Talk:Tuned mass damper

Tuned

What makes it tuned?— Preceding unsigned comment added by 67.123.78.206 (talk) 04:54, 3 January 2005 (UTC)

The section where it talks about large ocean passing vessels containing a mass damper is incorrect. To reduce harmonics and vibrations the transverse frames are adjusted in the stern framing to cancel out any significant vibrations. Maybe there is mass dampers in a cruise ship, but I know for a fact that commercial ships do not have mass dampers. The only damper system I have seen was a series of tanks that would flood against the rolling of the ship and serve to dampen the rolling of the ship.— Preceding unsigned comment added by Malarky (talk • contribs) 05:42, 5 August 2006 (UTC)

I deleted the Taipei 101 picture because it is not a tuned mass damper as tuned means that it is actively moved. it is just a mass damper that moves in relation to a buildings movment— Preceding unsigned comment added by 67.174.208.172 (talk) 11:26, 21 May 2007 (UTC)

No, you can have a passive tuned damper, that relies on an elastic element to give the tunig. You can also have an untuned mass damper, as you describe. I don't know what the Taipei one is.Greglocock 02:03, 22 May 2007 (UTC)

Hmm, 'mass damper' redirects here anyway... yamaplos— Preceding unsigned comment added by 66.68.138.150 (talk) 10:23, 26 March 2009 (UTC)

The tuned mass dampers in Taipei 101 are used to reduce oscillations under wind loading. The main tuned mass damper in Taipei 101 is designed for human comfort under wind loads. There are also two additional tuned mass dampers in the pinnacle to reduce fatigue loading. None are specifically designed to reduce earthquake loads. In event of an earthquake the pinnacle TMDs will be locked down, while the main mass is designed to be restrained by a snubber ring (see this paper by the designers). The problem with relying on tuned mass dampers for seismic response is that the frequency of most buildings under high-level seismic loading will vary due to non-linear effects. As a result, the formerly "tuned mass damper" becomes a dangerous lump of mass that is out of tune with the motion of the structure. If no-one has any objections, I shall add a paragraph to this effect to the article. I could also reinsert the Taipei 101 picture, since it is fully relevant. Muchado (talk) 02:03, 3 May 2011 (UTC)

What you are saying doesn't sound right at all, mass dampers damp some better than others, but all frequencies pretty well. Do you have a reference?Rememberway (talk) 02:19, 3 May 2011 (UTC)

Take a look at the image in the article. The response changes from a single peak to a double peak. The response reduction relies on the system being in the trough between the two peaks. Otherwise the response is still high (this image) - note that the words under this image in the article say the same thing. Muchado (talk) 03:13, 3 May 2011 (UTC)

No, it's still basically a low pass filter. I suppose if the earthquake was driving the building below the cut-off frequency then those frequencies would go straight through, and the mass could hit the stops, and you would prefer it not to.Rememberway (talk) 11:38, 3 May 2011 (UTC)

" it's still basically a low pass filter." Sort of, but it can (and in the case of small m/M ratios probably will) have resonances in the frequency range of interest. Greglocock (talk) 22:49, 3 May 2011 (UTC)

'How they work' section expansion

The explanation should be the longest section, yet it is the shortest. There should be a more thorough explanation, especially for the different types of dampers: Active, passive, pendulum active/passive, inverted pendulum, and liquid (all mentioned in the first external link [1]). Kreachure 22:41, 14 November 2006 (UTC)

Aye, there's a lot of hand-wavers on Wiki. If I can generate some good plots I'll try and explain it. Greglocock 08:39, 27 December 2006 (UTC)

Is that any good? is it too complex or too simple? or too confusing? Greglocock 09:25, 28 December 2006 (UTC)

Mess

This article is a mess. All those graphs and stuff without any caption or anything. What does this mean, and why are there no units? --Ysangkok 16:57, 26 January 2007 (UTC)

well I guess I asked for criticism. I've added captions. There is an explanation. There are no units becuase units are irrelevant, and there are no labels on the axes because that graphing package doesn't do them.. Greglocock 01:26, 23 February 2007 (UTC)

consider pulling material until citations are given

It's unacceptably bad form to present information gleaned from other sources without attribution. Moreover, it sets the poorest possible example for student users regarding what consitutes good scholarly work.

Hence, I would suggest the author and Wikipedia staff **pull this article** (until all information is cited that is not common knowledge to an educated laymen familiar with the field). The fact that plagiarism is not taken seriously enough by Wikipedia—its decree that "content must be verifiable" is demonstrably, historically toothless—and is one reason why faculty cannot allow its use by their students for serious work.)

