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Invermere, BC
Canada
176 Posts |
Posted - 03/20/2012 : 7:32 PM
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The length of your prussik might have something to do with it as well but the pulleys in the system in the following link will mind 5-6mm cord and work with 8mm. Thats what the setup is - a rated 2 person rescue load pre-rigged 4:1
I think you can just buy the pulleys but am not sure if they make a single or if they are all double pulleys.
http://www.rockexotica.com/products/pulleys/aztek_pulleys.html |
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 Kootenay Bud
2695 Posts |
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north van, bc
Canada
940 Posts |
Posted - 03/20/2012 : 8:58 PM
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here is a visual for the ones not quite understanding. I ran into the same problem 2 months ago (also building in my living room LOL..)
left is 6mm rope on 10mm. self minds. right is 5mm on 8mm. jams in pulley. what he's asking for is if there was a smaller pulley that was only for 8 or 9mm. (not for up to 11mm) as it would be more narrow and mind the 5mm.
this was my solution durring testing. the bachmann
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north van, bc
Canada
940 Posts |
Posted - 03/20/2012 : 9:18 PM
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quote:
Originally posted by johngenx
The cord is used to unload the rope during the anchor building process. Once the anchor is built, the rope is then tied into the anchor. Don't rely on the prussik to hold the fallen climber during the rescue.
but if you're building a 3:1 using the rope the fallen climber is on. you can't tie off to the anchor once you are pulling. You can tie if off durring the system building proccess ( while building 2nd anchor point, traveling pusik etc.) but once pulling all the climbers weight is going to be either on the traveling pulleys pussik while pulling, or the racheting / mending pulley pussik while not pulling. with no back up. all I see you could do is tie off towards the unused end of the rope. but you're still going to have a huge fall if the pussiks fail. like 30-40'+ depending how big the Z is.
if you were droping a 2nd rope down for rescue. then you could raise the first rope and keep trying it off as the backup. But I'm still not seeing a decent way to back up a single rope 3:1
I've only build one a couple times for pratice. so I'm curious.
I am signed up for a cravase rescue course later this spring. |
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Squamish, British Columbia
Canada
1007 Posts |
Posted - 03/20/2012 : 9:28 PM
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quote:
Originally posted by sandy
Try pulley with smaller sheave diameter: http://www.mec.ca/AST/ShopMEC/Climbing/UppersDowners/Pulleys/PRD~5021-198/petzl-mini-prusik-minding-pulley.jsp
I guess I'm belaboring the point, but you are still cool with 5 mm cord considering the reduction in strength due to knots? or even the note on the MEC site that says "for non-climbing functions"?
Good luck with it.
There have been various suggestions you could try - Tiblocs, more wraps on a 6 mm cord, different pulley, garda knots. Surely something will work.
I'm cool with using the 5mm Static Cord for glacier travel. I was recommended this rope at MEC specifically for that purpose. MEC don't consider prusiks a "climbing function".
See the description then answer to the questions on this item:
http://www.mec.ca/AST/ShopMEC/Climbing/RopesCordage/StaticRopeCord/PRD~0403-030/mammut-6mm-static-cord.jsp
Thanks again everyone for the advice and discussion. I'll be picking up a tibloc to test it out as well as trying out some different friction hitches.
More than likely I'll continue to use an ATC guide for the minding prusik and just use a pulley on the travelling prusik (unless using a redirect, this is actually the most important pulley in the system, giving the most mechanical advantage). I've been testing out a DMM revolver and Ultralegere for that purpose. |
Edited by - leimrod on 03/20/2012 9:43 PM |
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253 Posts |
Posted - 03/20/2012 : 10:02 PM
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Use 5mm cordelette for 8mm
You can use rigging plate to block the prusik knot from getting into the pulley. Just like this one
For 3:1 advantage(w/o using pulley), I like the combination of prusik and tiblock. A lot faster to set up.
..The knot on prusik is sometimes difficult to loosen up when ascending. I prefer to use tiblock when ascending.
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Edited by - bcroadtrip on 03/20/2012 10:32 PM |
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Squamish, British Columbia
Canada
1007 Posts |
Posted - 03/20/2012 : 10:03 PM
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quote:
Originally posted by smac
but once pulling all the climbers weight is going to be either on the traveling pulleys pussik while pulling, or the racheting / mending pulley pussik while not pulling. with no back up. all I see you could do is tie off towards the unused end of the rope. but you're still going to have a huge fall if the pussiks fail. like 30-40'+ depending how big the Z is.
