Down-Bearing for Old Board

[Farrell]

Thanks for the info Dale. Sounds like this will work well for me in
combination some of the general guidelines I have for new boards. BUT -
"Wish all new/young? techs. showed your persistence!"  Persistence maybe.
What I fear sometimes is a lack of common sense & talent! All we can do is
try, try, try though. And I do want to do what I do properly.

Specific comments interspersed below:

Terry Farrell
Piano Tuning & Service
Tampa, Florida
mfarrel2@tampabay.rr.com

----- Original Message -----
From: "Erwinpiano" <Erwinpiano@email.msn.com>
To: <pianotech@ptg.org>
Sent: Friday, February 02, 2001 10:26 AM
Subject: Re: Down-Bearing for Old Board


> Terry
>    Sorry I forgot to address that point. The answer is yes as to measuring
> the string gap at the string rest/aliquot  How large a piano is it and how
> old?

Estey grand. 4' 5" (yup, it's pretty big!). About 1930, but had a rough
life. All the strings were so rusted, most just fell right off. The guy got
the piano for free (it's a good one for me to learn on!!!).

> I think I'd like to know that before saying anything hard and fast but
> if the wood looks sound and you have new bearing values I'd push it pretty
> hard And always keep the dmp chsrs on.! I know what does that mean?
>         To answer that fully will require finding John H's. articles but
to
> cut to the chase the method I and many of my colleagues use is called a
> pre-stressed method of setting bearing and is easily adapted to fit your
> situation as well.  This method requires  that the board be at some
> reasonable R.H.(which it is ) then installing the plate and securing at
the
> block,nosebolts and a few places at the rim.  At that point pull a string
> thru agraffes over the bridge and see what you have in the way of a gap
> between string and rest .  Lets just assume at this point your bridge is a
> perfect original bridge and the height is good (which in your case is
> possible since your bearing is mystically so good).  Good meaning the too
> tall bridge will provide adequate bearing.

When I installed the 83 shims (well, maybe a few less), I really blocked the
board up from the rear. The framing on this thing is massive. It has five
big beams down there plus steel support rods (almost like a M&H octopus).
Anyway lots of spots to wedge and hammer. The board was so misshapen to
begin with, I just wedged and hammered as much as I dared - I was really
waiting for the board to just pop right out and land somewhere like a big
frisbie. I tried several times to convice the guy that the piano was junk
and the board was shot. He said "I don't care. Just make it look good."
Well, I can't do just that. I need to give it my best (somewhat reasonable)
shot at making it at least a bit piano-like!

>        The info gained from the next step will lead you to know if you
will
> lower or raise the plate shim or unshim string rest or install new bridges
> to get what you want .  Cut 4 thin/small maple wedges and starting at the
> central strut wedge one between the top of the bridge and the bottom of
> plate strut while pounding downward on the bd. near the strut . Repeat at
> each strut location then return to first and repeat cycle of pounding to
> ensure even preassure on the board.
>       As your pounding ( Pounding is not violent just firm and yes you do
> develop a feel for this and each boards resistance is different and will
> pre-compress  to varying degrees)

Let me see if I got this right (I have heard this/similar method described
before): I place wedges at all locations between bridge top and struts (this
piano has four sections, so I have a normal number of struts). While
?gently? pressing the wedge in, I pound firmly (not super hard) on board
near wedge so that wedge inches its way in between the bridge top and strut.
Do this in small stages in all wedge locations. Now I will have a compressed
board - presumably (ideally - but of course you don't know for sure)
compressed to a similar degree as it will be when strung up to pitch???  Is
that the idea?

> Once the bd. is compressed retake string
> thru agraffe. readings and over bridge. The gap I want to see is roughly
> 2.5mm in the top treble 2.25next section  down nd 2ish in the middle to
> bottom. Please these are not hard and fast and there. are variations we
all
> use depending on the sit. and are intended as a good starting point and
one
> I feel is safe for your siuation.    Usually the amount the board sinks is
> fairly predictable.  I.E. 3   m.m. at the central strut 2 or so at next
ten
> /treb. and 1ish at the top. and 1 or 2 on the bottom. Do not over pound
the
> bottom it needs to flex as it's near the rim glue joint

HERE IS MY BIG QUESTION: This sounds good. But a board more flexible than
"normal (whatever that might be)" will flex down or compress more with the
wedges, and a stiffer board will not flex as much. So, if I find that I have
a board that is either significantly more or less flexable than the norm,
can I assume that I would go with LESS (than average) downbearing on a
flexible board (so that I don't squish it too much), and MORE (than average)
downbearing on a stiff board????? I think that would be right.

AND yes, I wholley understand that none of these numbers are hard and fast.
One I'm sure needs to conduct a series of compression measurements, thunk
tests, pitch tests, grain counts, glue density tests, planetary alignment
analyses, and confer with the ghost of Beethoven, and of course integrate
all this info before you can know for sure what to do with downbearing. Then
the RH will go and change - aw, shucks.

>    Hope this helps and if I left anything crucial out ( like a lot o
stuff)
> Buzz me another post.This should get you started
>    Dale Erwin
> P.S.Wish all new/young? techs. showed your persistence!
>
>