[Ben Krasnow]’s Take On DIY Air Bearings

December 28, 2019 by Dan Maloney 6 Comments

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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Replica Proton Pack Is A Great Halloween Build

December 14, 2019 by Lewin Day 2 Comments

Way back in 1984, the Ghostbusters defended New York City from an onslaught of supernatural phenomena. In their honor, [BALES] created this costume for Halloween, replete with an amazing replica proton pack.

(We know, this is a little late for Halloween 2019, but just think about how early you’re going to be for Halloween 2020!)

While not actually capable of trapping and harnessing entities from the spirit realm, the replica pack nonetheless is impressive. Constructed primarily from EVA foam and PVC pipe, it’s built on a custom built Alice pack frame to make it easy to carry. The cyclotron scores some LEDs, and EL wire completes the neutrino wand. A rough-and-ready paintjob make the gear look well used, and the laser-printed labels go a long way to completing the look.

[BALES] didn’t skimp on the clothing side either. The olive drab overalls, an embroidered patch, and belt were sourced from Amazon, and a custom name badge was produced to complete the ensemble. We’re sure the costume was an absolute hit at Halloween, and gives us plenty ideas of our own. It would pair well with this PKE meter that actually detects radiation, too!

Burning Propane Beautifully Illustrates How A Tesla Valve Works

December 13, 2019 by Dan Maloney 42 Comments

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.

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3D-Printer And CNC Make This Russian Calculator Bilingual

December 13, 2019 by Dan Maloney 11 Comments

Let’s be clear right up front: there are probably more obvious solutions to the problem of using a Russian calculator when you don’t speak Russian than printing new keys and engraving translated markings on them. But easy solutions are boring and generally considered beyond the scope of Hackaday articles, so let’s dive in.

They say that mathematics is the universal language, but that’s only true to an extent. Still, even with our ~~limited~~ non-existent Cyrillic skills, the Russian keyboard on this RPN calculator isn’t that hard to figure out. But as [Amen] points out, in the midst of fevered calculations, one prefers not to mentally translate Χ→П to STO or remember that В↑ is the Enter key. So he printed a set of replacements for the confusing keys from PLA. While pondering how to safely fixture such small parts for the later engraving step, [Amen] hit on a genius solution: move the print bed to the CNC router and fixture everything in one go. The resulting characters are large enough to be legible and deep enough to be filled with air-drying polymer clay for contrast. After sanding and polishing, the calculator looks like it came from the Министерство электронной промышленности that way.

Honestly, we’d love to get a look inside this calculator. The insides of Russian electronics can be fascinating, and we’ve even seen entire forums dedicated to decapping Russian parts. But we understand the desire to keep it intact.

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Are You Getting Your Money’s Worth From Threaded Inserts?

December 12, 2019 by Dan Maloney 14 Comments

Have you ever wondered whether it’s worth the time and expense to install threaded inserts into your 3D-printed projects? [Stefan] from CNC Kitchen did, and decided to answer the question once and for all, with science.

If this sounds familiar, it’s with good reason: we covered [Stefan]’s last stab at assessing threaded inserts back in March. Then, he was primarily interested in determining if threaded inserts are better than threads cut or printed directly into parts. The current work is concerned with the relative value of different designs of threaded inserts. He looked at three different styles of press-in inserts, ranging in price from pennies apiece to a princely 25 cents. The complexity of the outside knurling seems not to be correlated with the price; the inserts with opposed helical knurls seem like they’d be harder to manufacture than the ones with simple barbs on the outside of the barrel, but cost less. And in fact, the mid-price insert outperformed the expensive one in pull-out tests. Surprisingly, the cheapest inserts were actually far worse at pull-out resistance than printing undersized holes and threading an M3 screw directly into the plastic.

[Stefan] also looked at torque resistance, and found no substantial difference between the three insert types. Indeed, none of the inserts proved to be the weak point, as the failure mode of all the torque tests was the M3 bolt itself. This didn’t hold with the bolt threaded directly into the plastic, of course; any insert is better than none for torque resistance.

We enjoyed seeing [Stefan]’s tests, and appreciate the data that can help us be informed consumers. [John] over at Project Farm does similar head-to-head tests, like this test of different epoxy adhesives.

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Tracking Wasted Time With A Ferrofluid Clock

December 10, 2019 by Dan Maloney 11 Comments

We know this project is supposed to be about developing a fine-looking ferrofluid clock, and not about the value of procrastination. But after watching the video below, see if you don’t think that procrastination has taken these two students further than expected.

We first ran into [Simen] and [Amund] several months ago when they launched their ferrofluid project in a fit of “There’s got to be more to life than studying.” It seemed then that building a good-looking, functional ferrofluid display would be a temporary distraction, but the problems posed proved to be far deeper and thornier than either of the electrical engineering students expected. The idea is simple: contain a magnetic fluid between two transparent panels and create pixels using an array of electromagnets to move dots of the fluid around. The implementation, however, was another matter, with the ferrofluid itself proved to be the biggest obstacle. All the formulas they tried seemed to coagulate or degrade over time and tended to stain the glass. While the degradation was never fully sorted, they managed to work around the staining by careful cleaning of the glass and using a saturated brine solution to fill the container.

Backed by 252 electromagnets and drivers on ten custom PCBs, the video below shows the (mostly) finished panel in action as a clock. We’re impressed by the smoothness of the movements of each pixel, even if there’s a bit of drooping at the bottom thanks to gravity. As for the future of the project, that’s unclear since [Simen] is headed off for a NASA internship. We’re not sure if that was despite or because of this procrastination-driven project, but we congratulate him either way and look forward to hearing more from both of them in the future.

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Conductive Tape Current Capacity Comparison

December 9, 2019 by Bob Baddeley 13 Comments

The world of DIY circuits for STEM and wearables has a few options for conductors. Wire with Dupont connectors is a standard, as is adhesive copper tape. There’s also conductive nylon/steel thread or ribbon. Which you choose depends on your application, of course, but as a general rule wire is cheap and ubiquitous while making connections is more challenging; copper tape is cheap and simple to use, but delicate and rips easily, so is best used for flat surfaces that won’t see a lot of stress or temporary applications; and conductive nylon thread or tape is better for weaving into fabrics.

The Brown Dog Gadgets team wanted to respond to a frequent question they are asked, what are the current limits for their Maker Tape (nylon/steel ribbon), so they ran some experiments to find out. In the name of Science you’ll see some flames in the video below, but only under extreme conditions.
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