Re: Carbon Fiber Seat Stays = Better Ride?

[Mark Hickey]

"Peter Cole" <[email protected]> wrote:

>Sandy wrote:
>> Dans le message de :
>
>> I wonder if you have the opportunity to read Le Cycle ; probably not.
> They
>> test the deflection of a frame, and don't agree with you. For
>example,
>> regarding the Scott DR1 Team issue (from the April 2005 issue, using
>their
>> very specific testing) :
>
>> Rear triangle deflection - 3.90 mm
>
>Wow! Almost 4mm! I guess we should all read the magazines more often!

I'd suggest reading them more carefully instead. There is NO (dang,
where's the larger bold font when I need it?) WAY the rear triangle on
any "non-suspension bike" deflects vertically 4mm. OK, I take that
back... there's no way it deflects 4mm vertically twice. ;-)

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

 

[Sandy]

Dans le message de news:[email protected],
Mark Hickey <[email protected]> a réfléchi, et puis a déclaré :
>
> I'd suggest reading them more carefully instead. There is NO (dang,
> where's the larger bold font when I need it?) WAY the rear triangle on
> any "non-suspension bike" deflects vertically 4mm. OK, I take that
> back... there's no way it deflects 4mm vertically twice. ;-)

Lateral deflection.

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

 

[[email protected]]

[email protected] wrote:
> I guess this boils down to vibrations rather than shock absorbing
from
> what has been offered by those who believe carbon fibre seat stays
> improve ride comfort.

I don't think it "boils down" to that at all I honestly can't remember
one source that seems to know what he, she or they is talking about
that mentioned shock absorption. It has come up a lot in this thread
and other so I may have missed something, if that is the case can you
do me a favour and point me back to the claim? Shock absorption is a
red herring, it has always been about vibration.

Don't get me wrong I do not wish to claim that CF stays will improve
ride comfort. Until there is an ASTM standard for "ride comfort" I
will argue that it can only be a personal thing, but discounting the
possibility is just as wrong as attempting to quantify the difference.
I will insist that there is a potential there, based entirely on the
known properties of the material.


>So let's get to the essence. What frequencies
> are being damped by these stays?

Not sure, can you tell me what frequencies of vibration are generated
by riding over different road surfaces, for example new velodrome wood,
fresh cured concrete, new asphalt and old asphalt? I don't think that
anyone will argue that you can't feel the difference in surfaces when
you ride over them. Anyway it is those frequencies (among others) that
are a concern of the claims.


>
> For example, let's use one as a sounding probe. If such a stay were
> held between the ear and a piece of vibrating machinery to asses some
> noises, as is often done in machine applications, would one expect to
> hear more or less using a steel seat stay or a carbon fibre one... or
> a 1/2 inch wooden dowel of equal length for that matter?

You would hear less with CF than steel and less with most woods than
CF.

>
> This reminds me of the rider who claimed he could feel the difference
> between 1.5mm diameter spokes and 2.0mm diameter ones,

Kind of reminds me of the guy claiming that the earth revolves around
the sun while everyone else was happy with the retrograde motion of the
planets as explained by the crystal spheres theory.

> I don't believe the claimed damping is in the
> acoustic range and it certainly isn't in the human touch range, or we
> would see some deflections.

Once again the deflection claim comes up, and well...How much
deflection do you see in in a lathe bed when it is in operation? IIRC
from your book you used a Bridgeport mill as one of the test fixtures
(might have been a different book not to sure now) what was that mill
made of? Grey Cast Iron ... why was it made of that and not say
Aluminium or Tool steel? Because in operation a mill or a lathe
generates vibrations that can adversely affect its operation and Grey
Cast dampens vibration, and does so without deflection. It is a
physical property of the material. Just as it is a physical property of
CF.

>
> [email protected]

As an aside I would have hoped for better from you, you've gone out of
your way to research one aspect of the bicycle and provided reams of
measurements, yet here you are arguing against a well-researched and
established phenomenon. There are reams of data showing that CF dampens
or attenuates vibration.

Say things like "the amount of damping is insignificant compared to
other options available" or "the average rider probably wont notice
a difference" and I wont scrap. Or say "the potential for a failure
at the CF is Alu./Ti. bond due to galvanic corrosion far outweighs any
comfort benefit for most riders" and I might even agree with you (I
would at lest hold the option open until such time as the manufacturer
explained how it was avoided.)

And I guess that is my whole point... it is possible, whether or not
any individual will notice or care depends on a huge number of other
factors. Just don't discard the possibility.

 

[[email protected]]

Sandy wrote:
> Dans le message de :
> news:[email protected],
> [email protected] <[email protected]> a réfléchi, et puis a
déclaré :
>
> > Perhaps I wasn't clear enough. What I'm saying is, the results (or
> > non-results?) of that steel tube blind comparison would, I believe,
be
> > the same in a blind comparison test of different frame materials.
>
> Ask yourself : when standing to climb a hill, is the chain/derailleur
rub
> (often encountered) present on all bikes ? Can you have this happen
without
> the rims flexing back and forth and rubbing the brake pads ? Or the
second
> without the first ?

