Hackaday Links: March 14, 2021

It’ll be Pi Day when this article goes live, at least for approximately half the globe west of the prime meridian. We always enjoy Pi Day, not least for the excuse to enjoy pie and other disc-shaped foods. It’s also cool to ponder the mysteries of a transcendental number, which usually get a good treatment by the math YouTube community. This year was no disappointment in this regard, as we found two good pi-related videos, both by Matt Parker over at Standup Maths. The first one deals with raising pi to the pi to the pi to the pi and how that may or may not result in an integer that’s tens of trillions of digits long. The second and more entertaining video is a collaboration with Steve Mould which aims to estimate the value of pi by measuring the volume of a molecular monolayer of oleic acid floating on water. The process was really interesting and the results were surprisingly accurate; this might make a good exercise to do with kids to show them what pi is all about.

Remember basic physics and first being exposed to the formula for universal gravitation? We sure do, and we remember thinking that it should be possible to calculate the force between us and our classmates. It is, of course, but actually measuring the attractive force would be another thing entirely. But researchers have done just that, using objects substantially smaller than the average high school student: two 2-mm gold balls. The apparatus the Austrian researchers built used 90-milligram gold balls, one stationary and one on a suspended arm. The acceleration between the two moves the suspended ball, which pivots a mirror attached to the arm to deflect a laser beam. That they were able to tease a signal from the background noise of electrostatic, seismic, and hydrodynamic forces is quite a technical feat.

We noticed a lot of interest in the Antikythera mechanism this week, which was apparently caused by the announcement of the first-ever complete computational model of the ancient device’s inner workings. The team from University College London used all the available data gleaned from the 82 known fragments of the mechanism to produce a working model of the mechanism in software. This in turn was used to create some wonderful CGI animations of the mechanism at work — this video is well worth the half-hour it takes to watch. The UCL team says they’re now at work building a replica of the mechanism using modern techniques. One of the team says he has some doubts that ancient construction methods could have resulted in some of the finer pieces of the mechanism, like the concentric axles needed for some parts. We think our friend Clickspring might have something to say about that, as he seems to be doing pretty well building his replica using nothing but tools and methods that were available to the original maker. And by doing so, he managed to discern a previously unknown feature of the mechanism.

We got a tip recently that JOGL, or Just One Giant Lab, is offering microgrants for open-source science projects aimed at tackling the problems of COVID-19. The grants are for 4,000€ and require a minimal application and reporting process. The window for application is closing, though — March 21 is the deadline. If you’ve got an open-source COVID-19 project that could benefit from a cash infusion to bring to fruition, this might be your chance.

And finally, we stumbled across a video highlighting some of the darker aspects of amateur radio, particularly those who go through tremendous expense and effort just to be a pain in the ass. The story centers around the Mt. Diablo repeater, an amateur radio repeater located in California. Apparently someone took offense at the topics of conversation on the machine, and deployed what they called the “Annoy-o-Tron” to express their displeasure. The device consisted of a Baofeng transceiver, a cheap MP3 player loaded with obnoxious content, and a battery. Encased in epoxy resin and concrete inside a plastic ammo can, the jammer lugged the beast up a hill 20 miles (32 km) from the repeater, trained a simple Yagi antenna toward the site, and walked away. It lasted for three days and while the amateurs complained about the misuse of their repeater, they apparently didn’t do a thing about it. The jammer was retrieved six weeks after the fact and hasn’t been heard from since.

Swarm Of Tiny Pirate Transmitters Gets The Message Out In Syria

They say that the first casualty of war is the truth, and that’s probably only more the case in a civil war. When one side in a conflict controls the message, the other side is at a huge disadvantage. Technology can level the playing field, and in the case of the Syrian Civil War, a swarm of tiny Raspberry Pi transmitters is helping one side get their message out.

We won’t pretend to understand the complexities of this war, but it’s clear that the Syrian government controls broadcast media and access to the internet, and is using them for propaganda while denying the opposition access to the same. A decentralized medium can get the message out under these conditions, and that’s exactly what Pocket FM does. Built around a Raspberry Pi and a frequency-agile FM transmitter, a Pocket FM can take multiple audio feeds and transmit them out to a 5km radius. Small enough to be packed up and deployed quickly and able to be powered by batteries or solar panels, the pirate transmitters can be here one minute and gone the next, yielding a robust network resistant to takedown attempts.

The network built around Pocket FM in Syria is small but growing, and it appears to be making a difference in the conflict. We find the concept of a decentralized network intriguing and potentially empowering, at least in situations where the letter of the law regarding broadcasting is not a prime consideration. That’s where projects like Airchat seek to build an unsanctioned network. The same goes for Tweeting on the Amateur Radio Band in a project aptly named HamRadioTweets.

We wonder how a fleet of these Pi-based transmitters could aid in recovery from natural disasters?

[via r/amateurradio and TomHiggins]

Halloween Props: Puking Pirate

With everyone’s favorite free-candy holiday approaching, [Slouriesr] set to work building a vomiting ghoul for his Halloween display. He’s calling it a puking pirate and it centers around a pump and some simple plumbing fixtures.

First, the vomit receptacle was made by adding a sink drain with a pop-up stopper to the bottom of a kitty litter bucket. The drain slows the evacuation of liquid into a five gallon bucket below. In that bucket you’ll find a float switch pump used to keep water off of a pool cover. As the bucket fills up the pump turns on and empties the water through a hose ending at the ghoul’s mouth. The result is a 20-second puke cycle sure to delight the trick-or-treaters. Sure, there’s a lot of work to be done to get this guy looking the part, but what a great idea!

Help keep us in the holiday spirit by sending the details on your latest prop build.

Argh, Thar Be A Big Wheel

If you’re marooned on a desert island, you want to have a Professor who can build useful items out of coconuts. [LostMachine] is one of those guys, and he’s currently building a land-loving pirate ship. The wacky vehicle will use the giant wheel above to propel the vessel while the captain sits comfortably in the lofty crow’s nest. A crack-pot concept? Not really, he plans to take this to Burning Man where it will be a fairly useful build compared to the folks who have really gone off the deep end.

The story here is the build quality. Take some time to watch his videos which we’ve embedded after the break. In the first, he details his method for creating a precisely level building surface on top of his uneven driveway. This is accomplished by welding supports in a circle that are level compared to the center point. He goes on to share his liquid-cooling system for cutting the pipe supports with a custom-built jig and an old windshield washer water system pump from an RV (second video). The final video shows the construction of the wheel which came in with 2000 welds and about 250-300 hours of construction time.

If you hadn’t guessed, [LostMachine] is a structural engineer. Unfortunately he was laid-off this spring which has put a damper in his building schedule. We hope that with a quality project like this in his portfolio a new job is just around the corner for him.

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