Discussion Topic |
|
This thread has been locked |
sawin
climber
Orange, CA.
|
|
|
Apr 15, 2008 - 08:33pm PT
|
This reminds me of air voyagers a ok idea if aware of the
vibration factors from seams breaking which open gates of
non locking carbiners. A fatality allegedly occured due to
the last broken seam which now loaded the air voyager with
a impact force greater than the seams. The gate of the
carbiner open due to vibration and now weakend dislodged
the rope of the climber as it bent open more.
What about addressing angles and weight factors from a fall
on a piece associated to the angle of crossing? Assuming not
all that read this thread are mathematicians, scientist or
engineers how about posting such a chart? I know they are
available.
|
|
Karl Baba
Trad climber
Yosemite, Ca
|
|
|
Apr 15, 2008 - 08:35pm PT
|
Mr. Tude writes
"This makes for a much stronger anchor and nullifies the benefit of a non-extending design.
Worst case scenario: Unexpectedly a piece pulls and the (3 pieces of pro) system extends roughly half of the length of the loop attached to the failed piece - typically around 1.2-1.5 feet. This suddenly lowers the power point and drops the falling climber an additional 1.2-1.5 feet plus another few inches of rope stretch. As this is a small portion of the typical fall distance and highly unlikely, I see omitting the Figure 8 as a safer (and faster)choice than the commonly advertised set-up in many situations."
What I don't see noted is "HOW" much stronger such an equalized anchor is in ACTUAL practice. SO much stronger that it's worth dropping a couple feet?
Now imagine this. The falling climber might get dropped or not (depending on whether it's a factor 2 fall or not. A non-factor two fall isn't very likey to pull the anchor since the direction of pull is up. Will the extra distance allow her to hit something?
But, perhaps more importantly, what is the impact of the extending belay on the belayer? Do you get knocked off the ledge? Is it harder to escape the belay if you're dangling off somewhere now? Did you get tossed around or against a rock suddenly? These are serious are real questions.
With a regular cordalette system, it only takes one good piece to keep everything safe and sane in the event of a problem. The belayer stays put and in control. In an extending system, who know what happens to the belayer. The extra strength, does it introduce more safety or more danger. Think about it for a minute.
Peace
karl
|
|
saho
Ice climber
Anaheim, CA
|
|
|
Apr 15, 2008 - 09:48pm PT
|
Hey Eric,
Thanks for fixing that!
All that math stuff is a little beyond me. I'm no physicist, just a carpenter (technically a Lather - as in metal lath and plaster).
Tolman Paul says:
"Not to mention one can outclimb the incoming thunderheads if they are actually climbing vs. building and tearing down complex anchors at the top of each pitch.
Am I missing something?"
The point of this anchor is to achieve exactly what you requesting. That is simplicity. The standardized cordelette is a great tool that is fast and easy to understand - keeping it simple. Since the second edition of Climbing Anchors by John Long and Bob Gaines pointed out that the cordellete is not safe enough in certain situations, there have been thousands of posts on the internet searching for the perfect anchor set-up. I still just use the cordelette. Most of the contraptions out there can be complex, confusing, and some are downright scary.
The Scream-o-let is a solution for the occasional situation on a multi-pitch climb where a high factor fall is a possibility. Simply add a screamer to each anchor point, then tie in your cordellete as normal. The Screamers absorb enough energy in a high factor fall to keep your already solid anchor from breaking.
If Screamers were integrated into my cordelette set-up I think I might be more likely to actually use them. Such as in the example below. Also the weight of extra carabiners would be saved.
Here is an illustration of my idea to actually have Screamers sewn into a rabbit runner. (the pic shows the webbing configuration with tape - not real stitching for illustration only)
|
|
sawin
climber
Orange, CA.
|
|
|
Apr 15, 2008 - 09:48pm PT
|
Modern Screamers are not bar tacked. They are sewn in 3 rows along the length of the webbing, not across, so they tear. My experience falling on them in recent years was that they are quite smooth. I have not seen people using lockers on them, maybe I just did not notice.
