Swedish Rocket Knives

There are trends in YouTube videos among various video producers. A few weeks ago, it was all about fidget spinners until some niche tech blog ran that meme into the ground. Before that, the theme was red-hot knives cutting through stuff. The setup was simple; just heat a knife up with a blowtorch, cut through a tomato or golf ball, hit stop on the high-speed camera, and collect that sweet, sweet YouTube money.

[David] from RCExplorer.se isn’t like most YouTube stars. He actually knows what he’s doing. When the latest trend of rocket-propelled knives hit the tubes, he knew he could blow this out of the water. He succeeded with a fantastic rocket-propelled machete able to slice through watermelons and fling itself into the woods behind [David]’s house.

Unlike most of the other YouTube stars trying their hand at rocket-powered slicers, [David] is doing this one right. He’s using hobby rocket motors, yes, but they’re reloadable. [David] crafted an engine casing complete with a proper nozzle machined out of stainless for this build. The rocket sled itself is an aluminum bracket bolted to a piece of carbon fiber plate that travels down a rail with the help of four skateboard wheels. A machete is then bolted to the plate, which is propelled down the track a bit faster than 200 km/h.

When it comes to rocket-propelled knives, the word ‘professional’ really doesn’t come into play. This, however, is an amazing piece of craftsmanship that you can check out in the videos below.

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Filaween 2.0 Is Go

[Thomas Sanladerer] is at it again: testing all of the 3D-printer filaments that are fit to print (with). And this year, he’s got a new and improved testing methodology — video embedded below. And have a search for “filaween2” to see what he’s reviewed so far. There’s some sexy filaments in there.

We really love the brand-new impact strength test, where a hammer is swung on a pivot (3D printed, natch), breaks through the part under test, and swings back up to a measurable height. The difference in swing height reflects the amount of energy required to break the test piece. Sweet physics.

[Thomas] ran a similar few-month-long series last year, and we’re stoked to see it return with all the improvements. Here’s to watching oddball plastics melt!

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A Chrome Extension For Being A Jerk

What do you do to someone you want to make suffer, slowly? Specifically, at around 70% speed. To [Stephen], the answer is clear, you hit them where it really hurts: YouTube.

Creatively named “Chrome Engine,” [Stephen]’s diabolical Chrome extension has one purpose: be annoying. Every day, it lowers playback rate by 1% on YouTube. It’s a linear progression: 100% the first day, 99% the second day, 98% the third day, etc. It only stops 30 days later, once it hits its target rate of 70% the original speed. This progression is designed to be slow enough not to be noticed. Its icon is nothing more than the standard Chrome icon as [Stephen] firmly believes in the tactic of hiding in plain sight.

But that’s not all, it’s the minute details that drive the ball home. For instance, rather than using local storage to keep track of playback speed, the Chrome sync storage is used. This ensures that, as long as the extension is installed, playback rate will be synchronized between all of your friend’s(if you can even call them that) devices. It even targets casual YouTube users: [Stephen] has specifically designed their extension so that it won’t drop playback by more than 1% at a time. If the victim goes on vacation, the playback speed won’t drop when they’re away and will resume as soon as they’re back.

The last feature, the one [Stephen] is the proudest of, is that the extension manages to keep the YouTube speed controls working as intended. If the victim tries to play at half speed, their videos will be at half speed … of the slower playback rate set by the extension. And it gets even better! You may not know this if you don’t dally around with playback rates, but the audio tends to stop playing when videos are reduced below 50% of their original speed. Fear not! [Stephen] has accounted for this idiosyncrasy! If the victim selects a speed at or above 0.5x, a minimum cap is added so that the actual playback rate will be equal to or above 0.5x. If they select slower than this, they don’t expect sound anyway, so all bets are off.

Check it out here, may your friends (frenemies?) beware. We’re adding it to our April Fools arsenal, even if it is a bit early.

