# Side loading trees when rigging



## r/ctree (Nov 13, 2002)

While I was at TCI I watched a demonstration that was done at the tree where a limb was lowered with port-a-wrap tied to an opposing tree. It was not discussed that when you lower wood in this manner you have to decrease your load greatly. I have read accident reports where this style of rigging was done and the tree was broken and the climber died. I think that when anyone does demonstrations they should discus the types and kinds forces a load can place on a tree. Proper training needs to be stressed.It is extremely important that you learn all that you can about the forces that a tree will take in all of the rigging methods that are used. I know that time was short and they needed to show alot of different ways to do things but not informing people about life threating situations involved with the different methods is irresponsiable.


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## geofore (Nov 14, 2002)

*rigging*

Back to engineering and physics. What kind of trees were they? How heavy was the load and how was it rigged in? How high was it rigged in the trees. You are asking for structural integrity of trees or green wood. Hard or soft wood? With so little to go on at best it would be a guess. What was the diameter of the second tree at the TIP and were the roots sound? Even if you know all this it is still a guess but an educated one that is better than just trying it on no information.


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## TheTreeSpyder (Nov 14, 2002)

At tear off was the hitch under the support anchor? (Swing) Was line pre/ self tightened? (Impact force) Was there a pulley on Upper Support Anchor? (2x loadforce on support) Then, up to 2x that if line is draped over limb to retrievable and remotely retrieve pulley, for total of almost 4x load force impact on Upper Support Anchor. Were the lines on Support pair-allel or open to wider angle (less load on Support). Was the line allowed to run (through metal/heat disapating devices only)? (So that not all of loadforce was applied to support, hitch and braking) Load shared by other upper supports?


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## Tom Dunlap (Nov 14, 2002)

I was part of that demo. All three of us emphasized that the demo that we did was part of a "Theater of the mind". We demonstrated some basic techniques that solve problems.

At the beginning of the demo we suggested the everyone do more homework before taking on new skills. The Art and Science of Practical Rigging is the best place to start.

In an earlier demo Mahl covered rigging false crotches. In that presentation he talked about the loading of anchor points.

When Mahk, Robert and I put our heads together we decided to show many techniques and encourage people to do their homework. When we only have fifty minutes, we can't go into too much depth on any subject.

We were very careful to cut only small limbs so that we never overloaded any of our rigging.

This all speaks to the fact that our profession, in the US, is just starting to provide good quality educational opportunities for field workers. Like any education, the students need to go to school and make sure they have instructors that know all of what they're supposed to teach. 

I spent time with a friend from the UK looking over the training requirements that they have in place. In order to do a variety of arbo tasks, workers must go through standardized training and be certified. While Paolo and I were talking I told him that the "Wild West" attitude of the US will prevent this training and certifying to be accepted in the US for many years. Everytime a new rule comes into being from the government, there is incredible resistance from the workers. Sometimes Americans think that they can do as they please and any regulations infringe on some "right". Too bad, the program that the UK has in place seems like a good plan to keep arbos alive and healthy.

Off the soapbox and off to work!

Tom


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## Joe (Nov 14, 2002)

r/ctree;

You picked a contoversial discussion topic.
Don't be discouraged from bringing it up. 

If you believe the loading from the type of rigging is more risky than what would be considered safer and more conventional, your argument should be supported with the accident report data along with what you know about this type of rigging. Not every1 knows what you are talking about nor how well they can take your word about the issue. 

Excuses will never replace what could and should be discussed about rigging. Doing homework, figuring the equations which help lead to the rules of thumb we use daily, is most important. I see the seminars as providing a lead to what needs to be learned. I don't think seminars are ment to replace in depth training. If 1 cannot build on the material from the seminars, the seminars are not providing adequate leads. IMO there is a valid complaint if forces due to rope and block angles were not at least mentioned. 

For those who want to know more about rigging, and forces in rigging, The Art and Science of Practical Rigging videos will be the best tree rigging resource. The work book is also good. 

Joe


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## Kneejerk Bombas (Nov 14, 2002)

I can't comment on the TCI seminar because I didn't see the whole thing. I had noticed they had set up a mini speed line at one point though. It is a lot to do and explain in a short time.

