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Partner slacklinejoe


Apr 28, 2008, 12:18 PM
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Re: [petsfed] SLACKLINE FAILURE! ! ! [In reply to]
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Do keep in mind, I use techniques that aren't widely adopted, so it's not likely you'll see them used elsewhere. I generally dislike using carabiners in my systems due to the frictions involved and the risk they might end up in my climbing pile by accident (yes, you can mark them, but stuff happens).

If you are using a technique of tensioning the line that essentially uses a line grab of sorts (prussic or cam buckle etc) to connect the tensioning system to the main line it frees you up to use different techniques to secure the main line to the tree and easily remove the tensioning system afterwards.

If your sling accomodates a cam buckle or harness buckle you can pull the line tight, then secure the main line to said buckle, then release and remove the tensioning system.

Harness buckles require a bit more fiddling (not much) to get double backed on the main line and are pretty much bomber as they aren't likely to damage the webbing or break due to their strength (4,000lbs).

Cam buckles offer more convenience since you basically pull the line tight, give the slack coming out of the cam buckle a quick yank to secure it and your good to start removing your tensioning system. The trade off is cam buckles do have teeth that can leave marks on the line in some situations but it is usually very mild. They are also not usually as strong as full grade harness buckles but they are usually strong enough for any lowline use (2,200 lbs or 3,300lbs). Either way, it's only a couple bucks to test them out and if rigged properly they should produce zero twists in the system.

The photo below will give you an idea of the slings and how it adapts to the line.

This is what I use as a rodeo line but you can set up the tensioning system on a seperate sling allowing you to use whatever you want (pulleys, carabiners, ratchets, a truck) and then easily remove the tensioning system.


(This post was edited by slacklinejoe on Apr 28, 2008, 12:24 PM)


majid_sabet


Apr 28, 2008, 12:41 PM
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Re: [slacklinejoe] SLACKLINE FAILURE! ! ! [In reply to]
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Let me ask a question from our slaking experts;

if you have 200 lbs slacking dude standing in the middle of a super tight 30 feet long piece of webbing with a MA ranging from 5:1 to 9:1 (whatever you normally use).

How much forces do you think your anchors are getting?





(This post was edited by majid_sabet on Apr 28, 2008, 12:43 PM)


Partner slacklinejoe


Apr 28, 2008, 12:45 PM
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Re: [majid_sabet] SLACKLINE FAILURE! ! ! [In reply to]
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majid_sabet wrote:
How much forces do you think your anchors are getting?
With your diagram - infinity.
You missed one of the parameters - sag - how much the line dips in the middle with the slacker standing on it.

If you assume it's a nice and tight line with 1' of sag in the middle the line load would be 1503.33lbs of tension. 1.5' would be 1000lbs. It would be the same load regardless of tensioning system and "perceived" pre-tension amount - the sag tells the real story.

Slackline Force Calculator


(This post was edited by slacklinejoe on Apr 28, 2008, 12:47 PM)


petsfed


Apr 28, 2008, 1:32 PM
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Re: [majid_sabet] SLACKLINE FAILURE! ! ! [In reply to]
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majid_sabet wrote:
Let me ask a question from our slaking experts;

if you have 200 lbs slacking dude standing in the middle of a super tight 30 feet long piece of webbing with a MA ranging from 5:1 to 9:1 (whatever you normally use).

How much forces do you think your anchors are getting?


[IMG]http://a.imagehost.org/0221/web.jpg[/IMG]

I don't feel like doing the integrals neccesary to tell you, but its not a simple answer. The slackline force calculator doesn't really answer it completely either, since it is actually a very complicated system. You've got what works out to be a semi-damped harmonic oscillator in 3 dimensions, with different damping terms in each direction, as well as a green's-function-style force term from the person on the line. I've been meaning to assemble a general equation based on a variety of parameters to find out, but it is so complicated that such a general equation would be a worthwhile master's thesis.


majid_sabet


Apr 28, 2008, 2:06 PM
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Re: [petsfed] SLACKLINE FAILURE! ! ! [In reply to]
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petsfed wrote:
majid_sabet wrote:
Let me ask a question from our slaking experts;

if you have 200 lbs slacking dude standing in the middle of a super tight 30 feet long piece of webbing with a MA ranging from 5:1 to 9:1 (whatever you normally use).

