Counter bearing treatment

[Delwin D Fandrich]

----- Original Message -----
From: Richard Moody <remoody@midstatesd.net>
To: <pianotech@ptg.org>
Sent: January 11, 2000 4:39 PM
Subject: Re: Counter bearing treatment


> 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.

I wrote a thing on tuning pin geometery a while back.  Nothing I have
encountered since has caused me to change my mind.



> 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.

With a modern action stack and a reasonable set of keys there must be a
minimum of 150 mm between the keybed and the bottom of the pinblock.  Or
whatever the lowest part of any casework there might be such as the
stretcher.  This will allow clearance for the action stack, including the
repitition lever upstop screws.  Typically, then, the string plane through
the tenor section will be a minimum of 40 mm above that.  This provides room
for a pinblock of reasonable thickness, a plate web and the appropriate
counterbearing bars, etc.  If you want to start designing your own piano,
keep in mind that these are minimums.



> 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.

Usually the tenor section string plane will be approximately even with the
top of the pinblock and/or the bottom of the tuning pin plate web.  There is
not magic here, it just works out that way.



> 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.

They could be but the hammer moldings would be pretty long.

Regards,

Del