Every now and then a project comes into the Hackaday feed that has so many levels of wrong about it that you really shouldn’t do it at home, but is amusing enough to feature anyway with a warning. So it is with [ArcaEge]’s Capacitor Alarm Clock, which wakes up its unfortunate owner by blowing up electrolytic capacitors with reverse voltage. If you survive, you’ll certainly be awake!

It’s inspired unsurprisingly by an [ElectroBoom] video, and the premise is simple enough. An ESP32 serves as the clock, and triggers a relay for the alarm, which in turn overloads a suitably low-voltage electrolytic capacitor in a socket. The resulting explosion which appears in a video we’ve placed below the break, wakes the slumberer.

We don’t have to tell you that this is not the safest of hacks, and is presented here only for your entertainment. But it does provide a few points of interest, for example in identifying the difference between capacitors with a vent, and those without.

This isn’t the first time we’ve seen a project based around exploding capacitors, and that one maybe was a don’t-do-this-at-home too.

Since the tail end of World War II, humanity has struggled to deal with its newfound ability to harness the tremendous energy in the nucleus of the atom. Of course there have been some positive developments like nuclear power which can produce tremendous amounts of electricity without the greenhouse gas emissions of fossil fuels. But largely humanity decided to build a tremendous nuclear weapons arsenal instead, which has not only cause general consternation worldwide but caused specific problems for one scientist in particular.

[Steve Weintz] takes us through the tale of [Dr. John C. Clark] who was working with the Atomic Energy Commission in the United States and found himself first at a misfire of a nuclear weapons test in the early 1950s. As the person in charge of the explosive device, it was his responsibility to safely disarm the weapon after it failed to detonate. He would find himself again in this position a year later when a second nuclear device sat on the test pad after the command to detonate it was given. Armed with only a hacksaw and some test equipment he was eventually able to disarm both devices safely.

One note for how treacherous this work actually was, outside of the obvious: although there were safety devices on the bombs to ensure the nuclear explosion would only occur under specific situations, there were also high explosives on the bomb that might have exploded even without triggering the nuclear explosion following it. Nuclear bombs and nuclear power plants aren’t the only things that the atomic age ushered in, though. There have been some other unique developments as well, like the nuclear gardens of the mid 1900s.

Researchers at Cornell University have developed a tiny, proof of concept robot that moves its four limbs by rapidly igniting a combination of methane and oxygen inside flexible joints.

The device can’t do much more than blow each limb outward with a varying amount of force, but that’s enough to be able to steer and move the little unit. It has enough power to make some very impressive jumps. The ability to navigate even with such limited actuators is reminiscent of hopped-up bristebots.

Electronic control of combustions in the joints allows for up to 100 explosions per second, which is enough force to do useful work. The prototype is only 29 millimeters long and weighs only 1.6 grams, but it can jump up to 56 centimeters and move at almost 17 centimeters per second.

The prototype is tethered, so those numbers don’t include having to carry its own power or fuel supply, but as a proof of concept it’s pretty interesting. Reportedly a downside is that the process is rather noisy, which we suppose isn’t surprising.

Want to see it in action? Watch the video (embedded below) to get an idea of what it’s capable of. More details are available from the research paper, as well.

The visual arts are a broad field, encompassing everything from the chiselling of marble sculptures to the creation of delicate landscapes in charcoal on paper. However, [Evelyn Rosenberg] has experimented with some altogether more radical techniques over the years, creating her explosively-formed detonographs.

The process of creating a detonograph starts with sketching out a design, and using it to create a plaster mold. The mold exists as a bas relief, upon which metal sheets are laid on top. Various different metals may be layered up to create varying effects, and other objects like leaves, branches, or lace may also be included in the stack up.

Then, the metal plate sitting atop the mold is covered with explosive powder. When this is detonated, it smashes everything together with great force. The metal sheet takes on the negative form of the bas relief mold, while also picking up imprints from any leaves or other objects included in the various layers. Dissimilar metals included in the stack-up may also weld together during this process.

With some post-processing like polishing and chemical treatments, the result is a beautiful metal artwork full of dimension and detail. It’s somewhat like an artistic take on the industrial process of explosive welding. Video after the break.

When you hear the name “Tesla”, chances are good that thoughts turn instantly to the company that’s trying to reinvent the motor vehicle and every industry that makes it possible. While we applaud the effort, it’s a shame that they chose to appropriate the surname of a Serbian polymath as their corporate brand, because old [Nikola] did so many interesting things in his time, and deserves to be remembered in his own right.

