string termination

[Overs Pianos]

Hi Carl,

>A lot of things about string terminations have bugged me for some time.

Me too. This is a topic which raises the level of pianotech list interest.

>Ron Overs promotes hardening of the capo bar, yet the agraffe is a 
>relatively soft material (brass).  The difference is that the capo 
>is straight and the agraffe is round.  Wouldn't the agraffe last 
>longer if it were heavily plated with chrome, nickel or??

It would last longer if it was plated with a hard or harden-able 
material. I think brass is a very poor material for string 
terminations. After re-profiling (both new and used agraffes) we have 
been plating them with Electroless Nickel for some years (since about 
1996). This plating is harden-able, and it plates with a uniform 
thickness in the string holes. Normal electoplating won't result in a 
uniform build-up of plating in the holes, which is why Chrome isn't a 
viable alternative plating material. Electroless Nickel plating is a 
process which, once started, is a purely chemical plating process. 
This is why it results in a useful build of plating in the holes.

For the most recently remanufactured piano we built, I decided to try 
just shaping the brass agraffe holes without plating and hardening. 
The results were very disappointing. The best results we have had to 
date are when the agraffes are Electonickel plated. We've been 
getting them plated with a thickness of 0.05 mm (2 thou). The next 
set we do will be plated with 0.75 mm to increase the strength of the 
plated surface. I have been suspicious that the plating is on 
occasion collapsing and flaking off, due to collapse of the soft 
brass substrate.

>Now under normal circumstances, the piano string is terminated 
>(pivoted) on the top surface of the agraffe.  Let's call that North. 
>Let's call the bottom of the agraffe South.  The other two surfaces 
>would be called east and west.
>
>At the bridge, the string is terminated at maybe SSE (south south east).
>
>Wapin claims that their vertical bridge pin encourages the string to 
>vibrate in the horizontal direction quicker before the energy has 
>been dissipated in the vertical mode and hence -longer sustain.
>
>Let's make it a given that the impact of the hammer is in a northern 
>direction.
>
>Stuart of Australia claims that their bridge termination increases 
>the vertical vibration of the string.   Hmmmm?  How does that effect 
>the sustain????

I've watched struck strings on the Stuart piano, and my observations 
are that the strings in his instruments behave like any other 
standard string termination. I have no reason to suspect the Wapin 
termination will be any different either.

>My esteemed colleuge from one of the fly over states suggests that a 
>string starts out vibrating vertically, slowly starts to drift 
>horizontally but never gets to true horizontal.  He also suggests 
>that a string tends to vibrate at 90 degrees of its termination.  I 
>want to find out if that is true.

The string certainly starts out vibrating in the vertical plane, then 
changes to an elliptical vibrating mode. It appears to degenerate 
into an essentially circular mode at the final decay stage.

>I don't really know, but it has been my assumption (maybe in error) 
>that the string vibrated vertically, slowly drifts elliptically, 
>approaches horizontal, then elliptically in the other direction and 
>then returns to vertical at a much lower level.  This would then be 
>a cyclical phenomenon. Sorry for the flurry of five dollar words.
>
>I've been thinking of a new bridge termination scheme for rebuilding 
>but I'm not going to proceed till I answer a basic question.

I suspect that you are about to join a few others, who are on this 
Darwinian quest.

>Here's my question:  A vibrating string has two terminations.  It is 
>excited in the northern direction.  (Ignore the strike point)  What 
>effect on tone will be the termination of the two ends of the 
>string????? Both north, one north and the other south, east or 
>west????   Or no big difference??
>
>I have recently found plans on the net to build an led stroboscope. 
>I will build this and look at a string under vibration. I could 
>stretch a wire across my garage and look at it with different 
>terminations.
>
>If some of you deep thinkers have an answer to my question that 
>makes common sense, I won't have to do this.  Give me your feedback.

It is a worthy field of investigation Carl. Conventional bridge pins 
suffer severe damage at the termination point. An intermediate 
solution would be hardened bridge pins, but it will be a costly 
exercise.

Ron O.
-- 
OVERS PIANOS - SYDNEY
    Grand Piano Manufacturers
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Web http://overspianos.com.au
mailto:ron@overspianos.com.au
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