Author Topic: A compressive source of tension?  (Read 9917 times)

paulj

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Re: A compressive source of tension?
« Reply #15 on: October 12, 2007, 05:12:48 AM »
Are there unresolved knot strength questions when dealing with these two types of climbing ropes?  One the references (the UK industrial one) said, all these knots tested at 50% or better, so as long as the rope is used with in that safety margin, don't worry about the knot.

On the other hand, with high modulus (very low stretch) ropes, knots are more of an unknown.  Some test at 30% or worse, with the rope either slipping out of the knot, or breaking due to strain-heating.  It is bad enough that manufacturer's like Samson say don't use any knots on their Amsteel Blue (a popular rope for offroad winching).  Maybe an innovative knot typer can find something that does work in this type of line.

Fishing and kite flying are other activities that used high strength line at close to its breaking strength.

paulj

Dan_Lehman

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Re: A compressive source of tension?
« Reply #16 on: October 12, 2007, 07:15:40 PM »
Fall factor etc.
http://www.bstorage.com/speleo/Pubs/rlenergy/Default.htm

Ah, another semi-myth of sorts.  Climbers cite "fall factor" w/o bothering to remark
that the forces generated also depend upon falling mass, which in standard testing
by UIAA protocol is about 180#, but YMMV as per individual climber masses--women,
e.g., are typically much lighter (Lynn Hill is a small person, but for stature!).  PMI did
a report on the loads generated by well heavier (maybe starting at 200#) masses,
and showed a significant narrowing of safety margins.

I also recall information shown in an old Chouinard catalogue in which although
the peak forces of long vs. short falls of equal FFs were also equal, their duration
was proportionate to the fall--i.e., long falls sustained the high load longer.  OTOH,
the significance of hard-to-specify small shock absorbers such as body flexing and
so on looms more significant for short falls, where an inch or several is a greater
proportion of the full length (ditto for knot compression).  One unseeming case of
severe loading comes when attaching to an anchor with a short and static sling,
reaching above that for some reason, and slipping upon it--short fall, big FF, and
really big impact forces!

(I'm not sure what Agent Smith means about falls w/FF>1 being subtracted from
a rope vendor's count, but that does seem to be about a rule of thumb on "severe",
and some vendors recommend subtracting the rope from use, not merely a count!
There was some discussion of this on RC.com, IIRC.  --and the point about actual
forces vis-a-vis climber weight was raised then.)

-----

The cited/linked reference makes assertions about the effects of the Fig.9 LK that
are contradicted by Dave Merchant's Life on a Line literature & postings
(on NSS's forum caves.forums.org, OnRope ?), where the latter asserts that the
rate of loading--i.p., "shock" loading--leads to greater weakening in the Fig.9 than
in e.g. the Overhand LK or even Fig.8 LK.  But here we see a case of not knowing
enough about the basis for these assertions, such as knot geometry & setting.

--dl*
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agent_smith

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Re: A compressive source of tension?
« Reply #17 on: October 13, 2007, 12:43:01 AM »
Dan Lehman is right about the mass of the falling person.

I did not provide the full picture with fall-factors and dynamic ropes.

EN 892 dynamic ropes are further divided into 3 categories as follows:
1. Single - where the rope is tested with an 80kg drop mass and must survive at least 5 EN 892 test falls (impact force must not exceed 12kN on first test fall)
2. Half - where the rope is tested with a 55kg drop mass and must survive at least 5 EN 892 test falls
3. Twin - where two rope strands are drop tested simultaneously (ie as the inseparable twins) with an 80kg drop mass and must survive at least 12 EN 892 test falls

EN 892 specifies a 5.0m free fall using a 2.8m rope specimen (hence the fall-factor of 1.78.... 5/2.8 = 1.78).

The test mass in an EN 892 fall IS important. Ropes are essentially defined by what mass they were tested with. There is a trend to find the holy grail of lighter and lighter ropes (meaning manufacturers are striving trying to find ways to reduce the diameter of their ropes - thereby making them lighter). The upshot is that ropes are generally getting thinner and thinner (something I would like to do but age seems to be slowing me down somewhat). I would theorise that rope manufacturers are looking for new and more advanced synthetics to weave the holy grail of ropes - anyone for a 'nano rope'.

