Weaponized Fidget Spinners

Fidget spinners were the hottest new craze at one point, but their 15 minutes of fame has well and truly passed. They’re great for fidgeting, and not a whole lot else. One of the main objectives around their use is to spin them as quickly as possible. After [Sushi Ramen] hurt himself after spinning one up with compressed air, however – a new and dangerous idea came to mind.

What you’re looking at is a fidget spinner sword, powered by compressed air. That alone is somewhat of a blessing, as it prevents this horrifying device from being easily man-portable. Through a breakneck build montage, we see almost fifty fidget spinners (in hyperchrome, no less) mounted to a shaft. The shaft is then attached to a hilt and a plastic line is artfully bent up to deliver compressed air at the pull of a trigger, causing the fidget spinners to rotate at moderate speed.

It’s true that the fidget spinners don’t receive a whole lot of torque from the compressed air and thus most of the damage is done purely by swinging the presumably quite heavy device at fragile glass objects. That said, with nothing ventured, nothing is gained, and we’re always glad to see research and development continuing in the fidget spinner space.

Looking for more effective ways to spin, and spin quickly? Check out this brushless motor setup. Video after the break.

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Their Battery is Full of Air

Storing electrical energy is a huge problem. A lot of gear we use every day use some form of battery and despite a few false starts at fuel cells, that isn’t likely to change any time soon. However, batteries or other forms of storage are important in many alternate energy schemes. Solar cells don’t produce when it is dark. Windmills only produce when the wind blows. So you need a way to store excess energy to use for the periods when you aren’t creating electricity. [Kris De Decker] has an interesting proposal: store energy using compressed air.

Compressed air storage is not a new idea. On a large scale, there have been examples of air compressed in underground caverns and then released to run a turbine at a future date. However, the efficiency of this is poor — around 40 to 50 percent — mainly because the air heats up during compression and often needs to be prewarmed (using energy from another source) prior to decompression to prevent freezing. By comparison, batteries can be 70 to 90 percent efficient, although they have their own problems, too.

The idea explored in this paper is not to try to store a power plant’s worth of energy in a giant underground cavern, but rather use smaller compressed air setups like you would use batteries to store power at the point of consumption. The technology is called micro-CAES (an acronym for compressed air energy storage).

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Cams and Pushrods Improve 3D-Printed Compressed Air Engine

Some folks just can’t leave well enough alone, and that often ends up being a good thing. Such is the case with this 3D-printed compressed air engine, which just keeps getting better.

The design has changed a lot since we first covered [Tom Stanton]’s attempts at reviving the powerplant from the glory days of the Air Hogs line of toys, which he subsequently built a plane around. The engine was simple, with a ball valve that admitted air into the cylinder when a spring mounted to the top of the piston popped it out of the way. That spring has always bothered [Tom], though, compelling him to go back to the drawing board. He wanted to replace the ball valve with one actuated by a cam and pushrod. This would increase the complexity of the engine quite a bit, but with the benefit of eliminating the fail point of the spring. With a few iterations in the design, he was able to relocate the ball valve, add a cam to the crankshaft, and use a pushrod to open the valve. The new design works much better than the previous version, sounding more like a lawnmower than a 3D-printed engine should. Check out the design process and some tests in the video below.

And speaking of lawnmowers that run on compressed air

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3D Printed Airplane Engine Runs on Air

One of the most important considerations when flying remote-controlled airplanes is weight. Especially if the airplane has a motor, this has a huge potential impact on weight. For this reason, [gzumwalt] embarked on his own self-imposed challenge to build an engine with the smallest weight and the lowest parts count possible, and came away with a 25-gram, 8-part engine.

The engine is based around a single piston and runs on compressed air. The reduced parts count is a result of using the propeller axle as a key component in the engine itself. There are flat surfaces on the engine end of the axle which allow it to act as a valve and control its own timing. [gzumwalt] notes that this particular engine was more of a thought experiment and might not actually produce enough thrust to run an airplane, but that it certainly will spark up some conversations among RC enthusiasts.

