Rope Break!

Great discussion folks, though I just came in on the tail end of it. Two points come up about the break coming at 8' from the point of attachment:

First, was the fall arrested completely, or was the piece allowed to run? Lots of energy can be absorbed over a longer time period if the piece is slowed down, but not stopped during it's descent.

Second, was the rope clipped while under tension by the piece slamming into the trunk ? Having the block slightly off to the side can take the running line out of the trajectory of the falling work.

Video is a great tool for catching mistakes in the making. Too bad it's an after the fact anylysis. I have a video clip of a buttcatch lowering operation to post, if this board allows it.
 
Be my guest, Oxman. The more the better!

"First, was the fall arrested completely, or was the piece allowed to run? Lots of energy can be absorbed over a longer time period if the piece is slowed down, but not stopped during it's descent"
The rope was allowed to run, but I feel that it could have been allowed to slow more gradually and probably was held a bit too tight.

"Second, was the rope clipped while under tension by the piece slamming into the trunk ? Having the block slightly off to the side can take the running line out of the trajectory of the falling work"

The rope never clipped the trunk (as far as I could see). I also try to keep the block slightly offset and this was the case here.

I still feel that this rope was beyond its' lifespan for the given circumstance. Too many cycles to failure to still treat it in this way.
rolleyes.gif
 
good points
I was on the other end of the rope that day and have been on the end of many rigging lines for Mark. Sometimes your heart starts to race, and you just don't do the right thing. I feel that after talking to many people about what happened, I didn't let the rope run long enough. I hope this topic will help climbers teach groundmen the proper way to do things. I think this site will be a good teaching tool for everyone.
 
hey Ropegod Nobodys perfect and from what Mark is saying the rope was close to its end.A great ground person is the best asset to any climber but we could start a whole new topic on that.The thing is is trying to identify when a rope has had to many cycles on it .
 
Just to be clear on something, running the ropes is as difficult of a task mentally as any aspect of tree care! Ropegod is a fantastic groundman and is not to blame for this mishap. The only way I think to have avoided this rope break was to have let the piece run almost to the ground or to have cut a smaller piece, not just this time but every time for the rest of this ropes' existence. There is a
"right" time to retire a rope- just before it breaks!
grin.gif
 
Hello Mark,

Another question for you(not about the actual line failure):

You responded to someone that the piece you were lowering when the line failed was 15 feet long. Is this correct? Wow, that is long! Diameter and weight was ?
Yet you also say the tree had major structural damage from the lightning. Well, I wasn't there, so I can't judge. But, in light of Peter D's tragedy, don't you think taking smaller pieces to lessen stresses on the tree would be a good thing? Or finding a way to free drop them?

I've been doing tree work for 28 years, and think I can rig pretty darn well. Still learning of course. And I'm sure a gear head. (Ask Dan K or Oxman.)However, in all those years, I can count on my fingers and toes the times I have lowered trunk wood. I have always found a way, often innovative, probably not unique, to free drop small pieces in a safe fashion. Or log lengths for that matter. Brush, tires (layered), mattresses, etc, etc. I once did a 36" dbh doug fir that ws surrounded by a cement patio, already cracked. I dropped everything right onto the patio, but had a lz of 2-3 layers each of brush and tires. When brush is not needed, we will lash 15-25 tires to- gether to keep them nice and compact. Brush does help to keep the bounce down. Of course conifer brush is best. Plenty of those out here in Seattle!!! (Wait til you see the ~11' dbh giant sequoia in Volunteer park, ISA 2002. Pretty amazingly big for only 100-120 years old!!!

Once I dropped (from ground level)two ~30 foot, 500 board foot doug fir logs directly down a sidewalk, with plants immediately on either side. We had built stacks of wood on either side of the cement, then bridged them with 6 foot logs, with tires underneath. Perfect! Did second one after self loader had cleared the first.

Looking forward to meeting you in July.

[ February 06, 2002: Message edited by: Roger Barnett ]
 
Hey Roger.
smile.gif
The section I cut was just over 14' long and stood about 55' off the ground. It was the first piece of wood I cut. The average diameter was 14". If you trust the chart, it weighed 560#. It also had a crotch in it near the cut that increased the dia, so I beefed up my estimates a bit. I also allow for some error on my part. We had about 40' of running room before it would've been completly stopped.

