Top Anchors on routes

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Nic Le Maitre
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Re: Top Anchors on routes

Post by Nic Le Maitre » Mon Sep 28, 2015 9:18 am

Old Smelly wrote:As an aside (maybe read wild goose chase) - are we going to consider in the long run that we cannot keep banging in new sets of anchors and chopping the old ones? Is there a sustainable solution? Do we even need to replace top bolts of we can get just the rings to wear and the bolts themselves do not corrode?
Trad climb or Warren's engineered nut placement anchor things
Old Smelly wrote:And then a Parthian shot -
Parting shot, not Parthian
BAbycoat wrote: BUT when you toprope off the top anchors or even abseil off them then they are typically the only thing preventing one from hitting the deck
If you don't top rope through the draws, you are not being very bright.
BAbycoat wrote: BUT when you toprope off the top anchors or even abseil off them then they are typically the only thing preventing one from hitting the deck
This is exactly what we have been saying ALL THE TIME. When you use the anchors you fatigue them, therefore we have two top anchors, one of which is hopefully unused and in excellent condition so that it is there to act as a backup in case the other one fails during a lower off. The shockloading in this situation is of NO CONSEQUENCE AS IT IS MUCH MUCH MUCH LESS THAN WOULD BE EXPERIENCED BY ANY OTHER BOLT DURING NORMAL USE.

Just because you have an opinion about the merits of equalized anchor systems does not mean that it is correct to apply your opinion to the placement of bolts on sport route top anchors.
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Re: Top Anchors on routes

Post by Justin » Mon Sep 28, 2015 9:34 am

A user asked me to add this photo with accompanying table:
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top_anchor_types_rings.jpg
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Old Smelly
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Re: Top Anchors on routes

Post by Old Smelly » Mon Sep 28, 2015 10:31 am

As per usual Nic - you are too quick to think that you are the always right... :pirat:

Parthian Shot: The correct term that got bastardised along the way;
https://en.wikipedia.org/wiki/Parthian_shot

I suspect you think you are always right...without really accepting that others may have some knowledge too...don't worry it is a common failing...

Not that you are that common...are you?

I also believe your opinions on the top anchors are just opinions - as I stated previously - so reiterating that back to me does not make the single top anchor system right either.

Your explanations are great by the way and I am sure that everyone follows exactly what you have been stating all along. :thumright
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Re: Top Anchors on routes

Post by Nic Le Maitre » Mon Sep 28, 2015 10:58 am

And once again you fail to read what you actually cite:
A common opinion holds that, in a case of folk etymology, the term parting shot, used similarly, developed as an eggcorn-like re-interpretation of "Parthian shot", meaning the term was corrupted through common parlance, however, the two phrases have separate histories.
I'm quite happy to accept new views based on solid evidence, it's what I do every day, it's called the scientific method. Every time one of us on this thread has stated reasons for what we are saying you have failed to engage critically with what we have said and continuously returned to your opinion on what is better without any evidence to back it up. You make no attempt to refute what we say, just continue on with your own fallacious opinion
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Re: Top Anchors on routes

Post by richardwardza » Mon Sep 28, 2015 1:04 pm

Old Smelly, this has been going backwards and forwards and I've been forming and re-forming opinions as the discussion has gone on.

I understand what you're saying and started off thinking the same, why load 1 point to 100% when you can spread it.
But I do also understand the other side, have 1 high, 1 low, load 1 fully and have 1 in perfect condition for in case there is a failure.

I think what you're getting at is over time, the 'perfect condition' anchor may not be so perfect anymore as it may have rusted or fatigued or whatnot.
However, this can be said of any bolt and any anchor and could happen with a 'side by side' configuration too.

IF, in this miniscule percentage situation, it does happen then I'd consider it a Freak occurrence, kind of like getting struck by lightning.
If this does happen, neither configuration is better as they both just had 2 anchors fail.

However, if only 1 anchor does go then I'd like my backup to be a 'perfect condition' anchor and not one that has been taking split load all it's life.

After that anchor does go I'm pretty sure that whoever comes to rebolt it will do an evaluation on all the bolts and do the magical stuff that happens while I sleep.

