Build A Super Cheap RC Trainer Plane With Foam

September 5, 2024 by 20 Comments

Once upon a time, RC planes were expensive models that took months to build and big money to equip with electronics. Since the 20th century though, powerful batteries have become cheap, as have servos and radio controllers. Combine them with a bit of old packing material and you can get a little RC trainer up and running for peanuts, as [Samm Sheperd] demonstrates.

[Samm] started referring to this as the “$5 trainer,” though he admits that it will cost more than that if you don’t have some bits and pieces laying around. He demonstrates how to cut cheap foamboard with a hot guitar string, and how to form it into a viable wing. That’s the most crucial part, with the fuselage and tail surfaces relatively simple by comparison. With that complete, it’s as simple as bolting on a motor, some servos, and control horns, and you’re up and running. You can even whip up a landing gear if you’re so inclined! Then, figure out your center of gravity, get it right, and then you’re pretty much ready to fly.

It’s a great primer on how to build a basic RC model, and if you do it right, it should have pretty forgiving handling, too. Plus, it’s so cheap that it should be easy to repair if you crash. Happy modelling! Video after the break.

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It’s Spreadsheets All The Way Down For This 80s Handheld

September 5, 2024 by 9 Comments

Unlike the today’s consumer computer market, the 1980s were the wild west in comparison. There were all kinds of different, incompatible operating systems, hardware, and programs, all competing against one another, and with essentially no networking to tie everything together. Some of these products were incredibly niche as well, only running one program or having a limited use case to keep costs down. Such was the Convergent WorkSlate, a computer that ran only a spreadsheet with any programs also needing to be built into a spreadsheet.

Upon booting the device, the user is presented with a fairly recognizable blank spreadsheet, albeit with a now-dated LCD display (lacking a backlight) and a bespoke keyboard and cursor that wouldn’t have allowed for easy touch typing. The spreadsheet itself is quite usable though, complete with formatting tools and the capability to use formulas like a modern spreadsheet program would. It also hosted a tape deck for audio and data storage, a modem for communicating with other devices, and an optional plotter-style printer. The modem port is how [Old VCR] eventually interfaces with the machine, although as one can imagine is quite a task for a piece of small-batch technology from the 80s like this. After learning how to send and receive information, a small game is programmed into the machine and then a Gopher interface is built to give the device limited Internet connectivity.

The investigation that [Old VCR] goes into on this project to get this obsolete yet unique piece of hardware running and programmed to do other tasks is impressive, and worth taking a look at especially because spreadsheets like this aren’t Turing-complete, leading to a few interesting phenomenon that most of us wouldn’t come across in the modern computing world. Since only around 60,000 units were ever made it’s difficult to come across these machines, but if you want to take a look at the spreadsheet world of the 80s without original hardware you can still run Lotus 1-2-3 natively in Linux today.

Thanks to [Cameron] for the tip!

High-Speed Jelly Launcher Destroys Toast

September 5, 2024 by 10 Comments

You shouldn’t play with your food. Unless you’re designing some kind of portable cannon to fling it across the room. That’s precisely what [Backhaul Studios] did.

The first step of designing the condiment cannon was deciding what it should fire. Little low-profile tubs of jelly ended up being the ideal. They were stout enough to survive high-speed flight, while their low height was good for aerodynamics. The cannon itself is built from metal and 3D-printed parts. Multiple iterations eventually landed on a flywheel launcher design with big brushless motors and large 6-inch discs. It sounds positively awful in action and can fling jam (jelly) packets at immense speed. From there, it was simply necessary to design a magazine feed system to enable high-speed full-auto jelly delivery.

If you’ve ever hucked ketchup packets at a brick wall, you’ve understood the joy of splattering condiments everywhere. This cannon is just a way to do that faster and more hilariously. We’ve seen other fun builds along these lines before, too. Video after the break.

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If Wood Isn’t The Biomass Answer, What Is?

September 5, 2024 by 120 Comments

As we slowly wean ourselves away from our centuries-long love affair with fossil fuels in an attempt to reduce CO2 emissions and combat global warming, there has been a rapid expansion across a broad range of clean energy technologies. Whether it’s a set of solar panels on your roof, a wind farm stretching across the horizon, or even a nuclear plant, it’s clear that we’ll be seeing more green power installations springing up.

