If you’ve never heard of a tensegrity structure, you should stop now and watch the video below. In it, [The Action Lab] shows a 3D printed table that is held up only with strings. We didn’t say suspended by strings but held up. Or so it appears. The model is from Thingiverse, but it is one of those things you have to see to believe.
The basic idea is pretty simple. Strings have a lot of tensile strength but collapse under the slightest compressive force. The arrangement of strings puts the force on the center string which is essentially hanging — the force is pulling the string down. The other three strings aren’t just for show, though, they keep the structure from tipping over in any one direction.
There are actually real-life examples of these kinds of structures. The video shows the Skylon at the Festival of Britain as one example and an Australian bridge. The video also makes the point that the human body uses tensegrity, since tendons are very similar to the strings in the model.
This would be a great experiment for a homeschooler or even kids cooped up in quarantine. The print itself doesn’t look very challenging, although the assembly might be a bit tricky.
This isn’t the first structure like this that we’ve seen. If the talk about tendons makes you think this might be useful in robotics, you’d be correct.
Continue reading “Table Held Up By Strings Teaches Physics”
Buying 3D-printer filament is little like eating potato chips: you can’t stop at just one. You start with basic black PLA, then you need a particular color for a special project, then you start experimenting with different plastics, and before you know it, you’ve got dozens of reels lined up. Trouble is, unless you move the in-use reel right over the printer, the filament can get a bit unruly as the printer sucks it up. What to do?
How about building an active strain relief system for your filament collection? That what [Daniel Harari] chose to do, and we have to say that it looks pretty slick. The idea is to keep the filament slack before it enters the printer’s extruder no matter where the reel is positioned relative to the printer. The active bit is a little like a low-force extruder, using a couple of pinch rollers from an old 2D-printer to pay out filament when needed. A clever sensor, consisting of a 3D-printed funnel and a copper wire contact loop, detects when the printer has taken up all the slack in the filament and triggers a payout from the feeder. In a nice touch, the feeder motor is controlled by a couple of 555s rather than a microcontroller. The short clip below shows the feeder being triggered and paying out a little more slack.
In the final analysis, this is just another in a long series of filament management projects, from dry-boxes to filament meters to end-of-spool alarms. It may be overkill, but [Daniel] put a lot of thought into it, which we always appreciate.
Continue reading “Active Strain Relief For 3D-Printer Filament”
[Robby Cuthbert,] an artist and designer based out of Fort Collins, Colorado is creating stable cable tables that are simultaneously a feat of engineering and a work of art.
[Cuthbert’s] tables are held together by 1/16″ stainless steel cables that exert oppositional tensions that result in a structurally stable and visually appealing coffee table. In his video, [Cuthbert] leads us through his process for creating his tables, step by step. [Cuthbert] starts by cutting out bamboo legs on his CNC mill. He then drills holes in each leg for cables and mounts each leg on his custom table jig. Then, he attaches the stainless steel cabling taking care to alternate tension direction. The cables are threaded through holes in the legs and affixed with copper crimps. After many cables, he has a mechanical structure that can support his weight that also looks fantastic. All in all, [Cuthbert’s] art is a wonderful example of the intersection of art and engineering.
If we’ve whet your appetite, fear not, we have featured many tension based art/engineering hacks before. You might be interested in these computer-designed portraits or, if the thought of knitting by hand gives you the heebie-jeebies, the Autograph, a string art printer might be more your style.
Video after the break.
Continue reading “Making Tension Based Furniture”
While it’s often thought of as a criminal activity, there’s actually a vibrant hobby community surrounding the art of lock picking. In the same way that white hat hackers try to break into information systems to learn the ways that they can be made stronger, so do those in the locksport arena try to assess the weaknesses of various locks. For the amateur, it can be exciting (and a little unnerving) to experience the ease at which a deadbolt can be picked, and if your concern is great enough, you can go a little farther and modify your locks to make them harder to defeat.
The lock in question was sent to [bosnianbill] by [Rallock67] with a device that [Rallock67] had installed using common tools. Known as a Murphy Ball, a larger-than-normal spring was inserted into one of the pins and held in place by a ball bearing. This makes the lock almost completely immune to bumping, and also made it much more difficult for [bosnianbill], an accomplished and skilled locksmith, to pick the lock due to the amount of force the spring exerted on the cylinder. The surprising thing here was that this modification seems to be relatively easy to do by tapping out some threads and inserting a set screw to hold in the spring.
Locksport and lockpicking are a great hobby to get into. Most people start out picking small padlocks due to their simplicity and ease. It’s even possible to pick some locks with a set of bobby pins. And, if you really want to see how easy it is to defeat some locks and/or how much good the TSA does for your overall security, you’ll want to take a look at this, too.
Thanks to [TheFinn] for the tip!
Continue reading “Modify Locks To Baffle Burglars”
While this mechanical mustache isn’t made for a Halloween costume, it certainly looks like part of one. Copper clad, brass, cable, and a few other bits come together in a similar style to tension based hands; the piece is then worn much like a Mardi Gras mask. To complete the rustic “old tyme” look [John] was after, the copper was tarnished using the vapor from a vinegar and salt solution. The finished assembly is steam punk delicious, but we’re saddened by the lack of steam punk eye brows to complete the look (or steam punk mutton chops, or steam punk goatee, or…)
[via Boing Boing]