A Quick And Easy Recipe For Synthetic Rubies

With what it takes to make synthetic diamonds – the crushing pressures, the searing temperatures – you’d think similar conditions would be needed for any synthetic gemstone. Apparently not, though, as [NightHawkInLight] reveals his trivially easy method for making synthetic rubies.

Like their gemstone cousin the sapphire, rubies are just a variety of corundum, or aluminum oxide. Where sapphire gets its blue tint mainly from iron, rubies get their pink to blood-red hue from chromium. So [NightHawkInLight]’s recipe starts with aluminum oxide grit-blasting powder and chromium (III) oxide, a common green pigment and one of the safer compounds in a family that includes spectacularly toxic species like hexavalent chromium compounds. When mixed together, the two powders are heated in a graphite crucible using an arc welder with a carbon electrode. The crucible appears to be made from an EDM electrode; we’ve seen them used for air bearings before, but small crucibles are another great use for the stuff. There’s some finesse required to keep the nascent rubies from scattering all over the place, but in the end, [NightHawkInLight] was rewarded with a large, deep pink ruby.

This looks like a fun, quick little project to try sometime. We wonder if the method can be refined to create the guts of a ruby laser, or if perhaps it can be used to create sapphires instead.

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[Ben Krasnow]’s Take On DIY Air Bearings

We’ve got to admit that watching [Ben Krasnow]’s new video on air bearings is tough. We found our eyes constantly checking the spherical air bearing in the foreground, which for the first eight minutes of the video just kept going. It was strangely hypnotic, and made it hard to concentrate on all the other cool stuff [Ben] was up to.

If the topic of air bearings seems familiar, it might be because we recently reported on DIY air bearings made from used EDM electrodes. [Ben] saw that too, and dusted off his old air bearing project. Literally, as it turns out, because the graphite blocks whose porosity and softness make them the perfect material for air bearings also makes for a dusty workshop. We’d recommend breathing protection of some sort while machining graphite. In addition to simple puck bearings, [Ben] came up with more complicated designs, including the aforementioned spherical bearing. He used the steel ball itself as a precision tool to grind the graphite out, first by coating it with abrasive and then by cutting grooves in it to act like a file. A cylindrical bearing was also cut, this time with sandpaper glued directly to the ground steel rod that would seat in the bearing.

[Ben]’s other innovation is vacuum preloading, where he applies both vacuum and pressure to the bearing plenum. The vacuum provides the force needed to capture the moving element while the pressure bears the load. It’s a careful balancing act, but it works well enough to capture the large steel ball and keep it turning effortlessly.

We really liked [Ben]’s take on air bearings, especially his thoughts on creating fully enclosed cylindrical bearings. Those could be useful for low-friction linear drives, and we look forward to seeing more on those.

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Used EDM Electrodes Repurposed As Air Bearings For Precision Machine Tools

If you’ve ever played air hockey, you know how the tiny jets of air shooting up from the pinholes in the playing surface reduce friction with the puck. But what if you turned that upside down? What if the puck had holes that shot the air downward? We’re not sure how the gameplay would be on such an inverse air hockey table, but [Dave Preiss] has made DIY air bearings from such a setup, and they’re pretty impressive.

Air bearings are often found in ultra-precision machine tools where nanometer-scale positioning is needed. Such gear is often breathtakingly expensive, but [Dave]’s version of the bearings used in these machines are surprisingly cheap. The working surfaces are made from slugs of porous graphite, originally used as electrodes for electrical discharge machining (EDM). The material is easily flattened with abrasives against a reference granite plate, after which it’s pressed into a 3D-printed plastic plenum. The plenum accepts a fitting for compressed air, which wends its way out the micron-sized pores in the graphite and supports the load on a thin cushion of air. In addition to puck-style planar bearings, [Dave] tried his hand at a rotary bearing, arguably more useful to precision machine tool builds. That proved to be a bit more challenging, but the video below shows that he was able to get it working pretty well.

We really enjoyed learning about air bearings from [Dave]’s experiments, and we look forward to seeing them put to use. Perhaps it will be in something like the micron-precision lathe we featured recently.

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Prototyping PCBs With Electrical Discharge Machining

Here at Hackaday, we thought we’d seen every method of making PCBs: CNC machining, masking and etching with a variety of chemicals, laser engraving, or even the crude but effective method of scratching away the copper with a utility knife. Whatever works is fine with us, really, but there still does seem to be room for improvement in the DIY PCB field. To whit, we present rapid PCB prototyping with electrical discharge machining.

Using an electric arc to selectively ablate the copper cladding on a PCB seems like a great idea. At least that’s how it seemed to [Jake Wachlin] when he realized that the old trick of cutting a sheet of aluminum foil using a nine-volt battery and a pencil lead is really just a form of EDM, and that the layer of copper on a PCB is not a million miles different from foil. A few experiments with a bench power supply and a mechanical pencil lead showed that it’s relatively easy to blast the copper from a blank board, so [Jake] took the next logical step and rigged up an old 3D-printer to move the tool. The video below shows the setup and some early tests; it’s not perfect by a long shot, but it has a lot of promise. If he can control the arc better, this homebrew EDM looks like it could very rapidly produce prototype boards.

[Jake] posted this project in its current state in the hopes of stimulating a discussion and further experimentation. That’s commendable, and we’d really love to see this one move along rapidly. You might start your brainstorming by looking at this somewhat sketchy mains-powered EDM, or look into the whole field in a little more detail.

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Magnetic Bearings Might Keep This Motor Spinning For Millennia

We see our share of pitches for perpetual motion machines in the Hackaday tips line, and we generally ignore them and move along. And while this magnetic levitation motor does not break the laws of thermodynamics, it can be considered a perpetual motion machine, at least for certain values of perpetuity.

The motor that [lasersaber] presents in the video below is unconventional, to say the least. It’s not a motor that can do any useful work, spinning at a stately pace beneath its bell-jar enclosure as it does. The design is an extension of [lasersaber]’s “EZ-Spin” motor, which we’ve featured before, and has the same basic layout – a ring of coils wired in series forms the stator, while a disc bearing permanent magnets forms the rotor. The coils, scavenged from those dancing flowerpot solar ornaments, are briefly energized by the rotor passing over a reed switch, giving the rotor a little boost.

The difference here is that rather than low-friction sapphire bearings, this motor uses zero-friction magnetic levitation using pyrolyzed graphite discs. The diamagnetic material hovers above a rare-earth ring magnet, supporting a slender vertical shaft that holds the rotor and another magnetic bearing at the top. It’s fussy to adjust, but once it’s stable, the only friction in the system should be the drag caused by air in the bell jar. [lasersaber]’s current measurements of the motor running at slow speed are hard to believe – 150 nanoamps – leading to an equally jaw-dropping calculated run-time on a single AA battery of 89 millennia.

[lasersaber] is the first to admit that he’s not confident with his measurements, but it seems clear that his motor will likely outlive any chemical battery used to power it. Whatever the numbers are, we like the styling of the thing, and the magnetic bearings are cool too.

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DIY Arc Light Makes An Unnecessarily Powerful Bicycle Headlight

Remember when tricking out a bike with a headlight meant clamping a big, chrome, bullet-shaped light to your handlebar and bolting a small generator to your front fork? Turning on the headlight meant flipping the generator into contact with the front wheel, powering the incandescent bulb for the few feet it took for the drag thus introduced to grind you to a halt. This ridiculous arc-lamp bicycle headlight is not that. Not by a long shot.

We’re used to seeing [Alex] doing all manner of improbable, and sometimes impossible, things on his popular KREOSAN YouTube channel. And we’re also used to watching his videos in Russian, which detracts not a whit  from the entertainment value for Andglophones; subtitles are provided for the unadventurous, however. The electrodes for his arc light are graphite brushes from an electric streetcar, while the battery is an incredibly sketchy-looking collection of 98 18650 lithium-ion cells. A scary rat’s nest of coiled cable acts as a ballast to mitigate the effects of shorting when the arc is struck. The reflector is an old satellite TV dish covered in foil tape with the electrodes sitting in a makeshift holder where the feedhorn used to be. It’s bright, it’s noisy, it’s dangerous, and it smokes like a fiend, but we love it.

Mounting it to the front of the bike was just for fun, of course, and it works despite the janky nature of the construction. The neighbors into whose apartments the light was projected could not be reached for comment, but we assume they were as amused as we were.

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Graphene From Graphite By Electrochemical Exfoliation

Graphene is an interesting material, but making enough of the stuff to do something useful can be a little tough. That’s why we’re always on the lookout for new methods, like this electrochemical process for producing graphene in bulk.

You probably know that graphene is a molecular monolayer of carbon atoms linked in hexagonal arrays. Getting to that monolayer is a difficult proposition, but useful bits of graphene can be created by various mechanical and chemical treatments of common graphite. [The Thought Emporium]’s approach to harvesting graphene from graphite is a two-step process starting with electrochemical exfoliation. Strips of thin graphite foil are electrolyzed in a bath of ferrous sulfate, resulting in the graphite delaminating and flaking off into the electrolyte. After filtering and cleaning, the almost graphene is further exfoliated in an ultrasonic cleaner. The result is gram quantity yields with very little work and at low cost.

There’s plenty of effort going into new methods of creating graphene these days, whether by barely controlled explosions or superheating soybean oil. But will graphene be the Next Big Thing? The jury is still out on that.

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