-Steve
I tore 6 rows of a long air voyager with a controlled fall from
a move above a roof over non-vertical slab approximately 80%
figuring the acute angle facing into the rock which allowed me
to run down approximately 30' after the 5-6' vertical fall.
Total stitches I believe were 16 each tested at approximately
750 lbs.. Non locking carbiners were used however after this
fall I used only locking carbiners on the remaining broken Air
Voyagers. No injury occured I immediately completed the climb
without lowering.
I'll add screamers to another rack when I buy/build it however
I'm also real about placements and equality of? Usually it's
not possible to obtain equality with load balancing on a
rock as it usually is with commercial rigging. The above photo
is close however bi-pod, tri-pod hooks with chokers on the
ground are more simple to obtain equal load balancing, and we
don't always get the best of crack formations at belays.
Thank's EB for the formulas. Appears the international test are
still being calculated with 16' falls.
|
|
saho
Ice climber
Anaheim, CA
|
|
|
Apr 15, 2008 - 10:08pm PT
|
Hi sawin,
I have only ever used Yates Screamers (the regular ones)
http://www.yatesgear.com/climbing/screamer/index.htm
They activate at about 550lbs.
I have no experience with Air Voyagers. Though I understand they were the bar-tacked design.
The Yates Screamers are super smooth IMO.
"Usually
it's not possible to obtain equality with load balancing on a
rock as it usually is with commercial rigging. "
I work in the commercial construction industry. There it is no legal to use as tie off protection anything other than a single point anchor good to 5,000 lbs. So equalization is not an issue there. So you are correct in your statement. Thus the on going discussion of anchors from the sliding x, to the equalette, to the triplette, and now the Scream-o-let :)
My goal is the best of both worlds - keeping it simple and safe.
-Steve
|
|
JAK
climber
The Souf
|
|
|
Apr 15, 2008 - 10:15pm PT
|
Tolman Paul, I like you. You're appropriately cranky. Kudos, brother.
That said, I like tech geekery as much as the rest of 'em.
|
|
Clint Cummins
Trad climber
SF Bay area, CA
|
|
|
Apr 15, 2008 - 10:21pm PT
|
Higher priority in saho's photos would be to have at least one of the anchor pieces good for an upward pull. We are talking about someone leading above this anchor, right?
I suppose when used in a belay anchor, screamers or similar don't need the locking biner, since rope is not running through the biner on the screamer to provide the vibration for gate flutter. [Edit: see Gobie's post below - the screamer activation provides the vibration for gate flutter, so locking biners are helpful in such a belay anchor.]
(This is all a bit academic to me, since I don't use screamers, cordelettes, or locking biners except one with my ATC).
|
|
saho
Ice climber
Anaheim, CA
|
|
|
Apr 15, 2008 - 10:41pm PT
|
You are absolutely right Clint,
Those illustration pics do not show the required upward pull piece.
They are simply illustrating the three piece downward pull aspect.
However, great that you pointed it out, because most of the time I see people neglecting the upward pull piece, which is even more critical in an all passive gear anchor as in those pics.
Thanks.
-Steve
|
|
johnboy
Trad climber
Can't get here from there
|
|
|
Apr 15, 2008 - 11:16pm PT
|
If anyones really worried about gate flutter, Trango Superfly lockers are only 41g a piece.
If a major concern is a high FF, wouldn't a screamer on the first piece (jesus nut) right off the belay be a good place for one? Also, if screamers activate just under 600lbs of force, would'nt you have some semi ripped sceamers (he was talking sewn into slings $$) after a few modest falls?
