Last week, [Al Williams] wrote up a his experience with a book that provided almost too much detailed information on how to build a DIY x-ray machine for his (then) young soul to bear. He almost had to build it! Where the “almost” is probably both a bummer because he didn’t have an x-ray machine as a kid, but also a great good because it was a super dangerous build, of a typical sort for the 1950s in which it was published.

Part of me really loves the matter-of-factness with which “A Boy’s First Book of Linear Accelerators” tells you how you (yes you!) can build a 500 kV van der Graff generator. But at the same time, modern me does find the lack of safety precautions in many of these mid-century books to be a little bit spooky. Contrast this with modern books where sometimes I get the feeling that the publisher’s legal team won’t let us read about folding paper airplanes for fear of getting cut.

A number of us have built dangerous projects in our lives, and many of us have gotten away with it. Part of the reason that many of us are still here is that we understood the dangers, but I would be lying if I said that I always fully understood them. But thinking about the dangers is still our first and best line of defense. Humility about how well you understand all of the dangers of a certain project is also very healthy – if you go into it keeping an eye out for the unknown unknowns, you’re in better shape.

Safety isn’t avoiding danger, but rather minimizing it. When we publish dangerous hacks, we really try to at least highlight the most important hazards so that you know what to look out for. And over the years, I’ve learned a ton of interesting safety tricks from the comments and fellow hackers alike. My ideal, then, is the spirit of the 1950s x-ray book, which encourages you to get the hack built, but modernized so that it tells you where the dangers lie and how to handle them. If you’re shooting electrons, shouldn’t the book also tell you how to stay out of the way?

It’s a great joke, and like all great jokes it makes you think. [Søren Fuglede Jørgensen] managed to cram a 15 M parameter large language model into a completely valid TrueType font: llama.ttf. Being an LLM-in-a-font means that it’ll do its magic across applications – in your photo editor as well as in your text editor.

What magic, we hear you ask? Say you have some text, written in some non-AI-enabled font. Highlight that, and swap over to llama.ttf. The first thing it does is to change all “o” characters to “ø”s, just like [Søren]’s parents did with his name. But the real magic comes when you type a length of exclamation points. In any normal font, they’re just exclamation points, but llama.ttf replaces them with the output of the TinyStories LLM, run locally in the font. Switching back to another font reveals them to be exclamation points after all. Bønkers!

This is all made possible by the HarfBuzz font extensions library. In the name of making custom ligatures and other text shaping possible, HarfBuzz allows fonts to contain Web Assembly code and runs it in a virtual machine at rendering time. This gives font designers the flexibility to render various Unicode combinations as unique glyphs, which is useful for languages like Persian. But it can just as well turn all “o”s into “ø”s or run all exclamation points through an LLM.

Something screams mischief about running arbitrary WASM while you type, but we remind you that since PostScript, font rendering engines have been able to run code in order to help with the formatting problem. This ability was inherited by PDF, and has kept malicious PDFs in the top-10 infiltration vectors for the last fifteen years. [Citation needed.] So if you can model a CPU in PDF, why not an LLM in TTF? Or a Pokemon clone in an OpenType font?

We don’t think [Søren] was making a security point here, we think he was just having fun. You can see how much fun in his video demo embedded below.

Now before you start asking yourself “best for what purpose?”, just have a look at the quality of the DIY PCB in the image above. [ForOurGood] is getting higher resolution on the silkscreen than we’ve seen in production boards. Heck, he’s got silkscreen and soldermask at all on a DIY board, so it’s definitely better than what we’re producing at home.

The cost here is mostly time and complexity. This video demonstrating the method is almost three hours long, so you’re absolutely going to want to skip around, and we’ve got some relevant timestamps for you. The main tools required are a cheap 3018-style CNC mill with both a drill and a diode laser head, and a number of UV curing resins, a heat plate, and some etchant.

[ForOurGood] first cleans and covers the entire board with soldermask. A clever recurring theme here is the use of silkscreens and a squeegee to spread the layer uniformly. After that, a laser removes the mask and he etches the board. He then applies another layer of UV soldermask and a UV-curing silkscreen ink. This is baked, selectively exposed with the laser head again, and then he cleans the unexposed bits off.

In the last steps, the laser clears out the copper of the second soldermask layer, and the holes are drilled. An alignment jig makes sure that the drill holes go in exactly the right place when swapping between laser and drill toolheads – it’s been all laser up to now. He does a final swap back to the laser to etch additional informational layers on the back of the board, and creates a solder stencil to boot.

