|
|
|
|
healyje
Oct 31, 2007, 5:56 PM
Post #76 of 96
(3298 views)
Shortcut
Registered: Aug 22, 2004
Posts: 4204
|
For cams, 'tugging' is occasionally useful if there is loose material on the sides of the crack or to 'set' it in a geometry which may incline the cam to walk. But something is sorely deficient if you can't tell whether it will stay and which way it will resist rope pull (you are carrying something more than sport draws so you can sling your cams appropriately, right?).
For passive, if you need to tug on a nut to know whether it's good or not then you're likely either not looking close enough or don't know what you're looking at. Rapping on suspect rock and listening is more useful than tugging if it's a matter of rock quality. If it's about 'setting' pro relative to using friction versus geometry to get it to stay, then tugging still isn't usually necessary - some steady pressure until you feel some "grit" biting is almost always adequate. If it is a matter of suspect geometry or a part of the placement shifting a bit and you are worried about a piece 'pulling through' the placement then a small tug might possibly be warranted.
The bottom line on passive pro is, if your second has to use a nut tool on every piece of your pro then, while you may think you're good, you actually completely suck. While this condition my be ok for a beginning or early intermediate leader, it is simply inconsiderate and lousy craft for anyone who claims to be an experienced trad leader.
|
|
|
|
|
highangle
Oct 31, 2007, 6:38 PM
Post #78 of 96
(3281 views)
Shortcut
Registered: Jun 16, 2004
Posts: 151
|
In reply to: That just doesn't happen. You display a fundamental lack of understanding here that may be at the root of your larger misunderstanding. As the force in the direction of the stem increases, the cam becomes more, not less likely to pull out. That's what makes a weak pull so useless in determining if the cam will hold a fall.
Yep, it does happen - the geometry of a cam is such that the greater the force on the stem, the greater the outward force of the cams (when place correctly). While I have not seen it personally, there are several instances where a cam placed in sandstone has held a fall, but then failed when an individual continued to hang from the cam.
The forces the instant the climber hit the piece were sufficient to create outward force on the lobes, creating a greater coefficient of friction between the lobes and the rock than the pull force on the stem. However, once the force on the piece decreased, the cams no longer had sufficient outward force on the crack and the cams ripped.
So, it depends - in good solid rock, with a good placement, a cam should -by design - be harder to pull out the greater the force exerted on the stem.
Edited to add: I am a tugger, sometimes. Tug on passive, wiggle active. Tugging does not really tell me what will hold a fall, but what won't. Early on, it was amazing what I placed but did not hold with a tug. Now, tugging is used only to set a piece slightly so it doesn't walk, or if I can't fully see the placement to make sure there isn't anything grossly wrong with the placement.
(This post was edited by highangle on Oct 31, 2007, 6:43 PM)
|
|
|
|
|
j_ung
Oct 31, 2007, 6:54 PM
Post #79 of 96
(3270 views)
Shortcut
Registered: Nov 21, 2003
Posts: 18690
|
cracklover wrote: j_ung wrote: Apologies if this has already been covered, but gear tuggers know if their cams will hold in a horizontal flare or if the angle is just too wide. Really? If I place a cam in a flaring crack, I will definitely not expect a hand-tugging to pull it out, but will make a judgement call as to whether a fall would extract it. Of course, I mostly aim for the least flaring part of it, or even for an area with a little bulge if I can find one to set even a single lobe behind. In my experience, as a crack flares more, it becomes unreliable to hold a cam in a fall long before the angle of the flare is high enough for a hand-tug to pull it out. What have you found, Jay? Oh - except if the crack is parallel on one side, and flaring on the other. In that case, a tug out tells me nothing - it'll still hold even on one cam. Instead, I tug/rotate it in the direction away from the flaring side and see what happens with the flaring lobes. This puts enough torque on the piece to definitely tell me whether the placement is good or not. GO
I've found this (scroll down to Flared Cracks and Friends), which I think illustrates fairly well the only time I think tugging on gear (in this context) has any real value.
For the lazy:
In reply to: The angle at which the block [cam] will start to slip is independent of the load applied. What this means in practice is that if you place a cam in a flare and pull on it, and it does not come out, (and so long as you do not disturb the placement), the cam will hold up to the limit of the unit or the rock.
