Doubling effect at pulley block

Angus · 19th March 2007, 08:06 PM

You've seen that footage??? When?

Ekka · 20th March 2007, 02:40 AM

I been, I seen twice and I sat front row.

He had Scotty there for demo, and he showed video of the log levitating technique using the blue and red ropes off other trees with dynamometers for tensioning and lift the log off the cut and moving it away. Very impressive mathematics, which I believe he also takes a lap top and crunches the numbers.

Where, GreenX Sydney maybe 2003 region.

He also displayed the wire core flip line that near cost him his life as the wire broke but he decided to use 2 flip lines. I mentioned to him (he may have forgotten) that it's a design flaw and all those wire core flip lines should be recalled and binned. I also believe he lost a friend or fellow worker to a big regnans, the guy fell. I'm not sure if that's flip line related or not.

I get my flip lines made, I use New England blue highV. They pull the blue core out and shove in 1/4" dia stainless wire. They then place the lot around a thimble and crimp it plus stitch it. Far safer.

I have shown this to many arb people and shops but to this day no-one gives a chit and the flip line where the wire core does all the flexing is still on sale by large "reputable" manufacturers.

If there was ever a person to change this procedure it would be Graeme with that flip line he has as evidence. The reason why this happens is because like getting a piece of wire and for ever bending it back and forth it eventually breaks ... same with his because he's climbing those large trees he advances his flip line with the wave technique, this puts a lot of stress on that wire core (and it's stiff wire) right where the thimble is, and it's only the wire that is there no rope.

I have put a pic of mine so you understand, mine is wire cored but not so stiff.

Angus · 20th March 2007, 07:32 AM

Ah righto, I had no idea!

Interesting stuff about the fliplines... The guy I reakon your talking about is Allistair Murray (sp?) I know he fell, I'm not sure in what circumstances though.

I hear what your saying about the fliplines. Does it cost you much extra to get that kind of work done?

Ekka · 20th March 2007, 01:14 PM

It costs maybe $80 a flip line depending on length, the guy can do any length you like, that includes the swaging etc.

TREE-SURFER · 20th March 2007, 04:07 PM

Ekka, you should sell them on Ebay, We're paying like 95 GBP's for a 3M flipline

TrevMcRev · 21st March 2007, 02:49 AM

Interesting refinement on the flipline ekka. If i cant find someone down here to that do you reckon i could get one made and sent down?

Ekka · 21st March 2007, 04:05 AM

Trouble is they're not tested or certified, like we'd have to get a few and test them then rate them wouldn't we?

They are a lot more pliable, they react more like natural rope so some people dont like them because of that ... I do as it's better on palm fronds and tighter bends, then again, I used one of the stiff ones not long ago and didn't like it, sort of had a mind of it's own.

Trev, what sort of adjuster do you use? Gibbs, Petzel, Moxham?? In other words can the flip line be made and you fit the adjuster later? You just cant do that with a moxham, that's got to be fitted when it's made.

If you use a snap hook that's gotta be fitted also when it's made.

Trev, if you want one just send me the required length of New England High Vee + 200mm for swage crimp, thimble and snap etc.

DBS · 2nd October 2007, 02:29 PM

I found a quick online calc for snatch block loads.

Thought I'd share.

Snatch Block Rigging Calculator

-Daryl

redstree · 17th October 2007, 06:09 AM

Quote:

Originally Posted by Ekka

Common scenario where a block is installed up the tree and you are lowering sections out.

The force at the block is double whatever the weight of the section is ... that's not taking into consideration friction or any dynamic loading if the section was falling.

Imagine you cut off a 100lb section. To stop it hitting the roof you need to apply force to the other end of the lowering rope ... if you apply 100lb then the section is stopped. So you have a 100lb on one side to stop it coming down and you have the weight of the section which is another 100lb. Total is 200lb on the pulley block.

Here's a quick sketch to illustrate.

It is because of the doubling of the load on the suspended block that I always recommend using rope or webbing slings that are double the SWL of the load bearing line. Sometimes this is not easy due to the construction of some of the blocks. They are not wide enough at the suspension point to fit the larger size rope, especially one covered with and extra layer to help prevent wear.