One of the green power options is biomass, the burning of waste plant matter as a fuel to generate power. It releases CO2 into the atmosphere, but its carbon neutral green credentials come from that CO2 being re-absorbed by new plants being grown. It’s an attractive idea in infrastructure terms, because existing coal-fired plants can be converted to the new fuel. Where this is being written in the UK we have a particularly large plant doing this, when I toured Drax power station as a spotty young engineering student in the early 1990s it was our largest coal plant; now it runs on imported wood pellets.

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Launching Model Airplanes With A Custom Linear Induction Motor

September 5, 2024 by 18 Comments

Launching things with electromagnetism is pretty fun, with linear induction motors being a popular design that finds use from everywhere in hobby designs like [Tom Stanton]’s to the electromagnetic launchers on new US and Chinese aircraft carriers. Although the exact design details differ, they use magnetic attraction and repulsion to create a linear motion on the propulsive element, like the sled in [Tom]’s design. Much like the electromagnetic catapults on a Gerald R. Ford-class carrier, electrical power is applied to rapidly move the sled through the channel, akin to a steam piston with a steam catapult.

Model airplane sparking its way through the launcher’s channel. (Credit: Tom Stanton, YouTube)

For [Tom]’s design, permanent magnets are used along both sides of the channel in an alternating north/south pole fashion, with the sled using a single wound coil that uses brushes to contact metal rails along both sides of the channel. Alternating current is then applied to this system, causing the coil to become an electromagnet and propel itself along the channel.

An important consideration here is the number of turns of wire on the sled’s coil, as this controls the current being passed, which is around 90 A for 100 turns. Even so, the fastest sled design only reached a speed of 44 mph (~71 km/h), which is 4 mph faster than [Tom]’s previous design that used coils alongside the channels and a sled featuring a permanent magnet.

One way to increase the speed is to use more coils on the sled, with a two-coil model launching a light-weight model airplane to 10.2 m/s, which is not only a pretty cool way to launch an airplane, but also gives you a sense of appreciation for the engineering challenges involved in making an electromagnetic catapult system work for life-sized airplanes as they’re yeeted off an aircraft carrier and preferably not straight into the drink.

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I2C For Hackers: Digging Deeper

September 5, 2024 by 20 Comments

Last time, I gave you an overview of what you get from I2C, basics like addressing, interface speeds, and a breakdown of pullups. Today, let’s continue looking into I2C capabilities and requirements – level shifting, transfer types, and quirks like combined transfers or clock stretching.

Level Shifting

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Getting Root On Cheap WiFi Repeaters, The Long Way Around

September 5, 2024 by 13 Comments

What can you do with a cheap Linux machine with limited flash and only a single free GPIO line? Probably not much, but sometimes, just getting root to prove you can is the main goal of a project. If that happens to lead somewhere useful, well, that’s just icing on the cake.

Like many interesting stories, this one starts on AliExpress, where [Easton] spied some low-cost WiFi repeaters, the ones that plug directly into the wall and extend your wireless network another few meters or so. Unable to resist the siren song, a few of these dongles showed up in the mailbox, ripe for the hacking. Spoiler alert: although the attempt on the first device had some success by getting a console session through the UART port and resetting the root password, [Easton] ended up bricking the repeater while trying to install an OpenWRT image.

The second attempt, this time on a different but similar device, proved more fruitful. The rudimentary web UI provided no easy path in, although it did a pretty good job enumerating the hardware [Easton] was working with. With the UART route only likely to provide temptation to brick this one too, [Easton] turned to a security advisory about a vulnerability that allows remote code execution through a specially crafted SSID. That means getting root on these dongles is as simple as a curl command — no hardware hacks needed!

As for what to do with a bunch of little plug-in Linux boxes with WiFi, we’ll leave that up to your imagination. We like [Easton]’s idea of running something like Pi-Hole on them; maybe Home Assistant would be possible, but these are pretty resource-constrained machines. Still, the lessons learned here are valuable, and at this price point, let the games begin.