Screamer in a bridge?

[Fl Canopy Stalker]

What are the rules of material degradation?

How do they apply to screamers under normal accepted use?

Do all the stitches in a screamer degrade at the same rate, due to using the screamer under a load that doesn't exceed the break strength of the first row of stitches? If not, what rate do they degrade at?

What's the rate of degradation of the stitches normally? Surely we have a formula for % of strength year over year. And we've probably boiled that down to "replace it every year, or five years, or ten years" based on basic math related to that. I'm asking for that data.

I can get behind your point. Its a reasonable one. I don't buy the end conclusion though. We may be able to get to that point. I'm not ruling it out. I'm also not saying that screamers are "safe" or "useful" or "exactly as they were to start" after being loaded for some time.

What I'm trying to arrive at, is what data, specifically, are you basing a very specific claim on - that screamers will degrade beyond usefulness in a time frame that is unacceptable, by being subjected to the loads generated through normal climbing activities.

Again, I'm not saying I couldn't be convinced this is true. I'm saying you're making a big leap from one set of facts, skipping a lot of stuff, and arriving at that conclusion. I'm interested in very specific information from the middle.

Can I ask you something in return? How do screamers work? What allows them to absorb shock because that is what they are designed to do correct? I understand the engineering behind their design. So I am asking you to explain to me your understanding of how they work

 

[kyler1945]

Can I ask you something in return? How do screamers work? What allows them to absorb shock because that is what they are designed to do correct? I understand the engineering behind their design. So I am asking you to explain to me your understanding of how they work

My understanding is that when the force exerted on the screamer exceeds a threshold (from what I've gathered from various suppliers, it's in the 2-3kN range, let's use 2kN for the conversation) stitches begin to pop. As long as the force continues to exceed that threshold, additional rows of stitching will continue to pop until that force threshold is not met, or you run out of stitches to pop. Each time a stitch or set of stitches breaks, energy is being expended to do so. This energy is therefore not being transferred to the other end of the screamer, or things downstream of it.

It's hard for me to believe that putting 1-1.9kn of force will have any impact on the stitches at the very end of this chain reaction. Why? Because of the friction imparted by the stitching thread weaving in and out of the webbing of the screamer. I can totally understand how the first stitches, and some number of stitches behind those, will be subject to "wear" from being loaded. But the force of being loaded can't transfer all the way down. I'd argue it can't transfer very far down regardless, otherwise all of the stitches would pop closer to the same time upon being hit with a high force. The whole premise assumes that the next layer of stitches isn't exposed to something like the force to break until the ones in front of it have broken.

This is why the manufacturers give a maximum amount of force reduction of say 2-3kN, and that number tracks sort of closely with the force required to break stitches. If you exposed it to a 15kN force, it wouldn't just all tear at the same time. It would reduce the felt force on the other end by something like 2-3kN for the amount of time it takes to tear through all the stiches.

If you understand the engineering behind the design, and can articulate it well, that would be far more effective than trying to get me to explain myself. Especially if the main goal is honest conversation arriving at useful conclusions.

 

[MNFarmHunter]

Reading though the thread (and I may have missed something), having a screamer within or part of the bridge would defeat the purpose of the bridge and potentially cause greater injuries.

The bridge is in effect a load distributing hitch anchored on each side of the saddle. This allow you to twist at height smoothly without fighting the saddle. Due to this uneven center point, a screamer couldn't be within the bridge itself due to the uneven deployment potential.

Extending this then to the bridge loops, the load distribution only works so long as there's an equal force applied to each anchor point. If screamers were built into each bridge loop, they would only equally deploy if the load remained balanced between them. However, as soon as one side began to deploy, the load would shift applying uneven forces on each loop causing uneven deployment.

Sewing into only one loop would probably be the worst option for the same load shifting reasons mentioned above. Since the anchor points would shift during deployment, the load distribution would also shift causing you to roll as you're also falling. Anatomically, our spines are designed to take a straight vertical load, not lateral loads. This is why we're told to lift with our legs.

In short, screamers are only effective if they are connected between a single, fixed load and a single, fixed anchor point and deploy vertically.

 

[Fl Canopy Stalker]

Reading though the thread (and I may have missed something), having a screamer within or part of the bridge would defeat the purpose of the bridge and potentially cause greater injuries.

The bridge is in effect a load distributing hitch anchored on each side of the saddle. This allow you to twist at height smoothly without fighting the saddle. Due to this uneven center point, a screamer couldn't be within the bridge itself due to the uneven deployment potential.

Extending this then to the bridge loops, the load distribution only works so long as there's an equal force applied to each anchor point. If screamers were built into each bridge loop, they would only equally deploy if the load remained balanced between them. However, as soon as one side began to deploy, the load would shift applying uneven forces on each loop causing uneven deployment.

Sewing into only one loop would probably be the worst option for the same load shifting reasons mentioned above. Since the anchor points would shift during deployment, the load distribution would also shift causing you to roll as you're also falling. Anatomically, our spines are designed to take a straight vertical load, not lateral loads. This is why we're told to lift with our legs.

In short, screamers are only effective if they are connected between a single, fixed load and a single, fixed anchor point and deploy vertically.

Exactly!!!!

