Single-Bolt Seatpost saddle slippage?

jim beam

JG wrote:
>> i'm aware of that design. and it doesn't have the immediate "dump" fail
>> mode of which jobst accuses it since the post head and the bottom of the
>> cradle are in compression.
>
> Uh, you mean the compression from the rider sitting on it!?!? That
> doesn't make it stable because actually it's under torque...

er, that's bending, not torque. and the degree depends on rider
position. any idea how seat rail positioning evolved?


> and if
> the rider didn't have his weight on the saddle , it wouldn't be a
> problem.
>
> Face it, neither you nor Jobst are competent to state the risk rate of
> one or two bolt designs.

really? personally, i feel pretty well qualified to differentiate
between torque and bending.


> Probably nobody is, as it would require well
> controlled actuary data sets with enough incidents to be meaningful.

nobody is qualified to assess risk of one design over another? that's
like saying that the only way you can assess whether a plane is
airworthy is to crash it so you have "enough incidents to be
meaningful"!!!

reality check: every single time you sit on your bike seat and it
doesn't break, that is an "incident" with a positive outcome. the
science of metal fatigue is well advanced and allows very high
confidence for given outcomes like this - provided a designer bothers to
read any of the last century's worth of research on the subject that is.


> That leaves only anecdote and thought experiment to persuade.

what good is "thought experiment" when one doesn't even grasp enough of
the fundamentals to understand the matter at hand?


>
> But why bother? What advantage does a one bolt design have, other
> than, "Look Ma! One bolt!", over its obvious drawbacks?

even clamp loading for one.

as with many things jobstian, grabbing onto one small element of a
design, then broadcasting it as if it's the whole story, leads to gross
misunderstanding. embarrassment for the broadcaster too, if they are
capable of receiving and not just transmitting.

here's reality: double bolt designs offer no significant safety over
single bolt because once one bolt goes, the other is unbalanced and
cannot sustain anything other than a trivial load. properly executed
single bolt designs otoh are absolutely strong enough for the job.
proven non-redundant design elements are used throughout a bicycle.
there's no logical reason, particularly in view of the above, that a
seat post clamp needs, or even can successfully utilize, two bolts.

Tom Kunich

"jim beam" <spamvortex@bad.example.net> wrote in message
news:t_-dnaWJtOGi2c3VnZ2dnUVZ_oDinZ2d@speakeasy.net...
> JG wrote:
>>
>> Uh, you mean the compression from the rider sitting on it!?!? That
>> doesn't make it stable because actually it's under torque...
>
> er, that's bending, not torque. and the degree depends on rider position.
> any idea how seat rail positioning evolved?

As you PEDAL you put rotational loads on the saddle back and forth. You do
understand that don't you?

>> Face it, neither you nor Jobst are competent to state the risk rate of
>> one or two bolt designs.
>
> really? personally, i feel pretty well qualified to differentiate between
> torque and bending.

And you demonstrated that exactly when?

>> Probably nobody is, as it would require well
>> controlled actuary data sets with enough incidents to be meaningful.
>
> nobody is qualified to assess risk of one design over another? that's
> like saying that the only way you can assess whether a plane is airworthy
> is to crash it so you have "enough incidents to be meaningful"!!!

I see.... You don't have a clue about aircraft design either.

jim beam

Tom Kunich wrote:
> "jim beam" <spamvortex@bad.example.net> wrote in message
> news:t_-dnaWJtOGi2c3VnZ2dnUVZ_oDinZ2d@speakeasy.net...
>> JG wrote:
>>>
>>> Uh, you mean the compression from the rider sitting on it!?!? That
>>> doesn't make it stable because actually it's under torque...
>>
>> er, that's bending, not torque. and the degree depends on rider
>> position. any idea how seat rail positioning evolved?
>
> As you PEDAL you put rotational loads on the saddle back and forth. You
> do understand that don't you?
>
>>> Face it, neither you nor Jobst are competent to state the risk rate of
>>> one or two bolt designs.
>>
>> really? personally, i feel pretty well qualified to differentiate
>> between torque and bending.
>
> And you demonstrated that exactly when?
>
>>> Probably nobody is, as it would require well
>>> controlled actuary data sets with enough incidents to be meaningful.
>>
>> nobody is qualified to assess risk of one design over another? that's
>> like saying that the only way you can assess whether a plane is
>> airworthy is to crash it so you have "enough incidents to be
>> meaningful"!!!
>
> I see.... You don't have a clue about aircraft design either.

tom, this conversation lacks two elements for continuation:

1. a point - because inability to understand the difference between
torque and bending is a fundamental prerequisite.

2. the scent of sincerity - all i smell from you right now is "let's you
and me fight".

one last thing - don't snip content out of context, and /definitely/ not
without annotation. thanks so much.

