Single-Bolt Seatpost saddle slippage?

On 11 Jun 2008 00:47:55 GMT, wrote:

John Forrest Tomlinson wrote:

The same goes for seat post saddle clamps. If the single bolt
fails, the rider falls onto the rotating rear wheel to produce an
involuntary colostomy.


If the degree of danger if the bolt breaks varies with different
designs, I don't understand why you say "the rider falls" as if that
is a consistent outcome.

You can only seriously say that having deleted what I had written and
reinserted. I explained why the single bolt is hazardous and the
difference between a heavy Schwinn attachment and a pseudo Campagnolo
attachment that uses a single bolt the original size. I included the
disclaimer: "I suspect these posts are the ones under discussion."

From your comment I'm not convinced you are posting in good faith.
Your question was anticipated and previously answered.

Here is what you wrote earlier:

That depends on how clever the design is. Old Schwinn balloon tired
bicycles had single bolt clamps that with bolt failure the saddle
could not fall away from under the rider as the current light weight
designs "racing" do. Old Campagnolo Record posts had two bolts with
which two bridge clamps allowed fore and aft sliding and by
differential tightening adjust the fore and aft tilt.

You wrote "that depends on the design" after saying that "If the
single bolt fails, the rider falls onto the rotating rear wheel"

Again, you made a definitive and comprehensive statement, and then
qualified it to apply to only some situations and not others. The
earlier statement was simply wrong in trying to be comprehensive.
That's all I'm saying and I'm saying it in quite good faith. And
laughing.

wrote:
John Forrest Tomlinson wrote:

The same goes for seat post saddle clamps. If the single bolt
fails, the rider falls onto the rotating rear wheel to produce an
involuntary colostomy.

For sure that's a potentially dangerous situation, but not quite
as definitely dangerous as you say. I've had it happen twice --
around 1992 and around 2002 and neither time did I hurt myself.

But yeah, reliability in that area is important. The seatposts on
my bikes are now single bolt, but sturdier (I hope). At least the
bolts are bigger.

That depends on how clever the design is. Old Schwinn balloon
tired bicycles had single bolt clamps that with bolt failure the
saddle could not fall away from under the rider as the current
light weight designs "racing" do. Old Campagnolo Record posts had
two bolts with which two bridge clamps allowed fore and aft sliding
and by differential tightening adjust the fore and aft tilt.

This attachment was reduced to a single bolt by others at a later
date without anyone questioning its safety and failure mode. I
suspect these posts are the ones under discussion.

If the degree of danger if the bolt breaks varies with different
designs, I don't understand why you say "the rider falls" as if that
is a consistent outcome.

You can only seriously say that having deleted what I had written and
reinserted. I explained why the single bolt is hazardous and the
difference between a heavy Schwinn attachment and a pseudo Campagnolo
attachment that uses a single bolt the original size. I included the
disclaimer: "I suspect these posts are the ones under discussion."

From your comment I'm not convinced you are posting in good faith.
Your question was anticipated and previously answered.

but jobst, you contradict yourself. upstream you say: "the saddle could
not fall away from under the rider as the current light weight designs
"racing" do." well, i've looked at every single one of my "racing" seat
posts, and not a single one will allow the seat to "fall away" in the
event of bolt breakage because the bottom cradle rests in compression on
the post head.

could it possibly be that you're contemplating some dim and distant
memory of some design you once saw and are using that as criticism for
the last 30 years of seat posts? because that would be entirely in
character with some of your other bizarre rants about equipment you
don't own or use.

how many brands do you possess btw? and how old are they? i ask
because every single one of the campy, ritchie, easton, weyless, or
other cheapo nameless brands i possess all have the cradle in
compression against the head.

oh, and on the subject of bolt breakage, the only bending or tensile
load on that bolt is from seat tilting. unless the seat is mounted at
the extreme of one or other end of its rails, there's not much fatigue
load. but you'd see that if you actually possessed a modern seat post.
or could be bothered to look at one.

John Forrest Tomlinson wrote:

The same goes for seat post saddle clamps. If the single bolt
fails, the rider falls onto the rotating rear wheel to produce an
involuntary colostomy.

If the degree of danger if the bolt breaks varies with different
designs, I don't understand why you say "the rider falls" as if that
is a consistent outcome.

