How about we tone it down a notch. I don’t know the right answer. I do know that there are many formulas out there to figure it and several online calculators from reliable climbing sources. Regardless of how it’s interpreted every one of them shows close or over the 4kn limit with a 3’ fall. Common sense or not jumping off a ladder has nothing to do with knforce on a static rope hooked into a static connection.
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CT RollNLock vs. Ropeman 1
- Thread starter Newhunter1
- Start date
The argument is not whether or not your body can handle a 3’ drop, although I think you’re missing the boat on that one as well.
The argument, to use your analogy, is that the ground will hold you up when you hit it after falling from 3’ above. And if it gives way, there’s another 15’ below ‘the ground’ that won’t give when your extremely strong back lands flat on it.
Taking a short position on risk aversion and promoting it to folks who may interpret in a wildly inappropriate way is, well, inappropriate.
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Dang...this is becoming more like archerytalk. Chill...I was asking for options and opinions. I understand that people love this sport but we still can have a discussion with being condescending.
I looked at the rollNLock and it was 70-80.00. I will still consider this and my ropemans whil still using a Prussic.
Sent from my iPhone using Tapatalk
I looked at the rollNLock and it was 70-80.00. I will still consider this and my ropemans whil still using a Prussic.
Sent from my iPhone using Tapatalk
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https://www.treestuff.com/store/catalog.asp?item=12216 and https://www.treestuff.com/faq.asp?faq_id=1 ... you're welcome
Thank you...and because this is cheaper I will now curse you (said in my nasely voice of Princess bride)
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ThePreBanMan
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You'll get no argument from me that the ground is stronger than the ropeman when it comes to breaking a fall. But that's not what we're talking about. We're talking about the force generated from a 3 foot fall. I used the analogy to point out that your math does not withstand examination. A 3 foot fall is not generating the forces your math says it is. To proof that I leverage common sense. Taking a step off a 3 foot elevation will not break your back or kill you, or harm most people in good health. But the forces you claim such a drop generate are most certainly fatal. So what's wrong, your math or everyone else's reality?
On the point of the body's ability to handle a 3' foot fall.... like I said, 3 days a week at the gym man. Up and down for reps of 10 to 15 for multiple sets. You're welcome to join me. There's video of people on YouTube doing far higher. JJ Watt can do 61 inches (5 feet). JJ Watt is still around last I checked too.
My point being that I think you've got a flaw in your formula somewhere. A 3 foot drop isn't generating the kind of force needed to kill anybody, or blow up the ropeman.
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Are you willing to use a ropeman as your connection point, climb 20’ In a tree, and force a surprise (someone drops the hatch under you when you’re not expecting it) fall where you drop 3’?
If not, are you willing to do the same exercise when you know the fall is coming?
If not, are you willing to do the same exercise, but only 4’ off the ground?
ThePreBanMan
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Again - no doubt that a surprise fall has far more potential for harm as you can't ready yourself. But that's not what we're talking about. We're speaking strictly in terms of the force generated. Because that number is what determines if the ropeman is safe.
4KN is half a ton roughly. If a 3-foot drop generated that kind of force (or more as the prior stated math indicates) I would have broken feet, legs, etc just from my gym routine.
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Sp we’re clear, Are you saying that with some common techniques used by common folks in this forum quite regularly, that 4kn of force cannot be generated, and thus, ropeman’s are safe for use?
you are not considering the fact that when you're doing box jumps you are bending your legs when you land. Your legs absolutely do absorb that much energy, the human body is an amazing thing. If you jump off step ladder from 3 feet and don't bend your legs you possibly could break your legs. Worse yet is if you jump off a step ladder and land on your rear end, you possibly could damage your spine. Here is a PDF if you're interested in the math, or you can just read the last paragraph. https://drive.google.com/file/d/16I7RvWBJ1X1fQ9u44UgVLmMsnNdqAii0/view?usp=drivesdk
The summary is, if you jump just 1.7 m and land without bending your knees you will break your legs.
also there are many tests on YouTube completed by reputable labs that show the forces generated in small drops. We really don't have to guess at this, the information is simple physics, and is out there.
predatorhunter
Well-Known Member
Confused, are we comparing the safety of a Ropeman 1 or like device to something else that will stop your fall at three feet and absorb enough energy to save you? Or are we saying anytime I fall three feet and suddenly have a deadly amount of force applied to me? This is a serious question because I am trying to figure out if this is a debate on one method being safer over another, or if any 3ft fall is extremely serious.
