Author Topic: Knot jamming test  (Read 2441 times)

Mobius

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Re: Knot jamming test
« Reply #15 on: July 21, 2018, 12:58:40 AM »

So I think your naming the structure 'infinity bend' may be in the same situation as your alleged 'M' bend...which Xarax also predates (did you check the link he gave?).


Xarax did not originate this bend. It had been discussed on this forum prior to Xarax ever taking a picture of it. I believe Dan Lehman when he told me that he had discussed this knot with Asher, prior to any Xarax image. Maybe we should name this knot a SmitHunter L Bend.

I gave the Infinity Bend a decent name several years ago when nobody showed much interest in it and I alone was promoting it. Now all of a sudden it is the Riggers X bend, really?

As for the alleged "M" bend (it is a bowline) is something I have been promoting with the tentative name M-Bowline in another thread. Xarax has apparently laid claim to this knot as well. I should have known better immediately and started calling the knot that I alone am promoting the "Xarax's  2013 2a.JPG image Bowline". Silly me ::)




agent_smith

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Re: Knot jamming test
« Reply #16 on: July 21, 2018, 11:43:42 AM »

per Mobius:
Quote
Xarax did not originate this bend.
I checked my previous post and I couldn't find the words; "Xarax originated this bend".
Where did you find these words?

per agent smith:
Quote
...and I believe that he was first to investigate the effect of crossing the tails in some known bends (I'll check with him...no doubt knotsaver will also confirm/refute shortly).

I thought that I stated that 'I believe' Xarax was first to investigate the effect of transposing the tails in some bends.

and:
Quote
Although I think Dan Lehman had also been aware of this 'X' modification for some time too...

And I thought that I stated that Dan Lehman had been aware of the 'X' modification (ie transposition of the tails).

I'll have to be more careful with my use of language next time, as it can be reconstructed to a different interpretation.

Mobius

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Re: Knot jamming test
« Reply #17 on: July 22, 2018, 12:10:45 AM »

The term 'Riggers X bend' (derived from #1425A) is one that Xarax I think prefers...and I believe that he was first to investigate the effect of crossing the tails in some known bends (I'll check with him...no doubt knotsaver will also confirm/refute shortly).


I would be much happier for Dan Lehman to name this knot, not have "Riggers X Bend" thrust upon us.

Some photos of SmitHunter #1425A
...and also the X version with crossed tails (which seems to be jam resistant).
After asking Mark and Dan about it in private I found out
that Asher had beaten us all to it ☺
Not me in that "us" --I think I beat Asher to it by
some years, and will lay claim in any case on account
of his dismissal of it vs. the correct assessment!   >:(

 ;)
« Last Edit: July 22, 2018, 01:53:52 AM by Mobius »

agent_smith

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Re: Knot jamming test
« Reply #18 on: July 22, 2018, 02:22:25 AM »
Although this is now somewhat drifting off topic - and distracting from Harolds good work....I nevertheless feel compelled to reply as follows...
[and I hope Harold finds time to conduct hobbyist/enthusiast testing (formerly backyard style testing) of the #1425A derived Riggers X bend :) Even though his testing may not actually be physically in his 'backyard'. And it may be a 'trial' rather than a 'test' :)

per Mobius:
Quote
I would be much happier for Dan Lehman to name this knot, not have "Riggers X Bend" thrust upon us

Hmmm I am not sure where you entertain the notional view of something being 'thrust' upon 'us'. No one is thrusting anything and I am not sure of the implication of the use of the term 'us'.

Xarax made this comment about what constitutes a new knot versus a modification to an existing knot (via direct email to me):

Per Xarax:
Quote
As I have told many times, in writing, I do not think that such a minor modification deserves to be considered as "tying a new knot"- even if the geometries and structures of the derived knots may become slightly different / better.

Ref Link: https://igkt.net/sm/index.php?topic=3125.msg18651#msg18651

A "new" knot is a knot that is unpublished, unknown, untied AND it is not an obvious variation, or even alteration, of a published, known, tied knot.
   
   What is an obvious variation or alteration of a knot ? I have examined the knots I have taken and published pictures of, especially the many bends : No wonder there were many: it is very easy for one to imagine a tangle of two ropes that prevent them from slippage, simple enough so we can claim it to be an "interesting" , and possibly, just possibly, a "practical""knot" as well.