You can only seriously say that having deleted what I had written and
reinserted. I explained why the single bolt is hazardous and the
difference between a heavy Schwinn attachment and a pseudo Campagnolo
attachment that uses a single bolt the original size. I included the
disclaimer: "I suspect these posts are the ones under discussion."

From your comment I'm not convinced you are posting in good faith.
Your question was anticipated and previously answered.

Here is what you wrote earlier:

So why did you delete that from this response? As you see, I
reinserted that paragraph and you deleted it once more. You didn't
have to get it from an earlier posting and add it here/


# That depends on how clever the design is. Old Schwinn balloon
# tired bicycles had single bolt clamps that with bolt failure the
# saddle could not fall away from under the rider as the current
# light weight designs "racing" do. Old Campagnolo Record posts
# had two bolts with which two bridge clamps allowed fore and aft
# sliding and by differential tightening adjust the fore and aft
# tilt.

You wrote "that depends on the design" after saying that "If the
single bolt fails, the rider falls onto the rotating rear wheel"

That's why I mentoned old Schwinn design that does not present this
hazard, thereby not making it dependent on one bolt but rather the
design of that one bolt clamp.

Again, you made a definitive and comprehensive statement, and then
qualified it to apply to only some situations and not others. The
earlier statement was simply wrong in trying to be comprehensive.
That's all I'm saying and I'm saying it in quite good faith. And
laughing.

You're creating your own entertainment at my expense. The single bolt
seat clamps that are a derivative of the earlier Campagnolo Record
seat post seemed to some to be an advance, but when the single bolt
breaks, the saddle falls backward, the load of the sit bones being
behind the pivot during at least part of the pedal stroke. This is
not apparent to many in the business or its users, so I think it is
worth mentioning the details.

By bolt failure the saddle can drop to the ground and the rider, still
attached to his pedals, land with his rectum on the rotating rear
wheel. I know this from a couple of incidents, so I mentioned it.
The injury was serious but repairable with emergency room sutures.

You needn't defend the single bolt seat post here at my expense. I
think there are better ways of discussing the merits of seat clamps
than with ad hominem argumentation. I explained that these seat posts
ignore the need for redundant bolts similar to stem and bar
attachments, and that the danger is not apparent.

Jobst Brandt

wrote:
John Forrest Tomlinson wrote:

The same goes for seat post saddle clamps. If the single bolt
fails, the rider falls onto the rotating rear wheel to produce an
involuntary colostomy.

If the degree of danger if the bolt breaks varies with different
designs, I don't understand why you say "the rider falls" as if that
is a consistent outcome.

You can only seriously say that having deleted what I had written and
reinserted. I explained why the single bolt is hazardous and the
difference between a heavy Schwinn attachment and a pseudo Campagnolo
attachment that uses a single bolt the original size. I included the
disclaimer: "I suspect these posts are the ones under discussion."

From your comment I'm not convinced you are posting in good faith.
Your question was anticipated and previously answered.

Here is what you wrote earlier:

So why did you delete that from this response? As you see, I
reinserted that paragraph and you deleted it once more. You didn't
have to get it from an earlier posting and add it here/


# That depends on how clever the design is. Old Schwinn balloon
# tired bicycles had single bolt clamps that with bolt failure the
# saddle could not fall away from under the rider as the current
# light weight designs "racing" do. Old Campagnolo Record posts
# had two bolts with which two bridge clamps allowed fore and aft
# sliding and by differential tightening adjust the fore and aft
# tilt.

You wrote "that depends on the design" after saying that "If the
single bolt fails, the rider falls onto the rotating rear wheel"

That's why I mentoned old Schwinn design that does not present this
hazard, thereby not making it dependent on one bolt but rather the
design of that one bolt clamp.

Again, you made a definitive and comprehensive statement, and then
qualified it to apply to only some situations and not others. The
earlier statement was simply wrong in trying to be comprehensive.
That's all I'm saying and I'm saying it in quite good faith. And
laughing.

You're creating your own entertainment at my expense. The single bolt
seat clamps that are a derivative of the earlier Campagnolo Record
seat post seemed to some to be an advance, but when the single bolt
breaks, the saddle falls backward, the load of the sit bones being
behind the pivot during at least part of the pedal stroke. This is
not apparent to many in the business or its users, so I think it is
worth mentioning the details.

