Opening the Gates on Biners

[Lumberjack]

Ok, we all know that when you open the gate on a biner, you reduce its strength by al least half, and normally much more.

My question is why? Is it that the gates upper rivet or key way locks with the top bar of the biner and offers a leveraged support to the major axis? That would explain how the wire gate biners work, with the small stiff wire would support the major axis with a (relatively) small force.


Anybody understand what I am saying?

Anybody know the answer?

Carl

 

[Burnham]

I think the logic might be the similar to that which gives us only half the load on each leg of our rope in a DdRT system.

A ring will always be stronger than a hook of the same construction, wouldn't it?

 

[NickfromWI]

Simply put, the closed carabiner can hold more weight because the load can be distributed through the entire carabiner, rather than just along the major axis.

To see this, take to similar paperclips, unfold them, then form these two shapes with them...

Now stick your fingers in there and pull in the direction of the red arrows. You should be able to tell that the one on the left (the open carabiner) will just straighten right out and the one on the right...well, you'll probably not even break it.

It's kindof like comparing a loop sling to an eye-eye sling.

In many carabiners, there is a bar in the gate that goes into the notch on the carabiner...this is the "splice" that keeps the carabiner together during heavy loads. As an aside, I don't like that sort of interface. That notch gets snagged on lots of things and has ruined many a rope. Much better are the keylock systems that Petzl and a few other manufacturers use. It's super smooth. As I've said before, I think all bar/notch carabiners should be avoided if possible. My personal favorite is the wire-lock method used by DMM, check it out!

Wire Lock Carabiners

Most carabiners that we tree guys will encounter can still hold a good 500-1000lbs open, but there's no reason a person should need to know that.

love
nick

 

[Burnham]

More like in the range of 7 to 10 kN open, Nick, for the several I have floating around nearby. That would be 1575 to 2250 lbs., wouldn't it?

 

[NickfromWI]

Yep, you're right....the ones around my house are around the same. I downgraded just in case....

love
nick

 

[Grigory]

Many aluminium carabiners, if they are not closed begin to be unbent already at loading 300 - 400 pounds. It is elastic deformation, after removal(distance) of loading they completely restore the form. If carabiners is closed, it is unbent within the limits of a backlash of a pin on a gate. Many carabiners with limiting loading 4000 - 5000 pounds do not open at loading 300 - 400 pounds!

I have a small collection carabiners, broken off under loading

 

[Grigory]

Broken carabiner 2

 

[Grigory]

Broken carabiner 3

 

[Grigory]

Broken carabiner 4

 

[NickfromWI]

Grigory, thanks for the pics...those are perfect!!!

For what it's worth, I twice climbed a tree using a keychain carabiner as my main attachment point. It was two different carabiners, one from Aerial Equipment which did have a pin on the gate and a notch to hold it on the carabiner. It would be considered the top-of-the line for keychain carabiners. The other was a cheapy that had no pin. The gate had a groove in it that the tip of the carabiner would set in, but they weren't connected in that groove.

I clipped onekeychain carabiner to the spliced eye of my climbing line, then to my saddle. Then I clipped a Petzl Ball lock 'biner to the eye and saddle. Because the keychain 'biner is smaller, it was holding all the weight, but if it just broke, Petzl woulda caught me.

I climbed about an hour with each carabiner. I took falls of about 3 feet (not fun on a very static anchor!). The Aerial one with the pin was undistorted after use. The cheapy one was bent open. I still have it.

Neat little experiment shows how carabiner react without that little pin.

love
nick

 

[Lumberjack]

Well I understand what has been said earlier. My thing was that the little pin doesn't equally share the weight with the major axis. My thought is that the pin simply holds down the leaver (top bar). The fulcrum is the spine of the biner, and the load is inbetween the two axises. If you load a biner on the side with the gate, it will fail at a lower rate, evidence that the pin doesn't share the load, rather support the major axis.

The pin offers a leveraged support to the major axis, not an equally shared load with it.


Carl