Tesla’s “Ground Shaking” Earthquake Machine worked a little too well. Tesla’s electro-mechanical oscillator is a steam-powered electric generator patented by Nikola Tesla in 1893. Later in life Tesla claimed one version of the oscillator caused an earthquake in New York City in 1898, gaining it the popular culture title “Tesla’s earthquake machine”. Tesla’s oscillator was a reciprocating electricity generator. Steam would be forced into the oscillator, and exit through a series of ports, pushing a piston up and down that was attached to an armature, causing it to vibrate up and down at high speed, producing electricity. The casing was by necessity very strong, as temperatures due to pressure heating in the upper chamber exceeded 200 degrees, and the pressure reached 400psi. Some versions used air trapped behind the piston as an “air spring”, increasing efficiency. Another variation used electromagnets to control the frequency of the piston’s oscillation.
“In 1898, Tesla claimed he had built and deployed a small oscillating device that, when attached to his office and operating, nearly shook down the building and everything around it,” says Shea Gunther at Revmodo. The device weighed just a few pounds, but Tesla was able to tune the timing of the oscillator at such a frequency that each little vibration added just a little more energy to the wave of flex in the building. “Given enough little pushes, even the largest structure could be shaken apart.” Realizing the potential terrors such a device could create, “Tesla said he took a hammer to the oscillator to disable it, instructing his employees to claim ignorance to the cause of the tremors if asked.”
Years later, in 1935 at his annual birthday party/press meeting, a 79-year-old Tesla related a story where he claimed a version of his mechanical oscillator caused extreme vibrations in structures and even an earthquake in downtown New York City according to reporter John J. O’Neill’s in his biography of Nikola Tesla. In that version, Tesla was experimenting with a small version of his mechanical oscillator at his laboratory on 46 East Houston Street near the Manhattan neighborhood of SoHo. Tesla said the oscillator was around 7 inches (18 cm) long, and weighing one or two pounds; something “you could put in your overcoat pocket”. At one point while experimenting with the oscillator, he alleged it generated a resonance in several buildings causing complaints to the police. As the speed grew he said that the machine oscillated at the resonance frequency of his own building and, belatedly realizing the danger, he was forced to use a sledge hammer to terminate the experiment, just as the police arrived. Other versions have Tesla smashing the device before the police arrive and have multi-ton equipment in the basement moving around. Another version has Tesla clamping an oscillator to a building under construction and causing it to vibrate so violently the steelworkers working on it left the building in a panic.
At the 1935 party Tesla also claimed the mechanical oscillator could destroy the Empire State Building with “Five pounds of air pressure” if attached on a girder and that he expected to earn $100 million from the oscillator within two years.