If a climber has a mass greater than 80kg (as I do!) the physics of the fall may exceed the test parameters given in EN 892 standard.

Each EN 892 test fall generates a fall-factor of 1.78 - which is severe in anyones language.

The conventional wisdom is to reduce the number of falls a rope can sustain by a factor proportional to the amount by which the climbers mass exceeds 80kg.

For example, I have a mass of 100kg (yes, I'm a big boy). This means I reduce the published number of falls a particular rope can sustain by 80/100 = 0.8.

Therefore, if I buy a 10 fall rated dynamic rope, I reduce its effective fall rating from 10 down to 8.

So for me, I treat a 10 fall rated rope as if it were actually an 8 fall rope.

Other than that, it is true to say that as more and more rope is payed out through the belay device, the fall severity becomes less and less.

Its ironic that it actually gets 'safer' as you climb higher!

Try explaining that one to novices and/or non climbers!


agent smith

 
« Last Edit: October 13, 2007, 12:47:57 AM by agent_smith »

Dan_Lehman

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Re: A compressive source of tension?
« Reply #18 on: October 13, 2007, 06:17:27 AM »
EN 892 dynamic ropes are further divided into 3 categories as follows:
1. Single - where the rope is tested with an 80kg drop mass and must survive at least 5 EN 892 test falls (impact force must not exceed 12kN on first test fall)
2. Half - where the rope is tested with a 55kg drop mass and must survive at least 5 EN 892 test falls
3. Twin - where two rope strands are drop tested simultaneously (ie as the inseparable twins) with an 80kg drop mass and must survive at least 12 EN 892 test falls
EN 892 specifies a 5.0m free fall using a 2.8m rope specimen (hence the fall-factor of 1.78.... 5/2.8 = 1.78).

And, believe it or not, there is one--now maybe more--rope that has been certified as all three
--viz., Beal's (aptly named) "Joker" (which is 9.1mm)
(and I also think that sizing by fractions of a millimeter is pushing things!).

Quote
The test mass in an EN 892 fall IS important.  ...
The conventional wisdom is to reduce the number of falls a rope can sustain by a factor proportional to the amount
by which the climbers mass exceeds 80kg.  For example, I have a mass of 100kg (yes, I'm a big boy). This means
I reduce the published number of falls a particular rope can sustain by 80/100 = 0.8.
Therefore, if I buy a 10 fall rated dynamic rope, I reduce its effective fall rating from 10 down to 8.

So for me, I treat a 10 fall rated rope as if it were actually an 8 fall rope.  ...
[Try explaining that one to novices and/or non climbers!]

I hope you aren't "explaining" this "conventional wisdom" to anyone anymore--it's dangerously mistaken!
You should read a version of PMI's report (PDF--available in HTML, too) at
www.safeclimbing.org/education/Heavy_Climbers_Beware.pdf
My guess is that your 100kg mass would see fewer than 8 falls in a 10-fall-rated rope,
as fall #1 = 10.1 kn/2260# vs. 8.3kn/2040# for 80kg mass (e.g., for the PMI rope used),
and not only is that well more severe than for the lesser mass--perhaps "2" falls ahead(?)--,
each successive fall will be made with the same heavier mass, and thus accelerate the
deterioration over what the lesser mass will do--NOT merely keep a supposed "2"-fall lead.
(You could think about reducing the acceptable FF by taking 0.8 of it, but that would
give 1.368 and PMI show the equivalent impact force coming only lower--1.23 or so.)

That aspect aside, I wonder what your thinking about the significance of the fall rating
of ropes is?  There are educated opinions that they aren't as readily translatable into
retirement criteria as you seem to imply.  (And for a while, at least, there was the issue
of different test labs generating different ratings--something the UIAA tried to clean up.)
But the figuring gets quite complicated by assessing falls & other history, and taking
into consideration actual mass/forces, for which there isn't a lot of test data put out
by anyone to refer to.  PMI made a start; it would be nice if they or others took this
insight into seeing the effects of an accumulation of such falls, both on the heavier
& lighter side of the 80kg standard.

