Cannondale's tests of disks and QRs

SuperSlinky wrote:
Peter Clinch said...

Or you could just bluster about saying it hardly ever happens, so it's
not a problem. Like Chernobyl, for example...

Bull****.

snip

there is the fact that almost none of us ride off-road tandems.

Oh look, you're saying it hardly ever happens, so it's not a problem.
Again.

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net http://www.dundee.ac.uk/~pjclinch/

James Annan vaguely muttered something like ...

"There is an air cylinder pushing forward and downward on the handlebar
stem area with 275lbs. 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."

The test seems fair enough, other than the "light hand force" used. I would
have thought varying and certainly much larger braking forces should have
been used for a 'complete' test, and probably larger cleats too.

That's not to say I agree or disagree with anything you or Cannondale have
said, mind, but a test like Cannondales, done with 'real-life' values, would
have helped either way ..

--
Paul ...

(8(|) Homer Rules !!!

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

Tony Raven wrote:

Haven't had the time to check whether you've already done it but would
be useful to have the whole report posted on your website so we can read
it all.

No, and I have not the time at the moment, but will certainly be
publishing parts of it in due course. Of course there is an easy option
for anyone who actually does want to read it all, without preferring to
hide behind the convenient excuse of being able to accuse me of
censoring aspects of it.

Is there any reference to how they come to these figures?

They say they read my web pages, and then did "an independent analysis
of the forces acting on the front hub". The results of this analysis,
however, were not provided to the CPSC. I hope it is reasonable to
expect that if they had found major discrepancies with my work they
would have contacted me to clear them up. And they obviously had "no
reasons to believe that anything is missing or over constrained in this
test".

I
would think that Cannondale have the benefit of having instrumented
their bikes in development and testing including their sponsored team
bikes and would have access to real life figures up to and including
international standard competition to guide their test set up.

I agree, that would seem to be a reasonable supposition. In fact they do
describe measurements from an instrumented bike which contributed to the
design of a separate test of wheel retention under extreme braking loads
(without the vibrational/unscrewing aspect - just "what happens if we
brake really really hard, once"). This test is separate from the
intermittent braking test, and substantially less interesting.


James
--
If I have seen further than others, it is
by treading on the toes of giants.
http://www.ne.jp/asahi/julesandjames/home/

James Annan wrote:


I agree, that would seem to be a reasonable supposition. In fact they do
describe measurements from an instrumented bike which contributed to the
design of a separate test of wheel retention under extreme braking loads
(without the vibrational/unscrewing aspect - just "what happens if we
brake really really hard, once"). This test is separate from the
intermittent braking test, and substantially less interesting.


What were the equivalent parameters in that test e.g. brake pressure,
headset load. It would give a reference point on what constitutes
"braking really hard" to compare with the repetitive braking test.

Tony

James Annan wrote:

Of course there is an easy option
for anyone who actually does want to read it all, without preferring to
hide behind the convenient excuse of being able to accuse me of
censoring aspects of it.


As you well know, reading the conclusions of the Crook & Feikh helmet
study is insuffient information to understand what they actually did.
Its only by reading the full report that you can get the full picture
and pick up their serious mathematical error that undermines the whole
conclusion. I am not accusing you of censoring it, its just that there
is a lot more information in there that could be useful to the debate.
Yes we could all go and get hold of it as you did but it seems somewhat
churlish to force us to do that seeing as you have a copy and a strong
interest in finding the truth.

Tony

Tony Raven wrote:


What were the equivalent parameters in that test e.g. brake pressure,
headset load.

The brake lever was locked on hard (with a zip-tie) and torque applied
directly to the rim. 200 pounds weight was applied vertically down at
the wheel (and 220 on the seatpost).

With this set-up, it took 258 pounds (at MTB rim radius) to pull a wheel
out even without a QR, which they take as evidence that the testing
procedure is sound. With an opened (but adjusted) QR, it broke the rear
of the LH dropout at 338 pounds, and with a very tightly clamped QR, the
brake could not hold above 355 pounds and no failure occurred. I suppose
the 2nd test of the 3 is marginally interesting.

It seems very obvious to me that this test is a fairly pointless one,
especially since a 258 pound force is required to remove a wheel even
when there is no QR at all. I think in real life, a much smaller braking
effort would generally suffice in that situation (due to
vibration/motion/not such a vast weight bearing down on the bicycle!).

It would give a reference point on what constitutes
"braking really hard" to compare with the repetitive braking test.

So, what do you think now?

James
--
If I have seen further than others, it is
by treading on the toes of giants.
http://www.ne.jp/asahi/julesandjames/home/

"Just zis Guy, you know?" wrote in message ...
James Annan wrote:

"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."

See Yellow Pages under "whitewash suppliers"

I did, and found a firm called Brian Hutton & Co. ;-)

David E. Belcher

James Annan wrote:

So, what do you think now?


Post the rest of the report and I'll give you my view of it. I don't
intend to play twenty questions where you release bits and then we have
to ask questions to discover other relevant facts or get refuted by bits
you haven't yet disclosed

Tony

"Paul - xxx" writes:

James Annan vaguely muttered something like ...

"There is an air cylinder pushing forward and downward on the
handlebar stem area with 275lbs. 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."

The test seems fair enough, other than the "light hand force" used.
I would have thought varying and certainly much larger braking
forces should have been used for a 'complete' test, and probably
larger cleats too.

How many 275 lb mountain bikers do you know?

Tim McNamara typed

How many 275 lb mountain bikers do you know?

I know one, and several men who weigh that much, who cycle occasionally.

--
Helen D. Vecht:
Edgware.