Gary <[email hidden]> wrote in message news:<fKkVd.119$Ru.17@okepread06>...
Quoted message said:from cyclingnews.com
plastic and brass or aluminium widgets
that fit inside the ends of the bar and are claimed to cancel high
frequency vibration and so improve comfort.
...If you add a weight to the end of a tube that's
supported at one end (which is the situation with a bike handlebar) then
it's going to have a different, and probably lower, harmonic frequency.
The key word in this quote is "weight".
The only way you're going to have a significant effect on the
vibration of a handlebar, merely by stuffing something in the end of
it, is if the thing you're stuffing has a significant mass.
I can see two options: either a tuned mass, or a damped seismic mass.
The tuned mass option would be to simply insert something heavy into
the handlebar to lower the first (and possibly higher) natural
frequency. Instead of going "ding" when you hit it, the bar would
"dong". If you knew the frequency of excitation (ie if "road buzz" was
concentrated at a fairly narrow frequency band), you could tune the
bars to _not_ resonate in that frequency range.
The damped seismic mass option is harder to envisage, because there's
probably not enough room inside a handlebar to make it work properly.
In essence, you want a substantial mass...heavy enough so that it has
enough inertia that it will remain pretty much stationary when pushed
around by a vibrating excitation. You would connect this mass to the
handlebar using a highly damped material - a soft rubber for example.
Then when the handlebar vibrates and the seismic mass doesn't, the
rubber has to stretch and relax to keep the two components connected.
Due to internal damping, rubber tends to absorb energy as it deforms,
and doesn't release as much energy as it relaxes. The vibration energy
is converted into low-grade heat.
Technically, either of these options _might_ be able to reduce the
amount of vibration experienced at the bars of a bike.
Practically, neither of these options would ever be used, because they
both involve adding substantial weights to the bike.
Unless you're riding a sub-UCI weight bike, and looking for places to
add mass to meet regulations, you're not going to insert lumps of lead
- rigidly or damped - up your handlebars. Even if you need the weight,
you'll probably be better off putting it down low, in the BB, rather
than high in the bar plugs, merely for handling reasons.
I'd rather have a better handling, slightly "buzzy" bike than a
top-heavy, ill-mannered, over-weight but better damped bike.
fs