UPDATE 12/5/2015

I redesigned the gear train, please print the gear files ending in "_UPDATED". The original gear train used 3:1 ration, which proved to be to high, and required too much torque to turn the handle. The new gears are a 2:1 ratio, and work great. Unfortunately to get the speed seen in my proof of concept video, the higher gear ratio would be needed. My new gear ratio works out as follows. 1:1 Bevel gears, 2:1 intermediate, 2:1 intermediate, and 18:16 final (this goofy ratio was needed to not have to redesign the case). That give a final ratio of 4.5:1. This means the final design is not as loud. The videos below show the final design in action. The video doesn't really showcase the sound very well, I believe the noise cancelling of my phone mic picking up the gear noise better than the siren noise. I assure you, while the final design is not at loud as my Proof of Concept" video, it is certainly still loud enough to grab someones attention.

Wave Blaster

#MakeItLoud

This is my entry into the "Thingiversity Fall STEAM Challenge: Make It Loud!", inspired by a "police alarm" toy I once had.

My design approach was centered rotor/stator design. I tried a few other designed based off of larger air sirens that have multiple tones (hi and low, creating the siren sound we are all used to) but I found that they didn't scale well. I ultimately decided to try designing the rotor with maximum air flow channels. The design worked quite well.

In my "Proof of Concept" video below, I tested the rotor assembly before I designed the gear box. The assembly was chucked in a router spindle I have, and spun at about 10000 RPM. In the video, you will see I have a Db meter on an old phone of mine. The first section of the video shows a background level of about 63 Db. I then turned on the spindle without the rotor assembly attached, which was about 83 Db. I then attached the rotor assembly, which peaked at about 104 Db. The is a gain of 21 Db!!! Much better than I expected. You'll notice it only spun for a few seconds. This was due to the fact that collet for my spindle wasn't a great fit for the drive pin.

With a successful rotor design I set about designing the gear box. Using a handheld tachometer, I determined I could achieve about 600 rpm with a cranking motion. This gave me a goal of designed a 16:1 ratio gear box 1(6*600=9600, close enough).

My designed needed a set of right angle bevel gears. For simplicity, I kept these 1:1 ratio. The bevel gear drive and intermediate gear, at a 3:1 ratio. That drivers a second intermediate gear at 3:1. The final gear is a 2:1 ratio. The math (1:13:13:1*2:1) gave me a gear ration of 18:1.

With the gear designed, all that was left was to design a case to house them, and handle to hold the whole thing. From that start I envisioned the final product to look like some kind of futuristic blaster pistol, hence the name "Wave Blaster"

All design was done in Autodesk Inventor. The Design Accelerator within Inventor was used for the gear tooth design. I chose a herringbone gear pattern because they are self aligning.