Equalizing the Belay

[scrambled_legs]

Just looking through belay anchors and have a question. A lot of instructions show a really bomber anchor all properly equalized and attatched directly to the harness. This makes sense to me but then I've seen a lot of people on rock or ice or whatever redirect the pull of the belay by clipping a draw through only one of the anchor points and rerouting the rope through the draw. Doesn't this ruin all the equalization made when setting up the belay. If the follower bails, all the weight is placed directly on the piece that the draw is clipped to. None of the other equalized pieces take the weight. You have to either take the fall on the harness or the tie in point of the equalized pieces in order to have an equalized belay no? I've seen some people place one screw or cam, seperate from the anchor and redirect the rope through that placement. This way if the follower bails the single piece may fail but won't compromise the equalized anchor. Any of this making sense to anyone else or any comments?

[DPS]

The safest way is to redirect through the power point. Use a screamer to be really safe.

[kurthicks]

redirecting the rope doubles the force on the anchor/piece.

the best way would be to belay direct with a munter or reverso from the master point... especially if your anchor is at all sketchy. the only reason to redirect in my opinion is just because you don't know any other options.

[Jason_Martin]

It is okay to redirect...and until recently most climbers were redirecting most of the time.

 

Dan indicated that you might redirect off of the powerpoint. This would be acceptable. However, the problem is that if you are tied into the powerpoint at a hanging belay, the distance between your hands and the powerpoint is going to be quite small. It will be very difficult to belay off of a redirected ATC if there is no room to do so.

 

Often redirecting takes place off of an area that is just as (SRENE, ERNEST, RENE -- pick your accronym) as the powerpoint. The area I'm referring to is the shelf. The shelf is the point found directly above the knot in your equalized cordellette wherein you may clip through all of the strands with a carabiner. As this is slightly further away from you, redirecting becomes easier.

 

There are three problems with redirecting. The first is that in the event of a fall it doubles the weight on the anchor. This shouldn't be a big deal. The second is that redirection often puts a lot of twists in the rope over a series of pitches. And the third is that it is difficult to make a quick and an effective belay escape when using this system.

 

The advantage is that when swapping leads, it may eliminate a small portion of time during the changeover at a belay station. This is especially true with multi-pitch sport climbs or climbs where there is not a lot of gear to transfer.

 

It may ultimately be "better" to use a autolocking device like a reverso or a GiGi or even a GriGri clipped to your shelf or your powerpoint to bring up your second. However, there is nothing wrong with using a redirect if that is what works in a given situation...

 

The notion that belaying directly off the anchor is the only way to do something is simply incorrect. There are many ways to belay. Some ways work better in some situations. Indeed, there are actually situations wherein it is not feasable to use an autolocking device on the anchor to belay up a second. There are situations where the only way to effectively belay a second is via a redirect. One example of this might be a belay station which is BELOW a traverse pitch. Autolocking devices on the anchor get pulled in weird and potentially dangerous directions in this particular example. (Obviously here, one would have to build a solid and equalized belay of some sort at the end of the traverse which would redirect the belay from the true station.)

 

It is true that redirecting doubles the weight on the anchor. But if your anchor can't handle this, then your anchor is no good. You'd hope that both you and your partner's weight would be okay hanging off of an anchor. If this is not the case, then there are other options, most of which revolve around body belays, not putting weight on a system that can't hold the weight of two people.

 

Jason

[downfall]

I've redirected by putting an additional piece above the anchor solely for the purpose or redirecting. It seems that this solves some of the problems with attaching to just one point or to the power point of the anchor and you still have the efficiency when swapping leads since the first piece of the next pitch is already in. Does anyone know any problems with this approach?

[Alpinfox]

Good post Jason.

 

The biggest advantage to redirecting the belay off of a higher piece is that if the second falls, the belayer gets pulled (slightly) in an upward direction rather than getting pulled (with more force) in a downward direction, potentially pulling the belayer off of his/her stance. I find it unnerving to get pulled downward when I'm belaying a second, so that is the main reason I redirect the belay. When I do a redirection, it is usually from a seperate piece that is not in the anchor system or I extend myself below the anchor and do a slingshot belay through the anchor.

 

 

Belay directly from the anchor using reverso-

Advantages: autolocking, belayer out of the system, no tug on belayer

Disadvantages: Can't belay the leader, so if swapping leads, need to move reverso to harness. Can be awkward if belayer is not somewhat below the reverso.

 

Redirect the belay-

Adv: tug on belayer is negligable and in upward direction. Ready for second to lead out.

