Quick Link Open (Unscrewed) Break Strength

Hello,

I can't seem to find any data on open-gate break strength for quick links. I'm not sure if I am simply searching with the wrong keywords, but I would greatly appreciate any information on the subject. Thanks!

How about give us some hints: 

Why might it be useful for us to learn about or know this?

or at least, How is it useful for you to know it?

A 40kn/10kn steel oval quick link broke which was left open during loading broke, and I was just curious to know the approximate force it took. It was loaded along the axis, with the threads completely disengaged. Carabiners have relatively high open gate to cross axis strength ratio, so I would have guessed that the quick link would hold a relatively large percentage of its 10kn rating.

There are wild variances in quicklink quality. All of them are significantly weaker open than closed.

Great discussion (with some data!) here:

Quick Link load tests

I have some camp quicklinks but they only quote major (40KN) and minor (10KN) axis strength...not gate open.  Presumably because and open gate quick link is highly unlikely versus a carabiner.   I wonder what the value is though....particularly relevant for fixed draws.  

That supertopo thread says: "Even with the threads open, these links require about 800 lbs to bend open."  That's pretty low!

dnoB ekiM wrote:

That supertopo thread says: "Even with the threads open, these links require about 800 lbs to bend open."  That's pretty low!

Scary low, considering the quality variation out there.  Ever bounce on an open cold shut?   Makes you really not want to use them!

In the video below, they did testing on an 8mm stainless steel quicklink. The results were Open:7.8kn Closed: 70kN

Its interesting to note that the quicklink in the open test, fully deforms and never breaks. If you look at carabiner open gate tests, the carabiner spine eventually breaks. So I'd say the quicklink requires a longer duration of force before failure.

From 

dino74 wrote:

In the video below, they did testing on an 8mm stainless steel quicklink. The results were Open:7.8kn Closed: 70kN

Its interesting to note that the quicklink in the open test, fully deforms and never breaks. If you look at carabiner open gate tests, the carabiner spine eventually breaks. So I'd say the quicklink requires a longer duration of force before failure.

From 

Is the time really relevant?

dino74 wrote:

Its interesting to note that the quicklink in the open test, fully deforms and never breaks. If you look at carabiner open gate tests, the carabiner spine eventually breaks. So I'd say the quicklink requires a longer duration of force before failure.

The difference is due to the ductility of the metals rather than strain duration.

Fredrik Ehne wrote:

Is the time really relevant?

Sure it does. I'm going to make up numbers for my example but lets say I apply 1200 pounds to my open quicklink and it fails after 5 seconds.

When I fall on my rope, I don't generate high forces for long periods of time.

This photo below is from http://www.cs.cmu.edu/~cline/Climbing/fall.html

The green line (Ignore the red line) is a ten foot fall factor one. 5000 samples over 2 seconds. Largest force generated is 1400 pounds.

Thats doesn't mean my 1200 pound open quicklink is going to fall. Just from eye balling it, I see there is only 0.05 seconds forces greater than 1200 pounds.

The open quick link will probably deform but may not necessarily fail. I'm just saying slow pull test doesn't always represent real world applications. Just look at DMM's nylon vs dyneema testing.

dino74 wrote:

Sure it does. I'm going to make up numbers for my example but lets say I apply 1200 pounds to my open quicklink and it fails after 5 seconds.

When I fall on my rope, I don't generate high forces for long periods of time.

This photo below is from http://www.cs.cmu.edu/~cline/Climbing/fall.html

The green line (Ignore the red line) is a ten foot fall factor one. 5000 samples over 2 seconds. Largest force generated is 1400 pounds.

Thats doesn't mean my 1200 pound open quicklink is going to fall. Just from eye balling it, I see there is only 0.05 seconds forces greater than 1200 pounds.

The open quick link will probably deform but may not necessarily fail. I'm just saying slow pull test doesn't always represent real world applications. Just look at DMM's nylon vs dyneema testing.

Hmm.....

The speed of the impact/force applied makes a very small difference because it allows the stainless steel to work harden more while it bends, however you are unlikely to ever notice the difference unless you are like me and bend and test stainless steel as part of your job. What you see in the video (the time difference) is merely an effect of the speed of the pull ram, once either the karabiner or the quicklink get over the critical force they fail, time plays no real role. 

apoet wrote:

A 40kn/10kn steel oval quick link broke which was left open during loading broke, and I was just curious to know the approximate force it took. It was loaded along the axis, with the threads completely disengaged. Carabiners have relatively high open gate to cross axis strength ratio, so I would have guessed that the quick link would hold a relatively large percentage of its 10kn rating.