For the critical nature in academia of proper training with regard to these issues, as well as for broader discussion and perhaps another view of the informational "threshhold" for citation, see the work of The Univ of Chicago's Ch. Lipson, "Doing Honest Work...", U of C Press, 2004 (ISBN 0226484734, available inexpensively from Amazon.com).

Meduban 03:59, 24 July 2007 (UTC)

Which bits are you concerned about? The maths? The graphs? Neither were 'gleaned', they are standard results. Check the atrribution of the images if you like. OH and add curly bracket curly bracket fact curly bracket curly bracket to the bits you want cited.Greglocock 05:43, 24 July 2007 (UTC)

Yes, it's confusing

The How they work section makes little sense to me. I have a background in physics but not mechanical engineering. Harmonic motion, resonance, damping, Bode plots are all fine. But...

• "Tuned mass dampers stabilize against violent motion caused by harmonic vibration." Why harmonic vibration? Perhaps something about resonance is meant? Is "motion caused by [motion]" the real intent?
• "the block moves in one direction as the structure moves in the other, thus damping the structure's oscillation" The "thus damping" is a logical stretch, since it hasn't been mentioned yet that there is a significant damping element between the bodies. If one imagines otherwise (as I first did), then motion of the block out of phase with the structure would be the last thing you'd want.
• Why is counterweight linked? Is the damper really a counterweight?
• Image:2dof sketch.png What is the blue line? Why is F1 an arrow and F0 a dot? Is the wavy thing supposed to be a spring or a resistor?
• "wheel and suspension arm" I've no idea what that means, yet it conjures up images that clash with the diagram. If there's going to be an analogy, it should be simple, mundane, restricted to translations, and carried throughout the paragraph.
• "a spring and damper k1/c1 between it and the body" What is "the body" referring to, as opposed to the "main mass"?
• "The force into the body is F0, this is what we are trying to minimise." Aren't we trying to minimize the motion of something?
• "adding a tuned mass of 10% of the baseline mass" Does this mean going from 10 kg to 10 + 1 = 11 kg, or does it mean going from 10 kg to 9.1 + 0.9 kg? What about "the proportion of the baseline mass used in the damper" in the next paragraph?
• Why are numerical forces and frequencies given, while dimensionless quantities like spring ratios are omitted?

In general, if the section is going to be so terse, then the language will have to become much more precise, and descriptions will have to be re-ordered to avoid assuming future knowledge.

I'm sorry to be so negative, but attempting to read the section was extremely frustrating, and I hope that piecing together what made it frustrating will help fix the problem. Melchoir (talk) 11:18, 25 June 2008 (UTC)

Good questions. This article certainly needs work. I'll try to field your questions.

• Regarding "harmonic vibration", my understanding is that these dampers work by changing the normal modes of the system. I think the author is using "harmonic vibration" as a synonym for "normal mode".
• Re: "thus damping": That's a kludgey sentence. I think they don't necessarily need to include a damping element as long as they shift the normal modes. As the graphs show, replacing one intense normal mode with two lesser ones. Also, for some frequencies the system with the damper is more excitable than without: the key is that the peak is reduced.
• Re: "counterweight", I guess that's what the weight in the damper is called. I don't have a textbook reference for this, though.
• Re: Image:2dof sketch.png, those are springs, not resistors. They are often drawn with the same symbol as resistors. I think the blue line is fixed. I would draw it with slashes coming off the top. I don't know what the x1 and x2 arrows are; I would draw them comming off the two masses. I have no idea why F0 is zero, unless it's supposed to be an unknown.
• Re: "wheel and suspension arm, etc.", I agree, it's a mess. I'll take a pass at fixing it. The final answers are dimensionless, so I think that's how he got away with not giving quantities for springs and dampers.

Anyway, I'll take a crack at it, but it could do with a better example. —Ben FrantzDale (talk) 00:28, 26 June 2008 (UTC)

Thanks Ben! It's much better already, especially with the motor part; there's a lot more to do though.

• I'm not so sure about identifying the normal modes with the responses at the peaks of the transfer function. Is that really the case?
• By dimensionless quantities I meant more like these questions: what is the relationship between the resonant frequency of the original spring system (∞, m1, k1, c1) and the additional spring system (m1, m2, k2, c2) in a well-designed tuned mass damper? What is the relationship between their Qs? Is it the case that c2 is a small fraction of c1, to choose a random example?