Xarax furthers states that:
Quote
Implementing a working definition - I had advanced the following :

" Now to the specific examples of my personal collection of bends:
   I have published pictures of those not-new, by my newest definition, knots :

   : double line Zeppelin bend, double line double overhand bend.
   : re-tucked Hunter s bend, true lover s bend, Rusty s/ ABoK#1450 bend,
   : un-tucked Sidewinder s bend, un-tucked 88 bend (S88 bend)
   : interchange free ends in the Rusty-S88 bend
   : twisted Hunter s bend, Hunter X bends, Zeppelin X bend, Water X bend.
   : interlocked trefoil (double overhand) hitch, interlocked clove hitches, interlocked cow hitches, interlocked strangle hitches, fig S or fig 8, interlocked with clove or constrictor, mid-line bends.
   : different dressings of the double 8 bend, of the Water bend, of the Diamond/75 DSC bend.
 
    I am very glad that, using this "new" "new knot" definition, I got rid of the burden of giving birth to so many "new" bends ! So, the order established via a more general definition, pays a lot. It achieves great economy. "

As for your suggestion of happiness that Dan Lehman ought to name the Riggers bend with transposed tails (and rejection of the 'X' term):
I personally hold the view that a simple transposition of the tails within an existing/known bend (ie end-to-end joining knot) does not constitute an entirely new creation. In my view, it is a modification.

This is why Xarax used the term 'X' to denote that the structure was not 'new' - rather, it was a modification.
The use of the term 'X' implied a 'crossing'. In this case, a crossing of the tails.
Applying this concept, we can thus have:
[ ] #1425A Riggers bend -----> Riggers X bend
[ ] Zeppelin bend -----> Zeppelin X bend

NOTE: Although Harry Asher had previously used the name 'Eastern Zeppelin' in his book 'The Alternative Knot Book' 1st published 1989, at illustration #94 on page 59). His concept for the use of the descriptor 'eastern' refers to a direction that one of the tails takes in relation to a reference frame. However, my view is that his reference frame for delineating an 'eastern direction' is arbitrary. His concept of 'up' and 'down' and cardinal points of the compass all require a fixed reference frame. Depending on the orientation of the knot tyer (and possibly if left or right handed) - and the orientation of the rope/cordage held, this direction could also be 'west' (note that one could mirror the diagrams drawn by Asher in his book to get a reversal of 'direction').

The notional concept of 'X' is directionless. It is simply a reference to a transposition of the tails.

And here is a reference to why i also thought Dan Lehman had been exploring the effect of transposing the tails in #1425A Riggers bend:
per Dan Lehman Ref Link: https://igkt.net/sm/index.php?topic=5357.msg35684#msg35684 Dated 26 May 2015
Quote
from Smith's topmost diagram of the knot, get the improved
version (better resisting jamming, if not also stronger)
by taking one (either) tail OVER the other en route to its
tucking through the central nipping zone and then finally
out UNDER (giving reciprocal "over" to opp. tail).
What this does is stuff tail material into the collaring bight
which prevents that from so tightly gripping the S.Part
and jamming --by significant degree, at least.

To be honest, I am not sure who first started to investigate jam resistance of #1425A Riggers bend via modification with transposed ('X') tails. Given that Dan Lehman posted this information in May 2015, obviously, he already had the concept in his mind.
Maybe Dan Lehman himself can advise?

I had also remember reading a post from Dan Lehman where he wrote that Phil D Smith's use of the name 'Riggers Bend' was bogus (his words). If memory serves me correct, Dan's reasoning was that widespread use of this bend was not apprarent by riggers working in the construction industry. Quite the opposite...in that Dan was unaware of any riggers who routinely used the #1425A 'Riggers bend'. And so I believe this is the reason why Dan thought the name 'Riggers bend' was 'bogus'.

