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
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
From Harold:
I certainly share the concerns of SS396 and others about the scientific rigor of my "backyard" testingI 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:
Two ABOK1425A Rigger's bends and two RiggerX/[b]Infinity [/b]bends were tied in seriesIf 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:
http://igkt.net/sm/index.php?topic=4561.0Xarax posed the following question in an email:
[size=10pt]My question is - why this particular X-ed variation, and not also the other one I had shown (in the above link)?[size=10pt]Xarax also commented that; ...[i]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:
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). [b]EN564 cords[/b] 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 [u]repeatability [/u]- 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 [i][b]repeatability [/b][/i]is desirable?
I’ll try to remember that.
Also, if you have to use a [b]tool [/b]to loosen and untie a knot - this (in my view) disqualifies it from being jam resistant. In other words, if you [u]can't[/u] 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.
the jamming threshold is likely to be probabilisticThat's been my experience. There seems to be some randomness, unless there are some variables that I am not aware of.
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). [b]EN564 cords[/b] 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.
: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!”
per Harold:
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…
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.
per Harold:
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…
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.
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
Perhaps my assumption is wrong,They are.
...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!).
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.
?!? 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!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.
... 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. )
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.
Great job Mark, thank you.
Does seem to be a better job of testing than I can do.
What is your test set up and would share a picture of your rig?
If I can, I would like to duplicate it.
SS
Thanks Scott,
I own a digital 5 ton load cell (brand ‘Dynafor’) - and so had a means to measure the force I was applying.
I used a 2 ton ‘lever hoist’ (basically a ratcheting chain block) - which is what I used to apply force.
I ran out of time today but, I am having another crack tomorrow where I will ramp up the force to 8kN and maybe a bit higher.
Will snap a few pics for you…
Mark
I deleted and moved my knot test report to ‘Knotting concepts and explorations’.