Ekka · 17th October 2007, 12:45 PM

The alternative which I do is a loop of rope, doubled rope.

Or have a really large eye spliced so when cow hitching to tree two parts of rope are at work.

I dont use whoopie slings but there's an option too.

Vector Tree · 10th February 2008, 07:23 AM

Forces are vectors, since they have a definite size and direction.
The direction of a vector determines which way a force is
acting. Since a rope can only support a load along its length,
the rope indicates which way the force is acting. If we turn a
rope through a pulley, the force is now acting in two directions?
the direction of each leg of the rope. The resulting force
on the pulley now depends on these two component forces and
the angle the rope enters the pulley. These two component
forces create a single force that would cause the pulley to move
toward the middle of this angle if it were free to move, much
in the way a bow and arrow works .
Why is this important in tree rigging? Well, if we can manage
to direct the force exerted on the block to act along the
length of a tree leader, as opposed to across the grain horizontally,
we utilize the natural columnar strength of the tree, which
can give us a greater working load limit. Everyone should understand
how a 2-inch diameter limb is much easier to break if
we step on its middle instead of standing it upright and stepping
on it end to end. It would be nearly impossible to break.
We can mimic this in the tree by incorporating more than one
block into our rigging.
In order to calculate the load on a block, we need to determine
two things: the load on the rigging line and a
block-loading factor. This loading factor is determined by the
angle by which the rope is deflected by the block. The angle
that we are referring to is not the angle between the two legs of
rope, but the angle between an imaginary line drawn straight
through the block from the load, and the leg of rope entering
the block from the friction device.
The greater the angle created by the block, the greater the
resultant force placed on that block. For example, a block that
turns a rope 180 degrees will see a load equal to twice that of
the load on the rope itself. Conversely, a line that enters the
block at 0 degrees or runs straight through the block would
create a resultant force of zero on that block. In the middle of
the road, we have a 90-degree angle. The block-loading factor
of a right angle would be 1.41 times the weight of the load.
How can this be useful in our day-to-day operations? We
can create lesser pulley angles on smaller rigging points or
structurally compromised parts of the tree and use a second
pulley to create a larger angle at a more beneficial spot to support
more of the load. This can be very useful when dealing
with co-dominant stems and other structural flaws. The rigging
line itself can act as a temporary cabling system to lace the
stems together.

Angle of Deflection Load Multiplier
30 o .52 x Load (L)
45 o .76 x (L)
60 o 1.00 x (L)
75 o 1.22 x (L)
* 90 o 1.41 x (L)
105 o 1.59 x (L)
120 o 1.73 x (L)
135 o 1.85 x (L)
150 o 1.93 x (L)
160 o 1.97 x (L)
180 o 2.00 x (L)
* Example: 90 o Rope
angle with 500 lb. load = 705 lbf. on Block
RESULTANT FORCE
ON BLOCK...

redstree · 10th February 2008, 05:28 PM

Well done! Very well explained.

Vector Tree · 10th February 2008, 05:58 PM

Thanks redstree, I saw ekkas drawings of the rope and pully, he has two drawings both with a load applied to a block but with diff rope angles through the block. his drawings are very illustrative but i just wanted to show actual forces due to diff rope angles. I have a degree in civil engineering so if you ever have a question just write.

treevet · 17th February 2008, 04:42 AM

[img]DSC00027[/img]
[img]DSC00028[/img]
[img]DSC00034[/img]

Just wanted to show a little unusual plug in friction device.

Sean Freeman · 17th February 2008, 05:30 AM

Hmmm your pics don't show up

Treelore · 17th February 2008, 07:48 AM

I cannot stand wire core flip lines. Have always been a cumbersome attribute to the climbing assembly. Seeing as the topic is crotches I have read through but noone has mentioned if it is only take downs. I hope we are not lowering limbs through crotches from trees to be retained????

