Carlton Reid on QR safety



jobst brandt wrote:

> Johnny Walker wrote:
>
>> oh, and since you obviously missed it countless times before, the
>> reason for /not/ front mounting a caliper is FATIGUE. cast alloys
>> such as those in forks and calipers ARE NOT GOOD IN TENSILE FATIGUE.
>> that's a pretty fundamental omission from someone that seems to feel
>> qualified to lecture on what comprises good engineering design.

>
> Oh hogwash! Nearly all current disk brake calipers have at least one
> of the two retaining bolts exerting tension on its attachment eye.
> Besides, fork stanchions, to which these are attached, are loaded in
> bending which naturally causes tension and compression about a neutral
> axis. Stop generating this stream of specious argumentation and offer
> something constructive.
>
> Just in case you don't have the URL for Webster's Dictionary at hand:
>
> Specious: 3 : having a false look of truth or genuineness


I disagree that "jim beam's" arguments have that quality, at least for
mildly educated readers.

--
Benjamin Lewis

Now is the time for all good men to come to.
-- Walt Kelly
 
Boyle M. Owl writes:

>> A rolled thread would not permit the parts to slide onto the shaft
>> unless the threads were a substantial size smaller which would
>> offer less strength than a cut thread of the shaft diameter.


> Hey Jobst, go crack open a Machinery's Handbook (whatever edition
> you may have - I've got 23 and 27) and look at rolled thread
> strength as opposed to cut thread strentgh, and get back to me, OK?
> You may have a PhD in physics, but neither a PhD nor educated
> opinion is any substitute for empirical results.


I don't see where that proves the thread on these bolts is rolled.
The ones I have for inspection do not have the classic bolt end, have
a thread whose major diameter is exactly the same as the bearing
surface of the shaft and show no classic rolled thread form but rather
has a single point thread runout at the transition to the shaft. That
doesn't prove that they aren't rolled but it definitely suggests that.

In response to your question above, I could also say that steel is
stronger than titanium. So what. That doesn't make a certain part one
metal or the other.

> Also, your gedankenexperiment saying that cut threads are the only
> ones possible because the brake hardware couldn't be pushed on to
> the bolt is bogus. What happens, in actuality, is that the diameter
> of the unthreaded screw blank is smaller than the finished ID so
> that the metal can flow up to the finished diameter for the crest
> (major diameter) of the thread.


The problem with that is the thread and shaft ate the same diameter
within less than 0.01mm, something that is not readily repeatable with
a rolled thread.

>> substantial size smaller which would offer less strength than a cut
>> thread of the shaft diameter.


> Bzzt - wrong. Whether a thread is rolled or threaded, the minor,
> major, and pitch diameters are _identical_.


> But not only that:


> All rolled threads are stronger than cut threads due to the fact
> that the tooling does not cut the grain of the material, but instead
> _deforms_ the grain instead. If you have a malleable material (like
> 1018 cold-rolled as opposed to a work-hardening material like D-2
> tool steel), your best bet is to use a rolled thread _every_time_.


I don't doubt that, but in some instances a rolled thread is
inappropriate for the other functions of the screw... as in this case.
You might do some measuring and micro-inspection of such bolts and
report what you find. The parts I inspected had machining centers in
both ends.

Just by the way, what moves you to use such an insulting tone when
discussing bicycle parts?

Jobst Brandt
 
James Annan wrote:
> Ed Pirrero wrote:
>
> > James Annan wrote:
> >
> >>Ed Pirrero wrote:
> >>
> >>
> >>>Since there seem to be fewer incidents than predicted from the
> >>>hypothesis,
> >>
> >>How many incidents are predicted?

> >
> >
> > Since, as you say, the force purported to exceed the ISO minimum, the
> > number should be greater than zero.
> >
> > State clearly whether or not this prediction is implied. If it is not
> > implied, then all this is an exercise in buffoonery. If it is implied,
> > then incidents of ejections should be greater than zero. *Especially*
> > considering the volume of disk brakes in use.

>
> There have been many incidents at varying levels of severity.


"Many" is not quantitative. Nor is it broken down by type or quality
of data.

Some guy said his QR slipped. OK.

The final mass measured was 34.9987g. What is the density of the
material?

These two pieces of data have exactly the same quality.