The build is also one of the first designs in what [gzumwalt] hopes will be a series of ever-improving engine designs. Perhaps he should join forces with this other air-powered design that we’ve just recently featured. Who else is working on air-powered planes? Who knew that this was a thing?

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Wield The Power of Molten Metal

[TheBackyardScientist] at it again with another super villain-esque demonstration of gadgetry: a liquid metal squirt gun.

The squirt gun has a compressed air tank like most others — more on that later — but to fire its primary ammunition, a nozzle that connects directly to an air compressor is needed. Again, like most guns of this nature, air is forced into the gun’s reservoir, displacing the pewter and expelling it out the gun’s barrel. Yes, pewter.

Working around the heat tolerances of thread seal tape, pewter has a low enough melting point that an airtight system is preserved — plus it’s really cool to fire a stream of liquid metal. The ammunition is made from pewter ware melted down and cast into pucks. These pucks are stacked into the gun’s magazine, melted with a propane torch and carefully loaded into the gun.

The built-in compressed air tank lacks the oomph to push out the pewter — hence the air compressor, but any lighter liquids or condiments are fair game for rapid-fire exercises. Yes, condiments.

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DIY Air Cannon Snags Drones from the Sky

Who hasn’t had the experience of a pesky drone buzzing around that family picnic, or hovering over a suburban backyard where bikini-clad daughters are trying to sunbathe in peace? A shotgun used to suffice for such occasions, but with this compressed-air powered drone catcher, there’s no need to worry about illegally discharging a firearm to secure some privacy.

Before the comment line lights up with outrage, the above scenarios are presented entirely in jest. We do not condone the use of force on a drone, nor do we look favorably on those who use drones in a way that even hints at an invasion of privacy. We can all get along, and even though we hope [Make It Extreme]’s anti-drone gun will never be used in anger, it’s still a neat build that gives us lots of ideas. The rig is essentially four coaxial narrow-bore compressed-air cannons, each launching a slug attached to the corner of a lightweight net. A fairly complex set of linkages sets the spread of the barrels, and a pair of old oxygen tanks serve as reservoirs for the compressed air. A fast-acting dump valve is tripped by an interesting trigger mechanism mounted to a complicated stock and grip; we’d have liked to see more on the fabrication of that bit. The video below shows a test firing that results in a clean takedown of a drone, although we doubt the owner of the quad would characterize it as such.

This build is a bit of a departure from [Make It Extreme]’s usual fare of DIY tools like a shop-built vise or big belt sander, or their unusual vehicles like an off-road hoverboard. But it’s always great to watch a good fabrication video, no matter what the subject.

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Launch Pad for Air-Water Rockets is Good Clean Fun for STEM Students

We have fond memories of air-water rockets, which were always a dime store purchase for summertime fun in the pool. Despite strict guidance from mom to shoot them only straight up, the first target was invariably a brother or friend on the other side of the pool. No eyes were lost, and it was good clean fun that was mercifully free of educational value during summer break.

But now a teacher has gone and ruined all that by making an air-water rocket launching pad for his STEM students. Just kidding — [Robert Hart] must be the coolest teacher in Australia when Friday launch days roll around. [Mr. Hart] wanted a quick and easy way to safely launch air-water rockets and came up with a pretty clever system. The core task is to pump air into the partially filled water bottle and then release it cleanly. [Robert] uses quick-disconnect fittings, with the female coupling rigged to a motor through a bicycle brake cable. The control box has a compressor, the release motor, and a wireless alarm remote, all powered by a 12-volt battery. With the male coupling glued to the cap of a bottle acting as a nozzle and a quick, clean release, flights are pretty spectacular.

There are many ways to launch an air-water rocket, from the simple to the complex. [Robert]’s build leans toward the complex, but looks robust enough for repeated use and makes the launch process routine so the kids can concentrate on the aerodynamics. Or to just enjoy being outdoors and watching things fly.

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