Without doing any research myself I'd bet it was a galvi steel one and corrosion/poor quality control played a factor.

Years ago on rc.com a mad scientist with a testing rig in his house tested quick links. He didn't test open, he tested finger tight vs wrench tight.

I seem to remember that none of them held their rated strength at finger tight. Most did with a pretty large standard deviation when tightened with a wrench.

He found that there was a rather huge standard deviation among identical quicklinks. Enough so, that if you're really serious about statistics, you probably shouldn't trust any quicklinks. Of course this isn't really a practical application of his data.

Use a wrench when installing chains. They'll stay there longer and be stronger. As for open gates, just orient the link so that gravity will screw down when vibrations are entered into the system.

King Tut wrote:

Without doing any research myself I'd bet it was a galvi steel one and corrosion/poor quality control played a factor.

The failure was a steel (not stainless) CAMP quicklink, which showed no visible corrosion and had been stored inside for the year since it's manufacture date. 

Thanks for the info everyone, I was just curious what approximate load the link saw to deform so badly. 

apoet wrote:

The failure was a steel (not stainless) CAMP quicklink, which showed no visible corrosion and had been stored inside for the year since it's manufacture date. 

Thanks for the info everyone, I was just curious what approximate load the link saw to deform so badly. 

Thanks very much for that.

What were the circumstances of the failure? Was it fallen on with the gate open? ie left as primary connection for a fixed draw or a bail link?

highaltitudeflatulentexpulsion wrote:

Years ago on rc.com a mad scientist with a testing rig in his house tested quick links. He didn't test open, he tested finger tight vs wrench tight.

I seem to remember that none of them held their rated strength at finger tight. Most did with a pretty large standard deviation when tightened with a wrench.

He found that there was a rather huge standard deviation among identical quicklinks. Enough so, that if you're really serious about statistics, you probably shouldn't trust any quicklinks. Of course this isn't really a practical application of his data.

Use a wrench when installing chains. They'll stay there longer and be stronger. As for open gates, just orient the link so that gravity will screw down when vibrations are entered into the system.

Some caution is advisable when tightening quicklinks with a wrench, over-tightening makes them weaker. The actual tightening torques are very low, according to Péguet (who are the best known manufacturer and the inventors) they are 6mm-1.2Nm (0.9ft lb), 8mm-3Nm (2.2ft lb), 10mm- 7Nm (5.2ft lb). In practice it´s almost impossible to measure without specialised equipment so the general rule is finger tight + 1/4 turn. Don´t crank them down hard!

King Tut wrote:

Thanks very much for that.

What were the circumstances of the failure? Was it fallen on with the gate open? ie left as primary connection for a fixed draw or a bail link?

It was being used in a tensioning system for a slackline. While I was pulling on the rope I noticed the quicklink deforming and realized what had happened. Luckily nothing broke before I could de-tension it.

apoet wrote:

It was being used in a tensioning system for a slackline. While I was pulling on the rope I noticed the quicklink deforming and realized what had happened. Luckily nothing broke before I could de-tension it.

thanks for that. I'd be sure to get it to the maker so they can see if it was properly hardened etc.

Interesting thread. I was thinking of using a larger link (that opens to allow a rope to pass into it) for at the top of sport routes instead of leave-it biners.  But just not tighten them, so each climber could easily unscrew them with their fingers and drop the rope through them and retighten lightly,  then lower or top rope off them. They're cheaper than biners and would last longer before needing to be replaced. So I was wondering also what the strength is if only hand tightened lightly. 

Troy Isakson wrote:

Interesting thread. I was thinking of using a larger link (that opens to allow a rope to pass into it) for at the top of sport routes instead of leave-it biners.  But just not tighten them, so each climber could easily unscrew them with their fingers and drop the rope through them and retighten lightly,  then lower or top rope off them. They're cheaper than biners and would last longer before needing to be replaced. So I was wondering also what the strength is if only hand tightened lightly. 

It's not uncommon that people do this, but very often debris gets into them, or someone comes along and overtightens them, or they otherwise rust/ seize shut, at which point they're barely better than just having chains.  Barely being that they're still an easily replaceable wear point