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Vertical Rigging....Can you see what I see?

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  • jdcalamia
    replied
    First let me apologize about the "rethinking your priorities" comment. You are absolutely correct in your line of thinking regarding an "unloaded belay" line. As far as buying into dogma passed on by others, sometimes that's all we have to go on. Maybe I bought into it, maybe I haven't, I try to keep an open mind. Especially here, so much great info that it's hard to read without getting a headache sometimes. I mean this is a good way, so please don't take it otherwise. My thoughts have been more along the lines of a tensioned belay (part of not seeing the whole picture here as previously mentioned) which like DC said would eliminate alot of the issues here, not without creating others. Just like anything else, everything is weighted upon the situation. I can't help but revert back to an earlier post about post-belay activation and having to haul on the belay with a piggy-backed MA system. I have always been taught, (right, wrong, or indifferent) to keep your options open (being able to use either line for either purpose) b/c you never know what may have to happen next. When can't possibly plan for every "what if". I'm a big believer in mirrored or two line systems if you will. It may be overkill, however I think it provides for more options and less potential for failure. Unless I am way off base here, utilizing carabiners vs pulleys in this situation limits the amount of hauling that can be done efficiently and increases the friciton if the belay line needs to be hauled on. Maybe it's me being stubborn, but I can't get past the idea of swapping biners for pulleys. Not saying your ideas are bad, or without credence or merit, just saying I'm still having a hard time wrapping my mind around it. Is there any literature out there on this practice, that might make a believer out of me?

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  • EricUlner
    replied
    Originally posted by DCFDRescue2 View Post
    I think biners in an unloaded belay line is a good thing. But if minimizing fall distance and impact force is the priority, and I agree that it is, why not use a tensioned belay system where the main and belay lines each share roughly half of the load? This eliminates the stretch in the belay line and significantly reduces fall length.
    Now you're bringing up an entirely different animal worthy of its own thread... or more. But life may get in my way of joining in that discussion for now. For now though, I'll say that some tension in the belay line when the load is within about 10 feet from the ground or a ledge can be a good thing. Otherwise, many other issues on the top side. And using Sterling's HTP rope instead of nylon takes care of quite a bit of the issue.

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  • DCFDRescue2
    replied
    Originally posted by EricUlner View Post
    Rethink priorities? The priority is to catch the load with the belay as soon as possible keeping the load from hitting something. I gave reasons for skipping the pulley in a previous post, with fair accuracy. You obviously ignored it and instead chose your priority- adhering to dogma given to you by someone else passing along dogma without understanding why the dogma. At least that what it seems. We're talking about a belay rope here. The rope that is supposed to only be "used" when it catches the falling mass. A belay rope is otherwise not receiving wear to speak of. If and when it does catch the falling mass, friction sufficient to stop the falling mass has to be applied to the rope. A belay rope will receive wear no matter what when catching the mass. If you want to maximize all of the friction having to be applied at just the belay device, I guess you can feel free to toe the dogmatic line and suit yourself. I'll choose to reduce the fall distance and impact forces instead.
    I think biners in an unloaded belay line is a good thing. But if minimizing fall distance and impact force is the priority, and I agree that it is, why not use a tensioned belay system where the main and belay lines each share roughly half of the load? This eliminates the stretch in the belay line and significantly reduces fall length.

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  • stickboy42
    replied
    yes, an obsessed one at that...

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  • EricUlner
    replied
    Originally posted by stickboy42 View Post
    I'll way in here. i agree with what eric is saying as it comes from a foundation in physics which is really the main thing that should govern what we do when it comes to force analysis on a system. his description on the forces involved as they pertain to friction in the a carabiner vs pulley are spot on and can be a huge factor in eliminating the force on a rescuer/patient in a dynamic event. it is prudent to point out that there hasn't been a proposal put on the table to switch biners for pulleys across the board but in the belay system only. we want efficiency in the haul and lower but in the belay additional friction absorbed at various points is a good thing.

