From simmon@daac.gsfc.nasa.gov Wed Feb 15 16:43:12 EDT 1995 Article: 28972 of rec.climbing Xref: dmssyd.syd.dms.CSIRO.AU rec.climbing:28972 Path: dmssyd.syd.dms.CSIRO.AU!metro!news.cs.su.oz.au!harbinger.cc.monash.edu.au!msunews!gmi!zombie.ncsc.mil!news.duke.edu!eff!news.umbc.edu!cs.umd.edu!newsfeed.gsfc.nasa.gov!usenet From: Rob Simmon Newsgroups: rec.climbing Subject: Re: Retiring Old Carabiners Date: 8 Feb 1995 17:28:25 GMT Organization: NASA Goddard Space Flight Center -- Greenbelt, Maryland USA Lines: 127 Message-ID: <3hauvp$h12@post.gsfc.nasa.gov> References: <3h621c$im1@newsbf02.news.aol.com> NNTP-Posting-Host: wrench.gsfc.nasa.gov liu@phoebus.sunnybrook.utoronto.ca (Godwin Liu) wrote: (stuff deleted) > > Breaking a Piece of Metal: > -------------------------- > > A metal is in danger of breaking, as I understand it, under several > conditions. If you take it beyond its ultimate tensile strength, it > can break right away. But up until that point, the stretching of a > metal is quite elastic.. i.e. after you stretch it, it returns to its > original shape, no worse the wear, UNLESS you are doing continuously > and it is warming up (the elastic properties may change with heat). > Secondly, if you fatigue something (like bending a bar, or paperclip, > back and forth several hundred times), it can break quite easily. > This does not appear to be the case for biners. To fatigue something, > you must take the metal beyond its elastic point, over and over again. > So you must regularly take your biner past 21kN or whatever the UIAA > standard is, several times, in, I gather, a fairly short period of > time to fatigue it. (I believe the standard is set on a metal's > breaking point, i.e. elastic limit). Also, I believe that the UIAA > lower limit is set by the fact that it is the maximum theoretical liit > of force that can be generated by a fall (fall factor 2). So you are > never going to get to those forces in the first place. > > If you do happen to take it beyond the elastic range, and it does NOT > break, then after it has cooled down, whatever, it goes BACK to being > elastic, granted that it may have been stretched into a shape which is > less strong. In this case, I would definitely say retire the guy, but > would this ever happen?? (considering my earlier point about the reason > for the UIAA limit) > > (more stuff deleted) NO! no, no, no, no, no! coming from a materials science background: stuff usually fails in two ways, ductile and brittle. ductile failure occurs when there's enough force inside the metal to move dislocations in the crystal structure through the lattice of atoms, resulting in deformation, and eventually breaking. (note that it doesn't have to break to fail, it just has to be deformed enough to be useless.) nylon, aluminum, and steel usually do this. brittle failure is where the material cracks or cleaves, usually along a specifc crystal plane or series of planes. alumina, glass, bricks, and rocks usually do this. now, plenty of things can cause something to fail before it has reached its maximum strength for a flawless material, like a stress concentration such as a nick, machining mark, or crack (which have the nasty property of weakening the material more the longer they get.) And (of course) there is no way to avoid these, so this is what causes failure in the real world most of the time. when things break they are following the path of least resistance, releasing energy the easiest way possible. an aside: ductile stuff generally extends pretty easily when you apply a load to it (ie not very stiff, low elastic modulus) but is pretty tough (won't break when shock loaded) this is because it's ductility tends to blunt cracks as they try to grow, reducing the stress concentration. as a general trend brittle stuff is stiffer than ductile stuff, but not as tough. There's no blunting of cracks, so the stress concentration increases with length. balancing stiffness (usually equated with "strength") with toughness is one of the things materials engineers try to do with their lives. now we come to the concept of fatigue, which is what causes most things to break in the real world. If you apply a stress to something it will always deform just a little bit. Initially this deformation reverses as soon as stress is relaxed. (elastic strain) Eventually, though, it becomes permanent. (plastic strain) during either