Watch The Diesel Effect In Ballistic Gelatin

October 13, 2016 by Donald Papp 41 Comments

A striking video appears to demonstrate an explosion via the diesel effect in clear ballistic gel. The diesel effect or “dieseling” refers to when a substance ignites from the effects of pressure, and it’s the operating principle behind the gadgets known as Fire Sticks or Fire Pistons.

Ballistic gel is a broad term referring to a large chunk of dense gel generally used in firearms-related testing to reliably and consistently measure things like bullet deformation, fragmentation, and impact. It’s tough, elastic, and in many ways resembles a gigantic gummi bear. Fans of Mythbusters (or certain DIY railguns) will recognize the stuff. Water-based blocks made with natural gelatin can be easily made at home, but end up with a yellow-brown color and have a limited shelf life due to evaporation. Clear blocks exist that are oil-based and don’t dry out like the water-based ones. It’s one of these that is in the embedded animation below.

Slow motion video capture is a natural companion to just about anything that you’d need ballistic gel for, and good thing — because the video captured what appears to be a diesel effect! The block is hit with a bullet, and as the bullet rapidly expands and dumps its energy into the gel, a cavity expands rapidly. During this process, some of the (oil-based) material in the cavity has been vaporized. After the expanded bullet exits (to the right of the gif above but easier to see in the video below), the cavity in the block begins to collapse. The resulting pressure increase appears to ignite the vaporized material, which explodes with a flash followed by some exhaust.

This effect has been observed in ballistic gel before, but this video shows a particularly clear ignition, followed by a secondary expansion of the cavity, then a flatulent-ish ejection of exhaust as the cavity collapses. If nothing else, it’s a very striking effect clearly captured on film. Slow-motion capture of destructive forces makes visible many things that would otherwise happen too quickly to perceive.

Continue reading “Watch The Diesel Effect In Ballistic Gelatin” →

An Easy Home Made Electroadhesive

October 12, 2016 by Jenny List 16 Comments

There was a time when if you wanted to scale a wall you had to turn a camera on its side and call [Adam West] or [Lionel Ritchie]. Unless you were a gecko, that is. Their host of tiny bristles and intramolecular forces allow them to run up walls and across the ceiling with ease.

You may have seen synthetic gecko-like adhesive surfaces using the same effect. Some impressive wall-climbing robots have used these materials, though they’ve all shared the same problem. Gecko adhesion can’t be turned off. Happily, for the robot wall climber unwilling to expend the extra force to detach a foot there is an alternative approach. Electroadhesives use electrostatic force to attach a plate held at a high potential to a surface, and today’s featured video is [Carter Hurd]’s home-made electroadhesive panel (YouTube).

He cites this paper and this description of the technology as the influences on his design, two aluminium foil electrodes sandwiched between plastic sheet and sticky tape. He applies 6kV from an Emco DC to DC converter to his plates, and as if by magic it sticks to his drywall. Of course, it’s not quite as simple as that, he tried several surfaces before finding the one it stuck to. Adhesion is fully under control, and such a simple device performs surprisingly well. The Emco converters are sadly not cheap, but they are an extremely efficient product for which he only needs a few AA cells on the low voltage side.

His full description is in the video below the break.

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Peculiar Fluid Dynamics Creates Hot And Cold Air

October 11, 2016 by Dan Maloney 61 Comments

We’re fascinated by things with no moving parts or active components that work simply by virtue of the shape they contain — think waveguides and resonators for microwave radiation. A similarly mystical device from the pneumatics world is the Hilsch Vortex Tube, and [This Old Tony] decided to explore its mysteries by whipping up a DIY version in his shop.

Invented in the 1930s, vortex tubes are really just hollow tubes with an offset swirl chamber. Incoming compressed air accelerates in the swirl chamber and heads up the periphery of the long end of the tube, gaining energy until it hits a conical nozzle. Some of the outer vortex escapes as hot air, while the rest reflects off the nozzle and heads back down the pipe as a second vortex inside the outer one. The inner vortex loses energy and escapes from the short end as a blast of cold air – down to -50°C in some cases. [Tony]’s build doesn’t quite approach that performance, but he does manage to prove the principle while getting a few good-natured jabs into fellow vloggers [AvE] and [Abom79].

