2026-03-11 07:00:29
IBM Selectric typewriters have a lot of unique parts that can be tricky to source, but one we didn’t think of was the clear acrylic(?) dust covers, that are apparently very hard to find in good shape. [Eric Strebel] has a few Selectrics that all have issues with these parts. While you could come close to recreating this piece with acrylic sheeting carefully bent to match the original shape, [Eric] has a different hammer to try in a new video: replicating it with a resin casting.
He uses de-gassed tin-cure silicone to create a mold for the original, with a bit of 3D printed PLA and foam board to hold the silicone to create the mold. That’s done in two steps to create a two-part mold, which is separated and cleaned before the resin goes in. The original part is actually a smoky plastic, rather than fully clear, but [Eric] is able to match it perfectly using a colourant in his clear epoxy resin. The resin is put into the mold with a simple gravity pour, though he does have a vibrator on it to help it flow. Curing is done under heat and pressure– 60 PSI. The results are amazing; once he adds a touch of paint to match the black finish on one face of the original, it’s very difficult to tell [Eric]’s casting from his master piece, except that the cast replicas are in better shape.
This particular part works very well for casting and not much else. While you could match the large curve by heat-bending a piece of smoky acrylic, there are lips along the edges of the part that would be tricky to reproduce. [Eric] also needed several, for his multiple typewriters, and this method is very efficient at producing multiple units since the mold is reusable.
While you might not have an IBM Selectric that needs a dust cover, this technique is equally applicable to all sorts of clear shapes. If you’re new to resin casting, we have a handy guide to replicating plastic parts to get you started in this kind of work. It’s not just large parts that can be replicated: you can even copy phonograph records, such is the fidelity of resin casting.
2026-03-11 04:00:21
This unusual clock by [Moritz v. Sivers] looks like a holographic dial surrounded by an LED ring, but that turns out to not be the case. What appears to be a ring of LEDs is in fact a second hologram. There are LEDs but they are tucked out of the way, and not directly visible. The result is a very unusual clock that really isn’t what it appears to be.
The face of the clock is a reflection hologram of a numbered spiral that serves as a dial. A single LED – the only one visibly mounted – illuminates this hologram from the front in order to produce the sort of holographic image most of us are familiar with, creating a sense of depth.
The lights around the circumference are another matter. What looks like a ring of LEDs serving as clock hands is actually a transmission hologram made of sixty separate exposures. By illuminating this hologram at just the right angle with LEDs (which are mounted behind the visible area), it is possible to selectively address each of those sixty exposures. The result is something that really looks like there are lit LEDs where there are in fact none.
[Moritz] actually made two clocks in this fashion. The larger green one shown here, and a smaller red version which makes some of the operating principles a bit more obvious on account of its simpler construction.
If it all sounds a bit wild or you would like to see it in action, check out the video (embedded below) which not only showcases the entire operation and assembly but also demonstrates the depth of planning and careful execution that goes into multi-exposure of a holographic plate.
[Moritz v. Sivers] is no stranger to making unusual clocks. In fact, this analog holographic clock is a direct successor to his holographic 7-segment display clock. And don’t miss the caustic clock, nor his lenticular clock.
2026-03-11 02:30:50
Debugging an application crash can oftentimes feel like you’re an intrepid detective in a grimy noir detective story, tasked with figuring out the sordid details behind an ugly crime. Slogging through scarce clues and vapid hints, you find yourself down in the dumps, contemplating the deeper meaning of life and the true nature of man, before hitting that eureka moment and cracking the case. One might say that this makes for a good game idea, and [Jonathan] would agree with that notion, thus creating the Fatal Core Dump game.
Details can be found in the (spoiler-rich) blog post on how the game was conceived and implemented. The premise of the game is that of an inexplicable airlock failure on an asteroid mining station, with you being the engineer tasked to figure out whether it was ‘just a glitch’ or that something more sinister was afoot. Although an RPG-style game was also considered, ultimately that proved to be a massive challenge with RPG Maker, resulting in this more barebones game, making it arguably more realistic.
