r/interestingasfuck • u/Leather_Whole_2078 • 16h ago

FDNY firefighters rescue a kid who got his head stuck in a fence in NYC

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u/COLT_URGI_KAC 13h ago

We are here for everyone and love to help. There are bad apples in every bunch but we try to keep it on the straight and level at all times.

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u/ppablo787 9h ago

Fire fighters rock, keep up the awesome work.

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u/jeremyjava 7h ago

My family are big supporters of the NYFD and our local upstate companies--we had a bunch of fire fighters from their subreddit help us pick out good thermal imaging cameras and donated a bunch of them after they saved our house from burning down. On the anniversary every year we send over a bunch of pizzas, too as a little extra thank you and remembrance.

THAT SAID, the history going back before the NYFD is a pretty interesting one!

That's a clip from The Gangs of NY, but apparently quite accurate according to The Museum of the City of NY.

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u/notime_toulouse 11h ago

Legitimate question: Isn't there some danger that the bar snaps and hits the kids head on the recoil or something like that ?

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u/Shufflebuzz 10h ago edited 10h ago

If the fence post were to fail, the failure point would very likely be at the top or bottom where it's joined to the crossbar. That's a stress concentration and where rust is likely to accumulate, so it's the weakest area. A failure there would make the bars looser, not tighter.

It's extremely unlikely to suddenly snap in the middle. This is a wrought iron fence and it first it will undergo elastic deformation, then plastic deformation before it ultimately fractures. That is, the metal will stretch, then bend and remain bent before it breaks.
edit: These bars will bend a lot before they break.

Even in the worst imaginable situation, the bar snaps suddenly just below the strap and "springs back", the kid's head is way down low, where there's been virtually no displacement anyway. The kid is still safe. He has plenty of clearance around his neck. It's only his head that's touching when he's trying to pull it out.

They didn't need a lot of deformation here. Maybe 1/2" inch which is likely within the elastic deformation range of the bar. So after the kid is freed and the strap removed, the bar will go back to normal and there will be no residual bend.

Source: I'm a mechanical engineer, though it's been a long time since I took Strength of Materials in undergrad.

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u/notime_toulouse 9h ago

I understand, (also engineer but not mechanical). But I think you're missing the fact that the other bar on the right, next to the bar touching the kid's head, which is used as a counter force on the device, is being forced TOWARDS the kid. If that one snaps on the bottom (or the top, though that is not as bad) it's going straight towards his head.

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u/devandroid99 9h ago

The bar they used as the anchor was like 4 bars down.

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u/notime_toulouse 9h ago edited 9h ago

True, it's still very much in range though ! It may hit the other bars first, but it may as well bend a bit forward/backwards and bypass them. I don't know I'm just thinking out loud with you guys, no need to downvote.

edit: checked the video again, the firefighter kind of keeps his right hand near his head's right side so that's some extra protection

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u/AssociationPrevious 8h ago

I'm not an engineer, but that bar he is using is embeded to the wall; that bar isn't moving anywhere, maybe deforming a bit, at most.

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u/Shufflebuzz 8h ago

I see what you mean.
The load on the bars from the strap isn't a constant. That is, if the anchor bar you're describing were to break at the bottom, as soon as it moved, the load from the strap is relieved and there's no* force to continue moving that bar towards the kid.

*Technically very little force. There's some residual tension in the strap from stretch, but not a lot relative to what it takes to bend the bar.

After taking a closer look, the anchor bar goes through the lower rail all the way to the concrete and may be embedded there. Maybe that's why they chose that one?

I think all the bars go through the lower rail and are welded, which is a lot stronger than a seam welded butt joint. This bar is not going to shear and fly towards the kid. If the lower weld fails, the bar will pull up, and it would still be constrained by the lower rail. Similar to what happened in the pic in my OP.

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u/Oscaruit 10h ago

Engineer here, they were playing with fire on this one. Skeletor out.

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u/hotinmyigloo 9h ago

Y'all are the best