Carabiner Failure

[panicked_bear]

This past week I got a swath of webbing in order to chase my dream of becoming a competent slackliner. Never having set one up before, I consulted youtube and found a technique using mechanical advantage that seemed relatively straightforward even for someone with my IQ.

Now for the interesting part.

I had fastened one end to a tree and had put a sling around the other tree with two wire gate biners ( gates facing the same direction) that the webbing would be fed through. As I applied pressure on the webbing I went back and glanced at the two biners and to my horror, one of them (never have taken a fall on it) looked like it was on the way to failure!

Specifically, the main body of the biner with the notch that the gate fits into was moving laterally away from the gate (not actually "moving" as i watched it, but there was about a 3cm gap). I immediately released tension on the system and the biner returned to normal.

To me this is a bit ponderous because there is no way that I was applying the max force on that biner (22kns ~). Could it have been doing this due to the way that the anchor sling was sitting on the biner? Or was it more likely to do with the fact that the gates were not reversed (I reversed the gates and put tension on the system again and there were no more problems).

It's a bit troubling to think about as I have never taken a fall on this biner (taken from a QD) and was not putting realistically THAT much stress on it and it looked like it was failing.

Or, am I just off my rocker and have no idea how much torque I was putting through that system?

Cheers for any insight into this matter. I think that I will retire said biner to keychain status in any case.

[gt29905]

Wiregates and all biners do stretch a bit when under load. They stretch to the point where the gate is pulled under considerable tension. That is why there is such a discrepancy between the forces that a biner can hold with and without the gate closed.

I don't have any experience setting up slacklines but I do know that the force generated on the system when a person applies their weight to the strand of webbing is VERY great.

With the "opposing gates" issue, I'm fairly certain the only reason for opposing the gates in an anchor or anywhere is to reduce the chance of the software, webbing and such, from twisting and opening the gates of the biners. I don't believe that simply setting two biners in opposite directions actually gives the system any additional strength. I could be wrong???

Just my two cents. I'm curious to see what more well informed individuals have to say on the matter. None the less, retiring that biner sounds like a good idea. For curiousity's sake, who is the manufacturer and what is the model?

[panicked_bear]

Wow thanks for the great info! The QD set is manufactured by "Wild Country Britain".

[1tacocat1]

when you connect two things with a straight line, such as two trees with a bit of webbing and then someplace in the middle apply perpendicular force with say your body weight you do put an incredible amount of force on the anchors. to test this, try parking a car on a gradually sloping hill and the tying a rope to the car and a stout tree up hill on the fall line. when the rope is set, put the car in neutral so that it weights the rope rolling down hill away from the tree. grab the rope in the middle and give it a tug. you will notice that the car will roll up hill toward you somewhat. you will only be able to do this for a few degrees of bend in the rope because the more bend you create the more weight of the car you are taking off the tree.

in the case of slack lining you are already putting a pretty good amount of stress on both anchors just by keeping the webbing taught, but when you stand on the webbing you are not only adding your weight to it, but compounding the stress already on the system by putting perpendicular force on the webbing.

was the gate of the bineer closed when you started? were the two bineers equalized? why did just one of the two bineers get stressed so severely while the other could hold its shape? it sounds like the one that failed was taking all the stress. in any case its a pretty cool demonstration of force, and a testament to the supportive power of trees.

good luck with the slack lining.

[shanja]

OK well before Will the gear geek jumps me on this, I'd like to say Gabe is 100% correct. Opposing gates is to reduce the chances of stuff (webbing etc) popping out of a biner....nothing to do with load sharing or strengthening a system.
Think about how you rig a slack-line. You are pulling anchors (pretty much) horizontally towards each other (angle of 180 degrees). Now add a person in the middle (ish). The angle you are getting (assuming normal conditions) is therefore about 150-135 degrees.
Would you be happy with this angle as an anchor when climbing? Hell no. As engineering savvy anchor builders/ physicist/ climbers John Long and Craig Luebben et al point out the angle between anchors is critical in determining how much force is applied to each anchor (tree + biner). The bigger the angle the more force is applied to EACH anchor point.....EVEN BEYOND THAT OF THE LOAD BEING HELD!!!!
For example, a 1000lb load held by anchors:
at 20 degrees = 500lb on each anchor (1000lb force)
at 40 degrees = 540lb on each anchor (1080lb force)
at 80 degrees = 700lb on each anchor (1400lb force)
at 120 degrees = 1000lb on each anchor (2000lb force)
at 140 degrees = 1350lb on each anchor (2700lb force)

So even if your load (slacklining dude/ette) is a mere 150lb, you are probably more than doubling that load on each anchor. Climbing biners are designed to hold dynamic loads and do stretch under force - but this is asking a lot. Hence for slacklining I'd really recommend you use a couple of cheap steel biners and save the climbing biners for climbing.
ALSO this shows why anchors made with death triangles or simple too large an angle between pro pieces are very likely to fail.