This is hands-down the most complete DIY PCB manufacturing process we’ve seen, and the results speak for themselves. We would cut about half of the corners here ourselves. Heck, if you do single-sided SMT boards, you could probably get away with just the first soldermask, laser clearing, and etching step, which would remove most of the heavy registration requirements and about 2/3 of the time. But if it really needs to look more professional than the professionals, this video demonstrates how you can get there in your own home, on a surprisingly reasonable budget.

This puts even our best toner transfer attempts to shame. We’re ordering UV cure soldermask right now.

Every once in a while, there’s a Hackaday article where the comments are hands-down the best part of a post. This happened this week with Al Williams’ Ask Hackaday: How Do You Make Front Panels?. I guess it’s not so surprising that the comments were full of awesome answers – it was an “Ask Hackaday” after all. But you all delivered!

A technique that I had never considered came up a few times: instead of engraving the front of an opaque panel, like one made of aluminum or something, instead if you’re able to make the panel out of acrylic, you can paint the back side, laser or engrave into it, and then paint over with a contrast color. Very clever!

Simply printing the panel out onto paper and laminating it got a number of votes, and for those who are 3D printing the enclosure anyway, simply embossing the letters into the surface had a number of fans. The trick here is in getting some contrast into the letters, and most suggested changing filament. All I know is that I’ve tried to do it by painting the insides of the letters white, and it’s too fiddly for me.

But my absolute favorite enclosure design technique got mentioned a number of times: cardboard-aided design. Certainly for simple or disposable projects, there’s nothing faster than just cutting up some cardboard and taping it into the box of your desires. I’ll often do this to get the sizes and locations of components right – it’s only really a temporary solution. Although some folks have had success with treating the cardboard with a glue wash, paint, or simply wrapping it in packing tape to make it significantly more robust. Myself, if it ends up being a long-term project, I’ll usually transfer the cardboard design to 3DP or cut out thin plywood.

I got sidetracked here, though. What I really wanted to say was “thanks!” to everyone who submitted their awesome comments to Al’s article. We’ve had some truly hateful folks filling the comment section with trash lately, and I’d almost given up hope. But then along comes an article like this and restores my faith. Thanks, Hackaday!

Everyone has a lightsaber or two lying around the house, but not everyone has a lightsaber that extends and retracts automatically. And that’s because, in the real world, it’s not an easy design challenge. [HeroTech]’s solution for the mechanism is simple and relies on an old magician’s trick: the appearing cane. (Video, embedded below.)

An appearing cane is a tightly coiled up spring steel sheet that springs, violently, to its full length when a pin is released, but they can’t retract while the audience is looking. This is fine for magic tricks, but a lightsaber has to be able to turn off again. Here, an LED strip does double duty as source of glow but also as the cable that extends and retracts the appearing cane spring. A motor and spool to wind up the LED strip takes care of the rest.

There are still a number of to-dos in this early stage prototype, and the one mentioned in the video is a tall order. Since the strip doesn’t illuminate out the sides, the lightsaber has two good viewing angles, and two bad ones. The plan is to rotate the LED strip quickly inside the sheath: an approach that was oddly enough used in the original movie prop, as demonstrated in this documentary. Doing this reliably in an already packed handle is going to be a challenge.

If you’re thinking you’ve seen a magic-cane lightsaber before, well, maybe you saw this video. And if you want a light saber with real lasers, check out this build that brings its own fog machine. Take that, Darth Vader!

Climbers care a lot about their ropes because their lives literally depend on them. And while there’s been tremendous progress in climbing rope tech since people first started falling onto hemp fibers, there are still accidents where rope failure is to blame.

This long, detailed, and interesting video from [Hard is Easy] follows him on a trip to the Mammut test labs to see what’s up with their relatively new abrasion-resistant rope. His visit was full of cool engineering test rigs that pushed the ropes to breaking in numerous ways. If you climb, though, be warned that some of the scenes are gut-wrenchingly fascinating, watching the ropes fail horribly in well-shot slow-mo.

Long story short, some climbing ropes are strong but stiff. These are called static ropes, and they’re rated to hold a given weight, and tested to breaking under a static load. The thinnest and strongest static ropes are made of Kevlar, and they are correspondingly very abrasion resistant, but they hurt to fall into.