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Re: Top Anchors on routes

Post by The Jimmy » Mon Sep 28, 2015 3:28 pm

Some good points have been raised by both the technical and non-technical contributors on this forum, but I think it's important to also just let sanity prevail:

1. While admitting that a statement in absolute terms on my behalf without the supporting calculations, info etc (which is another way of saying i'm too lazy, I don't know where my text books are right now and will someone else please check. Nic?) I am pretty confident in saying that, though theoretically possible, you as a 70kg climber are not going to fatigue a certified, well-placed and ARF approved lowering-off anchor through the amount of use you put on it through normal rock climbing. By the time the bolt is in any danger of failing in this way it is way WAY overdue for replacement due to other factors such as corrosion. And if you live on the Peninsula, Cormac Tooze would have already replaced it anyway because he can.

2. Not using an anchor does not "save" the anchor and guarantee it's reliability. Whether being loaded along with the other anchor or not, it's still sitting there corroding just the same as the other one and might also be subject to failure when loaded.

3. This thread is interesting and it's great to see other opinions. However, it is not like we have an anchor failure every week, at least not here in SA, so however doubtful some are and however many "what if" failure situations we can think up, though good to be aware of, we generally seem to be getting it right on our SA crags, so good job to those bolters.

The bigger concern in my opinion is that there are now more bolters than there have ever been before and who have varying degrees of bolting savvy, so education and safe practice methods are key to helping them get it right for everyone's sake.

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Re: Top Anchors on routes

Post by Old Smelly » Mon Sep 28, 2015 3:53 pm

Richard - yes that is a fair assessment. However one could just as easily consider that because the load has been shared between the two anchors that they would last considerably longer (this is fairly standard thinking when it comes to load cases) and so therefore they would be safer for much longer. As I mentioned before it is also less likely that one of these anchors would deteriorate at the same rate as the other one, so that in fact the one that did deteriorate faster may then ultimately fail and the load goes on to the other and there is then a point for replacement.

In some ways this would be similar to the single backed up anchor case, except for the fact that the single anchor would most likely age faster in terms of loading as it always carries all of the load and logically then need replacing sooner.

These are considerations. As Babycoat has spelled out if the loads are generally equalised in most cases this will make little or no difference in terms of the cycle of loading and only be relevant for lower off's. However as one almost always has a lower off and considering that the wear on one ring will most likely be double that of wear on two equalised rings we then have a dubious advantage (none at all actually) as the single anchor would need to replaced twice as often as the double one.

It appears to me that in this case equalised chains with rings on as shown by Babycoat is by far preferable to any other system. I suspect others may agree with this reasoned assesment.

So why would some of the more opinionated publishers on the forum go so far to push this single backed up anchor system and insist it has so much merit? Why ignore the obvious lack of advantage that has been stated over and over again and instead start personal attacks? I have no idea. The real issue remains the same - where are the real advantages that would make one adopt a single anchor over double equalised anchors?

Up to this point the objective of this thread is to determine what best practice would be. As I stated several times over this may not be in the mechanics but in the implementation - that is what people do with the new system, not just whether some people think that one system is theoretically better than another. In deference to Babycoat the outcome that he arrived at is helpful and probably should be the way to go.

With regards whatever else was stated I suspect there is no good response, nor does it deserve one. I do not think that this argument is as one sided as some may imply or that the arguments in favour of a single anchor carry that much merit - notwithstanding whether one claims their approach is better or not. I apologise if I seem to have disregarded other people's viewpoints on what they perceive is an open and shut case and if I have no evidence as to why equalised anchor systems are better than single point loaded systems.

The objective of the topic on the forum was to determine what the best practice should be in terms of top anchors and to see if the uneven anchors were indeed that. Maybe some are of this opinion after the discussion. I certainly am not but then I am only one of many climbers out there. Possibly with this "issue" raised there will be more engagement and hopefully climbers will be able to rationally assess what the best method is, without being shouted down by those who claim they know best.
Last edited by Old Smelly on Thu Oct 01, 2015 9:00 am, edited 1 time in total.
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Re: Top Anchors on routes

Post by Old Smelly » Mon Sep 28, 2015 4:15 pm

@ the Jimmy - good points and I think well reasoned.