Suffice it to say that this game is not designed to be a cheap copy of real debugging, but the real deal. You’re expected to be very comfortable with C, GDB, core dump analysis, x86_64 ASM, Linux binary runtime details and more. At the end you should be able to tell whether it was just a silly mistake made by an under-caffeinated developer years prior, or a malicious attack that exploited or introduced some weakness in the code.
If you want to have a poke at the code behind the game, perhaps to feel inspired to make your own take on this genre, you can take a look at the GitHub project.
2026-03-11 01:00:56
Alzheimer’s disease remains a frustratingly difficult condition to manage for the millions of patients affected worldwide and their families. The cause of the disease is still not properly understood, and by the time memory loss and cognitive decline become apparent, the underlying brain pathology has often been quietly building for decades.
Soon, though it may be possible to diagnose impending Alzheimer’s disease ahead of time, before symptoms have taken hold. New research suggests this could be achieved through a simple blood draw, providing clinicians and patients precious time to manage the condition and plan ahead.
A hallmark of Alzheimer’s disease is the buildup of amyloid and tau protein in the brain. Despite decades of research, the protein’s precise role in the disease remains somewhat unclear. Typically, Alzheimer’s disease is diagnosed by symptoms like memory loss and cognitive decline, with later investigation revealing the presence of elevated levels of these proteins in the brain. This investigation often involves brain imaging or invasive and painful spinal fluid tests.
However, researchers have developed a new predictive model that suggests it’s possible to estimate when a person will begin showing Alzheimer’s symptoms, based on a similar marker. The key ingredient is another protein called p-tau217, which circulates in the blood plasma and mirrors the slow, steady accumulation of amyloid and tau protein within the brain tissues.
Earlier research had previously established that p-tau217 levels tended to track alongside the rise of amyloid and tau buildup in the brain. This indicated that the level of p-tau217 in the blood could be a proxy for how far along the disease process has progressed. This allows the estimation of how many years remain before symptoms emerge for a given patient, with the research study suggesting this could be as specific as a margin of three or four years.
The research study drew on data from 603 older adults enrolled in two long-running studies — the Knight Alzheimer Disease Research Center at WashU Medicine and the multi-site Alzheimer’s Disease Neuroimaging Initiative. Plasma p-tau217 was measured using simple blood draws. One of the more interesting findings concerns age. The model revealed that the interval between elevated p-tau217 levels and symptom onset isn’t fixed. A person whose levels first ticked upwards at the age 60 might not develop noticeable cognitive problems for another two decades. But if that same elevation appeared at age 80, symptoms tended to follow within about eleven years. It suggests that younger brains appear to tolerate Alzheimer’s-related pathology for longer, while older brains are less able to withstand the protein buildup once the process gets underway.
Right now, p-tau217 testing is primarily used to help confirm an Alzheimer’s diagnosis in patients who are already experiencing cognitive trouble. It isn’t recommended for screening asymptomatic individuals outside of research settings. However, using p-tau217 as a predictive marker has obvious potential. If clinical trials for preventive Alzheimer’s drugs could enroll participants based on a predicted timeline for symptom onset, rather than waiting years for decline to actually happen, those trials could become dramatically shorter and cheaper to run, and more efficient in general. Perhaps more importantly, it has the potential to give patients a better understanding of what lies ahead, allowing them to plan ahead before cognitive symptoms become an unmanageable imposition on their life.
The research team has made their model development code publicly available on Github and created a web-based tool that lets other researchers explore the clock models in detail. Looking ahead, they note that combining p-tau217 with other blood-based biomarkers linked to cognitive decline could sharpen predictions even further. It’s still early days, but a future where a routine blood test could serve as an early-warning system for Alzheimer’s is looking more plausible than it did a few years ago.
2026-03-10 23:30:21
Who among us does not have a plethora of mains-powered devices on their workbench, and a consequent mess of power strips to run them all? [Jeroen Brinkman] made his more controllable with a multi-way switch box.