--dl*
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agent_smith

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Re: A compressive source of tension?
« Reply #19 on: October 13, 2007, 12:40:14 PM »
Thanks for remarks Dan.

You are entitled to your opinion as we all are - and I respect this.

However, I will make the following comments as a right of reply to your posted remark - "I hope you aren't "explaining" this "conventional wisdom" to anyone anymore--it's dangerously mistaken!"

Comments as follows:

1. I've read the report from PMI a few years ago... and it never purported to give reductions to the maximum published fall rating of a dynamic rope.
2. I have a very clear underpinning knowledge of the math involved.
3. I stand by my theory regarding 'rule of thumb' reductions to published fall ratings on dynamic ropes.
4. I have applied my own theory to myself over 24 years of continuous climbing - I have sustained countless numbers of falls - particularly while attempting new (unclimbed) routes on sight from the ground up. Obviously I am still alive, and I have never severed a rope (yet). Of course, this information cannot be verified by you - only by my numerous climbing partners over the years.
5. I have yet to see a rope manufacturer provide any advice or informative data to heavy (more than 80kg mass) recreational climbers about how they should treat published fall ratings on given on ropes. PMI nor any other rope manufacturer have given such advice (see #1 above). I suspect that no such advice or data will ever be forthcoming (why? you may ask - legal liability springs to mind).
6. Lets look at the data... a standard EN 892 test fall generates factor 1.78.
7. It is not possible to sustain a fall factor 1 or greater on a single-pitch route (a factor 1 fall implies the lead climber has hit the ground - or 'decked' as we say).
8. To sustain fall factors greater than 1, a lead climber needs to fall past (ie below) the belayer - for all intents and purposes, this can only happen on a multi-pitch route.
9. I count any fall of factor 1 or higher as one (1) fall of the life of the rope. This is very conservative.
10. I have a mass of 100kg. I then establish a proportionality factor by dividing the EN 892 figure of 80kg by my body mass of 100kg: 80/100 = 0.8. Therefore, if I purchase a 12 fall rope, I do the following: 12 x 0.8 = 9.6. This figure is then rounded DOWN to 9. I treat that rope as if it were a nine (9) fall rope. If I sustain nine (9) factor one (1) falls, I retire my climbing rope. Although I dont have any certified test data to prove my theory, I can attest that the rule of thumb has worked for me in real-world applications in the field.
11. In summary:
[ ] I advocate that any fall generating factor 1 or higher should be counted as one (1) fall towards the ultimate retirement of a climbing rope.
[ ] I advocate that heavy climbers reduce the published fall rating of their rope by an amount proportional to their body mass - for 100kg climbers, this figure is a 0.8 reduction off the published fall rating (used in conjunction with counting any fall of factor 1 or higher towards rope retirement). All fractions are rounded conservatively - eg if a figure of 0.86 is calculated, this is automatically rounded down to 0.8.
[ ] I am confident in my rule of thumb theory as it has been proven by empirical means over 2 decades.

agent smith


ps  I forgot to add, I own a Beal 'Joker' rope. Haven't fallen on it (yet)...

EDIT NOTICE:

I made a calculation error while typing quickly during the wee hours... see #10 above. I originally stated that I treat a 12 fall rated rope as if it were a 10 fall rope. This is incorrect. The correct reduction is nine (9).
« Last Edit: October 14, 2007, 02:31:30 AM by agent_smith »

squarerigger

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Re: A compressive source of tension?
« Reply #20 on: October 13, 2007, 03:06:15 PM »
Quote
11. In summary:
[ ] I advocate that any fall generating factor 1 or higher should be counted as one (1) fall towards the ultimate retirement of a climbing rope.
[ ] I advocate that heavy climbers reduce the published fall rating of their rope by an amount proportional to their body mass - for 100kg climbers, this figure is a 0.8 reduction off the published fall rating (used in conjunction with counting any fall of factor 1 or higher towards rope retirement). All fractions are rounded conservatively - eg if a figure of 0.86 is calculated, this is automatically rounded down to 0.8.
[ ] I am happy for any person to bring a lawsuit against me - I would be happy to defend my theory with the help of hired counsel in the court room!