The assumption that someone is more technical or non technical on the forum may be flawed - particularly if it is just an attempt to sandbag others into submission. I always suspect someone's argument must be weak if they try and obfuscate by saying they know more (or have better methods).

I do differ with you regarding bolting though - I see many horrorshow top anchors every time I sport climb! I agree that the bolts may be good and that whilst new one can assume they are much stronger than required. That's not how things fail though. Anchors may fail if after much use and cross loading and weird forces acting on them by how the rope runs through them they give way because of side forces and minor cracks or too much rounding of the edge of the holes cause a chain reaction of combining factors. So you can't always control that - so in climbing we adopt methods that rely on us using best practice to push up the Safety of the system. That is done everywhere in climbing - hence the fact that most gear can take a 2,5 ton load. It is also the reason why we should put up the best possible top anchors.

So if Nic is right and that is the best possible anchor system to use, then that is what we should be doing - the best possible practice that we can.

Personally I think that is better than everyone cobbling together their own version as to what is "acceptable" as an anchor. I hate getting to the top of a climb nicely bolted with hangers and there are some rusty chains barely held on to the shank of the bolts by a nut that hardly clamps on the chain at all! That terrifies me and makes me think that the only part of the system that gets used every time should be the best part! Along with this it should not confuse the user - otherwise why bother!
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Re: Top Anchors on routes

Post by BAbycoat » Mon Sep 28, 2015 6:20 pm

@Justin
Thanks for the pics. I found the new "attachment" button over the weekend.

@Smelly,

Let's call these "vertically aligned lower-offs", or VALOs for short. Single bolt anchors are different - they're dangerous and despicable.

NB: my thread contributions are to help you (and others) understand WHY VALOs are installed. This is NOT a user manual for bolting or a best practice consensus. Anyone considering bolting should speak to the regional experts ... which include Andrew, Andy and Cormac at a minimum. Please re-read Andy's brilliant summary of the best lower-off.

I'm also NOT advocating equalised chains. Equalising distributes the wear from lowering off. The whole point is to have unequal wear, so that one point remains unworn. One chain plus one bolt will come close to equalising, but a small (1cm?) difference is enough to avoid wear on the lower point. It's a subtle but important difference.

Regarding shiny hangars with rusty chains ... that's what happens when people go around attaching mailons and the like.

And I wholeheartedly agree that, the simpler anchors are, the better.

@Jimmy,

Thanks for your appeal to sanity. With respect, I politely disagree with your points.

1. Bolt should be installed for the long term. Please don't assume that good samaritans like Cormac will fix the problems.

2. Not using one point WILL save it from wear ... which is the the whole bloody point of the exercise. Corosion is a different issue. FYI, here's an example of wear from toproping
KJ2Q941.jpg
KJ2Q941.jpg (100.45 KiB) Viewed 2266 times
3. We did get it wrong in the Cape, at first. (We didn't know better at the time). That's why the ARF exists. Thankfully nobody got hurt in any bolt failures.

@Nic,

Chill. It seems you're on a mission today to take everyone down.
Last edited by BAbycoat on Tue Sep 29, 2015 2:15 am, edited 2 times in total.

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Re: Top Anchors on routes

Post by Nic Le Maitre » Tue Sep 29, 2015 9:46 am

I apologize if I insulted anyone but as Old Smelly has said, the entire point of this thread is to get the best possible top anchor setup. We have repeated shown why "equalized" anchors are not the best solution, even if they appear to be at first glance.

Fatigue, particularly High Cycle fatigue is of relevance: http://www.asminternational.org/documen ... pter14.pdf
See section 14.2. While steel has a higher endurance limit (i.e. a stress level that will not result in fatigue) than aluminium, it still has one, and it is lower in sheer than in longitudinal loading. VALO's avoid this known risk factor.

