Re: [Harp-L] Virtues vs liabilities of weighting the rivet end

[Vern <jevern@xxxxxxx>]

Joe described the most expeditious way.  Shorten a longer reed and use it in the existing slot.

The most exact way is to choose a standard reed of the desired pitch and shorten the slot.  One way to effectively shorten the slot is to weld or glue the shorter reed in a position where its tip has the proper clearance at the end of the slot.  

Being a Suzuki tech, I'm certain that you are adept at welding.   ;o)
I made a capacitive-discharge welder that worked but not very well.  I used a single one-farad capacitor charged to 15V and I think that it needs two.  A pure copper probe sticks to the weld and erodes rapidly.  A pure tungsten electrode generates all of the heat on top of the reed.  What is needed is a tungsten-and-copper matrix.  They make them for spot welders but thus far I haven't obtained one that can be shaped for this application. More work to be done here. If and when I develop a satisfactory DIY welder, I'll publish the design.

A variation of this would be to file a slot in the rivet-hole in the plate and use a bolt-and-nut.  This would be much easier than adding metal in the tip-end of the slot. You would need to fill any opening through which air could leak.  The bolt head would complicate the installation of a valve in a chromatic.

In general, the rivet end of a slot is much less critical.  Welding, glueing, or filing/slotting the rivet hole is much less ticklish than adding material in the tip end of the slot.

Vern
  

On Apr 3, 2011, at 11:26 AM, Gary Lehmann wrote:

> Hi Vern--
> So is there a solution to my problem?
> I can alter the reed slot and use a shorter reed--is this the most expeditious way?
> TIA,
> Gary
> 
> On Sun, Apr 3, 2011 at 11:24 AM, Vern <jevern@xxxxxxx> wrote:
> Joe has described the best way.
> 
>  Adding solder near the tip to lower pitch works because the object is simply to add weight.  Placing solder near the rivet to increase stiffness may raise the pitch but is likely to diminish the responsiveness of the reed. This is because the solder isn't springy and will absorb vibrational energy.  The highest stresses occur near the surface and the low strength of the solder might lead to early cracking.  It is not an appealing solution from an engineering point of view.
> 
> Vern
> 
> On Apr 3, 2011, at 11:01 AM, Joe Spiers wrote:
> 
> > Sometimes shortening a reed scavenged from a lower hole will give you some extra sharpness in pitch to work with, depending on the reed profiles.
> > Joe
> >
> > ----- Original Message ----- From: "Gary Lehmann" <gnarlyheman@xxxxxxxxx>
> > To: "harp-l" <harp-l@xxxxxxxxxx>
> > Sent: Sunday, April 03, 2011 11:07 AM
> > Subject: [Harp-L] Virtues vs liabilities of weighting the rivet end
> >
> >
> >> Hello all--
> >> I just did a repair job for a well known harpist, and one of his harps
> >> needing repair was a high D chromatic--a whole step higher than normal.
> >> So the donor reeds I had were not acceptable, and I had to raise the pitch
> >> of a reed using silver solder near the rivet end.
> >> Any thoughts on this use and how would you raise a reed beyond what could be
> >> done by removing material from the tip?
> >> I would not have had any tip left!
> >> How about some tips?
> >
> 
> 
>