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camtraks
Dec 7, 2010, 3:02 AM
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I am considering the use of a Purcell Prusik as an adjustable personal anchoring device in certain applications. I was wondering if anyone has done a force test on this to see where the Prusik starts to slip? If so, did you find a point where the slip rate caused the rope to start melting?
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catbird_seat
Dec 7, 2010, 5:22 AM
Post #3 of 47
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The Purcell has the lowest force:
For example, Fall Factor 1
Yates Spectra Daisy + Shorty Screamer
11.1 kN
Climb High 25mm Nylon Daisy
12.8 kN
Purcell Prusik (7mm nylon cord and 3 wraps)
9.1 lM
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summerprophet
Dec 7, 2010, 4:37 PM
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The purcells outperform most anything else out there. The 'slippage' acts as a load limiter and I believe small slippage begins to be observed around 7 to 9 kN. (don't quote me on that, my material is elsewhere)
As well, rope melting, while technically correct, implies a far greater impact than what really happens, realistically it is a surface glazing of the cord, rather than flames and sputtering plastic.
I use purcells for rescues, but despite their usefullness, never made it into my freeclimbing setup. To bulky compared to just clove hitching the lead line.
If you Google, Kirk Mauthner +Purcell test, you should come up with the original testing.
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healyje
Dec 7, 2010, 11:36 PM
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The topic has been flogged to death several times at this point. Bottom line? You don't want to take a short fall onto an anchor on any material. NEVER put yourself in a position to take such a fall. Any time such fall potential exists you should be on a rope.
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camtraks
Dec 8, 2010, 12:37 AM
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bill413, while many in this thread have devolved into a discussion about Nazi's which has nothing to do with the question I posed, I have been doing some reading on the original subject. I have to say that you have misinterpreted the data you are looking at. The low forces you have sited are a positive. It reflects the fact that the Purcell has excellent energy absorbtion. In the studies I have read, high forces seen by various lanyards is a sign of weakness in the device. As a static measurement it may be impressive, but it shows weakness in the the dynamic world of climbing. I would be fine to see this thread come to an end if contributors aren't interested in staying on subject. |
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philbox
Moderator
Dec 8, 2010, 3:12 AM
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I've hidden a whole bunch of posts in this thread. Some were flaming the OP with no reason, some were completely off topic. Play nice guys, this is the Lab forum after all. Who cares if this subject has been thrashed around before. Always good to explore whether any new understandings of a subject are out there.
So if you post does not show up, it was me. A couple of those posts did have some parts that could have been spared so if you want to repost then do so with the parts that are on topic.
Thank you all and I hope you understand my actions.
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bill413
Dec 8, 2010, 2:34 PM
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camtraks wrote: bill413, while many in this thread have devolved into a discussion about Nazi's which has nothing to do with the question I posed, I have been doing some reading on the original subject. I have to say that you have misinterpreted the data you are looking at. The low forces you have sited are a positive. It reflects the fact that the Purcell has excellent energy absorbtion. In the studies I have read, high forces seen by various lanyards is a sign of weakness in the device. As a static measurement it may be impressive, but it shows weakness in the the dynamic world of climbing. I would be fine to see this thread come to an end if contributors aren't interested in staying on subject.
I have not misinterpreted any data. Lower forces on a climber is generally a good thing.
I have posted to this thread about Godwin's law and about Sets. I have not posted about forces.
You clearly have me confused with someone else. Hopefully not Majid.
(This post was edited by bill413 on Dec 8, 2010, 2:38 PM)
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camtraks
Dec 8, 2010, 3:17 PM
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Sorry, plugged into the wrong place in the thread I guess.Point is someone interpreted the low force data as a negative when it is not....obviously you get it.I think PHILBOX must have removed the reply that I was trying to target. Just out of curiousity, if this subject has been beaten to death, would anyone like to point me to other (informative) forums on this site which discuss the subject...how about it philbox?
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binrat
Dec 29, 2010, 1:33 AM
Post #22 of 47
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philbox wrote: I love Purcell Prussiks. Does anyone else use the three on two method of tying. Very easy to adjust but still retains the ability to hold the load that is imposed. Once loaded and then released it is also easy to adjust.
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billl7
Dec 29, 2010, 1:41 AM
Post #23 of 47
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binrat wrote: philbox wrote: I love Purcell Prussiks. Does anyone else use the three on two method of tying. Very easy to adjust but still retains the ability to hold the load that is imposed. Once loaded and then released it is also easy to adjust. Thats the only proper way to tie it. I use the Purcell for many things including cleaning anchors on a route.
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philbox
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Dec 29, 2010, 3:26 AM
Post #24 of 47
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billl7 wrote: binrat wrote: philbox wrote: I love Purcell Prussiks. Does anyone else use the three on two method of tying. Very easy to adjust but still retains the ability to hold the load that is imposed. Once loaded and then released it is also easy to adjust. Thats the only proper way to tie it. I use the Purcell for many things including cleaning anchors on a route. What is the "three on two" method? Do you mean the three-wrap prusik around two cords?
No. The three on two method is that instead of tying a normal three wrap prussik you have one side of the prussik wrapped three times and the other side of the Prussik wrapped twice. The load side of the Prussik which is towards the load is wrapped three times to hold the load and the side away from the load is wrapped twice. This ensures very easy adjustability and ensures that the Prussik will definitely hold the load.
It's a bit of a trick to tie though. You have to tie the wraps first and then send the cord that you are wrapping around through the wraps. I generally wrap the wraps around two of my fingers. Three around one finger and two around the other finger.
You can't tie this method on a rope with a standard Prussik loop unless you do it at the end of the rope and pass the rope through the wraps.
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moose_droppings
Dec 29, 2010, 3:57 AM
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If you enlarge the pic you can see the three and two raps on the purple PP.
Edited to add Majid arrows.
(This post was edited by moose_droppings on Dec 29, 2010, 4:07 AM)
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