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csproul


Nov 11, 2009, 11:05 AM
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Re: [dingus] An anchor to analyze [In reply to]
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dingus wrote:
jt512 wrote:
I can count on my fingers the number of times I've climbed on an anchor that at least a 1% chance of failing, and still have 10 fingers left over. I have a feeling you could, too.

Jay

I'd dare say you've never climbed on any anchor where the probability of failure was more than opinion. Now I would accept your opinion as a matter of faith... and even be willing to stake my life on it (If you tell me your anchor is good I would believe it face value (and still inspect it when I got there hehe)).

But expressing it as a number is just a way of stating opinion, nothing more.

DMT
For such low probabilities, that is true. However, if we are talking about a toprope anchor with a 1 in 10 failure rate, then it wouldn't take too long to confirm this as more than opinion! Hell, even with 1 in 100 odds, it wouldn't take all that long for a group of top-ropers to accumulate enough falls to have a good chance at anchor failure.


dingus


Nov 11, 2009, 11:12 AM
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Re: [csproul] An anchor to analyze [In reply to]
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csproul wrote:
dingus wrote:
jt512 wrote:
I can count on my fingers the number of times I've climbed on an anchor that at least a 1% chance of failing, and still have 10 fingers left over. I have a feeling you could, too.

Jay

I'd dare say you've never climbed on any anchor where the probability of failure was more than opinion. Now I would accept your opinion as a matter of faith... and even be willing to stake my life on it (If you tell me your anchor is good I would believe it face value (and still inspect it when I got there hehe)).

But expressing it as a number is just a way of stating opinion, nothing more.

DMT
For such low probabilities, that is true. However, if we are talking about a toprope anchor with a 1 in 10 failure rate, then it wouldn't take too long to confirm this as more than opinion! Hell, even with 1 in 100 odds, it wouldn't take all that long for a group of top-ropers to accumulate enough falls to have a good chance at anchor failure.

I have never witnessed such an anchor, personally.

The one that spawned this thread isn't even in the same universe.

DMT


jt512


Nov 11, 2009, 11:13 AM
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Re: [dingus] An anchor to analyze [In reply to]
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dingus wrote:
jt512 wrote:
I can count on my fingers the number of times I've climbed on an anchor that at least a 1% chance of failing, and still have 10 fingers left over. I have a feeling you could, too.

Jay

I'd dare say you've never climbed on any anchor where the probability of failure was more than opinion. Now I would accept your opinion as a matter of faith... and even be willing to stake my life on it (If you tell me your anchor is good I would believe it face value (and still inspect it when I got there hehe)).

But expressing it as a number is just a way of stating opinion, nothing more.

DMT

Well, we know that the probability of failure of a randomly selected anchor in a randomly selected fall (including TR falls, the subject of the thread) is much less than 1% because, while there are thousands upon thousands of such falls every year, the number of total failures is on the order of one. Of course, individual anchors will vary in quality, but "probability of failure" of an individual anchor, as used in this thread, is ill defined. After all, once the forces of the fall are specified, a given anchor will either fail or it won't. The probability of the anchor failing is just the probability of a fall occurring that exceeds the anchor's failure threshold.

Jay


csproul


Nov 11, 2009, 11:13 AM
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Re: [dingus] An anchor to analyze [In reply to]
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dingus wrote:
csproul wrote:
dingus wrote:
jt512 wrote:
I can count on my fingers the number of times I've climbed on an anchor that at least a 1% chance of failing, and still have 10 fingers left over. I have a feeling you could, too.

Jay

I'd dare say you've never climbed on any anchor where the probability of failure was more than opinion. Now I would accept your opinion as a matter of faith... and even be willing to stake my life on it (If you tell me your anchor is good I would believe it face value (and still inspect it when I got there hehe)).

But expressing it as a number is just a way of stating opinion, nothing more.

DMT
For such low probabilities, that is true. However, if we are talking about a toprope anchor with a 1 in 10 failure rate, then it wouldn't take too long to confirm this as more than opinion! Hell, even with 1 in 100 odds, it wouldn't take all that long for a group of top-ropers to accumulate enough falls to have a good chance at anchor failure.

I have never witnessed such an anchor, personally.

The one that spawned this thread isn't even in the same universe.

