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Can prusiks be shock loaded?


Original Post
Jerel Lillywhite · · Astoria, Oregon · Joined Jun 2014 · Points: 5

Hey everyone,

Quick question for you. I am wondering if a prusik can be shock loaded. Or rather, I am wondering what would happen if a prusik was shock loaded. I have heard some possible scenarios such as the prusik could slip and melt through the rope or the prusik. Another is that it could sheath the rope. Does anyone have any knowledge and/or experience on the subject?

Thanks so much!

wivanoff · · Northeast, USA · Joined Mar 2012 · Points: 553
Jerel Lillywhite wrote:Hey everyone, Quick question for you. I am wondering if a prusik can be shock loaded. Or rather, I am wondering what would happen if a prusik was shock loaded. I have heard some possible scenarios such as the prusik could slip and melt through the rope or the prusik. Another is that it could sheath the rope. Does anyone have any knowledge and/or experience on the subject? Thanks so much!
I think too many variables to answer. How much load? How tight is the Prusik? What are relative rope diameters? How much rope is available to absorb energy? What do you mean by "shock loaded"? etc.

Why not Google "tandem Prusik belay"? The rescue industry has run some tests.
Ray Pinpillage · · West Egg · Joined Jul 2010 · Points: 180
This post violated Rule #1. It has been removed by Mountain Project.
Max Forbes · · Colorado · Joined Jan 2014 · Points: 108

They certainly aren't intended to be shock loaded, and shouldn't be used in a situation that could lead to shock load. I've seen Prusiks slip under body weight alone. If a Prusik runs over the rope long enough you also run serious risk of burning through the Prusik.

David Coley · · UK · Joined Oct 2013 · Points: 70

Hi, as the links that were posted show, the answer is reasonably well.

Remember, in a normal climbing situation, you don't shock load the prusik, even if take a fall on it, as it is on the rope, and the rope provides a dynamic element, hence no shock load.

ShaunG Gregg · · SF, CA · Joined Oct 2009 · Points: 1,511

In what scenario would a climber ever take a factor 2 fall onto a prusik knot?

20 kN · · Unknown Hometown · Joined Feb 2009 · Points: 1,346
Ray Pinpillage wrote:I wonder if anyone has ever tested the failure mode of a prusik in a drop test? If only there was a way to check internet resources for previously considered questions and answers? Hmmmmm, is there a solution to this new and fresh quandary? If only Bearbreeder wasn't out sending hard and teaching new climbers to lead 5.11, he'd surely have previously posted data coalesced and ready to post with interspersed l33t speak. What this site needs is a hero to swoop in a provide this much needed data. I am no hero but I am a good samaritan in times of need so here is the answer to your boggle: Google mutherf@cker, do you speak it? Do they speak English in Google? Go ahead, say Google again, I dare you.
Yes. Sometimes it slips, sometimes it holds. When it does slip, it's game over. It will often slide down the rope until it melts to failure, also damaging the larger rope in the process, or until the load is reduced greatly (e.g. the load decks). I find if you aggressively preweight and tighten the prusik prior to dynamic loading, then it is much more likely to hold. Loose prusiks slip easily during dynamic loading. Also, dynamic loading can greatly reduce the amount of force the prusik holds before slipping.

All in all, I would not consider a prusik to be a reliable option for stopping a dynamic fall unless the load was quite low (e.g. top rope loads).
bearbreeder · · Unknown Hometown · Joined Mar 2009 · Points: 3,065
Ray Pinpillage wrote:I wonder if anyone has ever tested the failure mode of a prusik in a drop test? If only there was a way to check internet resources for previously considered questions and answers? Hmmmmm, is there a solution to this new and fresh quandary? If only Bearbreeder wasn't out sending hard and teaching new climbers to lead 5.11, he'd surely have previously posted data coalesced and ready to post with interspersed l33t speak. What this site needs is a hero to swoop in a provide this much needed data. I am no hero but I am a good samaritan in times of need so here is the answer to your boggle: Google mutherf@cker, do you speak it? Do they speak English in Google? Go ahead, say Google again, I dare you.
well little ray if you would only stop trying to make everything into a personal attack and surfing for "cock" pics, rather than going out and climbing despite living "15 minutes away from a MAJOR climbing area" ... you would know the answer ... LOL

if you had bothered to actually to look around the manufacturers basic instructions you would have found this ...

