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maimed
Aug 23, 2007, 6:34 AM
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Yates Rocker
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roy_hinkley_jr
Aug 23, 2007, 4:46 PM
Post #28 of 39
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Where is this full study available online? This summary leaves a lot of important details out. The conclusions about the autoblock are doubtful at best.
For the OP, the Petzl Shunt is still an excellent device for the stated purpose (also the Ushba Basic). You have to read that report carefully to understand why it doesn't necessarily apply in this case.
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moose_droppings
Aug 23, 2007, 5:02 PM
Post #29 of 39
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roy_hinkley_jr wrote: For the OP, the Petzl Shunt is still an excellent device for the stated purpose (also the Ushba Basic).
Edited to put in the link;
http://www.thebikezone.org.uk/...kzone/selfbelay.html
You might want to read this about the Ushba basic.
Number 6 in the report.
Personaly I'd go with the Rocker or the Soloist, though HJ's got some good things to say about the Eddy.
(This post was edited by moose_droppings on Aug 23, 2007, 5:05 PM)
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roy_hinkley_jr
Aug 23, 2007, 5:09 PM
Post #30 of 39
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Again, READ the actual Lyons report. All of it. Not just some snippet or interpretation.w
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retep
Aug 25, 2007, 10:14 AM
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I have read the report, linked at the bottom of the above selfbelay site.
With regards to the Shunt failing the main issue is that if it hits a knot or other obstruction, possibly by wedging into a crack that the rope is going through, it will likely break as it's body fairly weak. It's designed with the assumption that it will never experience a large force, as it slips quite reliably, but if it can't slip it will likely break.
The same slip that makes it work, even with static rope, however means that it's quite possible to fall very long distances with the Shunt, especially with if a single smaller dynamic rope is being used. Potentially the user could fall the entire length of the rope, as was the case with dynamic rope in the testing in the Lyon report, and is also warned about in the instruction manual for the shunt.
Like a prussik it can also fail if the user grabs it.
Then again work at height uses the shunt with longer lanyards than a climber would, 3 feet is common.
The Ushba Stop-Lock cut the ropes completely, without any slippage, at 5.5kn.
Quite frankly, there's no way I'm using a device that can be easilly made to chop ropes with nothing more than a 2m factor 2 fall onto a dynamic rope. It's just too close to the way I'd use it top-rope soloing.
The shunt isn't so bad, although the slippage is an issue. But I'd definitely have to use a second backup rope, especially with how getting it caught in a crack or the like could so easily destroy it long before the force of the fall would destroy me.
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healyje
Aug 27, 2007, 8:48 AM
Post #32 of 39
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As someone who has been roped solo leading on a steady basis for 32 years on about every system and device (and who was an arborist) I suggest you take a hint from Russ and Bill Coe's posts.
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roy_hinkley_jr
Aug 27, 2007, 4:32 PM
Post #33 of 39
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retep wrote: Quite frankly, there's no way I'm using a device that can be easilly made to chop ropes with nothing more than a 2m factor 2 fall onto a dynamic rope. It's just too close to the way I'd use it top-rope soloing.
Then reading comprehension is a weak point for you. They were testing with 220 lbs in a factor 2 fall on static ropes, which it was never designed for. They never tested the Ushba on a dynamic rope or in a realistic scenrio for top-roping (it was an industrial test by Petzl reps and wasn't designed for climbing). If they had, they'd discover it's actually better than the other devices because it runs so easily and locks quickly without shredding the sheath. Rigged properly, it isn't possible to generate anywhere near that much force since falls are always well under 0.5.
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retep
Aug 29, 2007, 9:36 PM
Post #34 of 39
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In reply to: Then reading comprehension is a weak point for you. They were testing with 220 lbs in a factor 2 fall on static ropes, which it was never designed for. They never tested the Ushba on a dynamic rope or in a realistic scenrio for top-roping (it was an industrial test by Petzl reps and wasn't designed for climbing). If they had, they'd discover it's actually better than the other devices because it runs so easily and locks quickly without shredding the sheath. Rigged properly, it isn't possible to generate anywhere near that much force since falls are always well under 0.5.