The fact remains that the total verified ejection quantity is zero. Do
you dispute this fact, or do you try and circumlocute some more?

E.P.
 
[email protected] wrote:
>
>
> Just by the way, what moves you to use such an insulting tone when
> discussing bicycle parts?


It's the same tone you use. I guess it's only offensive in one
direction, hmm?

E.P.
 
[email protected] wrote:
> Ed Pirrero writes:
>
> >>>> definitely be curious to see evidence that they do. ;-)

>
> >>> From what you understand of the theory, consider this proposed
> >>> experiment.

>
> >>> Take a bicycle equipped with a disc caliper mounted on the back of
> >>> the fork. Loosen the quick release clamp until it is barely
> >>> engaged. Walk the bicycle at a brisk pace, then apply the front
> >>> brake.

>
> >> Hey! That's my experiment, except that I suggested it be done
> >> statically by applying the brake while pushing the bicycle forward
> >> by the bars. That demonstrates the effect adequately.

>
> > And the only thing it shows is the thing everyone already agrees
> > upon.

>
> > Is there anybody who actually believes that the ejection force
> > doesn't exist?

>
> I guess you haven't been following the argumentation on the subject
> closely enough, but then that isn't easy, considering the volume
> of rhetoric.


I have seen not a single post in this thread that disputes it. In the
beginning, there were some.

So, yes, I *have* been following along. Save your sanctimonius
******** for the unwashed.

> > This experiment answers no other questions, verifies no
> > calculations, and is not instructive in what the actual forces are.

>
> We have the calculations as well. That is one you should have read,
> considering it is your principal claim.


But this experiment *does not show that the force at the dropout is the
claimed one*. You are being deliberately obtuse.

> > Facetious, or disingenous. At this late stage in the discussion,
> > that's all you're being.

>
> You'll have to put more body on that to make it have meaning.


Hogwash. I judge it to be disingenous. I guess your expert witness
money is still at stake, hmmm?

E.P.
 
> [email protected] wrote:
>> A rolled thread would not permit the parts to slide onto the
>> shaft unless the threads were a substantial size smaller which would
>> offer less strength than a cut thread of the shaft diameter.


Boyle M. Owl wrote:
-snip vitriol-
> Also, your gedankenexperiment saying that cut threads are the only ones
> possible because the brake hardware couldn't be pushed on to the bolt is
> bogus. What happens, in actuality, is that the diameter of the
> unthreaded screw blank is smaller than the finished ID so that the metal
> can flow up to the finished diameter for the crest (major diameter) of
> the thread.


-jb-
> > substantial size smaller which would
> > offer less strength than a cut thread of the shaft diameter.


Boyle M. Owl wrote:
> All rolled threads are stronger than cut threads due to the fact that
> the tooling does not cut the grain of the material, but instead
> _deforms_ the grain instead. If you have a malleable material (like
> 1018 cold-rolled as opposed to a work-hardening material like D-2 tool
> steel), your best bet is to use a rolled thread _every_time_.


No one disagrees with that. Rolled threads are swell.

Back here on Earth, brake manufacturers find cut threads
adequate and have no incentive to further invest in tooling
_where no obvious problem exists_.

I hadn't thought about it before but Jobst makes a good
point about diameters and arm clearances. The present cut
thread brake bolt is the cheapest way to adequately solve
the problem. And with no change in scores of years without
problems they are indeed adequate, from LeeChi to Record.

--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971
 
The force to decellerate the front wheel is generated by my hand on the
brake lever, magnified by the mechanical advantage of the Hayes disk
brake. The wheel can and does put enough energy into the quick release,
provided that I increase my hand grip to maximum before the wheel comes
to a stop. Of course, much of the energy goes into deflecting the front
fork -- the whole bicycle shudders violently when I stop the wheel in
this manner.

But, in relative terms, the energy has got to be fairly low, around 50
foot-pounds or so, or probably about the same energy as I would exert
swinging a framing hammer. What's necessary to move the quick release
is a repeated application of a large force.

Haven't you ever replaced the headset in your bicycle? You repeatedly
hammer on the rocket tool to remove the press fit. Each blow applies
only a small amount of the total energy necessary to remove the bearing
race from the headset. Same thing with my spin and stop test. Low
energy involved, relative to the stored energy of a rider and bicycle.

