Re: [Harp-L] Brass vs Stainless Steel

["Björn Sigurdsson" <bjosi436@xxxxxxxxxxxxxx>]

Hi, when talking about that that steel reeds are thinner at the base than
brass, I get this idea of a reed that you make considerably thinner on the
middle and a bit thinner at the base - so it reminds of lying B in a shape.
My idea is: If I blow not so hard just the outer part will vibrate giving me
a tone, but when I blow with more pressure the whole reed while start to
vibrate, giving me a lower tone while the higher tone is still sounding.

What do you theory guys think, will it work in theory?

regards
Björn Sigurdsson
2008/9/5 Vern Smith <jevern@xxxxxxx>

>
> ----- Original Message ----- From: <jandkday@xxxxxxxxxxx>
> To: <harp-l@xxxxxxxxxx>
> Sent: Friday, September 05, 2008 6:32 AM
> Subject: [Harp-L] Brass vs Stainless Steel
>
> ..... I always thought brass to be a softer metal,
>> but does it's pliability make it easier to bend?  Stainless steel seems
>> stronger but is that a
>> good thing in a harp?   Any engineers want to chime in?  I'm in over my
>> head.
>>
>
> Definitions:
> "Stress" refers to the amount of force (per unit area) applied to a piece
> of metal.
> "Strain" refers to the stretch (per unit of length) as it deforms.
>
> When you stress a piece of metal, up to a point called the "elastic limit,"
> then release it, it will return to its original shape.  Below the elastic
> limit,  strain is proportional to stress. The elasticity of a metal is the
> ratio of stress divided by strain. Steel has a higher elasticity than brass,
> i.e. it takes more force to get a given amount of bending. Some steels have
> a stress level (lower than the elastic limit) called the "fatigue limit".
> Below that stress, you can exercise the metal for an unlimited number of
> cycles without fatigue failure.
>
> If you stress a metal beyond the elastic limit, it enters a plastic zone
> where strain is no longer proportional to stress and it will not return to
> its original shape.  Its behavior in thiis zone is described by its
> ductility.  Ductility is roughly the amount of strain it will take before it
> breaks. The opposite of ductility is brittleness. Brass is more ductile than
> steel.  Glass is an example of extremely low ductility and gold is an
> example of extremely high ductility.
>
> When we change the gap of a reed, we bend it beyond its elastic limit so it
> will not return to its original shape but will assume the new gap. Beryllium
> copper is a very elastic spring material with high resistance to fatigue.
>  However, it is very brittle and easy to break when re-gapping.
>
> Because of its higher elasticity, a SS reed will be thinner near the rivet
> where it bends than a brass reed of equivalent pitch and responsiveness.
> However, because SS is less dense than brass, it will be thicker at the tip
> than the equivalent brass reed.  If each is reed is designed to have the
> same pitch and responsiveness, there will be no perceptible difference in
> tone between reeds of different metals.
>
> Metallurgists may chide me for omitting some exceptions and qualifications.
> The rest of you may chide me for getting too technical.
>
> Vern
>
>
>
>
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Björn Sigurdsson
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58758 Linköping
+46 706 897257