06:01:39 Mon
Oct 16 2006
| Re: Testing of Rock Climbing Anchors |
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phm 11:29:45 Fri Sep 29 2006 |
Pircher M. (2006) “Testing of Rock Climbing Anchors”, Journal of Testing and Evaluation, ASTM, v34, n5, pp 416-422 Another one on the Design of Rock Climbing Anchors is in the pipeline. |
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shawkshaw 13:07:24 Fri Sep 29 2006 |
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rogerb 01:13:01 Tue Oct 3 2006 |
Either way, I think I've read it and the testing methods didnt match real rock very closely. The big unknown in real rock is the bond between the rock and the glue and to a lesser extent between the glue and the bolt. Unless the rock is crap (in which case the bolt shouldnt be there or needs to be 500mm long) 90% of the TLC needs to go into maximising the bond of the glue to the walls of the hole and making sure there arent big air bubbles inside the hole. That unknown is the main thing that worries me in bolting. |
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phm 09:56:38 Tue Oct 3 2006 |
I am pretty sure you will find the journal in the engineering library at USyd (under number 620.11205 3 according to the library website) or most other Unis in NSW. Otherwise google spits out the following link: http://journalsip.astm.org/JOURNALS/TESTEVAL/jte_home.html There is a problem with copyright laws when putting the paper in a public spot. Private copies are a different matter, though. |
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rogerb 23:02:20 Tue Oct 3 2006 |
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phm 06:38:41 Wed Oct 4 2006 |
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rogerb 02:15:47 Thu Oct 5 2006 |
"It was shown that an anchor in soft concrete [=sandstone] can exhibit the required strength through a number of loading cycles and then fail". and (paraphrased): "you cant assume an anchor is safe because everybody falls on it". The obvious conclusion is that we should make crux bolts stronger than bolts that are loaded only rarely. What is the opinion of the engineers on the best design for such a crux bolt? 1) Since failure in soft rock seems to occur progressively from the front of the drill hole, would a better design be a long hole drilled diagonally up (assuming that the steel is stiff enough to distribute the load all the way to the back of the hole)? 2) Is a U-bolt more suitable for a crux bolt than a welded ring? |
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petey_w 03:31:56 Thu Oct 5 2006 |
1) yes 2) yes |
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shawkshaw 04:25:05 Thu Oct 5 2006 |
steve at climbinganchors.com |
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phm 09:51:02 Thu Oct 5 2006 |
I would prefer to take the obvious conclusion a bit further: We should design bolts in a way that they don't display this failure mechanism at all. I have a principal problem with U-bolts: reliable bond between the bolt shafts and the glue is a lot harder to establish for U-bolts than for P-bolts. P bolts that are twisted into the fresh glue usually bond very well. U-bolts that are 'slided' (or hammered) in tend to bond unreliably. This was observed under lab conditions and would probably be worse in real vertical life. Drilling bolt holes diagonally upwards leads to a different loading situation all together - shifting the emphasis from shear to pull-out. I agree that this approach would probably alleviate the "crushing problem" but might lead to other problems - such as putting greater stresses on the glue-rock interface, another problem area as Roger has already pointed out. However, I have not done any tests on inclined anchors. |
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shawkshaw 10:13:51 Thu Oct 5 2006 |
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hatman 21:53:12 Thu Oct 5 2006 |
I know of quite a few ring bolts placed incorrectly (no notch) however even they still seem to be ok. Sure you can get them to fail in a lab test but under real worse case scenario wots the chance? |
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tnd 22:51:01 Thu Oct 5 2006 |
Agree about U-bolt glue distribution being problematic. I try to be really careful when placing them, buttering plenty of glue on to the legs before sliding them in. Do others think this is the right procedure? |
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tnd 23:05:56 Thu Oct 5 2006 |
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rogerb 23:56:00 Thu Oct 5 2006 |
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bundybear 00:26:48 Fri Oct 6 2006 |
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phm 08:27:37 Fri Oct 6 2006 |
A number of first bolts on climbs also show clear signs of rock crumbling away underneath the ring, quite similar to the first onsets of failure in the cyclic tests which I could observe in the lab. Factor 2 falls generate well in excess of the 15 kN mentioned above. And that's not taking into account a safety margin. "Buttering" the U-bolts was certainly practised for our tests, still we could not get the same degree of consistency in performance as for Ps. Fig 10 in my paper supports this. |
