Color-Changing Fibers Reveal Why Some Knots Hold And Others Don't

Chit Chat
1

https://www.iflscience.com/physics/color-changing-fibers-reveal-why-some-knots-hold-and-others-dont/

2

Nice find, thank you.
I wish I had some of that cord.

I am wondering if the use of the words ?strength and stronger? are not quite what they are indicating in the papers.
My takeaway is that they are perhaps implying better security.

SS

3

Here’s two related but different articles…
https://www.npr.org/2020/01/02/793050811/a-knotty-problem-solved
http://news.mit.edu/2020/model-how-strong-knot-0102

4

The article’s wording does appear ambiguous, but I would agree with your interpretation.

5

This article is certainly interesting. Knots can be considered by physics and mathematics, so sailors and mountaineers are very interested in certain types of knots, and separately they are tested on a tear test. And of course, from a practical point of view, it is necessary to know where the knots is used. :slight_smile:

6

Very interesting even exciting!
.
Usually i’d like calling the Reef by original name, rich sea heritage and salty roots.
But, to me, faults of Thief, Granny, Grief all stem from arrangements that pull out of the flat square form to de-stabilize.
The ‘SParts’ of Thief actually pull the shape form the Bitter Ends to diamond/out of Square as full force pulls the free ends
The ‘SParts’ of Granny stay flat Square while Bitter Ends side rotating 90degrees and destabilizes from the flat Square profile .
The Grief carries both out of Square faults.
All knots , as any other mechanix, must be held squarely to task to work,
especially a flexible/flimsy device of power!
.
i really think that is what they were trying to pass down unspoken in the name Square;
from a rough world with little text for these things before ABoK;
and closer to these very things seen in many things as common, that we have lost sight of.
At least, for me, i keep the word Square, as a reminder;
of the amount of ‘Square Lessons’ i see in this simplest joining of ends that carry thru all knots.
.
Simplest things on the cusp of fail have the fewest moving parts to examine but still can work;
also, if can find line between can and can’t/fail or not; and what makes that difference/flips the switch, can be very defining to all.
The Square family does that for me, faults included!
.
This new toy will show secrets not seen before thru it’s viewport into secret world inside knots.

Another toy i’ve always wanted to have is a Nip Meter, for pinch rollers to make sure huge presses etc. are even pressure all the way across etc. Expensive, but could show difference in pressures between rope turn and host at different positions for different insights into this world.

7

I’ve posted this video before and think it appropriate to link it here as well. https://www.youtube.com/watch?v=s3fHYGY3YTo
With thermal imagining there are color changes seen in loaded knots.
I wish someone(s) with IR camera and load cell access would do a series of different knots.

SS

8

Thanks much for this (which I don’t recall seeing previously
(I do miss things, alas))!

It’s a shame that they (1) aren’t explicit about their
using BOTH “perfect forms” –interior- & exterior-loaded
forms-- in this test, resp. upper & lower (which breaks).
And (2) they are confusing in their flipped-upside-down
presentation of the lower knot, sometimes (flipped).

IMO, if the form that broke IS really the one that CAN
be stronger, it will be so by setting the knot HARD with
the tail, to install the tail’s twin part to the SPart such
that it will not so easily be pushed aside as we see
here --that the SPart will at least for some significant
rise in force bear into this twin (whereas in the other
form, the interior strand SPart pulls away, and leaves
its twin so obviously unloaded sticking out almost
like another, small eye!).

(Someone w/YouTube membership is encouraged
to echo these observations into on-line view.
)

–dl*

9

BUT I ALSO --sooner but often later-- SEE THINGS
(which others miss).
–to wit:
???!
I must comment that the reference video above
apparently is assembled footage,
as the clearly seen Fig.8 eyeknot versions

and color’d or not metal hook/ring the are attached to <<<
CHANGE during this video.
To begin, the upper knot connects into >>a carabiner<<
and that 'biner into a big ORANGE HOOK,
and the bottom is tied into a metal-grey ring;
and the versions --interior- / exterior-loaded-- of Fig.8 eyeknots
are clearly seen in, resp. top/bottom, separation of twin
parts (interior SPart pulls away from twin, leaving it so
obviously unloaded at top of knot, towards the eye),

and hard compression by exterior SPart into its twin
pushing it wide aside, in the bottom (initially!);
BUT
just at the 1:00 mark, there is a jitter in the camera
and a BRIEF GLIMPSE of the >>exterior-loaded<< knot
connected >>directly<< into the orange hook (no 'biner)!!
(Re this “jitter” : I saw it initially, then on review did NOT
see it, then enlarged to full-screen and with video stopped
I was able to frame-by-frame-like get the orange hook into
a stopped frame-image --YES, it is there (and no 'biner),
for the exterior-loaded, soon-to-rupture, knot!).