I do agree with r/c that any time you are side loading a tree, it needs to be supported, usually with a guy rope or two. Setting up a speedline without a guy, should be a rarely used and considered a high risk technique for only the strongest trees and low, low rigging point.
It reminds me of a cambium saver, most guys try using one for the trees health and find out it's a heck of a lot easier to climb on one. That's how the guy rope worked it's way into my bag of tricks, I did it for safty a few times and found out how much better the speedline works with the tree guyed. 
I would no more consider a speedline without a guy, than I would a climb without a saddle.


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## Mahk (Nov 14, 2002)

r/c

Your point is well-taken. The possible danger of side loading a tree to the point of failure is a definite concern when using a speed line. This possibility was mentioned in the talk, but should perhaps have had more emphasis. I remember saying something like:

'If you wanted to fell this tree, then you might set things up in exactly this fashion. Put a rope high in the tree, anchor it to a distant point and apply some force/load to the rope. When using a speed line you have to be very careful not to dump loads into the speed line and not to overload the speedline with too big a piece.' 

Next time we should add more warnings and demonstrate catching a top with a lowering line and then transferring the load to the speedline. 

There is a lot to cover and some things will always be omitted, but issues of safety should be sparkiling clear. I appreciate constructive comments. Thanks.


Mahk


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## Kneejerk Bombas (Nov 15, 2002)

I noticed in that TCI set up the speedline itself was routed through a pulley, on the high end, then down to the base of the tree. 
Why was this done?
I wonder if the speedline was routed through the pulley, then back to an anchor point behind the tree, if this would be as good or better, than tieing it to the tree and tieing a guy rope.


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## Tom Dunlap (Nov 15, 2002)

Since Robert set up the rig, I can't address his reasons.

I think that the rope must have gone directly to the base of the tree since we didn't have any other option on the back side. That only changes the angle of the rope at the top redirect.

You're right I believe. This would put a deflection load as well as a compression load. A back guy or even a vertical guy would probably be a better option. 

You do have to admit though, considering what we put on the system, the limbs were so small that we were still within a good margin.

Thanks for the feedback. This helps us make better presentations next time.

Tom


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## Kneejerk Bombas (Nov 15, 2002)

Actually Tom, the tree at the show was guyed. It was tied to the ceiling girder. That probably wouldn't work as well on the job though.


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## Tom Dunlap (Nov 15, 2002)

Unless we can guy to a nearby cloud or Sky Hook 

Tom


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## John Paul Sanborn (Nov 15, 2002)

As long as you regularly admonish people to start low and slow (light n' slight??) when trying new rigging methods, you should be ok.

"learn how the different parts of the system react to the loads before you start putting big wood on. Remember (from the earlier session) that many techniques can multiply force to the anchor points."


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## r/ctree (Nov 15, 2002)

I talked to mark at the show about this peticular problem. I not saying that what you did was wrong. You guys did a wonderful job on your demos. What I saw hit home with me because I know that a climber died because he did noy know. The only way to educate is to study trees and the forces applied to them when rigging and teach other what has been learned. I have a question for you guys. Do you think that a 450 lb top can break a 13" tree four feet off the ground if the load line it anchored on a seperate tree trunk 25 ft away? I know the answer but what do you guys think. I want give out all that I know about this subject yet so maybe the disscussion can continue.


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## Stumper (Nov 15, 2002)

The fact that you posted these details implies that it did indeed happen. I can't imagine that happening on sound wood of most species without a high fall factor or some horrendous leverage factors. I look forward to hearing the details.


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## Tom Dunlap (Nov 15, 2002)

With enough drop, that 450# piece could put quite a load on the trunk. Combine that with some trunk defects and you have a failure.

What are the details?

Tom


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## geofore (Nov 16, 2002)

*load factor*

After a few days of rain I can see this load being dropped a few feet and the roots fail to hold and the whole tree comes up to greet you. If your lucky it will hang up on a lower limb and not knock you out of the tree. I was lucky and climbed down and cut the rope. You learn to pick on bigger trees and don't drop the tops, ease them out. Can you say EASE it out. You would not believe what the energy level is of the top after it goes six feet then tightens up.


