Technical Crane Question for you experienced operators!!

ROYCE

Well-Known Member
I have a pretty big hung up tree that I have to remove tomorrow with the crane and crew. My question revolves around the load chart. I am estimating that I will have to hold the tree that is hung up while the top is rigged out. This will have to be done because their are obstacles below. I am anticipating that the weight of this will be close to 17K pounds. My crane is a 30 ton.
Now, the LMI will read that with 60 feet of boom and at a degree of 78 I will be good for 7700 pounds. It reads this because that is the max pick allowed on a single part line. However, I do not have to pick the tree up, just set it down. Now, my load chart for the same set up reads around 22K pounds that I am able to pick ( granted with a two or three part line).
So, the question is......am I putting my crane at risk by trying to hold this whole tree weighing approx. 17K (grossly over rated but still) I understand that I will not be able to pick it up, I just need to set it down.
 

christreez

Active Member
I think it would put to much strain on the winch. Example when I unload logs off the bed of my truck I'm good for say 20k pounds with a 2 part line but I pull as hard as I can and winch maxes at 10500 I can boom up with it no problem but the winch is done. I would think putting another 7k pounds of pull would possibly pull the winch through the brake... and possibly exceed swl of cable?? Also not sure if the pulley at boom tip would appreciate the extra load

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ROYCE

Well-Known Member
I think it would put to much strain on the winch. Example when I unload logs off the bed of my truck I'm good for say 20k pounds with a 2 part line but I pull as hard as I can and winch maxes at 10500 I can boom up with it no problem but the winch is done. I would think putting another 7k pounds of pull would possibly pull the winch through the brake... and possibly exceed swl of cable?? Also not sure if the pulley at boom tip would appreciate the extra load

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I get what your saying, but I am not sure that would be the case. The winch would experience the same amount of force weather it was a single part line or a triple part line. If my thinking is correct. Also my cable has a braking strength of 38K pounds.
 

ROYCE

Well-Known Member
I don't have a large two or three sheeve block or I would just put that one, re-calibrate the LMI to have 3 reeving and then see what happens.
 

Drumbo

Active Member
I think you'd be fine but don't quote me on it.

I would think that since the crane will never see the full weight of the tree you'll be alright. Might not hurt to through some ropes on it and guy it to some nearby trees so you feel better.
 

ROYCE

Well-Known Member
I think you'd be fine but don't quote me on it.

I would think that since the crane will never see the full weight of the tree you'll be alright. Might not hurt to through some ropes on it and guy it to some nearby trees so you feel better.
Thats the plan as of right now. But you know how these things go. Sometimes you want a back up plant. That would be using the crane to hold it as I pop the top into another tree.
My first choice is to rig the top of the tree off the crane, taking off appprox. 5K pounds of weight. I would tie the larger stem section to the tree its leaning into. However, there are two of them that uprooted. So its not going to be an easy task.
 

christreez

Active Member
I get what your saying, but I am not sure that would be the case. The winch would experience the same amount of force weather it was a single part line or a triple part line. If my thinking is correct. Also my cable has a braking strength of 38K pounds.
If you had a two part line the winch would see half the load, think how a 5:1 mechanical advantage works. One guy pulls 100 pounds but lifts 500, in this case the winch is the man. 38k pound break strength with a 17k pound load is only a 2:1 factor, not the best. Your 7700 pound max single line pull takes this into account to give a 5:1 working load vs break strength

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chiselbit

Well-Known Member
Royce, would wedging a piece of steel " I " beam under the trunk help? I do that sometimes, sometimes I'll add some 4x4 posts in an A frame configuration to keep trunk from moving sideways off the I beam. Just throwing this out there as I have no idea what you're up against.
 

ROYCE

Well-Known Member
If you had a two part line the winch would see half the load, think how a 5:1 mechanical advantage works. One guy pulls 100 pounds but lifts 500, in this case the winch is the man. 38k pound break strength with a 17k pound load is only a 2:1 factor, not the best. Your 8k pound max single line pull takes this into account to give a 5:1 working load vs break strength

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Good point. The winch isn't exposed to that total weight when you add a sheeve block into the picture.
 

ROYCE

Well-Known Member
Royce, would wedging a piece of steel " I " beam under the trunk help? I do that sometimes, sometimes I'll add some 4x4 posts in an A frame configuration to keep trunk from moving sideways off the I beam. Just throwing this out there as I have no idea what you're up against.
I thought of that as well! Another option if needed. I think as of now I am going to stick with my first plan and take our section that are rated to 5K. I think that will handle what I need it to.
 

flyingsquirrel25

Well-Known Member
Royce if you look in work photos I just did one of these Friday. The tree was hung good in a tulip poplar tree so we added a heavy rope tied off on the ground to "hold" it if something released. We then picked pieces that were not under tension with the crane. Luckily I had plenty of high points to tie into. I Set a high rope first and then used the crane (second climbing line) to set slings, then worked back to the high point and cut the piece. Everything was cut from above in case something happened. At one point we had two supporting lines, and a ratchet strap holding everything up. We got to the last three pieces and the op pulled 4k on it and it stood back up some. He then released and it stayed. Big sigh of relief, it was getting dark. Biggest thing is take it slow, keep open lines of communication and have many eyes watching. And keep your wits about you!
If you go to my Facebook page you can see more pictures of Friday and one I did last summer with two cranes. They are a lot of fun to do but man you are mentally and physically exhausted when it's all done! Good luck. Joes got my number if you wanna chat!
 

craneguy1

Well-Known Member
You would want to multi reeve even if you were only going to set it down...the winch and the cable would only see half the load on a 2 part line....same reason why 9/16" with a working load of about 5800 pounds works...the more you reeve the less it sees.
 
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dbl612

Active Member
I get what your saying, but I am not sure that would be the case. The winch would experience the same amount of force weather it was a single part line or a triple part line. If my thinking is correct. Also my cable has a braking strength of 38K pounds.
your thinking is flawed. with a single part line the winch will see the full weight of that tree. way more than that winch brake should be subjected to even when lowering.
 

dbl612

Active Member
the comments posted here are pretty much indicative of why tree guys get in trouble with cranes. lack of basic crane operational knowledge. not trying to be harsh, but you must realize that cranes are rated for freely suspended loads, not impact or shock loads. why would you knowingly subject the machine and personnel to STUPID suggestions as posted here? they make bigger cranes for a reason, use them when needed, charge accordingly, and work safely.
 

ROYCE

Well-Known Member
the comments posted here are pretty much indicative of why tree guys get in trouble with cranes. lack of basic crane operational knowledge. not trying to be harsh, but you must realize that cranes are rated for freely suspended loads, not impact or shock loads. why would you knowingly subject the machine and personnel to STUPID suggestions as posted here? they make bigger cranes for a reason, use them when needed, charge accordingly, and work safely.
What I state here in the comfort of my recliner does not mean that is what I am going to do when I am set up in front of the tree. I air on the side of caution all the time. I wanted another option and opinion. I would have never tried what I was asking without first asking someone more experienced than I. ChrisTreez pointed out exactly what I was looking to know and hear.
I am also curious to if you read the whole thread and some of my comments after my initial question?
 
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