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AlanDoak
Trad climber
Boulder, CO
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Topic Author's Original Post - Mar 23, 2015 - 10:12am PT
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Wanting to put my mind at ease about solo top-roping with a microtraxion, I decided to do a (poorly controlled) scientific experiment.
Setup:
1) 10.2mm rope, 2007 vintage, fair condition.
2) myself, 152lbs.
3) Roughly factor 1 fall*: pulled myself up until my waist was at the carabiner, kipped a bit, and let go onto my harness. My intention was to generate a very aggressive test that exceeded anything you'd expect while solo top-roping or simul-climbing.
Results:
1) Visible core shot after 4 drops onto the same spot of the rope.
2) Moved the microtraxion up 3 inches.
3) Visible core shot after 4 more drops onto the same new spot of the rope.
4) Sheath separated on the fifth (9th total) drop. Minor/moderate melting and abrasion of core strands. Some of the visible core damage might have been from the core shot in the first 4 drops.
5) Test was halted due to lack of a boulder pad.
6) No visible effects on micro-traxion.
Conclusions:
1) Yer gonna die!
2) Back up the micro-traxion with something. It's possible to press the button while the cam is retracted, which will lock the device open. Never use a device in a non-redundant application that it's not tested and qualified for. I personally use a 2nd microtraxion, and periodically tie stopper knots if there's a rest stance.
3) After these tests, I feel a lot more comfortable that a fall won't chop the rope catastrophically. I know ST recommends a back-up rope, but I personally feel comfortable using a single line for my solo TR setup. Some people worry that teeth are going to chop through a rope, but these tests indicate otherwise.
*Note on fall factor: the fall forces were increased by the doubled section of rope in the knot, but decreased by biner flex, webbing stretch, wooden beam flex (6"x12"), and my squishy giblets.
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Slabby D
Trad climber
B'ham WA
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Mar 23, 2015 - 10:32am PT
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Seems like the lesson learned is be extremely careful anytime you're approaching the anchor while on a toothed caming device, TR soloing or jugging. But peeps should know that already.
Cool experiment on your part for sure.
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thirsty
climber
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Mar 23, 2015 - 10:49am PT
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I always top rope solo with the sort of set up I use for lead rope soloing, which is either a modified gri gri or a soloist. Sometimes you take hard falls top-roping as when you generate some slack in the system because it binds up while you are going through a crux section. Also – the more I use the lead systems top roping, the smother things go when I am leading. Why use a toothed cam that can damage the rope when there are much better options available?
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le_bruce
climber
Oakland, CA
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Mar 23, 2015 - 10:57am PT
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Hmm. Good food for thought.
You didn't use a shock cord or webbing to keep the micro up around your abdomen, right? Just a biner on the donut?
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steelmnkey
climber
Vision man...ya gotta have vision...
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Mar 23, 2015 - 10:58am PT
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Anyone who takes on the whole rope-soloing thing should know there are limitations to any soloing setup and you should always climb somewhat conservatively. At least in my opinion. Having said that, if you're worried about ripping into your rope with a toothed device, use a Microscender as your upper clamp with a 'trax backup. It has a machined interface for the rope and a cam without teeth. Less rope damage for when you're taking those giant rippers off your proj.
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AlanDoak
Trad climber
Boulder, CO
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Topic Author's Reply - Mar 23, 2015 - 11:17am PT
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Thirsty: Sure, people use a gri-gri for TR soloing. Why not you ask? First, a gri-gri doesn't feed as smoothly as an ascension device, which results in slack building up. Also, on a low angle or slower fall a gri-gri may take a while, or even fail, to catch.
I never use a device in a non-redundant application that it's not rated and certified for. A gri-gri is not certified for self-belay, which means backing it up with something. How to back up the gri-gri without making the system more cumbersome than it already is?
"Why use a toothed cam that can damage the rope..." It's exactly that fear of toothed cams that I wanted to test. It took 4 factor1 falls onto the exact same location of the rope to get a core shot. That's a lot of abuse!
Finally, I use a micro-traxion for simul-climbing and jumars for route cleaning, and these tests translate to those scenarios as well.
"Why use a toothed cam that can damage the rope when there are much better options available?".... By all means, use a Gri-Gri, or whatever you feel most comfortable with. But I don't agree that a Gri-Gri is obviously a better option, for the reasons stated above.
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AlanDoak
Trad climber
Boulder, CO
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Topic Author's Reply - Mar 23, 2015 - 12:17pm PT
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Le-bruce: The micro was tied snug directly into my harness tie-in loops with 5-mil accessory cord (tripled up). There was no chest harness, shock cord, etc.
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mike m
Trad climber
black hills
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Mar 23, 2015 - 12:37pm PT
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Why tie in with the accessory cord and not use a locking biner? Could tying in with the cord make a difference?
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WBraun
climber
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Mar 23, 2015 - 12:58pm PT
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Letting the belay device flop around on the harness in this type of application is not the best way to rig it.
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le_bruce
climber
Oakland, CA
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Mar 25, 2015 - 10:29am PT
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Thanks, Alan, good to know.
You probably already know this, but I think you'd have a hard time getting your sheath the tear if there were no "drop" in your drop test. When you rig it right, it's just a sag, never a drop - I think this is what WBraun is saying above.
With the shock cord or similar, I have zero problem mini'ing on a static. I don't think I'd have the guts to mini on a static line if I didn't use something up around the torso/shoulders to keep the device taught and high. My thinking is that there should never be a drop in a mini or micro session, only a sag - your testing bears that out, I think.
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NA_Kid
Big Wall climber
The Bear State
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Mar 25, 2015 - 11:55am PT
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The micro was tied snug directly into my harness tie-in loops with 5-mil accessory cord (tripled up)
Letting the belay device flop around on the harness in this type of application is not the best way to rig it.
Sounds like OP was trying to avoid the "flop" with the use of 5mm.
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Clint Cummins
Trad climber
SF Bay area, CA
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Mar 25, 2015 - 12:54pm PT
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Thanks for sharing.
It seems unlikely a factor 1 fall could happen in real (microtraxion fixed line) climbing.
More likely would be a 10' fall on 50' of rope.
Given that you don't get a core shot first time on the factor 1, that's a good sign, as you noted.
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