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Partner cracklover


Feb 21, 2006, 9:35 AM
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In reply to:
http://www.rockclimbing.com/...p.cgi?Detailed=69768

this takes the sliding x with limiter knots and allows it too be redundant and capable of multiple anchors. take a cordalette and loop it in half (or 2 big slings) (the doubling making the cordalette or sling redundant - an issue with most of our other systems)

The standard sliding-x becomes redundant the minute you put a limiter knot on each side. You don't need to double it over for this to occur.

GO


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Feb 21, 2006, 9:45 AM
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In reply to:
I have an eye infection

Damn. Hope it gets better soon.

In reply to:
4. A note: The main drawback (really the only drawback according to our testing) with the slinding x (to connect 2 pieces) is that the X sometimes binds on itself (the "clutch" effect), but this in entirely avoided by using an anodized widmouthed biner at the master point. Always use one and the slidng x is just about as good as it gets for use with two pieces--in both vertical and horizontal orientations.

I have a four foot sling I use made of tied cord. I've found that this does not bind up like sling material does.

In reply to:
5. Another note: There is little if any evidence of a strand breaking in a rigging system in any real world fall. Providing your gear is in good condition, the concern that a strand might break is a theoretical, not a real world, concern.

Let's separate the breakage issue from the issue of having a cord sliced/crushed. In most cases, I would not be comfortable with an anchor that requires 20 feet of cord which, if it is sliced anywhere along the length, would cause catastrophic failure of the entire anchor. This failure mode is not implausible.

GO


gordo


Feb 21, 2006, 10:11 AM
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Is it me...or is this the best thread ever? I've never seen 12 pages w/o flames on RC.com :D

I'm starting to think about a version with sling instead of cord, but don't have a really big sewn sling. Does spectra take a clove well?


sweetchuck


Feb 21, 2006, 10:24 AM
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I might have missed this somewhere, but I was wondering about the shock load thing, and whether the sliding x with the limiting knots is that much better than the plain old sliding x. I guess it might boil down to how much the rope recovers between the time the first piece blows and the second piece is weighted. By the way, great thread. Thanks John.


gordo


Feb 21, 2006, 10:57 AM
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Yeah, you'll have to read it all, mostly forst 3 pages. john's research has pretty well debunked the "shock load" thing. Bottom line...statistical evidence says it's no worse than extending the fall by whatever the extension is. IE adding like 1 foot to the fall.


tradklime


Feb 21, 2006, 11:08 AM
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Yeah, you'll have to read it all, mostly forst 3 pages. john's research has pretty well debunked the "shock load" thing. Bottom line...statistical evidence says it's no worse than extending the fall by whatever the extension is. IE adding like 1 foot to the fall.

With one important caveat, you are attached to the anchor with a section of dynamic rope.


sweetchuck


Feb 21, 2006, 11:14 AM
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I read the whole thread, and it seemed to debunk shockloading, but it seemed that John was careful to say that he only tested the x with limiting knots. Also, many of these rigs we are seeing incorporate limiting knots. I just wanted clarification.
Here are some quotes from John:
"when a Sliding X is configured with limiter knots, the few inches of extension will never produce a true shock load, or anything even approaching that kind of stress."
"In other words, the phobia about extension in the Sliding X (with limiter knots) producing "shock loading," or for that matter, ANY significant increase in loading, is looking almost certainly like another anchoring myth.
"
"What I'm saying here is that it was thought by some that the Sliding X (with limiter knots) was a poor choice because if one piece in the system failed the extension in the system would produce a "shock load" on the remaining piece(s)."
"we did a few tests to try and determine the degree of loading on a sliding x where one arm blows out and the other arm captures the entire load. The X had limiter knots and only extended, like, six inches."
"the main concern was to determine what happens to the dynamic load if one arm of a sliding x (with limiter knots) should blow out and the system should "extend" a few inches before the other arm holds."...