.:. My guess :: the testers, seeing both the knots and
the read-out of resp. heating, sensed that it was the
exterior-loaded knot AT THE BOTTOM that was going
to break, and they then stopped the loading and
reversed the setting, so that this knot was at the top,
IN VIEW OF THE FIXED-SOMEWHAT VIDEO CAMERA.

(Why is is sooooo damn hard to get facts about knots?)

–dl*

10

Yes, I am sure that they edited and sequenced the video. It may have been a very long one. To me, it is of no importance considering firstly that I could not have done it. Secondly, the information is there regardless of the editing and imo the salient points of the thermal images show to be valuable.

I believe if there are going to be comments about the shortcomings of another’s tests or demonstrations, then I propose that someone establish the perfect test scenario(s), submit them and the specimens (tied just the way they want them) and beg (or pay)that the tester provide the time and equipment.

To the point: Anything that can allow the interested persons to examine what takes place within a knot’s structure, especially an “in play” knot, is extremely useful.

Thermal imaging, color changing fibers, memory yarns, 3d software, etc., all very interesting.

A big Thank You, to those who have invested and performed these!

11

???
This is silly :: deceptive / misleading “information” is NOT
helpful but harmful. That is why I bothered to post the
CORRECT view of what was happening in the video,
so that viewers --possibly even those conducting and
otherwise associated with the very test-- can know
what DID happen, and not think something false.

–dl*

12

Why would seeing a video of a thermal image showing the heat generated in a knot, of any kind be silly??
Is there no merit or value to this?
Why would anyone say “silly, deceptive, misleading” to a fellow interested knot tyer?
What is the point of such a response? Does it further our knot forces understanding?
So what that they edited the video. I feel that they did not do it to push some hidden agenda. Perhaps to better reveal what they wanted to show? The internal heat stress on a particular knot?
IMO, the changing from a biner to the large hook did not influence this particular test indications enough to call it “silly, deceptive, misleading”.
Really…

13

Not what I said. The assertion that flipping a test
specimen upside-down w/o explicit notice of this,
and thereby potentially misleading an interested
viewer into believing that Knot_Upside broke and
Knot_Downside won when in fact it was that
Upside was Down
“is of no importance” --what you said–
is silly.
For those of us paying enough attention
–and I wonder if the test team had done so
(I’m guessing that they DID deliberately
load one and the other ends)–
to see that we had different knots under strain,
by the clear-cut indications of the knot deformations
early (prior to their becoming supertight bundles
less readily discerned of such details),
it is of much importance.
And, heck, if indeed they were knowingly putting
the two obvious --though seldom discussed-- loadings
of the common knot to test, point that out!
(Were it an accidental doing, one can of course
understand that it wasn’t known/cited.)

Is there no merit or value to this?
To the thermal imaging, yes, it looks "cool" --ah, the irony in that! Might we consider then that there is potential advantage to broad curvatures or --as CWarner put it-- extended/non-concentrated *nip* partly for enabling heat to be distributed and less weakening?! (Is there some paradoxical aspect in that where one has extended nip one also has more cordage movement (and frictional heating) --like a longer fall having more kinetic energy/force but also more rope to absorb ... ?!)

It strikes me as though the heated parts
shown are not in (full) agreement with those
“strain”'d parts shown in the Science-pub’d
article, which all come at curvatures (and
which significance I’ll suggest is more for
a single fibre than for a composite rope,
whose parts take various placements.
And, regardless, that strain ain’t everything
re failure --to my seeing, breakage comes
on concave not convex side of curves.

So what that they edited the video. I feel that they did not do it to push some hidden agenda. Perhaps to better reveal what they wanted to show?
Yes, quite :: as I said, they likely saw by eye and by thermal indications that the one knot was more likely to fail --they got the Hot Knot, Scott-- and so put it up where the lens aimed (better).
[b]Really...[/b]
;)
14

Incidentally, concerning the Science article,
I sent a query to the “corresponding author”
about what all of the cited knots were (in the
3D graph on p.74? which plots vs. 3 aspects).