At first sight it’s a bank of toggle switches, one for each socket. But this is far more than a wiring job, because of course there are a couple of microcontrollers involved, and each of those switches ultimately controls a relay. There are also status LEDs for each socket, and a master switch to bring them all down. Arduino code is provided, so you can build one too if you want to.
We like the idea of a handy power strip controller, and especially the master switch with the inherent state memory provided by the switches. This could find a home on a Hackaday bench, and we suspect on many others too. It’s by no means the first power strip with brains we’ve seen, but most others have been aimed at the home instead.
2026-03-10 22:00:15
After all the crashing and burning of Imperial Germany’s Zeppelins in the later part of WWI – once the Brits managed to build interceptors that could hit their lofty altitude, and figured out the trick of using incendiary rounds to set off the hydrogen lift gas – there was a certain desire in airship circles to avoid fires. In the USA, that mostly took the form of substituting hydrogen for helium. Sure, it didn’t lift quite as well, but it also didn’t explode.
Still, supplies of helium were– and are– very much limited, and at least on a rigid Zeppelin, the hydrogen wasn’t even the most flammable part. As has become widely known, thanks in large part to the Mythbusters episode about the Hindenburg disaster, the doped cotton skin in use in those days was more flammable than some firestarters you can buy these days.
That’s a problem, because, as came up in the comments of our last airship article, rigid airships beat blimps largely on Rule of Cool. Who invented the blimp? Well, arguably it was Henri Griffard with his steam-driven balloon in 1857, but not many people have ever heard his name. Who invented the rigid airship? You know his name: Ferdinand Adolf Heinrich August Graf von Zeppelin. No relation. Probably. Well, admittedly most people don’t know the full name, but Count Zeppelin is still practically a household name over a century after his death. His invention was just that much cooler.
That unavoidable draw of coolness led to the Detroit Airship Company and their amazing tin blimp. The idea was the brainchild of a man named Ralph Upton, and is startling in its simplicity: why not take the all-metal, monocoque design that was just then being so successfully applied to heavier-than-air flight, and use it to build an airship?
Of course everyone’s initial reaction to the idea is that it’s absurd: metal is too heavy to fly! They said that about airplanes once, too, but airships are surely a different matter. Airships must be lighter than air. Could a skin of aluminum really hold enough lift gas to keep itself in the air? Upton convinced no lesser lights than Henry Ford to back him, and the Detroit Aircraft Company ultimately found a customer for the design in the US Navy.
It helped that Upton wasn’t exactly the first to come up with this idea: David Schwarz had tried to build a metal airship at the end of the 19th century. Arguably it is he who invented the rigid airship, not my aura farming not-ancestor. His design had metal skin over an internal framework, rather than the lighter monocoque construction Upton was exploring. While it was by no means a success, being destroyed on its maiden flight, the fact that it had a maiden flight at all at least proved that metal structures could be made light enough to get off the ground.
The Detroit Airship Company’s first– and only, as it turned out– prototype was much more successful, as we will see. It was immediately nicknamed the “tin blimp” by the press after it was unveiled in 1929, that name was incorrect in every particular. It wasn’t tin, and it wasn’t a blimp. Well, not exactly, anyway. More on that later.
Compared to the various frames, longitudinal girders, bracing wires and fabric-backed gas bags of a Zeppelin-type airship, the ZMC-2’s balloon was simplicity itself. The balloon–if you can call it that–was a hollow spheroid built up of strips of 0.0095” (0.24 mm) Alclad sheeting. Alclad is a sort of metallic composite material: a sheet of duraluminum coated with a very thin protective layer of pure aluminum to provide corrosion resistance. The ZMC-2 was actually the first major use of Alclad, but hardly the last. At least for skins, most aircraft aluminum is actually alclad, as alloys with the desired strength-to-weight ratio are generally too vulnerable to corrosion to be exposed to the elements.
