Convert me from Natural crotch to Arbor block

Col2y · 12th March 2008, 10:47 PM

I use natural crotch because its simple and thats what ive been taught, but the more i look into it the more it looks like its the red headed step child of the arborist world

can anyone give me an arbor block 101 or links to one

anything and everything is appriciated because i have next to no experience with it

Cheers

Ekka · 13th March 2008, 03:52 AM

Both natural crotch and blocks have their uses.

Some trees/locations suit natural crotch whilst others are better with blocks.

Setting a block means climbing to the rigging point and then coming back down to cut lower limbs first. Also you can set more than one block, many combinations.

I do both, no hard and fast rules just a matter of what is best or fastest for the particular tree/site.

juniorgilman · 13th March 2008, 09:55 AM

I would be interested in hearing some pros & cons to using natural crotch or arborist block.

It would seem that on a prune job you would want to use the block for the same reason you use a friction saver on a climbing line.

I can also see not to climb to the top to set a block, if you don't have to for a smaller job or for the sake of time.

What are some of the other ups & downs?

quercus · 13th March 2008, 11:58 AM

there's no need to get to the top to set a block... throw at the highest crotch that seems good for your needs, pull a line through with a pulley and rigging line et voila. then secure the end to the base of the tree. Et voila... natural crotching and blocking at the same time. Best of both worlds...

George Hayduke · 13th March 2008, 12:34 PM

Quercus,

Floating false crotch works for rigging and climbing but this option demands a more complex understanding about rigging to mechanical disadvantage.

Take it away=

****

Minuses for natural crotch rigging=

Increased rope wear and quick deterioration
Unknown amount of friction generated by variety of tree bark
Unknown amount of friction generated by varitey of tree diameters
Limited to only natural locations

Pluses for using blocks and pulleys

Little rope wear
Known friction in block/pulley...theoretically zero
Since the friction is managed at the lowering device the groundies can make quick adjustments to take into account the estimated log/branch weight. The groundie can dial in the number of wraps very easily.
A sling can be choked anywhere on a bare stem/branch to locate the perfect rigging point

Ekka · 13th March 2008, 02:09 PM

Another big minus for blocks is the doubling effect of the load at the pulley.

If you do as Quercus suggests you actually 4x the load at the pulley.

If you use natural crotch then other than the initial dynamic load the force on the lowering point is the weight of the piece. Graeme McMahon rigs out large sections and takes the wraps up in the tree to prevent the doubling effect.

quercus · 13th March 2008, 11:51 PM

There's a time and place for everything ekka... But adjustable false crotching can be done...If the need arises and the opportunity is there, it saves some time and effort...

Ekka · 14th March 2008, 12:07 AM

Quote:

Originally Posted by quercus

There's a time and place for everything ekka...

Did I say there wasn't?

quercus · 14th March 2008, 03:39 AM

Quote:

Originally Posted by Ekka

Did I say there wasn't?

No ya didn't...

Ace Master · 14th March 2008, 04:24 AM

Yes,most of the time i natural crotch but you can set up pulleys block anywhere in the tree when needed(less rigging thinking with blocks),also we use the blocks alot with the grcs when lifting is needed. You must always be carful of the load forces, friction, Rope heat, tree limb stress, rigging point,crossing of ropes, and the tress heath.

jim1nz · 14th March 2008, 07:48 AM

Very good posts here. George, Ekka great.

Thought i would had, if your retaining the tree your rigging off, be sure to use a friction device as natural crotch rigging will absolutely hammer the cambium.

Also natural crotch rigging, taking wraps around the trunk with long ropes is a pain!

Some lowering systems twist ropes, especially wound laid ropes.

George Hayduke · 14th March 2008, 10:48 AM

Quote:

Originally Posted by Ekka

Another big minus for blocks is the doubling effect of the load at the pulley.

Before you walk away from that comment you need to elaborate. This isn't true.

The load on the rigging point will double even with natural crotches. Adding a block displaces friction but it doesn't change the load.

In GM's rigging he would wrap the down rope around the tree which displaces the friction, and the load, somewhat. It's too simplistic to say that the trunk wrapping eliminates the load...not actually true.

Pete Donzelli wrote an article about how more efficient blocks displace friction and it's effect on rigging.

Ekka · 14th March 2008, 02:50 PM

Quote:

Originally Posted by George Hayduke

Before you walk away from that comment you need to elaborate. This isn't true.

The load on the rigging point will double even with natural crotches. Adding a block displaces friction but it doesn't change the load.

In GM's rigging he would wrap the down rope around the tree which displaces the friction, and the load, somewhat. It's too simplistic to say that the trunk wrapping eliminates the load...not actually true.

Good point, maybe we need to expand on some techniques and variables.