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bolter 09:54:37 Thu Oct 12 2006 |
Bolter |
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rogerb 02:13:26 Mon Oct 16 2006 |
A bit of research on glue would go a long way towards improving anchors. How about treating the hole with something that makes the drilled surface more glueaphilic? Or using a more rockaphilic glue. Or both. |
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rogerb 02:14:45 Mon Oct 16 2006 |
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Cragx 03:02:32 Mon Oct 16 2006 |
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Cragx 06:01:39 Mon Oct 16 2006 |
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Glenn_Short 09:20:07 Mon Oct 16 2006 |
G'day Martin! Gotta throw my 2c worth in here. The "buttering" of Us seems to have always been a dodgy practice in my books. (Your fall Martin??) All the manufacturers state that anchors should be twisted into the grout. I've spoken to a number of their engineers and they stressed that cleaning the hole, using threaded rod and twisting the anchor in are the main ingredients for success in setting anchors. Hammer in capsules are made to overcome the problem of not being able to twist some anchors into glue where spin-ins can't be used. The epoxy used is much runnier than injection glue, with the idea that it "runs" into the threads. Injection glue doesn't do this. According to the engineers I've spoken to this leads to quite a few failures in the field. Earlier this year I was at Ramset when two of their consultants were there after a second visit to a building site where anchors had been buttered and pushed into injection glued holes (because an attached plate prevented rotation). The anchors had failed, resulting in a wall collapsing, they eventually changed the design to allow rotation on one and used hammer ins on the other. Mind you, I also think that mostly the glue and anchors are so overkill that they'll be more than good enough for climbing. Still, being a devout coward I still ponder the ones that just might fail... (I am also pretty sure that the old carrots I've broken off with a ring spanner were much dodgier) Just butter em up really well boys, I'd hate to get hit in the head by a falling u bolt after I've hit the deck! Cheers Shorty |
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hatman 20:21:35 Mon Oct 16 2006 |
P type 10mm rings when twisted in and notched properly, look like the best type of anchor. U type 10mm anchors are very strong (strongest?), however every efort must be made to get full glue coverage. (don't forget that U's have two legs) trad anchors are super crap as they use no glue at all. Intersting to note that some of the comercial anchors didn't not do so well on the chart. So I will go on trusting both U bolts and rings as the chance of faliure of either is so low that I am not worried. And I will in the future use ring bolts on new routes, mainly because i have hundreds of the suckers. I have to point out that getting a "loose" fit in the holes for a U is nigh on imposible. Getting the holes paralel is not easy when hanging on jumars 10m off the ground. In fact the U bolts are sometimes used in overhanging teritory because of the tight fit, so they don't fall out before the glue cures. In my experience a tap on the U is needed most of the time to get it in the last bit of the way. |
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Breezey 00:20:20 Tue Oct 17 2006 |
breeze at bridgeport.com.au thanks |
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tnd 01:30:08 Tue Oct 17 2006 |
Back at work Glenn? I bolted that slab beside Jugantor at Mt Boyce. It's on Roger's web site now. Grade 19. All on U's!  I think we get away with slightly less than perfect practices because we don't generate the same loads on the bolts. An engineering fixture is permanently loaded (by having a nut tightened on the threads) with a force trying to pull the stud straight out. Our fixtures are often never loaded, and when they are the load tends to be more or less perpendicular to the shaft. I prefer to use epoxy rather than the cheaper acrylic because it is stronger and helps make up for not being able to rotate the U bolts. hatman, I've found that with Steve's commercial U's (with consistent dimensions) you can make up a drilling jig and get the holes pretty well perfect every time. |
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bundybear 02:09:12 Tue Oct 17 2006 |
Yeah. Me too - they are great. EZ to get parallel perfect holes all the time. |
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hatman 07:24:23 Tue Oct 17 2006 |
but me thinks its a moot point, they are both satisfactory for what we ask. |
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rogerb 02:42:18 Thu Oct 19 2006 |
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Glenn_Short 06:53:31 Fri Oct 20 2006 |
 Wasn't it a U bolt that hadn't been put in properly?? I figure the only certainty with my climbing anchors is that I WILL fall on them! (If I can get high enough on the route to clip them - with a long stick - or a lasso - or send Pam up) Gkneaghall, your pieces of art at Medlow and Boyce do indeed look like masterpieces. Hope to get on them soonish, shall speak glowingly about them if I don't get scared. And yep, back at work, thanks for reminding me. Cheers G. |