So, contrary to popular belief, no tin was involved. And the sturdy aluminum spheroid was not at all flexible, so the ZMC-2 was not really any kind of blimp. It also was not, technically, a Zeppelin. It was a whole new beast: a metalclad airship.
There is a film of the ship being built, and it’s rather fascinating. The strips of alclad are rolled into conical sections and riveted together, with a bituminous material serving as sealant. Even today, you would not want to weld this material, so instead three and a half million 0.035” (0.89 mm) rivets hold the plates together. A special automated riveting machine was invented for the construction of the metalclad airship, which “sewed” three rows simultaneously at a rate of five thousand rivets per hour.
Just like most monocoque airplanes, then and now, the skin doesn’t hold the entire load: there were five circular frames, flanged and full of lightening holes just like the ribs of an aeroplane fuselage, of various diameters to help the ‘gas bag’ hold shape. The gondola would attach to two of these.
Amazingly, with all of those rivets and the low-tech sealant, the metalclad held helium much better than its rivals. Yes, helium. While more expensive than hydrogen, the US Navy had already transitioned away from that more volatile gas and had no interest in going back. All of their groundside infrastructure was centered around helium. If that meant that the fireproof metalclad would not be able to lift quite so much as it otherwise might, well, too bad.
Aside from outward appearance, the metalclad airship is similar to a blimp in some respects. For one, like the blimps that would go on to serve into and well past WWII, and unlike every Zeppelin ever built, the metalclad design had no internal subdivisions. The great metal balloon, 52 ‘8 ” in diameter (16 m) and 149’ 5” (45.5m) long, held two air bladders, one fore, and one aft, but was otherwise cavernously empty.
Just like the blimps, those air bladders were used for trim: by pressurizing the fore bladder, the nose becomes heavy and trims the blimp down; likewise pressurizing the rear bladder trims the nose upwards. With both under pressure, the overall excess lift of the gasbag is reduced slightly, though the hull was not designed to withstand enough pressure for that to be notably useful at affecting overall buoyancy. The maximum the ZMC-2’s hull could take was said to be about two inches of water, or 0.07 PSIg (0.5 kPa).
Also like a blimp, that pressure was required to resist the force of aerodynamic drag, at least at high speeds. The aluminum skin could hold its own shape, obviously, and even at low speeds it was safe to fly at atmospheric pressure, but at speeds above about half velocity never exceed (VNE) there was a risk of buckling the nose. So, like a blimp–or the balloon tanks on the much later Atlas rockets–gas pressure was used as reinforcement. For that reason, there was much consternation at the time–and since–whether to count the metalclad as a rigid or non-rigid airship. Ultimately the US Navy, whose code was “Z” for airship and “R” for rigid or “S” for non-rigid, called it ZMC– z-airship, metal clad. That dodged the issue well enough.
A larger ship might have been able to afford the weight of stronger aluminum to take the buffeting of high-speed flight, thanks to the square-cube law, but the comparatively tiny ZMC-2 lacked that lift capacity. Even larger ships were always intended to use pressure-reinforcement; it’s a key part of the metalclad concept. Why waste lift capacity on metal when the gas can do it for you? As it was, the useful load of the prototype ZMC-2 was only 750 lbs (340 kg). The ZMC-2 wasn’t designed for useful load, though; it was only ever meant as a testbed.
As a testbed, the ZMC-2 was reasonably successful, and also a complete failure. It was reasonably successful in that its logbooks recorded 2,265 incident-free hours over 725 flights between its debut in August 1929 and its grounding in August 1939. In those ten years, it was found to fly well, in spite of its oddities.
The control car, with its crew of two or three–plus four passengers–and a pair of 220 HP Wright Whirlwind engines, would not have looked out of place on a blimp of similar size. Its overall size was not unlike blimps Goodyear was flying. Nor was the ZMC-2 particularly speedy, or unusually slow with a top speed of 70 mph (113 km/h). Aside from the metal-clad construction, two things made the ZMC-2 stand out amongst its contemporaries. The empennage — the “tail” — was perhaps unique in airship history– as near as I can tell, the Detroit Airship Company was the only one to ever fit eight equally-spaced fins to the rear of an airship. All had control surfaces, and in practice, there was no control mixing: four acted as elevators, and four as rudders. It worked well enough, as the ship was apparently quite maneuverable.
