How can I make a mechanical siren?

Question

Is there any instructions on the web or anywhere?

Answer 1

I don't know where to get directions, but a mechanical siren is made with two cylinders, one rotating inside the other with slots in the sides. The slots passing each other set up oscillation, the frequency depending on the spacing of the slots and the rotational speed. Normally they are made to be mounted on a motor shaft so one end of the cylinder is open and the outer shell is extended in a cone to project the sound. I believe they can be made with rotating disks with slots. Yup
http://www.windworld.com/feature_pages/siren.htm
http://www.sentrysiren.com/warningsirens.php4
http://www.americansignal.com/products/mechanical_sirens.php