    we test our belay systems commonly to the bcctr standard in a worse case scenario with no additional friction from edges/carabiners. this shows us the force put on the belay device (540, tpb, id, etc) alone and from there we can see if the device is capable of catching the load, not failing, and not imparting a damaging force on the rescuer. this is a worse case scenario where the rope, rescuer and belay device are the sole energy absorbers. additional carabiners, edges, etc only serve to add friction and potentially reduce energy throughout the system. we do however need to be cognizant of where this energy is going to be absorbed and whether that point isn't going to damage any part of our belay system (obviously we wouldn't want to absorb energy over a sharp edge but a padded one or use a carabiner that wasn't rated high enough to take a potential belay failure load).

    something we don't talk about much either is fall distance. i think many teams train in facilities where potential falls are down a clean vertical face. in reality we may run into this but many times were are faced with a more natural setting of a nearby cliff. fall distance is key in the case of a belay activation and limiting the distance of this fall and striking something with there body (and then the litter landing in their lap). absorb this energy elsewhere, limit rope stretch and reduce fall distance = a belay system i'll take any day over some very efficient transfer off all the load onto me and the 2 prusiks that are going to fuse to the rope.

    that's my ramble for the night...

    mike
    Past RTR student Mike?

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  • ProgressiveRescue
    replied
    Mike,
    That was a great rant... You've sold me enough on re-direct beaner to go do some training with this. The more I sit here and think about it the more I'm liking it. I have.... been up since 4:30am with my 1 year old daughter so my thinking for the morning is over.
    Again.... Great rant,
    Mike

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  • stickboy42
    replied
    I'll way in here. i agree with what eric is saying as it comes from a foundation in physics which is really the main thing that should govern what we do when it comes to force analysis on a system. his description on the forces involved as they pertain to friction in the a carabiner vs pulley are spot on and can be a huge factor in eliminating the force on a rescuer/patient in a dynamic event. it is prudent to point out that there hasn't been a proposal put on the table to switch biners for pulleys across the board but in the belay system only. we want efficiency in the haul and lower but in the belay additional friction absorbed at various points is a good thing.

    we test our belay systems commonly to the bcctr standard in a worse case scenario with no additional friction from edges/carabiners. this shows us the force put on the belay device (540, tpb, id, etc) alone and from there we can see if the device is capable of catching the load, not failing, and not imparting a damaging force on the rescuer. this is a worse case scenario where the rope, rescuer and belay device are the sole energy absorbers. additional carabiners, edges, etc only serve to add friction and potentially reduce energy throughout the system. we do however need to be cognizant of where this energy is going to be absorbed and whether that point isn't going to damage any part of our belay system (obviously we wouldn't want to absorb energy over a sharp edge but a padded one or use a carabiner that wasn't rated high enough to take a potential belay failure load).

    something we don't talk about much either is fall distance. i think many teams train in facilities where potential falls are down a clean vertical face. in reality we may run into this but many times were are faced with a more natural setting of a nearby cliff. fall distance is key in the case of a belay activation and limiting the distance of this fall and striking something with there body (and then the litter landing in their lap). absorb this energy elsewhere, limit rope stretch and reduce fall distance = a belay system i'll take any day over some very efficient transfer off all the load onto me and the 2 prusiks that are going to fuse to the rope.

    that's my ramble for the night...

    mike

    Leave a comment:


  • EricUlner
    replied
    Originally posted by jdcalamia View Post
    Correct me if I am wrong here, but isn't the accepted practice to only use pulleys with sheaves that are at least 4 times the diameter of the rope being used. This is solely to avoid critical bends and damaging the rope. I'm a realist, the only reason I could even remotely think of using a carabiner in place of a pulley would be in dire straits and completely out of options, excluding RIT applications. Also, if increased wear on the rope is a non-issue for anyone involved in tech rescue, then you may want to rethink your priorities in the tech rescue world.
    Rethink priorities? The priority is to catch the load with the belay as soon as possible keeping the load from hitting something. I gave reasons for skipping the pulley in a previous post, with fair accuracy. You obviously ignored it and instead chose your priority- adhering to dogma given to you by someone else passing along dogma without understanding why the dogma. At least that what it seems. We're talking about a belay rope here. The rope that is supposed to only be "used" when it catches the falling mass. A belay rope is otherwise not receiving wear to speak of. If and when it does catch the falling mass, friction sufficient to stop the falling mass has to be applied to the rope. A belay rope will receive wear no matter what when catching the mass. If you want to maximize all of the friction having to be applied at just the belay device, I guess you can feel free to toe the dogmatic line and suit yourself. I'll choose to reduce the fall distance and impact forces instead.

