Tesla's electro-mechanical oscillator or earthquake machine is a steam-powered mechanical oscillator invented by Nikola Tesla

Nikola Tesla

Nikola Tesla was a Serbian-American inventor, mechanical engineer, and electrical engineer...

 in 1898. The machine which Tesla tested was small, around seven inches (178 mm) long, and weighing one or two pounds; something "you could put in your overcoat pocket". It was reported that in 1898 Tesla's New York lab was nearly shaken to pieces by this little device, operated by five pounds of air pressure

Pressure

Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...

 acting against a special pneumatic piston device.

Houston Street lab

Tesla established a laboratory on Houston Street in New York at 46 E. There, at one point while experimenting with mechanical oscillators, he allegedly generated a resonance of several buildings causing complaints to the police. As the speed grew it is said that the machine oscillated at the resonance frequency of his own building and, belatedly realizing the danger, he was forced to apply a sledge hammer to terminate the experiment, just as the police arrived.

Principle of operation

Tesla's oscillator is purely mechanical. Steam was forced into the oscillator, and exited through a series of ports, the net effect of which was to cause the armature to vibrate at high speed, within its casing. The casing was necessarily very strong, as temperatures due to pressure heating in the upper chamber exceeded 200 degrees, and the pressure reached 400psi. Other versions of the machine were created, designed to produce electrical power, both direct and alternating (without the need for rectifiers). Another variation used electromagnets to control the frequency of the piston's oscillation.

Attempted replication of earthquake effect

The Mythbusters

MythBusters

MythBusters is a science entertainment TV program created and produced by Beyond Television Productions for the Discovery Channel. The series is screened by numerous international broadcasters, including Discovery Channel Australia, Discovery Channel Latin America, Discovery Channel Canada, Quest...

 television program made a small machine based on the same principle, but driven by electricity rather than steam, to test the claimed earthquake effect; it produced vibrations in a large structure that could be felt hundreds of feet away, but no significant shaking, and they judged the effect to be a busted myth. The vibration effect achieved in the experiment may be similar to what the earlier mentioned 1898 reporters experienced.