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Tuned Mass Damper Beads

A general product for attenuating troublesome vibration
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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 fuel.

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 vibrating object.

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.

bs0u0155, Jul 16 2017

LAW 80 https://en.wikipedia.org/wiki/LAW_80
Handy. [8th of 7, Jul 16 2017]

Slough https://en.wikipedi.../wiki/Slough_(poem)
Wonderful [8th of 7, Jul 16 2017]

Practical mod fashion. http://1.bp.blogspo...ter_mod_revival.jpg
[bs0u0155, Jul 16 2017]

[link]






       I think the place to start would be with earrings for motocyclists; or perhaps brassieres.
MaxwellBuchanan, Jul 16 2017
  

       // Vespa scooter //   

       We recommend the LAW 80, a compact, inexpensive and highly effective device for street cleansing* <link>   

       // Slough //   

       Betjeman had that place nailed ...   

       <link>   

       *Also useful for removing noisy persons under the age of 21 years, french cars, traffic wardens, the welsh, BMWs, and Jeremy Corbyn.
8th of 7, Jul 16 2017
  

       A specific solution to the scooter problem already exists. Simply fit many mirrors with slightly different resonant frequencies, at least one pair will be useable at any given time <link>.
bs0u0155, Jul 16 2017
  

       Interesting - my motorcycle forum has arguments along these lines regarding fitting handle bar-end weights, and filling the hollow handlebars with lead shot.
normzone, Jul 17 2017
  

       //hollow handlebars with lead shot.// As it happens I have a unique offer on light weight aluminium lead shot for only 12x the price. Anodized titanium, even composite materials may be available for the right price.   

       Anyhow, a motorcycle forum where handlebar vibration is a common topic... Would this be a large capacity single cylinder Japanese motorcycle that may or may not be okayish off road? My vibration is a combination of a known design quirk exacerbated by the motocycle being worth much less than the valve shim job it needs.
bs0u0155, Jul 17 2017
  

       More likely a Royal Enfield ... "one bang per lamp post" at full chat ...
8th of 7, Jul 17 2017
  

       Ah, I was thinking klr650. It's the crocodile of the motorcycle world. It will be here when we're gone
bs0u0155, Jul 17 2017
  

       " As it happens I have a unique offer on light weight aluminium lead shot for only 12x the price. Anodized titanium, even composite materials may be available for the right price. "   

       Thanks, but I don't own a Ducati. My forum is a Moto Guzzi forum. And they say good things about the KLR 650 - crocodile indeed.
normzone, Jul 18 2017
  
      
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