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




On Mar 9, 2010, at 7:55 PM, Vern wrote:



On Mar 9, 2010, at 3:19 PM, joe leone wrote:

Leaving a sharp step in the rivet boss to reed shaft causes vibrations in the reed to transfer sonic waves to the sharp inside corner (where the reed is weak). Constant sonics at that point has the effect of singing high notes at a shell blown champagne glass, It can cause a fracture.


smokey joe

The simpler explanation is that any abrupt change in cross section causes a stress concentration. Wikipedia sez: "Geometric discontinuities cause an object to experience a local increase in the intensity of a stress field." A fillet at the base of the reed reduces the abruptness of the change in cross section and reduces the local stress.

But, but but, a filet is usually an ADDED feature. My explanation decrees a rounded cut into SOLID material. And (oh, btw) I know more than Wikipedia anyway. lolol

Please explain what you mean by "transfer sonic waves....sonics...."?

Sonics, phonics, potato potata, tomato tomata.


To what kind of waves do you refer, compressive waves or some kind of higher-frequency mode of transverse vibration? How do you know that such waves exist in harmonica reeds? What is your source of this information?

Sine waves. Source of information? Me. Take a 6' 3 3/4" (1 meter) long piece of wood wand 3/4" x 3/4" (18.81x18.81mm) in cross section. Leave 20cm full sized and then mill the rest down to 1/2" (12.54x18.81mm) ON the flat. Now holding the 20cm part, begin to whip this completed wand up and down casing it to whip/flex in an undulating fashion. It will fracture at the juncture of where you thinned out the wand. .

To fracture a glass, you must sing to it very loudly at its natural frequency of vibration. Are you referring to vibration at frequencies other than the reed's musical pitch?

No, continued flexing. Everything has a finite number of cycles of life in it. Even me. How unfortunate for everyone. :)


Jo-Jo (I don ha to cho ju any steenkin badges)


Vern







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