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Do Screamers Work?

Scott O · · Anchorage · Joined Mar 2010 · Points: 70
rocknice2 wrote: I took a 20 footer on a C3 000 with only two lobes engaged. Doesn't prove a thing until you know the whole story.
But that's why we have lab data.

rockandice.com/lates-news/c…
20 kN · · Unknown Hometown · Joined Feb 2009 · Points: 1,346
Scott O wrote: But that's why we have lab data. rockandice.com/lates-news/c…
That test doesent prove much in the real world because it ignores too many real-world variables. To get some legit data one would need to go to the crag with actual people and conduct some testing that is representative of real lead falls. Drop towers with fixed belays and steel weights wont cut it here. I still stand fast on my offer to go to the crag and take some actual falls on Screamers and record the results if someone has some spare ones they want to send on over. Also, that test was conducted by a BD employee and put on BD's website:

blackdiamondequipment.com/e…
patto · · Unknown Hometown · Joined Jul 2012 · Points: 25

Given that the majority of vast majority of real world falls is less than 5kN one wonders what is the marginal gear that people are fall on and how they assess the effect the screamer has had.... Even big "whippers" would normally be less than 5kN.... Personally I would be much more interested to see some videos of massive whippers complete with a load cell at the protection.

Likewise I've seen short falls on #0 and #1 (real, original) RPs... They are unrated but I've seen guidelines of the order 2-3kN.....

20 kN · · Unknown Hometown · Joined Feb 2009 · Points: 1,346
patto wrote: Personally I would be much more interested to see some videos of massive whippers complete with a load cell at the protection.
I lobed a few 25 footers onto a load cell and the highest I hit was around 3.9kN with a soft catch. I weigh 155 lbs. The results are on MP somewhere.
Scott O · · Anchorage · Joined Mar 2010 · Points: 70
20 kN wrote: That test doesent prove much in the real world because it ignores too many real-world variables. To get some legit data one would need to go to the crag with actual people and conduct some testing that is representative of real lead falls. Drop towers with fixed belays and steel weights wont cut it here. I still stand fast on my offer to go to the crag and take some actual falls on Screamers and record the results if someone has some spare ones they want to send on over. Also, that test was conducted by a BD employee and put on BD's website: blackdiamondequipment.com/e…
That's actually the opposite of how we do science. If your questions is "do screamers work," you isolate the screamer variable and test that. What you propose has terrible control of confounding variables. You'd have to have an enormous sample size of falls in "real lead falls" to even begin to cancel out noise.
cyclestupor · · Woodland Park, Colorado · Joined Mar 2015 · Points: 91
Scott O wrote: That's actually the opposite of how we do science. If your questions is "do screamers work," you isolate the screamer variable and test that. What you propose has terrible control of confounding variables. You'd have to have an enormous sample size of falls in "real lead falls" to even begin to cancel out noise.
I see your point, but the question is NOT "do screamers work?". The question IS "do screamers effectively reduce the force on the top piece during a lead fall".

Lab tests on screamers are inadequate, because the results of those tests can't be applied to lead falls. There are many more variables in a lead fall. those variables are not independent of behavior of the screamer. For example... having a screamer in the system also reduces the force felt by the belay, but tube style belay devices allow the rope to slip a bit when catching a fall (there is an activation force just like a screamer). Therefore the belay device nullifies the effectiveness of the screamer somewhat. The only way to know how much is to include the belay device in the test scenario.
20 kN · · Unknown Hometown · Joined Feb 2009 · Points: 1,346
Scott O wrote: If your questions is "do screamers work,"
It's not. What we could use more insight on is under what conditions they are advantageous and disadvantageous as well how they influence peak loading in real world falls. A drop tower does not adequately replicate those scenarios. There are many variables in real world testing but good data can still be had from replicating real-world scenarios.
CTB · · Cave Creek, AZ · Joined Jul 2015 · Points: 305
Eric Moss wrote:http://blackdiamondequipment.com/en_US/qc-lab-to-screamer-or-not-to-screamer.html Screamers don't dissipate energy, they increase the time that the anchor imparts skyward force on the system, thus decreasing kinetic energy of the fall.
Just go pick up a few of these and let this thread rest in peace already


patto · · Unknown Hometown · Joined Jul 2012 · Points: 25
20 kN wrote: I lobed a few 25 footers onto a load cell and the highest I hit was around 3.9kN with a soft catch. I weigh 155 lbs. The results are on MP somewhere.
Awesome!.... Thats pretty much what I've concluded myself without seeing too much data on it.

Back of the envelope calculations:
1. FF1.77=~8kN for typical climbing ropes... Typical FF is 1/2 that even for BIG whippers eg FF~0.9.... Assuming linear stiffness you get 8kN / 4 = 2kN at the climbers end... Which works out to be 2kN 8*1.6 = 3.2kN... For a big whipper.. (Rope drag could increase the effective FF so >3.2kN certainly believable.) ... EDIT.
2. If climbers where getting 4kN falls then they'd be hurting!
3. I've whipped on small gear.

Scott O wrote: That's actually the opposite of how we do science. If your questions is "do screamers work," you isolate the screamer variable and test that. What you propose has terrible control of confounding variables. You'd have to have an enormous sample size of falls in "real lead falls" to even begin to cancel out noise.
Isolating the effect of a screamer to a short rope, high fall factor fall without a soft body mass is worse science.
brenta · · Boulder, CO · Joined Feb 2006 · Points: 75
patto wrote: Assuming linear stiffness you get 8kN / 4 = 2kN at the climbers end...
I may be missing something, but the impact force (in the ideal case) is O(sqrt(fall factor)).
David Jaffe · · Unknown Hometown · Joined Jul 2015 · Points: 0

Of course the total force over time on the rope is the same. Energy is conserved. The real question is peak force that might goo higher than the placements ability to stay in the rock.

Does anyone know about this? Screamers always seemed like a pretty solid idea for A4 and up to me...

D Jaffe - 73 yo and no longer climbing :).

patto · · Unknown Hometown · Joined Jul 2012 · Points: 25
brenta wrote: I may be missing something, but the impact force (in the ideal case) is O(sqrt(fall factor)).
You are correct. That is the problem with back of the envelope calculations.. ;)
Alex Bury · · Ojai, CA · Joined Jun 2012 · Points: 2,376

Blows my mind that this debate is still going on. Do we really have no idea if screamers work??

Healyje · · PDX · Joined Jan 2006 · Points: 422

Some of us have at least a reasonable feel for the answer...



Guideline #1: Don't be a jerk.

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