S-bend stays?

Jhas said:

After last week's lively and informative discussion re "Cabon Fiber
Seat Stays = Better Ride?" I feel compelled to ask: can the same be
said for S-bend seat and chain stays? Lots of manufacturers claim that
s-bend stays add "vertical compliance" or increase lateral stiffness.
I'm having a difficult time believing any of it.

the fact is that they do increase compliance. the degree to which it
happens however depends on execution, material etc. for a demo of the
principle, google for "euler buckling". bent stays are essentially
pre-buckled. imo, bent seat stays are good, bent chain stays are bad.

I have two frames from the same manufacturer (Litespeed), made from the same
material (titanium), one with s-bend seat and chain stays and one without.
No discernible difference when shod with the same tyres pumped to the same
pressure.

OTOH, s-bend on the chainstay does serve a function in giving better heel
clearance because the stay initially comes in from the dropouts at a sharper
angle. I ride toes out and had to grind off the inside of the heels on my
Carnac touring shoes or they hit the chainstays just forward of the dropout
on my steel touring bike that has straight chainstays.

Nick

"Jhas" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

After last week's lively and informative discussion re "Cabon Fiber
Seat Stays = Better Ride?" I feel compelled to ask: can the same be
said for S-bend seat and chain stays? Lots of manufacturers claim that
s-bend stays add "vertical compliance" or increase lateral stiffness.
I'm having a difficult time believing any of it.

jim beam said:

Jhas said:

After last week's lively and informative discussion re "Cabon Fiber
Seat Stays = Better Ride?" I feel compelled to ask: can the same be
said for S-bend seat and chain stays? Lots of manufacturers claim that
s-bend stays add "vertical compliance" or increase lateral stiffness.
I'm having a difficult time believing any of it.

As you should.

Quoted message said:

Quoted message said:

the fact is that they do increase compliance. the degree to which it
happens however depends on execution, material etc. for a demo of the
principle, google for "euler buckling". bent stays are essentially
pre-buckled. imo, bent seat stays are good, bent chain stays are bad.

That is certainly reassuring, to imagine that curved stays are "buckled".
The advantages are what, exactly? I had an old fork that was locally
euler buckled after a crash. Perhaps I should have kept that, but somehow
I thought that would be a bad idea.

--

David L. Johnson

__o | Let's not escape into mathematics. Let's stay with reality. --
_`\(,_ | Michael Crichton
(_)/ (_) |

jim beam said:

Jhas said:

After last week's lively and informative discussion re "Cabon Fiber
Seat Stays = Better Ride?" I feel compelled to ask: can the same be
said for S-bend seat and chain stays? Lots of manufacturers claim that
s-bend stays add "vertical compliance" or increase lateral stiffness.
I'm having a difficult time believing any of it.

the fact is that they do increase compliance. the degree to which it
happens however depends on execution, material etc. for a demo of the
principle, google for "euler buckling". bent stays are essentially
pre-buckled. imo, bent seat stays are good, bent chain stays are bad.

What Jim writes above is in line with his theology, but could give
those who may be willing to spend a considerable amount of their
hard-earned on S-stays the wrong impression. That is, that they would
get a noticeably better ride from a bike with S-stays.

FWIW, I sell frames/bikes with and without S-stays (and get more money
for the ones with S-stays). But I go out of my way to ensure that I
don't ever give anyone the impression that an S-stay would make a
noticeable difference in ride quality. I'm not aware of any frame out
there with a radical enough "S" stay that it would act like anything
other than a straight stay in any meaningful way.

Jim also misses the fact that S-shaped chainstays DO make sense in
terms of heel clearance (for those who pedal heel-in) and tire
clearance. I'm not aware of any real performance improvement with an
S-shaped seat stay, though they do look kinda sexy.

Mark Hickey
Habanero Cycles
http://www.habcycles.com
Home of the $695 ti frame

David L. Johnson said:

jim beam said:

Jhas said:

After last week's lively and informative discussion re "Cabon Fiber
Seat Stays = Better Ride?" I feel compelled to ask: can the same be
said for S-bend seat and chain stays? Lots of manufacturers claim that
s-bend stays add "vertical compliance" or increase lateral stiffness.
I'm having a difficult time believing any of it.

As you should.

Quoted message said:

the fact is that they do increase compliance. the degree to which it
happens however depends on execution, material etc. for a demo of the
principle, google for "euler buckling". bent stays are essentially
pre-buckled. imo, bent seat stays are good, bent chain stays are bad.

