The OP's problem is quite a tough one : you want to be able
somehow to release a hitch=>
attachment remotely after it
has supported body weight (or more),
and yet in the "unweighted" state, even, there is still
someweight on it --of the very material (here, perhaps 60m of rope,
or around 7-10 pounds) ! (Btw, I wonder about the actual
pounds-force upon the anchor, if the mass of the rope having
been stretched down over some rocky surface now has its
mass hanging PLUS some frictional resistance to recovering
the tension put on during abseil --i.e., the difference between
hoisting the mass in air vs. dragging it against the rock?)
The main (though itself not purely reliable) input people at
the (down) end of the line can give is tension, but the
attachment must have just endured that.
All that occurs to me in crude terms is having some structure
that has a sort of counterbalance weight to it that is well
greater than the hanging line and yet well less than that
of line + rappeller, such that when the line is unweighted
by the latter, this weight effects the spilling of the attachment.
But beyond this crude idea, I've no manifestation in mind,
and wonder at the reliable provision of such a counterweight,
and to the effect of line + CW free-falling from on high,
and possible ensuing troubles of line snagging ... !
--from the pot to the frying pan.
--dl*
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