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Klarinet Archive - Posting 000694.txt from 2001/04

From: "Dee D. Hays" <deehays@-----.net>
Subj: Re: [kl] Response to Dee regarding cracks
Date: Sun, 29 Apr 2001 07:11:27 -0400

----- Original Message -----
From: "CLARK FOBES " <reedman@-----.com>
Subject: [kl] Response to Dee regarding cracks

> I don't know what your qualifications are as a repair person and i am not
> certain what you mean by "run the numbers". Cracks occur when clarinets
are
> played cold. I have pinned many, many clarinets that have cracked under
this
> condition. Oboes are notorious for cracking when played cold. In the few
> seconds it takes for a clarinet to crack I doubt that it would absorb
> enough moisture to cause the crack. Almost without exception the
clarinets
> i have pinned cracked under consitions where the player was outside or the
> room or hall were cold. You also stated that "The exception would be if
> there is a pre-existing flaw that couldn't be seen creating either an
> unusually weak spot or a stress riser".
>
> This is exactly the problem. The area between the two trill key tone holes
> is very weak and prone to cracking. If you think cracks can't occur when
> clarinets are cold because it is theoretically impossible then you had
> better make another type of investigation based on empirical evidence.

I am an engineer and have done quite a bit of work on stress in my 25+ year
career. When I say "run the numbers," I mean calculated the strength and
calculated the stress. A special interest of mine has been thermal failure
and fatigue (i.e. failure due to stresses induced by temperature gradients).
Now an interesting thing is that material thickness has no bearing on the
stress resulting from thermal effects. Only the temperature, material
properties, and stress risers are relevant.

Empirical evidence? Simple, if it were temperature, almost all wood
clarinets subjected to the cold would crack not just an occasional
instrument. There has to be some other factor. There have been far more
that did *not* crack than did. I belong to a generation where a large
number of students had used wooden student horns and marched with them. And
this was in Iowa winters, not Florida or some other benign climate. I
marched many a football game with a wooden horn where the temperatures were
below freezing.

As a long time engineer, I've seen too many cases where what "everyone
knows" as based on empirical evidence was wrong. This leads to solutions
that don't work because the root cause is identified incorrectly. Or it
leads to no effort to find a solution as people may view the problem as
unsolvable. We could undo history and go back to the caves by eliminating
every in our lives that "everyone knew" was impossible.

Dee Hays
Michigan

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