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andmaybegayer · 9 months

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For a different project I was reading about developments in induction heating technologies and realized I had a small misunderstanding about how induction stoves work.

So, the classic misunderstanding is in why steel works on an induction hob but aluminium doesn't. Most people assume this is because you need a magnetic material in order to induce a current, but if you know your physics you know this isn't true. You can induce a current in any conductor, and indeed inducing currents in aluminium is something that happens in industry all the time.

So then you get to my understanding of why you can't use aluminium and copper, which is that they're too good at conducting electricity. Induction generates a voltage that pushes a current through the material. Aluminium and copper are much better conductors than steel, so the generated potential is lower and the overall current is lower as a result of material interactions with the field, so you don't get nearly as much heat out of induction on aluminium as on steel. This was what I thought. This is also wrong, although it's closer.

The actual answer is one step deeper. Induction hobs have to operate at pretty high frequencies, usually 24-ish kHz, both for audible noise reasons and, crucially, because they rely heavily on the skin effect. Interestingly this makes that first wrong explanation kind of more correct, I'll get to that in a moment.

The skin effect is a thing that happens when you have an alternating current in a bulk material; the AC signal sets up magnetic fields that force current to flow in a thin layer closer to the surface of the solid rather than flowing evenly throughout the material. This increases the effective resistance of the material, since you end up with a reduced effective surface area through which current can flow. The skin effect gets more pronounced at higher frequencies, and it's part of why you'll see bundles of smaller cables used to conduct high power AC: each cable has its own skin that can carry more current than the same quantity of material in one bulk cable.

In the right kinds of steel and iron, 24kHz is enough to generate a current carrying skin only a few tenths of a millimeter thick, which has a high enough resistance to generate the heat needed for cooking. Ferromagnetic materials have very high magnetic permeability, which causes them to experience much stronger skin effects. Copper and aluminium, between their high conductivity and lower magnetic permeability, have much weaker skin effects, their skins at 24kHz are much thicker, and so you just can't kick up enough resistance to the current to generate heat, it just spins around in there getting kind of warm but you'd have a hard time actually cooking with it. Indeed, non-magnetic stainless steel also won't work on induction hobs, because it also has a much thicker skin effect.

So you have the "real answer" being a fun hybrid of the two incorrect explanations.

The main side effects I take away from this are twofold.

1) you can absolutely make an induction hob that will heat copper and aluminum and non-magnetic stainless steels, you just need a high enough frequency to generate a strong enough skin effect to generate heat. Panasonic makes one that uses 60+kHz induction under the brand "Met-all".

2) if you physically constrain the current by having a really thin piece of metal, you can induction heat it anyway. When I read this, I stopped, took out a piece of aluminium foil, and stuck it on my induction cooktop. It almost immediately got incredibly hot and I pulled it away before anything bad happened. Turns out you could definitely melt and maybe even vaporize aluminium this way. So don't do that. Apparently people do this with lightweight titanium cookware too, which would not be able to sustain the necessary currents in a large bulk solid but can if you thin the base of the pan out enough.

#cooking #induction #physics #material science #engineering

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bonebrokebuddy · 3 months

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@kodedgeekthings eyo you mentioned wanting a dpxdc prompt for Howard, Batman’s mechanic!

Harold misses fixing toys for kids and in his off hours has taken up the habit of answering questions on forums about machining, electrical, engineering, mechanics, and mechanical design that are often frequented by students.

One day, he comes across a request by a college student who is trying to assemble his own car out of scrap he bought from a local wrecking yard.

Ghostly_Boy states that he has previous experience in machining and can make replacements for broken or too-damaged parts if need be, but he doesn’t know where to start and what specific requirements he needs to reach to ensure it’s street legal.

Harold willing to help, he answers a few of Ghostly Boy’s clarifying questions:

- Great questions!

It’s good to note that if you’re not careful, fixing or making your own car from parts can be a moneysink and can cost you more than a brand new vehicle. - That being said, your first major step to ensuring you can drive the car is to get the title of the body/frame of the car you plan to build. It’ll have the VIN on a plate welded to the frame usually near the lower edge of the windshield wipers on the drivers side. It’s how the DMV identifies vehicles for licensing.

- Generally, you’ll at first get a “wreck out” title that shows the vehicle is listed as a total loss, but if you can assemble the parts for the car with that frame, the DMV can check if it’s properly running and road worthy & license for you to use it on public roads if you’ve done the proper paperwork.