 

[Fl Canopy Stalker]

My understanding is that when the force exerted on the screamer exceeds a threshold (from what I've gathered from various suppliers, it's in the 2-3kN range, let's use 2kN for the conversation) stitches begin to pop. As long as the force continues to exceed that threshold, additional rows of stitching will continue to pop until that force threshold is not met, or you run out of stitches to pop. Each time a stitch or set of stitches breaks, energy is being expended to do so. This energy is therefore not being transferred to the other end of the screamer, or things downstream of it.

It's hard for me to believe that putting 1-1.9kn of force will have any impact on the stitches at the very end of this chain reaction. Why? Because of the friction imparted by the stitching thread weaving in and out of the webbing of the screamer. I can totally understand how the first stitches, and some number of stitches behind those, will be subject to "wear" from being loaded. But the force of being loaded can't transfer all the way down. I'd argue it can't transfer very far down regardless, otherwise all of the stitches would pop closer to the same time upon being hit with a high force. The whole premise assumes that the next layer of stitches isn't exposed to something like the force to break until the ones in front of it have broken.

This is why the manufacturers give a maximum amount of force reduction of say 2-3kN, and that number tracks sort of closely with the force required to break stitches. If you exposed it to a 15kN force, it wouldn't just all tear at the same time. It would reduce the felt force on the other end by something like 2-3kN for the amount of time it takes to tear through all the stiches.

If you understand the engineering behind the design, and can articulate it well, that would be far more effective than trying to get me to explain myself. Especially if the main goal is honest conversation arriving at useful conclusions.

You nailed it man. So yes the stitches break away at roughly 550 lbs (2kN) under new conditions. I am about to attach some data studies about material degradation. It will all relate to normal degradation, how environment such as UV or water related to the degradation of polymers. It wasn’t a strength study. I think it’s important to understand that yes the first row or two of the screamer would be what was most effected by the strain from continuous work load, but the stitches behind them would also be naturally degrading. The screamers do not claim they absorb the total force when you fall on them. They reduce the shock by 2 to 3 kn. If you had a 15kN fall and each row completely absorbed 3 kN then after 5 rows, your whole fall would be broke correct? Ok keeping with that theory. Here’s a video of guys using dynamic rope on a rock wall they climb to the anchor point and tie in the screamer, it’s tight but not weighted. Again the man is 180 lbs he is using dynamic line and someone is below acting (jumping) as the belay man. He falls a claimed 2’ on a foot of dynamic rope although if you see the slack fed through it was clearly a little more. Theoretically his fall should generate about 3 kN. It only frays out the first row of stitches. It doesn’t fully break the first row. So he repeats the jump only falling a little further. A claimed 4’ which dynamic rope and someone belaying. Do you think that generated 12 or 15 kN? Remembering that yesterday we witnessed a static fall of 6’ and it didn’t generate 9kN. In this video watch what happens to the second drop. I say that because once the threads are degraded to a point, they break away much easier thus absorbing less shock. I get it you want data but again can you give me data that shows SPECIFICALLY that using a carabiner as a quick link for SRT is dangerous? Or are you going to give me the it’s technically cross loaded answer? You keep asking for data that you know doesn’t exist. However the logic behind it is generally applied across ALL other webbing based products used for climbing or safety restraints. But you are saying my end conclusion is incorrect because I don’t have a report about using a screamer in a manner and industry that it wasn’t intended for.

 

[Fl Canopy Stalker]

My understanding is that when the force exerted on the screamer exceeds a threshold (from what I've gathered from various suppliers, it's in the 2-3kN range, let's use 2kN for the conversation) stitches begin to pop. As long as the force continues to exceed that threshold, additional rows of stitching will continue to pop until that force threshold is not met, or you run out of stitches to pop. Each time a stitch or set of stitches breaks, energy is being expended to do so. This energy is therefore not being transferred to the other end of the screamer, or things downstream of it.

It's hard for me to believe that putting 1-1.9kn of force will have any impact on the stitches at the very end of this chain reaction. Why? Because of the friction imparted by the stitching thread weaving in and out of the webbing of the screamer. I can totally understand how the first stitches, and some number of stitches behind those, will be subject to "wear" from being loaded. But the force of being loaded can't transfer all the way down. I'd argue it can't transfer very far down regardless, otherwise all of the stitches would pop closer to the same time upon being hit with a high force. The whole premise assumes that the next layer of stitches isn't exposed to something like the force to break until the ones in front of it have broken.

This is why the manufacturers give a maximum amount of force reduction of say 2-3kN, and that number tracks sort of closely with the force required to break stitches. If you exposed it to a 15kN force, it wouldn't just all tear at the same time. It would reduce the felt force on the other end by something like 2-3kN for the amount of time it takes to tear through all the stiches.