"not apparent" is somewhat presumptive given that you attribute it to
all and sundry who may actually have bothered to contemplate such
matters. what's much more "not apparent" however is whether you're
prepared to address this single bolt's loading mode and discuss its real
world failure statistics. observation of manufacturer's torque spec
should enter into your discussion.



By bolt failure the saddle can drop to the ground and the rider, still
attached to his pedals, land with his rectum on the rotating rear
wheel.

you repeat [not just here, but have done so many times] this clinical
detail as if it's more important than potential femoral artery rupture
or testicular laceration. do you have some kind of proctological
interest in that particular injury? i mean, it's ok here in the bay
area you know.

I know this from a couple of incidents, so I mentioned it.
The injury was serious but repairable with emergency room sutures.

You needn't defend the single bolt seat post here at my expense.

eh? and why say it twice?


I
think there are better ways of discussing the merits of seat clamps
than with ad hominem argumentation.

the only person here getting close to ad hominem is you. jft simply
pointed out that your typically jobstian "definitive and comprehensive
statement" required qualification, and thus was not a "definitive and
comprehensive statement" at all. if you think thats personal attack,
you're losing the plot.


I explained that these seat posts
ignore the need for redundant bolts similar to stem and bar
attachments, and that the danger is not apparent.

how much redundancy do you need jobst? two front forks? two pedal
spindles each side? two crank arms each side? two brake levers each
side? double brake cables front and rear? two seat post tubes? we
gave up on biplanes years ago jobst - you can look for other ogres under
your bed.

I had a one bolt Campy for a long time. I would tighten it very hard
and it would still eventually slip. The original Avocet design was
perfect, and I was lucky to find a Suntour Superb in 27.0. I'd love a
Nitto Jaguar, but I'd have to be drunk to PayPal that kind of money.
I've never understood why two bolts is not universal. You keep the
angle and move the seat backward and forward by loosening and
retightening only one bolt, or keep the displacement the same and only
change the angle by loosening one bolt as you tighten the other.
Brilliant!

JG

JG wrote:
I had a one bolt Campy for a long time. I would tighten it very hard
and it would still eventually slip. The original Avocet design was
perfect, and I was lucky to find a Suntour Superb in 27.0. I'd love a
Nitto Jaguar, but I'd have to be drunk to PayPal that kind of money.
I've never understood why two bolts is not universal. You keep the
angle and move the seat backward and forward by loosening and
retightening only one bolt, or keep the displacement the same and only
change the angle by loosening one bolt as you tighten the other.
Brilliant!

not really. if one bolt breaks, the remainder of the cradle is
unbalanced and fails under trivial load. pointless really, especially
for a system where tilt load is the main fatigue factor. much better to
have a single bolt at what would effectively be the "neutral plane".

"JG" wrote in message
...
I had a one bolt Campy for a long time. I would tighten it very hard
and it would still eventually slip. The original Avocet design was
perfect, and I was lucky to find a Suntour Superb in 27.0. I'd love a
Nitto Jaguar, but I'd have to be drunk to PayPal that kind of money.
I've never understood why two bolts is not universal. You keep the
angle and move the seat backward and forward by loosening and
retightening only one bolt, or keep the displacement the same and only
change the angle by loosening one bolt as you tighten the other.
Brilliant!

JG

Back in the day there were a lot of complaints about mounting seats and
adjusting them with Campy 2 bolt style seatposts (and similar knockoffs).
It was partly due to not having a proper fitting 10mm wrench to get to the
bolt heads. The Avocet and similar 2 bolt seatposts that used socket head
cap screws accessible from the bottom was a great solution.

I've switched most of my bikes back to 2 bolt Campy seatposts.

Chas.

* * Chas wrote:
"JG" wrote in message
...
I had a one bolt Campy for a long time. I would tighten it very hard
and it would still eventually slip. The original Avocet design was
perfect, and I was lucky to find a Suntour Superb in 27.0. I'd love a
Nitto Jaguar, but I'd have to be drunk to PayPal that kind of money.
I've never understood why two bolts is not universal. You keep the
angle and move the seat backward and forward by loosening and
retightening only one bolt, or keep the displacement the same and only
change the angle by loosening one bolt as you tighten the other.
Brilliant!

