Chocolate fireguard
Active member
Aside from whether a 50% loss of strength in an 8mm anchor causes a dangerous situation (answer, no) that’s also a valid question.Does wear make sharper edges that could cut or chafe a rope (especially on a pull through) Id imagine this would cause a problem sooner than the metal failing
The first place to start would be an anchor that has supposedly been eroded from an “O” profile to a “D” profile due to pulldown, with the flat side horizontal, like in the first drawing. I think that’s how many people would initially imagine the situation.
The other anchor is some distance off to the right.
T1 is the tension in the vertical rope and T2 that in the horizontal one.
T is the resultant force applied by the rope to the anchor and so the force on the rope will be in the opposite direction. It will certainly risk damaging the rope.
But on pulldown the rope will tend to blunt that sharp edge.
So the obvious question is “how can that edge have developed due to pulldown in the first place?”.
And I think the obvious answer is “it can’t”.
If that setup continued in use then the hatched area on the left would be removed by successive ropes.
Applying that same argument to the RHS of the “D” and remembering that the downwards force there is minimal because of the other anchor off to the right, then starting with an unworn anchor I think the profile after about 50% of the metal has gone will be as in the second diagram.
There will be minor differences on that RHS if the other anchor is a little below or above, but nothing really on the load side. The rope would not be running over any sharp edges.
Apologies for the poor drawings.