Hi Agent Smith and hi to Dan also.  I do not have the luxury (a $200 luxury) of having a copy of EN892 in front of me to enable me to see what you are discussing for myself, and I suspect it may be a while before getting a copy from my local library.  Perhaps in the interests of education, fairness and propriety on this public forum one or both of you could see fit to quoting from that document verbatim?  I believe that both of you have some merit in some of what you are saying but I anticipate that other responses may become more entrenched without the advantage of published and open factual bases of opinions.  Opinions are just that, and I do not deny either of you the benefit of stating them to be so, but I draw the line at taking an adversarial stance between the two of you in open public forum without also posting educational material so that other readers and potential commenters may also benefit and learn.  Please keep your comments about life-saving equipment to facts supported by extracts in the form of educational information that we all can see and from which we all can draw conclusions.  Thank you.

SR

Dan_Lehman

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Re: A compressive source of tension?
« Reply #21 on: October 13, 2007, 09:58:19 PM »
2. I have a very clear underpinning knowledge of the math involved.
3. I stand by my theory regarding 'rule of thumb' reductions to published fall ratings on dynamic ropes.

But you haven't explained how it makes any sense, which I did (re my dismissing it).
The rope fells force, not FF; it degrades by force.

Quote
4. I have applied my own theory to myself over 24 years of continuous climbing - I have sustained countless numbers of falls

In the history of climbing-ropes use, as best assessed by the UIAA, ropes haven't failed,
except by being cut over a sharp edge:  this leaves room for a LOT of theories to survive
w/o tickling the rope-failure indicator.  Effects on protection, however, might be subtly apparent,
as a rope loses more energy absorption than expected.

Quote
5. I have yet to see a rope manufacturer provide any advice or informative data to heavy (more than 80kg mass)...

Nor have you seen one suggest the counting mechanism re falls that you use.
There are some guidelines however that recommend either retirement or close inspection
after a "severe" fall, and point to FF-1 as that--which, yes, ignores force (mass) for one factor of it.

Quote
[ ] I would be happy to defend my theory with the help of hired counsel in the court room!

Ah, the playing court for "junk science"!

Quote
ps  I forgot to add, I own a Beal 'Joker' rope. Haven't fallen on it (yet)...

No, probably still working out the complexity of FF counting given its triad of possible scenarios!   :D

 :)

SS369

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Re: A compressive source of tension?
« Reply #22 on: October 14, 2007, 01:36:30 AM »
Good evening/day, here is a link to some interesting reading that may help. The article has some graphs and rope physics for the climber/caver.
http://bstorage.com/speleo/Pubs/rlenergy/default.htm
SS

agent_smith

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Re: A compressive source of tension?
« Reply #23 on: October 14, 2007, 02:14:07 AM »
I thank Dan L for his reply. I also thank squarerigger for his post.

I would like to keep this thread informative and positive - as that is the spirit in which i choose to post on this forum.

As always, I respect the advice and opinions of Dan Lehman.

I am a little concerned that the subject matter of this thread may be deviating from the core business of knots and knot theory (and hence may not be of interest to many readers).

Be that as it may, I see that ropes and cordage in general is the base material from which a knot can be formed. So in a way, this discussion on ropes is linked to knots...

...

Without doubt, anyone who proposes a theory or a new concept (or any radical new approach to an old problem) is immediately placing him/herself in the firing line of the public (rather like politicians who must face public opinion on a daily basis).

My approach to reducing the published fall rating of a dynamic climbing rope is not supported by certified test data.

It is merely my opinion - so readers and would-be user groups would apply such concepts at their own risk. Merely because I choose to post this theory on the IGKT website is in no way to be implied as approved or endorsed by the IGKT.

Squarerigger made clear remarks about the EN 892 standards.

I sympathise with him and others who may be seeking to gain possession of this document.

Unfortunately, En 892 (and all other such standards) are copyright and are certainly not available for free in the public domain. One has to purchase such standards from the relevant standards body in their nation.

I cannot email or post extracts from EN 892 without attracting negative attention. However, I can identify key test requirements for fair and reasonable analysis by interested parties.

Thus far, all the posts in this thread have accurately reported the key test requirements.

