Serius Rope Outer Sheath Failure

Do you think that maybe the portawrap was wrapped wrong? As in not wrapped but pinched in between the bent bar and the bollard? The Rig N wrench was not in use when it broke and it was in a different section of line that normally sees the wrench. I would agree that I don't think I would recommend huge loads going through the wrench. My idea for it is the smaller to medium sized things, I can see how it would induce wear, especially with very large loads, but I am thinking that it got knicked somehow by something or went across a very tight bend radius somewhere. That is possible to do on a porty if wrapped wrong.
 
That's what I was thinking too. Wrapped wrong, ground guy didn't know or didn't want to own up. Mass hysteria ensues.

But I have glazed ropes at the porty with too big of pieces. The other thing is that the piece was just too big for that rope, plain and simple.
 
Not picturing the possible pinch point you're thinking of. Can you explain more? Also I've watched him wrap it and it appears correct. That's not saying he didn't make a mistake that time.

Levi, given a reasonably worn rope of the same mbs do you think 1200 or 1500 pounds is a failure weight? I know some dynamic loading comes into play and some of it is absorbed by stretch in the rope and the loading of the system but that is such a small percentage of the mbs? Not arguing with you. Trying to pick your brain. If you had someone load this rope with that weight and no damage was done would you immediately retire this rope from rigging? This is difficult to type my thoughts into words so bear with me as I try to explain. So at what point for you does it go from a hey never do that again to the rope is spent and toss it. For instance. 1000lb mbs. We should load about 100 lbs per the guideline although different ropes have different safety factors. So the climber not thinking about with puts 500 on it. It will certainly reduce the life span and if it's done repeatedly it's gonna kill the rope. However since it was only half of what it should break at can we go back to rigging 100lbs or do you think the fibers are damaged enough to cause a failure at this point. Now keep in mind this is hypothetical. I'm not saying this is what I did. I know the rope was in worse condition than most would find acceptable. I'm just trying to wrap my head around the 10% safety factor as it relates to the total Mbs. In my mind safety factor is a safe place for use but not the failure point. I hope I'm explaining this well and not sounding like an ignoramus. I think I could articulate it better spoken and not typed. I grasp the whole cycles to failure. For instance, hypothetically at 10% we could load the rope 1000 times. So does his mean at 50% we could load it 500 times? I know there's a lot of other factors that go into it and it's not an answerable question but maybe that explains what I'm trying to get at. Not saying I'd do that either. I would try my very best to stay in that ballpark of 10% as best as I could. Thoughts?
 
Hmm. Good questions. My statement that the piece was too big was based on several things. 1) as you and others had pointed out, the rope was very worn. 2) I would never personally put a #1300 piece on that line un-less maybe if it were entirely controlled with a GRCS or the like.

Honestly I don't think I've rigged very many pieces that heavy, if ever, so what do I know!
 
As far as using a rope after "over-loading" I really don't know. I have this old piece of velocity that I abused for years. Huge pieces on a vertical speedline, tons of NC rigging, pull rope, tagline, dirty, dirty, dirty. I finally broke it the other week using it to pull brush out of my trailer, which had been it's final use for awhile. I actually broke it bout half a dozen times. It broke in every way imaginable, complete failure at knots, midline failure several times (which I thought was odd) and finally a sheath failure like your rope.
 
I'm serious man, I highly doubt I've ever put a piece that big on a rope.

I usually start with a 5/8ths rope from the get go for what it's worth. But that's more because I'm too broke to have a wide range:cry:
 
Steve Connally said:
Not picturing the possible pinch point you're thinking of. Can you explain more? Also I've watched him wrap it and it appears correct. That's not saying he didn't make a mistake that time.
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I train my guys to alternate the CW/ CCW wrap on the POW to lessen hockles. I also specifically train that "the rope always gets wrapped in the same CW OR CCW direction during each rigging operation. People will want to put the initial bight on the barrel CW, then add wraps CCW, changing wrap direction 180 degrees.

Some will also NOT use the fairlead posts to keep it from bending backward when it has the very minimum wrap.



Was the piece strongly pretensioned preventing a floppy POW? Could 'flop' have had a turn of rope pin another turn to the barrel, locking it up?
 
Hell, I've never loaded a 1/2" rope with a piece over 200 lbs. before, that I can recall. That 10:1 should include any shock forces, so on a 6,000 lb. rope it's 600 lbs. including the shock forces if you want the rope to last awhile. With a 200 lb. log you don't have to drop it... just swinging it around on the rope will hit that 600 lbs. so I usually go with 15:1 just to give me a realistic weight for the pieces that I cut, that will not force me to retire a rope after a few months.

I understand that production work on a tight schedule makes people push the envelope... hopefully they can afford to replace ropes often. I can't, but I'm never on a tight schedule, so I choose to make a lot more cuts and spend more time getting the tree down if I want the convenience of the 1/2" rigging setups. Otherwise, I just grab the biggest damn ropes I own and try to git 'er done. On the right job, with the right help it's faster... but most of the time for me, it really isn't. In fact, it's usually slower, because the 1/2" setup is so much easier to move around in the tree when necessary.

I'm sure that rope, when new, probably would handle dropping a piece that big a few times. Then, break at the bollard on a 300 lb. piece that gets bounced a little. I just don't see using a 1/2" rope for those kinds of loads... but that's just me.
 
Just some thoughts...

I think it's important to remember that there is a reason they deem it a "safe" working load. I have confidence that it has been determined so through empirical data. If regularly using 50% of MBS was safe, they (manufacturers) would deem it so.

