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Climbing Disciplines:
Trad Climbing:
Sliding double X ??:
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jktinst
Jul 12, 2010, 3:28 PM
Views: 40107
Registered: Jun 29, 2010
Posts: 89
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(Edit 6 years later: since the link to sittingduck's illustration got broken, I included one of my own in a new post on pg2).
I got my initial trad training in France in the early 80s and stopped & re-started trad leading over the years as I moved around (England, W. & E.Canada). For the latest re-start, I decided to read up on the current "gospel"and bought Long&Gaines’ climbing anchors on the recommendation of Colin (niloc on the forum).
This made me realize that, for years, I’ve been doing the sliding X differently than what seems to be the commonly accepted manner (which is to make a single 180deg twist in the middle of a single one of the two strands of the sling and clipping both the straight and twisted strands together). For my part, I twist both strands before clipping them, making sure that I twist them both with the same clockwise (or counter-clockwise) turn. The latter point is vital since, if they are twisted in opposite directions, a failure of one of the two points could let the whole thing unravel.
Reading the book has also led me to think about and hunt for answers on 3-piece self-equalized, low-extension, redundant anchors on this forum & on ST.com but I will leave that for another post. In going through these monster threads on equalizing anchors, I have come across references to something variously referred to as "Craig’s short" or "sliding W" for equalizing 3 placements that is done with two twists but did not come across something like my two-arm "sliding double-X". Searches on various likely keyword combinations (forums & Google) did not turn up anything else either. As a newcomer to this forum trying to catch up on many lengthy discussions going back several years, covering a wide variety of related topics and, most of the time, with key photos no longer available, I may well have missed relevant references and apologize if this has already been covered before.
When I tried the regular sliding X after coming across its first illustration in the book, I thought that my system might actually have some advantages because, even though it introduces 2 twists instead of 1, it forces the crossings of the tape or cord to remain above the central locker and to slide through it side-by-side and in the same direction (and also because it uses up the exact same length of tape or cord on each strand, which could be useful when the strands are tied together with limiting knots).
In the regular configuration, the one twist places the crossing of the strand above the biner initially. However, by making just a half-turn around its main axis, the biner tends to end up in a more balanced and symmetrical position with the strands crossing on the inside of the biner (ie right under the"basket" bar of the biner, assuming you clipped it right side up). In the book, the "clutch effect" was blamed for a) limiting the dynamic equalization under load between two unequal arms of the sliding X, on average and b) occasionally causing much larger differences in the equalization. I would have liked to see a more detailed dissection of this effect in the book or the forum since it seems that different things might happen with the regular sliding X that could play a role in this:
1. If the biner is not allowed to make the half-turn and the crossing of the twisted strand is kept above the biner, the twist on only one strand means that when the strands slide through the biner, they run in opposite directions.
1a. If they run side by side (more likely with cord), the friction they would generate would be relatively small, but
1b. if they run one on top of the other (more likely with tape), with the straight strand jamming the twisted one against the underside of the basket bar, the braking effect in the event of a fall would be very high.
2. If the biner is allowed to make the half-turn, the two strands slide in the same direction but crossing one another on the underside of the basket bar where the loading would, again, increase the friction but, presumably, not to the same extend as in 1b.
The book mentions the possibility of restoring almost perfect equalization by using a large pear anodized biner combined with manually forcing the crossing to stay above it. Again, more details would have been handy since it seems that you could do the latter either by a) preventing the biner from making the half-turn and making sure that the strands remain side-by-side; or b) letting it make the half-turn but adding some sort of divider to move the crossing from under the basket bar to above it and keep it there during the test. It seems more likely that the authors were referring to the latter scenario but it would have been nice to know for sure.
The equalette, with its two central biners and no twisting or crossing makes a lot of sense as a solution to the clutch problem but, having long climbed with a very minimalist rack, I remain interested in 2-piece anchors that do not involve two central biners. It also seems that the sliding X is still in use by people who have adopted other aspects of the equalette but prefer to stick to a single central locker. So I was wondering if an extension-limited sliding double-X might be an option (assuming that it’s not some antiquated and long-discredited throw-back).
Of course, with the double X, you have to pay close attention to which way you twist the strands and, although the crossings are garanteed to stay outside of the biner, there are two of them instead of one for the regular sliding X. Without further drop tests, it's probably anyone’s guess how well the double X would equalize two unequal arms during a fall. My gut feeling would be « probably better than 1b or 2, about on par with 1a and definitely less well than a 2-biner equalette ».
Thanks in advance for any thoughts or criticisms.
Stéphane
(This post was edited by jktinst on Aug 17, 2016, 5:53 PM)
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Post edited by jktinst
() on Jul 15, 2010, 4:01 PM
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Post edited by jktinst
() on Aug 17, 2016, 5:53 PM
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