8 tonne rope failure, shock loading

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It did have some stretch as it was mooring type rope. 8 tonne was the SWL (if memory serves), so it was truly a friend that will be sadly missed.

Tirfers use wire rope.cable. A beautiful bit of kit that pulls harder than a schoolboy.
 
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Any pictures of the broken line? I'd guess the remaining
rope is only safe for a driveway barrier or maybe a tire swing?
In other words, out of service, cut into short pieces for xmas
gifts.
-Jason
 
Managed to get one image off my phone, by transfering to my wifes and sending it on.

You can see the two lines on the rhs, one is the 8 tonne line going to the tree stump above, the other line is the tirfor line. Im up on scaffolding preparing the base (well a few metres above the base) before the cut.Truck to right is mine and is where the tree ends up thankfully

Heres the set up of the job
 
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Fundamental errors made.

The "big line" was not pretensioned and not set at 90 degrees to the scarf (notch).

Trees follow scarfs, leans give weight, providing hinge wood never breaks then trees are delivered on scarf.

However gunning adjustments need to be made for lean.

All of this explained and showed in real life on this video. By the way, this is the most heavily viewed video in my collection, I suppose that is because fallers/forestry and arborists watch it.

http://www.arboristsite.com/showthread.php?t=34252

Diagram attached showing angles pertaining to your words.

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Also, in support of my video I made these diagrams so people get a better understanding.

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Been utilizing those techniques for years but could never draw it like
you :cheers:
 
Great thread!

Thanks everyone for an informative and interesting thread without any of the usual BS. I learn alot from threads like this, it's what arboristsite is all about. Impressive work!:clap:
 
I had an interesting learning experience on an extremely steep slope about 3 years ago in the moutains of Julian east of here on a county removal contract.

It was one of those contracts that involved shutting down traffic both ways on a major HWY called Banner Grade. Because of this the work had to be done at night in the wee hours of the morning. It was one of those contracts that had to be completed by a certain date or else get fined heavily for each day over it went.

It was winter and the rains would not let up as the completion date loomed closer and closer, so the owner of the company sat down with me to explain the pickle he was in if the job wasn't completed regardless of the weather. He threw some serious money on the table and let me have my picks of his best men and equipment in his 70+ man company.

So essentially I took on this nasty complicated night time job in the middle of a winter storm. I had two crews, a total of 10 veteran treeworkers, a bucket crew for road clearance, and I ran the removal crew complete with crane and whole tree chippers, the county guys shut down traffic and patrolled the 7 mile stretch we were working.

The problems started as the rain picked up and began washing boulders on the steep mountainside above us down onto the HWY on which we were working. My men started getting real nervous despite being paid triple their normal pay, and looked to me expecting me to shutdown the operation before something bad happened. They were disappointed when I merely assigned 2 men as spotters, one for each crew and kept on going as the rain kept falling in sheets.

The job progressed slowly but surely as we worked into the early morning hours driving around the many boulders and rocks now littering the rain soaked HWY. Only one removal was left to do, a big cedar on a steep down slope in such close proximity to high power lines that the crane could not be used on it. So I put on my gear, had my men tie a rope to me and lower me off the hwy and down to the big cedar, I clipped into the tree and untied the belaying rope, then I limbed the cedar out and dropped the top downhill away from the power lines up hill on the HWY, leaving a nice fat 80 foot pole.

The scary thing about this tree's location was that about 100 feet down the incredibly steep mountainside directly below it was a vertical drop off of many hundreds of feet with a raging river at the bottom that I could hear from the tree but could not see. We short sticked the crane below the power lines and yanked the top of the cedar and brush up onto the HWY and chipped it up.

All that was left now was the 80 foot pole and the job would be finished. I couldn't drop it up hill because of the power lines, and I couldn't piece it down without the logs tumbling down the slope and over the cliff into the river, which any licensed timber operator knows is a big no no. That left me with two choices, rigging and catching the wood in the storm, or dropping the stick downhill and trying to catch it with 3/4 inch steel chokers clevised together, one around the stump, the other about 15 feet up on the stick.

The men were already a little ticked off with me for insisting we finish the job in such foul dangerous conditions and weather, they wanted to get the heck out of there pronto and I didn't blame them for feeling that way.

I decided to drop the stick down hill and try and catch it with the steel chokers, I figured that if I minimized any slack in the chokers, the stick would not build up any momentum capable of snapping 3/4 inch steel chokers, but I was dead wrong, and it was an amazing sight to behold when those chokers failed. Of course I was tied off to the belaying rope when I dropped it downhill with my MS440 Magnum, and that big stick snapped those steel chokers like a piece of thread, but the amazing thing to see was the 3 foot flames lighting up the night at the exact point where the chokers separated. All that was left was a shredded section of steel choker around the stump.
That stick never slowed down even a little bit as it slid down that slope and over the cliff and finally splashed into the river and downstream, I presume.

None of the county guys were around to see my very convenient mistake, the guys were thrilled to see the job over(the cliff), only the crane operator was a little upset with me for destroying two of his long chokers and one of his big clevis'.

We loaded up and headed home and kept our mouths shut about my big rigging mistake in the middle of a storm that day, but I learned a valuable lesson about what a big green cedar stick can do to 3/4 inch steel chokers.