If you understand the engineering behind the design, and can articulate it well, that would be far more effective than trying to get me to explain myself. Especially if the main goal is honest conversation arriving at useful conclusions.

https://ttu-ir.tdl.org/bitstream/handle/2346/65981/Logan,%20April.pdf?sequence=1

 

[kyler1945]

You nailed it man. So yes the stitches break away at roughly 550 lbs (2kN) under new conditions. I am about to attach some data studies about material degradation. It will all relate to normal degradation, how environment such as UV or water related to the degradation of polymers. It wasn’t a strength study. I think it’s important to understand that yes the first row or two of the screamer would be what was most effected by the strain from continuous work load, but the stitches behind them would also be naturally degrading. The screamers do not claim they absorb the total force when you fall on them. They reduce the shock by 2 to 3 kn. If you had a 15kN fall and each row completely absorbed 3 kN then after 5 rows, your whole fall would be broke correct? Ok keeping with that theory. Here’s a video of guys using dynamic rope on a rock wall they climb to the anchor point and tie in the screamer, it’s tight but not weighted. Again the man is 180 lbs he is using dynamic line and someone is below acting (jumping) as the belay man. He falls a claimed 2’ on a foot of dynamic rope although if you see the slack fed through it was clearly a little more. Theoretically his fall should generate about 3 kN. It only frays out the first row of stitches. It doesn’t fully break the first row. So he repeats the jump only falling a little further. A claimed 4’ which dynamic rope and someone belaying. Do you think that generated 12 or 15 kN? Remembering that yesterday we witnessed a static fall of 6’ and it didn’t generate 9kN. In this video watch what happens to the second drop. I say that because once the threads are degraded to a point, they break away much easier thus absorbing less shock. I get it you want data but again can you give me data that shows SPECIFICALLY that using a carabiner as a quick link for SRT is dangerous? Or are you going to give me the it’s technically cross loaded answer? You keep asking for data that you know doesn’t exist. However the logic behind it is generally applied across ALL other webbing based products used for climbing or safety restraints. But you are saying my end conclusion is incorrect because I don’t have a report about using a screamer in a manner and industry that it wasn’t intended for.

I think the next step of this conversation gets beyond both of our capabilities.

I'm not asking for data I know isn't available. I know for a fact that there is data available on thread strength, and thread degradation due to environmental factors, and thread degradation due to being under load.

Not webbing or rope strength. Thread strength.

It should be quite easy to perform a calculation to determine whether screamers will still have a useful life after being exposed to loads below their thread breaking threshold. It should be quite easy to make a general assessment.

My contention was that you haven't done that math, or are not privvy to the data to do it. But it does exist.


If you have done it, then I apologize. Or if you have a strong enough understanding of the math behind thread strength, and degradation due to being under load, and can make those general assessments, I apologize.

But it doesn't seem to be the case.

Remember, environmental factors are the same whether the screamer is loaded or not. Those don't need to be discussed here. They're important but not relevant to the current conversation yet. This is specifically the claim that subjecting a screamer to loads below it's thread breaking threshold for some period of time, or some amount of load, that you never defined, will cause the thread to either become so weak as to make the energy absorption capabilities useless for our purposes, or the time that that process would occur in would make the interval for replacement outside of what could be useful.

I'm not discounting that material degrades from environmental factors or force being applied to it. I'm contending that it is possible to quantify those phenomenon, and then makes some basic assumptions and perform some basic equations to apply them to our problem here. You're acting as if the exact answers are unknowable because of SRT and Seatbelts under water. That's untrue. The data needed to get a very precise answer exists. Again, if you know something I don't, in the interest of everyone's attention span here, lay it on us.

 

[CooterBrown]

You nailed it man. So yes the stitches break away at roughly 550 lbs (2kN) under new conditions. I am about to attach some data studies about material degradation. It will all relate to normal degradation, how environment such as UV or water related to the degradation of polymers. It wasn’t a strength study. I think it’s important to understand that yes the first row or two of the screamer would be what was most effected by the strain from continuous work load, but the stitches behind them would also be naturally degrading. The screamers do not claim they absorb the total force when you fall on them. They reduce the shock by 2 to 3 kn. If you had a 15kN fall and each row completely absorbed 3 kN then after 5 rows, your whole fall would be broke correct? Ok keeping with that theory. Here’s a video of guys using dynamic rope on a rock wall they climb to the anchor point and tie in the screamer, it’s tight but not weighted. Again the man is 180 lbs he is using dynamic line and someone is below acting (jumping) as the belay man. He falls a claimed 2’ on a foot of dynamic rope although if you see the slack fed through it was clearly a little more. Theoretically his fall should generate about 3 kN. It only frays out the first row of stitches. It doesn’t fully break the first row. So he repeats the jump only falling a little further. A claimed 4’ which dynamic rope and someone belaying. Do you think that generated 12 or 15 kN? Remembering that yesterday we witnessed a static fall of 6’ and it didn’t generate 9kN. In this video watch what happens to the second drop. I say that because once the threads are degraded to a point, they break away much easier thus absorbing less shock. I get it you want data but again can you give me data that shows SPECIFICALLY that using a carabiner as a quick link for SRT is dangerous? Or are you going to give me the it’s technically cross loaded answer? You keep asking for data that you know doesn’t exist. However the logic behind it is generally applied across ALL other webbing based products used for climbing or safety restraints. But you are saying my end conclusion is incorrect because I don’t have a report about using a screamer in a manner and industry that it wasn’t intended for.

