Introduction: A Pocket Siren!

Picture of A Pocket Siren!

Have access to a laser cutter? Want to be really annoying?

Then you need to make a turbine whistle!

I designed it to work on the same principles as an air-raid siren, so you can imagine the noise... ;-)

(I have added an updated version in the final step. I've improved the manufacturing process, and added key-chain friendliness, but it's essentially the same, so I've not gone through and changed the original Making instructions.)

Step 1: Tools, Materials and Files

Picture of Tools, Materials and Files

I used my own laser cutter, but if you don’t have the tools for cutting acrylic, you can use an online service. To make it easier, I’ve even added a file to this step that you can upload yourself (it uses the dimensions of the updated version I mentioned in the introduction).

I used 3mm acrylic. You could use plywood, but it's not so nice in the mouth.

You'll also need thin dowel (I used a bamboo skewer), sandpaper, super glue, a sharp knife and a surface to work on (something safe to cut and glue on).

Attached to this step are the SVG and DXF files you'll need as well.

Step 2: Cutting

Picture of Cutting

Cut your acrylic, or wait for the mailman to deliver your lasercut parts.

(That's got to be the shortest step I have ever written!)

Step 3: Prepare the Turbine

Picture of Prepare the Turbine

The turbine needs to spin inside the whistle, but, being exactly the same thickness as the rest of the cut pieces, it will just jam.

To prevent this, you'll need to sand the turbine to be slightly thinner.

Place the turbine on the sandpaper, press firmly and evenly, and move it around in a circular motion. To make sure the sanding is even, regularly turn the turbine under your fingers.

You don't need to take a lot of the turbine off, just enough that the difference between the turbine and the surrounding acrylic is enough to catch your nail on.

Step 4: Make the Axle

Picture of Make the Axle

I didn't design and make this whistle straight as the final version - it went through a few "draft" versions first, and an early version had no axle, with the turbine spinning freely within the case. It worked, but not very well.

The axle I came up with is just a piece of bamboo skewer, shaved slightly so that it is a tight friction-fit in the hole of the bottom plate of the whistle's case. (If I could, I would have used an acrylic axle, but I couldn't find a source of thin acrylic rod.)

Trim the shaved bamboo to be thick enough to touch, or almost touch, the top plate of the case.

Step 5: Assembly

Picture of Assembly

Putting the whistle together isn't hard, but it can be fiddly, and you need to pay attention to getting parts the right way round.

Start by gluing the central layer to the bottom plate. Note how the channel directs air to the left of the axle. It is also important to line the central layer up accurately with the bottom plate - if it's more than a fraction of a millimetre out, the turbine will jam against the case.

Because the central layer is flexible, I found it easiest to glue and align the large triangular section in place, then carefully lift the thinner parts to drop a little glue between the layers and align them too.

Make sure you let the glue dry completely before doing anything else!

If any glue oozes into the area for the turbine, wipe or scrape it clear to prevent jamming.

When the glue is dry, drop the turbine over the axle. Check the photo for the orientation - the curved blades catch the air coming up the channel.

Finally, glue on the top plate. Again, be careful not to get any glue into the inside of the casing. You also need to get the plate the right way up - the curved pattern of circles needs to follow the curve of the turbine blades.

Wipe or scrape off any excess glue, let the rest of it dry properly, and you're ready to blow.

Step 6: The Whistle in Action

Picture of The Whistle in Action

I said earlier that the whistle works like an air-raid siren. Here's how;

The air you blow in blows out through the pattern of holes, and at the same time, it makes the turbine spin.

If there was no turbine, the air would just hiss out of the holes, but the holes and blades are designed so that the spinning turbine alternately covers and uncovers the holes, rapidly blocking and releasing the air in a series of pulses that make the noise you hear.

See (and hear) it in action here:

If you make your own, please, post video or audio of it working - I want to hear exactly how loud these can go!

Step 7: UPDATES!

Picture of UPDATES!

Attached to this file are updated versions of the files needed to cut the Pocket Siren.

The changes I have made are:

  • Turbine blades widened at the base - massive amounts of use revealed a weakness in the base of the first version.
  • Turbines engraved in the laser - rather than sanding them down, I placed a circle of engraving over the blades (watch your laser settings, make sure it's set to engrave).
  • No hole cut in the base layer - that small circle needs to be set to engrave.
  • Axle cut from the acrylic sheet - there's a small circle in the middle layer - save it, and glue it to the engraved dot on the base layer. This is very fiddly!
  • Lanyard/keychain loop added to the central layer.

