Bechstein hammer bore

[Richard Brekne]

Hi JD.

Well this sounds kinda interesting... and I am most certainly willing to 
give it a try... sounds easy enough to accomplish really.  That said... 
most of the advice I've seen coming through the woodwork goes along the 
lines that if the hammer is not perpendicular to the shank at contact 
with the string.... then thats where the energy loss kicks in.  At the 
Yamaha concert tech academy they specify 90 degrees. I've heard 
argumentations in favour of a 2 degree rake, in both directions for that 
matter but thats always been about the shank flexing.

 Be that as it may... let me see if I got this right. Grands only to 
begin with.... just so that thats out of the way.

String to key bed height minus hammer center to key bed height 
determines bore length as usual yes ?... then rake is determined by the 
offset from parallel that the string plane  to the  shank at  string 
contact for the resulting bore length ?   The bore length should put the 
hammer shank at parallel to the key bed at string contact yes ?  So 
string offset to the shank at contact can be figured from the key bed 
plane then ?

Cheers
RicB



    At 22:37 +0100 15/2/08, Richard Brekne wrote:

         >...I have to admit I have never taken into consideration the
        angle
         >of the strings to the key bed... I pretty much stick with a
         >perpendicular to shank hammer... tho I am most willing to
        listen to
         >reason why I should rather choose hammer perpendicular to string.


    It is most important, in the extreme treble especially, to have the
    hammer strike the string exactly at a right angle in both planes,
    otherwise there will be loss of energy.  On many grands the strings
    in the top section are at a considerable angle to the horizontal.
    The Bechstein C I am working on surprised me by being an exception to
    the rule, but the angle has to be measured and factored into the bore.

         >I also tend to go for a constant rake ( 90 degrees to shank)...


    Why? That is by no means standard.  Many pianos require a 2 degree
    outward rake and some older models require an inward rake.  With a
    Bechstein you can mess about with the rest rail but that doesn't mean
    you're not introducing errors in the geometry.  On pianos with
    individual rest cushions things have to be just right.

         >  ...and vary hammer bore to match string distance to keybed.


    Well, as I hope I've made clear, that's not good enough.  You'll get
    away with it through most of the scale but in the treble not only is
    it critical to have a right angle but if you don't measure the slope
    of the strings you won't be able to calculate it so that you do get a
    right angle.  It's a very common omission and it's the reason why so
    many people can't get the treble right, especially on Bechsteins and
    Blüthners.  Now if you're lucky to have a piano with the strings
    perfectly horizontal in the extreme treble, well and good, but it has
    to be known.

    On most pianos the slope of the strings diminishes to an
    insignificant amount by the time you get to the top break, but by
    that time, you're out of trouble anyway.

    JD