Both - sort of. One is getting implied, unfairly. And the other is the topic of discussion.
You’re right, it’s not very clear. That’s disappointing.
Everything I have ever seen or read tells me at the very least a 3 foot fall will hurt. it's a good idea to never put three foot of slack in your system.
I’d love to say I’m shocked that these numbers are even being disputed at this point, but little surprises me anymore.
Thanks for posting the graphic.
Folks, keep this in mind - there isn’t a right and wrong answer here. There are short and long positions (think stocks). You can never go wrong taking a long position on safety (being conservative or adding layers of protection etc). However, ALWAYS have your guard up when someone shorts a safety stance. Especially when they use more than one analogy to prove their point - if it takes more than one, you might need a better point.
No one here is telling you that using a ropeman in any manner will kill you. Unfortunately, someone here is telling you it definitely won’t. Please go read up on the subject. If you never have slack in your tether, you’re ‘probably’ fine(using a ropeman). I say probably because real life is messy, and you might be overlooking if and/or how much slack is in your tether at times.
A fall of 3’ is going to hurt, yes. And could be life threatening in its own right. The issue at hand is whether A-an average fellow doing things regularly discussed on this forum can generate force at or above the rating of the ropeman(4kn) and B - that the ropeman and your rope can tolerate that fall without a terminal failure.
My tag line says it all. This thread is a real life example.
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ThePreBanMan
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No - as I do not know what you quantify as "common techniques" and "common folks" as that's vague and imprecise language. I am taking the position that using the Ropeman 1 on a lineman's belt is fine though. So take that however you will. If someone else is of a different opinion - then do as you will. It's a free country.
Here is an example of someone taking a fall on this very form from a distance of 3 feet and was saved by the dreaded ropeman at the end of the lineman's belt when it got to the knot.
https://saddlehunter.com/community/...eman-1-and-linemans-belt-w-tree-sleeve.12429/
As a stand hunter (new to the saddle game) I've never used it as my tether to the tree. I make my own tether and it's Sterling Super Static and Sterling power cord for the prusik. Nothing is rated for less than 20 KN (the power cord).
But for a lineman's rope.... Come on man... No one has enough slack in their rope to fall far enough to generate the forces necessary to cause a failure. 3 feet is a huge amount of slack in a lineman's belt. Add to that I'm not convinced 3 feet would even cause the ropeman to fail. Add to that yet still, I'm not remotely convinced the "testing" was even accurate or applicable to hunting scenarios. Was it verified by another independent source? Did they try it with a superior quality abrasion-resistant rope like those made by Sterling?
Did you read the testing methodology? Did you catch the part where they say the testing methodology was holding 4 KN of force for 3 minutes on page 39 of the report? What kind of fall in a hunting scenario would generate that kind of force for that duration of time?
They "tested" ScentLok at Rutgers university too. That seems to be enough to convince some people that it works as well. Despite the study being financed by ScentLok, conducted in a controlled lab environment favorable to the results Scentlok wanted, conducted during discovery in a case where Scentlok was being sued and the results were unable to be reproduced by any testing done outside of those financed by Scentlok. But hey - they "tested" it. So it's gospel to some people.
The ropeman is for sale by some of the very people running this forum is it not?
https://tethrdnation.com/product/ropeman-1-mechanical-prusik/
.....is it your opinion that they're selling unsafe equipment?
What about the safety advantage the study cited that only the ropeman offers. Specifically how it will continue to operate correctly and safely even if grabbed by the operator. It was the only ascender that did. People tend to grab things when they start to fall right? Looks like those other ascenders didn't fare too well in that regard....
Also, why are we hung up on 4 KN as the "failure point" when the test states:
"Test performance: In all the tests the results reflect the design of the device. As a small body-loaded, toothed-cam ascender experience has shown a likelihood that the sheath of the rope would be stripped rather than the device slip. In a static pull this occurred at approximately 6 kN"
So considering all of this I think it's perfectly acceptable for use on a lineman's belt in a hunting application.
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Quite a few folks are using a ropeman on a lineman's belt - that has not been a point of contention at all here, or in any of the other discussions for that matter. This conversation has been specifically about use in a tether. With respect to a lineman's belt, and using a ropeman - I see no issue. But the reason I see no issue is not that you can't generate enough force to break the ropeman in the event of a fall while using the LB. It is because a lineman's belt IS NOT A FALL RESTRAINT DEVICE. It is a device implemented to help prevent falls by giving you better balance by having a minimum of three points of contact with your hands free (At least one foot, and both hips). It IS NOT INTENDED TO RESTRAIN YOU IN THE EVENT OF A FALL. Given those facts, I'm also ok with a ropeman on a lineman's belt. We agree on one thing, if for different reasons.
