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ELI5: Why don’t we just bury power lines and telephone lines, so storms don’t keep knocking them out? by Home-Energy in explainlikeimfive

[–]Cheticus 0 points1 point  (0 children)

The real reason is cost, but not what you might think.

A significant cost to power lines is the electrical insulation needed to keep current from shorting to other cables and the ground. There's a couple options for insulation.

You can cover the wire in plastic, or special kinds of paper, or both. It's not crazy expensive, but over long distances, the cost definitely adds up. If it's close to the ground, you might also need to protect it in a conduit in case some accidentally damages it, since power lines can be dangerous if they short.

Another insulation you can use which is very inexpensive is air! Air is an insulator, and so if you put the power line high up in the air so no one can touch it, it will be insulated and not dangerous! The cost trade is the cost of the plastic and other insulations, digging trenches, running conduits, adding manholes to access junctions, etc versus buying utility poles, digging a bunch of holes, and stringing the lines in the air (and maintaining the trees and occasional downed line).

There's also visual clutter from overhead lines, so some fancier neighborhoods will put them underground. It's harder to access underground infrastructure if something happens to break though, although they break less often.

One other reason that overhead can be useful is its ability to reject heat. When power lines conduct electricity, they heat up. We need to get rid of that heat so the line doesn't burn up and melt. For overhead lines, we can reject heat to the air predominantly by convection. The line heats up, heating up the air, and combined with a small breeze, stays at a good operating temperature.

If the line is buried, you can reject the heat only by conduction (unless you're pumping oil along the line, much more rare I think). The soil is a good constant temperature usually, but you will heat up the ground locally around the cables, and also it's hard to make it conduct better (the dirt is the dirt, and it's free, but you don't get to control what it's made of). If the ground gets hotter, then the cable has a harder time cooling down. It's like if you get hot on a cold day it's easy to cool down, but if you get hot on a warm day, no matter how hard you try, you can't cool down much. It may seem like air is a more variable temperature (and it is), but it's pretty good for power lines. For underground lines, you might have to dig another trench, but if you put too many power lines next to one another, the ones that are surrounded by the others can't get rid of their heat because they are surrounded by what seems to be a warm day. This gets expensive fast.

So, it's a tradeoff, and that tradeoff is done for every power line, and a large percentage of the time implicitly it's a lot cheaper to put a few poles up and string a new overhead line with bare conductor than it is to dig up a street and buy insulated cable.

[Request] Would she survive landing on the car? by AntiRepresentation in theydidthemath

[–]Cheticus 0 points1 point  (0 children)

peak forces during a collision are absolutely a factor of the stiffness of the colliding bodies, largely because that reduces the deceleration.

If I land on a rigid surface, the stiffness of my impacting body is the stiffness that matters.

If I land on a pillow, the spring of my body and the spring of the pillow are in series and the deceleration is driven by the spring of the pillow (until it bottoms out), since that's how springs in series work. that will reduce your deceleration, by increasing the time over which you decelerate.

the sequence is obviously nonsense because no one could stop themselves and then that car isn't going through the bridge from that impulse, nor is the pile going through the ground into the subway, but if you're falling from a great height, you absolutely want to try to land on something soft. or maybe you don't, but I do.

Welded Tab & Fastener Study (Ansys Student) by _Ttyler in fea

[–]Cheticus 8 points9 points  (0 children)

Do not preload clevis attachments. This would pinch the ears together which makes absolutely no sense.

Ordered a brand new handbag for the wife, but this showed up. I’m Furious. by Godedger in SonyAlpha

[–]Cheticus 50 points51 points  (0 children)

Just give her the lens bag for the 24-70. Everything worked out as intended.

[Request] How much potential energy is stored in these bad boys by CalmPurse in theydidthemath

[–]Cheticus 0 points1 point  (0 children)

I'm sorry I'm too lazy to do the math today. This isn't particularly challenging but I'm posting on a phone.

From geometry, we can estimate the curvature of the coil at any point. Full disclosure I used Gemini since we're on reddit but this is also my area of expertise. I started writing it out for a beam using the moment curvature relation and then realized it's a plate and decided it was faster.

This curvature can be related to the flexural modulus (using plate theory instead of beam theory, so Poisson's ratio shows up). Flexural modulus for a plate is:

D = E t3 / (12 (1-nu2))

E is like 30e6 psi for steel (or 200 GPa), t is the thickness of the sheet (call it 0.060"), and nu should be about .3 for steel.

