Brakes: changing from nutted to recessed?



Robin Hubert wrote:
> [email protected] wrote:
>
>> someone writes:
>>
>>
>>>> rolled thread bolts are generally not the same steel at that used
>>>> for any responsible cut thread bolt - it's cheaper/weaker material
>>>> because the better properties of the rolled thread allow it to be
>>>> used. /so/ cutting a thread into a rolled thread bolt is bad not
>>>> only because of the cut thread, it's bad because the material is
>>>> not appropriate for it! it this really so hard to understand?

>>
>>
>>
>>> I am shocked, shocked to hear that bicycle part designers use weaker
>>> materials that are deemed sufficient, when stronger materials are
>>> available! Is this bad design??? Surely a calculation of the
>>> fatigue properties and loading of these bolts would reveal the
>>> danger of this practice.

>>
>>
>>
>> Get some shock therapy. You may also be surprised that the low paying
>> bicycle industry does not have many competent engineers and that much
>> of the equipment is designed by what might best be called "hobbyists"
>> dabbling in engineering.
>>
>>
>>> This would have been a good argument if you had brought it up in
>>> your first post to this thread. But as the 20th post, after several
>>> other smokescreens, and refusals to post numbers or references, it
>>> looks like moving the goalposts. It's sophistry. I'm sure you get
>>> some kind of gratification out of this strategy of argument, and it
>>> gets you attention, but not everybody will play with you ad
>>> infinitum.

>>
>>
>>
>> I think most readers have recognized this, no useful contributions
>> arising from his postings. To me it's a lot of smartass sniping.
>>
>> Jobst Brandt

>
>
> Jobst, I may have missed it but I don't think you've weighed in on this
> brake bolt debate. What is your position on the original question and
> following discussion?
>
> Is a cut-thread (vs rolled) brake bolt reliable? Would periodic
> inspection be sufficient to prevent catastrophic results if not?
>
> For those curious I am test-piloting a Suntour Superbe that I threaded
> for recessed mount as did our OP. As you might've guessed, it's the
> front.


Er, that'd be the rear, actually.

>Only several thousand miles so far.
>
> Robin (your faithful test pilot) Hubert
 
[email protected] wrote:
> jim beam wrote:
>
>>jtaylor wrote:
>>
>>>But the testing has been done - millions of brake bolts using either type of
>>>thread in constant use in the real world,

>>
>>either type?

>
>
> Yes. Thread cutting predates thread rolling. I'd assume that over the
> 100+ years that bikes have been in existence, there have been millions
> of brake bolts of either type.


cast irons pre-date bessemer steels. are you advocating a roll back of
the evolutionary clock in materials as well?

>
> I'm curious - how much advantage do you think rolled threads have?
> Because tandem teams have been using caliper brakes roughly forever,
> and I've not heard of even tandem teams breaking these bolts.


frank, you're the engineer. i'm just the metallurgist. how about you
do a little work for a change? oh, wait, you can't do the math. my
mistake.

>
> If that's the case, the safety factor in the existing bolts must be at
> _least_ 2, since tandems can exert more than double the braking force
> of a single. And the OP was (AFAIK) riding a single. If the cut
> threads don't reduce the strength by half, the OP is in fine shape.
>
> And _certainly_ you can't possibly believe the strength of a cut thread
> is half that of a rolled thread... can you??


hmm, yet another engineer proving that he doesn't know the difference
between static and fatigue strength. /and/ one that presumes to teach
this stuff. i call it shameful.

>
> - Frank Krygowski
>
 
Sheldon Brown wrote:
> This ludicrous thread about an imaginary problem has already gone on way
> longer than it should, but for the paranoids I'll risk adding to it by
> pointing out the following:
>
> "Nutted" _rear_ brake bolts are the right length for recessed use in
> _front_, so the unmodified "rear" caliper can be installed in front
> without even the imaginary risk that the alarmists have warned of.
>
> The bolt that needs to be cut down is the "nutted" _front_, cut short to
> fit the _rear_ position of the frame.
>
> The stresses on the _rear_ brake bolt are such that even in the
> vanishingly unlikely event of a failure, no serious harm would ensue.
>
> Sheldon "Now Howabout Discussing REAL Problems?" Brown
> +-----------------------------------------------------------------+
> | Love seems the swiftest, but it is the slowest of all growths. |
> | No man or woman really knows what perfect love is until they |
> | have been married a quarter of a century. --Mark Twain |
> +-----------------------------------------------------------------+
> Harris Cyclery, West Newton, Massachusetts
> Phone 617-244-9772 FAX 617-244-1041
> http://harriscyclery.com
> Hard-to-find parts shipped Worldwide
> http://captainbike.com http://sheldonbrown.com
>


sheldon, that's the first sensible comment on this thread in nearly a
week. yes - not ideal, but a sensible compromise and one i'd go with.
 
