looser than I remembered. So there
might actually be something to the story. Time wil tell.

In the meantime, I continue to ride the bike, which is made by
Trek. In the case of a horrible accident involving the separation of
the
front wheel from the fork I'd be contributing to my demise with
my own negligence, unless of course my lawyer could show that
Trek had not exercised due diligence investigating the issue.

That may be part of the reason Cannondale spent the time and effort to
look
at the problem.

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...

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

wrote:
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.


The statement above by the Trek Man shows that Trek is aware of
a general problem with the usability of the current quick release
system, but the statement seems to me that the analysis was
done with the conclusion in mind.

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.

I ride very rough, rocky terrain, up to 20 percent grade, on my
full-suspension mountain bike with disc brakes. Since I became
aware of James Annan's alarming posts I have checked my QR's
and once found the front much looser than I remembered. So there
might actually be something to the story. Time wil tell.

In the meantime, I continue to ride the bike, which is made by
Trek. In the case of a horrible accident involving the separation of
the
front wheel from the fork I'd be contributing to my demise with
my own negligence, unless of course my lawyer could show that
Trek had not exercised due diligence investigating the issue.

That may be part of the reason Cannondale spent the time and effort to
look
at the problem.

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 thier
owners manuals?

What a novel concept!

Psycho Mike

Mike Causer 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.