UKC

So anyone used them - fallen on one- thinking rusty old pegs on sea cliffs

In reply to Ciderslider:

Chris Tan has:
http://www.kakibusok.plus.com/Equipment/CTDQ2/CTDQ2.htm

In reply to Ciderslider:

Yea used them a bit when I was climbing harder, winter mainly but used them on crux move peenuts and old pegs. I've never fell on one but slumped on one on an ice screw and it didn't even start to rip out.
I believe the thinking is to use one on the piece of pro before the marginal piece if at all possible. The thinking being that you have a good piece before the marginal one and you can reduce possible impact to it even more and turn a good piece into a bomber piece.

I never understood why screamers weren't made for the climber's harness instead of the gear placement - basically worn on the harness and then the climber would attach the rope to the screamer much like a VF lanyard.

The activation force would need to be lower (~1/2 the force needed for the screamer on the gear). It would save having to decide to place it and only one would be needed - seems to make sense for winter use.

I've spoken to a few people who think that the situations where they would really make a difference are fairly rare.
Other options such as a very stretchy rope, and a dynamic belay and DMM revolvers could also be considered.

I've bought one a long time ago... I might even have clipped it on a route once or twice, can't remember. Certainly never fallen on it or weighted it. I don't ever remember thinking "I could do with a screamer about now", where I have often thought "damn, not enough micro-cams" or "arse, could do with a hook for that" or "fecking sling isn't thin enough for that nanothread."
My conclusion being that for me, extra micro-cams/tri-cams/threads/lines of cocaine would get picked over a screamer.


In reply to duchessofmalfi:


If you had something like this, you would have to decide whether to use it before leaving the ground. It would also then apply to all placements on the pitch when really (not least for reasons of expense) you only want the screamer on one or two dodgy placements. If you fall off the well protected part of a route, you don't want to instantly trash and have to replace about £30 of screamer. Finally, if it was on your harness, if you did fall and rip it, you would either have to lower back to the belay, faff while hanging or climb the rest of the pitch with the full sling length dangling... would be horribly awkward for clipping gear after that.

In reply to Ciderslider:
They might work for short falls, but the physics of the situation suggests they can't possibly make much difference for long falls. (I'm speaking of fall length here; fall factor is not relevant.) Of course, you probably don't want to be even thinking about long falls on the kind of manky gear you'd put a screamer on so there's a chance they might do something.

There's also a chance they might not. Some tests a while ago by the CAI found little to no effect in and in some instances a slightly negative effect. The reason for this might be that by absorbing some fall energy, the screamer (after fully deploying) actually decreases slippage through the belay device, a mechanism that without the screamer would have reduced the gear impact more. If this is true, then users of gri-gri's and some of the newer assisted locking devices might have reason to be more interested in screamers than others. But they still won't do anything significant for long falls.

By the way, I've never met anyone who is knowledgeable about the technical details of the falling situation who believes any of the numbers on the Yates site, which look suspiciously as if they were simply computed according to some unknown set of assumptions. No one as far as I know has ever come close to replicating those numbers in any testing.

The screamer does do something in the Black Diamond tests http://blackdiamondequipment.com/en/qc-lab-to-screamer-or-not-to-screamer.h... . The fact that fall factors are part of the test protocol suggest a faulty understanding of the way screamers absorb fall energy, however. The lack of dependence on fall factor is seen in the fact that the observed reduction in impact to the anchor is about the same in the two different trials. In these tests the rope was anchored, whereas the CAI tests used a human belayer. The totally static belay in the BD tests may have emphasized screamer performance.

The screamer activation force is 2 kN or about 450 lbf (Yates either incorrectly converts 2 kN to 550 lbf or incorrectly converts 550 lbf to 2 kN rather than 2.45 kN). He mentions 2 kN a lot so I'll take 450 lbf as the activation threshold. I think a fully-deployed screamer is 2 feet long, so that means it can absorb 900 ft-lbs of fall energy. But it also increases the fall length by 2 feet, so adds 2 W ft-lbs of energy to the fall, where W is the weight of the falling climber. If we take a 180 lb climber, the net fall energy absorbed is 900 - 2 X 180 = 540 ft-lbs. That's the amount of fall energy in a 3 foot fall for the 180 pound climber.

So one way to think about what a screamer might do is to say that your top piece will see the same load reduction it would get if your fall was 3 feet shorter, i.e. you were 1.5 feet closer to the top piece when you fell. Put another way, a screamer does about what stepping down 18 inches before falling would do (if your belayer takes in the slack).