Please, avoid introducing red herrings! We're talking about absorbing
road shock and vibration, not lateral flex! I made this clear in the
next two sentences:

>
> > IOW: Make up four frames, all with the same wheelbase, angles,
trail,
> > size, etc. but different materials. Design them so the bottom
bracket
> > sway is the same (since that's easily felt, but not pertinent to
our
> > question).


Again, I made it clear that I'm talking about frames with identical
macroscopic deflection. That takes care of chain/derailleur rub as
well as rubbing brake pads.


>
> All deflections on a bicycle, from force applied in pedaling, or from
forces
> acting on the bike from the irregular road surface, are potentially
> perceptible, depending on the attention of the rider and the degree
of
> deflection. Also, as Mr Brandt inquired, the frequencies of
vibration need
> be examined. Composite appreciation of these effects are found in
riders'
> evaluations.

The supposed differences composites make would _not_ be found in
riders' evaluations, if the riders weren't told they were supposed to
be found!

> >
> > Briefly, the deflection of the other components is at least 100
times
> > greater than the deflection of the seat stays. (To me, this seems
> > very obvious, but we could repeat it all if you like.) Those
> > deflections are not just personal opinions. They're able to be
> > calculated, and they're able to be measured.
>
> I wonder if you have the opportunity to read Le Cycle ; probably not.
They
> test the deflection of a frame, and don't agree with you. For
example,
> regarding the Scott DR1 Team issue (from the April 2005 issue, using
their
> very specific testing) :
>
> Head tube deflection - 6 mm
> Bottom bracket deflection - 0.28 mm
> Rear triangle deflection - 3.90 mm

No, I don't read Le Cycle. But these figures cannot possibly be
in-plane deflections under any ordinary cycling load. In other words,
intentionally or not, you're introducing another red herring. Vertical
(in-plane) deflections of a bike frame are fractions of a millimeter.
Deflection of tires are several millimeters. Ditto for saddle
deflections. Seatposts deflect a significant amount in the vertical
direction, too. Seatstays do not.

You need to understand the difference between vertical and lateral
deflection before you can competently judge this issue.

Intuitively, I believe that tires and wheels
> affect comfort significantly more than frame materials, but comfort
is not
> the only objective here. Stability on bad roads is also prized.

? It seems we're moving to a different topic! Are you saying that
carbon fiber seat stays increase stability on bad roads? If so, we can
have fun with that claim as well!

- Frank Krygowski

 

[[email protected]]

[email protected] wrote:
>
>
> Once again the deflection claim comes up, and well...How much
> deflection do you see in in a lathe bed when it is in operation? IIRC
> from your book you used a Bridgeport mill as one of the test fixtures
> (might have been a different book not to sure now) what was that mill
> made of? Grey Cast Iron ... why was it made of that and not say
> Aluminium or Tool steel? Because in operation a mill or a lathe
> generates vibrations that can adversely affect its operation and Grey
> Cast dampens vibration, and does so without deflection. It is a
> physical property of the material. Just as it is a physical property
of
> CF.

Hold on. There's more to the use of cast iron in machine frames than
you imply.

First, it's true cast iron attenuates vibrations, and that makes it
useful in machine tool frames. But the vibration situation in
machining is much different than that of a moving bike. Because of the
specific number of gear teeth in mesh, the specific number of flutes on
a particular cutter, the specific speed of rotation, the specific
stiffness of the cutting tool, etc, it's possible to get resonance that
ruins surface finish. This fixed-condition high frequency resonance
isn't going to happen on a bike being ridden, unless you're briefly
riding over something like a steel grate bridge surface.

Second, don't ignore the fact that cast iron machine frames trump all
other materials based on cost, and on ease of casting. One could get
adequate rigidity from a cast aluminum mill frame, but it would need to
be somewhat larger (due to aluminum's lower modulus of elasticity) and
one _hell_ of a lot more expensive!

Personally, I'd bet CI's vibration damping effect in machine tool
frames is much less important than its cost and castability.


There are reams of data showing that CF dampens
> or attenuates vibration.

What we need is data showing that CF dampens vibrations that are
already isolated from the rider by a pneumatic tire and a suspended
saddle!

Seriously, if we were riding directly on the metal rim, and our butts
were perched directly on the top of the seatstay, you might convince me
that CF had some benefit. But that's not our situation at all!

> And I guess that is my whole point... it is possible, whether or not
> any individual will notice or care depends on a huge number of other
> factors. Just don't discard the possibility.

When a carbon fiber promoter arranges a proper blind test, that will
give this "possibility" some legitimacy. Until then, I look on it as
just as "possible" as, say, the geomagnetic booster.
http://sheldonbrown.com/geomag.html

- Frank Krygowski

 

[Sandy]

Dans le message de
news:[email protected],
[email protected] <[email protected]> a réfléchi, et puis a déclaré :
> Again, I made it clear that I'm talking about frames with identical
> macroscopic deflection. That takes care of chain/derailleur rub as
> well as rubbing brake pads.

