Have They Found A Complete UNIX V4?

November 9, 2025 by 19 Comments

If you’ve ever combed boxes of old tech detritus in search of a nugget of pure gold, we know you’ll appreciate the excitement of discovering, in a dusty University of Utah storeroom, a tape labelled “UNIX Original from Bell Labs V4 (See manual for format)”. If the tape contains what’s promised on the label, this is a missing piece of computer history, because no complete copies of this version are known to exist.

The tape will be delivered by hand to the Computer History Museum, where we hope its contents will be safely retrieved for archive and analysis. The reporter of the find, research professor [Rob Ricci], identifies the handwriting as that of Jay Lepreau, someone whose word on which UNIX version it contained could, we hope, be trusted.

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Hackaday Links: November 9, 2025

November 9, 2025 by 23 Comments

We’re always a wee bit suspicious about articles that announce some sort of “World’s first” accomplishment. With a couple of hundred thousand years of history, most of which wasn’t recorded, over which something like 117 billion humans have lived, any claims of primacy have to be taken with a grain of salt. So when the story of the world’s first instance of a car being hit by a meteorite came across our feed, we had to check it out. The car in question, a Tesla, was being driven in South Australia by veterinarian Andrew Melville-Smith when something suddenly crashed into its windshield.

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2025 Component Abuse Challenge: Dawg Gone LED Tester

November 9, 2025 by 23 Comments

The Hackaday 2025 Component Abuse Challenge is all about abusing electronic components in the service of making them do things they were never intended to. It’s not the 2025 Food Abuse Challenge, so in the case of [Ian Dunn]’s hot dog pressed into service as an LED tester, we’ll take the ‘dawg to be a component in its own right. And by any measure, it’s being abused!

Cooking hot dogs by passing an electric current through them has a long and faintly hazardous history to it — we’re sure we’ve heard of domestic hot dog cooker appliances that are little more than the mains supply on a pin at each end of a hot dog shaped receptacle. This one takes the ‘dawg in a bun with condiments, no less, and sticks an ordinary table fork wired up to the grid in each end. The LED testing is the cherry on the cake, because he simply sticks a pile of LEDs by their pins into the tasty sausage. It forms a crude potential divider, so there’s about enough volts across the gap between pins to light it up nicely.

We like this project on so many levels, though we’re not sure what heavy metals would leach out of those LED pins into the meat. If it’s inspired you to do something similar you still have a few days in which to enter the contest, so break out your convenience food and a pile of parts, and start experimenting!

2025 Hackaday Component Abuse Challenge

Concrete Lathe Turns Metal

November 9, 2025 by 41 Comments

Full disclosure. If you want a lathe capable of turning metal stock, you probably should just buy one. But what fun is that? You can do like [kachurovskiy] and build one with your 3D printer. If you are chuckling, thinking you can’t make 3D printed parts sturdy enough, you aren’t exactly wrong. [Kachurovskiy’s] trick is to 3D print forms and then cast the solid parts in concrete. The result looks great, and we don’t doubt his claim that it “can surpass many comparable lathes in rigidity and features.”

Even he admits that this is a “… hard, long, and expensive project…” But all good projects are. There’s a GitHub page with more details and informative videos below. The action shots are in the last video just before the six-minute mark. Around the seven-minute mark, you can see the machine cut a conical thread. Color us impressed!

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A central circular element is releasing steel ball bearings into a complex nest of eight intertwined plastic paths.

Mesmerizing Marble Runs From Procedural Generation

November 9, 2025 by 11 Comments

There are few things that can keep a certain kind of mechanically-inclined mind entranced as well as a marble run, and few structures that look as interestingly organic as procedurally-generated designs – combine the two and you get [Will Morrison]’s Marble Fountain.

[Will]’s first approach to generating a marble run was to have a script randomly place some points, generate a path following a spline through those points, and give that path a constant slope. This worked, but the paths it generated were a bit too simple to take full advantage of a 3D printer’s capabilities, so he next wrote a path solver to generate more complicated runs. The solver starts by generating a series of random line segments connecting the top and bottom of the run, then iteratively moves the segments into position. Each segment has to stay within the print volume, be evenly spaced with the others, maintain a constant slope, avoid segments from other tracks, and avoid distant segments of its own track. The result is a complicated network of tracks that keeps the marbles in motion without letting them fly out in fast sections. Continue reading “Mesmerizing Marble Runs From Procedural Generation” →

Target The Best AA, And Take No Flak

November 9, 2025 by 64 Comments

In this era of cheap lithium pouch cells, it might seem mildly anachronistic to build AA batteries into a project. There are enough valid reasons to do so, however, and enough legacy hardware that still takes AAs, that it’s worth spending some time deciding which batteries to use. Luckily for us, [Lumencraft] over on YouTube has done the legwork in the video embedded below, and even produced a handy-dandy spreadsheet.

Each battery in the test underwent three separate tests. There was the “leave it in a flashlight ’til it dies” test for real-world usage, but also discharge curves logged at 250mA and 2A. The curves for each are embedded in the spreadsheet so you can see what to expect, along with the calculated capacity at each discharge rate. 2A seems like a fairly brutal load for AAs, but it’s great to see how these cells react to extremes. The spreadsheet also includes the cell’s cost to create a value ranking, which will be of great use to our readers in the USA, where it appears [Lumencraft] is buying batteries. The world market is likely to have the same batteries available, but prices may vary by region, so it’s worth double-checking.

In the video, [Lumencraft] also takes the time to explain the four battery types commonly found in AA format, and the strengths and weaknesses of each chemistry that might cause you to prefer one over another for specific use cases, rather than going by his value rankings. Unsurprisingly, there’s virtually no reason other than cost to go for alkaline batteries in 2025. However, lithium-ion batteries in AA form don’t really outperform NiMH enough to make the added cost worthwhile in all applications, which is why the overall “best battery” is a “PowerOwl” NiMH. Li-ion’s unspectacular performance is likely in part due to the inefficiencies introduced by a built-in buck converter and safety circuitry. On the other hand, some people might really appreciate that extra safety compared to bare 18650 cells.

The results here aren’t too dissimilar to what we saw earlier this year, but we really appreciate [Lumencraft] publishing his results as a spreadsheet for easy reference. The only caveat is that he’s taking manufacturers at their word as to how many cycles the batteries will last.

Oh, and just to be 100% clear — we are talking about double-A batteries, not Anti-Aircraft batteries. If anyone has an anti-aircraft battery hack (especially if that hack includes double-A batteries powering the AA batteries), please send in a tip. 

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The Cardboard Airplane Saga Continues

November 9, 2025 by 23 Comments

History is full of engineers making (or attempting to make) things out of the wrong stuff, from massive wooden aircraft to boats made of ice and sawdust. [PeterSripol] is attempting to make an ultralight aircraft out of a rather wrong material: cardboard. In the previous installment of the project, a pair of wings was fabricated. In this installment, the wings find their home on an equally mostly cardboard fuselage, complete with rudder and elevator. 

The fuselage construction amounts to little more than a cardboard box in the shape of an RC airplane. Doublers provide additional strength in critical areas, and fillets provide a modicum of additional strength around seams. To support the weight of the pilot, a piece of corrugated cardboard is corrugated again, with an additional piece making up the floor. With the addition of a couple of side windows for comfort and visibility, the fuselage is completed, but additional components need to be added.

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