A testing laboratory such as Cannondale's could spin the front wheel to
full speed and then apply the brake in a controlled fashion and move
the wheel in the dropouts. My guess is that controlled testing will be
done only by a consultant working for a plaintiff when or if someone is
injured by this design defect.
 
[email protected] wrote:
> Old Crow writes:
>
>
>>>>no, the over-center was not an original feature - the old straight
>>>>lever campy qr's tighten all the way to the stop.

>
>
>>>You should take one of those apart. The original design clearly
>>>goes 'over center' to lock.

>
>
>
>>i did. it functioned as i described. i wouldn't use it because of
>>that.

>
>
> That's too bad, because even without taking it apart the over center
> feature is detectable both by inspection and manual action. I
> wouldn't be riding those original QR's if that were not the case. You
> are trying hard to avoid any credibility, if there was any.
>
> Jobst Brandt


just like your assertion that the traction cable on san francisco cable
cars are wound with longitudinal strands rather than helical strands,
you're wrong on this one jobst. regrettably, i've sold the hub so i
can't prove it to you, but i would if it still had it.
 
[email protected] wrote:
> Boyle M. Owl writes:
>
>
>>>A rolled thread would not permit the parts to slide onto the shaft
>>>unless the threads were a substantial size smaller which would
>>>offer less strength than a cut thread of the shaft diameter.

>
>
>>Hey Jobst, go crack open a Machinery's Handbook (whatever edition
>>you may have - I've got 23 and 27) and look at rolled thread
>>strength as opposed to cut thread strentgh, and get back to me, OK?
>>You may have a PhD in physics, but neither a PhD nor educated
>>opinion is any substitute for empirical results.

>
>
> I don't see where that proves the thread on these bolts is rolled.


jobst, i've done metallography on bolts like this. they're /definitely/
rolled. call one of your stanford engineering alumni buddies and have
them confirm it for you.

> The ones I have for inspection do not have the classic bolt end, have
> a thread whose major diameter is exactly the same as the bearing
> surface of the shaft and show no classic rolled thread form but rather
> has a single point thread runout at the transition to the shaft. That
> doesn't prove that they aren't rolled but it definitely suggests that.


eh? like this?
http://www.flickr.com/photos/38636024@N00/99524699/

>
> In response to your question above, I could also say that steel is
> stronger than titanium. So what. That doesn't make a certain part one
> metal or the other.


eh? red herring.

>
>
>>Also, your gedankenexperiment saying that cut threads are the only
>>ones possible because the brake hardware couldn't be pushed on to
>>the bolt is bogus. What happens, in actuality, is that the diameter
>>of the unthreaded screw blank is smaller than the finished ID so
>>that the metal can flow up to the finished diameter for the crest
>>(major diameter) of the thread.

>
>
> The problem with that is the thread and shaft ate the same diameter
> within less than 0.01mm, something that is not readily repeatable with
> a rolled thread.


rubbish. have you ever heard of q.c.?

>
>
>>>substantial size smaller which would offer less strength than a cut
>>>thread of the shaft diameter.

>
>
>>Bzzt - wrong. Whether a thread is rolled or threaded, the minor,
>>major, and pitch diameters are _identical_.

>
>
>>But not only that:

>
>
>>All rolled threads are stronger than cut threads due to the fact
>>that the tooling does not cut the grain of the material, but instead
>>_deforms_ the grain instead. If you have a malleable material (like
>>1018 cold-rolled as opposed to a work-hardening material like D-2
>>tool steel), your best bet is to use a rolled thread _every_time_.

>
>
> I don't doubt that, but in some instances a rolled thread is
> inappropriate for the other functions of the screw... as in this case.
> You might do some measuring and micro-inspection of such bolts and
> report what you find. The parts I inspected had machining centers in
> both ends.


jobst, pull some strings and do some metallography. you're wrong on
this one.

>
> Just by the way, what moves you to use such an insulting tone when
> discussing bicycle parts?


following your example perhaps?

>
> Jobst Brandt
 
[email protected] wrote:
> Andrew Muzi writes:
>
>
>>>>Hey jim - found those BROKEN brake bolts yet?
>>>>You've decided they are unsafe - show us the evidence...

>
>
>>>i've told you before, answer my questions and i will. what are you
>>>afraid of?

