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dangry
Trad climber
tahoma, ca
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Topic Author's Original Post - Jun 15, 2009 - 03:33pm PT
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I was out at Clark's Canyon this weekend, many of the old cold shuts have been replaced with "Mussy Hooks" or tow hooks. That's great and thanks to the folks for updating the anchors. But many of the anchors I saw had only one quick link, thus the hooks don't come to a single point. To me this looks a lot like the old "American triangle". With any rappel set the anchor is loaded inward at 180 degrees. In my opinion these new anchors are no better than the ones they replace. All should be lengthened to bring the hooks to a single point when loaded.
Am I wrong? Are these anchors "safe" or should links and chain be added to make them "safe". I understand someone has put out a lot of money and time changing out the cold shuts.
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couchmaster
climber
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Jun 15, 2009 - 03:36pm PT
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2 questions:
1st) What do you mean by 180 degrees? Does this image below hint at what you are discussing? So the pull is straight across? OMG!
How many rap/belay anchors have failed due to "American Triangle". If even a single failure is known to have occurred, please describe just that incident. Anyone can play for this question.
I'm curious.
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Rhodo-Router
Gym climber
a greasy pinscar near you
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Jun 15, 2009 - 03:39pm PT
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I'll give you a quarter if you can pull two bolts by lowering off a sport climb.
Find something else to worry about.
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dangry
Trad climber
tahoma, ca
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Topic Author's Reply - Jun 15, 2009 - 03:42pm PT
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OK so this might not be a big deal considering the strength of a bolt. I'm just bringing up an observation and asking a question.
180 degrees or straight across from each other.
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couchmaster
climber
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Jun 15, 2009 - 03:48pm PT
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No No, I don't mean to say it doesn't matter.
If it looks something akin to this below (with the addition of the Mussy Hooks, then it should be fixed and the folks who "upgraded" it should be clued in.
Better angle, more redundant:
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Ksolem
Trad climber
Monrovia, California
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Jun 15, 2009 - 04:04pm PT
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Pic #1 above is so wrong in so many ways...
Two mussy hooks or shuts across from each other are fine. For top roping, clip a runner or long draw into each one to make your center point. Last climber strings the rope through both anchors and raps or lowers.
Sure, the rope goes straight across, but there is no force multiplier, just some inward pull.
This should be Locker's cue:
Yer gonna die!
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Mighty Hiker
Social climber
Vancouver, B.C.
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Jun 15, 2009 - 04:08pm PT
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Both examples are wrong. The first, because the bolts are too close together, and because of the force geometry of the chains. The second, because the bolts are too close together, and in what appears to be in a partly-detached block.
The rock in 'sport' climbing areas is often suspect, and belay bolts in such areas placed too close together.
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dangry
Trad climber
tahoma, ca
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Topic Author's Reply - Jun 15, 2009 - 04:21pm PT
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coachmaster, yes once the hooks are loaded for rappel the hooks are drawn inward at each other.My understanding of the physics of anchors mean each bolt is taking more than 100 percent of the load. I'm by no means an expert. Nor have I heard of the American triangle causing a belay anchor to fail. I have read in several "how to" books that rigging an anchor in the "American Triangle" is not "bomb proof".
And of course any rappel anchor at a sport crag you add your own gear to TR through, any anchor given enough time can be sawed through.
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Ksolem
Trad climber
Monrovia, California
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Jun 15, 2009 - 04:26pm PT
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The big problem in pic 1 is the rope being strung across the chains. I think it looks like there is a spare link over by the right hand bolt which is the intended thread point? Less than ideal, but not suicidal as shown.
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kev
climber
CA
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Jun 15, 2009 - 04:30pm PT
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Ksolem,
Yeah I saw the first pick and thought WTF.
kev
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Evel
Trad climber
the cliffs of insanity
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Jun 15, 2009 - 05:49pm PT
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Most sport anchors are in fact a form of the American Death Triangle. Two cold shuts, Two Fixe rings, pretty much all two-bolt horizontal set-ups are not correct.
A vertially aligned two bolt anchor is the way to go.
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jstan
climber
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Jun 15, 2009 - 08:18pm PT
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Chains have the property of not stretching much under load. So if a horizontal chain link is tight you get force multiplication as 1/sin(ø) where ø is the angle of deviation from a straight line. For a 160# person the dependence of total force on angle goes as:
10 deg 500#
5 deg 900#
1 deg 4600#
That is with body weight. If you hold a 1000 # force in a fall you are talking close to 15 tons for 1 degree.
Everyone knows this but the facts did not seem to come through clearly in the posts.