Dynamic climbing ropes have some stretch, and are rated both for how gently they let you down and their maximum breaking force. These are mostly made of nylon, and they are tested by dropping a mass with an accelerometer onto a slack rope — a pretty good simulation of falling back off of a flat face like at the climbing gym.

Now what if you wanted an abrasion resistant dynamic rope? A couple of manufacturers have created custom Kevlar-nylon filaments where the Kevlar is wrapped loosely around the nylon. This filament is abrasion resistant because of the Kevlar, but gives like a nylon rope because the Kevlar fibers have slack built in.

Testing these ropes involved creating a custom test that drops a mass onto the rope, but pulls it across a 45-degree granite edge as it falls. These tests absolutely shred the normal nylon dynamic ropes, but the Kevlar-reinforced ropes held fast. They’re both fun and terrifying to watch.

We’ve said it before, and it’s said a number of times in this video: “you can’t improve what you can’t measure“. In this context, it’s a little sobering is that there isn’t an industry standard test for abrasion resistance, but it’s cool to see the Mammut folks working on it.

Last week, I stumbled on a marvelous book: “Giant Brains; or, Machines That Think” by Edmund Callis Berkeley. What’s really fun about it is the way it sounds like it could be written just this year – waxing speculatively about the future when machines do our thinking for us. Except it was written in 1949, and the “thinking machines” are early proto-computers that use relays (relays!) for their logic elements. But you need to understand that back then, they could calculate ten times faster than any person, and they would work tirelessly day and night, as long as their motors keep turning and their contacts don’t get corroded.

But once you get past the futuristic speculation, there’s actually a lot of detail about how the then-cutting-edge machines worked. Circuit diagrams of logic units from both the relay computers and the brand-new vacuum tube machines are on display, as are drawings of the tricky bits of purely mechanical computers. There is even a diagram of the mercury delay line, and an explanation of how circulating audio pulses through the medium could be used as a form of memory.

All in all, it’s a wonderful glimpse at the earliest of computers, with enough detail that you could probably build something along those lines with a little moxie and a few thousands of relays. This grounded reality, coupled with the fantastic visions of where computers would be going, make a marvelous accompaniment to a lot of the breathless hype around AI these days. Recommended reading!

How many Arduini does it take to make a tiny CRT Asteroids game? [Marco Vallegi] of MVV Blog’s answer: two. One for the game mechanics and one for the sound effects. And the result is a sweet little retro arcade machine packed tightly into a very nicely 3D printed case.

If you want to learn to curse like a Tuscan sailor, you can watch the two-part video series, embedded below, in its entirety. Otherwise, we have excerpted the good stuff out of the second video for you.

For instance, we love the old-school voice synthesis sound of the Speak and Spell. Here, playback is implemented using the Talkie library for Arduino, and [Marco] is using the BlueWizard software on a dated Macbook for recording and encoding. (We’d use the more portable Python Wizard ourselves.) Check out [Marco] tweaking the noise parameters here to get a good recording.

And since the Talkie Arduino library uses PWM on a digital output pin to create the audio, the high-frequency noise was freaking out his simple transistor amplifier. Here, [Marco] adds a feedback capacitor to cancel that high-frequency hash out.

The build needs to be quite compact, and the stacked-Arduino-with-PCB-case design is tight. And the 3D-printed case has a number of nice refinements that you might like. We especially like the use of thin veneers that cover the case all around with the build-plate’s surface texture, and the contrasting “Asteroids” logos are very nice.

All in all, this is a really fun build that’s also full of little details that might help you with your own projects. Heck, even if it just encourages you to play around with the Talkie library, it’s worth your time in our opinion. And while you’re at it, you can turn on the subtitles and pick up some vocab that’ll make your nonna roll over in her grave.

Part One: Rebuilding the CRT

Part Two: Adding Sound

Thanks [ZioTibia81] for the tip!

Porting DOOM to everything that’s even vaguely Turing complete is a sport for the advanced hacker. But if you are just getting started, or want to focus more on the physical build of your project, a simpler game is probably the way to go. Maybe this explains the eternal popularity of games like PONG, Tetris, Snake, or even Pac-Man. The amount of fun you can have playing the game, relative to the size of the code necessary to implement them, make these games evergreen.

Yesterday was Tetris’ 40th birthday, and in honor of the occasion, I thought I’d bring you a collection of sweet Tetris hacks.

