Another useless gimic?

Mike Holland <[email hidden]> wrote in message news:<[email hidden]>...

[snip]

Quoted message said:

No, not if the flexing is elastic. Then you get the energy back.
Just like a diver or gymnast does from a springboard.

[snip]

Dear Mike,

I blush to admit that I'm familiar enough with some of your
points to imagine that I follow you. I assure you that I
wasn't arguing for or against any of them (who would listen
to the likes of me?), just whining that the first flurry of
posts about the strange Colnago chain-stay were just calling
it names, not explaining what was wrong.

Later posts have offered far more content, the kind that even
I can parrot. I'm perfectly willing to throw stones at Colnago,
but I need help with my aim.

To put it another way, your post was far more interesting
than any snide remark that I can come up with (like how those
bulging cut-outs resemble tail-fins). They may be useless,
but I wanted to read about what the use was and why they
don't work.

However, one of your points that I repeated above troubles
me a little.

Elasticity involves restoring absorbed energy, but it's
always imperfect and energy is lost in the form of heat
and sound and so forth, even when steel balls bounce off
steel plates.

I may have snipped too much, but where does your thinking
lead? That is, do you favor increasing the elastic lateral
flex of the metal frame, heading toward the diving board
board end of the spectrum? Or would the most efficient
frame reduce lateral flex as much as possible, which is
what Colnago claims to be doing?

Isn't all lateral flex and elasticity wasted in terms of
making the bike go forward? Arguments that the effort
involved doesn't amount to much should address the question
of how much actually is involved--and my understanding is
that it takes a surprising amount of force to deflect the
rear frame of a bicycle.

I long for detailed reassurance that Colnago is right
or wrong. The voting is strongly against them, but I'd
hate to have someone who actually addressed the design
in question prove me to be wrong.

Is Colnago's weird frame going to be noticeably better,
roughly the same, or noticeably worse than good old
God-fearing round chain-stays? Why?

(I admire Sheldon Brown's web site, but I'm not up to
applying it to a new design and I'm much too impatient
to wait for widespread testing. Lord, how I love this
business of getting expert opinions for free!)

Thanks,

Carl Fogel

On 15 Oct 2003 01:01:29 -0700, [email hidden] (Carl Fogel)

Quoted message said:

to wait for widespread testing. Lord, how I love this
business of getting expert opinions for free!)

Yeah...expert...that's the ticket!

Quoted message said:

Thanks,

Carl Fogel

--
Rick "Expert In Everything Except Some Things" Onanian

Carl Fogel said:

Isn't all lateral flex and elasticity wasted in terms of
making the bike go forward? Arguments that the effort
involved doesn't amount to much should address the question
of how much actually is involved--and my understanding is
that it takes a surprising amount of force to deflect the
rear frame of a bicycle.

Once. On the next pedal stroke, nearly all the energy comes from it
undeflecting back to the centre position.
--
David Damerell <[email hidden]> Distortion Field!

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

Quoted message said:

Deep Freud Moors said:

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

Quoted message said:

Quoted message said:

Quoted message said:

I'm not JB, but according to the chart on the c40 page, a 100kg rider
will have 5% less vertical flex = 0.05 * 0.06mm = 0.003mm.

Let me guess... is that worth about 0.0000001psi in the tyre?

Yeah, that's a good point. There are so many other factors involved,
how could you possibly notice such a miniscule difference?
---
DFM

No problem. If you have an appropriate saddle of course.

Good one :-)

I was just trying to imagine how small 0.003 mm is. Take 1 mm, divide it
into units of 10. Take one of those units and divide into units of 10. Take
one of *those* units and divide it by 3. I don't think you'd pick that up
even with a granite saddle.

5 percent of buggerall is still buggerall.

Jeff

David Damerell <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

Carl Fogel said:

Isn't all lateral flex and elasticity wasted in terms of
making the bike go forward? Arguments that the effort
involved doesn't amount to much should address the question
of how much actually is involved--and my understanding is
that it takes a surprising amount of force to deflect the
rear frame of a bicycle.

Once. On the next pedal stroke, nearly all the energy comes from it
undeflecting back to the centre position.

Dear David,

I'm sorry, but I'm still missing something here.

Is the idea that as I push down on one pedal, some of my effort
goes into flexing the frame laterally on the downstroke, but that
I get most of this stored energy back on the upstroke of the same
pedal as the flexed frame returns to its unstressed center position?

If so, I'm worried about what the other pedal is doing and
where the frame is flexing on its downstroke.

Is the frame bending sideways slowly through each downstroke and
then snapping back to the center position much more quickly (a
jolt?) before slowly bending the other way under the pressure on
the other pedal? That is, slow or sustained bending for most of each
down stroke, followed by a quick release and snapping back to the
center?

