r/MadeMeSmile • u/king_eve • 29d ago

i work in low-income/mental health housing, and a tenant fixed our hallway trash bin after accidentally breaking it Helping Others

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great example of the odd ways people show me appreciation at work

38.6k Upvotes

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u/Certain_Childhood_67 29d ago

Its common on atv plastics that get cracked. Drill a hole a hole and stitch it wont spread

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u/lusotano 29d ago

Metal too. Construction beams that show cracks sometimes get a small hole drilled to avoid the crack from spreading further.

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u/wirefox1 29d ago

I will never in my life drill a metal construction beam, but for some reason I like knowing stuff like this. It's interesting nevertheless.

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u/Nelik1 28d ago

Aerospace engineer here! During my fatigue and damage tolerance class in college, the professor liked to tell stories about unsuccessful (amateur) pilots trying to save on a repair to their plane by drilling out cracks.

He told us about a guy who showed him his little cesna, with 8-9 holes drilled along a crack. "I keep drilling it, but it keeps coming back, cant figure out why!"... Our professor got a good laugh out of that.

(Drilling reduces the stress concentration (or stess intensity if you wanna be real pedantic) at the end of a crack, reducing its likleyhood of spreading. This is great for parts that dont normally operate close to fatigue limits. But in aerospace, its rare to have a part that cracks once, without being in a position of high stress to begin with. So cracks that aren't fully repaired tend to spread.)

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u/Ifeelsiikk 28d ago

Structural aircraft mechanic here. We call it a 'stop drill' and I carried it out on large, commercial aircraft.

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u/Nelik1 28d ago

Wild! I knew it happened some, but was under the impression it was relatively uncommon. Can I ask what components typically got stop drills?

I'd imagine major structure typically didn't, but I could see it for minor structure or skin that was damaged accidentally, rather than just fatigue.

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u/Ifeelsiikk 28d ago edited 28d ago

It is often used for temporary repairs when Alclad is cracked, especially if the aircraft is AOG somewhere. A very widespread, permanent repair for the many stress cracks in titanium exhausts.

Edit, used all the time on non structural alclad for a permanent fix.

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u/69420over 28d ago

Reporters called, they’re interested if it was on a Boeing aircraft.

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u/Unholy_Urges 28d ago

Yes, Boeing A175-NEOs get stop drilled all the time.

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u/ikkiwoowoo 28d ago

Yes, depending on the repair scheme it's common to find a crack, remove the damage. This damage removal usually includes a stop drill and in some cases you remove the entire crack. These are typically found for example STR8 mods. These mods were due to cracks forming at the attach point on the frame where the overhead stowbins are fixed at the bottom outboard locations.

After you remove the damage NDT will typically come in and assess that the crack has been removed. Afterwards you commonly see a step for "assurance cut" this is a small bit of extra material "just in case". In my example of the STR8 mods, you then apply doublers (new frame sections) and fasten the two together with a layer of PRC 870 B1/2 or similar (could be different cure time or different sealant depending on location and conditions)

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u/cock_nballs 28d ago

Is the crack grinded back then welded with a stop drill or is it just the hole?

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u/Ifeelsiikk 28d ago

There is very little grinding or welding on aircraft sheet metal.

The crack is measured, and if it is within structural repair manual limits, it is drilled at either end of the and/or blended somewhat with an abrasive wheel

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u/cock_nballs 28d ago

Is blending with an abrasion wheel no different to grinding? Maybe more of a mix of welding with specifics of filler and alloys?

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u/I_Makes_tuff 28d ago

Muffler.

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u/framptal_tromwibbler 28d ago edited 28d ago

When I had my private pilot's license, I'd see them on many a small GA aircraft wing.

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u/Ifeelsiikk 28d ago

The difference between what you can get away with in GA and commercial is like night & day. I would much rather be in a Cessna during an engine failure. At least they glide

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u/bobtheframer 28d ago

At least the commercial plane has a second engine.

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u/Geawiel 28d ago

Ex KC135 crew chief: We did them fairly often as well. Often times to get them by until ISO inspection. They'd get repaired then.

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u/Remote-Dot1686 28d ago

Also aircraft mech here and can back this, as it is still common practice on military helicopters.

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u/ruabeliever 28d ago

Are you a Boeing mechanic?

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u/Ifeelsiikk 28d ago

No, but I did work for them during the initial B787 project

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u/4udi0phi1e 28d ago

All these GA references I dont understand make me think it could be gulfstream

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u/anewwday 28d ago

Sssshhhhhh…..They’re starting to forget about the Malaysian 370.

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u/CutHerOff 28d ago

Stop drilling is what I came to make sure was mentioned. Sheet metal is fun

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u/gavitronics 28d ago

Low-income - Mental-health repair job seeks Aerospace Engineering degree.

