The Low-Down On Long-Wave: Unlicensed Experimental Radio

In the 125 years since Marconi made his first radio transmissions, the spectrum has been divvied up into ranges and bands, most of which are reserved for governments and large telecom companies. Amidst all of the corporate greed, the “little guys” managed to carve out their own small corner of the spectrum, with the help of organizations like the American Radio Relay League (ARRL). Since 1914, the ARRL has represented the interests of us amateur radio enthusiasts and helped to protect the bands set aside for amateur use. To actually take advantage of the wonderful opportunity to transmit on these bands, you need a license, issued by the FCC. The licenses really aren’t hard to get, and you should get one, but what if you don’t feel like taking a test? Or if you’re just too impatient?

Well, fear not because there’s some space on the radio spectrum for you, too.

Welcome to the wonderful world of (legal!) unlicensed radio experimentation, where anything goes. Okay, not anything  but the possibilities are wide open. There are a few experimental radio bands, known as LowFER, MedFER, and HiFER where anyone is welcome to play around. And of the three, LowFER seems the most promising. Continue reading “The Low-Down On Long-Wave: Unlicensed Experimental Radio”

Watch This Scaly Gauntlet’s Hypnotizing, Rippling Waves

[Will Cogley]’s mechanized gauntlet concept sure has a hypnotizing look to it, and it uses only a single motor. Underneath the scales is a rod with several cams, each of which moves a lever up and down in a rippling wave as it rotates. Add a painted scale to each, and the result is mesmerizing. This is only a proof of concept prototype, and [Will] learned quite a few lessons when making it, but the end result is a real winner of a visual effect.

The gauntlet uses one motor, 3D printed hardware, and a mechanical linkage between the wrist and the rest of the forearm. Each of the scales is magnetically attached to the lever underneath, which provides some forgiveness for when one inevitably bumps into something. You can see the gauntlet without the scales in the video, embedded below the break, which should make clear how the prototype works.

The scales were created with the help of a Mayku desktop vacuum former by making lightweight copies of 3D printed scales. Interestingly, 3D printing each scale with full supports made for a useful mold; there was no need to remove supports from underneath the prints, because they are actually a benefit to the vacuum forming process. When vacuum forming, the presence of overhangs can lead to plastic wrapped around the master, trapping it, but the presence of the supports helps prevent this. 3D prints don’t hold up very well to the heat involved in vacuum forming, but they do well enough for a short run like this. Watch it in action and listen to [Will] explain the design in the video, embedded below.

Continue reading “Watch This Scaly Gauntlet’s Hypnotizing, Rippling Waves”

Raspberry Pi Cluster Shows You The Ropes

Raspberry Pi clusters are a common enough project, but a lot of the builds we see focus on the hardware side of the cluster. Once it’s up and running, though, what comes next? Raspberry Pis aren’t very powerful devices, but they can still be a great project for learning how to interact with a cluster of computers or for experimental test setups. In this project from [Dino], four Pis are networked together and then loaded with a basic set of software for cluster computing.

The first thing to set up, after the hardware and OS, is the network configuration. Each Pi needs a static IP in order to communicate properly. In this case, [Dino] makes extensive use of SSH. From there, he gets to work installing Prometheus and Grafana to use as monitoring software which can track system resources and operating temperature. After that, the final step is to install Ansible which is monitoring software specifically meant for clusters, which allows all of the computers to be administered more as a unit than as four separate devices.

This was only part 1 of [Dino]’s dive into cluster computing, and we hope there’s more to come. There’s a lot to do with a computer cluster, and once you learn the ropes with a Raspberry Pi setup like this it will be a lot easier to move on to a more powerful (and expensive) setup that can power through some serious work.

Cortex 2 Is One Serious 3D Printed Experimental Rocket

Rocketry is wild, and [Foaly] is sharing build and design details of the Cortex 2 mini rocket which is entirely 3D printed. Don’t let that fool you into thinking it is in any way a gimmick; the Cortex 2 is a serious piece of engineering with some fascinating development.

Cortex 1 was launched as part of C’Space, an event allowing students to launch experimental rockets. Stuffed with sensors and entirely 3D printed, Cortex 1 flew well, but the parachute failed to deploy mainly due to an imperfectly bonded assembly. The hatch was recovered, but the rocket was lost. Lessons were learned, and Cortex 2 was drafted up before the end of the event.

Some of the changes included tweaking the shape and reducing weight, and the refinements also led to reducing the number of fins from four to three. The fins for Cortex 2 are also reinforced with carbon fiber inserts and are bolted on to the main body.

Here’s an interesting details: apparently keeping the original fins would result in a rocket that was “overstable”. We didn’t really realize that was a thing. The results of overstabilizing are similar to a PID loop where gain is too high, and overcorrection results in oscillations instead of a nice stable trajectory.

Cortex 2 uses a different rocket motor from its predecessor, which led to another interesting design issue. The new motor is similar to hobby solid rocket motors where a small explosive charge at the top of the motor blows some time after the fuel is gone. This charge is meant to eject a parachute, but the Cortex 2 is not designed to use this method, and so the gasses must be vented. [Foaly] was understandably not enthusiastic about venting hot gasses through the mostly-PLA rocket body. Instead, a cylindrical cartridge was designed that both encases the motor and redirects any gasses from the explosive charge out the rear of the rocket. That cartridge was SLA printed out of what looks to us like Formlabs’ High Tempurature Resin.

Finally, to address the reasons Cortex 1 crashed, the hatch and parachute were redesigned for better reliability. A servo takes care of activating the system, and a couple of reverse-polarity magnets assist in ensuring the hatch blows clear. There’s even a small servo that takes care of retracting the launch guide.

The rocket is only half built so far, but looks absolutely fantastic and we can’t wait to see more. It’s clear [Foaly] has a lot of experience and knowledge. After all, [Foaly] did convert a Makerbot printer into a CNC circuitboard engraver.