I agree with you about taking small pieces when the tree appears to be unsuitable for rigging impacts. However, this cut was made just below the worst of it, and I was in a bucket at that point. The remaining trunk was pretty thick and sturdy below. I probably could have cut small (firewood size) sections and chucked 'em. I didn't feel that it was the fastest way for this case. I still feel that the rope was just kept in the mix too long.

I too agree that free falling the wood is the safest way for many jobs, but given the site obstacles, integrity of the tree and the time involved, I belive that my choice was appropriate. I just should have switched to my heavy rigging rope one cut sooner! We then did just that and roped off two more logs. Once it was beneath the wires, we felled the trunk and brought the loader over.

I think that you make another great point when saying that you weren't there to judge. It is very hard to make my point without some visuals. Thanks for seeing that
.
grin.gif

I too look forward to meeting you in Seatle. Thanks for your posts.
 
Hey Mark,


Thanks for the extra info. Figured you knew exactly what to do! Helps to have a bucket, too. Being a one crew small outfit, I don't have that luxury. Not much use for 'em out here anyhow- small or hilly yards, too tall trees, etc.

Seattle Tree Pres.(DK's employer) and just a few other co's have 'em. STP owner used to say he'd never bother getting one. Nor do I have a loader, but do sometimes use a guy with a flatbed, dump 8 ton boom truck, a very versatile unit, except for the too short 40 foot boom. So, if not saleable as logs, we have to cut our wood anyhow. Paul Sisson, our resident gear freak, says he rarely free drops anything. No wonder the UW campus is in such good shape!!

Having a Madsen's power tuned 372 kinda helps too!! Just put a 24 bar on it, (32 normally), switched to an 8 tooth sprocket. Boy is she hungry! Next, the muffler is getting tricked out for 20% more hp.
Rip used it for a couple cuts at last summer's Arbormaster cause all he brought was a weeny 24" bar for his, kinda small for easy felling of big butts. I put his tach on it, cause I thought it was tuned too high by Madsen's. True, 15500 was rather hot!! Next, the muffler is getting tricked out for 20% more hp.
I'm sending my new 335 to Walker's in Canada to get a nice boost, on Duane Neustater's tip. Oh, sorry, heard u were a Stihl "slut"!
Congrats................ I guesssss.......

Have either the LD 2000 or GCRS? Opinions? DK wants to sell his Hobbs, but I don't like the action on it. Price is right tho!!
grin.gif
 
Yes it's true, I do favor Stihl (and have for a long time). I'm sure that we all have our favorite saws. I have used at least 7 different brands and just prefer Stihl. Sounds like your saws are running a bit better than the average guys, though. Not a bad idea!

I do have a GRCS. I've only used a Hobbs at the TCI Expo in the demo tree (so I really can't compare). I love the device and would replace it within 24 hours should it ever break!
 
Only ??? LOL

Let's see: Homelite, Echo, Sachs Dolmar, POOlan, Jonsered, Stihl, Husky. If I ran any mac's, it wasn't enough to count. So I guess we're about even, but I've been at at way longer. Love my 066 Mag's, 044's, 036's. Used to be, Stihl was a little more powerful and lighter for each saw class. Not any more, Husky has definitely caught up. I do like the torque and feel of Stihl's still.

Compared my stock 066/36" bar to the tuned 372. The 066 beat it by 12.2 sec to 12.7. not bad for an extra 12" of bar. Of course, stock hp is 7.7 (on these older Magnum's) to 5.4. I hear the new 385 is a better saw and maybe faster than the 395. And that new 357 is so smooth, plus a little lighter and maybe faster than a 036. And the 346 is way superior to a 026.The 3120 has always outperformed the 084/088.

I hear the Solo 651 beats ALL saws in its range, tho! Pi** poor dealer network.

Gee, how I digress, this thread was about ropes.

well, shut me up.....or...
...Saw me off...to quote a best tree bud..
 
Back to the ropes:

Different lines' ability to absorb energy vary dramatically.

Full static: some caving rope,
kevlar/ polyaramid fibre (Samson's AmSteel, Puget Sound Rope's Plasma line)Stretch is some 0.5% at 30% of tensile strength.

Semi static: some caving line, top rope rock climb line, double braided bull rope. stretch about 2% at 30%.

Semi dynamic: Arborist climb line: Stretch 1.5-2.5% at 200- 400 lb body weight. I dont know how much at 30% of tensile. I think it is around 6-8%, and maybe 20-30% at break, but just guessing. Don't take a long fall on it!