of these strains, a crack can be intiated in the material. (Since a crystal lattice isn't perfect, there are stress concentrations that cause local strains that cause fracture or plastic deformation. as an extra bonus, lots of techniques used to strengthen a material increase the likelyhood of crack formation. after crack initiation, very small stresses can cause elongation, so only a FEW CYCLES, AT LOW STRESSES can cause failure. materials differ widely in their response to fatigue - steel, for instance, can be fatigued forever at a low enough stress level. (really, as close to forever as we can measure.) ALUMINUM DOES NOT! even at a very very small stress, aluminum will still break after enough cycles. there are other things involved, like corrosive environements and the like, but I won't go into it. (except to say that 'biners that have been near the ocean should be wiped with fresh water and dried, and retired sooner than other biners) in conclusion: retire a biner after a big fall onto a hard surface. (possible crack initiation.) retire a biner with obvious nicks or dings retire a biner after you've used it for "a while" (who knows how long a while. maybe someone should write black diamond.) don't fidget with your 'biner by clicking the gate, after all, that's the weakest link in the chain, and they do add up. any comments/clarifications are welcome a good intro to materials science or physical metallurgy book would provide good reading, and lots of equation and diagrams that clarify things quite a bit. -rob simmon simmon@daac.gsfc.nasa.gov From simmon@daac.gsfc.nasa.gov Wed Feb 15 16:56:08 EDT 1995 Article: 29073 of rec.climbing Xref: dmssyd.syd.dms.CSIRO.AU rec.climbing:29073 Path: dmssyd.syd.dms.CSIRO.AU!its.csiro.au!mel.dit.csiro.au!munnari.oz.au!uunet!gatech!newsfeed.pitt.edu!godot.cc.duq.edu!news.duke.edu!zombie.ncsc.mil!cs.umd.edu!newsfeed.gsfc.nasa.gov!usenet From: Rob Simmon Newsgroups: rec.climbing Subject: Re: Failure of Aluminum (was Retiring Old Carabiners) Date: 10 Feb 1995 15:07:50 GMT Organization: NASA Goddard Space Flight Center -- Greenbelt, Maryland USA Lines: 171 Message-ID: <3hfvg6$23v@post.gsfc.nasa.gov> References: <3h621c$im1@newsbf02.news.aol.com> <3hauvp$h12@post.gsfc.nasa.gov> <3hb9vo$849@mozo.cc.purdue.edu> NNTP-Posting-Host: wrench.gsfc.nasa.gov Clarifications & additions to the discussions about breaking biners: me >: stuff usually fails in two ways, ductile and brittle. >: ductile failure occurs when there's enough force inside the metal >: to move dislocations in the crystal structure through the lattice >: of atoms, resulting in deformation, and eventually breaking. (note >: that it doesn't have to break to fail, it just has to be deformed >: enough to be useless.) >: nylon, aluminum, and steel usually do this. Godwin Liu: >So, as I understand it, you mean to say that aluminum, when it fails, >fails by means of ductile fracture (as opposed to brittle fracture). >The process you describe, is, I believe what I was trying to describe: *usually* It is possible for aluminum to fracture in a brittle mode, as in fatigue. Godwin Liu: >Let me elaborate on my earlier, admittedly simplified, explanation: >Several stages of a metal's response to stress: >1. A metal will first stretch elastically (i.e. stress leads to stretching, >and when stress is removed, metal returns to original shape.) >line 45 >2. The metal will then move into a plastic stretch (i.e. stress leads >to deformation.. when stress is removed, metal has been permanently >deformed) >3. As the metal stretches plastically, its strength has been changed, >and will lead to breakage. (ultimate tensile strength). >What I meant to say was that if you stay within region #1, you have >not "damaged" the biner (see important notes on fatigue below, >however). the 'ductile' fracture you describe sounds to me like what >happens when you go through regions #2, and #3. Yup. another rough definition of brittle vs. ductile fracture is that brittle occurs in the elastic range, and ductile occurs in the plastic range. The note on fatigue is VERY important, so we can't say "no worse for the wear." on to fatigue ... Godwin Liu: >Rob, can you give us an indication on the size of crack that matters? >Are we talking about microfractures? or large ones which can be >identified by visual inspection? Nope, I can't give you specific crack lengths. Wish I