action reg puzzler on M & H BB

[John Delacour]

At 9:08 am -0700 25/9/06, Mark Potter wrote:

>I am having a puzzling problem with a M & H BB grand action that I 
>have never encountered.  Complete regulation (w/new shanks& 
>hammers), everything works great with the exception of 3 notes - F6, 
>A#6,ÊG7 - Êin the high treble.  I cannot get this to happen on the 
>bench, and even in the piano when the notes are played softly, even 
>in a trill, they perform perfectly.  However, under continuous mf - 
>ff blows, as in tuning, after anywhere from 1 to 10 strikes (letting 
>the key all the way up), the hammer will get caught on it's way back 
>up by the back check, thereby not allowing it to strike.

What happens if you put the action on the bench, use the palm of your 
hand to prevent the hammer rising and press hard on the key?  If the 
jack escapes, then you need to move the rest position of the jack 
further under the roller.  As you must know, the black side of the 
jack at rest should be in a straight line with the hammer-head side 
of the roller moulding.

Have you got the proper lost motion at the fly?  In other words does 
the cradle support the hammer very slightly above the jack?  This 
lost motion should be barely perceptible when you tap the key 
lightly, but you must have lost motion so that the fly can return 
under the roller without impediment.

Finally, when you raise the key slowly to release the hammer from 
check, does the hammer rise positively? and are the three centres 
(lever, jack, cradle) nice and free?

JD