Two months later...

After a lot of use, the original version suddenly jammed solid and wouldn't do more than hiss. A lot of shaking and poking things through holes eventually dislodged a single turbine blade - it had snapped off. Once the snapped blade was gone, though, the turbine continued to work as before, with very little difference in the sound.

If you are going to reproduce this, you may want to explore the possibilities of changing the number of blades on the turbine - if there are fewer blades, they could be thicker, and thus stronger.


liquidhandwash (author)2015-06-03

Im going to make this for our schools open day, 100 grade sixes all with air raid sirens..... Oh yeah.. the staff will hate me!

Kiteman (author)liquidhandwash2015-06-03

Get video!!!

liquidhandwash (author)Kiteman2015-06-08

Hi Kiteman Ive redesigned the siren to make it easy for kids to make, so no glue required. I also replaced the axle with a piece of MIG wire, It make a huge differences to how it works. Much louder and even more annoying! the kids are coming next week so should be fun.

Kiteman (author)liquidhandwash2015-06-09

That sounds like it needs a full new instructable!

liquidhandwash (author)Kiteman2015-06-09

yeah Ive been thinking about it

Kiteman (author)liquidhandwash2015-06-09

Cool, I'm looking forward to seeing it.

liquidhandwash (author)Kiteman2015-06-11

Ive made a few to see if the kids can assemble them with out too much fuss, have a look here.

Kiteman (author)liquidhandwash2015-06-11

Oh, they sound awesome (love the second guy's face!) - you are *so* going to have to create your own instructable of those!

liquidhandwash (author)Kiteman2015-06-11

thanks kiteman, 120 odd grade sixes come on Wednesday so Ill post an instructable sometime after that.

Kiteman (author)liquidhandwash2015-06-11


liquidhandwash (author)Kiteman2015-06-19

Here a video of 130 all going at once, its truly horrible.

Kiteman (author)liquidhandwash2015-06-20

Oh, that is a great thing to wake up to!

Please, please, please tell me you're writing this up!!

liquidhandwash (author)Kiteman2015-06-23

Hi kiteman my ible is nearly finished, there is a summer fun comp coming up so i will publish it then. I used to be able to give people a sneak peak, but I dont think it works any more. try the link and see what happens I just need a few more photos.

Kiteman (author)liquidhandwash2015-06-23

Oh, I simply love it!

liquidhandwash (author)Kiteman2015-06-23

thanks kiteman, you could see the page ok?

Kiteman (author)liquidhandwash2015-06-23

Yes - the photography is great!

liquidhandwash (author)Kiteman2015-06-23

thanks i got a new camera, it works great.

liquidhandwash (author)Kiteman2015-06-20

thanks Kiteman Its on my to do list

paulsiew31 made it! (author)2014-11-04

3D printed with Marvel icons...Kids love it! Keep up the good job, man.

Kiteman (author)paulsiew312014-11-05

Awesome - you ought to do an instructable of your own!

krummrey made it! (author)2014-09-07

I finally made it - out of paper! :)
Also turned it into a Remix-Instructable:

AndyGadget made it! (author)2014-09-07

I've made a 3D printed version of this great build from Kiteman. Check it out here :

M.C. Langer (author)2014-09-04

Voted! Good job, man! :-)

Kiteman (author)M.C. Langer2014-09-05

Thank you!

AndyGadget (author)2014-09-03

Perfect item for a 3D printer, methinks. The .dxf files got a bit mangled when I imported them into Sketchup, then saved and imported into DesignSpark so I designed my own version from scratch. It's not particularly loud, but definitely along the right lines and plenty of room for experimentation with the turbine and holes etc.

I'll post a full Instructable after a bit more development.

AndyGadget (author)AndyGadget2014-09-04

A spot of vegetable oil on the rotor and axle worked wonders and stopped any binding at high speeds. Now the limiting factor is my eyeballs popping out from blowing too hard. Volume is a lot better, but it does feel like I've reached the limit for this particular design.

Kiteman (author)AndyGadget2014-09-04

Maybe make the rotor blades and vent-holes a closer match in shape, so that the air is shut off and released more abruptly?

