Forums: Climbing Information: The Lab:
Force test on a Purcell Prusik
RSS FeedRSS Feeds for The Lab

Premier Sponsor:

 
First page Previous page 1 2 Next page Last page  View All


camtraks


Dec 6, 2010, 7:02 PM
Post #1 of 47 (8592 views)
Shortcut

Registered: Dec 6, 2010
Posts: 3

Force test on a Purcell Prusik
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

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?


ptlong2


Dec 6, 2010, 7:43 PM
Post #2 of 47 (8559 views)
Shortcut

Registered: Aug 10, 2010
Posts: 102

Re: [camtraks] Force test on a Purcell Prusik [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

Obviously it will depend on the diameter of the cord, the type of prusik (number of wraps), and the nature of the loading.

Some good information here:

http://www.caves.org/...DaisyChains-2005.pdf

and here:

http://www.caves.org/...yardsPartII-2006.pdf




(This post was edited by ptlong2 on Dec 7, 2010, 2:46 PM)


catbird_seat


Dec 6, 2010, 9:22 PM
Post #3 of 47 (8507 views)
Shortcut

Registered: Apr 7, 2004
Posts: 425

Re: [camtraks] Force test on a Purcell Prusik [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

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


summerprophet


Dec 7, 2010, 8:37 AM
Post #9 of 47 (8348 views)
Shortcut

Registered: Jan 16, 2004
Posts: 764

Re: [camtraks] Force test on a Purcell Prusik [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

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.


healyje


Dec 7, 2010, 3:36 PM
Post #14 of 47 (8190 views)
Shortcut

Registered: Aug 22, 2004
Posts: 4199

Re: [camtraks] Force test on a Purcell Prusik [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (1 rating)  
Can't Post

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.


camtraks


Dec 7, 2010, 4:37 PM
Post #15 of 47 (8166 views)
Shortcut

Registered: Dec 6, 2010
Posts: 3

Re: [bill413] Force test on a Purcell Prusik [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

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.
In reply to:


Partner philbox
Moderator

Dec 7, 2010, 7:12 PM
Post #18 of 47 (8088 views)
Shortcut

Registered: Jun 26, 2002
Posts: 13104

Re: [camtraks] Force test on a Purcell Prusik [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

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.


bill413


Dec 8, 2010, 6:34 AM
Post #19 of 47 (8026 views)
Shortcut

Registered: Oct 19, 2004
Posts: 5674

Re: [camtraks] Force test on a Purcell Prusik [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

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.
In reply to:

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, 6:38 AM)


camtraks


Dec 8, 2010, 7:17 AM
Post #20 of 47 (8007 views)
Shortcut

Registered: Dec 6, 2010
Posts: 3

Re: [bill413] Force test on a Purcell Prusik [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

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?


Partner philbox
Moderator

Dec 14, 2010, 12:59 AM
Post #21 of 47 (7835 views)
Shortcut

Registered: Jun 26, 2002
Posts: 13104

Re: [camtraks] Force test on a Purcell Prusik [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

camtraks wrote:
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?

I really don't mind if a subject is warmed over and discussed again. Feel free to keep this thread going. It'd be different if it was a shoe thread though. Laugh

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.


binrat


Dec 28, 2010, 5:33 PM
Post #22 of 47 (7606 views)
Shortcut

Registered: Jul 27, 2006
Posts: 1155

Re: [philbox] Force test on a Purcell Prusik [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

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.


billl7


Dec 28, 2010, 5:41 PM
Post #23 of 47 (7599 views)
Shortcut

Registered: Oct 13, 2005
Posts: 1888

Re: [binrat] Force test on a Purcell Prusik [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

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?


Partner philbox
Moderator

Dec 28, 2010, 7:26 PM
Post #24 of 47 (7571 views)
Shortcut

Registered: Jun 26, 2002
Posts: 13104

Re: [billl7] Force test on a Purcell Prusik [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

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.


moose_droppings


Dec 28, 2010, 7:57 PM
Post #25 of 47 (7560 views)
Shortcut

Registered: Jun 7, 2005
Posts: 3356

Re: [billl7] Force test on a Purcell Prusik [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

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 28, 2010, 8:07 PM)

First page Previous page 1 2 Next page Last page  View All

Forums : Climbing Information : The Lab

 


Search for (options)

Log In:

Username:
Password: Remember me:

Go Register
Go Lost Password?
$8.28 (10% off)
$17.95 (10% off)
$134.99 (10% off)
$7.16 (10% off)



Follow us on Twiter Become a Fan on Facebook