Perhaps the most legendary piece of plastic in the hacker community is the humble "Cap'n Crunch" whistle. The free-in-cereal whistle was able to emit a piercing shriek at 2600Hz - the exact tone required to unlock the US phone network.
So, because it's all I seem to do these days, I turned my my trusty RepRapPro and decided to see whether it was possible to 3D print a whistle which could produce the same frequency.
Rather than do any funky customisations with radius or length, I simply scaled the whistle in Slic3r.
I made them at 75%, 85%, 100%, and 100%.
The print wasn't without issues. Because of the large opening, the top layer didn't seal properly - even on the smallest print.
The logo printed reasonably well - and the holes in the side were easily sealed with my fingers. But I might adjust the model for a thicker top layer.
The models come with an integrated "pea". The little ball in printed inside the barrel - a hard poke with a sharp stick set the ball free.
So, how did it sound?
Not bad! We broke out a tonal analyser on a smartphone and, on the smallest whistle, I managed to just about hit 2600Hz!
The 3D print is rather rough and was quite harsh on the lips - so it's worth sanding the final print down or rubbing some acetone on it before blowing.
For my next step I can go one of two ways. Either refine the existing whistle so it reliably produces the 2600Hz tone - or try to make a replica of the bo'sun whistle and then get that pitch perfect. Thoughts?
Oh, and the tone is really loud and annoying for anyone nearby!