So if he fell 4 feet on purpose then if I use one to one-stick with no Linesman's belt than I should be good

 

[Fl Canopy Stalker]

My understanding is that when the force exerted on the screamer exceeds a threshold (from what I've gathered from various suppliers, it's in the 2-3kN range, let's use 2kN for the conversation) stitches begin to pop. As long as the force continues to exceed that threshold, additional rows of stitching will continue to pop until that force threshold is not met, or you run out of stitches to pop. Each time a stitch or set of stitches breaks, energy is being expended to do so. This energy is therefore not being transferred to the other end of the screamer, or things downstream of it.

It's hard for me to believe that putting 1-1.9kn of force will have any impact on the stitches at the very end of this chain reaction. Why? Because of the friction imparted by the stitching thread weaving in and out of the webbing of the screamer. I can totally understand how the first stitches, and some number of stitches behind those, will be subject to "wear" from being loaded. But the force of being loaded can't transfer all the way down. I'd argue it can't transfer very far down regardless, otherwise all of the stitches would pop closer to the same time upon being hit with a high force. The whole premise assumes that the next layer of stitches isn't exposed to something like the force to break until the ones in front of it have broken.

This is why the manufacturers give a maximum amount of force reduction of say 2-3kN, and that number tracks sort of closely with the force required to break stitches. If you exposed it to a 15kN force, it wouldn't just all tear at the same time. It would reduce the felt force on the other end by something like 2-3kN for the amount of time it takes to tear through all the stiches.

If you understand the engineering behind the design, and can articulate it well, that would be far more effective than trying to get me to explain myself. Especially if the main goal is honest conversation arriving at useful conclusions.

https://www.ihsa.ca/PDFs/Products/Id/M035.pdf

I can attach tons on rigging and why/how safety factors are formed. The bottom line is there is no data that will give you specifically what you asked for. Manufacturers set their WLL based on their own internal safety factors (that mustat minimum match ANSI/OSHA minimums- if you want to buy some ANSI standards and post them for us, be my guest) those safety factors are based off of testing to find the breaking strength. If this screamer is attached asyour primary life support ie between the tether and your bridge and is the only thing holding your weight, you are weakening your system. Again it’s industry standards for rigging, for life support, for slings. You seem very intelligent but my goal is not to change your mind. You’re an adult. You make your own choices. All I can do is tell you as someone with a strong background in rigging, using both work positioning harnesses/FBH, and dealing with OSHA and ANSI standards each year (because they do change) that it wasn’t designed for your chosen use.Let me stress this again, I am not saying it will fail, I am saying it will fail to reduce the force as it is intended to do. Will it be less than static? Probably. Then again it may rip away quicker than the second fall in that video and the additional fall distance might make the force equal or higher than not having it there. Remember it’s designed to assist in the braking process, not completely arrest the fall on its own. Take it or leave it man. I feel like we side tracked this thread completely.

 

[Fl Canopy Stalker]

So if he fell 4 feet on purpose then if I use one to one-stick with no Linesman's belt than I should be good

Do you also have a belay guy who jumps when you fall to help reduce the force? Are you using that many feet of dynamic climbing rope? Lol if no, that should be your answer

 

[Fl Canopy Stalker]

I think the next step of this conversation gets beyond both of our capabilities.

I'm not asking for data I know isn't available. I know for a fact that there is data available on thread strength, and thread degradation due to environmental factors, and thread degradation due to being under load.

Not webbing or rope strength. Thread strength.

It should be quite easy to perform a calculation to determine whether screamers will still have a useful life after being exposed to loads below their thread breaking threshold. It should be quite easy to make a general assessment.

My contention was that you haven't done that math, or are not privvy to the data to do it. But it does exist.


If you have done it, then I apologize. Or if you have a strong enough understanding of the math behind thread strength, and degradation due to being under load, and can make those general assessments, I apologize.

But it doesn't seem to be the case.

Remember, environmental factors are the same whether the screamer is loaded or not. Those don't need to be discussed here. They're important but not relevant to the current conversation yet. This is specifically the claim that subjecting a screamer to loads below it's thread breaking threshold for some period of time, or some amount of load, that you never defined, will cause the thread to either become so weak as to make the energy absorption capabilities useless for our purposes, or the time that that process would occur in would make the interval for replacement outside of what could be useful.

I'm not discounting that material degrades from environmental factors or force being applied to it. I'm contending that it is possible to quantify those phenomenon, and then makes some basic assumptions and perform some basic equations to apply them to our problem here. You're acting as if the exact answers are unknowable because of SRT and Seatbelts under water. That's untrue. The data needed to get a very precise answer exists. Again, if you know something I don't, in the interest of everyone's attention span here, lay it on us.

I have two ideas that will blow your mind.. idea one you pay for a 3rd party testing lab to do a few drops… drop a) drop a 220 lbs dummy as intended with a screamer as a secondary. And a force meter. You’ll see a fully designed and functional screamer. Then drop B) you use it as the primary means of connection and drop ithe same dummy with the meter. Will this produce a different result??? Then drop C) you ask them to leave the dummy sitting up on the pole completely weighted into the screamer as the primary attachment and complete the drop with the same dummy and meter approximately 4-8 hours later. Will those results be the same? What if you wet the screamer since it rains and we sweat while hunting….? Now drop d) is the case study drop… you drop the same dummy with same meter hooked into a normal tether and prusik so you have the standard force to base your data on. Each drop test only costs around $400 so for about $1600 you can have all that data you’d ever want my friend.

