Author Topic: Soft Links Vs Mallions  (Read 3019 times)

Offline Mike Hopley

  • obsessive maniac
  • ***
  • Posts: 451
Re: Soft Links Vs Mallions
« Reply #25 on: December 04, 2019, 11:07:42 am »
Thank you, Mike, but I think that I managed to work that out for myself; I was merely making an observation.

Apologies for being patronising -- I was thrown off by the way your comment was phrased. :-[

I get the impression that using bigger / heavier carabiners is still common. For one thing, it's pretty expensive to replace them with a complete set of lighter models.

(I would like a set of snaplinks for rigging with more adventurous companions, but I'm not sure I can justify the expense.)

UK Caving

Re: Soft Links Vs Mallions
« Reply #25 on: December 04, 2019, 11:07:42 am »
Warmbac

Online mikem

  • forum hero
  • *****
  • Posts: 2843
  • Mendip Caving Group
Re: Soft Links Vs Mallions
« Reply #26 on: December 04, 2019, 11:46:40 am »
If you've got mud problems, then Grivel also do these at 39g:
https://www.bananafingers.co.uk/carabiners/grivel/plume-twingate

But maillons still lead on compactness & price (& you don't have to consider cross loading the gate). When comparing weight I guess you'd have to factor in the spanner as well - although it's a lot lighter than pliers for dealing with obstinate screws!

Offline Fulk

  • forum hero
  • *****
  • Posts: 3978
Re: Soft Links Vs Mallions
« Reply #27 on: December 04, 2019, 12:40:39 pm »
Quote
Apologies for being patronising -- I was thrown off by the way your comment was phrased. :-[
No problem – but thanks for apologising.

Offline Pony

  • regular
  • *
  • Posts: 49
  • Yorkshire karma. Its called comeuppence
Re: Soft Links Vs Mallions
« Reply #28 on: December 04, 2019, 01:14:06 pm »
Another point in the mallion v krab equation is of course time.
BTW when I said originally about weight savings with alloy krabs I neglected to state they were snap gates.

Offline GT

  • menacing presence
  • **
  • Posts: 179
Re: Soft Links Vs Mallions
« Reply #29 on: December 04, 2019, 09:20:46 pm »
Off topic a bit but worth considering if you're talking about soft shackles attached to anchors. The attached (hopefully) image tape/sling failed at 7kN

Online mikem

  • forum hero
  • *****
  • Posts: 2843
  • Mendip Caving Group
Re: Soft Links Vs Mallions
« Reply #30 on: December 04, 2019, 11:34:39 pm »
7kN was I believe the 1 inch tubular sling, others failed at lower loading, but it didn't say whether drop tests (I assume it was) or steadily increasing loads...

From Aussie website, who makes his money doing tests for rope access:
https://www.ropelab.com.au/category/free/articles/

Offline Chocolate fireguard

  • obsessive maniac
  • ***
  • Posts: 389
Re: Soft Links Vs Mallions
« Reply #31 on: December 05, 2019, 02:28:50 pm »
7kN was I believe the 1 inch tubular sling, others failed at lower loading, but it didn't say whether drop tests (I assume it was) or steadily increasing loads..

I know quite a few people who believe that a (say) 7kN load during a drop test is more likely to break something than a steady 7kN load, but I have yet to hear what I consider to be a convincing explanation of why that should be.

I'm not saying it isn't so - it's just that almost all of the explanations seem to concentrate on the fact that the load is there for a shorter time (it's "impulsive"), without any attempt to say why a load that is there for only a short time should be more damaging than the same load present for longer!

Now, if I heard someone say that some things (like knots?) often show obvious signs of melting at the failure point, and that in a slow steady pull more of the heat generated when the knot tightens escapes, then I might be convinced.

