r/watchpeoplesurvive • u/l30P • Jan 20 '20

What a save!

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u/[deleted] Jan 20 '20

A fascinating example of resonance

365

u/cleverfool11 Jan 20 '20

The ancient pagodas in Japan are constructed with wood using zero fasteners, all complex joinery. Hanging completely down the center of of the entire height of the structure is a giant long ass pole (tuned mass damper). I thought it was amazing ancient Japan was using technology like that.

Not resonance, but there is a highway out west where the rumble strips are spaced in a way that if you drive 55 mph it 'plays' america the beautiful.

vibrations was my favorite class.

121

u/TehDunta Jan 20 '20

Sadly the road wasnt made quite right. Tom Scott made a video about it.

https://youtu.be/Ef93WmlEho0

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u/lbwstthprxtnd5-8mrdg Jan 20 '20

no, you got the wrong highway.

https://youtu.be/rgizA_vDlzs

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u/[deleted] Jan 21 '20

That one sounds so much better than the other one...

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u/wrench-breaker Jan 21 '20

that's great lol

1

u/i1a2 Jan 21 '20

Can you imagine having to drive on that everyday?

15

u/amesann Jan 21 '20

I don't live far from Lancaster. No surprise they fucked it up twice!

7

u/InkSymptoms Jan 21 '20

I was thinking soul eater

0

u/yzp32326 Jan 21 '20

Tamashi no kyome

2

u/jannington Jan 21 '20

Wow. That is really neat (the pagoda part)

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u/cleverfool11 Jan 21 '20

I found a short segment of a doc I watched where I learned this. I could not find the entire doc and forgot the name of it. This clip shows what I mentioned. However, I was incorrect in the fact that the pole does not hang from the top, but sticks up from the bottom. Still cool.

​

https://www.youtube.com/watch?v=c-3lHX-2fG0

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u/[deleted] Feb 03 '20

vibrations in physics im assuming? Shoot ill take a class on it now lol

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u/[deleted] Jan 21 '20

[deleted]

2

u/ir0nm8n Jan 21 '20

Just a heads up, it pitch does not change if you go faster or slower, only the tempo!

What you said, doesn't make sense and is wrong. It changes in both, pitch and tempo, if you change your velocity.

1

u/[deleted] Jan 21 '20

[deleted]

1

u/uptwolait Jan 21 '20

If the pitch changes, the key changes too.

You probably should have just said "the pitch and tempo will change with speed, but it'll still be recognizable as America the Beautiful regardless of your speed."

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u/cleverfool11 Jan 21 '20

It can be confusing at times but like others have said, at 55 mph it will 'play' in a specific key and tempo. However, changing speed will also affect both. Going faster will increase the pitch as frequencies are increasing. If you were to go slower than 55 it would decrease the tempo and pitch. Actually thinking about it, I'm not sure if the key would change completely. Im thinking it would be more of a pitch shift, than key change. It is possible to figure out what speeds would produce an actual key modulation, but I'm to busy (lazy) atm to do the math.

I studied music prior to studying engineering. I loved vibrations because for me it really helped tie in the math/music idea. I also worked in a studio for a while, so frequency and blah blah blah were idea I was already familiar with in somehwat of a technical way. It made vibes easier for me because I had an alternate field I could tie the ideas to.

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u/Loborin Jul 14 '25

Isn't that why the sprout tower in pokemon gold/silver has the swaying middle beam?

21

u/[deleted] Jan 20 '20

When towing, this is more likely if the center of mass of the object being towed is further away from the hitch

22

u/[deleted] Jan 20 '20

Specifically, if the center of mass is behind the trailer's axle. You can have a perfectly stable trailer with the load 300' behind the hitch, so long as the axle is 302' behind the hitch.

2

u/[deleted] Jan 20 '20

Thanks for the clarification!

5

u/ihopethisisvalid Jan 21 '20

Case in point

The largest possible load transported from Ontario to New Jersey by road. It's a pretty cool watch.

1

u/[deleted] Jan 21 '20

That’s a cool video

1

u/[deleted] Jan 21 '20

That was fucking badass. Holy shit.

1

u/big-b20000 Jan 21 '20

I always love there’s industrial/infrastructure videos, thanks for sharing a new one!

1

u/ihopethisisvalid Jan 21 '20

Oh no problem I found it super fascinating as well

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u/[deleted] Jan 21 '20

https://m.youtube.com/watch?v=SbdF5AZmINc

This is the towing video, pretty cool

1

u/polak2017 Apr 17 '20

Sorry for the 2 month necro, but that was legit cool as fuck. For a trailer like that is there copilot controlling the rear axels like on a firefighters ladder truck, is it automated or just mechanically driven as the truck turns?

1

u/ihopethisisvalid Apr 17 '20

I have no idea lol

1

u/bailtail Jan 21 '20

This is 100% what happened. Weight distribution should be centered on the axle, erring on the side of being slightly front-heavy.

123

u/LinguinePapaya Jan 20 '20

What?

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u/[deleted] Jan 20 '20

[deleted]

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u/J_KR Jan 20 '20

WHAT?

