Karabiners

The grappling iron noticed at reference 1 involved two clips which I remembered as being called karabiners, remembered from an Outward Bound course taken in Aberdovey just about 50 years ago. Something you clipped onto a belt made up of maybe twenty 3mm strands, round and round the waist and tied with a single reef knot. Thinking about it now, I imagine the point of making a belt thus was that it was comfortable, effective and easy. A reef knot of 3mm strands being a lot more effective in this context than a reef knot of 15mm strands.

But these new karabiners involved a sprung joint which was also both notched and threaded, while I remember neither notch nor threading. They were also rounded triangular rather than rounded rectangular in shape.

I can see that having the thread means that one can lock the karabiner shut, a safety feature which has the upside that it is not going to open at a bad time, the downside that it would be hard to open quickly with one hand, should need arise. But what is the point of the notch? Does the rather feeble looking bit of steel making up the notch provide a bit of additional protection against the karabiner deforming, perhaps coming apart, under the stress of a sudden shock, the shock of the rope snatching at the end of a fall?

Once I explained to Bing that I was not talking about carbines, he came up with lots of images of karabiners, and it seems that triangular and threaded is the most popular variety, although the sort that I remember do come in, well down the results page.

I am fairly sure that my memory of rectangular rather than triangular is right, and I am fairly sure that the joint was just bevelled rather than notched. But I am not sure at all about the threading.

PS: notice also how the telephone has done something very odd with the angles of the two halves of the joint, which look quite out of alignment.

Reference 1: http://psmv3.blogspot.co.uk/2017/12/santa.html.