Serius Rope Outer Sheath Failure

Pelorus said:
No offence intended...
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None taken. But 750 cycles lifting at 5:1 is a far cry from dropping the load. I do a hell of a lot more of the latter than I do the former. If we assume a limb that is either butt tied or tip tied, since that probably accounts for the vast majority of rigging operations, one end of the limb is dropping at least a few inches and the other end is dropping much further so the shock load is significant. Add in the friction and bad rope radius issues, working rope angles, etc. and that 5:1 ratio you started with isn't 5:1 anymore. Blocking down spar wood drops the entire load onto the rope from whatever the distance is between the block and the attachment point of the rope, plus much of the weight falling the distance that the upper end of the chunk falls. In other words, once the chunk starts in motion it is accelerating and shock forces are generated, so it is falling as soon as it starts to tip. How far does that chunk of wood need to fall before the shock load doubles the forces?
 
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I just reread the thread and took a close look at your failure point. Here are the facts I see in the pictures.

Your red threads leading up to the failure are increasingly torn.
As we get closer to the failure the torn threads get longer.

Longer torn threads means more of the tread was cut most likely due to increased friction on the rope as we move closer to the failure.

Your rope shows a significant amount of torn threads along with heavy glazing in other areas as well.

The limb was a relatively large limb.

The has been in use for several months.

You wrapped the rope around the port a wrap the same way every time.

You have glazed the rope previously.

The working ends of the rope are always in the same two areas which expose these area to the same abuse every time you rope and use the portawrap.

What would we deduce from those facts??
 
Thanks for the great thread Steve. And thanks for all the great responses. You guys are really tearing this thread up.!! I just want to say that if I glaze a rope I feel I have done something wrong. It has happened often at the rope brake. A bad glaze for me will cause me to retire the rope to lighter duty.

Are you using x rings to distribute the friction. I have and it is nice because each x ring we consider to be 1/3 to 1/2 a wrap so we need less wraps on the brake and hence also less wear on the rope.

I retired my Sirius rope last week. It was used for some 500 pound pieces for sure with drop. I also put bollards on the tree when I do big stuff to reduce the chance of glazing. I know it's laborious and frankly sometimes you wonder if just buying ropes a bit more often isn't easier. My ropes usually last one or two years.

I retired the serious because it was acting wierd. Had a bit of a twist to it almost like one strand was tighter than all the others. It wasn't obvious, but since it was a year old and my big rope, I didn't trust it any more.
 
Jeff, a cycle is a cycle is a cycle. Negative blocking a largish spar might take me (let's be generous).....say 12 cycles. Usually less. Your Nebraska trees are mightier, so how 'bout 20, till you get that sucker down low enough to flop it or pull it over. How many of them big trees you dismantling every day?
Removals is basically all that I do. And I don't find myself replacing ropes very often.

edit - I wish Mr. Murphy would add to this discussion, as he has been doing some soul searching along the lines of snubbing stuff off, not letting it run, and measuring forces. (as posted on TH).
 
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I don't replace them very often, either, which was my point.

I wish I could find that damn video of the nutty Aussies trying to rig down a 5 ton dead euc spar chunk with a 1-1/4" bull rope. That was a 5:1 ratio for that rope. Cycles to failure was exactly ONE.

Some rope manufacturers (Yale, for one) have small print telling you that any instantaneous vertical load change, up or down, that exceeds 10% of the recommended (5:1) WLL will void the warranty. This is even true for Polydyne, which has amazing energy absorption properties.

Steve had said that he has dropped bigger pieces than the one that broke the rope, and from looking at the picture of the rope, that's certainly believable. That kind of cover fraying and glazing would indicate the loads weren't gently eased down with no shock loading.

So... the 5:1 WLL of the rope is 1580 lbs. and the allegedly 1300 lb. piece of pine was within that rating. Except, if he added only 158 additional pounds of load by dropping the piece about an inch or so... well, it rather makes the 5:1 WLL thing seem a bit silly. Perhaps that's why 10:1 or even 15:1 is more commonly used in arboriculture. Also, the rope was certainly not new, and we can assume that it's real MBS was seriously compromised due to previous heavy loading, can we not? Additionally, the Stein lowering device he was using doesn't have a 4" bollard, so the bend radius there is certainly less than the 8:1 ratio recommended by the rope OEMs. The RnW in line is another point of friction that isn't exactly conducive to those kinds of loads.

