[pianotech] Lost motion in Spinets

[Tom Driscoll]

Matthew,
On all verticals pushing down on the back of the key will compress the backrail cloth, lowering  the whippens and the backchecks will move.I have a vertical in the shop here and I set up one note with excessive lost motion and one with the hammer shank off the rail . On both notes the backchecks move when I tap the key.That test will tell you nothing
 What you are adjusting is the relationship between the top of the jack and the leather surface of the hammer butt.
The typical piano in the field will have excessive lost motion.To correct I
 lightly and repeatedly depress the key as I adjust the capstan (or dowell on a drop action) up until the backcheck and hammer wink at the same time. Then after adjusting a section I tap down firmly and rapidly with my fingertips on the back of the keys. If any hammers wink that means the  jack is too high and is holding the hammer shank off the rest rail . Turn that capstan down until the hammer doesn't move when the back of the key is thumped .
As a general rule the piano will let you know if a little bit of lost motion is required to ensure reliable repetition.
 The poorer the materials (70's disposapianos with cloth instead of leather on the butt for example)  are more likely to need some lost motion where a quality action will need little or no lost motion.Watch the jack top as you slowly release the key. It  should slip home against the butt felt square without hanging up on the butt .
When you grasp the principles and let the piano show you what it needs the answer will be right there.
Tom Driscoll RPT

    
  ----- Original Message ----- 
  From: Matthew Todd 
  To: pianotech at ptg.org 
  Sent: Thursday, February 19, 2009 9:08 PM
  Subject: [pianotech] Lost motion in Spinets


        I am just double checking to make sure that checking for and, in essence, correcting lost motion is the same in spinets as it is in consoles and studios.

        i.e. to check for lost motion in spinets you can push your finger down on the back of the key and see if there is any movement in the backchecks, and make adjustments accordingly.......or by tugging on the hammer rail.


        TODD PIANO WORKS 
        Matthew Todd, Piano Technician 
        (979) 248-9578
        http://www.toddpianoworks.com 



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