On the big-builds side of things, it’s hard to beat these MIT students who used colored lights in the windows of the Green Building back in 2012. They apparently couldn’t get into some rooms, because they had some dead pixels, but at that scale, who’s complaining? Coming in just smaller, at the size of a whole wall, [Oat Foundry]’s giant split-flap display Tetris is certainly noisy enough.

Smaller still, although only a little bit less noisy, this flip-dot Tetris is at home on the coffee table, while this one by [Electronoobs] gives you an excuse to play around with RGB LEDs. And if you need a Tetris for your workbench, but you don’t have the space for an extra screen, this oscilloscope version is just the ticket. Or just play it (sideways) on your business card.

All of the above projects have focused on the builds, but if you want to tackle your own, you’ll need to spend some time with the code as well. We’ve got you covered. Way back, former Editor in Chief [Mike Szczys] ported Tetris to the AVR platform. If you need color, this deep dive into the way the NES version of Tetris worked also comes with demo code in Java and Lua. TetrOS is the most minimal version of the game we’ve seen, coming in at a mere 446 bytes, but it’s without any of the frills.

No Tetris birthday roundup would be complete without mentioning the phenomenal “From NAND to Tetris” course, which really does what it says on the package: builds a Tetris game, and your understanding of computing in general, from the ground up.

Can you think of other projects to celebrate Tetris’ 40th? We’d love to see your favorites!

The triboelectric effect is familiar to anyone who has rubbed wool on a PVC pipe, or a balloon on a childs’ hair and then stuck it on the wall. Rubbing transfers some electrons from one material to the other, and they become oppositely charged. We usually think of this as “static” electricity because we don’t connect the two sides up with electrodes and wires. But what if you did? You’d have a triboelectric generator.

In this video, [Cayrex] demonstrates just how easy making a triboelectric generator can be. He takes pieces of aluminum tape, sticks them to paper, and covers them in either Kapton or what looks like normal polypropylene packing tape. And that’s it. You just have to push the two sheets together and apart, transferring a few electrons with each cycle, and you’ve got a tiny generator.

As [Cayrex] demonstrates, you can get spikes in the 4 V – 6 V range with two credit-card sized electrodes and fairly vigorous poking. But bear in mind that current is in the microamps. Given that, we were suprised to see that he was actually able to blink an LED, even if super faintly. We’re not sure if this is a testament to the generator or the incredible efficiency of the LED, but we’re nonetheless impressed.

Since around 2012, research into triboelectric nanogenerators has heated up, as our devices use less and less power and the structures to harvest these tiny amounts of power get more and more sophisticated. One of the coolest such electron harvesters is 3D printable, but in terms of simplicity, it’s absolutely hard to beat some pieces of metal and plastic tape shoved into your shoe.

The world of experimental self-built aircraft is full of oddities, but perhaps the most eye-catching of all is the JD-2 “Dyke Delta” designed and built by [John Dyke] in the 1960s. Built to copy some of the 1950’s era innovations in delta-style jet aircraft, the plane is essentially a flying wing that seats four.

And it’s not just all good looks: people who have flown them say they’re very gentle, they get exceptional gas mileage, and the light wing-loading means that they can land at a mellow 55 miles per hour (88 kph). And did we mention the wings fold up so you can store it in your garage?

Want to build your own? [John] still sells the plans. But don’t jump into this without testing the water first — the frame is entirely hand-welded and he estimates it takes between 4,000 and 5,000 hours to build. It’s a labor of love. Still, the design is time-tested, and over 50 of the planes have been built from the blueprints. Just be sure to adhere to the specs carefully!

It’s really fun to see how far people can push aerodynamics, and how innovative the experimental airplane scene really is. The JD-2 was (and probably still is!) certainly ahead of its time, and if we all end up in flying wings in the future, maybe this plane won’t look so oddball after all.

Zero backlash, high “gear” reduction, high torque transparency, silent operation, and low cost. What is this miracle speed reduction technology, you ask? Well, it’s shoelaces and a bunch of 3D printed plastic, at least in [Aaed Musa]’s latest installment in his series on developing his own robot dog.

OK, the shoelaces were only used in the first proof of concept. [Aaed] shortly upgrades to steel cable, and finds out that steel fatigues and snaps after a few hours. He settles on Dyneema DM-20, a flexible yet non-stretching synthetic rope.