How much forces do you think your anchors are getting?


[IMG]http://a.imagehost.org/0221/web.jpg[/IMG]

I don't feel like doing the integrals neccesary to tell you, but its not a simple answer. The slackline force calculator doesn't really answer it completely either, since it is actually a very complicated system. You've got what works out to be a semi-damped harmonic oscillator in 3 dimensions, with different damping terms in each direction, as well as a green's-function-style force term from the person on the line. I've been meaning to assemble a general equation based on a variety of parameters to find out, but it is so complicated that such a general equation would be a worthwhile master's thesis.


In reply to:
The mechanical advantage has no impact on the breaking strength of the line, realistically. Its not like you'd load the anchor with only 250+ or so if you used a 1:1 system, its the same no matter what tightening system you use. I use an (ideally) 9:1 system and we've had 300+ pounders on the line without failure. The key was that no gates ever opened up and we had a very simple tie off that stretched a bit.

A single person pulling on a 3:1 MA could apply 150 lbs of tension on an anchor with one hand. Same person with a 9:1 MA can put over 450 lbs of tension. A 200 ponder standing in the middle of 30 feet of webbing under 9:1 tension can put great deal of stress on biners if not carefully rigged.


(This post was edited by majid_sabet on Apr 28, 2008, 2:33 PM)


ja1484


Apr 28, 2008, 2:39 PM
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Re: [jt512] SLACKLINE FAILURE! ! ! [In reply to]
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jt512 wrote:
funkystumpy wrote:
jt512 wrote:
chalkfree wrote:
At what point did we all decide not to play nice?

When some hypersensitive idiot couldn't recognize a joke.

Jay

I apologize for not recognizing some joke that my sense of humor/knowledge base didn't pick up on, but there was no need to call me a hypersensitive idiot. I have seen far too many posts by you and jt512, where you slam someone for not much reason at all or for something that you two could have very easily ignored.

Are you sure there's no reason to call you a hypersensitive idiot?

Jay





Partner slacklinejoe


Apr 28, 2008, 3:05 PM
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Re: [majid_sabet] SLACKLINE FAILURE! ! ! [In reply to]
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majid,

With all due respect, your questions (and your answers) show you don't slackline much.

Most of these folks using 3:1's are using carabiners. The effective MA is actually only 1.75:1 to 1.5:1 due to friction. Even the 9:1 setups using multipliers often only yield 6.1:1 effective MA or less. Generally speaking you have to get quite a few brawn lads to generate a dangerously high load unless you are resorting to methods such as using vehicles to tighten things up.

The elasticitiy effect of webbing under tension greater than 400lbs allows a shock dampening effect that basically saves our buns by spreading the force of dynamic moves over a longer time and thus reducing peak forces in the system. That allows you to calculate for a static system and a lot of the time your pre-tension load will be very close to the load that you have when on it when walking - it's wierd but it's been tested over and over.

Also, the whole sag thing I mentioned is critical. Not just as a load thing but for practical walking applications. If you get a line too tight it's basically no fun to walk, it's twitchy and violent. That and the line's elasticity makes it very difficult to get the line tighter than a certain load as it just keeps stretching when the loads get high, much like a climbing rope - it'll reach plastic deformation and stretch pretty massive amounts before you'll actually break it.


petsfed


Apr 28, 2008, 3:33 PM
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Re: [majid_sabet] SLACKLINE FAILURE! ! ! [In reply to]
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majid_sabet wrote:
petsfed wrote:
majid_sabet wrote:
Let me ask a question from our slaking experts;

if you have 200 lbs slacking dude standing in the middle of a super tight 30 feet long piece of webbing with a MA ranging from 5:1 to 9:1 (whatever you normally use).

How much forces do you think your anchors are getting?


[IMG]http://a.imagehost.org/0221/web.jpg[/IMG]

I don't feel like doing the integrals neccesary to tell you, but its not a simple answer. The slackline force calculator doesn't really answer it completely either, since it is actually a very complicated system. You've got what works out to be a semi-damped harmonic oscillator in 3 dimensions, with different damping terms in each direction, as well as a green's-function-style force term from the person on the line. I've been meaning to assemble a general equation based on a variety of parameters to find out, but it is so complicated that such a general equation would be a worthwhile master's thesis.


