In this video I'll show how to build a resonant mechanical oscillator that's driven by an electromagnet. The electromagnet is pulsed by a circuit

with an adjustable frequency, so it can be fine tuned to run at the exact resonant frequency of the spring-mass system. In this case that

frequency is about 11 Hz. The driver basically just consists of a 555 timer and a MOSFET to turn the coil on and off. In the future, i think i

need to use a feedback controller to do this, because even when i get the system to resonate, it eventually drifts out of phase and resonance

dies off (even though the frequency is matched).

This type of device is commonly found in the compressor section of compact cryocoolers for infrared imaging and other sensors that require

extremely cold temperatures to operate. Suspending the compressor pistons on a flat spring or "flex bearing" and driving them at resonance allows

for high power and efficiency even with the relatively weak forces between the magnets and the coils. This is analogous to a flywheel on a

crankshaft, but is lighter, smaller, and more reliable. By avoiding the need for the bearings and linkages present in a rotary system, this kind

of devbice can achieve an extremely long service life (some are rated for over 200,000 hours of operation) inside a hermetically sealed unit.

This is part of my investigation into building my own refrigeration system (and eventually cryocooler) without HFC's/phase change refrigerants.

Several months ago i made a video showing how i built a compressed air turbine which I intended to use as a Brayton cycle cooler, and while it

did work, the extremely loud noise made it impractical in a home environment, so I'm now investigating reciprocating systems like Stirling/Pulse

Tube/Thermoacoustic/Gifford-McMahon-type devices for generating extremely low temperatures.



Music Used:

Kevin MacLeod - George Street Shuffle
Kevin MacLeod - Groove Groove (Yes, this is the same song that's in Kerbal Space Program)


STL Files:

https://www.thingiverse.com/thing:559...


Metal Spring DXF file:

https://drive.google.com/file/d/1OX4C...


Driver circuit schematic:

https://drive.google.com/file/d/1chrH...



Further reading on cryocoolers:


https://www2.jpl.nasa.gov/adv_tech/co...

https://www2.jpl.nasa.gov/adv_tech/co...


Fabrication shop i used for the metal springs:

https://sendcutsend.com/