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  • rescuedylan
    replied
    Originally posted by jdcalamia View Post
    Correct me if I am wrong here, but isn't the accepted practice to only use pulleys with sheaves that are at least 4 times the diameter of the rope being used. This is solely to avoid critical bends and damaging the rope. I'm a realist, the only reason I could even remotely think of using a carabiner in place of a pulley would be in dire straits and completely out of options, excluding RIT applications. Also, if increased wear on the rope is a non-issue for anyone involved in tech rescue, then you may want to rethink your priorities in the tech rescue world.
    For our uses I cant see very many reasons for not using a pulley durring a rescue ( not saying there is no reason for not, just few). Although if you look at alpin/mountainerring, using no pulleys for a MA is common. As long as long as you have no huge shock loading while the MA is in use there shouldnt be any real damage to the rope. If there is we should come up with a better way to tie into our harness (saying you tie into a biener). Just my thoughts, no tests to back it up.

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  • jdcalamia
    replied
    Correct me if I am wrong here, but isn't the accepted practice to only use pulleys with sheaves that are at least 4 times the diameter of the rope being used. This is solely to avoid critical bends and damaging the rope. I'm a realist, the only reason I could even remotely think of using a carabiner in place of a pulley would be in dire straits and completely out of options, excluding RIT applications. Also, if increased wear on the rope is a non-issue for anyone involved in tech rescue, then you may want to rethink your priorities in the tech rescue world.

    Leave a comment:


  • ProgressiveRescue
    replied
    Originally posted by EricUlner View Post
    No offense meant here Mike, but it seems to me that your take on this is that you've only one type of "wrench in your toolbox" to fix the problem if the belay were to be engaged- that being start hauling on the belay line as is. There are far to many variables per operation to have an internet conversation of well what would you do then if... Suffice it to say that carabiner friction can be dealt with rapidly if need be.
    Reduced forces in the belay system can and will reduce fall distance. The rope slippage at the belay device is definitely not the only contributing factor to fall distance. Many other points in the system that give. Unnecessarily increasing forces at the redirect and beyond may make the difference in your rescuer's ankles or more.
    Eric,
    Your right this is a conversation that really has to many variables to have online. I definitely think some points of view have been lost along the way. All in all I'd say this topic did however create some great conversation.
    Sta Safe,
    Mike

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  • EricUlner
    replied
    Originally posted by ProgressiveRescue View Post
    Eric,
    I can't say I agree with your thoughts simply based on the fact that in a Technical Rescue operation (this one being confined space) I want the most bang for my buck regarding my MAS and any rope that has the possibility of being introduced to one (belay line) Using carabiners as directional pulleys just creates to much friction for me in a system. I'm not overly concerned about impact forces on a belay catch simply because the belay devices we use today (540, I'D, ) have such a minuet slippage of rope the adverse effects on the rescuer or victim would be minimal if any.
    I'm not saying your thought process is wrong I just choose not to use pulleys in an application where their inefficiency will effect the efficiency of my hauling operation. I do believe there's a time and place for everything and if a rigging operation calls for a carabiner redirect for some reason....of course I'd use it.
    Thanks
    Mike Donahue
    No offense meant here Mike, but it seems to me that your take on this is that you've only one type of "wrench in your toolbox" to fix the problem if the belay were to be engaged- that being start hauling on the belay line as is. There are far to many variables per operation to have an internet conversation of well what would you do then if... Suffice it to say that carabiner friction can be dealt with rapidly if need be.
    Reduced forces in the belay system can and will reduce fall distance. The rope slippage at the belay device is definitely not the only contributing factor to fall distance. Many other points in the system that give. Unnecessarily increasing forces at the redirect and beyond may make the difference in your rescuer's ankles or more.