Also, I think I've misunderstood your last paragraph on two points. First, I'm lost on how a crack with two sides can have one of them parallel (parallel to what?) and the other not. My understanding is that a flare is a flare is a flare, e.g., if the two sides of the crack create an angle, it's flared regardless of how that angle is positioned in space. The only questions remaining are, one, does it flare outward (in which case, I tug), and will my cam survive the flare (which the tug tells me).
I'm also confused as to what you mean by "it'll hold on one cam." A camming device needs contact on both sides of the crack every single time, otherwise you won't need a tug. It'll fall right out as soon as you let it go. Down here in the south, we call one-sided cracks "faces." 
|
|
|
|
|
microbarn
Oct 31, 2007, 7:02 PM
Post #80 of 96
(3263 views)
Shortcut
Registered: May 12, 2004
Posts: 5920
|
j_ung wrote: I've found this (scroll down to Flared Cracks and Friends), which I think illustrates fairly well the only time I think tugging on gear (in this context) has any real value. For the lazy: In reply to: The angle at which the block [cam] will start to slip is independent of the load applied. What this means in practice is that if you place a cam in a flare and pull on it, and it does not come out, (and so long as you do not disturb the placement), the cam will hold up to the limit of the unit or the rock.
This relates back to testing cams in limestone too. People were talking about slime impeding friction, but if there is enough friction to hold a tug...then it will also hold a fall by the same logic.
|
|
|
|
|
j_ung
Oct 31, 2007, 7:05 PM
Post #81 of 96
(3261 views)
Shortcut
Registered: Nov 21, 2003
Posts: 18690
|
^ That seems to make sense, but I don't really know. Thank Gawd for Nuttall sandstone, eh?
|
|
|
|
|
climb_eng
Oct 31, 2007, 7:43 PM
Post #82 of 96
(3249 views)
Shortcut
Registered: Apr 23, 2007
Posts: 1701
|
I'm not clear what the mode of failure of the cams you were bouncing was. As I see it there are 3 modes of failure for a cam:
- Cam slippage: Cam slides out, causing no noticeable physical damage to the rock.
- Rock failure: includes rock breaking, cams tracking out, rock flex/deformation (eg. expando flake).
- Mechanical failure: Lobe deformation, cam breakage.
Certainly tugging probably won't help you in the case of rock breakage or mechanical failure, but I'm curious why you think it doesn't make a difference in terms of slippage.
In a smooth crack or a flare, I was under the impression that the outwards force (and therefore the friction force) is directly proportional to how hard the cam is pulled. Therefore, it will slip under any load if the effective friction coefficient is not high enough, whether it be a hard fall or a gentle tug. Conversely, if it doesn't slip with a gentle tug, it's shouldn't slip in a hard fall either.
Please explain to me where my logic is wrong.
* Edited to clarify modes of failure.
(This post was edited by climb_eng on Oct 31, 2007, 8:54 PM)
|
|
|
|
|
climb_eng
Oct 31, 2007, 7:51 PM
Post #83 of 96
(3245 views)
Shortcut
Registered: Apr 23, 2007
Posts: 1701
|
cracklover wrote: There's a chance, yes. But in my experience in placing cams, if it's such a poor placement that a tug in the direction of the stem of the cam would rip it out, it is a very very obviously poor placement to the naked eye.
This leads me to guess that you don't have much experience climbing smooth, slippery rock such as polished limestone, smooth quartzite or smooth basalt.
My experience climbing unpolished limestone is that pieces primarily fail due to rock breakage, but rockies limestone is a curriosity, rather than the norm.
I know for a fact that a cam placed in a parallel crack (it what would be considered a bomber placement in granite) of polished limestone will not hold under any load, be a gentle tug or a hard fall.
|
|
|
|
|
microbarn
Oct 31, 2007, 7:55 PM
Post #84 of 96
(3240 views)
Shortcut
Registered: May 12, 2004
Posts: 5920
|
climb_eng wrote: I'm not clear what the mode of failure of the cams you were bouncing was. As I see it there are 3 modes of failure for a cam: - Cam slippage. - Rock breakage. - Mechanical failure. Certainly tugging probably won't help you in the case of rock breakage or mechanical failure, but I'm curious why you think it doesn't make a difference in terms of slippage. In a smooth crack or a flare, I was under the impression that the outwards force (and therefore the friction force) is directly proportional to how hard the cam is pulled. Therefore, it will slip under any load if the effective friction coefficient is not high enough, whether it be a hard fall or a gentle tug. Conversely, if it doesn't slip with a gentle tug, it's shouldn't slip in a hard fall either. Please explain to me where my logic is wrong.
