It always seems odd to us that magnetic levitation seems to only find use in big projects (like trains) and in toys. Surely there’s a practical application that fits on our desktop. This isn’t it, but it is a cool way to turn a cheesy-looking levitating globe into a pretty cool Star Wars desk toy.
As projects go, this isn’t especially technically challenging, but it is a great example of taking something off the shelf and hacking it into something else. The globe covering came off, revealing two hemispheres. A circular hole cut out and inverted provides the main weapon. Some internal lighting and small holes provide light. Some fiber optic sanded and tinted green make the weapon fire. The rest is all in the painting.
There’s even a tiny imperial ship orbiting the killer man-made (or is that Sith-made) moon. If you want a bigger challenge, you might try bamboo. Or you can go minimalist and let your eyes and brain do most of the work.
Here at VCF, we stumbled across a gigantic contraption that spanned several tables. Rube Goldberg machine this was not. Instead, this device actually does something useful! [Tim Robinson’s] differential analyzer can solve differential equations through several stages of mechanical integrators. The result is a pen-plot graph of the solution to the input equation, input by displacing a rod as a function of time.
Differential analyzers have been around for over a century. [Tim’s] claim to fame is that this particular DA is constructed entirely from Meccano-branded parts. We’re thrilled to see Meccano, over 100 years old at this point, continue to find new uses outside the toy box.
The differential analyzer is riddled with mechanisms that are bound to swing some heads for a double-take. Since the input shaft that transmits the input function f(x), has very little friction, the result can only be carried through the remainder of the machine with some means of torque amplification. To do so, [Tim], and most other DA designers implement a torque analyzer. For [Tim], though, this feat proved to be more difficult (and more triumphant) than other solutions, since he’s using a set of parts that are entirely from Meccano. In fact, this feature took [Tim] through about 20 iterations before he was finally satisfied.
VCF West continues to run through the end of the weekend at the Computer History Museum in Mountain View, CA. If you haven’t already packed your bags for DEF CON, stop by for a few more bewildering brain teasers.
If the [realjohnnybravo] is the one from the show, it appears he finally managed to get a girlfriend, marry her, and produce at least one son. As the old schoolyard rhyme goes, first comes love, then comes marriage, then comes filling the whole *!$&# backyard with brightly colored plastic garbage. One of these items, a Power Wheels quad bike, suffered a blow from planned obsolescence leaving behind a traumatized child. [realjohnnybravo] decided to fix it.
He made frequent mention of how one could go to a store and purchase replacement gears for the toy. Perhaps it’s a German thing. Regardless, he shows experience with internet comments by justifying his adventure in gear manufacturing with, paraphrased, “I’m having fun and learning so back off you pedantic jerks.”
Resin casting is great, and is often overlooked vs 3D printing. He purchased some hardware store RTV silicone and some slow-cure resin. The faster cure resin would get too hot with this much volume and potentially burn.
Materials procured he took apart both gearboxes from the machine. He first made a silicone mold of the broken parts (from the good copies out of the working gearbox) and removed the master. Without a vacuum or pressure casting chamber, the molds came out a little rough and bubbly, but it’s nothing some work with a carpet knife can’t fix. For big gears like this it hardly matters. Next he poured the two part resin into the molds and waited.
After some finishing with regular woodworking tools the parts fit right into the voids in the defective gearbox. His son can once again happily whir around the lawn, until the batteries die anyway.
3D printers are celebrated for their capacity to replace missing or broken parts. How about an entire T-62 tank?
Now hold on a second — this is only a model replica. It is, however another expression of the myriad uses for 3D printers. Designed in Maya and requiring almost three weeks to print all 62 parts from about 70 meters of PLA filament. The assembly is not terribly involved, made easier by printing a few large sections such as the crew section and hull while the parts don’t get much smaller than the turret hatches. Nonetheless, he final product is about as true to life as you can get when designing the parts from scratch.
[Jason]’s at it again. This time the LEGO maestro is working on a LEGO BB-8 droid. As a first step he’s made a motorized monowheel that not only races along hallways and through living rooms at the peril of any passing people, but turns as well.
To drive it forward there’s an axle that runs across the center of the wheel and a motor that rotates that axle. He’s also included some weight bricks. Without the mass of those bricks for the rotation to work against, the motor and axle would just spin in place while the friction of the floor keeps the wheel from rotating. If you’ve seen the DIYer’s guide to making BB-8 drive systems, you’ll know that this is classified as an axle drive system.
For steering the monowheel left or right he has another mass located just above the axle. Shifting the mass to the left causes the monowheel to lean and move in that direction. Shifting the mass to the right makes the wheel move to the right in the same fashion. Being ever efficient, [Jason] has the motor that shifts the mass doubling as the mass itself.
As with any proof-of-concept, there are still some issues to work out. When turning the wheel left or right it can tip onto its side. Ridges on both sides of the wheel’s circumference reduce the chances of that happening but don’t eliminate it altogether. Also, the steering mass/motor doesn’t yet have a self-centering mechanism; after a turn it’s up to the person holding the remote control to find center. If the mass isn’t correctly centered after a turn, there tends to be some wobble.
As always, we’re looking forward to seeing how [Jason] solves those issues but first he’ll have to put it back together since, as you can see from the video below, it didn’t quite pass the stair test.
[ossum] had a stack of Amazon and Shapeways credits lying around after winning a few competitions. He had this dream of building an R/C car for a while, and decided now was the time. After ordering all the needed parts from Amazon, he made an extremely nice model of the car in Fusion 360. The CAD model is a great learning resource. If you want to learn how to use reference photos, parts, and more to build a detailed and useful CAD model we recommend downloading it as a Fusion archive and scrubbing through the timeline to see how he did it.
Some of the parts were sent off for laser cutting. Others were 3D printed. The rest he made himself. Thanks to his model, they all went together well. You can see his R/C rod racing in the video after the break.
Following one’s passion can lead to amazing results. Sometimes this results in technological marvels; other times, one marvels at the use of the technology. An exemplary display of the latter is The Citadel.
Over the course of three years, redditor [Shadowman39] pieced together this monstrous K’nex structure. With over 17 different paths(!), 45 different elements, and over 40,000 parts, you would expect some meticulous planning to go into its construction — but that’s not the case! [Shadowman39] assembled it largely on the fly with only a few elements needing to be sketched out and only the main elevator proving to be troublesome. Three motors power the structure — one for the main elevator, one for the smaller lifts on the bottom, and one for the release gates.
This is an absolute leviathan hobby project. To satiate the obvious curiosity of anyone who stumbles across this picture, its intricacies can be seen in the video: