Bloomin' Onion BR skirt--why?

Vintage Federal Sign And Signal Beacon Ray Light Model 17 Marine Rotating | eBay

It says beacon Ray model 17. It is in used condition with scratches and nicks. The glass is cracked along the top in two places. The light was tested and works. Needs to be cleaned up.

www.ebay.com

Every few years one of these is posted with the skirt completely sliced up and each time I wonder what the motivation was to do so:

1. Extra ventilation?
2. Ensure that it fits any roof angle?
3. Verify the new tin snips are sharp?
4. Ensure that no one steals it?
5. Some kind of artistic statement?

I'm not the sharpest tool in the shed as there's probably some simple explanation, but dang if I can find it...

 

[dmathieu]

Stress cracks in the brass. Happens on sirens too.

 

[Stampeed Valkyrie]

I'd venture that is correct. Brass is malleable, but also very brittle. Temp changes and the chrome coating probably doesn't help over the long term. Heating up and cooling down over the years.. basic physics primer 101..

 

[Maxim2Eng]

The manufacturing of the skirts uses a technique called metal spinning. It’s a quick and easy (cost effective) way to make the skirts instead of stamping or pressing them. One of the drawbacks is that spinning can create fractures in the brass that can lead to cracks over time.

 

[stansdds]

As Maxim2Eng mentioned, they are not stamped brass skirts, but spun brass. Micro-fractures are formed, then propagate over time with vibration, heating, and cooling cycles. Dropping the skirt on a hard surface likely does not help either and that can happen during installation and bulb or dome changes.

 

[tsquale]

Cool history lesson @Maxim2Eng and @stansdds

I had no clue that was how they were formed!

 

[AuroraBorealis]

Cool history lesson @Maxim2Eng and @stansdds

I had no clue that was how they were formed!

Yes, thanks to the experts for solving the mystery! Interesting how it "peels" uniformly...

 

[Maxim2Eng]

My wife took metal smithing/jewelery making at an art school…that’s how I learned about it (and that’s why she’s the better half).

 

[dmathieu]

They're always the better half!

 

[stansdds]

They're always the better half!

Mine certainly was.