Rigging within limits

pantheraba

More biners!!!
Joined
Jul 31, 2005
Messages
15,000
Location
near Atlanta
I had a 15"dbh oak leaning over my house...I had roped out the pieces over the house solo...cut them small enough to toss. That left a 45 foot leaning remainder. My inclination was to rig it out in pieces, swing them from the nearby sweetgum. My son suggested we take the whole piece...hang it and cut pieces off from the ground. Then we decided to see if we could just lower the whole thing.

I decided to see what the math thought about that...have not pushed equipment limits intentionally before.

Per TreeStuff rope data for Sampson 9/16" Stable braid:

Diameter: 9/16" (15mm)
Average Breaking Strength: 13,300lbs (6,000kg)
Work Load Limit: 2,600lbs (1,200kg)

One of the log charts I found was based upon log diameter midspan. I estimated 12" diameter mid log and worked out to a weight of 43 lbs per ft.

+ 43.00 lbs/ft
* 45.00 ft
-- -------------
+ 1,935.00 lbs for the spar.

I used another log chart and came up with a projected weight of just over 2,000 lbs.

So, using 3/4 Tenex, big block and a strong support tree and port-a-wrap we gave it a go. Probably ended up having the tree hung for about 10 minutes...it did not rotate out past the house like I planned and I had to set up a tag/pull line to pull it into the available drop slot.

I assume this is how y'all go about deciding whether to hang a tree or not?

The boys weren't crazy about coming outside for the show but that's life (we wanted them in sight, not running outside in the middle of the rigging operation). 1080 HD is an option.

<iframe width="560" height="315" src="https://www.youtube.com/embed/7tB22O4X-ws" frameborder="0" allowfullscreen></iframe>
 
Panteraba,

I enjoy rigging out the big stuff. It takes some careful planning and good equipment, but the satisfaction afterward is hard to beat.

It was a good thing that the tree slid backward as you were lowering it. The angle was getting a bit steep there, placing a pretty good side load on the supporting tree. If the tree being removed doesn't have room to slide back like that, it might be better to start cutting pieces while the tree is hanging in place. Lower it 3 or 4 feet at a shot, then remove another short piece. That will keep the weight hanging vertical on the supporting tree.

Joel
 
Well done, Gary!! I can't recall if I've already posted the vid of a cottonwood that we did a week ago. Look for it.
 
Slow Motion Perfect!
Easier to look good and fast plowing thru;
An old sleight of hand magician at Riley's Trick Shop in Chicago(gramps knew someone there) taught me he just looked fast,
cuz so clean and directed got job done w/o problem, had trained so slow mo camera couldn't catch his trix!


Panteraba,

I enjoy rigging out the big stuff. It takes some careful planning and good equipment, but the satisfaction afterward is hard to beat.

It was a good thing that the tree slid backward as you were lowering it. The angle was getting a bit steep there, placing a pretty good side load on the supporting tree. If the tree being removed doesn't have room to slide back like that, it might be better to start cutting pieces while the tree is hanging in place. Lower it 3 or 4 feet at a shot, then remove another short piece. That will keep the weight hanging vertical on the supporting tree.

Joel
.
Self equalized to the minimal loading; can 'feel' backpressure mount to do so before it slid back
With this setup Joel pro-poses, would look to lower sections right on trailer etc. cut/lower/cut.
BUT, would not want to cut so many times as to make tree top heavy in rig/flip uncontrolled.
Otherwise could brace boom/support tree higher and in direct opposite direction(s) of pull(s) (so if sweeping across would have 2 back supports to cover all angles).
.
Cute Kids, too bad there is no way they can comprehend lessons around them and what just happened
/what Dad just pulled off easily against 'all odds' as far as non-rigging folk are concerned; especially snuck down/ninja style!
.
Including bending/leverage line @ 2mins.







edit:
To the title 'within limits'; interesting factoid comes to mind.
This trick properly uses static line; no/low impact lift and lay.
But in dampening shock load another reason to stay in limits is if line tensile is 20xLoad it offers less elastic dampening of impacts than if 10xLoad.
Also, if have rope tensile 10xLoad, but support Load in 2:1 pulley system; impacts like 20xLoad system
So, staying within loading recommendations can mean not going under OR OVER recommended tensile ranges!
Rope can be too weak or too tuff to handle load properly, Goldilocks may need it just right!
 
  • Thread Starter Thread Starter
  • #14
Thanks for the feedback Kenny. Headed out the door for a yoga clinic...will read in detail later today.
 
Good one, Gary.

I'd consider just cutting it on an angle at the ground, so that it doesn't drop off the stump. Also, consider hanging the POW in the tree, or at an opposite angle to the layout, to compress rather than side-load your anchor tree.
 
  • Thread Starter Thread Starter
  • #19
Thanks...seemed worth sharing and always to get ideas from other folks.

I'd consider just cutting it on an angle at the ground, so that it doesn't drop off the stump. Also, consider hanging the POW in the tree, or at an opposite angle to the layout, to compress rather than side-load your anchor tree.

Good idea, Sean, on the angle cut to save that drop off the stump.

What do you mean by "hang the POW in the tree"? It was at the base of the gin pole....
 
You climbed the tree to anchor the block and retrieve, so you can do the same work with the POW instead. If you hang the POW up top, you have to get the right number of wraps and/ or use some supplemental ground friction (trunk wrap or second POW). You only have the force on the top-side POW and Gin Pole equal to the force on the rope from the piece (NOT the weight, as the ground holds some and the rope CAN lever if tied to close to the ground), and the hold-back force (force of the rigger's hand), rather than 'doubling' it with the block (max force is definitely not with the two legs of rope at 180*, and some block friction).