Jasper Janssen wrote:
> On Fri, 02 Dec 2005 07:09:07 -0800, jim beam <[email protected]> wrote:
>
>
>>either type? but you've yet to show evidence of a /single/ cut thread
>>on any oem brake. trying to assert an untruth as truth really doesn't
>>help your position. oh, maybe you were hoping no one would notice. sorry.

>
>
> It doesn't have to be OEM to be widely used.
>
> Jasper
>

really? where do you buy your after market pivot bolts?
 
[email protected] wrote:
> jim beam wrote:
>
>>rolled thread bolts are generally not the same steel at that used for
>>any responsible cut thread bolt - it's cheaper/weaker material because
>>the better properties of the rolled thread allow it to be used.

>
>
> Ah.
>
> Evidence?
>
> - Frank Krygowski
>


er, aren't you the engineering professor? do you know /anything/ about
materials?
 
Jasper Janssen wrote:
> On Thu, 1 Dec 2005 16:50:02 -0500, "Phil, Squid-in-Training"
> <[email protected]> wrote:
>
>
>>I think you're missing the point here. JB is attacking the tenets of BAD
>>DESIGN. Why would anybody in their right mind go about designing things
>>with internal 90-degree angles, factors of safety of 1.1, and cut threads?
>>Bad design means that the designer will continue designing products that may
>>not break in that one product, but if the methods are utilized in a future
>>product that doesn't hold, it could cause "personal injury or even death."

>
>
> Yeah. All that is completely irrelevant to this thread. This thread was
> about someone who needed more threads on his bolt and wanted to run a die
> round it until he had them, and jim beam being his alarmist self. It
> didn't have anything to do with design or with how the things are
> manufactured until he came in.
>
> Jasper


you sound like the other guy that thinks fatigue doesn't matter. maybe
you can get a cost cutting job at boeing too.
 
[email protected] wrote:
> someone writes:
>
>
>>>rolled thread bolts are generally not the same steel at that used
>>>for any responsible cut thread bolt - it's cheaper/weaker material
>>>because the better properties of the rolled thread allow it to be
>>>used. /so/ cutting a thread into a rolled thread bolt is bad not
>>>only because of the cut thread, it's bad because the material is
>>>not appropriate for it! it this really so hard to understand?

>
>
>>I am shocked, shocked to hear that bicycle part designers use weaker
>>materials that are deemed sufficient, when stronger materials are
>>available! Is this bad design??? Surely a calculation of the
>>fatigue properties and loading of these bolts would reveal the
>>danger of this practice.

>
>
> Get some shock therapy. You may also be surprised that the low paying
> bicycle industry does not have many competent engineers and that much
> of the equipment is designed by what might best be called "hobbyists"
> dabbling in engineering.


may be true in your world, but to say that's the case with a
manufacturer like shimano? simply ridiculous.

>
>
>>This would have been a good argument if you had brought it up in
>>your first post to this thread. But as the 20th post, after several
>>other smokescreens, and refusals to post numbers or references, it
>>looks like moving the goalposts. It's sophistry. I'm sure you get
>>some kind of gratification out of this strategy of argument, and it
>>gets you attention, but not everybody will play with you ad
>>infinitum.

>
>
> I think most readers have recognized this, no useful contributions
> arising from his postings. To me it's a lot of smartass sniping.


ah, so it's smartass sniping to point out when you're making stuff up
about things like fatigue and gyroscopic stability and deformation
theory and bearings and strength of structures, but it's ok when you
expose others' faults? i get it now. thanks for the explanation.
makes perfect sense.

>
> Jobst Brandt
 
jim beam wrote:
> [email protected] wrote:
> >
> > Yes. Thread cutting predates thread rolling. I'd assume that over the
> > 100+ years that bikes have been in existence, there have been millions
> > of brake bolts of either type.

>
> cast irons pre-date bessemer steels. are you advocating a roll back of
> the evolutionary clock in materials as well?


