replacing a back action on a 1909 Steinway B

[Jude Reveley/Absolute Piano]

This is a sound approach. Sometimes a modification will be required to the dags to prevent rubbing since the rear of the tray pivots lower when the axis of the tray is shifted in line with the flange. Kent Webb told me Steinway is going for a 15 degree angle of the underlever below horizontal at rest. There is a school of thought that there is another half stroke magic line from the balance rail to the flange through the keyend to underlever contact point, but I've rarely found this to be possible without considerable consequences. 

Jude Reveley, RPT
Absolute Piano Restoration, LLC
Lowell, Massachusetts
(978) 323-4545

----- Original Message ----- 
From: "Jon Page" <jonpage at comcast.net>
To: <pianotech at ptg.org>
Sent: Monday, May 12, 2008 7:52 AM
Subject: replacing a back action on a 1909 Steinway B


> Dave made a few good points for replacement of the back action.
> Another is to replace the older version without the brass set screw
> bushing because the wood is fragile and will not hold the screw tightly
> or simply cracks. One could install these inserts but another reason
> is to replace the old stiff sostenuto tabs with the spring-loaded tab version.
> 
> I also take the opportunity to move the tray pivot to be in line with the
> flange centers. This is accomplished by holding the end block and a flange
> to the rail and tapping the pin with a hammer to dimple the block.
> This makes the pedal lift the same motion as the key lift
> and there is no discrepancy with setting the upstop rail.
> 
> I also set the pivot height such that the key lifts the underlever to 
> a position
> parallel to the key bed. A pivot which is too high has the underlever at too
> steep of an angle and digs into the lifter felt causing drag and wearing
> a trench (which Dave mentioned). Reducing the lifting friction makes the
> action play more smoothly. Lifting beyond parallel is counter productive too.
> Lifting to parallel induces the least friction.
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