Variable-Nozzle Ducted Fan Provides Fluid Dynamics Lessons

October 19, 2023 by Bryan Cockfield 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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3D Printing A Carburetor Is Easier Than You Probably Think

May 11, 2022 by Al Williams 27 Comments

We’ve all been there. You see a cool gadget on the Internet to 3D print and you can’t wait to fire up the old printer. Then you realize it will take 8 different prints over a span of 60 hours, chemical post-processing, drilling, exotic hardware, and paint to get the final result. [Peter Holderith’s] carburetor design, however, looks super easy.

If you have experience with real-world carbs, you might wonder how that would work, but as [Peter] points out, carburetors are very simple at the core — nothing more than a venturi. All the extra pieces you think of are for special cases and not necessary for basic operation. We doubt, though, that you could really use the thing in its current form in your car. There are no mounts and since he printed it in PLA, it seems like a hot engine would be a bad idea. However, it does work well with water and an electric blower.

[Peter] mentions that with some more work and the right material, he has no doubt he could create a working practical carb. We think he’s right. But even in this form, it is a great educational project for a budding car enthusiast — like the old transparent V8 engine models, maybe.

Speaking of transparent, we’ve seen — or maybe not seen is a better phrase — a see-through carburetor that is also a good demonstrator. If you could perfect a 3D printed carb, it would make conversion projects a lot easier.

Printable Portable Mask Gives You The Numbers On Your Workout

January 16, 2022 by Dan Maloney 7 Comments

We’re currently in the midst of New Year’s Resolutions season, which means an abundance of spanking new treadmills and exercise bikes. And one thing becomes quickly obvious while using those machines: the instruments on them are, at best, only approximately useful for measuring things like your pulse rate, and in the case of estimating the calories burned by your workout, are sometimes wildly optimistic.

If precision quantification of your workout is your goal, you’ll need to monitor your “VO₂max”, a task for which this portable, printable mask is specifically designed. This is [Robert Werner]’s second stab at a design that senses both pressure differential and O₂ concentration to calculate the maximum rate of oxygen usage during exercise. This one uses a commercially available respirator, of the kind used for painting or pesticide application, as the foundation for the build. The respirator’s filter elements are removed from the inlets to provide free flow of air into the mask, while a 3D printed venturi tube is fitted to its exhaust port. The tube houses the pressure and O₂ sensors, as well as a LiPo battery pack and an ESP32. The microcontroller infers the volume of exhaled air from the pressure difference, measures its O₂ content, and calculates the VO₂ max, which is sent via Bluetooth to a smartphone running an exercise tracking app like Zwift or Strava.

[Robert] reports that his $100 instrument compares quite well to VO₂ max measurements taken with a $10,000 physiology lab setup, which is pretty impressive. The nice thing about the design of this mask is how portable it is, and how you can take your exercise routine out into the world — especially handy if your fancy exercise bike gets bricked.

A Tubular Fairy Tale You Control With Your Phone

January 6, 2021 by Kristina Panos 1 Comment

At first glance, this might appear to be a Rube Goldberg machine made of toys. The truth isn’t far off — it’s a remote-control animatronic story machine driven by its spectators and their phones. [Niklas Roy] and a team of volunteers built it in just two weeks for Phaenomenale, a festival centered around art and digital culture that takes place every other year.

A red ball travels through a network of clear acrylic tubes using 3D printed Venturi air movers, gravity, and toys to help it travel. Spectators can change the ball’s path with their phones via a local website with a big picture of the installation. The ball triggers animations along its path using break beam detection and weaves a different story each time depending on the toys it interacts with.

Here’s how it works: a Raspberry Pi 4 is responsible for releasing the ball at the beginning of the track and for controlling the track switches. The Pi also hosts a server for smartphones and the 25 Arduino Nanos that control the LEDs and servos of the animatronics. As a bonus animatronic, there’s a giant whiteboard that rotates and switches between displaying the kids’ drawings and the team’s plans and schematics. Take a brief but up-close tour after the break.

This awesome art project was a huge collaborative effort that involved the people of Wolfsburg, Germany — families in the community donated their used and abandoned toys, groups of elementary school kids were brought in to create stories for the toys, and several high school kids and other collaborators realized these drawings with animatronics.

Toys can teach valuable lessons, too. Take this body-positive sushi-snarfing Barbie for example, or this dollhouse of horrors designed to burn fire safety into children’s brains.

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A Crash Course In 3D Printed Venturi Pumps

February 8, 2019 by Tom Nardi 15 Comments

Venturi pumps, commonly referred to as aspirators, are a fantastic way of moving around things which you might not want spinning around inside of a pump, and one of the easiest ways to create a vacuum. According to his research, [Tuval Ben Dosa] believed such a device would be a good way to move corrosive gasses which would normally eat up a blower fan; all he had to do was figure out how to 3D print one to his specifications.

Put simply: if you take a “T” shaped pipe and pass a fluid (such as air or water) through the straight section, a vacuum will be created on the shorter side due to the Venturi effect. As long as you don’t mind the substance you wish to pump getting mixed into your working fluid, it’s a simple way to bring something “along for the ride” as the fluid makes its way through the pipe.

[Tuval] needed a way to remove the chlorine gasses produced by his PCB etching station, and an aspirator seemed like the perfect solution. He just needed to pump clean air through a Venturi, which would suck up the chlorine gas on the way through, and ultimately carry it outside. But he soon found that while a pump based on the Venturi effect is simple conceptually, getting it to work in the real world is a bit trickier. Especially when you’re dealing with something like 3D printing, which brings in its own unique challenges.

He tried modeling a few designs he found online in 3D and printing them out, but none of them worked as expected. The most common problem was simply that no vacuum was being generated, air was freely moving out of both sides. While [Tuval] doesn’t claim to have any great knowledge of fluid dynamics, he reasoned that the issue was due to the fact that most Venturi pumps seem designed to move water rather than air. So he designed a new version of the pump which had a more pronounced nozzle on the inlet surrounded by a cavity in which the gases could mix.

His modified design worked, and now anyone with a 3D printer can run off their own Venturi device for quickly and easily giving potentially harmful fumes or gases the boot. If this is one of those things you’d feel more comfortable buying than building, don’t worry, we’ve previously covered using a low-cost aspirator as a vacuum source in the home lab.

ERRF 18: New Products Make Their Debut

July 13, 2018 by Tom Nardi 6 Comments

While ostensibly the purpose of the recent East Coast RepRap Festival (ERRF) was to celebrate the 3D printing community and culture, it should come as no surprise that more than a few companies decided to use the event as an opportunity to publicly launch new products. Who can blame them? It’s not as if every day you have a captive audience of 3D printing aficionados; you might as well make the best of it.

Many creations were being shown off for the first time at ERRF, and we surely didn’t get a chance to see them all. There was simply too much going on at any given time to be sure no printed stone was left unturned. But the following printers, filaments, and accessories caught our attention long enough to warrant sharing with the good readers of Hackaday.

Keep in mind that much of this information is tentative at best, and things could easily change between now and when the products actually go on sale. These events serve as much as a sounding board for new products as they do a venue for advertising and selling them, so feedback received from show attendees may very well alter some of these products from what we saw at ERRF.

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