You are right, it's been a few months since I read the report completely, and forgot that the two Ushba's they had to test were destroyed before they could test them with the dynamic ropes like the other devices.
All the same, with that logic you'd almost be happily using toothed ascenders, their guaranteed to grab and with the "always well under 0.5" fall factor won't do any damage to the rope. Heck, a Petzl Ascension only pulls the sheath off, not chops the rope, at 6kn load.
I don't see the 100kg making much of a difference. With gear and a pack I probably weigh closer to that than the standard 80kg.
Finally you say that fall factors are always under 0.5, sure, but there's exceptions, like at the top of a climb. That said when I've been rope-soloing I've setup rigging to mitigate that when needed, but still, I'd rather have gear that's more forgiving. Given a significant enough usability advantage I can see your point, but heck, shunts aren't bad and I already have one. (and have tried them out for rope-soloing as well)
Anyway, Ushba stop-locks don't seem to be so easy to buy, if they are available at all, so it's a bit of a moot issue.
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slacklinejoe
Aug 30, 2007, 1:02 AM
Post #35 of 39
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Retep -
If you are willing to accept the advice from those which you solicitied it then why bother posting your original question?
May your luck not run out before your experience and knowledge exceeds the demands of what you are doing.
(This post was edited by slacklinejoe on Aug 30, 2007, 1:12 AM)
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retep
Aug 30, 2007, 1:43 AM
Post #36 of 39
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In reply to: If you are willing to accept the advice from those which you solicitied it then why bother posting your original question? May your luck not run out before your experience and knowledge exceeds the demands of what you are doing.
I think people are missing my goal here. I already know damn well the advantages and disadvantages of various systems, sure there are quibbles over one thing or another, but I have done my research. I was using the prussik in the first place because I was on vacation for a few weeks and didn't have all the gear I'd have liked to have. I climbed accordingly knowing the limitations of a prussik. I *do* know about the slippage issue, after all, I had tested it repeatedly under every way I could think of and found out pretty quick that it's easy to make a prussik fail. So I climbed with that knowledge. I also found that the way I tied it, with that specific rope and that specific cord, had seemed to mitigate that. Still, I was climbing as though I were free-soloing, well, free-soloing with the odd ability to take a rest anytime I wanted to.
In that research I also noticed that no-one had used a specific technique, the blake's hitch. I did some informal testing, which showed it'd likely be safer than a prussik. So I'd like to explore and test that idea in safe situations.
If I simply wanted to learn how to solo-climb I'd be posting in something other than the lab anyway.
My intent was to get some initial data, and do some more testing and maybe propose some ideas. I'm also interested in what exactly are the mechanisms of prussik's not catching, and I do have some ideas that I've tested.
But this thread has been way derailed and should really stop now.
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Tree_wrangler
Aug 31, 2007, 12:38 AM
Post #37 of 39
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In reply to: My intent was to get some initial data, and do some more testing and maybe propose some ideas. I'm also interested in what exactly are the mechanisms of prussik's not catching, and I do have some ideas that I've tested. But this thread has been way derailed and should really stop now.
Ok, but, I'll add one little tidbit before it ends.
The Blake's is a "new" knot. New, in that it was invented by arborist Jason Blake within the last 15 years or so. It was developed for the purpose of ascension, but that doesn't necessarily disqualify it for self-belay. It functions a little bit differently than a prusik, and was designed to work with large diameter rope, presumably the very same rope you're climbing on. You already know this.
It's very likely that the majority of the folks in this discussion have never even heard of a blake's hitch, let alone tied or used one. Heck, I'm a certified tree climber, and I never use one (the trees I climb are too big for it to be a functional tool in most cases).
Sooo.......this question would be better addressed on an arborist or tree-climbing site, at least for the time being. Most of those folks won't have thought about this issue either, but they'll be better qualified to discuss it, given their regular use of the knot. Friction knots as belay systems in general are probably worth asking about on those sites, since those folks use them with more frequency than the rock community. Remember though, "toproping" isn't part of their line of work, so take their responses witha grain of salt as well.