>
>
>>1.)The overwhelming bulk of brake center bolts have cut threads and

>
>
>>2.)failure is virtually unknown - even after being bent from hitting
>> the downtube in a crash.

>
>
>>Does anyone seriously dispute either statement?

>
>
>>If I recall, Mr Beam asserted that brake bolts have rolled threads
>>(which is a good idea, I suppose, but in the world we actually live
>>in, they don't) and hasn't yet had either the opportunity to look at
>>brake bolts closely or the grace to walk away from his hasty
>>statement. Did I miss anything?

>
>
>>I looked at vintage and modern brake bolts a few weeks ago but
>>tonight I shot a photo of a brand new Campagnolo Chorus caliper:

>
>
>>http://www.yellowjersey.org/photosfromthepast/CHRCALIP.JPG

>
>
>>Note that in the profile shot, the thread is clearly smaller than
>>(cut from ) the body of the bolt. Rolled threads are raised above
>>the base diameter.

>
>
>>OK, is this over yet?

>
>
> Probably not. What doubters do not recognize is that the brake anchor
> bolt on a typical side-pull brake has a boss that retains the return
> spring and serves as a backing for the caliper arms against which they
> tilt when braking. There is no reasonable and safe way to mount that
> boss except to make it integral with the bolt. That is, the bolt is
> machined from a rod that has the diameter of the boss.


wrong. it's rolled from a shaft with two diameters. the slimmer one
has threads rolled into it which increase the diameter to that of the
larger part. real simple.

> The thread
> cannot be rolled because the shaft serves as a bearing for the
> caliper.


eh? that's rubbish.

> A rolled thread would not permit the parts to slide onto the
> shaft unless the threads were a substantial size smaller which would
> offer less strength than a cut thread of the shaft diameter.


based on an entirely false assumption. wrong.

>
> Besides that, brake loads are not large, the major stress being
> bending at the integral anchor boss that has a suitably radiused
> transition to the shaft.


except that the bolt is threaded, and the threads are exposed to bending
stress. each thread is a stress riser, so, what do we do to mitigate
that? we roll the threads!!! /every/ major manufacturer does it.
frankly, it's shameful that you don't know that if you want to pose as
an expert. it's even worse to criticize someone that does know using
your false assumptions. but you're no stranger to that, are you.

>
> Jobst Brandt
 
Tim McNamara wrote:
> jim beam <[email protected]> writes:
>
>
>>James Annan wrote:
>>
>>>Ed Pirrero wrote:
>>>
>>>
>>>>James Annan wrote:
>>>>
>>>>
>>>>>Ed Pirrero wrote:
>>>>>
>>>>>
>>>>>>Zero
>>>>>>credibility.
>>>>>
>>>>>Yes, that seems a fair summary of your scientific background.
>>>>
>>>>And here we have a concise summary of James Annan. Takes the data
>>>>that fits his view, and rejects the rest.
>>>>
>>>>To real scientists, this is called "junk science".
>>>>
>>>
>>>How would you know what a "real scientist" would think? Have you
>>>ever met one? James
>>>

>>
>>he is one annan. he's all over the web if you know who you're
>>looking for.

>
>
> He's all over Usenet, anyway, but that's only proof of an Internet
> connection. I find nothing by him that is scientific or scholarly,
> certainly not in this newsgroup. Is he just another sock puppet of
> yours, perhaps?


the chickens taking up too much of the intellectual resources tim? "ed"
is not his real name. there, that was hard to figure out, wasn't it.
 
James Annan wrote:
> jim beam wrote:
>
>> James Annan wrote:
>>
>>> jim beam wrote:
>>>
>>>> James Annan wrote:
>>>>
>>>>> jim beam wrote:
>>>>>
>>>>>
>>>>>> James Annan wrote:
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>>> http://www.ne.jp/asahi/julesandjames/home/disk_and_quick_release/QRReport1.pdf
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> The Howat numbers are an order of magnitude lower than your risible
>>>>>>> "calculation" of the retention ability of a QR that you made up
>>>>>>> previously. They are similar to (often lower than) the estimated
>>>>>>> ejection force.
>>>>>>
>>>>>>
>>>>>>
>>>>>> they're lower if the qr is not tightened sufficiently [go figure -
>>>>>> obviously it would take a climatologist to work that one out] and
>>>>>> substantially higher when tightened correctly.
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> Please define "tightened correctly",
>>>>
>>>>
>>>>
>>>> i refer you to your favorite paper, howat. or failing that, read
>>>> manufacturer instructions some time.
>>>>
>>>>
>>>>> and describe how a rider can
>>>>> achieve this with no tools.
>>>>
>>>>
>>>>
>>>> read the shimano instructions. you /do/ read instructions don't you
>>>> annan?
>>>
>>>
>>>
>>>
>>> Yes, I do, which is why I asked you what you meant. And of course you
>>> ducked the question, because you are making this up as you go along,
>>> ducking and weaving as you go.