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## TheTreeSpyder (Nov 16, 2002)

Loading a rig in a upsidedown "U" like that in a Skinny, flexable "boinging" trees, one to the other at the tops can pull the 2 together, especially when impact loaded, very esay to get tossed!


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## r/ctree (Nov 18, 2002)

If memory serves me right the piece fell close to nine feet. Which ended up putting over 85000 lbs of persure on the tree trunk. The tree was resisto graphed into swiss cheese but no flaws were found. The main reason That I wanted to post this was to inform others that good wood can break if you load it to much. You need to calculate you loads and use sound rigging practices and not experiment on the job before you have been properly trained in the climbing and rigging practices that you use. Alot of people say time is money but how much time is your life worth?


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## Joe (Nov 20, 2002)

> _Originally posted by r/ctree _
> *If memory serves me right the piece fell close to nine feet.*



How did the distance the piece fell get measured that 9 feet was the total distance of fall? Did the top that was rigged come from a different tree or was the top from the tree which broke? 



> *Which ended up putting over 85000 lbs of persure on the tree trunk.*



What was used to conclude there was 85,000 lbs of pressure which caused the tree to break?



> * The tree was resisto graphed into swiss cheese but no flaws were found. *



I can't see using a resistograph for this specific circumstance to detect flaws in the wood after a break like the 1 being described. Was it resistographed before it was rigged?

Joe


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## Tom Dunlap (Nov 21, 2002)

If you estimated an 85k load I'll bet that there was probably a higher load. At some point, any tree will fail. Even the most structurally sound and defect free trunk can only take a certain load.

Take smaller pieces.

Tom


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## r/ctree (Nov 21, 2002)

You guys bring up some excelent questions. Could any explain to me why having documented evidence of the structural integeraty of the tree was not need when doing an investigation? That was the closest educated guess from where the rigging and cuts were made. According to the guy on the rope the load did not run. the calculations were entered into a program which gave us the forces applied to the tree. the point I am trying to get across is how much will any given tree withstand before failure? If anyone has some answers for this let me know where you can find the specifis data and research.


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## geofore (Nov 21, 2002)

*sideload*

At best it is a guessing game you come to learn over time spent working in trees. Green wood will hold only 70% of what kiln dried holds under ideal conditions and can be as low as 30%. Dead wood is to be trusted at 30% to ZERO of good wood load, take your hammer up with you and tap the tree to sound it if you don't have a meter. Your question is a good one for a carpenter or mechanical engineer to answer on loads to wood but out in the field is much different. Go out to a treeline and you will see the trees have trunks that are oval not round and this is because they are growing to withstand wind forces upon them. Side loads would be different here because of shape. 
What will it hold also depends on are the growth rings tight or wide. Most important is what kind of tree are you tying into, hardwood or softwood. There is no difinitive answer to the question because there are so many variables to consider, a rough estimate is what you come up with and your life depends on making the right desicision, a tough call. 
You want to know something about bending moment, shear, deflection, stress and elastic theory.


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## Kneejerk Bombas (Nov 21, 2002)

Another thing to throw into the mix is that no arborist ropes can hold 85,000#s. 
The tree failed long before 85,000 lb.s.


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## Tom Dunlap (Nov 22, 2002)

You need to do some research on wood strength information. Foresters have all of that information already. The Forest Products Lab in Madison, WI would be the first stop.

I agree Mike, in order to have a rope that could withstand 85k, we'd be stealing the anchor rope off one of the ore boats up in Duluth/Superior 

Tom


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## murphy4trees (Nov 22, 2002)

8,500 lbs. sounds more like it for 450 lbs. dropping 9'.
Daniel


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## Stumper (Nov 22, 2002)

Hmmm.... Geofore, the bending resistance of green wood is lower than that of dry wood but the resistance to breakage?. Green wood can flex much further. It may even take a 'set' (permanent deformation) but the increased flexibility makes it more difficult to break (speaking in generalities).

