Key Excursion

[Jon Page]

David,
A place to start might be at the back rail. LIft the underlever to a horizontal
position (which the key should lift to) and measure that height from 
the keybed.

The height of the key end lifter felt should be about 3/8" below that at rest.
ie. If the u/l lifts to 1 3/4" then the key end felt should be 1 3/8" at rest.
Proper thickness of felt is important. You need to check regulation and
the Magic Line for action efficiency.

One dealer had a B which had the key end felt at the proper height but the
action was mushy and heavy. The capstan/cushion contact point was above the
Magic Line. I remove one of the two underfelts strips from the back 
rail (!), reset
key height and the touchweight dropped and the action felt better.  I 
should have
installed thicker end lifter felt to bring it back to 1 3/8" because 
the stubborn
headed tech at the dealer reinserted the underfelt felt and drove the 
touch weight
back up. So a key more level was not as desirable as one with 
slightly more inclination.

If the backrail is too low, then the damper function is probably 
digging into the felt
and the key is too inclined to achieve spec. key height. I've lowered 
the pivot pin
holes 1/4" recently for better action feel.

I have altered key inclinations to produce more desirable touch 
weight and dynamic feel.
A key which starts off level has a mushy feel under the hand to my perception.

Bill, your x/y reference is the way I envision it and one would want 
the least friction
at a critical point in the keystroke, at letoff. But with the 
dynamics of the system,
at half blow may be sufficient.

I haven't recorded any tests or weight comparisons, just been 
optimizing each action
on the fly.
-- 

Regards,

Jon Page