Rigging Pull Tree

Brian;
Steel cable is the choice prefered by professional loggers on heavy trees.
There gets to be a point where too much stretch becomes a problem with heavy trees, but it shouldn't be a problem with a little twenty incher.
 
Rocky,

I tend to disagree with your concern about the use of wire rope. I'd definitely use our Plasma line for this operation, although any arbo bull line, being static anyhow with relatively low stretch, would suffice. The SWL of the cable means there's no chance of breaking it.
Not good using cable around power or course, but a dirty, worn or wet line could conduct electricity too.

As long as the tree will be felled close to 180 degrees from the lean, it should be an easy job.
 
The interesting thing with this thread is the lack of responses to the question of required force to pull the tree.
I thought this would be common knowledge for most certified arborists.
I know Dave is using a spread sheet to make the calculations but isn't there a hand held calculator designed for rigging that will do the same function?
Knowing what you're working with is a crucial part of this job and removing the guess work is something I'm more than interested in.
 
Before you guys inspired me to do the spreadsheet. I would set the lines, and pre tension the tree to see if I could move it (green only) if I could not flex the tree in the direction of pull, add more MA. Once it moved I would slack the lines off a bit and make the cut. For dead trees, just overkill the MA using experience as your guide.

Dave
 
Well nobody should feel too bad.
I went to the local sling and choker shop(crane supply) and not one person knew how to calculate the force or where to find it.
I can't access that spreadsheet Dave but if you could put it in a hand held calculator you would be rolling in dough.
 
Dave,
Icould not get your spread sheet to open up either, but I will show everyone how I came up with the 1200lb force through a scaled sketch along with the rigging book that I used as soon as I can get back from a job I'm going to look at.

Chris
 
This is very interesting. I agree with a lot of what was said here. First, I have no problem with what you intend to do. I would just say that you need to "engineer" the lift. Take time to calculate the lift and then choose the right gear and plan for the job.

Rocky, I wouldn't use wire rope either. Mainly because it is ridiculous to work with and the proximity of the energized conductors as well.

Roger, I would tend to think that your plasma line has the benificial charcateristics of wire rope, but is easier to work with, takes knots better and is much less conductive. I also agree with what you are saying refering to the lean. I feel that going 100% with the lean or totally against the lean are the best options.

Dave- incredible work. The math is fun to read.

Chris, why not use two systems if you feel slightly uncomfortable? Why not use a higher line with a 3/1 or 4/1 adjustable system, and a lower system with heavier gear to help support it ( I would use a GRCS here). I would also utylize wedges (like Kevin said) as well. Rig it right, cut the face and form the hinge. Put the wedges in and then relax and make that strap release with confidence!
 
Chris, I'm with Dave on this one.
1. Lose the tail hold
2. Definetely lose the come a long.
Like the guys are saying, get that 180degree pull, put the 5:1 with the Z rig or the 4:1 back-up, like Mark said, and let 'er buck.
That come a long is a no-go, you're creating a vector force. Maybe some of the mathematicians can explain to you how bad a vector force is.
Just my 2 cents.
 
</font><blockquote><font class="small">In reply to:</font><hr />
...This is why auto parts stores sell tow straps instead of chains for pulling out stuck vehicles....

[/ QUOTE ]

Yeah, so that when the strap pulls the bumper off, it recoils and cracks your windshield! :D

love
nick
 
This has been a great subject to follow and see what develops.

Through Chris's and Dave's illustrations and calculations I can see a basis for a more comprehensive work on the subject of vector forces, factors and calculation.

Rigging and pulling trees has always been a most intriguing part of our work and over the years I've seen it draw some of the largest crowds of spectators. Most of whom, I always felt in their subconscious, want to see you lose it.

Some aspects of keeping control of the tree while pulling it require as much gut feeling as correct calculations. Especially when dealing with side leaners. Using a holding line to swing the tree and another line to pull it.

Shape/form of the tree. Is there sweep in the lean? And are all the limbs on the lowside also? And are the limbs down low or way up high. As such, these factors in combination can double the force required to pull the tree. An increase in bulk and height will can add another 200-400% required force. 100' tall vs. 200' tall. That 200' tree can require more than twice the froce needed to pull the 100' tree. It comes to the point where you ask yourself, "can I handle it?" And how about your anchor? Yeah, you may have it all figured out correctly, but can the anchor handle it?

Condition of the tree. Is it rotten? In the stump? In the top? When I was rigging pull trees in the 70's and 80's, all old growth, it was an exception to have perfectly sound trees. Some were so scary I got the hell out of there when the fallers started cutting on them.

An old logger once told me, "Jer, you got to keep the weight of the tree under the rigging." How true. It's a good rule to stick by.

The rigging, in the woods weighed hundreds of pounds. We had to set rigging in the tree just to pull the rigging up. Setting at heights to 200 feet. Yeah, steel sucks, cuz it's so darn heavey and the splinters in it will rip you terribly, but it has abrasion resistance rope can never even come close to. However, I've seen it break to! No problem with the heavy logging equipment and winches we had. You had to be real gental to keep from breaking that inch and quarter cable.

In the urban environment "rope" is the choice of the trade. It's user friendly. And with the new synthetics the strength is right up there with steel. It's really amazing.

