3D printed siren

By | January 31, 2017

A short post on a project from a while ago. It’s about a 3D printed “air raid” siren, which uses a brushless motor from an old 3.5 inch hard disk drive. Some people requested the source files, which are included in this post.

The trick in making a lot of noise is to have a stator with a certain number of slots (6 in this case), and a rotor with an equal number of equal sized slots. When the rotor rotates, all slots will open and close at the same time, “chopping” the airflow. Air is pushed in an outward direction by the curved shape of the rotor blades.

The following video shows a short demonstration of the siren. It works quite well, although the camera microphone volume is automatically lowered as sound level increases. At full speed, it is loud enough to be painful to the ears. By the way, volume alert!

The hard drive spindle has a (rotor) diameter of 14.5mm, and a measured mounting hole radius of 10.12mm. The outer diameter of the rotor is 80mm, and a clearance of 1mm gives an inner stator diameter of 82mm. Solidworks files are attached, so that the design can be adapted for other motors. Also, probably some optimisation can be done to get a louder siren. The current design was a relatively quick test with no further iterations.

The three phase motor is driven with a hobby motor controller, Turnigh Plush 10A. These ESCs come in quite handy, I use them for a lot of projects.

The source files (stl and Solidworks) are combined in a zip file, which can be downloaded here.


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