I'm also troubled by the idea of "once." If it takes a lot of
energy to bend a frame to one side, followed by a slow or quick
elastic return to a center position, how does this help the next
bending?

Perhaps I'm using the wrong analogy? I'm thinking of a stiff
steel rod in a vise being bent from side to side fairly slowly
and imagining little or no help as I release the rod and it
snaps back to its unstressed center position. This model seems
more like lateral frame flex than a bouncing ball.

Another model would be a bow and arrow--a slow deflection of the
bow followed by a quick release of stored energy launches the
arrow, but it doesn't seem to help me draw the bow again.

Again, I'm sorry that I'm not following the physics here
and I do appreciate your effort to explain it. I suspect
that there's something obvious and crucial that I'm missing,
like the pre-tensioning that's essential to understanding
how bicycle wheels work.

Thanks,

Carl Fogel

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

Quoted message said:

(Alan Walker) said:

Saw a very expensive frame in my local bicycle shop with large
diamond-shaped holes in the chainstays. The carbon fibre tubes split
into two, then rejoined, leaving a hole.

That's what happens when bike buyers let silly people make their bikes
out of plastic. (They could have shaped the frame like a carousel
horse instead, but that would have been interesting, so of course they
didn't.)

In an episode of "Scientific American
Frontiers"

http://www.pbs.org/saf/1309/segments/1309-1.htm

"In his course called "How to Make (Almost) Anything," Gershenfeld's students
fabricate tangible
objects from the plans they design on computers, using computer-controlled
machines to cut through
materials ranging from plastic to steel. Alan tries out a one-of-a-kind
bicycle made by one student
based on a model of Matisse's Blue Nude Number Two."

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

Quoted message said:

I don't know whether it actually does so or if such
stiffness matters, but I was surprised by how much
apparently ignorant scoffing your post generated.
You'd think that rec.bicycles.tech posters would be
curious about a weird new frame from a respected
manufacturer.

"Vertical Flex: With the new C40 HP, the rear triangle flexes 5% more in the
vertical plane (see Figure 1 below); which should result in an increase in
comfort for the rider.

Lateral Flex: In addition, there was 3.5% less lateral flex (see Figure 2
below), thus increasing the torsional rigidity of the rear triangle. These
results should allow greater power transfer from the frame."

Question: what's 5% of nothing?

Answer: more than 3.5% of nothing.

This design is lame by their own admission...

"David L. Johnson" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

On Mon, 13 Oct 2003 19:51:48 +0000, Carl Fogel wrote:

As far as this goes, according to the website you mention:

Quoted message said:

http://www.trialtir-usa.com/2003-colnago/c40/c40-testing.html

Indeed has a chart purporting to list the 5% increase in vertical flex.
But the scale is revealing, it gives flex in millimeters X 10e4. At the
highest mass tested, 100Kg, the new frame flexed not 600 mm, but 600/10000
mm. .06mm. The old frame flexed 580/10000 mm, .058mm That .002mm
difference is what they are advertising.

Darn, their rear triangles flex .06mm at 100kg? No wonder my Cannondale beats
me up so bad, it probably only flexes .03mm.

(Carl Fogel) said:

[email hidden] (Chalo) wrote:

Quoted message said:

Quoted message said:

(Alan Walker) said:

Saw a very expensive frame in my local bicycle shop with large
diamond-shaped holes in the chainstays. The carbon fibre tubes split
into two, then rejoined, leaving a hole.

It's much more difficult to include such ugly and worthless
contrivances when the maker is constrained to a proper material.

Why is it harder to make these odd frame tubes with their
diamond holes out of metal (I assume this is your proper
material) than carbon fiber?

Carbon frames are made of strips of carbon cloth which are soaked in
epoxy resin and cured under pressure (or vacuum) in molds. Once the
(expensive and time-consuming) tooling is made, the forms available
are limited only by the shape of the mold or die, and the limitations
of strength and stiffness of the fiber that can be laid in it.

By contrast, a metal version of the Colnago F40 chainstay would be
made by welding together either segments of shaped tubing or shaped
sections that had been stamped or drawn to form halves of the desired
structure.

The shape can be had either way. However, in a metal frame it would
elevate both the cost and weight enough to call into question the
benefits of such a design (none) compared to its design tradeoffs. It
would be difficult to sell most buyers of metal frames a feature that
added maybe 25% to the cost of a frame, contributed about 1/2 lb. to
the weight, and weakened the structure overall.

Because of the high strength:weight ratio of CFRP, and because of its
particular production cost considerations, both the weight and cost
penalties of their chainstay design are reduced compared to a metal
frame of like design. But those penalties still exist when compared
to a more structurally optimized CFRP frame, and the benefit still
remains at nothing.

If that area of a bike frame could benefit from stiffening (and proven
designs indicate otherwise), then simply increasing the vertical
height of the chainstay would contribute much more stiffness at a much
lower weight than Colnago's silly conceit.