Just asking?
|
|
saho
Ice climber
Anaheim, CA
|
|
|
Apr 15, 2008 - 11:52pm PT
|
Hey johnboy,
"If a major concern is a high FF, wouldn't a screamer on the first piece (jesus nut) right off the belay be a good place for one? "
If you are in a situation where you can get in a good Jesus nut, and even if you don't have a Screamer on it, you probably don't need to bother with a Scream-o-let anchor. Just use a regular cordelette, or your regular preferred method.
"Also, if screamers activate just under 600lbs of force, would'nt you have some semi ripped sceamers (he was talking sewn into slings $$) after a few modest falls?"
As usually gets pointed out in this type of thread, the amount of times anyone actually falls directly onto an anchor with any high amount of force, is very rare. Have you ever fallen directly onto an anchor? If that is the case, just buy a new one$$$
-Steve
|
|
johnboy
Trad climber
Can't get here from there
|
|
|
Apr 15, 2008 - 11:54pm PT
|
^^^^
Thanks.
I do think this may be a good "lette" for ice climbing, apart from a few of the concerns Karl stated. There might be a couple of ways to negaite them too.
|
|
EB
Trad climber
|
|
|
Apr 16, 2008 - 12:10am PT
|
del cross writes:
Eric, I don't think that the angle has any bearing on the energy absorbed by a screamer. Shouldn't it simply be activation force times screamer elongation (Fc*Is)?
No. The energy absorbed by a screamer is as you say, however not all of that energy is available to slow the fall. Work is the "dot" product of the force vector and the distance vector. The dot product gives the angular dependence.
For three screamers you'd get 3*(Fc*Is). In your equation, when the pieces are in a vertical orientation (theta=0), you get 9*(Fc*Is). How's that possible?
Thank you for pointing this out. The factor of 3 in front of the equation for Es is a mistake. It should read: Es = Fa*ls*cos(theta) = Fc*(2*cos(theta)+1)*ls*cos(theta), which now reduces to 3*Fc*ls in the case where theta is 0.
What about fall energy from rope stretch and screamer elongation?
I think what you are asking here is, doesn't the fact that the rope (screamer) is stretching, increase the energy of the fall? The answer is no. The total fall energy is determined by the weight of the climber and the height of the climber above the anchor point at the time of the fall (multiplied by 2 in the case we are talking about). It is a common misconception that a stretching rope adds energy to the fall because it lengthens the fall. Rather, it is doing work on the climber, slowing his speed and decreasing his energy. Imagine instead of being attached to a rope, you fell on to a trampoline. You would not say that because you sank into the trampoline (extending the fall distance) that you increased the energy of the fall. That energy was determined by the height above the trampoline at the start of the fall.
Where's the belayer in this scenario? Does she also get pulled down and add to the fall energy as the screamers deploy?
I think if the belayer is correctly connected to the anchor, they won't add to the energy of the fall. In other words, if the connection from the belayer to the anchor is tight then the force of the fall simply gets transmitted through the belayer. If the belayer is not tight then yes, there would be an additional force of the belayer's fall, but that goes into the category of incorrect usage of the anchor, so I don't attempt to include it. In fact, when things are working correctly the presence of the belayer generally reduces the factor of the fall by introducing more dynamism into the system via stretching of the body, slipping of the rope through the belay device, movement of the harness, etc... I haven't included any of this as it simply makes things better. An exception to this is in a hanging belay where the weight of the belayer is on the anchor from the start. This is an additional force, but it is static so not nearly as large as the other forces in the system. Still I think it's correct to say that in a hanging belay, the anchor capacity is reduced.
