>>37672 >I still believe using this concept is objectively correct for us to pursue. Excellent! I do too, Kiwi. IMO, we're simply not likely to successfully manage all the tradeoffs needed for effective & pleasing robowaifus without incorporating design elements relying on tensegrity principles (whether they be 'canon', or no) into her frame & support systems. I'm personally excited by a specific thread on this very-cool topic. Thanks, OP! :^) https://en.wikipedia.org/wiki/Tensegrity https://www.youtube.com/watch?v=jnpshtyvWr0

>>37673 >related This straws+strings (jumbo drinking straws+ultra-high molecular weight fishing line, actually) approach is right up my alley, concerning building ultra-lightweight, very low-cost robowaifu skellingtons. Jumbo drinking straws are pretty much near the limits of physics in providing strong, lightweight (and cheap!) support structures in space.

>>37674 >ultra-high molecular weight fishing line BTW, slightly off-topic (but only slightly): this stuff can be woven into fabric. * Combined with good sewn textile patterns+vacuum forms+a little hardening resin (interior/concave sides only -- for smooth exteriors), this presents us all with interesting possibilities concerning our robowaifu's shells (very lightweight, resilient to impacts/resistent to punctures, reasonably inexpensive, easily-repaired). Properly-designed, these shells can then also directly provide 'support frames' for underlying internal tensegrity structures (perhaps with the addition of some simple interior 3D-printed hoops/'ribbing'). Lots of potential benefits, AFAICT. :^) --- * One example vendor http://uhmwpefiber.com/1-4-industrial-textile-fabric-fiber/

>>37675 Uhmwpe is a wonderful material but it creeps(lengthen over time with mininal stress) thus ruins tension over time. Collapse is easier when the critical length is not constrained properly. It is attractive to not create ball and socket joints that requires geometric accuracy and lubrication, and subsequent shielding away from liquids and dust but a ball joint is still dead simple and would hold such accuracy much better under compression load. Walking would be hard if joints are wobbling. But the idea that actuator/cable double as extra width against bending stuck with me. I sketched up a capstan actuated full motion joint with 2d extention and contraction as well as axial rotation hoping to creat a superior design over individual sets of wire and linear actuators. My afterthoughts later reminds me that individual sets of cable and actuator is going to be more resiliant and less likely to fail completely than one continuous cable running on capstan being the single point of failure. The number of motors is still 4, at least 3, and since I haven't ran the math, there may not be an attachment point solution that keeps the wire length constant. Without that exact solution, some range of motion would result in popping out the joint or snapping the wire unless I make one of the capstan ride on suspension, adds wire tensioner, or pneumatric cousion inside the joint as a hack job.

>>37676 Artbyrobot, is that you? :D >Uhmwpe is a wonderful material but it creeps(lengthen over time with mininal stress) thus ruins tension over time. Collapse is easier when the critical length is not constrained properly. Fair point. But I don't see much else that could easily fit into the same 'readily-accessible, relatively-inexpensive, lightweight, strong, durable, super-conformable, highly-adaptable, tensioning system' category apart from perhaps extremely-fine (even dangerously-so) stainless steel wire. And even that will sag with time & usage. Ideas? Carbon wires are exorbitantly costly and will be reserved only for the most topflight (read: super expensive!) robowaifus produced several years down the line from now. >It is attractive to not create ball and socket joints that requires geometric accuracy and lubrication, and subsequent shielding away from liquids and dust but a ball joint is still dead simple and would hold such accuracy much better under compression load. Beautiful. My own pottering about with this years ago turned into a 'cylinder & spindle' design, tensioned with big rubber bands, situated orthogonally up along the (also tensegrity-esque) 'spinal' column elements. You might think of them as lightweight, swivel-able 'ribs'. This approach allowed for very flexible (resiliently-bendy) internal support structures, for otherwise completely-inflexible components (eg, the so-called 'breadbox' electronics housing, et al) within the robowaifu's torso-volume. >My afterthoughts later reminds me that individual sets of cable and actuator is going to be more resilient and less likely to fail completely than one continuous cable running on capstan being the single point of failure. An important design consideration!

>>37676 >>37677 Slackening tension of support cables is a problem going back for many centuries (at least!) in the civil engineering & nautical worlds. The aviation industry solved this over 100 years ago with lightweight, inline (but manually-operated) turnbuckles, as a regular maintenance item. [1] Can these be a) designed to be very smol, and b) automated to re-tension periodically on their own (and without much additional cost+mass)? --- 1. [2] https://en.wikipedia.org/wiki/Turnbuckle 2. Also confer lockwire used to tie-down the turnbuckle after re-tensioning (a safety-critical item): https://en.wikipedia.org/wiki/Safety_wire

>>37678 >Slackening tension of support cables is a problem going back for many centuries (at least!) in the civil engineering & nautical worlds. Now that I think of this, surely that 'Old Italian Dude', the inimitable Leonardo di ser Piero da Vinci must have a solution for this. Anyone know if he had a re-tensioner system for his Mechanical Knight Bro? (Surely a precursor to Robowaifus if ever was. :^)

Various resources from the blog: http://jirolfing.blog.fc2.com/?date=201501 https://www.youtube.com/watch?v=k6FaULbOmnE https://www.youtube.com/watch?v=uMug6XzP1R4

>via: http://kennethsnelson.net/tensegrity/ Also, numerous animations (helpful to visualize the structures involved): http://kennethsnelson.net/animations/

>>37677 Hi chobitsu I m sorry that I don't know who that is. I am the newone posting uduki tsukasa on the other alog site and haven't used a user name yet. Some offers zero creep polymer ropes but tbh i don't trust their claim. Tension is the necessary evil for all thing except masonry buildings. Maintenance on exposed soft sides is what bond building is all about. Ideally the actuator self adapts to lengthened wires, and if not the robot has its own hand to tighten it and docking station should make it easy. Steel is probably the best wire. Piano tuning is seasonal only and probably due to temperature change. But don't get body parts caught in one and tempered carbon steel isn't the best against oxidation. (Just boil rust away) The cylinder and spindle idea cpunds interesting. Can the cylinder be blow molded like soda bottles? As for carbon, i think the best way to utilize them is making few layers graphene oxide by mixing graphite in milk whey protein in blender or magnetic stirbar for many hours, dry and adds that to any plastic/resin of at like .5% weight. Or be used as ink to print soft pcb https://www.markoneill.com/ACS-AMI-2020.pdf

