Bechstein hammer bore

[David Ilvedson]

How do you measure the angle of the strings?

David Ilvedson, RPT
Pacifica, CA  94044

----- Original message ----------------------------------------
From: "John Delacour" <JD at Pianomaker.co.uk>
To: "Pianotech List" <pianotech at ptg.org>
Received: 2/15/2008 2:57:34 PM
Subject: Re: Bechstein hammer bore


>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