DMT
Agreed, and I think that was kind of Jay's point too.


dingus


Nov 11, 2009, 11:33 AM
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Re: [jt512] An anchor to analyze [In reply to]
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jt512 wrote:
dingus wrote:
jt512 wrote:
I can count on my fingers the number of times I've climbed on an anchor that at least a 1% chance of failing, and still have 10 fingers left over. I have a feeling you could, too.

Jay

I'd dare say you've never climbed on any anchor where the probability of failure was more than opinion. Now I would accept your opinion as a matter of faith... and even be willing to stake my life on it (If you tell me your anchor is good I would believe it face value (and still inspect it when I got there hehe)).

But expressing it as a number is just a way of stating opinion, nothing more.

DMT

Well, we know that the probability of failure of a randomly selected anchor in a randomly selected fall (including TR falls, the subject of the thread) is much less than 1% because, while there are thousands upon thousands of such falls every year, the number of total failures is on the order of one. Of course, individual anchors will vary in quality, but "probability of failure" of an individual anchor, as used in this thread, is ill defined. After all, once the forces of the fall are specified, a given anchor will either fail or it won't. The probability of the anchor failing is just the probability of a fall occurring that exceeds the anchor's failure threshold.

Jay

Yes but the probability of a given anchor failing has no correlation to the statement of opinion expressed as a probability by climbers and passersby.

Hence my post.

DMT


seatbeltpants


Nov 11, 2009, 11:37 AM
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Re: [reno] An anchor to analyze [In reply to]
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reno wrote:
seatbeltpants wrote:
screw climbing on an anchor that has a 1% chance of blowing - but i'm terrified that some posters seem to have no worries climbing on an anchor that has a 1 in 5 chance of blowing?! russian roulette, anyone?

It must be comforting to do all your climbing on rock that is 100% solid, with all the gear you could possibly need to construct an anchor that is 100% safe from any possible chance of failure.

That sort of climbing has nothing in common with the kind of rock/ice/alpine/mountain climbing I've ever seen and done.

Maybe it's just me, but every anchor I've ever seen has potential to fail. Some have more potential than others.

for sure, and i expect we're probably on much the same page - god knows the rock in my neck of the woods can be chossy as hell and i'd never try to fool myself into thinking any placement is bombproof.

as dingus et al said above any numbers about chance of failure are pulled out of our arses so it's all just theoretical, but i'm pretty sure that if my partner built an anchor and reported that it had a 20% chance of failing i wouldn't climb on it. sometimes, for sure, you need to make the most of what's available and suck it up, hope for the best, and carry on.

i have a pretty low tolerance for that, though - i'm way too much of a pussy to climb ice or alpine.

your last line - "Maybe it's just me, but every anchor I've ever seen has potential to fail. Some have more potential than others." - is gospel in my book. someone who thinks that any anchor is completely incapable of failing needs their head checked.

steve


jt512


Nov 11, 2009, 11:38 AM
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Re: [dingus] An anchor to analyze [In reply to]
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dingus wrote:
jt512 wrote:
dingus wrote:
jt512 wrote:
I can count on my fingers the number of times I've climbed on an anchor that at least a 1% chance of failing, and still have 10 fingers left over. I have a feeling you could, too.

Jay

I'd dare say you've never climbed on any anchor where the probability of failure was more than opinion. Now I would accept your opinion as a matter of faith... and even be willing to stake my life on it (If you tell me your anchor is good I would believe it face value (and still inspect it when I got there hehe)).

But expressing it as a number is just a way of stating opinion, nothing more.

DMT

Well, we know that the probability of failure of a randomly selected anchor in a randomly selected fall (including TR falls, the subject of the thread) is much less than 1% because, while there are thousands upon thousands of such falls every year, the number of total failures is on the order of one. Of course, individual anchors will vary in quality, but "probability of failure" of an individual anchor, as used in this thread, is ill defined. After all, once the forces of the fall are specified, a given anchor will either fail or it won't. The probability of the anchor failing is just the probability of a fall occurring that exceeds the anchor's failure threshold.

Jay

Yes but the probability of a given anchor failing has no correlation to the statement of opinion expressed as a probability by climbers and passersby.

Hence my post.

DMT

My point is that until someone carefully defines what they mean by the probability of an individual anchor failing, there is nothing to talk about. The way "probability" is being used in this thread is meaningless.

