String vibrations (was Re: Stuart)

[Overs Pianos]

>At 8:25 AM -0700 22/9/03, Joseph Garrett wrote:
>It seems that the better sustain and clarity of the bridge agraffe is not
>due to the direction of the vibration, but simply because it provides a
>better termination (all metal) than the conventional bridge pin and wood
>termination.
>What do you think?

Hi Joe,

Yes, I suspect that when the agraffe is firmly fixed to the bridge 
(and they don't seem always to be, since they can exhibit falseness 
as well), they will produce a cleaner tone with better sustain than a 
conventionally pinned bridge. Like Phil Ford, I don't subscribe to 
the theory of any termination being capable of influencing the mode 
of vibration. Furthermore if it did, as Phil also mentioned, this 
would lead to a reduction in sustain with a higher initial sound 
pressure level. While I have no doubt that a properly executed bridge 
agraffe system could be very good, I suspect that some of the claimed 
benefits attributed to it is just 'smoke and mirrors'.

Two things worry me about using bridge agraffes (I admit that I am 
interested in using them at some point).

The first is that the agraffe takes up valuable bridge height. If, 
for example, the string plane is say 8 mm higher than the bridge on 
account of the agraffe taking up the space, a piano with such an 
agraffe will have only 24 mm high bridges if the string plane is 32 
mm above the panel. I consider 24 mm as an inadequate height for the 
long bridge, and all pianos which I have so far experienced with such 
low bridges seem to exhibit tonal problems. Therefore, the bridge 
agraffe should be designed with the lowest practical height between 
the top of the bridge and the string plane. Alternatively, one could 
build a panel with another bridge under the sound board as Grotrian 
did with some of their early grand pianos, but this would push the 
cost of the piano up quite a bit.

The second concern I have with using bridge agraffes is fixing them 
permanently to the bridge. Of the bridge agraffed pianos I have 
heard, I suspect that this can be a problem. It may be possible to 
achieve a good connection by using West system glue between the 
agraffe and the bridge, and using machine screws to secure the 
agraffe to the bridge, while at the same time gluing them into the 
bridge with West system. Stephen Paulello's agraffes are glued to the 
bridge. Take a look again at the following close-up image of his 
agraffe. A light blue adhesive can be seen at the junction of the 
agraffe with the bridge.

http://www.overspianos.com.au/plello1.jpg

Notice also that its quite a good design since it has a low height 
from the bridge to the string plane. Unfortunately, this design could 
not be used for trichord stringing.

Ron O.


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