In natural crotch rigging you will always have friction where the rope runs over the crotch. You'll know how much and how bad when you try to pull a load back up.

If you are wrapping up top as in this diagram always wrap from the top down or the branch outwards then toward the trunk. This will prevent the loaded line cinching the lowering rope and holding the load up.

When lowering in this fashion you will not be doubling the load at the rigging point, other than the initial dynamic shock if taking a head out etc once the load is fully braked and stopped the force on the tree is 1:1 or slightly higher depending on the wraps obviously. Here's where it gets interesting, if you are up in the tree and grab the lowering rope and lock it off up there or lower from up there then the force is a lot closer to if not exactly 1:1

However if the load was braked and held up (still, stopped etc) through a block it would be 2:1

And if it were through a suspended false crotch like Quercus says then it would be 4:1

newguy18 · 17th March 2008, 05:29 AM

I like using your method for lowering tops out.

I always thought there was more dynamic loading in natural crotch rigging but it sounds like theres less according to what i understand from ekka's post anyway.

Ekka · 17th March 2008, 05:52 AM

Dynamic loading.

Great question NG

I would say that there's more dynamic loading on the rope in natural crotch rigging than using a block.

When running through a block the load is absorbed by the rope over a greater length.

When the rope is through a natural crotch especially if wrapped as shown then there's a lot less rope to absorb the shock.

Now that's shock load on the rope not necessarily the anchor point, there's a difference.

In the Art & Science of Practical Rigging they put a dyno on the block to measure forces. Now on a well run piece the block still recorded a load of 7x weight of cut piece. In a locked off situation it went 11x

Now I assure you that if they could somehow measure the forces on the crotch of natural crotch rigging it wouldn't be so high and in a locked off situation not as high.

It would be possible to duplicate this theory and turn it into fact if I had a darn dyno.

On one example we tie the load to the dyno and dump it, that's a locked off natural crotch.

On the other we run the rope through a block to the ground and tie it off down there, the dyno is attached to the block and the tree then dump the same load same fall distance. I bet I know which will be worse, of course the one with the pulley coz of the doubling effect however as far as the rope is concerned there's a lot more of it to absorb the shock and could actually be less.

Is this making sense or do I have to go to paint shop?

Two things to consider, load on rope and load on anchor/crotch.

12th March 2008, 10:47 PM	#1 (permalink)
Col2y Gettin' motoring Join Date: Mar 2008 Location: ontario Posts: 13	Convert me from Natural crotch to Arbor block I use natural crotch because its simple and thats what ive been taught, but the more i look into it the more it looks like its the red headed step child of the arborist world can anyone give me an arbor block 101 or links to one anything and everything is appriciated because i have next to no experience with it Cheers

13th March 2008, 03:52 AM	#2 (permalink)
Ekka Eric Frei Administrator - Brisbane L5 (Dip) Hort Cert III Arb + some Join Date: Jan 2007 Location: Brisbane Posts: 5,664	Re: Convert me from Natural crotch to Arbor block Both natural crotch and blocks have their uses. Some trees/locations suit natural crotch whilst others are better with blocks. Setting a block means climbing to the rigging point and then coming back down to cut lower limbs first. Also you can set more than one block, many combinations. I do both, no hard and fast rules just a matter of what is best or fastest for the particular tree/site. __________________ 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

13th March 2008, 09:55 AM	#3 (permalink)
juniorgilman Gettin' motoring Join Date: Apr 2007 Location: Maidens, VA Posts: 35	Re: Convert me from Natural crotch to Arbor block I would be interested in hearing some pros & cons to using natural crotch or arborist block. It would seem that on a prune job you would want to use the block for the same reason you use a friction saver on a climbing line. I can also see not to climb to the top to set a block, if you don't have to for a smaller job or for the sake of time. What are some of the other ups & downs? __________________ Husky 385xp Husky 334t

13th March 2008, 11:58 AM	#4 (permalink)
quercus Afterburner is shakin' Join Date: Nov 2007 Location: belgium Posts: 414	Re: Convert me from Natural crotch to Arbor block there's no need to get to the top to set a block... throw at the highest crotch that seems good for your needs, pull a line through with a pulley and rigging line et voila. then secure the end to the base of the tree. Et voila... natural crotching and blocking at the same time. Best of both worlds...