Jay


LostinMaine


Nov 11, 2009, 11:57 AM
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Re: [jt512] An anchor to analyze [In reply to]
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jt512 wrote:
dingus wrote:
jt512 wrote:
dingus wrote:
jt512 wrote:
I can count on my fingers the number of times I've climbed on an anchor that at least a 1% chance of failing, and still have 10 fingers left over. I have a feeling you could, too.

Jay

I'd dare say you've never climbed on any anchor where the probability of failure was more than opinion. Now I would accept your opinion as a matter of faith... and even be willing to stake my life on it (If you tell me your anchor is good I would believe it face value (and still inspect it when I got there hehe)).

But expressing it as a number is just a way of stating opinion, nothing more.

DMT

Well, we know that the probability of failure of a randomly selected anchor in a randomly selected fall (including TR falls, the subject of the thread) is much less than 1% because, while there are thousands upon thousands of such falls every year, the number of total failures is on the order of one. Of course, individual anchors will vary in quality, but "probability of failure" of an individual anchor, as used in this thread, is ill defined. After all, once the forces of the fall are specified, a given anchor will either fail or it won't. The probability of the anchor failing is just the probability of a fall occurring that exceeds the anchor's failure threshold.

Jay

Yes but the probability of a given anchor failing has no correlation to the statement of opinion expressed as a probability by climbers and passersby.

Hence my post.

DMT

My point is that until someone carefully defines what they mean by the probability of an individual anchor failing, there is nothing to talk about. The way "probability" is being used in this thread is meaningless.

Jay

I just want a p-value or an ANOVA table to tell me if this anchor will hold!


I think the real "problem" is that we are trying to force quantitative measures on a qualitative analysis.


dugl33


Nov 11, 2009, 12:51 PM
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jt512 wrote:
My point is that until someone carefully defines what they mean by the probability of an individual anchor failing, there is nothing to talk about. The way "probability" is being used in this thread is meaningless.
Jay

Agreed, this sort of thinking implies that anchor failure is random chance, like picking the right number for the lottery.

Perhaps it's more on the mark to ask what is a reasonable margin of safety, and how do we get there. I would guess an engineer would look at test data, do some calculations, and then design something 5 times stronger (at least theoretically 5 times stronger) or whatever safety factor one chooses.

If you actually pull tested it, you would most likely not generate enough force to pull out the one lonely .75 camalot with one lonely biner, in a typical top-rope quantity of force.

Of course, this wouldn't meet our margin of safety, shit happens, standards.


sittingduck


Nov 11, 2009, 1:13 PM
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Re: [jt512] An anchor to analyze [In reply to]
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jt512 wrote:
dingus wrote:
jt512 wrote:
dingus wrote:
jt512 wrote:
I can count on my fingers the number of times I've climbed on an anchor that at least a 1% chance of failing, and still have 10 fingers left over. I have a feeling you could, too.

Jay

I'd dare say you've never climbed on any anchor where the probability of failure was more than opinion. Now I would accept your opinion as a matter of faith... and even be willing to stake my life on it (If you tell me your anchor is good I would believe it face value (and still inspect it when I got there hehe)).

But expressing it as a number is just a way of stating opinion, nothing more.

DMT

Well, we know that the probability of failure of a randomly selected anchor in a randomly selected fall (including TR falls, the subject of the thread) is much less than 1% because, while there are thousands upon thousands of such falls every year, the number of total failures is on the order of one. Of course, individual anchors will vary in quality, but "probability of failure" of an individual anchor, as used in this thread, is ill defined. After all, once the forces of the fall are specified, a given anchor will either fail or it won't. The probability of the anchor failing is just the probability of a fall occurring that exceeds the anchor's failure threshold.

Jay

Yes but the probability of a given anchor failing has no correlation to the statement of opinion expressed as a probability by climbers and passersby.

Hence my post.

DMT

My point is that until someone carefully defines what they mean by the probability of an individual anchor failing, there is nothing to talk about. The way "probability" is being used in this thread is meaningless.

