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Klarinet Archive - Posting 000001.txt from 2001/05

From: Gary Truesdail <gir@-----.net>
Subj: Re: [kl] Cracking clarinets
Date: Tue, 1 May 2001 00:20:16 -0400

Don't have time now, but you are all guessing. I do not pretend to be
the definitive expert but some experts that have been stating their
theories or claim to be stating fact are, IMO, off base and only
partially correct. The bore of a clarinet, upon expanding will expand
inwardly only a little bit (this is where the intonation problems of a
cold instrument comes from, disrupting the relationship between tone
hole size and placement and bore size and distance from mouthpiece tip)
and the molecular compaction results in an increased rigidity and
strength of the geometric object (the basis upon which an arched bridge
increases it's strength under load). Therefore, most expansion is in an
outwardly direction that will result in a parting of the wood cells. I
believe the % of moisture (H20 or oils) provides for an element of
flexibility that acts as a sort of buffer to absorb the stresses before
the wood parts, so the dryness of the wood will also have an effect. An
old clarinet that has already dried (and shrunk) all it is going too,
will be less likely to crack because of less possible movement from the
other possible (temperature/moisture) elements.

The above is offered as a stimulus to you all after a few glasses of
wonderful wine. Hopefully it will bring in some ideas from outside our
normal mode of thinking such as woodworking machinists, etc.,

Food for thought, jump on me, I'm ready, chain mail in place.

Gary T

"Lacy, Edwin" wrote:
>
> > Are newer instruments more prone to cracking than older, more conditioned
> horns, [.....]
>
> Once again, observation might lead us to conclude that newer instruements
> are more likely to crack. However, it is probably the case that if a wooden
> instrument is going to crack, it is more likely to do so when it is new. In
> other words, the fact that much older instruments rarely seem to crack may
> not be due to the fact that they are more conditioned or "broken in," but
> because the wood itself was relatively free of weak points.
>
> I've been hesitating to say this, because this always results in major howls
> on a list, but there is a major problem with the theory that heating the
> bore causes cracks by creating stresses when the wood of the bore tries to
> expand while the cooler exterior tries to remain at its original size. That
> problem is that when the wood of an instrument expands, it doesn't just
> expand outward; rather, it expands in all directions. Thus, when the wood
> expands, the bore of the instrument gets smaller; when the wood contracts,
> the bore gets larger.
>
> I know what is happening right now. Many people on the list are saying,
> "Everybody knows" that this isn't true. However, you don't have to take my
> word for it. Check with anyone who has had training in materials science.
> This is considered axiomatic in that field.
>
> Want a simple proof? Imagine a small cylinder of a material, such as
> grenadilla wood. Now, imagine that a thin disk is sliced from the cylinder,
> so thin that the the thickness is negligible. Now, consider what will
> happen when the wood expands. It will expand in all directions, from the
> center toward the edges, so that the circle becomes larger.
>
> Now, imagine a "doughnut" of the same material, large enough so that a thin
> slice can be cut that will be the same size as the other disk. Now, again
> imagine the material expanding. What happens? The material again expands
> in all directions. In other words, while points on the outer diameter are
> expanding outward, points on the inner diameter are expanding toward each
> other, or inward.
>
> The "doughnut" is analogous to a slice cut from a clarinet. (Warning:
> Don't try this on your good clarinet.)
>
> I think I know what the next question is: What happens if only one side of
> the disk is heated so that it alone expands. The answer is, that portion
> that is heated expands outward. So, if it is the bore of a clarinet that is
> heated, the sides will tend to expand toward each other.
>
> The next question would be, Wouldn't there be stresses created on the radii
> of the disk, between the heated and unheated portions? I think the answer
> is yes. The thing to be determined would be how severe the stresses were.
> But remember, we would be talking about stresses on the lateral axis of the
> instrument rather than the longitudinal one, which is not the kind of crack
> that a wooden instrument is normally subject to.
>
> Ed Lacy
> **************************************************************
> Dr. Edwin Lacy, Professor of Music
> University of Evansville
> 1800 Lincoln Avenue
> Evansville, IN 47722
> telephone (812)479-2252; e-mail: EL2@-----.edu
> **************************************************************
>
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