- Once that is done, it’s largely a case of getting the right parts and assembling them. Depending on how much you have to repair, you could be taking on a task that could give a challenge to even a seasoned mechanic. There may be additional paperwork depending on what exactly you need to repair, like the breaks, lights, steering, etc.

- If you want to build the car entirely from scratch, chassis and all, that’s an entirely different story with a much more complicated list of requirements to make it street legal, so getting a frame from a junkyard is a great first step!

- Make sure to keep all bills of sale, junkyard receipts, invoices and manufacturers’ certificates on any major parts you used in building the vehicle to prove its road worthy to the DMV when it’s complete!

Harold doesn’t always answer first but over time he’s found the adventures of this kid amusing and keeps up with it.

Ghostly_Boy keeps the forum updated with his progress:

The kid spontaneously deciding to scrap the wiring system and make his own in a span of 3 days, leaving experienced mechanics on the forum practically screaming at the kid for his updates showing him using random wires he salvaged and pigtailing them together to get the length of wire he needed.

Mixing not only multiple types of wires but ones that didn’t have the protection needed for auto use. DIY-ing his own relay and fuses he didn’t have and connecting the wrong grounds and switches. And planning on leaving the wires unwrapped and loose.

Leaving Ghost to promptly redo the wiring, correctly this time, within 78 hours.

Making a repair of a massive rusted hole on the passenger side by the bumper and the front tire via cutting 1/2in past the rust, grinding it pretty and clean, tac & seam welding the vintage aluminum housing material of a toaster to cover the hole to the response of Harold and many others in the forum just going “… I guess that would work?”

Harold and many others telling the kid that this “ectoplasm” material wasn’t cleared through the EPA’s Clear Air Act and could be illegal to drive with it as it’s fuel source unless he got the emissions tested & the center of gravity of the car adjusted to have the center of gravity a gas car has, it wouldn’t pass Federal Motor Vehicle Safety Standards. Nor would the previously untested on material make it easy or quick to get an Emissions testing certificate. Best to just stick with gas.

Removing what he thought was a “skid plate” that turned out to be another rusted out section on the frame on the bottom of his car and repairing it with steel he salvaged from an old medical table he had laying around. (To the multiple slightly confused commenters asking how Ghost had a spare medical table, he replied, “eh, my folks visit every so often and they’ve been giving me things they’re clearing out of the house so they can move closer to my older sister. I just so happened to get the ye olde medical table. They’re an odd couple of folks but that’s why I love them.”)

People just crying at the kid to go to rockauto.com and just buy the damn parts he needs for his car. (A good resource btw)

The kid kept cutting corners to save cash but through the badgering of Harold and many others that he actually would have to spend money to make this car be safe to drive in, he finally got it completed.

Ghost’s post of him leaving DMV waving the updated title to the car in its envelope in the air, titled, “THE DMV FINALLY SAID IT WASN’T A FIRE HAZARD! ONLY TOOK 2 YEARS! THANKS EVERYONE!” Got the most amount of responses he’d ever had with congratulations from lurkers and previous commenters.

Over the course of those two years, Danny learned how to draw his own wiring diagrams, properly solder and weld, and learning to actually plan out his projects so he got it right at least the fifth time instead of the 20th. Not bad for a kid that went straight from graduating high school with a 1.5GPA to construction jobs.

But after finally getting the car approved, Ghostly_Boy returns to the forum with a new problem. Lamenting that his parents keep coming over and “modifying” his car to no longer make it street legal.

At this point, about half of the answers to the submission think it’s either a joke project taken very, very seriously with a good chunk of money behind it, or a kid with parents that have narrowly avoided falling completely down the mad scientist rogue rabbit hole.

After all, what sort of parent would think that the DMV would approve to “anti-ghost missiles” being attached to the outer body of the car? Either way, the submissions always had video attached showing a demonstration, proving that Ghost wasn’t just completely yanking their chain. And a good amount of money would have to be sunken in to not only pay for the fines Ghostly continued to get from the additions to his car, but to actually manufacture and make a unique working product for each plea for help request.

Harold is not only taking notes on some of these defense measures but also decides to bring up the boy to Alfred. Intrigued, they together keep an eye on Ghostly_Boy. Bruce may be their employer, but they can handle a case or two on their own.

- I wanted Danny to try to make smth for himself now that he doesn’t have access to his parent’s lab anymore but he also doesn’t have access to ectoplasm so he’s fairly unfamiliar how to wire things Not for ectoplasmic standards.

Also I wanted to make a prompt where Danny had a good relationship with his parents & went into a fairly realistic job after high school with his fairly bad GPA so he’s saving up for a technical school via construction jobs as he doesn’t like the idea of working fast food for understandable reasons.