There are the known knots:
Re (Reef)
Gy (Granny)
Th (Thief)
Gf (Grief)
then come knots each with a subscript “A” & “B”:
[NOT SURE I HAVE THE FIRST 2 A/Bs CORRECT
TO WHAT IS GIVEN AND WHAT IS NOT --I KNOW
THEY SHOW ONE WITH A & ONE WITH B, THAT’S ALL.]
Ze-B (Zeppelin as is commonly shown)
Ze-A ?!
Ab-A (Butterfly as is commonly shown)
Ab-B ?!
As-A/B ?! (I guess “Ashley’s Bend (#1452)” but two?)
Hu-A/B ?! (I guess “Hunter’s Bend (#1425a)” but two?)
Bo-A/B ?! (I guess eyeknot “Bowline”, but two?)

.:. 8 unspecified knot designations.
I’ve guessed on Hu, As, & Bo but cannot produce
two versions for them (surely; I know diff. versions
but these aren’t of common reference);
I imagine that our “False Zeppelin” is included;
but not what the 2nd Butterfly would be (unless
it’s that non-interlocked_OHes thing); the Bowline
could be “right/left-handed” knots --or not.

Am yet awaiting reply.

–dl*

15

THE “WORSE” PART :
At time-image 0:52 we are looking at the
initially at bottom, exterior-loaded knot
and then ITS thermal image is presented (0:53)
in upside-down/top-knot-like orientation??!
AND THE THERMAL IMAGE IS FROM THE >>AWAY<<
SIDE to the viewer (note e.g. crossing of the pressed-wide
unloaded twin to the SPart --crosses OVER / under depending
on which-side viewing).
How VERY misleading. Yes, it is the knot just
seen in plain rope, but one would not realize this
–nor map the thermal image correctly onto the
rope-shown knot (as eye/Spart+tail sides are NOT
so obvious!)-- so as to comprehend where the heating
is going on the most (which is as we’d expect where
the SPart tightly wraps the eye legs).

So, it’s not merely that they at some time DID swap
the locations of the knots --evidence, the missing 'biner
initially connecting top knot (then >>interior-loaded one<<)
to orange hook–,
but that in immediate sequence imagery (per video timing)
there is this vertical AND front/back reversal !!!
(Which must’ve come by video display and not physical movement,
else that heating would be lost/diminished.)

ORRRR, maybe --noting changes that DID occur physically–
there is additional confusion in editing IN the (separate device)
THERMAL imagery, and that of final “break” should go with the
rope image of 0:52 --they now do match in orientation-- and
that of 0:53 belongs at the finish, as it matches that flipped-up
state of the knot. (Though then we can wonder at the shown

values/figures/temperatures<< that are with the thermal
imagery : maybe those are edited into image and done so
wrongly --well, the values are at right points but the images
wrong, as just noted.

.:. Scott, there is a lot of close-scrutiny expert analysis
just done here by me (IMO) which all is nice
(eventually figuring things out (or so I think)),
but all of which should NOT be needed,
had the testers done their job correctly !!
And absent seeing things correctly,
the test video misleads.

?!

–dl*

16

Thank you Dan for your most excellent sleuthing and criticizing.
Regardless, the only reason I injected the link was to add another interesting investigative method that could be of value to further knot force understanding.
Whether the tyers and video makers got something incorrect, according to you, at least they invested time , etc.
I guess you could leave your comments on their YouTube channel.

17

Firstly, I cannot, and don’t want to create a special account
just to post a comment. Others who might already be in a
position to do so are hereby invited to post my summary
below (you can refer to the IGKT forum as the source).
It would be interesting to see any follow-on comments.

Still going on.
At this point, I see things as follows:
0:20 shows START orientation, well enough (vis-a-vis
knots’ tightening) to see TOP knot as interior-loaded
–note how the uppermost, eyeleg-surrounding part is
left untensioned–
and BOTTOM knot as exterior-loaded
–the telltale compression of SPart into its twin,
pushing this part wide.

AND TOP eye legs cross UNDER, SPART crosses OVER
the parts turning around them;

SAME upper/lower UNDER/OVERs for BOTTOM knot, but as
it faces downwards its SPart & tail X UNDER, eyelegs OVER
–and the big ring around which eye is tied looks to be the
most position-stable structure of the system.
.:. knot bodies should remain pretty consistent in orientation.