In reply to:
The mechanical advantage has no impact on the breaking strength of the line, realistically. Its not like you'd load the anchor with only 250+ or so if you used a 1:1 system, its the same no matter what tightening system you use. I use an (ideally) 9:1 system and we've had 300+ pounders on the line without failure. The key was that no gates ever opened up and we had a very simple tie off that stretched a bit.

A single person pulling on a 3:1 MA could apply 150 lbs of tension on an anchor with one hand. Same person with a 9:1 MA can put over 450 lbs of tension. A 200 ponder standing in the middle of 30 feet of webbing under 9:1 tension can put great deal of stress on biners if not carefully rigged.

I must be brief, since I have to go to work shortly.

The tension of the line is not dependent on what system you use to pull it tight, just how tight you managed to pull it. The sag of the line (as joe put it) is described by the hyperbolic cosine of a term proportional to the inverse of the horizontal tension. Put most simply, its a hyperbolic function of the inverse of the force pulling on either tree. In other words, a line of a given tension will hang the same whether there's a tightening system pulling it tight, or if its just statically anchored at either end.

Imagine a spring scale attached to one end of a string that has been tied to the floor. As you pull up on the string, the spring scale will show how much force you're pulling on the string with. Suppose you push on the string, perpendicular to its length with some fixed deflection force. The measurement on the scale will change some noticeable amount. Now imagine that you rig something similar, but you use a tightening system (say a 3:1) to get the same force measurement on the spring scale, then you apply the same deflection force. The change in measurement on the spring scale will be the same.

To sum up, no matter how you tighten the line, if its the same tension, a given deflection force will increase the line tension by the same amount. If this were not the case, hauling systems would not work because increasing mechanical advantage would quickly blow out anchors.

Saying a system has a 3:1 mechanical advantage means two things: first, in the absence of friction, it means that the force that you pull on the rope with is multiplied by three. Second, it means that for every 3 feet of rope you pull out of the system, it pulls only 1 foot out of the line. Since work is force times distance, you can see that it saves no work to do it this way. It does decrease the force necessary to accomplish any given task though, which is significant.


crazy_fingers84


Apr 28, 2008, 3:39 PM
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  i definitely agree with the notion that the mechanical advantage of a pulley system is drastically reduced as a result of friction. the typical way to overcome this problem is to get more people to pull on the line. i have set up lines before with my truck and had them so tight that i have broken tubular webbing (never completely, it only tore about half way through). when i was done slackining i took the line down i saw what had happened. since that day i have been very cautious of my slackline failing. when i my friend told me what happened to her, it hit close to home. . .
thankfully nobody was hurt in this instance, but i think a lot of people out there can take something from this situation.
i guess when there is no slack in the webbingg, it is no longer a slackline. . . it requires a different rigging then a conventional slackline. i dont understand how we can predict the amount of force being put on a slackline with out evaluating each line independently. it seems like there are an infinite number of variables that could drastically change those calculations depending on how the rigger set the system up. but i am not a math person, so i will leave it to those guys to argue logistics.
in the case of this accident the line was abnormally tight. it would have helped to do a lot of things different in this situation. the two red flags here are the bootied biner, and the ultimate reason for failure being an open gate. CHECK YOUR GATES FOLKS! weird things happen in the real world, gates open. . . whatever. fuck buying steel carabiners for a lowline, that is overkill. i do see the utility in purchasing a locker for this reason.
usually when i set my line up, i pull it tight by myself. this how i like it, a dynamic line with a lot of movement. . . which is what i think makes slacklining fun anyway. and to answer the question of why participate in a lame sport like slackling, well i do it because it forces me to concentrate very intensely on the activity at hand. this is something i am always striving for when i am climbing, and it is refreshing to chase this feeling in a new venue. . .