In fact I'd be quite happy if we deleted everything after Andy's excellent post and locked this thread, leaving that as the last word.
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Re: Top Anchors on routes

Post by Old Smelly » Tue Sep 29, 2015 9:52 am

Babycoat I think the point I am trying to make is that you can't sugarcoat these anchors by calling them VALO's - they are single point anchors! Sure there is a backup but the anchor is the sole point of support for all intents and purposes for all of it's operation. Combine that with the fact that the Top Anchors are the hardest working part of the anchor system in a climb (in terms of the fact that the Top anchors always get loaded) and then add to that that in essence they are not "backed up" like the rest of the bolts on the climb and you will have to admit that the top anchors need to be the best bolts on the climb. Sure they are statically loaded but they are also loaded every time.

I wish to back track and say that I appreciate and take cognisance of the various technical reasonings that have been presented here. I also apologise if I seem unwavering in some of my viewpoints and not that keen to just accept what others have said. I do struggle with the assumption that because of a few supposedly technical arguments that the VALO system is now assumed to be "better" or the answer, which is why I keep coming back to this single loaded point argument.

Notwithstanding some of the things that have been said, I am still trying to see the best way forward.

As I said I respect the bolters BUT that does not mean they are doing the anchors right - otherwise why would I be asking how these anchors are better and how the common climber should be using them.

As to what I said last - notwithstanding Babycoats willingness to accept the VALO's - the real point was that from the diagrams there was an optimal solution AND it wasn't the VALO single anchor system.

SO - other than avoiding twisting your rope - which your gri gri does even better than the anchors - and the fact that a single anchor ring will most likely wear twice as fast as a load shared well between two sets of rings, are there any other merits to the Anchor System Single - which is what I am going to call it, or ASS System for short?

I gave some thought to the argument that Equalising the load was not technical or unscientific and I decided to look for examples in common use or nature. So initially I thought of a cow, or a table, and how the weight of these items is better spread over four legs. I thought there must be a mathematical model to show that a single legged table (or cow) would put a lot more load through that single leg and that every time the cow stood up, the forces going through that single leg would be much greater than if it had four legs. In this example I imagine the chances of the cows single leg giving way over time would be much more and that leg would have to be that much stronger than the four equivalent legs. With four legs the cow would be able to carry it's body weight over it's entire life - without any of them failing. With one leg it would only be a question of time!

Now forgive my rather empirical unscientific explanation (which no doubt you will argue is not the same) and let us look at what we can learn from the cow;

1. Shared load is almost always better - if you look beyond my shockingly bad example - you should be able to see that.
2. If something is repeatedly loaded ( I think you would call that cyclic loading O scientific ones) then a single support is inordinately worse - where is the stats guy to explain how much worse a single anchor would be then one with 2, 3, 4, 5, to the N values this would be - I suspect it will be a hyperbolic curve. If there was a way of quantifying how strong the anchor is then one of the "scientific" people could try and work out an S-N curve (I hope this is the right term) and work out the cyclic loading fatigue life on the single anchor and from that arc prove how much worse the ASS anchor system is...

3. And then back to the real point - lets not assume for a moment that the anchor is good and can take tons of load - because as I said before this is NOT a good assumption, then even my cow would rather be standing on two legs rather than one!

In short I do not believe the ASS system is superior and nor does my cow!
Last edited by Old Smelly on Tue Sep 29, 2015 4:31 pm, edited 6 times in total.
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Re: Top Anchors on routes

Post by Nic Le Maitre » Tue Sep 29, 2015 6:35 pm

Old Smelly wrote:Combine that with the fact that the Top Anchors are the hardest working part of the anchor system in a climb (in terms of the fact that the Top anchors always get loaded) and then add to that that in essence they are not "backed up" like the rest of the bolts on the climb and you will have to admit that the top anchors need to be the best bolts on the climb. Sure they are statically loaded but they are also loaded every time.
This is exactly why we want the other one of the two anchors at the top of the climb to remain unloaded and unused except in the event of the other anchor failing for whatever reason. Then it is in the best possible condition to receive the minor shock loading that will result.
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Re: Top Anchors on routes

Post by henkg » Tue Sep 29, 2015 7:34 pm

Out of habit, when rigging a top rope, leave the rope running through the last draw. Backs up the anchor.

