tensil strength and working strength

[millbilly]

This is my problem, I have a tulip poplar hung in an ash. The tulip might be leaning at 45 degrees uprooting and v crotched in the ash at about 50 feet . If I put a chain and pully above where it is hung in the ash, and tie it off, then under cut the tulip at the base and continue until it is just hanging in the ash then lower it down chunking off 2 foot pieces at the base.

My bull rope has a breaking strength of 12000 lbs and im guestimating the poplar weighs between 5000/6000 lbs will the rope hold it? The rope has been used to lower one other large limb its basicly new.

Is this a case of not trusting my equipment or what?

 

[Slvrmple72]

Time to get a climber. When in doubt chunk it out!

 

[DangerTree]

This is my problem, I have a tulip poplar hung in an ash. The tulip might be leaning at 45 degrees uprooting and v crotched in the ash at about 50 feet . If I put a chain and pully above where it is hung in the ash, and tie it off, then under cut the tulip at the base and continue until it is just hanging in the ash then lower it down chunking off 2 foot pieces at the base.

My bull rope has a breaking strength of 12000 lbs and im guestimating the poplar weighs between 5000/6000 lbs will the rope hold it? The rope has been used to lower one other large limb its basicly new.

Is this a case of not trusting my equipment or what?

Not enough information, need butt dia at breast height, density per cu. ft of green tree at cut season. Total tree height for weight est. Then some mechanical logic such as if the tree is hard crotched will it come free if the butt is freed if not what will happen then? What are the exposures such as power lines or homes. Is the risk of trying greater than you are prepared to accept. Is the penalty for failure more than you can afford? Also note that working or suspension rating for that rope is 10% of breaking strength or 1200lbs. Does the tree weigh more than that? Liability insurance seldom covers negligence such as the failure of ill suited equipment. Good luck and make good decisions.

 

[Ghillie]

If you have 6000 lbs hanging off one side of a pulley (block) in the tree, you will have 6000 lbs hanging off the other side too. You will (in this scenarion) have 12,000 lbs at the pulley (block). Is the pulley rated for that?

 

[the Aerialist]

In another scenario ...

If you have 6000 lbs hanging off one side of a pulley (block) in the tree, you will have 6000 lbs hanging off the other side too. You will (in this scenarion) have 12,000 lbs at the pulley (block). Is the pulley rated for that?

What if the 6000# piece drops 12 inches onto the rope and pulley?

 

[Ghillie]

What if the 6000# piece drops 12 inches onto the rope and pulley?

I did not even factor in dynamic loading of the block (a pulley is not intended for dynamic loading).

 

[Ghillie]

I figured a .25 second fall of 6000 lbs and came up with 6271 lbs foot.

 

[millbilly]

When I under cut at the base it will be a very gradual weight load. The cut will open up and the log will resting on the ground again just closer to the ash tree, I will continue undercutting untill the poplar is hanging with the butt inches off the ground and continue to lower the tree down cutting off 3 foot chunks untill I can lay it down

 

[Ghillie]

When I under cut at the base it will be a very gradual weight load. The cut will open up and the log will resting on the ground again just closer to the ash tree, I will continue undercutting untill the poplar is hanging with the butt inches off the ground and continue to lower the tree down cutting off 3 foot chunks untill I can lay it down

You are still out of the 10:1 safe working load range for the rope and I am guessing it is the same for pulley too.

I just wanted to point out what a lot of people overlook. that a loaded pulley has twice the weight force exerted on it.

 

[the Aerialist]

In practical terms ...

Your rope is 12,000 lbs tensile strength, using Gillie's numbers of 6271 lbs x 2 = 12,542 and thats more than the tensile strength, and far more than the WLL of your rope.

Why not just cut the top off of it and pull it out with a dump truck?

 

[DangerTree]

I figured a .25 second fall of 6000 lbs and came up with 6271 lbs foot.

Very good but your equation is based on static impact without the absorbsion factor of the length of rope running through the pulley ie. 150' 350' or 1000' would significantly reduce impact at the spar placement. Also in order for the pulley to be twice the initial load it must be lifted up vertically and pulled straight down. As the rope angle increases the load decreases until the load is being pulled straight up and is 1:1. So there are two more variables to factor in. Oh and what about slack take up and material stretch per ft.