>>
>>
>>
>> eh? you say: "describe how a rider can achieve this with no tools", i
>> quote the manufacturer instructions verbatim, and you start bleating
>> that i'm "ducking & weaving". holy **** annan, you got some serious
>> reality distortion issues going on there guy.
>>
>>>
>>> In fact, it is clear that the manufacturers' instructions do not
>>> guarantee that the QR will withstand a disk brake force. For starters,
>>> they do not instruct the user to chip all the paint off his fork
>>> dropouts.

>>
>>
>>
>> bwah bwah bwah. what other goal posts do you want to move?
>>
>>>
>>>
>>>>> You may find it helpful to refer to
>>>>> instructions provided by any QR manufacturer, or bike manufacturer, or
>>>>> retailer. Note that your method to ensure that the skewer is
>>>>> "tightened
>>>>> correctly" should guard against overtightening, as well as
>>>>> undertightening.
>>>>
>>>>
>>>>
>>>> hmm, so when, in print, a manufacturer instructs a user to tighten
>>>> "with
>>>> as much strength as possible", do you find that equivocal in any way?
>>>
>>>
>>>
>>>
>>> I find it worrying that any manufacturer would think it appropriate to
>>> give such instructions.

>>
>>
>>
>> eh? which way do you want it annan?
>>
>>>
>>>
>>>> do you seriously think you can break a qr by hand???
>>>
>>>
>>>
>>>
>>> That comment is particularly good timing, coming as it does just a few
>>> days after someone in a different thread mentions a case of just this
>>> happening. Are you actually claiming that it is not possible to
>>> overtighten a QR?
>>>
>>> First google hit:
>>>
>>> -----
>>> OVERTIGHTENING THE QUICK RELEASE MECHANISM MAY DAMAGE THE QUICK RELEASE
>>> ASSEMBLY. FOR FURTHER INFORMATION ON CORRECT ADJUSTMENT OF THE QUICK
>>> RELEASE TENSION, SEE ADDITIONAL INFORMATION BELOW:
>>>
>>> To properly close the quick release mechanism requires between 15
>>> and 45 pounds of force. [55 to 200 Newton]. If the required closing
>>> force is greater than 45 pounds, open the lever and loosen the
>>> mechanism adjusting nut. Close the lever again.
>>> -----
>>>
>>> I know that Salsa give an explicit range of 24-30 pounds of force on
>>> the QR lever.
>>>
>>> So, how about that "correctly tightened" thing. Care to try again?
>>>
>>> James
>>>

>>
>> that's an open cam skewer annan. we've discussed the failings of that
>> design before. oh, wait, you want to change the rules in the middle
>> of the game? sorry, my bad.

>
>
> Oh, so you agree that these skewers are not safe? That's a start.
>
> James


it's the only damned dog you have in the hunt annan. everything else
expired years ago.
 
Old Crow writes:

>>>>> no, the over-center was not an original feature - the old
>>>>> straight lever campy qr's tighten all the way to the stop.


>>>> You should take one of those apart. The original design clearly
>>>> goes 'over center' to lock.


>>> i did. it functioned as i described. i wouldn't use it because
>>> of that.


>> That's too bad, because even without taking it apart the over
>> center feature is detectable both by inspection and manual action.
>> I wouldn't be riding those original QR's if that were not the case.
>> You are trying hard to avoid any credibility, if there was any.


> just like your assertion that the traction cable on san francisco cable
> cars are wound with longitudinal strands rather than helical strands,
> you're wrong on this one jobst. regrettably, i've sold the hub so i
> can't prove it to you, but i would if it still had it.


