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'while back i promised i would get back to this thread with any relevant experience. a week or two ago, i spent a couple hours trying out various rope solo set ups using the cinch. there were two different setups which were designed (on paper) to catch all falls, inverted or not, by redirecting through a chest harness w/ or without a tiny pulley for friction. these looked good on paper but worked miserably on a rock.
the setup that worked best for me was a pretty standard rope solo setup, like what folks use with a grigri. basically, you load the cinch, hook it up upside down on the belay loop, and attach a cord through the convenient pivot hole to a chest harness to keep it in permanent feed-mode. this is like holding the cinch (or grigri) at the feed angle while throwing rope to a lead climber. it feeds as you climb, and in a normal fall, when the rope is siddenly feeding from above you, instead of below you, it will lock up as designed.
as you get farther away from the anchor, the weight of the rope on both sides of the cinch causes problems. my favorite setup so far is to occasionally tie small slipped overhands in the rope that sit on top of pieces of pro. these support the weight of hte rope so it does not back-feed while climbing. in a fall, they will pop free, giving you full rope stretch, plus an extra 8 inches of rope for every slip knot added to the system.
managing the weight of the feed line is more difficult. my favorite way as of now is to stack it in a small pack and carry it while leading, feeding it over my shoulder in small armfulls. this makes for a very friendly feed. yes, you have to lead with a pack on, but consider it alpine training. i dont intend to rope solo anything particularly hard, anyways.
downsides to the system is the uniquitous inverted fall problem. no, this system will theoretically not catch an inverted fall, as the cinch will think you are just climbing really really fast. i could not think of any clever solutions to this problem, short of buying a silent partner. the one thing i did to slightly attenuate the inverted fall danger is used a quick-release cord to hold the cinch in feed position.
explanation: the upside down cinch is held tight to a chest harness with some sort of cord. i will call this the 'feed cord'. i originally tried an elastic cord, in the hopes that in normal climbing the cinch would feed, but in a fall the elastic would stretch, effectively releasing the feed cord and locking the device. in practise, i could not get this to work reliably and it was a real headache.
i ended up tying a reasonably tight piece of accessory cord from cinch to chest harness (or a bit of webbing around your shoulder, or whatever. it is not load bearing in this application). however, i tied it so that in a fall i could quickly release the feed cord. i used a long piece of 6mm nylon, with a monkey's fist knot at the end. then i tied the chest harness to the cinch in a loop, with a slipped single sheet bend, with the monkey's fist knot as the release. i then fiddled with the knot until it was as tight as i wanted it (could not allow the cinch to drop low enough to lock up in normal climbing, but would not restrict my range of torso movement) and made sure the monkey fist pull cord was very close to the bend.
my idea, untested, is that as soon as i realize i am falling, or am about to fall, i can release the feed cord, thus freeing the cinch to lock up in any fall, inverted or not. this may be a bit of a stretch in some circumstances, but i and others often know we are about to fall, are in imminent danger of falling, or grab onto the rope while falling, so i think it is not completely unrealistic, and gives a bit more margin.
if the feed cord was released and you did not fall, you would still be on belay, albeit on a high-maintenance belay that would require hand feeding the rope until you could get to a rest stance or hang on gear to reset the feed cord.
the 6mm cord with a slipped sheet bend released easily and cleanly, and i do not anticipate problems with the release mechanism unless you dont actually get your hand on the MF knot.
that's the setup. i want to add one relevant bit of information.
i have recently been made aware of a failure mode of the cinch i did not know about. a third party recently tested (fall 05, i think) a number of belay devices, and the cinch was failing at lower loads than i would have expected. the two unexpected failure modes were a clamshelling of the device, thereby releasing the rope, probably with sheath damage, or an actual breaking of the device, in which the rope is released in proximity to sharp metal edges. neither of these sound good to me, particularly because the cinch would see higher loads in service as a rope solo device than a lead belay device, for which it was designed.
if one wanted to use a cinch as a fast feeding rope solo device that does not require modifications (instead of hte grigri), i would take these three considerations: 1) it is more important than ever to backup with a hard tie-in, should the device fail. 2) it is more important than ever to limit the forces on the device. build some shock absorption into the system, ie: a screamer on the anchor, etc. and put a lot of pro in at the start of each pitch. 3) maybe you should look up the load testing of the cinch and make you own decision.
and possibly 4) rope soloing is dangerous. more dangerous than normal leading. the cinch was not designed, or tested, as a rope solo device, and i make no claims about it being safe for such use. i do not know whether the load testing last fall (date?) changes anything about use of the cinch as a lead belay device. i do know that the cinch remains my favorite rope work, rigging, and work positioning device.
for my purposes, i am comfortable with some decreased safety margin. i am a pansy, and generally will not rope solo anything where i believe there is any chance of falling.
as for the future of this thread, i have very infrequent email access, but would welcome insight on any of the comments here, ways to improve systems and safety margins (without investing in a 200 dollar device), new information about cinch failure, etc.
i cant believe you read this far.