Before it’s all over, he got a five-bar linkage plotting with a pencil on the table and a quadriped leg jumping up and down on the table — to failure. All in all, it points to a great future, and we can’t wait to see the dog-bot that’s going to come out of this.

There’s nothing secret about using capstan drives, but we often wonder why we don’t see cable-powered robotics used more in the hacker world. [Aaed] makes the case that it pairs better with 3D printing than gears, where the surface irregularities really bind. If you want to get a jumpstart, the test fixture that he’s using is available on GitHub.

If you want to learn more about capstan drives, you absolutely need to check out our own [Sonya Vasquez]’s Cable Mechanism Maths. She brought some demos of her gear reduction mechanisms to Supercon, and they just feel like butter. (If I were a robot, that’s how I’d want my knees to feel.)

This neat video from the [Computer History Archives Project] documents the development of the Aiken Mark I through Mark IV computers. Partly shrouded in the secrecy of World War II and the Manhattan Project effort, the Mark I, “Harvard’s Robot Super Brain”, was built and donated by IBM, and marked their entry into what we would now call the computer industry.

Numerous computing luminaries used the Mark I, aside from its designer Howard Aiken. Grace Hopper, Richard Bloch, and even John von Neumann all used the machine. It was an electromechanical computer, using gears, punch tape, relays, and a five horsepower motor to keep it all running in sync. If you want to dig into how it actually worked, the deliciously named patent “Calculator” goes into some detail.

The video goes on to tell the story of Aiken’s various computers, the rift between Harvard and IBM, and the transition of computation from mechanical to electronic. If this is computer history that you don’t know, it’s well worth a watch. (And let us know if you also think that they’re using computer-generated speech to narrate it.)

If “modern” computer history is more your speed, check out this documentary about ENIAC.

Thanks [Stephen Walters] for the tip!

Watching a video about a scratch-built ultra-precise switch for metrology last week reminded me that it’s not always the projects that are the most elegant solutions that I enjoy reading about the most. Sometimes I like reading about hackers’ projects more for the description of the problem they’re facing.

A good problem invites you to brainstorm along. In the case of [Marco Reps]’s switches, for instance, they need to be extraordinarily temperature stable, which means being made out of a single type of metal to avoid unintentional thermocouple joints. And ideally, they should be as cheap as possible. Once you see one good solution, you can’t help but think of others – just reading the comments on that article shows you how inspiring a good problem can be. I’m not worried about these issues in any of my work, but it would be cool to have to.

Similarly, this week, I really liked [Michael Prasthofer]’s deep dive into converting a normal camera into a spectrometer. His solutions were all very elegant, but what was most interesting were the various problems he faced along the way. Things that you just wouldn’t expect end up mattering, like diffraction gratings being differently sensitive across the spectrum when light comes in from different angles. You can learn a lot from other people’s problems.

So, hackers everywhere, please share your problems with us! You think that your application is “too niche” to be of general interest? Maybe it’s another example of a problem that’s unique enough to be interesting just on its own. Let’s see what your up against. A cool problem is at least as interesting as a clever solution.

[Felipe Tavares] wasn’t satisfied with the boring default fonts on an HD44780-based display. And while you can play some clever tricks with user-defined characters, if you want to treat the display as an array of pixels, you’ve got to get out your scalpel and cut up a data line.

The hack builds on work from [MisterHW] who documented the bits going from the common display driver to the display, and suggested that by cutting the data line and sending your own bits, you could send arbitrary graphics. The trick was to make sure that they’re in sync with the display, though, which means reading the frame sync line in user code.

This done, it looks like [Felipe] has it working! If you can read Rust for the ESP32, he has even provided us with a working demo of the code that makes it work.

We can’t help but wonder if it’s not possible to go even lower-level and omit the HD44780 entirely. Has anyone tried driving one of these little LCD displays directly from a microcontroller, essentially implementing the HD44780 yourself?

Any way you slice it, this is a cool hack, and it opens up the doors to DOOM, or as [MisterHW] suggests, Bad Apple on these little displays . If you do it, we want to see it.

If your needs aren’t so exotic, the classic HD44780 display is a piece of cake to get working, and an invaluable tool in anyone’s toolbox.

I really enjoyed reading Anne Ogborn’s piece on making simple DIY measurement devices for physical quantities like force, power, and torque. It is full of food for thought, if you’re building something small with motors and need to figure out how to spec them out.

