[pianotech] Gluing Damper Felt

[David Love]

Sounds like a lot of futzing but I’m glad it works for you.  I prefer to just use the Spurlock jig (or something similar) set to the key end felt height and set the levers accordingly.  Avoiding any malformations or quirkiness with the tray felt helps not only with the lever height setting but any problems with sostenuto settings as well.  With most rebuilds I install tray capstan which gets adjusted for the pedal lift after all the levers are set to the key end felt height.  But there are obviously different ways to approach it.  

 

David Love

www.davidlovepianos.com

 

From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of Ed Foote
Sent: Sunday, February 28, 2010 8:41 AM
To: pianotech at ptg.org
Subject: Re: [pianotech] Gluing Damper Felt

 

 David writes:

Unless the tray is warped (which it often is) which means you’ll be setting the key lift timing different from one end to the other.  <<

 

Greetings, 
              This doesn't create a problem, since  I shim the tray felt so that all end-section keys lift their underlever at the same time (usually half of hammer travel).  While doing this,  the underlevers are resting on the tray, which is raised to whatever height the key ends require.    (I have damper heads in these trials, but they are way off the string, there to let me know when the underlever is contacted). If the lift at C5 is perfect, but at the same tray position, A0 lifts as soon as the key is touched, the tray felt needs to be shimmed up until A0 lifts properly. If at the same time, E6 is way late, either the felt needs to be thinned, the tray lowered, (causing C5 and A0 to get more shims), or the tray pivot point re-examined.  
    Once the sections are shimmed I can drop all the damper wires into the posts and snug them down.  They are usually very close together, and require some individual adjustment only.  Sometimes, say, when A0 needs to be shimmed up .60" and note 20 only needs to be lifted .030", the shim can be either tapered, or the difference split, meeting in the middle.  Those strips of red hard paper are readily split, as are the Renner part's boxes.  It isn't hard to hit a 1/4" strip  with a piece of 80 grit sand paper and taper it in a matter of seconds. 
  Once the tray lifts all the damper heads on the ends of the sections so closely I can't distinguish a difference, key timing differences are below the threshold of detection. ie, If I were to split the difference in the above example, notes 1 and 20 would be optimum, note 10 would be lifting .015" early  and note 11 would be .015" late( lifted by the key ends).  Whereas it may be detectable if a damper lifted on the tray .030" early, between keys, I don't think so. Normal felt wear is greater than this.   I usually taper, anyway, but battlefield conditions sometimes require chopping up whatever I can find on the floorboards of the car and sticking it in there with a dab of chewing gum to hold it...  
Another advantage of this approach is that once the tray is shimmed even, the entire damper timing can be changed very quickly, using the trapwork and the tray as the jig.  
Regards, 

 

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