bracing weak forks- inspired!

[sean freeman]

If the concern (which led JFL to suggest these compound bracing options) was to reduce the likelihood of creating an un-natural fulcrum along the lever arm that the limb represents then I wonder why the existing dynamic cabling systems are not seen as adequate?

[Tony Croft aka hamadryad]

http://www.tree-consult.org/images/pdf/eng/BracingISA.pdf

 

You mean like these?

[sean freeman]

Yes, they write good specs those Germans eh:sneaky2:

 

If you get the opportunity try to get hold of the German standard or BMP (not really sure what they call it:blushing:) relating to dynamic cable bracing... when I used to get paid to climb and do such things had the chance on a number of occaisions to work for a chap who was familiar with dynamic cabling specs.

 

In fact the last few commercial climbs I did were to install fall arrest/redirect systems into tree canopies something I really think should be utilised far more especially when confronted with veteran trees and high occupancy targets that cannot (or will not) be altered.

[Tony Croft aka hamadryad]

Yes, they write good specs those Germans eh:sneaky2:

 

If you get the opportunity try to get hold of the German standard or BMP (not really sure what they call it:blushing:) relating to dynamic cable bracing... when I used to get paid to climb and do such things had the chance on a number of occaisions to work for a chap who was familiar with dynamic cabling specs.

 

In fact the last few commercial climbs I did were to install fall arrest/redirect systems into tree canopies something I really think should be utilised far more especially when confronted with veteran trees and high occupancy targets that cannot (or will not) be altered.

 

Are you consulting sean? you certainly know your bunions! good post, never really thought about cables as a means to redirect a failure, is that what you meant?

[Amelanchier]

Isn't it assuming some degree of flex between the two points on the limb. Upper one goes out pulling lower one in? Initial flex increased but whole limb more controlled?

 

Yep. The closer the two attachment points on the target limb the less of a moment is generated around the pivot for a given force.

 

However, is this a good way for a limb to be moving? I don't think so. With a well spread out system (which I presume was the intention) the forces generated at point C could lead to failure. Which, I'd suggest, is not the point of bracing the tree...

Edited January 26, 2010 by Amelanchier
punctuation

[Amelanchier]

This is of course presuming conventional textile bracing cordage without shockabsorbers. Stick some stretch in the system and it might be a runner...

 

Edit: Nah changed my mind, - even with shockabsorbers to reduce peak loads and an average 10% cordage stretch, it's still a bad idea.

Edited January 26, 2010 by Amelanchier
in post

[paradise]

Tony I had the same thought when I saw the Z-brace - there's no space for movement in the system so what is the point of the pulleys? Potentially worse than useless in that it could be overly restrictive of movement.

 

The others look quite interesting though.

[sean freeman]

Are you consulting sean? you certainly know your bunions! good post, never really thought about cables as a means to redirect a failure, is that what you meant?

 

Thanks Hama, yes consulting is what I do for a dedicated company based in SE Qld in a suburb called Miami (which might seem weird except when you see the kind of canal estates that have totally destroyed the original ecosystem that was here before!)

 

Redirect is as you rightly deduced, intended to in the event of catastrophic failure catch and pull the (usually vry large) limb into a preferred area....normally against the stem.

 

I have attached some vry poor pics (sorry I was not there to inspect the system) of a redirect installed to manage the potential failure in half of a large veteran Lophostemon confertus. The tree has two co-dominant leaders frowming a very attractive rounded canopy but has a massive fire injury through almost 30% of the stem under one of the leaders and a visble crack extending up through the union. From memory it has twin 8 Ton Cobra linking the weakened half to the structurally sound half.

 

 

 

 

[Tony Croft aka hamadryad]

All good stuff, i shall reserve jugdment on the pulleys and potential for movement thing till Ive had time to really think about the possabilities, with a lot of help from dad!