String vibrations (was Re: Stuart)

[Erwinspiano@aol.com]

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       Hi  Ron O
   I have a (1950s I think) 6ft Sohmer I posted about earlier that has brass 
bridge aggraffes in the tenor  and first capo section but not in the bass.  
Since Phil Ford was in the shop the other day we looked at the bottom of it and 
it has a what looks like a 1/4" maple piece running under the bridge on the 
bottom of the board. He said it might be there to keep the bridge from rolling 
backwards because of the way the pressures are applied to the bridge.
   In this config. the strings come thru the agraffe and then up over a 
sligthly rounded hump then on to the hitch. This piano has a reverse crown board as 
well & sings like a soprano. In a previous Sohmer (also with reverse crown) I 
rebuilt ,the aggraffes screwed into the bridge with very fine machine 
threads.  Can you imagine how time consumning that was. Well at least possible if 
they was turned into the bridge with a drill etc. My point is they were still 
solid in the bridge and worked well after 70 yrs.
    Why wouldn't this system be a candidate for some one like you? 
      Dale Erwin


 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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