Micro Tesla Turbine is an Engineering Tour de Force

A corollary to Godwin’s Law ought to be that any Hackaday post that mentions Nikola Tesla will have a long and colorful comment thread. We hope this one does too, but with any luck it’ll concentrate on the engineering behind this tiny custom-built Telsa turbine.

For those not familiar with Mr. Tesla’s favorite invention, the turbine is a super-efficient design that has no blades, relying instead on smooth, closely spaced discs that get dragged along by the friction of a moving fluid. [johnnyq90]’s micro version of the turbine is a very accomplished feat of machining. Although at first the build appears a bit janky, as it progresses we see some real craftsmanship – if you ever doubt that soda can aluminum can be turned, watch the video below. The precision 25mm rotor goes into a CNC machined aluminum housing; the way the turned cover snaps onto the housing is oddly satisfying. It looks like the only off-the-shelf parts are the rotor bearings; everything else is scratch-made. The second video ends with a test spool-up that sounds pretty good. We can’t wait for part 3 to find out how fast this turbine can turn.

Size matters, and in this case, small is pretty darn impressive. For a larger treatment of a Tesla turbine, see this one made of old hard drive platters.

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A Slide Viewer Makes An Excellent Case For An OLED Project

Sometimes when browsing the websites of our global hackspace community you notice a project that’s attractive not necessarily because of what it does or its technology but because of its presentation. So it is with the subject of this article, [Kris] needed a house temperature monitor and found a 1960s slide viewer made an excellent choice for its housing.

The monitor itself is a fairly straightforward Arduino build using a couple of DS18B20 1-wire temperature sensors and a real-time-clock module and displaying their readings on a small OLED screen. Its code can be found on this mailing list thread if you are interested. The display presented a problem as it needed to be reasonably large, yet fairly dim so it could be read at night without being bright enough to interrupt sleep.

A variety of projection techniques were tried, involving lenses from a projection clock, a magnifying glass, and a Google Cardboard clone. Sadly none of these lenses had the required focal length. Eventually the slide viewer was chosen because it was pointed out that the OLED screen was about the same size as a photographic slide.

Slide viewers are part of the familiar ephemera of the analog era that most people over 60 may still have taking up drawer space somewhere but may well be completely alien to anyone under about 30. They were a magnification system packaged up into a console usually styled to look something like a small portable TV of the day, and different models had built-in battery lights, or collected ambient light with a mirror. The screen was usually a large rectangular lens about 100mm(4″) diagonal.

[Kris]’s Vistarama slide viewer came via eBay. It’s not the smallest of viewers, other models folded their light paths with mirrors, however the extra space meant that the Arduino fit easily. The OLED was placed where the slide would go, and its display appeared at just the right magnification and brightness. Job done, and looking rather stylish!

We’ve not featured a slide viewer before here at Hackaday, though we did recently feature a similar hack on an Ikea toy projector. We have however featured more than one digital conversion on a classic slide projector using LCD screens in place of the slide.

Via Robots and Dinosaurs makerspace, Sydney.

Wrangling High Voltage

Working with high voltage is like working with high pressure plumbing. You can spring a leak in your plumbing, and of course you fix it. And now that you’ve fixed that leak, you’re able to increase the pressure still more, and sometimes another leak occurs. I’ve had these same experiences but with high voltage wiring. At a high enough voltage, around 30kV or higher, the leak manifests itself as a hissing sound and a corona that appears as a bluish glow of excited ions spraying from the leak. Try to dial up the voltage and the hiss turns into a shriek.

Why do leaks occur in high voltage? I’ve found that the best way to visualize the reason is by visualizing electric fields. Electric fields exist between positive and negative charges and can be pictured as electric field lines (illustrated below on the left.) The denser the electric field lines, the stronger the electric field.

The stronger electric fields are where ionization of the air occurs. As illustrated in the “collision” example on the right above, ionization can happen by a negatively charged electron leaving the electrically conductive surface, which can be a wire or a part of the device, and colliding with a nearby neutral atom turning it into an ion. The collision can result in the electron attaching to the atom, turning the atom into a negatively charged ion, or the collision can knock another electron from the atom, turning the atom into a positively charged ion. In the “stripping off” example illustrated above, the strong electric field can affect things more directly by stripping an electron from the neutral atom, again turning it into a positive ion. And there are other effects as well such as electron avalanches and the photoelectric effect.

