air bearing

5 Articles

A hexagonal brass enclosure surrounds an aluminium fan with three blades. The fan has an integrated outer rim with a series of small holes around the rim.

Building A Rim-Driven Jet Engine

April 19, 2026 by 17 Comments

Rim-driven thrusters turn the normal propeller-motor arrangement inside out; rather than mounting the motor at the center of the propeller, they use a large hollow motor, with the blades attached to the inside of the rotor. They’re mostly used in ship propellers, though there have been some suggestions to use them in electric aircraft. [Integza], always looking for new and unusual ways to create propulsion, took this idea and made it into a jet engine.

Rather than using an electric motor, the fan in this design is propelled by miniature rocket nozzles along the edge. The fan levitates on a layer of high-pressure gas between the fan rim and the housing. To prevent too much pressurized gas from escaping, the fan and housing needed to fit together closely, but with minimal friction. A prototype made out of acrylic and resin and powered by compressed air proved that the idea worked, but [Integza] wanted to make to this a combustion-powered engine.

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DIY Air Bearings, No Machining Required

October 20, 2024 by 26 Comments

Seeing a heavy load slide around on nearly frictionless air bearings is pretty cool; it’s a little like how the puck levitates on an air hockey table. Commercial air bearings are available, of course, but when you can build these open-source air bearings, why bother buying?

One of the nice things about [Diffraction Limited]’s design is that these bearings can be built using only simple tools. No machining is needed past what can be easily accomplished with a hand drill, thanks to some clever 3D-printed jigs that allow you to drill holes with precision into stainless steel discs you can buy on the cheap. An extremely flat surface is added to the underside of these discs thanks to another jig, some JB Weld epoxy, and a sheet of float glass to serve as an ultra-flat reference. Yet more jigs make it easy to scribe air channels into the flat surface and connect them to the air holes through a bit of plaster of Paris, which acts as a flow restriction. The video below shows the whole process and a demo of the bearings in action.

[Diffraction Limited] mentions a few applications for these air bearings, but the one that interests us most is their potential use in linear bearings; a big CNC cutter using these air bearings would be pretty cool. We seen similar budget-friendly DIY air bearings before, including a set made from used graphite EDM electrodes.

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Turning A CMM Into A 3D Printer

January 6, 2021 by 47 Comments

There are two paths to owning a 3D printer: purchasing one or crafting your own 3D printer designed to your own exacting specifications. [Roetz 4.0] has decided to go this latter route and converted a 1.3-ton air-bearing Coordinate-measuring machine (CMM) into an FDM 3D printer. (Video, embedded below.)

A CMM is a tool used to precisely measure the geometry of an object via gently lowering a calibrated probe. We’ve seen scratch build printers before, but this particular build benefits from having the CMM machinery and its 18 air bearings. The CMM head is moved by [Roetz 4.0]’s own custom system, but it takes advantage of the bearings. After some careful CAD planning as well as a fair bit of milling, lathing, and prototyping, he had buttery smooth controlled motion.

With an off the shelf driver board wired together with a large red button, he was ready for a maiden test print. A determination to finish before the year was out pushed things along. There are still a few quirks to fix, like the hole in the air drying system but those can be tackled next year. Ultimately, we think the results are stunning and it was a journey we were glad to go on with [Roetz 4.0]. The final episode of the series is after the break.

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[Ben Krasnow]’s Take On DIY Air Bearings

December 28, 2019 by 6 Comments

We’ve got to admit that watching [Ben Krasnow]’s new video on air bearings is tough. We found our eyes constantly checking the spherical air bearing in the foreground, which for the first eight minutes of the video just kept going. It was strangely hypnotic, and made it hard to concentrate on all the other cool stuff [Ben] was up to.

If the topic of air bearings seems familiar, it might be because we recently reported on DIY air bearings made from used EDM electrodes. [Ben] saw that too, and dusted off his old air bearing project. Literally, as it turns out, because the graphite blocks whose porosity and softness make them the perfect material for air bearings also makes for a dusty workshop. We’d recommend breathing protection of some sort while machining graphite. In addition to simple puck bearings, [Ben] came up with more complicated designs, including the aforementioned spherical bearing. He used the steel ball itself as a precision tool to grind the graphite out, first by coating it with abrasive and then by cutting grooves in it to act like a file. A cylindrical bearing was also cut, this time with sandpaper glued directly to the ground steel rod that would seat in the bearing.

[Ben]’s other innovation is vacuum preloading, where he applies both vacuum and pressure to the bearing plenum. The vacuum provides the force needed to capture the moving element while the pressure bears the load. It’s a careful balancing act, but it works well enough to capture the large steel ball and keep it turning effortlessly.

We really liked [Ben]’s take on air bearings, especially his thoughts on creating fully enclosed cylindrical bearings. Those could be useful for low-friction linear drives, and we look forward to seeing more on those.

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Used EDM Electrodes Repurposed As Air Bearings For Precision Machine Tools

November 18, 2019 by 14 Comments

If you’ve ever played air hockey, you know how the tiny jets of air shooting up from the pinholes in the playing surface reduce friction with the puck. But what if you turned that upside down? What if the puck had holes that shot the air downward? We’re not sure how the gameplay would be on such an inverse air hockey table, but [Dave Preiss] has made DIY air bearings from such a setup, and they’re pretty impressive.

Air bearings are often found in ultra-precision machine tools where nanometer-scale positioning is needed. Such gear is often breathtakingly expensive, but [Dave]’s version of the bearings used in these machines are surprisingly cheap. The working surfaces are made from slugs of porous graphite, originally used as electrodes for electrical discharge machining (EDM). The material is easily flattened with abrasives against a reference granite plate, after which it’s pressed into a 3D-printed plastic plenum. The plenum accepts a fitting for compressed air, which wends its way out the micron-sized pores in the graphite and supports the load on a thin cushion of air. In addition to puck-style planar bearings, [Dave] tried his hand at a rotary bearing, arguably more useful to precision machine tool builds. That proved to be a bit more challenging, but the video below shows that he was able to get it working pretty well.

We really enjoyed learning about air bearings from [Dave]’s experiments, and we look forward to seeing them put to use. Perhaps it will be in something like the micron-precision lathe we featured recently.

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