And So Castings Made of (Kinetic) Sand . . . Turn Out Pretty Well, Actually

sand castingThat kinetic sand stuff is pretty cool. It’s soft, it builds motor skills, and outside of sprinkling it on carpet, it’s not messy. If you don’t know, it’s 98% sand and 2% polydimethylsiloxane, which is a major component of Silly Putty, and according to a certain yellow and red clown, it’s safe enough to put in chicken nuggets. [Chris]‘s wife bought him some, probably because she wanted to see him play around with something that isn’t potentially deadly for a change. In the course of researching its magical properties, he found out that it doesn’t really have a thermal breakdown point, per se. At high enough temperatures, It vitrifies like a sand castle in a mushroom cloud. Between this property and its malleability, [Chris] thought he’d have a reasonable substitute for founding sand. As you can see in his latest experiment, he was right. As a bonus, he managed to turn the benign into the dangerous.

[Chris] had never cast aluminium before, so he decided to start small by making an offset cam for a rotary broach. He packed some magic sand in a wax paper cup and shoved the cam in to make the negative. Then he cut down some aluminium rod and put it in a graphite crucible. He stuck his DC arc welder’s electrode down into the crucible and cranked it up to 50A. That wasn’t enough, so he went to 110. The crucible was soon glowing orange. He carefully poured the molten aluminium into the mold. Make the jump to see how it panned out.

Spoiler alert: there’s no cussin’ this time!

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Lego Technic Mechanical Seven Segment Display


Here’s a rather mesmerizing piece of Lego genius, displayed as a .GIF for your enjoyment. It’s a 7-segment display that is completely mechanical!

Built by [aeh5040], this beauty features 7 separate linkages that control each display segment. It’s powered off of a single motor which rotates a cylinder covered in small protrusions, similar to how music boxes work. As the cylinder rotates, the protrusions knock the main drive gears back and forth, flipping each segment between the ON and OFF states through a series of axle joints and bevel gears.

It makes rather satisfying sounds too!

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Self-Balancing Robot Uses Android and Lego NXT

LEGO NXT + Android = Self Balancing Robot

Self-balancing robots are pretty cool, but sometimes a bit too complex to make. [HippoDevices] shows us that it’s really not that hard, and you can even do it with Lego NXT and an Android device!

First step is to build your two-wheeled robot – go nuts! As long as the Lego NXT motors are strong enough you’ll be able to make most different shaped robots easy to balance. You’re going to need an Android ADK board to provide communication between the Lego motors and your Android device. [HippoDevices] is using their own design, called the Hippo-ADK which is on Kickstarter currently.

This allows your Android device to read the status and control the Lego Motors — from there it’s just a matter of programming it to balance according to the device’s gyroscope.

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Raspberry Pi Turns a Novelty Radio Into a Real Computer


[Strider19] remembers the 90’s, and a great little novelty radio he had back then. Shaped like a computer, the radio was a typical AM/FM affair, with the monitor serving as a speaker. His original radio was long gone, but [Strider19] was able to find a replacement on everyone’s favorite auction site. With the replacement radio in hand, he set his plan in motion: Turning it into an epic Raspberry Pi Case.

The Raspberry Pi fit great, but [Strider19's] 3.5″ composite monitor didn’t quite make it. Following in [Ben Heck's] footsteps, [Strider19] cut the LCD’s control PCB down to fit the case. A piece of clear polycarbonate protects the fragile LCD from poking fingers. The monitor’s button board, two USB ports, and an external composite input mounted nicely inside the former battery compartment at the rear of the CRT. There’s even enough room back there to hide a USB WiFi adapter.

The Raspi itself fit perfectly into the base of the radio, along with a DC to DC converter, USB hub, real-time clock module, and a whole bunch of wires used to extend the connectors.

The final result is awesome! Thanks to a request on [Strider19's] Reddit thread, we have pictures of Doom running on a (former) radio.  Even Windows 3.1 runs under DosBox, though it took a bit of tweaking to get the display settings just right. Now [Strider19] just needs to figure out how to turn that tiny keyboard into a working model. We think some old school cell phone keyboard hacking may be in order!


Upgraded Nerf Gun Keeps Track of your Ammo


[Paul] and his buddy [Jonathan] recently had a zombie themed Larp event to go to, so in the spirit of making the experience more realistic, they decided to upgrade their Nerf N-Strike Stryfe gun.

They started by cracking open the gun and making note of the available space for a few bells and whistles. Luckily, thanks to traditional plastic injection molding practices — there’s lots of room!

Upgrades include a magazine sensor, a jam sensor, a trigger sensor and a voltmeter to make the gun a little bit smarter. A knockoff Arduino Pro Mini takes in all these inputs and outputs it to a 7-segment LED display for easy visibility. Our favorite part is the ammo sensor, which keeps a tally of how many shots you’ve used. It’s simply an IR photo-diode and IR transistor in a Darlington configuration, connected to the GPIO interrupt pin on the fake Arduino.

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The Crane Game, Oculus Style

crane We’re pretty sure the Hackaday demographic is a a person who sees a giant tower crane lifting beams and girders above a skyline and says, “that would be fun, at least until I have to go to the bathroom.” Realizing the people who own these cranes probably won’t let any regular joe off the street into the cabin, [Thomas] and [screen Name] (see, this is why we have brackets, kids) built their own miniature version with an Oculus Rift.

Instead of a crane that is hundreds of feet tall, the guys are using a much smaller version, just over a meter tall, that is remotely controlled through a computer via a serial connection. Just below the small plastic cab is a board with two wide-angle webcams. The video from these cameras are sent to the Oculus so the operator can see the boom swinging around, and the winch unwinding to pick up small objects.

The guys have also added a little bit of OpenCV to add color based object detection. This is somewhat useful, but there’s also an approximation of the distance to an object, something that would be very useful if you don’t have a three-inch tall spotter on the ground.

Video below.

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Making a Nitinol Wire Inchworm


[Steven's] at it again with another cool science experiment that isn’t too difficult to do. This time he’s made himself a Nitinol wire inchworm, which actually moves across the table when you apply a switching electrical current to it!

Nitinol is a shape memory alloy which has a cool property that causes it to retain (and return to) a preset shape when heat (or electricity!) is applied. It’s actually quite simple — he’s wrapped the Nitinol wire tightly around a nail, and then heated it to set it to a coiled shape. Now the Nitinol spring can be stretched out flat, but as soon as it is heated, it will attempt to return to its coiled state!

Using some balsa wood and a few other odds and ends he’s taken advantage of this memory effect to make an electric inchworm — check it out after the break!

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