A Cycling & bikes forum. CycleBanter.com

Go Back   Home » CycleBanter.com forum » rec.bicycles » Techniques
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

Carlton Reid on QR safety



 
 
Thread Tools Display Modes
  #671  
Old February 17th 06, 03:26 PM posted to uk.rec.cycling,rec.bicycles.tech,alt.mountain-bike
external usenet poster
 
Posts: n/a
Default Carlton Reid on QR safety

Luke wrote:


The primary device, unlike the secondary, does not simply retain, it
secures. The difference between these two functions is the difference
between having and losing control of the bike.


I thought everyone here was was arguing against me that a loose QR was
not detectable by the rider until it got to the point the wheel was
ejected. Now you are trying to argue that a loose QR will be more than
detectable - it will loose you control of the bike. Which is it?


That's an amusing contradiction. The secondary retention device,
'preferably' takes over in such a manner as to clearly inform that the
QRs have failed to secure the wheel (what if the Lawyers' Lips cite
client privilege, keeping mum?), which in of itself constitutes an
unsafe condition, but is not considered so until the secondary
retention system fails also.


Its a standard analysis for single fault tolerant safety critical
equipment: a single fault shall not create an unsafe condition nor go
undetected. Otherwise an undetected failure can continue obscured by
the secondary system until the secondary system fails and makes the
original fault visible in a potentially unsafe way. Having a loose but
retained front wheel is not of itself unsafe. I've ridden that way with
disk brakes through my mistake a number of times although unlike many
here I pretty quickly knew something was wrong by the feel of the
steering and the knocking sound from the front wheel as the QR hit the
lawyers lips.


--
Tony

"The best way I know of to win an argument is to start by being in the
right."
- Lord Hailsham
Ads
  #672  
Old February 17th 06, 05:46 PM posted to uk.rec.cycling,rec.bicycles.tech,alt.mountain-bike
external usenet poster
 
Posts: n/a
Default Carlton Reid on QR safety

Tony Raven writes:

Tim McNamara wrote:
I considered the lawyer lips in their correct role: they are there
in case of *failure* of the QR to retain the axle in the dropout
and are not part of the retention system proper. If they lawyer
lips are what's holding your axle in the dropouts, that is because
of a *failure* of the QR to retain the axle. Relying on the lawyer
lips to hold in the wheel is simply horrendous incompetent design.


Its called fail safe design. If the primary retention device fails,
the secondary takes over preferably in a way that ensures it is
clear to the user that there has been a primary system failure.

For an unsafe condition to occur both the primary and secondary
systems have to have failed. All the calculations you are doing
only show how a primary failure might occur by the QR slipping.
What they have failed to address other than by speculation is how
the secondary system also fails which is a necessary condition for
the wheel to be ejected.


That's where we disagree, Tony. You seem to think that it is
acceptable for the QR to fail under the reaction force resulting from
disk brakes, because the lawyer lips are there to save you. I don't
think that it is acceptable for the design to be such that it makes it
possible that the QR will fail. No other brake design does this, just
disk brakes with the caliper mounted on the trailing side.

The laywer lips exist to prevent an *abnormal* occurrence- losing the
front wheel because the rider failed to properly close the QR. And
even then, the lawyer lips may very well never come into play during
riding, unless the rider tries to lift the front wheel. With disk
brakes, the ejection force is a normal occurrence and happens every
time the rider brakes. The primary retention system- the QR- must be
able to retain the wheel 100% of the time, no exceptions.

Given how often lawyer lips have come up in this and the previous
threads on the topic, there is no chance that anyone has forgotten
the lawyer lips. The intent of laywer lips is not to provide axle
retention for disk brakes, it is to prevent people who don't know
how to use QRs from losing their front wheels.


Correct but by default it should prevent a QR from exiting the fork
for forces many times the highest calculated here for an ejection
force. Unless you can demonstrate rather than speculate the
mechanism by which this also fails you have failed to show the two
necessary conditions for wheel ejection to occur - a slipping QR and
a verified mechanism for the QR to pass the lawyers lips.


We are apparently never going to agree on this. By default the lawyer
lips should not be required to keep the brakes from pushing the front
wheel out of the dropout. Period. There should be no way whatsoever
for the brake to create and ejection force on the axle. Period. As a
result I will never own a bike with disk brakes of this design.
  #673  
Old February 17th 06, 06:14 PM posted to uk.rec.cycling,rec.bicycles.tech,alt.mountain-bike
external usenet poster
 
Posts: n/a
Default Carlton Reid on QR safety

On Fri, 17 Feb 2006 09:19:21 +0000, Tony Raven wrote:

Given how often lawyer lips have come up in this and the previous
threads on the topic, there is no chance that anyone has forgotten the
lawyer lips. The intent of laywer lips is not to provide axle retention
for disk brakes, it is to prevent people who don't know how to use QRs
from losing their front wheels.

Correct but by default it should prevent a QR from exiting the fork for
forces many times the highest calculated here for an ejection force.


Sadly not. British Standard 6102-1:1999 (which is based on ISO
4210:1996 but has advanced in some respects) requires wheel retention by
the QR mechanism of 2300N (517lbf) for 30 seconds, but with open QR the
lips have to withstand a load of just 100N (22.5lbf). [Section 9.4.4]



Mike

  #674  
Old February 17th 06, 06:23 PM posted to uk.rec.cycling,rec.bicycles.tech,alt.mountain-bike
external usenet poster
 
Posts: n/a
Default Carlton Reid on QR safety


Tony Raven wrote:

I thought everyone here was was arguing against me that a loose QR was
not detectable by the rider until it got to the point the wheel was
ejected. Now you are trying to argue that a loose QR will be more than
detectable - it will loose you control of the bike. Which is it?


