Re: [Harp-L] Re: SS vs. Brass vs. Phosphor Bronze Reeds

[Vern <jevern@xxxxxxx>]

On Apr 18, 2011, at 2:05 AM, Brendan Power wrote:

>  As Vern says, until there is a rigorous scientific test, we shall just
> have to rely on anecdotal evidence............ 

> ..........However a test of different brand reeds (regardless of materials) should be
> possible. But after the debacle of lat year's infamous SPAH Comb Test, I'm
> steering well clear! 

Life-testing of reeds and the three previous SPAH/Buckeye comparison tests of comb materials are fundamentally different.

The materials tests were not a test of the materials per se but a test of people's ability to perceive whatever minuscule effects that the materials have on harmonica sound.  I disagree that it was a "debacle."  Before the test, the participants were happy and confident that they could discriminate among materials by playing the harps.  After the test, they were frustrated and chagrined that they could not do so under controlled conditions.  The same thing happened on the previous tests.  Any other result would have been surprising.

The life-testing of reeds is purely an engineering endeavor that would not involve artists or their egos. It would not have to be done at SPAH where suitable participants and witnesses are available. In fact, it would take much too long to do at SPAH.  It would be difficult and expensive because it would involve many harps/reeds, a careful design to make sure that they were all subjected to the same stresses, frequent performance checks to detect the time of failure, and accurate record-keeping and playing until more than half of the reeds fail.

> One thing we're forgetting in all this discussion of materials is the
> critical part played by reed profiling and milling............ 

Cracks start at stress concentrations that occur at abrupt changes of cross section of the reed.  These can be tool marks characteristic of a particular milling process.  Stress concentrations can also occur in a sharp corner at the base of the reed.  Polishing the reed can eliminate tool marks at the hazard of changing the reed design and possibly introducing other areas of high stress.  It can affect reed stiffness and impact responsiveness.  
> 
> So any test of pure materials for longevity would need to take these factors
> into account, which would be very complicated to arrange!

Maybe not.  A machine to cyclically flex-test specimens of various materials (not necessarily harmonica reeds) to fatigue failure could be simpler than a 
machine to test reeds.  That would eliminate many hard-to-control harmonica reed variables such as direction of milling.

Vern