could, though. There is a material property, KIC (kay *subscript* one cee) that relates crack length to applied stress that will cause growth, but it's tricky. It's based on energy arguments - energy of new surface created vs. energy released by reduction of stress. (actually that might be GIC.) Microfractures and internal fractures, so visual inspection isn't infallible. Godwin again: >I find it hard to believe that regular aluminum bar stock develops >significant fractures under conditions of top roping, even as the >anchor biners. well, it does. Aluminum, even under infinitesimal stresses, will eventually fail by fatigue. but we're talking A LOT of cycles. me: >: after crack initiation, very small stresses can cause elongation, >: so only a FEW CYCLES, AT LOW STRESSES can cause failure. >: materials differ widely in their response to fatigue - >: steel, for instance, can be fatigued forever at a low enough stress >: level. (really, as close to forever as we can measure.) Godwin: >there appears to be something of a double negative here. But I >am assuming that you mean that steel can be cycled at low stress >WITH these cracks, without fracture. I should have been more clear. If a material is put under severe stresses, cracks will develop that can then be propagated by low stress. Steel and Aluminum both will fail under these conditions. SO - a dropped biner should be retired. However, if the stress is ALWAYS low, (below the 'fatigue threshold') Steel will not suffer a fatigue failure. Aluminum does not have a fatigue threshold, so repeated stressing, no matter how low, will lead to fracture. SO - an "old" biner should be retired. certainly more than three months, certainly less than 25 years. (that narrows it down, doesn't it?) Godwin: >Conclusions on Biner Damage due to Fatigue: ------------------------------------------- >Even elastic strain can cause the initiation of small cracks, which >^^^^^^^^^^^^^^^^^^^ >weaken the material. In the case of aluminum, further stresses after >this crack intiation, cycled, can cause the aluminum to break. Thus, >theoretically, a biner CAN break under regular conditions of climbing, if >it is regularly put under conditions of load (because of fatigue). >SO, since it is difficult to evaluate these conditions, it may be >prudent to change your biners after repeated conditions of loading. YUP. me: >: there are other things involved, like corrosive environements and >: the like, but I won't go into it. (except to say that 'biners that >: have been near the ocean should be wiped with fresh water and dried, >: and retired sooner than other biners) Godwin: :I am still unclear on this matter. I thought that aluminum was quite :resistant to corrosion. In that, any newly exposed aluminum quickly :oxidized to a very thin layer of aluminum oxide, which does not have :nearly the same weakening effects as, say, rust, iron oxide. Aluminum is quite resistant to corrosion - in air, without the presence of chlorine. However, if some sea salt manages to get into a surface flaw or under the pin that holds the gate on - LOOKOUT! Corrosion may appear as a rough white bumpy area on the aluminum. This will severely weaken the 'biner, and get worse with time. Godwin: >Final Conclusions >------------------ >As my previous ones, but with: >Rob Simmon: >: retire a biner after you've used it for "a while" (who knows how >: long a while. maybe someone should write black diamond.) >But let's also be sensible. According to other posts in this thread, >no one appears to have ever heard of a modern biner design actually >breaking. Which gives us some confidence. Let's just not overdo it >with the confidence. I agree completely. I do want people to know, however, that the gear is not infallible forever. It's REAL close to begin with, but time takes its toll ... this is probably on the FAQ, but what are the numbers for BD, MSR, Lowe, Metolious, etc. etc.? especially the R & D departments. BD at least has a materials engineer on staff, who wrote in Climbing magazine about cracking of SLCDs ... Anyone on staff who reads this stuff who would like to reply? -rob simmon simmon@daac.gsfc.nasa.gov From simmon@daac.gsfc.nasa.gov Wed Feb 15 16:56:40 EDT 1995 Article: 29095 of rec.climbing Xref: dmssyd.syd.dms.CSIRO.AU rec.climbing:29095 Path: dmssyd.syd.dms.CSIRO.AU!news.dmpe.CSIRO.AU!mel.dit.csiro.au!munnari.oz.au!uunet!gatech!howland.reston.ans.net!agate!news.duke.edu!zombie.ncsc.mil!cs.umd.edu!newsfeed.gsfc.nasa.gov!usenet