Several people have suggested that they thought the scream-o-let idea sounded like too much bother. It seems pretty simple to me... You are carying slings anyway, so replace three of your slings with screamers. Use them in place of slings normally and then when that very unusual anchor comes along that has a chance of seeing a factor-2 fall, just clip the screamers in to each anchor piece. I often find myself extending anchor pieces anyway with a runner, so putting a screamer in instead doesn't seem like adding too much, especially if it improves the capacity of the anchor by 50% or more.
|
|
Gobie
Trad climber
Northern, Ca.
|
|
|
Apr 16, 2008 - 12:14am PT
|
Clint,
The flutter is not caused from the rope, its a by product of the screamer/air voyager activating. I only mentioned it because a lot of factors were being figured in and I wanted to reveal that although we can calculate things out on paper, in the real world we tend to overlook critical elements. I would never had believed the gate flutter thing myself had someone not videotaped it and showed it to me. I dont think anyone can contest that carabiners break as anyone climbing for a minimal amount of time has witnessed this happen. As far as opening one, a quick slap on the palm of your hand from less then an inch away opens most bar stock gates. If falling on the belay is the illustration then this is a reality as things are being smacked around. I agree fully that big disruptions to the belay can be prevented by adding oppositon to the anchor. I, like you, have always been a big fan of using the rope to tie everything together, even on my oppositional piece.
|
|
Gobie
Trad climber
Northern, Ca.
|
|
|
Apr 16, 2008 - 12:39am PT
|
Here is alink to a video. You have to watch it through but you can see a screamer being torn apart slowly, with lockers. Notice the vibration even when being pulled slowly.
UIAA video
|
|
Mungeclimber
Trad climber
sorry, just posting out loud.
|
|
|
Apr 16, 2008 - 02:44am PT
|
hrm, should all Screamers have lockers instead of wire gates?
|
|
Al_T.Tude
Trad climber
Monterey, CA
|
|
|
Apr 16, 2008 - 02:56am PT
|
Karl,
In response to my suggestion that the figure 8 knot on the cordelette sometimes be left off to maintain equalization you wrote:
What I don't see noted is "HOW" much stronger such an equalized anchor is in ACTUAL practice. SO much stronger that it's worth dropping a couple feet?
But, perhaps more importantly, what is the impact of the extending belay on the belayer? Do you get knocked off the ledge? Is it harder to escape the belay if you're dangling off somewhere now? Did you get tossed around or against a rock suddenly? These are serious are real questions.
I agree that these are important issues. This is how I see it:
With 3 solid pieces approximately equalized you have an ultra bomber system that will virtually never fail. This is what I want. With the load shared fairly equally between the pieces, the odds of one failing and causing a 2' drop of the belayer's power point and an additional 2' of climber drop is virtually nill. And even if this freak occurrence does happen, it is far from catastrophic.
Now let's tie the figure 8 knot and analyze. The asymetrical act of tying the knot produces unequal length loops guaranteeing that there is NO load direction that will produce even remotely close to evenly distributed loads between the pieces of pro. Try this with spring scales (like the ones fisherman use) and you will see what I mean.
Now, lets assume the impossible and assume that you were able to tie the perfect figure 8 knot that perfectly equalizes the 3 pieces. In this perfect world the pieces would be equalized when loaded in only one direction. As soon as the load pulls even a few degrees off from the anticipated direction (which will always happen)the load distribution goes from 33-1/3%, 33-1/3%, 33-1/3% TO 10%, 60%, 30%.
Move a few more degrees off perfect (which will happen in the real world) and we quickly hit 5%, 85%, 10%.
If the piece seeing 85% of a fall factor 2 load (which is what we are planning for here) happens to be anything less than exemplary we will possibly have a failure at that point.
Now we have 50% load on each of the two remaining pieces IF they are perfectly equalized - which they will not even remotely be. In reality we are likely looking at an 80/20 split or 100/0.
With 80-100% of the load on 1 piece, it's chance of failing is tremendously magnified. If it fails, we are now guaranteed to be placing 100% of our load on one randomly selected piece. You do not get to choose which piece this will be. This whole process takes place in a fraction of a second.
Once the last piece fails we have a catastrophic failure and two dead climbers plus whomever they hit on the way down.
Comparing these two scenarios it is clear to me that in most situations equalization (not tying the figure 8 knot) is FAR more important than non-extension.