It's clear you are talking about nothing in particular, or only about
manufacturing differences of a single model of bicycle.

>> All deflections on a bicycle, from force applied in pedaling, or
>> from forces acting on the bike from the irregular road surface, are
>> potentially perceptible, depending on the attention of the rider and
>> the degree of deflection. Also, as Mr Brandt inquired, the
>> frequencies of vibration need be examined. Composite appreciation
>> of these effects are found in riders' evaluations.
>
> The supposed differences composites make would _not_ be found in
> riders' evaluations, if the riders weren't told they were supposed to
> be found!

I guess you are the authority on the matter. Sorry I bothered to write.

>>> Briefly, the deflection of the other components is at least 100
>>> times greater than the deflection of the seat stays. (To me, this
>>> seems very obvious, but we could repeat it all if you like.) Those
>>> deflections are not just personal opinions. They're able to be
>>> calculated, and they're able to be measured.
>>
>> I wonder if you have the opportunity to read Le Cycle ; probably not.
> They
>> test the deflection of a frame, and don't agree with you. For
>> example, regarding the Scott DR1 Team issue (from the April 2005
>> issue, using their very specific testing) :
>>
>> Head tube deflection - 6 mm
>> Bottom bracket deflection - 0.28 mm
>> Rear triangle deflection - 3.90 mm
>
> No, I don't read Le Cycle. But these figures cannot possibly be
> in-plane deflections under any ordinary cycling load. In other words,
> intentionally or not, you're introducing another red herring.

You want numbers. Then you don't like them. OK.

> ? It seems we're moving to a different topic! Are you saying that
> carbon fiber seat stays increase stability on bad roads? If so, we
> can have fun with that claim as well!

Sorry I bothered you with the real world.
--
Bonne route,

Sandy
Verneuil-sur-Seine FR

 

[Derk]

[email protected] wrote:

> What we need is data showing that CF dampens vibrations that are
> already isolated from the rider by a pneumatic tire and a suspended
> saddle!
I always learned that diamond (classic) frames don't benefit from carbon
fiber, but that only "free forms", that are banned by the UCI, could
benefit from CF. Isn't that so?

Greetings, Derk

 

[Peter Cole]

Sandy wrote:
> Dans le message de :
> news:[email protected],
> Peter Cole <[email protected]> a réfléchi, et puis a déclaré
:
> > Sandy wrote:
> >> Dans le message de :
> >
> >> I wonder if you have the opportunity to read Le Cycle ; probably
> >> not. They test the deflection of a frame, and don't agree with
you.
> >> For example, regarding the Scott DR1 Team issue (from the April
2005
> >> issue, using their very specific testing) :
> >>
> >
> >> Rear triangle deflection - 3.90 mm
> >
> > Wow! Almost 4mm! I guess we should all read the magazines more
often!
>
> As opposed to the writers claiming zero, perhaps it has its
significance.
> If you weren't so intent on covering your overstatements, perhaps you
would
> have learned something new.

Wasn't it a rather large omission that the deflection was *lateral*,
not *vertical*? What is the *vertical* deflection? I'll bet it's a
*lot* closer to zero! Why don't you find out, *you* may learn something
new!

 

[[email protected]]

On 17 Apr 2005 13:15:56 -0700, "Peter Cole"
<[email protected]> wrote:

>
>Sandy wrote:
>> Dans le message de :
>> news:[email protected],
>> Peter Cole <[email protected]> a réfléchi, et puis a déclaré
>:
>> > Sandy wrote:
>> >> Dans le message de :
>> >
>> >> I wonder if you have the opportunity to read Le Cycle ; probably
>> >> not. They test the deflection of a frame, and don't agree with
>you.
>> >> For example, regarding the Scott DR1 Team issue (from the April
>2005
>> >> issue, using their very specific testing) :
>> >>
>> >
>> >> Rear triangle deflection - 3.90 mm
>> >
>> > Wow! Almost 4mm! I guess we should all read the magazines more
>often!
>>
>> As opposed to the writers claiming zero, perhaps it has its
>significance.
>> If you weren't so intent on covering your overstatements, perhaps you
>would
>> have learned something new.
>
>Wasn't it a rather large omission that the deflection was *lateral*,
>not *vertical*? What is the *vertical* deflection? I'll bet it's a
>*lot* closer to zero! Why don't you find out, *you* may learn something
>new!

Dear Peter,

If one rear triangle first bends 4 mm to one side and then 4
mm to another, while a different rear triangle bends
measurably less, should we expect to feel a difference in
the shock or vibration or road buzz?