 

[TreeSurfer]

id say its time to get one of,


these CMI 1” Capacity Arborist Block

these Eye Sling : SherrillTree Tree Care Equipment

200 feet of this Amsteel Blue : SherrillTree Tree Care Equipment

and one of these Good Rigging Ctl Sys : SherrillTree Tree Care Equipment

:stupid:

 

[flushcut]

This is my problem, I have a tulip poplar hung in an ash. The tulip might be leaning at 45 degrees uprooting and v crotched in the ash at about 50 feet . If I put a chain and pully above where it is hung in the ash, and tie it off, then under cut the tulip at the base and continue until it is just hanging in the ash then lower it down chunking off 2 foot pieces at the base.

My bull rope has a breaking strength of 12000 lbs and im guestimating the poplar weighs between 5000/6000 lbs will the rope hold it? The rope has been used to lower one other large limb its basicly new.

Is this a case of not trusting my equipment or what?

I would get some bigger gear. I would be thinking 7/8" or 1" if you want to hang 6g's with any kind of dynamic loading even if it is just a little fall. Also is your spar tree strong enough to hold that kind of weight? Don't forget to subtract strength loss due to the use of knots because that will eat up breaking strength the fastest.
Personally I would climb up cut the top of the poplar free, rig a block as you have said, free the trunk of the poplar and lower away keeping the root mass attached for counter balance.
But this is just typing I would need to see it and go from there. There could be a whole lot easier way to geter on the ground.

 

[tree md]

If you're gonna start hanging whole trees I would invest in a 3/4 inch bull line. I have hung many a tree with 3/4 and have even shocked the hell out of them before; Never had one break. Noway I'd want to do some of the stuff I have done with the 3/4 with a 5/8.

 

[Ghillie]

If you're gonna start hanging whole trees I would invest in a 3/4 inch bull line. I have hung many a tree with 3/4 and have even shocked the hell out of them before; Never had one break. Noway I'd want to do some of the stuff I have done with the 3/4 with a 5/8.

Why would you rather use 5/8 than 3/4?

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[Ghillie]

id say its time to get one of,


these CMI 1” Capacity Arborist Block

these Eye Sling : SherrillTree Tree Care Equipment

200 feet of this Amsteel Blue : SherrillTree Tree Care Equipment

and one of these Good Rigging Ctl Sys : SherrillTree Tree Care Equipment

:stupid:

The weak link is the deadeye sling with a WLL of 3400 lbs Which means you should limit your lowering load to 1700lbs. I guess I am going to have to figure out how to splice amsteel now too and make a deadeye sling.

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[tree md]

I think you misunderstood what I was saying Ghillie. I would only use a 3/4 for hanging whole trees or spars as I have done many times before. Not to say that I would rather use my 5/8 on 99% of the applications I use my bull lines for.

 

[Ghillie]

I think you misunderstood what I was saying Ghillie. I would only use a 3/4 for hanging whole trees or spars as I have done many times before. Not to say that I would rather use my 5/8 on 99% of the applications I use my bull lines for.

My apologies, in my haste I read noway as nowadays. Should have known better.

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[Ghillie]

Very good but your equation is based on static impact without the absorbsion factor of the length of rope running through the pulley ie. 150' 350' or 1000' would significantly reduce impact at the spar placement. Also in order for the pulley to be twice the initial load it must be lifted up vertically and pulled straight down. As the rope angle increases the load decreases until the load is being pulled straight up and is 1:1. So there are two more variables to factor in. Oh and what about slack take up and material stretch per ft.

Yes, stretch will decrease the load. But if your gear will not meet the WLL of a worse case scenario (dead stop, no stretch) why take a chance. Why risk your "cycles to failure" being equal to or less than 1?

At one time, I had the rigging program that SherrillTree offered and it factored in length of run. It would say "not safe" to some drops and then when you added 50` of run to the right, it would be okay. It was interesting but I do not have the formulas on hand to do the math.

And I am not sure what you are talking about 1:1 on the pulley? Straight up (vertical) is doubling the forces on the block and sling.

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[Ghillie]

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