If a carabiner is clipped to a hanger on top of other gear and loaded, is it weakened? By how much?
One way carabiners might fail weaker than their rated strength is if they’re levered, or in other words, placed on top of existing gear on a hanger and then loaded.
We’ve all clipped multiple pieces of gear into a hanger before. It happens. You arrive at an anchor and it's already got a rappel ring and your buddy is connected to it. Is that sketchy?
And what happens if you clip the first draw (the Jesus draw) above your PAS on a multi pitch and the leader whips. How much force will the carabiner hold if it's being levered against the bottom one?
The Setup
We built a drop tower with a bolted anchor, just like those you’d find at the top of a sport route. To simulate our system, we used:
12mm static rope
A Black Diamond HotWire Quickdraw (24kN)
200 pounds of dummy weight
It's hard to attach a bolt to a load cell, so we put it in a box between the dummy weight and our rope.
REFERENCE: Climbing gear is rated in kilonewtons (kN). This is an expression of force, and the kN rating on your gear demonstrates how much force the gear can withstand. 1kN is equal to about 225 pounds (102 kg) under Earth’s gravity.
Test 1: Clipping Above the Link on a Hanger
We started with simulating a situation where someone claimed their carabiner broke because it was clipped ABOVE the quicklink that was already on the hanger when they arrived.
Our first try broke the tiny soft shackle we had on the LineScale3 at 10.02kN. We wanted it to be weaker so we didn't break the LS3 but it was too weak. So we did it again.
Result: The rope (not the carabiner) broke in the knot - 17.63kN.
This is around the same force we get when we slow pull the rope, we just thought the carabiner would be weakened enough that we could use a rope.
Test 2: Clipping Above 2 Other Carabiners
The 2nd test is what we were most concerned with, stuffing the hanger with as many carabiners as possible and loading the top one.
RESULT: The carabiner on top broke at 13.69kN. It did weaken it almost by half!
Bonus Result, simultaneously the steel carabiner at the bottom of the rope holding the weight also broke! That is because it got cross loaded, which is another way a carabiner can break lower than it's rated strength.
Test 3: Clipping Below the Link - Properly
Anticipating this would be full strength, we needed something stronger than a rope. We used a span set to try and shock load the system enough to break the carabiner. Bonus result: we had to change the hanger for this test because 17kn then 13kn starts to deform a hanger a LOT.
Result: The dogbone broke at 16.09kN
Test 4: Clipping Above the Links AGAIN
Since the quickdraw’s dogbone broke at 16.09kN we just used a soft shackle. This plus a spanset should break... what we are trying to break!
Result: NOPE - The steel locking carabiner on the bottom crossloaded and broke at 17.08kN
Conclusion
It’s best to have the primary load-bearing piece on the bottom as you can see it can reduce the strength of a carabiner by half (test 2).
Sometimes—like on a multi-pitch or a big wall— you might need to clip a bunch of stuff to an anchor. A QUAD ANCHOR is one solution because then you have the shelf or masterpoint you can clip to or an HMS CARABINER (pear shape) can be clipped to the hanger and everything gets clipped to that like a poor man's rigging plate.
It's shocking how many things broke instead of what we were worried about. Careful not to cross load a carabiner... obviously... but we chased that rabbit in this VIDEO if you want to see more.
At this point, our dedicated team really wanted to go to lunch… so we called it a day.
Now, three drop tests aren’t much of a sample size, so don’t take this to the grave with you.
What's Next
What about carabiners that are loaded sideways?