A quick brush over the part with some sand paper and it quickly transforms from obviously plastic to metallic.

Learn Resin Casting Techniques: Cold Casting

July 14, 2016 by Gerrit Coetzee 36 Comments

Sometimes we need the look, feel, and weight of a metal part in a project, but not the metal itself. Maybe you’re going for that retro look. Maybe you’re restoring an old radio and you have one brass piece but not another. It’s possible to get a very metal like part without all of the expense and heat required in casting or the long hours in the metal fabrication shop.

Before investing in the materials for cold casting, it’s best to have practical expectations. A cold cast part will not take a high polish very well, but for brushed and satin it can be nearly indistinguishable from a cast part. The cold cast part will have a metal weight to it, but it clinks like ceramic. It will feel cool and transfers heat fairly well, but I don’t have numbers for you. Parts made with brass, copper, and iron dust will patina accordingly. If you want them to hold a bright shine they will need to be treated with shellac or an equivalent coating afterward; luckily the thermoset resins are usually pretty inert so any coating used on metal for the same purpose will do.

It is best to think of the material as behaving more or less like a glass filled nylon such as the kind used for the casing of a power tool. It will be stiff. It will flex a relatively short distance before crazing and then cracking at the stress points. It will be significantly stronger than a 3D printed part, weaker than a pure resin part, and depending on the metal; weaker than the metal it is meant to imitate.

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A Drone Photosphere Is Worth 4000 Times Pi Words

July 14, 2016 by Al Williams 13 Comments

One of the problems with a cheap drone is getting good video, especially in real time. Cheap hobby quadcopters often have a camera built-in or mounted in a fixed position. That’s great for fun shots, but it makes it hard to get just the right shot, especially as the drone tilts up and down, taking the camera with it. Pricey drones often have a gimbal mount to keep the camera stable, but you are still only looking in one direction.

Some cheap drones now have a VR (virtual reality) mode to feed signal to a headset or a Google Cardboard-like VR setup. That’s hard to fly, though, because you can’t really look around without moving the drone to match. You can mount multiple cameras, but now you’ve added weight and power drain to your drone.

MAGnet Systems wants to change all that with a lightweight spherical camera made to fit on a flying vehicle. The camera is under 2.5 inches square, weighs 62 grams, and draws less than 3 watts at 12 volts. It picks up a sphere that is 360 degrees around the drone’s front and back and 240 degrees centered directly under the drone. That allows a view of 30 degrees above the horizon as well as directly under the drone. There is apparently a different lens that can provide 280 degrees if you need that, although apparently that will add size and weight and be more suitable for use on the ground.

The software (see video below) runs on Windows or Android (they’ve promised an iOS version) and there’s no additional image processing hardware needed. The camera can also drive common VR headsets.

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Riding Shotgun In The Apollo 12 Lunar Lander

July 14, 2016 by Gregory L. Charvat 8 Comments

Last week we had a walk through of the Lunar Module’s source code with Don Eyles, who wrote the landing programs. Now you can take a rather thrilling ride to see Don’s code in action.

Below is an annotated video of the Apollo 12 landing, in real-time. It’s worth setting aside a quarter-hour to check it out. In an age where everyone is carrying around an HD (or way better) camera in their pocket, following along with radio broadcasts, still images, and small slivers of video might not sound that awesome. But it is!

The video takes us from Powered Descent Initiation through touchdown on the Moon with Pete Conrad and Alan Bean. As the audio plays out the video has annotations which explain what is going on and that translate the jargon used by the team. With the recently celebrated push to publish the source code you can even follow along as the video displays which program is running at that time. Just search for the program code and you’ll find it, like this screenshot of the P63 routine. The code comments are more than enough to get the gist of it all.