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peroxide
May 27, 2004, 4:18 PM
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FIRST OFF
Curiosity is always an awesome trait to have…
Yes climbing is not all about math but hey…when was www.rc.com ever totally about climbing.
EXECUTIVE SUMMARY:
Force and Energy are different. Energy = Force * distance applied. So while a longer factor 2 fall will create MORE energy...you will have more distance (rope) to absorb the energy....therefore the FORCE will be essentially constant for a given fall factor.
5 MINUTE PHYSICS FOR CLIMBERS
1) Falling
As you ascend the rock, you are building energy (gravity between you and the earth and everything else). This is easily calculated through the easy to remember equation:
MAX = PE mass * acceleration of gravity * height = Potential Energy
A solo climber who pops off will achieve nearly all this potential energy upon impact (minus air resistance and little things but come on...thats being picky). Higher he is the harder he falls. Since we are discussing falls less than 60m (the length of your common rope), air resistance can be considered to be ZERO.
Since air resistance is ZERO, potential energy (the energy you can get) and the kinetic energy (the energy you get at the end of a fall) are equal. Essentially whatever you put in you get out in the end (never ever really happens in the universe…you have to always pay taxes).
Just trust me on this…
So PE = KE (potential = kinetic)
Well KE = 0.5 * m * x2 = 0.5 * mass * distance squared
So if I dust of my calculator here and say a person jumps off a ladder at heights of 2, 4 and 6 meters (about 6, 12, and 18 feet), their speed at impact will be approx.
14, 20, 24 mph.
2) Falling on a static rope
If a rope is perfectly static then falling at the predescribed heights would be the equivalent to having a rope tied around your waist, have a friend gun a car to 14-24 mph and yank that rope tight. OUCH. This is why in the old days when ropes were not known for dynamic stretching you would do a dynamic hip belay. Letting the energy of the fall be absorbed on the back of the climber through friction (I did this while lowering a couch out of an apartment…I had lashing marks on my back)
3) Falling on a dynamic rope
A dynamic rope means that even though you paid for 60m, it will stretch if weighted (just jug a dynamic line and you will see how long it takes before you leave the ground).
This stretching can be described in non friendly science terms (but as stated above, I want to keep the lingo casual) or just to say that a certain amount of force (lets say your weight) will stretch the rope this many meters.
When you fall and the rope catches you, at that instant you are going at the 14-24 mph described above. But instead of stopping instantly, the rope begins to elongate. As the rope elongates, you decelerate (great word..just rolls off the tongue), and eventually come to a stop.
For a given fall factor, this deceleration is constant.
Why you ask… well you already understand how fall factors are calculated and why you can have a fall factor of 1.4 and fall 10, 20, or any number of feet. It just matters on length of fall and rope out between you and the belayer.
So lets look at 2 cases:
you have a fall factor of 1.5 in both cases but fall 10 feet in on and 20 feet in the other.
You will get to a higher speed in the 20 feet case but will have twice the rope out. So you have twice the rope out for twice the amount of energy absorption. So in the end you feel the same impact force and have the same deceleration.
But what happens when fall factor increases??
Well this means you have less rope out to absorb the energy…which means you have to decelerate FASTER….
4) The Anchor
SOOOOOOOOO…
Going back to the anchor…all falls of the same fall factor apply the same amount of force to the anchor. But, what ted is touching on is that the DURATION of the force before coming to a stop is longer.
The importance in duration is two fold:
--THE PIECE ITSELF IS OF MARGINAL STRENGTH (RPs, micro cams, etc.): If you load near the failure limit of the piece the microseconds will be critical if the piece partially fails and then drops the strenght well below its stated strength which is less than the appliec impact force.
--THE PIECE TO PLACEMENT FRICTION (soft rock, poor contact, thin cam in sandstone, etc.): If the force applied lasts to the point which passes the static coefficient of friction, which means the piece will begin to slip since the kinetic coefficient of friction is less, then the piece will fail.