Be careful what you ascribe to "everyone." There can be differences of
opinion on such matters, even among people who agree that brakes should
not be trying to eject the front wheel from the dropouts.

FWIW, I don't know of anyone interested in bicycling safety issues who
feels it's fine to ride a bike with a loose QR, whose axle is held in
place only by the lawyer lips. If you feel such riding is fine, you'll
have very few members on your team.

Having a loose but
retained front wheel is not of itself unsafe.


Again, I think that's a VERY uncommon attitude. Can you find any
safety literature that agrees with you?

I've ridden that way with
disk brakes through my mistake a number of times although unlike many
here I pretty quickly knew something was wrong by the feel of the
steering and the knocking sound from the front wheel as the QR hit the
lawyers lips.


Under what conditions were you riding? It may be one thing to ride on
ordinary pavement under ordinary speeds with a loose QR (although,
again, I doubt you'll find anyone else who says so); but I suspect it's
quite another thing to be barrelling hell-bent-for-leather down a steep
rocky hillside with a loose QR. I don't do such riding, but I suspect
the sounds and sensations would be severely muddied by the general
chaos involved.

And of course, if you _were_ pounding your way down a super-steep,
rocky hill and felt something funny in your front wheel, what would you
do about it? Slam on the front brake even harder so you could stop to
inspect? Good luck!

- Frank Krygowski

  #675  
Old February 17th 06, 08:00 PM posted to uk.rec.cycling,rec.bicycles.tech,alt.mountain-bike
external usenet poster
 
Posts: n/a
Default Carlton Reid on QR safety

Mike Causer writes:

On Fri, 17 Feb 2006 09:19:21 +0000, Tony Raven wrote:

Given how often lawyer lips have come up in this and the previous
threads on the topic, there is no chance that anyone has forgotten
the lawyer lips. The intent of laywer lips is not to provide axle
retention for disk brakes, it is to prevent people who don't know
how to use QRs from losing their front wheels.

Correct but by default it should prevent a QR from exiting the fork
for forces many times the highest calculated here for an ejection
force.


Sadly not. British Standard 6102-1:1999 (which is based on ISO
4210:1996 but has advanced in some respects) requires wheel
retention by the QR mechanism of 2300N (517lbf) for 30 seconds, but
with open QR the lips have to withstand a load of just 100N
(22.5lbf). [Section 9.4.4]


Wow. Of course, those are the legal standards and not actual
measurements. Laywer lips do vary in design from just a couple of
small bumps at the tips of the dropouts to flanges that are almost
half the height of the QR nuts.

But do the math. Since the ejection force is applied to only one
dropout, the British Standard requirements are effectively that the QR
has to withstand a pullout force of 108.5 lbf and the lawyer lips only
11.25 lbf! I can't help but think that decent quality skewers and
forks would exceed this handily, hopefully anyway since even moderate
braking with a current design disk brake would create a force that
would exceed those numbers.
  #676  
Old February 17th 06, 11:38 PM posted to uk.rec.cycling,rec.bicycles.tech,alt.mountain-bike
external usenet poster
 
Posts: n/a
Default Carlton Reid on QR safety

In article , Tony Raven
wrote:

Luke wrote:


The primary device, unlike the secondary, does not simply retain, it
secures. The difference between these two functions is the difference
between having and losing control of the bike.


I thought everyone here was was arguing against me that a loose QR was
not detectable by the rider until it got to the point the wheel was
ejected. Now you are trying to argue that a loose QR will be more than
detectable - it will loose you control of the bike. Which is it?


That's an amusing contradiction. The secondary retention device,
'preferably' takes over in such a manner as to clearly inform that the
QRs have failed to secure the wheel (what if the Lawyers' Lips cite
client privilege, keeping mum?), which in of itself constitutes an
unsafe condition, but is not considered so until the secondary
retention system fails also.


Its a standard analysis for single fault tolerant safety critical
equipment: a single fault shall not create an unsafe condition nor go
undetected. Otherwise an undetected failure can continue obscured by
the secondary system until the secondary system fails and makes the
original fault visible in a potentially unsafe way. Having a loose but
retained front wheel is not of itself unsafe. I've ridden that way with
disk brakes through my mistake a number of times although unlike many
here I pretty quickly knew something was wrong by the feel of the
steering and the knocking sound from the front wheel as the QR hit the
lawyers lips.


Succinctly, here's my argument: What you consider 'wrong' constitutes
an unsafe condition to me; and what precipitates this condition (QR
failing) is characterized as failure. I disagree with your notion that
'a loose but retained front wheel is not of itself unsafe'.

That's all folks.
Luke






  #677  
Old March 1st 06, 01:38 AM posted to uk.rec.cycling,rec.bicycles.tech,alt.mountain-bike
external usenet poster
 
Posts: n/a
Default Carlton Reid on QR safety

I believe his point was that a reader may indeed be interested, but having
no added information, would not post uselessly.

I also find it interesting and would like the option to read or plonk as it
suits me. The idea of posting to merely say "I find this interesting" is
kinda lame.

Oh crap, I just did that.

"Andy H" wrote in message
...

Then do just that, you have no potential problems do you? Do you have the
statistics to hand?

Andy H




 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Carlton Reid on QR safety James Annan Mountain Biking 674 March 1st 06 01:38 AM
Safety Case / Audit Al C-F UK 9 January 13th 05 09:30 PM
Helmet Law: Upgrade to Omnibus Safety Legislation Concerned Citizens Social Issues 0 November 27th 04 01:12 AM
Reports from Sweden Garry Jones General 17 October 14th 03 05:23 PM
Reports from Sweden Garry Jones Social Issues 14 October 14th 03 05:23 PM


All times are GMT +1. The time now is 03:14 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 CycleBanter.com.
The comments are property of their posters.