Re: [Harp-L] Powerbender tuning

[Vern <jevern@xxxxxxx>]

Adding material to a reed near the rivet to raise its pitch isn't likely to work out well.
Plastics and solder that are easy to add have high damping. Damping deadens the vibration by absorbing energy. (You couldn't make a very good reed out of pure blu-tac or solder!)

 It is not the mass of the reed near the rivet that you need to increase, it is the stiffness.  

What you need is a reed that is either stiffer or shorter.

Here are some possible solutions:
- Remove metal near the tip.  There is a limit to how much can be removed.
- Shorten the reed and use the solder or plastic to fill the space left in the tip of the slot.
- Replace the reed with one of the same length but higher in pitch....stiffer near the rivet.
- Install a tuning wire.*  

* This is a very small-diameter stainless steel wire (guitar "E" string or smaller) having one end attached to the plate and the other end touching the reed near the rivet.  In this case, you are adding the stiffness of the wire to the stiffness of the reed.   Moving the point of contact of the wire towards the rivet lowers pitch and towards the tip raises pitch.   Changing the amount of tension in the wire won't much affect the pitch of the reed because it doesn't change the spring constant of the system.  There should be just enough tension to keep the wire in contact with the reed and avoid bouncing and rattling.

Such wires are used to adjust the pitch of organ reeds.  I think that Wm Galison and perhaps others have experimented with tuning wires attached to the covers that can be brought in contact with the reeds to abruptly change their pitch.

Vern

On Sep 17, 2010, at 5:47 AM, Rick Dempster wrote:

> Yeah...I tried that too Ken. I figured the reason it doesn't work is because of the 'lever' factor. Bluetac is light; the weight of a given dollop of it is far more effective on the free end of the reed than it is near the rivet. With solder it's a different matter because of the density of the material. Not well explained, but I think it's right.
> RD
> 
>>>> Ken Hildebrand <airmojoken@xxxxxxxxx> 17/09/10 8:51 PM >>>
> I tried raising the pitch of a reed by adding weight to the base rivet-end (using Blu-Tac), but it did NOT work.  I think the reed looses its ability to vibrate properly.
> 
> Ken H in OH
> 
> 
> --- On Fri, 9/17/10, D Baker <dbakerzzz@xxxxxxxxxxx> wrote:
> 
>> From: D Baker <dbakerzzz@xxxxxxxxxxx>
>> Subject: [Harp-L] Powerbender tuning
>> To: harp-l@xxxxxxxxxx
>> Date: Friday, September 17, 2010, 3:06 AM
>> As soon as I read about Brendan's
>> Powerbender tuning I was impressed
>> with the practicality of it for contemporary music so I
>> decided to try
>> my hand at retuning, starting with some 5 USD harps I had
>> laying around.
>> Now I have done 4 harps and the results have been somewhat
>> successful,
>> enough that I have been able to try the tuning and found
>> that it is
>> everything Brendan has said. I have had some problems
>> tuning 9 and 10
>> draw up 3 semitones. I have taken the reeds down to foil
>> thickness on
>> the ends and have ruined one and replaced it only to have
>> the
>> replacement get so thin it had to be shortened. All of the
>> 10 draw reeds
>> have actually had to be shortened some, leaving a leaky air
>> gap at the
>> end. 10 draw is still playable but less than ideal. 
>> Does anyone know of a solution to this. Removing metal
>> further from the
>> tip doesn't seem to have enough pitch-raising effect. Does
>> adding
>> material at the base, such as Blue-tac raise the pitch?
>> 
> 
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>