Do Screamers Work?

Eric Moss wrote: I think this is half true. I think extension in itself adds the same amount of energy regardless of the fall (assuming equal extension). I think the reason screamers end up being counterproductive at a point is not because of this additional energy from extension, but rather because the action of the screamer undermines the dynamic belay. In other words, because the screamer is softening the fall, it deprives the belayer the opportunity to soften the fall. It would be awesome if you did some tests and I'd love to see the results!

Really? I think the energy added by someone falling an extra meter at 100m/s is vastly different to the energy added by someone falling one meter at 1m/s. Ke=0.5mv² and all that.

That is the correct formula for kinetic energy, but we need to be looking at the potential energy formula in this case, Pe=F*d (weight times height). As others have pointed out, the (d) in this equation should be two times the extension of the screamer.

Jim Titt wrote: Really? I think the energy added by someone falling an extra meter at 100m/s is vastly different to the energy added by someone falling one meter at 1m/s. Ke=0.5mv² and all that.

When a body is falling, its potential energy is being converted to kinetic energy. For a free falling body, the sum of two is constant.
For a body falling at 100m/s situation becomes a bit more complicated, since there is considerable energy dissipation due to air drag - terminal velocity for sky diver is around 50m/s.
Whichever way, if a body falls 1 m, potential energy converted to kinetic, or dissipated some way, is equal to the weight, aka mass*g.
If the body is falling at terminal velocity, that is velocity is constant, all potential energy is being dissipated.

Eric Moss wrote: See 20KN's post above. He/she is correct that there are indeed scenarios where two screamers in parallel should be used.

Look, you guys can calculate, engineer and test your lttle hearts out, it's a pointless exercise as the notion of two parallel screamers is just stupid.

Eric Moss wrote: I think this is half true. I think extension in itself adds the same amount of energy regardless of the fall (assuming equal extension). I think the reason screamers end up being counterproductive at a point is not because of this additional energy from extension, but rather because the action of the screamer undermines the dynamic belay. In other words, because the screamer is softening the fall, it deprives the belayer the opportunity to soften the fall. It would be awesome if you did some tests and I'd love to see the results!

I'm finding this muddled an incoherent. All this cogitating is never going to be in any way useful when tied into the sharp end.

I didn't bother to check if this has been posted here yet.

From http://yatesgear.com/climbing/screamer/use.htm

Italic Text
SCREAMER, SHORTY, ZIPPER & SCREAM AID Specifications:
Force needed for activation of a Screamer is >2kN.
Standard Screamer and Shorty Screamer reduce peak forces on protection anchors by 3-4kN.
Zipper Screamer reduces peak force on protection anchors by 6-7kN.
Force needed for activation of a Scream-Aid is >1.5kN , they can absorb 1.5-2kN making them useful for only the most marginal placements.

UIAA recommends that protection devices hold the following loads.
Ice Screws-8kN
Friends-10kN(Mfg. range 7-14kN).
Pitons-12kN
Wire Nuts-12kn(Mfg. range 10-12kN).
RP-2kn(Mfg range 2-10kN).
Slings-22kN
Maximum impact force allowed on climbing Dynamic rope 6-9kn(Depending on size, 10.5mm=9kN).
Maximum impact force generate to running belay(Protection Anchors) is 15 kn. 1kN=225lbf.

Here are some useful examples where Screamers and Zippers are most effective.
1) Any high fall factor falls. FF=.5-2(Use ZIPPERS).
2) Moderate FF falls on marginal protection. FF=.25-1 (Use Screamers or Shorty).
3) Very low FF Falls on very marginal protection. FF=.1 and below -Use SCREAM-AIDS

Example 1:
An Ice climber 175lb (80kg) has climbed 33ft(10m) above his belay. The climber places an Ice screw at 17ft(5m) above the belay. In the process of placing his second Ice Screw he slips and falls!! The climber placed a ZIPPER Screamer on his first piece of protection, which was 17ft(5m) above the belayer. The climber comes to rest next to his belayer, a little shaken but ok, the Ice Screw held the fall!
This was a Fall Factor 1 fall thus generating a force of 11kN to the Ice Screw. A Fall Factor 1 is a very substantial fall. Ice screws have a rated strength in the 8kN range. With out the use of a ZIPPER Screamer in this situation the Ice Screw would have surely failed. This would have resulted in the climber falling an additional 33ft(10m) coming to rest well below the belayer. This type of fall could have severe and fatal consequences. The use of a ZIPPER Screamer in this case reduced the peak force on the first Ice Screw placement from 11kN to 5kN.
In this same situation the use of a standard Screamer would have reduced the peak force on the Ice Screw placement from 11kN to 7kN. The use of a standard Screamer or a ZIPPER Screamer would have resulted in a similar outcome, as the Ice Screw should hold an 8kN peak load. In this situation a less than perfect Ice screw placement or a tied off Ice Screw would probably not hold unless the ZIPPER Screamer was applied.