But then, the obvious question is; Why did Phil D Smith give rise to the name 'Riggers bend' in his book?
« Last Edit: August 03, 2018, 02:11:44 AM by agent_smith »

Dan_Lehman

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Re: Knot jamming test
« Reply #19 on: July 22, 2018, 08:30:51 PM »
Although this is now somewhat drifting off topic ...
per Mobius:
Quote
I would be much happier for Dan Lehman to name this knot,
not have "Riggers X Bend" thrust upon us

Xarax made this comment about what constitutes a new knot versus a modification to an existing knot (via direct email to me):

Per Xarax:
Quote
As I have told many times, in writing, I do not think that such a minor modification
deserves to be considered as "tying a new knot" --even if the geometries
and structures of the derived knots may become slightly different / better.
...
A "new" knot is a knot that is :
 unpublished,
 unknown,
 untied,
  AND it is not an obvious variation, or even alteration,
  of a published, known, tied knot.
   
   What is an obvious variation or alteration of a knot ?
I have examined the knots I have taken and published pictures of,
especially the many bends : No wonder there were many :
it is very easy for one to imagine a tangle of two ropes that prevent
them from slippage, simple enough so we can claim it to be an "interesting",
and possibly, just possibly, a "practical""knot" as well.

Xarax furthers states that:
Quote
Implementing a working definition - I had advanced the following :
...
    I am very glad that, using this "new" "new knot" definition,
 got rid of the burden of giving birth to so many "new" bends !

As for your suggestion of happiness that Dan Lehman ought to name the Riggers bend
with transposed tails (and rejection of the 'X' term):
I personally hold the view that a simple transposition of the tails within
an existing/known bend (ie end-to-end joining knot) does not constitute
an entirely new creation. In my view, it is a modification.

This is why Xarax used the term 'X' to denote that the structure was not 'new'
--rather, it was a modification.
The use of the term 'X' implied a 'crossing' --in this case, a crossing of the tails.
Applying this concept, we can thus have:
[ ] #1425A Riggers bend -----> Riggers X bend
[ ] Zeppelin bend -----> Zeppelin X bend

NOTE: Although Harry Asher had previously used the name
'Eastern Zeppelin' in his book 'The Alternative Knot Book' 1st published
1989, at illustration #94 on page 59). ...

The notional concept of 'X' is directionless. It is simply a reference to a transposition of the tails.

And here is a reference to why i also thought Dan Lehman had been exploring the effect of transposing the tails in #1425A Riggers bend:
per Dan Lehman Ref Link: https://igkt.net/sm/index.php?topic=5357.msg35684#msg35684 Dated 26 May 2015
Quote
from Smith's topmost diagram of the knot, get the improved
version (better resisting jamming, if not also stronger)
by taking one (either) tail OVER the other en route to its
tucking through the central nipping zone and then finally
out UNDER (giving reciprocal "over" to opp. tail).
What this does is stuff tail material into the collaring bight
which prevents that from so tightly gripping the S.Part
and jamming --by significant degree, at least.

To be honest, I am not sure who first started to investigate jam resistance
of #1425A Riggers bend via modification with transposed ('X') tails.
Given that Dan Lehman posted this information in May 2015, obviously,
he already had the concept in his mind.
Maybe Dan Lehman himself can advise?

I had also remember reading a post from Dan Lehman where he wrote
that Phil D Smith's use of the name 'Riggers Bend' was bogus (his words).
If memory serves me correct, Dan's reasoning was that widespread use
of this bend was not apprarent by riggers working in the construction industry.
...
But then, the obvious question is; Why did Phil D Smith give rise to the name 'Riggers bend' in his book?

Whew, what a load ... crying out for (further OT) comment!

In short, knots nomenclature --including knot-names--
is a tough problem to get a grip on.

To cut to the chase on some of the above points, I've
been looking at so-far-known trio of *inventers* of
#1425a --viz., Phil Smith, Edward Hunter, & moi--
yielding a name "SmitHunter's" (nothing from "moi"  ;) ).
To which X's "X" qualifier for the better version does
seem to fit appropriately, as stated above.
But what if that knot had been first-to-knowledge,
and the 1425a one came as a variation to IT?!
Would you retrofit "X" into it, or try the amusingly
awkward "SmitHunterman's [<-there's moi!] Un-X Bend" ?!

For common parlance & understanding, X's "X" name works
--and working is more than one often gets, in knots nomenclature!

