Bechstein B hammer rake / more thoughts

[David Love]

I don't know about fudging but the hammer to string geometry at impact seems
to be of paramount importance.  While the shank horizontal at impact seems
to be a reasonable goal (and I can't really see any downside all other
things being equal) there are enough cases where it isn't and the action
response is not compromised in any way so in certain cases, as you
mentioned, I don't worry about it.  Piano work generally seems to have a
fair amount of the fudge factor present.   

David Love
davidlovepianos at comcast.net 
www.davidlovepianos.com

-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of John Delacour
Sent: Sunday, June 22, 2008 12:53 PM
To: Pianotech List
Subject: RE: Bechstein B hammer rake / more thoughts

At 13:19 -0700 21/6/08, David Love wrote:

>This seems overcomplicated.  Under normal conditions string height minus
>hammer flange center height = bore distance.  Hammer shank horizontal at
>impact. I don’t care whether the string is at a nominal incline to the
>bridge. 
>
>In other situations (like the Bechstein) where the formula above gives you
a
>bore distance that compromises stretch clearance, strike point access, or a
>just a hammer that is of reasonable length (and weight) I throw out the
>shank horizontal at impact requirement and go with a reasonable bore
>distance to get stretcher clearance and strike point accessibility and then
>add some rake to get the hammer perpendicular to the string at impact.
>Again, ignoring any nominal incline of the string.

That sounds to me like a good description of fudging from start to 
finish.  Heaven knows where this superstition concerning the 
horizontal shank at impact arose, but there is no scientific basis 
for it any more than there is any science behind the downward rake of 
the hammer on the old Steinway uprights.  The angle of the shank at 
impact, whether on a grand or an upright, is determined by the 
geometry of the whole set-up, which was generally carefully worked 
out to reduce the entrance height or (on an upright) the case depth 
to a minimum.  The majority of grands I have worked on are designed 
to have the shank exceed the horizontal and the hammers bored 
accordingly.

JD