Idea number two is even easier. You email customer service at Yates. Tell them the screamer model you use, tell them that you use it in a tree as the primary (only, or main) attachment for dynamic loading. Tell them that you are using it as your lanyard and ask them for the data you want since you know it exists. Maybe they will give you an email back that says absolutely our screamer is plenty strong enough and designed to be used under a continuous working load and as the primary means of absorbing a fall. Then post a copy of that email on here for all of us. At that point I will concede that your point of view is correct

 

[kyler1945]

https://www.ihsa.ca/PDFs/Products/Id/M035.pdf

I can attach tons on rigging and why/how safety factors are formed. The bottom line is there is no data that will give you specifically what you asked for. Manufacturers set their WLL based on their own internal safety factors (that mustat minimum match ANSI/OSHA minimums- if you want to buy some ANSI standards and post them for us, be my guest) those safety factors are based off of testing to find the breaking strength. If this screamer is attached asyour primary life support ie between the tether and your bridge and is the only thing holding your weight, you are weakening your system. Again it’s industry standards for rigging, for life support, for slings. You seem very intelligent but my goal is not to change your mind. You’re an adult. You make your own choices. All I can do is tell you as someone with a strong background in rigging, using both work positioning harnesses/FBH, and dealing with OSHA and ANSI standards each year (because they do change) that it wasn’t designed for your chosen use.Let me stress this again, I am not saying it will fail, I am saying it will fail to reduce the force as it is intended to do. Will it be less than static? Probably. Then again it may rip away quicker than the second fall in that video and the additional fall distance might make the force equal or higher than not having it there. Remember it’s designed to assist in the braking process, not completely arrest the fall on its own. Take it or leave it man. I feel like we side tracked this thread completely.

Are you saying that it is possible that it could still remain useful, even after it has been subjected to loads by the climber? However, because the tests and calculations to determine what that usefulness is, and for how long, have not been done, you err on the side of caution by defaulting to "it's not it's intended purpose, so it isn't worth discussing" and "don't do it"?

I'm not disagreeing with this position by the way. I'm in the exact same end position of "don't do it". It's the first part that's very different from your original position which was that you were very confident that whatever loading we would subject screamers to if they remained in line for normal climbing activities would make them so weak as to be useless. Not that the data isn't available, and in it's absence you'd exercise caution.

We definitely took a tangent. I'm happy to table it. I'm just really struggling to close the gap between these two things above. Again, I'm happy to concede that it is possible that loading a screamer below it's thread breaking threshold will weaken it to some degree. And doing it more will weaken it more. That makes complete sense in my head. But making the leap from the realm of possible, to "if you weight a screamer, at all, prior to using it to absorb a fall, it will definitely be too weak to offer any protection worth counting on", seems like a big leap.

If you're not making that claim, and you're simply defaulting to caution, I agree with that.


I'm not asking you to help change my mind as to whether it is a good idea to load a screamer and then use it to break a fall. I'm asking you to convince me that we know enough to definitively say exactly why that's the case. I'm not saying I'm right and you're wrong. I'm not even taking a position on the very specific thing I'm asking.

 

[kyler1945]

I have two ideas that will blow your mind.. idea one you pay for a 3rd party testing lab to do a few drops… drop a) drop a 220 lbs dummy as intended with a screamer as a secondary. And a force meter. You’ll see a fully designed and functional screamer. Then drop B) you use it as the primary means of connection and drop ithe same dummy with the meter. Will this produce a different result??? Then drop C) you ask them to leave the dummy sitting up on the pole completely weighted into the screamer as the primary attachment and complete the drop with the same dummy and meter approximately 4-8 hours later. Will those results be the same? What if you wet the screamer since it rains and we sweat while hunting….? Now drop d) is the case study drop… you drop the same dummy with same meter hooked into a normal tether and prusik so you have the standard force to base your data on. Each drop test only costs around $400 so for about $1600 you can have all that data you’d ever want my friend.

Idea number two is even easier. You email customer service at Yates. Tell them the screamer model you use, tell them that you use it in a tree as the primary (only, or main) attachment for dynamic loading. Tell them that you are using it as your lanyard and ask them for the data you want since you know it exists. Maybe they will give you an email back that says absolutely our screamer is plenty strong enough and designed to be used under a continuous working load and as the primary means of absorbing a fall. Then post a copy of that email on here for all of us. At that point I will concede that your point of view is correct

I have conceded twice now that testing after screamers have been loaded then subjecting them to falls probably doesn't exist.

I've been quite clear. I'm saying that thread strength is a known quantity. And thread degradation due to forces being applied to it is available.

This data can be used to figure out how to make a functional screamer - how do we know? Screamer testing shows consistent results.

We can take those consistent results, and do some basic equations, being quite conservative, on how much the thread will degrade after being subjected to loads below their break strength. And use that to draw conclusions about a screamer being useful for our purposes after being exposed to loads below it's thread breaking threshold.

I'm asking if you've done these equations. My guess is no. And of course you wouldn't, there's been no reason to. My other question, is are you so familiar with thread degradation rates due to being subjected to loads that you can make such a definitive statement as to the outcome of subjecting a screamer to constant loading? You might be. Again, I've been asking you to please share if you've got some information from your experience in the field to help us understand. But again, it doesn't sound like you do. Also ok, as why would this be useful to you?

