Awesome, thanks for the replies everyone. I kind of assumed it was an added form of safety incase one of the carabiners were to become unlocked.

This sparks another question for me though. While I agree that if I have the extra carabiner, I may as well use it to make my trip just that much safer, but why is this trend only seen in anchors? I've seen pictures of people using two carabiners on their anchors countless times but I have never seen someone using two biners to lock the rope on to their harness. Using the same logic, the carabiner you use to lock your harness to your rope could just as, if not more easily, become unlocked while banging against the rock face during the ascend.

Is this not done because it just opens a whole new can of worms of redundancy or is there a difference between the two, because I just don't see it. Or perhaps people do use two carabiners to lock their harness to the rope and I just haven't seen it yet?

I apologize for my ignorance, I'm new and I would just like to sponge up as much information as possible that can make my climbs safer.

Thanks in advance!

In general, climbers don't often clip the rope into their harness with carabiners. They usually tie the rope on. However, there are times when people do clip the rope to their harnesses instead of tieing in. In these cases I'd definitely use two opposite and opposed carabiners just as I would with a TR anchor. It is true that you could use one locker, but I'm usually worrying about the climbing and not tending the carabiner. Since I do not have my attention focused on assuring that the carabiner remains locked, I prefer to have 2 carabiners.

As for the carabiner used to attach a belay device, in that case you are able to check that it remains locked and thus one is ok.

One biner is ok.
Two is better, stronger, redundant, and less friction on the rope.
It make the rope slide over a larger area, allowing the rope to run smoother while belaying and lowering.
also the way the biners are opposed makes the possibility of the gates comming un screwed, and the gates opening and the roping comming un cliped is almost impossible with two lockers.

One biner is ok.
Two is ... less friction on the rope.

That was my surmise, but in a thread on anchors Jim Titt
remarked that the doubled 'biners would increase friction,
and in some quick play with weights, rope, & 'biners, his point
seemed to be confirmed (but it was a slight difference).

*kN*

That was my surmise, but in a thread on anchors Jim Titt
remarked that the doubled 'biners would increase friction,
and in some quick play with weights, rope, & 'biners, his point
seemed to be confirmed (but it was a slight difference).

*kN*

IIRC he said it was the same, since the total bend radius was the same for 1 vs. 2 carabiners

I do believe that two carabineers are easer on the rope due to that the cerconfernce over two biners is 2x the rope is not flexing nearly as much.

That was my surmise, but in a thread on anchors Jim Titt
remarked that the doubled 'biners would increase friction,
and in some quick play with weights, rope, & 'biners, his point
seemed to be confirmed (but it was a slight difference).

*kN*

Your memory is failing you! The friction increases the more karabiners you add (the rate of increase slows after loads though, say about 5 or 6).
Not that I´d be worrying about it in a top-roping context since its only about 10% more!

Your memory is failing you! The friction increases the more karabiners you add (the rate of increase slows after loads though, say about 5 or 6).
Not that I´d be worrying about it in a top-roping context since its only about 10% more!

You´ve been reading too many papers by rescuers, if you read all the way to the bottom of what I have written to the bibliography you will find after the link the following:- "Stephen Attaway on friction and deriving Amonton´s capstan formula. Interesting mathematics but flawed."
That was a polite hint that it is completely wrong.

And if you (or he for that matter) bothered to do the experimentation or review bending theory or try some test calculation using the theory and match the results to known experience you (and he) would discover that Amontons capstan theory is inapplicable in a circumstance where the bending object has any moment of inertia.
He is wrong and you are wrong.

The radius of an object doesn´t change by placing another object beside the first, any child can see that. And the result of adding one part of a radius offset to another is that the rope bends, straightens and bends again so the work of bending has to be done twice increasing the resistance.

Get a spring balance, pull a rope with a weight over a karabiner and then add more karabiners. You will see the truth.


Jim

That is blatantly incorrect. With two biners, the rope contact surface is more closely modeled as a box with rounded edges, not a cylinder that is twice the diameter of a single biner, as your post implies.

Having struggled to pull the graph out from a calc. file the quality is not the best but here´s lifting an 80kg weight as a 2:1 purchase , 10mm rope with various numbers of karabiners. Tape I´ve never tested but it should be the same effect just less noticeable.
The steps as the load is taken up are from the powered winch used to lift the load.

Your memory is failing you! The friction increases the more karabiners you add (the rate of increase slows after loads though, say about 5 or 6).
Not that I´d be worrying about it in a top-roping context since its only about 10% more!

What is the X axis?

Based on this, what are the implications on carabiner wear? Does that mean that a 3 carabiner TR setup would produce more wear than a 2 or 1 carabiner TR anchor?