hammer bore distance

[Scott Nelson]

Thanks, David. Makes sense now.
   
  Scott Nelson

David Love <davidlovepianos at comcast.net> wrote:
                Depends on how you define touchweight but with the shanks starting in more horizontal position you remove some friction.  Someone with the proper engineering vocabulary can give the proper explanation but I think it has to do with changing vectors as the hammer and shank travel in a circle.  The transition from horizontal to vertical movement produces the most friction.  Something like that.  Anyway, the downweight will drop and the upweight will increase.  A 4-5 mm change in blow distance can easily result in a change in the DW and UW of 2-3 grams (in opposite directions).  The balance weight won’t change since that is an average of the DW + UW, but the initial effort required to get things moving will diminish if you raise the hammer line and increase if you lower it.  It’s something to check if the customer feels that the action has gotten heavier over time, especially on a new action when a significant increase in the blow distance is not uncommon over
 the first several months.  Some pianists also like a smoother transition from break away (when the action starts moving) through the rest of the stroke (and some don’t).  You can achieve that by slightly short boring the hammers, rake them outward so that they still hit the string at 90 degrees and thus have the shank somewhat more horizontal in the rest position.   Of course, you can also just shorten the blow (assuming you deal with all the other stuff that goes along with that).   Not that I recommend it, necessarily, but for those pianists who want that feeling, it does offer an option.  
   
    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 Scott Nelson
Sent: Tuesday, October 23, 2007 6:43 PM
To: Pianotech List
Subject: RE: hammer bore distance
   
    Hi David,

     

    I'm not quite clear on what you are saying about short hammer bore hammers "must start  with the shanks rotated upwards"  Are you talking about  the fact that the relative position of a short- bore hammer shank, being higher (more horizontal) than a longer bore would could result in a different touchweight? 

     

    Thanks, 

     

    Scott Nelson

David Love <davidlovepianos at comcast.net> wrote:

    I think you've already received adequate postings on this subject but I did
want to comment that you do see hammers on some pianos bored short and
compensated for with a rake outward so that the hammer is at 90 degrees to
the string on contact even if the shank is not parallel (pretty common on
older Bechsteins). Boring hammers on the long side so that the shank
doesn't reach parallel (except for small amounts in anticipation of wear) is
less common unless there is a problem with hammer/belly rail clearance in
the treble and strike point issues forcing the hammer to be raked in. Still
1/4" would be excessive. Aside for getting things square at the string,
boring them long also can create touchweight problems as it will set the
shank at a lower angle when at rest and can increase the effort required to
move the key at break away. Interestingly, short bored hammers that must
start with the shanks rotated upward will produce the opposite effect. 

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 Cal Munson
Sent: Monday, October 22, 2007 8:56 AM
To: pianotech at ptg.org
Subject: hammer bore distance

Hello List,

I have gotten some hammers bored recently and have discovered in 
putting them on that the bore distance is about 1/4 inch greater than 
on the old set. Using a let-off jig, a small level and a gauge to 
measure the string height, I checked my hunch and it appears that 
the bore is indeed 1/4 inch too much (shank does not get all the way 
up to perpendicular)

I am wondering what would be considered reasonable tolerances in 
the ideal bore distance?

Cal Munson



   


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