However, to get into this situation in the first place requires pilot error since you are climbing above marginal pro (which is an inherent risk that is the responsability of the leader), running it out, or placing pro poorly (like in sandstone where using a thin cam instead of a metolius fat cam is more dangerous).
CORRECTIONS AND CLARIFICATIONS:
Please post or flame (posting nicely is far more effective and gentlemanly) away and I will do my best to expand, correct, or broaden the questions and answers.
Cheers,
Peroxide
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bandycoot
May 27, 2004, 4:30 PM
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In reply to: So, nope, I still don't see how a small cam is bomber...
They aren't, but they hold many falls. If you want to be perfectly safe, take up synchonized swimming. There is no fall potential there and probably lifeguards so save you if you start to drown. What do you want to hear, it COULD fail? There, you heard it. That is why we as climbers typically try to incorporate a SYSTEM of protection that consists of an anchor that is redundant and equalized, and more than on piece of protection while on lead. Have you ever heard the quote, "You're soloing until you have a second piece in." If you doubt the ability of one piece to hold a fall, put in more while you're on lead. Equalize them if that makes you feel better.
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paulraphael
May 27, 2004, 4:39 PM
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Nice physics lesson, Peroxide.
I want to emphasize one point:
The fall ENERGY absorbed by the rope does increase with fall distance, even if the fall factor stays the same. This is because kinetic energy increases with a square of the distance fallen, while energy absorbing rope length increases linearly. This does not translate into higher forces because the rope's stretch increases the DURATION of deceleration. However, each unit length of rope has to absorb more total energy in a long fall than in a short one, even if the fall factor is the same.
So what? It's important to know because a long fall is harder on your rope. Long falls should edge you towards retiring the rope sooner than short falls.
A 5 foot factor 1 fall will put about the same force on your body, your pro, and your anchor as a 10 foot factor 1 fall (all else being equal, bla bla bla) but the 10 foot factor 1 fall will be much harder on the rope. Each unit of length of that rope will have absorbed roughly twice as much energy in the longer fall (four times as much fall energy absorbed by only two times as much rope).
Just keep this in mind when evaluating your ropes, deciding how much time to let the rope recover, etc. etc..
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tedc
May 27, 2004, 4:50 PM
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In reply to: ....Super long physics lesson (removed)... .....In the end we are splitting hairs if we worry about this slight time discrepancy.
You think the difference between one piece and the whole anchor blowing is splitting hiars???..... You think the difference between the belayer feeling a hard tug and being pulled up 3' (and lifting all the nuts out of an anchor) is splitting hairs???
These are only two examples of where duration of force IS relevant.
In reply to: No one I know calculates fall factors as they are climbing…
Then how do you/they decide where to place pro?
I would suggest that if you don't, in some way, calculate fall factor as you lead then you are not ready to lead trad.
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peroxide
May 27, 2004, 6:18 PM
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Ted C...
I dont quite understand how my post advocates whippers and failing belays. My post was a pragmatic approach to the science.
The question posed was related to the physics of the situation. The time spans are irrevelant outside of theory...the effect on the rope life is serious (as mentioned in the above post...thanks for expanding on the lesson)
Obviously blowing the anchor is not the gameplan.
The basic gameplan should always be the following:
1) SRENE anchor with the most bomber gear you can place. Also it needs to be multidirectional.
2) Place the first piece as soon as possible (like immediately after the belay)
3) Early in the pitch the pieces should be more closely spaced than later in the pitch.
4) Rinse lather repeat
In reality this is the common practice of scared trad climbers in general. Being a little scared is good. I do not sit there and calculate fall factors...I think 98% of us are like this. We place to be comfortable which often accomplishes the concerns above.
