Why there's more to Tensegrity than 'Impossible Tables'

quite a few of the youtube channels have recently made impossible or floating table projects these use a combination of a rigid structure and tensions cables to give the impression of a floating tabletop in this example you can see that the tabletop is actually suspended by the central cable and the other cables act under tension to stabilize the top this is known as tensegrity a term originally coined by buckminster fuller in the 1960s which means tensional integrity this was also called floating compression by kenneth nelson who in fact claimed that buckminster fuller took credit for his discovery although according to wikipedia carles johansens had made similar structures years before snelson was born kenneth nelson built various tencegrity or floating compression sculptures including the needle tower and you can find lots of pictures on google images so rather than making another floating or impossible tensegrity table i'm going to make some different structures using tensegrity which are similar to kenneth nelson's tower but first let's look at the concepts this is a simple structure with three rigid members that i 3d printed and added elastic bands to to provide tension the top of all of the three sticks are attached together with elastic bands and so are the bottoms the tops of the sticks are then linked to the bottom of the next stick with another elastic band and that means we've got nine elastic bands in total and three rigid members the next example has four rigid members and that's exactly the same where the tops are all linked together with four elastic bands top and bottom and the further four elastic bands to link the top of each stick to the bottom of the next one the tension provided by the elastic bands holds all of the four rigid members in equilibrium so none of them touch each other in the next example i've got five rigid members and you can see the structures getting flatter each time i add an additional one this is because my bands are all still the same tension and ideally i need a higher tension on the top and bottom to bring the ends of the sticks closer together i decided to try stacking two four member structures together to make something similar to kenneth nelson's tower although i've got four members in each stage instead of the three that he had this seems to work okay it's a bit wobbly although that's mainly down to the compression in the elastic bands if they were rigid tension strings then it would probably be much more rigid i want to make something much bigger though so it's time for some bigger rigid sticks i found these plastic pipes on ebay which are furniture grade pvc pipe i also need some rigid cord so having opened the blind in my bathroom i discovered this handy chain which is quite tough because it has to roll the whole blind up and it's also got these little plastic beads on which engage with the gears i found you can buy something very similar on amazon on 20 meter rolls so i got a couple of those that seems to be nylon cord which is going to be really tough i 3d printed some ends to go on my tubes which are push fit and they also have these little castellations and a little ring around with some holes in to poke the cord through this means i can tension it and lock it in place and it won't easily pull out i 3d printed some tpu flexible ends that just push on and that means the cord won't pull out while it's slack and i'm assembling it and it also keeps it nice and tidy and makes feet for the structure so now it's time to assemble all of those i cut my pipes in half to roughly millimeter lengths and pushed all of the ends on i did a cad diagram to work out roughly what the structure would look like what angles the sticks will be at and then i can measure the ends in cad to find out roughly how long the strings need to be for each stage then it's just a matter of measuring them to length and cutting them and i made them about 50 millimeters longer so there's some slack to go through the castellation and lock into the end of the tubes i assembled this stage by stage linking all the tops and bottoms first and making sure those are on opposite sides and everything hangs together a bit like a rope ladder next it's time to link the vertical strings to the corners from the top of one to the bottom of the other and that's where it gets a bit tricky and a bit muddley to go around in a circle once three verticals are fitted i found it as best to stand it on its end to do the fourth one and that means the structure almost stands up as long as you're holding onto it there are a few issues to sort out like some strings that i've got tangled rounds and i managed to rotate most of the tubes so that everything faced in the right direction i found that my structure was a bit wobbly though so i went around and tensioned up all of the cables bit by bit making sure they're all the same length until i eventually got a fairly rigid structure it was time to add the next stage which involved removing some of the horizontal lines linking the tops and bottoms together cut those in half and fit another stick in between and this is so we can fit the next structure balancing on those cables those got fitted back in and i measured the ends to check that they were in the middle and then i worked my way around doing all four of them now it's time to link all of the tops of those together and put the next set of verticals in and as you can see that took me quite some time because there's nothing to balance the sticks on and they just fall over all over the place [Music] good [Music] so [Music] do [Music] so and here it is so you can see it's actually quite wobbly there's quite a lot of twist in it and it wobbles around like a giant spring however all my rigid members are suspended