The thread is starting to sound like a broken gramophone ....
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Re: Top Anchors on routes

Post by Old Smelly » Wed Sep 30, 2015 8:48 am

These look good to me:

http://gunksclimbers.org/2015-new-bolt-anchors-gunks/

ok maybe not the ones in the trees :pukel:
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Re: Top Anchors on routes

Post by BAbycoat » Thu Oct 01, 2015 5:00 am

The whole point is to not equalise. But Smelly refuses to get the point. *sigh* I feel like I've fallen for the most elaborate Troll on this site yet.

Aside: those Gunks anchors look like perfect candidates for galvanic corrosion. No thanks.

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Re: Top Anchors on routes

Post by Old Smelly » Thu Oct 01, 2015 8:40 am

I must apologise if you think I am trolling Babycoat. Like I said I agreed with your analysis of the pictures of the anchors as to which was the best one, so I do not quite get the assertion that one then backtracks from this and goes to the ASS system.

I also get that Nic is proposing that we always load a single anchor and that it is "dynamically" backed up - which I find a weird concept but clearly that is his argument.

I also understand what you were saying in terms of the fact that one can equalise the anchors for the people that would like to top rope, but that for the climber lowering off they will do so on a single statically loaded anchor (with the "dynamic" backup)

NOW can you get that most climbers arrive at the anchors with two equal length quickdraws and the knowledge that their buddy is going to climb after them. THEY will look at the unequal length anchors and say "@$#t what do I do with this k*%k arrangement?"

Now all the pontificating and reiteration as to one anchor being strong enough is meaningless to them and to my one legged cow, because spread loads are better! With all due respect to Nic this is a fact (a SCIENTIFIC fact).

I do get that for the climber that has cleaned the climb at these rather awkward anchors (because yes it makes the cleaning an f%@# up too) he can safely lower off on the single anchor (with the "dynamic" backup) if the bolt is safe. BUT the assumption that the bolt is safe and can take massive loads is an UNSCIENTIFIC Assumption! I cannot assume that for every bolt I encounter in the outdoors - nor would I think it a good idea to make such an ASSumption!

So YES I get that you have all decided that a single anchor is safe enough and that equalising is irrelevant but I refute the basis of your claims that this is a "Scientific" and logical decison. In fact yes I prefer the way those NEW anchors were done in the States as they appear to be safe and easy to work with and understand!

At this point I do agree that all discussion around the topic has been exhausted.I get that there is some sort of coalition that has already decided this is the way forward for everyone else, however I also believe that the commonly accepted practice of equalising anchors will continue and that these anomalous and awkward anchors will continue to frustrate and be rejected by a large portion of climbers. That is my opinion and is in no way meant to influence anyone else's viewpoint. I also get that in many ways my initial questions around who decided what way best for everyone whilst they stand back bemused and bewildered has been answered. Time alone will tell whether these VALO/ ASS anchors are well accepted. I must say for my part I genuinely was trying to find out what the thinking was behind the unequal anchors and at the same time how the normal climber should use them. I am unsatisfied with the reasoning but at least there is an answer - even if to my mind it is unsatisfactory and a step back.

Thank you for all your responses. All personal attacks aside I believe that clarity has been achieved as to what the agenda is with the unequal anchors.
Last edited by Old Smelly on Thu Oct 01, 2015 9:11 am, edited 4 times in total.
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Re: Top Anchors on routes

Post by Old Smelly » Thu Oct 01, 2015 8:45 am

Aside aside: Galvanic corrosion will ONLY take place if the materials are dissimilar, so if everything is stainless then the anchors will be great. There is also a point that if the surface area of the less Noble material is much greater than those of the more Noble material then there will be no actual galvanic corrosion. BUT yes those anchors are only great if the material is the same throughout - including the bolts!
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Re: Top Anchors on routes

Post by Nic Le Maitre » Thu Oct 01, 2015 9:44 am

BAbycoat wrote:The whole point is to not equalise. But Smelly refuses to get the point. *sigh* I feel like I've fallen for the most elaborate Troll on this site yet.
Couldn't agree more.

Right, one last attempt:
@OS: I am going to put a series of statements here and I'd like you say whether you agree with them or not.