(That's part of the reason for the curve on mine; the leading and trailing edgescare more aligned.)

AndyGadget (author)Kiteman2014-09-04

That's one of the things I was thinking of trying. There's not much of a mismatch at the mo; radial slots versus parallel blades; but it may well make a difference. I'll also try 7 blades / 8 slots which shouldn't work well at all as the peak amplitudes will be out of phase, but a rotor only takes 10 mins or so to print. I'll be opening out the air inlet gap hole as well to get more air into the thing.

I found that even though the rotor was free to spin, I got better results when I'd sanded it down to around 1.8mm (in the 2.5mm gap). I think the air needs to be allowed to circulate under the rotor to distribute the pressure.

Kiteman (author)AndyGadget2014-09-04

You might want to angle the vents - at the moment, the vents and blades cross like the blades of a pair of scissors. Try and aim for a more "chop" action.

Kiteman (author)AndyGadget2014-09-04

That's awesome!

It would make an entry into the Remix Contest.

ianmcmill (author)2014-09-04

Haha I loled on "Have access to a laser cutter? Want to be really annoying?".
Gonna give it a try on my 3D printer I have access to ;)

Kiteman (author)ianmcmill2014-09-04

Cool - post pictures when you do!

mamalove (author)2014-09-04

As a senior (citizen) I would love this product. The more advanced I get (in age) the more I need a comfort zone. This would lessen the anxiety? Great idea.

(Audreyobscura's Mama) Nancy

msraynsford (author)2014-09-03

Instead of sanding down the turbine piece you could have done a laser etch to make it thinner, it's a laser time consuming step but it sure beats doing it manually.

Kiteman (author)msraynsford2014-09-03

I'm still having trouble "balancing" the power of an etch (I don't think they're supposed to go right through, are they...?), and don't have much spare acrylic at the moment, but, yes, that's a plan, especially if I'm going to make batches.

krummrey (author)2014-09-01

I wonder if I can make one out of paper/cardboard....
Have to try.

Kiteman (author)krummrey2014-09-01

That would be fascinating to see. Keep me updated, would you?

rimar2000 (author)2014-08-29

Good work, RAF will recruit you, Kiteman!

Kiteman (author)rimar20002014-08-30

Haha! I hope not!

stubbsonic (author)2014-08-29

A couple questions come to mind, I wonder if the sound might be "tighter", or more resonant if there were fewer openings. Once the turbine spins past the first opening, I expect there's less pressure at subsequent sets of openings. Also, with so many pulses, there might be more phase cancellations. I suppose experimenting with covering some of the openings with tape could reveal any improvements.

The other (to me) obvious question is how big/low can we go with this?! A gi-normous siren whistle would be hard to put down.

Kiteman (author)stubbsonic2014-08-29

Regarding openings, I have no idea!

However, regarding size, just scale up the files as large as you have breath to blow!

stubbsonic (author)Kiteman2014-08-29

If you feel like tinkering, it would be a small matter to selectively
cover holes with gaffer tape.

I was even thinking that only ONE hole right somewhere past the opening (enough venting to keep the rotor moving) so that all the sound comes from that one spot. This might strengthen the sound.

enelson8 (author)2014-08-29

You should create an stl file for this so people could 3d print this!! Good job!

Kiteman (author)enelson82014-08-29

I don't have the software to do that, but I don't mind if somebody else has a go.

sol-bear (author)2014-08-29

If you made the horn a bit bigger, I am sure it would be quite annoying if it was hidden in the direct airflow on someones car.

Kiteman (author)sol-bear2014-08-29

Feel free to try...

mikeasaurus (author)2014-08-28

Fun project to get into laser cutting, and you included the cut files. Good man!

Kiteman (author)mikeasaurus2014-08-28


(There'd have been no point posting an instructable if I didn't include the files, would there?)

mikeasaurus (author)Kiteman2014-08-29

It happens all the time

Kiteman (author)mikeasaurus2014-08-29

Ah, but you know my attitude to sharing creativity.

About This Instructable




Bio: The answer is "lasers", now, what was the question? If you need help, feel free to contact me. Project previews on Tumblr & Twitter: @KitemanX
More by Kiteman:Fallen Astronaut 2Custom laser cut metal business cardsDashboard Phone Stand
Add instructable to: