Adjusting Drop -Reply

[Delwin D Fandrich]

Dave:

Hi

I came in on the middle of the exchange about the proper method of
adjusting the hammer drop screw. If this duplicates anything that went
on before, please accept my apology.

Perhaps it might be helpful consider the function of the drop screw. 

First of all, it is misnamed. The only time it has anything to do with
“hammer drop” is while the action is being regulated. The rest of the
time its function is to stop the motion of the repetition lever as the
wippen reaches the end of its cycle. Generally, this should happen at,
or just before jack let-off. If the repetition lever were not held down
slightly after jack let-off it would continue to press against the
hammershank knuckle and would subsequently hold the hammer against the
vibrating string causing all manner of possibly interesting—but
uncontrolled and generally undesirable—percussive noises to come from
the piano. A better name for this screw might be the “repetition lever
stop screw.”

During the old fashioned regulating process it was (usually) adjusted by
slowly pressing down on the key until the action cycle went through jack
let-off. The drop screw was then adjusted so that the hammer dropped by
an amount roughly equal to the let-off distance. In numbers this meant
that, if the jack let-off occurred at 1.5 mm then the hammer would drop
an additional 1.5 mm for a total of 3.0 mm. As the key aftertouch
distance was taken up the hammer would rise some amount known only to
the gods.

There were some problems with this method. Specifically, it did not take
into consideration the varying geometry of the different types of action
designs. If the action required a longer than normal amount of key dip,
say 10.5 to 11.0 mm to function reliably the hammer could end up
dangerously close to the string, especially in the bass section. 

Whatever procedure you choose to actually adjust the screw you should
end up with a setting that will insure that the hammer does not contact
the string with the key fully (and firmly) depressed. You should find
that, with the action correctly adjusted (including precise key height
and dip—aftertouch—settings) and with the keys fully depressed using
uniform pressure on each to hold them down, the hammers will end up
level and about 1.5 mm from the strings through the tenor and treble
sections. I generally like to see them end up about 2.0 mm from the
strings in the bass section for obvious reasons.

As to having the repetition lever contact the drop screw at the same
instant the heel of the jack contacts the jack let-off button; I’m not
convinced it matters all that much. I’ve run several tests using both
piano technicians and “concert” pianists and unable to compile any
statistically valid evidence that, during normal playing conditions,
either group could tell the difference between an action adjusted that
way and one adjusted so that the repetition lever contacted the drop
screw slightly early. The only way the technicians could tell the
difference was to cycle the action through let-off so slowly that the
hammer did not actually strike the string hard enough to produce any
sound.

I hope this helps.

ddf