Technical Crane Question for you experienced operators!!

[ROYCE]

So how'd it go?

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Went really well. I had it planned for the whole day..ended up taking about 6 hours. We were able to do another job on the way back to the shop.
I ended up doing it like I originally planned. We tied off the stems to an adjacent tree and then used the crane to remove the tops. First pick was 2800 and the second pick was 3200. My capacity was at 7700. After removing the top of the first one, the stem just stayed where it was and didn't fall down, or up. We removed the guy rope and was able to fell it. Removing the top cleared the tree of all obstacles.
The second larger tree we executed the same way. After removing the top the log section settled a bit. We used the GRCS and cranked the tree over sideways out of the pine it was hung up into.

 

[deevo]

Went really well. I had it planned for the whole day..ended up taking about 6 hours. We were able to do another job on the way back to the shop.
I ended up doing it like I originally planned. We tied off the stems to an adjacent tree and then used the crane to remove the tops. First pick was 2800 and the second pick was 3200. My capacity was at 7700. After removing the top of the first one, the stem just stayed where it was and didn't fall down, or up. We removed the guy rope and was able to fell it. Removing the top cleared the tree of all obstacles.
The second larger tree we executed the same way. After removing the top the log section settled a bit. We used the GRCS and cranked the tree over sideways out of the pine it was hung up into.

good job, glad all went well!

 

[dbl612]

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?

read everything just now

 

[dbl612]

read everything just now

appears everything was well below what you originally thought it was. sounds like it turned out well.

 

[craneguy1]

Nice amount of rootball/counter weight...be much different if it was just a messed up trunk with no dirt...glad you didn't need a new winch...or worse.

 

[BigWood]

Royce attaboy for asking, maybe a little more operator training wouldn't be a bad idea. I like that you took the cautious approach and didn't do it the way you originally posted.

 

[allmark]

I did one similar to this the other day. If the rootball is still intact you could stand it up without taking the weight of the full tree and cut sections off the bottom until it could handle the weight. This of course is only doable if there isn't going to be side load possible and your confident the base will remain. You would only subject the crane to the load you applied to it.
Definitely something that should be done with someone familiar with the technique first.

 

[rypie37]

Isn't the limiting factor of 7700 of 1-part line in reference to the breaking strength of the line itself? If so it would be folly to overload that no matter what the situation is.

 

[ROYCE]

Isn't the limiting factor of 7700 of 1-part line in reference to the breaking strength of the line itself? If so it would be folly to overload that no matter what the situation is.

No, the breaking strength of the line is 38,000 pounds.

 

[rypie37]

Okay, gotcha.

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.

So the 7700 pound of max pull from the winch on 1 part line applies to lowering as well?

 

[craneguy1]

You want to stay within the designed ratings yes.

 

[SRTsteve860]

speaking in terms of force vectors, and leverage:

lets assume that the crane is attached directly to the very tip of whatever log/trunk/spar is being controlled, and the other end of the tree is the uprooted stump basically acting as a hinge.

if the tree was of uniform weight over its entire length, with the tree laid fully horizontal, the crane would be supporting half the load, and the stump supporting the other half. anything closer to vertical would be less load on crane more load on stump.

but since trees are heavier the closer to the stump thanks to the taper, the crane would be experiencing less than half of the overall pick weight.

this is a very simple scenario, if you have to choke the tree farther back from the tip there would be additional forces to account for and the crane would experience more than 50% load.

just remember, if you have a tree leaning and it needs to sit down, its not the radius that its at when you pick, its when that log lays down that you need to be cognizant of.

-Steven

 

[craneguy1]

Now you're bringing up different forces and un-for-seen circumstances...now it gets really real...first and formost is the rootball...is it actually counterweight that can be relied upon or a force that has to be countered against? Valid arguments you bring...in terms of 50% what the crane is responsible for holding...it will vary depending on the angle of the load...anyone with experience utilizing an lmi can tell you that.

 

[craneguy1]

Also correct in the load radius...crane op has to know where the weight has to end up to make the pick...every pick has 3 stages to it...the lift, transition, and the set down. Farthest radius dictates the max weight to be lifted.