From: Rob Simmon Newsgroups: rec.climbing Subject: Re: Failure of Aluminum (was Retiring Old Carabiners) Date: 10 Feb 1995 15:16:47 GMT Organization: NASA Goddard Space Flight Center -- Greenbelt, Maryland USA Lines: 51 Message-ID: <3hg00v$23v@post.gsfc.nasa.gov> References: <3h621c$im1@newsbf02.news.aol.com> <3hauvp$h12@post.gsfc.nasa.gov> <3hb9vo$849@mozo.cc.purdue.edu> NNTP-Posting-Host: wrench.gsfc.nasa.gov bubb@tools.ecn.purdue.edu (Anthony R Bubb) wrote: > > True, look at it this way. Material deteriorate with cyclic loads. Steel > stops deteriorating after about 1,000,000 cycles. Aluminum just keeps on > going. I am not saying that you will ever load the material 1,000,000 > times though. That's probably why they use AL... no reason to believe > fatigue failure is a whole lot lower than steel, other than the the str is > lower to start with. AL and Steel do have about the same str to weight > ratios though. actually, the fatigue strength of Steel and Aluminum may be VERY different. In fact, the fatigue properties of two different types of the same metal could be very different, as well. It really has little to do with the yield strength or elastic modulous, and more to do with microstructure. (No, I don't have any numbers, my books are boxed up sitting under my old desk at CMU.) > The fatigue failure criterion used in design by mechanical enginerds > for withstanding cyclic loads (frequency effects not-withstanding) > is generally the Goodman Equation. If I recall correctly (and I don't > have a text handy to check) it states that a material will fail > when: > {(a/Syt + o/Sut) = 1.0/n} > (I might be mixing up the placement of Syt and Sut...) > > Where Syt = Yield str, Sut = ultimate Str, a= 1/2 peak-to peak amplitude > of load cycle, o = load average, and n = # of cycles. I don't seem to recall > the time-space between loads being relivant to this criterion. > rough guesstimate. > > It would take a LONG time to load the biner by a lead-fall 100 times > let alone a million. One can use VonMieses Criterion and the > Goodman Equation to predict how many times a biner would withstand > a particular load. > you only need ONE lead fall to start a crack, after that a top-roped fall could make it grow, eventually leading to failure. again, I encourage anyone who's really interested to read up on it, or at least send me a message in about a month when I get my textbooks back, and I'll be more specific. -rob simmon simmon@daac.gsfc.nasa.gov From eboltz@acoustica.mrd.bldrdoc.gov Wed Feb 15 16:57:48 EDT 1995 Article: 29158 of rec.climbing Xref: dmssyd.syd.dms.CSIRO.AU rec.climbing:29158 Newsgroups: rec.climbing Path: dmssyd.syd.dms.CSIRO.AU!metro!munnari.oz.au!uunet!dove.nist.gov!bldrdoc.gov!news From: eboltz@nist.gov (Eric S. Boltz) Subject: Re: Retiring Old Carabiners Message-ID: Sender: news@bldrdoc.gov Reply-To: eboltz@acoustica.mrd.bldrdoc.gov Organization: National Institute of Standards and Technology References: <3hauvp$h12@post.gsfc.nasa.gov> Date: Fri, 10 Feb 1995 17:04:37 GMT Lines: 33 Rob Simmon writes > ALUMINUM DOES NOT! even at a very very small stress, aluminum will > still break after enough cycles. As someone who has done F-testing of Al alloys, steels and composites I'd point out that the number of cycles, for small stresses, is in the tens to hundreds of millions for Al. > retire a biner after you've used it for "a while" (who knows how > long a while. maybe someone should write black diamond.) If you're loading it (let's say it's your TR locker(s) and you use them 4x/week. Let's also say each use is equivalent to 50 cycles. That gives you 10+ years till 100k cycles (a *very* safe # IMHO). For QD biners with no falls I'd go quite a bit longer. > don't fidget with your 'biner by clicking the gate, after all, that's > the weakest link in the chain, and they do add up. Huh? I guess if you're snapping it you could call that a cycle...this is why I buy biners with high open-gate strength. I would, however, retire long-dropped biners and any with visible damage that isn't just the tiny scratches one gets from the biner tapping the rock on the end of a sling. -E -- Eric S. Boltz Materials Research Engineer My views, opinions and statements in no way reflect those of the U.S. Gov't, the U.S. Department of Commerce or NIST. From