Disadv: High force on piece used for redirect. Belayer is in the system. If redirect piece isn't high enough, can make belaying kind of cramped and awkward.

 

Belay directly from harness -

As the belayer, you should make sure there is little or no slack between you and the anchor in this setup. I got yanked over a tree branch and scraped myself up pretty badly once when my second fell and I had some slack.

Adv: Simple, familiar setup.

Disadv: Belayer can be pulled off stance. Belayer is in the system.

[Rad]

I find that redirecting also makes belaying much more strenuous and slower.

 

I will redirect if I don't want to be pulled downward/off a stance or if my partner (plus pack) is large and/or expects to hang a lot.

 

In most cases, I find straight off the harness is faster and easier. As was mentioned above, when doing this it's important to any remove slack between you and the anchor. Otherwise nasty scrapes and worse may ensue. ouch.

[scrambled_legs]

Ok so I guess the books that I saw this in and the climbers doing it must be old school.

 

Redirecting doesn't double the force on the anchor! Simple physics shows that by redirecting the pull to an upward pull rather than downward is simply just that a 1:1 pully with no added forces. The point that I was making was that you often see people redirecting by clipping a draw to only one of the anchor pieces. This puts 100% of the fall on one piece and completely negates the whole equalized anchor.

 

The only added forces caused by redirecting is that wherever the rope is being redirected is where all the weight will be. If you belay directly from your harness, your stance will take some of the weight of the fall along with the anchor, unless its a hanging belay.

 

Thanks for clearing that up. I was starting to wonder if this was standard practice as I've noticed it more and more now that I've been looking for it.

[Alpinfox]

 

Redirecting doesn't double the force on the anchor!

 

I believe you are incorrect. In order to stop the falling lead climber, an equal force must act on the other side of the anchor (for simplicities sake, a pulley). The SUM of these two forces are felt by the anchor.

 

 

It's been a while since I took physics, but I think that's right.

 

I invite anyone who knows physics better than I to chime in as I'm pretty curious now.

 

A stupid diagram I made. Click on the "attachment" link to get a better view of it.

[Jason_Martin]

Redirecting doesn't double the force on the anchor! Simple physics shows that by redirecting the pull to an upward pull rather than downward is simply just that a 1:1 pully with no added forces.

 

If you're rope is running through the anchor and your belay device is on one end of the rope and the climber is on the other, if the climber falls the weight will be:

 

Your weight + the climber's weight

 

All on the anchor. Which as I stated in a previous post should not be a problem if you're redirecting through the powerpoint or the shelf. Doing this off of a single piece is not a good idea, because the combined weight of the belayer and the climber are placed on a single piece as opposed to an equalized anchor.

 

In additon to this, I didn't notice the post about the screamer before. A screamer really isn't going to do anything in this situation because a Second's fall shouldn't be very dynamic. Regardless of the screamer, the weight on the anchor as the end result will be the same.

 

Jason

Edited January 11, 2005 by Jason_Martin

[scrambled_legs]

It should be the same force required to stop the fall whether it's redirected or not. Equal opposite forces.

 

The only time the forces change when using pullys is if one rope travels further than the other. For example if the followers rope is static and a movement of 1 foot of the rope on his end produces a 1 foot pull towards the redirect point, then there is no added forces. If you have it rigged like in a setup for easing crevasse rescue, than the forces will change.

 

In a hanging belay the anchor is taking 100% of your weight plus any force exerted during a fall. If you're belaying directly from your harness or with an autoblock device, it is a static belay and 100% of the force will be absorbed by the anchor. If you redirect it, the belay will be slightly dynamic as the anchor isn't stopping you from moving upwards and some rope may slip through the redirect device as you travel upwards.

 

In a standing belay stance, Your legs will absorb some of the fall if it is a downwards pull and will take some of the forces of the anchor.

[Dru]

Force in a fall is greater than body weight. That's why copperheads pop when you fall on them. So the force on the anchor is more than two times bodyweight.

[ketch]

Scrambled, You are right about the movement issue. You are not correct about the force. When you fall this applies a force to the rope. It is redirected through a pulley (the carabiner) and then the force is resisted at an equal amount (minus friction) by the belayer.

 

If you look back at your basic physics or simple machines this is in effect a 2:1 pulley system which doubles the force that the pulley can excert. In this case the force applied to the anchor. In your example there is a flaw in that just because the rope does not move does not mean that the force is not applied.

 

I think that in your original question your are correct in that using one piece out of your anchor array can cause failure in a place you don't want it.

