I am trying to find a very strong Carabiner, for my father. I’m at the EMS web site, and I don’t understand what I am looking at. There is a rating or weight measure that I am not familiar with. The info for a particular carabiner appears as follows:
Weight in grams 75g
Closed Strength 24kN
Open Strength 7kN
Minor Axis Strength 7kN
What does kN mean here? I am unable to gauge the load-bearing ratings on these devices.
Help?
Cartooniverse
kiloNewton. A beaner has to resist a force, rather than hold a weight. A 200lb guy falling ten feet and then getting caught by a carabiner is going to put a lot more than 200lb of force on it. 24kN, or 24000 Newtons, is about 5400 lbf (pounds of force).
There’s math to figure out what you need for what sort of fall; you have to know the mass of the mass and its acceleration. However, if the weight isn’t moving, you could hang two of my car off that 75 gram bit of aluminum.
If you don’t need the rapid opening/closing, and you also are not concerned about weight, I strongly recommend you choose a steel “Rapid Link” instead. I’m holding one now that is smaller than any of my carabiners, but rated at 20,000 lbf. These are much cheaper, and much, much stronger than any carabiner of equal size. They are sometimes used by climbers as well for securing permanant fixtures or top ropes.
I’m not sure if you’re also asking what the three measurements mean. I’ll explain, just in case:
Closed Strength 24kN: This is the capacity of the biner if its gate is closed and the force is being put on it properly. In other words, if the force is being applied to the top curve and the bottom curve, as would be expected.
Open Strength 7kN: This is the capacity of the biner if the gate is open. It’s basically the strength of the C-shaped curve of metal that makes up the body of the biner. A properly closed gate turns the C into an oval, which is a lot stronger, so this number is quite a bit lower than the closed strength.
Minor Axis Strength 7kN: This is the capacity of the biner if force was applied across the biner, rather than along it, as it should be. So, if you were accidentally pulling on the gate instead of the curves at the top and bottom, this is what the strength would be.
The “closed strength” tells you what the strength will be if the biner is being used properly. The other two figures tell you what the strength would be if something goes wrong.
As a climbing instructor, I always rigged my climbs taking the lower numbers into account. So, I usually used 2 biners, gates in opposite orientations. (Also, the club had mostly non-locking ovals, so it was more likely that something would go wrong!) We were top-roping, so weight wasn’t a consideration.
An experienced climber, climbing with other experienced climbers, might be more likely to rig her climbs with the closed strength of the biner in mind.
When I worked for an outdoor retailer, I found that the steel biners were very popular among rescue workers and tree service guys. As Anthracite said, they’re much stronger and cheaper than an aluminum climbing biner. They’re also much heavier.
So, the real question is–what is your dad going to be using the carabiner for
He’s trying to rig a simple seat to be hung from the horizontals of his walker. He’s obese, older and somewhat infirmed. He showed me a piece of 900lb test climbing ribbon, proudly proclaiming it’s test weight…then showed me the Fastex Buckle he planned to use to capture both ends. He weighs roughly 285. The Fastex would have failed in short order, dropping him the 16 inches onto his tailbone. Disaster.
Hence my search for the best carabiner. We drove down to Campmor this morning. ( Moment of respectful silence for the very Mecca of sport related retailers. These people are hardcore. [b[Greenbean**, you’re just down the Parkway a shade, you hit them or do you favor E.M.S.? ). We found large irregularly shaped carabiners. Opposed to the straight ovals. With the larger neck area at the opening end, we could clasp around the aluminum tubing of the walker bar easily.
I told him to go to a shoe repairman, have the person use heavy duty thich waxed shoe thread, and stitch loops at each end of this length of climbing ribbon. Then, hook the carabiner around and through the ribbon.
Personally, I now see a 5,500 lb carabiner ( x2 ) and a 900 lb ribbon, holding up a person who is less than 300 lbs. Fine. But, those horizontal supports in the walker? They’re not the load-bearing members in that design. The top bars that are bent and go to the floor, are the load-bearing members. I still very much fear that he’ll rig up this seat web, and be sitting gaily away, and the horizontals will shear off at the rivet points. Yes, I know there are walkers that come with a built in seat, designed to bear heavy loads. He claims that they are too pricey ( not an issue with my parents, we’re not talking about a $ 500.00 walker here…), and he wants to do it his way.
He’s more stubborn than I am, and I’m a pain in the freakin’ ass. I don’t know how to convince him that jury-rigging this is just a bad idea all around. 
Thank you all for the input, however. Anth mentioned steel “Rapid links” instead. I wanna investigate them, for my own use.
DougC has a point, in that sometimes the Rapid Links are a bit rough. However, a quick sanding or even wirebrushing, then sanding, can make them nice and smooth. It’s also recommended that the threads be lubricated very slightly with a non-running lubricant (so it won’t get on the rope), perhaps graphite lock lubricant.
Well, Campmor came through. They are smooth and finished, and should do the job tenfold.
Burrs along the climbing rope…–shudder–