Now, at 0:26 we have our 1st thermal image (but no heat #s);
per knot shape it matches the exterior-loaded BOTTOM knot
BUT is showing OPPOSITE FACE (SPart crossing OVER?!).

(So, where is this thermal imaging device?! We see only
a blank white-ish wall behind our view from video camera?!
Have they gotten a later-after-changed-positions image?!)

At 0:41 we have a 2nd thermal image, of a narrow and
indiscernable knot blob which perhaps is consistent with
the TOP knot (interior-loaded), but it’s really hard to say.
Heat #s “23.7” at peak point.

At 0:45..51 we see the BOTTOM knot BUT OPPOSITE FACE
–SPart & tail Xing OVER, and bulging-wide twin part now
continuous before us, Xing w/tight SPart over eye legs
so which are crossing UNDER, newly?!
Has the knot been already flipped to top but image reversed?

Contrasting w/above, at 0:53 the new thermal image
(with heat #24.1 at peak area) is flipped upside-down,
and shows opp. face (now broken wide twin part as it
crosses UNDER eye legs now pointing upwards) to just-seen
(0:45ff) video of knot!?

And if one is QUITE DELICATE in advancing video images,
somewhere around 1:00 :xx there is the momentary glimpse
of the orange hook, biased to viewer’s right (i.e. near part of
hook), w/o any 'biner, holding this once-at-bottom knot
(w/faces as in just seen thermal image, SPart Xing UNDER,
upper/eyelegs OVER the turning parts.

At 1:11 is a thermal image of knot immediately pre-rupture,
heat #27.1 at peak. I guess that this image is shot looking
downwards, as tail looks shorter and the bulging part more
fully around … than in the video’s more perpendicular view?!

YET, in sharp contrast, at 1:19 we see a thermal image
–one brief view prior to “BREAK 1820” pasted across it–
an (1) OPPOSITE FACE (bulging part now unbroken, crossing
over all) and (2) eye facing DOWNwards.
THIS IS THE OPPOSITE FACE TO THE STARTING VIEW.

Okay, I hope that does it.
–dl*

18

I should add that the final video images of the broken
rope show a knot much less distorted than in the test
under compression --which I assume is unexceptional
(i.e., the real rope seen). Which points to how elastic
nylon is, and makes one wonder how a low-stretch
(Sterling HTP, e.g.) polyester rope would fare : same
loading but now w/material doing different things under
that load, and … what follow-on significance that has!?

And we should also wonder where the break occurs
in the interior-loaded knot, or for that matter in an
exterior-loaded one dress & set per my method noted
above, where one tries to keep that born-into twin part
from being pushed wide-aside as it was here.

The break here looks pretty clean/sharp/limited-in-length
(with maybe some slight extended damage on what was
the concave side bearing upon other parts).

                  • [added 1/22 Wednesday] - - - - - - - -

And I meant to remark at the bottom anchor of the
testing device, which is stabilized somehow with bungee?
cords left/right, and able to rise a little during the test?!
I wonder if this is to be somewhat more realistic of actual
breaks, where load doesn’t pause for some constant-distance
movement but continues the force on the structure!? I also
wonder how the knot is put around the ring,
for we have the upside-downing to explain and all ; the ring
looks large for that 'biner to just clip to!

–dl*

ps : Still no reply from the Science article’s Corresponding
Author --not (yet) corresponding w/ME! --I asked about
the specifications of the only symbol-ID’d knots, and of
the “20mm” rope size for those images which impressed
me more as cord and nearer thus to 2.0mm.

19

In any case, views into an inner world not had before; or at least to such confirming depth of tuning other observations towards.
Like microscope, thermal imaging, magnetic film, xray, colored forensic lighting etc.
.
i wouldn’t take first views as total story, perhaps not even contiguous here; but rather promises of where can go with this.
As data from this stacks over time, if they could keep on it;
consistencies to confirm or refute present views would have to be revealed.

20

I see a UKClimbing view into this which has more
knot indications, though I don’t find an answer to
my above query --except that in this view below
the “bowline” is clearly NOT but rather a sheet bend
(and other loadings, but always just 2 not 3).

www.ukclimbing.com/articles/features/knot_theory_in_practice_-_studying_the_mechanics_of_knots-12570

–dl*