Many objects feature moving parts, or, move relative to
other parts of the environment. In all cases this involves
forces interacting with mass*. The problem with mass lies
in the varied nature of how it responds to forces, some
matter is springy, some squidgy and so on.
A recent example
of matter encountered by me was a
Vespa scooter kindly left idling near my home. I've seen
many of these stylish Italian objects in the windows of
fashionable hair salons, above the bar in a nearby
restaurant and as props for photography. This one however
seemed to have been outfitted with a rudimentary
engine**. I looked in vain for the owner, hoping I could
inform them of recent advances in Japanese
manufacturing, sadly I assume the poor fellow had been
overcome by the cloud of partially combusted chainsaw
A closer inspection of the device demonstrated that
modest forces produced in the engine were mostly visible
in the wild vibration of the two rear view mirrors. The
vibration was such that the mirrors were essentially useless
at idling speed. Obviously, ethics would prevent any human
experimentation as to the vibrations of the mirrors at
higher engine/road speeds but even my finely
engineered*** motorcycle has a similar problem. At 70mph,
my mirrors vibrate to the point of uselessness too.
The reason is because the forces moving the mirror back
and forth arrive at a frequency that the particular
structure likes to resonate at. This can happen to
essentially any object. Buildings are objects. Taipei 101 is
an example of a building. Due to a catastrophic series of
planning mistakes and cumulative oversights throughout
the entire project, the tower was constructed in Taipei, a
location vulnerable to earthquake and typhoon threats****.
The height of the building means that it's natural resonant
frequency is close to those that earthquakes or typhoon
gusts might induce. To compensate for such fundamental
flaws, engineers installed a Tuned mass damper <link>. As
the building oscillates, it applies force to the mass via
energy sapping dampers, the mass chosen oscillates out of
phase with the building and supplies opposing forces, via
the same energy sapping dampers. This stops forces
building up and leading to failure of the structure.
Now, the idea. The crux of a tuned mass damper is a mass
held in place by an inefficient spring. My wing mirror
vibration problem was solved by filling some cavities in the
casing with silicone and embedded lead shot. Now, if I'd
been clever I could have run some calculations on how
springy I wanted my silicone and how much mass to use for
the balls, but I couldn't be bothered. Instead, what should
exist is a commercially available product. A range of beads
with lead masses in the center surrounded by polymer that
is a combined spring/damper. The beads could be tuned to
certain vibration ranges and then used to fill any offending
The beads could also be combined, perhaps a car wishbone
has a road-rumble vibration at 50Hz and a vibration from
the tire blocks at 2000Hz. Simply fill with a mix of the two
beads. 50Hz would be popular, great for casting into the
plastics of electronics for example.
*keep it broad in the introduction, draw them in,
everyone's got skin in the force-mass game.
**I wouldn't say the engine was agricultural... that implies
heavyweight pragmatism with compromised aesthetics.
This is more like the product of a talented engineer with
tremendous experience in the design and manufacture of
high end kitchen appliances, unfortunately the engineer
was in prison at the time. Materials and tolerances were
confined to melted cups and a stolen ruler.
***It's Japanese, so they haven't got it QUITE right. For
example, it had exactly the same amount of oil in it in May
as it did last October. More thoughtful British engineers
would aim for a carefully tuned oil loss rate. This prevents
owner complacency, flushes out debris that may otherwise
build up in the seal vents, and a little oil on the rear tire
ensures a lively rider experience.
****You simply don't get these problems in Slough.