Colnago chose the design they did because its [censored] factor
surpassed anything else they could concoct at such a low production
cost. Design of this sort has successfully squandered whatever
respect I might have had for the mainstream of the Italian bike
business. It has graduated from "style with function" to "style over
function", and I think that's a shame.

Fashion being what it is, Colnago's goofy see-through chainstays will
inevitably wind up on the [censored] heap with gems like PMP L-shaped cranks
and Rigi split seat tubes. Not until after parting a lot of fools
from their money, though.

http://www.classicrendezvous.com/Italy/PMP_main.htm
http://www.classicrendezvous.com/Italy/RIGI_main.htm

Chalo Colina

Carl Fogel said:

Quoted message said:

Saw a very expensive frame in my local bicycle shop with large
diamond-shaped holes in the chainstays. The carbon fibre tubes
split into two, then rejoined, leaving a hole.

Quoted message said:

Anyone who wants to pursue the matter will find it easiest
to search for Colnago and "high-power" with Google, that
being the name Colnago uses for this funny-looking frame
with a sort of diamond-cutout spliced into the chain-stay.

Quoted message said:

http://www.trialtir-usa.com/2003-colnago/c40/c40-testing.html

# Testing on vertical and lateral flex was performed at the
# Politechnico Di Milano Department of Aerospace Engineering (report
# dated 4 July 2002).

# Vertical Flex: With the new C40 HP, the rear triangle flexes 5% more
# in the vertical plane (see Figure 1 below); which should result in
# an increase in comfort for the rider.

# Lateral Flex: In addition, there was 3.5% less lateral flex (see
# Figure 2 below), thus increasing the torsional rigidity of the rear
# triangle. These results should allow greater power transfer from the
# frame.

# Thus the new distinctive Diamond Shaped Stays increase lateral
# rigidity while making the rear triangle more vertically
# compliant. These changes increase both the performance and comfort
# of the ride. The NEW Colnago C40 HP Is truly the state of the art in
# high performance cycling.

Something doesn't add up here. As most riders may have noticed,
evolution in frame building of old, where all frames were steel and
reducing weight was done by economizing on how much steel of the
classic wall thickness was used, the "rear triangle" had spindly thin
tubes and these got thinner walls when Reynolds 531 tubing was
introduced.

The rear triangle is actually a tetrahedron the most rigid 3D figure
possible for a given element size. In the bicycle it is is stressed
only in tension and compression; no torsion or bending, and that is
why it can use such small diameter tubes in contrast to other frame
elements. To change vertical compliance of the "rear triangle" by 5%,
changing the axial elasticity of the chainstay takes a huge change in
length, this being cosine error, the apparent change in length of an
element (seat stay) swept through an angle near the vertical.

The statements are at best lies of the second kind, those where with
careful interpretation the statement might be true but the message
delivered is completely false. The graph shown cannot be the
displacement of the saddle caused by the design of the chainstay.
What it is, I can't imagine, but it is not what one is lead to
believe. We see so many of these from politicians that we hardly
wince when bathed in them.

http://www.cbike.com/c-40_hp.htm

# Creating the most easily recognized and prestigious collection in
# framebuilding history, Ernesto Colnago has a way of capturing the
# hearts of cyclists with his creations. In his latest edition, the
# C-40HP (High Power), Ernesto Colnago uses a special chainstay design
# that enhances the overall performance of the bicycle. The HP (High
# Power) chainstay design offers two key advantages:

# Comfort Index - absorbs and eliminates road vibration more
# efficiently so less stress is transmitted to the rider. Torsional
# Rigidity - offers maximum torsion and power transmission when
# pedaling.

Torsional rigidity plays no role in the chainstay, but loss of
torsional rigidity is dependent on the smallest cross section of the
element in question. That this is not relevant is apparent through
the tiny diameter of chainstays where they enter the dropout.
Torsionally, the part surrounding the hole is at least half of the
normal tube.

Considering the size of bending in the links of the diamond must be to
make even a tenth of a millimeter, this is completely absurd. The
length change is the length of the side of the diamond times the sine
of the deflection angle. Assuming that is one degree, the cosine of 5
degrees is 0.9962, 6 degrees is 0.9945 the length is 20mm and that
times (0.9963-0.9945) gives 0.033mm. Now we take that and apply it to
the cosine of the seat stay angle and it barely gets into the
hundredths of mm. Meanwhile the tire and saddle flex many mm from
shock loads of interest... the ones to which they allude.

Jobst Brandt
[email hidden]

[email hidden] (Chalo) wrote in message news:<[email hidden]>...

Dear Chalo,

If I were a dog, I'd be lying on my side on the
ground with a blissful expression and my hind leg
twitching helplessly--yes, yes, that's it!