Jay

If the probability of failure is undefinable, maybe the climber should consider rigging the anchor in a way that changes said probability closer to zero?


jt512


Nov 11, 2009, 1:32 PM
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Re: [sittingduck] An anchor to analyze [In reply to]
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sittingduck wrote:
jt512 wrote:
dingus wrote:
jt512 wrote:
dingus wrote:
jt512 wrote:
I can count on my fingers the number of times I've climbed on an anchor that at least a 1% chance of failing, and still have 10 fingers left over. I have a feeling you could, too.

Jay

I'd dare say you've never climbed on any anchor where the probability of failure was more than opinion. Now I would accept your opinion as a matter of faith... and even be willing to stake my life on it (If you tell me your anchor is good I would believe it face value (and still inspect it when I got there hehe)).

But expressing it as a number is just a way of stating opinion, nothing more.

DMT

Well, we know that the probability of failure of a randomly selected anchor in a randomly selected fall (including TR falls, the subject of the thread) is much less than 1% because, while there are thousands upon thousands of such falls every year, the number of total failures is on the order of one. Of course, individual anchors will vary in quality, but "probability of failure" of an individual anchor, as used in this thread, is ill defined. After all, once the forces of the fall are specified, a given anchor will either fail or it won't. The probability of the anchor failing is just the probability of a fall occurring that exceeds the anchor's failure threshold.

Jay

Yes but the probability of a given anchor failing has no correlation to the statement of opinion expressed as a probability by climbers and passersby.

Hence my post.

DMT

My point is that until someone carefully defines what they mean by the probability of an individual anchor failing, there is nothing to talk about. The way "probability" is being used in this thread is meaningless.

Jay

If the probability of failure is undefinable, maybe the climber should consider rigging the anchor in a way that changes said probability closer to zero?

Huh?

Jay


aspiringloser


Nov 11, 2009, 1:48 PM
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Re: [robdotcalm] An anchor to analyze [In reply to]
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You should always jump with a hook knife. Some people who do CRW jump with more than one. If you're entangled with your main and you have time, you cut lines until you're free then you deploy the reserve. If you don't have time to cut yourself free you fire your reserve and hope for the best.


sittingduck


Nov 11, 2009, 1:51 PM
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Re: [jt512] An anchor to analyze [In reply to]
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jt512 wrote:
sittingduck wrote:
jt512 wrote:
dingus wrote:
jt512 wrote:
dingus wrote:
jt512 wrote:
I can count on my fingers the number of times I've climbed on an anchor that at least a 1% chance of failing, and still have 10 fingers left over. I have a feeling you could, too.

Jay

I'd dare say you've never climbed on any anchor where the probability of failure was more than opinion. Now I would accept your opinion as a matter of faith... and even be willing to stake my life on it (If you tell me your anchor is good I would believe it face value (and still inspect it when I got there hehe)).

But expressing it as a number is just a way of stating opinion, nothing more.

DMT

Well, we know that the probability of failure of a randomly selected anchor in a randomly selected fall (including TR falls, the subject of the thread) is much less than 1% because, while there are thousands upon thousands of such falls every year, the number of total failures is on the order of one. Of course, individual anchors will vary in quality, but "probability of failure" of an individual anchor, as used in this thread, is ill defined. After all, once the forces of the fall are specified, a given anchor will either fail or it won't. The probability of the anchor failing is just the probability of a fall occurring that exceeds the anchor's failure threshold.

Jay

Yes but the probability of a given anchor failing has no correlation to the statement of opinion expressed as a probability by climbers and passersby.

Hence my post.

DMT

My point is that until someone carefully defines what they mean by the probability of an individual anchor failing, there is nothing to talk about. The way "probability" is being used in this thread is meaningless.

Jay

If the probability of failure is undefinable, maybe the climber should consider rigging the anchor in a way that changes said probability closer to zero?

Huh?

Jay

The definition of the probability of failure in the anchor you captured, is that it is most likely not 0 (zero).
If the climber rigged that anchor with opposed and opposite carabiners at the masterpoint, he would change the probability of failure closer to zero.


dugl33


Nov 11, 2009, 2:03 PM
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Re: [sittingduck] An anchor to analyze [In reply to]
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To no one in particular, I know I'm new here, but what's up with the massive quote within a quote text strings?

Is it so hard to pick out the specific text you are responding to?

