Re: [Harp-L] Re: Steel Reeds

["Bob Laughlin" <rlaughlin@xxxxxxxxxxxx>]

http://en.wikipedia.org/wiki/Note

Under "Note Name", 1st paragraph:

"In order to differentiate two notes that have the same pitch class but fall
into different octaves, the system of scientific pitch notation combines a
letter name with an Arabic numeral designating a specific octave. For
example, the now-standard tuning pitch for most Western music, 440 Hz, is
named a' or A4."

BL


----- Original Message ----- 
From: "Rick Dempster" <rick.dempster@xxxxxxxxxxx>
To: "Rick Dempster" <rick.dempster@xxxxxxxxxxx>; <harp-l@xxxxxxxxxx>; "Orjan
Hansson" <harpoh@xxxxxx>
Sent: Wednesday, April 16, 2008 5:08 PM
Subject: [Harp-L] Re: Steel Reeds


> ...........ahh! I think I see....so draw 1 on a G harp would be A1, draw 3
D2 etc etc....yes?
>
> >>> "Rick Dempster" <rick.dempster@xxxxxxxxxxx> 17/04/2008 9:42 >>>
> Uh.....have I missed something? What the hell is 'G4' and 'A4'? I seem to
see it more & more.
> RD
>
> >>> Orjan Hansson <harpoh@xxxxxx> 17/04/2008 3:35 >>>
> Hi,
>
> I'm a long-time subscriber to harp-l (since 1998) and enjoy very much
> the discussions here, although I don't post very often. However, this
> issue with stainless-steel reeds interests me very much.
>
> Here is my experience: I bought a Seydel 1847 in G a year ago and after
> half a year of (much) usage the 4-draw reed (A4) became badly out of
> tune - almost down to G4. I tried to tune it without success. In fact,
> close examination revealed a tiny crack ca 4 mm from the rivet. I
> contacted Seydel and they kindly offered to repair the harmonica. So two
> weeks after sending it, I had it back with the reed replaced. That's
> great service!
>
> Now to my thoughts: Obviously, SS-reeds are prone to metal fatigue just
> as brass reeds. As I understand it, this can happen to any metal
> component that is subjected to a high number of deflections. This is
> very well explained in the article "Beyond the Basics - Performance Over
> Time: Fatigue Strength" that can be found here (I think someone posted
> this some time ago on the list but I don't remember who and when):
>
> http://www.copper.org/applications/industrial/DesignGuide/homepage.html
>
> Here is a quote from the article:
>
> "Fatigue occurs because micro cracks develop on the metals surface when
> it is cyclically stressed. With repeated bending these cracks propagate
> through the metal thickness to a point where the remaining sound
> structure fails by ordinary rupture (because the load can no longer be
> supported)."
>
> There is also a diagram which shows the relation between stress and
> number of cycles until fatigue sets in. The stress in turn is related to
> the deflection, which in the case of a harmonica reed depends on the
> blowing pressure. From the diagram one can conclude that a reed can last
> for a very large number of cycles if the stress (blowing pressure) is
> small. But if you increase the stress, the lifetime (number of cycles
> before metal fatigue sets in) can become drastically lower.
>
> The diagram in the article is specifically for a certain brass alloy.
> But I guess that similar behavior can be expected for any metal. It is
> only a matter of *how many cycles* the component can last for a certain
> stress and geometry. Is there any metallurgist on the list that can
> verify this? In fact it would be very interesting to see a comparison
> between brass and stainless steel (with compositions similar to
> harmonica reeds).
>
> Maybe someone with appropriate equipment can do an AB test? It would
> require blowing on reeds with a constant pressure until fatigue sets in,
> that is, when the pitch drops drastically. This might take several days.
> (100 million cycles of an A4 reed will take approx 63 hours!-)
>
> By the way (as a comment to smo-joe), the thickness of the SS-reeds in
> the Seydel 1847 seems to be comparable to ordinary brass reeds (judging
> by eye - I haven't measured exactly).
>
> Regards, Orjan
> http://ohw.se
>
> > On Apr 15, 2008, at 11:11 PM, lil Buddha wrote:
> >
> >> I am not a metallurgist, but from what I have read, steel does not
> >> share the
> >> same fatigue issues brass does.
> >> Many metals will eventually fail even with the smallest loads; the
> >> effects
> >> of the stress applied are cumulative. No so with steel. As long as the
> >> stress levels are kept below a certain level, the steel will never
> >> break.
> >> Theoretically at least. This would indicate that those who have caused
> >> failure in the stainless steel reeds are blowing harder than
necessary,
> >> attaining a failure level instantly rather than cumulatively.
> >> Anything can
> >> be broken. Failure of an object may be more the fault of the user  in
> >> these
> >> cases.
> >>
> >> Forgive me if this was addressed and I missed it.
> >> _
>
> To which smo-joe replied:
>
> > A reed must be made from anything spring. Steel is better in this
> > regard, However, given the immense strength (by comparison) of steel,
> > it stands to reason that the reeds would have to be MUCH thinner.
> > Since there is so little material involved, ANY flaw will contribute
> > to a failure.
> >
> > In an accordion, the reeds are huge (by comparison), and thus there
> > is less chance of failure. That, AND they have a pressure relief valve.
> > I agree with your synopsis
> >
> > smo-joe
> >
>
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