There are indeed three (3) sub-categories of dynamic rope as follows:

1. Single - where the rope is tested with an 80kg drop mass and must survive at least 5 EN 892 test falls (impact force must not exceed 12kN on first test fall)
2. Half - where the rope is tested with a 55kg drop mass and must survive at least 5 EN 892 test falls (impact force must not exceed 8kN on first test fall)
3. Twin - where two rope strands are drop tested simultaneously (ie in parallel as the inseparable twins) with an 80kg drop mass and must survive at least 12 EN 892 test falls (impact force must not exceed 12kN on first test fall)

EN 892 specifies a 5.0m free fall using a 2.8m rope specimen (hence the fall-factor of 1.78.... 5/2.8 = 1.78).

Go here for a pictorial overview of UIAA standard 101:   http://www.uiaa.ch/?c=310

This site provides a very good synopsis (but is incomplete) of the full EN 892 standard.

To purchase the full EN 892 or EN 1891 standard, you need to place an order through your national standards body. Go here for the international gateway page: http://www.cen.eu/catweb/cwen.htm

If you reside in England, go to: http://www.bsonline.bsi-global.com/server/index.jsp
If you reside in the USA, go to: www.nfpa.org (Note: The US is not a member of the European Union and CE marking is not mandatory)

The full titles of the standards are as follows:

EN 892:2004      Mountaineering equipment. Dynamic mountaineering ropes. Safety requirements and test methods
EN 1891:1998      Personal protective equipment for the prevention of falls from a height. Low stretch kernmantel ropes

For the USA:
NFPA 1983: Standard on Life Safety Rope and Equipment for Emergency Services, 2006 Edition
...

Now for the contentious area that I and Dan L are discussing...

When a person buys a dynamic rope, it will have a finite number of falls that it can sustain (given in the hang tag documentation that should be supplied with the rope).

Lets say that you purchase a rope that has a ten (10) fall rating.

At the present time, no rope manufacturer provides any information about how heavy climbers should treat such published fall ratings. (Note: I would respectfully ask that Dan L or anyone else provide me with information to the contrary).

What does this mean?

What should heavy climbers do?

There are no clear answers - only masses of confusing and conflicting information.

I am one of the many climbers who find themselves in a catch 22 situation where I want to climb, but I do so outside of EN 892 test parameters.

The PMI report discussed in previous posts does not clear up the situation.

I have used my own 'rule of thumb' approach to this age old problem, and I discussed the principle in a previous post. Here it is again:

[ ] I advocate that any fall generating factor one (1) or higher should be counted as one (1) fall towards the ultimate retirement of a climbing rope.
[ ] I advocate that heavy climbers reduce the published fall rating of their rope by a proportionality factor determined by dividing 80kg by their respective body mass. For example: A 100kg climber would divide 80/100 which yields 0.8. The published fall rating is then multiplied by 0.8 to give an 'adjusted' fall rating (used in conjunction with counting any fall of factor 1 or higher towards rope retirement). All fractions are rounded down conservatively - eg if a figure of 0.86 is calculated, this is automatically rounded DOWN to 0.8.

Note: Climbers who are lighter than 80kg gain no such benefit and should not attempt to increase the published fall rating of their rope merely on the basis of their lesser body mass.

I would also point out that each EN 892 test fall is very severe. They take a 2.8m length of rope and subject it to a 5.0m free fall using a mass specific to one of the 3 categories (single, half or twin). It is a rare event indeed for any climber to take a fall of magnitude 1.78. In my mind, it implies human error - I personally have never sustained a fall greater than factor one in 24 years of climbing. That is not to say that it doesn't happen - I am only suggesting that it hints of human error (or in some special cases, gross incompetence). The biggest risk factor in sustaining high impact force falls generally occurs when leaving a belay stance on a multi-pitch route. Although the risk is present, it can easily be mitigated by placing protection early and frequently when leaving a belay.

In the context that severe falls exceeding factor one are generally rare, my rule of thumb procedure for reducing published fall ratings is sound.

