Lost Motion Compensator & Regulation

[Dave Nereson]

----- Original Message ----- 
From: "Joey Recker" <joey@onkeypianotuning.com>
To: <pianotech@ptg.org>
Sent: Thursday, October 16, 2003 5:08 PM
Subject: Lost Motion Compensator & Regulation


> I have an old upright with a lost motion compensator.  I've done alot of
> repair to the action (taken it completely apart, re-pinned, replaced and
> re-assembled).  I am now ready to regulate it.  
>  
> Is there anything special I need to do during the regulation for the
> lost motion compensator?  
>  
> This piano is mine and I want to improve my regulating skills.
> Therefore, I intend on being super fussy on every step and doing every
> step several times.  In reading books on regulating I don't see any
> mention of a lost motion compensator, but mine has a bar which goes up
> to the hammer rest rail.  These bars can be adjusted a good bit with the
> use of a set screw at the mounting point.  When I took it apart I didn't
> mark it to note where it was set (stupid) but there has got to be some
> measure of exactly where the lost motion compensator should kick in, and
> in what order should I insert this step in the regulation procedure.  (I
> intend to follow the 25 steps in REBLITZ (page 37).
>  
> Thanks in advance for your input.
>  
> Joey
> 
      This step would be 24 a. or maybe 26.  As for the adjustment, it depends what type of compensator the action has -- they're not all the same, but the principle is the same.  The rod should "engage" the wippens or tails of the auxiliary levers or compensating levers (pinned to the wippens) as soon as the soft pedal is touched, or maybe with just a tiny bit of lost motion, like no more than 1/8", otherwise its purpose is partially defeated.  When the soft pedal is up, the hammer rail should of course rest on its cushions and not be help up off the action brackets by the l.m. compensator.  Nor should the jacks be hindered from returning under the butts, especially when releasing keys very gently with the damper pedal depressed (which removes any aid from the damper lever springs).  
    It's fairly self evident if you just depress a key very slowly, observing what the various little parts do when the soft pedal is depressed or not depressed.  The idea is to have minimal lost motion whether or not the soft pedal is engaged. 
    Sometimes the original rubber bushings for the vertical rod that connects the l.m. compensator rod to the hammer rail have become hard and brittle.  Then the mechanism can tend to "clank" when releasing the pedal.  They can be replaced with homemad leather bushings and felt punchings.   -- Dave Nereson, RPT