Questioning redundancy of TR solo set up I witnessed

Sorry if there is a better category for this question/observation. Another climber was top rope soloing a climb near me today. I’ve only just learned top rope solo from a course and haven’t been out yet myself but something seemed sketchy about the setup. I asked the guy a bit about it and he said it was redundant, but I don’t think it was. He had one rope that was running through an anchor at the top of the climb and tied in a big loose knot a the bottom (likely for the weight, not really a bundle). He had two nano traxions side by side on his belay loop, each attached to a strand of the rope. The rope was not fixed at the top, just running through the lockers on the anchor master point.

My thought was if one failed such that the rope can run freely through the traxion when he fell, the whole system would fail as the weight of being caught by the other would cause the rope to pull through the anchor since it’s not fixed. So I don’t think the system was redundant like he thinks it might be. It might even be more risky than another system since he has to do more work/be more careful when switching to rappel to descend on his system since if one device becomes unweighted while the other is weighted when trying to go on rappel, I think it could pull the unweighted side through and he would fall. He was tr soloing on an overhanging route so I saw him hanging out in free space and having to finagle some prussiks to unweight the traxions enough to switch to rappel, which just seems like a more complicated system than when you have two devices on separate fixed lines.  

I think I can try to contact the guy’s Facebook account and discuss with him to warn him, but I wanted to ask if my concerns were valid and my assessment of the system is accurate before doing so. 

What you describe is not redundant and is a silly way to TRS

wivanoffwrote:

What you describe is not redundant and is a silly dangerous way to TRS

FTFY

Jess Buchananwrote:

My thought was if one failed such that the rope can run freely through the traxion when he fell, the whole system would fail as the weight of being caught by the other would cause the rope to pull through the anchor since it’s not fixed. 

I think I can try to contact the guy’s Facebook account and discuss with him to warn him, but I wanted to ask if my concerns were valid and my assessment of the system is accurate before doing so. 

Might as well, could save his life. 

Op, your assessment is correct and hopefully the individual does not continue to TRS in this manner. That is a most unnecessarily precarious way to TRS. As for "redundancy," no there is none in a system like that. Spooky! 

Was the bottom of the rope fixed to a ground anchor by chance?   That would make the system a lot safer but still sounds like a pretty janky way to TRS.

I’ve on occasion converted a normal top rope setup to a TRS setup by fixing the bottom of the rope.  But this is generally not an ideal setup and adds some risk and complexity.

Mikey Schaeferwrote:

Was the bottom of the rope fixed to a ground anchor by chance?   That would make the system a lot safer but still sounds like a pretty janky way to TRS.

I’ve on occasion converted a normal top rope setup to a TRS setup by fixing the bottom of the rope.  But this is generally not an ideal setup and adds some risk and complexity.

No, there was no ground anchor at the bottom, just the two strands tied together in a big, loose overhand.

I did reach the guy on Facebook (I had a hunch if I looked for post in the local group looking for a partner, I’d find him and I was right). He was receptive to my concerns and said he had the same concerns when he first started using the system. He is very confident that it is unlikely that a nano traxion will fail and I guess values the easiness of being able to pull the rope to clean the set up more than true redundancy. I realize now he didn’t have an anchor at the top but just the rope running through the rap rings which is why it’s easier to clean.

So I think I’ve done more than my due diligence making sure he is aware of the risk and can only hope he reconsiders his choice of system. I watched him set up rappel before he started TR soloing and one end of his rope didn’t touch the ground. Another climber yelled up to him that it was a few feet off the ground (maybe 3-4ft) but he said it was alright. There was no knot in the end so I added one while he was still getting himself set up. A few feet that would be reduced some with the rope stretch probably isn’t a huge deal but generally the guy is operating a much different level of risk tolerance than I’m used to seeing. 

Jaren W wrote:

But since the issue has been raised, I’m curious about people’s intuition here. Which setup seems likelier to result in an accident? And what’s your reasoning for your choice? Note that the question isn’t, on which system would a fall be more severe.

• A single trax on a line fixed at the top.
• Two traxion devices, one on each strand of a loop tied at the bottom. 

Seems to me that two devices on a loop is likelier to result in an accident. Excuse me while I reveal my clumsiness with statistics but here we go:

Let's say the probability of a device failing is p.

With one rope and one device, the probability of an accident due to due device failure is, (obviously), p.

If I'm understanding the loop system as described by the OP, the system fails if either device fails, because then your weight goes onto only one strand, the loop freely rotates, and you fall until the knot hits the anchor or your body hits the ground. So the odds of that happening are p+p. In other words, the loop system doubles the likelihood of catastrophe.

Now, if you use two devices (which is what I do and I think really should be standard practice, to lay my cards out), you only die if both devices fail. Assuming those are independent events*, then the probability of an accident is p*p. And since probabilities are usually decimals, multiplying them together results in a much smaller number. QED.

*depends on the details of the setup.

ETA I think OP approached this situation with admirable mix of correctly noticing a flawed system, humility, concern for a fellow human's safety, and action.

