Large CFRP Frames (was: Wal-Mart Italian Road Bike for $1198)

SMS aka Steven M. Scharf wrote:
[...]
Carbon frames that large tend to have problems of too much flex, which
is what the reviews of the 64cm Madone found. Colnago seems to have
solved this problem in their carbon fiber frames and they go up to 65 cm.

The larger CFRP frames being too flexible is just poor engineering, and
has nothing to do with the inherent properties of CFRP.

--
Tom Sherman - Holstein-Friesland Bovinia
The weather is here, wish you were beautiful

Tom Sherman wrote:
SMS aka Steven M. Scharf wrote:
[...]
Carbon frames that large tend to have problems of too much flex, which
is what the reviews of the 64cm Madone found. Colnago seems to have
solved this problem in their carbon fiber frames and they go up to 65 cm.

The larger CFRP frames being too flexible is just poor engineering, and
has nothing to do with the inherent properties of CFRP.

To reduce the flex in the larger frames requires some engineering
enhancements because of the the inherent properties of carbon fiber.
Apparently Trek just made the frame larger, without understanding that
this wouldn't work.

Colnago describes what they did at
"http://www.colnago.com/en/catalogo2008/extremepower.php".

SMS aka Steven M. Scharf wrote:
Tom Sherman wrote:
SMS aka Steven M. Scharf wrote:
[...]
Carbon frames that large tend to have problems of too much flex,
which is what the reviews of the 64cm Madone found. Colnago seems to
have solved this problem in their carbon fiber frames and they go up
to 65 cm.

The larger CFRP frames being too flexible is just poor engineering,
and has nothing to do with the inherent properties of CFRP.

To reduce the flex in the larger frames requires some engineering
enhancements because of the the inherent properties of carbon fiber.

Specifically what properties? Elastic modulus - all solids have one,
just differing in magnitude. Steel, aluminium alloy and
titanium/titanium alloy frames also need to be designed differently in
larger sizes to keep them from being more flexible than smaller sizes.

Apparently Trek just made the frame larger, without understanding that
this wouldn't work.

Colnago describes what they did at
"http://www.colnago.com/en/catalogo2008/extremepower.php".

"The Extreme-Power was born to meet the demands of sprinters Alessandro
Petacchi and Erik Zabel of Team Milram and three time World Champion
Oscar Freire of Team Rabobank who all have a power output of 180 kg for
each pedal stroke."

WTF? When did the kilogram (kg) become a unit of power instead of mass?

Quick, notify the General Conference on Weights and Measures of this change!

Do people actually get paid to write this stuff?

--
Tom Sherman - Holstein-Friesland Bovinia
The weather is here, wish you were beautiful

The larger CFRP frames being too flexible is just poor engineering, and
has nothing to do with the inherent properties of CFRP.

To reduce the flex in the larger frames requires some engineering
enhancements because of the the inherent properties of carbon fiber.
Apparently Trek just made the frame larger, without understanding that
this wouldn't work.

Your information is... interesting. I've sold a number of these bikes, all
of them to people who rode other machines and were more than impressed with
how the Trek rode. Being too-flexy was never once mentioned. You could
(reasonably) argue that the sample size I refer to are those who have
actually purchased the bikes, which results in a strong bias. Except that I
don't have much of anything else to go on, because people-of-height who ride
them invariably buy them.

And the "engineering enhancements" are definitely there. The 5.5 version of
the frame doesn't use the same layup found on any of the other sizes, and
the fittings etc are unique, and specifically designed for, that size.
That's the case for every Trek size; there's nothing unusual about having to
do that. If a quality manufacturer were to build a 47cm frame the same way
they build a 58cm, the 47cm would be dramatically overbuilt (or the 58cm
underbuilt). With carbon fiber, there's no reason to do that, unless you're
trying to save money where it shouldn't be saved.

--Mike Jacoubowsky
Chain Reaction Bicycles
www.ChainReaction.com
Redwood City & Los Altos, CA USA


"SMS" wrote in message
...
Tom Sherman wrote:
SMS aka Steven M. Scharf wrote:
[...]
Carbon frames that large tend to have problems of too much flex, which
is what the reviews of the 64cm Madone found. Colnago seems to have
solved this problem in their carbon fiber frames and they go up to 65
cm.

The larger CFRP frames being too flexible is just poor engineering, and
has nothing to do with the inherent properties of CFRP.

To reduce the flex in the larger frames requires some engineering
enhancements because of the the inherent properties of carbon fiber.
Apparently Trek just made the frame larger, without understanding that
this wouldn't work.

Colnago describes what they did at
"http://www.colnago.com/en/catalogo2008/extremepower.php".

Tom Sherman wrote:
Colnago describes what they did at
"http://www.colnago.com/en/catalogo2008/extremepower.php".

"The Extreme-Power was born to meet the demands of sprinters
Alessandro Petacchi and Erik Zabel of Team Milram and three time
World Champion Oscar Freire of Team Rabobank who all have a power
output of 180 kg
for each pedal stroke."

WTF? When did the kilogram (kg) become a unit of power instead of
mass?
Quick, notify the General Conference on Weights and Measures of
this
change!
Do people actually get paid to write this stuff?

Watts your problem?

ZBicyclist wrote:
Tom Sherman wrote:

Colnago describes what they did at
"http://www.colnago.com/en/catalogo2008/extremepower.php".


"The Extreme-Power was born to meet the demands of sprinters
Alessandro Petacchi and Erik Zabel of Team Milram and three time
World Champion Oscar Freire of Team Rabobank who all have a power
output of 180 kg
for each pedal stroke."

WTF? When did the kilogram (kg) become a unit of power instead of
mass?
Quick, notify the General Conference on Weights and Measures of
this
change!
Do people actually get paid to write this stuff?


Watts your problem?



Ohm no! I erg you to stop this before this gets out of hand.
Paul O.

--

Paul D Oosterhout
I work for SAIC (but I don't speak for SAIC)