But I can't see that being a big consideration when a sling fails over an edge.
« Last Edit: December 05, 2019, 02:41:58 pm by Chocolate fireguard »

Online mikem

  • forum hero
  • *****
  • Posts: 2843
  • Mendip Caving Group
Re: Soft Links Vs Mallions
« Reply #32 on: December 05, 2019, 04:17:10 pm »
Not sure, but cavers / climbers are unlikely to create a steady load of that magnitude, but can produce such a shock load.

Offline Topimo

  • obsessive maniac
  • ***
  • Posts: 443
  • School of Karst Rocks. University of NiFe.
Re: Soft Links Vs Mallions
« Reply #33 on: December 05, 2019, 05:24:42 pm »
7kN was I believe the 1 inch tubular sling, others failed at lower loading, but it didn't say whether drop tests (I assume it was) or steadily increasing loads..

I know quite a few people who believe that a (say) 7kN load during a drop test is more likely to break something than a steady 7kN load, but I have yet to hear what I consider to be a convincing explanation of why that should be.

I'm not saying it isn't so - it's just that almost all of the explanations seem to concentrate on the fact that the load is there for a shorter time (it's "impulsive"), without any attempt to say why a load that is there for only a short time should be more damaging than the same load present for longer!

Now, if I heard someone say that some things (like knots?) often show obvious signs of melting at the failure point, and that in a slow steady pull more of the heat generated when the knot tightens escapes, then I might be convinced.

But I can't see that being a big consideration when a sling fails over an edge.

Rate of energy dissipation - the material has to deform and convert the kinetic energy into heat which is transferred to the environment and elastic potential energy stored in the material itself, load rates are very important with viscoelastic materials (such as UHMWPE - Dyneema). Load it gradually and the material has time to allow the hydrocarbon chains to align themselves with the tension. Load it rapidly and the stress in the material will be higher, breaking these Van der Waals bonds causing macroscale defects - i.e. cracks, tears, failure.

Offline andrewmc

  • junky
  • ****
  • Posts: 803
  • EUSS, BEC, YSS, prov. SWCC...
Re: Soft Links Vs Mallions
« Reply #34 on: December 06, 2019, 04:04:45 am »
'Full strength' (>20kN) 19g snapgates exist. That's probably hard to beat even with a soft shackle...

If using dyneema you could also tie directly to a resin anchor (since all the common sorts have well rounded edges).

Offline Chocolate fireguard

  • obsessive maniac
  • ***
  • Posts: 389
Re: Soft Links Vs Mallions
« Reply #35 on: December 06, 2019, 07:20:04 pm »
7kN was I believe the 1 inch tubular sling, others failed at lower loading, but it didn't say whether drop tests (I assume it was) or steadily increasing loads..

I know quite a few people who believe that a (say) 7kN load during a drop test is more likely to break something than a steady 7kN load, but I have yet to hear what I consider to be a convincing explanation of why that should be.

I'm not saying it isn't so - it's just that almost all of the explanations seem to concentrate on the fact that the load is there for a shorter time (it's "impulsive"), without any attempt to say why a load that is there for only a short time should be more damaging than the same load present for longer!

Now, if I heard someone say that some things (like knots?) often show obvious signs of melting at the failure point, and that in a slow steady pull more of the heat generated when the knot tightens escapes, then I might be convinced.

But I can't see that being a big consideration when a sling fails over an edge.

Rate of energy dissipation - the material has to deform and convert the kinetic energy into heat which is transferred to the environment and elastic potential energy stored in the material itself, load rates are very important with viscoelastic materials (such as UHMWPE - Dyneema). Load it gradually and the material has time to allow the hydrocarbon chains to align themselves with the tension. Load it rapidly and the stress in the material will be higher, breaking these Van der Waals bonds causing macroscale defects - i.e. cracks, tears, failure.

Topimo, you have PM.