simmon@eeel.nist.gov Wed Feb 15 17:01:07 EDT 1995 Article: 29028 of rec.climbing Xref: dmssyd.syd.dms.CSIRO.AU rec.climbing:29028 Path: dmssyd.syd.dms.CSIRO.AU!its.csiro.au!mel.dit.csiro.au!munnari.oz.au!spool.mu.edu!howland.reston.ans.net!news.sprintlink.net!uunet!dove.nist.gov!simmon From: simmon@eeel.nist.gov (Eric Simmon) Newsgroups: rec.climbing Subject: Re: Retiring Old Carabiners Date: 9 Feb 95 15:32:43 GMT Organization: NIST Lines: 76 Message-ID: References: <3h621c$im1@newsbf02.news.aol.com> <3havr7$h12@post.gsfc.nasa.gov> NNTP-Posting-Host: maxwell.eeel.nist.gov liu@phoebus.sunnybrook.utoronto.ca (Godwin Liu) writes: >Sorry to clog up this thread, but I must respond: >I wrote: >: > airplanes (which use the same grade aluminum), are not 'retired' every >: > three months even though they are used quite a bit more regularly than >: > biners. They also experience greater stresses, I believe. >Rob Simmon: >: one thing I forgot to add in my previouis post: >: remember that hawaiian airliner that lost a big chunk of fueselage >: in mid flight? that was caused directly by FATIGUE FAILURE OF >: ALUMINUM. it went something like this: >: mechanic inspects airplane >: mechanic sees crack in aluminum skin >: mechanic knows crack is not good >: mechanic paints over crack >: plane flies >: crack grows >: roof flies off >: stewardess gets sucked out of airplane, falls the height of 10 >: El Caps, goes splat. >I did not mean to suggest that airplanes never experience failure. >Nor bridges. We have seen plenty of them fail. I was just suggesting >that it would be ludicrous to expect airplanes to be changed every >three months, due to non-confidence in aircraft aluminum--EVEN THOUGH >they experience much higher stresses than we see in climbing equipment's >day to day life. In fact certain parts of airplanes ARE replaced on a set replacement schedule well before they exhibit ANY visible signs of wear. This is due to A) the fatigue properties of aluminum B) the dire consequences of an aircraft part failing. Just look at any aircraft maintenance schedule. Another information source is Carrol Smith's books on race car prep (which discusses fatigue and part replacement in great detail, after all, if a part on a race car fails, the consequences can be dire as well). How does this apply to biners? Well, biners should be retired after some set amount of use, regardless of visible wear. However, this might be a very long time. Biners are heavily over designed, so 10 years of heavy use might not be unreasonable to expect. The biner manufacturers should have hard data on when and how the biners fail. With this information, it would be easier to determine when to retire a carabiner. One other point. There are several sitiations where it is appropriate to replace a biner prematurely. 1) carabiner is dropped from moderate to substantial height. 2) carabiner is subjected to lead fall. 3) carabiner shows visible signs of wear (cracks, nicks, etc.) 4) carabiner is oxidized (usually due to exposure to saltwater) I guess what it comes down to is: Replace your carabiners frequently if you are excessively anal, or have a lot of money. Otherwise, use common sense, inspect your biners frequently and DON'T EXPECT THEM TO LAST FOREVER. -Eric simmon@eeel.nist.gov From wheenan@wizvax.com Wed Feb 15 17:02:21 EDT 1995 Article: 29133 of rec.climbing Xref: dmssyd.syd.dms.CSIRO.AU rec.climbing:29133 Newsgroups: rec.climbing Path: dmssyd.syd.dms.CSIRO.AU!news.dmpe.CSIRO.AU!mel.dit.csiro.au!munnari.oz.au!uunet!news.wizvax.com!wheenan!wheenan From: wheenan@wizvax.com (Walt Heenan) Subject: Re: Retiring Old Carabiners X-Newsreader: Trumpet for Windows [Version 1.0 Rev B] Sender: news@news.wizvax.com (news) Organization: Strategic Systems Lines: 22 Message-ID: References: <3h621c$im1@newsbf02.news.aol.com> <3h6jsu$jpe@mozo.cc.purdue.edu> <3hdd66$4cn0@rohcs1.uhc.com> X-Nntp-Posting-Host: heenan.wizvax.com Date: Fri, 10 Feb 1995 01:54:12 GMT In article <3hdd66$4cn0@rohcs1.uhc.com> kkokal@rohcs1.uhc.com (Kevin Kokal) writes: <<>> >While at Purdue, I did a research project on the failure characteristics >of the Chouinard Light D's, specifically the ones experiencing the >hairline cracks around the gate pin. <<>> >The cracked biners consistently pulled apart at half the rated strength. I've got a ton of old Chouinard (and not so old BD) light D's. Does anyone know the answers to