Interesting Biomechanics

[Bundle 2]

yes your going to say it is shear!

 

shear going at 45 degress due to fiber compression!

 

Umm...45* to what? 45* infact. Not 45* to the shear plane. Along the shear plane?

Guess I was thinking it "shear failure" as you rightly point out. I could argue with my shadow and win twice....

Compression forces but not compression failure, shear failure along shear planes ( not at 45* to anything (except o*))

This has me looking up a good explanation!

[Tony Croft aka hamadryad]

I believe a picture is appropriate!

 

[sean freeman]

In my limited understanding the 45 degree angle of these fibre buckles is indiciative of notch compression forces, buckles around a notch whos living and surounding fibres are aligned and optomised according to the design rules of nature.

 

The compression force is diverted in a 45degree angle according to the "force cone" theories/thinking tool of C. Mattheck. i think this buckling occurs in rapid grown trees competing to gain light and hieght, as is a classic for Eucs, this as I understand it requires some unbalanced investment in cellulose as aposed to lignin. This due to the over reaching of the balance between competing and succeding, strong, but only strong enough to stand but also compete. This leaves a weakness in the trees compression strengths as lignin is in lower supply hence the compression forces form these chequered patterns in the bark around the force lines of notches.

 

i hope I have explained myself in a readable and usable way! if not i will try again!

 

 

I think you have explained yourself well Hama, and the picture (which I have seen before in a slightly different form) is very good too:001_cool:...however in terms of explaining the small number of trees that exhibit this braided or chequered pattern I am not convinced that the description is completely accurate nor that the concepts of greater levels of cellulose over lignin satisfactorily describe what we are observing.

 

Hopefully in the next 12 months some funding will be gained to (amongst other things) enable microtomes to be cut of this 'braiding' and a clearer idea of how the cells might differ in crosssection can be gained.

 

i think this buckling occurs in rapid grown trees competing to gain light and hieght

 

Rate of growth may well be a big part in this, however many individual trees with this characteristic have established in open ground with insiginificant competition, trees (of the same species) in virtually identical growing conditions do not manifest the characteristic. Other (apparently) equally fast growing Eucs do not seem to manifest the patterning. It is reported in Hornbeam (A.Cowan) amongst other UK species...not sure that this species fits the criteria described?

 

I think there are a range of factors at play, cell structure is a big part of it no doubt. It is worth reminding ourselves that wood cells are by their physical construction (irrespective of lignin:cellulose ratios) much stronger in tension than compression, and that the pre-stressing of cells plays a critical role in maintaining structural integrity within the tree or its parts.

 

Cassian Humphreys is putting together an article for the Arbor Age mag here in Oz detailing his observations of what he has coined 'Braided Reaction Wood', I will direct him to this thread your thoughts will doubtless be of great interest to him as well.

[Bundle 2]

Mmm...consider the modifications that are present in reacti0n wood structure....On a cellular level, the design matrix within walls so named S1,S2 & S3 (Schwarze, Engels, Mattheck) This helical model is employed there. Presumably for strength..?

 

edit.."helical model" was a bad term but I think does illustrate it adequately...?

[Tony Croft aka hamadryad]

I honestly think, you are trying to overcomplicate what is to me, (and I am dumb) a simple matter.

 

but the revelations revealed within the research might be very interesting and prove me to be the flim flam man I am!

[David Humphries]

I believe a picture is appropriate!

 

[ATTACH]37519[/ATTACH]

 

 

 

and there was me thinking you were focussing on Claus at that moment, especially as he smiled specifically for you as he said......

 

"Ya sure, take zee picture my friend"

 

 

 

 

 

.

[Tony Croft aka hamadryad]

and there was me thinking you were focussing on Claus at that moment, especially as he smiled specifically for you as he said......

 

"Ya sure, take zee picture my friend"

 

.

 

LOL, taking photos of the slides ONLY!

 

its a way for me to mull over the stuff that I do not yet quite grasp fully and give me the time I need to think and maybe discover a few things rather than walk away so overwhelmed that my brain hurts and all is lost as soon as i walk out the door!

 

Claus told me that his greatest honor is to have his teaching reflected back at him, you have to admire the man when all he wants is to deliver the very best lesson and be sure you got it, and value from his teaching.

 

there are those that say he has an ego, but this is not true, he is a very humble guy i sincerely hope he doesnt stop doing this teaching, he is rather good at it.

[Bundle 2]

I honestly think, you are trying to overcomplicate what is to me, (and I am dumb) a simple matter.

 

but the revelations revealed within the research might be very interesting and prove me to be the flim flam man I am!

 

Not much anyone can say to that is there...!

[Tony Croft aka hamadryad]

Not much anyone can say to that is there...!

 

Well despite popular belief tim, i am well aware I am "overreaching" and having ideas "above my remit"

 

i would rather be engaged in what facsinates me and stimulates me mentaly, and look the fool, than sit at the back, silent, hoping no one will notice and ask me a direct question!

 

if i am wrong, I am wrong, but if i never "engage" how will i ever know or learn?

[sean freeman]

if i am wrong, I am wrong, but if i never "engage" how will i ever know or learn

 

Hama, we are all wrong most of the time when it comes to trying to interpret the complexities displayed in the trees we visit, Claus included....though I agree his seminars are thought provoking and very stimulating.

 

I firmly believe professional ego is one of the greatest obstacles to progress, that having been said, you have a group of Arbs here on this forum that share pictures and thoughts that (for me at least) reflect where I hope our profession should be heading:001_cool:.

 

It is a great relief to find that the small group of tree passionate people I mix with have a group of fellow travellors amongst the ranks of UK professionals:001_smile:.