[pianotech] Downbearing question

[William Truitt]

Hi Al:

I popped my answer out as I was running out the door this morning.
Downbearing is a force, and distance bearing (what we are talking about
here) is a measure that allows one to calculate the amount of force with
which the string is pressing down against the bridge.  

I have used a Fowler dial gauge to quickly take bearing values for almost 30
years.  I find it useful in the field as a quick diagnostic tool,
particularly for things like voicing.  I can often hear problems of
excessive or inadequate bearing when tuning and voicing, and dropping the
gauge on the bridge often confirms what my ear is hearing.  This can keep
you from barking up the wrong tree in voicing - trying to fix the hammer to
fix a problem that is really in the soundboard system, and where you can
make the piano sound worse rather than better.

I don't know how the span of your feet on your gauge compares to mine, but
if they are different, then each of us would get a different reading on the
same piano.  And the time of year has an effect - you will generally get
more of a reading in the summer compared to the winter.  My guess is that
your readings are in a good range.

Will

-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of Al Guecia/AlliedPianoCraft
Sent: Thursday, July 30, 2009 9:09 AM
To: pianotech at ptg.org
Subject: Re: [pianotech] Downbearing question

Thanks Will. I usually read about 5 to 8 thousandths with my dial gauge 
micrometer and wasn't sure if 10 to 12 was too much.

Mike, the measurement is within one inch on either side of the bridge. I use

a string to set the downbearing, but I like to check it when it's strung 
with a dial gauge micrometer. The readings are lower on a "B" or "D" of 
course, but pretty consistent on smaller pianos. After I set the downbearing

and restring the piano I usually get about 6 to 8 thousandths in the bass 
and tenor and about 20 to 25 in the treble with my dial gauge.

The reason I need to replace the strings, is someone killed the bass strings

by trying to clean them with some kind of cleaner. I decided to replacing 
the wire strings because I don't want two different size tuning pins and 
also to replace the agraffes and polish the v-bar which I can do without 
pulling the plate.

Al G

--------------------------------------------------
From: "Mike Spalding" <mike.spalding1 at verizon.net>
Sent: Thursday, July 30, 2009 7:52 AM
To: <pianotech at ptg.org>
Subject: Re: [pianotech] Downbearing question

> Al,
>
> Downbearing is an angle, not a linear measure.  10 to 12 thousandths only 
> has meaning if we know over what length of string it drops 10 to 12 
> thousandths.
>
> That said, if you have some amount of positive downbearing throughout, 
> then there may be no need to change it.  There are a lot of other reasons 
> to pull the plate during restringing.  How is it that this piano needs new

> strings, but doesn't need any work on the bridges, agraffes, or v-bar, and

> doesn't need a new pinblock?
>
> Mike
>
> Al Guecia/AlliedPianoCraft wrote:
>> I never got a response to this question. Did my email get through?
>> I am restringing a Steinway M. Before I pulled the strings I read a 
>> composite down bearing of 10 to 12 thousandths across the bass and tenor 
>> bridges with a dial gauge micrometer. My question is, how much 
>> downbearing is too much.  Is 10 to 12 thousandths too much. At what point

>> would it be worth pulling the plate to adjust it. The soundboard and 
>> bridges are in good condition.
>>  Al G
>