This 3D-Printed Air Raid Siren Packs the Decibels, and Was Tested to Destruction and Beyond
After the first few prototypes literally exploded, do-it-yourselfer Brandon tweaked the design to fix a rather glaring flaw.
Brandon, one half of the YouTube do-it-yourself duo the Honest Brothers, has designed and built a 3D-printable air raid siren — and tested it to destruction with what turns out to be a rather too powerful pair of drone motors.
"As a mid-westerner, instead of that impending doom [siren] meaning OMG my house is about to be blown to smithereens by bombs," Brandon says, "it's OMG my house is about to be blown to smithereens by a tornado. Despite being a fairly simple device, [air raid sirens] invoke a visceral sense of unease. It's as though humanity stumbled upon the trumpets of the apocalypse."
A classical air raid siren, responsible for the iconic and extremely loud droning sound, is made up of two parts: one which rotates and one which stays in place. Vents in the stationary part, the stator, are blocked and exposed as the rotator does what its name implies — pushing air through a port and creating the sound.
Traditionally, the siren is turned by hand — reliable electricity not always guaranteed in a war or other disaster zone. Brandon's 3D-printed version, though, is driven by a pair of motors originally destined for a drone, two electronic speed controllers (ESCs), and a DigiSpark ATtiny85 development board.
"In my original design," Brandon notes of the testing process, "the rotors would expand under high speed. This led to some rather catastrophic results involving the rotor blowing up and breaking my glasses. My solution for this was to print a small ring around the top of the rotors to stiffen the rotor where it would resist the centripetal forces due to spinning quickly."
More information is available in the above video, while 3D-print files for the project have been published to Thingiverse under the Creative Commons Attribution license. "The spacer pieces will probably need to be modified to fit your specific drone motors," Brandon notes for anyone thinking of printing their own.