?? Rolling back the clock? Are you pretending _no_ threads are cut
these days? Why do you think machine shops have die sets?

All I'm saying is that it's safe for the OP to cut those threads.
You've provided no evidence that it's not, and you've provided no
evidence that brake bolts in general have significant risk of failure,
whether rolled thread or cut thread. If _no_ rolled threads fail when
properly installed, it's unlikely the small difference made by cutting
the thread will be significant.

> > I'm curious - how much advantage do you think rolled threads have?
> > Because tandem teams have been using caliper brakes roughly forever,
> > and I've not heard of even tandem teams breaking these bolts.

>
> frank, you're the engineer. i'm just the metallurgist. how about you
> do a little work for a change?


This site
http://www.mech.uwa.edu.au/DANotes/threads/fatigue/fatigue.html lists
stress concentration factors of 2.8 for cut threads, vs. 2.2 for rolled
threads. IOW, the cut threads have roughly 25% worse stress
concentration. That's not much difference.

That does not mean, of course, that the cut threads are even _that_
much worse in this situation. As you may know, both Goodman's
Criterion and the more conservative Soderberg Criterion for fatigue
failure apply the stress concentration only to the alternating
component of stress. In normal bolting practice, the (steady) bolt
preload is much larger than the fluctuation in load caused by any
varying external load.

So, more briefly: the advantage of rolled threads would be much less
than even 25%.

We could, I suppose, attempt to work out the actual ratio of safety
factors, but there's no need. Again, we know tandems often run
ordinary caliper brakes. We know that they apply more than twice the
braking force of a single bike (like the OP's), and so far we know of
no tandem failures. This is a quick way of telling that the safety
factor in ordinary brake bolts is significantly greater than two.
Consequently, the slight decrease in safety factor for the OP cutting
his threads is of no consequence.

> > And _certainly_ you can't possibly believe the strength of a cut thread
> > is half that of a rolled thread... can you??

>
> hmm, yet another engineer proving that he doesn't know the difference
> between static and fatigue strength. /and/ one that presumes to teach
> this stuff.


:) I didn't say "static strength." If you think about it, you may
realize "fatigue strength" is a type of strength. But, if you're
really going to split hairs, the proper criterion is "Safety factor in
this situation."

> i call it shameful.


I'm not bothered. From what I can tell, your opinion carries little
weight.


- Frank Krygowski
 
jim beam wrote:
> [email protected] wrote:
> > jim beam wrote:
> >
> >>rolled thread bolts are generally not the same steel at that used for
> >>any responsible cut thread bolt - it's cheaper/weaker material because
> >>the better properties of the rolled thread allow it to be used.

> >
> >
> > Ah.
> >
> > Evidence?
> >
> > - Frank Krygowski
> >

>
> er, aren't you the engineering professor? do you know /anything/ about
> materials?


I know more than most folks, but I don't know that. AFAIK, bolt are
graded by material strength, and a metric 8.8 bolt (for example) has
the same properties whether the threads are cut or rolled.

But if I'm wrong, I'm willing to learn. Why not provide information
and evidence, instead of just insults?

- Frank Krygowski
 
Robin Hubert writes:

>>>> rolled thread bolts are generally not the same steel at that used
>>>> for any responsible cut thread bolt - it's cheaper/weaker
>>>> material because the better properties of the rolled thread allow
>>>> it to be used. /so/ cutting a thread into a rolled thread bolt
>>>> is bad not only because of the cut thread, it's bad because the
>>>> material is not appropriate for it! it this really so hard to
>>>> understand?


>>> I am shocked, shocked to hear that bicycle part designers use
>>> weaker materials that are deemed sufficient, when stronger
>>> materials are available! Is this bad design??? Surely a
>>> calculation of the fatigue properties and loading of these bolts
>>> would reveal the danger of this practice.


>> Get some shock therapy. You may also be surprised that the low
>> paying bicycle industry does not have many competent engineers and
>> that much of the equipment is designed by what might best be called
>> "hobbyists" dabbling in engineering.


>>> This would have been a good argument if you had brought it up in
>>> your first post to this thread. But as the 20th post, after
>>> several other smokescreens, and refusals to post numbers or
>>> references, it looks like moving the goalposts. It's sophistry.
>>> I'm sure you get some kind of gratification out of this strategy
>>> of argument, and it gets you attention, but not everybody will
>>> play with you ad infinitum.