Well I still ride on those hubs and they are in hand and they have an
eccentric circular cam whose position is over-center when closed.
They are the same as the later ones with curved lever except that the
lever is straight.

About cable cars, you must have misinterpreted what was said. I know
how cables are made and that they cannot be bent around corners unless
they are helically wound. I have explained that often on this forum
and for cable cars, I posted pictures:

http://www.gmerch.net/cablecar/stand_large.jpg

Jobst Brandt
 
[email protected] wrote:
> Johnny Walker wrote:
>
>
>>oh, and since you obviously missed it countless times before, the
>>reason for /not/ front mounting a caliper is FATIGUE. cast alloys
>>such as those in forks and calipers ARE NOT GOOD IN TENSILE FATIGUE.
>>that's a pretty fundamental omission from someone that seems to feel
>>qualified to lecture on what comprises good engineering design.

>
>
> Oh hogwash! Nearly all current disk brake calipers have at least one
> of the two retaining bolts exerting tension on its attachment eye.


and the dominant one, the one with the highest load, is in compression!
don't you feel shame when you b.s. like this?

> Besides, fork stanchions, to which these are attached, are loaded in
> bending which naturally causes tension and compression about a neutral
> axis.


eh? you sound like mcnamara! exactly how much stress do you think it
takes to fatigue the smooth surface of a 40+mm lower fork stanchion???

> Stop generating this stream of specious argumentation and offer
> something constructive.
>
> Just in case you don't have the URL for Webster's Dictionary at hand:
>
> Specious: 3 : having a false look of truth or genuineness
>
> It seems you are competing for chief sophist of wreck.bike, from the
> things you write.
>
> Sohphist: 3 : a captious or fallacious reasoner
>
> Jobst Brandt


ah, the old jobstian ad hominem. that makes your spectacular
drivellings about "cut thread" brake bolts somehow less inaccurate does
it? get with the facts jobst, do the metallography. and don't portray
your assumptions as fact.
 
Boyle M. Owl wrote:
> Michael Press wrote:
>
>> Take a bicycle equipped with a disc caliper mounted on the back of the
>> fork. Loosen the quick release clamp until it is barely engaged. Walk
>> the bicycle at a brisk pace, then apply the front brake.

>
>
> I've sat here and read this thread and watched you repeatedly make this
> same request for an "experiment". Your first ideas to have someone ride
> a bicycle with the front QR "barely engaged" to 25MPH was not only
> _ludicrous_ but it was also _dancing with the liability boogyeman_. I
> could only imagine what might have happened if someone did what you
> requested and hurt himself. Using your logic, they should have rightly
> sued _you_ along with suing the fork manufacturer.
>
> Talk about hoisting oneself upon one's own petard.
>
> You're asking for people to use a QR _improperly_ to prove some sort of
> point about pullout force. Well, the only point is upon your head. If
> you don't wear a hat, it won't show.
>
> IOW, you're just a mere troll. Git along little troll, git along, git
> along...*fr0h slap!*
>
> And here is your punishment, to be tortured by Safety Dance, but
> reworded to _my_ lyrics.
>
> S-s-s-s A-a-a-a F-f-f-f E-e-e-e T-t-t-t Y-y-y-y
> Safety, troll!
>
> I can troll if I want to
> I can leave your posts behind
> 'Cause your posts don't troll and if they don't troll
> Well they're no posts of mine
> I say, we can troll where we want to
> A goatse they can always find
> And I can act like we come from the GNAA
> Leave the moderations far behind
> And we can troll.
>
> --
> BMO


that's a good one!
 
Ed Pirrero wrote:
> [email protected] wrote:
>
>>Ed Pirrero writes:
>>
>>
>>>>>>>>The issue of loosening threaded fasteners is well-known in
>>>>>>>>mechanical engineering. Perhaps you think that the laws
>>>>>>>>governing such things are different for bicycles?

>>
>>>>>>>Yes it is as are the methods of preventing it - and two of those
>>>>>>>methods are built into a standard QR. Perhaps you think those
>>>>>>>measures work everywhere in engineering except bicycles

>>
>>>>>>Other brakes don't create an ejection force, and neither should
>>>>>>disk brakes. Simple as that.

>>
>>>>>And there you have it. An *opinion*. Which is what most of this
>>>>>argument boils down to, in the end.