The other oddity helped with this maneuverability: the airship’s fineness ratio. It was oddly squat, at only 2.83. Like much in the world of airships, the concept of a fineness ratio is borrowed from the naval world– there, it is the ratio between a ship’s length and its beam, or width. For a flying ship, it’s the length to diameter of the gas bag, but the effect is the same. Picture a racing skiff vs a coracle, or a whitewater kayak. The racing skiff has a very high fineness ratio, which gives it high speed and low maneuverability as it cuts through the water. A coracle or whitewater kayak, on the other hand, has a low fineness ratio, often less than two, so that they can turn on a dime. They’re also incredibly difficult to keep going in a straight line. The ZMC-2 wasn’t quite that squat, but from the boating analogy I can only imagine it was a handful to keep on a straight course at times.
The only reason I dare call the fabulous tin blimp a failure is because there was no ZMC-3, or -4, or N≠2. It was indeed the only metalclad to ever fly.
It wasn’t the cute little prototype’s fault; it was the timing. The Detroit Aircraft Company launched the ZMC-2 with big plans– Upton’s first design was for a larger express passenger/cargo airship of 1,600,000 cu.ft. (45,307 m³) gas volume, compared to the meager 200,000 cu.ft. (5,663 m³) of the prototype. There was interest in the bigger designs, but the ZMC-2 would need to prove the concept– which it did, in August 1929. Then in October, the stock market crashed, the Great Depression hit, and there was a lot less money available for pie-in-the-sky ideas like metalclad airships.
The interest was there, mind you. The U.S. Army liked what they saw, and went hat-in-hand in 1931 to Congress asking for 4.5 million to buy a 20-ton-lift model that would have been larger than the Graf Zeppelin. At that point, Congress felt there were other priorities. Later on, Detroit’s metalclad design was The Navy’s preferred choice to replace the ill-fated Akron and Macon, but there were problems with funding and the Detroit Aircraft Company didn’t have a hangar big enough to build the thing in anyway.
That was the end of it. Though there was no notable metal fatigue or corrosion, the ZMC-2 flew less and less as the odds of a successor dropped. Some accounts claim it was grounded completely in 1939; others imply a handful of flights until US entry into WWII. With the war on, aluminum was in short supply and the ZMC-2 was broken up for scrap in 1941. It was simply too small for the antisubmarine duty the Navy’s blimps were being put to, and too weird to use as a training ship. Though the gondola was kept for a time as a learning aide for ground school, it was not preserved. It is likely that no physical trace of the fabulous tin blimp remains.
Ultimately, the ZMC-2 was successful in proving that a metalclad airship could fly. During the various aborted attempts at an ‘airship renaissance’, various proposals for metalclads or similarly-built composite ships have been put forth, but as with Ralph Upton’s larger designs, no capital sufficient for construction ever materialized.
In spite of my praise of the non-rigid airship’s ability to shift with the winds– going so far as to say “Blimps win” in my last article, based on the historical record, I for one would love to see a metalclad fly again. Maybe it’s just the Rule of Cool– rigids are cooler, and metalclads are cooler yet. Maybe the image of the doughty ZMC-2 buzzing about like a giant, clumsy bumble bee has made me sentimental for the design. Maybe it’s just that there’s potential there. Thanks to the great Nan ships, we’ve got a pretty idea of what non-rigid airships are capable of. ZMC-2 only scratches the surface of what a metalclad could do; perhaps someday we’ll find out. With modern lithium-aluminum alloys being that much lighter, or the ‘black’ aluminum of carbon composites, we could probably build something exceeding Ralph Upton’s wildest dreams… if there was money to pay for it.