>> I think most readers have recognized this, no useful contributions
>> arising from his postings. To me it's a lot of smartass sniping.


> Jobst, I may have missed it but I don't think you've weighed in on
> this brake bolt debate. What is your position on the original
> question and following discussion?


> Is a cut-thread (vs rolled) brake bolt reliable? Would periodic
> inspection be sufficient to prevent catastrophic results if not?


Stress on a brake bolt is at the forward end in bending for which its
diameter is designed. The thread at the other end is of the (front)
brake bolt is relatively immaterial as long as it is tight because it
serves only to press the bolt collar against the fork crown where it
and the shaft as positioner resist bending torque of braking. Tension
loads are trivial compared to the bending loads so the thread is not a
high stress location. Therefore the whole discussion is a bagatelle.

> For those curious I am test-piloting a SunTour Superbe that I
> threaded for recessed mount as did our OP. As you might've guessed,
> it's the front. Only several thousand miles so far.


Don't give it another thought!

By the way, you may have noticed that Old Crow, as usual, did not
directly commit himself to saying anything about the appropriateness
of such a modification or whether it presented a failure hazard, aka
"beat around the bush."

Jobst Brandt
 
[email protected] wrote:
> jim beam wrote:
>
>>[email protected] wrote:
>>
>>>jim beam wrote:
>>>
>>>
>>>>rolled thread bolts are generally not the same steel at that used for
>>>>any responsible cut thread bolt - it's cheaper/weaker material because
>>>>the better properties of the rolled thread allow it to be used.
>>>
>>>
>>>Ah.
>>>
>>>Evidence?
>>>
>>>- Frank Krygowski
>>>

>>
>>er, aren't you the engineering professor? do you know /anything/ about
>>materials?

>
>
> I know more than most folks, but I don't know that. AFAIK, bolt are
> graded by material strength, and a metric 8.8 bolt (for example) has
> the same properties whether the threads are cut or rolled.


static != fatigue.

>
> But if I'm wrong, I'm willing to learn. Why not provide information
> and evidence, instead of just insults?
>
> - Frank Krygowski
>

frank, i cited a paper with exactly that kind of information. i'm not
spoon feeding you. in addition, there are a myriad of engineering texts
that cover this stuff. even jobst touches this subject it in his book.
 
[email protected] wrote:
> Robin Hubert writes:
>
>
>>>>>rolled thread bolts are generally not the same steel at that used
>>>>>for any responsible cut thread bolt - it's cheaper/weaker
>>>>>material because the better properties of the rolled thread allow
>>>>>it to be used. /so/ cutting a thread into a rolled thread bolt
>>>>>is bad not only because of the cut thread, it's bad because the
>>>>>material is not appropriate for it! it this really so hard to
>>>>>understand?

>
>
>>>>I am shocked, shocked to hear that bicycle part designers use
>>>>weaker materials that are deemed sufficient, when stronger
>>>>materials are available! Is this bad design??? Surely a
>>>>calculation of the fatigue properties and loading of these bolts
>>>>would reveal the danger of this practice.

>
>
>>>Get some shock therapy. You may also be surprised that the low
>>>paying bicycle industry does not have many competent engineers and
>>>that much of the equipment is designed by what might best be called
>>>"hobbyists" dabbling in engineering.

>
>
>>>>This would have been a good argument if you had brought it up in
>>>>your first post to this thread. But as the 20th post, after
>>>>several other smokescreens, and refusals to post numbers or
>>>>references, it looks like moving the goalposts. It's sophistry.
>>>>I'm sure you get some kind of gratification out of this strategy
>>>>of argument, and it gets you attention, but not everybody will
>>>>play with you ad infinitum.

>
>
>>>I think most readers have recognized this, no useful contributions
>>>arising from his postings. To me it's a lot of smartass sniping.

>
>
>>Jobst, I may have missed it but I don't think you've weighed in on
>>this brake bolt debate. What is your position on the original
>>question and following discussion?

>
>
>>Is a cut-thread (vs rolled) brake bolt reliable? Would periodic
>>inspection be sufficient to prevent catastrophic results if not?