    Leave a comment:


  • rescuedylan
    replied
    Mike, do you by any chance know what kind of confind space this was? Or maybe have more pics/information from this? It is a little difficult to critique some of this without more of the picture. Im not a big fan of the angles of the anchor, but again not sure how much space they had to work with from anchor to hole/ walkway/ drop off. Are we assuming that they are working off a walkway or are they going into a pipe? Both are confind spaces in the enviorment they appear to be at, but still hard to know.

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  • ProgressiveRescue
    replied
    Originally posted by EricUlner View Post
    The side of the belay rope going from the redirect pulley to the belay has greater strain energy in it because of the pulley's efficiency. Say at 90% efficiency for the pulley, the redirect anchor will be taking 1.9 units on tension- 1 unit on the load side and 0.9 unit on the belay side. Therefore, the anchor holding that pulley is feeling more load than with less efficient pulley. An inefficient pulley- i.e. carabiners- won't allow as much strain energy to be in the strand of rope going down to the belay. With carabiners being in the 50ish % range of efficiency, the redirect anchor will instead feel around 1.5 units of tension, and the belay around 0.4 less units of tension. All of those units of tension I mention would of course be in some form of dynamic impact, should the belay actually engage.

    As for your concern about having to gang onto the belay rope- I don't have the big picture regarding this particular set-up because you hadn't provided that. My comments were aimed at the zoomed-in image you provided only. If I could see the rest of the scene, I have a feeling that I'd probably not set up like that anyway with the 2X1 anchorage. Probably would use an offset, like a dynamic deflection coming in from somewhere else in order to make it easier for the rescuer to get into position on the system.
    Eric,
    I can't say I agree with your thoughts simply based on the fact that in a Technical Rescue operation (this one being confined space) I want the most bang for my buck regarding my MAS and any rope that has the possibility of being introduced to one (belay line) Using carabiners as directional pulleys just creates to much friction for me in a system. I'm not overly concerned about impact forces on a belay catch simply because the belay devices we use today (540, I'D, ) have such a minuet slippage of rope the adverse effects on the rescuer or victim would be minimal if any.
    I'm not saying your thought process is wrong I just choose not to use pulleys in an application where their inefficiency will effect the efficiency of my hauling operation. I do believe there's a time and place for everything and if a rigging operation calls for a carabiner redirect for some reason....of course I'd use it.
    Thanks
    Mike Donahue

    Leave a comment:


  • EricUlner
    replied
    Originally posted by ProgressiveRescue View Post
    Can you explain your answer better? If you replace the pulleys with beaners and are forced to piggyback onto the belay for emergency egress purposes you're going to pick up a lot of unwanted friction. Also...maybe I'm misunderstanding what you're saying but how is replacing the pulleys with beaners going to reduce the load?
    Thanks,
    Mike Donahue
    The side of the belay rope going from the redirect pulley to the belay has greater strain energy in it because of the pulley's efficiency. Say at 90% efficiency for the pulley, the redirect anchor will be taking 1.9 units on tension- 1 unit on the load side and 0.9 unit on the belay side. Therefore, the anchor holding that pulley is feeling more load than with less efficient pulley. An inefficient pulley- i.e. carabiners- won't allow as much strain energy to be in the strand of rope going down to the belay. With carabiners being in the 50ish % range of efficiency, the redirect anchor will instead feel around 1.5 units of tension, and the belay around 0.4 less units of tension. All of those units of tension I mention would of course be in some form of dynamic impact, should the belay actually engage.

    As for your concern about having to gang onto the belay rope- I don't have the big picture regarding this particular set-up because you hadn't provided that. My comments were aimed at the zoomed-in image you provided only. If I could see the rest of the scene, I have a feeling that I'd probably not set up like that anyway with the 2X1 anchorage. Probably would use an offset, like a dynamic deflection coming in from somewhere else in order to make it easier for the rescuer to get into position on the system.
    Last edited by EricUlner; 12-10-2010, 12:14 AM. Reason: clarity

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