Since the top piece impact is lowered to the level of a fall that is 3 feet shorter, it is clear that for long falls one can't expect the three feet to make much difference. It also makes it clear that the fall factor has nothing to do with the load reduction.

I've said these things before and usually get excoriated by folks who love their screamers and are convinced they do more than I've said here. Maybe so, but I've yet to hear a convincing explanation of how this can happen. I'd be happy to hear one, because I own a screamer or two and wish I could expect more from them.

In reply to rgold:

I never really believed in these myself.
A friend of mine had a couple on his rack back in the 90s but they never got used in a fall. One thought was that, as it rips opened in segments, it could have a sought of jack hammer effect on a marginal placement. A guy who I knew who climbed hard grit routes said he didn't like them as the extra distance you would fall as they ripped out could make the difference on hitting the ground/ledge.
In summary I think they are almost useless to the 'ordinary' climber but could be of use on specific projects where you knew beforehand that they would be needed.

In reply to duchessofmalfi:


It would be twice as long/bulky too for the same effect and it would mean extra fall length even if you were being caught by the bomber hex you got in just above the rotten peg or stumpy screw you wanted it for.

jk

In reply to Hooo:



I don't think he has ever actually used one / fallen on one though.

In reply to Ciderslider:

I know this is aid climbing but I met a guy who had just bailed from Zenyatta Mondatta on El Cap.
He was pretty shaken up after taking a 20 footer onto a blue Alien. His screamer on the Alien ripped full length slowing him down but then two lobes ripped off the Alien which then popped before the Head just below the Alien held.....

E

In reply to ByEek:

>>I don't think he has ever actually used one / fallen on one though.

He has - I was belaying him at the time! The gear still ripped, but by that stage the "screamer" had stretched so much his bum was only a couple of feet off the deck.

In reply to Dan Arkle:


I've not done the maths, but it seems plausible that a Revolver might actually increase the force if it's on the top runner. They would certainly decrease the force if used on other runners (less rope drag meaning more rope can absorb the energy of the fall). On the top runner they increase the pulley effect, but this might be counteracted by the fact that the rope would stretch more. I'd be interested to hear if someone has done the maths on it.

In reply to Ciderslider:

I am convinced that I am alive because of one put on a good solid screw before 15m of crud and a dodgy cornice. My pal took the winger which was so huge it ripped all the manky belay. The only piece left was the good screw and the completely ripped screamer on it.

The fact that it was a sideway pull that ripped the belay (coming out of an ice cave) may mean that lots of energy will have been absorbed? I have one with me in winter when on ice routes or very bold turf routes. Never bothered in summer or safe winter routes.

This is no scientific proof of their real use.

I have seen guides on the continent that put a screamer on their harness with maillons and tie in on the other end? Never tried it myself.

In reply to rgold:

Not that anyone really cares, but an error in my analysis of the screamer effect made it too generous. Here is the correction.

The screamer starts off at about a 3" length and fully deploys to 24" length so extends 21". BUT this also allows 21" of rope through the lower biner, so full deployment adds 2 X 21" = 42" = 3.5 feet, not 2 feet, to the fall distance. The net fall energy absorbed for the 180 lb faller is thus 900-3.5 X 180 = 270 ft-lbs, not the 540 ft-lbs I previously said. That's the amount of fall energy in only a 1.5 foot fall for the 180 lb climber, not a 3 foot fall.

So, for a 180 lb climber, the screamer only has an effect equivalent to an 18" shorter fall, i.e. stepping down 9" and having the slack taken in. If the fall is short enough, 1.5 feet could be a significant reduction. For example for the 9 foot fall in the BD test, a 1.5 foot reduction would be a 17% reduction in fall distance, which is also coincidentally the peak load reduction observed in the BD test. For the 2 foot fall, a 1.5 foot reduction would be a 75% reduction in fall height; BD observed a 26% reduction in peak load.

By the way, in addition the totally static belay, there is another possibly misleading aspect to the BD tests. After the screamer fully deploys, it is an ordinary 1" tape runner and will, in that capacity, absorb some fall energy by stretching. Consequently, a better idea about screamer effectiveness might be to compare the screamer peak loads with 1" tape runner peak loads, rather than comparing the screamer to a steel chain.

In reply to rgold:


I do.