Offline caver63751

  • Newbie
  • *
  • Posts: 3
Re: Soft Links Vs Mallions
« Reply #36 on: December 23, 2019, 04:16:57 am »
Pertaining to the potential application Topimo mentioned of remote/deep caves, I've recently done a comparison of connector types. I realize prices may be different in the UK—I included them here for the sake of comparison. I intentionally omitted the Petzl Speedy due to high cost ($10 USD for me). Also of note, there are other non-locking carabiners in the 20-25 g range that may cost less than the Edelrid Nineteen G, which is currently the lightest on the market if I'm not mistaken.

screw link, stainless steel, 6mm, wide opening (from Zoron Manufacturing; we tested N=3 to ultimate tensile strength of ~40 kN)
41 g
$2.53 USD (quantity discount)

carabiner, Cypher Firefly II, screw gate
42 g
$4.29 USD (pro discount through distributor)

carabiner, Edelrid Nineteen G, non-locking
19 g
$7.50 USD (no discount for me)

cord, Beal Pure Dyneema, 120 cm (120 cm seems to be a good length for attaching to standard or AS hangers)
18 g
$3.24 USD (pro discount through distributor)

Offline Ian Ball

  • junky
  • ****
  • Posts: 773
Re: Soft Links Vs Mallions
« Reply #37 on: December 23, 2019, 10:24:29 am »
screw link every time   ;)

Offline pwhole

  • forum hero
  • *****
  • Posts: 1624
  • TSG, DCA, PDMHS
    • Phil Wolstenholme website
Re: Soft Links Vs Mallions
« Reply #38 on: December 23, 2019, 02:45:29 pm »

I know quite a few people who believe that a (say) 7kN load during a drop test is more likely to break something than a steady 7kN load, but I have yet to hear what I consider to be a convincing explanation of why that should be.

I remember at school bending bars of McCowan's Highland Toffee slowly (and eventually stretching them out), but you could still snap them if you moved your hand quickly enough. Are the two issues related perchance? As in there's a threshold velocity that suddenly overcomes structural stability? ;)

Offline langcliffe

  • forum hero
  • *****
  • Posts: 2374
    • Caving Routes in the Northern Dales
Re: Soft Links Vs Mallions
« Reply #39 on: December 23, 2019, 03:03:38 pm »
screw link every time   ;)

You won't be saying that at my age when your fingers don't work as well as they used to!

Offline Ian Ball

  • junky
  • ****
  • Posts: 773
Re: Soft Links Vs Mallions
« Reply #40 on: December 23, 2019, 05:11:31 pm »
screw link every time   ;)

You won't be saying that at my age when your fingers don't work as well as they used to!

 :thumbsup:  spanner to the rescue.

Offline Mike Hopley

  • obsessive maniac
  • ***
  • Posts: 451
Re: Soft Links Vs Mallions
« Reply #41 on: December 23, 2019, 06:27:04 pm »
Also of note, there are other non-locking carabiners in the 20-25 g range that may cost less than the Edelrid Nineteen G, which is currently the lightest on the market if I'm not mistaken.

I think the 19g is a bit too small for rigging. For another ~3 grams, you can get something more practical (Camp Nano 22).

In their "current" book, the French Caving School even mention rigging with carabiners that are not full strength -- i.e. strong accessory carabiners like this one. This now seems a little mad, given that we have full-strength carabiners that are lighter and cost about the same.

Offline andrewmc

  • junky
  • ****
  • Posts: 803
  • EUSS, BEC, YSS, prov. SWCC...
Re: Soft Links Vs Mallions
« Reply #42 on: December 24, 2019, 10:38:56 am »
If you were feeling really ballsy, you could rig on DMM XSRE snapgates, rated to 4kN and only 8g :p

It's probably worth remembering though that rope is about 50g a metre so you can save more by making sure you have the right length ropes... Even making loops larger than they need to be will add extra weight.

Offline JB

  • junky
  • ****
  • Posts: 907
  • Eldon Pothole Club
Re: Soft Links Vs Mallions
« Reply #43 on: December 26, 2019, 08:14:05 am »
Interesting topic. Looking at how you tie those things in and faff about trying to tighten elastic o-rings over them they’re not for me. Cold hands and gloves could put a stop to your trip I would think.

