Emulating biology to make tiny robots

Quick video talking about rolling contact/compliant joints. These emulate how joints in nature work (two rolling surfaces held together with tension).
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[@tHaH4x0r]

Cool stuff. I work a lot with flexures, didn't expect you to make a video on a compliant mechanism. These kinds of joints are indeed quite common in low friction robotics and mechanisms (such as tele-operation with haptic feedback). Your joint has very low sideways support stiffness, as the compliant elements you used are essentially wire flexures (at least as long as you keep the wire in tension). They are compliant in the bending mode about the knee axis of rotation (which you obviously want), but also a similar bending mode in the rotation axis perpendicular to the knee rotation axis and perpendicular to the length of the constraint. Pure rotations in your design are somewhat compensated for due to the spacing of the wires, but pure translations sideways I expect the joint to have nearly zero support stiffness as well. If you want to improve this, use blade flexures of some kind. You can perhaps just use thin metal sheets to fabricate these out of, I believe they are common in hobby stores for scale models. Considering the scale of the joint, the metal sheet you need to use is likely so thin you could cut it with a razor blade. Alternatively you could add a supporting flexure in parallel with the joint you already have (for example a folded leaf), but to do that properly is likely too hard without experience in flexural design. If you want, I can give you a book recommendation that would significantly help you with such joint design (and mechanical constraint design in general).

[@zchrode]

how abt u just give me the book

[@BreakingTaps]

Awesome, thanks for the info! Pinning so more folks can see this. And definitely interested in that book recommendation! Mea culpa, I opted for cable/line because I didn't want to figure out how to mechanically secure thin spring steel ribbons. 😅 But after building these I can definitely see what you mean regarding unwanted motion in the perpendicular direction. Will do some reading and see how to incorporate that in a small package (probably just some M1.5 screws holding them down or something)

[@tHaH4x0r]

@@BreakingTaps The book is called "Exact Constraint: Machine Design Using Kinematic Principles" by Douglas Blanding. Sounds like a tough pill, but especially the first few chapters (the most important ones) are very well written and totally readable without a mathematical background. It specifically addresses how to constrain bodies together, to get certain desired motions. Warning: Once you have learned the knowledge in this book, you will start to see poorly designed mechanisms everywhere you go ;) The book might be hard to find, but I heard that some pirates might have some copies lying around as well, although I'd never advocate for such purposes ;) As further reading if you want to dive a bit deeper into flexure design specifically (which is very closely related to exact constraint design, and builds upon those principles), Johnathan Hopkins has a series here on youtube titled 'Compliant Mechanism Lecture Series'. A warning for some people, there's some undergraduate math involved for a few lectures, but you can quite safely skip those without missing too much. A bit more background for those interested: There's only a couple of research groups in the world who are renowned for flexure designs, and his 'flexible research group' at UCLA is one of them. He is most well known for coming up with the 'FACT' framework, which is a convenient way to envision/design compliant mechanisms using a visual system (the FACT chart).

[@berlinberlin4246]

​@@tHaH4x0r thank you for sharing!

[@LimabeanStudios]

@@tHaH4x0r Your comments here are exactly the sort of insights I've been itching for thanks a ton. Can't wait to dive into that book.

[@JinKee]

Finally robots can also have bad knees.

[@jamesyoungquist6923]

Hahahaha nice 👏🏻. I've been waiting for when robots can finally replace humans in the personal injury category as well

[@bob2859]

I've seen rolling contact joints used for telescope pointing and some 3d-printed flexures, but never considered non-circular profiles. Can't wait to see the teeny-tiny birdbot in action!

[@Insultthumb]

I too am an expert in the art of rolling joints

[@Dan-gs3kg]

You can see an example of such joints in bow cams

[@LimabeanStudios]

Suddenly dislocating joints make a lot more sense seeing this. I can see this rolling geometry allowing for some cool variable strength grippers

[@badlaamaurukehu]

Now only for some form of synthetic synovial fluid...

[@_droid]

These are also considerably lighter than metal ball bearings. The main problem with these is strength. Biology has incredible designs for ligaments, bones, etc that are very difficult to match with traditional materials. Fun stuff!