>
>
> Stress on a brake bolt is at the forward end in bending for which its
> diameter is designed. The thread at the other end is of the (front)
> brake bolt is relatively immaterial as long as it is tight because it
> serves only to press the bolt collar against the fork crown where it
> and the shaft as positioner resist bending torque of braking. Tension
> loads are trivial compared to the bending loads so the thread is not a
> high stress location. Therefore the whole discussion is a bagatelle.


er, exactly /where/ does the bending occur jobst? it wouldn't be in the
pivot bolt between the nut & the fork front would it? with bending
creating maximum stress at the skin? where the threads run? hmmm.
bending stress at a thread... isn't that a text book fatigue no-no? i
mean, you seem to regard a similar situation as an issue worthy of
attention since you advocate "correcting the spoke line" in your book.
you /have/ seen a pivot bolt and a fork before, right?

>
>
>>For those curious I am test-piloting a SunTour Superbe that I
>>threaded for recessed mount as did our OP. As you might've guessed,
>>it's the front. Only several thousand miles so far.

>
>
> Don't give it another thought!
>
> By the way, you may have noticed that Old Crow, as usual, did not
> directly commit himself to saying anything about the appropriateness
> of such a modification


as usual, you didn't bother to read. did you. don't you hate it when
you do that?

> or whether it presented a failure hazard, aka
> "beat around the bush."
>
> Jobst Brandt


"preconceptions and lack of research R us"
 
[email protected] wrote:
> jim beam wrote:
>
>>[email protected] wrote:
>>
>>>Yes. Thread cutting predates thread rolling. I'd assume that over the
>>>100+ years that bikes have been in existence, there have been millions
>>>of brake bolts of either type.

>>
>>cast irons pre-date bessemer steels. are you advocating a roll back of
>>the evolutionary clock in materials as well?

>
>
> ?? Rolling back the clock? Are you pretending _no_ threads are cut
> these days? Why do you think machine shops have die sets?


holy mackerel. don't you have any shame? or are you suddenly going to
show us a waggonload of hitherto unknown brake manufacturers that cut
not roll?

>
> All I'm saying is that it's safe for the OP to cut those threads.
> You've provided no evidence that it's not, and you've provided no
> evidence that brake bolts in general have significant risk of failure,
> whether rolled thread or cut thread. If _no_ rolled threads fail when
> properly installed, it's unlikely the small difference made by cutting
> the thread will be significant.


for an engineer, and engineering professor, you're scarily thin on
design principles frank. and apparently appropriate material for an
application doesn't even make it into the krygowski landscape.

>
>
>>>I'm curious - how much advantage do you think rolled threads have?
>>>Because tandem teams have been using caliper brakes roughly forever,
>>>and I've not heard of even tandem teams breaking these bolts.

>>
>>frank, you're the engineer. i'm just the metallurgist. how about you
>>do a little work for a change?

>
>
> This site
> http://www.mech.uwa.edu.au/DANotes/threads/fatigue/fatigue.html lists
> stress concentration factors of 2.8 for cut threads, vs. 2.2 for rolled
> threads. IOW, the cut threads have roughly 25% worse stress
> concentration. That's not much difference.


eh? so if a bolt fatigues at 65% of yield at that point, but not at
40%, that's not much difference?

>
> That does not mean, of course, that the cut threads are even _that_
> much worse in this situation. As you may know, both Goodman's
> Criterion and the more conservative Soderberg Criterion for fatigue
> failure apply the stress concentration only to the alternating
> component of stress. In normal bolting practice, the (steady) bolt
> preload is much larger than the fluctuation in load caused by any
> varying external load.
>
> So, more briefly: the advantage of rolled threads would be much less
> than even 25%.


[squirm]

>
> We could, I suppose, attempt to work out the actual ratio of safety
> factors, but there's no need. Again, we know tandems often run
> ordinary caliper brakes. We know that they apply more than twice the
> braking force of a single bike (like the OP's), and so far we know of
> no tandem failures.


show me a tandem brake with a cut thread! as if this is not a
ridiculous argument already.

> This is a quick way of telling that the safety
> factor in ordinary brake bolts is significantly greater than two.
> Consequently, the slight decrease in safety factor for the OP cutting
> his threads is of no consequence.


go work for boeing frank. i'm sure they have an opening for you in the
finance department.

>
>
>>>And _certainly_ you can't possibly believe the strength of a cut thread
>>>is half that of a rolled thread... can you??

>>
>>hmm, yet another engineer proving that he doesn't know the difference
>>between static and fatigue strength. /and/ one that presumes to teach
>>this stuff.

