Counter bearing treatment

[Newton Hunt]

Dear Richard, and incidentally list,

Have you opened a can of worms!!!

OK let's look at a couple of things here.

> I am not sure if the geometries of where the tuning pins have to be 

Good termination of speaking lengths are defined by the angles of
deflection of the strings from the primary termination, v-bar, capo
bar or agraffe or agraffe pins.

On upright termination is done through the use of pressure bars.  The
deflection should be only enough to prevent the strings from dancing
on the v-bar during a hard blow.  More deflection is undesirable
because the string renders poorly.

On grands the string deflection is provided by bars or felts behind
the agraffes or capo bars.  Same criteria applies.

> It might be that to have a grand action that up strikes strings means
> the strings must be within  x amount in height from the action.

Wrong direction.  Whatever the string height the hammers need to be
bored to equal the height of the strings from the keybed and minus the
height of the hammer centerpin.  Most else is irrelevant with certain
exceptions.

> Thus to fit a pinblock full of pins right above the action, the pin block might
> have to occupy a higher level than the strings.

Observation will show this to be contra-indicated.  Plate thickness,
string height, pin height, angle of deflection all contribute.

> If the pins must be higher than the strings then you have problems of necessarey plate structure to accomodate this. 

Chickerings could give you a major debate on this issue.  Go look at a
couple.

One other point I wish to make:

The angle of the tuning pin hole should be such that so the string
leaving the tuning pin coil when it is 1/8" from the plate and is at
90 degrees to the pin.  It matters not one wit what that angle is as
long as those conditions are met.  The heights of the bearing bars,
felts, etc., dictate the angle of the tuning pin hole.

If you can find an action model or drawing with plate fraction and
strings you will grasp some of the problems the designers had to
contend with.

Now that should all make sense don't yo think?

		Newton

Richard Moody wrote:
> 
>  Jon, List
>         I am not sure if the geometries of where the tuning pins have to be in a
> grand piano are because of the need for counter bearing, or the cause of
> it.  It might be that to have a grand action that up strikes strings means
> the strings must be within  x amount in height from the action.  The
> action can only be (or strike) so high vertically from the keys.  Thus to
> fit a pinblock full of pins right above the action, the pin block might
> have to occupy a higher level than the strings.  Or is it because agraffes
> are used?  (I should look on the Ivers and Pond hulk I have).  If the pins
> must be higher than the strings then you have problems of necessarey plate
> structure to accomodate this.
>         I have often wondered why in grands the pins are highter than the strings
> or why they could not be the same level as in uprights.   Perhaps my guess
> above is close to the answer.   I used to spend hours on the telephone
> with questions like these. I  heard talk about the "ski slope", but have
> forgotten.  ---rici wonder
> 
> ----------
> > From: Jon Page <jonpage@mediaone.net>
> > To: pianotech@ptg.org
> > Subject: Counter bearing treatment
> > Date: Monday, January 10, 2000 7:23 PM
> >
> > I recently restrung a Baldwin R and instead of recovering
> > the tenor counter-bearing with felt, I replaced it with a half
> > round bearing bent to the curve. Tuning is this area is much
> > easier and there seems to be no adverse sympathetic
> > vibrations. I am considering this replacement on another
> > popular brand with a wide felt area in this location.
> >
> > Aside from "tradition" and/or cosmetics is there a real reason
> > for this application?
> >
> > I think I read somewhere of the availability of hardened or rolled
> > steel for this purpose. I just utilized a rod I had and fashioned a
> > half-round suitable for the application.
> >
> > My experience has been that felt in this area creates a considerable
> > amount of friction, whereas a steel counter-bearing creates less.
> >
> > What say you ,
> >
> >
> > Jon Page,   piano technician
> > Harwich Port, Cape Cod, Mass.
> > mailto:jonpage@mediaone.net
> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~