Wear and tear results from usage and will result in strength reductions in a bolt

Equalizing top anchors results in wear and tear on both anchors

Equalizing top anchors will not prevent shock loading as the load on the remaining point will go from less than 100% to 100% suddenly should one point fail

With VALOs there will be more of a shockload than for Horizontally Aligned Lower Offs (HALOs) as the load will go from 0% to 100% on the remaining bolt

With the amount of rope in service when lowering off/top ropeing off "Vertically Aligned Lower Offs" (VALOs) the shock load will be very minor and well within the expected performance of the bolt

With correctly placed VALOs there will be very little time for the load to accelerate between the loaded bolt failing and the unloaded bolt catching (see "C" or "D" in the picture below) resulting in even lower shock loads

Image

With correctly placed VALOs there is no chance for inexperienced climbers to rig an American Death triangle (and inexperienced climbers seem to be the main focus of your questions)

With correctly placed VALOs there is no twisting of the rope

With HALOs the possibility exists for inexperienced climbers to setup a system that results in a load greater than 100% of the downward force on EACH anchor

With VALOs like "C" or "D" in the picture above it is less likely that the bolts will be placed too close together by inexperienced bolters

Thanks
Happy climbing
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Re: Top Anchors on routes

Post by Old Smelly » Thu Oct 01, 2015 10:57 am

Good points Nic and I think I would say that I do believe C or D are the best options on Anchor systems.

As to whether one anchor is better than two - you know my view on this - though the way you have posed your questions as statements seems to lead to the conclusion that you want and that is difficult to dispute when put that way. It is very well put and succint. It denies my assertion that two anchors when often loaded will bear the load with a lot less strain on the two anchors than one would - thus the life of the single anchor being much shorter -which I still contend to be true. It also does not account for one bad bolt being repeatedly loaded being better that the load shared over said bad bolt and another - thus a higher chance of NO anchor failure - but we have been through this and we seem to disagree over the assumption of quality of bolts. At this time our lines of reasoning do not seem to converge and I cannot really concede that one anchor bears the load better than two.

It seems to agree with my argument that the loading on the equalled anchors will be borne better than the more severe shockload on the lower anchor in the VALO but what the hey as you say the forces are comparable, so let that go.

So maybe the comparison is not so bad at all. Thank You for going to the pains of pointing that out. I would still rather go for C or D and not B - which is what most of my concern has been over.

Thank You once again for your input from everyone. Happy climbing.
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Re: Top Anchors on routes

Post by XMod » Fri Oct 02, 2015 6:40 pm

OMG! This... - again!
Once more for the record below is a proper sport route top anchor (obviously you would place two)
sport anchor.jpg
sport anchor.jpg (22.35 KiB) Viewed 2083 times
any other arrangements made up bits of hardware chains shoved over a bolt stud (especially chain that is too small to put a biner through) is just bloody irresponsible bolting!!!! Please do not take cost as a reason for making crap anchors. Believe me paying for someone's medical bills will cost you a LOT more! If you cant afford proper hardware, you cant afford to bolt - PERIOD!

There is absolutely nothing wrong with two anchors at the same height placed at least 200mm apart in solid rock nowhere near a crack or incipient crack (that anchor at Ramset is a time bomb with no real strength at all - replace it asap!). The 'death triangle' refers to a sling threaded in (yes!) a triangle through two anchors with a lower angle (formed by the sling) of more than 30 degrees. There is no way these forces apply in the case of two top anchors as they are a 'V', NOT a triangle (DOH!). Additionally if you clip two draws into the anchors the lower biners meet in the middle - nullifying any sideways force. Same applies to the anchor shown above.

DO IT RIGHT or don't do it at all.

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Re: Top Anchors on routes

Post by henkg » Sat Oct 03, 2015 5:04 pm

Old Smelly, you are a fine one to call other people's methods unscientific. Please do tell what fall factor is incurred on a top rope rig with 50m dynamic rope out and one anchor failing, resulting in what 30cm extension?
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Re: Top Anchors on routes

Post by richardwardza » Sun Oct 04, 2015 3:41 pm

I guess the solution could be very simply - when top roping clip in the last bolt on the route and then even if lightning stikes the dog, the titanic resurfaces and I onsight a 24, and both anchors do fail then you still have the last anchor for backup.