>>37682 >Hi chobitsu I m sorry that I don't know who that is. Just a Nihongo pronunciation of "Chobits", the mango/animu that created the board's mascot Chii (cf. >>495 ), who inspired me personally regarding the possibilities of robowaifus. That's all. <---> >and haven't used a user name yet. We tend to namefag here b/c as a (mostly-)consistent group of engineers, artists, etc., working towards common goal(s), we can 'cut to the chase' (get to the main point) easier by getting to know one another as a community. >tl;dr Imagine working at a big engineering firm together where you yourself, and every.other.anon. in the building all have 50 First Dates [1] syndrome. It would be pretty hard trying to get anything practical done together in such a scenario, for a highly-complex project (such as conceptualizing/researching/designing/prototyping/testing/manufacturing/distributing effective & appealing opensource robowaifus [& kits] -- all from scratch). And stylometry only goes so far! Therefore by consensus our board culture uses namefagging, typically. OTOH -- we are Anonymous; through & through. So yeah, it's a bit of a weird (and fun!) mix having many of us with a moniker, yet still absolutely maintaining the OG Anon mindset toward one another. Don't think I know of many other boards like us in that regard (and a few other regards, as well). >ttl;dr Use a name, or don't. Perfectly fine either way, Anon. <---> >and if not the robot has its own hand to tighten it and docking station should make it easy. Interesting idea. OTOH, structural lines for tensegrity tension are going to (at least conceptually) spread all throughout her internal skellington/support-structures. Hundreds of them, I'd imagine. It'd certainly be hard for a human to do maintenance on such a collection! :D >Steel is probably the best wire. It is better than fishing line in many ways, that's certain. But cost & mass are two of the highest priorities in the long litany of concerns we all have to balance here on /robowaifu/ . If we can find a set of reliable sources for extremely-fine, high tensile-strength stainless steel wire, then that might be a real consideration. Otherwise the mass of hundreds of such steel wires throws the "equation" right out balance. UHMW fishing line is currently much, much better for us in these (availability/cost/mass) [2] regards, IMO. >Can the cylinder be blow molded like soda bottles? Great question! A few of us here constantly keep manufacturability concerns in mind at all times. And personally, I'm always on the lookout for """alternative sourcing""" (read: waste recycling) materials ideas, so that men around the world can have some chance at building their own robowaifus out of whatever's at hand. >carbon/graphene >flexi-PCBs >information linked-to, for everyone's benefit Thanks! Nice ideas like that are always welcome here, Anon. Cheers. :^) --- 1. https://www.imdb.com/title/tt0343660/

>>37678 > Can these be a) designed to be very smol, and b) automated to re-tension periodically on their own (and without much additional cost+mass)? I had an idea on this topic: Since my designs are using jumbo drinking straws (thin plastic tubes) for the floating tensegrity 'rods' (cf. idea-related : >>37674 ), and the fishing lines travel down inside the straws...why not insert smol, motor-driven line tensioners inside the straw tube as well? Not only could they be used as (re)-tensioning devices, but they could actually assist with initially assembling the tensegrity structures (within jigs) as well. The proverbial "Two birds, one stone." <---> They'd need to be: a) very compact (fit down snug inside straws/tubes) b) lightweight (in total, at least; probably have only a few strategically-placed around the tensegrity structures -- drawing everything tight together) c) inexpensive (perhaps 3D-printed frames around cheap, tiny motors) d) effective (the motors would turn some kind of friction feed [possibly a tiny triple-rubber-wheel arrangement, each offset 120' around the central 'feed zone' core]) e) lockable, when not in use (perhaps drawing the 3-wheel feeder head back up into a 'compression funnel' to squeeze & lock the ensconced line in-place). Ideas?

>>37683 I'd stay Anon for now, maybe for another 2 weeks or when it got too confusing. Distilled ideas and works can and do live without authorship. Ultimately both steel and UHMWPE are used to anchor things in the sea and some plant fiber are resistant to salt too. I just think less tweeking is better. https://www.mcmaster.com/product/9667K25 Looks like they are selling 3 feet of pianowire in a pack of 6 for 10 dollar. I don't think it would break the bank. As for weight, tensile elements are usually not heavy when compression element has to add additional width to hold bending stress to prevent buckling. The cable is half of the weight to the tower and not counting the concrete floor slabs. https://www.goldengate.org/bridge/history-research/statistics-data/design-construction-stats/ >>896 Straws will be weak in the other two directions. Id thicken it like water pipes in profile. Specific strength are good when only the self weight is concerned like running and jumping. But in case of user falling over, stepping on or a bookself falling all over the robot, foreign bodies weight justifies absolute strength to save her from total rebuild. Besides, air weight stuffs are afraid of air blowing. A 70kg companion can easily have 20 to 30kg dedicated to structural strength while 1 steel bike is like 10 kg. This isn't a nasa mission where a large tower of rocket fuel are spent to send a tiny peak to the orbit and repeat to send a smaller fraction to mars. In civilized world there are power sockets everywhere to power the battery and in rural area plenty of hydrocarbon to burn. One more thing is that uhmwpe are one of the best at sliding, used as joint replacement, and many glue cannot stick to it. I think gluing requires resin and solvent like in ballistic plates. I don't think friction drive would work on slipery rope but either a pulley, wench or capstan with many loops would work.

>>37685 Thanks Anon! I'll look into that information. I appreciate your valuable input here. Cheers. :^)

A /comfy/ Fishing Bro Anon made an interesting post about fishing lines: https://trashchan.xyz/comfy/thread/13171.html#13313

>>37676 Please share more illustrations and post updates as you build your joint mechanism. >>37679 >Da Vinci's Knight Excellent example of a design that could be adapted to tensegrity principles. Floating shell panels using variable length cords to move about is the future coming from the past. In this case, the ropes creep wasn't factored. Da Vinci likely just used thick enough rope that the creep wasn't an issue for the machines expected life. >>37682 >Zero creep rope Not physically possible. You are wise for realizing their lie. Creep can be incredibly small given the right material is used for expected tension. Notably, many elastronomers (such as silicone and rubber), tend to have favorable creep given their cost.. >>37683 >Steel is heavy It also has a catastrophic failure mode that would be devastating for her master hugging her. I've been whipped by a steel cable that snapped suddenly. >>37684 >Dynamic line tensioners embedded in her tubes Definitely potential in this concept. Not too far off from the research presented here; https://www.frontiersin.org/journals/robotics-and-ai/articles/10.3389/frobt.2019.00111/full >>37685 >70kg My personal goal is 10kg or less for MaidCom. Every gram adds cost to building, maintaining, and powering her. Tensegrity as a concept is primarily used because it can provide heaps of durability relative to mass compared other construction methods. >Capstan A great mechanism for adjusting tension and/or actuating her parts.