I have been assuming(perhaps incorrectly) that the 85000 lb figure was supposed to be the stress at the location of failure. Dropping 450 lbs 9' won't yield 85000 lbs of force BUT if the force generated is transfered to the end of a lever (treetop) them the force at the opposite end of the lever could reach that quite conceivably. introducing leverage makes it possible to generate tremendous forces without breaking a rope of much lower tensile strength.

No offense intended but leaving aside the fact that a failure occurred, this whole scenario gives the impression of some very imprudent rigging.


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## geofore (Nov 22, 2002)

*imprudent rigging*

If this guy is rigging for the first time he will make a mistake or two. Green wood does have flexability but a sudden load may not give it time to flex that is where you stress ease it down. The TIP may be able to handle a load slowly but not suddenly. I'm sure that is why we have safe working load vs tensile strength on our equipment. You can expect it to handle the SWL all the time but not the sudden leap to max or over max load before failure. Guessing what wood will hold is at best tricky. A furmula that will always work for wood loads will not work as a hard and fast rule all the time because wood varies from tree to tree. 
I know from experience the trees I pulled down today would break in half when the roots broke loose or they would break just because one part of the tree can't go that fast and stay in one piece. The kind of thing that happens when you knock down a tall smokestack made of bricks. I've done that before also. Had the trees been green instead of dead they would fall down in one piece because they could flex, bend as they fall. Dead and punky they can't stand the strain and break in two or more pieces on the way down. 
It may not be imprudent rigging as much as not taking up the slack beforehand. The way it was rigged may have been right but letting the piece free fall 9' may have been where the whole thing went wrong. It would be like tying a blake and not dressing it. The knot was tied right but not dressed, the result would be a fall before sudden impact. Don't take up the slack and things go wrong. Would it have held if it were loading the rigging at 450# per second or 8,500# instantly? My money is on the slow loading vs instantanious load.


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## TheTreeSpyder (Nov 22, 2002)

How about a drawing? For i have had trouble getting the picture from the start and like to understand these things and their impact and lessons on all of our work.


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## Joe (Nov 23, 2002)

> _Originally posted by r/ctree _
> *You guys bring up some excelent questions. Could any explain to me why having documented evidence of the structural integeraty of the tree was not need when doing an investigation?*



The tree could have been dissected with a chainsaw to come to the same conclusion-no flaws present in the wood.



> *That was the closest educated guess from where the rigging and cuts were made.*



Anyone can make an educated guess. What one uses to make that guess is what is important.



> *According to the guy on the rope the load did not run.*



You weren't on the job when this occurred?
This would mean the information given is second hand knowledge and it isn't clear how far the load fell and how much it weighed. It is possible to know how far the friction device was from the tree. This doesn't mean if it were located on the same tree it wouldn't have broke.



> *the calculations were entered into a program which gave us the forces applied to the tree.*



How can we know the information was interpreted correctly? Is it a certainty pressure is what caused the tree to break?



> *the point I am trying to get across is how much will any given tree withstand before failure? If anyone has some answers for this let me know where you can find the specifis data and research. *



Perhaps this is a question being asked to the posters here. A few of the posters have already started working with what they know and are giving freely. They don't mind helping, they're proving it, and these guys are alright.

Joe


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## Joe (Nov 28, 2002)

There is enough data to support the idea side loading trees can cause structural failure in tree stems. Because of this fact
one also needs to be aware when a friction device is used to lower a load, one is side loading the tree no matter where that friction device is located. It's common sense when one takes large pieces, there is more of a chance for failure.

When a fricton device is anchored away from
the tree being rigged with the load hanging there and no motion, the block will point away from the stem, not down it's length. This is enough to show there is a side loading of the stem. The block points in the direction of the resultant tensions in the lowering line. The vertical component of this resultant force is what people will be thinking about when rigging.
Because it is there doesn't mean there is great danger of stem failure. If a large enough piece is removed, the stem will fail no matter where the friction device is located. 

The late Dr. Peter Donzelli (The Art and Science of Practical Rigging videos and workbook) had also addressed the issue of sling tensions from the resultant tensions of lowering lines. It can be shown through trigonometry along with empirical data, the actual tension of the rigging block sling is lowered by an increase in the angle made by the lowering line when the friction device is located away from the tree being rigged. What Dr. Donzelli warns us about is a couple is made on the stem when the sling angle points away from it.