Tom Kunich

"jim beam" <spamvortex@bad.example.net> wrote in message
news:PL2dnbeeCbFa1M3VnZ2dnUVZ_vzinZ2d@speakeasy.net...
> Tom Kunich wrote:
>> "jim beam" <spamvortex@bad.example.net> wrote in message
>> news:t_-dnaWJtOGi2c3VnZ2dnUVZ_oDinZ2d@speakeasy.net...
>>> JG wrote:
>>>>
>>>> Uh, you mean the compression from the rider sitting on it!?!? That
>>>> doesn't make it stable because actually it's under torque...
>>>
>>> er, that's bending, not torque. and the degree depends on rider
>>> position. any idea how seat rail positioning evolved?
>>
>> As you PEDAL you put rotational loads on the saddle back and forth. You
>> do understand that don't you?
>>
>>>> Face it, neither you nor Jobst are competent to state the risk rate of
>>>> one or two bolt designs.
>>>
>>> really? personally, i feel pretty well qualified to differentiate
>>> between torque and bending.
>>
>> And you demonstrated that exactly when?
>>
>>>> Probably nobody is, as it would require well
>>>> controlled actuary data sets with enough incidents to be meaningful.
>>>
>>> nobody is qualified to assess risk of one design over another? that's
>>> like saying that the only way you can assess whether a plane is
>>> airworthy is to crash it so you have "enough incidents to be
>>> meaningful"!!!
>>
>> I see.... You don't have a clue about aircraft design either.
>
> tom, this conversation lacks two elements for continuation:
>
> 1. a point - because inability to understand the difference between torque
> and bending is a fundamental prerequisite.

Perhaps you can explain to me why you're arguing about bending when the rest
of us are discussing the fact that if the bold on a single bolt mechanism
breaks that you have ROTATIONAL forces applied to it?

> 2. the scent of sincerity - all i smell from you right now is "let's you
> and me fight".

You are the one that picks a fight with everything that Jobst writes. Often
you have to really stretch it to force his writing into some sort of form in
order to criticize it.

At times it appears that you actually have a mechanical education but then
you start trying to argue that the important forces on a single bolt
seatpost are BENDING after the bolt has been broken?

> one last thing - don't snip content out of context, and /definitely/ not
> without annotation. thanks so much.

Perhaps you'd be kind enough to take your own advice?

jim beam

Tom Kunich wrote:
> "jim beam" <spamvortex@bad.example.net> wrote in message
> news:PL2dnbeeCbFa1M3VnZ2dnUVZ_vzinZ2d@speakeasy.net...
>> Tom Kunich wrote:
>>> "jim beam" <spamvortex@bad.example.net> wrote in message
>>> news:t_-dnaWJtOGi2c3VnZ2dnUVZ_oDinZ2d@speakeasy.net...
>>>> JG wrote:
>>>>>
>>>>> Uh, you mean the compression from the rider sitting on it!?!? That
>>>>> doesn't make it stable because actually it's under torque...
>>>>
>>>> er, that's bending, not torque. and the degree depends on rider
>>>> position. any idea how seat rail positioning evolved?
>>>
>>> As you PEDAL you put rotational loads on the saddle back and forth.
>>> You do understand that don't you?
>>>
>>>>> Face it, neither you nor Jobst are competent to state the risk rate of
>>>>> one or two bolt designs.
>>>>
>>>> really? personally, i feel pretty well qualified to differentiate
>>>> between torque and bending.
>>>
>>> And you demonstrated that exactly when?
>>>
>>>>> Probably nobody is, as it would require well
>>>>> controlled actuary data sets with enough incidents to be meaningful.
>>>>
>>>> nobody is qualified to assess risk of one design over another?
>>>> that's like saying that the only way you can assess whether a plane
>>>> is airworthy is to crash it so you have "enough incidents to be
>>>> meaningful"!!!
>>>
>>> I see.... You don't have a clue about aircraft design either.
>>
>> tom, this conversation lacks two elements for continuation:
>>
>> 1. a point - because inability to understand the difference between
>> torque and bending is a fundamental prerequisite.
>
> Perhaps you can explain to me why you're arguing about bending when the
> rest of us are discussing the fact that if the bold on a single bolt
> mechanism breaks that you have ROTATIONAL forces applied to it?

eh? a bolt is loaded in tension or shear. it's only subject to
rotation when it's being fastened.


>
>> 2. the scent of sincerity - all i smell from you right now is "let's
>> you and me fight".
>
> You are the one that picks a fight with everything that Jobst writes.

that's misrepresentation - i don't bother with the majority of his
emissions - only the stuff that's "tech" and blatantly wrong.


> Often you have to really stretch it to force his writing into some sort
> of form in order to criticize it.
>
> At times it appears that you actually have a mechanical education but
> then you start trying to argue that the important forces on a single
> bolt seatpost are BENDING after the bolt has been broken?

see above.


>
>> one last thing - don't snip content out of context, and /definitely/
>> not without annotation. thanks so much.
>
> Perhaps you'd be kind enough to take your own advice?
>

i haven't snipped a single letter in this thread. you otoh have snipped
whole paragraphs that in fact answered points that you have then tried
to argue against. not very honest of you.