[@ZeroG_Bandit]

I'd love to see a video that is a marriage of mat sci + biology, to bridge the gap between tissue level architecture of bone, tendon, ligament, and muscle and the structure of the musculoskeletal system.

[@BongoWongoOG]

@@ZeroG_Bandit carbon fibre wrapping might be the key?

[@Dan-gs3kg]

RF85 for the cams

[@Dan-gs3kg]

​@@BongoWongoOGlike kernmantle ropes? Sheath braid and core fibers?

[@BongoWongoOG]

@@Dan-gs3kg pretty much, max strength and low weight

[@chir0pter]

I love how in picking up the rolling-contact leg it instantly is recognizable as something more biological and light, as opposed to the bigger clunkier mechanical bearing-based design These rolling contact joints are something I became interested in recently while trying to find a compliant but weight-bearing hinge, and came across a paper from the 2000s where they used it to make satellite solar panel deployment mechanisms

[@5eurosenelsuelo]

Can you share the name of that paper?

[@chir0pter]

@@5eurosenelsuelo “Tape-spring rolling hinges” watt and pellegrino 2002

[@Kazuron]

That rolling contact point joint version looks eerily like a real leg. I was listening to what you were saying, but my brain immediately went "oh, thats a bird leg"

[@fxm5715]

I first learned of this joint as a kid, with the Rubik's Magic puzzle. That thing fascinated me, not for the puzzle, but for the compound folding joints it used.

[@Cssfiend]

I also thought of a toy immediately, but a jacob's ladder instead

[@fxm5715]

@@Cssfiend Ah, right, the Jacob's Ladder! I think I was a bit too young to be fascinated/confused by that when I first experienced it, plus the Magic implemented the joint in two dimenstions, not just one. But yes, certainly an earlier example in toy form.

[@jimmcintosh3718]

I am impressed that not only have you recapitulated the human knee joint, but also the cruciate ligaments which support it.

[@zyxwvutsrqponmlkh]

2:14 That undesired movement is called "Side Fumbling", and what you have created there are some rudimentary marzlevanes.

[@shanevonknuth]

Have you seen how small they can get the retro encabulators now? I know it's more a vanity project to even have one now since they just invert the gram-meters duo-planially now, but it's nice to see.

[@Yezpahr]

10:08 That's how my last digit of my ring finger dangles if I stretch my other fingers and contract the ring finger entirely. Try it. Probably works because it's the same type of mechanism lol. 9:27 And I felt that in my knee.

[@sueh1224]

wow that ring finger trick looks so bizarre

[@veedrac]

...I regret learning what this comment taught me.

[@renxula]

Interesting! Works with other fingers too, but maybe my ring finger is the floppiest.

[@untitledphysicist3205]

Something to think about if you are not already would be to use nylon for the joints, nylon is self lubricating so it should reduce friction. It may not have a huge impact as friction is already low but it may be worthwhile to test.

[@johncochran8497]

Doubt that nylon would do anything. Those are rolling joints, NOT sliding joints. since there's no surface to surface sliding, having a low friction material is irrelevant.

[@constantinosschinas4503]

​@@johncochran8497 irrelevant, or even make things worse by introducing unwanted sliding.

[@ytrew9717]

@@johncochran8497 but aren't rolling joint contacting each other and thus creating friction on surface to surface rolling?

[@johncochran8497]

@@ytrew9717 Yes, but the friction is intended to PREVENT sliding. The idea to use nylon because of "lower friction" is akin to saying that we should use nylon for car tires because of "lower friction" and it would be even better if we slathered those nylon tires with grease to lower the friction even more.

[@ytrew9717]

@@johncochran8497 ​thank you, but why would it bad if it slides instead of rolling (stupid question but ...)?

[@Vaasref]

Did we just see the start of Mecha-Dabchick ?

[@MadelynRusco]

my first thought at seeing the thumbnail too

[@arachnenet2244]

Had the same idea haha

[@drillerdev4624]

I would actually love to hear Barnaby's opinion on the subject from a puppeteer standpoint Can you imagine an animatronic Dabchick?