in tensegrity and all of my tensioners seem to work so the structure stands up without any of the rigid pieces touching each other it was time to add the third stage which i did in a similar fashion but i'll spare you the funny music and now we can see we've got the three-stage sculpture with all of those members not touching each other or suspended in tensegrity by the cables it is very wobbly though and it really wobbles and oscillates like a giant spring it looks pretty good though and i really like the top view which is the view we saw originally from kenneth nelson's needle tower i decided to try and get rid of all the springiness by adding some more tension cords so i've made every stage into a triangle now instead of just having single verticals i did this on all three stages and i'm hoping that'll take out lots of the twist and lots of the spring this has held quite a bit to get rid of some of the twist in each stage which allows each stick to cascade round in the direction it's facing however it is still quite springy because the stages are still just suspended on those strings around the top and bottom of each of the stages as you can see this still allows compression between the stages which is where most of the wobble is coming from as the tower gets taller so now each stages tensioner chords make up two triangles however we can still see compression where those stages are balanced on the horizontal strings that turns the whole thing into a big spring it makes sense to add some vertical tension between these stages and that should stop the compression provided we do it on all four sides of the structure so having added those you can see us pull the structure down so the sticks aren't so vertical and they're lying flatter but they aren't touching each other still so we still have a tensegrity sculpture and the whole structure is much more rigid so you can see there's hardly any wobble in that now it really is a very rigid structure i consider going back and re-tensioning everything to make those sticks stand up more vertically as they were to start with but i'm pretty happy of the way it looks and the structure's really good so now i just need to find a practical use for it i found these covered lights on amazon which are movement activators each one comes with a magnet on the back for mounting and also a magnetic plate with a 3m sticky pad on each one takes three aaa batteries i wanted to make more diffused colored covers for them so that's what i was 3d printing so strip the lights down so i can use the guts from these lights and mount them to the tensegrity tower i made bases for them which i can stick the sticky pad to which is metal and sticks to the magnet and the base has a place to thread a zip tie through and a piece that fits perfectly on my sticks these get zip tied onto the structure wherever i want them and due to the fact there's only one zip tie and the sticks are smooth i can move those all around and position them but i can also tension them up so they're pretty tight and stay in place the lights stick on with their magnet and the 3d printed covers i've made just fit on and those are just a push fit and that light can still be moved around and aligned however i want it to be these lights have a sensor in the middle so the movement activated and i left to place it in my 3d printed diffusers so that sensor still pokes out and has quite a wide angle view so i quite like the look of this we could have of course put a table top on top and made a side table or something like that but i think there's enough tensegrity tables on youtube for now so it's the first time in a while i've done a project which doesn't have coding or mechanical moving parts or electronics in it as such but i've quite enjoyed doing this project it's been quite interesting to get this structure to stand up and make it rigid and have it look like something even if it is a bit of an experimental lifestyle product i've quite enjoyed doing a normal makeup project this week i'm not having to worry about making a robot work but there's plenty more stuff like that coming up now there are robots that actually use 10 segregated structure so you can check those out on youtube just by searching for tensegrityrobot mostly research machines but the point is they can roll all over so for something like exploring mars or something like that they can handle rough terrain just by altering the lengths of those tension chords so i do have another experimental robot structure coming up next week so perhaps i'll come back to this it'll be really good if i did actually make a robot using a combination of tensegrity and the thing that's coming next week so don't forget to subscribe if you want to see what that is and like the video if you liked it and i will publish all the 3d printed parts for this the ends for these tubes so you can use blind cord to make a similar structure and these pieces for the lights so if you'd like to support me on patreon then you can check out the link in the description to this video or youtube channel membership and patrons and youtube channel members can get access to all the videos early up to a week early and sneak peeks and pictures of what's coming up so you can be part of all that discussion so check those out alright that's all for now [Music] you

Channel: James Bruton

Views: 119,054

Keywords: tensegrity, tension, compression, tension compression, tensegrity table, impossible table, impossible table project, tensegrity table project, tensegrity sculpture, tension compression project, make a tensegrity scultpure, how to make a tensegrity sculpture, self supporting structure, interesting engineering structure, self supporting tower, 3d printed tensegrity tower

Id: RQFEtOj8jh0

Length: 13min 23sec (803 seconds)

Published: Mon Feb 01 2021