I try to use the 15:1 ratio because without a load cell in line all the time, there's no good way to know what kind of shock forces are being applied. The videos I've seen showing drop tests usually show extremely low cycles to failure using loads that are nowhere near the 5:1 ratio. If the weight of the pieces are at or near that ratio, and it drops more than a foot, I can easily see the rope failing in your 12-cycle example. My entire point was that using the 5:1 WLL ratio (to decide if a piece is too big, or not) is probably a bad idea if you want the rope to last more than one season. The 10:1 ratio for his rope is 790 lbs. The 15:1 ratio is about 525 lbs. All shock loading forces included. Reduced for anything that might reduce rope strength, such as less than ideal bend radius or high friction points. Hence, my belief that 200 ~ 250 lbs. wood weight is a more realistic size to shoot for with a 1/2" rope, if your goal is to get as much life out of the rope as you can while still getting the job done.
 
Additionally, the Stein lowering device he was using doesn't have a 4" bollard, so the bend radius there is certainly less than the 8:1 ratio recommended by the rope OEMs.

For clarification. Stein states the RC 1000 is good for rope diameters up to 14mm. Per Stein.
 
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baumeister said:
I just reread the thread and took a close look at your failure point. Here are the facts I see in the pictures.

Your red threads leading up to the failure are increasingly torn.
As we get closer to the failure the torn threads get longer.

Longer torn threads means more of the tread was cut most likely due to increased friction on the rope as we move closer to the failure.

Your rope shows a significant amount of torn threads along with heavy glazing in other areas as well.

I guess I have been doing it wrong all these years. I thought the wear was noticible but I don't see the "heavy glazing" as compared to many other ropes I've seen. My rope guys are less experienced than they think they are so I get lite glazing often. Much of the time its the fuzz on the rope and not actual glazing of the fibres.

The limb was a relatively large limb.

The has been in use for several months.

You wrapped the rope around the port a wrap the same way every time.

I suppose he does. We'll discuss that. I also try to switch ends fairly often so the wear is distributed.

You have glazed the rope previously.

Yes, IMHO it wasn't that bad

The working ends of the rope are always in the same two areas which expose these area to the same abuse every time you rope and use the portawrap.

What would we deduce from those facts??
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I deduce that I've got it wrong. My rope man is inexperienced, I'm not providing the proper guidance, Wrong rope size for the job. It's clearly multiple mistakes I've made that added up to this incident. However, not that it makes it rite, I've done it the way I do it for a long time. Again, not that it's rite but...... there are only three factors that changed in the entire scenario from my methods in the past. 1. different rope than I've used over the years, 2. Stein Porty and not a port-a-wrap. 3. Rig-n-wrench. I'm thinking addition one of the 3 factors contributed. Now you can argue that it was bound to happen sooner or later and you are probably rite. What are the odds of getting lucky for 15 years and then one day, pop? There has to be an X factor in all of this.

I'm not being defensive, or maybe I am. Maybe I'm embarrassed that after years of tree work, I've got 5 pages of posts showing my ignorance out there for everybody to see, and some folks I respect a lot looking at it. I've gotta say I have not ever had this happen like this before. I don't think I can say why it didn't happen any more than why it specifically happened. The break testing and the lab results will surely add some facts to the mix.

I do have to say, again, I appreciate the feedback. It has made me question many of my methods.
 
Steve Connally said:
I deduce that I've got it wrong. My rope man is inexperienced, I'm not providing the proper guidance, Wrong rope size for the job. It's clearly multiple mistakes I've made that added up to this incident. However, not that it makes it rite, I've done it the way I do it for a long time. Again, not that it's rite but...... there are only three factors that changed in the entire scenario from my methods in the past. 1. different rope than I've used over the years, 2. Stein Porty and not a port-a-wrap. 3. Rig-n-wrench. I'm thinking addition one of the 3 factors contributed. Now you can argue that it was bound to happen sooner or later and you are probably rite. What are the odds of getting lucky for 15 years and then one day, pop? There has to be an X factor in all of this.

