Do Screamers Work?

Kedron Silsbee wrote:" 1. use a screamer when you anticipate a short fall, even if it's high fall factor, but don't expect it to make a huge difference to the maximum impact force.

But I would be very careful using them to catch high fall factor falls. They can worsen the effect. Just throwing out a quick example, assume a 7 foot fall on 7 feet of rope. Normally FF1. If we add in an extra 2' of extension as a result of the screamer deploying, now we are taking a 9 foot fall on 7' of rope which is FF1.29.

One of the problems with energy absorbing lanyards is they have a fixed activation force and a fixed amount of energy they can displace, but are used in a highly variable environment. This means that when you're taking a small fall on that #1 RP rated for 2kN 190' out on that A4 pitch, you have to reach 2kN before the thing will activate, which is obviously not that useful. On the other hand, if you whip off that same #1 RP only 10' out of the belay, now you're looking at a fall that could produce in excess of 10kN with a lanyard that activates at 2kN, which is too low. This is why Yates invented other types of screamers like the Scremer Aid, which activates at 1kN or 1.5, I forget which, and their long screamer, which has more rip material to displace more energy.

If you used a lanyard down low, close to the belay, I would place two in parallel to double the activation force to 4kN. That would allow more energy to be displaced and lessen the chance of the increase FF adding more energy than the screamer is removing.

Energy absorbing lanyards are common in commercial rope access and via ferrata, and they work fine in those situations. However, those situations are a lot more controlled. First, the lanyards are much longer, often as much as four feet long, and they use more stitching with higher activation forces. They are also used in a scenario that is a lot more controlled. When a tech is using a Petzl ASAP, there is really only so many ways he can fall on the thing, and all of the options involve falling no more than a few feet when using the device correctly. In via ferrata, the lanyards are rated for a max of FF5, which is about 15' or so.

I've only used them in two scenarios, but in those scenarios I've blown a couple of dozen of them.

The first scenario is when I want to equalize a nest of micro / marginal pro such that the nest has time to equalize completely before taking a load. In that instance I use a razor to steeply pre-slice the screamers so that the tacks start blowing with next to no force and then ramp to full-tack tearing.

The second scenario is on a single piece of pro which is deficient in some way and I want the loading to ramp up to the full load and hopefully see some lessening of the force however marginal.

In those scenarios, falls taken have blown various percentages of tacks from 25% on up to a %100 percent of tacks, but usually in the 30-40% range. In those instances we'd just sport tape them back together and use them until they were completely blown. So those two dozen screamers probably held more like forty or so falls.

I'm pretty Edisonian so have to admit I don't know or really care about the math involved or the testing beyond idle curiosity. All I know is I wouldn't have wanted to fall on any of those pieces directly and I started using them because one of my micro-nests of pro blew without a screamer and never blew again thereafter with one.

YMMV...

People are overthinking this by a long shot. Screamers are air bags.

Kedron Silsbee wrote: Furthermore, apparently it has been shown in testing that a screamer rips under a smaller force if it is loaded at high speed.

Err no. The maximum force while it is tearing rises.

Eric Moss wrote:I mean, in what publication are these factors identified?

The CAI tests are available in their archives, in Italian naturally. Padua is where they do their testing.

Right. I can barely make sense of the CAI tests, but they do seem to suggest that screamers are counterproductive after a point. I cannot discern at what point this occurs or what particular factors cause this. Any idea? I'm trying to create a precise guide for using screamers.

If screamers are counterproductive after a point, doesn't this suggest that nylon runners (vs dyneema) would be counterproductive after a point?

Jim Titt wrote: Err no. The maximum force while it is tearing rises.

Really - I'm surprised the maximum impact force is larger than without the screamer then - I had assumed that this was because the screamer tore at a force less than twice the weight of the climber, so the climber kept accelerating as it was tearing. Is there an easy explanation for why the maximum impact force increases compared with no screamer if the climber is decelerating as the screamer tears?

My best guess at this point is that it has to with a screamer allowing tension to equalize between climber side and belayer side, where normally the belayer-side tension is about 2/3 the climber side tension. Then, because of the pulley effect, there ends up being more force on the pro.

This explanation would raise more questions, such as: why not use a carabiner with more friction to reduce the pulley effect and force on the pro?

