Re: [Harp-L] REED REPLACEMENT

[joe leone <3n037@xxxxxxxxxxx>]

On Dec 6, 2009, at 3:37 AM, Vern wrote:

> The (Young's) modulus of elasticity of spring brass and phosphor  
> bronze is the same, 15x10^6.
> If both the brass and bronze reeds were the same thickness near the  
> rivet where they flex, their performance in the harp would be  
> identical.  However the density of the bronze is a bit greater  
> because the % of copper is higher.  This means that the bronze reed  
> would be a bit thinner at the tip to have the same pitch.

Right. Brass is cu & zn (atomic numbers 63.54 & 65.37) whereas Bronze  
is cu & sn (numbers 63.54 & 118.69) Ergo, depending on the amalgum,  
Bronze is generally heavier. So, as such, the reeds would have to be  
thinner. You can also get a disparity when comparing reeds of virgin  
brass with those of recycled brasses. I believe that Hering reeds are  
virgin brass and this is what makes them a little less robust than  
Hohners.
> In copper-alloy reeds, The thickness where it flexes determines the  
> stiffness of a reed.  A stiffer reed must also be thicker at the  
> tip to have the same pitch.
>
> The square root of the RATIO of (stiffness where it bends)  / (mass  
> of the tip) determines pitch.  If one copper-alloy reed is stiffer  
> than another, it is because it is thicker where it bends, not  
> because its material is different.
>
> Joe is correct that you can make a reed less stiff by shaving it  
> where it bends.  This will make it go flat.  Then you must shave  
> the tip to get it back up to pitch. I suppose that means you have  
> shaved the whole thing.
>
> If you can find a replacement reed with the correct pitch, width  
> and length, I suggest that you don't need to worry about the  
> material.  By time you get it tuned and playing, differences in  
> stiffness won't be perceptible.
>
> IF you cut a longer reed off to fit a shorter slot, you are  
> changing the design in unpredictable ways. Even if you can tune it  
> to the desired pitch , unless you have Joe's unusual talent, the  
> stiffness can be way off.

Everything you wrote is true (to my knowledge..which is limited).  
That's why I know better than to mess with you lolol. As for the  
chopping of reeds, I generally get to work with reeds with weighted  
tips. I seem to have good luck as the weight is only there for the  
weight dear..now that Mackie is back in town.....giggle. Once you  
shave the weight OFF, you wind up with...guess what...a reed.
> LeOne LeOnly