Rope from cyffty tested

[tomferry]

I did a trip to cyffty with glynn & Joel back when we had cal access . We did change some ropes , 1 of them was in the ladder way climb into cyffty from parc 3 this is in very dirty water which I suspect is rather maybe “toxic ?” It was certainly
Very old I have read a fair amount of trip reports which say there was ropes here a blooming long time ago ! I sent it to this guy for the testing here is the results !! I believe if you was at the top of this rope, fell through all the ladder hatch ways, it would have been 50+m getting towards the 60m mark ?

Here is the rope in situ

https://flic.kr/p/2o1mPWx

There is photos of the old wooden wheel barrow in that album , the mine closed in 1921 this is suspected to of been left then . 102 years ago still full of the lead ore which Roy fellows discovered.

 

[ChrisJC]

Looks like it would have taken a static load of 1.2 tonnes before breaking which seems good to me.

Chris.

 

[CJ]

Well that's settled it then, when you told me about sending it off I had no idea which way it was going to go... And it held it's own pretty well

 

[CJ]

Have you got any spare, I could do with some rope for my cowtails. Should work nicely with my snapgates

 

[tomferry]

I am glad it got his bench dirty . I certainly no the feeling of that sh”t in my ear drums for a week after the trip . My favourite part was his knot tying.

 

[tomferry]

Have you got any spare, I could do with some rope for my cowtails. Should work nicely with my snapgates

Don’t pollute this thread with the cow tails talk ! Inglesport will be sold out of screw gates soon !!!

 

[Bob Mehew]

Have a read of bca_long_term_rope_tests

Whether 'static' testing with a tensile machine replicates the behaviour of a dynamic situation, i.e. arresting a falling person which takes place in under a tenth of a second, is something I have not (yet) been able to confirm. Hopefully one day.

 

[BikinGlynn]

That's pretty interesting, I'd still b pretty confident it would hold ya in a fall

 

[Edwardov]

I have been watching this guy for years so lovely to see some dirty local Welsh rope making an appearance!

 

[mikem]

If you freefell that distance it would be the cowstails that break, not the rope (or the anchors might fail)

 

[Fjell]

Have a read of bca_long_term_rope_tests

Whether 'static' testing with a tensile machine replicates the behaviour of a dynamic situation, i.e. arresting a falling person which takes place in under a tenth of a second, is something I have not (yet) been able to confirm. Hopefully one day.

The guy who makes the videos often tests the same rope dynamically and statically and gets similar peak load numbers as far as I can tell, and it breaks in the same places. He has a static cell and a 10kHz dynamic one on a drop rig.

What will prob change is the force generated for a given FF between ropes of different age and use. You cannot easily estimate this from a static test unless you also measure strain and use analogues.

Much above 7kN is going to severely damage you. Thus I would think that virtually any undamaged knotted SRT rope (of any age and class B or better) will survive a fall that will kill you. So that isn’t a problem worth worrying about.

If you want a more interesting question, does binding the core to the sheath (as in some new Beal ropes) make the situation worse or better in a shock load situation with ascenders and descenders? I do wonder about ascenders in particular as the sheath sliding absorbs energy without cutting the core. Have they really tested it?

 

[mikem]

The nice thing to know is that the cocktail of chemicals that has presumably been running down this rope hasn't damaged it, however, without testing the water there is no way of knowing which (apart from iron, & presumably not including too much sulphur...)

 

[ChrisJC]

Lead and Zinc compounds.

Chris.

 

[mikem]

Which usually contain other delights such as mercury & arsenic! But I was thinking more of stuff that might deteriorate the nylon.

 

[royfellows]

Totally brilliant! As near as I can fix the age of the rope, and its 10mm Edelrid Superstatic, it was well used back in 1996 when I originally fitted it. There is a similar section of the same rope in some old stopes, the safest way up through Cwffty workings. An obvious ladderway up has the top section removed. I did this deliberately because it was insecure, an accident waiting to happen. It was redepolyed in the "Earthquake Section" to regain the passage from the level floor which is slowly falling into the stopes below..
Anyway, the rope, nearest guess is 28 -29 years so you not far out.