I used very precise language - and I used it with a purpose. Some people here will assume that because they don't do the exact thing that might be dangerous, that they are safe. My point was to broaden the scope of how people are climbing/using their tethers, and I did it with intent. I want people to consider this from a broader perspective, not read one guy on a forum saying "it's fine" and then do it.
You still seem to be missing the overall point here. No one is telling anyone not to use a ropeman, for any purpose. There are a few points that I'm making, and that I am making an assumption the others who disagree with you here are making:
- The ropeman limit of 4kn was listed by people who know way more than you or I. Taking the position that it wasn't tested properly or they don't know what they're doing is fine. You have every right to believe that. But if you think that, and your response to that rating is to assume it's low, is truly mind blowing. But for the rest of folks, especially people who have no concept of what goes into those ratings, the best bet is to assume it is correct, or too high.
- You are continuing to say that a person cannot generate that 4kn force with a short fall. Since you're eager to speak in precise language here, look at the graphic posted above. The equation used to calculate those numbers is very simple, and not really debatable. Your opinion on this is not based in fact, and is easily refuted. Again, see above graphic.
- The last point is most important. Regular people, doing regular things, regularly take a large risk with respect to the above information. What do I mean by that? People WELL over 200lbs (the weight of the person used in the above calculations), are regularly introducing enough slack in their tether, to generate the length of fall that exceeds the rating of the ropeman. Does this mean that it will fail? Does the actual answer to that matter? I don't think so. If they're ok taking that risk - cool. No one is going to judge them for it. However, it is incredibly irresponsible for you to tell people that they will be fine, that science/physics don't matter, because you can exercise at the gym. None of your experience is relevant to the actual risk being discussed.
It sounds like it's possible that you're taking this stance assuming that everyone is talking about using a ropeman on a lineman's belt. That is not the discussion at hand. If so, hopefully we can clear that up. I don't think you have bad intentions. I'm just not sure you understand fully what the ramifications of your words might be. You understand them from your perspective. The people on the internet breezing through it might interpret it very differently. Looking forward to getting on the same page here...
For the record I’m not trying to be argumentative with this post but I think it needs to be addressed so that no one misinterprets your logic and inadvertently makes a bad decision. Also for the record, I am a practicing Mechanical Engineer with 30 years of work experience so I’m not making these numbers up. The calculations are very straight forward given some basic assumptions which I will try to make clear as I go.
While it’s true that the speed you develop from a 3 foot fall off a platform is the same as the speed you would develop jumping off a 3 foot step ladder, the force generated from that speed is not equivalent in the two cited instances. The force experienced is the mass of the body multiplied by the rate of acceleration applied to it. In this instance that acceleration is the deceleration from that common speed to the point that you reach a complete stop.
For a 200lb man falling 1 meter from rest (approx. 3 feet) the speed at impact will be approximately 4.43 m/sec (13.9 ft/sec) for both cases.
The major difference in the two cases, jumping off a ladder or falling on a slack line is the distance over which the slowing process is applied. The longer the distance, the lower the rate of acceleration.
When you jump off a step ladder you naturally flex your knees to absorb the impact over some short time/distance. Assume that you flex your knees 6” (.152 meters) from the point you first touch the ground to the point where your motion stops. This relates to an average deceleration of approximately 64.4 m/s^2 and an average landing force of approx. 5.8kN (1300 lbs).
For the case of falling on a 3 foot slack rope assume a total length of rope of 6 ft (3 ft hanging off the girth hitch and 3 ft slack hanging from your bridge). At an elongation factor of 3% for static rope that equates to an expected rope stretch of approximately .18 ft (.055 meters) from the time the rope starts to come taut to when it finishes stretching. In that shorter distance the average deceleration is approx. 179m/s^2 resulting in an average landing force of approx. 16 kN (3650 lbs).
This shows that you will experience a significantly higher force from the sudden stop associated with hitting the end of a rope that you will from landing off of an equivalent height jump to the ground.
This is one reason sport climbers prefer to use dynamic lines with higher elongation factors. A rope with a 10% elongation factor, and the associated longer deceleration distance, reduces the fall force to something on the order of 4.8kN for the same fall.