Maybe I'll feel differently when I've broken the 10,000 posts threshold. Unsure


jt512


Nov 11, 2009, 2:15 PM
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Re: [dugl33] An anchor to analyze [In reply to]
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dugl33 wrote:
To no one in particular, I know I'm new here, but what's up with the massive quote within a quote text strings?

Is it so hard to pick out the specific text you are responding to?

Uh oh.

Jay


jt512


Nov 11, 2009, 2:20 PM
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Re: [sittingduck] An anchor to analyze [In reply to]
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sittingduck wrote:
jt512 wrote:
sittingduck wrote:
jt512 wrote:
My point is that until someone carefully defines what they mean by the probability of an individual anchor failing, there is nothing to talk about. The way "probability" is being used in this thread is meaningless.

Jay

If the probability of failure is undefinable, maybe the climber should consider rigging the anchor in a way that changes said probability closer to zero?

Huh?

Jay

The definition of the probability of failure in the anchor you captured, is that it is most likely not 0 (zero).
If the climber rigged that anchor with opposed and opposite carabiners at the masterpoint, he would change the probability of failure closer to zero.

You are confusing definition of probability with estimate of probability. My point was that no one has come up with what "probability" means in this context; therefore, it is meaningless to attempt to estimate a value of that probability.

Jay


(This post was edited by jt512 on Nov 11, 2009, 2:23 PM)


dugl33


Nov 11, 2009, 2:38 PM
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jt512 wrote:

You are confusing definition of probability with estimate of probability. My point was that no one has come up with what "probability" means in this context; therefore, it is meaningless to attempt to estimate a value of that probability.
Jay

Top rope it 10,000 times. Record the number of failures, divide by 10,000. There you go -- probability of failure.


reno


Nov 11, 2009, 2:47 PM
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seatbeltpants wrote:
reno wrote:
seatbeltpants wrote:
screw climbing on an anchor that has a 1% chance of blowing - but i'm terrified that some posters seem to have no worries climbing on an anchor that has a 1 in 5 chance of blowing?! russian roulette, anyone?

It must be comforting to do all your climbing on rock that is 100% solid, with all the gear you could possibly need to construct an anchor that is 100% safe from any possible chance of failure.

That sort of climbing has nothing in common with the kind of rock/ice/alpine/mountain climbing I've ever seen and done.

Maybe it's just me, but every anchor I've ever seen has potential to fail. Some have more potential than others.

for sure, and i expect we're probably on much the same page -

**SNIP**

your last line - "Maybe it's just me, but every anchor I've ever seen has potential to fail. Some have more potential than others." - is gospel in my book. someone who thinks that any anchor is completely incapable of failing needs their head checked.

Yep, we are on the same page, we just didn't know it. Cheers, dude.


Rudmin


Nov 11, 2009, 3:00 PM
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jt512 wrote:
dingus wrote:
jt512 wrote:
I can count on my fingers the number of times I've climbed on an anchor that at least a 1% chance of failing, and still have 10 fingers left over. I have a feeling you could, too.

Jay

I'd dare say you've never climbed on any anchor where the probability of failure was more than opinion. Now I would accept your opinion as a matter of faith... and even be willing to stake my life on it (If you tell me your anchor is good I would believe it face value (and still inspect it when I got there hehe)).

But expressing it as a number is just a way of stating opinion, nothing more.

DMT

Well, we know that the probability of failure of a randomly selected anchor in a randomly selected fall (including TR falls, the subject of the thread) is much less than 1% because, while there are thousands upon thousands of such falls every year, the number of total failures is on the order of one. Of course, individual anchors will vary in quality, but "probability of failure" of an individual anchor, as used in this thread, is ill defined. After all, once the forces of the fall are specified, a given anchor will either fail or it won't. The probability of the anchor failing is just the probability of a fall occurring that exceeds the anchor's failure threshold.

Jay

I clearly defined the probability of failure to be measured over the one day use of an anchor, as in between set up and take down. When I brought up the subject of probability. I think this makes the most sense in defining failure rather than a certain chance each time you fall on it.


Partner drector


Nov 11, 2009, 3:02 PM
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Re: [dugl33] An anchor to analyze [In reply to]
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dugl33 wrote:
jt512 wrote:

You are confusing definition of probability with estimate of probability. My point was that no one has come up with what "probability" means in this context; therefore, it is meaningless to attempt to estimate a value of that probability.
Jay

Top rope it 10,000 times. Record the number of failures, divide by 10,000. There you go -- probability of failure.