>
>
> :) I didn't say "static strength." If you think about it, you may
> realize "fatigue strength" is a type of strength. But, if you're
> really going to split hairs, the proper criterion is "Safety factor in
> this situation."


so if you know what you're doing, why are you so consistently
deliberately ambiguous? anyone would think you didn't want to admit
weakness in your argument.

>
>
>> i call it shameful.

>
>
> I'm not bothered. From what I can tell, your opinion carries little
> weight.
>
>
> - Frank Krygowski
>

i'm not an engineering professor. you are. and you collect a paycheck
for it too. that gives you responsibilities as soon as you open your
mouth and try making out like i don't know what i'd doing, not a license
to duck and dive when the math gets hard.
 
jim beam wrote:
> [email protected] wrote:
> >
> >
> > This site
> > http://www.mech.uwa.edu.au/DANotes/threads/fatigue/fatigue.html lists
> > stress concentration factors of 2.8 for cut threads, vs. 2.2 for rolled
> > threads. IOW, the cut threads have roughly 25% worse stress
> > concentration. That's not much difference.

>
> eh? so if a bolt fatigues at 65% of yield at that point, but not at
> 40%, that's not much difference?


That sentence indicates you don't understand how this sort of design is
done. Hell, you don't seem to understand the diffference between
ratios and subtraction!

> >
> > That does not mean, of course, that the cut threads are even _that_
> > much worse in this situation. As you may know, both Goodman's
> > Criterion and the more conservative Soderberg Criterion for fatigue
> > failure apply the stress concentration only to the alternating
> > component of stress. In normal bolting practice, the (steady) bolt
> > preload is much larger than the fluctuation in load caused by any
> > varying external load.
> >
> > So, more briefly: the advantage of rolled threads would be much less
> > than even 25%.

>
> [squirm]


OK, Jim, if mentioning some standard methods used in fatigue design
looks like "squirm" to you, then you're not capable of discussing this
further. I'm joining the many others who are no longer wasting their
time on you.

- Frank Krygowski
 
[email protected] wrote:
> jim beam wrote:
>
>>[email protected] wrote:
>>
>>>
>>>This site
>>>http://www.mech.uwa.edu.au/DANotes/threads/fatigue/fatigue.html lists
>>>stress concentration factors of 2.8 for cut threads, vs. 2.2 for rolled
>>>threads. IOW, the cut threads have roughly 25% worse stress
>>>concentration. That's not much difference.

>>
>>eh? so if a bolt fatigues at 65% of yield at that point, but not at
>>40%, that's not much difference?

>
>
> That sentence indicates you don't understand how this sort of design is
> done. Hell, you don't seem to understand the diffference between
> ratios and subtraction!


eh? is there /no/ depth to your shame?

>
>
>>>That does not mean, of course, that the cut threads are even _that_
>>>much worse in this situation. As you may know, both Goodman's
>>>Criterion and the more conservative Soderberg Criterion for fatigue
>>>failure apply the stress concentration only to the alternating
>>>component of stress. In normal bolting practice, the (steady) bolt
>>>preload is much larger than the fluctuation in load caused by any
>>>varying external load.
>>>
>>>So, more briefly: the advantage of rolled threads would be much less
>>>than even 25%.

>>
>>[squirm]

>
>
> OK, Jim, if mentioning some standard methods used in fatigue design
> looks like "squirm" to you, then you're not capable of discussing this
> further. I'm joining the many others who are no longer wasting their
> time on you.
>
> - Frank Krygowski
>

frank, you've consistently avoided every pertinent point in this and
every other debate we've ever had. with heavy doses of deliberate
distortion thrown in just for spice, your /only/ interest being argument
- the science can be damned for all the interest you ever pay it. but
at last, we have something on which we both agree, professor, you are
indeed wasting your time.
 
Johnnie Walker writes:

>>>>>> rolled thread bolts are generally not the same steel at that
>>>>>> used for any responsible cut thread bolt - it's cheaper/weaker
>>>>>> material because the better properties of the rolled thread
>>>>>> allow it to be used. /so/ cutting a thread into a rolled
>>>>>> thread bolt is bad not only because of the cut thread, it's bad
>>>>>> because the material is not appropriate for it! it this really
>>>>>> so hard to understand?


>>>>> I am shocked, shocked to hear that bicycle part designers use
>>>>> weaker materials that are deemed sufficient, when stronger
>>>>> materials are available! Is this bad design??? Surely a
>>>>> calculation of the fatigue properties and loading of these bolts
>>>>> would reveal the danger of this practice.