Full dynamic mt climb line: Stretch 4-6% at body weight, and up to 70% at break point.

These figures are just guesses from memory, I didnt look anything up.

These figures tell you the importance of not slam dunking wood onto a low stretch line. Or, for times when the run distance is limited, to stay way below the SWL.

As well, the multiple shocks on a line are a good reason to retire it after a reasonable period. When I started high angle rock climbing in 1973, my first rope was rated for one fall. Now they are rated for 6-15. Technology has certainly advanced. ( A fall factor of two would be a fall of some 16 feet on eight feet of rope. I forget the exact UIAA test distance.)After that a rope is supposed to be retired or downgraded to top roping.

Also keep in mind UV degradation. I just heard a story about a fellow I know. He left a fairly new 0.5 dbl braid line hanging in a tree for several months (which sure showed a lack of horse sense) Later, they caught a fair sized piece with it, and what do you know, it failed.

By the way that Plasma line is rated at 31000 lb tensile at 0.5". Stronger than steel. (The four inch line is something like 1.4 million pounds!!)It is the ultimate speed line when no rope sag is wanted. Just watch your anchors or guy them back!!!

to quote TD;

Strong limbs and snug rope!
 
Great stuff, Roger. All good info to know. I love the high strength of exotic fiber, just wish that it would absorb some shock.

Does anyone else out there use exotic fiber for a rigging sling? I use a 3/4" polyester sheath with a spectra core. It is rated for over 39,000#. I feel very confident when rigging big wood with this anchor. I've just come to realize that the tree may now be the weak link.
rolleyes.gif
 
Great info at Puget Sound Ropes website:
http://www.psrope.com/psrope/default.asp

Check out the 14800 lb 5/8th nylon double braid. It has about double the stretch of polyester, so it might be great for lowering when you have plenty of room below. It stretches 7.5% at 10% tensile and 12% at 20%. Due to the better energy absorption, the SWL should be higher than a more static line. So, a 1480 lb piece would stretch about 4.5 feet with 60 feet of line out, assuming the belayer didnt let it run at all.
Not bad, but I'm not sure I'd want that much stretch for an all purpose line! Then again, that's a bit heavier than most of you gurus take on a regular basis, I'd reckon.

Four feet of fresh powder in the hills the last few days, I'm outa here!!

For any skiers: "To turn is to admit defeat"
tongue.gif
cool.gif
 
Mark, do you think the rope would have broken if you were using a three quarter inch bull line instead? sometimes we have mixed ropes, meaning manufactures,and a 3/4 may have the same weight load as a 5/8.however, the 3/4 will absorb more inpact. I dont know if this was your case, but do you think it would have held on /
 
Yeah, I think more fiber would have helped. A newer line would have been better as well. You make another good point, some manufacturers produce better quality products than others. Maybe a different make would have resulted in a successful lowering operation (rather than a free fall).

[ February 10, 2002: Message edited by: MARK CHISHOLM ]
 
Hi Mark, my name is Greg Liu a friend of Gary Abrogina. I'm from Norhtern Cali.
The qustion is this: Do you think if you were using a 3/4 in bull line rated the same tinsil stength, that it would have broken? My understanding from Don Blair is, that the 3/4 will handle more absorbtion than the even though the rating is the same.


Thanks

Greg
 
Hi Greg. I'm sorry if I didn't answer your question more directly. Yes I do believe that the 3/4" line would have been a better choice. If a 5/8 line has the same rating as a 3/4 line, I believe the 3/4 line will absorb more energy. I believe this because the 3/4 line has more rope fiber to share the load.
Say hi to Gary for me.
smile.gif
 
In explaining how to lower a load to the groundman I have mostly eliminated the use of lower. I try to use the term
'guided decent'
seems that everyone will hang on until the piece is finished moving and then proceed to lower the load.

Using different terms or ways of explaning what you want/need often works far better than repeating ourselves.
 
"The rope broke 8 feet from it's end"

It's this about the place you would expect the load to come to a stop on the pully? I realize with the right diameter pully the bend ratio of the rope would be within guidlines...but still..this is a bend. Any dirt in the rope would cut fibers more at this location also. After 3 years the number of cycles to failure must have hit the magic number. My guess is that the rope was wearing internally and of course this was not visible to the user.

Respectfully,
 
You must log in or register to reply here.

New threads New posts

Back
Top Bottom