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Clint Cummins
Trad climber
SF Bay area, CA
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Jun 15, 2009 - 08:41pm PT
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[referring to anchors with 2 bolts at the same level with Mussy/tow hooks or Fixe double ring hangers, the original post]
Not a triangle (if you are lowering).
Not dangerous.
It is a triangle if you are rappelling, but the angle is likely under 20 degrees (see couchmaster's diagram) and gets close to zero quickly. Forces too small to be dangerous.
The "vertically aligned" bolt type anchor is nice for some things (like minimizing friction when pulling the rope). It requires more chain to create, though (assuming the bolts are a "safe" distance apart - at least 2 times the depth of the holes). It is not so good for a hanging belay with 2 people hanging there - some horizontal separation is nicer for that situation.
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Greg Barnes
climber
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Jun 15, 2009 - 08:50pm PT
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Like Clint said, no worries. But there is a worry about adding chains to Mussy hook systems:
You have to watch out for the back side of the gates on Mussy hooks - they can shred rope sheaths. This is basically only a problem on anchors on slabby rock - but many at Clark are just that (even when the climb is steep). So the location and spacing of the bolts can be very important. With a chain added in, even if it is done correctly, if someone clips a Mussy hook on the end of a twisted chain, it might force the rope over the sharp back side of the gate. Do NOT go adding chains to Mussy hook setups unless you know what you are doing.
Also, if you are at some area such as Area 13 where you can lead one route and go clip the anchor of another to TR the other route, use your gear not the Mussy hooks to set up both anchors (which you ought to do anyway). In other words, if you clip more than 2 Mussy hooks (2 at one anchor, then 1 or 2 at the other anchor), the backside of the gates of the inner Mussy hooks can damage the rope sheath.
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lightboi
Trad climber
MN
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Jun 15, 2009 - 09:24pm PT
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In the rock and roll world we often have to suspend a point somewhere in space. Tools such as this rigging calculator
http://design.cablepick.com/rigging
help make the math easier
It translates very well to climbing anchor loads. One can see the relationship of angle to load as well as different length of legs(ie making the chains different lenghts.
enjoy!!!
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couchmaster
climber
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Jun 15, 2009 - 09:27pm PT
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Hold it hold it Greg. I've never used Fish's hooks, never even seen them in action, what are you saying there again? I can see that a rope could possibly be damaged on the back of the sharp gate, and that if you add a link to the equation it would turn the hook sideways (so add 2 links, not 3, 4 but not 5 etc. Additionally, the act of adding chains will make the possibility of a hook turning sideways, and thus causing a rope sawing action, increase. Whereas in the configuration shown in the picture, it is relatively stable, add more links and it gets floppy.
Is that what is being discussed?
From Fish's site: http://www.fishproducts.com/catalog/bolting.html
To Dangry, I can see that most likely, the hooks are NOT 180 degrees and pulling directly into each other. As John Stanard says if I understand him, there is less force on a non-static ( webbing) application as well. In fact, you can look up and get a calculation on this, but be aware that decreasing the spacing of the bolts so that the hooks touch together as you would like, will at some distance, decrease the strength of the wedge anchors. There is a trade off going on here you need to be aware of. This from the Thunderstud site, you can fish around for similar info. They are not saying that a 1/2 x 7" anchor that is 4" from another anchor has a bigger NET reduction in force than a 3/8 x 3" or 1/4 x 2", as the 1/2" diameter anchor is still significantly stronger, but the percentage of strength reduction is higher. Not knowing what exactly you are looking at, nor the depth and diameter or brand of anchor that was utilized in the replacement, I can only guess what the installer was thinking, but I bet you are better than good in this application.
"The forces on a ThunderStud® wedge anchor are transferred to the material that it is installed in. If the anchors are installed too close together, it can cause an interaction of the forces, thus reducing the holding power of the anchor. As a rule of thumb, the concrete anchor industry has established a minimum standard of ten (10) anchor diameters for spacing between anchors and five (5) anchor diameters from an unsupported edge. When vibration or sudden impact are part of the load condition anchor spacing should be increased. "
You can look around and get various Mfg actual numbers.
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Majid_S
Mountain climber
Bay Area
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Jun 15, 2009 - 09:32pm PT
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this place is worse than RC.noob
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Jaybro
Social climber
Wolf City, Wyoming
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Jun 15, 2009 - 09:33pm PT
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We're all gonna die. check this sh#t out and do the best for everyone each time. who does that?
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jstan
climber
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Jun 15, 2009 - 10:39pm PT
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Speaking as an RC.noob.
The original placement was fairly clearly installed by someone who is not aware of the tradeoffs. If that is the case why are we to presume the bolt installation itself was not similarly poor?
