Prolific Videos Show Altair 8800 Recreation

January 2, 2020 by 24 Comments

The January 1975 issue of Popular Electronics introduced the Altair 8800 and hit the newsstands in December of 1974, so it is only natural that around the New Year people start thinking about the old computer. [Shadowtron] did more than think about it. He ordered some replica PCBs and is building a new one. Even better, he’s posted an amazing number of videos (up to number 56 as I write this) detailing his progress. You can find part 1, below.

The boards are from Trailing Edge Technology. There’s a backplane board (about $100) as well as a few boards to fit it available for about $30 each — unpopulated, of course.

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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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Diving With An Unlimited Air Supply

December 21, 2019 by 82 Comments

If you want to explore underwater, you have a few options. You can hold your breath. You can try to recycle your air. You can carry your breathing air with you as in SCUBA. You can stick a tube up like a snorkel, or you can have air sent down to you from the surface. EXOlung falls into this last category, but unlike many other surface solutions, it has a twist: it never runs out of power before you do. Watch the video below and you’ll see how it works.

A buoy puts a snorkel up out of the water, and a tube lets you dive up to 5 meters away. There’s a small tank on your chest, and your body’s motion serves to fill the tank from the outside air supply. As your legs extend and retract, you fill the tank and then put the tank’s air at ambient pressure so you can breathe. As a bonus, by varying how you inhale and exhale, you can control your buoyancy and, therefore, your depth.

The system does require you to strap your legs up to the apparatus. However, other similar systems have compressors or batteries which can fail or run down, meaning there can be a limit on how long you can stay under. EXOlung claims there is no limit to how long you can stay under.

The cost looks to be around 300 Euro, although for a bit more you can get one that uses different materials to withstand higher pressures. That one has a 7-meter hose.

Another approach is to just carry a little air and remove the CO2 from it and rebreathe it. We’ve also seen a risky surface air pump that uses wind power.

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See How Wildly Different Air Conditioners Can Be (On The Inside)

December 15, 2019 by 16 Comments

Air conditioners are easy to take for granted. From refrigerators to climate control, most of us would miss them dearly if they disappeared. That’s part of what draws [Josh Levine]’s interest in air conditioners, and he has provided an interesting tour of several different units and how different they can be, despite all working in basically the same way.

That white PCB is crucial (for running the bluetooth speaker and LED flashlight, that is.)

One way that air conditioners try to stand out is by being quiet, and the bulk of noise comes from the fans and the compressor. One unit (the Haier Serenity) aimed to be the quietest unit possible, but while this effort had mixed results at best it is still interesting to see [Josh] give a tour of the different ways they tried to reduce noise (YouTube, embedded below). Noise-limiting elements include the unusual step of using separate motors for the indoor and outdoor fans, and even little counterweights to ensure they are perfectly balanced, just like wheel weights on automobile tires.

Another notable air conditioner is the Zero Breeze, a portable unit that was the product of a Kickstarter campaign. Features included (either bizarrely or predictably, you be the judge) a bluetooth speaker and an LED flashlight. [Josh] more than half suspected the product would never actually ship, but was pleasantly surprised. Not only did it deliver, it turned out to be a pretty nice design with only a couple of mildly head scratching moments (YouTube, also embedded below).

There are a few more to check out in the roundup on [Josh]’s web site, which he also compares and contrasts with his own DIY unit which we featured in the past.

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WWII Aircraft Radio Roars To Life: What It Takes To Restore A Piece Of History

December 12, 2019 by 59 Comments

I’ve been told all my life about old-timey Army/Navy surplus stores where you could buy buckets of FT-243 crystals, radio gear, gas masks, and even a Jeep boxed-up in a big wooden crate. Sadly this is no longer the case. Today surplus stores only have contemporary Chinese-made boots, camping gear, and flashlights. They are bitterly disappointing except for one surplus store that I found while on vacation in the Adirondacks: Patriot of Lake George.

There I found a unicorn of historical significance; an un-modified-since-WW2 surplus CBY-46104 receiver with dynamotor. The date of manufacture was early-war, February 1942. This thing was preserved as good as the day it was removed from its F4F Hellcat. No ham has ever laid a soldering iron or a drill bit to it. Could this unit have seen some action in the south Pacific? Imagine the stories it could tell!

My unconventional restoration of this radio followed strict rules so as to minimize the evidence of repair both inside and out yet make this radio perform again as though it came fresh off the assembly line. Let’s see how I did.

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US Air Force Says They’re Developing An Open Source Jet Engine; We Say Show Us The Design

November 27, 2019 by 46 Comments

The economies of scale generally dictate that anything produced in large enough numbers will eventually become cheap. But despite the fact that a few thousand of them are tearing across the sky above our heads at any given moment, turbine jet engines are still expensive to produce compared to other forms of propulsion. The United States Air Force Research Laboratory is hoping to change that by developing their own in-house, open source turbine engine that they believe could reduce costs by as much as 75%.

The Responsive Open Source Engine (ROSE) is designed to be cheap enough that it can be disposable, which has obvious military applications for the Air Force such as small jet-powered drones or even missiles. But even for the pacifists in the audience, it’s hard not to get excited about the idea of a low-cost open source turbine. Obviously an engine this small would have limited use to commercial aviation, but hackers and makers have always been obsessed with small jet engines, and getting one fired up and self-sustaining has traditionally been something of a badge of honor.

Since ROSE has been developed in-house by the Air Force, they have complete ownership of the engine’s intellectual property. This allows them to license the design to manufacturers for actual production rather than buying an existing engine from a single manufacturer and paying whatever their asking price is. The Air Force will be able to shop ROSE around to potential venders and get the best price for fabrication. Depending on how complex the engine is to manufacture, even smaller firms could get in on the action. The hope is that this competition will serve to not only improve the design, but also to keep costs down.

We know what you’re thinking. Where is the design, and what license is it released under? Unfortunately, that aspect of ROSE seems unclear. The engine is still in development so the Air Force isn’t ready to show off the design. But even when it’s complete, we’re fairly skeptical about who will actually have access to it. Open Source is in the name of the project and to live up to that the design needs to be available to the general public. From a purely tactical standpoint keeping the design of a cheap and reliable jet engine away from potential enemy states would seem to be a logical precaution, but is at cross purposes to what Open Source means. Don’t expect to be seeing it on GitHub anytime soon. Nuclear reactors are still fair game, though.

[Thanks to Polymath99 for the tip.]

Bamboo Skewers Launch Airship

November 19, 2019 by 1 Comment

We have to admit, we like airships. There’s something about the image of a stately zeppelin floating over Manhattan that just makes us imagine the future. There are not many airships anymore, but you can always build your own. [Crafty Robot] shows how to use one of their boards to make a simple and easy controlled balloon. Honestly, they don’t give you many details, but we know how to turn motors and servos. We loved their construction with hot glue and bamboo. Effective, and fun to say.

The bamboo skewers are easy to find and make a lightweight frame. Some drone motors provide thrust and some simple RC servos control the angle of the props. Nice and simple.

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