Carl Fogel

 

[[email protected]]

On 17 Apr 2005 09:03:20 -0700, [email protected] wrote:

>
>[email protected] wrote:
>>
>>
>> Once again the deflection claim comes up, and well...How much
>> deflection do you see in in a lathe bed when it is in operation? IIRC
>> from your book you used a Bridgeport mill as one of the test fixtures
>> (might have been a different book not to sure now) what was that mill
>> made of? Grey Cast Iron ... why was it made of that and not say
>> Aluminium or Tool steel? Because in operation a mill or a lathe
>> generates vibrations that can adversely affect its operation and Grey
>> Cast dampens vibration, and does so without deflection. It is a
>> physical property of the material. Just as it is a physical property
>of
>> CF.
>
>Hold on. There's more to the use of cast iron in machine frames than
>you imply.
>
>First, it's true cast iron attenuates vibrations, and that makes it
>useful in machine tool frames. But the vibration situation in
>machining is much different than that of a moving bike. Because of the
>specific number of gear teeth in mesh, the specific number of flutes on
>a particular cutter, the specific speed of rotation, the specific
>stiffness of the cutting tool, etc, it's possible to get resonance that
>ruins surface finish. This fixed-condition high frequency resonance
>isn't going to happen on a bike being ridden, unless you're briefly
>riding over something like a steel grate bridge surface.
>
>Second, don't ignore the fact that cast iron machine frames trump all
>other materials based on cost, and on ease of casting. One could get
>adequate rigidity from a cast aluminum mill frame, but it would need to
>be somewhat larger (due to aluminum's lower modulus of elasticity) and
>one _hell_ of a lot more expensive!
>
>Personally, I'd bet CI's vibration damping effect in machine tool
>frames is much less important than its cost and castability.

[damp]

Dear Frank,

Here's a table showing the damping capacity of some metals:

Table 4. Relative Damping Capacity
Material x 10^4
White Iron 2-4
Malleable Iron 8-15
Ductile Iron 5-20
Gray Iron,
Fine Flake 20-100
Gray Iron,
Coarse Flake 100-500
Eutectoid Steel 4
Armco Iron 5
Aluminum 0.4

¥Natural Log of the Ratio of Successive Amplitude

http://www.castingsource.com/tech_art_grayiron.asp

I may be misunderstanding the table, but at first glance
gray cast iron appears to have from 50 to 1,250 times as
much damping capacity as aluminum.

Carl Fogel

 

[[email protected]]

Arthur James writes:

>> I guess this boils down to vibrations rather than shock absorbing
>> from what has been offered by those who believe carbon fibre seat
>> stays improve ride comfort.

> I don't think it "boils down" to that at all I honestly can't
> remember one source that seems to know what he, she or they is
> talking about that mentioned shock absorption. It has come up a lot
> in this thread and other so I may have missed something, if that is
> the case can you do me a favour and point me back to the claim?
> Shock absorption is a red herring, it has always been about
> vibration.

OK, then tell me what I missed and what the advantage is that is being
claimed. I didn't see anything else that remained after the previous
100 responses but the discussion seems to have a life of its own.

> Don't get me wrong I do not wish to claim that CF stays will improve
> ride comfort. Until there is an ASTM standard for "ride comfort" I
> will argue that it can only be a personal thing, but discounting the
> possibility is just as wrong as attempting to quantify the
> difference. I will insist that there is a potential there, based
> entirely on the known properties of the material.

You say that so what structural properties could they be and where
would the energy be dissipated? Unless the material has significant
viscous losses, there won't be any significant damping. You seem to
be trying to keep the flame of belief in road shock non-transmission
alive in spite of what has been presented.

>>So let's get to the essence. What frequencies are being damped by
>>these stays?

> Not sure, can you tell me what frequencies of vibration are
> generated by riding over different road surfaces, for example new
> velodrome wood, fresh cured concrete, new asphalt and old asphalt?
> I don't think that anyone will argue that you can't feel the
> difference in surfaces when you ride over them. Anyway it is those
> frequencies (among others) that are a concern of the claims.

Hold it. You are the one proposing that it has "potential" to absorb
road shock, not I. So please present the frequencies it MIGHT dampen.
That one can feel the difference of riding over smooth or rough
surfaces is not disputed, only that seat stay material has no effect
on this sensation.

>> For example, let's use one as a sounding probe. If such a stay
>> were held between the ear and a piece of vibrating machinery to
>> asses some noises, as is often done in machine applications, would
>> one expect to hear more or less using a steel seat stay or a carbon
>> fibre one... or a 1/2 inch wooden dowel of equal length for that
>> matter?

> You would hear less with CF than steel and less with most woods than
> CF.

Try it. No mechanic who has listened to machine noises (gear boxes
etc.) believes that a wooden dowel give any different report than a
metal rod. I certainly have no problem with either material in that
use and cannot hear a difference. The only difference would be in the
high frequencies where metals resonate. This is not something you can
FEEL but rather something in the acoustic realm.

>> This reminds me of the rider who claimed he could feel the
>> difference between 1.5mm diameter spokes and 2.0mm diameter ones,

> Kind of reminds me of the guy claiming that the earth revolves
> around the sun while everyone else was happy with the retrograde
> motion of the planets as explained by the crystal spheres theory.

