when trad climbers encounter bolts and get confused?

Isn't it called "American Death Triangle"?

Isn't it called "American Death Triangle"?

Nope. I'm pretty sure the ADT is a single sling between two (mostly-)parallel bolts.

Nope. I'm pretty sure the ADT is a single sling between two (mostly-)parallel bolts.

Can't tell from the angle of the photo, but does it have to be parallel points? It has two main attributes of the ADT - reliance on a single sling and extension of of the anchor (if one point fails, the forces on the remaining point will be tremendous).

That isnt'a triangle. It's a V.

The issue with the ADT is that it increases forces on the bolts. Here, there is no triangle. There is no force amplification. There's also no equalization. It's basically a belay off one bolt with the second bolt as a backup. There's two 'legs' on that sling, but one of them is the attachment to the photographer, so that's not an equalization leg.

It's hard to say why it's set up that way, perhaps there is a belay stance? But then the bolt position wouldn't make sense. I'd probably try to sling the two bolts together and then hang on the lower one, sort of ghetto equalized.

I dunno, it kinda looks like a triangle to me

I dunno, it kinda looks like a triangle to me
[image]http://www.rockclimbing.com/cgi-bin/forum/gforum.cgi?do=post_attachment;postatt_id=5176;[/image]

I dunno, it kinda looks like a triangle to me

ADT on the left. Correct rigging on the right.

[image]http://www.climbing.com/print/techtips/Trad.224-1.gif[/image]

both wrong

never tie webbing directly on hangers

I stand corrected. I took another look and it likely is a triangle. I didn't realize that runner went from the lower bolt to the locker with the clove. hard to see.

Just because it has a triangular component doesn't necessarily mean it's an ADT. As pointed out earlier, the key aspect of the ADT is the force multiplication and, secondarily, the lack of redundancy if constructed of a single piece of webbing.

I assume these guys made it out alive, but if I climbed up to find that's what my partner built, I'd slap him in the back of the head and re-rig it before leading on (and it would take all of 30 seconds). Granted it's a slab and the leader clipped the high bolt, so bombing onto the anchor isn't likely to happen, but let's say it's a different situation. Factor 2 one of those and the safety of the entire team is not a foregone conclusion.

Even a slab/friction climb can have unexpected forces. There's a route on GPA posthumously named Anchors Away....

I thought by now you'd have learned...
it depends - on the hangers, the webbing, and the situation (eg: rap vs belay anchor, temporary or semi-permanent, etc.).

If I'm doing a dozen raps off of GPA and the bolt anchors don't have chains or quick links (many don't), you can be damned sure me or any other climber is not leaving a pair of biners at each station, nor are we carrying twenty or more quick links. We're tying or girth hitching webbing to the hangers, as has been done for the last half century.

Last year, RRG, two climbers fell to their death when their old anchor (webbings ) broke apart. you leave webbing so does 100s of climbers and soon ,you'll have CF of webbings all over the face of the rock.


now I have learned a lot

Which is exactly what I see in the picture. Plus teeny little nubs for tails.

I assume these guys made it out alive, but if I climbed up to find that's what my partner built, I'd slap him in the back of the head and re-rig it before leading on (and it would take all of 30 seconds). Granted it's a slab and the leader clipped the high bolt, so bombing onto the anchor isn't likely to happen, but let's say it's a different situation. Factor 2 one of those and the safety of the entire team is not a foregone conclusion. If the supertape is old and perma-tied into a sling, it's like showing up an hour late and giftless for your date with death. Maybe death let's you kiss her, or maybe she's not that easy. Who can say?

Which is why any in-situ webbing should be inspected, backed-up, cut-out and replaced, etc. Just because it's there doesn't mean it's trustworthy.

Have you ever actually spent any time in Yosemite or done any routes?

and how exactly would you re-rig it?

no, I sit on a chair with a big belly , troll on RC and for some reasons, I happen to knowcritique all these sh*.

I am surprised that nobody has thought to comment on force multiplication due to pulley effects. The belayer himself is putting more than his body weight on the lower bolt. But I guess he would be pulled upward in a leader fall anyways, so w/e. If the climber had clipped through what the leader is using to anchor himself, there would be big problems in a fall.

