Retrotechtacular: Fluid Coupling


We realize the transmission fluid of an automobile’s automatic transmission is used to transfer the power from the engine to the drive shaft. But after watching this Department of Defense video from 1954 we now have a full understanding of the principles involved in fluid coupling. Like us, you probably have seen a diagram of a transmission which shows the fan-like blades that are affected by the moving fluid. But it’s worth watching the 12-minute clip after the break to understand how that liquid is moving and why that matters so much in the design. The motion of the rotors, along with the design of the enclosure, causes the fluid to move in a continual corkscrew —  the shape of slinky whose ends have been attached to each other. This type of illustration leads to an intuitive understanding of how it’s possible to facilitate an efficient power transfer using a liquid.

Check out some of the comments left in the Reddit thread regarding this film. We agree with [Runxctry]; there’s something about the format of the presentation that makes these informative and engaging to an almost addictive level. But maybe it’s just the engineering geek deep inside that’s cause these feelings?

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Ice record single needs six hours in the deep freeze before you can listen


This delightful marketing ploy requires the listener to fabricate their own record out of ice. The band Shout Out Louds wanted to make a splash with their newest single. So they figured out how to make a playable record out of ice. The main problem with this is the grooves start to degrade immediately when the ice begins to melt. So they shipped a mold of the record and a bottle of water to a select few listeners (just ten in all). Hear the result in the video after the break.

Now if you want to make something like this for yourself we can help you out just a bit. The mold is made of silicone and it wasn’t so long ago that we saw a guide for those new to mold making. The raw material isn’t that hard to find either. The project above tried several different approaches and found the best results can be attained with plain old distilled water. No, the one hard part is figuring out how to make your own master. If you’ve got a way of doing this in the home lab, please tells us about it!

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Wave that roman candle around without risking your digits


Some people don’t mind missing a finger or two, but we’re quite attached to all of ours. That’s why we’ve never held on to the fireworks after lighting the fuse. [Dzl] and his son wanted to be (at least somewhat) safe while still having that kind of fun. So they built this rig which lets you wave around a roman candle from a safe distance. It’s not strictly limited to one type of firework either. You can see there is a PVC barrel which will send a bottle rocket off in whichever direction the thing is pointed. As you’ve guessed, a test run is shown off in the video after the jump.

The rig is build from laser cut nylon parts. Don’t fret if you lack the equipment to automatically reproduce this. It’s not that hard to fabricate these types of parts by hand. And the motors that make it go are just hobby servos rigged for continuous rotation. [Dzl] did add external potentiometers for position feedback.

This is a tame way to celebrate the New Year, which is nice if yesterday’s project was a bit too hard-core for you.

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Make your own plastic friction welder


[Fran] shows us how to build a plastic friction welder. It’s a method of connecting plastic pieces. While it’s new to us, apparently this type of tool was given to kids about forty years ago to use with craft project (when plastic was all the craze).

The tip of the friction welder is a styrene rod. If it’s spun fast enough the friction will cause the material to heat to the melting point, depositing a bead of styrene into the joint. The tool seen here is a cheap DC rotary tool acquired from Harbor Freight. It really did a horrible job, but [Fran] discovered that it was the power supply that was under-rated. When she replace the wire that feeds it and used her bench supply it spit out 16,000 rpm without any trouble. The welding rods can be found at the craft store and fit the chuck of the tool quite nicely. You can see her demo in the video after the break. The seam she’s working on comes out very strong, surviving a slew of violent whacks on the workbench.

We’ve seen a few other methods of welding plastic. One used a tool much like a soldering iron, the other depends on ultrasonic waves and clamping pressure.

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Tamagotchi hacking, in depth

In this strangely fascinating talk, you can follow along as [Natalie Silvanovich] reverse engineers some tomogotchi. Even if you have no interest whatsoever in tomogotchi, you’ll probably pick up a trick or two by listening to how she went about taking over the toy. She can now push her own images to the screen, and evolve her tomogatchi at will.

Listening to her story you might be able to pick up a few tricks as she takes almost every angle possible. She uncovers the black blobs, she attempts to socially engineer her way into datasheets, decaps chips, she dumps and breaks down code. It is also worth noting that, in the beginning, internet electronics enthusiasts were adamant that it just had a PIC processor inside and they were wrong. Having an internet full of experts is a wonderful thing, except when it isn’t.

Then again, having that internet full of experts might be her savior in the end, she’s missing a piece of software and asking if anyone has it available.

[via Adafruit]

Building a hardware security module


[Stefan] was nervous about putting the secret key for his Amazon Web Services account in his config file. In the security world, storing passwords in plain text is considered a very bad thing. but luckily there are ways around it. [Stefan]‘s solution was to make a hardware security module out of the newest ARM-powered Arduino Due.

The build puts the secret key for [Stefan]‘s AWS account right in the firmware of the Arduino Due (with the security bit on the Arduino flipped, of course). A Python web service then receives sign requests and talks to the Due over a serial port. The Due then signs the request and sends it off to another bit of Python code that handles the AWS API.

Hardware security modules are frequently used by three-letter government agencies to manage cryptography keys and ensure their data are encrypted properly. Instead of a hardware module costing tens of thousands of dollars, [Stefan]‘s only cost the price of an Arduino Due; not too shabby for a hardware security module that can sign more than 2000 requests per second.

Ringing in the new year with an Arduino and Calcium Carbide


It’s the first we’ve heard of it, but a New Year’s Eve tradition in The Netherlands called Carbidschieten sounds like it’s just up our alley. Basically, a small chunk of calcium carbide and a little bit of water is placed in a metal milk churn. The carbide decomposes into acetylene and a flame is held up to a small hole in the milk churn. The resulting explosion sends the lid of the milk churn across a field and much fun is had by all.

[Edwin Eefting],  [Johan Postema], [Elger Postema] are exploding 1000 liters of acetylene this New Years and needed a safe way to detonate their celebration. They came up with an electronic ignition system based on an Arduino that probably makes just as much noise as the explosion itself.

The build is basically an Arduino with a few relays. When a pair of buttons are pressed for longer than a second, the Arduino goes into countdown mode with the requisite alarms and ringing bells. When it’s time to fire the carbide cannon, a power supply is turned on that heats up a glow plug, igniting the acetylene. It’s a great build, and adds an adequate amount of safety for an event involving exploding 1000 liters of acetylene.

You can check out the videos of the countdown timer after the break, or check out the Facebook group here.

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