The most common reason for retiring ropes is general wear and tear on the outer sheath (where the inner core has become exposed). Age is another factor - but heavy usage patterns usually cause sheath damage before the age limit is reached (Note: rope manufacturers do not universally agree on the lifespan of a rope - and this is another gray area). One group of climbers is 'sport climbers'; this group is more likely than not to approach the fall rating published by the rope manufacturer.

My remark about defending myself against would-be litigants was a pun and I meant no harm - I am happy to withdraw the said remark. Here is another pun: I can only assume that a few US citizens are reading this post and are right now planning future lawsuits against me... I wish them all the best - but they should be advised that my ex wife owns everything I ever had (including my dog).

..

So there you have it, a rule of thumb for building in at least some margin of risk reduction in the face of the present status quo - where the prevailing situation is to ignore the problem and let nature take its own course.

Well, I have embraced the problem and done something about it - and my own empirical field testing has thus far proven me right (but I have no documented evidence to show anyone).

Disclaimer: Any person placing reliance on agent smiths 'rule of thumb' reductions to fall ratings do so at their own peril. No liability will be accepted for any injury, death or loss incurred as a result of relying on the said information.


By the way, there is a wealth of information published by the many rope manufacturers who are very conservative. Another gray area is with respect to rope lifespan (as stated above).

Oh no, here I go again, producing theories where there was only mass confusion... the big question: How long does a EN 892 / EN 1891 rope last? Try answering that question from the point of view of a new rope stored in a cool dry place and never used...

It is to the rope manufacturers advantage to create a situation where confusion and doubt prevails. This obviously leads to healthy annual rope sales figures where climbers retire their ropes early (yes, this can be seen as good). However, I see no reason to retire a rope for no sound reason. I am a believer in criteria and not hysteria.

Rope manufacturers enjoy the present status quo - as it works in their favour. Its kind of like making a product that never wears out... is this commercially viable?

I leave you to ponder your own thoughts...


agent smith


Edits:
1. Added info on EN standards
2. Added further elaboration regarding falls and severity of falls
« Last Edit: October 14, 2007, 10:04:29 AM by agent_smith »

SS369

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Re: A compressive source of tension?
« Reply #24 on: October 14, 2007, 02:26:14 PM »
Good Day, here is another hopefully helpful link for the question "What heavy climbers need to know"?  If the link fails to get you there, I have the .pdf file on board so just ask and ye shall receive.
SS

http://www.safeclimbing.org/education/Heavy_Climbers_Beware.pdf.

agent_smith

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Re: A compressive source of tension?
« Reply #25 on: October 15, 2007, 08:45:54 AM »
SS369 (or just SS to his mates),

I think you'll find that link has already been posted by Dan Lehman...

By the way, the page that link points to does nothing to address the issue of what to do about fall ratings for particular dynamic rope brands and models.

We have already rehashed Newtons laws of physics - we understand and acknowledge that bigger people create bigger impact forces (this is obvious). Whilst I'm not fat, I am a 'big' boy at 100kg mass.

The UIAA test #101 and EN 892 standard only call for a dynamic rope to be tested with an 80kg mass. That decision was based on a perception of the Earth's average mass (I believe that they were taking females into consideration when choosing this arbitrary number).

So 80kg it was and 80 kg it remains to this day.

So where does that leave climbers like me who have a mass exceeding 80kg?

I definitely want to climb - I am a confessed 'rock-a-holic' and have been for the past 24 years (and I'm not planning to stop any time soon).

Do rope manufacturers want to shut down climbers who have a mass exceeding 80kg? I dont think so - I mean, it would have an impact on rope sales and possibly be discriminatory. Besides, how would you legislate to stop 'big boys' like me from climbing? I can see it now, an arrest without warrant policy at all cliffs controlled by the State.

But realistically, SS or Dan or anyone else, are there any rope manufacturers out there who are tackling this issue head on and publishing guidelines based on data? Do rope manufacturers carry out testing with drop masses beyond 80kg and count how many falls their ropes can sustain before snapping like a carrot? Does a 10 fall rated rope (single category) actually fail after 8 drops with a 100kg mass?

My opinion is that I dont think anyone is doing such testing... but I could be wrong.

Also, getting back to the original topic of this thread, where exactly does a dynamic rope break when it reaches its fall rating during EN 892 drop testing? Does the rope break/fracture at the 10mm deflection ring or does it break at clamped anchor points? I suspect it breaks at the deflection ring.