Example 2:
A Rock climber 175lb(80kg) has climbed 100ft(30m) above his belay. He placed six various protection anchors, SLCD's, wired nuts, and clipped a couple bolts. He is now at the 5.9 crux of this climb. The crack is very thin and our climber can only find a placement for a #3 RP(Rated at 5kN). Being a novas climber, but having a rack of all the cool gear he opts to place a shinny new SHORTY Screamer to this RP. The climber now tries for the crux move; at this point he is 8ft(2.5m) above the RP. He falls. Will the RP hold his fall???
The climber comes to rest 16.5ft(5m) below the crux move. This was a Fall Factor .33 fall thus generating a force of 7kN to the protection point with the #3RP. A #3 RP is has a rated strength of 5kN. A Fall Factor .33 is a very moderate fall, but with out the use of the Screamer the RP would surely have failed. This would have resulted in the climber falling an additional amount to his last piece of protection(If it held!). The use of a Screamer in this case reduced the peak force on the RP placement from 7kN to 4kN, resulting in the placement holding. In this same situation the use a ZIPPER Screamer could have reduced the peak force on the RP placement from 7kN to 2kN. The ZIPPER could have allowed a #0(strength 2.2kN) or #1 RP(strength 3.6kN) to have a high probability of holding.

Example 3:
An Aid climber 175lb(80kg) has climbed 132ft(40m) above his belay. The climber placed 12 various protection anchors, SLD, wired nuts, clipping a few bolts and pounding a tied off pin. He is now at very thin spot in the crack and can only find a placement for a #1 RP(Rated at 3.6kN). The placement is solid but our experienced aid climber knows it can only hold about 800lbf(3.6kN). He opts to place a SHORTY Screamer to the #1 RP. The climber now works his way to the top step of his Etriers and places a #2 copperhead. At this point he is 6.5ft(2m) above the #1RP. He tests his #2 Copperhead and transfers his weight to the Copper Head, it pulls!!! Will the #1RP with the SHORTY Screamer attached fail or hold?
This fall generated a Fall Factor .1 thus generating a force of 1,000lbf(4.6kN) to the protection point with the #1 RP. Fall Factor .1 is a very light fall, but the #1RP is not very strong!! A #1 RP is has a rated strength of 3.6kN. With out the use of the Screamer the RP would probably have failed. This would have resulted in the climber falling an additional amount to his last piece of protection(If it held!). The use of a Screamer in this situation reduced the peak force on the #1 RP placement from 4.6kN to 2kN, resulting in the placement holding. The minimum force needed for activation of a Screamer is >2kn. In this situation the SHORTY Screamer could have theoretically reduced the peak force on the RP placement from 4.6kN to 1.5kN. The minimum activation needed for Screamer is >2kN therefore the Screamer in this situation only opened up about 80% or 8.5 of the 11" possible full exhaustion of the Screamer.

Example 4:
An Aid climber 175lb(80kg) has climbed 132ft(40m) above his belay. The climber placed 12 various protection anchors, SLCD's, wired nuts, clipping a few bolts and pounding a tied off pin. He is now at very thin spot in the crack and can only find a placement for a #0 RP. Even though the placement seems good our experienced aid climber knows it can only hold about 600lbf(2.2kN). He opts to place a SCREAM-AID instead of a SHORTY Screamer to this #0 RP. The SCREAM-AID was chosen because the force needed for activation of a standard Screamer is >2 which is the above the breaking strength of the #0 RP.
The climber now works his way to the second step of his Etriers and places a #0 copperhead. At this point he is 3.3ft(1m) above the #0RP. He tests his #0 Copperhead and transfers his weight to the Copper Head, it pulls!!! Will the #0 RP with the SCREAM-AID attached fail or hold?
This fall generated a Fall Factor .05 thus generating a force of 850lbf(3.8kN) to the protection point with the #0 RP. Fall Factor .05 is a very light fall, but the #0 RP is also a really weak placement. A #0 RP has a rated strength of 2.2kN. This would have resulted in the climber falling an additional amount to his last piece of protection(If it held!). The use of a SCREAM-AID in this case reduced the peak force on the RP placement from 3.8kN to 1.8kN, resulting in the placement holding. The minimum force needed for activation of a SCREAM-AID is >1.5kn. Italic Text

Are climbers taking terminal velocity whippers now? How long are the ropes you guys use 500-600 meters?

