Cannondale's tests of disks and QRs

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

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."

"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...

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

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

"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.

"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.

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."

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.

Helen Deborah Vecht said...

James Annan typed

"A light hand force of 5 lbs was

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

[1] measured by hand surgeon doing research.

--
girlie

A bike rider using the brake but not wanting to lock the wheel or go
OTB? What do you think would happen if you used that 100lb grip on the
brakes going 15.5 mph? Oy, this topic is getting very tired, and all the
dweebs trying to concoct a grand conspiracy theory about it is just
pathetic. In fact, I would suspect that the typical grip on the brake
lever at 15.5 mph would be much less than 5 lb.