Re: Carbon Fiber Seat Stays = Better Ride?

[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]]

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]

 

[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]]

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

 

[41]

[email protected] 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 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 th at 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.

You got that right about no one who knows what they are talking about
saying carbon stays have better shock absorption:
---------------------------------------------------------------------------
From: jim beam <[email protected]>
Newsgroups: rec.bicycles.tech,rec.bicycles.misc
Subject: Re: Carbon Fiber Seat Stays = Better Ride?
NNTP-Posting-Date: Tue, 12 Apr 2005 23:40:50 EST
Message-ID: <1113367253.2bb81eb175d67bd3b4bc3ce2e8ca8604@teranews>

Steve Sr. wrote:
> I have seen carbon fiber seat stays being advertized as improving the
> "comfort" and the ride "quality" of a bike. Serotta even goes so far
> as putting a bearing at the dropout end on their high end bikes to
> allow the seat stays to flex and act as springs to soften the ride.
Or
> at least this is what is claimed. Other manufacturers make similar
> claims.
>
> So given a regular full titanium frame like a Litespeed Tuscany how
> much if any difference would be made by having the seat stays made of
> carbon fiber?


it should have a noticably softer ride. materials people are very
familiar with the superior shock transmission characteristics of
composites. that's why tools like hammers that otherwise cause
repetitive strain injuries are so often made with composite shafts.
[in
this case, wood can also be called a composite.]

the trouble with this group however is that the people making the
loudest "it makes no difference" noises would never do anything
definitive like rent instumentation that would quantify the situation -

it would prove them luddites. as for actually /riding/ a bike with
such
new fangled technology? well, that's just not going to happen. no
siree bob.
-----------------------------------------------------------------------------

How shocking- NOT.

 

[David Damerell]

Quoting [email protected] <[email protected]>:
>[email protected] wrote:
>>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.

They laughed at Galileo, but they also laughed at Bozo the Clown...

[Sagan, Randi et al]
--
David Damerell <[email protected]> Kill the tomato!
Today is Gloucesterday, April.

 

[Peter Cole]

41 wrote:

> it should have a noticably softer ride. materials people are very
> familiar with the superior shock transmission characteristics of
> composites. that's why tools like hammers that otherwise cause
> repetitive strain injuries are so often made with composite shafts.
> [in this case, wood can also be called a composite.]

Of course that's how they're *marketed*. How many people would be in
the market for "shock reducing" handles if they were wearing inflatable
gloves?

> the trouble with this group however is that the people making the
> loudest "it makes no difference" noises would never do anything
> definitive like rent instumentation that would quantify the situation
-
>
> it would prove them luddites. as for actually /riding/ a bike with
> such
> new fangled technology? well, that's just not going to happen. no
> siree bob.
>
-----------------------------------------------------------------------------
>
> How shocking- NOT.

Yeah, we'll just trundle down to the local rental center and rent a
logging accelerometer and then go crunch the numbers. Maybe we could
rent an instrumented shaker table and get a certified report, that
should only cost a few grand. (I used to supervise vibration testing in
aerospace components). You guys are talking through your hats.

Problem is, since you guys have no physics/matsci/engineering to back
up your magazine article claims, you obviously put no faith in it. I'm
skeptical you'd accept test data anyway.

It's a non-solution to a non-problem anyway. You get RSI in your butt?

 

[41]

Peter Cole wrote:
> 41 did not write:

[crazy stuff]
>
-----------------------------------------------------------------------------

did write:
> >
> > How shocking- NOT.


> It's a non-solution to a non-problem anyway. You get RSI in your
butt?


Must you use JB style attribution for this? As indicated above, I wrote
none of that except the last line above.

 

[Peter Cole]

41 wrote:
> Peter Cole wrote:
> > 41 did not write:
>
> [crazy stuff]
> >
>
-----------------------------------------------------------------------------
>
> did write:
> > >
> > > How shocking- NOT.
>
>
> > It's a non-solution to a non-problem anyway. You get RSI in your
> butt?
>
>
> Must you use JB style attribution for this? As indicated above, I
wrote
> none of that except the last line above.


I didn't, your quoting style is random.

 

[jim beam]

[email protected] wrote:
> 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
>
ok frank, let's try a little experiment. buy a balloon and blow it up.
no helium, just plain old air. don't forget to knot the neck.

experiment 1: the static load.
with the balloon back in the palm of the hand, balance a quarter on top.
feel the weight? try another quarter. feel the weight again? what's
the force on your hand? it's 0.4 ounces force [about 1N]. that's the
same regardless of balloon inflation, meaning that the balloon transmits
100% of any applied static force.

experiment 2: the dynamic load.
hold that balloon in the palm of your hand & tap it with a drinking
straw or a pencil, something light. can you feel the tap through the
balloon with your hand? ok, now, get an old bike saddle, place that in
your hand, with the rails uppermost. balance the balloon between the
two rails. tap the balloon again with the straw. still feel it? how
can that be? the balloon's inflated to much lower pressure than any
bike tire, has a much weaker side wall, and above all is being subject
to trivial loading.

