tesla supposedly came up with a pocket sized device that he attached to a building and almost shook down a city block with. i would assume this would be some sort of mechanical oscillator tuned at the resonance frequency of the building infrastructure. this is all taken from that tesla documentary on the history channel (i think).
any truth to this tale?
Probably not
The Master on Tesla.
Sounds highly suspect; a complex structure like a building is unlikely to have a single resonant frequency; the individual components might, but if you were to oscillate one of them, another attached component with a different resonant frequency would quickly damp it out.
And yes, before anyone says, bridges can have a single resonant frequency, but they are much different structures to city buildings.
Also, since the Verizzano Narrows Bridge (I think that’s the one) collapsed so spectacularly on camera in winds far lower than it was designed to withstand, engineers have taken harmonic resonance into account when building things.
…except when they designed the London Milennium Bridge, which was a disaster and had to be retrofitted with massive oil dampers.
Here’s a picture and description of the machine. It was pretty small for what was claimed for it.
Here’s a book on Tesla’s earthquake machine.
Here’s a list of Tesla’s patents. He invented a lot of strange stuff, so it wouldn’t be completely out of character for him to design a powerful mechanical oscillator. Of course the story of this invention has been mutating in the minds of the public for over seventy years. It’s likely that the only way to get an accurate description of the device and its capabilities would be to examine Tesla’s original records.
It was the Tacoma narrows bridge, not Verazzano.
If the “head” of the oscillator were to be in contact with the object being oscillated, what would prevent the oscillator from being destroyed?
That’s the Tacoma Narrows bridge.
You’re lucky Robert Moses isn’t around to hear you dis the seventh longest suspension bridge in the world.
There’d be no stress as long as the oscillator vibrates at the same frequency and amplitude as the object. The trick is to slowly increase the amplitude of the oscillation, while maintaining the correct frequency. There’s not a lot of stress added with each stroke, but the effect is additive over time.
You can demonstrate the phenomena by repeatedly pushing on a flag pole: At first push it hardly moves, but if you keep it up, and push each time the pole is moving away from you, it doesn’t take long to build up a large motion at the top of the pole. It’s not even hard work, until you start trying to push out of phase or at the wrong frequency.
Hey, I said, “I think that’s the one.”, not, “Its the crappy ass Verizzano Narrows Bridge that fell down.” Sheesh!
Oh, supposedly a variation of Tesla’s earthquake machine was used as an agitator for scientific research up until the invention of microprocessors, as it was the only device that could be set up to oscillate in a controlled manner and not get thrown out of whack by the vibrations it generated.
Tesla patented a number of different “earthquake machines.”
From looking at the patents, it is apparent that he was pursuing a types of electric motors and generators. Rather than using rotating parts, Tesla was using linear vibrators. They ran off high pressure (NOT oscillating pressure,) so they could be used as steam engines.
Similar devices (thumper trucks) are used by oil companies for underground surveys. One of Tesla’s claims for his device was that it could be used to detect distant geological structures underground.
As for buildings… any skyscraper has a very low “fundamental frequency,” or sway-period. But like any musical reed, it has hundreds of overtones extending far above the fundamental frequency. And not just overtones, but multiple modes themselves with overtones (think Bessel Functions.) Since Tesla’s vibrator wasn’t designed to be efficient at so low as the sway-period of buildings, we can presume that the story of the skyscraper involved faster vibrations (if the story was true.)
Bridges are similar: they have a fundamental wiggle-frequency, plus many higher overtones, plus torsional modes which themselves have a fundamental and overtones. If one of the overtones happens to match the period of human walking motions, that’s bad news.
In one of the Tesla biographies there’s a story where Tesla actually connected his vibrator to a skyscraper under construction one night, and tuned it to one of the resonances. The result was falling tools and boards, and the workers all came clambering down quickly.
But if his story is true, then what did he use as a power supply? The mechanical oscillator was small enough to carry around, but I would imagine that the power supply would have to be large. (Since some of his oscillators were electrical, maybe it was a big battery.)
Tesla’s work has attracted lots of groundless speculation. But it has also attracted lots of groundless scoffing. I don’t know which is worse: thoughtless people who make up stories, or thoughtless people who disparage a claim without even inspecting the evidence. In logic these are called “type 1 and type 2 errors.” I suspect that many sensible people are so disgusted with the wild speculation that they go too far in the other direction, becoming irrational scoffers. It’s the THOUGHTLESS response which is the problem, so the proper response to thoughtless speculation should be thoughtful investigation. Too often the response instead is thoughtless scoffing.
I don’t know about Tesla, but I know that Doc Savage defeated an evil genius who had an earthquake machine, saving the world yet again.
Way to go, Doc!
RR
more conspiracy theory for you guys: at the end of that documentary, they talked about how the government came in and dug through all of his files looking for plans to some of his speculated work.
Yes, this was about the “Death Ray” that Tesla was trying to sell to the US govt. when he died.
The plans apparantly ended up in Tesla’s homeland (Serbia). Since that time they have been published. His device is very simple, but I don’t know if anyone has built one and verified that it does anything.
The power supply was a large VandeGraaff machine which used moving air as it’s belt. The “ray” was a stream of extremly tiny metal fragments which were electrically charged and then propelled through a vacuum. (Both tungsten and mercury were mentioned.) This effect is well known today, it’s called “electrospray” and is used to generate the particle beam in modern mass spectrometers. Tesla’s trick was to generate the beam in a vacuum, accelerate it across tens of megavolts DC, then pass it into the air through a high-powered aspirator pump. Sort of like a proton accelerator, but using atomic clusters rather than subatomic particles. He claimed that the beam was effective over hundreds of miles, and could transfer energy at rates of thousands of watts.
Maybe it behaved like a water-jet cutter?