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Cannondale's tests of disks and QRs



 
 
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  #11  
Old September 16th 04, 03:45 AM
jim beam
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James Annan wrote:
jim beam wrote:

James Annan wrote:
snip

"The conclusion is that the braking action of disc brakes is not causing
the quick release mechanism to unscrew. This test is unable to cause
loosening. At this time there are no reasons to believe that anything
is missing or over constrained in this test."


james, did you check out the pics i posted of my own disk brakes?



Yes, but if you thought I'd be interested in a single case of "my wheel
didn't slip" then you have missed the point very very badly indeed.


polite as always. james, the point is not my "single case" but the lack
of cases that you present to the contrary. post some pics of forks
evidencing slippage if you please. dismissal of evidence that
contradicts your accusations does not add credibility to your case.

bottom line is this; put yourself in the position of a manufacturer.
are you going to pay attention to a guy on the net who, with respect,
misses a vital part of their analysis, then descends to personal attack
when challenged, or are you going to rely on your distributor network's
return data?

trust me, i have been carefully on the lookout for potential ejection
problems among all the people i've ridden mountain with since you raised
this issue, and you may be interested to learn that i have actually seen
one case of slip! but problem is, there was no ejection and it was
clearly attributable to an open cam skewer, badly crudded up, that the
rider couldn't be bothered to close properly. so, like a broken chain
that's attributable to it not being fitted correctly or an under-clamped
brake cable slipping and causing brake failure, the only disk wheel
slippage i've seen was due to incorrect skewer deployment. and even
then, if i hadn't been specifically looking for the slippage, the rider
would never have known because he hadn't, nor had he /ever/ had, any
problems! certainly not anything as serious as ejection.

now, to address your cannondale point, it is clearly a carefully guarded
response, but i fail to see how you'd expect anything else in the face
of a serious liability threat that's not supported by any statistical
evidence. mtb brakes changed from cantilever to linear p.d.q. once it
was established that incorrect usage combined with fouling could send a
rider over the bar. i don't know the numbers, but i'll wager there were
not many o.t.b's before manufacturers made the switch, however
statistically unlikely. unless disk brake ejection is actually
evidenced, then who is going to fix a problem that doesn't exist?


Now, have you any "reasons to believe that anything is missing or over
constrained in this test"?

Inquiring minds want to know...

James


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  #12  
Old September 16th 04, 08:13 AM
James Annan
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jim beam wrote in message ...

polite as always. james, the point is not my "single case" but the lack
of cases that you present to the contrary. post some pics of forks
evidencing slippage if you please.


http://www.velotech.de/saz_12_-_03_-_05.pdf

which I found by googling a previous post of mine in r.b.t, so don't
pretend you haven't seen it before. Unfortunately, I can't find the
rebuttal that you presumably offered, so I'd be grateful for a
reminder.

now, to address your cannondale point, it is clearly a carefully guarded
response, but i fail to see how you'd expect anything else


Is this really all you can bring yourself to say about it?

Let me remind you of their test:

"A light hand force of 5 lbs was applied to the brake lever every 10
seconds for 3 seconds duration. This caused braking torque to be applied
to the wheel. The drums had 3 equally-spaced cleats (0.5" high the same
as those used on wheel fatigue test T027) to create bumps for the front
wheel to go over."

And then we have:

"Conclusion:

"The conclusion is that the braking action of disc brakes is not causing
the quick release mechanism to unscrew. This test is unable to cause
loosening. At this time there are no reasons to believe that anything is
missing or over constrained in this test."


You describe that as "carefully guarded, but i fail to see how you'd
expect anything else"!

Remember that this is not just something they happened to have done
and offered to throw into the ring, but a piece of work they were
specifically commissioned to do by the CPSC in order to investigate
whether there was a potential danger.

Have you really no "reasons to believe that anything is missing or
over constrained in this test"? You have no opinion beyond "carefully
guarded, but i fail to see how you'd expect anything else"?

I would be equally amused to hear Mark Hickey's assessment of this
test, and Tony Raven's, too.

James
  #13  
Old September 16th 04, 08:54 AM
Paul - xxx
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James Annan vaguely muttered something like ...

"A light hand force of 5 lbs was applied to the brake lever every 10
seconds for 3 seconds duration. This caused braking torque to be applied
to the wheel. The drums had 3 equally-spaced cleats (0.5" high the same
as those used on wheel fatigue test T027) to create bumps for the front
wheel to go over


How was the 5 lbs measured ?