Aside from a few good examples, what I really took home from this piece is how easy it can be to take approximate measurements. Take the push stick, which is a spring-loaded plunger in a transparent barrel. You use it to measure force by, well, squeezing the spring and reading off how far it deflects. That’s obvious, but the real trick is in calibration by pushing it into a weighing scale and marking divisions on the barrel. That quickly and easily turns “it’s pressing this hard” into an actual numerical force measurement.

The accuracy and precision of the push stick are limited by the quality of your scale and the fineness of the pen tip that you use to mark the barrel. But when you’re just looking to choose among two servo motors, this kind of seat-of-the-pants measure is more than enough to buy the right part. Almost any actual measurement is better than a wild-ass guess, so don’t hold yourself to outrageous standards or think that improvised quantitative measurement devices aren’t going to get the job done.

Al Williams quoted a teacher of his as saying that the soul of metrology is “taking something you know and using it to find something you don’t know”, and that sums up this piece nicely. But it’s also almost a hacker manifesto: “take something you can do and use it to do something that you can’t (yet)”.

Got any good measurement hacks you’d like to share?

What’s solder for, anyway? It’s just the stuff that sticks the parts to the PCB. If you’re rapid prototyping, possibly with expensive components, and want to be able to remove chips from the board easily when you spin up the next iteration, it would be great if you didn’t have to de-solder them to move on. If only you could hold the parts without the solder…

That’s exactly the goal behind [Zeyu Yan] et al’s SolderlessPCB, which uses custom 3D printed plastic covers to do the holding. And it has the knock-on benefit of serving as a simple case.

In their paper, they document some clever topologies to make sure that the parts are held down firmly to the board, with the majority of the force coming from screws. We especially like the little hold-down wings for use with SMD capacitors or resistors, although we could absolutely see saving the technique exclusively for the more high value components to simplify design work on the 3DP frame. Still, with the ability to automatically generate 3D models of the board, parts included, this should be something that can be automated away.

The group is doing this with SLA 3D printing, and we imagine that the resolution is important. You could try it with an FDM printer, though. Let us know if you do!

This is the same research group that is responsible for the laser-cut sheet-PCB origami. There’s clearly some creative thinking going on over there.

Our own Dan Maloney has been on a Voyager kick for the past couple of years. Voyager, the space probe. As a long-term project, he has been trying to figure out the computer systems on board. He got far enough to write up a great overview piece, and it’s a pretty good summary of what we know these days. But along the way, he stumbled on a couple old documents that would answer a lot of questions.

Dan asked JPL if they had them, and the answer was “no”. Oddly enough, the very people who are involved in the epic save a couple weeks ago would also like a copy. So when Dan tracked the document down to a paper-only collection at Wichita State University, he thought he had won, but the whole box is stashed away as the library undergoes construction.

That box, and a couple of its neighbors, appear to have a treasure trove of documentation about the Voyagers, and it may even be one-of-a-kind. So in the comments, a number of people have volunteered to help the effort, but I think we’re all just going to have to wait until the library is open for business again. In this age of everything-online, everything-scanned-in, it’s amazing to believe that documents about the world’s furthest-flown space probe wouldn’t be available, but so it is!

It makes you wonder how many other similar documents – products of serious work by the people responsible for designing the systems and machines that shaped our world – are out there in the dark somewhere. History can’t capture everything, and it’s down to our collective good judgement in the end. So if you find yourself in a position to shed light on, or scan, such old papers, please do! And then contact some nerd institution like the Internet Archive or the Computer History Museum.

Do you like your cup of tea to be cooled down to exactly 54 C, have a love for machining, and possess more than a little bit of a mad inventor bent? If so, then you have a lot in common with [Chronova Engineering]. In this video, we see him making a fully mechanical chime-ringing tea-temperature indicator – something we’d be tempted to do in silicon, but that’s admittedly pedestrian in comparison.

The (long) video starts off with making a DIY bimetallic strip out of titanium and brass, which it pretty fun. After some math, it is tested in a cup of hot water to ballpark the deflection. Fast-forward through twenty minutes of machining, and you get to the reveal: a tippy cup that drops a bearing onto a bell when the deflection backs off enough to indicate that the set temperature has been reached. Rube Goldberg would have been proud.

OK, so this is bonkers enough. But would you believe a bimetallic strip can be used as a voltage regulator? How many other wacky uses for this niche tech do you know?

Thanks [Itay] for the tip!