FAIL

There is no pulley effect, a pulley requires a mechanical advantage, there is none.

a lot of n00bs on here seem to misunderstand pulley systems. always ask yourself if I pull 1 foot of rope here, how high does the load move....if it is 1 foot, then there is no multiplication of forces, it is a 1 to 1 redirect.

Any way it doesnt even matter in this case, as the load is split (albeit poorly) due ot the clove hitch pulling down on the lower bolt.

I wouldnt set it up like this, but I wouldn't give a fuck if my partner did...it is not going to fail.

FAIL

There is no pulley effect, a pulley requires a mechanical advantage, there is none.

a lot of n00bs on here seem to misunderstand pulley systems. always ask yourself if I pull 1 foot of rope here, how high does the load move....if it is 1 foot, then there is no multiplication of forces, it is a 1 to 1 redirect.

Any way it doesnt even matter in this case, as the load is split (albeit poorly) due ot the clove hitch pulling down on the lower bolt.

I wouldnt set it up like this, but I wouldn't give a fuck if my partner did...it is not going to fail.

Troll or stupid or both. That top bolt is acting as a pulley, same as in American Triangle.

Nothing in the ADT acts as a pulley.

I would consider multiplication of force a pulley effect

Then you should find a dictionary and look up the word pulley.

You aren't even considering the load on the pulley/anchor. Physics fail.

and how exactly would you re-rig it?

OK, the guy in the blue shirt is leading, and moving up.
The guy with the camera is snapping the action.
So where's the belayer?

I'd guess that the photographer is the belayer.

I think my leader was safe at the time, but a one-handed belay is asking for trouble.

No, if you know what you're doing, it isn't. But then you say you "think" your leader was safe instead of knowing he was safe, so maybe for you it is asking for trouble.

BTW, on the climb in the photo in question - a 5.11 friction slab - and where the leader is in the photo...a lead fall from there could probably be caught with two fingers. I've caught 50' sliding slab falls without even weighting the anchor.

Sorry, I couldn't resist posting my comment.

Recently, some safety reporters on TV were reporting how the highway cops were targeting careless driving habits. One guy was caught combing his hair with one hand, and drinking coffee with the other. "So tell me sir," asked the cop nicely, "who was driving your car?"

I'm sure the belayer is managing his left hand on brake, while he snaps his leader. I've done that too. I think my leader was safe at the time, but a one-handed belay is asking for trouble.

It really is hard to get good action shots of climbers climbing.

–noun, plural -leys.
1.a wheel, with a grooved rim for carrying a line, that turns in a frame or block and serves to change the direction of or to transmit force, as when one end of the line is pulled to raise a weight at the other end: one of the simple machines.
2.a combination of such wheels in a block, or of such wheels or blocks in a tackle, to increase the force applied.
3.a wheel driven by or driving a belt or the like, used to deliver force to a machine, another belt, etc., at a certain speed and torque.
http://dictionary.reference.com/browse/pulley

Did you not notice the requirement of the presence of objects fitting meaning 1 in meaning 2? Because you're clearly literate.

Your definition means that most simple machines are pulleys. You can define pulley that way if you want, but it's not a usual or useful definition.

What do you think?

So are you saying carabiners used in a haul system are not acting as pulleys? Have you ever set up a slackline? If you don't think the carabiners are acting as pulleys in that case then yes, we won't agree on this topic, but almost everyone else will consider it a pulley system. The wheel is there to reduce friction yes, but no totally eliminate it. The carabiner works in the same way just with more friction. To say one is a pulley and the other is not when rigged in the same way IMO doesn't make any sense. They still give you the same mechanical advantage(minus the loss to friction).

We're talking about the ADT, which doesn't have any pulley components. Of course a slackline or a haul system has pulleys. The ADT is effectively a single piece of line strung between two points.

The carabiner works in the same way just with more friction. To say one is a pulley and the other is not when rigged in the same way IMO doesn't make any sense. They still give you the same mechanical advantage(minus the loss to friction).

The carabiner is indeed acting as a pulley with friction, but a single carabiner or pulley attached to a fixed position provides no mechanical advantage.