>>
>>>>>Some force exists, and folks have opinions on how it should, or
>>>>>should not, be addressed. While opinions are interesting, and
>>>>>fodder for lengthy usenet discussions, they do not rise to the
>>>>>level of fact or data.

>>
>>>>>The militant will vehemently disagree, of course. As always.

>>
>>>>How about a practical test.

>>
>>>[same non-data-producing "test" snipped]

>>
>>Interesting. You cite all the exchanges above but choose to leave out
>>that with which you take issue.

>
>
> No, not really interesting. It's not an informative or enlightening
> test, nor is that the only example even in this thread of the test
> being proposed.
>
> Does this test show the magnitude of the forces involved? Does it show
> the peak magnitude of the possible forces? Does it take into account
> any of the potentially complicating factors that may have been
> overlooked or even discounted up to now?
>
> No? Then what does it show? Nothing that folks don't already all
> agree on. So it's worthless.
>
> "In other news, water is wet."
>
>
>>Is that too voluminous to include in your lengthy derision of same?

>
>
> Derision? Try and rein in your overactive imagination. If you were
> interested in the complete answer to the questions posed, you would not
> work so hard to avoid them.
>
>
>>>The QR20 axle system is close to this.

>>
>>So?

>
>
> The system you "designed" exists already. No need to re-invent it.
>
>
>>>Maybe all forks will be that way in 10 years. But until the problem
>>>is backed with something more than a FBD and the opinions of some
>>>usenetters, it seems somewhat unlikely.

>>
>>>Class action lawsuit, if one could round up a big enough class.

>>
>>Oh, you want more severely injured bicyclists before changing anything
>>on a system that has obvious problems.

>
>
> Logical fallacy: strawman.
>
> Can anyone one of you pro-redesign-it-now folks actually *not* resort
> to juvenile tactics to make your points?
>
> Stick to engineering. Your rhetorical skills are weak.


er, i beg to differ on that. his rhetorical skills /far/ outshine his
engineering skills - he doesn't know a rolled thread bolt when he sees
one. absolutely amazing.

>
> E.P.
>
 
[email protected] wrote:
> Dave Wissenbach writes:
>
>
>>When and if the time comes to replace the fork I'll purchase a
>>replacement from a manufacturer who has made design changes which
>>rectify the problem. (Marzocchi appears to be using a forward angle
>>on some of their fork dropouts this year.)

>
>
> Hold the phone! The primary problem is a reversing load that tends to
> loosen a QR. That the load is in the wrong direction for conventional
> dropouts Makes it doubly hazardous. The solution is to get rid of the
> road-bicycle type QR and institute a reliable retention mechanism that
> does not rely on friction... Or place the caliper ahead of the fork.
>
> Jobst Brandt


hold the phone indeed.

1. we get rid of the qr /if/ it's not retaining the axle with sufficient
force, which it clearly is.

2. caliper ahead of the fork has been abandoned by engineers that
fortunately know more about materials than you do! your comprehension
of fatigue is abysmal jobst.
 
dvt wrote:
> jim beam wrote:
>
>> the much-vaunted "howat" paper shows retention exceeding the "annan
>> factor" by a substantial margin.

>
>
> Where is that shown? I find the opposite.
>

use figues VIII & IX to work it out.
 
Marvin wrote:
> jim beam wrote:
>
>>James Annan wrote:
>>
>>>jim beam wrote:
>>>
>>>
>>>
>>>>"interference between materials"??? "dead end"? so how come /i/ am
>>>>the poor dolt that had to point out that axle faces are serrated and
>>>>that subsequent indentation significantly increases retention force?
>>>>i can't see you bothering to point out such trivial details tim.
>>>>
>>>
>>>All I need to do is point to the pictures that jim beam so kindly
>>>provided:
>>>
>>>http://home.comcast.net/~carlfogel/download/nishiki_before.jpeg
>>>http://home.comcast.net/~carlfogel/download/nishiki_indent.jpeg
>>>
>>>Of course, a particularly dull-witted person might not wonder why it is
>>>that someone (who?) bothered to scrape the paint off the dropout of an
>>>old fork that happened to be lying around, nor what the picture might
>>>have looked like had the fork end been left normally painted. But I
>>>think most people reading this thread will have got the message clearly
>>>enough.

