This is how to make a working air raid siren that makes a really cool noise and is fun to make in a weekend. If you are new to woodworking or just want something fun to make, this is the project for you. This is a simple project that does not require any expensive tools or lots of materials so it is good for beginners. it does not look nice but is functional. This is just my designs and ideas but you can adapt it to your own ideas and resources.
You will need:
Some chipboard/ MDF/ any wood board as this does not matter. Just use what you have available.
Epoxy resin or just regular wood glue.
A bench grinder/ motor/ drill,/angle grinder any kind of tool that can spin. you can adapt my designs and plans for what you have available and your own ideas.
coping saw/ bandsaw/ scroll saw you can use what tools you have available.
screwdriver if you are using a bench grinder.
wrenches if you are using a bench grinder.
safety gear: Eye protection(must), air protection, gloves, hearing.
Step 1: Printing the Sheets
First, you will need to print out the designs onto A4. Attached are the word document to print, pictures of the templates in case you can not download, and the SolidWorks design in case you want to view that.
Step 2: Cutting Out the Centre Circles
Now you will need to cut out all of the parts out onto the wood. The thickness of your wood does not matter as long as each layer uses the same thickness of wood as the inner and outer sections. For mine, I did not have the right thickness as I designed, so I used what I had. Starting with the inner circles, cut them out according to the templates, there will be three. The bottom circle will need a hole drilled with the same diameter as the bench grinder shaft you will be attaching it to. Then the other two will need a large hole which is around 30mm in diameter(check templates), this can be done by drilling a hole and using a coping saw.
Step 3: Cutting Out the Blades
Next, you will need to cut out all of the blades. Using the templates, cut out one of them using a craft knife, then draw onto the wood and cut out using a coping saw or band saw. Once you have that one piece, it is now easier to draw around that wood piece to draw out the rest of the blades. Cut out and repeat for both sized blades.
Step 4: Assembling the Inner Part
Now you have all of the inner section pieces cut out, you will need to glue it all together using epoxy or wood glue. You should have already cut out the template, so lay that over the bottom circle. Where the blades are on the template, pierce through onto the wood using a knife or nail several points so that you know roughly where the blades will go. With those points, you can now lay the blades onto the wood, draw around, number, and glue down. Repeat for the other layer, and glue on the top circle.
Step 5: Making It a Circle
You will most likely have blades that are sticking out, and a circle that is not very circular. As a result, we will use sandpaper to sand it round. First, cut off large parts of the blades that may be sticking out using your saw. Now attach the whole piece to the bench grinder or appropriate motor, and use really low grit(40) sandpaper to safely make this circular by running it over whilst spinning. It is important for you to wear goggles, air protection(if you have), gloves, also put the sandpaper over a piece of wood so that your hands do not touch or get caught in whilst spinning.
Step 6: Back Plate Attachment
Next, we will be working on the outer assembly, and how to attach it to the bench grinder or whatever you are using. Cut out a large circle with the same diameter as the outer section of the template. This part is now where it gets janky. First, drill out a hole for the shaft. Now on your bench grinder, you should have three holes which are used to attach the spark guard. Use some paper to draw the location of these points and drill onto your wood back plate. If the bolts are short you will need to countersink them with a larger drill bit, being careful not to drill through the wood. On mine, I had to remove lots of material that was rubbing onto the bench grinder washers which is why it looks terrible but functional. Just do whatever you have to do.
Step 7: Cutting the Outer Parts
Using the templates, cut out all of the outer circles and components. use methods similar to step 4.
Step 8: Outer Section Assembly
The outer section will need to be glued together. Place the inner section inside the first outer layer. Then place the blockers (I do not know what to call them) where there is a gap and a blade is not there in that layer. use the template and same method as step 6 if you do not understand.
Step 9: Final Assembly
Now you have all of the components, you will need to finally assemble it. The direction you glued on the blades determines which direction the motor should be going/ which side of the grinder you will be attaching to. Keep this in mind if you are going to make this. The concave part of the blade should be turning and be hitting the air first (see picture)
Screw the back plate onto the grinder using the bolts included, attach the inner circle assembly making sure it is tight. Now aline the outer section so that it does not hit or rub against the inner circle assembly (use clamps). once you understand this part, glue the outer assembly to the back plate and use clamps till it is dry.
Step 10: Testing
Now you have finished and it is all dry, you can now test it. Wear some goggles in case a piece goes flying off. Clamp it down. On turning it on, you should hear a cool load noise which is like an air raid siren. Make sure you do not disturb your neighbours. In person, it sounds a lot better than this terrible video. To see the full potential of making an air raid siren out of wood, watch Mathias wendalls video where he made a larger one and has a build video.
areas to improve:
accuracy matters so that there is not a large uneven gap between inner and outer circle.
include a top lid to make it more airtight( between the large gap).
add a megaphone like a shape to amplify the sound.
Step 11: Final Thoughts
I hope you enjoyed reading this or having ago. This is a great project for beginners as it does not require many materials, and is not that difficult. Hopefully, you understood my instructions as I already made it and was trying to explain the steps. You should appreciate my thumbnail as I had to learn stupid photoshop to make that clickbait thumbnail just to be ironic (should have added more arrows and some emojis ?☠️ though).
Don't forget to like.
Thank you, Have a great day.