People tie the knot in their cordelettes all the time. Why haven't we heard of a rash of failures?
Primarily because:
0)Leaders very rarely pull all of their pieces and place a FF2
or near FF2 downward load on their anchor
0)Often there are multiple pieces of bomber pro at the anchor
0)Modern dynamic ropes do an amazing job of limiting peak load
by extending the load over time
0)Leaders very rarely pull all of their pieces and place a FF2
or near FF2 downward load on their anchor (so significant it bears repeating)
Does this mean that we should continue to use what's been working (If it ain't broke, don't fix it)?
No. We were given oversize brains to continually improve our lot. I think the figure 8 knot popular in cordlette use in most situations weakens our anchors and fools us into thinking that we have constructed a SERENE anchor.
|
|
rgold
Trad climber
Poughkeepsie, NY
|
|
|
Apr 16, 2008 - 10:44am PT
|
Eric wrote: I think what you are asking here is, doesn't the fact that the rope (screamer) is stretching, increase the energy of the fall? The answer is no. The total fall energy is determined by the weight of the climber and the height of the climber above the anchor point at the time of the fall (multiplied by 2 in the case we are talking about). It is a common misconception that a stretching rope adds energy to the fall because it lengthens the fall. Rather, it is doing work on the climber, slowing his speed and decreasing his energy. Imagine instead of being attached to a rope, you fell on to a trampoline. You would not say that because you sank into the trampoline (extending the fall distance) that you increased the energy of the fall. That energy was determined by the height above the trampoline at the start of the fall.
Eric, this is wrong. Indeed, when you sink into the trampoline, you do increase the fall energy (the total loss of potential energy), and the "common misperception" that you mention is an integral feature of every derivation of the maximum rope tension that occurs in stopping a fall. The total fall energy is the product of the weight of the climber and the distance fallen, period. The fact that, during some of that distance, there may be an upward force acting on the climber contributes to a reduction in what might be called the net fall energy, but it does not simply cancel the portion of the fall during which an upward force acted.
|
|
Karl Baba
Trad climber
Yosemite, Ca
|
|
|
Apr 16, 2008 - 11:12am PT
|
Thanks for the detailed reply AL Tude (not Al Dude, whom some of us know)
Al wrote
"With the load shared fairly equally between the pieces, the odds of one failing and causing a 2' drop of the belayer's power point and an additional 2' of climber drop is virtually nill. And even if this freak occurrence does happen, it is far from catastrophic"
Yes and no. It's not particularly unknown for one anchor piece to fail because it was placed improperly, because it had a crappy placement because the leader wanted three placements and there was only two good ones. I've seen it and even had it happen to me (cause it didn't matter cause I had a non-extending system)
This is a complex enough scenario that I think the geeks need to put their hard hats and safety glasses on to supplement the pencil protectors, and do some real world testing. Bonus points if some Sedona Sandstone is used to provide actual bad rock-placements
Peace
Karl
|
|
Gobie
Trad climber
Northern, Ca.
|
|
|
Apr 16, 2008 - 11:54am PT
|
Al,
Where is your redundancy when you take the fig 8 out of the cordalette? How strong is your cordalette? Even though you have equalized your protection you have limited yourself to one piece in that if the cordalette (which is loaded 100%) fails you now are left with this equation
100%-100%=nothin'
Im with Karl, I want real world data. If we are going to base it all on speculation then why not just use one carabiner for the belay, its says on the side of it it can hold 5000 lbs?
(I was being sarcastic, I know why).
I like to call it the act of God equation. A little humility goes a long way in accepting you cant account for everything on paper.
|
|
sawin
climber
So., CA.
|
|
|
Apr 16, 2008 - 01:19pm PT
|
Q.
I like to call it the act of God equation.
R.
Physics are the laws that govern the universe!
|
|
|
SuperTopo on the Web
|
Let us know!