Fibre buckling or constriction - Opinions Please

[daltontrees]

Well you did ask.

 

Unfortunately the scan is upside down again. Can't seem to fix it.

 

First and second page fairly self explanatory, interestingly Wagener and Mattheck arrive at the same result (see end of second page) about the critical value for strength loss.

 

Third page is attempt at the calculus. I tried derivation can't be done so I tried antiderivative by integration, basically every time you integrate you add unknown constants and by second antiderivative you are sunk. Would like to see th actual hosepipe kinking or shell buckling equatiion, because that's what is missing and what cannot possibly be derived by calculus.

img017.pdf

[treeseer]

" we have only the fairly convincing body of evidence from Mattheck that failures increases dramatically in all species an all sizes after t/R falls below 0.3."

 

If you're that convinced, I have a splendid used car you'd love to buy. The engine's broken and the tires are flat, but ooooo the paint job is new, and it's peer-reviewed!

 

I haven't seen any data for trees >30". Smiley's sample was extremely limited (next door to me; I know the trees well), but he happily extrapolated to draw sketchy conclusions.

That .3 formula, combined with the myth that reduction cuts should be to 1/3-sized laterals, has brought down 1000's of stable and easily saveable trees. Assessors might consider the first 3 letters in BIOmechanics before concluding ANYthing.

[Gary Prentice]

I'm still at work trying to sort a saw out, but I'll read your calculations when I get home Jules.

 

Valid points Guy, you may want to keep checking in cos I think I've some queries on SIA next:lol:

[treeseer]

I'm still at work trying to sort a saw out, but I'll read your calculations when I get home Jules.

 

Valid points Guy, you may want to keep checking in cos I think I've some queries on SIA next:lol:

 

I hope your saw is easier to sort out than this mathematical mess!

 

re SIA queries, I'll keep my peace.

[Tony Croft aka hamadryad]

lol

 

mechanics is pretty easy when You leave out all the BS surrounding it!

[daltontrees]

Chill out everybody, we're just kicking some numbers about to see wherther Wagener and Mattheck are consistent. Wouldn't buy a used tree from either of them, as it happens, But |I think it is interesting to see that both their formulae result in the same thing, namely at t/R greater than 0.35 they both say strngth isn't compromised. As ever, anyone using a lower t/R ratio to justify tree removal without any other reasons is a twit or a fraudster.

[treeseer]

I think it is interesting to see that both their formulae result in the same thing, namely at t/R greater than 0.35 they both say strngth isn't compromised. As ever, anyone using a lower t/R ratio to justify tree removal without any other reasons is a twit or a fraudster.

 

Thanks Jules for that positive view.

 

Tony I agree that relatively speaking mechanics does not look that hard. But biomechanics is nigh unto undefinable!

Edited July 5, 2014 by treeseer

[10 Bears]

I'll have to beg to differ with 10Bears, I think there may be some confusion in where data was collected. Smiley wrote mainly on Oaks after hurricane Hugo (I think) and Gruber based his work on two cultivated forest stands. Matthecks original work doesn't clarify whence the data came from but Fink states - refuting Gruber, that it was untouched virgin forests and I think it may have been over a number of countrys....

I don't think, which is an issue, that Mattheck ever published all the collected data or the sources.

 

I am not confusing the data source with the other investigations, but to be fair, I am reporting information that was given to me by a couple of lecturers at Myerscough, one of whom suggested that Mattheck told him this was a storm event/forest as described - but I only have the lecturers word for it.

 

The other issue you raised that I have put in bold - this has always been my primary concern ie not being transparent in the research and allowing repeatability, just take Matthecks word for it!

[Tony Croft aka hamadryad]

All grist for the mill Jules, I followed this last night on my phone and will return this evening. I've twenty odd pdf's that I've read, including Bonds article. Kane et al -2001 & 2004 are particularly interesting. I'll post them up later.

 

I'll have to beg to differ with 10Bears, I think there may be some confusion in where data was collected. Smiley wrote mainly on Oaks after hurricane Hugo (I think) and Gruber based his work on two cultivated forest stands. Matthecks original work doesn't clarify whence the data came from but Fink states - refuting Gruber, that it was untouched virgin forests and I think it may have been over a number of countrys.

 

Later data was for over 1200 trees - Australia , N. America & Europe for the body language book.

 

 

 

I don't think, which is an issue, that Mattheck ever published all the collected data or the sources.

 

Please publish the calculus if you've done it, I've no shame admitting that I'm struggling on the understanding.

 

You know, you really ought to check with the man himself before making assumptions on such things, His data is compiled continuously, and from many places in many woods and trees all over the world.

 

I will come back to this point with something to clarify, as a VTA practitioner I would consider it my duty to make sure The method and its science are not unduly battered by somebody with a clear dislike for the background science of it.

 

People crack me up, I mean he got us all talking mechanics! and VTA is and always will be the basis of all models methods from here to infinity!

 

Others just want a piece of the credit!

[daltontrees]

I agree VTA is a pretty good system for inspecting trees and so mforth. But please rmember that its primamry use in Britain just now is to decide if a tree passes or fails the foreseeability of failure test, even though it is really aimed at going beyond that nad estimating the remaining strength when a defect is confirmed.

 

I'm going to state the blimmin' obvious (again) and say that t/R rtios and Wagener ratios are nit statements or mechanisms for stating whether failure is foreseeable. They are at best thresholds for when you need to start thinking about the foreseeabiltiy of failure.

 

And I'm going to stick my neck out and say that it will never be possible to create a direct and reliable link (and I mean mathematically) between extent of hollowness and relative likelihood of failure. It doesn't mean we shouldn't try. It definitely doesn't mean we shouldn't have a bit of harmless fun speculating in even the most unscientific of ways. But if the t/R ratio could speak, like Mark Twain it might say " Reports of my death are greatly exaggerated". It's a tool, an amber light, a twinge that sends us to the doctor to catch a disease while it's cureable.

 

One other crass quote, but one that I have always liked. "Rules are there for the guidance of the wise and the absolute adherence of fools". VTA sits in my VTA toolbox beside the binoculars, magnifying glass, increment borer and my common sense.