Diaphragm Air Engine

One of the tricky parts of engineering in the physical world is making machines work with the available resources and manufacturing technologies. [Tom Stanton] has designed and made a couple of air-powered 3D printed engines but always struggled with the problem of air leaking past the 3D-printed pistons. Instead of trying to make an air-tight piston, he added a rubber membrane and a clever valve system to create a diaphragm air engine.

This GIF is worth 115 words

A round rubber diaphragm with a hole in the center creates a seal with the piston at the top of its stroke. A brass sleeve and pin protrude through the diaphragm, and the sleeve seals create a plug with an o-ring, while the pin pushes open a ball which acts as the inlet valve to pressurize an intermediate chamber. As the piston retracts, the ball closes the inlet valve, the outlet valve of the intermediate chamber is opened, forcing the diaphragm to push against the piston. The seal between the piston and diaphragm holds until the piston reaches its bottom position, where the pressurized air is vented past the piston and out through the gearbox. For full details see the video after the break.

It took a few iterations to get the engine to run. The volume of the intermediate chamber had to increase and [Tom] had to try a few different combinations of the sleeve and pin lengths to get the inlet timing right. Since he wanted to use the motor on a plane, he compared the thrust of the latest design with that of the previous version. The latest design improved efficiency by 366%. We look forward to seeing it fly! Continue reading “Diaphragm Air Engine”

Autonomous Sentry Gun Packs A Punch And A Ton Of Build Tips

What has dual compressed-air cannons, 500 roll-on deodorant balls, and a machine-learning brain with a bad attitude? We didn’t know either, until [Leo Fernekes] dropped this video on his autonomous robot sentry gun and saw it in action for ourselves.

Now, we’ve seen tons of sentry guns on these pages before, shooting everything from water to various forms of Nerf. And plenty of those builds have used some form of machine vision to aim the gun onto the target. So while it might appear that [Leo]’s plowing old ground here, this build is chock full of interesting tips and tricks.

It started when [Leo] saw a video on TensorFlow basics from our friend [Edje Electronics], which gave him the boost needed to jump into an AI project. The controller he ended up with looks for humans in the scene and slews the turret onto target, where the air cannons can do their thing. The hefty ammo is propelled by compressed air, which is dumped into the chamber using a solenoid valve with an interesting driver that maximizes the speed at which it opens. Style points go to the bacteriophage T4-inspired design, and to the sequence starting at 1:34 which reminded us of the factory scene from RoboCop.

[Leo] really put a ton of work into this project, and the results show. He is hoping to get an art gallery or museum to show it as an interactive piece to comment on one possible robot-human future, presumably after getting guests to sign a release. Whatever happens to it, the robot looks great and [Leo] learned a lot from it, as did we.

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Used Soda Stream Cylinder Becomes DIY Canned Air

Soda Stream machines use a cylinder of compressed CO2 to carbonate beverages, and cylinders that are “empty” for the machine’s purposes in fact still have a small amount of gas left in them. User [Graldur] shared a clever design for using up those last gasps from a cylinder by turning it into a makeshift compressed air gun, the kind that can blow crumbs or dust out of inconvenient spots like the inside of a keyboard. It’s 3D printed in PETG with a single seal printed in Ninjaflex.

[Graldur]’s 3D printed assembly screws onto the top of an “empty” cylinder and when the bottom ring is depressed like a trigger, the valve is opened slightly and the escaping gas is diverted through a narrow hole in the front. As a result, it can be used just as you would a can of compressed air. The gas outlet even accommodates the narrow plastic tubes from WD-40 cans (or disposable compressed air cans, for that matter) if more precision is required.

The design is intended for use with nearly-empty cylinders, but even so, [Graldur] also points out that it has been designed such that it can never fully actuate the cylinder’s release valve no matter how hard one presses, so don’t modify things carelessly. We also notice the design keeps the user’s hand and fingers well away from the business end of things.

This device also reminds of somewhat of a past experiment which used 3D printing to create serviceable (albeit low pressure) 3D printed compressed air tanks in custom shapes.

Get Compressed Air From Falling Water With The Trompe

If you’re like us, understanding the processes and methods of the early Industrial Revolution involved some hand waving. Take the blast furnace, which relies on a steady supply of compressed air to stoke the fire and supply the oxygen needed to smelt iron from ore. How exactly was air compressed before electricity? We assumed it would have been from a set of bellows powered by a water wheel, and of course that method was used, but it turns out there’s another way to get compressed air from water: the trompe.

As [Grady] from Practical Engineering explains in the short video below, the trompe was a clever device used to create a steady supply of high-pressure compressed air. To demonstrate the process, he breaks out his seemingly inexhaustible supply of clear acrylic piping to build a small trompe. The idea is to use water falling around a series of tubes to create a partial vacuum and entrain air bubbles. The bubbles are pulled down a vertical tube by the turbulence of the water, and then enter a horizontal section where the flow evens out. The bubbles rise to the top of the horizontal tube where they are tapped off by another vertical tube, as the degassed water continues into a second vertical section, the height of which determines the pressure of the stored air. It’s ingenious, requiring no power and no moving parts, and scales up well – [Grady] relates a story about one trompe that provided compressed air commercially for mines in Canada.

Need an electricity-free way to pump water instead of air? Check out this hydraulic ram pump that takes its power from the water it pumps.

Continue reading “Get Compressed Air From Falling Water With The Trompe”

Unconventional Drone Uses Gas Thrusters For Control

You’ve got to hand it to [Tom Stanton] – he really thinks outside the box. And potentially outside the atmosphere, to wit: we present his reaction control gas thruster-controlled drone.

Before anyone gets too excited, [Tom] isn’t building drones for use in a vacuum, although we can certainly see a use case for such devices. This is more of a hybrid affair, with counter-rotating props mounted in a centrally located duct providing the lift and the yaw control. Flanking that is a triangular frame supporting three two-liter soda bottle air reservoirs, each of which supplies a down-firing nozzle at each apex of the triangle. Solenoid valves control the flow of compressed air from the bottles to the nozzles, providing thrust to stabilize the roll and pitch axes. As there aren’t many off-the-shelf flight control systems set up for reaction control, [Tom] had to improvise thruster control; an Arduino watches the throttle signals normally sent to a drone’s motors and fires the solenoids when they get to a preset threshold. It took some tuning, but [Tom] was eventually able to get a stable, untethered hover. And he’s right – the RCS jets do sound amazing when they’re firing, as long as the main motors are off.

This looks as though it has a lot of potential, and we’d love to see it developed more. It reminds us a bit of this ducted-prop drone, another great example of stretching conventional drone control concepts to the limit.

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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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