Melchoir (talk) 05:46, 27 June 2008 (UTC)

Yes the article is much better. The answer to your last question is that it depends on what you are trying to achieve. If oyur original system is lightly damped then it is common to use a lot of damping at c2. The equations are well known, but rather too long to put on this article, and are rather unwieldy to solve, from memory. Most vibration engineers work off charts in textbooks.Greg Locock (talk) 06:35, 27 June 2008 (UTC)

That's a shame. I guess I was looking for an explanation of why a tuned mass damper works, in addition to an exposition of the fact that it works. Melchoir (talk) 19:15, 28 June 2008 (UTC)

Well, setting the equations up is easy enough, high school physics in fact, it is just that the analytical solution is messy. Here it is, I think

www.geocities.com/greglocock/gallery/harmonic_solution.png

Clear as mud, I know. Greg Locock (talk) 02:44, 29 June 2008 (UTC)

Yeah, I don't think equations would be the way to go here. Melchoir (talk) 02:53, 29 June 2008 (UTC)

Oh, well, verbally. The damper goes into resonance at about the same frequency as the main system. Consequently its spring/damper is very strongly excited, so if it has a significant damping element it sucks energy out of the main system. In fact the main mode of the original system is split into two modes, the lower frequency one being the two masses moving in phase, the second they move out of phase. The separation in frequency of the two modes is controlled by the ratio of the hd mass to the main mass. As you can see from the complexity of that equation the behaviour is not intuitive. Roughly speaking practical systems are tuned to either move the main mode away from a troubling excitation frequency, or to add damping to a resonance that is difficult or expensive to damp directly. An example of the latter is a crankshaft torsional damper. Greg Locock (talk) 03:11, 29 June 2008 (UTC)

Ah, excellent! Is there any reason not to write something similar in the article?

I figured that the resonant frequencies must be close, or you wouldn't get any interaction. But that might not be obvious to other readers, and even I wasn't sure.

Also, by "difficult or expensive to damp directly" I suppose you mean trying to supplement c1. When this isn't practical, a tuned mass damper is plan B? This is again the sort of basic background information that might be obvious to you but not to me. The article has some great examples of applications for tuned mass dampers, but what makes them the right solution isn't mentioned. Melchoir (talk) 03:27, 29 June 2008 (UTC)

I'll take a different tack on "why?" Suppose you have a yardstick. Hold it at the middle and shake it. If you shake it at the right frequency, it will resonate. The combination of its mass and stiffness gives it a particular natural frequency in the primary bending mode, and you've found it. Now, suppose you attached a bunch of little rubber arms of various lengths to the yardstick. Now when you shake it, they flail about, and furthermore you'll have a lot of trouble getting it to vibrate harmonically—all the little arms will vibrate at all different speeds. What you have done is changed all of the resonant modes of the system and the strengths of those modes. There are still an infinite number of vibration modes, but none are particularly strong anymore. This isn't tuned, but it would be a way of changing the vibration modes. Backing off from this example, you could imagine that adding a carefully-selected a mass, damper, and spring, you could get a similar effect. —Ben FrantzDale (talk) 05:32, 29 June 2008 (UTC)

what about laundry washer machines?

Some have something that would be like a damper, in the case of the one I repaired it was a block of concrete, attached with steel cables to parts of the mechanism. When going through the spinning cycle, they tend to shake a lot until whatever it is that happens does happen, and the resonant shacking calms down. yamaplos —Preceding unsigned comment added by 66.68.138.150 (talk) 22:25, 26 March 2009 (UTC)

No... you misunderstand. The concrete block adds inertia, there is no deliberate damping added. Muchado (talk) 02:03, 3 May 2011 (UTC)

Are these anti-vibration dampers?

This is a picture of part of the (3-phase?) power cables feeding the facilities at the end of South Gare at the mouth of the River Tees in the north east of England. Of particular interest are the devices attached to the cables. Are these a type of vibration damper? There is typically one of these devices per wire on each span between posts. Stuffed cat (talk) 20:33, 13 April 2009 (UTC)

I'm not an expert, but I've always assumed those orange balls are to help aircraft pilots notice power lines. - Blueguy 72.150.217.91 (talk) 00:44, 14 August 2009 (UTC)

Stockbridge dampers are added to cables to damp out oscillations. What you are showing appears to be a visibility aid, although by connecting the cables together, it may perform another purpose as well. Muchado (talk) 02:03, 3 May 2011 (UTC)

Delete this article?