>>37689 >It [steel cabling/wire] also has a catastrophic failure mode that would be devastating for her master hugging her. I've been whipped by a steel cable that snapped suddenly. Great point!! Safety is certainly a very-high priority concern for us here. Thanks for pointing that one out. > https://www.frontiersin.org/journals/robotics-and-ai/articles/10.3389/frobt.2019.00111/full Wow! That paper is loaded with great information, thanks Kiwi. Here's a copy, just so it doesn't get memory-hole'd on us. > >Tensegrity as a concept is primarily used because it can provide heaps of durability relative to mass compared other construction methods. This. Its literally the whole point behind this research! (Well, that and the fact it also offers us at least some improved potential for highly-lifelike motions/deformations/etc. Important points for hugging & dancing with our waifus! :D Cheers, Anon. :^)

>>37691 >>37687 I doubt I was actually helpful. Good luck working things out.

Do we even have any materials that have better tensile strength compare to flexural and compressive strength? Besides steel rope suspension bridges I can't really think of any common uses for this building method. But on the notion of elastic elements, perhaps nitinol might be a good idea. Nitinol doesn't have as much tensile strength, but is more elastic.

>>37689 I did the joint calculation. Good news is during axial rotation, from neutral ( V ) to maximum rotation ( [X] ), assuming zero radius capstan and zero radius ball socket joint, and assume the span and height is 1 to 1, the length change is only 1.5%, less if span is less than height. And one can easily get 180 degree of travel axially like how we turn our hands/arms/head. An intuition on how the geometry works is that the trace of 2 fixed point sharing a wire is an elipse. This will be all the possible position of the capstan in 2d. Rotate around the long axis gives elipsoid which is the surface which the opposing capstan can be in 3d. The top of the elipsoid is flat enough that a circular path is not far from the true surface. >bad news However planar movement like leaning forward/backward/left and right as a hinge would slack the tension. Turning 90 degree make make 20% of the cable length into slack. Not good for joints but gives a good insight that one can place the wire by bending the joint first, wrap it in and then straighten it out. >new design Hinge movement is needed. To modify the existing architecture for that task, the assumption that the center ball joints are too small to collide with wires are taken back. Tendons in real animal joints are locked in place by other tendons than to freely slide past and loosen on the contracted side. Similarly an enlarged ball joint with wire guides can be placed to lock wire in place. More math is needed to calculate the right geometry given the segments are more complex and the axial rotation is negativelly affacted the bigger the ball is. >wire whipped Ouch!

>>37691 No! It was really very helpful, Fishing-Anon. I hope you'll interject with more good advice here on /robowaifu/ whenever you'd like to (though you should visit over on our main board at Alogs then). Thanks & cheers, Anon. :^) >>37693 That's a good question Anon. Honestly, I haven't had much time to delve into Materials Science sufficiently to be able to answer these types of questions very well. But Fishing-Anon seemed to know something about this, though (cf. https://trashchan.xyz/comfy/thread/13171.html#13371, et al). Maybe Kiwi or our other legit engineers here can provide more insights as well? Cheers. :^)

>>37694 >based hross limb-analyzer Biomimicry is king! :D

>>37695 Will a version of this thread be made on the main board? >But Fishing-Anon seemed to know something about this, though (cf. https://trashchan.xyz/comfy/thread/13171.html#13371, et al). Sorry as this is only barely tangentialy relatted to tensgrity. As to that particular post, Curv and Tegris are fused thermoplastics made of layers of woven polypropylene fabric. These products are commonly used as stiffeners in duty belts, plate carrier cumberbunds, etc.. Picrel is a Curv holster adapter very much so capable of surviving a person falling on it. There is a vidio from the maker of a guy doing pull ups on one without ripping the anchoring screws out of the material. Anyway, I am no engineer, but I believe it would make an ideal semi-regid anchor bed for mounting just about anything. It would give to absorb impact and flex to aid in body softness. I believe it would probably also work very well in thin bands for reinforcing/support a flexible shell exterior. A bit of elasticity could be added by using shock cord anchors on the bands (look up the cumberbund adjustment for a Crye JPC 2.0 for an idea). The video below is of a simple Curv belt. There is no reason to watch all of it, but it gives an idea of how the material will flex. These styles of belts remain very stiff and resist sagging downward as weight is added to them. https://youtube.com/watch?v=frMwLYlL6A4[Embed]

>>37700 >Will a version of this thread be made on the main board? Yes! It will be this very thread in fact (once it's been merged over from here by Robi & myself Kiwi did it because he's impatient :^) ). Other threads that fit properly will simply be merged into already-standing threads there on Alogs ( /meta , R&D, etc.) A few like this one will remain as new threads there. Once we return & are fully re-merged over there, we'll put this (our bunker) board into a relative 'deep freeze' (a few threads here will still be unlocked, however: like backups, filepile, & comfy bunker). This board will then be unlisted from the overboard & webring (rn we have both listed on the WR, lol). Make sense, Anon? update: The move has now begun! (cf. https://trashchan.xyz/robowaifu/thread/55.html#970 ) <---> Excellent post, Anon. This sounds like a great materials resource that could be used in many ways for the structural & internal support aspect of a good robowaifu (whether she's a tensegrity-based design or no). Thanks! I trust your instincts are well-qualified. BTW, most of us are amateurs (or at least relatively-so, considering the vast swath of disciplines involved here! :D So please make yourself at home, Anon. Cheers. :^)

>>37690 Thanks for saving the PDF! >>37693 >Materials with greater tensile than compressive strength Stainless steel buckles under lower pressure than it'll undergo plastic elongation. >Common uses Though "true" tensegrity is rarely used outside of bridges, stadiums, and other large architectural works, the core of the concept is commonly used. Tents, umbrellas, folding chairs, etc... use a mix of compressive and tensile loading to min-max durability per material use. >Nitinol elastic elements Clever idea, makes fantastic springs. It is expensive so, using it in series with another material may be needed depending on scale and budget. >>37694 Looks like you're making a mechanism functionally similar to a stewart platform. I've been contemplating similar concepts. >Tendons in animals All animals use tensegrity in their musculoskeletal systems. Studying how tendons and muscles interact with skeletons provides great examples to learn from. I appreciate you bringing up how faschia and tendons can overlap to limit motion. Frankly, I overlooked that other animals also have mechanisms we can learn from. Thanks for broadening my perspective. >>37695 >Kiwi can provide more insights I'm passionate about tensegrity and want to help others. >>37700 Interesting material, similar to cloth in a resin binder. Depending on geometry, it could easily work for either compressive or tensile elements. >>37702 Any estimates for when this thread will be moved? Turns out, now

