Has anyone ever made triple-toned sirens?

[Robert Gift]

What I mean is that it is most likely just the number of stators that is adjustable.

Wrapping metal bands around some rows will not completely work in making the other rows louder, as the metal bands will not prevent the air from staying inside. You'd have to weld the bands to the stator walls.

I meant to fit them tightly to the outside stator port rings to close them.

See! Wouldn't this be a fun siren to play with?!

[SirenMadness]

It sure would.

Some old sirens use braking-systems for codes, instead of solenoids. Wearing of that system is the reason for it not being employed in sirens anymore.

Moving stators? You seem to read my mind! I devised that idea sometime back!

Daniel, that is a reasonable thought.
There could be a magnetic brake with a disc attached to it and the shaft of the motor, at the top of the motor assembly.

[Robert Gift]

It sure would. :D

Some old sirens use braking-systems for codes, instead of solenoids. Wearing of that system is the reason for it not being employed in sirens anymore.

Moving stators? You seem to read my mind! I devised that idea sometime back! :P

Daniel, that is a reasonable thought.
There could be a magnetic brake with a disc attached to it and the shaft of the motor, at the top of the motor assembly.

How would that work?

They actually braked certain rotors to a halt?!
Then they would speed up again?!
Must have sounded interesting but also worn the brakes and the clutches.

Are there any recordings of such?

Thank you,

[SirenMadness]

The rotors did not brake to a complete halt, but slowed down fast, causing a yelp signal. Sirens with small rotors were exceptionally good with that. The timings of the intervals of the motor being off also might have been faster.

[Robert Gift]

Interesting.

So, the whole siren (all rotors) were slowed quickly by the brake, then sped up from the motor?

I would think just a faster on/off cycle would be good enough without need of brakes.

Thanks, Peter

[SirenMadness]

A faster cycle of wailing would not necessarily be as distinctive as a cycle of isolated intervals of peak motor-R.P.M., which is known as a yelp.

Also, we are still sceptical as to whether there is a braking-system.

[Daniel]

I believe some sirens reversed the motor to slow it down quickly. I heard a recording of an Allertor doing this, and the wind-down lasted about a second. They called it the yelp signal, but each yelp sequence took several seconds to complete. The old Sterling sirens had a coding option using a brake, which would give a similar sound. The only efficient means of coding a mechanical siren is an intake or exhaust damper. This also yields a distinct on/off sound rather than merely a faster wind-down, though some setups like the 3T22 did not completely block all the airflow. Of all of these, only the Thunderbolt 1003 could really compete with air horns for coding ability.

[SirenMadness]

Reversing the polarization of the motor would be more efficient, as there is no material-to-material friction involved in the process of magnetic induction on a material. Some modern electric trains use polarization-reversal to slow themselves down.
Don't forget that the HLS series are also technically good at doing coded signals, though the inconsistency of the initial flux of air pressure at the point of the rotor would not allow for a completely clean "honk."

[jerrylovessirens]

Well with Ac powered single-phase motors, you would switch the power from brushes to field, then to field to brushes. Im guessing this is how the Allertors did it. Would cause enough negative acceleraion to slow the chopper down really fast!!