James Annan <
[email protected]> wrote in message news:<
[email protected]>...
> SuperSlinky wrote:
>
> > Actually, I would venture to guess that most people are put off by your snide, arrogant
> > attitude.
>
> I guess there may be some truth in that.
Then one must agree that "toning it down" may be in order.
> All I have to offer in my defence is that it gets a bit tedious replying to the same old
> objections time after time after time. It's been 2 months already!
The real objections have never been adequately addressed. It's a circular discussion, because the
same evidence is being offered up to explain away the objections - no new info has been forthcoming.
> You may agree that I have 'made my point', but nevertheless there are some who continue to
> disagree...
The disagreement comes because you state your case with certainty, using inductive reasoning as the
basis for your logical conclusion. So, let us recap:
You state that the brake can cause wheel ejection. I agree - the force diagram is clear enough to
support that contention.
You state that the QR binding tension might not be enough to counteract the forces involved in disk
brake actuation, which can move the QR in the drop-out. I agree that the possibility exists. Your
math shows how it might be possible.
Stop. So far, we have some hypotheses, well-supported by math and physics. Right up to this point, I
feel as though you have done a good job in calling into question the set-up as currently used. Now,
we get to the tough part:
The unscrewing mechanism. In other applications of repeated assymetric forces on a screw-type
fastener, loosening has been observed. OK, so far. Now, it seems as though the test rig for the
experiment to verify your hypothesis should be simple at this point. Not cheap, but simple. If it is
indeed as much of a certainty as you seem to think it is, then it should be easily verified.
This set of experiments would remove any question of misapplication (using a cross-country set-up on
a fast downhill, for instance) or other user error (QR done up incorrectly.) It could be tested on a
variety of tire/wheel/brake/fork combos, just to find correlation with other physical factors - that
is, is a cheap, flexy suspension fork more likely to eject, as opposed to a well-built rigid fork?
As an experimental scientist, I understand the challenges of a properly set-up experiment. The
evidence you have collected has absolutely no controls at all. I do not even know if wheel ejection
happens more often with rim or disk brakes! (As a percentage of total in use.) What is the
frequency, and what is the real risk, here?
You will note that I do not dismiss, nor do I minimize any part of your idea. I am calling for MORE
DATA. Data with controls. Data compiled by those who have the understanding of the significance of
the experiments, and can control them down to the smallest, least significant detail. Operating
temperature? Etc. etc.
This has been the undercurrent to most of the objections. There are some cranks who might dismiss
you idea out-of-hand, but those folks seem to be few and far between.
I will tell you this: I have a disk-brake MTB. A coil-in-oil single-crown fork, running mechanical
disk brake on a Shimano LX hub and skewer. The lever is on the side opposite the caliper, and when
closed, is pointing toward the rear, approximately perpendicular to the ground. When I first heard
of the unscrewing mechanism, I took a scribe and made a small scratch in the paint on the QR and on
the drop-out, such that the marks line up. Both sides. I do not remove my wheel between ridings, and
my riding would be considered "cross-country." My downhill sections are bumpy and rocky, with plenty
of non-vertical loads on the front wheel (turning, not hitting bumps straight on, roots that are not
perpendicular to the direction of travel, etc.) I have not yet removed the wheel, and I look at the
register marks every time I stop for any reason.
I have ridden approximately 200 trail miles in that time. Exactly half has been fast descent. How
much do you think the skewer has moved in the last month? If your answer was "zero," then you are
correct. Why should I think, from the data collected, that I should see movement next month? And
yes, I saw your post where you suggest it could happen "all at once." Frankly, I do not see how we
get from a regime of "not moving at all over the course of 200 miles" to "all at once in 300 feet"
over the same type of terrain. And remember, this experiment that I am performing is actually more
controlled than any of the evidence you present in your website, where absolutely NOTHING is known
about the prior condition of the QR before ejection, or the notice that it was loose.
I would ask that you not just "snip and dismiss" as you have done with other posters. If you
feel I have unfairly summarized or characterized, please indicate that. I will re-iterate - I am
not attacking your hypothesis. I *am* questioning it's significance, frequency and lack of
controlled data.
Spider