I think your probabilities are off, but your point still stands. 

If the probability that one device fails is p, then the probability that either device fails (or both fail) is the sum of the following three terms: 

1. the probability that both devices fail, which is p*p
2. the probability that device A fails, but not device B: p*(1-p)
3. the probability that device B fails, but not device A: (1-p)*p

The sum of these three is p*p + 2*p*(1-p) = 2p - p*p. Probabilities are always between 0 and 1, so it's still the case that 2*p - p*p ≥ p. 

The loop system is not quite twice as dangerous, but it is still more dangerous than a single device system. 

 Tying a figure of eight on a bight, or two alpine butterflies with a clip in point between them would surely solve the sketchiness factor here… seems silly to not do that. I don’t really understand the ease of cleaning either.. assuming you hiked to the top of the cliff to set up the TR, I generally just untie my big knot and drop the rope down and hike back out. But each scenario is different! If one micro failed he’s definitely going to pay for it. And they do tend to get stuck open sometimes…

I think I would prefer 1 device on a fixed line vs the system described as I think switching to rappel to descend may involve less potential for a failure or mishap. While switching on the two devices on an unfixed loop, you have to make sure that one device doesn’t become disengaged while the other is weighting the rope, right? I didn’t get a good look at the climber setting up to change to rappel but I think he put a prussik above the devices to unweight and be able to get his atc on for the rappel. I’d guess it’s a similar procedure for the one device on the fixed line but at least you don’t worry about the potential for the rope to start running through the anchor if something goes awry. I am not sure the loose overhand that was a foot or so off the ground would be enough to jam the rap rings should the rope start running with enough distance to keep him hitting the ground. Just want to note that I learned two ascending/progress capture devices on two fixed lines which seems somewhat simpler to switch to descend as you can unlock one device to set up rappel underneath it while weighting the other device. I otherwise learned using a grigri, either with another backup device or alone, which obviously transitions to rappel straightaway. 

I appreciate everyone’s thoughts, like I said it’s not the system for me or one I was aware of until I had seen it. I have no judgement of anyone that decides a single device system is for them and was aware that many people decide to use those systems. I was taught that choosing that is part of a person’s personal risk assessment when choosing to top rope solo. In this situation, I was concerned enough to reach out to the climber because his explanation of the system made it sound like he thought there was redundancy and I didn’t think it was right for someone to possibly be making their risk assessment with perhaps missing or inaccurate information. Which is why I wanted to check that my assessment of it not being redundant was accurate first before saying something. As JarenW said, in the moment I could not ascertain an immediate danger so didn’t say anything in person. But it was on my mind enough to not let it go without some further thought. 

I need to be pedantic and point out that the described system technically is redundant. The climber would fall half the distance to the ground before the knot collides with the disabled device. Obviously still a terrible system.

Austin Donisanwrote:

I need to be pedantic and point out that the described system technically is redundant. The climber would fall half the distance to the ground before the knot collides with the disabled device. Obviously still a terrible system.

Keep in mind that the rope ends are tied together in a "big, loose overhand" intended mostly to keep them off the ground. The system is also not redundant in the event of a rope cut or if a device fails in any way that results in it disconnecting from the harness or rope.

Jess Buchananwrote:

He had two nano traxions

This is a problem as they bite the rope too much. I'd use the NT below a toothless device like a CAMP Lift.

Here is a different perspective.  I use two devices on two fixed strands, not because I think any part of the hardware or material in the system might fail, but because I know that I can and will make mistakes.  For example I might forget to attach one of the devices or I might attach one of the lockers incompletely so that gate is not fully closed and locked.  The point being that I would have to make more than one mistake for the system to fail.  

In this guy's case, he only needs to make one mistake for his system to fail.

For an example, he attaches one device, then gets a text that he needs to respond to, then forgets to attach the other device and starts climbing.  Now he is free soloing.

Jaren W wrote:

I’m probably not alone in my habit of saying aloud each step of the process, even when alone and particularly at the beginning of a session and again when I’m getting tired.

This is part of the "point and call" method employed in railways by conductors in Japan. I'm a big fan of this whether solo or with a partner. It would be interesting to have a separate thread devoted to self-check methods, especially for multi-pitch LRS I think.

giraud bwrote:

This is a problem as they bite the rope too much.

what?

Jaren W wrote:

Great idea, and nice of you to volunteer to start it!   

haha done: https://www.mountainproject.com/forum/topic/126918954/rope-solo-self-checks 

I did once find that my micro was locked open about 40ft off the ground. Luckily I had a nano underneath as backup. I couldn’t figure out for sure how it had been locked open, but I have to assume I probably did it inadvertently without realizing. To Mike G’s point, sometimes we mess up. Good to be redundant.

If I follow jess' description, the guy not only was NOT redundant, he Introduced another point of failure for no good reason. Bad idea.

OP, I would pass Mikey Schaefer's comment to the climber if you haven't already - anchoring both ends to a ground anchor (or 1st bolt) would be a huge improvement within the constraint of "retrievable w/o getting to the top".