If the top bolt breaks, the
climber will be held under the
next quickdraw by the Prusik
knot.
Technique tested on a 4 m
fall with an 80 kg weight,
using a 7 mm Prusik
cordelette and a single
9.7 mm rope.
Observations:
• fall arrested
• cordelette and rope intact


from petzl

but nope ... you just have to make snide remarks and personal attacks without providing any useful information

BTW, since you are trying to make it a personal attack heres my partner sending her first 5.11 a few days ago ...

Junkyard Patio, 5.11a, Forgotten Wall, Chekeamus Canyon, Squamish

no doubt youll try to counter with more personal attacks and "cock" pics

;)
Taylor-B. · · Valdez, AK · Joined Oct 2009 · Points: 3,055

I 'm a big fan of the tandem prusik belay for glacier travel and crevasse rescue. And I've also put it to actual use in those scenarios with favorable outcomes. Yes, the prusiks do cause sheath slippage with use and especially with the smaller diameter ropes.

Ray Pinpillage · · West Egg · Joined Jul 2010 · Points: 180
20 kN wrote: Yes. Sometimes it slips, sometimes it holds. When it does slip, it's game over. It will often slide down the rope until it melts to failure, also damaging the larger rope in the process, or until the load is reduced greatly (e.g. the load decks). I find if you aggressively preweight and tighten the prusik prior to dynamic loading, then it is much more likely to hold. Loose prusiks slip easily during dynamic loading. Also, dynamic loading can greatly reduce the amount of force the prusik holds before slipping. All in all, I would not consider a prusik to be a reliable option for stopping a dynamic fall unless the load was quite low (e.g. top rope loads).
There are a few climbing clubs in this area that set up fixed lines and then have clients use prusiks as a top rope belay. I haven't heard of anyone falling but it matches the the OP scenario. Short of keeping your hand on the hitch there is not real way for the prusik to reliably lock. I assume they think the climbing is easy enough that the chance of a fall is minimal.

Here is a video of someone using the technique. youtube.com/watch?v=Dp3bfcj…
Ray Pinpillage · · West Egg · Joined Jul 2010 · Points: 180
bearbreeder wrote: well little ray if you would only stop trying to make everything into a personal attack and surfing for "cock" pics, rather than going out and climbing despite living "15 minutes away from a MAJOR climbing area" ... you would know the answer ... LOL if you had bothered to actually to look around the manufacturers basic instructions you would have found this ... If the top bolt breaks, the climber will be held under the next quickdraw by the Prusik knot. Technique tested on a 4 m fall with an 80 kg weight, using a 7 mm Prusik cordelette and a single 9.7 mm rope. Observations: • fall arrested • cordelette and rope intact but nope ... you just have to make snide remarks and personal attacks without providing any useful information BTW, since you are trying to make it a personal attack heres my partner sending her first 5.11 a few days ago ... no doubt youll try to counter with more personal attacks and "cock" pics ;)
You're predictable.
bearbreeder · · Unknown Hometown · Joined Mar 2009 · Points: 3,065
Ray Pinpillage wrote: You're predictable.
says the guy whose first post is ALWAYS a personal attack, as evidenced by this thread !!!

LOL

as you dont climb you would never know this ....

but back to the original topic .. the purcell prusik has been tested exhaustively in short factor 1 and even 2 falls ... and was originally developed for SAR purposes here in BC

if you actually tried using one or reading up on it you might learn something ... they are basically well prusiks

Lanyards Part II: An Examination of Purcell Prusiks as Personal Restraint Lanyards

caves.org/section/vertical/…

;)
Dylan B. · · Unknown Hometown · Joined Mar 2006 · Points: 521
Ray Pinpillage wrote: If only Bearbreeder wasn't out sending hard and teaching new climbers to lead 5.11, he'd surely have previously posted data coalesced and ready to post with interspersed l33t speak.
You're seriously criticizing a guy for climbing a lot, being knowledgable about it, and sharing his knowledge?
Ray Pinpillage · · West Egg · Joined Jul 2010 · Points: 180
bearbreeder wrote: says the guy whose first post is ALWAYS a personal attack, as evidenced by this thread !!! LOL as you dont climb you would never know this .... but back to the original topic .. the purcell prusik has been tested exhaustively in short factor 1 and even 2 falls ... and was originally developed for SAR purposes here in BC if you actually tried using one or reading up on it you might learn something ... they are basically well prusiks caves.org/section/vertical/… ;)
That graph was in the link I post at the top of this page.
bearbreeder · · Unknown Hometown · Joined Mar 2009 · Points: 3,065
Ray Pinpillage wrote: This graph was in the link I post at the top of this page.
and yet you rushed into personal attacks rather than explain things ..

simply because you didnt read the links you posted but wanted to get a word in for your personal attacks !!!

if you actually looked deeper you would have found more information on at what force the various knots fail or damage the rope

VERTICAL RESCUE TRAINING WORKSHOP REPORT: EQUIPMENT TESTING

paci.com.au/downloads_publi…

;)
Ray Pinpillage · · West Egg · Joined Jul 2010 · Points: 180
bearbreeder wrote: and yet you rushed into personal attacks rather than explain things .. simply because you didnt read the links you posted but wanted to get a word in for your personal attacks !!! if you actually looked deeper you would have found more information on at what force the various knots fail or damage the rope paci.com.au/downloads_publi… ;)
That sheet was on page two of the search I provided. Welcome to 2006, don't stop now, you've almost posted google in its entirety.
NC Rock Climber · · The Oven, AKA Phoenix · Joined Dec 2009 · Points: 60

Ray is an asshole. It is a well know fact. This thread is just one in a huge list of threads where he proves it.

Carry on.

bearbreeder · · Unknown Hometown · Joined Mar 2009 · Points: 3,065
Ray Pinpillage wrote: That sheet was on page two of the search I provided. Welcome to 2006, don't stop now, you've almost posted google in its entirety.
WOW .. you finally read something

seems rather curious that you simply post up a google search and "claim" you are helping folks

but you spend a LOT of time looking for "cock" pics and post them up fully on MP ... guess we know whats more "relevant" for you !!!

if you diligently spent that time climbing and reading up on things you would have found goodies such as this ...

Random  Rope  and  System  Testing   Fishers  Fire  Department  

Random  Rope  and  System  Testing   Fishers  Fire  Department  

Random  Rope  and  System  Testing   Fishers  Fire  Department  

Random  Rope  and  System  Testing   Fishers  Fire  Department  

advancedrescue.com/resource…

anyways im off to climb have fun !!!

to the OP


if you do decide to use a prusik ... make sure you back it up with a catastrophe knot if nothing else

;)
Ray Pinpillage · · West Egg · Joined Jul 2010 · Points: 180
NC Rock Climber wrote:Ray is an asshole. It is a well know fact. This thread is just one in a huge list of threads where he proves it. Carry on.
Sometimes sure.

Forums are strange, the same information is requested over and over and over. You (proverbial) found this forum but you can't find other sites? A simple search provides all of the technical data as well as videos showing actual tests run for the OP's question. This information has been available for years and is found in about 20 seconds in the link I provided. Anyone can look at the information and learn.
I don't think there is any value in repeating the words or work of other people for users who refuse to take the time to look for themselves. It's why I make fun of Bearbreeder, not because I think he's a bad person or insincere, but because he acts as the search function perpetuating the problem.
Hillbill · · Indianapolis · Joined Jul 2012 · Points: 360
Ray Pinpillage wrote: Sometimes sure. Forums are strange, the same information is requested over and over and over. You (proverbial) found this forum but you can't find other sites? A simple search provides all of the technical data as well as videos showing actual tests run for the OP's question. This information has been available for years and is found in about 20 seconds in the link I provided. Anyone can look at the information and learn. I don't think there is any value in repeating the words or work of other people for users who refuse to take the time to look for themselves. It's why I make fun of Bearbreeder, not because I think he's a bad person or insincere, but because he acts as the search function perpetuating the problem.
Whether this topic is being requested over and over and over or not it's very informative regardless. I am sure there are plenty of sites where this same question was asked and the same answers were given...but I like MP as do many others...and I don't feel like searching through the other sites. It's not laziness it's just personal preference. I never would have came up with this question about shock-loading prusik knots in the first place...but it's an interesting topic. Thanks to the person who asked the question and thanks to the people who like sharing what they find on the subject. And thanks to MP for allowing repetitive information.....geeze
Jerel Lillywhite · · Astoria, Oregon · Joined Jun 2014 · Points: 5

Hey guys,

Thanks so much for looking into and helping to answer my question. Contrary to the beliefs of some in this forum, I did search on google for quite a while before coming to Mountain Project and asking for help. I just didn't know the best terms to search for. I had been searching for "prusik failure" and not coming up with much. Using many of the terms you guys posted I was able to find a lot more stuff. Also, with the links many of you posted I was able to answer all of my questions and think through the ideas I had been planning on using the prusiks for in the first place.

I don't use Mountain Project much, but I would recommend that if the posts are becoming too repetitive for some people that they put the computer down and get outside and climb instead. I went twice this weekend climbing everything from fun from 10.as to some harder 12s. Great times. You should try it.

Guideline #1: Don't be a jerk.

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