You mean that carbon fiber seat stays absorb vibrations transmitted
through a pneumatic tire through a bicycle saddle to soft tissue in
the buttocks to make a perceptible difference? It isn't clear to what
your comment refers. I am referring to that claim.

>> I don't believe the claimed damping is in the acoustic range and it
>> certainly isn't in the human touch range, or we would see some
>> deflections.

> Once again the deflection claim comes up, and well... How much
> deflection do you see in in a lathe bed when it is in operation?

You don't and there isn't if the lathe is designed for the load you
put on the tool post.

> IIRC from your book you used a Bridgeport mill as one of the test
> fixtures (might have been a different book not to sure now) what was
> that mill made of? Grey Cast Iron... Why was it made of that and
> not say Aluminium or Tool steel? Because in operation a mill or a
> lathe generates vibrations that can adversely affect its operation
> and Grey Cast dampens vibration, and does so without deflection. It
> is a physical property of the material. Just as it is a physical
> property of CF.

These are metallic acoustic waves that are damped by cast iron
although there are plenty of machine tools build of cast steel. The
problem is cost and at best acoustic damping. The static modulus of
elasticity of cast iron and steel are the same, the principal
ingredient being iron. Pleas don't infuse herrings, red or others
into this carbon seat stay claim.

> As an aside I would have hoped for better from you, you've gone out
> of your way to research one aspect of the bicycle and provided reams
> of measurements, yet here you are arguing against a well-researched
> and established phenomenon. There are reams of data showing that CF
> dampens or attenuates vibration.

Pleas show a reference to these reams of data (distilled) to support
damping of vibrations tansmitted from peneumatic tires to the rider
sitting on a saddle. That is what has not been presented here and
might add something to the discussion. Don't be so cindescendingly
petulant and decry my lack of technical skills.

> Say things like "the amount of damping is insignificant compared to
> other options available" or "the average rider probably wont notice
> a difference" and I wont scrap. Or say "the potential for a failure
> at the CF is Alu./Ti. bond due to galvanic corrosion far outweighs any
> comfort benefit for most riders" and I might even agree with you (I
> would at lest hold the option open until such time as the manufacturer
> explained how it was avoided.)

How about giving out with your take on this matter with reasons why
one should believe that aspect rather than writing editorials of
presentations with which you seem to disagree in such a tangent manner
that your point of view has gotten lost.

> And I guess that is my whole point... it is possible, whether or not
> any individual will notice or care depends on a huge number of other
> factors. Just don't discard the possibility.

Why not? I see no supporting evidence for that "possibility."

[email protected]

 

[[email protected]]

On 17 Apr 2005 09:03:20 -0700, [email protected] wrote:

>
>[email protected] wrote:
>>
>>
>> Once again the deflection claim comes up, and well...How much
>> deflection do you see in in a lathe bed when it is in operation? IIRC
>> from your book you used a Bridgeport mill as one of the test fixtures
>> (might have been a different book not to sure now) what was that mill
>> made of? Grey Cast Iron ... why was it made of that and not say
>> Aluminium or Tool steel? Because in operation a mill or a lathe
>> generates vibrations that can adversely affect its operation and Grey
>> Cast dampens vibration, and does so without deflection. It is a
>> physical property of the material. Just as it is a physical property
>of
>> CF.
>
>Hold on. There's more to the use of cast iron in machine frames than
>you imply.
>
>First, it's true cast iron attenuates vibrations, and that makes it
>useful in machine tool frames. But the vibration situation in
>machining is much different than that of a moving bike. Because of the
>specific number of gear teeth in mesh, the specific number of flutes on
>a particular cutter, the specific speed of rotation, the specific
>stiffness of the cutting tool, etc, it's possible to get resonance that
>ruins surface finish. This fixed-condition high frequency resonance
>isn't going to happen on a bike being ridden, unless you're briefly
>riding over something like a steel grate bridge surface.
>
>Second, don't ignore the fact that cast iron machine frames trump all
>other materials based on cost, and on ease of casting. One could get
>adequate rigidity from a cast aluminum mill frame, but it would need to
>be somewhat larger (due to aluminum's lower modulus of elasticity) and
>one _hell_ of a lot more expensive!
>
>Personally, I'd bet CI's vibration damping effect in machine tool
>frames is much less important than its cost and castability.
>
>
> There are reams of data showing that CF dampens
>> or attenuates vibration.
>
>What we need is data showing that CF dampens vibrations that are
>already isolated from the rider by a pneumatic tire and a suspended
>saddle!
>
>Seriously, if we were riding directly on the metal rim, and our butts
>were perched directly on the top of the seatstay, you might convince me
>that CF had some benefit. But that's not our situation at all!
>
>> And I guess that is my whole point... it is possible, whether or not
>> any individual will notice or care depends on a huge number of other
>> factors. Just don't discard the possibility.
>
>When a carbon fiber promoter arranges a proper blind test, that will
>give this "possibility" some legitimacy. Until then, I look on it as
>just as "possible" as, say, the geomagnetic booster.
>http://sheldonbrown.com/geomag.html
>
>- Frank Krygowski

Dear Frank,

Here are three more links about damping capacity.

