balance point rigging

murphy4trees

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The term balance point rigging was just used by Cory in the video thread: http://www.treebuzz.com/forum/showflat.php?Cat=0&Number=188543&page=0&vc=&PHPSESSID=

This is concept that Mark Chisholm teaches in his rigging seminars, and was used extensively to safely manage monster pieces by my teacher, Big Jon Grier. Its an advacned technique with many applications. Allowing a lot more control of movement thus reducing shock loads, and improving control for ground men. There has been some good discussion at the above thread. Worth reading if you have an interest.

The basic idea is to tie off a piece getting lowered, at or near its balance point (center of gravity), steer it to 4 or 5 o'clock with the notch, and let is swing smoothly into rope until nearly all the weight of the limb is on the rope before the hinge tears, thus greatly reducing shock loads. Real pretty and fun for both climber and ground crew, though both have to work together to keep it safe.

I used the same concept today in two different jobs, not to control shock loads, but to make the pieces easier to handle on the gound.

First job was a dry 21" dbh, 60-65' white pine, backyard on the low side of a 4' retaining wall from the driveway. Rigging the trunk off itself, tied the pieces a little high above the notch so they came down balanced, allowed for easier control and more ground clearance when using the chipper's winch to pull the pieces onto the driveway.

Second job was a broken hanging 35' maple lead, maybe 12-14". Customer had cut all the brush off. It was hung up on the ground at nearly a 45º angle. Tied it off a good ways down from the break. Cut the tips back to where it was floating balanced which made it easier to handle, to pull out away from the bushes under the tree, onto the lawn.

Not rocket science, but did make the jobs a little easier.
 
It has little to do with 'balance point' and has everything to do with rope tension. By tying the piece off further away from the cut, it tensions the rope as the piece falls away from the rigging point.

You still don't want to tie too close to the balance point because that will result in the work flipping around.

Be aware that this can put incredible forces on the rigging point if the rope is locked down. I'm talking 5x-10x the weight of the work or more, and it can break out the tree. Ask me how I know. :|:
 
Be aware that this can put incredible forces on the rigging point if the rope is locked down. I'm talking 5x-10x the weight of the work or more, and it can break out the tree. Ask me how I know. :|:


Very good point Brian. It can definitely be a useful technique if applied correctly.
 
I wish I could touch type! :whine:

:? If not touch, what do you use? Voice activated?

Typing and spelling is like trying to flap my arms to fly. Doesn't work well for me. My voice activated system is called "Sylvia". Are there other options?? :D

Dave
 
When you mess with leveraging forces that you don't fully understand, it can go wrong in a hurry. Think of that limb as a giant prybar pulling at the rigging. A 30' limb can generate many thousands of pounds of force on the rigging point. If you rig a limb to where the tie off point is 10' from the rigging point and notch it so that it ends up 20' from the rigging point before the hinge breaks, then there's a good chance something may fail. It's a balancing act where you have to match the amount of rope stretch to the falling distance before the hinge separates. If you're swinging the limb sideways then that gives you a lot more margin since the load is transferred slowly from the hinge to the rope. But if your hinge is aimed in a direction where it forces the load onto the rigging with no relief then you'll never know what is going to break first.

I wish I had pictures of what I did a few months ago on the job where I put the pine tree top through the carport. I rigged one limb to the limb above it, then notched the bottom limb down and out toward the driveway (away from the rigging point). As the limb started to move, it greatly increased the distance between the rigging point and the point there the limb was tied. It quickly exceeded the rigging limits and broke out my rigging point, sending the whole mess down through the carport. If my rigging point had not broken, then the rope would have.
 
I did that a couple of times on thursday swinging a limb from over a house without it dropping much. I used a limb balancer because I seem to be unable to estimate the balance point close enough. Butch, I had typing in Jr. High and it has stuck with me. That's how special I am.:D
 
The only downside to this method is the person working the hole HAS to be on their toes. Any hesitation in running the rope can increase the chance of striking the climber. Butt tying with a high line angle minimizes this greatly, and again it's up to the hole man to run the ropes smoothly and the climber is in the clear instantly.
 
Man, i can't believe i agree with Brian; but still a very useful technique for support and steering, can even get some stuff to spin around from front to back horizontally. But, as Wiley points out, you have to be able to also invoke the equal and opposite force of tension relief too! But.... the closer to balance point can have an effect also of a dampened drop of the head on line, due to the ballast of the butt end above the hitch. Also, any length not below the hitch, is 'free clearance' in compaired to butt hitching the same. Clearance, less shock loading, head tipping down more slowly can add up to a great help for total clearance. The length above the hitch, can also be sude as a lever to place weight/impact on if head were to get hung/ or if that is how you found it. Can sometimes slam another piece on a line on to the butt end and lift head out of lock; or have ground pull, or redirect to truck pull etc. to free head.
 
In treework there's always times to balance a load and times to keep it butt heavy or tip heavy. All depending on the situation. and depending on the situation sometimes you have to think about it either way.
 
Allowing a lot more control of movement thus reducing shock loads, and improving control for ground men.

So let me get this right, a piece flipping about it's own axis is in more control?! :cry:

This is concept that Mark Chisholm teaches in his rigging seminars, and was used extensively to safely manage monster pieces by my teacher, Big Jon Grier. Its an advacned technique with many applications. ....
.... Not rocket science, but did make the jobs a little easier.

Is there any scientific data with dynamometer to support these claims or is Mark C and Big J simply advocating Voodoo science? :angel3:
 
I always use a tag line on a balanced limb, helps control any twirling or uncontrolled movement when suspended in mid air.
 
With more control, and less impacting can take bigger more confident-ally .. for perhaps less time...

Tag line is very good for some stuff. i would tie mine near butt end, then ground control adjustmeant effort is leveraged from that point to the pivot of the rig hitchpoint. This also can be used for cutting, let hang, then ground crew pivots around; lifts head to weave thru with this lever to tag line. If head gets hung, or that is how you found it, can impact into tag, to lift head some and (moving quickly) free head from lock. This can even just be a short line, or 2 slings (1 on primary load and 1 on impacting adjustmeant load after the fact. For, the shorter the reach on this short rig line, the less elasticity in that system, the more raw impact incurred by primary load with hung head. Once again this would not be possible if just butt hitched; for then have no ballast nor lever against head's downward pull. Hear are some ancient drawings from another wierld:

Show the self tensioning theory: Shows the self tensioning theory

Shows moving away from support on the horizontal axis too; that gives more tension to pull even harder sideways-and in doing so creating stronger hinge in response (while horizontal self tensioning weakens hinge); so that now we have a stronger hinge and a tighter line guiding and supporting to start. Further allowing more downward cut to keep line tight as the load now moves closer to support(to compensate for Natural tendency for line to slacken as load moves towards support on either axis)...

And more recently redoing a too faded drawing or rather didn't make it thru some kind of file conversion: Adding some tourque to limb powerd by line tension we are adjusting now; thus line pulls to side and so does 'flip'(sometimes slightly upwards at 1 point for more clearance) push in same direction..
 
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