I like your 3 modes of failure. Where would a flexing flake figure into this list?
|
|
|
|
|
climb_eng
Oct 31, 2007, 8:35 PM
Post #85 of 96
(3231 views)
Shortcut
Registered: Apr 23, 2007
Posts: 1701
|
Good point, I'd group in in with Rock breakage, which should perhaps be called surface failiure or something like that.
|
|
|
|
|
cracklover
Oct 31, 2007, 9:39 PM
Post #86 of 96
(3218 views)
Shortcut
Registered: Nov 14, 2002
Posts: 10162
|
j_ung wrote: I've found this (scroll down to Flared Cracks and Friends), which I think illustrates fairly well the only time I think tugging on gear (in this context) has any real value. For the lazy: In reply to: The angle at which the block [cam] will start to slip is independent of the load applied. What this means in practice is that if you place a cam in a flare and pull on it, and it does not come out, (and so long as you do not disturb the placement), the cam will hold up to the limit of the unit or the rock.
The key phrase here is "the limit of the ... rock." In my experience, cams in undulating cracks do fine even when sufficient force is put on them for the rock to start to fail. That is not the case with cams in flares. Enough force to start to break a bunch of crystals, and whoop, out it comes. Not something that happens from a tug with your hand, though.
In reply to: Also, I think I've misunderstood your last paragraph on two points. First, I'm lost on how a crack with two sides can have one of them parallel (parallel to what?) and the other not. My understanding is that a flare is a flare is a flare, e.g., if the two sides of the crack create an angle, it's flared regardless of how that angle is positioned in space. The only questions remaining are, one, does it flare outward (in which case, I tug), and will my cam survive the flare (which the tug tells me).
Sorry - I wasn't clear. Imagine an fcu in a horizontal crack. I meant that the lobes on the right side of the cam are in a parallel crack, but the lobes on the left are in a flare. In such a case, tug straight out, and the two "good" lobes on the right (or one lobe, in the case of a tcu) will hold all the force you can apply with a tug. But tugging the cam away from the flared side (towards your right) puts enough torque on it to see if the lobes on the flared side will hold - and by extension, whether the whole placement will hold.
In reply to: I'm also confused as to what you mean by "it'll hold on one cam." A camming device needs contact on both sides of the crack every single time, otherwise you won't need a tug. It'll fall right out as soon as you let it go. Down here in the south, we call one-sided cracks "faces."
Ha! I hope my explanation above makes a little more sense now.
Cheers, and Happy Halloween to all! GO, signing off for the night.
GO
|
|
|
|
|
climb_eng
Oct 31, 2007, 10:20 PM
Post #87 of 96
(3210 views)
Shortcut
Registered: Apr 23, 2007
Posts: 1701
|
cracklover wrote: The key phrase here is "the limit of the ... rock." In my experience, cams in undulating cracks do fine even when sufficient force is put on them for the rock to start to fail. That is not the case with cams in flares. Enough force to start to break a bunch of crystals, and whoop, out it comes. Not something that happens from a tug with your hand, though.
Ha.... alright, looks like we're all talking about the same thing.
MY conclusion: Tugging is useful to determine if the cams slip rather then engage, although even the most gentle pull should tell you this. It is useless in determining the actual integrity of the piece/rock if the cam does engage.
Plan of action: I will continue to give cams a gentle tug to ensure they engage. I won't reef the shit out of them since it generally serves no purpose.
-JP
|
|
|
|
|
antiqued
Nov 1, 2007, 1:10 AM
Post #88 of 96
(3185 views)
Shortcut
Registered: Aug 18, 2005
Posts: 243
|
I don’t have rgold’s analysis handy, but it follows simply from the ideal spring assumptions. An ideal spring has a force (F) proportional to the displacement of the spring from the neutral position.
