HLS restoration

[Nelso90]

There's a guy over in Germany who restored an HLS 273!
http://www.zone-eins.de/f0c59c97e010590 ... /index.php
Look at the inner stator, it's got 4 bushings that reduce the clearance between the rotor and stator, that's pretty cool. He even has a test video.
http://www.zone-eins.de/f0c59c97e010590 ... /index.php
Pretty neat huh?
I don't know if the person who did this is on the board, but if you're on here, speak up! This is a really cool restoration!

[Daniel]

If I had a machine shop, I'd be building a dual-tone version right now. It's amazing how small these siren heads are in comparison to their sound output. How does an HLS compare with a Thunderbolt for decibels?

[SirenMadness]

Very nice! The HLS variants are really one of the best sirens out there!

[Nelso90]

It's 124 decibels at 100 Feet.

Here's the chopper, the 4 tubes lead to the outer horns.

Here are those bushings I was talking about.
This is a really efficient design!

[AllSafe]

I thought the 273s were louder than that considering the air pressure they use

[Klauskinski]

Of course they are louder. He used a lower air pressure for testing. Otherwise it would be too loud.

[Robert Gift]

I really expect the copper colored chopper to be closer tolerance to the stator. Looks like several mm separation.
Or is that space taken up by the dark grey "bushings" in the bottom picture?

[SirenMadness]

The stator is inside the chopper, possibly so that the displacement of air is more efficient.

[Robert Gift]

The stator is inside the chopper, possibly so that the displacement of air is more efficient.

What!! Please explain.

[Klauskinski]

The stator actually is inside the chopper: the part on the 2nd picture with the black surrounded air holes fits into the copper colored chopper you can see on the first pic. That's enough for producing a sound. The four "holes" around the chopper lead the sound downwards to the horns. That's the "secret".