I'm simply trying to close the gap between some information, and some conclusions drawn from it. That's all.


It seems to me, that if screamers were this sensitive, there would be warnings slapped all over their packaging and websites that stress that if they've been subjected to loads below their thread breaking threshold for any period of time, they will not function properly. But you don't see that. All I can find are the default answers of "if you fall on one, replace it" or "replace after X years" just like every other piece of equipment.

Let me ask a simpler question.

Best case scenario, a screamer is kept in an airtight container out of UV light, and under complete slack until the moment its exposed to the forces of a fall.

Worst case scenario a screamer with an activation threshold of 2kN is held under tension at 1.9kN indefinitely until all the threads weaken and pop and its' now useless.

Now take a screamer exposed to sunlight, sweat, rain, dirt, and a person subjecting it to 1.5kN of force for a total of two hours over the course of a dozen climbs in a hunting season. It's then subjected to the forces of a 3' fall. Do you think the results of this are closer to the best case scenario or the worst case scenario?


And then a second question. Do you think the answer is knowable?

 

[EricS]

I wouldn’t put a screamer on a bridge but something similar could be built into the bridge loops. Similar to the webbing tethers made for harnesses. It would require a good bit of r&d to determine how many stitches and a lifespan. Plus I don’t think anyone is calling saddles fall arrest devices yet.

 

[Fl Canopy Stalker]

I have conceded twice now that testing after screamers have been loaded then subjecting them to falls probably doesn't exist.

I've been quite clear. I'm saying that thread strength is a known quantity. And thread degradation due to forces being applied to it is available.

This data can be used to figure out how to make a functional screamer - how do we know? Screamer testing shows consistent results.

We can take those consistent results, and do some basic equations, being quite conservative, on how much the thread will degrade after being subjected to loads below their break strength. And use that to draw conclusions about a screamer being useful for our purposes after being exposed to loads below it's thread breaking threshold.

I'm asking if you've done these equations. My guess is no. And of course you wouldn't, there's been no reason to. My other question, is are you so familiar with thread degradation rates due to being subjected to loads that you can make such a definitive statement as to the outcome of subjecting a screamer to constant loading? You might be. Again, I've been asking you to please share if you've got some information from your experience in the field to help us understand. But again, it doesn't sound like you do. Also ok, as why would this be useful to you?

I'm simply trying to close the gap between some information, and some conclusions drawn from it. That's all.


It seems to me, that if screamers were this sensitive, there would be warnings slapped all over their packaging and websites that stress that if they've been subjected to loads below their thread breaking threshold for any period of time, they will not function properly. But you don't see that. All I can find are the default answers of "if you fall on one, replace it" or "replace after X years" just like every other piece of equipment.

Let me ask a simpler question.

Best case scenario, a screamer is kept in an airtight container out of UV light, and under complete slack until the moment its exposed to the forces of a fall.

Worst case scenario a screamer with an activation threshold of 2kN is held under tension at 1.9kN indefinitely until all the threads weaken and pop and its' now useless.

Now take a screamer exposed to sunlight, sweat, rain, dirt, and a person subjecting it to 1.5kN of force for a total of two hours over the course of a dozen climbs in a hunting season. It's then subjected to the forces of a 3' fall. Do you think the results of this are closer to the best case scenario or the worst case scenario?


And then a second question. Do you think the answer is knowable?

I don’t think the answer is “knowable”. Again unless you lead a field study or paid for testing you couldn’t know. That’s why mathematics and formulas are only subjective in this scenario. Everyone talks about variables. There would be variables. We know the sewn strength of each row and we’ve established there will be degradation. How much? That’s a variable. But again working on the premises of Working Load Limit (again industry standard for all rope and webbing safety products) 185 lbs of constant load is best case scenario for it to be fully functional. I can play the game of hypotheticals all day. I’m still waiting for you to produce me that data on carabiner failures while using them as the quick link for SRT. I’m sure you don’t do that right? If you don’t, why? Is it not safe? Why isn’t it safe? Side loaded…. What makes you decide that a carabiner in that connection is technically side loaded? Let’s go over best and worst case scenarios. Best case scenario is you fall and the carabiner remains in line this not fully side loaded and it holds. Worst case scenario is you fall and it snaps. But what if your rope is dynamic and your fall factor is a 1:1 on a wet day. Would scenario 1 or scenario 2 be more likely to happen? What if the tree is twice as wide as the carabiner is long? I can’t tell people what to do. All I can do is tell you that it’s not intended to be used in that manner and this is why. I don’t cross load my carabiner not because you provide data, but because I know it is not safe. I also do not use a screamer as a tether attachment point because it’s meant to assist in reducing force during fall arrest, it’s not made to be the primary arrest in the fall. If it’s weakened and breaks all stitches quickly, you’ve now introduced additional distance into your fall. For some that fall could be on static rope. In my mind that is a no no. Not because of data, but because of my understanding of the materials and the design behind them. You can play the “I’m a smart mathematical guy” on the internet. I’ll play the dumb ol redneck from Florida. But if you really wanted these answers you’re asking, you’d email them to these questions to the manufacturer or you’d pony up some money (surely that behind all that intellect is a well paid successful college graduate with $1600 for testing) my guess is though that you don’t really want those answers. You enjoy getting rises out of people. I don’t get upset though brother. I just read all this and laugh.
PS. Let me know when you get my data for the underwater seatbelt functionality too please

 

[Fl Canopy Stalker]

I wouldn’t put a screamer on a bridge but something similar could be built into the bridge loops. Similar to the webbing tethers made for harnesses. It would require a good bit of r&d to determine how many stitches and a lifespan. Plus I don’t think anyone is calling saddles fall arrest devices yet.