majid_sabet


Apr 28, 2008, 4:22 PM
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Re: [crazy_fingers84] SLACKLINE FAILURE! ! ! [In reply to]
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crazy_fingers84 wrote:
i definitely agree with the notion that the mechanical advantage of a pulley system is drastically reduced as a result of friction. the typical way to overcome this problem is to get more people to pull on the line. i have set up lines before with my truck and had them so tight that i have broken tubular webbing (never completely, it only tore about half way through). when i was done slackining i took the line down i saw what had happened. since that day i have been very cautious of my slackline failing. when i my friend told me what happened to her, it hit close to home. . .
thankfully nobody was hurt in this instance, but i think a lot of people out there can take something from this situation.
i guess when there is no slack in the webbingg, it is no longer a slackline. . . it requires a different rigging then a conventional slackline. i dont understand how we can predict the amount of force being put on a slackline with out evaluating each line independently. it seems like there are an infinite number of variables that could drastically change those calculations depending on how the rigger set the system up. but i am not a math person, so i will leave it to those guys to argue logistics.
in the case of this accident the line was abnormally tight. it would have helped to do a lot of things different in this situation. the two red flags here are the bootied biner, and the ultimate reason for failure being an open gate. CHECK YOUR GATES FOLKS! weird things happen in the real world, gates open. . . whatever. fuck buying steel carabiners for a lowline, that is overkill. i do see the utility in purchasing a locker for this reason.
usually when i set my line up, i pull it tight by myself. this how i like it, a dynamic line with a lot of movement. . . which is what i think makes slacklining fun anyway. and to answer the question of why participate in a lame sport like slackling, well i do it because it forces me to concentrate very intensely on the activity at hand. this is something i am always striving for when i am climbing, and it is refreshing to chase this feeling in a new venue. . .


it is funny that you guys thank god that no one got hurt but if the same person fell and became paralyzed, then all of you were back in here with photos and diagrams, physic and math calculation with KN poping from every angle analyzing the fuc* out of every pieces of gear involved with the incident.

My suggestion is that you slackers should analyze your rigging behaviors and come up with a safety guidelines for you own rig. Seriously think about the forces and failures before someone get hurt.


(This post was edited by majid_sabet on Apr 28, 2008, 4:25 PM)


shaun_the_conqueror


Apr 28, 2008, 4:24 PM
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I would be very skeptical of any of the numbers that little force generator puts out and I wouldn't suggest relying on them, especially if you're going to rig a highline. Mainly because I do not know how the calculation is being made, what variables are involved, and who the person is who came up with it and whether or not they are credible in the first place.

One thing I want to point out for anyone who is rigging a primitive system, is that you can easily avoid flying gear in the case that you have biner failure, anchor failure, or pulley failure. In this particular case the easiest thing one could have done to prevent a flying biner, was to tie the loose end of the slackline itself to the anchor. All tension would have been lost, hoewever there would not have been any flying gear. The same thing could also be done if you were to have a pulley in place of the primitive system.

Generally slackline anchor rigging relies on tri-loading a carabiner on both ends. This isn't really a good idea since carabiners aren't designed for this. 2 solutions which still involve tri-loading to prevent anchor failure would be, decrease the angle created when tri-loading a biner, and maybe use a steel carabiner as others have suggested.

My personal solution to prevent tri-loading is this.


I use 11mm static rope threaded through 1" webbing. I always tie off the slackline to the anchor incase something in the pulley breaks or a biner decides its had its final day. A couple things that I've changed, is that there is 2 rap rings on each anchor, and I use an SBI pulley block instead of the primitive system or shitty ass ratchets that are way more prone to failure then the primitive system.

Reasons for using this:
1) Ultimate adjustable tree slings... just make your anchor 10ft long.
2) Anchor is now bomber as hell. You can replace the aluminum biners with steel if you wish.
3) The line is ALWAYS perfectly flat if you use line lockers with the rap ring technique.

What you need to watch out for if you adopt this method:
1) Make sure you inspect your biners that are in contact with the rap rings if you use steel rap rings.
2) make sure your clove hitch stacks properly or you're gonna lose all tension first step on the line.
3) Inspect your webbing that the 11mm is threaded through for damage so you can replace it and save your 11mm from being messed up.

I've been using the same anchor system for almost a year now. if you use proper tree protection, you won't have to ever replace the webbing.


Partner slacklinejoe


Apr 28, 2008, 4:45 PM
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Re: [shaun_the_conqueror] SLACKLINE FAILURE! ! ! [In reply to]
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I've got a couple issues I'd like to point out with your setup Shaun.

First, putting the carabiner under load where it is being flexed against the tree's bark has been known to push open gates or even break them from the prying load.

Second - Are you sure your method of padding is sufficent? It looks like the left side is just abraiding against the tree but the right side is using the upright stick to protect the tree's bark. Maybe it just blending and is hard to make out on the photo.

