Variable-Nozzle Ducted Fan Provides Fluid Dynamics Lessons

October 19, 2023 by 15 Comments

Any student new to the principles of fluid dynamics will be familiar with Bernoulli’s principle and the Venturi effect, where the speed of a liquid or gas increases when the size of the conduit it flows through decreases. When applying this principle to real-world applications, though, it can get a bit more complex than a student may learn about at first, mostly due to the shortcomings of tangible objects when compared to their textbook ideals. [Mech Ninja] discovered this while developing a ducted fan based around an RC motor.

The ducted fan is meant to be a stand-in for a model jet engine, based around a high-powered motor generally designed for drone racing. Most of the build is 3D printed including duct system, but in order to improve the efficiency and thrust beyond simple ducting, [Mech Ninja] designed and built a variable nozzle to more finely control the “exhaust” of his engine. This system is also 3D printed and can restrict or open up the outflow of the ducted fan, much like a real jet engine would. It uses two servos connected to collars on the outside of the engine. When the servos move the collars, a set of flaps linked to the collars can choke or expand the opening at the rear of the engine.

This is where some of the complexity of real-life designs comes into play, though. After testing the system with a load cell under a few different scenarios, the efficiency and thrust weren’t always better than the original design without the variable nozzle. [Mech Ninja] suspects that this is due to the gaps between the flaps, allowing air to escape and disrupting the efficient laminar flow of the air leaving the fan, and plans to build an improved version in the future. Fluid dynamics can be a fairly complex arena to design within, sometimes going in surprising directions like this ducted fan that turned out better than the theory would have predicted, at least until they accounted for all the variables in the design.

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2023 Hackaday Supercon: The Rest Of The Talks

October 19, 2023 by 2 Comments

The 2023 Hackaday Superconference is only two weeks away, and we’re happy to announce the second half of the slate. As always, this is a great mix of well-known Hackaday faces, and folks we haven’t yet met. Whether they’re fixing up the Apollo Guidance Computer, building their own airplanes, trapping rubidium atoms, or teaching robots to sail, this is another super interesting round of talks.

Tickets are sold out, the badges are almost done, and we’re in the home stretch! We can smell the tacos from here. If you’re joining us, we hope you’re excited. If you’re not able to, we’ll stream as much as we can.

All that remains is the mystery of the keynote speaker.  Stay tuned! Continue reading “2023 Hackaday Supercon: The Rest Of The Talks” →

Reverse-Engineering The Mechanical Bendix Central Air Data Computer

October 19, 2023 by 9 Comments

Before the era of digital electronic computers, mechanical analog computers were found everywhere. From the relative simplicity of bomb sights to the complexity of fire control computers on 1940s battleships, all the way to 1950s fighter planes, these mechanical wonders enabled feats which were considered otherwise impossible at the time.

One such system that [Ken Shirriff] looked at a while ago is the Bendix Central Air Data Computer. As the name suggests, it is a computer system that processes air data. To be precise, it’s the mechanism found in airplanes that uses external sensor inputs to calculate parameters like altitude, vertical speed, Mach number and air speed.

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You’ve Got Mail: Grilled, Scrambled, And Other Delicious Stamps

October 19, 2023 by 8 Comments

Well, we’re just zipping right through this series, no? So far we’ve looked at various postal machines and how they work to flip mail around, cancel the postage, and sort it, all in a matter of seconds. We explored the first automated post office and found out why it was a failure, and we learned why it all depends on ZIP code. Now, it’s finally time for some really fun stuff: the stamp trivia.

Now I’m no philatelist by any standard, though I do have a few hundred stamps strewn about the house. The danger in philately is that you learn all sorts of cool things about stamps and their history, and you just want to buy more and more of them. So let’s go!

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A Typewriter For The Paperless Age

October 19, 2023 by 9 Comments

Writing is, as any of the Hackaday crew will tell you, a task which requires concentration. For your best work there’s a need to be in that elusive Zone, and for some that means making the experience as distraction free as possible. For them there’s an entire class of minimalist word-processors and text editors which reduce the UI to nothing more than the text. [Adam Blumenberg] has taken this a step beyond software with his digital typewriter, a single-purpose Raspberry Pi-based cyberdeck that serves only for distraction-free writing.

There’s not a lot in the way of descriptive text at the above link but in a way there doesn’t need to be as the photographs tell the story. A mechanical keyboard and a wide but not very tall display fit with the Pi in a fairly rudimentary wooden case, and running Focuswriter it leaves very little in the way of distraction. In that sense it’s not quite so much a cyberdeck in its application as something more like the smart digital typewriters from a few decades ago without the printer, but we can see that it makes for a very handy writing implement. Sadly the job of writing for Hackaday requires constant access to online sources on a larger screen, or we’d be tempted to try one ourselves.

The one-purpose writing computer is an idea we’ve seen before from time to time, for example in this one with an e-paper display.

Simple Circuit Keeps Process Control Loops In Tune

October 19, 2023 by 7 Comments

Spare a moment’s pity for the process engineer, whose job it is to keep industrial automation running no matter what. These poor souls seem to be forever on call, fielding panicked requests to come to the factory floor whenever the line goes down. Day or night, weekends, vacations, whatever — when it breaks, the process engineer jumps.

The pressures of such a gig can be enormous, and seem to have weighed on [Tom Goff] enough that he spent a weekend building a junk bin analog signal generator to replace a loop calibrator that he misplaced. Two process control signaling schemes were to be supported — the 0 to 10 VDC analog signal, and the venerable 4-20 mA current loop. All that’s needed for both outputs is an Arduino and an LM358 dual op-amp, plus a few support components. The 0-10 V signal starts as a PWM output from the Arduino, with its 0-5 V average amplified by one of the op-amps set up as a non-inverting amp with a gain of 2. With a little filtering, the voltage output is pretty stable, and swings nicely through the desired range — see the video below for that.

The current loop output is only slightly more complicated. An identical circuit on a separate Arduino output generates the same 10 V max output, but a code change limits the low end of the range to 1 V. This output of the op-amp is fed through a 500-Ω trimmer pot, and the magic of Ohm’s Law results in a 4-20 mA current. The circuit lives on a piece of perf board in a small enclosure and does the job it was built for — nothing fancy needed.

And spoiler alert: [Tom] found the missing loop calibrator — after he built this, of course. Isn’t that always the way?

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The Birdy44 Keyboard Is Something To Crow About

October 18, 2023 by 6 Comments

The funny thing about keyboard end game is that it usually involves more than one keyboard. Rare is the board that is great for both home and away. Having finished their dactyl build, [RalphCoder13] was looking to build something slimmer and more portable, and the Birdy44 was born.

This hand-wired beauty uses a pair of Waveshare RP2040 Zeros and features a pair of 40mm Cirque track pads that were salvaged from a Steam controller.

As you may have guessed, there are 44 Kailh Chocs that sit underneath a combination of MBK and 3D-printed keycaps. Our favorite part might be the tenting legs, which are optional and connect magnetically.

Part of portability is how you decide to carry the thing. You probably don’t want it naked and loose in your backpack if you can avoid it, right? To that end, he designed a nice little case for the halves. The original plan was to use magnets to hold them in place inside the topless case, but that didn’t work out so well, so he added wide elastic bands to stretch around the case.

Is this still not portable enough for you? Check out this folding split keyboard.

Via KBD