Mark Twain's "Life on the Mississippi" is still
fun to read because it gives the layman the
comfortable illusion that he understands how
to pilot a steamboat.

Now you've given me the comfortable illusion that
I understand why Colnago used carbon-fiber instead
of metal--a weird shape is easier to create with a
mould than by shaping and welding.

You even topped it all off with those bizarre web pages.
That L-shaped crank is marvelous! I'd never have known
about it without your kind effort.

Thanks!

Carl Fogel

Mike Holland said:

Carl Fogel wrote:

Quoted message said:

Quoted message said:

effort is needed to create that tiny wiggle in such a stiff
arrangement of tubing?

Not much, and you get it back on the upstroke.

On second thought, that doesnt make sense.
The frame absorbs energy by flexing as pedal weight increases,
and returns energy as stress is reduced on the latter part
of each stroke, down or up.

To go back to the topic, don't worry too much about stiffness,
as a little flex won't hurt. A touring frame needs to be stiffer
to avoid wobbles under heavy load.

The real trick in frame design is the strength-vs-weight tradeoff.
And of course, cost.

Carl Fogel said:

Is the idea that as I push down on one pedal, some of my effort
goes into flexing the frame laterally on the downstroke, but that
I get most of this stored energy back on the upstroke of the same
pedal as the flexed frame returns to its unstressed center position?

Sorry, that was my mistake. See other post.
The frame absorbs a little energy in the early part of a stroke,
and releases it in the later part, as your power decreases.
Its only of theoretical interest really.

Quoted message said:

If so, I'm worried about what the other pedal is doing and
where the frame is flexing on its downstroke.

If you are riding hard, the other foot is pulling up and adding
to the flex.

Quoted message said:

Is the frame bending sideways slowly through each downstroke and
then snapping back to the center position much more quickly (a

no. no snapping.

Peter Cole said:

"David L. Johnson" <[email hidden]> wrote

Quoted message said:

Quoted message said:

Indeed has a chart purporting to list the 5% increase in vertical flex.
But the scale is revealing, it gives flex in millimeters X 10e4. At the
highest mass tested, 100Kg, the new frame flexed not 600 mm, but 600/10000
mm. .06mm. The old frame flexed 580/10000 mm, .058mm That .002mm
difference is what they are advertising.

Darn, their rear triangles flex .06mm at 100kg? No wonder my Cannondale beats
me up so bad, it probably only flexes .03mm.

Oh, the humanity....

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

Chalo <[email hidden]> scribed in
<[email hidden]>:

Quoted message said:

http://www.classicrendezvous.com/Italy/PMP_main.htm

ROFLMAO!

Quoted message said:

http://www.classicrendezvous.com/Italy/RIGI_main.htm

well, nice if you want a shorter bike that you can't ride nohands

swarf, steam and wind

--
David Forsyth -:- the email address is real /"\
http://terrapin.ru.ac.za/~iwdf/welcome.html \ /
ASCII Ribbon campaign against HTML E-Mail > - - - - - - -> X
If you receive email saying "Send this to everyone you know," / \
PLEASE pretend you don't know me.

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

[snip]

Dear Jobst,

To paraphrase a movie that I missed, you had me at the
tetrahedron.

The rest of your explanation of how the rear frame works
was just as nice, so clear that I could half-close my
innumerate eyes and fondly imagine that I followed the
final cosines (I have to take that stuff for granted).

This is the kind of comment that I was hoping for,
something that explains why the odd Colnago chain-stays
are unlikely to be practical.

Thanks,

Carl Fogel

Carl Fogel said:

This is the kind of comment that I was hoping for, something that explains
why the odd Colnago chain-stays are unlikely to be practical.

It's not particularly that they would be impractical, no more than the
ridges they put on the main tubes, or any of their other marketing
gimmicks. But they offer no advantage, so are just tail fins. (I even
have a car with tail fins, too.)

--

David L. Johnson

__o | "What am I on? I'm on my bike, six hours a day, busting my ass.
_`\(,_ | What are you on?" --Lance Armstrong
(_)/ (_) |

Peter Cole said:

In an episode of "Scientific American
Frontiers"

http://www.pbs.org/saf/1309/segments/1309-1.htm

"In his course called "How to Make (Almost) Anything," Gershenfeld's students
fabricate tangible
objects from the plans they design on computers, using computer-controlled
machines to cut through
materials ranging from plastic to steel. Alan tries out a one-of-a-kind
bicycle made by one student
based on a model of Matisse's Blue Nude Number Two."

Check these bikes made out of Lexan on a laser cutter:

http://web.media.mit.edu/~saul/icycle/icycle.htm
http://web.media.mit.edu/~saul/iapweb/parts.htm

That's certainly not "proper" materials, but it's cool as all get-out.

Chalo Colina