13th March 2008, 12:34 PM	#5 (permalink)
George Hayduke Banned Join Date: May 2007 Location: Slickrock, USA Posts: 93	Re: Convert me from Natural crotch to Arbor block Quercus, Floating false crotch works for rigging and climbing but this option demands a more complex understanding about rigging to mechanical disadvantage. Take it away= **** Minuses for natural crotch rigging= Increased rope wear and quick deterioration Unknown amount of friction generated by variety of tree bark Unknown amount of friction generated by varitey of tree diameters Limited to only natural locations Pluses for using blocks and pulleys Little rope wear Known friction in block/pulley...theoretically zero Since the friction is managed at the lowering device the groundies can make quick adjustments to take into account the estimated log/branch weight. The groundie can dial in the number of wraps very easily. A sling can be choked anywhere on a bare stem/branch to locate the perfect rigging point

13th March 2008, 02:09 PM	#6 (permalink)
Ekka Eric Frei Administrator - Brisbane L5 (Dip) Hort Cert III Arb + some Join Date: Jan 2007 Location: Brisbane Posts: 5,664	Re: Convert me from Natural crotch to Arbor block Another big minus for blocks is the doubling effect of the load at the pulley. If you do as Quercus suggests you actually 4x the load at the pulley. If you use natural crotch then other than the initial dynamic load the force on the lowering point is the weight of the piece. Graeme McMahon rigs out large sections and takes the wraps up in the tree to prevent the doubling effect. __________________ 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

13th March 2008, 11:51 PM	#7 (permalink)
quercus Afterburner is shakin' Join Date: Nov 2007 Location: belgium Posts: 414	Re: Convert me from Natural crotch to Arbor block There's a time and place for everything ekka... But adjustable false crotching can be done...If the need arises and the opportunity is there, it saves some time and effort...

14th March 2008, 04:24 AM	#10 (permalink)
Ace Master Fly'n Join Date: Aug 2007 Location: Australia, Vic, Melbourne Posts: 222	Re: Convert me from Natural crotch to Arbor block Yes,most of the time i natural crotch but you can set up pulleys block anywhere in the tree when needed(less rigging thinking with blocks),also we use the blocks alot with the grcs when lifting is needed. You must always be carful of the load forces, friction, Rope heat, tree limb stress, rigging point,crossing of ropes, and the tress heath. __________________ The Mt Dandenong Ranges Tree Specialists

14th March 2008, 07:48 AM	#11 (permalink)
jim1nz Afterburner is shakin' Join Date: Jan 2007 Location: Tauranga, New Zealand Posts: 296	Re: Convert me from Natural crotch to Arbor block Very good posts here. George, Ekka great. Thought i would had, if your retaining the tree your rigging off, be sure to use a friction device as natural crotch rigging will absolutely hammer the cambium. Also natural crotch rigging, taking wraps around the trunk with long ropes is a pain! Some lowering systems twist ropes, especially wound laid ropes. __________________ SPEED ALWAYS FOLLOWS TECHNIQUE

17th March 2008, 05:29 AM	#14 (permalink)
newguy18 Tree World Icon Join Date: Jun 2007 Location: Live Oak Florida home of the crapiest trees you will ever see. Posts: 2,185	Re: Convert me from Natural crotch to Arbor block I like using your method for lowering tops out.I always thought there was more dynamic loading in natural crotch rigging but it sounds like theres less according to what i understand from ekka's post anyway. __________________ Have your say join us today. http://www.youtube.com/watch?v=Xzkd_m4ivmc http://www.youtube.com/watch?v=Xzfzb...eature=related http://www.youtube.com/watch?v=x-OqK...eature=related

17th March 2008, 05:52 AM	#15 (permalink)
Ekka Eric Frei Administrator - Brisbane L5 (Dip) Hort Cert III Arb + some Join Date: Jan 2007 Location: Brisbane Posts: 5,664	Re: Convert me from Natural crotch to Arbor block Dynamic loading. Great question NG I would say that there's more dynamic loading on the rope in natural crotch rigging than using a block. When running through a block the load is absorbed by the rope over a greater length. When the rope is through a natural crotch especially if wrapped as shown then there's a lot less rope to absorb the shock. Now that's shock load on the rope not necessarily the anchor point, there's a difference. In the Art & Science of Practical Rigging they put a dyno on the block to measure forces. Now on a well run piece the block still recorded a load of 7x weight of cut piece. In a locked off situation it went 11x Now I assure you that if they could somehow measure the forces on the crotch of natural crotch rigging it wouldn't be so high and in a locked off situation not as high. It would be possible to duplicate this theory and turn it into fact if I had a darn dyno. On one example we tie the load to the dyno and dump it, that's a locked off natural crotch. On the other we run the rope through a block to the ground and tie it off down there, the dyno is attached to the block and the tree then dump the same load same fall distance. I bet I know which will be worse, of course the one with the pulley coz of the doubling effect however as far as the rope is concerned there's a lot more of it to absorb the shock and could actually be less. Is this making sense or do I have to go to paint shop? Two things to consider, load on rope and load on anchor/crotch. __________________ 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

17th March 2008, 09:20 AM	#16 (permalink)
newguy18 Tree World Icon Join Date: Jun 2007 Location: Live Oak Florida home of the crapiest trees you will ever see. Posts: 2,185