#dpxdc #bones writes #i have about 3 dozen ideas for dpxdc ideas to do with Howard #I’m going to be a manufacturing engineer.#i got so many ideas for this dude teaching one of the batkids or a visitor to the batcave about how cad programs work #& why he’s using x material for its purpose #instead of y material #like this dude could just be any of my automation profs

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pizzazz-party · 17 days

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Day twenty six! This is the last request in this challenge. I was asked to do a take on a sketch by Stan Sakai. The requester didn’t ask for the cowboy hat to be added, but I really wanted it.

#finally finished. for now anyway. this is as finished as it’s going to be for a while.#usagi yojimbo #miyamoto usagi #artists on tumblr #I don’t actually know anything about westerns #I googled ‘cowboy poses’ looking for reference material and what came up were images labeled ‘sexy cowboy poses’ but I think it came out ok #can I still say I googled something if I use duck go go as my search engine?#pizzazz art

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ddeck · 2 months

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it's that time of the year when i remember i have clone ocs as well

#sorry beloved i forgor what your armor design was and all the brainstorming material was lost in the great autumn art purge #he was a combat engineer before uhh the everything #star wars #the clone wars #tcw #clone oc #deckdraws

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mostlysignssomeportents · 7 months

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Deb Chachra's "How Infrastructure Works": Mutual aid, the built environment, the climate, and a future of comfort and abundance

This Thursday (Oct 19), I'm in Charleston, WV to give the 41st annual McCreight Lecture in the Humanities. And on Friday (Oct 20), I'm at Charleston's Taylor Books from 12h-14h.

Engineering professor and materials scientist Deb Chachra's new book How Infrastructure Works is a hopeful, lyrical – even beautiful – hymn to the systems of mutual aid we embed in our material world, from sewers to roads to the power grid. It's a book that will make you see the world in a different way – forever:

https://www.penguinrandomhouse.com/books/612711/how-infrastructure-works-by-deb-chachra/

Chachra structures the book as a kind of travelogue, in which she visits power plants, sewers, water treatment plants and other "charismatic megaprojects," connecting these to science, history, and her own memoir. In so doing, she doesn't merely surface the normally invisible stuff that sustains us all, but also surfaces its normally invisible meaning.

Infrastructure isn't merely a way to deliver life's necessities – mobility, energy, sanitation, water, and so on – it's a shared way of delivering those necessities. It's not just that economies of scale and network effects don't merely make it more efficient and cheaper to provide these necessities to whole populations. It's also that the lack of these network and scale effects make it unimaginable that these necessities could be provided to all of us without being part of a collective, public project.

Think of the automobile versus public transit: if you want to live in a big, built up city, you need public transit. Once a city gets big enough, putting everyone who needs to go everywhere in a car becomes a Red Queen's Race. With that many cars on the road, you need more roads. More roads push everything farther apart. Once everything is farther apart, you need more cars.

Geometry hates cars. You can't bargain with geometry. You can't tunnel your way out of this. You can't solve it with VTOL sky-taxis. You can't fix it with self-driving cars whose car-to-car comms let them shave down their following distances. You need buses, subways and trams. You need transit. There's a reason that every plan to "disrupt" transportation ends up reinventing the bus:

https://stanforddaily.com/2018/04/09/when-silicon-valley-accidentally-reinvents-the-city-bus/

Even the cities we think of as motorists' paradises – such as LA – have vast, extensive transit systems. They suck – because they are designed for poor people – but without them, the city would go from traffic-blighted to traffic-destroyed.

The dream of declaring independence from society, of going "off-grid," of rejecting any system of mutual obligation and reliance isn't merely an infantile fantasy – it also doesn't scale, which is ironic, given how scale-obsessed its foremost proponents are in their other passions. Replicating sanitation, water, rubbish disposal, etc to create individual systems is wildly inefficient. Creating per-person communications systems makes no sense – by definition, communications involves at least two people.

So infrastructure, Chachra reminds us, is a form of mutual aid. It's a gift we give to ourselves, to each other, and to the people who come after us. Any rugged individualism is but a thin raft, floating on an ocean of mutual obligation, mutual aid, care and maintenance.

Infrastructure is vital and difficult. Its amortization schedule is so long that in most cases, it won't pay for itself until long after the politicians who shepherded it into being are out of office (or dead). Its duty cycle is so long that it can be easy to forget it even exists – especially since the only time most of us notice infrastructure is when it stops working.

