[pianotech] Hammer Flange Friction

[Floyd Gadd]

Don,
I remember either hearing or reading the idea that to some degree the backcheck wire in a vertical action absorbs and releases energy when properly regulated in such a way as to contribute to the possibility of early jack return.  In fact, what I remember about the conversation is the backcheck wire being referred to as the repetition spring of the vertical action.  Any comments on this?

Floyd Gadd


Tom wrote:

Don
This is a new revelation for me. I've always assumed that the general design of the upright action limited any possibility for the jack to reset in the half position. I have 8 new Steinway 1098 uprights I'm dying to give this a shot at.
Tom Servinsky
  ----- Original Message ----- 
  From: PAULREVENKOJONES at aol.com 
  To: pianotech at ptg.org 
  Sent: Friday, June 04, 2010 5:56 PM
  Subject: Re: [pianotech] Hammer Flange Friction




  In a message dated 6/4/2010 4:30:20 P.M. Central Daylight Time, donmannino at ca.rr.com writes:
    Paul,

     

    3 reasons off the top of my head:

    1. The hammer head control tends to be better, less fishtailing.  In uprights the jack contact point is very close to the hammer butt center, and stress on the center is high.  The motion of the hammer mass is also in a different direction compared to the jack's force.  So a more firmly controlled center tends to improve the tone.

  Yes
   

    2. Hammer springs can be strong in many upright pianos, and they return the hammer too fast in many cases.  This can reduce the repetition rate by getting in the way of good jack return. If the jack spring is strong and hammer return is a little slowed, then the jack can reset without the wippen having to drop all the way to rest.

  This is the reasoning that I had and I have to admit that it is only intuitive, not measured reasoning. 
   

    3. Setting the hammer friction at 6 - 8 grams can induce enough damping factor to reduce hammer bounce, which also improves the consistency of repetition.

     

    Do these fit in OK with your ideas?

  Yes, as I said above. Number 2 is primary, I think. Jack return...

  Thanks, Don.

  Paul
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