Thanks for the pictures Scott. Glad to see someone else has encountered the same issue with that pulley.
In regards to backing up your system, here's what I was thinking. I haven't tested this, and can imagine there might be a problem with the ratcheting prusik. If an ATC guide was used to mind the prusik couldn't it be set up in this configuration?
This would also lock off in case the rope was let go and the prusiks failed. |
Edited by - leimrod on 03/20/2012 10:05 PM |
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Surrey, BC
Canada
212 Posts |
Posted - 03/21/2012 : 4:24 PM
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quote:
Originally posted by leimrod
Thanks for the pictures Scott. Glad to see someone else has encountered the same issue with that pulley.
In regards to backing up your system, here's what I was thinking. I haven't tested this, and can imagine there might be a problem with the ratcheting prusik. If an ATC guide was used to mind the prusik couldn't it be set up in this configuration?
This would also lock off in case the rope was let go and the prusiks failed.
Take it one step further; use the ATC in guide mode and ditch the prussik altogether. I have practiced using this method several times and it seems to work great although I think it creates a little more friction. I use a DMM revolver for the redirect which seems to compensate for some of that loss. |
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Kootenay Bud
2695 Posts |
Posted - 03/21/2012 : 5:22 PM
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quote:
Originally posted by smac
but if you're building a 3:1 using the rope the fallen climber is on. you can't tie off to the anchor once you are pulling. You can tie if off durring the system building proccess ( while building 2nd anchor point, traveling pusik etc.) but once pulling all the climbers weight is going to be either on the traveling pulleys pussik while pulling, or the racheting / mending pulley pussik while not pulling. with no back up. all I see you could do is tie off towards the unused end of the rope. but you're still going to have a huge fall if the pussiks fail. like 30-40'+ depending how big the Z is.
if you were droping a 2nd rope down for rescue. then you could raise the first rope and keep trying it off as the backup. But I'm still not seeing a decent way to back up a single rope 3:1
Spelling errors aside  , you are right. |
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Squamish, British Columbia
Canada
1007 Posts |
Posted - 03/21/2012 : 7:52 PM
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quote:
Originally posted by skeletalmachine
Take it one step further; use the ATC in guide mode and ditch the prussik altogether. I have practiced using this method several times and it seems to work great although I think it creates a little more friction. I use a DMM revolver for the redirect which seems to compensate for some of that loss.
That's what I initially imagined I'd be doing but when I was running some real world drills I realized it would not be possible.
If someone falls into a crevasse and I am arresting their fall with nobody else around I will need to build an anchor and free myself from the system. The rope that the person is hanging from will be taut. To use the ATC guide in guide mode to free myself from the system would require me getting a bite of rope to put through the belay device. This would simply not be possible in this scenario.
So I will have to use a prusik on the rope to release myself. This prusik will become the ratcheting prusik for the z-pulley set up.
The ratcheting prusik has to be used, so using the ATC guide in guide mode might offer a backup. |
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Finally stopping that crazy suffering that is ice, climbing to concentrate on great ski tours!
3504 Posts |
Posted - 03/21/2012 : 9:55 PM
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| Yes, you tie the rope to the anchor, but the prussik is holding them as you raise them. But, how the hell far down in the crevasse are they? If for some reason they've taken a big fall, then yeah, I'd pop a new knot into the anchor once in a while to minimize the risk of a big fall. At the worst case, if the cord lets go, the victim re-falls onto the anchor, which is at least on the dynamic rope and not static cord. |
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canine loving, machete-toting bushwhacking lake seeker, Indiana Jones hat-wearing off-road 4x4 guru
Surrey Hole, BC
Canada
6773 Posts |
Posted - 03/21/2012 : 10:26 PM
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Lots of good, variable advice for all, should be made a sticky somewhere  |
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Surrey, BC
Canada
212 Posts |
Posted - 03/21/2012 : 11:59 PM
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quote:
Originally posted by leimrod
That's what I initially imagined I'd be doing but when I was running some real world drills I realized it would not be possible.