There are other instances of him not mentioning the limiting knots, but if they are unnecessary I doubt he would be including them in his test. I am just looking for some clarification. I suppose it's a matter of degree, as the limiting knots would certainly reduce the forces to some degree, but how much and is it really worth it? Just wondering.
sc


pastprime


Feb 21, 2006, 11:50 AM
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Cracklover, ref. the last anchor pictured in your post of yesterday, 2/20; (the one in front of the door): I've used that anchor set up from time to time, and felt fine about it in the right circumstances. Something to be aware of though, unless there is something above and out of the photo change things, is that when equalized, the left hand piece is taking half the load, with the other half being distributed between the other two pieces. I've used this distribution on purpose when I had one bomber placement and a couple more that didn't inspire as much confidence. You just want to make sure that if you do have a weak piece, it isn't the one that carries the largest load.


jimfix


Feb 21, 2006, 12:14 PM
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Ok, I had a quick play with the "gordolette" (nice one on the naming BTW). And yes it is a very good system, if a little fiddly to tie the cloves for the backup biners.

However when I tried to rig it for 4 pieces of pro It didn't seem so good. The extension was greater and the equalization less. Admittedly this may have been due to the shortish length of cordelette I was using. I also used only 2 backup/joining biners (between the outer arms and the adjacent inner arm). Perhaps a third biner is needed to join the inner two arm. I ran out of time to investigate this.

If anyone post pic's of an extended system for 4 pieces it would be appreciated.


vivalargo


Feb 21, 2006, 12:30 PM
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I was going to hold off on making a definitive statement on "Shock Loading" till I had time to work up what Jim at Sterling had actually found from his tests. But since it seems some folks simply can't let the thing go (nor should they till the data's in), here's basically what Jim scribbled down after doing some tests to try and create a shock load in a normal set up with a pretty stout dynamic fall (factor 1--80 kilo load dropped on 10.2 nylon rope connected to a two annchor point equalette).

Wrote Jim:

Leg failure test of Equalette.

All the same set up as previous unequal leg tests but with the short leg
connected with a 'fuse'. The 'fuse' is meant to break around 2kN. To save some time I also kept using the same cord and dynamic rope that I had just tested the Equalette unequal_arm with (see results below). Note: Using the same piece of climbing rope increases the chances of a shock load since after repeated drop testing, the rope looses it's stretch and becomes little more than a piece of static line.

The force/time curve is quite jagged at the beginning indicating lots of vibration. I can see on the curve the point at which the 'fuse' fails. Immediately after the 'fuse' blows there is a sharp drop in force followed by a normal looking curve. The peak force varied depending on the tenacity of the 'fuse'. The stronger the 'fuse' the lower the peak force on the remaining leg, the weaker the 'fuse' the higher the peak force on the remaining leg. Predictable but still interesting. No catastrophic shock load occurs a result of the extension.

6mm PC Equalette

short long

3.11 2.99
3.58 3.93
4.38 4.26
4.45 5.21
---------------------

The important thing to see is that the secondary loading is roughly the same as the initial loading--meaning there is no "load multiplication" between the initial leg failure and the mass slamming onto the remaining anchor point. Half the time it's less--the rest it's the same or a little more--at most about .75 kN, or 168 lbs. And that's only on the last drop, when the nylon rope was already stretched like crazy. And that's all on a rig with the limiter knots basically 10 inches apart--pretty far by normal standards.

My impression is that a true shock load can be understood in terms of the kind of shock we see in human beings. Shock usually means the level of stress or injury was greater than the resilience of the person's biology. In climbing systems, all the components have a degree of resilience, and these are by and large only maxed out when a section of unbelayed static line or high tensile strength cord sustains a dynamic load that is transmitted directly to the anchor. Like when a leader clips off to an anchor with a tech cord daisy, climbs up two feet and slips, falling 4 feet directly onto the anchor. You can bust biners this way, because the gear can't handle mass decelerating that quickly. Stretch and give allow the mass to decelerate slower. In a shock load you basically have the equavilant of a head on collision--something that's not going to happen when you're on a dynamic climbing rope that is running through a belay device, and when you're clipped into the anchor with the climbing rope.
Here, extension simply means that the next anchor that holds will be subjected to basically the same load--maybe a bit less--as that which blew out the first leg/piece. In other words, the initial loading is not multiplied through extension, it is simply passed on, sometimes at a lesser weight, depending on the strength of the "fuse" (failed arm).