Again, not trying to be argumentative, just trying to provide some clarification. Hope this helps.
Edit: For the record I really like my Ropeman 1's and still use them on my lineman's belts. I have however quit using them on my tether when I'm one sticking up the tree as I do get slack in my tether when climbing using that method. For me, it's just not worth the risk.
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@ThePreBanMan
Tethrd and saddlehunter.com share a love for saddle hunting. But tethrd doesn’t run this site and big Red doesn’t run theirs.
Tethrd and saddlehunter.com share a love for saddle hunting. But tethrd doesn’t run this site and big Red doesn’t run theirs.
For anyone not trusting their Ropeman 1, I will pay you $10 each to my door! Trying to help you out here.
John H.
John H.
ThePreBanMan
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I would agree - as a fall arrest device - bad idea. That's not what it's designed for. The manufacturer makes that quite clear. It's an emergency ascender for rock climbing applications. I never advocated nor would ever advocate it's use as such and I do not use it in that capacity myself.
But my take on this thread is that people are coming across as "use it and you're a fool with a death wish:, when in reality nothing could be further from the truth.
The testing results...
http://www.hse.gov.uk/research/crr_pdf/2001/crr01364.pdf
...were examining it for use in industrial applications, not hunting applications. Additionally, the testing also showed that the rope makes a BIG difference. Some ropes doubled the performance of others. The folks here are just selectively taking the results of the poorest performing rope when citing this study as reason to abandon the ropeman. They also say "the ropeman cuts the rope" while neglecting to mention that it took 3 consecutive fall factor 2 drop tests on the same dynamic rope before that happened. I think everyone would agree that once your equipment arrests a fall once - you replace it. Pretty much every manufacturer includes that in their instructions. Everyone I've seen anyway. So again - not applicable to hunting scenarios here. We use static line and it should be replaced after arresting a single fall. So I see people citing the worst-case scenario with a total absence of any context. That test is totally not applicable to our use case.
The testing methodology also included bearing that load for an extended period of time. That is not something that occurs in a hunting scenario. It only needs to bear it for a split second (the moment the fall is arrested)
The 4 tests they conducted included:
Minimum working strength: Device to hold a force of 4 kN for 3 minutes.
Minimum static strength: Hold a force of 12 kN for 3 minutes.
Dynamic performance: Peak impact force and slippage with a fall factor 2 drop with a 100 kg mass.
***but from what distance. The document doesn't say... That's an important piece of the puzzle! It says see appendix 14.4.5 for info and there is no such appendix in the document.
Ultimate static strength: Initially it was intended as a final test to load all the devices to destruction. However, the severity of the minimum static strength test meant that most devices had already reached their limits during this test.
But my take on this thread is that people are coming across as "use it and you're a fool with a death wish:, when in reality nothing could be further from the truth.
The testing results...
http://www.hse.gov.uk/research/crr_pdf/2001/crr01364.pdf
...were examining it for use in industrial applications, not hunting applications. Additionally, the testing also showed that the rope makes a BIG difference. Some ropes doubled the performance of others. The folks here are just selectively taking the results of the poorest performing rope when citing this study as reason to abandon the ropeman. They also say "the ropeman cuts the rope" while neglecting to mention that it took 3 consecutive fall factor 2 drop tests on the same dynamic rope before that happened. I think everyone would agree that once your equipment arrests a fall once - you replace it. Pretty much every manufacturer includes that in their instructions. Everyone I've seen anyway. So again - not applicable to hunting scenarios here. We use static line and it should be replaced after arresting a single fall. So I see people citing the worst-case scenario with a total absence of any context. That test is totally not applicable to our use case.
The testing methodology also included bearing that load for an extended period of time. That is not something that occurs in a hunting scenario. It only needs to bear it for a split second (the moment the fall is arrested)
The 4 tests they conducted included:
Minimum working strength: Device to hold a force of 4 kN for 3 minutes.
Minimum static strength: Hold a force of 12 kN for 3 minutes.
Dynamic performance: Peak impact force and slippage with a fall factor 2 drop with a 100 kg mass.
***but from what distance. The document doesn't say... That's an important piece of the puzzle! It says see appendix 14.4.5 for info and there is no such appendix in the document.
Ultimate static strength: Initially it was intended as a final test to load all the devices to destruction. However, the severity of the minimum static strength test meant that most devices had already reached their limits during this test.
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