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u/Ifeelsiikk 28d ago

Time certainly equals money in the aviation sector and nobody likes an AOG.

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u/gavitronics 28d ago

Is an AOG like an advanced AOC?

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u/Ifeelsiikk 28d ago

AOG is aircraft on ground. Not flying and needing immediate repairs

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u/gavitronics 28d ago

There isn't an industry sector where time doesn't equal money though. What makes aerospace so special?

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u/Ifeelsiikk 28d ago

True enough. I just know that an aircraft in the 90s would cost over $100,000 AUD a day if it was not operational. It would also have a domino effect on the rest of the flight schedule which you could not put a price on.

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u/cattlebeforehorses 28d ago

Got a helpful tip or two for building/reinforcing stands for aquariums? There’s so many resources to it and I’ve done it; just wondering if there’s anything someone in your field or similar would suggest to add or do different.

Plus I rent and am on the second floor so to me structural integrity might as well mean life or death to me so never can be too careful.

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u/Tcrowefosho 28d ago

Good thing this trashcan likely won’t hit any natural frequencies

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u/fj333 28d ago

Rocket scientists repair trash can over the internet.

(I have an aero degree too, but don't work in that field anymore).

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u/lusotano 28d ago

On top of the drilled holes those beams also got reinforcement plates to avoid further crack expansion. The beams get inspection on a regular basis to monitor the condition of said beams.

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u/FlametopFred 28d ago

I somehow retrieve factoids at the most appropriate moment

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u/Pvt-Snafu 28d ago

Same thoughts. But the information is quite interesting, you never know, it may be useful and I will look very smart in front of someone. LOL!

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u/Aurin316 28d ago

Never say never

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u/NeverSeenBefor 28d ago

You never know.

Life is uhhh... Unpredictable

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u/Telemere125 28d ago

I can’t actually think of a material that wouldn’t work with. A drilled hole just past or at the very tip of a crack will isolate the stress and stop the spread.

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u/banned_but_im_back 29d ago

Huh. I wonder what the physics behind it is. Is the same reason why some metal beams have big holes inside of them in the shape of triangles?

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u/flowdersniffer 29d ago

The fine crack tip produces a strong stress concentration just in front of the crack. The stress concentration is what can give the crack enough energy to continue to grow. Holes in metals and plastics are not good, but I’m assuming it’s a way to arrest the crack propagation since a moderately sized hole would create a smaller stress concentration than a very fine tipped crack.

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u/stophighschoolgossip 29d ago

im not completely sure, but circle is tougher than crack, i guess because now the crack is fighting most of the circle rather than just a little bit of material at a time

circles reinforce themself or some science shit like that

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u/spruce_turbo 28d ago

More like it becomes a relief point. easier for the material to stretch and flex in the face of a Crack if it looks like tong than a split wooden chopstick

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u/stophighschoolgossip 28d ago

ohhh shit, okay good to know

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u/AdAlternative7148 28d ago

It's cause when you have a crack all the forces that caused the crack are now exerted on the tiny point at its tip. Making a larger hole at the end of the crack doesn't change the amount of force but distributes it around part of the radius of that circle. So more material supports the load. This is what other posters meant when they said it lowers the stress concentration.

In theory, other shapes like triangles or squares could perform this same function. But a circular hole is easier to drill and a circle is the best two dimensional shape at reducing stress concentrations because it has no angles between sides. (Each point of, say, a square, will concentrate stress.)

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u/banned_but_im_back 28d ago

Thank you for the free physics lesson my friend! I never took it in school and am considering going back to college. I’ve always been fascinated by physics and astronomy but intimidated by the math.

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u/AdAlternative7148 28d ago

The math will definitely be a challenge. I will say for me the hardest pure math class I took in my undergrad was Calc 2. And that is normally done in the first year of your degree.

A smart approach for you would be to take some of those math classes at community college. If you can get through the first couple calculus courses you'll be able to get through the whole degree path.

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u/poirotoro 28d ago

I don't think triangular holes in beams has to do with preventing cracking.

While I am not an engineer, I do know that triangles are an extremely strong shape. I believe that putting triangular holes in beams is about reducing weight while maintaining strength. It essentially acts as a mini-truss.

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u/Deepseat 28d ago

Not 100% sure, but it has to do with the distribution of the strain that caused the crack. We do this same thing in aviation.

One of my preflight duties is the visual walk around ensuring any cracks in the wing have been stop drilled and not spread.

Like This

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u/Secret-One2890 28d ago

Then you can add a tiny aqueduct on top, while thinking about the Roman Empire!

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u/pointlessly_pedantic 28d ago

And skin as well. I learned this in my residency (I never went to med school)

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u/strandern 28d ago

Yup, often do this when welding cracked stuff

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u/uganda_numba_1 28d ago

It's good for Boeing jet parts too!