Re the "bogus" aspect of some knots naming, well, given
the double-entendre aspect of E.H.'s name, one could see
it going (esp. sans capitalized "h") as an indicator that
somehow hunters --of what?-- used the knot; or, I guess,
for that matter did smithies use it?!
Naming can seem a solvable problem at least when
considering some (mere) 10-20 knots set within some
particular application; but trying to work in the entire
infinite (or merely so-far-known-to-knot-tyers) field
of knots leads me to ... no good result.


As for the long debate about "new",
in a similar spirit if not exact reasoning,
I count all differences as "new" and prefer thus
to diminish the signficance of that adjective
--that "new" in itself can be trivial (either in the
degree of difference, or in the given knot's intrinsic,
useful value << NB !!

And, to further complicate the matter, there is the
issue of "dressing & setting" --things that can lead
to pretty contrasting results, including quite different
*knots*, IMO.  (Beyond this and along these lines,
one can wonder about the *identity* of a knot changing
per force?!  --"nipping turns" opened into helixes, e.g.?!
< argh & sigh ^^(n+1)   :o   ???  >


This was one reason I opposed Derek Smith's notion to hand
out certificates of *new*ness creation to those eager-for-fame
would-be inventers; I feared encouraging more knotting nonsense
(I have plenty of my own originated such stuff --literally STILL
some heaps/clumps of *new* knots to record in illustration
(or, with a sigh partly of relief, to just discard "into the waste
basket" (H.Prohaska)).  --same relief Xarax feels in his raising
the bar for *new*; but I lower the presumed importance of it.

For who can know so well what is in fact human-wise *known*?!
What if the infamous zeppelin bend later shows up in some
historical digging around, or in some heretofore isolated human
community?

As for creativity/inventiveness, were any of us to meet some
little/young person who, left out of sight with curiosity playing
among our pretty ropes and who doing so came up with some
batch of well-known & indeed well-regarded knots,
should some acclaim for invention be denied?

To the particular case of "SmitHunterman's" bend",
*I* probably am well enough right-dated as having taken
fondness for the "X" version, which I had tested circa
1985?  (I can I think exact-date this --as I have the test
correspondence (fyi, about 65% vs. 62% of these two
versions --small victory in one case, 1/4" nylon laid rope).)
I was dismayed that Asher quickly dismissed it (in his earlier
A New System of Knotting), just as I'm dismayed with
AshLEY's lack of precision for #1452 & his unenthusiasm
for it & same-digits #1425 (which can lead to interesting
& useful eye knot(s)).

In my own world, I'm abashed to admit such changes of
heart/opinion, recently (re-)inventing the Final Solution
to securing the bowline, proudly documenting it (well,
a bit of special note in the quick drawing), only to later
find it well shown among other options and without
even a hint of its later-believed superiority!  --and this
not something coming from a change of materials!
(Nor did I mean to say "wouldn't".)


--dl*
====

SS369

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Re: Knot jamming test
« Reply #20 on: July 22, 2018, 11:16:26 PM »
Regardless of the who, what, where and when stuff, there ought to be some smart idea or technique to qualify and determine a jamming threshold.
Some tool(s) that measures strain, say a clamp coupled with a tension device to a particular knot component (determined ahead of time). Or could a certain "decided upon" rope be loaded to X load and then rated by a small delegation, then averaged?
The specimens tied and photographed so all can view the particulars.

So many brains here...

SS

Harold Kahl

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Re: Knot jamming test
« Reply #21 on: July 23, 2018, 05:21:49 AM »
I certainly share the concerns of SS396 and others about the scientific rigor of my "backyard" testing, and I am literally doing it in my back yard. For one thing, my results are not always repeatable. Sometimes the same knot will jam or not jam in different trials, for reasons unknown to me. Also, there is definitely a skill and strength factor in untying these knots. However, lacking anything better, as far as I know, I shall continue.

With that, here are the results of my testing of the Hunter/Rigger's bend vs the RiggerX/Infinity, with a Kalmyk loop and a couple of zeppelin bends thrown in. Unfortunately, I screwed up the video recording of the zeppelins.
Two ABOK1425A Rigger's bends and two RiggerX/Infinity bends were tied in series with two Zeppelin bends, and a Kalmyk loop on each end of the string to connect to the come-along that I use for tensioning. The rope was tightened to 180 lbs as indicated on a digital hanging scale. The standard Rigger's/Hunters bends both required a pair of pliers to get untied, and both took around 2 and a half minutes. The RiggerX or Infinity if you prefer, both came untied in about a minute 20 seconds. I used a pair of pliers on one of them; the other did not need tools. The Kalmyk loop came loose in 19 seconds after some effort. I screwed up the video of untying the zeppelin bends but they were comparable to the RiggerX. One Zeppelin needed pliers to untie and one did not.