Mike Maas guys his trees. His solution to prevent side loading is sound and for some a common practice. If one is afraid of side loading a tree when rigging, guy it.

Joe


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## TheTreeSpyder (Nov 29, 2002)

Sometimes we redirect off the base of the host tree with a block (so that the stress of the load/impact comes down columnar strength of the spar), to another anchor with the Porty ready. This keeps the Porty out of the way of the loads. And it is alot easier to pretighten across that horizontal waist level line, than vertically, for the so challenged especially!!

i believe in guying trees, even if Mike does!!! Also i believe in rigging tops in such questionable conditions (as i think we are speaking), perpendicular to the 'floppy' axis of the spar. What i mean is like perpendicular to it's lean, instead of just rigged of the 'normal' side of it's lean. If i am redirecting the rigging line around for gathered strength/ friction of several Upper Supports, i set the force of the pulls likewise, unless i just can't, or am looking to turn that 'floppiness' around to aid instead of hinder, and use it like a giant spring!

i think that the sideloading could be more severe if the pull was directed horizontally across or aslightly higher during the final snap on the spar's movement, to another redirect, from high angle support.


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## treeclimber165 (Nov 29, 2002)

> _Originally posted by Joe _
> * ........ It can be shown through trigonometry along with empirical data, the actual tension of the rigging block sling is lowered by an increase in the angle made by the lowering line when the friction device is located away from the tree being rigged....
> Joe *


I guess I knew this, but never really thought about it. I just assumed everyone knew this. It's really obvious if you are roping down limbs with your lowering line rigged through two separate crotches in a canopy. The higher crotch (with the tighter angle on the rope) will take more of the weight. If you think about it, a rope passing through a block at a 180* angle will have to hold 2X the weight of the limb being rigged (not counting impact loads). But a rope passing through a block in a straight line won't put any tension on the block at all. So therefore a rope passing through a block at a 90* angle will put a load on the block equal to the weight of the limb being rigged.

In this crude drawing, the higher fork on the right will take about 2/3 of the total load (4/3 the weight of the limb). The lower fork on the left will only take about 1/3 (2/3 the weight of the limb).


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## TheTreeSpyder (Nov 29, 2002)

i disect it like this whenst putting these rigs together:

Actual load percentages will depend on angles of lines on supports, nos. of supports, degree of support(running/hanging) and friction i think. 

Pulleys placing more load on overhead support anchors of the system, at same angles, as you can't beat the force of the load on the support system, you can only beat the reudced load on the control line, this is reduced by friction, which pulleys don't do. This is the only way i can see to reduce the total load on supports, from the force presented. 

After that it goes to spreading that presented total load over multiple supports, at X angles. The final fine tuning would be reducing load force by reducing impacting(speed and drop) and/or possibly running the load (so that it isn't all being supported). i think that those are the total variables to watch, after that, reduction in load mass input into the system would be final.

Of course; prestretching the lines to reduce impacting, 2/1, adding an extra line, leg on load etc. all plays into all that folding out of it. But i find that the above factors to be all inclusive of the diagnosis of forces and strategies presented in that day's puzzle.


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## Mahk (Nov 29, 2002)

> _Originally posted by treeclimber165 _
> If you think about it, a rope passing through a block at a 180* angle will have to hold 2X the weight of the limb being rigged (not counting impact loads). But a rope passing through a block in a straight line won't put any tension on the block at all.
> 
> These two staments are correct.
> ...


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## Joe (Nov 30, 2002)

> _Originally posted by treeclimber165 _
> *I guess I knew this, but never really thought about it. I just assumed everyone knew this. It's really obvious if you are roping down limbs with your lowering line rigged through two separate crotches in a canopy.*


 B.S.



> * So therefore a rope passing through a block at a 90* angle will put a load on the block equal to the weight of the limb being rigged.*



This is why Mark is correct about his statement that there will be 1.41 times the load on a sling with a 90° angle made with the rope by the block.

How one starts is sum(add) tensions from the vertical and horizontal components of each leg of line.