Some compression would occur as the rope deflected around the ring - and there would be friction too.


agent smith










paulj

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Re: A compressive source of tension?
« Reply #26 on: October 16, 2007, 12:03:27 AM »
How about doing some tests in lighter weight cord in the safety and comfort of your own home?  With some testing you may find a weight that can be dropped the requisite 5 times.  Then try some larger weights and see how the drop count changes.

paulj

Stoatstail

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Re: Continuing saga of knot strength and theory
« Reply #27 on: October 16, 2007, 10:33:03 AM »

Other user groups such as fisherman, decorative knot tyers, do not put their lives 'on the line' in quite the same context. This might spark a debate but I'm going to go out on a limb here and say that exposure to falls from height ranks higher in terms of apparent and immediate need of accurate and reliable knot data.

As someone with both a professional interest in working at height and as a lifelong fisherman I would say that Dereks theories are equally interesting to both parties and that that real interest within both communities would, with the greatest respect to Derek, be fairly low.

Both climbers, rope access personnel and fishermen are interested in when, ie. at what load, a knot causes a rope or line to fail, not why or where in the knot it fails. I cant imagine that as you plummet from the crag you are wondering whether the line will fail at or in the first bend in the knot, just whether its going to fail at all !.

If someone gave me good protocols and/or a sensible methodology for testing break strength of knots in monofilament I would go off and do it....., in a sort of frivolous, non-risky manner  :)
If someone gave you the same for kernmantle ropes, given your obvious passion for your sport, presumably you would do the same. Statistically useful data on the strength of common knots in commonly used materials is what we are after.

May be we should start another thread.....may be there already is one, if there isn't there should be.

Back to compression ? ?

DerekSmith

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Re: Continuing saga of knot strength and theory
« Reply #28 on: October 16, 2007, 06:52:07 PM »

Other user groups such as fisherman, decorative knot tyers, do not put their lives 'on the line' in quite the same context. This might spark a debate but I'm going to go out on a limb here and say that exposure to falls from height ranks higher in terms of apparent and immediate need of accurate and reliable knot data.

As someone with both a professional interest in working at height and as a lifelong fisherman I would say that Dereks theories are equally interesting to both parties and that that real interest within both communities would, with the greatest respect to Derek, be fairly low.

Both climbers, rope access personnel and fishermen are interested in when, ie. at what load, a knot causes a rope or line to fail, not why or where in the knot it fails. I cant imagine that as you plummet from the crag you are wondering whether the line will fail at or in the first bend in the knot, just whether its going to fail at all !.

If someone gave me good protocols and/or a sensible methodology for testing break strength of knots in monofilament I would go off and do it....., in a sort of frivolous, non-risky manner  :)
If someone gave you the same for kernmantle ropes, given your obvious passion for your sport, presumably you would do the same. Statistically useful data on the strength of common knots in commonly used materials is what we are after.

May be we should start another thread.....may be there already is one, if there isn't there should be.

Back to compression ? ?



LOL   thank you so much Stoatstail for bringing the thread back to the subject posted.  While I have been studying the nature of the fluff in my navel the world has been hurling itself (and one another) off a test rock face to see how big you have to be to get all the way to the bottom.  I agree, the topic is hot enough to warrant a thread of its own without being interspersed with boring little bits on how to squeeze threads to death.  I also agree, that attempting to understand the mechanics of the minutiae will be of no interest to most 'users', no matter what the level of life dependency is involved.  Most people will only be happy with the final answers -- 'A' is 'best', 'Z' is 'worst' and they won't care a fig as to why.

I used to drive my mother crazy with that word -- Why? --  Today my nickname is 'Dot-counter' because while others are away looking at the bigger picture, I can be found picking away, trying to understand the fundamental details -- 'counting the dots'.  I believe emphatically that not only the Devil, but also the Answer can generally be found in the detail.

So although this has been a really interesting excursion, it hasn't shed any light on the question posed (but then - perhaps no one but an anorak is really bothered).

So, at the risk of killing this thread stone dead, I echo your sentiment -- anyone for compression ??