[@tardigrademicro]

fuck yeah

[@capuchinosofia4771]

I was literally thinking on how this could be used for puppets! Lol

[@NerdOracle]

I too am fascinated by rolling joints 🔥

[@user-ie1tz5rm8x]

They let u play wit matches?

[@CroneKorkN]

And are good for making contact.

[@aaronhokanson6718]

I started my version of this back in 05. Here's what I learned. You can make them cams to increase torque advantage to position ratio. The "ligament" cables tent to abrate on each other and the groves. I was able to mitigate this some by Drafting the groves by 5°. That's as far as I got. Good luck.

[@barmetler]

It's like these glasses cases! With the three stripes, if you know what I'm talking about. Edit: I think they're called "magic cases". They were all the rage back in the late 00's

[@radioactive_nrg]

Was just about to comment that! They also come as calculators, pen cases, manicure sets and probably a lot more.

[@coyotedomino]

yesss those and jacob's ladders

[@hashemmehyar9614]

I usually do a makeshift rolling contact joint to explain why training the opposite of a muscle is just as important. Also helps with teaching correct deadlift form and anterior pelvic tilt.

[@cauemarchionattiausec1754]

I've been rolling some joints myself and these are really cool!

[@drewsipher]

Any references on how to design the curves in the joints?

[@stalincat2457]

Judging by 2:43 it's as simple (cough) as moving the axles closer or further apart. The string will want to keep the hinge in the least tensioned position. Moving the leg will either abrubtly tension the cord, creating an "end stop' or when turned the other way will gradually increase tension. That would mean that the neutral "strength" can also be adjusted by varying the amount of rope ever so slightly.

[@ModelLights]

As others have mentioned, you have ligaments, self-correction, etc involved in biology. It will be difficult to get this 'tight'. Ball bearings are 'loose' when small, and overkill for a small, slow joint. Sleeve and pin type bearings especially with bronze may get you a much better, more precise joint. When you go small scale like this, you quickly want to start studying watches, almost every consideration you can possibly come up with has already been done in that field. Or you could make the leg about 4x longer, probably still doable and that would get the same error and play down to a more reasonable percentage of the over overall motion. Not knocking it if you want to try it at all, but off hand it's just very hard to reduce the inherent play in something like this, vs instant high precision with a sleeve bearing type system.

[@nirodper]

was looking for this comment, a simple bushing is the correct thing for this application, cheaper, more precise and more durable than any of the other options

[@brynyard]

I've seen those with stainless steel bands, they provide a bit of stability/stiffness to the joint as well. Nice design :)

[@jazzdirt]

Dyneema was engineered to replace steel cables.. It's lighter and non corrosive and way stronger..

[@cheyannei5983]

​​@@jazzdirtDyneema has a problem with losing strength due to heat/UV exposure, the friction from knots will significantly weaken dyneema more than other materials which is a pain since it's hard to attach stuff to it otherwise. I think that's where spliced and woven dyneema comes in though

[@brynyard]

@@jazzdirt not cable and not steel, but thin shims (< .1mm) and stainless (316). And since the shims are constrained (wedged between the surfaces) they have a lot of sideways strength, so it improved the sideways stability. Not saying "this is the way", just mentioning another design I've seen.

[@jazzdirt]

@@brynyard Yeah, when I studied Material science engineering that's what they were going for... Eventually it turns out to be more useful in uses where you would otherwise use Kevlar... But the thing they set out to do was to make a strand that was stronger then steel... To make lighter cables.. but it's not suited for that as @cheyannei5983 also pointed out.... I never finished the Material science engineering study... I just know the faculty was working on Dyneema when I was studying there... Studying engineering was trying to do the sensible thing.. I always knew I wanted to make music and I always have.. so that's where I eventually ended up...

[@SarahKchannel]

I used on a previous project, related to hands and fingers, neodymium magnet and steel balls to form a joint. The Magnet was sort of inverse cone shaped to give a pan for the ball to sit in. Added some 'guards' on the side as your joint has to prevent the lateral displacement. Worked really well, rolled like nothing, but was compliant enough for a joint to dislocate when stressed to far.