T=tension of the line.

sum=add

x=vertical component

y=horizontal component

The vertical components of each leg are:

(sum)[Tcos 180° + Tcos 270°] = T(-1)+0=-1

(sum)[Tsin 180° + Tsin 270°] = 0 + T(-1)=-1

T can represent any line tension which is =
to the weight of the load. I chose 1 for simplicity. It needs to be understood T is the same for both vertical and horizontal components in this example.

What we're interested in knowing is the tension of the sling attached to the lowering block. This means we need to know the resultant tension along with the angle the resultant tensions make with the rigging block sling.

To do this we use the pythagorean theorem
to sum the 2 components we found earlier.

R=resultant force or in this case tension.

^2=the power of 2 or squared

sqrt=square root

The formula we use to find the resultant tension is R^2=x^2+y^2 and R=sqrt(x^2+y^2) Therefore:

R^2=(-1)^2+(-1)^2

The square of a negative # is a positive #.

R^2=1+1

R^2=2

Take the square root of both sides of the equation to get:

sqrt(R^2)=sqrt(2)

The square root of a square, like that of R, is simply R. Therefore

R=sqrt(2) and sqrt(2)=1.41

Therefore R-the resultant force or tension- is 1.41. This is the tension of the sling attached to the rigging block.

To find the angle the sling makes due to the tensions in the line, take the inverse tangent of the vertical components divided by the horizontal components.

tan^(-1)[(-1)/(-1)]=45°+180°=225° which is a 3rd quadrant angle because both x and y components are negative. Otherwise, a rope which makes a 90° angle through a block will make a resultant angle of 45° which is an equal distance between the 2 legs. 



> *In this crude drawing, the higher fork on the right will take about 2/3 of the total load (4/3 the weight of the limb). The lower fork on the left will only take about 1/3 (2/3 the weight of the limb). *


 Watch making these kind of statements till they're correctly understood.

Joe


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## Kneejerk Bombas (Nov 30, 2002)

> _Originally posted by Joe _
> * B.S.
> *



I like your style... but disagree. Anyone who has used 2 blocks in a tree knows this.



> _Originally posted by Joe _
> * Watch making these kind of statements till they're correctly understood.
> *



Do you carry a laptop into the tree with you and do the math before each cut? Common sense and good intellectual intuition trump a math whiz in a tree anytime.


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## Joe (Nov 30, 2002)

> _Originally posted by Mike Maas _
> *I like your style... but disagree. Anyone who has used 2 blocks in a tree knows this.*


 :Eye::Eye: 




> *Do you carry a laptop into the tree with you and do the math before each cut?*



This would be ideal. I read an article in TCI magazine titled "Opposing Pendulums".
In this article a guy put together 1 or more removals where he did use a laptop computer to figure line tensions, weights and other junk. I can't state for fact it was before each cut, but he used one to do the job. Imagine the stuff one could learn doing this daily for awhile.




> *Common sense and good intellectual intuition trump a math whiz in a tree anytime.*



Well, I really am trying to make a point. A guy can get himself into trouble if the limits are pushed based on this type of thinking. There is an approach one can use to come to correct conclusions. Correct conclusions = more efficient use of resources. The math in that specific post is a tool that will help overcome the incorrect conclusion of the sling tension *"if"* one decides to believe it to give a correct conclusion. I believe what I learned through the math in that post to be true. So do many other people. There may be a time when some person did something based on their intuition without support of the math that gets them into serious trouble, like when underestimating sling tensions based on intuition. One needs to be careful with what they know or don't know. Safety can be thrown into this argument. 

:angel:


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## Joe (Nov 30, 2002)

> _Originally posted by TreeCo _
> *It's been twenty five years since I've done vector analysis.*



It's sort of refreshing and conjures up old memories eh?



> *If the load were 100 lbs. the load pulley would have a load of about 183 lbs.*



I found about the same resultant tension. A chart in the book On Rope labels the resultant as 185% of the load. 



> *The redirect pulley would have 70.7 lbs.*



Well, it's really 76.5 lbs. On Rope states it's 77% of the load which would make it 77 lbs.  When natural crotch rigging these figures will change dramatically.



> *Using two pulleys in this fashion changes the angles of the forces in directions in which the tree would be expected to be stronger if the tree has no defects.
> 
> 
> 
> ...



