overcentering justified?

Bob Hull hullfam5@yahoo.com
Wed, 20 Aug 2003 06:19:17 -0700 (PDT)


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David Love <davidlovepianos@earthlink.net> wrote:Bob:
 
What do you mean that in order to get the note to play well you need 41mm blow?  Do you mean repetition, or do you mean regulation?  Did the piano regulate properly before you changed the action parts?  A Steinway D should regulate at 48 mm.  Forty-one mm is too short a blow for that piano.  
 
What is the dip?  It should be 10 - 10.5 mm.  Rotation of the wippen rail can be checked by measuring the spread between the hammer flange center pin and the wippen flange center pin.  It should be 112.75 mm (4 7/16"), for a Hamburg.  If it's less than that you can shim the top of the whippen flange out to increase the spread.  Before I went plugging holes in the hammers and redrilling, I would make sure that you have all the other regulation specs in order.  If you measured a 2" bore and that's what you have, then I would check everything else before I reduced the bore to by that much! .  Sometimes plate elevations are set wrong and sometimes the stack is set too low.  I would take a few extra hammers from an old set bored at 48 mm and experiment with changing the stack position.  Raise the stack using some metal washers to the standard bore dimension and see where the convergence lines fall when the action is regulated.  While your at it, check the articles that appeared in the
 journal a few years back on action elevations by Bob Hohf.
 
Should you decide to plug and redrill, then plugging with a dowel, or hammer shank will work fine.   
  
David Love
davidlovepianos@earthlink.net
,

 
 


David,

The old hammers with the bore distance of 48 mm had a blow of 1 3/4 and a dip of 7/16 to a 13/32.  Let off was very close, just backed down enough to not block, drop was a little much - 1/4 inch or more on some.  It plays well and  repeats well with this regulation.  I do not want the dip to be that much with the new hammers, and I want the drop to be tiny.  

In trying to understand your response I may need to clarify: The 41 mm blow I spoke of was what the new hammer with the 2 inch bore distance seemed to call for.  I tried to regulate a new hammer with that 2 inch bore at 45 mm blow (any more and it was resting on the cushion); 390 dip, and around .031 aftertouch.  I also checked all other regulation areas on this sample.  It would play with these specs but it would not repeat real quickly like another sample that was regulated with a short blow of 41 or 42 mm.  I also regulated the glides on the center rail to make sure key height wasn't being affected by how the old regulation.  I believe the keys were being elevated .5 to 1 mm by glides being turned down too low. 

The 2 inch bore gives me a hammer that is almost exactly level shank, but since the strings are not level I need to match my shank level to them, not just have a bubble that is in in center. 

you said "use metal washers and raise the stack to the standard bore dimension" - do you mean the 48 mm hammer bore dimension that a Hamburg D calls for?  I am wondering now why my measurement of string height (near the hammer strike point) didn't give me a shank that matched the string angle?  I want to recheck that.

 I will work more on try some samples before I plug the new ones and redrill.

Thanks,

Bob Hull


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