these are not tricks. these are demonstrations of the fundamentals we
have here. buying, essentially on faith, the old jobstian fantasy that
tire deflection somehow negates all other structural behavior is as
incomplete a view of reality as is flat earth theory. any static force
applied to the tire /is/ completely transmitted to the rider while the
two are in equilibrium. any force changing with time is still
transmitted to the rider, but at rates which depend on the reaction of
structure. this includes tire, wheel, frame, saddle, etc. /all/ have
different characteristics, something jobst seems never to be able to
acknowledge, but an understanding of which is /essential/ to an accurate
description of this situation. merely repeating jobst's half formed
misunderstandings makes no progress whatsoever.

 

[Peter]

jim beam wrote:

> experiment 1: the static load.
> with the balloon back in the palm of the hand, balance a quarter on top.
> feel the weight? try another quarter. feel the weight again? what's
> the force on your hand? it's 0.4 ounces force [about 1N]. that's the
> same regardless of balloon inflation, meaning that the balloon transmits
> 100% of any applied static force.

It's closer to 0.1 Newton, but I'm really not sure what you're trying to
prove here. There's certainly no question that the weight of the rider
would be transmitted through the frame to the road surface.
>
> experiment 2: the dynamic load.
> hold that balloon in the palm of your hand & tap it with a drinking
> straw or a pencil, something light. can you feel the tap through the
> balloon with your hand? ok, now, get an old bike saddle, place that in
> your hand, with the rails uppermost. balance the balloon between the
> two rails. tap the balloon again with the straw. still feel it? how
> can that be? the balloon's inflated to much lower pressure than any
> bike tire, has a much weaker side wall, and above all is being subject
> to trivial loading.

The relevant question would be whether, with the balloon still in place,
we could feel the difference between the shock transmitted if the saddle
is a Brooks Pro or a Flite. I contend that the presence of the balloon
would make it hard to notice the shock-absorbing effects of the saddle.
Similarly, I contend that the presence of a rather soft tire makes it
hard to notice the shock-absorbing effects of the much more rigid frame
although there may well be differences in high-frequency vibrations
(such as the sound of a steel frame vs. a CF one when subject to an
impulse).

No one has claimed that the presence of the tire prevents us from
feeling any bumps in the road - that's not the question.

 

[Mark Hickey]

jim beam <[email protected]> wrote:

>experiment 2: the dynamic load.
>hold that balloon in the palm of your hand & tap it with a drinking
>straw or a pencil, something light. can you feel the tap through the
>balloon with your hand? ok, now, get an old bike saddle, place that in
>your hand, with the rails uppermost. balance the balloon between the
>two rails. tap the balloon again with the straw. still feel it? how
>can that be? the balloon's inflated to much lower pressure than any
>bike tire, has a much weaker side wall, and above all is being subject
>to trivial loading.

The contention is whether or not you can tell the difference between
tapping on the balloon with a shaft made of carbon fiber, steel,
aluminum or titanium (assuming all have the same outside diameter and
weight). If you tapped your knuckle directly you probably could
discern the difference between at least a couple of them. But since
the balloon (or tire, rim, spokes, seatpost, saddle) has so much more
compliance than the skin over your knuckle, it masks that difference.

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

 

[[email protected]]

[email protected] wrote:
Arthur James writes:

That would be Andrew

Following up with some severe snipping...

>
> 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.

>
> Hold it. You are the one proposing that it has "potential" to absorb
> road shock, not I.

Actually I don't claim "absorb" or "road shock" those are YOUR words, I
even wrote..

> > 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.

I have maintained that it dampens vibration..

> 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.

Then I must ask by what mechanism are you feeling this? You mention
later..

> vibrations transmitted through a pneumatic tire through a bicycle
saddle > to soft tissue in the buttocks.

To this I'll reply yes that is exactly what I'm talking about,
vibrations transmitted through the frame material. You accept that they
can be felt and that they are transmitted through the frame. By
extension a frame material that transmits vibration with greater or
lesser efficiency should feel different.


> > 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.

UM, no? That isn't so..
I'll grant that anything is better than nothing but with the exception
of the stethoscope with the little probe attached the favorite seems to
be the giant slot screwdriver /prybar, you know, the one with the
translucent yellow handle.

Carl found some links discussing the different materials and their
properties, there are lots of journal articles text books and materials
guides that discuss the same thing.

> 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?

I've been very careful not to quantify any difference perceptible or
otherwise. I'm arguing for the potential or possibility. There are too
many other factors at play to make a definitive claim.

> It isn't clear to what
> your comment refers. I am referring to that claim.

I'm referring to the person that has the perfectly acceptable
scientific answer to an issue and wont notice that there is a simpler
and more elegant answer because it contradicts one of his fundamental
beliefs.


> Don't be so condescendingly petulant and decry my lack of technical
skills.