You say you've thought about all the available systems, but none are suited to toproping in your area. I'm not familiar with all the systems, of course, but have found that my silent partner is perfectly adequate for toproping (and bombproof), provided that you understand it will take 5 or 6 feet + to halt the fall. It's kind of like leading with a partner in that scenario, but you're never run-out. The expense is a factor, but any outdoor sport is expensive, so if you're into climbing, you might as well accept this and pony up the dough. (Rafting, for instance, requires about $5000-$8000 worth of gear to get it all together. Even buying the gear you need to ski (including tickets, gas, etc.) can be a couple of thousand. Backcountry gear isn't cheaper, either. So...get used to plunking down dollars, or take up racquetball (which requires a court membership?)
Everyone else........remember, it's basically irrelevant that Royal Robbins burned out prussiks taking a monster lead fall. Our friend here is toproping. Whether or not the prussik will grab the rope quickly and adequately is a valid question, and quite frankly, it sounds like it is not a good tool for toproping because of this issue. A solid backup knot in the actual climbing rope will eliminate the ground from the equation though. The point though, is that discussions of how knots will behave in the most extreme situations retards knowledge of how they will behave in normal, commonly encountered situations.
Anyhow, I'm still curious about the limits of a blake's as well.....I just don't know the answer, and I'm not sure that anyone else does either!
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knudenoggin
Sep 2, 2007, 4:45 AM
Post #38 of 39
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Tree_wrangler wrote: Ok, but, I'll add one little tidbit before it ends. The Blake's is a "new" knot. New, in that it was invented by arborist Jason Blake within the last 15 years or so. It was developed for the purpose of ascension, but that doesn't necessarily disqualify it for self-belay. It functions a little bit differently than a prusik, and was designed to work with large diameter rope, presumably the very same rope you're climbing on. You already know this.
The ProhGrip (as I like to call it) aka "Blake's Hitch" was developed
(also) by Heinz Prohaska, as published circa 1986 in an Austrian mountain
guides document, and in Nylon Highway--the spelos' journal--in issue
#30 of May 1990. Jason apparently had independent similar ideas.
"designed to work with large diameter rope": this is ambiguous re which
rope; an appeal of the ProhGrip is that it works with relatively small
dia. rope objects (what it's tied to), i.e. equal size. (Reflect on the
admonitions to smaller dia. cord for Prusik hitches relative to the climbing
line's approx. 10mm. Arborists use the ProhGrip in the same rope as
they're climbing--although this is a comparatively flexible rope!)
Heinz recommends increasing the numbe of turns above the tucked end
for improved grip is slickness of the hitched rope seems the problem,
and increase turns over the tucked end if small diameter or stiffness of
the hitching rope is. He presents the hitch in both rope & webbing; it
is in single-strand in both cases. One can make a like knot with a sling
similar to the Klemheist hitch, in which just one side of the collaring bight
is wrapped over at the load end; twin strand knots seem to have less
strong grip.
Also in the Nylon Hwy article Heinz presents another gripping hitch
("klemmknoten"), also instantiated in both single & twin strand media.
For use with a sling, put a bight-end across the rope w/enough sticking
beyond it for a finishing tuck-through, then wrap around and come up
below this perpendicular bight and continue wrapping now upwards past
it three times (YMMV); finally then making a longer wrap and arc around
down to pass through the initial bight-end. (Thus, more like the Hedden
or upside-down Klemheist.)
In reply to: this question would be better addressed on an arborist or tree-climbing site, at least for the time being. Most of those folks won't have thought about this issue either, but they'll be better qualified to discuss it, given their regular use of the knot.
ropes--which are polyesterly not so elastic! Beware transferring knotted
structures from one environment into another--materials and practices
differ, here. (Actually, re materials, for the hitch one wants a pretty
flexible material--more important than size.)
*kN*
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sixleggedinsect
Sep 2, 2007, 5:11 AM
Post #39 of 39
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two idle thoughts:
1) no stats about various prussik materials and diameters and wraps will give you a foolproof setup. the stiffness and coatings on the rope and prussik cord both change everything. i do believe they can be completely safe for a toprope setup, but it requires some thought and would only really be a good idea if you (like you say was the case) didnt have a more appropriate device on hand.
2) my vote for best solo toprope device: trango cinch. smoother faster feed than grigri. no dicking around to set up to lower. it has its ups and downs like anything else, but in my experience, more ups than anything else.
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