[Harp-L] Re: Re: Yellow Brass (was GM) (Vern) (geoff atkins)

["geoff atkins" <geoffatkins@xxxxxxxxxxxxxx>]

Geoff Atkins
Waves within reeds

Waves within the reed are generated as reactions to the oscillation of the
reed.
The "waves" within the reeds progress axially to the reed length, increasing
in magnitude as they approach the point of fixity (that's why reeds don't
usually break at the extreme tips). They comprise pairs of opposed
compressive and tensile stresses on the extreme surfaces which alternate
every half cycle. (i.e. like stretching a rubber cord *along* its length
then letting go).
The forces of compression and tension lessen and equate to zero at the
neutral axis, (unless the scoring locally changes the NA position)
They don't make the sound, they strain the metal.

The root of the milling is the weakness where the problem begins:
compressive wave cycle increases forces on the metal crystalline structure.
tensile forces tend to open the interstices of the crystals, eventually
forming a gap which we to our dismay experience as a cracked reed.

Sorry I thought it was clear the first time.

In design, the filet is the curved shape of the junction of two planes,
irrespective of whether it is achieved by milling or by a "filet"
("fill-it") weld.
(The latter is actually nearer an internal chamfer).

I also enjoy playing the harp.

Best regards
Geoff Atkins


> From: Vern <jevern@xxxxxxx>
> Subject: Re: [Harp-L] Re: Re: Yellow Brass (was GM) (Vern)
> To: "geoff atkins" <geoffatkins@xxxxxxxxxxxxxx>
> Cc: harp-l@xxxxxxxxxx
> Message-ID: <E932C940-A53E-4F33-B71F-7842521C8FCD@xxxxxxx>
> Content-Type: text/plain; charset=us-ascii
> 
> Atkins has summarized the source of stresses in harmonica reeds as I
> understand it... but without addressing the questions in my previous post.

>