In either case, we wanted to keep those electrons in the electrically conductive wires or other surfaces and their loss constitutes a leak in a very real way.

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Forming Voltron’s Blazing Sword For Real

Activate interlock! Dynotherms connected! Infracells up! Mega thrusters are go! If you grew up in the 80’s you undoubtedly know that quote means it’s time to form Voltron. The 1984 Lion Force Voltron series has shown an incredible amount of staying power. These 5 lions have come together to form no less than 3 reboot series, the most recent coming out just this month from Dreamworks and Netflix.

[Matt and Kerry Stagmer], blacksmiths for the Man at Arms web series haven’t forgotten Voltron either. Every episode of the original series ended with the mighty robot defeating enemies using an iconic blazing sword. While they might not be able to bring us 5 robot lions which join together to form one mega robot, [Matt and Kerry] can bring us a human sized version of Voltron’s sword (YouTube).

Starting with a high-resolution image of a toy version of the sword, [Matt] traced the outline. The shape was sent over to a plasma cutter. Rather than cut one sword, two outlines were cut. One in 1/4″ steel, the other in 3/16″. A CNC was used to cut grooves in the 1/4″ section. These grooves became the manifold for propane gas jets. Separate jets were cut around the perimeter of the sword. With this complete, the two pieces were carefully TIG welded together.

This sword isn’t all prop and no chop. The upper sections were heat-treated and sharpened to a razor edge. We won’t go so far as to call this practical. It wields more like an ax than a sword. At the end of the day it doesn’t really matter though – this blazing sword is completely awesome.

Open Source Cloud Chamber

If you are a certain age, there were certain science toys you either had, or more likely wanted. A chemistry set, a microscope, a transparent human body, and (one of several nuclear toys) a cloud chamber. Technically, a Wilson cloud chamber (named after inventor Charles Wilson) isn’t a toy. For decades it was a serious scientific tool responsible for the discovery of the positron and the muon.

The principle is simple. You fill a sealed chamber with a supersaturated water or alcohol vapor. Ionizing radiation will cause trails in the vapor. With a magnetic field, the trails will curve depending on their charge.

If you didn’t have a cloud chamber, you can build your own thanks to the open source plans from [M. Bindhammer]. The chamber uses alcohol, a high voltage supply, and a line laser. It isn’t quite the dry ice chamber you might have seen in the Sears Christmas catalog. A petri dish provides a clear observation port.

We’ve covered cloud chamber builds before, ranging from the simple to ones that use thermoelectric coolers.

The Almost Useful Machine

[Alex] is no stranger to making machines of negligible utility. A few years ago he made the Almost Useless Machine, a solar-powered system that cuts through a 20mm dowel rod while you wait (and wait, and wait). Enamored by the internet’s bevy of powered hacksaws, he sought to build a sturdier version that’s a little more useful. Approximately five months of free time later, he had the Almost Useful Machine.

It runs on a wiper motor and a recycled power supply from a notebook computer. [Alex] rolled his own board for controlling the motor with an ATtiny25. The circuit turns potentiometer movement into PWM, which controls the motor through a MOSFET. After the cut is finished, an endstop microswitch  immediately cuts the motor.

Every bit of the chassis is aluminum that [Alex] machined by hand. Don’t have that kind of setup? How about a powered hacksaw with a 3D-printed linkage? Make the jump to see it in action, and stick around for the two-part time-lapse build video.

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An Atari ST Rises From The Ashes

We’ve all made rash and impulsive online purchasing decisions at times. For [Drygol] the moment came when he was alerted to an Atari 1040STe 16-bit home computer with matching monitor at a very advantageous price.

Unfortunately for him, the couriers were less than careful with his new toy. What arrived was definitely an ST, but new STs didn’t arrive in so many pieces of broken ABS. Still, at least the computer worked, so there followed an epic of case repair at the end of which lay a very tidy example of an ST.

He did have one lucky break, the seller had carefully wrapped everything in shrink-wrap so no fragments had escaped. So carefully applying acetone to stick the ABS together he set to work on assembling his unexpected 3D jigsaw puzzle. The result needed a bit of filler and some sanding, but when coupled with a coat of grey paint started to look very like an ST case that had just left the factory. Adding  modern SD card and USB/Ethernet interfaces to the finished computer delivered a rather useful machine as you can see in the video below the break.
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