F=k*x
It takes energy to stretch a spring. A spring held extended by a distance x has a stored energy
E= ½ *k*x^2
Energy is conserved. A weight which is lowered provides energy which must go into either velocity or spring extension in this simple case.
Potential energy lost = m*g*h (m mass, g - acceleration of gravity, h - height lost).
Suppose we take a spring and dangle it, put a trapdoor just under it, and then attach a weight to the spring. Now the weight is entirely born by the trapdoor. When the trapdoor opens, the initial force of the spring is zero, so the weight starts accelerating at g. As the spring takes up more and more of the weight, the acceleration slows, but when the spring takes the entire force of gravity, the weight is still moving, and will slow to zero velocity at a greater extension, then rebound back up. A simple way to calculate this is to balance the energy in the spring with the energy available from falling. Since the height lost (h) and the spring extension are the same in this case,
m*g*h = 0.5*k*h^2
Multiply by 2, divide by h
k*h^2 = 2m*g*h
k*h =2m*g
Or F=k*h = 2*m*g, while the gravitational force on the weight is only m*g.
Thus the force on the strand of rope going to a climber on a fall factor 0 is twice the climber’s weight, if the rope acts as an ideal spring. The force on the protection would be (2-friction)*2mg, or ~~3.4 mg.
I’m sure rgold explains it more elegantly, but this is the conclusion cracklover is referring to. There are lots of little assumptions here, but the most important one is the ideal spring behavior of the rope.
|
|
|
|
|
antiqued
Nov 1, 2007, 1:24 AM
Post #89 of 96
(3182 views)
Shortcut
Registered: Aug 18, 2005
Posts: 243
|
microbarn wrote: j_ung wrote: I've found this In reply to: The angle at which the block [cam] will start to slip is independent of the load applied. What this means in practice is that if you place a cam in a flare and pull on it, and it does not come out, (and so long as you do not disturb the placement), the cam will hold up to the limit of the unit or the rock.
Continuing today's dose of physics, the above statement from Wild Country is unaccompanied by data, and is probably derived from the underlying physics with some simplifying assumptions. The slipping angle of a block on a plane is independent of the load applied (exceptions are designated rock failure by definition, perhaps?)
However the actual angle of contact stays the same only if the unit and the rock do not deform under load. Anybody looking at used small aliens recognizes that the cam lobes can deform under load, and severe loads will deform the axles of units as well. Either of these deformations will change the actual contact angle slightly from the designed cam angle, and may cause slipping under high load in a marginal placement. Similarly, even minor flexing of a flake could do the same thing.
|
|
|
|
|
antiqued
Nov 1, 2007, 2:07 AM
Post #90 of 96
(3179 views)
Shortcut
Registered: Aug 18, 2005
Posts: 243
|
No physics in this post!!
I don't usually tug or yank gear. The exceptions are usually nuts in flares, where I am relying on the 'stickiness' of the nut to resist any sidewards pull from a fall or from the rope path. Tugging at various angles gives me a sense of the margin. Since I have only once fallen on such a nut, I don't know if it does me much good.
However, new routing once on a lightly traveled cliff, I placed a small TCU in a perfect letterbox on the side of a dihedral. I had a good stem, so I gave it a hard tug, and the upper 1/4 inch of the letterbox flew right off! The rock overall wasn't the best, as the talus field testified, but there was no warning sign that I saw, and the area that failed was too small to do tapping (as healyje mentioned) without a small hammer and a stethoscope.
It hasn't changed my behaviour on well traveled cliffs, (could never happen at the Gunks!) but it is one bonafide incident of successful tugging.
|
|
|
|
|
notapplicable
Nov 1, 2007, 2:34 AM
Post #91 of 96
(3174 views)
Shortcut
Registered: Aug 31, 2006
Posts: 17771
|
antiqued wrote: No physics in this post!! I don't usually tug or yank gear. The exceptions are usually nuts in flares, where I am relying on the 'stickiness' of the nut to resist any sidewards pull from a fall or from the rope path. Tugging at various angles gives me a sense of the margin. Since I have only once fallen on such a nut, I don't know if it does me much good. However, new routing once on a lightly traveled cliff, I placed a small TCU in a perfect letterbox on the side of a dihedral. I had a good stem, so I gave it a hard tug, and the upper 1/4 inch of the letterbox flew right off! The rock overall wasn't the best, as the talus field testified, but there was no warning sign that I saw, and the area that failed was too small to do tapping (as healyje mentioned) without a small hammer and a stethoscope. It hasn't changed my behaviour on well traveled cliffs, (could never happen at the Gunks!) but it is one bonafide incident of successful tugging.