By its nature rock is highly defective. When two bolts are close together the strain fields from each may well inter-react and will do so in the presence of defects. This is what leads to material failure.
In my post above one thing I was saying is that since nylon stretches, if nylon is in the system you will not have such small angles and such large force multiplication for two horizontally placed bolts. With chain, what you see is what you will get.
Apriori it also makes little sense to place two bolts in any piece of rock that appears to be separate from its surroundings. You think you have redundancy. You could be surprised.
Anyone aware of current emphasis being placed upon personal safety and who then goes and installs a personal safety device is depending upon remaining anonymous or upon the fact they and their family are both dirt poor.
I infer from this that it will take only a few egregious equipment failures to cause a radical change in currently accepted practices.
If it comes to this, it will not be pretty.
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couchmaster
climber
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Jun 18, 2009 - 02:17pm PT
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Thanks John, since there is no pictures detailing what the OP is discussing at Clarks,nor any route names or corresponding collaboration, I was thinking that given the OP was saying that there was a 180 degree pull, and that he wanted the Mussy hooks to be touching, that in fact it was not a 180 degree pull, but instead the spacing is far enough that the rope runs through both hooks straight across.
If this is the case, and we do not really know, then it's probably not a 180 degree angle at all as Ksolem suggests on the 4th post or so. Looking at the picture and visualizing what Greg noted above as well, adding a second link would turn the hook so it would parallel the wall/trap the rope, and the attendant issues with that.
This should give us all pause and prod us all to remember that each placement that we come across was and is an individual and potential iffy proposition. There are a few places where this is not the case (say Beacon Rock where Joseph replaced each and every rap anchor with a rock solid brand new installation containing identical materials, cataloged and detailed what he did publicly, and left a brass washer stamped with the replacement date on each one so future generations have some information).
Any info on this from anyone else? Pictures or drawings?
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crusher
climber
Santa Monica, CA
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Jun 18, 2009 - 02:43pm PT
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Greg didn't you and/or Alan replace/add new anchors at Clark? At any rate my point being as far as I know nothing at Clark was retro'd by people who didn't know what they were doing.
I think I know what the OP is talking about in terms of the remaining open anchor hooks there - they're not bolted into the rock so tightly as to not swivel inward some when threaded for a rap or a lower off. I've never personally been concerned with them but to each his own, take a look and make your own determination.
I think the musseys are fine...last person to climb can lower off of them or rap off - they're set like they are in The Gorge.
The most recent Mammoth Area guide book (Marty Lewis) has section on Clark Canyon if anyone wants to read about the gear there.
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Largo
Sport climber
Venice, Ca
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Jun 18, 2009 - 03:28pm PT
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I've driven myself half mad in these kinds of discussions. Ultimately, I've found it useful to consider every anchor in terms of two factors: a) the known or calculated reliability of the primary components in the anchor array, and B), how said components are linked or rigged together.
In other words, the primary anchors (bolts, nuts, pegs, cams, et al) and the rigging (chains, shuts, slings, etc.).
General rule: The sketchier the primary anchors, the more important it becomes to consider SRENE rigging strategies.
Two bomber, 3/8" bolts set in diamond hard granite and you can tie them off most any which way and the thing will likely hold fast. Start working with wires in horizontal cracks, sketch rock, etc., and no-extension, equalization and so forth become meaningful, even life-saving (though rarely, IMO).
Another thing, anytime you're using inflexible chain to connect two bolts, it's very dificult to build the set up so loading is somewhat equally distrubted betwen both bolts. And even if things are "perfect," off-axis loading will put most if not all the weight on one or the other bolt. With good bolts is good rock this is almost certainly not a factor. Move onto choss and it's almost always better to use nylon, even if you need to leave something behind.
JL
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pimpdaddy
climber
manchester, vermont
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Jun 18, 2009 - 03:46pm PT
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The anchors that have been replaced in Clarks are fine.
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HighDesertDJ
Trad climber
Arid-zona
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Jun 18, 2009 - 03:56pm PT
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The anchors at Clark's Canyon have been how the OP describes for at least 12 or so years. There is a huge difference between your rope through hooks like that and an American Triangle. It is true that it increases the forces, and it is probably not the ideal setup but so long as the bolts are solid and the placements are solid there is nothing inherently unsafe about it.
The American Triangle is dangerous not simply because it increases the force (which a decent bolt anchor can easily handle when used for lowering or rappelling) but because there is no redundancy in the anchor. If the webbing fails at one spot the entire anchor fails. In a mussy hook situation if a bolt failed the other bolt will still catch you.
