Downbearing - Setting with a loose board

[Farrell]

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"Of course you took measurments of the olde bridges."

What good is that going to do for you? New soundboard + different panel =
thickness + new rib scale + different crowning + different downbearing =
=3D different bridge height. Better to build soundboard. Clamp =
soundboard in place (screws, clamps, whatever), install plate and then =
measure how tall you need your bridges. Otherwise you may be sadly =
surprised.   :-(

"I drop the plate, adjust to approximate placement and mark the struts. =
Remove plate, rough cut for plate clearance."

That's only if you install a bridge cap prior to setting downbearing. If =
you set downbearing first, you don't need to worry about that. When I =
build my bridge root I simply keep in short enough to fit under the =
struts (unless, of course, you have some wierdo piano that has the strut =
cutting down into the root).

"I then use cardboard shims between the plate and the soundboard."

That was essentially what I did when installing a new board in an =
upright - where you could closely inspect to see if the soundboard was =
snug up to the rim at every point. On a grand you can't see that joint =
everywhere, and I would still fear that the soundboard was not snug up =
to the rim. Someone else suggested temporarily screwing the soundboard =
down to the rim - I like that idea. But thanks anyway Joe. What works =
for one, may not be the best course of action for another, etc.

Terry Farrell



  Terry asked: "How do others approach this task?"

  =20
  Terry,
  I use the "Plate bolts". Fit the board to the rim. Of course have the =
rough bridge heights. (Of course you took measurments of the olde =
bridges.<G>) The worst one is clearing the plate struts. I drop the =
plate, adjust to approximate placement and mark the struts. Remove =
plate, rough cut for plate clearance. Once you have the struts cleared, =
drill for the plate bolts and insert them. (All of them.<G> ) I then use =
cardboard shims between the plate and the soundboard. (Front rail "card" =
punchings are good.) Cinch down, lightly and get out the string. Saw =
cuts in several places. (or router trimmer cuts, is easier.) This will =
get you in the ball park fairly quickly. The rest is in/out many times =
w/plate to fine tune the D.B. It's tedious, but can be done in less than =
a day. YMMV!<G>
  Best Regards,
  Joe Garrett, R.P.T.
  Captain, Tool Police
  Squares R I
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