the following: A. Do the BD light D's have the same problem? B. Are the cracks visible to naked eye inspection? C. Should I just retire'em all? Awaiting replies with big plans and sweaty palms. From Clyde_Soles@nile.com Fri Feb 17 13:16:42 EDT 1995 Article: 29059 of rec.climbing Xref: dmssyd.syd.dms.CSIRO.AU rec.climbing:29059 Subject: Re: Failure of Aluminum (was Retiring Old Carabine Date: Fri, 10 Feb 95 09:50:35 MDT Message-ID: <00189B6D.fc@nile.com> X-FirstClass: 0x59F8 0x00189B6D 0x000F4B1A 0x000F4B1A 0x0000 Newsgroups: rec.climbing Path: dmssyd.syd.dms.CSIRO.AU!metro!news.cs.su.oz.au!harbinger.cc.monash.edu.au!msunews!gmi!zombie.ncsc.mil!news.duke.edu!news-feed-1.peachnet.edu!insosf1.infonet.net!solaris.cc.vt.edu!swiss.ans.net!potogold.rmii.com!nilenet!Clyde_Soles From: Clyde_Soles@nile.com (Clyde Soles) Organization: Dimensions Online X-HoloGate: 1.1.2b3 (Unregistered Copy) Lines: 9 In message ID <3hb9vo$849@mozo.cc.purdue.edu> on 2/8/95, Anthony R Bubb wrote: > Well, that 21kn is a FAILURE str, defined as catastrophic, I believe. Other > than that, you were on the right track, but had a few things a bit mixed up. Not quite. This is a pass/fail test where the biner must not break at 22 kN with no deformation that affects operation at 14 kN. Any other claim is not tested or endorsed by the UIAA. From douglas.moore@mgmtsys.com Thu Mar 2 15:29:07 EDT 1995 Article: 29291 of rec.climbing Xref: dmssyd.syd.dms.CSIRO.AU rec.climbing:29291 Path: dmssyd.syd.dms.CSIRO.AU!its.csiro.au!mel.dit.csiro.au!merlin!harbinger.cc.monash.edu.au!msunews!agate!howland.reston.ans.net!math.ohio-state.edu!magnus.acs.ohio-state.edu!csn!cateye!douglas.moore Distribution: world Newsgroups: rec.climbing Subject: Re: Stuck carabiners From: douglas.moore@mgmtsys.com (Douglas Moore) Message-ID: <90.11255.645@mgmtsys.com> References: <3hdcb6$9eu@mozo.cc.purdue.edu> Date: Sun, 12 Feb 1995 18:02:00 -0500 Organization: SVIS 304-592-2682 800-SOFT-VAL Lines: 13 AB| Alot of times this can happen when the bire is weighted, and the | gate disurbed... the biner is "stretched" in tension, and then the | gate can be screwed up further. Once unweighted, it is "set". This can definitely happen and causes alot of problems. Some manufacturers make gate locking carabiners where this can not happen. Now the problem with dirt in the thread while caving is a hard one to get around. I've had some lock to the point that hammers and vice grips won't budge the thread. /\+/\ Douglas Moore (NSS 33064) /\+/\ Karst Sports: Caving, Climbing, & Rescue (304) 592-2600 e-mail: karst.sports@mgmtsys.com for information and price list From lambert@uni2a.unige.ch Fri Mar 3 13:50:46 EDT 1995 Article: 29320 of rec.climbing Xref: dmssyd.syd.dms.CSIRO.AU rec.climbing:29320 Newsgroups: rec.climbing Path: dmssyd.syd.dms.CSIRO.AU!its.csiro.au!mel.dit.csiro.au!merlin!harbinger.cc.monash.edu.au!msunews!uwm.edu!math.ohio-state.edu!jussieu.fr!univ-lyon1.fr!swidir.switch.ch!news.unige.ch!ugun2a!lambert From: lambert@uni2a.unige.ch Subject: Re: Retiring Old Carabiners Message-ID: <1995Feb15.183639.1@ugun2a> Lines: 23 Sender: usenet@news.unige.ch Organization: University of Geneva, Switzerland References: <3h621c$im1@newsbf02.news.aol.com> <3h6jsu$jpe@mozo.cc.purdue.edu> <3ha3pp$rk3@src-news.pa.dec.com> Date: Wed, 15 Feb 1995 16:36:39 GMT In article <3ha3pp$rk3@src-news.pa.dec.com>, murray@src.dec.com (Hal Murray) writes: > An interesting thread... > > If you don't trust your toys, retire them. When you do, please send them to me. When > I get a chance, I'll break them and tell everybody how strong they were. Or get one > of your ME friends at a testing lab to do it. (Sounds like a good school project.) > > Years ago, we broke an old biner. Early Chouinard, I think. It went at roughly rated > strength. Just one sample. It was probably 15 years old. Moderate use. > I've broken lots of biners and runner (most of them new) on test equipment. I also broke two old Eiger ovals. The things had been red anodized, but were entirely silver when I broke them. They had both been dropped from great height (perhaps more than once), and one had been in use as a rappel anchor for a long time and had noticeable grooves in the apexes. Both broke at the rated strenght of 3,000 pounds. FYI. It's true, tied slings break at lower strengths than sewn runners, fisherman's knots are weaker than water knots in tubular webbing. Tom