Strength of baby krabs

[Lophophaps]

I have a number of baby krabs abut 60 mm long and was wondering how strong they are. This is not for leading a grade 26 but static loading of a person in an emergency. There are many types of aluminium, all with different properties.

One of least strong cites 18,000 psi. Call it 10,000. The diameter of the baby krab is 6 mm, so the area = pi X 3 X 3 = 28.3 square mm.
1 pound = 0.4536 kg
1 square inch = 25.4 X 25.4 = 645
10,000 X 0.4536 kilograms/645 square mm
= 4536/645 = 7.03 kg/square mm
X 28.3 sq mm = 200 kg.

Factor in another half and you get 100 kg breaking. Use two krabs in opposition and it should be safe.

It's been a while since I studied applied mechanics, so the above needs to be taken under advisement. Is there anyone who can comment on the above? Thanks.

[beean]

Any photos of said biners? You could make a basic 3:1 rig and try to break one. Hang a lawn mower or esky full of water or something you know the rough weight from one end.

If you're even remotely considering using one or two or even three for emergency use, perhaps look at getting a full strength biner, such as a CAMP Nano 22 (22grams), Metolius Mini (22grams) or an Edelrid 19g (19grams). Ropes can jerk or slip which may add a bit of a dynamic load to the load being lifted.

[Orion]

Don't do it.

[GPSGuided]

Krab?

[Moondog55]

Krab?

Climbing carabiner
Don't do it
Rated krabs are so light and comparatively cheap that it simply isn't worth the risk. I'd rather trust my life to 3 turns of VB cord or a chain joiner
I'm a cheapskate and this is one thing I will never do
Rated chain joiners are about the same cost as a cheap climbing krab anyway and krabs are way stronger

[MickyB]

Krab?

Thanks GPS. Thought I was the only one who didn't know.

[Lophophaps]

Thanks for the above. I carry three small krabs and they might be used in an emergency if it is safe. This is what I am attempting to determine. If I use all three, my figures above suggest that there is a safety factor of about five times for a static weight of 100 kilograms. It would be very easy to set up a lowering system such that if the krabs all break then a much stronger sling can take the load.

This is not for climbing Frenchmans, The Castle in the Budawangs or a cliff in the Blue Mountains. It's for a short section where a rope is unexpectedly needed.

A picture is at
http://www.amazon.com/Liroyal-Mini-Alum ... B00KUO0SGC

[Moondog55]

I'm familiar with them, I wouldn't trust them dynamic with 10 kilos. They may look like aluminium but far too often they are diecast alloy types to get the cost down.

A triple loop of 3.75mm cord will be far stronger even with an overhand knot. If weight is a worry use Zing-It in a double or triple loop
http://www.mammut.ch/store/INT/en/know- ... s/handling
http://www.bogong.com.au/climbing/carab ... -gate.html
http://www.bogong.com.au/climbing/carab ... biner.html

This may sound pedantic and it is but gear hooks are NOT krabs

[Scottyk]

the amazon add says "NOT FOR CLIMBING"
says it all really
Do not hang off these......... EVER!

[ithomas]

You must realise that the physics of ropes, pulleys, falls and loads is the same whether you are at Frenchmans Cap or on a ladder in your own backyard. You need rated tools to do the job safely. In rigging or climbing or load hauling, relatively small movements and loads can generate enormous forces in multiple directions. The cheap karabiner look-a likes are inadequate in most situations and potentially disastrous in an emergency. Just chuck them out or leave them at home. You seem reluctant to discard your carefully thought out calculations - think again.
Ian

[Gadgetgeek]

I know some people that have used keychain krabs as a belay tie in, just to see what would happen. Backed up obviously. They were surprisingly strong. HOWEVER that was pretty controlled, and its really easy to get into uncontrolled situations, and to add a possibly dodgy piece of gear into the mix could be fatal. Cheap rated lockers are great, you can get the camp nanos in a six pack. 6 or 7 mm cord is plenty strong for a lot of things, and thick enough to hold as a handline, But you can do thinner for weight. up to you.

[Lophophaps]

The calculations are the best I can make, and advice on their accuracy was sought. So far there has been scant response on this point. I asked as I'm very aware that the krabs are not for climbing, are not rated and may be dangerous. My figures suggest that a static load could be lowered on two or three of these krabs. Static loads on the axis may be acceptable. Using two krabs with the gates in opposition can assist.

Two or three gear krabs are carried as a matter of course, used on every trip for gear. I see no harm in using them for clipping gear.

Scenario. A party member twists an ankle and cannot down-climb a short bluff. You have some cord or rope but no climbing krabs. Would it not assist knowing what gear krabs can take? Backed up it can be safe. This is all I'm asking - how much can these krabs take so that in a situation like the preceding you know what can and cannot be done? Note the backup, UIAA certified rope or multiple strands of cord.

For a walk when there is a certain need for a rope I carry 20 metres of 7 mm kernmantle, breaks at about 1800 kilograms static or 19 kN. Anything thinner than 7 mm risks being cut by sharp rocks and in my view is ill-advised. I also carry a few rated krabs and some slings. Belaying is with an Italian hitch, crossed krabs, twisted crabs or as a last resort a waist belay.

[Moondog55]

The mistake you made was in assuming that the producer in China didn't cheat.
You simply cannot make assumptions about the alloy or the manufacturing process when doing the calculations
My own keychain clips are sailing units and rated and cost just as much as a climbing krab
You also need to seriously think about liability in these litigious times
As I said in my other post, they can handle 10 kilo safely in my opinion
The Nite-Ize are rated and the rating for something of a similar size is 10 pounds
http://www.amazon.com/Nite-Ize-SB234-03 ... 160%2C160_

[Orion]

A human life is on the other end and you want to use toy carabiners.

You don't know what the alloy is or how it was treated. You haven't even attempted to calculate the strength of the gate; that might be the weak point. You could test one of them if you had the equipment but you don't know anything about the QC so you'd have to test many of them to get a sense of that. And then there might be differences between lots.

Are you even sure what the loads will be? When someone simply slumps onto a rope the peak force is about double their bodyweight. A top anchor adds a factor of about 2/3 more. And it's not that difficult to generate much larger forces with a slip.

Modern climbing carabiners are very light. You can buy ones that weigh 25g or less. So what are you doing, saving a few dollars?

[GPSGuided]

Thanks GPS. Thought I was the only one who didn't know.

I thought it must have been some magic word and equipment. Tried to work out based on the proposed use and I still couldn't work it out. All thanks to MD55 for enlightening.

[icefest]

Don't. I tried putting up a hammock using similar once.

It hurt.

You can get a rated climbing carabiner at 19g.

[GPSGuided]

I actually have a hand full of these 'krabs' as my son won them at a pinball gaming parlour a few years ago. That, should be more than indicative of their quality and function.