Take the Tesla valve. In essence a diode for fluids, the Tesla valve uses a tortuous path to allow flow in one direction but severely restrict it in the other. Understanding how it works isn’t necessarily intuitive, though, which is why [NightHawkInLight] chose to demonstrate the Tesla valve principle with exploding propane. It’s not new territory to him; we’ve covered his propane-powered rifle in the past.

The swirling blue and green flame front in those experiments make burning propane the perfect working fluid to demonstrate how the Tesla valve works. The video below tells the tale, with high-speed footage showing the turbulence that restricts the reverse flow. The surprise discovery is that in the forward direction, the burning gas actually seems to accelerate as it moves down the valve; hypersonic Tesla plasma cannon, anyone?

We’ve seen Tesla valves before, including one made from a “Shrinky Dink”. That did a pretty good job of visualizing the flow patterns that make the valve work, but there’s a huge showmanship gap between tiny channels filled with colored water and the explosive decomposition of a fuel-air mix. It’s a bit riskier, and standard “don’t try this at home” disclaimers apply, but luckily [NightHawkInLight] still has his eyebrows, so he must be doing something right.

A high school friend once related the story about how his father, a chemist for an environmental waste concern, disposed of a problematic quantity of metallic sodium by dumping it into one of the more polluted rivers in southern New England. Despite the fact that the local residents were used to seeing all manner of noxious hijinx in the river, the resulting explosion was supposedly enough to warrant a call to the police and an expeditious retreat back to the labs. It was a good story, but not especially believable back in the day.

After seeing this video of how the War Department dealt with surplus sodium in 1947, I’m not so sure. I had always known how reactive sodium is, ever since demonstrations in chemistry class where a flake of the soft gray metal would dance about in a petri dish full of water and eventually light up for a few exciting seconds. The way the US government decided to dispose of 20 tons of sodium was another thing altogether. The metal was surplus war production, probably used in incendiary bombs and in the production of aluminum for airplanes. No longer willing to stockpile it, the government tried to interest industry in the metal, but to no avail due to the hazard and expense of shipping the stuff. Sadly (and as was often the case in those days), they just decided to dump it.

Environmental Chemistry

The final resting place was to be Lake Lenore, a biologically dead alkali lake near the Grand Coulee in eastern Washington state. The 3,500 pound (1,600 kg) ingots were unceremoniously rolled down into the lake, and the ensuing explosions were pretty spectacular. The video below is newsreel film from the event; it’s pretty low quality, so you might want to check out what just a pound of sodium does when it hits the water.

Watching sodium react so violently with water might just put you in the mood to get in on this action yourself. That’s understandable, but probably not a great idea. Had Lake Lenore not already been devoid of aquatic life in 1947, it might well have been after the government got done with it. Sodium combines with water to produce an aqueous solution of sodium hydroxide and copious amounts of hydrogen gas, in a violently exothermic fashion. None of this is good for critters and it’s likely to be received poorly by law enforcement and wildlife protection agencies alike.

How Metallic Sodium is Made

If you insist on trying your hand at making your own sodium metal you’ll face some challenges. On a commercial scale, metallic sodium is made by electrolysis of molten sodium chloride. With temperatures pushing 800°C and currents in the kiloamp range, it’s not exactly DIY-friendly.

There are non-electrolytic methods, though, and NurdRage has a helpful guide to a solvent extraction of sodium that is much easier and yields a fair amount of the pure metal. It’s not without its drawbacks, though; the best solvent is dioxane, a carcinogenic and noxious substance in its own right.

If you do choose to make sodium, or just order some online, please have a plan for disposing of it. We know that times were different back in the 40s, and that Lake Lenore was already dead, but it’s hard to watch that video and not cringe.

[via r/whoadude]

Madison, WI hackerspace Sector67 is in a period of transition as they move from their current rented location to a new property that will be their permanent home a half mile away. Last Wednesday (September 20, 2017) an unfortunate propane explosion in the new building led to the injury of Chris Meyer, the founder and director of the hackerspace.

The structure has been stabilized and renovation is continuing, but Chris was seriously burned and will be in the hospital for at least a month with a much longer road to complete recovery. It is fortunate that nobody else was injured.

This accident comes at a time when Sector67 essentially has two spaces to maintain; the existing space is still running, but many of the members are focused on the construction of the new space. The building needs significant work before the move can take place. Currently the roof is being raised so that the building can go from one awkward-height story to two normal stories, doubling the size. An expiring lease and imminent demolition of the current location by developers means the clock is still ticking on the move, and this explosion means Sector67 will have to work even harder, and without the presence and constant effort of the person who has been leading the project.

A GoFundMe campaign for Sector67 has been started and is well on its way towards helping Chris and Sector67.