bracing weak forks- inspired!

[Tony Croft aka hamadryad]

I have always wondered what we can do about the rigidity of bracing systems, this spec by JFL is insipred and I will be looking at ways to use/create this.

 

very nice

 

http://www.flac.uk.com/wp-content/uploads/2009/12/Compound-bracing.pdf

[TimberCutterDartmoor]

Like it; especially the last setup - figured out how it aims to compensate for wind sail - clever!

[Amelanchier]

We've seen these before somewhere on a thread by Bundle2. I appreciate the design aims but doubt the Y and Z rig systems are effective.

 

The Y seems intended to distribute the energy created by the roll of the limb? You could achieve this with less equipment by bracing before the union...

 

I can't see the Z rig functioning at all. It creates a pivot central to the sytem which acts on the limbs between points A & C (or B & D), problem is - the limb is attached to the tree and can't rotate around that axis. Pointless IMO.

[Tony Croft aka hamadryad]

We've seen these before somewhere on a thread by Bundle2. I appreciate the design aims but doubt the Y and Z rig systems are effective.

 

The Y seems intended to distribute the energy created by the roll of the limb? You could achieve this with less equipment by bracing before the union...

 

I can't see the Z rig functioning at all. It creates a pivot central to the sytem which acts on the limbs between points A & C (or B & D), problem is - the limb is attached to the tree and can't rotate around that axis. Pointless IMO.

 

The Y bracing system must surely just allow the two sub branches to move but without excessive movement, I mean to as far as the limit and fracture stress point. My only doubt is its ability to stop barn door fracture of the main union.

 

The Z sytem is going to be incapable of stopping barn door also but IMO it will assist in slowing down whilst still enabling sudden movemnets in high winds. as the pulleys and ropes work on each other they will have the effect of cushioning the force.

 

I think these are simple diagramatic examples, hence i said i would be looking at ways to make them work. I think there is a great deal of merit in a system that allows for a greater degree of natural movement for stresses to encourage adaptive growth and this needs some consideration before being written off and dismissed so easily Tony.

[Amelanchier]

As below

 

Where does the extra rope come from to allow movement?

Edited January 26, 2010 by Amelanchier

[Tony Croft aka hamadryad]

As below

 

Where does the extra rope come from to allow movement?

 

Yes all the distances increase! thats the whole point isnt it!

 

The rope moving through the pulleys?

 

Tensioned this system cant allow the limb to move so far as to creat fracture surely, and in any case it is taking out the "shock force" resonance or sudden upward then downward forces from big gusts would be well dealt with surley?

[Silver Back]

I would suggest that pulleys would encourage a twisting effect, Z appears just plain over complicated, 4 attachment points instead of 2, extra unnecessary cable just so you can put a cable in the wrong place, X I think should work in opposite pairs and Y has the potential to run through. These may work but doesn't look like a correct design for the job, only IMHO

[Tony Croft aka hamadryad]

I would suggest that pulleys would encourage a twisting effect, Z appears just plain over complicated, 4 attachment points instead of 2, extra unnecessary cable just so you can put a cable in the wrong place, X I think should work in opposite pairs and Y has the potential to run through. These may work but doesn't look like a correct design for the job, only IMHO

 

I never said the system was perfect! I said (in not so many words) that this needs to be looked at, developed further etc

 

Allowing movement in a bracing system simply has to be benificial as it allows for loads to generate "optimisation" growth. Due to the axiom of uniform stress (Claus mattheck) general bracing systems overly support the structure as the tree continues to grow in size they even support more as they tension. That has serious implications in bio mechanical loading points as the tree re adapts its growth with the support offered by cabling.

 

As i mention in another thread, and it appears others have been working on the idea for a long time too, the perfect solution, for some genus at least is to create or encourage natural grafts. beech trees are really good examples and have the highest potential to be gained due to thier propensity to included and weak "stazi ears" forks.

 

The bottom line is that no current bracing system is perfect, probably never will be a perfect system other than natural grafts, but i suggest that with further work, evaluation and application these basic designs have great potential.

 

JFL deserves a round of applause for at least going some way to moving this up a notch or two, I dont see anyone else having any (none natural) alternatives or better solutions, I stand to be corrected......

Edited January 26, 2010 by Tony Croft aka hamadryad

[TimberCutterDartmoor]

As below

 

Where does the extra rope come from to allow movement?

 

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?

[Tony Croft aka hamadryad]

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?

 

Thanks for making me see what tony means!

 

Tony, do you mean that there is little movement in the bottom attachment but greater at the higher point so asking where the extra rope/slack comes from. So as to increase the avaliable movement of the top portion.

 

i think i understand your issue with it, and im not wording it well! But i can see your point and get it. Your right too and I need to go away and speak to my rather ecelant and quiet mad engineering father!