>>37704 >Thanks for saving the PDF! Y/w! Remember 1984 bro... >I'm passionate about tensegrity and want to help others. Same. I'm just too ignorant about how to assemble these things ATM though -- seems complicated! How the heck do you build something like that with just two hands!? :D >Any estimates for when this thread will be moved? As I related (https://trashchan.xyz/robowaifu/thread/55.html#970 ) the plan is about a week from now. a) I need to do a modest rewrite on BUMP, but circumstances are stalling that rn. b) Robi will need to complete his BUMP-to-Lynxchan importer scripting first as well. Since these are both indeterminate-timeframe imperatives, it's tough to pin down rn. Hopefully my estimate will come off... we'll see! :^) <---> That being said, there's nothing to prevent you -- Mr. Moderator -- from getting started early with a new Tensegrity bread there today! You don't say? :^) (Thanks for the reminder.) -Kiwi Also, please be giving some thought now about how you think we should merge all these threads here, together on Alogs after the 'move' of these trash/robowaifu/ threads over there. Some (like this one) are clearly new breads. However, most of these Bunkerfest threads definitely should be merged back into aleady-standing threads there on Alogs. Please remember we have a limited 'thread budget' (and we've never liked having dupe threads about on /robowaifu/ , regardless). I'll like to leave that task fully in your hands+Greentext anon's to decide, if possible Kiwi. Cheers. :^)

>>37693 >>37704 I forgot to mention, I know nitinol can change shape with heat, and elastic like rubber bands can emit heat when stretched, so I was thinking that nitinol and elastic could be used together to boost the strength somehow.

>>37716 That's really an interesting idea, Anon. Sort of a 'smart material' type of behavior at that point, I'd say. Cheers. :^)

>>37702 >>37704 >>37705 Heh. :DD <---> You did a great job migrating this thread, Kiwi. Crosslinking, etc., all look good. Nice to have this cool new bread back home here! :^) Forward!!

Another link from a Doctor studying the skeleton and how it's actually a Tensegrity-Truss. https://web.archive.org/web/20151007045949/http://www.biotensegrity.com/tensegrity_truss.php

>>37735 Excellent research material, Grommet. Thank you, Anon. :^) <---> Tensegrity is very-likely how we are going to win this race as amateurs, against all the FAGMAN (((groups))) and even against the baste Chinese!! :D Remember the Wright Brothers!!

Fishing-bro Anon made another post: https://trashchan.xyz/comfy/thread/13171.html#13823 Tool might be useful somehow within a tensegrity jig assembly?

>>37693 Kevlar? It's maybe not as strong as steel cable, but it's a lot lighter. It's a good candidate if you want to make a pulley system to act as robot musculature.

>>38998 UHMWPE https://en.wikipedia.org/wiki/Ultra-high-molecular-weight_polyethylene Stronger and lighter than steel. Reasonable cost.

>>39004 UHMWPE Biomaterials Handbook, Third Edition: Ultra High Molecular Weight Polyethylene in Total Joint Replacement and Medical Devices B06087D4902577C582627AA847946FBC

>>39004 I know the Marvelbrain is kinda embarrassing, but it made me think of Spiderman's silk, how it's also described as stronger and lighter than steel

>>39004 That stuff is pretty strong. It will stop a bullet if you really need it to.

>>39013 Forgot vid https://m.youtube.com/watch?v=LDP8sItGYw0&pp=ygUMdWhtd3BlIGFybW9y0gcJCdgAo7VqN5tD

>>39004 > (UHMWPE -related : >>39010 )

>>38623 Fishing anon here. I don' think you would have any need to join different types of line end to end, so I doubt it would be a useful tool. If you are wanting to make a continuous loop by joining line to itself for some reason, this tool is not appropriate. The FG knot works by forcing the crisscrossing PE line to dig into and pinch the surface of a fluorocarbon or monofilament leader. It is a specialty knot that is smooth and narrow for sliding easily through eyes when casting. There are many more simplistic knots that would be more useful. https://www.netknots.com/ >>38998 Kevlar cordage/thread is relatively expensive and outright weaker than a PE fishing line based on diameter. It is very resistant to heat, but I doubt that is relevant for any robowaifu tensegrity application. It would also potentially damage things it rubbed across: (I would mute this idiot's video): https://www.youtube.com/watch?v=LpJlisA1gBY >>39014 It's completely irrelevant, but I would guess that plate would have pretty sketchy backface deformation. In more serious/professional plates, UHMWPE (or Kevlar, etc.) is used as a reinforcing backer behind ceramic. Here is an Interesting body armor testing channel of for anyone bored: https://www.youtube.com/@BuffRANGE

>>39037 >FG knot While the FG knot appears to put less stress on the line. Meaning it would break at the knot less. It's is too complicated, for me anyways. The best way to join two ropes or lines and sheets or any different size ropes, sheets, fabrics, tapes or whatever is, drum roll, the Zeppelin knot!! This is the knot used to tie up Zeppelin air ships. Can you imagine the vast stress and pull on a rope tied to a large Zeppelin airship? Way high. And no matter how hard it's pulled on if the tension is released it's super easy to untie. There's nothing better. https://www.skytopia.com/project/articles/knot/knots.html You can make a better hitch from a zeppelin knot than a bowline which I really detest no matter how popular it is. It's not near as good and hard to untie after being stressed. The Zeppelin will come right loose no matter how hard you pull. The grapple hitch is not so bad either. although I like an "adjustable gripe hitch" better as I find it easier to remember. https://www.animatedknots.com/adjustable-grip-hitch-knot

Zeppelin knot mnemonic. B and Q, B over the top and through, Q under the bottom and through. Or the more racy version of 69.

>>39043 I agree the FG knot is completely inappropriate for this application. The knot does have near 100% yield strength but it is only intended for a very specific niche. I do not doubt the utility of your knots with rope, but adjustable friction knots are not generally used with fishing line. Compared to rope, PE fishing line is much more slick and flexible (thus the many elaborate high friction knots). I would suspect knots like those could slip apart or slide around under normal fishing usage conditions. Those knots are probably perfectly fine for use in a tensegrity project though. From a dexterity/manipulation perspective, being able to untie or lossen a knot made with a very low diameter line might be very difficult and potentialy infeasible.