If someone falls into a crevasse and I am arresting their fall with nobody else around I will need to build an anchor and free myself from the system. The rope that the person is hanging from will be taut. To use the ATC guide in guide mode to free myself from the system would require me getting a bite of rope to put through the belay device. This would simply not be possible in this scenario.
So I will have to use a prusik on the rope to release myself. This prusik will become the ratcheting prusik for the z-pulley set up.
The ratcheting prusik has to be used, so using the ATC guide in guide mode might offer a backup.
Yes, you have to transfer the load from yourself on to the anchor using a prussik. In practise I have used a long prussik cord with a tied off munter at the anchor. Once the ATC is installed above the prussik I transfer onto it with the munter. After the load is transferred on to the ATC I slide the now unused prussik on the rope down and use that as the redirect prussik. This saves me the step of tying another prussik. I started doing this because I found a self minding prussik to be too finicky in practice. |
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Squamish, British Columbia
Canada
1007 Posts |
Posted - 03/22/2012 : 08:48 AM
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quote:
Originally posted by skeletalmachine
After the load is transferred on to the ATC I slide the now unused prussik on the rope down and use that as the redirect prussik. This saves me the step of tying another prussik. I started doing this because I found a self minding prussik to be too finicky in practice.
Good idea, I'm going to try it out. I've found my ATC guide seems finicky in locking in guide mode when using an 8mm rope, have you found this? |
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 | Dru
Mountain Grammar Police
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Sardonic sandbagging scoundrel, Cascade Climbers lobotomized spraymeister, space blanket flyer, new millennium vulgarian betaboy and friend to all squids
Climbing, a mountain
Canada
∞ Posts |
Posted - 03/22/2012 : 09:23 AM
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quote:
Originally posted by leimrod
I've found my ATC guide seems finicky in locking in guide mode ?
What kind of biner are you using in the locking loop? Unless it's got perfectly round cross-section, problems will arise. Most modern lightweight lockers aren't round. |
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Surrey, BC
Canada
212 Posts |
Posted - 03/22/2012 : 4:12 PM
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| I haven't had a problem with 8mm rope in the ATC-Guide. I normally use a BD Rocklock with the ATC but find it works well with a BD Vaporlock as well. I haven't tried anything else. |
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Squamish, British Columbia
Canada
1007 Posts |
Posted - 03/23/2012 : 07:52 AM
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quote:
Originally posted by Dru
What kind of biner are you using in the locking loop? Unless it's got perfectly round cross-section, problems will arise. Most modern lightweight lockers aren't round.
You're right, I'm using a biner with a T shaped cross-section, the BD Nitron I believe. It's definitely reducing surface contact friction. I've got some biners that have a round cross-section which I will start to use. |
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| Dru
Mountain Grammar Police
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Sardonic sandbagging scoundrel, Cascade Climbers lobotomized spraymeister, space blanket flyer, new millennium vulgarian betaboy and friend to all squids
Climbing, a mountain
Canada
∞ Posts |
Posted - 03/23/2012 : 09:26 AM
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| The problem with the T isn't that friction is reduced but that when friction occurs the biner rotates about its axis and can bind at inconvenient times. Round stock biner doesn't rotate. |
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Vancouver, BC
Canada
1111 Posts |
Posted - 03/25/2012 : 7:36 PM
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Leigh, when you say the 6mm won't bite enough, do you mean while hanging from the prusik off the 8mm? I have the same rope and the 6mm cord and it seems to work ok. I've only hung from it once and tried to ascend using two prusiks but it worked with no slipping that I could see. Maybe it has something to do with the dampness in squamish... . |
Edited by - thecamel on 03/25/2012 7:39 PM |
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Surrey, BC
Canada
212 Posts |
Posted - 03/27/2012 : 5:36 PM
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quote:
Originally posted by thecamel
Leigh, when you say the 6mm won't bite enough, do you mean while hanging from the prusik off the 8mm? I have the same rope and the 6mm cord and it seems to work ok. I've only hung from it once and tried to ascend using two prusiks but it worked with no slipping that I could see. Maybe it has something to do with the dampness in squamish....
I find the Mammut brand 6mm cord MEC sells isn't very compatible with 8mm rope due to the stiffness of the sheath. I have been using New England Prusik cord in 6mm. It is much softer, knots better, and grips a single strand of 8mm perfectly when used in a prusik. |
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Prusik minding pulley for 8mm rope?