Jay

The carabiner is indeed acting as a pulley with friction, but a single carabiner or pulley attached to a fixed position provides no mechanical advantage.

Jay

The force felt by the fixed pulley/anchor is twice the force applied. That is what I meant by mechanical advantage. If you didn't fix the anchor/pulley and instead hung your object from the biner/pulley, it would move half the distance and require half the force compared to pulling it directly up.

Uh, no.

Whether I pull rope from the top, right at the anchor or from the bottom as the belayer makes no difference. 1 foot for me is 1 foot for the climber. The only way it would change is if I were to pull up on the anchor itself, and since that has never been a situation we were looking at, I consider the point to be moot.

Maybe I wasn't clear in what I was explaining. Yes the distance you pull on either end of the rope is the same. In that sense it is a redirect. The way a single pulley can have mechanical advantage is to hang the object to be moved from the pulley itself. In that case the force is 1/2 and the distance moved is 1/2. Like this:

The reason this applies to the ADT is the doubling of the force felt by the anchor/biner/pulley(minus friction and angles).

No, that doesn't apply to an American Triangle (AT) at all. A pulley attached to the load affords a mechanical of 2. In an AT the "pulleys" aren't attached to the load but to fixed positions, so there is no mechanical advantage. Rather, for any angle at the bottom of the triangle, there is a greater force on the bolts due to the horizontal arm of the triangle, relative to a V-shaped anchor with same angle.

Jay

Yes no mechanical advantage. I shouldn't have ever used that term. Force mutliplication, even on a fixed point at a redirect is by definition a pulley effect though.

No, that doesn't apply to an American Triangle (AT) at all. A pulley attached to the load affords a mechanical of 2. In an AT the "pulleys" aren't attached to the load but to fixed positions, so there is no mechanical advantage. Rather, for any angle at the bottom of the triangle, there is a greater force on the bolts due to the horizontal arm of the triangle, relative to a V-shaped anchor with same angle.

Jay

Yes no mechanical advantage. I shouldn't have ever used that term. Force mutliplication, even on a fixed point at a redirect is by definition a pulley effect though.

As far as I am aware nothing is "by definition" a pulley effect, because, as far as I am aware, "pulley effect" is not a real term in physics or engineering. I've never seen the term used by anyone other than climbers on the internet.

Jay

Jay - prepare to be amazed:

http://pubs.acs.org/...bs/10.1021/ma061037s

Argh. Not all force multiplication falls under 'pulley effect.' I can make a lever with a bit of bar stock. Does my lever use the pulley effect?

Jay - prepare to be amazed:

http://pubs.acs.org/...bs/10.1021/ma061037s

The SR gels have a unique characteristic called the “pulley effect” that the cross-links made of α-cyclodextrin molecules in a figure-eight shape can slide along the polymer chain.

Yes you are right I shouldn't have been so general in my statement. But the multiplication of force in an ADT on one of the anchor points is a pulley effect.

If you say so. Like I said, no physics reference that I have ever seen defines or refers to such a "pulley effect."

Jay

I'm not even remotely amazed. They are not using the term "pulley effect" to mean whatever it is that climbers think it means.


Jay

Fine, would you be happier if I said a pulley by definition has a force multiplying effect?

No, because it doesn't, unless you include in your definition the trivial case of a single fixed pulley having a force multiplier of 1; that is, output force = 1 x (input force).

Jay

Fundamental Concept 2: Pulleys are force magnifiers! When the two weighted legs of the
rope passing through a pulley, are maintained in a parallel configuration, the forces brought to
bear on the pulley’s point of attachment are doubled! Said another way, whenever a pulley is
used, it automatically transmits an increased force to its point of attachment, by a ratio of 2:1.
(We’ll find out why a bit later.)

Please take a look at this PDF and tell me if it is wrong then. I don't have any of my physics books on hand but the concept should be the same.
http://www.ncstaff.net/...y%20MA%20Systems.pdf

The author is confused. In the very next sentence he states that this [single fixed pulley] is a "good thing" because the pulley "doubles the force, helping us to move the object." Then, in so-called "Fundamental Concept 3" he implies that this is 2:1 mechanical advantage, which it isn't. Note that the article is written by somebody who puts "Esq" after his name. That means he's a lawyer, and he wants us to know it (perhaps he's warning the reader that what follows is not likely to be good physics).