>>39046 >adjustable friction knots are not generally used with fishing line I should have been more clear about that. The Zeppelin with a couple of stopper knots on the ends would be good for any type line. Even without the stopper knots it would likely be fine, but just in case... The knot is known for never coming even if not tied up tight. It one of those knots most people do not know but has great features including not being stressful at the knot compared to others. The others I threw in as being really nice knots I liked but yes you are correct they are not appropriate for fishing line.

The knot is known for never coming "loose"...

>>39047 I decided to do some testing with PE line on the zeppelin knot and the grapple hitch out of curiosity. These performed very poorly, much more so than I anticipated. I tied both knots with the heaviest braided line I had on hand, 40 lbs test YGK XBRAID UPGRADE X-8. The zeppelin knot pulled apart under maybe 8-10 lbs of pull ( I did tie small overhand stopping knots). The friction of the knot pulling apart melted the surface of the line. This was impossible for me to capture on camera, but the line feels crunchy and the outside surface has fused a bit. A very bulky and complex stopper may have held it together, but that would be a bit self defeating in terms of effort. The grapple hitch was a complete failure. The knot, no mater how tightly cinched, will slide up and down the line under strain. As it did so, it frayed and destroyed the line.

>>39049 I tied another zeppelin knot with large dropper loops as stops on the tag ends. I made sure to moisten and properly set the knot before pulling on it. The knot slipped under light loading again, but the larger stoppers functioned. Unfortunately, the knot slipping still melted the surface of the line and caused it to fail at what I would guess was about 15 lbs of pull.

This thread -- and particularly @Fishing anon's inputs -- have encouraged me all the more that pulley-and-cord based approaches to distal actuation (elbows/wrists, knees/ankles) is the correct course for my design work [1][2]. I hope to soon begin some new prototypes with UHMWPE cords & low-friction plates, combined with aluminum tubing & struts/etc., assembled with 3D-printed fixtures/joints/etc., into a basic humanoid skellington prototype frame system. In the later stages of assembly for it, tension everything down, tightly-knit-together using tensegrity-'alike' approaches (using more PE cording). Its not "pure" tensegrity maybe, but many good benefits will still be there for us, I think. (Plus, it will be much simpler -- assembly-wise -- to just 'strap down' everything together using tensioning lines, after the fact. Throw a few [4-6, maybe?] strategically-located aluminum turnbuckles into the mix for simple re-tensioning maintenance further after the fact, and Bob's your Uncle! :^) <---> Should that go swimmingly, then I'll probably move from thence onto using so-called LARP-foam (EVA) to 'bulk out' her volumetric appearance(s) in very low-mass, comfy- feeling/looking ways. --- 1. Hey, it was good enough for Leonardo da Vinci!! (cf. >>37689, >>37679, et al) :DD 2. Because of the 'Thrown Weight' problem. >tl;dr Keep the actuator/battery masses located as close to the pelvic/thorax volume as possible.

>>39054 If you don't already have UHMWPE line for the pulley system, I would suggest going with something like the pictured 200 lbs test AFW Downrigger Braid. It should be more than strong enough to resist any realistic stresses. There are definitely stronger and/or cheaper cords not marketed as fishing lines, but they appear to be much less tightly weaved. I have not had any in hand for examination though. I assume (very likely incorrectly) a loose weave could cause durability issues by staining portions of cord unevenly in a moving system. As an alternative to using distal pullies, maybe look at incorporating fishing rod guides. Small aluminum oxide ones for casting rods would probably work well and are very cheap. The double footed varieties would be more sturdy. You could even use some of the line and super glue, epoxy, etc. to fix their feet in place on the skellington.

>>39060 POTD Thanks Fishing anon! I'll buy some of these things soon-ish to begin prototyping investigations with them. Cheers, Anon. :^)

After looking at random products for ideas, I believe there is potential in providing adjustable tension to a PE support system with an A-Just-A Bubble or an imitation of it. I believe you could pass a loop of line through it and adjust the length of the loop to set your tension. It might be possible to tension multiple line with one device as well. This would be both cheap and extremely light. https://www.youtube.com/watch?v=wxLITFtpPmI

>>39050 I stand corrected. I really love this knot it's done me great service and due to it's construction, the way it circles and clinches I had no doubt it would be magnificent but...apparently I'm wrong. Maybe the turn is too tight. Out of curiosity could you do the same test, with the same line, with a FG knot? So I look up PE and find that "supposedly" PE 40 pounds should take 400 pounds force. I notice the line you show is 50 pounds???? Was it another? At some time in the future I wish to tie a short line onto a longer line so that I have several short lines at intervals along the longer line. What knots do you suggest for this. FG knot? Couple others I like because they're easy to remember. Blake's hitch (for one way pull only)(you could use many loops to spread the stress)(I like this one too) https://en.wikipedia.org/wiki/Blake's_hitch https://en.wikipedia.org/wiki/Prusik_knot For some reason I look at the FG hitch and think,"I'll never remember that". Solely my failing. Some knots or hitches just seem natural to me and easy to remember. Blake's and Zeppelin, adjustable grip hitch are some that just easily stick in my head and "I assumed", and we know how dangerous that can be, that they worked equally well on all types of rope.

>>39054 >Throw a few [4-6, maybe?] strategically-located aluminum turnbuckles into the mix for simple re-tensioning A idea. If you can monitor the angle of the limbs, whether the cable is loose or tight makes no difference. A small amount of stretch means you just pull the actuator a little further til the angle is correct. Deletes a part.

I got the info on PE rating from this page https://www.oceanbluefishing.com/magazine/pe-rating-fishing-line-diameter-chart/ I think a fail written by an AI that confused things as their charts don't line up with what they are saying. I hate all these AI pages and pages and pages that show up first in search engines that often have faulty info. William Casey (CIA Director), "We'll know our disinformation program is complete when everything the American public believes is false." This was supposedly verified by a member who was in the cabinet meeting when he said it. It's a vile crime that US government organizations should have disinformation fed to the US population as one of their goals. Though I think we need intelligence services I sometimes think it would be better to not have them at all, even with all the deficits of this action, if they are going to constantly try to discombobulate the populations minds.

>>39049 Thanks for testing this it's very helpful.