[@danway60]

Thats pretty cool, thank you for sharing! Point about the bearings: Ball bearings are generally meant for high speed, low dynamic load, rotating applications. For small, low speed and impact loads such as those joints, I think you'd be better off using bushes/sleeve bearings instead. That being said, rolling contact joints are awesome!

[@theavaliengineer]

Very hyped to see you take on this project! A potential source of inspiration to look for might be IRIM Koreatech's LIMS-Ambidex system- they hve a very effective implementation of a rolling contact joint for the elbows of their bot. Their pulley system is one of a kind.

[@alexandervarakosov]

Neat! This is the same joint that was commonly used on early aircraft to attach control surfaces and is still used on models today.

[@DurzoBlunts]

I thought I've seen these before in Lego sets from the 90s. 3612 part # from the aqua zone kits

[@TDOBrandano]

Ah, compliant rolling contact joints. Nicholas J. Seward designed an elbow driven delta 3d printer based on the concept, though it was only a concept prototype (the Reprap Gus Simpson). He used herringbone gears to keep the parts aligned through the rolling motion,. maybe it would scale sufficiently well down with plain gears?

[@aserta]

0:58 i get a ton of micro bearings from old odometers. Whenever i go shopping for replacement parts i made it a purpose to get at least 10 of those, because inside there are sub mm shaft ball bearings that are pretty high quality. Not only are they bearings in the regular sense, but at least one of them is also a side load one (usually the one that's on the main shaft from where the spedo cable would pop in). But we're talking pre-90's odometers. Most modern ones (if they even have mechanical ones) have plastics inside, teflon revolution.

[@lunarz7117]

When I first saw this on Twitter, I was like- This can be used in micro scale Models! Use this as a Steering Hinge in a Hotwheels car or a Model Kit!

[@atalhlla]

I wondered why you didn’t do the figure-8 in all 4 slots, then realized that keeping them separate is necessary to prevent the cable from wearing against itself. Very nice joint and explainer!

[@funkydozer]

It’s a great joint solution for sure, very effective. But not like animal joints, the bones of which do not roll against each other but have a cartilage pad between that allows the bones to slide against each other, which prevents bone wear. Would be interesting to see a design worked up using nylon or graphite cartilage to slide two ‘bones’ against each other

[@J_CtheEngineer]

We all know you’re secretly making a robot for barnaby Dixon.

[@gamerscomplete]

never heard of rolling contact joints before, but it makes total sense. you never dissapoint with your videos, thanks for all the work you put in to share knowledge with us all

[@spokehedz]

These are also used, I think, in old hard disk mechanisms for the stepper motor to move the heads. It was a little metal strip that wrapped around the output shaft.

[@jbrownson]

You take on the coolest projects, and actually mostly succeed, love it

[@jimurrata6785]

Im in a hospital bed looking at getting 2 new knees. You don't know how topical this is!

[@charlvanniekerk8009]

Im so glad you uploaded, I desperately needed something epic to watch

[@ryebis]

Cool idea and build. Watches and other small devices do use small bearings, but the way they're are used is different.

[@BongoWongoOG]

Never seen this mechanism before, I can see a huge range of applications for this, especially as the fastennings and 'ligaments' can be designed to attach to the housing. Very nice, wish my mechano when I was a kid had these joints !

[@alexharvey9721]

I did that once when I was trying to achieve basically the same thing. Was amazed at how well it worked actually. Very well suited to 3d printing and I can't imagine a more cost effective solution. Actually amazing low friction and durable too. I didn't know it was a thing though. Mine were more bone shaped with grooves like small gear teeth to stop the 2 ends sliding/slipping. With the elasticity of the fishing line it makes not only a very strong joint, but just like bones it would dislocate if you applied too much force in the wrong direction, which meant you could just push it back together for an easy fix (so I didn't bother with the side bits or vertical grooves, as just 2 gear like ends and enough tension in the line would make it hard enough to dislocate and virtually indestructible). Had almost forgotten about it until I saw this. Leg looks awesome, I'm looking forward to seeing how it turns out!