That is certainly reassuring, to imagine that curved stays are "buckled".
The advantages are what, exactly? I had an old fork that was locally
euler buckled after a crash. Perhaps I should have kept that, but somehow
I thought that would be a bad idea.

that's bent, as in bending beam, not compression buckled, per euler.
but i guess engineering was not your point.

"Jhas" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

After last week's lively and informative discussion re "Cabon Fiber
Seat Stays = Better Ride?" I feel compelled to ask: can the same be
said for S-bend seat and chain stays? Lots of manufacturers claim that
s-bend stays add "vertical compliance" or increase lateral stiffness.
I'm having a difficult time believing any of it.

It's marketing b*llsh*t.

Some pedants will claim that there IS an added degree of compliance but if
so it is vastly smaller than that produced by the tyres. Suspect anyone who
insists on this of having a hidden agenda...

Jhas said:

After last week's lively and informative discussion re "Cabon Fiber
Seat Stays = Better Ride?" I feel compelled to ask: can the same be
said for S-bend seat and chain stays? Lots of manufacturers claim that
s-bend stays add "vertical compliance" or increase lateral stiffness.
I'm having a difficult time believing any of it.

Hetchins supposedly did it because British amateur racing rules didn't permit
large identification badges on bikes and wanted brand recognition.

Ya know, tubes make such [censored] springs in anything other than torsion I wouldn't
really expect it to work.

Ron

In article <1113829678.ff940e043a380ff9b29ac0028169990d@teranews>, jim beam
says...

Quoted message said:

the fact is that they do increase compliance. the degree to which it
happens however depends on execution, material etc. for a demo of the
principle, google for "euler buckling".

Physics, abstract
physics/0501099
Euler buckling in red blood cells: An optically driven biological micromotor

Authors: A. Ghosh, S. Sinha, J. A. Dharmadhikari, S. Roy, A. K. Dharmadhikari,
J. Samuel, S. Sharma, D. Mathur

We report the observation of an optically driven micromotor of biological
origin. A single red blood cell (RBC) folds when placed in an optical trap. The
folded RBC is birefringent and rotates in circularly polarized light. Optical
forces permit a high degree of control over the speed and direction of rotation
of such a micromotor. This cellular micromotor has potential applications in
micromanipulation, possibly like an "optical screwdriver" to apply torques at
the micron scale. A simple theoretical model captures the main observed features
and makes predictions that are successfully tested.

Acutally what happens is that the bent seat stays cause Euler buckling of your
red blood cells of your butt. This results in better oxygen delivery and hence
less discomfort. The claim that it also improves you speed is however false.

Hetchins supposedly did it because British amateur racing rules didn't
permit
large identification badges on bikes and wanted brand recognition.

Ya know, tubes make such [censored] springs in anything other than torsion I
wouldn't
really expect it to work.

The Hetchins story isn't really true. There are plenty of oddball
English frame designs that play more on the English love of the odd
than marketing or engineering.
Phil Brown

A shy person asked:

Quoted message said:

After last week's lively and informative discussion re "Cabon Fiber
Seat Stays = Better Ride?" I feel compelled to ask: can the same be
said for S-bend seat and chain stays? Lots of manufacturers claim that
s-bend stays add "vertical compliance" or increase lateral stiffness.
I'm having a difficult time believing any of it.

Bent _seat_ stays could _theoretically_ add a weensy bit of compliance,
but I don't believe it would be detectable.

I own a "curly" Hetchins, which is a very pretty, nice riding frame, but
I don't detect any difference in rear compliance due to the curls.

http://sheldonbrown.org/hetchins

Modern bikes with curved _chainstays_ do it for reasons of clearance.
They're wide in front for tire clearance, then scoot inward for heel
clearance.

This design is most commonly seen on round, non-tapered chainstays.
Bending the chainstays into an "S" curve is a cheaper way to get the
desired clearance than ovalizing and tapering the stays.

Sheldon "Follow The Money" Brown
+-------------------------------------------------------+
| Military conscription is the worst form of slavery. |
| A more enlightened age will consider it a War crime. |
+-------------------------------------------------------+
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

That's a beautiful bike, Sheldon, but who ya callin' shy? ;-)

On 18 Apr 2005 05:49:34 -0700, "Jhas" <[email hidden]>

Quoted message said:

After last week's lively and informative discussion re "Cabon Fiber
Seat Stays = Better Ride?" I feel compelled to ask: can the same be
said for S-bend seat and chain stays? Lots of manufacturers claim that
s-bend stays add "vertical compliance" or increase lateral stiffness.
I'm having a difficult time believing any of it.