>>39066 I was also looking at corsets and hoop skirts for squish-able body design ideas. I imagine a soft torso, or maybe a thigh, could be based on the hoop skirt. PE lines anchored at the top and bottom could suspend springy plastic bands of Curv, Tegris, or some similar plastic product. >>37700 I'm not sure what the best way to bring the ends of the hoop together would be. My fist thought was feeding the ends trough some kind of keeper and anchoring them with shock cord so the hoop could expand and compress. >>39067 >>39069 >>39070 When knots in PE fishing line slip, the friction destroys/melts the surface of the line, causing it weaken and fail. To form most fishing knots correctly, you actually need lubrication (spit or something) to keep the line from destroying itself. >PE 40 pounds should take 400 pounds force >I notice the line you show is 50 pounds???? Was it another? For fishing line ratings, it would defiantly be only the listed 40 lbs. The 50 lbs spool pictured was the only image I could find. The line I used came off of a reel and I no longer have the original spool. >At some time in the future I wish to tie a short line onto a longer line so that I have several short lines at intervals along the longer line. What knots do you suggest for this. FG knot? If you are talking about adjoining the short lines to the main line at a perpendicular angle, I would suggest not doing that at all and using only one line. Try looking at a dropper loop knot. You could just make VERY long loops: https://www.netknots.com/fishing_knots/dropper-loop . If that is not appropriate, I don't have any meaningful suggestions. The two knots you listed should both function. Adding more wraps, maybe 10 or so, to the Blake's hitch would help. You would need some additional knot to create the loop for the Prusik knot. I would try a King Sling (skip the threading it through something part) : https://www.netknots.com/fishing_knots/king-sling . You could also loop the Prusik knot around the main line additional times to keep it from sliding up and down the main line. >Out of curiosity could you do the same test, with the same line, with a FG knot? I have no heavy leader lines available to appropriately test an FG knot. The knot is for really only for combining a PE main line to a leader of fluorocarbon or monofilament. I'll try one of braid to braid in the morning, but I expect it will pull apart easily. >>39068 I assume he means in the static structure?

>>39072 >>39071 Whoops, no .png files huh?

>>39067 >>39071 When knots in PE fishing line slip, the friction destroys/melts the surface of the line, causing it weaken and fail. Sorry, that was unclear. The Zeppelin knot failed because it allowed the super slick line to slip in the knot. If you modified it to multiple have extra passes in the pictured step, it might do better.

I tested a braid to braid FG knot and a modified zeppelin knot with 6 twist per tag end. The FG knot eventually pinched the leader end off at maybe 70-80% breaking strength. The end of the knot that broke fused together from the heat. This was better than I expected. The modified zeppelin knot failed almost instantly. It might have held 3-4 lbs of pull.

>>39071 >>39073 >hoop-skirts Great idea, Anon! This has been discussed on /robowaifu/ before, and I'm still convinced its a good idea today. I personally see a kind of 'tensegrity cage' (probably also including your hoops at the outer perimeter) underlying an intentionally-designed shell of LARP foam to fill out the silhouette of our robowaifus. Again, good thinking Anon. Cheers. :^)

I love these hand-drawn graphics ITT! GG, Anon.

>>39066 This is excellent, but the outer 'bobber' shell of the pictured device is far too bulky for our purposes here on /robowaifu/ , I think. Any chance we could ditch that shell, and just use a 'spindle' (or even narrower) mechanism to turn for tightening up the slack? (Preferably, this process would simply be a hex tool inserted right through the shell, then rotated for re-tensioning maintenance...no shell disassembly required.)(or even better : fully-automated retensioning, completely internally! But let's all just take one step at a time here, eheh. :^) <---> The issue is the extremely-tight volumes around the hips & shoulders where several of these (w/ at least 4 for each leg & arm) need to be wedged into place... given the distal actuation requirements -- eg; both of the knees and further of the ankles (w/ 4 PE cords [2 cords per tightener] for each of these joints [extensor + retractor; x2 ]). Combined with the already-tightly packed volume of 3 major actuation systems for, eg, the hip itself (x2 ), plus the further 4 smol'r actuators (x2 ) for the knee/ankle also nearby -- then these big bobber shells are deffo a nogo right in that same complex, proximal volume.

>>39082 I was thinking something like that could be used in the torso to tension lines for "shell" parts. Something like >>39071 might be able to be able to have independent adjustable tension for all the lines with one device. I don't think it would be useful in the pulley system lines as Grommet suggested >>39068 . As far as I can tell,the bobber is just using a twisted latex rubber tube. Anything that could hold one end of the tube stationary while allowing you to rotate the other and lock it in place should work. A "U" of tube fixed at both ends might be more practical to make. You could feed the lines through and then twist the "U" and hook it over some kind of peg.

>>39085 >>39082 Couldn't the same cord and motor be used to extension and retraction if you used a rubbery pulley and wrapped the line around a it a few times? In any case, I think you could adjust tension by using bolts as the anchors and twisting them. It would be almost like tuning a guitar. I would suggest getting partial threaded socket head cap screws, wrapping the non-threaded part in electrical tape, tying the knot form the video, and gluing the knot all the way around the bolt with super glue. Thread looker would probably be needed. This would allow you to tighten the lines with a hex key. https://www.mcmaster.com/products/socket-head-cap-screws/socket-head-screws-2~/threading~partially-threaded/drive-style~hex/ https://www.youtube.com/watch?v=cghRdGdkLPg&t=216s Using something like a small eye bolt for the anchor bolt would easier to do for experimenting.

