JD Can you point us to a good technical paper or article on what you are talking about? Dean Dean May cell 812.239.3359 PianoRebuilders.com 812.235.5272 Terre Haute IN 47802 -----Original Message----- From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of John Delacour Sent: Friday, February 15, 2008 5:58 PM To: Pianotech List 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
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