"Rake" = Vertical Pitch/Keith Roberts

[Farrell]

I'm very interested in where this thread may go. Unfortunately I do not have any expertice to lend. Perhaps someone like Darrell Fandrich, who has designed an innovative upright action, might have some insight into this?

Terry Farrell
  
----- Original Message ----- 
From: <BobDavis88@aol.com>
To: <pianotech@ptg.org>
Sent: Thursday, March 13, 2003 1:20 AM
Subject: Re: "Rake" = Vertical Pitch/Keith Roberts


> joegarrett@earthlink.net writes:
> 
> > Also, there
> > are times, for whatever reason is beyond me, the line from the butt flange
> > center pin is closer to the strings than Hammer bore distance dictates. 
> 
> The reason I have heard for this is that the center of gravity is behind the 
> center pin, so gravity aids the hammer return. 
> 
> It may be properly called vertical pitch, but all the hammer makers I talk to 
> at least recognize the term "rake." I confess that's what I use. Anyway, the 
> center pin to string being shorter than the bore seems fairly common, so it's 
> needed to put the hammer head perpendicular to the string, or in the case of 
> some pianos like the older Steinways, a little overcentered. Shortening the 
> bore in order to cut the rake (excuse me, vertical pitch) changes 
> relationships between the jack and the butt. It might work and it might not, 
> as it would throw the butt forward and could cause the jack to skip out. 
> 
> Keith's original interest was in how to deduce the correct bore distance from 
> scratch, where the original hammers might or might not be present for 
> evidence. I couldn't answer him right off at the meeting Monday, but upon 
> reflection, apart from looking at the rest position of the hammer rest rail 
> with a normal thickness of cushion, I would guess that the primary factor 
> would be the ability of the jack to push for the best power, and return 
> efficiently under the butt.  
> 
> Bob Davis
>