[Nigel]

Hello there, does anyone happen to know off hand if anywhere in Sheffield or the surrounding Peak stocks screamers (shock absorbing quickdraws)? Cheers!

[Andy B]

If you can't get hold of regular ones you could maybe get some old ASAP lanyards of Adam and Aide, but I don't know how the deployment forces compare. I'm sure Adam does though.

[Paul B]

there were loads in CragX when I last did a shift (admittedly approaching a year now). I doubt they've all sold (they had all sorts from regulars to ice, if not they'll be able to get you some double quick).

(Shark - I don't actually work in the shop any more so this isn't advertising).

EDIT: http://www.cragxclimbing.com/search?q=screamer

I think you might even be able to purchase and collect these days too.

[grimer]

I once saw some in Decathlon!

[Paul B]

Did it say Quechua on it? and if so, would you buy it?

Edit: It turns out they even do a smartphone these days:
http://www.quechuaphone.com/

[TobyD]

Hello there, does anyone happen to know off hand if anywhere in Sheffield or the surrounding Peak stocks screamers (shock absorbing quickdraws)? Cheers!

outside always used to do the petzl version, which I've used quite a lot.

[masonwoods101]

Www.needlesports.com ? Maybe

[Johnny Brown]

We could order you some in if you can't find any. There is a lot of chat on the American forums about how "they don't work". I wouldn't agree with such a simplistic analysis, but they offer less 'help' than you might expect. Thin ropes and a soft catch are arguably more effective on any fall of length.

[duncan]

outside always used to do the petzl version, which I've used quite a lot.

Used a lot as in attached in vague hope or actually deployed? A wad point depends on your answer!

There is a lot of chat on the American forums about how "they don't work". I wouldn't agree with such a simplistic analysis, but they offer less 'help' than you might expect. Thin ropes and a soft catch are arguably more effective on any fall of length.

Is there any 'real world' testing of screamers or the just the usual theorising?

Thin ropes are something I've thought about in the past and El Mocho's mentioning them for Parthian reminded me. <usual theorising>Thin ropes are stretchier, and so potentially offer slower deceleration and lower impact. Data suggests otherwise though: Mammut Phoenix (8.0mm) impact is 6 / 9.5 kN whereas Genesis (8.5mm) is 5.6 / 8.3 kN. Perhaps a fatter rope has better energy absorbing properties? I realise there are other variables than rope diameter so is this just an unlucky example? I'd like to know since it seems a fairly crucial thing to understand when dealing with shoddy gear.

[Johnny Brown]

I've done a fair bit of reading on falling physics and my conclusion is that modelling rope stretch is way beyond simple physics. Real tests are much more useful. There is no question that screamers absorb energy. The debate revolves around the limited energy that they can absorb, which is exacerbated by their deployment effectively lowering the runner; thereby increasing the length of the fall and the energy that has to be absorbed. They are most effective in short, high fall factor falls, and least effective on long falls.

Petzl/ Charlet screamers deploy at around 2.5kN. The longer ones have more capacity to absorb energy. Industrial screamers have much more capacity but deploy at ~5kN (max 6) which is too high to protect dodgy placements.

I'm most familiar with Beal ropes, that seem to have a more simple thinner = lower impact force. Though the tests in half-ropes use smaller test weights so be careful to compare like with like. Sport ropes may have more mass in the sheath which raises impact forces.

[dave]

I don't think its useful to think of screamers as "absorbing energy", mainly because they don't hold on to it very long, its more that they will change a bit of energy to another form. They might dissipate a bit of energy to their surroundings during a fall (i.e. by heating up or making a noise) or temporarily store some if they stretch a bit, but compared to the total energy being considered in a fall situation I doubt its a deal breaker. Looks like the main benefit is in increasing the time of impact i.e. lowering impulse on the climber.

Like Jb sez, thin ropes and a decent belay aught to have more effect. Though obviously with falls where a  lot of force is being generated a thin stretchy rope is likely to get knackered sooner or reach its elastic limit or yield point sooner (I don't recall hearing of any instance of that happening in climbing though).