Another comment is the very good state of the timbers in Cwffty compared to the Parc workings, I would say that in the 19th Century they fitted good timber, while in the 20th they used rubbish.

 

[tomferry]

The ochre as I call it definitely drys your skin out a bit -but it’s not as strong as other local ish mines.

The rope up to the 10 fathom level is now replaced with a “fresh” retired rope with a Y hang . Your old rope from here is in the ochre with probably another 60m to act as a pull cord to get through the sediment. The rope up to the drainage level is still the 1 you left still around a roof pillar, you need this as the short wooden ladder is just wire strands now . Regarding the cat walk ropes these are exactly the same but the route is badly blocked and dangerous.

 

[Bob Mehew]

The guy who makes the videos often tests the same rope dynamically and statically and gets similar peak load numbers as far as I can tell, and it breaks in the same places. He has a static cell and a 10kHz dynamic one on a drop rig.

What will prob change is the force generated for a given FF between ropes of different age and use. You cannot easily estimate this from a static test unless you also measure strain and use analogues.

Much above 7kN is going to severely damage you. Thus I would think that virtually any undamaged knotted SRT rope (of any age and class B or better) will survive a fall that will kill you. So that isn’t a problem worth worrying about.

If you want a more interesting question, does binding the core to the sheath (as in some new Beal ropes) make the situation worse or better in a shock load situation with ascenders and descenders? I do wonder about ascenders in particular as the sheath sliding absorbs energy without cutting the core. Have they really tested it?

The location of the break is usually the first bend of the active rope within the knot assuming there is no defect somewhere else. See Pieranski et al for the theory.

10 kHz is a bit slow for dynamic work. The interesting feature is the force v time plot shows a slip / stick phenomena within the knot which is visible in high speed photography (20 kHz frame rate). So when a certain force is exceeded, the rope within the knot slips feeding rope into the section between knots. In doing so it tightens the knot so eventually the knot 'grips' the rope again and stops slippage. This slip / stick phenomena is dependent upon friction and as you may be aware the behaviour of static and kinetic friction is extremely difficult to characterise. Hence my postulate that static testing could be different from dynamic testing.

One can 'measure' strain in dynamic work, we were doing it directly on the now deceased Bradford rig. However, there is also some clever maths one can use to provide a measure.

We have tested used old ropes which broke between 6 and 9 kN. It is also worth noting that the human frame has a reasonable shock absorbing capacity. So the forces seen by a human will be less than that seen using a steel mass. The 6 kN threshold used in standards relates to what an ordinary person should be able to withstand and not be harmed. The survivable force is quite high for fit youngsters, see Crawford's work. But there have been injuries, notably one guy who severely damaged a vertebrae with a fall of just a few metres.

I'm not sure if the sheath directly contributes much strength. Its role is to compress the core so the strands in the core better share the load; hence the improved capacity of a kernmantle rope compared to a same weight per unit length of a hawser laid rope.

 

[Fjell]

I’m pretty sure I know exactly which bolt failed at Rowten because I thought it was very much a bad ‘un prior to that. It impressed on me the need to avoid short rebelays or have a back up to it (a strop for instance).

Has the unicore type rope been tested with jammers? I could not find a test. Is there a bigger risk of just shearing the whole thing?

 

[Cantclimbtom]

... ... ...
I'm not sure if the sheath directly contributes much strength. Its role is to compress the core so the strands in the core better share the load; hence the improved capacity of a kernmantle rope compared to a same weight per unit length of a hawser laid rope.

When ascending a rope with a toothed jammer, the sheath takes most of the load. Look what happens if the sheath fails (simulated with a knife)

 

[mikem]

However, damage doesn't occur like that. A unicore is safer, but a standard rope will bunch on the central strands.