This siren is printed in 3 pieces: the motor mount, the chopper and the 2 port stator.

Motor Size: 24mm

Chopper Shaft Hole Size: 2.5mm

Screw Hole Size: 2.5mm

I made the chopper’s shaft hole slightly bigger than the 2mm motor shaft because at 2mm the shaft doesn’t fit correctly so I put glue in the hole and before attaching it to the motor. The motor that I use is a 280 size brushed dc motor.

Here’s the link to the zip file with the stl files in it: https://www.gronto.com/wp-content/uploads/2025/10/2port_siren_pieces.zip