Creating A Supersonic Trebuchet

August 9, 2026 by Maya Posch 27 Comments

As awesome as trebuchets are, the fact that medieval engineers didn’t create versions capable of launching supersonic projectiles is a bit of a bummer. Fortunately it’s possible to correct this oversight with modern insights and technologies, as [Tom Stanton] demonstrates in a recent video.

While a traditional trebuchet is fairly straightforward, using a heavy weight moving an arm around a pivot that has the projectile attached to the other side, a few tweaks can make it much more lethal. One change is to have the projectile’s rope wound around the arm, forcing an additional pass around the arm to gain velocity. The other is to use a gearing system which uses the dropping weight’s energy more efficiently.

One complication here is that the arm now takes a few rotations to come up to speed, meaning that the release of the payload has to be controlled exactly, with only about an 0.0025 second release window. The solution was both low-tech and effective: since the arm is attached to a drum that the rope is wound onto, the moment enough rope is unwound from the dropping weight, a latch inside the drum is released to launch the projectile.

In a first test with a 10 kg weight, the projectile reached a velocity of around 528 km/h, which definitely was a good start, but also showed just how not aerodynamic the arm was. Some redesigns later of the entire trebuchet, the entire system was tested again with 10 kg and achieved a projectile velocity of 634 km/h. From there it was time to ramp up the weight to the full 40 kg, which theoretically should hit supersonic speeds.

Unfortunately the first attempt hit a mere 1,152 km/h (716 mph), which is just shy of the sound barrier at 1,235 km/h at 39% system efficiency and some components clearly breaking apart. Some more redesigns later and with a lighter projectile at 4 grams, a 40 kg weight achieved an arm speed of 2,342 rpm. The projectile now left the sling with 346.4 m/s, or 1,249 km/h, with an audible snap as the sound barrier got broken.

Even if the era of trebuchets in warfare is well and truly past, they remain fascinating physics demonstrations, with this case in point.

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The Stages Of Grief In Repairing A Trinitron Found In The Trash

August 9, 2026 by Maya Posch 28 Comments

Sometimes you see a project just staring at you with proverbial puppy dog eyes and you just cannot look away. In the case of a once rather nice Sony TV it was the smooth 32″ Trinitron CRT that gave [Happychoice] that look when he came across it along the side of the road. Naturally he had to beg the owner of the junkyard to please let him adopt the pupp^Wjunked TV and attempted an ill-advised repair.

Some later sleuthing revealed that this poor TV had been sitting on the side of that road for at least six years, exposed to the worst that the Italian weather and local fauna could do to it, so it was no surprise that all he got out of it even after cleaning and some repairs was a sad triple-blink of the power LED. This indicated that something on the control board was very unhappy about the status of the power supply.

Over the course of a few months this project went correspondingly from careful optimism down to the depths of depression, through the fields of bargaining and into the blue skies of acceptance of a likely far more involved repair session than originally assumed. That said, the CRT itself looks to be in pretty good nick, as do the PCBs barring the few sketchy resistors that already got replaced.

We would like to congratulate [Happychoice] on the acquisition of a fun new repair project and wish him all the luck on bringing this beast of a TV back to life.

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The Chinese Smart Glasses Proving That Smart Glasses Can Be Repairable

August 9, 2026 by Maya Posch 21 Comments

It’s often claimed that wearable devices cannot have user-replaceable batteries or even be serviceable at all due to how compact and waterproof they must be, yet there are plenty of examples belying those claims. So too for smart glasses with their compact size and the need to be fully waterproof. They would be certified e-waste as soon as the built-in battery stops being a battery, assuming these claims were true. Recently [iFixit] bought a few Chinese smart glasses to see just how repairable they are, with the Rokid one being very surprising.

The first nice feature of both two Chinese smart glasses is that they have an external battery that clips on in addition to an internal one. Internally they’re quite similar, both featuring a Qualcomm Snapdragon AR1 Gen 1 SoC with 32 GB of eMMC storage, in addition to micro-LED projectors.

Of the two glasses in the video, the Quark one isn’t that dissimilar from the Ray-Ban and Meta ones, requiring fairly destructive heat and prying to get inside. The Rokid one is however very easy to get into, with very light glue that makes it easy to get into, as well as a very servicing-friendly internal architecture including its battery. This is a pattern that extends to its external battery module, giving a glimpse at what such devices ought to look like in a repair-friendly world.

As is to be expected for an [iFixit] video, a significant part of it is spent lamenting the ills of glued-in batteries, including the recent decision by the EU to exempt many wearable devices from its new right to repair regulations involving built-in batteries. In light of the teardown of the Rokid smart glasses in this video, as well as previous Pixel Watch 4 and Fairbuds teardowns, it certainly seems reasonable to enforce user-replaceable batteries for these wearables as well.

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High-Density Parchment Paper Papertronics With Laser-Carved Hydrophilic Channels

August 8, 2026 by Maya Posch 6 Comments

Paper as a substrate for electronic circuits is not very common, but promising for flexible circuits with low cost and easy recyclability. That said, paper is not an easy material to work with when printing traces, as the cellulose material is both absorbent and irregular, limiting the resolution and accuracy of so-called papertronics. Even when using higher-quality paper with wax-based masks this resulted in poor resolution issues, so [Zahra Rafiee] et al. opted to approach the problem from the other direction, by using hydrophobic parchment paper as the base combined with a laser.