I personally don’t think anyone ever will call them fall arrest devices. Too much force is delivered to your waist, back and stomach. You bring up full body harnesses straps with the fold over……. Would you happen to know why aren’t those straps continuously weighted?

 

[kyler1945]

But again working on the premises of Working Load Limit (again industry standard for all rope and webbing safety products) 185 lbs of constant load is best case scenario for it to be fully functional.

I can set aside the assumptions about me and personal attacks on my character, because I think I found something in there that gets us closer to agreement.

You're saying that because we have an established procedure for determining WLL, and we know the break strength of the stitching, so we can arrive at what force we could apply before retiring the system based on those recommendations?

You're basing your conclusions on the fact that if we maintain the protocol with WLL limits on the stitching, we would be limited to subjecting them to 1/3 of their break strength. Anything beyond that would put us in "don't use it territory"?

This I can get behind. I think this is the jump I was looking for. Am I summing up that conclusion properly?

 

[Fl Canopy Stalker]

I can set aside the assumptions about me and personal attacks on my character, because I think I found something in there that gets us closer to agreement.

You're saying that because we have an established procedure for determining WLL, and we know the break strength of the stitching, so we can arrive at what force we could apply before retiring the system based on those recommendations?

You're basing your conclusions on the fact that if we maintain the protocol with WLL limits on the stitching, we would be limited to subjecting them to 1/3 of their break strength. Anything beyond that would put us in "don't use it territory"?

This I can get behind. I think this is the jump I was looking for. Am I summing up that conclusion properly?

Definitely not attacking you man. Honestly up until today I’ve agreed verbally with almost every post I’ve seen you make. You definitely are an intellectual type. I personally do not have that going for me. I have a strong understanding of safety for rigging and harnesses. My back ground is in maritime and electrical power. We deal with standards, inspections, and testing to a ridiculous extent. I am just saying you could have the answers you want from an email to the manufacturer. (Or about $2000 worth of drop testing ) seriously though. Yes we know the break strength of the stitches are 2.5kN. That is per row. The rows are designed to break away individually though as you pointed out. So they do not have the cumulative effect of slings that are sewn in to achieve a continuous SPI. Using the WLL of roughly 550 lbs, 1/3 of that load would be standard working load {before the stretching, friction (which is a huge factor in how threads produce holding strength), abrasion produced from moving/shifting ect while under load, along with basic gradual degradation would all factor how much strength would be lost} HOWEVER if you use the screamer as your only or primary connection from your bridge to your tether’s prusik or mechanical, then it is now used for life support. There is a whole different standard for that. The minimum is usually 10 times the load rating or 3000 lbs whichever is higher (for work positioning harnesses). When you calculate your break strength, it is done at the weakest point of your connection. The first row of those stitches break at 550. So 1/10th of 550 is…. 55. Now I know you’re thinking yea but there are more stitches and losing one row doesn’t render it useless. You are correct. It does not. But if you fell with the first row compromised, the remainder of the screamer will absorb less force because the first row is gone hence less deceleration. Let’s say you don’t fall, but it’s compromised. How do you know? Can you visually look at a bartack and know it is still safe if it isn’t frayed or nothing appears broken or lose? So you take it out again because it looks fine. You’re one sticking up. You swing a little to the side, advance your stick so that you can continue your climb. The compromised first row busts. You didn’t break the second row and you think I’m still tied in and it has many more rows so I am fine. Then that fall occurs. Now you have a screamer as your main arrest lanyard. It’s already missing a row like the guy in the video with the second drop. Again I know these are what if’s but are definitely possible. Ok so you suffer a fall while your tether is slacked. It’s down about waist level or maybe a little lower and you were about to advance it when the fall occurred. You are above a 1:1 fall factor already with about 18” of slack. You can fall about 24” total but at a high fall factor. That alone is bad enough. But you have that compromised screamer as your primary attachment so that high force fall breaks all the other rows of stitching. Theoretically it is slowing your fall speed and reducing your impact force, right? Well yes BUT now that all those stitches have broke your 10” screamer is wide open and allowed a secondary dynamic load of 10 extra inches. Only now your fall factor went from a 1.25:1 fall to a full on 2:1 fall with a secondary peak impact. Maybe the screamer holds, maybe it doesn’t? Regardless every bit of that shock absorption is now mitigated when that second dynamic event occurs. Again this is pending variables which we cannot account for. That is the reason they are used as a secondary force arrester and not a primary one. If someone uses it as their bridge or as their tether, the screamer will in fact absorb the entire force of the fall and still be expected to catch you. On a dynamic rope with someone at the bottom performing belay functions that is probably perfectly fine but in our application a belay person is not likely. And most of us are on static rope as well. That’s why I said what I said. It’s not data driven, it is purely me doing risk assessments and applying design logic. I could calculate forces then subtract the 550 for deceleration for stitches and the recalculate how much the second dynamic event would generate but I do not truly believe those calculations would be accurate. Both from a variable stand point but also from just not knowing how many stitches might remain following the initial portion of the fall. Again sorry if my response attacked your character, that is not my intention. I actually enjoy conversations like these if they can get people thinking. However we both know the data doesn’t exist for this scenario and I do not make screamers or sell them. So I can’t give you advice or insider information on them. I can only apply safety standards and make a recommendation based on my personal knowledge/experience. However there are ASTM standards for harnesses, for slings, for rock climbing gear. For like $75 you could become a member of ASTM and sit on a technical committee. You can get standards books from them and I know for fact that they would enjoy a safety first approach like yours to setting standards for saddles. I highly recommend some of you join. They need your input before a couple of companies push for standards that fit their personal agendas.