JL


Partner cracklover


Feb 21, 2006, 12:35 PM
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In reply to:
Cracklover, ref. the last anchor pictured in your post of yesterday, 2/20; (the one in front of the door): I've used that anchor set up from time to time, and felt fine about it in the right circumstances. Something to be aware of though, unless there is something above and out of the photo change things, is that when equalized, the left hand piece is taking half the load, with the other half being distributed between the other two pieces. I've used this distribution on purpose when I had one bomber placement and a couple more that didn't inspire as much confidence. You just want to make sure that if you do have a weak piece, it isn't the one that carries the largest load.

Yes, you're absolutely right. My aim is not to get an equal load on every piece*, but a reasonably distributed load. I think that's the best you can do. And a hell of a lot better than a standard cordelette configuration.

GO

* Getting truly equal loads is impossible from a practical perspective no matter the anchor system - the different angles will create different forces.


Partner climboard


Feb 21, 2006, 12:40 PM
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In reply to:
Snip

There are other instances of him not mentioning the limiting knots, but if they are unnecessary I doubt he would be including them in his test. I am just looking for some clarification. I suppose it's a matter of degree, as the limiting knots would certainly reduce the forces to some degree, but how much and is it really worth it? Just wondering.
sc

I am wondering the same thing. How much extension is too much? What length arm does it take to generate an extra 4Kn of force for example?

Were tests done with different degrees of extension to test the difference in force?


Partner cracklover


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JL, have you had them test the hanging belay? In other words, in addition to the 80kg weight on the dropped end of the rope, hang another 80 kg weight directly (or with a short piece of "tie-in" rope) on the anchor.

I'd be curious to see what happens to the force on the remaining anchor when "fuse" breaks and the 80kg weight drops to the end of the limiter knot. This should create a true, but very small, shock load. A true test of each system is whether the shock load from this fall is within reasonable bounds (both for the climber and the remaining anchors).

GO


healyje


Feb 21, 2006, 1:27 PM
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John,

Thanks for the postings inspite of the sore eyes...

Could you clarify your use of the terms equalette, duo glide, and quad? Are they three different things or are you using a couple interchangeably?


slcliffdiver


Feb 21, 2006, 2:38 PM
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In reply to:
I was going to hold off on making a definitive statement on "Shock Loading" till I had time to work up what Jim at Sterling had actually found from his tests. But since it seems some folks simply can't let the thing go (nor should they till the data's in), here's basically what Jim scribbled down after doing some tests to try and create a shock load in a normal set up with a pretty stout dynamic fall (factor 1--80 kilo load dropped on 10.2 nylon rope connected to a two annchor point equalette).
JL

Here's my problem with this. If the belayer is doing a non redirected belay he/she is potentially being accelorated by the tension the rope to the falling climber in addition to gravity. In effect creating a potentatial higher than factor one fall factor (in terms of the belayers velocity versus amount of rope he's connected to). I don't have an good idea about how bad this can potentially be and have never seen anyone else model this through experiment or math. Basically my ignorance is making me uncomfortable. I think it's very likely the patto's and your assertion earlier that for short extentions the body flexes enough to prevent this from being a real problem is correct. However at this point from my perspective it's still an educated guess.

Personally up until this thread I've been operating under the priniple that if I'm connected to more rope (with out being connected also with some static material) as the belayer than the potential extention I was probably good to go and at a rope length around double the potential extention I'd be happy very for a hanging belay. My delima may be one of memory I think I probably worked out myself or with someone else the theoretical upper limit for an belayer accelorated by a falling climber and gravity years ago and worked this into my comfort zone. But it's been a good while and my memory is fuzzy on the subject.