[@guytech7310]

Plain bearings are always an option. small Bronze bushing bearings. Consider that heavy equipment like excavators, Bulldozers, Use plain bearings for maximum strength.

[@NeoIsrafil]

I mean, to be perfectly honest with you ive got bearings with a 1mm id and 3mm od, and ive seen smaller ones, but these will be SUPER useful for a few ideas i had a while back so thank you for teaching it anyway ^_^

[@olec7125]

I highly recommend getting into knots, a solid knot makes a huge difference.

[@Rick_Cavallaro]

I did not know that human joints followed this principle. I assumed they were more of the ball & socket variety. I learned something today.

[@Personnenenparle]

I've designed a rolling joint like that couple years ago. Adding some meshing teeths like gears to prevent slipping improves stiffness and accuracy of the movements very well. Not sure you can add with the sizes you are working with tho

This solves a 3d printing problem I had for a long time, thanks!

[@karsnoordhuis4351]

Its a very cool mechanism that suits this project really well but since its a low load, slow moving joint, woulnt a bronze/oilite or teflon bushing be a suitable alternative to miniature ball bearings?

[@BreakingTaps]

Definitely an option! I have a design for the smallest oil bushings McMaster sells somewhere in my CAD folder and it probably would work well, although I spent more of the "design volume" then dealing with limiting range of motion. But very viable, and I probably should have mentioned bushings!

[@dekutree64]

Yeah, it was a revolution for me when I realized that using ball bearings for low-speed joints is stupid. Teflon is a wonder material. The overall structure ends up so much smaller and lighter weight for the same strength, and you can buy meters of tube for a few bucks and 3D print jigs to hold it and guide a razor blade to slice off precise lengths effortlessly. For larger bearings I use teflon sheet, and cut flat circles for the thrust surface, and strips to wrap around into radial bearings. Strips are easy to cut, but flat circles are pretty fiddly. But it is nice that you only need to buy one sheet to make any diameter bearings you want.

[@BirnieMac1]

@@BreakingTapsanother really fancy option is iglidur z; I’m working on my uni’s student formula and we’ve been using them for a lot of brushings because theyre basically self lubricating teflon bushings with better mechanical properties (around 0.05 to 0.14 u w/ steel iirc) Though we had a bit of issue with them being too low friction and slippage was happening in other places the company were super helpful though and they made a lot of different sizes and could be another lot to check out you end up looking for polymer bushings

[@BrooksMoses]

Also worth noting is that McMaster often isn't a great supplier for tiny things on that scale. A better option for tiny bushings would be Northwest Short Line, who do parts for model trains. Along those lines, the "needlepoint bearings" that are often used for model traincar wheels can also work well down to quite small sizes. Those are a simple mechanism where the ends of the axles are pointed to sharp points, and they snap into small conical recesses that have a bit larger angle than the axle points. Typically the axles are steel, and the sockets are a delrin-like plastic, though I've also seen this in brass.

[@RectalRooter]

@@BreakingTaps Yeap -- gonna keep asking What happened to the Space Shuttle / spaceX ceramic heat tiles ?

[@JTCF]

I've had a glasses case that used the same principle. Beyond the flexure joint itself you just had it operate like hinges, but you could flip it all the way around to change the color! The bands holding it together has different colors on the two surfaces. It was a pretty cool mechanism and I liked fidgeting with it.

[@paaabl0.]

Really cool project! You're right that this type of joints is rarely spotted in hobby projects

[@FlyGamingChannel]

So excited for this video after seeing your community post!

[@TheMadManPlace]

Very nice work - congratulations. Those components out of aluminium with a very thin stainless steel cable for no stretch could become a joint that is suitable for a bipedal or quadrupedal robot. The kinematic and inverse kinematic calculations would be much more accurate with a very stable joint. Also, actuating the joint with an actuator in the "body" and driving "lines" that run down to the joint keeps the weight and therefor the inertia way down - whats not to like? Try to find a build buddy at the show that lives near to you that has a small 5 axis mill capable of cutting aluminium properly and I can see this bird strutting and jumping around.