This makes infrastructure precarious even at the best of times – hard to commit to, easy to neglect. But throw in the climate emergency and it all gets pretty gnarly. Whatever operating parameters we've designed into our infra, whatever maintenance regimes we've committed to for it, it's totally inadequate. We're living through a period where abnormal is normal, where hundred year storms come every six months, where the heat and cold and wet and dry are all off the charts.

It's not just that the climate emergency is straining our existing infrastructure – Chachra makes the obvious and important point that any answer to the climate emergency means building a lot of new infrastructure. We're going to need new systems for power, transportation, telecoms, water delivery, sanitation, health delivery, and emergency response. Lots of emergency response.

Chachra points out here that the history of big, transformative infra projects is…complicated. Yes, Bazalgette's London sewers were a breathtaking achievement (though they could have done a better job separating sewage from storm runoff), but the money to build them, and all the other megaprojects of Victorian England, came from looting India. Chachra's family is from India, though she was raised in my hometown of Toronto, and spent a lot of her childhood traveling to see family in Bhopal, and she has a keen appreciation of the way that those old timey Victorian engineers externalized their costs on brown people half a world away.

But if we can figure out how to deliver climate-ready infra, the possibilities are wild – and beautiful. Take energy: we've all heard that Americans use far more energy than most of their foreign cousins (Canadians and Norwegians are even more energy-hungry, thanks to their heating bills).

The idea of providing every person on Earth with the energy abundance of an average Canadian is a horrifying prospect – provided that your energy generation is coupled to your carbon emissions. But there are lots of renewable sources of energy. For every single person on Earth to enjoy the same energy diet as a Canadian, we would have to capture a whopping four tenths of a percent of the solar radiation that reaches the Earth. Four tenths of a percent!

Of course, making solar – and wind, tidal, and geothermal – work will require a lot of stuff. We'll need panels and windmills and turbines to catch the energy, batteries to store it, and wires to transmit it. The material bill for all of this is astounding, and if all that material is to come out of the ground, it'll mean despoiling the environments and destroying the lives of the people who live near those extraction sites. Those are, of course and inevitably, poor and/or brown people.

But all those materials? They're also infra problems. We've spent millennia treating energy as scarce, despite the fact that fresh supplies of it arrive on Earth with every sunrise and every moonrise. Moreover, we've spent that same period treating materials as infinite despite the fact that we've got precisely one Earth's worth of stuff, and fresh supplies arrive sporadically, unpredictably, and in tiny quantities that usually burn up before they reach the ground.

Chachra proposes that we could – we must – treat material as scarce, and that one way to do this is to recognize that energy is not. We can trade energy for material, opting for more energy intensive manufacturing processes that make materials easier to recover when the good reaches its end of life. We can also opt for energy intensive material recovery processes. If we put our focus on designing objects that decompose gracefully back into the material stream, we can build the energy infrastructure to make energy truly abundant and truly clean.

This is a bold engineering vision, one that fuses Chachra's material science background, her work as an engineering educator, her activism as an anti-colonialist and feminist. The way she lays it out is just…breathtaking. Here, read an essay of hers that prefigures this book:

https://tinyletter.com/metafoundry/letters/metafoundry-75-resilience-abundance-decentralization

How Infrastructure Works is a worthy addition to the popular engineering books that have grappled with the climate emergency. The granddaddy of these is the late David MacKay's open access, brilliant, essential, Sustainable Energy Without the Hot Air, a book that will forever change the way you think about energy:

https://memex.craphound.com/2009/04/08/sustainable-energy-without-the-hot-air-the-freakonomics-of-conservation-climate-and-energy/

The whole "Without the Hot Air" series is totally radical, brilliant, and beautiful. Start with the Sustainable Materials companion volume to understand why everything can be explained by studying, thinking about and changing the way we use concrete and aluminum:

https://memex.craphound.com/2011/11/17/sustainable-materials-indispensable-impartial-popular-engineering-book-on-the-future-of-our-built-and-made-world/

And then get much closer to home – your kitchen, to be precise – with the Food and Climate Change volume:

https://pluralistic.net/2021/01/06/methane-diet/#3kg-per-day

Reading Chachra's book, I kept thinking about Saul Griffith's amazing Electrify, a shovel-ready book about how we can effect the transition to a fully electrified America:

https://pluralistic.net/2021/12/09/practical-visionary/#popular-engineering

Chachra's How Infrastructure Works makes a great companion volume to Electrify, a kind of inspirational march to play accompaniment on Griffith's nuts-and-bolts journey. It's a lyrical, visionary book, charting a bold course through the climate emergency, to a world of care, maintenance, comfort and abundance.

