Tesla's resonation machine

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http://www.excludedmiddle.com/earthquake.htm

all the links i come across seem to say the same thing. tesla invented a device that can oscillate specifically to the frequency of anything and shake it apart. and one day the device got stuck on and he had to smash it with a sledge hammer. i understand how he claims to match the frequency of the object and turn up the amplification until the object shatters. but this raises some red flags. if this is as destructive as claims say, why have we not researched this. something the size of a shoebox that can drop a bridge seems like it would interest the military. the device would also need a large ammount of energy.

so i guess ill say i don't believe such a device is possible, and i am still trying to figure out y tesla(as skinny as he was) had a sledge hammer in his lab.
 

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  • #2
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i guess my question would be if their is any plausibility to this device?
 
  • #3
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Mythbusters did test a similar device, and it produce strong oscillations on a large bridge, but nothing dangerous or destructive. They had deemed it busted, but they were also not necessarily attempting to achieve success you could say, i.e. no further testings or developments.
 
  • #4
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Tesla's device is somewhat misunderstood.

Mechanical resonance, like it's electromagnetic counterpart, can result in stresses and strains that exceed the materials' load-bearing abilities. Whether this works or not to smash something depends on the "Q" or quality factor of the resonating system. If the Q is very high, then on each resonant cycle very little energy is lost to say heat. In an LC circuit you'd say that the resistance was low. A high Q allows you to accumulate large energy from a low power source by resonant buildup or accumulation. When a singer shatters a wine glass it happens because a) glass makes an excellent, virtually lossless spring and b) it fractures abruptly. No singer can shatter an unfired clay cup. It absorbs the acoustical energy in real time turning it into heat and it can deform in plastic fashion.

Tesla understood resonance better that most engineers today. The high voltage coil that bears his name is not a simple transformer. It is a resonating LC primary coupled to a secondary coil which also supports two simultaneous resonant modes; the secondary is tuned as an LC circuit *and* the vertical length is adjusted to be a resonant quarter-wave transmission line (which provides a whole separate voltage step-up mechanism working in addition to the primary-secondary turns ratio.)

Tesla's device allegedly combined this concept of cascaded resonance with an undisclosed coupling device tying an electromagnetic oscillation source to an electromechanical transducer having the remarkable ability to project a "wave of mechanical resonance" forward at a target object. In other words (so the lore goes) he found a way to launch a propagating wave of pressure that was not acoustical in support. Not EM, but driven by EM. Not acoustical in nature but delivering a pressure or stress to the target much the way a sound wave might, but with more spectacular results.

Personally I believe he actually did this but his theories were simply not up the task of correctly modeling or explaining what he had found.

Energy requirements are not necessarily large; it depends on the object. If you want to pop a steel rivet you'll need less than a few thousand joules. To take down a steel bridge would take a lot of energy.

But the stone or wooden foundation of an older type of bridge could be stressed to the fracture point with a concentrated stress somewhat like the wine glass.
 
  • #5
AlephZero
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... having the remarkable ability to project a "wave of mechanical resonance" forward at a target object. In other words (so the lore goes) he found a way to launch a propagating wave of pressure that was not acoustical in support. Not EM, but driven by EM. Not acoustical in nature but delivering a pressure or stress to the target much the way a sound wave might, but with more spectacular results.
Oh dear. I reallly get annoyed when an intelligent and rational discussion of what somebody did or thought suddenly goes woo-woo with a "wave of mechanical resonance".

Actually, boring conventional acoustic waves can cause quite a bit of damage if they are in the wrong place.

I once saw a jet engine completely destroyed, simply by running it at the wrong distance away from an object that reflected some of the sound of the exhaust back towards the engine, and set up a standing wave (like an organ pipe, but without the actual pipe) between the engine and the reflector. Fifteen seconds later, there was a very loud bang, and a terminally non-functional engine. It took us a lot longer than 15 seconds to figure out WHY it had "just blown up for no reason".
 