Video showing how I tie the Rigger and the RiggerX:
https://www.youtube.com/watch?v=XQM1VoLTN4c&t=15s
Video of me untying the knots after loading:
https://www.youtube.com/watch?v=Y7hmZN8k7ho
« Last Edit: July 23, 2018, 05:25:57 AM by Harold Kahl »

agent_smith

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Re: Knot jamming test
« Reply #22 on: July 23, 2018, 03:29:43 PM »
From Harold:
Quote
I certainly share the concerns of SS396 and others about the scientific rigor of my "backyard" testing
I wouldn't be concerned.
Nobody is going to hold you to the same accountability or scientific rigor as a certified, accredited test lab.
Just continue to test and make discoveries.

Harold, a comment I would make is that you tend to show only one side of the knot specimens in your videos. It would be nice if you did a slow rotation so we could see all sides.
Also, if you have to use a tool to loosen and untie a knot - this (in my view) disqualifies it from being jam resistant. In other words, if you can't untie a knot by hand, it has jammed.

Per Harold:
Quote
Two ABOK1425A Rigger's bends and two RiggerX/Infinity bends were tied in series
If you are trying to appease just one person, I think you can quietly drop the use of 'infinity' - its not needed.

Xarax has pointed me to the following thread:
Quote
http://igkt.net/sm/index.php?topic=4561.0

Xarax posed the following question in an email:
Quote
My question is - why this particular X-ed variation, and not also the other one I had shown (in the above link)?
Xarax also commented that; ...simply crossing the tail ends in any given 'bend' is not a guarantee that it will (as a result of such a modification) become jam resistant. The matter remains open for further investigation.[/size][/size][/i]

From his comment - I am unclear if Xarax is warranting jam resistance in the Riggers/Hunters X bend. I recall in past correspondence that he normally requires knots to be loaded at least to 50% of its MBS yield.

...

per Scott:
Quote
there ought to be some smart idea or technique to qualify and determine a jamming threshold.
I agree... and the jamming threshold is likely to be probabilistic.
In terms of rope/cordage used in any such testing, I would suggest 'human rated' type material such as climbing/abseiling/rescue rope (ie rope/cord that is certified to some standard such as EN1891 / EN892 or EN564). EN564 cords are known as 'accessory cord' (ie prusik cord) - and are relatively cheap. The reason why I suggest such material is that it will at least be of a consistent/known quality.
And (most importantly) it will allow for consistency and repeatability - in that, other testers could also purchase EN564 cord. In contrast, cheap cords purchased from home hardware type stores will be difficult to replicate by others (particularly other testers from different nations). EN certified cordage is universally available around the world. Presumably, the concept of repeatability is desirable?
« Last Edit: July 24, 2018, 04:04:48 AM by agent_smith »

Harold Kahl

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Re: Knot jamming test
« Reply #23 on: July 23, 2018, 06:24:43 PM »

Harold, a comment I would make is that you tend to show only one side of the knot specimens in your videos. It would be nice if you did a slow rotation so we could see all sides.
I'll try to remember that.
Quote
Also, if you have to use a tool to loosen and untie a knot - this (in my view) disqualifies it from being jam resistant. In other words, if you can't untie a knot by hand, it has jammed.
True, but I think we can assume the knot would be relatively jam resistant at lesser loads, in comparison to a knot that is just hopelessly jammed and you can't even get a purchase on it with a tool. So, I think it's still a useful piece of information.
Quote

the jamming threshold is likely to be probabilistic
That's been my experience. There seems to be some randomness, unless there are some variables that I am not aware of.
Quote
In terms of rope/cordage used in any such testing, I would suggest 'human rated' type material such as climbing/abseiling/rescue rope (ie rope/cord that is certified to some standard such as EN1891 / EN892 or EN564). EN564 cords are known as 'accessory cord' (ie prusik cord) - and are relatively cheap. The reason why I suggest such material is that it will at least be of a consistent/known quality.
Probably, but I can get 100 feet of the stuff I use for a few bucks at Home Depot.