[scrambled_legs]

Hey Ketch,

 

I don't think I'm wrong on this one. If you only use one pulley to reverse the direction of pull you have a 1:1 ratio. Try threading the rope through a biner. Pull down on one side and see how far your hand goes up on the other. It's the same distance and a 1:1 ratio. It only changes once you start to get into complex pully setups like on crevasse rescue.

[Jason_Martin]

I don't think I'm wrong on this one. If you only use one pulley to reverse the direction of pull you have a 1:1 ratio. Try threading the rope through a biner. Pull down on one side and see how far your hand goes up on the other. It's the same distance and a 1:1 ratio. It only changes once you start to get into complex pully setups like on crevasse rescue.

 

Hate to be critical, but you're wrong.

 

I'm sure this is in more recent editions of Freedom of the Hills on a different page. But if you have the 5th edition, check out page 330.

 

"The single-pulley gives rescuers a 2-to-1 mechanical advantage."

 

In other words this is a C-pulley system that you are referring to as a 1-to-1 advantage. The reason it seems difficult to pull is because of friction. The C-Pulley definately has a 2-to-1 ratio.

 

You are however right about the idea that belaying off of your harness may take some of the impact off of the anchor and place it into the belayer. The only time I belay off my harness or my body is when I don't think I can build a belay that is solid enough to go directly off of. As such, my body becomes part of the system.

 

Jason

[scrambled_legs]

Ok, I've done some drawing and don't have the tools to show you on here so I'll have to try and explain it.

 

There are three forces acting on an anchor with a pulley (draw) redirecting the pull. 1 the force of the fall, lets say 500Ibs. 2 the weight of the belayer, lets say 150Ibs. If there is no pulley than 650Ibs is immediately exerted on the anchor. If there is a pulley, andother force comes into play, friction. If there is 0 friction, the 150Ib weight (belayer) will be pulled upwards until reaching the pulley (draw). Until then only 150Ib's of force can be placed on the anchor on the followers side. Anymore force will only raise the belayer. So the total force at this point is the 150Ibs of the belayer and the 150's exerted by the person falling. Once it hits the draw, the full 500Ibs of force applies and the anchor now holds 650Ibs. On the other hand if there is enough friction exerted at the draw to not allow any rope to feed through, then the pulley (draw) essentially is acting as a knot and the full 500Ibs plus the 150Ibs is exerted on the anchor.

 

The only way the draw will act as a 2:1 pulley is if the belayer is anchored himself. If the belayer has a way of exerting more force than his body weight, downwards on the belay, then this force will also be applied to the anchor. If there is 0 friction and the belayer is firmly anchored to the rock and not able to move than a potential 500Ibs of downwards force could be exerted on both sides of the pully system making a total of 1000Ibs exerted on the anchor. Because the 150Ib's of the belay is already applied as a downward force it can not be added to the overall weight. If 650Ib's is exerted on the belay side, the follower would be lifted. On the other hand if there is enough friction at the draw to not allow the tie down anchor to become tight, then only 650Ib's is exerted on the anchor. Am I making any sense yet? From what I've experienced there has always been sufficient friction to stop the fall in a maximum of a two foot upward pull. This movement makes the belay dynamic and although 500Ib's may be required to stop the fall immediately, less weight may also stop the fall over time. If you move while catching a fall you are actually exerting less than the required force to stop it on the anchor. For example if you move up 3 feet before stopping a 500Ib fall, You've probably only used 300 Ib's to stop it. This force is created through the body weight of the belayer and the friction at the redirect point. If there is a knot at the redirect point then 500Ib's will automatically be directed to it. A fall that requires 500Ib's to stop immediately may only require 300Ibs with 3 feet of rope passing through the redirect point. If this happens than the total force is only 300Ibs plus 150Ibs for the weight of the belayer. Just think of putting the brakes on the car. The force to stop the tires immediately is a lot larger than over a distance.

Edited January 13, 2005 by scrambled_legs

[Alpinfox]

Check it yo:

web page <----- CLICK HERE!

^^^^^^^CLICK THERE!

 

 

"The load on a pulley is equal to the sum of the loads on the ropes on either side of it."

[crazyjizzy]

You understand the dynamics, and the stressors correctly. Remember, Jason Martin is a god damn playwrite, not a vocation known for strength in math and physics. He is correct about the c-pulley and a 2:1 ratio. But as a "redirect" the anchor will feel load X and X' = 2X, but there is no mechanical advantage to the belayer.