This was not a lesson in trad leading and SRENE belay setups (covered correctly and incorrectly in other posts and forums). Just the physics. So don't get all flustered... and if you feel that a part of the message implies negligence (and is setting a gumby up for a death trap) then I can add a note on technique to clarify.
cheers
Peroxide
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hugepedro
May 27, 2004, 8:26 PM
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Bigga,
Trust me, trad climbers know the limitations of our gear. Small cams are bomber when they are used correctly. Bomber does not mean they will never fail under any circumstance. If you ever take anything approaching a factor 2 fall on a small cam, you were not using it correctly. High fall factors are unusual. To me, anything above .5 is high, so I set and rig pro to avoid that situation, and if I have to use small cams, nuts, whatever, in a high fall factor situation, I place more than 1 piece and equalize. See? Never relying on a single micro cam where the fall factor could be high (well, except for those situations where I’m running it out with confidence). As long as you do this your main concern will be the quality of your placements, not the physical limitations of your gear.
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dredsovrn
May 27, 2004, 8:33 PM
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In reply to: The impact force on most ropes range from 8.5 kn to 9.5 kn.
Thats what I love about Bluewater Excellence ropes (well, one of the many things). 5.9kn impact force. Took my first fall on a Metolius #1 TCU (8kn).
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bigga
May 27, 2004, 9:03 PM
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Hoowaa,
who woulda thaught it would have gotten this far. This is getting a bit funny.... anyone sensing alot of tension in this room?
Just to set a few things straight...
Bandycoot... I'm not looking for answers of "yes its safe" so I can feel better. If you haven't been reading all the posts this hasn't been about that. I haven't yet graduated up to trad level, I've only been climbing for three years, and I'm not right now considering it... so as far as my own personal piece of mind is concered... the answer does nothing for me.
The reason I've been driving everyone crazy with all these question is because it seems I may have figured out a design for a new piece for small cracks that is absolutely bomber. And I mean seriously bomber (if it works the way the mathematics involved in it say it should) by far outdoing any cam (not bragging here, I haven't tested it yet so can't even tell you for sure if the thing works) and I wanted to know if such a thing is of any use to trad climbers or if they are secure with there cams as is.
That, my friend, is all. nothing more. I realise the questions by now must be getting quite tidious and irritating to people, and I've tried to keep my questions as much as possible to private messaging to Engineers etc. on the site who have been nice enough to help. But sometimes what I need is the opinion of a larger group and rockclimbing.com seems to be full of people who are both knowledgable and willing to help and I can't pass that up.
Alrighty then.thats me... Wow, three pages of posts on this subject .....
enjoy folks
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gds
May 27, 2004, 9:23 PM
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Perhaps I'm missing something.
I find the physic all very interesting but not really on point.
I don't know about some folks but when I'm leading I always try to place the biggest piece I can (considring such issues as need for future gear, anchors, etc)
So when I'm putting in a small cam or brass nut it is because I can't find anything better. Of course a RP isn't as bomber as a #5 Camalot! But somethimes it is all you can get.
And if my memory is correct much of the smaller gear transitioned to free climbing from aid. So theoriginal idea was to hold body weight rather than a fall. Free climbers adopeted these pieces becasue, while not perfect, they were better than what there was.
The physics is interesting and improtant in the theoretical sense but when actually leading I think the first instinct is/should be to get in the best piece possible in the situation.
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tedc
May 27, 2004, 9:28 PM
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In reply to: The time spans are irrevelant outside of theory...
Your physics is fine. (I guess, I didn't check.)
Your conclusion was absolutely incorrect.
Your statement, quoted above, is wrong and, yes, dangerous to anyone who doesn't know any better.
I'm not flustered. I'm just calling BS.
I already gave two examples of how time IS relevant in REALITY.
Need another.
You are climbing and plugging cams on an Indian Creek splitter. You get up 10' and take a little (FF0.5) fall (Foot slipped right :wink: ). Batman up and check your piece. It barely moved. You think "Sweet, bomber gear". You keep climbing and putting in cams, lets say 80 more feet. Now you take another fall (must be a little over your limit, dude :? ). It's another FF0.5. This time your cam trenches a 3" grove in the crack. Unfortunately, it was only placed 2.9" deep and you are off for a big ride.
What the hell happened?
Same force...looooonger time.
Now apologize to all the nice noobs for trying to get them killed.
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tedc
May 27, 2004, 9:31 PM
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In reply to: Perhaps I'm missing something. I find the physic all very interesting but not really on point.