Dan_Lehman

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Re: Knot jamming test
« Reply #24 on: July 24, 2018, 12:29:09 AM »
...
per Scott:
Quote
there ought to be some smart idea or technique to qualify and determine a jamming threshold.
I agree... and the jamming threshold is likely to be probabilistic.
In terms of rope/cordage used in any such testing,
I would suggest 'human rated' type material such as climbing/abseiling/rescue rope
(ie rope/cord that is certified to some standard such as EN1891 / EN892 or EN564).
...  The reason why I suggest such material is that it will at least be of a consistent/known quality.
:o
I'm reminded of the old joke ::
a person walking in the city encounters
another person who is searching around
the sidewalk for something;
P1 "What are you looking for?
P2 "I dropped my pen in the alley."
P1 "Then why are you looking out on the sidewalk?"
P2 "Because the light's better!"


 ;)

agent_smith

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Re: Knot jamming test
« Reply #25 on: July 24, 2018, 04:12:58 AM »
per Harold:
Quote
Probably, but I can get 100 feet of the stuff I use for a few bucks at Home Depot.

As I noted previously:

The reason why I suggest EN certified cordage is because it will at least be of a consistent/known quality (because it is manufactured to conform to a standard).
And (most importantly) it will allow for consistency and repeatability - in that, other testers could also purchase EN564 cord. In contrast, cheap cords purchased from home hardware type stores will be difficult to replicate by others (particularly other testers from different nations). EN certified cordage is universally available around the world. Presumably, the concept of repeatability is desirable?

I live in Australia and I doubt if I could purchase the same cord you purchased locally at your home hardware store. Yet I could easily purchase EN564 cord locally - and so could anyone else. Its reasonably priced.

At the end of the day - money is an issue for hobbyist/enthusiast class testers - so they (likely) will purchase the cheapest cords available. It is still worth inquiring on the price of EN564 cords...
« Last Edit: August 03, 2018, 02:14:20 AM by agent_smith »

Harold Kahl

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Re: Knot jamming test
« Reply #26 on: July 24, 2018, 10:28:23 AM »
I think what I am testing is knots, not rope.  If I tie two knots in the same rope off the same reel bought at the hardware store, and load them in series with each other, then it should give me some idea of the relative jam resistance of the  two knots. My test of hardware store rope may not apply to your EN564 cord purchased in Australia, but then your test of EN564 would not necessarily apply to my hardware store rope, which might be what I am really interested in.

Although all EN564 rope may meet certain specifications, that doesn't mean all brands will be the same or even all samples from the same factory would be identical. Whereas, the hardware store rope should be pretty much the same a few feet away along its length.

Perhaps my assumption is wrong, and a certain knot could outperform another knot in one type of rope, but not in another type of rope. That would be interesting to know, but you'd have to test the knots in both types of rope to find out.

agent_smith

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Re: Knot jamming test
« Reply #27 on: July 24, 2018, 11:42:50 AM »
per Harold:
Quote
I think what I am testing is knots, not rope.
And knots are constructed from rope/cord!
Harold, it matters what type of materials you use. For example, there is:
[ ] dyneema
[ ] fishing line
[ ] monofilament
[ ] 'el cheapo' no name brand cordage purchased from a home hardware store in someones nation (country)
[ ] and then there is cordage manufactured to conform to a strict standard eg EN 564

Without the rope/cord, the knot wouldn't exist. Its a marriage of the two...

Quote
My test of hardware store rope may not apply to your EN564 cord purchased in Australia, but then your test of EN564 would not necessarily apply to my hardware store rope, which might be what I am really interested in.

You miss the point. I cannot purchase your no name brand el cheapo cord here in Australia to precisely match the cord you purchased in your respective country. But, both of us could easily purchase the same type of EN564 cord in both our countries.
I could then try to replicate your test here in Australia - and we could compare results.

Quote
Although all EN564 rope may meet certain specifications, that doesn't mean all brands will be the same or even all samples from the same factory would be identical.

Wrong - in the sense that manufacturers of human rated cordage will be strongly motivated to achieve consistent levels of quality - because peoples lives are at stake!.