>>>> Get some shock therapy. You may also be surprised that the low
>>>> paying bicycle industry does not have many competent engineers and
>>>> that much of the equipment is designed by what might best be called
>>>> "hobbyists" dabbling in engineering.


>>>>> This would have been a good argument if you had brought it up in
>>>>> your first post to this thread. But as the 20th post, after
>>>>> several other smokescreens, and refusals to post numbers or
>>>>> references, it looks like moving the goalposts. It's sophistry.
>>>>> I'm sure you get some kind of gratification out of this strategy
>>>>> of argument, and it gets you attention, but not everybody will
>>>>> play with you ad infinitum.


>>>> I think most readers have recognized this, no useful contributions
>>>> arising from his postings. To me it's a lot of smartass sniping.


>>> Jobst, I may have missed it but I don't think you've weighed in on
>>> this brake bolt debate. What is your position on the original
>>> question and following discussion?

>>
>>
>>> Is a cut-thread (vs rolled) brake bolt reliable? Would periodic
>>> inspection be sufficient to prevent catastrophic results if not?

>>
>>
>> Stress on a brake bolt is at the forward end in bending for which its
>> diameter is designed. The thread at the other end is of the (front)
>> brake bolt is relatively immaterial as long as it is tight because it
>> serves only to press the bolt collar against the fork crown where it
>> and the shaft as positioner resist bending torque of braking. Tension
>> loads are trivial compared to the bending loads so the thread is not a
>> high stress location. Therefore the whole discussion is a bagatelle.


> er, exactly /where/ does the bending occur jobst? it wouldn't be in the
> pivot bolt between the nut & the fork front would it? with bending
> creating maximum stress at the skin? where the threads run? hmmm.
> bending stress at a thread... isn't that a text book fatigue no-no? i
> mean, you seem to regard a similar situation as an issue worthy of
> attention since you advocate "correcting the spoke line" in your book.
> you /have/ seen a pivot bolt and a fork before, right?


Campagnolo brakes in my collection have threads at the end of the
pivot bolt and are one piece with the boss that holds the return
spring where it butts against the fork crown. Shimano uses a stepped
bolt that has a rolled thread. The thread in question is at the far
end of the bolt where no bending loads occur.

http://bike.shimano.com/media/cycli...nents/BR/EV-BR-5501_v2_m56577569830538405.pdf

>>> For those curious I am test-piloting a SunTour Superbe that I
>>> threaded for recessed mount as did our OP. As you might've
>>> guessed, it's the front. Only several thousand miles so far.


>> Don't give it another thought!


>> By the way, you may have noticed that Old Crow, as usual, did not
>> directly commit himself to saying anything about the
>> appropriateness of such a modification


> as usual, you didn't bother to read. did you. don't you hate it
> when you do that?


>> or whether it presented a failure hazard, aka
>> "beat around the bush."


> "preconceptions and lack of research R us"


Speak for yourself.

Jobst Brandt
 
[email protected] wrote:
> Johnnie Walker writes:
>
>
>>>>>>>rolled thread bolts are generally not the same steel at that
>>>>>>>used for any responsible cut thread bolt - it's cheaper/weaker
>>>>>>>material because the better properties of the rolled thread
>>>>>>>allow it to be used. /so/ cutting a thread into a rolled
>>>>>>>thread bolt is bad not only because of the cut thread, it's bad
>>>>>>>because the material is not appropriate for it! it this really
>>>>>>>so hard to understand?

>
>
>>>>>>I am shocked, shocked to hear that bicycle part designers use
>>>>>>weaker materials that are deemed sufficient, when stronger
>>>>>>materials are available! Is this bad design??? Surely a
>>>>>>calculation of the fatigue properties and loading of these bolts
>>>>>>would reveal the danger of this practice.

>
>
>>>>>Get some shock therapy. You may also be surprised that the low
>>>>>paying bicycle industry does not have many competent engineers and
>>>>>that much of the equipment is designed by what might best be called
>>>>>"hobbyists" dabbling in engineering.

>
>
>>>>>>This would have been a good argument if you had brought it up in
>>>>>>your first post to this thread. But as the 20th post, after
>>>>>>several other smokescreens, and refusals to post numbers or
>>>>>>references, it looks like moving the goalposts. It's sophistry.
>>>>>>I'm sure you get some kind of gratification out of this strategy
>>>>>>of argument, and it gets you attention, but not everybody will
>>>>>>play with you ad infinitum.