  • #6
alt
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Oh dear. I reallly get annoyed when an intelligent and rational discussion of what somebody did or thought suddenly goes woo-woo with a "wave of mechanical resonance".

Actually, boring conventional acoustic waves can cause quite a bit of damage if they are in the wrong place.

I once saw a jet engine completely destroyed, simply by running it at the wrong distance away from an object that reflected some of the sound of the exhaust back towards the engine, and set up a standing wave (like an organ pipe, but without the actual pipe) between the engine and the reflector. Fifteen seconds later, there was a very loud bang, and a terminally non-functional engine. It took us a lot longer than 15 seconds to figure out WHY it had "just blown up for no reason".
Kinda like Joshua and the battle of Jericho ?

Up to the walls of Jericho
He marched with spear in hand
Go blow them ram horns, Joshua cried
'Cause the battle is in my hands

Then the lamb ram
sheep Horns began to blow,
The trumpets began to sound,
Joshua commanded the children to shout
And the walls came tumbling down!
 
  • #7
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Oh dear. I reallly get annoyed when an intelligent and rational discussion of what somebody did or thought suddenly goes woo-woo with a "wave of mechanical resonance".
I couldn't agree more which is why I put the phrase in quotes indicating that it was the terminology of the time and not something I'm advancing as viable theory. It isn't.
 
  • #8
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There really isn't any way to get rid of damping.

This limits amount of energy that can be applied to an oscillating object.

The "vibrating girder" can effectively be damped by whatever suspends it.........or even a wet comforter thrown over it.
 
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  • #9
AlephZero
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There really isn't any way to get rid of damping.
Oh yes there is. Find some pictures of the Tacoma Narrows bridge.

There are also mechanical ways that damping can disappear when you don't want it to, without any fluid dyamics forces involved.
 
  • #10
AlephZero
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Kinda like Joshua and the battle of Jericho ?
Nope, the analogy would be the other way round. When they blew the trumpets, nothing happened to the walls, but the trumpeters exploded.
 
  • #11
alt
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Nope, the analogy would be the other way round. When they blew the trumpets, nothing happened to the walls, but the trumpeters exploded.
Ah ! I see that now. If there was no reflecting object, do you suppose that similar damage might have been done to, say, a second object (engine ?) at that distance ?
 
  • #12
AlephZero
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The engine was on a test bed, not an aircraft. The exhaust gas was directed into a silencer (a bit bigger than the one on your car!) to take out most of the low frequency energy and reduce the noise, and turn the gas flow vertically upwards. There is no "airtight" connection between the engine and the silencer.

On this occasion, for whatever reason, the engine was at different distance from the silencer than usual. A standing wave of pressure built up in the air between the engine and the silencer intake, which had the same frequency as a vibration mode in last turbine wheel at the back of the engine. The wheel broke.

Under "normal" circumstances there would never be anything at that distance behind a running engine, and if there was, it would soon be fried! Under normal conditions there is nothing that could possibly excite that particular mode of vibration, so it wasn't on anybody's list of things to be worry about.

We had probably been "playing 2 feet from the edge of a cliff" testing engines for the previous 40 or 50 years without falling over the edge, or even thinking this was a dangerous place to be. Sometimes you learn engineering lessons the hard way.
 
  • #13
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Oh yes there is. Find some pictures of the Tacoma Narrows bridge.

There are also mechanical ways that damping can disappear when you don't want it to, without any fluid dyamics forces involved.
There was a huge amount of energy applied to that bridge.

Everything is damped in varying degrees........otherwise something oscillating would never stop oscillating once whatever energy that exciting it has stopped being applied.
 
  • #14
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The engine was on a test bed, not an aircraft. The exhaust gas was directed into a silencer (a bit bigger than the one on your car!) to take out most of the low frequency energy and reduce the noise, and turn the gas flow vertically upwards. There is no "airtight" connection between the engine and the silencer.

On this occasion, for whatever reason, the engine was at different distance from the silencer than usual. A standing wave of pressure built up in the air between the engine and the silencer intake, which had the same frequency as a vibration mode in last turbine wheel at the back of the engine. The wheel broke.

