Walking Arm Trebuchet Is Different, But Effective

For many of us, our first encounter with the famous trebuchet was Age of Empires II, or perhaps a documentary on historical siege engines. However, many people continue to pursue builds of their very own, exploring designs new and old. The walking arm trebuchet is a good example, which uses an unconventional design to great effect.

The design eschews a rigid frame, instead consisting of simply an arm and a triangular leg assembly. The arm is held upside down, and is launched by allowing the trebuchet to collapse forward to rest on the triangular leg. The triangular leg is fitted with spikes which dig into the ground, and the arm then pivots around, launching the projectile. The design is reportedly quite efficient, similar to a floating arm trebuchet, with a very simple design. Performance was so good, it netted a clean sweep of the 2018 Vermont Pumpkin Chuckin’ festival.

There’s a wide variety of ways to go about building a trebuchet, and we’ve featured some before. You can even instrument your payloads to quantify performance. Video after the break.

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Even Joke Torpedoes Are Pretty Hard To Get Right

It’s rare that makers get involved in out-and-out munition production. It’s dangerous, and usually frowned upon by local authorities. That said, it can be fun to experiment around, and [Ivan] does just that, attempting to launch a 3D-printed torpedo from a kayak. The build may have been done as a marketing exercise, but it raises some interesting questions about naval engineering.

The first revision consists of a 3D-printed hull, containing a rubber-band powered propeller. A soda bottle filled with compressed air is then used as a warhead, fitted with a contact fuse to release its charge on impact. Unfortunately, initial tests were underwhelming, with the rubber band mechanism failing to provide any real forward propulsion.

A trip back to the drawing board was due, and the design was revived with a brushless motor powerplant instead. This allowed the torpedo to trawl, albeit slowly, through the water. It also proved that the compressed air “warhead” could successfully discharge, albeit with less of a bang, more of a whimper.

The build, while undertaken for the sake of fun, does highlight some of the engineering challenges inherent in building a working torpedo. There were issues with buoyancy, as well as providing the torpedo with enough power to move quickly in the water. On top of this, the matter of guidance is also an important one. We’d love to know how the Hackaday commentariat would go about solving these issues when undertaking their own build – let us know down below. We’ve seen others tackle similar builds before, too. Video after the break.

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Subaru Coils Make A Great HV Power Source

High-voltage experimenters are a unique breed. They’re particularly adept at scrounging for parts in all kinds of places, and identifying how to put all manner of components to use in the service of the almighty arc. [Jay] is one such inventor, and recently came across a useful device from Subaru.

The device in question is an ignition coil from the Subaru Outback. It consists of a pair of high-voltage transformers, connected together, in a wasted-spark setup to run four-cylinder engines. Having sourced the part from a friend, [Jay] realised that with some modification, it would make a great high-voltage power source. The first job was to figure out how to remove the internal electronics that drive the transformers. In this case, it was a simple job of hacking off a chunk of the case, removing the interfering hardware. With this done, it’s possible to directly access the transformer connections.

In [Jay]’s experiments, the device is run in an anti-parallel configuration, to produce higher than normal voltages at the output. In various tests, it’s demonstrated running from both a classic 555 circuit, as well as a ZVS driver. For future projects, [Jay] intends to use this setup to drive a large voltage multiplier, also noting it can be used with Tesla coils and plasma balls with the right additional hardware.

While [Jay] doesn’t include any specific model numbers, reports are that these coils are readily available in a variety of 1990s and 2000s Subaru vehicles. Others have used similar hardware to create high voltage projects, too – this stun gun is a great example. Video after the break.

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AI Makes Hyperbolic Brain Hats A Reality

It isn’t often that the world of Hackaday intersects with the world of crafting, which is perhaps a shame because many of the skills and techniques of the two have significant overlap. Crochet for instance has rarely featured here, but that is about to change with [Janelle Shane]’s HAT3000 neural network trained to produce crochet hat patterns.