You had the POW at the ground, and went vertically up the Gin Pole, then out at an angle, with maximum force the rope and block/ sling/ Gin Pole (side-loaded) probably when it was leaning with the greatest rope angle.

If you anchor your POW at the ground or hold the rope for the top-side POW to form an inverted-V, you will compress the Gin Pole rather than side loading it. If you expect maximum force on the rope with a 30 degree rope-to-gin-pole angle, you can anchor the ground-POW or less importantly, have the top-side-POW Rope-man at an opposite angle of 30 degrees, 180* to the force. Capiche?

If you want a face cut, do it inches off the ground. Consider if you want a stump shot, flush horizontal-cut and back-cut, or a reverse stump shot. If you need to keep the tree at the original 'gun', then a stump shot.

If you want it to slip back, a flat back-cut only will leave a bit of holding wood. As you lower it, the force of the tree pushing back toward the stump can rip it, and allow it to slide backward over the stump (general area).

In your case, you needed it severed from the hinge in order to tip it to the side from the lean.




What I mean about leverage is that if you have the rope tied to close to the butt, as with rigging in the tree, you will form a 3rd class lever, increasing your load on the rope.


http://www.ohio.edu/people/williar4/html/haped/nasa/simpmach/lever.htm 1st class, 2nd class, 3rd class levers. I learned 1st, 2nd, and 3rd class levers in regards to moving multi-ton boulders with a couple of rock bars on trail projects, either moving them out of the way, or into place when building rock structures like retaining walls and drains.
 
  • Thread Starter Thread Starter
  • #21
Wow...thanks for taking the time to pass that info along. I'll wade through it and learn something. I capisce.
 
The 3 lever classes extend to rope and pulley; but just as with hard levers(way i keep straight):
All cases look at stationary point as pivot and moving input/outputs of the simple machine.
If non moving pivot is between moving input/output(so input output MUST move in opposite directions see/saw): 1st class Lever
The other 2 classes have non moving pivot is on end/not between so moving input/output are in same direction;
only difference is:
2nd class lever has input arc farthest from pivot, concentrating denser force into smaller distance of output arc(slower speed in trade).
3rd class lever has input closer to pivot, so dilutes/ lessens power out to longer distance arc of output(faster speed in trade).
2nd/3rd difference imageries: 2nd class input arc outside, work output inside basket in between/carried will with more power; 3rd class load is outer arc/has leverage over inner input arcs
.
Rig pulls higher than support of trunk as both pivot and support, so 3rd class lever.
Higher line in opposite direction to bolster would give:
more 2nd class leverage power support ; placing load pull between stump pivot and rope support
AND arrange balance of pull directions more down the inline, roman column type support of support tree/ than across. (as stated)
.
i'd have a line higher for the back support, simply throwlined, reeving thru.
Target: Each leg of the line anchored even with start/stop position of load, equal and opposite direction at these focuses, then so covers sweep between.
.
Can pre load line some and let rig pull back support tree straight, and/or tighten support line, even pull this line perpendicular to leverage some as temp.support during process.
.
comparison : rope/pulleys as lever classes:
Same 1 non moving pivot and input and outputs both move.
1st class lever: pulley doesn't move, pull 1 end down, other end goes up
2nd class lever: 1 end doesn't move, pull other end, so input is farthest point form other end
>> gives 2:1 type lift on pulley/load as closer to stationary pivot/end
3rd class lever: 1 end doesn't move, pull on pulley, so input closest to non moving pivot and load on other end
>>loses 1/2 power/ gains 2x speed; pulley pulls equally against dead-end anchor/pivot and load
lever_classes.png

.

(until i figured these out, didn't really have it with power/distance as reciprocals)
10 speed bike example:
bike fastest when on largest front sprocket and smallest rear sprocket. WHY?(bugged me a long time)
Front sprocket input is pedal, cranks smaller arcs inside so concentrates power; is 2nd class lever
>>want to maintain speed, so don't concentrate input all the way to smaller sprocket losing speed.
>>use larger front sprocket to concentrate power least/maintain as much speed as possible
Transfer thru chain
Rear sprocket becomes input, tire is output/wider arc, so diluting power to more distance 3rd class lever
>>Go for smallest sprocket on rear to dilute power most to tire, which gives more speed!
Reason for largest sprocket in front yet smallest in rear for more speed: front is 2nd class lever, rear is 3rd.
Front sprocket: trying not to concentrate power in too much, rear: trying to dilute power to most distance.
.
Lose distance/gain power reciprocals so pervasive: bottle jack magic example
push down 2" into small cylinder to lift only 1/4" on large cylinder (oil more spread out inside) gives 8:1 !
.
i think of same volume of water in long aquarium, push 1 end glass towards other; water covers less distance but raises higher/more power on glass.
Same volume, nothing for free, just re-apportioned.
.
Soft rope or standard lever; i always look to use 1st class lever(equal/opposite direction lever) to see if can capture equal/opposite of effort and place against load again
.
 
Thank you to put a lot of your time in theses explanations.:thumbup:
Often, it isn't easy at all to word out some phenomenons. They seem obvious at first look because we see them since a long time, like a natural thing. But in fact not so much because we never have really though about it, leading to less than accurate applications or worse, misconceptions.
The difference in dampening by the rope elasticity's in srt or ddrt is an example.
Nice work on the levers :yes:
 
Back
Top