This is a mechanical siren that has been designed to be fitted to an arrow and fired into the air to create a loud siren sound, kinda how a German dive bomber works.

its powered by airspeed so you could fix this to anything you want, car, boat, motorcycle, rc plane.

it begins to make noise at 25 mph, at 60 mph it is piercingly loud,

this build requires one 608 bearing ( 8 x 22 x 7 ) these are cheap and common bearings used on skateboards and fidget spinners, i used unsealed ones and they worked fine the bearing fits into the fin base tightly and may need to be pressed in.

the rotor slides down the shaft but not all the way down, about 1- 1.5mm gap. make sure to match up the height so the ports completely close while rotating

some trimming and fitting may be required for the stator and rotor clearance, if you can get it to spin but there is resistance, you can use an air compressor or blower to spin it up and it will self clearance by melting away the parts that are rubbing.

clean out any debris and spray with wd-40 for good results.

i fire these from my 150 lb re-curve crossbow.

The outside must spin freely while the inside rotor is stationary, in enters into the front, and is chopped up but the rotor as it passes through the square holes.

these are heavier than normal arrowheads and have a ton of drag, so be careful firing these from compound bows, i am not responsible for any injuries or damage, please use your judgment and wear safety glasses and gloves at least.

these are a super fun project, i enjoyed tinkering with these and the noise they make is satisfying.