I'm not being defensive, or maybe I am. Maybe I'm embarrassed that after years of tree work, I've got 5 pages of posts showing my ignorance out there for everybody to see, and some folks I respect a lot looking at it. I've gotta say I have not ever had this happen like this before. I don't think I can say why it didn't happen any more than why it specifically happened. The break testing and the lab results will surely add some facts to the mix.

I do have to say, again, I appreciate the feedback. It has made me question many of my methods.
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Take it easy on yourself Steve it happened life goes on. I am sitting here learning a huge amount of information that otherwise I would have never learned that in and of itself is priceless. Just look at every failure as a learning experience if one does that it makes for better guy. These guys are nit picking everything they can to try to help you and me become educated or to look at all the facts we possibly can so we don't make the same mistakes.

As to the comment of stein RC1000 the point I believe was being made there was the drum is not as large as a 4" used in the days of past. Personally my fav is the stein RC3000 as I like how it straps to the tree and the radius.
 
I just didn't have the room for the big stein since I'm basically a full service tree company out of a pick up bed box and I refuse to clutter the mega can with tree stuff. Ian not taking anything as a cut to me personally. Just a wake up call I wasn't mentally prepared for.
 
Steve Connally said:
I'm not being defensive, or maybe I am. Maybe I'm embarrassed that after years of tree work, I've got 5 pages of posts showing my ignorance out there for everybody to see, and some folks I respect a lot looking at it. I've gotta say I have not ever had this happen like this before. I don't think I can say why it didn't happen any more than why it specifically happened. The break testing and the lab results will surely add some facts to the mi
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FIRST: yes, very educational thread on one of my favorite things to dissect on a routine basis. Well said magnum.


Yes, with new equipment it does make it very frustrating to try and figure out. I just wanted to add what I saw in the rope. My ropes used to look like yours too. It is only out of curiosity that I try not to glaze them anymore. Can you post pictures of the Hardware that was used along with the way the rope was installed in said hardware. Maybe just take pics on your next removal if you still use the same system :).

If too much trouble I get it. I have a large dead ash to remove with lots of room. Think I'm gonna do some testing and will post pics when I do. I will try to glaze some old ropes. Wish I could afford a dynometer.
 
baumeister said:
FIRST: yes, very educational thread on one of my favorite things to dissect on a routine basis. Well said magnum.


Yes, with new equipment it does make it very frustrating to try and figure out. I just wanted to add what I saw in the rope. My ropes used to look like yours too. It is only out of curiosity that I try not to glaze them anymore. Can you post pictures of the Hardware that was used along with the way the rope was installed in said hardware. Maybe just take pics on your next removal if you still use the same system :).

If too much trouble I get it. I have a large dead ash to remove with lots of room. Think I'm gonna do some testing and will post pics when I do. I will try to glaze some old ropes. Wish I could afford a dynometer.
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Will try my best to make the pictures happen. Production production production you know.
 
The lowering device companies usually use 4.5:1 as a minimum diameter for the portable devices. It's a compromise, because the 8:1 recommended by the rope OEMs would make for some rather big, heavy devices. The smaller diameters just mean you have to accept that it's not ideal and adjust loads accordingly, or accept shorter rope lifespans. It would be nice if they were more forthcoming with this information, but the advertising folks are well aware that it doesn't help sell the product if there's a lot of caveats and fine print in the ads.

Steve, I'm not questioning your judgement or anything... I am trying to point out that we tend to look for this simplistic formula for what is the right size piece to drop onto a given size rope, and there really isn't a simple one. Everything we do to the rope is bad for it! With climbing lines, the OEMs are a little more forthcoming about what is happening to the rope. They tell you to immediately retire one if you fall more than about a foot or so on it. That's because the physics of what happens to the polymer molecules when you stretch them isn't a happy picture. Have you ever wrapped up a sling or extension cord with a rubber band, only to discover when you took it off that it had stretched to twice its original size and broke as soon as you tried to stretch it, again? A rope is lots tougher and more resilient than a latex rubber band, but the same thing is still happening to a rope that is shock loaded. Weaker and weaker it gets. I think we tend to think that rigging ropes are magical, or maybe we just expect too much from them. That's my only point, really. If we use it over and over we are destroying it, slowly but surely, no matter what the load. Smaller loads just take longer to do it.

