Self Equalizing or Sliding X Anchor

[512dude]

I read this article at the ASCA's website and was wondering what you guys think and what you typically use? Anyone seen any empirical data on the issue?

 

_____________________________________________________

 

" The Sliding X "

 

Many climbers use a "sliding X" to equalize two pieces - ususally beginner climbers with bolt anchors. You should NEVER use this except in two specialized cases (see below). While the sliding X does equalize the pieces, it assumes that neither could break, since if one does break, there is severe extension in the system - enough that it would likely cause the carabiners to break. Since it assumes neither piece would break, it's a stupid system - if neither would break, there's no need for equalization. If one might break, then there is WAY too much extension. This is why many call it the "death X." Instead, use one sling off of each bolt or piece. You can tie one shorter to approximately equalize the pieces if needed.

 

The two cases where the sliding X is used:

 

equalizing tenuous pieces in a larger anchor - for instance, two poor nuts in a large natural pro anchor. The nuts are equalized, then the sliding X is equalized with other pieces through a cordelette, webolette, or other non-extending method.

equalizing two very tenuous pieces in extreme aid - for instance, a hook and a bashie on A4 terrain.

 

 

[Off_White]

How many anchor failures has anyone heard of from this?

 

I've heard of the American Death Triangle, but not the "death x"

 

Carabiners must be much more fragile than I thought if 12 to 18 inches of shock load is enough to break them.

 

Any test data?

 

Reminds me of that time I woke up in a bathtub full of ice with this note...

[Rad]

There will be a shockload if one piece fails, but this concern about breaking the carabiner doesn't sound very credible. I use the X from time to time (including last weekend). If you find solid data please post. Thanks.

 

[rob]

Long's 2nd edition of his anchors book has a lot of good data about the sliding X and the "shock-load" worry. You should pick it up, I thought it was a great read.

 

[G-spotter]

wasn't there like a 30 page thread about this last week?

[fenderfour]

"if neither would break, there's no need for equalization."

 

This is a flawed statement. If I only clip one bolt at the anchor, it has to hold the entire load. If I clip two bolts with a "Death X" the load will be distributed between the two, making them less likely to fail.

[512dude]

If there was G-spotr can you link us to the thread?

 

Thx

 

PS.

This link has a nice pictoral discussion... Anchor Analysis

Edited July 20, 2007 by 512dude

[fig8]

We talking a sliding x with no limiter knots? Adding limiter knots still provides good equalization, and reduces the amount of potential extension.

 

[bstach]

Try here, 512dude:

 

http://www.cascadeclimbers.com/forum/ubbthreads.php/ubb/showflat/Number/692897/page/0/fpart/1

 

And you might find this useful for the future:

http://www.cascadeclimbers.com/forum/ubbthreads.php/ubb/search

[dan_forester]

anybody ever seen a carabiner break? seems like if it's not loaded across the gate or bent over an edge this would be pretty rare.

[G-spotter]

"if neither would break, there's no need for equalization."

 

This is a flawed statement. If I only clip one bolt at the anchor, it has to hold the entire load. If I clip two bolts with a "Death X" the load will be distributed between the two, making them less likely to fail.

 

if you clip two bolts with a Death Triangle, each bolt will perceive a higher load than if you had just clipped one bolt due to the angle of the sling causing force multiplication. skull

[catbirdseat]

Since the sliding-X was labelled the "death x" some testing has been done which has shown that, in the event of failure of one of the two bolts, the maximum loading of the remaining piece (bolt) does not exceed the initial loading on the anchor system. In other words, "shock loading" is a myth.

 

And this makes sense, doesn't it? The climber is attached to a dynamic rope. That rope absorbs the energy which results from extension in the same way that it absorbs energy from the initial fall.

 

Limiter knots will reduce extension and will reduce the load on the remaining bolt in event of a failure, but they are a hassle to tie and, worse, to remove after having been loaded. I don't use limiter knots on bolts. I sometimes use them on gear.

[catbirdseat]

anybody ever seen a carabiner break? seems like if it's not loaded across the gate or bent over an edge this would be pretty rare.

I've not seen it with my own two eyes, but it happens. When it does it isn't usually possible to know for certain why it happened. In the case of Goran Kropp's accident, for example, the best guess was that the carabiner was trapped in the crack, preventing it from rotating, and it thus broke from cross-loading.

[512dude]

Cat,

 

can you provide your source? Where did you get this info and who did what testing?

 

Thx,

 

Since the sliding-X was labelled the "death x" some testing has been done which has shown that, in the event of failure of one of the two bolts, the maximum loading of the remaining piece (bolt) does not exceed the initial loading on the anchor system. In other words, "shock loading" is a myth.