>>
>>eh? that's spectacular b.s. that is a fork i happened to have laying
>>about. the paint was already off. the snide implication that i somehow
>>"prepared" it to alter the result is as bogus as it is desperate. it
>>also shows incredible ignorance if you think a simple paint layer offers
>>any significant resistance to steel indentors.

>
>
> Yes, it does. I did the experiments, I reported the results. Google
> for them if you can't remember.
>
>
>>i can see b.s. may be the only way you could have any come-back on the
>>evidence annan, but resorting to such a pathetic diversion is below even
>>you. integrity and credibility go hand in hand, in case you never
>>learned it before. [why did you leave scotland again?]
>>
>>
>>>Of course, for those who are still unconvinced, there is also Marvin's
>>>comment posted earlier:
>>>
>>>"Every new bike I assembled today, I checked before and after on the
>>>indentations. All of them embossed the paint to a fairly minor degree
>>>with a single clamping, repeated clampings on one test subject made
>>>them a little more obvious. None of them were to the same level as jim
>>>beam's example above."
>>>
>>>
>>>James

>>
>>straw clutch city. that was from a single thumb-pressure application.
>>what now - suggest i have some kind of digital deformity and super-human
>>strength so the result can be "ignored"? do the math on the indentation
>>force. no, wait, /google/ for the math on the indentation force - it's
>>been done for you. but i warn you, you'll be straying into retention
>>force territory annan - you probably won't want to go there.

>
>
> Oh, pull your head out of your ****, Beam. As I said at the time
> (google for the post if you want), that was repeated on several
> different bikes, one of which I checked repeatedly to see if this
> embossing got more obvious over time. I don't think I reported it, but
> I took one skewer and ramped it as tight as my padded hands could cope
> with (far tighter than any recommendation) - still didn't emboss
> through the virgin paint to the metal. These aren't exactly super
> thick tough paint jobs we're talking about here, either.


with respect, marvin, you seem to be implying that somehow the paint
only indents and the metal is unscathed. maybe you should remove the
paint with solvent /after/ you've done your indent test. then you'll
see that the metal does indeed deform under the paint.

>
> So my actual, experimental evidence suggests that on new bikes you
> don't have a metal to metal interface no matter what you do to the QR.
> This substantially lowers the required pullout force.


that's like saying that because you have an oil film separating the
teeth when meshing in a gear box, that torque is not transmitted! i
don't think you understand what you're looking at.

>
> Now if you've got a larger sample size, I'd love to hear it.


google. i've posted my own, thanks.

> Until
> then I think I'm one of the only people who's even attempted actual,
> unbiased experiments on this topic - ironically enough, something I
> recall Beam complaining loudly about the lack of. Funny how he
> complains even louder when things don't go his way.


eh? that makes no sense. your misinterpretation of results is not my
problem.
 
Benjamin Lewis wrote:
> jim beam wrote:
>
>
>>Benjamin Lewis wrote:
>>
>>>jim beam wrote:
>>>
>>>
>>>>Tim McNamara wrote:
>>>><snip drivel>
>>>>
>>>>>I see. And that situation is insurmountable? The designers are
>>>>>incompetent to deal with that? Good heavens. Might as well go back
>>>>>to V-brakes, dude. Oh wait, those are mounted on the front too- no
>>>>>doubt there are millions of them being ripped off of forks even as we
>>>>>speak.
>>>>
>>>>oh dear. sorry tim, zero points. do the math on the force at the
>>>>brake bosses compared to a disk tab. look at the comparative size
>>>>differences too and use that to estimate stress.
>>>
>>>How can we "look at the size differences" on a non-existent design?

>>
>>eh? disk tabs and brake bosses exist. do we have a communication
>>problem?

>
>
> Disk tabs on front mounted calipers do not exist. If they did, an
> intelligent designer would make them larger.


that's only considering the tabs - the calipers have the same problems
as well.

>
>
>>>That stress is greater on rear mounted disk brake tabs than on
>>>cantilever bosses is true, but irrelevant.

>>
>>it's /highly/ relevant in fatigue!

>
>
> The stress on rear-mounted disk tabs is irrelevant in a discussion of
> front-mounted disk tabs.
>


not when front mounted calipers are subject to unfavorable fatigue
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