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charlesjmm
Apr 25, 2006, 7:22 AM
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Jim, an important precaution : please make sure the backup loop is set to the proper length, otherwise, you risk introducing an unpredictable biner-biner clash in a failure scenario.
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adnix
Apr 25, 2006, 11:43 AM
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Why don't you guys fix some easy-to-use knot/device for Sliding X? Something similar to quicklocks in Petzl harness. It shouldn't be too hard if you put some hours into it.
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charlesjmm
Apr 25, 2006, 1:23 PM
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Adnix, just take a look at the "No solution to...." thread.
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adnix
Apr 25, 2006, 2:53 PM
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In reply to: Adnix, just take a look at the "No solution to...." thread.
In practice I very seldom use any knots with slings since they are bitch to untie and they rack very bad if not untied. Especially if you fall on the knot the only solution for opening is a knife.
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jimdavis
Apr 25, 2006, 9:51 PM
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In reply to: Jim, an important precaution : please make sure the backup loop is set to the proper length, otherwise, you risk introducing an unpredictable biner-biner clash in a failure scenario.
I'm not sure what your refering to...do you have a picture? or what is it about the backup strand length thats the issue?
Thanks,
Jim
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charlesjmm
Apr 26, 2006, 1:21 AM
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Jim, I’m referring to the length of the backup loop relative to the main strand. For illustration purposes, the pictured anchor is set up with an excessively long backup loop. As a result of placement failure, see how the placement biner crashes with the master biner; not good.
http://i49.photobucket.com/...roublettetoolong.jpg
I have obtained excellent results placing pre-set overhand knots 25 inches apart on a 48 inches sling, which allows for versatility in anchor arrangements, ample equalization range and contained extension while avoiding biner-biner clash.
Carrying the sling pre-set creates a very useful tool and saves you from wasting time checking for contained extension.
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jimdavis
Apr 26, 2006, 1:28 AM
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^^ I see. Yeah, good point to keep in mind, especially considering that there would probably be a good sizes piece of pro hanging off that biner in a real failure.
Thanks charlesjmm,
Jim
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adnix
Apr 26, 2006, 8:52 AM
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In reply to: I have obtained excellent results placing pre-set overhand knots 25 inches apart on a 48 inches sling, which allows for versatility in anchor arrangements, ample equalization range and contained extension while avoiding biner-biner clash.
This will be my new tool and official truth. Thank you very much for your input! :D
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glowering
May 19, 2006, 6:37 PM
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Sorry to dredge this thread up again, haven't checked it in a while.
I strongly suspect that the loss of equalization in a slidingX in the tests Largo had done were the result of binding of the slidingX (from webbing on webbing contact or additional friction created from the wrap/tension of the strand of webbing that wraps around the biner) at the power point biner, NOT from additional friction from running accross two strands of webbing/cord.
It is a fact of physics that additional surface area does not increase friction. Although this is highly nonintuitive. Friction is determined by force and coefficient of friction of the materials in question. If you double the surface area you halve the force over the new area.
Anyway, for regular anchors I have just been using a limited knot slidingX, tied offset in a 48" sling, on two pieces (with a *gasp* :shock: slightly sloppy slidingX at the power point :lol: ). I put a third piece in for a backup/first piece off the belay. If I did come across 3 marginal placements in an anchor I would have a lot of good options in my bag of tricks, partly in thanks to this thread.
Charles, nice idea on the powerpoint. My only concern would be the excess loose webbing hanging around. It could possibly get jammed into the biners or an autolocking belay device at the powerpoint, etc. I would just leave the backup strand slightly loose. Is there an advantage of your method over the sloppyX? It seems like it would be a little slower to setup, due to having to retie at least one knot for each anchor.
I have been able to leave the "offset limited knot sliding sloppy X :wink: " set up on my harness and get the belay setup in about 10 seconds.
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112
May 19, 2006, 7:03 PM
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In reply to: It is fact of physics that additional surface area does not increase friction. Although this is highly nonintuitive. Friction is determined by force and coefficient or friction of the materials in question. If you double the surface area you halve the force over the new area.
It amazes me how many times this comes up (but I guess it shouldn't amaze me). Coeficient of friction is an approximation to a HIGHLY complex phenomina. It does sufficiently predicte forces encounter in MANY (but not all) situations in real life. However, it is not an absolute. Surface area DOES matter as well as many other factors.
I know your instructor covered this (or they should be FIRED) because mine did. Once the yield strength (which is an approximation itself - based on the assumption of a homogenious material) of either of the 2 materials in contact is surpased (which is a function of surface area) the coefficient of friction no longer reasonably predicts the forces to be encountered. Therefore you should ALWAYS check to ensure that the yield strength of either of the 2 materials is NOT surpased. Then and only then can you use the APPROXIMATION of coefficient of friction with any coffidence.
