Bad Idea For Desoldering Actually Might Be Pretty Smart

This video on building a DIY desoldering iron says it all right up front: this is stupid and dangerous, and you shouldn’t do it. But that doesn’t mean it doesn’t work, or that it doesn’t have potential to be turned into something else.

The story begins, as it often does these days, on the pages of Amazon as [AnotherMaker] shopped for a real desoldering setup. Despite a case of sticker shock, he took the plunge on a nice Hakko vacuum desolderer, but as is also often the case, it failed to arrive. Rather than accept defeat, [AnotherMaker] purchased a cheap-o soldering iron and a brass tee fitting for small-bore tubing that would chuck nicely into the spot where the stock tip once lived, giving him a way to both melt solder and move air.

Unfortunately, rather than applying a vacuum, he chose to blast 100 PSI compressed air through the tip, which certainly moves a lot of solder, perhaps at the cost of burns and eye injuries. The potential for accidental short circuits is pretty high too, but c’mon — it’s not like we all haven’t flicked or dropped a board to desolder something. Is this really much different?

As fraught with peril as this method may be, [AnotherMaker] is onto something here. Perhaps adding a 3D-printed venturi generator could turn that blast of air into a vacuum. Or maybe a vacuum pump for a manual pick-and-place would do the trick too.

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Vacuum Dragster Uses Syringes For Propulsion

Atmospheric pressure is all around us, and capable of providing a great deal of force when used properly. As Otto Von Guericke demonstrated with his Magdeburg hemispheres over 350 years ago, simply removing air from a chamber to create a vacuum can have astounding results. More recently, [Tom Stanton] has used vacuum to power a small 3D-printed dragster.

In the dragster build, a typical plunger syringe is plugged at the end, and the plunger pulled back. Atmospheric pressure acts against the vacuum, wanting to push the plunger back towards its original position. To make use of this, a string is attached to the plunger, causing it to turn a gear as it moves forward, driving the rear wheels through a belt drive. With the correct gear ratio on the belt drive, the dragster is capable of spinning its tires and shooting forwards at a quick pace.

The work is a great follow on from [Tom]’s earlier vacuum experiments, using syringes as small rockets.  It reminds us of the classic CO2 dragsters from high school competitions, and would be a great project for any science class. Video after the break.

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A Robotic Stylist For Your Lockdown Lengthened Locks

It’s perhaps easy to think that despite the rapid acceleration of technology that there are certain jobs that will never be automated out of existence. Generally the job said to be robot-proof is the one held by the person making the proclamation, we notice. But certainly the job of cutting and styling people’s hair could never be done by a robot, right?

We wouldn’t bet the farm on it, although judging by [Shane Wighton]’s quarantine haircut robot, it’ll be a while before the stylists of the world will be on the dole. Said to have sprung from the need to trim his boyishly long hair, the contraption is an object lesson recreating the subtle manual skills a stylist brings to every head they work on — there’s a reason it takes 1,500 hours or more of training to get a license, after all. [Shane] discovered this early, and realized that exactly replicating the manual dexterity of human hands was a non-starter. His cutting head uses a vacuum to stand the hair upright, 3D-printed fingers to grip a small bundle of hair, and servo-driven scissors to cut it to length. The angle of attack of the scissors can be adjusted through multiple axes, and the entire thing rotates on a hell-no-I’m-not-putting-my-head-in-that-thing mechanism.

To his great credit, [Shane] braved the machine as customer zero, after only a few non-conclusive life-safety tests with a dummy head and wig. We won’t spoil the ending, but suffice it to say that the thing actually worked with no bloodshed and only minimal damage to [Shane]’s style. The long-suffering [Mrs. Wighton], however, was not convinced to take a test drive.

In all seriousness, kudos to [Shane] for attacking such a complex problem. We love what he’s doing with his builds, like his basketball catcher and his robo-golf club, and we’re looking forward to more.

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An Affordable Home Made Vacuum Chamber

The term “vacuum” means many different things depending whether you are working on space equipment, scientific instruments, or even internal combustion engines. In our sphere it is so often used as a means to draw bubbles out of resin castings, for which it is a relatively easily achievable partial vacuum. It’s something [Fab] is using, in a vacuum chamber made from Plexiglass.

A simple Plexiglass box would collapse under the air pressure on its own, so to mitigate that it’s made from a piece of tube, and with an internal frame of aluminium extrusion with 3D printed joints to strengthen it from the inside. A pressure sensor allows regulation of the pump that drives the vacuum, and connections are made to the chamber using pneumatic hose connectors. It’s not immediately clear how it is sealed, whether there are nay gaskets or other sealant, or whether air pressure pushing the parts together provides enough of a seal.

We’ve featured a lot of vacuum chambers made for this purpose over the years, and we’d be interested to know what vacuum pump is being used here. If  you’re curious too and want to build your own, perhaps you could try a fridge compressor.

Variable Mirror Changes Shape Under Pressure

Unless you’re in a carnival funhouse, mirrors are generally dead flat and kind of boring. Throw in some curves and things get interesting, especially when you can control the curve with a touch of your finger, as with this variable surface convex mirror.

The video below starts off with a long but useful review of conic constants and how planes transecting a cone can create circles, parabolas, or ellipses depending on the plane’s angle. As [Huygens Optics] explains, mirrors ground to each of these shapes have different properties, which makes it hard to build telescopes that work at astronomical and terrestrial distances. To make a mirror that works over a wide range of distances, [Huygens Optics] built a mirror from two pieces of glass bonded together to form a space between the front and rear surface. The front surface, ground to a spherical profile, can be deformed slightly by evacuating the plenum between the two surfaces with a syringe. Atmospheric pressure bends the thinner front surface slightly, changing the shape of the mirror.

[Huygens Optics] also built an interferometer to compare the variable mirror to a known spherical reference. The data from the interferometer was fed to a visualization package that produced maps of the surface shape, which you can easily see changing as the pressure inside the mirror changes. Alas, a deeper dive into the data showed the mirror to be less than perfect, but it’s fascinating to think that a mirror can flex enough to change from elliptical to almost parabolic with nothing more than a puff of air.

We’ve seen a couple of interesting efforts from [Huygens Optics] before, including this next-level spirit level. He’s not all about grinding glass, though — witness this investigation into discriminating metal detectors.

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Robot Arm Sucks In A Good Way

Building a robot arm is fun, but no longer the challenge it once was. You can find lots of plans and kits, and driving the motors is a solved problem. However, there is always one decision you have to make that can be a challenge: what effector to put on the end of it. If you are [MertArduino] the answer is to put suction at the end. If you need to grab the right things, this could be just the ticket for reliably lifting and letting go. You can see a video of the arm in action, below.

The arm itself is steel with four servo motors and comes in a kit. The video shows the arm making a sandwich under manual control. We suspect he might have put it under Arduino control but there’s no sudo for making sandwiches.

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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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