>
>
>>>>>I think most readers have recognized this, no useful contributions
>>>>>arising from his postings. To me it's a lot of smartass sniping.

>
>
>>>>Jobst, I may have missed it but I don't think you've weighed in on
>>>>this brake bolt debate. What is your position on the original
>>>>question and following discussion?
>>>
>>>
>>>>Is a cut-thread (vs rolled) brake bolt reliable? Would periodic
>>>>inspection be sufficient to prevent catastrophic results if not?
>>>
>>>
>>>Stress on a brake bolt is at the forward end in bending for which its
>>>diameter is designed. The thread at the other end is of the (front)
>>>brake bolt is relatively immaterial as long as it is tight because it
>>>serves only to press the bolt collar against the fork crown where it
>>>and the shaft as positioner resist bending torque of braking. Tension
>>>loads are trivial compared to the bending loads so the thread is not a
>>>high stress location. Therefore the whole discussion is a bagatelle.

>
>
>>er, exactly /where/ does the bending occur jobst? it wouldn't be in the
>>pivot bolt between the nut & the fork front would it? with bending
>>creating maximum stress at the skin? where the threads run? hmmm.
>>bending stress at a thread... isn't that a text book fatigue no-no? i
>>mean, you seem to regard a similar situation as an issue worthy of
>>attention since you advocate "correcting the spoke line" in your book.
>>you /have/ seen a pivot bolt and a fork before, right?

>
>
> Campagnolo brakes in my collection have threads at the end of the
> pivot bolt and are one piece with the boss that holds the return
> spring where it butts against the fork crown. Shimano uses a stepped
> bolt that has a rolled thread. The thread in question is at the far
> end of the bolt where no bending loads occur.
>
> http://bike.shimano.com/media/cycli...nents/BR/EV-BR-5501_v2_m56577569830538405.pdf


maybe i missed it; does that explain how the bolt doesn't bend? it's
loaded perpendicular to its axis - by definition that means bending. to
argue otherwise is like attributing spoke elbow fatigue to residual
stress rather than the non-axial bending which is actually occurring.

>
>
>>>>For those curious I am test-piloting a SunTour Superbe that I
>>>>threaded for recessed mount as did our OP. As you might've
>>>>guessed, it's the front. Only several thousand miles so far.

>
>
>>>Don't give it another thought!

>
>
>>>By the way, you may have noticed that Old Crow, as usual, did not
>>>directly commit himself to saying anything about the
>>>appropriateness of such a modification

>
>
>>as usual, you didn't bother to read. did you. don't you hate it
>>when you do that?

>
>
>>>or whether it presented a failure hazard, aka
>>>"beat around the bush."

>
>
>>"preconceptions and lack of research R us"

>
>
> Speak for yourself.
>
> Jobst Brandt
 
"jim beam" <[email protected]> wrote in message
news:[email protected]...

> >
> > Yeah. All that is completely irrelevant to this thread. This thread was
> > about someone who needed more threads on his bolt and wanted to run a

die
> > round it until he had them, and jim beam being his alarmist self. It
> > didn't have anything to do with design or with how the things are
> > manufactured until he came in.
> >
> > Jasper

>
> you sound like the other guy that thinks fatigue doesn't matter. maybe
> you can get a cost cutting job at boeing too.


But in _this_ case, it does indeed not matter.

Properly fastened brake bolts do not fail, whether they have cut or rolled
threads. Fatigue is not an issue. Th original poster can go right ahead
and run the die down his brake bolt - it will not result in "...a disaster
waiting to happen."
 
"jim beam" <[email protected]> wrote in message
news:[email protected]...

> >
> > Yeah. All that is completely irrelevant to this thread. This thread was
> > about someone who needed more threads on his bolt and wanted to run a

die
> > round it until he had them, and jim beam being his alarmist self. It
> > didn't have anything to do with design or with how the things are
> > manufactured until he came in.
> >
> > Jasper

>
> you sound like the other guy that thinks fatigue doesn't matter. maybe
> you can get a cost cutting job at boeing too.


But in _this_ case, it does indeed not matter.

Properly fastened brake bolts do not fail, whether they have cut or rolled
threads. Fatigue is not an issue. Th original poster can go right ahead
and run the die down his brake bolt - it will not result in "...a disaster
waiting to happen."