20th March 2007, 07:32 AM	#28 (permalink)
Angus Gettin' motoring Join Date: Mar 2007 Location: Victoria, Australia Posts: 16	Ah righto, I had no idea! Interesting stuff about the fliplines... The guy I reakon your talking about is Allistair Murray (sp?) I know he fell, I'm not sure in what circumstances though. I hear what your saying about the fliplines. Does it cost you much extra to get that kind of work done? __________________ www.sherbrooketreeservice.com

20th March 2007, 01:14 PM	#29 (permalink)
Ekka Eric Frei Administrator - Brisbane L5 (Dip) Hort Cert III Arb + some Join Date: Jan 2007 Location: Brisbane Posts: 5,664	It costs maybe $80 a flip line depending on length, the guy can do any length you like, that includes the swaging etc. __________________ Remember to use the "search" function, if you have answers/questions post them so everyone can benefit. Free Tree and Green Industry Link Directory Qualified Brisbane Tree Lopping Brisbane Tree Care, Consultations and Arborist Reports Forum Sponsors

20th March 2007, 04:07 PM	#30 (permalink)
TREE-SURFER Afterburner is shakin' Join Date: Feb 2007 Location: Isle of Man,UK. Posts: 401	Ekka, you should sell them on Ebay, We're paying like 95 GBP's for a 3M flipline __________________ The Aerial Arborist Isle of Man Tree Surgeon\| All Aspects of Tree Work Andy@Aerial-Arborist.co.uk What experts say about TOPPING

21st March 2007, 02:49 AM	#31 (permalink)
TrevMcRev Astronaut Join Date: Feb 2007 Location: Melbourne, Victoria, Australia. Posts: 670	Interesting refinement on the flipline ekka. If i cant find someone down here to that do you reckon i could get one made and sent down? __________________ Melbourne Arborist, Total Tree Care, Pruning, Tree and Stump Removal

21st March 2007, 04:05 AM	#32 (permalink)
Ekka Eric Frei Administrator - Brisbane L5 (Dip) Hort Cert III Arb + some Join Date: Jan 2007 Location: Brisbane Posts: 5,664	Trouble is they're not tested or certified, like we'd have to get a few and test them then rate them wouldn't we? They are a lot more pliable, they react more like natural rope so some people dont like them because of that ... I do as it's better on palm fronds and tighter bends, then again, I used one of the stiff ones not long ago and didn't like it, sort of had a mind of it's own. Trev, what sort of adjuster do you use? Gibbs, Petzel, Moxham?? In other words can the flip line be made and you fit the adjuster later? You just cant do that with a moxham, that's got to be fitted when it's made. If you use a snap hook that's gotta be fitted also when it's made. Trev, if you want one just send me the required length of New England High Vee + 200mm for swage crimp, thimble and snap etc. __________________ Remember to use the "search" function, if you have answers/questions post them so everyone can benefit. Free Tree and Green Industry Link Directory Qualified Brisbane Tree Lopping Brisbane Tree Care, Consultations and Arborist Reports Forum Sponsors

19th March 2007, 08:06 PM	#26 (permalink)
Angus Gettin' motoring Join Date: Mar 2007 Location: Victoria, Australia Posts: 16	You've seen that footage??? When?

2nd October 2007, 02:29 PM	#33 (permalink)
DBS Fly'n Join Date: Jul 2007 Location: CT USA Posts: 196	Re: Doubling effect at pulley block I found a quick online calc for snatch block loads. Thought I'd share. Snatch Block Rigging Calculator -Daryl

17th October 2007, 12:45 PM	#35 (permalink)
Ekka Eric Frei Administrator - Brisbane L5 (Dip) Hort Cert III Arb + some Join Date: Jan 2007 Location: Brisbane Posts: 5,664	Re: Doubling effect at pulley block The alternative which I do is a loop of rope, doubled rope. Or have a really large eye spliced so when cow hitching to tree two parts of rope are at work. I dont use whoopie slings but there's an option too. __________________ Remember to use the "search" function, if you have answers/questions post them so everyone can benefit. Free Tree and Green Industry Link Directory Qualified Brisbane Tree Lopping Brisbane Tree Care, Consultations and Arborist Reports Forum Sponsors