>>39082 So many typos. : (

>>39087 >So many typos. : ( LOL! Its said that people edit their documents to fix the errors. By all appearances, I, Chobitsu, edit my posts to add them!! :D >tl;dr I've always needed a good editor, Anon. If you're willing to post a correction of my post for me ITT, then I'm willing to go back in and fix some things with it. Cheers, Anon. :^)

>>39085 Excellent! This is a great concept about the 'U-tube' locking peg. Yes, I consider it will be needed to (re-)tension not only the shell, but the primary torso framework itself. Like @Kiwi, my low-mass goals are pretty significant (mine in particular are likely even more austere -- think: the 'human-powered flight' planes [1][2] ). Having components that lightweight will benefit from being 'strapped together' internally (much like the functions fascia [3] serves within humans' musculoskeletal systems). >issues w/ pulleys Yeah, the tightener mechanisms will need to be situated in such a way they don't interact with the guide-eyes/pulleys at all. Nor with the actuation drive-rotors. My presumption here is that we can devise some sort of 'guide rail' system, that keeps the tensioners both out of the way, and allows them to slide along with the PE cords during actuation. Maybe the rails could be situated within, eg, the thigh volumes? >redacted : (cf. >>39095, >>39101 ) Good thinking, Anon...nice graphic BTW! Thanks & cheers. :^) --- 1. https://en.wikipedia.org/wiki/Human-powered_aircraft 2. https://www.youtube.com/watch?v=Nug0Oho-b1k 3. https://en.wikipedia.org/wiki/Fascia

>>39086 >Couldn't the same cord and motor be used to extension and retraction if you used a rubbery pulley and wrapped the line around a it a few times? Ahh, the ol' 'double winding spool' trick, ehh (think: two spindle spools rigidly-attached axially...one wind goes one way, the other wind in the opposite)? :^) Yes, I think it's likely a feasible approach. There will be 'winding-rates going out of sync' issues if the changes in 'spool lay diameter' of the wound filaments isn't properly managed somehow. (OTOH, with the relatively-short throw distances involved with a humanoid's limb systems, this is likely negligible and easily-resolved in software.) This dual-purpose 'extensor/retractor' on a single actuator drive rotor is certainly something on my plate to investigate when time & resources allow me to. Good thinking, Anon. >In any case, I think you could adjust tension by using bolts as the anchors and twisting them. It would be almost like tuning a guitar. That is a great analogy! Do they make anything like a 'torque-wrench hex key', do you know? Guitars can use sound as the feedback mechanism for judging proper tension. We'd need a useful way to do the same for this scenario as well. >I would suggest getting partial threaded socket head cap screws, wrapping the non-threaded part in electrical tape, tying the knot form the video, and gluing the knot all the way around the bolt with super glue. Thread looker would probably be needed. >This would allow you to tighten the lines with a hex key. Yeah, that would be perfect. I presume we could devise some sort of 'neutral pose maintenance access panel' that would allow us to go in and retension all the lines at the same time (one panel per limb)? >Using something like a small eye bolt for the anchor bolt would easier to do for experimenting. Good thinking. Anything we can do to simplify testing/manufacture will make the entire set of processes easier on everyone! Great ideas, Anon. Your graphic really helps, too! Cheers. :^)

>>39091 >Ahh, the ol' 'double winding spool' trick, ehh Just a normal pulley or roller of some kind. The blue direction would be extension and the red would be contraction for a particular joint. Some kind of guide would be needed to keep cord spaced out properly on the pulley/roller. The line would never wind in multiple layers on the spool in this layout. >Do they make anything like a 'torque-wrench hex key', do you know? There are small torque wrenches like picrel that use 1/4" bits. There are also small, in-line, torque drives and limiters also based around 1/4" bits. I'm sure there is more variety on these, but that is all I am aware of. >Yeah, that would be perfect. I presume we could devise some sort of 'neutral pose maintenance access panel' that would allow us to go in and retension all the lines at the same time (one panel per limb)? For this to work, the screws would probably need to be at the extreme end of each cord system. A tiny access hole for each screw could be made directly above or below them in the outer shell. If you used an appropriately long screw, It could stick out away from the skeleton and be flush with the exterior. >>39089 >the tightener mechanisms will need to be situated in such a way they don't interact with the guide-eyes/pulleys at all. Nor with the actuation drive-rotors. My presumption here is that we can devise some sort of 'guide rail' system, that keeps the tensioners both out of the way, and allows them to slide along with the PE cords during actuation. Maybe the rails could be situated within, eg, the thigh volumes? Using fixed adjusters as anchors at the distal end of the cord would be much easier to set up and it would cut down on the number of parts and weight.

>>39071 >If you are talking about adjoining the short lines to the main line at a perpendicular angle, I would suggest not doing that at all and using only one line A little off topic but to make it clear I'll tell you what the point was. I like sailing videos. I saw this one group that caught next to no fish sailing across the Atlantic while another group caught all sorts of fish doing the same BUT the first group only had one hook and artificial bait on the line. The second, who caught all the fish, had several in a row attached to along line. My guess. The first was going to fast for the fish so they missed it but the second could see one go by then see another coming up and they would bite. The dropper loop looks good but, for me anyways, I think the Blake, even if not as good, suits me because I can easily remember it and the knot I can remember is better than, no knot at all, no matter how good it is. I'm not sure why this is but some knots, for me, just stick in my head while others I constantly struggle how to tie them. Don't know why. Thanks for your reply.

>>39074 I don;t get that picture. Looks like a regular zeppelin to me BUT if you are talking about making extra loops for the B and Q, then I actually thought of that also but didn't say anything about it.. Clarify. You make a "b" and the "O" part of the "b" . and the "q", is two or more loops before you run the line through the center.

>>39076 >FG knot...70-80% breaking strength....zeppelin knot failed almost instantly. It might have held 3-4 lbs I;m guessing the sharp turn, with small line, put more stress on it. The FG with more loops and straight pull, far better. I wonder. Could a zeppelin be better with larger ropes, like used to hold an actual airship, because that is the knot they used for that task.

>>39089 >tension not only the shell, but the primary torso framework itself I see, said the blind man. I was only thinking about the limb actuation, not body parts.

>>39095 Ahh, OK, now I've got it. Excellent! Heh, I think my obsession surrounding thrown weight was keeping me from seeing the idea of putting the tensioning screws at the far end of the rig. Makes sense now. Maybe we can find some kind of specialty very-lightweight screws for this. Isn't magnesium really lite but strong? Also, glad to hear about the smol torque wrenches/limiters. Thanks again, Anon. Your diagrams really help! Cheers. :^)

>>39099 Heh, when you're shooting for <25Kgs of mass, you need to get inventive!! :^)

>>39097 >I don;t get that picture It's just from the website you shared. I added more passes of the tag end through the "O" of the "b" and 'q" in an attempt to add enough friction to keep it from moving. >>39098 The zeppelin bend is made to be untied for mooring lines, etc. and simply does not have enough static friction to keep the knot from sliding apart with the very slippery PE fishing line. It's not exactly breaking when it fails: it's either untying or melting. If the knot does not simply pull apart, the fibbers sliding across each other under tension heat up enough to start melting, resulting in a snap. Rope would not have the same issue as it has a much higher friction coefficient. It wouldn't start sliding, so it wouldn't damage itself.

