[pianotech] Jack and Damper Spring Tension Targets

[Gene Nelson]

I was shown one method but it is mainly for new, replacement back actions or if you have it out on the bench.
As I only install springs to the top wound bichord this is what I do.
Hold the damper tray upside down. Spring tension should hold the lowest lever for note A-0 fast against the tray felt and the top bichord should be suspended about 30mm+/- from it. All the others should be adjusted so that they taper evenly between the two in a nice straight line.
Works fine for me and when measured with the expensive gram gauge it turns out to be close enough to the Renner spec.
Gene
  ----- Original Message ----- 
  From: Gregor _ 
  To: pianotech at ptg.org 
  Sent: Thursday, July 30, 2009 2:33 AM
  Subject: Re: [pianotech] Jack and Damper Spring Tension Targets


  The damper spring tension should decrease from bass to treble. Sometimes I see in old pianos a pencil line on the damper levers which goes diagonal over all the levers of one area (bass, tenor, treble). I was told that this line was used to measure the spring tension, but I was not told how exactly that procedure works. Does anybody know?

  Gregor

  ------------------------------------------
  piano technician - tuner - dealer
  Münster, Germany
  www.weldert.de




  > From: fg at floydgadd.com
  > To: pianotech at ptg.org
  > Date: Wed, 29 Jul 2009 06:03:25 -0500
  > Subject: Re: [pianotech] Jack and Damper Spring Tension Targets
  > 
  > Hi Gregor,
  > 
  > Ted's CAUT post of Oct 15/07 is quoted below. He was responding to a post
  > from David Ilvedson, as noted.
  > 
  > What I'm exploring here is new ground for me, and I'm trying to establish
  > points of reference.
  > 
  > Thanks for your interest!
  > 
  > Floyd Gadd
  > 
  > 
  > Gregor wrote:
  > 
  > That´s what I was wondering about, too. And how do you do it? Do you
  > dismount the whippen including the jack for measuring?
  > 
  > Concerning the damper spring: 40 grams on which damper? Bass or treble?
  > 
  > Gregor
  > 
  > 
  > 
  > [CAUT] Upright geometry problem (Nordiska)
  > Ted Sambell edward.sambell at sympatico.ca
  > Mon Oct 15 13:25:30 MDT 2007
  > 
  > 
  > Several years ago I attended the Europiano convention in Germany, at which
  > engineers from Schimmel dealt with this question. For the jacks, simply use
  > a force gauge, placing the feeler on the jack heel and moving the jack
  > forward with it. The recommended reading is 30 grams, not more. To check
  > the damper springs, mount the action on the bench horizontally with the
  > dampers uppermost and use the force gauge on the damper felt to press
  > downwards about the distance of the damper lift. The optimum reading is 40
  > grams. The engineers said that increasing the spring strength above this
  > does not improve damping efficiency. In my experience I have found that
  > excessive spring strength also causes hammer bobbling.
  > 
  > Ted Sambell
  > 
  > >I know how to reduce or increase the tension it is getting it even that I'm
  > >wondering about...some sort of gram gauge pulling on the damper? Maybe it
  > >is simply trying to pull the spring towards you the same amount for each
  > >damper?
  > >
  > > David Ilvedson, RPT
  > 


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