10th February 2008, 07:23 AM	#36 (permalink)
Vector Tree Gettin' motoring Join Date: Dec 2007 Location: florida Posts: 11	Forces are vectors, since they have a definite size and direction. The direction of a vector determines which way a force is acting. Since a rope can only support a load along its length, the rope indicates which way the force is acting. If we turn a rope through a pulley, the force is now acting in two directions? the direction of each leg of the rope. The resulting force on the pulley now depends on these two component forces and the angle the rope enters the pulley. These two component forces create a single force that would cause the pulley to move toward the middle of this angle if it were free to move, much in the way a bow and arrow works . Why is this important in tree rigging? Well, if we can manage to direct the force exerted on the block to act along the length of a tree leader, as opposed to across the grain horizontally, we utilize the natural columnar strength of the tree, which can give us a greater working load limit. Everyone should understand how a 2-inch diameter limb is much easier to break if we step on its middle instead of standing it upright and stepping on it end to end. It would be nearly impossible to break. We can mimic this in the tree by incorporating more than one block into our rigging. In order to calculate the load on a block, we need to determine two things: the load on the rigging line and a block-loading factor. This loading factor is determined by the angle by which the rope is deflected by the block. The angle that we are referring to is not the angle between the two legs of rope, but the angle between an imaginary line drawn straight through the block from the load, and the leg of rope entering the block from the friction device. The greater the angle created by the block, the greater the resultant force placed on that block. For example, a block that turns a rope 180 degrees will see a load equal to twice that of the load on the rope itself. Conversely, a line that enters the block at 0 degrees or runs straight through the block would create a resultant force of zero on that block. In the middle of the road, we have a 90-degree angle. The block-loading factor of a right angle would be 1.41 times the weight of the load. How can this be useful in our day-to-day operations? We can create lesser pulley angles on smaller rigging points or structurally compromised parts of the tree and use a second pulley to create a larger angle at a more beneficial spot to support more of the load. This can be very useful when dealing with co-dominant stems and other structural flaws. The rigging line itself can act as a temporary cabling system to lace the stems together. Angle of Deflection Load Multiplier 30 o .52 x Load (L) 45 o .76 x (L) 60 o 1.00 x (L) 75 o 1.22 x (L) * 90 o 1.41 x (L) 105 o 1.59 x (L) 120 o 1.73 x (L) 135 o 1.85 x (L) 150 o 1.93 x (L) 160 o 1.97 x (L) 180 o 2.00 x (L) * Example: 90 o Rope angle with 500 lb. load = 705 lbf. on Block RESULTANT FORCE ON BLOCK...

10th February 2008, 05:28 PM	#37 (permalink)
redstree Gettin' motoring Join Date: Oct 2007 Location: USA Posts: 23	Re: Doubling effect at pulley block Well done! Very well explained. __________________ Drive a MINI, the most fun you can have with your trousers on.

10th February 2008, 05:58 PM	#38 (permalink)
Vector Tree Gettin' motoring Join Date: Dec 2007 Location: florida Posts: 11	Re: Doubling effect at pulley block Thanks redstree, I saw ekkas drawings of the rope and pully, he has two drawings both with a load applied to a block but with diff rope angles through the block. his drawings are very illustrative but i just wanted to show actual forces due to diff rope angles. I have a degree in civil engineering so if you ever have a question just write.

17th February 2008, 04:42 AM	#39 (permalink)
treevet Astronaut Join Date: Dec 2007 Location: Cincinnati Posts: 598	Re: Doubling effect at pulley block [img]DSC00027[/img] [img]DSC00028[/img] [img]DSC00034[/img] Just wanted to show a little unusual plug in friction device.

17th February 2008, 05:30 AM	#40 (permalink)
Sean Freeman PDF King & Arborist Extrodinaire Join Date: Feb 2007 Location: Townsville Nth Queensland & Gold Coast Sth Queensland Posts: 1,521	Re: Doubling effect at pulley block Hmmm your pics don't show up __________________ Sean Trees are poems that earth writes upon the sky, We fell them down and turn them into paper, That we may record our emptiness. - Kahlil Gibran

17th February 2008, 07:48 AM	#41 (permalink)
Treelore Banned Join Date: Feb 2008 Location: Brisbane Posts: 117	Re: Doubling effect at pulley block I cannot stand wire core flip lines. Have always been a cumbersome attribute to the climbing assembly. Seeing as the topic is crotches I have read through but noone has mentioned if it is only take downs. I hope we are not lowering limbs through crotches from trees to be retained????