We’ve covered vortex tubes before, but as usual [Tony]’s build shines because he machines everything himself, and because he tries to understand what’s making it work. The FLIR images and the great video quality are a bonus, too.

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The Collatz-O-Matic: A State Machine With Style!

October 10, 2016 by Donald Papp 2 Comments

If you have ever thought that working out a Collatz sequence by hand was alright but lacked buttons and lights, the Collatz-o-matic by [mechatronicsguy] has you covered!

The device is a type of Tag system calculator. [mechatronicsguy] explains that a Tag system is a method of computing similar to a Turing machine; it consists of a read & write FIFO array (or tape or queue) of indeterminate length, and at every step the system reads the symbol at the “head”, deletes a fixed number of symbols from the “head”, and depending on what that first symbol was, appends one or more symbols to the “tail”. Then the process repeats with whatever new symbol is at the head.

The Collatz-o-Matic uses an RGB LED string to represent the queue, and is set up in the following way:

Delete two symbols (tags) from the front of the queue.
If the first symbol deleted was:
1. A – then write BC to the rear of the queue
2. B – then write A to the rear of the queue
3. C – then write AAA to the rear of the queue

Numbers are as easily represented as any other symbol, and the Collatz conjecture is that no matter what integer you start with, the system (probably) always eventually reaches state 1. There is video of the device demonstrating exactly that embedded below. Continue reading “The Collatz-O-Matic: A State Machine With Style!” →

Two Words That Don’t Mean What You Think They Do

October 9, 2016 by Elliot Williams 23 Comments

When you hear “gravity waves” or “sprites”, you’d think you would know what is being discussed. After all, those ripples in space-time that Einstein predicted would emanate from twin, colliding, black holes were recently observed to much fanfare. And who doesn’t love early 8-bit computer animations? So when we were browsing over at SpaceWeather we were shocked to find that we were wrong twice, in one photo (on the right). Continue reading “Two Words That Don’t Mean What You Think They Do” →

NASA Knows Where The Meteors Are

October 8, 2016 by Elliot Williams 30 Comments

NASA has been tracking bright meteoroids (“fireballs”) using a distributed network of video cameras pointed upwards. And while we usually think of NASA in the context of multi-bazillion dollar rocket ships, but this operation is clearly shoe-string. This is a hack worthy of Hackaday.

The basic idea is that with many wide-angle video cameras capturing the night sky, and a little bit of image processing, identifying meteoroids in the night sky should be fairly easy. When enough cameras capture the same meteoroid, one can use triangulation to back out the path of the meteoroid in 3D, estimate its mass, and more. It’s surprising how many there are to see on any given night.

You can watch the videos of a meteoroid event from any camera, watch the cameras live, and even download the meteoroid’s orbital parameters. We’re bookmarking this website for the next big meteor shower.

The work is apparently based on [Rob Weryk]’s ASGARD system, for which the code is unfortunately unavailable. But it shouldn’t be all that hard to hack something together with a single-board computer, camera, and OpenCV. NASA’s project is limited to the US so far, but we wonder how much more data could be collected with a network of cameras all over the globe. So which ones of you are going to take up our challenge? Build your own version and let us know about it!

Between this project and the Radio Meteor Zoo, we’re surprised at how much public information there is out there about the rocky balls of fire that rain down on us every night, and will eventually be responsible for our extinction. At least we can be sure we’ll get it on film.

Feel Better About Yourself With These Ugly Repairs

October 7, 2016 by Gerrit Coetzee 50 Comments

A fun thread over at the EEVblog forum starts off with [TerraHertz]’s triangle-peg, square-hole capacitor repair job and goes entertainingly down-hill from there.

Everything from horrifying eBay purchases to work (horror) stories can be found in this thread. But you can learn something too. Did you know the correct way to fix a mercury switch stored in the incorrect orientation is to whack it against a table really hard?

We enjoyed the cigarette box shroud used to fix a graphics card with a defective fan. We’re still not sure about the person who managed to Dremel bits off a graphics card and end up with a working PCI-e card. That one may be a troll.

Regardless, it’s a lot of fun, spanning the hilariously bad and the seriously impressive. We would not be surprised if some of these people met the devil at the crossroads for some soldering skill. Do any of you have an interesting or ugly repair to share? We’d love to see it.