>Ok, this rusted, bent bucket of logic here is rattling in my head. I >don't question Jon's procedures lightly! > How does installing counterbearings change the position of the >wire in the agraffe? It would seem,(among that rust, again), that >the relative position of the wire in the agraffe is going to be >dependent on the pitch the string needs to be, not what happens >between the agraffe and the pin. > I have this little voice in my head saying it was the reduction >of drag that made the difference. My fuzzy logic is that the higher counter bearing increased the overall length of the string segment from agraffe to tuning pin. Hence the wire bend at the agraffe being pulled towards the tuning pin. What affect then lowering the tension to pitch has yet to be reconciled. The reason I'm giving some credence to the pitted wire theory is that as I was adding shims the skipping diminished. A .016" shim on the c/b felt helped but left a little jumping. Doubling the shim made it a little better. Going to the 1/8" half-round on the plate was better but still a few pinged. Adding a .016" shim under that reduced it more but it wasn't until I shimmed the half-round with a .035 shim that the rendering smoothed out. It could be that the elevation of the wire off the c/b felt reducing drag is the solution but as I was lifting the wire with the offset screw driver the wire kept pinging until the wire was (I presume) pulled back from the agraffe. Because if it were just drag on the felt and not pitted wire, the wire would move still smoothly through the agraffe, wouldn't it? Next time, I'll mark the wire at the agraffe and insert the half-round and see what affect the higher c/b termination has on that string placement. Ultimately I think it's a little of each. I wish I had a junker around to do more testing. These shims ended up being .160". I think that .187" (3/16) will be even better but R.J. Leahy Co. won't have that stock in until May. It sure saved the day from having to restring the section. Regards, Jon Page -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://ptg.org/pipermail/pianotech.php/attachments/20100414/cda83f00/attachment.htm>
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