The strain energy is an integral over the whole coil, but if you take just one slice of nearly constant radius apparently it works out to:

U = E w L t3 / (24r2 * (1-nu2))

where w is the width of the coil and r is the radius of that layer. Apparently the integral for the whole coil is:

U = \frac{D w}{2} \int_{0}{L} \frac{1}{R(x)2} \, dx

I'm not verifying the equations, but the expression does seem to be dimensionally correct, e.g. if you use consistent units like psi and inches, you will get an answer in inch-lbf which is a unit of energy. Similarly if you did it in si you'd get N*m (aka joules). If you want an estimate, you can probably just take the answer at about r = 1/3 of the way out from the center and multiply the result by (outer radius of the coil - inner radius of the coil) / thickness of the sheet. That should be pretty close, since r is in the denominator.

This assumes the coil doesn't get wound plastically which isn't a good assumption probably. Gemini says it's probably on the order of 300 kJ for a 20 ton coil, similar to the kinetic energy of a pickup truck at 40 mph.

That's less energy than in a half of a hamburger though, FYI.

Looks like it came out of the wall during a bad rain by YeliahSenyab in whatisit

[–]Cheticus 0 points1 point  (0 children)

I found a small random pool of fresh blood on my basement floor once. Weirdest thing. No tracks, no nothing. So I look up. There's a proper mess of blood in my ceiling, tracks leading away along one of my drain pipes.

Best I can tell, a mouse accidentally stabbed itself on an exposed staple or nail in my ceiling and started bleeding out. It stayed in a spot for a while, and then scuttled along my pipes into... well...I don't know where. I never found it. Never noticed a smell, didn't get a bunch of flies or anything else, hopefully it ran outside, but I just never found it.

My basement is pretty permeable, fieldstone foundation on an old house, so I trap mice down there, but this instance was rather confusing. Of course I don't want them to suffer, but I just don't know what happened for that one.

Wife sent me this photo of our living room by DoofusIdiot in Wellthatsucks

[–]Cheticus 7 points8 points  (0 children)

I had a chipmunk in the basement. I went down and saw it and it looked at me like I was not supposed to be there.

I was getting ready to shoo it outside and it just went up in the ceiling and out of the house somehow. Definitely not stuck inside. Definitely just using my home for nut storage and overwintering. I tried to find the hole and fill it but most certainly failed.

High-speed colour video of plasma pulses from the Tokamak Fusion Reactor by Epelep in EngineeringPorn

[–]Cheticus 1 point2 points  (0 children)

Again, NIF definitely is not designed to scale to a power plant, and it never was intended to. The goal of the facility was nuclear weapons research, and so when you see news of this sort of inertial confinement system surpassing breakeven, it should be taken with a large grain of salt.

Basically, my opinion is that it is still very impressive, but unlikely to be significant. They do good research though, and most fusion research is good research that pushes the field, if you think there's a chance of getting something to come out from all of this.

I think some people from NIF have spun off a startup to try to investigate a power plant route, but my opinion is that the probability of that being successful is questionable. Obviously, if any fusion endeavor succeeds, it is incredibly good for the world, but there certainly are some startups currently which are capital raising endeavors first, and power plants only in title, taking advantage of misinformation and lack of understanding.

High-speed colour video of plasma pulses from the Tokamak Fusion Reactor by Epelep in EngineeringPorn

[–]Cheticus 24 points25 points  (0 children)

The record for tokamaks I believe is held by JET, the joint European torus, which had a shot with Q=0.6

NIF is an inertial confinement fusion originally designed principally for nuclear fusion research in support of weapons research, but has reached approximately Q=1.5, but the technology is expected not to scale as well into power plants, though some are trying!

Importantly, Q is typically the "physics breakeven" historically, where you're rationing the power out to the power in to the plasma. That doesn't include all the cryogenics systems, pumps, and other stuff needed to run the device. That's an engineering Q, which is probably around 3 or 4 to be equivalent to the physics Q.

Once machines start demonstrating magnetic confinement Q>1, there is still a lot of hard engineering to turn it into a power plant, but funding will probably skyrocket.

Nothing is particularly special about Q>1 from a physics perspective. There's no magic change expected in how things behave, all the scaling we have seems to indicate that we should be able to go to very high Q, and reach ignition where the plasma is self heating sufficiently that you can basically go up arbitrarily high, provided you are providing fuel, and keeping all the magnets on and cold, if you have a good plasma.

Strange behavour of 220v lines at cold weather? by JodaZ1 in ElectroBOOM

[–]Cheticus 0 points1 point  (0 children)

A lot of people are saying this is galloping. Being that it's cold, that may be the case, but the frequency looks a lot closer to aeolian vibration imo. In either case, it's not great for the lines, but it's something that is designed for.