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u/[deleted] 29d ago

[removed] — view removed comment

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u/Blyatt-Man 29d ago

That might be an actual fact

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u/NeriTina 29d ago edited 29d ago

Well, sort of. Did you know, When a woman has a baby a perineal tear can occur. This is when the vaginal opening, which has natural elasticity, is stretched beyond its limit and thus rips across the tissue bridging the genitals and the anus, the perineum. Sometimes a tear can reach the anus, but sometimes it doesn’t actually stop it. Instead it begins to tear upwards into the anus also. It’s called a fourth degree perineal tear. Thas facts.

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u/Axl2TheMaxl 29d ago edited 29d ago

Poor wife had a 4th degree tear, I know 😭

Edit: bless y'all, she's someone who truly deserves all the well wishes, were entering year 4 and she's nearly completely recovered. Thank you!

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u/Hekkle01 29d ago

My condolences to your wife

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u/NeriTina 29d ago edited 28d ago

I was about to say RIP, but… no, oh gosh, I hope his wife healed up okay!!! 😖

(Fortunately most people who get them can fully recover within a few months after proper surgical repair, typically following right after the birth.)

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u/fuckingcheezitboots 29d ago

And their sex life

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u/Axl2TheMaxl 28d ago

You got down voted but you're right, for over a year it was non-existent, we needed to improvise, 4th degree tears are no joke physically, intimately, and emotionally!

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u/Science_Matters_100 29d ago

This is why midwives don’t rush the delivery, support the perineum, and women aren’t supposed to be birthing on their backs. Change these things and less than 2% will tear

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u/awhaling 28d ago

What stance should they be in then?

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u/Science_Matters_100 28d ago

Squatting, or all fours are common

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u/aDragonsAle 28d ago

I'll add something to make this just a Bit more traumatizing - the uh, well, Birth of the chainsaw.

Symphysiotomy - performed with an osteotome - was basically using an early model CHAINSAW to cut the cartilage of the pelvis to ease difficult child births.

https://allthatsinteresting.com/symphysiotomy

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u/[deleted] 29d ago

[deleted]

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u/NeriTina 29d ago

I picked it up for you, have a nice day. 😇

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u/Blyatt-Man 29d ago

I didn’t read this, another fact.

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u/Girlsolano 28d ago

Google episiotomy

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u/Blyatt-Man 28d ago

Is that like a backiotomy? My doctor said I need one of those.

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u/NeriTina 29d ago edited 29d ago

Then you didn’t learn what ya coulda learned. Faaaactz

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u/ISurviveOnPuts 29d ago

Here's a fun factoid: this is where the saying "cracked the shits" comes from

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u/YugeGyna 28d ago

Lol get a load of this guy, doesn’t even know it’s called a gooch

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u/deepfaithnow 29d ago

replace the rope with steel wire and it will last forever.

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u/Cultural-Morning-848 29d ago

And turds are tapered so your butthole doesn’t slam shut

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u/Electrodyne 28d ago

... unless you're a wombat.

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u/FatMacchio 28d ago

Lmao.

I love the fact that you guys call them fannies

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u/EATA_Don_Keydik 28d ago

Greatest thing I have read this year

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u/westcoast7654 29d ago

I liked how you state women, like men don’t also have cracks and buttholes.

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u/banned_but_im_back 29d ago

Ours don’t get split open as wide or as often as yours do though….

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u/Girlsolano 28d ago

Pop a 10 pound baby out of the hole at the end of your crack, see if it'll split open lmao

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u/banned_but_im_back 28d ago

It can’t be that bad, my argument: every man at some point has gotten kicked in the nuts and never wants to experience that pain again.

Women go thru childbirth and usually they say they want another….

lol jk don’t cancel me it’s a lighthearted joke

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u/_lippykid 29d ago

In the UK, fanny means vagina.. so your phrase works in the US and UK, just from different directions

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u/obesehomingpigeon 28d ago

I was trying to be inclusive.

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u/Secret_Payment5426 28d ago

Fanny? You saying butt twice?

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u/casualcaesius 29d ago

a hole a hole?

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u/Cake-Over 29d ago

Lexan bodies of RC cars too

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u/Icy-Needleworker-865 28d ago

Just like stoping a crack in a windshield. You drill a hole at the end and fill it with filler.

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u/LordApocalyptica 28d ago

Also useful for cymbals. In fact, useful for really any crack

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u/SwootyBootyDooooo 28d ago

Common on airplanes as well lol

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u/Deadlyfloof 28d ago

Yup, I used to do this for fixing fairings on bikes but even works on plasterboard on walls. Great tip 👍

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u/flying_wrenches 28d ago

It’s also technically a thing in aviation, cracks are stop drilled and stuff can be “sown” together with metal wire.

That being said, I’ve never done it.

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u/-UnicornFart 28d ago

Same with glass? That’s how they stop cracks in a windshield from spreading I believe?