By the way, there are MANY students seeking their Phd whoes primary focus of study IS friction in very specific cases were the coefficient of friction does not applyor rather does NOT reasonablt predicte the forces to be encountered.
Ken
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rgold
May 19, 2006, 7:36 PM
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"The tables that list purported values of mu [coefficient of friction] are all false...the friction is never due to "copper on copper," etc. but to the impurities clinging to the copper...It is quite difficult to do accurate quantitative experiments in friction, and the laws of friction are still not analyzed very well...although the law F= mu N is fairly accurate once the surfaces are standardized, the reason for this form of the law is not really understood...at the present time in fact, it is impossible even to estimate the coefficient of friction between two substances."
---Richard Feynmann, Lectures on Physics Vol 1, p 12-4, 1963.
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glowering
May 19, 2006, 8:18 PM
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I guess I shouldn't have stated "fact", but should have used "generalization" :wink: . It has also been a looong time since my last physics class.
But in climbing anchors are we really entering a realm where this relationship breaks down?
The "law" of gravity also breaks down near relativistic speeds, but I don't think any climbers are that fast yet.
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davidji
May 19, 2006, 8:40 PM
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In reply to: But in climbing anchors are we really entering a realm where this relationship breaks down?
It's an approximation that works well for some cases. Your equating it with gravity seemed a little silly.
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112
May 19, 2006, 9:16 PM
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In reply to: The "law" of gravity also breaks down near relativistic speeds, but I don't think any climbers are that fast yet.
I agree it is a very good starting point in analysis, if not the only one we have (sometimes).
My Fluids instructor use to always say, refering to the applicability of models to reality, "It depends on how hard you squint". :lol: :lol: :lol: :lol:
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wannabe
May 20, 2006, 12:53 AM
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You haven't had a lesson in fluid dynamics until you eaten at Taco Express. That's all I'm sayin. :shock:
Vince
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charlesjmm
May 20, 2006, 1:00 PM
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In reply to: Sorry to dredge this thread up again, haven't checked it in a while. I strongly suspect that the loss of equalization in a slidingX in the tests Largo had done were the result of binding of the slidingX (from webbing on webbing contact or additional friction created from the wrap/tension of the strand of webbing that wraps around the biner) at the power point biner, NOT from additional friction from running accross two strands of webbing/cord. It is a fact of physics that additional surface area does not increase friction. Although this is highly nonintuitive. Friction is determined by force and coefficient of friction of the materials in question. If you double the surface area you halve the force over the new area. Anyway, for regular anchors I have just been using a limited knot slidingX, tied offset in a 48" sling, on two pieces (with a *gasp* :shock: slightly sloppy slidingX at the power point :lol: ). I put a third piece in for a backup/first piece off the belay. If I did come across 3 marginal placements in an anchor I would have a lot of good options in my bag of tricks, partly in thanks to this thread. Charles, nice idea on the powerpoint. My only concern would be the excess loose webbing hanging around. It could possibly get jammed into the biners or an autolocking belay device at the powerpoint, etc. I would just leave the backup strand slightly loose. Is there an advantage of your method over the sloppyX? It seems like it would be a little slower to setup, due to having to retie at least one knot for each anchor. I have been able to leave the "offset limited knot sliding sloppy X :wink: " set up on my harness and get the belay setup in about 10 seconds.
Glowering, to ambience the issue, I’ll say that the improved Troublette came to life as a result of seeking for ways to minimize equalization’s biggest enemy: FRICTION. The design turned out to be a useful tool applicable as part of an anchor matrix or as a power point in itself. As you point out, the knotted sliding X equally qualifies for these chores; the improved Troublette simply provides for enhanced equalization qualities as it avoids the binding problem.
As to the possibility of the backup strand interfering other gear, your proposal of leaving the backup strand slightly loose is certainly the solution; just bear in mind that the backup strand also controls the equalization range; therefore, by minimizing the backup strand’s length you are also reducing the equalization range. It’s the eternal compromise at play….. Exercising tidiness at the anchor is always advisable.
Regarding rigging time, what I’ve experienced is that the improved Troublette accommodates a broader range of placements configurations. This allows for slack while placing the individual anchors on rock as they don’t need to be conveniently close to each other. In the end, total rigging time (viewed as setting anchors on rock AND subsequent rope work) turn out to be equivalent.
Lastly, I second the notion of leaving the sling pre-set as it makes life so much easier.
Charlesjmm
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sittingduck
May 30, 2006, 3:42 PM
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After reading this long thread I will change one thing in my method of building trad belay anchors. I will drop the figure 8 to collect all the strands that I used to do when rigging my cordalette. No stopping knots what so ever from now on.
