Touchweight

[A440A@AOL.COM]

Ted writes:

>  a Church's grand action that
>needed regulation  
>While the action was on the bench I took touchweight
>measurements and everything was within spec.   
<snip>
 Well, I regulated
>the action and everything adjusted well.  On the bench the action played
>normally with a heavy blow and also with a light blow.  However, when I
>returned the action to the piano and secured the cheek blocks some of the
>hammers failed to go into check on a light blow.    
> <snip>.  I guess
>this is a good example where bench regulation isn't always the most
>accurate method.

Greetings, 
    Yes, performance level work requires some things be done in the piano, 
but there are procedures that a tech can do to get very close on the bench. 
   Before taking the action home, level the keys in the piano and set the key 
dip on the end of each section.  (I set key-dip by the aftertouch priority 
method, so this means that the keys on each end of each section need to have 
the let-off, hammer-blow, and keydip set in the piano).  
    Then, with the action on the bench, you can shim the rails up or down to 
restore the indexing keydip(and aftertouch) that you set in the piano, and 
the let-off rack can be set to the let-off of each end hammer on a per 
section basis.  With these two dimensions restored on the bench, the rest of 
the action in each section can be brought to the same limits.  This will 
usually get you very close to what you will see when the action is back in 
the piano. Don't trust it blindly, but it will allow you to do a lot more at 
home. (don't forget to set the jacks, springs, and balancier height for the 
section ends also!)  
    Let-off and drop are critical factors, and their distance will depend on 
the expected performance.  If reliability is paramount, a simple 1/16" will 
usually suffice for everything but the lower bass. If you want maximum 
sensitivity, you will have to set the let-off by the string excursion limits, 
and the drop as well.  
Regards, 
Ed Foote 
(the keydip/aftertouch doesn't affect the "weight", but it certainly changes 
the perception of how the action feels)