Klarinet Archive - Posting 000744.txt from 2001/04

From: "Dee D. Hays" <deehays@-----.net>
Subj: Re: [kl] Cracking clarinets
Date: Mon, 30 Apr 2001 22:20:21 -0400

----- Original Message -----
From: "CLARK FOBES " <reedman@-----.com>
Subject: [kl] Cracking clarinets

> Dee,
>
> I am having some trouble with some of your assertions.
>
> You made a broad statement that it was nonsense that clarinets crack
because
> of the differential in expansion from bore and surface due to a rapid
> variance in temperature. This statement also included information about
wood
> and its relative psi. Your statement does not take into consideration that
> wooden instruments are not made from a material that is uniformly dense or
> without grain or flaws, that they are not solid tubes and that they are
> pierced with many posts and holes that stress and weaken the wood.

I said it does not reconcile the available data. Note also that I have said
several times that such stresses could reveal an existing flaw. However,
that makes the flaw the root cause not the subsequent failure when subjected
to thermal gradients. By the way, I did take into acount that it is a
cylinder and I did take into account that wood is non-homogenous.

>
> You also seem to think that because some clarinets DO NOT crack under the
> circumstances that I described (Marching in Iowa winters was your
example)
> that this somehow disproves my theory. I am willing to bet that some
> clarinets DO crack under the circumstances that you described.

The uncracked clarinets are just as important a piece of data as the cracked
ones. Any proposed cause must account for the fact that X% crack and Y% do
not crack. Otherwise you are going down the wrong trail. This is standard
in formal problem analysis.

>
> I never stated that all clarinets will crack under the circumstance of
> temperature variance. I believe, as you do, that clarinets that crack are
> either weak or flawed in the area of the crack. But for the flaw to turn
> into a crack there must be a precipitating event and I believe that one of
> these events is sudden temperature variance between the bore and the
> surface.

If the flaw is the problem, there can be any number of precipitating events.
That doesn't make those events the cause. The flaw is still the root cause.
A major point in doing good designs is whether or not it is robust to
precipitating events.

>
> Whether you believe it or not and you think this part of "urban legend"
> there is a preponderance of evidence garnered by many, many artisans for
as
> many years as clarinets have been made that clarinets will and do crack
> under the circumstances I described. I have witnessed clarinets and oboes
> crack at the absolute beginning of rehearsals either outdoors or in cold
> halls. I see many clarinets each winter that need to be pinned and most
> players start with "the hall was really cold.."
>
> If you still believe me to be wrong then you won't have any problem
putting
> your clarinet in the freezer for an hour and then begin practicing on it
> immediately after taking it out. It may or may not crack, but it is not a
> bet I would want to make.

Focusing on the thermal gradients is like treating a patients symptoms. You
won't cure the patient but just make him more comfortable. By the way since
I have no way of knowing if my instrument is flawed, so I wouldn't run this
test.

Let's just look at two proposed causes and look at whether or not they
really work.

1. The clarinet cracks due to thermal gradients (inside warm, outside
cold).
a. Doesn't explain why some horns don't crack.
b. Doesn't explain why some horns that are treated extremely well do crack.
i.e. I'm talking about instruments that are never subjected to temperature
extremes, humidity extremes, and so on.
c. Does it make sense in light of the available analytical results? Nope.

2. The clarinet cracks due to flaws, either inherent in the raw material or
induced during manufacture, which then give way under even mild stresses.
a. Does it account for uncracked horns? Yes. There were no flaws.
b. Does it account for horns that cracked in the cold? Yes. Very mild
load could be too much for the flaw.
c. Does it account for horns that cracked in changing humidity levels?
Yes. Humidity causes major dimensional changes and thus major loads.
d. Does it account for horns that crack due to seemingly mild bumps? Yes.
No one is going to admit that they might have lightly bumped the horn
against the arm of the sofa. Or cases jostling around in a vehicle and so
on.
e. Does it explain why the cracks seem to start or end at a post or tone
hole? Yes. A manufacturing variation could have caused a flaw or added to
an existing flaw in the material.
f. Does it make sense in light of the available analytical ? Yes.

Cause #2 is by far the more likely because it better matches the available
facts. It also allows a wider variety of cracked horns to be described by
proposed cause. Finally, cause #2 makes it possible for research to be
directed to pinpoint sources of flaws and eliminate them eventually leading
to fewer and fewer cracked horns. You can examine cracked horns for
manufacturing flaws like radii being too tight, hole edges being to sharp or
chipped and so on. You can start designing a series of tests to determine
which factor or combination thereof allows you to duplicate the failure at
will. If you can't duplicate the failure at will, you haven't defined the
real cause of the problem You can also embark on a program to develop a
method determine if the wood has inherent flaws and should be pitched before
any manufacturing time is wasted on it.

What do you get with cause #1? Not much. You have a problem that has no
path for solution. Thus no one will work on a solution. You can't
duplicate the failure at will.

Dee Hays
Michigan

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