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phm 16:14:15 Fri Oct 27 2006 |
Roger, you are correct in pointing out that in Figure 10 some of the highest failure loads were measured for U bolts – but also some of the lowest. That means, that the spread of the results was found to be much greater for Us than for Ps. A common way of nominating a ‘design strength’ for a bolt would be to use a value one (or two) standard deviations conservatively away from the mean test result. And this value was found to be worse for Us than for Ps due to the greater spread of test results. Glenn, I agree, buttering is an inadequate method of ensuring mechanical bond between bolt and glue. With U-bolts twisting is not an option – hence my previous comments about Us. I also have a problem with capsule glue – namely with the fact that the quantity of glue is pre-determined. This is problematic in soft rock where hole diameters often differ significantly from the nominal diameter of the drill bit (or your tooth brush for that matter). Also, on steep climbs capsules are very difficult to use. Hatman, yes indeed, some of the commercial anchors are clearly not designed to give high strength in soft rock. I am not sure what you mean with trad anchors. Tnd, I disagree with your comments about engineering structures. An airbag in a car is only ever loaded once, but then the probability of the airbag working properly in this one case should be very high. Similar principles apply for climbing anchors in my opinion. Hatman again, yes two legs in a U are certainly an advantage – but only if both legs work properly. If one leg fails, the whole anchor fails. |
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Glenn_Short 07:47:30 Mon Oct 30 2006 |
Yeah, I know, capsules have their limits. That's why some of my routes have 6inch bolts cartridge glued in at the crux! Hey, I'm even contemplating putting in some rings! (Blame Giles) Have to start climbing harder so I can clip em. Keep the good info coming. Some of those bolts are starting to scare me and I don't have much fear threshhold left! Cheers G. |
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Miiiitch 06:51:30 Fri Dec 1 2006 |
-Drilling a hole in rock creates micro fractures in the rock around the hole..... when drilling two holes close together these fractures can link up and create a weakness in the rock. Has anyone ever told you to drill close (350mm) to a crack or another bolt ???? Have you ever wondered why bolts aren't drilled near cracks or other bolts???? U-bolts consist of two holes drilled much closer together. No one in their right mind would put two individual bolts that close together.... why is that? As rightly said by someone else before, if one of these legs fail... both fail... there is no redundancy with U's. It scares me when someone writes on a forum that U-bolts are the strongest anchors around.... I know you only mean well but the long term reliability of them is very questionable in my books. I make no claims at being any sort of expert.... actually i would be lucky if i could pass myself off as an idiot ...however... everywhere i look on the internet I see warnings about U bolts.... there seems to be many better alternatives... save your drill's battery power, take the time and put in a ring bolt... someone will be very grateful 10 years down the track. For a more trustworthy source try this guy: Glue - Inswww.climbargolis.com/Glue-inBoltDesign.htm if u scroll through the tech data its plain to see this guy knows his bolts, tests anchors up to 75Kn!!! When was the last time you belayed a elephant? Describes anchor failures as bolt, glue or rock related. To continue with my laymans ranting: it's nice to have pretty little graphs showing breaking points of different anchors, why dosent someone conduct these tests in sandstone instead of concrete (chossy weak sandstone aswell!).... i don't climb concrete... do you? Is concrete really a suitable substitute for sandstone (any rock for that matter?) just because they might break at similar forces? does concrete and sandstone behave the same when you drill big holes in them? Are they chemically similar?.... Not too completely rip up U's..... I think they make kickass rap anchors. Don't like them as lead anchors but i still use 'em (somethin always better than nothin) Peace. |
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shawkshaw 07:34:32 Fri Dec 1 2006 |
http://www.climbinganchors.com/Sandstone%20Bolt%20Testing.pdf U's are fine |
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hatman 20:39:52 Mon Dec 4 2006 |
I am also no expert, and before you go making spite full (although perhaps acurate) comments about the state of my mind I suggest you read my posts again and see that I was just trying to draw a conclusion from the data. I was not stating that I thought U's are the best option. In fact currently all i use is rings. Although in the past I have placed a few U's as lead anchors and taken many and repeated falls on some of them no problems. |
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Cragx 20:52:04 Mon Dec 4 2006 |
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