If you'd like an essay-formatted version of this post to read or share, here's a link to it on pluralistic.net, my surveillance-free, ad-free, tracker-free blog:

https://pluralistic.net/2023/10/17/care-work/#charismatic-megaprojects

My next novel is The Lost Cause, a hopeful novel of the climate emergency. Amazon won't sell the audiobook, so I made my own and I'm pre-selling it on Kickstarter!

#pluralistic #books #reviews #deb chachra #debcha #engineering #infrastructure #free energy #material science #abundance #scarcity #mutual aid #maintenance #99 percent invisible #colonialism #gift guide

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carlyraejepsans · 5 months

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aro papyrus warrior forever..... however. papyton doth compel me

#it's one of those ships where like. i CAN very clearly see the appeal and how they would work well together and complement one another #both as people and as characters with their own individual arcs. but there's just so little material of them interacting in the canon #that my brain doesn't have a lot of Things to latch onto when i think about them #but lo and behold. robot x engineer fixing him up sharing a private moment of vulnerability #is a mental image that NEVER disappoints #so I'm rotating them in my brain

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fuckyeahfluiddynamics · 2 months

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#3D printing #engineering #fluid dynamics #granular material #manufacturing #physics #science

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clausmotherthree · 3 months

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Team Fortress 2 Mercenary Ages - given all of the canon information we know!

Scout - 27

In the TF2 Comic “The Naked and the Dead,” Spy (Scout’s biological father) states that Scout was conceived 27 years ago, making Scout 27. This is the only 100% confirmed age.

Soldier - mid 40s to early 50s

It’s stated in Soldier’s description that he attempted to join the army during WWII. If we assume Soldier was a young adult when he attempted to enlist, he would now be in his mid 40s to early 50s during the events of TF2.

Pyro - unknown

There is very little information out there on Pyro. It would be impossible for me to accurately identify their age.

Demoman - mid 30s

The only information I have in regards to demoman’s age comes from a line his mother says in the book “Valve Presents Volume 1: The Sacrifice and Other Steam-Powered Stories” in which Demo’s mother remarks: “No demoman worth his Sulfur ever had an eye in his head past thirty!” Which means Demo is most likely somewhere in his 30s.

Heavy - mid 40s to early 50s

In the update comic “Meet the Director,” it is revealed that Heavy was sent to a North Siberian Gulag in September 1941 alongside his mother and sisters. Heavy also canonically has a PhD in Russian literature, as revealed through his dialogue in the game ‘Poker Night at the Inventory.’ It would take around 9 years to obtain that PhD, meaning- depending on if he obtained the degree before or after 1941, he would be either in his mid 40s or early 50s.

Engineer - early to mid 30s

Engineer designed and built the Sentry under contract from TF industries in 1965, with him also spending 10 years in the West Texas oil fields- assuming Engineer was 18 before this date, he would be in his early to mid 30s during the events of TF2.

Medic - late 30s to early 40s

Medic’s description explicitly states that he was “Raised in Stuttgart, Germany during an era when the Hippocratic oath had been downgraded to an optional Hippocratic suggestion,” This implies that Medic was brought up during, or just before, WWII. The word ‘raised’ heavily implies the Medic to still be in adolescence during this era, making him surprisingly younger than expected, with him being around his late 30s to very early 40s during Team Fortress 2.

Sniper - early 30s

In the Team Fortress 2 comic ‘Blood in the Water’, Miss Pauling directly states that New Zealand sunk 40 years ago- in the same comic, Sniper is shown as a baby in a flashback, 10 years after New Zealand sunk. This makes Sniper out to be 30 or 31 in the TF2 present.

Spy - unknown, estimated early-mid 50s

Given Spy’s secretive nature, it’s difficult to deduct how old he is. However, since he has a 27 year old son, it’s likely that he is in his mid 50s. There is a single comic panel (Found in ‘Unhappy Returns’) depicting Spy’s hair to have a grey tint to it, further emphasising this fact.

#feel free to let me know of any mistakes ive made/anything ive missed #there’s a lot of debate about the merc’s ages #especially given all the retconns and contradictory evidence within tf2 #so i tried my hardest to stick solely to 100% canon tf2 material instead of common headcanon and popular fanmade materal #i didnt include any community info (i.e the track terroriser) as im trying to only reference completely canon material #ok Cool hope u all enjoy #tf2 #team fortress 2 #team fortress two #medic tf2 #scout tf2 #sniper tf2 #pyro tf2 #demoman tf2 #heavy tf2 #spy tf2 #engineer tf2 #soldier tf2

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