Wouldn't it be better to fall on the anchor 10,000 times and record the number of failures? What does "top rope it..." mean? Once you explain that very clearly and with some charts and equations, we can then get to worrying about probabilities. Please include the dynamic properties of the rope and the weight of the belayer in the definition. Direction of the any fall is also important since the anchor may fail every time if the direction of pull it up while it may never fail if the direction of pull is exactly as the anchor is configured to allow.

Dave


swoopee


Nov 11, 2009, 3:08 PM
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Re: [drector] An anchor to analyze [In reply to]
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Okey everyone, just shut up and climb.


jt512


Nov 11, 2009, 3:22 PM
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Re: [dugl33] An anchor to analyze [In reply to]
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dugl33 wrote:
jt512 wrote:

You are confusing definition of probability with estimate of probability. My point was that no one has come up with what "probability" means in this context; therefore, it is meaningless to attempt to estimate a value of that probability.
Jay

Top rope it 10,000 times. Record the number of failures, divide by 10,000. There you go -- probability of failure.

Shouldn't the definition depend on the anchor being weighted? Or fallen on?

Edit: Oops...GUed by drector.

Jay


(This post was edited by jt512 on Nov 11, 2009, 3:24 PM)


jt512


Nov 11, 2009, 3:25 PM
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Re: [Rudmin] An anchor to analyze [In reply to]
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Rudmin wrote:
I clearly defined the probability of failure to be measured over the one day use of an anchor, as in between set up and take down. When I brought up the subject of probability. I think this makes the most sense in defining failure rather than a certain chance each time you fall on it.

Then that makes of one of us who thinks that.

Jay


sittingduck


Nov 11, 2009, 3:44 PM
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Re: [jt512] An anchor to analyze [In reply to]
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jt512 wrote:
sittingduck wrote:
jt512 wrote:
sittingduck wrote:
jt512 wrote:
My point is that until someone carefully defines what they mean by the probability of an individual anchor failing, there is nothing to talk about. The way "probability" is being used in this thread is meaningless.

Jay

If the probability of failure is undefinable, maybe the climber should consider rigging the anchor in a way that changes said probability closer to zero?

Huh?

Jay

The definition of the probability of failure in the anchor you captured, is that it is most likely not 0 (zero).
If the climber rigged that anchor with opposed and opposite carabiners at the masterpoint, he would change the probability of failure closer to zero.

You are confusing definition of probability with estimate of probability. My point was that no one has come up with what "probability" means in this context; therefore, it is meaningless to attempt to estimate a value of that probability.

Jay

So what? The value of probability of that anchor failing was high enough to catch your attention and post pictures of it here, right?


dugl33


Nov 11, 2009, 3:48 PM
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Re: [drector] An anchor to analyze [In reply to]
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drector wrote:
dugl33 wrote:
jt512 wrote:

You are confusing definition of probability with estimate of probability. My point was that no one has come up with what "probability" means in this context; therefore, it is meaningless to attempt to estimate a value of that probability.
Jay

Top rope it 10,000 times. Record the number of failures, divide by 10,000. There you go -- probability of failure.

Wouldn't it be better to fall on the anchor 10,000 times and record the number of failures? What does "top rope it..." mean? Once you explain that very clearly and with some charts and equations, we can then get to worrying about probabilities. Please include the dynamic properties of the rope and the weight of the belayer in the definition. Direction of the any fall is also important since the anchor may fail every time if the direction of pull it up while it may never fail if the direction of pull is exactly as the anchor is configured to allow.

Dave

My own humor is so obvious to me, yet I can't tell if you are joking...

The scenario is "Dad toproping his kids" on this particular anchor. Odds of anchor failure equals what?

You are not really testing, nor can you test this, unless you randomly have kids do their thing. Some will hang, some will flash, all will lower at some point. Some, with enough tests, will climb above the anchor. Some of these, with enough tests, will manage to fall on the anchor from a point above the anchor. You know, seemingly random circumstances a statistically significant number of times.

You are proposing an entirely different test scenario...and your test would seem more rigorous, except it would miss the goofball kid that simply unclips himself and leans back.

I think I'll shut up and climb now.

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