Regarding the calculator: it's triometric based. The explainations on how it works is on a link on that page. I based the calculator on Eric Matthes' work. He did a very good job breaking it down on his site, and with his permission I turned it into a web based application. So far the results have been very in line with field tests with dynomometers.


petsfed


Apr 28, 2008, 5:09 PM
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slacklinejoe wrote:
Regarding the calculator: it's triometric based. The explainations on how it works is on a link on that page. I based the calculator on Eric Matthes' work. He did a very good job breaking it down on his site, and with his permission I turned it into a web based application. So far the results have been very in line with field tests with dynomometers.

Its actually a very good first order approximation. Its primary failings are that it doesn't deal with the motion of the slacker, side to side motion, stretch in your tie-off, etc. Since the anchor force goes to infinity at zero sag, the approximation is clearly wrong at that limit. Real forces don't do that. However, the approximation does what its supposed to do, so in that sense it works.


shaun_the_conqueror


Apr 28, 2008, 6:33 PM
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The whole tree is properly protected using branches in the photos posted, you're absolutely right, it is hard to see. I actually don't leave the carabiners resting against the tree because as you stated "the gates can be pushed open" and this is correct. I try and keep the carabiners closer to the rap rings. I use carpet to pad trees when I can, but when circumference of the trees exceeds my 5ft pieces of crapet, I have to resort to using branches. As far as the calculations you use go, I'll have to read more about it. I wouldn't trust a static load fixed in one posistion to assume the whole rigging is safe though.


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Apr 28, 2008, 6:52 PM
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As mentioned, oned of the limitation of the calculator is dynamic loads. The assumptions of the calculations are listed on that site.

However, as I mentioned above the dynamic (shock absorbing) capabilities of webbing when under loads that let it's elasticity go to work help dampen the effects of jumps and surfing moves etc. Tests have shown normal surfing wiggles the load but overall not as much of an impact as I'd have expected. Jumping right next to the anchor does impact loads but again, I was suprised at how little the loads really were even on lines that "felt" insanely tight.

Oh, and to the infinity issue - your right, you can't measure a load like that using the system - that's because you'd have broken any piece of equipment well before you approach a zero change in deflection on the line. Simply put, as far as I know it's actually impossible to reach that condition using a flexible medium such as rope or webbing, you'll just manage to break it trying to get your preload.

Worth noting - similar physics apply on the "american death triangle" for climbing anchors. As the bottom point's angle gets larger the loads get levered much, much higher - in theory to the same situation of a slackline.


(This post was edited by slacklinejoe on Apr 28, 2008, 7:02 PM)


billcoe_


Apr 29, 2008, 8:17 PM
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No one has mentioned work hardening of the aluminum in the carabiner.

Before it is assumed that the gate was open and then the breakage issue totally dismissed, I think it's worth thinking of the work hardening effect. Take any piece of aluminum and bend it. You can do this for awhile, until it finally snaps. For climbing, biners do not see this repeated cycling and metal movement, at least not to this degree even when aid climbing long routes: however, as this was a dedicated biner to a slackline system, is it not appropriate to ask how many times the line was set up before this carabiner failed. Could be something there.

I wonder if testing can determine the if the malleability of the metal in that carabiner had changed since it was manufactured, and if that may have been due to excessive or repeated load cycling from setting up the slackline repeatedly. Bet Black Diamond would like to take a look at it b4 one of these BD biners - even a bottied one, snaps then hits some poor kid in the temple and kills them.

May I suggest you contact the Black Diamond company and ask if they would like to follow up on this idea and look at the failed piece of equipment? This would be an excellent place to start, as their products, as much as anyone else's, is tested and checked to a high standard before it hits the streets. If nothing else, watching what happened to Hugh Banners company when the family of the dumb son-of-a bitch who died rappelling when he IMPROPERLY used an HB carabiner (and it failed due to his own stupidity and rashness) sued them, I would want to be proactive and look at this if I were with BD.

The life you save with the info gleaned may be your own. Who can say?

Regards to all

Bill


majid_sabet


Apr 29, 2008, 11:56 PM
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billcoe_ wrote:
No one has mentioned work hardening of the aluminum in the carabiner.

