jim beam wrote in message m...
Carl Fogel wrote:
snip

Why does a carbon fork, often claimed to damp
vibration better than metal, need a layer of
metal mesh to damp vibrations?

How does including Kevlar and nickel in the
Super Muscle Fork save weight while maintaining
strength? Isn't nickel a denser and weaker metal
than the titanium used in the plain muscle fork?

good questions! nickel alloys are not necessarily weak, often quite the
reverse, but they are /cheaper/ than ti!!!

to be honest, i have a hard time filtering out any tech from the
marketing with that columbus blurb, but as i understand it, the reason
composites are good for vibration is because the fibers are embedded in
a polymer matrix. the modulus of the polymer is very low and for small
deformation amplitudes, you're riding on polymer, not high modulus graphite.

what a mesh would do is effectively provide a large volume of polymer
between high density layers of graphite fibers and therefore provide a
zone of "insulation" between different regions of the component. so,
provided that "insulation" layer of polymer can be persuaded to remain
intact at high load, and the mesh would hopefully have this effect as
well as separation, then that could be the reason. but for the
definitive answer, you'll need to ask someone with more composites
experience than i.

jb

Dear Jim,

Most of that went over my head (not your fault, I
have lots of clearance).

But the Columbus site seems to say that they use
cheaper nickel mesh (I found "carbon nickel" mentioned)
to make the more expensive version of the fork--which
somehow ends up being lighter than the cheaper
titanium mesh version.

cheaper plain muscle fork = titanium = 380 grams
expensive super muscle fork = nickel-carbon = 340 grams

I browsed a bit more and found this page describing the
Super Muscle Fork further on the same site:

http://www.framebuilding.com/what.htm

"In the fork column, Columbus has inserted Kevlar
layers, which through their ability to resist cuts
and abrasions, reduce the risk of cuts caused by the
clamps of the handlebar stem, which are particularly
sharp."

Again, I'm wary. Perhaps Kevlar resists cutting better
than plain carbon fiber, but I seem recall reading that
Kevlar is usually cut with ordinary scissors--its
virtues do not include any great resistance to cuts.

There must be some prices somewhere, but I didn't find
any when I looked.

Carl Fogel