There are 3 categories of dynamic rope as follows:
1. Single ropes - must survive 5 test falls using 80kg drop mass
2. Half ropes - must survive 5 test falls using 55kg drop mass
3. Twin ropes - must survive 12 test falls using 80kg drop mass (tested as a double strand).
Ahhh, I'd not realized #3 --a distinct, higher (much) requirement
for twin ropes !! ?! (Rather, I thought that they were req'd to be
= single ropes in drop-test forces,
and typically DID register more drops,
and otherwise had the benefit of being
more cut-resistant (and allowing full abseil
on the halved rope vs. knotting single lengths
together --possibly of different types & sizes).
((or I forget that I knew this)) )
Hmmm, makes me wonder about fall-catch efficiency
PER WEIGHT of rope!? --and getting frustrated in
a now quick attempt to get grams-per-metre or
other comparative weight info. Seems like the
12-falls limit shows considerable gain in efficiency
for the twin ropes!?
Eventually, the rope breaks.
What is of interest is precisely where the rope breaks.
That is, does rope failure occur at the F8 knot interface with the test mass?
OR;
Does rope failure occur at the orifice (the rope deflects through an orifice which simulates a carabiner).
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EN892 extract:
If breakage occurs at the knot, the test is declared invalid,
and the test shall be repeated starting with a new test sample.
If further test samples break at the knot, the fact shall be recorded,
but the test results stand.
Only one repeat test due to breakage at the knot is allowed.
Another news-to-me and surprising information
--breaking in the knot is considered bad form??!!
Most interesting.
(Another datum to have is break force --to see e.g.
if breaks at the bar (expected per test) come anywhere
near what we'd expect for a Fig.8 EKnot (65%, say). )
Thanks,
--dl*
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