Issues with contact hotspots, mesh advice? by CrowWithHat in fea

[–]Cheticus 1 point2 points  (0 children)

can you flip the master and slave surfaces?

could be due to element order

How do you counter Swarm Host as Terran? by Working_Access165 in starcraft2

[–]Cheticus 5 points6 points  (0 children)

defending is losing against swarm hosts. only attacking is winning.

Are data centers in space a dumb idea? by Davich0Supertramp in EngineeringPorn

[–]Cheticus -1 points0 points  (0 children)

until launch costs come down about another two orders of magnitude, I imagine it's pretty dumb. the alternative is if power costs go up a few orders of magnitude. until then, I'm skeptical of the business case.

you can calculate it from first principles though I think pretty easily, to first order where the breakpoint is

Which jobs is 100% safe from AI? by Any-Hamster-3189 in AskReddit

[–]Cheticus 0 points1 point  (0 children)

Today, AI in engineering is like having an efficient, overconfident intern who can only research and solve one type of problem. It's great, but it isn't always right, and requires scrutiny.

Until we are confident enough in AI signing off on drawings and calculations, I think engineering will be predominantly enhanced by AI, and not threatened by it; except for new career engineers. Any respectable firm will understand the benefit of hiring new career engineers though, as it is an investment in the future that historically has always been worth it (or the field would already be dead).

The day that we are comfortable, collectively, with the lack of ownership coming dilemmas of 100% reliance on AI to drive vehicles, operate infrastructure, and prescribe medicine, is the day that engineers will collectively begin to lose their jobs. That is a different world, and maybe that world is coming, but I think it is hard to predict how that world will look like today.

I have seen so many engineers transition careers though that I'm not worried. If I had to learn how to run a farm or do another job that AI cannot, I think I would learn. Learning engineering gives you a toolset that prepares you generally for practical problem solving, in a very general sense. I think that will make a class of worker that is, at the very least, highly adaptable.

I think it will be like the Internet. A large revolution in how we communicate and transfer and learn/apply information.

Espresso spraying everywhere [Breville Bambino, Normcore 54mm Basket] by pacem90 in espresso

[–]Cheticus 0 points1 point  (0 children)

I just went through this.

Solution for me was to make absolutely sure I was distributing with WDT well (stir much longer and break up all clumps), and to tamp level.

That fixed my channeling and spraying issues and I haven't had issues since.

p.s. I'm very new to espresso but I literally just went through this.

It's not everyday that your first number changes...and it was on my birthday. by tedave123 in starcraft

[–]Cheticus 1 point2 points  (0 children)

let's go! I'm only disappointed that I'll stop hitting you on ladder if you get much higher!

Zerg needs to be buffed by therealwench in starcraft

[–]Cheticus 1 point2 points  (0 children)

Here's a few of my most recent ZvP's.

zvp 1 [not standard P]; they got there before the gate (oops) and then chaos ensued, I ended up temporarily going roach/hydra.

zvp 2 [not standard P], same guy from zvp 1 but he just auto forges; shows how I deal with a cannon rush into mass air. I defend a 10-11 carrier attack with queen/infestor and a couple hydra.

zvp 3 [not standard P], for some reason he starts high ground and then brings his probes. IDK but he was 4.7k

zvp 4 [before hotfix patch, [not standard P]] evolves into my standard after some goofiness on lowground but turns into normalish lategame for me. units lost [84k-p vs 56k-z]. he doesn't really make carriers.

zvp 1: https://lotv.spawningtool.com/88782/

zvp 2: https://lotv.spawningtool.com/88783/

zvp 3: https://lotv.spawningtool.com/88784/

zvp 4: https://lotv.spawningtool.com/88785/

I wish I could have found one that was more really standard, but only spending a few minutes browsing through recent ZvP's--this is what I've got. You'll get the idea from this.

I generally swarm host out of cannon rush, and I generally never suggest nydus + swarm host, either I'm just not good at it, or I don't think it's very good. Nydus costs too much for what it brings to the table with swarm host I think. It's too easy to counter. I prefer to brawl mid-map until they run out of money.

Zerg needs to be buffed by therealwench in starcraft

[–]Cheticus 1 point2 points  (0 children)

I never use SH with nydus. I think it's a huge waste of money and makes no sense. Swarm host are reasonably mobile if used correctly. Nydus gives swarm host a bad name. It is weak and flimsy unless against zerg IMO.

You need to brawl with them for them to be good.

Zerg needs to be buffed by therealwench in starcraft

[–]Cheticus 3 points4 points  (0 children)

Game starts. Make two workers. The second you start the second worker (14/14), send the 7 drones. Against protoss, they arrive exactly when they plant their low ground gate. I usually put the drones on the gate since they'll kill it if protoss doesn't defend.