You aren't missing anything. We are just "off-topic".
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alpnclmbr1
May 27, 2004, 10:07 PM
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In reply to: In reply to: The time spans are irrevelant outside of theory... Your physics is fine. (I guess, I didn't check.) Your conclusion was absolutely incorrect. Your statement, quoted above, is wrong and, yes, dangerous to anyone who doesn't know any better.
Peroxide is right and you are way wrong.
In reply to: You are climbing and plugging cams on an Indian Creek splitter. You get up 10' and take a little (FF0.5) fall (Foot slipped right :wink: ). Batman up and check your piece. It barely moved. You think "Sweet, bomber gear". You keep climbing and putting in cams, lets say 80 more feet. Now you take another fall (must be a little over your limit, dude :? ). It's another FF0.5. This time your cam trenches a 3" grove in the crack. Unfortunately, it was only placed 2.9" deep and you are off for a big ride. What the hell happened? Same force...looooonger time.
This is so unlikely as to be useless. Running it out 20 feet and whipping for 45 feet on soft sandstone.
A .5ff near the ground is common, to get a .5ff 90 feet up a route you have to do something stupid.
Most gear placements fail relatively instantaneously. They can either hold the force applied or they can't. The time of the load is irrelevant in this respect. The time span of the load is mainly a factor of the elasticity of the rope. A longer lasting impact force is just a matter of the rope needing more time to absorb the force it is capable of absorbing.
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gds
May 27, 2004, 10:17 PM
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In reply to: most gear placements fail instantaneously
I guess you don't watchclimbing movies :)
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tedc
May 28, 2004, 3:03 PM
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In reply to: A .5ff near the ground is common, to get a .5ff 90 feet up a route you have to do something stupid.
Right. now explain why a .5ff 90 feet up a sandstone crack is stupid while the same ff near the ground is OK, and you will have proved my point.
ff.5=ff.5. Or does it??
(And don't tell me the fall is dangerous because there isn't a much cleaner fall than a vertical featurless face.)
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bandycoot
May 28, 2004, 3:24 PM
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Bigga: You do know that most gear will hold more than it advertises right? They just low ball it for liability and other reasons. If you have invented something that is the shit, cool! I have a friend who has started a climbing gear company before and I could probably get you in touch with him if you're interested in manufacturing and producing this thing, he could possibly help. He loves widgets and gadgets that are new and related to climbing. He's up on Mt. Denali playing until July though.
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jt512
May 28, 2004, 3:31 PM
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If we ever get a FAQ, this post needs to go in it.
-Jay
In reply to: FIRST OFF Curiosity is always an awesome trait to have… Yes climbing is not all about math but hey…when was www.rc.com ever totally about climbing. EXECUTIVE SUMMARY: Force and Energy are different. Energy = Force * distance applied. So while a longer factor 2 fall will create MORE energy...you will have more distance (rope) to absorb the energy....therefore the FORCE will be essentially constant for a given fall factor. 5 MINUTE PHYSICS FOR CLIMBERS 1) Falling As you ascend the rock, you are building energy (gravity between you and the earth and everything else). This is easily calculated through the easy to remember equation: MAX = PE mass * acceleration of gravity * height = Potential Energy A solo climber who pops off will achieve nearly all this potential energy upon impact (minus air resistance and little things but come on...thats being picky). Higher he is the harder he falls. Since we are discussing falls less than 60m (the length of your common rope), air resistance can be considered to be ZERO. Since air resistance is ZERO, potential energy (the energy you can get) and the kinetic energy (the energy you get at the end of a fall) are equal. Essentially whatever you put in you get out in the end (never ever really happens in the universe…you have to always pay taxes). Just trust me on this… So PE = KE (potential = kinetic) Well KE = 0.5 * m * x2 = 0.5 * mass * distance squared So if I dust of my calculator here and say a person jumps off a ladder at heights of 2, 4 and 6 meters (about 6, 12, and 18 feet), their speed at impact will be approx. 