A single fixed pulley doesn't really "do" anything, except change the direction of force needed to hold a weight. It doesn't help you move an object attached to it. Moving the object requires the same amount of force as if you had attached the rope to it directly.

Jay

A single fixed pulley doesn't really "do" anything, except change the direction of force needed to hold a weight. It doesn't help you move an object attached to it. Moving the object requires the same amount of force as if you had attached the rope to it directly.
Jay

A single fixed pull does "do" something more than chance the direction of a rope. It increases the force on whatever is "fixing" that pulley.

Like I said, climbers use the term "pulley effect" all the time. The term seems unnecessary if you understand basic statics, and it seems to inevitably lead to confusion with mechanical advantage.

Jay

Please take a look at this PDF and tell me if it is wrong then. I don't have any of my physics books on hand but the concept should be the same.
http://www.ncstaff.net/...y%20MA%20Systems.pdf

This is poorly written. If I hang 100 lbs on one strand and 100 lbs on the other, I've started with 100 + 100 = 200 lbs. So 200 total lbs of crap equaling 200 lbs on the anchor isn't really a force magnifier in my book. I could just as easily omit the pulley, still 200 lbs of crap loading the anchor.

Thanks. That is what I have been trying to communicate, albeit poorly.

Jay

Calling the left carabiner "A" and the right one "B":

It's true that the rope will not pull on A with anything but a re-directed force of the same magnitude (no mechanical advantage here). That said, since "A" must resist that force (equally, but opposite in magnitude?), the total force that "B" feels would be the force of the rope plus the (equivalent) force that "A" is resisting the rope with. That is to say, "B" feels a downward pull of 2x rope force (mechanical advantage here, yes?).

Why does it even matter whether or not "the pulley effect" is defined outside of the context in which we're speaking?

This is poorly written. If I hang 100 lbs on one strand and 100 lbs on the other, I've started with 100 + 100 = 200 lbs. So 200 total lbs of crap equaling 200 lbs on the anchor isn't really a force magnifier in my book. I could just as easily omit the pulley, still 200 lbs of crap loading the anchor.

The author clarifies frame of reference a bit later on with traveling vs. fixed pulleys.

That is because you are not attaching any weight to the pulley itself. In that case it is just a redirect as has already been explained previously. If you hang a 200lb weight from the a single pulley with the other end of the rope fixed, it only takes you 100lb of force to lift that 200lb item. That is magnification of force/mechanical advantage/whatever you want to call it.

The point is that the second bolded sentence does not support the first. If it did, we could say, for the same reason, that a bolt was a force magnifier. In fact, the exclamation point at the end of the second sentence is rather comical, since all the author is proving is that if you hang twice the weight off any point of attachment, the force on that point of attachment is doubled (!).

Jay

How? Without the pulley, your 100lb force you exert can only lift 100lbs. With the pulley you can lift 200lbs. You have now multiplied your effective force by 2.

The author argues: "When the two weighted legs of the rope passing through a pulley, are maintained in a parallel configuration, the forces brought to bear on the pulley’s point of attachment are doubled." Therefore, "[p]ulleys are force magnifiers."

The first sentence is true, but the second sentence does not follow from it. If it did then it would also be valid to argue the following: When two weighted strands of rope are fixed to a bolt, the force is doubled. Therefore bolts are force magnifiers. As above, the first sentence is true, but the second sentence does not follow from it.

In neither case is the pulley or the bolt acting as a force multiplier. In both cases the force on the bolt or pulley are 2w by the simple fact that you've got two strands of rope hanging from the bolt or pulley, each with a force of w on it.

Jay

If both ropes are fixed to the bolt, only 1 rope has a tension equal to W. The other strand would be under no tension, and the bolt would have a force equal to W.

The fact that the bolt acts as a pulley(both strands connected running over the pulley) is what is necessary to cause tension in both lines doubling the force on the bolt.

Quit shooting at everything that moves Dick Cheney.

I was helping your point. "Pully effect" only shows up in translated chemical articles and climbing sites.