Yep, yep and that is all Micro and I have been saying. Not everyone needs to yank on all gear all of the time. There are some circumstances under which testing gear can and has yielded surprising results. My basic contention is that tugging is one of many ways a climber can analyze the overall viability of their placement.
Now, some how all the anti-tuggers (you scoundrels you) have neglected to address the faulty logic created by citing the possibility of having a piece fail when subjected to a swift yank as reason not to test gear. Then in the same breath saying that tugging on gear cannot and will not generate any useful data for the climber.
How can this be I say? If you yank on a piece of gear and it fails (regardless of why it fail, user error or not) to hold, how is this not valuable information and a justification for employing this method (under some circumstances) to test gear?
|
|
|
|
|
microbarn
Nov 1, 2007, 10:44 AM
Post #92 of 96
(3157 views)
Shortcut
Registered: May 12, 2004
Posts: 5920
|
notapplicable pointed out my questions.
antiqued, thanks for the explanation. I am reassured by this.
slowly easing your weight onto the rope while in a top rope situation means ~1.7 times the climber's weight.
falling while in a top rope situation means ~3.4 times the climber's weight.
|
|
|
|
|
dr_monkey
Jun 12, 2008, 5:38 AM
Post #94 of 96
(3028 views)
Shortcut
Registered: Nov 16, 2005
Posts: 81
|
It's been some time since I have done anything but lurk, but after reading all of this thread I thought that for once I might have something to add.
Whether I tug or not doesn't depend on what kind of rock, or the type of placement, but what I want the piece to do. For instance...
Heading into the crux, feeling confident, and I want to send? Place it, maybe give her a little tug and go.
I just want the piece to hold just in case.
Sketched out, thirsty, bad rock, got too MOOOVE, and thinking, "I should have bailed four pitches ago, but it's too late now."? Place it, shake and swear, take a deep breath or two and go. Maybe tug and asses, maybe not. Hard to tell, the piece just needs to give me the confidence to go, and it does.
Completely stupid with fear, but still thinking "I should be able to climb this it is only 5?"
Place it, don't breathe on it, then rationalize to myself, "At least it will slow me down" then make one move and discover bomber nut placement. Yup, that piece is stupid, didn't need it, shouldn't even be climbing. Ought to be drinking beer instead....
Speaking of which...
|
|
|
|
|
stymingersfink
Jun 12, 2008, 6:03 AM
Post #95 of 96
(3024 views)
Shortcut
Registered: Aug 12, 2003
Posts: 7250
|
notapplicable wrote: michaellane wrote: One interesting thing we noted was how important "setting" the piece was. A simple tug on the gear before it's loaded made a difference in whether the gear held or popped. Even some compromised placements that were spit out when we didn't "set" the piece held fast when the gear was "set" prior to the load Link here - http://www.rockclimbing.com/...iew&post=1908493 - Hmmmmmm, sounds like gear tuggers might know a little something after all. I all seriousness though, I do think that is something everyone should see and its not gonna get many eyes on it in I&A, so I brought it out here.
|
|
|
|
|
notapplicable
Jun 12, 2008, 12:19 PM
Post #96 of 96
(2985 views)
Shortcut
Registered: Aug 31, 2006
Posts: 17771
|
stymingersfink wrote: notapplicable wrote: michaellane wrote: One interesting thing we noted was how important "setting" the piece was. A simple tug on the gear before it's loaded made a difference in whether the gear held or popped. Even some compromised placements that were spit out when we didn't "set" the piece held fast when the gear was "set" prior to the load Link here - http://www.rockclimbing.com/...iew&post=1908493 - Hmmmmmm, sounds like gear tuggers might know a little something after all. I all seriousness though, I do think that is something everyone should see and its not gonna get many eyes on it in I&A, so I brought it out here. ^^i'm NOT reading that^^
Oh I wouldnt read that whole thread If I were you either, half the post could be mini novels.
|
|
|
|
|
|