 

[catbirdseat]

I read it on RC.com in the super long Improved Sliding-X thread and also it's mentioned in Long's new book on anchors.

 

There was a thread here on cc.com not too long ago where some of this was discussed. I think it was mattp who said something to the effect that bolts are super strong when placed correctly. If a bolt looks solid and does not show signs of obvious corrosion and the rock is sound, it probably is a good bolt. It might not be. There is a small chance that it was placed incorrectly or over torqued.

 

If it fails, which is unlikely, you have another very strong bolt backing it up. The chances of two bolts failing are vanishingly small. I can't think of a case in which it has happened. Perhaps Dru will step in with his encyclopedic memory (and googling skill).

Edited July 20, 2007 by catbirdseat

[high_on_rock]

Since the sliding-X was labelled the "death x" some testing has been done which has shown that, in the event of failure of one of the two bolts, the maximum loading of the remaining piece (bolt) does not exceed the initial loading on the anchor system. In other words, "shock loading" is a myth.

 

And this makes sense, doesn't it? The climber is attached to a dynamic rope. That rope absorbs the energy which results from extension in the same way that it absorbs energy from the initial fall.

 

Limiter knots will reduce extension and will reduce the load on the remaining bolt in event of a failure, but they are a hassle to tie and, worse, to remove after having been loaded. I don't use limiter knots on bolts. I sometimes use them on gear.

 

I agree with Catbird on all of this

[rob]

I think it was Craig Connally disprove the whole "shock-loading" thing (assuming a dynamic rope)?

 

You should pick up that book, dude, and read it. It references tons of new tests done on the sliding X, equalette, etc.

Edited July 20, 2007 by robmcdan

[selkirk]

So shorten the arms and limit the extension. I use this for quite a few top rope anchors while cragging, and just throw and overhand in the arms to limit extension in the case of failure. Max extension would be 8 or 10 inches, but maintains the equalization through a reasonable range.

 

Besides, while it might be a "shock load" the only place I've ever really used this anchor is on Sport routes, at which point it's no like your taking a static factor 2 onto the anchor, but most likely a dynamic top rope fall.

[counterfeitfake]

"shock loading" is a myth.

 

And this makes sense, doesn't it? The climber is attached to a dynamic rope. That rope absorbs the energy which results from extension in the same way that it absorbs energy from the initial fall.

 

Of course there's more to it- how far away is the climber? The closer he gets the less extension possible. Where is the belayer clipped in, and what with? With extension he falls too. If it's a daisy chain that's static, and if it's a knot in the rope, six inches isn't going to offer much shock absorption. How much other crap is hanging from the anchor? Haul bags usually get tied off with a static line.

 

I think the more interesting and potentially relevant point with the sliding x is friction from the webbing running against itself.

[fig8]

Limiter knots will reduce extension and will reduce the load on the remaining bolt in event of a failure, but they are a hassle to tie and, worse, to remove after having been loaded.

I haven't found limiter knots to be a hassle at all, even after the leader lowers through the system on bolts after topping out... and if something were to happen to really load them, I'd be glad they were there. Anyway, I don't mind a bit of hassle to add safety to a system... my life is worth the extra 55 seconds.

 

[Cobra_Commander]

you guys are worrying about bolts failing? Bolts similar to those off of which people whip 20 feet, repeatedly? I don't think you need to worry too much about your toprope anchor in that case.

 

You could also just use two quickdraws (ducks). Thousands of people do, and they're still here.

[corvallisclimb]

anybody ever seen a carabiner break? seems like if it's not loaded across the gate or bent over an edge this would be pretty rare.

 

I've broken a few funking out pitons, but this is mabey 1 every year doing so, so pretty excessive use as a funk biner. Usually the metal starts to deform before it breaks.

[fig8]

you guys are worrying about bolts failing? Bolts similar to those off of which people whip 20 feet, repeatedly? I don't think you need to worry too much about your toprope anchor in that case.

 

You could also just use two quickdraws (ducks). Thousands of people do, and they're still here.

 

Depends on the bolt and the rock, and the fact that the bolts might take repeated 20 foot whippers... that will put some stress on the bolt and or rock over time, and can have some cummulative effect. All situations aren't equal. Draws are fine in some cases, but in others the bolts are back from an edge, and I'll use a sliding x with limiter knots to keep the rope from sliding over the edge. Besides, this discussion isn't just about bolts, it is about the sliding x... my point is that I don't find limiter knots to be a big hassle.

[Cobra_Commander]

I've found over-analyzing safety actually creates unsafe situations.

[fig8]

Sure, which is why I just use a standard double runner with pre-tied limiter knots in most cases. I don't have to spend much time analyzing anything. And if it ends up being overkill in some cases, BFD.