It is because of my respect for your technical skills that that I was
disappointed.
And as far as condescension goes maybe I should introduce you to my pal
Mister Kettle?


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

Well the claim is based on some potential change in comfort.
Absent a Metric for comfort we have to deal with perception.

IF comfort is affected by "vibrations transmitted through a pneumatic
tire through a bicycle saddle to soft tissue in the buttocks." WHERE
"one can feel the difference of riding over smooth or rough surfaces"
THEN (my words now) a frame material that transmits vibration less
efficiently than others MAY effect comfort.


(1) Carl found some links on the subject and a quick Google search
turned
up lots of info on vibration transmission and damping.

this paper may be helpful

http://computing.breinestorm.net/chromosomes+fitness+determines+operations+parameters/

There is a little blurb on hysteretic damping here

http://www.earsc.com/HOME/engineering/TechnicalWhitePapers/Vibration/index.asp?SID=61

here is another paper covering the issue though you have to buy this
one
http://www.aiaa.org/content.cfm?pageid=406&gTable=mtgpaper&gID=59836

as a side note
http://www.acpt.com/article2.html

and reams of cites to publications.

 

[[email protected]]

Andrew James writes:

>> 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.

>> Hold it. You are the one proposing that it has "potential" to
>> absorb road shock, not I.

> Actually I don't claim "absorb" or "road shock" those are YOUR
> words, I even wrote..

>>> 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.

> I have maintained that it dampens vibration..

OK, call it that but damping is absorption and dissipation of the
exciting energy by that material through mechanical losses.

>> 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.

> Then I must ask by what mechanism are you feeling this? You mention
> later...

>> vibrations transmitted through a pneumatic tire through a bicycle
>> saddle to soft tissue in the buttocks.

> To this I'll reply yes that is exactly what I'm talking about,
> vibrations transmitted through the frame material. You accept that
> they can be felt and that they are transmitted through the frame.
> By extension a frame material that transmits vibration with greater
> or lesser efficiency should feel different.

I refer you to Peter Cole's response:

---------------------------------------------------------------------
This is kind of bizarre. A sprung system is defined by spring and
mass. It is also known as a resonant system. This is because both
the spring and mass are energy storage components. As a time-varying
force is applied, the spring begins to absorb energy, then transmits
force to the mass, which begins absorbing energy, the energy (after
initial excitation) is passed back & forth between the 2 components,
gradually diminishing from whatever losses are in the path (damping).

You can't talk about the spring while ignoring the mass, you're
throwing out half the model. You don't have a resonant system
anymore. The exact first-order model of tires, frame and rider is
that of a mass suspended by 2 springs in series. The math for this is
simple. I don't know what's up with the balloons, saddles and
quarters, but it doesn't model a bike and rider.

Since the spring constant (amount of deflection per unit force) is much
greater (yes, Sandy, 10x, maybe 100x) for tires than frames (whatever
material), the frame "spring" can be safely ignored as it makes no
significant contribution.
---------------------------------------------------------------------

>>> 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.

> UM, no? That isn't so..
> I'll grant that anything is better than nothing but with the exception
> of the stethoscope with the little probe attached the favorite seems to
> be the giant slot screwdriver /prybar, you know, the one with the
> translucent yellow handle.

The point is that the frequencies of interest are not attenuated by
the solid materials I cited. The differences to which you allude are
higher acoustic ones that have no effect on ride comfort and cannot
pass through the tire to the CF seat stay. These amplitudes are in
the micrometers and not ones transmittable by tires and saddles, much
less the flesh of a human body.

> Carl found some links discussing the different materials and their
> properties, there are lots of journal articles text books and
> materials guides that discuss the same thing.

....as inapplicable as are the rest of the arguments for CF road shock
damping.

>> 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?

> I've been very careful not to quantify any difference perceptible or
> otherwise. I'm arguing for the potential or possibility. There are
> too many other factors at play to make a definitive claim.

At this point I think I'll follow another thread in this newsgroup.

[email protected]

 

[[email protected]]

[email protected] wrote:
> Andrew James writes:
>
>
> I refer you to Peter Cole's response:
>
> ---------------------------------------------------------------------
> This is kind of bizarre

A material can be both ridged and damp vibration. It is not necessary
for it to be sprung.


> >> 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.

> The point is that the frequencies of interest are not attenuated by
> the solid materials I cited. The differences to which you allude are

Those examples were yours.. if you want to float them fine but it is
your red herring not mine. and you are wrong.

> higher acoustic ones that have no effect on ride comfort and cannot
> pass through the tire to the CF seat stay. These amplitudes are in
> the micrometers and not ones transmittable by tires and saddles, much
> less the flesh of a human body.

Well what about those vibrations that you postulate that you can feel
and are transmitted through the frame?


>
> ...as inapplicable as are the rest of the arguments for CF road shock
> damping.

Once again you talk of road shock .. too bad the discussion is not
about road shock.

> At this point I think I'll follow another thread in this newsgroup.

Perhaps that is best... stick to what you know..