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Single-Bolt Seatpost saddle slippage?



 
 
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  #21  
Old June 11th 08, 03:07 PM posted to rec.bicycles.tech
jim beam
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Default Single-Bolt Seatpost saddle slippage?

Tom Kunich wrote:
"John Forrest Tomlinson" wrote in message
...

I was simply pointing out that a bolt breaking doesn't
necessarily result in injury -- which you said it did, at first,
without qualification.


I'm beginning to get the idea that John is starting to use the group to
work off his aggressions


that's not an accurate assessment of this situation. this is one of
jobst's favorite games - the switch between aggressor and victim.

rather than admit to [and correct] one of his frequent mistakes, jobst
vociferously and personally attacks instead. then, when the aggressee
defends [naturally, because defense of the mistake is unjustified],
jobst switches and plays the victim of an "unwarranted" attack!

it's grossly inappropriate and highly childish, but apparently a
successful strategy when it comes to soliciting sympathy from those who
are susceptible to suggestion.


which obviously is one of the problems with
groups in general. I suppose it is getting to be time to ignore his
postings if they aren't going to add anything.

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  #22  
Old June 11th 08, 03:40 PM posted to rec.bicycles.tech
John Forrest Tomlinson
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Default Single-Bolt Seatpost saddle slippage?

On Wed, 11 Jun 2008 07:07:24 -0700, jim beam
wrote:

Tom Kunich wrote:
"John Forrest Tomlinson" wrote in message
...

I was simply pointing out that a bolt breaking doesn't
necessarily result in injury -- which you said it did, at first,
without qualification.


I'm beginning to get the idea that John is starting to use the group to
work off his aggressions


that's not an accurate assessment of this situation. this is one of
jobst's favorite games - the switch between aggressor and victim.


It's possibly true, but in this case I simply and politiely pointed
out an inconsistency in what Jobst wrote and he then starts
questioning "good faith" rather than simply saying "Yeah, I mispoke"
and leaving it at that.

So I get annoyed.

Tom is still an ass regardless.

  #23  
Old June 11th 08, 03:48 PM posted to rec.bicycles.tech
JG
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Posts: 295
Default Single-Bolt Seatpost saddle slippage?

Jim, it appears you have done what you constantly accuse Jobst of
doing - talked about something you haven't actually looked at.

The Campy SR post has a semi-circular top with the bolt below on an
inner radius. If it breaks, the clamp wants to slide off. The
Suntour Superb has a cradle top. Should one bolt fail, the clamp is
still cradled on the top of the post.

JG

  #24  
Old June 11th 08, 04:07 PM posted to rec.bicycles.tech
jim beam
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Posts: 5,758
Default Single-Bolt Seatpost saddle slippage?

JG wrote:
Jim, it appears you have done what you constantly accuse Jobst of
doing - talked about something you haven't actually looked at.

The Campy SR post has a semi-circular top with the bolt below on an
inner radius. If it breaks, the clamp wants to slide off. The
Suntour Superb has a cradle top. Should one bolt fail, the clamp is
still cradled on the top of the post.


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. furthermore, the design which jobst holds up
as "superior" really isn't because one bolt at either end of a two-bolt
clamp is incapable of preventing tipping, so you're pretty much in the
same position.

as for ability to follow this thread, you're still making the mistake
jobst wants you to make. jobst's response is that of the righteous
victim. in reality, /he's/ the [unjustified] aggressor - and you need
to learn that distinction. if you can't follow the technical argument,
you're in a difficult position because in most cases, it would be
correct to assume that a "victim" was the one being wronged. but in
this case, the "victim" is actually the one doing the attacking, so
you're [successfully] being suckered.

  #25  
Old June 11th 08, 05:37 PM posted to rec.bicycles.tech
Tom Kunich
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Posts: 6,456
Default Single-Bolt Seatpost saddle slippage?

"Bill Sornson" wrote in message
...
Tom Kunich wrote:
"John Forrest Tomlinson" wrote in message
...

I was simply pointing out that a bolt breaking doesn't
necessarily result in injury -- which you said it did, at first,
without qualification.


I'm beginning to get the idea that John is starting to use the group
to work off his aggressions which obviously is one of the problems
with groups in general. I suppose it is getting to be time to ignore
his postings if they aren't going to add anything.


I plonked ol' Flogittodeathlinson because he's personally abusive and uses
dishonest, weasel tactics (like snipping material to hide or, much worse,
alter meaning).


I've been bending over backwards to give him a break because he's been a
REAL(tm) bicycle racer which is rare on these groups. Originally he had a
lot of good things to add and was a nice conservative voice from the pack.
Lately however, he's gotten pretty weird.

  #26  
Old June 11th 08, 06:39 PM posted to rec.bicycles.tech
John Forrest Tomlinson
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Posts: 6,564
Default Single-Bolt Seatpost saddle slippage?

Tom Kunich wrote:
I've been bending over backwards to give him a break because he's
been a REAL(tm) bicycle racer which is rare on these groups.
Originally he had a lot of good things to add and was a nice
conservative voice from the pack. Lately however, he's gotten pretty
weird.


No Tom, I just got fed up with your nonsense and stopped being
"polite".

Plus, as the US goes to hell it's even more disturbing to hear nuts
like you and Sorni defending evil. Voting for, say, Bush 1 or Reagan
is something we can disagree on and discuss. Supporting, say, Bush 2
for his second term, after what he's done to the constitution, the
economy and our soldiers is inexcusable and defense of it really shows
who you are. I wish I'd understood you earlier.

  #27  
Old June 11th 08, 07:04 PM posted to rec.bicycles.tech
Tom Kunich
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Posts: 6,456
Default Single-Bolt Seatpost saddle slippage?

"John Forrest Tomlinson" wrote in message
...

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.

Supporting, say, Bush 2
for his second term, after what he's done to the constitution, the
economy and our soldiers is inexcusable and defense of it really shows
who you are. I wish I'd understood you earlier.


What service were you in?

  #28  
Old June 11th 08, 09:19 PM posted to rec.bicycles.tech
JG
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Posts: 295
Default Single-Bolt Seatpost saddle slippage?

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... 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. Probably nobody is, as it would require well
controlled actuary data sets with enough incidents to be meaningful.
That leaves only anecdote and thought experiment to persuade.

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

JG
  #29  
Old June 11th 08, 10:31 PM posted to rec.bicycles.tech
jim beam
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Posts: 5,758
Default Single-Bolt Seatpost saddle slippage?

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.


  #30  
Old June 11th 08, 10:39 PM posted to rec.bicycles.tech
Tom Kunich
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Posts: 6,456
Default Single-Bolt Seatpost saddle slippage?

"jim beam" wrote in message
...
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.

 




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