As an ex Torque Control Engineer (Desoutter / Georges Renault) I feel the
tests would be more relevant using a range of braking forces from light to
as much as possible, commensurate with the force a human hand can exert ...
and varying the pads, configuration of forks, bumps etc as well as having a
'control' set. Maybe they are running more tests and you have interim
results ?

Did they have a specification to work to for the tests ?


--
Paul ...

(8(|) Homer Rules !!!

"A tosser is a tosser, no matter what mode of transport they're using."


  #14  
Old September 16th 04, 09:29 AM
Dave Kahn
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"S o r n i" wrote in message ...
Helen Deborah Vecht wrote:


Umm... I used to have a grip of 100lb...
girlie


What are you doing Friday night?


Note the tense. Unfortunately it's relevant in Helen's case.

--
Dave...
  #15  
Old September 16th 04, 09:47 AM
Just zis Guy, you know?
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Helen Deborah Vecht wrote:

Umm... I used to have a grip of 100lb[1]. Of what would 5lb be
representative?


A rider on a disk-brake equipped Cannondale being very, very careful not to
make the QR come undone ;-)

Guy
--
May contain traces of irony. Contents liable to settle after posting.
http://www.chapmancentral.co.uk

88% of helmet statistics are made up, 65% of them at Washington
University


  #16  
Old September 16th 04, 10:05 AM
Simon Brooke
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in message , jim beam
') wrote:

James Annan wrote:
jim beam wrote:

James Annan wrote:
snip

"The conclusion is that the braking action of disc brakes is not
causing the quick release mechanism to unscrew. This test is unable
to cause loosening. At this time there are no reasons to believe
that anything is missing or over constrained in this test."

james, did you check out the pics i posted of my own disk brakes?


Yes, but if you thought I'd be interested in a single case of "my
wheel didn't slip" then you have missed the point very very badly
indeed.


polite as always. james, the point is not my "single case" but the
lack
of cases that you present to the contrary. post some pics of forks
evidencing slippage if you please. dismissal of evidence that
contradicts your accusations does not add credibility to your case.


Darth Ben of Kinetics carried out his own independent tests and observed
slippage under braking, with properly tightened skewers; and published
his results on the net. If this happens in 0.01% of bicycles that's
still an awful lot of very nasty crashes. The fact that it doesn't
happen in 99.9% of bicycles is good news but does not prove there is no
problem.

--
(Simon Brooke) http://www.jasmine.org.uk/~simon/

;; better than your average performing pineapple

  #17  
Old September 16th 04, 10:53 AM
Helen Deborah Vecht
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"Paul - xxx" typed


How was the 5 lbs measured ?


As an ex Torque Control Engineer (Desoutter / Georges Renault) I feel the
tests would be more relevant using a range of braking forces from light to
as much as possible, commensurate with the force a human hand can exert ...


This is, I believe' in the 100-200lb range and consistent with panic braking.

IMHO all bike equipment has to cope well with maxima.

--
Helen D. Vecht:
Edgware.
  #18  
Old September 16th 04, 10:55 AM
Helen Deborah Vecht
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"Just zis Guy, you know?" typed


Helen Deborah Vecht wrote:


Umm... I used to have a grip of 100lb[1]. Of what would 5lb be
representative?


A rider on a disk-brake equipped Cannondale being very, very careful not to
make the QR come undone ;-)

^^^

Wrong smiley, Guy. :-(

--
Helen D. Vecht:
Edgware.
  #19  
Old September 16th 04, 11:19 AM
Paul - xxx
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Helen Deborah Vecht vaguely muttered something like ...
"Paul - xxx" typed


How was the 5 lbs measured ?


As an ex Torque Control Engineer (Desoutter / Georges Renault) I feel the
tests would be more relevant using a range of braking forces from light
to as much as possible, commensurate with the force a human hand can
exert ...


This is, I believe' in the 100-200lb range and consistent with panic
braking.


I'd suggest it may well be more than that .. and there should, if using good
engineering principles, be a large margin for error.

IMHO all bike equipment has to cope well with maxima.


And beyond ...

--
Paul ...

(8(|) Homer Rules !!!

"A tosser is a tosser, no matter what mode of transport they're using."


  #20  
Old September 16th 04, 12:05 PM
Jim Smith
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Helen Deborah Vecht writes:

"Paul - xxx" typed


How was the 5 lbs measured ?


As an ex Torque Control Engineer (Desoutter / Georges Renault) I feel the
tests would be more relevant using a range of braking forces from light to
as much as possible, commensurate with the force a human hand can exert ...


This is, I believe' in the 100-200lb range and consistent with panic braking.


Measuring grip strength is actually a pretty common activity.

http://snipurl.com/93vp

100 - 200 lbs is consistent with athletic men.
 




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