Taking the GPT-2 neural network trained on Internet text  and further training it with a stack of crochet hat patterns, she was able to generate AI-designed hats which her friends on the Ravelry yarn forum set to crochet into real hats. It’s a follow-up to a previous knitting-based project, and instead of producing the hats you might expect it goes into flights of fancy. Some are visibly hat-like while others turn into avant-garde creations that defy any attempt to match them to real heads. A whole genre of hyperbolic progressions of crochet rows produce hats with organic folds that begin to resemble brains, and tax both the stamina of the person doing the crochet and their supply of yarn.

Perhaps most amusingly the neural network retains the ability to produce text, but when it does so it now inevitably steers the subject back to crochet hats. A Harry Potter sentence spawns a passage of something she aptly describes as “terrible crochet-themed erotica“, and such is the influence of the crochet patterns that this purple prose can even include enough crochet instructions to make them crochetable. It would be fascinating to see whether a similar model trained with G-code from Thingiverse would produce printable designs, what would an AI make with Benchy for example?

We’ve been entertained by [Janelle]’s AI work before, both naming tomato varieties, and creating pie recipes.

Thanks [Laura] for the tip.

Analyzing Data To Build Better Surfboards

In the world of surfing, the equipment available is as diverse and varied as the enthusiasts themselves. Different boards are optimized for different conditions and styles, and the industry continues to innovate towards ever greater performance. [DARK-labs] aim to bring data analysis into the field to help create boards personalised to the individual.

The goal is to use a sensor network embedded in a surfboard to analyze the style of a particular surfer. This data is then used to identify characteristics such as stance and foot preference, which can then be used to optimize a board design to suit. Once a CAD model is created along these guidelines, it can then be CNC machined and turned into a finished board, ready to hit the waves.

It’s a project that we expect will capture the interest of many a surfer, and we wouldn’t be surprised to see the concept take further strides in coming years. We’ve featured some other board hacks, too – this electric build is particularly compelling. 

Cheap Sensors And An SDR Monitor Conditions In This Filament Drying Farm

We don’t know where [Scott M. Baker] calls home, but it must be a pretty humid place indeed. After all, he has invested quite a bit in fancy vacuum storage containers to keep his 3D-printer filament dry, with the result being this sensor-laden filament drying farm.

[Scott] wasn’t content to just use these PrintDry containers without knowing what’s going on inside. After a little cleaning and lube to get all the containers working, he set about building the sensors. He settled on a wireless system, with each container getting a BME280 temperature/humidity/pressure sensor and an SYN115 315-MHz ISM band transmitter module. These go with an ATtiny85 into a compact 3D-printed case holding a little silica desiccant. The transmitters are programmed to comply with ISM-band regulations – no need to run afoul of those rules – while the receiver is just an SDR dongle and a Raspberry Pi running rtl_433. The long-ish video below details design and construction.

The idea behind these vacuum containers would seem to be to pull out humid air and prevent it from coming back in. But as [Scott] quickly learned from his telemetry, following the instructions results in the equivalent atmospheric pressure of only about 2700′ (823 meters) elevation – not exactly a hard vacuum. But as [Scott] points out, it’s enough to get a nice, tight seal, and his numbers show a lowered and constant relative humidity over time.

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RCA Created Video Records Too Late

It is easy to find technology success stories: the PC, DVD, and cell phone are all well-documented tales. However, it is a little harder to find the stories behind the things that didn’t quite take off as planned. As the old saying goes, “success has many parents but failure is an orphan.” [Technology Connections] has a great video about RCA’s ill-fated SelectaVision video disc systems. You can see part one of the video below.

RCA started working on the system in the 1960s and had they brought it to market a bit earlier, it might have been a big win. After all, until the VCR most of us watched what was on TV when it was on and had no other options. You couldn’t record things or stream things and f you didn’t make it home in time for Star Trek, you simply missed that episode and hoped you’d get luckier when and if they reran it during the summer. That seems hard to imagine today, but a product like the SelectaVision when it was the only option could have really caught on. The problem was of course, that they waited too late to bring it to market. The video also makes the point that the system contained a few too many technical compromises.

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