The experiment I would like to see the results of is a mass approaching the weight of a climber connected to an anchor with diffrent lengths of rope and or other materials and have the falling climber mass attached to that with a rope and maybe real world belay device slippage added into the equation. I'd also be happy with a mathmatical model that explored the upper bounds for the system. I prefer volunteers fir the math because it's been a long time since I've done anything like this and I'm guesing their are people here who could crank this out in several minutes and I'm guessing it'll take me several hours at least (more than a wee bit rusty). But I'll give it a go if there are no takers for a while just don't expect anything soon.

Also I'm wondering if seat belt, paracute and ejection seat testing has any relevant data on body flex and how this relates to force transmition of a body to material. For experimental purposes they may have something more relistic to use than a hunk of iron. I have a semi defunct 100 lb water punching bag that I'd be willing to donate to any testing along these lines.

I do think it's likely that short extentions for the belayer probally aren't much of a problem even being acclorated by a falling leader if they are connected with a reasonable lenght of nylon (in anchor or to power point). But belayer acceloration and body flex are both speculative in terms of their how much effect they contribute and for what conditions at this point for me. We have a wealth of experience and intellegence in this thread so I'm hoping for something more definitive than intuition in addressing the effect of a belayer being accelorated into the anchor and it's effect on potential shock loading.


tradklime


Feb 21, 2006, 2:56 PM
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Here's my problem with this. If the belayer is doing a non redirected belay he/she is potentially being accelorated by the tension the rope to the falling climber in addition to gravity. In effect creating a potentatial higher than factor one fall factor (in terms of the belayers velocity versus amount of rope he's connected to).

I don't see how this could be worse (on the anchor) than if the belay was redirected through the anchor power point.

Regardless, rope slipping through the belay device should mitigate an related problems.

I know you wanted to see math on this but I think John's early testing indicated that many factors mitigate the potential "shock load".


vivalargo


Feb 21, 2006, 3:54 PM
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You can't tell everything from one round of tests, even the test we did with Sterling, which are upwards of 200 drops tests and counting. But my sense of the whole shock loading thing is just this:

A true shock load--meaning a force that has capacity to actually break components of the roped safely system--is not so much a matter of the size of the "load," but the system that is decelertaing (catching) said load. When there is a lot of static components in the system, like tech cord and static line, a dynamic load is deceleratd very quickly, meaning the peak loading happens very fast, in a split second. Even moderate loads, when they are caught in this way, can bust the gear apart. But when the load is slowed down over time, as happens when there is give and flex in the system, virtuall no load that can occur in a rock climbing fall can destroy the gear so long as the system is set up correctly.

In his excellent book, The Mountaineer's Handbook, Craig Connolly went into great detail about this very point, showing how even if you were belaying a leader on a static rope, slip at the belay device would greatly reduce the speed at which the load was absorbed. According to Connolly, normal tube or plate belay devices function far differently than the inflexible anchor tie off normally found in the lab tests. It can be no other way since the maximum force a modern belay device can put on the rope without slipping is 2 or 3 kN. That means the maximum force that any fall can put on the belayer is south of 600 lbf. After that, the rope starts slipping, dispursing the load over time.

Does that clear it up?

JL


healyje


Feb 21, 2006, 4:15 PM
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That does. I do, however, believe folks buying your book are looking concrete take aways from the research where possible such as:

- "don't use static cord in an anchor"
- "recommend the use Xmm dynamic cord"
- "we prefer the equalette in these situations"

I can certainly understand you would be hesitant to make any further "cordallete"-like statements this time around and also rather wait and have people buy the book to get the final recommendations from your research. But for those of us participating here it would be nice to hear a few of you conclusions and any clear preferences for anchor construction relative to the AE, equalette, quad, and duo glide designs we've been discussing.