I pulled a tree a couple of months ago. Old growth Bishop pine, only about 90' tall and 30 inch on the stump. Not tall, but it had size. Trunk was straight for about 30' and then swept back 10' over the county road, power, telephone, cable, two homes. All the limbs where in the top, all on the back side and reached well over the county road. I rigged the tree with 5/8 Stable braid, 80'. The stem was about 12". It divided there into several wind blown spars. Oh, I had a good anchor, a large redwood stump right in lead with the lean. Though it was quite the reach, nearly 200 feet. I put a 3 block purchase on the Stable braid about 40' from the anchor. Using 3 rope comealongs gave me about 6,000 lbs on the top. If I really needed it.

After tightening up the system to a fine tune I went and cut the tree. With all the tension and stretch in the ropes the tree picked up to nearly plumb, but not quite. Went to the anchor and used two comealongs to tighten the system back up and then one comealong finished it.

Actual time on the stump was but a few minutes. Setting it up then tearing it down and packing it up took a few hours.

I've rigged and pulled lots bigger trees in the woods using shear brute force, but that Bishop pine was a pull tree that will always stick in my mind. Because, before taking it on, I walked around it for some time looking at the angles and thinking about everything thats been said in this discussion. I felt confident with it and went ahead. All on eyeball and gut feeling.

Hope to see more posts and follow ups like this one. It's been great.

Roger Barnett, send me your address so I can send you a DVD of the Tree House Project. Yeah, finally got it done.

Jerry B
 
Hi, guys;

I have a few comments to make about the rig in the picture. If the anchor tree(spar pole ) is in line with the direction of fall for the tree being removed(pull tree), it would be an advantage to place the lead of the rope (tail hold), to the anchor tree. If not where the snatch block is located, at least to the base of the anchor tree. If experience tells you the anchor tree cannot handle the load of a 2:1, guy the anchor tree if possible. To attach the lead of the line to the anchor tree, I'd use some type of eye-and-eye sling made of extra strong webbing to eliminate damage to the anchor tree. This will keep the m.a. as close to 2:1 as can be accomplished. I'd also advise placing the come-a-long at the base of the anchor tree. Doing this will reduce tension in the anchor tree's snatch block sling. Try to use a wide sling made of fiber, it's constructed like webbing, to try to eliminate damage to the anchor tree. Anchor the come-a-long behind the anchor tree if possible. I'll also comment this topic really is Jerry B.'s domain.

Using a 2:1 as described by me means the tension of the pull line from the come-a-long is doubled. It also means your come-a-long needs to have twice as much cable as needed to pull the tree over. Example: if the tree needs to travel 10 feet before it will fall on it's own, 20 feet of cable needs to be used from the come-a-long.

When the lead of the rope is terminated elsewhere, besides where the snatch block is located, then the m.a. of the simple rig is less than 2:1. This also means the angle the rope makes while running through the snatch block in the pull tree widens and loses power. The good thing about pulling the tree over is the tree requires less torque to reach vertical as it approaches a vertical position. This doesn't mean the 2 factors, widening angle of the lines in the rig and required torque to pull the tree over cancel each other. This relatioship would need to be shown through mathematics before 1 could make that connection.

Ultimately, the riggers and fallers are the best judges for setting the rig.


Dave: your spread sheet is nice, but, I'd like to see the equations, not the results from them.

Joe
 
Well I had a whole response typed out but lost the post. I hope you guys can see my sketch of the computations.

Jerry, I'm glad you replied to the posts. I knew it would be right up your ally.

Chris
 

Attachments

  • 7892-RIGGING-CALCS.webp
    7892-RIGGING-CALCS.webp
    17.2 KB · Views: 68
Joe and any one else that is interested,
attached are my chicken scratches for figuring out the formula in the spreadsheet.

</font><blockquote><font class="small">In reply to:</font><hr />
"I can't access that spreadsheet Dave but if you could put it in a hand held calculator you would be rolling in dough."

[/ QUOTE ]

Kevin, any of the spreadsheets I have done over the years (speedlines, DWT, and now lean) can be loaded into a Palm Pilot or a decent calculator. Yet no dough to roll in?!?

Dave
 

Attachments

  • 7894-leancalcs 001.webp
    7894-leancalcs 001.webp
    53.4 KB · Views: 79
Dave, I was thinking about a calculator like the "construction master".
Something small that would estimate all the specific rigging forces that we use and yet sell for under $200.
I know I would buy it and I'm pretty sure there would be a market for it.
 
Kevin,
With the weights we deal with, mis-estimates can drastically affect the numbers. If you misjudge the height, lean or diameter of a tree, the numbers can be off by many hundreds or thousands of pounds. If anyone attempted to trust this imaginary calculator, they might just attempt to sue the manufacturer for their bad results because they trusted a calculator instead of their common sense.

IMO, most good treemen have a natural sense about approximating weights. If they don't, the calculator will only multiply their inaccuracies. You put a rope on it and watch the tree as you pull, seeing how much effort results in how much movement. Much more effective than a calculator 99.99% of the time.
 
You must log in or register to reply here.

New threads New posts

Back
Top Bottom