However you mention one time use of say... 50% of MBS and does that mean you can us it at such a weight for less cycles. I am confident in my instincts when I guess that when using heavier loads on a rope the cycles to failure is decreased exponentially. I welcome any data that proves or disproves this but I would caution against believing that a doubling of weight will reduce cycles to failure in a direct correlation.
 
Was the piece strongly pretensioned preventing a floppy POW? Could 'flop' have had a turn of rope pin another turn to the barrel, locking it up?[/QUOTE]

I believe it was adequately pretensioned. He does a pretty good job at that even when I don't want him to. I also use the strap above the device so there is no flop of the device.

Jeff,

I appreciate your insight. I do hear you. I have learned quite a bit from this thread. I have never had this happen in 15 years. I have also only ever had one rope snap from weight, but that rope was spent and was the companies rope that should have been taken out of service. It was some years ago when I first learned the gear was crap and then started providing my own rope. I feel like I've been pushing the envelope to make the rig n wrench work for more situations than maybe it was intended for. I have always rigged with at least 5/8 rope until the rnw came out. So basically I have tried to adjust my tried and true methods to incorporate a cool piece of gear. I can see how all the elements came into play, although I will still be interested in what the break testing results are and what NE rope says.
 
It'll be interesting to see what the manufacturer and treestuff come back with.

Duty cycles, bending radius, knots, rope geometry, loads, static and dynamic, all these things come into play.

Yes, if you load a rope at a higher percentage of its MBS you'll reduce the duty cycles. It's likely to do so in an exponential manner. It's like you are reducing the MBS each time, i.e., that 500 lb load now represents a higher % of the MBS than it did the first time around. When the rope is bent the outer portion of the sheath takes on the full load while the inner portion remains unloaded. Basically, the outer sheath portion has mechanically a lower MBS, fewer fibers carry the load as it were. Now those previous loads were acting on only those few fibers thus weakening them AND the overall capacity of the rope.

Let's say hypothetically, that those fibers strength is reduced 50% but the rope itself is reduced let say 25% or even less. Those stressed fibers are localized to the point that was running through the bend on the outside at the point when the load was highest. What's the likelihood that will occur every time the rope is put into service? Pretty remote but still a chance. When the rope is loaded it is stretched and deformed specially at a bend. The higher the load, the greater the flattening out, the more loading on the outer portion of the rope in the bend.

You've got a convergence point happening where load size, bend ratio, MBS degradation will meet to create the perfect conditions for failure. Add to that the human element whereby a moment's hesitation at a given point, maybe stopping the rope slightly faster and you've got a spike in the load that exceeds the out sheath's MBS.

Once you've put that rope into service it is degrading and losing its MBS. It's possible to look at it as savings in the bank that you can't add to, maybe more an inheritance with no interest; each withdrawal reducing the amount available for the future.
 
Do you think the 16 strands handle the bend better due to the construction? Maybe a old braided rope is a better example as it has no outer sheath. Just curious. So for example the construction of the Hawkeye as opposed to the construction of the Sirius. I'm assuming the 16 strand has more strength carrying capacity in the core strands than the Sirius which may have a higher strength percentage on the sheath. My only assumption of this is the Sirius flattens through the wrench more than the Hawkeye. Kinda like how some ropes flatten in the rope runner more than others. I realize the key in all this is working within the safety factor but could it be possible that the ropes that flatten more, rely more on the sheath than core on the bend would experience more wear from the hard bend of the wrench? So why I'm suggesting is a softer handed rope, one with more pliability may in general be a less than optimal choice for rigging through the rnw. Perhaps the stiffer, more firmly constructed ropes will experience less wear from being used with the rnw.
 
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JeffGu said:
Hell, I've never loaded a 1/2" rope with a piece over 200 lbs. before, that I can recall. That 10:1 should include any shock forces, so on a 6,000 lb. rope it's 600 lbs. including the shock forces if you want the rope to last awhile...I usually go with 15:1 just to give me a realistic weight for the pieces that I cut, that will not force me to retire a rope after a few months...I just don't see using a 1/2" rope for those kinds of loads... but that's just me.
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Somehow or other our arb. forefathers managed to do this stuff using Manila rope....they musta cut lots of very small pieces. but I doubt that.
1/2" rope is my trusted weapon in this war, and is usually retired to lesser tasks after several months of active front line duty. It has earned it's keep many times before then anyway.
a proficient groundman + climber can accomplish a lot with a little. OTOH, inexperienced help mismanaging pieces less than even 200 lb can result in sadness.
 
It's not wear its tension. as a rope wraps around a device and is loaded the fibers against the device are not under tension to the same degree as the fibers that are on the side of the rope away from the device.
 
TS site says there are transverse fibers to indicate overloading and looking at the pictures there seems to be a "spiral" of wear on Steve's rope could this have been an indicator or have I just never looked at worn rope that close?
 
Pelorus said:
Somehow or other our arb. forefathers managed to do this stuff using Manila rope..
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Our forefathers? Hell, I started out in Junior High School working summers for a landscape/tree guy... all he had was manila ropes except for some pieces of 3/8" and 1/2" hardware store 3-strand nylon, which I used to make a lanyard. No adjuster. I'd either wrap it around the trunk when it was too long, or tie knots in it to shorten it up. We rigged with 5/8" and 1" manila ropes that smelled like a rat's nest and usually looked like one, too. The old guy kept them in Army Surplus Store duffel bags that didn't smell much better than the ropes. We quite often broke 1" ropes with loads that a modern 1/2" rigging rope would scoff at. My point was that cycles at 200 lbs. can go on for a very long time, at 500 lbs. that time is ridiculously shortened. At over 1000 lbs. load it's going to last about as long as a new Ferrari would last in the Baja 1000.
 
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