Again, thanks for all your and your team's work on this and I agree this has been one of the best and most useful threads to pass by on RC.com for some time.


tradklime


Feb 21, 2006, 4:15 PM
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In reply to:
When there is a lot of static components in the system, like tech cord and static line, a dynamic load is deceleratd very quickly, meaning the peak loading happens very fast, in a split second. Even moderate loads, when they are caught in this way, can bust the gear apart.

John, have you, or do you plan to, repeated the same exact drop test with a section of static material in place of the length of climbing rope?

I am curious if the drop of a few inches (or 5 in this case?) would actually generate gear breaking forces. The repeated falls on the same section of rope may indicate that size of the load (ie. generated form a very short fall verses a fall of several feet) may make a considerable difference.


jeremy11


Feb 21, 2006, 4:33 PM
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cracklover wrote
In reply to:
The standard sliding-x becomes redundant the minute you put a limiter knot on each side. You don't need to double it over for this to occur
[and in the very next post...]
Let's separate the breakage issue from the issue of having a cord sliced/crushed. In most cases, I would not be comfortable with an anchor that requires 20 feet of cord which, if it is sliced anywhere along the length, would cause catastrophic failure of the entire anchor. This failure mode is not implausible.


think systems here. the ends are not redundant, there is only one loop. the sliding x part is sort of redundant - cut either strand and you have basically an american death triangle - so if EITHER piece rips you are done. the basic sliding x is not sufficiently redundant.
My doubled rig is - cut any strand on the ends and it is still good, cut any strand in the sliding x part and you still have a sliding x, and one side can pull without catastrophic failure.


that is exactly the problem my system addresses. the sliding x is not redundant (unless you use two which is more complex).

the real world solution is the best compromise for KISS and SRENE
KISS - mine is pretty simple - not as simple as the basic sliding x, but more versatile, and not as complex as the other recent good ideas.
Solid - applies to placements - the most important part of anchor building!!

Redundant - my doubled cordalette setup is, the basic sliding x is not,
most of our fancy equalizer rigs are not, except the gordolette, which is
not really simple
Equalized - all of the proposed systems are, mine equalizes at least two
pieces and can include any number of backups
Not Extending - this has been debunked, and my rig keeps extension to an
acceptable level. I would not be comfortable with the extension of my
butterfly alpine equalizer.

All anchor setups should be put through the filters of KISS and SRENE.


kachoong


Feb 21, 2006, 4:37 PM
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In reply to:
Again, thanks for all your and your team's work on this and I agree this has been one of the best and most useful threads to pass by on RC.com for some time.
Indeed! I second this comment.... great work! I've said it previously, but it's great to see open-mindedness in regards to evolution of the safety of this sport. Are we seeing the beginnings of a paradigm shift of sorts with regards to belay imagination and set up?

I know for years I continually used the rope I was tied into to set up two, three and four point equalised anchors.... then I discovered people were using a cordelette to minimise rope use and increase efficiency.... so I adapted to this knowledge and use one in a lot of situations, although a lot of the time, I still back up with the rope I was tied to.... now it seems I may be back to the old ways.... whatever rope is left, a few clove hitches and on belay....

....great thread.... now I'm patiently awaiting the outcome of these tests....


slcliffdiver


Feb 21, 2006, 4:44 PM
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In reply to:
In reply to:
Here's my problem with this. If the belayer is doing a non redirected belay he/she is potentially being accelorated by the tension the rope to the falling climber in addition to gravity. In effect creating a potentatial higher than factor one fall factor (in terms of the belayers velocity versus amount of rope he's connected to).