In order for an article to be useful, it has to actually explain the subject and provide information about it. An article along the lines of "A superdeluxe is a type of widget. Superdeluxe cars are cars with a superdeluxe, here's a list. Superdeluxe cameras are cameras with a superdeluxe. Here's a few examples", etc, does not provide information. There's no point in having the article.

There was an in depth explanation here of what a Tuned mass damper is. It needed cleaning up, but it was unquestionably the part of the article that actually answered the question people come to this wikipedia page to ask. This was deleted, three times!, by one editor who had technical objections to it.

So what's the point in the article now? Why have it? I proposed a deletion, but that was reverted. I'm proposing it again. The article needs to actually describe the subject, it can't tiptoe around it, otherwise there's no good reason to have it in Wikipedia.

The other alternative is to do what the editor who deleted the content should have done in the first place and clean it up a little, but given the complaints seem to be more than just WP:OR and going into the substantive ("this is basically teaching the math directly to the reader which isn't the purpose of Wikipedia") - meaning the editor would have removed it even if the content had been easier to read and contained more references - I don't see that as worthwhile. What's the point in cleaning something up if it'll be deleted again?

Bite the bullet: if you're going to erase enough content from an article that it no longer describes the subject, at least have the honesty to propose the article's deletion. --66.149.58.8 (talk) 20:40, 20 October 2009 (UTC)

Not understanding an article is not a reason for part or entire deletion .Wdl1961 (talk) 22:24, 20 October 2009 (UTC)

I think 66.149 is exaggerating to make a point. I'd point out to the editor who is tring to delete that section that there is mathematical terminology in the article, but no actual difficult maths. if the explanation is confusing, thentag it that way, and dsicuss why it is confusing here. I am not a mind reader. Greglocock (talk) 00:03, 21 October 2009 (UTC)

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Quiet dishwashers

Tuned-mass dampers get a lot of the credit [2] ~Kvng (talk) 15:13, 1 April 2021 (UTC)

active mass damper?

It seems that this article describes passive dampers. I would think that there would also be active dampers. I have heard of active dampers being used for automobile shock absorbers, that work much better. Gah4 (talk) 08:09, 16 December 2021 (UTC)

Active shock absorbers are very different to active mass dampers. Neither have much to do with TMDs, the subject of this article. Greglocock (talk) 09:35, 16 December 2021 (UTC)

Well, except that one might choose active dampers instead of passive dampers. I wasn't suggested it should be in this article, but maybe should have its own article, and a see also. Gah4 (talk) 10:15, 16 December 2021 (UTC)

Active vibration controlGreglocock (talk) 21:18, 16 December 2021 (UTC)

Seems slightly different, but maybe as close as they come. I was watching a show about The Steinway Tower and at the time thought it was an active damper. So, are there no active building dampers? Gah4 (talk) 06:19, 17 December 2021 (UTC)

Active needs a continuous power source, which in an earthquake may not be great assumption. Given that the frequency of interest is well known, it seems to me that a robust mechanical system mounted at the antinode of the modeshape (or more than one) is likely to be cheaper - lump of concrete on rubber blocks, than an active system, and more reliable. I've worked on both passive and active absorbers, you only go active if the frequency of interest changes during use or you want bragging rights. A simple active absorber can be as simple as a voice coil and a mass, trouble is you need to be able to turn all the absorbed energy into heat via the amplifier, so the control amplifiers tend to be rather expensive. Greglocock (talk) 21:54, 17 December 2021 (UTC)

As far as I know, it is more for wind. It seems that The Steinway Tower has 26 million dollar condos. The TV show about them showed the company that hand made the doorknobs, with cast brass using 160 year old technology. I suspect that they can afford the power cost. The higher units, with better view, will have more wind sway, which people don't like so much. Probably easiest to dissipate power through a fluid, but if you design right you can put it back into the power grid, and even get paid for it. (That is, wind energy.) Gah4 (talk) 23:00, 17 December 2021 (UTC)

I don't think there's any practical technology currently that works like that. Electric motors/generators scale according to power. It would take stupendous power to make a skyscraper move opposite to, or to collect the energy from an earthquake. If you think there is, feel free to link it here, but I don't think you'll find anything. GliderMaven (talk) 01:05, 18 December 2021 (UTC)

After the Surfside condominium collapse, I wondered about active cathodic protection. I found a paper which turned out (I e-mailed the author) to be written by someone who tried to sell such systems 40 years ago, but found it a hard sell. But also, that takes much less power. But also, I was only suggesting for reducing wind motion, not earthquakes. Buildings can easily survive motion that is very uncomfortable to people living in them. Gah4 (talk) 13:27, 18 December 2021 (UTC)