IMO, any frame "feature" that claims to use flexure to improve the
ride is either snake oil or a misfeature. The main purpose of the
frame is to be a *frame*, to provide the rigid structure that keeps
all of the other components aligned. Any flexing that may occur is
incidental and largely of value only to the marketing droids.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

"Mark Hickey" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

FWIW, I sell frames/bikes with and without S-stays (and get more money
for the ones with S-stays). But I go out of my way to ensure that I
don't ever give anyone the impression that an S-stay would make a
noticeable difference in ride quality. I'm not aware of any frame out
there with a radical enough "S" stay that it would act like anything
other than a straight stay in any meaningful way.

What is also often skipped is the fact that a straight tube is stronger, and
so a curved tube if not to be weaker must be heavier.

And _that_ difference is orders of magnitude greater than any extra
"compliance".

Ed said:

Acutally what happens is that the bent seat stays cause Euler buckling of your
red blood cells of your butt. This results in better oxygen delivery and hence
less discomfort. The claim that it also improves you speed is however false.

And it's not effective in the older. "blue blood" family lines of
certain eastern states.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

Jhas said:

After last week's lively and informative discussion re "Cabon Fiber
Seat Stays = Better Ride?" I feel compelled to ask: can the same be
said for S-bend seat and chain stays? Lots of manufacturers claim
that s-bend stays add "vertical compliance" or increase lateral
stiffness. I'm having a difficult time believing any of it.

My bike has carbon seat stays and rides real nice.

My bike doesn't have any S-stays and rides real nice.

Therefore, carbon stays are worthwhile and S-stays are useless gimmicks.

HTH, BS

Mark Hickey said:

Quoted message said:

Quoted message said:

After last week's lively and informative discussion re "Carbon
Fiber Seat Stays = Better Ride?" I feel compelled to ask: can the
same be said for S-bend seat and chain stays? Lots of
manufacturers claim that s-bend stays add "vertical compliance" or
increase lateral stiffness. I'm having a difficult time believing
any of it.

Quoted message said:

Quoted message said:

the fact is that they do increase compliance. the degree to which
it happens however depends on execution, material etc. for a demo
of the principle, google for "euler buckling". bent stays are
essentially pre-buckled. imo, bent seat stays are good, bent chain
stays are bad.

Quoted message said:

What Jim writes above is in line with his theology, but could give
those who may be willing to spend a considerable amount of their
hard-earned on S-stays the wrong impression. That is, that they
would get a noticeably better ride from a bike with S-stays.

Quoted message said:

FWIW, I sell frames/bikes with and without S-stays (and get more
money for the ones with S-stays). But I go out of my way to ensure
that I don't ever give anyone the impression that an S-stay would
make a noticeable difference in ride quality. I'm not aware of any
frame out there with a radical enough "S" stay that it would act
like anything other than a straight stay in any meaningful way.

Quoted message said:

Jim also misses the fact that S-shaped chainstays DO make sense in
terms of heel clearance (for those who pedal heel-in) and tire
clearance. I'm not aware of any real performance improvement with
an S-shaped seat stay, though they do look kinda sexy.

This fits well with those who believe that the curl (offset) on
classic road (and track) forks is for shock absorption (springiness),
meanwhile ignoring that if this were so, forks would break from
flexing there and straight forks, are angled at the fork crown, are
noticeably harsher to ride. This is all part of bicycle religion. It
requires faith.

A little Euler jargon can also go a long way with the faithful.

[email hidden]

"jtaylor" wrote: (clip) a straight tube is stronger, and so a curved tube
if not to be weaker must be heavier. (clip)
^^^^^^^^^^^^
Furthermore, making the tube heavier to keep the needed strength reduces the
compliance, so even that tiny advantage is largely lost.

Leo Lichtman said:

Quoted message said:

(clip) a straight tube is stronger, and so a curved tube if not to
be weaker must be heavier. (clip)

Quoted message said:

Furthermore, making the tube heavier to keep the needed strength
reduces the compliance, so even that tiny advantage is largely lost.

Furhtermore, where in machinery do we find a buckling compression
spring to cushion vibration, either with a slight buckling initiating
S-bend or a carbon fiber.

[email hidden]

jim beam wrote:
----8<---cut
bent stays are essentially

Quoted message said:

pre-buckled. imo, bent seat stays are good, bent chain stays are bad.

Can't resist this one - what advantage would Colnago's C40/50 fish lips
chain stays have, then? Apart from marketing gimmick, as was discussed
earlier last year ... /Robert