Climbing Sling Myths

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The image of a sling straight vs doubled vs girth hitched and it's relative strengths float around and is taken as doctrine. So we tested it.

Straight (broke 30%+ above MBS or the same as the chart)
Test 1: 29.02kn
Test 2: 27.62kn
Doubled (should get around 56kn)
Test 3: 53.58kn
Test 4:52.26kn
Wrapped 3x (should get around 56kn)
Test 5: 43.90kn
Test 6: 47.76kn
Doubled Twice (should get around 112kn)
Test 7: 78.72kn
Test 8: 82.82kn
Girth Hitch (should get 50% or 14kn)
Test 9: 25.22kn
Test 10: 23.48kn

Girth hitch with a 22kn MBS dyneema sling 15.48kn
Girth hitch nylon sling directly on hanger 9.50kn

Intro
00:41 The Test
03:41 Reddit
07:29 Straight
08:02 Doubled
09:04 Wrapped
10:26 Doubled Twice
13:11 Girthed
15:02 Conclusion
17:05 Extra Test
18:48 Ending
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Комментарии
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Watching this channel is making me realize that I'm a snob. I go in assuming that a couple of free-spirit climbing bums aren't going to teach me anything about stress and strain. I'm a mechanical engineer, after all. And then they teach me stuff and I feel bad for being an a***ole.
I really like the work you guys are doing.

thbyg
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I've done a course on theoretical physics last semester and we learned some things about slings/ropes and how they behave force-wise under certain setups. The biggest issue with the theoretical rope stuff is (at least in my course) that the rope is seen as one-dimensional most of the time, so it only matters how often it is wrapped around something. If the rope is a three-dimensional object, meaning that it has a mass and more importantly friction, only the friction between the rope and the surface is calculated, while the friction between overlapping parts of the rope is neglected. These are some pretty massive simplifications in comparison to real-life but obviously, theoretical physics should only give us a general of how some things behave during certain situations, and then it's up to guys like you to test it under real circumstances. Keep up the great work!

edwinmahlo
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Hello. I'm an Entertainment Industry rigger, turned engineer. A few thoughts on things:
1. Have a look at your industrial slings. A choke (or girth hitch), should be good for 80% of strength. That's in a straight line pull. This is on every sling I've ever used.
2. If you choke something, then fold the sling back over itself, it will continue to decrease in strength, depending on the angle. Folded all the way over, you should end up at 50% of 80%, so 40% strength.This is from when I did my IRATA level 1 (many years ago now).
3. MBS is minimum breaking strength. In order to have that as a minimum, everything should be breaking a bit above this. The weakest one made needs to break at MBS. It's a minimum.
4. That minimum might not be based on a straight line pull. The manufacture might account for things like doubling it over etc, then work backwards from there (that's a theory).
5. The one with the wraps actually opens up the other side, giving you a bit of a bridle angle. It's pretty small, but its there. Might be worth playing with the numbers to compare it that way too (I'm happy to help with that if you like)
6. The ones where it was double double folded (that's a technical term I think), you get a bit of twisting and weird compression of the fibers going on. I was still really surprised it went at 78 not 88.
7. In general, wrapping a tensioned line around something decreases the tension as it goes around. This is why winch drums need a minimum of three wraps on them. After that, there's no tension in the line. This is something I'd like to do more research on, but it's a real thing. So When you wrap the sling around the shackle pin, there is something interesting going on there in terms of directing forces inwards weirdly and if the wraps are over top of each other, then you'll be getting weird compression and heat build up.

This was a great video though! I like your guys stuff. If you want to discuss any of this stuff with me, the entertainment industry is still pretty quiet, you know, with The Plague stalking the Land, so I have a bit of spare time. Leave me a replay and I'll drop you an email.

scottstewart
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Excellent video. I think a lot of people are missing the real gold of this episode. It's testing how to make a sling stronger... so if you're rapping off some old tat that you shouldn't be, at least we know how much (%) we can increase the strength with various configurations.

EvanWisheropp
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I don’t climb and I don’t plan on it in the future, and this entirely seems outside of content I would normally watch but I find it fascinating none the less. Thank you for the content you create!

johncorder
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"It's not that helpful when you're trying to research something just to find your own research". Aka the terrifying moment you realise you're the subject matter expert now..

Great work as always guys!

tomedinburgh
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Thank you very much. An interesting idea from Bobby to test gear multiple times with 50% load and then break it! I am stoked with 45 K subscribers. This channel is GOLD!!

daniilkulikov
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Could you use a thermal camera on the slings to see the warmth build up during the strain test?

cosmiceon
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I work on communication towers and these forces happen often we just get told some of this information it's nice to see it for real and a few good tips well done

kirkgarren
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Holy mother of Tradclimbing I love your Videos! They really make my day better and are super interesting.

marcushofmann
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I'm not a slackliner, but I find this information very useful for my job as a tower technician. We use the wrapped slings and girth hitched slings often on towers. We don't measure anything in KN, but we pull loads in the range of 1000lbs from very abused slings using those methods without problems. Keep up the great content!

TheRedlaser
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Been watching your channel for a few months now, just donated! Really appreciate all the hard work you guys do, and the production value is insane!

trevdawgable
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I reckon if the sling is just doubled, than it self equalizes the load easily, whilst when it's wrapped around than the wrap pinches the sling and force might not be distributed evenly, resulting in lowered strength, whith one part of the sling getting more load than the other. Seeing Your test is always an improvement for my intuition. Visual thinking is king.

petrnews
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Loving these videos man. Thanks so much.

TristanAnderson
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18:45 OK this is what I think! You guys are just awesome! Thank you so much for everything you do! Greetings from Austria!

lionknives
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The wrapped sling introduces an angle to the attached leads of the sling, would be interesting to divide the measured breaking strength by the angle cosines to see if the straight tensile breaking force is close to the original double looped variation

amiller
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Hey, the reason for decreased strength is due to overlapping the straps. When they are under that much tension they will lock together rather than slip past each other. That will lock the length once the load gets high enough (well below MBS). Once you do that the shortest length will see a much higher load. The best way to mitigate that problem is to use longer test pieces so you can use larger shackles. This will allow you to avoid overlapping the test pieces.

phreload
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Thanx guys! I spent years doing rigging with my job, variables can be a &!+<# when suspending a heavy load or actually using your fall arrest gear. I tested everything before we bought any quantity.

O.L.D_RC
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"African elephant..." Showing an Asian elephant 😅

noonesenemy
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I've watched this video like four times now. This channel is such a great reference and I hope more people support it.

joeyebeling