14, 20, 24 mph. 2) Falling on a static rope If a rope is perfectly static then falling at the predescribed heights would be the equivalent to having a rope tied around your waist, have a friend gun a car to 14-24 mph and yank that rope tight. OUCH. This is why in the old days when ropes were not known for dynamic stretching you would do a dynamic hip belay. Letting the energy of the fall be absorbed on the back of the climber through friction (I did this while lowering a couch out of an apartment…I had lashing marks on my back) 3) Falling on a dynamic rope A dynamic rope means that even though you paid for 60m, it will stretch if weighted (just jug a dynamic line and you will see how long it takes before you leave the ground). This stretching can be described in non friendly science terms (but as stated above, I want to keep the lingo casual) or just to say that a certain amount of force (lets say your weight) will stretch the rope this many meters. When you fall and the rope catches you, at that instant you are going at the 14-24 mph described above. But instead of stopping instantly, the rope begins to elongate. As the rope elongates, you decelerate (great word..just rolls off the tongue), and eventually come to a stop. For a given fall factor, this deceleration is constant. Why you ask… well you already understand how fall factors are calculated and why you can have a fall factor of 1.4 and fall 10, 20, or any number of feet. It just matters on length of fall and rope out between you and the belayer. So lets look at 2 cases: you have a fall factor of 1.5 in both cases but fall 10 feet in on and 20 feet in the other. You will get to a higher speed in the 20 feet case but will have twice the rope out. So you have twice the rope out for twice the amount of energy absorption. So in the end you feel the same impact force and have the same deceleration. But what happens when fall factor increases?? Well this means you have less rope out to absorb the energy…which means you have to decelerate FASTER…. 4) The Anchor SOOOOOOOOO… Going back to the anchor…all falls of the same fall factor apply the same amount of force to the anchor. But, what ted is touching on is that the DURATION of the force before coming to a stop is longer (we are talking about very very small time spans here). In the end we are splitting hairs if we worry about this slight time discrepancy. No one I know calculates fall factors as they are climbing…. Its been a while since I have played with physics 101 so all corrections or suggestions for edits are welcome.. Cheers, Peroxide |
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taualum23
May 28, 2004, 3:34 PM
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[quote="bigga"]I may have figured out a design for a new piece for small cracks that is absolutely bomber. And I mean seriously bomber (if it works the way the mathematics involved in it say it should) by far outdoing any cam (not bragging here, I haven't tested it yet so can't even tell you for sure if the thing works) and I wanted to know if such a thing is of any use to trad climbers or if they are secure with there cams as is.[/quote]
OK, a piece for small cracks that is absolutely bomber, and you want to know id such a thing is of any use to traddies?
Well, if it works, and has benefits above what is out there, then yes, and I'll take a set. If you need help real world testing, let me know, I love to play with gear.
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gunkiemike
May 28, 2004, 3:35 PM
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In reply to: Bigga, Trust me, trad climbers know the limitations of our gear. Small cams are bomber when they are used correctly. Bomber does not mean they will never fail under any circumstance.
A friend of mine broke a nearly new gold WC Zero cam by falling a few feet on it right off the ground. A visit to Petzl's fall force calculator site indicated a peak force that - surprise - exceeded the piece's rating. And it wasn't the placement that failed (the rock was undamaged and the crack was solid) it was the axle bending that let the cam lobes blow. A Screamer would probably have made the difference. As would choosing a higher rated piece e.g. an Alien for that particular size range.
So small cams are NOT necessarily bomber, and it doesn't take a huge whip to cause them to fail. Ditto your small wired pieces, which as someone noted in this thread, are rated for less than 10 kN. Hell, even 10 kN is weak by my standards, which is why I have so much slung passive gear on my rack.
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peroxide
May 28, 2004, 3:37 PM
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alpnclmbr1 wrote:
A .5ff near the ground is common, to get a .5ff 90 feet up a route you have to do something stupid.
tedC
Right. now explain why a .5ff 90 feet up a sandstone crack is stupid while the same ff near the ground is OK, and you will have proved my point.
ff.5=ff.5. Or does it??