That’s it, I will go on using the cordalette, backed up with my climbing ropes clove hitched to all the pieces in the anchor, leaving just enough slack for the cordalette to work.
Peace
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fitzontherocks
Aug 28, 2006, 1:34 PM
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OK, I've searched for the link to the pictures of the sliding x with limiting knots in the outer legs and can't find it. Can anybody post it, please? Thanks.
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maxtrax
Aug 28, 2006, 2:03 PM
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Just build a normal sliding x then unclip one leg at a time and put in an overhand knot then reclip the leg to your pro. I generally put the knots about 5-6 inches on either side of my master point (when using a shoulder lenght sling). I think there's a picture of it within the first 6-8 pages of this thread.
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glowering
Aug 28, 2006, 3:40 PM
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In reply to: I've searched for the link to the pictures of the sliding x with limiting knots in the outer legs and can't find it. Can anybody post it, please?
Here's some photos of a sliding X with limiter knots.
It pays to dress the limiter knots so they are clean.
I leave it pre-tied and almost never adjust the knots. If one side is too long I'll throw an overhand or 8 in that arm to shorten it. Or if one side is too short, I'll extend to that piece with another sling.
For racking I just leave my master point big locking caribiner clipped in the X, then twist the arms and clip the arms to the master biner.
I have it tied so that the strand that circles the biner has a little slack in it, then there is no binding so it get's the best possible equalization, but there is still redundancy (so I'm not dependant on a single strand of a sling).
I'll clip this to two bolts or two pieces of pro for my anchor. If I want a third piece of pro in my anchor I just use a sling from that piece to my master point caribiner with a little slack in it.
I find this is very fast, often faster than a cordelette and I get the best possible equalization from two pieces with the least amount of gear.
http://img249.imageshack.us/img249/748/x2dr.jpg
Here's the max seperation:
http://img144.imageshack.us/img144/8400/xfar8tq.jpg
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cracklover
Sep 13, 2006, 8:22 PM
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In reply to: Anyone put these anchors to the test yet?
Yes, I use these modern rigs exclusively whenever I rig up a cordelette (perhaps 20% of my trad anchors). Mostly I've used the Mooselette, because it's so quick and easy to rig, and eqalizes so well, but I've used and enjoyed the CharlesJMM rig, too.
I haven't seen a factor two fall on them yet (thank god!) but I have certainly put them to the test. For example, I slept on the Mooselette. Not just me, either - I hung myself and my partner, our double portaledge, all our gear, food, water, etc, off the Mooselette.
GO
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devils_advocate
Sep 13, 2006, 10:42 PM
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Devils_advocate moments ago at his desk, in his cubicle:
Damn this Excel file, it’s full of bugs. I should just start clean and reprogram in the whole database. Or... maybe I’ll jump on RC.com and waste some time. *thinking* Option 2 wins.
He opens Internet Explorer and clicks on the first entry under Favorites: Rockclimbing.com. He waits patiently for the screen to load and checks an email or two; still waiting. He goes and grabs a cup of water, pretends to be interested in whatever inane conversation he gets pulled into at the watercooler and slips away back to his desk; still waiting. He then tries the Close IE - Open a new browser technique a couple of times... finally gets through:
Sweet. Well, lets see what’s going on in the forums today. Top of the list: Top Roping Questions. Meh, probably some guy with 6 locking biners talking about his technique for setting up TR. Next down: CCH Aliens. Those poor guys, I don’t think they’ll ever live this down. Next down: How to attract a trad mentor. Heh, yeah, grow breasts, that’s how. Next down...
An uncomfortable feeling strikes our websurfer. Palms get sweaty, throat tightens... wild animals come out of the woodwork sensing panic, looking for a victim. He double checks the line to make sure he is reading it correctly:
Improved Sliding X: Is it Really Safer?
Oh God no. Say it isn’t so. Tell me that’s not... THE thread. Somebody must have made a second, a smaller one, a much smaller one. They wouldn’t bring that one back... would they.
With a cheesy B-Horror Movie stupidity he moves his cursor over to the link. Heart pounding, eyes focused. Some guy in the audience stands up and yells “Don’t click the damn link, moron”. He clicks the link.
Go to page 1,2,3...58,59,60. OH GOD NO. AAHHHHHHHHHHHHHHHHHHH!!!
I’ll be at Belview if anyone needs me.
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bill413
Sep 13, 2006, 11:32 PM
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Well, being in Belview should give you enough time to read thru the whole thread....
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jimdavis
Sep 14, 2006, 1:53 AM
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:twisted: ................................................ BUMP! ....... :lol:
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