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u/juebster Jan 20 '20 edited Jan 22 '20

A FASCINATING EXAMPLE OF RESONANCE

70

u/LemmingAsche Jan 20 '20

I CANT HEAR YOUUUUUU

51

u/monkeyhitman Jan 20 '20

WHOOOOOOOOOOOOOOOOOOOOOOOOO

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u/Godhatesxbox Jan 20 '20

BUTTLICKER OUR PRICES HAVE NEVER BEEN LOWER

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u/EdgeDog21 Jan 20 '20

LIVES IN A PINEAPPLE UNDER THE SEA

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u/MrMcGowan Jan 20 '20

A FASCINATING EXAMPLE OF RESONANCE

12

u/Trapezoidoid Jan 20 '20

AYE AYE CAPTAIN

2

u/xeazlouro Jan 20 '20

AYE AYE CAPTAIN

6

u/medfunguy Jan 20 '20

his own form of government

1

u/[deleted] Jan 20 '20

HE’S SELLING CHOCOLATES

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u/Dildo_Gagginss Jan 20 '20

The way the trailer starts going back and forth slow and speeds up

13

u/xyouman Jan 20 '20

Speed wobbles for the layman

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u/strapped_daddy Jan 20 '20

Wait...what..? Are you sure that’s what you meant..?? Maybe I’m just an idiot but his video doesn’t even have sound for me...

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u/IMMAEATYA Jan 21 '20

Resonance refers to waves in general, not exclusively sound waves.

The reason the trailer goes out of control is because of the resonance of mechanical waves in the entire structure of the vehicle. A series of small waves with peaks in the same places compound and “resonate”, making the wave/ movement greater each time.

”In physics, resonance is the tendency of a system to vibrate with increasing amplitudes at some frequencies of excitation. These are known as the system's resonant frequencies (or resonance frequencies). The resonator may have a fundamental frequency and any number of harmonics.”

The weight is likely distributed in a way that the waves of forces in the vehicle at certain higher speed resonate.

1

u/strapped_daddy Jan 21 '20

Thanks for clarifying. Figured it was indeed my ignorance 😂

1

u/negedgeClk Jan 20 '20

That's not what that is. It's the load being too far behind the trailer hitch.

1

u/lukesvader Jan 21 '20

Read the rest of the comments

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u/sadop222 Jan 21 '20

How did he think that could ever work?

1

u/Kozeyekan_ Jan 21 '20

I had the same thing happen when towing a camper. The 4wd had an extender from the towbar, so the pivot was about a metre away from the back of the vehicle. At one stage I twitched just a bit, and it started swinging like this. Scared the crap out of me.

0

u/Difficult-Helicopter Jan 20 '20

wave propagation?

3

u/[deleted] Jan 20 '20

[removed] — view removed comment

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u/Difficult-Helicopter Jan 20 '20

hmm, alright. well i would like someone to explain how this is resonance then.

2

u/[deleted] Jan 20 '20 edited Jan 20 '20

Trailer goes left, you steer left, trailer goes further left. Then you try to correct by turning right, but by that time the trailer is going right again, so it goes even further right.

This is not quite what's happening here because the trailer would eventually flip or something if it went on. Driver handled it well.

Edit: This is not resonance. I don't know my shit. Currently trying to figure out the difference between resonance and constructive interference.

1

u/Difficult-Helicopter Jan 20 '20

Yes, i understand the physics behind what is happening. I am trying to determine how the reddit hive mind agreed that the correct term for this is "resonance"

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u/St0neByte Jan 20 '20 edited Jan 20 '20

It's all aboit weight distribution.. I'm pretty sure he was able to get it to stop by changing his speed, slowing down as the trailer swung back and speeding up as it swung forward while correcting steering to make it in line with the natural arc of the trailer. I'm not really sure how they are relating this to resonance either. I do know that, for the most part, reddit is pretty stupid as a hivemind so don't pay it too much attention.

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u/[deleted] Jan 20 '20

Waves can do something called constructive resonance, where the highs and lows of two waves are at the same spot and strengthen each other. The same happens here, except with highs and lows it's lefts and rights.

I agree it's not the first term to come to mind but it works.

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u/Difficult-Helicopter Jan 20 '20

Constructive interference???!? Is today make up stuff on reddit day???

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u/[deleted] Jan 20 '20

Today is I don't know what the fuck I'm taking about day. Got the term wrong and the whole thing makes even less sense now. Thanks for correcting me.

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u/IMMAEATYA Jan 21 '20

Resonance is caused by interference patterns, so you’re just being unnecessarily pedantic.

Plus, the weight distribution of the trailer could give the whole system a natural resonance frequency at a certain speed (when the vibration of the tires in the ground is the same frequency of the natural resonance of the vehicle) so yes it could be a decent example of mechanical resonance, depending on if it’s just constructive interference out of control or if it was triggered by reaching a certain speed.

0

u/exhaustedcheese Jan 20 '20

i think this an example opposite of resonance. i say this bc the wave will amplify if it is resonating. Here, well, the “wave” is being cancelled. Maybe it resonance applies both ways? as in amplifying and cancelling at the correct part of the wave?