Pinblock Separation Repair & Pitch Change

Farrell mfarrel2@tampabay.rr.com
Thu, 30 Oct 2003 08:08:45 -0500


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Differing opinions regarding the benefit of lowering pitch prior to =
drawing a pinblock/backpost separation back together have been expressed =
on this list. I am one that generally feels more comfortable lowering =
pitch. I thought it might be of benefit to put some numbers on potential =
pitch changes.=20

Yesterday I did one of these repairs on a late model (1980s) Baldwin =
Acrosonic console. It had an approximate 1/4-inch separation between the =
pinblock and the backposts and deadwood back assembly. The separation =
had been "repaired" in the past with something that appeared to be =
silicone bathtub adhesive - surprisingly (?) the separation appeared to =
have widened since the application of the silicone. The piano was tuned =
at that time (and presumably tuned at standard pitch).=20

Prior to my repair the piano was fairly uniformly 75 cents flat. I =
dropped the pitch to between 200 and 250 cents flat prior to any =
clamping. I yucked in West System epoxy thickened with #403 Microfibers. =
(A fine fiber blend, is used as a thickening additive with =
resin/hardener to create a multi-purpose adhesive, especially for =
bonding wood. Epoxy thickened with microfibers has good gap-filling =
qualities while retaining excellent wetting/penetrating capability.)  I =
drew the gap closed slowly going back and forth among the six 3/4" pipe =
clamps (of which two got bent pretty good!). The separation appeared to =
close very close to 100%.

I then checked pitch again. Piano was fairly uniformly about 75 cents =
flat. Therefore, it appears that closing the 1/4-inch gap resulted in a =
pitch increase of approximately 150 cents.

I will be going back to the job on Friday morning to install a few =
through bolts, remove clamps, pitch raise and tune. If there is anyone =
out there that perhaps has not seen this repair done (or whoever for =
whatever reason) wants to see a few photos, I will take them Friday =
morning. Let me know.

Terry Farrell
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