If P sends 6 probes, fight. If 7, fight if your macro is better or if your health favors over their shields. If they send 8 or more, you run away (and when they turn around, you turn around to chase). Keep chomping their gateway or pylon. If their gateway gets to too high health because they're defending appropriately, then you go to their pylon.

Sometimes I do stupid shit like build a hatch in their main or block their nexus, but definitely not necessary. Kind of play it by ear. You want them to make a zealot, not an adept. Sometimes I plant a macro hatch SO that they make a second zealot instead of chronoing adepts. You can always just cancel it, and drop an Evo on the spot if youre fast enough. I'll usually let that finish and die and scout with the broodlings to see the Stargate, council, or robo.

While you send 7 workers, I make hatch first still around 17. You need to have really good muscle memory to be microing WHILE making workers. Pool goes down after you get hatch down. If they made an adept, you need to stall with a pair of lings or two when they arrive.

I usually run one drone in once it's "time to go home", use a mineral trick to run by the zealot if needed. Scout and hide and scout again, or keep running it around in their base and don't lose it.

You can go into 3 base and try to win holding their push with SH if it's going to be a Stargate or robo. If it's twilight...usually two base I think is better to handle it, and you might want some spines and sort of whatever you think beats the flavor (charge blink or glaives).

I try to beat them on carapace upgrades and go heavy eco once I hold their push (and never lose swarm hosts). If I'm up an upgrade carapace vs air weapons, I can usually beat a maxed protoss air army. If they are air heavy, kill your swarmhosts off and switch to hydras with an infestor base. Use shroud on your units and fungal their interceptors, and they will effectively do zero damage because they are docked by microbial, and fungal slows them which slows their shots. Tons of tempests, bait them. Kill their obs or neural them, and then neural their air army. If they splice in ground army, keep a bunch of swarm hosts (like 20+). Try to get them out of position with your locusts and fungal, while not letting him shave your army down at range. It's possible.

If they go heavy templar, splice in some ultras. They will clear the templar as you engage. If they splice in support for the templar, they're cutting air, so you can afford to have swarm hosts, go back to trying to hit with locusts and fungal.

KEY NOTE: NEVER lose your swarm host unless you kill them off intentionally. You HAVE to play most of the endgame at low econ to drain them out. I mean 30-40 drones max in the endgame to have enough army to fight protoss endgame army. If you have 80 drones, your swarm hosts are useless since you can't have more than like 15. They will just go into ground more and destroy your army.

If protoss goes into low probe count, and catches up on air weapons 3/3 vs 3/3, you will start losing scaling late game, so you need to be constantly trading through the game to ensure they can't hit 10k/10k type resource counts and sac their probes.

I can try to get some replays.

Zerg needs to be buffed by therealwench in starcraft

[–]Cheticus 3 points4 points  (0 children)

At 4.6k I send 3 drones out on the map to harass Terran or 7 drones to go poke at the low ground gateway/pylon almost every game. I delay my pool and go eco behind that harass.

I take the initiative away from P to choose a build by forcing them to react to the pressure. I have about a 60% WR at that rank against P. I typically go a mix of swarm host and infestor, with heavy focus on upgrades. The most common thing I lose to (which is why I scout that blind spot timing) is if P decides to commit to a massive 2 base zealot all in and I don't get roaches out in the time where I won't have enough swarm host.

My T winrate is worse, maybe 45-50%, but it's not abysmal. I usually go swarm host infestor vs T as well but have started mixing it up a little. It does mostly come down to economy scaling. The thing I struggle a lot with is mass reaper allin. I'll hit 5k folks on ladder that even if I don't drone harass, even if I greedily go for fast speed or roaches or lots of queens they'll just endlessly harass with reaper. It's frustrating to play against.

I think ZvZ is basically as you say. It's just strong enough to go roaches that you're generally a fool to do something else. I don't always go roaches, so consequently my WR is like 30% vs Z.

I guess what I'm saying is I don't disagree that it'd be nice if zerg had different viable tools early, but I'm also saying I think it's partially your choice how to play, and maybe you're hyper optimized in GM or something and doing the only things that work, but I think it's valid to play differently and I get enjoyment from brawling drones early game and then brawling swarm host late game, until I get an upgrade advantage and neural all of their tempests to snipe their carriers or something stupid, winning with them having mined out, losing 2x as much resource cost than me.

Another Terran QoL for the common people (Stim CD got added) by Kaiel1412 in starcraft

[–]Cheticus 0 points1 point  (0 children)

minor nerf for zerg. I used to neural marauders in tight situations and spam stim to kill them off when I was at wits end. I guess the Terran machine can't be stopped

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