[scrambled_legs]

You're right, the total load on the pulley is equal to the sum of the two forces. The weight of the belayer and the weight of the fall. The only way the belayer can exert a higher downward force on the pulley is if he is anchored to the rock the pulley than becames a 2:1 ratio because the belayer is fixed. A two inch pull from the followers end will pull the pulley down 1 inch and exert twice the force provided there is no friction. If the friction is so high it is the same as having the pulley clove hitched as a clove hitch is exactly that a high friction knot. When the follower falls all of his force is exerted on the pulley plus the weight of the belayer. The belayer is unable to exert anymore force other than his own weight on the pulley unless he has something holding him down beyond his body weight!

[scrambled_legs]

Alpinfox if you read into the article more it simply states that those are the forces felt at each end. If a climber falls 66% of his weight is transferred through the friction pulley (carabiner) to the belayer. The sum of these two forces will equal the total load on the pulley. If the force is as large as is depicted in the diagram (445Ibs) then the belayer will be pulled upwards unless he weighs 445Ibs or is anchored to something that does. Every action has an equal and opposite reaction. In order to stop that 445Ib upward pull there needs to be 445Ib's of downward pull. If the belayer isn't anchored he will slowly reduce the force of the climber's fall by resisting his pull with his weight combined with the friction of the Carabiner.

 

If the Carabiner provides 66% friction than we can have an opposite formula showing that a 150Ib climber can provide 200+Ibs of resistance to the falling climber. If the faller weighs less than 200Ibs an infinite amount of resisting distance will eventually slow and stop his fall. The distance between the belayer and the pulley limits how quickly the fall has to be stopped. A 198Ib climber will pull a 150Ib belayer up to the pulley system with a relativley small fall. At that point the pulley no longer acts as a pulley but rather a knot attatching all the weight to the anchor but no more. There is no way to apply more than the belayers weight on his side of the rope unless he is anchored to something else.

[goatboy]

On the "c pulley" -- I believe it makes a difference WHERE the pulley is located in the system.

 

The traditional C Pulley is located on the climber being extricated or hauled up, BELOW the anchor, with the rope FIXED on one end, going down to the Pulley, and then being hauled from above. This does in fact yield a C Pulley 2:1 force.

 

I believe it is different when the pulley is located at the anchor above.

 

Does this ring any bells?

[ketch]

I think you are correct but only in a perfect situation. In our world things such as inertia exist. When a climber falls the force is exerted on the biner. Part of the force is resisted as friction in the biner. The rest is redirected to the belayer. At the catch the belayer is static and will feel the impact at full force. This is more than enough to set the belayer in motion. Some of the force is resisted with the weight of the belayer, another portion is spent in accelerating the belayer upwards. Part of the disparity that I see in this discussion is in this issue. The force that it takes to move the belayer is more than the weight of the belayer. While I would agree that the total force is not a perfect doubleing of the impact, it is definatley well above the sum of the weights. By going with the double concept you end up with a positve saftey margin. If you go the sum of the weights it becomes a negative margin.

 

Sounds like a fun day to get a few load cells and a case of some good brew. We can take turns falling and catching while trying to get good measurments.

[Jason_Martin]

You understand the dynamics, and the stressors correctly. Remember, Jason Martin is a god damn playwrite, not a vocation known for strength in math and physics. He is correct about the c-pulley and a 2:1 ratio. But as a "redirect" the anchor will feel load X and X' = 2X, but there is no mechanical advantage to the belayer.

 

True, I am a playwright. But in my day job I deal with a lot of climbing related issues. As such in different posts I've dealt with both of the issues that you address in this comment.

 

I think the problem with this entire thread is that there are a number of different things being talked about here. Following is a breakdown of the issues:

 

1) Where within an anchor is it appropriate to redirect a belay?

 

2) What kind of weight is put on an anchor as a result of a redirect?

 

3) What is a 2-to-1 ratio and where might it exist within an anchor?

 

4) What kind of weight is put onto a piece or an anchor in a fall. The type of fall has not really been distinguished. Lead fall vs. a second falling.

 

The result of all this is that people are dealing with different questions throughout their posts. As such, many are being taken out of context in referance to the element that they are supposed to be addressing. I propose that the issues that are not directly related to redirecting off of a single piece vs. redirecting off the anchor be moved to a new thread.

 

Jason

[Dru]

...maybe in newbies forum

this is the ice forum.

[Harkin_Banks]

when you can't tie a knot, tie a lot!

 

 

This is perhaps the worst drawing in the history of the human race. Marmosets on meth could produce a better diagram than this.