I'll buy this statement.

Joe


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## TheTreeSpyder (Dec 1, 2002)

Well, wee kinda ain't in the tree now!

i think that the math in the tree is kinda extreme for my taste, i generally am interested in tendencies and ranges for competant aproximations and understanding what kind of support, steering and brakeforce is needed for a particular path and how the line can be laced to what available points to maximize the grace-full overpowering of a giant, and the lessons learned there in. These approximations are then worked with a 8-10+/1 Safety Factor.

But, on the ground i think that we could investigate the numbers to make sure that all on occasions they backup the men-tall images that we guide our decisions by. Joe leaves me behind on the numbers a lot(which i used to think i was gifted at!!), but then he is whom i will turn to ask something before running my mouth! (Well sometimes); even if i end up not agreeing, i still listen and try to digest all that he says!

If you start with a pulley support directly at the center of the clock, and the tie off back to the load itsef; the Support Load is = to the load (all supports terminate at the load and support only). Detatch the control line from the load and hold it @6o'clock (next to the load). The Support Load is now 2x load! The support, now has 2 pulls on it, the load line and the control line pulling down, with a pulley (no friction), the control line must match the load; so the load is the force pulling on the OverHead Support, with 2/1 leverage! As the angle between the load and the control line opens up from 6o'clock to 12o'clock; that plley in the center of the line goes from bearing 2xload to 0#, depending on the angle of bend around the pulley! 

These figures are for non frictional supports, slide friction in, and the control line load lessens, thereby reducing Support Load, control line load can be reduced to 0 with total brake force of friction = to load; thereby reducing Support System Load to = Load


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## Joe (Dec 1, 2002)

> _Originally posted by TheTreeSpyder _
> *Well, wee kinda ain't in the tree now!
> On the ground we can investigate the numbers to learn on all occasions the numbers backup the men-tall images for which to guide our decisions.*



This is doing homework. We don't do homework in the tree. We adjust what we learned on the ground in the tree. It looks like the Spyder made a bigger web to capture more informaton. 

It's funny a TreeSpyder would climb a tree, make a web, then disassemble that support I thought Spyders would use to make a web to capture food. I think we have encountered the 1st TreeSpyder that eats the actual tree itself.  

Joe


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## r/ctree (Dec 8, 2002)

It seems to me that so of you think that accident site investigation is totaly inaccurate. I not going to be able to point out all of the good and logical statements made by all of you and reply to them . You guys make some excelent points about loads angles and friction. The guy in question will never be able to learn form his mistake ( DOA ). Thats why I started this thread and have deen working on a load calculation program. Just for all the SA out their my dad has been helping me with some of the cal because he has a mechanical and structural eng degrees. When you start looking at what is involoved with figuring out all the forces that are applied it gets complicated quick. what I am looking for is a way to scientifically back up the so called commen sense approach to tree work that we all use daily.


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## TheTreeSpyder (Dec 10, 2002)

> _Originally posted by r/ctree _
> *When you start looking at what is involoved with figuring out all the forces that are applied it gets complicated quick. What I am looking for is a way to scientifically back up the so called commen sense approach to tree work that we all use daily. *



Well, i'm with that! Fact is, i've been waiting for others to say so, for it A)Would so obviously be in everone's best interest and B)It seems that a number of us are trying to all ways and always do the same thing. Let alone, individual passions!

i think that the first thing to do would be just to name all of the adjustable elements, and static ones. In the end, all we are doing is guessing in the field, doing that more knowledgeabley is the way to go! Generally, i think that it comes down to an experienced craftsman, assessing and polishing up the most strategic points of power and weakness in a rig, to strategically increase the most positive chances for success. 

Usually, i learn the most running everything tweaked to maximum, then stand to witness the first componenet alteration/failure and it's resultant output to test my presently running understanding against. Work in Progress!


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## r/ctree (Dec 11, 2002)

I total agree know matter how much we can prove with math it will always be a guess. If we learn more about what we do we can never go wrong whrn doing that. If anyone has websites or e-mail for contacts or information about tree strengths (capacities) it would be appreciated. It would help me with my project.


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