I've jumped out of this discussion. But I have to jump back in for this comment.

Jim Titt wrote: Really? I think the energy added by someone falling an extra meter at 100m/s is vastly different to the energy added by someone falling one meter at 1m/s. Ke=0.5mv² and all that.

Jim!? Are you sure you don't want to re-check that statement? Basic physics and all. Work = Force X Distance

patto wrote:I've jumped out of this discussion. But I have to jump back in for this comment. Jim!? Are you sure you don't want to re-check that statement? Basic physics and all. Work = Force X Distance

I shall consider it over the next few days as it´s a holiday and I´m going climbing :-)

kevin deweese wrote:Being a novas climber, but having a rack of all the cool gear he opts to place a shinny new SHORTY Screamer to this RP.

Yup.

Eric Moss wrote:That is the correct formula for kinetic energy, but we need to be looking at the potential energy formula in this case, Pe=F*d (weight times height). As others have pointed out, the (d) in this equation should be two times the extension of the screamer.

Seriously Eric, what's the point of all this?

Eric is Elena with an Engineering degree instead of a Nursing license.

I think the more pertinent point is why are you guys reading this thread if you aren't interested in exploring the topic like Eric is?

The problem is that while this kind of 'exploring' may feed some intellectual curiosity, it has limited value on the sharp end and - from the discussion here - a very real potential for causing one to entirely missing the forest for the trees. The idealized technical minutiae are worse than worthless if you don't have the common sense and intuition necessary for their real world application on lead.

Mark E Dixon wrote:Eric is Elena with an Engineering degree instead of a Nursing license.

I don't think Eric has an engineering degree; I think he took high-school physics. Hell, he might even still be in high-school physics.

n00b wrote: I don't think Eric has an engineering degree; I think he took high-school physics. Hell, he might even still be in high-school physics.

Well high school physics gives you enough basis for understanding most of what is at play in climbing statics and dynamics. So I'm not really sure what your point is here.

I would have more confidence in this discussion with a high achieving student in high school physics than a run-of-the-mill engineer.

patto wrote:I think the more pertinent point is why are you guys reading this thread if you aren't interested in exploring the topic like Eric is?

Jim Titt's comments are usually worth reading, no matter what the topic.

Mark E Dixon wrote: Jim Titt's comments are usually worth reading, no matter what the topic.

I do agree. Though in this case Eric's was schooling Jim Titt in high school physics. ;-)

(Sorry Jim! I'll put this down to the fact that you had better things on your mind like ACTUAL climbing! :-) )

patto wrote: Well high school physics gives you enough basis for understanding most of what is at play in climbing statics and dynamics. So I'm not really sure what your point is here. I would have more confidence in this discussion with a high achieving student in high school physics than a run-of-the-mill engineer.

I think that the point was more about the attitude than the knowledge base. This has changed long ago from an interesting discussion on a technical topic, into... something else.

Eric, if you really want to discuss this (as opposed to just poke people to get a rise out of them), consider adjusting your approach.

Dear Kyle,

I'm very sorry if I hurt your feelings or those of anyone else. I really don't want to antagonize anyone. I'm trying to learn more about climbing safety (more, apparently, than the climbing community knows at this point). Sometimes that requires challenging conventional wisdom and I know from experience that can be quite upsetting.

20 kn might do some testing to illuminate this subject, which would be awesome and hugely appreciated. Testing is the only way we can answer these questions for sure. To this end, I will petition Yates and Petzl to use their resources to determine the practical limits of their shock absorbers.

Many of you are frustrated with our inconclusive analysis thus far. This is understandable and I share your frustration, but please realize that it is part of the process of decrypting the mystery of screamers. Be patient, for new information will emerge.

Love,
Eric

Eric Moss wrote:To this end, I will petition Yates and Petzl to use their resources to determine the practical limits of their shock absorbers. Love, Eric

Both Yates, and Black Diamond tested screamers, data is publicly available. There is also information from 3rd party sources available as well, a bit of googling away

Keep in mind - not everyone who cares about a specific climbing issue will participate in verbal exchanges that only increase entropy