[@augurelite]

i love how diverse all your projects are! And i always learn something new. great video as usual

[@chernoboogaloo]

Thank you very much for sharing this. I found the video very interesting, and appreciate that you put the time and effort into printing a scaled-up model to show us how it works and how to thread it.

[@atomatopia1]

Super cool concept. Have you considered making the contacting parts concave+convex and giving them gear-like teeth? It seems like they might help support the joint against any kind of slippage in the wrong directions

[@AustinSpafford]

I can’t believe it was only upon seeing this video that I realized the old wooden toy “Jacob’s ladder” is a series of rolling contact joints (one inner ribbon, two outer ribbons). Another example of how simple and robust they can be.

[@Illure]

I've seen that in some toys but they used a band instead of a string. They were fun to fiddle with

[@ReplicateReality]

This is so amazing, ive had this exact kind of robot in mind for a long time, using ligaments and natural bone structure, mimicking nature, im going to have to copy the motor attachment method because I haven't figured out how to power the ligaments but this is like the coolest thing ever, I literally have a 5+ year old playlist on youtube for "tiny robots"

[@marctoygrr178]

this is so cool! thanks for making such a clear and simple demo :D

[@slakjawnotsayin5451]

This had nothing to do with what I was trying to find on YT, but I was fascinated by it and had to watch it anyway! That is so cool man!!!

[@aqueuse]

I have tried to do that basically all my life, so I'm very hyped to see your full version of this tiny robot with motors etc

[@SeanCMonahan]

So hyped! I said yes when you asked whether people would be interested in a standalone video on these types of joints. Glad to see you decided to make one 😊

[@VyTheWitch]

it reminds how nanoscopic insect have lashes looking wings because at this scale air is to thick to be navigated with "paddles" It's basically the same here, you adapted your technology to the scale, with something not expected in the robotic field, that's awesome, you can be absolutly proud of yourself, keep up the good work !

[@memejeff]

Amazing video man. Looking forward to seeing the finished project.

[@orphax1925]

nice video, if you want very small pivot assemblies there are also some very, veeery small bronze bushings that due to their size and low friction have extremely small resistant torque, they're not very interesting to show but it gets the job done

[@AerialWaviator]

Fascinating project, and joint mechanism. Look forward to seeing more videos as you work to build up the mechanism into a working robotic limb. Neat idea to make a scaled up version for demo, it really helped show details.

[@Mad_Catter_]

This is really great! Awesome work so far, I was thinking of designing something far different than your avian concepts, I'm aiming more rudimentary/simple in nature and would love for you to keep posting this kind of content. I truly appreciate what you have covered so far. I'm not big on STEM, never did good in school, I just love to tinker.

[@gonzalocobosbergillos4980]

Really nice! I have used this kind of braided fishing line to change the angle of rotation, when gears were too small to work reliabily. I hope to see this project advancing, it's very cool!

[@KaletheQuick]

Very nice to see a video about this. That 'Open Hand' thing had a video come out a month or two ago and I was surprised to see ball bearings instead of this.

[@jamesskyrimoblivion]

Thank you, I'm definitely going to integrate this joint into one of my future projects :) so cool!

[@ChatNoirLe]

Been playing with super elastic nitinol as the joint surface and tension mechanism, having the joints roll on the wire directly in grooves on the joint surfaces provides sideways stability, though now the joint is easy to pull apart without additional tension cords perpendicular to joint surface.

[@Gounesh]

Holy grail of mechanical joints! As many (if not all) biological beings with joints, we have proprioception and there's a constant feedback of tentioning and loosing stabilizators (in our case muscles) without being aware. This is looking extremely similar to knee joint (with missing couple stabilizing tendons) but with the right tention sensing feedback and a good enough processor, we might see this everywhere as it looks cheap and clever. World loves cheap and clever! Thanks for sharing!

[@ulforcemegamon3094]

You could also make it so that it reacts to changes instantly , one good example is "Birdbot" , it uses cables as tendons and they react to changes instantly , also is way less bulkier than other designs and is scalable

[@JasonCummer]

Cool neat to see other versions and innovations of this. I worked on and off last year on a simpler banded version of complient rolling joints. Tricky but rewarding . Interesting you use of fishing line

[@sethswheelhouse]

THANK YOU! I was one of the people who commented on the post because it might help my research with finger prosthetics! Thank you so much!