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Largo
Sport climber
Venice, Ca
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Jun 18, 2009 - 04:19pm PT
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He wrote: "The American Triangle is dangerous not simply because it increases the force (which a decent bolt anchor can easily handle when used for lowering or rappelling) but because there is no redundancy in the anchor. If the webbing fails at one spot the entire anchor fails."
The term "American Triangle" was originally used to describe common rap points/anchors at the top of popular climbs in Yosemite. Often times these climbs would feature two pins bashed into a horizontal crack with a shitload of slings fed through the eyes of the pins. Or else there would be two bolts on top of a short free climb, for example, Lunatic Fringe, with slings stuffed through the bolt hangers.
In both cases the sling configuration described a triangle, with downward force generating sometimes sizable inward load multiplication on the pins and bolts. If one placement blew, the slings were still fed through the other placement so only if that blew as well would the whole shebang fail.
Considering how sketchy some of these anchors were, it's amazing that more of them didn't blow. With modern sport bolts, anchor failure (anchor actually pulling out) is very rare, and is almost always due to the rigging screw ups (like not correctly girth hitching the slings together, etc.), not the anchors getting yanked out. In fact I'm not sure there's any documented case of a modern sport (bolt) anchor failing, though plenty of folks still get dropped and bungle their tie ins and tie offs.
JL
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couchmaster
climber
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Jun 18, 2009 - 04:28pm PT
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JL Said "In fact I'm not sure there's any documented case of a modern sport (bolt) anchor failing, though plenty of folks still get dropped and bungle their tie ins and tie offs. "
Do you (OR ANYONE!) know of some with old short rusty 1/4"ers that failed John?
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couchmaster
climber
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Jan 21, 2015 - 01:58pm PT
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Me either. Just the single Rawl Stud on Anchors Away that 2 people were reportedly simultaneously jugging on. In fact, I consider the "American Death Triangle" essentially a myth. Everyone uses them and they work fine. Good for internet arguments but little else.
BTW, learned a good tip from Jim Titt of DMM. If you install Fixe anchors that have the hooks, if you can install them so the hooks touch each other, it will reduce oscillation and result in less material being rapidly worn off as you rap and pull ropes: especially in gritty rock. (that's my summation, he may have a differing clarification of what he actually said)
ie, not this:
This
Pictures of my anchors, placed @ a year apart. Changed my placement strategy due to Jim Titts words. The anchor Mfg recommend 4X the diameter of the wedge anchor spacing for optimum strength, so it's a fine line to get both that and have them touch given the length of the Fixe Stainless hook anchors. By this time I'd had to retire a DMM biner which I had used for belay/rap biner on my ATC that developed a deep groove in a single day from a multiple rap down on a wet day. I figured that even though the anchors are stainless and not Aluminum, to go with his wisdom. Thus they started being placed closer together so as to optimize the material lifespan. Also, this rock did not seem to have developed fracture planes like many other rock substances do so that didn't need to be considered.
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Killer K
Boulder climber
Sacramento, CA
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Jan 21, 2015 - 02:19pm PT
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The worst part is the a$$holes you get in your rope when you lower off an anchor with the chains too far apart. And I agree tr on yer own shite.
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Camahoo
Trad climber
Dead Pine Ridge, Ca
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Aug 30, 2016 - 01:40pm PT
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This anchor is perfect!
what your not seeing in the picture, is the guys girlfriend is pregnant and she wants to keep it.
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labrat
Trad climber
Erik O. Auburn, CA
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Aug 30, 2016 - 02:36pm PT
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Wow!
Not much else to say....
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this just in
climber
Justin Ross from North Fork
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Aug 30, 2016 - 08:37pm PT
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what your not seeing in the picture, is the guys girlfriend is pregnant and she wants to keep it.
That's funny. Sorry
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scaredycat
Trad climber
Berkeley,CA
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Aug 30, 2016 - 10:51pm PT
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The anchor in d2r2's photo is totally bizarre, but it could be worse. At least it's redundant w.r.t the failure of either anchor. OK, with the same gear, it could be a whole lot better, too.
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Ed Hartouni
Trad climber
Livermore, CA
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Aug 30, 2016 - 11:35pm PT
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The classic "American Triangle"
how come they always used white slings BITD?
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Stephen McCabe
Trad climber
near Santa Cruz, CA
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Aug 31, 2016 - 01:26am PT
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Don't know if it was a serious question. However, many didn't start out white, but became white after too long in the sun. See the blue where it was shaded?
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Ed Hartouni
Trad climber
Livermore, CA
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Aug 31, 2016 - 10:47pm PT
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ahhh, serious question... I thought this was a RC.noob thread! so I put in the question...
but maybe the humor was a bit too wry...
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| Messages 1 - 36 of total 36 in this topic |
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