[dangerflower]

you didn't mention whether or not the biner was a locking biner...just due to the way that the force would be applied to the biner because of the slackline set-up, i think that it would be important to use locking biners...the usual rule of opposing gates applies to different types of forces that occur in normal climbing situations, no?

if the biners were locking, then i have no idea...sorry...^^

(sorry, just going to edit my post here!!!^^ just saw that you said they were wire gate biners! have never seen a locking wire gate biner, so i'm going to assume that would be a 'no'. ^^kk) as for supertopoz's post, i've also used ratchet pulleys for slacklines and LOVE them! super easy for set-up and take down!..^^)

[supertopoz]

Ever heard of gate flutter.

When falling, the rope running through quick draws causes them to vibrate. This vibration causes gate flutter. When the timing is all wrong the gate my not be as closed as you would hope it to be.

The solution,
Wire gate binners. which do not suffer from gate flutter. :D

Kid you not

http://www.coolsportz.com/rock-climbing-carabiners/default.htm

Don't believe everything you read on the net,
But........
Under load, Haulbags, hanging belays and such, many screw gates will not open. The gate stretches into it's grove and will not budge.

Setting up a slack line in Korea. Head into a local hard ware store and get your self one of these.

http://img.alibaba.com/photo/101144711/Ratchet_Lashing_Tie_Downs.jpg

A Ratchet pulley.
the small sizes work with climbing tape. Best of all not caribiners needed, ratchets are cheap less than 5000 and you can tighten up as much as you like, then lock if off safely.

[panicked_bear]

When i look back on it, the tape sling WAS off center a little bit on the biner that failed. They were only QD wire gate biners. The problem was that the slackline was set up way too long and way too low, so we were really cranking on it.

I have since learned a WAY easier method of setting up slacklines with only 2 locking gate biners.


NB. Is there a "How To" section in KOTR? Some place that we can post videos or pics to help with group education on things? That would be cool.

[bhylenski]

Supertopoz is spot on, I only use wire gates for hauling and for the rope end of my quickdraws (a bit of paranoia for the quick draws), but gate flutter is real and being a 90kg guy, a bit of paranoia when it comes to carabiner strength is recommended.

As for your biners, it's quite common for you to have a stress fracture or failure in your biner. You'd be surprised how simply dropping a biner out of your hand onto another biner or onto concrete (floors like in our apts.) can cause damage to the gate side or ends of a biner. I'm not saying this is the problem, but this is just one of many reasons I have never used biners in horizontal, opposing anchor slacklines. I set one up in Sokcho a few times for camping weekends and the ratchet pulleys that supertopoz recommended work perfectly. I used these same ratchets in Thailand (mailed from Japan) to re attach a bunch of slacklines, roof restraints and stair cables after the Tsunami in 2004. You can find them in any hardware shop or on gmarket. Print out the picture and take it with I believe I bought my first pair at Emart, but the hardware store will have higher quality options.

Save the biners and your cash for more necessary reasons like catching the Brits on their "one" fall.

Good Luck!

[panicked_bear]

Awesome advice thanks bhylenski, ill check out emart for sure. If I've been using screwgate biners for my slackline would you recommend that I stay away from using them for climbing from now on, or do you reckon that they will still be ok to use?

[bhylenski]

Well, if I say they're probably fine, then something happens I'd feel awful.

But, if it were me and the screw gates did not show any signs of failure during setup testing then they're probably ok. But, if you've used them for slacklining, not just testing. Then just set them aside as slacklining only. I don't even use my webbing for climbing, once it's been used for slacklining...I just cut it up for "bail" gear in the mountains.

Most screw gates will work just fine for slacklining, but as others have said, steel biners are cheaper and tend to be just as reliable for slacklining. Grab some ratchet pulleys, a few steel biners just in case and you're all set.

Good Luck, post a photo once you got it setup, maybe a video of you testing it out! I still know climbers, who have never heard of this...the new folks would probably enjoy it as well.

Cheers
Bryan

[Les]

I've never had problems with the 5 biner set-up. like you, all i needed was you-tube.
http://www.youtube.com/watch?v=4jpB4zfzQuo&feature=channel_page
alas, the sound seems now to be missing, but here is a less enthusiastic version of essentially the same set-up.

http://www.youtube.com/watch?v=18qbgwCn2ZA

If the line you're setting up is quite long, you're going to need much more tension on the line, else you'll be walking on the ground. Try going for about 20-30 feet. One person could get this line tight enough using 5 biners without a ratchet. I only use a locking biner on the one side alone, and on the other are 4 pretty cheap straight gate biners. On this side with the 4, I suspect the stress between the 4 biners would not be equally distributed due to the huge friction you've created in the system. But still, never had any problems. I'm still stoked on joining a group for a serious SL sess.