If both anchors and the last bolt fail at the same time then I guess it was probably your time to go anyway...

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Re: Top Anchors on routes

Post by Nic Le Maitre » Mon Oct 05, 2015 9:45 am

XMod wrote:There is absolutely nothing wrong with two anchors at the same height placed at least 200mm apart in solid rock nowhere near a crack or incipient crack (that anchor at Ramset is a time bomb with no real strength at all - replace it asap!). The 'death triangle' refers to a sling threaded in (yes!) a triangle through two anchors with a lower angle (formed by the sling) of more than 30 degrees. There is no way these forces apply in the case of two top anchors as they are a 'V', NOT a triangle (DOH!). Additionally if you clip two draws into the anchors the lower biners meet in the middle - nullifying any sideways force. Same applies to the anchor shown above.
It doesn't have to be a triangle to generate large sideways forces on the anchor, here is a table of the effect of varying the angle and the load at the master-point/BFK/meeting point of two quickdraws on a two point anchor:
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And no X-mod, it doesn't make any difference if
XMod wrote:you clip two draws into the anchors the lower biners meet in the middle
since the resultant force on the anchors still has sideways and downwards components
Happy climbing
Nic

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ScottS
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Re: Top Anchors on routes

Post by ScottS » Mon Oct 05, 2015 12:40 pm

Nic Le Maitre wrote:It doesn't have to be a triangle to generate large sideways forces on the anchor, here is a table of the effect of varying the angle and the load at the master-point/BFK/meeting point of two quickdraws on a two point anchor
Nice figure!

I think it would be much more informative if the colour scale mapped to percentage (or proportion) of the static load carried by each anchor (in this figure ranging from about 50% best case to 288% worst case on the chart). I predict that you'll get horizontal colour bands showing the increasing proportion of anchor load with angle.

For bonus points compute the anchor loads as a proportion of the safe working load for a "properly" placed bolt in "good" rock. Figuring out the safe working load is the hard part :wink:

Here's Petzl's summary of the table:
escalade-grde-voie-relais-triangule-24.png
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At the chaaaaains boet!!

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Nic Le Maitre
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Re: Top Anchors on routes

Post by Nic Le Maitre » Mon Oct 05, 2015 1:17 pm

The values in the table are the loading per anchor for the given angle and the given load

So top left cell, 20 degree angle, 80kg load, 41kg/anchor

Or if you use the 100kg column, 20 angle = 51kg/anchor or 51% of the downward force.

If you want to calculate your safe working load you will need to know the anchor strength, your minimum breaking strain of the gear and your safety factor all of which vary according to where you are, the rock type and the relevant legislation in place in that area. Too many unknowns to solve that one.
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Nic

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Re: Top Anchors on routes

Post by henkg » Thu Nov 10, 2016 12:16 pm

Old Smelly wrote: Lets looks back at the three legged cow and point out that shared load will extend the life of each anchor way more then if you load one until it fails and then load the next one. That is logical.

Sigh. In the context of the recent failure at the Mine, you are making an assumption that the wear is due to climbers weighing the system. Failure could have been caused due stress corrosion cracking which is not induced by climber, but by stresses of the bolt tension and chemistry.
You may still be here tomorrow, but your dreams may not. Cat Stevens

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Re: Top Anchors on routes

Post by Gobsmacked » Thu Nov 10, 2016 12:36 pm

I recommend that we attempt to find some UIAA guidelines on top anchors.
Last edited by Gobsmacked on Thu Nov 10, 2016 12:54 pm, edited 3 times in total.

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Nic Le Maitre
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Re: Top Anchors on routes

Post by Nic Le Maitre » Thu Nov 10, 2016 12:43 pm

Again assuming facts that are not in evidence...

Please do tell me where you found out the bolt configuration at the top of this route was two bolts on the same horizontal plane and loaded equally?

EDIT: This post now makes no sense as a result of Gobsmaked changing the entirety of his post, but I'll leave it up anyway as the question still stands.
Happy climbing
Nic

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Re: Top Anchors on routes

Post by Hector » Thu Nov 10, 2016 1:21 pm

Oops, I think OS may have just let the cat out of the bag about his closely-guarded true identity...
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