The nice thing about the inks used with papertronics that they aren’t just traces, but can also be functional elements like resistors, which is also demonstrated in the paper. The channels for the inks are created using a 50 Watt CO₂ laser, which etches away the silicone coating on the parchment paper. The achieved resolution in the article is around 250 µm for line widths and 300 µm line spacing, which is much better than that for wax-based alternatives.

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Hacking A $6000 Cotton Candy Machine To Fully Control It

August 7, 2026 by Maya Posch 7 Comments

Some of the cotton candy options by the machine. The Chinese text reads 'flower type'. — Some of the cotton candy options by the machine. The Chinese text reads ‘flower type’.

Having a fully automated cotton candy vending machine in your possession is a great thing, but not if you do not have full access to its software. With [Block’s Retro Repairs] getting ghosted by the manufacturer on regaining account access to the machine he bought used for $300, there was little left but to try and break into the system.

We previously covered the journey in getting the vending machine back into a state where it’d actually reliably produce cotton candy again, a process which is quite tedious and temperamental. After a lot of fiddling with sensors and temperature settings this was fixed, but still left the issue that as a vending machine it should allow the owner to set prices and such. Sadly this could only be done remotely via a special account, which access to had been left with the previous owner.

Despite the very custom exterior, the vending machine runs what is effectively an Android system, consisting of an industrial computer board wired into a lot of stepper drivers and other control boards. To the extreme delight of everyone involved, it was possible to access the Ct Terminal application with adb and its product database on the device’s storage. Unfortunately writing back a changed database file didn’t change anything in the UI, so for a few months the project languished.

After nearly bricking the system and ending up factory resetting the control software including temperatures, it actually improved the performance of the machine and produced cotton candy, so that was one win. Ultimately the solution was to modify the original app, but a combination of weak coding skills and the app being in Chinese led him to use free LLM coding chatbots to assist here.

This resulted in a custom settings menu being added with the ability to modify pricing, no need for online access any more and a very nice cotton candy vending machine for the private arcade where presumably friends and family can enjoy cheap or even free cotton candy. Finally having the machine sealed against ant intrusion was also a major improvement.

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Chernobyl’s Robots, Or The Hackathon From Hell

August 7, 2026 by Maya Posch 21 Comments

When the Chernobyl Nuclear Power Plant’s #4 reactor experienced an extreme criticality event on that infamous day in 1986, the resulting steam explosion and lack of any kind of containment building meant that parts of the core were scattered throughout the site. In an extensive update to the original 2023 video, the [Chornobyl Family] covers the mad scramble to design robots to perform on-the-ground measurements, and ultimately remove all this debris for safe disposal.

The TR-1A, an early debris removal robot. (Source: Chornobyl Family, YouTube)

This essentially took the form of a hackathon, involving teams from all over the USSR and allied nations, creating the most diverse range of robots that 1980s Soviet technology and later Western technology could muster.

Many of these robots didn’t perform very well, or at all, mostly due to the bypassing of any kind of testing before deployment. Especially at the beginning of the clean-up the robots were being pushed into the high-radiation zones as soon as they were finished, with not only mechanical issues being a problem, but also with e.g. inaccurate radiation measurements by the RR-1 robot, that overstated measurements by more than a factor of ten. Meanwhile the RR-2 and RR-3 were too top-heavy and after deployment by helicopter simply tipped over. Eventually manual measurements proved to be faster and safer.

Early debris removal robots like the TR-1A were rather simplistic, with successive generations of robots over the next weeks and months improving on it. The use of a combustion engine instead of batteries provided to be a boon, as combustion engines are far less affected by radiation.

The BAER Beloyarets used an airport cart as the basis, with its electronics relying on vacuum tube technology and relays, with an internal combustion engine. This proved to be one of the most reliable designs and it’s been largely preserved on display in the Chornobyl Exclusion Zone, with many others of these robots also being on display around the nuclear plant or in the city of Chornobyl.

Overall an absolutely dizzying number of robotic designs were invented on the spot, adapted from existing designs or repurposed for operation in a high-radiation zone. Eventually bulldozer designs like the STR-1 helped to push radioactive debris off the roofs into containers, massively reducing the radioactive contamination of the area.

The fact that following #4’s RUD the other three RBMK units were able to keep operating safely without risks to its operators, and with the zone now safe for tourists, is a real testament to the success of the worst hackathon imaginable. Many of the lessons learned are relevant today, including during the decommissioning of Fukushima Daiichi’s melted-down cores.

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NASA’s Just Prolonged Voyager 2’s Science Mission With A Big Bang

August 6, 2026 by Maya Posch 37 Comments

Letting go is hard, especially when it concerns an irreplaceable space probe like the two Voyagers. Fortunately JPL engineers have managed to pull off a ‘big bang’ switch on Voyager 2, involving two heaters and another device that was kept on to keep providing sufficient heat to the spacecraft to allow it to keep functioning. After all, while the vacuum of space isn’t cold, out in deep space you’re radiating away all your precious heat.

Unfortunately the official press release is exceedingly limited in details, but The Register was kind enough to nag a NASA spokesperson about it, and gave us some technical details. The short version is that these heaters don’t just keep the electronics within a happy operating range, they also keep the fuel lines warm and capable of providing fuel for attitude adjustments.

With this switch, apparently enough of the rapidly diminishing power from the RTG has been freed up that the Voyager 2 has just gained a whole extra year on its extended mission. The JPL team hopes to perform the same switch on the Voyager 1 spacecraft soon, giving it a similar boost to its expected lifespan, before both of them go quiet in the depths of space.

Thanks to [Mark Stevens] for the tip.