Kedron Silsbee wrote: Really - I'm surprised the maximum impact force is larger than without the screamer then - I had assumed that this was because the screamer tore at a force less than twice the weight of the climber, so the climber kept accelerating as it was tearing. Is there an easy explanation for why the maximum impact force increases compared with no screamer if the climber is decelerating as the screamer tears?

Don't assume a screamer decelerates every fall. At a certain point the screamer dissipates less energy than is being added due to the falling speed of the climber. That's why they work at relatively slow speed [short falls] but not at high speed [big whips]. So during a big fall the screamer is not decelerating the climber but merely allowing the climber to accelerate less, but still accelerate.

rocknice2 wrote: Don't assume a screamer decelerates every fall. At a certain point the screamer dissipates less energy than is being added due to the falling speed of the climber. That's why they work at relatively slow speed [short falls] but not at high speed [big whips]. So during a big fall the screamer is not decelerating the climber but merely allowing the climber to accelerate less, but still accelerate.

How does the speed of the fall affect the efficiency or operation of the screamer?

Eric Moss wrote: Any idea?

Yea, I and others have already said it on this very page! Go back and read. You're not going to get an exact number. Rarely is anything in climbing exact.

Lot of way over-thinking the proposition going on...

I'm curious is a device like Knong Kisa or Slyde better than a screamer? They work on friction so it should be a continuous decrease until nut at the end of the rope.

If the belayed locks and really holds the brake tight, I don't think there is that much of a difference between a atc or a grigri type of device. Unless it is a really big fall. I don't see many people belay like the guy does in this video, at 1:14. That makes the belay more dynamic.
youtu.be/grYj8nOA0xY

Kyle Tarry wrote: Also, I think that the nylon vs. dyneema distinction, when used in the context of protection/draws, is a fallacious argument. When a dynamic rope is in the system, the difference between them is so small it hardly matters.

This paper would suggest otherwise: blackdiamondequipment.com/e…

When it comes to life and death, I'll take 4.7 or 4.8 percent improvement.

20 kN wrote: Yea, I and others have already said it on this very page! Go back and read. You're not going to get an exact number. Rarely is anything in climbing exact.

That is why we science. All I've heard is to not use a screamer in a "high" or "fast" or "hard" fall. The support for these sketchy guidelines is also sketchy. I'm holding us to a higher standard because we deserve to know what we're dealing with when our lives are on the line. There are answers, but we have to be committed to finding them. It won't be easy, but let's solve this thing for real.

JulianG wrote:Unless it is a really big fall.

No reason the rope should be running through an atc even in a big fall if you lock it up.

Kyle Tarry wrote: Nobody can give you a black and white description of when to use screamers. Your best bet is probably not to use them at all, then you can get back to worrying about equalettes.

Just because you can't provide a clear guide for when to use screamers doesn't mean nobody can. Also, rude.

Eric Moss wrote: This paper would suggest otherwise: blackdiamondequipment.com/e… When it comes to life and death, I'll take 4.7 or 4.8 percent improvement.

That's because they tested the samples in a steel drop tower, with a steel weight, and a 100% static belay on a short, harsh fall. That test is not even remotely close to indicative of real-world unless we are talking about a roped lead solo, and even that is still a fair bit different than what they tested.

In the real world, the elongation of the dogbones will create a much smaller effect, likely far too small to reliably measure. That 4% improvement on the drop tower probably translates to less than 1-2% in the real world. By contrast, I have measured in the real world differences of 30%+ when providing a soft catch vs a hard catch.

Well, as someone who has blown through quite a few of them I laid out two scenarios for their use on rock. Again, it's not really rocket science. I climb over marginal, but better than nothing gear a lot and I only use screamers occasionally. My main use of them is in my lead rope soloing anchors which constitutes about 75% of my climbing.

Eric Moss wrote: That is why we science. All I've heard is to not use a screamer in a "high" or "fast" or "hard" fall. The support for these sketchy guidelines is also sketchy. I'm holding us to a higher standard because we deserve to know what we're dealing with when our lives are on the line. There are answers, but we have to be committed to finding them. It won't be easy, but let's solve this thing for real.

Bull. You're trolling the forum. If you were seriously asking questions, you wouldn't be making bald-faced and flatly false pronouncements about something you know nothing about.