 

[kyler1945]

Definitely not attacking you man. Honestly up until today I’ve agreed verbally with almost every post I’ve seen you make. You definitely are an intellectual type. I personally do not have that going for me. I have a strong understanding of safety for rigging and harnesses. My back ground is in maritime and electrical power. We deal with standards, inspections, and testing to a ridiculous extent. I am just saying you could have the answers you want from an email to the manufacturer. (Or about $2000 worth of drop testing ) seriously though. Yes we know the break strength of the stitches are 2.5kN. That is per row. The rows are designed to break away individually though as you pointed out. So they do not have the cumulative effect of slings that are sewn in to achieve a continuous SPI. Using the WLL of roughly 550 lbs, 1/3 of that load would be standard working load {before the stretching, friction (which is a huge factor in how threads produce holding strength), abrasion produced from moving/shifting ect while under load, along with basic gradual degradation would all factor how much strength would be lost} HOWEVER if you use the screamer as your only or primary connection from your bridge to your tether’s prusik or mechanical, then it is now used for life support. There is a whole different standard for that. The minimum is usually 10 times the load rating or 3000 lbs whichever is higher (for work positioning harnesses). When you calculate your break strength, it is done at the weakest point of your connection. The first row of those stitches break at 550. So 1/10th of 550 is…. 55. Now I know you’re thinking yea but there are more stitches and losing one row doesn’t render it useless. You are correct. It does not. But if you fell with the first row compromised, the remainder of the screamer will absorb less force because the first row is gone hence less deceleration. Let’s say you don’t fall, but it’s compromised. How do you know? Can you visually look at a bartack and know it is still safe if it isn’t frayed or nothing appears broken or lose? So you take it out again because it looks fine. You’re one sticking up. You swing a little to the side, advance your stick so that you can continue your climb. The compromised first row busts. You didn’t break the second row and you think I’m still tied in and it has many more rows so I am fine. Then that fall occurs. Now you have a screamer as your main arrest lanyard. It’s already missing a row like the guy in the video with the second drop. Again I know these are what if’s but are definitely possible. Ok so you suffer a fall while your tether is slacked. It’s down about waist level or maybe a little lower and you were about to advance it when the fall occurred. You are above a 1:1 fall factor already with about 18” of slack. You can fall about 24” total but at a high fall factor. That alone is bad enough. But you have that compromised screamer as your primary attachment so that high force fall breaks all the other rows of stitching. Theoretically it is slowing your fall speed and reducing your impact force, right? Well yes BUT now that all those stitches have broke your 10” screamer is wide open and allowed a secondary dynamic load of 10 extra inches. Only now your fall factor went from a 1.25:1 fall to a full on 2:1 fall with a secondary peak impact. Maybe the screamer holds, maybe it doesn’t? Regardless every bit of that shock absorption is now mitigated when that second dynamic event occurs. Again this is pending variables which we cannot account for. That is the reason they are used as a secondary force arrester and not a primary one. If someone uses it as their bridge or as their tether, the screamer will in fact absorb the entire force of the fall and still be expected to catch you. On a dynamic rope with someone at the bottom performing belay functions that is probably perfectly fine but in our application a belay person is not likely. And most of us are on static rope as well. That’s why I said what I said. It’s not data driven, it is purely me doing risk assessments and applying design logic. I could calculate forces then subtract the 550 for deceleration for stitches and the recalculate how much the second dynamic event would generate but I do not truly believe those calculations would be accurate. Both from a variable stand point but also from just not knowing how many stitches might remain following the initial portion of the fall. Again sorry if my response attacked your character, that is not my intention. I actually enjoy conversations like these if they can get people thinking. However we both know the data doesn’t exist for this scenario and I do not make screamers or sell them. So I can’t give you advice or insider information on them. I can only apply safety standards and make a recommendation based on my personal knowledge/experience. However there are ASTM standards for harnesses, for slings, for rock climbing gear. For like $75 you could become a member of ASTM and sit on a technical committee. You can get standards books from them and I know for fact that they would enjoy a safety first approach like yours to setting standards for saddles. I highly recommend some of you join. They need your input before a couple of companies push for standards that fit their personal agendas.

Power generation or transmission?

 

[Fl Canopy Stalker]

Power generation or transmission?

Transmission and distribution.