The first link gives damping capacity equations at the very
end and then points to the second link, in which tuning
forks of identical size but different materials are struck
and the results detailed:

http://silver.neep.wisc.edu/~lakes/VEnotes.html

Looking at the picture of the forks, I suspect that one is
nowhere near the same dimensions, but the others look fairly
similar.

Browsing the research leads to page, with a rather cluttered
and interesting yellow graph titled "stiffness-loss map"
that plots stiffness versus damping.

http://silver.neep.wisc.edu/~lakes/VE.html

Steel and aluminum show up on the upper left, and appear to
show damping around 10^-3.

Composites show up in an arc at the upper right (at the same
level of stiffness) and appear to show damping around 10^-1
on a scale where a rightward position means more damping--an
improvement of two orders of magnitude. These are, however,
high-performance composites, so it's not clear how closely
they resemble the stuff in bicycle frames.

Rubber, bone, polystyrene, lead, and other materials are
also plotted.

Carl Fogel

 

[[email protected]]

On 17 Apr 2005 09:03:20 -0700, [email protected] wrote:

>
>[email protected] wrote:
>>
>>
>> Once again the deflection claim comes up, and well...How much
>> deflection do you see in in a lathe bed when it is in operation? IIRC
>> from your book you used a Bridgeport mill as one of the test fixtures
>> (might have been a different book not to sure now) what was that mill
>> made of? Grey Cast Iron ... why was it made of that and not say
>> Aluminium or Tool steel? Because in operation a mill or a lathe
>> generates vibrations that can adversely affect its operation and Grey
>> Cast dampens vibration, and does so without deflection. It is a
>> physical property of the material. Just as it is a physical property
>of
>> CF.
>
>Hold on. There's more to the use of cast iron in machine frames than
>you imply.
>
>First, it's true cast iron attenuates vibrations, and that makes it
>useful in machine tool frames. But the vibration situation in
>machining is much different than that of a moving bike. Because of the
>specific number of gear teeth in mesh, the specific number of flutes on
>a particular cutter, the specific speed of rotation, the specific
>stiffness of the cutting tool, etc, it's possible to get resonance that
>ruins surface finish. This fixed-condition high frequency resonance
>isn't going to happen on a bike being ridden, unless you're briefly
>riding over something like a steel grate bridge surface.
>
>Second, don't ignore the fact that cast iron machine frames trump all
>other materials based on cost, and on ease of casting. One could get
>adequate rigidity from a cast aluminum mill frame, but it would need to
>be somewhat larger (due to aluminum's lower modulus of elasticity) and
>one _hell_ of a lot more expensive!
>
>Personally, I'd bet CI's vibration damping effect in machine tool
>frames is much less important than its cost and castability.
>
>
> There are reams of data showing that CF dampens
>> or attenuates vibration.
>
>What we need is data showing that CF dampens vibrations that are
>already isolated from the rider by a pneumatic tire and a suspended
>saddle!
>
>Seriously, if we were riding directly on the metal rim, and our butts
>were perched directly on the top of the seatstay, you might convince me
>that CF had some benefit. But that's not our situation at all!
>
>> And I guess that is my whole point... it is possible, whether or not
>> any individual will notice or care depends on a huge number of other
>> factors. Just don't discard the possibility.
>
>When a carbon fiber promoter arranges a proper blind test, that will
>give this "possibility" some legitimacy. Until then, I look on it as
>just as "possible" as, say, the geomagnetic booster.
>http://sheldonbrown.com/geomag.html
>
>- Frank Krygowski

Dear Frank,

Here are three more links about damping capacity.

The first link gives damping capacity equations at the very
end and then points to the second link, in which tuning
forks of identical size but different materials are struck
and the results detailed:

http://silver.neep.wisc.edu/~lakes/VEnotes.html

Looking at the picture of the forks, I suspect that one is
nowhere near the same dimensions, but the others look fairly
similar.

Browsing the research leads to page, with a rather cluttered
and interesting yellow graph titled "stiffness-loss map"
that plots stiffness versus damping.

http://silver.neep.wisc.edu/~lakes/VE.html

Steel and aluminum show up on the upper left, and appear to
show damping around 10^-3.

Composites show up in an arc at the upper right (at the same
level of stiffness) and appear to show damping around 10^-1
on a scale where a rightward position means more damping--an
improvement of two orders of magnitude. These are, however,
high-performance composites, so it's not clear how closely
they resemble the stuff in bicycle frames.

Rubber, bone, polystyrene, lead, and other materials are
also plotted.