If you (for example) purchased Sterling 5mm EN564 accessory cord, I could purchase the exact same cord here in Australia and then I could try to repeat your test and see if I obtain the same results. I of course assume new cord/rope (not material that has been heavily used and/or aged. Accessory cord that conforms to EN564 is relatively cheap. You can buy it and pay by the meter (or 'feet' if you are from the USA).
Sterling ropes and cords are widespread and can be purchased in most countries.
Edelrid is another rope/cord manufacturer.
Manufacturers exert strict quality assurance control over production of their cords/ropes - they have to because peoples lives depend on it. Climbers/abseilers can purchase Sterling/Edelrid/Bluewater/Edelweiss etc ropes/cords with confidence and certainty that the product will perform to specifications.
Here are some example links:
Link: https://sterlingrope.com/store/climb/cordage/accessory-cords
Link to Sterling 5mm cords: https://sterlingrope.com/store/climb/cordage/accessory-cords/5mm-accessory-cord
Link to Edelrid 5mm cords: https://media.edelrid.de/images/attribut/71479-03e%20(Powerloc%20Expert%20SP%205%20mm)%20EC-Conf.pdf

Quote
Perhaps my assumption is wrong,
They are.

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...a certain knot could outperform another knot in one type of rope, but not in another type of rope.
Obviously, the material matters.
eg fishing line, dyneema, monofilament, el cheapo no name brand, bungy/elastic cords, etc
Knot behavior under load will be different for different materials.
If repeatability is thought to be a desirable goal, then we need to be using similar materials so another tester living in a different nation can try to replicate your results.

...

Harold, at the end of the day, you are a 'backyard' tester and you are acting in isolation with a very limited budget and no third party calibrated force generating machinery (which is by and large the definition of a backyard tester). And there is nothing wrong with being a backyard tester :)  I'm just hoping to be able to repeat your tests to see if I can obtain the same results. That's how science is done - someone tests and publishes a paper with a conclusion. Others around the world then try to repeat that test to confirm or refute the results.

Anyhow, you have made up your mind and that's it.
There is little more I can add to convince you of another viewpoint.

I write all this in good faith and its just my feedback...its not intended as an attack or to insult you (so hopefully you haven't interpreted it that way!).
« Last Edit: August 03, 2018, 02:16:22 AM by agent_smith »

Dan_Lehman

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  • Posts: 3797
Re: Knot jamming test
« Reply #28 on: July 24, 2018, 11:38:19 PM »
I think what I am testing is knots, not rope.
This is a key point, in that your "knots" clearly
here means "arrangement for cordage ..." and
not the actual-factual material item tested.
My "... because the light is better" joke was to
note the folly of testing in something unlike what
will ultimately be of actual interest/use --and this
shows the importance of material (and forces).

It's a matter debate how well attributes of the
latter can be carried by the former.
Quote
Quote
although all EN564 rope may meet certain specifications,
that doesn't mean all brands will be the same or even all
samples from the same factory would be identical.
Wrong.
?!?  No, quite right, but mitigated in degree; and w/o even
adding the factor of usage & age to the so-spec'd whichever-brand vs.
another ropes!

Quote
... I cannot purchase your no name brand el cheapo
 cord here in Australia to precisely match ...
Hmmm, could we devise some cordage-characteristic
measures so that we could match (or come close to,
or know some degree of the divergence from ...) the
materials?  --thinking of those bend/stiffness measures
for climbing ropes, and ... how to gauge friction, or
compressibility ?!


But before we (over-)worry about duplicating results
--something, btw, getting some bit of press for things
deemed more important (than knots) in science!--,
we can content ourselves with just decently presented
results.

(In certain cases, perhaps, we could even share some
not-too-heavy materials!  Recently just *harvested*
some more venetian-blinds pull cord core&sheath,
adding to a growing stock of this fine cord ("fine"
in several senses, IMO!).  For the first time, today
I separated core (gradual twist, I think) & mantle
in a line. )


--dl*
====

Harold Kahl

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  • Posts: 73
Re: Knot jamming test
« Reply #29 on: July 26, 2018, 11:26:27 AM »
Thanks for the testing, Mark. I'd be interested to see how the standard Rigger's/Hunter's bend performs under the same conditions and maybe the zeppelin bend, if you are planning additional tests.