***********
Lets take two different ff falls of 0.5
Fall 1: 20 feet off the ground
This translates to a fall 5 feet above your last piece.
In my opinion and alpclimber..very common.
Fall 2: 90 feet off the ground
This translates to fall from 22 feet above your last piece.
Why is fall 2 more "stupid" than fall 1?
22 feet above your last piece is getting bold.
45 feet of fall gives you lots of distance to hit stuff and if you swing/push away from the rock get ready to hit the wall hard.
Normally, (just look at how people sew a crack up) this just doesnt happen unless you are blasting for the belay and pitch off or a poorly placed piece pulls. Both can be interpreted as pilot error.
This would be what I think alpclimber is getting at.
Nonetheless, falling sucks.
peroxide
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jt512
May 28, 2004, 3:48 PM
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In reply to: The reason I've been driving everyone crazy with all these question is because it seems I may have figured out a design for a new piece for small cracks that is absolutely bomber. And I mean seriously bomber (if it works the way the mathematics involved in it say it should) by far outdoing any...
A page-and-a-half ago you couldn't even calculate impact force. Something tells me this new invention of yours isn't going to live up to your "mathematics."
-Jay
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peroxide
May 28, 2004, 4:26 PM
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Are all posters to this thread liable both in terms of future royalties or lawsuits???
Now where is that edit button again....and lets see if my lawyer is free to chat...
Peroxide
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curt
May 28, 2004, 4:42 PM
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In reply to: In reply to: In reply to: The time spans are irrevelant outside of theory... Your physics is fine. (I guess, I didn't check.) Your conclusion was absolutely incorrect. Your statement, quoted above, is wrong and, yes, dangerous to anyone who doesn't know any better. Peroxide is right and you are way wrong.
Ted is right--so there. HaHa.
Curt
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thomaskeefer
May 28, 2004, 4:55 PM
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One other thing to muddy the water..
Above, people were talking about pulling pieces instantly.. well that just does not happen even though it seems instant.
This can be dangerous..
A piece that is going to pull does so when the force it is capable of holding is met and then pops just after if the load continues to increase (as in a fall and the rope ceasing to continue stretching).
Now what you have is a situation where a good deal of the stretch (aka ability to absorb force and keep it from the gear and climber) in the rope is gone. Now when you hit that next piece there is a much harsher impact on the gear because the rope is behaving closer to a static line than it had before... something to think about when placing psychological pieces...
Flame on..
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tedc
May 28, 2004, 5:43 PM
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In reply to: If we ever get a FAQ, this post needs to go in it. -Jay In reply to: Reasonably good physics lesson excluded..... (we are talking about very very small time spans here). In the end we are splitting hairs if we worry about this slight time discrepancy. Cheers, Peroxide
Only if FAQ stands for: Frickin Asinine Quote
Sorry, the rest IS good but if you get the answer WRONG you get no credit for your work. This isn't physics class. It's climbing; way up off the ground. Partial credit is like being partially dead.
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tedc
May 28, 2004, 5:45 PM
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peroxide & alpnclmbr,
It hurts my brain to discuss this with you when you can't stick to the subject. Is the duration of the loading in a long fall relevant to the safety of your protection system?
In the previous example I specifically said that you ain't going to hit anything in a 45 foot ff.5 at I.C. Is this fall still dangerous??? Why??
In reply to: Above, people were talking about pulling pieces instantly.. well that just does not happen even though it seems instant. This can be dangerous..
I feel a little better knowing that at least someone else understands this.
In reply to: In reply to: In reply to: In reply to: The time spans are irrevelant outside of theory... Your physics is fine. (I guess, I didn't check.) Your conclusion was absolutely incorrect. Your statement, quoted above, is wrong and, yes, dangerous to anyone who doesn't know any better. Peroxide is right and you are way wrong. Ted is right--so there. HaHa. Curt
Wheeew. I was waiting for that.
I knew I was. :D
peroxide and alpnclmbr can go climbing and let Newton do the teaching.
Unless there is someone out there still listening who doesn't understand this subject I am done hammering on these two hard heads.
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