[Oldmanmatt]

Surely the principle transfer of energy is in that which is required to break the stitching?
This must result in an "arrest/release" cycle. A series of (admittedly) minute arrests and energy transfers?
Therefore it would seem unlikely (as a thought experiment only) that the additional fall length would increase the overall severity.
At the trigger, 2.5 kN of the fall must be transferred to the screamer?
Thus the fall which follows (which can be viewed as a discreet event (?)) must be the original, minus the trigger?

Then, unless the fall was perfectly inline with the placement, the initial trigger would also provide a deflection or change in fall direction. This in turn would again reduce the ultimate fall force upon the gear/harness (much like the "bridge swing effect")?

And so on, as each stitch fails.

Guess there must be test data out there somewhere.

If this butterfly mind of mine remembers, ten minutes from now, what it was supposed to be doing (despite vomiting kids, idiot employees and the distraction of a Sci-fi movie), I'd like to explore this further.

Anyone else keen? Maybe we can come up with an alternate design, that might be more effective?

[SA Chris]

I knew this girl.......

[Nigel]

Cheers for all that chaps, seems like my questions have been answered. I’ll check out CragX, need some new 5.10s anyway. JB I have pm’d you to tap up your wisdom. I will leave the floor open for the developing discussion on screamers’ effectiveness…

P.S. Was waiting for that one Chris! Thought people would go for the innuendo angle straight off, I know I would.

[SA Chris]

Glad I didn't disappoint!

[danm]

I mostly agree with JB. I did see some test results on Screamers a few years back, which concluded that they don't provide any advantage, but when you looked more closely at the tests done, the picture was more complicated. The general view these days by experts (by that I mean manufacturers, CEN working group bods etc) is that Screamers are most useful when there is not much rope out and the first runner you place to protect the belay isn't as good as you need it to be. A good example might be the first screw after the belay on a multi pitch winter route. As more rope comes into play, the properties of the rope become more important.

As well as a low impact force rope and a good dynamic belay (assuming you can still keep the climber off the deck!), a much more important factor than lots of climbers realise is the importance of keeping friction in the running rope low. If you really feel the fall at the belay this is good if the top runner is shit, because it means the whole rope has come into play and can stretch. Those falls on wandering routes or where you haven't extended properly where the belayer hardly notices can be the most likely to pop a runner because you effectively raise the fall factor by shortening the active length of rope. Rope manufacturers have started to alert people to this: http://bealplanet.com/sport/anglais/savoir-servir-corde-page.php

[Johnny Brown]

I don't think its useful to think of screamers as "absorbing energy"

I guess a better explanation is that they change the shape of the force/time curve to give a lower, flatter peak. IE reduce peak impact forces by absorbing forces over a longer time period. (In ideal circumstances. More typically, they just put a step in the rising limb of the curve).

Screamers are most useful when there is not much rope out and the first runner you place to protect the belay isn't as good as you need it to be.

Yes. I think they might have their place on grit routes where you face a short fall onto a shit runner.

[petejh]

More useful than screamers in most situations are, like JB and others say, skinny ropes with the lowest impact force you can get. But also revolvers - these are great for reducing impact force by reducing friction throughout the system. I use revolvers instead of screamers on crappy top pieces on mixed routes, also angle-changes.

[Johnny Brown]

You need to decide where you want the impact force to be lowest. Typically figures assume on the climber, but for UK trad the force on the runner is a bigger worry. Revolvers on the top piece may increase forces by increasing the pulley effect. I questioned a rep on this when they were first introduced, and was told the flex in the biner at peak load traps the wheel and stops it moving, but I think he was bullshitting me.

[danm]

Once again JB is right, when analysing a fall you have to decide whether to consider the peak force on the climber, top runner or at the belay. Revolvers and well extended runners below the top piece will improve the chances of that piece, if crappy, to withstand the force of the fall. I've heard the same thing about the Revolver wheel not moving freely at high loads, makes sense as compression of the bearing surface tends to lock up simple pulleys unless they are expressly designed not to.

[Adam Lincoln]

You are welcome to one of a few Absorbica l57 lanyards that I've got lying around Nige, but as Adam says, probably not ideal for the job in question. Nothing wrong with them, just we have lost the serial number tags.

[Zods Beard]

If it helps I've heard the majority of your Mums are screamers.