Tom Kunich

"jim beam" <spamvortex@bad.example.net> wrote in message
news:qbydnTEAz6_ayc3VnZ2dnUVZ_sLinZ2d@speakeasy.net...
> Tom Kunich wrote:
>>
>> Perhaps you can explain to me why you're arguing about bending when the
>> rest of us are discussing the fact that if the bold on a single bolt
>> mechanism breaks that you have ROTATIONAL forces applied to it?
>
> eh? a bolt is loaded in tension or shear. it's only subject to rotation
> when it's being fastened.

Ahh, I see - you don't understand that we're talking about the SADDLE and
not the bolt. No wonder you don't have any answers that make sense.

>>> 2. the scent of sincerity - all i smell from you right now is "let's you
>>> and me fight".
>>
>> You are the one that picks a fight with everything that Jobst writes.
>
> that's misrepresentation - i don't bother with the majority of his
> emissions - only the stuff that's "tech" and blatantly wrong.

Your idea of "blatant" and the Encyclopedia Britannica are substantially
different.

jim beam

Tom Kunich wrote:
> "jim beam" <spamvortex@bad.example.net> wrote in message
> news:qbydnTEAz6_ayc3VnZ2dnUVZ_sLinZ2d@speakeasy.net...
>> Tom Kunich wrote:
>>>
>>> Perhaps you can explain to me why you're arguing about bending when
>>> the rest of us are discussing the fact that if the bold on a single
>>> bolt mechanism breaks that you have ROTATIONAL forces applied to it?
>>
>> eh? a bolt is loaded in tension or shear. it's only subject to
>> rotation when it's being fastened.
>
> Ahh, I see - you don't understand that we're talking about the SADDLE
> and not the bolt. No wonder you don't have any answers that make sense.

pleeese. the saddle rails bend. what next - discuss the torque effect
of sweat on leather. give us a break.


>
>>>> 2. the scent of sincerity - all i smell from you right now is "let's
>>>> you and me fight".
>>>
>>> You are the one that picks a fight with everything that Jobst writes.
>>
>> that's misrepresentation - i don't bother with the majority of his
>> emissions - only the stuff that's "tech" and blatantly wrong.
>
> Your idea of "blatant" and the Encyclopedia Britannica are substantially
> different.

tom, if you want to play, play it straight. thanks.

smokey

On Jun 9, 10:47*pm, Andrew F Martin <andrew.franklin.mar...@gmail.com>
wrote:
> I've got a Madone with the Bontrager single-bolt Seat Mast. 3 straight
> races I've hit a bump and had the saddle nose drop significantly.
> Anybody else have this problem with a single-bolt design? *I'm 180 and
> do tent to slide forward to the nose of the saddle (Arione) when I'm
> digging hard.
>
> My shop said to try carbon prep, and it seems a lot stickier, but
> setting up the angle was a pain. *Any alternatives? *Anybody know of
> an aftermarket Madone Seat Mast with a traditional 2-bolt design?


One thing that I've used successfully on slipping metal parts is
automotive valve lapping compound. It stopped the metal post from
slipping down in my steel framed Lemond. It might also work on your
seat post head. It can be found at any auto parts store.

Smokey

Luke

In article <POudnWnpNOpTjs3VnZ2dnUVZ_rzinZ2d@earthlink.com>, Tom Kunich
<cyclintom@yahoo.> wrote:

> "John Forrest Tomlinson" <usenetremove@jt10000.com> wrote in message
> news:v530545k1kgic5vt7pqv1i042g4i4vanpd@4ax.com...
> >
> > No Tom, I just got fed up with your nonsense and stopped being
> > "polite".
>
> Because you've gone over the edge don't blame it on someone else.
>
> > Plus, as the US goes to hell it's even more disturbing to hear nuts
> > like you and Sorni defending evil.
>
> I find it interesting that you seem intent on spelling Sorinson's name
> incorrectly. That has a great deal to say about you.

Let's give BS his due: his name is spelled S-O-R-N-S-O-N!

John Forrest Tomlinson

On Thu, 12 Jun 2008 12:22:08 -0700 (PDT), smokey
<smokeystrodtman@gmail.com> wrote:

>valve lapping compound

What is that?

Dan O

On Jun 12, 3:54 pm, John Forrest Tomlinson <usenetrem...@jt10000.com>
wrote:
> On Thu, 12 Jun 2008 12:22:08 -0700 (PDT), smokey
>
> <smokeystrodt...@gmail.com> wrote:
> >valve lapping compound
>
> What is that?

Gritty paste.

A Muzi

> smokey <smokeystrodtman@gmail.com> wrote:
>> valve lapping compound

John Forrest Tomlinson wrote:
> What is that?

Not much different from toothpaste, essentially.
It's used to lap in valve to valve seat interface; i.e., metal polishing
paste. IIRC they're both diatomaceous earth.
--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971
** Posted from http://www.teranews.com **