Half a croissant, on a plate, with a sign in front of it saying '50c'
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Screw-link chain

  [vote for,

A chain uses metalworking technology to make a rope stronger than can be made with natural fibers. A chain is famously as strong as its weakest link. Unlike a rope, a broken chain cannot easily be repaired or lengthened with a knot or even with hand tools.

In the screwlink chain, each link is a coil rather than a closed circle/oval. The coil is screwed into the one preceding it. The hollow axis of each coil is perpendicular to the length of the chain. Each turn of the coil bears part of the load, making it stronger than a loop by spreading the load out. Longer coils can bear heavier loads.

One can increase strength further by adding coils not only in series but in parallel. A given coil meshes not only with coil in front and behind but also to the side or possibly both sides. For a large coil in which the diameter of the metal rod is substantially smaller than the diameter of the entire coil, one coil can have 6, 8 or more partners. As lateral coil partners increase the screw-link chain gets wider, and eventually might be wrapped laterally around to meet itself, forming a pipe-like structure.

When not under tension, a given coil link can be unscrewed by hand and replaced. The entire thing can be broken down into component coils and stored in a box.

A metalworking technology that can produce a chain can produce a coil.

This would also be a geometry for nanostructures or synthetic proteins.

bungston, May 20 2016

Screw Link http://www.antiquel...ducts/bg/12942N.jpg
And here I thought this Idea would feature a chain of these links, each of which has a screw portion (and a nut portion) for connecting to another link. [Vernon, May 21 2016]

Chain mail. For the Knights who say Ni! http://www.amazon.c...Armor/dp/B00AMQPY5I
Can be shipped though probably not through the mail. [whatrock, May 21 2016]

Hammerlock http://www.tiedowns...om.au/hammer-locks/
Don't know how many times you want to assemble/disassemble though.... [Custardguts, May 23 2016]

Menai Suspension Bridge https://en.wikipedi...i_Suspension_Bridge
Oh look, chains.... [8th of 7, May 23 2016]

Clifton Suspension Bridge https://en.wikipedi...n_Suspension_Bridge
.... and more chains.... [8th of 7, May 23 2016]

Conwy Suspension Bridge https://en.wikipedi...y_Suspension_Bridge
.... and more chains. [8th of 7, May 23 2016]


       "Chains" assembled from split-rings (key rings) are Baked. "Chainmail" garmemts for re-enactors are often produced by interlocking small keyrings, and have the advantage over traditional mail that they can be repaired without tools and adjusted in size to fit the wearer.
8th of 7, May 21 2016

       A split ring is a coil of a sort. I can see how this would be convenient for re-enactors. I am also sure there is a word describing the structural requirements of a chain qua tow rope / barge mooring line vs chain as used in mail. I suspect a split ring would not resist pull as well as a solid link. Maybe a coil would not either.
bungston, May 21 2016

       It would depend on many factors ; the diameter of the link, the size and cross-section of the material, the tempering, the material itself, its modulus of elasticity. And probably how the load is applied - constant strain vs. shock loading.   

       Don't make us do math at you...   

       Chain has a great advantage over steel wire rope in that it is inherently much more flexible without experiencing fatigue due to flexion. Conversely, wear between adjacent links can be an issue, and hawsers are typically stronger weight-for-weight than chains.   

       Interlinked coils are going to have different flexion characteristics at different axes normal to the longitudinal surface, shirley?
8th of 7, May 21 2016

       [whatrock], for that link tagline, you deserve no mercy whatsoever.
8th of 7, May 21 2016

       I was under the impression that the chainmail of the Knights who say Ni was a combination of knitted jumpers and silver spray paint.
mitxela, May 21 2016

       [8th] Nice summary of chain vs wire and rope, though it is a very interesting idea. I would like the ability to make and augment my own custom chain without the need of bolt cutters, splicing or welding, and to keep common partners handily stored nearby.   

whatrock, May 22 2016

       Ahrrgh !   

       All right, all right, we'll get you your shrubbery... we just hope you like it.
8th of 7, May 23 2016

       If the main aim is being able to take the chain apart and make it into custom lengths etc, then maybe try hammerlocks (link). I'm guessing they'll wear out after a few assembly cycles though. You can also use some other types of joiner link, but they're all heavily compromised in terms of strength and fatigue resistance. I won't let joiners of any kind (other than grabs) in any lift I'm in charge of.   

       When comparing chain and cable, you also need to take into consideration the ability of a cable to pass through sheaves, something chain does (even on chain sheaves) rather poorly. Secondly, chain has a nasty habit of locking up over corners, putting links in side-bending mode, which is something like 10% as strong as the normal load rating of said chain (the newer square link chain in up to 120 grade is a bit better but still heavily susceptible). I've seen many, many nasty failures because people think chain is somehow stronger or even tougher than cable. Lastly, for a given weight, cable beats out chain by a factor of at least 2 - you don't see chain supported bridge spans, or machine booms do you?   

       And even more lastly - the yielding failure mode for your coils will be unwinding, which is a pretty scary concept. Basically as it starts to yield, it will get weaker rather than stronger... Runaway failures... Yeesh, you can keep that.
Custardguts, May 23 2016

       // you don't see chain supported bridge spans //   

       Apart from a large number of suspension bridges, no...   

       To be fair, most are "bar and pin" variations on the "chain" concept, with rigid vertical rods coupling the load of the bridge deck.   

8th of 7, May 23 2016

       See now I would not consider bar and pin to be a chain for starters - certainly not comparable to modern welded chain. Also, your examples are all over 150 years old - so strength/weight optimisation was likely not a deciding factor. Maybe I should have put the word "modern" in there somewhere. Not even sure high strength steel cable was available at that time for structures.
Custardguts, May 23 2016

       Numerous small rigid elements, with flexible joints between them. That fits the definition of "chain".   

       The examples were selected on aesthetic grounds, but there are numerous much more modern examples. But no, steel cable wasn't available - wrought iron was the principal material.
8th of 7, May 24 2016

       I should have specified: the idea here is supposed to be something a blacksmith can make. I imagine (but would like to learn further) some sort of technological innovation made (iron) wire possible in the last 300 years and I think to make cable one must first make wire. I have watched videos where they make wire by pulling rods through successively smaller orifices. It was not intuitively obvious to me that this procedure was possible or would result in wire.   

       That would be fine nerd reading: a single word titled book along the lines of "Salt" or "Orrerys": "Wire".
bungston, May 24 2016

       I suppose I was just saying that you should use the right material for the job at hand, and when it comes to static load holding, chain is rarely the right material.   

       Chain is specifically useful in a narrow range of contexts whereby it's toughness, ease of shortening via grabs, compact slack storage, and/or sectional thickness (read : resistance to corrosion) are a requirement. What it certainly isn't, is efficient in terms of weight and cost per load capacity. A rigid tension element is the most efficient if suitable, followed by cable.   

       The screwlink chain is an interesting idea but I just can't think of a usage where it would be optimal.   

       //A metalworking technology that can produce a chain can produce a coil.// - Actually a coil is probably a lot easier. It's the weld in the chain link that's the hardest to achieve full strength by. If you can draw the wire for a chain link you can coil it.
Custardguts, May 24 2016

       What if you didn’t weld the chain link, because it was a Möbïüs strip, but 90° phase shifted such that the inside also becomes the outside of the cylindrical section?
Ian Tindale, May 25 2016

       /It's the weld in the chain link that's the hardest to achieve full strength by/   

       I wonder why the ends of the link were / are not turned back to candycane each other, obviating the need for a weld. Each link would be heavier. For a precious metal chain though, this would be fine.
bungston, May 25 2016


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