>>39107 >It wouldn't start sliding, so it wouldn't damage itself. From what I understood of the chemical/physical discussions of UHMWPE, the reaaaally long chains create a tremendous number of covalent bonding sites -- thus the strength. But that the polymer chains themselves were particularly prone to breaking down at a relatively low temperature -- thus the melting issue. Please correct me if I'm wrong here.

>>39101 >magnesium Magnesium screws like the one pictured are used in some orthopedic surgeries as an alternative to titanium. Magnesium embedded in bone is actually bioabsorbable. I'm not seeing much out there for other applications, but Maruemu Works and Melfast appear to make magnesium socket head cap screws. I can't find any for sale though. Maruemu's stuff might be available though some Japanese retailer and Melfast appears to only do bulk commercial sales. Aluminum would probably be the way to go, if you think the higher cost is worth it. https://www.mcmaster.com/products/~/material~7075-aluminum/material~2024-aluminum/?s=aluminum+socket+head+cap+screws >>39108 >thus the melting issue. This is very much the case. There is a relatively large amount of surface area on the braided line, and the friction of dragging it over itself can quickly bring it to the 270 °F or so point it starts melting at. >It wouldn't start sliding, so it wouldn't damage itself. I didn't intend to imply rope would fail in the same way. If a natural fiber rope slid in a knot, It believe would start peeling itself apart and shedding fibers until what was left it was week enough to snap.

>>39124 >Aluminum would probably be the way to go, if you think the higher cost is worth it. Certainly that's fine for prototyping work ATM. Bookmarked. <---> Now let's move on to the rods/struts. I'm planning on aluminum tubes, simply b/c that easily-obtainable at 'big-box' hardware stores here in Burgerland (Lowe's, Home Depot). But what I'd really like is carbon fiber tubes that are very strong & slightly compliant. Any leads there? (Please remember I'd like our lifesize [~150cm] robowaifus to be able to lift & carry 100Kgs of weight for 15Km [Fireman's Carry or backpack] across level terrain.) For a loose analogy of the use case; as a rock-climber I can tell you that its your bones, not your muscles that give you your primary strength during climbs. Thus the importance of high- compression/tensile strength rods (+ low-friction UHMWPE pads inside joints, ala replacement knees, etc. [1] ) for our robowaifu's skellington. <---> >There is a relatively large amount of surface area on the braided line, and the friction of dragging it over itself can quickly bring it to the 270 °F or so point it starts melting at. It's remarkable stuff, and I'm really glad it exists for us robowaifuists! I don't think this temperature is going to be a frequent problem for our usages here -- as long as we keep it it well clear of hot actuator/etc. cases! :^) --- 1. ( >>39006 )

>>39126 https://www.mcmaster.com/products/carbon-fiber-tubing/ >Please remember I'd like our lifesize [~150cm] robowaifus to be able to lift & carry 100Kgs of weight for 15Km. What's going to be the power source? All the muscles/actuators in the world don't matter if you don't have to energy to use them.

>>39128 Thanks! (Lol, they kicked me out with 'Please Log In' before I could see it.) Any rough ranges on the prices for tubes suited for building robowaifu's skellingtons, GreerTech? >power source? We've had this discussion at length in our Power & Energy bread : ( >>37810 ). Our primary ME here (& I wholeheartedly agree with him on this) say its lithium ion batteries. Its the only practical solution for us still yet. BTW, this kind of derails our Tensegrity bread. If we need much discussion on this, then let's please have it there thanks. :^)

>>39132 >Any rough ranges on the prices for tubes suited for building robowaifu's skellingtons, GreerTech? What thickness and total length do you need? >power source? I don't have any new discussion on it, my only concern is that it would take an e-bike sized battery to carry a 220 lb (100 kg) weight for 9 miles (15 km), not to mention any computer systems.

>>39133 >What thickness and total length do you need? It varies, depending on the part in question. The thigh 'bone' will need to be the thickest & strongest, so let's start there. Maybe 18" long X 1.25" diameter (unsure about the wall thickness, but let's guesstimate about 1/8")? >e-bike sized battery Given. In fact I'd estimate two of them. Somehow that's got to all be fitted inside the torso as well. Hey, if this was easy everyone would be doing it!! :^)

>>39134 Thigh bones alone would be $104.30 I would just go with aluminum

>>39135 Thanks Anon! Now we have a tent-peg in the ground for it. Yeah, this will probably need to go in the higher performance/higher cost robowaifus. I'll go with aluminum for now. Cheers, GreerTech. :^)

>>39136 Might it be better to do some prototyping in wooden dowels?

>>39136 However, I did find these. I don't know why McMaster Carr is more expensive, but I'm more inclined to believe them https://www.amazon.com/ARRIS-500mm-Wrapped-Carbon-Surface/dp/B00TF8V9KI/ https://www.amazon.com/FANCYWING-Surface-Wrapped-Quadcopter-Multicopter/dp/B0B99PG6W7/

>>39137 Yes. And in fact I've actually already done some efforts with various quality dowel rods (White Ash, I think maybe?) Wood should definitely give sufficient compression strength for cheap robowaifus around the home (doing light, menial tasks [laundry, dishes, etc.]) It doesn't stand up very well to outdoors environments AFAICT (maybe they just need a good treatment to help with this). Good thinking, Anon! :^) >>39139 Thanks!! This is actually inexpensive enough to give some consideration now. Probably best to do the prototyping with aluminum in the meantime, then test out replacements with the CF rods after the designs are all working well, for better performance. Need to be frugal with costs during this stage as well. >I don't know why McMaster Carr is more expensive, but I'm more inclined to believe them As am I. :^)

>>39141 Speaking of Futurama...

>>39142 Lol. I don't recall seeing that one! :D

>>39139 The cheaper tubes might use a poorer quality epoxy. There are no also listed msi ratings, so they are probably a made with a week low modulus fiber. The orientation and alternation of the wraps would also be a factor. The Amazon ones look to be made from tube a of loose twill weave. The three McMaster Car options have different materials. One has all the fibbers running in a single direction, one with a tighter weave, and the last has crisscrossed alternating wraps with a much high modulus fiber. >>39142 >>39143 Curse you merciful Poseidon!

>>39145 Their pictures are terrible, but the last McMaster Car's last option is probably similar in construction to a fancy fishing rod blank. The first option probably would be a bad choice as its outer layer could potentially splinter into sharp needle-like fragments.

>>39146 This is a good point. And thanks for the reminder! I'll plan to use a safety box around when doing the skellington failure tests! Cheers. :^)