I love the Stein devices, but I have noticed that the welding is pretty rough. I've thought about grinding and sanding the welds smooth where the rope contacts them... but that means the zinc plating will be gone. Not sure if that's such a big deal, though, since the rope wears it off fairly quickly, anyway?

I've often wondered if those crude welds aren't going to wear the rope faster.
 
I also wonder that if friction in the canopy as opposed to the trunk will cause us to rethink our rope wear and size of the load. My thoughts on this come from the simple reasoning that the rope under load at impact is shorter. Shorter means less mass to absorb the shock load is what I'm thinking. Anyone care to agree or disagree?
 
Steve Connally said:
I deduce that I've got it wrong. My rope man is inexperienced, I'm not providing the proper guidance, Wrong rope size for the job. It's clearly multiple mistakes I've made that added up to this incident. However, not that it makes it rite, I've done it the way I do it for a long time. Again, not that it's rite but...... there are only three factors that changed in the entire scenario from my methods in the past. 1. different rope than I've used over the years, 2. Stein Porty and not a port-a-wrap. 3. Rig-n-wrench. I'm thinking addition one of the 3 factors contributed. Now you can argue that it was bound to happen sooner or later and you are probably rite. What are the odds of getting lucky for 15 years and then one day, pop? There has to be an X factor in all of this.

I'm not being defensive, or maybe I am. Maybe I'm embarrassed that after years of tree work, I've got 5 pages of posts showing my ignorance out there for everybody to see, and some folks I respect a lot looking at it. I've gotta say I have not ever had this happen like this before. I don't think I can say why it didn't happen any more than why it specifically happened. The break testing and the lab results will surely add some facts to the mix.

I do have to say, again, I appreciate the feedback. It has made me question many of my methods.
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You are all good man. No reason to doubt all ur skills. Just keep the wrench off the big shit and watch for the glazed lines. If you aren't confident in ur ground guys just adjust ur rigging. I rig one way with guys I trust and another with guys I don't. Each can be done safely. Just set ur mind to a larger safety margin and keep ripping. Everybody has there own style, maybe after this u might not "trust" certain pieces of gear. Back off a little and go with what u are confident in, and keep cutting. great thread!
 
monkeylove said:
Anyone care to agree or disagree?
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I agree, as well. I thought about that a lot when I was going through the advantages and disadvantages of rings vs. pulleys, the RnW, etc. because there are certainly some differences that affect the rope significantly. In the end, I decided that there was something that would negate all my postulating on it. If my rigging rope isn't new, and has been shock loaded excessively, somewhere along its length is the weakest of all weakest links... a damaged core section that I can't necessarily know the location of. So, I'm about to drop a chunk of wood, and if that section of rope is closer to the block or ring the rope will break there... if it is closer to the lowering device, it will break there... and I'm going to be stuck thinking there must be a reason it broke where it did. And I'm going to be thinking it has something to do with where my friction is, or where a bad bend radius or a bad rope angle is. And it might have nothing at all to do with any of that! It might be that the weakest link was that invisible section of damaged core in the rope, and it was all about where that section ended up being located, by pure chance or by some rigging scenario from last month when I had too many wraps here, too small of a pulley there, or whatever caused the rope to be stressed excessively at that spot on that day.

It's frustrating, and is one of the reasons I go so conservative on load size. If I can keep these rope stresses and sheath/core damage consistent enough, maybe the other factors will be more relevant to what needs rethinking. Maybe. With a new rope, when it breaks, it seems that you can quickly sort out what went wrong. With a well used rope, not so much. Unless of course you can see where the chainsaw cut halfway through the rope.
 
Break testing results came in today


Hi Steve,

I've attached the testing data we got from your rope. We broke them in 6 foot sections with girth eye stitches on both ends. All 6 pieces broke at the stitch.

What this data means is that in a perfect statistical distribution, 99+% of the tests would break over the 3 sigma number of 5200 lbs.

Keep in mind the loss of strength compared to the manufacturer's MBS rating of 7900lbs.


So what's the rope overloaded at that specific time it broke at 1200lbs? What do you all Make of the numbers?
 

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