I was looking at 3D printed whistles the other day and wondered how hard it would be to make one that just snaps onto a jacket zipper, so you'd always have a whistle with you. Looked at someone's 3D whistle to come up with basic design, experimented making different size chambers for multiple tones and futzed around with variety of ideas to attach zipper pull vs. easy printing. Spoiler alert, most zipper pulls are 2mm thick and 12mm wide, except all of those that aren't!
#3dPrinting #whistles
"x-ray" view of inside of whistle. As you blow air in the top it splits into two thin channels, which then guide air by the opening of two different sized chambers before exiting side of whistle. The size (and shape?) of chamber controls the frequency of the whistle.
Bottom has an opening for zipper pull to be pushed into, there's a 4mm pin with chamfer to make it slightly easier to push the zipper in with, but difficult for it to come back out.
A yellow rounded rectangle (42x22x4.5mm) hanging off zipper pull, other end has opening to blow into for loud whistle sound.