Carl Fogel

 

[jim beam]

[email protected] wrote:
> I guess this boils down to vibrations rather than shock absorbing from
> what has been offered by those who believe carbon fiber seat stays
> improve ride comfort. So let's get to the essence. What frequencies
> are being damped by these stays?
>
> For example, let's use one as a sounding probe. If such a stay were
> held between the ear and a piece of vibrating machinery to asses some
> noises, as is often done in machine applications, would one expect to
> hear more or less using a steel seat stay or a carbon fiber one... or
> a 1/2 inch wooden dowel of equal length for that matter?
>
> This reminds me of the rider who claimed he could feel the difference
> between 1.5mm diameter spokes and 2.0mm diameter ones, something that
> could be as great as riding over a sheet of copier paper lying on the
> road (aka 0.003"). I don't believe the claimed damping is in the
> acoustic range and it certainly isn't in the human touch range, or we
> would see some deflections. So where is it once more?
>
> [email protected]

that old saw? jobst, you're deliberately fudging. .003" /is/
detectable. run your finger over the edge of a feeler gauge. run a
pencil over the edge of a feeler gauge. look at damon rinard's web site
to see what a difference skinny spokes make to lateral stability.

 

[[email protected]]

[email protected] wrote:
>
>
> Dear Frank,
>
> Here's a table showing the damping capacity of some metals:
>
>
>
> I may be misunderstanding the table, but at first glance
> gray cast iron appears to have from 50 to 1,250 times as
> much damping capacity as aluminum.

I know CI has much more damping capacity than aluminum, and this
certainly has some merit. However, I think this is somewhat less
important to machine tool manufacturers than the low cost and the
excellent castability of CI.

But we're discussing an irrelevant side point.

(FWIW, I don't think a cast iron seat stay would increase the ride
quality of a bike.)

- Frank Krygowski

 

[[email protected]]

[email protected] wrote:
>
> Dear Frank,
>
> Here are three more links about damping capacity....

You fail to explain how this is pertinent to the problem at hand. Are
you hinting that an essentially undeformable seat stay, isolated at
both ends by flexible material, will attenuate road vibrations or
shock? If so, please explain in detail.


- Frank Krygowski

 

[[email protected]]

jim beam wrote:
> [email protected] wrote:
> > I guess this boils down to vibrations rather than shock absorbing
from
> > what has been offered by those who believe carbon fiber seat stays
> > improve ride comfort. So let's get to the essence. What
frequencies
> > are being damped by these stays?
> >
> > For example, let's use one as a sounding probe. If such a stay
were
> > held between the ear and a piece of vibrating machinery to asses
some
> > noises, as is often done in machine applications, would one expect
to
> > hear more or less using a steel seat stay or a carbon fiber one...
or
> > a 1/2 inch wooden dowel of equal length for that matter?
> >
> > This reminds me of the rider who claimed he could feel the
difference
> > between 1.5mm diameter spokes and 2.0mm diameter ones, something
that
> > could be as great as riding over a sheet of copier paper lying on
the
> > road (aka 0.003"). I don't believe the claimed damping is in the
> > acoustic range and it certainly isn't in the human touch range, or
we
> > would see some deflections. So where is it once more?
> >
> > [email protected]
>
> that old saw? jobst, you're deliberately fudging. .003" /is/
> detectable. run your finger over the edge of a feeler gauge. run a
> pencil over the edge of a feeler gauge. look at damon rinard's web
site
> to see what a difference skinny spokes make to lateral stability.

 

[[email protected]]

jim beam wrote:
>
>
>
> that old saw? jobst, you're deliberately fudging. .003" /is/
> detectable. run your finger over the edge of a feeler gauge. run a
> pencil over the edge of a feeler gauge.

??

Are you _really_ saying that 0.003" is detectable by a rider's butt??
When that butt is on a saddle that flexes up to 1/4"?? And is riding
on a tire that deflects at least 1/8"??

All sorts of things are "detectable," given adequate instrumentation.
Let's restrict the discussion to the detection tools at hand - to whit,
the rider's butt!

- Frank Krygowski

 

[jim beam]