I don't see how this could be worse (on the anchor) than if the belay was redirected through the anchor power point.
Big mass (belayer) hiting a short length of hopefully dynamic (edit:said static) material at a relatively fast speed? Basically the question for me is it possible for the belayer to be speed up enough by the falling climber to have what amounts to a high fall factor fall. The answer is neither intuitively or mathmatically obvious to me.
In reply to:
Regardless, rope slipping through the belay device should mitigate an related problems.
Not neccisarily see above it's mostly about how fast the belayer is traveling not the climber. Rope slippage will provid an upper limit to how fast a falling climber can potentially accelorate a belayer but I still don't know what this value is.
In reply to:
I know you wanted to see math on this but I think John's early testing indicated that many factors mitigate the potential "shock load".
If you early testing in this thread. I reread carefully and I don't see this particular issue being adressed by "the testing itself". I maybe that I missread but this is my perspective.

I'm not saying that I believe extentions on the order of what John is saying are problematic. As long as your tied in with a rope I'm strongly guessing they aren't and operated from this "assuption" up until I started to think things over as a result of this thread. I'd just prefer that they be "proven" not to be in one fashion or another. I'm not even discounting the likelyhood that it has been proven already I'd just like to hear about it and the study or math if this is the case.

I'm pretty sure there's a relatively simple formula that can give upper limits for the force exserted by the belayer on an extending anchor. If they don't count for body flex they'd be a lot harher than reallity for short extentions. But even unneccesarily harsh upper limits can sometimes be instructive. It's enirely possible I'm being hard headed and missing something about this. Just looking for somebody with a chisel and good aim to break through.


kachoong


Feb 21, 2006, 5:00 PM
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Re: Improved sliding x: Is it really safer? [In reply to]
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Here's my problem with this. If the belayer is doing a non redirected belay he/she is potentially being accelorated by the tension the rope to the falling climber in addition to gravity. In effect creating a potentatial higher than factor one fall factor (in terms of the belayers velocity versus amount of rope he's connected to).

I don't see how this could be worse (on the anchor) than if the belay was redirected through the anchor power point.
Big mass (belayer) hiting a short lenth of hopefully static material at a relatively fast speed? Basically the question for me is it possible for the belayer to be speed up enough by the falling climber to have what amounts to a high fall factor fall. The answer is neither intuitively or mathmatically obvious to me.
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Regardless, rope slipping through the belay device should mitigate an related problems.
Not neccisarily see above it's mostly about how fast the belayer is traveling not the climber. Rope slippage will provid an upper limit to how fast a falling climber can potentially accelorate a belayer but I still don't know what this value is.
The belayer is 'falling' onto the anchor in how many situations? I can think of one main scenario. When the leader has fallen past the belay, ripping all pieces, and the belayer is catching the leader directly on his harness along with a failing anchor.

I guess that is a scenario we must think about when discussing all that is in this thread. However, what I'm also thinking of is another scenario where the leader falls onto the powerpoint of a failing anchor that you are belaying them from (ie. directly off the anchor) The belayer theoretically does not move at all.

If in this scenario, the belayer is belaying off his harness and the rope runs through the powerpoint (which more than likely is above him slightly), the leader falls and pulls the belayer upwards..... no?

Does that make sense? I'm just trying to think of a scenario where the leader falls onto the anchor, making it fail (ie. pieces pop) and the belayer also 'falls' onto the anchor while the leader is theoretically still falling due to an extended anchor.


slcliffdiver


Feb 21, 2006, 5:01 PM
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Re: Improved sliding x: Is it really safer? [In reply to]
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That means the maximum force that any fall can put on the belayer is south of 600 lbf. After that, the rope starts slipping, dispursing the load over time.

Does that clear it up?

JL

Thanks, if I had some current physics competence it'd probably clear it up quickly. I'll try and work through this by next week unless someone beats me to it.

I know I'm repeating myself in a way but I don't trust the clarity of my writting. Just because the max a climber can exert on a belayer is 600 lbs doesn't neccesarily mean that the max force it can contribute to the force on the anchor if the force is used to accelorated the belayer through space and then have him hit the anchor. Or at least that's the unknown for me now.


moose_droppings


Feb 21, 2006, 5:20 PM
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All anchor setups should be put through the filters of KISS and SRENE.
I personally do not believe this is possible. And doesn't the "s" in srene already stand for simple.

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