[@StormBurnX]

I had JUST gone on a Breaking Taps binge this weekend because I realized I missed this kind of content. Just went to the channel, sorted by oldest, and clicked play. It was great, I highly recommend it especially for people who might be new to the channel! The style is different but the quality is the same and the themes are still interesting and useful

[@Srfingfreak]

Salto 1-P uses bushings for this very reason - but these joints are SUPER COOL! (also very sensible for a biomimetic robot)

[@HolmesHobbies]

Fantastic little demonstration of the rolling joint!

[@mdrdprtcl]

Very satisfying joint movement, and it does look cool!

[@Woodat]

If you do have to go the bearing route, the smallest I know of are 681 bearings. 1mm thick, 3mm diameter, 1mm centre hole.

[@WhitmanTechnological]

This joint is very cool. Thanks for sharing!

[@carnsoaks1]

Our knee is a.Rolling and Sliding contact joint. But so complicated, with ligaments and meniscus providing tension at specific "points" during motion. Make one with plastic.

[@renxula]

Cool, that looks useful! Orienting the print to avoid stair-stepping on the contact surface would be good, but then those channels would pose a problem. It could be solved in various ways though.

[@wrightrj03yt]

This is fascinating, thanks for the explanation!

[@caujka]

Wonderful joint! Thanks for sharing!

[@segelsonproduction]

Cool idea, thanks for sharing! Much inspiring! 👍

[@babbagebrassworks4278]

This is brilliant, love these joints, reminds me of the wood block and ribbons puzzles. Or sewing model airplane control surfaces in figure 8 pattern.

[@costantinoskitsios]

Actually, you need the highest amount of friction for the rolling joint to work properly. Otherwise, the whole assembly will slip and the contact surfaces will stay still. Thank you for the shearing and you did a great design, to be honest.

[@TheNadOby]

Great video. Now I will wait patiently and later enjoy your video about that Dyneema tendons that do not stretch too much, actually stretch enough to make control really, really hard. Bu man, your robot looks so cool in CAD, cannot wait to see it materialize.

[@sreal-iron5898]

very impressive, thanks for spreading the knowledge

[@samk2407]

That's very cool, it's shockingly similar to how a human knee works with the acl, mc and pcl basically stabilizing the knee along that rolling contact

[@joegroom3195]

Very neat and simple way to create a joint, thanks for posting it! While watching this, my son asked if you were going to use rubber bands, which gave me the thought... If you needed a simple/light weight way to return the joint, a rubber band as a muscle would work. The other muscle to activate the joint could be how you have it designed, which appears to be a solenoid attached to the fishing line. Essentially a joint activated in one direction with a return spring. It would work to lift the leg after it's been extended.

[@eugenechelovechniy]

1:52 I wasn't ready for this

[@sloppycee]

You should build a passthrough hole and tie off into it so that its a bit cleaner without having to loop around the sides.

[@bartspeet930]

Really neat stuff! If you want to prevent rotation, you could impose a gear teeth row on the outer 'bearing surfaces' so that the movement is not only constrained by the (flexible) rope.

[@ThaBullykid]

Wow cool project! Can't wait to see more about it.

[@michellezhang820]

Very tiny, but I love it. 3D printing has been a big help for it.

[@the.curryspice]

This is amazing work! Looking forward to your builds :D May I suggest making small indentations on the sides of the lower part of the hinge so that the cable can be kept more secure and flush against the plane of the joint?

[@Datdus92]

I think you might be able to use clear heat shrink around the joints for more stability! Very cool!

[@MarwinO3]

Very interesting rolliong mechanism design and knotting technique.

[@owenkegg5608]

Awesome! Definitely going to play with this hinge type.

[@Trust_me_I_am_an_Engineer]

Thank you for a very enlightening video!

[@olivierconet7995]

Awesome. This gives me many ideas for new designs...