Under "normal" circumstances there would never be anything at that distance behind a running engine, and if there was, it would soon be fried! Under normal conditions there is nothing that could possibly excite that particular mode of vibration, so it wasn't on anybody's list of things to be worry about.

We had probably been "playing 2 feet from the edge of a cliff" testing engines for the previous 40 or 50 years without falling over the edge, or even thinking this was a dangerous place to be. Sometimes you learn engineering lessons the hard way.

Did anybody hear any "beating" or was the suspect frequency higher of lower than human hearing range?
 
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  • #15
to the OP

the Tesla lecture on mechanical and electrical oscillators was given Friday, august 25, 1893 to the congress of electrical engineers in a hall adjoining the the agricultural building at the world's fair in Chicago.

the vibrations are isochronous (to perfection) and produce resonance waves in the materials. I have read an account of the lecture but never the transcription of the lecture (if one exists).

Tesla was demonstrating and lecturing on the perfect nature of the device's oscillation more than the effects of the machine. He did however call it an "earthquake" machine, I feel this is probably more pop sci hype of the day than anything real.

If you're interested in the machine, the book "the inventions, researches and writing of Nikola Tesla" by Thomas Commerford Martin 1995, barnes and noble books is a good place to start. He did many much more fascinating things than this, I particularly liked his work on wireless transmission of electricity.

as for the mythbusters show, I have two things to say.

1) It's not real science and you should never ever use them to support a claim for or against a scientific concept. It's like quoting star trek to support hyper dimensional drives. They are both entertainment.

2) the show is quite entertaining and I've seen them all. :)
 
  • #16
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1) It's not real science and you should never ever use them to support a claim for or against a scientific concept. It's like quoting star trek to support hyper dimensional drives. They are both entertainment.
They may not be the most scientific bunch, but their demonstrations are certainly acceptable for at least a baseline validation.
 
  • #17
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Well, what if electromagnetic waves go through piezoelectric such as granite? Sure, granite is a mix of unaligned crystals, but nonetheless, when all of randomly aligned crystals flex, that makes the whole bulk expand a little. Electromagnetic waves can turn into far ultrasound.

Though I think Tesla simply used an allegory or two regarding operation of Tesla coil, or made a few remarks regarding possibility of electrical resonance in the Earth's conductive core, and then it sort of got hyped beyond any proportion.
It literally took hundred years until we started using tesla coil circuitry for practical purposes in LCD fluorescent lamp inverters (those are literally tesla coil based, resonant zero voltage switching with resonant loosely coupled secondary, allows to get the transformer size down, for laptops).
 
  • #18
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After 'Galloping Gertie', IIRC, bridge designers took care to configure their deck sections to mitigate vortex formation and, by careful stiffening, made the structure have resonant frequencies outside the 'working' range...

This caution seems to have been overlooked for that infamous Thames foot-bridge, where any initial wobble forced pedestrians into lock-step, amplifying the excursion. IIRC, it had to be retrofitted with cross-bracing and dampers...

AFAIR, big bridges in earthquake and typhoon areas generally have mass dampers and other dissipative elements, to be sure, to be sure...
 
  • #19
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I won $20 from a friend when I bet him I could scare all the birds off of the power pole wires by using nothing but pushing on the pole with my hands.

Pretty amazing how far that pole ended up shaking and it did scare the birds off the wires for about 2 poles in either direction.
 
  • #20
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Speaking of power poles, I assume they were installed prior to the understanding of such things or a different gauge of wire was needed after the poles were installed but around here (central illinois) every now and again you will see wind spoilers on power lines to kill their abilty to establish a wave capable of self destruction.
 
  • #21
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I think that with single source resonance it would be difficult to break something apart, (not impossible). With several sources and some slight frequency and phase variation, constructive interference becomes involved, energy can be focused. If you shake something with enough energy, and the right frequency, bad things can happen.
I have seen the ground under my feet role like waves.
 

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