Down bearing

[Isaac OLEG SIMANOT]

David,

When apparent downbearing is small it is very easy to be fooled by these
commercial 3 feet gauges sold. They will show you a gap behind the bridge,
where it goes in a slant, and you can take that for down bearing showing.
After that, if you use the string method You will see that the sting goes in
a straight line from one end to the other.
Is it what gives your input unclear ?
If you move the gauge at every possible place before and after the bridge,
you will have a better figure and see bridge roll, the slant on the top of
the bridge and how it is related to "measured" down bearing.

It is way more precise to have some home made gauges of different lengths,
that can help you to ascertain the existing bridge and strings segment
geometry.
BTW if your gauge have only 2 feet  I can't see how it works
The measuring gauge with a bubble, while not so accurate as we can think,
can add some information too.

I feel it is necessary :
- to learn to use the sound as a DB appreciation (but this seems to me a
long process to learn for a beginner (?))
- To check crown BEFORE & AFTER unstringing.
- To use the same method of measure before and after if you want to compare
things and try to deduct something.

I remember reading some very instructive lectures on these subjects in old
(! 8 years) PUT journal issues, and these are now available on the CD ROM
reprints. at these times it helped me to understand why what different
gauges where showing was different of the real picture.

Illustrations are needed there.

Hope and so on .

There is an old adage that says, the less you know about DB and crown, more
happy you live !

Much respected by many "restorers" there.

Another says " In the factory, it worked to put 1mm there, 2 there and 3
there, so it may work the same 40 years after that "


Regards

Isaac OLEG

Francium




> -----Message d'origine-----
> De : owner-pianotech@ptg.org [mailto:owner-pianotech@ptg.org]De la part
> de Daniel Lindholm
> Envoyé : samedi 30 mars 2002 23:11
> À : pianotech@ptg.org
> Objet : Re: Re: Downbearing
>
>
> Hi David
>
> When the strings where on we used one of those metal-
> thingys with two leveled 'legs'. One leg on the sounding
> part of the string and one on the part of the string that
> rested on the bridge. If you can wip it, it tells you that
> you got positive downbearing. If it stands firmly on the
> string, it tells you that you either have zero or negative
> downbearing.
>
> As for asking our instructor, we did. He couldnt come up
> with any better theory than we did with the cast iron and
> soundboard actually getting compressed between the cast
> iron pins and the tuning pins, increasing the positive or
> negative crown of the soundboard, altering the downbearing.
>
> I suspect that even though it has alot of negative
> downbearing right now, when the strings are off, it would
> get back to what it was (positive) before removing the
> strings, if we restrung it and tuned it.
>
> > Hello Daniel -
> >
> > At this point I would ask you how you went about taking
> downbearing
> > measurements.  The rest of your question seems to reflect
> some basic
> > confusion which might be best addressed by your
> instructors.
>
> Thanks,
> Daniel Lindholm / Sweden
>
>