Like lots of people i’m sure I’m after ease of use, versatility and strength so prefer to use full strength screwgate karabiners (if you end up with two people on a rope for some reason proper karabiners reassuring).

Offline Ian Ball

  • junky
  • ****
  • Posts: 773
Re: Soft Links Vs Mallions
« Reply #44 on: December 26, 2019, 12:44:16 pm »
7kN was I believe the 1 inch tubular sling, others failed at lower loading, but it didn't say whether drop tests (I assume it was) or steadily increasing loads...

From Aussie website, who makes his money doing tests for rope access:
https://www.ropelab.com.au/category/free/articles/

Nice website  :thumbsup:

Offline Tseralo

  • player
  • **
  • Posts: 97
  • TSG
    • louisemcmahon.co.uk
Re: Soft Links Vs Mallions
« Reply #45 on: December 26, 2019, 04:40:53 pm »

I know quite a few people who believe that a (say) 7kN load during a drop test is more likely to break something than a steady 7kN load, but I have yet to hear what I consider to be a convincing explanation of why that should be.

I remember at school bending bars of McCowan's Highland Toffee slowly (and eventually stretching them out), but you could still snap them if you moved your hand quickly enough. Are the two issues related perchance? As in there's a threshold velocity that suddenly overcomes structural stability? ;)

A big difference is heat, at least in rope if you do a drop test you can melt knots especially ones that are not set well as it tightens suddenly. At speed ropes rub on each other without having time to dissipate the heat where as a slow pull would set the knot and even though the same amount of friction/energy is generated it will dissipate slower.

The same issue could be seen if you were testing a descender etc.

I would guess the same could happen in other materials at a more molecular level? but i'm not a physicist and am happy to be corrected.

Offline Chocolate fireguard

  • obsessive maniac
  • ***
  • Posts: 389
Re: Soft Links Vs Mallions
« Reply #46 on: December 26, 2019, 09:43:08 pm »

I know quite a few people who believe that a (say) 7kN load during a drop test is more likely to break something than a steady 7kN load, but I have yet to hear what I consider to be a convincing explanation of why that should be.

I remember at school bending bars of McCowan's Highland Toffee slowly (and eventually stretching them out), but you could still snap them if you moved your hand quickly enough. Are the two issues related perchance? As in there's a threshold velocity that suddenly overcomes structural stability? ;)

Sorry, I just saw this post.

I think what you’re describing is called strain rate dependence.

Over the last few years, whenever I remember, I have been looking for information on it and nylon, but without much success.

It seems that many (most?) materials exhibit it, but not significantly under the conditions of temperature and strain rate components are designed for. I have found a few mentions that some physical properties of polymers are sensitive to strain rates, but no actual figures that can be applied to ropes.

Strain is the change in a dimension (length in our case) divided by the original dimension.  The average strain rate is that strain divided by the time taken.

A drop test to break on a new 1m length of caving rope will produce a rope stretch of perhaps 30% and take perhaps 200 milliseconds as the knots tighten. That gives a strain rate of 0.3/0.2, or 1.5 per second.

So we are talking about strain rates of “a few per second” for a dynamic test and possibly “a few hundredths per second” for a slow stretch. This difference of a couple of orders of magnitude is important for a toffee bar or a piece of silly putty, but I haven’t found anybody who has done work on nylon at these rates.

Bearing in mind that the break happens in the knot, that a knot will convert several hundred Joules of energy to heat and that after a drop test it is not remarkable to find  the broken end of rope showing signs of melting (and sometimes stuck to another part of the sample), it would surprise me if the time for the heat to spread throughout the knot during a test was not important.

Not much of this would apply to a sewn sling failing over an edge.

Any info on strain rate measurements on nylon will be gratefully received.