i've done some testing with scales on lines after trying to find a friendly SRT friction hitch to descend on as Tom and Mike Maas where(or maybe try to beat'em to it!). For this descending on friction hitch in SRT seemed such a rather elusive thing to try to capture.
In my crazy imagery from these tests:
A friction hitch needs to unload pretty much to slide smoothly; besides the half loadded effect of DdRT. Or else, a 125# climber could descend as smoothly on a given hitch in SRT as a 250# climber descends in DdRT. For, if the only key were the 2/1 DdRT advantage/effect; this would work.
If any load has 2 legs of support(conjoined or seperate), and one leg starts to fail or stretch, the other 'buddy' leg takes the strain. This is partially why a Square Knot is okay as a knot around a package and not as a free hanging bend (besides the ability of a Square around a package to stabilize and not be able to spin if around/pressed into a package as it's mount/host); for if the "DdRT" of the Square Knot around the package starts to slip at the knot (that i think of more as a jam of pitting the euql and opposites agaisnt each other); the static side/ flip side of the package's rope, can take the strain. In the SRT mode of trying to use the Square as a bend; it loses this 'buddy' line as a stabilizer; as well as the stabilizing effect against the package. Stabilization very important to this 'jam'; a Granny doesn't sit Square/ stabilized and can fail for similar reasons/ mechaincs i theorize.
In DdRT, the static/terminated at saddle leg of the support takes the load as we slide hitch, lessening/unloading the tension on the dynamic/friction hitch side(scales on static side ond friction hitch say so); it has the static / buddy leg to take over; as the system still tries to lend support. In SRT, there is no alternative/ buddy leg, and as we go to slide the hitch, the system still tries to support us, and grips harder, or fails/ burns from increased friction, doesn't slide smoothly/ safely. The scale on hitch doesn't unload.
i think also, this is why we can safely DdRT on the tight bight of 2 1/2" rings or ART; but should not lower a load remotely thru same; using FS or ART as redirect. Lowering a load thru such a tight bight, works more force around the tight bight; and suffers weaknesses of such action and the leveraged loss of the supporting fibers that are singled out to carry the load around the bight. But, in lowering self, the system has the option of jumping the force across to the static side of the line, without going through the tight bight; more accentuated with the friction of the rings i think. So, this is more like just a termination on a tight bight, than cranking force across/through such a tight bight(?).
Spock Out,