[email protected] wrote:
> jim beam wrote:
>
>>[email protected] wrote:
>>
>>>
>>>But the number of hits on Google isn't the number I was looking
>
> for.
>
>>>After all, if you google "space alien abduction" you get about
>
> 174,000
>
>>>hits. Do you therefore figure space alien abductions are nearly
>
> twice
>
>>>as likely as carbon fiber vibration absorption?
>>
>>i don't think vibration absorption "likely" - i've seen it tested in
>
> the
>
>>lab!
>
>
> On a bicycle? If so, give us the results! If not, you'll have to
> clearly demonstrate that the situation is close enough to be
> equivalent.
>
> Here's a proposal for a simplified lab test: One vertical seatstay
> tube of steel, versus one of carbon fiber. Use a shaker table or other
> mechanism to vibrate the bottom. Mount an accelerometer at the top,
> hook it to data acquisition equipment. Sound good so far?
>
> But we're not done, and this is the critical part: Between the
> vibrator and the tube, put a 1" diameter rubber tube inflated to 100
> psi, to simulate the tire. And at the top, between the tube and the
> accelerometer, put a bicycle seat. And put a 150 pound weight on the
> seat. Now measure the difference in vibration amplitude at the seat's
> top.
>
> Of course, if you want to do a better job, you can find a way to model
> the spokes, the seatpost, etc. Or hell, just mount a bike frame,
> vibrate the botttom of the rear tire and measure the effect at the
> saddle's top surface. Just don't forget the 150 pound weight on the
> saddle.
>
>
>>returning to the debate, "my" claims are not extroardinary, merely
>>statements of fact.
>
>
> Classic! IOW:
> "Here's proof of my views: 'MY VIEWS ARE TRUE!' There! Guess I showed
> you!"
>
> read andrew's description of the factors that
>
>>influence vibration absorption in carbon composites. as for "tire &
>>saddle" stuff, again, it's wrong to confuse static with dynamic
>>properties.
>
>
> You'll need to explain that in much more detail. If there are specific
> inertial effects you're imagining, you'll have to explain them. In
> particular, you'll have to explain how they get attenuated by a stiff
> carbon tube, but do not get attenuated by an air cushion (the tire) and
> a sprung hammock (the saddle).
>
>
>
>>>Do you know of a blind test where riders could distinguish frames
>
> that
>
>>>were identical except for the carbon stays? Alternately, do you
>
> know
>
>>>of instrumented tests that clearly showed a significant difference?
>>
>>can't say i've bothered to look...
>
>
> Ah.
>
> because i have some familiarity with the
>
>>theory of the materials.
>
>
> As do I.
>
> you are right, quantification is a good
>
>>objective, but frankly, i doubt the value for this group as some of
>
> its
>
>>most vocal members will disregard any fact you care to present...
>
>
> Ah.
>
> because
>
>>"it doesn't fit" their preconceptions, education be damned.
>
>
> Funny!
>
>
>
>>let me ask, have you ridden a bike that's been converted from a steel
>
> to
>
>>a carbon fork? [conversion of an existing bike eliminates all other
>>variables.] if you do that with a bike you own & love, you will be
>
> able
>
>>to differentiate a "before" & "after" of the carbon vibration
>>transmission quite easily. same for a carbon seat post.
>
>
> No, I haven't. A friend has. She says "Well, I _think_ it makes a
> difference." And it probably does - but the difference she feels could
> come from many factors besides the material difference. IOW, the
> replacement fork is unlikely to be an exact match for her steel fork in
> static stiffness, in rake (offset), in mass... and it's _certainly_ not
> an exact match in appearance!
>
> There's a POWERFUL placebo effect in everything related to cycling.
> That's why heartfelt convictions aren't nearly as convincing as real
> data, or as convincing as the results of physics-based calculations, or
> as convincing as blind comparison tests. So far, all you've provided
> are heartfelt convictions.
>
> - Frank Krygowski
>
frank, since we're touching on the fascinating subject of human
psychology, how about we debate the subject of human denial when faced
with irrefutable fact? compared to the spectacular manifestations of
human denial we see here r.b.t., the placebo effect is just for kids.
there definitely seems to be comfort in your not being unique in this
phenomenon.

there was an amazing tv show that touched on this a few years ago.
there was some woman came here some time after ww2 claiming to be the
escaped princess anastasia of the former russian royal family. long
story short, dna evidence conclusively proved this woman was just a
german runaway with a visual resemblance, nothing more. _but_ an
incredible coterie of "supporters" swore up down & sideways, even when
confronted conclusive genetic fingerprinting, that she /was/ the
princess! these "supporters" had never resided in the pre-revolutionary
russian state, never knew her before here arrival here, had never been
related to any of the tsar's family, had no corroborative supporting
material whatsoever, just a "belief" that the story they'd been told was
true. and damn, if they didn't build their whole lives around militant
denial! just amazing. maybe it was the romance of the story that
attracted them to it. bit like "my old bike's still just as good as any
of that new fangled stuff".

and that frank, is what we see here on r.b.t. facts for material
properties are easily available from much more authoritative sources
than myself. someday, if i'm bored & have time, i may indeed rent the
gear for you. i may even go over to my mother's place & see if she
still has my old undergrad study material. in the mean time, just get
on google and search for "real data" there.

http://www.google.com/search?hl=en&q=egyptian+river&btnG=Google+Search

 

[[email protected]]

jim beam wrote:
>
> > There's a POWERFUL placebo effect in everything related to cycling.
> > That's why heartfelt convictions aren't nearly as convincing as
real
> > data, or as convincing as the results of physics-based
calculations, or
> > as convincing as blind comparison tests. So far, all you've
provided
> > are heartfelt convictions.
> >
> > - Frank Krygowski
> >
> frank, since we're touching on the fascinating subject of human
> psychology, how about we debate the subject of human denial when
faced
> with irrefutable fact?

IOW, how about you abandond the subject of the thread entirely?

Sorry, Jim. No matter how you spin it, and no matter how convinced
_you_ are, I'll have to see direct proof before I believe a rigid
carbon fiber tube somehow attenuates vibrations that pass through an
inflated tire, a spoked wheel, a seatpost and a padded, flexible saddle
with a large mass on top.

When you present direct evidence, you can begin to call your views
"irrefutable fact."

- Frank Krygowski