Meet The Video DJ Machine

Have you ever wanted to perform as a DJ but found the equipment expensive as well as intimidating? Well, your prayers have been answered by [Dror Ayalon] who has designed Nomnom 2. It is an open source, music mixing project that uses up to 16 video clips to give you control of your next hit album.

You are given charge of a physical control panel that has 16 buttons and four knobs. Each button can be used to turn on or off a particular clip while the knobs control the repetition rate, volume, speed and playable length of each track. An Arduino sits under the buttons and is responsible for sending the information to an application that runs in your web browser. The browser app uses the NexusUI library to control playback of the audio clips and bring to life the entire experience.

[Dror Ayalon] has been busy polishing his project and there are some neat videos of him demonstrating it so check out the videos below. The code is available for down from GitHub and the BOM is available at the Hackaday.io project page. The web app can be ported to a desktop app using electron and a PCB can be designed for the controller for future versions.

For now, it is incredible to see hardware and software, come together in such a harmonious fashion. This may be the start of something wonderful but if you are just looking for a way to annoy the neighbors, check out the Midi Musical Siren instead. Continue reading “Meet The Video DJ Machine”

Celebrating A Subscriber Milestone With A Copper YouTube Play Button

YouTube channels unboxing their latest “Play Button Award,” a replica of the famous logo in silver, gold, or faux-diamond depending on the popularity of the channel, are getting passé. But a metalworking channel that makes its own copper Play Button award to celebrate 25,000 subs is something worth watching.

[Chris DePrisco] is a bit of a jack-of-all-trades, working in various materials but with a strong focus on metalwork. He recently completed a beefy home-brew vertical milling center; we covered his attempt to leverage that platform by adding an extruder and turning it into a large bed 3D printer. For the Play Button build, [Chris] turned to the VMC to mill a mold from what appears to be a block of graphite; good luck cleaning that mess up. He melted copper scrap in a homemade electric furnace and poured it into the preheated mold — a solid tip for [The King of Random]’s next copper casting attempt. The rough blank was CNC machined and polished into the Play Button, and finally mounted behind glass neatly inked with paint pens in the versatile VMC. The final result is far nicer than any of the other Button awards, at least in our opinion.

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The Elements Converge For ±.002 In Tolerance

What can be accomplished with just a torch and compressed air? We can think of many things, but bringing a 17-foot-long marine shaft into ±.002 in tolerance was not on our list.

Heat straightening (PDF) utilizes an oxy-acetylene flame that is used to quickly heat a small section of a workpiece. As the metal cools, it contracts more than it expanded when heated, resulting in a changed volume. With skill, any distortions on a shaft can theoretically be straightened out with enough time (and oxy-acetylene). Heat straightening is commonly applied to steel but works on nickel, copper, brass and aluminum additionally.

[Keith Fenner’s] standard process for trueing stock is sensitive enough that even sunlight can introduce irregularities, but at the same time is robust enough to carry out in your driveway. However, even though the only specialty tools you need are a torch, compressed air and work supports, watching [Keith] work makes it clear that heat straightening is as much an art as it is a science. Check out his artistry in the video below the break. Continue reading “The Elements Converge For ±.002 In Tolerance”

[CNLohr] Reverses Vive, Valve Engineers Play Along

[CNLohr] needs no introduction around these parts. He’s pulled off a few really epic hacks. Recently, he’s set his sights on writing a simple, easy to extend library to work with the HTC Vive VR controller equipment, and in particular the Watchman controller.

There’s been a lot of previous work on the device, so [Charles] wasn’t starting from scratch, and he live-streamed his work, allowing others to play along. In the process, two engineers who actually worked on the hardware in question, [Alan Yates] and [Ben Jackson], stopped by and gave some oblique hints and “warmer-cooler” guidance. A much-condensed version is up on YouTube (and embedded below). In the links, you’ll find code and the live streams in their original glory, if you want to see what went down blow by blow. Code and more docs are in this Gist.

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