Slinky Walks Down Stairs and Picks up 80m Band

Originally intended as a way to stabilize sensitive instruments on ships during World War II, the Slinky is quite simply a helical spring with an unusually good sales pitch. But as millions of children have found out since the 1940’s, once you roll your Slinky down the stairs a few times, you’ve basically hit the wall in terms of entertainment value. So what if we told you there was yet another use for this classic toy that was also fun for a girl and a boy?

As it turns out, a cheap expandable metal coil just so happens to make for a pretty good antenna if you hook it up right. [Blake Hughes] recently took on this project and provided some detailed pictures and information for anyone else looking to hook a couple of Slinkies to their radio. [Blake] reports excellent results when paired to his RTL-SDR setup, but of course this will work with whatever kind of gear you might be using at these frequencies.

Before anyone gets out the pitchforks, admittedly this isn’t exactly a new idea. There are a few other write-ups online about people using a Slinky as a cheap antenna, such as this detailed analysis from a few years ago by [Frank Dörenberg]. There’s even rumors that soldiers used a Slinky from back home as a makeshift antenna during the Vietnam War. So this is something of an old school ham trick revived for the new generation of SDR enthusiasts.

Anyway, the setup is pretty simple. You simply solder the RF jack of your choice to two stretched out Slinkies: one to the center of the jack and one to outside. Then run a rope through them and stretch them out in opposite directions. The rope is required because the Slinky isn’t going to be strong enough when expanded to keep from laying on the ground.

One thing to keep in mind with a Slinky antenna is that these things are not exactly rated for outside use. Without some kind of treatment (like a spray on acrylic lacquer) , they’ll quickly corrode and fail. Though a better idea might simply to be to think of this as a temporary antenna that you put away when you’re done with. Thanks to the fact that the Slinky doesn’t get deformed even when stretching it out to maximum length, that’s relatively easy to accomplish.

If you’re looking for a good RTL-SDR to go along with your new Slinky antenna, check out this roundup of some of the options that are on the market as of 2017. You’ll probably need an upconverter to get down to the 80m band, so you might as well build that while you’re at it.

Spice Up Your Bench With 3D Printed Dancing Springs

Not all projects are made equal. Some are designed to solve a problem while others are just for fun. Entering the ranks of the most useless machines is a project by [Vladimir Mariano] who created the 3D Printed Dancing Springs. It is a step up from 3D printing a custom slinky and will make a fine edition to any maker bench.

The project uses 3D printed coils made of transparent material that is mounted atop geared platforms and attached to a fixed frame. The gears are driven by a servo motor. The motor rotates the gears and the result is a distortion in the spring. This distortion is what the dancing is all about. To add to the effect, [Vladimir Mariano] uses RGB LEDs controlled by an ATmega32u4.

You can’t dance without music. So [Vladimir] added a MEMs microphone to pick up noise levels which are used to control the servo and lights. The code, STL files and build instructions are available on the website for you to follow along. If lights and sound are your things, you must check out the LED Illuminated Isomorphic Keyboard from the past. Continue reading “Spice Up Your Bench With 3D Printed Dancing Springs”

We Can Now 3D Print Slinkys

A mark of a good 3D print — and a good 3D printer — is interlayer adhesion. If the layers of a 3D print are too far apart, you get a weak print that doesn’t look good. This print has no interlayer adhesion. It’s a 3D printed Slinky, the kind that rolls down stairs, alone or in pairs, and makes a slinkity sound. Conventional wisdom says you can’t print a Slinky, but that didn’t stop [mpclauser] from trying and succeeding.

This Slinky model was made using a few lines of JavaScript that output a Gcode file. There is no .STL file, and you can’t edit this CNC Slinky in any CAD tools. This is also exceptionally weird Gcode. According to [mpclauser], the printer, ‘zigzags’ between an inner and outer radius while constantly increasing the height. This is the toolpath you would expect from a 3D printed Slinky, but it also means the usual Gcode viewers throw a fit when trying to figure out how to display this thing.

All the code to generate your own 3D printable Slinky Gcode file is up on [mpclauser]’s Google Drive. The only way to see this print in action is to download the Gcode file and print it out. Get to it.

Wooden Escalator Fit for a Slinky

Our favorite mechanical master of woodworking, [Matthias Wandel], is at it again, this time making an endless staircase for a Slinky. Making an escalator out of 2×4’s and other lumber bits looks fairly easy when condensed down to a two and a half minute video. In reality a job like this requires lots of cuts, holes, and a ton of planning.

The hard part of this build seemed to be the motor arrangement. There is a sweet spot when it comes to Slinky escalator speeds. Too fast, and you’ll outpace the Slinky. Too slow, and the Slinky flies off the end of the escalator. Keeping the speed in check turned out to be a difficult task with the coarse speed control of a drill trigger. The solution was to ditch the drill and build a simple hand crank mechanism. The Slinky now can cascade down stairs as long as your arm holds out.

Join us after the break for 3 videos, the making of the escalator, a 140 step demonstration video, and a followup video (for geeks like us) explaining where the idea came from, whats wrong with the machine and possible improvements.

Thanks to [Jim Lynch] for the tip

Continue reading “Wooden Escalator Fit for a Slinky”