JG

Back in the day there were a lot of complaints about mounting seats and
adjusting them with Campy 2 bolt style seatposts (and similar knockoffs).
It was partly due to not having a proper fitting 10mm wrench to get to the
bolt heads. The Avocet and similar 2 bolt seatposts that used socket head
cap screws accessible from the bottom was a great solution.

I've switched most of my bikes back to 2 bolt Campy seatposts.


let's say the front bolt breaks for some reason. how would the rear
bolt alone stop the seat bending the clamp and tilting off the bracket?

On 11 Jun 2008 03:23:14 GMT, wrote:

John Forrest Tomlinson wrote:

The same goes for seat post saddle clamps. If the single bolt
fails, the rider falls onto the rotating rear wheel to produce an
involuntary colostomy.

If the degree of danger if the bolt breaks varies with different
designs, I don't understand why you say "the rider falls" as if that
is a consistent outcome.

You can only seriously say that having deleted what I had written and
reinserted. I explained why the single bolt is hazardous and the
difference between a heavy Schwinn attachment and a pseudo Campagnolo
attachment that uses a single bolt the original size. I included the
disclaimer: "I suspect these posts are the ones under discussion."

From your comment I'm not convinced you are posting in good faith.
Your question was anticipated and previously answered.

Here is what you wrote earlier:

So why did you delete that from this response?

Because it wasn't relevant, but you were trying to make it lool like I
was up to somethign deceptive, which I wasn't. If you want to rag on
my usenet skills, go ahead, but you shouldn't assign motive to those
lack of skills.
As you see, I
reinserted that paragraph and you deleted it once more. You didn't
have to get it from an earlier posting and add it here/


# That depends on how clever the design is. Old Schwinn balloon
# tired bicycles had single bolt clamps that with bolt failure the
# saddle could not fall away from under the rider as the current
# light weight designs "racing" do. Old Campagnolo Record posts
# had two bolts with which two bridge clamps allowed fore and aft
# sliding and by differential tightening adjust the fore and aft
# tilt.

You wrote "that depends on the design" after saying that "If the
single bolt fails, the rider falls onto the rotating rear wheel"

That's why I mentoned old Schwinn design that does not present this
hazard, thereby not making it dependent on one bolt but rather the
design of that one bolt clamp.

Again, you made a definitive and comprehensive statement, and then
qualified it to apply to only some situations and not others. The
earlier statement was simply wrong in trying to be comprehensive.
That's all I'm saying and I'm saying it in quite good faith. And
laughing.

You're creating your own entertainment at my expense.

Yes. The entertainment is that I point out a tiny inconsistency in
what you wrote, and you use the occasssion to suggest I was posting
"in bad faith." If by bad faith you mean trying to be deceptive,
you're wrong. The only "bad faith" is some small enjoyment is
pointing out a tiny error on your part. So I enjoy that? So what?

The single bolt
seat clamps that are a derivative of the earlier Campagnolo Record
seat post seemed to some to be an advance, but when the single bolt
breaks, the saddle falls backward, the load of the sit bones being
behind the pivot during at least part of the pedal stroke. This is
not apparent to many in the business or its users, so I think it is
worth mentioning the details.

By bolt failure the saddle can drop to the ground and the rider, still
attached to his pedals, land with his rectum on the rotating rear
wheel. I know this from a couple of incidents, so I mentioned it.
The injury was serious but repairable with emergency room sutures.

You needn't defend the single bolt seat post here at my expense. I
think there are better ways of discussing the merits of seat clamps
than with ad hominem argumentation. I explained that these seat posts
ignore the need for redundant bolts similar to stem and bar
attachments, and that the danger is not apparent.

I'm not knowledgeable enough about engineering to comment on all of
the above, so I won't even try. I'm not even discussing the merits of
seatposts. I was simply pointing out that a bolt breaking doesn't
necessarily result in injury -- which you said it did, at first,
without qualification. If you want to try to disparage my statement
in some way to preserve your ego or make me look foolish, go ahead.
If I were in your situation, I'd simply let it go.

"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.