on 3/12/00 I posted a message re fractometer
readings which was totally ignored. Is this
because nobody knows? or cos its easier to discuss valuations and bark damage. do I need to be curt to get a response?

Reply to post by gavin donaldson, on March 23, 2000 at 03:21:57:

I don't know anyone who's using the Fractometer. I did just come across a discussion in Wessoly, Lothar, 1995. "Boring is no way for reliable fracture diagnosis." Stadt und Grun. 9:635-640.

Wessolly suggests A) that even if material strength were the most important issue a very large catalogue of sample strengths of various species would be required for reference and it does not exist... but that even if it did material strength does not account for the more important aspects of geometry and loading, B) Fractometer values are determined radially... with small diameter sample prone to fracture at the annual rings... while the stresses to be understood occur longitudinally, C) the values have "only limited local predictive power," and D) the values "scatter" to much for his confidence in them.

I've paraphrased a little, don't know if any of it is right or wrong. These are direct attacks and there's no disclosure of any rebuttal or defense by Mattheck.

That's all I have to contribute, except I think you might find a Journal of Arboriculture article on the Fractometer, try looking through the abstracts on the ISA site.

Reply to post by gavin donaldson, on March 23, 2000 at 03:21:57:

No reason to get curt.... We all just thinking our here I believe Bill Graham at the Morris Arboretum was collecting data on fractometer values for a selection of species but I have not seen anything published. Beyond that, I dont know anyone using on regularly.

Wayne

Reply to post by gavin donaldson, on March 23, 2000 at 03:21:57:


Kurt,

When I was very young, I thought I could insist on answers--exactly when I wanted them--but as I grew older, I found that answers came when they wanted.

You take risks about answers when you write into a free advice site, even it is labelled ask the experts.

I don't think much at all of the fractometer. Bending the core sample of a tree most likely means bending exactly that sample. Inferences about the "strength" or the "decay potential" of a tree are difficult for me to follow. Perhaps I'd understand it more if someone showed me the relationship of actual failures in trees to the apparently haphazard choosing of sample locations. The fractometer we're talking about is this: http://www.walesch.ch/WAL_W/WAL_WI/WAL_WIF/Image10.gif and the sample is expected to split against the center anvil. OK, what does that tell me--and how many comparative tables must I build to find a relationship to issues of trees falling over or dropping limbs?

Indeed, I have a hard time with the concept of an isolated failure point of a certain length and diameter of a core teaches us much since the core ordinarily rests in a synergistic unbroken association with its surrounding wood fibers of many years growth. Perhaps core samples of the cassions of Sears Tower can predict when it will fall over.

Most failures in trees involve some corresponding presence of dynamics which cannot be scaled up by this incremental, almost microscopic, bending of a core from somewhere in the diameter of a tree.

Although Mattheck would have us believe otherwise, trees are not monolithic materials. They are laminates. And while the examination of laminate interfaces is interesting, it also factoidal.

It might not be that the prediction of safety margins in trees can ever be driven by factoid information, but instead requires the larger picture that is the world of statics and dynamics and how big beasts attempt to cope with them.


By the way, here is another fractometer: http://www.terratek.com/fracto_1.htm

http://www.walesch.ch/WAL_W/WAL_WI/WAL_WIF/Image10.gif

Reply to post by gavin donaldson, on March 23, 2000 at 03:21:57:

I have not seen any other published tables of data on various species. I suspect that like much else, those who collect the data just have no reason or means to publish it. And much of it may be uncontrolled testing.

Bill Graham of Morris Arboretum did try a little testing a few years ago, with the help of Gerry Posner of NY, and myself (I had the only unbroken borer in three states, I think). I don't think Graham published anything, or came up with much useable data.

The Fractometer, as Bob W pointed out, measures bending and breaking forces at one point along the core at a time. Small differences in position of the core can make a difference. If the core is turned just a bit, your readings may change.

Keep in mind what the device is intended to do- it measures the breaking strength of the wood. The idea is NOT that it extends over a large area and predicts tree failure. It can be used to identify incipient decay, however. Decay fungi breakdown the cellulose or lignin, and can weaken the wood substantially before it can be detected in other ways (visually, Resistograph, etc.) So testing with a Fractometer may help identify incipient decay where other techniques cannot. It should be able to tell you if the wood three inches deep is infected or not- a good thing to know, I suppose. That's the theory. I won't vouche for how accurate it is, or if it works in practice. I have very limited experience with it myself so far. I'm saving my money for an arboricultural tricorder.

Live long and prosper. \\//

Reply to post by Scott Cullen, on March 23, 2000 at 03:21:57:

Scott,

You have said it well. Failure and in particular limb failure is offten associated with
tensile failure of the wood. A core can still be useful in checking for decay but most
reliablely with the use of a microscope where hyphae are easilly vissible and damage from
metabolites can be seen as staining or cell deteriation. It seems to me though that most
failures do not occure with slight deteriation but rather with major faults.

Perhaps we need a machine to measure the tensile strength of wood.

Reply to post by Russ Carlson, on March 23, 2000 at 03:21:57:

thank you all for your input re fractometer.I suspect that many readings will be reqd. and interpretation will be difficult.Russ,what is a tricorder?what does it measure?

Reply to post by gavin donaldson, on March 24, 2000 at 01:10:29:

Ouch! your teeth must hurt biting in that one!

Then clue is in the Vulcan parting

Reply to post by Scott Cullen, on March 23, 2000 at 03:21:57:


I think there's an obligation to honestly examine every new idea in the hope it can help make a difference, but I'm always troubled when it gets immediately catapulted into the magic bullet category.

I have read that the fractometer indicates both decay and strength.

The cores may seem to be radial, but as you can see from the picture of a 600 year old fir, there can be significant transverse presentations--and how I rotate a core relative to the anvil offers two (at least) longitudinal shears. I can test potato chips with a hammer. Certainly something does happen, but how meaningful and predictive is the test?

We can find fragments of issues and conditions, but tying them together is a staggering task. It's ok if it doesn't occur on our watch. It will happen, undoubtedly, but let's not always push hyperbole into the the vacuum

Reply to post by jps, on March 26, 2000 at 04:08:42:

Who needs consultants or tricorders? Program NOMAD to wander the universe and ruthlessly seek out and destroy hazard trees. Anything left will by definition be OK.

Peace and Long Life.