The following article is courtesy of Black Diamond Equipment.
Whether it's at the local gym or a dreamy vacation cliff in the Mediterranean, we've all been there: You finish a sport
climb and are ready to clip your rope through the anchors (e.g., cold shuts, leaver biners, chain links, etc.) when you notice that countless lowerings
and top roping have left gnarly rope grooves in the anchors. Will these grooved-out anchors hold? Will the sharp edges trash my rope?
Recently a friend of mine was doing his part at a local sport crag by replacing old bolts and rope-grooved anchors. He pulled these off and wanted me to
test them to see how weak they were. (I'm not going to get into the technicalities, pluses or minuses of different kinds of anchors and am not condoning
anything in anyway—I'm just looking at only one style of cold shut, one test, two data points, just out of curiosity more than anything.)
the rope groove of the test samples, the reduction in thickness was about 25%. Therefore, the used cold shuts would be 25% weaker, right? Wrong.
- The two rope-grooved samples tested to 2330 lbf and 2522 lbf, before they deformed and slipped open.
- The new cold shut stretched all the way open at a load of only 1466 lbf.
So how and why did the rope-grooved cold shuts withstand a higher load than a brand new one? Take a look at these testing photos (the new cold shut is
on the left):
The rope groove forces the rope to stay in line with the main axis and direction of load of the cold shut, whereas with a new cold shut, as the load increases,
the rope is able to slide out and cantilevers it open at a reduced load. So rather than reduce the tensile strength of the shut due to removal of material,
the groove seats the rope onto the spine so that the shut holds more weight before it starts to deform.
Conclusions, Comments, Remarks
- Rope-grooved cold shuts keep the load in line with the strongest axis and therefore can withstand a higher load before deformation.
Just because a rope-grooved anchor may be stronger, however, doesn't make it better. The sharp edges of rope-grooved anchors and biners can potentially
damage the rope's sheath. If you see anchors or biners out in the field that look beat up, do your part and replace them. You can also use your own
quickdraws or biners at anchors in order to save on wear and tear of the fixed anchors.
Be safe out there,
Kolin Powick (KP) is a mechanical engineer hailing from Calgary, Canada. He has over 20 years of experience in the engineering field and served as Black Diamond’s Director of Quality for over 11 years. He is currently their Climbing Category Director. If you have a technical question for KP, please email him at firstname.lastname@example.org and he will TRY to respond.
To help make more climbers safer climbers, Rock and Ice has teamed up with Black Diamond Equipment to present the information here.