How NOT to install a T135 (as in Allens old T135s)

[Robert Gift]

Every T-135 I've ever seen either in person or in picture has been mounted on a pole exactly like that.

Wow. Thanks Gill.
The pole looks way too small for the weight and size (wind load) of that siren. They must be much stronger than I could ever have believed.
Now, if installers only knew what size foundation was necessary...

another classic example of people posting when they dont know what they are talking about. If you're not sure, DONT POST. Or ask. rob, i know you want to contribute, but contribute what you are sure you know is right.

What is wrong with my post?
Please regale me with your acumen.

[Jim_Ferer]

Let's play nice, guys.

The foundation of any overhead structure is an issue. A heavy object on a pole embedded in the ground is a powerful lever ("moment arm") and foundations have to be larger than you think.

Here's the anchor bolts for one end of an overhead sign structure in Woodside (Queens) New York:



The structure that's going on it is a lot heavier than a siren, but it's also anchored at both ends; there's no cantilever.

Now here's the foundation:



That's three meters deep. My company has put up railroad catenary towers (for the train power wires) with 18 foot deep foundations we had to mine a shaft for.

There's lots of other things to consider mounting a siren, mostly the weight of it, the height of the installation, it's cross-section to be caught by the wind, and whether the center of gravity is eccentric to the center of the pole. A hollow metal pole is more likely to have a buckling failure than a wooden one, which will fracture if it fails.

Most of the time a pole well-embedded in the ground is way stronger than what's needed for an ordinary siren; but if there's any doubt somebody needs to talk to an engineer. A honking big siren like a T-135 needs somebody to think.

[Robert Gift]

Wow! 18 feet deep? Never wood have imagined.
How tall is the pole requiring 18 feet!
Or is this an issue of soil strength?

Was the problem with that T-135 not it's foundation?
Thanks for the pictures and info.

[Travis]

Wow! 18 feet deep? Never wood have imagined.
How tall is the pole requiring 18 feet!
Or is this an issue of soil strength?

Was the problem with that T-135 not it's foundation?
Thanks for the pictures and info.

I think the rule of thumb is something like 10% o/ length + 6ft. = how deep the pole should be.

[Robert Gift]

I think the rule of thumb is something like 10% o/ length + 6ft. = how deep the pole should be.

For a wood utility pole, planted in the ground, it is 10% plus 2 feet.
So, a 45' utility pole should be 6.5 feet deep, revealing a pole which is 38.5 feet tall.

[Joey P 3]

its amazing how the sirens look so small on the pole, but when next to them they're at least about your size!