If you've ever seen a high caliber rifle's muzzle flash at night, that's exactly what that choker looked like when it separated that night, and all my worries went over a cliff and floated downstream.

jomoco
 
TM- I think JPS gave some great advice. It is time to step up your line choice. Not in size, but in materials. It may cost you more, but you could get a line maybe 1 or 1.5 inches in diameter that can handle double what you got out of that 4" line. 4 inch rope is a waste of space and a waste of energy to carry around.

Is this sort of stuff available in Oz? Anything made of dyneema/spectra, technora, vectran...

Glad this all worked out alright.

love
nick
 
The line was fine but I shock loaded it with a LARGE falling tree, it was at least 2/3 of its way over before the tension came on. I should have figured a way of pre tensioning the line by sending the tree towards the house at the start of the cut. If I had done this, it woud have not been a problem.

I think if the line was twice or 3 times its strength there was still a chance of breaking it due to the size of tree, position of rope, direction of fall and the all destroying shock loading. I have snapped 18mm line and it sounds like a rifleshot, this was like a cannon a moment before the ground shook when the tree hit the floor.

The rope had done alot of work, but not shock loaded until then. It had been used as a far reaching anchor line and was my "go to" line for jobs like this. I miss it.

I do understand and agree with what you say nick but I will buy a simular line if I can, I have alot of other ropes (spectra, stable braid etc) and they get alot of use. I called this an 8 tonne line but since then I have rechecked with a provodor and its closer to 25 tonne. Big lines are a real PITA but they are very rugged and when working around machines etc its good to have a line thats easily visable and have there place in the right situation. Its been great.
 
Finding a suitable anchor for a side rope with nothing in the way is always a challenge.

Rather than a sloping scarf use the horizontal scarf with adjusted gun. You'll have more hinge wood across it.

Correct!
 
Hi Timber. Mighty difficult and technically challenging job! That is one huge line! I was thinking spectra would be good for this application....maybe, but do you want some dynamic properties in this application, i.e., a bit of give? I'd think a little would be good to minimize shock loading? If not, you'd only need 5/8 Plasma or Amsteel Blue, rated at ~55,000 pounds. Pricey but a lot easier to handle. And 1 inch Plasma is 110000 pounds rated, lists for ~$11 a foot. I could probably get it for you for $6-7 from my supplier. don't know how much it would cost to ship it to ya though!

To preload, you could have installed a prussic on the line, and then pretensioned it with a tirfor or any mechanical advantage method.
 
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That was a 4" diameter line? Larger marine lines are measured in circumference (4" circum = 1 1/4" dia). That's a mighty big line to be toting around if its 4" in diameter.
 
That was a 4" diameter line? Larger marine lines are measured in circumference (4" circum = 1 1/4" dia). That's a mighty big line to be toting around if its 4" in diameter.

It was a bear of a line. Huge. I had a few other tree companies comment on it including some guys that turned on up on the job and said "thats the kind of rope I would want doing this." It was kinda hollow, or should that be not tightly bound and if you squeezed it the diameter lessened a little.


The tree can be seen on google earth at 41 19'52.42S 174 47'21.15E
The image on earth is at least 5 years old from what I can tell. The tree was leaning towards the east.

I am going to invest in some amsteel or plasma or spectra or something simular.

Nice jeep cj, have the seen the mitsubishi 2.7 turbo jeeps? I want one!
 
That was a 4" diameter line? Larger marine lines are measured in circumference (4" circum = 1 1/4" dia). That's a mighty big line to be toting around if its 4" in diameter.

Good catch, it must be circular measure. 100 feet of 1/2 in line would weigh about 8 or 9 lbs. TM's rope weighs about 10 times that much. The diameter of the rope would then be a little over 3 times as much, or roughly 1 1/2 inches.
 
It was a bear of a line. Huge. I had a few other tree companies comment on it including some guys that turned on up on the job and said "thats the kind of rope I would want doing this." It was kinda hollow, or should that be not tightly bound and if you squeezed it the diameter lessened a little.


The tree can be seen on google earth at 41 19'52.42S 174 47'21.15E
The image on earth is at least 5 years old from what I can tell. The tree was leaning towards the east.

I am going to invest in some amsteel or plasma or spectra or something simular.

Nice jeep cj, have the seen the mitsubishi 2.7 turbo jeeps? I want one!


Timber, would you be interested in 300 feet of 1/2 inch spectra? 24,000 lb tensile....As light as it is, the shipping prolly wouldn't be bad....and I'll sell it for 1.50 US per foot...it is almost brand new. Retail is probably 2.50 a foot.....
 
Good catch, it must be circular measure. 100 feet of 1/2 in line would weigh about 8 or 9 lbs. TM's rope weighs about 10 times that much. The diameter of the rope would then be a little over 3 times as much, or roughly 1 1/2 inches.

You couldnt get your hand around the line, only about half way. I did get a knot in it that required careful use of a sledgehammer and wedges and running it over with a truck to get undone.

I would be interested in that line RB, It does depend on the shipping though as that can have a huge effect on price, I just ended up paying some rip off artist $89 to ship a $13 part the size and weight of a couple silver dollars from the US. Dont ask, long story!
 

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