Before it is assumed that the gate was open and then the breakage issue totally dismissed, I think it's worth thinking of the work hardening effect. Take any piece of aluminum and bend it. You can do this for awhile, until it finally snaps. For climbing, biners do not see this repeated cycling and metal movement, at least not to this degree even when aid climbing long routes: however, as this was a dedicated biner to a slackline system, is it not appropriate to ask how many times the line was set up before this carabiner failed. Could be something there.

I wonder if testing can determine the if the malleability of the metal in that carabiner had changed since it was manufactured, and if that may have been due to excessive or repeated load cycling from setting up the slackline repeatedly. Bet Black Diamond would like to take a look at it b4 one of these BD biners - even a bottied one, snaps then hits some poor kid in the temple and kills them.

May I suggest you contact the Black Diamond company and ask if they would like to follow up on this idea and look at the failed piece of equipment? This would be an excellent place to start, as their products, as much as anyone else's, is tested and checked to a high standard before it hits the streets. If nothing else, watching what happened to Hugh Banners company when the family of the dumb son-of-a bitch who died rappelling when he IMPROPERLY used an HB carabiner (and it failed due to his own stupidity and rashness) sued them, I would want to be proactive and look at this if I were with BD.

The life you save with the info gleaned may be your own. Who can say?

Regards to all

Bill

Back in my biner gate post in LAB, Dingus posted an research articles from the MTI where two guys did a study on biner's fatigue and stress issues. It is worth reading.


iheartsublime


Jun 8, 2008, 8:22 PM
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Re: [crazy_fingers84] SLACKLINE FAILURE! ! ! [In reply to]
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WOW!!! thats all that i can say...she is very lucky...i dont know where you got the carabiner from but tape on a carabiner usually means its retired...that might have been it...nice slackline...orange is the shiz!


petsfed


Jun 8, 2008, 8:54 PM
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Re: [iheartsublime] SLACKLINE FAILURE! ! ! [In reply to]
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iheartsublime wrote:
WOW!!! thats all that i can say...she is very lucky...i dont know where you got the carabiner from but tape on a carabiner usually means its retired...that might have been it...nice slackline...orange is the shiz!

NO.

Tape on a carabiner means that the carabiner has tape on it.

There's no universal system to mark gear, no agreed on tape/nail polish/spray paint/goat urine mark that means retired, or slacking only, or master power point for the big red pig.

If tape means "retired", then every piece of metal I own, with exception to 3 carabiners and a big bro, must be retired.

Dumbass.


iheartsublime


Aug 26, 2008, 12:14 PM
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Re: [petsfed] SLACKLINE FAILURE! ! ! [In reply to]
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keyword is "might" buddy!

who argues with people in a forum...get a life.


carbonrx8


Aug 26, 2008, 12:41 PM
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Re: [iheartsublime] SLACKLINE FAILURE! ! ! [In reply to]
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iheartsublime wrote:
keyword is "might" buddy!

who argues with people in a forum...get a life.
That was a very snappy and timely comeback.


petsfed


Aug 26, 2008, 2:49 PM
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Re: [iheartsublime] SLACKLINE FAILURE! ! ! [In reply to]
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iheartsublime wrote:
keyword is "might" buddy!

who argues with people in a forum...get a life.

I know this is gonna run contrary to the elan of this site, but please, PLEASE try to refrain from speculating on failure modes when you haven't got the good sense to critically examine your beliefs beforehand.

I'm certain that if the carabiner had been retired from regular use do to concerns about its safety, the OP would've mentioned it (and justly be flamed for being so stupid).

My response, ire and all, was motivated mostly because even a slightest bit of thinking would've revealed the ridiculousness of your statement. Please consider thinking before typing in the future.


iheartsublime


Aug 27, 2008, 6:13 AM
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OK


USnavy


Oct 6, 2008, 2:28 AM
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Re: [petsfed] SLACKLINE FAILURE! ! ! [In reply to]
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When a carabiner fails in the closed gate position there is generally a high level of deformation present on the body of the carabiner. Additionally, the pin on the gate or the nose on the carabiner is usually broken off. I see none of theses items present in the pictures, which leads me to believe it was an open gate failure.


shaun_the_conqueror


Oct 6, 2008, 9:17 AM
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I just wanted to point out that I recently retired a biner which I found had a fracture on the gate coming down from the pin. Further more, the very tip of the gate was some what skewed. I outlined the skewed gate and fracture in the images below. Check your gear people! With the tensions and line lengths I use, this fractured gate could have made for a painful time.




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