Wednesday, 2 September 2009

Cross Loading Carabiners

There was a photo of a broken carabiner posted on UKC today via a link to York Climbers. The photo has now been taken down for some reason, but it showed a DMM Phantom wire gate with a buckled gate and the gate misplaced on the outside of the nose.

There was some debate on how this happened and speculation that trust in wire gates may be lowered. Simon at DMM had a quick look at how this may have happened.

"I have not seen a biner look like this outside of a test lab and so spent a bit of time looking at different scenarios for this happening. The gate had obviously been cross loaded in an uneven manner against a hard object and we looked at how this could happen. We tried to replicate the situation using different bolts in different orientations at different angles .

In theory the twisting force needed to damage the carabiner in this manner could be applied with poorly orientated (or loose) bolts if the carabiner at the bolt end of the quickdraw rotates 180 degrees so that the carabiner is upside down with the wire gate levering/pressing against the hanger at right angles. It is then possible if the carabiner is trapped/has restricted movement that the quickdraw sling can apply a levering action onto the top side of the carabiner and hence the wire gate.

I have tried to replicate this in the image above (a/apologies for the ring in the background, I did not have any plain bolts of this type on hand. b/The quickdraw is on the wrong way round- it just was easier to set up the shot with the tadpole holding the draw in place). The critical factor is that the orientation and shape of the bolt of the bolt facilitates the the biner hanging up and being trapped as the load is applied i.e. it happens much more easily in sheet steel bolts with small apartures that have twisted and sit 90 degrees out of position.

It is also possible to achieve this by getting another carabiner nose engaged in between the wires of the gate and a twisting moment then being applied to one of them whilst the other is held firm.

I hope that makes sense"

Personally I use Phantoms as my trad draws (weight), but use Shadows for sports (burly, keylock and fast to clip) - but then I'm lucky enough to have two sets of draws.

There is more information on climbing carabiners on my site in the tabs below the main text.

Plus there is more info on gear at the new Climbing in Spain site.

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